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GEO2017-00032 for BLD2017-00534 - BLD Engineering / Geo-tech Reports - 10/18/2016
V V rJ, Le Geotechnical Report for Hawkins Garage 12780 NE North Shore Road, Belfair Parcel No. 32234-50-00038 Mason County, Washington October 18, 2016 Project#16151 Prepared For: Steven Hawkins 12781 NE North Shore Road cXXP��Fc`Y of ST,4T Belfair, Washington 98528 a Prepared By: Envirotech Engineering, PLLC -�a��'k<4 3045 PO Box 984 10/18/16 Belfair, Washington 98528 Phone: 360-275-9374 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 ZZ1Upslope 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........................................................................................................................4 3.1 FIELD METHODS,SAMPLING AND FIELD TESTING................................................................................................5 3.2 GENERAL GEOLOGIC CONDITIONS.......................................................................................................................5 3.3 SPECIFIC SUBSURFACE CONDITIONS.....................................................................................................................6 3.3.1 Gmundwater.................................................................................................................................................7 4.0 ENGINEERING ANALYSES AND CONCLUSIONS..........................................................................................8 4.1 SLOPE STABILITY..................................................................................................................................................8 4LlSlope Stability Analysis................................................................................................................................9 4.2 EROSION..............................................................................................................................................................10 4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION.................................................................................................10 4.3.1 Liquefaction................................................................................................................................................11 4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS............................................................................11 4.5 LATERAL EARTH PRESSURES..............................................................................................................................11 4.6 ON-SITE AND OFF-SITE IMPACTS........................................................................................................................12 5.0 ENGINEERING RECOMMENDATIONS........»............................................................».................................13 5.1 BUILDING FOUNDATION RECOMMENDATIONS....................................................................................................13 5.1.1 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 Exeavadon..................................................................................................................................................14 5.Z2 Placement and Compaction of Native Soils and Engineered Ftll.............................................................1 S 5.Z.3 Retaining Wall BackjUl..............................................................................................................................16 5.2.4 Wd Weather Considerations......................................................................................................................16 5.3 BUILDING AND FOOTING SETBACKS....................................................................................................................16 5.4 SURFACE AND SUBSURFACE DRAINAGE...............................................................................................................16 5.5 VEGETATION BUFFER AND CONSIDERATIONS.....................................................................................................16 5.6 TEMPORARY AND PERMANENT EROSION CONTROL...........................................................................................17 5.7 SEPTIC DRAINFIELDS...........................................................................................................................................17 5.8 STRUCTURAL MITIGATION..................................................................................................................................17 6.0 CLOSURE.................»................................................................................................».......................................18 Appendix A-Site Plan Appendix B-Soil Information Appendix C-Slope Stability Appendix D—Erosion Control 1.0 INTRODUCTION Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned garage located at 12780 NE North Shore Road, identified as parcel number 32234-50-00038, 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 September 28, 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 I- or 2-story garage, 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: • 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 Envirotech Engineering, PLLC 12780 NE North Shore Road PO Box 984 page 1 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 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. r wea�Maxae l �� �f _ 4 � Project / r c \ r* ae aa��tao •p x� � Ba ti k� I��toa �- eauon•a ao 40 VR Vicinity Map from Mason County Website Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 2 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the Project was gathered on September 28, 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 driveway. Vegetation on and near the Project consists primarily of secondary growth firs, cedars, 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 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. fCritical ascending slopes, with grades exceeding 40%appear to be within 300 feet of the planned development. The maximum critical slope is approximately 46% with a vertical relief of about 18 feet. fDescending grades are generally located to the south of the planned development.These slopes are relatively minor within 300 feet of the Project,with no apparent slope grades of at least 15%with a vertical relief of at least 10 feet. 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 is an apparent water body or wetland located upslope from the planned development. It does not appear that it would significantly influence the Project. r JY y ^ i Envirotech Engineering,PLLC 12780 NE North Shore oad PO Box 984 page 3 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 � 1 I 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. 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. .k ,fie :*v� ,,� � +► �y,'i@+6 . ...3�, ,�►� �.,�' Aerial Photo from Google Website 3.0 SUBSURFACE INVESTIGATION Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 4 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 Information on subsurface conditions pertaining to the Project was primarily gathered on September 28,2016 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 soils within test pits and/or nearby banks extending to depths of up to 8 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 loose to medium dense soils in the upper 60 inches, and very dense soils from 60 inches 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, Qe. 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. The"Geologic Map of the Skokomish Valley and Union 7.5-minute Quadrangles,Mason County, Washington" by Michael Polenz, Jessica L. Czajkowski, Gabriel Legorreta Paulin, Trevor A. Conteras, Brendon A. Miller, Maria E. Martin, Timothy J. Walsh, Robert L. Logan, Robert J. Carson, Chris N. Johnson, Rian H. Skov, Shannon A. Mahan, and Cody R. Cohan, June 2010, provides the following caption(s)for the project area: V ashon advance outwash—Pebbles,cobbles.and F"] sand:gray to tan:generally compact.but commonly cohesionless:clasts well rounded.Nell sorted.clean.very thinly to thickly bedded. �Pd Pre-Fraser northern-source drift,undisided—Till and ounvash consisting of cobble to pebbl gravel with occasional boulders and a sandy to clayey matrix. Envirotech Engineering, PLLC 12780 NE North Shore Road PO Box 984 page 5 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 .11 g1C� f• ., fit\ � ; �;. ic Project Qa€ .lJS�fi�i"S n. Points W t 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 6 feet of natural ground were generally observed to be moist, brown silty sand with gravel(SM). Soils below the upper 6 feet layer were observed to be mostly grey,low moisture,silty sand with gravel(SM),locally known as hardpan.The hardpan may extend to depths greater than 50 feet.This is based on nearby well reports,site geology,and/or 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 Very Gravelly Sandy Loam, Ek, with 15% - 30% slopes. The soil designations are depicted in the aerial photograph below, and descriptions are provided in Appendix B of this report. Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 6 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 i 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,PLLC 12780 NE North Shore Road PO Box 984 page 7 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 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 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,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: s Smk 1:244W Project g za a Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 8 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 Map from Washington State Department of Ecology Website According to the Resource Map from the Washington State Department of Natural Resources (DNR),the Project is 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: Project i Resource Map from Washington State Department of Natural Resources Website SOILS—on Resource ltan only Hydric Soils Highly Unstable Highly Erodible Highly Unstable dt HigW Frodible No Data or Gravel Pits SLOPE—on Resource\Ian onlc _Medium Slope Instability _High Slope Instability 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 soils. STABLE software has been repeatedly checked with manual calculations, and consistently proved to be a very conservative program. The following soil properties were Envirotech Engineering, PLLC 12780 NE North Shore Road PO Box 984 page 9 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 I used in the analysis, and are based on observed conditions, known geology, and/or published parameters: Upper 6 feet soil depth Soil unit weight: 130 pcf Angle of internal friction: 32 degrees Cohesion: 0 psf Soils below 6 feet in depth Soil unit weight: 140 pcf Angle of internal friction: 40 degrees Cohesion: 400 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 1.6 and 1.1, 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 USCS 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 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 Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 10 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 There are no known faults beneath this Project. The nearest Class `A' or Class `B' fault to this property is the Hood Canal Fault Zone Fault Zone, in which is approximately 4.5 miles to the west 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. 4.3.1 Liquefaction The potential for liquefaction is believed to be low to moderate 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 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 Retaining walls may be utilized for this Project. The 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. An equivalent fluid unit weight used for structural design may be estimated as the product of the backfill soil unit weight and the earth pressure coefficient for at-rest pressures. Retaining walls should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of the Envirotech Engineering, PLLC 12780 NE North Shore Road PO Box 984 page 1 I Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 following: At-Rest Active Native Soils 55 pcf 35 pcf Engineered Fill Soils 45 pcf 28 pcf See the Earthwork Construction Recommendations Section for details concerning the use of native soils,engineered fill and placement of backfill. In addition to the aforementioned lateral earth pressures, retaining walls designed as catchment walls for resisting impacts due to shallow landslides shall also consider the dynamic force of potential debris flow.Catchment walls should be designed to resist the additional dynamic force of 250 pcf.This, in part, is based on a flow depth of 3 feet,velocity of 5 fps,debris density of 3.1 pcf, and a slope gradient of 28 degrees. 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,PLLC 12780 NE North Shore Road PO Box 984 page 12 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 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 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 12780 NE North Shore Road PO Box 984 page 13 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 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,PLLC 12780 NE North Shore Road PO Box 984 page 14 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 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. FOOTING COMPACTED NATIVE SOILS OR ENGINEERED 1 FILL 1 II UNDISTURBED SUBGRADEI 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 95% 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, PLLC 12780 NE North Shore Road PO Box 984 page 15 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 5.2.3 Retaining Wall Backfill As previously mentioned, significant retaining structures are anticipated for this Project. 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 Due to potential debris flow,the building location should have a minimum setback from the local ascending slope toe equal to '/z the slope height. The toe of the ascending slope is delineated as a grade break in which the ascending slope is in excess of 40%. Envirotech recommends the garage setback to be zero with mitigation provided in this report. 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 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. For this project,we recommend that roof runoff have ordinary roof downspouts with splashblocks. 5.5 Vegetation Buffer and Considerations Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 16 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 18,2016 20162016 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 (grades over 40%). 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. 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 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 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. 5.7 Septic Daainfields 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 necessary for this project. A catchment wall should be incorporated into the upslope side of the new building foundation. The wall should extend at least 3 feet above the backfill grade. We suggest the wall extends 2 to 3 feet beyond the garage footprint. Envirotech Engineering,PLLC 12780 NE North Sho re Road PO Box 984 page 17 Parcel 32234-50-00038 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 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. Michael Staten,P.E. Staff Engineer Geotechnical Engineer Envirotech Engineering,PLLC 12780 NE North Shore Road PO Box 984 page 18 Parcel 32234-50-00038 Belfair, Washington 98528 Mason County,Washington Ph. 360-275-9374 October 18,2016 20162016 APPENDIX A SITE PLAN 40± PROPOSED SEPTIC DRAINFIELD AREA SCALES 1'=40' 0 10 20 40 PROPERTY LINE 80- - +1 +1 TOP OF SLOPE In 1n CU (j A 6' CUT BANK `r PROPOSED CACHMENT WALL SILT FENCE 40 PR❑P❑SED DRIVEWAY_ 3' DITCH PROPOSED STRUCTURE 4 ± SILT FENCE A PROPOSED CULVERT NOTES: NORTH SHORE ROAD 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. HAWKINS CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND 12780 NORTH SHORE ROAD INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 32234-50-00038 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 SLOPES, WATER FEATURES, ETC.., WITH RELATION TO THE PROPERTY PO BOX ECH LINES MUST BE VERIFIED BY THE OWNER. RECOMMENDATIONS IN THE SLOPE INDICATOR BELFAIR, WASHINGTON 98528 984 GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC., WITH BELFAI5-9374 RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC EXISTING CONTOUR FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING ljo.T P TEST PIT SITE PLAN PROPERTIES. APPENDIX B SOIL INFORMATION TEST PIT LOG TEST PIT NUMBER TP-1 PROJECT: Hawkins Geotechnical Report DATE OF LOG: 9/28/2016 PROJECT NO: 16151 LOGGED BY: RJM CLIENT: Steven Hawkins EXCAVATOR: N/A LOCATION: Parcel 32234-50-00038 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 SM Brown, moist, loose to medium dense SILTY SAND with GRAVEL. Gravel is T. primarily well-graded and subangular. Sand is mostly medium. Low plasticity. 1 2 a 3 .� -II �1 4 j _ 'II 5 _ Light brown, dense 6 Excavation terminated at approximately 6.0 feet 7 8 9 10 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. SCALE: 1'=20' 0 5 10 20 EXISTING GRADE 2�4'� SILTY SAND WITH GRAVEL (SM) EXISTING GRADE CATCHMENT WALL. SEE REPORT PROPOSED STRUCTURE EXISTING \VERY DENSE GRADE GLACIAL TILL SECTI❑N 6- PROJECT/ OWNER/ LOCATION, SINGLE FAMILY RESIDENCE GE❑TECHNICAL REPORT HAWKINS 12780 NORTH SHORE ROAD PARCEL 32234-50-00038 MASON COUNTY, WASHINGTON NOTESi ENGINEERi 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 LOGS>, AND/OR EXPERIENCE IN THE GENERAL AREA. SOIL PROFILE Map Unit Description:Everett very gravelly sandy loam,15 to 30 percent slopes--Mason County, Washington Mason County, Washington Ek—Everett very gravelly sandy loam, 15 to 30 percent slopes Map Unit Setting National map unit symbol: 2t62c Elevation: 30 to 900 feet Mean annual precipitation: 35 to 91 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Everett and similar soils: 80 percent Minor components: 20 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Everett Setting Landform: Moraines, eskers, kames Landform position (two-dimensional): Backslope Landform position(three-dimensional): Side slope Down-slope shape: Convex Across-slope shape: Convex Parent material: Sandy and gravelly glacial outwash Typical profile Oi- 0 to 1 inches: slightly decomposed plant material A - 1 to 3 inches: very gravelly sandy loam Bw-3 to 24 inches: very gravelly sandy loam C1 -24 to 35 inches: very gravelly loamy sand C2-35 to 60 inches: extremely cobbly coarse sand Properties and qualities Slope: 15 to 30 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Capacity of the most limiting layerto 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: Low(about 3.2 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (noninigated): 4e Hydrologic Soil Group: A Other vegetative classification: Droughty Soils (G002XS401 WA), Droughty Soils(G002XN402WA) USDA Natural Resources Web Soil Survey 10/18/2016 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description:Everett very gravelly sandy loam,15 to 30 percent slopes--Mason County, Washington Hydric soil rating: No Minor Components Alderwood Percent of map unit: 10 percent Landform: Ridges, hills Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope, nose slope, talf Down-slope shape: Linear, convex Across-slope shape: Convex Hydric soil rating: No Indianola Percent of map unit. 10 percent Landform: Eskers, kames, terraces Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: No Data Source Information Soil Survey Area: Mason County, Washington Survey Area Data: Version 11, Sep 15, 2015 USDA Natural Resources Web Soil Survey 10/18/2016 Conservation Service National Cooperative Soil Survey Page 2 of 2 seen card wo. W 38681 — 1Of "'r" WATER WELL REPORT UNIOUEvmLLID.4 ABV_950 second Copy—Owner's Copy STATE OF WASHINGTON Water Right panne No. L Thkd Copy-Drater's Copy Oa (1) OWNER- N. Don Corliss _Addeas N. Shore Rd. Belfair, WA. 98528 W Mason -SSE R_ 1M SW 1NSec 26 T.22N N., 3W WM. (2) LOCATION OF WELL: couna (20) STREET ADDRESS ofWELLiornesies ., N. Shore Rd. Belf air, WA 98528 (3) PROPOSED USE (S Domastie Irrduatrial C Muniapd ❑ (LWELLLOG or ABANDONMENT PROCEDURE DESCRIPTION Ll Irrigation fba by nwW,charsceer•alM of malarial and atryrturs,and show thicknses or wi eftH d DsWrrter Test Wes © an@Wm of the m&NKW in each W"Mum Penetrated.wllh at 1e661 one entry for each ion. TYPE OF WORK: owner's number of well RROM To >C O (If moro fish one) - - ISATERfAL Q Abandoned❑ Now well Method:Dug❑ Bored O Deepened Cable% Driven❑ C Reconditioned❑ Ptotery❑ Jetted D _'p�. Irdiae. and & ravel 20 35 }' (6) DIMENSIONS: Diameter at wen tea— 61 t — DrI'le°--g4---ee" Depth o+�rn0'•'�wBN 91` n L. and & ravel w some water 35 42 (6) CONSTRUCTION DETAILS: C Casino Installed: Diem.from�Q_ e.m_ $2---nrown c a aye 1 4 Welded _ Elam.born_ Lw"narallieda — -- n 71 77 t Threaded ❑ -• Dian'.tt0'n---h'm' BTid & ravel w Some water iJ psrroratlons; Yea❑ No Q _ C 1 8c gravel Type of perforator used - - slzE of perforenona— ---in.by__ 89 94 penorationsfrom b — " ose sand & ravel w water (a perforations from tt•toft.No n. !D perforations from Strome: Yes[� No❑ - = manufacturers Neme __Cook— - r ♦' iYpe Stainless wire man _�No. l � cc Dism. Slot sae —tL to _ L orovel packed: Yes❑ No® Sue of gravel } Orevel placed from fLto_ fL - To what depth? tt• - r liurteoa test: Yes® No❑ - O Material used in seal _Bentoni - — Z old airy strata contain unusable water? Yes❑ No® - fJ1 Type of water? Depth of strata_ Mathod Of sealing rrtreta oA - -- O � m PUMP: Man rays Hama Grundif os ,H.P. O 1>/19794 .t9, comps Lnd•taxteoe eWraion Wont Started_- (8) WATER LEVELS: .ate�„eea bl,rd_ -- —N 0 n.below top of was Dens- - V >�e�vN-_�Ll—_i_— WELL CONSTRUCTOR CEA'T1FiCATiON: LU Artsaian wasswe -- Ibe.W mQuars indi Date— responsibility for construction of this well. and its O Aneven water is oorrtrbW by 1 Constructed ertdlor accept - Grp a eTc} compliance with all �t a e trucOns to my best knonrladg9 and beheluction standards.Materials ueed end the information reported (2) WELL TESTS: Drawdown is amount wrier level is lowered below stalk level Was a pump lest made?Yes❑ No&] It yes.by whore? NAME EYWd: gaLlmin.with tt.drawdown alter Ins. �iriron"�i s�'r. Address 98528- — Rt CL M (Signed) / 74'< License No.7 q'1 0 Reroverlr data(tine taken as zero when pump turned of)(water level measured from wag top to water level) Water Level Time Water Leval O1 Tin* Wafer Level Time Contractor's Registr — — — — — No. %I SDI1100A Data Dec. 1994 to� (USE ADDITIONAL SHEETS IF NECESSARY) Date of test _ salter teat 1'4—gel./min.with_ 2Q— h.dr wdown att"'--1--hire. Ecology is an Equal Opportunity and Affirmative Action emPiGYer•For spe- Artest gsl.lmin.wnh sleet set at tt•for M.. del accommodation needs,contact the Water Resources Program at(206) Artesian Now g.p.m. Dale 407-6600.The TDD number is(206)407-6006. TomperaW re of water Was a chemical anatYsrs made? Yes❑ No ECY 060-1-2016931''f L APPENDIX C SLOPE STABILITY P 7'I v»QTaoccy ZW ZOOZ�3^IHYSS - CIOClS Tg S T SAT2LT-,Z ortu2uAQ _ aTz38 - Q suz�{tti�14 _ -4oaCo� c3 S 8 6 1. 0 i� i A ;1 1 I 1 00 Z O 6 T O 8 T O 1- T O 9 T 09 T 0 17 T O 8 T O Z T �Q T T 00 STABLE Slope Stability Analysis System New User Project : Hawkins Datafile: Dynamic Bishop STABLE Version 9.03.00u Bishop TITLE Dynamic UNITS (Metric/Imperial) I GEOMETRY DEFINITION POINTS NO. X Y 1 0.000 0.000 2 50.000 -10.000 3 90.000 -28.000 4 135.000 -46.000 5 135.000 -52.000 6 0.000 -6.000 7 50.000 -16.000 8 90.000 -34.000 9 18.500 -3.700 10 135.000 -54.000 it 185.000 -54.000 12 26.290 -5.260 13 34.080 -6.820 14 41.870 -8.370 15 49.660 -9.930 16 57.450 -13.350 17 65.240 -16.860 18 73.030 -20.360 19 80.820 -23.870 20 88.610 -27.370 21 96.390 -30.560 22 104.180 -33.670 23 111.970 -36.790 24 119.760 -39.910 25 127.550 -43.020 26 135.340 -54.000 27 143.130 -54.000 28 150.920 -54.000 29 158.710 -54.000 30 166.500 -54.000 LINES Lo X Hi X SOIL 1 2 1 2 3 1 3 4 1 4 5 1 6 7 2 7 8 2 8 5 2 5 10 2 10 11 2 STABLE&V02WAssociates Ltd Printed on: 18/10/16 @ 11:15:46 Page: 1 STABLE Slope Stability Analysis System New User Project Hawkins Datafile: Dynamic Bishop SOILS SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT. 1 SM CONTINUOUS-BLACK 0.00 32.0 130.000 2 HP CONTINUOUS-BLUE 400.00 40.0 140.000 PORE PRESSURE SPECIFICATION SOIL PIEZO RU EXCESS Y/N/P Value Value 1 N 0.000 0.000 2 N 0.000 0.000 PIEZOMETRIC SURFACE POINT POINT PORE PRESSURES POINT PRESSURE SLIP DIRECTION (+/- X) = + SLIP-CIRCLES AUTOMATIC Circle Centre Grid Extremities 148.000 ****fi*fi**xfixfi*fi * fi 18.500 * * 166.500 * * 0.000 X spacing -- no. of cols (max 10)- 10 Y spacing -- no. of rows (max 20)= 20 Grid 1 Circles through point 9 Grid 2 Circles through point 12 Grid 3 Circles through point 13 Grid 4 Circles through point 14 Grid 5 Circles through point 15 Grid 6 Circles through point 16 Grid 7 Circles through point 17 Grid 8 Circles through point 18 Grid 9 Circles through point 19 STABLE02002 MZAssociates Ltd Printed on: 18/10/16 @ 11:15:46 Page: 2 cl'OLl 2:-C X-- X1-,;f z D T I-- a T -F ff -c- -4 1-- cl s ILT -r rA I-- H -4 C)aN C CD-.X Ift A T El,/I T 00 - Z9 06 - T 08 OZ- ' T 0 9 T 0 9 OF7 , T 0 C O Z ' T 'OT T 00 I STABLE Slope Stability Analysis System New User Project Hawkins Datafile: Static Bishop STABLE Version 9.03.00u Bishop +x++««x++++«+xx«+++«++«x««x+x++++++++x+««+x«+x+xxxx«««+xxx TITLE Static UNITS (Metric/Imperial) I ««+«x+++xx«««««x++x«++xx«xxx+++xx++++++x+++««xx+++xxx«x+«+ GEOMETRY DEFINITION POINTS NO. X Y 1 0.000 0.000 2 50.000 -10.000 3 90.000 -28.000 4 135.000 -46.000 5 135.000 -52.000 6 0.000 -6.000 7 50.000 -16.000 8 90.000 -34.000 9 18.500 -3.700 10 135.000 -54.000 11 185.000 -54.000 12 26.290 -5.260 13 34.080 -6.820 14 41.870 -8.370 15 49.660 -9.930 16 57.450 -13.350 17 65.240 -16.860 18 73.030 -20.360 19 80.820 -23.870 20 88.610 -27.370 21 96.390 -30.560 22 104.180 -33.670 23 111.970 -36.790 24 119.760 -39.910 25 127.550 -43.020 26 135.340 -54.000 27 143.130 -54.000 28 150.920 -54.000 29 158.710 -54.000 30 166.500 -54.000 LINES Lo X Hi X SOIL 1 2 1 2 3 1 3 4 1 4 5 1 6 7 2 7 8 2 8 5 2 5 10 2 10 11 2 STABLE02002 MZAssociates Ltd Printed on: 18/10/16 @ 11:13:07 Page: 1 STABLE Slope Stability Analysis System New User Project Hawkins Datafile: Static Bishop SOILS SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT. 1 SM CONTINUOUS-BLACK 0.00 32.0 130.000 2 HP CONTINUOUS-BLUE 400.00 40.0 140.000 PORE PRESSURE SPECIFICATION SOIL PIEZO RU EXCESS Y/N/P Value Value 1 N 0.000 0.000 2 N 0.000 0.000 PIEZOMETRIC SURFACE POINT POINT PORE PRESSURES POINT PRESSURE SLIP DIRECTION (+/- X) _ + SLIP-CIRCLES AUTOMATIC Circle Centre Grid Extremities 148.000 #+##++«*#*«*+#* * * 18.500 * * 166.500 + # 0.000 X spacing -- no. of cols (max 10)= 10 Y spacing -- no. of rows (max 20)= 20 Grid 1 Circles through point 9 Grid 2 Circles through point 12 Grid 3 Circles through point 13 Grid 4 Circles through point 14 Grid 5 Circles through point 15 Grid 6 Circles through point 16 Grid 7 Circles through point 17 Grid 8 Circles through point 18 Grid 9 Circles through point 19 STABLE82002 MZAssociates Ltd Printed on: 18/10/16 @ 11:13:07 Page: 2 APPENDIX D EROSION CONTROL GEOTEXTILE FABRIC 2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC WRAP AROUND TRENCH TO AT LEAST ENTIRE OR EQUIVALENT OR BETTER AND WIRE MESH BOTTOM OF TRENCH 0.5 FT BEFORE PLACING G @ 6 FT MAX. O.C. RAVEL 2'x2'x5' WOOD POST OR Imo— 6 FT —►� 12' DEEP, 8' WIDE TRENCH EQUIVALENT OR BETTER EXISTING FILLED WITH 3/4' TO 1 1/2' GROUND SURFACE 069089 2 T WASHED GRAVEL or VEGETATION DIRECTION OF --- 11 2.5 FT 12' DEEP, 8' WIDE WATER FLOW GROUND SURFACE EXISTING 2.5 FT VEGETATION TRENCH FILLED WITH t T 12' 3/4' TO 1 1/2' 2.5 FT WASHED GRAVEL OR 8' BOTTOM EXTENTS OF GEOTEXTILE FABRIC SILT FENCE - DETAIL N.T.S. N.T.S. HAY OR STRAW MATTING ENERAL NOTES, 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 HESE 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. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE 4. HAY OR STRAW IS SUBJECT TO BLOWING. KEEP MOIST OR TIED NSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY, DOWN. 3. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN LACE UNTIL PCLOTRELREAS AVE BEEN PERMANENTLY STABILIZED. PERMANENT EROSION CONTROL NOTES, EMPORARYOR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND SEEDING FOR RAW SLOPES ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A 1. BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES, MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR, GRASS SEEDING , THES, LEVEL SPREADERS AND SEDIMENT BASINS. 2 LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE, EPTEMBER, HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF OR PERPENDICULAR CLEWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS AGGRESS HE ❑WNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING . SEEDING RECOMMENDATIONS, THE SLOPE, 3 R OTHER APPROVED TREATMENT. 3. DATIONS, AS SHOWN BELOW, AND SHOULD BE APPLIED AT THE RATE OF 120 POUNDS PER ACRE. RY SEASON (MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE 4. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE FOSTER AND PROTECT THE ROOT STRUCTURE. THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , 5. SEED BEDS PLANTED BETWEEN NE NE ER 1 AND APRIL 30, B Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR, UNLESS IMMEDIATE GEOTEARMORING OF THE SEED BED WILL BE NECESSARY, (e.g., TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL 6. FER FERTILIZERS JUTE MAT, CLEAR PLASTIC COVERING). PEAS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED 6. FERTILIZERS ARE TO BE USED ACCORDING IZ SUPPLIERS' HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS, RECOMMENDATIONS. AMOUNTS SHOULD T MINIMIZED, ESPECIALLY PEE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED ADJACENT TO WATER BODIES AND WETLANDS. LAN OF ACTION. UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE. ERFORMED DURING THE FOLLOWING PERIODS- MARCH 1 TO MAY 15, AND AUGUST 15 TO CTOBER 1, SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION PROPORTIONS PURITY GERMINATION F THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE NAME BY WEIGHT(%) (%) (7) ❑ SATISFACTORY GROWTH. IN THE EVENT THAT PERANENT STABILIZATION IS NOT OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, REDTOP (AGROSTIS ALBA) 10 92 90 LASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY No LATER THAN ANNUAL RYE (LOLIUM MULTIFLORUM) 40 98 90 EPTEMBER 30. CHEWING FESUE 40 97 80 (FESTUCAN THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT (JAMESTO N, BRUB A COM, S ADO CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE WHITE BANNER, SHADOW, KOKET) WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION WHITE DUTCH CLOVER 10 96 90 ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT <TRIFOLIUM REPENS) EAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR MULCHING HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED 1. MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000 ONSTRUCTION ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE EMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED POUNDS PER ACRE. O AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT GREATER THAN (HORIZONTALNERTICAL). TRANSPORT OFF-SITE IS OBSERVED. 3. MULCHING SHOULD LD BE USED IMMEDIATELY AFTER SEEDING OR IN AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. ALL LL CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1. 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. ILT 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 GEOTECHNICAL REPORT EACH BARRIER TO AVOID USE OF JOINTS, IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED HAWKINS TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT 12780 NORTH SHORE ROAD BOTH ENDS TO THE POST. PARCEL 32234-50-00038 3. STANDARD FILTER FABRIC SHALL BE FASTENED USING I' STAPLES OR TIE WIRES (HOG RINGS) @ 4 IN MASON COUNTY, WASHINGTON 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'X14 GAUGE OR EQUIVILENT. THE WIRE MESH MAY BE ELIMINATED IF P❑ BOX 984 XTRA-STRENGTH FILTER FABRIC (MONOFILAMENT), AND CLOSER POST SPACING IS USED. BELFAIR, WASHINGTON 98528 . A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE 360-275-9374 OSTS AND UPSLOPE FROM THE SILT FENCE, 7. SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT, EROSION CONTROL l EO ZO ►� ^ OCC�� -- c{ ZlJ 1 -7 - 00�� � PLANNING RECEIVED Mason County Department of Community Development JUN 12 2011 Submittal Checklist For a Geotechnical Report 615 W. Alder Street Instructions: This checklist must 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 Steven Hawkins Parcel# 32234-50-00038 Site Address 12781 NE North Shore Road (1) (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) 8 (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) 10 (7) (a)Appropriate restrictions on placement of drainage features Located on page(s) 16 (b) Appropriate restrictions on placement of septic drain fields Located on page(s) 18 (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) 13, 15 Page 1 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. 1 (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) 17 (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) 16 (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 vegetation removal. Located on page(s) 18 (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 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) 12 (11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. Located on page(s) 16-18 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) 18 (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 Map(s) Site Plan i, 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 October 18, 2016, and entitled Hawkins Garage 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) a �V CLYp,S 43045 NA L Y.;v Page 2 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.