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HomeMy WebLinkAbout03680 - Technical Information Report - Geotechnical 0 V to GEOTECHNICAL ENGINEERING REPORT KELSEY'S CROSSING RENTON, WASHINGTON FOR GEONERCO PROPERTIES WA, LLC JULY 2012 34:,e3c ROBINSON NOBLE July 5, 2012 Mr. Jamie Waltier Geonerco Properties WA, LLC 1441 North 34th Street, Suite 200 Seattle, Washington 98103 • Geotechnical Engineering Report Kelsey's Crossing Renton, Washington RN File No. 2563-004A Dear Mr. Waltier: This letter serves as a transmittal for three copies of our report for the Kelsey's Crossing project, located on the northeast corner of the 120th Avenue Southeast and Southeast 192nd Street intersection in the City of Renton. The explorations identified undisturbed glacial soils at depths that should provide adequate bearing capacity for the planned improvements. We appreciate the opportunity of working with you on this project. If you have any questions regarding this report, please contact us. Sincerely, ACIPP dri Rick B. Powell, PE Principal Engineer RBP:BAG:am Three Copies Submitted Six Figures Appendix A 3011 South Huson Street, Suite A 17625 130th Avenue NE, Suite 102 Tacoma,Washington 98409 www.robinson-noble.com Woodinville,Washington 98072 P: 253.475.7711 I F: 253.472.5846 P:425.488.0599 I F: 425.488.2330 . - ' - ---- -- ---- - ' ' --' -' --- ' ---- ' ' ' - - -' ^ . ' TABLE OF CONTENTS INTRODUCTION 1 PROJECT DESCRIPTION 1 SCOPE 1 SITE CONDITIONS 2 Surface Conditions 2 Geology 2 Explorations 3 Subsurface Conditions 3 Hydrologic Conditions 3 GEOLOGIC HAZARDS 4 Erosion Hazard 4 Seismic Hazard 4 CONCLUSIONS AND RECOMMENDATIONS 4 General 4 Site Preparation and Grading 5 Structural Fill 5 General 5 Materials 5 Fill Placement 5 Temporary and Permanent Slopes 6 Foundations 6 Lateral Loads 7 Slabs-On-Grade 7 Drainage 8 Detention Pond 8 Utilities 9 Pavement Subgrade 9 CONSTRUCTION OBSERVATION 10 USE OF THIS REPORT 10 Robinson Noble, Inc INTRODUCTION This report presents the results of our geotechnical engineering investigation at your proposed single-family residential project, Kelsey's Crossing, in the Renton area of King County, Washington. The site is located at the intersection of 120th Avenue Southeast and Southeast 192' Street, as shown on the Vicinity Map in Figure 1. You have requested that we complete this report to evaluate subsurface conditions and provide recommendations for site development. For our use in preparing this report, we have been provided with a copy of the planned site layout by Barghausen Consulting Engineers, Inc., dated January 28, 2008, that shows the proposed lot layout and stormwater detention facility location. PROJECT DESCRIPTION The development will consist of a total of 13 single-family residences, a stormwater detention facility, a park and a private access roadway. We have been provided with a preliminary road and drainage plan which shows the proposed building pad elevations, and thereby understand that site grading will include minor cuts and fills. Due to the gently sloping ground conditions and the proposed building pad elevations within the site, it seems likely that cuts or fills will not be much more than about 2 feet in any area. A storm water detention facility is planned in the southeast corner of the site. SCOPE The purpose of this study is to explore and characterize the subsurface conditions and present recommendations for site development. Specifically, our scope of services as outlined in our Services Agreement, dated June 13, 2012 includes the following: ■ Review available geologic maps for the site. ■ Explore the subsurface soil and groundwater conditions using backhoe excavated test pits. ■ Evaluate pertinent physical and engineering characteristics of the soils encountered in the explorations based on our experience. ■ Prepare a geotechnical report containing the results of our subsurface explorations, and our conclusions and recommendations for geotechnical design elements of the project. Our report will include: • Description of the geologic materials encountered. • Description of depth to groundwater, if encountered. • Discussion of seismicity at the site along with seismic design parameters including Site Class and site coefficients based on current IBC criteria. • Recommendations for shallow foundations including allowable soil bearing values, minimum footing sizes, soil parameters for lateral load resistance, and footing drains. • Estimate the total and differential settlements of spread footings and floor slabs for variable loading within the building. • Geotechnical recommendations and considerations for support of concrete slab-on-grade floors. Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 2 • Recommendations for pavement subgrade preparation. • Recommendations for earthwork and site preparation. An evaluation of the effects of weather and/or construction equipment on site soils and mitigation of any unsuitable soil conditions at the site will be included. SITE CONDITIONS Surface Conditions The rectangular-shaped project site is about 2.13 acres in size and has maximum dimensions of approximately 316 feet in the east-west direction and 293 feet in the north-south direction. Access to the site is provided by 120`h Avenue SE, extending north from SE 192' Street. The site is bordered by existing single-family residences to the north and east, SE 192" Street to the south and 120th Avenue SE and a stormwater detention pond to the west. A layout of the site is shown on the Site Plan in Figure 2. The ground surface within the site is generally gently sloping down to the east and south. The foundation slab of a demolished single-family residence currently sits within the site. The site is vegetated mostly with grass, blackberry bushes and several small- to- medium sized alder trees. Geology Most of the Puget Sound Region was affected by past intrusion of continental glaciation. The last period of glaciation, the Vashon Stade of the Fraser Glaciation, ended approximately 14,000 years ago. Many of the geomorphic features seen today are a result of scouring and overriding by glacial ice. During the Vashon Stade, areas of the Puget Sound region were overridden by over 3,000 feet of ice. Soil layers overridden by the ice sheet were compacted to a much greater extent than those that were not. Part of a typical glacial sequence within the area of the site includes the following soil deposits from newest to oldest: Artificial Fill (af) — Fill material is often locally placed by human activities, consistency will depend on the source of the fill. The thickness and expanse of this material will be dependent of extent of fill required to grade land to the desired elevations. Density of the fill will depend on earthwork activities and compaction efforts made during the placement of the material. Approximately 2 feet of fill was disclosed in Test Pits 1 and 2. Recessional Outwash (Qvr) — These deposits were derived from the stagnating and receding Vashon glacier and consist of mostly of stratified sand and gravel, but include unstratified ablation and melt-out deposits. Recessional deposits were not compacted by the glacier and are typically not as dense as those that were. Vashon Till (Qvt) — The till is a non-sorted mixture of clay, sand, pebbles, cobbles and boulders, all in variable amounts. The till was deposited directly by the ice as it advanced over and eroded irregular surfaces of previously deposited formations and sediments. The till was well compacted by the advancing glacier and exhibits high strength and stability. Drainage is considered very poor in the till. Vashon Till was observed in all of the explorations. Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 3 The geologic units for this area are mapped on the Geologic Map of the King County, Washington, by Derek B. Booth and Aaron P. Wisher (GeoMapNW, 2006). The site is mapped as being underlain by a deposit of glacial till. Our site explorations encountered fill and glacial till. Explorations We explored subsurface conditions within the site on June 22, 2012, by excavating seven test pits with a rubber-tired backhoe. The test pits were advanced to depths ranging from 4.2 to 7.2 feet below the ground surface. Samples were obtained from the test pits at various depths. The test pits were located in the field by an engineer from this firm who also examined the soils and geologic conditions encountered, and maintained logs of the test pits. The approximate locations of the test pits are shown on the Site Plan in Figure 2. The soils were visually classified in general accordance with the Unified Soil Classification System, a copy of which is presented as Figure 3. The logs of the test pits are presented in Figures 4 through 6. Subsurface Conditions A brief description of the conditions encountered in our explorations is included below. For a more detailed description of the soils encountered, review the Test Pit Logs in Figures 4 through 6. In Test Pits 1 and 2 we generally encountered a surficial layer of topsoil that was less than 1/2 foot in thickness. The topsoil consisted of loose, dark brown silty sand with roots and organics. This was underlain by approximately 2 feet of loose to medium dense silty sand with gravel and bricks that was interpreted to be fill. The fill was underlain by a few inches of buried topsoil over medium dense silty sand with gravel and dense to very dense silty sand with gravel and trace cobbles interpreted to be glacial till in Test Pit 1 and by dense to very dense silty sand with trace gravel interpreted as glacial till in Test Pit 2. In Test Pits 3 though 7, we generally encountered a surf icial layer of topsoil that was less than 1 foot in thickness. Underlying the topsoil we encountered loose to medium dense silty sand with varying amounts of gravel. These deposits were underlain by dense to very dense silty sand with varying amounts of gravel that was interpreted to be glacial till. The glacial till extended to the depths explored in all of the test pits. Hydrologic Conditions Shallow groundwater seepage was not encountered in any of the test pits. However, we observed iron oxide staining in the glacial till soils, which can be an indicator of a perched water zone. The dense to very dense till interpreted to underlie the site is considered poorly draining. During the wetter times of the year, we expect perched water conditions will occur as pockets of water on top of the till layer. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Volumes of perched groundwater vary depending upon the time of year and the upslope recharge conditions. Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 4 GEOLOGIC HAZARDS Erosion Hazard The erosion hazard criteria used for determination of affected areas includes soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types (group classification), which are related to the underlying geologic soil units. We reviewed the Web Soil Survey (WSS) on the U.S. Department of Agriculture's Natural Resources Conservation Service (NRCS) website for the King County Area, Washington to determine the erosion hazard of the on-site soils. The site surface soils were classified using the NRCS classification system as Alderwood gravelly sandy loam (Unit 1). The corresponding geologic unit for these soils is till, which is in agreement with the soils encountered in our site explorations. The erosion hazard for the soil is listed as being slight for the gently sloping conditions at the site. Seismic Hazard It is our opinion based on our subsurface explorations that the Soil Profile in accordance with Table 1613.5.2 of the 2009 International Building Code (IBC) is Site Class C. We used the US Geological Survey program "U.S. Seismic Design Maps Web Application." We have included the Design Maps Summary Report as Appendix A in this report. The seismic design parameters are: SS 134.0% g S, 45.6% g Fa 1.0 F„ 1.3 Site specific coefficients and adjusted maximum considered earthquake spectral response acceleration parameters apply as shown in Section 1613.5 of the IBC. Based on the USGS data and Tables 1613.5.6(1) and (2), the site has Seismic Design Category D. Additional seismic considerations include liquefaction potential and amplification of ground motions by soft soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table. The underlying medium dense to very dense till soils are considered to have a low to very low potential for liquefaction and amplification of ground motion. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the site is compatible with the planned development. The underlying medium dense recessional outwash soils and very dense glacial till deposits are capable of supporting the planned structures and pavements. We recommend that the foundations for the structures extend through any fill, topsoil, loose, or disturbed soils, and bear on the underlying medium dense or firmer, native glacial soils, or on structural fill extending to these soils. Based on our site explorations, we anticipate these soils will generally be encountered at typical footing depths. It should be noted that approximately 2 feet of undocumented fill was Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 5 encountered in Test Pits 1 and 2. Based on our explorations, these areas will require minor overexcavation for structure and pavement support. Site Preparation and Grading The first step of site preparation should be to strip the vegetation, topsoil, fill, or loose soils to expose medium dense or firmer native soils in pavement and building areas. Approximately 2 feet of fill was observed in Test Pits 1 and 2. The excavated material should be removed from the site, or stockpiled for later use as landscaping fill. The resulting subgrade should be compacted to a firm, non-yielding condition. Areas observed to pump or yield should be repaired prior to placing hard surfaces. The on-site glacial till likely to be exposed during construction is considered highly moisture sensitive, and the surface will disturb easily when wet. We expect these soils would be difficult, if not impossible, to compact to structural fill specifications in wet weather. We recommend that earthwork be conducted during the drier months. Additional expenses of wet weather or winter construction could include extra excavation and use of imported fill or rock spalls. During wet weather, alternative site preparation methods may be necessary. These methods may include utilizing a smooth-bucket trackhoe to complete site stripping and diverting construction traffic around prepared subgrades. Disturbance to the prepared subgrade may be minimized by placing a blanket of rock spalls or imported sand and gravel in traffic and roadway areas. Cutoff drains or ditches can also be helpful in reducing grading costs during the wet season. These methods can be evaluated at the time of construction. Structural Fill General: All fill placed beneath buildings, pavements or other settlement sensitive features should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is observed by an experienced geotechnical professional or soils technician. Field observation procedures would include the performance of a representative number of in-place density tests to document the attainment of the desired degree of relative compaction. Materials: Imported structural fill should consist of a good quality, free-draining granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about 3 inches. Imported, all-weather structural fill should contain no more than 5 percent fines (soil finer than a Standard U.S. No. 200 sieve), based on that fraction passing the U.S. 3/4-inch sieve. The use of on-site soil as structural fill will be dependent on moisture content control. Some drying of the native soils may be necessary in order to achieve compaction. During warm, sunny days this could be accomplished by spreading the material in thin lifts and compacting. Some aeration and/or addition of moisture may also be necessary. We expect that compaction of the native soils to structural fill specifications would be difficult, if not impossible, during wet weather. Fill Placement: Following subgrade preparation, placement of the structural fill may proceed. Fill should be placed in 8- to 10-inch-thick uniform lifts, and each lift should be spread evenly Robinson Noble, Inc • Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 6 and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas, and within a depth of 2 feet below pavement and sidewalk subgrade, should be compacted to at least 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D1557 compaction test procedure. Fill more than 2 feet beneath sidewalks and pavement subgrades should be compacted to at least 90 percent of the maximum dry density. The moisture content of the soil to be compacted should be within about 2 percent of optimum so that a readily compactable condition exists. It may be necessary to overexcavate and remove wet surficial soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction. Temporary and Permanent Slopes Temporary cut slope stability is a function of many factors, such as the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable temporary cut slope geometry. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations, since the contractor is continuously at the job site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. For planning purposes, we recommend that temporary cuts in the near-surface weathered soils be no steeper than 1.5 Horizontal to 1 Vertical (1.5H:1 V). Cuts in the dense to very dense till may stand at a 0.75H:1V inclination or possibly steeper. If groundwater seepage is encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. Measures taken may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than 4 feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to local and WISHA/OSHA standards. Final slope inclinations for granular structural fill and the native soils should be no steeper than 2H:1 V. Lightly compacted fills, common fills, or structural fill predominately consisting of fine grained soils should be no steeper than 3H:1 V. Common fills are defined as fill material with some organics that are "trackrolled" into place. They would not meet the compaction specification of structural fill. Final slopes should be vegetated and covered with straw or jute netting. The vegetation should be maintained until it is established. Foundations Conventional shallow spread foundations should be founded on undisturbed, medium dense or firmer soil. If the soil at the planned bottom of footing elevation is not suitable, it should be overexcavated to expose suitable bearing soil. Footings should extend at least 18 inches below the lowest adjacent finished ground surface for frost protection. Minimum foundation widths should conform to IBC requirements. Standing water should not be allowed to accumulate in Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 7 footing trenches. All loose or disturbed soil should be removed from the foundation excavation prior to placing concrete. For foundations constructed as outlined above, we recommend an allowable design bearing pressure of 2,000 pounds per square foot (psf) be used for the footing design. IBC guidelines should be followed when considering short-term transitory wind or seismic loads. Potential foundation settlement using the recommended allowable bearing pressure is estimated to be less than 1-inch total and 1/2-inch differential between footings or across a distance of about 30 feet. Higher soil bearing values may be appropriate with wider footings. These higher values can be determined after a review of a specific design. Lateral Loads The lateral earth pressure acting on retaining walls is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement, which can occur as backfill is placed, and the inclination of the backfill. Walls that are free to yield at least one-thousandth of the height of the wall are in an "active" condition. Walls restrained from movement by stiffness or bracing are in an "at-rest" condition. Active earth pressure and at-rest earth pressure can be calculated based on equivalent fluid density. Equivalent fluid densities for active and at-rest earth pressure of 35 pounds per cubic foot (pcf) and 55 pcf, respectively, may be used for design for a level backslope. These values assume that the on-site soils or imported granular fill are used for backfill, and that the wall backfill is drained. The preceding values do not include the effects of surcharges, such as due to foundation loads or other surface loads. Surcharge effects should be considered where appropriate. The above drained active and at-rest values should be increased by a uniform pressure of 7.0H and 21.6H psf, respectively, when considering seismic conditions. H represents the wall height. The above lateral pressures may be resisted by friction at the base of the wall and passive resistance against the foundation. A coefficient of friction of 0.5 may be used to determine the base friction in the native glacial soils. An equivalent fluid density of 275 pcf may be used for passive resistance design. To achieve this value of passive pressure, the foundations should be poured "neat" against the native dense soils, or compacted fill should be used as backfill against the front of the footing, and the soil in front of the wall should extend a horizontal distance at least equal to three times the foundation depth. A factor of safety of 1.5 has been applied to the passive pressure to account for required movements to generate these pressures. The friction coefficient does not include a factor of safety. All wall backfill should be well compacted. Care should be taken to prevent the buildup of excess lateral soil pressures due to overcompaction of the wall backfill. Slabs-On-Grade Slab-on-grade areas should be prepared as recommended in the Site Preparation and Grading subsection. Slabs should be supported on medium dense or firmer native soils, or on structural fill extending to these soils. Where moisture control is a concern, we recommend that slabs be underlain by 6 inches of pea gravel for use as a capillary break. A suitable vapor barrier, such as heavy plastic sheeting, should be placed over the capillary break. An additional Robinson Noble, Inc • Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 8 2-inch-thick damp sand blanket can be used to cover the vapor barrier to protect the membrane and to aid in curing the concrete. This will also help prevent cement paste bleeding down into the capillary break through joints or tears in the vapor barrier. The capillary break material should be connected to the footing drains to provide positive drainage. Drainage We recommend that runoff from impervious surfaces, such as roofs, driveway and access roadways, be collected and routed to an appropriate storm water discharge system. The finished ground surface should be sloped at a gradient of 5 percent minimum for a distance of at least 10 feet away from the buildings, or to an approved method of diverting water from the foundation, per IBC Section 1803.3. Surface water should be collected by permanent catch basins and drain lines, and be discharged into a storm drain system. We recommend that footing drains be used around all of the structures where moisture control is important. The underlying till may pond water that could accumulate in crawlspaces. It is good practice to use footing drains installed at least 1 foot below the planned finished floor slab or crawlspace elevation to provide drainage for the crawlspace. At a minimum, crawlspaces should be sloped to drain to an outlet tied to the drainage system. If drains are omitted around slab-on-grade floors where moisture control is important, the slab should be a minimum of 1 foot above surrounding grades. Where used, footing drains should consist of 4-inch-diameter, perforated PVC pipe that is surrounded by free-draining material, such as pea gravel. Footing drains should discharge into tightlines leading to an appropriate collection and discharge point. Crawlspaces should be sloped to drain, and a positive connection should be made into the foundation drainage system. For slabs-on-grade, a drainage path should be provided from the capillary break material to the footing drain system. Roof drains should not be connected to wall or footing drains. Our experience with gently-sloping till sites is that the volume of water collected by residence foundation drains and routed to the stormwater detention system is insignificant when considered in the storm drainage design. We do not expect that the foundation drain water will impact the design of the stormwater detention system. Detention Pond If a storm water detention pond is planned, it should be excavated into the underlying native soils. We recommend that any fill berms be constructed of soils having a maximum permeability of 1 x 10-5 centimeters per second (4 x inches/second). The on-site till encountered in our test pit explorations meets this criterion. We should evaluate any proposed berm fill material prior to construction of the berm. If a pond is to be constructed, the cut slopes of the pond should be no steeper than 3H:1V on the inside of the detention pond and no steeper than 2H:1V above the water table or on the outside portions of the pond berms. Inside slopes as steep as 2H:1V are possible but may require maintenance until vegetation is established. Areas with seepage may require a blanket of rock spalls or other measures to limit sloughing. Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 9 Where any berms for the pond are to be constructed, the topsoil and loose soils should be removed down to the medium dense to very dense till. Areas to receive new fill should be stripped of unsuitable surface soils and compacted to a firm, non-yielding state prior to placement of the new fill. The excavation should be kept dry to allow the proper placement of structural fill. Structural fill should be placed and compacted as discussed in the Structural Fill subsection of this report. We recommend that the fill in any pond berms be compacted to a minimum of 92 percent of its maximum dry density as determined by the ASTM D1557 compaction test procedure. After each lift of the fill in a berm is compacted to specification, the surface should be scarified to a depth of 2 inches prior to placement of the next lift. The purpose of the scarification is to reduce the risk of creating preferential seepage paths through the pond or berms. It will be important to compact the face of any pond fill embankments. This should be made explicit to the contractor performing the on-site work. Uncompacted soils on a berm face will be more susceptible to erosion and sloughing. If groundwater seepage is encountered within a cut slope face, a layer of rock spalls may be necessary to minimize erosion of the slope face. The spall layer can be placed at the time of construction, or in the future if sloughing of the slope is observed. Utilities Our explorations indicate that deep dewatering will not be needed to install standard depth utilities. Anticipated groundwater is expected to be handled with pumps in the trenches. We also expect that some groundwater seepage may develop during and following the wetter times of the year. We expect this seepage to mostly occur in pockets. We do not expect significant volumes of water in these excavations. The soils likely to be exposed in utility trenches after site stripping are considered highly moisture sensitive. We recommend that they be considered for trench backfill during the drier portions of the year. Provided these soils are within 2 percent of their optimum moisture content, they should be suitable to meet compaction specifications. During the wet season, it may be difficult to achieve compaction specifications, therefore, soil amendment with kiln dust or cement may be needed to achieve proper compaction with the on-site materials. Pavement Subgrade The performance of roadway pavement is critically related to the conditions of the underlying subgrade. We recommend that the subgrade soils within the roadways be prepared as described in the Site Preparation and Grading subsection of this report. Prior to placing base material, the subgrade soils should be compacted to a non-yielding state with a vibratory roller compactor and then proof-rolled with a piece of heavy construction equipment, such as a fully- loaded dump truck. Any areas with excessive weaving or flexing should be overexcavated and recompacted or replaced with a structural fill or crushed rock placed and compacted in accordance with recommendations provided in the Structural Fill subsection of this report. Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 10 CONSTRUCTION OBSERVATION We should be retained to provide observation and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, and to provide recommendations for design changes, should the conditions revealed during the work differ from those anticipated. As part of our services, we would also evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. USE OF THIS REPORT We have prepared this report for Geonerco Properties WA, LLC and its agents, for use in planning and design of this project. The data and report should be provided to prospective contractors for their bidding and estimating purposes, but our report, conclusions and interpretations should not be construed as a warranty of subsurface conditions. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractors' methods, techniques, sequences or procedures, except as specifically described in our report, for consideration in design. There are possible variations in subsurface conditions. We recommend that project planning include contingencies in budget and schedule, should areas be found with conditions that vary from those described in this report. Within the limitations of scope, schedule and budget for our services, we have strived to take care that our services have been completed in accordance with generally accepted practices followed in this area at the time this report was prepared. No other conditions, expressed or implied, should be understood. oOo Robinson Noble, Inc Geotechnical Engineering Report Kelsey's Crossing Renton, Washington July 5, 2012 RN File No. 2563-004A Page 11 We appreciate the opportunity to be of service to you. If there are any questions concerning this report or if we can provide additional services, please call. Sincerely, Robinson Noble, Inc. ,eat a 5J,Lt /' Barbara A. Gallagher, PE Senior Project Engineer fr* 'pig , i 1.Z. ., r ..., ,At r I/C5 9_0 ii... 4 1;, :.. r \its 30540S: ttkv 44tTSISSia..*44y: ' '44,MAL " ► tAL Rick B. 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I —I I / I � illi �I I kI �_ 4� k ,) 5 \ I 6 t81 ,• I 1 �1 I\ I's PROPOSED u IURNAROUA At II II d I \\� __ I �, i 188 E TP-2 ,s• 4 / r esat m�r OSOL 1 TP-3 / £ fp — ,.... \ 1su',I.`• ' 6C/St lc / I �i Cur� S9' 25 '1 ` �_—_ 20' ' \I e / -I— _______ --• jI / � lyl;- f.. II N BSBL �J� I -a P /�I 7 I I I' 00 _ii J 14 I /�� / / r ! L-- i B��--- TRACTB-- - j /TP-g IIII 1 BSBL r. / * / I E- N SII ,� ' J I I / . °El I LEGEND TROT'C' [� DRAI FACILITIES ,i us Y,a r.l s i TP-5 n' r -- iOp 0.A x '' zsTt 1;,,, ,,,,...., ;":-11 Nir `� 20' E«rltm10 fJ TP-7 . I,I 64k,,, I 84' + ge l / 107 / Number and Approximate s�,` ' i ; 4h,. F---i2•/RICHT-OF-WAY DEDICATION11 Location of Test Pit } NQY1309.11/315.33'(C)stss (P) I e ... � Scale 1"=40' ���,� ��+ t ����.% �t ,3 �.,, c: �a , .E.192ND:STREET, Yc�* ��.r,.fiwri . .go : EB o� x _ , > Note:Basemaptaken PM' RBP Figure 2 from"Preliminary Plat of Kelsey's Crossing" July 2012 Site Plan ROBINSON` prepared byBarghausen Consulting Engineers, 2563-004A NOBLE Inc-dated„2R/2008. Geonerco Properties, LLC: Kelsey's Crossing Unified Soil Classification System MAJORGROUP GROUP NAME DIVISIONS SYMBOL GRAVEL CLEAN GRAVEL GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL COARSE - GRAINED MORE THAN 50%OF GP POORLY-GRADED GRAVEL COARSE FRACTION SOILS RETAINED ON NO.4 GRAVEL SIEVE WITH FINES GM SILTY GRAVEL GC CLAYEY GRAVEL MORE THAN 50% RETAINED ON SAND CLEAN SAND SW WELL-GRADED SAND,FINE TO COARSE SAND number 200 SIEVE SP POORLY-GRADED SAND MORE THAN 50%OF COARSE FRACTION SAND PASSES NO.4 SIEVE WITH FINES SM SILTY SAND SC CLAYEY SAND SILT AND CLAY INORGANIC ML SILT FINE- GRAINED LIQUID LIMIT CL CLAY LESS THAN 50% SOILS ORGANIC OL ORGANIC SILT,ORGANIC CLAY MORE THAN 50% SILT AND CLAY INORGANIC PASSES NO.200 SIEVE MH SILT OF HIGH PLASTICITY,ELASTIC SILT LIQUID LIMIT CH CLAY OF HIGH PLASTICITY.FAT CLAY 50%OR MORE ORGANIC OH ORGANIC CLAY.ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS 1) Field classification is based on Dry-Absence of moisture, dusty, dry visual examination of soil in general to the touch accordance with ASTM D 2488-83. 2) Soil classification using laboratory Moist Damp, but no visible water tests is based on ASTM D 2487-83. Wet-Visible free water or saturated, 3) Descriptions of soil density or usually soil is obtained from consistency are based on below water table interpretation of blowcount data, visual appearance of soils, and/or test data. —dmPM: RBP King County Figure 3 ROBINSONuly 2012 Unified Soil Classification System __ NOBLE 2563-004A Geonerco Properties, LLC: Kelsey's Crossing • LOG OF EXPLORATION DEPTH USC SOIL DESCRIPTION TEST PIT ONE 0.0-0.5 SM Dark brown, silty sand with grass roots (loose, moist) (Topsoil) (MC = 18.9%) 0.5-2.0 SM Red-brown, silty sand with gravel, wood, brick (loose to medium dense, moist) (Fill) 2.0-2.3 SM Dark brown, silty sand with roots (loose, moist) (Buried Topsoil) (MC = 11.0%) 2.3-3.0 SM Red-brown, silty sand with gravel (medium dense, moist) (MC = 20.2%) 3.0-4.0 SM Gray and red-brown silty sand with gravel and trace cobbles (dense to very dense, moist) (Weathered Glacial Till) 4.0-6.5 SM Gray to gray brown, silty sand with gravel (very dense, moist) (Glacial Till) (MC = 11.9%) Samples were collected at 0.5, 2.3, 3, and 6.5 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 6.5 feet on 6/22/2012 TEST PIT TWO 0.0-0.3 SM Dark brown, silty sand with grass and young tree roots (loose, moist) (Topsoil) 0.3- 1.8 SM Red-brown, silty sand with gravel (loose to medium dense, moist) (Fill) (MC = 23.9%) 1.8-2.1 SM Dark brown, silty sand with roots (loose, moist) (Buried Topsoil) 2.1 -7.2 SM Brown-gray with iron oxide staining, cemented silty sand and trace gravel (dense to very dense, moist) (Weathered Glacial Till) Samples were collected at 1.5, 2.2, 3.0 and 7.2 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 7.2 feet on 6/22/2012 ROBINSON NOBLE, INC. FILE NO 2563-004A FIGURE 4 • LOG OF EXPLORATION DEPTH USC SOIL DESCRIPTION TEST PIT THREE 0.0— 1.5 SM Dark brown, silty sand with grass and blackberry roots (loose, moist) (Topsoil) 1.5—3.3 SM Red-brown, silty sand with trace gravel and rootlets (medium dense, moist) 3.3—4.3 SM Brown-gray, cemented silty sand (dense to very dense, moist ) (Weathered Glacial Till) Sample was collected at 2.7 and 4.3 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 4.3 feet on 6/22/2012 TEST PIT FOUR 0.0—0.8 SM Dark brown, silty sand with blackberry bush roots (loose, moist) (Topsoil) 0.8—2.2 SM Red-brown, silty sand with gravel (loose to medium dense, moist) (MC = 29.3%) 2.2—5.0 SM Brown-gray, silty sand with gravel and trace cobbles (dense to very dense, moist) (Weathered Glacial Till) Samples were collected at 1.4 and 5 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 5.0 feet on 6/22/2012 TEST PIT FIVE 0.0—0.5 SM Dark brown, silty sand with grass and blackberry bush roots (loose, moist) (Topsoil) 0.5—2.3 SM Red-brown, silty sand with trace gravel (loose to medium dense, moist) (MC = 14.6%) 2.3—4.6 SM Brown-gray with slight iron oxide staining, silty sand with gravel (dense to very dense, moist) (Weathered Glacial Till) Samples were collected at 1.5 and 4.6 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 4.6 feet on 6/22/2012 ROBINSON NOBLE, INC. FILE NO 2563-004A FIGURE 5