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Home My WebLink AboutMiscEarth Solutions NWuc Gcoccchmcal Eng1ncer111g Cieul ugy Em 1ru nmeJ1tal Sc1t:nt1:,ts Construct1on vf on1toring _._) SEP O 4 2014 ~,~TYO'" ~-, .. .1to l ·1 ...... GEOTECHNICAL ENGINEERING STUDY RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST ANO LINCOLN COURT NORTHEAST RENTON , WASHINGTON ES-3450 PREPARED FOR CMC DEVELOPMENT Augwt 21, 2014 ' , , )t 1'\Avl \ ,' I, ) Step en H. Avrtl Staff Geologist . Kyle R. Campbell, P.E. Principal GEOTECHNICAL ENGINEERING STUDY RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST AND LINCOLN COURT NORTHEAST RENTON, WASHINGTON ES 3450 Earth Solutions NW, LLC 1805 -138"' Place Northeut, Suite 201 Bellevue, Wahington 98005 Phone: 425-449-4704 Fax: 425-449-4711 Toll Free: 886-338-8710 Important Information About Your -~-------Geotechnical Engineering Report Geotechnical Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their ciients. 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 soletytor 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 proiect except the one originally contemplated. Read Ute 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 Geotechnicaf Engineering Report Is Based on A Unique Set ol Project-SpecH1c Factors Geotechnical engineers consider a number of unique, proiect-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 proiect. • not prepared for the specific site explored. or • completed before impcrtant 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--1Jven 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 pertormed. Do not roly 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 at additional testing or analysis could prevent major problems. Most Geotechnicaf 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 iudgment 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 constnuction recommendations included in your report. Those recommendations are not final, because geotechnical engi- neers develop them principally from judgment illld opinion. Geotechnical engineers can finalize their recommendations only by observing actual \,, subsurtace conditions revealed during construction. The geotechnica/ engineer who developed your reporr wnnot assume responsibility or /1abilfty for the report's recommendations if that engineer does not perform construction observa/ion. A Geotechnieal 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 Q1Jotechnical engineer to review perti- nent elements of ttle 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 ,cceptable, but recognize that separating fogs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors l'able for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent cost'y problems, give ;on- tractors the complete geotechnical engineering report, bu/preface it with a clearly written letter of transmittal. In that letter, advise contractors that ttle report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage ttlem 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 pertorm 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 geotechnical engineering is far less exact ttlan other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To nelp reduce llie risk of such outcomes. geotecr.nical engineers cornrnunly include a variety of explanatory provisions in ttleir reports. Sometimes labeled "limitations' many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end. to help others recognize ttleir own responsibilities and risks. Read these provisions closely Ask questions. Your geotechmcal engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The equipment, techniques. and personnel used m pertorm a geoenviron~ mental study differ significantly from those used to pertorm a geotechnicaf study. For that reason, a geotechnicai engineering report does not usually relate any geoenvironmental findings, conclusions, or recommendations; e.g .. about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated environmental problems have fed to numerous project la1'lures. Ii 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 oi mold from growing on indoor surtaces. 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, 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 ouilding surtaces dry. Wr,ile groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed irttflis report, ttle geotechnical engineer in charge of this project is not a mold prevention car.sultan!; none of the services per- formed in connection with the geotechnica/ engineer's study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this repot1 will not of itself be sufficient to prevent mold from growing In or on the structure involved. Rely, on Your ASFE-Mamber Geotechncial Engineer ror Adlfttional 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 infonmation. -------------------------------------·------' ASFE 1111 IHI PIIIIO. 11 EUU 8811 Coles,ille Road/Suite G106. Silver Spring, MD 20910 Telephone: 301/565-2733 Facs,mile: 3011589-2017 e-mail: i;ifo@asfe.org www.asfe.org Copyright 2004 by ASFE, 111c. Owl/cation, reproduction, or copyirrr; of tnis document. in who It! ar in part /Jy any means wharsaever. is strictly f)(ohibited, except with ASFE's specific wriffen {Jt1rmission. Excerpting, q11otfnt1, or ottwwise extracting warding from this document is permitted only wim the express written p8rmission of ASFE. and only for purposes rd scholarly research or IJOak review. Only mf!mbers of ASFf may use tt11S document as a complement ta or as an element of II geotechnical engineeni1g report: Any other firm, individual, or other entity that so uses this document without Qeing ;in ASFE member could be committirrg r1egligerrt or intentional (fraudufent) misroprnsentation. IIGER06045 OM / August 21, 2014 ES-3450 Civic Development 18211 -240th Avenue Southeast Maple Valley, Washington 98038 Attention: Mr. Joe Pruss Dear Mr. Pruss: Earth Solutions NW LLC • Geotechnical Engineering • Construction Monitol"ing • Environmental Sciences Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Renton Short Plat, Lincoln Avenue Northeast and Lincoln Court Northeast, Renton, Washington". In general, the site is underlain primarily by areas of fill (in the east and central portion of the site) underlain by glacial till. In our opinion, the proposed residential structures can be supported on conventional continuous and spread footing foundations bearing on competent native soil encountered at depths between two to four feet; or structural fill. Groundwater seepage was not observed at any of the test locations. However, seepage should be expected during grading activities, particularly during winter, spring and early summer months. Recommendations for foundation design, site preparation, drainage, and other pertinent recommendations are provided in this study. We appreciate the opportunity to be of service to you on this project. If you have questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC /• S'1·. -,~ I :\A\. 17,:,, ·\ ' \ , 1 I I,-· VV \UJ , _; \\14 Step. h n H. Avril ) Staff eologist :J 1805 -136th Place N.E., Suite 201 • Bellevue, WA 98005 • (425) 449-47U4 • FAX (415) 449-47'11 Table of Contents ES-3450 INTRODUCTION ....................... . General ......... ____ ............................................. . Project Description ........................ .. SITE CONDITIONS ..... . Surface ............ . Subsurface .......................... . Fill ............................................ . Topsoil ............................................................ . Native Soil .. . .. . .. . .. . .. . .. . .. . . . . . ....................... . Geologic Setting ................................................ .. Groundwater...... .. .............................. . DISCUSSION AND RECOMMENDATIONS ............................... . General... .. .. .. .. .. .. .. .. . .. .. .. .. . . .. .. . .. . . .. .. .. .. .. .. . ..... . Site Preparation and General Earthwork ....................... . Wet Season Grading ................ .. In-situ Soils ................................................................... .. Imported Soils ............................................................... . Structural Fill .......................................................... . Foundations ............................................................. . Seismic Design Considerations .......... .. Critical Areas Assessment.. .................................................. .. Slab-On-Grade Floors .......................... .. Retaining Walls ................................... .. Drainage ............................................... . Excavations and Slopes ............................ .. Utility Trench Backfill .. Pavement Sections ..... . LIMITATIONS ...................... . Additional Services ..... . Earth Solutions NW, LLC PAGE 1 1 2 2 2 2 2 2 3 3 3 3 3 4 5 5 5 5 6 6 6 7 7 8 8 9 9 10 10 GRAPHICS Plate 1 Plate 2 Plate 3 Plate 4 APPENDICES Appendix A Appendix B Table of Contents Cont'd ES-3450 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 General GEOTECHNICAL ENGINEERING STUDY RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST AND LINCOLN COURT NORTHEAST RENTON, WASHINGTON ES-3450 INTRODUCTION This geotechnical engineering study was prepared for the proposed residential development to be constructed on the west side of Lincoln Avenue Northeast in Renton, Washington. The site is comprised of a single tax parcel; and is located at the intersection with Lincoln Court. The purpose of this study was to develop geotechnical recommendations for the proposed development. Our scope of services for completing this geotechnical engineering study included the following: • Reviewing the project details; • Excavation, logging and sampling oftest pits excavated at the site; • Engineering analyses of data obtained through the site exploration, and; • Preparation of this report. The following documents/maps were reviewed as part of our report preparation: • Conceptual Drainage Control, Tree Cutting/Inventory, Generalized Utility & Grading Plan, by Encompass Engineering & Surveying, Sheet 1 of 1, dated June 3, 2014; • King County iMap online resource; • Geologic Map of Washington, Southwest Quadrant, by Walsh, et al, 1987, and; • Washington State USDA Soil Conservation Survey (SCS). Project Description We understand the site will be developed with three single-family residential structures, on-site roadways, parking areas, and associated improvements. Finalized grading plans were not available at the time of this report production; however, given the topographic change across the site, we anticipate grading activities will likely involve cuts and fills on the order of ten feet or less to establish the final design grades. Civic Development August 12, 2014 ES-3450 Page 2 Final building loads were not available at the time of our report. However, we anticipate wall loads for one to two-story single-family residential structures will be on the order of 1 to 2 kips per lineal foot; and slab-on-grade loading of 150 pounds per square foot (psf). On-site infiltration of stormwater from downspouts is being proposed for the subject project. If the above design estimates are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to confirm that our geotechnical recommendations have been incorporated into the final design. SITE CONDITIONS Surface The site is located on the west side of Lincoln Avenue Northeast, at the intersection with Lincoln Court Northeast in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map). The site is roughly rectangular in shape and consists of a single tax parcel. The site is currently undeveloped and moderately vegetated with fir, maple, and general native undergrowth. The existing site topography descends gently from the street elevation towards the west; with elevation change on the order of approximately 34 feet. Subsurface A representative of ESNW observed, logged and sampled five test pits excavated with a track- hoe across the site. The test pits were excavated for the purposes of characterizing the subsurface conditions. The approximate locations of the test pits are depicted on the Test Pit Location Plan (Plate 2). Please refer to the test pit logs provided in Appendix A for a detailed description of the subsurface conditions. Fill Fill was encountered at all but one of the test pit locations. The area on-site where fill was not encountered was in the northwest corner of the site, near the property boundary. In general the fill was observed extending to a depth of approximately three to four feet. Fill soil should be anticipated in any excavation on this site. The silty sand with gravel (Unified Soil Classification, SM) fill may be suitable for support of foundations; however a representative of ESNW should be retained during the construction phases of the site development to evaluate the suitability of any on-site soils for use as structural fill or bearing of foundations. Topsoil Topsoil was encountered at all of the test pit locations extending to depths of between about six to ten inches below existing grade. Topsoil is not suitable for use as structural fill nor should it be mixed with material to be used as structural fill. Topsoil or otherwise unsuitable material can be used in landscaping areas if desired. Earth Solutions NW, LLC Civic Development August 21, 2014 Native Soil ES-3450 Page 3 Underlying the topsoil and fill, native soil consisting primarily medium dense to dense glacial till consisting of silty sand with gravel (SM) was encountered extending to the maximum exploration depth of ten feet below existing grades. The native soil transitioned from a medium dense condition to dense at approximately four feet in depth at most of the test pit locations. Geologic Setting The referenced geologic map resource identifies glacial till (Qgt) deposits across the site and surrounding areas. The referenced SCS soil survey identifies Alderwood Gravelly Sandy Loam (AgC and AgD) series soils across the site and surrounding area. Alderwood gravelly sandy loam soils consist of glacial till formed on morraines and till planes; and typically present a low to moderate erosion hazard; and are somewhat well drained. The native soil conditions observed at the test pit locations are generally consistent with glacial till deposits. Groundwater Groundwater was not observed at any of the test pit locations during the fieldwork (August 2014). However, seepage should be expected at some locations, particularly during the winter, spring and early summer months. Perched groundwater is typically observed on sites underlain by glacial till soil; and is usually encountered at the contact between the weathered and unweathered till deposits. 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 flow rates are higher during the wetter, winter months. DISCUSSION AND RECOMMENDATIONS General In our opinion, construction of the proposed residential development is feasible from a geotechnical standpoint. The proposed buildings can be supported on conventional continuous and spread footing foundations bearing on competent native soil, existing competent fill or at least two feet of structural fill. Slab-on-grade floors should be supported on a firm and unyielding subgrade. Recommendations for foundation design, site preparation, drainage, and other pertinent geotechnical recommendations are provided in the following sections of this study. This study has been prepared for the exclusive use of Civic Development 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. Earth Solutions NW, LLC Civic Development August 21, 2014 Site Preparation and Earthwork ES-3450 Page4 Site preparation activities will involve site clearing and stripping, and implementation of temporary erosion control measures. The primary geotechnical considerations associated with site preparation activities include building pad subgrade preparation, underground utility installations, and preparation of pavement subgrade areas. Temporary construction entrances and drive lanes, consisting of at least 12 inches of quarry spalls can be considered in order to minimize off-site soil tracking and to provide a stable access entrance surface. Erosion control measures should consist of silt fencing placed along the down gradient side of the site. Soil stockpiles should be covered or otherwise protected to reduce soil erosion. Temporary sedimentation ponds or other approaches for controlling surface water runoff should be in place prior to beginning earthwork activities. Topsoil and organic-rich soil was encountered generally within the upper six to ten inches at the test pit locations. Topsoil and organic-rich soil is not suitable for direct foundation support, nor is it suitable for use as structural fill. Topsoil or organic-rich soil can be used in non-structural areas if desired. A representative of ESNW should observe the initial stripping operations, to provide recommendations for stripping depths based on the soil conditions exposed during stripping. Subgrade conditions expected to be exposed throughout the proposed building and pavement areas will likely be comprised of silty sand with gravel glacial deposits. After the completion of site stripping the subgrade conditions should be evaluated by a representative of ESNW. A proofroll utilizing a fully loaded solo dump truck may be necessary to evaluate the suitability of the exposed native soils prior to placement of fill. ESNW should be retained during this phase of earthwork to observe the subgrade conditions and other earthwork activities. The soils exposed throughout subgrade areas should be compacted to structural fill specifications prior to constructing the foundation, slab, and pavement elements. The subgrade throughout pavement areas should be compacted as necessary and exhibit a firm and unyielding condition when subjected to the proofrolling with a loaded solo dump truck. Overexcavation and replacement with crushed rock may be necessary, depending on the conditions encountered during construction. Structural fill soils placed throughout foundation, slab, and pavement areas should be placed over a firm base. Loose or otherwise unsuitable areas of native soil exposed at subgrade elevations should be compacted to structural fill requirements or overexcavated and replaced with a suitable structural fill material. Where structural fill soils are used to construct foundation subgrade areas, the soil should be compacted to the requirements of structural fill described in the following section. Foundation subgrade areas should be protected from disturbance, construction traffic, and excessive moisture. Where instability develops below structural fill areas, use of a woven geotextile below the structural fill areas may be required. A representative of ESNW should observe structural fill placement in foundation, slab, and pavement areas. Earth Solutions NW, LLC Civic Development August 21, 2014 Wet Season Grading ES-3450 Page 5 The moderate moisture sensitivity of the on-site soil will make grading during periods of rain somewhat difficult. Mass grading should take place during the late summer months when conditions are more favorable. If grading takes place during the wetter winter, spring or early summer months, a contingency in the project budget should be included to allow for export of native soil and import of structural fill as described below. In-situ Soils The soils encountered throughout the majority of the test sites have a moderate sensitivity to moisture and were generally in a moist condition at the time of the exploration (August 2014). In this respect, the in-situ soils may not be suitable for use as structural fill if the soil moisture content is more than 4 to 5 percent above the optimum level at the time of construction in the case of the silty sand soil encountered at a number of the test pits locations. In general, soils encountered during the site excavations that are excessively over the optimum moisture content will require moisture conditioning prior to placement and compaction. Conversely, soils that are below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. If the in-situ soils are determined to not be suitable for use as structural fill, then use of a suitable imported soil may be necessary. In our opinion, a contingency should be included in the project budget for exporting unsuitable soil and importing structural fill; or moisture conditioning recommendations can be provided upon request based on field observations during the construction phase of on-site work. Imported Soils 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 defined as the percent passing the #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, at moisture contents above the optimum level and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D-1557). Soil placed in utility trenches, pavement areas and in the upper 12 inches of slab-on-grade areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones, depending on the responsible utility district or jurisdiction. Earth Solutions NW, LLC Civic Development August 21, 2014 Foundations ES-3450 Page 6 Based on the results of our study, the proposed residential buildings can be supported on conventional spread and continuous footings bearing on competent native soils encountered between two and four feet below existing grades, competent existing fill or new structural fill. Loose soil exposed at foundation subgrade elevations can be compacted in place. Provided foundations are be supported as described above, the following parameters can be used for design of new foundations: • Allowable soil bearing capacity • Passive earth pressure • Coefficient of friction 2,500 psf 300 pcf (equivalent fluid) 0.40 A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor-of-safety of 1.5. With structural loading as expected, total settlement in the range of one and one half inch and differential settlement of about one inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Design Considerations The 2012 IBC recognized the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.1-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. Liquefaction is a phenomenon where saturated or loose soils suddenly lose internal strength in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. The referenced liquefaction susceptibility map of King County indicates the site and surrounding areas exhibit a low liquefaction susceptibility. In our opinion, site susceptibility to liquefaction can be characterized as low. The absence of a uniformly established shallow groundwater table is the primary basis for this characterization. Critical Areas Assessment ESNW has reviewed the City of Renton critical areas map available on-line in a GIS format. This utility identifies critical areas in the form of landslide, erosion, and steep slope hazards. Critical areas were observed on the subject site upon review of the available reference material. A moderate landslide hazard is identified for portions of the site. There are steep slope areas identified on the west side of the adjacent property. An erosion hazard area is identified for the northern portion of the site in the green belt area. In our opinion, the landslide hazard and erosion hazard on the subject site is minimal due to the relative density of the underlying soil, and the lack of groundwater in the subgrade. Earth Solutions NW, LLC Civic Development August 21, 2014 ES-3450 Page 7 No signs of erosion, surface seeps, or hummocky terrain was observed during our fieldwork (August 2014). As such, it is our opinion that the slopes on and around the subject site demonstrate a stable condition in their current state: and given the recommendations provided in this study for erosion control and site grading are adhered to, the potential for soil movement in the future as a result of the proposed development is minimal. The relative density of the underlying soil on the subject site, the absence of evidence pointing towards past soil movement on the site, and the lack of groundwater is the basis for this conclusion. Slab-On-Grade Floors Slab-on-grade floors for residential buildings constructed at this site should be supported on a firm and unyielding subgrade. Where feasible, the existing native soils exposed at the slab-on- grade subgrade level can be compacted in place to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. 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 (percent passing the #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 a vapor barrier is to be utilized it should be a material specifically designed for use 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 can be used for retaining wall design: • Active earth pressure (yielding condition) 35 pcf (equivalent fluid) • At-rest earth pressure (restrained condition) 55 pcf • Traffic surcharge for passenger vehicles 70 psf (rectangular distribution) (where applicable) • Passive earth pressure 300 pcf (equivalent fluid) • Coefficient of friction 0.40 • Seismic surcharge (active condition) 6H* • Seismic surcharge (restrained condition) 12H* ·where H equals retained height Earth Solutions NW, LLC Civic Development August 21, 2014 ES-3450 Page 8 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 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. A typical retaining wall drainage detail is provided on Plate 3. Drainage Groundwater was not observed during the fieldwork (August 2014). However, groundwater should be anticipated in deeper site excavations particularly during the wetter winter and early spring months. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide recommendations to reduce the potential for instability related to seepage effects. Infiltration of stormwater runoff from downspouts and roadways is feasible on the subject site, given the subsurface conditions ESNW observed at the test pit locations. However, infiltration of stormwater on sites underlain by glacial till can be slow. We recommend a rate of 0.13 inches per hour or less be used for design of the infiltration facilities. Given that the site is underlain by glacial till, an overflow system should be included in the design. In our opinion, foundation drains will be necessary on the subject site. A typical foundation drain detail is provided as Plate 4. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Based on the soil conditions encountered at the test pit locations, the soils encountered within the majority of the development envelope, and where groundwater seepage is exposed, are classified as Type C by OSHA/WISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.5H:1V (Horizontal:Vertical). The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. In areas where no groundwater is observed, the soil will be classified as Type A. Temporary slopes over four feet in height in Type A soil must be sloped no steeper than 0.75H: 1V. ESNW should observe site excavations to confirm the soil type and allowable slope inclination. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Earth Solutions NW, LLC Civic Development August 21, 2014 ES-3450 Page 9 Permanent slopes should maintain a gradient of 2H: 1 V, 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, and to provide additional excavation and slope recommendations, as necessary. Utility Support and Trench Backfill In our opinion, the soils anticipated to be exposed in utility excavations should generally be suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities. Some of the native soils are moisture sensitive and will therefore be difficult to use as structural trench backfill if the moisture content of the soil is high. Moisture conditioning of the soils will likely be necessary prior to use as structural backfill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the specifications of the applicable jurisdiction. Seepage should be anticipated within utility trench excavations. Caving of the trench sidewalls due to hydrostatic pressure or the cohesion less nature of the site soils should be anticipated by the contractor. Pavements The performance of site pavements is largely related to the condition of the underlying subgrade. To provide 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 as recommended 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 will require remedial measures such as overexcavation, placement of a geotextile and thicker crushed rock or structural fill sections prior to pavement. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections can be considered: • 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, ATB and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to at least 95 percent of the maximum dry density. Final pavement design recommendations can be provided once final traffic loading has been determined. If areas of seepage are exposed in roadway excavations, drains should be installed in these areas to allow removal of the water. Specific recommendations and details for roadway drainage can be provided upon request. Earth Solutions NW, LLC Civic Development August 21, 2014 LIMITATIONS ES-3450 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 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 ,... "'4'~-. ~f ' , ... ~·t .. l . ~··'"' ,·- ' ' Reference: ,,.. ,t King County, Washington Map 626 By the Thomas guide Rand McNally 32nd Edition ""'•1" ·.ct ..... • ... ,;,.l"I\. NORTH 8 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. '*, ~.- .,-..... ~-:.)•,: • 1.'H'• .,. , . .,{{"'{ • Vicinity Map Renton Short Plat Renton, Washington Drwn. GLS Date 08/20/2014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate -t'.I!!".' lla,1_ ITP-4 -•-I r; .) r -.•- ITP-5 LEGEND TP-1 -!-Approximate Location of I ESNW Test Pit, Proj. No. ES-3450,Aug. 2014 Subject Site Proposed Lot Number 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 dient at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: ThlS 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. ITP-3 -•-I 2 I -•- TP-21 TP-1 I -•- ,., j 0 1 "=30' • Drwn. GLS Test Pit Location Plan Renton Short Plat Renton, Washington Date 08/2012014 Proj. No. Checked SHA Date Aug. 2014 Plate 60 wJ z z _J 0 u z _J 3450 2 .. NOTES: • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 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" Drain Rock. LEGEND: Free Draining Structural Backfill 1 inch Drain Rock 18" Min . Structural Fill SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING • utions NWLLc eermg, Construction Monitoring lronmenml Sciences RETAINING WALL DRAINAGE DETAIL Renton Short Plat Renton, Washington Drwn. GLS Date 0812012014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate 3 Slope ... ~t 2" (Min.) Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of ru . . . ...... .,. ...... ............. rl'•rl'•l'•rl'•,1' .............. rl'•rl'•.l'•J'•rl' ............. 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal; native soil or other low permeability material. 1" Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING • Drwn. GLS FOOTING DRAIN DETAIL Renton Short Plat Renton, Washington DateOS/20/2014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate 4 Appendix A Subsurface Exploration ES-3450 The subsurface conditions at the site were explored by excavating a total of five test pits excavated across accessible portions of the property. The subsurface explorations were completed in August of 2014. The approximate test pit locations are illustrated on Plate 2 of this report. Logs of the test pits are provided in this Appendix. The test pits were excavated to a maximum depth of 10 feet below existing grades. Earth Solutions NW, LLC Earth Solutions NWLLc SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS COARSE GRAINED SOILS MORE THAN 50% OF MA TE RIAL IS LARGER THAN NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4$1EVE SAND AND SANDY SOILS CLEAN GRAVELS {UTILE OR NO FINES) GRAVELS WITH FINES (APPRECJABLE AMOUNT OF FINES) CLEAN SANOS (LITTLE OR NO FINES) SANDS WITH MORE TlWI 50% FINES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE SILTS AND CLAYS SILTS AND CLAYS AMOUNT OF FINES) LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS GW WELL-GRADED GRAVELS, GRAVEL - SANO MIXTURES, LITTLE OR NO FINES POORL Y-GRAOED GRAVELS, GP GRAVEL-SANO MIXTIJRES, UTllE DR NO FINES GM SILTY GRAVELS, GRAVEL-SANO- SILT MllITURES GC CLAYEY GRAVEL.S, GRAVEL-SAND- Cl.A Y MIXTURES SW WELL-GRADED SANDS, GRAVELLY SANOS, LIT'n..E OR NO F1NE$ SP POORLY-GRADED $ANOS, GRAVELLY SAND, UTTLE. OR NO FINES SM SILTY SANDS, SAND· SILT MIXTURES SC CLAYEY SANDS, SAND -CLAY MIXTURES INORGANIC Sll TS AND VERY FINE ML SANOS, ROCK FLOUR, Sil TY OR CLAYEY FINE SANOS OR CLAYEY SIL TS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO CL MEDIUM PLASTICITY, GRAVELLY CLAYS. SANDY CLAYS, SILTY ClAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MH INO~GANIC Sil TS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS CH INORGANIC CLA.YS OF HIGH PLASTICITY OH ORGANIC Cl.A YS OF MEDIUM TO HIGH PLASTICITY. ORGANIC SILTS PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS 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. ~ w z Earth Solutions NW 1805 -136th Place N. E., Suite 201 Bellevue, Washington 98005 Telephone 425-449-4704 TEST PIT NUMBER TP-1 Fax: 425-449-4711 CLIENT Civi Developmef!L_ PROJECT NUMBER 3450 PROJECT NAME .. Renton _Short Plat_-·---·----- ~R~~EC_!_LOCATION Renton, V!Jc.a=s=h=in=g=to=n==== PAGE 1 OF 1 DATE STARTED 8/4l1_4 COMPLETED 8/4/14 __ _ GROUND ELEVATION JOO fl GROUND WATER LEVELS: TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided EXCAVATION METHOD LOGGED BY SHA __ _ CHECKED BY ~1-111 __ _ ATTIME OF EXCAVATION AT END OF EXCAVATION AFTER EXCAVATION NOTES Oe~th Qf_TOpJ>p_j_l_ & _§_Q_g_ §":_Q_,¥~-~Qtl w (l_ :i: >-0:: en 0 1--UJ 'i: (0 ~E' "'"' TESTS (.) a_o w-_J:. en cl: _J 0 (l_:, ::i :liZ CJ ,,, 0 1TPS MC= 7.70% SM 3.9 __ 5 MC= 17.90% ] . 9._0 MATERIAL DESCRIPTION TOPSOIL ---------- Brown silty SAND with gravel, medium dense to dense, moist (Fill) Brown silty SAND wfth gravel, medium dense to dense, moist (Native Contact)(Weatherea nl) -becomes very dense and unweathered 197_0 -~---------- Test pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. 191 0 ----------~~~-~~1 Bottom of test pit at 9.0 feet. ill~-~--~-------~-~-~----------------------------------~ ~ w z w Earth Solutions NW 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 TEST PIT NUMBER TP-2 Fax: 425-449-4711 CLIENT G.i'~iJ)_evelopment PROJECT NUMBER =3~4~5~0===·-·----. PROJECT NAME Renton_ Sh_ort Plat -- ?ROJECT LOCATION ~~ntqnLWashinqton PAGE 1 OF 1 ----------------------------------· ___ ,, ________ _ DATE STARTED 8/4/14 COMPLETED 814/14 GROUND ELEVATION 195 ft __ GROUND WATER LEVELS: TEST PIT SIZE EXCAVATION CONTRACTOR -~!!~nt_l:'rQ'Ji_g~d_ EXCAVATION METHOD ____ _ ATTIMEOFEXCAVATION LOGGED BY ciH_/1 ____ _ CHECKED BY SHA ____ _ AT END OF EXCAVATION --·------------------ NOTES Deptt!__of Topsoil & Sod 1 O": blackberry bl!filt_~.$-AFTER EXCAVATION -=------- I UJ 0. I I >-"' .... UJ t21 w<Xl TESTS w-.... ::;; Cl 0.::, ::.z ;Ji 0 __§_ MC=21.30% <ti u 'i:ci <.i "-o "' ~--' ::i (!) MATERIAL DESCRIPTION ,'.._' TOPSOIL PS r, ,~.:_," 1.0 -----·-------____ 1,91_,Q Brown silty SAND with gravel, medium dense to dense. moist (fill) SM, _;,;.1<44"4,_.o__ _ _ _ -·-··· --···· _______ _ _ ____ 19.'l9. SM ''j' _Jj_ ,'l~ Brown silty SAND with gravel, medium dense to dense, moist (Native Contact)(Weathered Till) -becomes very dense, slightly cemented. and unweathered --~--___ ]B7=-0 ---rest pii"terminated at B.o feet belOWexisting gr8d8. No groundwater encountered during excavation. Bottom of test pit at 8.0 feet. <!)L__.L_ _ _J ______ ...L._..J.._J._ _____________________________ __, i 2 Earth Solutions NW 1805 -136th Place NE., Sutte 201 Bellevue, Washington 98005 Telephone: 425-449-4704 TEST PIT NUMBER TP-3 PAGE 1 OF 1 Fa>::: 425-449-4711 CLIENT Qi_vi pe~_I_QQIT)enl PROJECT NAME _R,enton ~QQ_rt Plat ____ ------· ___ ·--·-·------···-·· PROJECT NUMBER _.:}4_5,_Q PROJECT LOCATION fuJ_n!2_1::i.,_WE.:S~t~o~n====== DATE STARTED 614114 _____ COMPLETED §14/H _ GROUND ELEVATION 188 ft __ _ TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided .. GROUND WATER LEVELS: EXCAVATION METHOD LOGGED BY _SHA CHECKED BY _§HA _____ _ AT TIME OF EXCAVATION AT ENO OF EXCAVATION AFTER EXCAVATION -:: NOTES Depth of Topsoil & Sod 8": field_grass ________ _ 5_ TESTS MC= 15.70% MC= 20.00% MC= 12.50% Fines= 22.80% cti t.i If) ::j SM MATERIAL DESCRIPTION -------------------- Brown siJty SAND with gravel, medium dense, moist (Fill) -becomes dense to very dense -becomes very dense and unweathered -decreased fines content, cemented gg.5 18_6Q 10_ 10.0 -------------_______ 1Il9 Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 10.0 feet. ~'--'-----___j_____-------'--'---------'-------------------------------' r m ~ '!i • Earth Solutions NW 1805. 136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 TEST PIT NUMBER TP-4 Fax: 425-449-4 711 CLIENT ~ivi ~v_el_Qfl_n:,er:i!_ PROJECT NAME Renton_ Short Plat ----.:---::-=:_.~~JECT LOC~ll~~---~~D_t~'1__\(v~shi_ng_~pn PAGE 1 OF 1 PRO~ECT NUMBE'!_ J~-5~-;::- DA TE ST AR TED 61~114_ COMPLETED 814/1_4 GROUND ELEV A TION _jg_f!__ __ GROUND WATER LEVELS: TEST PIT SIZE EXCAVATION CONTRACTOR Cli~r:i!_Prqvided EXCAVATION METHOD LOGGED BY SHA ______ CHECKED BY _:;l_lj!I __ AT TIME OF EXCAVATION -::_ AT ENO OF EXCAVATION ~ NOTES _Dep~h of Topsoil & ~og 8_": blackt,eny bushes 0 TESTS MC= 11.30% Fines:::: 42.60% Cl) (,J Cl) :j (,J :i: c., "-o ;:;_ _, CJ !TPSL '' -'· i -· C o,_~ ' _.J., AFTEREXCAVATION -_____________ _ MATERIAL DESCRIPTION TOPSOIL _________ ------------··-__________________ 1u,Bc,_1.,_.,5 1 Brown silty SAND with gravel, dense, moist (Weathered Till) -becomes very dense, cemented, and unweathered Test plt terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. Bottom ot test pit at 8. O feet 174.Q ~._____. __ J_ ____ _J._...___. _________________________ __. ' ~ ~ w z • Earth Solutions NW 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Civi Dev_elQ:pment PROJECT NUMBER _;1450 ___ _ DATE STARTED -~[~_:1.4 __ COMPLETED 8/4/14 EXCAVATION CON1RACTOR Client Pr_ovided __ _ EXCAVATION METHOD LOGGED BY SHA _______ _ CHECKED BY SHA ___ _ NOTES Depth of Topsoil~-§_® 8": horsetails __ _ I ~g Cl 0 TESTS "' () (/) :::, TOPSOIL TEST PIT NUMBER TP-5 PAGE 1 OF 1 PROJECT NAME Renton Short Plat,, _______________ _ PROJECT LOCATION Renton. _ _WashinQ!QD ===~ GROUND ELEVATION ~-ft GROUND WATER LEVELS: TEST PIT SIZE AT TIME OF EXCAVATION ____ _ AT END OF EXCAVATION AFTER EXCAVATION MATERIAL DESCRIPTION -------~---· · -·---------- MC= 5.90% TPSL ~ o.s SP-<~pc~~B~ro-wn poorly graded SAND with silt, mediUITI-deriSe to dense, moist (Fill) _193.:§ ] 5 MC =9.70% 1 ~ 1 I SM SM L~ I -becomes very dense and unweathered Test pit terminated at 9.D feet below existing grade. Na groundwater encountered during excavation. Bottom of test pit at 9.0 feet. i!i,.._____,__ _ __,__ ____ ~_l..-J...._ _____________________ __, • Earth Solutions NW GRAIN SIZE DISTRIBUTION 1805-136th Place N.E., Suoe 201 Bellevue, WA 96005 Telephone: 425-284-3300 PROJECT NAME R!3nton Short Plat ~ROJ~_T_NU_M_B_ER ES-34=··cc50'=== U.S. SIEVE OPENING IN INCHES ---______ _f'._R_OJ_EC:..:.Tc::LO.:_C:::_A:c_n.oN Renton li.S. SIEVE NUMBERS 6 4 3 2 1.5 1 r.t 1/23/8 3 4 6 810 1416 20 30 40 5060 100140200 100 10 1 0.1 GRAIN SIZE IN MILLIMETERS HYDROMETER O.Q1 0.001 [coBBLES [ ~~~~vEgrs;' :.d::Nj fine -J---SILTORCLAY _-j --- Sj'.lE!Cimen ldentifi~n_i.___ __ -_ --_ --Gia_ ssification . . ___ _[LL I-PL Pl Cc·-· Cu ' r•± ~--_ 9.0ft. t __ Brown_ Silty SAND, SM i __ _ __ ! ta<l TP-4 __ ~.Oft. 1 : ____ _ Gray Silty SAND, SM ________ ---c_ r-_ g I I ~ ---------------+-----+--·r---+- ~ -+---------------·---~-------· -----·---·------------ ~ ! ~ __ .,__ __ § ir~~~en ldentific;~~~ _Q~zo J- 0 ~:~ 3 + 0 ~13~8 _D10 l_ %~~ver+ %!~;d ! __!,Silt_2J.s %Cl,iy ~ --,_ -----------~-· ·---·----------·-----t . -------r----------: ----~ 01 TP-4 3.0ft. 19 0.179 · , , 2.2 ' 55.2 , 42.6 :z i -----~---E·-----1 -------1----+-----t-~-r __ ~ --------·-------. -----·--+-------------·------:-------r---~ ··--t ------ ! ----~--------. --1----1------~-----~ G I ' ' .. EMAIL ONLY Report Distribution ES-3450 Civic Development 18211 -240th Avenue Southeast Maple Valley, Washington 98038 Attention: Mr. Joe Pruss Earth Solutions NW, LLC Er1con1pass ~ ENGINEERING Ii, SUtVEYING ~ PRELIMINARY TECHNICAL INFORMATION REPORT for Carpenter Short Plat 36xx Lincoln Ave NE Renton, WA 98056 September 3, 2014 Encompass Engineering Job No. 13708 Prepared For Joe Pruss 18211 240th Ave SE Maple Valley, WA 98038 SEP ll 4 2D14 Western Washington Division llastern Washington Division 165 NE Juniper St., Ste 20 I, Issaquah, WA 98027 [08 East 2"d Street, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: ( 425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net SECTION I: SECTION II: SECTION III: SECTION IV: SECTIONV: SECTION VI: SECTION VII: SECTION VIII: SECTION IX: SECTION X: TABLE OF CONTENTS PROJECT OVERVIEW CONDITIONS AND REQUIREMENTS SUMMARY-NIA OFF-SITE ANALYSIS FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN CONVEYANCE SYSTEM ANALYSIS AND DESIGN-NI A SPECIAL REPORTS AND STUDIES OTHER PERMITS--NA ESC ANALYSIS AND DESIGN BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT-NI A OPERATIONS AND MAINTENANCE MANUAL-NIA SECTION 1 PROJECT OVERVIEW Site Address: King County Tax Parcel: Project Overview 36xx Lincoln Ave NE, Renton WA, 98056 334570-0235 This project involves the development of a vacant 0.56 acre parcel into three single-family lots. The parcel is covered with grass/brush and about 35 significant trees. The site slopes down to northwest approximately 10% to 30%. Per the SCS Soil maps, the site is underlain with Alderwood, gravelly sandy loam. This is confirmed in the attached geotechnical engineering study. Proposed Drainage Controls 2009 KC SWDM Core Requirements Section 1.2.1 Core Requirement # 1: Discharge at the natural location • The pervious portions of the developed site will continue to sheet flow northwest towards the natural discharge area. The new impervious surfaces will drain to limited infiltration BMP's, then overflow into the public storm system. Section 1.2.2 Core Requirement #2: Offsite Analysis • An offsite drainage analysis is provided in this Preliminary TIR. Section 1.2.3 Core Requirement #3: Flow Control • This project will involve adding about 700 sq-ft of new impervious surface in the public R/W, so flow control is not being proposed for the improvements in the public R/W. Limited infiltration BMP's will be provided for new impervious surfaces on the lots, which will overflow into the public storm system. Section 1.2.4 Core Requirement #4: Conveyance System • The conveyance calculations will be provided with the final engineering plans. Section 1.2.5 Core Requirement #5: Erosion and Sediment Control • A temporary erosion control plan will provide BMP's to be implemented during construction. Section 1.2.6 Core Requirement #6: Maintenance and Operations • A maintenance and operations manual is provided in the TIR as determined with City review of the final engineering plans/design. Section 1.2.7 Core Requirement #7: Financial Guarantees and Liability • The developer will arrange for any financial guarantees and liabilities required by the permit. Section 1.2.8 Core Requirement #8: Water Quality • There will be less than 5,000 sq-ft of new PGIS so water quality measures are not needed, but the aforementioned BMP's will provide some water quality enhancement. 2009 KC SWDM Special Requirements Section 1.3.1 Special Requirement #I: Other Adopted Area-Specific Requirements • NIA Section 1.3.2 Special Requirement #2: Floodplain/Floodway Delineation • NI A there are no FEMA floodplains/floodways in the area Section 1.3.3 Special Requirement #3: Flood Protection Facilities • NIA Section 1.3.4 Special Requirement #4: Source Control • Source control is not required for this project. Section 1.3 .5 Special Requirement #5: Oil Control • NI A Oil control is not required for this project. 1'EW CS T'l'PE ! Rl,,._18.l,2± INV .. 180.67 MIN. 1:z' (JIISI PAVING I • I j__ __ _ I I CB FIIM~l96.04 12"ADS E i'IY,,,192-5-ol- /_ __ I I W.DEN $':!: OH EJtST SIDE FOR N' MIN r'AVlltG WIDltt • '-L HJJ45700216 \\l'/f!---1~-ii~:i~~J ! -;-;t, -1 I, ~ ~ I I "":,. '°"""--..-:...J.----''-Jo-00L1~(~' 1~ C ! ] It' DI. WATEFI uNE-'I'-... I I i' ,,..,, 1--- I , ~ ""'"" I ff ;!:: ' 0 Ell I ,,, I I I I i,, i1"'""" : Site Plan 1" = 40' iMAP .• \.::. ..:.;.T' =. SITE m 1 • ,· Renton •.•.• ..-. 5,""' •. ,,r; ,,1 + Oate:6/412014 Soun;:e: ,(mg Gounty iMAP -Property !ntormalloo (http:/lwww.metrotc.ga,,/GISliMAP} 7 ..,:--,. ',2 •. JT ·ST •: ;: -: Newcastle z ·, Co ,-;~ "t .. ~ ·:;.;. ~Vicinity Map 350ft ~ King County SECTI0N2 CONDITIONS AND REQUIREMENTS SUMMARY SECTI0N3 OFF-SITE ANALYSIS Project Overview This project involves the development of a vacant 0.56 acre parcel into three single-family lots. The parcel is covered with grass/brush and about 35 significant trees. The site slopes down to northwest approximately 10% to 30%. Per the SCS Soil maps, the site is underlain with Alderwood, gravelly sandy loam. This is confirmed in the attached geotechnical engineering study. Downstream Drainage Existing Conditions Northwest Drainage Basin Runoff from the site generally drains northwest from the subject site. About half portion of the run off drains into a CB at point (A) and apparently through a 6-inch pipe releases into a densely vegetated wooded area. Also other half portion of the runoff drains into the aforementioned vegetated wooded area. Eventually, runoff drain into a ditch at point (B) with approximately 1: 1 side slope for a total of 560-feet downstream. From point (B) runoff continues north along the Jones Ave NE and drains through a 12-inch concrete pipe from point (C) into a ditch with approximately 1 :3 side slope at point (D) for a total of 1,410-feet downstream. From point (D) runoff drains west through a 24-inch concrete pipe that crosses Jones Ave NE and enters into May Creek at point (E) for more than V. miles downstream. From point (E) the creek continues to northwest and at point (F) then crosses 405 Highway through a large diameter culvert or bridge and continues west, and eventually entering into Lake Washington. Developed Conditions North Overflow Drainage Basin Runoff from the existing frontage paving and also from the proposed onsite infiltration BMP overflow pipes collects in an 18" CB/pipe system draining north down the middle of Lincoln Avenue NE adjacent to the east side of the site (G). This storm system continues north about 700' where stream flows come in from the east and the storm system becomes a dual 12" system on both sides of the street (H). This storm system continues north another 200' where flows enter a ditch along the west side of the street (I). Ditch flows enter a 30" pipe crossing under NE 40'h street a little further north, then discharges into a deep ditch also on the west side of the street, about 1100' downstream from the site. This deep ditch continues to flow north to beyond V. mile downstream from the site where it enters a 36" culvert crossing the access road to a condo development. This drainageway continues north at least another V. mile before draining into Lake Washington. There were no apparent downstream drainage problems. Photo I: Vegetated wood area on the northwest side of the subject property -Photo 2 : May creek t N Downstream Drainage ... \ -.---.\ ·' ' i 1" = 200' SECTION 4 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Drainage Design This project will involve adding about 700 sq-ft of new impervious surface in the public R/W, so flow control is not being proposed for the improvements in the public RJW-runoff from the new frontage improvements will be routed into the existing CB/pipe storm system in Lincoln Avenue NE. Limited infiltration BMP's will be provided for new impervious surfaces on the lots, which will overflow into the public storm system. Per the attached geotechnical engineering study, limited infiltration will be provided on each lot to provide BMP's to attenuate runoff from the new roof/driveway impervious surfaces. Final design will be provided with the final engineering design/plan set. Because there will be less than 5,000 sq-ft of new paving, water quality treatment in not required. SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN SECTION 6 SPECIAL REPORTS AND STUDIES Earth Solutions NWLLC Geotechnical Engineering Geology Environmental S..:::ientists Cmstruction \lonitoring .. •• ,-:~-, r'""' .. -.... GEOTECHNICAL ENGINEERING STUDY -, RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST AND LINCOLN COURT NORTHEAST RENTON, WASHINGTON ES-3450 PREPARED FOR CIVIC DEVELOPMENT August 21, 2014 Kyle R. Campbell, P.E. Principal GEOTECHNICAL ENGINEERING STUDY RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST AND LINCOLN COURT NORTHEAST RENTON, WASHINGTON ES-3450 Earth Solutions NW, LLC 1805 • 136th Place Northeast, Suite 201 Bellevue, Washington 98005 Phone: 425-449-4704 Fax: 425-449-4711 Toll Free: 866-336-8710 Important Information About Your --~--Geotechnical Engineering Report Suosurface problems are a principal cause of constructron delays, cost overruns, clarms, and disputes The following rnfo1mat1on is provided to help you manage your risks. Geotechnical Services Are Performed lor Specific Purposes, Persons, and Projects Geotechnical engineers structure their ser1ices to meet the specific needs of their clients. A geotechnicai engineering study conducted for a civil engi- neer may not fulfill the needs of a co.1struction contractor or even another civil engineer. Because each geotechnical engineering study is unique. each geotechnical engineering report is unique prepared solely for the client. Ne one except you should rely on your geotechnical engineering report w1trout first conferring with the geatechnical oogineer who prepared it. And no one -no/even you -should apply the report for any purpose or proiect except !he 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. • elevation. configuration. location, orientation. or weighr of the proposed structurn, • composition of the design team. or • project ownership. As a genera1 rule, aiways inform your geotechnical engineer of pro1ect changes-,iven minor ones-and request an assessment of their impact. Geotechnical engineers cannot 1ccept responsibi/1/y or liability for problems that occur because their reports do not consider developments of which they were not informed. SUIJ8urface Conditions Can Change , A Geotechnical Engineering Report Is Based on A Unique Set or Project-Specific Factors A geotechnical engineering report is based on conditions that existed at the time the study was pertormed. Do not reiy on a geotechnical engineer- ing report whose 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. \ 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 preierences; tne 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 Jccess 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 lor 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 ottice building, or trnm a light industrial plant to a refrigerated warehouse, Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurtace conditi@s 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 abcut subsurtace conditions throughout the site. Actual subsurtace 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 -----·--------------------____________ / . -·---~-··· ----------~~ ----------- sutsurtace conditions revealed during construc,:on. r~e geotechmcal engineer who deve/opell your report canner assume responsibility or liability !or the report's recommendat1ons if that engineer does not periorm construction observation A Geotechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports nas resulted in costly problems Lower that risk by having your gee- technical engineer confer .vith appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the ,jesign team's plans and specifications. Contractors can also rrnsinterpret a geotechnical engineering report. Reduce ihat nsk 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 aesign drawings. Only photograor,c or electronic reproduction ,s acceptabie. but recognize that separal!ng logs from the report can elevate nsk. Give Contractors a Complete Report and Guidance Some owners ard design professionals mistakenly believe they can make contractors liable for unanticipated subsurface condrtrons by limiting what they provide for bid preparation. To help prevent costly problems, give :on- tractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors tr,at the report was not prepared for purposes of bid development and that the report's accuracy is limiied; encourage them to confer with the ,Jeotechnical engineer who prepared the report (a modest fee may be requiredi and/or to cor,duct additional study to obtain the specific types of informanon 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 geotecr,nical engineering is far less exact than other engineering disci- plines. This ,ack of understanding has created unrealistic expectations that have iea to disappointments. claims, and disputes To ne,p reduce the 01sk of such outcomes, geotechnical engineers commonly include a variety ol explanatory prnvisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where qeotechnical 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 geoenvimn- menlal study differ significantly from those used to pertorm a geotechnical study, For that reason. a geotechnical engineering report does not usually relate any geoenvironmental 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 failures. If you have ~ot yet obtained your own geoen- vironmental information. ask your geotechnical consultant for risk man- agemem guidance. Do not rely on an environmental repoitprepared 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 mo,d from growing on indoor surtaces. To be effective, a; such strategies sr,ould be devised for the express purpose of meld prevent'on, integrated into a com- prehensive plan, and executed with diligent oversight by a professiona mold prevention consultant. Because just a small amount of water or moisture can !ead to the development of severe mold infestations, a num- ber of mold prevention strategies locus 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 geolechnical engineer in charge of this project is not a mold ,reventicn 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· lion. Proper implementation of the recommendations conveyed in this reporl will not of itself be sufficient to prevent mold from growing in or on the structure involved. Rely, on Your ASFH1ember Geotechncial Engineer lor Additional Assistance Membership in ASFE(The Bes! People on Earth exposes geotechnical engineers to a wide array oi nsk management techniques that can be of genuine benefit tor everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more :nfornaUon. ASFE Tl!l.1 lell Pe1111 •• Eart11 8811 Colesville Road/Suite G;Q6, Silver Spring MD 109,:; ,elepnone 301/565-2733 Facsimile: 301 /589-2017 a-mail: info@asfe.orq www.asfe.org Copyright 2004 /Jy ASFE, rnc. Dup/fcation, reproducrion. or copy mg of this document, tn whole ar in part. Oy any means whatsoever, is stn'crly prohibited, except with ASFE's specific written permission &cerptfng. quoting, or otnerwise extractinq '!,/Ording from fhis document is oermittsd only with the express written permission of ASFE, and only for pur{Jases of scholariy research or book raview. Only memoers at ASFE may use fflis document as a complem<Jnt to or as an ::1/emenf of a geotectm1cal engineermg report Any other firm, mdivrdual, or other entity that w uses rhis document without being an ASFE member could be committing r,egligent or int!!nffonal (fraudulent) misr'Jpresentation. IIGER06045 OM August 21, 2014 ES-3450 Civic Development 18211 -240th Avenue Southeast Maple Valley, Washington 98038 Attention: Mr. Joe Pruss Dear Mr. Pruss: Earth Solutions NW LLC • C~nLec:'11, (_.cll t.:ng:rrwr~rin~ • Cinst~:J1 !](111 ,\1\nni,":.,·ing • E·tvi;nnmem._11 Scc11r·1'C. Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Renton Short Plat, Lincoln Avenue Northeast and Lincoln Court Northeast, Renton, Washington". In general, the site is underlain primarily by areas of fill (in the east and central portion of the site) underlain by glacial till. In our opinion, the proposed residential structures can be supported on conventional continuous and spread footing foundations bearing on competent native soil encountered at depths between two to four feet; or structural fill. Groundwater seepage was not observed at any of the test locations. However, seepage should be expected during grading activities, particularly during winter, spring and early summer months. Recommendations for foundation design, site preparation, drainage, and other pertinent recommendations are provided in this study. We appreciate the opportunity to be of service to you on this project. If you have questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Table of Contents ES-3450 INTRODUCTION .................................................................. . General .................................................................... . Project Description.............................. . . ................ . SITE CONDITIONS ............................................................... . Surface ....................................................................... . Subsurface ................................................................. . Fin .................................................................. . Topsoil ........................................... . Native Soil . . .. . . . . . . . . . . . . . . ....................... . Geologic Setting ................................................. . Groundwater ................................................................ . DISCUSSION AND RECOMMENDATIONS ................................. . General .................... . Site Preparation and General Earthwork .......................... . Wet Season Grading ............................................ . In-situ Soils .................................................................... . Imported Soils ............................................................... . Structural Fill ...................................... . Foundations .............................................................. . Seismic Design Considerations ..................................... . Critical Areas Assessment. .................................................... . Slab-On-Grade Floors ................................................... . Retaining Wans ............................................................ . Drainage .................................................................................. . Excavations and Slopes . . ................................................. . Utility Trench Backfill ................................................... . Pavement Sections ...................................................... . LIMITATIONS ........................................................................ . Additional Services .................................... . Earth Solutions NW, LLC PAGE 1 1 2 2 2 2 2 2 3 3 3 3 3 4 5 5 5 5 6 6 6 7 7 8 8 9 9 10 10 GRAPHICS Plate 1 Plate 2 Plate 3 Plate 4 APPENDICES Appendix A Appendix B Table of Contents Cont'd ES-3450 Vicinity Map Test Pit Location Plan Retaining Waif Drainage Detail Footing Drain Detail Subsurface Exploration Test Pit Logs Laboratory Test Results Earth Solutions NW, LLC GEOTECHNICAL ENGINEERING STUDY RENTON SHORT PLAT LINCOLN AVENUE NORTHEAST AND LINCOLN COURT NORTHEAST RENTON, WASHINGTON ES-3450 INTRODUCTION General This geotechnical engineering study was prepared for the proposed residential development to be constructed on the west side of Lincoln Avenue Northeast in Renton, Washington. The site is comprised of a single tax parcel; and is located at the intersection with Lincoln Court. The purpose of this study was to develop geotechnical recommendations for the proposed development. Our scope of services for completing this geotechnical engineering study included the following: • Reviewing the project details; • Excavation, logging and sampling oftest pits excavated at the site; • Engineering analyses of data obtained through the site exploration, and; • Preparation of this report. The following documents/maps were reviewed as part of our report preparation: • Conceptual Drainage Control, Tree Cutting/Inventory, Generalized Utility & Grading Plan, by Encompass Engineering & Surveying, Sheet 1 of 1, dated June 3, 2014; • King County iMap online resource; • Geologic Map of Washington, Southwest Quadrant, by Walsh, et al, 1987, and; • Washington State USDA Soil Conservation Survey (SCS). Project Description We understand the site will be developed with three single-family residential structures, on-site roadways, parking areas, and associated improvements. Finalized grading plans were not available at the time of this report production; however, given the topographic change across the site, we anticipate grading activities will likely involve cuts and fills on the order of ten feet or less to establish the final design grades. Civic Development August 12, 2014 ES-3450 Page2 Final building loads were not available at the time of our report. However, we anticipate wall loads for one to two-story single-family residential structures will be on the order of 1 to 2 kips per lineal foot; and slab-on-grade loading of 150 pounds per square foot (psf). On-site infiltration of stormwater from downspouts is being proposed for the subject project. If the above design estimates are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to confirm that our geotechnical recommendations have been incorporated into the final design. SITE CONDITIONS Surface The site is located on the west side of Lincoln Avenue Northeast, at the intersection with Lincoln Court Northeast in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map). The site is roughly rectangular in shape and consists of a single tax parcel. The site is currently undeveloped and moderately vegetated with fir, maple, and general native undergrowth. The existing site topography descends gently from the street elevation towards the west; with elevation change on the order of approximately 34 feet. Subsurface A representative of ESNW observed, logged and sampled five test pits excavated with a track- hoe across the site. The test pits were excavated for the purposes of characterizing the subsurface conditions. The approximate locations of the test pits are depicted on the Test Pit Location Plan (Plate 2). Please refer to the test pit logs provided in Appendix A for a detailed description of the subsurface conditions. Fill Fill was encountered at all but one of the test pit locations. The area on-site where fill was not encountered was in the northwest corner of the site. near the property boundary. In general the fill was observed extending to a depth of approximately three to four feet. Fill soil should be anticipated in any excavation on this site. The silty sand with gravel (Unified Soil Classification, SM) fill may be suitable for support of foundations; however a representative of ESNW should be retained during the construction phases of the site development to evaluate the suitability of any on-site soils for use as structural fill or bearing of foundations. Topsoil Topsoil was encountered at all of the test pit locations extending to depths of between about six to ten inches below existing grade. Topsoil is not suitable for use as structural fill nor should it be mixed with material to be used as structural fill. Topsoil or otherwise unsuitable material can be used in landscaping areas if desired. Earth Solutions NW, LLC Civic Development August 21, 2014 Native Soil ES-3450 Page 3 Underlying the topsoil and fill, native soil consisting primarily medium dense to dense glacial till consisting of silty sand with gravel (SM) was encountered extending to the maximum exploration depth of ten feet below existing grades. The native soil transitioned from a medium dense condition to dense at approximately four feet in depth at most of the test pit locations. Geologic Setting The referenced geologic map resource identifies glacial till (Qgl) deposits across the site and surrounding areas. The referenced SCS soil survey identifies Alderwood Gravelly Sandy Loam (AgC and AgD) series soils across the site and surrounding area. Alderwood gravelly sandy loam soils consist of glacial till formed on morraines and till planes; and typically present a low to moderate erosion hazard; and are somewhat well drained. The native soil conditions observed at the test pit locations are generally consistent with glacial till deposits. Groundwater Groundwater was not observed at any of the test pit locations during the fieldwork (August 2014). However, seepage should be expected at some locations, particularly during the winter, spring and early summer months. Perched groundwater is typically observed on sites underlain by glacial till soil; and is usually encountered at the contact between the weathered and unweathered till deposits. 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 flow rates are higher during the wetter, winter months. DISCUSSION AND RECOMMENDATIONS General In our opinion, construction of the proposed residential development is feasible from a geotechnical standpoint. The proposed buildings can be supported on conventional continuous and spread fooling foundations bearing on competent native soil, existing competent fill or at least two feet of structural fill. Slab-on-grade floors should be supported on a firm and unyielding subgrade. Recommendations for foundation design, site preparation, drainage, and other pertinent geotechnical recommendations are provided in the following sections of this study. This study has been prepared for the exclusive use of Civic Development 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. Earth Solutions NW, LLC Civic Development August 21, 2014 Site Preparation and Earthwork ES-3450 Page4 Site preparation activities will involve site clearing and stripping, and implementation of temporary erosion control measures. The primary geotechnical considerations associated with site preparation activities include building pad subgrade preparation, underground utility installations, and preparation of pavement subgrade areas. Temporary construction entrances and drive lanes, consisting of at least 12 inches of quarry spalls can be considered in order to minimize off-site soil tracking and to provide a stable access entrance surface. Erosion control measures should consist of silt fencing placed along the down gradient side of the site. Soil stockpiles should be covered or otherwise protected to reduce soil erosion. Temporary sedimentation ponds or other approaches for controlling surface water runoff should be in place prior to beginning earthwork activities. Topsoil and organic-rich soil was encountered generally within the upper six to ten inches at the test pit locations. Topsoil and organic-rich soil is not suitable for direct foundation support, nor is it suitable for use as structural fill. Topsoil or organic-rich soil can be used in non-structural areas if desired. A representative of ESNW should observe the initial stripping operations, to provide recommendations for stripping depths based on the soil conditions exposed during stripping. Subgrade conditions expected to be exposed throughout the proposed building and pavement areas will likely be comprised of silty sand with gravel glacial deposits. After the completion of site stripping the subgrade conditions should be evaluated by a representative of ESNW. A proofroll utilizing a fully loaded solo dump truck may be necessary to evaluate the suitability of the exposed native soils prior to placement of fill. ESNW should be retained during this phase of earthwork to observe the subgrade conditions and other earthwork activities. The soils exposed throughout subgrade areas should be compacted to structural fill specifications prior to constructing the foundation, slab, and pavement elements. The subgrade throughout pavement areas should be compacted as necessary and exhibit a firm and unyielding condition when subjected to the proofrolling with a loaded solo dump truck. Overexcavation and replacement with crushed rock may be necessary, depending on the conditions encountered during construction. Structural fill soils placed throughout foundation, slab, and pavement areas should be placed over a firm base. Loose or otherwise unsuitable areas of native soil exposed at subgrade elevations should be compacted to structural fill requirements or overexcavated and replaced with a suitable structural fill material. Where structural fill soils are used to construct foundation subgrade areas, the soil should be compacted to the requirements of structural fill described in the following section. Foundation subgrade areas should be protected from disturbance, construction traffic, and excessive moisture. Where instability develops below structural fill areas, use of a woven geotextile below the structural fill areas may be required. A representative of ESNW should observe structural fill placement in foundation, slab, and pavement areas. Earth Solutions NW, LLC Civic Development August 21, 2014 Wet Season Grading ES-3450 Page 5 The moderate moisture sensitivity of the on-site soil will make grading during periods of rain somewhat difficult. Mass grading should take place during the late summer months when conditions are more favorable. If grading takes place during the wetter winter, spring or early summer months, a contingency in the project budget should be included to allow for export of native soil and import of structural fill as described below. In-situ Soils The soils encountered throughout the majority of the test sites have a moderate sensitivity to moisture and were generally in a moist condition at the time of the exploration (August 2014). In this respect, the in-situ soils may not be suitable for use as structural fill if the soil moisture content is more than 4 to 5 percent above the optimum level at the time of construction in the case of the silty sand soil encountered at a number of the test pits locations. In general, soils encountered during the site excavations that are excessively over the optimum moisture content will require moisture conditioning prior to placement and compaction. Conversely, soils that are below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. If the in-situ soils are determined to not be suitable for use as structural fill, then use of a suitable imported soil may be necessary. In our opinion, a contingency should be included in the project budget for exporting unsuitable soil and importing structural fill; or moisture conditioning recommendations can be provided upon request based on field observations during the construction phase of on-site work. Imported Soils 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 defined as the percent passing the #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, at moisture contents above the optimum level and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D-1557). Soil placed in utility trenches, pavement areas and in the upper 12 inches of slab-on-grade areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones, depending on the responsible utility district or jurisdiction. Earth Solutions NW, LLC Civic Development August 21, 2014 Foundations ES-3450 Page 6 Based on the results of our study, the proposed residential buildings can be supported on conventional spread and continuous footings bearing on competent native soils encountered between two and four feet below existing grades, competent existing fill or new structural fill. Loose soil exposed at foundation subgrade elevations can be compacted in place. Provided foundations are be supported as described above, the following parameters can be used for design of new foundations: • Allowable soil bearing capacity • Passive earth pressure • Coefficient of friction 2,500 psf 300 pcf (equivalent fluid) 0.40 A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor-of-safety of 1.5. With structural loading as expected, total settlement in the range of one and one half inch and differential settlement of about one inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Design Considerations The 2012 IBC recognized the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.1-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. Liquefaction is a phenomenon where saturated or loose soils suddenly lose internal strength in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. The referenced liquefaction susceptibility map of King County indicates the site and surrounding areas exhibit a low liquefaction susceptibility. In our opinion, site susceptibility to liquefaction can be characterized as low. The absence of a uniformly established shallow groundwater table is the primary basis for this characterization. Critical Areas Assessment ESNW has reviewed the City of Renton critical areas map available on-line in a GIS format. This utility identifies critical areas in the form of landslide, erosion, and steep slope hazards. Critical areas were observed on the subject site upon review of the available reference material. A moderate landslide hazard is identified for portions of the site. There are steep slope areas identified on the west side of the adjacent property. An erosion hazard area is identified for the northern portion of the site in the green belt area. In our opinion, the landslide hazard and erosion hazard on the subject site is minimal due to the relative density of the underlying soil, and the lack of groundwater in the subgrade. Earth Solutions NW, LLC Civic Development August 21, 2014 ES-3450 Page 7 No signs of erosion, surface seeps, or hummocky terrain was observed during our fieldwork (August 2014). As such, it is our opinion that the slopes on and around the subject site demonstrate a stable condition in their current state; and given the recommendations provided in this study for erosion control and site grading are adhered to, the potential for soil movement in the future as a result of the proposed development is minimal. The relative density of the underlying soil on the subject site, the absence of evidence pointing towards past soil movement on the site, and the lack of groundwater is the basis for this conclusion. Slab-On-Grade Floors Slab-on-grade floors for residential buildings constructed at this site should be supported on a firm and unyielding subgrade. Where feasible, the existing native soils exposed at the slab-on- grade subgrade level can be compacted in place to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. 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 (percent passing the #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 a vapor barrier is to be utilized it should be a material specifically designed for use 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 can be used for retaining wall design: • Active earth pressure (yielding condition) • At-rest earth pressure (restrained condition) • Traffic surcharge for passenger vehicles (where applicable) • Passive earth pressure 35 pcf (equivalent fluid) 55 pcf 70 psf (rectangular distribution) 300 pcf (equivalent fluid) • Coefficient of friction 0.40 • Seismic surcharge (active condition) 6H* • Seismic surcharge (restrained condition) 12H* •where H equals retained height Earth Solutions NW. LLC Civic Development August 21, 2014 ES-3450 Page 8 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 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. A typical retaining wall drainage detail is provided on Plate 3. Drainage Groundwater was not observed during the fieldwork (August 2014). However, groundwater should be anticipated in deeper site excavations particularly during the wetter winter and early spring months. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide recommendations to reduce the potential for instability related to seepage effects. Infiltration of stormwater runoff from downspouts and roadways is feasible on the subject site, given the subsurface conditions ESNW observed at the test pit locations. However, infiltration of stormwater on sites underlain by glacial till can be slow. We recommend a rate of 0.13 inches per hour or less be used for design of the infiltration facilities. Given that the site is underlain by glacial till, an overflow system should be included in the design. In our opinion, foundation drains will be necessary on the subject site. A typical foundation drain detail is provided as Plate 4. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Based on the soil conditions encountered at the test pit locations, the soils encountered within the majority of the development envelope, and where groundwater seepage is exposed, are classified as Type C by OSHA/WISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.5H:1V (Horizontal:Vertical). The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. In areas where no groundwater is observed, the soil will be classified as Type A. Temporary slopes over four feet in height in Type A soil must be sloped no steeper than 0.75H: 1V. ESNW should observe site excavations to confirm the soil type and allowable slope inclination. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Earth Solutions NW, LLC Civic Development August 21, 2014 ES-3450 Page 9 Permanent slopes should maintain a gradient of 2H:1V, 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, and to provide additional excavation and slope recommendations, as necessary. Utility Support and Trench Backfill In our opinion, the soils anticipated to be exposed in utility excavations should generally be suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities. Some of the native soils are moisture sensitive and will therefore be difficult to use as structural trench backfill if the moisture content of the soil is high. Moisture conditioning of the soils will likely be necessary prior to use as structural backfill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the specifications of the applicable jurisdiction. Seepage should be anticipated within utility trench excavations. Caving of the trench sidewalls due to hydrostatic pressure or the cohesion less nature of the site soils should be anticipated by the contractor. Pavements The performance of site pavements is largely related to the condition of the underlying subgrade. To provide 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 as recommended 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 will require remedial measures such as overexcavation, placement of a geotextile and thicker crushed rock or structural fill sections prior to pavement. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections can be considered: • 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, ATB and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to at least 95 percent of the maximum dry density. Final pavement design recommendations can be provided once final traffic loading has been determined. If areas of seepage are exposed in roadway excavations, drains should be installed in these areas to allow removal of the water. Specific recommendations and details for roadway drainage can be provided upon request. Earth Solutions NW, LLC Civic Development August 21, 2014 LIMITATIONS ES-3450 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 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 ,~· ,. Reference: King County, Washington Map626 By the Thomas guide Rand McNally 32nd Edition NORTH 8 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. • ··.t • . . ~• ..• ·.< Vicinity Map Renton Short Plat Renton, Washington Drwn. GLS Date 08/20/2014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate . ':'.·'-i:-: . .. -.; :.:·.: • vu•4 " . -I&-.... • ,. '31] - ITP-4 -•- I 180 ~ 3, 190 r ---·-ITP-5 200 LEGEND ' TP-1 -~-Approximate Location of I ESNW Test Pit, Proj No. ES-3450, Aug. 2014 , Subject Site ; Proposed Lot Number 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 I 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. 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. i90 ITP-3 -•-' I ' L'. I -•- TP-21 TP-1 I -•---; -l NORTH 8 0 1 "=30' • Test Pit Location Plan Renton Short Plat Renton, Washington ,2 Diwn GLS Date 08/20/2014 Proj. No. Checked SHA Date Aug. 2014 Plate wJ z WJ ::J z C LL: ~ z ' --' 0 u z ' -- 3450 2 18" Min. 111 111 000000000 0• o Oo ,() o " o oO 0 o ·= 0° o O 0 ()0 ~o" o Q 004)000 (j 0 0 ° o O o o Q 0 O O 0 0 0 0 00 0 00 oo 0 0 00 0 0 0 0 0 6 0 000° 0 0 0 0 .9 0 0 " 0" o Q O o Q o 0 = 0 Q o o " "O O o o 0 0 o 0 0 0 0 0 0 0 0 0 oOoooO og 00 0°0 o Oo o 0 oo0 o,.oO 0 0 0 o OUoOooOO o "' "' "' 0"' o o"' "'o ""0 "o Q oO O o Q (5 0 o O 0 o O 0 0 ° ""' "' ~ Clo OQ0°o Q oa Vo 0 0 0 0 0 0 0 0 0 00 0 00 0 Cc:, 0 OQO 0 0 0 0 0 Oo o Q 0 Ocoo Q Oo : " Q o <>o 0 0 oQ o O o O Q, "'Q o o"'oo 00 0 ° Oo O o O 6' (/"' o Q Oo% 0 O~ 0 111 NOTES: • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. Structural Fill • Sheet Drain may be feasible in lieu of Free Draining Backfill, per ESNW recommendations. SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. LEGEND: 0°0 0 o "o O O Free Draining Structural Backfill o 0 ..... ............... :,~:,!:,~w. 1 inch Drain Rock •rl'•l'•l'•.I'• • RETAINING WALL DRAINAGE DETAIL Renton Short Plat Renton, Washington Drwn. GLS Date 08/20/2014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate 3 Slope .. -t 2" (Min.) Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of rn . . ' 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal; native soil or other low permeability material. 1" Drain Rock SCHEMATIC ONLY -NOTTO SCALE NOT A CONSTRUCTION DRAWING • -Solutions NWLLc ng. Construction Monitor ng ...-onmental Sciences Drwn. GLS FOOTING DRAIN DETAIL Renton Short Plat Renton, Washington Date 08/2012014 Proj. No. 3450 Checked SHA Date Aug. 2014 Plate 4 Appendix A Subsurface Exploration ES-3450 The subsurface conditions at the site were explored by excavating a total of five test pits excavated across accessible portions of the property. The subsurface explorations were completed in August of 2014. The approximate test pit locations are illustrated on Plate 2 of this report. Logs of the test pits are provided in this Appendix. The test pits were excavated to a maximum depth of 10 feet below existing grades. Earth Solutions NW, LLC Earth Solutions NWLLc SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS GRAPH LETTER TYPICAL DESCRIPTIONS COARSE GRAINED SOILS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER TI-IAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE TI1AN SO% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SAND AND SANDY SOILS CLEAN GRAVELS (UTILE OR NO FINES} GRAVELS WITH FINES (APPRECIABLE AMOUNT OF FINES) CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH MORE THAN 50% FINES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE SILTS AND CLAYS SILTS AND CLAYS AMOUNT OF FINES) LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT WELL-GRADED GRAVELS, GRAVEL- SANO MIXTURES, LJTIU: OR NO FINES POORLY-GRADED GRAVELS, GRAVEL-SANO MIXTURES, ume ORNOFlNES SILTY GRAVELS, GRAVEL-SANO- SILT MIXTURES CLAYEY GAAVELS, GRAVEL. SAND. CLAYMIXTU~ WELL-GRACED SANOS, GRAVELL V SANOS, UTTI..E OR NO FINES POORLY-GRADED SANDS, GRAVELLY SANO, LITTI.E OR NO FINES SILTY SANDS, SAND-SILT MIXTURES CLA. VEY SANOS, SANO -CLAY MIXTURES INORGANIC SIL TS AND VERY FINE SANOS, ROCK FLOUR, SIL TY OR CLAYEY FINE SANOS OR Cl.A YEV SILTS WITH SLIGHT PLASTICITY INORGANIC Cl.A VS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SIL TS ANO ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILT$, MICACEOUS OR DIATOMACEOUS FINE SANO OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY ORGANIC Cl.A VS OF MEDIUM TO HIGH PLASTICITY, ORGANIC Sil TS PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS 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. § >--tl w ~ >--z i, ;: <> S! ~ i ~ t I ~ ~ w z w " • Earth Solutions NW 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Civi Developmer1J ----------------- TEST PIT NUMBER TP-1 PAGE 1 OF 1 PROJECT NAME Renton Short Plat ___ ····-··---_ ~ROJECT NUMBER 3450 PROJECT LOCATION )~_enton...._\o_'Vas_hing!Qn --------- L - -------·····-··-·-·-- DATE STARTED __ll/4/14 _____ _ COMPLETED _,8~/4ccl_c14'-------GROUND ELEVATION _200 ft GROUND WATER LEVELS: TEST PIT SIZE EXCAVATION CONTRACTOR Cl~~n~t~P~ro~v~id~e~d~--------·-··-· EXCAVATION METHOD ---------__ AT TIME OF EXCAVATION -____ ---------------- LOGGED BY _,S,eHA=-----CHECKED BY _,S,eH_eAe_ __ _ NOTES Depth ofTqp_§_Qjl ~ Sod 6": bare soil AT END OF EXCAVATION ----------------- AFTER EXCAVATION _ UJ "->-0: <Ji I .... UJ 6:2 UJ ID TESTS () w--'2 <Ji 0 "-:, ::i 2Z ;;i a ITPS MC= 7.70% SM --·-- SM . u :i: C> "-o ~ .... C> ·-'-----'-' )? i I I I ' 0,5 3.0 MATERIAL DESCRIPTION TOPSOIL ·--· -------·-------------------------------- Brown silty SAND with gravel, medium dense to dense, moist (Fill) Brown silty SAND with gravel, medium dense to dense, moist (Native Contact)(Weathered Till) -becomes very dense and unweathered __ 197.Q. C -MC= 17.90% L - I i ! ----c--c-cc=-c-cc-,-----cc~-------c----cc---c----Test pit tenninated at 9.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 9.0 feet. 191 0 ~ a ~ 8 ~ " h ~ Cl § 2 ;,; i ~ C: I "' ~ w z w Cl • Earth Solutions NW 1805-136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Civ.i p~'{~!QfIB1 ... e .. nt.___ _________________ --·------ TEST PIT NUMBER TP-2 PAGE 1 OF 1 PROJECT NAME Renton Short Plat --· ·------------- P_R_OJE_CT NUMBE_R, 0 34,,.,,_5,..o________ =--__ =======-PROJECT LOCATTON ____ ~~-nton, Washington _____ ~==~-~•---~•~~ DATESTARTED "'8~/4~/1~4'------COMPLETED ~/4/14 EXCAVATION CONTRACTOR _Client Provided_ _ GROUND ELEVATION _1_!1_5 ft_ GROUND WATER LEVELS; EXCAVATION METHOD ------------- TEST PIT SIZE LOGGED BY ,,Secl:fecAc__ ____ _ CHECKED BY _§HA ___ _ AT TIME OF EXCAVATION -=----- AT END OF EXCAVATION =----_ AFTER EXCAVATION -NOTES .Qfilltti ofIQpsoil & Sod_JO": blackberry bushes l 0 w .. )-0:: >-w w"' ... :; o.::, ~z "' vi TESTS u en :::i TPSL, C) :i: <.? "-o ~ ... <.? -' '- -- MATERIAL DESCRIPTION TOPSOIL -------- 1.0 L -·------------·~-~,o L MC =21.30% L - L 1 I I I I I 't SM ' i i I ' ' I SM I I I I 4.0 Brown silty SAND with gravel, medium dense to dense. moist (Fill} --------------------c-----------------------------'"''-"1.Q Brown silty SAND with gravel, medium dense to dense, moist (Native Contact)(Weathered Till) -becomes very dense, slightly cemented, and unweathered I I h---11-. 3,0 _____ --------------------------____ 167,Q Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 8.0 feet. ~ .. ~ g "' :, ~ z a ,'. " S! ;; i .: ~ ;. ~ w z w "' - Earth Solutions NW • 1805 -136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Civi DevefQQmE!nt ___ _ PROJECT NUMBER __e.450 __ DATE STARTED Jll4/H COMPLETED _8/411'1 _ EXCAVATION CONTRACTOR Client Provided ______ ·--·---- EXCAVATION METHOD LOGGED BY SHA ___________ _ CHECKED BY __.,Se_He::A,__ __ _ NOTES Depth of ToQ§Qff_~ .~od 8''.: field grass w a. :,: >-"' rn 0 f-W r'-" 5:= w"' TESTS t.i a.o w-~:. VJ j?~ C a.:::, ::i :.z (.') .,: VJ 0 ifPSL ~ cos TOPSOIL TEST PIT NUMBER TP-3 PAGE 1 OF 1 PROJECT NAME Renton Short Plat __________ -------------- PROJECT LOCATION Re!)t_~~-Was_hingt(J!1 __ .========-- GROUND ELEVATION _188_ft _____ TESTPITSIZE __ GROUND WATER LEVELS, AT TIME OF EXCAVATION _-______ -------------- AT END OF EXCAVATION - AFTER EXCAVATION MATERIAL DESCRIPTION I ~ Brown silty SAND with gravel, medPum dense, moist (Fill) SM / ? MC= 15.70% ! I i i ' I 2.0 ·---Brown SiltY-SANo with Qi-avel, medium dense, moist (Native Contact)(Weathei-ed Tiilj -becomes dense to very dense I--5 __ _ MC=20.00% I I I I-- L I MC= 12.50% Fines= 22.80% SM I ! ' I I I -becomes very dense and unweathered --decreased fines content, cemented . i_ 1Q,Q_ ______ ---_ ---.... -----------·------------.J?"~--0 Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. Bottom oftest pit at 10.0 feet. v ~ ~ Q "' ~ ~ ~ z " ._ "' /ii ;,; J J ! I!, ;; m ~ w z w " L C Earth Solutions NW • 1805. 136th Place N.E., Suite 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CUENT Civi Development---·---·--·---- PROJECT NUMBER 3450 _ _ ___ _ CATE STARTED 814114 COMPLETED 8/411_± __ _ EXCAVATION CONTRACTOR Client Provided __ _ EXCAVATION METHOD LOGGED BY .fill!',________ CHECKED BY .§.l:IA __ -··- NOTES Depth of Topsoil & Sod 8": blackberry bushes TESTS 0 '1l'SL . TOPSOIL TEST PIT NUMBER TP-4 PAGE 1 OF 1 PROJECT NAME Renton Short Plat ____________ .. _ PROJECT LOCA~~~ Rento_n, Washir:,g!on_ ____ _ __ ---=;:..;;._ --·--·-· GROUND ELEVATION 182ft TEST PIT SIZE ~------·- GROUND WATER LEVELS: ATTIME Of EXCAVATION -= _______ _ AT ENC OF EXCAVATION - AFTER EXCAVATION -----------·-····----- MATERIAL DESCRIPTION 181.5 • Bi-own silty SAND wil:tiQfave{ dense: fTiofsT(\IVeatnered Till) MC= 11.30% Fines :: 42.60% -becomes very dense, cemented, and unweathered ~--~ -- C • i ~-Jl!_O --T8st pit ternlinated ai-B.o"f"eetbeiOW-eXi-stirlQ-Qf3de -No grOUridwater encountered during _Fi:.Q excavation. Bottom of test pit at 8. O feet ' i ~ ~ g ~ :> ~ ~ "' ~ " ~ j ~ ~ ~ ;; m ~ w z w "' • Earth Solutions NW 1805 -136th Place N.E., su;te 201 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT _Ci~{_Qe~~ffiEWt ---·--------- TEST PIT NUMBER TP-5 PAGE 1 OF 1 PROJECT NAME _Renton Sho_rt Plat _____ -----·----···· P'ROJECT NUMBER ~3,04~50~------------.---~-------~====== ____ ~ROJECT LOCATION __ Renton_,_ Washing_!QD_ DATE STARTED .fil1114 __ COMPLETED !li1L14 ____ ·---__ TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND ELEVATION _194_ft GROUND WATER LEVELS: EXCAVATION METHOD --·------------~----------ATTIME OF EXCAVATION -=---------. LOGGED BY -~HA __ CHECKED BY ~S~HA=----------AT ENO OF EXCAVATION -=------- NOTES Depth of Topsoil & Sod B": horsetails ___________ _ AFTER EXCAVATION--------·------ 0 UJ a. >-" 1-W UJ tll -'::; a.::, ::; z ;;<; TESTS MC= 5.90% ITPSL C.:c SP- SM SM ! MC=9.70% i MATERIAL DESCRIPTION 0.5 TOPSOIL Brown-POorry graded SAND With silt, medium dense to-dense. moist(Fi1TI _, ______ _ 2.0 ·becomes very dense and unweathered -f-Li_~------------------. ' -·-------------.. J~ ' Test pit terminated at 9.0 feet below extstrng grade. No groundwater encountered during excavation. Bottom of test pit at 9.0 feet. I ' ; I Appendix B Laboratory Test Results ES-3450 Earth Solutions NW, LLC • Earth Solutions NW GRAIN SIZE DISTRIBUTION 1805 -136th Place N.E., Sufte 201 Bellevue. WA 98005 Telephone: 425-284-3300 PROJECT NAME Renton Short Plat CLIENT Civic Development PROJECT NUMBER ES-3450 PROJECT LOCATION Rell!On ·=· =s===========ci -U.S. SIEVE OPENING IN INCHES i U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 1.5 1 r.. 1/23/8 3 4 6 810 1416 20 30 40 so 60 100140200 100 I . : J ! I I I I' ! t I 'I!' ! I :::I-+:~-l--:1 =_ +:=_-==::::::=:=:= '-+L!-1-'-+,--/-;~ ~ \ • fJ. t++c-+--+--+---H- 1 +-:H!'-4--+-f-+----1 ! 70 -----+---++++-+-<-+-+--+-L 651-+-+--l--f++-+++-+-+-+----+W-l--'-"-+-+--· ~Hiri··++-+1+--~---+l++-+-+--1-+--+---+++- 1 +-l--f-"-+---,----l eo -1~-----H+++-+-+-+----1+1-+++-J--11 1 --+\1--4->++-H-+-+-4--+++-el--,-+-+--+---< SSH'--+--+----<1·144.-+-+'-+--+----+-+++-l-+-+---l-+---fF \ \\ ,I '-i~-I [--l~-~- 50 -------++i+Hf-11---1 t -1 ! t f +ut -~H-H-+-+-l-y--+++1 +H-,+--+--+, --1 45 --+-+--H~ --1--t--! -I 11 Ti ' '. +-,I '1 I j i ! ! · I i ' • :f--,_+-~-+~-:·:::,~::_:;_ ... ;_-,;_-:_+:;:~:-:f-·+· ---+i---_---+!+Hl+f-J__+i--+l-''h+\--.µI ,+H+-H-I -/H~+i_~:=:=:==--l- 30f-+--+---+-----+l+!I +t~r i :-+1-l-+---+----+l+Hi-+-+-+--+---\cH+-+-+ --+---+1+++-1, ~f-+-+---, 25f--+-+--111 --I ' ii-l-! -+---+---+4--1-il-11. 1-l--r--+M-H-f-+--+--+--+++++-1-+--+--+----< 20 -~--I' i I . 1 1+H-l----+!+l-4-H--+--H+t--H- 15 ,_ --,_ ~ __ _J[f+I I ++1--+-l---,--il . -,----1 ,_ --+---+H+++-+-+--f--·*+-+-i-l--t--1--+- i i Ii I 10 1· I I . 'I , 1· '""1' L 5 , t -, __ ~+--·µ.,.I I +++-l, --+--II -1· 1-t --!-I! --+---f a I / i I i I Ii I : -- I -I 'i --_f-_ -----ls I -I I, I I . i ' I I I I - I \ ;+++++-1-+-l--+H++-+-H-+---+++-,+-I--H-+--l---fH-+++-+4~1---H++f--l-H-+----1 i \ -+i-++i--+-+-+--+----l-i++++-+--+--1----l-W-1,-l-l-K--\J--- I I I I ~- -- I ' I I' ---~ : I I I --·- i I I 1 ' I I ! i i I I I i I 100 10 0.1 O.D1 0.001 GRAIN SIZE IN MlLLIMETERS ------- I i ~OBBLES I -· Gf<AVEL ! -SAND --~ -----coarse I~-~_coarse [ medium=1 fine _,, ________ _ SILT OR CLAY _] LL PL Pl Cc Cu ~------------~-------------------------T--~--~-- _S~imen Identification_ ~ ________ _:C:.:la::s:::s:.:ifi:.:1c:::a=t::.:io:.:n'-----------+-=::_1-:...=-+--'--'--+-=-+--=-=--J ~ n TP-3 _ ___ _9_.0ft_. -f-----Brown Silty SAND, SM ______ -----+----+----+---+--~f----< ~ ;::1 TP-4 _3_.0ft_'-+-----------G_ray Silty SAND, SM -----------t----1---___ __ g ·•···· --5 --------------------------+----+---t------+---+----l o,---------------------------------------- ~ j-Sp-e-cim_e __ n ld_e_n_tifica-tio_n_ -0-10 ·0-~-o---!--D-3_0 ______ -D10 l %~ravel %Sand "tsi,t o/.Clay- ,'.1----i------------l---------;: .:::l TP-3 9.0ft. 19 __ __ll_._~83 I 0.108 --·· 3.0 _ -+ 7 4.2 : 22.8 ~ @! TP-4____ _ _3.~~'. ______ _!_~ _ ____ll_-_179 ~--_ -+--2,!__, __ 55.2 __ __j__ 1 42.6 f:3 ) I ~-+-------------+-----------!----··------i -i---------------1 ffi,§2 1 -+:1 ---------+----1----1--------+---+-----~--~+------l EMAIL ONLY Report Distribution ES-3450 Civic Development 18211 -240th Avenue Southeast Maple Valley, Washington 98038 Attention: Mr. Joe Pruss Earth Solutions NW, LLC SECTION 7 OTHER PERMITS SECTION 8 ESC ANALYSIS AND DESIGN SECTION9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT SECTION 10 OPERATIONS AND MAINTENANCE MANUAL