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16107 74TH PL W.PDFIIIIIIIIIIII5952 16107 74TH PL W ADDRESS: TAX ACCOUNT/PARCEL NUMBER: W l���� ow O 1 C) G C BUILDING PERMIT (NEW STRUCTURE): q 0`l JtJ� COVENANTS (RECORDED) FOR: -1! CMWU lA aC 7/ 1 2 ( b IV S) CRITICAL AREAS: 7 7. DETERMINATION: ❑ Conditional Waiver ❑Study Required Waiver DISCRETIONARY PERMIT #'S: DRAINAGE PLAN DATED: PARKING AGREEMENTS DATED: EASEMENT(S) RECORDED FOR: PERMITS (OTHER): PLANNING DATA CHEC: SCALED PLOT PLAN DA SEWER LID FEE $: ' LID #: C:�? l U SHORT PLAT FILE: �! LOT: BLOCK: SIDE SEWER AS BUILT DATED: SIDE SEWER PERMITS) #: Vo2 GEOTECH REPORT DATED: ZZ�gZ� STREET USE / ENCROACHMENT PERMIT #: FOR: WATER METER TAP CARD DATED: it -.2 U OTHER: LATEMP\DSTs\Forms\Street File Checklist.doc 4. pop' Io 2(a >Ik �1.�00o e T \N (00 STREET FILE II `' o o1. LAI Z ' 0 2 y cc w 34 . ROpf w t OIL m - �, '+ a 2 _ — S�3 Fa 9 S 3ILI,Flu l AIGHO `' . h V / E �.14 ��T iut j tt o 's • F q .. .. ... , ^!V r� 91 94 Oo .. tU-..T ENV: � ,.,�,$� � A/�3 . _.. r> ` - �- �;•- l ��,�'�..._.==-�. �7Y r, .r 145 . 44 f �.l, `��i;b19`�t T}y,yy�� � ��**�}.j fy &t' "�'�,o,�t,",�,�/h ' .ti�,�'¢.�t.� '�. 7�.��yi�' �T^ ��'`r'�{µ'�{�•.,.'f,p"yby+cyicy.F. , �> .r war^ �, °f�,�q�y ¢'`` �-.f3fi`FTt'YweF3� 'B4fi F w'�"+'/ t17i T tr ��' 'i%>S �,`.✓,M� '�tti��� . t ^R"' �'.�• �' r -f_ CITY OF tMEMFILE SIDE SEWER PERMIT ,89p.,t 9qz - - PERMIT 6112 8420 Address of Construction: Property Legal Description (Include all easements): RECEIVED n -oyo - no nb NOV 1 8 1992 PUBLIC WORKS DEpT. Owner and/or Contractor: State License No. L X Single Family ❑ Multi -Family (No. of Units ) ❑ Commercial ❑ Public IAZN)C- (0VV)JG4Y11/ L (.A(LW.S Building Permit No. 931 Invasion into City Right-of-Way:y No ❑ Yes RW Construction Permit No. Cross other Private Property: Flo ❑ Yes Attach legal description /and copy of recorded easement I certify -That I have read and shall comply with all city requirements as indicated on the back of the Permit Card. Dat * CALL DIAL -A -DIG (1-800=424\5555) BEFORE ANY EXCAVATION :OFFICE USE ONLY * FOR INSPECTION CAL4. PUBLIC WORKS DEPT. Permit Fee: -?d • , �6 771-MIssuged By Trunk Charge: rs ' Uv Date Issued:��2-- Assessment Fee: Receipt No.: Lid No.: Partial Inspection: Date Initial Comments Reason Rejected: Date -Initial - Final Inspection Approved: Datel I-01V Initia ** PERMIT MUST BE POSTED ON JOB SITE ** White Copy: File, Green Copy: Inspector Buff Copy: Applicant Revised 3.190 Side Sewer Drawing w The City of Edmonds EASEMENT NO. _. -._-"_-_-_.-"----------------------------- NEW CONSTRUCTION REPAIRS ❑ LID NO ................... .ASMT. NO, -____-_._...__---- OWNERCONTRACTOR-----------------•------•--------•-•-----------•-------------------------•-------- PERMIT NO. JOB ADDRESS ..,..1-U._-- ----` T----C.'---`-.-_,__ LEGAL DESCRIPTION: LOT NO- ------ ------------------------------- BLOCK NO. -------------------------•---.------ w t cnCD O i to cq C c: n p Qn ; cr p - -3c: sna 9: ; TNi��.a � El to �. s ' c: i C` r PWW-0001-11/75 (REV.11/78) NAME OF ADDITION ------------------------------------------------------------------------------------------- t Nrv�% —1L i 7L. Approved: DATE ` L..G �J._ /... B i Y --- Site Information �• 4PRECEIVED C rkica. Areas C hec kHst APR 2 4 1992 PERMIT COUNTER Project Name:�rL,��( �acnJZt Permit Number: 2 Site Location: %Q0,V L07 10 Lz2i� � Property Tax Account Number: Approximate Site Size cres or square feet): �`o Have you filled out a Critical Areas Checklist for a project on this site before? �C� General Site Conditions 1. Has the site been cleared or logged? Date of most recent action: Soils / Topography 2. In the Snohomish County Soil Survey, what is the mapped soil type(s)? rcx - 3. 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 of horizontal distance.) _Steep: grades of greater than 30% present on site. Comments 1H ydrology/'Vegetation 4. Site contains areas of year-round standing water: 0 5. 6. 7. 8. Site contains areas of seasonal standing water: N 0 Approx. Depth: Site is in the floodway ND floodplain )�,�of a water course. Site contains a creek or an area where water flows across the grounds surface? N_b flows are year-round? Flows are seasonal? Site is primarily: forested ; meadow ;shrubs ; mixed 9. Obvious wetland is present on site: Mr) 10. Wetland inventory or map indicates wetland present on site: 11. Critical Areas inventory or map indicates any Critical Area on site:yC� ............... ......_.. _ _ .. _ ....__......... ....... ...__........ . Use :Only ---------------___------------ _ :or �--- - ,_ _Y_ __ STUDY. REQU.IRED:_Critical areas study is required. -- Z 4,6105 ccsmp aA_ waaiM1e�l 111111W 1. , 4 699-19y City of Edmonds Critical Areas Checklist 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. With a signed copy of this form, the applicant should also submit a vicinity map of the parcel with enough detail that City staff can find and identify the subject parcel(s). In addition, the applicant is encouraged to include any other pertinent information or studies in conjunction with this Checklist to assist staff in completing their preliminary assessment of the site. I have completed the attached. Critical Area Checklist and attest that the answers provided are factual, to the best of my knowledge (fill out the appropriate column below). Owner / Applicant: Name Title Street Address . City, State, ZIP Phone Signature Date Applicant Representative: Name e�LAJ N Title Street Address ��6' 0/4 2Z G 7-7,-� City, State, ZIP Phone y `�r2� ii a Date CITY OF EDMONDS CONSTRUCTION PERMIT APPLICATION OW ER NAh1E/NAME F BUSINESS ,� ¢ (LURM Liz P_-A MAILING ADDRESS CITY ZIP TELEPFfJ JUM &co 4..L10 WA 23OI 1 ``��C �. NAME L) ADDRESS 1059 q - A,t,z a CITY ZIP TELEPHONE NUMB3ERR •) ?/ USE —KRMIT ZONE '? 11 �J UMBEI ADDRESS / (_) / /; I _ A � - 9205. 31 SUITE/APT p LEGAL DESCRIPTION CHECK SUBDIVISION 1py5'jj) LID N tx- F,�, - /- 1"9 2 () PUBLIC RIGHT OF WAY PER OFFICIAL STREET MAP. TESCP Approved ❑ RW Permit Required ❑ EXISTINGREQUIRED DEDICATION Street Use Permit Req'd ❑ PROPOSED 1 I� �(7 ', � >>1rer,- Inspection Required Sidewalk Required ❑ C REMARKS B �•G• WI61n1 f-'I y4AL,. Niel6e4 I NL f • IZ(Z ►!� . „f"�^ ENGINEERING MEMO DATED 12 R VIEW By ADDRESS _j2l6v ILL) I4ETER SI� !�-,.., ,BUILDING SUPPLY SIZE NG OF FIXTURES CITY TELE fM .. REMARK / v �qp sT It^MGE9li �� �O C71 i^ Legal Description of Property - include all easements 0- 0- 51 OF — W W 0 � Property ---yam9 Tax Account 0Z4+ CM — D1 D —OOO Parcel No. ! NEW RESIDENTIAL OLUMBING ADDITION COMMERCIAL I REMODEL ❑ APT.BLDG. - I* G DIN FENCE REPAIR CYOS. ( X _FT) DEMOLISH O S VE 9WIAh�ddL ❑ INSERT WALL/ . HOT TUB/S144 GARAGE RETAINING CARPORT ® ROCKERY RENEWAL Z _. O a (TYP USE, BUSINESS OR ACTIVITY) EXPLAIN: f it L. 2 wNUMBER OF STORIES JNOF o l-T-j',�� DWELLING QN'� m /'� UNITS O 0 DESCRIBE WORK TO BE DONE (ATTACH PLOT PLAN) SIGN AREA SEPA REVIEW AD NO. ALLOWED PROPOSED co,EXEMPT �). . /3 4 EXP ` SHHHO% ELINE a / / 4- VARIANCE OR Cu PLANNING REVIEW BY 8 7' ATE (V_ 15 y_1Z � z- SETBACKS - F HEIGHT LOT C�OJVER GE' FRONT' e) SIDE t:.,/ REAR /" 7� _ ECK D �� TYPE OF CONSTRUCTION COD SPECIAL INSPECTOR AREA OCCUPANCY REQUIRED GROUP VES REMARKS PROGRESS INSPECTIONS PER UBC 305 S0/45 RoPv, 45Y /CX91'-J CX- 5rA1mr4a1AV ray 61sr rgVAF v FINAL INSPECTION REQUIRED,. VALUATION, PLAN CHECK FEE BUILDING HEAT OURCE: GLAZING 2da-70 O/D PLUMBING Plan Check No. 0 MECHANICAL GRADING/FILL This Permit covers work to be done on private property ONLY. Any construction on the public domain (curbs, sidew?Iks, -driveways, marquees, etc.) will require separate permission. STATE SURCHARGE Permit Application: 180 Days_'_, Permit Limit: 1 Year - Provided Work is Started Within 180 Days . STORM DRAINAGE FEE ENG.:INSPECTION FEE "Applicant, on behalf of his or her spouse, heirs, assigns and successors in interest, agrees to indemnify, defend and hold harmless the City of Edmonds, Washington, its officials, employees, and agents from any and all claims for damages of whatever nature, arising directly or indirectly from the issuance of this permit. Issuance of this permit shall not be deemed to modify, waive or reduce any requirement of any city ordinance nor limit in any way the City's ability to enforce any ordinance PLAN CHECK DEPOSIT TOTAL AMOUNT DUE provision." I hereby acknowledge that I have read this application; that the information given is correct; and that I am the owner, or the duly authorized agent of the owner. I agree to comply with city and state laws regulating construction; and in doing the work authoriz• ed thereby, no person will be employed in violation of the Labor Code of the State of Washington relating to Workmen's Compensa• ATTENTION THIS PERMIT AUTHORIZES ONLY THE WORK NOTED ATTENT ON IT IS UNLAWFUL TO USE OR OCCUPY A BUILDING OR STRUCTURE UNTIL A FINAL INSPECTION HAS BEEN MADE AND APPROVAL OR A CERTIFICATE OF OCCUPANCY HAS BEEN GRANTED. UBC CHAPTER 3. INSPECTION DEPARTMENT CITY OF EDMONDS CALL FOR INSPECTION 771-0220 HEIGHT OCCUPANT LOAD / a 3 z Z Z Q (L 0 Z s 5 m YI�i✓ �. 98 . � _ , APPLICATION APPROVAL This application is not a permit until' signed by the Building Official or his/,her Deputy; and fees are paid, and receipt is acknowledged in space pro)if'ded. TE 01 RIGINAL — File YELLOW — Inspector PINK — Owner GOLD — Assessor • ��� ��� fit-/ Pz TERRA ASSOCIATES, Inc. ' ° ' ° Consultants in Geotechnical Engineering, Geology • ' • ' ` and ' Environmental Earth Sciences 11 IJ LJ 1 `� � R A:IN ��- .� Project T-840-5 January 22, 1992 Stephen R. Sullivan AIA The Sullivan Company 7215 175th Street SW Edmonds, Washington 98020 Subject: Derry Residence Lot 10, Lorian Woods Edmonds, Washington References: Geotechnical Report, Project T-840-1 Meadowdale Beach, Lots 54 to 57 Lorian Woods Approved Construction Plans Sheets 1 thru 6, by Dowl Engineers Preliminary Plans for Derry Residence by The Sullivan Company Dear Mr. Sullivan: We understand the Derry residence will be constructed on Lot 10 south of the existing Anderson residence, as shown on Sheet 2 of Dowl's Lorian Woods drawings. The stability of this property was discussed in the referenced geotechnical report. In our opinion, the probability of earth movement on this lot within a period of 25 years most likely is less than ten percent and the lot therefore is suitable for residential construction. This risk of earth movement will be further reduced by improvements to subsurface drainage afforded by the residence's foundation drains, and by removing from the lot a weight of spoil that exceeds the weight of the residence. The preliminary plans we have examined are consistent with the intent of the referenced geotechnical report and are therefore acceptable. In our opinion, the risk of damage to the proposed residence and to adjacent properties from soil movement will be minimal, subject to the conditions set forth in the report. Once the residence's foundations are constructed and backfilled, the potential for soil movement should decrease, for the reasons noted above. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821-7777 ' f The Sullivan Company Project T-840-5 January 22, 1992 Page 2 The preliminary plans indicate ground floors at Elevation 99 feet, which is below present grades on ' the site, except at the southwest comer. As explained in the referenced geotechnical report, the soil at Lorian Woods is landslide debris, which may provide relatively poor bearing conditions for conventional footings. To explore subsurface conditions on Lot 10, we excavated three test pits to ' elevations a few feet below the proposed footing bearing grade. Figure 1 shows the approximate test pit locations and the residence's ground floor footprint. Logs of the test pits are reported on Table A ' The test pits encountered both silty and sandy landslide debris, as expected. No free groundwater or excessive organic material was observed in the pits. Caving of the pit walls did not occur during the ' brief period the pits were open. Based on the test pits, it appears that conditions generally satisfactory for conventional spread ' foundations will be exposed on the bottom of the proposed excavation. However, bearing conditions worse than those observed in the test pits may be present at locations not explored, or may result from rainfall or from adverse groundwater conditions that may be present at the time the excavation ' is made. Bearing conditions are most likely to be satisfactory if the excavation is opened during the dry summer season. In any case, bearing conditions should be examined before footing forms are constructed. Unsuitable materials, if present, should be removed to firm ground and the ' overexcavations backfilled with quarry spalls or washed gravel, or with compacted pit -run gravel. Alternatively, pin piles of two -inch -diameter steel pipe driven with a jackhammer could be used, if needed, to compensate for unsatisfactory bearing conditions: ' To reduce the risk of foundation settlements due to possible uneven bearing conditions, we recommend proportioning footings for a maximum bearing stress of 1200 pounds per square foot and ' using extra steel reinforcement in the footings and the foundation walls. In addition, we recommend combining any interior footings into strips and connecting them to nearby foundation wall footings. ' The east perimeter foundation walls should be designed for an equivalent fluid weight of 50 pounds per cubic foot (pcf), plus a uniform stress of 100 pounds per square foot. For other walls that support lateral soil stress, the 50-pcf equivalent fluid weight can be reduced to 40 pcf. Where the ground floor is below outside final grades, perforated drainpipe and free -draining backfill should be installed outside the basement walls and connected to the storm water catch basin near the southwest corner of the lot. ' In order to construct the lower ground floor at Elev 99, a cut to depths about ten feet below present grades must be made for the east foundation wall. In our opinion, a cut this deep is acceptable on ' Lot 10 because the backslope east of the excavation rises only a short distance to level ground. There is virtually no risk that the excavation might endanger either the Lorian Woods driveway and utilities or the slopes east of the driveway. ' Nevertheless, care should be taken in making this excavation. Because the landslide debris is loose, it may stand only briefly on steep slopes. We recommend trimming temporary slopes more than ' about four feet high at approximately 1 horizontal to 1 vertical. If groundwater is encountered, flatter slopes may be required. The water level in the observation well we installed in Test Pit 2 should be read before the excavation is opened. Excavation slopes will be most stable if the ' groundwater level is below the proposed bearing grade, as it is at the present time. The Sullivan Company • • Project T-840-5 January 22, 1992 Page 3 We appreciate the opportunity to review your preliminary plans. We expect the City will require that our firm review the construction plans submitted for permit. We will be pleased to provide this service after the plans are prepared. In addition, the City likely will require that a completed Environmental Checklist be included with the submittal package. The checklist can be filled out by yourself and the Derrys. Please call if you have any questions concerning the checklist's few geotechnical questions. Sincerely, TERRA ASSOCIATES, INC W-. W 1; #4":-��Jl William il m Bailey Project Manager WB/mp enc: Figure 1 Table A cc: Bill Derry 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 TABLE A LOGS OF TEST PITS Test Pit No. 1 Depth, ft Description 0-1.5 Slash and topsoil. 1.5-4 Brown silty fine sand, wet and loose. 4-13 Fractured silts on uphill side of pit, brown silty fine sand on downhill side of pit. Some light caving, no seepage. Test Pit No. 2 Depth, ft Description 0-1 Topsoil and slash. 1-8 Stiff brownish gray silt. qu=1.5 to 2.0 tsf. 8-9 Brown silty fine sand. 9-13 Tan -gray mixture of sand, silt and pebbles. qu=1.5 to 2.0 tsf. Becomes tan -gray clayey silt with hard chunks, wet. qu=1.5 to 2.5 tsf. No seepage, no caving. Groundwater observation well installed. Test Pit No. 3 Depth, ft Description 0-10.5 Gray -tan silty clay, wet, with hard chunks. qu=1.5 to 3.5 tsf. No seepage, no caving. Derry Residence Project T-840-5 1' 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 930200 0475 'ok, TREIT Rk PF8 11 40 COVENANT OF NOTIFICATION AND INDEMNIFICATION/HOLD HARMLESS 4 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: 1. Description of Subject Property. This; covenant - notification and indemnification/hold harmless relates to a tract of land at the street address of IGIC37 -7 yi-EL 7�cE (insert street address), Edmonds, Snohomish County, Washington and legally described as: VOLUME I WE�n-D-s OF �c i D 4"" -7'�l oL4 o00 - o I O - Ocxb 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 i 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 WSS52079A/0006.040.034 WSS/klt 02/08/90 the risks associatedwith development are contained in building / permit file number _`7 2,053 (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. 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 th'le 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 Planning Department, City Hof Edmonds, 505 Bell Street, Edmonds, Washington 98020, 3. I_hdemnification 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, its11officers, agents and employees e WSS52079A/0006.040.034 -2-'i WSS/ klt 02/08/90 arising from and out of such development. In addition, the OWNERS on behalf of themselves,l, their successors in b interest, heirs and assignees, do hereby promise to indemnify and hold harmless the City of•Edmonds, its officers, agents and emp loyees from any loss, claim, liability or damage of any kind or nature to persons or property either on or off the site resultingfrom or out of earth subsidence or landslide hazard, arisingfrom m or out of the issuance of any permit(s) authorizing development of the site, or occurring or 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 Reauiremente In addition to any bonding which may be required during the course of development, the Community Services Director has/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 or � der to provide for the financial responsibilities established through the indemnification and hold harmless agreement above: ��HIS ��QVl2�r-(BUT MUST- '3� Co7-i o f �N42 �2cxjA L L i�-t-Tc�� [ insert insurance' re `� �1Ux�S �'�` • Z'7 . Z quirements and time pe¢iod, if any --if no insurance required, so state.] Q WSS52079A/0006.04.0.034 WSS/klt -3- 02/08/90 S. Coll", v ant 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. DONE this c�g day of r� , 199- OWN By. By: By: STATE OF WASHINGTON ) ss: COUNTY OF I certify that I know or have satisfactory evidence that l signed this instrument and acknowledged' Q WSS52079A/0006.040.034 -4- WSS/k1t 02/08/90 9 3 uz ® 417 Qa it to be (his/her) free and voluntary act for mentioned in this instrument.+'' DATED thisY of 19 921�da .ej NOTARY PUBLIC ,T My commission expires: STATE OF WASHINGTON ) ) ss: COUNTY OF ) I certify t at I know or have satisfactory evidence that 6j-%114h1 E. errU signed this instrument and acknowledged it to be (his/her) free and voluntary act for the ur mentioned in this instrument. DATED this 21f( day of NOTARY UBLIC My commission expires: STATE OF WASHINGTON ) COUNTY OF ss: ) I certify that I know or have satisfactory evidence that signed this instrument, on oath stated that (he/she) was authorized to execute the instrument and acknowledged it as the (title) of (name of party on behalf of whom instrument was executed) to be the free and, voluntary act of such party for the uses and purposes mentioned in this ins I DATED this day of WSS52079A/0006.040.034 WSS/klt 02/08/90 , 199_. NOTARY PUBLIC My commission expi I d N O �? w o <. '*1 r rl -� fV 7 o it? c.1sW3 EO X CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: www.d.edmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering GARY HAAKENSON MAYOR Mr. William Derry, President February 24, 2006 Lorian Woods Homeowners Association 16107 741h Place West Edmonds, Washington 98026 Dear Mr. Derry: In response to a recent localized slide, City officials conducted a site inspection on January 31, 2006 and observed slide damage to have occurred on private property west of Sequoia Ridge Lot 3. Debris from this slide extended downslope onto Tract A and near the base of Lot 2 undeveloped property itl the plat of Lorian Woods. Accompanying City officials was a representative of Landau Associates, the City's professional geotechnical consultant. Landau, Associates conducted a site reconnaissance and subsequently prepared a report (copy enclosed dated; 2/17/06) that describes the observed slide. The purpose of this letter is to alert the Homeowners Association of the current situation as we know it, so that the Association may take whatever action deemed appropriate. The City recommends that Association representatives visit the site with a professional Geotechnical Engineer for an independent assessment of Tract A property to provide recommendations about any possible site restoration that may be advisable to undertake to protect this property. If your geotechnical engineer requires restoration, slope mitigation or improvements, an approved permit from the City is required in advance, pursuant to City Ordinance #2661, which regulates the Earth Subsidence Landslide Hazard Area of North Edmonds. Please note the slide debris from Sequoia Ridge Lot 3 also damaged portions of the existing City drainage facility along the slope of the Lorian Woods plat. The City's geotechnical consultant is recommending that restoration of the drainage system not be performed at this time pending further evaluation. If you have any questions about the City drainage facility contact Public Works Director, Noel Miller at 425-771-0235. Please contact me should you have any questions regarding permit requirements or other concerns at 425-771-0220 extension 1226 during normal City business hours. Sincerely, oloft4^7� Jeannine L. Graf Building Official, C.B.O. Cc: Duane Bowman, Development Services Director Noel Miller, Public Works Director Dave Gebert, City Engineer ° Incorporated August 11, 1890 ° Sister City - Hekii an, Japan N X February 17, 2006 City of Edmonds Development Services Department 121 5`h Avenue North Edmonds, Washington 98020 Attn: Don Fiene Assistant City Engineer RE: BOSCH PROPERTY LANDSLIDE 16116 72ND AVENUE WEST EDMONDS, WASHINGTON Dear Mr Fiene: LANDAU ASSOCIATES REk !.7y� F >t FEB f 00�1� This letter provides a summary of our observations and recommendations related to a landslide observed on the northwest side of the Bosch residence at 16116 72"d Avenue West (also known as Lot 3 of the Sequoia Ridge Plat) in Edmonds, Washington. The purpose of our services was to observe the site conditions and to provide recommendations to the 'City of Edmonds (City) Building Official and Engineering Division staff related to our assessment of landslide conditions and the potential for an imminent hazard to City -owned facilities, the general public, or the private property residents. Our services were requested by Don Fiene, Assistant City ,'Engineer, on January 31, 2006 and confirmed by Task Order No. 06-01 under Landau Associates' On -Call and Emergency / Disaster Response Geotechnical Engineering Agreement with the City of Edmonds. BACKGROUND AND OBSERVATIONS Don Fiene, Assistant City Engineer; Ann Bulls, Assistant Building Official; Damon Roth, and Dennis Stettler of Landau Associates observed the above -described landslide on the afternoon of January 31, 2006. The landslide was viewed from below, looking up from 73`d Place West, and from the top, looking down from the yard of the Bosch residence at 16116 72"d Avenue West. Mr. Bosch spoke to us briefly during our site visit and provided some background information. Our observations were limited to brief visual observations. No measurements were taken and no attempts were made to closely examine the slope or slide debris, other than what could be readily seen by standing at the bottom or top of the slope. We understand that the landsliding was observed by a resident of 73`d Place West on Monday, January 30, 2006, at about 4:30 p.m. The landslide was preceded by over a month of unusually wet weather with precipitation significantly above typical winter rainfall levels. ENVIRONMENTAL ( GEOTECHNICAL ( NATURAL RESOURCES 130 2nd Avenue South • Edmonds, WA 98020 • (425) 77&0907 • Fax (425) 778-6409 • ..Iandauinc.com SEATTLE • SPOKANE • TACOMA • PORTLAND The landslide occurred at the top of a steep, northwest -facing slope immediately west of the northwest corner of the Bosch residence. The location of the current landslide corresponds approximately to the location of a previous landslide that occurred on about February 13, 2005, as documented in a.letter by Landau Associates to the City dated February 22, 2005. On September 16, 2003, ground cracking was also observed by Landau Associates and City personnel at the top of the bluff at this approximate location. This ground cracking was documented in a Landau Associates letter to the City dated September 25, 2003. The previously observed ground cracking had been noted when Landau Associates and City personnel were onsite observing a landslide on the same slope that had occurred about 200 ft north of the current landslide location. Following the observation of ground cracking in' 2003, sections of heavy tarp were reportedly placed over the ground by Mr. Bosch and secured in place by driven steel rebar. At the time of our observation on February 14, 2005, the heavy plastic tarps were still in place, but the ground beneath the tarps at the location of the previous ground cracking had failed and slid downslope. At the time of our most recent observations on January 31, 2006, the plastic tarps were still in place over a portion of the top of the slope. The 2005 landslide created a headscarp that was estimated to be approximately 8 to 10 ft from the northwest corner of the house and about 5 to 6 ft from a porch. The upper portion of the 2005 slide formed a steep scarp area, which flattened to a slight "bench" about 20 ft below the top of the scarp. Soil exposed in the upper portion of the slope appeared to be relatively dry at the time of our 2005 site visit. At the slight "bench," seepage and wet zones were observed in 2005 with seepage flowing downslope through the recent slide debris and ultimately emerging as surface water drainage that was intercepted by catch basins along the edge of 73'd Place West. Slide debris in 2005 had been deposited or flowed into the area at and below the "bench" and was mixed with the trees and undergrowth on the lower portions of the slope. The extent of the current landslide as observed on January 31, 2006, appeared to be within the general boundaries of the 2005 landslide. The top of the 2006 landslide did not appear to extend to the top of the 2005 headscarp and as such there appeared to be little to no additional loss of ground from the top of the bluff. Some of the material involved in the 2006 landslide may represent landslide debris and colluvium that had accumulated mid -slope on the "bench" observed at the time of the 2005 landslide. The 2006 landslide debris produced an accumulation of soft, wet soil mixed with organic material near the base of the slope on Lot. 2 of the Lorian Woods subdivision. Seepage was observed coming down lower portions of the slope and emerging from the base of the landslide debris at the toe of the landslide. The 2006 landslide destroyed a drainage structure that formed a portion of the City's landslide drainage system in this area. Remnants of the dislocated drainage structure (including a large diameter 2/17/06 \\Edmdata\projects\074\133\Fileroom\R\BoschL. dslide_ltr.doc 2 LANDAU ASSOCIATES corrugated metal pipe that formed the collection structure) are present near the toe of the landslide debris. Segments of black, corrugated pipe was also observed near the base of the slope. This pipe material did not appear to be a part of the City's drainage system. Mr. Bosch indicated that he had previously observed someone (thought to be the property owner from Lot 2 in the Lorian Woods subdivision) working on the slope to apparently try to intercept some of the seepage and springs emerging from the slope. ASSESSMENT AND RECOMMENDATIONS We offer the following comments and assessment to address the City's questions on whether the landslide and present condition pose an imminent hazard to City -owned facilities, the general public, or the occupants of the Bosch residence and downslope residences. This assessment is based on a limited observation of the site conditions and our experience with similar landslide conditions, and not on a detailed evaluation of the site conditions. Our limited assessment for the purpose of assessing imminent risk should not be construed as a replacement for a detailed geotechnical evaluation and recommendations developed by a licensed geotechnical consultant retained by the property owners to address the longer - term risk posed by the landslide hazard. The location of the recent landslide appears to be consistent with the general location of a landslide in 2005 and ground cracking observed in 2003. The 2006 landslide involved only surficial materials and there was no evidence that the landslide represents a larger, deep-seated failure. The entire bluff in the Meadowdale area is a known landslide hazard zone. The observed landslide is consistent with other naturally occurring landslides along the Meadowdale Bluff. Springs and seepage emerge from this slope above the Lorian Woods subdivision and the slopes above these springs are subject to repeated landsliding and slope movement as the landslide headscarp continues to retreat. The landslide on this slope last year had removed the vegetation and exposed the soil on the upper portions of the slope to rainfall and erosion. Landslide debris from 2005 that had accumulated near the midpoint and lower on the slope had the opportunity to become wet from the recent heavy rainfall events and the rainfall was apparently sufficient to reinitiate the landslide at this location. The observed landslide was likely caused by the heavy precipitation over the last month or more, possibly combined with natural groundwater seepage zones that are present in the steep portions of the bluff. The seepage zones and the observed landslide are located well above a City interceptor drainage system and the landslide debris actually flowed down and destroyed a portion of the drainage system. The purpose of the City drainage system is to capture some of the localized surface water and water emerging from springs on the slope that would otherwise infiltrate into the ground below the drainage system. Implementation of the drainage system and other drainage improvements in the Meadowdale 2/17/06 \\Edmdata\projects\074\133\Fileroom\RNBoschLmdslide_ltr.doc 3 LANDAU ASSOCIATES area is thought to contribute to the overall increased stability of the Meadowdale landslide complex located downslope from the location ofthe interceptor drainage system. The interceptor drainage systems do not reduce the groundwater levels in the slopes above the systems or reduce the seepage from these areas. Accordingly, it is our opinion that the observed landslide was not caused by or related to the presence of the City's interceptor drainage system. The landslide, has impacted and destroyed some of the City drainage facilities located on the lower portion of the slope. It is our opinion that the presence of the landslide debris and the recurring slope movement at this location make restoration of the City drainage system impractical at this location at this time. We suggest that this situation be re-evaluated for possible maintenance or improvements during drier weather in late spring or summer. The landslide occurred on private property and extended into adjacent private property. Therefore, the general public traveling on public rights -of -way would not be affected by this landslide. With respect to the Bosch residence, the 2006 landslide has not materially changed the slope condition as compared to the condition following the 2005 landslide. Landau Associates provided comments and recommendations in our February 22, 2005 letter following the 2005 landslide and the 2006 landslide does not alter the general findings or recommendations of that letter. The debris from this landslide extends into an undeveloped lot within the Lorian Woods subdivision. The owner of this property should be advised of this condition. Mudslides and landslide debris from the bluff above can impact any development on the property below and any future development plans should consider and address this issue. This letter was prepared for the exclusive use of the City of Edmonds for specific application to 0 the evaluation of public safety concerns related to the Bosch property landslide. Within the limitations of scope, budget, and schedule, our services have been conducted in accordance with generally accepted geotechnical practice. No other warranty, express or implied, is made as to the professional opinions and 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 regarding this letter or if we may be of further assistance. LANDAU ASSOCIATES, INC. Dennis R. Stettler, P.E. Principal DRS/rgm 2/17/06 \\Edmdata\projects\074\133Tdil oom\R\Bosch La dslide_Itr.doc 4 LANDAU ASSOCIATES loc. 1891, SET FILE CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: www.dedmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering February 24, 2005 Mr. William Derry, President Lorian Woods Homeowners Association 16101 740'Place West Edmonds, Washington 98026 Dear Mr. Derry: GARY HAAKENSON MAYOR In response to a recent localized slide, City officials conducted a site inspection on February 14, 2005 and observed slide damage to have occurred on private property west of Sequoia Ridge Lot 3. Debris from this slide may have pushed onto or near Tract A and Lot 5 property in the plat of Lorian Woods. Accompanying City officials was a representative of Landau Associates, the City's professional geotechnical consultant. Landau Associates conducted a site reconnaissance and subsequently prepared a report (copy enclosed) that describes the observed slide. , The purpose of this letter is to alert you of the current situation as we know it, so that you may take whatever action you deem appropriate. Since you may be unaware of this condition, the City recommends that Association representatives visit the site with a professional Geotechnical Engineer for an independent assessment of Tract A property to provide recommendations about any possible site restoration that may be advisable for you to undertake to protect this property. If your geotechnical engineer requires restoration, slope mitigation or improvements, an approved permit from the City is required in advance, since all work must comply with City Ordinance #2661, which regulates the Earth Subsidence Landslide Hazard Area of north Edmonds. Please contact me should you have any questions regarding permit requirements or other concerns at 425-771-0220 extension 1226 during normal City business hours. Sincerely, Jeannine L. Graf Building Official, C.B.O. Cc: Duane Bowman, Development Services Director Dave Gebert, City Engineer • Incorporated August 11, 1890 • February 22, 2005 City of Edmonds Development Services Department 121 50' Avenue North Edmonds, Washington 98020 Attn: Jeannine L. Graf Building Official RE: BOSCH PROPERTY LANDSLIDE 16116 72ND AVENUE WEST EDMONDS `WASHINGTON Dear Ms. Graf: BUILDING FEB 2 3 2005 LANDAU ASSOCIATES This letter provides a summary of our observations, assessment, and recommendations related to a landslide observed on the northwest side of the Bosch residence at 16116 72"d Avenue West (also known as Lot 3 of the Sequoia Ridge Plat) in Edmonds, Washington. The purpose of our services was to observe the site conditions and to provide recommendations to the City of Edmonds (City) Building Official related to our assessment of site conditions and the. potential for an imminent hazard to City -owned facilities, the general public, or the private property residents related to the landslide. Our servi.ces,were.requested by.Don Fiene, Assistant City Engineer, on February 14, 2005 and confirmed by Task Order No. 05-01 under Landau Associates' On -Call and Emergency / Disaster Response Geotechnical Engineering Agreement with the City of Edmonds. BACKGROUND Don Fiene, Assistant City Engineer, Ann Bullis, Assistant Building Official, and Dennis Stettler of Landau Associates observed the above -described landslide on the afternoon of February 14, 2005. The landslide was observed from 73`d Place West below the slide and from the top in the yard of the Bosch residence at 16116 72nd Avenue West. Mr. Bosch spoke to us during our site visit and provided background information. Our observations were limited to brief visual observations and no measurements were taken and no attempts were. made to closely examine the slope or slide debris, other than what could-be.readily seen by standing, at the top of the slope. We understand that the landslide occurred on Saturday, February 12, 2005. Periods of heavy rain occurred_ sporadically _.on , that day, but otherwise the period preceding the landslide was a period of relatively drier than normal winter precipitation. ENVIRONMENTAL I GEOTECHNICAL I NATURAL RESOURCES 130 2nd Avenue South • Edmonds, WA 98020 • (425) 778-0907 • fax (425) 778-6409 • www.landauinc.com SEATTLE • SPOKANE • TACOMA • PORTLAND r 6 The landslide occurred at the top of a steep, northwest -facing slope immediately west of the northwest corner of the Bosch residence. The location of the landslide corresponded to the location of ground cracking observed by Landau Associates and City personnel on September 16, 2003 and documented in a Landau Associates letter to the City dated September 25, 2003. The previously observed ground cracking was noted when Landau Associates and City personnel observed a landslide on the same slope that occurred about 200 ft north of the current landslide location. Following the observation of ground cracking in 2003, sections of heavy tarp were reportedly placed over the ground by Mr. Bosch and secured in place by driven steel rebar. At the time of our observation on February 14, 2005, the heavy plastic tarps were still in place, but the ground beneath the tarps at the location of the previous ground cracking had failed and slid downslope. The landslide formed a steep slope with a headscarp located about 5 to 6 ft from a porch of the Bosch residence. The headscarp was estimated to be approximately 8 to 10 ft from the northwest corner of the house. Soil observed in the upper 3 to 5 ft of the headscarp area appeared to be similar to fill. Mr. Bosch indicated that his recollection of this area prior to the house construction as compared to the present topography suggests that some fill may have been placed in this area. According to a letter dated October 31, 2003, Cornerstone Geotechnical, Inc. (a geotechnical consultant retained by Mr. Bosch in 2003) also interpreted the near -surface soil in this area to be fill. Below this fill layer, a soil that appeared to be very dense, gray, fine sand that formed a smooth surface was exposed in some areas of the landslide scarp. This exposed, gray soil appears to be sand of glacial origin that is typically found along the bluff in this area. The sand is typically underlain by fine-grained silt and clay along the slope and groundwater seepage typically emerges on the slope near the contact of the sand and the low -permeability silt and clay below it. The upper portion of the slide formed a steep scarp area, which flattened to a slight "bench" about 20 ft below the top of the scarp. Soil exposed in the upper portion of the slope appeared to be relatively dry. At the slight "bench," seepage and wet zones were observed with seepage flowing downslope through the recent slide debris and ultimately emerging as surface water drainage that was intercepted by catch basins along the edge of 73`d Place West. We suspect that the seepage zone corresponds to the location of the silt and clay layer that is present along the. Meadowdale Bluff. Slide debris had been deposited or flowed into the area at and below the "bench" and was mixed with the trees and undergrowth on the lower portions of the slope. 02/22/05 S:\WPROCkO74\129\BoschLandslide—itr.doc 2 LANDAU ASSOCIATES ASSESSMENT The location of the recent landslide appears to be consistent with the location of ground cracking we observed in 2003. The ground cracking was an early indication of slope movement and failure at this location. The heavy tarp protecting this area from rainfall infiltration was probably effective for a period of time, but ultimately the steep slope with ground cracks was going to fail. The landslide that occurred at this location is relatively consistent with other landslides that have occurred along this slope at various locations. The top of this steep slope or bluff forms the headscarp of the much larger Meadowdale landslide complex. The bluff in the Meadowdale area is a known landslide hazard zone. The observed landslide is consistent with other naturally occurring landslides along the Meadowdale Bluf£ Springs and seepage emerge from this slope above the Lorian Woods subdivision and the slopes above these springs are subject to repeated landsliding and slope movement as the landslide headscarp continues to progress back. If fill had been placed at the top of the slope as a part of the house construction, that condition could reduce the stability of the slope. However, even without fill at the top of the slope, the steep slope in this area is subject to landsliding. The observed landslide was likely caused by natural groundwater seepage zones that are present in the steep portions of the bluff. The seepage zones and the observed landslide are located well above a City interceptor drainage system. The purpose of the City drainage system is to capture some of the localized surface water and water emerging from springs that would otherwise infiltrate into the ground below the drainage system. Implementation of the drainage system and other drainage improvements in the Meadowdale area is thought to contribute to the overall stability improvements of the Meadowdale landslide complex located downslope from the location of the interceptor drainage system. The interceptor drain system is at and below about elevation 180 ft on the slope east of 73`d Place West. In comparison, the top of the bluff on the Bosch property at the location of the subject landslide is near elevation 255 ft, about 75 ft above the highest point of the interceptor drain system. The interceptor drainage systems do not reduce the groundwater levels in the slopes above the systems or reduce the seepage from these areas. Accordingly, it is our opinion that the observed landslide was not caused by or related to the City's interceptor drainage system. The landslide has encroached into the yard adjacent to the northwest corner of the residence and left very little room between the top of slope and the house. Left alone, we would expect that this oversteepened landslide scarp would continue to fail and progress back so that it would eventually encroach into the northwest corner of the residence. Landsliding along this slope (and Puget Sound bluff slopes in general) typically produce landslide scarps that extend back from several feet up to 10 ft or so back from the top crest of the slope during each landslide event. The time period for the slope to 02/22/05 S:\WPROC\074\129\Bosch Landslide IV.doc 3 LANDAu ASSOCIATES encroach back to the house is very difficult to estimate, but could conceivably occur over a number of months to many years. RECOMMENDATIONS We recommend that the owners of the house retain a geotechnical consultant to evaluate the slope condition in detail, assess the present and future risk, and develop specific recommendations to protect the house and limit the potential for additional landslides to damage the house. We offer the following comments and assessment to address the City's questions on whether the landslide and present condition pose an imminent hazard to City -owned facilities, the general public, or the occupants of the Bosch residence and downslope residences. This assessment is based on a cursory observation of the site conditions and our experience with similar landslide conditions, and not on a detailed evaluation of the site conditions. Our limited assessment for the purpose of assessing imminent risk should not be construed as a replacement for a detailed geotechnical evaluation and recommendations developed by a geotechnical consultant retained by the property owner to address the longer -term risk posed by the landslide hazard. The landslide occurred on private property and extended into adjacent private property. Therefore, the general public traveling on public rights -of -way would not be affected by this landslide. From the readily available vantage points below and above the landslide, it was not possible to determine if the landslide debris extended far enough downslope to impact the City's interceptor drainage system number 1-A. Surface water carrying silt and fine sand was observed emerging onto the pavement surface at 73rd Place West and may require maintenance activities to better collect this surface water at the roadway location and to maintain clean and functioning storm water catch basins. It does not appear that the landslide threatens any other City -owned facilities. The oversteepened landslide scarp could continue to progress back until it eventually encroaches on the house foundation. The time period for this to occur is difficult to predict. We have not examined the building plans, but we understand that the house itself is supported on deep piles. The porch, however, may only be supported on spread footings. The pile foundations provide some protection to the structure and, therefore, provide improved life safety as compared to a structure supported solely on shallow foundations. However, additional slope movement or landsliding in the future could progress back to the house foundation and damage the pile foundation, ultimately damaging or endangering the house. We expect that landsliding of the scale typically observed on the bluffs in this area (typically extending back from the top of the slope a distance on the order of several to 10 ft for each landslide event) could damage the pile foundation. However, a landslide of this magnitude would be unlikely to pose an immediate life safety issue for occupants of the residence. 02/22/05 S:\WPROC\074\129\Bosch Landslide Itr.doc 4 LANDAu ASSOCIATES The debris from this landslide extends into an undeveloped lot within the Lorian Woods subdivision. The owner of this property should be advised of this condition. Mudslides and landslide debris from the bluff above can impact any development on the property below and any future development plans should consider and address this issue. This letter was prepared for the exclusive use of the City of Edmonds for specific application to the evaluation of public safety concerns related to the Bosch property landslide. Within the limitations of scope, budget, and schedule, our services have been conducted in accordance with generally accepted geotechnical practice. No other warranty, express or implied, is made as to the professional opinions and advise included in this report. We appreciate this opportunity to be of service to the City of Edmonds. Please call if you have any questions regarding this letter or if we may be of further assistance. LANDAU ASSOCIATES, INC. �Q`S .2 ov,.n o!� Dennis R. Ste{£, Principal Steven R. Wright, P.E. Associate DRS/SZW/ccy No. 074129.010.011 02/22/05 S:\WPROCkO74\i29\BoschLandslide—itr.doc 5 LANDAU ASSOCIATES lnc.1891 January 9, 2002 CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0226 • FAX (425) 771.0221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering Mr. William Derry President Lorian Woods Homeowners Association 16107 74th Place West Edmonds, Washington 98026 Dear Mr. Derry: GARY HAAKENSON MAYOR The City is in receipt of your letter dated December 30, 2001 to the Development Services Director. You requested a number of actions from the City. The City has the following responses. In regards to the issue of stopping work on all construction within the Sequoia Ridge short subdivision, at present time we cannot comply with this request as we are unaware of any facts which would legally support our taking this action at this time. We have taken corrective action relative to violations of permit conditions on the Bosch residence within the Sequoia Ridge development. Until the wood debris has been removed from the slope, the City maintenance workers cannot perform inspections, repairs or maintenance to our drainage system. You have received a separate letter from the City requesting removal of this debris. - The City is not responsible for maintaining private drainage systems and will not do any work on these private drainage systems. Based upon the information from the City's Geotechnical engineer, it appears ,the landslide occurred due to natural forces related to heavy rainfall at the time of the landslide. Surficial earth movement is an inherent characteristic of the landslide mass. The City has designated me to be the contact person for all matters related to the landslide, please do not hesitate to direct any written correspondence to me as I will assure that the appropriate City staff person will respond to any and all inquiries. Sincerely, Jeannine L. Graf Building Official Cc; Dave Gebert, City Engineer • Incorporated August 11, 1890 • Sister City - Hekinan. Janan 890-19C.- CITY OF EDMONDS 250 - 5TH AVE. N.. EDMONDS. WA 98020 • (206) 771-0220 • FAX (206) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works . Planning . Parks and Recreation . Engineering March 5, 1993 William and Barbara Derry 16107 74th Place West Edmonds, WA 98020 LAURA M. HALL MAYOR Re: MEADOWDALE ORDINANCE PUBLIC LIABILITY INSURANCE REQUIREMENTS Lot 10, Plat of Lorian Woods Dear Mr. and Mrs. Derry: Your request for a waiver from the public liability insurance requirements of Chapter 19.05.050 of the Edmonds Community Development Code and Ordinance #2866 was brought to my attention on March 4, 1993 by Jeannine Graf, Acting Building Official. After consultation with Scott Snyder, City Attorney, and site inspections by personnel from both the Engineering and Building . Departments, as Community Services Director I have exercised the authority given me under Chapter 19.05 and have determined that it would be appropriate for the City to grant your request for a waiver. Decisions such as this are based on site specific conditions and made only after review of the potential loss, to both public utilities and private property which could be attributable to your development. In the case of your development it was determined that in the event of a landslide, or similar earth movement, damage would be negligible. It was fortunate that, due to the conditions of your specific site, the City was able to arrive at a decision that has enabled you to proceed with was final approval on your project. Mrs. Derry, it was a pleasure meeting you. If I can be of further assistance, please do not hesitate to call on me. Sincerely, gaw Paul Mar Community Services Director cc: City Attorney Acting Building Official Fi le • Incorporated August 11, 1890 • Sister Cities International — Hekinan, Japan 0 ICE TO PERMITTEE AND/OR OWNER STREETdRik, TIAL APPROVAL ❑ VIOLATION ❑ CORRECTIONS REQUIRED ❑NO PERMIT — STOP WORK — REMOVE CONSTRUCTION OR OBTAIN PERMIT AND MAKE WORK COMPLY WITH BUILDING LAWS. ❑CONSTRUCTION IS NOT IN ACCORDANCE WITH APPROVED PLANS AND PERMIT — STOP WORK. MAKE EXISTING WORK COMPLY WITH APPROVED PLANS AND PERMIT OR REMOVE IT. ❑ STOP WORK — UNTIL AUTHORIZED TO CONTINUE BY INSPECTOR. ❑CORRECTIONS LISTED BELOW MUST BE MADE BEFORE WORK CAN BE APPROVED. ❑ WORK DESCRIBED BELOW HAS BEEN INSPECTED AND IS APPROVED. ❑CONTACT INSPECTOR AND ❑ ARRANGE FOR APPOINTMENT. RECALL FOR INSPECTION. cJ . THE ACTIONS OR CORRECTIONS INDICATED ABOVE ARE REQUIRED WITHIN DAYS OR PENALTIES IMPOSED BY LAW MAY BE APPLIED. FOR INSPECTIONS CALL: r BUILDING DIV. SPECTOR / 3 PUBLIC WORKS CITY OF DATE ❑ FIRE DEPT. EDMONDS CITY OF EDMONDS 250 STH AVENUE NORTH, EDMONDS, WA 98020 (206) 771-3202 �14 RCW_-197-11-970 Determination of Nonsignificance (DNS) DETERMINATION OF NONSIGNIFICANCE Description of proposal: New Single Family Residence Proponent: William.& Barbara Derry, 19825 95th Av N.E., Bothell, WA 98011 Location of proposal, including street address if any: 16107 74th Pl. W. Lead agency: CITY OF EDMONDS The lead agency for this proposal has determined that it does not have a probable significant adverse impact on the environment. An environmental impact statement is not required under RCW 43.21.030(2)(c). This decision was made after review of -a completed environmental checklist and other information on file with the lead agency. This information is available to the public on .request. XX There is no comment period for this DNS. This DNS is issued under 197-11-340(2); the lead agency will not act on this proposal for 15 days from the date below. Comments must be submitted by .1992. Responsible Official: Jeffrey S. Wilson Position/Title: Current Planning Supervisor, Department of Community Services - Planning Division Phone: 771-0220 Address: City of Edmonds, 250 5th Avenue North, Edmonds WA 98020 Date: Signature: ' XX You may appeal this determination to RobgrtChave, Planning Manager, at 250 Sth Avenue North, Edmonds, WA 98020, no later than JJ✓Cy / 3 , 1992, by filing a written appeal citing the reasons. You should be prepared to make specific factual objections. Contact Jeffrey S. Wilson to read or ask about the procedures for SEPA appeals. XX Posted on JUL� 2— . 1992, at the Edmonds Public Library, Edmonds Community Services Building, and the Edmonds Post Office. XX Distribute to "Checked" Agencies along with a copy of the Checklist. Mailed to the following along with the Environmental Checklist: XX Department of Ecology Environmental Review Section P.O. Box 47703 Olympia, WA 98504-7703 XX Applicant: William & Barbara Derry. 19825 95th Av N.E. Bothell, WA 98011 Page 1 of 1 (((FILE #)))EN/(((DATE))).SEPA _ XX Agent: Steven R. Sullivan 18596 76th. Av. W. Edmonds, WA 98026 Attachments PC: Building Permit application plan check # 630 SEPA Notebook Robert Chave, Planning Manager Page 2 of (((FILE #)))ENI(((DATE))).SEPA MEMORANDUM CITY OF EDMONDS PLANNING DIVISION 250 STH AVENUE NORTH, EDMONDS, WASHINGTON 98020 TO: JEFFREY S. WILSON, AICP ]PONSIB FILIAL FROM: John Bissell, Code Enf. Tech DATE: July 1, 1992 SUBJECT: ENVIRONMENTAL, DETERMINATION FOR DERRY SINGLE-FAMILY BUILDING PERMIT APPLICATION AT 16107 74TH PLACE WEST, BUILDING PLAN CHECK NO. 630 I have had the opportunity to visit the site, review the environmental checklist , and geotechnical report prepared Terra Associates. A copy of which are filed in th for this permit. e official file Based on my review of all available information and adopted policies of the City, I recommend that a Determination of Nonsignificance.be issued. Review by Responsible Official: I concur Comments: I do not concur Jeffrey S. Wilson Attachments Pc: BUILDING PLAN CHECK NO. 630 Robert Chave, Planning Manager . c4� Date B630ENn-1.92.SEPA LANDAU BUILDING, A ASSOCIATES, Jum 2 5 1992 INC. Geoenvironmental Engineering and Technologies June 24, 1992 City of Edmonds 250 Fifth Avenue, North Edmonds, WA 98020 ATTN: Ms. Sharon Nolan RE: PRELIMINARY GEOTECHNICAL REVIEW PROPOSED DERRY SINGLE-FAMILY RESIDENCE LOT 10, LORIAN WOODS SUBDIVISION 16107 74TH PLACE WEST EDMONDS, WASHINGTON Dear Ms. Nolan: In accordance with your request, Landau Associates, Inc. has completed a preliminary review of the geotechnical aspects of the submittal associated with the proposed project. This review was conducted using the requirements of City Ordinance No. 2661 and the Uniform Building Code as a standard for comparison. Documents reviewed are listed in Attachment 1 to this letter. Our review of the documents indicates that, in general, the submittal is complete. However, some minor issues associated with the proposed residence require resolution in accordance with City Ordinance No. 2661. Our specific comments are as follows: 1. Grading quantities are not presented on the grading plan, nor is a driveway slope profile provided. Grading quantities should be requested to determine if a conditional use permit will be needed. Since most of the home's access is already in place, it is our opinion that a driveway profile would add little to the present submittal. 2. Temporary and permanent erosion controls are not called out on the plans but are mentioned in the Environmental Checklist. Requirements for temporary erosion control during construction should be provided. 3. Although the geotechnical declaration (reference 1.d.) is stamped, the reviewed copy of the geotechnical letter (reference 1.c.) is not. Since the January 22, 1992 letter contains engineering design parameters, it is our opinion that the letter should be properly sealed by a licensed engineer. 4. Terra Associates' June 6, 1989 report for the then -proposed subdivision notes that basement cuts should not exceed about 8 ft in height. In Terra Associates' June 22, 1992 letter Terra states that the proposed lower floor elevation is at 99 ft, which Terra states would result in a cut of about 10 ft. The final plans, however, show a basement floor elevation of 96 ft. By lowering the home 3 ft, the planned excavation cut will go to about 13 ft (based on Terra's 10 ft estimate with the lower floor at Elevation 99). Terra Associates should comment on the appropriateness of a cut of this P.O. BOX 1029 • EDMONDS, WASHINGTON 98020-9129 - (206) 778-0907 - FAX (206) 778-6409 magnitude, and on the need to step the basement or terrace the excavation (as noted in their June 6, 1989 report). 5. For the benefit of the contractor, the footing drain detail on sheet 2 might be better shown in the manner of sheet 7, rather than referencing the soil report. 6. The owner should be advised of the need for periodic maintenance of the drainage system. 7. It is unclear whether the 100 psf uniform stress recommended by Terra Associates applies to walls other than the east perimeter wall. While it is reasonable that it does not, and this is the assumption of the structural engineer, it could be more explicitly stated that this is the case. 8. Along a portion of the west side of the existing access drive, supporting soil has been cut to a slope steeper than 1:1 (horizontal to vertical). Unless some form of support is provided, eventual failure of the road shoulder is likely. Whomever has responsibility for maintaining this drive should be notified of the current situation, and be made aware that eventual improvements in the form of a rockery or retaining wall will probably be needed. 9. The geotechnical report does not state the date of the test pit explorations, which is important, particularly in light of the lack of water in the pits on a site which might be expected to have some groundwater present. 10. On page 2 of Terra Associates' January 22, 1992 letter they indicate that an observation well was installed in Test Pit 2. If this well meets the definition of a well per Chapter 173-160 WAC, the owner should be notified that the well must be either: 1) properly decommissioned by a licensed well driller, or 2) protected during and after home construction. We recommend that the above concerns be addressed by the appropriate design professional, with a resubmittal to the City. Landau Associates would be pleased to review the responses provided when they become available. Should you have any questions concerning this project, please do not hesitate to contact the undersigned. DMW / WDE/tam 74039.10 06/24/92 EDMOND6\DERRYGEO.RPT OA LANDAU ASSOCIATES, INC. By: Dean M. White, P.E. Project Manager William D. Evans, CPG Senior Geologist LANDAU ASSOCIATES, INC. • • ATTACHMENT 1 REFERENCES 1. Project Manual - assembled by the Sullivan Company, Inc. and containing, among other items: a. Landslide Hazard Vicinity Map - excerpted from 1984 GeoEngineers report b. Environmental Checklist - signed by Stephen Sullivan on 4/28/92 c. Geotechnical Letter, Project T-840-S, dated 1 /22/92 by Terra Associates, Inc. d. Geotechnical Declaration, Project T-840-S, dated 4/29/92 by Terra Associates, Inc. 2. Project Plans - cover plus 13 sheets prepared by the Sullivan Company, Inc., dated 4/27/92; sheets 2-S, 7, and 11 sealed by Cornelius D. Vanden Ende, P.E.; sheet 13 sealed by James R. Conner, P.L.S. w LANDAU ASSOCIATES, INC. TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences Project T-840-5 ?� C?s � April 29, 1992 Stephen R. Sullivan AIA The Sullivan Company 18596 76th Avenue West Edmonds, Washington 98026 Subject: Derry Residence, Lorian Woods Lot 10, Edmonds Geotechnical Engineer's Declaration References: Geotechnical Report, Project T-840-1 Meadowdale Beach, Lots 54 to 57 Letter Report, Project T-840-5, January 22,1992 Dear Mr. Sullivan: We have examined the construction drawings for the Derry residence and the environmental checklist, which we understand are those that will be submitted for permit. In our judgment, the final plans are consistent with the recommendations in the referenced geotechnical report and letter. In addition, we have examined the earth section of the environmental checklist and take no exceptions to the answers provided. The geotechnical report discusses landslide hazards at,the Lorian Woods development. In summary; in our opinion the probability of earth movement on Lot 10 within a period of 25 years most likely is less than ten percent. The lot therefore is suitable for residential construction, as provided by Ordinance 2661. The risk of damage to the proposed residence and to adjacent properties from soil movement will be minimal, subject to the conditions set forth in the report. 'Some mitigation of the landslide risk will be afforded by the residence's foundation drains, which should improve subsurface drainage, and by the basement excavation, which will remove a weight of spoil greater than the weight of the residence. This residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be eliminated. Property owners assume all residual risks. The geotechnical recommendations and declarations associated with the project do not provide a warranty, either expressed or implied, against loss or damage to persons or property. We appreciate the opportunity to examine these documents. Please call if you have any questions. Sincerely, TERRA ASSOCIATES, INC Willi(4 ai1 f. Proi'ecG%Iaaaaer Anil BIj1,-RE PiesideFit ya' �- w� EXPIRES t 2/09/93 cc: q -',712525 W1[lows Road, Suite 101, Kirkland, Washington 98034 0 Phone (206) 821-7777 kTRUCTURAL DESIGN AS%CIATES, INC. CONSULTING ENGINEERS 5630. 198TH ST. S.W. P.O. BOX 5366 LYNNWOOD. WA98046 PHONE: (206)775.7434 Fax: 775-7435 1�T C April 21, 1992 The Sullivan Company attn: Mr. Steve Sullivan 18596 - 76th Avenue West Edmonds, Washington 98026 subject: Derry Residence, Lot 10, Lorian Woods, Edmonds, Wash. - DECLARATION STATEMENT - Our Ref.: Letters\91-362.rjh s i Dear Steve: f This letter is to inform you that our office has reviewed the geotechnica.l reports from Terra Associates, Inc. No. T-840-1, dated June 6, 1989, and No. T-840-5, dated January 22, 1992. The review indicates that the lot is in an area subject to ground failure. "...the probability of earth movement on this lot within a period of 25 years most likely is less than ten percent...". It is impossible to guarantee future slope stability, regardless of how well it is investigated or engineered, and there are always risks associated with construction in a known hazardous area. Among these risks is the possibility of the loss or damage to your property and life, as well as the property and life of neighbors, public and private, due to soil failure. :F ' L Because of the unpredictable nature and wet condition of the soils, owners must assume responsibility for the risks of .building and living in this known hazardous area. The reports, recommendations, opinions, designs and specifications, associated with this project are professional opinions only, and are not to be construed as a warranty, expressed or implied, against loss or damage. STRUCI'URAL ENGINEERING DESIGN AND INVESTIGA1"1C>N nlw rni_)Nf>AT10NS 0 RFTn�Nirlr�. o ?��:� • .. r.•-, • - o-r,'.r•„c"�:`- m ;,r.r•. 11 I The Sullivan Company Page 2 of Two DECLARATION STATEMENT To the best of our knowledge and understanding, the building plans, submitted with the permit application substantially incorporate the above mentioned reports' recommendation. Careful and conscientious application of the above referenced recommendations during and after construction will apparently not increase the risk associated with this site. Respectfully submitted, STRUCTURAL DESIGN ASSOCIATES, INC. by: Kase Vanden Ende, P.E. president . KVE/eve �y s.D.A- Lettm\91-362.gh April 21,1992 i 7 • SPREET FILE I, Stephen R. Sullivan AIA, licensed to practice architecture in the State of Washington_, have reviewed the report by Terra Associates, Inc. I understand its recommendations and have incorporated them into the final design of the Derry residence at Lot 10, Lorian Woods in Edmonds, WA. E; 1 I have transmitted a copy of the report to Bill and Barbara Derry, owners of said property, and have explained to them { the risk of loss due to slides and the responsibility of i living on a steep slope site. t a Done this .� day of l ARCHITEC .: By ' Presid t, The Sullivan Co. Inc. 1 ' i� STATE OF WASHINGTON ) )ss: COUNTY OF !� ) I �ertify that I know or have satisfactory evidence that _STly 10 X&-Zhow signed this instrument and acknowledge it to be.,(.his/her) free and voluntary act for the purposes mention 1d:•in this instrument. Dated this day of 199,E Not Public My commission expires: � •.; •• t'�,.: . ,: of �-r a , - STREET FILE The undersigned owners, William and Barbara Derry, fully warrant all information submitted in support of this project proposal, located at Lorian Woods, Lot 10 in Edmonds, WA, and do hereby promise to indemnify and "hold harmless the City of Edmonds and its agents from any errors or omissions located 'herein., Done this day of 19. OWNER By: By: STATE OF WASHINGTON ) t COUNTY OF )ss: ,540h-MIS14 ) I certify t at I know or have satisfactory evidence that signed this instrument and acknowledge it to be (his/her) free and voluntary act for the purposes mentioned in this instrument. ed / o. this day of 199 Notary Public My commission expires: / STATE OF WA TON siqkEET F I •)ss: COUNTY OF I certify hat I know or have satisfactory evidence . that Arrq signed this instrument and .acknowledged it to be (his/her) free and voluntary -act for the, puVposps mentioned in this instrument. 0 3 DATED this�daof f�. NOT RY 146BLIC MY commission expires: STATE OF WASHINGTON )ss: COUNTY 0 I certify that I know or have satisfactory evidence that signed this instrument on oath stated that h . _(he/she) was authorized to execute the instrument and acknowledged it as the.V�11�1­1117 �title) of ......... . , 47 (name of party on behalf of whom instrument was executed) to . he.free and voluntary act of such party for the uses and purposes mentioned in this instrument. DATED this,30 f�'day of 199 NO PUBLIC MY commission expire7s,�:� 1E WW%* fib S-TREET FILE We, the applicant, Stephen R. Sullivan AIA, and owners, William and Barbara Derry, of a proposed residence at Lot 10, Lorian Woods in Edmonds, WA, are fully aware of the risks associated with developing in an area with potentially unstable soils. We accept this responsibility and well advise, in writing, any prospective, purchasers of the site, or any prospective purchasers or residential leasees of structures or portions of a structure on the site, of the slide potential of the area. Done this day of 199A. OWNEI By: By: APPLICAN By: Prpsifnt, The Sullivan Co. Inc. STATE OF WASHINGTON ) )Ss: COUNTY OF S�nhrrrnisl'� ) I certify that I know or have satisfactory evidence that 1Lr�GtrcLrzt signed athis instrument and acknowledged it to be (his/her) free and voluntary act for the purposes mentioned in this instrument. 'fated this day of ► 199in oZ v 0 /( NOTAR PUBLIC w My commision expires. / m • GREET FILE The undersigned owners, William and Barbara Derry, fully warrant all information submitted in support of this project proposal, located at. Lorian Woods, Lot 10 in Edmonds, WA, and do hereby promise to indemnify and hold harmless the City of Edmonds and its agents from any errors or omissions located herein. Done this day of 44z- i / , 199 Z . OWNER(S) By: By. STATE OF WASHINGTON ) • )ss: COUNTY OF w► ) I certify that I know or have satisfactory evidence: tha.tr , r signed this instrument and acknow.]edge:: y,!�;c-:;'''=,;. it to be (his/ r) free and voluntary act for the .purgoee'��.,,,;::' . r ;... mentioned in this instrument. a e• ::y . r,r Dated this day of 199 Notary blic My commission expires: 21 ENGINEERS COST ESTIMATE STREET FILE mosommilmommmummmmmmommommoomn UNIT UNIT ITEM DESCRIPTION OF WORK ISSUE QTY COST TOTAL I,>47jrx- 414ve_ 2v 30 • /l�td�� af�`.ry AtTAY05 3 2�ZJ �'OYcdcE �l/�G t cs3 E� / (06 d AGO Qo�i,�„� /L"C.rs/� S�+w Pipes tCicL G.� Za �3S 7Gm 8 lore/ 7AI 27 /Z 3Z4 4, ti�.mort Z'/ c,s 23 /4 376 ,,o� _Exhibit 6 TERRA .ASSOCIATES, InC, • • • . • • AA Consultants in Geotechnical Engineering, Geology • and Environmental Earth Sciences Project T-840-1 June 6,1989 Robert and Joann Anderson 7370 North Meadowdale Road Edmonds, Washington 98020 Subject: Geotechnical Report Meadowdale Beach, Lots 54 to 57 Edmonds, Washington Dear Dr. and Mrs. Anderson: We have completed the geotechnical studies you authorized for your property in the Meadowdale area of Edmonds. The site location is shown on the Vicinity Map, Figure 1. The tract, referred to herein as the Anderson property, includes Lots 54, 55 and 56 of the Plat of Meadowdale Beach and most of Lot 57. We understand that you intend to subdivide this property into approximately ten lots for single-family residences. A final plat has not been developed at this time. The purpose of the present study is to assess landslide hazards on the property and provide general recommendations for site improvements, and for grading, drainage and foundations for residential construction. The work completed includes 1) a review of soil reports and other information in City files, 2) examination of air. photos of the site vicinity, 3) a .visual examination of the property, including shallow soil explorations made by hand, and 4) exploration of subsurface conditions using test borings and test pits.; This report describes our findings and summarizes our recommendations. After the property has been subdivided, the City may require a geotechnical evaluation of the construction proposed for each individual lot. Such work is not within the scope of the present study. , SUMMARY The existing site topography and a possible plat with ten lots is shown on Figure 2. The property slopes downward from east to west. The. central portion of the site includes a relatively flat bench. The steep slopes at the east side extend beyond the property line. A lower bench occupied by several residences lies beyond the west property line. 15301 N.E. 90th Street • Redmond, Washington 98052 • Phone (206) 881-5570 • FAX No. 869-9173 Mailing Address: P.O. Box 3338 • Redmond, Washington 98073 Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 2 The Anderson property is part of a large ancient landslide. The area that failed extends along 75th Place West from Meadowdale County Park southward to about the 165th block and from the bluff on the east to the shoreline. The original landslide probably occurred several thousand years ago. Parts of this landslide have been active into recent times and possibly are still active. The records indicate that landslides occurred in Meadowdale during the winters of 1946-47, 1955-56 and during the 1960s and 1970s. Local residents report that no detectable earth movements and no building damage occurred on the Anderson property during any of these events. In 1979, the 40-year record of landslide events in the Meadowdale area was studied by Roger Lowe Associates Inc and the landslide hazards were evaluated. Several possible landslide categories were identified, based largely on topographic features existing at the time of the study. A map that identified the landslide hazards and estimated failure probabilities was developed for the entire Meadowdale area. The Lowe study identified three categories of potential landslides on the Anderson property, " as summarized on Figure 3. Most of the property where the subsoils are believed to be ancient landslide debris was classified as previously failed material susceptible to renewed landslide movements. On the central bench, the probability that landslides of this type (4A) might occur within 25-year periods was estimated at 25 percent, the lowest rating given any area believed to be located on the old slump material. This relatively low rating was given because no landslides have occurred on the bench during historic times. The western slopes below the bench were rated at 35 percent, only slightly higher than the 25-percent rating given the bench. Because areas on the Anderson property at the northwest and the southwest corners were believed to have been affected by three major landslides since the 1940s, The Lowe report assigned these areas a rating of 90 percent. However, because residents on property adjacent these corners of the Anderson property report that no damage to buildings and no perceptible earth movements occurred during these events, the rating of 90 percent assigned these areas likely was unwarranted. The steep slope east of the bench was mapped as generally undisturbed materials susceptible to shallow debris slides (3B) and to avalanches from further up the slope (2C). A relatively low probability of occurrence was assigned to landslide events of these types. The Lowe' report recommended groundwater control as likely the most economical measure for landslide risk reduction. Consequently, in 1980 through 1985, sanitary sewers, storm sewers, and subsurface interceptor drains were installed around and within the Meadowdale landslide. Interceptor Drains 1A and 1B were installed on the, Anderson property: at the locations shown on Figure 2. Since that time, a lowering of the groundwater table throughout the landslide mass has been documented. Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 3 In 1985, GeoEngineers, Inc evaluated the effects of the improved surface and subsurface drainage and concluded that the probability of landslide occurrence had been reduced in much of the area believed to be most susceptible to failure. On the Anderson property, the estimated probability that the old slump material might move again within a 25-year period was reduced by a factor of about three. Based on our test pits and borings and other available information, we conclude that all the Anderson property below the bluff is underlain by landslide debris, mostly loose sands mixed with silts, clays and buried vegetation, including trees.. The depth of the debris probably exceeds 60 feet under the central bench and likely is in the range of 30 to 40 feet at the west property line. Figure 4 summarizes our conclusions concerning generalized subsurface conditions on the site. Figure 4 also illustrates ground water conditions on the site observed during our field work, which was performed during winter months. The water table appears; to be about five to six feet below the ground surface along the west property line but near the ground surface on the slopes to the east. On the bluff, springs were observed where sandy soils outcrop above fine-grained materials. Based on these observations and our professional judgment, we agree generally with the landslide hazards assessment in the Lowe report. Figure 5 summarizes our assessment of present landslide hazards on the Anderson property and shows landslide occurrence probabilities consistent with the latest evaluation by GeoEngineers, Inc. In our opinion, Figure 5 is not adequate for assessing risk at individual residential lots. Firstly, the probabilities appear to apply only to the large-scale slumps that were the Lowe report's primary concern. In our opinion, while the low probabilities presented for the areas on the eastern slopes are believed to be suitable for large-scale slumps, they may underestimate the average occurrence intervals of the small-scale slides and avalanches that typically occur on steep ground. Secondly, available evidence suggests that most of the residences within areas supposedly affected by the landslides of record withstood those events with little or no damage. Consequently, probabilities of landslide occurrence, as presented in the Lowe report, probably exaggerate the risk of landslide damage to individual residences. Figure 6 presents a risk assessment that we believe is applicable to individual residential lots on the Anderson property. The probabilities presented are intended as measures of the risk of landslide damage rather than landslide occurrence. On Figure 6, the 30-percent ratings on Figure 5 at the northwest and the southwest comers have been reduced, reflecting the reports of local residents that the landslides responsible for the 30-percent ratings caused no perceptible earth movements on the Anderson property and no damage to residences adjacent these areas. Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 4 In our opinion, the present risk is low enough to justify development of the Anderson property, provided the design and construction procedures used do not impair the present stability, and provided also that future property owners are properly informed of the landslide hazards that exist, as required by the City's Ordinance 2661, and accept full. responsibility for them. In order to develop the property without increasing the risk of landslide damage on adjacent property, and without unreasonable. risk to the proposed residences, we recommend that certain measures be incorporated in the construction proposed for each lot. These include: 1) Homes should be adapted to the present topography, using split- and multi -level construction where suitable. 2) Where slopes are steeper than 15 degrees, fill should not be placed under the building footprints. Ground floors above the present grade should be framed over crawl spaces. 3) Slab -on -grade ground floors may be used in cuts, and' on fills placed on slopes flatter than 15 degrees. 4) Basement cuts should not exceed about eight feet in height. If deeper cuts are required on steep slopes, the basement should be stepped and the excavation terraced. 5) Basement walls and perimeter foundation walls should be designed for lateral soil stresses suitable for the backslope angles. 6) Because landslide debris may provide relatively uneven support for foundations, buildings should have conventional wood -framed construction supported on reinforced concrete foundations. Concrete masonry is not recommended and brick. veneer should be used only in small panels. 7) In general, conventional spread foundations may be used. Home sites where landslide debris is expected to provide poor bearing conditions should be explored with test pits before final plans are prepared. 8) Setbacks from both ascending slopes and descending slopes should comply with the requirements in the Uniform Building Code. 9) Pile and pier foundations may be considered as a means for improving foundation performance where soils are poor, and to satisfy setback requirements. 10) . Landscaping should preserve the existing topography to the extent practical. Fills should not be placed on slopes steeper than 20 degrees. Fill slopes should be graded not steeper than 25 degrees. Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 5 11) Cuts should be limited to heights of about eight feet. Cuts up to four feet may be supported by rockeries. Higher cuts should be supported with reinforced concrete retaining walls. 12) Site drainage, should be improved by installing drain rock bedding and perforated drain pipe in the trenches with all new storm sewers, as was done in the LID 210 storm sewers. 13) Home owners should improve drainage on their lots by diverting surface water into the storm water system. Perforated drain pipes tightlined to the storm sewers should be provided 'around all perimeter foundation walls and basement walls and behind all, retaining walls. Rain gutters should discharge to the storm sewers in tightlines different from those used for the foundation drains. The following sections of this report discuss our findings and present our conclusions and recommendations in greater detail. Our report. has been prepared specifically for this project. It is intended for the exclusive use of yourselves and your representatives. Our work has used methods and procedures consistent with . local foundation engineering practices. We provide no other warranty, expressed or implied. We do not guarantee project performance in any respect, only that our work meets normal standards of professional care. SITE SURFACE CONDITIONS The project site is located south of North Meadowdale Road and east of the 74th Place West right-of-way in the Meadowdale area of Edmonds, Washington. The Anderson property includes Lots 54, 55 and 56 of the Plat of Meadowdale Beach and part of Lot 57. In plan it measures about 350 feet by 650 feet and includes approximately 5.3 acres. The Anderson residence is located on Lot 55 in the west center of the site. As shown on Figures 2 and 4, the eastern third of the property is a slope that gradually steepens toward the east. The upper slope climbs steeply to a bluff with its crest near Elev 250 to 300 off the site. to the east. At the time our study was performed, two small surface sloughs were noted on these steep eastern slopes. The central area of the property is a bench about 100 to 120 feet wide covered with grass, ivy and scattered trees. Grades on the bench vary from about Elev 120 in the north to Elev 150 in the south. The Anderson residence and a shed to the south are located on this bench. Several firs up to 47 inches in diameter and other large trees, straight-trunked and vertical, are located just south of the house. To the west the bench slopes down to the 74th Place West right-of-way. The grade change from the -bench to the west property line ranges from ten feet at the north to about 50 feet at the south. Typical slope inclinations are in the range of 20 to 25 degrees with local areas as steep as 45 degrees. Robert and Joann Anderson Project T-840-1 June 6,1989 Page 6 In 1984, as part of the LID 210 work completed by the City, Interceptor Drains 1A and 1B were installed on the Anderson property, approximately as shown on Figure 2. ' At the time of our study, many areas of the property, especially the east slopes, were wet from snow melt, rainfall, seepage and springs. Surface water not collected by the interceptors descends to the bench, runs downslope in watercourses around the Anderson home, then continues on to catch basins and other drainage features. The central bench on the Anderson property extends off the site to the north, where it is occupied by single-family residences. Other residences are located on a lower bench west and south of the Anderson property. All of these structures are supported on the slide debris that is part of the Meadowdale landslide complex. We understand that prior to the construction of the Anderson residence in 1965, six cabins and a house had been present on the Anderson property for many years. When these buildings were demolished in 1963, none are reported to have showed any evidence of landslide damage. REVIEW OF RECENT LANDSLIDE ACTIVITY The original landslides in the Meadowdale area are believed to have occurred several thousand years ago. The area involved extended from the bluff to the shoreline and from Meadowdale County Park on the north southward to about the 165th block. Landslide activity in this area has continued during historic time. The most readily . accessible records describe the landslide activity during only the most recent 40 years. The records may not be complete. The landslide records indicate that much of the ancient landslide south of the present wharf was active in the winter of 1946-47. The same area is believed to have been active again in the 1960s. The area affected extended more than 400 feet east of the railroad. These events explain the 4A90 hazard rating the Lowe report gave the southwest comer of the Anderson property, as shown on Figure 3. However, residents near the Anderson property during these landslides report that no damage occurred on their property or on the Anderson property during either event. During the same winter of 1946-47, a slide that blocked North Meadowdale Road did occur in the road cut on the Anderson property about 70 feet east of the present driveway. This slide probably was not related to the other landslide activity that occurred that winter. In the winter of 1955-56, landslides were reported at two locations north of North Meadowdale Road. The Lowe report concludes that during that winter the active area probably extended over most of the ancient landslide north of the wharf. These slides explain the Lowe report's 4A90 hazard rating shown on Figure 3 for the northwest, comer of the Anderson property. However, residents near the Anderson property report that no damage occurred on their property or on the Anderson property during that winter. Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 7 Numerous other smaller landslides have occurred within the past 40 years, most of them at the toe of the slope near the railroad. At least two larger slides were reported. In 1970, a slide just north ofthe wharf crossed.to the east side of 75th Place West, causing minor pavement disruption, which recurs periodically. In 1973, a , slide near the 158th block adjacent the railroad extended upslope to the west edge of 75th Place West. On the Anderson property, the ancient landslide mass has not undergone perceptible movements during the 40-year period of record. In addition, only minor sloughing has been observed on the eastern slopes since the Anderson home was constructed in 1965. Since that time, no avalanche .debris has reached the toe of the slope at the east side of the bench. We reviewed stereoscopic air photos that show the property vicinity during the years 1947, 1955 and 1970. Pavement disruption on 75th Place West west of the property, due probably to the 1970 slide noted above, can be seen on the 1976 photos. The 1955 photos show bare soil on the eastern slope above Lot 57 off the Anderson property. This scar probably was part of the residential construction going on at that time above the slope crest. FIELD EXPLORATION AND LABORATORY TESTING Our field work on the Anderson property was performed on February 14 through 17, 1989. Subsurface conditions were explored by drilling two standard penetration test borings to depths .50 and 69 feet below existing grades. In addition, six test pits were dug with a backhoe to depths that ranged from 12 to 19 feet below existing grades. The borings were made by Drilling Unlimited Inc of Olympia. A skid -mounted drill rig was used for one boring and a truck -mounted rig for the second. Continuous flight, hollow -stem augers were used to advance and support the boreholes. The test borings and pits were located by measuring from site features shown on the survey plan provided us. The approximate locations explored are shown on Figure 2. Ground surface elevations reported for the locations explored were estimated by interpolating contour lines shown on the survey plan. The field exploration was continuously monitored by an engineering geologist from our firm. A log was prepared for each boring and test pit. The soils observed were classified in general accordance with the system described on Figure 7. Logs of the borings and pits are presented on Figures 8 through 15. These logs report our interpretation of the field logs and reflect the results of laboratory examination and testing of the field samples. In each boring,. standard .penetration tests -were performed at selected intervals by driving a sampler with a two-inch outside diameter using a 140-pound hammer falling 30;inches. The results of these tests are the N-values reported on the boring logs. Robert and Joann Anderson June 6, 1989 Project T-840-1 Page 8 Representative soil samples were placed in closed containers and taken to our laboratory where they were again examined. The. field moisture content of each sample was measured. Field visual classifications were checked by running Atterberg tests and sieve analyses on selected samples. All the test results are recorded on the boring logs. Ground water observation wells were installed in both borings. SUBSURFACE CONDITIONS The locations explored on the Anderson property are shown on Figure 2. The following discussion is general in nature. . For more specific information regarding conditions observed at the locations explored, refer to the logs of borings and test pits, Figures 8 through 15. Boring 1 at the south end of the central bench was drilled to a depth 50 feet below existing grade.' The soils observed are mostly loose silty fine to medium sands mixed with clays and silts. Based on the relatively low N-values in Boring 1, as reported on the log, and the mixed appearance of the material, we believe that all the soil is landslide debris derived from the Esperance and Whidbey formations exposed on the bluff to the east. The base of the ancient landslide is at an undetermined depth below the bottom of the boring. Boring 2 at the north end'of the central bench encountered about 30 feet of loose sandy soil with chunks of clay and wood debris, similar to the soils recovered in Boring 1. Below the 30-foot depth, silts and clays were encountered, generally very stiff but becoming hard within the final eight feet of the borehole. Subsurface conditions in Boring 2 are similar to conditions reported by Lowe for a borehole about 150 feet northwest of Boring 2: The upper 30 to 50 feet is slide debris. The deeper clays and silts are believed to be part of the Whidbey formation and may or may not be part of the ancient landslide. All the test pits on the Anderson property encountered slide debris: loose silty sands with chunks of stiff to hard clays and silts. Trees buried in slide debris were uncovered in Test Pits 2 and 4. No stratification similar to that in the undisturbed Esperance sands near the top of the bluff was observed in any of the pits. Test Pits 2 and 4 through 6, which were excavated on the eastern slope, encountered ground water at shallow depths well above the toe of the slope. The sidewalls in Test Pits 2 and 4 collapsed as the pits were being dug. A ground water observation well installed years ago by the City is located near the southwest comer of the property. A log of the borehole is not available. We understand from discussions with the geologist who installed the well that the depth of the boring is in the range of 24 feet and all the material drilled was landslide debris. At the present time, the water level in this well is five to six feet below the ground surface. Robert and Joann Anderson Project T-840-1 June 6,1989 Page 9 With the possible exception of the Whidbey hard clays in the bottom of Boring 2, intact native soils were observed on this site only at fresh exposures on the bluff at the east margins of the property. Figure 4 shows a generalized profile of the native soils and the overlying landslide materials. Near the toe of the bluff, both native soils and ancient landslide debris are covered with slope wash and avalanche debris deposited since the original landslide. As noted above, in Test Pits 2 and 4, trees were observed buried in debris. The Whidbey formation is exposed on the bluff above the debris. In some areas near Elevs 170 to 190, the Whidbey soils are pebbly silts and sands. Further up the bluff, the Whidbey soils are finer, mostly silts and clays with seams of fine sand. The Esperance sands of the Vashon glaciation lie above about Elev 220 to 230. There are springs at the contact between the Esperance sands and the underlying Whidbey clays. PRESENT LANDSLIDE HAZARDS The Anderson property lies within the boundaries of the Meadowdale landslide studied in 1979 by Roger Lowe Associates, Inc. The purpose of that study was to assess the various landslide hazards present in different areas and evaluate the risk that a landslide event might occur. The Lowe report classified three categories of possible landslides on the Anderson property, as summarized on Figure 3: 1) 'avalanches of debris from the steep slope at the east side of the. site (2C); 2) landslides on the east slope in material that has never before failed (3B); and 3) renewed movements of the ancient landslide materials beneath the central bench and the western slopes (4A). The first two categories were considered to have relatively low 'risk, only a two to five percent chance of occurrence within a period of 25 years. The possibility that a failure in the third category would occur within 25 years was estimated to be about 25 percent on the central bench and 35 percent on the western slopes.. Because, major landslides that occurred in 1946-47 and .in 1955-56 were believed to have extended onto the Anderson property, small areas at the northwest corner and the southwest comer were assigned a 90 percent chance of failure within periods of 25 years. The Lowe report concluded that a reduction of ground water levels in the landslide complex likely was the most effective means of reducing the risk of additional landslides. Consequently, during the early 1980's, the City installed sanitary sewers, storm sewers, and subsurface interceptor drains at various locations on and around the Meadowdale landslide. Interceptor Drains 1A and 1B were installed on the Anderson property at the locations shown on Figure 2. Robert and Joann Anderson June 6, 1989 Project T-840-1 Page 10 In 1985, GeoEngineers Inc evaluated the effects of these new drainage facilities and concluded that the landslide hazard had been significantly reduced in many areas that had high risk. Landslide occurrence probabilities of 90 percent in 25 years were reduced to 30 percent in 25 years. Similarly, ratings of 25 and 35 percent in 25 years were reduced to 10 percent in 25 years. Our explorations on the Anderson property disclosed subsurface conditions generally consistent with the landslide categories described in the Lowe report (see Figure 3). However, when applied to more localized areas, these categories are not always descriptive of the landslide processes actually occurring or most likely to occur. For example, in the steep areas on the bluff where undisturbed soils occur, the Lowe report distinguishes between slumps (3A) and more shallow slides (313). However, on the old landslide debris west of the bluff, all the recent and the anticipated landslide activity was classified as renewed slump movements (4A) although much of the recent activity was recognized as having characteristics of relatively shallow earthflows or debris slides. Figure 5 presents a landslide hazard map for the Anderson property that we believe better describes the slope movements that could occur. It retains the general features of the Lowe reportmap but has been adjusted to better fit local geology, to and drainage conditions. On the steep bluff at the east margin of the property, the Lowe report indicates that slumps (3A) may occur in the exposed Esperance sands, but are unlikely. The probability of such failures is low because the springs on the bluff provide much better drainage'for the sands than existed at the time the ancient landslide occurred. Nevertheless, the overly, steep face of the bluff is constantly being loosened by weathering and plant growth. Shallow surface slides result from these processes. They usually are small in area and of little consequence for construction further down the slope since downslope movement of the debris commonly is hindered by vegetation on the lower slopes. On Figure 5, to distinguish these shallow slides from more massive slumps (3A), we have used the Lowe report category 3B, debris slides in material that has not previously failed. As shown on Figure 4, the Whidbey formation is exposed on the steep eastern slope below the Esperance sands. On Figure 5, this area is the second zone west of the east property line. The Lowe report indicates that shallow debris slides (313) .are expected as weathering and plant growth gradually loosen this material. This zone is also at risk due to avalanches of debris from the Esperance sands above (2C). A massive slump (3A) is also possible. However, for the present drainage conditions and bluff topography, a slump would likely, be confined to the overlying Esperance sands. The third zone from the east property line is below the zones where undisturbed native soils are exposed, but upslope from the ancient landslide debris (4A). The near -surface soils are colluvium from the bluff (see Figure 4). Due to surface water from the springs on the bluff, the ground water table is near the ground surface: The landslide hazards in this area are shallow slides in steeper, wetter zones of colluvium (413) and avalanches from slides occurring higher up the slope (2C). Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 11 The fourth zone from the east property line on Figure 5 is the lower slope at the east side of the central bench. This zone and the remainder of the property to the west are underlain by ancient landslide debris. The east boundary of this zone approximates the trace of the old failure plane on the present ground surface (see Figure 4). The landslide hazards include avalanches off the slopes to the east (2C) and renewed activity of the old slump debris (4A). There is an additional risk of shallow slides in the old slump debris or in colluvium that has accumulated since the ancient landslide occurred (0). These latter failures are most likely to occur on the steeper slopes to the north during unusually wet winters. - 'Me remainder of the site includes the central bench and the slopes to the west. The major landslide hazard in this area is renewed activity in old slump debris (4A). In addition, the east side of the bench may receive avalanches from the slope to the east (2C). There is little chance such an avalanche would carry across the bench and down the western slopes. However, the west side of the property has locally steep debris slopes where shallow slides (4B) may occur during unusually wet weather. The west corners of the site are classified in the Lowe report as having the highest landslide risk on the Anderson property. These areas also have risks due to landslide hazards other than renewed slumps, as shown on Figure 5. A numerical probability of occurrence is presented on Figure 5 for the multiple hazards in each of the various areas. The probabilities. shown are consistent with those in the Lowe report, as modified by the 1984 assessment by GeoEngineers, Inc. In our opinion, the landslide occurrence probabilities shown on Figure 5 for the central portion of the property are reasonable considering the historical record of fairly large-scale landslide events. The 10-percent rating has been assigned arbitrarily to areas where renewed movements of the old slump material have not been reported and are not believed to have occurred within historic times. The bench on the Anderson. property is such an area. Applying the conclusions of the Lowe report elsewhere on the Anderson property presents some difficulties. Firstly, the 30-percent rating was given the west comers of the Anderson property because these areas were believed in the Lowe report to have been affected by landslides in the 40-year record. However, downslope neighbors of the Anderson property who lived through those events report that no perceptible slope movements occurred on their property or on the Anderson property.during any landslide of record. Consequently, the original 90-percent ratings, and the current 30-percent ratings, probably are too conservative, based on the available evidence. Secondly, with regard to the eastern slopes, landslide occurrence probabilities in the range of only two to five percent, as assigned by the Lowe report (see Figure 3), are understandable only as estimates of the chance that a large-scale event in the native, undisturbed bluff soils might occur. We agree that the probability of large-scale slumps of Robert and Joann Anderson June 6,1989 Project T-840-1 , Page 12 the bluff is low, as predicted by Figure 3. However, we believe these low prob calused es underestimate the frequency of small-scale landslide events in overlythough small in scale, by weathering, erosion, and excessive ground water. Such events, could cause significant hazards for residences located on the slide area or in the path of an avalanche. A third difficulty in applying the Lowe report to residential lots is that probabilities of landslide occurrence may not represent the risk of damage eto residences, ces,indit icthis few the primary concern of home owners. The historical record at horns have actually been damaged by the landslides that have occurred. If all the homes within a defined landslide area were not damaged by the landslides that oof rland t e he probability of residential damage must be less t probability occurrence. Unfortunately, the relationship betweelandslide o place. e and landslide occurrence cannot easily be evaluated and vanes fromp probability that a landslide will damage home ndslll increase as ide will occur remaansrcons esity ant Dines increases, even though the probability that the la on A qualitative risk assessment that incorporntial lots on thes the e property.ations above is oIn our Figure 6. We recommend its use for reside opinion, the risk is lowest on the central bench, whichwe do Followingtthe argument Bve has ove, we rienced any landslide activity during the 40 years of record. believe the probability of landslide damage likely is less as shown on Figure 5 an five* percent n 25 years, base on a landslide occurrence probability of ten percent, On the western slopes, the risk is higher than on the bench, due primarily to the influence of locally steep slopes, and to the proximity of downslope areas with higher landslide occurrence probabilities. The risk at the toe of the eastern slopes, in our opinion, edebris and to avalanchesoff ribench, due to the threat of small slides of overly wet slop not steeper slopes to the east. Slides in the debrison the lower slopes drainage improvementsarently sand to occurred during the 40 years of record. Due to the recent the additional drainage improvements that will be effected d io ulcbrease rSlldes off the upper home owners, the frequency of occurrence of such slides is not expect occurringare with slopes that might cause avalanches on the lower slop i s pip; re etla d to hindranby the average return period of ten to 20 years. Due to their heavily vegetated lower slopes, no avalanches have reached the lower slopes during the past 30 years. In our opinion, residences located on the upper slopes would be closer to potential small-scale landslide activity and thus would e'1tPerience to be se%cted aseater lhome sitesse these areas are comparatively inaccessible, they are unlikely Robert and Joann Anderson Project T-840-1 June 6, 1989 Page 13, DISCUSSIONS AND RECOMMENDATIONS General Figures 5 and 6 and the preceeding pages describe the landslide hazards and risks present on various sections of the Anderson property. The hazards can be separated into two general groups: 1) large-scale, relatively deep-seated slope movements caused by renewed activity off the ancient landslide; and 2) small-scale, comparatively shallow slides. These latter slides may be avalanches off the oversteepened bluff at the east margins of the site, or slides in colluvium that have accumulated below the bluff. Within the past 40-odd years, large-scale activity has not affected the Anderson property. Moreover, the drainage system installed by the City under LID 210 has improved the large-scale stability and reduced the risk that a future large-scale event will affect the property. At the present time, the probability of occurrence of a large-scale event is believed to be less than 30 percent in 25 years everywhere on the property, and in the range of 10 percent in 25 years on the central bench, the western slopes and the lower eastern slopes. In our opinion, the probability of landslide damage is significantly smaller than these estimated probabilities of landslide occurrence, as illustrated by Figure 6. The risk of a landslide activity, both large-scale and small-scale, is now low enough to justify development of the Anderson property. This applies to all the lots shown on Figure 2. Some lots have higher risk than others, but on all lots, the risk is small enough to warrant development. On all lots, residual risks exist that cannot be eliminated. As required by the .City's Ordinance 2661, future lot owners should be fully informed regarding the residual landslide risks, both large-scale and small-scale, and their purchase agreements should require them to accept full responsibility for these risks. While efforts to further reduce the risk of large-scale landslides, in our opinion, are not warranted, the risk from small-scale slides may be either increased or decreased, depending on the construction on the individual lots. Lot owners should be held to construction and maintenance standards that will reduce their risk as much as practical. The,paragraphs below in this section of the report describe recommended measures to reduce the risk of small-scale landslides. These measures, however, will neither entirely remove the hazard nor eliminate the risk. Residences constructed most everywhere on the Anderson property will be supported on old landslide debris. In general, conventional spread foundations may be used. However, our test pits indicate that on some building sites bearing conditions on the debris may be relatively poor. Building supported on such material should be expected to experience small settlements. Consequently, in our opinion, the Anderson property is best suited for wood -framed construction with stiff exterior wall sheathing. ,Concrete masonry walls, which can develop cosmetic damage with only small settlements, are not recommended. Brick veneer should be used sparingly. Lot owners who wish to reduce the risk of cosmetic damage caused by settlement may consider supporting their homes on pile or pier foundations. Robert and Joann Anderson June 6,1989 Project T-840-1 Page 14 Working conditions on the Anderson property may be excessively wet during the winter months, especially on the eastern slopes. We recommend scheduling all site work for the drier months from April to October. Site Improvements In order to subdivide the Anderson property, only limited site improvements are necessary. To provide access to the interior lots, the existing driveway must be extended, approximately as shown on Figure 2. Either concrete or asphaltic pavement may be supported on the landslide debris on the Anderson property. In either case, the subgrade should be proofrolled to assure it is firm and unyielding. The uppermost twelve inches of the subgrade should be compacted "to 95 percent of its ASTM D 15.57 maximum dry density. Site soils may be too wet to achieve this level of compaction. In that case, a clean bank -run gravel or crushed rock should be imported and a subbase constructed at least twelve inches thick. Asphalt pavement should have a base course of crushed rock. at least four inches thick and a surface course of asphaltic concrete at least two inches thick. Concrete pavement should be at least five inches thick. It may be placed directly on the subgrade, provided the work is done in dry weather. A base course of crushed rock a few inches thick may, be needed in wet weather. We recommend extending the storm sewers to the end of the new driveway. This will . provide an opportunity to install additional drainage at the toe of the east slopes and provide a place where lot owners can discharge their foundation drains and roof gutters. The storm sewers should be tightlined. To pick up ground water seepage intercepted by the trench, drain rock bedding and perforated drain pipe should be installed in the excavations, as was done with the LID 210 storm sewers. The drain pipe should be placed at the lowest invert practical. The trench should be lined with filter cloth and backfilled with pea gravel; except within two feet of the surface. Other utilities should be bedded and backfilled in accordance with AWPA standards. All utility trench backfill should be at least moderately compacted. Under pavement, backfill in utility excavations should satisfy the proofrolling and compaction recommendations above. Cuts and Fills Residences and landscaping should be designed to fit the existing topography. Homes on the relatively flat central bench may be conventional construction. If desired, fills up to about three feet in depth may be used to raise grades. Foundations and slab -on -grade ground floors may be supported on properly compacted fills. Robert and Joann Anderson June 6, 1989 Project T-840-1 Page 15 Homes built on sloping ground should be multi- or split-level, as suited to the present topography. Basement cuts into the slope should not exceed eight feet in height. Deeper basements should be terraced. Fills floors above not resent gradlaced es should be framed over crder homes on slopes awl er than about 15 degrees. Ground P spaces. Cuts and fills in landscaped areas should be minimized., Cuts up to four feet high may be supported by rockeries, provided high maintenance and a risk of failure is acceptable. For higher cuts or where better performance is desired, reinforced concrete retaining walls should be used. All retaining structures should have backfill drains near their footings connected with tight lines to the storm water system. 'Foundations In general, wood4ramed residential construction may be supported on conventional spread foundations. However, because most of the property is underlain by landslide debris, bearing conditions at some building sites may be. relatively poor, especially on the lower eastern slopes, where our test pits uncovered trees and other vegetation buried within the debris. Preliminary building plans, once prepared, should be reviewed to evaluate likely foundation requirements. Following the review, exploration of the building site with test - pits may be recommended. Where needed, the pits should extend several feet below the intended footing bearing grades. To provide suitable bearing for footings, unsuitable materials, if found, should be removed to depths at least two feet below the footings and replaced with compacted gravel or rock fill. Where buildings overhang slopes or are located close to slope crests, the foundations should be stepped down to bear well below present grades. Setback requirements, as described below, should be satisfied. Where conventional foundations for such applications are not practical, pier or pile foundations should be considered. Since these piles likely will be supported entirely in debris, careful attention should be paid to estimating design capacity. Buildings supported on landslide debris may experience settlement due to the excessive and variable compressibility of the debris. Home owners who wish to reduce the risk of poor foundation performance may consider using pile or pier foundations to support their residences. The use of these deep foundations will reduce the risk of damage caused by settlements due to unsuitable bearing materials present at shallow depths. However, deep foundations likely will not reduce the property damage if a future landslide occurred on the site. Consequently, deep foundations should not be viewed bproperty owners as a means of reducing their risk of landslide damage. Robert and Joann Anderson Project T-840-1 June 6,1989 Page 16 Setbacks From Ascending Slopes In order to provide protection from slope drainage, erosion, and shallow failures, the Uniform Building Code requires that buildings be set back from ascending slopes. Residences constructed on the central bench well away from the steep eastern slopes will be exposed to very little risk of this type. However, building sites on the eastern slopes may have only minimal setbacks and thus higher risks of damage caused by these potentiatsmall-scale failures. UBC-requires a minimum setback of 15 feet. On slopes not overly steep, this requirement can be satisfied by excavating a bench behind the residence and supporting the low . cut with a retaining wall. On steeper slopes, the code's intent can be satisfied, in our opinion, by constructing the foundation wall adjacent the slope to a height where the top of the wall is 15 feet from the face of the slope. Since these small setbacks are catchment areas for debris sliding off the slopes above these homes, where the setbacks meet only the minimum UBC requirements, the rear walls of the buildings, in our opinion, should be designed to withstand debris impacts. Setbacks from Descending Slopes For setbacks from descending slopes steeper than 18 degrees, we recommend complying with the UBC requirement of 40 feet or one-third the height of the slope, whichever is less. The slope height may be measured to the next lower bench of significant width. Where it is desired to construct within the normal setback zone, the intent of the code, in our opinion, can be satisfied by lowering the foundations. Where the slopes are high, pile or pier foundations may be necessary. Basement and Foundation Walls Because homes on the Anderson property will be supported on old landslide debris, foundation bearing conditions may be relatively poor. Building settlements that vary from place to place should be expected. In order to reduce the risk of poor, foundation performance that may result from these variable settlements, we recommend using only cast -in -place concrete foundation walls and basement walls, properly reinforced. In general, residences on sloping sites should be stepped to fit the present topography. Basements are recommended since they will assure that many of the foundations will bear well below finish outside grades. We recommend limiting basement cuts to a maximum of eight feet. If a two -level basement is desired on a steep site, the basement should be stepped to fit the slope so that a terraced cut can be made with each terrace not more than eight feet high. Robert and Joann Anderson Project T-840-1 June 6,1989 Page 17 All basement walls and foundation walls should be provided with - perimeter footing drains. The drains should consist ofa perforated pipe within an envelope of washed stone, all enclosed by filter fabric. The walls should be treated with dampproofing. A drainage course should be placed outside the wall and connected to the footing drain. This wall drain may be either free -draining gravel backfill or a manufactured drain attached to the wall after the dampproofing has been applied. Soil lateral stresses for structural design of foundation walls and basement walls .will depend on the steepness of the backslopes and other factors and should be selected specifically for each building site. Site Drainage At the present time, surface runoff, rainfall and seepage from the bluff and near -surface ground water are collected on the eastern slopes by Interceptor Drains 1A and 1B. These recent improvements have significantly dried up the Anderson property. Some water undoubtedly passes under the drains and reaches the ground water. Since the water table presently is well below the ground surface at the west property line, the present large-scale stability of the Anderson property, in our judgment, is adequate to justify subdivision of the property. However, measures to improve site drainage can be obtained at little premium cost by incorporating them into any storm sewer extensions that may be needed, as discussed in the Site Improvements section above. To reduce the risk of local, small-scale sloughing of steep slopes due to excessive surface water and high ground water, other. drainage measures should be installed as part each lot owner's construction. Each lot should be landscaped so that all surface water is collected and conveyed into catch basins connected to the storm sewer system. All basement, foundation, and retaining walls should be provided with perforated footing drains, as described above. The drains should connect to the storm water system with tight lines. Cleanouts should be provided. Rain gutters should be connected to the storm water system using tight lines separate from those used for basement drains. Stability During Construction The present stability of sloping sites will be disturbed by construction activities on the individual lots and the risk of slope failures will be highest at that time. The risk is mainly to builder's operations close to , the disturbed area. Builders can minimize their risk by using good construction practices. Surface water should be diverted into catch basins and the site dried up prior to making any excavations. Excavation sidewalls should be sloped back at safe angles or supported with temporary shoring. Where excavations encounter ground water, perimeter ditches should be constructed to control the water. J 1 Robert. and Joann Anderson Project T-840-1 June 6, 1989 Page 18 Excavations on the individual lots may create hazards on adjacent lots, depending on how the buildings are sited and on the construction sequence for adjacent buildings. Problems of this type are unlikely, but should be considered on a lot -by -lot basis. Since a slope failure in landslide debris initiated by an excavation on. the Anderson property would not progress upslope into native, undisturbed material, temporary excavations will cause no risk for neighbors of the Anderson property. Excavated materials stockpiled on steep slopes would place neighbors downhill at risk. Excavated material for use as backfill should be stockpiled on gentle slopes where adjacent property is not endangered. Surplus material should immediately be hauled off the site. Post -Construction Stability In our opinion, the development of residential construction on the Anderson property will not have adverse impacts on the landslide hazards that affect the Anderson property and the neighboring property. Implementation of the drainage measures recommended herein will lower the groundwater table and reduce the current risk of landslides on the Anderson property and on the property downslope. Construction on the Anderson property will not affect the stability of the bluff and thus will not adversely affect neighboring property to the east. . Slope Vegetation Maintaining healthy vegetation on slopes is important for controlling erosion and reducing the risk from small-scale landslides. The existing vegetation on steeper slopes outside construction areas should be preserved to the extent practical. Trees that might topple onto the buildings should be trimmed back but not removed. Catch basins and storm drain lines should be kept clear of debris and free -flowing. During construction, stripped soils should be covered with straw or otherwise protected to reduce erosion. All landscaping around the residences should be _installed as soon as practical after the buildings have been completed. CLOSURE The analyses and recommendations submitted herein are based on data obtained from test borings, test pits and visual observations of soil exposures. However, subsurface conditions elsewhere on the site may differ from those observed at the locations explored. The nature and extent of any such variations may not become evident before construction. If variations are observed during construction, Terra Associates, Inc. should be requested to evaluate the actual site conditions and review the recommendations in this report prior to proceeding with the construction. Robert and Joann Anderson Project T-840-1 June 6,1989 Page 19 The following figures are included and complete this report: Figure 1 Vicinity Map Figure 2 Exploration Location Plan Figure 3 Landslide Hazards from Lowe Report 1979 Figure 4 Generalized Geologic Cross -Section Figure 5 Landslide Hazard Map Figure 6 Residential Risk Map Figure 7 Legend for Test Pits and Borings Figures 8 through 15 Logs of Test Borings and Test Pits We appreciate the opportunity to -provide these services. Please contact us whenever. we may be able to assist you, and please call if you have any questions concerning our report. Respectfully submitted, TE ASSO TES, INC Charles R. Lie Engineering Geologist Vi al William Bailey Project Manager 1 AnButail, PE President i 0 BUT Q� w A SH y�� Q O co � W O`�SFG S.ONA% oo , plytill Z,6 r I/ !/ /1 /r/ / / /, „•// 1 ���} / ,/ // / f ! ' , \ .�Ii � Ili , '���•' • �:;a� ��� 1 � � , � �.:. .90 V21 9ry11 .cti �'.1c:1 i ' /� . I !` / .. :�IIl ltl+f iIIt. 411�1 JIn 1• f8 � / / 77JJ J �- .l / I II•li � IIII``\r .� ' �Ila� 11"1 i � r 2• �� ,r/,1"0.p,°'iu" y...• �� ; I iIII�-.�IIII\ �,.j:: �1 ,.1 ,•1111'11, �11111, 1•I II (/ IIi� I• 111111 Iti I '•••,.4 \ .1\II 111,11, gfx/g p1 I •-•lr��';•1 i'11i lli lh j1114 �' >? 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J;, � T I ' d / a jI'/ill�lH�lin;ii�iL'iT/�'•��/� /� SI+.. / O � A � //lli I,I;�,,,IIIUI I 17 i � i ♦ ♦'��. �;�4r ��f l4 .• A , 11 l,,lll ,I�Ir 1111 I / ' 1 1 , I ♦ / / � � / ' •ii4Mi1'�i�'�ii i i! i � II '♦ Il I � `i,�: %: /� � t r,�F; A �'1�ItA•� !/:+ ' /i % / 11 11111 � I II I / I ♦ i � • ' ♦'T � I � l i / r fft�5(/ • y, " / a co •±,%r .'f%�/YYI\• /��,.-a _;�yr�' \ n2! 31110MOOV3W 'N '�W11�� �hti "� i?i sa♦i �Igl J a a Z ~ N LANDSLIDE HAZARDS .1 \\ A25 4A Renewed movements in old slump material 2C Avalanches of encroaching landslide material 3g Debris slides in materials that have not previously 6iled9p O t ; + 1 - Ile two trailing digits indicate the estimated probability , 3 02:• of occurrence, in percent, during a 25-year period i 35. This figure copied from Figure 5 in the final repots on the Meadowdale i Area Landslide Hazards Investigation J " d •I;� ,I 1 �/ i by Roger Lowe Associates Inc,1979 J tt 2� 2 is 31302 .r�4A� ANDERSON PROPER C:0\1�,_ Scale: 1 -300 J � 1 � 4490`3B02 �l \ .� � � .' �-. ._ � li i - it `^ • i' LANDSLIDE HAZARDS FROM LOWE REPORT TERRA ANDERSON PROPERTY ASSOCIATES MEADOWDALE BEACH EDMONDS Figure 3 Geotechnical Consultants Proj. No. 840-1 Date 3/89 i I 320 280 240 200 p� F a 160 Approximate present grand water table B-1 (oNset) ? 7 120 City Piez (offset) i r ' Slump debris from ancient landslide 80 This figure is for illustrative purposes only. The subsurface conditions shown are an interpretation of the conditions observed in test borings and pits, and other available information. Variations may exist between actual conditions and the conditions shown. Probable ancient. failurs plane Ground lost since the ancient landslide Present ground surface VASHON DRIFT Spring OneEsperanoe Sands /y.4 \\ VnyvQ WHDBEY FORMATION Pebbly sands and sits Possible seepage zone buried under colluvium Coiluvium with buried trees (avalanche 8 slide debris) TERRA U1:Nt�`"t_t�t, ` MULU%; ANDERSONF ASSOCIATES MEADOWDAILE BEA( loceotechnical Consultants Proj. No. 840-1 Date 3/1 LANDSLIDE HAZARDS 3A Slumps in inaterials that have not previously failed 3B Shallow landslides in oversteepened slopes that have not previously failed 2C Avalanches of encroaching landslide material 4A Renewed movements of old slump material 4B Shallow landslides in previously -failed material The trailing digits indicate the estimated combined probability of occurrence, in percent, during 25-year periods Site Survey by Group Four, Inc Job No 88-8020 Scale: 1'- eo, .i.i�s.aL+aw LOT 4:��. � � 3�� � ��,•. ' TERRA Noceotechnical ASSOCIATES Consultants LANDSLIDE ANDERSON MEADOWDALE B proj. W.840-I Date 3/ —cr It 0 x co IL z III l�s' 'I' :/ V) uj �om 2 13 UJI w z co 0 -4 w z CL ri 47 LU 0 < u -7,57;5 -.:Xt it < o LL 1410W 1 co -IL4 Y,;p�.:''if�''"'Iln�piA' h' } e � 1 1 `I Js.. � `•\ '\1 � I III I'll,, till, Qv w\V. iI N. 1/ V itrL' W A cd A CC ev 2 22 CIO 1:4 q in 0 co CD 31VOMOOY3V4 N ZO Its 0 z 0 0 Cg 03 cqs LL 16. CL 0 SOIL CLASSIFICATION SYSTEM LETTER MAJOR DIVISIONS SYMBOL GRAPH. SYMBOL TYPICAL DESCRIPTIO Clean GW IPIGRAVELS :.o Well -graded gravels, gravel -sand mixtures, J Gravels o.'' : " little or no fines. GP Poorly -graded gravels, gravel -sand mixtures. � O More than 50% of (less than 0 m coarse fraction 5% fines). little or no fines. Gravels GM Silty gravels, ravel -sand -silt mixtures, C) °' is larger than w z H y No. 4 sieve. with tines. non -plastic fines. GC Clayey gravels, gravel -sand -clay mixtures. < E > plastic fines. CC 0 0 oo SANDS Clean SW Well -graded sands, gravelly sands, Sands little or no tines. f° N More than 50% of. (less than SP Poorly -graded sands or oravelly sands, r z 5% tines). . little or no fines. . Q d C coarse fraction SM Silty sands, sand -silt mixtures; CSands : is smaller than non -plastic fines. No. 4 sieve. with fines. Sc Clayey sands, sand -clay mixtures, Plastic fines. J SILTS AND CLAYS ML Is, silts and very fine sands, rock flour, silt or claye fine sands or clayey silts with Cf)o o Liquid limit is less than 50°,6. CL Inorganic clays of Iow to. medium plasticity, ravetly clays, sandy clays, silty clays, lean Q L11 E N o ' OL Organic silts and organic clays of low z o Z �i��i plasticity. CC CO w N SILTS AND CLAYS MH Inorganic silts, micaceous or diatomaceou's 'sandy !� fine or silty soils, elastic. V �, > Liquid limit is greater than 50%. CH . Inorganic clays of high plasticity; fat clays. 111 z y OH i i i Organic clays of medium to high plasticry, 'organic, Lt: i i i sots. HIGHLY ORGANIC SOILS PTA �- Peat and other highly organic soils. DEFINITION OF TERMS AND SYMBOLS- I 2" OUTER DIAMETER SPLIT SPOON SAMPLER _._...... C TORVANE READING,-tsf R 2.4" INNER DIAMETER RING SAMPLER OR SHELBY TUBE SAMPLER qU PENETROMETER READING, tsf P SAMPLER PUSHED W MOISTURE, percent of dry weight �C SAMPLE NOT RECOVERED PCf DRY DENSITY, pounds per cubic foot Q_ WATER LEVEL (DATE) LL LIQUID LIMIT,percent WATER OBSERVATION WELL PI PLASTIC INDEX N STANDARD PENETRATION, blows per foot TERRA LEGEND FOR BORING & TEST PIT LOGS ANDERSON PROPERTY ASSOCIATES MEADOWDALE BEACH EDMONDS Proj. No. & l Date 3/89 Figure 7 Geotechnical Consultants BORING NO. I Logged By CRL Date 2/14/89 ELEV. 1421 Graph CS Soil Description Depth Sample Blows jam). Qu. tsf Ft. Ivy ground cover, 18" duff & topsoil SSp Grey fine SAND, some silt 5 = 8 4 sm Grey silty fine to medium SAND with 10 _ 11 15 silt zones, some orange stain Same, less silt. 15 = 3 22 ml Grey non -plastic SILT 20 I 14 35 3/15/89 -- sm Grey silty fine SAND 25 = 8 32 ml Grey clayey SILT with thin sand lenses 30 Z 21 33 2.0 to 4.5+ ml/ Mixed grey SILT et silty fine SAND 35 9 29 Same 40 I 24 25 ml cl Grey clayey SILT 45 = 10 33 2.5 to 3.5 Boring terminated at depth 50 feet Ground water observation well installed J BORING LOG TERRA ANDERSON PROPERTY �....- ASSOCIATES MEADOWDALE BEACH EDMONDS • Proj. No. 840-1 Date 3/89 1 Figure 8 Geotechnical Consultants IL i BORING NO. 2 Logged By CRL Date 2/16/89 ELEV. 1201 Graph CS CS Soil Description Depth (ft.) Sample Blows (%°�0) Qu tsf Ft. Concrete slab ml/ Grey silty fine SAND and clayey SILT, = 4 26 sm some orange stain 5 Grey silty fine SAND with clay 5 33 10 3/15/89 Same, with some organics = 5 24 15 Same, with hard clay chunks & wood = 13 46 20 sm Grey silty fine to medium SAND = 10 19 25 No recovery = 21 30 ml Grey sandy SILT = 12 31 35 Grey SILT = 22 31 40 ml/ cl Grey clayey SILT with sandy zones Z 17 37 2.5 45 Same- I 31 24 31.5 50 ch Grey CLAY = 24 38 3.5 55 Same' = 25 36 2.5 60 Grey CLAY, thin bedding = 35 35 4.5 65 t CH Same LL=75; PI=4 = 95/9" 23 4.5+ BORING LOG TERRA ANDERSON PROPERnr - ASSOCIATES MEADOWDALE MACH EDMOWS - Proj. No. 840-1 Date 3/89 Figure 9 Geotechnical Consultants Logged By CRL Date 2/14/89 Depth (ft.) USCS 0 5 10 .15 20 TEST PIT NO. I Soil Description Elev. 141± W N 12" duff and topsoil 39 sm Brown silty fine SAND, loose, moist 16 Same, grading tan to grey,, medium dense, dry 7 Brown silty fine to medium SAND ml Brown SILT 25 sm Brown silty medium SAND, some gravel, chunks of hard clay, med dense ' Same, marbled gray -brown -orange 20 Test pit completed at depth 182 feet tto ground water observed .�° TERRA R ASSOCIATES W . Geotechnical Consultants TEST PIT LOGS ANDERSON PROPERTY MEADOWDALE BEACH EDMONDS Proj. No. 840-1 Date 3/89 Figure 10 Logged By' CRL Date 2/14/89 Depth (ft.) USCS 0 5 10 15 20 TEST PIT NO. 2 Soil Description Elev. ' 1471 W N 9" duff and topsoil Mixed .brown and grey sand, silt and clay cl Grades to CLAY chunks, soft to hard, with numerous logs 38 sm Grades to gray silty SAND with organics 33 Test pit completed at depth 14 feet Ground water seepage at depth 4 feet and below Sidewalls collapsed TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS ANDERSON PROPERTY MEADOWDALE BEACH EDMONDS Proj. No. 840-1 Date 3/89 jFigure 11 Logged By CRL Date 2/15/89 Depth (ft.) USCS 0 10 1s 20 TEST -.PIT NO. 3 Soil Description Elev. 1391 W N 12" duff and.topsoil sm Brown silty fine SAND._. 21 ml Grey brown non -plastic SILT 26 Tan clayey SILT, chunks of hard clay 41 qu=2.0 to 4.Ots sm Brown silty fine to medium SAND 15 cl Grey CLAY 34 qu=4.Otsf Test pit completed at depth 19 feet No brouhd water observed TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS ANDERSON PROPERTY MEADOWDALE BEACH EDMONDS Proj. No. 840-1 I Date 3/89 1 Figure 12 i Logged By CRL Date 2/15/89 Depth (ft.) USCS 0 5 10 15 20 TEST PIT NO. 4 15A± Elev. W Soil Description N 18" duff and topsoil 43 Grey silty fine SAND with numerous sm trees, loose 33 Test pit completed at depth 12 feet Ground water seepage at depth 3 feet and below Sidewalls collapsed TEST PIT LOGS TERRA ANDERSON PROPERTY .. AA ASSOCIATES, MEADOWDALE BEACH EDMONDS Geotechnical Consultants Proj. No. 840-1 Date 3189 Figure 13 Logged By CRL Date 2/15/89 Depth (ft.) USCS 0 5 10 15 20 TEST PIT NO. 5 Soil. Description Elev. 137± W N 12" duff and topsoil 27 sm Grey silty SAND with orange stain, wet. loose 27 Test pit completed at depth 12 feet Heavy ground water seepage in upper 2 feet TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS ANDERSON PROPERTY MEADOWDALE BEACH EDMONDS Proj. No. 840-1 Date 3/89 Figure 14 Logged By CRL Date 2/15/89 Depth (ft.) USCS 0 5 10 15 20 TEST PIT NO. 6 Soil Description Elev. '142± W N 12" topsoil 35 sm Grey silty fine SAND with zones of soft clay and chunks of hard clay, loose 33 c Test pit completed at depth 15 feet Moderate ground water seepage below depth 6 feet TERRA .. ASSOCIATES Geotechnical Consultants . TEST PIT LOGS ANDERSON PROPERTY MEADOWDALE BEACH EDMONDS Proj. No. 840--1 I Date 3/89 1 Figure 15 TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences STREET FILE Project T4840-5 January 22,1992 Stephen R. Sullivan AIA The Sullivan Company 7215175th Street SW Edmonds, Washington 98020 Subject: Derry Residence Lot 10, Lorian Woods Edmonds, Washington References: Geotechnical Report, Project T48 1 Meadowdale Beach, Lots 54 to 57 Lorian Woods Approved Construction Plans Sheets 1 thru 6, by Dowl Engineers Preliminary Plans for Derry Residence by The Sullivan Company Dear Mr. Sullivan: We understand the Derry residence will be constructed on Lot 10 south of the existing Anderson residence, as shown on Sheet 2 of Dowl's Lorian Woods drawings. The stability of this property was discussed in the referenced geotechnical report. In our opinion, the probability of earth movement on this lot within a period of 25 years most likely is less than ten percent and the lot therefore is suitable for residential construction. This risk of earth movement will be further reduced by improvements to subsurface drainage afforded by the residence's foundation drains, and by removing from the lot a weight of spoil that exceeds the weight of the residence. The preliminary plans we have examined are consistent with the intent of the referenced geotechnical report and are therefore acceptable. In our opinion, the risk of damage to the proposed residence and to adjacent properties from soil movement will be minimal, subject to the conditions set forth in the report. Once the residence's foundations are constructed and backfilled, the potential for soil movement should decrease, for the reasons noted above. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821-7777 1 1 1 1 1 1 1 1 1 1 1 1 The Sullivan Company Project T-840-5 January 22,1992 Page 2 The preliminary plans indicate ground floors at Elevation 99 feet, which is below present grades on the site, except at the southwest corner. As explained in the referenced geotechnical report, the soil at Lorian Woods is landslide debris, which may provide relatively poor bearing conditions for conventional footings. To explore subsurface conditions on Lot 10, we excavated three test pits to elevations a few feet below the proposed footing bearing grade. Figure 1 shows the approximate test pit locations and the residence's ground floor footprint. Logs of the test pits are reported on Table A - The test pits encountered both silty and sandy landslide debris, as expected. No free groundwater or excessive organic material was observed in the pits. Caving of the pit walls did not occur during the brief period the pits were open. Based on the test pits, it, appears that conditions generally satisfactory for conventional spread foundations will be exposed on the bottom of the proposed excavation. However, bearing conditions worse than those observed in the test pits may be present at locations not explored, or may result from rainfall or from adverse groundwater conditions that may be present at the time the excavation is made. Bearing conditions are most likely to be satisfactory if the excavation is opened during the dry summer season. In any case, bearing conditions should be examined before footing forms are constructed. Unsuitable materials, if present, should be removed to firm ground and the overexcavations backfilled with quarry spalls or washed gravel, or with compacted pit -run gravel. Alternatively, pin piles of two -inch -diameter steel pipe driven with a jackhammer could be used, if needed, to compensate for unsatisfactory bearing conditions: To reduce the risk of foundation settlements due to possible uneven bearing conditions, we recommend proportioning footings for a maximum bearing stress of 1200 pounds per square foot and using extra steel reinforcement in the footings and the foundation walls. In addition, we recommend combining any interior footings into strips and connecting them to nearby foundation wall footings. The east perimeter foundation walls should be designed for an equivalent fluid weight of 50 pounds per cubic foot (pcf), plus a uniform stress of 100 pounds per square foot. For other walls that support lateral soil stress, the 50-pcf equivalent fluid weight can be reduced to 40 pcf. Where the ground floor is below outside final grades, perforated drainpipe and free -draining backfill should be installed outside the basement walls and connected to the storm water catch basin near the southwest corner of the lot. In order to construct the lower ground floor at Elev 99, a cut to depths about ten feet below present grades must be made for the east foundation wall. In our opinion, a cut this deep is acceptable on Lot 10 because the backslope east of the excavation rises only a short distance to level ground. There is virtually no risk that the excavation might endanger either the Lorian Woods driveway and utilities or the slopes east of the driveway. Nevertheless, care should be taken in making this excavation. Because the landslide debris is loose, it may stand only briefly on steep slopes. We recommend trimming temporary slopes more than about four feet high at approximately 1 horizontal to 1 vertical. If groundwater is encountered, flatter slopes may be required. The water level in the observation well we installed in Test Pit 2 should be read before the excavation is opened. Excavation slopes will be most stable if the groundwater level is below the proposed bearing grade, as it is at the present time. The Sullivan Company January 22,1992 1 Project T-840-5 Page 3 We appreciate the opportunity to review your preliminary plans. We expect the City will require that our firm review the construction plans submitted for permit. We will be pleased to provide this service after the plans are prepared. In addition, the City likely will require that a completed Environmental Checklist be included with the submittal package. The checklist can be filled out by yourself and the Derrys. Please call if you have any questions conceming the checklist's few geotechnical questions. Sincerely, TERRA ASSOCIATES, INC �1 `1 Mrr•�_ 7�AM� William Bailey Project Manager WB/mp enc: Figure 1 Table A cc: Bill Derry 1 1 1 1 1 k _._ TP y; TP-3 - I Approx Scale: 1 inch = 20 feet N (C Notes: 1) Photocopied from Preliminary Plans by The Sullivan Company, undated 2) For lot location, see Sheet 2 of Lorian Woods plans by Dowl Engineers, File No. 201-50 TERRA TEST PIT LOCATION PLAN DERRY RESIDENCE ASSOCIATES LOT 10, LORIAN WOODS ` Geotechnical Consultants Proi. No. 840-5 1 Date 1 /92 Figure TABLE A LOGS OF TEST PITS Test Pit No. 1 Depth, ft Description 0-1.5 Slash and topsoil. 1.5-4 Brown silty fine sand, wet and loose. 4-13 Fractured silts on uphill side of pit, brown silty fine sand on downhill side of pit. Some light caving, no seepage. Test Pit No. 2 Depth, ft Description 0-1 Topsoil and slash. 1-8 Stiff brownish gray silt. qu=1.5 to 2.0 tsf. 8-9 Brown silty fine sand. 9-13 Tan -gray mixture of sand, silt and pebbles. qu=1.5 to 2.0 tsf. Becomes tan -gray clayey silt with hard chunks, wet. qu=1.5 to 2.5 tsf. No seepage, no caving. Groundwater observation well installed Test Pit No. 3 Depth, ft Description 0-10.5 Gray -tan silty clay, wet, with hard chunks. qu=1.5 to 3.5 tsf. No seepage, no caving. Derry Residence Project T-840-5 I TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences Project T-840-5 April 29, 1992 Stephen R. Sullivan AIA The Sullivan Company 18596 76th Avenue West Edmonds, Washington 98026 Subject: Derry Residence, Lorian Woods Lot 10, Edmonds Geotechnical Engineer's Declaration References: Geotechnical Report, Project T-840-1 Meadowdale Beach, Lots 54 to 57 Letter Report, Project T-840-5, January 22,1992 Dear Mr. Sullivan: We have examined the construction drawings for the Derry residence and the environmental checklist, which we understand are those that will be submitted for permit. In our judgment, the final plans are consistent with the recommendations in the referenced geotechnical report and letter. In addition, we have examined the earth section of the environmental checklist and take no exceptions to the answers provided. The geotechnical report discusses landslide hazards at the Lorian Woods development. In summary, in our opinion the probability of earth movement on Lot 10 within a period of 25 years most likely is less than ten percent. The lot therefore is suitable for residential construction, as provided by Ordinance 2661. The risk of damage to the proposed residence and to adjacent properties from soil movement will be minimal, subject to the conditions set forth in the report. Some mitigation of the landslide risk will be afforded by the residence's foundation drains, which should improve subsurface drainage, and by the basement excavation, which will remove a weight of spoil greater than the weight of the residence. This residence will be constructed in an area of known landslide hazards. The risk of landslide cannot be eliminated. Property owners assume aU residual risks. The geotechnical recommendations and declarations associated with the project do not provide a warranty, either expressed or implied, against loss or damage to persons or property. We appreciate the opportunity to examine these documents. Please call if you have any questions. Sincerely, TERRA ASSOCIATES, INC Wlllia06§,a!1 •:```. ,.Anil . ;RE::..•:,t.. ;,.'' . ;:,.> Pieside�it try.�.EXPIRES 12/09/93 cc. .tom- %t3525:W1(lows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821-7777 IF ,e!o77'ftftft��� Joe 1040 vie_---- r--- --- ''-' _ 44, 1 % t -ITS lAl __. A- -CM-776 IOZ,Ofl r-1-� lot; q4 �Io V ID FP -q- - "Al L ot CPO � / V L,� I"1 I ICI U Iz. � -� '` .,�._ Ar �= �I -TOP Or. 4-4-P VA LNve ALT IE . Col.0000/ Y d, J, 3 ij Project: DERRY RESIDENCE- - Job No. 61-36�;,. April 16,1992' By: SSL S T R 1_1 C T Ll R A L NOT ca,::)r_� C-C -a A. G F N E R A L The following notes and are not Intended to supersede structural are su pplemenl�ry the specifications and/or details shd wn on the drawings. b. COD gi& STANDARDS, �5 Uniform Building Code (U.B.C)i 1988 edItlo n. A Cl Cl Sp�-15' b C.- E S b iiiii L-0 A D S, Roof (snow 25 Livia Load P U 40 v.6 Load I Floors,., LI Stair's & Exils, 100 -Live Load 'Wind P�Pff Hi "0" Speed C. 80 Exp. ­Sel mlozond 3 b F 0 ti-N b A'T ION D A T A: Soil bearing Information per Terra Amc-,. Inc. Report No. T� -840-5. 2.. Extend till footings down to undisturbed sell bf.the specified strength with a mlnlmurin of V-6" below adjacent grade. Cit.. 3 Center -all footings on columns and walls above unless specifically dimensioned 4 Compacted fill to be %Wl graded and granular with not more than 5% passing a. 200 Move. Pldce In 84nch loose lifts and compact toi 95% Modified AASHO density at A Fliii�� optl' urn moisture content.,� M R E I N F. Q N c R r= E. 1; Concrete ofJollowing 28 -day btreogth: Alk-1 F 5 sac cernbritIcyd (min.'2.000 pal): mdx. 6 gal. water/sack for fodndationsi slabs on k d d footings, except precast wall panels. gra a an MOAVim size aggrdg6to 1 -1/2"i Maximum slump 4% rr Add aster Builders Poizollth per mfr'd recommendations to all concrete 6xcept'i Q H MNTF-t footings Concrete foVbxt6ri6r' W"aft and slabs exposed 'to. detrimental che�ilcals to be air. entrained (5% dir).. 2_', ', Reinforcing stool ASTM A-61 6: grade 60 for #5 and larger, bars, grade 40 fdi '1­1 h . Ap. other sizes. I I tj I An fnr 11fornnarojitra �iani flos istirrune dnrl Anwate Detafl, fabricate and place In accordance with thd latest edition of X0.1. "Manual of 47, :Standard Practice". 4 Submit shdpdr wings for opl�.rovaii prior to: fabrication. Ii<y . o I 3. Concrete cover on reinforcind steel (clear dimentions):': Vertical faces,expoged. to earth or.weather ..... 2". Bottom of footings ............. 3 sla -on grac ......... b lo (frorn top) 1-1/2" Lop main reinfordement 42-bar dl6ftnoters minimum. 4 Lop till field �Ilces 24 dlai With minim.urn of 12" Bond oUtd fo ting bars 12 Inches or use corner bars at all corners and wa 41EEAT IZ Intersb6tIonto I nilhuoUi #5 bats In top, of foundation walls and In footings. 6 Prov do two co 6owbifoundatloh walls to footinq with #Sxl'-6" long @ 24" o.c. HIG;,H. t-EOF-16', Embed 6. IrAdfooting. No shearkeys required. 6. Rolnfor60 6tound Wall 6nd slab openings with aides of 12'; or greater with two 45 �:l bars extefidlhg 24 Inches beyond. corners on 6.11 four sldbs. Provide one extra #5 diagonal bari 4'.V long at each.corhdr. P�Z. 7 17� 7, Slab on grade:, . Roll 6nd moisten tuborade boior� pout. Whbro vapor b War required, Install under 2 - I,e APPROVED BY PLANNING 166h6a of clbdn coarse, sand. r Insi6i 86Wcut btatk dbntrol joints Within 24 hoUrd bt pour 6 1 21p-Stdp. 1-66ato at coldmd.:" Maximum s acing:, 12'-0" for 4-Inch, non-relnfotced slabs, 40'-0" foii slabs with,.' bUoportbd j2x12- 2.BRW2.8 wire mesh., Ion of materials to be prevent6 Vlbtgtd'bll cohbrpte� Sbgr6gat d. 9" P1966 no fill agdInst foundation or basement walls until floors are In place, or n' adequately th r-r= I L �A `Wds have bee or6d to resid lateral earth pressure and concrete has attained Its.fdII alto F R M B P iR A Kti I kna ­PW All lumber to be grvided per Book No". 16 of th West Coast Lumber Inspectio Kilkift n ZO. "i e Bureau: a. SE. wide beam PA e7 141: 1`1j.2 t6rijolstq, ra46" -I'A framing, platesi bracing and 4 Hr No.1 for post --d �-'4 b-inmi. 44,� SETBACKS" HF 'Stud' f,,r 2"x4" s'uds. 6 '11— 1� the V.F. P.A. !'National Design Specification' as 2., Corrp:y with latl% RME LOTCOVE mo led bythl 'J ' C, 11rber requirements. BUILDING HEIGHT 1'rn6w, b, kl;n d-led. 3. At' 2 Inch I SIDEWALKS— 4-� Jr [at;- anl rafters t) *,avo'2" thick solid blocking at supports. -me -With"10d-nails @ 12"'o.c. sta-g-gered. 5. SplkG all laminated mbers­ioUet�u + STREET'DEDICATION 4zt�7 lions at supports drily. Ir2millillairIkKI Splice lamina 6. LdmInatd,tWoJU hde' 4, vg 11,helght studs to.6rippleb b r headerb and block solid to bedrl' %"lot �,M Provide but W3'16hers for all bolts bearing on wood. tff U 8. All halls shal be common wire nails. W -OAASTATEMENT ET '411f I-VY E�MENT HOUSE STAT GUEST 9. Glue -laminated timbers, Douglas Fir, A.I.T.C.-gimdl�§: Combination 24F-V4 for simple spans; 24F-V8.for cantileve condition _Dry % FL66D AREA ip ?5-� of Use. OTHER AtchilecturW Appearance grade whBi <67k-0 r/`!e re exposed to view. Fabricating plant A.I.T.C. Inspected. Wrap Individual m embers. �n Submit shopdrawings for review prior to fabrication. e, :,ijA!j t 1� �W; j 10. Plywood: Roof sheathing to be 1 �/32� C-D INT-APA. plywood with exterior blue, P. 1.. 24/0 (Use r 5-ply for panelized roofs). Nailing 8d @ 6", o.c. at panel edges, 2" o.c. at Iniormedlate sUoportii. All c-b INT-'APA pl ood with 6xierlor glue, P.I. 48/24. blue Subflooring to be 314", T& YW and nail with ib q @ 6' b.c. at panel edges 10d @ 10" 6.c. at Intermediate supports.' Odentdd strand board of equal strength may be substituted fo? plywood. Provide space between bottorn choidt and perpendicular non -bearing Walls and connect with Simpson 91 s STC each bldo; -q, 11. Pre-tabridated'members to. be designed by 6 Washington State licensed '14 structural ofiglneee and In accordance With requirements shown. Submit complete shopdrawings With engineer's seal for rbviow prior to fabrIcd1lon. STRIJOTORAL STEEL, 4f All steel except tubing: ASTM A-36. Tubular section: ASTM A500' Grade B. All bolts: ASTM A-307. :ation, erection and detailing In 2. All fabric accordance with the latest edition of 'Manual of Steel Construction* of the A:merlcan Institute of Steel Construction. '5 1� 3. All welding by WASO certified welders In accordance with "Welding Handbook' I allV by the American Welding Society. 4. . All welds to be 3/16" minimum continuo Us fillet Welds Using ASW A5, E70XX electrodes. li,41 0211 �,M "47. 5. Field burning of hole; Is not allow' d Without Inspection by engineer. 6. Provide washers on bolted connections. t , 7. Ali steel not embedded In concrete or masonry to receive one shop coat of an ap ved primer paint; Apply two coats of heavy asphaltic paint to all steel exposed to eapro rth. 8. Submit complete shopdrawings for review prior to fabricati' Is — on. ZONE, H.' M iscr=LLANEQUq, SETBACKS: Contractor to verify all dimensions In.the field. FRONT 4 2, Provide temporary bracing as required Until all permanent connections and Ings have been Installed. SIDE stiffen 3.: Verify size and location of all openings In floor, roof and w ails with mechanical and electrical Work. :REAR ----------------- .,I e 4.. Prd-fabiilcated Items to be handled an,� Iftstalled per mfr's recommendations A, OTHER HEIGHT 'Pr—T^— Or H U M, W 15, DF `b0 I L -AIZ1"64 1 I'ZOO y Cl r T ING"DEF"AR-rMENT BUILD WORK, aAwnA WILL 5E- 69 jjyt:>5. or Z 6, Z-0 �7_ Mgt ADDRESS rA1?11r or_� 114141�1' 1PR0jF1_-(1T- OWNER rl�f FL011 �10i�t Fr,- W V A- P PE t W/ IZ: 1.0420t.;Ik, ri 0 0 ":4 APPRO.V ED DAT i1A WU4 100 T, 14 0 P BLDG, OFFICIAL ALL' WILI.,., f�e �Oe-ATr,-Q 10 C4t�t')IT1014IB-P -$PAr..5 PERMI'T N B E R A' "�TA?LC-I�p Two -Mg 45`�C_. INA �1/4 PTu ilour- ewE M _r 19,1611 Axel( 4/40r/114�5/7mf leo 4/1, It A; i:A Jo lee, IkF.CE .;j` ell' wl .44' OUNTER PERMIT 0 C. ITY;, -COPY A 'w f —T 04A A 11-4 -�-.)T A T I ---::)T I 0's F=� 11114 PAT 10 fi�- e',OC= M r- t,-I.T PI -A t--A a ppa F2_ Frp-A t-1 I ca F L--AFi I W C41:11.D 5;o.. -609. 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