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Home My WebLink AboutGEO2015-00012 BLD2014-00861, BLD2014-00903 - BLD Engineering / Geo-tech Reports - 3/20/2015 MASON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT Planning Division P O Box 279, Shelton, WA 98584 (360)427-9670 Geotechnical ReportReview Acceptance Letter March 20, 2015 PIONEER BUILDERS P O BOX 1094 PORT ORCHARD WA 98366 Case No.: GE02015-00012 Parcel No.: 122085112001 Project Description: GEO REPORT for BLD2014-00861 and BLD2014-00903 The Geotechnical Report for PIONEER BUILDERS has been received and reviewed by the Planning Department. The report was prepared by Michael Staten dated 3/6/2015. Based on the certification provided by the licensed engineer/geologist, the referenced Geotechnical Report was prepared in general accordance with the requirements in the Mason County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.5. Mason County considers the review valid until such time as scope of project, site conditions, and/or regulations change. Should the scope of work, site conditions, and/or regulations change after the original review, then an addendum from the original author of the report may be required to address these changes. The report would only be re-reviewed if a permit for development were submitted after these changes occur. Mason County does not certify the quality of the work done in this Geotechnical Report. Please contact me at (360) 427-9670, ext. 365 if you have questions. Sincerely, Allan B?rden Land Use Planner Mason County Planning Department Comments: 3/20/2015 Page 1 of 1 GE02015-00012 _ o6/2 g Geotechnical Report for Pioneer Builders, Inc. Two Single Family Residences 120 E Cardinal Court 130 E Cardinal Court Parcel Nos. 12208-51-12001 & 12208-51-12004 Allyn, Mason County, Washington March 6, 2015 Project#1523 Prepared For: Pioneer Builders, Inc. PO Box 1094 CLYD Port Orchard, Washington 98366 G,�Ptio WASH IV Prepared By: ° Envirotech Engineering Q- 31,c/'5lp � PO Box 984 °� �F430 TfQ Belfair, Washington 98528 oNALE�G` Phone: 360-275-9374 a r 1.0 INTRODUCTION Envirotech Engineering(Envirotech)has completed a geotechnical investigation for two planned single family residences located at 120 and 130 E Cardinal Court, identified as parcel numbers 12208-51-12001, and 12208-51-12004, Allyn, Mason County, Washington. See the vicinity map on the following page for a general depiction of the site location. The geotechnical investigation was conducted at the request of the proponent of the property, Pioneer Builders Inc., in support of the proposed development as detailed below. The proposed development,as provided herein,and the surrounding area that may influence the development, is identified throughout this report as the Project. An initial geotechnical evaluation of the Project was conducted by Envirotech on February 23, 2015. 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 during the geotechnical investigation. Other Project information was obtained by Envirotech. The properties are currently undeveloped. The planned development consists of 1-or 2-story single family residences,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: Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page I Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 • 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; • 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 references concerning slope stability, and review water well reports from existing wells near the Project; • Collect bulk samples 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 fmdings, and make recommendations for foundations, drainage, slope stability, erosion control, earthwork construction requirements, and other considerations. l I EERRR� I (/ E MO11001{ 1 / EERAWE III E ALTA DR.� g Project ' � E 1 0 / 3 E STATE RDUTE 3D2 �t OPR f) ESKYLARK CT EPP ][ E WARBLERCT LLDw ESWA CT E—wR�ERE�#11RE CARDINAL CT• $ Y D 1 f� Deb I i \ � �.6��.—��ROtOR�RpI) Es0Y9EM811p �,EEIEfRM0011_ � Vicinity Map from Mason County}�Website TI 11 Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 2 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 � f 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the Project was gathered on February 23, 2015 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 The property is accessed from Cardinal Court, an existing paved roadway. The Project is currently undeveloped land as previously mentioned. The access road extends near the north property line. Beyond the property, rural residential development exists. Vegetation on and near the Project consists primarily of firs, maples, 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 page. 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%, are located approximately 25 feet to the southeast of the planned development on parcel -12004. The maximum critical slope is approximately 47%with a vertical relief of approximately 20 feet. 2.2.1 Upslope Geomorphology The upland area of the property and beyond is generally situated on a 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 significantly influence the Project. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 3 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 2.4 Slope and Erosion Observations The slope grades 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. These slope instability indicators or other significant 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 surficial slope failures were not observed during the site visit. F tF F� Project Aerial Photo from Mason County Website Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 4 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 ■ f 3.0 SUBSURFACE INVESTIGATION Information on subsurface conditions pertaining to the Project was primarily gathered on February 23, 2015 by a representative with Envirotech. Specific 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 soils within test pits extending to depths of up to 3 feet below the existing 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 36 inches,and very dense soils below to the depth of terminous. 3.2 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 formed 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. According to the "Interactive Geologic Map, 1:100,000 Quadrangle," as depicted by the Department of Natural Resources, this Project consists mostly of glacial till, Qg. Glacial Till is usually described as "unsorted, unstratifred, highly compacted mixture of clay, silt, sand, gravel, and boulders deposited by glacial ice of the Puget lobe; gray; may contain interbedded stratified silt, and gravel; sand-size fraction is very angular and contains abundant polycrystalline quartz, which distinguishes this unit from alpine till;cobbles and boulders are commonly striated and(or) faceted; although unweathered almost everywhere, may contain cobbles or small boulders of deeply weathered granitic rock." Vashon lodgment till—Unsorted,unstratified mix of clay,silt,sand,gravel,and sparse boulders; t typically supported by a sandy matrix;mostly Y�com act,resembling concrete. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 5 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 Oa� 7 Ow 09t owl, G= Project 00, CIA �1171 Op s `a #�« F Ox .OR — �• 1 u. of -� .K t a 1 nx oy� Geological Map Department of Natural Resources Washington State 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 Soil Conservation Service(SCS)descriptions. The Project is currently composed of native soils without indications of borrowed fill. Within test pit locations, soils within the upper 3 feet of natural ground were observed to be moist, brown silty sand with gravel (SM) or moist, gray poorly graded sand (SP). Soils below the upper 3 feet layer were observed to be mostly grey, very dense glacial till, locally known as hardpan. The hardpan may extend to depths greater than 50 feet. This is based on nearby site geology and/or Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 6 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 ! 7 knowledge of the general area. 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. According to the "Soil Survey of Mason County," by the United States Department of Agriculture, Soil Conservation Service, the site soils are described as Everett Gravelly Sandy Loam, with 0%to 5% slopes. The soil designations are depicted in the aerial photograph below, and descriptions are provided in Appendix B of this report. 4, F . R ' . I' R • + V+.. t Soil Survey From USDA Natural Resources Conservation Service 3.3.1 Groundwater From the water well report(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. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 7 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 • f 4.0 ENGINEERING ANALYSES AND CONCLUSIONS The following sections present engineering analyses and conclusions with relation to the existing conditions and proposed improvements of the Project. This section includes slope stability, erosion, seismic considerations, lateral earth pressures, and impacts to both on-site and off-site properties. 4.1 Slope Stability Landslides are natural geologic processes, and structures 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, excessive and/or repeated surficial slope movements, if not repaired, may represent a threat to the structural integrity of the slope. If this situation does arise, the slope shall be inspected by a geotechnical 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 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. This delineation is primarily dependent upon slopes and convergence. Secondly, lithology and precipitation are modeled within this delineation. In summary, this designation is based on mapping without field observations or knowledge of the specific site geology or soils. A Resource Map from the DNR Forest Practices Application Review System is provided on the next page: Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 8 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 % 17 0 1706682 � AA Project 17066559 2 1706664 + t3 + k � � s * F i Dewreaex Lake �1 06640 170042 F +706844 ,* 'v. 4` `:_,• ' ��. a _ S Puget Sou sad Or-4 +1706620 {70M2 i ;�� + 4 Resource Map from Washington State Department of Natural Resources Website Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 9 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 f Y SOILS—On Resource Map onh H dric Soils ' .. Hiehh•L:nstable Highh•Erodible X Hwhly Unstable S Hiehly Erodible No Data or Gravel Pits SLOPE—On Resource Nialoah- Mcdium Slope Instability' High Slope Instabilit•: 4.1.1 Slope Stability Analysis Based on site geology, a non-circular slope stability analysis should be performed. However, the Simplified Bishop Method (circular analysis), as presented herein, was utilized. Although the method of circles does not fit the site conditions, Envirotech certifies that our analysis is more conservative for these project conditions than other conforming slope stability models. For this Project and level of geotechnical investigation, our conclusions or recommendations would not be changed by this variation in analysis. Where applicable,our slope stability analysis utilizes the subsurface angle of repose. 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 soils. 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 3 feet soil depth Soil unit weight: 120 pcf Angle of internal friction: 34 degrees Cohesion: 0 psf Soils below 5 feet in depth Soil unit weight: 140 pcf Angle of internal friction: 40 degrees Cohesion: 400 psf Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 10 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 L Based on the slope stability analysis, minimum factors of safety were determined to be greater than 1.5 relative to static slope failures, and greater than 1.1 with relation to seismic conditions. See the slope stability information in Appendix C for a depiction of input parameters and example of outputs. 4.2 Erosion Based on the USCS description of the Project soils, the surface soils are considered low to 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 Loam 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 (Hb), and Kitsap Silt Loam on slopes 15%or greater(Kc). 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 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. 4.3 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 Tacoma Fault Zone, in which is approximately 3 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 estimation 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. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page I I Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 4.3.1 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. 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 Engineering 120& 130 E Cardinal Court PO Box 984 page 12 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 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 internal 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 inches 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. 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 15 inches shall be placed at a minimum of 18 inches below the existing ground surface. For single story structures, foundation widths may be reduced to 12 inches. 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 Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 13 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 may be completed upon a site inspection by a geotechnical engineer after the foundation excavation is completed. 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, granular material (Retained on U.S. Sieve #10 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 120& 130 E Cardinal Court PO Box 984 page 14 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 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. F❑❑TING COMPACTED NATIVE SOILS OR ENGINEERED I FILL 1 I I—I 17 —1 1 UNDISTURBED SUBGRADE Both engineered fill and native soils used as compacted fill 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 90% of the modified Proctor maximum dry density (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. Permanent cut and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an engineer. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 15 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 March 6,2015 .. r 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 backfill 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 recommendations are followed as presented in this report, the factor of safety for slope stability is sufficient for a 15 feet footing setback from the face of the nearby descending slopes exceeding 40%. See the figure below and the Site Plan in Appendix A for an illustration of the setbacks. STRUCTURE TOP OF SLOPE SLOPE FACE _ I IT �-- SETBACK SETBACK FOOTING 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 would 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 Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 16 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 March 6,2015 •1 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 roof infiltration is located outside of the geotechnical setbacks provided in this report,conforming to the Mason County Small Parcel Stonmwater Plan. 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 is an excellent measure to minimize sutficial slope movements and erosion on slope faces and exposed surfaces. By removing trees, the root strength is decreased over time, thereby lowering the `apparent' cohesion of the soil. Transpiration is decreased, which results in additional groundwater, increased pore water pressure and less cohesion/ friction of the soil particles. Stormwater runoff also increases, and, fewer plants will create less absorption of the force from raindrops,thereby creating the potential for erosion hazards. Vegetation Buffer—Vegetation shall not be removed from the face of the critical slope. For this project the buffer can be zero feet from the top of the 40 degree 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 vegetation, 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 Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 17 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 . . y 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, if 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 has been established. Permanent erosion 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. The following Surface and Subsurface Drainage Section may have additional recommendations with relation to permanent erosion for surface drainage features. 5.7 Septic Drainfields The approximate location of the septic drainfields are presented on the Site Plan in Appendix A of this report. Based on the septic drainfield locations 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. Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 18 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 6.0 CLOSURE 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 McNearny E.I.T Staff Engineer Envirotech Engineering 120& 130 E Cardinal Court PO Box 984 page 19 Parcels 12208-51-12001 &-12004 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 6,2015 APPENDIX A SITE PLAN SCALE+ I INCH = 60 FEET 0 15 30 60 260 CARDINAL CT r - T - T I Q I PROPERTY J I LINE I ti I I I TP2 PROPOSED HOUSE A 7P1 APPROXIMATE TOP OF SLOPE 25% A PROPSED / 240 r - T - T - i HOUSE / �APPROXIMATE TOP OF SLOPE EXCEEDING 40% Z _---APPROXIMATE TOE OF I� SLOPE EXCEEDING 40% I q I I I + + / 37 r� 220 TEMPORARY ER❑SI❑N r CONTROL, IF NECESS ARY A 15FT BUILDING SETBACK FROM SLOPES EXCEED NG 40 %. SEE REPORT S❑ILS: MEDIUM DENSE SAND AND SILTY SAND WITH GRAVEL (SM/ SP) ❑VERLYING VERY DENSE GLACIAL TILL NOTES: PROJECT/ OWNER/ LOCATION: 1. EROSION CONTROL MAY BE REQUIRED FOR THIS SITE. GENERAL LOCATIONS SINGLE FAMILY RESIDENCE ARE DEPICTED, AND ALTERNATIVES MAY BE UTILIZED AS EXPLAINED IN THE GEOTECHNICAL REPORT GEOTECHNICAL REPORT. 2. CONTOURS WERE NOT PREPARED BY A LICENSED LAND SURVEYOR. PIONEER BUILDERS, INC CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND 120 & 130 E CARDINAL COURT INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCELS 12208-51-12001 & -12004 REPORT. MASON COUNTY WASHINGTON 3, BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR. LOCATIONS TEMPORARY ENGINEER: OF SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP OF SLOPES, TOE ++ +EROSION CONTROL ENVIROTECH ENGINEERING OF SLOOPES, WATER FEATURES, ETC.., WITH RELATION TO THE PROPERTY PO BOX 984 LINES MUST BE VERIFIED BY THE OWNER. RECOMMENDATIONS IN THE SLOPE INDICATOR BELFAIR, WASHINGTON 98528 GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC.. WITH 360-275-9374 RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC _-80- EXISTING CONTOUR FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING PROPERTIES. TPIe TEST PIT SITE PLAN APPENDIX B SOIL INFORMATION VERTICAL AND HORIZONTAL SCALE, I INCH = 40 FEET 0 111 20 40 PROPOSED HOUSE MEDIUM DENSE SILTY SAND (SM) EXISTING GRADE DENSE GLACIAL TILL SECTI❑N A-A PROJECT/ OWNER/ LOCATION, SINGLE FAMILY RESIDENCE GEOTECHNICAL REPORT PIONEER BUILDERS, INC PARCELS 12208-51-12001 & -12004 MASON COUNTY, WASHINGTON NOTES, ENGINEER, 1) MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENVIROTECH ENGINEERING POSITIVE DRAINAGE PO BOX 984 2) THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF BELFAIR, WASHINGTON 98528 THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. 360-275-9374 LOWER DEPTHS ARE BASED ON SITE GEOLOGY, WELL LOG(S), AND/OR EXPERIENCE IN THE GENERAL AREA, SOIL PROFILE TEST PIT LOG TEST PIT NUMBER TP-1 PROJECT: Pioneer Geotechnical Report DATE OF LOG: 2/23/2015 PROJECT NO: 1523 LOGGED BY: MCS CLIENT: Pioneer Builders, Inc. EXCAVATOR: N/A LOCATION: Parcel 12208-51-12001 & -12004 DRILL RIG: None Mason County, Washington ELEVATION: N/A INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A SOIL STRATA, STANDARD PENETRATION TEST DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE AND TEST DATA DEPTH N 10 30 50 0 . . .. . .. . ............................ SM Brown, moist, loose to medium dense SILTY SAND with GRAVEL. Gravel is primarily well-graded and subangular. 1 Sand is mostly medium. Low plasticity. 2 very dense hardpan 3 Excavation terminated at approximately 3.0 feet 4 5 6 7 8 9 110 No Groundwater Encountered ENVIROTECH ENGINEERING This information pertains only to this boring and should not be Geotechnical Engineering interpreted as being indicitive of the entire site TEST PIT LOG TEST PIT NUMBER TP-2 PROJECT: Pioneer Geotechnical Report DATE OF LOG: 2/23/2015 PROJECT NO: 1523 LOGGED BY: MCS CLIENT: Pioneer Builders, Inc. EXCAVATOR: N/A LOCATION: Parcel 12208-51-12001 & -12004 DRILL RIG: None Mason County, Washington ELEVATION: N/A INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A SOIL STRATA, STANDARD PENETRATION TEST DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE AND TEST DATA DEPTH N 10 30 50 0 .. . ... ... . ................................ . . SP Gray, moist, loose to medium dense POORLY GRADED SAND. Sand is mostly medium. No plasticity. 1 2 very dense hardpan 3 Excavation terminated at approximately 3.0 feet 4 5 6 7 8 9 110 No Groundwater Encountered ENVIROTECH ENGINEERING This information pertains only to this boring and should not be Geotechnical Engineering interpreted as being indicative of the entire site. Custom Soil Resource Report Mason County, Washington Eg—Everett gravelly sandy loam, 0 to 5 percent slopes Map Unit Setting National map unit symbol: 2hk9 Elevation: 50 to 500 feet Mean annual precipitation: 55 to 90 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period. 160 to 180 days Farmland classification: Prime farmland if irrigated Map Unit Composition Everett and similar soils: 100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Everett Setting Landform: Terraces Parent material: Glacial outwash Typical profile H1 - 0 to 10 inches: gravelly ashy sandy loam H2- 10 to 24 inches: extremely gravelly sand H3-24 to 60 inches: very gravelly sand Properties and qualities Slope: 0 to 5 percent Depth to restrictive feature: 20 to 40 inches to strongly contrasting textural stratification Natural drainage class: Somewhat excessively drained Capacity of the most limiting layer to transmit water(Ksat): High (1.98 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low (about 1.5 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Other vegetative classification: Droughty Soils (G002XN402WA) Ek—Everett gravelly sandy loam, 15 to 30 percent slopes Map Unit Setting National map unit symbol: 2hkc Elevation: 50 to 500 feet Mean annual precipitation: 55 to 90 inches Mean annual air temperature: 48 to 50 degrees F 12 APPENDIX C SLOPE STABILITY STABLE Slope Stability Analysis System New User Project Pioneer Builders 2 Datatile: DYNAMIC Bishop STABLE Version 9.03.00u Bishop TITLE DYNAMIC +xxxxx++xx+xxxxxxxxxxxxxxxxxxxxxxxx+xxx+x++xxxxx+xx+xx+xxx UNITS (Metric/Imperial) = M x+xxx+,r+tr+xxxxx+++xxxx*++x+++xx+xx+x+x+xx+++xx+xx++xxxxx+ GEOMETRY DEFINITION POINTS NO. X Y 1 0.000 0.000 2 46.000 0.000 3 71.000 -6.000 4 94.000 -17.000 5 154.000 -26.000 6 174.000 -26.000 7 0.000 -3.000 8 46.000 -3.000 9 71.000 -9.000 10 94.000 -20.000 11 154.000 -29.000 12 174.000 -29.000 13 17.400 0.000 14 24.730 0.000 15 32.050 0.000 16 39.380 0.000 17 46.710 -0.170 18 54.030 -1.930 19 61.360 -3.690 20 68.680 -5.440 21 76.010 -8.400 22 83.340 -11.900 23 90.660 -15.400 24 97.990 -17.600 25 105.320 -18.700 26 112.640 -19.800 27 119.970 -20.900 28 127.290 -21.990 29 134.620 -23.090 30 141.950 -24.190 31 149.270 -25.290 32 156.600 -26.000 LINES Lo X Hi X SOIL 1 2 1 2 3 1 3 4 1 4 5 1 5 6 1 7 8 2 8 9 2 STABLE02002 MZAssociates Ltd Printed on: 06/03/15 @ 13:44:29 Page: 1 STABLE Slope Stability Analysis System New User Project Pioneer Builders 2 Datafile: DYNAMIC Bishop 9 10 2 10 11 2 11 12 2 xx+xxx+x+xxx+xxx+x+xx++++xxxxxxxxxx++x+x+*+++xx+++xxxx++++ SOILS SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT. 1 Sand CONTINUOUS-BLACK 0.00 34.0 120.000 2 TILL CONTINUOUS-BLUE 400.00 40.0 140.000 3 Building CONTINUOUS-BROWN 0.00 0.0 1000.000 PORE PRESSURE SPECIFICATION SOIL PIEZO RU EXCESS Y/N/P Value Value 1 N 0.000 0.000 2 N 0.000 0.000 3 N 0.000 0.000 PIEZOMETRIC SURFACE POINT POINT PORE PRESSURES POINT PRESSURE x+xx++xxx++x+++++x+xxxxxxxx++xxxxxxxxxxxx+xx++++++++xx++x+ SLIP DIRECTION (+/- X) = + +++++xx++x++++xxxx+x+xxxxxxx++x+++x++x+xxx+xx+x+++x+xxxx+x SLIP-CIRCLES AUTOMATIC Circle Centre Grid Extremities 139.200 x x 17.400 * * 156.600 + x x xxxx+x+x+x++x+ 0.000 X spacing -- no. of cols (max 10)= 10 Y spacing -- no. of rows (max 20)= 20 Grid 1 Circles through point 13 Grid 2 Circles through point 14 Grid 3 Circles through point 15 Grid 4 Circles through point 16 STABLE02002 MZAssociates Ltd Printed on: 06/03/15 @ 13:44:29 Page: 2 • i 1 . 00 1 . 10 1 . 2 O 1 . 30 1 . 40 1 . 50 1 . 60 1 . 70 1 . 8 O 1 . 90 2 . 00 1 09 P r o e c t P i o n e e r B u i 1 d a r s 2 D -itafile static Analysis Bishop S9 ASJ,W^-2002 MZ A.... e.s Ltd 100 1 10 1 . 2 O 1. _ 3 O 1 . 40 1 . 50 1 . 60 1 70 1 80 1 . 90 2 . 00 1 _ 81 P r o e c t P i o n e e r B u i l d e r s 2 D a t a f i 1 e D Y N AM 2 C Analysis Bishop STABLE-2002 MZ A....L.to■ Ltd r .. APPENDIX D EROSION CONTROL GE❑TEXTILE FABRIC GEOTEXTILE FABRIC r WRAP AROUND TRENCH 2'x2' WOOD POST BETYP) AND WIRE MESH TO AT LEAST ENTIRE OR EQUIVALENT DR BETTER BOTTOM OF TRENCH E 6 FT MAX. D.C. 0.5 F7 BEFORE PLACING GRAVEL Imo— 6 FT —� 2'x2'x5' WOOD POST OR \\\ 12' DEEP, 8' WIDE TRENCH f EQUIVALENT OR BETTER EXISTING FILLED WITH 3/4' TO 1 1/2'11 GROUND SURFACE WASHED GRAVEL or VEGETAT�N 2 2 T DIRECTION OF �� .S�FT 12' DEEP, 8' WIDE WATER FLOW EXISTING GROUND SURFACE TRENCH FILLED WITH 1 T 12' 3/4' TO 1 1/2' 2.5 FT 2.5 FT WASHED GRAVEL OR VEGETATION g• 1 BOTTOM EXTENTS OF 1 GEOTEXTILE FABRIC SILT FENCE - DETAIL SILT FENCE - CROSS SECTION N.T.S. N.T.S. HAY OR STRAW MATTING ENERAL NOTESi 1, STRAW SHALL BE AIR DRIED, AND FREE FROM WEED SEEDS AND COARSE MATERIAL, SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON 2, APPLY AT APPROXIMATELY 75 TO 100 POUNDS PER 1000 SQUARE THESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR FEET OF GROUND. HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. 3. MINIMUM THICKNESS SHALL BE 2 INCHES. 2. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE 4. HAY OR STRAW IS SUBJECT TO BLOWING. KEEP MOIST OR TIED INSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY. DOWN. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN LACE UNTIL THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED. PERMANENT EROSION CONTROL NOTES EMPORARY EROSION CONTROL NOTES- SEEDING FOR RAW SLOPES OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND 1. BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES, ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE SWALES, LEVEL SPREADERS AND SEDIMENT BASINS. MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE, ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR. GRASS SEEDING FOLLOWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS ACCROS LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH OR PERPENDICULAR TO THE SLOPE, EPTEMBER. HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF 3. SEEDING RECOMMENDATIONS, AS SHOWN BELOW, AND SHOULD BE HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING APPLIED AT THE RATE OF 120 POUNDS PER ACRE. R OTHER APPROVED TREATMENT. 4. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO RY SEASON (MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE FOSTER AND PROTECT THE ROOT STRUCTURE, EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO 5. SEED BEDS PLANTED BETWEEN NOVEMBER 1 AND APRIL 30, NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE ARMORING OF THE SEED BED WILL BE NECESSARY, (e.g., THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING). Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR. UNLESS IMMEDIATE 6. FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS' TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL RECOMMENDATIONS. AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY REAS CLEARED DR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ADJACENT TO WATER BODIES AND WETLANDS. HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS, REE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION LAN OF ACTION. UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE. ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE ERFORMED DURING THE FOLLOWING PERIDDS MARCH 1 TO MAY 15, AND AUGUST 15 TO PROPORTIONS PURITY GERMINATIO CTOBER 1. SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION NAME BY WEIGHT(%) (%) (7) F THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE ❑ SATISFACTORY GROWTH. IN THE EVENT THAT PERANENT STABILIZATION IS NOT REDTOP (AGROSTIS ALBA) 10 92 90 OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, ANNUAL RYE (LOLIUM MULTIFLORUM) 40 98 90 LASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY NO LATER THAN CHEWING FESUE 40 97 80 EPTEMBER 30. (FESTUCA RUBRA COMMUTATA) (JAMESTOWN, BANNER, SHADOW, KOKET) N THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT WHITE DUTCH CLOVER 10 96 90 CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE (TRIFOLIUM REPENS) WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT MULCHING EAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. 1. MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000 ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED POUNDS PER ACRE. DNSTRUCTION ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE 2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES EMDVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED GREATER THAN 2,1 (HDRIZONTAL-VERTICAL). TO AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 3. MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. ALL TRANSPORT OFF-SITE IS OBSERVED. AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1. 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. ILT 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 TABILIZED 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 PROJECT/ OWNER/ LOCATION: 1. GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE OR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS 2. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GE❑TECHNICAL REPORT EACH BARRIER TO AVOID USE OF JOINTS. IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED PIONEER BUILDERS TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT PARCELS 12208-51-12001 & -12004 BOTH ENDS TO THE POST, MASON COUNTY, WASHINGTON 3. STANDARD FILTER FABRIC SHALL BE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) 2 4 IN PACING. 4. POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET, AND ENGINEER! DRIVEN SECURELY INTO THE GROUND. ENVIROTECH ENGINEERING WIRE MESH SHALL BE 2'X2'XI4 GAUGE OR EQUIVALENT. THE WIRE MESH MAY BE ELIMINATED IF PO BOX 984 EXTRA-STRENGTH FILTER FABRIC (MONDFILAMENT), AND CLOSER POST SPACING IS USED. BELFAIR, WASHINGTON 98528 6. A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE 360-275-9374 POSTS AND UPSLOPE FROM THE SILT FENCE, 7, SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT. EROSION CONTROL � l � �St �a(z Mason Co Linty Department Co munity Development Sui)._jl," C; .eckiie.For a Geoieciinicai Report: instructions: This checkfis!must be submitted with a Geotecnnical Report and completed-sued,and stamped i y the licensed professional(s) rho prepared the Geotechnicai Report for review by Mason County pursuant Eo the basis fer the conciusion_ ApplicaritfOwner !_"fai7P2r' ur'I ,rs, Parcel# Site Address / `✓ /3 (t) (a)A discussion of general geologic conditions in the vicinity of the proposed deveioprnefi: Located on page(s) 5 (b) A discussion of specffc so:_e��- Located on page(si (c) A discussion of ground water conditions Lacwted an rage(s) 7 . (d) A discussion of the upsiope g¢cznorphology s_uc:a ed on paga(s) 3 (s) A discussion of the location:of ualand waterbodies and wetlands Located an page(s) 3 ( "k usscuss:;r.of iasiary of lands5de acif•, ty in the activity in the vicinity,as available in the referenced maps at d records z ccof--d on page(s) (2) A site plan :vt ich identifies the im o;tant oevelbpment and geologic features. Lccated on fvtap{s) S;f i lc (3) Locations and logs of exploratci ho ns or probes_ L� aiGci 011 M18ill's' S' J (4) The area of the proposed development, the boundaries of the hazard,and associated-buff=_ s and setbacks shelf be delineated(top, bath sides,and toe)on a geologic map of the site. LL'LQ�or7 Map(s) `7 A' /�l Gi 0 (d) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and v(r£iill?incorporates T.f'.e S 'lsy3f op d grade changes. Lmv U UI i IVre (Q) in p#:{3 :'„a£`':w'<'its`ofsj-'.e Sp3bSfE��i#alf� fli3�Ed>€ti'��+'e��fs•�ar!d sm:5�lic 0-2� ?r" conditions-Analysis should examine worst case- _The anasYSis shonid include the i' Yls 'i ui�i� 's Li u` f.W 4i2s_die a�.alf[iN�il staffs;safety f acor is 1-5.the minirn m seismic safety factor is 1_1_and the quasi-siaftffii ana eras sehoutd be a Q=afue of Q_ib_ Located on pace(s) /0 (f) (a)"pp opriate restrictions on placement of drainage matures Lacrated on page(s) /9 (b; Accro^riaty=es sc cps on pia aenF of septic dr alit gelds Located on page(s) i ) Appropriate resstricftons on piac ernent ofconapacted ffils and foofirms Located o;l page(s) /3 Page 13,"2 Form Effective June 2008 ?isclai.Frer: Mason County doe-s not ru the quaff ty of the work done iri ti1.1S Geot✓ t,-nV a,•I l�fJ J1 t. (d) Recommended buffers from th-e landslide hazard areas shoreline'biuffs and the tops of other siopas on the property Located on page(s) I�• (e) Re-commended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) / b (8) ilecorni—nendaborts for the preparation o;a detailed clearing and grading pian whilich SPBt;5f;;aiiy identir-res vegetatfon to be removed, a schedule for vegeiation removal and replanting, and the method of vegetation removal. Located on page(s) 17 (9) 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 siope from erosion, iandslides and hams ful construction methods. Located on page(s) An analysis of both on-sne and off site impacts or the proposed developmeni- Located on page(s) /- (F-f) Specifications of;final development conditions such as, vegetative management,drainage, erosion control, and buffer widths. Located on page(s) l� -%�✓ (12) Recorf mendations for the preparation of structural mitigation or details of other proposed mitigation. L€acated on page(s) f (l3) A srta-map drawn to s=_►.e shaming the p fppert;4qundaries,scale,-norf4 avow, and the?ocatfon and Padre of eAsting and proposed development on the sites. f S h$Te-b y c a ri 5-y-`s'isucr E.-2itasiy r 0$ p us y ihat i afn a de,ii e n g irseer iicenn-ed.i3 the J�-afvc of WQ-st h!gion W In-9)ec 1aiizea knowiedge of ycv aiiisi.�cci eoii saGai eiryii;e a: yr%� cut at£�'iS't E3s'ca'ie 6j�y�" S i�� wa.co aY`SHIS Scam of Rlepone, dated 1 4c-r (? . 2�/�.and entitled J"/�I L2Ea" �jU�IC4 rS . /h c, / f yo al the fn" rC'iex�, OF Me Masors to14araty •.ram Odd-Mam e.Laiii.dsiide _rd'SecOon,is plete and trrae,that lie assessment de;;ons es conclusively that the risks posed by the landsUde hazard can be rnMgated thn ough the ifi^.ii3tS2u "a:.[rFrin i ui.0 3 a�s�u!r�"H3ceeii=_'a�ies,�etei:r siS�6<ti3i"ts}aE $3'e Su a Manne[as TO 1 rs eV09ie"- = '��3:��'��Kati met=�e3e✓i��a-��a�-Q��f.��aim St rnial ARM;- '' .•ice Page 2 of 2 Form Effer.*ive June 2008 1�1is�;� jrYcr� Mason�County does not c= diffV the^ualfty of the woCIN-done in this er'`.seviec:. J}i�^.•^i Mason County Review Checklist For a Geotechnical Report Instructions: This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report is reviewed for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the Report should explain the basis for the conclusion. The Report is also reviewed for clarity and consistency. If the drawings, discussion, or recommendations are not understandable, they should be clarified. If they do not appear internally consistent or consistent with the application or observations on site, this needs to be corrected or explained. If resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director. Applicant's Name: G��' Permit# Parcel# Vus `51 ` l y0O Date(s) of the Document(s) reviewed:Z� l Z7t •� . (2�Y3 ` (1) (a)A disc9ssion of general geologic conditions in the vicinity of the proposed development, OK? V Comment: (b) A disc sion of specific soil types OK? LZ Comment: (c) A disc sion of ground water conditions OK?Comment: (d) A disclAssion of the upslope geomorphology OK? Comment: (e) A disc sion of the location of upland waterbodies and wetlands OK?Comment: (f) A discussion of history of landslide activity in the activity in the vicinity, as available in the referynced maps and recor s OK? V Comment: (2) A site pla which identifies th i r=4 ,1_ velopment and geologic features. OK?�Comment: - (3) Locations d logs of exploratory holes or probes. OK?Comment: (4) The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks s I be delineated (to , b sid and toe)on a geologic map of the site. OK? V Comment: tGr1 (5) A minimum of one cross section at a stale which adequately depicts the subsurface profile, and which incoWrates the details of ropo ed grade ch nges. OK? ✓ Comment: (6) A description and results of slope stabili y ana ses performed for both static and seismic loading conditions.Analysis should examine worst case failures. The analysis should include the Simplified Bi op's Method of Circles. The minimum static safety factor is 1.5, the minimum seismic s ty factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15. OK? Comment: (7) (a)Approp late restrictions on placement of drainage features OK? Comment: (b) Appropnate restrictions on placement of septic drain fields OK? ✓ Comment: (c) Appropriate restrictions on placement of compacted fills and footings OK? c/ Comment: (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Page 1 of 2 Form Effective June 2008 OK? Comment: � 7. (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other s pes on the property. OK. V Comment: f 0 (8) 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 egetation removal. OK? V Comment: (9) 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 frgrryerosion, landslides and harmful construction methods. OK? (/ Comment: (10) An analysis f both on-site and off-site impacts of the proposed development. OK? t�Comment: (11) Specifications of final development conditions such as, vegetative management, drainage, erosion con ol, and buffer widths. OK? Comment: (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. OK? V Comment: (13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and natur of existing and p o cged development on the site. OK? Comment: f Are the Documents signed and stamped? Type and#of License: �� to If not approved, what is the next action/recommendation for further action? Reviewed by on Time spent in review: SECOND REVIEW/UPDATE: Reviewed by on Time spent in second review: THIRD REVIEW/ UPDATE: Reviewed by on Time spent in third review: Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment Page 2 of 2 Form Effective June 2008 Mason County Deparfiment of Community Development jtibDiiiai v,--jeC H51 i'or a Geoiecnnical Repo insiruciicns. This checkiisf must be submitfed iMth a Geoiechr=ical Report and completed, siened, and stamped by the licensed rrofession3l(s)who prepared the Geoiechnical Report for review by Mason County pursuant to :he +. aSoi!'v:JF.i1ty z�5vui: .v:''finance_ _`a i wle?i?YaJc6nd to be not applicai3i8, Urrli;rapsori J7FtiiF1C explain the basis for the connrcii iS4on- el- Applicani/Ot,vner I iL217621e- /3ci,l � S: �hc , Parcel i Z2 '✓ 5� �1 Z0 j —j2�O .ii2 guts;cS� %2 0 130 E C ;✓�l✓1a(/ tr!/U r �'l//y{ {1) (a)A discussion of general geologic conditions in the vicinity of the proposed develop,—tent: Located on page(s) 5 (I3) ii oiSCUSSIOnr tit specalc SON Vklpes Located on page(s) J( (c) A discussion of ground grater conditions d on age{Sj F --it'e - ' 7 -Ci... F-.u.Jv (d) A discussion of the upslope peomorphology `vc:aiec i an pages i 3 ,I A discussion of Hhe location of upland waterbodiies and wetlands Located on pages) 3 Y discu55icr:01 i:is"or y of ianasiide actiivity in the activity in the vicinity,as available in the referenced maps and records !occ;cd on pagcls? (2) A site plan ufiich identifies the r ant development and geologic features. Located on rvlap(s) (3) Locations and logs of exploratory hobs or probes_ L0t;aieci of MaFrsSj (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. i-Oca=d t�r1 IYia��S1 (5) A r,Finirrium, of one cross section at a scale which adequately depicts the subsurface profile, and which incorporates the details-of roposed grade changes. :3 :ies-m n4: n and-esuf c to r i�.st fF f7) s FY..0 F2 � :F `�`Y S L'c`SF��filF;�-3ira(VseS S3P,t'�3€37�'�l�tr%�u�!ate_.:^,apd se:Srr:.� Gonditions_Analysis should examame worst casefalkires_The analysis should include the iSr:t 3 ___ U ad`�'-e Guy:eS_ ?he 3tiiF inmf n s`t3fic SaIei f`dcior is E_Yi,the rniaii}lum seismic safety,;actor is 1_1_and-the quasi-staff-c annasysis coeifjents should be a,--1Fse of 0-15- Located on nage(s) j (7) (a`Apnropriata r astrictionns on placement of drainage features LJCai?d on pages) I %fib: _ ppr0priat-- astr iciions or.plac:.rent of septic oa a!n 'eids Located on page(s) /1� l%) .'a 3i vpi icic restriC.uanS Ji3 placemeni or compacted 0s;and foofings Located on pages) /.3 IS'!'- _ Page I of 2 Form Effective June 2008 Disclaimief_ Mason County does not r_-erffu fh,, rnsa[iF�r c Q in {.,sc r .4; r r? �- pf th work don tie•. �.eetC,.,,:..;; {d) Recom;;ended buffers from the iandsUde hazard areas shoreline bluffs and the tops of other siopes on ine prope Located on pages) /R . (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the p roperiy- Located or, pages) (t5) kecon"irniendaiions for the preparation of a detailed clearing and grading pia; Vifii(:I specicc; idea if ies vegetation to be removed, a schedule for vegetation removal and repianting, and the method of vegetation removal. i_ccaied on page(s) (7 {9} 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 ii om erosion, iandslides and harm, ful construction methods. i Located on page(s) / v j An anaiysis of both on-site and off impaciS of the proposed deveioprnent. Located on page(s) /2 (i i) Spec ficaiions of final development conditions such as,vegetative management, drainage, erosion control, and buffer widths. Located an page(-,} d 1ri (12) Recommendations for the preparation of structural mitigation or details e:other proposed mitigation- Located on page(-,) ('i 3; A s=R mapdrawn scale showing the p�pperty.Ogundaries,scale,north arrow, and the!ocaiion and nature of existing and proposed development on the site. here-by cer i7f under i-ar tally Oi i3e#u y alai i am a ch-rii engineer iiCensed it the Ji3?c O:e�11avSSi3irEgiOri lrv++ sj}eGi3tl�e�34nOW eOg2 0= •T...,,...,e...:,..: = - �,... a �•.�..-e..,...a ::.. r.�_ c geotev": 'uywcvyivai�'iij ?ereii'n3 itr a yEv:tige5t cir ea'ic�rae�+"'35� cincSi ci:,rsn�eit as ut''v�ecec Eta cr7r :'f;��F' sae- �a s -:s iss ru_� C.W tc'- _' 'ems=--'e 'er.i ai-l- Report, da ed /14c-r ('. ZDI�,and entitled j Res 41C- 1 IVO 11 1 k!� Gt A4 i vt C 2 S 9s€e.�a i��i 9 �tEew ua`eiec ilr�Sriie County Onj:fne: Landslide Hazard Simon, is ca mp?eete and?rue,that the assessment demonsirtes conclusively that flha risks posed by the landsllde hazard can be mitigated through the include�ec7'air%i"er]si ai i,c^S a'e �±i=naicieiac�'<aieS,as,u itsai Qli @�a7"'aaa aialrcFe Sires`#G crtariitei 35 $c�+oSe c3 ` yea 3 w;_ �;�€�i p?fib§o.heal5ah atld aet' Q-&gi—zctFi_^e e. - r£.YDL �43045�� AL Page 2 of 2 Form Effective Jrine 2008 il�Sigri irs.cr_ fSA S.ir noun{�'J.+�S not^,?rt-^ the^u�litl a r! s -e a �----� e v f the wort,done In this �._r;'Mic mica+ _ TABLE OF CONTENTS 1.0 INTRODUCTION..................................................................................................................................1 1.1 PROJECT INFORMATION.....................................................................................................................1 1.2 PURPOSE OF INVESTIGATION 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..................................................................................................6 3.3.1 Groundwater...............................................................................................................................7 4.0 ENGINEERING ANALYSES AND CONCLUSIONS.......................................................................8 4.1 SLOPE STABILrry................................................................................................................................8 4.1.1 Slope Stability Analysis.............................................................................................................10 4.2 EROSION............................................................................................................................................11 4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION.............................................................................11 4.3.1 Liquefaction..............................................................................................................................12 4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS.......................................................12 4.5 LATERAL EARTH PRESSURES...........................................................................................................12 4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................12 5.0 ENGINEERING RECOMMENDATIONS.......................................................................................13 5.1 BUILDING FOUNDATION RECOMMENDATIONS................................................................................13 S1.1 Bearing Capacity.......................................................................................................................13 5.1.2 Settlement..................................................................................................................................14 5.1.3 Concrete Slabs-on-Grade..........................................................................................................14 5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS......................................................................14 5.2.1 Excavation.................................................................................................................................14 5.2.2 Placement and Compaction of Native Soils and Engineered Fill...........................................1 S 5.2.3 Retaining Wall Backfill............................................................................................................16 5.2.4 Wet Weather Considerations....................................................................................................16 5.3 BUILDING AND FOOTING SETBACKS.................................................................................................16 5.4 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................16 5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................17 5.6 TEMPORARY AND PERMANENT EROSION CONTROL.......................................................................17 5.7 SEPTIC DRAINFIELDS........................................................................................................................18 5.8 STRUCTURAL MITIGATION...............................................................................................................18 6.0 CLOSURE............................................................................................................................................19 Appendix A-Site Plan Appendix B-Soil Information Appendix C-Slope Stability Appendix D—Erosion Control