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Home My WebLink AboutEX12_Geotechnical_ReportEarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineering Construction Observation/Testing Environmental Services 15365 N.E.90th Street,Suite 100 Redmond,WA 98052 (425)449-4704 Fax (425)449-4711 www.earthsolutionsnw.com GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON,WASHINGTON ES-7334 EXHIBIT 12 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 PREPARED FOR MAINVUE WA, LLC March 16, 2021 _________________________ Keven D. Hoffmann, P.E. Senior Project Manager _________________________ Kyle R. Campbell, P.E. Principal Engineer GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON, WASHINGTON ES-7334 Earth Solutions NW, LLC 15365 Northeast 90th Street, Suite 100 Redmond, Washington 98052 Phone: 425-449-4704 | Fax: 425-449-4711 www.earthsolutionsnw.com 03/16/2021 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Geotechnical-Engineering Report Important Information about This Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project. Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities. The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions. Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical- engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project. Do not rely on this report if your geotechnical engineer prepared it: • for a different client; • for a different project or purpose; • for a different site (that may or may not include all or a portion of the original site); or • before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations. Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems. Read this Report in Full Costly problems have occurred because those relying on a geotechnical- engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full. You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys. Typical changes that could erode the reliability of this report include those that affect: • the site’s size or shape; • the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria; • the composition of the design team; or • project ownership. As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered. Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed. This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation. This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical- engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to: • confer with other design-team members; • help develop specifications; • review pertinent elements of other design professionals’ plans and specifications; and • be available whenever geotechnical-engineering guidance is needed. You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction- phase observations. Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect. Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes. To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance. Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies. Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists. Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation. Telephone: 301/565-2733 e-mail: info@geoprofessional.org www.geoprofessional.org DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 March 16, 2021 ES-7334 MainVue WA, LLC 1110 – 112th Avenue Northeast, Suite 202 Bellevue, Washington 98004 Attention: Ms. Lisa Cavell Greetings, Ms. Cavell: Earth Solutions NW, LLC (ESNW) is pleased to present this geotechnical report for the subject site. Our investigation indicates the proposed short plat is feasible from a geotechnical standpoint generally as planned. The site is underlain primarily by recessional outwash sand, with varying fines content. The proposed residential structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill. We anticipate competent native soil suitable for support of foundations will be encountered beginning at a depth of about two feet below existing grades. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations, compaction of the soil to the specifications of structural fill or overexcavation and replacement with suitable structural fill will likely be necessary. This report provides geotechnical analyses and recommendations for the proposed short plat. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Keven D. Hoffmann, P.E. Senior Project Manager 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 •(425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Table of Contents ES-7334 PAGE INTRODUCTION ................................................................................. 1 General..................................................................................... 1 Project Description ................................................................. 2 SITE CONDITIONS ............................................................................. 2 Surface ..................................................................................... 2 Subsurface .............................................................................. 2 Topsoil and Fill ............................................................. 3 Native Soil ..................................................................... 3 Geologic Setting ........................................................... 3 Groundwater ................................................................. 3 Critical Areas Review ............................................................. 3 DISCUSSION AND RECOMMENDATIONS ....................................... 4 General..................................................................................... 4 Site Preparation and Earthwork ............................................. 4 Temporary Erosion Control ......................................... 4 In-Situ and Imported Soil ............................................. 5 Structural Fill ................................................................ 5 Subgrade Preparation .................................................. 6 Excavations and Slopes .............................................. 6 Foundations ............................................................................ 6 Seismic Design ....................................................................... 7 Slab-on-Grade Floors ............................................................. 8 Retaining Walls ....................................................................... 8 Drainage................................................................................... 9 Infiltration Testing & Design ....................................... 9 Permeable Pavement Design ...................................... 10 Soil Properties for Groundwater Protection .............. 11 Drywells & Gravel-filled Trenches .............................. 11 Utility Support and Trench Backfill ....................................... 11 LIMITATIONS ...................................................................................... 12 Additional Services ................................................................. 12 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Table of Contents Cont’d ES-7334 GRAPHICS Plate 1 Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail APPENDICES Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Test Results DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC GEOTECHNICAL ENGINEERING STUDY PROPOSED SHORT PLAT 1400 ABERDEEN AVENUE NORTHEAST RENTON, WASHINGTON ES-7334 INTRODUCTION General This geotechnical engineering study was prepared for the proposed short plat to be constructed southeast of the intersection between Northeast 15th Street and Aberdeen Avenue Northeast, in Renton, Washington. This report was prepared to aid the subject project with respect to the currently proposed site layout. To prepare this report, the following scope items or services were completed:  Subsurface exploration to characterize the soil and groundwater conditions.  In-situ infiltration testing.  Laboratory testing of representative soil samples collected on site.  Review of on-site critical areas.  Engineering analyses and recommendations for the proposed short plat. The following documents and resources were reviewed as part of our report preparation:  Draft ALTA/NSPS Land Title Survey, prepared by Barghausen Consulting Engineers, Inc., dated November 21, 2020.  Geologic Map of King County, compiled by Derek B. Booth, Kathy G. Troost, and Aaron P. Wisher, dated March 2007.  Online Web Soil Survey (WSS) resource, maintained by the Natural Resources Conservation Service (NRCS) under the United States Department of Agriculture (USDA).  Liquefaction Susceptibility of King County (Map 11-5), endorsed by the King County Flood Control District, dated May 2010.  Renton Municipal Code (RMC).  Online COR Maps Resource, maintained by the City of Renton.  2017 City of Renton Surface Water Design Manual. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 2 Earth Solutions NW, LLC Project Description We understand the existing residential structures will be removed, and a short plat will be constructed. At the time this report was prepared, neither a formal site plan nor building load values were available for review. However, we anticipate the proposed residential structures will be two to three stories and constructed using relatively lightly loaded wood framing supported atop conventional foundation systems. Based on our experience with similar developments, we estimate wall loads of about 1 to 2 kips per linear foot and slab-on-grade loading of 150 pounds per square foot (psf) will be incorporated into the final design. Grade cuts and fills to establish individual-lot subgrade and finish grade elevations are expected to be less than five feet. Retaining walls or rockeries may be constructed across the plat to accommodate grade transitions, where necessary. A stormwater infiltration facility will likely be constructed within the topographically low area of the site (southeastern corner). If the above design assumptions either change or are incorrect, ESNW should be contacted to review the recommendations provided in this report. ESNW should review final designs to verify the geotechnical recommendations provided in this report have been incorporated into the plans. SITE CONDITIONS Surface The subject site is located southeast of the intersection between Northeast 15 th Street and Aberdeen Avenue Northeast, in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map). The site is comprised of one tax parcel (King County Parcel No. 334390-1680), totaling about 1.68 acres. The site is currently occupied by a single-family residence and various outbuildings. The existing topography descends generally from north to south, with an estimated 10 to 15 feet of elevation change across the site. Vegetation consists mainly of lawn areas, with several scattered trees. Subsurface An ESNW representative observed, logged, and sampled six test pits on June 4, 2020. The test pits were excavated at accessible locations within the property, using a trackhoe and operator retained by our firm. The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with both Unified Soil Classification System (USCS) and USDA methods and procedures. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 3 Earth Solutions NW, LLC Topsoil and Fill Topsoil was generally encountered within the upper six inches of existing grades at the test locations. The topsoil was characterized by a dark brown color, the presence of fine organic material, and small root intrusions. Fill was encountered at TP-2 to a depth of roughly six inches below the existing ground surface (bgs). The fill contained wire debris and trace root intrusions. Fill was not encountered elsewhere on site. Native Soil Underneath the topsoil, the native soil consisted primarily of poorly graded sand with varying silt content. Within roughly the upper two-and-one-half to five feet of existing grades, sand with appreciable fines content (USCS: SP-SM or SM) was encountered. The native soil graded to comparatively cleaner sand (USCS: SP) at depth, except at TP-4. The native deposits were observed primarily in a “moist” or “moist to wet” condition at the time of the exploration. The maximum exploration depth was roughly 18.5 feet bgs. Geologic Setting Based on our review of the referenced geologic map, the site is underlain by recessional outwash (Qvr). Recessional outwash was deposited by glacial meltwater and is readily comprised of silt, clay, sand, and gravel. The referenced WSS resource identifies Indianola loamy sand (Map Unit Symbol: InC) across the site and surrounding area. The Indianola series was formed in eskers, kames, and terraces. Based on our field observations, the native soil encountered on site is generally consistent with the information presented in the referenced geologic and soil mapping resources. Groundwater Groundwater was not encountered at the test locations during the June 2020 exploration. Nonetheless, transient, perched groundwater seepage may develop seasonally and may be encountered within site excavations depending on the time of year and extent of grading activities. Seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the winter, spring, and early summer months. Critical Areas Review To evaluate the presence of critical areas on site, we reviewed RMC Chapter 4-3 and the online COR Maps resource. The RMC provides designation and definition criteria for identifying critical areas and developing appropriate site development plans to limit adverse impacts to critical areas both on and off site. Based on our review, the site is mapped within Zone 2 of a Wellhead Protection Area (WPA). No other critical areas (including coalmine hazard, high erosion hazard, flood hazard, landslide hazard, regulated slopes, and seismic hazard) are mapped on site or immediately adjacent to the site. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 4 Earth Solutions NW, LLC With respect to the mapped WPA, the proposal should comply with the requirements of RMC 4- 3-050, particularly concerning activities that are not permitted within a WPA. Residential plats are commonly constructed within WPAs and critical aquifer recharge areas, including those that incorporate stormwater infiltration into the final design. Based on our understanding of the project, the proposal does not intend to incorporate activities that would adversely impact the WPA or would otherwise be prohibited under the RMC. ESNW can provide additional consulting and plan review services pertaining to the WPA, upon request. DISCUSSION AND RECOMMENDATIONS General Based on the results of our investigation, construction of the proposed short plat is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include site preparation and earthwork, suitability of on-site soil as structural fill, subgrade preparation, temporary excavations, building foundations, and stormwater facility construction. Site Preparation and Earthwork Site preparation activities should consist of installing temporary erosion control measures, removing existing structural improvements, and performing site stripping within the designated clearing limits. Subsequent earthwork activities will involve mass grading and utility installations. Temporary Erosion Control The following temporary erosion and sediment control (TESC) Best Management Practices (BMPs) are offered:  Temporary construction entrances and drive lanes, consisting of at least six inches of quarry spalls, should be considered to both minimize off-site soil tracking and provide a stable access entrance surface. Placing geotextile fabric underneath the quarry spalls will provide greater stability, if needed.  Silt fencing should be placed around appropriate portions of the site perimeter.  When not in use, soil stockpiles should be covered or otherwise protected to reduce the potential for soil erosion, especially during periods of wet weather.  Temporary measures for controlling surface water runoff, such as interceptor trenches, sumps, or interceptor swales, should be installed prior to beginning earthwork activities.  Dry soils disturbed during construction should be wetted to minimize dust.  When appropriate, permanent planting or hydroseeding will help to stabilize the site soil. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 5 Earth Solutions NW, LLC Additional TESC BMPs, as specified by the project civil engineer and indicated on the plans, should be incorporated into construction activities. TESC measures may be modified during construction as site conditions require but should be discussed with and approved by the site erosion control lead. In-Situ and Imported Soil On-site soil exposed during earthwork and grading activities will likely consist primarily of silty sand and poorly graded sand with silt. The native soil possesses moderate moisture sensitivity and will not be suitable for use as structural fill unless the soil is at (or slightly above) the optimum moisture content at the time of placement and compaction. If the on-site soil cannot be successfully compacted, the use of an imported soil may be necessary. In our opinion, a contingency should be provided in the project budget for export of soil that cannot be successfully compacted as structural fill if grading activities take place during periods of rainfall activity. We recommend avoiding construction-equipment tracking across the native soil and generally active site work during periods of heavy rainfall; such disturbance has the potential to degrade the native soil beyond a workable state. Imported soil intended for use as structural fill should consist of a well-graded, granular soil with a moisture content that is at (or slightly above) the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded, granular soil with a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines:  Structural fill material Granular soil*  Moisture content At or slightly above optimum †  Relative compaction (minimum) 95 percent (Modified Proctor)  Loose lift thickness (maximum) 12 inches * Existing soil will not be suitable for use as structural fill unless at (or slightly above) the optimum moisture content at the time of placement and compaction. † Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 6 Earth Solutions NW, LLC Subgrade Preparation Following site stripping, ESNW should observe the subgrade to confirm soil conditions are as anticipated and to provide supplementary recommendations for subgrade preparation, as necessary. In general, foundation subgrade surfaces should be compacted in situ to a minimum depth of one foot below the design subgrade elevation. Uniform compaction of the foundation and slab subgrade areas will establish a relatively consistent subgrade condition below the foundation and slab elements. Supplementary recommendations for subgrade improvement may be provided at the time of construction and would likely include further mechanical compaction or overexcavation and replacement with suitable structural fill. Excavations and Slopes Excavation activities are likely to expose medium dense silty sand and/or poorly graded sand. Based on the soil conditions observed at the test pit locations, a maximum inclination of one-and- one-half horizontal to one vertical (1.5H:1V) is recommended for temporary excavations and slopes. Per Federal Occupation Safety and Health Administration and Washington Industrial Safety and Health Act standards, the native soil classifies as Type C. Steeper temporary inclinations with dense, undisturbed native soil (such as 1H:1V) may be feasible but must be evaluated by ESNW on a case-by-case basis during construction. Permanent slopes should be planted with vegetation to both enhance stability and minimize erosion and should maintain a gradient of 2H:1V or flatter. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations, as necessary. Foundations The proposed residential structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill. We anticipate competent native soil suitable for support of foundations will be encountered beginning at a depth of about two feet bgs. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations, compaction of the soil to the specifications of structural fill or overexcavation and replacement with suitable structural fill will likely be necessary. Provided the structure will be supported as described above, the following parameters may be used for design of the new foundations:  Allowable soil bearing capacity 2,500 psf  Passive earth pressure 300 pcf  Coefficient of friction 0.40 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 7 Earth Solutions NW, LLC A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The passive earth pressure and coefficient of friction values include a safety factor of 1.5. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. Most of the settlement should occur during construction when dead loads are applied. Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test pit locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class D* Mapped short period spectral response acceleration, S S (g) 1.437 Mapped 1-second period spectral response acceleration, S 1 (g) 0.492 Short period site coefficient, Fa 1.000 Long period site coefficient, Fv 1.808† Adjusted short period spectral response acceleration, S MS (g) 1.437 Adjusted 1-second period spectral response acceleration, S M1 (g) 0.890† Design short period spectral response acceleration, S DS (g) 0.958 Design 1-second period spectral response acceleration, S D1 (g) 0.593† * Assumes medium dense native soil conditions, encountered to a maximum depth of 18.5 feet bgs during the June 2020 field exploration, remain medium dense (or dense) to at least 100 feet bgs. † Values assume Fv may be determined using linear interpolation per Table 11.4-2 in ASCE 7-16. As indicated in the table footnote, several of the seismic design values provided above are dependent on the assumption that site-specific ground motion analysis (per Section 11.4.8 of ASCE 7-16) will not be required for the subject project. ESNW recommends the validity of this assumption be confirmed at the earliest available opportunity during the planning and early design stages of the project. Further discussion between the project structural engineer, the project owner, and ESNW may be prudent to determine the possible impacts to the structural design due to increased earthquake load requirements under the 2018 IBC. ESNW can provide additional consulting services to aid with design efforts, including supplementary geotechnical and geophysical investigation, upon request. Liquefaction is a phenomenon where saturated or loose soil suddenly loses internal strength and behaves as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered low. The absence of a shallow groundwater table and the relatively dense characteristics of the native soil were the primary bases for this opinion. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 8 Earth Solutions NW, LLC Slab-on-Grade Floors Slab-on-grade floors should be supported on firm and unyielding subgrades consisting of competent native soil or at least 12 inches of new structural fill. Unstable or yielding subgrade areas should be recompacted or overexcavated and replaced with suitable structural fill prior to slab construction. A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel should be placed below each slab. The free-draining material should have a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If used, the vapor barrier should consist of a material specifically designed to function as a vapor barrier and should be installed in accordance with the manufacturer’s specifications. Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for retaining wall design:  Active earth pressure (unrestrained condition) 35 pcf  At-rest earth pressure (restrained condition) 55 pcf  Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)  Passive earth pressure 300 pcf  Coefficient of friction 0.40  Seismic surcharge 8H psf* * Where H equals the retained height (in feet) The passive earth pressure and coefficient of friction values include a safety factor of 1.5. Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with free-draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. If drainage is not provided, hydrostatic pressures should be included in the wall design. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 9 Earth Solutions NW, LLC Drainage Discrete zones of perched groundwater seepage should be anticipated in site excavations depending on the time of year grading operations take place. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches, interceptor swales, and sumps. ESNW should be consulted during preliminary grading to both identify areas of seepage and provide recommendations to reduce the potential for seepage-related instability. Finish grades must be designed to direct surface drain water away from structures and slopes. Water must not be allowed to pond adjacent to structures or slopes. In our opinion, foundation drains should be installed along building perimeter footings. A typical foundation drain detail is provided on Plate 4. Infiltration Testing & Design In accordance with the 2017 City of Renton Surface Water Design Manual (2017 RSWDM), one small-scale Pilot Infiltration Test (PIT) was completed during the fieldwork. The PIT was completed at TP-3 by excavating a test pit with a roughly three-foot by four-foot base infiltration surface. The infiltration test was completed at a depth of about five feet bgs and followed the PIT procedure prescribed in the 2017 RSWDM. Based on the results of the PIT, the following design parameters are recommended:  Imeasured (measured infiltration rate; TP-3) 44 inches per hour (in/hr)  Ftesting 0.5 (small-scale PIT)  Fgeometry 0.75 (assumed)  Fplugging 0.9 (medium sand)  Idesign (calculated infiltration rate; TP-3) 14.8 in/hr ESNW should be contacted to review stormwater management plans if infiltration is used for design. Supplementary recommendations and/or testing may be necessary depending on the size, depth, and siting of infiltration facilities. Per pages 5-51 and 5-52 of the 2017 RSWDM, the native soil underneath an infiltration facility is expected to inherently possess specific characteristics to minimize groundwater contamination. The test results provided in the Soil Properties for Groundwater Protection section of this report indicate the native soil in the proposed infiltration facility area does not meet the groundwater- protection requirements, mainly due to suboptimal cation exchange capacity (CEC) values and rapid infiltration rates. Accordingly, water quality treatment will need to be provided prior to infiltration. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 10 Earth Solutions NW, LLC Permeable Pavement Design We understand permeable pavement may be incorporated into the final design. Because the permeable roadway surface would be used for occasional emergency vehicle access, the design must comply with H-20 loading specifications. Based on the soil conditions encountered at the exploration locations, the following permeable pavement sections are offered to meet H-20 loading specifications from a geotechnical standpoint:  Permeable base course (for either permeable asphalt or permeable concrete) o Minimum thickness: 12 inches o Material: Permeable ballast per WSDOT 9-03.9(2), or approved equivalent o Void content: 30 to 40 percent  Permeable asphalt o Minimum thickness: 3 inches of permeable warm-mix asphalt (WMA) underlain by 4 inches of asphalt-treated permeable base o Permeable hot-mix asphalt (HMA) is allowed in lieu of WMA, but WMA is preferred  Permeable concrete o Minimum thickness: 6 inches o Unit weight: 120 to 135 pcf o Void content: 18 to 20 percent Per page C-76 of the 2017 RSWDM, the native soil underneath the permeable pavement surface must meet minimum CEC and organic content (OC) values of 8 meq/100 g and 1.0 percent, respectively. The test results provided in the Soil Properties for Groundwater Protection section of this report indicate the native soil expected to underlie permeable pavement areas will not meet these minimum requirements. Accordingly, a six-inch sand layer must be included in the design beneath the permeable pavement. ESNW should be retained to observe pavement installation activities and provide applicable consulting and testing services. Supplementary recommendations may be provided at the time of construction, as needed. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 11 Earth Solutions NW, LLC Soil Properties for Groundwater Protection Representative soil samples were analyzed for CEC, OC, and grain size distribution. The results of the relevant testing are summarized in the table below, and the laboratory data is provided in Appendix B. Test Pit Depth (ft bgs) CEC (meq/100 g) OC (%) % Passing No. 4 Sieve % Passing No. 40 Sieve % Passing No. 100 Sieve TP-1 2.0 5.6 2.5 99.8 67.0 10.3 TP-2 2.0 7.9 3.4 (not sieved) TP-3 5.0 3.7 1.4 (not sieved) TP-3 10.5 2.8 1.1 98.3 23.0 2.1 TP-4 2.5 5.4 2.5 (not sieved) TP-5 3.0 5.1 2.0 100 82.5 24.4 TP-6 2.5 8.1 3.8 99.6 78.0 25.4 Drywells & Gravel-filled Trenches Where drywells and/or gravel-filled trenches are incorporated into the final design, it is our opinion the dominant soil grain size should be considered “medium sand”. Per page C-47 of the 2017 RSWDM, drywells must contain at least 90 cubic feet of gravel per 1,000 square feet of impervious surface served. Gravel-filled trenches must be at least 30 feet in length per 1,000 square feet of impervious surface served. ESNW can provide additional consulting services and recommendations for full infiltration BMPs, upon request. Utility Support and Trench Backfill In our opinion, the native soil will likely be suitable for support of utilities. Remedial measures may be necessary in some areas to provide support for utilities, such as overexcavation and replacement with structural fill and/or placement of geotextile fabric. Groundwater seepage may be encountered within utility excavations, and caving of trench walls should be anticipated given the cohesionless nature of site soils. Depending on the time of year and conditions encountered, dewatering or temporary trench shoring may be necessary during utility excavation and installation. In general, the native soil may not be suitable for use as structural backfill throughout utility trench excavations unless the soil is at (or slightly above) the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soil may be necessary at some locations prior to use as structural fill. Each section of the utility lines must be adequately supported in appropriate bedding material. Utility trench backfill should be placed and compacted to the specifications of structural fill previously detailed in this report or to the applicable specifications of the presiding jurisdiction. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 MainVue WA, LLC ES-7334 March 16, 2021 Page 12 Earth Solutions NW, LLC LIMITATIONS This study has been prepared for the exclusive use of MainVue WA, LLC, and its representatives. The recommendations and conclusions provided in the geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. No warranty, express or implied, is made. Variations in the soil and groundwater conditions observed at the test pit locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions provided in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provided testing and consultation services during construction. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 1 Earth Solutions NWLLC Geotechnical Engineering,Construction EarthSolutionsNWLLC EarthSolutions NW LLC Obser vation/Testing and Environmental Services Vicinity Map Vaughn Short Plat Renton,Washington NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Reference: King County,Washington OpenStreetMap.org NORTH SITE Renton DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Plate Proj.No. Date Checked By Drwn.ByEarthSolutionsNWLLCGeotechnicalEngineering,ConstructionObservation/TestingandEnvironmentalServicesEarthSolutionsNWLLCEarthSolutionsNWLLCTestPitLocationPlanVaughnShortPlatRenton,WashingtonNORTH NOT -TO -SCALE NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Test Pit,Proj.No. ES-7334,June 2020 Subject Site Existing Building TP-1 MRS KDH 03/09/2021 7334 2 TP-1 TP-2 TP-3 TP-4 TP-5 TP-6ABERDEEN AVENUE N.E.N .E. 1 5 T H S TR EE T 300 290 300 290292 294 296 298 302 304 306 292 294 296 298 302 304 306 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 3 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineer ing,C onstr uction Observation/Testing and Environmental Services Retaining Wall Drainage Detail Vaughn Short Plat Renton,Washington NOTES: Free-draining Backfill should consist of soil having less than 5 percent fines. Percent passing No.4 sieve should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free-draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: Free-draining Structural Backfill 1-inch Drain Rock 18"Min. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Drwn.MRS Checked KDH Date Mar.2021 Date 03/09/2021 Proj.No.7334 Plate 4 Earth Solutions NWLLC Geotechnical Engineering,Construction Observation/Testing and Environmental Services EarthSolutionsNWLLC EarthSolutions NW LLC Footing Drain Detail Vaughn Short Plat Renton,Washington Slope Perforated Rigid Drain Pipe (Surround in Drain Rock) 18"Min. NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal:native soil or other low-permeability material. 1-inch Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Appendix A Subsurface Exploration Test Pit Logs ES-7334 Subsurface conditions on site were explored on June 4, 2020. Six test pits were excavated using a trackhoe and operator retained by our firm. The approximate locations of the test pits are illustrated on Plate 2 of this study. The test pit logs are provided in this Appendix. The test pits were advanced to a maximum depth of about 18.5 feet bgs. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 GRAVEL AND GRAVELLY SOILS CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES WELL-GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES POORLY-GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY SILTS AND CLAYS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SOIL CLASSIFICATION CHART (APPRECIABLE AMOUNT OF FINES) (APPRECIABLE AMOUNT OF FINES) (LITTLE OR NO FINES) FINE GRAINED SOILS SAND AND SANDY SOILS SILTS AND CLAYS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS LETTERGRAPH SYMBOLSMAJOR DIVISIONS COARSE GRAINED SOILS TYPICAL DESCRIPTIONS WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLEAN GRAVELS GRAVELS WITH FINES CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH FINES LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Earth Solutions NW LLC DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 292.5 290.5 275.5 MC = 9.5% Fines = 5.0% CEC = 5.6 meq/100g OC = 2.5% MC = 6.0% Fines = 3.1% MC = 4.7% MC = 4.6% MC = 4.9% Fines = 2.1% MC = 7.9% MC = 6.4% MC = 5.9% TPSL SP- SM SP 0.5 2.5 17.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist [USDA Classification: slightly gravelly SAND] -notably coarser [USDA Classification: slightly gravelly coarse SAND] Test pit terminated at 17.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 293 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 PAGE 1 OF 1 TEST PIT NUMBER TP-1 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 290.5 287.5 272.5 MC = 12.3% CEC = 7.9 meq/100g OC = 3.4% MC = 6.6% Fines = 4.5% MC = 8.8% MC = 8.0% MC = 7.7% MC = 7.5% Fines = 3.5% MC = 6.1% TPSL SP- SM SP 0.5 3.5 18.5 Dark brown TOPSOIL, trace roots to 1.5', wire debris (Fill) Brown poorly graded SAND with silt, medium dense, moist to wet Gray poorly graded SAND, medium dense, moist [USDA Classification: slightly gravelly SAND] -notably coarser [USDA Classification: slightly gravelly SAND] Test pit terminated at 18.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 291 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 PAGE 1 OF 1 TEST PIT NUMBER TP-2 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 290.5 288.0 280.5 MC = 7.5% CEC = 3.7 meq/100g OC = 1.4% MC = 16.5% MC = 13.0% Fines = 1.1% CEC = 2.8 meq/100g OC = 1.1% TPSL SP- SM SP 0.5 3.0 10.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist Gray poorly graded SAND, medium dense, moist -infiltration test -increased moisture content to BOH due to infiltration test -notably coarser [USDA Classification: slightly gravelly coarse SAND] Test pit terminated at 10.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 291 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 PAGE 1 OF 1 TEST PIT NUMBER TP-3 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 302.5 298.5 293.5 MC = 12.0% CEC = 5.4 meq/100g OC = 2.5% MC = 22.2% MC = 20.9% TPSL SP- SM SM 0.5 4.5 9.5 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist to wet Brown silty SAND, medium dense, wet -light iron oxide staining -notably coarser -becomes gray Test pit terminated at 9.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 303 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 PAGE 1 OF 1 TEST PIT NUMBER TP-4 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 297.5 294.0 289.0 MC = 11.5% Fines = 10.4% CEC = 5.1 meq/100g OC = 2.0% MC = 8.8% MC = 6.6% TPSL SP- SM SP 0.5 4.0 9.0 Dark brown TOPSOIL Brown poorly graded SAND with silt, medium dense, moist to wet [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist Test pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 298 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 PAGE 1 OF 1 TEST PIT NUMBER TP-5 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 297.5 293.0 288.0 MC = 13.5% Fines = 14.7% CEC = 8.1 meq/100g OC = 3.8% MC = 5.9% MC = 5.2% TPSL SM SP 0.5 5.0 10.0 Dark brown TOPSOIL Brown silty SAND, medium dense, moist to wet [USDA Classification: slightly gravelly SAND] Gray poorly graded SAND, medium dense, moist Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. NOTES Depth of Topsoil & Sod 6": grass GROUND ELEVATION 298 ft LOGGED BY KTK EXCAVATION METHOD TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: CHECKED BY KDH DATE STARTED 6/4/20 COMPLETED 6/4/20 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0 5 10 PAGE 1 OF 1 TEST PIT NUMBER TP-6 PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GENERAL BH / TP / WELL - 7334.GPJ - GINT STD US.GDT - 3/16/21Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Appendix B Laboratory Test Results ES-7334 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 5.0 3.1 2.1 4.5 3.5 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Brown Slightly Gravelly Sand. USCS: SP-SM. USDA: Gray Slightly Gravelly Sand. USCS: SP. USDA: Gray Slightly Gravelly Coarse Sand. USCS: SP. USDA: Gray Slightly Gravelly Sand. USCS: SP. USDA: Gray Slightly Gravelly Sand. USCS: SP. 6 60 PERCENT FINER BY WEIGHTD10 0.263 0.29 0.491 0.234 0.34 0.399 0.422 0.913 0.366 0.568 GRAIN SIZE DISTRIBUTION 100 2.77 2.38 3.29 2.92 2.69 LL TP-01 TP-01 TP-01 TP-02 TP-02 0.144 0.177 0.278 0.125 0.211 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 9.5 9.5 9.5 4.75 9.5 %Silt 1.20 1.13 0.95 1.19 0.96 TP-01 TP-01 TP-01 TP-02 TP-02 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 2.0ft. 4.0ft. 12.0ft. 5.0ft. 16.0ft. 2.00ft. 4.00ft. 12.00ft. 5.00ft. 16.00ft. PL PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GRAIN SIZE USDA ES-7334 VAUGHN SP.GPJ GINT US LAB.GDT 10/22/20Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 1.1 10.4 14.7 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Gray Slightly Gravelly Coarse Sand. USCS: SP. USDA: Brown Slightly Gravelly Sand. USCS: SP-SM. USDA: Brown Slightly Gravelly Sand. USCS: SM. 6 60 PERCENT FINER BY WEIGHTD10 0.45 0.165 0.166 0.846 0.278 0.314 GRAIN SIZE DISTRIBUTION 100 3.03 3.78 LL TP-03 TP-05 TP-06 0.279 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 9.5 4.75 9.5 %Silt 0.86 1.33 TP-03 TP-05 TP-06 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 10.5ft. 3.0ft. 2.5ft. 10.50ft. 3.00ft. 2.50ft. PL PROJECT NUMBER ES-7334 PROJECT NAME Vaughn Short Plat GRAIN SIZE USDA ES-7334 VAUGHN SP.GPJ GINT US LAB.GDT 10/22/20Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Am Test Inc. 13600 NE 126TH PL Suite C Kirkland, WA 98034 (425) 885-1664 www.amtestlab.com Professional Analytical Services ANALYSIS REPORT EARTH SOLUTIONS NW Date Received: 10/19/20 15365 NE 90TH ST Date Reported: 10/27/20 REDMOND, WA 98052 Attention: KEVEN HOFFMANN Project Name: VAUGHN SP Project #: ES-7334 All results reported on an as received basis. _________________________________________________________________________________________________ AMTEST Identification Number 20-A017147 Client Identification TP 01, 2' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.6 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.5 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017148 Client Identification TP 02, 2' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 7.9 meq/100g 0.5 SW-846 9081 JDR 10/27/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017148 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 3.4 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017149 Client Identification TP 03, 5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 3.7 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 1.4 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017150 Client Identification TP 03, 10.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 2.8 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 1.1 %SM 2540G DM 10/23/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017151 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017151 Client Identification TP 04, 2.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.4 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.5 %SM 2540G DM 10/23/20 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017152 Client Identification TP 05, 3' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 5.1 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 2.0 %SM 2540G DM 10/23/20 DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 EARTH SOLUTIONS NW Project Name: VAUGHN SP AmTest ID: 20-A017153 _________________________________________________________________________________________________ AMTEST Identification Number 20-A017153 Client Identification TP 06, 2.5' Sampling Date 06/04/20 Conventionals PARAMETER RESULT UNITS Q D.L.METHOD ANALYST DATE Cation Exchange Capacity 8.1 meq/100g 0.5 SW-846 9081 JDR 10/27/20 Miscellaneous PARAMETER RESULT UNITS Q D.L.METHOD ANLST DATE Organic Matter 3.8 %SM 2540G DM 10/23/20 _________________________________ Kathy Fugiel President DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56 Earth Solutions NW, LLC Report Distribution ES-7334 EMAIL ONLY MainVue WA, LLC 1110 – 112th Avenue Northeast, Suite 202 Bellevue, Washington 98004 Attention: Ms. Lisa Cavell EMAIL ONLY Barghausen Consulting Engineers, Inc. 18215 – 72nd Avenue South Kent, Washington 98032 Attention: Mr. Barry Talkington, P.E. Mr. Tom Barghausen, P.E. DocuSign Envelope ID: 112E161D-80DF-4685-9512-FD7A57D17E56