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16113 75TH PL W.PDF16113 75T H P L W ADDRESS: 4 -� �,% I TAX ACCOUNT/PARCEL NUMBER: BUILDING PERMIT (NEW STRUCTURE):_ COVENANTS(RECORDED)FOR: w CRITICAL AREAS: �fD/E�TERMINATION: ❑ Conditional Waiver ❑ Study Required ❑ Waiver DISCRETIONARY PERMIT #'S: DRAINAGE PLAN DATED: PARKING AGREEMENTS DATED: EASEMENT(S) RECORDED FOR:_ PLANNING DATA CHECKLIST DATED: SCALED PLOT PLAN DATED: SEWER LID FEE $: SHORT PLAT FILE: SIDE SEWER AS BUILT DATED: SIDE SEWER PERMIT(S) Its GEOTECH REPORT DATEI STREET USE / ENCROACHMENT PERMIT #: FOR: WATER METER TAP CARD DATED: OTHER: LID LOT: BLOCK: L:\TEMP\DST's\Forms\Street File Checklist.doc #P20 GMT Ou4C Critical Areas Checklist CA File N°: Site Information (soils/topography/hydrology/vegetation) L. Site Address/ Location tP i lJ ia} 2 Property Tax Account Number: 00 513,105 0T)p D 3. Approximate Site Size (acres or square feet): 4. Is this site currently developed? _ yes; no. If yes; how is. site developed? 5. Describe the general site topography. Check all that apply. Flat: less than 5-feet elevation change over entire site. Rolling: slopes on site generally less than 15% (a. vertical rise. of 104eet ,over a horizontal distance of 66-feet). Hilly: slopes present on site of more than 15% and less than 30% (a vertical rise of 10-feet over, a horizontal distance of 33 to 66-feet). Steep: grades of greater than 30% present on site (a vertical rise of 10-feet over a horizontal distance of less than 33-feet). Other (please describe): 6. Site contains areas of year-round standing water. Approx. Depth: 7. Site contains areas of seasonal standing water: ; Approx., Depth: What season(s) of the year? 8. Site is in the floodway floodplain of a water course. 9. Site conbdm,.a creek or an area where water flows across the grounds surface? Flows are year-round? Flows are seasonal? (What time of year? ). 10. Site is primarily: forested ; meadow ; shrubs nixed urban landscaped (lawn, shrubs etc) 11. Obvious wetland is present on site: 1. 2. 3. 4. For City Staff Use Only Plan Check Number, if ai C Site is Zoned? Y 7, SCS mapped soil gTe(s)? tical Areas inventory or CA. map indicates Critical Area on site? PasSI b �� Q rU S Ii1� w. S j Q>_WT Site within designated earth subsidence landslide hazard area? DETERMINATION Reviewed by: WAIVER Date: i /0 g #P20 City. of Edmonds Development Services Department Planning Division Phone: 425.771.0220 Fax: 425.771.0221 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 the application 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 fi-om-observations of the site or data available at City Hall (Critical areas inventories, maps, or soil surveys). Date Received: City Receipt #: Critical Areas File #: _ Q 20 o Ayo 4a Critical Areas Checklist Fee: $135.00 Date Mailed to Applicant: A property owner, or his/her authorized representative, must ' fill out the checklist,. sign and date it, and submit it . to the City. The City will review the checklist, make a precursory site visit, and make a determination of the subsequent steps necessary to 'complete a development permit application. Please submit a vicinity map, along with the signed copy of this form to assist City staff in finding and locating the specific piece of property described -on' `this form. In addition, .the, applicant shall ' include other pertinent information .(e.g.. site plan, topographyy map, etc.) or studies in conjunction with this Checklist to assistant staff in completing`their' preliminary assessment of the site. The undersigned applicant, and his/her/its; heirs, and assigns, in consideration on the processing of the application agrees to release, indemnify, defend and hold the City of Edmonds harmless from any and all damages; including reasonable .attorney's fees, arising from anyaction. or infraction based- in whole or..part upon false, misleading, inaccurate .or incomplete information furnished by.the applicant, his/her/its agents or employees. By my signature, I certify that the information and exhibits herewith submitted are true and correct to the best of my knowledge and that I am authorized to file this application on the be .f)of the owner as listed below. SIGNATURE OF APPLICANT/AGENT DATE Property Owner's Authorizati By.my signature, I certify that I ve authorized the above Applicant/Agent to apply for the subject land use application, and grant my permission for the public officials and the staff of the City of Edmonds to enter the subject property for the purposes of inspection and posting attendant to this application. SIGNATURE OF OWNER DATE PLEASE PRINT CLEARLY Owner/Applicant: (�Applicant Representative: ijiclo RA Name —7— Dame zip Email address (optional): City Sdie Zip Telephone: 45 — 7 7 Email Address (optional): 0a.Lts CITY OF EDMONDS CRITICAL AREAS RECONNAISSANCE REPORT Site Location: 16113 75'h Place West Tax Acct. Number: 00513105900800 Determination: Study Required Determination #: CRA-2008-0040 Applicant: Jaime Hawkins (Engineering) Owner: City of Edmonds CRITICAL AREAS RECONNAISSANCE REPORT: STUDY REQUIRED During review and inspection of the subject site, it was found that the site contains and/or is adjacent to critical areas, including Geologically Hazardous Areas, pursuant to Chapters 23.40 and 23.80 of the Edmonds Community Development Code (ECDC). The subject parcel slopes gradually east -west at approximately 20%, according to the City's LIDAR data. This qualifies the slope as an erosion hazard. Immediately adjacent to 751h Place, the parcel slopes east -west more steeply at approximately 50%, which qualifies as a potential landslide hazard. GENERAL CRITICAL AREAS REPORT REQUIREMENTS Critical Areas Reports identify, classify, and delineate any areas on or adjacent to the subject property that may qualify as critical areas. They also assess these areas and identify any potential impacts resulting from your specific development proposal. If a specific development proposal results in an alteration to a critical area, the critical areas report will also contain a mitigation plan. You have the option of completing the portion of the study that classifies and delineates the critical areas and waiting until you have a specific development proposal to complete the study. You may also choose to submit the entire study with your specific development application. • Please review the minimum report requirements for all types of Critical Areas that are listed in ECDC 23.40.090.D. There are additional report requirements for different types of critical areas (see below). • Note that it is important for the report to be prepared by a qualified professional as defined in the ordinance. There are options on how to complete a critical areas study, and there is an approved list of consultants that you may choose from. You may contact the Planning Division for more information. • General Mitigation Requirements for all Critical Areas are discussed in ECDC 23.40.110 through 23.40.140. STUDY REQUIREMENT — EROSION HAZARD AREA It appears that this property contains or is adjacent to an Erosion Hazard Area. Erosion Hazard Areas include: • Those areas with Alderwood and Everett series soils on slopes of 15 percent or greater. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs or ground water seepage. • Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope. DEVELOPMENT PROPOSALS ASSOCIATED WITH EROSION HAZARD AREAS Development within an Erosion Hazard Area must meet additional criteria. • For erosion hazard areas with suitable slope stability, the only critical area study needed is an erosion and sediment control plan prepared in compliance with the requirements set forth in Chapter 18.30 ECDC as part of the construction documents. This option is at the director's discretion, per Edmonds Community Development Code section 20.80.050.G. • In areas where the slope stability is not suitable, projects within Erosion Hazard Areas will require a report by a licensed Geotechnical Engineer or other qualified professional. Note that it is important for the report to be prepared by a qualified professional as defined in the ordinance. • Report requirements are given in ECDC 23.80.050, and more generally in ECDC 23.40.090. D. • Development standards are given in ECDC 23.80.060 and 23.80.070. STUDY REQUIREMENT — LANDSLIDE HAZARD AREA It appears that this property contains or is adjacent to a Landslide Hazard Area. A Landslide Hazard Area is any area with a slope of forty percent (40%) or steeper and with a vertical relief of ten (10) or more feet (except areas composed of consolidated bedrock). • Landslide Hazard Areas are further defined and illustrated in ECDC 23.80.020.6. • In addition to the general requirements for Critical Areas reports referenced above, specific Critical Area report requirements for Landslide Hazard Areas are provided in ECDC 23.80.050. DEVELOPMENT PROPOSALS ASSOCIATED WITH LANDSLIDE HAZARD AREAS Development is restricted within a Landslide Hazard Area and its buffer. • Projects that will intrude into these areas will require a report by a licensed Geotechnical Engineer. • The criteria that are applied depend on the amount that the buffer is reduced • The buffer can be reduced to a minimum of ten (10) feet (with an additional 15' building setback per ECDC 23.40.280) if a report is prepared that meets the standards listed in ECDC 23.80.050. The alteration must also meet the requirements listed in ECDC 23.80.060. • In addition, proposals to reduce the buffer to less than ten (10) feet must comply with the design standards listed in ECDC 23.80.070.A.3. ALLOWED ACTIVITIES Certain activities are allowed in or near critical area buffers as specified in ECDC 23.40.20. If you have any questions about whether your proposed development qualifies as an allowed activity, please contact a Planner for more information. 2 EXEMPT DEVELOPMENT PROPOSALS Certain development proposals may be exempt from Critical Areas Requirements (ECDC 23,40.230). If you think that a specific development proposal may be exempt, contact a Planner for more information. F& Name Signature Date NOTE: Cited sections of the Edmonds Community Development Code (ECDC) can be found on the City of Edmonds website at www.ci.edmonds.wa.us. 3 fh C. 1 B90 CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS. WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: wwwdedmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering October 31, 2008 Brian McIntosh, Director Edmonds Parks, Recreation & Cultural Services 700 Main Street Edmonds, WA 98020 RE: Request for waiver per ECDC 19.10.070 16113 751h Place West, Edmonds Dear Brian, GARY HAAKENSON MAYOR STREET FILE We received your request for waiver to allow an irrigation system for the proposed park at 16113 75th Place W. The site is located in the Earth Subsidence Landslide Hazard Area which is regulated under ECDC 19.10. Irrigation systems are specifically prohibited in the Earth Subsidence Landslide Hazard Area as set forth in ECDC 19.10.070D unless a waiver is first obtained per ECDC 19.10.070E. Your request for waiver was sent for peer review by our geotechnical consultant, Landau Associates, as permitted in ECDC 19.10.070.E. It is their opinion that the information contained in the request did not demonstrate that the requirements of ECDC 19.10.070D were addressed. A copy of their Technical Memorandum dated October 28, 2008 is attached for your information. It has not been clearly demonstrated that the irrigation system will have no reasonable likelihood of triggering or otherwise contributing any landslide hazard or earth subsidence risk either on the subject site or in the neighboring earth subsidence or landslide hazard area as set forth in ECDC 19.10.070E. Therefore, it is my determination that the request for waiver for the proposed irrigation system is denied. Ann Bullis, CBO Building Official • Incorporated August 11, 1890 • Sister City - Hekinan, Japan • • LANDAU ASSOCIATES TECHNICAL MEMORANDUM nMIGEOWCW"IWILIMRESOMCS TO: Ann Bullis, Building Official City of Edmonds Building Department FROM: Dennis R. Stettler, P.E. ( ` DATE: October 28, 2008 REC�� RE: GEOTECHNICAL REv1EW cc, 31 2005 162"D STREET PARK IRRIGATION SYSTEM 13U1 �1NG EDMONDS, WASHINGTON ® A@.m INTRODUCTION This technical memorandum provides our geotechnical review comments related to the request by the City of Edmonds Parks, Recreation & Cultural Services Department (City Parks) to waive the requirements of Edmonds Community Development Code (ECDC) Chapter 19.10.070D.3 related to the prohibition of irrigation systems as a part of the plans submitted to the City of Edmonds (City) Building Official for the proposed 162"`' Street Park. This geotechnical peer review was accomplished at the request of the Building Official in accordance with Task Order No. 08-19 of Landau Associates' On -Call Geotechnical Engineering Services Agreement with the City_ Landau Associates has previously provided review comments for the project to the City in a technical memorandum dated May 5, 2008 for the original permit application submittal and in a technical memorandum dated August 13, 2008 for a resubmittal of the permit application documents. In both of those previous reviews, we pointed out that an irrigation system for the proposed park was shown on the plans. In accordance with ECDC 19.10.070D.3, irrigation systems are prohibited within the North Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA). Irrigation systems, as well as other surface water features with the potential to allow infiltration of storm water into the groundwater, are prohibited because of the adverse impact of any increase in groundwater levels to overall slope stability within this hazard area. According to ECDC 19.10.070E, this prohibition shall apply unless the applicant "requests a waiver based upon the written analysis of a geotechnical engineer which clearly establishes that the proposed improvement will have no reasonable likelihood of triggering or otherwise contribute to any landslide hazard or earth subsidence risk either on the site or in the .neighboring earth subsidence or landslide hazard area." Further, "the burden of proof shall always be upon the applicant to establish by a clear preponderance of the evidence that no such risk ivill be created by the improvement. Any geotechnical engineering report provided in any review shall consider not only the risk incurred due to or during construction of the otherwise prohibited improvement, but also the potential impacts due to failure 130 2nd Avenue South • Edmonds, WA 98020 • (425) 778-0907 • tax (425) 778-6409 • www.landauinc.com to maintain the improvement, damage through reasonably foreseeable events such as earthquakes or other acts of God, or the reasonably foreseeable negligence of the owner or future owners." We have used the stated criteria above in our review of the request for waiver. We have received the following additional information forwarded by the City for review: • Letter to the Edmonds Building Official from Brian McIntosh, Director, Edmonds Parks, Recreation & Cultural Services, dated October 7, 2008. • Letter regarding Irrigation of 162"' Street Park, 76`h Avenue West and 75h Place West Walkway Improvements, Edmonds, Washington prepared by HWA Geosciences, Inc., dated October 6, 2008. REVIEW COMMENTS City Parks notes that it plans to use the irrigation system only in the dry season, at the end of the dry season all irrigation pipes would be shutoff, and an automatic flow control valve would be installed that could sense abnormal flow beyond what is programmed and shut the irrigation system down automatically. These are all prudent steps to limit the potential for excessive surface water to be introduced to the site. The letter from HWA points out that a shallow trench subdrain system will be included to remove excess water from the site. The HWA letter alludes to the potential for the irrigation system to leak and considers it likely that the leaking water would remain near the surface and not reduce slope stability. However, the depth of this trench subdrain syste►n appears to be only several feet deep and it would probably remove some, but not all excess water that could potentially infiltrate. The HWA letter also qualifies their opinion on the provision that the irrigation system is properly maintained_ The proposed flow control valve and trench subdrain design elements address only the fact that they may limit the introduction of surface water; however, the proposal of an irrigation system constitutes an overall increase in the potential for introduction of surface water to groundwater and therefore an increase of the potential for soil movement. Based on the specific wording of ECDC 19.10.70D, it is our opinion that the applicant has not demonstrated that "...the proposed improvement will have no reasonable likelihood of triggering or otherwise contribute to any landslide hazard or earth subsidence risk... " or has not established that "...a clear preponderance of evidence that no such risk will be created by the improvement. " We suggest that the planting plan for the 162nd Street Park be reviewed and more drought -tolerant planting materials be selected that are not dependent on an automatic irrigation system for survival. We suggest that hand watering be accomplished, as necessary, until the planted materials are initially established. 10/2=8 \\Edmdata\projects\074\150�FileRoom\R\162ndStPark_IrrigationReview_TM.doc LANDAU ASSOCIATES 2 CLOSURE This technical memorandum has been prepared for use by the City of Edmonds in evaluating the request for waiver of the prohibition of an irrigation system for the City's 162nd Street Park. This geotechnical peer review by Landau Associates does not lessen the requirements for the applicant's geotechnical consultant and other design professionals to prepare an appropriate design for the site conditions. We appreciate this opportunity to be of service to the City. Please contact us if you have any questions, or if we may be of further service. DRS/rgm 10/28/08 \\Edmdata\projects\074\150\FileRoomW\162ndStPark_IrrigationReview_TM.doc LANDAU AssocIATES 3 1, .1!iA rI I(:f !. 'I"PO; N'i Ann Bullis, Building Official City of Echrionds 121 5°i Avenue North fidnionds, WA. 98020 Dear Ms. Bulbs, GAttY 11AAKENSON MAYOR October 7, 2008 ('lease accept this letter as an ofiacial request of waiver in regard to section 19.10.070 D.3, the Issuance and denial of perlllits in the Edmonds City Development Code. This section deals with the relationship Of groundwater to Stability within this earth SUbsicicnee. and landslide area. 'file City oft rrionds Parks & Recreation Department proposesto construct a neighborhood park on land ,It I fit" lI Street & 75°' Place West that was acquired by the City irr 1991. The development plans call flora controlled irrigation system to ensure survival of the planned vegetation and the small. grassy area which. are very important components of this park.. 1t should be noted that irrigation w011ld take place only in the dry season so no water would be added to the site when the area is most probe to slides. At the end of the dry season all irrigation pipes would be shut off at the meter. In addlilon, the Parks Department will install an "autOnlatic flow C011t Ol valve" that senses abnormal flow beyond what is prograrrurled Ulld ShUtS the IYYlf;atloll system down alttolllaticafly. Ralph 1:3oirum of FIWA Gcoscierrces is very familiar with this area and the design plans tor this project and his assessment is also attached. Thmik you for your consideration of this request and please let rile know if have.ally questions or need clarification. Sincerely, �., Brian McIntosh, Director F'(hllonds Parks, Recreation & (`ultural Services � ;,:. i,l, r;t.rt:.'�i • • s .. ,` i Flit.) ° `;i�t:rr (�'siu - t INktrr.ul..IGs{�cti7 .October G; 2008 HWA Project ito. 2006- 171-2 i City of l:?dInonds Parks & Recreation 700 Main Street Edmonds, Washington 98020 Attn: Mr. Brian McLntosh, Parks.& Recreation Director RE4 IRRIGATION OF 162'" S'CRCs(: [ 111mm,. 76rtt AvrtvUF WEST AND 7S•rtt PLACE, WEST WALKWAY hiI'll OVEM1t,NTS 1?1).NIONUS, h'VAsrttyc, roiv 17car iMr. iMclntosh: \Vc understand irrigaticnlsystcnls are prohihitt:d in the Inners a % aivcl. is s'ranccd based oll Ow. FCC a,n111ICI IdatiOil (&Ille t;CotOGlinica) Cilgiraccr. BOSO1 pail the W Hlt r,f unr studies of., the site, our t'Cet1t11111e1Klallolls .ft?t' desi"ll and construc11011 t.lf the, proposed 1)3rk, and our rcvie\v o the park's design, it It; trill' w6onimendatloll that a Winver Oc t;l'a1lted alloy Lllf; installation ol'an irrigation system. The, cul loll( do ioll ot'the park includes installation elf a french sltbdrain system to_ ivillovc Oxuc;;s Witter from 1.11t: Site its \vuH as constrllctloal of 8 buttressing fill to increase the Stability ol; the C,onsidcrin;; IN, clayey nature oftho native soils it the silt, it is likely that most %vatm, le alcirl, front the irri„tltiou system would rcmain near tlita-surfact, inhere it \e<uald neat rc:daacc: sl,al,c: stability. \\dater �cre:pilll; kill) tht: wils would he rull6vcrd by the subrh•ain gste.,nl. Providiut; that it is properly rnaiutaulecl and tllrJICd off dui ing Ilse \vct mullahs, it is our opinion thaat all it ri`,aho,a system call sally he.installed and operated can this site withoutincaeased risk of' instability. We appreciate illc opportunity Io provide. (wicchnical service.': oil this projcc•t, Sincerely, S tint'. tA.<c4 ` n t Ralph Via. 13o11-un1, P.F. Geotechnical Engillur, Principal Cc: Tani Stafford, Gray & Oshortie, hnc: $TREET FILE w.: g.. CITY OF E D M O N A.. S (:1ARY I- AAKENSON MAYOR 3Pf&t3 _ i �.,; rd -. � , •r.t: r;t,:,, ,. '•to), ,. :, �.,; 77: �, r: , .. > i ... l L li .-1 : An Bullis, Building Official REISUBOctober , 2008 City of f;dnIonds 121 5`I' Avenue North 70�6 FArrionds, VGA 98020 SULD Dear Ms. Bullis, Please accept this letter as an official request of waiver in regard to section 19.10.07/0 D.3, the ISsuance and denial of permits in the Edmonds City Development Code. This section deals with the relationship Of groundwater to stability within this Cal th subsidcuCC and landslide area. Tile City of l".dmonds Parks & Recreation .Department proposes to construct a ticiglrbut-hood park On land at I62`1 Street & 75"' Place %Vest that was acelui -Ul tw the City in 1001. The development plans call for a controlled irrigation system LO erisur'c SLIIWIval of the planners vegetation and the small grassy area which arc very Important components of this park. It should be noted that irrigation Would take place only in the dry season su no \vatcr would be added 1.0 the site +vhen the area is most prone to slicks. At the cnd of 1hc. dry season all irrigation pipes would be shut Off at the meter. In addition, -the Parks Department will install an "autouaatic flOw control valve" ihat sen5rti ahnc+rmal ilo w beyond what is programincd and shuts the ierigatIOII system down autonrrtically. Ralph I3oirum of FIWA Geosciences is very Familiar with this area and the design plans for this project and his assessment is also attached. 'Thank you for your consideration Of this request and please let me know if have any questions or need clarification. Sincerely; Brian Mdnto sh, Director F.Anionds .Parks, l:ecrcation & Cultural Services a'10�j -OISa kGEOSCIENCES INC. echnical & Pavement Engineering • Hydrogeologr • Geoenvironmental • Inspection & Testing October 6, 2008 HWA Project No. 2006-171-21 City of Edmonds . Parks & Recreation 700 Main Street Edmonds, Washington 98020 Attn: Mr. Brian McIntosh, Parks & Recreation Director - RE: IRRIGATION OF 162ND STREET PARK OCT 0 2000 pTYNOF ELaMONC 76TH AVENUE WEST AND 75TH PLACE WEST WALKWAY IMPROVEMENTS EDMONDS, WASHINGTON Dear Mr. McIntosh: We understand irrigation systems are prohibited in the Meadowdale area unless a waiver is granted based on the recommendation of the geotechnical engineer. Based on the results of our studies of the site, our recommendations for design and construction of the proposed park, and our review of the park's design, it is our recommendation that a waiver be granted allowing installation of an irrigation system. The current design of the park includes installation of a trench subdrain system to remove excess water from the site as well as construction of a buttressing fill to increase the stability of the site. Considering the clayey nature of the native soils at the site, it is likely that most water leaking from the irrigation system would remain near the surface where it would not reduce slope stability. Water seeping into the soils would be removed by the subdrain system. Providing that it is properly maintained and turned off during the wet months, it is our opinion that an irrigation system can safely be installed and operated on this site without increased risk of instability. We appreciate the opportunity to provide geotechnical services on this project. Sincerely, A CLOIALIft HWA GEOSCIENCES INC. Ralph N. Boirum, P.E. MS Geotechnical Engineer, Principal Cc: Tani Stafford, Gray & Osborne, Iric. 14— 13 c- fho. 1890 • CITY OF EDMONDS C_ 700 MAIN ST • EDMONDS, WA 98020 • (425) 771-0230 • FAX (425) 771-0253 PARKS, RECREATION AND CULTURAL SERVICES DEPARTMENT Ann Bullis, Building Official City of Edmonds 121 5`h Avenue North Edmonds, WA 98020 Dear Ms. Bullis, GARY HAAKENSON MAYOR October 7, 2008 Please accept this letter as an official request of waiver in regard to section 19.10.070 D.3, the Issuance and denial of permits in the Edmonds City Development Code. This section deals with the relationship of groundwater to stability within this earth subsidence and landslide area. The City of Edmonds Parks & Recreation Department proposes to construct a neighborhood park on land at 162"d Street & 751h Place West that was acquired by the City in 1991. The development plans call for a controlled irrigation system to ensure survival of the planned vegetation and the small grassy area which are very important components of this park. It should be noted that irrigation would take place only in the dry season so no water would be added to the site when the area is most prone to slides. At the end of the dry season all irrigation pipes would be shut off at the meter. In addition, the Parks Department will install an "automatic flow control valve" that senses abnormal flow beyond what is programmed and shuts the irrigation system down automatically. Ralph Boirum of HWA Geosciences is very familiar with this area and the design plans for this project and his assessment is also attached. Thank you for your consideration of this request and please let me know if have any questions or need clarification. Sincerely, V0 Brian McIntosh, Director Edmonds Parks, Recreation & Cultural Services • Incorporated August 11, 1890 • Sister City - Hekinan, Japan • ram\ � • 0 HWAGEOSCIENCES INC. Gevtechnieal & Pavement Enfiineering - Hydrngeoingp - GecienvirOtmwwal - Insprctitut � 1'tr5tirt� July 14, 2008 HWA Project No. 2006-171-21 Gray & Osborne, Inc. 701 Dexter Avenue North, Suite 200 Seattle, Washington 98109 Attn: Ms. Tani Stafford, P.E. Project Manager STREET FILE RECEIVED JUL 212008 DEVELOPMENT SERVICES COUNTER LOGICAL HAZARDS ASSESSMENT 76TH AVENUE WEST AND 75TH PLACE WEST WALKWAY IMPROVEMENTS EDMONDS; WASHINGTON Dear Tani: This letter is an addendum to the original geotechnical report as requested by the Hearing Examiner. In compliance with the City of Edmonds Critical Areas Ordnance ECDC 23.80.060, Development Standards, we offer the following: The proposed 76th Avenue West and 75th Place West Walkway Improvements Project, including the proposed park at 162nd Street has been designed in such a way that it will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions; it will not decrease slope stability on adjacent properties; and it will not adversely impact other critical areas. The proposed construction will result in increased stability in some areas, including the stabilization of an existing landslide on the park property, with no impact in other areas. In our opinion buffers are not applicable to this project as the work will include construction of retaining walls and fill placement to increase the stability of steep slopes. We appreciate the opportunity to provide geotechnical services on this project. Sincerely, HWA GEOSaENCES IN, Ralph N. Boirum, P.E. Geotechnical Engineer, Principal APPROVED BY PLANNING Ol-1A.pg BI.D. -7,00$, 0192 SMP.�-0og• 002-(o 19730 - 64th Avenue W. Suite 200 Lynnwood, WA 08036.5957 Tel: 425.774' 0106 Fax: 425.774J714 wwwhwageacom .:- STREET FILEIA Asso U .ASSOCIATES TECHNICAL MEMORANDUM TO: Ann Bullis, Building Official City of Edmonds Building Department FROM: Dennis R. StettIer, P.E. cJ> DATE: August 13, 2008 RE: GE- OTECHNICAL RESUBMITTAL REVIEW 162*7D STREET PARK EDMONDS, WASHINGTON INTRODUCTION This technical memorandum provides our geotechnical review of a resubmittal of geotechnical documents and plans submitted to the City of Edmonds (City) for the proposed development of the City's 162nd Street Park. The purpose of this geotechnical review was to review portions of the resubmittal package and assess whether our initial geotechnical peer review comments as contained in our Technical Memorandum dated May 5, 2008 have been addressed, and to assess compliance with City development and building permit requirements as contained in Edmonds Community Development Code (ECDC) Chapter 19.10. ECDC Chapter 23.80, and City of Edmonds Retaining Wall Permit Submittal Requirements (as contained in City I-landout 1362). We were requested to focus our review on Plan Sheets S-11 and L-1 through L-16 (those plan sheets specifically pertaining to the proposed 162i1 Street Park) and not those pertaining to the proposed 76"' Avenue West/75°i Place West walkway improvements portion of the overall project. This geotechnical peer review was accomplished in accordance with Task Order No. 08-17 of Landau Associates' On -Call Geotechnical .Engineering Services Agreement with the City. We have received the following information forwarded by the City for review as a part of the resubmittal: O Construction Document ,Set Plans for 162"" Street Park (includes Sheets S-11 and L -1 through L-16) prepared by SIB & Associates, Inc. and Gray & Osborne, Inc. for the City of Edmonds Parks and Recreation Department, dated May, 2008. o Revisetl Geotechnical Report, 76"' flvenue 11'est LC 75"1 Place West, Walkivav Improvements, Ednionds, 6Vashingron prepared for Gray & Osborne, Inc. by 14WA GeoSciences, Inc., dated November 16, 2007 (Revised May 30, 2008). o Mentorandian Re: 162"r Street Park Wall, 761' Avenue titest/75`i' Place West Walkivay- Irnprovenients, Edmonds, Washington, prepared for Gray & Osborne by HWA GeoSciences, Inc., dated April 1, 2008. 130 2nd Avenue South a Edmonds, WA 98020 e (425) 778.0907 e tax (425) 778-6409 a :vtvw.landauinc.com C • PLAN REVIEW We reviewed the revised plans for the park development to assess their consistency with: our May 5, 2008 review comments; geotechnical recommendations contained in the HWA Geosciences, Inc. (HWA) report; and with the provisions of ECDC 19.10 and ECDC 23.80. The issues that we had previously identified and their resolutions are outlined below: The plans show a retaining wall and up to 10 ft of fill placed above existing grades on and near the base of the slope on the park property. The park development plan considered in the original geotechnical report did not address the effect of the proposed retaining wall and fill on the slope stability. The revised HWA report uses the results of slope inclinometer monitoring and slope stability analyses to analyze the existing slope configuration and the effect of a proposed buttress fill at the toe of the slope that has shown recent slope movement. The stability analyses demonstrate an improvement in slope stability. Although the configuration of the wall and fill currently planned is somewhat different than the slope configuration analyzed in the revised geotechnical report, the beneficial effect of placing fill near the toe of the slope should still be beneficial. • The plans indicate that the retaining wall planned on the park property would be supported on 2-ft diameter augercast piles installed to a depth of 10 ft. The original submittal provided limited information related to this design. The revised HWA report and the HWA Memorandum dated April 1, 2008 address the geotechnical recommendations for the wall support and those recommendations have been incorporated into the plans. • The planned retaining wall as shown on the original plans is composed of a modular block wall; but the geogrid or geotextile reinforcement of the backfill behind the wall that was recommended in the original HWA report was not shown. The resubmitted plans now show geogrid reinforcement consistent with the HWA geotechnical report recommendations. • The original retaining wall details did not show how the drainage pipe behind the wall will be connected to the site drainage system. This information is now shown on the resubmitted plans. • The original geotechnical report recommends a deep trench subdrain (8 to 10 ft deep) near the toe of the eastern slope on the park property. The revised geotechnical report recommends a 4 to 5 ft deep trench drain. A subdrain is shown on the plans (Sheet L-4) with a note to see the Civil Plans for the invert elevations. The invert elevation information was not apparent on the plan sheets that we were provided for the original submittal and we are not able to find that information in our current review of the resubmittal. Confirm that the slope drain is at an appropriate location and depth consistent with the geotechnical report recommendations, and provide invert elevations on the plans. City requirements for retaining wall permits (see City Handout B62) and the provisions for permits as contained in the City's ESLHA documents outline the requirements for calling for Building Inspections by the City during construction, and Special Inspection Requirements that call for the Geotechnical Engineer of Record to monitor the construction to verify the site conditions and construction and to submit Field Reports to the City. The requirements for City Building Inspections and ,Special Inspections by the Geotechnical Engineer of Record should be included on the design plans. 8/13108 \\Edmdata\projects\074\150\WIP\R\162ndStPark_ResubmitReviewTM.doc 2 LANDAU ASSOCIATES • Plan sheets L-14 through L-16 relate to irrigation. However, the City has identified that site improvements that introduce water into the ground within the ESLHA (including watering or irrigations systems) are prohibited (ECDC 19.10.070.D). The plans should be revised to reflect this requirement. GEOTECHNICAL REPORT REVIEW The original geotechnical report did not reference or address the specific requirements of ECDC 19.10 or ECDC 23.80 related to projects within the North Edmonds ESLHA. We had recommended that the HWA report be updated to address the landslide hazard discussion and background as required by ECDC 19.10. The revised geotechnical report is not substantially different than the original report and does not specifically reference or address the specific requirements of ECDC 19.10 or ECDC 23.80. The revised HWA report has considered the results of recent slope inclinometer readings and addressed slope stability at the park by specific analyses of the slope before and after construction, as requested in our previous review comments. CLOSURE This technical memorandum has been prepared for use by the City of Edmonds in evaluating the adequacy of construction documents resubmitted for the City's 162nd Street Park. The focus of this review was the geotechnical aspects of the documents. The purpose of the review was to assess the adequacy of the documents for compliance with City requirements contained in ECDC 19.10, ECDC 23.80, City of Edmonds Retaining Wall Permit Submittal Requirements, and conformance with conventionally accepted geotechnical engineering practices. This geotechnical peer review by Landau Associates does not lessen the requirements for the applicant's geotechnical consultant and other design professionals to prepare an appropriate design for the site conditions. We appreciate this opportunity to be of service to the City. Please contact us if you have any questions, or if we may be of further service. DRS/rgm 8/13/08\1Edmdata\projectsk074\15O\WIP\R\162ndStPark_ResubmitReviewTM.doc 3 LANDAU ASSOCIATES LANDAU .ASSOCIATES TECHNICALMEMORANDUM Fiavrmr� IGEOMC CALIR LQ4rEsou:ees TO: Jeannine Graf, Building Official City of Edmonds Building Department FROM: Dennis R. Stettler, P.E. ��r DATE: May 5, 2008 RE: GEOTECHNICAL PEER REVIEW 162"" STREET PARK EDMONDS, WASHINGTON INTRODUCTION STREET FILE This technical memorandum provides our geotechnical peer review of technical documents and plans submitted to the City of Edmonds (City) for the proposed development of the City's 162nd Street Park. The purpose of this geotechnical peer review was to review portions of the submittal package and assess its compliance with City development and building permit requirements as contained in Edmonds Community Development Code (ECDC) Chapter 19.10, ECDC Chapter 23.80, and City of Edmonds Retaining Wall Permit Submittal Requirements (as contained in City Handout B62). This geotechnical peer review was accomplished.in accordance with Task Order No. 08-07 of Landau Associates' On -Call Geotechnical Engineering Services Agreement with the City. We have received the following information forwarded by the City for review: 0 Construction Document Set Plans for 162"`1 Street Park (includes Comer Sheet, Sheets L-1 through L-4, S-11, L-7, L-8, and L-11 through L-13 prepared by SB & Associates, Inc. and. Gray & Osborne, Inc. for the City of Edmonds Parks and Recreation Department, dated February 25, 2008. O Geotechnical Report, 76"' Avenue West & 75"' Place West, Walktivav Improvements, Edmonds, Washington prepared by HWA Geosciences, Inc., dated November 16, 2007. Development of the park will include grading, construction of retaining walls, and construction of various park amenities. The project is located within the designated North Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA) and is therefore subject to the provisions of ECDC 19.10 related to the ESLHA and ECDC 23.80 related to Geologically Hazardous Areas. Portions of the typical pert -nit application for development within the ESLHA (such as vicinity maps, North Edmonds ESLHA Map with signatures, various owner and design team declarations) that are intended to inform the private property owners of the risk associated with development do not apply to this project, since the City is the property owner and is well aware of the risks posed by this landslide hazard area. However, other 130 2nd Avenue South • Edmonds, WA 98020 • (425) 778-0907 • fax (425) 778-6409 • www.landauinc.com 0 0 technical requirements of ECDC 19.10 and ECDC 23.80 that address slope stability and hazard reduction do apply to the proposed project. PLAN REVIEW We reviewed the plans for the park development to assess their consistency with the geotechnical recommendations contained in the HWA Geosciences, Inc. (HWA) report and with the provisions of ECDC 19.10 and ECDC 23.80. We identified a number of inconsistencies between the plans and the geotechnical report that should be addressed: The plans show a retaining wall and up to 10 ft of fill placed above existing grades on and near the base of the slope on the park property. The park development plan considered in the geotechnical report (see Figure 6 of the HWA report) apparently did not consider the effect of the proposed retaining wall and fill on the slope stability. The HWA report states on page 6 "Because placement of fill on the downslope side of the road would add to the weight of a potential landslide, reducing stability of the slope, we recommend that filling be avoided to the extent possible." The geotechnical report needs to address the appropriateness of the proposed retaining wall/fill configuration. The effect of' this proposed grading on overall slope stability needs to be addressed and it must be demonstrated that the stability is improved over existing conditions or the grading needs to be altered. The plans indicate that the retaining wall planned on the park property would be supported on 2-ft diameter augercast piles installed to a depth of 10 ft. The bottom of these piles would still be within landslide debris. No geotechnical recommendations are provided specifically for this wall to assess the appropriateness of this design. The HWA geotechnical report recommends that elevated walkways and other structures should be supported on pin piles installed to a depth of 20 to 25 ft (which in this area is thought to be through the existing landslide debris). The proposed wall support and geotechnical recommendations need to be consistent. The planned retaining wall is composed of a modular block wall that extends to heights of up to 6 to 7 ft above the final grade according to Plan Sheet S-11. No geogrid or geotextile reinforcement of the backfill behind the wall is indicated on the plans. The HWA geotechnical report states that "Block walls higher than twice the block depth should include geogrid reinforcing which extends back from the face of the wall a horizontal distance equal to at least 0.7 times the free-standing wall height." If the wall remains at its planned height, geogrid reinforcing needs to be provided or the type of wall changed to be consistent with the geotechnical recommendations. • Retaining wall details appropriately show drainage material and a drainage pipe behind the retaining wall. However, it is not clear from the plans that the drainage pipe behind the wall will be connected to the site drainage system. Provide a connection from the drainage pipe behind the retaining wall to the site drainage system. • The geotechnical report recommends a deep trench subdrain (8 to 10 ft deep) near the toe of the eastern slope on the park property. A slope drain is shown on the plans (Sheet L-4) with a note to see the Civil Plans for the invert elevations. That information was not apparent on the plan sheets that we were provided for review. The slope drain appears to be located near the 5/5/08 \\Edmdata\projects\074\150\FileRoomXR%162ndStPark_PeerReview_TM.doc 2 LANDAU ASSOCIATES toe of the new slope instead of the toe of the existing slope. No typical detail for the deep trench subdrain is provided on the plan sheets that we were provided for review. Confirm that the slope drain is at an appropriate location and depth consistent with the geotechnical report recommendations, and provide a typical detail consistent with the recommendations of the geotechnical report. hi addition, COnSlder constructablllty issues with respect to excavating an 8 to 1Oft deep trench near the toe of a potentially unstable slope. It may be appropriate to require temporary shoring or specifically limit the horizontal extent Of trench that can be open at any time in order to reduce the potential for initiating a slope failure during construction. • City requirements for retaining wall permits (see City Handout 1362) and the provisions for permits as contained in the City's ESLHA documents outline the requirements for calling for Building Inspections by the City during construction, and Special Inspection Requirements that call for the Geotechnical Engineer of Record to monitor the construction to verify the site conditions and construction and to submit Field Reports to the City. The requirements.for City Building Inspections and Special Inspections by the Geotechnical Engineer of Record should be included on the design plans. • The Drawing Index calls out plan sheets L-14 through L-16 related to Irrigation. These plan sheets were not provided to us for review. However, the City has identified that site improvements that introduce water into the ground within the ESLHA (including watering or irrigations systems) are prohibited. The plans should be revised to reflect this requirement. GEOTECHNICAL REPORT REVIEW The geotechnical report does not reference or address the specific requirements of ECDC 19.10 or ECDC 23.80. There are a number of requirements for grading and retaining wall permits for projects within the ESLHA that are not addressed by the HWA geotechnical report. The geotechnical report should be revised or supplemented to address the specific City requirements for geotechnical reports as contained in the City's "Geotechnical Report Guidelines" document for projects in the North Edmonds ESLHA. The report references the 1979 Geotechnical Report by Roger Lowe Associates, but does not reference any of the more recent comprehensive landslide hazard area studies of the area, including the 2007 Landau Associates report as required by ECDC 19.10. HWA describes the landslide history and references the Roger Lowe Associates report to conclude that large-scale ground movement occurred between two and three thousand years ago. The HWA report further states that "No large-scale earth movements have been recorded for this area in modern times." The implication of the discussion in the report seems to be that no large-scale movements have occurred in historical times, and that is not consistent with the available historical information. Significant landslides occurred in this area in 1947 and 1955-56 that would be considered by most people to be large-scale. We recommend the HWA report be updated to address the landslide hazard discussion and background as required by ECDC 19.10. 5/5/08 \\Edmdata\projects\074\150\FileRoom\R\162ndStPark_PeerReview_TM.doc 3 LANDAU ASSOCIATES The HWA report addresses slope stability at the park and the influence of placing fill along the toe of the slope in only a general way. It does not appear that stability analyses were conducted for either the existing conditions or the stability after the planned fill and retaining wall is constructed. Placement of the proposed fill and retaining wall may increase the stability of the slope above (east of) this location, but since the wall and fill will be placed on about 20 ft of landslide debris, the stability downslope (to the west) could be adversely affected. Slope stability analyses of the existing and proposed slope configuration needs to be conducted. . The HWA report also provides the results from monitoring of an inclinometer on the adjacent property that documents recent slope displacement and notes that another inclinometer was installed in boring BH-1 that was drilled on the park property as a part of this project. The HWA report states that "A definitive stabilization design will require additional measurements in the two slope indicator casings over the course of the coming winter to determine the location of the slide plane and performing stability analyses to develop stabilization measures. That additional analysis is not within the present scope of work; however, we recommend that this additional analysis be performed and the results incorporated into the park design." To our knowledge, this work was not done. We recommend that additional monitoring of the slope inclinometers be conducted and slope stability analyses be conducted to assess current conditions and the expected slope stability conditions during and.following construction of the proposed park retaining wall, grading, and drainage improvements. The site of the park and the proposed construction are within a Geologically Hazardous Area as defined in ECDC 23.80. Consequently, the provisions and requirements of ECDC 23.80 apply to this project. The geotechnical report for the project addresses some of the ECDC 23.80 requirements, but limited information is provided for other issues. The geotechnical report should address all of the report requirements of ECDC 23.80.050, including, but not limited to the extent of the geologic hazards area; the relationship of the existing and proposed construction to the geologic hazard; a hazards assessment of the overall slope; the history of the site regarding previous landslides, erosion, or grading; the stability of the slope before and after the proposed retaining wall construction; a discussion of how the proposed retaining walls maintains or reduces the pre-existing level of risk presented by the geologic hazard; and related requirements outlined in ECDC 23.80.050. CLOSURE This technical memorandum has been prepared for use by the City of Edmonds in evaluating the adequacy of construction documents submitted for the City's 162" d Street Park. The focus of this review was the geotechnical aspects of the documents. The purpose of the review was to assess the adequacy of the documents for compliance with City requirements contained in ECDC 19.10, ECDC 23.80, City of 5/5/08 \\Edmdata\projects\074\150\FileRoomU2\162ndStPark_PeerReview_TM.doc 4 LANDAU ASSOCIATES T. Edmonds Retaining Wall Permit Submittal Requirements, and conformance with conventionally accepted geotechnical engineering practices. This geotechnical peer review by Landau Associates does not lessen the requirements for the applicant's geotechnical consultant and other design professionals to prepare an appropriate design for the site conditions. We appreciate this opportunity to be of service to the City. Please contact us if you have any questions, or if we may be of further service. DRS/rgm 5/5/08 \\Edmdata\projects\074\150\FileRoom\R\162ndStPark_PeerReview_TM.doc 5 LANDAu ASSOCIATES 1-1 Materifts Testing & Consutng, Inc. Geotechnical Engineering • Special Inspection • Materials Testing REPORT OF FIELD INSPECTION CLIENT: Woodman Construction ATTN: Lachlan Foss ADDRESS: 3 Lake Bellevue Dr. Ste. 201 Bellevue, WA 98005 M.T.C. PROJECT #: DATE: PROJECT: PROJECT ADDRESS: STRUCT. ENGINEER: CIVIL ENGINEER: ARCHITECT: CONTRACTOR: PERMIT NO.: Report #F 22345 08BO45-01 April 28, 2008 PCC-12 Grocery Store 9803 Edmonds Way, Edmonds, WA 2007-1881 Inspection Performed: Fab Shop Weld Inspection Time Onsite: Temp: Any Deficiencies Noted: ❑ Need Engineer's Approval ❑ Other ❑ MTC on site for fabrication shop inspection. MTC inspected 14 column and some miscellaneous parts at Stainless Steel Fabrications shop in Custer, Washington. All parts inspected to fabrication drawings and AWS D1.1 requirements. REPORTED BY: S.Barrie, WABO Inspector pn REVIEWED BY: Niall Hackett, Technical Director original: DISTRIBUTION: Iachlan�cJwoodmanconstruction.com cc: bullis(cr�,ci.edmonds.wa.us cc: cc: cc: cc: All results apply only to actual locations and materials tested. As a umtual protection to clients. the public and ourselves, all reports are submitted as the—fiideutial property of clicuts. and authotiution for publication ofstacuouts. conclusions or extracts from or regarding our reports is reserved pending our Britten approval. Corporate Office — 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 21 18 Black Lake Blvd SW • Olympia, WA 98512 • Phone (360) 534-9777 • Fax (360) 534-9779 2126 East Bakerview Road, Suite #101 • Bellingham, WA 98226 • Phone (360) 647-6061 • Fax (360) 647-8111 Website Address: www.mtc-inc.net Rev. 07/07 • 5Ters on • c4 � • 8 :: t pyn STATE OF WASHINGTON DEPARTMENT OF ECOLOGY Northwest Regional Office • 3190 160th Avenue St • Bellevue, Washington 98008-5452 • (425) 649-7000 September 10, 2008 certify that 1 mailed a copy of this document to the persons and addresses listed herein, postage prepald,.b a receptacle for United StaMr. Brian McIntosh, Parks Director washi gt it In �v — City of Edmonds Parks and Recreation Dept. onr rr o 700 Main Street Edmonds, WA .98020 Dear Mr. McIntosh: ST11 bl[ FILE Subject: City of Edmonds Permit # SM-2008-26 —Approved Mr. McIntosh - Applicant Shoreline Substantial Development Permit # - 2008 NW 30038 Purpose: Notification of Receipt .of Approved Substantial Development Permit (SDP) On August 29, 2008, the Department of Ecology received notice that the City of Edmonds approved your application for an SDP. Your permit is for developing a neighborhood park at the NW corner of 751h place west and 162"d Street SW, within shoreline jurisdiction of Puget Sound. Bylaw, local governments must review all SDPs for compliance with the following: • The Shoreline Management Act (Chapter 90.58 RCW) • Ecology's Substantial Development Permit approval criteria (Chapter 173-27-150 WAC) • The Edmonds Local Shoreline Master Program Local governments, after reviewing the SDP for compliance, are required to submit the SDPs to Ecology for filing. Your approved SDP has been received and filed by Ecology. What Happens Next? Before you begin activities authorized by this permit, the law requires you to wait at least 21 days from the date we received the decision letter from the City of Edmonds on 'August 29, 2008. This waiting period allows anyone who (including you) disagrees with any aspect of this permit, to appeal the decision to the state Shorelines Hearings Board. You must wait for the* .conclusion of an appeal before you can begin the activities authorized by this permit. CIO i r Edmonds Parks and Recreation September 10, 2008 Page 2 of 2 If no appeal is submitted you may begin activities any after September 19, 2008, The Shorelines Hearings Board will notify you by letter if they receive an appeal. We recommend, however, you contact the Shorelines Hearings Board before you begin permit activities to ensure no appeal has been received. They can be reached at (360) 459-6327 or hU,:f/www.eho:wa. ovBoards/SHB.M.' . If want to appeal this decision, you can find appeal, instructions (Chapter 46148 WAC) at the Shorelines Hearings Board website above.. They are also posted on the website of the Washington State Legislature at: http://apps.leg.wa. ovg /wac. Other federal, state and local permits may be required in addition to this shoreline permit. Jf this permit is NOT appealed, this letter constitutes the Department of Ecology's final notification of action on this permit.. If you have any questions about this letter, please contactme at (425) 649-4253. Sin r , David Pater, Shorelands Specialist Shorelands and Environmental Assistance. Program DP:cja cc: Rob Chave, City of Edmonds, Development Services Department STREET FILE APR 2 2 2008 BUILDING OFDEDMONDS j 4`�3 �v�!'�GV GEOTECHNICAL REPORT 76t' Avenue West A 75t' Place West Walkway Improvements Edmonds, Washington HWA Project No. 2006-171-21 Prepared for Gray & Osborne, Inc. November 16, 2007 MW HWAGEOSCIENCES INC. • Geotechnicnl Engineering • Hydrogeology • Geoenvirontnental Services • Inspection & Testing TABLE OF CONTENTS Page 1. INTRODUCTION...........................................................................................................1 1.1 SITE AND PROJECT DESCRIPTION.................................................................I 2. EXPLORATIONS AND GEOLOGIC CONDITIONS............................................................2 2.1 SUBSURFACE EXPLORATIONS.......................................................................3 2.2 GENERAL GEOLOGIC CONDITIONS..............................................................3 2.3 LANDSLIDE HISTORY....................................................................................3 2.4 SUBSURFACE CONDITIONS............................................................................4 2.5 GROUND WATER CONDITIONS.....................................................................5 2.6 LABORATORY TESTING................................................................................5 3. RECOMMENDATIONS..................................................................................................6 3.1 GENERAL.......................................................................................................6 3.2 EARTH RETAINING STRUCTURES.................................................................6 3.3 PILE SUPPORTED WALKWAYS.....................................................................7 3.4 PAVEMENTS...................................................................................................7 3.5 PARK DESIGN................................................................................................8 3.5.1 Stability..........................................................................................8 3.5.2 Park Drainage..............................................................................8 3.5.3 Foundation Design.......................................................................9 3.5.4 Park Pavement.............................................................................9 4.0 CONDITIONS AND LII UTATIONS................................................................................9 LIST OF FIGURES (FOLLOWING TEXT) Figure 1 Figures 2-4 Figure 5 Figure 6 Figure 7 Figure 8 J Figure 9A & 9B Appendices Vicinity Map Site and Exploration Plan Park Property Exploration Plan Proposed Park Plan Cross Section A -A' Log of Previous Test Boring HWA-1 Boring HWA-3 Inclinometer Plot Appendix A: Field Exploration Figure A-1. Legend of Terms and Symbols Used on Exploration Logs Figures A-2 - A-13 Logs of Test Boritigs BH-1 through BH-3 and Hand Borings HH-1 through HH-9 Appendix B: Laboratory Testing Figure B-1 Particle Size Distribution Test Results Figure B-2 Liquid Limit, Plastic Limit, and Plasticity Index of Soils (Atterberg Limits) GEOTECHMCAL REPORT WALKWAY IMPROVEMENTS 76TH AVENUE WEST AND 75TH PLACE WEST EDMONDS, WASHINGTON 1. INTRODUCTION This report presents geotechnical recommendations for design and construction of the proposed walkway improvements to 76`h Avenue West and 75d' Place West in Edmonds, Washington. The purpose of this work was to assess geotechnical conditions along the project alignment and provide recommendations for design and construction of the proposed improvements. 1.1 Site and Project Description The project is located in the Meadowdale area of Edmonds, which is located along the shoreline of Puget Sound north of the city. The area is indicated on the Vicinity Map, Figure 1. The project will include construction of a walkway along 76 h Avenue West and 75 h Place West extending from Meadowdale Beach Road north to North Meadowdale Road, with some additional improvements north to the King County Park. The project will include development of a park at the north-west corner of 75 h Place West and 162nd Street SW. Three conceptual designs for the proposed improvements were developed during preliminary studies. We understand Concept 1 was selected for final design and construction. Under the selected concept, the new sidewalk will be located along the east (upslope) side of the roadway from Meadowdale Beach Road north to 162°d Street SW. Cuts into the hillside will be required for the new sidewalk in much of this area. The cuts will be typically 3 to 4 feet in height but will be up to 12 feet high in some areas. From 162°d Street SW north to North Meadowdale Road the new walkway will be located on the western side of the road. Since placing fill along the top of the slope could reduce the stability of the slope and is to be avoided, the new sidewalk will be supported on small diameter pipe piles where there is insufficient existing flat area. North of North Meadowdale Road two pull-outs will be constructed on the east side of the road for vehicle parking, and one 130-foot-long section of pile -supported walkway is planned on the west side of the road. Development of the proposed park will include regrading the site and construction of a driveway, walkways, lawn and play areas. We understand an interpretive overlook is planned adjacent to 75 h Place West. A plan of the proposed park is presented on Figure 6. Novemberl6, 2007 HWA Project No. 2006-171-21 2. EXPLORATIONS AND GEOLOGIC CONDITIONS 2.1 Subsurface Explorations Subsurface information for the project was obtained by advancing three hollow stem auger borings designated BH-1 through BH-3; nine hand borings designated HH-1 through HH-9; and three DCP soundings performed in concert with hand borings HH-7 HH-8 and MI-9. Boring BH-1 was conducted by Davies Drilling Inc. using a track mounted CME-75 drill rig with a 3.25 inch OD hollow stem auger. Borings BH-2 and BH-3 were drilled by Environmental Drilling using a truck mounted B-61 drill rig with an 8 inch OD hollow stem auger. Boring BH-1 is located in the northeast section of the proposed new park. Borings BH-2 and BH-3 are located along the proposed sidewalk alignment where a new solider pile wall will be installed on the east side of 76`h Avenue West and 75`' Place West. Hand holes HH-1 through HH-6 are located along the east side of 76th Avenue West and 75 h Place West along the alignment of the proposed sidewalk. Hand holes HH-7 through HH-9 along with their associated DCP soundings are located along the west side of 75 h Place west between 162nd Street West and North Meadowdale beach road. Borings were advanced either at the edge the City right of way, or in the middle of the right travel lane, as shown in Figures 2-4. A 2-inch diameter ground water monitoring well was installed in BH-2 with screen from a depth of 15 to 25 feet and a silica sand filter from a depth of 12 to 30 feet. A slope inclinometer casing was installed in BH-1 after the completion of the boring. The casing was installed to a depth of 35 feet below the ground surface and was incased in cement grout. A baseline reading for future measurements was taken on October 20 2007. Borings were located using a site map provided by Gray & Osborne inc. by measuring from existing structures shown on the base map provided. A legend of the terms and symbols used on the boring logs is presented in Figure A-1. Summary boring logs are presented in Figures A-2 through A-13. Standard Penetration tests were performed at 2.5-foot or 5-foot intervals in all three borings. The Standard Penetration test consists of driving a 2-inch O.D. split -spoon sampler a distance of 18 inches into the bottom of the borehole with a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler each of three 6-inch increments was recorded, and number of blows required to cause the last 12 inches of penetration was termed the Standard Penetration Resistance (N-value). This value is an indicator of the relative density or consistency of the soils. Whenever 50 or more blows were required to cause 6 inches of penetration, driving was stopped and the number of blows and corresponding penetration were recorded. Samples recovered from the split spoon sampler were disturbed but were representative of the soils encountered. Final Geotechnical Report 2 HWA GeoSciences Inc. November16, 2007 HWA Project No. 2006-171-21 An HWA geologist monitored the drilling and logged the borings. Soil samples were obtained from the borings at intervals of 2.5 to 5.0 feet, classified in the field, and representative portions were placed in plastic bags. These soil samples were taken to our Lynnwood, Washington, laboratory for further examination and testing. Pertinent information including soil sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence were recorded on the exploration logs. The stratigraphic contacts shown on the individual boring logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and ground water conditions depicted are only for the specific date and locations reported and, therefore, are not necessarily representative of other locations and times. 2.2 General Geologic Conditions Geologic information for the project site was obtained from the published geologic map for the area; Booth, D. B., Cox, B. F., Troost, K. G., and Shimel, S. A., 2004, Composite geologic map of the Sno-King area: University of Washington, Seattle Area Geologic Mapping Project, scale 1:24,000. This map indicates that the surficial geology of the area consists of Pre -Fraser terrestrial deposits, overlain by Vashon-stade advance outwash, a unit of mostly clean sand with some gravel, overlain by Vashon-stade glacial till a non -stratified and non -sorted mixture of clay, silt, sand, and gravel. The terrestrial deposits reside mainly in the northern portion of the sidewalk alignment while the till and advance deposits are seen in the southern portion of the alignment. The area is also overlain by landslide colluvium deposited by the ancient Meadowdale slide. The landslide deposits occur throughout most of the site and are surficial above the glacial and pre -glacial terrestrial deposits. 2.3 Landslide History The majority of the project alignment lies within the North Edmonds Earth Subsidence and Landslide Hazard Area, which is described in detail in a report titled "Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington" prepared by Roger Lowe Associates in 1979. According to the Roger Lowe Associates report, this area of Meadowdale experienced large-scale ground movement between two and three thousand years ago. This slide was approximately 3,200 feet long and up to 650 feet wide. The head scarp is easily distinguishable above 75`h Place West. The cause of this large-scale earth movement is inferred to be progressive shoreline erosion by wave action; the waves eroded the toe of the slope, which over -steepened it and eventually led to land sliding. Construction of the Great Northern Railroad, which is currently owned by Burlington Northern Santa Fe, along the beach, has halted the shoreline erosion process since it armors the toe of the slope from wave erosion. Final Geotechnical Report 3 HWA GeoSciences Inc. Novemberl6, 2007 HWA Project No. 2006-171-21 1 No large-scale earth movements have been recorded for this area in modern times. However, subsequent to the ancient slide, the mass of soil within the body of the slide has experienced numerous small-scale adjustments. This type of post -slide adjustment is common and typically occurs in the form of shallow earth slumps. More recently, sliding occurred in the area in January 1997, after heavy snowfall was followed immediately. by several inches of rain. Sliding occurred at several locations on the eastern side of 75t' Place West and debris from one slide flowed across the street and came to rest on the western side the road. Landslides occurred throughout the Puget Sound Region at that time and are described in more detail in the paper by Gerstel et al. titled "Puget Sound Bluffs: The Where, Why, and When of Landslides Following the Holiday 1996/97 Storms" (in Washington Geology, vol. 25, no. 1, March 1997). The study by Roger Lowe Associates also indicates that the stability of the Meadowdale area is highly sensitive to groundwater levels. Improvements to local site drainage, l including the installation of sewers and storm drains, have had a positive impact on the stability of the area. 2.4 Subsurface Conditions Based on the results of our exploration program, the soils underlying the project area were observed to consist of Pre -Fraser terrestrial deposits overlain by colluvial depoits and small localized quantities of fill. This observation is consistent with the soils unit mapped in the area by Booth ET. Al., by Roger Lowe Associates, and as encountered during previous drilling undertaken by HWA to evaluate the subsurface conditions for other projects in this area in the past. (HWA, 2003). Following are descriptions of the soil deposits encountered in our explorations in the order of stratigraphic (depth) sequence by which they were deposited or placed, with the youngest unit described first. Detailed descriptions of the soils are presented in the exploration logs in Appendix A. A legend of the terms and symbols used on the boring logs is presented in Figure A-1. Summary boring logs are presented in Figures A-2 through A-13. Fill — Fill, consisting of loose to medium dense silty sand to sandy silt was identified in the locations of BH-1, BR-3, HH-1 and HH-7 through HH-9, and ranged from 1.25 to 7 feet thick. The fill was usually identified adjacent to the road, most likely from the grading of the roadway during the initial construction. To so' — Topsoil consisting of light brown to dark brow, silty sand with gravel was identified in HH-1 through HH-5. In all of the hand holes the topsoil consisted of loose to medium dense surficial material with abundant roots and rootlets being present. Depths ranged from 0.5 to 2.0 feet in depth. Final Geotechnical Report 4 HWA GeoSciences Inc. Novemberl6, 2007 HWA Project No. 2006-171-21 Colluvium — Colluvium was encountered in all of the borings and in hand holes HH-2, HH-6 and HH-9. It generally consisted of very soft to medium stiff clays and silts with interspersed pieces of colluvial clays and silts, with seams of sand. The majority of the colluvium has experienced some oxidation mottling, and the seams of sand tended to be wetter than the surrounding fine grained material. Colluvial Blocks — Colluvial blocks were encountered in Borings BH-2 and BH-3 under the softer colluvial material that overlies it. In the case of these explorations colluvial blocks refers to disturbed native soils that are denser then the overlying material, but still exhibit some variability in density and an irregularity in the soil that does not correspond with native undisturbed glacial and pre -glacial terrestrial deposits. For example in BH-3 loose poorly graded sand was encountered from 18 to 26 feet between very stiff clay and a hard laminated silt. It is not known when or how these materials were mobilized in the past, but they do exhibit some signs of disturbance. Recessional Outwash — Loose to medium dense glacial outwash consisting of light brown silty sand with gravel to gravelly sand with silt was identified in HH-3 through HH-5. The recessional outwash was encountered on the uphill (east) side of the sidewalk alignment in the area where a slope cut will occur for the new sidewalk. At the locations of TP-1 and TP-16, thin layers of silty sand were encountered from 0.5 to 1.0 foot thick, which appeared to consist of recessional outwash. These soils were loose to medium dense and directly overlie the glacial till. 2.5 Ground Water Conditions Ground water seepage was encountered in borings BH-1 and BH-2 and HH-2. We expect, however, that actual ground water depths will vary depending on the season, variation in local subsurface conditions, and other factors. The project alignment is near the toe of the hillside, which is a ground water discharge area. Consequently, springs and seeps occur at numerous locations along the alignment where groundwater emerges from the ground. 2.6 Laboratory Testing Representative soil samples obtained from the subsurface explorations were returned to the HWA laboratory for further examination and testing. Laboratory tests, as described below, were conducted on selected soil samples to characterize relevant engineering properties of the on -site soils. Moisture Content of Soil: The natural moisture content of all soil samples (percent by dry mass) was determined in general accordance with ASTM D 2216. The results are shown at the sampled intervals on the test pit logs in Appendix A. Final Geotechnical Report 5 HWA GeoSciences Inc. ' Novemberl6, 2007 _j HWA Project No. 2006-171-21 i Particle Size Analysis of Soils: Selected samples were tested to determine the particle size distribution of material in general accordance with ASTM D 422. The results are summarized on Figure B-1, Appendix B, which also provides information regarding the classification of the samples and the moisture content at the time of testing. Liquid Limit, Plastic Limit, and Plasticity Index of Soils (Atterberg Limits): Selected samples were tested using method ASTM D 4318, multi -point method. The results are reported on the attached Liquid Limit, Plastic Limit, and Plasticity Index reports, Figure B-2. 3. RECOMMENDATIONS 3.1 GENERAL Construction of a walkway along 76t' Avenue West and 75t' Place West will require excavation into the toe of the slope on the up -slope (eastern) side of the roadway in some areas, and placement of fill or a pile supported partially -elevated walkway on the downslope side of the road. Because placement of fill on the downslope side of the road would add to the weight of a potential landslide, reducing the stability of the slope, we recommend that filling be avoided to the extent possible. As a result, we recommend that walkways and walkway approach structures on the downslope side of the road be pile - supported wherever there is insufficient existing flat terrain. Development of the propose park will include regrading the site and construction of a driveway, walkways, lawn and play areas. We understand an interpretive overlook is planned adjacent to 75t' Place West. Because of the relatively high ground water level and the presence of an existing landslide on the -property, we recommend the installation of a deep trench subdrain across the park. More detailed recommendations for park design are presented in Section 3.5. 3.2 EARTH RETAINING STRUCTURES Cuts along much of the eastern side of the alignment will be 3 to 4 feet tall. In our opinion, the most cost-effective way of retaining these shallow cuts would be with modular block walls such as Keystone blocks, or with rockeries. Block walls up to about 4 feet high (twice the depth of the block) may be made by stacking blocks without need for geogrid reinforcing. Block walls higher than twice the block depth should include geogrid reinforcing which extends back from the face of the wall a horizontal distance equal to at least 0.7 times the free-standing wall height. Geogrid reinforcing should be placed between every second layer of blocks. We recommend the use of Tensar BX1200 geogrid, or equivalent, wherever geogrid reinforcing is needed. Final Geotechnical Report 6 HWA GeoSciences Inc. November16, 2007 HWA Project No. 2006-171-21 Because of the horizontal space required for block walls, it may be desirable to use soldier pile and lagging walls where the retained height of the cut exceeds about 4 feet. Soldier pile and lagging walls would consist of 4-inch or larger H piles set in concrete in pre -drilled holes. Lagging consisting of treated timber or precast concrete panels would be placed between the soldier piles. The size of the H-pile section would depend on the height of the wall and the horizontal spacing of the piles. Soldier piles should be designed to resist an equivalent fluid pressure equal to 55 pounds per cubic foot (pcf) plus one pcf for each degree of upward inclination of the backslope. We recommend the soldier pile walls be tall enough that the backslope inclination does not exceed 2H to IV. Fill could be placed behind the soldier pile walls as necessary to flatten the slope. Soldier piles which are set into concrete in predrilled holes should penetrate below finished grade at least 1.5 times the wall's free-standing height. We do not recommend driving soldier piles because: 1) driving and maintaining pile alignment may be difficult in dense gravelly soils, 2) vibrations from pile driving can cause landslides, and 3) a concrete -filled hole provides better lateral resistance than a driven pile. Piles which are driven in place would need to extend to a depth equal to twice their free-standing height. Backfill behind the lagging should consist of I V4-inch minus crushed rock. Soldier pile and lagging walls constructed as recommended above are typically permeable and will allow the passage of moderate amounts of seepage. Where significant volumes of water are expected, such as at existing springs, a slotted drain pipe and crushed rock backfill should be placed to intercept the flow and convey it through the wall to the storm drain system. 3.3 PQ,E SUPPORTED WALKWAYS Where pile support of walkways and approach structures is required, we recommend the use of 2-inch diameter extra -strong steel pipe. When driven to less than 1 inch of penetration in 1 minute of driving with a 90 psi jackhammer, each pile should be capable of supporting 2 tons of vertical load (allowable capacity) with an adequate factor of safety. Pile installation can actually be accomplished with a backhoe-mounted compactor (hoepac), but testing to verify capacity should be done with a jackhammer. Piles will develop their bearing in native soils below any fill, and pile lengths will vary considerably. Pile lengths could average 20 to 25 feet. 3.4 PAVEMENTS Where new street pavement is required, the pavement subgrade should be proof -rolled to verify that it is dense and unyielding. Any soft or spongy material should be replaced with 1 %<-inch-minus crushed rock. The pavement section should consist of at least 6 inches of crushed rock (CSBC) and 3 inches of asphalt. Final Geotechnical Report 7 HWA GeoSciences Inc. November 16, 2007 HWA Project No. 2006-171-21 1 3.5 PARK DESIGN A plan showing the park property with existing ground surface contours and the location of boring BH-1 is presented on Figure 5. A cross section through the park property showing BH-1, the previous boring HWA-3, and the assumed failure plane of the existing landslide is shown in Figure 7. The proposed layout of park facilities is shown on Figure 6. 3.5.1 Stability As indicated on Figure 5, the park property slopes downward from 75`h Place West about -� 2H to IV for approximately 20 vertical feet. The site then slopes gradually to 751' Avenue West. Our previous studies indicate that a landslide exists on the north end of the park property and the adjacent property to the north The slide is still moving as l evidenced by renewed cracking in the pavement of 75th Place West. Readings from an inclinometer casing installed in the street right-of-way in front of the adjacent property to the north, shown in figure 9A and 9B indicate that the slide is about 18 feet deep at the western side of 75t' Place West. As part of the current study, HWA installed an inclinometer casing in BH-1 so that any earth movements at that location can be detected. Based on our previous studies and the existing site geometry, it appears likely that the existing slide terminates at the toe of the slope on the east side of the park and does not involve most of the park site. The results of future measurements in the two inclinometer casings will confirm or deny that assumption. Assuming that the existing landslide is confined to the north end of the slope on the eastern side of the park, the proposed park development can proceed without stabilizing the slide, providing the City is willing to accept that portions of the park as well as the roadway and the utilities within its right-of-way will continue to be affected by the sliding. Current plans for park development include placing fill along the toe of the slope below the roadway, which will tend to increase the stability of the slide but may not be sufficient to prevent future movement. A definitive stabilization design will require additional measurements in the two slope indicator casings over the course of the coming winter to determine the location of the slide plane and performing stability analyses to develop stabilization measures. That additional analysis is not within the present scope of work; however, we recommend that this additional analysis be performed and the results incorporated into the park design. 3.5.2 Park Drainage We believe the installation of a trench subdrain across the park property is necessary to remove excessive moisture for park development and maintain stability of the lower portion of the park; however, it may or may not be effective in stabilizing the existing landslide. Final Geotechnical Report 8 HWA GeoSciences Inc. Novemberl6, 2007 HWA Project No. 2006-171-21 We recommend the construction of a trench subdrain across the park. The subdrain would consist of an 8 to 10-foot-deep trench extending roughly north -south along the toe of the eastern slope and then turning westward near the north property line to daylight at the western edge of the park. The approximate location of the proposed trench drain is shown on Figure 6. A 6-inch diameter slotted plastic pipe would be placed in the bottom of the trench and the trench would be backfilled with 1 %4-inch-minus crushed rock. The trench subdrain would intercept and remove ground water seepage from the site and would serve as a shear key to reduce the potential for future sliding. 3.5.3 Foundation Design Structures in the park may be supported on spread footings providing they can tolerate some settlement. The soils are capable of supporting structures at allowable bearing pressures up to 1,500 psf; however, some settlement is likely due to the loose, soft and variable nature of the soils. Structures that can not tolerate 2 inches of total and 1 inch of differential settlement should be supported on small diameter pipe piles as described in Section 3.3. Column footings should have a minimum width of 24 inches and wall footings should have a minimum width of 18 inches. Footings should bear at least 18 inches below the lowest adjacent finished grade. 3.5.4 Park Pavement Any pavements within the park that will carry vehicular traffic should be constructed as accordance with the recommendations in Section 3.4. We recommend that pavements for walkways and trails consist of 6 inches of 1 V4-inch minus crushed rock overlain by 1 %2 inches of asphalt. 4.0 CONDITIONS AND LIMITATIONS We have prepared this report for Gray & Osborne and the City of Edmonds for use on this project. This data and report should be provided to prospective contractors for their bidding or estimating purposes, but the conclusions and interpretations presented should not be construed as a warranty of the subsurface conditions. Experience has shown soil and ground water conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations and may not be detected by a geotechnical study. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, HWA should be notified for review of the recommendations of this report, and revision of such if necessary. Final Geotechnical Report 9 HWA GeoSciences Inc. November16, 2007 HWA Project No. 2006-171-21 We recommend that HWA GeoSciences be retained to provide monitoring of . construction sufficient to verify that the construction of retaining walls and the driving of foundation piles is accomplished in accordance with our recommendations and with the approved plans and specifications. The scope of work did not include environmental assessments or evaluations regarding the presence or absence of hazardous substances in the soil, surface water, or ground water at this site. HWA does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if he considers any of the recommended actions presented herein unsafe. We appreciate the opportunity to be of service. Sincerely, HWA GEOSCIENCES INC. Ralph N. Boirum, P.E. Geotechnical Engineer Principal Final Geotechnical Report 10 HWA GeoSciences Inc. November 16, 2007 1 HWA Project No. 2006-171-21 1 References Roger Lowe Associates Inc., 1979, Final Report, Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington, for the City of Edmonds, consultant report dated October 16, 1979. Gerstel et al. "Puget Sound Bluffs: The Where, Why, and When of Landslides Following the Holiday 1996/97 Storms" (in Washington Geology, vol. 25, no. 1, March 1997). HWA Geosciences Inc., 2002-099-21, Geotechnical Report, Nguyen Property Slope Stabalization 16018 75`h Place West Edmonds, Washington, consultant report dated November 8, 2002. Booth, D. B., Cox, B. F., Troost, K. G., and Shimel, S. A., 2004, Composite geologic map of the Sno-King area: University of Washington, Seattle Area Geologic Mapping Project, scale 1:24,000 Final Geotechnical Report 11 HWA GeoSciences Inc. lowrd s f 76h Avenue West and 75 Place West S from Meadowdale Beach Road to �'' •�r North Meadowdale Beach Road. Cl h. ._.! �� 11 . -- :.' aM•- �.. •.. T. � i •��1,' �' F.��'• - ,•a.._� ".. t� l: t � � �15 ! •�i i� � /1 �- n su . �e o asp ueu®r�5 can vas 3Mw 1M= usw i--1 iM ft Smk 1. AM Dedt 14.2 Dab= WCSii SITE AND VICINITY MAP 76T" AVE W & 75T" PL W HWAGEOSCIENCES INC. WALKWAY IMPROVEMENTS EDMONDS, WA FIGURE NO. JECT NO. 2006-171 LEGEND HH-9 -i HAND HOLE DESIGNATION AND APPROXIMATE LOCATION BH-3 BOREHOLE DESIGNATION AND APPROXIMATE LOCATION HWA-3 � � HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: 1-9 �vwwk-� - 90,11 F11NA(EOSMCCESs I11C 76th -75th Walkway Improvements Edmonds, Washington cM LJ W n 0 1-4 LL. Li Z J 2 U F- Q 100' 200' SCALE: 1"=100' SITE AND EXPLORATION PLAN 10.24.07 1 2006-171-21 LLI L7 LL. Lv Z J 2 U F- Q E LEGEND HH-9 -$- HAND HOLE DESIGI BH-3 - BOREHOLE DESIGNATION AND APPROXIMATE LOCATION HWA-3 HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: ACOSMNaSINC 76th -75th Walkway Improvements m Edmonds, Washington SITE AND EXPLORATION PLAN ►■ LLJ U LL. LJ Z J 2 U F- Q 10, By 3. 10.24.07 1 2006-171-21 4 (M LLJ W Z) L7 1- 4 L.L. LJ Z J 2 U H Q LEGEND HH-9 -pt HAND HOLE DESIGNATION AND APPROXIMATE LOCATION BH-3 BOREHOLE DESIGNATION AND APPROXIMATE LOCATION HWA-3 HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: N UMA M%GMCMCBINC 76th -75th Walkway Improvements Edmonds, Washington N = o0 o -° OD q 100' 20Y ` KALE. 1"=100' SITE AND EXPLORATION PLAN I 10.24.07 1 2006-171-21 cn Z n N O ° `m O fn z z O 2 O V tz o of b eg_.7_--- o C a. C A cr a .<. w CD / ° CD ato 1' 24- r,. , ! / of �I Mm N0FM-'H �IN BL,OcK 41 �L 9 0 cn n 6 D0) >r = rn zK* Sn;go 0-4 cn D9-0 m r- z� z M N p O `m 0) 9 v z o z 0 Er 0 CD LEGEND m A' (WEST) 80 70 60 W 50 w o 40 1-4 - w 30 J w 20 10 0 0 EXPLORATION DESIGNATION AND SITE PLAN SYMBOL N-VALUE - (BLOWS/FOOT) STANDARD PENETRATION TEST NONSTANDARD PENETRATION TEST WATER LEVEL AT TIME OF DRILLING WATER LEVEL MEASURED IN PIEZOMETER ON THE DATE INDICATED. INFERRED GEOLOGIC CONTACT SAND PACK AND SCREEN INTERVAL BOTTOM OF BORING i 100 120 (FEET) 140 W Z Q J IZ 160 l- W c V J W Ld n LL 110 L'' L- A O E-3 200 220 A (EAST) 80 70 60 I- 50 w w 40 0 a 30 w J W 20 10 \ 0 \ 240 The subsurface conditions shown are based on widely spaced borings HORIZONTAL SCALE: 1 "=20' and test pits and should be considered approximate. Further, the contact 0' 10' 20' 40' lines shown between units are interpretive in nature and may vary laterally or vertically over relatively short distances on site. 0' 10' 20' 40' VERTICAL SCALE: 1 "=20' DRAWN BY ERC FIGURE NO. 76th-75th Walkway Improvements CROSS SECTION + s � �a <VLW�+WL\ VG1711\�+. Q1ECK BY DC Edmonds, Washington A-ADATE PROJECT NO. AND FIELD MAPS\HWA 2006-171 C.DWG 11,0],0] 2006-171-21 DRILLING COMPANY: Gregory Drilling Inc. LOCATION: See Site & Exploration Plan, Figure 2 DRILLING METHOD: Hollow -stem Auger, CME 45 C track rig DATE STARTED: 9/1312002 SAMPLING METHOD: SPT w/ Autohammer DATE COMPLETED: 9/13/2D02 SURFACE ELEVATION: 70 * feet LOGGED BY: B. Thurber U O x O y am g v o ai 0 SM Loose, brown, silty, fine to medium SAND, dry. Some coarse sand, trace fine gravel and organics. [ROAD FILL] ML Very loose, brown and gray with heavy rust -mottling, very SM sandy SILT to very silty fine SAND, wet Interbedded. Some partly decomposed wood fragments. [EXISTING LANDSLIDE DEBRIS] Grades to gray, silty SAND and sandy SILT with organics, wet______ ________ ____ ML Soft, blue -gray with brown streaks, clayey SILT with party decomposed wood fragments, moist Mixed / swirled SP appearance.-__- _____________� CH-\Loose..aray. slightly slity. fine to medium SAND wet Medium stiff, gray, green -gray, and brown -gray, CLAY, with micaceous fine SAND laminae, with party decomposed woody debris, moist Sand laminae at high angles, and clay laminations in sample tip are planar and at 60-degree angle. (OLD SLIDE DEBRIS) @17.5 feet: Gray and dark gray, CLAY, moist Laminae disturbed by fine angular offsets. Some dark gray slickensides at approx. 30 degrees. CH @ 20 feet: Grades to stiff. No bedding apparent, fine blocky texture. Long wood fibers caught in tip. Very stiff, gray to dark gray, fat CLAY, moist Finely laminated, bedding approximately horizontal. [WHIDBEY FORMATION] Includes occasional light gray laminae of coarse silt / very fine sand. 5 -1 I 10-I 1 15 ---1 1 20 1 25 --1 1 30 -1 DESCRIPTION Borehole terminated at 31.5 feet Inclinometer casing (34nch diameter) installed to 30 feet, and backfilled with bentonite grout to 2 feet 35 Bentonite chips backfilled from 1 to 2 feet; 104nch diameter flush monument set in 1 That of concrete to surface. m w Q -- w Standard Penetration Test LU a. ? � L N uJ Q (140 lb. weight, 30" drop) W 1- rl Blows per foot ur a Q. W , �� W Z M x z 3 x O f- w rai) ai a.. O t9 S-1 2-2-2 S-2 2-2-4 S-3 2-2-2 GS S4 1-1-1 %F. Q S-5 1-1-2 S-6a 1-2-3 S-6b S-7 2-3-6 S-8 3.6-8 AL AS-9 4-6-9 AL 4 S-10 6-8-11 40 —r For a proper understanding of the nature of subsurface conditions, this exploration log should be read in conjunction with the text of the geotechnical report. NOTE: This log of subsurface conditions applies only at the specified location and on the data indicated and therefore may not necessariy be indicative of other times and/or locations. ................:....:....:....:....:....:.... ......................:....:....:....:.. ..................................:....:.... A: ...�...:�.:� .:....:....:....:....:... ................................................. ......� • 1-5 r-10 I 1-15 F- 25 -30 -35 0 20 40 60 80 100 Water Content (%) Plastic Limit 1— 0 Liquid Limit Natural Water Content NGUYEN RESIDENCE BORING: gon 16108 75TH PLACE WEST HWA-3 IMMSCM(TS WC, EDMONDS, WASHINGTON PAGE: 1 of 1 BORING 2002099.GPJ 11/15/07 PROJECT NO.: 2002-099-21 FIGURE- 8 r� CN co O m 't O O O O O N O O N O N N O m N CO O to O to N to N (4) Hld3a O IT O O N O O O O. O W CL N m O N -M 6- C a0 v N cc CR O m CO Z O O 0 O cM O z o ti z r CO w a N c. 0) Z J W a2Q LO a6 W p 3:20 Q Q W CEO J V z �n z w V cn O O to O to N to N (4) Hld3a O IT O O N O O O O. O W CL N m O N -M 6- C a0 v N cc CR O m CO Z O O 0 O cM O z o ti z r CO w a N c. 0) Z J W a2Q LO a6 W p 3:20 Q Q W CEO J V z �n z w V cn O �7 a, 4-1 N N d d O r M C) Q � d � s IM m 5, ti o O Z ch r tD d E O C O m I-t O O O O O N 00 N p N N M co ` m in N CO Hld3a d z d z U to w C) z N a O O � J a � w z 0 W Jw a2 x w w o O >3: Z U ti O Cl) �IL0 Z 0 O O Ch Q w}2 w o ?� Q _ ~ J Z v O C) m O N O z 0 o o a o > w 0 O ': O Appendix A Soil Boring Logs RELATIVE DENSITY OR CONSISTENCY VERSUS SPT N-VALUE COHESIONLESS SOILS COHESIVE SOILS Appro)dmate Approximate Density N (blows/ft) Relative Density(%) Consistency N (blows/ft) Undrained Shear Strength (psf) Very Loose 0 to 4 0 - 15 Very Soft 0 to 2 <250 Loose 4 to 10 15 - 35 Soft 2 to 4 250 - 500 Medium Dense 10 to 30 35 - 65 Medium Stiff 4 to 8 500 - 1000 Dense 30 to 50 65 - 85 Stiff 8 to 15 1000 - 2000 Very Dense over 50 85 - 100 Very Stiff 15 to 30 2000 - 4000 Hard over 30 >4000 USCS SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS Coarse Gravel and Clean Gravel •' GW Well -graded GRAVEL Gravely Soils Grained 01111a or no fines) GP Poorly-gmded GRAVEL Soils c Q More than 50% of coarse Gravel with o GM Silty GRAVEL Fraction Retained Feces (appreciable on No. 4 Sieve amount of fines) GC Clayey GRAVEL Sand and Clean Sand ••• SW Well -Waded SAND More than Sandy Soils Gale or no fines ( ) SP Poorly 50% Retained -graded SAND 50% or More on No. of Coarse Sand with - $M Silty SAND 200 Sieve Passing Fines (appreciable size No. No. 4 Sieve amount of fines) SC Clayey SAND ML SILT Fine Silt Grained and Liquid Limit CL Lean CLAY Sorts Clay Less than 50% — OL Organic SILT/Organic CLAY MH Elastic SILT 50% or More Sin Liquid Urnit Passing and 50% or More CH Fat CLAY No. 200 Sieve Clay Size OH Organic SILT/Organic CLAY Highly Organic Soils — PT PEAT r �r COMPONENT DEFINITIONS COMPONENT SIZE RANGE Boulders Larger than 12 in Cobbles 3 In to 12In Gravel 3 to to No 4 (4.5mm) Coarse gravel 3 in to 3/4 in Fine gravel 314 in to No 4 (4.5mm) Sand No. 4 (4.5 mm) to No. 200 (0.074 mm) Coarse sand No. 4 (4.5 mm) to No. 10 (2 0 mm) Medium sand No. 10 (2.0 mm) to No. 40 (0.42 mm) Fine sand No. 40 (0.42 mm) to No. 200 (0.074 mm) Silt and Clay Smaller than No. 200 (0.074mm) TEST SYMBOLS %F Percent Fines AL Atterberg Limits: PL = Plastic Limit LL = Liquid Lima CBR California Bearing Ratio CN Consolidation DO Dry Density (pcf) DS Direct Shear GS Grain Size Distribution K Permeability MD Moisture/Density Relationship (Proctor) MR Resilient Modulus PID Photoionization Device Reading PP Pocket Penetrometer Approx Compressive Strength (tsf) SG Specific Gravity TC Triaxial Compression TV Torvane Approx. Shear Strength (tsf) UC Unconfined Compression SAMPLE TYPE SYMBOLS ®2.0" OD Split Spoon (SPT) (140 lb. hammer with 30 in. drop) IShelby Tube a3-1/4" OD Split Spoon with Brass Rings OSmall Bag Sample Large Bag (Bulk) Sample Core Run Non-standard Penetration Test (3.0" OD split spoon) GROUNDWATER SYMBOLS Q Groundwater Level (measured at time of drilling) 1 Groundwater Level (measured in well or open hole after water level stabilized) COMPONENT PROPORTIONS PROPORTION RANGE DESCRIPTIVE TERMS < 5% Clean 5 -12% Slightly (Clayey, Silty, Sandy) 12 - 30% Clayey, Silty, Sandy, Gravelly 30-50% Very (Clayey, Silty, Sandy, Gravelly) Components are arranged in order of increasing quantities. NOTES: Soil classifications presented on exploration logs are based on visual and laboratory observation. Soil descriptions are presented in the following general order. MOISTURE CONTENT Demfticons/sfency, color, modifier (rf any) GROUP NAME, additions to group name (rf any), moisture DRY Absence of moisture, dusty, content Proportion, gradation, and angulanly of constituents, additional comments. dry to the touch. (GEOLOGIC INTERPRETATION) MOIST Damp but no visible water. Please refer to the discussion In the report text as well as the exploration logs for a more WET Visible free water, usually complete description of subsurface conditions. soil is below water table. 90A, 75th-76th Walkway improvements LEGEND OF TERMS ANDSYMBOLS USED ON Meadowdale HMGEOSQENCB INC. Edmonds, WA EXPLORATION LOGS PROJECTNO.: 2006-171-21 FIGURE* A-1 LEGEND 2006-171-21.GPJ 11/15/07 DRILb1NG COMPANY: Davies Drilling SURFACE ELEVATION: t feet DATE STARTED: 10/102007 DRILLING METHOD: Hollow stem Auger DATE COMPLETED: 10/102007 SAMPLING METHOD: Cat Head SPT LOGGED BY: P. Pearson LOCATION: See Figure 2 U w m w Z Standard Penetration Test w a. y cow Cr U (140 ib. weight, 30" drop) O O o- Z a. rn W W Blows per foot x W co2 a of 2 ►� x 0. .. ami o = ti DESCRIPTION rn CO - a O o- U) 0 0 10 20 30- 40 50 0 SM Loose, Brown, slightly silty, fine to Medium SAND, moist with S-1 1-1-4 r° 1 1 1C 1 15 1 20 1 25 1 30 35 40 45 roots and rootlets. [FILL] Soil becomes sillier then sandy again. CL Loose, yellowish gray, sandy SILT, moist, trace organics. ML \---------ICOLLWWMJ------- —� Soft, bluish gray, silty CLAY, moist. Older, black trace organics. Soft, bluish gray to brownish gray, silty CLAY, wet Some dense chunks of day also. ----------------------- Medium stiff to stiff, gray, silty CLAY, moist. Trace CL laminations observed. 2 inch sandy layer. CH ----------------------- Stiff to very stiff, gray, CLAY, moist Slickenslides observed. [PRE -GLACIAL TERRESTRIAL DEPOSITS] Hard, gray, CLAY with fine sand, slightly moist Subvertical cracks with fine sands. Horizontal laminations observed. Hard, massive, gray, fine sandy, CLAY, moist to wet e+onng termrnatea at sb.o teet Derow surface. Inclinometer casing was installed with grout from 2.5 feet above ground surface to 35 feet below ground surface. Ground water observed at 10 feet and 35 feet at time of exploration. S-2 3-2-3......:....:....1...............:....:.... S-3 1-1-2 �....:....:... �.......;....;....;....;... 10 S-3 4-4 ......A...:0.!.... .... .................. 15 -6 .........:.... �.. .� .... .... ....:........ 20 S-5 3-8-15 S-6 10-21-35 ;....:� ti}---�....:....:..........:>>• 25 0 20 40 60 80 100 Water Content (%) Plastic LimnLiquid Limit Natural Water Content NOTE: This log of subsurface conditions applies only at the speed location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. am 75th-76th Walkway Improvements BORING: Meadowdale BH-1 HMQOSMNCB INC. Edmonds, WA PAGE: 1 of 1 PZO 2008-171 21.GPJ 11/15J07 PROJECT NO.: 2006-171-21 FIGURE: A-2 DRIL(ING COMPANY: Environmental Drilling Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/25/2007 DRILLING METHOD: Hollow Stem Auger DATE COMPLETED: 10/25/2007 SAMPLING METHOD: SPT Auto Hammer LOGGED BY: V. Atkins LOCATION: See Figure 2 U) co U O N LU CO) 0 1 5- 1 10 — 1 20 —I 1 25 --i 1 30-4 DESCRIPTION SP 1-2 inches of Asphalt over sand and gravel base course over brown, 000dy graded SAND with oravel fi0. ML Stiff, brown silt with day, moist [COLLUVIUNQ Loos] brown, fine SAND with silt�li�h�oxidized mist. Medium stiff, brown, SILT with sand, with trace dark orange ------------------------- oo wet opdized silty sand seams, moist. Stiff, gray, SILT to clayey sift with seams of fine sand and ------------------------ ML day, moist Sand seams are wet fragments in sample., ,Wood Stiff to very stiff, brown to olive brown organic SILT, moist ML Very stiff, gray to olive gray, sandy SILT, wet [COLLUVIAL BLOCKS] ---------------------- Medium dense, gray, fine sandy SILT, wet. SM Very sfa, gray, CLAY, moist CL High plasticity. Boring was terminated at 31.5 feet below ground surface. Ground water seepage was encountered at 15 feet below ground surface. A ground water monitoring well was installed 35 with screen from15-25 feet, and sand from 12 to 30 feet ro W Co w ¢ Standard Penetration Test w w r j L U n w U (140lb. weight, 30" drop) Z C F•- W A Blows per foot of Q 2E o uJ — = uri U a> <n o) o O a y 0 10 20 30 40 50 py 0 S-1 2-4-5 S-2 2-2-5 :�.:...�............... 5 S-3 3-7-8 r S 4 4-4-8 :....:� ..:....:.........:....:........ 10 S-5 5-8-8 �I S-6 3-8-11 :.. � ............ 15 �I S-7 4 7-12 :....:....:. r ....:....:....:....:....:.... 20 u . ....:....:....:.� S-8 4-7-12 25 S-9 6-9-15 30 L40 0 20 40 60 80 100 Water Content (%) Plastic Limit Liquid Limit Natural Water Content NOTE: This log of subsurface conditions applies only at the specked location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 75th-76th Walkway Improvements BORING: MWA, Meadowdale BH-2 HWL Q0SMNCES INC. Edmonds, WA PAGE: 1 of 1 PZO 2008-171 21.GPJ 11/15/07 PROJECT ND.: 2006-171-21 FIGURE: A-3 DRILLING COMPANY: Environmental Drilling Inc. LOCATION: See Figure 2 DRILLING METHOD: Hollow Stem Auger DATE STARTED: 10/25/2007 SAMPLING METHOD: SPT Auto Hammer DATE COMPLETED: 10/2512007 SURFACE ELEVATION: t feet LOGGED BY: 0. Coltrane rn U J O = O N ~ad g v (3 - N DESCRIPTION 0 7 inches of asphalt at surface. = SM Medium dense, olive brown to light brown, silty fine SAND with gravel, moist Of UJ mW W az W Standard Penetration Test a P� _ U � Q (140 lb. weight, 30" drop) W W W C m ~' O A Blows per foot Ja a 3 W x Co rail a a I O cc (9 W 0 10 20 30 40 50 a 5 [FILL) Medium dense to dense, olive brown, silty SAND to sandy S-1 4-9-9 S-2 5-6-10 ML SM SILT, with fine SAND seams, moist: Oxide mottling in seams S-3 5-8-15 of fine SAND. 10 T[COLLUVIUM] S-4 11-15-16 Grdvetly drilling from 11 to 11.5 feet BGS. _ _ _ _ _ _ _ CL ML Very stiff, gray to olive gray, silty CLAY with seams of gray S-5 7-9 silty fine SAND, moist. SILT has organic smell. 13 [COLLUVIAL BLOCKS] 15 MS-6 4-6-10 �. SP----------------------- Loose, gray, poorly graded, fine to medium SAND with silt and trace fine gravel, moist to wet 20 S-7 2-3-7 25 Drilling became hard at 25-26 feet BGS. _ S-8 6-12_23 ML Hard, olive gray to olive brown, laminated SILT, moist S-8a 30M m Mediudense gray silty fine SAND, wet S-9 7-12-12 Boring was terminated at 31.5 feet below ground surface. Minor ground water seepage was encountered during the exploration, but there was no standing ground water in the 35 hole after the auger was removed. 40-- For a proper understanding of the nature of subsurface conditions, this exploration log should be read in conjunction with the text of the geotechnical report. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. u ................. ...:....A ..:....:....:....:....:....:.... 5 ............................................ ♦: ....-....'....'......:....'....:.... 10 ........................................... :....: ............................ 15 :......:....:....:......... ............ 20 .............................:...�..:....:... 25 ...........—30 :....:....:....:....:....:....:....:....:... 35 0 20 40 60 80 100 Water Content (%) Plastic Limit I -- 0 I Liquid Limit Natural Water Content UVA 75th-76th Walkway Improvements BORING: Meadowdale BH-3 HMGEOSCUNCES INS Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-1 71-21 FIGURE: A-4 BORING 2006.171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 N Ir W U U W Z -` W m } D y= U inQ p rA 1- W W W ip H = Ca co J —1 o y D DESCRIPTION ra» a O 0 w 0 O SM Medium dense, brown, sandy SILT with gravel, roots and rootlets, moist. [FILL/OLD TOPSOIL] S-1 0 1 Medium dense, brown silty SAND with gravel, roots and SM woodchips. Less moist than above. S-2 O 2 Loose, yellowish brown Silty SAND with gravel, organics and - - - - - - - - - - - - - - - - - - - - - S-3 SM pieces of wood. No ground water. 0 3 1 4 I 5 Hand hole was terminated at 4.0 feet below ground surface. No groundwater seepage was encountered during the exploration. 1 6 - -I 1 7 --1 1 8 —j NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 0 1 2 3 —5 1 —7 1 8 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content 75th-76th Walkway Improvements HH-1 MWA HAND HOLE: Meadowdale HA WSMNCH ITC. Edmonds, WA PAGE: 1 of 1 HANDHDL 2000-171-21.43PJ 11/15/07 PROJECT NO.: 2006-171-21 FIGURE: A-5 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 co W w L) of U w COL. Co D Q in rQ Fw— m } Nt N 0 N W d(L w W e F W O M d U y g g 3 a DESCRIPTION N wa a O 0- 2- 3- 4- 5- 0 S-1 O S-2 6 Hand hole was terminated 5.5 feet below ground surface. Ground water seepage was encountered at 5.0 feet below ground level and stabilized at 4.7 feet below ground level after exploration. 7- 8— NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. Q 0 1 I-3 1 �m —8 0 20 40 60 so 1D0 Water Content (%) Plastic Limit 1---40-- I Liquid Limit Natural Water Content 75th-76th Walkway Improvements HAND HOLE: WWI, I Meadowdale HH-2 1MGFASQENCES INC Edmonds, WA PAGE: 1 of PROJECT. NO.: 2006-171-21 FIGURE: A-6 HANDHOL 200G-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/82007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 co Nof w U _ W m Q N Co w N J } F :3 L U N Q y _ OJ rn W W W fp I- O uID w 0 F- o U DESCRIPTION ai y a s O t'.7 a wo 0 --r 1 3-1 1 4 --I 1 5--A 1 6--A 1 7--A Loose, light brown, silty SAND with gravel and roots, moist [TOPSOIL] ------------- SM Loose, light yellowish brown, silty SAND with gravel and wood chips. gravels are fine to medium. Soil is moist but less so than above. [RECESSIONAL OUTWASH] Hand hole was tenninated at 2.25 feet below surface level. No ground water seepage was encountered during exploration. 8-1 NOTE: This log of subsurface conditions applies only at the specfed location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 0 20 40 60 80 100 Water Content (%) Plastic Limit 1 --0 Liquid Limit Natural Water Content hi 1 I-4 1 � ■ 75th-76th Walkway Improvements HAND HOLE: BOA I HH-3 Meadowdale HMGMWNCEB INC. Edmonds, WA PAGE: 1 of IIANDHOL 2008-171-21.GPJ 11/15/07 PROJECT NO.: 2006-171-21 FIGURE' A-7 DRILLING COMPANY. HWA Geosciences Inc- SURFACE ELEVATION: t feet DRILLING METHOD: Hand Bucket Auger DATE STARTED: 101at2007 SAMPLING METHOD: GRAB DATE COMPLETED: 10/8/2007 LOCATION: See Figure 2 LOGGED BY: D. Coltrane c 3 m w U W a z W w J Z v~i W O tocco W ro ~ `v .J a J (L 3 ui Z O y DESCRIPTION N a s ~O Of w 0-1 1—] 1 2--1 1 5 ---I 1 6-4 1 7 --A SM I Medium dense, brown, silty SAND with gravel, roots and rootlets, moist [TOPSOIL (WEATHERED OUTWASH] SM Loose, light yellowish brown silty, gravely SAND, moist J. (RECESSIONAL OUTWASH] Hand hole was terminated at 2.5 feet below surface level. No ground water seepage was encountered during exploration. 0S-1 0 S-2 8 - -r NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 0 20 40 60 80 100 Water Content (%) Plastic Limit 1 40 Liquid Limit Natural Water Content O r-0 a ■ SE -7 1 75th-76th Walkway Improvements HAND HOLE: HH-4 MI WMeadowdale HWAGEOSCIENCES WC Edmonds, WA PAGE: 1 of 1 HANDHOL 2008-171-21.GPJ 11/15/07 PROJECT NO.: 2006-1 71-21 FIGURE: A-8 DRIWNG COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/812007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 3 m W U Z� W _ N J n• 7F � U) N fn fn Q .-. m O Z v1 Lu O 1- e: p Z y v a U N a. rL g y 3 W = F=' o DESCRIPTION y v¢j a 8 O k(7 0 0 2 3 4 5 O S-1 0 S-2 Hand hole was terminated at 5.0 feet below surface level. No ground water seepage was encountered during exploration. 6- 7- 8— NOTE: This log of subsurface conditions applies only at the specified location and on the data indicated and therefore may not necessarily be indicative of other times and/or locations. SM Loose, very dark brown, silty SAND with organic material, moist. [TOPSOIL] Loose, light yellowish brown, gravely SAND with silt SM andcobbles. Moist [RECESSIONAL OUTWASH) Loose, very light yellowish brown, silty, gravely SAND. Sand SM is fine, gravel is coarse. Soil becomes less gravely below 3.0 feet, moist. r 1-3 1 �--5 1 —7 1 0 20 40 60 80 100 Water Content (%) Plastic Limit 1 19 Liquid Limit Natural Water Content 75th-76th Walkway Improvements HAND HOLE: MT, Meadowdale HH-5 HMGEOSC LACES INC Edmonds, WA PAGE: 1 of 1 HANDHOL 2008-171 21.GPJ 11/15Po7 PROJECT NO.: 2006-171-21 FIGURE: A-9 DRJLLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: DRILLING METHOD: Hand Bucket Auger SAMPLING METHOD: GRAB LOCATION: See Figure 2 t feet DATE STARTED: 10/8/2007 DATE COMPLETED: 10/8/2007 LOGGED BY: D. Coltrane N cr w U m m Lu °} D Z yt W Sa)O F Z to c U) H x al to O to a s t° o: Z w >- o) gg d w W t= x a o toDESCRIPTION cn rn a $ O c� Wo 0 Loose -medium dense, tight olive gray, sandy SILT with 0 organics. Soil was dumpy with some debris, moist. [COLLUVIUM] S-1 1 ML Soft, light olive gray, silty CLAY. Chunks of silty sand, pieces 2 of wood, and roots, moist S-2 O 2 3 3 CL Loose, light gray to yellowish brown, silty CLAY, moist. ML 4 4 5 S-3 O :....:....:....:....:....:....:....:....:.... 5 6 Hand hole terminated at 5.5 feet below surface level. No 6 ground water seepage was encountered during exploration. 7 7 8 0 20 40 60 80 100 8 Water Content (%) Plastic Limit 1-0 Liquid Limit Natural Water Content NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 75th-76th Walkway Improvements HAND HOLE: gon Meadowdale HH-6 HMWSMNCES INC. Edmonds, WA PAGE: 1 of 1 HANDHOL 2008.171-21.GPJ 11/15/07 PROJECT NO.: 2006-171-21 FIGURE: A-10 DRI�LING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/19/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/19/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 N cc w w Z Of va z ^ r y ¢ Non -Standard Penetration Resistance r, O Z r- 5 H p (17.6 lb. weight, 22.6" drop) I m i U J g J g W I z o x Z O O j a. r}n DESCRIPTION rn N a n O 0 p 0 SM Loose, olive brown silty SAND with gravel, roots and rootlets 0 present, moist [FILL] S-1 ' 2 Piece of old asphalt at 2.25 feet below ground surface. SP Medium dense, gray gravelly fine to medium SAND with silt 0 S 2 3 roots and rootlets, moist OLD TOPSOIL Hand hole was terminated at 3.0 feet below ground surface. 4 No ground water seepage was encountered during the exploration. 5 6 7 8 11 12 13 14 NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. A6: 33 3 ♦ 4 :....:....:....:....:....:....:....: 5 ♦ 9 ♦ :....:....:....:....:....: 10 ♦ 11 :♦ 12 0 20 40 . 60 so 100 Water Content (%) Plastic Limit 1---41 Liquid Limit Natural Water Content 13 14 15 HAND HOLE: iRVA 75th-76th Walkway Improvements HH-7 ��_� Meadowdale H.MGMSCUNCEB INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE* A-1 1 HANDHOL 2006-171-21.GPJ 11/15/07 b6iILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/19/2007 ' DRILLING METHOD: Hand Bucket Auger SAMPLING METHOD: GRAB DATE COMPLETED: 10/19/2007 LOCATION: See Figure 2 LOGGED BY: D. Coltrane CO 5 o: m w z� y a � z F °y' N ►�' rnw W ~ Q Non -Standard Penetration Resistance j O HOro N J w F- Z (17.8 lb. weight 22.6' drop) an a. M U J a s W y 3 w O = y D DESCRIPTION y U3 a s ~O it 0 o o SM Loose, light brown, silty SAND with gravel, roots and rootlets, 0 moist. 1 [FILL] - OS1 -i 1 2 2 SM __ Loose, brown, silty SAND with gravel, burnt wood bits, 3 roots, and rootlets, moist S-2 OLD TOPSOIL O 3 4 Hand hole was terminated at 3.2 feet below ground surface. No groundwater seepage was encountered during the : : 4 exploration. 1 5 . 5 6 6 7 7 6 9 10 11 12 13- 14- NOTE: This log of subsurface conditions applies only at the speed location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations 9 I-10 1 13 : 14 0 15 20 40 60 80 100 Water Content (%) Plastic Limit 1 --0 Liquid Limit Natural Water Content 75th-76th Walkway Improvements HAND HOLE: awl, Meadowdale HH-8 HMGEOSMNCFS INC. Edmonds, WA PAGE: 1 of 1 HANDHOL 2006-171-21.GPJ 11/15/07 PROJECT NO.: 2006-171-21 FIGURE: A-12 .DRIWNG COMPANY: HWA Geosclences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/19/2007 -DRILLING, METHOD: Hand Bucket Auger DATE COMPLETED: 10/19/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 rn w Z W va Co j ^ N a)y Lu ¢ Non -Standard Penetration Resistance °-� W Z G O y 0 (17.6 lb. weight, 22.6° drop) v y to U w a w s wm � 3 W j a o U) D Sa o I= w DESCRIPTION U) ai a$ O 0 p 0 1 2- 3- 4- 5- 6- 7- 8- 9- 10- SM 1.5 inches of Beauty Bark on surface. Loose to medium dense, olive brown, silty SAND with gravel, roots and rootlets, moist pieces of plastic and cemented soils present X. (COLLUVIUM/FILL] MIL Soft, to loose, layers of olive brown, sandy SILTwith trace SM gravel, mottled olive brown fine silty SAND with rootlets, and grayish brown sandy SILT with trace gravel, roots, rootlets, and pieces of burnt wood present, moist [COLLUVIUM] Hand hole was terminated at 11.25 feet below ground surface. Minor groundwater seepage from the excavation walls was observed during the exploration. 0 OS1:♦: 1 ♦ 2 O S-2 f 3 ♦ 4 S-3 :..�.... ....:.. 5 0 ♦ 6 :♦ 7 OS4 ♦: ♦ 8 ♦ ♦ ♦ 9 O S 5 ;...�...;.... j ..:....:....:.. 10 ♦ :» 1 ♦-» * 11 ♦: » 12 13 I IC 0 20 40 60 80 100 Water Content (%) Plastic Limit f --40 Liquid Limit Natural Water Content �EThis log of subsurface conditions applies only at the specified location and on the date indicated log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. UWA 75th-76th Walkway Improvements HAND HOLE: HH-9 Meadowdale F WAGEoSC NCZ INC Edmonds, WA PAGE: 1 of 1 PROJECT NO • 2006-171-21 FIGURE: A-13 HANDHOL 2006-171-21.GPJ 11/15/07 Appendix B Geotechnical Laboratory Testing 0 MENOMONEE _ 1 1 1 - ---------- M ii �d N N 01 > O O (O �0 o o c� a J a U N 0 N N m CP NO V 0 0 N 0 z w O IL LL CD 0 0 0 J J ... F- J 0 55 cy 13) I\N CO LO IT cC O o0 (id) X3aNl ,UIOI-LSVId O co 0 O N ■ U Q U � J U N N C 0 o a �a0d, � �. N N � N J 47 n N M U � co 0 N Cl) Z O H U g } U f- U U U N rn O) lQ O Y ` Q J r m � � N = N H a o o �n o (O � to � a N CO M J 0 N Q J m f- 4:�OL15�-aIIFR STREET FILE RECEIVED MAY 3 0 2008 ENGINEERING DIVISION REVISED GEOTECHNICAL REPORT 76th Avenue West A 75th Place West Walkway Improvements Edmonds, Washington HWA Project No. 2006-171-21 Prepared for Gray & Osborne, Inc. November 16, 2007 (Revised May 30, 2008) ffo,', � HWAGEOSCIENCES INC. • Geotechnical Engineering • Hytlrogeology, • Geoettvirontnental Services • Inspection & testing S r-. ' HWA GEOSCIINCES INC. Geotechnical 6 Pavement Engineering Hydrogeolog} Gcoeln-irornnetital • Inspection c= Testing May 30, 2008 HWA Project No. 2006-171-21 Gray & Osborne, Inc. 701 Dexter Avenue North, Suite 200 Seattle, Washington 98109 Attn: Ms. Tani Stafford, P.E. Project Manager REVISED GEOTECHNICAL REPORT 76TH AVENUE WEST AND 75TH PLACE WEST WALKWAY IMPROVEMENTS EDMONDS, WASHINGTON Dear Tani: As requested, HWA GeoSciences Inc. completed stability analyses studies for the proposed park improvements at 162nd Street and included their results into this revised geotechnical report for 76`h Avenue West and 75th Place West Walkway Improvements. The results of our investigations and geotechnical recommendations for the proposed facilities are presented in this report. We appreciate the opportunity to provide geotechnical services on this project. Sincerely, HWA GEOSCIENCES INC. Ralph N. oirum, P.E. Geotechnical Engineer Principal Enclosure: Revised Geotechnical Report Lyr 19730 - 64th Avenue' TABLE OF CONTENTS Paze 1. INTRODUCTION...........................................................................................................1 1.1 SITE AND PROJECT DESCRIPTION.................................................................1 2. EXPLORATIONS AND GEOLOGIC CONDITIONS ............................................................2 2.1 SUBSURFACE EXPLORATIONS.......................................................................2 2.2 GENERAL GEOLOGIC CONDITIONS...............................................................3 2.3 LANDSLIDE HISTORY.....................................................................................3 2.3 SUBSURFACE CONDITIONS............................................................................4 2.5 GROUND WATER CONDITIONS......................................................................5 2.6 LABORATORY TESTING.................................................................................5 1.1 SITE AND PROJECT DESCRIPTION.................................................................1 3. RECOMMENDATIONS..................................................................................................6 3.1 GENERAL.......................................................................................................6 3.2 EARTH RETAINING STRUCTURES.................................................................6 3.3 PILE SUPPORTED WALKWAYS.....................................................................7 3.4 PAVEMENTS...................................................................................................7 3.5 PARK DESIGN................................................................................................8 3.5.1 Stability..........................................................................................8 3.5.2 Park Drainage..............................................................................9 3.5.3 Foundation Design.......................................................................9 3.5.4 Park Pavement.............................................................................10 4.0 CONDITIONS AND LIMITATIONS................................................................................10 LIST OF FIGURES (FOLLOWING TEXT) Figure 1 Vicinity Map Figures 2-4 Site and Exploration Plan Figure 5 Park Property Exploration Plan Figure 6 Proposed Park Plan Figure 7 Cross Section A -A' Figure 8 Log of Previous Test Boring HWA-i Figure 9A & 9B Boring HWA-3 Inclinometer Plot Figure 10 Boring BH-1 Inclinometer Plot Figure 11 Stability Analysis of Existing Slope Figure 12 Stability Analysis with Proposed Buttress Appendices Appendix A: Field Exploration Figure A-1. Legend of Terms and Symbols Used on Exploration Logs Figures A-2 - A-13 Logs of Test Borings BH-1 through BH-3 and Hand Borings HH-1 through HH-9 Appendix B: Laboratory Testing Figure 13-1 Particle Size Distribution Test Results Figure B-2 Liquid Limit, Plastic Limit, and Plasticity Index of Soils (Atterberg Limits) REVISEDGEOTECIIMCAL REPORT WALKWAY IMPROVEMENTS 76TR AVENUE WEST AND 75TH PLACE WEST EDMONDS, WASHINGTON 1. INTRODUCTION This report presents geotechnical recommendations for design and construction of the proposed walkway improvements to 76th Avenue West and 75th Place West in Edmonds, Washington. The purpose of this work was to assess geotechnical conditions along the project alignment and provide recommendations for design and construction of the proposed improvements. 1.1 Site and Project Description The project is located in the Meadowdale area of Edmonds, which is located along the shoreline of Puget Sound north of the city. The area is indicated on the Vicinity Map, Figure 1. The project will 'include construction of a walkway along 76th Avenue West and 75th Place West extending from Meadowdale Beach Road north to North Meadowdale Road, with some additional improvements north to the King County Park. Theproject will include development of a park at the north-west corner of 751h Place West and 162' Street SW. Three conceptual designs for the proposed improvements were developed during preliminary studies. We understand Concept 1 was selected for final design and construction. Under the selected concept, the new sidewalk will be located along the east (upslope) side of the roadway from Meadowdale Beach Road north to 162"d Street SW. Cuts into the hillside will be required for the new sidewalk in much of this area. The cuts will be typically 3 to 4 feet in height but will be up to 12 feet high in some areas. From 162°d Street SW north to North Meadowdale Road the new walkway will be located on the western side of the road. Since placing fill along the top of the slope could reduce the stability of the slope and is to be avoided, the new sidewalk will be supported on small diameter pipe piles where there is insufficient existing flat area. North of North Meadowdale Road two pull-outs will be constructed on the east side of the road for vehicle parking, and one 130-foot-long section of pile -supported walkway is planned on the west side of the road. Development of the proposed park will include regrading the site and construction of a driveway, walkways, lawn and play areas. We understand an interpretive overlook is planned adjacent to 75th Place West. A plan of the proposed park is presented on Figure 6. May 30, 2008 HWA Project No. 2006-171-21 2. EXPLORATIONS AND GEOLOGIC CONDITIONS 2.1 Subsurface Explorations Subsurface information for the project was obtained by advancing three hollow stem auger borings designated BH-1 through BH-3; nine hand borings designated HH-1 through HH-9; and three DCP soundings performed in concert with hand borings HH-7 HH-8 and HH-9. Boring BH-1 was conducted by Davies Drilling Inc. using a track mounted CME-75 drill rig with a 3.25 inch OD hollow stem auger. Borings BH-2 and BH-3 were drilled by Environmental Drilling using a truck mounted B-61 drill rig with an 8 inch OD hollow stem auger. Boring BH-1 is located in the northeast section of the proposed new park. Borings BH-2 and BH-3 are located along the pro�osed sidewalk alignment where a new solider pile wall will be installed on the east side of 76 Avenue West and 75`h Place West. Hand holes HH-1 through HH-6 are located along the east side of 76th Avenue West and 751h Place West along the alignment of the proposed sidewalk. Hand holes HH-7 through HH-9 along with their associated DCP soundings are located along the west side of 75`h Place west between 162°d Street West and North Meadowdale beach road. Borings were advanced either at the edge the City right of way, or in the middle of the right travel lane, as shown in Figures 2-4. A 2-inch diameter ground water monitoring well was installed in BH-2 with screen from a depth of 15 to 25 feet and a silica sand filter from a depth of 12 to 30 feet. A slope inclinometer casing was installed in BH-1 after the completion of the boring. The casing was installed to a depth of 35 feet below the ground surface and was incased in cement grout. A baseline reading for future measurements was taken on October 241h 2007. Readings were subsequently taken February 22, 2008. Plots of the readings from BH-1 are presented on Figure 10. Borings were located using a site map provided by Gray & Osborne inc. by measuring from existing structures shown on the base map provided. A legend of the terms and symbols used on the boring logs is presented in Figure A-1. Summary boring logs are presented in Figures A-2 through A-13. Standard Penetration tests were performed at 2.5-foot or 5-foot intervals in all three borings. The Standard Penetration test consists of driving a 2-inch O.D. split -spoon sampler a distance of 18 inches into the bottom of the borehole with a 140-pound hammer falling 30 inches. The number of blows required driving the sampler each of three 6-inch increments was recorded, and number of blows required to cause the last 12 inches of penetration was termed the Standard Penetration Resistance (N-value). This value is an indicator of the relative density or consistency of the soils. Whenever 50 or more blows were required to cause 6 inches of penetration, driving was stopped and the number of blows and corresponding penetration were recorded. Samples recovered from the split spoon sampler were disturbed but were representative of the soils encountered. 200617121 Revised Geotechnical Report.doc 2 RWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 An HWA geologist monitored the drilling and logged the borings. Soil samples were obtained from the borings at intervals of 2.5 to 5.0 feet, classified in the field, and representative portions were placed in plastic bags. These soil samples were taken to our Lynnwood, Washington, laboratory for further examination and testing. Pertinent information including soil sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence were recorded on the exploration logs. The stratigraphic contacts shown on the individual boring logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and ground water conditions depicted are only for the specific date and locations reported and, therefore, are not necessarily representative of other locations and times. 2.2 General Geologic Conditions Geologic information for the project site was obtained from the published geologic map for the area; Booth, D. B., Cox, B. F., Troost, K. G., and Shimel, S. A., 2004, Composite geologic map of the Sno-King area: University of Washington, Seattle -Area Geologic Mapping Project, scale 1:24,000. This map indicates that the surficial geology of the area consists of Pre -Fraser terrestrial deposits, overlain by Vashon-stade advance outwash, a unit of mostly clean sand with some gravel, overlain by Vashon-stade glacial till a non -stratified and non -sorted mixture of clay, silt, sand, and gravel. The terrestrial deposits reside mainly in the northern portion of the sidewalk alignment while the till and advance deposits are seen in the southern portion of the alignment. The area is also overlain by landslide colluvium deposited by the ancient Meadowdale slide. The landslide deposits occur throughout most of the site and are surficial above the glacial and pre -glacial terrestrial deposits. 2.3 Landslide History The majority of the project alignment lies within the North Edmonds Earth Subsidence and Landslide Hazard Area, which is described in detail in a report titled "Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington' prepared by Roger Lowe Associates in 1979. According to the Roger Lowe Associates report, this area of Meadowdale experienced large- scale ground movement between two and three thousand years ago. This slide was approximately 3,200 feet long and up to 650 feet wide. The head scarp is easily distinguishable above 751h Place West.. The cause of this large-scale earth movement is inferred to be progressive shoreline erosion by wave action; the waves eroded the toe of the slope, which over - steepened it and eventually led to land sliding. Construction of the Great Northern Railroad, which is currently owned by Burlington Northern Santa Fe, along the beach, has halted the shoreline erosion process since it armors the toe of the slope from wave erosion. No large-scale earth movements have been recorded for this area in modern times. However, subsequent to the ancient slide, the mass of soil within the body of the slide has experienced numerous small-scale adjustments. This type of post -slide adjustment is common and typically occurs in the form of shallow earth slumps. 200617121 Revised Geotechnical Report.doc 3 HWA Geo Sciences Inc. May 30, 2008 HWA Project No. 2006-171-21 More recently, sliding occurred in the area in January 1997, after heavy snowfall was followed immediately by several inches of rain. Sliding occurred at several locations on the eastern side of 75`h Place West and debris from one slide flowed across the street and came to rest on the western side the road. Landslides occurred throughout the Puget Sound Region at that time and are described in more detail in the paper by Gerstel et al. titled "Puget Sound Bluffs: The Where, Why, and When of Landslides Following the Holiday 1996/97 Storms" (in Washington Geology, vol. 25, no. 1, March 1997). The study by Roger Lowe Associates also indicates that the stability of the Meadowdale area is highly sensitive to groundwater levels. Improvements to local site drainage, including the installation of sewers and storm drains, have had a positive impact on the stability of the area. For several years sliding has been occurring at the northeast corner of the proposed 162❑d Street park property. This sliding has been very slow, but is visible in cracks and subsidence in the pavement of 751h Place West. HWA has been monitoring this slide for several years for the property owner to the north of the park. HWA installed an inclinometer casing in the shoulder of 75'h Place West several years ago. Measurements in this casing indicate a shear plane at depths of 16 to 20 feet. The toe of the slide appears to be at the base of the steep portion of the slope. 2.4 Subsurface Conditions Based on the results of our exploration program, the soils underlying the project area were observed to consist of Pre -Fraser terrestrial deposits overlain by colluvial deposits and small localized quantities of fill. This observation is consistent with the soils unit mapped in the area by Booth ET. Al., by Roger Lowe Associates, and as encountered during previous drilling undertaken by HWA to evaluate the subsurface conditions for other projects in this area in the past. (HWA, 2003). Following are descriptions of the soil deposits encountered in our explorations in the order of stratigraphic (depth) sequence by which they were deposited or placed, with the youngest unit described first. Detailed descriptions of the soils are presented in the exploration logs in Appendix A. A legend of the terms and symbols used on the boring logs is presented in Figure A-1. Summary boring logs are presented in Figures A-2 through A-13. Fill — Fill, consisting of loose to medium dense silty sand to sandy silt was identified in the locations of BH-1, BH-3, HH-1 and HH-7 through HH-9, and ranged from 1.25 to 7 feet thick. The fill was usually identified adjacent to the road, most likely from the grading of the roadway during the initial construction. Topsoil — Topsoil consisting of light brown to dark brow, silty sand with gravel was identified in HH-1 through HH-5. In all of the hand holes the topsoil consisted of loose to medium dense surficial material with abundant roots and rootlets being present. Depths ranged from 0.5 to 2.0 feet in depth. 200617121 Revised Geotechnical Report.doc 4 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 Colluvium — Colluvium was encountered in all. of the borings and in hand holes HH-2, HH-6 and HH-9. It generally consisted of very soft to medium stiff clays and silts with interspersed pieces of colluvial clays and silts, with seams of sand. The majority of the colluvium has experienced some oxidation mottling, and the seams of sand tended to be wetter than the surrounding fine grained material. Colluvial Blocks — Colluvial blocks were encountered in Borings BH-2 and BH-3 under the softer colluvial material that overlies it. In the case of these explorations colluvial blocks refers to disturbed native soils that are denser then the overlying material, but still exhibit some variability in density and an irregularity in the soil that does not correspond with native undisturbed glacial and pre -glacial terrestrial deposits. For example in BH-3 loose poorly graded sand was encountered from 18 to 26 feet between very stiff clay and a hard laminated silt. It is not known when or how these materials were mobilized in the past, but they do exhibit some signs of disturbance. Recessional Outwash — Loose to medium dense glacial outwash consisting of light brown silty sand with gravel to gravelly sand with silt was identified in HH-3 through HH-5. The recessional outwash was encountered on the uphill (east) side of the sidewalk alignment in the area where a slope cut will occur for the new sidewalk. At the locations of TP-1 and TP-16, thin layers of silty sand were encountered from 0.5 to 1.0 foot thick, which appeared to consist of recessional outwash. These soils were loose to medium dense and directly overlie the glacial till. 2.5 Ground Water Conditions Ground water seepage was encountered in borings BH-1, BH-2 and HH-2. We expect, however, that actual ground water depths will vary depending on the season, variation in local subsurface conditions, and other factors. The project alignment is near the toe of the hillside, which is a ground water discharge area. Consequently, springs .and seeps occur at numerous locations along the alignment where groundwater emerges from the ground. 2.6 Laboratory Testing Representative soil samples obtained from the subsurface explorations were returned to the HWA laboratory for further examination and testing. Laboratory tests, as described below, were conducted on selected soil samples to characterize relevant engineering properties of the on -site soils. Moisture Content of Soil: The natural moisture content of all soil samples (percent by dry mass) was determined in general accordance with ASTM D 2216. The results are shown at the sampled intervals on the test pit logs in Appendix A. 200617121 Revised Geotechnicat Report.doc 5 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 Particle Size Analysis of Soils: Selected samples were tested to determine the particle size distribution of material in general accordance with ASTM D 422. The results are summarized on Figure B-1, Appendix B, which also provides information regarding the classification of the samples and the moisture content at the time of testing. Liquid Limit, Plastic Limit, and Plasticity Index of Soils (Atterberg Limits): Selected samples were tested using method ASTM D 4318, multi -point method. The results are reported on the attached Liquid Limit, Plastic Limit, and Plasticity Index reports, Figure B-2. 3. RECOMMENDATIONS 3.1 GENERAL Construction of a walkway along 761h Avenue West and 751h Place West will require excavation into the toe of the slope on the up -slope (eastern) side of the roadway in some areas, and placement of fill or a pile supported partially -elevated walkway on the downslope side of the road. Because placement of fill on the downslope side of the road would add to the weight of a potential landslide, reducing the stability of the slope, we recommend that filling be avoided to the extent possible. As a result, we recommend that walkways and walkway approach structures on the downslope side of the road be pile -supported wherever there is insufficient existing flat terrain. Development of the propose park will include regrading the site and construction of a driveway, walkways, lawn and play areas. We understand an interpretive overlook is planned adjacent to 75`h Place West. Because of the relatively high ground water level and the presence of an existing landslide on the property, we recommend the installation of a trench subdrain across the park. HWA has evaluated measurements taken in an inclinometer casing installed on the park property and performed stability analyses to evaluate the effectiveness of placing a buttressing fill along the toe of the slope. The results of these studies indicate that the existing slide daylights at the toe of the road embankment, and that placement of fill along this toe will increase the stability of the slope. Results of the stability analyses and more detailed recommendations for park design are presented in Section 3.5. 3.2 EARTH RETAINING STRUCTURES Cuts along much of the eastern side of the roadway alignment will be 3 to 4 feet tall. In our opinion, the most cost-effective way of retaining these shallow cuts would be with modular block walls such as Keystone blocks, or with rockeries. Block walls up to about 4 feet high (twice the depth of the block) may be made by stacking blocks without need for geogrid reinforcing. Block walls higher than twice the block depth should include geogrid reinforcing which extends back from the face of the wall a horizontal distance equal to at least 0.7 times the free-standing wall height. Geogrid reinforcing should be placed between every second layer of blocks. We recommend the use of Tensar BX1200 geogrid, or equivalent, wherever geogrid reinforcing is needed. 200617121 Revised Geotechnical Report.doc 6 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 Because of the horizontal space required for block walls, it may be desirable to use soldier pile and lagging walls where the retained height of the cut exceeds about 4 feet. Soldier pile and lagging walls would consist of 4-inch or larger H piles set in concrete in pre -drilled holes. Lagging consisting of treated timber or precast concrete panels would be placed between the soldier piles. The size of the H-pile section would depend on the height of the wall and the horizontal spacing of the piles. Soldier piles should be designed to resist an equivalent fluid pressure equal to 55 pounds per cubic foot (pcf) plus one pcf for each degree of upward inclination of the backslope. Passive resistance approximated by a 300 pcf equivalent fluid pressure may be used against the buried portion of structures to resist lateral forces. We recommend the soldier pile walls be tall enough that the backslope inclination does not exceed 2H to IV. Fill could be placed behind the soldier pile walls as necessary to flatten the slope. Soldier piles which are set into concrete in predrilled holes should penetrate below finished grade at least 1.5 times the wall's free-standing height. We do not recommend driving soldier piles because: 1) driving and maintaining pile alignment may be difficult in dense gravelly soils, 2) vibrations from pile driving can cause landslides, and 3) a concrete -filled hole provides better lateral resistance than a driven pile. Piles which are driven in place would need to extend to a depth equal to twice their free-standing height. Backfill behind the lagging should consist of 11/4-inch minus crushed rock. Soldier pile and lagging walls constructed as recommended above are typically permeable and will allow the passage of moderate amounts of seepage. Where significant volumes of water are expected, such as at existing springs, a slotted drain pipe and crushed rock backfill should be placed to intercept the flow and convey it through the wall to the storm drain system. 3.3 PILE SUPPORTED WALKWAYS Where pile support of walkways and approach structures is required, we recommend the use of 2-inch diameter extra -strong steel pipe. When driven to less than 1 inch of penetration in 1 minute of driving with a 90 psi jackhammer, each pile should be capable of supporting 2 tons of vertical load (allowable capacity) with an adequate factor of safety. Pile installation can actually be accomplished with a backhoe-mounted compactor (hoepac), but testing to verify capacity should be done with a jackhammer. Piles will develop their bearing in native soils below any fill, and pile lengths will vary considerably. Pile lengths could average 20 to 25 feet. 3.4 PAVEMENTS Where new street pavement is required, the pavement subgrade should be proof -rolled to verify that it is dense and unyielding. Any soft or spongy material should be replaced with 1'/4-inch- minus crushed rock. The pavement section should consist of at least 6 inches of crushed rock (CSBC) and 3 inches of asphalt. 200617121 Revised Geotechnical Report.doc 7 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 3.5 PARK DESIGN A plan showing the park property with existing ground surface contours and the location of boring BH-1 is presented on Figure 5. A cross section through the park property showing BH-1, the previous boring HWA-3, and the assumed failure plane of the existing landslide is shown in Figure 7. The proposed layout of park facilities is shown on Figure 6. 3.5.1 Stability As indicated on Figure 5, the park property slopes downward from 75th Place West about 2H to IV for approximately 20 vertical feet. The site then slopes gradually to 75th Avenue West. Our previous studies indicate that a landslide exists on the north end of the park property and the adjacent property to the north. The slide is still moving as evidenced by renewed cracking in the pavement of 75th Place West. Readings from an inclinometer casing installed in the street right- of-way in front of the adjacent property to the north, shown in figure 9A and 9B indicate that the slide is about 18 feet deep at the western side of 75th Place West. As part of the current study, HWA installed an inclinometer casing in BH-1 so that any earth movements at that location can be detected. The results of measurements in this casing indicate that the existing slide terminates at the toe of the slope on the east side of the park and does not involve most of the park site. Because the existing landslide is confined to the north end of the slope on the eastern side of the park, the proposed park development can proceed without stabilizing the slide, providing the City is willing to accept that portions of the park, as well as the roadway and the utilities within its right-of-way, will continue to be affected by the sliding. Current plans for park development include placing fill along the toe of the slope below the roadway, which will tend to increase the stability of the slide. In order to evaluate the stabilizing influence of such fill, HWA performed a series of computer -model stability analyses. An analysis was first performed to estimate the strength of existing soils on the hillside by assuming a factor of safety of 1.0 for the existing slope. The results of this analysis are shown on Figure 11. Soil strength parameters developed from this model were then used to determine the changes in factor of safety for various buttress fill configurations. The results of one such analysis is shown on Figure 12. These analyses indicated that the planned 5-foot high buttressing fill along the toe of the slope will increase the stability of the slope by about 17 percent. These analyses also indicated that: ■ The buttressing fill should extend to the top of the slope (as shown on Figure 12) to prevent failure planes with lower factors of safety from day -lighting higher up on the slope above the buttress. ■ Buttress fills thicker than 5 feet will produce correspondingly higher factors of safety. 200617121 Revised Geotechnical Report.doc 8 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 Because the proposed fill extends only part way across the toe of the slide, the actual increase in factor of safety from a 5-foot fill will be less than 17 percent. To maximize the increase in stability, we suggest placing as much fill as the park configuration will allow, including placement of fill on the adjacent property to the north. We understand that for the purpose of park space utilization, it is desirable to retain the buttressing fill with a retaining structure. To further increase the stability of the slope we recommend that this retaining structure be founded on drilled piers which extend vertically downward (approximately 10 feet) to extend through the soft clay into the underlying medium stiff clay. These piles, consisting of 24-inch diameter concrete cylinders on 6- to 8-foot centers will provide additional shearing resistance across potential slide planes in the soft clay. The result will be a significant increase in the stability of the slope. A reinforced concrete footing can be cast along the tops of the piers and the retaining structure can be constructed of Keystone -type blocks. We recommend that geogrid reinforcement be included in the buttress fill in accordance with Section 3.2. 3.5.2 Park Drainage We believe the installation of a trench subdrain across the park property is necessary to remove excessive moisture for park development and enhance the stability of the lower portion of the park. We recommend the construction of a trench subdrain across the park. The subdrain would consist of a 4 to 5-foot-deep trench extending roughly north -south along the toe of the eastern slope and then turning westward near the north property line to daylight at the western edge of the park. Finger drains extending up -slope from the trench drain, spaced about 25 feet apart will further increase drainage. The approximate location of the proposed trench drain is shown on Figure 6. A 6-inch diameter slotted plastic pipe would be placed in the bottom of the trench and the trench would be backfilled with 1'/4-inch-minus crushed rock. The trench subdrain would intercept and remove ground water seepage from the site. 3.5.3 Foundation Design Structures in the park may be supported on spread footings providing they can tolerate some settlement. The soils are capable of supporting structures at allowable bearing pressures up to 1,500 psf, however, some settlement is likely due to the loose, soft and variable nature of the soils. Structures that can not tolerate 2 inches of total and 1 inch of differential settlement should be supported on small diameter pipe piles as described in Section 3.3. Column footings should have a minimum width of 24 inches and wall footings should have a minimum width of 18 inches. Footings should bear at least 18 inches below the lowest adjacent finished grade. 200617121 Revised Geotechnical Report.doc 9 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 3.5.4 Park Pavement Any pavements within the park that will carry vehicular traffic should be constructed as accordance with the recommendations in Section 3.4. We recommend that pavements for walkways and trails consist of 6 inches of P/4-inch minus crushed rock overlain by 1'/2 inches of asphalt. 4.0 CONDITIONS AND LIMITATIONS We have prepared this report for Gray & Osborne and the City of Edmonds for use on this project. This data and report should be provided to prospective contractors for their bidding or estimating purposes, but the conclusions and interpretations presented should not be construed as a warranty of the subsurface conditions. Experience has shown soil and ground water conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations and may not be detected by a geotechnical study. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, HWA should be notified for review of the recommendations of this report, and revision of such if necessary. We recommend that HWA GeoSciences be retained to provide monitoring of construction sufficient to verify that the construction of retaining walls and the driving of foundation piles is accomplished in accordance with our recommendations and with the approved plans and specifications. The scope of work did not include environmental assessments or evaluations regarding the presence or absence of hazardous substances in the soil, surface water, or ground water at this site. HWA does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if he considers any of the recommended actions presented herein unsafe. 200617121 Revised Geotechnical Report.doc 10 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 We appreciate the opportunity to be of service. Sincerely, HWA GEOSCIENCES INC. Ralph N. Boirum, P.E. Geotechnical Engineer, Principal Principal 200617121 Revised Geotechnical Report.doc 11 HWA GeoSciences Inc. May 30, 2008 HWA Project No. 2006-171-21 References Roger Lowe Associates Inc., 1979, Final Report, Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington, for the City of Edmonds, consultant report dated October 16, 1979. Gerstel et al. "Puget Sound Bluffs: The Where, Why, and When of Landslides Following the Holiday 1996/97 Storms" (in Washington Geology, vol. 25, no. 1, March 1997). HWA Geosciences Inc., 2002-099-21, Geotechnical Report, Nguyen Property Slope Stabalization 16018 75rh Place West Edmonds, Washington, consultant report dated November 8, 2002. Booth, D. B., Cox, B. F., Troost, K. G., and Shimel, S. A., 2004, Composite geologic map of the Sno-King area: University of Washington, Seattle -Area Geologic Mapping Project, scale 1:24,000 200617121 Revised Geotechnical Report.doc 12 HWA GeoSciences Inc. LEGEND HH-9 HAND HOLE DESIGNATION AND APPROXIMATE LOCATION BH-3 BOREHOLE DESIGNATION AND APPROXIMATE LOCATION H WA-3 HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: -1 - - - - ffolk I lffi%aosm(zftc ('M w ry LD H Li W Z H J U Q 5- 100' 200' SCALE: 1"=100' 2 'Rolm NO. 2006-171-21 T LJ ry 0 r-� LL. LJ Z H J S U H Q LEGEND HH-9 HAND HOLE DESIG BH-3 BOREHOLE DESIGNATION AND APPROXIMATE LOCATION HWA-3 HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: ►, LJ L7 1--i LL W Z J S U H Q E )0' i 3 2006-171-21 LLJ LD F-4 LL LeJ z i--1 U F— Q LEGEND HH-9 HAND HOLE DESIGNATION AND APPROXIMATE LOCATION BH-3 BOREHOLE DESIGNATION AND APPROXIMATE LOCATION HWA-3 HWA PREVIOUSBOREHOLE DESIGNATION AND APPROXIMATE LOCATION BASE MAP PROVIDED BY: UWA I I HM(W.SMNas Ixc 76th -75th Walkway Improvements Edmonds, Washington O 0 (D OD 100' 200' SCALE: 1"=100' SITE AND EXPLORATION PLAN tAww BY EFK------- - IECKEO BYRNI ATE PROJECT NO. 10.24.07 2006-171-21 d z z z U) 0 3: F- z F- W < 0 < Of 2 w > Lc) 0 w U) >< 06 Q_ 0 w Z,> : Ezz —0 w >- 2 > < 0 w w 0 < tit ui IL CD 4:3 Ul. ML, Aijul A' (WEST) 80 70 60 w 50 w v o_ 40 F•- J30 W 20 10 0 0 LEGEND = EXPLORATION DESIGNATION m AND SITE PLAN SYMBOL N-VALUE - (BLOWSIFOOT) 20 STANDARD PENETRATION TEST (29) NON-STANDARD PENETRATION TEST WATER LEVEL AT TIME OF DRILLING WATER LEVEL MEASURED IN PIEZOMETER ON THE DATE INDICATED. 50/3" --?--_ _-_ -- INFERRED GEOLOGIC CONTACT 35 SAND PACK AND SCREEN INTERVAL BOTTOM OF BORING 71-21 76TH-75-TH z� W W w W �Q J l", a- a- w A o I o � � w w r. J U LD t3 (/) Q (h W A 1 A lT t'' Q W c Z A LLJ � _ .. LLJ W W EJ as LLJ E#fi ...::4. In �— — — — — — —� — — .•: . :°-——— — — — — —— '!• �r-��? j" _ — — S�Mf—to-Kar-T S2CT -&" CLAYS S - -CPRE=L7� �CIAL TERRESTRIAL DEPOSITS) 40 60 80 100 120 140 160 180 (FEET) The subsurface conditions shown are based on widely spaced borings and test pits and should be considered approximate. Further, the contact lines shown between units are interpretive in nature and may vary laterally or vertically over relatively short distances on site. 200 220 A (EAST) 80 70 �_60 ._M*, L._ v 40 0 H Q 30 w J W 20 10 T_ 0 240 HORIZONTAL SCALE: 1 "=20' 0' 10' 20' 40' 010' 20' 40' VERTICAL SCALE: 1 "=20' VAM%GwS 76th-75th Walkway Improvements CT1iNCESINC Edmonds, Washington 1 71 XSEC.DWG CROSS SECTION A -A' DRAWN BY EFK FIGURE NO. CHECK BY DC 7 PRO3ECT NO. DATE 11.07.07 2006-171-21 DRILLING COMPANY: Gregory Drilling Inc. LOCATION: See Site & Exploration Plan, Figure 2 DRILLING METHOD: Hollow -stem Auger; CME 45 C track rig DATE STARTED: 9/13/2002 SAMPLING METHOD: SPT w/ Autohammer DATE COMPLETED: 9/13/2002 SURFACE ELEVATION: 70 t feet LOGGED BY: B. Thurber uJ Standard Penetration Test U uJ o m Q F- c W Q (140 lb. weight, 30" drop) J J w �- Z Blows per foot N = w J w -1 �� Q CL Co U Z o x O H a� o m D DESCRIPTION w U)) a O 0 o w r E I 1C I 1E I 2C I 2E I 3C SM Loose, brown, silty, fine to medium SAND, dry. Some coarse sand, trace fine gravel and organics. [ROAD FILL] ML Very loose, brown and gray with heavy rust -mottling, very SM sandy SILT to very silty fine SAND, wet. Interbedded. Some parity decomposed wood fragments. [EXISTING LANDSLIDE DEBRIS] Grades to gray, silty SAND and sandy SILT with organics, wet_ ML Soft, blue -gray with brown streaks, clayey SILT with partly decomposed wood fragments, moist. Mixed / swirled SP appearance.-----------------� CH Loose -gray, slightly silty, fine to medium SAND wet. Medium stiff, gray, green -gray, and brown -gray, CLAY, with micaceous fine SAND laminae, with partly decomposed woody debris, moist. Sand laminae at high angles, and clay laminations in sample tip are planar and at 60-degree angle. (OLD SLIDE DEBRIS) @17.5 feet Gray and dark gray, CLAY, moist. Laminae disturbed by fine angular offsets. Some dark gray slickensides at approx. 30 degrees. co 20 feet: Grades to stiff. No bedding apparent; fine blocky CH texture. Long wood fibers caught in tip. Very stiff, gray to dark gray, fat CLAY, moist Finely laminated, bedding approximately horizontal. FORMATION] [WHIDBEY Includes occasional light gray laminae of coarse silt / very fine sand. S-1 2-2-2 S-2 2-2-4 S-3 2-2-2 GS Q S-4 1-1-1 %F S-5 1-1-2 S-6a 1-2-3 S-6b S-7 2-3-6 S-8 3-6-8 AL S-9 4-6-9 AL S-10 6-8-11 Borehole terminated at 31.5 feet Inclinometer casing (3-inch diameter) installed to 30 feet, and backfilled with bentonite grout to 2 feet. 35 Bentonite chips backfilied from 1 to 2 feet; 10-inch diameter flush monument set in 1 foot of concrete to surface. 40 For a proper understanding of the nature Of subsurface conditions, this exploration log should be read in conjunction with the text of the geotechnical report. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 10 20 30 40 50 �n F-5 H 10 1 F-15 1 t— 20 1 [— 35 1 '"40 20 40 60 80 100 Water Content (%) Plastic Limit 1-0-1 Liquid Limit Natural Water Content NGUYEN RESIDENCE BORING: 16108 75TH PLACE WEST HWA-3 JMGEOSMNCESINC EDMONDS, WASHINGTON PAGE: 1 of 1 PROJECT NO.: 2002-099-21 FIGURE: 8 BORING 2002099.GPJ 11/15/07 O 0 N O CV) 0 0 O O N N O 0 N V I o Ln 0 N (U) H1d3O Un o N co O N 0 H d O N N C O a z 0� a C. > _O o W N 0 0 0 N G1 m to O O z O 0 0 r- ci o ' z ~ Cl U Cl W W C) D 0 N a 0 J a � w z F- J W W a o->� z ti0�j J C' W z 0 c' >QD Q Q W _ ~ J (O z V z 0-4 Un w w V O w C.7 Q N (fl O m 'IT O O O O O N O O N M 00 T O L N (D O O T m• I• O O O N O O N O O O I Hld3a O Z T z U W O o O cl: N EL - U) w Z I- J w w a� Q w O F-0o z ��0 < ; Q Q Q w _ ~ J Z (fl V 2 V w O OPP 1 (S043ul) UOIIBInap size-y U7 O to O LO N t) ti I� U) N O O O O 1 O O O O ti O O U� O C o t U-) N > E R C ° O O o II m W X U-) N m O O U� O U) O tN (D m � a> m E fA O N N CL C N O > C m p .0 N CD j 3 [6 X O O > O 'N d Q O. O g� O 3 d w u) E o o� E 0 U)m a``ni c O CL V OD C. O N N N O 0 LO O1 N L O V C N O C X O O �6 m L N N > O N 0 O O O O O M O O O �-- � N N M M V (;aa;) y;daa 0 O O N M N N t O V C O X • O C 16 � a o� o •5 d to o 0C) o U') O LOO N N M M V (3aad) 43da(3 co O O N N 0 IL Z 0 U) P Q aw = Q W ~ 0 (n N� w O G G Q > W O Z J CO Q J ti U Z in Safety Factor 0.00 0.25 0.50 0.75 _ 1.00 *„ 1.25 1.50 ® 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00+ 0 Material: Fill Strength Type: Mohr -Coulomb Unit Weight: 110 Ib/ft3 Cohesion: 250 psf Friction Angle: 30 degrees Water Surface: None 99) Material: Stiff - Hard Clay Strength Type: Mohr -Coulomb Unit Weight: 110 Ib/ft3 Cohesion: 800 psf Friction Angle: 20 degrees — Water Surface: None Existing Slope - Assumed FS = 1.0 1' 1.01 44 T 00 Material: Soft Clay Strength Type: Mohr -Coulomb Unit Weight: 100 Ib/ft3 Cohesion: 325 psf Friction Angle: 0 degrees Water Surface: None ]7) Material: M Stiff Clay Strength Type: Mohr -Coulomb Unit Weight' 100 Ib/ft3 Cohesion: 400 psf Friction Angle: 20 degrees Water Surface: None Figure 11 Scale 1:235.7 200 Safety Factor 0.00 0.25 0.50 0.75 . _ 1.00 1.25 0 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 0 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 0 6.00+ Material: Stiff - Hard Clay Strength Type: Mohr-Coul( Unit Weight: 110 Ib/ft3 Cohesion: 800 psf Friction Angle: 20 degrees Water Surface: None Existing Slope With 5-foot-Thick Buttressing Fill 80 Figure 12 Scale 1:191.1 I Appendix A Soil Boring Logs RELATIVE DENSITY OR CONSISTENCY VERSUS SPT N-VALUE COHESIONLESS SOILS COHESIVE SOILS Approximate Density N (blowstft) Approximate Consistency N (blowslft) Undrained Shear Relative Density(%) Strength (psf) Very Loose 0 to 4 0 - 15 Very Soft 0 to 2 <250 Loose 4 to 10 15 - 35 Soft 2 to 4 250 - 500 Medium Dense 10 to 30 35 - 65 Medium Stiff 4 to 8 500 - 1000 Dense 30 to 50 65 - 85 Stiff 8 to 15 10DO - 2000 Very Dense over 50 85 - 100 Very Stiff 15 to 30 2000 - 4000 Hard - over 30 >4000 USCS SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS Coarse Grained Soils Gravel and Gravelly Soils Clean Gravel (little or no fines) •' GW Weu-graded GRAVEL o Q GP Poorty-graded GRAVEL More than 50% of Coarse Gravel with o GM Silty GRAVEL Fraction Retained Fines (appreciable on No. 4 Sieve amount of fines) GC Clayey GRAVEL Sand and Clean Sand SW Nell -graded SAND More than Sandy Soils (little or no fines) •. SP Poorty-graded SAND 50% Retained on No. 200 Sieve Size 50% or More of Coarse Fraction Passing No. 4 Sieve Sand with es (appreciable Fines amount of fines) •: SM Silty SAND SC Clayey SAND ML SILT Fine Sill CL Lean CLAY Grained Soils and Liquid Limit Less than 50 % Clay _ QL Organic SILT/Organic CLAY MH Elastic SILT 50% or More No. 200 Sieve Silt Liquid Limit and 50% or More Clay y CH Fat CLAY Size OH Organic SILT/Organic CLAY Highly Organic Soils PT PEAT 1 1l COMPONENT DEFINITIONS COMPONENT I SIZE RANGE Boulders Larger than 12 in Cobbles 3 in to 12 in Gravel 3 in to No 4 (4.5mm) Coarse gravel 3 in to 3/4 in Fine gravel 314 in to No 4 (4.5mm) Sand No. 4 (4.5 mm) to No. 200 (0.074 mm) Coarse sand No. 4 (4.5 mm) to No. 10 (2.0 mm) Medium sand No. 10 (2.0 mm) to No. 40 (0.42 mm) Fine sand No. 40 (0.42 mm) to No. 200 (0.074 mm) Silt and Clay Smaller than No. 200 (0.074mm) TEST SYMBOLS %F Percent Fines AL Afterberg Limits: PL = Plastic Limit LL = Liquid Limit CBR California Bearing Ratio CN Consolidation DO Dry Density (pcf) DS Direct Shear GS Grain Size Distribution K Permeability MD Moisture/Density Relationship (Proctor) MR Resilient Modulus PID Photoionization Device Reading PP Pocket Penetrometer Approx. Compressive Strength list) SG Specific Gravity TC Triaxial Compression TV Torvane Approx. Shear Strength (tsf) UC Unconfined Compression SAMPLE TYPE SYMBOLS ®2.0" OD Split Spoon (SPT) (140lb. hammer with 30 in. drop) IShelby Tube 3-1/4" OD Split Spoon with Brass Rings OSmall Bag Sample ® Large Bag (Bulk) Sample aCore Run Non-standard Penetration Test (3.(" OD split spoon) GROUNDWATER SYMBOLS Q_ Groundwater Level (measured at time of drilling) 1 Groundwater Level (measured in well or open hole after water level stabilized) COMPONENT PROPORTIONS PROPORTION RANGE DESCRIPTIVE TERMS < 5% Clean 5 - 12% Slightly (Clayey, Silty, Sandy) 12 - 30% Clayey, Silty, Sandy, Gravelly 30-50% Very (Clayey, Silty, Sandy, Gravelly) Components are arranged in order of increasing quantities. NOTES: Soil classifications presented on exploration logs are based on visual and laboratory observation. Soil descriptions are presented in the following general order. MOISTURE CONTENT Density/consistency, color, modifier Cif any) GROUP NAME, additions to group name Cif any), moisture DRY Absence of moisture, dusty, content. Proportion, gradation, and angularity of constituents, additional comments. dry to the touch. (GEOLOGIC INTERPRETATION) MOIST Damp but no visible water. Please refer to the discussion in the report text as well as the exploration logs for a more WET Visible free water, usually complete description of subsurface conditions. soil is below water table. 75th-76th Walkway Improvements LEGEND OF TERMS AND SYMBOLS USED ON Meadowdale HMGEO$CATLENCS INC Edmonds, WA EXPLORATION LOGS PROJECTNO.: 2006-171-21 FIGURE: A-1 LEGEND 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: Davies Drilling SURFACE ELEVATION: t feet DATE STARTED: 10/10/2007 DRILLING METHOD: Hollow stem Auger DATE COMPLETED: 10/10/2007 SAMPLING METHOD: Cat Head SPT LOGGED BY: P. Pearson LOCATION: See Figure 2 (0 1uJ U w V Z Standard Penetration Test U o CO w (140 lb. weight, 30" drop) J Z N = y c H w HA Blows per foot m 2s Fig m y a s —+ Z w O W F EL U ai p = O W= vi Wadi o U) > DESCRIPTION vQi a a 0 10 20 30 40 50 O 0 0 5 10 15 20 25 3 0 3 `. SM Loose, Brown, slightly silty, fine to Medium SAND, moist with roots and rootlets. [FILL] Soil becomes sittier then sandy again. CL Loose, yellowish gray, sandy SILT, moist, trace organics. `--------[COLL9AU-11,1--------� ML Soft, bluish gray, silty CLAY, moist Older, black trace organics. Soft, bluish gray to brownish gray, silty CLAY, wet. Some dense chunks of day also. CL Medium stiff to stiff, gray, silty CLAY, moist. Trace laminations observed. 2 inch sandy layer. CH Stiff to very stiff, gray, CLAY, moist. Slickenslides observed. [PRE -GLACIAL TERRESTRIAL DEPOSITS] Hard, gray, CLAY with fine sand, slightly moist. Subvertical cracks with fine sands. Horizontal laminations observed. 5 Hard, massive, gray, fine sandy, CLAY, moist to wet. S-1 1-1-4 .... :.. .. .:....:.... .. 5 S-2 3-2-3 S-3 1-1-2 j 10 S-3 446 S-5 3-8-15 _ A : :. ..:.... .... :---- 20 .......... 5» 2 S-6 10-21-35 :» 30 S-7 9-18-32 3 �.. 5 S-8 13-27-50/5 » Boring terminated at 36.5 feet below surface. Inclinometer casing was installed with grout from 2.5 feet above ground surface to 35 feet below ground surface. 40 Ground water observed at 10 feet'and 35 feet at time of exploration. 45 NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. ...:....: :.... 40 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content BORING: 75th-76th Walkway Improvements BH-1 Meadowdale HMGE0SMNCES INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-2 PZO 2006-171-21.GPJ 11/15/07 S-1 1-1-4 .... :.. .. .:....:.... .. 5 S-2 3-2-3 S-3 1-1-2 j 10 S-3 446 S-5 3-8-15 _ A : :. ..:.... .... :---- 20 .......... 5» 2 S-6 10-21-35 :» 30 S-7 9-18-32 3 �.. 5 S-8 13-27-50/5 » Boring terminated at 36.5 feet below surface. Inclinometer casing was installed with grout from 2.5 feet above ground surface to 35 feet below ground surface. 40 Ground water observed at 10 feet'and 35 feet at time of exploration. 45 NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. ...:....: :.... 40 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content BORING: 75th-76th Walkway Improvements BH-1 Meadowdale HMGE0SMNCES INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-2 PZO 2006-171-21.GPJ 11/15/07 Boring terminated at 36.5 feet below surface. Inclinometer casing was installed with grout from 2.5 feet above ground surface to 35 feet below ground surface. 40 Ground water observed at 10 feet'and 35 feet at time of exploration. 45 NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. ...:....: :.... 40 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content BORING: 75th-76th Walkway Improvements BH-1 Meadowdale HMGE0SMNCES INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-2 PZO 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: Environmental Drilling Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/25/2007 DRILLING METHOD: Hollow Stem Auger DATE COMPLETED: 10/25/2007 SAMPLING METHOD: SPT Auto Hammer LOGGED BY: V. Atkins LOCATION: See Figure 2 1 5 1 10 1 15 1 20 1 25 30 35 40 ro w w O Z Standard Penetration Test Lu o- Co j - r w (140 lb. weight, 30" drop) Z N rn c u~i U W ♦Blows per foot m try w Q F as 2 (L 2 Z o 2 Ow 2 ELN W DESCRIPTION U) U) a O a UUi 0 10 20 30 40 50 0 0 SP 1-2 inches of Asphalt over sand and gravel base course over brown. oDorIv graded SAND with gravel fill. ML Stiff, brown silt with Gay, moist (COLLUVIUM] M — — brown-ne withilt SAND s, sli-htlkoxidized, moist — ILoose CL Medium stiff, brown, SILT with sand, with trace dark orange wet oxidized silty sand seams, moist. Stiff, gray, SILT to clayey silt with seams of fine sand and ML day, moist. Sand seams are wet fragments in sample. M [qWood — — Stiff to very stiff, brown to olive brown organic SILT, moist. ML Very stiff, gray to olive gray, sandy SILT, wet. [COLLUVIAL BLOCKS] — — — — — — — — — — — — — — — — — — — — — — Medium dense, gray, fine sandy SILT, wet SM — — — — — — — — — — — — — — — — — — — — — — Very stiff, gray, CLAY, moist. CL High plasticity. Boring was terminated at 31.5 feet below ground surface. Ground water seepage was encountered at 15 feet below ground surface. A ground water monitoring well was installed with screen froml5-25 feet, and sand from 12 to 30 feet S-1 2-4-5 ............ S-2 2-2-5 V S-3 3-7-8 .... �.�... .... .... . ... ... :... .... 10 S 4 4-4-8 S-5 5-8-8 ' - ....:. :. ....:. ..... 15 S-6 3-8-11 .: S-7 4-7-12 S-8 4-7-12 S-9 6-9-15 : 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 20 1 35 1 BORING: 75th-76th Walkway Improvements BH-2 Meadowdale Hi CA0$CIENCES INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-3 PZO 2006-171-21.GPJ 11/15/07 01 DRILLING COMPANY: Environmental Drilling Inc. LOCATION: See Figure 2 DRILLING METHOD: Hollow Stem Auger DATE STARTED: 10/25/2007 SAMPLING METHOD: SPT Auto Hammer DATE COMPLETED: 10/25/2007 SURFACE ELEVATION: t feet LOGGED BY: D. Coltrane U) U -J O v) a Im � U (D > o 0) DESCRIPTION 0 7 inches of asphalt at surface. SM Medium dense, olive brown to light brown, silty fine SAND with gravel, moist W w U m o_ 2 Z - � ~ w V1 L U CO W W W C 1'-<o J a- h W Z 2 23 aa cn rn a O 0 _ [FILL] S-1 4-9-9 5 S-2 5-6-10 ML Medium dense to dense, olive brown, silty SAND to sandy SM SILT, with fine SAND seams, moist. Oxide mottling in seams S-3 5-8-15 of fine SAND. 10 [COLLUVIUM] S-4 11-15-16 Gravelyrillinghom 11 to 11.5 feet BGS. CL ML — — — — — — — Very stiff, gray to olive gray, silty CLAY with seams of gray S-5 7-9-13 silty fine SAND, moist. SILT has organic smell. ]COLLUVIAL BLOCKS] 15 S-6 4-6-10 1 20- 1 25 - 1 30- 1 35 - 40 - — — — — — — — — — — — — — — — — — — — — — — SP Loose, gray, poorly graded, fine to medium SAND with silt and trace fine gravel, moist to wet S 7 2-3 7 UDrilling became hard at 25-26 feet BGS. — S-8 6-12-23 ML Hard, olive gray to olive brown, laminated SILT, moist S-8a SM Medium dense, gray, silty fine SAND, wet S-9 7-12-12 Boring was terminated at 31.5 feet below ground surface. Minor ground water seepage was encountered during the exploration, but there was no standing ground water in the hole after the auger was removed. .. 0. Standard Penetration Test (140 lb. weight, 30" drop) A Blows per foot 10 20 30 40 A: ........ For a proper understanding of the nature of subsurface conditions, this 0 20 40 60 80 exploration log should be read in conjunction with the text of the water Content(%) geotechnical report. Plastic Limit I--0 Liquid Limit Natural Water Content NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. —5 — 10 — 15 r— 40 100 75th-76th Walkway Improvements BORING: got, BH-3 Meadowdale HMGEOSCIENCEB INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171 -21 FIGURE: A-4 BORING 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: i feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 rn m w Z - w c� w o U) N J in W w ~ Z = m m a n- of y w z o U) Z) DESCRIPTION ran (n O a s O ((.7 0 SM Medium dense, brown, sandy SILT with gravel, roots and rootlets, moist. (FILLIOLD TOPSOIL] O S-1 1 SM Medium dense, brown silty SAND with gravel, roots and woodchips. Less moist than above. S-2 2 Loose, yellowish brown Silty SAND with gravel, organics and n S-3 SM pieces of wood. No ground water. U 3 1 4- 1 5- 1 6- 1 7- 1 8- Hand hole was terminated at 4.0 feet below ground surface. No groundwater seepage was encountered during the exploration. NOTE: This log of subsurface conditions applies only at the speed location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. F-1 1 F-2 1 F-3 1 H7 1 '-- 8 0 20 40 60 80 100 Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content HAND HOLE: 75th-76th Walkway Improvements HH-1 aM I Meadowdale HMGEOS(HNCES INC. Edmonds, WA PAGE: 1 of PROJECT NO.: 2006-171-21 FIGURE: A-5 _ HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 DESCRIPTION SM Loose, dark brown, silty SAND with Gravel and organics. Moist (TOPSOIL] SM Loose, light olive brown, silty SAND with rootlets and chunks of grayish clay below 1.5'. [COLLUVIUMI ML Soft, olive brown, SILT with sand, chunks of gray day, small woodchips and bits of charcoal. w U of Lu m Z H W d L t- Q Z U ~ W [O N Z 3 0 � Q a : O 0S-1 n S-2 Q 6 Hand hole was terminated 5.5 feet below ground surface. Ground water seepage was encountered at 5.0 feet below ground level and stabilized at 4.7 feet below ground level after exploration. 7- 8-- NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. • ro H a w 0 13� I-3 5 6 7 8 0 20 40 60 80 100 Water Content (%) Plastic Limit 1-41--{ Liquid Limit Natural Water Content HAND HOLE: 75th-76th Walkway Improvements HH-2 gon Meadowdale HWAGEoSmNcs We Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-17 1 -21 FIGURE: A-6 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 ' DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/812007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 U) U N J_ O = O N a 2 U o U) Z) 0 1 3- 4- 5- 6- 7- 8- NOT DESCRIPTION SM Loose, light brown, silty SAND with gravel and roots, moist [TOPSOIL] SM Loose, light yellowish brown, silty SAND with gravel and wood chips. gravels are fine to medium. Soil is moist but less so than above. [RECESSIONAL OUTWASH] W w U m Z W d UL Q j Z U Cn w U S w co 1-' D Nof z 3 Q w o 1--of v) U a 8 O 0 0S1 Hand hole was terminated at 2.25 feet below surface level. No ground water seepage was encountered dunng exploration. This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 1 •: 0 1 3 4 5 F-7 1 0 20 40 60 80 100 - Water Content (%) Plastic Limit 1 ♦—{ Liquid Limit Natural Water Content 75th-76th Walkway Improvements HAND HOLE: HH-3 Meadowdale HMGEOS(HNCES NC. Edmonds, WA PAGE: 1 of 1 PROJECTNO.: 2006-171-21 FIGURE: A-7 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 w cgi wayyy < U w (D J_ U W O V) W J W J W Crl Z N 3 o v}) D DESCRIPTION N U 0 a..8 O 0 0 .. SM Medium dense, brown, silty SAND with gravel, roots and rootlets, moist. [TOPSOIL/WEATHERED OUTWASH] t- 2- 3- 4- 5- 6- 7- S-1 SM I Loose, light yellowish brown silty, gravely SAND, moist S-2 [RECESSIONAL OUTWASH] I U Hand hole was terminated at 2.5 feet below surface level. No ground water seepage was encountered during exploration. 8 J NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. S ww 0 r0 I— 3 1 F-4 1 t— 5 1 0 20 40 60 80 100 - Water Content (%) Plastic Limit 1--0 Liquid Limit Natural Water Content JI HAND HOLE: 75th-76th Walkway Improvements HH-4 Meadowdale HMGEOSCIENCEB INC Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-8 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/8/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 101812007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 U)ri> m w z w m U o} Q v J W W F- T 0 N J w -.1Q_ f0 N Z O o cn � DESCRIPTION U)i ai a s O 0 0 1 2 3 4 5 S-1 ✓ 0 0S2 Hand hole was terminated at 5.0 feet below surface level. No ground water seepage was encountered during exploration. 6- 7- 8— NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. SM Loose, very dark brown, silty SAND with organic material, moist. [TOPSOIL] Loose, light yellowish brown, gravely SAND with silt SM andcobbles. Moist [RECESSIONAL OUTWASH] Loose, very light yellowish brown, silty, gravely SAND. Sand SM is fine, gravel is coarse. Soil becomes less gravely below 3.0 feet, moist. I-1 1 0 20 40 60 80 100 Water Content (%) Plastic Limit ! --0 Liquid Limit Natural Water Content 5 6 7 HAND HOLE: 75th-76th Walkway Improvements HH-5 90 1 Meadowdale HMGEOSCONCH INC. Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171 -21 FIGURE: A-9 HANDHOL 2006-171-2LGPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/6/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/8/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 fU 1 3 1 4 DESCRIPTION Loose -medium dense, light olive gray, sandy SILT with organics. Soil was dumpy with some debris, moist. [COLLUVIUM[ - - - - - - - - - - - - - - - - - - - - - - Soft, light olive gray, silty CLAY. Chunks of silty sand, pieces ML of wood, and roots, moist. ---------------------- Loose, light gray to yellowish brown, silty CLAY, moist CL ML w U Ld m Z co W n D U L U U) Q Z F C ui H a- a c0 Z w 2 2 z 3 0 s O o cair U)i a TO O (7 S-1 O 0S2 5 S3 O 6 Hand hole terminated at 5.5 feet below surface level. No ground water seepage was encountered during exploration. 7- 8— NOTE: This log of subsurface conditions applies only at the speed location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. r— 0 k.l ' "—B 0 20 40 60 80 100 Water Content (%) Plastic Limit I --is Liquid Limit Natural Water Content HAND HOLE: 75th-76th Walkway Improvements HH-6 Meadowdale HMCIOSIMNCFS WC, Edmonds, WA PAGE: 1 of PROJECT NO.: 2006-171-21 FIGURE: A-10 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING CQMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/19/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/19/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 m z Ua w' L Q Non -Standard Penetration Resistance .-. w w (17.6 lb. weight, 22.6" drop) d 0 Z d 2 2 N z = O H o o DESCRIPTION ai ran 0af a. a O ( p 0 0 SM Loose, olive brown silty SAND with gravel, roots and rootlets present, moist. [FILL] 1 O S-1 � 1 2 :; '.: 2 3- 4- 5- 6- 7- Piece of old asphalt at 2.25 feet below ground surface. OS-2 Medium dense, gray gravelly fine to medium SAND with silt, roots and rootlets, moist. TOLD TOPSOIL] Hand hole was terminated at 3.0 feet below ground surface No ground water seepage was encountered during the exploration. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. 3 4 5 7 1 B 1 L 9 10 � 11 :A 12 13 14 0 20 40 60 BO 100 15 Water Content (%) Plastic Limit (--♦—i Liquid Limit Natural Water Content 75th-76th Walkway Improvements HAND HOLE: U01, I HH-7 Meadowdale HMGE0S(HNUS INC Edmonds, WA PAGE: 1 of 1 PROJECTNO.: 2006-171-21 FIGURE: A-11 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: t feet DATE STARTED: 10/19/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/19/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 w U Co 2 z -- Fa- L ILL!a Q Non -Standard Penetration Resistance (n rn �w (17.6 lb. weight22.V' drop)N Z H m w aa N n 3 o N D DESCRIPTION N y 0 a s O (9 a 0 0 SM Loose, light brown, silty SAND with gravel, roots and rootlets, moist. (FILL] A 1 1 OS-1 Alp 2 2 oose, brown, silty SAND with gravel, burnt wood bits, roots,3 ]!!]:�and rootlets, moist. O S-2 3 OLD TOPSOIL 4 Hand hole was terminated at 3.2 feet below ground surface. '» 4 No groundwater seepage was encountered during the exploration. A A: 5- 6- 7- 8- 9- 10- 11- 12- 13- 14- 15- I NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated 1\ and therefore may not necessarily be indicative of other times and/or locations. . : ...; .. ; ; ..If_10 11 12 13 14 �15 0 20 40 60 80 100 Water Content (%) Plastic Limit 1 0 I Liquid Limit Natural Water Content HAND HOLE: 75th-76th Walkway Improvements HH-8 gon Meadowdale HMGEO$CIENCH INC Edmonds, WA PAGE: 1 of 1 PROJECT NO.: 2006-171-21 FIGURE: A-12 HANDHOL 2006-171-21.GPJ 11/15/07 DRILLING COMPANY: HWA Geosciences Inc. SURFACE ELEVATION: i feet DATE STARTED: 10/19/2007 DRILLING METHOD: Hand Bucket Auger DATE COMPLETED: 10/19/2007 SAMPLING METHOD: GRAB LOGGED BY: D. Coltrane LOCATION: See Figure 2 N N U J_ O = m U F- rn uj a U)i D DESCRIPTION 0 1 2 3- 4- 5- 6- 7- 8 9 10 11 12 13 14 15 1.5 inches of Beauty Bark on surface. SM Loose to medium dense, olive brown, silty SAND with gravel, roots and rootlets, moist. pieces of plastic and cemented soils present [COLLUVIUM/FILL] ML Soft, to loose, layers of olive brown, sandy SILT with trace SM gravel, mottled olive brown fine silty SAND with rootlets, and grayish brown sandy SILT with trace gravel, roots, rootlets, and pieces of burnt wood present, moist. [COLLUVIUM] Hand hole was terminated at 11.25 feet below ground surface. Minor groundwater seepage from the excavation walls was observed during the exploration. of w U m a Z� W Q Non -Standard Penetration Resistance Z 0)r c_ � o (17.6 lb. weight, 22.6" drop) J J w N Z a 0. 2 2 z o w x D O (n ai a a O of a D S-1 D S-2 0 S-3 0S-4 0S5 NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated and therefore may not necessarily be indicative of other times and/or locations. L *:A A 0 1 2 HAND HOLE: 75th-76th Walkway Improvements HH-9 Meadowdale HMGEOSCIENCO INC. Edmonds, WA PAGE: 1 of , PROJECT NO.: 2006-17 1 -21 FIGURE: A-1 3 HANDHOL 2006-171-21,GPJ 11/15/07 Appendix B Geotechnical Laboratory Testing cn LO MENNEN 0 MENNEN Emmommmmmm ---------- � ®��- - - - � EMEMEMEME■ M �o O a rn (4o N N O > o o co �� o o c� a J a J J U g co 0 o 0 N N N N lD Z a c m 0 .o T a 0 o Z Q N L � Oa T Z T t6 C [0 O o m N 0 Q. N '- N U a M rn FFO LQ j ` 3 � x U u� �n � o � _ = Q) N a � o 0 W � ui o 0 a CO 0 O - rco 0 coJ � �_ J LL D c� CD O N 0 0 (O (Id) 0 C) 0 0 0 C7 N r- X3GNl AiIOIlSVld ■ U � U � J U 0 d N N N J � h N M U 0 Z O H U c� > cn g } J " g w w T N l4 �1 CM (0 -0Y .Y_. 0 U U U co c ILO N M N H d CD CD �n o � N co� N �a J d 0 N Q � m HQ� w �U)M LL J L.L d- VO RESUB . MEMORANDUM STREET FILE JUL 10 2008 MEMORANDUM I" o�rvo A ovr OFp0% To: Tani Stafford / Gray & Osborne Inc. From: Ralph Boirum / HWA GeoSciences Inc. Date: April 1, 2008 RE: 162ND STREET PARK WALL 76TH AVENUE WEST / 75TH PLACE WEST WALKWAY IMPROVEMENTS EDMONDS, WASHINGTON Development of the new park at 162nd Street in Edmonds will include a low (4-foot nominal) modular block (MSE) wall to retain fill along the north east corner of the park. The purpose of this fill is to weight the toe of the slope and increase the stability of an existing landslide. To further increase the stability of this slope, the wall will be founded on auger cast concrete piles. These piles will extend through the slide plane to bear in more stable soils. The following recommendations are presented for design and construction of the piles and retaining wall: ■ Auger cast concrete piles should be 24-inches in diameter on 6-foot centers, located along the centerline of the wall, • Concrete should achieve a 3,000psi 28-day compressive strength. ■ Piles should extend at least 10 feet below the existing grade. • A reinforcing cage consisting of four vertical No. 7 bars should extend to the bottom of each pile. ■ A 24-inch wide (minimum) footing/pile cap should extend across the tops of the piles to support the retaining wall. ■ Horizontal layers of geogrid consisting of Tensar BX-1200, or equivalent, should be placed across the top of the modular blocks and extending at least 5 feet into the fill at nominal depths of 16 and 36 inches below the top of the wall. ■ Prior to placing fill, a 12-inch thick layer of 1'/4-inch-minus crushed rock should be placed over the existing subgrade as a drainage layer. The crushed rock should contain no more than 5 percent fines (material passing the No 200 mesh sieve). ■ The crushed rock should be compacted to a dense and unyielding condition. ■ Fill consisting of spoil excavated from other areas of the project may be placed above the crushed rock, providing they are not too wet for proper compaction. ■ Fill should be compacted to at least 92 percent of its modified Proctor maximum density. ■ A 4-inch (minimum) diameter slotted plastic drain pipe should be placed in the crushed rock fill along the back of the retaining wall. This drain pipe may flow into the trench subdrain or to the storm drain system. SNOHOMISH COUNTY WASHINGTON 76TH AVENUE WEST / 75TH PLACE WEST WALKWAY AND 162ND STREET PARK PROJECT (MEADOWDALE BEACH RD TO NORTH MEADOWDALE ROAD) A u,r c.on drtiaY,s APPROVED BY PLANNING 2.G6Vw4v 09.2-4.09 - Planning Conditions ( gsuant to file #Sh1-2008-26 1 I .'JI lill >h::ll M: "n n:dia:+ 1 :❑r,:md ::ond::cnr.,l, ::4:rgiidshalim,icnni:un ,n_;rn:c ur im•:e:uti�: f:: Ih;,l wot lj he dci; nncnt it i.<i'I'he :\h;+I,,.ard shadl rn.ai:lc erne ar_n ,w the tcrst til,le o? the iur.k or on 6th Placo I0. om m thr.,'icinn,' cl' IL•: nne;ae rail crossing Ih;a -xatns %c;itors „I : 'nit" the n��hl-o . r: r "I I I 1, � ua_g• shall be ;d the :'ity's dsctct:on. 'I he t'ily n:c, r�n;al,: or In',00V the sign if the ,:;ro: w,,! u:c;:d die mil cro>e;nu cl,a:,ge, ;uc6 a.:; I;w use changes lrom lIc to ;,I mile. o! it ::;.I:IV deeI(,!:; or i., r:nanent 1,rim!es are inslalb;d. MICHAEL PLUNKETT PROJECT NO. E6DA/c245 CITY OFFICIALS GARY HAAKENSON 5Pmqt, t 5 peano�s � �11 N I N61 o ftu.• ('.0Nyt11.}� vk �ric�u 67 Akfi&e0pvOr Pato4 6*0 OE4 Pj 3lVocwm,1- eaq,5 aaA DMNr0Zl PI,ALY.W VI�r W PIL& Z 4*wA,nn",3 4 3 h NW WAD147 A . MAYOR SUBMIT ALL SPECIA L INS PEc - - •":� REPORTS TO CI TY Y BUILDING INSPECTOR ON A WEEKLY BASIS T FILE zo�_611 ga bI -U35 1l RESUB JAN 2 0 2009 BURMEFA&Wr FiESU6 JUL ��pp�� 10 2gq0'��08 �OrTYNOF ONWir DEAN N A DAWSON RON WAM BOLT PEGGY PRITCHARD OLSON D.J. WILSON STEVE BERNHEIM DAVID ORVIS COUNCIL MEMBER NOEL MILLER, PE PUBLIC WORKS DIRECTOR Sc� C3 APP V AS NUTED GINEERING 7 c D 400 `OaVlfty 8C 08b030ne, Inc. CONSULTING ENGINEERS 701 DEXTER AVENUE NORTH SUITE 200 SEATTLL WASHINGTuN 98109 (206) 284-0880 BRIAN KcINTOSH PARKS, RECREATION & CULTURAL SERVICES DIRECTOR i� - SYMBOL LEGEND ABBREVIATIONS AVE AVENUE EXISTING PROPOSED DESCRIPTION AC ASBESTOS CEMENT PIPE ADJ ADJUST w` •?'<,; ASPHALT CONC. PAVEMENT/ ALT ALUM ALTERNATE ALUMINUM ASPHALT WALKWAY ANSI AMERICAN NATIONAL STANDARDS INSTITUTE AP ANGLE POINT �-� ;.w�;.;A+n, GRAVEL SURFACING ASPH ASPHALT ASTM AMERICAN SOCIETY OF TESTING AND MATERIALS �;---� 1=� CONCRETE SURFACING ASSY ASSEMBLY BF BLIND FLANGE ® CEMENT CONCRETE SIDEWALK BLDG BUILDING BLK BLOCK BO BLOW OFF — CURB BVCE BEGIN VERTICAL CURVE ELEVATION BVCS BEGIN VERTICAL CURVE STATION RIGHT-OF-WAY LINE CTR CENTER -- -- - -- - - CAP CORRUGATED ALUMINUM PIPE CB CATCH BASIN CENTERLINE OF ALIGNMENT CI CAST IRON CENTER LINE CLR CLEARANCE CONTOUR LINE CMP CORRUGATED METAL PIPE CO CLEANOUT E BURIED ELECTRICAL CONIC CONCRETE C CONDUIT T BURIED TELEPHONE CONN CONNECTION CONTR CONTRACTOR W WATER MAIN (SIZE AS NOTED) CONT CONTINUOUS CPLG COUPLING G GAS MAIN CY CUBIC YARD CONT CONTINUED S —+- S -y SANITARY GRAVITY SEWER CL CLASS CIF CUBIC FEET --- F--- SANITARY FORCE MAIN CFS CUBIC FEET PER SECOND DC DEGREE OF CURVATURE D D STORM DRAIN (SIZE AS NOTED) DI DUCTILE IRON DIA DIAMETER DITCH DOT DEPARTMENT OF TRANSPORTATION DIM DIMENSION DWGS DRAWING(S) }--D CULVERT (SIZE & TYPE AS NOTED) D DRAIN EDP EDGE OF PAVEMENT E EAST y ---ar- FENCE (TYPE AS NOTED) EA EACH EL ELEVATION EL ELBOW © POWER VAULT ELEC ELECTRICAL EVCE END VERTICAL CURVE ELEVATION _ ELEC END VERTICAL CURVE STATION ® TELEPHONE VAULT EXIST EXISTING FIG FIGURE FIN FINISHED 0 MANHOLE FL FLANGE FT FEET 0 CATCH BASIN F FORCE MAIN GA GALV GAUGE GALVANIZED ® ® STORM DRAIN MANHOLE GI GALVANIZED IRON GV GATE VALVE POLE WITH GUY WIRE HDPE HIGH DENSITY POLYETHYLENE PIPE HMA HOT MIX ASPHALT BY OTHERS INSIDE DIAMETER -0- POWER / TELEPHONE / GUY POLE ID E INVERT ELEVATION INV INVERT INCH ¢--� LUMINAIRE L LENGTH LB POUND LF LINEAR FEET JX YARD LIGHT MAX MAXIMUM MFR MANUFACTURER MH MANHOLE ® PEDESTAL (AS NOTED) MIN MINIMUM MJ MECHANICAL JOINT DG GATE VALVE , MISC MISCELLANEOUS N NORTH ® 0 WATER METER NO NUMBER NTS NOT TO SCALE 11 OC ON CENTER t FIRE HYDRANT OD OUTSIDE DIAMETER PI POINT OF INTERSECTION o _ MAIL BOX (NOTED) PP POWER POLE PM POINT OF VERTICAL INTERSECTION a SIGN PE PLAIN END PERF PERFORATED D PVC POLYVINYL CHLORIDE PVMT PAVEMENT TREE (CONIFER) PVT POINT OF VERTICAL TANGENT PC POINT OF CURVATURE PT QTY POINT OF TANGENCY QUANTITY TREE (DECIDUOUS) R RADIUS RED REDUCER r^� SHRUBS REINF REINFORCE REOD R/W REQUIRED RIGHT-OF-WAY SL SLOPE BUILDINGS S SOUTH SCH SCHEDULE' SF SQUARE FEET C3mcm ROCK WALL SHT SHEET SPECS SPECIFICATIONS MODULAR BLOCK WALL SQ SQUARE STA STATION STD STANDARD ® ® SOLDIER PILE WALL TC TOP OF CURB TEL TELEPHONE ® GRAVITY BLOCK WALL THRU THROUGH TYP TYPICAL PILE SUPPORTED WALKWAY VERT VERTICAL W W/ WEST WITH — C— TOP OF CUT W/O WITHOUT — I— TOE OF FILL WHATCOM PEND OKANOGAN •REI FERRY SKAGIi STEVEN �LA I CLALLAM o SNOHOMISM XFFERSON CHELAN ATRE uANE DDGcs uHCOLN IAASON KING SPOKANE I GRAYS CRANT HARBOR PIERCE KITTiTAS I GYM IA ADAMS WHITMAN TH RST PAC7Fl LEW9S FRANKU RFl AHKIAI(M YAKIMA UMBIA WU SKAMANIA BENTON WALLA WALLA ASOTIN K KUCKITAT-- i VICINITY MAP NOT TO SCALE INDEX SHEET NO. DESCRIPTION G-1 VICINITY & LOCATION MAPS, SYMBOL LEGEND, ABBREVIATIONS, & INDEX G-2 SURVEY CONTROL, CENTERLINE ALIGNMENT, AND SITE MAP SCHEDULE Al TO Aar WALKWAY C-1 TO C-7 PLAN AND PROFILE C-8 EROSION CONTROL DETAILS C-9 INTERSECTION CONTROL C-10 DRIVEWAY PROFILES C-11 TO C-12 STORM DETAILS C-13-C14 TYPICAL WALKWAY SECTION C-15 WALKWAY DETAILS C-16 TO C-18 MISCELLANEOUS DETAILS C-19 GRAVITY BLOCK RETAINING WALL DETAILS C-20 MODULAR BLOCK WALL PROFILE C-21 MODULAR BLOCK WALL AND ROCK WALL DETAILS C-22. TO C-25 CHANNELIZATION & SIGNING PLAN C-26 CHANNEUZATION & SIGNING DETAILS C-27 TO C-30 CROSS SECTIONS LA-1 TO LA-3 WALKWAY PLANTING PLAN S-1 GENERAL STRUCTURAL NOTES AND TYPICAL DETAILS S-2 TO S-3 SOLDIER PILE WALL PROFILE S-4 SOLDIER PILE WALL DETAILS S-5 TO S-6 WALKWAY FRAMING PLAN S-7 TO S-10 ELEVATED WALKWAY DETAILS S-11 PARK WALL PROFILE AND DETAILS SCHEDULE Be PARK L-1 TESC PLAN L-2 DEMOLITION PLAN L-3 SITE PLAN L-4 GRADING AND DRAINAGE L-5 SITE LAYOUT L-6 PLAY AREA LAYOUT AND GRADING L-7 SWING AREA LAYOUT, GRADING AND DETAILS L-8 TO L-9 PLAY AREA DETAILS L-10 TO L-11 SITE DETAILS L-12 PLANTING PLAN L-13 PLANTING DETAILS IGATIDN PL ON SCHEDULE D NOTES IRRIGATIO LS LOCATION MAP NOT TO SCALE 0 1' 2' TWO INCHES AT FULL SCALE IF NOT, SCALE ACCORDINGLY I V) r W z %I z 4 rw W 0 y: b! m � S 0 d J z Li � 1- > i r/i o c� i X W o Z 3w = z c0 J F aD �Z day1-20 0; H Z W Ga to C4 c ~�0km W W m ;ZO.O0. IIjin > } Q 2 H c�� x � ->o m.3 s SHEET: G-1 OF: 2 JOB NO.: 06713 _ DWG: \PLANSET\LEGEND 6' PERFORATED FINGER DRAIN SEE NOTE 6 6` UNDERDRAIN PIPE PER SHEET C-11 6'X6' TEE O 25' 2'-3'X12' PILE CAP #3 p STIRRUPS O 02006 Edition IRC w/WAC Amendments 2' CL TYP. B" D.C. )92006 Edition, IBC /�w/WAC Amendments 4 - #5 BARS CONT. 02006 Edition UPC W/WAC Amendments EQ. SPACED TOP & BOT. and Appendices A, B• C4 I 02006 Edition UAC�.w/WAC Amendments 02006 Edition IFOC w/WAC Amendments O02006 Edith IFC w/WAC A nwndments Cl' CONC. AUGER CAST I_ES 0J2006 Edition VIAQ WAC C 1-13 11 W/4 W/4 - /7 VERTS (W/10' MIN HOOKS I a PILE GAP) �2006 Edition WSBC WAC 51-11 k M3 ©TIES (4 O 6' O.C. TOP k/�/vp��}J{`G BALANCE O 12` O.C.) `" - _ "�•V �� I 1 f��1'l/1//A/EjG/1sfCG�i��rilt� CONCRETE FOOTING/WALL CAP DETAIL SCALE: 3/4`=1' 5 j ^6d lxi - TOPSOIL/BARK MATCH PER PLANTING PLAN. 4 HIGH CORNER R _+.. ..I�,.. j DRAINING GRANULAR FILL 4" HIGH CORNER PER THE MANUFACTURES STONE MODULAR RE MMENDATIONS BLOCK UNIT (TYP.) 8* HIGH CORNER MA, Wete't STONE MODULAR 11 MATERIAL FOR-ERI 12` CAST IN PLACE Q WALL DRAIN „a5 ion ditt m4- CONCRETE FOOTING/WALL CAP O o APPROVED BY PLANNING U ro z Z - �Ci ���i�•�i� O I AUGER CAST PILE PCX SM^ 0 U^ ! 6`X6" TEE O 25' O.C. NOTES: 1. SET REBAR CAGE IN PRE -DRILLED LEAN CONCRETE (1.5 SACK MIX) CASING. CHIP & 2. PROVIDE FREE DRAINING BACKFILL FOR 1'-6` MAX. BEHIND WALL 3. PILES SPREAD AT 6' ON CENTER UNLESS OTHERWISE NOTED ON THE PLANS. 4. ALTERNATE COURSES OF 8' HIGH AND 4` HIGH CORNERSTINE MODULAR BLOCK UNITS. 5. PILES SHALL EXTEND 10 FEET INTO EXISTING GROUND. S. 6` DIA. PERFORATED FINGER DRAIN SHALL CONNECT WALL DRAIN BEHIND WALL TO UNDER DRAIN PIPE IN FRONT OF WALL AT 25 FOOT INTERVALS ALONG THE WALL, FROM STA 0+00 TO STA. 1+25 7. PIPE FOR WALL DRAIN, FINGER DRAIN AND UNDERDRAIN SHALL BE 6` DIA. PERFORATED HIGH DENSITY POLYEVYLENE, CORRUGATTED PIPE WITH SMOOTH INTERIOR. B. HORIZONTAL LAYERS OF GEOGRID, TENSAR SX-1200 OR EQUAL SHALL BE PLACED ACROSS THE TOP OF THE MODULAR BLOCKS AND EXTEND 5 FEET INTO THE FILL AT NOMINAL DEPTHS OF 16 AND 36 INCHES BELOW THE TOP OF WALL. PILE SUPPORTED PARK RETAINING WALL SECTION NOT TO SCALE ems" �9 3� 8 r O a� �Ol�p 8 7�NN $^�co z an a �o M(AzW Wm a.ZW PARK WALL PLAN SCALE: 1`=20' 66......: . ... 66.. i T.O.W. EL-53.00 ; .. ..: ... ...... ..... .. .. . . IrLLIT 0 W. EL=51.00 60 ; ..... .......:.:.........:...... . :. ; .............. T.O W: EL=49:00 : .. ............................. ........ yo0onNc.' ' i I I I I T Rwr EL=46 00 .. 46=ae:oo: .. 46 • EXI6•TMIG iG,RAOE AT..: e :.: gorr(W (V WALL (TYI► )::.:. i 40 € FINISHED GRAi AT :::::: 40 _......... 90TTOM gF wntLf�Yw)..... .. 36 Ni o0 a.804 I`o ao a.� z a" z N m a Z W 6 R m PARK WALL PROFILE APPROX. STA 00+00 TO APPROX STA 01+66 HORIZONTAL SCALE: 1`-20' VERTICAL SCALE: 1`-5' STREET FILE -U3 Mo 0 .�� �� N O Lo ui 0 20 2009 7N pM� n o E1m:nzw zw JUL 10 2008 0 1` 2' TWO INCHES AT FULL SCALE. IF NOT, SCALE ACCORDINGLY 8 p o N N U 0 Z ZZ yy Z 3 U a w a o `Ji' o �i a II— J .w vi z ccW 0 11- dN Z 3 I— C 0 moo i-- Z W < W ~�0 IL= T+zbe IC = <cc IL �Lu N <ad a V a be d SHEET: s-11 OF: 11 JOB NO.: 06713/STRUCT DWG: WALL -PROFILES i �ia<-Ply 4#3 754di /�W