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HomeMy WebLinkAboutEx 08_Geotech Report.pdf 13705 Bel-Red Road, Bellevue, Washington 98005 Phone: (425) 649-8757 / E-mail: info@geogroupnw.com December 7, 2022 G-5744 Mr. Yan Lifshaz P.O. Box 53046 Bellevue, Washington 98015 Subject: Geotechnical Engineering Report, Proposed Residence 5501 NE 10th Street Renton, Washington Reference: Geotechnical Engineering Study, Proposed Residential Short Plat, 5521 NE 10th Street, Renton, Washington (Project G-2320). GEO Group Northwest, Inc., August 31, 2006. Dear Mr. Lifshaz: GEO Group Northwest, Inc. has completed this updated geotechnical engineering report regarding the proposed construction of a single-family residence at the above-subject location in Renton, Washington. This report updates our previous geotechnical engineering report dated August 31, 2006, for a four-lot short plat which includes the property (the project site) that is the subject of this report. Site Description The project site is located in a residential area of Renton, Washington, as illustrated in Plate 1 – Site Location Map. The site is irregular in shape and has a size of approximately 11,000 square feet. The northern boundary of the site abuts NE 10 th Street. The east side of the site abuts a lot occupied by a single-family residence having the address of 5515 NE 10 th Street. Property to the Mr. Yan Lifshaz G-5744 December 7, 2022 Page 2 GEO Group Northwest, Inc. south and west of the site consists of wetland area. The configuration of the site and existing conditions are illustrated in Plate 2 - Site Plan. The site has a moderate southwest facing slope. At the base of the slope is the wetland area which occupies the southwest to western part of the site. Topographic survey information indicates that the slope area has inclinations of up to approximately 38 percent grade Geologic Overview According to the published geologic mapping for the local area, subsurface soils at the site consist of glacial till (Qgt) in the upland area, and lake bottom and bog type deposits (Qlp) in the lower wetland area. The glacial till deposits typically consists of compact, unsorted mixtures of silt, sand, gravel, and cobbles deposited and directly overridden by the Puget Lobe glacier. The bog deposits typically are composed of soft peat, organic silt, and clay. Soils Investigation GEO Group Northwest, Inc., explored subsurface soil conditions on and near the site property by excavating and logging two exploratory test pits, TP-4 and TP-5, on August 8, 2006. The test pits were excavated by a backhoe and were completed to depths of 5.5and 7.5 feet below ground surface, respectively. Soil samples were collected and returned to our office for moisture content and grain-size distribution testing. The test pit locations are shown on Plate 2 - Site Plan. In test pit TP-4 located just east of the southeastern part of the site property, the upper approximately 5.5 feet of soils consisted of relatively medium dense to dense silty sand fills, underlain with approximately 1.5 feet of mottled, medium dense sandy silt to silty sand (interpreted to be weathered native soil), and then dense silty sand with gravel glacial till at the bottom of the test pit at 7 feet. In test pit TP-5 in the northwest part of the site, loose to medium dense silty sand was found to a depth of 4 feet, and was underlain with dense silty sand with gravel glacial till to the bottom of the test pit at 5.5 feet. The test pit logs are provided in Appendix A. No groundwater seepage was encountered in the test pits. It should be noted, however, that groundwater conditions may fluctuate seasonally, depending on rainfall, surface runoff and other factors. Mr. Yan Lifshaz G-5744 December 7, 2022 Page 3 GEO Group Northwest, Inc. Updated Site Reconnaissance On August 1, 2022, a geologist from our office performed a visual reconnaissance of the project site and adjacent properties. We observed no evidence of landslides or soil movement (e.g., hummocky topography, tension cracks in soils, scarps, etc.), and no evidence of springs or seeps on the site or adjacent properties as visible from the site property. The topography and conditions on the project site appeared to be similar to those observed during our investigation in 2006, but we observed that a single-family residence had been built on the east adjacent parcel. Geologic Critical Areas Review City of Renton GIS mapping indicates that sensitive slope and erosion hazard areas are present on the project site. The mapping does not indicate the presence of protected slope or seismic hazard areas on or in proximity to the project site. The sensitive slope and soil erosion hazard areas indicated by the City’s GIS mapping are illustrated in Plate 3 – Regulated Slope Areas and Plate 4 – Erosion Hazard Area. Regulated Slope Areas City of Renton regulations identify sensitive slopes as areas which are subject to severe risk of earthquake damage as a result of seismically induced ground shaking, slope failure, settlement, or soil liquefaction, which typically occurs in areas underlain by cohesionless soils of low density and a shallow groundwater table. Slope areas on the site typically have inclinations between 25 and 40 percent grade, and do not include slopes steeper than 40 percent and more than 10 feet high. The 25 to 40 percent slope areas meet the criteria for being considered sensitive slope areas per City of Renton regulations. Development of these slope areas typically is permitted but with possible conditions regarding the implementation of soil erosion control and site stability measures. Erosion Hazard Area Soils on the project site were found to include a surficial layer of loose, fine sandy silty soil approximately 4feet thick. The underlying soils typically consisted of medium dense to very dense silty sand with gravel and cobbles and are interpreted to be glacial till soils. The surface was observed to be vegetated with a mix of grasses, weeds, and brush. During our visits in 2006 and 2022, we observed no evidence of soil erosion or slope movement on the project site. Mr. Yan Lifshaz G-5744 December 7, 2022 Page 4 GEO Group Northwest, Inc. Based on the conditions we observed, we conclude that the slope areas having inclinations greater than 15 percent grade on the project site meet the criteria for classification as high erosion hazard areas per the City of Renton critical areas regulations. These areas are susceptible to erosion of the surficial loose soils if they are denuded and exposed surface water flows or heavy precipitation. In order to mitigate the potential for soil erosion on the site during and following development, we recommend that the following measures be implemented:  Exposed cuts and soil stockpiles should be covered with plastic sheeting when they are not being worked.  Silt fencing should be installed along the down-slope and cross-slope sides of the ground disturbance area, to control soil and sediment-laden runoff.  Construction traffic entrances should be built and stabilized at the start of the project and maintained as appropriate.  Water should not be permitted to flow over the tops of excavations or over areas of exposed slopes. Analysis of Modifications to Geologically Hazardous Area Development Standards Based upon our observations and interpretations of the site conditions, it is our opinion that the site is currently stable. The proposed development of the site will not increase the potential for soil erosion from the disturbed areas during or after construction, provided the recommendations contained in this report are properly implemented. With regard to landslide hazard, it is our opinion that the soils underlying the site have minimal potential for instability associated with landslides because of 1) their medium dense to dense character, and 2) the absence of unsupported slopes having inclinations steeper than 40 percent and heights greater than 10 feet. Therefore, we conclude that the site does not contain landslide hazard areas or protected slope areas. In our opinion, no additional measures beyond those discussed in this report are recommended for the project to address landslide hazard, slope stability, or soil erosion. Mr. Yan Lifshaz G-5744 December 7, 2022 Page 5 GEO Group Northwest, Inc. STORMWATER INFILTRATION EVALUATION Based upon the soil conditions found during our investigation, it is our opinion that the soils on the site property consist of relatively impermeable glacial till below depths of approximately 4 feet relative to existing grade. The overlying weathered soils typically contain a significant proportion of fines and are expected to have relatively low infiltration rates. Infiltration into the weathered soils is anticipated to result in lateral westward migration of the infiltrated water along top of the glacial till soils, potentially leading to soil erosion or sloughing on the slope. Based on these considerations, it is our opinion that other means for stormwater management should be used for the project. One option consists of dispersion trenches along the base of the slope area. CONCLUSIONS AND RECOMMENDATIONS Site Preparation and General Earthwork Clearing and Subgrade Preparation The construction area should be stripped and cleared of surface vegetation, debris, uncontrolled fills, and other deleterious materials. Silt fences should be installed downhill and cross-slope of the prepared area to prevent sediment-laden surface runoff from being discharged off-site. During construction, exposed soil slopes (including stockpiles) should be covered with plastic sheeting when they are not being worked. Relatively flat areas can be covered with either plastic sheeting, hog fuel, or straw to mitigate erosion. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. During construction, loose surfaces should be sealed at night by compacting the surface to reduce the potential for moisture infiltration into the soils. Temporary Excavations and Slopes Under no circumstances should temporary excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than four feet in height should be sloped at an inclination no steeper than 1H:1V unless otherwise approved by the geotechnical engineer. Excavations into the very dense, glacial till soils may be sloped up to Mr. Yan Lifshaz G-5744 December 7, 2022 Page 6 GEO Group Northwest, Inc. 1H:2V (Horizontal:Vertical) in inclination, provided that no water seepage or other adverse conditions are encountered. Permanent cut and fill slopes at the site should be inclined no steeper than 2H:1V. Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the excavated area. During wet weather exposed cut slopes should be covered with plastic sheeting during construction to minimize erosion. If groundwater seepage is encountered during construction, excavation should be halted and the cut slopes should be re-evaluated by the geotechnical engineer. Structural Fill Structural fill consists of earthen materials used to achieve design site elevations below buildings and below non-structurally supported slabs, sidewalks and driveways. Materials to be used as structural fill should not contain deleterious materials nor rocks or lumps larger than 3 inches in its greatest dimension. Structural fill material should be placed at or near its optimum moisture content. If the material is too wet to be compacted to the required degree, it will be necessary to dry the material by aeration (which may be difficult) or replace the material with an alternative suitable material, in order to be capable of achieving the required compaction. We anticipate that the silty sand site soils (both the loose shallow soils and the underlying glacial till soils) may be difficult to compact to structural fill specifications during wet weather because of their moisture sensitive character. Consequently, if earthwork occurs during the wet winter months of the year, an imported granular material that is not moisture sensitive may be needed for structural fill. We recommend that such a material have a fines content (passing a #200 sieve) of less than 5 percent. If the on-site soils are to be used as structural fill, it will be necessary to segregate the topsoil and any other organic- or debris-containing soil, because such soils typically are unsuitable for use as structural fill. Excavated on-site material that is stockpiled for later use as structural fill should be protected from rainfall or contamination with unsuitable materials by covering it with plastic sheeting until it is used. If the material is particularly dry, it may need to be moisture conditioned before it can be used as structural fill. Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness. Structural fill under buildings should be compacted to at least 92 percent maximum density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Structural fill in Mr. Yan Lifshaz G-5744 December 7, 2022 Page 7 GEO Group Northwest, Inc. pavement subgrade areas should be compacted to at least 90 percent of the maximum dry density, with the exception of the upper twelve (12) inches. The top twelve (12) inches should be compacted to at least 95 percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). We recommend that we be retained to evaluate the suitability of structural fill material and to monitor the compaction work during construction for quality assurance of the earthwork. Driveway Support and Pavement We recommend that the proposed driveway be supported on unyielding native soil or on structural fill as necessary to achieve design grades. The prepared driveway subgrade should be proof-rolled with a piece of heavy construction equipment such as a fully loaded dump truck or vibratory roller under the observation of the geotechnical engineer. Any soft spots or disturbed areas detected should be re-compacted or excavated and replaced with compacted structural fill. The pavement section for the driveway should consist of at least 4 inches of base course overlain with at least 2.5 inches of asphalt. Foundations The proposed residence can be supported on conventional strip and column footing foundations that bear on either 1) medium dense or dense native soils, 2) compacted structural fill placed on top of medium dense or dense native soils, or 3) a compacted subgrade of loose to medium dense soils that is prepared to a dense condition by using a hoe-pack under the observation and approval of the geotechnical engineer. Our recommended minimum design criteria for foundations supported in these manners are as follows: - Allowable bearing pressure, including all dead and live loads = 2,000 psf - Minimum depth to bottom of perimeter footing below final exterior grade = 18 inches - Minimum depth to bottom of interior footings below top of floor slab = 18 inches - Minimum width of wall footings = 16 inches - Minimum lateral dimension of column footings = 24 inches December 7, 2022 G-5744 Mr. Yan Lifshaz Page 8 GEO Group Northwest, Inc. - Estimated post-construction settlement = ½ inch - Estimated post-construction differential settlement; across building width = ½ inch 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 existing undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural fill. Our recommended parameters are as follows: - Passive Pressure (Lateral Resistance) · 350 pcf equivalent fluid weight for compacted structural fill · 350 pcf equivalent fluid weight for native dense soil. - Coefficient of Friction (Friction Factor) · 0.35 for compacted structural fill · 0.35 for native dense soil Conventional Concrete Retaining Walls Permanent basement walls restrained horizontally on top are considered unyielding and should be designed for a lateral soil pressure under the at-rest condition; while conventional reinforced concrete walls free to rotate on top should be designed for an active lateral soil pressure. 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 yielding retaining walls; · 45 pcf for 25% sloped backfill; · 60 pcf for 50% sloped backfill; December 7, 2022 G-5744 Mr. Yan Lifshaz Page 9 GEO Group Northwest, Inc. 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 permanent unyielding retaining walls; · 60 pcf for 25% sloped backfill; · 75 pcf for 50% sloped backfill; Passive Earth Pressure · 350 pcf equivalent fluid weight for structural fill · 350 pcf equivalent fluid weight for native dense soil Base Coefficient of Friction · 0.35 for structural fill · 0.35 for native dense soil We recommend that a vertical drain mat, Miradrain 6000 or equivalent, be used to facilitate drainage behind permanent concrete basement walls and retaining walls. The drain mat core is placed against the wall with the filter fabric side facing the backfill. The drain mat extends from the finished surface grade, down to the footing drain pipe. A minimum 18 inches of clean, free- draining, washed rock, crushed rock, or pea gravel should be placed in the bottom of the footing trench. These recommendations are schematically illustrated in Plate 5 – Typical Retaining Wall Drainage Detail. We recommend using an imported relatively free-draining pit-run sand or gravel as structural backfill behind the walls. This material should have less than 5 percent fines (that portion of the total weight passing a #200 sieve). Backfill material behind retaining walls should be compacted to 90 percent of the maximum dry density determined by ASTM D 1557-91 (Modified Proctor). Slab-On-Grade Floors We understand that the proposed residence may have slab-on-grade concrete floors. We recommend that the subgrade for these floors be prepared to a relatively dense condition by the means described the foundations recommendations in this report. December 7, 2022 G-5744 Mr. Yan Lifshaz Page 10 GEO Group Northwest, Inc. To avoid moisture build-up on the subgrade, slab-on-grade floors should be placed on a capillary break, which is in turn placed on the prepared subgrade. The capillary break should consist of a minimum of a six (6) inch thick layer of free-draining crushed rock or gravel containing no more than five (5) percent finer than No. 4 sieve. A vapor barrier, such as a 6-mil plastic membrane, is recommended to be placed over the capillary break beneath the slab to reduce water vapor transmission through the slab. Two to four inches of sand may be placed over the barrier membrane for protection during construction. Drainage Surface Drainage GEO Group Northwest, Inc., recommends that surface water be directed away from buildings and retaining walls or be intercepted and conveyed to other appropriate locations. We also recommend that concentrated surface water not be directed to flow onto the slope area, because of the potential for soil erosion. Instead, we recommend that surface water be to an approved discharge location, such as a stormwater facility or the wetland area. Subsurface Drainage We recommend that drains be installed around the perimeter foundations of new residences or other buildings that are constructed on site. The drains should consist of a four (4) inch minimum diameter perforated rigid drain pipe laid at or near the bottom of the footing at a gradient sufficient to generate flow toward the tightline location. The drain line should be bedded on, surrounded by, and covered with a free-draining rock, pea gravel, or other free- draining granular material. The drain rock and drain line should be completely surrounded by a geotextile filter fabric, such as Mirafi 140N or equivalent. After the drains are installed, the excavation should be backfilled and compacted to surface grade. These recommendations are schematically illustrated in Plate 6 – Typical Footing Drain Detail . Roof downspouts and foundation footing drains should be tightlined separately to their respective appropriate discharge locations. We also recommend that sufficient cleanouts be installed at strategic locations in both drainage systems to allow for future periodic maintenance. December 7, 2022 G-5744 Mr. Yan Lifshaz Page 11 GEO Group Northwest, Inc. CLOSING We appreciate the opportunity to provide you with geotechnical engineering services for your project. Please feel welcome to contact us if you have any questions regarding this letter or desire additional geotechnical services. Sincerely, GEO GROUP NORTHWEST, INC. Keith Johnson William Chang, P.E. Project Geologist Principal Engineer Plates and Attachments: Plate 1 – Location Map Plate 2 – Site Plan Plate 3 – Regulated Slope Areas Plate 4 – Erosion Hazard Areas Plate 5 – Typical Retaining Wall Drainage Detail Plate 6 – Typical Footing Drain Detail Attachment A – Test Pit Logs 12/7/2022 12/7/2022 Source: King County GIS, 2021. SITE LOCATION MAP 5501 NE 10TH STREET RENTON, WASHINGTON SCALE:1" = 2000' DATE: 12/7/2022 MADE: KJ CHKD: WC JOB NO:G-5744 PLATE 1 PROPOSED RESIDENCE Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. PROJECT SITE SCALE 1" = 60' DRAWN BY KJ CHECKED BY WC DATE PROJECT NO.G-5744 PLATE PROPOSED RESIDENCE 55XX NE 10TH STREET RENTON, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc.SITE PLAN LEGEND EXPLORATORY TEST PIT (APPROXIMATE LOCATION)TP-1 60 1200 SCALE: 1 INCH = 60 FEET TP-5 TP-3 TP-4 TP-2 TP-1 LOT A LOT C PROPERTY LINE LOT Adapted from: Bretzke Lot Line Adjustment Site Plan, by GeoDimensions, dated 6/22/2006; and King County Assessor quarter section map NE 10-23-05, dated 7/7/2019. Source: City of Renton GIS. SCALE:As Shown DRAWN:KJ CHECKED:WC DATE: 12/7/2022 PROJECT NO.:G-5744 PLATE 3 REGULATED SLOPE AREAS PROPOSED RESIDENCE 5501 NE 10TH STREET RENTON, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. Sensitive and Protected Slope Areas SITE Source: City of Renton GIS. SCALE:As Shown DRAWN:KJ CHECKED:WC DATE: 12/7/2022 PROJECT NO.:G-5744 PLATE 4 EROSION HAZARD AREA PROPSOED RESIDENCE 5501 NE 10TH STREET RENTON, WASHINGTON Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. High Erosion Hazard and Landslide Hazard Areas SITE SCALE NONE DATE 12/7/2022 MADE KJ CHKD WC JOB NO.G-5744 PLATE 5 PROPOSED RESIDENCE 5501 NE 10TH ST RENTON, WASHINGTON NOTES: 1.) Do not substitute rigid PVC pipe with flexible corrugated pipe. 2.) Perforated PVC pipe should be tight jointed and laid with perforations oriented downward. The pipe should be gently sloped to provide flow toward the tightline or discharge location. 3.) Do not connect other drainage lines into the wall drainage system. 4.) Backfill should meet structural fill specifications if it will support driveways, sidewalks, patios, or other structures. Refer to the geotechnical engineering report for structural fill recommendations. NOT TO SCALE WALL GEOTEXTILE FILTER FABRIC Non-woven (Mirafi 140N, or equivalent), wrapped around the drain rock FOOTING DRAINAGE MAT The mat should extend from near top of wall downward into the drain rock at the bottom of the wall; recommended where the backfilled wall height is 4 feet or greater. WALL BACKFILL Granular soil or aggregate. Refer to geotechnical report for specific recommendations. DRAIN LINE Minimum 4-inch diameter, rigid PVC perforated pipe; lay pipe to have sufficient gradient toward discharge. WASHED DRAIN ROCK Bedded entirely around the drain line. TYPICAL RETAINING WALL DRAINAGE DETAIL Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. TYPICAL RETAINING WALL DRAINAGE DETAIL SCALE NONE DATE 12/7/2022 MADE KJ CHKD WC JOB NO.G-5744 PLATE 6 TYPICAL FOOTING DRAIN DETAIL PROPOSED RESIDENCE 5501 NE 10TH ST RENTON, WASHINGTON NOTES: 1.) Do not substitute rigid PVC pipe with flexible corrugated pipe. 2.) Perforated PVC pipe should be tight jointed and laid with perforations oriented downward. The pipe should be gently sloped to provide flow toward the tightline or discharge location. 3.) Do not connect other drainage lines into the footing drainage system. 4.) Backfill should meet structural fill specifications if it will support driveways, sidewalks, patios, or other structures. Refer to the geotechnical engineering report for structural fill recommendations. NOT TO SCALE GEOTEXTILE FILTER FABRIC Non-woven fabric (Mirafi 140N, or similar), wrapped around the drain rock. FOOTING BACKFILL Refer to geotechnical report for material recommendations. DRAIN PIPE Minimum 4-inch diameter, rigid PVC perforated pipe. WASHED DRAIN ROCK Bedded entirely around the drain pipe. TYPICAL FOOTING DRAIN DETAIL Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. GEO Group Northwest, Inc. ATTACHMENT A G-5744 TEST PIT LOGS CLEAN GRAVELS GW (little or no fines)GP DIRTY GRAVELS GM (with some fines)GC CLEAN SANDS SW (little or no fines)SP DIRTY SANDS SM (with some fines)SC Liquid Limit < 50%ML Liquid Limit > 50%MH Liquid Limit < 50%CL Liquid Limit > 50%CH Liquid Limit < 50%OL Liquid Limit > 50%OH Pt Sieve Size (mm)Sieve Size (mm) SILT / CLAY #200 0.075 SAND 0 - 4 0 -15 Very Loose < 2 < 0.25 Very soft FINE #40 0.425 #200 0.075 4 - 10 15 - 35 26 - 30 Loose 2 - 4 0.25 - 0.50 Soft MEDIUM #10 2.00 #40 0.425 10 - 30 35 - 65 28 - 35 Medium Dense 4 - 8 0.50 - 1.00 Medium Stiff COARSE #4 4.75 #10 2.00 30 - 50 65 - 85 35 - 42 Dense 8 - 15 1.00 - 2.00 Stiff GRAVEL > 50 85 - 100 38 - 46 Very Dense 15 - 30 2.00 - 4.00 Very Stiff FINE 0.75" 19 #4 4.75 > 30 > 4.00 Hard COARSE 3" 76 0.75" 19 COBBLES BOULDERS ROCK FRAGMENTS ROCK PLATE A1E-mail: info@geogroupnw.com Description Bellevue, Washington 98005 Blow Counts N Relative Density, % Friction Angle N, degrees Description Blow Counts N Unconfined Strength qu, tsf 76 mm to 203 mm > 203 mm > 76 mm 13705 Bel-Red Road >0.76 cubic meter in volume Phone: (425) 649-8757 HIGHLY ORGANIC SOILS PEAT AND OTHER HIGHLY ORGANIC SOILS SOIL PARTICLE SIZE GENERAL GUIDANCE FOR ENGINEERING PROPERTIES OF SOILS, BASED ON STANDARD PENETRATION TEST (SPT) DATA FRACTION U.S. STANDARD SIEVE Passing Retained SANDY SOILS SILTY & CLAYEY SOILS INORGANIC CLAYS OF LOW PLASTICITY, GRAVELLY, SANDY, OR SILTY CLAYS, LEAN CLAYS Less Than Half by Weight Larger Than No. 200 Sieve INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS ORGANIC SILTS & CLAYS (Below A-Line on Plasticity Chart) ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY ORGANIC CLAYS OF HIGH PLASTICITY FINE-GRAINED SOILS SILTS (Below A-Line on Plasticity Chart, Negligible Organics) INORGANIC SILTS, ROCK FLOUR, SANDY SILTS OF SLIGHT PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS, FINE SANDY OR SILTY SOIL CLAYS (Above A-Line on Plasticity Chart, Negligible Organics) Cu = (D60 / D10) greater than 4 Cc = (D30)2 / (D10 * D60) between 1 and 3 POORLY GRADED GRAVELS, AND GRAVEL-SAND MIXTURES LITTLE OR NO FINES SILTY SANDS, SAND-SILT MIXTURES CONTENT OF FINES EXCEEDS 12% ATTERBERG LIMITS BELOW "A" LINE with P.I. LESS THAN 4 CLAYEY SANDS, SAND-CLAY MIXTURES ATTERBERG LIMITS ABOVE "A" LINE with P.I. MORE THAN 7 More Than Half by Weight Larger Than No. 200 Sieve SANDS WELL GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES CONTENT OF FINES BELOW 5% Cu = (D60 / D10) greater than 6 Cc = (D30)2 / (D10 * D60) between 1 and 3 (More Than Half Coarse Fraction is Smaller Than No. 4 Sieve) POORLY GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES CLEAN SANDS NOT MEETING ABOVE REQUIREMENTS CLEAN GRAVELS NOT MEETING ABOVE REQUIREMENTS SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES CONTENT OF FINES EXCEEDS 12% GM: ATTERBERG LIMITS BELOW "A" LINE. or P.I. LESS THAN 4 SOIL CLASSIFICATION & PENETRATION TEST DATA EXPLANATION UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) MAJOR DIVISION GROUP SYMBOL TYPICAL DESCRIPTION LABORATORY CLASSIFICATION CRITERIA CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES GC: ATTERBERG LIMITS ABOVE "A" LINE. or P.I. MORE THAN 7 COARSE- GRAINED SOILS GRAVELS (More Than Half Coarse Fraction is Larger Than No. 4 Sieve) WELL GRADED GRAVELS, GRAVEL-SAND MIXTURE, LITTLE OR NO FINES CONTENT OF FINES BELOW 5% 0 10 20 30 40 50 60 0 10 20 30 40 50 60 70 80 90 100PLASTICITY INDEX (%)LIQUID LIMIT (%) CL-ML CL MH or OH U-Line PLASTICITY CHART FOR SOIL PASSING U.S. #40 MESH SIEVE 7 4 CH Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. ML A-Line ML or OL TEST PIT NO.TP - 4 LOGGED BY:KJ DATE EXCAVATED:8/8/2006 GROUND ELEV:434' (+/-) DEPTH USCS SOIL DESCRIPTION SAMPLE Water OTHER TESTS/ ft. No. % COMMENTS 1 2 3 4 5 6 7 8 9 10 TEST PIT LOG PROPOSED RESIDENCE 5501 SE 10TH STREET RENTON, WASHINGTON JOB NO:G-5744 DATE:12/7/2022 PLATE A2 Bottom of test pit at 7.5 feet below ground surface. Fill to approximately 5.5 feet. No groundwater observed. ML- SM 1 Dark brown SILTY SAND, damp, loose, sand is mostly fine grained, occasional small (to 1" diameter) roots (TOPSOIL). 14.83 13.5 SM 2 13.1 22.24 Dark brown SILTY SAND, medium dense to dense, damp, sand is somewhat graded, 20-25% fines, trace debris (FILL). Dark brown SILTY SAND to SANDY SILT, medium dense, damp, sand is predominantly fine grained, trace gravel and cobble. Brown, as above. Gray SILTY SAND with gravel and cobble, damp, dense, 20%fines (GLACIAL TILL). BULK 5 11.1 ML- SM SM Mottled brown, olive, and gray SANDY SILT to SILTY SAND, damp, medium dense, minor black organics and oxide stain (SUSPECTED WEATHERED NATIVE SOIL). SM Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc. TEST PIT NO.TP - 5 LOGGED BY:KJ DATE EXCAVATED:8/8/2006 GROUND ELEV:432' (+/-) DEPTH USCS SOIL DESCRIPTION SAMPLE Water OTHER TESTS/ ft. No. % COMMENTS 1 2 3 4 5 6 7 8 9 10 TEST PIT LOG PROPOSED RESIDENCE 5501 SE 10TH STREET RENTON, WASHINGTON JOB NO:G-5744 DATE:12/7/2022 PLATE A3 Bottom of test pit at 4.5 feet below ground surface. No groundwater observed. SM 1 4.23 9.1 SM 2 10.6 Strong brown SILTY SAND, loose to medium dense, dry to damp, 40%+ fines, sand is mostly fine and medium grained, minor gravel. Brown SILTY SAND with gravel, damp, medium dense, sand is somewhat graded, 25% fines. SM-Gray-brown SILTY SAND, damp, dense, 10-15% fines, sand is mostly fine and medium grained with some gravel and cobble (GLACIAL TILL). BULK Geotechnical Engineers, Geologists, & Environmental Scientists GEO Group Northwest, Inc.