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HomeMy WebLinkAboutRS_Geotechnical_Report_170518_v1.pdfGEOTECHNICAL REPORT U.S. Bank Expansion 2500 East Valley Road Renton, Washington Project,'No. T-7638 Terra Associates, Inc. � � A ► i Prepared for: Strada Da Valle, LLC Seattle, Washington April 11101017 TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences April 17, 2017 Project No. T-7638 Mr. Brad Merlino Strada Da Valle, LLC 5050 — 1 st Avenue South, Suite 102 Seattle, Washington 98134 Subject: Geotechnical Report U.S. Bank Expansion 2500 East Valley Road Renton, Washington Dear Mr. Merlino: As requested, we have conducted a geotechnical engineering study for the subject project. The attached report presents our findings and recommendations for the geotechnical aspects of project design and construction. The soils observed in the test boring consist of approximately 9.5 feet of fill overlying native lacustrine and alluvial deposits. Groundwater was encountered about 12 feet below existing site grade. Based on our study, there are no geotechnical conditions that would preclude the planned development. In our opinion, the addition can be supported on conventional spread footings bearing on a subgrade of existing fill material that has been mechanically compacted in place or on structural fill that is placed on a compacted subgrade. Floor slabs can be similarly supported. We trust the information provided in the attached report is sufficient for your current needs. If you have any questions or need additional information, please call. Sincerely yours, TERRA ASSOCIATES, INC. John T J. ShI ,�ie0P.E. w P ,4 w �TSr /O IN AL 12220 113th Avenue NE, Ste. 130, Kirkland, Washington 98034 Phone (425) 821-7777 • Fax (425) 821-4334 TABLE OF CONTENTS Pau No. 1.0 Project Description .............. ...................................................................................1 2.0 Scope of Work ...................... :.................... ....................... ............................................... l 3.0 Site Conditions................................................................................................................ 2 3.1 Surface................................................................................................................2 3.2 Soils....................................................................................................................2 3.3 Groundwater.......................................................................................................2 3.4 Geologic Hazards................................................................ ..............................2 3.4.1 Erosion Hazard Areas....................................................................3 3.4.2 Steep Slope Hazard Areas.............:...::.::...:;.::..........................................3 3.4.3 Landslide Hazard Areas...........................................................................4 3.4.4 Seismic Hazard Areas..............................................................................4 3.4.5 Coal Mine Hazard Areas........... — . ... .... .................................................. 5 3.5 Seismic Design Parameters................................................................................5 4.0 Discussion and Recommendations..................................................................................6 4.1 General...............................................................................................................6 4.2 Site Preparation.................................................................................................. 6 4.3 Structural Fill and Backfill.................................................................................7 4.4 Foundations........................................................................................................ 7 4.5 Slab -on -Grade Floors......................................................................................... 8 4.6 Utilities............................................................................................................... 8 5.0 Additional Services......................................................................................................... 9 6.0 Limitations......................................................................................................................9 Fivires VicinityMap ....................................................................................................................... Figure 1 ExplorationLocation Plan.................................................................................................. Figure 2 Appendices Field Exploration and Laboratory Testing Appendix A Liquefaction Analysis Results Appendix B Geotechnical Report U.S. Bank Expansion 2500 East Valley Road Renton, Washington 1.0 PROJECT DESCRIPTION The project consists of constructing a single -story addition to the northern side of an existing office building. A site plan prepared by Cornerstone Architectural Group, dated March 2, 2017 indicates the addition will have a footprint of approximately 2,460 feet. We understand that the addition will be constructed with concrete walls and a concrete slab -on -grade floor matching the existing office structure. We expect structural loading will be relatively light with columns carrying 100 to 150 kips and continuous bearing walls carrying 4 to 6 kips per foot. The recommendations contained in the following sections of this report are based on the above design features. We should review any changes in the geotechnical aspects of the design plans as they are developed to verify that our recommendations are valid for the proposed construction and to amend or modify our report, as necessary. 2.0 SCOPE OF WORK Our scope of work was completed in accordance with our authorized proposal dated March 23, 2017. On April 1, 2017, we observed subsurface conditions in the area of the planned addition in a test boring drilled to a depth of 51.5 feet below existing ground surface. Using the information obtained from our subsurface exploration, we performed analyses to develop geotechnical engineering recommendations for project design and construction. Specifically, this report addresses the following: • Soil and groundwater conditions ■ Geologic Hazards per the City of Renton Municipal Code • Seismic design parameters per the current International Building Code (IBC) • Site preparation • Structural fill and backfill • Foundations • Slab -on -grade floors • Utilities It should be noted that the recommendations outlined in this report regarding drainage are associated with soil strength, erosion, and stability. Design and performance issues with respect to moisture as it relates to the structure environment are beyond Terra Associates' purview. A building envelope specialist or contractor should be consulted to address these issues, as needed. April 17, 2017 Project No. T-7638 3.0 SITE CONDITIONS 3.1 Surface The project site is within an existing office park located between East Valley Road and State Route 167 (SR 167), approximately 450 feet north of the intersection of East Valley Road and SW 27th Street in Renton, Washington. The location of the site is shown on Figure 1. A sidewalk and planter, and concrete -paved parking and driveway areas currently occupy the location of the addition. Existing surface grades are relatively flat. 3.2 Soils The soils observed in the test boring consist of approximately 9.5 feet of fill overlying native lacustrine and alluvial deposits. The fill soils generally consist of loose to medium dense, moist, silty fine sand to fine sandy silt with varying amounts of gravel and scattered brick fragments, and stiff, moist, clayey silt with scattered angular siltstone fragments. The native alluvial deposits consist predominantly of fine to medium sand, sand with silt, and silty sand that are in a very loose to medium dense condition between depths of about 12 and 38 feet, and a medium dense condition below 39 feet. All of the soil samples collected below a depth of 12 feet were wet. Soft, moist, peat was encountered between the fill and the alluvial sediments between depths of about 9.5 and 12 feet. A map titled Geologic Map of the Renton Quadrangle, King County, Washington by D.R. Mullineaux, dated 1965 shows the site soils mapped as lacustrine peat deposits (Qlp). This mapped soil unit is consistent with the native soils observed in the test boring. Detailed descriptions of the subsurface conditions observed in the test boring presented on the Boring Log attached in Appendix A. The approximate location of the test boring is shown on Figure 2. 3.3 Groundwater We observed groundwater in the test boring below a depth of approximately 12 feet. Considering our field work occurred on April 1st, we expect that the observed groundwater level is generally representative of the seasonal high. 3.4 Geolo i� c Hazards We evaluated potential geologic -related hazards at the subject site as defined in Section 4-3-050G5 (Geologically Hazardous Areas Defined) of the Renton Municipal Code (RMC). Geologic hazards are defined by the RMC as "Areas which may be prone to one or more of the following conditions: erosion, flooding, landslides, coal mine hazards, or seismic activity." Page No. 2 April 17, 2017 Project No. T-7638 3.4.1 Erosion Hazard Areas Section 4-3-050G5c of the RMC defines erosion hazards as follows: i. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential, and a slope less than 15 percent. ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having severe or very severe erosion potential, and a slope more than 15 percent. The soils underlying the site are mapped as Tukwila muck (Tu), which are described by the NRCS as having a slight erosion potential. Based on the above criteria, the site is categorized as having a low erosion hazard. In our opinion, no significant erosion hazard exists in the project area. In our opinion, the erosion potential of site soils in the planned development area would be adequately mitigated with proper implementation and maintenance of Best Management Practices (BMPs) for erosion prevention and sedimentation control. All BMPs for erosion prevention and sedimentation control will need to be in place prior to and during site grading activity, and should conform to City of Renton requirements. 3.4.2 Steep Slope Hazard Areas Section 4-3-050G5a of the RMC defines steep slopes as follows: i. Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of 25 percent to less than 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of 40 percent or greater with a vertical rise of less than 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; (c) abutting an average slope of 25 percent to 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. This definition excludes engineered retaining walls. ii. Protected Slopes: A hillside, or portion thereof, characterized by an average slope of 40 percent or greater grade and having a minimum vertical rise of 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. In our opinion, steep slope hazards do not exist at the site. As discussed, site topography is relatively flat. In our opinion, slope areas that meet the above criteria and that pose a potential steep slope hazard do not exist at the site. Page No. 3 April 17, 2017 Project No. T-7638 3.4.3 Landslide Hazard Areas Section 4-3-050G5b of the RMC defines landslide hazards as follows: i. Low Landslide Hazard (LL): Areas with slopes less than 15 percent. ii. Medium Landslide Hazard (LM): Areas with slopes between 15 percent and 40 percent and underlain by soils that consist largely of sand, gravel, or glacial till. iii. High Landslide Hazards (LH): Areas with slopes greater than 40 percent, and areas with slopes between 15 percent and 40 percent and underlain by soils consisting largely of silt and clay. iv. Very High Landslide Hazards (LV): Areas of known mapped or identified landslide deposits. In our opinion, no landslide hazard exists at the site. With the relatively flat topography, based on the above criteria, the site would be classified as having a low landslide hazard. 3.4.4 Seismic Hazard Areas Section 4-3-050G5d of the RMC defines seismic hazards as follows: Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils generally have site classifications of A through D, as defined in the International Building Code, 2012. ii. High Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils. These soils generally have site classifications E or F, as defined in the International Building Code, 2012. Based on soil conditions observed in the test boring and our knowledge of the area geology, per Chapter 16 of the current International Building Code (IBC), it is our opinion that site soil classification "D" would apply to the subject site. However, because the loose, saturated soils observed in the upper approximately 35 feet of the test boring are susceptible to liquefaction during a severe seismic event, it is our opinion that the seismic hazard at the site would be classified as high. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine-grained sands underlying the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction; thus, eliminating the soil's strength. We completed a liquefaction analysis using the computer program LiquifyPro following procedures outlined by Seed and Idriss. The analysis was completed using a ground acceleration of 0.38 g which was determined in accordance with the National Earthquake Hazards Reduction Program (NEHRP) recommendations outlined in Federal Emergency Management Agency (FEMA) publication P-750. This value is equivalent to SDs/2.5. The results of the liquefaction analysis are attached in Appendix B. Page No. 4 April 17, 2017 Project No. T-7638 The results of our analysis indicate soil liquefaction could occur during the design earthquake event. Analysis indicates that liquefaction could result in total settlements of three inches, one-half of which would likely be differential in nature. In our opinion, this amount of settlement would not structurally impair the building but would likely result in cosmetic damage to the structure. If the owner is not willing to accept the risk of cosmetic building damage requiring repair should liquefaction induced settlements occur foundations would need to be supported on ground improved with stone columns. Based on our experience with similar sites and structures, structural design elements are also available to mitigate potential damage caused by the seismic -related soil settlements. 3.4.5 Coal Mine Hazard Areas Section 4-3-050G5e of the RMC defines coal mine hazards as follows: i. Low Coal Mine Hazards (CL): Areas with no known mine workings and no predicted subsidence. While no mines are known in these areas, undocumented mining is known to have occurred. ii. Medium Coal Mine Hazards (CM): Areas where mine workings are deeper than 200 feet for steeply dipping seams, or deeper than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by subsidence. iii. High Coal Mine Hazard (CH): Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than 200 feet in depth for steeply dipping seams, or shallower than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by collapse or other subsidence. We found no record of historical coal mining activities on or extending below the subject site. In our opinion, no coal mine hazard exists at the site. 3.5 Seismic Design Parameters Based on soil conditions observed in the test boring and our knowledge of the area geology, per Chapter 16 of the current IBC, site class "D" should be used in structural design. Based on this site class, in accordance with the IBC, the following parameters should be used in computing seismic forces: Seismic Design Parameters (2012/2015 IBC) Spectral response acceleration (Short Period), SMS 1.424 Spectral response acceleration (1 — Second Period), SMl 0.796 g Five percent damped .2 second period, SDS 0.949 Five percent damped 1.0 second period, SDI 0.530 The above values are for Latitude 47.45632°N and Longitude -122.21809°W, and were obtained from the United States Geological Survey (USGS) Ground Motion Parameter Calculator accessed on April 12, 2017 at the web site http:llearthquake.usgs govfdesignmaps/us/alication.rD)h . Page No. 5 April 17, 2017 Project No. T-7638 4.0 DISCUSSION AND RECOMMENDATIONS 4.1 General In our opinion, there are no geotechnical conditions that would preclude the project as currently planned. Some of the soils underlying the site are susceptible to liquefaction during a severe seismic event that could result in settlement at the ground surface of about three inches, one-half of which would likely be differential in nature. As discussed, settlements of this magnitude would not structurally impair the building but would likely result in cosmetic damage to the structure. We observed peat in the test boring between depths of about 9.5 and 12 feet. Peat soils are typically susceptible to long-term consolidation under loads; however, with the relatively light structural loading, and because the peat has been overlain by approximately 9.5 feet of fill since at least 1991, we do not expect any significant post construction settlement that would require mitigation due to additional consolidation of the peat. In our opinion, the addition can be supported using conventional spread footings bearing on a subgrade of existing fill material that has been mechanically compacted in place to a create a dense uniform condition. The existing fill soils observed in the test boring contain a sufficient amount of fines that will make them difficult to compact as structural fill when too wet. The ability to use the existing fill soils as structural fill will depend on the soil moisture content and prevailing weather conditions at the time of construction. If site excavation occurs during wet weather, the owner should be prepared to import clean granular material for use as structural fill and backfill or to use additives such as cement or lime to stabilize the soil for compaction. Detailed recommendations regarding the preceding issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 4.2 Site Preparation Site preparation should include complete removal of pavements, sidewalk and curb, existing vegetation, and other deleterious material from the area of new construction. Existing buried utilities that will be abandoned should be excavated and removed or sealed to prevent water accumulation. Utilities beneath new foundations should be removed. Once site preparation operations are complete, the exposed subgrade should be mechanically compacted to an unyielding state using a hydraulic hoe -pack or vibratory drum roller. The existing fill soils that will be exposed in the area of the new addition consist predominantly of silt and fine sand that will be easily disturbed by normal construction activity when wet. If disturbed, the soil will not be suitable for support and the affected material would need to be removed and grade restored with structural fill. To reduce the potential for subgrade disturbance, particularly during wet weather, consideration should be given to placing a six-inch layer of one- to two-inch sized crushed rock or a four -inch layer of lean concrete on completed subgrades to serve as a working surface. Page No. 6 April 17, 2017 Project No. T-7638 4.3 Structural Fill and Backfill Once site preparation operations are complete, grading to establish desired building elevations can be initiated. In order to achieve proper compaction of building fill, the existing subgrade must be in a relatively stable condition. If an excessively soft and yielding subgrade is observed and it cannot be stabilized in place by aeration and compaction, stabilizing by the use of an additive, such as cement or lime will need to be considered. Alternatively, the unstable soils can be excavated and replaced with clean granular structural fill. Typically, stabilization of soft yielding soils that cannot be stabilized in place (due to excess moisture) requires amending or otherwise removing and replacing affected soils to a depth of 12 to 18 inches with clean granular structural fill. Using the existing fill materials for structural fill will require careful control of the soil moisture content to facilitate adequate compaction. As such, the ability to use the site soils as structural fill will depend on the natural soil moisture content, the prevailing weather conditions at the time of construction, and the ability of the contractor to properly moisture condition the soil. During the normally dry summer months, the contractor should be prepared to dry soils that are wet of optimum by aeration. Alternatively, stabilizing the moisture in the soil with cement or lime can be considered. Moisture conditioning of soils that are dry of optimum would require the addition of water to the soils and thoroughly blending the material prior to compaction. If grading activities are planned during the wet winter months and the on-site soils become too wet to achieve adequate compaction, the contractor should be prepared to treat soils with cement or lime, or import wet weather structural fill. If an additive is used, additional Best Management Practices (BMPs) for its use will need to be incorporated into the Temporary Erosion and Sedimentation Control plan (TESC) for the project. For wet weather structural fill, we recommend importing a granular soil that meets the following grading requirements: U.S. Sieve Size Percent Passing 6 inches 100 No. 4 75 maximum No. 200 5 maximum* *Based on the 3/4 -inch fraction. Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural fill. Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of 95 percent of the soil's maximum dry density, as determined by American Society for Testing and Materials (ASTM) Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction should be within two percent of its optimum, as determined by this ASTM standard. In nonstructural areas, or for backfill in utility trenches below a depth of 4 feet, the degree of compaction can be reduced to 90 percent. 4.4 Foundations Foundation support for the addition may consist of conventional spread footing foundations bearing on a subgrade consisting of existing fill material that is mechanically compacted in place to an unyielding, dense condition or on structural fill placed on a mechanically compacted subgrade. Perimeter foundations exposed to the weather should bear at a minimum depth of 1.5 feet below final exterior grades for frost protection. Interior foundations can be constructed at any convenient depth below the floor slab. Page No. 7 April 17, 2017 Project No. T-763 8 We recommend designing foundations for a net allowable bearing capacity of 2,000 pounds per square foot (psf). For short-term loads, such as wind and seismic, a one-third increase in this allowable capacity can be used in design. With structural loading as anticipated and this bearing stress applied, estimated foundation settlements of about 1 Yz inches and differential settlement of 3/4 -inch should be expected. For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth pressures acting on the sides of the footings can also be considered. We recommend calculating this lateral resistance using an equivalent fluid weight of 300 pounds per cubic foot (pcf). We recommend not including the upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This value assumes the foundations will be backfilled with structural fill, as described in Section 4.3 of this report. The values recommended include a safety factor of 1.5. 4.5 Slab -on -Grade Floors Slab -on -grade floors may be supported on a subgrade prepared as recommended in Sections 4.2 and 4.3 of this report. Immediately below the floor slabs, we recommend placing a four -inch thick capillary break layer of clean, free -draining, coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slabs. The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission. Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel to protect it from damage during construction, and aid in uniform curing of the concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will be ineffective in assisting in uniform curing of the slab, and can actually serve as a water supply for moisture transmission through the slab and affecting floor coverings. Therefore, in our opinion, covering the membrane with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot be effectively drained. We recommend floor designers and contractors refer to the 2003 American Concrete Institute (ACI) Manual of Concrete Practice, Part 2, 302.1R-96, for further information regarding vapor barrier installation below slab -on -grade floors. 4.6 Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA), or City of Renton specifications. As a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 4.3 of this report. As noted, the existing fill soils are moisture sensitive and will require careful control of moisture to facilitate proper compaction. If utility construction takes place during the winter or if it is not feasible to properly moisture condition the excavated soil at the time of construction, it may be necessary to import suitable wet weather fill for utility trench backfilling. Utility excavations extending to depths greater that about 9.5 feet will likely encounter soft peat and wet, fine-grained alluvial deposits that would not be suitable for reuse as trench backfill. Page No. 8 April 17, 2017 Project No. T-7638 5.0 ADDITIONAL SERVICES Terra Associates, Inc. should review project designs and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design. We should also provide geotechnical services during construction to observe compliance with our design concepts, specifications, and recommendations. This will allow for expedient design changes if subsurface conditions differ from those anticipated prior to the start of construction. 6.0 LIMITATIONS We prepared this report in accordance with generally accepted geotechnical engineering practices. No other warranty, expressed or implied, is made. This report is the copyrighted property of Terra Associates, Inc. and is intended for specific application to the U.S. Bank Expansion project in Renton, Washington. This report is for the exclusive use of Strada DaValle, LLC and their authorized representatives. The analyses and recommendations presented in this report are based on data obtained from the on-site test boring. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the recommendations in this report prior to proceeding with construction. 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U.S. BANK EXPANSION Consultants in Geotechnical Engineering RENTON, WASHINGTON Geology and go Environmental Earth Sciences Proj. No.T-7638 Date APR 2017 Figure 1 REFERENCE: SITE PLAN BY CORNERSTONE ARCHITECTURAL GROUP INOTE THIS SITE PLAN IS SCHEMATIC. ALL LOCATIONS AND DIMENSIONS ARE APPROXIMATE. IT IS INTENDED FOR REFERENCE ONLY AND SHOULD NOT BE USED FOR DESIGN OR CONSTRUCTION PURPOSES. LEGEND: Terra Associates, Inc. Consultants in Geotechnical Engineering A AA Geology and Environmental Earth Sciences IS APPROXIMATE BORING LOCATION 0 15 30 APPROXIMATE SCALE IN FEET EXPLORATION LOCATION PLAN U.S. BANK EXPANSION RENTON, WASHINGTON Proj. No.T-7638 I Date APR 2017 1 Figure 2 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING U.S. Bank Expansion Renton, Washington On April 1, 2017, we explored subsurface conditions at the site by drilling one test boring to a depth of 51.5 feet with a trailer mounted drill rig using hollow -stem auger drilling methods. The boring was located in the field by measuring and sighting relative to existing structure and surface features. The boring location is shown on Figure 2. The Boring Log is presented as Figure A-2. An engineering geologist from our office conducted the field exploration, maintained a log of the test boring, classified the soils and recorded groundwater levels, collected representative soil samples, and observed pertinent site features. Soil samples were obtained from the test borings in general accordance with ASTM D-1586 test procedures. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure A-1. Representative soil samples obtained from the test boring were placed in sealed plastic bags and taken to our laboratory for further examination and testing. The moisture content of all soil samples was measured and is reported on the Boring Log. Grain size distribution was also determined on five samples with results shown on Figures A-3 and A-4. Project No. T-7638 MAJOR DIVISIONS LETTER TYPICAL DESCRIPTION SYMBOL Clean GW Well -graded gravels, gravel -sand mixtures, little or no fines. Gravels (less GRAVELS than 5% �, More than 50% fines) GP Poorly -graded gravels, gravel -sand mixtures, little or no fines. J O ca N of coarse fraction N Ta Cn is larger than No. GM Silty gravels, gravel -sand -silt mixtures, non -plastic fines. a`) > 4 sieve Gravels with GC Clayey gravels, gravel -sand -clay mixtures, plastic fines. Z is •0—' E fines Q C) o a (7 0L Clean Sands SW Well -graded sands, sands with gravel, little or no fines. vWj o a z SANDS (less than Qy o More than 50% 5% fines) SP Poorly -graded sands, sands with gravel, little or no fines. Oo of coarse fraction SM Silty sands, sand -silt mixtures, non -plastic fines. U :2 is smaller than No. 4 sieve Sands with SC Clayey sands, sand -clay mixtures, plastic fines. fines L ML Inorganic silts, rock flour, clayey silts with slight plasticity. U .� SILTS AND CLAYS p To Limit is less than 50% CL Inorganic clays of low to medium plasticity. (Lean clay) WLiquid CU 'U) OL Organic silts and organic clays of low plasticity. Z Eo R o N MH Inorganic silts, elastic. u•, o O Z SILTS AND CLAYS LU Z C o Liquid Limit is greater than 50 /o CH Inorganic clays of high plasticity. (Fat clay) LL m� o OH Organic clays of high plasticity. HIGHLY ORGANIC SOILS PT Peat. DEFINITION OF TERMS AND SYMBOLS CO Standard Penetration 2" OUTSIDE DIAMETER SPILT SPOON SAMPLER Density Resistance in Blows/Foot 2.4" INSIDE DIAMETER RING SAMPLER OR p Very Loose 0-4 SHELBY TUBE SAMPLER N Loose 4-10 = Medium Dense 10-30 1 WATER LEVEL (Date) O Dense 30-50 V Very Dense >50 Tr TORVANE READINGS, tsf Pp PENETROMETER READING, tsf Standard Penetration Consistancy Resistance in Blows/Foot W DD DRY DENSITY, pounds per cubic foot Very Soft 0_� = Soft LL LIQUID LIMIT, percent O Medium Stiff 4-8 V Stiff 8-16 PI PLASTIC INDEX Very Stiff 16-32 Hard >32 N STANDARD PENETRATION, blows per foot Terra UNIFIED SOIL CLASSIFICATION SYSTEM U.S. BANK EXPANSION Associates, Inc. RENTON, WASHINGTON Consultants in Geotechnical Engineering Geology and Environmental Earth Sciences Pro No.T-7638 1• Date APR 2017 Figure A-1 g LOG OF BORING NO. B-1 Project: U.S.Bank Expansion Figure No. A-2 Project No: T-7638 Date Drilled: April 1, 2017 Client: Strada Da Valle, LLC_.... ....... . . .... _. Driller: Boretec _ Logged By: JCS Location: Renton, Washington Depth to GroundwaterApprax. 12 ft _ Approx. Elev: NA m Z Consistency/ I SPT (N) Moisture (D Soil Description Relative Density Blows/foot Content (%) r a n E o U) 10 30 50 0 _ IFILL: 5 inch Concrete Slab. Medium Dense Gray sandy SILT with gravel to silty SAND with gravel, fine 24.5 ■ 44.5 3 203.8 sand, fine gravel, trace of clay, moist, trace off brick fragmernts. 28.7 8 5 I (MUSM) Loose I FILL: Gray clayey SILT to sandy, clayey SILT, moist, scattered Stiff 10 I angular siItstone fragments_ (ML) Soft • Ir I , Dark brown PEAT, moist. (PT) • 15— I Gray -brown silty SAND to SAND with silt, fine sand, wet, Loose ■ numerous sandy silt partings and seams. (SM/SP-SM) 20 I Dark gray -brown SAND, fine to medium grained, moist to wet. Medium Dense • (SP) 25 I ■ 30 Gray silty SAND to SAND with silt, fine to medium sand, wet. Very Loose to I (SM/SP-SM) Loose - Trace of fine shell fragments below 33 feet. 35- 5 40 40 I 45 Gray SAND to SAND wth silt, fine to medium grained, trace of Medium Dense I coarse sand, wet, scattered shell fragments, trace of dark brown organic seams and wood fragments. (SP/SP-SM) 50 I Boring terminated at 51.5 feet. 55 Groundwater encountered below approximately 12 feet. 60 J I NOTE: This borehole log has been prepared for geotechnical purposes. This information pertains only to this boring location and should not be interpeted as being indicative of other areas of the site 12 18.7 5 24.5 9 44.5 3 203.8 7 28.7 8 31.5 15 1 23.7 2 1 22.8 6 1 22.6 5 1 23.8 20 1 25.8 22 1 20.3 24 1 21.4 NTerra Associates, Inc. Consultants in Geotechnical Engineering Geology and. Tested By: FQ i u aV'Coarse Fine Silt ClayMaterial Description� D silty SAND:i silty SANDSANDProject No. T-7638 Client: Strada De Valle, LLC 7:Re arks:Project: U.S. Bank Expansion 0 sted April 5, 2017EiT sted April 5, 2017-o Location: B-1 Depth: 2.5' Ar sted April 5, 20171[3 Location: B-1 Depth: 12.5'i& Location: B-1 Depth: 20'Terra Associates, Inc. Tested By: FQ Tested By: Particle Size Distribution Report C CE C C C C C O N m O �0 O O O V O N 100 0 90--- I 80 80 I I I I I I I I I I I I I 1 1 l I i I l l I I I 70 I I I I I I I W60 I 1 I I I I! I I ! I I I I I I I I I Z I I I l i I I I I I I 1 1 1 1 I I I l Z 50 I I I I I I I W I I 1 11 I I 6 1 1 1 W 40 I i I I I i f I 1 I l l l 30 20 I I I I I I I I I I I I I I 1 1 I I I I I I I I! I 10 1 1 I 1 I I I I I I I I I I I 1 I I I I I I I I I I 01 1 ! I I I I 11 l I I I I I I 100 10 1 0.1 0.01 0.061, GRAIN SIZE _ mm. % Gravel % Sand % Fines %+3" _ Coarse Fine Coarsel Medium Fine Silt Clay 0 0.0 0.0 1.4 3.4 45.0 32.8 17.4 ❑ 0.0 0.0 1.0 2.7 59.1 30.0 7.2 LL PL D D D Q30 DIS D CrC 0_ 1.0248 0.5329 0.4229 0.2329 1.1188 0.6489 0.5444 0.3550 0.1988 0.1435 1.35 4.52 Material Description USCS AASHTO o silty SAND SM I❑ SAND with silt SP -SM Project No. T-7638 Client: Strada De Valle, LLC Remarks: Project: U.S. Bank Expansion oTested April 5, 2017 ❑Tested April 5, 2017 o Location: B-1 Depth: 30' ❑ Location: B-1 Depth: 45' Terra Associates, Inc. Kirkland, WA Figure A-4 Tested By: APPENDIX B LIQUEFACTION ANALYSIS RESULTS LIQUEFACTION ANALYSIS U.S. Bank Expansion Hole No.=B-1 Water Depth=2.5 ft Ground Improvement of Fi11=9.5 ft Shear Stress Ratio Factor of Safety Settlement 0 1 0 1 5 0 (in.) 0 I- -- -. j I T -T -f-1' T I i I IZ f-TTTITT 10 20 30 4- 40 50 60 70 fs1-1 CRR CSR fs1 Shaded Zone has Liquefaction Potential CivilTech Corporation B-1 10 Saturated — Unsaturat. — Magnitude=7 Acceleration=0.388 Soil Description Peat silty SAND to SAND with silt SAND silty SAND to SAND with silt SAND to SAND with silt