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22214 98th Ave. W geotech reportDecember 22, 2021 ES-8203 Select Homes, Inc. 8304 — 212' Street Southwest Edmonds, Washington 98026 Attention: Ms. Kayla Nichols Subject: Geotechnical Evaluation Proposed Single -Family Residences 22214 — 98t" Avenue West Edmonds, Washington Reference: RAM Engineering, Inc. Preliminary Short Plat L h ons «C Earth Solutions NW LLC Geotechnical Engineering, Construction Observationjesting and Environmental Services Department of Ecology Stormwater Management Manual for Western Washington Amended December 2014 James P. Minard Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles Washington, 1983 United States Department of Agriculture (USDA) Web Soil Survey (WSS) Edmonds City Code Chapter 23.80 (Geologically Hazard Areas) Dear Ms. Nichols: As requested, Earth Solutions NW, LLC (ESNW) has prepared this geotechnical evaluation report for the proposed single-family residences. As part of our scope of services, we completed a subsurface exploration, laboratory and engineering analyses, in -situ infiltration testing, and prepared this written report with our findings and recommendations for the proposed project. Based on our evaluation, the proposed project is feasible from a geotechnical standpoint. 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Select Homes, Inc. December 22, 2021 Project Description ES-8203 Page 2 The subject site is located at 22214 — 98th Avenue West in Edmonds, Washington, as illustrated on the attached Vicinity Map (Plate 1). The site consists of one tax parcel (Snohomish County parcel number 0045070030-0002) totaling approximately 1.03 acres of land. The property is currently developed with a single-family residence, outbuildings, and associated improvements. The subject site is bordered to the north, south, and west by single-family residences and to the east by 98th Avenue West. Site topography consists of a local knob feature; the existing building pad area in the southeastern portion of the property is gently sloped, and the site moderately descends to the west, north, and northeast. We estimate total elevation change across the site of approximately 40 feet and slope gradients of up to approximately 30 to 40 percent; isolated areas of less than 10 feet in height may be 40 percent or steeper. The slopes are vegetated with mature trees and ferns. Based on ESNW's understanding of the proposed development, the subject site will be redeveloped with three single-family residences and associated improvements. We anticipate grading activities will include cuts and fills of about four to six feet to establish the planned building alignments. However, grading plans were not available at the time this report was prepared. We understand infiltration and low impact development methods are being evaluated for stormwater management. Site improvements will also include underground utility installations. At the time this report was prepared, specific building load values were not available. However, we anticipate the proposed residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads on the order of one to two kips per linear foot and slab -on - grade loading of 150 pounds per square foot (psf). If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. Subsurface Conditions As part of this geotechnical evaluation, an ESNW representative observed, logged, and sampled three test pits on October 19, 2021, excavated at accessible locations within the proposed development area, using a mini-trackhoe and operator provided by the client. The approximate locations of the test pits are depicted on the Test Pit Location Plan (Plate 2). Please refer to the test pit logs provided as an attachment to this report for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with the Unified Soil Classification System (USCS) and USDA methods and procedures. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 Topsoil and Fill ES-8203 Page 3 Native topsoil was observed extending to depths of approximately four to seven inches below the existing ground surface (bgs). The topsoil was characterized by dark brown color and fine organic material. Fill was observed at test pit location TP-2. The fill was observed to extend to a depth of roughly five and one-half feet bgs. The fill was characterized primarily as silty sand with gravel (USCS: SM), and was encountered in a moist condition at the time of exploration. Additionally, fill may be present within proximity to existing structural improvements. Where fill is encountered during construction, ESNW should be consulted to evaluate the suitability for support of the proposed structures and/or reuse as structural fill. Native Soil Underlying the topsoil and limited fill, native soil at the test pit locations was observed to consist primarily of silty sand (USCS: SM). Overall soil relative density generally increased with depth. The native soil was generally observed in a weakly cemented condition beginning at about three and one-half to four feet bgs, except where fill was encountered. Geologic Setting The referenced geologic map resource identifies Vashon till (Qvt) across the site and surrounding areas. As reported on the geologic map resource, Vashon till typically consists of a nonsorted mixture of clay, silt, sand, pebbles, cobbles, and boulders. The till was deposited directly by ice advanced over previously deposited sediment and rocks. In addition, the referenced WSS resource identifies Alderwood gravelly sandy loam and Alderwood-urban land complex (Map Unit Symbol: 3 and 5, respectively) as the primary soil units underlying the subject site. The Alderwood series was formed in glacial till plains. Based on our field observations, native soils on the subject site are generally consistent with the geologic setting outlined in this section. Groundwater Groundwater seepage was not observed at the test pit locations during the fieldwork (October 2021). However, seepage should be expected in deeper excavations at this site, particularly during the winter, spring, and early summer months. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. Geologically Hazardous Areas Assessment As part of this geotechnical evaluation, the referenced chapter and section of the Edmonds City Code (ECC) was reviewed. The site contains sloped topography; the following is a geologically hazardous areas assessment for the site and proposed project. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 Slope Reconnaissance ES-8203 Page 4 During our fieldwork, we performed a visual slope reconnaissance of the sloped areas of the site. The main focus of our reconnaissance was to identify signs of instability or erosion hazards along the site slopes. The typical instability indicators include features such as head scarps, tension cracks, hummocky terrain, groundwater seeps along the surface and erosion features such as gulleys and rills. During the slope reconnaissance, no signs of erosion or slope instability were observed. The slopes are vegetated with mature trees and ferns. Erosion Hazard Areas — ECC 23.80.020.A. With respect to erosion hazard areas, section 23.80.020 of the ECC defines erosion hazards as "at least those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation Service as having a `moderate to severe', `severe', or `very severe' rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank erosion. Within the city of Edmonds, erosion hazard areas include: Those areas of the city of Edmonds containing soils that may experience severe to very severe erosion hazard. This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or greater: a. Alderwood soils (15 to 25 percent slopes); b. Alderwood/Everett series (25 to 70 percent slopes), and; c. Everett series (15 to 25 percent slopes). 2. Coastal and stream erosion areas which are subject to the impacts from lateral erosion related to moving water such as stream channel migration and shoreline retreat; 3. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs or ground water seepage, and; 4. Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope." The native soil is generally consistent with Alderwood series soils. Based on the ECC definition, the areas sloped greater than 15 percent within and adjacent to the property classify as erosion hazard areas. In our opinion, the proposed construction will not increase the erosion hazard for the site or adjacent properties, provide typical Best Management Practices (BMPs), such as silt fences, covering exposed soil, and permanent landscaping, are implemented during and after construction as warranted. Earth Solutions NW. LLC Select Homes, Inc. ES-8203 December 22, 2021 Page 5 Landslide Hazard Areas — ECDC 23.80.020.B. With respect to landslide hazard areas, section 23.80.020.B. of the ECDC defines landslide hazard areas as "areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any combination of soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Within the city of Edmonds, potential landslide hazard areas include: 1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and landslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985 report of GeoEngineers, Inc., and further discussed in the 2007 report by Landau Associates; 2. Coastal areas mapped as class U (unstable), UOS (unstable old slides) and URS (unstable recent slides) in the Department of Ecology Washington coastal atlas; 3. Areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps published by the United States Geological Survey or Washington State Department of Natural Resources; 4. Any slope of 40 percent or steeper that exceeds a vertical height of 10 feet over a 25-foot horizontal run. Except for rockeries that have been engineered and approved by the engineer as having been built according to the engineered design, all other modified slopes (including slopes where there are breaks in slopes) meeting overall average steepness and height criteria should be considered potential landslide hazard areas; 5. Any slope with all three of the following characteristics: a. Slopes steeper than 15 percent; b. Hillsides intersecting geologic contacts with relatively permeable sediment overlying a relatively impermeable sediment, and; c. Springs or ground water seepage; 6. Any area potentially unstable as a result of rapid stream incision or stream bank erosion; 7. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or deposition of stream -transported sediments, and; 8. Any slopes that have been modified by past development activity that still meet the slope criteria." Earth Solutions NW. LLC Select Homes, Inc. ES-8203 December 22, 2021 Page 6 As discussed previously, no indications of instability were observed during our slope reconnaissance. Based on review of available topographic data, there are no areas within or immediately adjacent to the site which area sloped 40 percent or steeper for a vertical height of at least 10 feet. Much of the sloped areas are steeper than 15 percent, however, the site is underlain by high strength glacial till deposits and no springs or groundwater seepage were observed; in this respect, the site slopes do not meet criterion 5. Based on our study, no landslide hazard areas (as defined above) are located within or immediately adjacent to the subject site. If the recommendations in this report are incorporated into the design and construction of the proposed project, it is our opinion the project is feasible from a geotechnical standpoint. Temporary Erosion Control The following temporary erosion control measures should be considered: • Temporary construction entrances and drive lanes, consisting of at least six inches of quarry spalls, should be considered to both minimize off -site soil tracking and provide a stable access entrance surface. Placing geotextile fabric underneath the quarry spalls will provide greater stability if needed. • Silt fencing should be placed around appropriate portions of the site perimeter. • When not in use, soil stockpiles should be covered or otherwise protected to reduce the potential for soil erosion, especially during periods of wet weather. • Temporary measures for controlling surface water runoff, such as interceptor trenches, sumps, or swales, should be installed prior to beginning and concurrent with earthwork activities. • Surface water should not be directed to or dispersed over steeply sloped areas. • Dry soils disturbed during construction should be wetted to minimize dust and airborne soil erosion. • When appropriate, permanent planting or hydroseeding will help to stabilize site soils. Additional Best Management Practices, as specified by the project civil engineer and indicated on the plans, should be incorporated into construction activities. Temporary erosion control measures may be modified during construction as site conditions require, as approved by the site erosion control lead. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 Excavations and Slopes ES-8203 Page 7 Based on the soil conditions observed at the subsurface locations, the following allowable temporary slope inclinations, as a function of horizontal to vertical (H:V) inclination, may be used. The applicable Federal Occupation Safety and Health Administration and Washington Industrial Safety and Health Act soil classifications are also provided: • Areas exposing groundwater seepage 1.51-1:1V (Type C) • Loose soil 1.51-1:1V (Type C) • Medium dense native soil 1 H:1 V (Type B) • Dense to very dense "hardpan" native soil 0.751-1:1V (Type A) Permanent slopes should be planted with vegetation to enhance stability and to minimize erosion, and should maintain a gradient of 2H:1 V or flatter. The presence of perched groundwater may cause localized sloughing of temporary slopes. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations, as necessary. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines: • Structural fill material • Moisture content • Relative compaction*** • Loose lift thickness (maximum) Granular soil* At or slightly above optimum** 95 percent (Modified Proctor) 12 inches * Existing soil may not be suitable for use as structural fill unless at (or slightly above) the optimum moisture content at the time of placement and compaction. ** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. ***Relative compaction of 90 percent can be considered for mass grading activities. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. If structural fill is placed on sloped grades, the slope should be keyed and benched prior to placing fill. ESNW should review grading plans and provide additional recommendations as necessary. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 Foundations ES-8203 Page 8 The proposed structures can be supported on conventional spread and continuous footings bearing on undisturbed, competent native soil, compacted native soil, or new structural fill. Competent native soils, suitable for support of the foundation, should be encountered beginning at depths of approximately two to three feet bgs, except where existing fill is present. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations during site preparation activities, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with granular structural fill will be necessary. Structural fill should consist of suitable granular soils compacted to 95 percent of Modified Proctor (ASTM D1557). Compaction of the soil to the levels necessary for use as structural fill will be difficult during wet weather conditions. Organic material exposed at foundation subgrade elevations must be removed and grades restored with structural fill. Provided the structures will be supported as described above, the following parameters can be used for design of the new foundations: • Allowable soil bearing capacity 2,500 psf • Passive earth pressure 300 pcf (equivalent fluid) • Coefficient of friction 0.40 The passive earth pressure and coefficient of friction values include a safety factor of 1.5. A one- third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. Retaining Wall Recommendations Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters can be used for retaining wall design: • Active earth pressure (unrestrained condition) • Active earth pressure (backslope) • At -rest earth pressure (restrained condition) • At -rest earth pressure (backslope) • Traffic surcharge (passenger vehicles) • Passive earth pressure • Coefficient of friction • Seismic surcharge * Where H equals the retained height. 35 pcf 50 pcf 55 pcf 70 pcf 70 psf (rectangular distribution) 300 pcf 0.40 8H* Earth Solutions NW. LLC Select Homes, Inc. ES-8203 December 22, 2021 Page 9 The passive earth pressure and coefficient of friction values include a safety factor of 1.5. Additional surcharge loading should be included in the retaining wall design if necessary. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with at least 18 inches of free -draining material or sheet drainage that extends along the height of the wall. The upper one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall and connected to an approved discharge location. Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test pit locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class D* Mapped short period spectral response acceleration, Ss (g) 1.280 Mapped 1-second period spectral response acceleration, S1 (g) 0.450 Short period site coefficient, Fa 1.200 Long period site coefficient, F„ 1.850t Adjusted short period spectral response acceleration, Sens (g) 1.536 Adjusted 1-second period spectral response acceleration, SM1 (g) 0.832t Design short period spectral response acceleration, SIDS (g) 1.024 Design 1-second period spectral response acceleration, SD1 (g) 0.549t Assumes dense native soil conditions, encountered to a maximum depth of 8.0 feet bgs during the October 2021 field exploration, remain dense to at least 100 feet bgs. t Values assume Fv maybe determined using linear interpolation per Table 11.4-2 in ASCE 7-16. As indicated in the table footnote, several of the seismic design values provided above are dependent on the assumption that site -specific ground motion analysis (per Section 11.4.8 of ASCE 7-16) will not be required for the subject project. ESNW recommends the validity of this assumption be confirmed at the earliest available opportunity during the planning and early design stages of the project. Further discussion between the project structural engineer, the project owner, and ESNW may be prudent to determine the possible impacts to the structural design due to increased earthquake load requirements under the 2018 IBC. ESNW can provide additional consulting services to aid with design efforts, including supplementary geotechnical and geophysical investigation, upon request. Earth Solutions NW. LLC Select Homes, Inc. ES-8203 December 22, 2021 Page 10 Liquefaction is a phenomenon where saturated or loose soil suddenly loses internal strength and behaves as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered low. The depth of the regional groundwater table and the relatively dense characteristics of the native soil were the primary bases for this opinion. Drainage Temporary measures to control surface water runoff during construction would likely involve passive elements such as interceptor trenches and sumps. ESNW should be consulted during preliminary grading activities to evaluate seepage areas and provide recommendations to reduce the potential for seepage -related instability. Finish grades should be designed to direct surface water away from structures and slopes. Grades adjacent to buildings should be sloped away at a gradient of either at least 2 percent for a horizontal distance of up to 10 feet or the maximum allowed by adjacent structures. In our opinion, foundation drains should be installed along building perimeter footings. Infiltration Evaluation As indicated in the Subsurface Conditions section, native soils encountered during our fieldwork were characterized primarily as silty sand with and without gravel. Based on the results of USDA textural analyses, the native soils at depth were classified primarily as gravelly sandy loam and gravely fine sandy loam with fines contents of about 23 to 37 percent. In -situ testing was completed in accordance with the Small-scale Pilot Infiltration Test (PIT) procedure, as outlined in Volume III, Chapter 3, Page 526 of the 2014 SMMWW. The testing was completed at a depth of approximately four feet at TP-3. The in -situ rate obtained during testing was 0.125 inches per hour. Based on subsurface conditions observed before, during, and after the PIT, it is our opinion that the low measured infiltration rate represents horizontal movement of the water rather than vertical infiltration. Based on the relatively impermeable glacial till soils and adjacent sloped topography, it is our opinion that infiltration is infeasible and is not recommended from a geotechnical standpoint. On -site Stormwater Management Pursuant to City of Edmonds stormwater management requirements, implementation of on -site stormwater BMPs are required for proposed developments in accordance with specified thresholds, standards, and lists. The intent of BMP implementation is to infiltrate, disperse, and retain stormwater runoff on site to the extent feasible. The table below summarizes our evaluation of low impact development methods, as outlined in the referenced stormwater manual, from a geotechnical standpoint. It is instructed in the referenced stormwater manual that BMPs are to be considered in the order listed (from top to bottom) for each surface type, and the first BMP that is determined to be viable should be used. For completeness, however, we have evaluated each listed BMP for the proposed surface type. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 ES-8203 Page 11 BMP Viable? Limitations or Infeasibility Criteria Lawns and Landscaped Areas T5.13: Post -construction soil quality and depth (Volume V, Maybe* Limitation: Infeasible on slopes greater than 33 percent. Chapter 11 Roofs Limitations: Not recommended within 50 feet of slopes T5.30: Full dispersion (Volume V, Maybe* steeper than 15 percent. Potential downgradient impacts Chapter 3) must be evaluated. T5.10A: Downspout full infiltration systems (Volume III, Chapter 4) No Infeasibility: Infeasible due to relatively impermeable soil and sloped topography. Roofs Bioretention (Volume V, Chapter Infeasibility: Infeasible due to relatively impermeable soil 5) No and sloped topography resulting in reasonable concerns about erosion, slope failure, or downgradient flooding. T5.10B: Downspout dispersion Limitations: Not recommended within 50 feet of slopes systems (Volume V, Chapter 4) Maybe* steeper than 15 percent. Potential downgradient impacts must be evaluated. T5.10C: Perforated stub -out Limitations: Not recommended within 50 feet of slopes connections (Volume V, Chapter Maybe* steeper than 15 percent. Bottom of trench should be at 4) least one foot above unweathered till (hardpan) which may be infeasible. T5.30: Full dispersion (Volume V, Limitations: Not recommended within 50 feet of slopes Chapter 5) Maybe* steeper than 15 percent. Potential downgradient impacts must be evaluated. T5.15: Permeable pavement Infeasibility: Infeasible due to relatively impermeable soil (Volume V, Chapter 5) No and sloped topography resulting in reasonable concerns about erosion, slope failure, or downgradient flooding. Bioretention (Volume V, Chapter Infeasibility: Infeasible due to relatively impermeable soil 5) No and sloped topography resulting in reasonable concerns about erosion, slope failure, or downgradient flooding. T5.12: Sheet flow dispersion Limitations: Not recommended within 50 feet of slopes T5.11: Concentrated flow Maybe* steeper than 15 percent. Potential downgradient impacts dispersion Volume V, Chapter 5 must be evaluated. * Viability stated from a geotechnical standpoint and should be determined by site storm designer with respect to setbacks and flow paths. Limitations The recommendations and conclusions provided in this geotechnical evaluation report are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test pit locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical evaluation report if variations are encountered. Earth Solutions NW. LLC Select Homes, Inc. December 22, 2021 Additional Services ES-8203 Page 12 ESNW should be retained to provide additional geotechnical services in association with this project, including testing and consulting services during construction. ESNW should have an opportunity to review final project plans with respect to geotechnical recommendations provided in this letter. We trust this letter meets your current needs. Should you have questions, or if any additional information is required, please call. Sincerely, EARTH SOLUTIONS NW, LLC Adam Z. Shier, L.G. Project Geologist Attachments: Plate 1 — Vicinity Map Plate 2 — Test Pit Location Plan Test Pit Logs Grain Size Distribution T • wR 61 WA y 63 03 keSSl0NA1- 12/22/2021 Henry T. Wright, P.E. Senior Project Manager cc: RAM Engineering, Inc. Attention: Mr. Rob Long, P.E. (Email only) Earth Solutions NW. LLC EdlllOndS_- Sprague Street C'P o' Sprague Street - _- EdmondS �� WA 524 z° _= Ferr7erminal V Bell Street y - --- �\ y c� \` N ;- Edmonds ° Edlllonds_" ....-- — - — -- Main StreeL c X�� Dayton Street Dayton Street - - s a Maple Way \ \ X v Maple Street (Maple Street < Yost Park ca _ Alder Street \ \ - - - - Walrrt Street Walnut Street Walnut Street_ eii 3 \� _ _ a y oa __-ErJmo7d5 _ o -_ Drive d w (Holly Cedar Street -Marsh_ =_9 - - - --_ - -- w o Howell way S Spruce Street - -' Ed on ce Street QowaOrn W -_ - Edmonds Hemlock Way. ay City Pork SLaurel P ,m'I Street 215[h St<¢¢t Southwest Pine Street � --Pine Street m Chas pintreet e�s-Pine Street 216th Street Southwest 216th Street Southwest J Eleme m sch 2111,11 Street Southwest j Fir Street. a m 218th 5 \�o\ III 9n \\ 2IA < J Bella Coola Road F \ \ P -- Elm street elm Street =220[h St[eet.5outhwest_ a dal\ — — _— ��� Elm J.J21 6 � - f i m Noy D `w m 90 � WA104 aa 'eW fr otl(aneQa'P°�a Kulshan Roa2 dP � 224th Street Southwest o� g \ I a Esperance o¢ dde o P 9onquin Roaa F 6Sm St,Pef Southwest o oq ❑ a 2261h out Street Sh wood "ci SOV- sGy J o47d �O m omo 228th Street Southwest 228th Street Sout I > S < > eer Drii N°R2=D m Sherwood � �r ek 'i Forest,o� n Woodway � I� s� Ji 1\ 231st Street Southwest yi 232nd Street Southwest N� Holly Lane A of P Q 6� Edmonds /� 0 Maple Lane Heights n a� t Nottingham Road K12 Madrona Lane 3�I [1 3 3 _ o a 11 236[h Place Southwest o I I p` @ 236th_St " :E �; N Madrona 3 K-8 school - tnwestSnoline —, 238th Street Southwest.. e Elementary 237Ch Place/ $Ch001 _ \\ ` 7 238th s[reetsoUthwie \ Al \ ea Reference: NORTHSnohomish []N County, Washington- eering, Consfruction LOb OpenStreetMap.org a ce Vicinity Map 22214 - 98th Avenue W. Edmonds, Washington NOTE This plate may contain areas of color ESNW cannot be Drwn. MRS Date 11/19/2021 Proj. No. 8203 responsible for any subsequent mislnleip�elallon of the lnfo�mallon iesulling from black & white iepioduclions of this plate. Checked AZS Date Nov. 2021 Plate 1 LEGEND Approximate Location of TP-1 _ ESNW Test Pit, Proj. No. ES-8203, Oct. 2021 Subject Site Existing Building O 0 D NORTH < NOT - TO - SCALE NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproduclions of this plate. NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and I or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. Drwn. MRS Date 11/19/2021 Proj. No. 8203 Checked AZS Date Nov. 2021 Plate 2 I w Z w Q co Earth Solutions NWLLC SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETTER GRAVEL AND CLEAN GRAVELS ''� I.�•� � � � A. GW WELL -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES GRAVELLY SOILS (LITTLE OR NO FINES) ° �o ° �o o pOo p Q Q oQ GP POORLY -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES COARSE GRAINED SOILS MORE THAN 50% OF COARSE GRAVELS WITH FINES o Q 0 °° o o p GM SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES FRACTION RETAINED ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) �±� V CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES SAND AND CLEAN SANDS �+ SW WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES MORE THAN 50% OF MATERIAL IS LARGER THAN SANDY NO. 200 SIEVE SIZE SOILS (LITTLE OR NO FINES) ::. SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SANDS WITH FINES c `M SILTY SANDS, SAND - SILT MIXTURES MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) cC �7 CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY FINE GRAINED SOILS SILTS AND LIQUID LIMIT LESS THAN 50 CLAYS CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS SIZE SILTS AND LIQUID LIMIT CLAYS GREATER THAN 50 CH CLAYS OF HIGH PLASTICITY PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS '/ ` 1/ 01/ 01/ N \„ \„ „ 0 0„ PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. y Earth Solutions NW, LLC TEST PIT NUMBER TP-1 15365 N.E. 90th Street, Suite 100 PAGE 1 OF 1 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-8203 PROJECT NAME 22214 - 98th Avenue W. DATE STARTED 10/19/21 COMPLETED 10/19/21 GROUND ELEVATION EXCAVATION CONTRACTOR Client Provided LATITUDE 47.79745 LONGITUDE-122.36535 EXCAVATION METHOD GROUND WATER LEVEL: LOGGED BY AZS CHECKED BY HTW SZ AT TIME OF EXCAVATION NOTES Depth of Topsoil & Sod 7": grass L = }� H L U 2 w g TESTS Q O MATERIAL DESCRIPTION ❑ 2 Z U Q U 0 TPSL Dark brown TOPSOIL, roots .'-. 6 0.Brown silty SAND with gravel, loose to medium dense, moist MC = 6.2% SM 3.0 MC = 5.2% Gray silty SAND, medium dense, moist Fines = 26.2% [USDA Classification: gravelly sandy LOAM] -becomes dense, moderately cemented 5 SM Test pit terminated at 8.0 feet below existing grade due to refusal on very dense till. No groundwater encountered during excavation. No caving observed. v Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TEST PIT NUMBER TP-2 PAGE 1 OF 1 PROJECT NUMBER ES-8203 PROJECT NAME 22214 - 98th Avenue W. DATE STARTED 10/19/21 COMPLETED 10/19/21 GROUND ELEVATION EXCAVATION CONTRACTOR Client Provided LATITUDE 47.79748 LONGITUDE-122.36476 EXCAVATION METHOD GROUND WATER LEVEL: LOGGED BY AZS CHECKED BY HTW SZ AT TIME OF EXCAVATION NOTES Depth of Topsoil & Sod 2": grass L }� U = H L Lu g TESTS Q O MATERIAL DESCRIPTION w QZ U t.7 0.5 Dark brown TOPSOIL (Fill) Brownish gray silty SAND with gravel, loose to medium dense, moist (Fill) MC = 13.0% Fines = 23.0% 1 N [USDA Classification: very gravelly sandy LOAM] SM MC = 10.9% 5.5 Brown silty SAND, loose to medium dense, moist SM nnr. = 11 70/ 8.0 Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. v Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TEST PIT NUMBER TP-3 PAGE 1 OF 1 PROJECT NUMBER ES-8203 PROJECT NAME 22214 - 98th Avenue W. DATE STARTED 10/19/21 COMPLETED 10/19/21 GROUND ELEVATION EXCAVATION CONTRACTOR Client Provided LATITUDE 47.79772 LONGITUDE-122.36513 EXCAVATION METHOD GROUND WATER LEVEL: LOGGED BY AZS CHECKED BY HTW SZ AT TIME OF EXCAVATION NOTES Depth of Topsoil & Sod 4": exposed soil L = }� H L U w Lu g TESTS Q O MATERIAL DESCRIPTION ❑ 2 Z � Q 0 TPSL — Dark brown TOPSOIL, roots Brown silty SAND, loose to medium dense, moist SM -roots - MC = 3.9% 2.0 Gray silty SAND, medium dense to dense, damp _ MC = 3.3% becomes dense to very dense, moderately cemented Fines = 22.7% -infiltration test SM 5 MC = 6.0% Fines = 36.5% [USDA Classification: gravelly sandy LOAM] 7.0 [USDA Classification: slightly gravelly fine sandy LOAM] Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. No caving observed Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 MWRedmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-8203 U.S. SIEVE OPENING IN INCHES 100 95 90 85 80 75 70 65 x w 60 m 55 w 50 z LL 45 z w rr 40 w a 35 30 25 20 15 10 5 0 GRAIN SIZE DISTRIBUTION PROJECT NAME 22214 - 98th Avenue W. U.S. SIEVE NUMBERS I HYDROMETER 1/4H[:>•�=l.�:fI11�1L'!IL741SGIISSIS.1W111111111IUl1111lB511412i I�11®■■■u�■i���■III■■■�■■■�■■111�■■■�■■��II�®1 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS COBBLES GRAVEL SAND SILT OR CLAY coarse fine coarse medium fine Specimen Identification Classification Cc CU • TP-01 3.50ft. USDA: Gray Gravelly Sandy Loam. USCS: SM. m TP-02 2.00ft. USDA: Gray-Brn Very Gravelly Sandy Loam. USCS: SM with Gravel. A TP-03 4.00ft. USDA: Gray Gravelly Sandy Loam. USCS: SM. * TP-03 7.00ft. USDA: Gray Slightly Gravelly Fine Sandy Loam. USCS: SM. Specimen Identification D100 D60 D30 D10 LL PL PI %Silt %Clay 0 TP-01 3.5ft. 37.5 0.521 0.106 26.2 m TP-02 2.Oft. 19 2.684 0.157 23.0 A TP-03 4.Oft. 19 0.592 0.145 22.7 * TP-03 7.Oft. 19 0.219 36.5