The URL can be used to link to this page

BLD20100984.pdfSTATUS: ISSUED 2/22/2011 Expiration Date: 2/22/2012 Parcel No: 00434209100500 CITY OF EDMONDS 121 5TH AVENUE NORTH - EDMONDS,WA 98020 PHONE: (425) 771-0220 - FAX: (425) 771-0221 Permit #: BLD2010' 4841 Project Address: 710 ALDER ST, EDMONDS' ALLAN S& HEATHER TOWNSEND THE LEREN CO. INC. CASCADE GENERAL CONTRACTINGINC. 710 ALDER ST PO BOX 12863 PO BOX 6773 EDMONDS, WA 98020-3416 MILL CREEK, WA 98082- LYNNWOOD, WA 98036- (425) 712-8086 Ext. (425) 776-6007 Ext. (425) 754-5885 Ext. LICENSE #: CASCAOC980QK EXP: 12/21/2012 129 SQ FT ADDITION AND REMODEL. VALUATION: $133,158 PERMIT TYPE: Residential PERMIT GROUP: 02 - A ti Kin imUn GRADING: N CYDS: 0 TYPE OF CONSTRUCTION: RETAINING WALL ROCKERY: N OCCUPANT GROUP: OCCUPANT LOAD: FENCE: N ( 0 X 0 FT.) CODE: 09 OTHER: N ------- OTHER DESC: ZONE: RS -6 NUMBER OF STORIES: 0 VESTED DATE: NUMBER OF DWELLING UNITS: 0 LOT #: BASEMENT: 870 IST FLOOR: 1456 2ND FLOOR: 0 BASEMENT: 0 IST FLOOR: 129 2ND FLOOR: 0 3RD FLOOR: 0 GARAGE: 600 DECK: 0 OTHER: 0 13RD FLOOR: 0 GARAGE: 0 DECK: 0 OTHER: 0 tEQU1RED: N = 20' PROPOSED: 20'+ REQUIRED: W = 5' PROPOSED: 5' JREQUIREMS= 15' PROPOSED: 15'+ IEIGHT ALLOWED:25 PROPOSED:24.8 REQUIRED: E = 5' PROPOSED: 5.5' >ETBACK NOTES: I AGREE TO COMPLY WITH CITY AND STATE LAWS REGULATING CONSTRUCTION AND IN DOINGTHE WORK AUTHORIZED THEREBY, NO PERSON WILL BE EMPLOYED IN VIOLATION OF THE LABOR CODE OF THE STATE OF WASHINGTON RELATING TO WORKMEN'S COMPENSATION INSURANCE AND RCW 18:27. THISAEUIQATION ISNQT A PERMIT UNTIL SIGNED BY THE BUILDING OFFICIAL OR 141. �R DEPUTY AND ALL FEESARE PAID (et" - z e -A tl ====�l p lamo I Sip tuie Print Name ate eleas d By Date ATTENTION ITIS UNLAWFUL TO USE OR OCCUPY A BUILDING OR STRUCTURE UNTIL A FINAL INSPECTION HAS BEEN MADE AND APPROVAL ORA CERTIFICATE OF OCCUPANCY HAS BEEN GRANTED. UBC 109/ IBCI 10/ IRCI 10. = ONLINE L7_1 APPLICANT = ASSESSOR OTHER � STATUS: ISSUED BLD20100984 • Critical Areas Conditions: -Follow the recommendations in the geotechnical report dated 7/8/09 and memorandum dated 12/22/10 by Nelson Geotechnical Associates, Inc. - Use Best Management Practices for protection of the stream. - Construction materials and equipment shall be stored within the existing driveway or in the backyard and shall not otherwise be stored between the house and stream • House is not approved to contain an Accessory Dwelling Unit (ADU). • Lot line stakes must be in place at the time of foundation/setback inspection. • Obtain Electrical Permit from State Department of Labor & Industries. 425-290-1309 • Submit all special inspection reports to the City Building Inspector on a weekly basis. • Final approval on a project or final occupancy approval must be granted by the Building Official prior to use or occupancy of the building or structure. Check the job card for all required City inspections including final project approval and final occupancy inspections. • Any request for alternate design, modification, variance or other administrative deviation (hereinafter "variance") from adopted codes, ordinances or policies must be specifically requested in writing and be called out and identified. Processing fees for such request shall be established by Council and shall be paid upon submittal and are non-refundable. Approval of any plat or plan containing provisions which do not comply with city code and for which a variance has not been specifically identified, requested and considered by the appropriate city official in accordance with the appropriate provision of city code or state law does not approve any items not to code specification. • Sound/Noise originating from temporary construction sites as a result of construction activity are exempt from the noise limits of ECC Chapter 5.30 only during the hours of 7:00am to 6:00pm on weekdays and 10:00am and 6:00pm on Saturdays, excluding Sundays and Federal Holidays. At all other times the noise originating from construction sites/activities must comply with the noise limits of Chapter 5.30, unless a variance has been granted pursuant to ECC 5.30.120. • Applicant, on behalf of his or her spouse, heirs, assigns, and successors in interests, agrees to indemnify defend and hold harmless the City of Edmonds, Washington, its officials, employees, and agents from any and all claims for damages of whatever nature, arising directly or indirectly fromthe issuance for this permit. Issuance of this permit shall not be deemed to modify, waive or reduce any requirements of any City ordinance nor limit in any way the City's ability to enforce any ordinance provision. • REQUIRED SPECIAL INSPECTIONS FOR TMS PROJECT: 1) Excavation, grading, & site preparation 2) Soil bearing verification 3) Placement of fill & compaction 4) Footing drain 5) Temporary Erosion Control 6) Final Erosion Control 7) Site retaining wall/ rockery construction. 8) General site monitoring 9) Final letter from geotechnical engineer of record • Maintain erosion & sedimentation control per city standards. THIS PERMIT AUTHORIZES ONLY THE WORK NOTED. THIS PERMIT COVERS WORK TO BE DONE ON PRIVATE PROPERTY ONLY. ANY CONSTRUCTION ON THE PUBLIC DOMAIN (CURBS, SIDEWALKS, DRIVEWAYS, MARQUEES, ETC.) WILL REQUIRE SEPARATE PERMISSION. PERMIT TIME LIMIT. SEE ECDC 19.00.005(A)(6) CALL FOR INS PECTIONS BUQJDING 425 771-0220 EXT. 1333 ENGINEERING 425 771-0220 EXT. 1326 FIRE 425 775-7720 PUBLIC WORKS 425 771-0235 1 PR&TREATMENT 425 672-5755 1 RECYCLING 425 275-4801 When calling for an inspection please leave the following information: Permit Number, Job Site Address, Type of Inspection being redmested Contact Name and Phone Number, Date Prefereed and whether you arefer mornine or afternoon. B•Erosion Control/Mobilization • B-Fngineering Final • B-Setbacks • &Footings • B-Foundation Wall B-Foundation Drainage • B-Slab Insulation B-Plumb Rough In • B-Gas Test/Pipe • B-Mechanical Rough In • B-Roof Sheathing • B-Height Verification B-Framing • B-WallInsulation/Caulk • B-Insulation/Energy • B-Sheetrock Nail • B-Roof Tear Off • B-Building Final Inspection Comments BLD20100984 02 - Addition Applied: 12/22/2010 Issued: 02/22/2011 Expires: 02/22/2012 Address: 710 ALDER ST, EDMONDS INSPECTION DATE INSPECTOR ACTION 1001 - E-Erosion Control/Mobilization 06/13/2011 ZULAUF CMP Comment: ok to final 1077 - E-Engineering Final 06/13/2011 ZULAUF CMP Comment: ok to final 1106 - B-Setbacks 02/23/2011 LAWLER CMP Comment: 1108 - B-Footings 02/23/2011 LAWLER CMP Comment: 1110 - B-Foundation Wall 02/23/2011 LAWLER CMP Comment: 1126 - B-Plumb Rough In 03/18/2011 STEINIKE CMP Comment: 1128 - B-Gas Test/Pipe 03/23/2011 LAWLER CMP Comment: 1130 - B-Mechanical Rough In 03/23/2011 LAWLER CMP Comment: 1132 - B-Exterior Wall Sheathing 03/22/2011 LAWLER CMP Comment: and retrofit holdowns 1133 - B-Roof Sheathing 03/22/2011 LAWLER CMP Comment: 1140 - B-Height Verification 04/05/2011 STEINIKE COM Comment: Letter received but needs to be signed. 1140 - B-Height Verification 06/20/2011 STEINIKE CMP Comment: 1142 - B-Framing 04/06/2011 STEINIKE COM Comment: OK but need letter for height verification. 1142 - B-Framing 06/20/2011 STEINIKE CMP Comment: 1144 - B-Wall Insulation/Caulk 04/06/2011 STEINIKE CMP Comment: 1150 - B-Sheetrock Nail 04/12/2011 STEINIKE COM Comment: Still have outstanding corrections from Frame inspection. 1150 - B-Sheetrock Nail 06/20/2011 STEINIKE CMP Comment: 6/20/2011 10:45:38 AM Page 1 of 2 Fi SPECTION _ DATE INSPECTOR ACTION 1158 - B -Building Final 06/09/2011 STEINIKE PAR Comment: Still waiting on height check letter and final engineering approval. 1158 - B -Building Final Comment: 06/20/2011 STEINIKE CMP 6/20/2011 10:45:38 AM Page 2 of 2 OV EDVO �p° SPECIAL INSPECTION AND TESTING AGREEMENT 1..., Permit #: ,poi- 6 I Project: Adgt-fire„�,�. Fsr. 7 89� Prior to issuance of a permit, this forte must be completed in its entirety and returned to the City for approval. The completed form must have signatures of acknowledgment by all parties. DUTIES AND RESPONSYBMITIES Special Inspection Firm. and Special Inspectors: The Special Inspection firm of S""— n,�) will perform special inspection for the following types of work (separate forms must be submitted if more than one firm is to be employed): ❑ Reinforced Concrete ❑ Bolting in. Concrete ❑ Prestressed Concrete ❑ Shotcrete ❑ Structural Masonry ❑ Structural Steel/Welding ❑ High Strength Bolting ❑ Spray applied Fireproofing ❑ Smoke Control Systems ❑ Lateral Wood ❑ Structural Observation X Grading/soils ❑ Other ❑ Other All individual inspectors to be employed on this project will be WABO certified for the type of work they are to inspect. If inspection is for work that is not covered by the WABO categories, or the inspector is not WABO certified, a detailed resume of the inspector and firm must be submitted. The resume must show that the inspector and the firm are qualified by education and experience to perform the work and testing required by the project design and specifications. The work shall be inspected for conformance with the plans and specifications approved by the City. Revisions and addenda sheets will not be used for inspection, unless they have been approved by the City. Inspection records shall include: A daily record to be maintained on site, itemizing the inspections performed. Any nonconforming work shall be brought to the immediate attention of the contractor for. resolution. A weekly report shall be submitted to the City; detailing the inspections and testing performed, listing any nonconforming work and resolution of nonconforming items. A final report shall be submitted to the building department prior to the Certificate of Occupancy being issued. This report will indicate that inspection and testing was completed in conformance with the approved plans, specifications and approved revisions or addenda. Any unresolved discrepancies must be detailed in the final report. RECEIVED L•�Building New Folder 2010\FormslSpc6al inspection form.doclo/25/2010 C. ®ry FvB 0/ 2011 DEVELOPMENT SERVICES COUNTER Contractor: The contractor shall provide the special inspector or agency adequate notification of work requiring inspection. The City approved plan and specifications must be made available, at the jobsite for the use of the special inspector and the City inspector. The contractor shall maintain all daily inspection reports, on site, for review by all parties. The special inspection functions are considered to be in addition to the normal inspections performed by the City and the contractor is responsible for contacting the City to schedule regular inspections. No concrete shall be poured or other work covered until approval is given by the City inspector. Buildine Department: The building department shall review any revisions and addenda. The City inspector will monitor the special inspection functions for compliance with the agreement and the approved'plans. The City inspector shall be responsible for approving various stages of construction to be covered and for work to proceed. Design.Professionals: The architect and/or engineer will clearly indicate on the plans and specifications the specific typcs of special inspection required. and shall include a schedule for inspection and testing. The architect and/or engineer will coordinate their revision and addenda process in such a way as to insure that all required City approvals are obtained, prior to work shown on the revisions being performed in the field. Owner: The project owner, or the architect or engineer acting as the owners agent, shall employ the special inspector or agency. ENFORCEMENT A failure of the special inspector or firm to perform in keeping with the requirements of the IBC, the approved plans and this document, may void this agreement and the Building Official's approval of the special inspector. In such a case a new special inspector and/or firm would need to be proposed for approval. A failure of the design and/or construction parties to perform in accordance with this agreement may result in a STOP WORK notice being posted on the project until nonconforming items have been resolved. ACKNOWLEDGMENTS I have read and agree `to comply with the terms and conditions of thi eeemment Owner:klllm / s'G� V� se ••l ` Sigaatur �i'/� Date /1 Y l2D M GXn�! Special Insp.-K"!14 at,� 69pnature fit. �J Sar% 6c= T ACCEPTED rA'R�T�HE CITY OF EDMONDS BUILDING DEPT, By: Dater LABAding New Folder 20107ormslSpeciul inspection rorm.docl0/25/2010 Date: 'hr- .11 Date: J 4 L ,Date: RECEIVED FEB 04 2011 Co"PV DEVELOP ENT S RV16ES r:y N_z �10 k"rn�� 10 C. FL� rrt�OxOrtl cn m -n 3 �.1o71 Oi Q) m u a� rn x — x C O ? rt <� sa r ii Ul Q. m N N rn O rn Y M -S, 00 rnrn vv U3 �v r .ni �v o LO r�r Or F-1 rnrn xz rn z-1 Orn v �rn DO �rn d ON O� Q m m m rn x x x x zz26z OiOiOOO vvNa 70rn--ivr N rn rn R1rn� a r- -0 m �D ti r- zion X O U►z�izp —Z0 n O� p� a1 (1 rn N N K3 7C' 3 rn -3 l7i �N1�D O �OiA 3 Oz fD rt tttN �1D ND O 3U'O z �O Dt z Orn i O rnz OzN p Or z >m r rn(j) v> X rn x—i 00 O O Ov AJOa N1 D 6 r 0 N N (D ttipi5tD- w :K I- NZrZ c, (j) M rtl O O z rn 'a ca O rt O O_ a CL � N H O rrr CA ME PIL m GO 9,uapa ;uamaoiow onto:«t:as e;c, ie a aq Au uor;z uoo 44 aatyaatP 7u!pltnq t a% 'SuWWP io uejda;ra atP uo UALOW ar uotltpuoa io aininals ,Bm t� gatta =Mq#A JO $NJpig-8aa 'nopoz!ldds;ice sa<T ap jo adooi otp opcsano s!cp �qm uoflipuoo 84ts Jr WnPnos lutpitnq pamm t.-Aun xo 2u juuojuoouou ablu lU -u `a Spuw ?no Amjc, aotmu9;umrr aip 2mli ;tuad .to 8u!.wol{e y: Ma cL igt.,t aq IMT. sea's�r gs.;F,,ids:� 41 t;A stEn ur Iuctpojq OV F u,yo City of Edmonds CJ -� "�, Site Classification Worksheet - �n�. i x90 The project's Classification serves to identify the specific Stormwater Management requirements applicable to your site. Complete the worksheet below to determine whether your project falls into the classification of a Larae Site, Small Site (Category 1 or Category 2), or a Minor Site. Sten 1: Determine the Exempt Impervious Surface Area for your project and enter it on line 1 of the table (yellow box). Sten 2: Determine the Replaced Impervious Surface Area for your project and enter it on line 2 of the table below dividing the total between Exempt and Non -Exempt (orange and blue boxes); either or both may be zero. Sten 3: Determine the New Impervious Surface Area for your project. If a portion of the new impervious surface area is also Non -Exempt Replaced Impervious Surface Area subtract this from the total of the new impervious surface area. Enter the final value on line 3 of the table below (blue box). Sten 4: Add the values in the Non-exempt column for lines 2 and 3 and enter it into line 4 (green box). Where does the existing site runoff discharge? (Check all that apply) See Watershed Map Fi re -B, Handout 4 Supplement Chapter 2.3 ❑ Direct Discharge ❑ Edmonds Way Basin ❑ Creek or Lake Basin Line Type Area (square Feet) Impervious surface: How much and what type? (fill in colored boxes) See Definitions, Handout pg 9 Figure -C, Handout pg 7 Supplement Chapter 2.2 & Figure -C 1• Exempt 2 Eyxwem t Non -Exempt z .,,�ero-••t'.,'dg `+r* _. 7y fit , Replaced 16 Examples, Handout pg 10 3. New /5!% 4• Total Replaced +New (Non -Exempt) = n . (add numbers in blue boxes) Land -disturbing activity area See Definitions, Handout pg 9 Supplement Chapter 8 sf Grading, Fill or Excavation Area I�2 sf roject convert % acre or of native vegetation to E ❑ YES NO n or landscaped area? Proceed to the Proiect Classification Chart (Figure D, pg 8) and use the data collected above to follow the flow chart and determine the classification of your project. � ❑ Large Site (Handout E72a) El Small Site (Handout E72b) `��girg gtL �. t V( ®c) C ffy 2 2oio Revised on 719110 E72 - Stonnwater Management Erosion Control-FINAL2 Page S of 11 'k6EYEl2FFfi'ft' T -SERVIDES DT•!3. �I SSV OF.E[ifdDND.S This page intentionally left blank. Revised on 719110 E72 - Stormwater Management Erosion Control-FINAL2 Page 6 of 11 NELSON GEOTECHNICAL 11 � A ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office Engineering-Geology Branch 17311 —135"' Avenue NE, A-500 437 East Penny Road Woodinville, WA 96072 Wenatchee, WA 98801 (425) 486-1669 FAX(425)481-2510 (509) 665-7696 FAX (509) 665-7692 (425) 337-1669 Snohomish County RECEIVED MEMORANDUM DEC 2 2 2010 DEVELC 7Y CTR. OF EDMONDS DATE: December 22, 2010 W TO: Mr. Allen Townsend ��r�of '9'Q JZ f Zzl%D CC: Mr. Tom Leren — The Leren Company, Inc. FROM: Khaied M. Shawish, PE �. Updated Foundation Support Recommendations Townsend Addition 710 Alder Street Edmonds, Washington NGA File No. 813009 This memorandum provides our updated foundation recommendations for your single family residence addition project located at 710 Alder Street in Edmonds, Washington. We previously prepared a geotechnical engineering evaluation report dated July 8, 2009 which provided recommendations for site development. We understand that plans have changed from constructing a basement addition to constructing a 4 -foot by 30 -foot addition along the south side of the upper floor. For our use in preparing this memo, we have been provided with a site plan and Plan Sheets 1 through 6 titled "Townsend Residence," dated July 14, 2010, prepared by The Leren Company, Inc. The plans indicate that the new addition foundation will consist of a monopour thickened edge foundation. The new slab/foundation will also be connected to the existing concrete retaining wall through rebar dowels. Our previous explorations encountered up to seven feet of loose fill underlying the proposed new addition area, which is most likely wall backfill. We recommend that the new foundations bear on competent native material or structural fill extending down to competent soil. Alternatively, the new addition footings could be supported on pin piles driven through the loose fill and terminating into the native material. We recommend that we be retained at the beginning of construction to observe the foundation subgrade prior to the placement of concrete forms. Upon our observation of the foundation subgrade, we Townsend Addition Edmonds, Washington December 22, 2010 NGA File No. 813009 Page 2 can provide specific recommendations for the different foundation support options. We must observe and approve the foundation subgrade in writing prior to placement of any concrete for this memorandum to be valid. We trust this memorandum should satisfy your needs at this time. Please contact us if you have any questions or require additional services. NELSON GEOTECHNICAL ASSOCIATES, INC. GEOTECHNICAL ENGINEERING EVALUATION TOWNSEND RESIDENCE ADDITION 71.0 ALDER STREET EDMONDS, WASHINGTON FOR MR. ALLAN TOWNSEND NELSON GEOTECHNICAL N G A ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office 17311 — 135"' Avenue NE, A-500 Woodinville, WA 98072 (425) 486-1669 FAX (425) 481-2510 (425) 337-1669 Snohomish County July 8, 2009 Allan Townsend 710 Alder Street Edmonds, Washington 98020 Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, Washington NGA File No. 813009 Dear Mr. Townsend: Engineering -Geology Branch 437 East Penny Road Wenatchee, WA 98801 (509) 665-7696 FAX (509) 665-7692 We are pleased to submit the attached report titled "Geotechnical Engineering Evaluation — Townsend Residence Addition — 710 Alder Street — Edmonds, Washington." This report summarizes the existing surface and subsurface conditions within the site and provides recommendations for the proposed site development. Our services were completed in general accordance with the proposal signed by .you on June 13, 2009. The site generally slopes gently to steeply dowri from the southern property line to the northern property line along Alder Street. The site is currently occupied by a single-family residence with a basement and associated concrete driveway. The planned improvements will include removal and reconstruction of the upper level of the residence and extending the existing basement foundation along the south side of the residence. Cuts on the order of eight feet will be needed for the basement addition. A shoring wall is anticipated along the eastern property line for the excavation of the basement. Stormwater is proposed to be directed to an existing stormwater system. We performed four hand auger explorations within the proposed development area. We have concluded that the site is generally compatible with the planned development. We have recommended that the new addition be founded on medium dense or better granular native soil for bearing capacity and settlement considerations. Our explorations indicated that the site is underlain by advance outwash and transitional bed deposits. The site slope appears to be stable under current conditioins. However, there is a potential for shallow sloughing and erosion events to occur on the steep slope. The new addition is planned to be within approximately 17 feet from the toe of the steep slope. It is our opinion that these setbacks are adequate provided that all of the recommendations presented in this report are incorporated into the plans and followed during construction. In the attached report, we have included recommendations for site grading, foundation support, retaining walls and site drainage. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Summary - Page 2 We recommend that NGA be retained to review the geotechnical aspects of the project plans prior to construction. We recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated; and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. We appreciate the opportunity to provide service to you on this project. Please contact us if you have any questions regarding this report or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Khaled M. Shawish, PE Principal Three Copies Submitted cc: Tom Leren — The Leren Company, Inc. via email TABLE OF CONTENTS INTRODUCTION.......................................................................................................................................1 SCOPE.........................................................................................................................................................1 SITECONDITIONS...................................................................................................................................2 SURFACECONDITIONS ................................. ..............................................................................................2 SUBSURFACECONDITIONS.........................................................................................................................2 HYDROLOGIC CONDITIONS...............................................................:...:....................................................3 SENSITIVE AREA EVALUATION.........................................................................................................4 SEISMIC HAZARD..................................................................................................... ................................... EROSIONHAZARD........................:.........................................................................................................:...4 LANDSLIDE HAZARD/SLOPE STABILITY....................................................................................................5 CONCLUSIONS AND RECOMMENDATIONS....................................................................................5 GENERAL...................................................................................................................................................5 EROSION CONTROL AND SLOPE PROTECTION MEASURES................................................................ ....7 SITEPREPARATION AND GRADING............................................................................................................7 STRUCTURESETBACKS..............................................................................................................................8 TEMPORARY AND PERMANENT SLOPES......................................................................................................9 FOUNDATIONS...........................................................................................................................................10 STRUCTURALFILL...................................................................................................................................11 SHORINGWALL.......................................................................................................................................12 SLAB-ON-GRADE.........................................................................................................................:...........13 RETAININGWALLS...................................................................................................................................14 SITEDRAINAGE........................................................................................................................................15 USEOF THIS REPORT..........................................................................................................................tb LIST OF FIGURES Figure 1 —Vicinity Map Figure 2 — Site Plan Figure 3 — Cross-section A -A' Figure 4 — Soil Classification Chart Figure 5 — Hand Auger Logs Figure 6 - Conceptual Soldier Pile Wall Detail NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the proposed Townsend residence addition in Edmonds, Washington. The project site is located at 710 Alder Street, as shown on the Vicinity Map in Figure 1. The purpose of this study is to explore and characterize the site's surface and subsurface conditions and to provide geotechnical recommendations for site development. For our use in preparing this report, we have been provided with an untitled, undated site plan and south elevation prepared by The Leren Company showing the existing residence, proposed development locations, and property boundaries. The site is currently occupied by an existing residence with a daylight basement. The planned improvements will include removal and construction of the upper level of the residence and extending the basement to the south. A steep north -facing slope is located along the southern portion of the property that extends off site to the south. The existing residence is setback approximately 31 feet from the toe of the steep slope. The new addition will extend as close as approximately 17 feet from the toe of the slope. An excavation approximately eight feet deep will be needed for the construction of the new basement. The existing and proposed site layouts are shown on the Site Plan in Figure 2. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions, and provide recommendations for site development. Specifically, our scope of services includes the following: 1. Review available soil and geologic maps of the area. 2. Explore the subsurface soil and groundwater conditions within the site with hand tools. 3. Map the conditions on the site slopes and evaluate slope stability. 4. Provide recommendations for residence setback from the steep slopes. 5. Provide recommendations for earthwork and slabs -on -grade. 6. Provide recommendations for foundation support. 7. Provide recommendations for temporary and permanent slopes. 8. Provide recommendations for temporary shoring, if needed. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 2 9. Provide recommendations for retaining walls. 10. Provide recommendations for site drainage and erosion control. 11. Document the resultsof our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The property is a rectangular shaped parcel covering approximately 0.15 acres. The southern portion of the site consists of a steep north -facing slope that descends down from a vacated alleyway and the southern property line to, the relatively level backyard area. The site then slopes gently to moderately down from the backyard area to the northern property line along Alder Street. The site is currently occupied by an existing single-family residence with a daylight basement in the central portion of the property. The northern portion of the property is covered with grass, landscaping plants and a man-made creek/drainage area. The property is bordered to the north by Alder Street, to the west and east by existing residential properties and to the south by a vacated alleyway. The steep north -facing slope and backyard area within the southern portion of the property is vegetated with large, mature evergreen trees, grass, and miscellaneous underbrush. We measured an overall slope inclination of approximately 25 degrees, (47 percent) as shown on Cross-section A -A' in Figure 3. The steep slope is approximately 12 feet in height. We did not observe surface water on the site or seepage on the slope during our site visit on June 24, 2009. We also did not observe any signs of recent slope movement. Subsurface Conditions Geology: The geologic units for this area are shown on the Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangle, Washington, by James P. Minard (U.S.G.S., 1983). The site is mapped as Advance outwash (Qva) with Transitional Beds (Qtb) and undivided Till (Qtu) mapped nearby. The advance outwash is described as clean, pebbly sand. The transitional beds are described as clay, silt and fine to very fine sand. The undivided till is described as compact, nonsorted clay silt sand and gravel similar to Vashon Till. Our explorations generally encountered fine to coarse sand and gravel NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 3 generally consistent with the description of advance outwash underlain by silty sand with: gravel and silt with sand consistent with the description of undivided till. and transitional bed deposits, respectively. Explorations: We visited the site on June 24, 2009 to explore the subsurface conditions within the proposed development area with hand auger explorations. The approximate locations of our explorations are shown on. the Site Plan in Figure 2. A geologist from Nelson Geotechnical Associates, Inc. (NGA) was present during the explorations, examined the soils and geologic conditions encountered, and maintained logs of the explorations. The soils were visually classified in general accordance with the Unified Soil Classification System, which is presented in Figure 4. The logs of our explorations are presented as Figure 5. The following paragraph contains a brief description of the subsurface conditions encountered in the explorations. For a detailed description of the subsurface conditions, the hand auger logs should be reviewed. In Hand Augers 1 through 3, we encountered approximately 4.5 to 6.0 feet of loose to dense, brown to red -brown silty fine to medium sand with varying amounts of gravel and fine to medium sand with gravel and trace silt that we interpreted as advance outwash deposits. Underlying the advance outwash in Hand Augers 1 through 3, we encountered dense, gray silty fine to coarse sand with gravel that we interpreted as undivided till deposits. Hand Augers 1, 2 and 3 met refusal and were terminated within the undivided till at depths of 7.0, 6.0 and 5.0 feet below the existing ground surface, respectively. In Hand Auger 4, we encountered approximately 7.0 feet of loose to medium dense, brown silty fine to medium sand with gravel that we interpreted as undocumented fill placed behind the basement retaining walls. Underlying the fill, we encountered stiff, blue -gray silt with fine sand that we interpreted as transitional bed deposits. Hand Auger 4 was terminated within the transitional bed soils at a depth of approximately 8.0 feet below the existing ground surface. Hydrologic Conditions Moderate groundwater seepage was encountered between approximately 4.5 and 5.5 feet below the existing ground surface in Hand Augers 1 through 3. We interpreted this seepage to be perched water. Perched water occurs when surface water infiltrates through less dense, more permeable soils, such as the NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 4 advance outwash deposit, and accumulates on top of a relatively low permeability material, such as the undivided till and transitional bed deposits. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of groundwater to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2006 International Building Code (IBC) for seismic site classification for this project. Since medium dense to dense sand and silty sand deposits were encountered underlying the site, the site conditions best fit the IBC description for Site Class D. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion by soft deposits. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. The advance outwash and transitional bed soils interpreted to underlie the site have a low potential for liquefaction or amplification of ground motion. The medium dense to dense glacial soils interpreted to form the core of the site slope are considered stable with respect to deep-seated slope failures. However, the overlying loose surficial materials on the slope have the potential for shallow sloughing failures during seismic events. Such events should not affect the planned structures provided the foundations are designed with the depths and setback distances from the slope as described in the Foundations and Structure Setback subsections of this report. Erosion Hazard The criteria used for determination of erosion hazard areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey of Snohomish County Area. Washington, by the Soil Conservation Service (SCS) was reviewed to determine the erosion hazard of the on-site soils. The site surface soils were classified using the SCS classification system as Everett gravelly sandy loam, 15 to 25 percent slopes. This unit is listed as having a moderate erosion hazard. The on-site soils should have a low hazard for erosion where the vegetation is not disturbed. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 5 Landslide Hazard/Slope Stability The criteria used for evaluation of landslide hazards include soil type, slope gradient, and groundwater conditions. A steep west -facing slope with a gradient of approximately 25 degrees (47 percent) and a height of approximately 12 feet is located above the planned development area. We did not observe evidence of past erosion or sloughing on this slope during our site visit. We did not observe seepage on the slopes during our visit. Relatively shallow failures as well as surficial erosion are natural processes and could occur on the steep slope. It is our opinion that while there is potential for erosion, soil creep, and shallow failures within the loose surficial soils on the steep slope, the potential for deep-seated slope failure under current site conditions is low. Proper site grading and drainage as recommended in this report should help maintain current stability conditions. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the planned development is feasible from a geotechnical standpoint, provided that our recommendations are incorporated into the design and construction of this project. The steep north - facing slope is considered stable with respect to deep-seated failures. However, there is a potential for shallow sloughing and erosion events to occur on the slope. We anticipate that during periods of extended rainfall and/or as a result of seismic activity, shallow slough -type failures may originate on the slope. The new addition will be as close as approximately 17 feet from the toe of the slope. The planned structure setback should allow for normal slope recession during a reasonable life span of the structures providing that no material or water is allowed to reach the slope. This is further discussed in the Structure Setback subsection of this report. Our explorations indicated that the planned development area is generally underlain by competent native glacial deposits. The underlying medium dense/stiff or better native soils should provide adequate support for the planned structure. We recommend that the structures be designed utilizing conventional spread foundations. Footings should extend through any undocumented fill, organic soil, or loose NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 6 materials, and be founded on the underlying medium dense/stiff or better native soils or structural fill extending to these soils. Based on our explorations, medium dense soils should typically be encountered approximately one to two feet below the existing surface in the planned building area. The main geotechnical aspect of this project is the planned excavation along the eastern property line for the basement walls. This excavation will be on the order of eight feet deep. Due to the expected depth of the excavation and boundary constraints, we anticipate that a shoring wall will be needed to retain the cut. The most likely shoring system that will be utilized on this site is a driven cantilever soldier pile wall with timber lagging. We do not anticipate that the use of tiebacks for the shoring system would be feasible due to the close proximity of the planned cut to site boundaries. Due to the close proximity to neighboring structures, we recommend that all of the adjacent structures be monitored before, during, and after the installation of the shoring walls to minimize the risk to the residence and any other structure. The soils anticipated to be encountered during excavation are considered to be moisture -sensitive and may disturb when wet. We recommend that construction take place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays should be expected due to the wet conditions. Additional expenses could include the need.for placing a blanket of rock spalls on exposed subgrades, construction traffic areas, and paved areas prior to placing structural fill. Under no circumstances, should water be allowed to flow over, or concentrate on the slope, both during construction and after construction has been completed. We recommend that stormwater runoff from the roof drains, paved areas, and yard drains be collected and tightlined to a suitable discharge point. The slope should be protected. from erosion. We recommend that all disturbed areas be replanted to re- establish. vegetation as soon as possible. The steep slope should not be disturbed or graded for the placement of the addition or any other structures. No fill of any sort should be placed on the slope, or near the top of the slope, without a specific geotechnical evaluation. Stormwater runoff should not be allowed to, concentrate or flow over the slope. Specific recommendations for erosion control are presented in the Erosion Control and Slope Protection Measures -subsection of this report. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 7 Erosion Control and Slope Protection.Measures The erosion hazard for the on-site soils is interpreted to be moderate, but the actual hazard will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site or flowing over the steep slope on the western side of the property. Stockpiles should be covered with plastic sheeting during wet weather and stockpiled material should not be placed on the slope. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential for areas not stripped of vegetation should be low. Protection of the setback and steep slope areas should be performed as required by the City of Edmonds. Specifically, we recommend that the setback area and slope not be disturbed or modified through placement of any fill or removal of the existing vegetation. No additional material of any kind should be placed on the slope or be allowed to reach the slope, such as excavation spoils, lawn clippings, and other yard waste, trash, or soil stockpiles. Trees should not be cut down or removed from the steep slope unless a mitigation plan is developed, such as the replacement of vegetation for erosion protection. Replacement of vegetation should be performed in accordance with the City of Edmonds code and should be approved by the City. Any proposed development within the slope setback area, other than light decks or patios, should be the subject of a specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slopes. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping any fill/modified ground or loose soils to expose medium dense or better native soil in foundation, slab -on - grade, and pavement areas. The stripped materials should be removed from the site or be stockpiled for later use as landscaping fill. Stockpiles should be covered with plastic sheeting during wet weather, and should be kept away from the steep slope. If the ground surface should appear to be loose after stripping, it should be compacted to a non -yielding condition. Areas observed to pump or weave during compaction should be over -excavated and replaced NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 8 with properly compacted structural fill or rock spalls. If loose soils are encountered in the pavement areas, the loose soils should be removed and replaced with rock spalls or granular structural fill. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades should be maintained in a semi -dry condition. If wet conditions are encountered, alternative site stripping and grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading and covering exposed subgrade with a layer of.crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted as this could cause further subgrade disturbance. In wet conditions it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around prepared subgrade. Shallow groundwater, if encountered, should be intercepted with cut off drains and routed around the planned grading area, or the groundwater should be controlled with sump -pumps or dewatering systems. Structure Setbacks Uncertainties related to building near steep slopes are typically addressed by the use of building setbacks. The purpose of the setback is to establish a "buffer zone" between the structure and the slope so that ample room is allowed for normal slope recession during a reasonable life span of the structure. In a general sense, the greater the setback distance, the lower the risk of slope failures impacting the structure. From a geological standpoint, the setback dimension is based on the slope's physical characteristics, such as slope height, surface angle, material composition, and hydrology. Other factors such as.historical slope activity, rate of regression, and the type and desired life span of the . development are important considerations as well. The new addition will be as close as approximately 17 feet from the toe of the slope. It is our opinion that this planned setback distance is adequate for the structure. We should be retained to evaluate the residence foundation setback distances and subgrade soil prior to placing foundation forms. Any proposed development within the setback area, other than light decks or patios, should be the subject of a NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 9 specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slopes, during or after construction. Temporary and Permanent Slopes Grading plans were not available at the time this report was prepared. However, we understand that shoring walls may be used to support the eastern cut for the basement addition. Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads. adjacent to the excavation, length of time a cut remains open, and the presence of surface water or groundwater. It is exceedingly difficult under these variable conditions to estimate a. stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since they are continuously at the job site, able to observe the soil and groundwater conditions encountered and able to monitor the nature and condition of the cut slopes. The following information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the near surface topsoil, weathered soil and/or loose -to medium dense/stiff soils be no steeper than 2 Horizontal to 1 Vertical (2H:1V). If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include . covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. Permanent cut and fill slopes should be no steeper than 2H:1V. However, flatter inclinations maybe required in areas where loose soils are encountered. Permanent slopes should be planted and the vegetative cover should be maintained until it is established. We should review the project plans and visit the site to evaluate excavations for this project. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 10 Foundations Conventional shallow spread foundations for the addition should be placed on undisturbed medium dense or better native soils or be supported on structural fill extending to those soils. These soils were generally encountered one to two feet below ground surface. Where undocumented fill or less dense soils are encountered at the planned footing elevation, the subgrade should be over -excavated to expose suitable bearing soil. The over -excavation may be filled with structural fill, or the footing may be extended down to the bearing native soils. If footings are supported on structural fill, the fill zone should extend outside the edges of the footing a distance equal to at least one-half of the thickness of the fill placed below the bottom of the footing. Footings, including interior footings, should extend at least 18 inches below the lowest adjacent finished ground surface for frost protection and bearing capacity considerations. Foundations should be designed in accordance with the 2006 International Building Code (IBC). Footing widths should be based on the anticipated loads and allowable soil bearing pressure. Water should not be allowed to accumulate in footing trenches. All loose or disturbed soil should be removed from the foundation excavation prior to placing concrete. For foundations constructed as outlined above, we recommend an allowable design bearing pressure of not more than 2,000 pounds per square foot (psf) be used for the design of foundations supported on the medium dense or better native soils or structural fill extending to the competent native soils. A representative of NGA should evaluate the foundation bearing soil. We should be consulted if higher bearing pressures are needed. Current IBC guidelines should be used when considering increased allowable bearing pressure for short-term transitory wind or seismic loads. Potential foundation settlement using the recommended allowable bearing pressure is estimated to be less than one -inch total and 'Y2 -inch differential between adjacent footings or across a distance of about 30 feet based on our experience with similar projects. Lateral loads may be resisted by friction on the base of the footing and passive resistance against the subsurface portions of the foundation. A coefficient of friction of 0.35 may be used to calculate the base friction and should be applied to the vertical dead load only. Passive resistance may be calculated as a triangular equivalent fluid pressure distribution. An equivalent fluid density of 200 pounds per cubic foot NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 11 (pcf) should be used for passive resistance design for a level ground surface adjacent to the footing. This level surface should extend a distance equal to at least three times the footing depth. These recommended values incorporate safety factors of 1.5 and 2.0 applied to the estimated ultimate values for frictional and passive resistance, respectively. To achieve this value of passive resistance, the foundations should be poured "neat" against the native medium dense soils or compacted fill should be placed against the footing. We recommend that the upper one -foot of soil be neglected when calculating the passive resistance. Structural Fill General: Fill placed beneath foundations, pavement, or other settlement -sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored byan an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a representative number of in-place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation and Grading subsection prior to beginning fill placement. Materials: Structural fill should consist of a good quality, granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about three inches. All-weather structural fill should contain no more than five -percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4 -inch sieve). The use of some of the on-site soils as structural fill may be feasible but will be dependent on moisture content of the material at the time construction takes place. The organic topsoil should not be used as structural fill. We should be retained to evaluate proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All filling should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts: All structural fill should be compacted to a minimum of 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactible NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009. NGA File No. 813009 Page 12 condition exists. It may be necessary to over -excavate and remove wet soils in cases where drying to a r compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of coml action. Shoring Wall General: Cuts on the order of eight feet or more in height are anticipated along the eastern property line of the site for the purpose of constructing the proposed basement addition. Due to the depth of the excavation, the close proximity to neighboring residences, and soil and groundwater conditions, a shoring wall is recommended to retain this cut during construction. The shoring wall can be made permanent and be incorporated into the basement walls. The most practical wall system for use on this site may be a driven soldier pile wall with timber lagging. This wall system is most compatible with the site conditions. A driven soldier pile wall typically consists of a series of steel H -beams driven vertically with a constant spacing between the beams (typically four to six feet). The beams are driven with a hydraulic hammer and embedded below the bottom of the planned excavation a distance equal to one to two times the height of the cut to be shored. The steel beams are extended above finished ground surface to provide shoring capabilities for the cut. The beams are typically spanned by pressure treated timber lagging or concrete panels. The H -beam size, embedment, and pile spacing are dependent on the nature of the soils anticipated in the cut and at depth below the cut, cut height, surcharge loads on the wall, drainage conditions, and final geometry. Soldier Wall Design: An experienced structural engineer licensed in the State of Washington should design the shoring wall. The wall designer should be provided a copy of this report, and we should be retained to review the shoring wall design prior to construction. The lateral earth pressure acting on the shoring wall will be dependent on the nature and density of the soil behind the wall, structure and traffic loads on the wall, and the amount of lateral wall movement that may occur as material is excavated from the front of the wall. If the shoring wall is free to yield at least one -thousandth' of the retained height, an "active" loading condition develops. If the wall is restrained from movement by stiffness or bracing, the wall is considered in an "at -rest" loading condition. Active and at -rest earth pressure can be calculated based on equivalent fluid densities. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 13 The shoring wall should be designed to resist a lateral load resulting from a fluid with a unit weight of 35 and 50 pounds per cubic foot (pcf) for the active and at -rest loading conditions, respectively. These loads should be applied across the pile spacing above the excavation line. A lateral load of equivalent fluid density of 40 pcf should be applied an the pile diameter below the excavation line. These loads can be resisted by a passive pressure of 200 pcf and the medium dense/stiff or better soils. The passive pressure should be applied on two -pile diameters below the excavation line. These values of the passive pressure incorporate a factor of safety of 2.0. A drainage system should be installed for the shoring wall. Minimum'/ -inch gaps should be maintained between the lagging elements to allow water seepage through the wall. All voids left behind the timber lagging should be filled with free draining material such as pea gravel or washed rock. A composite drain should be installed between the timber lagging and the .concrete wall to promote drainage. The composite drain should be connected to the footing drain. Roof drains should not be connected to wall or footing drains. The shoring wall and recommended drainage concepts are illustrated in the Conceptual Soldier Pile Wall Detail, in Figure 6. This figure is not intended for use in construction or final design; the structural engineer should provide the final wall drainage detail. Shoring Wall Installation: A shoring contractor experienced with soldier pile wall construction should install the shoring wall. We recommend that the H -piles be driven into place using a hydraulic hammer, with a minimum energy rating of 1,200 ft -lb. The pile spacing and embedment should be determined by the structural engineer. In addition to the minimum recommended embedment, the piles should be driven to a refusal criteria of less than one inch of movement during 10 seconds of continuous driving. We should be retained to observe shoring wall installation on a full time basis. Stab -on -Grade Slabs -on -grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection of this report. We recommend that all floor slabs be underlain by at least six inches of free -draining gravel with less than three percent by weight of the material passing Sieve #200 for use as a capillary break. We recommend that the capillary break be hydraulically connected to the footing drain system to allow free drainage from under the slab. A suitable vapor barrier, such as heavy plastic sheeting (6 -mil minimum), should be placed over the capillary break material. An additional 2 -inch thick NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 14 moist sand layer may be used to cover the vapor barrier. This sand layer is optional and is intended to protect the vapor barrier membrane during construction. Retaining Walls Retaining walls will be used for the basement additions. The lateral pressure acting on subsurface retaining walls is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement which can occur as backfill is placed, wall drainage conditions, and the inclination of the backfill. For walls that are free to yield at the top at least one thousandth of the height of the wall (active condition), soil pressures will be less than if movement is limited by such factors as wall stiffness or bracing (at -rest condition). We recommend that walls supporting horizontal backfill and not subjected to hydrostatic forces, be designed using a triangular earth pressure distribution equivalent to that exerted by a fluid with a density of 35 pcf for yielding (active condition) walls, and 50 pcf for non -yielding (at -rest condition) walls. . These recommended lateral earth pressures are for a drained granular backfill and are based on the assumption of a horizontal ground surface behind the wall for a distance of at least the subsurface height of the wall, and do not account for surcharge loads. Additional lateral earth pressures should be considered for surcharge loads acting adjacent to subsurface walls and within a distance equal to the subsurface height of the wall. This would include the effects of surcharges such as traffic loads, floor slab loads, slopes, or other surface loads. We could consult with you and your structural engineer regarding additional loads on retaining walls during final design, if needed. The lateral pressures on walls may be resisted by friction between the foundation and subgrade soil, and by passive resistance acting on the below -grade portion of the foundation. Recommendations for frictional and passive resistance to lateral loads are presented in the Foundations subsection of this report. All wall backfill should be well compacted as outlined in the Structural Fill subsection of this report. Care should be taken to prevent the buildup of excess lateral soil pressures, due to over -compaction of the wall backfill. This can be accomplished by placing wall backfill in eight -inch loose lifts and compacting the backfill with small, hand -operated compactors within a distance behind the wall equal to at least one - NELSON GEOTECHNICAL ASSOCIATES, INC, Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No, 813009 Page 15 half the height of the wall. The thickness of the loose lifts should be reduced to accommodate the lower compactive energy of the hand -operated equipment. The recommended level of compaction should still be maintained. Permanent drainage systems should be installed for retaining walls. Recommendations for these systems are found in the Subsurface Drainage subsection of this report. We recommend that we be retained to evaluate the proposed wall drain backfill material and observe installation of the drainage systems. Site Drainage Surface Drainage: Final site grades should allow for drainage away from the planned structures. We suggest that the finished ground be sloped at a minimum gradient of three percent for a distance of at least 10 feet away from the buildings. Surface water should be collected by permanent catch basins and drain lines,. and be discharged into an appropriate discharge system. Water should not be allowed to collect in any area where footings, slabs, or pavements are to be constructed. Surface water generated from paved areas and roof drains should be routed into permanent catch basins and then tightlined into an appropriate stormwater facility. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavations and collect the water into ditches and small sump pits where the water can be pumped out and routed to a suitable discharge point. We recommend the use of footing drains around the planned structures and behind retaining walls. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum four -inch -diameter, rigid, slotted or perforated, PVC pipe surrounded by free -draining material, such as washed rock, wrapped in a filter fabric. We. recommend that an 18 -inch - wide zone of clean (less than three -percent fines), granular material be placed along the back of the walls above the drain. Washed rock is an acceptable drain material, or a drainage composite may be used instead. The free -draining material should extend up the wall to one foot below the finished surface. The top foot of backfill should consist of low permeability soil placed over plastic sheeting or building paper to minimize surface water or fines migration into the footing drain. Footing drains should discharge into NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 16 tightlines leading to an appropriate collection and discharge point with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to footing drains. USE OF THIS REPORT NGA has prepared this report for Allan Townsend and his agents for use in the planning and design of the development planned on this site only. The scope of our work does not include services related to construction safety precautions and our recommendations are not intended to direct the contractors' methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. There are possible variations in subsurface conditions between the explorations and also with time. Our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. A contingency for unanticipated conditions should be included in the budget and schedule. All people who own or occupy homes on hillsides should realize that landslide movements are always a possibility. The landowner should periodically inspect the slope, especially after a winter storm. If distress is evident, a geotechnical engineer should be contacted for advice on remedial/preventative measures. The probability that landsliding will occur is substantially reduced by the proper maintenance of drainage control measures at the site (the runoff from the roofs should be led to an approved discharge point). .Therefore, the homeowner should take responsibility for performing such maintenance. Consequently, we recommend that a copy of our report be provided to any future homeowners of the property if the home is sold. We recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. We should be contacted a minimum of one week prior to construction activities and could attend pre -construction meetings if requested. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time this report was NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 17 prepared. No other warranty, expressed or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Townsend Residence Addition 710 Alder Street Edmonds, WA July 8, 2009 NGA File No. 813009 Page 18 It has been a pleasure to provide service to you on this project. If you have any questions or require further information, please call. Sincerely; NELSON Lee 9. Beilah Staff Geologist TECHNICAL ASSOCIATES, INC. Michael D. Rundquist, PE Senior Engineer LSB:KMS:pkw Six Figures Attached NELSON GEOTECHNICAL ASSOCIATES, INC. VICINITY MAP Not to Scale r —0 St $ c- alb• `;�5 (��'� .., ! ; � � �; ; � .. ti�:c PUqrsold /—fl ffA002. Project Site _ ._... Yc3t:park 17 L L `c 1 <:. Icedes i I kmt !ri .. �? 5 .._ i R 21" jSm--- r'..___ � _+-,�.__—__.�.� - �-:._.. i I� ._.' ._— I --•i ,�, i ;.�..._..—..._� is �. 11_J Data Q20veNaVT�. QrTete�idas Edmonds, WA Project Number NELSON GEOTECHNICAL No. Date I Revision By CK 813009 Townsend Addition NGA ASSOCIATES, INC.� ��, original DPN LSB Vicinity Map GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 1 173,,.,3%A W.� Sn h-fth Carry (425)339 -IM p2P4M160rFur81-1970 —w-, -b h.aon Planned addition LEGEND • Property line Site Plan Alder Street Number and approximate location of hand auger A AI Approximate location of cross-section Reference: Site Pian based on field measurements and observations. . v . ® . Haase . S I 0 20 40 Scale: 1 inch = 20 feet Project Number NELSON GEOTECHNICAL No. Date Revision By CK 52 813009 ASSOCIATES, INC. a Townsend Addition N A 1 6/26/09 Original DPN LsB a Site Plan GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 2 173n_13%A... NE. A M Smhomhh Gou* (1� 337.1669 (424=wA eeM W-atrhw6:h.an (563) 6667898 19/F-481-2510 wr.,.n.lwye.•ch.aom ; E E-7 c m • � z ;a > d ca m E O rn Q C p �O ti C 'a O O N ccU to C 7 .2— Q p Q C.. CL O rA M O U C N U '� a1 CL _ rn O C [n Tp. O W m X ' c-'6 a) Q a) a) z 05 ,<— N O Ln N 4- N U C O M C) N NI of a) I� F_O v a) 1— O Project Number NELSON GEOTECHNICAL No. x Revision (n V M N T_ O E E-7 c m • � z ;a > d ca m E O rn Q C p �O ti C 'a O O N ccU to C 7 .2— Q p Q C.. CL O rA M O U C N U '� a1 CL _ rn O C [n Tp. O W m X ' c-'6 a) Q a) a) z 05 ,<— N O Ln N 4- N U C O M C) N NI of a) I� N 0 4 C m 0) F_O v a) 1— O Project Number NELSON GEOTECHNICAL No. x Revision J (` 03 O z d' M N O W m n m o 3 V m U a X • iti as uol ena a ewlxo�dd �� ) 13 b a 6/26/09 Original Z ��Ji(' 2 yr A tea, 22 CL 17511.185M A». NE Ad00 477 E d Pam, fte YWomnvOe, WA88M WYil411w.WA 08801 If25 188.18®/FU481-2510 (500)W&780, • • Q (9 N 0 4 C m 0) F_O v a) 1— O Project Number NELSON GEOTECHNICAL No. x Revision J (` 03 O z d' M N O W m n m o 3 V m U a X ° as uol ena a ewlxo�dd �� ) 13 b a 6/26/09 Original Z o LSB a a tea, 22 CL N 0 4 C m 0) F_O v a) 1— O Project Number NELSON GEOTECHNICAL No. Date Revision By CK o 813009 Townsend Addition Cross -Section A -A' ASSOCIATES, INC. N � A GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 6/26/09 Original DPN o LSB a a Figure 3 17511.185M A». NE Ad00 477 E d Pam, fte YWomnvOe, WA88M WYil411w.WA 08801 If25 188.18®/FU481-2510 (500)W&780, Q (9 z UNIFIED SOIL CLASSIFICATION SYSTEM GROUPSYMBOL MAJOR DIVISIONS GROUP NAME CLEAN GW WELL -GRADED, FINE TO COARSE GRAVEL COARSE- GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50 % OF COARSE FRACTION GRAVEL GM SILTY GRAVEL RETAINED ON SOILS NO.4 SIEVE WITH FINES GC CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND SAND SP POORLY GRADED SAND MORE THAN 50 % RETAINED ON MORE THAN 50 % NO. 200 SIEVE OF COARSE FRACTION SAND SM SILTY SAND PASSES NO. 4 SIEVE WITH FINES SC CLAYEY SAND FINE - SILT AND CLAY ML SILT INORGANIC GRAINED LIQUID LIMIT CL CLAY LESS THAN 50 % SOILS ORGANIC OL ORGANIC SILT, ORGANIC CLAY SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT INORGANIC MORE THAN 50 PASSES LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FLAT CLAY NO. 200 SIEVE 50 % OR MORE ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: 1) Feld classification is based on visual SOIL MOISTURE MODIFIERS: examination of soil in general accordance with ASTM D 2488-93. Dry - Absence of moisture, dusty, dry to the touch 2) Soil classification using laboratory tests is based on ASTM D 2488-93. Moist -Damp, but no visible water. V. f 3) Descriptions of soil density or Wet - Visible free water or saturated, a consistency are based on usually soil is obtained from interpretation of blowcount data, below water table visual appearance of soils, and/or test data. g C Project Number NELSON GEOTECHNICAL No. Date Revision By CK P 813009 Townsend Addition Soil Classification Chart ASSOCIATES, INC. -___N GA GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 6rz6✓09 a;gil,al DPN LS8 Figure 4 17311 -135Th Aw NE A.Wa VN00ca IS, WA96072 Swhwdah Cmvq `425)13/-1635 'Hana"eaMhahn 509)065.7886 C (425)466-16691 Pox 481.7510 pyy,, WN gn .Kfi. „ 2 HAND AUGER ONE 0.0-0.5 0.5-6.0 6.0-7.0 HAND AUGER TWO 0.0-0.5 0.5-5.5 6.0-6.5 HAND AUGER THREE 0.0-4.5 4.5-5.0 HAND AUGER FOUR 0.0-7.0 7.0-8.0 DPN:LSB LOG. OF EXPLORATION USC SOIL DESCRIPTION SM BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL (LOOSE, MOIST) SP RED -BROWN FINE TO MEDIUM SAND WITH GRAVEL AND TRACE SILT (MEDIUM DENSE TO DENSE, MOIST TO WET) SM GRAY, SILTY FINE TO COARSE SAND WITH GRAVEL (DENSE, WET) SAMPLES WERE COLLECTED AT 2.5 AND 6.5 FEET MODERATE GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 5.5 FEET HAND AUGER CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 7.0 FEET ON 6124/09 SM BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL (LOOSE, MOIST) SP RED -BROWN FINE TO MEDIUM SAND WITH GRAVEL AND TRACE SILT (MEDIUM DENSE TO DENSE, DRY TO WET) SM GRAY, SILTY FINE TO COARSE SAND WITH GRAVEL (DENSE, WET) SAMPLES WERE COLLECTED AT 3.0 AND 6.0 FEET MODERATE GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 5.0 FEET HAND AUGER CAVING WAS ENCOUNTERED FROM 0.5 TO 4.0 FEET HAND AUGER WAS COMPLETED AT 6.5 FEET ON 6/24/09 SP RED -BROWN FINE TO MEDIUM SAND WITH GRAVEL AND SILT (MEDIUM DENSE TO DENSE, MOIST TO WET) SM GRAY, SILTY FINE TO COARSE SAND WITH GRAVEL (DENSE, WET) SAMPLES WERE COLLECTED AT 6.0 AND 7.5 FEET MODERATE GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 4.5 FEET HAND AUGER CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 5.0 FEET ON 6/24/09 SM BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL AND TRACE ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) ML BLUE -GRAY SILT WITH FINE SAND (STIFF, MOIST) SAMPLES WERE COLLECTED AT 6.0 AND 7.5 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED HAND AUGER CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 8.0 FEET ON 6/24/09 NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 813009 FIGURE 5 Conceptual Soldier Pile Wall Detail NOT FOR CONSTRUCTION USE Washed rock drainage behind lagging X (6 OD r rn 3 0 CL X W Concrete wall Miradrain drainage matting full height & width centered between piles, installed with fabric to lagging Waterproofing membrane a along length of wall 4. Pressure treated timber ~ lagging with 1/4 -inch gap between boards Multiflow drainage collector 4 -inch diameter weep holes Basement slab 0 • 4 -inch diameter PVC pipe tightlined a : to storm drainage system Wall Embedment (typically 1.5 to 2.0 times exposed wall height) NOT TO SCALE I. 0 0 Project Number NELSON GEOTECHNICAL NO. Date Revision By CK Townsend Addition ASSOCIATES, INC.$ NGA 813009 Conceptual Soldier Pile GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 7mos� Original ISS KMS a Figure 6 Wall Detail 17311.135t A -NF- •= I�n�aeo-tesolFv.�-aso - „x.ono.osa.�„ �