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Home My WebLink AboutGeoTechnical Engineering Study - GEO General - 3/21/2014 t t� Geoteehnieal Engineering Geology Environmental Scientists Construction Monitoring y. r tir .a r. 1: �14 _ r 1 GEOTECHNICAL ENGINEERING STUDY-.."• PROPOSED WILSON SINGLE FAMILY RESIDENCE 10801 NORTHEAST NORTH SHORE ROAD MASON COUNTY (BELFAIR), _ WASHINGTON ES-3283 . ' 06 180 13 ii1' ?1 tk,201 _ Bellc�u( 1§A )80{j3k^ :AU. PREPARED FOR WASHINGTON FEDERAL SAVINGS C/O BARGHAUSEN CONSULTING ENGINEERS, INC. March 21, 2014 Stephen H. Avril Staff Geologist R CA WAsy��Ac� w� 2 O RRt7 & S/ONAL�G Kyle R. Campbell, P.E. Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED WILSON SINGLE-FAMILY RESIDENCE 10801 NORTHEAST NORTH SHORE ROAD MASON COUNTY (BELFAIR), WASHINGTON ES-3283 Earth Solutions NW, LLC 1805— 136th Place Northeast, Suite 201 Bellevue, Washington 98005 Ph: 426-449-4704 Fax: 425-449-4711 Toll Free: 866-336-8710 impoplant Infopmation About Geotechnical Engineering Report Geotechnical SerVICes Are Perfmpmed for • elevation,configuration,location,orientation,or weight of the Specific Purposes, Person, and Projleds proposed structure, Geotechnical engineers structure their services to meet the specific needs of • composition of the design team,or their clients.A geotechnical engineering study conducted for a civil engi- • project ownership. neer may not fulfill the needs of a construction contractor or even another civil engineer.Because each geotechnical engineering study is unique,each As a general rule,always inform your geotechnical engineer of project geotechnical engineering report is unique,prepared solelyfor the client.No changes—even minor ones—and request an assessment of their impact. one except you should rely on your geotechnical engineering report without Geotechnical engineers cannot accept responsibility or liability for problems first conferring with the geotechnical engineer who prepared it.And no one that occur because their reports do not consider developments of which —not even you—should apply the report for any purpose or project they were not informed. except the one originally contemplated. SubsuMace Conditions Can Change Read the Rd[Report A geotechnical engineering report is based on conditions that existed at Serious problems have occurred because those relying on a geotechnical the time the study was performed.Do not rely on a geotechnical engineer- engineering report did not read it all.Do not rely on an executive summary. ing reportwhose adequacy may have been affected by:the passage of Do not read selected elements only. 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 A Geotechnical Engineering art is Based on tions.Always contact the geotechnical engineer before applying the report A Unique Set of Pftd-Spec IC Factors to determine if it is still reliable.A minor amount of additional testing or Geotechnical engineers consider a number of unique,project-specific fac- analysis could prevent major problems. tors when establishing the scope of a study.Typical factors include:the client's goals,objectives,and risk management preferences;the general Meat Geotechnical Findings Are Professional nature of the structure involved,its size,and configuration;the location of Opinions the structure on the site;and other planned or existing site improvements, Site exploration identifies subsurface conditions only at(hose paints where such as access roads,parking lots,and underground utilities.Unless the subsurface tests are conducted or samples are taken.Geotechnical engi- geotechnical engineer who conducted the study specifically indicates oth- neers review field and laboratory data and then apply their professional erwise,do not rely on a geotechnical engineering report that was: judgment to render an opinion about subsurface conditions throughout the • not prepared for you, site.Actual subsurface conditions may differ—sometimes significantly— • not prepared for your project, from those indicated in your report.Retaining the geotechnical engineer • not prepared for the specific site explored,or who developed your report to provide construction observation is the • completed before important project changes were made. most effective method of managing the risks associated with unanticipated conditions. Typical changes that can erode the reliability of an existing geotechnical A Reports Recommendations Are Alf Final engineering report include those that affect: • the function of the proposed structure,as when it's changed from a Do not overrely on the construction recommendations included in your parking garage to an office building,or from a light industrial plant report. Those recommendations are not final,because geotechnical engi- to a refrigerated warehouse, neers develop them principally from judgment and opinion.Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. The geotechnical have led to disappointments,claims,and disputes.To help reduce the risk engineer who developed yourrepoft cannot assume responsibility or of such outcomes,geotechnical engineers commonly include a variety of liability for the report's recommendations if Mat engineer does not perform explanatory provisions in their reports.Sometimes labeled"limitations" construction observation. many of these provisions indicate where geotechnical engineers'responsi- bilities begin and end,to help others recognize their own responsibilities A Geotechnieal Engineering Report Is Subject to and risks.Read these provisions closely.Ask questions.Your geotechnical Misinterpretation engineer should respond fully and frankly. Other design team members'misinterpretation of geotechnical engineering reports has resulted in costly problems.Lower that risk by having your geo- Goeenvironmental Concerns Are Not Covered technical engineer confer with appropriate members of the design team after The equipment,techniques,and personnel used to perform a geoenviron- submitting the report.Also retain your geotechnical engineer to review perti- mental study differ significantly from those used to perform a geotechnical rent elements of the design team's plans and specifications.Contractors can study.For that reason,a geotechnical engineering report does not usually also misinterpret a geotechnical engineering report.Reduce that risk by relate any geoenvironmental findings,conclusions,or recommendations; having your geotechnical engineer participate in prebid and preconstrudion e.g.,about the likelihood of encountering underground storage tanks or conferences,and by providing construction observation, regulated contaminants. Unanticipated environmental problems have led to numerous project failures.If you have not yet obtained your own geoen- Do Not Redraw the Engineer's Logs viionmental information,ask your geotechnical consultant for risk man- Geotechnical engineers prepare final baring and testing logs based upon agement guidance. Oo not rely on an environmental report prepared for their interpretation of field logs and laboratory data.To prevent errors or someone else. omissions,the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Obtain Professional Assistance To Deal with Mold Only photographic or electronic reproduction is acceptable,but recognize Diverse strategies can be applied during building design,construction, that separating logs from the report can elevate risk. operation,and maintenance to prevent significant amounts of mold from growing on indoor surfaces.To be effective,all such strategies should be Give Contractors a Complete Report and devised for the express purpose of mold prevention,integrated into a com- Guidanee prehensive plan,and executed with diligent oversight by a professional Some owners and design professionals mistakenly believe they can make mold prevention consultant.Because just a small amount of water or contractors liable for unanticipated subsurface conditions by limiting what moisture can lead to the development of severe mold infestations,a num- they provide for bid preparation.To help prevent costly problems,give con- ber of mold prevention strategies focus on keeping building surfaces dry. tractors the complete geotechnical engineering report,but preface it with a While groundwater,water infiltration,and similar issues may have been clearly written letter of transmittal.In that letter,advise contractors that the addressed as part of the geotechnical engineering study whose findings report was not prepared for purposes of bid development and that the are conveyed in this report,the geotechnical engineer in charge of this report's accuracy is limited;encourage them to confer with the geotechnical project is not a mold prevention consultant;none of the services per- engineer who prepared the report(a modest fee may be required)and/or to formed In connection with the geotechnical engineer's study conduct additional study to obtain the specific types of information they were designed or conducted for the purpose of mold preven- need or prefer.A prebid conference can also be valuable.Be sure contrac- tion. Proper implementation of the recommendations conveyed tors have sufficient time to perform additional study.Only then might you in this report will not of itself be sufficient to pro vent mold from be in a position to give contractors the best information available to you, growing in or on the structure involved. while requiring them to at least share some of the financial responsibilities Rely, on Your ASFE Member 6eoteeimehll stemming from unanticipated conditions. Engineer for Additional Assistance Read Responsibgity Provisions Closely Membership in ASFE/The Best People on Earth exposes geotechnical Some clients,design professionals,and contractors do not recognize that engineers to a wide array of risk management techniques that can be of geotechnical engineering is far less exact than other engineering disci- genuine benefit for everyone involved with a construction project.Confer plines.This lack of understanding has created unrealistic expectations that with you ASFE-member geotechnical engineer for more information. ASFE The test Hers on lorill 8811 Galesville Road/Suite G106,Silver Spring,MD 20910 Telephone:3011565-2733 Facsimile:301/589-2017 e-mail:info@asfe.org www,asfe.org Copyright 2004 by ASFE,Inc.Duplication,reproduction,or copying of this document in whale or in part,by any means whatsoever is suktly prohibited,except with ASFE§ specific written permission.Excerpting,quoting,or otherwise extracting wording from this document is permitted only with the express written permission of ASFE,and only for purposes of scholarly research or book review Only members of ASFE may use this document as a complement to or as an element of a geotechnical engineering report Any other firm,individual,or other entity that so uses this document without being art ASFE member could be committing negligent or intentional(fraudulent)misrepresentation. IIGEe06045otil 1 V Earth k Solutions NWLLC March 21, 2014 Earth Solutions NW LLC ES-3283 • Geotechnical Engineering • Construction Monitoring • Environmental Sciences Washington Federal Savings c/o Barghausen Consulting Engineers, Inc. 18215 —72nd Avenue South Kent, Washington 98032 Attention: Mr. Tom Barghausen Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Wilson Single-Family Residence, 10801 Northeast North Shore Road, Mason County (Belfair), Washington". The site is generally underlain by advance outwash deposits comprised of gravel, silt, and sand in a medium dense grading to dense condition. Groundwater was not observed at the test pit locations during the fieldwork (March 2014). In our opinion, the proposed construction of a single-family residence, septic drainfield, and associated improvements as currently planned is feasible from a geotechnical standpoint provided the recommendations detailed in this report are followed. Based on our study, the proposed residential structure should be supported conventional shallow foundation bearing on dense native soil or structural fill. The steep slopes located on-site and should be considered sensitive. Site designs should be developed in a manner which minimizes impacts to the slopes and associated buffers. Geotechnical recommendations related to the proposed site development are provided in this geotechnical engineering study. If you have questions regarding the content of this report, please call. Sincerely, EARTH SOLUTIONS NW, LLC Stephen H. Avril Staff Geologist 1805-136Ih Place N.E.,Suite 201 • Bellevue,WA 98005 • (425)449-4704 • FAX(425)449-4711 Table of Contents ES-3283 PAGE INTRODUCTION ........................................................................ 1 General .......................... ......................................... ...... 1 Project Description ........................................................... I Surface............ .......................................... ..................... 2 Subsurface....................................................................... 3 Geologic Setting....................................................... 3 Groundwater...................................................................... 4 Critical Area Assessment.................................................... 4 Landslide Hazard Assessment .................................. 4 Erosion Hazard Assessment ..................................... 4 Fish and Wildlife Habitat Conservation Areas.................. 5 Analysis of Proposal and Mitigating Measures............. 5 DISCUSSION AND RECOMMENDATIONS....................................... 5 General.............................-......... .................................... 5 Site Preparation and Earthwork............................................ 6 Foundation Excavations......... .......................... ....... 6 In-situ Soils.............................................................. 6 ImportedSoil........................................................... 6 Structural Fill Placement............................................ 6 Slope Fill Placement................................................. 7 Erosion Control....................................................... 7 Foundations................................................ .................... 7 Slab-on-Grade Floors......................................................... 8 Seismic Considerations......................... ................................ 8 RetaininaWalls................................................................. 8 Excavations and Slopes ................................................... 9 Utility Support and Trench Backfill....................................... 9 Drainage.......................................................................-- 9 LIMITATIONS.............................................................................. 10 Additional Services....... .......................................... ......... 10 Earth Solutions INK LLC Table of Contents Cont'd ES-3283 GRAPHICS Plate 1 Vicinity Map Plate 2 Test Pit and Hand Hole Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail APPENDICES Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Test Results Sieve Analysis Results Earth Solutions NW,LLC GEOTECHNICAL ENGINEERING STUDY PROPOSED WILSON SINGLE-FAMILY RESIDENCE 10801 NORTHEAST NORTH SHORE ROAD MASON COUNTY (BELFAIR), WASHINGTON ES-3283 INTRODUCTION General This geotechnical engineering study was prepared for the proposed single-family residence to be constructed on the south side of Northeast North Shore Road in the Belfair area of Mason County, Washington. The approximate location of the subject property is illustrated on the Vicinity Map (Plate 1). The purpose of this study was to develop geotechnical recommendations for the proposed site development including the proposed house to be located along the shoreline and associated septic system to be located on the slope located north of Northeast North Shore Road. Our scope of services for completing this geotechnical engineering study included the following: • Subsurface exploration including excavation of four test pits, two using an excavator, and two using hand tools; • Engineering analyses, and; • Preparation of this report. The following documents were reviewed as part of preparing this geotechnical engineering study: • Boundary and topographic survey prepared by Barghausen Consulting Engineers, dated April 3, 2013; • Mason County Ordinance 17.01, Geologic Hazards. Project Description We understand the property will be developed with a single-family residence designated as Lot 39. An on-site septic drainfield is to be located on the ascending slope above Northeast North Shore Road in conjunction with associated improvements for the proposed residential development. The approximate limits of the subject property are illustrated on the Test Pit Location Plan (Plate 2). Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 2 March 21, 2014 The residential structure planned for the property is to be located north of the bulkhead at the shoreline. Final Plans were not available at the time of production of this study; however we anticipate the new home will likely consist of relatively lightly-loaded wood-framing supported on conventional foundations. Based on our experience with similar developments, we anticipate wall loads on the order of 1 to 2 kips per lineal foot and slab-on-grade loading of 150 pounds per square foot (psf). An on-site septic system for the lot will be incorporated into site designs. The system is proposed to be located on the ascending slope north of Northeast North Shore Road. Current design details include installation of a septic tank along the north side of right-of-way which will then pump effluent up the hill to a drain field. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report, and provide supplement recommendations. Surface The subject site is located east of the intersection between Northeast North Shore Road and Northeast Canyon Drive in the Belfair area of Mason County, Washington. The site consists of a single residential parcel which is bordered to the north, west, and east by forest; and to the south by the Hood Canal. The proposed residential structure is to be constructed behind a bulkhead at the shoreline, south of Northeast North Shore Road. The proposed location of the septic system associated with the residence is to be sited on the ascending slope located north of Northeast North Shore road. A natural slope ascends about 150 feet on the north side of Northeast North Shore Road. Vegetation across the slope consists of forest growth with a moderate understory. The slope is currently undeveloped and no indications of past grading were observed at the time of the site visit with the exception of a pathway cut into the hill which runs towards the north. The proposed building envelope is to be located on the north side of the bulkhead located at the shoreline. The bulkhead appears to be in good condition, is approximately eight feet in height measured from the beach elevation. There is a lawn area located behind the bulkhead which was likely backfilled using fill during construction to create a level area currently being used as a side yard to the existing single-family residence. Rockeries are located to the north of the side yard area, which ascend towards the road grade approximately six feet. Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 4 March 21, 2014 Groundwater Groundwater seepage was not encountered at the test pit locations at the time of our fieldwork (March 2014). In our opinion, perched seepage zones may be encountered in the deeper site excavations, such as utility excavations. 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 seepage flow rates are higher during the wetter, winter months. Critical Areas Assessment As part of our report preparation, we assessed the site in terms of critical areas as defined in the Mason County Municipal Code Chapter 17.01.100 — Landslide Hazard Areas, 17.01.104 Erosion Hazard Areas, 17.01.102 Seismic Hazard Areas, and Fish and Wildlife Habitat Conservation Areas. The Washington State On-Line Coastal Atlas identifies the slope located to the north of Northeast North Shore Road as having an intermediate slope stability rating. It is our opinion that the slope on the subject site will have a low susceptibility to sliding due to the relatively large granular (gravelly) nature of the soil present in the substrate; as opposed to typical advance outwash soil which is typified by more fined grained sands with silt and gravel. Landslide Hazard Assessment Based on review of the referenced topographic survey, the ascending slope along portions of the northern site is inclined more than 40 percent with a vertical relief of over ten feet in areas; and is estimated to be on the order of 150 feet in height. The slope is vegetated with a mixture of deciduous, fir, and cedar trees with a moderate understory. There were no signs of slope failure such as head scarps, bare slopes or groundwater seeps along the surface during the slope reconnaissance conducted during the fieldwork. In our opinion, the steep slope along the western and southern site boundary would exhibit a low to moderate risk for shallow landslide hazard activity in the present condition. We would expect landslide activity to be limited to surficial debris flow type failures. Our reasoning for this conclusion is that ESNW observed no signs of bedrock, or a consolidated silty layer of soil within the substrate than can be considered a plane of weakness; which would increase the risk of a slope failure if excess moisture is introduced to the slope subsurface conditions. Erosion Hazard Assessment The slopes throughout the majority of the site are underlain primarily by course grained deposits. The soils encountered during our fieldwork would exhibit a low to moderate erosion hazard. In our opinion, the use of Best Management Practices (BMPs) during construction, and the incorporation of the recommendations provided in this report, will adequately mitigate the erosion hazard at the site. Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 3 March 21, 2014 Subsurface A representative of ESNW observed, logged and sampled four test pits. Two test pits were excavated on the slope using an excavator; and two test pits were excavated adjacent to the bulkhead using hand tools. The hand-excavated test pits were located within the proposed building footprint for purposes of assessing soil conditions, characterizing and classifying the site soils and assessing the near-surface groundwater conditions. Limited amounts of fill may exist behind the bulkhead at the shoreline. However, the soil conditions observed behind the bulkhead at the test pit locations were in a dense condition during our fieldwork (March 2014). The approximate locations of the test pits are illustrated on the Test Pit Location Plan (Plate 2). Please refer to the soil logs provided in Appendix A for a more detailed description of the subsurface conditions. We observed the test pits which were excavated by ADC to supplement the subsurface conditions within the proposed location of the septic system. The soil conditions observed at the proposed septic system location were similar in nature to those encountered at the test pits observed by ESNW which were located down-slope from ADC test locations. The subsurface conditions observed at the proposed septic system location consisted of poorly graded gravel with silt and sand (Unified Soil Classification GP-GM) in a dense condition. Medium dense grading to dense poorly graded gravel with silt and sand (GP-GM) was encountered extending to the limits of exploration (11 feet below existing site elevations at the test locations). It is our opinion that the subsurface conditions across the slope; including Lot 39, Lot 40, and at the proposed location of the low-impact septic system are relatively consistent. No signs of groundwater or a confining layer were observed at any of the test pit locations. Geologic Setting The referenced geologic map of Washington Northwest Quadrant (Dragovich at. al.) 2002, identifies Advance outwash (Qga) across the site and surrounding area; and glacial till (Qgt) to the north of the slope located on the north side of Northeast North Shore Road. The glacial till is mapped for off-site regions to the north of the subject site. The Washington State Web Soil Survey (SCS) generally describes the near-surface soil deposits, and indicates the site is underlain by Everett gravelly sandy loam. These soils are described as excessively well drained, forming on terraces. The erosion hazard for these soils is described as low to moderate. In general, the soils observed at the site are consistent with the map designations as described by the SCS resource. Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 5 March 21, 2014 The proposed septic system will be located within a steep slope area. The site soils consist of silty sand overlying dense gravel. Given the soil gradation and density, and the groundwater conditions across the site, in our opinion the risk of seismically induced liquefaction is low. In our opinion, the proposed development plans will not increase the risk of landslides on the slope located above Northeast North Shore Road where the proposed low-impact septic system to be constructed, given the relative density and granular nature of the underlying substrate present on the slope; and the low volume of discharge estimated to be released by the low- impact septic system. Fish and Wildlife Habitat Conservation Areas The subject site includes shoreline habitat area at the southern portion of the property. As part of the production of this report, we reviewed the proposed site layout. The proposed site development includes construction of a single-family residence to be sited behind (north) of the bulkhead currently located adjacent to the beach on the Hood Canal. It is our understanding that there will be no alteration to the bulkhead or beach area on the site. As such it is our determination that there will be no deleterious impacts to the critical shoreline on the property given best management practices (BMP) are undertaken to mitigate possible erosion/migration of soil via stormwater runoff from the development envelope into surrounding critical areas. Analysis of Proposal and Mitigating Measures Based on review of the referenced site plan, limited alterations are planned for the steep slope or landslide hazard areas on the subject site during construction of the septic system. The proposed residential structure is located in an area where grading would be minimized. The proposed location for the septic system is sited on a level area within the slope complex. In our opinion, the proposed development will not increase the potential for instability along the steep slopes and therefore conforms to the Critical Areas Requirements outlined in Chapter 17 of the Mason County Code. In our opinion, the potential for debris flow activity can be adequately mitigated by controlling surface water runoff above the slopes, and maintaining vegetative cover on the slopes. This assessment does not account for unforeseen or changed conditions or the slope conditions uphill from the subject site. Surface water should not be allowed to flow over or pond above the slopes and vegetative cover should be maintained along the existing slopes. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, the proposed construction of a single-family residence and associated on-site septic system is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, maintaining slope stability, and structural fill placement and compaction. Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 6 March 21, 2014 In our opinion, the soils generated from cuts throughout the site are suitable for use as structural fill. The soils encountered at the exploration sites generally have a moderate sensitivity to moisture, and placement and compaction of these soils during wet weather conditions may be difficult. In our opinion, imported material should be used for structural fill if the native soils cannot be moisture conditioned for adequate compaction results. This study has been prepared for the exclusive use of WA Fed and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork The primary geotechnical considerations during the proposed site preparation and earthwork activities will involve building pad area subgrade preparation, structural fill placement and compaction. Foundation Excavations In our opinion, the new residence can be supported on continuous or spread footings. Soil suitable for adequate foundation support should be encountered between one to three feet below existing site elevations within the proposed development envelope. If adequate bearing conditions are not exposed at the design footing elevations, overexcavation and backfill with suitable structural fill material will be necessary. In-situ Soils From a geotechnical standpoint, the coarse-grained soils encountered at the test sites are generally suitable for use as structural fill. The moisture sensitivity of the native soils can be generally characterized as moderate with respect to the poorly graded gravel with silt and sand. The soils encountered at the test sites were generally in a moist to wet condition at the time of the exploration (March 2014). Imported Soil Imported soil intended for use as structural fill should consist of a well-graded granular soil with a maximum aggregate grain size of six 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. 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 fill areas. The geotechnical engineer should observe cleared and stripped areas of the site prior to structural fill placement. Earth Solutions NK LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 7 March 21, 2014 Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway areas. Fills placed to construct permanent slopes, retaining wall, and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in maximum 12-inch loose lifts and compacted to a relative compaction of 95 percent, based on the maximum dry density as determined by the Modified Proctor Method (ASTM D-1557-02). Slope Fill Placement In general, fill placement on the steep slope areas should be avoided. Fill can be placed elsewhere on site to accomplish the design grading. ESNW should review the final grading plans to confirm the recommendations in this report are incorporated. Erosion Control Temporary erosion control measures should include, at a minimum, silt fencing placed along the downslope perimeter of the construction envelope, and a construction entrance consisting of quarry spalls, as needed, to minimize off-site soil tracking and to provide a firm surface. Surface water should not be allowed to flow over any temporary or permanent slopes. Interceptor drains or swales should be considered for controlling surface water flow patterns, as appropriate. A representative of ESNW should observe the erosion control measures, and provide supplemental recommendations for minimizing erosion during construction, as necessary. Foundations Based on the results of our study, the proposed residential structure can be supported on conventional spread and continuous footings bearing on competent native soil or structural fill placed over competent native soil. Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. For design the following parameters can be used for the foundation design: • Allowable soil bearing capacity 2,500 psf • Passive earth pressure 250 pcf • Coefficient of friction 0.40 The passive earth pressure and friction values provided above assume the foundations are backfilled with structural fill. A factor-of-safety of 1.5 has been applied to these passive resistance and friction values. For short term wind and seismic loading, a one-third increase in the allowable soil bearing capacity can be assumed. Earth Solutions NK LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 8 March 21, 2014 With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of approximately one-half of an inch. The majority of the settlements should occur during construction, as dead loads are applied. Slab-On-Grade Floors Slab-on-grade floors should be supported on competent native soil or 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 will be used, it should be a material specifically designed for that use and should be installed in accordance with the manufacturer's specifications. Seismic Considerations The 2009 International Building Code specifies several soil profiles that are used as a basis for seismic design of structures. If the project will be permitted using the 2009 IBC, based on the soil conditions observed at the test sites, Site Class D, from table 1613.5.2, should be used for design. The 2012 IBC recognizes ASCE for seismic site class definitions. If the project will be permitted under the 2012 IBC, in accordance with Table 20.3-1 of ASCE, Minimum Design Loads for Buildings and Other Structures, Site Class D, should be used for design. In our opinion, liquefaction susceptibility at this site is low. The relative density and gradation of the site soils is the primary basis for this designation. In our opinion there is little risk of lateral spread due to the soil gradation and relative density. Retaining Walls Retaining walls should be designed to resist earth pressures and applicable surcharge loads. For preliminary design, the following parameters can be assumed for retaining wall design: • Active earth pressure (yielding condition 35 pcf(equivalent fluid) • At-rest earth pressure (restrained condition) 55 pcf • Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution) • Passive earth pressure 250 pcf(equivalent fluid) • Coefficient of friction 0.40 • Allowable soil bearing capacity 2,500 psf Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 9 March 21, 2014 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. The geotechnical engineer should review retaining wall designs to verify the 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 (surface seal) soil, if desired. A rigid, perforated drain pipe should be placed along the base of the wall, and connected to an approved discharge location. Where desired, the use of a sheet drain in lieu of free draining backfill can be considered. However, the geotechnical engineer should review the proposed use of sheet drain, and provide supplement drainage recommendations. Excavations and Slopes The Federal and state Occupation Safety and Health Administration (OSHA/WISHA) classifies soils in terms of minimum safe slope inclinations. Based on the soil conditions encountered during our fieldwork, the site soils would generally be classified by OSHANVISHA as Type C. Temporary slopes over four feet in height in Type C soils should be sloped no steeper than 1.5H:1V (Horizontal:Vertical). The geotechnical engineer should observe temporary and permanent slopes to verify that the inclination is appropriate, and to provide additional grading recommendations, as necessary. If temporary slopes cannot be constructed in accordance with OSHA/WISHA guidelines, temporary shoring may be necessary. Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with an appropriate species of vegetation to enhance stability and to minimize erosion. Utility Support and Trench Backfill In our opinion, the soils observed at the test sites are generally suitable for support of utilities. Excessively loose, organic, or otherwise unsuitable soils encountered in the trench excavations should not be used for supporting utilities. In general, the on-site soils observed at the test sites 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. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable specifications of the city or county jurisdiction. Drainage Groundwater seepage was not observed at the test locations explored during March 2014. Localized zones of groundwater seepage may be encountered in the site excavations and utility excavations. Temporary measures to control groundwater seepage and surface water runoff Earth Solutions NW,LLC Washington Federal Savings ES-3283 c/o Barghausen Consulting Engineers Page 10 March 21, 2014 during construction will likely involve interceptor trenches, sedimentation ponds, and sumps areas. In our opinion, perimeter drains should be installed at or below the invert of the building footing foundations. A typical footing drain detail is provided on Plate 3 of this report. Where conveyance will occur over sloped areas of the site, we recommend using fuse-welded joints, HDPE UV-resistant piping and anchors. The approved discharge point should incorporate an energy dissipator system. Water discharge shall not occur on or above the steep slope areas of the site. LIMITATIONS 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 sites 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 1 ` + 98528 1 �mJ jKo�nOmi- Ho ci�J pA' T { na 9� . _. N W E ` /-SITE _.._ .._ _ . X _r f w r 985,92 a Rif nm , 0r 722N -T21N � n Reference: NORTH h,xv Mason County, Washington Map 17 Seven County Street Atlas „ nr ByAGood Map Company, Inc. VICIr11ty Map 2008 Wilson Lot 39 Mason County, Washington NOTE:This plate may contain areas of color.ESNw cannot be Drwn. GLS Date 03/11/2014 Proj. No. 3283 responsible for any subsequent misinterpretation of the information Checked SHA Date Mar. 2014 Plate 1 resulting from black&white reproductions of this plate. $t. / L( o/ 39 vv vv \ `\\ Primary A\ \\ \ Pf \eea el ^. rved DraI Dfelndeld \ Pit;, Lp139 \ se' well Reams Easement/ \ �\ \ Line \ Lot tO D TP-1 APproxirnate� DraiO4elti 4.ocetion fTwo4 \ / L/TP_'2 \\ / tof Loot93 ts 39&400A i 1 �i' Proposed ,,Lot 41 ot \ Lot 39 D,ain5xld Location TrenepoM1 Pipe LEGEND Proposed i \ Residence —LApproximate Location of s; e°9e seotic°Taan TP-1 I ESNW Test Pit, Proj. No. HH-2�— \ ES-3283, Mar. 2014 NORTH� —Approximate Location of HH-1 I ESNW Hand Hole, Proj. No. ES-3283, Mar. 2014 „ Subject Site - —-1 0 40 80 160 Existing Building V=ao' � Cale n Feet Proposed 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 Test Pit and Hand Hole Location Plan existing and/or proposed site features.The information illustrated Wilson Lot 39 is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes Mason County, Washington or interpretation of the data by others. NOTE:This plate may contain areas of color.ESNW cannot be Drwn. GLS Date 03/11/2014 Proj. No. 3283 responsible for any subsequent misinterpretation of the information Checked SHA Date Mar. 2014 Plate 2 resulting from black&white reproductions of this plate. 18" Min. o° o° ° o °� ` = vo = o °°mo ° °°°oob° °o°°, O° 0 O° d o ° °°° ° o°° °o °°o °°�° °o ° o0 6 . °o 00 o ` 0 °0 °o�°o o o° °0 ° °° o°° °.0 o° 0°0 ° °o0 °° o ° ° ° 0 ° Structural °° °°°° ° °�° Fill 08' o ° ° 8 ° ° o ° o°°o 0 0% °o °o° �° ID 11= °o o 0 ° o °` III ° ° ° 1 � 1• \ Perforated Drain Pipe NOTES: (Surround In Drain Rock) • 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 SCHEMATIC ONLY- NOT TO SCALE of Free Draining Backfill, per ESNW NOT A CONSTRUCTION DRAWING recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. LEGEND: o°o ° f 1 1 ° o6,0 Free Draining Structural Backfill - - {.{.{.; rti?tir4{ti 1 inch Drain Rock RETAINING WALL DRAINAGE DETAIL •f.r.1.1. Wilson Lot 39 Mason County, Washington Drwn. GLS I Date 03/13/2014 Proj. No. 3283 Checked SHA Date Mar. 2014 Plate 3 Slopes t$;';(hA sit.):: .r}r}r111f1r11 1 ti ti ti.4.ti 'rti: r.r1r.r. +11! Lr1. 1.1 2"(Min.) Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. SCHEMATIC ONLY- NOT TO SCALE • Surface Seal to consist of NOTA CONSTRUCTION DRAWING 12"of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal; native soil or other low permeability material. 3111 r.r.r.r•r 6' 1 1 .y.y.\.ti. ... .. l4r1J111r 1" Drain Rock FOOTING DRAIN DETAIL Wilson Lot 39 Mason County, Washington Drwn. GLS I Date 03/13/2014 Proj. No. 3283 Checked SHA Date Mar. 2014 Plate 4 Appendix A Subsurface Exploration ES-3283 The subsurface conditions were explored by advancing four test pits at the approximate locations illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed in March 2014. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. Earth Solutions NW,LLC Earth Solutions NWLLC SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS CLEAN WELL-GRADED GRAVELS,GRAVEL• GRAVEL GRAVELS ��S Gw FSAND INES MIXTURES,LITRE OR NO AND GRAVELLY eQ^ ��° POORLY-GRADED GRAVELS, SOILS (LITTLE OR NO FINES) O�o O GP GRAVEL-SAND MIXTURES,LITRE OQ°O OR NO FINES COARSE ° GRAINED MORE THAN 50% GRAVELS WITH •� 0 GM SILTMI%TURESLTY ,GRAVEL SAND- FINES SOILS OF COARSE O ° FRACTION RETAINED ON NO. 4 SIEVE A(MAPPREOUNTCIABLE FINES) GC CLAYEY CLAY MIXTURESGRAVELS,GRAVEL-SAND • CLEAN SANDS Sw WELL-GRADED SANDS,GRAVELLY MORE THAN 50% SAND SANDS,LITTLE OR NO FINES OF MATERIAL IS AND LARGER THAN SANDY ••• POORLY-GRADED SANDS, NO.200 SIEVE SOILS GRAVELLY SAND,LITTLE OR NO SIZE (LITTLE OR NO FINES) SP FINES SANDSWITH SM MIXTURES OF SAND-SILT MORETHAN50% FINES OF COARSE FRACTION PASSING ON NO. CLAYEY SANDS,SAND-CLAY 4 SIEVE AMOUNT OF FINES) SC MIXTURES INORGANIC SILTS AND VERY FINE ML RANDS,ROCK FLOUR,SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY SILTS INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY,FINE AND LIQUID LIMIT CL CLAYS,SANDY CLAYS,S LTYLLY GRAINED CLAYS LESS THAN 50 CLAYS,LEAN CLAYS SOILS — — OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS,MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO.200 SIEVE SIZE SILTS AND LIQUID LIMIT CH INORGANIC CLAYS OF HIGH CLAYS GREATER THAN 60 OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICT',ORGANIC SILTS u u .SWAMP HIGHLY ORGANIC SOILS � � PT HIEGAH OHRGGAMC CONTEN SILS WITH u i i DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. Earth Solutions NW TEST PIT NUMBER TP-1 1805-136th Place N.E.,Suite 201 PAGE 1 OF 1 Bellevue,Washington 98005 Telephone: 4264494704 Fax: 425-4494711 CLIENT Washington Federal o Bdro --_-_-. PROJECT NAME Wilson.Lot 39 ...-_ PROJECT NUMBER 3283 —_ — PROJECT LOCATION Mason Coumy,Washington - _. ._-- DATESTARTED 3/3/14 COMPLETED 3/3/14. GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Nov_astar _—,____._ GROUND WATER LEVELS: EXCAVATION METHOD _ _ __ AT TIME OF EXCAVATION — -_-.- -..-_..._—___--- LOGGED BY SHA _ CHECKED BY SHA AT END OF EXCAVATION ...........-- NOTES _Depth of-Topsoil&Sod 12" _.----.---._ AFTER EXCAVATION — w ant O vi TESTS ai O MATERIAL DESCRIPTION o 0. 0 TOPSOIL TPSL,, , Brown silly,SAND with gravel,medium dense,moist(Duff) MC=7.40% SM _ _s.o -increased gravel content Brown poorly graded GRAVEL with sift and sand,dense,moist 0 C MC=9.90% Fines=5.70% o bi GP- GM v o� 10 � __ -- — Test pit tegninated at 11.0 feet below existing gratle.Noo groundwater encountered during excavation. Bottom of test pit at 11.0 feet. a a T is N F 2 d LL r_ J¢m W 2 W L7 Earth Solutions NW TEST PIT NUMBER TP-2 1805-136th Place N.E.,Suite 201 PAGE 1 OF 1 Bellevue,Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT _Washington Federal clo Be _._ PROJECT NAME Wilson Lot 39__.-___..-_____.--_ PROJECTNUMBER 5263 _ ^___._--... PROJECT LOCATION _MeWOrl Count' W,_ ashmetOn ..--. DATE STARTED _3/3114 COMPLETED .3/3/14 GROUNDELEVATION TESTPITSIZE EXCAVATION CONTRACTOR _Nova_star GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY .SHA CHECKED BY SHA AT END OF EXCAVATION NOTES Depth of Topsoil 8.Sod 16" fams AFTER EXCAVATION w >_ U c-c ul o' TESTS N O MATERIAL DESCRIPTION jz O N 0 TOPSOIL TPSL '= Brown poorly graded GRAVEL with silt and sand,dense, moist 0 -cobbles 0 5 a -increased sand content GP- GM 0 n c( MC=10.20% 10 .19_0__._..__- Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 10.0 feet. a a FN 2 6 y$ F W_ Earth Solutions NW BORING NUMBER HH-1 1805-136th Place N.E.,Suite 201 PAGE 1 OF 1 Bellevue,Washington 98005 Telephone: 425-44941704 Fax: 425449.4711 CLIENT Washin ton Federal do Barghausen PROJECT NAME Wilson Lot 39 _.. .....__— PROJECT NUMBER 3283 PROJECT LOCATION Mason County,Washington DATE STARTED 313114 COMPLETED 313114 _. GROUND ELEVATION --------- HOLE SIZE _ DRILLING CONTRACTOR ESNW Rep _ _— GROUND WATER LEVELS: DRILLING METHOD Hand Auger ATTIME OF DRILLING — -- LOGGED BY SHA------,---- CHECKED BY SHA.................___ AT END OF DRILLING NOTES Depth Of Topsoil&Sod 47 grass ._ ___ AFTER DRILLING w i vi w m U = MATERIAL DESCRIPTION W� d= V � Q Z [7 N 0 PSL_ 0.5 TOPSOIL_ _ _ Brown silty SAND with gravel,medium dense to dense,moist SM Brown poorly graded GRAVEL with silt and sand,dense,moist GP- GM � - Hand Hole terminated at 3.0 feet below existing grade.No groundwater encountered during excavation. Bottom of hole at 3.0 feet. a 0 Vi F 2 U pi 1 F<_ K W 2 W U Earth Solutions NW BORING NUMBER HH-2 1605.136th Place N.E.,Suite 201 PAGE 1 OF 1 Bellevue,Washington 98005 Telephone: 4254494704 Fax: 4254494711 CLIENT _Washington_FeCeral do Barghausen .___ PROJECT NAME Wilson Lot 39 PROJECT NUMBER 3283 __.. PROJECT LOCATION Mason_CountY Washington DATE STARTED 3/3/14 COMPLETED 3/3114 _ GROUNDELEVATION __. HOLESIZE DRILLING CONTRACTOR ESNW Rep_ _� GROUND WATER LEVELS: DRILLING METHOD Hand CA per AT TIME OF DRILLING LOGGED BY SHA CHECKED BY SHA, AT END OF DRILLING NOTES Depth of Topsoll 4 Sod 4 .press AFTER DRILLING _— w F w TESTS vOi MATERIAL DESCRIPTION Ov 2z C7 N 0 TP_SL u ' 0.5 TOPSOIL Brown poorly graded GRAVEL with silt and sand,medium dense,moist MC=13.20% GP- GM -becomes dense 0 Test pit terminated at 3.0 feet below existing grade.No groundwater encountered during excavation. Bottom of hole at 3.0 feet. a E 'a x m w Z w U' Appendix B Laboratory Test Results ES-3283 Earth Solutions NW,LLC Earth SolutionsPlace GRAIN SIZE DISTRIBUTION 1805-138th Pl Place N.E.,Suite 201 Bellevue,WA 98005 Telephone: 425-284-3300 CLIENT WA Fed do Bamhausen —, _ PROJECT NAME Wilson—Lot 39 .—..— PROJECT NUMBER ES-3283 PROJECT LOCATION Mason Co U.S.SIEVE OPENING IN INCHES I U.S.SIEVE NUMBERS I HYDROMETER 6 4 3 2 1 3/4 12W8 3 4 6 810 1416 20 30 40 60 60 100140200 100 95E 85 45— 7065 x 55 — m z5U LL z W 0 40 -__ K a 30 -- -- 25 15 5 - 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS COBBLES GRAVEL SAND SILT OR CLAY -- m- coarse One Coarse mediu �— fine- _ Specimen Identification Classification LL PL PI Cc Cu a o TP-1 6.0111. Brown Poorly Graded GRAVEL with Slit and Sand,GP-GM 0.35 84.74 a - - 0 5 Specimen Identification D100 D60 D30 D_10 %Gravel %Sand %Silt %Clay o TP-1 8.0R. 37.5 14A91 0.938 0.171 68.6 35.7 5.7 w u Report Distribution ES-3283 EMAIL ONLY Washington Federal Savings c/o Barghausen Consulting Engineers 18215 —72"d Avenue South Kent, Washington 98032 Attention: Mr. Tom Barghausen Earth Solutions NW,LLC