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CANOD.pdf1�NELSON GEOTECHNICAL G A GEOTECHNICAL ENGINEER$ 8c GEOLOGISTS ASSOCIATES, INC. Main office - En adMca�' riti a.*a° c'wgy Branch - _ 17311 - 135"' Ave NE, A-500 5526 lndaastry Lane, 02 Woodinville, WA 98072 East Wenatc6c, WA 98802 (425) 456-1669 ° FAX (425) 481-2510 (509) 665®7696 FAX (509) 665-7692 MEMORANDUM DATE: May 19, 2016 TO: Mr. Derek Abbott FROM: Khaled M. Shawish, PE Lee S. Bellah, LG RE: Abbott Residence — Landscaping Plan Review 16404 — 75"' Place West Edmonds, Washington NGA File No. 917515 Up. ?1 ,. 0, 010 This memorandum documents our opinions and recommendations for the proposed landscaping plan at your residence project located at 16404 — 75th Place West in Edmonds, Washington. We previously prepared a geotechnical engineering evaluation for the project titled "Prelimfim y Geotechnical Engineering Evaluation — Abbott Residence — 16404 - 751 Place West — Edmonds, Washington," dated March 27, 2015. For our use in preparing this memo, we have been provided with a landscaphig plan prepared by Ronald D. Johnson, Architect, dated May 12, 2016. The overall development plan for the site includes the construction of anew single-family residence and detached garage structure along with associated pavement areas and underground utilities. We also understand that as a part of the proposed landscaping, plan that you wish to plant shrubs, ground cover, mulch and trees throughout the proposed development area within the eastern portion of the site. We have been requested to provide our opinion and recommendations regarding the proposed landscape plan in accordance with the City of Edmonds Code. Based on our review of the proposed plans, it is our opinion that the proposed landscaping plan is feasible from a geotechnical standpoint. It is also our opinion that the proposed landscaping plan should not Geotechnical Memorandum NGA File No. 917515 Abbott Residence — Landscaping Plan Review May 19, 2016 Edmonds, Washington Page 2 adversely impact the site slope areas or neighboring properties if our recommendations are incorporated into the proposed plans and construction. The proposed development area and site slopes are proposed to be vegetated with numerous shrubs, plants, and trees, it is our opinion that the lower -lying shrubs, plants and mulch should be feasible for vegetating the site slope areas. However, if larger tree species are planted on or near the site slopes, they could have adverse impacts to the residence and slope stability as they mature. We recommend that larger trees be limited on the sloping areas, and if they are planted on the slopes, they should be maintained to reduce their size_ These types of trees may need to be removed later if they pose a future risk to the residence or slope stability. After all of the plants are installed, it appears that the remaining exposed ground will be covered with mulch or grass. Any exposed soils should be covered and maintained until vegetation is established. We recommend that the sloping areas within the site that receive vegetation be monitored throughout the wet season and repairs be implemented immediately should any signs of erosion or plant die off be observed. NGA should be retained to observe and evaluate the landscaping after it is installed and provide any further recommendations as needed during construction. We trust this memorandum should satisfy your needs at this time. Please contact if you have any questions or require additional services. NELSON GEOTECHNICAL ASSOCIATES, INC. M.C. LANDiSiCAPE P.O.BOX 2144. SNOHOMISH, WA 98291. (425) 220 9509 PROPOSAL DATE: 5-19-2016 ACH NW LLC PROPOSAL: 2031 16404 75" PL W Edmonds, WA DESCRIPTION OF WORK TO BE PERFORMED: Flower beds • Amend the sub grade to a depth of twelve inches • Remove the large debris from the soil • Amend tine sub grade with i a inches of s -way Lopsoii in the flower beds • Install the plants to the design • Upon completion of the plantings topdress the flower beds with Black Cedar Grove Mulch Paver pads • Excavate the soil in preparation for the pavers and haul away • Install a compacted gravel base • Install Roman Cobblestone pavers for the patios • Set the paver edging on concrete + ri-Au�: i aa.. =3; r -5.0 N.ua oa.w ins % Note: This price does not include warranty on the plants. Removing existing plants, lawn, preparing the sub grade or adding lawn in the back yard are not included in this price. I Ll Proposal is subject to change after 30 days. M.C. Landscape proposes to furnish all labor and materials for the work described above. Any alterations or changesmay result in additional fees. M.C. Landscape is not responsible for permits on this project. 50% of the total cost of the project is due on start date. The balance is due upon completion of project. THANK Y TT JAVIER MUNIZ m. c.landscape@comcast.net 11TY COPY WLSCII GEOTECHNICAL ---�NGA sCCIATFs, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office 17311 — 1351b Ave NE, A-500 Woodinville, WA 98072 (425) 486-1669 - FAX (425) 481-2510 DATE: May 6, 2015 TO: Mr. Derek Abbott CC: Mr. Ron Johnson FROM: Khaled M. Shawish, PE Lee S. Bellah, LG Engineering -Geology Branch 5526 Industry Lane, #2 East Wenatchee, WA 98802 (509) 665-7696 - FAX (509) 665-7692 MEMORANDUM RE: Updated Geotechnical Recommendations Abbott Residence Structural Slab Pin Piles 16404 75`e Place West Edmonds, Washington NGA File No. 917515 RECEIVED Exp. July 28, 2015 This memo presents our updated geotechnical recommendations and opinions regarding the alternative structural slab -on -grade support for the residence project located at 16404-75a` Place West in Edmonds, Washington. We have previously prepared a geotechnical engineering evaluation for the project titled "Preliminary Geotechnical Engineering Evaluation — Abbott Residence — 16404 75`h Place West — Edmonds, Washington," dated March 27, 2015. In that report, we provided recommendations for the proposed site development including recommendations for supporting the residence foundations and structural slab -on - grades on a deep foundation system consisting of augercast piles. Your architect Mr. Ron Johnson has requested our opinion regarding supporting the slabs -on -grade on 4 -inch driven pin piles instead of the proposed augercast piles. In our opinion, supporting only the residence structural slabs -on -grade on 4 -inch driven pin piles is feasible from a geotechnical standpoint. We recommend that all exterior and major interior foundation elements still be supported on the augercast piles as recommended in our previous report. Detailed recommendations regarding the pin piles are included below. Geotechnical Engineering Memorandum NGA Project No. 917515 Abbott Residence Structural Slab Pin Piles May 6, 2015 Edmonds, Washington Page 2 We recommend that the proposed structural slabs -on -grade be supported on 4 -inch pin piles to transfer foundation loads to the underlying native competent materials found below the landslide debris. Our explorations did not encounter any significant debris within the landslide deposits, however there is a possibility that some obstructions may impede some of the piles. There should be contingencies in the budget and design for additional/relocated piles to replace piles that may be obstructed by debris. We also recommend that excavation equipment be available on site during pile installation so that shallow obstructions can be removed from the planned pile locations. We recommend that the 4 -inch pipe piles be driven using a tractor -mounted hydraulic hammer, with an energy rating of at least 1,100 foot -lb. For this pile and hammer size, we recommend a design capacity of eight tons for each pile driven to refusal. The refusal criterion for this pile and hammer size is defined as less than one -inch of movement during 15 seconds of continuous driving at a rate of 550 blows per minute or higher. We recommend using galvanized schedule 40 pipe for the 4 -inch pin piles. Maintaining these recommendations for minimum hammer size and refusal criteria is essential for obtaining a successful outcome. Final pile depths should be expected to vary somewhat and will depend on the depth of the loose material, the nature of the underlying competent soils, and groundwater conditions. The pin piles should penetrate a minimum of five feet into the competent native soils below the landslide debris in order to develop the design capacity. Based on our explorations, we would recommend that the piles be driven to a minimum depth of 30 feet below the ground surface to achieve the minimum embedment depth into the competent native soils. Piles that do not meet this minimum embedment criterion should be rejected, and replacement piles should be driven after consulting with the structural engineer regarding the new pile locations. The piles should be spaced a minimum of three feet apart to avoid a grouping effect on the piles. 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. PRELIMINARY GEOTECHNICAL ENGINEERING EVALUATION ABBOTT RESIDENCE 1640475 TH PLACE WEST EDMONDS, WASHINGTON PREPARED FOR DEREK ABBOTT RECEIVED DEC 1 2015 h�ly 0 . CITY COPY Main Office 17311 — 1351h Ave NE, A-500 Woodinville, WA 98072 (425) 486-1669 • FAX (425) 481-25 10 March 27, 2015 Mr. Derek Abbott 221 185"' Place SW Bothell, WA 98012 NELSON GEOTECHNICAL A.SSOCI, TES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Preliminary Geotechnical Engineering Evaluation Abbott Residence 16404 75" Place West Edmonds, Washington NGA File No. 917515 Dear Mr. Abbott: Engineering -Geology Branch 5526 Industry Lane, lit East Wenatchee, WA 98802 (509) 665-7696 - FAX (509) 665-7692 DEC 10 201'5 OEVELOPMENT SERVICES GR CITY OF EDMONDS We are pleased to submit the attached report titled "Preliminary Geotechnical Engineering Evaluation — Abbott Residence —16404-75'h Place West — Edmonds, Washington." This report summarizes the existing surface and subsurface conditions within the project site, and provides geotechnical recommendations for design and construction of the proposed site improvements. Our services were completed in general accordance with the proposal signed by you on February 12, 2015. The site is situated on gently to moderately sloping ground above to the right-of-way for the Burlington Northern Santa Fe railroad and the shore of Puget Sound. The site is currently occupied by an existing single-family residence within the upper eastern portion of the property along 75'h Place West. We understand that the proposed development plans consist of removing the existing residence and constructing a new single-family residence in the approximate location of the current structure. Retaining walls and shoring systems may be needed to construct the proposed structure into the sloping ground depending on final proposed elevations. Specific grading, and utility plans were not available at the time this report was prepared. Stormwater management plans have also not been finalized at this time, but we understand that they will likely include tightlining the runoff down to the bottom of the slope or into an existing storm system within the vicinity of the property. We therefore should be retained to review final development plans prior to applying for a permit. The site is mapped as part of the large historic/prehistoric Meadowdale Landslide complex area now known as the North Edmonds Earth Subsidence & Landslide Hazard Area (ESHLA). The site is located in the designated "Zone A" within the lower portion of the slide complex. This report provides information and discussion to fulfill the requirements of the City of Edmonds for construction within this area. Based on our site reconnaissance and explorations, and our review of the preliminary plans, we have concluded that development of a single family residence on this site should be feasible, from a Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Summary - Page 2 geotechnical standpoint. We did not observe signs of recent deep-seated slope failures or earth subsidence on the property. The proposed development area appears to be relatively stable under current conditions. The recommendations presented in this report should aid in maintaining and/or improving the current stability conditions observed at the site. Based on the landslide debris and shallow perched groundwater conditions encountered in our explorations, we recommend supporting the planned residence on a deep foundation system consisting of drilled augercast piles in order to advance the structure loads through the loose/soft upper soils down to the more competent native deposits at depth. Specific recommendations for foundation design and installation are provided in the attached report. In the attached report, we have also provided general recommendations for site grading, slabs -on -grade, structural fill placement, retaining walls, erosion control, and drainage. These recommendations are preliminary in nature. We should be retained to review and comment on final development plans and observe the earthwork phase of construction. We strongly recommend that all runoff generated within this site, including roof downspouts, driveways, yard and footing drains, and all runoff entering the property from the road or adjacent properties, be collected in a tightline and routed to the bottom of the slope or into an approved discharge system. No water should be infiltrated or dispersed within the site or near the site slopes. Such activity may cause sliding within the site slopes. We should be retained to review final grading and drainage plans prior to construction. We also 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. 1 Khaled M. Shawish, PE Principal cc: Ron Johnson — Johnson Architects Table of Contents INTRODUCTION.......................................................................................................................................................1 SCOPE..........................................................................................................................................................................1 SITECONDITIONS...................................................................................................................................................2 SIIIII�`ACE C'ONDITIONs. .....»........., ... ........ 2 SUBSURFACE CONDITIONS- ............ . . ..... ......,...,,.., ..... ........ ......:,.,....,,.....,....,,2 IIYI)RO O61C%'OND111ONS...„... .............. ................. ,...... ...... ....,,............. ,....... .......,. 4 SENSITIVEAREA EVALUATION..........................................................................................................................4 SEISMICHAZARD.......................................................................................................................................................4 EROSIONHAZARD......................................................................................................................................................5 LANDSLIDEHAZARD/SLOPE STABILITY.....................................................................................................................5 CONCLUSIONSAND RECOMMENDATIONS.....................................................................................................6 GENERAL.................................................................................................................................................................... 6 EROSION CONTROL AND SLOPE PROTECTION MEASURES ....,.... ........ ......... ................... -,........,.,.8 SI I I: PRI.I"ARA I ION AND 1.mltADIN(T �yy TEMPORARY AND PERMANENT SLOPES ......... ,.,,.,. ........... ... , ,,..,.. ,............... .. ,.......„,...9 DEEPFOUNDATIONS.................................................................................................................................................10 STRUCTURALFILL....................................................................................................................................................12 RETAININGWALLS...................................................................................................................................................13 STRUCTURALSLABS.................................................................................................................................................14 PAVEMENTSUBGRADE.............................................................................................................................................14 SITEDRAINAGE........................................................................................................................................................15 USEOF THIS REPORT...........................................................................................................................................16 LIST OF FIGURES Figure 1 — Vicinity Map Figure 2 — Site Plan Figure 3 — Cross-section A -A' Figure 4 — Soil Classification Chart Figure 5 and 6 — Boring Logs NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence 16404 -75th Place West Edmonds, Washington INTRODUCTION This report presents the results of our preliminary geotechnical engineering evaluation for the proposed Abbott Residence project. The address for the site is 16404 -75th Place West in Edmonds, Washington, as shown on the Vicinity Map in Figure 1. The purpose of the study is to explore and characterize the surface and subsurface conditions at the site and provide general geotechnical recommendations for site development. For our use in preparing this report, we have been provided with a boundary and topographic survey titled "16404 75t' Pl. W., Edmonds, WA," dated March 3, 2015, prepared by D.R. Strong Consulting Engineers. The site is situated on gently to moderately sloping ground that descends from 75th Place West to the right-of-way of the Burlington Northern Santa Fe (BNSF) railroad and the shore of Puget Sound. An existing single-family residence is located within the upper eastern portion of the property along 75th Place West. Project plans consist of removing the existing residence and constructing a new single- family residence in the same approximate location of the existing structure. Stormwater plans have not been finalized at this time, but we anticipate that runoff generated on this site will be tighlined to discharge at the bottom of the slope or into an existing stormwater system within the vicinity of the property. The current site layout is shown on the Site Plan in Figure 2. The site is mapped as part of the large historic/prehistoric Meadowdale Landslide area now known as the North Edmonds Earth Subsidence & Landslide Hazard Area (ESHLA). Slide movement from the large- scale slide complex and smaller localized slides within the complex can both affect this property. The residence design will take this into consideration. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions, and provide opinions and recommendations for the proposed site development. Specifically, our scope of services includes the following: 1. Review available soil and geologic maps of the area. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence Edmonds, Washington NGA File No. 917515 March 27, 2015 Page 2 1 Explore the subsurface soil and groundwater conditions within the site with two approximately 20- to 30 -foot deep geotechnical borings using a limited access drill rig. The drill rig was subcontracted by NGA. 3. Map the conditions on the slope and evaluate current slope stability conditions. 4. Perform laboratory classification and analysis of soil samples, as necessary. 5. Provide recommendations for earthwork, foundation support, and slabs -on -grade in accordance with the City standards for development in the North Edmonds ESLHA. 6. Provide recommendations for temporary and permanent slopes. 7. Provide recommendation for deep foundation support, as needed. 8. Provide recommendations for residence retaining walls. 9. Provide recommendations for subgrade preparation. 10. Provide recommendations for site drainage and erosion control. 11. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site is situated on a gentle to moderate west -facing slope overlooking Puget Sound. The property is currently occupied by an existing single-family residence within the upper eastern portion of the property that is planned to be removed as a part of the proposed development plan. The ground surface within the property slopes gently to moderately down to the west from 75`h Place West to the existing railroad tracks and Puget Sound at gradients in the range of approximately 6 to 27 degrees (11 to 51 percent). The existing site conditions, site topography, and interpreted subsurface conditions are presented on Cross Sections A -A' in Figure 3 The site is generally vegetated with grass, landscaping vegetation, and sparse trees. The site is bordered to the north and south by existing residential properties, to the east by 75th Place West and to the west by the BNSF railroad tracks and Puget Sound. The existing and proposed site conditions are shown on the Site Plan in Figure 2. Subsurface Conditions Geology: The geologic units for the site vicinity are shown on the Preliminary Geologic Map of the dmonds East and Ed nonds West Qtiadrangles, Snolionlish and Kin., Counties Washington, by Mackey NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 3 Smith (U.S.G.S., 1975). The site is mapped as old landslides (Qols) with Whidbey Formation deposits mapped nearby. The old landslide deposits are described as large slumps that occurred during the ablation of the Puget Lobe of the Vashon ice sheet by lowering of water -table level. The Whidbey Formation is described as nonglaical river flood plain deposits consisting of clay, silt, and sand with a few lenses of small pebbles. We generally encountered landslide debris underlain by clay with silt, and fine sand that we interpreted as native Whidbey Formation soils. Explorations: The subsurface conditions within the site were explored on March 5, 2015 by drilling two borings using a limited -access drill rig to depths of approximately 26.5 to 31.5 feet below the existing ground surface. The approximate locations of our explorations are shown on the Site Plan in Figure 2. A geologist from NGA was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the borings. A Standard Penetration Test (SPT) was performed on each of the samples during drilling to document soil density at depth. The SPT consists of driving a 2 -inch outer -diameter, split -spoon sampler 18 inches using a 140 -pound hammer with a drop of 30 inches. The number of blows required to drive the sampler the final 12 inches is referred to as the "N" value and is presented on the boring logs. The N value is used to evaluate the strength and density of the deposit. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 4. The logs of our borings are attached to this report and are presented as Figures 5 and 6. We present a brief summary of the subsurface conditions in the following paragraphs. For a detailed description of the subsurface conditions, the boring logs should be reviewed. At the surface of the boring explorations, we encountered approximately 2.5 feet of loose/soft brown -gray silty fine to medium sand and fine sandy silt with varying amounts of gravel and organics that we interpreted as undocumented fill soils. Underlying the undocumented fill, we encountered approximately 15.0 to 17.5 feet of very loose/soft to stiff, gray to blue -gray silty fine sand with trace organics and clay with varying amounts of silt and fine sand that we interpreted as landslide debris. Below the landslide debris in both borings, we encountered very stiff to hard/dense blue -gray clay with silt and fine sand with trace silt that we interpreted as native Whidbey Formation deposits. Both of our borings were terminated within the native Whidbey Formation deposits at depths in the range of approximately 26.5 to 31.5 feet below the existing ground surface. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 4 Hydrologic Conditions Groundwater seepage was encountered in both our explorations at approximately 3.5 feet. However, wet to saturated conditions were encountered sporadically throughout the upper soil horizons. We interpreted this moisture to be groundwater collecting within sandier/less dense lenses of the subsurface, possibly generated from upslope. It is our opinion that the groundwater observed within our explorations is perched water. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of relatively low permeability materials. The more permeable soils on this site would consist of the sand seams found within the landslide debris. The low permeability soil consists of underlying silt. 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 perched groundwater to decrease during drier times of the year and increase during wetter periods. However, due to the large area of recharge, there may be areas of seepage and wet soils on this site even in the drier times of the year. SENSITIVE AREA EVALUATION Seismic Hazard Older landslide debris and medium stiff to hard cohesive soils were encountered underlying the site. Based on the 2012 International Building Code (IBC), the site conditions best fit the description for Site Class E. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion by soft or loose geologic deposits. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the medium dense/stiff or better native soils interpreted to underlie the site have a low potential for liquefaction or amplification of ground motion; however these materials could experience instability as a result of significant seismic activity. The competent cohesive soils interpreted to form the core of the site slopes are considered stable with respect to deep-seated slope failures. However, the overlying loose surficial materials and landslide debris throughout the site have the potential for shallow sloughing failures during seismic events. Such events should not affect the planned residence provided our recommendations for foundation support are incorporated in the project designs. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 5 Erosion Hazard The criteria used for determining the erosion hazard for the site soils includes soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to the vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey o1`Snolwomish 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 Alderwood-Everett gravelly sandy loams, 25 to 70 percent slopes. These soils are listed as having a moderate hazard of water erosion, and on the steeper portions of the slope the erosion hazard is considered high. These soils should have a low to moderate hazard for erosion in areas that are not disturbed and where the vegetation cover is not removed. Landslide Hazard/Slope Stability The criteria used for the evaluation of landslide hazards include soil type, slope gradient, and groundwater conditions. The site slopes gently to moderately down to the west. Groundwater seepage was not observed on the sloping portions of the property during site visit. This site and the overall site vicinity lies within an ancient landslide area. The site and vicinity have been relatively stable for a very long period of time, and development in the area has taken place in the form of single-family residences, roadways, and underground utilities. Although the likelihood of the ancient slide to become active in the forseable future is very low, extreme environmental conditions coupled with inadequate human practices could, in theory, re -activate the ancient landslide. Such external factors could include severe and elongated weather events and/or significant seismic activity. The site falls within "Zone A" of the North Edmonds Earth Subsidence and Landslide Hazard Area Report prepared by Landau Associates for the City of Edmonds. This designation requires that certain features be included (or excluded) in the design. Such features include the restriction of cuts and fills, the need for tightlining runoff into an approved system, the need to design foundations and retaining walls to withstand high lateral earth pressures and potential loss of soil beneath parts of the foundation, the need to vegetate slopes with deeply rooted drought -tolerant vegetation, and the elimination of any and all irrigation systems. We have addressed all of these requirements in the remainder of this report. We encountered what we interpreted as older landslide debris to depths of about 20 feet below the existing ground surface. Medium dense/stiff undisturbed native soils were encountered below this NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 6 material, which we interpret the core of the slope at depth to consist primarily of this relatively stable material. Potential deep-seated slide planes were reported to be up to 100 feet deep below ground surface within the area; however, we did not observe signs of recent deep-seated slope failures on the property and do not anticipate that such failures will occur during the expected life of the structure. Localized areas of surface instability and surface sliding can occur on steep slopes, particularly where modified through grading activities. Backwasting (movement of near -surface soil) through soil erosion processes or local surface slides is common to slopes, particularly where the soils are exposed to weathering. Normal surface erosion and shallow sloughing failures should be expected to continue on the steeper portions of the site, but we have provided geotechnical recommendations for deep -foundation support, erosion control, and other development considerations that should reduce the potential impact of site development on the site slopes. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion, from a geotechnical standpoint, that the site should be compatible with the proposed development of a single-family residence, provided that the geotechnical recommendations presented in this report are incorporated into project plans and followed during construction. The proposed development area appears to be relatively stable under current conditions. However, the historic landslide mapped at the site could be reactivated by extreme natural conditions and/or poor grading and/or drainage activities within the site and by other human activity in the general site vicinity. We consider this potential to be extremely low. To alleviate potential site instability concerns, we recommend that the entire residence be supported on a deep foundation system consisting of augercast piles extending through the upper landslide debris and terminating into the competent undisturbed soils at depth. This is further described in the Deep Foundations subsection of this report. We should be retained to review the project plans prior to applying for a permit, and to monitor earthwork and foundation system installation during construction In general, the site currently appears generally stable with respect to deep-seated movement. However, the site vicinity is mapped within an older landslide complex and our explorations encountered evidence of past ground movement. The potential for landslide and erosion hazards will depend on how the site is graded and how surface water and near surface water are controlled. We recommend that site grading be kept to a minimum and that grading and site drainage plans be subjected to geotechnical engineering review prior to construction. This review would include specific stability analysis of proposed cuts and NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 7 fills and would provide recommendations for accomplishing the desired grading while maintaining long- term stability. Grading plans were not finalized at the time of this report, but we anticipate that cuts may be needed to allow construction of the residence foundation. If these cuts cannot be sloped back to a safe inclination due to site constraints, we recommend that the cuts be shored with a soldier pile retaining wall or a similar system. The need for a shoring system should be determined during final design. This potential wall could be designed as a permanent wall and incorporated into the residence foundations. We provide recommendations for temporary and permanent cut slopes in the Temporary and Permanent Slopes section of this report. We recommend that if a slab -on -grade is utilized in the lower portions of the proposed residence that the slab be designed as a structural slab and be supported on the deep foundation system. Other hard surfaces, such as paved areas or walkways that are supported on the existing soil have some risk of future settlement, cracking, and the need for maintenance. To reduce this risk, we recommend over -excavating a minimum of two feet of the upper soil from the slab and pavement areas and replacing this material with compacted pit run or crushed rock structural fill. This recommendation is only for hard surfaces to be supported on grade and does not apply for the lower floor structural slab. Even with the recommended treatment, some settlement of the underlying loose material should be anticipated. The control of surface and near -surface water is very important for the long-term stability of the site and on the steeper portions of the site slopes. We highly recommend that temporary and final site grading be designed to direct surface water away from the structures and away from the site slopes. Final drainage plans have not been developed at this time, but we understand that all stormwater generated on the site will be collected in tightlines and transported to the bottom of the slope to the west of the property or into an existing stromwater system within the vicinity of the property. No water should be infiltrated or dispersed within the site. We discuss general site drainage in the Site Drainage subsection of this report. The soils encountered within our explorations are considered extremely moisture sensitive and will disturb easily when wet. We recommend that construction take place during extended periods of dry weather if possible. If construction takes place during wet weather, additional expenses and delays should be expected due to the wet conditions. Additional expenses could include the need to export on- site soil, the import of clean, granular soil for fill, and the need to place a blanket of rock spalls or crushed NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 8 rock in the construction traffic areas and on exposed subgrades prior to placing structural fill or structural elements. In this report, we have also provided recommendations for drainage, erosion control, and other development considerations intended to reduce the potential impact of development on the site and the site slopes. We should be retained to review final project plans prior to construction. We also 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. Erosion Control and Slope Protection Measures The erosion hazard for the on-site soils is considered moderate to high, 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 slope waddles should be erected to prevent muddy water from leaving the site or flowing over the site slopes. 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 to moderate. Also, irrigation systems should not be installed within the property. Protection of the site slopes should be performed as required by the City of Edmonds. Specifically, we recommend that the slopes not be disturbed or modified through placement of any fill or future structures outside the planned development areas. No additional material of any kind should be placed on any portion of sloping ground, such as excavation spoils and soil stockpiles. Trees may be cut down and removed from the slopes as long as a mitigation plan is developed for maintaining slope stability, such as the replacement of vegetation for erosion protection. A vegetation cover should be preserved on the slopes. Replacement of vegetation should be performed in accordance with the City of Edmonds code. Under no circumstances should water be allowed to concentrate on the slopes. Any sloping areas disturbed during construction should be planted with vegetation as soon as practical to reduce the potential for erosion. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 9 Site Preparation and Grading Plans for site grading should be devised such that cuts and fills are kept to a minimum. Site preparation should consist of excavating the residence footprint down to planned elevations. If shoring walls are needed to support cut excavations, we recommend that the excavation for the building should only be attempted after the shoring systems are installed. Site preparation should also consist of stripping any organic topsoil and/or loose/soft soils in areas that will support foundations, slabs -on -grade, pavement, or structural fill. The stripped material should not be stockpiled in any area between the top of the slope and the residence footprint. If the exposed soils are loose/soft, they should be compacted to a non -yielding condition. Areas observed to pump or weave during compaction should be over -excavated and replaced with rock spalls. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed and the exposed subgrade maintained in a semi -dry condition. In wet conditions, the exposed subgrade should not be compacted, as compaction of a wet subgrade may result in further disturbance of the soils. A layer of crushed rock may be placed over the prepared areas to protect them from further disturbance. The site soils are considered extremely moisture sensitive and will disturb easily when wet. We recommend that earthwork construction take place during periods of extended dry weather, and suspended during periods of precipitation if possible. If work is to take place during periods of wet weather, care should be taken during site preparation not to disturb the site soils. This can be accomplished by utilizing large excavators equipped with smooth buckets and wide tracks to complete earthwork, and diverting surface and groundwater flow away from the prepared subgrades. Also, construction traffic should not be allowed on the exposed subgrade. A blanket of rock spalls should be used in construction access areas if wet conditions are prevalent. The thickness of this rock spall layer should be based on subgrade performance at the time of construction. For planning purposes, we recommend a minimum one -foot thick layer of rock spalls. Temporary and Permanent Slopes 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 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 nature NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 10 and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. 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 on-site material be no steeper than two units horizontal to one unit vertical (2H:1 V). If groundwater seepage is encountered, we would expect that flatter inclinations would be necessary. We should be retained to specifically review proposed geometry for significant cuts planned on this site. We recommend that cut slopes be protected from erosion. Erosion control measures may include covering cut slopes with plastic sheeting and diverting surface water 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 3H:1 V. However, flatter inclinations may be required in areas where loose soils are encountered. Permanent slopes should be covered with erosion control matting and vegetated. The vegetative cover should be maintained until established. We should specifically review all plans for grading on this project. We do not recommend placing irrigation systems near the slopes. Deep Foundations Due to the presence of a thick layer of landslide debris, shallow perched groundwater, and caving conditions encountered in our explorations within the proposed residence area, we recommend that the entire residence be supported on 16 -inch diameter augercast piles extending a minimum of five feet into competent native soils. Based on our explorations, we recommend that the piles be a minimum of 30 feet deep below current ground surface to satisfy this requirement. However, depending on the actual depth of the slide debris at the specific pile locations, some of the piles may need to be extended deeper than 30 feet to achieve the minimum five foot embedment into competent native soils. This can be confirmed in the field during pile installation. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 11 Augercast piles are installed with a hollow -stem auger advanced to the desired pile depth. After reaching a minimum recommended penetration into bearing soils, a pressure head is created when grout is pumped into the hollow stem of the auger before starting auger withdrawal. After the grout head is developed, withdrawal of the auger is timed to maintain the grout pressure head and avoid intrusion of loose soil into the sides of the pile excavation or discontinuity or "necking" of the pile. The actual volume of the concrete pumped into each pile is recorded and compared with the theoretical volume of the pile. Piles with a ratio of actual to theoretical great volume less than 1.1 should be re -drilled. The augercast piles should provide the necessary vertical support for the structure as well as some lateral resistance. The success of this method will depend, in part, on site access for the drill rig and other equipment needed for pile installation. Obstructed piles should be relocated and/or additional piles installed. Some discussion on relocation of piles should be made with your structural engineer prior to start of drilling. It is usually best to make any changes while the drill rig is on site. For preliminary design, we recommend that the piles extend a minimum of 30 feet below the existing ground surface and penetrate a minimum of 5 feet into the underlying competent native granular and fine- grained soils to provide adequate end bearing and friction capacities. The competent native material was encountered at approximately 20 to 25 feet below the existing ground surface within the proposed residence area. We present design friction, end bearing, and total axial compression capacities for 16 - inch diameter augercast piles, installed as recommended, in the following table. The friction component should be used to resist uplift forces only. The provided values do not include the weight of the piles. If the piles weight will be utilized to resist uplift forces, the buoyant unit weight and adequate safety factors should be used. Pile Diameter Total Pile Depth (Feet) Design Friction (Tons) Design End Bearing (Tons) (Inches) (use only for uplift) (vile capacity) 16 30 1025 Lateral resistance on the piers could be calculated based on an equivalent fluid density of 200 pounds per cubic foot (pcf) applied to two pile diameters. The upper 20 feet should be neglected for the purpose of calculating the lateral resistance. If this is not feasible, some of the piles may be battered to provide lateral resistance. Also passive resistance on competent backfill around grade beams could be utilized. The upper foot of material should be neglected. We should be retained to review pile design and observe NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 12 augercast pile installation. Structural Fill General: Fill placed beneath foundations, pavements, and other settlement -sensitive structures, or behind retaining walls should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards and is monitored by 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 prepared as outlined in the Site Preparation and Grading subsection of this report. Sloping areas to receive fill should be benched prior to fill placement. The benches should be level and at least four feet wide. 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 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). We do not anticipate placement of significant volumes of structural fill for this project. The on-site soils consist of moisture -sensitive silty materials and slide debris. We recommend that the on-site material not be used as structural fill. We should be retained to evaluate the suitability of proposed structural fill materials at the time of construction. 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 underlying building areas and pavement subgrade 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 compactable condition exists. It may be necessary to over - excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence Edmonds, Washington NGA File No. 917515 March 27, 2015 Page 13 Retaining Walls We understand that retaining walls may be incorporated into project plans. We recommend that retaining walls be kept as short as possible. 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, the inclination of the backfill, and other possible surcharge loads. 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 40 pcf for yielding (active condition) walls, and 60 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 and foundation loads, slopes, or other surface loads. Also, hydrostatic and buoyant forces should be included if the walls could not be drained. We could consult with the structural engineer regarding additional loads on retaining walls during final design, if needed. All wall backfill should be well compacted; however, 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 thin loose lifts and compacting it with small, hand -operated compactors within a distance behind the wall equal to at least one-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. Retaining walls that are part of the residence should be supported on auger -cast piles as described above. Retaining walls associated with driveway grading and other landscaping plan should be kept under four feet in height and should be supported on a minimum of two feet of rock spalls to reduce the potential for differential settlement of the walls. The active pressure on the walls can be resisted by friction on the bottom of the wall footing and passive resistance on the below -grade portion of the footing. We NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 14 recommend using a design soil bearing pressure of no more than 1,500 pounds per square foot (psf) along with a friction coefficient and passive resistance values of 0.35 and 200 pcf, respectively. The upper one foot of material should be neglected when calculating the passive pressure. 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 drainage system installation. Structural Slabs As mentioned earlier, we recommend that if a lower floor slab is utilized, that this slab be designed as a structural slab fully supported on the deep foundation system. We recommend that slabs be underlain by at least six inches of free -draining gravel with less than three percent by weight passing the 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 moist sand layer may be used to cover the vapor barrier. This sand layer may be used to protect the vapor barrier membrane and to aid in curing the concrete; however, this sand layer is optional and is intended to protect the vapor barrier membrane during construction. Other slabs and hard surfaces that may be supported on the existing soils should be underlain by a minimum of two feet of railroad ballast in addition to the capillary break and vapor barrier. Pavement Subgrade Pavement subgrade preparation should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. Depending on the tolerance to pavement cracking, we recommend that the upper two feet of the existing material be removed and replaced with granular structural fill or crushed rock. The pavement subgrade should be proof -rolled with a heavy, rubber -tired piece of equipment, to identify soft or yielding areas that may require repair prior to placing any structural fill and prior to placing the pavement base course. We should be retained to observe the proof -rolling and recommend repairs prior to placement of the asphalt or hard surfaces. The pavement section should be thickened to further reduce the effects of settlement due to the landslide debris, but potential long-term cracking should still be expected. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence Edmonds, Washington NGA File No. 917515 March 27, 2015 Page 15 Site Drainage Surface Drainage: The finished ground surface should be graded such that stormwater is directed to an appropriate stormwater collection system. Water should not be allowed to collect in any area where footings, slabs, or retaining walls are to be constructed. Final site grades should allow for drainage away from the structure and away from the site slopes. 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 structure and slopes. Surface water should be collected by permanent catch basins and drain lines, and be discharged into an appropriate discharge system. Under no circumstances should water be allowed to flow uncontrolled over the site slopes or excavation walls. We recommend that all stormwater generated on the site, including roof downspouts, footing drains, pavement and yard drains, and any water flow from the road, be tightlined to the bottom of the slope to the west or into an approved system within the vicinity of the property. If the stormwater is tightlined to the bottom of the slope, we recommend that the pipe should end with a perforated tee section approximately eight feet long that is capped on both ends and embedded onto a crushed rock pad at the toe of the slope along the railroad tracks. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavations and collect water into ditches and small sump pits where the water can be pumped out of the excavations and routed into an appropriate outlet. We recommend the use of footing drains around the planned structure 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 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 the migration of surface water or silt into the footing drain. Footing drains should discharge into 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. NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation NGA File No. 917515 Abbott Residence March 27, 2015 Edmonds, Washington Page 16 Roof drains should also be installed around the structure. Roof drains should consist of gutters and downspouts collecting stormwater runoff from the roof. The downspouts should discharge to catch basins and 4 -inch minimum diameter, rigid, PVC tightline pipes. The drains should be directed into catch basins and then into the controlled drainage system. The footing and roof drains should discharge via independent (separate) tightlines into catch basins/cleanouts leading to the stormwater system. Surface water from the driveway and yard areas should also be collected in a catch basin and tightlined separately to the stormwater system. USE OF THIS REPORT NGA has prepared this preliminary report for Mr. Derek Abbott 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. We recommend that we be retained to review final project plans and provide consultation regarding specific structure placement, site grading, foundation support, and drainage. We also 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. All people who own or occupy homes on or near 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 as soon as possible. The probability that landsliding will occur is substantially reduced by the proper maintenance of drainage control measures at the site (the runoff from the impervious surfaces NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence Edmonds, Washington NGA File No. 917515 March 27, 2015 Page 17 should be led to an approved discharge point). Therefore, the homeowner should take responsibility for performing such maintenance. 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 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. 1 NELSON GEOTECHNICAL ASSOCIATES, INC. Preliminary Geotechnical Engineering Evaluation Abbott Residence Edmonds, Washington NGA File No. 917515 March 27, 2015 Page 18 We appreciate the opportunity to provide service to you on this project. If you have any questions or require further information, please call. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Lee S. Bellah, LG Project Geologist 0,7 552 5 NAL Exp. July 28, 2015 Khaled M. Shawish, PE Principal LSB:KMS:cja Six Figures Attached NELSON GEOTECHNICAL ASSOCIATES, INC. ject Nun 917515 Figure 2 „ co . � Q—) a u U p r � t O a J 2 ° C +y, ; �- m w � C a a C \ \ a a C r a a C x O t 2.1 a C CU C a s VI 9 a CU C CO is as 1 tl as tl — N p E C ® l aa C X N < a ak a \ O p N Z w l C. E �± CL L 4 O O Ci V S d Z2 Q O a * a U a 0 NELSON GEOTECHNICAL No. Date Revision By CK Abbott Residence N p ASSOCIATES, INC. 1 3/16/15 Original DPN LS13 Site Plan GEOTECHNICAL ENGINEERS & GEOLOGISTS 1'Wt71WhAw,K,,A, 'liis aentaPn ;rnwnmy Pwl'"ddp 337-7889 W.4'�W9uB'.'e•Mdh 9'pgP WNgrwll.nhMlnm474iGMF898&76BB (q;1L1+68Gm2Bu'B Kf.x °G81.9SG4Yamx+,an ch.can c a0i N .0 > co N N N E 0 c � o C � O N O O 0 N C E O Q O v a c a c � N U r, W CL 12 w 0 m - O W pI X:: f6 > N Q b N Z�L W N O O N O m N W U C M N Mn d 7 In l9 N E N a 4T 0 0 c CU d d E 0 c_ U d L c m t m 0 rn M000 y+ w v O LU Lj 1 r c a0i N .0 > co N N N E 0 c � o C � O N O O 0 N C E O Q O v a c a c � N U r, W CL 12 w 0 m - O W pI X:: f6 > N Q b N Z�L W N O O N O m N W U C M N Mn d 7 In l9 N E N a 4T 0 0 c CU d d E 0 c_ U d L c m t m Project Number NELSON GEOTECHNICAL No. Date Revision By CK 917515 Abbott Residence �N�3A ASSOCIATES, INC. 1 3/70/15 Original DPN Iss Cross -Section A -A' GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 3 97W -935h Av tdE,aro6 4—ld Penny 0880 WW6-11659 WA 96072 WBIIB h ,&7 80609 (425) 466-1669 /F®x 469-2598 Bug) 66&7696 0 rn y+ w N O� O Lj pN O r r (1901) u01tena13 a}ewixalddy c N : C 2 o O a . 0 w N O 00 N 7 fn (Q m > N E z a H —y U)I I 0 O �L I a r "R7, m Tfir,° r CO C) O &G U) Project Number NELSON GEOTECHNICAL No. Date Revision By CK 917515 Abbott Residence �N�3A ASSOCIATES, INC. 1 3/70/15 Original DPN Iss Cross -Section A -A' GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 3 97W -935h Av tdE,aro6 4—ld Penny 0880 WW6-11659 WA 96072 WBIIB h ,&7 80609 (425) 466-1669 /F®x 469-2598 Bug) 66&7696 0 y+ w N O� O Lj pN O r r (1901) u01tena13 a}ewixalddy m : C 2 o O a . 0 w Project Number NELSON GEOTECHNICAL No. Date Revision By CK 917515 Abbott Residence �N�3A ASSOCIATES, INC. 1 3/70/15 Original DPN Iss Cross -Section A -A' GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 3 97W -935h Av tdE,aro6 4—ld Penny 0880 WW6-11659 WA 96072 WBIIB h ,&7 80609 (425) 466-1669 /F®x 469-2598 Bug) 66&7696 UNIFIED SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS GROUP NAME SYMBOL CLEAN GW WELL -GRADED, FINE TO COARSE GRAVEL COARSE- GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50 GM SILTY GRAVEL OF COARSE FRACTION OF 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 SC WITH FINES 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) Field 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 Moist - Damp, but no visible water. is based on ASTM D 2488-93. 3) Descriptions of soil density or Wet - Visible free water or saturated, consistency are based on usually soil is obtained from interpretation of blowcount data, below water table visual appearance of soils, and/or test data. Project Number 1 NELSON GEOTECHNICAL No. Date Revision By CK 917515 Abbott Residence NC7A AssoclATEs, INC. 1 3/10/15 Original DPN LSB Soil Classification Chart GEOTECHNICAL ENGINEERS & GEOLOGISTS FI ure 4 9 173111351h Ave NE,ASD° Swhomleh C—ty (425) 337-1669 WoodioNlle WAEk6lT72 Wenp0c*C a(SOQ)6657696 (424y1, 461%1669 0 lbw U1,2610 +aMvnrnlc °upM1Au'Al.mm �S BORING LOG B-1 Approximate Ground Surface Elevation: —60 ft Soil Profile Sample Data Penetration Resistance rn c (Blows/foot - del) Piezometer 10 20 30 40 50 50+ H Installation - ;, �� ------ Ground Water Description a c �° o a g Moisture Content Data m U c� L (Percent - N) (Depth in Feet) 0 0 fn fn 10 20 30 40 50 50+ co 0 co l� Dark brown-gray, fine sandy silt with trace organics and 4 iron-oxide staining (soft, moist) FILL 3 Dark gray, silty fine sand with trace organics and .., • ,. iron-oxide staining (very loose, wet) , -no iron-oxide staining q -with interbedded fine sand and silt seams and tracegacs orni (soft, wet o saturated) ML 19 Dark brown silt (very stiff, moist) ML 10 103 Gray clay with silt and trace slickensides (soft, wet) -becomes stiff, moist 8 CL 15 1_ 1 5 .... ..... ......... .......... ........ 15 16 Blue and gray clay with silt (very stiff, moist) -becomes stiff 10 20 .. 20 11 CL 25 .. . , ,.,, ... ., .. .. ,... ........ -25 14 LEGEND ❑ Solid PVC Pipe r, Concrete M Moisture Content ❑ Slotted Depth Driven and Amount Recovered PVC Pipe Bentonite A G Atterberg Grain-size Limits Analysis with 2-inch O.D. Split-Spoon Sampler mmi Monumenti Cap Native Soil DS Direct Shear to Piezorneter Depth Driven and Amount Recovered * Liquid Limit Q Silica Sand PP P Pocket Sample Penetrometer Pushed Readings, tons/ft with 3-inch Shelby Tube Sampler + Plastic Limit Water Level T Triaxial NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by engineering tests, analysis and judgement. They are not necessarily representative of other times and locations. We cannot accept responsibility for the use or Interpretation by others of Information presented on this log. Project Number NELSON GEOTECHNICAL No. Date Revision By CK zs w Abbott Residence ""NGA ASSOCIATES, INC. 917515 7 3116195 Odglnel DPN LSB $ Figure 5 Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS GI. Page 1 of 2 12511>135h A.,NE4W A $ A1mG (066 $:r6.1 W .1 WAW?2�� '"�,ti (a2b1 ro.WtlFIa N Nva 481,26110 wwx. natinae�uaunan cme�a BORING LOG B-1 (cont.) i= 0 Soil Profile Sample Data Penetration Resistance (Blows/foot - 9) 10 20 30 40 50 50+ ' " y H Piezometer Installation - Slotted PVC Pie P Bentonite A Atterberg Limits Depth Driven and Amount Recovered P G Grain -size Analysis with 2 -inch O.D. Split -Spoon Sampler l Z Ground Water Moisture Content Description a m PP Pocket Penetrometer Readings, tons/ft Silica Sand p Sample Pushed 3 a Plastic Limit Data NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by englneedng tests, analysis and Judgement. They are not necessarily o T m o V t (Percent - ■) o (Depth in Feet) GEOTECHNICAL C7 (D fn Revision � d 10 20 30 40 50 50+ J Abbott Residence v C � I Gray, fine sand with trace silt (dense, moist) Sp 33 9 . Figure 5 Boring Log GEOTECHNICAL Boring terminated below existing grade at 31.5 feet on 3/5/15. Groundwater seepage was encountered at 3.5 Page 2 of 2 1731Wd VMA-NCi,.A-WO (425)Awl"aIFaQ1-"la W' $ , � m Z feet during drilling 35 . 35 ..1....1..1..1...1.11..1..]...1.111.11.....1111...1_..11 140 11 -4...... 1 11 1111...11.l1-11-]1-. .] 145 ..,{......... V ........ .R ......... N.........1.•... I X 50 i.........1........1... �...... y.........f ,..... III 1-55 LEGEND �, Solid PVC Pipe ^w Concrete M Moisture Content ° 1111 Slotted PVC Pie P Bentonite A Atterberg Limits Depth Driven and Amount Recovered P G Grain -size Analysis with 2 -inch O.D. Split -Spoon Sampler l Monument/ Cap Native Soil DS Direct Shear Depth Driven and Amount Recovered * to Piezometer Liquid Limit � PP Pocket Penetrometer Readings, tons/ft Silica Sand p Sample Pushed with 3 -inch Shelby Tube Sampler + Plastic Limit Water Level T Triaxial NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by englneedng tests, analysis and Judgement. They are not necessarily ''... representative of other times and locations. We cannot accept responsibility for the use or interpretation by others of information presented on this log„ Project Number GEOTECHNICAL No. Date Revision By CK Abbott Residence v C 9 . Figure 5 Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS Page 2 of 2 1731Wd VMA-NCi,.A-WO (425)Awl"aIFaQ1-"la W' $ , � m Z OIG B-2 Approximate Ground Surface Elevation: -72 ft Soil Profile LOG Sample Data P Penetration Resistance (Blows/foot - 0) 10 20 30 40 50 50+' Moisture Content °I H ° Piezometer Installation - Ground Water Data 0 21 t a o 0 0 Description w P E o O m E 5 (Percent - M) m c (Depth in Feet) c7 fn U CO 0 d 10 20 30 40 50 50+' a I I I I _J Brown -gray, silty fine to medium sand with gravel, trace 6 organics, and iron -oxide staining (loose, moist) SM Gray, fine sandy silt with trace organics and iron -oxide staining (soft, wet) 3 ML Blue- — — — — — gray, silty fine sand with trace organ—ics, interbedded ,° 5 - -- - • 5 silt and silt chunks (very ry Ioose, saturated) �" . 2 � SM 2 Blue -gray clay with silt and trace fine sand with — — — 10 .. � .,. .. 10 interbedded silty fine sand seams (medium stiff, moist) 6 CL Blue -gray clay with silt (stiff, moist) 11 15 .. ........ -15 CL 20 ,. 20 -becomes very stiff 17 hard -becomes 41 Boring erminated ls ow ng ade at 26.5 on seepage asrenco encountered att3.0 3/5/15.tGroundwater ` feet during drilling LEGEND ❑ Solid PVC Pipe Concrete M Moisture Content Q Slotted PVC Pipe 21 Bentonite A Atterberg Limits Depth Driven and Amoaartt. Recovered G Grain -size Analysis with 2 -inch O.D. Splil-Spoon Sampler Monument/ Cap Native Soil DS Direct Shear ` to Piezometer PP Pocket Penetrometer Readings, tons/ft Depth Driven and Amount Recovered Q Silica Sand P �r Liquid Limit P Sample Pushed, with 3 -inch She#tay Tube Sampler + Plastic Limit Water Level T Triaxial NOTE: Subsurface conditions depleted represent our observations at the time and location of this exploratory hole, modified by engineering tests, analysis and judgement. They are not necessarily representatithers of his log. of other presented on IHNICAL NUnlberesandlocatlons.WecennotacceptresponslbllllyfortheuseorinterpretationbyoNELSONGEOTECIon PrOJeCtVe No. Date Revision By CK �. 917515 Abbott Residence NGA ASSOCIATES, INC. 3110115 'odglnal DPN Asa ' 1 Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS Figure 6 1731143150A. 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