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16109 73RD PL W.PDF16109 73RD PL W ,5z,Y•4 73�d �/•ate Gar TAX ACCOUNT/PARCEL NUMBER: 00 -79O4 00000600 BUILDING PERMIT (NEW STRUCTURE): /�l/DO agOs COVENANTS (RECORDED) FOR: / /ol,�1 5klw/Cq O6aS��Z- CRITICAL AREAS : �(ll's Ia _ DETERMINATION: ❑ Conditional Waiver ❑ Study Required Q/Waiver DISCRETIONARY PERMIT #'S: DRAINAGE PLAN DATED: -1 _21-00 PARKING AGREEMENTS DA' EASEMENT(S) RECORDED FOR: PERMITS (OTHER): M PLANNING DATA CHECKLIST DATED: -7-Z 7 -qT Z�- Z 3 :�9B, SCALED PLOT PLAN DATED: IT-9 q SEWER LID FEE LID #: 210 SHORT PLAT FILE: IPRQ /--f -/ 1-04111/ a4 LOT: BLOCK: SIDE SEWER AS BUILT DATED: ^7zD'30 VO SIDE SEWER PERMIT(S) #: �G GEOTECH REPORT DATED: Z 2-0-Co Z "G STREET USE / ENCROACHMENT PERMIT #: FOR: WATER METER TAP CARD DATED: < 0r 2 OTHER: c�/�lC%- }fityuJo.✓�i% 7' i� Cyr-cj�1 /��C �r/�; LATEMP\DSTs\FornulStreet File Checklist.doc - 4041�S 11' *cove 12pqc W. 'pe PAMO Ole (WAM VI/ AAPI�� 4 TO Ore- Rm WtO Af 4F— AQ;rea. C) (1) rt,? 1!It ,',},i'•tl 't! �I3" t ` � � i 1 t . t � tl k �AA -06 '16 lib Gml 9W7 01 ------ AN0 Km I UJA, OJIW'2J40' ------ - - Hr-S M14 IfI1411f- /oc /Cm y T T FILE "rm,4104 Ulm, CO)jc sus WA&4LUJkAf I At - USE CITY,OF EDMONDS ZONE PERMIT ; ,,r- CONSTRUCTION PERMIT APPLICATION NUMBER J08 li' UITE/APT N OWNER NAMADDRESSElNAME OF BUSINESS 7 ' ' LEGAL DESCRIPTION CHECK SUBDIVISION NO. LID NO. w MAILING ADDRESS" ,% CC �. - t C." O 4 �+ ' PUBLIC RIGHT OF WAY PER OFFICIAL STREE MAP. - TESCP Approved LY CITY ZIP TELEPHONE NUMBER RW Permit Required A/ri0 _1 (,e. K - ti EXISTING REQUIRED DEDICATION Street Use Permit Req'd A JO PROPOSED ' �� Inspection Required yp� 0- NAME cc (//J'-/,.�.a,,, _ SidewalkRequiredr,.�v O O /' {�V��IY ._ � _ i s MET IZ t LIN SIZY, NO. OF FIXTURES PRV REQUIRED W W ADDRESS YES)( NO O 3 cc REMARKS� ..,Z aIr CITE(.:PHON M, ZIP TEL NUER W xnl7"?`n"�✓".� ».y! , �.. Fr [o J JS i.!.� Cc.r✓T L7 J . LT NAME. c:7"u. /"lf..� .ter-�/lt r� ��, [n �c (�- /n (' _ _ w I ,c n-.'..i f-k t� � ; u1C�r' i�� ' .� % Vu. %C"1:- !I E� �' 1I`7i()•+%14�i1J ¢ ADDRESS " , <i0!L• lh IP (7C.�It'�� Ai ....a..�....�..... M0 DATED REVI ED BY ¢ CITY ZIP TELEPHONE NUMBER "d IP J (7 f) (! T > Z t ' i ) ' ! (� n FIRE MEMO DATED i r p �j REVIEWED BY W Lr STATE LICENSE NUMBER EXPIRATION DATE LL VARIANCE OR CU ADB p - SHORELINE p Legal Description Of Property include all easement ;'` ,+� J /�-p SERA REVIEW SIGNAREA HEIGHT ZO of i,� h d" P C' �i/� ��©�J - f l�r -- %t�rt f� C MPLjETE EXEMPT ALLOWED - PROPOSED ALLOWED PROPOSED a 1 wi EX ! ! I u lj 1 � ct' �_ �' /�r•G_.c%. Gi/' ��f ;d'/P o'1 �c?� 5 E" w I LOT COVERAGE REQUIRED SETBACKS (FT.) PROPOSED SETBACKS (FT.) IDE REAR p ALLOWED PROPOSED FRONT SIDE REAR FRONT UR c7 § z Property `j z Tax Account c U TAR IN REVIEW DATFJ a Parcel No. �.� �I�--U/,1C--16Uf7 �I REMARKS NEW RESIDENTIAL PLUMBINGIME. HI Al COMPUANCE OR ADDITION COMMERCIAL CHANGE OF USE -f-(" n REMODEL APT. BLDG. SIGN REPAIR ®G c�Gl CYDS. FEI NCE x—� CHECKEDBY TYPE OF CONSTRUCTION CODE GRC AN7L DEMOLISH ❑ INSERWOODST HOT SWIM POOL HOT TUB SPA REQUIRED SPECTOR Aq4 a 0�•/ GARAGE RETAINING WALL/ YES /r� CARPORT pki ROGIGfi1Y RENEWAL REMARKS (TYPE of USE, BusNESS OR ACT Tv) Exa. �N: PROGRESS INSPECTIONS PER UBC 108 0 �' ?i2fdtrrLP�$)� +3+�/.•!t° ,2. s'�'.�+`ftr7�w'1. t7 W NUMBER NUMBER OF CRITICAL OF wqy DWELLING AREAS .,P �1 a 0 STORIES 3 UNITS NUMBER `% ��' ��,J�-! fi r T e.a `� N0' �'V1^11S X. 4eL 'el_W11. 51 DESCRIBE WORK T BE DONE ATTACH PLOT LAN) 4e�T74/ FINAL INSPECTION REQUIRED VALUATION FEE / PLAN CHECK FEE /07- 54,—,,R 30 %o 46"AA� Z %� 1/BUILDING HEAT SOURCE: GLAZING / A6 el. / Q % PLUMBING f Plan Check No. rt f 69 (9 MECHANICAL r '� This Permit covers work to be done on private property ONLY. GRADING/FILL Any construction on the public domain (curbs, sidewalks, e driveways, marquees, etc.) will require separate permission. SYAtE�sUACHARGE 6Nf , 5Q Permit Application: 180 Days Permit Limit: 1 Year - Provided Work Is Started Within 180 Days STORM DRAINAGE FEE 3 L.) "Applicant, on behalf of.his or her.spouse, heirs, assigns and ENG. INSPECTION FEE { ; in successors in interest, agrees to indemnify, defend ;and hold W harmless the City of Edmonds, Washington, its officials, J employees,and a ents from an and all claims for damages f tG%iS.3/ rla�� t•� ✓S[I r'S e)r e .. �9 Y ges o c whatever nature, arising directly or indirectly from the issuance = of this permit. Issuance of this permit shall not be deemed t0 PLAN -CHECK' DEPOSIT - omodify, waive or reduce any requirement of any city ordinance ~ x nor limit in any way the City's ability to enforce any, ordinance TOTAL AMOUNT DUE / ) provision." 1 hereby acknowledge that I have read this application; that the r information given is correct; and that I am the owner, or the duly ATTENTION APPLICATION APPROVAL authorized.. agent of the owner. I agree to comply with city and THIS PERMIT state laws regulating construction; and in doing the work authoriz- AUTHORIZES This application is not a permit until ed thereby, no person will be employed in violatio' of the Labor ONLY THE signed by the Building Official or his/her Code of the State of Washington relating to WorkmeN Compensa• WORK NOTED Deputy; and fees are paid, and receipt is lion lnsura no RCW 18.27. INSPECTION acknowledged in space provided. SIGNATURE (LWNV OR AGENT.)----___ r DATE SIGNED DEPARTMENT OFFICIAL'S SIGNATURE DATE CITY OF EDMONDS r� CALL FOR ATTENTION 'REii+s�D DATE �'`" INSPECTION ' IT IS UNLAWFUL TO USE OR OCCUAA'BUILDING OR STRUCTURE UNTIL A FINAL INSPECTION HAS BEEN MADE AND APPROVAL OR 771-0220 ORIGINAL — File YELLOW — Inspector A CERTIFICATE OF OCCUPANCY HAS BEEN GRANTED. UBC SECTION 109 ,! (,.,. -' /, !r 1 I 1 10247 /;yf ?) ,�7 PINK - Owner GOLD - Assessor S :''�.•---•o.,�r •.'+'�. � .Y—�"^\7cc :--{'.:l. �; ,s ,� .. -.»-,. _ :1. „�,,.: ,:..:r` •.'• i"'. ,�:., ,;F:.:�s:-G- ! - Nrv�.r:: Si2!hK1 4 � GaM�yarstti�e'7n��ffi?&} RECE1VFn OCT 215 2000 �11 Ci of EdonPERMITmds NO: 9225 SIDE SEWER PERMIT PERMIT EXPIRES JZAY S '11c. 189- Address of Construction: bf �� Ly" ' LID # Property Tax Account Parcel No. `/'9D6 • ��—,��%� Attach copies of all access and utility Owner and/or Contractors, - Contractor License #: C, LC'2A) Single Family ❑ Multi -Family (No. of Units ❑ Commercial (No. of Units ) ❑ Public Verified and Approved by I (La" . t7k)L _Building Permit Invasion into City*Right-of Way: '❑ Yes )] No *RW Construction Permit # Cross other:* *Private Property:-. ' ❑ Yes r'O" No *.*Attach legal description and copy of recorded easement. Owner or contractor signature and acknowledgement statement: By signing for this permit -I certify that I have read the City's public handout entitled Lqj Date Side Sewer Specifications, and shall comply with all City requirements outlined therein: `a CALL DIAL. -A-DIG (1-800-425-5555) BEFORE ANY EXCAVATIO W FOR INSPECTION CALL 425-771 OWextension.i"49 24 HOUR NOTICE REQUIRED FOR ALL INSPECTION REQUESTS NOTE: IF JOB SITE IS NOT READY FOR INSPECTION WHEN INSPECTOR ARRIVES A $45 RE -INSPECTION FEE WILL BE CHARGED. Job Site Ready YES NO Date: Initial: Partial Inspection: N e L nw,o L'%dx Date: P Io•3v-c�lnitialfj Partial Inspection: Date: Initial: . FINAL INSPECTION APPROVED: Date: ©I Initial:M_As-built to Street File: '6- PERMIT MUST BE POSTED ON JOB SITE White Copy: File Green Copy: Inspector Buff Copy: Applicant L;temp;bl dg;forms;sspenn itj Ig4/00 �L Side Sewer Drawing The City of Edmonds NEW CONSTRUCTION OWNER............................................................. L JOB ADDRESS ------ J3 ts EASEMENT NO . ............ .............. LIDNO - ------------------ AsmT. NO . . .............. REPAIRS ❑ 'Oft PERM]T No. 771 CONTRACTOR ---- (—O� ... LEGAL DESCRIPTION: LOT NO. _ ............................ I ...... BLOCK NO. -_.................. ------------ ....................................................................... .............................................................. 1-1 .......... I ............. ............................ NAME OF ADDITION ....................................... ......... 1(0109 0 Approved: I A 0-2000... .6 DATEW ...-... ...................... ..... B Y/M /_... 4 � 111A.�Or - -------------- pWW.00()1-11175 (REV-11176) Water Service Drawing The City of Edmonds EASEMENTNO . ............................................ NEW CONSTRUCTION REPAIRS El LID NO . .................. . ASMT. NO . ........ ......... OWNER............................................................................................ ... CONTRACTOR ................. .................................................................. PERMIT NO. JOB ADDRESS ALO�.0.-� ...... �3-f� ..... 3A ... I ................... LEGAL DESCRIPTION: 1-071". NO. .............. ................. ..... BLOCK NO. ................................... NAME OF ADDITION ..... ................................ A .............. ....... .................................... .......... u C., Ca CD CD C, f-7 p Ey- 'D Cn M C-3 Z. q ri C %cc C!, tol = Cr Approved: Mb WvVV-0001-1 1175 (REV.11 1178) DATE ... .................... By 1p ................................ PLANNING DATA NAME: TA11- SITEADDRESS: Il��q %� � LATE: ZONING: APLAN CHK#: PROJECT DESCRIPTION: AW :5 CORNER LOT (Yes/No) FLAG LOT (Yes/No) SETBACKS: Required Setbacks: Front: Left Side: 'C'9' Right Side:-,,9— Rear: (9— Actual Setbacks: Front: �_Left Side: Right Side:_�Rear: Street map checked for additional setback required? (Yes/No) LEGAL NONCONFORMING LAND USE DETERMINATION ISSUED (Y/N) LOT COVERAGE: Maximum Allowed: Actual: BUILDING HEIGHT: ,, // ' Maximum Allowed: /✓J- S Actual Height: 1W Datum Point: Datum Elevation: A.D.U. CREATED?: SUBDIVISION: CRITICAL AREAS #: 10 J A0 SEPA DETERMINATION: LOT AREA: lW OTHER: PLANNING DATA NAME: f ■ 10 DATE: 2 I • / ♦ / �2M ��SIA Plan Review By A ILE NO. I s T, fitical Areas Checklist ----------------- ----------------------------------------- Site Information (soils/topography/hydrology/vegetation) 1. Site Address/Location: % 6 / D S' 7V '`? i7 /Gi C Gr/�, �oll�o��s 2. Property Tax Account Number: 79a4/- —DUD--oU6—C)d0��j�r dnn �—oa Lo7`vl 3. Approximate Site Size (acres or square feet): V oo o 4. Is this site currently developed? yes; _&o. If yes; how is site developed? 5. Describe the general site topography. Check all that apply. Flat: less than 5-feet elevation change over entire site. Rolling: slopes on site generally less than 15% (a vertical rise of 10-feet over a horizontal distance of 66-feet). Hilly: - slopes present on site of more than 15% and less than 30% ( a vertical rise of 10-feet over a horizontal distance of 33 to 66-feet). Steep: grades of greater than 30% present on site (a vertical rise of 10-feet over a horizontal distance of less than 33-feet). Other (please describe): 6. Site contains areas of year-round standing water: /Vb ; Approx. Depth: 7. Site contains areas of seasonal standing water: -Alo ; Approx. Depth: What season(s) of the year? /1/6, 8. Site is in the floodway Alo floodplain of a water course. 9. Site contains a creek or an area where water flows across the grounds surface? Flows are year- round? Flows are seasonal? (What time of year? ). 10. Site is primarily: orested , meadow : shrubs ; mixed urban landscaped (lawn,shrubs etc) 11. Obvious wetland is present on site: 1410 __-- --------------------------------- For City Staff Use Only ------- -------- ------------------------------------- Site is Zoned? 2. SCS mapped.soil.,type(s)? 7 r" s — 3. Wetland inventory or C.A.map indicates wetland present on site? 4. Critical Areas inventory or C.A..map indicates Critical. Area on site? Y 5 Site within designated earth subsidence. landslide hazard area?, S :1 6: Site designated on the Environmentally Sensitive Areas Map? bETER1ViINATION ^ca chk.doc; Rev 10/03/97 0 ORECEIVV City of Edmonds NAW CRITICAL AREAS CHECKMW WUNTEF The Critical Areas Checklist contained on this form is to be filled out by any person preparing a Development Permit Application for the City of Edmonds prior to his/her submittal of a development permit to the City. The purpose of the Checklist is to enable City staff to determine whether any potential Critical Areas are, or may be, present on the subject property. The information needed to complete the Checklist should be easily available from observations of the ' site or data available at City Hall (Critical Areas inventories, maps, or soil surveys). An applicant, or his/her representative, must fill out the checklist, sign and date it, and submit it to the City. The City will review the checklist, make a precursory site visit, and make a determination of the subsequent steps necessary to complete a development permit application. Please submit a vicinity map along with ' the signed copy of this form to assist City staff in finding and locating the specific piece of property described on this form. In addition, the applicant shall include other pertinent information (e.g., site plan, topography map, etc.) or studies in conjunction with this Checklist to assist staff in completing their preliminary assessment of the site I have completed the attached Critical Areas Checklist and attest that the answers provided are factual, to the best of my.knowledge (fill out the appropriate column below). Owner/Applicant: 41 Name Street Address City State Zip Telephone Signature Date c: recepdo nl j analcac 1, doc Applicant Representative: Name Street Address City State Telephone Signature Date Zip (over) City of Edmonds Critical Areas Determination Applicant: Chun H. Park Determination #: CA-98-156 Project Name: Permit Number: Site Location: 16109 73`.d Pl W Property Tax Acct #: 7904-000-006-0006 Project Description: non -project specific A site inspection has revealed a site which appears to contain or be adjacent to slopes of 40% or greater with a vertical elevation change of more than 20 feet. Based on the above findings, it is determined that there is potentially a steep slope critical area on or adjacent to the site. A Critical Areas Study is required to delineate the boundaries of this potential critical area, the buffers and setbacks. For the steep slopes, a licensed surveyor must create a topographic map of the site that indicates all areas that slope 40% or more and have a vertical "gain of 20 feet or more within the 40% slopes. The map must also show the location of the steep slope buffers and setbacks. If the property owner wishes to apply for a specific development permit which they feel would not impact the Critical Areas located on the site, they may submit their proposal to the Planning Department for review. If the Planning Department finds that the proposed development permit will not adversely impact a Critical Area or its buffers, a conditional waiver may be issued on a project by project basis. John Bissell Name i 11 i re June 29, 1998 Date CITY OF EDMOND5 BARBARA FAHEY MAYOR 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works • Planning/Building • Parks and Recreation * Engineering * Wastewater Treatment Plant June 29, 1998 Chun H. Pak 3828 N.E. I10th Seattle, WA 98125 Subject: Determination regarding Critical Areas Checklist # 98-156 Dear Applicant: Enclosed please find a copy of the Critical Areas Checklist you submitted. The "DETERMINATION" reached by the City is located on the reverse side of the form (bottom of page). It is very important for you to retain a copy of this Critical Areas Checklist "DETERMINATION" for your records. IMPORTANT INFORMATION TO BE NOTED:. PLEASE EXAMINE THIS" DETERMINATION" FOR ADDITIONAL REQUIREMENTS. YOU MAY NEED TO SUBMIT ADDITIONAL INFORMATION SUCH AS AN ENVIRONMENTAL CHECKLIST OR CRITICAL AREAS STUDY. The 'DETERMINATION' for the Critical Areas Checklist you submitted is a site -specific determination not a project -specific determination. a Permit applications include the following: Building Permits Conditional Use Permits Subdivisions Variances Applications to the ADB* Land Use Applications Any other development permit applications. Enc: Critical Areas Determination * Architectural Design Board Thank you. Sharla Graham Acting Planning Secretary C: R eception\Ja na\C R LTR. doc 0 Incorporated August 11, 1890 O Sister Cities International — Hekinan, Japan . i_ f Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer .� STRErt� FILE July 27, 1998 Mr. Chun H. Pak 3828 N. E. 110th 1 Seattle, Washington 98125 Subject: Geotechnical Evaluation Proposed New Residence 16109 - 73rd Place West, Edmonds, Washington This engineering report presents the results of a geotechnical evaluation of Lot No. 6 at 16109 - 73rd Place West, Edmonds, Washington. This evaluation was required due to owner and architect concerns, as well as City of Edmonds requirements. REFERENCES: • Location map (figure 1) • Geotechnical Report of the overall Lorian Woods property for Robert and Joanne Anderson, dated June 6, 1989, by Terra Associates, Inc. • Site photographs • Proposed Mr. Chun Pak house design by Mr. Phil King, Designer BACKGROUND: Lot No. 6 (16109 - 73rd Place West, Edmonds, Washington) of the overall Lorian Woods Development, exists along the private road 73rd Place West (see Lorian Woods layout map). Lot No. 6 is approximately sixty foot (60') deep and seventy-eight foot (78') wide, in an approximate rectangular shape. Lot No. 6 has never been developed. Surrounding lots in Lorian Woods have been developed within the last six years. The property immediately behind (easterly) of the Pak Lot No. 6 is understood to have been dedicated as Native Growth Protection Area, or green belt designation. The primary geotechnical aspects affecting the proposed single family residence development of Lot 6 are slopes and drainage. Lot No. 6 contains gentle to moderate topography [from five percent (5%) to thirty percent (30%) slopes]. The slopes behind (easterly) of the Pak lot contain slopes at approximately 2H:1 V. SOILS - FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE • DESIGN & PERMIT - LEGAL 17814 8th Ave. N.W. • Shoreline, Washington 98177 • (206) 546-9217 - FAX 546-8442 0 40 Pak Page two The slopes behind the Pak lot evidence significant and year-round ground water and seepage outflow. It is understood that the City of Edmonds has required the installation of a significant number of intercept and deep drain wells. EVALUATION: Visual assessment of Lot No. 6 revealed no evidence of any geotechnical distress. No slides, no settlements, no tension cracks, no creep, nor any significant erosional degradation were observed. As mentioned, seepage groundwater "trickle" flows were observed, and are evident in the photographs with regard to street discharge into the existing storm water system. This engineer obtained a copy of the Terra Associates, Inc., geotechnical report, dated June 6, 1989 from the City of Edmonds. This report provides extensive geotechnical analysis and slope stability evaluation. This engineer reviewed the test bore holes, as well as the backhoe-dug test pit information in the Terra report. This engineer's direct experience in the area verifies the stratigraphy reported in the Terra report. In order to augment the existing site geotechnical information, soil test pits were hand -dug by this engineer in the proposed location of the Pak residence. All of the five (5) hand -dug test pits contained similar findings, namely: 0" to 4" Organics, roots, and organic silt 4" to approx. 14" Silty sand, moist, medium dense 14" to approx. 34" (bottom of Increasingly dense sandy silt / sandy silt hand -dug test hole) Seepage water was evident in all test pits. o water was encountered in any of the three test pits. All test pit walls remained vertical and stable. No sloughing or caving occurred. CONCLUSIONS / RECOMMENDATIONS: Based on the findings of this investigation, review of the June 6, 1989 Terra Associates, Inc., report, and experience with similar sites in the area, Lot No. 6 is geotechnically approved for the proposed Mr. Chun H. Pak single family residence, per Phil King designs, subject to the following: • Standard reinforced continuous and spread footings. Allowable bearing pressure: 2,000 p.s-t • Equivalent fluid pressure of 35 p.c.f. is recommended for any retaining wall design provided drainage zone is inspected and verified by this engineer. • For retaining wall design, use friction factor of 0.55 and passive pressure of 350 p.c.f. Pak Page three An intercept "French -type drain" is recommended along the eastern property line and graded to "wrap around" the new Pak residence. This intercept ditch will be approximately thirty-six inches (36") deep, and provide seepage pressure release around the Pak residence (specific designs provided prior to site grading).' • Geotechnical inspection by this engineer prior to any foundation concrete placement. The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed native soils or on structural fill placed above native soils. See the later sub -section entitled General Earthwork and Structural Fill for structural fill placement and compaction recommendations. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty- four (24) inches, respectively, and should be bottomed at least eighteen (18) inches below the lower adjacent finish ground surface. Depending on the final site grades, some overexcavation may be required below footings to expose competent native soils. Unless lean concrete is used to fill the over excavated hole, the width of the overexcavation at the bottom must be at least as wide as the sum of two times the depth of the overexcavation and the footing width. For example, an overexcavation extending two feet below the bottom of a three-foot wide footing must be at least seven feet wide at the base of the excavation. Footings constructed according to the above recommendations may be designed for an allowable soil bearing pressure of three thousand (3,000) pounds per square foot (p.s.f.). A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that total post -construction settlement of footings founded on competent, native soils (or on structural fill up to five (5) feet in thickness) will be about one-half inch, with differential settlements on the order of one -quarter inch. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the bearing soils, or by passive earth pressure acting on the vertical, embedded portions of the foundations. For the latter condition, the foundations must either be poured directly against undisturbed soil or the backfill placed around the outside of the foundation must be level structural fill. We recommend the following design values be used for the foundation's resistance to lateral loading: Parameter Design Value Coefficient of Friction 0.55 Passive Earth Pressure 350 p.c.f. Pak Page four Where: (1) * p.c.f. is pounds per cubic.foot. (2) Passive earth pressure is computed using the equivalent fluid density. We recommend that a safety factor of at least 1.5 be used for design of the foundation's resistance to lateral loading. SLABS -ON -GRADE: Slab -on -grade floors may be supported on undisturbed, competent native soils or on structural fill. The slabs may be supported on the existing soils provided these soils can be recompacted prior to placement of the free -draining sand or gravel underneath the slab. This sand and gravel layer should be a minimum of four (4) inches thick. We also recommend using a vapor barrier such as 6-mil. plastic membrane beneath the slab with minimum overlaps of 12 inches for sealing purposes. PERMANENT FOUNDATION AND RETAINING WALLS: Retaining walls backfilled on one side only should be designed to resist lateral earth pressures imposed by the soils retained by these structures. The following recommended design parameters are for walls less than twelve (12) feet in height which restrain level backfill: Parameter Active Earth Pressure* Passive Earth Pressure Coefficient of Friction Soil Unit Weight Where: Design Value 35 p.c.f. 350 p.c.f. 0.55 125 p.c.f. (1) p.c.f. is pounds per cubic foot (2) Active and passive earth pressures are computed using equivalent fluid densities. For restrained walls which cannot deflect at least 0.002 times the wall height, a uniform lateral pressure of one hundred (100 p.s.f. should be added to the active equivalent fluid pressure). The values given above are to be used for design of permanent foundation and retaining walls only. An appropriate safety factor should be applied when designing the walls. We recommend using a safety factor of at least 1.5 for overturning and sliding. • Pak Page five The above design values do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads will be placed above the walls. If these conditions exist, then those pressures should be added to the above lateral pressures. Also, if sloping backfill is desired behind the walls, then we will need to be given the wall dimensions and slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of the wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. Placement and compaction of retaining wall backfill should be accomplished with hand -operated equipment. Retaining Wall Backfill Backfill placed within eighteen (18) inches of any retaining or foundation walls should be free -draining structural fill containing no organics. This backfill should contain no more than five (5) percent silt or clay particles and have no particles greater than four (4) inches in diameter. The percentage of particles passing the No. 4 sieve should be between twenty-five (25) and seventy (70) percent. Due to their high silt content, if the native soils are used as backfill, a drainage composite, such as Mirafi and Enkadrain, should be placed against the retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. the purpose of these backfill requirements is to assure that the design criteria for the retaining wall as not exceeded because of a build-up of hydrostatic pressure behind the wall. The subsection entitled General Earthwork and Structural Fill contains recommendations regarding placement and compaction of structural fill behind retaining and foundation walls. EXCAVATION AND SLOPES: In no case should excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts up to a height of four (4) feet deep in unsaturated soils may be vertical. For temporary cuts having a height greater than four (4) feet, the cut should have an inclination no steeper than 1:1 (Horizontal: Vertical) from the top of the slope to the bottom of the excavation. Under specific recommendations by the geotechnical engineer, excavation cuts may be modified for site conditions. All permanent cuts into native soils should be inclined no steeper than 2:1 (H:V). Fill slopes should not exceed 1:1 (H:V). It is important to note that sands do cave suddenly, and without warning. The contractors should be made aware of this potential hazard. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an Pak Page six appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. DRAINAGE CONSIDERATIONS: Footing drains are recommended at the base of all footings and retaining walls. These drains should be surrounded by at least six (6) inches of one -inch -minus washed rock wrapped in non -woven geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At the highest point, the perforated pipe invert should be at least as low as the bottom of the footing and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. Groundwater was observed in the test pits during the field work. Seepage into the planned excavation is possible, and likely if excavation occurs during winter months, and if encountered should be drained away from the site by use of drainage ditches, perforated pipe, French drains, or by pumping from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Any exposed slopes to be covered with plastic to minimize erosion. Final site grading in areas adjacent to buildings should be sloped at least two (2) percent away from the building, except where the area adjacent to the building is paved. GENERAL EARTHWORK AND STRUCTURAL FILL: The proposed building and pavement areas should be stripped and cleared of all surface vegetation, all organic matter, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill. NOTE: Specific clearing limits to be established at pre -construction meeting with City of Edmonds Building Department. Structural fill is defined as any fill placed under the building, behind permanent retaining or foundation walls, or in other areas where the underlying soils needs to support loads. This engineer should observe site conditions during and after excavation prior to placement of any structural fill. All structural fill should be placed in horizontal lifts with a moisture content at or near the optimum moisture content. The optimum moisture content is that moisture content which results in the greatest compacted dry density. The moisture content of fill soils is very important and must be closely controlled during the filling and compaction process. Pak Page seven The allowable thickness of the fill lift will depend on the material type, compaction equipment, and the number of passes made to compact the lift. In no case should the lifts exceed twelve (12) inches in loose thickness. The following table presents recommended relative compaction for structural fill: Location of Fill Placement Beneath footings, slabs or walkways Behind retaining walls Beneath pavements Minimum Relative Compaction 95% 90% 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum relative compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D-1557-78 (Modified Proctor). Use of On -Site Soils If grading activities take place during wet weather, or when the silty, on -site soils are wet, site preparation costs may be higher because of delays due to rains and the potential need to import granular fill. The on -site soils are generally silty and thus are moisture sensitive. Grading operations will be difficult when the moisture content of these soils exceeds the optimum moisture content. Moisture sensitive soils will also be susceptible to excessive softening and "pumping" from construction equipment traffic when the moisture content is greater than the optimum moisture content. Ideally, structural fill which is to be placed in wet weather should consist of a granular soil having no more than five (5) percent silt or clay particles. The percentage of particles passing the No. 200 sieve should be measured from that portion of the soil passing the three -quarter -inch sieve. The use of "some" on -site soils for fill material may be acceptable if the upper organic materials is segregated and moisture contents are monitored by engineering inspection. DRAINAGE CONTROLS: Existing Lot No. 6 runoff is directed into the existing storm water system in 73rd Place West. This engineer understands that the City of Edmonds has approved of the existing storm water system. Discussions with existing neighbors have revealed no Pak Page eight evidence of any malfunctions of the existing storm water system. Proper construction of the Pak residence along with the recommended east property line intercept trench will provide good drainage controls for Lot No. 6. Compliance with standard storm water detention methods in accordance with the City of Edmonds requirements are geotechnically acceptable. �«Z0II VAR All foundation concrete (footings, stem walls, slabs, any retaining walls, etc.) shall have a minimum cement content of 5-1/2 sacks per cubic yard of concrete mix. INSPECTION: The recommendations of this report are only valid when key geotechnical aspects are inspected by this engineer during construction: • Soil cuts • Foundation subgrade verification • Retaining wall, or rockery placement • Any fill placement • Eastern property line intercept drainage ditch with appropriate tight -line "wrap around" release • Subsurface drainage installation SUMMARY: The proposed Mr. Chun H. Pak single family residence on Lot No. 6, Lorian Woods, Edmonds is geotechnically viable when constructed in accordance with the recommendations herein, compliance with City of Edmonds approved plans and requirements, and key geotechnical inspection during construction. STATEMENT OF MINIMAL RISK: The plans and specifications for the Mr. Chun H. Pak residence at Lot 6 of Lorian Woods, as designed by Phil King, Designer, have been reviewed by this engineer and conform to the recommendations of the analysis and report and, provided that those conditions and recommendations are satisfied during the construction and use, and inspected and verified by this engineer, the area disturbed by construction will be stabilized and remain stable and will not increase the potential for soil movement, and the risk of damage to the proposed development and from the development to adjacent properties from soil instability will be minimal. Pak Page nine CLOSURE: The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering principles and practice. No other warranty, either express or implied, is made. The conclusions are based on the results of the field exploration and interpolation of subsurface conditions between explored locations. If conditions are encountered during construction that appear to be different than those described in this report, this engineer should be notified to observe the situation and review and verify or modify the recommendations. If there are any questions, do not hesitate to call. M6, aA,,- �- 1/ I Dennis M. Bruce, P.E. Geotechnical / Civil Engineer RIM • 40 U*J O CQ A ON I T'E" Property"Addr ✓70 --E#dfiqs,Washingto'n Legal Description:. • Assessor's Parcel Nuh1b4-1---- I .-i---,e 12� 1 3�21 p.0001 000 1 Recorded , ded 50 Snohomish 01/25 9 9 C, unty I have read the requireffiefit0-fdr4ccespry dwelling units contained in Chapter 20.21 of I ) the Edmonds Community `evPl0,6mb,n�'-Cod0&nd understand that an accessory dwelling unit, including a second kitchim,'.is ited for two years after occupancy by the current owner (unless a waiVqr is gnomphy-Ae Community Services Department) and until after a conditional use permit has be6h approved by the City of Edmonds Hearing Examiner. I also understand that approval of a conditional use.per'mit is subject to a public ,. hearing, and neither this statement nor thelssuadce*,or a ibuilding permit shall act to limit the discretion or the City in the review 9f any.dppljc;ation for a conditional use permit. e-7 Property Owner Signature. I Y- I- X-I 4W, C'17 P"q Date: cz . . ....... .. .. ............. STATE OF WASHINGTON COUNTY OF SNOHOMISH) I certify that I know or have satisfactory evidence that signed this instrument and acknowledge it to be _bisAwffree and vokintary act for the uses and purposes mentioned in this instrument. Notary's pressor n%s died. Dated- JAt, ,ss so I re of -.: :0,NOTAI? t blic: S PUBLIC C�� - cdc gat. ppointment it THIS DOCUMENT MUST BE RECORDED WITH THE SNOHOMISH COUNT-K.AiWF1b1(.- 1 . f s' I RETURN ADDRESS: City of Edmonds, City Clerk 121 5th Avenue North Edmonds, WA 98020 Reference #: CONFORMED COPY 200006050422 06/05/2000 01:16 PM Snohomish P.0007 RECORDED County COVENANT OF NOTIFICATION AND INDEMNIFICATION/HOLD AARMI ESS Grantor(s): (1)('':/ti r4 H (2) Z/ r-Ax, J .T k' Additional on pg. Grantee(s): City of Edmonds Legal Description (abbreviated): 'Sec___,:�_Twn .c2 Rng__Z4_Qtr OR Lot 4� Block 000. Plat 000 Assessor's Tax Parcel EIV(s): (1)7 90 �L—d00 —Doi—OODti (2) _assessor's Tax Parcel EN not yet assigned CITY OF EDMONDS APPROVED FOR RECORDING BY: _ DATE., ---T__ GE OF Under the review procedures established pursuant to the State Building Code, incorporating amendments promulgated by the City of Edmonds, and as a prerequisite to the issuance of a building permit for the construction of a residential structure and attendant facilities, the undersigned OWNERS of property do hereby covenant, stipulate and promise as follows: W 1. Description of Subject Property E ED FOR RECORDING: DATE� OF This covenant of notification and indemnification/hold harmless relates to a tract of land at the street address of 1/10 , ,�'� `e , �✓ 2 �.9, 9�0 (insert street address), Edmonds Snohomish /County, Washington and legally described as: Lrs"7` L_o�/�?� 1r✓av�� S 12Pl— 2142, 111�I'lln(2_ 2. Notification and Covenant of Notification The above referenced site (hereinafter "subject site") lies within an area which has been identified by the.City of Edmonds as having a potential for earth subsidence or landslide hazard. The risks associated with development of the site have been evaluated by technical consultants and. engineers engaged by the applicant as a part of the process to obtain a building permit for the subject site. The results of the consultant's reports and evaluations of the risks associated with development are contained in building permit file numberQQCA_� (insert number) on file with the City of Edmonds Building Department. Conditions, limitations, or prohibitions on development may have been imposed in accordance with the recommendations of the consultants in the course of permit issuance. E PROVED FOR RECO ING:: DA. OGE ` OF The conditions, limitations, or prohibitions may require ongoing maintenance on the part of any owner or lessee or may require modifications to the structures and earth stabilization matters in order to address future or anticipated changes in soil or other site conditions. The statements and conditions proposed by the OWNERS' geotechnical engineer, geologist, architect and/or structural engineer are hereby incorporated by reference from the contents of the file as fully as if herein set forth. Any future purchaser, lessee, lender or any other person acquiring or seeking to acquire an interest in the property is put on notice of the existence of the content of the file and the City urges review of its contents. The file may be reviewed during normal business hours or copies obtained at the Building Department, City of Edmonds, 121 5th Avenue North, Edmonds, Washington 98020. 3. Indemnification and Hold Harmless. The undersigned OWNERS hereby waive any and all liability associated with development, stating that .they have fully informed themselves of all risks associated with development of the property and do therefore waive and relinquish any and all causes of action against the City of Edmonds, its officers, agents and employees arising from and out of such development. In addition, the OWNERS on behalf of themselves, their successors in interest, heirs and assignees, do hereby promise to indemnify and hold harmless the City of Edmonds, its officers, agents and employees from any loss, claim, liability or damage of any kind or nature to persons or property either on or off the site resulting from or out of earth subsidence or landslide hazard, arising from or out of the issuance of. any permit(s) authorizing development of the site, or occurring or APPROVED FOR RECORDING: BY;-� DA'TE;ST'Oc� PAGE OF (— arising out of any false, misleading, or inaccurate information provided by the OWNERS, their employees, or professional consultants in the course of issuance of the. building permit. 4. Insurance Requirement. In addition to any bonding which may be required during the course of development, the Community Services Director /has not (strike one) specifically required the maintenance of an insurance policy for public liability coverage in. the amount and for the time set forth below in order to provide for the financial responsibilities established through the indemnification and hold harmless agreement above: 5. Covenant to Touch and Concern the Land This covenant of notification and indemnification/hold harmless touches and concerns the subject tract and shall run with the land, binding, obligating and/or inuring to the benefit of future owners, heirs, successors and interests or any other person or entity acquiring an interest in property, as their interest may appear. This provision shall not be interpreted to require a mortgagor or lender to indemnify the City except to the extent of their loss nor to obligate such persons to maintain the insurance above required. APPRVED FOR RECO G: BY:_ DATE: l PAGE_ OF DONE this day of _ A-V Qus l ,19993, OWNER(S) By: By: B C4` STATE OF WASHINGTON ss:COUNTY OF ) I certify that I know or have satisfactory evidence that b 2 n 1'f,oAn QA r , signed this instrument and acknowledged it to b (hi er) -free and voluntary act for the purposes mentioned in this instrument. g yy O� J • <S DATED Fla :�°C%OTAR Va- c PUBLIC Op, L:\TEMPRBUILDINGIMEADO W\COVENANT J 199L. NOTARY k'TPAC My commission expires: 0� APPROVED FOR RECONING: BY:�_ DATE:! l �iJ PAGE —(o— OF STATE OF WASHINGTON ) ss: COUNTY OF Int) I certify that I know or have satisfactory evidence that WE Clio") signed this instrument and acknowledged it to be (hi free and voluntary act for the purposes mentioned in this instrument. DATED tn�w '',199NOTARY PUBLIC My commission expires: ,-14-j L:ITEMPIBUILDINGIMEADOwkCOVENANT 0 W STATEMENT ON ACCESSORY DWELLING UNITS Property Address: Edmonds, Wash Legal Description: Lot 1#6 141110d , GLS ;:) fw 72/a f Assessor's Parcel Number:' 7 9 0 4Z --DOD -- DD 6 — o 0,0 I have read the requirements for accessory dwelling units contained in Chapter 20.21 of the Edmonds Community Development Code and understand that an accessory dwelling unit, including a second kitchen, is prohibited for two years after occupancy by the current owner (unless a waiver is granted by the Community Services Department) and until after a conditional use permit has been approved by the City of Edmonds Hearing Examiner. I also understand that approval of a conditional use permit is subject to a public hearing, and neither this statement nor the issuance of a building permit shall act to limit the discretion of the City in the review of any application for a conditional use permit. ..) - / Property Owner Signature: Date: /- STATE OF WASHINGTON• ) COUNTY OF SNOHOMISH ) I certify that I know or have satisfactory evidence that (hun i l on PA0, '- 0 ► ci)o n p4 t- signed this instrument and acknowledge it to be Wslfier free and voluntary act for the uses and purposes mentioned in this instrument. Notary . us� be smudged. Dated: "" F+ �p Signature of L1h66,k w ►''? :A,OTARk�-.2 Notary Public: 'CIO - : '* ct� PUBLIC , �q zoPN Residing at: _ ��'�'�%/L �6,5)l q. e: . My Appointment E L� THIS DOCUMENT MUST BE RECORDED WITH TnE? SNOHOMISH COUNTY AUDITOR. SNAP" -'A. -GRAM FROM: 'olfd- DATE: ATTENTION 0 F: CIlU /V /b �o � - �3 ?� �� • lam. __My _G�-uze.rL �, -� . i }k Snap ' ,73 t* replanting witn the trait trees you aesire. I have included Tree Hazard Evaluation Forms for each tree for your review. We are dedicated to the safety, health and aesthetics of trees. If I can be of further assistance, please contact my office at 425-793-4408. Sinc rely, G� Duane M. Anderson Certified Arborist C x r, U DA/sd �. `� 5 tL �,a �`-t°�^w��tirt.:�- '� i_' _ ;.Il )•_._t Y; {Pl;�i•��Itt�'1, n ee a Lanuscape apeotansm mc. • Duane 'Andy" Anderson BBB Certified Arborist cape Specialists Inc. BBB Wash Contractors License #BLUER1, S98105 "Delivering 1st Class Service" VEMBU 1 Issaquah Rd. • Renton, WA 98059 Complete Residential & Commercial Services (877) 643-3328 (425) 226-3858 Fax Cell: (206) 423-0065 f� R)�- �O roll Free: (877) 643-3328 Fax: (425) 226-3853 email: BlueRibbonTL 3lueRibbonTL@yahoo.com %+ @yahoo.com February 2, 2004 - Mr. Chun. H. Pak 16109 73`a Place West Edmonds, WA 98026 Re: Hazardous Tree Evaluation Dear Mr. Pak: I have reviewed the two alder trees located behind your home and given the nature of alder trees in that area, a prudent course of action appears obvious. The trees in question have been previously topped and will not be as healthy as they might otherwise have been. Also, due to the nature of native alder trees, they grow very quickly and have relatively short life spans. These particular trees also lean toward your home and the lean will continue to increase given time. (Please note the trees in the nearby lot for an example of the lean increase). These two trees may not be an immediate hazard to your home, but, in the not too distant future, they will definitely become hazards and additionally more difficult and costly to remove. You have indicated that you desire to plant medium sized fruit trees in that area. With that in mind and the nature of alders in the future, I would recommend removal of these two alders now, whereby decreasing the cost and alleviating future hazards and replanting with the fruit trees you desire. I have included Tree Hazard Evaluation Forms for each tree for your review. We are dedicated to the safety, health and aesthetics of trees. If I can be of further assistance, please contact my office at 425-793-4408. Sin rely, uane M. Anderson 4, Certified Arborist O ,��ll �� •r: ,!i cS7Q DA/sd � a ctv� `��, c;-, U"t 1W 1,11E HAZ4.9D EVAL iW10fFdWJW-- SiWAMMM; 7? HAZAIMIUMM: MaWLOcatjon: Falum + + TaW Hazard of part RaO owner. public private tatknown pomidjai " Ong kwAam acdon needed Date: Neeft forglar inspecWn Date fit last inspection: I --- ---- Dead Cm TOE CHARACTEROM DIME r 4.ciie� -- I( sweat, ow # do koww — Form:: C generanysymmebic Cminor asymmetry M4;ioraqmMfftrY MU10111313mut O sfag'headed Crown class: 0 dominant 0 Co4orniflant '(:I Intermediate C1 SWPIOSSO —(L,71 -' Z Uwe crown ratio: Age Gk= 8-,'ry re- asluceil OftAh can C- Prual"MONT. OcrU"dnei--CSSSiV*d*MW WdqMS alecled tri m W us: rspecilyM 0WftM WhNic OMldrde CunuSssal Aft 0 C pgM special Val TREE IMALMH Faaam ealar- 0 normal [3d*nft EPkwwjul Y N ---- --- OGd*s FOWN d@Mftr . g" 0SWU 'Led stm Z: norm! ❑13 Small' Nwd dW PMft E3 0 iserlge poor IV;jOle6adQ - - - _0 UNWOMMIL JD Van% -- Was ids d develoPMOM 000MM 0 Pwr OWN 0~ vigor Cb= r ved" Z110-gr4e W 13 Poor bujor pesWdbeum SITE CONDITIONS inGus;Z; park E3 a . pan spasm 0 nawralnd bl 0 woodlamWomst Site Character. 'Efft'dence C) commercial Cf-al El shrub border C wireak UndSGSPG type:" C3 parkway C; raised fed C] container::] mound 0 law Iffflagom -j �--nona C3K"uM C:inadequate C-EXCUShm OtIvOk"Wed . " Ramat site ftwbam? Y I E3 construcliOn 0 soil disrJ(ballca D we ft don t O W dWAu = She dearinp % dripline Oft** 0% 26-M 50-75% 75-IM - ft W, fig SWL %ddpWo % dripita grade lowered:C3 kWlhT,* W soil proMmix C3 1 0 0OXN900111 advuft to" 13 rid!: 0 Ocav asp — fft: -- DINAMIC1101M OW 00W VWW head rites Di-d-9190u1-- E9k D- . 3— Tw-- tD,-WuW upo vlowifle 03bob" obdoww 02b*"MvW Dviii�w Iti prone • pmanigg wine dkeftc TARGET 0-01 E331nd" 1 C] utay rows use U0dW Tmv OpMM :;vWk OPMOStrian 10 E3 W 1- 11 111 F Can Togo! b8mma Y(4) Can osellemog"a Y(O use c3fimentuse C accasionail use owipper v4- rMor Th Inte"tio" Socft im of AMoMn M1211M no sibilify for cGjMkWW" or alcomalandgims darimd train it UW forts t n�'a l': ;�B3�I�Ftly'7tlff 13 REAL ESTATE TAX OB DANTINI ST 4 LINES OF LEGAL DESCRIPTI RIAN WOODS BLK 000 D-00 LOT 6 I�[P�lt,EAp EDMONDS SCHOOL DISTRICT NO 15 2,819.46 Voter Approved %: STATE 1,950.09 Amount: CITY Of EDMONDS 1,878.01 Land: INS #501�� SNOHOMISHCOUNTY -CNT 836.99 SNOISLE REGIONAL LIBRARY 280.04 Improvements: Levy Code: STEVENS MEMORIAL HOSPITAL 217.57 Levy Rate: Gross Tax: - Exemption: + Spec Assessmnt: Total Tax: Total Tax: 7.982.15 PAK CHUN H 16109 73RD PL W EDMONDS, WA 98026-M '11111111111111111111111111111�11'/1111111111111/11111�111111 :EP THIS PORTION D r 0 13 ,, 19/d,, r- :a 3,392.73` 212,000 400,500 00217 13.0321 7,982.16 0.00 0.00 7,982.18 1•ur:, w,Auv TOTAL`: 3,991.08 3,991.00 BUTE RIBB ANN Tree & Landscape Specialists Inc. Duane'Andy' Anderson Certified Arborist Twash Cmtrad= License OBLUERTS981 U5 A "Delivering ist Class Service" ral Complete Residential & Commercial Services Cell: (206) 423-0065 l�K Toil Free: (877) 643-3328 Fax: (425) 228 3853 .mod email: BlueRibbonTLCyahoo.com .;; +,."+r:^.�^,•:. ,1 - t -� - r { �� 1� it f 11 i�i i +. f . II / H �:�t Ini'F: P Gtllka i A �t.6M •: 1 17 wt I , all .ena Op? ;; ;:: , ^ a� 2 ti C - 51107 sr ♦ .'�'w 4 , •_ ; 11170 ti w � 7 aft w ; 24.02 TRACT. L • w / O Of t.rrr ,ram y $ PRIVATE DRIVE w TRACT "A" COMM(W MtfA ' / rI 1071 r / 1�'�'r• t1A)« ss•w•» c TRACT '"A" ---- ;^ COMMON AREA 1 1 3 41aw«R C 5 i ' • • alas sr, , R 4ti• d 0 � �•% i err �g for D/ ,.' • 1 t r � •{r.� • . 1 r % •v 41, �a # 10 5 q• 0• es C • + +osr tr / t ff u' / SR s » s S3, w 1 •S .tr8 t owe, / !+ / w 4r! IL _a r v ' w i o 9 + aiissat�.. 4 '. i J w 9.00 N R . dyne J a 1b �: e Y 't g001�N It ats.... z s i4 b � a S /t. 14 r .. . �. �•� f q� Iry Inc.1$9� January.16, 2003 CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 r FAX (425) 771-0221 Website: www.oi.edmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Mr. Chung Pak 16109 73d Place West Edmonds, Washington 98026 RE: Localized slide Dear Mr. Pak: GARY HAAKENSON MAYOR In response to a localized slide, City officials conducted a site inspection on December 20, 2002 and observed a slope failure on private property to the east of your residence at 16109 73id Place West in Edmonds. Accompanying City officials were representatives of Landau Associates, a professional geotechnical consultant of the City. Landau Associates conducted a site reconnaissance and subsequently prepared a report (copy enclosed) that describes the observed slide. The report states that the loose/soft deposits associated with the landslide are present on private property in the landslide path and can easily move downhill particularly during wet weather conditions. Although the report also states that the existing landslide does not pose an imminent. risk to nearly residences or to the general public, property owners in the vicinity of the landslide should be alerted to the condition of the slope. The purpose of this letter and copy of the Landau. Associates report satisfies this notification. Further, as a potentially affected residence to further sliding you may want to consider hiring a State licensed'Geotechnical Engineer to prepare an independent assessment of the slope and to provide recommendations about the possible future impacts of landsliding. Sincerely, Jeannine L. Graf Building Official, C.B.O. •. Incorporated August 11, 1890 • Sister Citv - Hekinan. Japan ,.I January 9, 2003 City of Edmonds, Development Services Department 121 5'h Avenue North Edmonds, Washington 98020 RECEIVED Attn: Mr. Dave Gebert JAN 10 2003 RE: LANDSLIDE EVALUATION ENGINEERING DIVISION MEADOWDALE AREA — SOUTH LORIAN WOODS EDMONDS, WASHINGTON Dear Mr. Gebert: This letter summarizes our observations and recommendations related to a landslide that occurred on the steep slope; east of 73'd Place West, in the southeastern part of the Lorian Woods plat. At the request of the City of Edmonds (City), Deborah Ladd and Dennis Stettler of Landau Associates visited the site on December 20, 200'1-al6ng with City of Edmonds personnel Dave Gebert, Don Fiene, Anne Bullock, and Jim Kammerer. The purpose of our visit was to assess site conditions and identify any imminent hazard to City -owned facilities, the residents, and the general public. Out services were provided under Task Order No. 18 of our on -call Geotechnical Engineering Services Agreement with the City: BACKGROUND. AND OBSERVATIONS The landslide is located in the. southeast part of the Lorain Woods subdivision, on the slope above the residence at 16119 73'd Place West. The landslide crosses the City's interceptor drainage system "1B" and lies immediately south of catch basin CB #17 in this system. The approximate location of the landslide, along with a schematic showing the City's drainage system is shown on the attached site map, Figure 1. We understand that the landslide occurred sometime between December 13 and December 20, 2002 (between regular site visits by the City maintenance personnel). At the time of our visit, we accessed parts of the slide using paths originating on the north side of the residence at 16109 73'd Place West and the north and south sides of the residence at *16119 73'd Place West. The landslide occurred during a period of moderate rainfall (23 inches of precipitation was recorded at Sea-Tac Airport between December 13 and December 19, 2002 and a maximum 24-hr precipitation amount of 1.31 inches was ENVIRONMENTAL GEOTECHNICAL_ I NATURAL RESOURCES 130 2nd Avenue South • Edmonds, WA 98020 • (425) 778-M7 • fax (425) 778-6409 www.landauinc.com SEATTLE - SPOKANE • TACOMA PORTLAND • • recorded on December 14). Overall rainfall for the water year beginning in October 2002 has been considerably below normal. The landslide has mudflow characteristics, with an estimated width of about 15 ft and a total length of 40 ft or greater. The landslide initiated about 20 to 30 ft. (vertical distance) above the City's interceptor drainage system 1B and slightly south of CB #17 in this system. The landslide debris extended about 10 fl below (west) of CB #17. The estimated elevation of the top of the slide is at about 200 to 210 ft elevation, an elevation similar to approximate groundwater seepage elevations observed in a glacial sand unit within the bluff. The failed soil zone is estimated to be about 3 to 4 ft thick (measured perpendicular to the slope face). Below the landslide scarp (at the top of the slide), the landslide appears to involve the surficial layer of soil on the slope along with small to medium-sized trees and other surficial vegetation. The mudflow and vegetative material is currently resting on small benches near (above. and below) CB _#17. The landslide occurred on private property, did not extend to public facilities other than the City's interceptor drainage system, and did not impact any residences. Silty water; along with some fine sand and silt had flowed into small drainages in and near the backyard of the residence. at 16.119 73'd Place West. Soil conditions exposed near the top of the slide area appear to be glacial in origin and consist.of . outwash sand and gravel overlying fine-grained, silty and clayey deposits. These conditions are similar to soils exposed in other parts of the Meadowdale area at similar, elevations. The exposed soil after sliding was standing near vertical with a bench visible about 10 ft below the slide scarp. At the time of our visit, defined seepage paths had not yet developed and seepage was observed generally flowing over the mud accumulation at the base of the slide zone. Groundwater seepage was also observed from other locations on the hillside. At the time of our visit, no seepage was observed flowing into CB #17, although Mr. Kammerer (City Public Works) reported that seepage had previously flowed into CB #17 and Landau Associates' personnel observed a flow rate of about 1.5 gpm in January 2002 at that location. CAUSE OF SLIDING The bluff in the Meadowdale area is a_ known landslide hazard zone. The observedlandslide is consistent with other naturally -occurring landslides that occur along the Meadowdale bluff, typically during or following an intense rainfall event during the wet winter. season.. There was no evidence of construction or other human activities that would lead to landsliding. It is our opinion that the landslide originated in native granular soil above a seepage zone on the steep part of the upper slope. Although the specific cause of the observed landsliding is not known, seepage occurring near the contact between 01ID8/03 gEdrrnas%*pr0M74%109Meadowdale Slide - Dec 2002.doc 2 LANDAu ASSOCIATES • • granular sand and gravel deposits and underlying fine-grained deposits is a typical and. significant contributing factor to slope failures in the Puget Sound area. As discussed in Landau Associates' Drainage Evaluation Lorain Woods/Meadowdale Area report (July 25, 2002),, the City's interceptor drainage systems capture surface. water. that .would. otherwise . infiltrate into the large-scale Meadowdale Slide below the interceptor drainage system. The interceptor drainage systems do not reduce groundwater levels in the slopes above the systems. The observed landslide was likely caused by natural groundwater seepage an estimated .10 to 20 ft above the City's interceptor drainage system 1B and CB #17. Accordingly, it is our opinion that the observed landslide was not caused by or related to the City's interceptor drainage system. RISK TO CITY OF EDMONDS FACILITIES OR STRUCTURES The landslide may have damaged a small part of a City -owned interceptor drainage system. Specifically, based on the lack of observed flow into CB #17, the trench drain associated with CB #17 may have been clogged or damaged. We recommend that the City continue regular observations near CB #17 to determine and document the routing of seepage in this vicinity. The existing landslide does not appear to pose a risk to any other City -owned facilities. However, there is a large accumulation of soft soil above CB #17 that could move downhill, particularly if the soil in this area becomes saturated. Accordingly, City maintenance personnel shouldexercise care when working in this area. OTHER RECOMMENDATIONS Loose/soft soil deposits associated with the landslide are present on private property in the landslide path both above and below CB #17. These deposits of soil can easily move downhill, particularly during wet weather. Although the existing landslide does not pose an imminent risk to the nearby residences or to the general public, property owners in the vicinity of the landslide (particularly the residence at 16119 73rd Place West) should be alerted to the condition of the slope. The potentially affected residences should consider an independent assessment of the slope and the possible future impacts of landsliding. OLD8AD3 \EdffmSxwprW074U09Udeadowdale Slide . Dec 2002.doc 3 L ANDAu AssoclATEs This letter was prepared for the exclusive use of the City of Edmonds. Within the limitations of scope, schedule, and budget, our services have been conducted in accordance with generally accepted geotechnical engineering practice. No other warranty, express or implied, is made as. to the professional advice included in this report. We appreciate this opportunity to be of service to the City of. Edmonds. Please call if you have any questions or if we may be of further service. LANDAU ASSOCIATES, INC. Deborah Ladd, P.E. Senior Engineer Dennis R. Stettler, P.E. Principal DL/DRS/ccy No. 074109.011 Attachment: Figure 1, Site Map 01/08/03%%EdrrnasXwproe4741109Neadowdale Slide - Dec 2002.doc 4 LANDAU ASSodiATES Adlik if •,f � Il `�'___ '' %J�T/ .J 'i, ',' �;.. • lr I 1. .r.' i'//�� -- ♦ ♦- a: Z;:'r. 'DRAINAGE SYSTEM 1A, ; /' i •� Sri rl_ ••/•''•" fr 1, ,:/ r li / r I , , I• ',, ' •/ `; ;;;,..:: r • n� i I+ �� l :4,'1 at. 11;",,1,, IiI' ♦ 1j ' '1 , :t'i _ ,I �/' ,i{l, : .l,{((. I LORIAN• NZ WOODS . r r :j: ,f,iit: '•.(r• i, ♦ (--SEQUOIA_-- '� ;• �„%}s'1�, I/ �; n7�ii; l,'.:I , it , ��'� 'ii'' ,.I ' 11 - , / �: r,;�•;�f 1 I�• '}t' i`x'�, i., ,. •%iIl'i''i I'I I� pptg, �� -RIDGE_ /;= �.. j I I I , � i � - '� -.� j-!'I�''I• /' ' •i-rtill� II' (I�I) ii III � f 11. : -- — -`♦ �:' 11i1 1 ♦ �� II IIIIli TI ,I; r'� I " ; I , I►R��iI� II I{ IL. , ,,(},.. IIj 4 ; ' II/i �'I, '� ,•/ /_ r,t //;I, { !ii III II,. 1�11}► I, ,! 5 :,,:.�,I / • � tj / ` li• l ! �' .�� .� -1.. � tl•� I I,`�I+r�l/��I�I_ �C'�1 !/ ' .i�1j+7, 11 1-,_ ♦ (�P• �v_. Ili1ffill 1 III i ♦�' ,.1.4 �Ji' -� �.• ',f I• •,•% 11,1�'!` ` f '� \ ' ! %• Iil'tI III `I III III Ill t•l l" :I t +p ¢P)f .L .�!/'• !j � 5-r ,i}• , r`."),'�•rit, ��•�1� � ilii / DRAINAGE SYSTEM 11113 rt/ ;i �,''�� —`:', 'ir''�!'II 'I i I) ',{i',II�II}Illilll�lil Ililt{':I li,•?.• st _ ill. I►�� I IIII Ilil P. I L► II'l :r::: : \ I ' I� l Ih t'• A. Siij r! ! ..f /, t ! 1 •♦ `'r •!fr _r _i .II ';. 'S•.%�.i/-/ �.�:''_ �-• i•. '\/ f r i 1 ! CCY, `•` Adapted from: R.W. Beck 2000 ' 0 100 200 Drainage Evaluation +' Scale in Feet Lorian Woods/Meadowdale I Edmonds, Washington I _ I i (K 1nC.189v April 26, 2001 0 • CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771.0221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Phillip & Miriam Lehn Green Tara Incorporated 16202 72nd Avenue West Edmonds, Washington 98026 RE: Slope Stability Consultation Dear Mr. & Mrs. Lehr, GARY HAAKENSON MAYOR L, E In response to your Associated Earth Sciences report dated 3/15/01 regarding a landslide that occurred on or near property you own at 16202 72nd Avenue West; City consultants have investigated the noted slope failure and a copy of the Landau Associates report dated 4/19/0.1 is attached. After . reviewing this report and the information you previously supplied me, it is my determination as Building Official, that no further investigation or mandatory slope mitigation (including temporary or permanent slope protection) appear to be warranted at this time and therefore will not be imposed by me for any of the upslope or downslope properties. Meadowdale property owners have a general awareness of landslide hazards and risks associated with steep slope property. Property owners generally understand the landslide hazard risks inherent with private property in or near this area. It continues to be important for such properties to take measures to best manage such risks, including but not limited to, utilizing professional geotecluiical"expertise"-to- furtfiei`-investigate 'and' evaluate the landslide risks, monitoring slope movement, implementing. slope and/or drainage improvements, developing recommendations for site specific mitigating measures, etc. Should there be a change in the future conditions or any new information develops I would welcome the impute and will review the matter in light of any new information provided me. Thank you, 4%�49Z� Jeannine L. Graf Building Official Cc: Duane Bowman, Development Services Director Dave Gebert, City Engineer Carol Walker, Property Owner @ 16209 75'' Place West Mary Neering, Property Owner @ 16119 73nd Place. West Steven & Joan Johnson, Property Owners @16121 74`h Place West Chun Pak, Property Owner @ 16109 73rd Place West • Incorporated August 11, 1890 • Sister Citv - Hekinan. Japan Landau Associates Environmental and Geotechnical Services City of Edmonds Development Services Department 121 5 h Avenue N. Edmonds, WA 98020 Attn: Jeannine Graf Building Official RE: SLOPE STABILITY CONSULTATION 16202 72ND AVENUE WEST EDMONDS, WASHINGTON Dear Ms.. Graf. April 19, 2001 1!ect � APR ? �V�® 3 ?041 GryNop bFp, EDMpNp NT At your request, we conducted a limited review of slope stability and risk issues at 16202 72nd Avenue West (subject property) and several properties to the west of this property, including the Walker property and the southernmost property within the Lorian Woods subdivision. As part of our review, we visited the site on April 4, 2001 and looked at a letter to Phillip Lehn (owner of the subject property) prepared -by Associated Earth Sciences, Inc. (AESI), dated March 15, 2001, and a letter to the City of Edmonds prepared by AESI, dated March 16, 2001. We did not review the March 6, 2001 digital images referenced in the letter to Mr. Lehn or the results of a March 12, 2001 reconnaissance reportedly conducted by Adapt Engineering, as mentioned in AESI's March 15, 2001 letter. During our site visit, we observed the area of the February 13, 1998 landslide referenced in the AESI March 15, 2001 letter. We also reviewed letters prepared by Landau Associates in 1998 for the City -of- E on =pertaining to this landslide: The 1998'landslide area reinams largely overgrown. A near -vertical exposure of sandy soil is present near the headscarp area as present in 1998 and noted in the March 15, 2001 AESI letter. In addition, we noticed a zone of hard, gray, fractured, silt and clay exposed further downslope below the zone of exposed sandy soil. Large chunks of silt and clay (cobble to boulder size) have spalled off of this near -vertical soil exposure. This silt and clay exposure is evident from the property below, but is not visible from the subject property at the top of the slope. At the top of the west -facing slope near the west side of the subject property, we observed a small ground crack in sandy soil north of the 1998 landslide area. The crack appeared to be relatively recent (probably within the last several months). We suspect that the crack may have been more evident when observed by others in February, as it was partially obscured at the time of our visit (probably due to weather and rain influence on the sandy soil). The observed ground crack was within or adjacent to the top of the headscarp of the overall slope. This headscarp could have been associated with older 130 2nd AVENUE SOUT14 - EDMONDS, WA 98020 (425) 778-0907 - Fax: (425) 778-6409 - Toll Free: (800) 552-5957 - E-mail: info@landauinc.com Seattle (Edmonds) Tacoma Portland (Lake Oswego) Spokane movement at this location rather than recent movement associated with the small ground crack. Vegetation obscured the extent of ground cracking or movement, if any, on the property immediately to the north of the subject property. The 24- to 36-inch headscarp located to the south of the observed ground crack referenced in the AESI letter was not as obvious to us. We agree that similar topographical and geological factors that were involved with the 1998 landslide are likely present in the area of recently observed movement and ground cracking. In fact, similar conditions likely exist along most of this bluff extending to the north and south of this property, and not specifically just at the observed location. We agree that there is risk of future landsliding on this bluff. This risk existed before the observed ground cracking. In our opinion, the observed ground cracking occurring near the location of an existing landslide headscarp does not necessarily represent a new risk. The ground cracking is simply the current, visible evidence of a long-term slope risk that is present at this lc-.ation. We --would ,expect to see various indications of slope movement at `different locations along this slope over time. Because there is currently visible evidence of some movement at this particular location, that could imply that this location may be more likely to be involved in future slope movement than adjacent areas where no movement is currently evident. We concur that it is appropriate to share the information regarding recently observed slope conditions with the neighboring residents. By AESI copying the March 16, 2001 letter to a number of surrounding residents, this notification may have already occurred. We understand that the toe of the February 13, 1998 landslide came onto property owned by Mrs. Walker. It is not clear to us whether this property was included in the notification of nearby residents, but probably should be. Since the subject property and properties to the west are all within the City of Edmonds' "Meadowdale Earth Subsidence and Landslide Hazard Area" as defined in Ordinance #2661, we assume that all of the affected residents are fully aware of the.landslide risk inherent wi?th.the_,property_in.this-area: In -particular, property _that has been developed since the "Meadowdale Ordinance" has been in effect have all required specific geotechnical studies and the identification of landslide hazard and risk as a part of the permitting and development process for newer residences. We are aware that geotechnical studies associated with the development within the Lorian Woods subdivision at the toe of the subject slope have identified this slope as a landslide hazard. In our opinion, it is difficult to determine whether the ground crack present near the existing, oversteepened headscarp location would progress to result in only localized sloughing and slope movement at this location, or progress to a larger slope movement similar to the 1998 landslide. The recent notification of current conditions by AESI to the neighboring property owners and the general awareness of landslide hazards and risks that have been previously communicated to the property owners is important. Since the slope is located on private property, .it would appear that it is the responsibility of 04/19/01 S:\WPROC\074\092\16202-72nd-Itr.doc LANDAu AssoclATEs 2 • the individual property owners to understand the landslide risks inherent with property in this area and take measures to best manage these risks. Measures that could be taken by the property owners include, but are not limited to, monitoring slope movement, implementing slope and/or drainage improvements, and retaining a consultant to further investigate and evaluate the landslide risks and develop recommendations for site -specific mitigating measures that could be implemented. We appreciate this opportunity to be of service to the City of Edmonds. Please call us if you have any questions regarding this letter or if we may of further assistance. LANDAU ASSOCIATES, INC. . By: Dennis R. Stettler, P.E. Principal and � w Steven R. Wright, P.E. Senior Engineer DRS/SRW/jzs 04/19/01 SAWPROC\074\092\16202-72nd-Itr.doc LANDAu AssoclATEs 3 rh C. 1 gcjv • .ET FILE CITY OF E D M O N D S GARY HAAKENSON MAYOR 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Mr. Chun Pak March 23, 2001 3828 Northeast 110"' Street Seattle, Washington 98125 RE: Slope Investigation @ 16109 73rd Place West Dear Mr. Pak, Please be advised, it has been reported to me as Building .Official for the City of Edmonds that the recent earthquake triggered earth movement on or near property you own at 16109 73rd Place West, Edmonds. The City was provided a report prepared by Associated Earth Sciences, Inc., as retained by Mr. Phil Lehn, that states, "...the risk of landslide activity affecting the existing homes located at the toe of the slope is also considered to be extremely high." A copy of the report is enclosed for your information. The City does not endorse nor dispute the findings or conclusions made in the report, but under Uniform Building Code and statutory provisions, as Building Official; I=am obligated to investigate the matter. Therefore, pursuant to City Ordinance #2661 which regulates the Meadowdale Earth Subsidence Landslide .Hazard Area and Uniform Building Code Section 102 and 104.2.3; the City and it's consultants, -request permission to enter upon land you own at 16109 73rd Place West, to investigate the noted slope failure. Our inspection will not involve any intrusive action. Pending the result of this investigation the Building Official may be forced to require further investigation and slope mitigation to ascertain temporary and permanent slope protection and habitability of your residence. If you choose. to grant City Officials access to conduct this 'investigation please sign the following statement and return it to me as soon as possible. I Chun Pak, property owner at 16109 73rd PI W, hereby grant permission for City Officials and their agents and consultants to enter my property as described in this letter. Thank you, te / Chun ak Date Ch Building Official:, - Cc: Duane Bowman, Development Services Director Dave Gebert, _City Engineer APR 1 2 2001 • Incorporated August 11, 1890 • Sister City, . Hekinan, .Japan 1PC. 189v April 26, 2001 REET FILE (�/09' 73GAW CITY OF E D M O N D S GARY HAAKENSON 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771.0220 • FAX (425) 771-0221 MAYOR DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Phillip & Miriam Lehn Green Tara Incorporated 16202 72nd Avenue West Edmonds, Washington 98026 RE: Slope Stability Consultation Dear Mr.A Mrs. Lehi, In response to your Associated Earth Sciences report dated 3/15/01 regarding a landslide that occurred on or near property you own at 16202 72°d Avenue West; City consultants have investigated the noted slope failure and a copy of the Landau Associates report dated 4/19/0.1 is attached. After reviewing this report and the information you previously supplied me, it is my determination as Building Official, that no further investigation or mandatory slope mitigation (including temporary or permanent slope protection) appear to be warranted at this time and therefore will not be imposed by me for any of the upslope or downslope properties. Meadowdale property owners have a general awareness of landslide hazards and risks associated with steep slope property. Property owners generally understand the landslide hazard risks inherent with private property in or near this area. It continues to be important for such properties to take measures to best manage such risks, including but not limited to, utilizing professional geotecluiicalexpertise to further investigate and evaluate the landslide risks, monitoring. slope movement, implementing slope and/or drainage improvements, developing recommendations for site specific mitigating measures, etc. Should there be a change in the future conditions or any new information develops I would welcome the impute and will review the matter in light of any new information provided me. Thank you, 2 Jeannine L. Graf V Building Official Cc: Duane Bowman, Development Services Director Dave Gebert, City Engineer Carol Walker, Property Owner @ 16209 75'h Place West Mary Neering, Property Owner @ 16119 73°d Place West Steven & Joan Johnson, Property Owners @16121 70 Place West Chun Pak, Property Owner @ 16109 73rd Place West • Incorporated August.11, 1890 • Sister Citv - Hekinan. Japan • Landau Associates Environmental and Geotechnical Services 0 April 19, 2001 City of Edmonds Development Services Department ftc 121 5h Avenue N. AP Edmonds, WA 98020 R ?3 tpmf' oFp 1?001 Attn: Jeannine Graf EDMOTbENT Building Official �s RE: SLOPE STABILITY CONSULTATION 16202 72ND AVENUE WEST EDMONDS, WASHINGTON Dear Ms.. Graf: At your request, we conducted a limited review of slope stability and risk issues at 16202 72nd Avenue West (subject property) and several properties to the west of this property, including the Walker property and the southernmost property within the Lorian Woods subdivision. As part of our review, we visited the site on April 4, 2001 and looked at a letter to Phillip Lehn (owner of the subject property) prepared by Associated Earth Sciences, Inc. (AESI), dated March 15, 2001, and a letter to the City of Edmonds prepared by AESI, dated March 16, 2001. We did not review the March 6, 2001 digital images referenced in the letter to Mr. Lehn or the results of a March 12, 2001 reconnaissance reportedly conducted by Adapt Engineering, as mentioned in AESI's March 15, 2001 letter. During our site visit, we observed the area of the February 13, 1998 landslide referenced in the AESI March 15, 2001 letter. We also reviewed letters prepared by Landau Associates in 1998 for the City of Edmonds pertaining to $his landslide. The 1998 landslide area remains laigely overgrown. A near -vertical exposure of sandy soil is present near the headscarp area as present in 1998 and noted in the March 15, 2001 AESI letter. In addition, we noticed a zone of hard, gray, fractured, silt and clay exposed further downslope below the zone of exposed sandy soil. Large chunks of silt and clay (cobble to boulder size) have spalled off of this near -vertical soil exposure. This silt and clay exposure is evident from the property below, but is not visible from the subject property at the top of the slope. At the top of the west -facing slope near the west side of the subject property, we observed a small ground crack in sandy soil north of the 1998 landslide area. The crack appeared to be relatively recent (probably within the last several months). We suspect that the crack may have been more evident when observed by others in February, as it was partially obscured at the time of our visit (probably due to weather and rain influence on the sandy soil). The observed ground crack was within or adjacent to the top of the headscarp of the overall slope. This headscarp could have been associated with older 130 2nd AVENUE SOUTH - EDMONDS, WA 98020 (425) 77840907 - Fax: (425) 778-6409 - Toll Free: (800) 552-5957 - E-mail: info@landauinc.com Seattle (Edmonds) Tacoma Portland (Lake Oswego) Spokane movement at this location rather than recent movement associated with the small ground crack. Vegetation obscured the extent of ground cracking or movement, if any, on the property immediately to the north of the subject property. The 24= to 36-inch headscarp located to the south of the observed ground crack referenced in the AESI letter was not as obvious to us. We agree that similar topographical and geological factors that were involved with the 1998 landslide are likely present in the area of recently observed movement and ground cracking. In fact, similar conditions likely exist along most of this bluff extending to the north and south of this property, and not specifically just at the observed location. We agree that there is risk of future landsliding on this bluff. This risk existed before the observed ground cracking. In our opinion, the observed ground cracking occurring near the location of an existing landslide headscarp does not necessarily represent a new risk. The ground cracking is simply the current, visible evidence of a long-term slope risk that is present at this location. We would expect to see various- indications of slope movement at different locations along this slope over time. Because there is currently visible evidence of some movement at this particular location, that could imply that this location may be more likely to be involved in future slope movement than adjacent areas where no movement is currently evident. We concur that it is appropriate to share the information regarding recently observed slope conditions with the neighboring residents. By AESI copying the March 16, 2001 letter to a number of surrounding residents, this notification may have already occurred. We understand that the toe of the February 13, 1998 landslide came onto property owned by Mrs. Walker. It is not clear to us whether this property was included in the notification of nearby residents, but probably should be. Since the subject property and properties. to the west are all within the City of Edmonds' "Meadowdale Earth Subsidence and Landslide Hazard Area" as defined in Ordinance #2661, we assume that all of the affected residents_are_f illy aware.of the landslide -risk inherent with-ft-property in this.area. In particular, property that has been developed since the "Meadowdale Ordinance" has been in effect have all required specific geotechnical studies and the identification of landslide hazard and risk as a part of the permitting and development process for newer residences. We are aware that geotechnical studies associated with the development within the Lorian Woods subdivision at the toe of the subject slope have identified this slope as a landslide hazard. In our opinion, it is difficult to determine whether the ground crack present near the existing, oversteepened headscarp location would progress to result in only localized sloughing and slope movement at this location, or progress to a larger slope movement similar to the 1998 landslide. The recent notification of current conditions by AESI to the neighboring property owners and the general awareness of landslide hazards and risks that have been previously communicated to the property owners is important. Since the slope is located on private property, it would appear that it is the responsibility of 04/19/01 S:\WPROC\074\092\16202-72nd_Itr.doc t.ANDAu ASSOCIATES 2 I the individual property owners to understand the landslide risks inherent with property in this area and take measures to best manage these risks. Measures that could be taken by the property owners include, but are not limited to, monitoring slope movement, implementing slope and/or drainage improvements, and retaining a consultant to further investigate and evaluate the landslide risks and develop recommendations for site -specific mitigating measures that could be implemented. We appreciate this opportunity to be of service to the City of Edmonds. Please call us if you have any questions regarding this letter or if we may of further assistance. DRS/SRW/jzs 04/19/01 SAWPROC\074\092\16202-72nd 1tr.doc LANDAU ASSOCIATES, INC. By: Dennis R. Stettler, P.E. Principal and E; � 0 Steven R. Wright, P.E. Senior Engineer LANDAU AssociATEs 3. Associated Earth Sciences, Inc. March 15, 2001 AESI Project No. BE01022A Green Terra, Inc. 16202 72nd Avenue West Edmonds, Washington 98026 Attention: Mr. Phillip Lehn Subject: Limited Slope Reconnaissance 16202 72nd Avenue West Edmonds, Washington Dear Mr. Lehn: WA tp BUI!ltiNC '-'E"AhrMENT GsY OF EUMC)NDS At your request, we are providing the following summary of a limited slope reconnaissance of your property at 16202 72nd Avenue West in Edmonds, Washington. Our slope reconnaissance was performed_ on February 13, 2001. The subject property consisted of 'approximately 1.56 acres of developed residential property bordered by a steeply sloping hillside. to the west. The existing Lehn residence is located in the northem .portion of the site. The steep hillside sloped down, toward the west, at an average slope inclination on the order of IRIV (Horizontal:Vertical). Total vertical relief of the slope was approximately 120 feet. A surf cial' landslide, which involved- the entire height of the slope, was reported to have occurred on February 13, 1998. The slide occurred below the southwest corner of the subject property and consisted of rapidly moving mud. and debris.. The slide debris moved over* the entire height of the hill and caused damage to the private property below. 'Damage to the upslope property consisted of loss of a portion of the upper slope and damage to a former gazebo. During our slope reconnaissance, we noted that the majority of the slide debris had been overgrown with dense ground cover with the exception of the headscarp-area, which consisted of near vertical, bare sandy soils. _ During our reconnaissance, we also noted the presence of an approximately 40-foot-long; 24- to 36-inch headscarp below the northwestern corner of the subject property. This headscarp was approximately 70 feet north of the 1998 landslide area. The crack was visible on the subject property (Lehn property) through landscaped areas west of an existing rockery. The scarp was . Corporate Office • 911 Fifth Avenue, Suite 100 • Kirkland, WA 98033 • Phone 425 827-7701 • Fax 425 827-5424 West Sound Office • 179 Madrone Lane North • Bainbridge Island, WA 98110 • Phone 206 780-9370 • Fax 206 780-9438 Phillip Lehn AESI Project No March 15, 2001 Page 2 BE01022A inferred 'to' continue onto the neighboring property .to the north but was obscured by heavy ground cover. The scarp appeared to be the result of recent earth movement on the slope. Following our site visit, we also reviewed a total of seven digital images recorded by Mr. Lehn on March 6, 2001. These images illustrate conditions at the site shortly after the February 28, 2001, magnitude 6.8 earthquake experienced by the Puget Sound region. The pre-existing scarp appeared to have lengthened to the south by approximately 10 feet and has increased - to approximately 48 inches. The scarp, previously located west of and outside the footprint of the existing rockery on the Lehn property; has extended approximately 7 .feet.uphill and to the cast, and is now within the rockery footprint. Displacement of the rockery has occurred west of the new scarp location. The earth movement activity, as evidenced by the February 1998- landside, the pre-existing scarp observed during our February 2001 reconnaissance, and apparent reactivation.of the pre-existing scarp during the February 28, 2001 earthquake represents an extremely high risk of imminent landsliding in this area. Based on the topographic and inferred geologic conditions at the site, the same topographical, geological and hydrogeological factors, which precipitated the 1998 landslide, are likely present in the area of the currently observed movement. Therefore, the risk of landslide activity affecting the existing homes located at the toe of the slope is also considered to be extremely high, Future significant earth movement will have additional adverse impact to your property. Since a significant increase in rainfall could reinitiate the earth movement at any time, we recommend this area be closely monitored for signs of recurring movement. We further recommend that the downslope residents be notified immediately of the high risk of landslide activity on the slope. Further study and mitigation for the area to reduce the risk of future landslide activity should be performed immediately. We recommend that this .information be shared with the downslope -residents. �It is- our understanding that the geotechnical consultant (Adapt Engineering), representing one of the downslope residents performed a post -earthquake reconnaissance of the site on March 12, 2001. Information gathered during this field visit and any other previous field visits made by Adapt Engineering, or -any other consultant, should be evaluated immediately to help determine the appropriate course of action to reduce the landslide hazard to your property and the downslope residents. . ' .., • / • Phillip Lehn . AESI Project No. BE01022A March 15, 2001 Page 3 If you have any questions or require any additional information, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. West Sound Office oFWEWA T�'� 8802� �}- . �Sf�NALFIIG� . EXPIRES 6/22,0 Robert F. Cousins, P.G. John L. Peterson, P.E. Project Geologist Senior Geotechnical Engineer cc: Stephan Fjelstad, Law Offices of Karen A. Willie W:\GEOTECH\Lehn Property BE01022\BE01022A Lehn Crack Laetter.doc Dennis M. Bruce. P:..€ M.S.C.E, M.B.A. Geotechnical /Civil Engineer RECEIVED September 8, 2000 . SEP 14 2000 DEVELOPMENT SERVICES CTR. CITY OF EDMONDS City of Edmonds Building Department 121 Fifth Avenue North Edmonds, Washington 98020 Subject: Final Report - Geotechnical Inspections Pak Residence 16109 - 73rd Place West, Edmonds Permit No. 98-266 This engineering report presents a summary of all geotechnical inspections with regard to the Pak new single family residence at 16109 - 73rd Place West, Edmonds, Washington. l 11 _ 1 .. U • July 10, 2000 inspection report by D. Bruce, P.E.. • City of Edmonds approved plans • Numerous geotechnical reports, recommendations and evaluations • Construction photographs INSPECTIONS: As stated in the July 10, 2000 inspection report, this engineer has provided on - site inspections for the Pak project with regard to geotechnical and foundation aspects. Site grading, excavation, temporary eco-block wall, foundation bearing, footing recommendations, and concrete footing placement have been previously discussed and approved. Since July 10, 2000, this engineer has performed twice -weekly inspection observations of the project. Foundation stem walls were successfully placed. Backfill material meeting City of Edmonds standards, normal good practices, and this engineer's on -site recommendations were successfully placed. SOILS * FOUNDATIONS * SITE DEVELOPMENT * INSPECTION * DRAINAGE * DESIGN & PERMIT * LEGAL P.n. Box 55,%2 * Shoreline. Washinatnn 9815.5 * (2061 54&9217 * FAX (206)54"442 1 • • J ' Pak Property Page two The perimeter footing drains, as well as intercept drains, were successfully tightlined-connected in the northwest cornerof the Pak lot into a new catch basin. This catch basin subsequently released the storm water and seepage pressure flow into the existing storm water system in the overall Lorian Woods complex (see photographs). The rear (easterly) foundation stem wall was successfully placed. It is important to note that the temporary eco-block shoring worked successfully throughout the excavation and stem wall phase of this project. Temporary erosion control and sedimentation measures were successfully maintained throughout the project. Straw bales and siltation fencing were properly installed and maintained. Note: As previously stated in engineering reports, and as discussed in numerous meetings with City of Edmonds personnel, it is essential that the City of Edmonds maintain the proper clean out of the drainage system up slope and behind (easterly) of the Pak residence. On occasion, an inlet catch basin may become clogged with debris or excessive silt. It is very important that regular monitoring, observation, and clean out occur to maintain the current proper drainage intercept control and release that occurs on the slope behind and above the Pak residence. This engineer understands that the City of Edmonds is committed to proper maintenance of their drainage system. Based on this engineer's on -site inspections, recommendations from the numerous geotechnical reports, and experience with similar projects, the following are concluded and recommended: • All geotechnical aspects of the new Pak residence have been successfully completed. • Final landscaping measures have yet to be installed. It is essential that the City of Edmonds regularly inspect, monitor, clean out, and modify the rear (easterly) up slope drainage system behind the Pak residence. Pak Residence Page three If there are any questions, do not hesitate to call. F11- e u 0 0 ` Dennis M. ' Bruce, P.E. Geotechnical / Civil Engineer 4 J Dennis M. Bruce. EX M.S.C.E, M.B.A. Geotechnical /Civil Engineer -� T v E� July 10, 2000 .)UL 1 J 2000 DEVELOPMENT S;zRVICES C T R. CITY Jr" EDiJCNDS City of Edmonds Building Department 121 Fifth Avenue North Edmonds, Washington 98020 Subject: Geotechnical Inspections - Pak Residence 16109 - 73rd Place West, Edmonds No. 98-266 This engineering report presents a summary of geotechnical inspections to date with regard to the Pak new single family residence at 16109 - 73rd Place West, Edmonds, Washington. • City of Edmonds approved plans • Numerous geotechnical reports, recommendations and evaluations • Representative construction photographs by D. - Bruce, P.E. This engineer has provided daily on -site inspections of the Pak project with regard to geotechnical aspects. Project clearing and grading began May 23, 2000 (see photographs). The soil conditions were as anticipated by the geotechnical reports and this engineer's experience. The ecology block temporary shoring began on May 26, 2000. All blocks were well embedded per this engineer's recommendations. Block linkage, batter and drainage zone backfill were in accordance with this engineer's designs and normal, good practices. The ecology block wall was six (6) block high at the rear, and tapering on the north and south sides to "fit the site Subgrade ballast rock was imported to provide a better working surface for the trackhoe during site grading and excavation. The subsurface seepage pressures were contained by means of a perimeter french drain and directed north into the existing drainage channel. SOILS * FOUNDATIONS * SITE DEVELOPMENT * INSPECTION * DRAINAGE * DESIGN& PERMIT * LEGAL R0. Box 5.5.502 * Shoreline. Washinaton 98155 * (206) .W-9217 * FAX (206) .rA&A442 Re: Pak Residence, 16109 - 73rd Place West, Edmonds July 10, 2000 Page two This engineer made specific recommendations to widen out foundation footing form work to better allow for any variations in subgrade bearing. Subgrade bearing of 2,000 p.s.f. was verified. Contractor properly installed footing form work and reinforcing steel. The foundation footing concrete was placed on June 7, 2000 (see photographs). After footing cure, form work, reinforcing steel and stem wall concrete was placed to complete the foundation aspects of the Pak residence. Additional perimeter drainage pipes were placed (both north and south sides). A new catch basin was installed at the northwest corner of the Pak lot to "tie-in" to the existing drainage channel (per discussions and agreements with City of Edmonds drainage engineers). The lower level concrete slab was placed on July 5, 2000. Based on this engineer's on -site inspections, recommendations from the numerous geotechnical reports, and experience with similar projects, the following are concluded and recommended: • All geotechnical aspects of the new Pak residence have been successfully completed to date. • This engineer continues to provide on -site geotechnical inspections. If there are any questions, do not hesitate to call. EXPIRES 12/23/ 2= DMB:vb, lot Dennis M. Bruce, P.E. Geotechnical / Civil Engineer Landau Associates Environmental "and Geotechnical'Services. REC�►yEp Ms Lara Knaak' - , APR 00 . 1 0 ' of Edmonds'. � - CitY _ , Community Development Department' DEVELOPMENT SERVICES 121 'Sth Avenue North; 2nd Floor CITY OF EDMONDS CTF• Edmonds; WA 98020 - RE: GEOTECHNICAL RESPONSE TO RESUBMITTAL-OF CONSTRUCTION DOCUMENTS_ PROPOSED PAK.SINGLE FAMILY'RESIDENCE . ' LOT 6 LORIAN WOODS, DEVELOPMENT 16109.73TH A w PLACE EST , EDMONDS, WASHINGTON Dear Ms. Knaak: This, lette_r provides Landau au Associates response to. res ubmitted- documents for the proposed Pak single.family residence: The most,recent *set- of documents provided to us, (City of -Edmonds. packet date stamped 3/27/00), represents a relatively complete submittal, per, requirements of City of. Edmonds' (City) Ordinance 2661,' (although three of the documents should be updated to reflect design changes that have occurred over the asC ear and a half)., Previous Landau' Associates review letters are' dafed October 9 P Y � _ _ , 19.98,:May 28,, 1999 and December 9, 1999: Our 9- 1999'letter lists then -current issues 'that needed attention and/or.clarificafion. -•~ This current review .of resubmitted documents indicates • that most ' of .those, issues have n , w.' n " o ' bee addressed,' although ..there :ace still several thaf ;are 'of : some. concern to us._ However, rather than go through additional reviews, we. recommend- that these issues be addressed through special inspections-. ,and/or conditions ,attached to the building permit. The issues of concern. and recommended ,special scu sed i neaterinsPections/conditions are-didetail below: 1. Updating of Documents:. - The; August 17, 41998 En ineer,'s'Decldration and LEAD PROFESSIONAL -STATEMENT b Nick Lehtineri, P.E. are now. -outdated and should be reissued to reflect the current` desi n an . g designation of lead design professional. ,The July"16;1998 Environmental Checklisf submitted. by:' ;the applicant contains inaccurate information and should' also be 'updated.. It is .unknown if the Phil King STATEMENT that accompanied the submittal , is current,': as it is undated. We. understand the City is addressing issues with these documents. ' 2 • w - F TA MA. A 4_4-18_3 ' WAPATO CREEK PLACE 4..10 - ..OTH STREET E. -'SUITE CO 98 . (253) 926-2493 Fax: (253) 9_6-_531 E-mail: infoOlandauinc.com. I • Edmonds - Portland: S okane Tacoma ma - 2. Temporary Excavations: In previous review fetters we expressed;concern regarding support of'temporary excavations, mainly due to the presence of poor quality soil and possible groundwater' inflow that could destabilize , steep slopes. ,For. example,• to accomplish the ^excavation for the dwelling's, basement level it appears that. a steep cut, (greater than'. 45 degrees' and, up 'to, about 18 -ft in height); will. be necessary to maintain. the excavation, within:, the property lines.- The ,geotechnical engineer= for - the project. has maintained in-sev era)"letters to the City. stacked, blocks will be ade uate to.support ort this - Y - ecology . q- PP excavation, but to date,no temporary shoring plan has been provided. -We understand that the area ,outside ,of ,the property -.lines, is "common: space", but,,we- are :unaware if slope easementswill.be needed.if the excavation -extends, beyond the parcel,limits., Also, the plans show a`Cit storm drain about 5. to 6 feet. u sloe east 'of the r w , ( ) property line that ould'be , P Y upslope P Pe Y = threatened: -if the excavation slopemoves. The potential .for offsite excavation,- the City's storm drain`; "and .'the threat to workers at the top/toe of the'ezcavation are of'concern to us: _ We 'recommend - the City address these' issues.. by -,',attaching ' the; following• . special- inspections/conditions to the building permit. , a Re uire monitoring f' h '• -o t e City stormdrain,s stem throughout construction of the. '• ) q � Y Y.. - . g home. b •Re uire,field visits and a submittal b 'the ggeotechnical en •neer.durin ' immediate) q Y ft th v a er a exca ation is c m le w o to e...before form ork.s erected creatin a c nfined ' P g g o space).', If ten, 'or sfiorin is required, the 'submittal to ahe City, should p az'Y g q � Y. o d be in'the form of, an engineered design; properly signed -and sealed.: If `the geotechnical ' en ineer'believes that an open cut will remain stable the submittal to the Cite should g P . . Y be in the form of:a signed and sealed letter "stating',this -opinion,'. and summarizin an ; . P g Y requirements for slope monitoring by the contractor. 3. Permanent Support East Slope: - p , P P The•Land Clearing and Tree,Cutting Plan in.the current submittal, shows'a'4-to 8 ft'high permanent. concrete retainingwall alon the g. east property line. The, civil: drawings show a rockery of similar height . at this location.' We understand that a -rockery is planned. We also understand the City issues separateY. building permits for rockeries within -the Meadowdale area. Details concerning the City storm drain line and specifics concerning the rockery.are not,contained in the submittal. Accordingly, it is" not. possible.'to'.accurately, assess the potential threat to"the storm drain :. line. from the excavation/rockery.. -Therefore, we'recommend' the building permit for this rockery contain ; a special inspection provision,'such as: -'a) Construction of the east rockery shall bebased on'field conditions observed -by, the geotechnical engineer.and shall be. of adequate, size and shape, -and contain sufficient reinforcement;, to insure, that the'City's storm drain line immediately. to .the.east is pof threatened. The rockery and, -any. necessary:reinforcement/special backfill/drainage,shall be constructed on the ..subject site:' 0"7/00 I:XPROJECT1074%079 1,O\pakresubmitvw_ttr doc LANDAU. ASsocIATES 2 - 01 4: Drainage: The.Drainage,Plan; Sheet D-1, is incomplete with respect to showing footing And, rockery drains, and• any'house underdrains'or yaid.drains-that, may be required.: It is also not clear that adequate slope is available to remove water -from the-'footing/under-slab drainage systems. We, suggest the City, include, "as. a special condition of the permit; an inspection' requirementsuch:as: a)'. The geotechnical engineer shall inspect,each drain system.before-it is'covered to insure that it is constructed of•the proper materials, set at the correct depth, and has adequate slope. 5. Bearing Capacity: In our December 9,19991etier; we -pointed out an inconsistency -regarding the design 'soil; bearing ; pressure.and minimum footing size (Item 15). "The geotechnical engineer -recommends' 1,500 psf and the structural engineer designed the foundation using 'a bearing pressure- of 2;000 psf. Our review of the resubmitted documents indicates that, this item has not been addressed. , An "acceptable resolution to this item is' to. include,,verification..of the proper design bearing, pressure as a special inspection item for the geotechnical engineer: In addition to the above, we.recommend. th "City require -,the geotechnical engineer, perform - :special inspections, to verify. that slab/pavement subgrades and .zones of compacted ;backfilI have been - properly prepared/installed. ,For all special, inspections, or'• regular inspections, 'requested by' 'the , owned .contractor, the geotechnical engineer should submit to' the City a written field report summarizing the conditions observed, any, deficiencies,' and any recommendations thatinay have been made at the time ' of the site visit•to.correct observed deficiencies. 'The inspection reports should be'. provided -to the City within' 1 to 5-days of the visit, or sooner•'if serious deficiencies are noted: - Upon; completion of construction, the geotechnical engineer should submit a summary` report to the City verifying that the special inspections/conditions, were, completed' and 'that construction was in "accordance with the approved.construction document's:' Submittal of the summary -1"ett6i,should be one of the . permit . special 'conditions.'- All deviations from the approved construction 'documents. ,should be" - highlighted;in,the summary. letter. The letter should be signed and'sealed by the geotechnical engineer. . In summary, it is our opinion that the 'current submittal .meets the general 'requirements of Ordinance 2661, though some issues; still remain (as outlined above): The City could,allow the project -to move forward and' issue the building permit; subject to' special geotechnical inspections;and conditions, as noted above, or as'otherwise required by the City. ' In -addition, ,the applicant needs to secure a separate building permit for rockery construction, which should also contain the special inspections and, -conditions noted above: . 04/07/00 1:%PRQ1EC11074W79.101pakresubmkrvw_Rr.doc LANDAU Assoc ATEs 3 • CITY OF EDMONDS CITY HALL • THIRD FLOOR 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0247 • FAX (425) 771-0252 OFFICE OF THE MAYOR rn c 18°ty March 7, 2000 Mr. Dennis Bruce, P.E. P.O. Box 55502 Shoreline, WA 98155 Dear Mr. Bruce, I wish to update you on some of my findings since our meeting last week. GARY HAAKENSON MAYOR 1) You should have received a letter from Ms. Graf outlining her concerns on the six issues that we identified on the Landau review letter. 2) You should submit the complete application packet that John Gurnee said was ready. 3) I asked how Landau was chosen from the list of four to do the work on this project; I was told that Mr. Pak chose them from the list when he first applied. 4) My investigation of where the wrong topography map came from, led to it having been submitted by Phil King. 5) Landau's Meadowdale specialist was transferred from Edmonds to Tacoma and they decided to keep him on Edmonds cases because of his knowledge. I have been led to believe that he did not make a site visit, just as you suspected. This is inexcusable and I will notify Landau of that fact. 6) Because of the incorrect topographical information, we.,have extendedithe Paks perrfiif application, deadline.until June..18, 2000.17 7) The issue of who will pay the Landau fees is still unresolved. Clearly, Landau spent time working on the wrong information. Clearly, a site visit would have brought the problem to a head more quickly. I look for your guidance on resolution of this issue. I hope we are successful in getting your project back on schedule soon. Sincerely, Gary Haakenson Mayor GH\lbc C:\Mayor00\Bruce1tr.doc cc: Jeannine Graf, Building Official John Gurnee Mr. and Mrs. Pak • Incorporated August 11, 1890 • s I�c.18o�0 CITY OF EDMONDS • 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771.0220 • FAX (425) 771-6221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Mr. Dennis Bruce, P.E. March 3, 2000 Post Office Box 55502 Shoreline, Washington 98155 RE: Pak SFR @ 16109 73'd Place West, Plan Check #98-266 GARY HAAKENSON MAYOR The purpose of this letter is to outline the remaining outstanding geotechnical related issues that must be addressed in detail by the lead design professional, geotechnical engineer of record or other applicable design team professional for this project. The following items are a synopsis of the Landau Associates review letter dated 12/9/99 and are not new items. 1) Section 19.05.030.B.1 of Ordinance #2661 requires that geologic evaluations be performed by, or reviewed and approved by, a geologist. An evaluation of the risk of earth movement of the slope east of the proposed residence is required, including evaluation of the existing bluff condition and anticipated bluff erosion or movement. The geologic assessment must ,evaluate the potential for debris flows from the east slope and what, if any, protective measures are needed on the Pak property. If a debris containment or deflection wall is required based on this assessment, the geotechnical engineer of record must coordinate placement and design parameters (plans must be stamped by a State licensed engineer). 2) As previously stated in a letter from the City Engineer dated 12/30/99, the City has no plan to further upgrade the existing drainage system located to -the east of the Pak property. The 4/4/99 Bruce report anticipates a significant dewatering effort to allow construction of the foundation. The City anticipates no changes to the drainage system in the near future and plans to maintain the system as in the past. Therefore, the upslope drainage and surface and groundwater impacts to the Pak site must be addressed at this time by the geotechnical engineer of record. The drainage plan shall also consider the spring located north of the Pak parcel. The significance of the spring demonstrates that the property is within a groundwater discharge zone and that groundwater levels. will be near the surface on a year round basis. The drainage plan must include details for properly managing groundwater associated with this and other springs near the property as well as; the location and size of pipes, interceptor drain details, connection details, invert elevations, catch basin type and location, location of cleanouts, required foundation drains, etc. The report must also include maximum seasonal groundwater levels and determine whether permanent dewatering is required. Note, City Ordinance #2661 requires that the -drainage plan be prepared and stamped by a State licensed civil engineer. • Incorporated August 11, 1890 • 0!] _-- ^-- 1 I -�- - -'- T - - - Mr. Bruce Page Two March 3, 2000 3) The plot plan must clearly indicate all proposed retaining walls, rockeries, ecology block walls, etc. proposed for this project. The geotechnical engineer of record shall provide specific design parameters (lateral earth pressures, drainage, etc.) for such walls. The wall design must be stamped and signed by a State licensed engineer. 4) Resolve the discrepancy on the foundation design, footing size and sack mix. The structural engineered plans are based on 2000 psf. bearing capacity with 18 inch wide footings and 5 sack mix concrete. The 4/4/00 Bruce report cites 1500 psf bearing capacity, 24 inch wide footings and the 7/27/98 Bruce report calls out 5 %2 sack concrete mix. 5) Mr. Bruce's 4/5/99 landslide risk analysis appears linked to City improvements of the hillside drainage system that, is not proposed by the City. The City has repeatedly indicated that there are no plans to improve the existing system but will continue to inspect, monitor and provide maintenance when needed. Mr. Bruce must reassess the site risk based on the City's planned drainage related activities to the upslope drainage system, the findings of the geologic assessment of the bluff and adjacent east slope and the proposed drainage plan. 6) ' The 1989 Terra Associates report submitted for plat development was. not required to address Ordinance #2661 concerns with regard to -individual lot development. Although the Terra Associates report is certainly an information resource the findings are general in nature and are not a complete geologic evaluation of the east slope. It is my understanding that the Pak's believe they have a complete application submittal ready to be delivered to the City. If the submittal addresses the items outlined in this letter it is appropriate that the packet be submitted.at this time. Please contact Lara Knaak, Development Services Coordinator to schedule an appointment for submittal. If you have any questions please feel free to contact me at 425-771-0220. Thank you, �aJf �e�e. raf G Building Official Cc: Mayor Haakenson Mr. & Mrs. Pak John Guemee Construction Dennis M. Bruce, P.E. 0 FILE M.S.C.E., M.B.A. Geotechnical/Civil Engineer February 20, 2000 City of Edmonds c% Mr. Chun Pak 3828 N. E. 110th Street Seattle, Washington 98125 Attn: James C. Walker, P.E., City Engineer RECEIVED MAR 171000 DEVELOPMENT SERVICES CTR. CITY OF EDMONDS Subject: Chun Pak Lot . Lot 6, Lorlan Wood Development, Meadowdale Area 16109 - 73rd Place West, Edmonds, Washington This engineering report presents to summarize the geotechnical issues relating to Chun Pak's Lot No. 6 in the Lorian Woods Development. • June 6, 1989 report by Terra Associates, Inc., allowing development in Lorian Woods, subject to conditions • Proposed Mr. Chun Pak house plans by Mr. Phil King, Designer • July 27, 1998 geotechnical evaluation report by D. Bruce, P.E. for Mr. Pak • October 9, 1998 review report by Landau Associates, Wade Gilbert, P.E. • April 4, 1999 additional geotechnical information report by D. Bruce, P.E. • May 28, 1999 supplemental geotechnical review by Landau Associates, Inc., Edward Heavy, P.E. • June 9, 1999 additional soil test pit investigation, test pit logs, and photographs. • June 11, .1999 meeting with City of Edmonds, Mr. Pak, Landau Associates, designer and this engineer, to clarify issues • June 18, 1999 on -site photographs and investigation by City of Edmonds Drainage Department and Public Works Department regarding needed repairs and improvements to City of Edmonds drainage system directly behind and above Mr. Pak's lot. • December 22, 1999 letter to City of Edmonds expressing concerns regarding review process and lack of direction from City of Edmonds • December 30, 1999 correspondence from James C. Walker, P.E., discussing submittal standards, drainage issues, and seasonal restrictions on grading. SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 • (206) 546-9217 • FAX 546-8442 Pak, Lot 6, Lorian Wood Development February 20, 2000 Page two Numerous geotechnical reports and responses have been furnished the City of Edmonds beginning July 27, 1998. It is understood that the City of Edmonds does not do any review or evaluation in-house, and relies on their outside consultant, Landau Associates, for review. Numerous lengthy memorandum have been issued by Landau Associates over the past year and one-half. It is understood that no site evaluation or visit had occurred prior to December 3, 1999. The following numbers will refer to the latest memorandum (December 9, 1999) from Landau Associates: 1. Geologist Landau Associates recommends that an experienced geologist evaluate the slopes and landslide issues that may apply to Mr. Pak's Lot No. 6. A complete, thorough geologic evaluation has been performed and discussed in the Terra Associates, Inc., June 6, 1989 report. Engineering geologist, Mr. Charles R: Lie, P.E., (in addition to Anil Butail, P.E., and William Bailey, project manager) participated in the 1989 report. This engineer has thoroughly read, understands, and agrees with the landslide/ geologic discussion in the report. The conclusion of the Terra Associates, Inc., report is, " ... We believe the probability of landslide damage likely is less than five percent in twenty-five years ... See figure 5." 'As discussed in the 1989 Terra report, and as discussed in numerous geotechnical reports by D. Bruce, P.E., the drainage situation above and behind Mr. Pak's lot has improved and will lessen the probability of any hillside instabilities. The December 9, 1999 Landau report states, "In our opinion, this geologic assessment remains a high priority and should be completed prior to any future geotechnical review." The geologic assessment has been done. The potential for debris flow from the adjacent slopes are greatly reduced by the recent improved City of Edmonds drainage work and maintenance. This recent is of existing drains, as well as the installation of the additional catch basin drain (as recommended on -site by this engineer to City of Edmonds Drainage Engineer), further dries out the slope east of Mr. Pak's lot. Thus, this engineer declares that the potential for debris flow from the adjacent slope affecting Mr. Pak's house is not significant. • • Pak, Lot 6, Lorian Wood Development February 20, 2000 Page three 2. Up slope Drainage: As discussed in this engineer's October 7, 1999 report, additional maintenance and new catch basin was recommended for the City of Edmonds system behind Mr. Pak's lot. This engineer has inspected and observed the properly completed maintenance work and new catch basin. This work, as performed by the City of Edmonds, satisfies this engineer's concern regarding the functionality of the existing system. Excessive surface runoff no longer trickles onto Mr. Pak's lot. The Landau report "suggests that the City advise the applicant of its current position regarding this drain system, and of the need for the applicant to prepare a development plan which accommodates the expected range of operating conditions of the City's drainage system." Evidently, Landau is concerned that the City may not maintain its drainage system. This engineer has every confidence in the City. of Edmonds drainage maintenance department and believes that the City of Edmonds will perform proper maintenance. As declared, certified, and notarized, Mr. Pak acknowledges and understands the significance of proper drainage control. 3. Drain System: Landau raises concerns regarding the effectiveness of a shallow drain system to control conditions during construction. This engineer has significant experience in foundation engineering and approves of the proposed ten to twelve foot (10' - 12) maximum excavation. Qualified, experienced contractors understand the importance of proper temporary drainage during the excavation phase. These "construction issues" are not geologic in nature, and are the responsibility of the contractor and the on -site inspecting geotechnical engineer. Apparently there is concern for the "spring" just north of the Pak parcel. The presence of this seasonal drainage course is now noted in the environmental check list. 4. Topographic Map: Please refer to overall property developer, Robert A. Anderson, letters of June 24, 1999 and January 14, 2000 regarding the topographic map prepared by Group 4, Inc. The topographic map meets standards for site surveying and topography, including legal description. Evidently, this same topographic map has been reviewed by the City of Edmonds and approved for the existing homes within Lorian Woods. This engineer approves of the topographic map. 5. Soil Conditions/Footings: This engineer concurs that suitable soil conditions exist for the footings recommended for Mr. Pak's house. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page four 6. Seasonal Ground Water: As discussed in the October 7, 1999 report, the clogged. and insufficient City of Edmonds up slope drains created excessive runoff water into one of the soil test pits. Thus, the ground water level observed in the test pits represent a maximum. Proper construction techniques and temporary, as well as permanent, drainage measures will manage this ground water. 7. Temporary Shoring. As previously discussed, stacked ecology blocks may be required if actual excavations and soil conditions dictate. This engineer has designed and inspected numerous foundation excavations; and the stacked ecology block method has proven successful (numerous examples within the City of Edmonds jurisdiction are available). If it is unclear to Landau Associates how a two foot thick ecology block wall can be constructed one foot away from the property line, this engineer welcomes their observation during Mr. Pak's project. This engineer declares, "all temporary and permanent retaining structures can be accommodated within this space (private property of Mr. Pak), and still leave room for any required home -related features, especially those which may be required by code. 8. Clarification of Retaining Wall: See revised plans. 9. Drainage Issues: As previously discussed, the City of Edmonds improvements and maintenance to their existing drainage system satisfies this engineer's concerns as raised in the October 7, 1999 report. As also previously discussed, practical construction techniques will manage any ground water during the foundation construction phase. Finally, proper footing drains and waterproofing membrane (such as asphaltic emulsion, Volclay, etc.) will be applied. 10. Rockeries: Some small (less than five feet in total height) rockeries are envisioned for Mr. Pak's final grading. See revised plans by Phil King, designer. 11. Storm Water Management. See revised plans and civil storm water management designs by Nick Lehtinen. Additionally, the existing "Lorian Woods stream" allows for convenient and effective discharge release. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page five 12. Interceptor Drain: See revised plans. No east (up slope) French Drain is planned. 13. Foundation Drainage: See revised plans to clarify foundation drainage. 14. Supplemental Review: This engineer has thoroughly reviewed the revised plans and approves them for construction. 15. Conflict with Concrete Mix Design: See revised plans. Clarified: 16. Seasonal Construction: This engineer agrees with Landau Associates that "winter time construction could be allowed (provided the city waives the current restriction)." It is unsure who within the City of Edmonds actually evaluates the proposal and might issue this waiver. 17. Risk Analysis: In this engineer's opinion, the probability of earth movement on Lot No. 6 within a period of twenty-five (25) years, is less than ten percent (10%). Thus, according to City of Edmonds Ordinance No. 2661, the lot is suitable for residential use. The risk of damage to the Pak residence and to adjacent properties will be minimal, subject to the conditions set forth in this engineer's report and subject to this engineer's on -site inspections during the construction phase. Additional mitigation of potential landslide risk will occur due to the actual construction of the Pak residence, installation of proper footing drains which will improved subsurface drainage, and also due to the basement excavation, which will remove a weight of soil greater than the weight of the residence. The Pak residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be totally eliminated, and property owners knowing assume all residual risks. The geotechnical recommendations and declarations associated with the Pak project do not constitute a warranty, either expressed or implied, against loss or damage to persons or property. 18. Check List Items: All required check list items have been reviewed by this engineer, project designer, project contractor, and owner. We believe the submittal requirements have been satisfied, and are herewith submitted. • Geotechnical issues relating to the development of Lot No. 6 have been submitted throughout the past year and one-half. This engineer declares that the requirements of City Ordinance No. 2661 and Chapters 19.05 and 20.15 of E.C.D.C. have been met. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page six • It is hoped that the City of Edmonds technical person will review all submittals and allow Mr. Pak to construct his residence, as many of his future neighbors in Lorian Woods have done. If there are any questions, do not hesitate to call. EXPIRES 12/23/ DMB:vlb �000 Dennis M. Bruce, P.E. Geotechnical / Civil Engineer r (D co t o If fi /p,v '7 .co 971 -3 S.- -;s C6 ;d! / �� I 1, (' ii I ; �1 J �, , \� �;I , ll. !; Lidh n,l I'I�i' I i j (/� / �/'• / / ,.I /' II' I \\ 'i: X� CL 4:I'. it �u, Inll 1!1 I( o I' •II«�,h�, �\ \ \ �� ,1. ,11 ,1 1 1 1 ''1. ' 1 I � Ii IIvi, 17 it It r 1 I, , I II Ilrrll III I'..�,L. �I 1 IrJ _ ��: Tt w. ,'L,'�II Illl It ,I ,lend, I �' I r /, 4///, '.,,,''��Il ,;;li �/�/,;;l;;lll�il��lil�lli � %i�` �;�tT�.��f� �i��l�,�� I �. I�';;''; ;'//�'''; I: f'/r�'� if', II JI JII II I�/'I: / / / �1. •/>> .�u�. - � Ili;`.\ 1 .$ 7. —j ;Zml `Nb ,rl,�glli�,'l�',rlj///rr /9 I + 3 � C1 .4.V/.�/ 1.�., � / 1, fit? JI 41 111 10 1: lit I ao, It I I'l";J !,Jill 11 1 -CY r Of V 'MI 31vomQQv3v1l 'N LU Fro/ Sp Lu -j misit =1ai uj z 0 2 a� LOU z 0 EE 5 Z < Z 0 Co ROW < 5 -.,j CC 0 0 '.c e o LUx 0 Rui LL 0) 1 lhC. 189v 0 so CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771.0221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Mr. Dennis Bruce, P.E. March 3, 2000 Post Office Box 55502 Shoreline, Washington 98155 RE: Pak SFR @ 16109 73'd Place West, Plan Check #98-266 GARY HAAKENSON MAYOR The purpose of this letter is to outline the remaining outstanding geotechnical related issues that must be addressed in detail by the lead design professional, geotechnical engineer of record or other applicable design team professional for this project. The following items are a synopsis of the Landau Associates review letter dated 12/9/99 and are not new items. 1) Section 19.05.030.B.1 of Ordinance #2661 requires that geologic evaluations be performed by, or reviewed and approved by, a geologist. An evaluation of the risk of earth movement of the slope east of the proposed residence is required, including evaluation of the existing bluff condition and anticipated bluff erosion or movement. The geologic assessment must evaluate the potential for debris flows from the east slope and what, if any, protective measures are needed on the Pak property. If a debris containment or deflection wall is required based on this assessment, the geotechnical engineer of record must coordinate placement and design parameters (plans must be stamped by a State licensed engineer). 2) As previously stated in a letter from the City Engineer dated 12/30/99, the City has no plan to further upgrade the existing drainage system located to the east of the Pak property. The 4/4/99 Bruce report anticipates a significant dewatering effort to allow construction of the foundation. The City anticipates no changes to the drainage system in the near future and plans to maintain the system as in the past. Therefore, the upslope drainage and surface and groundwater impacts to the Pak site must be addressed at this time by the geotechnical engineer of record. The drainage plan shall also consider the spring located north of the Pak parcel. The significance of the spring demonstrates that the property is within a groundwater discharge zone and that groundwater levels will be near the surface on a year round basis. The drainage plan must include details for properly managing groundwater associated with this and other springs near the property as well as; the location and size of pipes, interceptor drain details, connection details, invert elevations, catch basin type and location, location of cleanouts, required foundation drains, etc. The report must also include maximum seasonal groundwater levels and determine whether permanent dewatering is required. Note, City Ordinance #2661 requires that the drainage plan be prepared and stamped by a State licensed civil engineer. Incorporated August 11, 1890 Sister City - Hekinan, Japan Mr. Bruce Page Two March 3, 2000 3) The plot plan must clearly indicate all proposed retaining walls, rockeries, ecology block walls, etc. proposed for this project. The geotechnical engineer of record shall provide specific design parameters (lateral earth pressures, drainage, etc.) for such walls. The wall design must be stamped and signed by a State licensed engineer. 4) Resolve the discrepancy on the foundation design, footing size and sack mix. The structural engineered plans are based on 2000 psf bearing capacity with 18 inch wide footings and 5 sack mix concrete. The 4/4/00 Bruce report cites 1500 psf bearing capacity, 24 inch wide footings and the 7/27/98 Bruce report calls out 5 %2 sack concrete mix. 5) Mr. Bruce's 4/5/99 landslide risk analysis appears linked to City improvements of the hillside drainage system that is not proposed by the City. The City has repeatedly indicated that there are no plans to improve the existing system but will continue to inspect, monitor and provide maintenance when needed. Mr. Bruce must reassess the site risk based on the City's planned drainage related activities to the upslope drainage system, the findings of the geologic assessment of the bluff and adjacent east slope and the proposed drainage plan. 6) The 1989 Terra Associates report submitted for plat development was not required to address Ordinance #2661 concerns with regard to individual lot development. Although the Terra Associates report is certainly an information resource the findings are general in nature and are not a complete geologic evaluation of the east slope. It is my understanding that the Pak's believe they have a complete application submittal ready to be delivered to the City. If the submittal addresses the items outlined in this letter it is appropriate that the packet be submitted at this time. Please contact Lara Knaak, Development Services Coordinator to schedule an appointment for submittal. If you have any questions please feel free to contact me at 425-771-0220. Thank you, oafeanrune L. Graf Building Official Cc: Mayor Haakenson Mr. & Mrs. Pak John Guernee Construction • • OBERT A. ANDERSON. M.D January 14, 2000 Mr. Chun Pak 3828 N.E. 110t` Seattle, WA 98125 Dear Mr. Pak: 614 Daniels Drive NE E. Wenatchee, WA 98802-4036 Tel/fax (509) 886-3708 E-mail nh[&MSN.com The Group 4 topographical survey of the Lorian Woods land, which was paid for by us as developers and incorporated into the Terra Associates final plan accepted by the city of Edmonds and its consultants for implementation in the Lorian Woods planned unit development, has been made available to you with our concurrence to facilitate the development and application for a building permit for your lot 6 of the development. Please accept this as our contribution to your plans and building project. Sncely yours, r obert A. Anderson, M.D. Lorian Woods Developer RECEIVED MAR 2 7 DEVELOPMENT CTR. EDMONDS THFET FILE A, 1 ROBERT A. ANDERSON. M.D. 614 Daniels Drive NE E. Wenatchee, WA 98802-4036 Tel/fax (509) 886-3708 E-mail nhfP_MSN.com June 24, 1999 . Chun Pak 3828 N.E. 1106' Seattle, WA 98125 Dear Chun and Ui Chon: The City of Edmonds required a topographical survey that we had done by Group 4 at the start of our development. Subsequently, all final plans were prepared and accepted by the city on maps drawn to the same scale (one inch = thirty feet) as the original topographical survey. Landau can superimpose these two copies taken from the topographical survey and the final plat showing lot locations. The city did not require that these two requirements (final plan and topographical map) be combined. Landau did not require such a map for any of the previous owners when they built their homes. Landau can also get ALL THESE RECORDS from the City of Edmonds, who should be keeping all documents of this nature for at least 10 years. I hope this helps. Best regards, Robert Anderson 1 1 r r�.�- BARBARAFAHEY �y CITY OF EDMONDS MAYOR '' 1. . 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425)•771.0221 DEVELOPMENT SERVICES DEPARTMENT IhC.1890 Planning • Building • Engineering December 30, 1999 Dennis Bruce P. O. Box 55502 Shoreline, WA 98155 SUBJECT: Incomplete Resubmittal for Lot 6, Lorian Wood Dear Mr. Bruce, The Landau letter dated December 9, 1999 was sent to assist you with preparation of a complete application. Until your submittal meets the minimum standard detailed in ECDC section 19.05, the review process can not be continued. Please note that Landau made a site visit on December 3, 1999 following completion of the work Don Fiene discussed with the Public Works department. The routine maintenance by Public Works did not eliminate the " spring" west of the LID 210 drainage system. The LID 210 drainage system was installed to reduce the risk of deep-seated or large-scale movement in the area. That system was not intended to reduce the risk of debris flow by collecting all water emerging from the slope and can not be expected to perform that function. The geotechnical report must determine what measures the owner will undertake to reduce risk or hazard. You should also be aware that the Building Official does not allow any excavation or drainage installation work in the Landslide Hazard area to start until approximately May when the dry season begins. If you have any questions, please call Jeannine Graf or me at (425) 771-0220. Sincerely, James C. Walker, P.E. City Engineer CC: Ray Miller Lara Knaak Jeannine Graf Barbara Fahey Gary Haakenson • Incorporated August 11, 1890 • Sister City - Hekinan, Japan LJ • Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer D U II D I N G December 22, 1999 City of Edmonds J A N 3 — 2000 121 Sth. Avenue North Edmonds, Wa 98029 Attn: Ms. Lara Knaak RE: letter dated December 9, 1999 from Landau Associates to City of Edmonds Concerning Proposed Pak single family residence at Lot 6, Lorian Woods Development Dear Ms. Knaak: We, the design team for Mr. Pak, are in receipt of a copy of the letter dated December 9, 1999 from Landau Associates to you. Who sent it to us and what are we supposed to do with this letter? It is not addressed to Mr. Pak or anyone of the Pak design team. There is no accompanying letter from the City of Edmonds. Is this letter for informational purpose only or are we supposed to respond to some or all of the number items? (Some obviously do not apply as they have already been either addressed, completed, the City has the required documents, or Landau Associates are still referring to the wrong documents.) We are not clear on what additional information the City wants from us. No one at the City has contacted any of us to tell us what additional requirements or information they need us to meet or provide for this project, if any. It is very difficult to understand why this process has taken so long (Landau letter dated 2 months after Bruce report and documents were sent to the City), especially since our July meeting with Ray Miller, several key City of Edmonds employees and Bill Evans from Landau Associates. It was at this meeting that the turn around time, from Landau to the City on any additional consulting work for this project, would be one week Mr. Pak has invested both considerable time and money in his attempt to obtain his building permit. Building costs have risen dramatically since this application was first submitted. Any further delays will inevitably add to his costs as the price of construction continues to increase. Since the City has not asked us for any additional information or documents since our October 7, 1999 submittal, we would like to have the permit issued immediately. Regards, Dennis Bruce, PE - lead professional for The Pak Design Team Cc: Barbara Fahey, mayor Gary Haakenson, mayor elect Ray Miller, AICP James Walker, PE Don Fiene, PE Gordon Hyde Jeannine Graf Chuen Pak Dr. Robert Anderson Wayne W. Foley, attorney at law Phil King John Gurnee �1S M . B� of WA SIR, G h 17405 A�0 Q4C/STBRF ONAL EXPIRES 12/23/ SOILS FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE - DESIGN & PERMIT - LEGAL P.O. Box 55502 - Shoreline, Washington 98155 - (206) 546-9217 - FAX 546-8442 Landau Associates Environmental and Geotechnical Services City of Edmonds 121 5th Avenue North Edmonds, WA 98020 Attn: Ms. Lara Knaak RECEIVED DEC 1 41999 DEY C�EOFF EDMVICES ONDS t:7R December 9, 1999 RE: RESPONSE TO PARTIAL RESUBMITTAL OF CONSTRUCTION DOCUMENTS PROPOSED PAK SINGLE FAMILY RESIDENCE LOT 6, LORIAN WOODS DEVELOPMENT 16109 73TH PLACE WEST EDMONDS, WASHINGTON Dear Ms. Knaak: This letter provides Landau Associates' response to resubmitted documents for the proposed Pak single family residence. Resubmitted documents include an October 7, 1999 letter by Mr. Dennis M. Bruce, P.E. (geotechnical engineer and lead design professional), and three drawings: 1) a drawing dated July 12, 1999 which appears to be a site plan; .2) a Drainage, Land Clearing and Tree Cutting Plan, revised November 23, 1998; and 3) a drawing (Plot Plan). showing grading and height calculations, revised June 14, 1999. The firm(s)/individual(s) responsible for preparing the drawings are not identified on the plans. The additional information was submitted to the City of Edmonds (City) as part of a response to our previous two letters (October 9, 1998 and May 28, 1999), which provide comments on documents submitted as part of the initial building permit application. In our October 9, 1998 and May 28, 1999 letters we listed several issues that needed additional attention and clarification. The current submittal addresses some of the outstanding issues, but many still must be resolved to meet the requirements of City Ordinance 2661 and Chapters 19.05 and 20.15 of ECDC. The pace and current status of this application are of concern to us. While the applicant has made several submittals, the information which has been provided for our review has typically been incomplete or technically lacking. This has resulted in project delays and added expense for the applicant, while leaving the project in a state of flux. The following numbered comments address geotechnical and related issues regarding the current status of the application; however, at least one additional review should be anticipated (assuming the next submittal is "complete"). WAPATO CREEK PLACE • 4210 - 20TH STREET E. • SUITE F • TACOMA. WA,98424-1823 (253) 926-2493 Fax: (253) 926-2531 E-mail: info@landauinc.com Edmonds Portland Spokane Tacoma On December 3, 1999 Messrs. William Evans and Edward Heavey (Landau Associates) visited the slope above (east of) the Pak property. The visit was requested by the City, and was directed at observing slope -related features associated with the City's drainage system. The Pak parcel and nearby properties were observed during the reconnaissance. Charges for the visit are not being posted to the Pak project observations from the trip are incorporated below, where relevant. 1.J A significant issue that still requires addressing is the proper evaluation of the risk of earth movement adjacent to the site, (e.g. debris flows), which could impact the proposed residence. In our October 9, 1998 letter we expressed concern that this. risk had not been adequately characterized and recommended that a geologist, experienced with Puget Sound bluff processes, evaluate the slope east of the proposed residence. Mr. Bruce responded in his April 4, 1999 letter that he had observed the slope over the winter of 1998/1999, and based on his observations, concluded that there were no problems with the slope. Mr. Bruce's observations were of a geologic basis. Section 19.05.030.B.1 of Ordinance 2661 requires that geologic evaluations be performed by, or reviewed and approved by, a geologist. In our May 28, 1999 letter, we reiterated the need for a slope evaluation by an experienced geologist. Mr. Bruce responded in his October 7, 1999 letter, citing that it is his opinion that the site is stable and will remain stable, provided the City addresses drainage issues. Mr. Bruce makes no statement in his October 7, 1999 letter regarding current/future stability of the adjacent slope, which is identified in the June 6, 1989 Tema Associates, Inc. report as the highest risk area within the plat. In our opinion, this geologic assessment remains a high priority and should be completed prior to any future geotechnical review. The geologic assessment should evaluate the potential for debris flows from the adjacent slope and what, if any, protective measures are needed. Review of aerial photographs may be useful during this assessment, as well as a review of City files regarding debris flows/landslides within the City over the past several years. If a debris containment/deflection wall is advised based on this study, the lead design professional must coordinate placement and design parameters. 0According to Mr. Bruce, upslope drainage issues will be addressed by the City. Mr. Bruce assumes City improvements/maintenance will increase site stability and aid in home construction. However, we spoke with Mr. Jim Walker, City Engineer, who informed us that the City is not considering replacement/improvements to the existing drainage system at this time. Currently, the City plans to maintain the drainage system as in the past (e.g. weekly inspections, cleaning inlets, periodic minor system upgrades, etc.). We suggest the City advise the applicant of its current position regarding this drain system, and of the need for the applicant to prepare a development plan which accommodates the expected range of operating conditions of the City's drainage system. The. assumptions should be conservative, and include provisions for blockage of the system which could last for several hours/days. We disagree with Mr. Bruce's conclusions regarding City drain system operation, relative to construction related/long-term livability issues for the proposed dwelling. The City's system is shallow in nature and attempts to intercept surface and near -surface water flow. However, in a geologically active area, such as the base of the Meadowdale Landslide scarp, (where water discharge points and rates can vary substantially over the years), it is unreasonable to 12m/99 I:%PROJECM74b79,lMpaMirdmwl_gr.dm t..ANDAu AssociAms 2 expect a shallow drain system to control conditions during construction (for an excavation approaching 20 ft in depth), and even more unreasonable to expect such a system to provide drainage control over the life span of a dwelling. During our reconnaissance of the slope/City drain system, we noted substantial flow from a "spring" just north of the Pak parcel (west of one of the City's catch basins). According to the City, this is a year-round feature that is not known to be related to the City's drain system. This spring is not shown on any of the drawings or addressed in any of the reports which we have reviewed to date. The presence of this spring is not noted in the applicants Environmental Checklist. The presence of the spring demonstrates that the property is within a groundwater discharge zone, and that groundwater levels near the spring will be at or near the ground surface on a year-round basis. We recommend the City require the lead design professional/geotechnical engineer to describe this spring, (and any others in close proximity to the lot), and provide design details for properly managing groundwater associated with the spring(s). 4. A complete topographic map of the site and nearby area has yet to be submitted. The July 12, 1999 drawing is incomplete and does not meet the requirements of Ordinance 2661. It is .missing the following: not prepared for this project and not stamped by a licensed surveyor; no legal description of the property is included; proposed new site contours are not shown; datum point is not shown; existing features within 50 ft of the property are not shown; and existing underground utilities are not clearly shown. It appears that the topographic survey data shown on the drawing is from a 1988 topographic survey of Lorian Woods Development, prepared by Group Four, Inc. We spoke with a representative of Group Four regarding the use of their topographic survey. They were unaware of its use and have not approved of its use by the applicant. The applicant should submit a topographic map meeting the requirements of Ordinance 2661. 5. Characterization of site soil conditions now appears adequate to address most of the foundation support and temporary excavation concerns, though groundwater conditions need further evaluation (as discussed in following Items 6 and 8). Based on review of test pit logs in the October 7, 1999 letter, it appears that soil conditions have been characterized to a depth of about 16 ft below existing grades. Based on the location of the test pits shown on the 7/12/99 Plan, the explorations extend to about elevation 135 to 138 ft. Footing level for the proposed structure is at about elevation 139 ft. From the test pit logs, it appears that suitable bearing soil is present at test hole #1 at about elevation 140 ft, and in test hole #2 at about elevation 139 ft, which are above the proposed basement level. No further action is recommended for this item, provided the owner is prepared to "step" the foundation down to firm bearing from east to west. If design footing elevations change, this item should be revisited. We have disregarded soil data from Mr. Bruce's July 27, 1998 original report since it is not clear that the parcel had been properly located relative to original and revised plat lot layouts. Similarly, we have disregarded test pit information from Mr. Bruce's April 4, 1999 report, as test pit TP-Pak is shown as having been excavated on adjacent Lot 5. 06. Maximum seasonal ground water level at the site has not been identified. The test pits logs indicate groundwater seepage at about depth 5 ft in test hole #1 and about 7 ft in test hole #2; however, our site observations suggest groundwater levels at the ground surface just north of the site. Therefore, it is unknown if the groundwater levels observed in the test pits represent 12/0 M 1.%PROJECT074W79.10\pakthirdrvwl_Rr.dx LANDAU ASSOCEATES 3 a minimum, maximum or intermediate groundwater level. The geotechnical engineer should provide additional information and discussion regarding the seasonal high groundwater elevation for use in design. 7. Issues raised regarding temporary and permanent excavations have, in our opinion, not been adequately addressed to date. It is our understanding that stacked "ecology blocks" could be used to support temporary and permanent excavations. As stated in our May 28, 1999 letter, temporary shoring should be designed by a licensed engineer registered in the State of Washington (could be hired by the contractor), and the shoring plans submitted to the City as part of the building permit application. The geotechnical engineer must provide specific design parameters, such as recommended lateral earth pressure(s), allowable soil bearing pressure, drainage requirements, etc. for design of temporary shoring. In addition, potential impacts to the existing groundwater drainage system on the slope to the east of the site from open and/or shored excavations need to be addressed. The permanent retaining wall along the east property line, (and portions of the north and south property limits), must be similarly designed. A slope easement to allow temporary excavation offsite may assist in planning temporary excavations and permanent wall systems. However, the City's 12-inch storm drain line parallel to the east property line, and adjacent Lot 7, may.be problematic for solutions which involve offsite excavation. If slope easements have been obtained, the design should reflect the easement limits and how these adjacent offsite items will be addressed; if not, temporary and permanent on -site shoring/wall details must.be shown. Construction of a soldier pile wall may be required along the east property line, even if slope easements have been obtained. The geotechnical engineers October 7, 1999 response to the above is a statement that "...the temporary shoring technique of stacked ecology blocks will satisfy the geotechnical conditions for the residence excavation." This response does not address the above issues. WAC 296-155 Part N, Section 657.3.d, Option 4, requires that support systems not meeting the criteria established under Options 1, 2, or 3, are to be desIged by a registered professional engineer. We recommend that the City require that the applicant submit temporary and permanent wall designs, stamped by a licensed structural engineer registered in the State of Washington. Lastly, it is unclear to us how a 2-ft thick ecology block wall can be constructed 1 ft away �. from the property line and still leave room for walkways; steps, roof overhangs, etc. (the j home is to be 5 to 6 ft from the property line). The lead design professional will need to verify that all temporary and permanent retaining structures can be accommodated within this space, and still leave room for any required home -related features, especially those which may be required by code. ( 8.) The October 7, 1999 Dennis Bruce letter, and November 23, 1998 Drainage, Land Clearing, and Tree Cutting Plan, make reference to a concrete retaining wall, with a maximum height of 8 ft, along the east property line. No details or design information (structural calculations, etc.) have been provided to the City for review or comment. In addition, the geotechnical engineer has not provided specific design parameters (lateral earth pressures, drainage, etc.) for the wall. We recommend that the geotechnical engineer supply the necessary information for structural design of the wall and the applicant provide plans and details of the proposed wall. If this wall is the same as the ecology block wall cited in Item 7, this comment can be disregarded (as long as Item 7 is addressed). 12/09/99 1:1PROJECTW74W79.10Npakthirdrvwl_Rr.doc LANDAU ASSOCIATES 4 �9 The April 4, 1999 supplemental report by Mr. Bruce anticipates a significant dewatering effort to allow construction of the foundation. We recommended in our May 28, 1999 letter that a dewatering plan be submitted to the City as part of the construction documents. The geotechnical engineer's response in the October 7, 1999 letter is as follows: "When the City of Edmonds drainage system behind the Pak lot is properly'functioning, the Pak lot incurs no severe geotechnical or foundation excavation problems. If however, the City of Edmonds drainage system is not properly functioning, or not properly maintained, excessive groundwater flows onto the property. This excessive water flow would greatly increase construction and foundation costs for Mr. Pak." As discussed above, we understand that the City anticipates no changes to the drainage system in the near future, and plans to maintain the system as in the past. Therefore, it appears that surface and groundwater impacts will need to be addressed for foundation construction. Permanent dewatering to keep the dwelling's basement dry should be part of this assessment. The City may also want the applicant to describe what negative effects permanent dewatering may have on the nearby spring(s) (see item 3), or if stream buffers apply in this case. 10. Our comments regarding rockery walls at the site, as noted in our October 9, 1998 and May 28, 1999 letters, have still not been addressed fully. The revised drawings do not show 'A rockeries, but it is unclear if rockeries are still planned for the site: If rockeries are still planned, the comments in our October 9, 1998 and May 28, 1999 letters should be addressed i by the applicant. 11. In our October 9, 1998 letter, we pointed out conflicting information regarding disposal of site stormwater. One plan (original plan included with the grading and drainage calculations) indicates an infiltration trench west of the house and one plan (original Land Clearing and Tree Cutting Plan) shows a detention facility connected to existing stormwater facilities. The latest drawings appear to indicatethat roof downspouts and foundation drains will be connected to the existing storm drain. The drawings provide little detail regarding the drainage system. We recommend that a proper drainage plan, showing such items as type, location and size of pipes (stormwater, sanitary sewer, and water); connection details; invert elevations; catch basin type and location; locations of cleanouts; etc. be submitted by the applicant. The drainage plan should be prepared by an experienced civil engineer licensed in the State of Washington, per Ordinance 2661. 12. In our October 9, 1998 letter, we questioned the need of the "French -type" interceptor drain east of the planned dwelling. In our May 28, 1999, we again identified this issue. The drain is not shown on the latest drawings. We do not know it the interceptor drain is still being considered. If" so, the geotechnical engineer needs to address the concerns listed in our October 9, 1998 letter. 13. In our October 9, 1998 letter, we pointed out that there are conflicting details regarding foundation drainage details on the architectural drawings. No revised architectural drawings have been received, thus, it appears that this issue still needs to be resolved. 14. In his October 7, 1999 letter Mr. Dennis Bruce states that, "The project plans are approved subject to resolution of the City of Edmonds drainage situation and inspection by the engineer." In view of the deficiencies identified in the proceeding paragraphs, the plans will require additional revision. Therefore, the geotechnical engineer will need to complete supplemental review of the resubmitted plans. 12/09W 1:1PROJECTb74W79.IONp"irdrvW-hr.dm LANDAU AssoclATEs 15. Mr. Bruce notes in his July 30, 1998 statement that he has reviewed the structure plans and specifications and they conform with his geotechnical recommendations. The structural plans which we reviewed were sealed on July 14, 1998, and appear to reflect initial geotechnical recommendations, rather than current ones. For example, the structural engineer is basing his design on a 2,000 psf bearing capacity, 18-inch wide footings, and 5 sack mix concrete, whereas Mr. Bruce, in his April 4, 1999 report, cites recommendations for 1,500 psf bearing capacity and 24-inch wide footings. In his July 27, 1998 report, Mr. Bruce recommends a minimum cement content of 5 1/2 sacks per cubic yard of concrete mix. The lead design professional needs to carefully review the submittal to eliminate conflicts such as these. The City may need to determine which engineer (geotechnical or structural) should be providing the concrete mix design. 16. The October 7, 1999 Dennis Bruce letter indicates that winter time construction is feasible. Paragraph 20.15B.080.A.1 of the City of Edmonds Critical Areas Ordinance specifically limits clearing and grading activities within sensitive areas to between May 1 and September 30. If shoring and dewatering issues can be satisfactorily resolved, it is our opinion that winter time construction could be allowed (provided the City waives the current restriction). 17. Mr. Bruce's April 5, 1999 landslide risk analysis appears to be linked to City's improvements of the hillside drain system. As noted previously, the City has indicated it has no plans to improve the system, but does plan on continued inspections and minor maintenance. Accordingly, Mr. Bruce needs to reassess site risk based on, 1) the City's planned drainage - related activities, 2) the geological assessment of the adjacent slope, and 3) any changes required as a result of full compliance with City Ordinance and Code provisions. A revised risk statement is needed. 18. Several of the required checklist items have yet to be submitted by the applicant. These items include Affidavit of Notice of Application, Applicant/Owners Liability Landslide Acknowledgment, and Applicant/Owner Covenant to Notify and Hold.Harmless. The above items need to be submitted to the City for review and approval prior to issuance of the building permit. The resubmitted documents address some of the issues raised in our October 7, 1998.and May.28, 1999 letters, but significant issues/concerns still remain to be addressed. We recommend that the lead design professional review the comments contained in this letter, (and the ordinance requirements for the geotechnical report, topographic map, drainage plan, grading plan, etc.), and respond in detail. The applicant should not interpret the above to mean minor edits to the existing submittal. We have significant concerns about temporary and permanent site dewatering/drainage, temporary and permanent shoring/retaining ' structures; (including protection of the City's drain system), and proper characterization of the stability of the adjacent slope. Unless a serious effort is made to address these items, (and others as noted above and in previous letters), we are concerned that the project will remain on a review "treadmill". 12/09/99 I:IPROJECT10741079.10\oakthirdrvwl-I[r.doc LANDAU AssociATEs 6 Please call if you have questions concerning this review, or require the services of Landau Associates for subsequent review services. EJH/WDE/jas LANDAU ASSOCIATES, INC. By: Edward J. Heavey, P.E. Senior Engineer and William D. Evans, C.P.G. Associate 12/09/99 1:wROJECT1074a79.101paMhirdrvwl_nr.doc W LANDAU Assoc1ATEs Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer October 7, 1999 City of Edmonds RECEIVED Community Services Division NOV 0 9 1999 121 Fifth Avenue North Edmonds, Washington 98020 DEVELOPMENT SERVICES CTR. CITY OF EDMONDS Attn: Mr. Ray Miller, Director Mr. Don Fiene, P.E. Ms. Janine Graf, Building Official Subject: Mr. Chun Pak Lot - Lot No. 6, Lorian Woods 16109 - 73rd Place West, Edmonds, Washington Hopefully, this engineering report will allow the City of Edmonds to issue a building permit for Mr. Chun Pak's Lot No. 6 at Lorian Woods development, at 16109 - 73rd Place West. Numerous reports, responding reports and meetings have occurred regarding Mr. Pak's desire to build a single family residence in Lorian Woods, similar to the already -developed lots. This report is an attempt to briefly summarize the issues and, hopefully, resolve them. References: • June 6, 1989 report by Terra Associates, Inc., allowing development in Lorian Woods, subject to conditions • Proposed house plans for Mr. Pak by Phil King, Designer • July 27, 1998 geotechnical evaluation report by D. Bruce, P.E., for Mr. Pak • October 9, 1998 review report by Landau Associates, Wade Gilbert, P.E. • April 4, 1999 additional geotechnical information report by D. Bruce, P.E. • May 28, 1999 supplemental geotechnical review by Landau Associates, Inc., Edward Heavy, P.E. • June 9, 1999 additional soil test pit investigation, test pit logs, and photographs. • June 11, 1999 meeting with City of Edmonds, Mr. Pak, Landau Associates, designer, and this engineer, to clarify issues • June 18, 1999 on -site photographs and investigation by City of Edmonds Drainage Department and Public Works Department regarding needed repairs and improvements to City of Edmonds drainage system directly behind and above Mr. Pak's lot. SOILS • FOUNDATIONS • SITE DEVELOPMENT - INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 • (206) 546-9217 • FAX 546-8442 City of Edmonds / Pak Lot Page two Synopsis: As stated in this engineer's July 27, 1998 and April 4, 1999 reports, up slope drainage control is essential to maintain slope stability behind Mr. Pak's lot. This engineer has assessed, investigated and discussed the conditions of the City of Edmonds drainage system behind Mr. Pak's lot. It is understood that City of Edmonds geotechnical reviewer, Landau Associates, has not assessed the site, has not assessed the existing drainage system behind Pak Lot No. 6, nor has made any evaluation regarding the suitability of existing conditions. At the June 11, 1999 meeting, it was acknowledged that no discussions have occurred between City of Edmonds Drainage Division, Public Works maintenance, and Landau Associates. This is most unfortunate. This engineer recommended, on June 18, 1999, to Don Fiene and Public Works director, the need for improved drainage intercepts and maintenance directly behind Mr. Pak's lot. All parties acknowledged the drainage needs, and indicated that new culverts, new pipes and new tight line discharge lines would be installed. As of October 7, 1999, this engineer understands that such work has not vet occurred. This is unfortunate. The reason the drainage improvements are important and necessary are as follows: The June 9, 1999 supplemental test pits indicated the presence of dense, stable foundation soils (similar to Terra Associates, Inc., report dated June 6, 1989). However, supplemental soil test pit No. 1 in the vicinity of the northeast portion of Pak lot encountered excessive seepage ground water flow. The excessive flow was not encountered in test pit No. 2. Subsequent up slope investigations directly behind supplemental test pit No. 1 revealed clogged and insufficiently sized City of Edmonds drainage system. The clogged silt and debris was removed and immediately the amount of ground water flow into supplemental test pit No. 1 was greatly reduced. This simple cause and effect is noteworthy. When the City of Edmonds drainage system behind the Pak lot is properly functioning, the Pak lot incurs no severe geotechnical or foundation excavation problems. If, however, the City of Edmonds drainage system is not properly functioning, or not properly maintained, excessive ground water flows onto and into Mr. Pak's lot. This excessive water flow would greatly increase the construction and foundation costs for Mr. Pak. This should not occur. City of Edmonds / Pak Lot Page three It is sincerely hoped that the promised drainage improvements behind Mr. Pak's lot will actually be installed and properly maintained. Project Plans: Please refer to the following: • Revised November 23, 1998 Phil King Drainage, Land Clearing and Tree Cutting plan. • Site plan and lot layout dated July 12, 1999 by Phil King, including supplemental test pit locations. • Project Plans dated July 13, 1998 by Phil King, revised June 14, 1999. • Revised Plot Plat dated June 14, 1999 by Phil King • Project structural details by H.N. Lehtinen, engineers. The Pak development plans require a concrete retaining wall (maximum height eight feet [8']) along the east property line (typically one foot inside actual property line). This concrete retaining wall will allow* a benched, or staggered tier approach for the foundation work for the Pak residence. The actual rear Pak foundation wall will. be approximately six foot (6') away from this property line retaining wall. The finished floor elevation for the lower level / garage is 139.5 (see plans). As previously stated, if the off -site drainage problems are properly controlled and improved by the City of Edmonds, the temporary shoring technique of stacked ecology blocks will satisfy the geotechnical conditions for residence excavation. Note: As discussed, this engineer does not believe that a significant or potential debris avalanche risk exists to the Pak residence. However, the rear retaining wall could be designed with two to three foot (2' - 3') of "free board" to allow localized erosional sloughing material to collect and not ooze onto the Pak residence itself. The potential risk for any localized surficial sloughing hinges on up slope property owners proper drainage discharge, and avoidance of destructive top -of -slope cutting. As discussed, this engineer's evaluation of the up slope property verified that proper drainage currently exists, and no evidence of any top -of -slope soil cutting was observed. Not to belabor the point, but the greatest contributor to any landslide or sloughing risk to the Pak residence lies with the malfunction, clogging, under - designed or poorly maintained City of Edmonds drainage system. If good drainage 0 • City of Edmonds / Pak Lot Page four design and maintenance cannot be assured, perhaps the City of Edmonds should install a massive catchment wall east of Mr. Pak's property. Foundations: Based on the findings of the June 9, 1999 supplemental test pits, and experience with similar properties, this engineer recommends normal, standard, reinforced concrete foundations. As discussed, however, lack of proper drainage control by the City of Edmonds system will result in excessive seepage waters into the Pak excavation. If, somehow, construction goes ahead without good drainage, the additional costs of piling would be required to offset the ground water seepage from the City of Edmonds systems. Project Plans: This engineer has discussed and reviewed the revised project plans with Phil King, Designer, and proposed project contractor, John Guerney. The current project plans are geotechnically approvedsubject to resolution of the City of Edmonds drainage situation and inspections by this engineer. Seismic Hazard: The largest earthquakes which have generally occurred in the Puget Sound area are sub -crustal events, with epicenters ranging from 50 to 70 kilometers in depth. For this reason, no surficial faulting or earth rupture as a result of deep seismic activity has been documented to date in the Snohomish County region. Therefore, based on existing geologic data, the risk of surface rupture impacting the proposed Pak residence is low. Refer to Terra Associates original report from June 6, 1989 for further discussion of seismic and landslide potential. Please note that the lot numbering system has changed from the 1989 report. Construction Timing - If, as previously stated and requested, the City of Edmonds drainage system is properly improved, there are no geotechnical restrictions against construction during any time of the year. 0 • City of Edmonds / Pak Lot Page five Obviously, winter season construction will result in more than normal delays resulting from bad weather or slightly mushier site. In some ways, however, construction during the winter season will assist in defining the adequacy of the City of Edmonds drainage system. In short, it is to Mr. Pak's advantage to have his foundation exposed during "worst case" weather events in order to verify that the City of Edmonds drainage system is fully capable. This engineer has considerable experience with summertime construction that revealed no drainage problems, only to discover nine months later than the drainage mitigation system was inadequate (unfortunately after foundations have been built and back -filled). Summary: • Phil King Designer plans, as of July, 1999, are geotechnically approved. • Normal foundation techniques and temporary ecology block shoring are geotechnically viable, if City of Edmonds drainage system is improved and properly maintained. The remote possibility of localized sloughing from the rear hillside can be mitigated by a two to four foot (2' - 4') height extension above the proposed property line retaining wall. • Geotechnical inspections by this engineer are required during key phases of construction. Statement of Minimal Risk (RestatedlY The plans and specifications for the Chun Pak residence at Lot No. 6, Lorian Woods, as designed by Phil King (as of July, 1999) have been reviewed by this engineer and conform to the recommendations of the analysis and report and, provided that those conditions and recommendations are satisfied (especially the City of Edmonds drainage issue) during the construction and use, and inspected and verified by this engineer, the area disturbed by construction will be stabilized and remain stable and will not increase the potential for soil movement, and the risk of damage to the proposed Pak residence and from the Pak residence to adjacent properties from soil instability will be minimal. City of Edmonds / Pak Lot Page six Permit: It is more than time to issue Mr. Pak's permit If there are any questions, do not hesitate to call. �1S M . B� 4� pF WAStj�,y 00 40 P 4 c7 ONAL ECG EXPIRES 12/23/ 0 DMB:vIb cc: Mr. Chun Pak IZ, .14, " 44_&� Dennis M. Bruce, P.E. Geotechnical / Civil Engineer So1L EST �rTS I -f.p, it PAY ICE- /erHu iu PANG L oR IAN W 00 As IG101 73 DAJE 4 l LOT � W. ez M c OF flZOPoSEN itJ=-S14E,AdCE • SEA S17'lr PLAN 3Y PNIL K/N91 .AEstGIV£ O T'o 1 a Top.solL i ZuFF e)ka*Wlc �6FSelS 5.:. T• GENE SAt oC�. Coatlt; I To s �• dv__ I ' '�„ -� ` wt-�rN SILTY SArN� Mli4dvtit QENSE� Sp uE i � I SI�NtFt C/}NT �(Z,DU1�W��TE� Cd'rY �� C'LO�roFD �l11JSUF�lCtE'NT ei¢Pl4C1TY To UPJCopE' LC> MOpj,.s 1 wre7kCEPT .�IeA/NS �bJ�L�CTLy �T FT /NcPEASiNGLY ,�E/UsE �i T SANt'a w SILT LFNsES. GCE `l T. � •t:Ns� � l2F ,dENSE To VE�.Y Gt Uocwf<-E & lW,Ij N= WREW Tots &W61t. 00CLo64'ED UPSLoPt: LRAIN I) sLowIFa Tc TR18K.LF. NEAR S. E. CoQNER �� L� ,� PY, S. E d oCA-�ED aEE SITE PGN . P pRo posEh nAFS 1"k gNC6 f r� �uP F ORGd�NtC �t;�RIS i o l4 =;;p ToIIPCOIL. , stt,-r'r &Ol w c F: T• V F/N S._ A N h oc t. r'c�B81E S W tT ►t �$A/ 4 � 7 ARE i ! I�AE>D SE . Oil U PSLO �• E ' T•TIGICkLE G� o�un�k-rivA or I S Ltlo 14 -N�.� C L0G6 C6 AgOV t: I C t•rY 010 Eblac Wps �.�ltl Ns �1S M. ��FW \S LoCATib&J. F/IlT / t; TO w� TH G dW F� • 4 M e c C1 PTpT , dW Clot►N6 bENSE c� 7 %� �to Sl4N� w( St LT LENSES. • �i p J v- t ` QF PT t{ 17405 JAr �� Qfcl V. �Y�V �1T WALLS �STAB.LE it E4�lA t u V E iR.'fkc A• L ONAL EN j ,e.TE4 T1"CS CoMP1.,,E EXPIRES 12/23/ 1 i JUN-10-1999 THU 08:46 AM LANDAU ASSOCIATES FAX NO, 2539262531 P. 02/06 0 Landau Associates Environmental and Gonirld-1ca1 Services May 28, 1999 City of Edmonds 121 5th Avenue North Edmonds, WA 98020 Attn: Ms. Lara Knaak RR: SIJPPLEMF.NTAI, GvEOTF.CHNICAL REVIEW PROPOSED PAK RESIDENcr. LOT 6, LORIAN WOODS WNFLOPMENT 16109 73TH PLACE WEST r4,DhIONDS, WASHINGTON Dear Ms. Knaak: This letter provides Landau Associates' review comments on additional geotechnical information prepared by Mr. Dennis M. Bruce, P.E., (dated April 4, 1999), related to the above -referenced project. 'The additional geotechnical information was submitted to the City of Edmonds (City) as part of a response to our preliminary review. Our preliminary review comments are summarized in an Octohcr 9, 1998 letter to the City. In our October 9, 1998 letter, we listed several issues that needed additional attention and clarification, which are briefly listed below: 1. Outdated site plan and topographic information. 2. Inadequate investigation of subsurface conditions. 3. Issues associated with temporary excavations to construct foundations. 4. Potential impacts to existing groundwater drainage system on the slope to the cast of the site from open or shored excavations. 5. Inconsistency in recommended allowable soil bearing pressure between the Tara & Associates (Terra) 1991 geotechnical report and the initial 1998 Dennis M. Bruce Geotechnical report. 6. Possible conflict of the house location and a buried tightline discharge ripe associated with the drainage system on the slope to the cast. 7. Conflicting information in the submittal package regarding site stormwater drainage. S. Conflicting details regarding the foundation drainage system and lack of specifications of material types. 9. Issues associated with a rockery planned for the yard area cast of the house, and other smaller rockeries. 10. issues regarding a proposed "French -type" interceptor drain along the eastern property line. WAPAVO LaL LIK PLACE • 4210 - 20TI1 STRF.F.T F. • SI)ITE F • TAC OMA. WA95424-W.1 (253) 920.2493 Nx: (253) 924.2531 L-rnail: inro@1htndauiacxont E.dlnontk Portland 5po4.n11c Tacomsi JUN-10-1999 THU 08:46 AM LANDAU ASSOCIATES FAX NO. 2539262531 P. 03/06 11. Incomplete statement of risk by the geotechnical engineer. 12. Incomplete discussion regarding potential differential settlement of the structure. 13. Contradictory statements between the environmental checklist and other documents submitted. 14. Inadequate evaluation of the slope above the residence. 15. In addition, several items were not included in the original submittal, including: Critical Areas Checklist; Lead Design Professional Designation and Statement; Affidavit of Notice Application; Applicant/Owner Liability Landslide Acknowledgment Declaration; and Applicant/Owner Covenant to Notify and Hold Harmless. The supplemental geotechnical report prepared by Mr. Dennis M. Bruce, I'.E. (dated April 4, 1999) addresses or partially addresses above items 2, 3, 4, 5, 9, 10, 11,12, and 14. Items number I, 6, 7, 8, 13, and 15 were not addressed in the supplemental geotechnical report. According to the supplemental geotechnical report, an additional test pit (Test Pit — Pak) was excavated to a depth of about 13 ft below existing ground surface. The test pit was located about 30 ft east of the reported location of Terra's 1989 test pit, (TP-2), and is reportedly in the vicinity of the proposed residence. However, infonnation provided to us in the original submittal does not contain an accurate drawing showing the actual location of the proposed house, and since the resubmillal also does not contain an accurate drawing, we cannot verify the test pit location. We recommend the City require submittal of an accurate site plan which shows lot lines, the proposed house location, the locations of all relevant exploration points, and any other items required by the ordinance. The ground surface elevation at the test pit Test Pit -Pak location, as estimated from a figure attached to the supplemental report, is about elevation 153 to 154 ft. Therefore, the test pit terminated at about elevation 140 to 141 ft. The construction plans still indicate a basement finished floor elevation of 138 ft. [Note: Because of the proposed basement elevation, we recommended in our October 9, 1998 letter that additional subsurface explorations be completed and extended to elevation 132 ft or lower to adequately evaluate subsurface soil and groundwater conditions.] The test pit excavated by Mr. Bruce did not extend deep enough to characterize expected foundations soil types. In addition, the soil types (e.g. fill, slide debris, glacial soil, etc.) encountered in the test pit arc not identified, and typical modifiers (e.g. moisture contents) are not presented for all soil layers. We recommend the City require site explorations which extend below foundation level. Since the design anticipates the use of "pin piles", the explorations must be deep enough so that pin pile criteria can be developed. To address our comments on temporary shoring (above item 3), the supplemental geotechnical report states that temporary excavations will not exceed 12 ft vertical and recommends using stacked ecology blocks for temporary shoring. It appears from the report that temporary shoring will be contractor designed. Temporary shoring should be designed by a licensed engineer registered in the State of Washington (could be hired by the contractor), and the shoring plans submitted to the City as part of 05t?.A09 I:TROJECT\074107%101pok:upplomonuLlir.doc LANDAU ASSMIATEN 2 JUN-10-1999 THU 08:47 AN LANDAU ASSOCIATES FAX NO, 2539262531 P. 04/06 the building permit application. In addition, the geotechnical engineer must provide specific design parameters, such as recommended lateral earth pressure(s), allowable soil bearing pressure, drainage requirements, etc. for design of temporary shoring. The supplemental report anticipates a significant dewatering effort to allow construction of the foundations. Since this appears to be a critical component of the project, we recommend that a dewatering plan be submitted to the City as part of the construction documents. As a minimum, the plan should include a written description of applicable dewatering methods, discharge points, erosion/sedimentation control, monitoring requirements, and abandonment of the system. The plan could be prepared by the geotechnical engineer, lead design professional or a qualified contractor. Though the supplemental report concludes that properly shored temporary excavations will not create any threat to adjacent residences, the supplemental report does not discuss potential impacts of temporary excavations or temporary shoring on the existing drainage system to the east (item 4 above). We recommend that the geotechnical engineer review and comment on this issue. A revised maximum allowable bearing pressure of 1,500 psf is recommended in the supplemental report, which is more consistent with the 1,200 psf maximum allowable bearing pressure recommended by Terra in their 1991 report (item 5 above). No specifics are provided regarding what is proper bearing soil. In test pit TP-2, excavated by Terra in 1991, slide debris with logs was encountered. If encountered, would this soil be suitable to support a 1,500 psf bearing pressure? We recommend that the geotechnical engineer review and comment on what coil type(s) the recommended soil bearing pressure applies to, and provide guidance if unsuitable soil is encountered at proposed foundation depths. If pin piles will be the recommended solution for unsuitable bearing soil, a typical detail and installation specifications must be provided with the submittal. [As an aside, the owner should be advised of the cost of this alternate foundation support system. Once the excavation is underway, the owner will be committed to going ahead with piles (if required), or may be faced with the prospect of having to backfill the excavation and/or re-design/abandon the project.) In our October 9, 1998 letter, we questioned the wisdom of using a rockery to support the slope east of the house (item 9 above). We recommended consideration be give to an engineered wall system, such as a cast -in -place concrete retaining wall with catchment capacity, since near -surface upslope soil consists predominantly of landslide debris, and debris flows off the eastern bluff will likely occur in the future. Though Mr. Bruce indicates that a reinforced concrete retaining wall (catchment wall) would be a better choice, he defers the decision to the owner. Without this issue being resolved prior to the City issuing the building permit, there will be no requirement for the owner to build such a wall, even if strongly recommended by the geotechnical engineer. Therefore, it is our opinion that the geotechnical engineer and owner must discuss the risks associated with a rockery and a decision made regarding the 05/2e/99 I:V'ROJECT\074b79,10\paksupplemanl l-ltr.Ooc LANDAU ASSOCIATES 3 JUN-10-1999 THU 08:48 AM LANDAU ASSOCIATES FAX NO. 2539262531 P. 05/06 proposed wall. Once a wall type is selected, the geotechnical engineer must provide design recommendations and material specifications, and an assurance that the wall will prevent downslope creep of the slope debris (such creep could Iead to failure of the City's drain system). Our comments regarding other rockery walls at the site, as rioted in our October 9, 1998 letter, were not addressed in the supplemental report. This includes rockeries to support till and/or soil that cannot stand vertically on its own, and which needs to be permitted according to City guidelines. The supplemental report does not address rockery design or construction. We recommend that the geotechnical engineer address the above. Any rockery design should include details and specifications for wall drainage and drainage discharge. In our October 1998 letter, we questioned the need of the "French -type" interceptor drain (item 10 above). Our questions/concerns regarding this drain were not addressed in the supplemental report. In response to item 11 above, the supplemental report states that .in the engineer's opinion, the probability of earth movement on lot 6 within a 25-year period is less than 10 percent. No probability of damage due to earth movement from offsite sources is given, even though the earlier Terra report stales the highest risk areas within the plat are along the steep eastern bluff. In our opinion, the risk of failure of the slope to the east has yet to be adequately evaluated (item 14 above). Though Mr. Bruce made periodic observations of the slope during the period of October 1998 and March 1999 (6-month period), the slope has not been evaluated by a geologist experienced with Puget Sound bluff processes, as recommended in our initial letter. The fact that only small events have been noted in approximately the last 40-year period may be increasing the risk of future, larger failures, and should be considered during the geological evaluation. Our recommendation that the lead design professional should use the findings from that study to evaluate site constraints and/or the need for supplemental engineered features (such as catchment/deflection walls, Brugg"m cable retaining systems, reinforced foundation walls. "soft" walls/floors, special drainage, selective tree removal, etc.) is still valid. The current risk statement from Mr. Bruce assumes that the City will maintain and improve the existing storm drainage system to the east of the proposed residence in order to minimize landslide potential and hazards. It is our understanding that the City is responding to this issue. The applicant should be trade aware that the existing storm drain system to the cast is within a known landslide hazard area, and because of that, there is a higher than normal risk of failure of the system due to soil creep and other mass wasting processes. Therefore, the lead design professional and geotechnical engineer should consider potential failure of the existing storm system when evaluating the landslide potential/erosion hazards of the slope to the east. The supplemental report provides additional discussion regarding "normal" differential settlement of the structure (item 12 above). However, the supplemental report does not address the concern of D541.6AD 1:%PnOiECT074\07D.10baksuDOlementaLllr.doe LANDAU ASSOCIATIS 4 JUN-10-1999 THU 08:49 AM LANDAU ASSOCIATES FAX NO, 2539262531 P. 06/06 potential differential settlement of foundations underlain by organic material, such as encountered in Terra's test pit, TP-2; or for potential cosmetic damage caused by uneven settling as a result of using differing foundation elements. The supplemental report does indicate that if poor foundation .oil is present, pin piles with grade beams will be used to support the structure. As noted above, [lie supplemental report provides no geotechnical recommendations to support this foundation type (e.g. pipe size, allowable capacity, driving criteria, corrosion protection, etc.), or that changing the foundation system will require additional structural engineering and resubmittal of the foundation plans to the City for approval. Lastly, the supplemental report indicates that pin piles will likely be used to support the chimney, though this option is not included on the construction drawings and no recommendations are provided for pin pile foundations. We recommend that the geotechnical engineer review and respond to these issues. Though the April 4, 1999 supplemental geotechnical report prepared by Mr. Dennis M. Bruce addresses many of the items contained in our October 9, 1998 letter, several significant issues/concerns still remain to be addressed. In addition, our comments on other portions of the project documents have yet to be addressed, but should be prior to resubmittal or issuance of a building permit. We recommend that the geotechnical engineer review the comments contained in this letter, (and the ordinance rucluirements for a geotechnical report), and respond as appropriate; and that the City require the lead design professional to submit all documents in a complete form. Please call if you have questions concerning this review, or require the services of Landau Associates for subsequent review services. ex�tRes `�Yti �, F*YWDE/jas 050.0t99 IAMOJEM074 0' 9 10WksuDelememal_Ilr.dar. LANDAU ASSOCIATES, INC. By: Edward J. Ideavey, P.E. Senior Engineer and William D. Evans, C.P.G. Associate t.ANDAU A.s\fx:IATIiq 5 Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer p�q+u CNE�� April 4, 1999 RECE'V City of Edmonds APR a , 121 Fifth Avenue North �liv ► of 6 . Edmonds, Washington 98020 Attn: Ms. Lara Knaak Subject: Additional Geotechnical Information Proposed Pak New Residence Lot 6, Lorian Wood Development, Meadowdale Area 16109 - 73rd Place West, Edmonds, Washington This engineering report presents the results of additional geotechnical investigation with regard to the proposed Mr. Chun Pak residence at Lot No. 6 of the Lorian Woods Development. Understood proposed address: 16109 - 73rd Place West, Edmonds, Washington. This additional geotechnical investigation was required due to City of Edmonds request dated October 8, 1998 from reviewer, Ms. J. Graf. It is understood that the City of Edmonds has no in house geotechnical engineer review capacity, and relies on outside consultants. The proposed Pak residence project is understood to have been reviewed by Landau Associates, Inc., with their findings presented in an October 9, 1998 review report. It is further understood that no engineer or geologist from Landau Associates has actually been to Mr. Pak's site. Thus, the Landau Associates, Inc., October 9, 1998 review is based solely on submitted reports and plans. REFERENCES: • July 27, 1998 geotechnical evaluation report for proposed Pak residence, by D. Bruce, P.E. • Proposed Mr. Chun Pak house plans by Mr. Phil King, Designer • Topographic Map of Lorian Woods Development prepared by Group 4, Inc., for Mr., Robert Anderson • Geotechnical Report of Lorian Woods property dated June 6, 1989, by Terra Associates, Inc. • Site plan and cross-section layout prepared by designer, Mr. Phil King SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 - (206) 546-9217 • FAX 546-8442 City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page two BACKGROUND: This engineer prepared a geotechnical evaluation and report for the proposed Pak residence, dated July 27, 1998. City of Edmonds subconsultant,'Landau Associates, Inc., prepared a document and plan paperwork review dated October 9, 1998, raising numerous geotechnical issues. The Landau October 9, 1998 report was signed, but not certified, by Wade Gilbert, P.E. It is understood that Mr. Gilbert is no longer with the Landau firm. This engineer conducted additional .geotechnical investigations (test pit) and observation over the severe rainy winter season from October, 1998 through March, 1999, in attempts to respond to geotechnical concerns raised by the October 9, 1998 Landau report. WINTER OF 1998/1999 PERFORMANCE: This engineer conducted numerous site observations- between October of 1998 through March of 1999. Of crucial importance (as discussed in the July 27, 1998 geotechnical evaluation), was drainage control. This engineer verified that the existing storm water system of drains and tightlines is owned and maintained by the City of Edmonds. Discussions with City Engineer, James C. Walker, P.E., and City of Edmonds Hydraulics Engineer, Don Fiene, P.E., verified the existing drainage system on the slope behind (easterly) of the Pak Lot No. 6, is owned and maintained by City of Edmonds. Further, Mr. Fiene conducted an on -site investigation and verified to this engineer that the drains, catch basins, and tightlines are functioning appropriately, and were approved by the City of Edmonds at that time. This engineer relayed how important it is to the overall viability of Lorian Woods, and particularly Lot No. 6, that the City of Edmonds maintain good monitoring and repairs to the drainage system. This engineer conducted observations of the Pak building Lot No. 6, as well as the relatively steep slope to the east. In the period of time from October, 1998, through March, 1999, this engineer observed no evidence of any localized sliding, sloughing, soil creep or significant erosional degradation. Further, this engineer conducted an exploratory investigation of the top -of -bluff properties to the east. The top -of -bank was found to be dense, native soil, with no disturbance or evidence of current instabilities. Obviously, historic erosional sloughing has occurred near the top -of -slope.. • • City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area . April 4, 1999 Page three ADDITIONAL SOIL TEST PIT: This engineer undertook an additional soil test pit (dug by backhoe) in the vicinity approximately thirty feet (30') east of Terra & Associates 1989 Test Pit 2. It is understood that this 1999 Test Pit -Pak, is in the vicinity of the anticipated Pak residence (per site plan layout). The results of the backhoe-dug Test Pit -Pak are as follows: 0" to 7" Ground cover, organics, and organic silt soft, moist 7" to 4' Grey, silty, fine sand, with occasional roots and some orange stain. Moist, loose 4" to approx. 8' Grey, silty fine to medium sand. Occasional zone of silt. Medium dense. 8' to 13' (bottom of Fine to medium sand. Grades increasingly dense Test Pit -Pak) Ground water encountered at four foot (4') depth. Test pit walls remained "reasonably stable". Some sidewall sloughing occurred, but not collapsing. CONCLUSIONS / RECOMMENDATIONS: Based on the findings of this and previous geotechnical investigations, as well as review of previous Terra Associates, Inc., reports for the overall Lorian Woods project, and the Nearing residence on adjacent Lot No. 7, and experience with similar properties, the following are concluded and recommended: • Discussions with project designer (Phil King), project contractor .(John Gurnee), and project owner (Mr. Chun Pak), verified that no soil cut will exceed twelve feet (12') in vertical dimension. This engineer confirms and reguires that no soil cut will exceed twelve feet (12') (vertical). This engineer recommends the use of temporary shoring consisting of ecology blocks. Properly staggered and embedded ecology block wall could be installed at 1 H:6V slope. • This engineer anticipates a significant dewatering of the Pak excavation due to material removal. Normal, good ground excavation practices (sumps, pumps, • City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page,_four tightline release into proper discharge, etc.) will assist the excavation -and foundation phase of this project. • The twelve foot maximum soil cut, combined with proper temporary shoring utilizing ecology blocks, will not create any geotechnical threat the adjacent Nearing residence, subject to this engineer's on -site inspections. This engineer recommends a revised bearing capacity of 1,500 p.s.f. This engineer requires a minimum footing width of twenty-four inches (24"). It is foundation contractor's duty to properly excavate and manage the site. If subgrade conditions degrade, over -excavation and backfill with structural gravel will be required (as discussed in the July 27, 1999 report). If excavation contractor is unable to "control" the site, and excessive subgrade disturbance results, this engineer will require a pin -pile with reinforced arade beam foundation along the eastern portion of the Pak residence. Drainage: Normal footing drains are recommended (as discussed in the July 27, 1998 report). Currently, there is an excess of surficial storm water runoff that inundates the access drive (see photographs). This engineer understands'that City of Edmonds verifies the adequacy of their up slope drainage system. This engineer believes that additional maintenance and improvements by the City of Edmonds may be required. Nevertheless, this engineer will proceed with the Pak development, anticipating additional drainage impacts from the City of Edmonds system. Specifically, an access road cut will be required, along with additional discharge piping into the apparent "open brook" that exists along the west side of access road (see photographs). • This engineer agrees with the Landau report comment questioning the use of filter fabrics. This engineer strongly recommends proper gravel annulus be placed around all drainage pipes. This engineer understands the concern regarding request for a,,rear catchment wall. This engineer has duly informed project designer, project contractor, and project owner over the "risk" of surficial slide debris from the" rear eastern slopes. All involved parties agree that the location of the Pak house will be sufficiently distant from the base of the steep slope. This engineer has no objection to installing a catchment wall along the rear (eastern) Pak property line, however, this engineer feels strongly that that is an owner's choice. City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page five Rear Rockery: The proposed rear rockery along the eastern property line of the Pak residence may be constructed in accordance with normal rockery standards. Depending upon site management and specific location of temporary ecology block shoring, a reinforced concrete retaining wall (catchment wall) may be a better choice. Again; this would be an owner's choice, based on recommendations from this geotechnical engineer during the construction phase. Landslide Hazard: In this engineer's opinion, the probability of earth movement on Lot No. 6 within a period of twenty-five (25) years, is less than ten percent. (10%). Thus, according to City of Edmonds Ordinance No. 2661, the lot is suitable for residential use. The risk of damage to the Pak residence and to adjacent properties will be minimal, subject to the conditions set forth in this engineer's report and subject to this engineer's on -site inspections during the construction phase. It is essential that the City of Edmonds properly maintain and improve the existing storm water control system in the hillside east of the Pak property in order to minimize landslide potential and landslide hazards. Additional mitigation of potential landslide risk will occur due to the actual construction of the Pak residence, installation of proper footing drains which will improved subsurface drainage, and also due to the basement excavation, which will remove a weight of soil greater than the weight of the residence. The Pak residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be totally eliminated, and property owners knowing assume all residual risks. The geotechnical recommendations and declarations associated with the Pak project do not constitute a warranty, either expressed or implied, against loss or damage to persons or property. Settlements: As discussed and required, a minimum footing width of twenty- four inches (24") is required. Experience has proven that such properly constructed footings result in estimated total settlements of less than one-half inch (.5"), and estimated differential settlements of less than one -quarter inch (.25"). As discussed, failure of excavation and foundation contractor to "properly maintain the site" will result in this engineer's requirements of pin -pile with reinforced grade beam foundations. This engineer does not, at this time, require pin -piles, but does anticipate their use, particularly under the masonry chimney. • • City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page six SUMMARY: • The proposed Pak residence on Lot No. 6, Lorian Woods, Edmonds is geotechnically viable, subject to the recommendations of this engineer and City of Edmonds building requirements. • Additional geotechnical exploration and analysis verified viability of the proposed Pak residence. ADDENDUM: NOTE: If any additional questions arise, or issues are unclear, this engineer stronaly recommends an on -site meeting with City of Edmonds technical personnel and their consultants. If there are any questions, do not hesitate to call. EXPIRES 1212N 'I DMB:vIb cc: Chun Pak, Owner James C. Walker, P.E. City of Edmonds City Engineer Phil King, Designer John Gurnee, Contractor Dennis M. Bruce, P.E. Geotechnical / Civil Engineer t '.00T- 9-98 FRI 16.24 LANDAU TACOMA LANDAU ASSOCIATES, INC. E,wronmental and Qootechn—1 56MOes City of Edmonds 121 5th Avenue North Wnionds, WA 98020 Attn: Ms, Lars Knaak RE: PRELIKU A V GF.OTECHNICAL RHVIEW PROPOSED PAK RE3IDL'.NCE LOT 6, LORL&N WOODS DEVELOPMENT 16109 73TH PLACE WEST NICADOWDALE AREA EDMONDS, WASHINGTON FAX NO, 2639262631 P. 02 October 9,1998 Dear Ms. Knaak: In accotdancc with your request, we have completed a preliminary geotechnical review of plans and other submitted documents concerning construction of the proposed Pak residence. Since the proposed residence is located within the Meadowdale slide area, our review follows the general to cluirements outlined within City Ordinance No. 2661 and Chapters 19.05 and 20.15 of the Edmonds Community DeveloPmcnt Code (ECDC). A list of the documents we reviewed (including earlier site -related material from our tiles), is included as Attachment 1. In 1989, Landau Associates reviewed a gtxoteclulical report prepared by Terra Associates, Inc. (Terra) for the proposed Anderson short plat project (subsequently known as Lorian Woods), which includes tho vides general geotechnical information relative to overall subject Lot 6. Terra's report, June b, 1989, pro development of the short plat and states that the platted property is suitable for construction of single-family residGlces. In our letter to the City dated November 17, 1989, Landau Associates concluded that Terra had provided an adequate description of the property and that their conclusions appeared reasonable for the information obtained at that time. However, we further stated in our letter that development of individual lots would depend on adequate characterization of soil and groundwater conditions at each individual lot, and would require lot specific geoteeltnieal design and constriction criteria not provided in Terra's 1989 report. The short plat was approved by the City, and we. understand some of the individual lots have been developed. As part of our current review, we also reviewed Terra's 1991 geoteehnicai report prepared for development of Lot 3 of Lorian Woods. These reports are fisted on Attachment 1, along with a sulnmary of documents submitted by the applicant. WAPATO CRFEK PLACE , 4210.20TII STREiT U. • SUITE F • TACOMA, WA 91142.1.1 M73 (?53 92b--7Q93 1 PX- (235) Y2t1-2531 E•Mail; Infu(chl, adnuinc.ca- F.dmv�id� S l,pkn � TauYna OCT- 9-98 FR[ 16:25 LAN TACOMA FAX NO. 2639262631 P.03 • The Lorian Wotxls development is situated on a topographic bench within the Meadowdale slide area. According to Tetra's 1989 report, the bench is composed primarily of slide debris associatedwith large-scale, ancient landsliding. To the cast of the bench is a relatively steep bluff -lope (landslide headsearp) composed of undisturbed native soil that rises upward toward the east to a crest about 100 to 150 ft above the bench. Typical bluff slope inclinations vary from less than 40 percent near the toe to more than 1)0 percent in upper e toe of the bluff are attributed to debris flows and smaller slides portions of the slope. The flatter slopes at th off the steeper upslope portions of the headscarp. To the west, the bench slopes down to 74th Place West at generally similar inclinations. Lot 6 is located on the east side of 73rd Place West at the toe of the bluff slope. According,to the topography shown on tha 1999 prelitninary plat, elevations across the lot vary from about 144 ft along the west boundary to about 170 ft near the northeast comer. From the toe of the bluff slope, the lot slopes downward to 73rd Place West at grades of between about 10 to 35 percent. Terra's 1959 assessment of site conditions is bast- in pals on subsurface information from several test pits and two borings advanced w part of their 1999 study_ We understand that Ternes test pit TP-2 is Icx at on Lot 6 near the street (preliminary plat). Other nearby explorations by Terra include test pit TP-4 on Lot 5 (preliminary plat) and buying B-1 located just west of Lot? (prelimintuy plat). Conditions encountered in test pits TP-2 and TPA consisted of mixed soil containing organics and numerous logs (e.g., landslide debris}_ Groundwater seepage was encountered within 3 to 4 ftof the,ground surface, and the side walls of the test pits were reported to have collapsed during excavation. Conditions encountered in boring B-1 are similar. and suggest that the slide debris at the site extends well below the bottom of test pit TP-2 (over 14 ft). While the document package we received was relatively complete, some items required by the application checklist wera not included. The items not included are: Checklist Item Number Description 1 Critical Areas Checklist 2 Lead Design Professional Designation and Statement i 1 Affidavit of Notice of Application 12 Applicant/Owners Liability Landslide Acknowledgment Declaration is Applicant/Owner Covenant to Notify and Hold Harmless The lack of these documents did not signiftt:tintty affect our ability to perform this preliminary geotechnical review. la/o9/49 G1Pti0]IP4T\071\674,10\PAK1.LTB 2 LANDAJ ASSOCIATES OCT- 9-98 FRI 16:26 AND411 TACOMA 0 0 FAX NO, 2539262631 P. 04 Our review of the Documents submitted for this project (and of material from our files) indicates several issues which require additional attention or clarification. These are sunimarized as follows: plans related to this project are bused on survey information prepared in January 1988 and a • preliminary short plat prepared in 1989. Since those documents were prepared, the common improvements have been installed and residences have been'conslrueted in the Lorian Woods subdivision. None of the submitted dxument,5 clearly indicate the poFition of the house with respect to the lot boundaries shown on the preliminary plat, nor is it cloar from the submitted documents where the actual lotboundaries, common improvements, orexisting houses an . located. The architectural plans are signed by Phil Ding, but are not stamped. Based on our understanding of the submitted infortrtation, and assuming that the lot boundaries are as shown on the preliminary plat, it appears that part of the house will be localcxl on the north end of Lot I. Either we have misinterpreted the house location --the actual platted lot boundaries are different from those shown on the preliminary plat —or the submittal package shows an incorrect location_ It has beets over ten years since the site topogrdphic snap was prepared. Ground surface changes are likely to have occurred at the site over Tile past dccade and ccrtt7inly have occurred where adjacent common improvements have been constructed. Using outdated information as a basis for design could lead to an improperly designed structure and result to significant and costly prohlcans during construction and over the long-term According to the requirements of ordinance 2661, a topographic map must be submitted showing the property lines, off -site structures within 50 ft I f the property, lower floor and footing locations of off -site structures within 54 ft of the property, existing underground utilities on- and off -site, and the proposed, inished grade contours. In our opinion, the submiuod documents do not provide that information as of the time of submittal and should not be used for purposes of design or locating the house. subsurface conditions do not appear to have been adequately investigated. under Ordinance 2661, site specific geotechnical explorations arc generally required as part of the geotechnical investigation. The explorations should extend to a depth that includes the soil influenced by or supporting the foundations. For spread footings, that depth is usu111y a point below the base of the footing equal to a distance of at least twice the width of the footing. Floor elevations on Sheet 1 of the plans indicate that the basement floor elevation will be 138 ft. Footing elevations are expected to be least 2 ft lower. Accordingly, site specific explorations should extend to an elevation of about 132 ft. or lower, in order to dewrttnine soil conditions below IN: footing. At tale northeast corner of the home, this would require explorations to at least 23 ft. Sitc specific explorations for the proposed dwelling include five hand -excavated test pits accomplished by Dennia M. Bruce as part of the current project geotechnical investigation, and test pit TP-2 excavated by Terra in 1.989. As described in Brace's July 27, 1998 geotechnical report, the five current test pits wem cxcavattd to depths of less than 3 ft below existing site grades. Based on the topography indicated on the pt�liminary plat (which may not be current), the current test pits would not have penetrated much below an elevation of about 140 ft. Ourcopy of Brace's geotechnical report did not contain a map showing the location of the current hand -excavated test pits. Based on our understanding of the proposed location of the house and of Torra's test pit TP-2, TP-2 is located outside of the apparent footprint of the house. Similarly, Terra's test pit TP-4 and boring B-1 are off site and relatively close to the street (Prelinunary plat). 3 t-ANOAu AsSOCIATEs f0/D9/98 L\PROJSCl'�o73\u�,1D�ALi.C7r: OCT- 9-98 FRI 16:26 LANDAU TACOMA FAX NO. 2639262631 P,05 With the exception of boring B-1. none of the explorations conducted at or near the proposed house location extend to, or below, elevation 132 ft. Consequently, the explorations listed above do not meet all of the requirements of ordinance 2661. In addition, no explorations of appropriate depth or Intent have been eonducted'at the back of the lot where existing site grades are significantly higher. As a result, there does not appear to be sufficient site subsurface information available at this time to adequately address site geotechnical issues, particularly those described in the following paragraphs. According to the house elevations shown on Sheet I of the plans, the basetneni floor rlcvation will be 138 ft and the main floor elevation will be 149 ft. The main floor elevation will be slightly above the finished grwnd surface along the cast (uphill) side of the house. According to contours shown on the drainage plan (which approximate the elevations shown on the preliminary plat), the basement floor will range from about 15 to 20 ftbelow existing site grades at the'southeast and northeast corners of the house, respectively. Excavations for the footings will extend about 2 ft (or more, depending on exposed subgrade eonditiuna) b4low the basement door elevation. The depth of excavation required to construct the footings and basement concerns us for the following reasons: 1. Soil and groundwater conditions expected at the site would likely be classified as Tyre C according to excavation safety guidelines described in Part N of Chapter 296-1.55 of the Washington Annotated Code (WAC). For Type C soil, WAC 295-155 limits slopes of less than 20 ft in height to an inclination of 1 �hH:I V (horizontal to vertical), or flatter. Excavation slopes higher than 20 ft must be designed by a geotechnical engineer. Bruce-$ geotect+nlcal report recommends that temporary slopes not be steeper than i 1t 1 V, which appears to suggest that slopes could be steeper than allowed under WAC 295-155. Given the reported presence of shallow groundwater and collapsing soil conditions (Terra 1989), it is our opinion that slopes stceprr than IVzH:I V ntay be inappropriate_ In fact, actual temporary slopes may need to be flatter than 15hH:1 V. 2. Based on our understanding of the hou3c. position and site topography, temporary slopes of IIAH:1V may not daylight because of the steep slope to the owt of the house. Accordingly, excavation for the house and foundations will likely require temporary shoring- The geotechnical report does not provide recommendations for temporary shoring. Relatively deep explorations for shoring design may be required. 3. Information in the documents we reviewed implies that the adjacent lots have been developed (we did not do a reconnaissance to verify this). ff open excavation without shoring is attempted, the excavations would likely extend onto neighboring properties, particularly Lot 7 to the south. Beyond requiring a constniction easement to accomplish, such an excavation could impact existing structures on those lots. Since the site data (including the outdated site topographic survey) does not provide current information for a distance of 50 ft beyond the property bounclaries (as required under Ordinance 2661), the potential for such impart cou ld exist for both open and shored excavations and should be addressed in the geotechnical report. 4_ If open or shored excavations are accomplished, there is the potential for those excavations to impact the existing groundwater drainage system on the slope to the east of the site. Excavation design and execution should include provisions for protecting the groundwater drainage eystem. Those provisions should be clearly indicated on the plans. 3n/o9i9e :�,a o7ect�o-a�o .iouaacl.�Te 4 LANDAU ASSOGIATE8 OCT- 9-98 FRI 16:27 LANDAU. TACOMA FAX NO, 2539262631 P106 S• Subgrade conditions for the footings are unknown since the explorations did not extend to below the anticipated footing subgrade. elevation. Bruce recommends (and the plans or show) of an allowable bearing pressure of 2,000 pounds per square foot (psf) be consistent with existing soil conditiots below the expected footing elevation. It should be noted that for Lot 3 of the Lorian Woods development, Terra (Terra 1991) recommended an allowable beating pressure of 1,200 psf for footings supported by coil conditions Similar to those found on Lot 6. 'In the abkrice of specific soil information at depth, it is our opinion that it is premature to recommend an allowable bearing pnessure'of 2,000 psf. In addition, the geotechnieal report recommends both a 2,000 psf and a 3,000 psf allowable Mooring pressure. Only one beating pressure should be provided, unless specific alternate applications are described. Based on our interpretation of the location of the house, it appears that the house will willb drainage e located over a buried tight line discharge pipe associated with the existing upslope �, u .system. if so, excavation for the house would require removal and relocation of the tight line pipe. The location of the pipe line should be confirmed (along with other existing site conditions), and plains should be preps for pipe line relocation, if required. There is conflicting Information in the submittal package regarding site etorrnwater drainage. The plans included with the grading and drainage calculations show an infiltnition trench located to the west of the house. The land clearing and tl, a cutting plan shows a dctentiun pipe ntt the end of the driveway with an apparent discharge to existing common storrnwater facilities. 'The geotechnieal report discusses connection to existing stormwater facilities in the street. In our opinion. discharge to existing tight line stcmnwater facilities would be preferred. Discharge to an infiltration trench embedded in the slide &,bris would be contrary to efforts undertaken in the Meadowdale area since the mid-1980s to control and lower area -wide groundwater levels- We suggest that all references to such a discharge system be removed from thesubmittal documents. If a detention system is to be constructed, a drainage plan with calculations should be submitted as part of the application. - Sheets 9 and 10 of the house plans show three conflicting, details of the foundation drainage System. Foundation drainage design is discussed in the Votechrucal report, but specifications regarding material type and placement are not included in the plans or in any other submitted document. A building section detail on sheet 9 calls for connecting the footing drain to an approved drainage system. Basement wall details on Sheet 10 call for the clralns to daylight to gravel. Foundation drainage, pauticularly along buried basement walls, may be critical at this site. It is our opinion that the footing drains should be tightlined to an existing stormwater collection system. We suggest that the design professionals reassess the foundation drainage issue and rcvise the plans to eliminate inconsistencies and provide a suitable and buildable foundation drainage system. There is a growing consensus within the gcotechnieal community that filter fabrics, if improperly matched to site soil conditions, plug and ccage to function over time. If that were to happen at the site, the function of the foundation drain could he adversely affected. We are not suggesting that a fabric should not be. used (or that those recommended are inappropriate); we are suggesting that the geotechnical engineer revisit using a filter fabric and confirm that his rec otntnendation5 arc appropriate, LANDAU ASSOCIATES 10/09/99 1•`.V1t0)6l"r\074\".10\PAK1.LTR .00T— 9-98 FRI 16:28 LANDAU TACOMA FAX N0. 2639262631 P.07 Dennis Bruce's report makes Specific recommendations for foundationlrctaining wall bncktill, which are not reflected on the drawings. Backfill material type(s), quantities and compaction requirements should be clearly shown on the drawings. The plans indicate that a large rockery is planned for the yard area to the east of the house and smaller isolated rockeries will be located along the north and south walls of the house. A large rockery to the cast of the house is currently shown on the plans, and will range from about d to 8 ft in height and likely retain fill or existing eolluvium/slide debris. In light of the probably need for temporary shoring, as noted previously; and the potential for debris flows from the bluff (discussed below), we recommend the lead design professional and geotechTtical enginee►• re- evaluate the planned rockery along the east (uphill) side of the borne. Consideration should be given to encompassing the temporary shoring with the permanent wall. In our opinion, a cast -in - pure concrete retaining wall, with catchment.capaeity and designed for impact loads, is the minimum retaining system which should be allowed at this location. Elsewhere on the property, rockery walls that are higher than 3 ft and support fill or soil that cannot stand vertically on its own must be permitted. according to City guidelines. In addition, an engineered design lady need to be prepared for the rockery permit. The geotechnical report does not address rockery design or construction, and a rockery design is not provided on die plans. We recommend that a rockery design be prepared coneietetit with City guidelines and guidelines published by the Associated Rockery Contractors. The design should include details and specifications for wall drainage and drainage discharge. • A "French type" interception drain along the eastern property line is recommended in the geotechnical report. The drain would be about 36 inches deep, and, we assume, be connected to existing stormwater collection facilities. Based on our understanding of site conditions, it appears that the drain would be constructed in backiill for the house basement walls, or along the alignment of the existing city trunk storm drain line. In either case, we question the utility of installing the drain. We su9Frt that the need for the French drain be re-examined using up-to-date site information. If it is determined the drain is needed, subsequent submittals should include drain design details and specify how collected drainage is to be discharged_ • The geoteclurical declaration and stat.eincnt of risk by Dennis Bruce appeals to be incomplete. According to our understanding of the application chcckliA the geotechnical engineer must include "an evaluation setting forth the statistical probability (percentage) of earth movement within a 25-year period, the susceptibility of the task, or hazard to correction, by on -site improvements and the measures taken to mitigate the risk or hazard." Dennis Bruce has included the phase in the quotations in his statement of risk_ It is our understanding that the above phrase is intended to provide direction to the l cotechrdcal engineer, and not for inclusion in the text of the statement. Bruce does state in the geotechnical report that the risks imposed by the development, both on- and off -site will be minimal The City should review these statements and determine if they are acceptable. The geotechnical report provides estimated total and differantial settletnents of about r/2 in and � in, respectively, for footings founded on competent native soil or structural, fill. As described above, the native soil underlying the site to below the expected footing elevations appears to be relatively soft or loose slide debris containing buried trees and organic material. It is possible that voids may be preseut or could develop over time within the slide debris due to clecomposition of buried trees and other organics. Based on these conditions, we would expect the compressibility 10/09/98 I: PK0JttCT\074NW9.ra\PAK11TR 6 LANDAU AsSOGIATES 4CT- 9-98 FRI 16:29 LANDAIITACOMA FAX N0, 2539262.531 P.OB of die slide debris to vary across the site depctrding on the consistency of the slide debris, the thickness of organic zones, and the presence of voids. Accordingly, it is possible that total and differential settlements across the house footprint could be higher than those described in the geotechnical report, and that some long-term settlement of the structure could occur. A discussion on potential impacts to the planned three-story masonry chimney and other brick work dtrc to potential future settlement, should be provided by Mr. Bruce: Information provided in the environmental checklist appears to contradict conditions described in the geotechnical report and information contained in other submitted documents. For example, the checklist states that site grades are not steeper than 18 percent, while the geotechnical report states that the site grades vary from 5 to 30 percent. Our own calculations Indic arc that Site grades may be steeper than 30 percent. Part of the submival process includes input to and review of the environmental checklist by the geotechnical engineer_ We suggest mfining tile. environmental checklist based on current site information and with input by the geotechnical cogincar_ The 1989 Terra Report describes site risks due to various landslide activity which could occur on subdivision property, and concludes that the highest risk areas are associated witll the eastern bluff. While Terra also concurs that all lots. as proposed in 1989, are "buildable," the lot line configuration apparently'changed after the report was issued. In addition, Terra notes that debris flows from the bluff areas have not reached the lower slopes for the past 30 years (now 39 years). home) The fact that Terra encountered "numerous logs" in test pit TP-2 (west of the proposed demonstrates,that larger debris flows have likely reached the proposed home site. in the not -too - distant past. • In our opinion, the slope above the proposed residence should be evaluated by a geologist experienced with Puget Sound bluff processes. Natural and human causc;d runoff at the top of the bluff, ground crackslother evidence of pending slope failure and/or any other pertinent features should be evaluated during that inspection. The fact that only small events have been noted in approximately the Iasi 40-year period may be increasing the risk of future, larger failures, and should be considered during the evaluation. The lead design professional should use the findings from that study to evaluate cite constraints and/or the need for supplemental engineered features (such as catchment/deflection walls, Brugg`rm cable retaining systctnsg�rein forced foundation walls, "soft—'walls/floors, special drainage, selective tree removal, etc.). In summary, the information provided in the stlbmittltl package is dated, incomplete, and inconsistent.` Bayed on the kdza. of the house, we anticipate the project represents a significant investment. That investment could be jeopardized and lives threatened by basing the design on .Information that is neither current (site topography) nor sufficient (subsurface soil and slope conditions). A de-Rign based on up-to-date and complete information would result in better structural performance, would limit construction claims due to unforseon conditions, and reduce risks to property and life due to future landslides. We recommend that the documents be returned to the applicant for further action. A lead clu—sign professional shouldbe designated. The lead design professional should review the plans and other documents -and make whatever appropriate changes are necessary it, order to be consistent with the requirements of Ordinance 2661. In addition, the design professionals (Geotechnical Engineer, Structural Engineer, and Civil 7 tANDAu ASSOCIATES 10J0719s L\PRAJECT`'1074\Ui4.rC\PAKI.LTR ` OCT- 9-98 FRI 16:30 LANDAU TACOMA FAX NO, 2539262531 P, 09 Engineer responsible for site stormwatcr drainage dcsign) should evaluate and comrn( rnt on specific issues raised herein, plmse call if you have questions eonceming this review, or require the services of Landau Associates for subsequent review services. LANDAU ASSOCIATES, INC, By: ;�,�Wade Gilbert, P,E. Senior Project Geoteeltnical Fngineer Reviewed by: William D. Evans, CPG Associate JWG/WDE/cyb No. 74079.10 Attachments: List of Documents Reviewed 1010919P t:u,xOJECT\O%410/9.101PAK1.I:IR S LANDAU ASSOCIATES OCT- 9-98 FRI 16:30 LANDp1I. TAC011A FAX NO, 2539262531 P, 10 ATTACHMENT 1 LIST Oft NIATERIAI,S REVIEWED • Shea s 1 through 10, Proposed Residence for Mr. and Mrs. Clear. Pak, Phil King Designs, MY 13, 1998. • Sheet 1, Robert Anderson Topography, Group Four, Inc., January 18, 1988, • Shea 2, Preliminary Plat Topography, Existing Utilities, Existing Drainage System, Marge Tree Survey, Lorian Eatcates PRD, DOWL Engineers, September 26,1989. • Plot Plan (residence layout), unknown origin, undated. Environmental Checklist, Chun Pak, data erased. Land Ckmiring and free Cutting Plan, Lot h Lorian Woods, origin unknown, undated. • Geoteehnical Evaluation, Proposed New Residence, I6109 - 73rd Place blast, Edmonds, Washington, Dennis M. Bruce, P-E:, July 27, 1998. • Grading and Drainage Calculatiore.x jor Chun Pak, H. N. Lehtinen. August 7, 1998. Statement (geotechnieal declaration), Dennis M. Bruce, P.E., July 30, 1998. • Engineer's Declaration, Nick Lehtlnen, Engineer, August 17, 1999. • Vicinity Map, undated. • Report of Geotechnical Consultation, GeoEngincers, Inc., February 28, 1985. • Review of Geoteehnical Report and Proposed Subdivision Plmis, Proposed Anderson Subdivision (Lorian Estates), Meadowdale Area, Edmonds, Washington, Landau Associates, Inc., November 17, 1989. • Geotechnical Review, Proposed Lorian Woods Subdivision, A•leadowdule Area of Edmonds, Washington, Landau Associates, Inc., June 25, 1990. • Georev]Wcal Report. Meadow Beach, Lots 54 to 57, F.dnwnds, Washington (for Robert, nd Joann Anderson), Terra Associates, Inc.. June 6,1989. •. Warhol Residence, Lot3, Lorian Woods, Edmonds, Washington, Terra Aisociaw,,,, Inc., June 11, 1991. e0t091ga e:srxolec-rso74\079.takraxi.L7x 9 LANDAU ASSOCIATES I FPOM : N.LEHTINEN Engineering PHONE NO. : ^06+252+'2'73 Aug. 17 1998 05:47PM P1 H N Lehtinen Structural/ Civil Engineers 3216 Wetmore Ave. Everett, WA 98201 (425)252-2373 LEAD PROFESSIONAL STATEMENT AUG 18 1, the Engineer submit a signed and stamped statement on the design drawings that I have reviewed the geotechnical reports and understand its recommendations. I have explained to Chun H. Pak the risk of loss due to slides on the site, and has report and established measures to reduce the potential risk of injury of damage that might be caused by any earth movement predi ted the report. AA r ri AUG STATEMENT aTREET FILE I, the geotechnical engineer prepared the report and submit a signed and stamped statement to the Building Department. I duly state that in my judgment the plans and specifications prepared by the structural engineer conform to the recommendations in the geotechnical report and, that the risk of damage to the proposed development, or to the adjacent properties, from soil instability will be minimal, subject to the conditions set forth in the report, and that the proposed development will not increase the potential for soil movement and, the statement include, as a condition, an evaluation setting forth the statistical probability (percentage) of earth movement within a 25 year period, the susceptibility of the risk, or hazard to correction, by on -site improvements and the measures taken to mitigate the risk or hazard. LOT #-& Geotechnical Engineer Dennis M. Bruce, P.E. 17814 8th Ave. N.W. Shoreline, WA 98177 (206) 546-9217 FAX (206) 546-8442 r'12 ul �c 114de IA p�/faIt- -#131q y lt,pjl e ol�r �l�lg9. S/;f /� /0%. RECEIVE®®® MAR 2 7 2000 STATEMENT DEVELOPMENT SERVICES CTR. CITY OF EDMONDS I,.the applicant/owner of the site submit a signed and notarized statement to the Building Department. I duly state that the accuracy of all permit submittal information is warranted by myself in a form which relieves the City and its staff from any liability associated with reliance on such permit application submittals. While an application may reference the reports of prior public consultants to the City, all conclusions shall be those of myself and my design professionals and, that I understand and accept the risk of developing in an area with potential unstable soils and that I will advise, in writing, any prosective purchasers of the site, or any prospective lessees of structures on the site, of the slide potential of the area. Property Owner - Chun H. Pak 3828 NE 110th Seattle, WA 98125 (206) 365-1230 D,464! 31L$law 9 STATE Of WASIIINGTON, IACKNOWLEDGMENT - Individual ss. County of 61 ()if this day persmtally appenred before site � /�� k. _ to file known to be ire individual(s)described in and who executed fire within and foregoing iustrutucnl, and acknowledged Ihat /Z� signed the same as f free nfid voluntary act and deed, for the uses and purposes therein mentioned. GIVEN under my hand and official seal this la Ae-e day of diet� , I 9!5� 2. �►•: NOT 10 � �9< :za . a y� :9pG&LICA Ge L �•'4/QIr9 ZQ-•i Hillary Public in •a`nu..••••`Q�� tile State of IVaslrills (on, residing at o•'K'•••:••�ASHG a00 Myuppuifihocul expires S'1'A'fE Of- WASIIINGTON, ACKNOWLEDGMENT - Corpotale s s. Co utly of On this day of 19__, befune fife, the ufiderslgned, a Nuuay Public in and for the State u( Washington, duly eummissioned and sworn, personally appeared _ and _, to file known to be the President and Secretary, respectively, of the corporation that executed the foregoing insttunrcnt, and acknowledged the said iaslruntasl to be due flee and voluntary act and deed of said corporation, for the uses and putposcs therein mentioned, and not oath slated 11141 autlwrlted to execute the said Instrmnent and that due seal affixed (if ally) is the corporate seal of said cotporatiou. Witness my hand and official seal hetetn affixed the day and year fast at - Notary Public in and far the State of 111whington, resisting fir My :yryrtrinuncnt expires This jurist is page of -- and is allached W d;utcd 00- l.c-_998 ad; aeAl1 FP.OII JIrl' ;?1rur : TY CORP. 116, TO :�_: 1 . 0 Enginesx s D :,clamtion the Enpaee�r of Record,.= subnutdng a signed az�d stamped rian statement o.1 the dtawir�gs and ,Oils ,.report fot loud °foLn° and have Woods. Y ha:,:. read and undetstanG its recdlomme daP-pVnee . / draw ings incorporated tho:.e recommendati(ms into anc; nave escaalishc.j measures to rcJLice the potentia dicted�ir. tf3dL ri V t a� k.zujt'� ► Y zny cd]L'l�i 1I10`em p i !1C IV Cx 1 V xv ilcl iid: vtcii A ade aware of the risk of Litt: rcpvrC•' k' 7 loss due to slides on the site. 'v �'e::11�JS. Pne �'G'CiCtt, VA ';5201 (425) 252-y373 1> e4" lol/yp JUL 1: 2 1999 DEVELOPMENT SERVICES Cff'Ff!� CITY OF EDMONDS OCT- 9-98 FRI 16!24 LANDAU TACOMA FAX NO. 2630262631 P,02 LANDAU AASSOCIATES, INC. Environmental and Qootechnnal Sttvlces October 9,1998 City of Edmonds 121 Sth Avenue North 'TR�' �- Edmonds, WA 98020 � t � FILE Attn: Ms. Lara Knaak RE: PRELIMINARY CEoTE,CHNicAi. R wiRw F'ROPOSF:D PAK RE9IDEAICE I,OT ti, LO LAN WOOI?S Di y-ELOPMENT 16�109 73T1I PLAc►E'IVE, NWMW0KEE-ARFA EDMONDS, WASHINGTON Dear Ms. Knaak: in accordar= with your request, we have completed a preliminary geotechnic:al review of plans and other submitted documents concerning construction of the proposed Pak residence- Since the proposed residence is located within the Meadowdale slide area, our review follows the general wquirements outlined within -City Ordinance No. 2661 and Chapters 19.05 and '20-15 of the Edmonds Community Development Code (ECDC). A list of the documents we reviewed (including earlier site -related material from our files), is included as Attachment 1. In 1989, Landau Associates reviewed a gcote_schnical report prepared by Terra Associates, Inc. (Terra) for die proposed Anderson short plat project (subsequently known as Lorian Woods), which includes the subject Lot 6. Terra's report, June 6, 1989, provides general geotechnical information relative to overall development of the short plat and states that die platted property is suitable for construction of single-family residGlces. In our letter to the City dated November 17, 1989, Landau Associates concluded that Terra had provided an adequate description of the property and that their conclusions appeared reasonable for the information obtained at that time. However, we further stated in our letter that development of individual lots Would depend on adequate ch=cterization of soil and groundwater conditions at each individual lot, and would require lot specific geoteehnical design and constnuction criteria not provided in Terra's 1989 report - The short plat was approved by the City, and we understand some of the individual lots have been developed. As part of our current review, we also reviewed Terra's 1991 geotechnical report prepared for development of Lot 3 of I orian Woods. These reports are listed on Attachment 1, along with a summary of documents submitted by the applicant. wAPATo CRFEK PLACE • 4210. 20T11 S rizEf,T L.. SUrrE F • TACOMA WA 913424-1 M73 (2i3} 925 7497 FOE' 21D 920-2531 E-M311: lalu@Laudeuinc.cem F-dmvnlds 61,.?Ann TauLn� *OCT- 9-98 FRI 16!26 LANDAU TACOMA FAX NO. 2639262631 P.03 The Lorian Woods development is situated on a topographic bench within the Meatlowdaie slide area. According to Terra's 1989 report, the bench is composed primarily of slide debris associated with large-scale, ancient landsliding. To the cast of the bench is a relatively steep bluff elope (landslide headscarp) composed of undisturbed native sail that rises upward toward the east to a crest about 100 to 150 ft above the bench. Typical bluff slope inclinations vary from less than 40 percent near the toe to more than 100 percent in upper portions of the slope. The flatter slopes at the toe of the bluff are attributed to debris flows and smaller slides off the steeper upsiope portions of the headscarp. To the west, the bench slopes down to 74th Place West at generally similar inclinations. Lot 6 is located on the east side of 73rd Place West at the toe of the bluff slope. According to the topography shown on the 1989 preliminary plat, elevations across the lot vary from about 144 ft along the west boundary to about 170 ft near the northeast corner. From the toe of the bluff slope, the lot slopes downward to 73rd Place West at grades of between about 10 to 35 percent. Tetra's 1989 assessment of site conditions is based in pan on subsurface information from several test pits and two borings advanced w part of their 1999 study. We understand that Terra's test pit TP-2 is located aii Lot 6 near the street (preliminary plat). Other nearby explorations by Terra include lest pit TPA on Lot 5 (preliminary plat) and buying B-1 located just west of Lot 7 (preliminary plat). Conditions encountered in test pits TP-2 and TP-4 consisted of mixed soil containing organics and numerous lags (e.g., landslide debris). Groundwater seepage was encountered within 3 to 4 ft of the ground surface, and the side walls of the test pity were reported to have collapsed during excuvation. Conditions encountered in haring B-1 are similar, and suggest that the slide debris at the site extends well below the bottom of test pit TP-2 (over 14 ft). While the document package we received was relatively complete, some items required by the application checklist were not included. The items not included are: Checklist Item Number Description Critical Areas Checklist 2 Lead Design Professional Designation and Statement I l Affidavit of Notice of Application 12 Applicant/Owner's Liability Landslide Acknowledgment Declaration 15 Applicant/Owner Covenant to Notify and Hold Harmless The lack of these documents did not significantly affect our ability to perform this preliminary geotechnical review. to/tl9/00 L\PAOJMT\071\679.10�,PAVI.LTiL 2 LANDAu Asso(:IATEs OCT- 9-98 FR 116 : 26 ! AND411 TACOMA FAX NO. 2639262631 P, 04 our review of the documents submitted for this project (and of material from our files) indicates several issues which require additional attention or clarification. These aresurraT"arized as follows: • Plans related to this project are based on survey information prepared in January 1988 and a preliminary short plat prepared in 1989. since those documents were prepared. the common improvements have been installed and rmidences have been constructed in the Lorian Woods subdivision. None of the submitted documents clearly indicate the position of the house with respect to the lot boundaries shown on the preliminary plat, not is it cledr from the submitted documents where the actual lot boundaries, common improvements, or existing houses an; located. The architectural plans are signed by Phil King, but are not stamped. Based on our understanding of the submitted information, and assuming that the lot boundaries are as shown on the preliminay plat, it appeals that par[ of the house will be lmaLed on the north and of Lot' . Either we have misinterpreted the house location --the actual platted lot boundaries are different from those shown on the preliminary plat --or the submittal package shows an incorrect location. It has been over ten years since the site topographic reap was prepared. Ground surface changes are likely to have occurred at the site over tine past decade and certainly hava occurred where adjacent common unprovements have been constructed. Using outdated information as a basis for design could lead to an improperly designed structure; and result In significant and costly problems during construction and over the long-term. According to the requirements of Ordinance 2661, a topographic map must be submitted showing the property lines, off -site structures within 30 ft of the property, lower floor and footing locations of off -site structures within 50 ft of the property, existing underground utilities on- and off -site, and the proposed finished grade contours. In our opinion, the submitted documents do not provide that information as of the time of submittal and should not be used for purposes of design or locating the house. Subsurface conditiats do not appear to have been adequately investigated. Under Ordinance 2661, site specific geotechnical explordtions are generally required as part of the geotechnical investigation. The explorations shmild extend to a depth that includes the soil influenced by or supporting the foundations. For spread footings, that depth is usually a point below the bwe of the footing equal to a distance of at least twice the width of the footing. floor elevations on Sheet 1 of the plans indicate.that the basement floor elevation will be 138 ft Footing elevations arc expected to be least 2 ft lower. Accordingly, site specific explorations should extend to an elevation of about 132 ft, or lower, in order to determine soil conditions below the footing. At the northeast corner of the home, this would require explorations to at least 23 ft. Site specific explorations for the proposed dwelling include five hared -excavated test pits accomplished by Dennis M. Bruce as part of the current project geotechnical investigation, and test pit TP-2 excavated by Tcrra in 1989. As described in Brace's July 27, 1998 geotechnical report, the five current test pits were excavated to depths of leas than 3 ft below existing site grades. Based on the topography indicated on the pruliminary plat (which may not be current), the current test pits would not have penetrated much below an elevation of about 140 ft. Our copy of Bruce's geotechnical report did not contain a map showing the location of the current hand -excavated test pits. Based on our understanding of the proposed location of the house and of Torra's test pit TP-2, TP-2 is located outside of the apparent footprint of the house. Sin►ilarly, Tetra's test pit TP4 and boring 19-1 am off site and relatively close to the street (preliminary plat). 10l09/ea L•iPRU)&GT107a\U7S,,l0%.PALl.L7k 3 LANOAu ASSOCIATES OCT- 9-98 FR1 16:26 LAND6II TACOMA FAX NO. 2639262631 P106 With the exception of boring B-l. none of the explorations conducted at or near the proposed house location extend to, or below, elevation 132 fL Consequently, the explorations listed above do not meet all of the requirements of ordinance 2661. In addition, no explorations of appropriate depth or intent have bccn conducted at the hack of the lot where existing site grades are significantly higher. As a result, there does not appear to be sufficient site subsurface infarntation available at this time to adequately address site geotechnical ieeues, particulauly those described in the following paragraphs. According to the house elevations shown on Sheet I of the plans, the basement floor elevation will be 138 ft and the main floor elevation will be 149 ft. The main floor elevation will be slightly above the finished ground surface along due east (uphill) side of the house. According to contours shown on the drainage plan (which approximate the elevations shown on the preliminary plat), the basement floor will range from about 15 to 20 ft below existing site grades at the southeast and northeast corners of the house, mspect.iveiy_ Excavations for the footings will extend about 2 ft (or more, depending on exposed subgrade cvnditiuue) below the basement floor elevation. The depth of excavation required to construct the footings and basement concerns us for the following reasons, I. Soil and groundwater conditions expected ar the site would likely he classified as Tyre C according to excavation safety guidelines described in Part N of Chapter 296-155 of the Washington Annotated Code (WAC). For Type C soil, WAC 295-155 limits slvpcg of less than 20 ftin height to an inclination of 11/214:IV (horizontal to vertical), or flatter. Excavation slopes higher than 20 ft must be designed by a geotechnical engineer. l3nice's geotechnical report recommends that temporary slopes not be steeper than 1 HA V, which appears to suggest that slopes could be steeper than allowed under WAC 295-155. Given the reported presence of shallow groundwater and collapsing soil conditions (Terra 1989), it is our opinion that slopes stcepor than lVzH:l V ntay be inappropriate_ In fact actual temporary slopes may need to be flatter than IV'14:1 V. 2. Based on our understanding of the house position and site topography, temporary slopes of IIAH:1V may not daylight because of the steep slvpc to the east of the house. Accordingly, excavation for the house and foundations will likely require temporary shoring. The geotechnical report does not provide recommendations for temporary shoring. Relatively deep explorations for shoring design may be required. Information in the documents we reviewed implies that the adjacent lots have becn developed (we did not do a reconnaissance to verify this). if open excavation without shoring is attempted, the excavations would likely extend onto neighboring properties, particularly Lot 7 to the south. Beyond requiring a eonsttuction easement to accomplish, such an excavation could impact existing structures on those lots. Since the site data (including the outdated site topographic survey) does not provide current information for a distance of 50 ft beyond the property boundaries (as required under Ordinance 2661), the potential for such impact could exist for both open and shored excavations and should be addressed in the geotechnical report, 4. if open or shored excavations are accomplished, there is the potential for those excavations to impact the existing groundwater drainage system on the slope to the east of the Site. Excavation design and execution should include provisions for protecting the groundwater drainage eystem. Those provisions should be clearly indicated on the plans. IO/09/98 t:\16:0]BCI�O%�� •lO�PA[7.LTR 4 LANDAj ASSOCIATES OCT- 9-98 FRI 16:27 LANDAU TACOMA FAX NO, 2539262531 P,06 S. Subgrade conditions for the footings are unknown since the explorations did not extend to below the anticipated footing subgradc elevation. Bruce recommenduhich rnaporl�ma snot an allowable bearing pressure of 2.000 pounds per square foot (psf) y be consistent with existing soil conditions below the expected footing elevation. It should be: noted that for Lot 3 of the Lorian Woods development, Terra (Terra 1991) recommended an allowable beating pressurc of 1,200 psf for footings supported by sail conditions similar to those found on Lot 6. In the abscncc of specific soil information at depth, it is our opinion that it is premature to recommend an allowable beating pressure of 2,000 psf. In addition, the geotechnical report recommends both a 2,(M psf and a 3,000 psf allowable bearing pressure. Only one beating pressure should be provided, unless spcctfic alternate applications are described. Based on our interpretation of the location of the house, it appears that the house will be located over a buried tight line discharge pipe: associated with the existing upslope groundwatcr drainage system. if so, excavation for the house would require removal and relocation of the tight line pipe. The location of the pipe line should be confirmed (along with other existing site conditions), and plans should be prepared for pipe line relocation, if required. There is conflicting information in the submittal package regarding site etorrnwater drainage. The plans included with the grading and drainage calculations show an infiltration trench located to the west of the house. The land clearing and tree cutting plan shows a dctentivn pipe at the end of the driveway with an apparent discharge to existing common stor<nwater facilities- The geotechnieal report discusses connection to existing stotinwater facilities in the street. in our opinion. discharge to existing tight line st[mnwater facilities would be preferred, Discharge to an infiltration trench embedded in the slide (Loris would be contrary to efforts undertaken in the Meadowdale area since the mid-1980s to control and lower area -wide groundwater levels. We suggest that all references to such a discharge system be removed from the subnuttafl documents. if a detention system is to be constructed, a drainage plan with calculations should be submitted as part of the application. Sheets 9 and 10 of the house plans show three conflicting details of the foundation drainage system. Foundation drainage design Is discussed in the wotccluucnl report, but specifications regarding material type and placement are not included in the plans or in any other submitted document. A building section detail on Sheet 9 calls for connecting the footing drain to an approved drainage system. Basement wall details on Sheet 10 call for the clralrs to daylight to gravel. Foundation drainage, Vulicularly along buried basement walls, may be critical at this site. It is our opinion that the footing drains should be tightlined to an existing st.ormwater collection system. We suggest that the design professionals reassess the foundation dtninage issue and mvise the plans to eliminate inconsistencies and provide a suitable and buildable foundation drainage system - There is a growing consensus within the gcotcchnical community that filter fabrics, if improperly matched to site soil conditions, plug and cease to function overtime. If that were to happen at the site, the function of the foundation drain could be adversely affected. We tom not suggesting that a fabric should not be used (or that those recommended are inappropriate); we arc suggesting that the geutechnical engineer revisit using a fr1U:r fabric and confirm that his rec conmendations arc appropriate. 10/0ei98 1:1,i'ROJ6CI'\074\079.tu\PAICt,LTR 5 LANDAU ASSOCIATES OCT- 9-98 FRI 16:28 LANDA11 TACOMA FAX NO. 2639262631 P.07 Dennis Bruce's report makes specific recommendations for foundationlrctaining wall backfill, which are not reflected on the drawings. Backfill materiail type(s). quantities and compaction requirements should be clearly shown on the drawings. The plans indicate that a large rockery is planned for the yard area to the east of the house and smaller isolated rockeries will be located along the north and south walls of the from se.aboA to large rockery to the cast of the house is currently shown on the plaits, and will rang ft in height and likely retain fill or existing cotluviumislide debris. In light of the probably need for temporary shoring, as nixed previously, r+nd the potential fur debris flaws from the bluff (discussed below), we recommend the lead design professional and geotec:hnical engineer re- evaluate the planned rockery along the east (uphill) side of the home. Consideration should be given to encompassing the temporary shoring with the permanent wall. in our opinion, a cast -in - pure concrete retaining wall, with catchment capacity and designed for impact loads, is the minimum retaining system which should be allowed at this location. Elsewhere on the property, rockery walls that are higher than 3 ft and support fill or soil that cannot stand vertically on its own must be permitted, according to Cily guidelines. In addition, an engineered design may need to be prepared for the rockery permit. The geotec:hnical report does not address rockery design or construction, and a rockery design is not providedd on die plans. We recommend that a rockery design be prepared coneistent with City guidelines and guidelines published by the Associated Rockery contractors. The design should include details and specifications for wall drainage and drainage discharge. A "French -type" interception drain along the eastern property line is recommended itr lure Eeotechnical report. The drain would be about 36 inches deep, and, we assume, be. connected to existing stormwater collection facilities. Based on our understanding of site conditions, it appears that the drain would be constructed in backfill for the house basement walls, or along the alignment of the existing city tank storm drain line. In either case, we question the utility of instulfing the drain. We suggest that the need for the French drain be rc-exanuncd using up-to-date site information. If it is determined the drain is needed, subsequent submittals should include drain design details and specify how collected drainage is to be discharged_ The geotecimical declaration and statement of risk by Dennis Bruce appears to be incomplete. According to our understanding of the application c;hccklist, the geotechnical engin"r must include "an evaluation setting forth the statistical probability (percentage) of earth movement within a 25-year period, the susceptibility of the risk, or hazard to correction, by on -site improvements and the measures taken to mitigate the risk or hazard." Dennis Bruce has included the phase in the quotations in his statement of risk_ It is our understanding that the above phrase is intended to provide direction to the 900teclmical engineer, and not for inclusion in the text of the statement_ Bruce does state in the geotechnical report that the risks imposed by the development, both on- and off -site will be minimal. The City should review these statements and &-tcrmine if they are acceptable. • The geotechnieal report provides estimated total and differential settlements of tbnut ►/2 in and !/a in, respectively, for footings founded on competent native soil or structural fill. As described to above, the native soil underlying the site to below the expected footing elevations appearsbe relatively soft or loose slide debris containing buried trees and organic material. It is possible that voids may be present or could develop over time within the slide debris due to decomposition of buried trees and other organics. Based on these conditions, we would expect the compressibility 10/09198 1:\11N0JBCf\e74N07Y.r0\PAK11TR 6 LANDAu AsSOG ATE9 -OCT- 9-98 FR I 16 : 29 LANDAI I TACOMA FAX NO. 2539262531 N, 08 of the slide debris to vary across the site depending on the consistency of the slide debris, the thickness of organic zones, and the presence of voids. Accordingly, it is possible that total and differential settlements across the house footprint could be higher than those described in the geothnicitl report, and that some 1Gna term Settlement of the structure could occur. A discussion on potential impacts to the planned three-story masonry chimney and other brick work due to potential future settlement, should be provided by Mr. Bruce. • Information provided in the environmental checklist appears to contradict conditions described in the geotechnical report and information contained in other submitted documents. For example, the checklist states [fiat site grades are not steeper than 18 percent, while the geowchnical report states that the site grades vary from 5 to 30 percent Our own calculations indicam that site grades may be steeper than 30 percent. part of the submittal'process includes input to and review of the environmental checklist by the geotee finical engineer. We suggest mfining the environmental checklist based on current site information and with input by the geotechnical cng,inecr_ The 1989 Terra Report describes site risks due to various landslide activity which could occur on subdivision property. and concludes that the highest risk areas are associated with the eastern bluff. While Terra also concurs that all lots. as proposed in 1999, are "buildable," the lot line configuration upparently changed after the report was issued, in addition, Terra notes that debris flows from the bluff areas have not rewhed the lower slopes for the past 30 years (now 39 years). The fact that Tcrra cn;;ountored "numerous logs" in test pit TP-2 (west of the proposed home) demonstrates that larger debris flows have likely reached the. proposed home site in the not -too - distant past. • In our opinion, the slope above the proposed residence should be evaluated by a geologist experienced with Puget Sound bluff processes. Natural and human causui tunoff at the top of the bluff, ground erackslother evidence of pending slope failure and/or any other pcltinctit features should be evaluated during that inspection. The fact that only small events have been noted in approximately the Iasi 40-year period may be increasing the risk of future, larger failures, and should be considered during the evaluation. The lead design professional should use the. findings from that study to evaluate cite constraints andlor the need for supplemental engineered features (such as catchment/deflection walls, R uggTM cable retaining systems, rein forced ('uundation watts, "soft" walls/floors, special drainage, selective tree removal, etc.). In summary, the information provided in the yixbtnittal package is dated, incomplete, and inconsistent. Bayed on the site of the house, we anticipate the project represents a significant investment. That investment could be jeopardized and lives threatened by basing the design on Informadou that is neither current (site topography) nor sufl-rcicttt (subsurface soil and slope condition;), A design based on up-to-date and complete information would result in better structural performance, would limit construction claims due to unforseen conditions, and reduce risks to property and life due to future landslides. We recommend that the documents be returned to the applicant for further action. A lead cl-ign professional should.be designated. The lead design professional should review die plans and other documents and make whatever appropriate changes arm necessary in order to be con6istent with the requirements of Ordinance 2661. In addition, the design professionals (Geotechnic al Engineer, Stnictural Engineer, and Civil LANDAU ASSOCIATES 10109)9B L•\pgpjgCl".o7d\t17J.iC\pAKr_LTR OCT- 9-98 FRI 16:30 LANDAU TACOMA FAX NO. 2539262531 P,09 Engineer responsible for site stormwater drinnagc design) should evaluate and comment on specific issues raised herein. pimse call if you have questions concerning tt-ds review, or require the servlccs of Landlsu Associates for subsequent review services. LANDAU ASSOCIATES, INC. By: ;...Wade Gilbert, P,E. Senior Project Geoteehnical Fngineer Reviewed by: f William D. Evans, CPG Associate IWO/WDF1cyb No. 74079.10 Attachments: List of Documents Reviewed 10/09/99 I:U'ltOJECP\074\W9.10\PAhl-L7R 8 LANDAU ASSOCIATES OCT- 9-98 FRI 16:30 1.ANDp1t TACOMA FAX N0, 2539262531 P110 ATTACHMENT 1 LIST OF MATERIALS REVTENN78D • Sheets 1 through 10, Proposed Residence for Mr. and Mrs. Ch"r. Pak., Phil King Design&, July 13, 1998. • Sheet 1, Robert Anderson Topography, Group Pour, Inc., January 18, 1988. • Sheet 2, Preliminary Plat, Topography, Existing Utilities, Existing Drainage. Syetem, Marge Tree Survey, Lortan Estaaes PRD, DOWL Engineel5. September 26,1989. Plot Plan (residence layout), unknown origin, undated. Environmental Checklist, Chun Pak, date crowd. • Land Clearurg and Tree Cutting Plan, Lot 6 Lorian Woods, origin unknown, undated. • Geotechnical Evaluation, Proposed New Residence, 16109 - 73rd Place. West, Edmonds, Washington, Dennis M. Bruce, P-E„ July 27, 1998. • Grading and Drainage Calculatiorwfor Chu": Pak,14. N. Lehtinen. August 7, 1998. Statement (geotechnieal declaration), Dennis M. Bruce, P.E., July 30, 1998. • Engineer's Declaration, Mick Lehtinen, Englneer, August 17, 1998. ■ Vicinity Map, undated. Report of Geotechnical Consultation, GeoEngineers, Inc., February 28, 1985. • Review of Geotechnical Report and Proposed Subdivision Plans, Proposed Anderson Subdivision (l t)rian Estates), Meadowdale Area, Edmonds, Washington, Landau Associates, Inc., November 11, 1989. • Geotechnical Review, Proposed Lorian Woods Subdivision. Aleadowdale Area of Edmonds, Washington, Landau Associates, Inc., June 25, 1990. ■ Gooteclutical Report. Meadow Beach, Lots 54 to S7, Edmonds, Washington (for Robert anct Joann Anderson), Terra Associates, Inc.. June 6, 1989, • Warhol Residence, Lot 3, Lorian Woods, Edmonds, Washington, Tcrrn Associates, Inc., June 11, 1991. 9 LANDAU ASSOCIATES 10/09/98 E\PROIEC'r\u74\079-10k1'AK1.L7R RETURN ADDRESS: City of Edmonds, City Clerk 121 5th Avenue North Edmonds, WA 98020 Reference #: CONFORMED COPY 200006050422 06/05/2000 01:16 PM Snohomish P.0007 RECORDED County COVENANT OF NOTIFICATION AND INDEMNIFICATION/HOLD HARMLESS Grantor(s): (2)1U. e�h,. A✓ , Additional on pg. Grantee(s): City of Edmonds Legal Description (abbreviated): 'Sec_ Twn .c� 7 Rng_QtrJ ' OR Lot 4� Block 00 0 Plat 000 Assessor's Tax Parcel EN(s): (1) -7 90 V--d 00 —DOS—OO D 6 (2) _--Assessor's Tax Parcel EN not yet assigned CITY OF EDMONDS APPROVED FOR RECORDING BY:�_ DATEzivilot)AGE It OF Under the review procedures established pursuant to the State Building Code, incorporating amendments promulgated by the City of Edmonds, and as a prerequisite to the issuance of a building permit for the construction of a residential structure and attendant facilities, the undersigned OWNERS of property do hereby covenant, stipulate and promise as follows: APPROVED FOR RECORDING: BY: DATE: PAGE Q— OF (_ 1. Description of Subject Property . This covenant of notification and indemnification/hold harmless relates to a tract of land at the street address of /,4'10,Y (insert street address), Edmonds Snohomish /County, Washington and legally described as: _ !�•�,� rc�S E� Spa ,d>en>.`S�� i r.�n"� � f�.yi �7`a� r•7' / l� 2. Notification and Covenant of Notification The above referenced site (hereinafter "subject site'l lies within an area which has been identified by the.City of Edmonds as having a potential for earth subsidence or landslide hazard. The risks associated with development of the site have been evaluated by technical consultants and. engineers engaged by the applicant as a part of the process to obtain a building permit for the subject site. The results of the consultant's reports and evaluations of the risks associated with development are contained in building permit file number� (insert number) on file with the City of Edmonds Building Department. Conditions, limitations, or prohibitions on development may have been imposed in accordance with the recommendations of APPROVED FOR RECO ING: BY: \� DA. O PAGE OF the consultants in the course of permit issuance. The conditions, limitations, or prohibitions may require ongoing maintenance on the part of any owner or lessee or may require modifications to the structures and earth stabilization matters in order to address future or anticipated changes in soil or other site conditions. The statements and conditions proposed by the OWNERS' geotechnical engineer, geologist, architect and/or structural engineer are hereby incorporated by reference from the contents of the file as fully as if herein set forth. Any future purchaser, lessee, lender or any other person acquiring or seeking to acquire an interest in the property is put on notice of the existence of the content of the file and the City urges review of its contents. The file may be reviewed during normal business hours or copies obtained at the Building Department, City of Edmonds, 121 5th Avenue North, Edmonds, Washington 98020. 3. Indemnification and Hold Harmless The undersigned OWNERS hereby waive any and all liability associated with development, stating that they have fully informed themselves of all risks associated with development of the property and do therefore waive and relinquish any and all causes of action against the City of Edmonds, its officers, agents and employees arising from and out of such development. In addition, the OWNERS on behalf of themselves, their successors in interest, heirs and assignees, do hereby promise to indemnify and hold harmless the City of Edmonds, its officers, agents and employees from any loss, claim, liability or damage of any kind or nature to persons or property either on or off the site resulting from or out of earth subsidence or landslide hazard, arising from or out of the issuance of any permit(s) authorizing development of the site, or occurring or APPROVED FOR RECORDING: BY � DATE—S- PAGE 4 OF —to— arising out of any false, misleading, or inaccurate information provided by the OWNERS, their employees, or professional consultants in the course of issuance of the. building permit. 4. Insurance Requirement. In addition to any bonding which may be required during the course of development, the Community Services Director #/has not (strike one) specifically required the maintenance of an insurance policy for public liability coverage in- the amount and for the time set forth below in order to provide for the financial responsibilities established through the indemnification and hold harmless agreement above: 5. Covenant to Touch and Concern the Land This covenant of notification and indemnification/hold harmless touches and concerns the subject tract and shall run with the land, binding, obligating and/or in to the benefit of future owners, heirs, successors and interests or any other person or entity acquiring an interest in property, as their interest may appear. This provision shall not be interpreted to require a mortgagor or lender to indemnify the City except to the extent of their loss nor to obligate such persons to maintain the insurance above required. APPROVED FOR RECO ING: BY:E_ DATE: l PAGE_ OF DONE this /0 day of 1996, OWNER(S) By: By: By STATE OF WASHINGTON ) ) ss: COUNTY OF I certify that I know or have satisfactory evidence that C- h on i- ur+ QA IGs signed this instrument and acknowledged it to b (hi er) free and voluntary act for the purposes mentioned in this instrument. � n0�W,4 5- i MAIM L:\TEMP\BUILDING\MEADOVACOVENANT 0 199L. A�l1ii1 NOTARY C My commission expires: - dJ APPROVED FOR RECORDING: BY:\?--, _ DATE: PAGE _(Q_ OF STATE OF WASMNGTON ) ss: COUNTY OF Ir ) I certify that I know or have satisfactory evidence that WE h 0-1 P %, signed this instrument and acknowledged it to be (hi& free and voluntary act for the purposes mentioned in this instrument. DATED this _ a il 100 A , �s o NOTARY PUBLIC My commission expires: L:ITEMPIBUILDING%MEADOW-%COVENANT '� Landau Associates Environmental and Geotechnical Services 90, City .of Edmond - 121 5th Avenue North Edmonds, WA 98020 Attn: 'Ms. Lara Knaak R� . A�lv '11-- °Ey t oP�r ' iy99 �ry OF f '�oN ss CN May 28, 1999 RE: SUPPLEMENTAL GEOTECHNICAL REVIEW PROPOSED PAK RESIDENCE LO 6_ LORIAN WOODS DEVELOPMENT r6 09 73TIi PLACE WEST EDMONDS, ASHINGTON Dear. Ms. Knaak: This letter provides Landau Associates' review comments on additional geotechnical information prepared by,Mr. Dennis M. Bruce, P.E., (dated April 4, 1999), related to the above -referenced project. The additional geotechnical infonmation was submitted to the City of Edmonds (City) as part of a response to our preliminary review. Our preliminary review comments- are summarized in an October 9, 1998 letter to the City. In our October 9, 1998 letter, we listed several issues that needed additional, attention and clarification, which are briefly listed below: 1. Outdated site plan and topographic information. 2. .Inadequate investigation of subsurface conditions. .3. Issues associated, with temporary excavations to construct foundations. 4. Potential impacts to existing groundwater drainage system on the slope to the east of the site from open or shored excavations. 5. Inconsistency in recommended allowable soil bearing pressure between the Terra &'Associates (Terra) 1991 geotechnical report and the initial1998 Dennis M. Bruce Geotechnical report. 6.. Possible conflict of the house location and a buried tightline. discharge pipe associated with the drainage system on the slope to the east. 7: Conflicting infortnation in the submittal package regarding site stormwater drainage. 8. Conflicting details regarding .the foundation drainage system and lack of specifications of material types. 9:. Issues associated with a- rockery planned for the yard area east of the house, and other smaller rockeries. . 10. Issues regarding a proposed "French -type" interceptor drain along the eastern property line. WAPATO CREEK PLACE 4210 - 20TH STREET E. SUITE F • TACOMA. WA 98424-1823 (253) 926-2493 Fax: (253) 926-2531 E-mail: info@Iandauinc.com Edmonds Portland Spokane Tacoma 11. Incomplete statement of risk by the geotechnical engineer. 12. Incomplete discussion regarding potential differential settlement of the structure. 13. Contradictory statements between the environmental checklist and other documents submitted. 14. Inadequate evaluation of the slope above the residence. 15. In addition, several items were not included in the original submittal, including: Critical Areas Checklist; Lead Design Professional Designation and Statement; Affidavit of Notice Application; Applicant/Owner Liability Landslide Acknowledgment Declaration; and Applicant/Owner Covenant to Notify and Hold Harmless. The supplemental geotechnical report .prepared by Mr. Dennis M., Bruce, P.E. (dated. April 4, 1999) addresses or partially addresses above items 2, 3, 4; 5, 9, 10, 11,12, and 14. Items number 1, 6, 7; 8, 13, and 15 were not addressed in the supplemental geotechnical report:, According to the supplemental geotechnical report, an additional test pit (Test Pit — Pak) was excavatedto a depth of about 13 ft below existing ground surface. The test pit was located about 30 ft: east of the reported location of Terra's 1989 test pit, (TP-2), and is reportedly in the vicinity of the. proposed residence. However, information provided :to us in the original submittal does not contain an accurate drawing showing the actual location of. the proposed house, and since the resubmittal also does - not contain an accurate drawing, we cannot verify the test pit location. We recommend the City require submittal of an accurate site plan which shows lot lines, the proposed house location; "the locations of all relevant exploration points, and any other items required by, the ordinance. The ground surface elevation at the test pit Test Pit -Pak location, as estimated from a figure attached _to the supplemental report, is about elevation 153 to "154 ft.. Therefore, the test pit terminatedat about elevation 140 to 141ft. The constructionplans still indicate a basement finished floor elevation of 138 ft. [Note: Because of the proposed basement elevation, we recommended in our October 9; 1998 " letter.that"additional subsurface explorations be completed and extended to -elevation 132 ft.or lower to adequately evaluate subsurface soil and groundwater conditions.] The test pit excavated by Mr. Bruce did - not extend deep enough to characterize expected foundations soil- types.- In addition, the .soil types (e.g.. fill, slide debris, glacial soil, etc.) encountered in the test pit are not identified, and typical modifiers (e.g. . moisture contents) are not presented for all soil layers. We recommend the City require site explorations which extend below foundation level. Since the design anticipates the use, of "pinpiles", the explorations must be deep enough so that pin pile criteria can be developed: To address our comments on temporary shoring (aboveitem 3),'the supplemental geotechnical report states that temporary excavations will not exceed 12 ft, vertical and recommends using, stacked ecology blocks for temporary shoring. It appears from the report that temporary shoring will be contractor designed. Temporary shoring should be designed. by a licensed engineer. registered in the -State . of Washington (could be hired by the contractor), and the shoring plans submitted to the City'as"-part of 05/28/99 I:tPROJEC1'T074�079.101paksupplemental_I[r.da LANDAU ASSOCIATES 2 the building permit application.. In addition, the geotechnical engineer, must provide specific design - parameters, such as recommended. lateral earth .pressure(s), allowable soil bearing pressure, drainage requirements, etc. for design of temporary shoring. The 'supplemental report anticipates a significant dewatering effort to allow construction of the foundations. Since this appears to be a critical component of the project, we recommend that a dewatering plan be submitted to the City as part of the construction documents. As a minimum, the plan should include a. written description of applicable dewatering methods, discharge points, erosion/sedimentation control, monitoring requirements, and abandonment of the system. The plan could be prepared by the geotechnical engineer, lead design professional or a qualified contractor. Though the supplemental report concludes that properly shored temporary excavations will not create, any threat to adjacent residences, the supplemental report does not discuss potential impacts .of temporary excavations or temporary shoring on the existing drainage system to the east (item 4 above). We recommend that the geotechnical engineer review and comment on this issue. A :revised maximum allowable bearing pressure of 1,500 psf is recommended in the supplemental report, which is more consistent with the 1,200 psf maximum allowable bearing pressure recommended by Terra, in their 1991 report (item 5 above). No specifics are. provided regarding whatis proper bearing soil. In test,pit TP-2, excavated by Terra in 1991, slide debris with logs was encountered. If encountered, would this soil be suitable to support a 1,500 psf bearing pressure?. We recommend that the geotechnical engineer review and comment on what soil type(s) the recommended soil bearing pressure applies to, and provide guidance if unsuitable soil is encountered at proposed foundation depths. If pin piles: will be the recommended solution for -unsuitable bearing soil, a typical detail and installation specifications must be provided with the submittal. (As an aside,. the owner should be advised of the cost of this ,alternate foundation support system. Once the excavation is underway, . the owner will . be committed to going ahead with piles (if required), or may be faced with the prospect of having to backfill the excavation and/or re-design/abandon the project.] In our October 9, 1998 letter, we questioned the.wisdom.of using a rockery to support the slope east of the house (item 9 above). We recommended consideration be give to, an.engineered wall system,- --such as a cast -in -place .concrete retaining wall with catchment capacity, since near -surface upslope. soil - consists predominantlyof landslide debris, and debris flows, off the eastern bluff will likely occur in. the future. Though Mr: Bruce indicates that a reinforced concrete retaining wall (catchment wall), would be a better choice, he defers the decision to the owner. Without this issue being .resolved prior to the City issuing the building permit; there will be no requirement for the. owner to build such a wall, even if strongly recommended by the geotechnical engineer. Therefore, it is our opinion that the geotechnical .engineer and owner must discuss the risks' associated with a rockery and'a decision made regarding the,, 05/28/99 I:\PROJECrQ74\079.10\paksupplemental_Rr.doc LANDAU ASsoc[ATES 3 proposed . wall. Once a. wall type is selected, the geotechnical engineer must provide design recommendations and material specifications, and an assurance that the wall will prevent downslope . t creep of the slope debris (such .creep could- lead to failure of the City's drain system). Our comments regarding other rockery walls at the site, as noted in our October 9, 1998 letter, were not addressed in the supplemental report. This. includes rockeries to support fill and/or soil that cannot stand vertically on its own, and which needs to be permitted according to City guidelines. The supplemental, report does not address rockery design or construction. We recommend that the geotechnical engineer address the above. Any rockery design should include details and specifications for wall drainage and drainage discharge. In our October 1998 letter, we questioned the need of the "French -type" interceptor drain (item 10 above). Our questions/concerns regarding this drain were not addressed in the supplemental report. In response to item 11 above, the supplemental report states that in the engineer's opinion, the probability of earth movement on Jot 6 within a 25-year period is less than 10 percent. No probability of damage due to earth movement' from offsite sources is given-, even though the earlier Terra report states the highest risk areas within the',plat are along the steep eastern bluff. In our opinion, the risk of failure of the slope to the east has yet.to be • adequately evaluated (item 14 above). Though Mr. Bruce made periodic observations of the slope during the period of October 1998 and March 1999 ,(6-month period), the slope has not been evaluated by a geologist experienced with Puget Sound. bluff processes, as recommended in -our initial letter. The fact that only. small events have been noted in. approximately the last 40-year period may be increasing the risk of future, larger failures, and should be considered during the geological evaluation. Our recommendation. that the lead design professional should use the findings from that study .to evaluate site constraints and/or the need for supplemental engineered features (such as catchment/deflection walls, BniggTm cable retaining systems, reinforced foundation walls, "soft" walls/floors, special drainage, selective tree removal; etc.) is still valid. . The current risk statement from Mr.. Bruce assumes that the City will maintain and improve the existing storm drainage system to the east of the proposed residence in order to minimize landslide potential and hazards. It is' our 'understanding .that the City is responding to this issue. The applicant should be made aware that the existing storm drain system to the east is within a known landslide hazard area, and because of that, there is a� higher than normal risk of failure of the system due to soil creep and other, mass wasting processes. Therefore; the lead design, -professional and geotechnical engineer should consider potential failure of.the, existing storm system when evaluating the landslide potential erosion - hazards of the slope to the east. The supplemental report provides additional discussion regarding "normal" differential settlement of the structure (item 12 above). However, the supplemental report does not address the concern of 05/28M I:\PROJECT\074\079.10\paksupplemental_ttr.doc LANDAU ASSOCIATES 4 potential differential settlement of foundations underlain by organic material, such as encountered in Terra's test pit, TP-2; oe for potential cosmetic damage caused by uneven settling as a result of using differing foundation' elements. The supplemental report does indicate that if poor foundation soil is present, pin piles with grade beams will be used to support the structure. As noted above, the supplemental report provides no geotechnical recommendations to support this foundation type (e.g. pipe size, allowable capacity, driving criteria, corrosion protection, etc.), or that changing the foundation system will require additional structural engineering and resubmittal of the foundation plans to the City for approval. Lastly, the supplemental report indicates that pin piles will likely be used to support the chimney, though this option is not included on the construction drawings and no recommendations are provided for pin pile foundations. We recommend that the geotechnical. engineer review and respond to these issues. Though the April 4, 1999 supplemental geotechnical report prepared by Mr. Dennis M. Bruce,, addresses many of the items contained in our October 9, 1998 letter, several significant issues/concems stillremain to be addressed. In addition, our comments on other portions of the project documents have yet to be addressed, but should be prior to resubmittal or issuance of a building permit. We recommend that the geotechnical engineer review the comments contained in this letter, (and the ordinance requirements for a geotechnical report), and respond as appropriate; and that the City require the lead. design professional to submit all documents in a complete form. Please call if you have questions concerning this review, or require the services of Landau, 'Associates for subsequent review services. E IRES _ ti EJH/WDE/jas LANDAU ASSOCIATES, INC. By: Edward.J. Heavey, P.E. Senior Engineer and William D. Evans, C.P.G. Associate 05/28/99 1APROJECTN074\079.IOtpaksupplemental_hr.doc LANDAU Associm,Es 5 Dennis M. Bruce, P.E. L. M.S.C.E., M.B.A. July 27, 1998 Mr. Chun H. Pak 3828 N.E. 110th Seattle, Washington 98125 Geotechnical/Civil Engineer Subject: Geotechnical Evaluation Proposed New Residence 16109 - i3rd PlaceWest; dmonds, Washington This engineering report presents the results of a geotechnical evaluation of Lot No. 6 at 16109 - 73rd Place West, Edmonds, Washington. This evaluation was required due to owner and architect concerns, as well as City of Edmonds requirements. REFERENCES: • Location map (figure 1) • Geotechnical Report of the overall Lorian Woods property for Robert and Joanne Anderson, dated June 6, 1989, by Terra Associates, Inc. • Site photographs • Proposed Mr. Chun Pak house design by Mr. Phil King, Designer BACKGROUND: Lot No. 6 (16109 - 73rd Place West, Edmonds, Washington) of the overall Lorian Woods Development, exists along the private road 73rd Place West (see Lorian Woods layout map). Lot No. 6 is approximately sixty foot (60') deep and seventy-eight foot (78') wide, in an approximate rectangular shape. Lot No. 6 has never been developed. Surrounding lots in Lorian Woods have been developed within the last six • years. The property immediately behind (easterly) of the Pak Lot No. 6 is understood to have been dedicated as Native Growth Protection Area, or green belt designation. The primary geotechnical aspects affecting the proposed single family residence development of Lot 6 are slopes and drainage. Lot No. 6 contains gentle to moderate topography [from five percent (5%) to thirty percent (30%) slopes]. The slopes behind (easterly) of the Pak lot contain slopes at approximately 2H A V. SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION DRAINAGE • DESIGN & PERMIT • LEGAL 17814 8th Ave. N.W. • Shoreline, Washington 98177 (206) 546-9217 FAX 546-8442 Pak Page two The slopes behind the Pak lot evidence significant and year-round ground water and seepage outflow. It is understood that the City of Edmonds has required the installation of a significant number of intercept and deep drain wells. EVALUATION: Visual assessment of Lot No. 6 revealed no evidence of any geotechnical distress. No slides, no settlements, no tension cracks, no creep, nor any significant erosional degradation were observed. As mentioned, seepage groundwater "trickle" flows were observed, and are evident in the photographs with regard to street discharge into the existing storm water system. This engineer obtained a copy of the Terra Associates, Inc., geotechnical report, dated June 6, 1989 from the City of Edmonds. This report provides extensive geotechnical analysis and slope stability evaluation. This engineer reviewed the test bore holes, as well as the backhoe-dug test pit information in the Terra report. This engineer's direct experience in the area verifies the stratigraphy reported in the Terra report. In order to augment the existing site geotechnical information, soil test pits were hand -dug by this engineer in the proposed location of the Pak residence. All of the five (5) hand -dug test pits contained similar findings, namely: 0" to 4" Organics, roots, and organic silt 4" to approx. 14" Silty sand, moist, medium dense 14" to approx. 34" (bottom of Increasingly dense sandy silt / sandy silt hand -dug test hole) Seepage water was evident in all test pits. o water was encountered in any of the three test pits. All test pit walls remained vertical and stable. No sloughing or caving occurred. CONCLUSIONS / RECOMMENDATIONS: Based on the findings of this investigation, review of the June 6, 1989 Terra Associates, Inc., report, and experience with similar sites in the area, Lot No. 6 is geotechnically approved for the proposed Mr. Chun H. Pak single family residence, per Phil King designs, subject to the following: • Standard reinforced continuous and spread footings. Allowable bearing pressure: 2,000 p.s.f. • Equivalent fluid pressure of 35 p.c.f. is recommended for any retaining wall design provided drainage zone is inspected and verified by this engineer. • 'For retaining wall design, use friction factor of 0.55 and passive pressure of 350 p.c.f. Pak Page three An intercept "French -type drain" is recommended along the eastern property line and graded to "wrap around" the new Pak residence. This intercept ditch will be approximately thirty-six inches (36") deep, and provide seepage pressure release around the Pak residence (specific designs provided prior to site grading). • Geotechnical inspection by this engineer prior to any foundation concrete placement. The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed native soils or on structural fill placed above native soils. See the later sub -section entitled General Earthwork and Structural Fill for structural fill placement and compaction recommendations. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty- four (24) inches, respectively, and should be bottomed at least eighteen (18) inches below the lower adjacent finish ground surface. Depending on the final site grades, some overexcavation may be required below footings to expose competent native soils. Unless lean concrete is used to fill the over excavated hole, the width of the overexcavation at the bottom. must be at least as wide as the sum of two times the depth of the overexcavation and the footing width. For example, an overexcavation extending two feet below the bottom of a three-foot wide footing must be at least seven feet wide at the base of the excavation. Footings constructed according to the above recommendations may be designed for an allowable soil bearing pressure of three thousand (3,000) pounds per square foot (p.s.f.). A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that total post -construction settlement of footings founded on competent, native soils (or on structural fill up to five (5) feet in thickness) will be about one-half inch, with differential settlements on the order of one -quarter inch. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the bearing soils, or by passive earth pressure acting on the vertical, embedded portions of the foundations. For the latter condition, the foundations must either be poured directly against undisturbed soil or the backfill placed around the outside of the foundation must be level structural fill. We recommend the following design values be used for the foundation's resistance to lateral loading: Parameter Design Value Coefficient of Friction 0.55 Passive Earth Pressure 350 p.c.f. Pak Page four Where: (1) p.c.f. is pounds per cubic foot. (2) Passive earth pressure is computed using the equivalent fluid density. We recommend that a safety factor of at least 1.5 be used for design of the foundation's resistance to lateral loading. SLABS -ON -GRADE: Slab -on -grade floors may be supported on undisturbed, competent native soils or on structural fill. The slabs may be supported on the existing soils provided these soils can be recompacted prior to placement of the free -draining sand or gravel underneath the slab. This sand and gravel layer should be a minimum of four (4) inches thick. We also recommend using a vapor barrier such as 6-mil. plastic membrane beneath the slab with minimum overlaps of 12 inches for sealing purposes. PERMANENT FOUNDATION AND RETAINING WALLS: Retaining walls backfilled on one side only should be designed to resist lateral earth pressures imposed by the soils retained by these structures. The following recommended design parameters are for walls less than twelve (12) feet in height which restrain level backfill: Parameter Active Earth Pressure* Passive Earth Pressure Coefficient of Friction Soil Unit Weight Where: Design Value 35 p.c.f. 350 p.c.f. 0.55 125 p.c.f. (1) p.c.f. is pounds per cubic foot (2) Active and passive earth pressures are computed using equivalent fluid densities. For restrained walls which cannot deflect at least 0.002 times the wall height, a uniform lateral pressure of one hundred (100 p.s.f. should be added to the active equivalent fluid pressure). The values given above are to be used for design of permanent foundation and retaining walls only. An appropriate safety factor should be applied when designing the walls. We recommend using a safety factor of at least 1.5 for overturning and sliding. Pak Page five The above design values do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads will be placed above the walls. If these conditions exist, then those pressures should be added to the above lateral pressures. Also, if sloping backfill is desired behind the walls, then we will need to be given the wall dimensions and slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of the wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. Placement and compaction of retaining wall backfill should be accomplished with hand -operated equipment. Retaining Wall Backfill Backfill placed within eighteen (18) inches of any retaining or foundation walls should be free -draining structural fill containing no organics. This backfill should contain no more than five (5) percent silt or clay particles and have no particles greater than four (4) inches in diameter. The percentage of particles passing the No. 4 sieve should be between twenty-five (25) and seventy (70) percent. Due to their high silt content, if the native soils are used as backfill, a drainage composite, such as Mirafi and Enkadrain, should be placed against the retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. the purpose of these backfill requirements is to assure that the design criteria for the retaining wall as not exceeded because of a build-up of hydrostatic pressure behind the wall. The subsection entitled General Earthwork and Structural Fill contains recommendations regarding placement and compaction of structural fill behind retaining and foundation walls. EXCAVATION AND SLOPES: In no case should excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts up to a height of four (4) feet deep in unsaturated soils may be vertical. For temporary cuts having a height greater than four (4) feet, the cut should have an inclination no steeper than 1:1 (Horizontal: Vertical) from the top of the slope to the bottom of the excavation. Under specific recommendations by the geotechnical engineer, excavation cuts may be modified for site conditions. All permanent cuts into native soils should be inclined no steeper than 2:1 (H:V). Fill slopes should not exceed 1:1 (H:V). It is important to note that sands do cave suddenly, and without warning. The contractors should be made aware of this potential hazard. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an Pak Page six appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. DRAINAGE CONSIDERATIONS: Footing drains are recommended at the base of all footings and retaining walls. These drains should be surrounded by at least six (6) inches of one -inch -minus washed rock wrapped in non -woven geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At the highest point, the perforated pipe invert should be at least as low as the bottom of the footing and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. Groundwater was observed in the test pits during the field work. Seepage into the planned excavation is possible, and likely if excavation occurs during winter months, and if encountered should be drained away from the site by use of drainage ditches, perforated pipe, French drains, or by pumping from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Any exposed slopes to be covered with plastic to minimize erosion. Final site grading in areas adjacent to buildings should be sloped at least two (2) percent away from the building; except where the area adjacent to the building is paved. GENERAL EARTHWORK AND STRUCTURAL FILL: The proposed building and pavement areas should be stripped and cleared of all surface vegetation, all organic matter, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill. NOTE: Specific clearing limits to be established at pre -construction meeting with City of Edmonds Building Department. Structural fill is defined as any fill placed under the building, behind permanent retaining or foundation walls, or in other areas where the underlying soils needs to support loads. This engineer should observe site conditions during and after excavation prior to placement of any structural fill. All structural fill should be placed in horizontal lifts with a moisture content at or near the optimum moisture content. The optimum moisture content is that moisture content which results in the greatest compacted dry density. The moisture content of fill soils is very important and must be closely controlled during the filling and compaction process. Pak Page seven The allowable thickness of the fill lift will depend on the material type, compaction equipment, and the number of passes made to compact the lift. In no case should the lifts exceed twelve (12) inches in loose thickness. The following table presents recommended relative compaction for structural fill: Location of Fill Placement Beneath footings, slabs or walkways Behind retaining walls Beneath pavements Minimum Relative Compaction 95% 90% 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum relative compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D-1557-78 (Modified Proctor). Use of On -Site Soils If grading activities take place during wet weather, or when the silty, on -site soils are wet, site preparation costs may be higher because of delays due to rains and the potential need to import granular fill. The on -site soils are generally silty and thus are moisture sensitive. Grading operations will be difficult when the moisture content of these soils exceeds the optimum moisture content. Moisture sensitive soils will also be susceptible to excessive softening and "pumping" from construction equipment traffic when the moisture content is greater than the optimum moisture content. Ideally, structural fill which is to be placed in wet weather should consist of a granular soil having no more than five (5) percent silt or clay particles. The percentage of particles passing the No. 200 sieve should be measured from that portion of the soil passing the three -quarter -inch sieve. The use of "some" on -site soils for fill material may be acceptable if the upper organic materials is segregated and moisture contents are monitored by engineering inspection. DRAINAGE CONTROLS: Existing Lot No. 6 runoff is directed into the existing storm water system in 73rd Place West. This engineer understands that the City of Edmonds has approved of the existing storm water system. Discussions with existing neighbors have revealed no Pak Page eight evidence of any malfunctions of the existing storm water system. Proper construction of the Pak residence along with the recommended east property line intercept trench will provide good drainage controls for Lot No. 6. Compliance with standard storm water detention methods in accordance with the City of Edmonds requirements are geotechnically acceptable. CONCRETE: All foundation concrete (footings, stem walls, slabs, any retaining walls, etc.) shall have a minimum cement content of 5-1/2 sacks per cubic yard of concrete mix. INSPECTION: The recommendations of this report are only valid when key geotechnical aspects are inspected by this engineer during construction: • Soil cuts • Foundation subgrade verification • Retaining wall, or rockery placement • Any fill placement • Eastern property line intercept drainage ditch with appropriate tight -line "wrap around" release • Subsurface drainage installation SUMMARY: The proposed Mr. Chun H. Pak single family residence on Lot No. 6, Lorian Woods, Edmonds is geotechnically viable when constructed in accordance with the recommendations herein, compliance with City of Edmonds approved plans and requirements, and key geotechnical inspection during construction. STATEMENT OF MINIMAL RISK: The plans and specifications for the Mr. Chun H.. Pak residence at Lot 6 of Lorian Woods, as designed by Phil King, Designer, have been reviewed by this engineer and conform to the recommendations of the analysis and report and, provided that those conditions and recommendations are satisfied during the construction and use, and inspected and verified by this engineer, the area disturbed by construction will be stabilized and remain stable and will not increase the potential for soil movement, and the risk of damage to the proposed development and from the development to adjacent properties from soil instability will be minimal. Pak Page nine CLOSURE: The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering principles and practice. No other warranty, either express or implied, is made. The conclusions are based on the results of the field exploration and interpolation of subsurface conditions between explored locations. If conditions are encountered during construction that appear to be different than those described in this report, this engineer should be notified to observe the situation and review and verify or modify the recommendations. If there are any questions, do not hesitate to call. ig4814 Dennis M. Bruce, P.E. Geotechnical / Civil Engineer Fu: • Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer p�Au �NEc� April 4 1999 City of Edmonds 121 Fifth Avenue North Edmonds, Washington 98020 Attn : Ms. Lara Knaak 1 ;m, APR o OE�M� ON of Subject: Additional Geotechnical Information Proposed Pak New Residence Lot 6, Lorian Wood Development, Meadowdale Area M16109 - 73rc! hla'ce� W�est/Edmonds, Washington This engineering report presents the results of additional geotechnical investigation with regard to the proposed Mr. Chun Pak residence at Lot No. 6 of the Lorian Woods Development. Understood proposed address: 16109 - 73rd Place West, Edmonds, Washington. This additional geotechnical investigation was required due to City of Edmonds request dated October 8, 1998 from reviewer, Ms. J. Graf. It is understood that the City of Edmonds has no in house geotechnical engineer review capacity, and relies on outside consultants. The proposed Pak residence project is understood to have been reviewed by Landau Associates, Inc., with their findings presented in an October 9, 1998 review report. It is further understood that no engineer or geologist from Landau Associates has actually been to Mr. Pak's site. Thus, the Landau Associates, Inc., October 9, 1998 review is based solely on submitted reports and plans. REFERENCES: • July 27, 1998 geotechnical evaluation report for proposed Pak residence, by D. Bruce, P.E. • Proposed Mr. Chun Pak house plans by Mr. Phil King, Designer • Topographic Map of Lorian Woods Development prepared by Group 4, Inc., for Mr. Robert Anderson • Geotechnical Report of Lorian Woods property dated June 6, 1989, by Terra Associates, Inc. • Site plan and cross-section layout prepared by designer, Mr. Phil King SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 • (206) 546-9217 • FAX 546-8442 City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page two BACKGROUND: This engineer prepared a geotechnical evaluation and report for the proposed Pak residence, dated July 27, 1998. City of Edmonds subconsultant, Landau Associates, Inc., prepared a document and plan paperwork review dated October 9, 1998, raising numerous geotechnical issues. The Landau October 9, 1998 report was signed, but not certified, by Wade Gilbert, P.E. It is understood that Mr. Gilbert is no longer with the Landau firm. This engineer conducted additional geotechnical investigations (test pit) and observation over the severe rainy winter season from October, 1998 through March, 1999, in attempts to respond to geotechnical concerns raised by the October 9, 1998 Landau report. WINTER OF 1998/1999 PERFORMANCE: This engineer conducted numerous site observations between October of 1998 through March of 1999. Of crucial importance (as discussed in the July 27, 1998 geotechnical evaluation), was drainage control. This engineer verified that the existing storm water system of drains and tightlines is owned and maintained by the City of Edmonds. Discussions with City Engineer, James C. Walker, P.E., and City of Edmonds Hydraulics Engineer, Don Fiene, P.E., verified the existing drainage system on the slope behind (easterly) of the Pak Lot No. 6, is owned and maintained by City of Edmonds. Further, Mr. Fiene conducted an on -site investigation and verified to this engineer that the drains, catch basins, and tightlines are functioning appropriately, and were approved by the City of Edmonds at that time. This engineer relayed how important it is to the overall viability of Lorian Woods, and particularly Lot No. 6, that the City of Edmonds maintain good monitoring and repairs to the drainage system. This engineer conducted observations of the Pak building Lot No. 6, as well as the relatively steep slope to the east. In the period of time from October, 1998, through March, 1999, this engineer observed no evidence of any localized sliding, sloughing, soil creep or significant erosional degradation. Further, this engineer conducted an exploratory investigation of the top -of -bluff properties to the east. The top -of -bank was found to be dense, native soil, with no disturbance or evidence of current instabilities. Obviously, historic erosional sloughing has occurred near the top -of -slope. City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page three ADDITIONAL SOIL TEST PIT: This engineer undertook an additional soil test pit (dug by backhoe) in the vicinity approximately thirty feet (30') east of Terra & Associates 1989 Test Pit 2. It is understood that this 1999 Test Pit -Pak, is in the vicinity of the anticipated Pak residence (per site plan layout). The results of the backhoe-dug Test Pit -Pak are as follows: 0" to 7" Ground cover, organics, and organic silt soft, moist 7" to 4' Grey, silty, fine sand, with occasional roots and some orange stain. Moist, loose 4" to approx. 8' Grey, silty fine to medium sand. Occasional zone of silt. Medium dense. 8' to 13' (bottom of Fine to medium sand. Grades increasingly dense Test Pit -Pak) Ground water encountered at four foot (4) depth. Test pit walls remained "reasonably stable". Some sidewall sloughing occurred, but not collapsing. CONCLUSIONS / RECOMMENDATIONS: Based on the findings of this and previous geotechnical investigations, as well as review of previous Terra Associates, Inc., reports for the overall Lorian Woods project, and the Nearing residence on adjacent Lot No. 7, and experience with similar properties, the following are concluded and recommended: • Discussions with project designer (Phil King), project contractor (John Gurnee), and project owner (Mr. Chun Pak), verified that no soil cut will exceed twelve feet (12') in vertical dimension. This engineer confirms and requires that no soil cut will exceed twelve feet (12') (vertical). This engineer recommends the use of temporary shoring consisting of ecology blocks. Properly staggered and embedded ecology block wall could be installed at 1 H:6V slope. • This engineer anticipates a significant dewatering of the Pak excavation due to material removal. Normal, good ground excavation practices (sumps, pumps, City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page four tightline release into proper discharge, etc.) will assist the excavation and foundation phase of this project. • The twelve foot maximum soil cut, combined with proper temporary shoring utilizing ecology blocks, will not create any geotechnical threat the adjacent Nearing residence, subject to this engineer's on -site inspections. This engineer recommends a revised bearing capacity of 1,500 p.s.f. This engineer requires a minimum footing width of twenty-four inches (24"). It is foundation contractor's duty to properly excavate and manage the site. If subgrade conditions degrade, over -excavation and backfill with structural gravel will be required (as discussed in the July 27, 1999 report). • If excavation contractor is unable to "control" the site, and excessive subgrade disturbance results, this engineer will require a pin -pile with reinforced grade beam foundation along the eastern portion of the Pak residence. Drainage: Normal footing drains are recommended (as discussed in the July. 27, 1998 report). Currently, there is an excess of surficial storm water runoff that inundates the access drive (see photographs). This engineer understands that City of Edmonds verifies the adequacy of their up slope drainage system. This engineer believes that additional maintenance and improvements by the City of Edmonds may be required. Nevertheless, this engineer will proceed with the Pak development, anticipating additional drainage impacts from the City of Edmonds system. Specifically, an access road cut will be required, along with additional discharge piping into the apparent "open brook" that exists along the west side of access road (see photographs). • This engineer agrees with the Landau report comment questioning the use of filter fabrics. This engineer strongly recommends proper gravel annulus be placed around all drainage pipes. This engineer understands the concern regarding request for a rear catchment wall. This engineer has duly informed project designer, project contractor, and project owner over the "risk" of surficial slide debris from the rear eastern slopes. All involved parties agree that the location of the Pak house will be sufficiently distant from the base of the steep slope. This engineer has no objection to installing a catchment wall along the rear (eastern) Pak property line, however, this engineer feels strongly that that is an owner's choice. City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page five Rear Rockery: The proposed rear rockery along the eastern property line of the Pak residence may be constructed in accordance with normal rockery standards. Depending upon site management and specific location of temporary ecology block shoring, a reinforced concrete retaining wall (catchment wall) may be a better choice. Again, this would be an owner's choice, based on recommendations from this geotechnical engineer during the construction phase. Landslide Hazard: In this engineer's opinion, the probability of earth movement on Lot No. 6 within a period of twenty-five (25) years, is less than ten percent (10%). Thus, according to City of Edmonds Ordinance No. 2661, the lot is suitable for residential use. The risk of damage to the Pak residence and to adjacent properties will be minimal, subject to the conditions set forth in this engineer's report and subject to this engineer's on -site inspections during the construction phase. It is essential that the City of Edmonds properly maintain and improve the existing storm water control system in the hillside east of the Pak property in order to minimize landslide potential and landslide hazards. Additional mitigation of potential landslide risk will occur due to the actual construction of the Pak residence, installation of proper footing drains which will improved subsurface drainage, and also due to the basement excavation, which will remove a weight of soil greater than the weight of the residence. The Pak residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be totally eliminated, and property owners knowing assume all residual risks. The geotechnical recommendations and declarations associated with the Pak project do not constitute a warranty, either expressed or implied, against loss or damage to persons or property. Settlements: As discussed and required, a minimum footing width of twenty- four inches (24") is required. Experience has proven,that such properly constructed footings result in estimated total settlements of less than one-half inch (.5"), and estimated differential settlements of less than one -quarter inch (.25"). As discussed, failure of excavation and foundation contractor to "properly maintain the site" will result in this engineer's requirements of pin -pile with reinforced grade beam foundations. This engineer does not, at this time, require pin -piles, but does anticipate their use, particularly under the masonry chimney. City of Edmonds Re: Pak, Lot 6, Lorian Wood Development, Meadowdale Area April 4, 1999 Page six SUMMARY: • The proposed Pak residence on Lot No. 6, Lorian Woods, Edmonds is geotechnically viable, subject to the recommendations of this engineer and City of Edmonds building requirements. • Additional geotechnical exploration and analysis verified viability of the proposed Pak residence. ADDENDUM: NOTE: If any additional questions arise, or issues are unclear, this engineer stronaly recommends an on -site meeting with City of Edmonds technical personnel and their consultants. If there are any questions, do not hesitate to call. EXPIRES 12/23/ DMB:vIb cc: Chun Pak, Owner James C. Walker, P.E. City of Edmonds City Engineer Phil King, Designer John Gurnee, Contractor Dennis M. Bruce, P.E. Geotechnical / Civil Engineer Dennis M. Bruce_, P.E M.S.C.E, M.B.A. Geotechnical /Civil Engineer RECEIVED September 8, 2000 SEP 14 2000 DEVELOPMENT SERVICES CTR. CITY OF EDMONDS City of Edmonds Building Departme'r 121 Fifth Avenue North EET Edmonds, Washington 98020 FILE Subject: Final Report - Geotechnical Inspections Pak es.iden.ce. 161'09 = 73rd PI ceAWceW,'Edmonds Permit No. 98-266 This engineering report presents a summary of all geotechnical inspections with regard to the Pak new single family residence at 16109 - 73rd Place West, Edmonds, Washington. • July 10, 2000 inspection report by D. Bruce, P.E. • City of Edmonds -approved plans • Numerous geotechnical reports, recommendations and evaluations • Construction photographs As stated in the July 10, 2000 inspection report, this engineer has provided on - site inspections for the Pak project with regard to geotechnical and foundation aspects. Site grading, excavation, temporary eco-block wall, foundation bearing, footing recommendations, and concrete footing placement have been previously discussed and approved. Since July 10, 2000, this engineer has performed twice -weekly inspection observations of the project. Foundation stem walls were successfully placed. Backfill material meeting City of Edmonds standards, normal good practices, and this engineer's on -site recommendations were successfully placed. SOILS * FOUNDATIONS * SITE DEVELOPMENT * INSPECTION * DRAINAGE * DESIGN & PERMIT * LEGAL P.O. Box S5.502 * ShorPlinP. Washinaton 98155 * 12061546-9217 * FAX 1206) 54Fr8442 Pak Property Page two The perimeter footing drains, as well as intercept drains, were successfully tightlined-connected in the northwest corner of the Pak lot into a new catch basin. This catch basin subsequently released the storm water and seepage pressure flow into the existing storm water system in the overall Lorian Woods complex (see photographs). The rear (easterly) foundation stem wall was successfully placed. It is important to note that the temporary eco-block shoring worked successfully throughout the excavation and stem wall phase of this project. Temporary erosion control and sedimentation measures were successfully maintained throughout the project. Straw bales and siltation fencing were properly installed and maintained. Note: As previously stated in engineering reports, and as discussed in numerous meetings with City of Edmonds personnel, it is essential that the City of Edmonds maintain the proper clean out of the drainage system up slope and behind (easterly) of the Pak residence. On occasion, an inlet catch basin may become clogged with debris or excessive silt. It is very important that regular monitoring, observation, and clean out occur to maintain the current proper drainage intercept control and release that occurs on the slope behind and above the Pak residence. This engineer understands that the City of Edmonds is committed to proper maintenance of their drainage system. Based on this engineer's on -site inspections, recommendations from the numerous geotechnical reports, and experience with similar projects, the following are concluded and recommended: • All geotechnical aspects of the new Pak residence have been successfully completed. • Final landscaping measures have yet to be installed. • It is essential that the City of Edmonds regularly inspect, monitor, clean out, and modify the rear (easterly) up slope drainage system behind the Pak residence. Pak Residence Page three If there are any questions, do not hesitate to call. �I M. `Qp WABd,� G A� O i�aos S C$ NAL E�yG je ers im T O DMB:vlb Dennis M. Bruce, P.E. Geotechnical / Civil Engineer Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer February 20, 2000 P City of Edmonds c/o Mr. Chun Pak 3828 N. E. 110th Street Seattle, Washington 98125 Attn: James C. Walker, P.E., City Engineer Subject: Chun Pak Lot Lot 6, Lorian Wood Development, Meadowdale Area 16109 - 73rd Place West, Edmonds, Washington This engineering report.presents to summarize the geotechnical issues relating to Chun Pak's Lot No. 6 in the .Lorian Woods Development. • June 6, 1989 report by Terra Associates, Inc., allowing development in Lorian Woods, subject to. conditions • Proposed Mr. Chun Pak house plans by Mr. Phil King, Designer • July 27, 1998 geotechnical evaluation report by D. Bruce, P.E. for Mr. Pak • October 9, 1998 review report by Landau Associates, Wade Gilbert, P.E. • April 4, 1999 additional geotechnical information report by D. Bruce, P.E. • May 28, 1999 supplemental geotechnical review by Landau Associates, Inc., Edward Heavy, P.E. • June 9, 1999 additional soil test pit investigation, test pit logs, and photographs • June 11, 1999, meeting with City of Edmonds, Mr. Pak, Landau Associates, designer and this engineer, to clarify issues • June 18, 1999 on -site photographs and investigation by City of Edmonds Drainage Department and Public Works Department regarding needed repairs and improvements to City of Edmonds drainage system directly behind and above Mr. Pak's lot. • December 22, 1999 letter to City of Edmonds expressing concerns. regarding review process and lack of direction from City of Edmonds • December 30, 1999 correspondence from James C. Walker, P. E., discussing submittal standards, drainage issues, and seasonal restrictions on grading. SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 • (206) 546-9217 • FAX 546-8442 Pak, Lot 6, Lorian Wood Development February 20, 2000 Page two Numerous geotechnical reports and responses have been furnished the City of Edmonds beginning July 27, 1998. It is understood that the City of Edmonds does not do any review or evaluation in-house, and relies on their outside consultant, Landau Associates, for review. Numerous lengthy memorandum have been issued by Landau Associates over the past year and one-half. It is understood that no site evaluation or visit had occurred prior to December 3, 1999. The following numbers will refer to the latest memorandum (December 9, 1999) from Landau Associates: 1. Geologist Landau Associates recommends that an experienced geologist evaluate the slopes and landslide issues that may apply to Mr. Pak's Lot No. 6. A complete, thorough geologic evaluation has been performed and discussed in the Terra Associates, Inc., June 6, 1989 report. Engineering geologist, Mr. Charles R. Lie, P.E., (in addition to Anil Butail, P.E., and William Bailey, project manager) participated in the 1989 report. This engineer has thoroughly read, understands, and agrees with the landslide/ geologic discussion in the report. The conclusion of the Terra Associates, Inc., report is, " ... We believe the probability of landslide damage likely is less than five percent in twenty-five years ... See figure 5." As discussed in the 1989 Terra report, and as discussed in numerous geotechnical reports by D. Bruce, P.E., the drainage situation above and behind Mr. Pak's lot has improved and will lessen the probability of any hillside instabilities. The December 9, 1999 Landau report states, "In our opinion, this geologic assessment remains a high priority and should be completed prior to any future geotechnical review." The geologic assessment has been done. The potential for debris flow from the adjacent slopes are greatly reduced by the recent improved City of Edmonds drainage work and maintenance. This recent "unclogging" of existing drains, as well as the installation of the additional catch basin drain (as recommended on -site by this engineer to City of Edmonds Drainage Engineer), further dries out the slope east of Mr. Pak's lot. . Thus, this engineer declares that the potential for debris flow from the adjacent slope affecting Mr. Pak's house is not significant. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page three 2. Up slope Drainage: As discussed in this engineer's October 7, 1999 report, additional maintenance and new catch basin was recommended for the City of Edmonds system behind Mr. Pak's lot. This engineer has inspected and observed the properly completed maintenance work and new catch basin. This work, as performed by the City of Edmonds, satisfies this engineer's concern regarding the functionality of the existing system. Excessive surface runoff no longer trickles onto Mr. Pak's lot. The Landau report "suggests that the City advise the applicant of its current position regarding this drain system, and of the need for the applicant to prepare a development plan which accommodates the expected range of operating conditions of the City's drainage system." Evidently, Landau is concerned that the City may not maintain its drainage system. This engineer has every confidence in the City of Edmonds drainage maintenance department and believes that the City of Edmonds will perform proper maintenance. As declared, certified, and notarized, Mr. Pak acknowledges and understands the significance of proper drainage control. 3. Drain System: Landau raises concerns regarding the effectiveness of a shallow drain system to control conditions during construction. This engineer has significant experience in foundation engineering and approves of the proposed ten to twelve foot (10' - 12) maximum excavation. Qualified, experienced contractors understand the importance of proper temporary drainage during the excavation phase. These "construction issues" are not geologic in nature, and are the responsibility of the contractor and the on -site inspecting geotechnical engineer. Apparently there is concern for the "spring" just north of the Pak parcel. The. presence of this seasonal drainage course is now noted in the environmental check list. 4. Topographic Map: Please refer to overall property developer, Robert A. Anderson, letters of June 24, 1999 and January'14, 2000 regarding the topographic map prepared by Group 4, Inc. The topographic map meets standards for site surveying and topography, including legal description. Evidently, this same topographic map has been reviewed by the City of Edmonds and approved for the existing homes within Lorian Woods. This engineer approves of the topographic map. 5. Soil Conditions/Footings: This engineer concurs that suitable soil conditions exist for the footings recommended for Mr. Pak's house. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page four 6. Seasonal Ground Water: As discussed in the October 7, 1999 report, the clogged and insufficient City of Edmonds up slope drains created excessive runoff water into one of the soil test pits. Thus, the ground water level observed in the test pits represent a maximum. Proper construction techniques and temporary, as well as permanent, drainage measures will manage this ground water. 7. Temporary Shoring. As previously discussed, stacked ecology blocks may be required if actual excavations and soil conditions dictate. This engineer has designed and inspected numerous foundation excavations, and the stacked ecology block method has proven successful (numerous examples within the City of Edmonds jurisdiction are available). If it is unclear to Landau Associates how a two foot thick ecology block wall can be constructed one foot away from the property line, this engineer welcomes their observation during Mr. Pak's project. This engineer declares, "all temporary and permanent retaining structures can be accommodated within this space (private property of Mr. Pak), and still leave room for any required home -related features, especially those which may be required by code. 8. Clarification of Retaining Walt See revised plans. 9. Drainage Issues: As previously discussed, the City of Edmonds improvements and maintenance to their existing drainage system satisfies this engineer's concerns as raised in the October 7, 1999 report. As also previously discussed, practical construction techniques will manage any ground water during the foundation construction phase. Finally, proper footing drains and waterproofing membrane (such as asphaltic emulsion, Volclay, etc.) will be applied. 10. Rockeries: Some small (less than five feet in total height) rockeries are envisioned for Mr. Pak's final grading. See revised plans by Phil King, designer. 11. Storm Water Management See revised plans and civil storm water management designs by Nick Lehtinen. Additionally, the existing "Lorian Woods stream" allows for convenient and effective discharge release. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page five 12. Interceptor Drain: See revised plans. No east (up slope) French Drain is planned. 13. Foundation Drainage. See revised plans to clarify foundation drainage. 14. Supplemental Review: This engineer has thoroughly reviewed the revised plans and approves them for construction. 15. Conflict with Concrete Mix Design: See revised plans. Clarified. 16. Seasonal Construction: This engineer agrees with Landau Associates that °winter time construction could be allowed (provided the city waives the current restriction)." It is unsure who within the City of Edmonds actually evaluates the proposal and might issue this waiver. 17. Risk Analysis: In this engineer's opinion, the probability of earth movement on Lot No. 6 within a period of twenty-five (25) years, is less than ten percent (10%). Thus, according to City of Edmonds Ordinance No. 2661, the lot is suitable for residential use. The risk of damage to the Pak residence and to adjacent properties will be minimal, subject to the conditions set forth in this engineer's report and subject to this engineer's on -site inspections during the construction phase. Additional mitigation of potential landslide risk will occur due to the actual construction of the Pak residence, installation of proper footing drains which will improved subsurface drainage, and also due to the basement excavation, which will remove a weight of soil greater than the weight of the residence. The Pak residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be totally eliminated, and property owners knowing assume all residual risks. The geotechnical recommendations and declarations associated with the Pak project do not constitute a warranty, either expressed or implied, against loss or damage to persons or property. 18. Check List Items All required check list items have been reviewed by this engineer, project designer, project contractor, and owner. We believe the submittal requirements have been satisfied, and are herewith submitted. • Geotechnical issues relating to the development of Lot No. 6 have been submitted throughout the past year and one-half. This engineer declares that the requirements of City Ordinance No. 2661 and Chapters 19.05 and 20.15 of E.C.D.C. have been met. Pak, Lot 6, Lorian Wood Development February 20, 2000 Page six • It is hoped that the City of Edmonds technical person will review all submittals and allow Mr. Pak to construct his residence, as many of his future neighbors in Lorian Woods have done. If there are any questions, do not hesitate to call. EXPIRES 1?J23/ DMB:vlb ME Dennis M. Bruce, P.E. Geotechnical % Civil Engineer Dennis M. Bruce, P.E. M.S.C.E., M.B.A. Geotechnical/Civil Engineer October 7, 1999 City of Edmonds R E C E I V E D Community Services Division NOV 0 9 1999 121 Fifth Avenue North Edmonds, Washington 98020 DEVELOPMENT SERVICES CTR. CITY OF EDMONDS Attn: Mr. Ray Miller, Director Mr. Don Fiene, P.E. Ms. Janine Graf, Building Official Subject: Mr. Chun Pak Lot - Lot No. 6, Lorian Woods 16109 - 73rd Place West, Edmonds, Washington Hopefully, this engineering report will allow the City of Edmonds to issue a building permit for Mr. Chun Pak's Lot No. 6 at Lorian Woods development, at 16109 - 73rd Place West. Numerous reports, responding reports and meetings have occurred regarding Mr. Pak's desire to build a single family residence in Lorian Woods, similar to the already -developed lots. This report is an attempt to briefly summarize the issues and, hopefully, resolve them. References: • June 6, 1989 report by Terra Associates, Inc., allowing development in Lorian . Woods, subject to conditions • Proposed house plans for Mr. Pak by Phil King, Designer • July 27, 1998 geotechnical evaluation report by D. Bruce, P.E., for Mr. Pak • October 9, 1998 review report by Landau Associates, Wade Gilbert, P.E. • April 4, 1999 additional geotechnical information report by D. Bruce, P.E. • May 28, 1999 supplemental geotechnical review by Landau Associates, Inc., Edward Heavy, P.E. • June 9, 1999 additional soil test pit investigation, test pit logs, and photographs. • June 11, 1999 meeting with City of Edmonds, Mr. Pak, Landau Associates, designer, and this engineer, to clarify issues • June 18, 1999 on -site photographs and investigation by City of Edmonds Drainage Department and Public Works Department regarding needed repairs . and improvements to City of Edmonds drainage system directly behind and above Mr. Pak's lot. SOILS • FOUNDATIONS • SITE DEVELOPMENT . INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL P.O. Box 55502 • Shoreline, Washington 98155 • (206) 546-9217 - FAX 546-8442 City of Edmonds / Pak Lot Page two Svnousis: As stated in this engineer's July 27, 1998 and April 4, 1999 reports, up slope drainage control is essential to maintain slope stability behind Mr. Pak's lot. This engineer has assessed, investigated and discussed the conditions of the City of Edmonds drainage system behind Mr. Pak's lot. It is understood that City of Edmonds geotechnical reviewer, Landau Associates, has not assessed the site, has not assessed the existing drainage system behind Pak Lot No. 6, nor has made any evaluation regarding the suitability of existing conditions. At the June 11, 1999 meeting, it was acknowledged that no discussions have occurred between City of Edmonds Drainage Division, Public Works maintenance, and Landau Associates. This is most unfortunate. This engineer recommended, on June 18, 1999, to Don Fiene and Public Works director, the need for improved drainage intercepts and maintenance directly behind Mr. Pak's lot. All parties acknowledged the drainage needs, and indicated that new culverts, new pipes and new tight line discharge lines would be installed. As of October 7, 1999, this engineer understands that such work has not yet occurred. This is unfortunate. The reason the drainage improvements are important and necessary are as follows: The June 9, 1999 supplemental test pits indicated the presence of dense, stable foundation soils (similar to Terra Associates, Inc., report dated June 6, 1989). However, supplemental soil test pit No. 1 in the vicinity of the northeast portion of Pak lot encountered excessive seepage ground water flow. The excessive flow was not encountered in test pit No. 2. Subsequent up slope investigations directly behind supplemental test pit No. 1 revealed clogged and insufficiently sized City of Edmonds drainage system. The clogged silt and debris was removed and immediately the amount of ground water flow into supplemental test pit No. 1 was greatly reduced. This simple cause and effect is noteworthy. When the City of Edmonds drainage system behind the Pak lot is proaerly functioning, the Pak lot incurs no severe geotechnical or foundation excavation problems. If, however, the City of Edmonds drainage system is not properly functioning, or not properly maintained, excessive ground water flows onto and into Mr. Pak's lot. This excessive water flow would greatly increase the construction and foundation costs for Mr. Pak. This should not occur. City of Edmonds / Pak Lot Page three It is sincerely hoped that the promised drainage improvements behind Mr. Pak's lot will actually be installed and properly maintained. Project Plans: Please refer to the following: • Revised November 23, 1998 Phil King Drainage, Land Clearing and Tree Cutting plan. • Site plan and lot layout dated July 12, 1999 by Phil King, including supplemental test pit locations. • Project Plans dated July 13, 1998 by Phil King, revised June 14, 1999. • Revised Plot Plat dated June 14, 1999 by Phil King • Project structural details by H.N. Lehtinen, engineers. The Pak development plans require a concrete retaining wall (maximum height eight feet [8'1) along the east property line (typically one foot inside actual property line). This concrete retaining wall will allow a benched, or staggered tier approach for the foundation work for the Pak residence. The actual rear Pak foundation wall will. be approximately six foot (6) away from this property line retaining wall. The finished floor elevation for the lower level / garage is 139.5 (see plans). As previously stated, if the off -site drainage problems are properly controlled and improved by the City of Edmonds, the temporary shoring technique of stacked ecology blocks will satisfy the geotechnical conditions for residence excavation. Note: As discussed, this engineer does not believe that a significant or potential debris avalanche risk exists to the Pak residence. However, the rear retaining wall could be designed with two to three foot (2' - 3') of "free board" to allow localized erosional sloughing material to collect and not ooze onto the Pak residence itself. The potential risk for any localized surficial sloughing hinges on up slope property owners proper drainage discharge, and avoidance of destructive top -of -slope cutting. As discussed, this engineer's evaluation of the up slope property verified that proper drainage currently exists, and no evidence of any top -of -slope soil cutting was observed. Not to belabor the point, but the greatest contributor to any landslide or sloughing risk to the Pak residence lies with the malfunction, clogging, under - designed or poorly maintained City of Edmonds drainage system. If good drainage City of Edmonds / Pak Lot Page four design and maintenance cannot be assured, perhaps the City of Edmonds should install a massive catchment wall east of Mr. Pak's property. Foundations: Based on the findings of the June 9, 1999 supplemental test pits, and experience with similar properties, this engineer recommends normal, standard, reinforced concrete foundations. As discussed, however, lack of proper drainage control by the City of Edmonds system will result in excessive seepage waters into the Pak excavation. If, somehow, construction goes ahead without good drainage, the additional costs of piling would be required to offset the ground water seepage from the City of Edmonds systems. Project Plans: This engineer has discussed and reviewed the revised project plans with Phil King, Designer, and proposed project contractor, John Guerney. The current project plans are geotechnically approvedsubject to resolution of the City of Edmonds drainage situation and inspections by this engineer. Seismic Hazard: The largest earthquakes which have generally occurred in the Puget Sound area are sub -crustal events, with epicenters ranging from 50 to 70 kilometers in depth. For this reason, no surficial faulting or earth rupture as a result of deep seismic activity has been documented to date in the Snohomish County region. Therefore, based on existing geologic data, the risk of surface rupture impacting the proposed Pak residence is low. Refer to Terra Associates original report from June 6, 1989 for further discussion of seismic and landslide potential. Please note that the lot numbering system has changed from the 1989 report. Construction Timina If, as previously stated and requested, the City of Edmonds drainage system is properly improved, there are no geotechnical restrictions against construction during any time of the year. City of Edmonds / Pak Lot Page five Obviously, winter season construction will result in more than normal delays resulting from bad weather or slightly mushier site. In some ways, however, construction during the winter season will assist in defining the adequacy of the City of Edmonds drainage system. In short, it is to Mr. Pak's advantage to have his foundation exposed during "worst case" weather events in order to verify that the City of Edmonds drainage system is fully capable. This engineer has considerable experience with summertime construction that revealed no drainage problems, only to discover nine months later than the drainage mitigation system was inadequate (unfortunately after foundations have been built and back -filled). Summary: • Phil King Designer plans, as of July, 1999, are geotechnically aamoved. • Normal foundation techniques and temporary ecology block shoring are geotechnically viable, if City of Edmonds drainage system is improved and properly maintained. • The remote possibility of localized sloughing from the rear hillside can be mitigated by a two to four foot (2' - 4') height extension above the proposed property line retaining wall. • Geotechnical inspections by this engineer are required during key phases of construction. Statement of Minimal Risk (Restated): The plans and specifications for the Chun Pak residence at Lot No. 6, Lorian Woods, as designed by Phil King (as of July, 1999) have been reviewed by this engineer and conform to the recommendations of the analysis and report and, provided that those conditions and recommendations are satisfied (especially the City of Edmonds drainage issue) during the construction and use, and inspected and verified by this engineer, the area disturbed by construction will be stabilized and remain stable and will not increase the potential for soil movement, and the risk of damage to the proposed Pak residence and from the Pak residence to adjacent properties from soil instability will be minimal. City of Edmonds / Pak Lot Page six Permit: It is more than time to issue Mr. Pak's permit. If there are any questions, do not hesitate to call. �1S M . B� Hof WASf1,�, G .0fc7Ma 0 R ONAL ti�G EXPIRES 12/23/. DMB:vIb cc: Mr. Chun Pak 4c, C� /�, " Dennis M. Bruce, P.E. Geotechnical / Civil Engineer RETURN ADDRESS: City of Edmonds, City Clerk 121 5th Avenue North Edmonds, WA 98020 Reference #: CONFORMED COPY 200006050422 06/05/2000 01:16 PM Snohomish P.0007 RECORDED County COVENANT OF NOTIFICATION AND INDEMNIFICATION/HOLD HARMILESS Grantor(s): (1) (2) ram" e,17, I✓ . Additional on pg.. Grantee(s): Cityof Edmonds Legal Description (abbreviated):'Sec�Twn .c" 7 Rngtr1� OR Lot Block 000 Plat .ZDO Assessor's Tax Parcel ID#(s): (1) 7 90 V_-000—D0S-00 D 6 (2) __—Assessor's Tax Parcel ID# not yet assigned CITY OF EDMONDS APPROVED FOR RECORDING BY:_ Ja DATE:;AGE OF Under the review procedures established pursuant to the State Building Code, incorporating amendments promulgated by the City of Edmonds, and as a prerequisite to the issuance of a building permit for the construction of a residential structure and attendant facilities, the undersigned OWNERS of property do hereby covenant, stipulate and promise as follows: .9) 1. Description of Subject Property APPROVED FOR RECORDING: BY: -A?> DATE: PAGE Q_ OF This covenant of notification and indemnification/hold harmless relates to a tract of land at the street address of ///0 ,�� ,'1214 Z-- P_ • A (insert street address), Edmonds Snohomish County, Washington and legally described as: "h 1'14 J-/ fZ'�•L��.S` �`� J190�10.7�>.Sd� �e.fn/(.� i./r��.•i,.d7�-n 2. Notification and Covenant of Notification The above referenced site (hereinafter "subject site's lies within an area which has.been identified by the.City of Edmonds as having a potential for earth subsidence or landslide hazard. The risks associated with development of the site have been evaluated by technical consultants and. engineers engaged by the applicant as a part of the process to obtain a building permit for the subject site. The results of the consultant's reports and evaluations of the risks associated with development are contained in building permit file number(insert number) on file with the City of Edmonds Building Department. Conditions, limitations, or prohibitions on development may have been imposed in accordance with the recommendations of APPROVED FOR RECO ING: BY: DA. O PAGE OF U - ] the consultants in the course of permit issuance. The conditions, limitations, or prohibitions may require ongoing maintenance on the part of any owner or lessee or may require modifications to the structures and earth stabilization matters in order to address future or anticipated changes in soil or other site conditions. The statements and conditions proposed by the OWNERS' geotechnical engineer, geologist, architect and/or structural engineer are hereby incorporated by reference from the contents of the file as fully as if herein set forth. Any future purchaser, lessee, lender or any other person acquiring or seeking to acquire an interest in the property is put on notice of the existence of the content of the file and the' City urges review of its contents. The file may be reviewed during normal business hours or copies obtained at the Building Department, City of Edmonds, 121 5th Avenue North, Edmonds, Washington 98020. 3. Indemnification and Hold Harmless The undersigned OWNERS hereby waive any and all Iiability associated with development, stating that they have fully informed themselves of all risks associated with development of the property and do therefore waive and relinquish any and all causes of action against the City of Edmonds, its officers, agents and employees arising from and out of such development. In addition, the OWNERS on behalf of themselves, their successors in Interest, heirs and assignees, do hereby promise to indemnify and hold harmless the City of Edmonds, its officers, agents and employees from any loss, claim, liability or damage of any kind or nature to persons or property either on or off the site resulting from or out of earth subsidence or landslide hazard, arising from or out of the issuance of. any permit(s) authorizing development of the site, or occurring or A APPROVED FOR RECORDING: BY;- DATE:. -TIC PAGE OF �-- arising out of any false, misleading, or inaccurate information provided by the OWNERS, their employees, or professional consultants in the course of issuance of the. building permit. 4. Insurance Requirement. In addition to any bonding which may be required during the course of development, the Community Services Director /has not (strike one) specifically required the maintenance of an insurance policy for public liability coverage in. the amount and for the time set forth below in order to provide for the financial responsibilities established through the indemnification and hold harmless agreement above: 5. Covenant to T uch and —Concern the Land, This covenant of notification - and indemnification/hold—harmless-touches—and concerns -the subject tract and shall run with the land, binding, obligating and/or in to the benefit of future owners, heirs, successors and interests or any other person. or entity acquiring an interest in property, as their interest may appear. This provision shall not be interpreted to require a mortgagor or lender to indemnify the City except to the extent of their loss nor to obligate such persons to maintain the insurance above required. ' I * APPR�VED FOR RECO G: BY: DATE• 1 PAGE OF DONE this day of A-y z0.5 199e, OWNER(S) By: By: III C� By STATE OF WASHINGTON r� - - . ,_, )ss: COUNTY OF Oh VVf- I certify that I know or have satisfactory evidence that signed this instrument and acknowledged it to b "(hi er) "free and voluntary act for the purposes mentioned in this instrument. g Wz� - - - - -- -- o' n F n : i°c;OTAR �.. Pu--�C �Ir "'N OF WAS DATED L:ITEMMUMI)INGIMEADOWTOVENANT I J 199L. NOTARY' C My commission expires: a OJ + . 1 APPROVED FOR RECO ING: DATE: PAGE �_ OF STATE OF WASHINGTON ) ss: COUNTY OF ) I certify that I know or have satisfactory evidence that _ h 0,1 P4 signed this instrument and acknowledged it to be (hi& free and voluntary act for the purposes mentioned in this instrument. U P ol LATEMPIBUII.DINGIMEADMCOVENANT NOTARY PUBLIC My commission expires: y� 199 A M.S.C.E., M.B.A. Mr. Chun H. Pak 3828 N. E. 110th Seattle, Washington 98125 Geotechnical / Civil Engineer Y�/ July 27, 1998 y Subject: Geotechnical Evaluation Proposed New Residence 16109 - 73rd Place West, Edmonds, Washington This engineering report presents the results of a geotechnical evaluation of Lot No. 6 at 16109 - 73rd Place West, Edmonds, Washington. This evaluation was required due to owner and architect concerns, as well as City of Edmonds requirements. REFERENCES: • Location map (figure 1) • Geotechnical Report of the overall Lorian Woods property for Robert and Joanne ,Anderson, dated June 6, 1989, by Terra Associates, Inc. • Site photographs • Proposed Mr. Chun Pak house design by Mr. Phil King, Designer BACKGROUND: Lot No. 6 (16109 - 73rd Place West, Edmonds, Washington) of the overall Lorian Woods Development, exists along the private road 73rd Place West (see Lorian Woods layout map). Lot No. 6 is approximately sixty foot (60') deep and seventy-eight foot (78') wide, in an approximate rectangular shape. Lot No. 6 has never been developed. Surrounding lots in Lorian Woods have been developed within the last six years. The property immediately behind (easterly) of the Pak Lot No. 6 is understood to have been dedicated as Native Growth Protection Area, or green belt designation. The primary geotechnical aspects affecting the proposed single family residence development of Lot 6 are slopes and drainage. Lot No. 6 contains gentle to moderate topography (from five percent (5%) to thirty percent (30%) slopes]. The slopes behind (easterly) of the Pak lot contain slopes at approximately 2H:1V. SOILS • FOUNDATIONS 17814 8th. Ave. N. SITE DEVELOPMENT. • INSPECTION • DRAINAGE • DESIGN & PERMIT • LEGAL W. Shoreline, Washington..98177 • (206) 546-9217 ,i FAX 546-8442 r. . Pak Page two The slopes behind the Pak lot evidence significant and year-round ground water and seepage outflow. It is understood that the City of Edmonds has required the installation of a significant number of intercept and deep drain wells. EVALUATION: Visual assessment of Lot No. 6 revealed no evidence of any geotechnical distress. No slides, no settlements, no tension cracks, no creep, nor any significant erosional degradation were observed. As mentioned, seepage groundwater "trickle" flows were observed, and are evident in the photographs with regard to street discharge into the existing storm water system. This engineer obtained a copy of the Terra Associates, Inc., geotechnical report, dated June 6, 1989 from the City of Edmonds. This report provides extensive geotechnical analysis and slope stability evaluation. This engineer reviewed the test bore holes, as well as the backhoe-dug test pit information in the Terra report. This engineer's direct experience in the area verifies the stratigraphy reported in the Terra report. In order to augment the existing site geotechnical information, soil test pits were hand -dug by this engineer in the proposed location of the Pak residence. All of the five (5) hand -dug test pits contained similar findings, namely: 0" to 4" Organics, roots, and organic silt 4" to approx. 14" Silty sand, moist, medium dense 14" to approx. 34" (bottom of Increasingly dense sandy silt / sandy silt hand -dug test hole) Seepage water was evident in all test pits. o water was encountered in any of the three test pits. All test pit walls remained vertical and stable. No sloughing or caving occurred. CONCLUSIONS / RECOMMENDATIONS: Based on the findings of this investigation, review of the June 6, 1989 Terra Associates, Inc., report, and experience with similar sites in the area, Lot No. 6 is geotechnically approved for the proposed Mr. Chun H. Pak single family residence, per Phil King designs, subject to the following: • Standard reinforced continuous and spread footings. Allowable bearing pressure: 2,000 p.s.f. Equivalent fluid pressure of 35 p.c.f. is recommended for any retaining wall design provided drainage zone is inspected and verified by this engineer. • For retaining wall design, use friction factor of 0.55 and passive pressure of 350 p.c.f. Pak Page three An intercept French -type drain is recommended along the eastern property line and graded to "wrap around" the new Pak residence. This intercept ditch will be approximately thirty-six inches (36") deep, and provide seepage pressure release around the Pak residence (specific designs provided prior to site grading). • Geotechnical inspection by this engineer prior to any foundation concrete placement. The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed native soils or on structural fill placed above native soils. See the later sub -section entitled General Earthwork and Structural Fill for structural fill placement and compaction recommendations. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty- four (24) inches, respectively, and should be bottomed at least eighteen (18) inches below the lower adjacent finish ground surface. Depending on the final site grades, some overexcavation may be required below footings to expose competent native soils. Unless lean concrete is used to fill the over excavated hole, the width of the overexcavation at the bottom must be at least as wide as the sum of two times the depth of the overexcavation and the footing width. For example, an overexcavation extending two feet below the bottom of a three-foot wide footing must be at least seven feet wide at the base of the excavation. Footings constructed according to the above recommendations may be designed for an allowable soil bearing pressure of three thousand (3,000) pounds per square foot (p.s.f.). A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that total post -construction settlement of footings founded on competent, native soils (or on structural fill up to five (5) feet in thickness) will be about one-half inch, with differential settlements on the order of one -quarter inch. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the bearing soils, or by passive earth pressure acting on the vertical, embedded portions of the foundations. For the latter condition, the foundations must either be poured directly against undisturbed soil or the backfill placed around the outside of the foundation must be level structural fill. We recommend the following design values be used for the foundation's resistance to lateral loading: Parameter Design Value Coefficient of Friction 0.55 . Passive Earth Pressure 350 p.c.f. 1 Pak Page four Where: (1) p.c.f. is pounds per cubic foot. (2) Passive earth pressure is computed using the equivalent fluid density. We recommend that a safety factor of at least 1.5 be used for design of the foundation's resistance to lateral loading. SLABS -ON -GRADE: Slab -on -grade floors may be supported on undisturbed, competent native soils or on structural fill. The slabs may be supported on the existing soils provided these soils can be recompacted prior to placement of the free -draining sand or gravel underneath the slab. This sand and gravel layer should be a minimum of four (4) inches thick. We also recommend using a vapor barrier such as 6-mil. plastic membrane beneath the slab with minimum overlaps of 12 inches for sealing purposes. PERMANENT FOUNDATION AND RETAINING WALLS: Retaining walls backfilled on one side only should be designed to resist lateral earth pressures imposed by the soils retained by these structures. The following recommended design parameters are for walls less than twelve (12) feet in height which restrain level backfill: Parameter Active Earth Pressure* Passive Earth Pressure Coefficient of Friction Soil Unit Weight Where: Design Value 35 p.c.f. 350 p.c.f. 0.55 125 p.c.f. (1) p.c.f. is pounds per cubic foot (2) Active and passive earth pressures are computed using equivalent fluid densities. For restrained walls which cannot deflect at least 0.002 times the wall height, a uniform lateral pressure of one hundred (100 p.s.f. should be added to the active equivalent fluid pressure). The values given above are to be used for design of permanent foundation and retaining walls only. An appropriate safety factor should be applied when designing the walls. We recommend using a safety factor of at least 1.5 for overturning and sliding. • • Pak Page five The above design values do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads will be placed above the walls. If these conditions exist, then those pressures should be added to the above lateral pressures. Also, if sloping backfill is desired behind the walls, then we will need to be given the wall dimensions and slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of the wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. Placement and compaction of retaining wall backfill should be accomplished with hand -operated equipment. Retaining Wall Backfill Backf ill placed within eighteen (18) inches of any retaining or foundation walls should be free -draining structural fill containing no organics. This backfill should contain no more than five (5) percent silt or clay particles and have no particles greater than four (4) inches in diameter. The percentage of particles passing the No. 4 sieve should be between twenty-five (25) and seventy (70) percent. Due to their high silt content, if the native soils are used as backfill, a drainage composite, such as Mirafi and Enkadrain, should be placed against the retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. the purpose of these backfill requirements is to assure that the design criteria for the retaining wall as not exceeded because of a build-up of hydrostatic pressure behind the wall. The subsection entitled General Earthwork and Structural Fill contains recommendations regarding placement and compaction of structural fill behind retaining and foundation walls. EXCAVATION AND SLOPES: In no case should excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts up to a height of four (4) feet deep in unsaturated soils may be vertical. For temporary cuts having a height greater than four (4) feet, the cut should have an inclination no steeper than 1:1 (Horizontal: Vertical) from the top of the slope to the bottom of the excavation. Under specific recommendations by the geotechnical engineer, excavation cuts may be modified for site conditions. All permanent cuts into native soils should be inclined no steeper than 2:1 (H:V). Fill slopes should not exceed 1:1 (H:V). It is important to note that sands do cave suddenly, and without warning. The contractors should be made aware of this potential hazard. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an • • Pak Page six appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. DRAINAGE CONSIDERATIONS: Footing drains are recommended at the base of all footings and retaining walls. These drains should be surrounded by at least six (6) inches of one -inch -minus washed rock wrapped in non -woven geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At the highest point, the perforated pipe invert should be at least as low as the bottom of the footing and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. Groundwater was observed in the test pits during the field work. Seepage into the planned excavation is possible, and likely if excavation occurs during winter months, and if encountered should be drained away from the site by use of drainage ditches, perforated pipe, French drains, or by pumping from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Any exposed slopes to be covered with plastic to minimize erosion. Final site grading in areas adjacent to buildings should be sloped at least two (2) percent away from the building, except where the area adjacent to the building is paved. GENERAL EARTHWORK AND STRUCTURAL FILL: The proposed building and pavement areas should be stripped and cleared of all surface vegetation, all organic matter, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill. NOTE: Specific clearing limits to be established at pre -construction meeting with City of Edmonds Building Department. Structural fill is defined as any fill placed under the building, behind permanent retaining or foundation walls, or in other areas where the underlying soils needs to support loads. This engineer should observe site conditions during and after excavation prior to placement of any structural fill. All structural fill should be placed in horizontal lifts with a moisture content at or near the optimum moisture content. The optimum moisture content is that moisture content which results in the greatest compacted dry density. The moisture content of fill soils is very important and must be closely controlled during the filling and compaction process. • C� Pak Page seven The allowable thickness of the fill lift will depend on the material type, compaction equipment, and the number of passes made to compact the lift. In no case should the lifts exceed twelve (12) inches in loose thickness. The following table presents recommended relative compaction for structural fill: Location of Fill Placement Beneath- footings, slabs or walkways Behind retaining walls Beneath pavements Minimum Relative Compaction 95% 90% 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum relative compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D-1557-78 (Modified Proctor). Use of On -Site Soils If grading activities take place during wet weather, or when the silty, on -site soils are wet, site preparation costs may be higher because of delays due to rains and the potential need to import granular fill. The on -site soils are generally silty and thus are moisture sensitive. Grading operations will be difficult when the moisture content of these soils exceeds the optimum moisture content. Moisture sensitive soils will also be susceptible to excessive softening and "pumping" from construction equipment traffic when the moisture content is greater than the optimum moisture content. Ideally, structural fill which is to be placed in wet weather should consist of a granular soil having no more than five (5) percent silt or clay particles. The percentage of particles passing the No. 200 sieve should be measured from that portion of the soil passing the three -quarter -inch sieve. The use of "some" on -site soils for fill material may be acceutable if the upper organic materials is segregated and moisture contents are monitored by engineering inspection. DRAINAGE CONTROLS: Existing Lot No. 6 runoff is directed into the existing storm water system in 73rd Place West. This engineer understands that the City of Edmonds has approved of the existing storm water system. Discussions with existing neighbors have revealed no J Pak Page eight evidence of any malfunctions of the existing storm water system. Proper construction of the Pak residence along with the recommended east property line intercept trench will provide good drainage controls for Lot No. 6. Compliance with standard storm water detention methods in accordance with the City of Edmonds requirements are geotechnically acceptable. CONCRETE: All foundation concrete (footings, stem walls, slabs, any retaining walls, etc.) shall have a minimum cement content of 5-1/2 sacks per cubic yard of concrete mix. INSPECTION: The recommendations of this report are only valid when key geotechnical aspects are inspected by this engineer during construction: • Soil cuts • Foundation subgrade verification • Retaining wall, or rockery placement • Any fill placement • Eastern property line intercept drainage ditch with appropriate tight -line "wrap around" release • Subsurface drainage installation SUMMARY: The proposed Mr. Chun H. Pak single family residence on Lot No. 6, Lorian Woods, Edmonds is geotechnically viable when constructed in accordance with the recommendations herein, compliance with City of Edmonds approved plans and requirements, and key geotechnical inspection during construction. STATEMENT OF MINIMAL RISK: The plans and specifications for the Mr. Chun H. Pak residence at Lot 6 of Lorian Woods, as designed by Phil King, Designer, have been reviewed by this engineer and conform to the recommendations of the analysis and report and, provided that those conditions and recommendations are satisfied during the construction and use, and inspected and verified by this engineer, the area disturbed by construction will be stabilized and remain stable and will not increase the potential for soil movement, and the risk of damage to the proposed development and from the development to adjacent properties from soil instability will be minimal. Pak Page nine CLOSURE: The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering principles and practice. No other warranty, either express or implied, is made. The conclusions are based on the results of the field exploration and interpolation of subsurface conditions between explored locations. If conditions are encountered during construction that appear to be different than those described in this report, this engineer should be notified to observe the situation and review and verify or modify the recommendations. If there are any questions, do not hesitate to call. Dennis M. Bruce, P.E. Geotechnical / Civil Engineer 1ON .I �f ♦ I CIEI'-�1!�PP.;1�_Pl ., uri u R .� all Z SCALE 11 30' t��AL pESG�? 1 �'T•1.oN Lois S4, 5vo, 5(v 4 r77 OF 745 FLAT of to ALS F`-,dC14 IN vol- . 5 DE PLATS SNo�n�1�+� GOUN-rY,�VAs�i�N�-;�N \ \\ \ \ \ \� \ \ \ \ \ \�\•., \ `\ �\ Y` \ ��`r \,�ti 6.. - _ _ _ - - --- -- !; IB'COL LEGTDR 24"COLTD a3A( CJ rJ7, \ \♦ \\ \ \\ \\ \ \\ _ �\ \� , i� 178-- R �_� �-' I'�Z PIP_ Z , S \ •'lJ �� -'`__ -- _ \ �-� �'�P�iZ'f `r' L i N ILA /`I 1 , \� \\\ ♦ \ / 1°\\ \�J � ` �\ \ \\ \\\ ' /Q� ~'�— 148 `__ �1 -"""'� �b (6L �4 - - �_ \\\`��`_—�—e 4-vERK STAND PIPE �`V WaTF-V- Mlb►IN r-L ` , \ \ `♦ 1WE I C8 1�46 ---- _ .i Ib0 - �;4,. COILECTdR \�—�l�i I"��.CZ�( '� °' �?✓iZ. 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