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2021.0018 Yelm Development Geotechnical ReportEarth Science + Technology Geotechnical Engineering Services Report Yelm Development Yelm, Washington for D&B Retail Development September 14, 2015 Geotechnical Engineering Services Report Yelm Development Yelm, Washington for D&B Retail Development September 14, 2015 1101 South Fawcett Avenue, Suite 200 Tacoma, Washington 98402 253.383.4940 Geotechnical Engineering Services Report Yelm Development Yelm, Washington Prepared for: D&B Retail Development 6402 Tacoma Mall Blvd. Tacoma, Washington 98409 Attention: Dale Pinney Prepared by: GeoEngineers, Inc. 1101 South Fawcett Avenue, Suite 200 Tacoma, Washington 98402 253.383.4940 Basel Kitmit Geotechnica Engineer `nnis (D,3� Thompson, PE nior Geotechnical Engineer BK:DJT:tt File No. 22013-001-00 September 14, 2015 Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record. GWENGINEER� September 14, 2015 | Page i File No. 22013-001-00 Table of Contents INTRODUCTION AND PROJECT UNDERSTANDING ................................................................................................. 1 SCOPE OF SERVICES ............................................................................................................................................... 1 SITE CONDITIONS ..................................................................................................................................................... 2 Published Literature ............................................................................................................................................ 2 Surface Conditions............................................................................................................................................... 3 Subsurface Explorations ...................................................................................................................................... 3 Subsurface Conditions ........................................................................................................................................ 3 General .......................................................................................................................................................... 3 Soil Conditions .............................................................................................................................................. 3 Groundwater Condition ................................................................................................................................. 4 CONCLUSIONS AND RECOMMENDATIONS ............................................................................................................ 4 General ................................................................................................................................................................. 4 Stormwater Infiltration ......................................................................................................................................... 4 General .......................................................................................................................................................... 4 Soil Infiltration Rates .................................................................................................................................... 5 Site Development and Earthwork ....................................................................................................................... 6 General .......................................................................................................................................................... 6 Clearing and Stripping .................................................................................................................................. 6 Temporary Excavations, Support and Dewatering ...................................................................................... 6 Permanent Cut and Fill Slopes ..................................................................................................................... 7 Surface Drainage .......................................................................................................................................... 7 Erosion and Sedimentation Control ............................................................................................................. 7 Subgrade Preparation and Evaluation ......................................................................................................... 8 Subgrade Protection and Wet Weather Considerations ............................................................................. 8 Fill Materials ......................................................................................................................................................... 9 General .......................................................................................................................................................... 9 Select Granular Fill ........................................................................................................................................ 9 On-Site Soil .................................................................................................................................................... 9 Fill Placement and Compaction ....................................................................................................................... 10 General ....................................................................................................................................................... 10 Area Fills and Bases ................................................................................................................................... 10 Trench Backfill ............................................................................................................................................ 10 Seismic Design Considerations ........................................................................................................................ 10 General ....................................................................................................................................................... 10 Seismic Design Criteria .............................................................................................................................. 11 Liquefaction Potential ................................................................................................................................ 11 Shallow Foundations ........................................................................................................................................ 11 Foundation Support ................................................................................................................................... 11 Bearing Capacity ........................................................................................................................................ 12 Foundation Drains ...................................................................................................................................... 12 Footing Bearing Surface Preparation ........................................................................................................ 12 Foundation Settlement .............................................................................................................................. 12 September 14, 2015 | Page ii File No. 22013-001-00 Lateral Resistance ..................................................................................................................................... 13 Conventional Subgrade and Retaining Walls .................................................................................................. 13 Drainage ..................................................................................................................................................... 13 Design Parameters .................................................................................................................................... 13 Building Pads and Floor Slabs ......................................................................................................................... 14 Pavement Recommendations .......................................................................................................................... 14 Asphaltic Concrete Pavement ................................................................................................................... 14 LIMITATIONS .......................................................................................................................................................... 15 LIST OF FIGURES Figure 1. Vicinity Map Figure 2. Site Plan APPENDICES Appendix A. Field Explorations and Laboratory Testing Figure A-1. Key to Exploration Logs Figures A-2 through A-11. Logs of Test Pits Figures A-12 and A-13. Sieve Analysis Results Appendix B. Report Limitations and Guidelines for Use September 14, 2015 | Page 1 File No. 22013-001-00 INTRODUCTION AND PROJECT UNDERSTANDING GeoEngineers is pleased to present this geotechnical report to support development and construction of the proposed Yelm Development project located at 1301 Yelm Avenue East in Yelm, Washington as shown in Figure 1. Our understanding of this project is based on our discussions with you and/or members of your design team, including Larson and Associates (project civil engineers), and review of conceptual plans provided. Based on review of aerial photographs and on-site observations, the parcel is generally flat, removed of trees and is surfaced with grass vegetation. Abandoned single family homes surround the property in the south, east and west. The property is irregular in shape; the overall size is on the order of 3.7 acres. The property is divided into three lots as shown on our Site Plan, Figure 2. We understand that three retail buildings and a surrounding parking lot area are proposed for and will cover the majority of the site. The proposed structures will consist of single-story retail shopping and restaurant type buildings. The exterior walls and interior columns will be supported by conventional spread footings. Stormwater for each retail building and the parking lot area will be handled by underground infiltration trenches that will generally be located in the southwest portion of the parcel behind the proposed developments. We understand that the stormwater infiltration trenches within Lots 1 and 3 will be located at depths of approximately 5 to 7 feet below ground surface (bgs) and at a depths of approximately 9 to 10 feet bgs within Lot 2. The Washington State Department of Ecology (Ecology) 2012 Stormwater Management Manual for Western Washington (SWMMWW) Volume III will be used as a guideline for stormwater design, including stormwater infiltration. Additional improvements include asphalt concrete parking and installation of underground utilities. SCOPE OF SERVICES The purpose of our services was to evaluate soil and groundwater conditions as a basis for developing recommendations to support the proposed site improvements and to determine infiltration characteristics of the underlying soil. Our specific scope of services for this study includes: 1. Reviewing existing in-house information on subsurface conditions. 2. Visiting the site, marking out, identifying potential test pit locations and coordinating clearance of existing utilities. 3. Exploring subsurface conditions at the site by conducting 10 test pit explorations. The test pits were located around the proposed structures and within proposed infiltration areas (note that the SWMMWW requires a minimum of two test pits per infiltration facility or trench). Eight test pits were excavated to depths of approximately 10 to 12-feet and two test pits were excavated to depths of approximately 15 to 16 feet. 4. Performing laboratory tests consisting of eight grain-size analyses on selected soil samples obtained from the test pits. 5. Providing a discussion of the surface and subsurface conditions encountered. September 14, 2015 | Page 2 File No. 22013-001-00 6. Providing an estimate of infiltration rate(s) of soil collected in the explorations. Our estimate(s) are based on the laboratory grain-size analysis and requirements presented in the 2012 SWMMWW. 7. Providing geotechnical seismic design information in accordance with International Building Code (IBC) criteria and discussing our opinion on the potential for liquefaction. 8. Providing recommendations for design of shallow foundations including recommendations for foundation design, including bearing surface preparation, removal of uncontrolled fill, soft, organic or otherwise unsuitable material, backfill compaction and drainage recommendations. We include recommendations for allowable bearing capacity, estimates of settlement, and lateral resistance. 9. Providing recommendations for conventional below-grade building walls and retaining wall structures, including allowable soil bearing pressures, settlement (total and differential) estimates, lateral earth pressures (seismic, active and passive) and coefficient of friction for evaluating sliding resistance. We also discuss backfill material and compaction requirements and drainage recommendations. 10. Providing recommendations for support of on-grade floor slabs, including modulus of subgrade reaction, capillary break, vapor retarder and underslab drainage, as appropriate. 11. Providing a recommended asphalt concrete pavement (ACP) section based on our experience and typical practice in this area. 12. Providing recommendations for site preparation and earthwork. We discuss clearing and stripping, temporary and permanent cut slopes, suitability of on-site soils for use as structural fill, specifications for imported soil for use as structural fill, wet weather considerations for earthwork and fill placement and compaction requirements. 13. Providing recommendations for site drainage and control of groundwater that may be encountered. 14. Preparing a geotechnical report commensurate with the scope described above. Our report presents our findings and recommendations and including summary logs of the explorations and a plan view showing the exploration locations. SITE CONDITIONS Published Literature Based on review of geologic maps in our files, Vashon recessional outwash sand and gravel is the dominant, near-surface, geologic material mapped in the immediate project area. This material is commonly known as Steilacoom gravel. Vashon recessional outwash was deposited by melt water streams in front of the most recent glacier during its retreat from the Puget Sound region approximately 10,000 to 15,000 years ago. These deposits generally consist of permeable sand, or sand and gravel. Cobbles and boulders can also be encountered in this deposit, depending on the depositional history. Glacial till and/or advance outwash is commonly encountered at depth below the recessional outwash. The United States Department of Agriculture (USDA) Soil Conservation Service (SCS) Soil Survey of Pierce County Area, Washington, maps the project area as Spanaway gravelly sandy loam, 0 to 3 percent slopes (110). This soil unit is described as being formed in glacial outwash. It is further described as generally having positive soil characteristics for small commercial buildings. These characteristics include but are not limited to being somewhat excessively drained, little erosion hazard, and low resistance to compaction. However, this soil unit is described as being “very limited” in regards to shallow excavations (i.e., trenches September 14, 2015 | Page 3 File No. 22013-001-00 or holes excavated to a maximum depth of 5 to 6 feet below ground surface) and will potentially require “major soil reclamation, special design, or expensive installation procedures”. We interpret part of this statement to refer to the potential for excessive caving of sidewalls that may occur during excavation below grade and accompanying shoring, trench boxes, or similar soil support options. Surface Conditions The project area is located west of the intersection of East Yelm Avenue, Bald Hill Road SE, and Creek Street SE in Yelm, Washington. The project area is irregular in shape and is flat or slightly sloping down to the northwest. A paved road loops around the interior of the site giving access to residences that bordered the western, southern and eastern perimeter of the site. The residences are abandoned and some of the structures that are visible from aerial photographs have been removed. A gas line was noted to exist between the access road and the front of the abandoned residences. Vegetation in the majority of the property is low growing grasses. Trees of various sizes exist along the perimeter of the property. We did not observe standing water or indications of wet surface conditions during our time on site. Subsurface Explorations Our understanding of subsurface conditions at the project site is based on conditions disclosed in 10 test pits excavated at the approximate locations shown in Figure 2. Details of the exploratory program, laboratory testing program and test pit logs completed for this study are presented in Appendix A. Subsurface Conditions General We categorized soil layers encountered in our explorations into the following units in the order in which they are generally encountered: a weathered outwash, an upper outwash, and a lower outwash. The upper outwash was present within all test pit locations except in TP-7 where the lower outwash was overlain by the weathered outwash. Grass or sod and significant organics are typically present within the top 3 to 6 inches of the explorations. The weathered outwash generally is in a loose to medium dense condition and consists of silty sand with gravel, gravel with silt and sand and occasional organic material. The upper outwash generally is in a medium dense condition and consists of one or more layers of gravel with sand and occasional cobbles (up to 1 foot in diameter), silty sand, and sand with silt. The lower outwash generally is in a medium dense to dense condition and consists of gravel with sand and occasional cobbles up to and potentially greater than 1 foot in diameter. All the explorations terminated in the lower outwash. Soil Conditions We observed approximately 3 inches of sod at the surface in all of the explorations with the exception of test pits TP-2, TP-3 and TP-4. TP-2 surface soils consisted of a 3-inch layer of gravel base rock that is present along the shoulder of the existing northwestern access road. Weathered outwash was observed at the ground surface of test pit locations TP-3 and TP-4. In TP-1 through TP-4 and TP-8 the weathered outwash is present from the below the ground surface, sod, or gravel base and extends approximately to depths of 2 to 3.5 feet bgs. The weathered outwash overlies the upper outwash. The upper outwash extends approximately to depths of 6 to 7 feet bgs. We did not observe the upper outwash in TP-7, only the lower outwash unit. The lower outwash extends to the full depths explored in the test pit explorations. September 14, 2015 | Page 4 File No. 22013-001-00 In TP-5, TP-6, TP-9 and TP-10 the weathered outwash extends approximately to depths of 2 and 3 feet bgs. The weathered outwash overlies the upper outwash and extends approximately to depths of 7 and 8 feet. The lower outwash extends to the bottom of the test pit explorations. Groundwater Condition No groundwater seepage was observed during our explorations. Ecology’s reports for monitoring wells completed in the project vicinity were reviewed and indicated static groundwater is encountered at depths between 26 feet and 59 feet bgs at the well locations. Based on our observations, and review of Ecology’s reports for monitoring wells combined with the relatively flat topography of the surrounding area, static groundwater elevation is expected to be well below the depths of the test pit explorations completed for this project. Groundwater conditions should be expected to vary as a result of season, precipitation and other factors. Depending on the time of year, it is possible that some groundwater seepage may be encountered below or within the weathered outwash. CONCLUSIONS AND RECOMMENDATIONS General Based on the results of our study, it is our opinion that the site is generally suitable for the proposed development with regard to geotechnical considerations. A summary of the primary geotechnical considerations for the proposed development is provided below, and is followed by our detailed recommendations. ■ Granular soils were generally encountered; however, we did observe that some of the near-surface site soil has a higher fines (silt and clay-sized particles passing the U.S. Standard No. 200 sieve) content. Soil with a higher fines content is more sensitive to small changes in moisture content and may be difficult, if not impossible, to work and compact during wet weather conditions. This material can also be susceptible to disturbance from construction traffic when wet, or if earthwork is performed during wet weather. ■ The proposed structures may be satisfactorily supported on continuous and isolated shallow foundations supported on the well compacted weathered outwash or the medium dense or dense native soils or on structural fill that extends to these soils. ■ Floor slabs may be supported on well compacted weathered outwash or the underlying outwash soils. ■ The glacial outwash deposits can contain cobbles and boulders. The contractor should be prepared for this possibility. ■ On-site stormwater infiltration appears feasible based on the subsurface conditions observed. Greater infiltration rates will likely be obtained at depth. We provide preliminary infiltration rate recommendations below. Stormwater Infiltration General Soil consisting of the lower outwash material is typically encountered below Elevation 344.5 feet to 342 feet in the explorations completed in the project area. In general, it is our opinion that the natural soils encountered in the lower outwash within our explorations should have adequate permeability to infiltrate September 14, 2015 | Page 5 File No. 22013-001-00 stormwater from the site. We did not encounter groundwater seepage, staining or other indications of seasonal shallow groundwater in the explorations. Soil Infiltration Rates Stormwater infiltration rates for the site soils were established based on the 2012 Ecology SWMMWW Volume III in conjunction with the sieve analysis results presented in Appendix A, Figures A-12 and A-13. TABLE 1. SOIL INFILTRATION RATES1 Test Pit No. Soil Sample No. Soil Sample Elevation (feet) Percent Fines2 D10 Size (mm)3 USCS4 Soil Classification Recommended Long-term Design Infiltration Rate5 (Inches per Hour) 1 1 345.5 12.5 N/D SM 2(6) 1 2 341 2 0.8 GP 20(7) 2 3 337.5 2 0.52 GW 20(7) 3 2 339.5 1 10.7 GW 20(7) 4 3 336.5 1 0.79 GP 20(7) 5 2 345.5 13.4 N/D SM 2(6) 5 3 342 2 0.87 GP 20(7) 6 2 342 2.3 0.68 GP 20(7) Notes: 1 For selected soil samples. 2 Fines = Silt and clay-sized particles passing U.S. No. 200 (0.75 mm) sieve. 3 Based on ASTM C 136 Soil Gradation Test. 4 Unified Soil Classification System (USCS). 5 Based on grain-size analysis and the procedures outlined in the 2012 Ecology SWMMWW Volume III Table 3.8. 6 Design infiltration rate determined using USDA soil texture method provided in the 2005 Department of Ecology Stormwater Management Manual. 7 Calculated infiltration rates were greater than presented and were limited to 20 inches per hour. We completed explorations within the areas of the infiltration trench locations indicated on the plans provided by Larson and Associates, Inc. We expect that the relatively clean gravel soils encountered in the test pits should have adequate permeability and storage capacity to infiltrate stormwater. We recommend that a long-term design infiltration rate of 20 inches per hour be used for sizing facilities located within the lower outwash below approximate Elevations 344.5 feet to 342 feet. The value(s) presented above are for the specific samples tested and are an estimate of subsurface infiltration properties at various depths. We recommend that the project plans include provisions for GeoEngineers to observe subsurface conditions during construction to check that the preliminary infiltration rate(s)and soil conditions used for design are appropriate for the conditions encountered. Site- and location- specific testing may also be required by local jurisdictions. Stormwater should be treated in accordance with current regulations prior to infiltration. To help reduce clogging of infiltration facilities, we recommend they be protected during construction with siltation control facilities such as temporary settling basins, silt fences and hay bales. Suspended solids can clog the soil and reduce the infiltration rate. Periodic sweeping of paved areas, during and following construction, will September 14, 2015 | Page 6 File No. 22013-001-00 help extend the life of the infiltration facilities. Equipment should not be permitted in the infiltration areas after they are excavated to grade because of the potential for compaction of the subgrade that could reduce the infiltration rate of the soil. Site Development and Earthwork General We anticipate that site development and earthwork will include clearing and stripping of surface vegetation, constructing foundations and then placing and compacting fill and backfill materials. We expect that the majority of site grading can be accomplished with conventional earthmoving equipment. The following sections provide recommendations for stripping, excavation, erosion control, subgrade development, fill materials, fill placement and compaction. Clearing and Stripping Based on our observations at the site, we estimate that the depth of stripping could be on the order of 3 inches to 1 foot. For estimating purposes we suggest a depth of stripping of 6 inches. Greater stripping depths may be required to remove localized zones of loose or organic-rich soil. In addition, demolition around existing structures may cause localized disturbance and require greater stripping depths. The primary root systems of shrubs should be completely removed. Stripped material should be transported off site for disposal or processed and used as fill in landscaping areas. We did encounter cobbles/boulders during our subsurface investigation, confirming our experience that cobbles/boulders can be present in the glacial deposits in the area. Accordingly, the contractor should be prepared to remove cobbles/boulders, if encountered during grading or utility excavations. Boulders may be removed from the site or buried in landscape areas. Voids caused by boulder removal should be backfilled with structural fill. Temporary Excavations, Support and Dewatering Excavations deeper than 4 feet should be shored or laid back at a stable slope if workers are required to enter. Shoring and temporary slope inclinations must conform to the provisions of Title 296 Washington Administrative Code (WAC), Part N, “Excavation, Trenching and Shoring.” Regardless of the soil type encountered in the excavation, shoring, trench boxes or sloped sidewalls will be required under Washington Industrial Safety and Health Act (WISHA). The contract documents should specify that the contractor is responsible for selecting excavation and dewatering methods, monitoring the excavations for safety and providing shoring, as required, to protect personnel and structures. We provide additional recommendations in regard to temporary and permanent shoring below. In general, temporary cut slopes should be inclined no steeper than about 1-1/2H:1V (horizontal:vertical). This guideline assumes that all surface loads are kept at a minimum distance of at least one-half the depth of the cut away from the top of the slope and that seepage is not present on the slope face. Flatter cut slopes will be necessary where seepage occurs or if surcharge loads are anticipated. We observed caving in our explorations; therefore, some sloughing and raveling of cut slopes should be expected. Temporary covering with heavy plastic sheeting should be used to protect these slopes during periods of wet weather. Based on our explorations, we do not expect groundwater to be a major factor during shallow excavations and earthwork. However, some perched groundwater could occur in the near-surface soil depending on the September 14, 2015 | Page 7 File No. 22013-001-00 time of year of construction. We anticipate that groundwater handling needs will typically be lower during the late summer and early fall months. We anticipate that shallow perched groundwater can typically be handled adequately with sumps, pumps, and/or diversion ditches, as necessary. Ultimately, we recommend that the contractor performing the work be made responsible for controlling and collecting groundwater encountered. Permanent Cut and Fill Slopes Based on site grades and the proposed construction, we anticipate that only minor cutting and filling will be required for this project. However, if permanent slopes are necessary, we recommend they be constructed at a maximum inclination of 2H:1V. Where 2H:1V permanent slopes are not feasible, protective facings and/or retaining structures should be considered. To achieve uniform compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to expose well-compacted fill. Fill placement on slopes steeper than 5H:1V should be benched into the slope face and include keyways. The configuration of the bench and keyway depends on the equipment being used. Bench excavations should be level and extend into the slope face. We recommend that a vertical cut of about 3 feet be maintained for benched excavations. Keyways should be about 1-1/2 times the width of the equipment used for grading or compaction. Exposed areas should be re-vegetated as soon as practical to reduce the surface erosion and sloughing. Temporary protection should be used until permanent protection is established. Surface Drainage Surface water from roofs, driveways and landscape areas should be collected and controlled. Curbs or other appropriate measures such as sloping pavements, sidewalks and landscape areas should be used to direct surface flow away from the buildings, erosion sensitive areas and from behind retaining structures. Roof and catchment drains should not be connected to wall or foundation drains. Erosion and Sedimentation Control Potential sources or causes of erosion and sedimentation can be influenced by construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. Implementing an erosion and sedimentation control plan will reduce the project impact on erosion- prone areas. The plan should be designed in accordance with applicable city, county and/or state standards. The plan should incorporate basic planning principles, including: ■ Scheduling grading and construction to reduce soil exposure. ■ Re-vegetating or mulching denuded areas. ■ Directing runoff away from denuded areas. ■ Reducing the length and steepness of slopes with exposed soils. ■ Decreasing runoff velocities. ■ Preparing drainage ways and outlets to handle concentrated or increased runoff. ■ Confining sediment to the project site. September 14, 2015 | Page 8 File No. 22013-001-00 ■ Inspecting and maintaining control measures frequently. Some sloughing and raveling of exposed or disturbed soil on slopes should be expected. We recommend that disturbed soil be restored promptly so that surface runoff does not become channeled. Temporary erosion protection should be used and maintained in areas with exposed or disturbed soils to help reduce erosion and reduce transport of sediment to adjacent areas and receiving waters. Permanent erosion protection should be provided by paving, structure construction or landscape planting. Until the permanent erosion protection is established and the site is stabilized, site monitoring may be required by qualified personnel to evaluate the effectiveness of the erosion control measures and to repair and/or modify them as appropriate. Provision for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. Subgrade Preparation and Evaluation Subgrade areas should be thoroughly compacted with heavy, smooth-drum vibratory equipment to a uniformly dense and unyielding condition prior to placement of structural fill or structural elements. We recommend that prepared subgrades be observed by a member of our firm, who will evaluate the suitability of the subgrade and identify any areas of yielding, which are indicative of soft or loose soil. The exposed subgrade soil should be proof-rolled with heavy rubber-tired equipment or probed with a 1/2-inch-diameter steel rod, as appropriate depending on prevailing conditions. If soft or otherwise unsuitable areas revealed during probing or proof-rolling cannot be compacted to a stable and uniformly firm condition, we recommend that: 1) the subgrade soils be scarified (e.g., with a ripper or a farmer’s disc), aerated and recompacted; or 2) the unsuitable soils be removed and replaced with structural fill, as needed. Subgrade Protection and Wet Weather Considerations The wet weather season generally begins in October and continues through May in western Washington; however, periods of wet weather can occur during any month of the year. In our opinion, site grading and fill placement could be considered during wet weather, but it should be noted that some of the soils encountered in our explorations contain a significant amount of fines and will be susceptible to disturbance during extended periods of wet weather. Soil with high fines content is very sensitive to small changes in moisture and is susceptible to disturbance from construction traffic when wet or if earthwork is performed during wet weather. If wet weather earthwork is unavoidable, we recommend that the following steps be taken. ■ The ground surface in and around the work area should be sloped so that surface water is directed away from the work area. The ground surface should be graded so that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. ■ Earthwork activities should not take place during periods of heavy precipitation. ■ Slopes with exposed soils should be covered with plastic sheeting. ■ The contractor should take necessary measures to prevent on-site soils and other soils to be used as fill from becoming wet or unstable. These measures may include the use of plastic sheeting, sumps with pumps and grading. The site soils should not be left uncompacted and exposed to moisture. September 14, 2015 | Page 9 File No. 22013-001-00 Sealing the surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will help reduce the extent to which these soils become wet or unstable. ■ Construction traffic should be restricted to specific areas of the site, preferably areas that are surfaced with working pad materials not susceptible to wet weather disturbance. ■ Construction activities should be scheduled so that the length of time that soils are left exposed to moisture is reduced to the extent practical. ■ Protective surfacing such as placing asphalt-treated base (ATB) or haul roads made of quarry spalls or a layer of free-draining material such as well graded pit-run sand and gravel may be necessary to protect completed areas. Typically, minimum gravel thicknesses on the order of 24 inches are necessary to provide adequate subgrade protection. ■ During periods of wet weather, concrete should be placed as soon as practical after preparation of the footing excavations. Foundation bearing surfaces should not be exposed to standing water. Should water infiltrate and pool in the excavation, it should be removed before placing structural fill or reinforcing steel. Subgrade protection for foundations consisting of a lean concrete mat should be considered if footing excavations are exposed to extended wet weather conditions. Fill Materials General Material used for structural fill should be free of debris, organic contaminants and rock fragments larger than 6 inches. The workability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines increases, soil becomes increasingly more sensitive to small changes in moisture content. We recommend that structural fill and trench backfill material consist of material similar to “Select Borrow” or “Gravel Borrow” as described in Section 9-03.14 of the Washington State Department of Transportation (WSDOT) Standard Specifications. If construction is performed during wet weather, we recommend using select granular fill as described below. If prolonged dry weather prevails during the earthwork phase of construction, a somewhat higher fines content may be acceptable. Select Granular Fill We recommend select granular fill for construction during wet weather conditions, consist of well-graded sand and gravel or crushed rock with a maximum particle size of 6 inches and less than 5 percent fines by weight based on the minus 3/4-inch fraction. Organic matter, debris or other deleterious material should not be present. In our opinion, material conforming to WSDOT Specification 9-03.9 (Aggregates for Ballast and Crushed Surfacing), 9-03.10 (Aggregate for Gravel Base), or 9-03.14 (Borrow) is suitable for use as import fill material during wet weather with the exception that the fines content should be less than 5 percent based on the minus 3/4-inch fraction. In addition, some larger particle sizes are acceptable, as described above. On-Site Soil During dry weather and periods of light rain fall any non-organic on-site soil may be considered for use as fill provided it meets the criteria described above and can be compacted as recommended. When the fines content in the soil exceeds about 5 percent, the soil becomes more sensitive to moisture. Portions of the on-site soil contain enough fines to be moisture sensitive and may not be suitable for use as fill during extended periods of wet weather and/or if exposed to wet conditions. Even when properly compacted, this September 14, 2015 | Page 10 File No. 22013-001-00 material can be easily disturbed and will soften when exposed to moisture. Based on our subsurface explorations, on-site material in the top approximate 6 feet will typically not be suitable for use as drainage material, for use behind retaining walls, or as a capillary break material. Use of on-site soils for drainage material should be evaluated on a case-by-case basis, and approved by the engineer. Fill Placement and Compaction General To obtain proper compaction, fill soil should be compacted near optimum moisture content and in uniform horizontal lifts. Lift thickness and compaction procedures will depend on the moisture content and gradation characteristics of the soil and the type of equipment used. The maximum allowable moisture content varies with the soil gradation and should be evaluated during construction. Silty soil and other fine granular soil may be difficult or impossible to compact during persistent wet conditions. Generally, 12-inch loose lifts are appropriate for steel-drum vibratory roller compaction equipment. Compaction should be achieved by mechanical means. During fill and backfill placement, sufficient testing of in-place density should be conducted to check that adequate compaction is being achieved. Area Fills and Bases Fill placed to raise site grades and materials under pavements should be placed on subgrades prepared as previously recommended. In general, area fills and bases should be compacted to at least 95 percent of the maximum dry density (MDD) determined by ASTM International (ASTM) Test Method D 1557 (modified Proctor). Trench Backfill For utility excavations, we recommend that the initial lift of fill over the pipe be thick enough to reduce the potential for damage during compaction but generally should not be greater than about 18 inches. In addition, rock fragments greater than about 1 inch in maximum dimension should be excluded from this lift. In paved and structural areas, trench backfill should be uniformly compacted in horizontal lifts to at least 95 percent of the MDD in the upper 2 feet below subgrade. Fill placed below a depth of 2 feet from subgrade in paved areas must be compacted to at least 90 percent of the MDD. In nonstructural areas, trench backfill should be compacted to a firm condition that will support construction equipment, as necessary. Seismic Design Considerations General The site is located within the Puget Sound region, which is seismically active. Seismicity in this region is attributed primarily to the interaction between the Pacific, Juan de Fuca, and North American plates. The Juan de Fuca plate is subducting beneath the North American plate. It is thought that the resulting deformation and breakup of the Juan de Fuca plate might account for the deep focus earthquakes in the region. Hundreds of earthquakes have been recorded in the Puget Sound area. In recent history, four of these earthquakes were large events: 1) in 1946, a Richter magnitude 7.2 earthquake occurred in the Vancouver Island, British Columbia area; 2) in 1949, a Richter magnitude 7.1 earthquake occurred in the Olympia area; 3) in 1965, a Richter magnitude 6.5 earthquake occurred between Seattle and Tacoma; and 4) on February 28, 2001, a magnitude 6.8 earthquake occurred at Nisqually near Olympia. September 14, 2015 | Page 11 File No. 22013-001-00 Research is currently underway regarding historical large magnitude subduction-related earthquake activity along the Washington and Oregon coasts. Geologists are reporting evidence that suggests several large magnitude earthquakes (Richter magnitude 8 to 9) have occurred in the last 1,500 years, the most recent of which occurred about 300 years ago. No earthquakes of this magnitude have been documented during the recorded history of the Pacific Northwest. Local design practice in Puget Sound assumes that the magnitude felt from such an earthquake is about the same as from the existing design earthquake because of the distance. Seismic Design Criteria Seismic design may be performed using the equivalent static force procedure outlined in the 2012 IBC using the design parameters provided below. TABLE 2. SEISMIC DESIGN PARAMETERS 2012 IBC Spectral Response Accel. at Short Periods (SS) = 1.244 Spectral Response Accel. at 1 Second Periods (S1) = 0.495 Site Class = C Site Coefficient (FA) = 1.0 Site Coefficient (FV) = 1.51 Liquefaction Potential Liquefaction refers to a condition where vibration or shaking of the ground, usually from earthquake forces, results in development of excess pore pressures in loose, saturated soils and subsequent loss of strength in the deposit of soil so affected. In general, soils that are susceptible to liquefaction include loose to medium dense “clean” to silty sands that are below the water table. In our opinion, the potential for liquefaction at this site is low. Shallow Foundations Foundation Support Proposed structures can be satisfactorily founded on continuous wall or isolated column footings supported on densely compacted weathered outwash or undisturbed native soils below the weathered outwash, or on structural fill placed over these materials. If the bearing surface is loose or disturbed it must be compacted to a dense, unyielding condition or the loose soil removed and replaced with compacted structural fill. As noted above, the weathered outwash material contains fine-grained material and will be susceptible to disturbance if wet or compacted during periods of rain. This should be considered during site development and depending on the time of year. The weathered outwash material must be thoroughly compacted to a uniformly dense and unyielding condition prior to construction of foundations. The exterior footings should be established at least 18 inches below the lowest adjacent grade. The recommended minimum footing depth is greater than the anticipated frost depth. Interior footings can be founded a minimum of 12 inches below the top of the floor slab. Isolated column and continuous wall footings should have minimum widths of 24 and 18 inches, respectively. September 14, 2015 | Page 12 File No. 22013-001-00 Bearing Capacity We recommend that footings founded as recommended be proportioned using an allowable soil bearing pressure of 4,000 pounds per square foot (psf). The allowable soil bearing pressure may be increased to 6,000 psf for footings greater than 4 feet in width. The bearing pressures apply to the total of dead and long-term live loads and may be increased by one-third when considering total loads, including earthquake or wind loads. These are net bearing pressures. The weight of the footing and overlying backfill can be ignored in calculating footing sizes. Foundation Drains In general, it is our opinion that foundation drains are not necessary for this project as we have considered some water near the base of the footing in the foundation design recommendations presented. However, due to the fine-grained nature of the weathered outwash, some foundation excavations may experience seepage, depending on the time of year of excavation. In addition, some areas may exhibit wet conditions near the surface depending on how foundations are backfilled, the design of the final grade surrounding the building and other improvements such as irrigation. The use of foundation drains should be determined on a case-by-case basis and consider items such as soil conditions exposed during construction, the presence of seepage or evidence of seepage during excavation, surrounding irrigation lines, direction of the surface water flow surrounding the structure(s), and maintenance programs in place. In some instances, the backfill area around foundations is converted to landscape areas and it is common for surface water to accumulate in these areas, which may require maintenance. Footing Bearing Surface Preparation Footing excavations should be performed using a smooth-edged bucket to limit bearing surface disturbance. The foundation bearing surface should be recompacted as necessary to a dense, non-yielding condition. Loose or disturbed materials present at the base of footing excavations should be removed or compacted. Foundation bearing surfaces should not be exposed to standing water. Should water infiltrate and pool in the excavation, it should be removed before placing structural fill or reinforcing steel. If foundation bearing surfaces will be exposed to wet weather and/or construction traffic, we recommend that they be protected using a crushed rock or lean-mix concrete. Typically, 8 to 12 inches of crushed rock or 4 inches of lean-mix concrete is adequate for protection. We recommend that a member from our firm observe foundation excavations before placing reinforcing steel in order to confirm that adequate bearing surfaces have been prepared or provide recommendations for removal of unsuitable soil. Unsuitable bearing materials should be recompacted or removed and replaced with compacted structural fill as recommended by the geotechnical engineer. Foundation Settlement We estimate that settlement of footings designed and constructed as recommended will be less than 1 inch, for an assumed loading condition of up to 200 kips per column and 6 kips per lineal foot for continuous footings. Differential settlements between comparably loaded isolated column footings or along 50 feet of continuous footing should be less than 1/2 inch. Settlement is expected to occur rapidly as loads are applied. Settlements could be larger than estimated if footings are placed on loose or disturbed soil. We should be contacted if foundation loads are anticipated to be greater than described above. September 14, 2015 | Page 13 File No. 22013-001-00 Lateral Resistance The ability of the soil to resist lateral loads is a function of frictional resistance, which can develop on the base of footings and slabs and the passive resistance, which can develop on the face of below-grade elements of the structure as these elements tend to move into the soil. For footings and floor slabs founded in accordance with the recommendations presented above, the allowable frictional resistance may be computed using a coefficient of friction of 0.40 applied to vertical dead-load forces. The allowable passive resistance on the face of footings, grade beams or other embedded foundation elements may be computed using an equivalent fluid density of 300 pounds per cubic foot (pcf) for undisturbed on-site soils or structural fill extending out from the face of the foundation element a distance at least equal to two and one-half times the depth of the element. The passive earth pressure and friction components may be combined provided that the passive component does not exceed two-thirds of the total. The passive earth pressure value is based on the assumptions that the adjacent grade is level and that groundwater remains below the base of the footing throughout the year. The top foot of soil should be neglected when calculating passive lateral earth pressures unless the foundation area is covered with pavement or slab-on-grade. The lateral resistance values include a safety factor of approximately 1.5. Conventional Subgrade and Retaining Walls Drainage Positive drainage is imperative behind any retaining structure. This can be accomplished by providing a zone of free-draining material behind the wall with perforated pipes to collect seepage water. The drainage material should consist of coarse sand and gravel containing less than 5 percent fines based on the fraction of material passing the 3/4-inch sieve. The wall drainage zone should extend horizontally at least 18 inches from the back of the wall. Perforated smooth-walled rigid PVC pipe having a minimum diameter of 4 inches should be placed at the bottom of the drainage zone along the entire length of the wall, with the pipe invert at or below the elevation of the base of the wall footing. The drainpipes should discharge to a tightline leading to an appropriate collection and disposal system. An adequate number of cleanouts should be incorporated into the design of the drains in order to provide access for regular maintenance. In general, roof downspouts, perimeter drains or other types of drainage systems should not be connected to retaining wall drain systems. Design Parameters The pressures presented assume that backfill placed within 2 feet of the wall is compacted by hand- operated equipment to a density of 90 percent of the MDD and that wall drainage measures are included as previously recommended. For walls constructed as described above, we recommend using an active lateral earth pressure corresponding to an equivalent fluid density of 35 pcf for the level backfill condition. For walls with backfill sloping upward behind the wall at 2H:1V, an equivalent fluid density of 55 pcf should be used. This assumes that the tops of the walls are not structurally restrained and are free to rotate. For the at-rest condition (walls restrained from movement at the top) an equivalent fluid density of 50 pcf should be used for design. For seismic conditions, we recommend a uniform lateral pressure of 8H (where H is the height of the wall) psf be added to these lateral pressures. Note that if the retaining system is designed as a braced system but is expected to yield a small amount during a seismic event, an active earth pressure condition may be assumed and combined with the uniform seismic surcharge pressure. September 14, 2015 | Page 14 File No. 22013-001-00 The recommended pressures do not include the effects of surcharges from surface loads. If vehicles will be operated within one-half the height of the wall, a traffic surcharge should be added to the wall pressure. The traffic surcharge can be approximated by the equivalent weight of an additional 2 feet of backfill behind the wall. Additional surcharge loading conditions should also be considered on a case-by-case basis. Retaining wall foundations may be designed using the allowable soil bearing values and lateral resistance values presented above in the “Shallow Foundations” section of this report provided that bearing surfaces are prepared as recommended. We estimate settlement of retaining structures will be similar to the values previously presented for building foundations. Building Pads and Floor Slabs A modulus of subgrade reaction of 350 pounds per cubic inch (pci) can be used for designing the building floor slab provided that the subgrade consists of dense native soil or structural fill and has been prepared in accordance with the “Site Development and Earthwork” section of this report. Settlement for floor slabs designed and constructed as recommended are estimated to be less than 3/4 inch for a floor load of 250 psf. We estimate that differential settlement of floor slabs will be 1/2 inch or less over a span of 50 feet providing that the fill below the slab is compacted as specified. The subgrade soils are non-expansive, so heave is not anticipated beneath the floor slab. We recommend that on-grade slabs be underlain by a minimum 6-inch-thick capillary break layer to reduce the potential for moisture migration into the slab. The capillary break material should consist of a well- graded sand and gravel or crushed rock with a maximum particle size of 3/4 inch and less than 5 percent fines. The material should be placed as recommended in the “Fill Placement and Compaction” section of this report. If dry slabs are required (e.g., where adhesives are used to anchor carpet or tile to the slab), a waterproof liner may be placed as a vapor barrier below the slab. Pavement Recommendations Asphaltic Concrete Pavement Pavement subgrades and fill should be prepared and placed as previously described. The crushed rock base course should be moisture conditioned near the optimum moisture content and compacted to at least 95 percent of the MDD determined in accordance with ASTM D 1557 test procedures. An appropriate number of in-place density tests should be conducted on the compacted base course to check that adequate compaction has been obtained. Crushed rock base course should conform to applicable sections of 4-04 and 9-03.9(3) of the WSDOT Standards. For this project, we based the recommended pavement sections described below on an assumed in-situ California Bearing Ratio (CBR) between 20 and 25. The heavy-duty pavement section thickness is based on a traffic loading of about 1,000,000, 18-kip equivalent single-axle loads (ESALs); we used a design life of 10 years. The standard-duty section is appropriate for areas that will not be exposed to heavy truck loads. Hot mix asphalt (HMA) should conform to applicable sections of 5-04, 9-02 and 9-03 of the WSDOT Standards. The recommended pavement sections assume that final improvements surrounding the pavement will be designed and constructed such that stormwater or excess irrigation water from landscape areas does not infiltrate below the pavement section into the crushed base. September 14, 2015 | Page 15 File No. 22013-001-00 STANDARD-DUTY ASPHALTIC CONCRETE PAVEMENT ■ 2 inches of hot mix asphalt. ■ 4 inches of crushed surfacing base course and/or top course compacted as recommended. ■ 12 inches compacted depth of granular native subgrades and/or imported structural fill compacted to 95 percent MDD (ASTM D 1557) and in a firm and unyielding condition. HEAVY-DUTY ASPHALTIC CONCRETE PAVEMENT ■ 3 inches of hot mix asphalt. ■ 6 inches of crushed surfacing base course and/or top course compacted as recommended. ■ 12 inches compacted depth of granular native subgrades and/or imported structural fill compacted to 95 percent MDD (ASTM D 1557) and in a firm and unyielding condition. LIMITATIONS We have prepared this report for the exclusive use by D&B Retail Development and their authorized agents for the Yelm Development project located at 1301 Yelm Avenue East in Yelm, Washington, Washington. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Please refer to Appendix B titled “Report Limitations and Guidelines for Use” for additional information pertaining to use of this report. µ SITE Vicinity Map Figure 1 Yelm DevelopmentYelm, Washington 2,000 2,0000 Feet Data Source: Mapbox Open Street Map, 2015 Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Projection: NAD 1983 UTM Zone 10N \\tac\projects\22\22013001\GIS\2201300100_Task100_F01_VM.mxd Date Exported: 09/14/15 by cchelf TP-1 TP-8 TP-2 TP-9 TP-10 TP-3 TP-4 TP-7 TP-5 TP-6 YELM AVE.E.(S.R.507) LOT 1 LOT 2 LOT 3 Feet 060 60 Notes: 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Base survey drawing provided by Larson and Associates. Proposed features provided by architect firm. Projection: NAD83 Washington State Planes, South Zone, US Foot.\\TAC\Projects\22\22013001\00\CAD\Sheetfiles\2201300100_F2.dwgTAB:F2DateExported:09/14/15-11:14bycvanslykeYelm DevelopmentYelm, Washington Site Plan Figure 2Vertical Datum: Thurston County Datum (NGVD 29). TP-1 Test pit number and approximate location Legend APPENDIX A Field Explorations and Laboratory Testing September 14, 2015 | Page A-1 File No. 22013-001-00 APPENDIX A FIELD EXPLORATIONS AND LABORATORY TESTING Subsurface Explorations Soil and groundwater conditions at the proposed development site were explored by excavating 10 test pits on August 14, 2015. Subsurface exploratory services were subcontracted to GeoEngineers, Inc. Eight of the test pit explorations extended to depths between 10 and 12 feet below surrounding site grades. The remaining test pit explorations extended to depths between 15 and 16 feet below surrounding site grades. The locations of the test pits were determined by pacing and visual triangulation from existing site features such as roadways and property corners. The elevations presented on the test pit logs are based on a site plan obtained from Larson and Associates Land Surveyors and Engineers Inc. The locations and elevations of the explorations should be considered approximate. Locations of the explorations are provided on the Site Plan, Figure 2. Our field representative obtained samples, classified the soils, maintained a detailed log of each exploration and observed groundwater conditions where applicable. The samples were retained in sealed plastic bags to prevent moisture loss. The soils were classified visually in general accordance with the system described in Figure A-1, which includes a key to the exploration logs. Summary logs of the explorations are included as Figures A-2 through A-11. The densities noted on the test pit exploration logs are based on the difficulty of excavation, observations of caving and our experience and judgment. Laboratory Testing Soil samples obtained from the test pits were transported to our laboratory and examined to confirm or modify field classifications, as well as to evaluate engineering properties of the soil. Representative samples were selected for laboratory testing. Laboratory testing included moisture content determination conducted in general accordance with ASTM International (ASTM) D 2216 and grain-size analyses conducted in general accordance with ASTM C 136. The sample test depths and moisture content test results are shown on the exploration logs. Sieve analysis results are presented in Figures A-12 and A-13. AC Cement Concrete %F AL CA CP CS DS HA MC MD OC PM PI PP PPM SA TX UC VS CC Asphalt Concrete No Visible Sheen Slight Sheen Moderate Sheen Heavy Sheen Not Tested NS SS MS HS NT ADDITIONAL MATERIAL SYMBOLS Measured groundwater level in exploration, well, or piezometer Measured free product in well or piezometer Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit Graphic Log Contact Groundwater Contact Material Description Contact Laboratory / Field Tests Sheen Classification Percent fines Atterberg limits Chemical analysis Laboratory compaction test Consolidation test Direct shear Hydrometer analysis Moisture content Moisture content and dry density Organic content Permeability or hydraulic conductivity Plasticity index Pocket penetrometer Parts per million Sieve analysis Triaxial compression Unconfined compression Vane shear Sampler Symbol Descriptions NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to be representative of subsurface conditions at other locations or times. GRAPH Topsoil/ Forest Duff/Sod Crushed Rock/ Quarry Spalls Blowcount is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted). See exploration log for hammer weight and drop. A "P" indicates sampler pushed using the weight of the drill rig. FIGURE A-1 2.4-inch I.D. split barrel SYMBOLS TYPICAL KEY TO EXPLORATION LOGS CR DESCRIPTIONSLETTER TS GC PT OH CH MH OL GM GP GW DESCRIPTIONS TYPICAL LETTER (APPRECIABLE AMOUNT OF FINES) MAJOR DIVISIONS POORLY-GRADED SANDS,GRAVELLY SAND PEAT, HUMUS, SWAMP SOILSWITH HIGH ORGANIC CONTENTS CLEAN SANDS GRAVELS WITH FINES CLEAN GRAVELS HIGHLY ORGANIC SOILS SILTS AND CLAYS SILTS AND CLAYS SAND AND SANDY SOILS GRAVEL AND GRAVELLY SOILS (LITTLE OR NO FINES) FINE GRAINED SOILS COARSE GRAINED SOILS SW MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE CL WELL-GRADED SANDS,GRAVELLY SANDS SILTY GRAVELS, GRAVEL - SAND- SILT MIXTURES LIQUID LIMIT GREATER THAN 50 SILTY SANDS, SAND - SILTMIXTURES (APPRECIABLE AMOUNT OF FINES) SOIL CLASSIFICATION CHART LIQUID LIMIT LESS THAN 50 SANDS WITH FINES SP (LITTLE OR NO FINES) ML SC SM NOTE: Multiple symbols are used to indicate borderline or dual soil classifications MORE THAN 50% OF COARSE FRACTION PASSING NO. 4 SIEVE CLAYEY GRAVELS, GRAVEL -SAND - CLAY MIXTURES CLAYEY SANDS, SAND - CLAYMIXTURES INORGANIC SILTS, ROCK FLOUR,CLAYEY SILTS WITH SLIGHT PLASTICITY ORGANIC SILTS AND ORGANICSILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUSOR DIATOMACEOUS SILTY SOILS ORGANIC CLAYS AND SILTS OFMEDIUM TO HIGH PLASTICITY INORGANIC CLAYS OF HIGHPLASTICITY MORE THAN 50% PASSING NO. 200 SIEVE MORE THAN 50% RETAINED ON NO. 200 SIEVE WELL-GRADED GRAVELS,GRAVEL - SAND MIXTURES POORLY-GRADED GRAVELS,GRAVEL - SAND MIXTURES INORGANIC CLAYS OF LOW TOMEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTYCLAYS, LEAN CLAYS GRAPH SYMBOLS Standard Penetration Test (SPT) Shelby tube Piston Direct-Push Bulk or grab Continuous Coring 1 SA 2 SA 3 Grass and topsoil Brown silty sand with gravel (loose to medium dense, dry to moist) Yellowish-brown silty fine to medium sand with occasional gravel (medium dense, moist) Gray fine to coarse gravel with sand occasional cobbles and trace silt (dense, moist) Increased sand content Test pit completed at 12 feet No groundwater seepage observed Moderate caving observed at 3.5 to 6 feet TS SM SM GP 9 4 %F=13 %F=2 Cobble/boulders; up to 1 foot in diameter observed Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)348347346345344343342341340339338337Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-1 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-2 Sheet 1 of 1 1 2 3 SA Gravel, base rock Brown silty fine sand with gravel (medium dense, moist) Yellow-brown fine to medium sand with silt, occasional gravel (medium dense, moist) Yellow-gray fine to coarse gravel with occasional cobbles and sand and trace silt (medium dense, moist) Grades to with sand and medium dense to dense Test pit completed at 12 feet No groundwater seepage observed Moderate caving observed at 0 to 7 feet GW SM SP-SM GW 4 Cobble/boulders; up to 1 foot in diameter observed %F=2 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)348347346345344343342341340339338337Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-2 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-3 Sheet 1 of 1 1 2 SA 3 Brown silty fine sand with gravel (loose, dry to moist) Yellow-brown fine to medium sand with silt, occasional gravel (medium dense, moist) Gray medium to coarse gravel with sand and occasional cobbles and trace silt (medium dense, moist) Test pit completed at 16 feet No groundwater seepage observed Moderate caving observed at 0 to 6 feet SM SP-SM GW 2 Cobble/boulders; up to 1 foot in diameter observed %F=1 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 16.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 SAMPLE Graphic LogElevation (feet)349348347346345344343342341340339338337336335334Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-3 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-4 Sheet 1 of 1 1 2 3 SA Brown silty fine sand with gravel (loose, dry) Yellow-brown fine to medium sand with silt and occasional gravel (medium dense, moist) Gray fine to coarse gravel with sand and occasional cobbles and silt (medium dense, moist) Grades to with sand and dense Test pit completed at 15.5 feet No groundwater seepage observed Moderate caving observed at 0 to 6 feet SM SP-SM GP 3 Cobble/boulders; up to 1 foot in diameter observed %F=1 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 15.5 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 SAMPLE Graphic LogElevation (feet)349348347346345344343342341340339338337336335334Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-4 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-5 Sheet 1 of 1 1 2 SA 3 SA 4 Grass and topsoil Brown fine to coarse gravel with sand and silt and occasional cobbles and organic matter (roots) (loose to medium dense, dry) Yellow-brown fine to coarse gravel with sand, occasional cobbles, trace silt (medium dense to dense, moist) Yellow silty fine sand (medium dense, moist) Brown-gray fine to coarse gravel with sand and occasional cobbles and trace silt (medium dense to dense, dry to moist) Grades to moist Test pit completed at 12 feet No groundwater seepage observed Moderate caving observed at 2.5 to 12 feet bgs TS GP-GM GP SM GP 6 3 %F=13 Cobble/boulders; up to 1 foot in diameter observed %F=2 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)351350349348347346345344343342341340Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-5 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-6 Sheet 1 of 1 1 2 SA Grass and topsoil Brown fine to coarse gravel with silt and sand and occasional cobbles and organic matter (roots) (medium dense, dry) Yellow-brown fine to coarse gravel with sand, occasional cobbles and trace silt (medium dense, dry) Yellow-brown silty fine sand (medium dense, dry) Gray-brown fine to coarse gravel with sand and occasional cobbles and trace silt (medium dense to dense, dry to moist) Test pit completed at 11 feet No groundwater seepage observed Minor caving observed at 1 to 11 feet TS GP-GM GP SM GP 3 Cobble/boulders; up to 1 foot in diameter observed %F=2 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 11.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 SAMPLE Graphic LogElevation (feet)351350349348347346345344343342341Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-6 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-7 Sheet 1 of 1 1 2 Grass and topsoil Brown fine to coarse gravel with silt, sand and occasional organic matter (roots) (medium dense, dry) Brown-gray fine to coarse gravel with sand and occasional cobbles and trace silt (medium dense to dense, moist) Sand becomes medium to coarse Test pit completed at 10 feet No groundwater seepage observed Minor caving observed at 3 to 10 feet TS GP-GM GP Cobble/boulders; up to 1 foot in diameter observed Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 10.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 SAMPLE Graphic LogElevation (feet)351350349348347346345344343342Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-7 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-8 Sheet 1 of 1 1 2 Topsoil and grass Brown silty fine to medium gravel with sand and occasional organic matter (roots) (medium dense, dry) Yellow-brown fine to medium sand with silt and occasional gravel and trace cobbles (medium dense, moist) Yellow-brown fine to coarse gravel with sand and trace silt (medium dense to dense, moist) Test pit completed at 11.5 feet No groundwater seepage observed Moderate caving observed at 3.5 to 11.5 feet TS GM SP-SM GP Cobble/boulders; up to 1 foot in diameter observed Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 11.5 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 SAMPLE Graphic LogElevation (feet)348347346345344343342341340339338Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-8 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-9 Sheet 1 of 1 1 2 3 Topsoil and grass Brown silty fine to coarse gravel with sand and occasional organic matter (roots) (medium dense, dry) Yellow-brown fine to coarse gravel with sand (medium dense to dense, moist) Yellow-gray fine to medium sand with silt and occasional gravel (medium dense, dry to moist) Gray fine to coarse gravel with sand and occasional cobbles and trace silt (medium dense to dense, moist) Test pit completed at 12 feet No groundwater seepage observed Minor to moderate caving observed at 4 to 12 feet TS GM GP SP-SM GP Cobble/boulders; up to 1 foot in diameter observed Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)349348347346345344343342341340339338Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-9 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-10 Sheet 1 of 1 1 2 3 Grass and topsoil Brown silty fine to coarse gravel with sand and occasional organic matter (roots) (medium dense, dry) Gray-brown fine to coarse gravel with sand and occasional cobbles (medium dense, dry to moist) Yellow-brown fine sand with silt (medium dense, moist) Gray fine to coarse gravel with sand and occasional cobbles and trace silt (dense, moist) Test pit completed at 11 feet No groundwater seepage observed Minor to moderate caving observed at 4.5 to 11 feet TS GM GP SP-SM GP Cobble/boulders; up to 1 foot in diameter observed Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Tacoma: Date:9/15/15 Path:P:\22\22013001\GINT\2201300100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTECDate Excavated: Equipment: Logged By:8/14/2015 Komatsu PC120 Total Depth (ft) BK 11.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 SAMPLE Graphic LogElevation (feet)350349348347346345344343342341340Sample NameTestingMATERIAL DESCRIPTION GroupClassificationEncountered WaterMoistureContent, %REMARKS Log of Test Pit TP-10 Yelm Development Yelm, Washington 22013-001-00 Project: Project Location: Project Number:Figure A-11 Sheet 1 of 1 Note: This report may not be reproduced, except in full, without written approval of GeoEngineers, Inc. Test results are applicable only to the specific sample on which they wereperformed, and should not be interpreted as representative of any other samples obtained at other times, depths or locations, or generated by separate operations or processes.The grain size analysis results were obtained in general accordance with ASTM D 6913..Figure A-12 Sieve Analysis Results Yelm Development Yelm, Washington 22013-001-00 Date Exported: 08/21/15EXPLORATION NUMBERDEPTH(ft)LABORATORY SOIL CLASSIFICATIONTP-1TP-1TP-2TP-33.5 811.510Silty sand (SM)Poorly graded gravel with sand (GP)Well-graded gravel with sand (GW)Well-graded gravel (GW)SYMBOLSANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERS3/8”3” #20 #200#40 #60#1001.5” #10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZE Note: This report may not be reproduced, except in full, without written approval of GeoEngineers, Inc. Test results are applicable only to the specific sample on which they wereperformed, and should not be interpreted as representative of any other samples obtained at other times, depths or locations, or generated by separate operations or processes.The grain size analysis results were obtained in general accordance with ASTM D 6913..Figure A-13 Sieve Analysis Results Yelm Development Yelm, Washington 22013-001-00 Date Exported: 08/21/15EXPLORATION NUMBERDEPTH(ft)SOIL CLASSIFICATIONTP-4TP-5TP-5TP-61369.59.5Poorly graded gravel with sand (GP)Silty sand (SM)Poorly graded gravel with sand (GP)Poorly graded gravel with sand (GP)SYMBOLSANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERS3/8”3” #20 #200#40 #60#1001.5” #10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZE APPENDIX B Report Limitations and Guidelines for Use September 14, 2015 | Page B-1 File No. 22013-001-00 APPENDIX B REPORT LIMITATIONS AND GUIDELINES FOR USE1 This appendix provides information to help you manage your risks with respect to the use of this report. Geotechnical Services are Performed for Specific Purposes, Persons and Projects This report has been prepared for the exclusive use by D&B Retail Development and their authorized agents. This report is not intended for use by others, and the information contained herein is not applicable to other sites. GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted geotechnical practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated. A Geotechnical Engineering or Geologic Report is Based on a Unique Set of Project-Specific Factors This report has been prepared for the Yelm Development project located at 1301 Yelm Avenue East in Yelm, Washington. GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates otherwise, do not rely on this report if it was: ■ not prepared for you, ■ not prepared for your project, ■ not prepared for the specific site explored, or ■ completed before important project changes were made. For example, changes that can affect the applicability of this report include those that affect: ■ the function of the proposed structure; ■ elevation, configuration, location, orientation or weight of the proposed structure; ■ composition of the design team; or 1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org. September 14, 2015 | Page B-2 File No. 22013-001-00 ■ project ownership. If important changes are made after the date of this report, GeoEngineers should be given the opportunity to review our interpretations and recommendations and provide written modifications or confirmation, as appropriate. Subsurface Conditions Can Change This geotechnical or geologic report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by manmade events such as construction on or adjacent to the site, or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. Always contact GeoEngineers before applying a report to determine if it remains applicable. Topsoil For the purposes of this report, we consider topsoil to consist of generally fine-grained soil with an appreciable amount of organic matter based on visual examination, and to be unsuitable for direct support of the proposed improvements. However, the organic content and other mineralogical and gradational characteristics used to evaluate the suitability of soil for use in landscaping and agricultural purposes was not determined, nor considered in our analyses. Therefore, the information and recommendations in this report, and our logs and descriptions should not be used as a basis for estimating the volume of topsoil available for such purposes. Most Geotechnical and Geologic Findings Are Professional Opinions Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then applied our professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. Geotechnical Engineering Report Recommendations Are Not Final Do not over-rely on the preliminary construction recommendations included in this report. These recommendations are not final, because they were developed principally from GeoEngineers’ professional judgment and opinion. GeoEngineers’ recommendations can be finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability for this report's recommendations if we do not perform construction observation. Sufficient monitoring, testing and consultation by GeoEngineers should be provided during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork activities are completed in accordance with our recommendations. Retaining GeoEngineers for construction observation for this project is the most effective method of managing the risks associated with unanticipated conditions. September 14, 2015 | Page B-3 File No. 22013-001-00 A Geotechnical Engineering or Geologic Report Could be Subject to Misinterpretation Misinterpretation of this report by other design team members can result in costly problems. You could lower that risk by having GeoEngineers confer with appropriate members of the design team after submitting the report. Also retain GeoEngineers to review pertinent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering or geologic report. Reduce that risk by having GeoEngineers participate in pre-bid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Exploration Logs Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering or geologic report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering or geologic report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only then might an owner be in a position to give contractors the best information available, while requiring them to at least share the financial responsibilities stemming from unanticipated conditions. Further, a contingency for unanticipated conditions should be included in your project budget and schedule. Contractors are Responsible for Site Safety on their Own Construction Projects Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to on-site personnel and to adjacent properties. Read These Provisions Closely Some clients, design professionals and contractors may not recognize that the geoscience practices (geotechnical engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. GeoEngineers includes these explanatory “limitations” provisions in our reports to help reduce such risks. Please confer with GeoEngineers if you are unclear how these “Report Limitations and Guidelines for Use” apply to your project or site. Geotechnical, Geologic and Environmental Reports Should not be Interchanged The equipment, techniques and personnel used to perform an environmental study differ significantly from those used to perform a geotechnical or geologic study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually relate any environmental findings, conclusions or September 14, 2015 | Page B-4 File No. 22013-001-00 recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding a specific project. Biological Pollutants GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention, or assessment of the presence of Biological Pollutants in or around any structure. Accordingly, this report includes no interpretations, recommendations, findings, or conclusions for the purpose of detecting, preventing, assessing, or abating Biological Pollutants. The term “Biological Pollutants” includes, but is not limited to, molds, fungi, spores, bacteria, and viruses, and/or any of their byproducts.