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HomeMy WebLinkAboutBLD2017-00626 - GEO Geological Review - 8/16/2017RECEIVED AUG 16 2017 VV. A€der Street Geotechnical Report for Brown Single Family Residence 191 Totten Shores Drive Parcel No. 22031-50-00053 Mason County, Washington July 14, 2016 Project 01696 Prepared For: Terry Evans P.O. Box 1551 Shelton, Washington 98584 Prepared By: Envirotech Engineering, PLLC PO Box 984 Belfair, Washington 98528 Phone: 360-275-9374 0 Zo, 7 CC0 Mason County Department of Community Development Submittal Checklist For a Geotechnical Report Instructions: This checklist muss be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed professional(s) who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain the basis for the conclusion. Applicant/Owner Terry Evans Parcel# 22031-50-00053 Site Address (1) 191 Totten Shores Drive, Shelton (a) A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) 5 (b) A discussion of specific soil types Located on page(s) 6 (c) A discussion of ground water conditions Located on page(s) 7 (d) A discussion of the upslope geomorphology Located on page(s) 3 (e) A discussion of the location of upland waterbodies and wetlands Located on page(s) 3 (f) A discussion of history of landslide activity in the activity in the vicinity, as available in the referenced maps and records Located on page(s) 6 (2) A site plan which identifies the important development and geologic features. Located on Map(s) Site Plan (3) Locations and logs of exploratory holes or probes. Located on Map(s) Site Plan/ Soil Logs (4) The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall be delineated (top, both sides, and toe) on a geologic map of the site. Located on Map(s) Site Plan (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which incorporates the details of proposed grade changes. Located on Map(s) Soil Profile (6) A description and results of slope stability analyses performed for both static and seismic loading conditions. Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of Circles, The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1. and the quasi -static analysis coeffients should be a value of 0.15. Located on page(s) 9 (7) (a) Appropriate restrictions on placement of drainage features Located on page(s) 15 (b) Appropriate restrictions on placement of septic drain fields Located on page(s) 17 (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) 12. 14 Page 1 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. (8) (9) (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) 16 (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) 15 Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation removal. Located on page(s) 16 Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) 10 (10) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) 11 (11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. Located on page(s) 15-17 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) 17 (13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and proposed development on the site. Located on Ma. s Site Pear, Michael C Staten hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. I also certify that the Geotechnical Report, dated 7/14/16 and entitled Brown Singe Family Residence meets all the requirements of the Mason County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) 7/14/16 Page 2 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. Table of Contents 1.0 LNTRODUCTION ...... ..... ......... ............... —„ ....... ..................... .. ... ............. 1 1.1 PROJECT INFORMATION 1 1.2 PURPOSE OF LNVESTIGATION ,AND SCOPE OF WORK 1 2.0 SURFACE CONDITIONS 3 2.1 GENERAL OBSERVATIONS 3 2.2 TOPOGRAPHY 3 2.2.1 Upslope Geomorphology 3 2.3 SURFACE DRAINAGE 3 2.3.1 Upslope Water Bodies 3 2.4 SLOPE AND EROSION OBSERVATIONS 4 3.0 SUBSURFACE INVESTIGATION 5 3.1 FIELD METHODS, SAMPLING AND FIELD TESTING 5 3.2 GENERAL GEOLOGIC CONDITIONS 5 3.3 SPECIFIC SUBSURFACE CONDITIONS 7 3.3.1 Groundwater 8 4.0 ENGINEERING ANALYSES AND CONCLUSIONS . 9 4.1 SLOPE STABILITY 9 4.1.1 Slope Stability Analysis 11 4.2 EROSION 11 4.2.1 Shoreline Recession 12 4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION 12 4.3.1 Liquefaction 12 4.4 LANDSLIDE, EROSION AND SEISMIC HAZARDS CONCLUSIONS 12 4.5 LATERAL EARTH PRESSURES 13 4.6 ON-SuL AND OFF-SITE IMPACTS 13 5.0 ENGINEERING RECOMMENDATIONS 14 5.1 BUILDING FOUNDATION HECONWIENDATIONS 14 5.1.1 Bearing Capacity 14 5.1.2 Settlement 15 5.1.3 Concrete Slabs -on -Grade 15 5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS 15 5.2.1 Excavation 15 5.2.2 Placement and Compaction of Native Soils and Engineered Fill 16 5.2.3 Retaining Wall Backfill 17 5.2.4 Wet Weather Considerations 17 5.3 BUILDING AND FOOTENG SETBACKS 17 5.4 SURFACE AND SUBSURFACE DRAINAGE 17 5,5 VEGETATION DUFFER AND CONSIDERATIONS 18 5.6 TEMPORARY AND PERMANENT EROSION CONTROL 18 5.7 SEPTIC DRAINFIELDS 19 5.8 STRUCTURAL MITIGATION 19 6.0 CLOSURE 20 Appendix A - Site Plan Appendix B - Soil Information Appendix C - Slope Stability Appendix D -Erosion Control - 1.0 INTRODUC 110N Envirotech Engineering CEnvirotech) has completed a geotechnical investigation for a planned single family residence located at 191 Totten Shores Drive, identified as parcel number 22031- 50-00053, Mason County, Washington. See the vicinity map on the following page for a general depiction of the site location. An initial geotechnical evaluation of the Project was conducted by Envirotech on June 9, 2016. It was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were present within 300 feet of the planned development. Based on this site characteristic, the proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason County Resource Ordinance (MCRO) 17.01.100. During the site visit by Envirotech, surface and subsurface conditions were assessed. After completion of the field work and applicable Project research. Envirotech prepared this geotechnical report which, at a minimum, conforms to the applicable MCRO. As presented herein, this report includes information pertaining to the Project in this Introduction Section; observations of the property and surrounding terrain in the Surface Conditions Section; field methods and soil descriptions in the Subsurface Investigation Section; supporting documentation with relation to slope stability, erosion, seismic considerations, and lateral earth pressures in the Engineering Analyses and Conclusions Section; and, recommendations for foundation, settlement, earthwork construction, retaining walls, erosion control, drainage, and vegetation in the Engineering Recommendations Section. 1.1 Project Information Information pertaining to the planned development of the Project was provided by the proponent of the property. The planned development consists of a 1- or 2 -story single family residence, new on-site septic system, and other ancillary features typical of this type of development. Approximate building footprint and other proposed features with relation to existing site conditions are illustrated on the Site Map provided in Appendix A of this report. 1.2 Purpose of Investigation and Scope of Work The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the Project in order to provide geotechnical recommendations that should be implemented during development. The investigation included characterizing the general Project surface and subsurface conditions, and evaluating the suitability of the soils to support the planned site activities. In order to fulfill the purpose of investigation, the geotechnical program completed for the proposed improvements of the Project include: o Review project information provided by the Project owner and/ or owner's representative; ® Conduct a site visit to document the site conditions that may influence the construction and performance of the proposed improvements of the Project; a Define general subsurface conditions of the site by observing subsoils within test pits and/ or cut banks, review geological maps for the general area, research published Envirotech Engineering, PLLC PO Box984 Beifair, Washington 98528 Ph. 360-275-9374 page 1 191 Totten Shores Drive Parcel 22031-50-00053 Mason County, Washington July 14.20t6 references concerning slope stability, and review water well repons from existing wells near the Project * Collect bulk samples, as applicable, at various depths and locations; • Perform soils testing to determine selected index and/or engineering properties of the site soils: • Complete an engineering analysis supported by the planned site alterations, and the surface and subsurface conditions that were identified by the field investigation, soil testing, and applicable project research; and, • Establish conclusions based on findings, and make recommendations for foundations, drainage, slope stability, erosion control, earthwork construction requirements, and other considerations. Project ap from Mason County Website Envirotech Engineering, PLLC PQ Box 984 Belfair, Washington 98528 Ph. 360-275-9374 page 2 91 Totten Shores Dune Parcel 22031-50-00053 Mason County, Washington July 14,2016 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the Project was gathered on June 9, 2016 by a representative with Envirotech. During the site visit, the type of geotechnical investigation was assessed, site features were documented that may influence construction, and site features were examined that may be influenced by construction. This Surface Conditions Section provides information on general observations, vegetation, topography, drainage and observed slope/ erosion conditions for the Project and surrounding areas that may impact the Project. 2.1 General Observations Currently, the property is vacant with an existing garage and driveway. Vegetation on and near the Project consists primarily of secondary growth firs, madronas, and other trees and shrubbery common to this area of the Pacific Northwest. An aerial photo of the Project and immediate vicinity is provided on the following parte. 2.2 Topography The topographic information provided in this section was extrapolated from a public LIDAR source, and incorporated observations and field measurements. Where necessary, slope verification included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site Plan in Appendix A in this report for an illustration of general topography with respect to the planned development. Critical descending slopes, with grades exceeding 40% appear to be within 300 feet of the planned development. The maximum critical slope is approximately 52% with a vertical relief of about 20 feet. Ascending grades are generally located to the southeast of the planned development. These slopes are relatively minor within 300 feet of the Project, with no apparent slope grades of at least 15%. 2.2.1 Upslope Geomorphology The upland area of the property and beyond is generally situated on a hillside and crest of glacial origin. 2.3 Surface Drainage Runoff originating upslope of the development is mostly diverted away from the property by accommodating topography. Excessive scour, erosion or other indications of past drainage problems were not observed within the immediate vicinity of the planned development. 2.3.1 Upslope Water Bodies There are no apparent water bodies or wetlands located upslope from the planned development that would siognificantly influence the Project. 'pnvirotech Engineering, PLLC PO Box 984 Belfair, Washington 98528 Ph. 360-275-9374 page 3 91 Totten Shores Dti 8 Parcel 22031-50-00053 Mason County, Washington July 14, 2016 2.4 Slope and Erosion Observations The slope gradients near the Project signal a potential landslide or erosion hazard area. Some indicators that may suggest past slope movements include: * Outwash of sediments near the bottom of the slope, * Fissures, tension cracks, hummocky ground or stepped land masses on the face or top of the slope, and parallel to the slope, * Fine, saturated subsurface soils, * Old landslide debris, * Significant bowing or leaning trees, or, ▪ Slope sloughing or calving. Except for nearby shoreline erosion, these slope instability indicators or other s bgnifieant mass wasting on the property or within the general vicinity of the Project were not observed or discovered during research. Indications of past landslides, current unstable slopes, deep-seated slope problems, or surfieial slope failures were not observed during the site visit. Aerial Photo from Google Website Ensarotech Engineering, PCLC PO Box 984 Deifair. Washington 95528 Pk 360-275-9374 page 4 -- 191 -Totten -Shores Drive Parcel 22031-50-00053 Mason County. Washington July 14, 2016 3.0 SUBSURFACE INVESTIGATION Information on subsurface conditions pertaining to the Project was primarily gathered on June 9, 2016 by a representative with Envirotech. Applicable information on field methods, sampling, field testing, general geologic conditions, specific subsurface conditions, and results from soil testing are presented in this section of the report Appendix B of this report includes pertinent information on subsurface conditions for the Project, such as subsoil cross-section(s), test pit log(s), and applicable water well report(s). Water well reports were utilized to estimate ground water levels, and if sufficient, were used in identifying subsoil types. Applicable test pit locations are depicted on the Site Plan provided in the appendix of this report. 3.1 Field Methods, Sampling and Field Testing Information on subsurface conditions for the Project was accomplished by examining sods within test pits and/ or nearby banks extending to depths of up to 5 feet below the natural ground surface. Information on subsurface conditions also included reviewing geological maps representing the general vicinity of the project, and water well reports originating from nearby properties. Soil samples were not obtained from this project. Envirotech measured the relative density of the near -surface in-situ soils by gauging the resistance of hand tools. Within testing locations, field testing results generally indicated medium dense soils in the upper 5 feet to the depth of terminous. 32 General Geologic Conditions In general. soils at the project are composed of materials from glacial advances. The geologic conditions as presented in the `Geologic Map of Washington," compiled by J. Eric Schuster, 2002 indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated deposits, and dominantly deposited from glacial drift, including alluvium deposits. This project is located within the Puget Lowland. Typically, "lower tertiary sedimentary rocks unconformably overlie the Crescent Formation." as revealed in the Geologic Map. Initial sedimentary rocks were fomled from shales, sandstones and coal deposits from rivers. During the Quaternary period, the Puget Lowland was covered by numerous ice sheets, with the most recent being the Fraser glacier with a peak of approximately 14,000 years ago. Upon the glacial retreat, the landscape was formed by glacial erosion glacial drift deposits. The "Geologic Map of the Squaxin Island 75 -minute Quadrangle, Mason County, Washington" by Robert L. Logan, Michael Polenz, Timothy J. Walsh, and Henry W. Schasse, 2003, provides the following caption(s) for the project area: Envirotech Engineering, PLLC PO Box 984 Bel€air, Washington 98528 Ph. 360-275-9374 191 Totten Shores Drive Parcel 22031-50-00053 Mason County, Washington July 14, 2016 Oct U-- 1..ti,orted and hit:Lvy, comfm(b:(1 \ lure oi c Naild.utd acl Liet,o!,itctl ilirecLk K ice trriii, fercticittU Itojirt. nitti Not:itit tithere tigittittiegi. ger: iirtit permeittidtty: rtt tintuit:tit, mac tea but gtsti :tripygitititil: mitts; \rcr fcel, r:lot it‘i#11tll 0 -hit; lti ilitllC ttettinietitr. FLetedItlid Will sUteL tti tillmtlillItlitIthltIttTLN iCtiti !kill 1 lit Ilia lit Of ittl WI; Mid till thitt itio thin; ttiliiirittiittilit, mzk the UL 'LL t1Uc ;trc till till alt it\ hi:I/c deptthitt: tleakk Acitrittileti modern Hill Chi.: Mil tllitt it'd.: HCLI ft LtrIll IL: ft itmig d uildcr I \ in:r2 h,J toftCno dius,tion Ersirotech Engineering, PLLC PO Box 984 Bent, Washington 98528 Ph. 360-275-9374 page 6 19i TiTattertantta Driste - Parcel 22031-50-00053 Mason County, Washington lidy 14, 2016 Qgt Geological Map Department of Natural Resources Washington Stare 3.3 Specific Subsurface Conditions The following subsurface conditions are estimated descriptions of the Project subgrade utilizing information from the depth of penetration at all testing. sampling, observed and investigated locations. Soils for this project were primarily described utilizing the Unified Soil Classification System (USCS) and the Natural Resource Conservation Service (NRCS) descriptions. The Project is currently composed of native soils without indications of borrowed fill. Within test pit locations, soils within the upper 5 feet of natural ground were generally observed to be dry, grey silt (ML) with clay and gravel. Based on nearby well reports, the silt layer extend to at Least 80 feet. The relative densities of the soil within selected test pits are provided above in Section 3.1. Expanded and specific subsurface descriptions, other than what is provided in this section, are provided in the soil logs located in Appendix B of this report. EnYifotech Engineering, PLLC PO Box 984 Belfair, Washington 98528 Ph. 360-275-9374 page 7 191 Totten Shores Drive Parcel 22031-50-00053 Mason County, Washington July 14, 2016 According to the "Soil Survey of Mason County," by the United States Department of Agriculture, Natural Resource Conservation Service, the site soils are described as Alderwood Gravelly Sandy Loam, Ac, with 1595 - 30% slopes. The soil designations are depicted in the aerial photograph below, and descriptions are provided in Appendix B of this report. Soil Survey Fronz USDA Natural Resources Conservation Service 3.3.1 Groundwater From the water well repot (s) and knowledge of the general area, permanent groundwater is at least 50 feet directly below the property at the building pad location. Surface seepage or perched groundwater at shallow depths was not observed on-site, nor indicated on the well reports. However, some groundwater is expected to flow directly above the hardpan on occasion. Enviratech Engine 90 Box 934 Belfair. Wa;hin_ton 98528 Ph. 300-275-9374 PLLC page 8 191 Totten Shores Drnve Parcel 22031-50-00053 Mason Count_y.Washington July 14. ^--016 4.0 ENGINEERING ANALYSES AND CONCLUSIONS The following section includes slope stability, erosion, seismic considerations. and impacts to both on-site and off-site properties. 4.1 Slope Stability Landslides are natural geologic processes, and smuctures near slopes possess an inherent risk of adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering cannot eliminate these risks for any site with sloping grades because gravity is constantly inducing strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will exacerbate these strains. Geotechnical engineering considers excessive wet weather and `design' earthquakes in order to provide an acceptable factor of safety for developing on or near sloping terrain with relation to current engineering protocol. These factors of safeties are based on engineering standards such as defining engineering properties of the soil, topography, water conditions. seismic acceleration and surcharges. Surface sloughing or other types of surficial slope movements usually do not affect the deep-seated structural capability of the slope. However, repeated surficial slope movements, if not repaired, may represent a threat to the structural integrity of the slope. If any slope movement arises, the slope should be inspected by an engineer. Subsequently, maintenance may be required in order to prevent the possibility of further surficial or deep seated slope movements that may be damaging to life and property. According to the Coastal Zone Atlas of Mason County, Washington, the Project is within and near terrain labeled 'Stable' and `Unstable' regarding potential landslide activity. Descriptions of these mapping units may be found in the aforesaid Atlas. A Stability Map from the Coastal Zone Atlas for the general area of' this Project is provided below: Map from Washington State Department of Ecology Website Emirotecil Engineerin PO Box 984 Belfair, Washington 98528 Ph. 360-275-9374 page 9 191 Totten Shores Drive Parcel 22031-50-100053 Meson County. Washington July 14. 2016 According to the Resource Map from the Washington State Department of Natural Resources (DNR), the Project is not within terrain labeled 'highly unstable' relating to soils. DNR labeled portions of this project as medium and high slope instability with relation to slopes. A Resource Map from the DNR Forest Practices Application Review System is provided below: Resource Map from Washington State Department of Natural Resources Website -SOILS — 4n RE -source 3t=e 0 -- sic Soils -_st.,iv trnstaiile Highly Erodible oda! L.c' t_rra=ei Di: SLOPE-- On genet: ce Mao err le&m Slope Envirotech Dngineetnng, PLLC PO Pox 984 Bellair, Washington 98528 Ph. 360-275-9374 page 10 n Jnore Parcel 22031-50-00053 Mason County. Washington July 14.2016 4.1.1 Slope Stability Analysis The Simplified Bishop Method, utilizing 'STABLE' software, was used to analyze the static stability of the site slopes. Seismic conditions were estimated utilizing worst case scenario values from the static analysis, a quasi -static analysis coefficient of at least 0.15. and applying the applicable values to STABLE software. Various radii's and center points of the circle were automatically selected, and produced factor of safeties in a graphical and tabular format. Worst case scenario values were used in the slope stability analysis in regards to topography, surcharges, water content, internal friction and cohesion of the site sods. STABLE software has been repeatedly checked with manual calculations, and consistently proved to be a very conservative program. The following soil properties were used in the analysis, and are based on observed conditions, known geology, and/or published parameters: Upper 5 feet soil depth Soil unit weight: Angle of internal friction: Cohesion: 110 pcf 27 degrees 40 psf Based on the slope stability analysis, unacceptable factors of safety could be present on and near the critical slope, but do not reflect conditions where development is expected to occur. For this Project, at the location of the proposed development, minimum factor of safeties for static and dynamic conditions were estimated to be 3.1 and 1.9, respectively. See the slope stability information in Appendix C for a depiction of input parameters and example of outputs. 4.2 Erosion Based on the LSCS description of the Project soils, the surface soils are considered moderately erodible. According to the Resource Map from the Washington State DNR, as provided above. the Project is not within terrain labeled `highly erodible.' This Project is not within an erosion hazard area as defined by the MCRO. Erosion hazard areas are those with USDA SCS designations of River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loarn on slopes 15% or greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd), Harstine Gravelly Sandy Loam on slopes 15% or greater (iib), and Kitsap Silt Loam on slopes 15% or greater (Kell. It is our opinion that minor erosion control recommendations provided in this report is sufficient for the development of this Project, and additional engineered erosion control plans are not required. Temporary and permanent erosion control measures are required for site development. Extents of temporary erosion control will mostly depend on the timeliness of construction. moisture content of the soil, and amount of rainfall during construction. Soil erosion typical to the existing site conditions and planned disturbance of the Project include wind-borne silts during dry weather, and sediment transport during prolonged wet weather. Sediment transport could be from stormwater runoff or tracking off-site with construction equipment. The Temporary and Permanent Erosion Control Section (Section 5.6) of this report consist of specific erosion controls to be implemented. Additional erosion control information and Etivirotech Engineering, PLLC PO Box 984 Beifair. Washing on 98528 Ph, 360-275-9374 page 11 191 Totten Shores Drive Palen] 22031-50-00053 Mason County, Washington July 14, 2016 specifications may be found in the latest addition of the "Stormwater Management Manual for Western Washington," prepared by the Washington State Department of Ecology Water Quality Program. 4.2.1 Shoreline Recession Due to the close proximity of a shoreline, an evaluation of the shoreline recession rate for this Project was completed. The future shoreline regression will be zero on the subject property with ordinary care and maintenance of the existing bulkhead. 4.3 Seismic Considerations and Liquefaction There are no known faults beneath this Project. The nearest Class 'A' or Class 'B' fault to this property is the Olympia Structure, in which is approximately 1.5 miles to the south of this Project. This information is based on the USGS Quaternary Fault and Fold Database for the United States. Potential landslides due to seismic hazards have been considered,. and are addressed in the Slope Stability Analysis Section provided earlier in this report. Soils immediately below the expected foundation depth for this Project are generally Type D, corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the regional seismic zone is 3 for this Project. The estimated peak ground acceleration ranges from 0.50g to 0.60g. This esthnation is based on the United States Geological Survey (USGS) National Seismic Hazard Project in which there is an estimated 2% probability of exceedance within the next 50 years. 43.1 Liquefaction The potential for liquefaction is believed to be low for this Project. This is based, in part, on the subsurface conditions such as soil characteristics and the lack of a permanent shallow water table. Subgrade characteristics that particularly contribute to problems caused from liquefaction include submerged, confined, poorly -graded granular soils (i.e. gravel, sand, silt). Although gravel- and silt -sized soil particles could be problematic, fine and medium grained sands are typically subjected to these types of seismic hazards No significant saturated sand stratifications are anticipated to be within the upper 50 feet of the subsoil for this Project. 4.4 Landslide, Erosion and Seismic Hazards Conclusions DNR did not indicate historic landslide activity near the Project. Mapped slope conditions, as delineated by the Departments of Ecology and/ or Natural Resources, were considered in our slope stability assessment. Based on the proximity and severity of mapped delineations with respect to the proposed development, results of the aforesaid slope stability analysis, observed surface conditions, and other pertinent information, it is our opinion that the proposed development may occur in accordance with the recommendations in this geotechnical report. Envirotech Engine ing, PLLC PQ Box 984 Belfair. Washington 98528 Ph. 360-275-9374 191 Totten Shores Drive Parcel 22031-50-00053 Mason County, Washington July 14, 2015 4.5 Lateral Earth Pressures Lateral earth pressures exerted through the backfill of a retaining wall are dependent upon several factors including height of retained soil behind the wall, type of soil that is retained, degree of backfill compaction, slope of backfill, surcharges, hydrostatic pressures, earthquake pressures, and the direction and distance that the top of the wall moves. Significant retaining structures are not anticipated for this Project. If retaining walls are later planned for this Project, prescriptive requirements from the County should be adhered to. For retaining structures with a height exceeding County prescriptive requirements, additional design parameters must be accounted for in the retaining wall analysis, and recommendations should only be provided by a qualified engineer after the type of backfill is acquired, inclination of backfill slope is estimated, and the final wall height is determined. 4.6 On -Site and Off -Site Impacts From a geotechnical position, it is Envirotech's opinion that the subject property and adjacent properties to the proposed development should not be significantly impacted if all recommendations in this report are followed. This opinion is based on the expected site development, existing topography, existing nearby development, land cover, and adhering to the recommendations presented in this report. Future development or land disturbing activities on neighboring properties or properties beyond adjacent parcels that are upslope and/or downslope from the subject property could cause problems to the subject property. For this reason, future development or land disturbance near the subject property should be evaluated by a geotechnical engineer. Envirotech tingineering, PLLC PO Box 984 Belfair, Washington 98528 Ph. 360-275-9374 page 13 9 Totten Shores Drive Parcel 22031-50-00053 Mason County: Washington July 14. 2016 5.0 ENGINEERING RECOMMENDATIONS The following sections present engineering recommendations for the proposed improvements of the Project. These recommendations have been made available based on the planned improvements as outlined in the Introduction Section of this report; general observations including drainage and topography as recapitulated in the Surface Conditions Section; soil/ geologic conditions that were identified from the geotechnical investigation that is summarized in the Subsurface Investigation Section; and, Project research, analyses and conclusions as determined in the Engineering Analysis and Conclusions Section. Recommendations for the Project that is provided herein, includes pertinent information for building foundations, earthwork construction, building and/ or footing setbacks, drainage. vegetation considerations, and erosion control. 5.1 Building Foundation Recommendations Recommendations provided in this section account for the site development of a typical one- or two-story, single family residential structure. The recommended allowable. bearing capacities and settlements as presented below, consider the probable type of construction as well as the field investigation results by implementing practical engineering judgment within published engineering standards Evaluations include classifying site soils based on observed field conditions and soil testing for this Project. After deriving conservative relative densities, unit weights and angles of interned friction of the in-situ soils, the Terzhagi ultimate bearing capacity equation was utilized for determining foundation width and depth. Foundation parameters provided herein account for typical structural pressures due to the planned type of development. A structural analysis is beyond the scope of a geotechnical report, and a structural engineer may be required to design specific foundations and other structural elements based on the soil investigation. Stepped foundations are acceptable, if warranted for this Project. Continuous, isolated, or stepped foundations shall be horizontally level between the bottom of the foundation and the top of the bearing strata. The frost penetration depth is not expected to extend beyond 12 niches below the ground surface for this Project under normal circumstances and anticipated design features. 5.1.1 Bearing Capacity Existing in-situ soils for this Project indicates that the structure can be established on shallow, continuous or isolated footings. Foundations shall be established on relatively undisturbed native soil that is competent and unyielding. Alternatively, foundations may be constructed on selective re -compacted native soil or compacted engineered fill as described in the Earthwork Construction Recommendations Section of this report. For a bearing capacity requirement of no more than 1500 psf, a minimum continuous footing width of 12 inches (15 inches for 2 -story structures) shall be placed at a minimum of 18 inches below the existing ground surface atop unyielding soils. For a columnar load of no more than 3 tons, a circular or square isolated foundation diameter or width shall be at least 24 inches. Foundation recommendations are made available based on adherence to the remaining recommendations that are provided in this report. Alterations to the aforementioned foundation recommendations may be completed upon a site inspection by a geotechnical engineer after the foundation excavation is completed. Envirotech Engineering, PLLC PO Box 984 Belfair, Washington 98528 Ph. 360-275-9374 191. Totten Shores Drive Parcel. 22031-50-00053 Mason County. Washington July 14, 201 .5 5.1.2 Settlement Total and differential settlement that a structure will undergo depends primarily on the subsurface conditions, type of structure, amount and duration of pressure exerted by the structure, reduction of pore water pressure, and in some instances, the infiltration of free moisture. Based on the expected native soil conditions, anticipated development, and construction abides by the recommendations in this report, the assumed foundation system may undergo a maximum of 1,0 inch total settlement, and a maximum differential settlement of 0.75 inch. 5.1.3 Concrete Slabs -on -Grade Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted coarse. aranular material (Retained on U.S. Sieve 4410 or greater) that is placed over undisturbed, competent native subgrade or engineered fill per the Earthwork Recommendations Section below. The recommendations for interior concrete slabs -on -grade as presented herein are only relevant for the geotechnical application of this Project. Although beyond the scope of this report, concrete slabs should also be designed for structural integrity and environmental reliability. This includes vapor barriers or moisture control for mitigating excessive moisture in the building. 5.2 Earthwork Construction Recommendations Founding material for building foundations shall consist of undisturbed native soils to the specified foundation depths. Compacted engineered fill, or selective re -compacted native soils may be used to the extents provided in this Earthwork Construction Recommendations Section. The following recommendations include excavations, subgrade preparation, type of fill, and placement of fill for building foundations. 5.2.1 Excavation Excavation is recommended to remove any excessive organic content or other deleterious material, if present, beneath foundations and to achieve appropriate foundation depth. Additional sub excavation will be required for this Project if the soils below the required foundation depth are loose, saturated. not as described in this report, or otherwise incompetent due to inappropriate land disturbing, or excessive water trapped within foundation excavations prior to foundation construction. All soils below the bottom of the excavation shall be competent, and relatively undisturbed or properly compacted fill. If these soils are disturbed or deemed incompetent, re -compaction of these soils below the anticipated footing depth is necessary. Excavations shall be completely dewatered, compacted, and suitable before placement of additional native soil, engineered fill or structural concrete. Envirotech Engineering. PLL,C P6 Bos 984 Belfair. Washington 98528 Ph. 360-275-9374 page 15 191Totten Sbdi3 Drive: Parcel 2203 1-50-0005 3 Mason County, Washington July 14.2016 5.2.2 Placement and Compaction of Native Soils and Engineered Fill For engineered fill or disturbed native soils that will be utilized as fill material directly beneath foundations, observation and/ or geotechnical testing is required prior to foundation construction. The following placement and compaction requirements are necessary. For disturbed native soils or engineered fill beneath foundations, limits of compacted or re -compacted fill shall extend laterally from the bottom edge of the foundation at a rate of one horizontal foot for each foot of compacted or re -compacted fill depth beneath the foundation. See the illustration below. COMPACTED NATIVE SOILS OR ENGINEERED FILL FOOTING i i 1 � i UNDISTURBED SUBSRA;DE Both engineered fill and native soils used as compacted fit should be free of roots and other organics, rocks over 6 inches in size, or any other deleterious matter. Because of moisture sensitivity, importing and compacting engineered fill may be more economical than compacting disturbed native soils. Engineered fill shall include having the soils retained on the No. 4 sieve crushed (angular), and should consist of the following gradation: U.S. Standard Sieve % Finer (by weight) 6" 100 3" 60 — 100 No.4 20-60 No. 200 0 - 8 Table 1 Partical Size Distribution of Engineered Fill Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native soils and engineered fill, respectively. Each lift should be uniformly compacted to at least 95% of the modified Proctor maximum dry- densiry (ASTM D 1557) and within 3% of optimum moisture content. Each lift surface should be adequately maintained during construction in order to achieve acceptable compaction and inter -lift bonding. Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined excavations exceeding 4 feet should conform to OSHA safety regulations. Peiuianent cut and fill slopes shall be limited to a slope of 2:1. unless otherwise approved by an engineer. Envirotech Engineering. PLLC PO Box 984 Belfair, Washington 98528 Ph, 360-275-9374 page 16 Totten Shores Drive - Parcel 22031-50-00053 la on County, Washington July 14-2016 5.2.3 Retaining Wall Backfill As previously mentioned, significant retaining structures are not anticipated for this Project, However, if used, native soils may be used as retaining wall backfill for this Project. Backfill may also consist of engineered fill or borrow materials approved by a geotechnical engineer. Placement, compaction and extents of retaining wall baclditl should also be specified by a geotechnical engineer or qualified professional. 5.2.4 Wet Weather Considerations Due to the types of subsurface soils, additional provisions may be required during prolonged wet weather. Every precaution should be made in order to prevent free moisture from saturating the soils within excavations. if the bottom of excavations used for footing placement changes from a moist and dense/ hard characteristic as presented in this report to muck or soft, saturated conditions, then these soils become unsuitable for foundation bearing material. If this situation occurs, a geotechnical engineer should be notified, and these soils should be completely removed and replaced with compacted engineered fill or suitable native material as presented in this section. 5.3 Building and Footing Setbacks Provided that assumptions relating to construction occur and recomrnendations are followed as presented in this report, the factor of safety for slope stability is sufficient for a 50 feet footing setback from the face of the nearby descending slopes exceeding 4099. See the figure below and the Site Plan in Appendix A for an illustration of the setbacks. From the illustration above, structures may be located closer to the top of slope by extending the foundation deep enough to maintain the recommended setback. In addition, the required setback may be reduced by mitigation, and subsequently wound require additional geotechnical studies. 5.4 Surface and Subsurface Drainage Positive drainage should be provided in the final design for all planned residential buildings. Drainage shall include sloping the ground surface, driveways and sidewalks away from the Project structures. All constructed surface and subsurface drains should be adequately maintained during the life of the structure. If drainage problems occur during or after construction, additional engineered water mitigation will be required immediately. This may include a combination of swales, berms, drain pipes, infiltration facilities, or outlet protection in order to divert water away En, is ii cch Engiiieen .g. PLIC PO Boy. 984 Betfair, WashingLon 98528 Ph. 360-275-9374 page 17 79T'Tuuen horns D_ e Parcel '22031-50-0 0053 Mason County, Washington July 14. 2016 from the structures to an appropriate protected discharge area. Leakage of water pipes, both drainage and supply lines, shall be prevented at all times. If impervious thresholds are exceeded per Mason County code, then engineered stormwater management plans are required for this project. The drainage engineer must coordinate with a geotechnical engineer for input with relation to slope stability prior to submitting drainage plans. If stormwater management plans are not required for this project, then the following recommendations should be followed. Both footing perimeter drains and roof drains are required for this Project. Subsurface water intercepted in the footing perimeter drains, and stormwater collected from roof drains shall be separately tight -lined to the recommended outlet. Roof and foundation drains may share a tightline if an above ground drainage outlet is allowable and a backflow preventer is installed within the pipe system in order to prevent roof water from entering the foundation area, For this project, we recommend that any drainage facility is located outside of the 50 feet building setback from the top of slope. 5.5 Vegetation Buffer and Considerations For this project, we believe that a detailed clearing and grading plan is not warranted unless Mason County thresholds are exceeded, and basic vegetation management practices should be adhered to. Vegetation Buffer — Vegetation shall not be removed from the face of the critical slope or within a distance of 10 feet beyond the top of the slope. However, any tree deemed hazardous to life or property shall be removed, If tree removal is necessary, then stumps and roots shall remain in place, and the underbrush and soil shall remain undisturbed as much as possible. Any disturbed soil shall be graded and re -compacted in order to restore the terrain similar to preexisting conditions and drainage patterns. See the Site Plan in Appendix A of this report for a depiction of the vegetation buffer, 5.6 Temporary and Permanent Erosion Control Erosion control during construction should include minimizing the removal of vegetation to the least extent possible. Erosion control measures during construction may include stockpiling cleared veeetation, silt fencing. intercepting swales, berms, straw bales. plastic cover or other standard controls. Although other controls may be used, if adequate, silt fencing is presented in this report as the first choice for temporary erosion control Any erosion control should be located down-slope and beyond the limits of construction and clearing of vegetation where surface water is expected to flow. if the loss of sediments appears to be greater than expected, or erosion control measures are not functioning as needed, additional measures must be implemented immediately. See Appendix D for sketches and general notes regarding selected erosion control measures. The Site Map in Appendix A depicts the recommended locations for erosion control facilities to be installed as necessary. Permanent erosion control may also be necessary if substantial vegetation has not been established within disturbed areas upon completion of the Project. Temporary erosion control should remain in place until permanent erosion control bas been established. Permanent erosion Ehvirti t ch Eng iieeiin . PLLC PO Eo; 984 Bel lair, Washington 98528 Ph. 360-275-9374 191 Totten Shores DiPie - - Parcel 22031-50-00053 Mason County, Washington July 14, 2016 control may include promoting the growth of vegetation within the exposed areas by mulching, seeding or an equivalent measure. Selected recommendations for permanent erosion control are provided in Appendix D. Additional erosion control measures that should be performed include routine maintenance and replacement, when necessary, of permanent erosion control. vegetation, drainage structures and/or features. 5.7 Septic Drainftelds The approximate location of the septic drainfield is presented on the Site Plan in Appendix A of this report Based on the septic drainfield location with relation to the existing and proposed topography, the drainfields are not expected to adversely influence critical slopes. This is also based on compliance with all recommendations in this report. 5.8 Structural Mitigation With respect to landslide alleviation or slope improvements, structural mitigation is not necessary for this project. This determination is based on the anticipated improvements of the project, engineering conclusions, and compliance with all recommendations provided in this report. EnvitotechEn ineerina PLLC PO Box 984 Beifair, Washington 98528 Ph. 360-275-9374 191 Totten Shores Drive Parcel 22031-50-00053 Mason County. Washington July 14. 2016 6.0 CL©SU Based on the project information provided by the owner, the proposed development, and site conditions as presented in this report, it is Envirotech's opinion that additional geotechnical studies are not required to further evaluate this Project. Due to the inherent natural variations of the soil stratification and the nature of the geotechnical subsurface exploration, there is always a possibility that soil conditions encountered during construction are different than those described in this report. It is not recommended that a qualified engineer performs a site inspection during earthwork construction unless fill soils will influence the impending foundation. However, if native, undisturbed subsurface conditions found on-site are not as presented in this report, then a geotechnical engineer should be consulted. This report presents geotechnical design guidelines, and is intended only for the owner, or owners' representative. and location of project described herein. This report should not be used to dictate construction procedures or relieve the contractor of his responsibility. Any and all content of this geotechnical report is only valid in conjunction with the compliance of all recommendations provided in this report. Semantics throughout this report such as `shall,' `should' and `recommended' imply that the correlating design and/or specifications must be adhered to in order to potentially protect life and/ or property. Semantics such as 'suggested' or `optional' refer that the associated design or specification may or may not be performed, but is provided for optimal performance. The recommendations provided in this report are valid for the proposed development at the issuance date of this report. Changes to the site other than the expected development, changes to neighboring properties, changes to ordinances or regulatory codes, or broadening of accepted geotechnical standards may affect the long-term conclusions and recommendations of this report. The services described in this report were prepared under the responsible charge of Michael Staten, a professional engineer with Envirotech. Michael Staten has appropriate education and experience in the field of geotechnical engineering in order to assess landslide hazards, earthquake hazards, and general soil mechanics. Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or require additional information. Sincerely, Envirotech Engineering Robert Me earny, E.I.T. Staff Eng neer 7 Ili. Michael Staten, P.E. Geotechnical Engineer Enrotech hnnineer v;ng, PLLC' PO Box 984 Belfair. Washington 98523 Ph, 360-275-937a page 20 191 Totten Sve — — Parcel 22031-50 00053 Mason County, Washington July 14.2016 APPENDIX A SITE PLAN CCo OW Ow LIG- zx ww 00 4 I :1:::: tiw 00 , \ \ OW :Llii RP \<IWO rew'ar\ APPENDIX 13 SOIL INFORMATION / ( LJ CD \( oix \j\ G /=�0 tal §// =, Z I— • z_ / I\/ -CO WON I TO ACHIEVE CC Vrt,i0 11.42 Z MZ CX CPICT TEST PIT LOG TEST PIT NUMBER TP -1 PROJECT: Evans Geotechnical Report PROJECT NO: 1696 CLIENT: Terry Evans LOCATION: Parcel 22031-50-00053 Mason County, Washington NITIAL DEPTH OF WATER: N/A DATE OF LOG: 6/9/2016 LOGGED BY: RJM EXCAVATOR: N/A DRILL RIG: None ELEVATION: N/A FINAL DEPTH OF WATER: N/A SOIL STRATA, DEPTH SAMPLERS AND TEST DATA DESCRIPTION LL STANDARD PENETRATION TEST DEPTH CURVE 10 30 50 Gray, Dry silt with clay and trace gravel. Gravel is primarily subrounded, Low plasticity. Light brown, dense ■E■■E■ 11111 1 z E■■■0■ ■■■■E■ MEM M MMM EOMEMM MMM MMM ME MMMMM MMMEMEM M MMM MMMM EMMEM... MEM■■■' M ■■■■1■M MEEM■EMM! MMM„ ME 6■■■■■M s sMMOMMO 10 Excavation terminated at approximately�MM 5.4 feet MEMWM.MMMMM, MEM ■EEMEE M■■■■■: MMM" EMM■E'. NEEOO', MEM■° MM MMM MEMOS=' nnw MM. NM MMM MM ■■M MMMEEE MM `i., MUM= ■■■EE ■■■■■■ MEM MM No Groundwater Encountered This information pertains only to this boring and should not be interpreted as being irdicitrve of the entire site. ENVIROTECH ENGINEERING Geotechnical Engineering Map Unit Description: Cloquallum silt loam, 5 to 15 percent slopes—Mason County, Washington Mason County, Washington Cc—Cloquallum silt loam, 5 to 15 percent slopes Map Unit Setting National map unit symbol: 2hjn Mean annual precipitation: 50 to 75 inches Mean annual air temperature: 50 degrees F Frost -free period: 175 to 205 days Farmland classification: Farmland of statewide importance Map Unit Composition Cloquallum and similar soils: 100 percent Estimates are based on observations, descriptions: and transects of the mapunit. Description of Cloquallum Setting Parent material: Silty lacustrine deposits with volcanic ash Typical profile H9 - 0 to 9 inches: silt loam H2 - 9 to 32 inches: silt loam H3 - 32 to 60 inches: silty clay loam Properties and qualities Slope: 5 to 15 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately low to moderately high (0.06 to 0.20 inthr) Depth to water table: About 24 tc 36 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: High (about 11.3 inches) Interpretive groups Land capability classification (imgated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: C Other vegetative classification: Soi3s with Moderate Limitations (G002XN502WA) Data Source information Soil Survey Area: Mason County, Washington Survey Area Data: Version 11, Sep 115, 2015 L USDA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/1/2016 Page 1 of 1 L 0 0 0 z ( a �-a c 0 0 to E 0 1 0 -104- w 0 e el es The Department of Ecology does NO Fite Original and Prat Copy with DaMmtem of Ecology Second Copy —Ostriars copy Third copy—Omar's Copy WATER WELL REPORT (2) OWNER: Nene a 211 (21 LOCAT)ON OF WELL: tax, cry (2a) STREET ADDRESS OF WELL iv nearest (3) PROPOSED USE: Domestic ❑ irrigation ❑ 00 ter Start Cary So. V/0Cr7735 UN0UE WELL I.D.a A E c 3:2%'. STATE OF WASHINGTON [Mater RI phi PerrN, Pi!). A'e %50 1 I hese ill V713CCIC t 1�d, 9a thJ , 4786--60 ;a 31 T. 2o N.p z � (10) WELL LOG Or ABANDONMENT PROCEDURE DESCRIPTION Formetron: Dexr%e by o r, character, size of notarial and structure, and show throbnes of ewilirs era Ib. kind and nature of the material ;n sad) stratum penstrai8. with et least ere entry Ior Odd, charge M inlematron. Industrial 0 Tae. Well 0 Municipal 0 Other _ (4) TYPE OF WORK: q11 mora mere thnuman orbealr of we Abandoned 0 New wan Matted: Dug ❑ Deepened C Gag Racwi -coed 0 Fwtaiy ❑ ENSIGNS: Dlarnsterci wail E DtIlIed I X \ _feet, Depth of completed well Sawed 0 Drama0 Jaded❑ at Iona: Yes Q Type or perimeter used SIZE of pericas ons pe.mre6ons from perfreform from pertorations tem No ❑ Manufacturers Name Con k Type S S Gan. fi Skit size ,12 Diem. Set size in. by it 10 ft.to ft. to 3'ioreeoo: Yeo e ?AR 03109 true from ft to T Uttar/ El; ?RiLLING DNI? Gravel petlaot Yes ❑ Pb Sae W gravel Gravel placed tram ft, to ft Sanest seat: Yea.k No 0 To what dieeab? ) g MaterialuSed in seal C e.rv`t"t7xo A Did any stramwNa'in unusa$de water? Yes 0 No g Type of watery Dopth of share Method al sealing stats on (7) PUMP: Marrafaoturera Nannie Type: (8) WATER LEVELS: Lsrasudare Seems R_ above mean sea lanai Stabs mel 1 0 t n babe too of wan Date 4 T?I P, III Artesian presrnn es. per squire nun Date Artesian setme controlledby (9) WELL TESTS: drawdown is amount water Most is lowered aaaw start level Was a pump test mae?Yes ❑ No If yea, by whom? Yield: patimin. with ft. drawdown attar Work darted WELL CONSTRUCTOR CERTIFICATION: I constructed andler =opt responsibility ter construction tY this wall, and its wmp'6nee wile all Washington well construction standards. Materials used enc tea inlomtati n repartee alcove are cue 50 my beat knawle�:lt. ga and ballet <r eeH £J tor,G/ 66ua s� ;meson F1R11, e gjle 65�1 oti NAME 0. tt. aawdown atter Airiest gat intl. wilt stem eat at tt. tar Artesian Prow g -p.m. Date Temperature of water Was a chemical aratyais made? Yes No 0 ECY05e,t-201o$0V 1 'Y05 t u'9 f'1 Date 2 "F 7— ? i0 (USE ADDITIONAL SHEETS 3F NEC.ESSARY) logy is an Equal Opportunity and Affirmative Action employer, For:npo alai accommodation needs, corrtact the Water Resources Program at (266) 497-6600. The TDD number is (206) 407-6006, APPENDIX C SLOPE STABILITY STABLE Slope Stability Analysis System New User Project : Evans Detente: Static Bishop STABLE Version 9.03.00u Bishop ___LE Static UNITS (tletric/Imnerlel) GEOMETRY DEFINITION POINTS N0, X Y 1 0.000 0.000 2 50.000 0.000 3 136.000 -20.000 4 162.500 -34.000 5 213.000 -34.000 6 21.300 0.000 7 30.270 0.000 8 39.240 0.000 9 48.210 0.000 10 57.170 -1.670 11 66.140 -3.750 12 75.110 -5.840 13 54.080 -7.930 14 93.050 -10.010 15 102.020 -12.100 16 110.980 -11.190 17 119.950 -16.270 18 128.920 -18.350 19 137.890 -21.000 20 146.860 -25.740 21 155.830 -30.470 22 164.790 -34.00C 23 173.760 -34.000 24 182.730 -34.000 25 191,700 -34.000 LINES Lo X Hi X SOIL 1 2 1 2 3 3 1 5 SOILS SOIL NAME LINETYP3-PEN COHESION FRICTION 0617 WT. 1 5, 1_ 0000. °0N3 300L L?03: `:0.06 2 _ : , 0...- 1 10.000 0000. _ 0000. POSE 96155092 SF 0//1011105 STABLEe2002 64Z Associates Ltd Printed an: 05707/16 @ 09:26:37 Page: STABLE Slope Stability Analysis System New User Project : Evans Datalila : Static : Bishop SOIL P1810 20 EXCESS Y%Xi? Value Value 1: 0.000 0.000 PIEZ^OMETPJC SURFACE POINT P'311T PORE PRESSURES P01141 PRESSURE SLIP 011001105 (= 7- X) _ + SLIP -CIRCLES AUTOMATIC Circle Centre Grid Extremities 170.400 21.300 9 191.700 0.000 x spacing -- no. o'_ cols (_ax 10)= 10 Y spacing -- no. of rows (mag 20)= 20 Grid 1 Circles through point 6 Grid 2 Circles through point ` Grid 3 .s through point 8 Grid 4 Circles through point 9 Grid 5 Circles through point IC Grid 6 Circles through point 11 Grid ] Circles through point_ 12 Grid 8 Circles through point 13 Grid 9 Circles through point 14 Grid 10 Circles through point 15 Grid 11 Circlesugh pcint 26 Grid 12 Circles through point 17 Grid 13 Circles through point 18 Grid 14 Circles through point 19 Grid 15 Circles through point 20 Grid 16 Circles through point 21 -Grid _____ 1] 22 Grid 18 Circles through point 23 Grid 19 Circles through point 24 Grid 23 Circles through point 25 STABLE02002 141Z Associates Ltd Printed on: 05/07116 @ 09:26:37 Page: 2 _60 F raja_,.. Data TA 1.., Dyra_;m. _. Pro7.j e c. 13 3 a 3 s atai.11e Statjc; 7,, no l.vsis 0 S. P. 0 p 60 APPENDIX D EROSION CONTROL EOTEXTILE FABRIC WRAP AROUND TRENCH TO AT LEAST ENTIRE BOTTOM OF TRENCH BEFORE PLACING GRAVEL 12' DEEP, 8' WIDE TRENCH FILLED WITH 3/4' TO 1 1/2' WASHED GRAVEL or VEGETAT DIRECTION DF WATER FLOW NERAL NOTES 2'x2'x5' WOOD POST OR EQUIVALENT OR BETTER EXISTING GROUND SURFACE Sit T FENNY - CROSS SI'CT 14 T,S, 2'x2' WOOD POST (TYP) OR EQUIVALENT OR BETTER 6 FT MAX. OCT EXISTING GROUND SURFACE GEGTEXTILE FABRIC AND WIRE MESH 6 FT —4-I 12' DEEP, 8' WIDE TRENCH FILLED WITH 3/4' TO 1 1/2' WASHED GRAVEL OR VEGETATION BOTTOM EXTENTS OF GEDTEXTILE FABRIC SILT FENCE - DETAD NTS, SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. . ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE NSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN LA,ERUNTILRTS EROSION CONTROL BEEN PERMANENTLY STABILIZED. OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR GRASS SEEDING LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH EPTEMBER. HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF E OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING OTHER APPROVED TREATMENT. Y SEASON (MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR. UNLESS IMMEDIATE TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL REAS CLEARED OR OTHERWISE DISTURBED MUST DE APPROPRIATELY STABILIZED HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS, REE DRAINING MATERIAL., ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED AN OF ACTION, UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, ERTIUZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE ERFORMED DURING THE FOLLOWING PERIODS: MARCH 1 TO MAY 15, AND AUGUST 15 TO CTUBER 1, SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION F THE PROJECT IS IMMINENT AND THE ENV IROMENTAL CONDITIONS ARE CONDUCIVE 0 SATISFACTORY GROWTH. IN THE EVENT THAT PERANENT STABILIZATION IS NOT OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, LASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY NO LATER THAN EPTEMBER 30. N THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE OWNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION DF ALL EROSION ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT EAST ONCE EVERY WEEK, THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINT£RUPTED DNSTRUCTIDN ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE EMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED i0 AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT RANSPORT OFF-SITE IS OBSERVED. LL CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE OVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC HEETING, EROSION BLANKETS, FREE DRAINING MATERIAL, ETC., WITHIN 5 DAYS AFTER AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED. ICT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC., WILL NOT BE VIEWED AS DEQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT EING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY 4811.1ZED 5 DAYS AFTER HAVING BEEN CLEARED, ALL CONSTRUCTION ACTIVITY ON HE SITE, EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL MMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN PPROPRIATELY PROTECTED OR STABILIZED. SILT FENCE HAY OR STRAW MATTING — 0.5 FT 2 FT 117 2.5 FT 1. STRAW SHALL BE AIR DRIED, AND FREE FROM WEED SEEDS AND COARSE MATERIAL, 2. APPLY AT APPROXIMATELY 75 TO 100 POUNDS PER 1000 SQUARE FEET OF GROUND. 3, MINIMUM THICKNESS SHALL BE 2 INCHES, 4, HAY OR STRAW IS SUBJECT TO BLOWING. KEEP MOIST OR TIED DOWN. PERMANENT EROSION CONTROL NOTES' SEEDING FOR RAW SLOPES 1. BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES, SWALES, LEVEL SPREADERS AND SEDIMENT DASINS. 2. THE SEED BED SHALL 8E FIRM WITH FAIRLY FINE SURFACE, FOLLOWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS ACCROSS DR PERPENDICULAR TO THE SLOPE 3. SEEDING RECOMMENDATIDNS, AS SHOWN BELOW, AND SHOULD BE APPLIED AT THE RATE OF 120 POUNDS PER ACRE, 4. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO FOSTER AND PROTECT THE ROOT STRUCTURE. 5. SEED BEDS PLANTED BETWEEN NOVEMBER i AND APRIL 30, ARMORING OF THE SEED BCD WILL BE NECESSARY, (e.9., R TILES, JUTE MAT, CLEAR PLASTIC COVERING), 6. FE 6. FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS' RECOMMENDATIONS, AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY ADJACENT TO WATER BODIES AND WETLANDS, USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE, NAME PROPORTIONS PURITY GERMINATION BY WEIGHT(%) (X) (Z) REDTOP (AGROS TIS ALBA) ANNUAL RYE (LOLIUM MULTIFLORUM) CHEWING FESUE (FESNCA RUBRA COMMUTATA) (JAMESTOWN, BANNER, SHADOW, KOKET) WHITE DUTCH CLOVER (TRIFOLIUM REPENS) MULCHING 10 40 40 92 90 98 90 97 80 10 96 90 1. MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000 POUNDS PER ACRE. 2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES GREATER THAN 21 (HORIZONTALNERTICAL). 3. MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. ALL AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1. GEGTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL OR THE PUGET SOUND BASIN; OR APPLICABLE COUNTY STANDARDS . GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF ACH BARRIER TO AVOID USE OF JOINTS, IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED t0GETHER ONLY AT A SUPPORT PEST WITH A MINIMUM 6 -INCH OVERLAP AND SECURELY FASTENED AT 0TH ENDS TO THE POST. STANDARD-FIETER PABk1L SHALL BE FASTENED -USING' STAFLES-oR'rIE WIRE (HOG RINGS) 2 4 1N PACING, 4. POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS IN THIS SHEET, AND RIVEN SECURELY INTO THE GROUND, WIRE MESH SHALL BE 2'X2'X14 GAUGE OR EQUIVILENT. THE WIRE MESH MAY BE ELIMINATED IF XTRA-STRENGTH FILTER FABRIC (MONOFILAMENT), AND CLOSER POST SPACING IS USED, A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE OS TS AND UPSLOPE FROM THE SILT FENCE. SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT. PROJECT/ OWNER/ LOCATION: SINGLE FAMILY RESIDENCE GEOTECHNICAL REPORT EVANS 191 TOTTEN SHORES DRIVE PARCEL 22031-50-00053 -MASON COUNTY; ;WASHINGTON ENGINEER' ENVIROTECH ENGINEERING PO BOX 994 BELFAIR, WASHINGTON 98528 360-275-9374 EROSION CONTROL