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539 HOMELAND DR.PDF11111111111111 11743 539 HOMELAND DR PREPARED FOR MR. WES DAWSON May 11, 2012 en H. vril owpi i Stephen H. Cr Staff Geologist Raymond A. Coglas, P.E. Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCE 539 HOMELAND DRIVE. EDMONDS, WASHINGTON ES-2265 Earth Solutions NW, LLC 1805 - 136th Place Northeast, Suite 201 Bellevue, Washington 98005 Ph: 425-449-4704 Fax: 425-449-4711 Toll Free: 866-336-8710 AUG - 7 2013 DEVELOPMENT SEHVIL;ES CTFI. CITY OF EDMONDS TABLE OF CONTENTS ES-2266 PAGE INTRODUCTION......................................................................... General........................................................................... Promect Description ............................................................ SITECONDITIONS ...................................................................... 2 Surface............................................................................. 2 Subsurface....................................................................... 2 Geologic Map and Soil Review ................................... . 2 Groundwater..................................................................... 3 CRITICAL AREAS AND GEOLOGIC HAZARDOUS AREAS ASSESSMENT..................................................................................... Site and Construction Plans ......................................................... 3 Assessment of Geolo-gical Characteristics ................................ 3 Landslide Hazards .............................................................. 3 ErosionHazards ................................................................. 4 Minimum Critical Area Buffer and Setback ................................. 4 DISCUSSION AND RECOMMENDATIONS ....................................... 4 General............................................................................. 4 Site Preparation and Earthwork ............................................ 5 Temporary Erosion Control ......................................... 5 Excavation................................................................... 5 Structural Fill Placement ............................................ 5 Excavations and Slopes .................................................... 6 Utility Support and Trench Backfill ....................................... 6 Foundations..................................................................... 7 Seismic Considerations ......................... ................................ 7 Slab -on -Grade Floors ......................................................... 7 Cast -In -Place Retaining Walls .............................................. 8 Drainage........................................................................... 8 LIMITATIONS............ :*,**'*"'**'*'*"""*"'*****"""*""'***"***"**'*"*"*"* 9 Additional Services ............................................................ 9 Earth Solutlons NW, LLC TABLE OF CONTENTS ConVd ES-2265 GRAPHICS PLATE I VICINITY MAP PLATE 2 TEST PIT LOCATION PLAN PLATE 3 RETAINING WALL DRAINAGE DETAIL PLATE 4 FOOTING DRAIN, DETAIL APPENDICES Appendix A Subsurface Exploration Test Pit Logo Appendix B Laboratory Test Results E2rth Solutions NW, LLC May 11, 2012 ES-2265 Mr. Wes Dawson 539 Homeland Drive Edmonds, Washington 98020 Dear Mr. Dawson: Earth LSolutions NWLIC I Earth Solutions NW LLC • Geotechnical Engineering • Construction Monitoring • Environmental Sciences Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Single -Family Residence, 539 Homeland Drive, Edmonds Washington". Based on the results of our study, construction of the proposed residence as planned is feasible from a geotechnical standpoint. Based on our field exploration the native soils underlying the proposed residential building site consist primarily of medium dense to very dense glacial till deposits. Groundwater seepage was not observed during our field exploration (April 2012). Provided in this study are geotechnical recommendations for the proposed site development including foundation design parameters, slope stability assessment, and other pertinent geotechnical considerations. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this Geotechnical Engineering Study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Stephen H. Avril Staff Geologist 1805 - 136th Place N.E., Suite 201 9 Bellevue, WA 98005 0 (425) 449-4704 0 FAX (425) 449-4711 a M Geolechn.nicol Engineeping Repopt -Wedmical Services Are Performed for SpecMc PmWses, Persons, and R*cts Geotechnical engineers structure their services to meet the specific needs of their clients. A geatechnical engineering study conducted for a civil engk no , er may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study isunique, each geotechnical engineering report is unique, prepared solelyfor the client No one except you should rely on your geotechnical engineering report without first conferring with the geotechnicall engineer who prepared it And no one — not emn you — should apply the report for any purpose or project except the one originally contemplated. Road ft M Report Serious problems have occurred because those relying on a geotechnicall engineering report did not read it all. Do not rely an an executive summary. Do not read selected elements only. A Gootedmical 8*eeP=IngoM Is Based on A MdW got 011 factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, * its size, and configuration; the location Of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that was: not prepared for you, not prepared for your project, not prepared for the specific site explored, or completed before important project changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, elevation, configuration, location, orientation, or weight of the proposed structure, composition of the design team, or project ownership. As a general rule, alvays inform your geotechnical engineer of project changes --even minor ones --and request an assessment of their impacL Geotechnical engineers cannot accept responsibility or fiabllo forproblems that occur bemuse their reports do not consider devvlopments 0 f which they were not informed "surlace Conditions Can Cum A geotechnicall engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geolechnical 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- bons. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most GOBIRCMCFA FWkW APO Prolle 0111111dons Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ --sometimes significantly — from those indicated in your report. Retaining the gootechnical 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 118COMOMMM Am Ot Final Do not overrely on the construction recommendations included in your report Those recommendations are not final, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. N geotacchnical engineer who developedyour report cannot assume responsibility or liability for the repoit's recommendations ff that engineer does not perfonn, construction observation. A - - - � - - a ' d fionerillia Report Is goat to NNoterpretalion Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technid engineer confer with appropriate members of the design team after submitting the report. AJso retain your geotechnical engineer to review perti- nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. no Riot Redpw tM Boneer's Low 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 geotechnicall engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that seWing logs from the report can elevate risk Give ContratoIrs a Complete Report md Gwftce Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- Wors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to coryfer 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 suffidient hme 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 Nqmllilft PPOVWM CIMIY Some clients, design professionals, and contractors do not recognize that geotechnicall engineering is far less exact than other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce the risk of such outcomes, gootechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled 'limitations* many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Gooenviraimental Concern APO Not Covered The equipment, techniques, and personnel used to perform a geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any 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 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 PpofesslonW ASOMM To 01081 WIM OW Diverse strategies can be applied during building design,* construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the agiress puipose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed intis report, the geotechnical engineer in charge of this project is not a mold prevention consultant none of the serWces per- formed In connection with the geolechnical engineert study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself be sufficient to prvvent mold from growing in or on the structure Involved. Rft on Your A&9E-Menftp Geetedwilld figineer fop AddMml Assbam 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 A.SFE-member geotechnical engineer for more information. ASFr= The 8091 P68018 20 IWO 8811 Colesville Road/Suite G106, Sliver Spring, MD 20910 Telephone: 301/565-2733 Facsimile: 301/589-2017 e-mail: infol0aste,org www.aste.org Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, In whole or In part, by any means whatsoever, Is strictly prohibited, except with ASFn specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission ofASFE, and only for purposes of scholarly research or book review. Only members of ASIT may use this document as a complement to or as an element of a geotechnical engineering report. Any other firm, Individual, or other entW that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. 11GER06045.010 GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCE 539 HOMELAND DRIVE EDMONDS, WASHINGTON ES-2265 INTRODUCTION General This Geotechnical Engineering Study was prepared for the proposed single-family residence to be constructed at 539 Homeland Drive in Edmonds, Washington (see Vicinity Map, Plate 1). The subject site is located on the north side of Homeland Drive where a single-family residence currently is sited to the northeast of a natural ravine which descends towards the southwest. The purpose of this study was to prepare geotechnical recommendations for the proposed development. Our scope of services for completing this Geotechnical Engineering Study included the following: Review of The City of Edmonds Development Standards Section 20.1513.110 Geologically hazardous areas; * Subsurface exploration, laboratory testing, engineering analysis, and; * Preparation of this report. As part of our report preparation, pertinent sections of the following documents were reviewed: Boundary and Topography for Mr. Wes Dawson 539 Homeland Drive Edmonds, Washington prepared by Allied Land'Surveying, Inc., dated 10-19-2011; The Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, USGS Map MF-1541, and; * The USDA Soil Conservation Survey (SCS) of Snohomish County. Project Description The site is located on the north side of Homeland Drive, adjacent to a natural ravine containing a small stream. The project site is a currently developed with a single-family residence. The proposal includes demolition of the current structure and construction of a single-family residence and associated improvements. The building construction will consist of relatively light wood -framing and conventional foundations. Perimeter and interior continuous footing loads are estimated to be on the order of 1 to 2 kips per lineal foot. Slab loading is estimated to be on the order of 150 pounds per square foot. Earth Sofutions NW, LLC Mr. Wes Dawson ES-2265 May 11, 2012 Page 2 We anticipate footings will follow the existing grade to the extent practical in order to minimize site excavations. The maximum cuts for the proposed structure foundations will be on the order of two to three feet. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify that our geotechnical recommendations have been incorporated into the design. - SITE CONDITIONS Surface The site is located on the north side of Homeland Drive in Edmonds, Washington. The approximate location of the subject property is illustrated on the Vicinity Map (Plate 1). The property consists of a single tax parcel which is 0.49 acres in size. The approximate limits of the property are illustrated on the Test Pit Location Plan (Plate 2). The site consists of an irregular shaped lot which contains a ravine at the southwest side of the property with a local high elevation of about 108 feet. The ravine meets the criteria for a "steep slope" according to the descriptors provided by the City of Edmonds Municipal Code. The ravine is approximately 28 feet deep; and a stream is present at the bottom which emanates from a culvert under Homeland Drive from an adjacent property. The topography across the lot is generally flat with the exception of the ravine. The site is developed and vegetated with lawn and landscape areas. Subsurface The approximate locations of the test pits are illustrated on the Test Pit Location Plan (Plate 2). The test pit logs are provided in Appendix A. An ES,NW representative observed, logged and sampled two test pits using a mini -tracked excavator contracted by ESNW. The test pits were excavated to depths of five feet below existing grades (April 2012). The following is a general description of the soil conditions encountered at the test sites. In general the subject property is underlain by medium dense to very dense silty sand consistent with Vashon glacial till deposits. The glacial till deposits at test location TP-1 were overlain by three feet of fill soil. This material was observed to be in a loose to medium dense state; and is more than likely a remnant of past grading activity associated with the building pad construction. In general soil relative density generally increased with depth. Groundwater was not observed at our test pit locations. Geologic Map and Soil Map Review As part of our report preparation, we reviewed available maps regarding soil conditions for the subject site. The referenced geologic map identifies glacial till deposits (Qgt) across the subject property. Earth Solutions NW, LLC Mr. Wes Dawson ES-2265 May 11, 2012 Page 3 The Soil Survey of Snohomish County identifies Alderwood-Urban land complex soils (Map Unit 5) 2-8 percent slopes across the site and surrounding area. Alderwood-Urban land complex series soils formed in till plains and are comprised of gravelly sandy loam. This map designation is consistent with our findings during fieldwork. Groundwater ESNW did not encounter groundwater seepage duiring our subsurface exploration (April 2012). However, zones of persistent or chronic groundwater seepage are not uncommon, and can be encountered during any time of year. Groundwater seepage rates fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater seepage and flow rates are higher during the wetter, winter months. CRITICAL AREAS AND GEOLOGIC HAZARDOUS AREAS ASSESSMENT As part of this geotechnical engineering study and critical areas report, we reviewed the City of Edmonds Critical Area Ordinance (Chapter 23.80). Per the City of Edmonds Critical Areas Report requirements, the following topics related to development plans and site conditions are addressed. Site and Construction Plans Construction of a single-family residence is planned for the site. The maximum cuts for the proposed structure foundations will be on the order of two to three feet. The attached Test Pit Location Plan (Plate 2) illustrates the approximate site topography. ESNW observed no signs of surface seeps, hummocky terrain, head scarps, or rilling during our fieldwork. The overall stability of the steep slope areas can be characterized as good based on our field observations. Assessment of Geological Characteristics The referenced geologic map identifies glacial till deposits across the subject property. The native soils encountered at the test pit locations consisted primarily of. medium dense to very dense silty sand consistent with the geologic map designations. Landslide Hazards With respect to landslide hazard areas, 32.80.020 of the Edmonds City Development Code (ECDC) defines landslide hazard areas as slopes of 40 percent or greater with a vertical rise of more than ten feet. Earth Solutions NW, LLC Mr. Wes Dawson ES-2265 May 11, 2012 Page 4 The natural slope present at the southwest portion of the subject site is greater than 40 percent with a vertical rise of more than ten feet and meets the current criteria for landslide hazard designation. Landslide areas located on slopes greater than 40 percent are regulated pursuant to ECDC 20.15B.110(D). This condition exists on the subject site. Overall stability of the slopes can be characterized as good when considering the relative density of the till soils underlying the site. Typical indicators of instability such as head scarps, tension cracks, hummocky terrain, and erosion features such as rills were not observed. Therefore, in our opinion the sloped areas of the site exhibit and possess good stability with respect to landslide activity. Erosion Hazards In our opinion site soils would be moderately susceptible to erosion. Based on our assessment ' f of the on -site conditions during ieldwork, the planned development will not increase the erosion hazard at the site, provided appropriate Best Management Practices are implemented during the earthwork and development activities. General guidelines for erosion control are provided in the Site Preparation and Earthwork section of this study. Minimum Critical Area Buffer and Setback In our opinion, the proposed grading and development activity can be completed as currently planned without additional setback or buffer requirements given that the proposed footprint will mimic the current single-family residences footprint. The proposed development will not result in an increased potential for* landslide activity. This opinion does not cover unforeseen or changed conditions. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of the single-family residence as planned is feasible from a geotechnical standpoint. In our opinion, the proposed setback of 25 feet from the steep slope is suitable given the planned development will mimic the existing footprint of the single-family residence. Stormwater from the new development should be managed to minimize off -site flow towards the steep slope; and vegetative cover disturbance on and around the slope is recommended to be kept to a minimum. The primary geotechnical considerations are associated with foundation support and drainage. In our opinion, the proposed single-family residence can be supported on conventional shallow foundations supported on competent or recompacted native soil or structural fill. We anticipate competent native soil capable of providing adequate foundation support will be encountered at. depths of between two to four feet below existing grades. Overexcavation may be required under foundation elements depending on the condition during grading activities. ESNW should be onsite during foundation excavation to confirm conditions are as anticipated and to provide supplemental recommendations for foundation subgrade preparation. Earth Solutions NW, LLC Mr. Wes Dawson ES-2265 May 11, 2012 Page 5 In our opinion, the soils generated from cuts throughout the majority of the site should generally be suitable for use as structural fill if they are at or near optimal moisture content at the time of placement. A representative of ESNW should be on -site during fill placement to confirm that adequate compaction is achieved. This report has been prepared for the exclusive use of Mr. Wes Dawson and his representatives. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Site preparation will likely include removing existing vegetation from the construction envelope including, but not limited to trees, brush and topsoil. Temporary Erosion Control Temporary erosion control measures should include, at a minimum, silt fencing placed along the downslope perimeter of the construction envelope and at the top of the ravine. A construction entrance consisting of at least six inches of quarry spalls should be considered in order to minimize off -site soil tracking and to provide a firm surface for on -site traffic. Surface water should not be allowed to flow over temporary or permanent slopes. Interceptor drains or swales should be considered for controlling surface water flow patterns. The geotechnical engineer should observe the erosion control measures, and provide supplemental recommendations for minimizing erosion during construction, as necessary. If temporary discharge of stormwater offsite is planned during construction, turbidity monitoring should be performed, as required by the City of Edmonds. Excavations Based on the subsurface conditions encountered during our fieldwork, medium dense to very dense silty sand soils are anticipated to be encountered in the planned excavations. The soils anticipated to be encountered in the proposed excavations can be characterized as having a moderate sensitivity to moisture. During periods of extended precipitation, placement and compaction of the excavated soils could be difficult. The presence of localized perched groundwater seepage was not observed at our test sites ,however, groundwater seepage could be encountered in the planned excavations. The geotechnical engineer should observe the excavations, and provide supplemental recommendations for drainage when necessary. Structural Fill Placement In general, areas to receive structural fill should be sufficiently stripped of organic matter and other deleterious material. The majority of the organic matter associated with trees, brush, root balls, and groundcover should be removed from the proposed fill and cut areas. Earth Solutions NW, LLC Mr. Wes Dawson ES-2265 May 11, 2012 Page 6 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 the building pad areas should be placed in maximum 12-inch loose lifts and compacted to a relative compaction of 90 percent, based on the maximum dry density as determined by the Modified Proctor Method (ASTM D-1557-02). If the on -site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as structural fill should consist of a well graded granular soil with a maximum aggregate'grain size of four inches, and 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. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (W.ISHA) provide soil classification in terms of temporary slope inclinations, The existing weathered native soil where groundwater is present is classified as Type C by OSHANVISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.5H:1V (Horizontal:Vertical). The undisturbed dense glacial till where no groundwater is exposed is classified as Type A. Temporary slopes over four feet in height in Type A soils must be sloped no steeper than .75H:lV. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. The geotechnical engineer should observe temporary and permanent slopes to verify that the inclination is appropriate for the exposed soil, and to provide additional grading recommendations, as necessary. Utility Support and Trench Backfill The native soils anticipated to be exposed during utility trench excavations would include firm silty sand deposits. In general, the on -site soils observed at the test sites described in the referenced reports should be suitable for use as structural backfill in the utility trench excavations, provided the soil is at or near the optimum moisture content at the time of placement and compaction. Areas of the onsite soils, however, may not be suited for utility trench backfill, and should be further evaluated by the geotechnical engineer at the time of construction. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable specifications of the City of Edmonds. Groundwater should be expected in deep utility trench excavations. Earth Solutions NK LLC Mr. Wes Dawson May 11, 2012 Foundations ES-2265 Page 7 In our opinion, the proposed single-family residence can be supported on conventional shallow foundations supported on competent or recompacted native soil or structural fill. We anticipate competent native soil capable of providing adequate foundation support will be encountered at foundation elevations or at depths of between two to four feet below existing grades elsewhere. Loose or otherwise unsuitable soil should be removed and replaced with structural fill. Assuming the foundations will be supported as described above, the following parameters can be used for the foundation design: • Allowable soil bearing capacity • Coefficient of friction • Passive resistance • Wind and seismic • Total settlement e Differential settlement 9 Minimum Steep Slope Setback 2,500 psf 0.40 (foundation /soil interface) 350 pcf (structural backfill) allowable one-third Increase 1.0 to 1.5 inches 0.5 to 0.75 inches 25 feet A facto r-of-safety of 1.5 had been included in the friction and passive resistance values. Seismic Considerations The 2009 International Building Code specifies several soil profiles that are used as a basis for seismic design of structures. Based on the soil conditions observed at the test pit locations, Site Class C, from table 1613.5.2, should be used for design. In our opinion, liquefaction susceptibility at the site can be characterized as'low. The relative density of the native soil and lack of a shallow groundwater table is the primary basis for this opinion. Slab -On -Grade Floors Slab -on -grade floors should be supported on a minimum of one foot of structural fill. A capillary break consisting of a minirhum 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). Installation of an approved vapor barrier should be installed below the slab. The vapor barrier must be a product specifically design ed for that purpose and installed in accordance with the manufacturer's specifications. Earth Solutions INK LLC Mr. Wes Dawson May 11, 2012 Cast -In -Place Retaining Walls ES-2265 Page 8 Retaining walls should be designed to resist earth pressures and any applicable surcharge loads. For design, the following parameters can be assumed for retaining wall design: 9 Active earth pressure (yielding wall) 9 At -rest earth pressure (restrained wall) 0 Passive resistance 9 Coefficient of friction 35 pef (equivalent fluid) 50 pcf 350 pcf (equivalent fluid) 0.40 Additional surcharge loading from foundations, sloped backfill, or other loading 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, as.appropriate. The geotechnical engineer should review retaining wall designs to verify that appropriate earth pressure values have been incorporated into design and to provide additional recommendations. 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 rigid, perforated drain pipe should be placed along the base of the wall, and connected to an appropriate discharge location. A typical retaining wall and drainage detail is illustrated on Plate 3 of this report. Drainagge Although not observed during our field exploration, the presence of groundwater seepage should be expected in the building site excavations. Temporary measures to control groundwater and surface water runoff during construction will likely involve the use of interceptor trenches, sumps and associated conveyance systems. The geotechnical engineer should observe site conditions during the grading and utility installation and provide supplement recommendations for drainage, as appropriate. In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. A typical footing drain detail is provided on Plate 4 of this report. Water should not be allowed to flow over the adjacent slopes. Provisions should be included in site designs to either tightline drainage elements to the base of the slope or convey runoff to an approved discharge point away from the slope area. Earth Solutions NW, LLC Mr. Wes Dawson May 11, 2012 LIMITATIONS ES-2265 Page 9 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 pit 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 study. ESNW should also be retained to provide testing and consultation services during construction. Eadh Solutions NW, LLC SRACKEM LANDING A, SEAT IF M04 '/'IA ),%YTU?., S WORKS 2 3) 1D4 Si, WILDLIFE REFUGE AMON't z t 6jA LL- D6 cny.0 PARK I RK -PINE.- PINE o kv AV �84TH ST tlj All, > I!E UNN)T. tS SIE �F 18ST11 8k HUTT :,Y N�" 5w ?tjgm P PARK 18?TH! xlw" J., 161111 PL 186TH �ST Sw - v sw le 187TH ST SVI'l ST SYV C XONIA 'e�OAWM OL ��IZFIINS ERt ST �w sea, Uj on-f-I > - Ks - 9689M 189f 1> n! " PL )�� 01A%( 2 IM" -1$z $w > SvVAni OF Sw JH ERILV PL '4 U511 21 :i. SVI rh I I SIERRA 0'.0 191ST jkC11141 . 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K Svi 2161H ST, IGP� ri v r ST c 3-- 30 2� k �19TA Z 91 ST ST SIN 2?0TR(Q1! 1 220TIl 22(mi PI ST J'� SW I _Aq "mai ?_?i$j PL Z2_1 S! PL Svj 5 SRI S VIYSVI � ... .. .. Fe NORTH Reference: Snohomish County, Washington Map 454 By The Thomas Guide Rand McNally 32nd Edition INOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information result — ing from black & white reproductions of this plate. Existing Existing 90 Residence 110 S-hed! TP-1 Exisfing DM* Resider= 7 - T . . . . . . . . . . I FQ '17 go - 100 LEGEND TP-1-1— Approximate Location of ESNW Test Pit, Proj. No. ES-2265, April 2012 Subject Site Existing Building NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based an data provided by the client at the time of our study. ESNW cannot be responsible for subsequent desi gn 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. NORTH oChN, ;4W 0 20 40 80 1"=40' Scale in Feet JI- 'U'i 18" Min. 0 0 0 . 0 0 0o dD 0 a 00 00" 0. do 0 0 o b o -0 * 0.0 '0 01 0 00 0 0 0 00 .0 0. 0.- : : 0 0 00 .0 , 0 0 .0 6. 0-0 *—. . 0 0 6 10 0 . oo a oo .0 0. -0 0. .0 .-0 - 0 0 Cr 0 0 . . - 09 -0 0 0 00 . 0 C 0 -00 - 00 c6 cc 0 -0 '0 0000 0. OR - 00 0. 0 C�O . a J 4, 0 0 0 0 . 0 ()�. -0 0 0... 0 . 00 0 .0 . a 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: 0.000, 0 0, .0 Free Draining Structural Backfill 1 inch Drain Rock Structurai Fill \ Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Perforated Rigid Drain Pipe (Surround with V Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Sea[ to consist of 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Sea[; native soil or other low permeability material. V Drain Rock SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING APPENDIX A SUBSURFACE EXPLORATION ES-2265 Subsurface conditions at the site were explored by excavating two test pits. The approximate locations of the test pits are illustrated on the Test Pit Location Plan. The logs are provided in this Appendix. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. Earth Solutions NW, LLC Earth Solutions NWLLc SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETrER GRAVEL AND CLEAN GRAVELS 00 16 GW WELL -GRADED GRAVELS, GRAVEL SAND MIXTURES, LITTLE OR NO FINES '00 '0 GP POORLY -GRADED GRAVELS, GRAVEL - SAND MD(TURES. LITTLE OR 140 FINES GRAVELLY SOILS AJTTLE OR NO FINES) COARSE GRAINED SOILS MORE THAN 50% OF COARSE FRACTION GRAVELS WITH FINES 0 0 (;M SILTY GRAVELS, GRAVEL -SAND - SILT MD[TURES GC CLAYEY GRAVELS. GRAVEL - SAND - CLAY MDCTURES RETAINED ON NO. 4 SIEVE (APPRECLAUE AMOUNT OF FINES) MORE THAN 50% OF MATERIAL IS SAND AND CLEAN SANDS SW WELL -GRADED SANDS, GRAVELLY SANDS. LITTLE OR NO FINES SP POORLY -GRADED SANDS, GRAVELLY SAND. LITTLE OR NO FINES LARGERTHAN NO. 200 SIEVE S12E SANDY SOILS (LITTLE OR NO FINES) MORE THAN 50% OF COARSE SANDS WITH FINES SM SILTY SANDS, SAND - SILT MD(TURES FRACTION CLAYEY SANDS, SAND - CLAY MIXTLIRES PASSING ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR. SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY FINE GRAINED SOILS SILTS LIQUID LIMIT AND LESS THAN 50 CLAYS CL INORGANIC CLAYS OF LOWTO MEDIUM PLASTICITY, GRAVELLY CLAYS. SANDY CLAYS, SILTY CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% OF MATERIAL IS MH INORGA14C SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR Sh4ALLERTHAN SILTY SOILS NO. 200 SIEVE SIZE SILTS LIQUID LIMIT AND GREATER THAN 50 CLAYS CH INORGANIC CLAYS OF HIGH PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY. ORGANIC SILTS HIGHLY ORGANIC SOILS LU I pT PEAT. HUMUS. SWAM 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. Earth Solutions NW TEST PIT NUMBER TP-1 805 136th Place N.E., Suite 201 PAGE 1 OF 1 lowBellevue, Washington 98005 Telephone: 425-284-3300 CLIENT Wes Damon PROJECT NAME Damon Single Family Residence PROJECT NUMBER 2265 PROJECT LOCATION Edmonds, Washinaton DATE STARTED 4/16112 COMPLETED 4/16112 GROUND ELEVATION 108 It TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUNDWATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION NOTES Depth Topsoil & Sod 6": grass AFTER EXCAVATION — ul IL it Ui W X C3 ui TESTS jj Q. 6 MATERIAL DESCRIPTION w z 96 0 TPSL TOPSOIL 107.5 Brown silty SAND with gravel, loose, moist (Fill) MC 15.40% Sm 106.5 Brown silty SAND with gravel, medium dense, moist MC 9.20% Sm -Glacial Till, becomes dense to very dense and cemented with iron o)dde staining 5 MC 8.90% Fines 33.40% 15.0 103.0 Test pit terminated at 5.0 feet below e)dsbng grade. No groundwater encountered during excavation. Bottom of test pit at 5.0 feet S2 0 Ui M z W 0 1 1 1 1 1 Earth Solutions NW TEST PIT NUMBER TP-2 805 136th Place N.E., Suite 201 PAGE 1 OF 1 lowBellevue, Washington 98005 Telephone: 425-284-3300 CLIENT Wes Dawson PROJECT NAME Dawson Single Family Residence PROJECT NUMBER 2265 PROJECT LOCAT10N Edmonds W hingt6n DATE STARTED 4/16/12 COMPLETED 4/16/12 GROUND ELEVATION -108 ft TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVA11ON METHOD AT TIME OF EXCAVATION LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION NOTES Depth of Top rass AFTER EXCAVATION W IL � 0� . (6 W W Co TESTS (j IL MATERIAL DESCRIPTION ul —12 (L C6 a 2 z 0 T P S L TOPSOIL 107.5 - Brown sitty SAND with gravel, loose, moist .I SM 2.0 108.0 Brown silly SAND with gravel, medium dense, moist MC 12.20% SM -Glacial Till, becomes cemented, dense to very dense and gray 5 MC 10.50% 5,0 103.0 Test pit terminated at 5.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 5.0 feet. 0 03 APPENDIX B LABORATORY TEST RESULTS ES-2265 Earth Solutions NW, LLC