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Geotechnical Study.pdfGeotechnical Engineering Geology Environmental Services Construction Observationll'esting RECEIVED JAN232019 DEVELOPMENT SEFMCES COUNTER GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCES 22810 EDMONDS WAY EDMONDS, WASHINGTON ES-5932 y 1805 - VT rax • �,,�►.�`!�'r ",� � ��fis�Zufi��nst�r•.S,oita 'r"-�,�-�-'"'T'`•" —.. � Geotechnical Engineering Report - Geotechnical Services Are Pepfopmed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi- neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solelyfor the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one —not even you —should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary Do not read selected elements only. A Geotechnical Engineeping Report Is Based on A Unique Set of Project -Specific Factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that 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. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, • elevation, configuration, location, orientation, or weight of the proposed structure, composition of the design team, or • project ownership. As a general rule, always inform your geotechnical engineer of project changes ---even minor ones --and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineer- ing reportwhose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctua- tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ —sometimes significantly — from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. A Report's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those recommendations are not final, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. The geotechnical engineer who developed your report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation. A Geetechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Engineer's Logs Geotechnical engineers 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 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 mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, butpreface 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 the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac- tors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognize that igeotechnical engineering is far less exact than other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where geotechnical engineers' responsi- bilities 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 equipment, techniques, and personnel used to perform a geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenviron mental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated environmental problems have led to numerous project failings. If you have not yet obtained your own geoen- vironmental information, ask your geotechnical consultant for risk man- agement guidance. Do not rely on an environmental report prepared for someone else. Obtain Professional Assistance To Deal with Mold Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the express purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in -this report, the geotechnical engineer in charge of this project is not a mold prevention consultant; none of the services per- formed in connection with the geotechnical engineer's study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself be sufficient to prevent mold from growing in or on the structure involved. Rely, on Your ASFE-Member Geotechncial Engineer top Additional Assistance Membership in ASFE/The Best People on Earth exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more information. ASFE The Best People an Earth 8811 Colesville Road/Suite G106, Silver Spring, MD 20910 Telephone:301/565-2733 Facsimile:301/589-2017 e-mail: info@asfe.org www.asfe.org Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with ASFE's specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission ofASFE, and only for purposes of scholarly research or book review. Only members of ASFE may use this document as a complement to or as an element of a geotechnical engineering report Any other firm, individual, or other entity that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. IIGER06045.0M May 29, 2018 ES-5932 Kisan Enterprises, LLC 20607 State Route 9 Snohomish, Washington 98296 Attention: Ms. Yvette Johnson Dear Ms. Johnson: Earth I Solutions N W «< Earth Solutions NW I_l_c Geotechnical Engineering, Construction Observationjesting and Environmental Services Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Single -Family Residences, 22810 Edmonds Way, Edmonds, Washington". Based on the results of our study, construction of the proposed single-family residences at the subject site is feasible from a geotechnical standpoint. The proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent native soils, suitable for support of foundations, should be encountered beginning at a depth of roughly two feet below existing grades across the majority of the site. Slab -on -grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This report includes recommendations for foundation subgrade preparation, foundation and retaining wall design parameters, drainage, the suitability of on -site soils for use as structural fill, and other pertinent geotechnical recommendations. 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 ia m;;u�e I E. Suruda, G.I.T. Staff Geologist 1805 - 136th Place N.E., Suite 201 0 Bellevue, WA 98005 • (425) 449-4704 • FAX (425) 449-4711 Table of Contents ES-5932 PAGE INTRODUCTION...................................................................... General......................................................................... Project Description......................................................... . SITE CONDITIONS.................................................................... 2 Surface........................................................................... 2 Subsurface...................................................................... 2 Geologic Setting ..................................................... 2 Groundwater................................................... 3 Geological Hazards Assessment ........................................ 3 DISCUSSION AND RECOMMENDATIONS ..................................... 3 General.......................................................................... 3 Site Preparation and Earthwork ......................................... 3 Temporary Erosion Control ............................................. 4 In -Situ Soils....................................................................... 4 StructuralFill..................................................................... 4 Excavations and Slopes ........................................... 4 Foundations.................................................................. 5 Seismic Considerations ........................... ... ................... 5 Slab -on -Grade Floors ....................................................... 5 Retaining Walls................................................................ 6 Drainage......................................................................... 6 Infiltration Evaluation ............................................ 7 Low Impact Development ......................................... 7 Stormwater Vault Design ......................................... 8 Utility Trench Support and Backfili.................................... 9 Pavement Sections........................................................... 9 LIMITATIONS............................................................................ 10 Additional Services.......................................................... 10 Earth Solutions NW, LLC GRAPHICS Plate 1 Plate 2 Plate 3 Plate 4 APPENDICES Appendix A Appendix B Table of Contents Cont'd ES-5932 Vicinity Map Test Pit Location Plan Retaining Wall Drainage Detail Footing Drain Detail Subsurface Exploration Test Pit Logs Laboratory Test Results Earth Solutions NW, LLC GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCES 22810 EDMONDS WAY EDMONDS, WASHINGTON ES-5932 INTRODUCTION General This geotechnical engineering study was prepared for the proposed single-family residential structures to be constructed at 22810 Edmonds Way, in Edmonds, Washington. To complete the scope of services detailed in our proposal, we performed the following: • Subsurface exploration and characterization of soil and groundwater conditions by way of test pits excavated at accessible areas of the site; • Laboratory testing of soil samples obtained during subsurface exploration; • An infiltration evaluation based on observed soil conditions and two small-scale Pilot Infiltration Tests (PITs); • Geotechnical engineering analyses, and; • Preparation of this report. The following documents and resources were reviewed as part of our report preparation: • Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington, prepared by James P. Minard, dated 1983; • Department of Ecology 2012 Stormwater Management Manual for Western Washington, Volume III Hydrologic Analysis and Flow Control BMPs, dated August 2014; • Edmonds City Code, Chapter 23.80 (Geologically Hazardous Areas), and; • Online Web Soil Survey (WSS) resource provided by United States Department of Agriculture (USDA), Natural Resources Conservation Services. Project Description Based on our review of the preliminary site plan, the existing single-family residence will be demolished, and 20 new single-family residential structures will be constructed. We anticipate grade cuts of up to four feet will be necessary to establish the planned building alignments and roadway improvements. Site improvements will also include underground utility installations. Earth Solutions NW, LLC Kisan Enterprises, LLC ES-5932 May 29, 2018 Page 2 At the time this report was prepared, specific building load values were not available. However, we anticipate the proposed residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads of approximately one to two kips per linear foot and slab - on -grade loading of roughly 150 pounds per square foot (psf) will be incorporated into the construction. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations provided in this report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. SITE CONDITIONS Surface The subject site is located at 22810 Edmonds Way, in Edmonds, Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of one residential tax parcel (Snohomish County Parcel Number 270336-001-023-00) totaling approximately 0.71 acres of land area. The property is currently developed with a single-family residence and associated improvements. The majority of the site is relatively level, with a gently descending slope on the north side of the property adjacent to Edmonds Way. The subject site is bordered to the west, south, and east by residential developments, and to the north by Edmonds Way. The Test Pit Location Plan (Plate 2) illustrates the approximate limits of the property. Subsurface Five test pits were excavated in accessible portions of the site for purposes of assessing soil and groundwater conditions. The test pits were advanced to a maximum depth of approximately 10 feet below existing grade. Please refer to the test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. Fill was encountered at TP-3 and TP-4 to depths of approximately two and one-half to three feet. The fill was characterized as loose, well -graded sand with silt (Unified Soil Classification System: SW). Seepage was observed within the fill layers and was present until the contact with the native soil. Underlying the fill, soil conditions observed at test pit locations consisted of medium dense well - graded sand (USCS: SW), medium dense poorly graded sand (USCS: SP), and silty sand with gravel (USCS: SM). Overall soil relative density increased with depth. Geologic Setting According to the referenced geologic map resource, the subject site is underlain by advance outwash (Qva) and glacial till (Qvt) deposits. According to the referenced NRCS soil survey, the subject site consists of Everett series soils (Map Unit: 17). Everett series soils were formed in glacial moraines and are classified as outwash deposits. Outwash soils are consistent with observations made in the field. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Groundwater ES-5932 Page 3 Groundwater seepage was observed at TP-3 and TP-4 beginning at depths of one to two feet during our fieldwork on March 30, 2018. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater elevations and flow rates are higher during the winter, spring and early summer months. Geological Hazards Assessment As part of this geotechnical engineering study, the referenced chapter of the Edmonds City Code (ECC) was reviewed. Per the ECC requirements, the site was reviewed for erosion, landslide, and seismic hazards. No such hazards were observed to be present on the site or within 200 feet of the site. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of the proposed residential structures at the subject site is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, temporary excavations, retaining walls, infiltration and drainage, and the suitability of on -site soils for use as structural fill. The proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered beginning at a depth of roughly two feet below existing grades across the majority of the site. Slab -on -grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This study has been prepared for the exclusive use of Kisan Enterprises, LLC and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Based on the referenced site plans and given the existing topography, we anticipate grading for the project will involve cuts of up to about four feet to establish building pad and foundation subgrade alignments. Silt fencing and temporary erosion control measures should be placed along the perimeter of the site prior to beginning grading activities. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Temporary Erosion Control ES-5932 Page 4 Temporary construction entrances, consisting of at least six inches of quarry spalls, can be considered to minimize off -site soil tracking and to provide a temporary road surface. Silt fences should be placed along the margins of the property. Interceptor swales and a temporary sediment pond may be necessary for control of surface water during construction. Erosion control measures should conform to the Washington State Department of Ecology (DOE) and City of Edmonds standards. In -Situ Soils From a geotechnical standpoint, the soils encountered at the test pit locations are generally suitable for use as structural fill provided the moisture content of the soils is at or slightly above the optimum level at the time of placement and compaction. The site soils were generally in a moist condition at the time of the exploration on March 30, 2018. Based on the conditions encountered during our fieldwork, the sandy soils generally have a low sensitivity to moisture. Silty sands observed at TP-5 and underlying the sands at TP-3 and TP- 4 have a higher sensitivity to moisture. If the on -site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as structural fill should consist of a well -graded granular soil with a moisture content that is at or near 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, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D- 1557). For soil placed in utility trenches underlying structural areas, compaction requirements are dictated by the local city, county, or utility district, and in general are specified as 95 percent relative compaction. Excavations and Slopes The native soils encountered at the test pit locations primarily consisted of outwash sands in a medium dense condition. Temporary slopes should maintain a gradient of no steeper than 1 Horizontal :1 Vertical (1 H:1 V). If groundwater is present within a cut, the temporary slope gradient should be no steeper than 1.5HAV. The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. ESNW should observe site excavations to confirm the soil type and allowable slope inclination are appropriate for the soil exposed by the excavation. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Earth Solutions NW, LLC Kisan Enterprises, LLC ES-5932 May 29, 2018 Page 5 Permanent slopes should maintain a gradient of 2HAV, or flatter, and should be planted with vegetation to enhance stability and to minimize erosion. A representative of ESNW 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 a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered beginning at a depth of roughly two feet bgs across the majority of the site. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. Provided the structures will be supported as described above, the following parameters can be used for design of the new foundations: Allowable soil bearing capacity 2,500 psf • Passive earth pressure 300 pcf (equivalent fluid) • Coefficient of friction 0.40 A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Considerations The 2015 International Building Code recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual Site Class D should be used for design. In our opinion, site susceptibility to liquefaction is low. The soil relative density and the absence of a uniformly established, shallow groundwater table are the primary bases for this opinion. 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 structural fill. Unstable or yielding areas of the subgrades 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 the slab. The free -draining material should have a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based on the minus three-quarters 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 specifications of the manufacturer. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Retaining Walls ES-5932 Page 6 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 (yielding condition) At -rest earth pressure (restrained condition) • Traffic surcharge (passenger vehicles) Passive earth pressure . Coefficient of friction • Seismic surcharge * Where applicable ** Where H equals the retained height (in feet) 35 pcf 55 pcf 70 psf (rectangular distribution) * 300 pcf 0.40 6H psf ** Where sloping or other surcharge conditions will be present, supplemental recommendations and design earth pressure values should be provided by ESNW. 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 one foot of the wall backfill may consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall and should be connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. Drainage Groundwater seepage was observed at TP-3 and TP-4 at depths of one to two feet during our fieldwork on March 30, 2018. Groundwater seepage should be anticipated in site excavations, particularly in the winter, spring, and early summer months. Temporary measures to control groundwater seepage and surface water runoff during construction will likely involve passive elements such as interceptor trenches and sumps, as necessary. Surface water should not be allowed to flow over sloped areas and should not be allowed to pond near the top of sloped areas or retaining structures. Surface grades must be designed to direct water away from buildings. The grade adjacent to buildings should be sloped away from the buildings at a gradient of at least 2 percent for a horizontal distance of four feet or more (as setbacks allow). In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. A typical footing drain detail is provided on Plate 4. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Infiltration Evaluation ES-5932 Page 7 We understand drywells, trenches, or other small-scale methods are proposed for on -site infiltration. For design, the long-term infiltration rate was evaluated using the results of two small- scale Pilot Infiltration Tests (PITs) completed at a depth of three feet in TP-1 and five feet in TP- 2. No infiltration occurred after the initial soaking period. It should be noted that these are not typical results for infiltration into more granular soils types as those found on site. Infiltration testing was attempted at varying depths at both testing locations. On this basis, we do not recommend infiltration be incorporated into this project. ESNW should be notified of any changes to stormwater management designs. Low Impact Development The following table provides our evaluation and recommendations regarding low impact development (LID) BMPs for the proposed project: BMP JViable? Limitations of Infeasibility Criteria Lawns and LandaoapedA as T5.13: Post -construction soil quality and Considered infeasible on slopes of 33 percent or _T depth Volume V. Chapter 5) Yes greater. Roofs - T5.30: Full dispersion (Volume V, Chapter No T5.30: Dispersion is not recommended due to a lack 5) of adequate vegetated flow paths. T5.10A: Downspout full infiltration systems T5.10A: Infiltration is infeasible with a design rate of 0 (Volume III, Chapter 3) No inches per hour. Bioretention (Volume V, Chapter 7) No Infiltration is infeasible with a design rate of 0 inches per hour. T5.10B: Downspout dispersion systems (Volume III, Chapter 3) T5.10C: Perforated stub -out connections (Volume III, Chapter 3) Other Hard Surfaces _ T5.30: Full dispersion (Volume V, Chapter 5) T5.15: Permeable pavement (Volume V, Chapter 5) Bioretention (Volume V, Chapter 7) T5.12: Sheet flow dispersion T5.11: Concentrated flow dispersion (Volume V, Chapter 5) No T5.10B: Dispersion is not recommended due to a lack of adequate vegetated flow paths. Yes No limitations. No T5.30: Dispersion is not recommended due to a lack of adequate vegetated flow paths. No T5.15: Infiltration is infeasible with a design rate of 0 inches per hour. No Infiltration is infeasible with a design rate of 0 inches per hour. No T5.12: Dispersion is not recommended due to a lack of adequate vegetated flow paths. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Stormwater Vault Design ES-5932 Page 8 We understand a stormwater vault is proposed for this property. Vault foundations should be supported on competent native soil or crushed rock placed on competent native soil. Final storm vault designs must incorporate adequate buffer space from property boundaries such that temporary excavations to construct the vault structure can be successfully completed. Perimeter drains should be installed around the vault and conveyed to an approved discharge point. The presence of perched groundwater seepage should be anticipated during excavation activities for the vault. The following parameters may be used for stormwater vault design: e Allowable soil bearing capacity (dense native soil) 5,000 psf e Active earth pressure (unrestrained) 35 pcf • Active earth pressure (unrestrained, hydrostatic) 80, pcf e At -rest earth pressure (restrained) 55 pcf e At -rest earth pressure (restrained, hydrostatic) 100 pcf • Coefficient of friction 0.40 e Passive earth pressure 300 pcf • Seismic surcharge 6H* * Where H equals the retained height (in feet) The vault walls should be backfilled with free -draining material or suitable sheet drainage that extends along the height of the walls. The upper one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall and connected to an approved discharge location. If the elevation of the vault bottom is such that gravity flow to an outlet is not possible, the portion of the vault below the drain should be designed to include hydrostatic pressure. Design values accounting for hydrostatic pressure are included above. ESNW should observe grading operations for the vault and the subgrade conditions prior to concrete forming and pouring to confirm conditions are as anticipated, and to provide supplemental recommendations as necessary. Additionally, ESNW should be contacted to review final vault designs to confirm that appropriate geotechnical parameters have been incorporated. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 Utility Trench Support and Backfill ES-5932 Page 9 In our opinion, the soils observed at the test pit locations are generally suitable for support of utilities. The on -site soils may not be suitable for use as structural backfill in the utility trench excavations unless the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable requirements of the City of Edmonds of other responsible agency. Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications detailed in the Site Preparation and Earthwork section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade conditions may require remedial measures, such as overexcavation and replacement with structural fill or thicker crushed rock sections, prior to pavement. For relatively lightly loaded pavements subjected to passenger vehicles and occasional truck traffic, the following sections may be considered for preliminary design: • Two inches of hot mix asphalt (HMA) placed over four inches of crushed rock base (CRB), or; • Two inches of HMA placed over three inches of asphalt treated base (ATB). The HMA, CRIB and ATB materials should conform to WSDOT specifications. All soil base material should be compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by ASTM D1557. Additionally, city or county Road Standards may supersede the recommendations provided in this report. Road standards utilized by the City of Edmonds may supersede the recommendations provided in this report. Earth Solutions NW, LLC Kisan Enterprises, LLC May 29, 2018 LIMITATIONS ES-5932 Page 10 The recommendations and conclusions provided in this 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. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test 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 provide testing and consultation services during construction. Earth Solutions NW, LLC ::III, I�.M s - '•-. -�� tt 14` Iri• i' -_.1 t�� _ QRe gay,^ rt Ii 26 !aK � - 5I •• 25' _T� ll fw R I Ja/ i w 9W- ,� °'LO :' avM�sN:'�',/ �I etc° ►� IT t T Y s r t 17151 �R zeds tt7� i if dt 1-S. sH � :4� ; �c2{R" lbMGtVi" 14 � s 35 Aevxwajuujt - y in n Y+f M n 36 y s !jai�i ; f1Y tfa N 9M l �-� it1Y e •� Pt !IIRTH0 ur ..lq%ftr _ 7` 1gM♦t� MALE Ju,c s si a nngr Lis '� _ • ,. 291 ttro � N • I� � St t � ��' rutYt ¢ ; ins `ttk-1�tti 116 a wift ' aw�y�1N�•�� e c �iM a+at 1'r xN u M ' 11MN� �S I9•'t, X' - A i hY:7Yt7Q7 !� ^'AfSFi,NE�rl�i�p to a Intl 's JYIKC p4n 1 J �cti,>' V ♦WTI Y t DWI p vi '_ � YN Ls 14�,Si r•. r =; • jkT . AB ri �nK , gt4fiw PAM '4 Q FL 11 s ; ,Mari 1 y r fn wool v iT "�'irirr r�ltl� w Reference: NORTH I I Snohomish County, Washington Map 474 ,. By The Thomas Guide Rand McNally Vicinity Map 32nd Edition Kisan Townhomes Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be nnA,n KADC nota n�101 /001 A Drni Kin FC�27 responsible for any subsequent misinterpretation of the information "' "" '"" "' "" "�' ., I I v�. I Y JaJL resulting from black & white reproductions of this plate. Checked SES Date May 2018 Plate 1 LEGEND TP-1 I Approximate Location of — ■ — ESNW Test Pit, Proj. No. ES-5932, Mar. 2018 Subject Site Proposed Building Existing Building 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. NOT - TO - SCALE Earth Solutions NW ��c Test Pit Location Plan Kisan Townhomes Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drwn. MRS Date 05/21 /2018 Proj. No. 5932 responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Checked SES Date May 2018 Plate 2 II -III- III r, NOTES: 18" Min. 00 0 G 0O G CC) O n O DO o oe_ 000 oQ o O tlplpp� po 0 0 0 0 0 0 0 00 QOoo 0 00 0� o p o 0 0 0 0 0 0 0 o O' o oaQ o0 c o� 8 0 00 0 0 o 0 0 0--*Cr 00 0 0 o O o Do 0 0 o 0 0 0 o0 , 0 00 00 00 0 p 0 o 0 00 00 ( o 0 0 �00 000 0 00 0 00 O c d o0 0 0 Oo o O c0 0 0 0 0 0 0 C 0 0 00 ' o p 00 0 �O O 0 Cb O0o0O. C O 6. 0 00 O O 0 o O D Q o 0 0 0 C n 0 00 0 2Y 00p0 0 0 0 0 00 0 0 0 0O o o 0 0 0 0 00000 a 00 O 8 o00 p e o 0 Oow 0 Oo 00 0 0 � 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. 0 Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: 00 �0 (-) 0 o Free -draining Structural Backfill 0 n o 1-inch Drain Rock Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT CONSTRUCTION DRAWING Earth Solutions Nil, RETAINING WALL DRAINAGE DETAIL Kisan Townhomes Edmonds, Washington Drwn. MRS Date 05/21/2018 Proj. No. 5932 Checked SES Date May 2018 Plate 3 Perforated Rigid Drain Pipe (Surround in Drain Rock) 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. r.r.r.f. ,, ftirtir;.• 1-inch Drain Rock SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Earth Solutions FOOTING DRAIN DETAIL Kisan Townhomes Edmonds, Washington Drwn. MRS Date 05/21 /2018 Proj. No. 5932 Checked SES Date May 2018 Plate 4 Appendix A Subsurface Exploration ES-5932 The subsurface conditions at the site were explored by excavating two test pits at the approximate locations illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed on March 30, 2018. The test pits were excavated to a maximum depth of approximately 10 feet bgs. Logs of the test pits advanced by ESNW are presented in Appendix A. 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. Earth Solutions NW, LLC Earth Solutions NWLLC SOIL CLASSIFICATION CHART SYMBOLS TYPICAL MAJOR DIVISIONS GRAPH I LETTER DESCRIPTIONS CLEAN �� GW WELL -GRADED GRAVELS, GRAVEL - MIXTURES, LITTLE OR NO GRAVEL GRAVELS �' 0. FINESSAND AND GRAVELLY SOILS (LITTLE OR NO FINES) GP POORLY -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE Q 0,0 C OR NO FINES COARSE '" ° '° ° GRAINED GRAVELS WITH D GM SILTY GRAVELS, GRAVEL -SAND - SOILS MORE THAN 50% FINES o SILT MIXTURES OF COARSE iQ o FRACTION RETAINED ON NO. 4 SIEVE (APPRECIABLE GC CLAYEY GRAVELS, GRAVEL - SAND - AMOUNT OF FINES) CLAY MIXTURES CLEAN SANDS SW DED SANDS, WELL-GSANDS, LITTLE MORE THAN 50% SAND OR NO OF MATERIAL IS AND SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO LARGER THAN NO.200 SIEVE SANDY SOILS FINES) SIZE (LITTLE OR NO FINES SANDS WITH SM SILTY SANDS, SAND - SILT MORE THAN 50% FINES MIXTURES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE SC CLAYEY SANDS, SAND - CLAY AMOUNT OF FINES) MIXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO SILTS FINE LIQUID LIMIT CL MEDIUM PLASTICITY, GRAVELLY GRAINED LESS THAN 50 LAYDS CLAYS, LEAN CCCLYASS, SILTY SOILS - _ OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO.200 SIEVE SIZE SILTS AND LIQUID LIMIT `+I I INORGANIC CLAYS OF HIGH CLAYS GREATER THAN 50 PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS „ Lit,'„ 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. Earth Solutions NW TEST PIT NUMBER TP-1 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 WAIN Telephone: 425- 49-4704 Fax: 425-449-4711 PROJECT NUMBER ES,5932 PROJECT NAME Kisan Townhomes _ DATE STARTED 3/30/18 _ COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION — NOTES Depth of Topsoil &Sod 6":grass AFTER EXCAVATION -- ui v _ '✓ �� _ TESTS p MATERIAL DESCRIPTION 0. Z � 0 T r SL •" �' o y Dark brown highly organic TOPSOIL, root intrusions to 1' Gray well -graded SAND with sift, medium dense, moist to wet MC = 17.50% SW- SM -becomes wet 4.5 Gray poorly graded SAND with gravel, medium dense to dense, moist = MC 8.50% [USDA Classification: very gravelly coarse SAND] SP 8.0 -becomes wet MC = 16.90% Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 8.0 feet. Earth Solutions NW TEST PIT NUMBER TP-2 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-4494711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3130/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION — NOTES Depth of Topsoil & Sod 3": nrass AFTER EXCAVATION — w }W U _ Q I— W W TESTS a. O MATERIAL DESCRIPTION 0. Q Z (� 0 Gray poorly graded SAND, medium dense, damp MC = 5.50% MC = 10.30% -becomes dense, wet 5 SP MC = 8.50% MC = 15.60% 10 MC = 13.30% _ 10.0 [USDA Classification: slightly gravelly SAND) _ Fines = 3.70% Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 10.0 feet. 1805 -136th Place N.E., Suite 201 PAGE 1 OF 1 Bellevue, Washington 98005 40 Earth Solutions NW TEST PIT NUMBER TP-3 Telephone: 425- 49-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30/1 B COMPLETED 3130/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION NOTES Depth of Topsoil & Sod 6": arm AFTER EXCAVATION — W CL _ w W W M TESTS vi U 0 MATERIAL DESCRIPTION Qz (3 t/S 0 Gray well -graded SAND with silt, loose, wet (Fill) SW -groundwater seepage MC = 9.50% 2.5 Gray silty SAND with gravel, dense to very dense, damp MC = 6.90% SM -weakly cemented 5 5.0 Gray poorly graded SAND with silt, medium dense to dense, moist SM :... MC = 10.00% 8.5 Test pit terminated at 6.5 feet below existing grade. Groundwater seepage encountered at 1.0 foot during excavation. No caving observed. Bottom of test pit at 6.5 feet. Earth Solutions NW TEST PIT NUMBER TP-4 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER _ ES-5932 _ PROJECT NAME Kisan Townhomes DATE STARTED W30N 8 COMPLETED 3130118 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SES _ CHECKED BY HTW AT END OF EXCAVATION — NOTES Surface Conditions: fill AFTER EXCAVATION — _ w w o g a TESTS vi O MATERIAL DESCRIPTION z 0 Gray well -graded SAND with silt and gravel, modium dense, moist (Fill) SW MC = 8.70% -groundwater seepage 3.0 Gray silty SAND with gravel, dense damp to moist 5 _ MC = 7.70% Fines = 15.90% [USDA Classification: gravelly loamy SAND] SM e.o -becomes moist MC = 11.30 °� _ Test pit terminated at 8.0 feet below existinggrade. Groundwater seepage encountered at 2.0 feet during excavation. No caving observed. Bottom of test pit at 8.0 feet. Earth Solutions NW TEST PIT NUMBER TP-5 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 WASU Telephone: 425-449-4704 Fax: 425-4494711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30118 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION — NOTES Depth of Topsoil & Sod 3": duff AFTER EXCAVATION — w W C U TESTS IL J MATERIAL DESCRIPTION p p� Z C9 0 Cl) TPSIL' = ' aa�Dark brown highly orgento TOPSOIL _ Brown silty SAND with gravel, medium dense, damp to moist MC = 11.60% SM I -becomes moist 4.5 `i MC = 10.30% Brown poorly graded SAND with silt and gravel, medium dense, moist Fines = 9.00% [USDA Classification: very gravelly coarse SAND] SP- SM 5 -becomes wet MC = 13.70% Test pit terminated at 7.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 7.5 feet. Appendix B Laboratory Test Results ES-5932 Earth Solutions NW, LLC W �19NIC�IY IYIIYYWIYIIIIW�lllllll 1IN j�mjjlHlllllll�■NIIIY�■ mom 11111 la n■IIIII�� I�� MOURNIN i11111101111111111111111111 OEMIII�I �II�l1��■IWIWp■IAellll IIm�MMYlII II�j1�■IIIC�IA��INII��INIIII� � in 11��11111�■Mlllllvllllll�la�!Ih��11��INl ll�■Illllllnlllllll�� Illl��i!I�11 ��IINII� 11�■IIIIIII��IIIIII 8 am Report Distribution ES-5932 EMAIL ONLY Kisan Enterprises, LLC 20607 State Route 9 Snohomish, Washington 98296 Attention: Ms. Yvette Johnson Earth Solutions NW, LLC