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REVIEWED BLD2022-1092+Geotechnical_Report+9.27.2022_11.50.23_AM+3131228RECEIVED ............REVIEWEp........... BY Earth Sep 27 2022 CITY OF EDMONDS CITY OFEDMONDS BLD2022-1092 E BUILDING DEPARTMENT' DEVELOPMENT SERVICES DEPARTMENT ................................................ May 4, 2021 Earth Solutions NW LLC ES-7841 Ceotechnical Engineering, Construction Observation/Testing and Environmental Services Select Homes, Inc. 16531 — 13th Avenue West, Suite A107 Lynnwood, Washington 98037 Attention: Ms. Kayla Nichols Subject: Geotechnical Evaluation Proposed Single -Family Residences 19508 — 88th Avenue West Edmonds, Washington Reference: 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 Web Soil Survey (WSS) Edmonds City Code (ECC) 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 project. As part of our scope of services, we completed a subsurface exploration, in -situ infiltration testing, laboratory and engineering analyses, 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. Protect Description The subject site is located at 19508 — 88th Avenue West in Edmonds, Washington. The subject site consists of two parcels (Snohomish County parcel numbers 2704180030-3200 and -3400) covering 0.96 acres. The property is currently developed with a single-family residence and associated improvements. Based on ESNW's understanding of the proposed development, the boundary lines will be adjusted to create two residential lots behind the existing residence, with access along the southern property line. The subject site generally descends towards the west with total elevation change on the order of 10 to 15 feet. The subject site is bordered by single-family residences on the north, south, and west sides, and 88th Avenue West to the east. 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Select Homes, Inc. ES-7841 May 4, 2021 Page 2 We anticipate grading activities will include cuts and fills of about two to four feet to establish the planned building alignments. 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 March 15, 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 United States Department of Agriculture (USDA) methods and procedures. Topsoil and Fill Native topsoil was observed extending to depths of approximately 3 to 12 inches below the existing ground surface (bgs). The topsoil was characterized by dark brown color and fine organic material. Fill was not encountered within the test pits. If fill is encountered during construction, ESNW should be consulted to verify the suitability for support of the proposed structures and/or reuse as structural fill. Native Soil Underlying the topsoil, native soil conditions at the test pit locations was observed to consist primarily of silty sand (USCS: SM). Overall soil relative density increased with depth, extending to the maximum exploration depth of about seven feet bgs. The native soil was generally observed in a weakly to moderately cemented condition at about four feet bgs. Earth Solutions NW. LLC Select Homes, Inc. May 4, 2021 Geologic Setting ES-7841 Page 3 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-urban land complex (Map Unit Symbol: 6) 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 Natural groundwater seepage was not observed at the test pit locations during the fieldwork (March 2021). However, light seepage was documented after the infiltration test at TP-1 when the test pit was advanced to eight feet bgs. 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 of the ECC was reviewed. Based on our investigation and review, there are no geologically hazardous areas present on or adjacent to the site. Foundations 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. 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 Earth Solutions NW. LLC Select Homes, Inc. ES-7841 May 4, 2021 Page 4 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 Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for retaining wall design: • Active earth pressure (unrestrained condition) • At -rest earth pressure (restrained condition) • Traffic surcharge (passenger vehicles) • Passive earth pressure • Coefficient of friction • Seismic surcharge * Where H equals the retained height (in feet) 35 pcf 55 pcf 70 psf (rectangular distribution) 300 pcf 0.40 8H psf* The passive earth pressure and coefficient of friction values include a safety factor of 1.5. Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Retaining walls should be backfilled with free -draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. 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. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. Earth Solutions NW. LLC Select Homes, Inc. May 4, 2021 Seismic Design ES-7841 Page 5 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 boring locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class C* Mapped short period spectral response acceleration, Ss (g) 1.294 Mapped 1-second period spectral response acceleration, S1 (g) 0.457 Short period site coefficient, Fa 1.200 Long period site coefficient, F„ 1.500 Adjusted short period spectral response acceleration, SMs (g) 1.553 Adjusted 1-second period spectral response acceleration, SM1 (g) 0.685 Design short period spectral response acceleration, SIDS (g) 1.036 Design 1-second period spectral response acceleration, SD1 (g) 0.457 * Assumes very dense soil conditions, encountered to a maximum depth of 7 feet bgs during the March 2021 field exploration, remain very dense to at least 100 feet bgs. Based on our experience with the project geologic setting (glacial till) across the Puget Sound region, soil conditions are likely consistent with this assumption. In our opinion, the site susceptibility to liquefaction is negligible. The native soil relative density and the absence of an established, shallow groundwater table are 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. A typical footing drain detail is attached to this letter (Plate 4). Earth Solutions NW. LLC Select Homes, Inc. May 4, 2021 Infiltration Evaluation ES-7841 Page 6 As indicated in the Subsurface Conditions section, native soils encountered during our fieldwork were characterized primarily as silty sand glacial till deposits. Based on the results of USDA textural analyses, the native silty sand soils at depth were classified primarily as slightly gravelly sandy loam with fines contents of about 32 to 36 percent. In -situ testing was completed in accordance with the Small-scale 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 and one-half feet at TP-1. The in -situ rate obtained during testing was 1.25 inches per hour. The test pit was advanced deeper after completion of the test and light water seepage from the test was observed at a depth of about five feet, indicating that some of the measured infiltration traveled horizontally rather than vertically. Because the infiltration rate obtained from in -situ testing is considered to be a short-term rate, correction factors must be applied in order to determine a long-term design rate. The correction factors outlined below were used in accordance with Table III-3.3.1 of the 2014 SMMWW outlined in Volume III, Chapter 3, Page 529. The correction factors, along with the measured infiltration rate, were incorporated into the following equation: Ksat design = Ksat initial x CFv x CFr x CF.. • Measured (Ksat initial) 1.25 inches per hour • Site variability CFv = 0.5 • Test method CFt = 0.5 • Degree of influent control CFm = 0.9 • Long-term design infiltration rate (Ksat design) 0.28 inches per hour The design infiltration rate is applicable to facilities located in proximity to the infiltration test location and depth. Infiltration facilities must incorporate overflow provisions. If overflow provisions are not or cannot be included, ESNW does not consider the native glacial till a suitable receptor for infiltration facilities from a geotechnical standpoint. ESNW should be retained to observe the construction of infiltration facilities on the subject site in order to confirm soil conditions are as anticipated and perform confirmation infiltration testing at the infiltration design depth and locations. Overexcavation of low permeability lenses may be required. Supplementary geotechnical recommendations may be provided at the time of construction, where necessary. Earth Solutions NW. LLC Select Homes, Inc. May 4, 2021 Discussion ES-7841 Page 7 Infiltration should be situated as high in the native soil as possible, to provide maximum capacity for infiltration. Infiltration into the upper soil zone will require protection from traffic, compaction or other activities that may impede or otherwise degrade the infiltration capacity. The weathered section of the glacial till deposit is susceptible to unintentional compaction if subject to vehicle/machine traffic, and fill placement. In order to preserve the undisturbed infiltration characteristics of the weathered section, any area that will have shallow infiltration facility must be identified and protected prior to, and throughout, mass earthwork operations. Failure to do so may reduce the infiltration characteristics of the near surface soils. Based on subsurface conditions observed before, during, and after the PIT, it is our opinion that the low measured infiltration rate represents horizontal infiltration as well as vertical infiltration, which was exhibited by the seepage observed after advancing the test pit deeper. Infiltration into native soils would move laterally along the relatively impermeable unweathered till soils, with some infiltrating vertically. Potential offsite impacts (basements, crawlspaces, utilities, etc.) should be evaluated prior to final engineering and facility construction. Additionally, ESNW should review the proposed grading and drainage plans to confirm the recommendations in this report are followed, and to provide additional recommendations as necessary. 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 types. Earth Solutions NW. LLC Select Homes, Inc. May 4, 2021 ES-7841 Page 8 BMP Viable? Limitations or Infeasibility Criteria Lawns and Landscaped Areas T5.13: Post -construction soil quality and depth (Volume V, Yes None. Chapter 5) Roofs T5.30: Full dispersion (Volume Limitation: Adequate vegetative flow paths will likely not V, Chapter 5) Maybe* be available. T5.10A: Downspout full Limitation: Infiltration facilities should be shallow and infiltration systems (Volume III, Yes designed with overflow. Chapter 3) Roofs Bioretention Volume V, Chapter p Yes Limitation: Infiltration facilities should be shallow and 7) designed with overflow. T5.10B: Downspout dispersion Maybe* Limitation: Adequate vegetative flow paths will likely not systems (Volume III, Chapter 3) be available. T5.10C: Perforated stub -out Limitation: Soil and groundwater conditions to be verified connections (Volume III, Chapter Yes during installation. 3 T5.30: Full dispersion (Volume Maybe* Limitation: Adequate vegetative flow paths will likely not V, Chapter 5) be available. T5.15: Permeable pavement Yes Limitation: Infiltration facilities should be shallow and (Volume V, Chapter 5) designed with overflow. Bioretention (Volume V, Chapter Yes Limitation: Infiltration facilities should be shallow and 7) designed with overflow. T5.12: Sheet flow dispersion T5.11: Concentrated flow Maybe* Limitation: Adequate vegetative flow paths will likely not dispersion (Volume V, Chapter be available. 5 * Viability to be determined by storm designer. 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. May 4, 2021 Additional Services ES-7841 Page 9 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 4/2021 Henry T. Wright, P.E. Senior Project Manager Attachments: Plate 1 — Vicinity Map Plate 2 — Test Pit Location Plan Plate 3 — Retaining Wall Drainage Detail Plate 4 — Footing Drain Detail Test Pit Logs Grain Size Distribution cc: RAM Engineering, Inc. Attention: Mr. Rob Long, P.E. (Email only) Earth Solutions NW. LLC ie ❑c.? ❑ YQ -._Qp SefeetS /X//,( \ T�/ 179Ch -J -'----- .. 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Environmental Services OpenStreetMap.org40 Vicinity Map 19508 - 88th Avenue West Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information Drwn. CAM Date 04/09/2021 Proj. No. 7841 resulting from black & white reproductions of this plate. Checked AZS Date Apr. 2021 Plate 1 � � I E::D F-I I I 350 { .360 -_ _ ---I TP-1 T- ' ❑ 1 TP-� 'm I El I ------------- \� 10 1 I F -I I I I I ------� ---- --- -----------—-------!------------ 196TH STREET S.W. LEGEND TP-1 Approximate Location of — ■ — ESNW Test Pit, Proj. No. ES-7841, March 2021 Subject Site Existing Building 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 / 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. NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. NORTH NOT - TO - SCALE Test Pit Location Plan 19508 - 88th Avenue West Edmonds, Washington Drwn. CAM Date 04/09/2021 Proj. No. 7841 Checked AZS Date Apr. 2021 Plate 2 18" Min. 00 0o o oUoo 00 o 00 0o00�° �o 00000 o B 00 o o 0 o00 0 0 0 o 0 0 0 00 00 'o o o �o o oao 0 0000oo 8o 00 0 0 0 o o 0 o O o o oo Oo 00 o -0 000 o 0 0 0 o 0 o O o o 0 0 0 0 o0 00C 0 o 0 0o oo0 'o o O o O o0 0 0 O coo 00 0 0 0o Oo O oo o 0 0 oo o o ogoo o�000 oo oo o o 6 o o o 0 o00�00 0 oo o0 09' 0000 0 o o oo o ° o o oo. 0 0 oo 0 o 0 0o 0 o 0 d o 0 0 6 o o oo Oo0 0o O o o 0 o 0 �r.'r ?� NOTES: • Free -draining Backfill should consist of soil having less than 5 percent fines. Percent passing No. 4 sieve should be 25 to 75 percent. • Sheet Drain may be feasible in lieu of Free -draining Backfill, per ESNW recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: 0 .0- O 0 oo 00 Free -draining Structural Backfill 1-inch Drain Rock .}.r.r.r. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Retaining Wall Drainage Detail 19508 - 88th Avenue West Edmonds, Washington Drwn. CAM Date 04/09/2021 Proj. No. 7841 Checked AZS Date Apr. 2021 Plate 3 Perforated Rigid Drain Pipe (Surround in Drain Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal: native soil or other low -permeability material. ti.ti•ti•ti• 1-inch Drain Rock r�r�r�r�r ti•ti•ti•ti• SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Footing Drain Detail 19508 - 88th Avenue West Edmonds, Washington Drwn. CAM Date 04/09/2021 Proj. No. 7841 Checked AZS Date Apr. 2021 Plate 4 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 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 ' 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 c 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 CI I INORGANIC CLAYS OF HIGH 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. 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-1 PAGE 1 OF 1 PROJECT NUMBER ES-7841 PROJECT NAME 19508 - 88th Avenue West DATE STARTED 3/15/21 COMPLETED 3/15/21 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION -- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 10"-12": grass AFTER EXCAVATION - L = }� H L U w Lu g TESTS Q O MATERIAL DESCRIPTION ❑ 2 Z � Q C0 0 Dark brown TOPSOIL TPSL ,'/. i.i _ 1.0 Brown silty SAND, loose to medium dense, moist MC = 10.4% - SM _ 3.0 Gray silty SAND, medium dense, moist MC = 15.2% MC = 19.7% 5 Fines = 32.3% SM infiltration test at 4.5' [USDA Classification: slightly gravelly sandy LOAM] -light groundwater seepage from infiltration test MC = 14.5% Fines = 36.4% 7.0 [USDA Classification: slightly gravelly sandy LOAM] Test pit terminated at 7.0 feet below existing grade. Groundwater seepage encountered at 5.0 feet during excavation. No caving observed y Earth Solutions NW, LLC TEST PIT NUMBER TP-2 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-7841 PROJECT NAME 19508 - 88th Avenue West DATE STARTED 3/15/21 COMPLETED 3/15/21 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION -- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 8": grass AFTER EXCAVATION - L = }� H L U 2 w g TESTS Q O MATERIAL DESCRIPTION ❑ 2 Z U Q U 0 TPSL - Dark brown TOPSOIL I- oql 0 Brown poorly graded GRAVEL with silt and sand, loose to medium dense, moist GP - MC = 11.0% GM Fines = 10.1 % ° 2.5 [USDA Classification: extremely gravelly sandy LOAM] Gray silty SAND with gravel, medium dense to dense MC = 15.8% weakly cemented 5 SM MC = 15.3% 7.0 Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. y Earth Solutions NW, LLC TEST PIT NUMBER TP-3 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-7841 PROJECT NAME 19508 - 88th Avenue West DATE STARTED 3/15/21 COMPLETED 3/15/21 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION -- LOGGED BY AZS CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 3": grass AFTER EXCAVATION - L }� U = H L 2 w g TESTS Q O MATERIAL DESCRIPTION ❑ 2 Z Q U U 0 TPSL Dark brown TOPSOIL Brown silty SAND, loose to medium dense, moist MC = 14.1 % SM 2.0 Gray silty SAND, medium dense to dense, moist MC = 13.4% -weakly cemented SM 5 MC = 16.1% 7.0 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 ' Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 GRAIN SIZE DISTRIBUTION PROJECT NUMBER ES-7841 PROJECT NAME 19508 - 88th Avenue West U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS I HYDROMETER 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 rc � 1/4N[:>•�= l.�:f I loll L'!I L74i�Us Ui.1�1:71�1 Ul1�l L' 1114411 I■11®■■■ui■■�\AID■■■■■■WII�■■■■■■■■III®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 4.50ft. USDA: Gray Slightly Gravelly Sandy Loam. USCS: SM. m TP-01 7.00ft. USDA: Gray Slightly Gravelly Sandy Loam. USCS: SM. A TP-02 2.00ft. USDA: Brown Extremely Gravelly Sandy Loam. USCS: GP -GM with Sand. 3.81 232.83 Specimen Identification D100 D60 D30 D10 LL PL PI %Silt %Clay • TP-01 4.5ft. 19 0.359 32.3 m TP-01 7.Oft. 19 0.31 36.4 A TP-02 2.Oft. 37.5 17.06 2.183 10.1