The URL can be used to link to this page

Geotechnical Report. Edmonds.pdf GEOTECHNICAL ENGINEERING STUDY PAB ROPOSED PARTMENTUILDING 9516EW DMONDS AY E,W DMONDSASHINGTON G-4205 Prepared for Ethan Sorrelgreen and Judy Lackey 1902 - 31 st Avenue S. Seattle, WA 98144 October 14, 2016 By GEO GROUP NORTHWEST, INC. 13705 NE Bel-Red Rd Bellevue, WA 98005 Phone: (425) 649-8757 October 14, 2016G-4205 Ethan Sorrelgreen and Judy Lackey st 1902 - 31 Avenue S. Seattle, WA 98144 GES Subject: EOTECHNICALNGINEERINGTUDY PAB ROPOSED PARTMENTUILDING 9516 Edmonds Way Edmonds, Washington 98020 Dear Mr. Sorrelgreen and Ms. Lackey: This report presents the results of our geotechnical site evaluation for a proposed apartment building at 9516 Edmonds Way, in Edmonds, Washington. We understand the apartment building will be two-stories, with parking located under the building and partially below grade. The scope of work for this study included a site reconnaissance, review of the area geologic map, review of the preliminary site development plan, excavation of five test pits, characterization of the subsurface conditions, collection of representative soil samples, laboratory testing of the soil samples for moisture content, engineering analysis and preparation of this report. SC URFACEONDITIONS The subject parcel, Parcel No. 27033600100900, is approximately 0.29 acres in size and is vacant. It is located on the south side of Edmonds Way, approximately as illustrated on the Vicinity Map, Plate 1. The site is bordered by undeveloped property to the southwest and residential developed properties to the northeast and southeast. The northern three-quarters of the site is relatively flat and level. Ground elevations range from approximately 338 feet near the northwest corner of the parcel to elevation 344 feet near the southeast property corner, as indicated on the Site Plan, Plate 2, adapted from the boundary and topographic survey of the parcel. A portion of an abandoned house foundation (identified on the survey as “concrete wall”) is located across the south end of the parcel. The ground elevation steps up about 3 feet at the foundation. An existing gravel driveway is located across the north end of the site and a PUD easement and a W.N.G. easement are located along the north property 13705 Bel-Red Rd Bellevue, Washington 98005 Phone 425/649-8757 Fax 435/649-8758 October 14, 2016G-4205 Geotechnical Engineering ReportPage 2 9516 Edmonds Way, Edmonds line. The site is vegetated with grasses, blackberry vines, with a few evergreen and deciduous trees. SC UBSURFACEONDITIONS Geology 1 According the area geologic map, the site soils are mapped as Advance Outwash (Qva) deposits consisting of sand and gravel. The Advance Outwash was deposited by streams issuing from the advancing ice sheet during the Fraser glaciation period that ended some12,000 years ago and was glacially consolidated. Subsurface Investigation GEO Group Northwest, Inc., evaluated the site conditions by excavating five test pits with a trackhoe excavator. The test pits extended to a depth of up to 8 feet below the ground surface. No groundwater was encountered. The test pits were located approximately as illustrated on the Site Plan, Plate 2. In general, the site soils consist of about 1.5 feet of silty sand with some gravel, underlain by sand with varying amounts of gravel. The soil type encountered appears to match the Advance Outwash deposit, as indicated on the area geologic map. Soils are dense below a depth of about 2 to 2.5 feet. CONCLUSIONS AND RECOMMENDATIONS Based on the site conditions, it is our opinion that the subject property is suitable for the proposed two-story apartment building structure. Dense soil suitable for supporting a spread footing foundation was encountered below a depth of about 2 to 2.5 feet. The clean sandy site soil is suitable for infiltration below a depth of 1.5 to 2.5 feet. __________________________ 1 Minard J. P., 1985, “Geologic Map of the Bothell Quadrangle, Snohomish and King Counties, . Washington,” U. S. Geological Survey, Map MF-1747, Scale 1:24,000 GEO Group Northwest, Inc. October 14, 2016G-4205 Geotechnical Engineering ReportPage 3 9516 Edmonds Way, Edmonds SSS EISMICITY AND ITETABILITY Based on the soil conditions encountered, the site is seismically classified as Site Class C, in accordance with the International Building Code and ASCE Chapter 20. The site appear to be stable. No groundwater seepage was observed and no groundwater was encountered in the test pits. It is our opinion that the risk is low for deep seated slides to occur based on the lack of groundwater and the minimal slopes on the site. The potential for liquefaction and/or lateral spreading is negligible based on the presence of the glacially consolidated Advance Outwash soil. No known faults intersect the subject property and the risk of surface rupture, as a result of a large magnitude seismic event, is interpreted to be very low. No geotechnical seismic mitigation measures are recommended, with the exception of the addition of design criteria for seismically induced dynamic soil loads on permanent basement walls and retaining walls. BFR UILDING OUNDATION ECOMMENDATIONS Soils suitable for supporting spread footing foundations were encountered at a depth of 2 to 2.5 feet below the existing ground surface. Foundations should be supported directly on dense soil or on structural fill that extends down to the dense soil. The following foundation design criteria is applicable to spread footing foundations that are supported on dense soil or structural fill: Allowable bearing pressure, including all dead and live loads:= 2,000 psf Minimum depth to bottom of perimeter footing below adjacent final exterior grade:= 18 inches Minimum depth to bottom of interior footings below top of floor slab: = 12 inches Minimum width of strip wall footings: = 16 inches Minimum lateral dimension of column footings:= 24 inches Estimated post-construction settlement:= 1/4 inch Across building width:= 1/4 inch GEO Group Northwest, Inc. October 14, 2016G-4205 Geotechnical Engineering ReportPage 4 9516 Edmonds Way, Edmonds A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the crushed rock or recycled concrete or the material compacted adjacent to the foundation. Our recommended parameters are as follows: Passive Pressure (Lateral Resistance):350 pcf equivalent fluid weight Coefficient of Friction (Friction Factor):0.35 BW&RW ASEMENTALLSETAININGALLS Permanent basement walls restrained horizontally on top are considered unyielding and should be designed for lateral soil pressure under the at-rest condition. Conventional reinforced cantilever walls free to rotate on top should be designed for an active lateral soil pressure. Walls should be fully drained to prevent a buildup of hydrostatic pressure, as discussed in the Drainage section of this report. The following design criteria is for a fully drained wall backfill condition. Active Earth Pressure Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002 times the wall height should be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of 35 pcf for level backfill behind the wall. At-Rest Earth Pressure Walls supported horizontally by floor slabs are considered unyielding and should be designed for lateral soil pressure under the at-rest condition. The design lateral soil pressure should have an equivalent fluid pressure of 45 pcf for level ground behind the wall. Seismic Earth Pressure In addition to the above lateral soil pressure, a rectangular pressure of 6H should be added to the above lateral soil pressures for permanent basement and retaining walls to account for seismically induced dynamic soil loads. GEO Group Northwest, Inc. October 14, 2016G-4205 Geotechnical Engineering ReportPage 5 9516 Edmonds Way, Edmonds 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 both undisturbed soils and engineered structural backfill. The base friction that can be generated between concrete and undisturbed bearing soils or structural fill may be based on an assumed 0.35 friction coefficient. S--GF LABONRADELOORS We understand the area below the building will be parking. The floor slab should be supported on dense undisturbed soil or on structural fill that extends down to the dense soil. For dry storage and living space, 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 four (4) inch layer of gravel or crushed rock containing no more than five (5) percent fines passing the No. 4 (1/4-inch) sieve. A 5/8-inch crushed rock with no minus fraction is an acceptable material for use as a capillary break (peagravel is not recommended). To reduce water vapor transmission through the slab into dry storage areas, 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). D RAINAGE The sandy site soil is suitable for infiltration and subsurface footing drains are not required. Basement walls and retaining walls should be drained to prevent the buildup of hydrostatic pressure. We recommend backfilling with free-draining granular sand and gravel material, such as the clean sand and gravel site soil. Below grade walls should be sealed with a water-proofing material. GEO Group Northwest, Inc. October 14, 2016G-4205 Geotechnical Engineering ReportPage 6 9516 Edmonds Way, Edmonds I NFILTRATION The site soils are suitable for on-site infiltration of storm water. In accordance with the Washington Department of Ecology Manual (WDOE manual) titled, “Stormwater Management in Western Washington, Volume III, Hydrologic Analysis and Flow Control Design/BMPs, dated February 2005, the site soils below a depth of 1.5 feet to 2.5 feet are classified as Sand by the USDA soil classification method. We recommend using a long term (design) infiltration rate of 2 inches per hour in accordance with Table 3.7 of the 2005 WDOE manual. No high groundwater indicators were observed, such as zones of oxidation. SPE ITEREPARATION AND ARTHWORK Prior to site disturbance, erosion control measures should be installed down gradient, such as silt fencing, to prevent sediment-laden surface runoff from being discharged offsite. The building area, driveways and sidewalks should be cleared and grubbed of surface vegetation and organics. Loose trench backfill soil from the previous site development, such as encountered in test pit TP- 5, should be removed and replaced with structural fill. During wet weather, exposed soils should be protected with straw mulch and cut slopes protected with plastic sheeting. For permanent erosion control disturbed soils should be landscaped and mulched upon completion of the site work SF TRUCTURALILL Structural fill is defined as fill soil that supports building foundations, floor slabs, patios, porches, retaining walls, driveways, sidewalks, and pavements. Structural fill should be free of organic and other deleterious substances, and have a maximum size of three 3-inches. During wet weather we recommend structural fill material be a free draining, granular material, containing no more than 5 percent fines (silt and clay-size particles passing the No. 200 mesh sieve based on the fraction passing the 3/4 sieve). The clean sandy site soil should be useable as structural fill during wet weather. GEO Group Northwest, Inc. October 14, 2016G-4205 Geotechnical Engineering ReportPage 7 9516 Edmonds Way, Edmonds Structural fill material should be placed and compacted at or near the material’s optimum moisture content and in lifts that are 10-inches thick or less. Below slab-on-grade floors, foundations, and other structural elements, structural fill should be compacted to a minimum of 95 percent of the material’s maximum dry density, as determined by ASTM Test Designation D- 1557 (Modified Proctor). For driveways, structural fill should be compacted to 90 percent, with the exception of the top 12-inches which should be compacted to 95 percent. Fill behind retaining walls and basement walls should be compacted to a minimum of 90 percent (95 percent if supporting structural elements). Trench backfill and compaction within the public right-of- way must meet the city specifications. TPCF EMPORARY AND ERMANENTUTS AND ILLS Temporary excavations should not be sloped greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than 4 feet should be sloped at an inclination of 1H:1V (Horizontal:Vertical). It is the responsibility of the contractor to provide a safe work environment, including stable open cuts. If groundwater seepage is encountered, excavation should be stopped and the geotechnical engineer review the site conditions. Permanent cut and fill slopes should be inclined no steeper than 2H:1V. Steeper permanent fill slopes can be achieved with the use of geogrid for lateral support. Slopes that are to be maintained or mowed should be sloped at 3H:1V, or less. Fill slopes should consist of granular material compacted to 90 percent of the materials maximum dry density. If supporting structural elements the fill should be compacted to structural fill specifications. LIMITATIONS 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, our experience, and engineering 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 GEO Group Northwest, Inc. APPENDIX A USCS SOIL CLASSIFICATION LEGEND AND TEST PIT LOGS GEO Group Northwest, Inc. LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) LABORATORY GROUP MAJOR DIVISIONTYPICAL DESCRIPTIONCLASSIFICATION SYMBOL CRITERIA Cu = (D60 / D10) greater than 4 WELL GRADED GRAVELS, GRAVEL-SAND GW CLEAN Cc = (D30 * D30 / D10 / D60) between 1 and 3 MIXTURE, LITTLE OR NO FINES GRAVELS DETERMINE GRAVELS PERCENTAGES (little or no POORLY GRADED GRAVELS, AND GRAVEL-SAND OF GRAVEL AND GPNOT MEETING ABOVE REQUIREMENTS fines)MIXTURES LITTLE OR NO FINES (More Than SAND FROM Half Coarse GRAIN SIZE ATTERBERG LIMITS BELOW Grains Larger DISTRIBUTION Than No. 4 GMSILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES"A" LINE. DIRTY CURVE.CONTENT COARSE Sieve) or P.I. LESS THAN 4 GRAVELSOF FINES GRAINED COARSE EXCEEDS SOILS ATTERBERG LIMITS ABOVE GRAINED (with some CLAYEY GRAVELS, GRAVEL-SAND-CLAY 12% GC"A" LINE. SOILS ARE fines)MIXTURES or P.I. MORE THAN 7 CLASSIFIED AS FOLLOWS: WELL GRADED SANDS, GRAVELLY SANDS, Cu = (D60 / D10) greater than 6 More Than Half SW CLEAN Cc = (D30 * D30 / D10 / D60) between 1 and 3 < 5% Fine Grained: LIITLE OR NO FINES by Weight SANDS GW, GP, SW, SP Larger Than SANDS No. 200 Sieve (little or no POORLY GRADED SANDS, GRAVELLY SANDS, > 12% Fine SPNOT MEETING ABOVE REQUIREMENTS fines)LITTLE OR NO FINES (More Than Grained: Half Coarse GM, GC, SM, SC; ATTERBERG LIMITS BELOW Grains Smaller Than No. 4 5 to 12% Fine SMSILTY SANDS, SAND-SILT MIXTURES"A" LINE DIRTYCONTENT Sieve) Grained: use dual with P.I. LESS THAN 4 SANDSOF FINES symbols. EXCEEDS ATTERBERG LIMITS ABOVE (with some 12% SCCLAYEY SANDS, SAND-CLAY MIXTURES"A" LINE fines) with P.I. MORE THAN 7 Liquid Limit INORGANIC SILTS, ROCK FLOUR, SANDY SILTS SILTS 60 ML < 50%OF SLIGHT PLASTICITY (Below A-Line on Plasticity A-Line PLASTICITY CHART Chart, Negligible (%) Liquid Limit INORGANIC SILTS, MICACEOUS OR 50 FOR SOIL PASSING MH Organic) CH or OH > 50%DIATOMACEOUS, FINE SANDY OR SILTY SOIL NO. 40 SIEVE FINE- PLASTICITY INDEX INDEX GRAINED GRAINED( INORGANIC CLAYS OF LOW PLASTICITY, SOILSSOILS 4040 Liquid Limit CLAYSCLAYS CLGRAVELLY, SANDY, OR SILTY CLAYS, CLEAN < 30% (Above A-Line (Above A-Line CLAYS STICITY on Plasticity on Plasticity 3030 Chart, Negligible Chart, Negligible Liquid LimitINORGANIC CLAYSOFHIGHPLASTICITY, FAT LiquidLimitINORGANICCLAYSOFHIGHPLASTICITYFAT CH More Than Half More Than Half Organic)Organic) CL or OLCL or OL > 50%CLAYS by Weight by Weight A 2020 SlSmaller Than lTh MH or OH No. 200 Sieve Liquid Limit ORGANIC SILTS AND ORGANIC SILTY CLAYS OF ORGANIC OL < 50%LOW PLASTICITY SILTS & CLAYS 10 (Below A-Line 7 on Plasticity CL-ML OL or ML Liquid Limit 4 OHORGANIC CLAYS OF HIGH PLASTICITY Chart) > 50% 0 010 HIGHLY ORGANIC SOILSPtPEAT AND OTHER HIGHLY ORGANIC SOILS LIQUID LIMIT (%) SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) U.S. STANDARD SIEVE PassingRetainedSANDY SOILSSILTY & CLAYEY SOILS FRACTION SizeSize SieveSieve Unconfined Blow BlowRelativeFriction (mm)(mm) Strength Counts CountsDensityAngleDescriptionDescription q N N%Ø, degree u, tsf SILT / CLAY #2000.075 SAND 0 - 4 0 -15Very Loose< 2< 0.25Very soft FINE#400.425#2000.075 4 - 10 15 - 35 26 - 30Loose 2 - 40.25 - 0.50Soft MEDIUM#100#400.425 10 - 30 35 - 65 28 - 35Medium Dense 4 - 80.50 - 1.00Medium Stiff COURSE#44.75#102 30 - 50 65 - 85 35 - 42Dense 8 - 151.00 - 2.00Stiff GRAVEL > 50 85 - 100 38 - 46Very Dense 15 - 302.00 - 4.00Very Stiff FINE19#44.75> 30> 4.00Hard COURSE7619 E Group Northwest, Inc. COBBLES 76 mm to 203 mm GO BOULDERS > 203 mm Geotechnical Engineers, Geologists, & Environmental Scientists ROCK > 76 mm FRAGMENTS 13705 Bel-Red Rd Bellevue, WA 98005 PLATE A1 Phone (425) 649-8757 Fax (425) 649-8758 ROCK >0.76 cubic meter in volume TEST PIT: TP-1 WJL9/20/2016343.8 feet +/- LOGGED BYLOG DATE:GROUND ELEV. DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOILSPTION DECRINo.%COMMENTS -Probe1" SAND with silt, darkgray, dense,some roots, damp SM S110.9 1 -Probe10" SAND with gravel, brown, medium dense, medium grained SP- S27.8 2 sand, some silt, damp SM -Probe1" 3 SandyGRAVEL, gray, subrounded, dense, well-graded gravel, Sidewall caving S31.4 GW medium to coarse-grained sand, with cobbles to 10", damp 4 (no binder in sand & gravel) 5 S42.1 Gravelly SAND, gray, dense, medium to coarse-grained sand, 6 SP subrounded gravel, damp 7 SAND with some gravel, gray, dense, medium-grained, 4.7 SP S5 8 TP Location: SE Corner of Total depth = 8.2 feet.Nogroundwater encountered. 9 Lot Nohigh ground water table indicators observed. TEST PIT: TP-2 WJL9/20/2016341.5 feet +/- LOGGED BYLOG DATE:GROUND ELEV. WJ9//.ee/ DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOIL DESCRIPTIONNo.%COMMENTS -Probe 3" SMSilty SAND, brown, dense to medium dense, roots, damp 1 2 , brown, medium dense, fine to coarse- SAND with some gravel S13.7 -Probe 9" SW grained, damp 3 -Probe2" -6" 4 2.8 S2 Gravelly SAND to SAND with gravel, lightbrown to gray, 5 SP dense, fine to medium-grained, damp 6 7 TP Location: S32.0 SW Corner of 8 Lot Total depth = 7.5 feet;No groundwaterencountered. No highgroundwater table indicators observed. 9 TESTPITLOGS PROPOSED APARTMENT BUILDING Group Northwest, Inc. GEO 9516 EDMONDS WAY BOTHELL, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists G-404610/4/16A2 JOB NO.DATE PLATE TEST PIT: TP-3 WJL9/20/2016338 feet +/- LOGGED BYLOG DATE:GROUND ELEV. DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOILSPTION DECRINo.%COMMENTS -Probe5" -7" Silty SAND, brown, dense,some roots, damp SM 1 S114.1 -Probe6" 2 -Probe2" SAND with gravel, gray, dense, fine to coarse-grained., damp SW to moist 3 -Probe0" to SP S23.6 4 SANDwith gravel, gray, very dense,medium-grained, S39.0 partially cemented, glacially consolidated 5 TP Location: Middle of Lot Total depth = 5 feet.Nogroundwater encountered. 6 Nohigh ground water table indicators observed. 7 8 9 TEST PIT: TP-4 WJL9/20/2016338.7 feet +/- LOGGED BYLOG DATE:GROUND ELEV. WJ9//.7ee/ DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOIL DESCRIPTIONNo.%COMMENTS Silty SAND, dark brown, medium dense, roots, damp SM 1 -Probe 1" , brown, dense, some gravel damp Silty SAND SP 2 S16.0 -Probe 1" Gravelly SAND, brown, dense, medium to coarse-grained, 3 damp SPto SW 4 SAND with some gravel, brown, dense, fine to coarse-grained, S24.9 damp 5 6 S310.4 TP Location: , gray, dense, medium-grained, moist SAND SP NE Corner of Total depth = 6 feet;No groundwaterencountered. Lot 7 No highgroundwater table indicators observed. 8 9 TESTPITLOGS PROPOSED APARTMENT BUILDING Group Northwest, Inc. GEO 9516 EDMONDS WAY BOTHELL, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists G-404610/4/16A3 JOB NO.DATE PLATE TEST PIT: TP-5 WJL9/20/2016338.2 feet +/- LOGGED BYLOG DATE:GROUND ELEV. DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOILSPTION DECRINo.%COMMENTS -Probe2" Silty SAND with some gravel, brown, dense,some roots, damp SM 1 S15.3 (Fill) Abandonedgas pipe at 30" 2 SP- SAND with some silt, light brown, medium dense, damp, Drain tile and SM (abandoned gas line, washed gravel and drain tile (Fill) washed rock at 3 east end of TP 4 SAND, gray, medium dense (dense at 4.5 feet), medium- S24.3 SP grained, damp 5 TP Location: S32.7 NW Corner of 6 Total depth = 5.5 feet.Nogroundwater encountered. Lot Nohigh ground water table indicators observed. 7 8 9 TEST PIT: . LOGGED BYLOG DATE:GROUND ELEV. DEPTHSAMPLEWaterOTHER TESTS/ ft.USCSSOIL DESCRIPTIONNo.%COMMENTS 1 2 3 4 5 6 7 8 9 TESTPITLOGS PROPOSED APARTMENT BUILDING Group Northwest, Inc. GEO 9516 EDMONDS WAY BOTHELL, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists G-404610/4/16A4 JOB NO.DATE PLATE