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City of Edmonds Critical Area Notice of Decision Applicant: - I() - � , '.. Property Owner Critical Area File 4: o I i � Permit N-urnber: Site Location: Parcel Number: Project Description: G) _s 2, 3(,) El Conditional Waiver. No critical area report is required for the project described above, 1, — There will be no alteration of a -Critical Area or its required buffer. 2. _ The proposal, is an allowed activity pursuant to ECDC 23.40.220, 23.50.220, and/or 23-80,040. 3. — The proposal is exempt pursuant to ECDC 23.40.230, Cn D Erosion Hazard. Project is within erosion hazard area. Applicant must prepare an erosion and sediment control plan in compliance with ECDC 18.30. A Critical Area Report Require' d The proposed project is within a critical area and/or a critical area 'buffer and a critical area report is required. A critical area report has been submitted and evaluated for compliance with the following criteria pursuant to ECDC 23.40.160: 1. The proposal minimizes the impact on critical areas in accordance with ECDC 23,40, 120, Mitigation sequencing; 2. The proposal does not pose an unreasonable threat to the public health, safety, or welfare on or off the development proposal site; 3. The proposal is consistent with the general purposes of this title and the public interest; 4� Any alterations permitted to the critical area are mitigated in accordance with ECDC 23.40.110, Mitigation requirements. 5. The proposal protects the critical area functions and values consistent with the best available science and results in no net loss of critical functions and values; and 6. The proposal is consistent with other applicable regulations and standards. ❑ Unfavorable Critical Area Decision. The proposed project is not exempt or does not adequately mitigate its impacts on critical areas and/or does not comply with the criteria in ECDC 23,40.160 and the provisions of the City of Edmonds critical area regulations. See attached findings of noncompliance. Favorable Critical Area Decisiom The proposed project as described above and as shown on the attached site plan meets or is exempt from the criteria in ECDC 23.40,160, Review Criteria, and complies with the applicable provisions of the City of Edmonds critical area regulations. Any subsequent changes to the proposal shall void this decision pending re -review of the proposal. El Conditions. Critical Area specific condition(s) have been applied to the permit number referenced above. See referenced permit number for specific condition(s), /7 Y J-I-A,aw 2;11�,I-ILI - Reviewer Signature Date Appeals: Any decision to approve, condition, or deny a development proposal or other activity based on the requirements of critical area regulations may be appealed according to, and as part of, the appeal procedure, if any, for the permit or approval involved. Revised 12/16/2010 CRITICAL AREA EVALUATION & GEOTECIINICAL REPORT PROPOSED SINGLE FAMILY RESIDENCE 15911® 74TH PLACE WEST EDMONDS, WA G®3598 Prepared For Mr. Leroy Saunders c/o Mr. Laurey Tobiason Tobiason & Company, Inc. Seattle, WA 98166®4016 February 25, 2014 GEO GROUP NORTHWEST, INC. 13240 NE 20th Street, Suite 10 Bellevue, Washington 98005 Phone: (425) 9®8757 AN r o u Immu INEwm=M 1RwLTANw NYABLM �1111uunpp- February 25, 2014 Northwest, Inc. Mr. Leroy Saunders c/o Mr. Laurey Tobiason Tobiason & Company, Inc. Seattle, WA 98166-4016 Subject: CRITICAL ARE A EVALUATION & GEOTECHNICAL REPORT Proposed Single Family Residence 15911 - 74' Place West Edmonds, WA Dear Mr. Saunders and Mr. Tobiason, (.","ook.,dudmal Fngin(,K,,rs, Godoc.0sts & Environrnentzfl Scienfists At your request, GEO Group Northwest, Inc., has prepared this report for the purpose of providing a critical area evaluation and geotechnical engineering report for the proposed construction of a single family residence in accordance with ECC 23.40 and 23.80. The project site is located within an area designated as the North Edmonds Earth Subsidence Landslide Hazard Area. Our work in preparing the report included review of the proposed site development plan provided, site reconnaissance, exploration of the site soils, review of files at the City of Edmonds for the neighboring properties and review of maps and documents related to North Edmonds Earth Subsidence Landslide Hazard Area, including: "City of Edmonds Landslide Hazards Map, Figure 1," 1985, by GeoEngineers, hic., based on the "Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington, 1979, by Roger Lowe Associates, Inc. 2. "Report of Geotechnical Consultation, Property Value Appraisals and Assessments, Meadowdale Landslide Area, Edmonds, Washington," 1985, by GeoEngineers, Inc. 3. "North Edmonds Earth Subsidence and Landslide Hazard Areas Summary Report, Edmonds, Washington," 2007, by Landau Associates. 1324) NE 20M Suk,, W m 113(!'.fllovue, Ww..,,Ihhn,jon 98005 Flhono 425/649-8757 Fax 125/649 8758 February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 2 Proposed SFR, 15911 - 74' Place W, Edmonds SITE DESCRIPTION The subject lot is located at the north end of 74" Place West at the dead-end of the street, north of the North Meadowdale Road, as illustrated on the Vicinity Map, Plate 1. The lot is identified as Snohomish County Parcel No. 00513300003201. The lot is 26,573 sf in size, slightly trapezoidal in shape, and measures approximately 228 feet east/west along the south property line and 120 feet north/south along the west property line, as illustrated on the Topographic Site Plan, Plate 2. The lot is bordered to the west by the undeveloped right-of-way of 74`' Place West, to the north and south by residential developed properties, and to the east by a steep slope which appears to be the eastern margin of the North Edmonds Earth Subsidence Landslide Hazard Area. Topographically, the eastern quarter of the lot slopes steeply down to the west. The lot survey provided did not include elevations of the steep slope in the eastern portion of the site, however based on a previous topographic survey, dated May 12, 2004, obtained from the City file, the upper portion of the slope as having a gradient of 80 to 85 percent and the lower portion of the slope with a gradient of 50 percent. The lower portion of the slope appears to be collected slide debris (colluvium). Localized areas on the slope face appear to exceed 100 percent where the landslide scarp is exposed. The total height of the slope is estimated at about 100 feet. The middle portion of the lot is relatively flat and level and is bordered along the north property line by a 10 to 14 foot tall slope with a gradient of 38 to 50 percent that slopes down to the south. The western quarter of the lot slopes down westerly at a gradient of 36 to 56 percent with a slope height of about 22 feet at the northwest corner and about 20 feet at the southwest corner. Elevations on the survey range from 95 feet at the southwest corner to about 136 feet along the north property line. The elevation of the flat middle portion of the lot ranges from 116 feet to 121 feet. A surface exposure of groundwater seepage was observed at the toe of the slope in the northeastern corner of the middle portion of the lot, approximately as illustrated on the Topographic Site Plan, Plate 2. Water is also present on the slope face in the southeastern corner of the lot, most of which is being collected in a corrugated pipe near the southeast corner of the lot and a catchbasin located at toe of the slope and routed in a storm pipe located in a 10 foot wide storm sewer easement along the south property line. The site is serviced by public stormwater and sanitary sewer facilities. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74"' Place W, Edmonds G-3598 Page 3 The middle and western portions of the lot have been cleared of vegetation (principally blackberries based on the remaining debris). The steep slope to the east is vegetated with brush, immature and mature Alder and Maple trees (predominant), and a few Maple and evergreen trees. PROPOSED SITE DEVELOPMENT Based on the plans provided, a two-story wood framed home is proposed to be constructed in the middle flat portion of the lot, as illustrated on the Site Plan, Plate 3. The main floor has a planned finished floor elevation of 118 feet. An attached garage will located at the back of the home and an asphalt driveway is planned around the north side of the home off of 74`' Place West. The house plan also includes a hot -tub near the southwest corner of the house and a water feature at the back entry to the house. A tiered ecology block wall is planned on the north side of the driveway to retain the cut required to construct the driveway. The planned height of the walls is 4 feet to 6 feet with 6 feet of separation between the walls. A new catchbasin and drainage Swale is proposed between the house and toe of the slope to the east. The slope west of the house is proposed to be graded at 2H: IV. GEOLOGY & SOILS INVESTIGATION According to the area geologic maps the site soils are mapped near the contact of the Pre -Fraser Glaciation deposits identified as Transitional Beds (Qtb) and Olympia Gravel (Qog). Transitional beds are described as glacial and non -glacial deposits consisting mostly of massive, thick or thin beds and laminae of medium to dark gray clay, silt and fine to very fine sand. The fine-grained sediment is described as having been deposited in lakes, some distance from the ice front, and in fluvial systems prior to the advance of the glacial ice. The Olympia Gravel is described as consisting of stratified, fluvial sand and gravel. The gravel is mostly pebble size and the unit is locally oxidized and weakly cemented so that it stands near vertically in fresh exposure. The Olympia gravel underlies the Transitional beds. Minard J. P., 1983, "Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington," U.S. Geological Survey, Miscellaneous Field Studies, Map MF -1541, Scale 1:24,000. GEO Group Northwest, Inco February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74" Place W, Edmonds G-3598 Page 4 Based on the Soil Survey of Snohomish County 2, the site soil is mapped as Alderwood gravelly sandy loam, 15 to 25 percent slopes, which is described as consisting of moderately deep, moderately well drained gravelly to very gravelly sandy loam on till plains with a moderate water erosion potential. The unit consists of dark grayish brown to yellow brown, with a weak medium subangular blocky structure that overlies weakly cemented to compact glacial till (hard pan) at a depth of 20 to 40 inches. This soil description does not match the findings of our subsurface investigation. Subsurface Investigation Two borings were drilled to investigate the sites subsurface soil and groundwater conditions. The approximate boring locations are illustrated on the Topographic Site Plan, Plate 2. Boring B-1 was drilled to a depth of 56.5 feet at the east side of the lot and boring B-2 was drilled to a depth of 61.5 feet at the west side of the lot. Standard penetration tests were performed as the boring were advanced and soil samples collected. Soils encountered in boring B-1 principally consisted of very loose to medium dense silty sand with occasional gravel to a depth of 43 feet, underlain by very stiff to hard silt with some clay to the total depth of the boring. Soils encountered in boring B-2 principally consisted of loose to medium dense silty sand with some gravel to a depth of 34 feet, underlain by medium dense sand with some gravel and varying amounts of silt. Dense sand was encountered at a depth of 60 feet. A cross section with the borings and soil classifications is included on Plate 4. Please refer to the boring logs in Appendix A for more detail on the soil conditions encountered. Hydrology In Boring B-1 groundwater was measured at a depth of 4.25 feet. Soils below this depth were saturated down to the silt at 43 feet. The water appears to be perched on top of the silt. In Boring B-2, groundwater was measured at a depth of 28.9 feet. A zone of oxidized red brown mottled sand was encountered below 16.5 feet indicating seasonal groundwater movement below that depth. There is evidence of groundwater seepage in the colluvium at the toe of the steep slope to the east and surface water was observed on the face of the slope, as indicated on the Site Plan, Plate 2. No seepage was observed on or below the slopes along the north property line or 2 Soil Survey of Snohomish County Area Washington, 1983, U.S. Department of Agriculture, Soil Conservation Service. February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 5 Proposed SFR, 15911 - 74'h Place W, Edmonds in the western portion of the site. GEOLOGIC HAZARD ASSESSMENT The North Edmonds Earth Subsidence Landslide Hazard Area is described as a large, deep- seated, ancient landslide within the Meadowdale area that was previously identified as the Meadowdale Landslide Area. The landslide includes a massive down -set block of land (landslide mass) that extends from the steep bluffs at the eastern edge of the slide to Puget Sound. Large scale sliding was reported in 1947 and damaging slides have been recorded since that time. In the past, development was limited due to the landslide hazard. Infrastructure was installed in 1984, under Local Improvement District (LID) No. 210, including public sanitary sewer, storm sewers and interceptor drains, which had the effect of lowering the groundwater levels within the slide area and lowering the risk to new development. Since 1988, residential development has been allowed under specific conditions, development guidelines and requirements, with the intent to limit risks for a property owner and the adjacent properties. Substantial landslide hazard risk exists within the North Edmonds Earth Subsidence Landslide Hazard Area. The landslide hazard risks are estimated to range from less than 10 percent probability of occurrence in 25 years to about 30 percent probability of occurrence in 25 years (GeoEngineers, 1985). The landslide hazard risk depends on regional and site-specific conditions, including topography, geology, surface water, groundwater, and vegetation conditions. The GeoEngineers Landslide Hazard Map (1984), indicates the project site is located within an area with four landslide hazard probability zones: 1. Western portion of site (4A30) Hazards from ground failure in previously failed material; slumps; with a 30 percent probability of occurrence during a 25 -year period. 2. Toe of steep slope (2CO2, 4A10) Hazards from encroaching landslide materials and hazards from ground failure in previously failed material; debris avalanches and slumps; with a 2 to 10 percent probability of occurrence during a 25 -year period. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74' Place W, Edmonds G-3598 Page 6 3. Steep upper slope (2CO2, 3802) Hazards from encroaching landslide materials and hazards from ground failure in material that has not previously failed; debris slides and debris avalanches; with a 2 percent probability of occurrence during a 25 -year period. FILE REviEw Files at the City of Edmonds were reviewed to identify previous grading, site development, history of unstable soils, landslides, erosion problems, and to review geotechnical and critical area study reports for the subject property and adjacent properties. Files reviewed included the property to the south at 15915 - 74' Place West, the subject lot, and the property to the north at 7324 - 158' Street SW. We found no reported active landslide activity, debris flows, mud flows, or erosion problems for the subject property, adjacent lots, or reported for the immediate vicinity of the project site. No topographic surveys were included in the files that would help identify historical site grading that may have occurred on the project site. The home to the south, 15915 - 74`' Place West, was constructed in 2004 and the files included a geotechnical report, peer review letters and a final geotechnical construction monitoring letter. The final geotechnical construction monitoring letter indicates the home is supported on sixty- three 3 -inch diameter pipe piles that were driven to depths of 31 feet to 53.5 feet. Two soil boring logs were included in the geotechnical information and medium dense to dense silty sand was encountered at a depth of about 25 feet and water was encountered at depths of 10.5 feet and 18 feet. The description of the site conditions and steep slope behind the house are similar to the project site conditions, with the exception that the denser soil was encountered at a shallower depth on the adjacent property. The home to the north at 7324 158`' Street SW, was constructed in 1985. File records indicate the home was designed to be supported on a conventional spread footing foundation. According to the Snohomish County Assessor's website the home has a basement. The project site files included a geotechnical report by Dennis Bruce, P.E. (2001) for addresses 15911, 15915 and 15917. It appeared that the subsurface site investigation for the geotechnical February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74`' Place W, Edmonds G-3598 Page 7 report was performed on the neighboring lot to the south. The files also included supplemental geotechnical reports by Mr. Bruce (2005, 2006) for the subject lot, prepared for a site development plan that was not constructed. The files reviewed also included a Critical Areas Study by Wetland Resources (2002) for addresses 15911, 15915 and 15917. Wetlands were not identified on the subject lot. Based on the site topography, our site investigation and the geologic and geotechnical studies that have been completed in the area, it is our opinion that the geometry of the property is the result of the deep-seated movement of the North Edmonds landslide. The steep slope along the back of the lot appears to be part of the larger landslide scarp that defines the eastern margin of the North Edmonds Earth Subsidence Landslide Hazard Area. Potential landslide hazard risks for the site include reactivation and deep-seated movement of the larger landslide landmass. There is also the potential risk of slumps, debris flows, mud flows and debris avalanches from the steep slope in the eastern portion of the site. The home will be supported on a pile foundation, however the piles will not mitigate movement of the landmass and significant structural damage should be expected if large-scale reactivation of the North Edmonds landslide should occur or should a mud flow, debris flow or debris avalanche impact the house. Recent slide activity in the area includes a debris flow that occurred in the winter of 2000 that demolished a residential carport at the north end of 75' Place West. Slope Stability Evaluation The slopes along the north property line and in the western portion of the lot appear to be stable and the risk of slumping, mud or debris flows appears to be minimal. Surficial slumping, debris flows and debris avalanches are possible on the steep slope to the east. The trunks of some of the trees on the slope are curved indicating soil creep of the surficial soil layer. Seismic activity or a 100 -year storm event could increase the risk of slope failure and result in localized slumping, debris flows, mud flows or debris avalanches. The site is not located near the top of a bluff, so bluff retreat will not impact the site, with the exception of the accumulation of debris at the base of the slope. It is our professional opinion, that construction and placement of the home will not negatively impact the stability of the slope over the estimated life of the structure and will not adversely impact neighboring properties. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74' Place W, Edmonds Evaluation of Impact of Proposed Development on Steep Slope Areas The proposed construction of the house, driveway and proposed 21-1: IV grading on the west side of the site will not decrease the stability of the slopes, the stability of adjacent properties, or adversely impact other critical areas. The proposed tiered ecology block walls along the north property line will have heights of up to 6 feet and will retain cuts. The temporary open cuts should have limited exposure time of 24 hours or less and the horizontal cut sections should be limited to 15 feet or less, as discussed in the ecology block wall section of this report. It is our opinion that the ecology block walls can be constructed without negatively impacting the stability of the slope or the stability of adjacent properties, provided the recommendations contained herein are followed, including performing the work during the dry season, limiting the exposure time of the cut faces, installation of drainage and construction monitoring by the geotechnical engineer. Site Drainage & Erosion Evaluation Surface water coming off the steep slope to the east is being collected and routed to the stormwater sewer. A drainage swale is proposed between the house and toe of slope to collect seepage and route it to the stormwater system. Soil erosion was observed at a intermittent seep in the northeastern comer of the site. Armoring the soil in the seep area with 2 -inch to 4 -inch crushed rock, underlain by geotextile filter fabric, Mirafi 140N or equivalent, is recommended to mitigate soil erosion. We are not aware of any subsurface drainage facilities currently installed on the site. Subsurface footing drains are recommended around the perimeter of the house and at the base of retaining walls and ecology block walls. The site soil contains silt and exposed soils have a moderate to high water erosion potential on the slopes during storm events. Temporary erosion and sediment control measures should be installed during construction, as discussed in the Erosion Control section of this report. Management of stormwater, landscaping and mulching at the completion of the project will provide satisfactory permanent erosion control and the proposed development will increase surface water discharge or sediment to adjacent properties beyond predevelopment conditions. GE O Group Northwest, Inc. Critical Area Evaluation & Geotechnical Report Page 9 Proposed SFR, 15911 - 74"' Place W, Edmonds It is our opinion that the proposed 10 foot buffer from the toe of the slope to the east and 15 foot building setback from the buffer is acceptable provided the east wall of the garage is designed as a 6 foot tall catchment wall should slide debris impact the garage. The geologic hazards can not be practically mitigated by design measures in the development of a single family residential lot, however the following measures are recommended: IW Erosion control measures should be installed prior to the start of carthwork. 2. Earthwork to occur during the dry summer months, 3.. The structure is to be pile supported. 4. The cast wall of the garage should be designed as a catchment wall with a height of 6 feet above the finished grade, Windows should be excluded from the east wall of the garage in. the event trees are carried with the slide debris. 5. Temporary cuts should not exceed III: IV (Horizontal: Vertical), except for construction of the ecology block walls. Permanent cut and fill slopes should not exceed 2H: IV. 6. If changes are made to the final site development plans, the revised plan should be reviewed by the geotechnical engineer to verify that the plans conform to the geotechnical M'M 7. 'temporary cuts, construction of retaining walls, ecology block walls, subsurface drainage, and the installation of piles should be inspected and monitored by tile geotechnical engineer at the time of construction. & Vegetation on the steep east slope should be maintained in a natural condition arld not be modified, with the exception of the removal of dangerous trees as determined by a qualified arborist. In accordance with the International Building Code (IBC) and ASCE Chapter 20, the site classification is Site Class D (stiff soil with 15 < N >-50 in the top 100 feet), based oil the soil conditions encountered. During a strong motion earthquake, the potential risk of liquefaction, GEO Group Northwest, Ine. February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 10 Proposed SFR, 15911 - 74' Place W, Edmonds lateral spreading and surface rupture is a low, based on the site conditions and subsurface conditions encountered. We are recommending the house be pile supported to mitigate impacts to the house resulting from potential settlements due to the loose condition of the site soil. No geotechnical seismic mitigation measures are recommended, with the exception of the addition of design criteria for seismically induced dynamic soil loads on permanent concrete retaining walls. CATCHMENT WALL - EAST WALL ore GARAGE, In the event that a slide impacts the structure, we recommend the east wall of the garage be designed as a catchment wall to a height of 6 feet above the finished grade. The east garage wall should be designed to resist a lateral earth pressure imposed by an equivalent fluid unit weight of 35 pcf. Windows should be excluded from the cast wall of the garage to prevent piercing of the windows in the event trees are carried with slide debris. From a geotechnical perspective, inclusion of the proposed hot tub and water feature should not impact the stability of the site. The hot tub and water feature should not drained onto the ground surface during maintenance. We recommend they be plumbed to drain to the sewer. The water feature should be lined with a welded seam geomembrane that drains to the storm sewer in the event of a leak. TEMPORARY EXCAVATIONS The stability of temporary cut slopes is a function of many factors, including soil type, geonictry, surcharge loads, amount of time the cut is open, and the presence of subsurface seepage. it is the responsibility of the contractor to maintain sale slope configurations, '"Me excavation should be monitored by the geoteclinical engineer. If gtorartc w,atg r see excavation of cut slopes should be halted and the stability of the cut slope evaluated by the geotechnical . ........ ... engineer. GEO Group Northwest, Inc. February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page I I Proposed SFR, 15911 - 74" Place W, Edmonds Temporary cut slopes should not exceed 1.1.1;1 V, except when constructing the ecology block walls. If temporary cuts will not stand nearly vertical, then back sloping will be necessary. Permanent cut and fill slopes should be inclined no steeper than 2H:1 V. Permanent fill slopes and the slope along the west side of the house should be compacted during grading. Permanent slopes of 3H: IV, or less, are recommended if slopes are to be mowed and maintained. EROSION CONTROL The site work should be performed during the dry surnmer months due to the moisture sensitive soils present at the site. Temporary erosion and sediment control measures, such as perimeter silt fencing, should be installed prior to the start of grading. A crushed rock construction entrance should be installed to mitigate the tracking of mud onto the street. During wet weather, exposed site soils should be covered with straw mulch or protected with plastic sheeting to mitigate erosion. Water runoff should be mitigated with the use of crushed rock check dams, hay bales, silt fencing and covering of exposed soil with plastic sheeting to reduce suspended sediment and velocity of storm water runoff. SUBGRADE PREPARATION Soils supporting ecology block walls, retaining walls, and the driveway should be grubbed and stripped of topsoil and soils containing wood or organic debris. Base soils should be firm and non -yielding. If loose or unsuitable soils are present we recommend the subgrade be evaluated by the geotechnical engineer. Compaction of the subgrade, or removal of the loose or unsuitable soil and replacement with compacted structural fill or crushed rock may be required. Placement of a geotextile to provide separation between the soil subgrade and structural fill or crushed rock, may be necessary. STRUCTURM, FILL Structural fill is defined as compacted engineered fill soil used to support building foundation loads, floor slabs, patios, porches, retaining walls, sidewalks, and pavements. Backfill behind CMU and other types of retaining walls, should also be compacted to structural fill specifications. During dry weather, any non-organic granular soil may be used as structural fill, provided the material is near the optimum moisture content for compaction purposes, and the material achieves GEO Group Northwest, Ine. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74" Place W, Edmonds the compaction specifications when compacted. During wet weather we recommend an imported pit run sand and gravel material with the following specifications: I Free draining, granular material, which contains no more than 5 percent fines (silt and clay -size particles passing the No. 200 mesh sieve); 2. Free of organic and other deleterious substances; 3. Maximum size of three -inches. Structural fill material should be placed and compacted at or near the material's optimum moisture content. The optimum moisture content is the water content in soil that enables the soil to be compacted to the highest dry density for a given compaction effort. If feasible, the site grading and earthwork should be performed during the dry summer months. Soils containing organics, debris and/or rubble should not be used as structural fill. STRUCTURAL FILL COMPACTION SPECIFICATIONS Structural fill should be placed at or near the material's optimum moisture content and be compacted in 10 -inch thick lifts, or less. Structural fill supporting structural elements and the retained soil behind CMU type retaining walls should be compacted to a minimum of 90 percent of the material's maximum dry density, as determined by ASTM Test Designation 17-1557 (Modified Proctor), with the exception of the top 12 -inches of the driveway which should be compacted to 95 percent. Structural fill within the street right-of-way and trench backfill above utilities should be compacted to the city or utility district specifications. GEO Group Northwest, Ine. February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 13 Proposed SFR, 15911 - 74' Place W, Edmonds FOUNDATIONS The structure should be supported on a deep foundation system consisting of either concrete pile or steel pipe piles based on the soil conditions. Augercast Concrete Piles The structure may be supported on concrete piles installed using the augercast method due to the groundwater conditions encountered. The augercast method uses a top -head driven auger drill that is suspended from a crane. The auger bit is advanced to the desired depth, the auger is then extracted and at the same time cement grout is pumped into the hole through the bottom of the auger. This method displaces groundwater in the hole as the grout is being pumped and results in an intact finished concrete pile. Piles should be reinforced with steel cages (rebar cage, plus center bar) and should have a minimum diameter of 14 inches. The rebar cage should be centered in the hole and the center bar extend to the bottom of the pile. The number of piles, pile spacing, steel reinforcement, and grade beam requirements should be designed by the structural engineer. Pile tops (caps) should be tied together with grade beams to generate lateral resistance. The pile spacing and number of piles required will need to be designed by the structural engineer. The following recommended allowable design parameters assume that the pile caps are tied together with grade beams and the piles are adequately reinforced to resist shear loads. If lateral forces are to be resisted by the cantilever action of a pile group, then the piles should be structurally tied together with a moment resisting frame or beams. The following table provides the allowable pile capacities that may be used for design. The pile design capacity calculations included a design safety factor (SF) of SF=3 and are based on the subsurface conditions encountered in Boring B-1 with a minimum embedment of 10 feet into the very stiff to hard silt below the depth of 43 feet (total pile length of 53 feet). When compared to the soil conditions encountered in Boring B-2, the conditions encountered in Boring B-1 had lower pile design values, so the following design values are based on Boring B-1. February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 14 Proposed SFR, 15911 - 74" Place W, Edmonds Pile Pile Pile Allowable Allowable Diameter Length Embedment Axial Loading Uplift (inches) (feet) (feet (tons) S) 14 53 10 17 8 ................ 16 53 to 23 11 18 53 10 29 14 24 53 10 52 26 No reduction in pile capacity is required if the pile spacing is at least three times the pile diameter. A one-third increase in the above allowable pile capacities can be used when considering short- term transitory wind or seismic loads. We recommend lateral pile loads be resisted by using an allowable passive soil resistance of 350 pcf equivalent fluid pressure acting over twice the diameter of the pile. We estimate the maximum total post -construction settlement should be 1/4 inch or less, and the differential settlement across building width should be 1/4 inch or less. MIM=I The foundation may be supported on 3 -inch or larger diameter steel pipe piles, Galvanized pipe is recommended for corrosion protection. Pile tops (caps) should be tied together with grade beams to generate lateral resistance. The pile spacing and number of piles required will need to be designed by the structural engineer. The pipe piles should penetrate through the loose soils and be driven to refusal. Piles should be inspected by the geotechnical engineer refusal verified during installation. The following are the recommended allowable bearing capacity and refusal criteria for several pile sizes: GELD Group Northwest, Ine. Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74"' Place W, Edmonds M.M. Pipe pile Pile Hammer Hammer Refusal Criteria Allowable Diameter Specification T Weight (Seconds Per Inch) Yert 3 inch Schedule 40 TB325* 850 lb 10 6 tons 4 inch Schedule 40 TB425* 1100 lb to 10 tons 6 inch Schedule 40 TB725* 2700 lb 10 15 tons (* Teledyne Hammer) Refusal criteria may be different for other hammer weights and manufactures and should be adjusted in the field, as required. By themselves, pipe piles generate minimal lateral capacity and no allowable uplift resistance. For uplift capacity we recommend installing helical anchors. Lateral forces should be resisted by the passive earth pressures acting on grade beams and the friction with the subgrade. Lateral forces may also be resisted with battered piles. To fully mobilize the passive pressure resistance, the grade beams must be poured "neat" against compacted fill. Our recommended allowable passive soil pressure for lateral resistance is 350 pcf equivalent fluid weight and a coefficient of friction of 0.35. For the pile supported foundation, we estimate the maximum total post - construction settlement should be 1/4 inch or less and the differential settlement across building width should be 1/4 inch or less. 311 �141 , 11 �Ikl �11� Geotechnical design criteria is provided in the event the project plans are revised to include conventional concrete retaining walls. Cantilever retaining walls free to rotate on top should be designed for an active lateral soil pressure. Active Earth Pressure Conventional reinforced concrete walls should be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of 35 pcf for level backfill above the wall. Seismic Earth Pressure In addition to the above lateral soil pressure, a rectangular pressure of 6H should be added to the lateral soil pressure for permanent basement and retaining walls to account for seismically induced dynamic soil loads. Gly® Group Northwest, Ine. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - %4`'' Place W, Edmonds EM The above design values are based on the wall being fully drained. The design values do not include the effects of surcharges. For the sloped ground above the wall, a surcharge load equivalent to 50 percent of the soil height above the wall should be considered in addition to the above soil pressures. Traffic surcharges can be assumed to be equivalent to 2 feet of soils (soil unit weight = 130 pcf). Passive Earth Pressure and Base Friction The available passive earth pressure that can be mobilized to resist lateral forces may be assumed to be equal to 350 pcf equivalent fluid weight for the site soil and engineered structural backfill. The base friction that can be generated between concrete and soil or structural fill may be based on an assumed 0.35 friction coefficient. Retaining all Drainage A vertical drain mat, Miradrain 6000 or equivalent, may be used to facilitate retaining wall drainage, or the walls may be backfilled with a clean free -draining granular soil or clean crushed rock. If installing a vertical drain mat, the plastic core is placed against the wall with the filter fabric side facing the backfill. The drain mat should extend from the finished surface grade down to the base of the wall. The bottom of the drain mat should be bedded in the washed rock surrounding the footing drain, as illustrated on the Footing Drain Detail, Plate 5. Footing drains should outlet to the storm drain. The wall backfill should be compacted to 90 percent, or in accordance with the manufacture's recommendations, to prevent clogging of the geotextile filter fabric on the drain mat. Based on the loose surficial soil conditions encountered in the borings we recommend slab -on - grade floors be structurally supported due to potential settlement caused by floor loads from counters, cabinets, refrigerators, etc. Floor slabs should be reinforced with steel reinforcement bar. Slab -on -grade floors should be placed on a capillary break to prevent wicking of moisture through the slab. The capillary break should consist of a minimum of six (6) inch thick free -draining layer of clean crushed rock (no minus fraction), such as 5/8 -inch crushed rock, or gravel containing no more than five (5) percent fines passing the No. 4 (1/4 inch) sieve. To reduce water vapor GED Group Northwest, Inc. February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74th Place W, Edmonds G-3598 Page 17 transmission through the slab we recommend installing a 10 -mil reinforced vapor barrier, such as Moistop® by Fortifiber Corporation, between the capillary break and concrete floor slab. Two to four inches of sand may be placed over the membrane for protection during construction (optional). 1 Water should not be allowed to stand in areas where footings, slabs, or pavements are to be constructed. During construction, loose surfaces should be sealed at night by compacting the surface to reduce moisture infiltration into the soils. Final site grades should allow for drainage away from the building. We suggest that the ground be sloped at a gradient of three (3) percent for a distance of at least ten feet away from the building except in areas that are to be paved. Final site grades and impervious areas should be designed to collect surface water into catch basins and be tight -lined for discharge into the storm drain system. If water seepage is encountered during excavation, the geotechnical engineer should evaluate the site conditions. Provided the excavation is stable, we recommend sloping the bottom of the excavation to one or more shallow sump pits, and pumping the water to the storm system or an appropriate discharge location. Footing Drains Subsurface footing drains should be installed around the perimeter of the foundation and behind retaining walls. Footing drains should consist of a four (4) inch minimum diameter, perforated, rigid drain pipe laid at or near the bottom of the footing with a gradient sufficient to generate flow. The drain should be bedded in washed drain rock and the drain rock protected from clogging with geotextile filter fabric, such as Mirafi 140N, or equivalent, as illustrated on the Footing Drain Detail, Plate 5. The drain rock should extend up to the base of the vertical drain mat, if a drain mat is installed. Footing drains should discharge the storm drain system. Roof, yard, and other drain lines should not be connected to the footing drain system. The footing drain should be separately tight -lined to the discharge point. We recommend that sufficient clean - outs be installed to allow for periodic maintenance of the footing drains and roof down -spout tight -line systems. l��Tl�fR�7►1�it�R�# fT�l February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 18 Proposed SFR, 15911 - 74`' Place W, Edmonds Seep Soil erosion was observed at a intermittent seep in the northeastern corner of the site, approximately as illustrated on Plate 2. Armoring the seep area with 2 -inch to 4 -inch crushed rock, underlain by geotextile filter fabric, Nlirafi 140N or equivalent, is recommended to mitigate soil erosion. ECOLOGY BLOCK WALLS Tiered ecology block walls are proposed along the north side of the driveway and are needed to limit the slope of the driveway. The ecology block walls (ECW's) are in an area with limited slope height of 10 to 22 feet and the walls will be facing cuts. It is our opinion that the proposed EBW's will not trigger or otherwise contribute to the existing landslide hazard or earth subsidence risk either on the site or in the earth subsidence or landslide hazard area. Both walls have a planned height of 4 feet to 6 feet. The walls will be separated by 6 feet, so the upper wall will not surcharge the lower wall. Geogrid reinforcement is not required. Blocks should be battered into the slope at 1H:6V. The base blocks should be embedded a minimum of 9 inches, or 3 inches for each foot of wall height for wall greater than 3 feet tall. Soil supporting the blocks should be firm to provide proper support. Loose or unsuitable base soil should be evaluated by the geotechnical engineer, and may require replacement with crushed rock. A near vertical cut is desirable behind the walls provided the soils are firm, self standing and water seepage is not encountered. We recommend limiting the size of the exposed open cuts to a horizontal width of 15 feet or less and constructing the walls concurrently as the cut is made. Cuts should not be left unsupported more than 24 hours. Good drainage behind the wall is essential for stability. A footing drain should be installed at the base of the back of the walls consisting of a four -inch diameter perforated rigid PVC pipe bedded in free -draining ballast or crushed rock. The perforated drain should be directed to a positive and permanent discharge location at the end of the wall. A minimum 12 inch zone of free -draining angular crushed rock should be installed behind the wall concurrently as the wall is constructed. GEO Group Northwest, Ince February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74`h Place W, Edmonds 1 G-3598 Page 19 Pavement performance is strictly related to the condition of the underlying subgrade. If subgrade is inadequate, no matter what pavement section is constructed, settlement or movement of the subgrade will be reflected up through the asphalt -concrete surfacing. To avoid this, the subgrade should be compacted and proof -rolled with a loaded dump truck under the observation of the geotechnical engineer. Areas of soft, wet or unstable subgrade may require over -excavation and replacement with compacted structural fill or crushed rock. Subgrade stabilization recommendations should be provided by the geotechnical engineer based on an evaluation of the subgrade conditions. Pavement sections and design specifications for county or city roadways should follow their design standards. The pavement section should consider the traffic load, such as garbage trucks. For private parking areas and the driveway we recommend the pavement section consist of the following: NAVY TRAFFIC AREAS Class "B" Asphalt Concrete (AC) Crushed Rock Base (CRB) Asphalt Treated Base (ATB) LIGHT TRAFFIC Class "B" Asphalt Concrete (AC) Crushed Rock Base (CRB) Asphalt Treated Base (ATB) 3 -inches, over 6 -inches, or 3 -inches 2 -inches, over 4 -inches, or 2 -inches During construction, GEO Group Northwest should provide geotechnical monitoring/inspection services. This will allow us to confirm that the subsurface conditions are consistent with those described in this report and allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. It will also allow us to evaluate whether the February 25, 2014 Critical Area Evaluation & Geotechnical Report Proposed SFR, 15911 - 74`' Place W, Edmonds G-3598 Page 20 geotechnical aspects of the construction activities conform to the contract plans, specifications, and geotechnical engineering recommendations. Geotechnical construction monitoring inspections should include: ® Site excavation ® Pile installation ® Retaining walls ® Structural fill placement and compaction ® Footing drain installation ® Subgrade preparation for the slab -on -grade floor and the driveway While on the site during construction, we will not direct or supervise the contractor or the contractor's work, nor will we be responsible for providing or reviewing on-site safety or dimensional measurements. We request that the contractor provide a minimum of 24 hours advance notice to perform inspections so that we can arrange to have personnel available. 1 This report has been prepared for the specific application to the subject project. The findings and recommendations stated herein are based on our field observations, the subsurface conditions encountered in our site exploration, our experience, and judgement. The recommendations are our professional opinion derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. In the event that the site or soil conditions vary during site work, GEO Group Northwest, Inc., should be notified and the recommendations herein re-evaluated, and where necessary, be revised. GEO Group Northwest, Inc., should be retained to review the final design plans to confirm that the plans conform to the recommendations contained in this report. 1 I I I.�. . February 25, 2014 G-3598 Critical Area Evaluation & Geotechnical Report Page 21 Proposed SFR, 15911 - 74`' Place W, Edmonds Please contact us if you have any questions regarding this report. Sincerely, GE® GROUP NORTHWEST, INC. Wade J. Lassey Engineering Geologist pF WAs/yj William Chang, P.E. ��;�, q 20114 Principal �ss� G/STEAL Attachments: Plate 1 - Vicinity Map Plate 2 - Topographic Site Plan Plate 3 - Site Plan Plate 4 - Cross Section A - A' Plate 5 - Footing Drain Detail Appendix A - USCS Soil Classification Legend and Boring Logs 51115111111ril �11 1 `N ash, Q t� 7 A'3 , ax,;. 1 r SSCY HAMIRNEM GE® Group Northwest, Inc. O 100002000 Approximate Scale: 1 inch =1000 feet VICINITY M" roup Northwest, Inc. PROPOSED SAUNDERS RESIDENCE Geotechnical Engineers, Geologists, & 15911- 74th PI West Environmental Scientists Edmonds, Washington 96095 'YM 'SONOW03 —1- -- Im-Pi I -w3dl S HI 9,r T 9 '14 .93 V'7d HI PL fie WE SIMMER suolsuguilcloaDIMM tN e � mem gmo .4 6 / $ ��� � w oil awl-�o-.o� ,I n j 1 i0$ 2• ipY Ox w'i � , �o s°f Asa 1 42 z a i /Ya $ I � `•�O' O2 rte' — J— — — -- 2/ 'f_Sp `- � (�-(' n�� b� I/ o,�„--,__ —' J°•4y°-J-c.JXI-}IY'O J' k'tt 4 I FOUNDATION WALL 0 SLAB Slope to drain G,4:P74Lc�?'� H�'t11C: 6"to 12"Relative 0 ® 0 Impermeable Cap 0 0 GEOTEXTILE O FILTER FABRIC N, or equivalent) nt) equivalent) \\ WASHED DRAIN ROCK FOOTING DRAIN: Minimum 4 -inch diameter slotted or perforated rigid PVC pipe with positive gradient to discharge 0 0 o 0 O O o O GRADE BEAM 0 o o -a® Invert Pile NOTES: 1.) Do not replace rigid PVC pipe with flexiible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should be tight jointed and laid with perforations or slots down, with positive gradient to discharge. 3.) Do not connect roof downspout drains to the footing drain lines. roup Northwest, Inc. Geotechnical Engineers, Geologists, & ® Environmental Scientists TYPICAL FOOTING DRAIN PROPOSED SAUNDERS RESIDENCE r 15911- 74th P' West Edmonds, a 1.1 1 SCALE NONE I DATE 2/20/14 MADE WJL, I CH W JC>a tv®. G-3598 PLATE 1 O o 0 e o 0 o o 0 0 0 o 0 O O o O GRADE BEAM 0 o o -a® Invert Pile NOTES: 1.) Do not replace rigid PVC pipe with flexiible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should be tight jointed and laid with perforations or slots down, with positive gradient to discharge. 3.) Do not connect roof downspout drains to the footing drain lines. roup Northwest, Inc. Geotechnical Engineers, Geologists, & ® Environmental Scientists TYPICAL FOOTING DRAIN PROPOSED SAUNDERS RESIDENCE r 15911- 74th P' West Edmonds, a 1.1 1 SCALE NONE I DATE 2/20/14 MADE WJL, I CH W JC>a tv®. G-3598 PLATE 1 1 1 1 ;. BORING LOGS GE® Group Northwest, Inc. f • . .. .- • ' c. • UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) MAJOR DIVISION GROUP TYPICAL DESCRIPTION LABORATORY CLASSIFICATION CRITERIA OF SLIGHT PLASITCtTY SYMBOL PEAT AND OTHER HIGHLY ORGANIC SOILS Plasticity Chart, SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) CLEAN GW WELL GRADED GRAVELS, GRAVEL -SAND CH Cu = (D80 / D10) greater than 4 FINE-GRAINED Negligible GRAVELS SOILS MIXTURE, LITTLE OR NO FINES DETERMINE Cc = (0302) / (D10' 680) between 1 and 3 DIATOMACEOUS, FINE SANDY OR SILTY SOIL PERCENTAGES OF GRAVELS (Ilittle or no Liquid Limit POORLY GRADED GRAVELS, AND GRAVEL -SAND GRAVEL AND SAND 40 Friction Angle (More Than Half fines) GP MIXTURES LITTLE OR NO FINES FROM GRAIN SIZE NOT MEETING ABOVE REQUIREMENTS COARSE- Coarse Grains CLAYS Z DISTRIBUTION INORGANIC CLAYS OF HIGH PLASTICITY, FAT N Negligible 30 ATTERBERG LIMBS BELOW GRAINED SOILS Larger Than No. 4 CURVE CLAYS Sieve) DIRTY GM SILTY GRAVELS, GRAVEL -SAND -SILT MIXTURES 0.4 0.15 "A" UNE Weight Larger < 2 GRAVELS Very soft ORGANIC SILTS AND ORGANIC SILTY CLAYS OF #40 CONTENT or P.I. LESS THAN 4 < 50% OL LOW PLASTICITY 0. OF FINES CLAYS CLAYEY GRAVELS, GRAVEL -SAND -CLAY ATTERBERG LIMITS ABOVE MEDIUM 10 (with someGC (Below A -Line on EXCEEDS 1296 10-30 35.65 fines) Medium Dense MIXTURES COARSE GRAINED Medium Stiff "A" LINE #4 4.75 #10 200 OH SOILS ARE 4 0 or P.I. MORE THAN 7 8-15 15-30 1.00-2.00 200-4.00 Stift Very Stiff GRAVE- CLASSIFIED AS SANDS CLEAN SW WELL GRADED SANDS, GRAVELLY SANDS, FOLLOWS: Cu = (680 / Di 0) greater than 8 SANDS > 30 LITTLE OR NO FINES Hard Cc = (0307) / (D10 ' D60) between 1 and 3 (Mote Than Half 19 Group e COBBLES More Than Half by Coarse Grains (little or no SIR POORLY GRADED SANDS, GRAVELLY SANDS, < 5% Fine Grained: NOT MEETING ABOVE REQUIREMENTS Weight Larger Smaller Than No. fines) LITTLE OR NO FINES GW, GP, SW, SP FRAGMENTS Than No. 200 4 Slew) PLATE Al DIRTY SM SILTY SANDS, SANDLT MIXTURES SI ATTERBERG LIMITS BELOW "A" LINE Sieve > d 12% Fine Graine: SANDS GM, GC, SM, SC CONTENT OF with p I LESS THAN 4 FINES ATTERBERG LIMBS ABOVE (with some 5 to 12% Fine EXCEEDS 12% fines) SC CLAYEY SANDS, SAND -CLAY MIXTURES Grained: use dual "A" LINE symbols with P. 1. MORE THAN 7 SILTS Liquid Limit ML INORGANIC SILTS, ROCK FLOUR, SANDY SILTS (Below A -Una on < 50% 0 10 20 30 40 50 60 70 80 90 100 110 OF SLIGHT PLASITCtTY Pt PEAT AND OTHER HIGHLY ORGANIC SOILS Plasticity Chart, SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) U.S. STANDARD SIEVE Liquid Limit CH SILTS, MICACEOUS OR FINE-GRAINED Negligible 50 SOILS Organic) > 50% MHINORGANIC DIATOMACEOUS, FINE SANDY OR SILTY SOIL rmemolinwA CLAYS Liquid Limit (MM) INORGANIC CLAYS OF LOW PLASTICITY, 40 Friction Angle (Above A -Lina on < 30% CL GRAVELLY, SANDY, OR SILTY CLAYS, CLEAN Plasticity Chart, CLAYS Z uid Li Limit q INORGANIC CLAYS OF HIGH PLASTICITY, FAT N Negligible 30 Organic) > 54% CH CLAYS _ V More Than Half by 0.4 0.15 t��/ 20 Weight Larger < 2 Liquid Limit Very soft ORGANIC SILTS AND ORGANIC SILTY CLAYS OF #40 Than No. 200 ORGANIC SILTS 8 < 50% OL LOW PLASTICITY 0. Sieve CLAYS 0.25-0.50 Soft MEDIUM 10 200 (Below A -Line on 7 10-30 35.65 26-35 Medium Dense Plasticity Chart) Liquid rid0LLiimit Medium Stiff COARSE #4 4.75 #10 200 OH ORGANIC CLAYS OF HIGH PLASTICITY 4 0 0 10 20 30 40 50 60 70 80 90 100 110 HIGHLY ORGANIC SOILS Pt PEAT AND OTHER HIGHLY ORGANIC SOILS LIQUID LMT (%) SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) U.S. STANDARD SIEVE FRACTION CH or OH SANDY SOILS SILTY & CLAYEY SOILS , 5,111111 Size rmemolinwA (Mm) Sieve (MM) Blow Counts Relative Density 0 10 20 30 40 50 60 70 80 90 100 110 HIGHLY ORGANIC SOILS Pt PEAT AND OTHER HIGHLY ORGANIC SOILS LIQUID LMT (%) SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) U.S. STANDARD SIEVE FRACTION Passing Retained SANDY SOILS SILTY & CLAYEY SOILS Size Size SIeVe (Mm) Sieve (MM) Blow Counts Relative Density Friction Angle Description Blah, Counts Unconfined Strength Description SILT / CLAY #200 0.075 N % �, degree N qu, tsf SAND 0.4 0.15 Very Loose < 2 < 0.25 Very soft FINE #40 0.425 W" 0.075 4-10 15-35 20-30 Loose 2 - 4 0.25-0.50 Soft MEDIUM #10 200 #40 0.425 10-30 35.65 26-35 Medium Dense 4.8 0.50-1.00 Medium Stiff COARSE #4 4.75 #10 200 30-50 > 50 65-85 85-100 35-42 38-46 Dense Very Dense 8-15 15-30 1.00-2.00 200-4.00 Stift Very Stiff GRAVE- FINE 19 #4 4.75 > 30 > 4.00 Hard COARSE 76 19 Group e COBBLES 76 mm to 203 mm BOULDERS > 203 mm ' Geotechnical Engineers, Geologists, a Environmental Scientists ROCK > 78 mm FRAGMENTS 13240 NE 20th StreK Suite 12 Bellevue, WA 98005 Phoria (425) 64"757 Fax (425) a4"758 PLATE Al ROCK >0.76 cubic meter in volume BORING NO. Logged By: WJL Date Drilled: 1/22/14 Surface Elev. 118 feet Depth USCS Soil Description SAMPLE SPT (N) Blows per 6 -inches Water Content % Drilling/ Sampling Information & Observations Type No. Sl 1, l,2 27.8 N= 3 Silty SAND, dark brown to brown, fine- N'=6 SM grained, some organics, very loose, damp S2 6, 2, 3 16.6 N= 5 5 ®® ®®®®®®®®®®®®®®®®®® N'=10 r level measured ra�t4.25 S3 2, 2, 2 t8 8 feet below SiltySAND, brown to light brown to a fine- � �' Y� N_gnd surface. grained, very loose to medium dense, occasional wood inclusions, occasional fine gravel, wet S4 2, 2, 2 34.3 N=4 10 N'= 8 Gray T S5 3, 5, 4 28.8 1 N=9 SM N'=16 S6 2, 2, 4 23.6 N=6 15 N'= 10 S7 2, 2, 3 19.3 N=5 N'= 7 S8 3, 6, 12 15.3 N= 18 20 ®® ®®®®®®®®®®®®®®®®®® N'=24 S9 4, 5, 5 22.5 N= 10 N'= 13 S 10 2, 4, 4 17.3 N= 8 25 SM/ Silty SAND, gray, with some interbeds of silt N'=10 ML and sandy silt, loose to medium dense, wet Sit 3, 2, 3 19.0 N= 5 N'= 6 S12 2, 2, 3 13.3 N=5 30 N'= 5 S13 5,6,5 13.9 N=11 ®® ®®®®®®®®®®®®®®®®®® N'=11 S14 6, 12, 9 --- No Sample Recovery SM Silty SAND, with interbeds of gravelly sand N= 21 N'= 19 35 with silt, gray, loose to medium dense, wet S15 4, 8, 9 15.5 N= 17 ®®®®®®®®®®®®®®®®® N'=15 Silty SAND to SAND with some silt, gray, S16 4,3,3 15.1 LSSPM-S loose, wet N=6 N'= 6 LEGEND: 2 -inch O.D. Split Spoon Sample Interval N: Number of blow counts for 1 foot of sampler advancement. Sampler driven with 140 lb. Hammer (Standard SPT) N': Overburden correction BORING LOG JC`oup Northwest, Inc. PROPOSED SAUNDERS RESIDENCE Geotechnical Engineers, Geologists, & 15911 - 74TH PL WEST Environmental Scientists EDMONDS, WASIIINGTON JOB NO. G-3598 DATE 1/23/14 PLATE A2.1 BORING NO. Logged By: WJL Date Drilled: 1/22/14 Surface Elev. 118 feet USC5 SOIL DeSCTlilOTl SAMPLE +/- Depth (ft) p SPT (N) Blows per 6 -inches Water Content % Drilling/ Sampling Information & Observations Type No. S17 2,3,3 13.3 SM to Silty SAND to SAND with some silt, gray, N=6 SP -SM loose, wet N'= 5 43 feet: Drilling Change, Firmer Drilliing. 45 S18 9, 12, 13 37.7 N= 25 SILT, gray, some clay, very stiff to hard, ML medium plasticity, moist 50 S19 7, 12, 13 32.0 N= 25 55 S20 10, 14, 18 32.5 N= 32 Total Depth = 56.5 feet. 60 Groundwater bevel Measured At 4.25 feet below the ground surface. Drilling Co: Geologic Drill Borehole backfilled with bentonite chips 65 70 75 LEGEND: 2 -inch O.D. Split Spoon Sample Interval Sampler driven with 140 lb. Hammer (Standard SPT) EN-Proup Northwest, Inc. Geotechnical Engineers, Geologists, & Environmental Scientists N: Number of blow counts for 1 foot of sampler advancement. N': Overburden correction e,V 1.gt- 11g" 1�g 15911 , I EDMONDS, WASHINGTON JOB NO. G-3598 I DATE 1/23/14 1 PLATE A2.2 BORING NO. B-2 Logged By: WJL Date Drilled: 1/22/14 Surface Elev. 116 feet Depth � t� USCS Soil Description SPS SPT (N) Blows per 6 -inches Water Content % Drilling/ Sampling Information & Observations Type No. Silty SAND, brown, fine-grained, some S1 2, 2, 2 24.2 SM organics, very loose, damp N=4 ®® ®®®®®®®®®®®®®®®®® N'=8 S2 6, 5, 5 13.7 N= 10 5 Silty SAND, light brown to grayish brown, fine- N'=20 SM grained, loose to medium dense, occasional fine S3 3, 3, 2 9.6 gravel, damp N=5 N'= 10 I S4 11, 19, 18 8.3 * Driving Rock N= 37* 10 — — — — — — — — — — — — — — — — — — — — SM/ Silty SAND, light brown, fine-grained, medium S5 815 SP -SM 10.6 N= ML ML ®® dense, with thin interbeded silt lenses, damp ------------------_ N'= 27 15 Silty SAND, light brown, fine-grained, medium S6 8, 11, 14 16.8 SM dense, damp, some mottling at 16.5 feet N=25 N'= 36 20 SAND to sandy SILT, some gravel, light SM/Silty brown to oxidized red brown mottling, fine- s7 N 13 7,6 17.5 ML grained, medium dense, damp N'= 16 25 Silty SAND with some gravel, oxidized red S8 5, 7, 8 14.2 SM brown, fine-grained, medium dense, moist N=15 N'= 17 30 ®® — — — — — — — — — — — — — — — — — Water level measured SP Gravelly SAND, grayish brown, fine to S9 12,11,11 9.2 at 28.9 feet below medium- grained, medium dense, wet N= 22 ground surface. N'= 21 ------ 35 ® — — — — — — — — — — — — — — — — — S 10 9, 15, 17 13.0 SP -SM SAND, brown, some silt and gravel, fine to N= 32 & medium grained, and fine to coarse grained, N'= 29 SW -SM medium dense, wet LEGEND: 2 -inch O.D. Split Spoon Sample Interval Sampler driven with 140 lb. Hammer (Standard SPT) roup Northwest, Inc. Geotechnical Engineers, Geologists, & Environmental Sdentists N: Number of blow counts for I foot of sampler advancement. N': Overburden correction 15911 - 74TH PL E_ JOB NO. G-3598 I DATE 1/23/14 1 PLATE A3.1 BORING NO. B-2 Logged By: WJL Date Drilled: 1/22/14 Surface Elev. 118 feet +/- Depth (g) USCSSoil Description escr1� SAMPLE SPT (N) Blows per 6 -inches Water Content % Drilling/ Sampling Information & Observations Type No. S11 3, 8, 8 13.4 N= 16 N'=32 45 S12 4,5,5 14.1 N= 10 N'=20 SP -SM SAND, brown, some silt and gravel, fine to 50 & medium grained, and fine to coarse grained, SW -SM medium dense, wet S13 8, l0, 7 10.8 N= 17 N'= 34 55 S14 10,11,12 11.0 N= 23 N'=17 60 Dense TT S15 12, 19, 24 14.2 N= 43 N'=30 Total Depth = 61.5 feet. Groundwater Level Measured At 25.9 feet below the 65 ground surface. Drilling Co: Geologic Drill Borehole backfilled with bentonite chips 70 75 LEGEND: 2 -inch O.D. Split Spoon Sample Interval N: Number of blow counts for I foot of sampler advancement. Sampler driven with 140 Ib. Hammer (Standard SPT) N': Overburden correction BORING LOG roup Northwest, o West, Inc a PROPOSED SAUNDERS RESIDENCE Geotechnical Engineers, Gedogists, & 15911 - 74TH PL WEST Environmental scientists EDMONDS, WASHINGTON JOB NO, G-3595 DATE 1/23/14 PLATE A3.2 1f S � M H 121 O :Ids p � SID311HD'S b bM SGNOhCi2'hA 3h'd H.LI L , In 0 d ar9 t7v u ' od lL ry y Oryfi �R' iW Om v Lrm cv""j >1A p' p sw, 4m fJ �,,� at��qq dtt' -Iry ��m *' f1r,d C�V�%atx6uA" J�Gw }�PGi�a tLQWfd0 dF dal d OI O 0. iJJ u m m o <19' ���1�7��m��L?am°mn nlUi�'s 0-(1),o0)E, Jax o� -A9 nmc M 30 y7cy N n � ES LU I omit (z syrup 4s Xm0.'i W' _I_QQCt�. 0.,F addil F A d LLml n so 46w �WCWi d0.` 1\ p� wU a � p tL 1 Jai Pm a m F w0 z��Q«�n P m1Y� ma -u wGG�-1 d Sz"0' p�224�pj Lit?, ❑t�V�� °d dmd Qyy�ot, i� w dad � pydl- dS� L��G <°aN o00 'amsP A Afl i any wd Kd vla� �L��w n�Uzlpu wq d {1m1wS ©GSw w t ,� n tKn �i•Pd m mwm uH d Taal ¢n �i m, 1 �I d�'a 4w>�?i mn is o u4z �d >GttK a�P �3x w0 s d£�lp j >� { doiva mnr� my�q }� b d a }-"{0.}fl 6 dLpmmm FQ;tfl -lo {�t°awi S� ',wtNmv� 11i 201NiM 4az d i } a S z o c