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Home My WebLink AboutGEO2018-00064 SFR - BLD Engineering / Geo-tech Reports - 10/11/2018 RECEIVED OCT 1 1. 2018 615 W. Alder Street Geotechnical Report for Campbell Single Family Residence 21261 E State Route 3, Belfair Parcel No. 12206-44-02010 Mason County, Washington October 5, 2018 Project#18174 Prepared For: Kevin Campbell 310 E Lakeland Drive Allyn, Washington 98524 Prepared By: i Envirotech Engineering, PLLC �� ,�43 Zr PO Box 984 SSr ' 10/5/18 Belfair, Washington 98528 Phone: 360-275-9374 r r � 0 MASON COUNTY COMMUNITY SERVICES Geotechnical Report Building,Planning,Environmental Health,Community Health 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 is found not applicable, the report should explain the basis for the conclusion. Note: Unless specifically documented, this report does not provide compliance to the International Residential Code Sections R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section 1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes. Applicant/Owner Kevin Campbell Parcel# 12206-44-02010 Site Address 21261 E State Route 3 Belfair (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) 7 (c) A discussion of ground water conditions, Located on page(s) 8 (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 vicinity, as available in the referenced maps and records. Located on page(s) 12 (2) A site plan which identifies the important development and geologic features. Located on Map(s) Site Plan—Appendix A (3) Locations and logs of exploratory holes or probes. Located on Map(s) Site Plan and Soil Lops (Appendix B) (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 (Appendix B) (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 coefficients should be a value of 0.15. Located on page(s) 10 (7) (a) Appropriate restrictions on placement of drainage features, Rev. February 2018 1 f � 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) 14 and 16 (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) 17 (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes. 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) 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 slope from erosion, landslides and harmful construction methods. Located on page(s) 11 (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 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 5, 2018, and entitled Campbell �`�� CLY sr Single Family Residence, meets all the requirements of �`��°t WAS '% the Mason County Resource Ordinance, Geologically Hazardous Areas Section, is complete and true, that the assessment demonstrates conclusively that the risks 4304s ` posed by the landslide hazard can be mitigated through �6STFR� �:. SsION ►.V; 10�5�18 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. Page 2 of 2 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. 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 21 ToPoGRAP1IY........................................................................................................................................................3 2.2.1 Upslope Geonlorphology..............................................................................................................................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 STABILITY..................................................................................................................................................8 41.1 Slope Stability Analysis..........................................................-....................................................................9 4.2 EROSION..............................................................................................................................................................10 4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION.................................................................................................10 4.3.1 Liquefaction................................................................................................................................................10 4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS............................................................................11 4.5 LATERAL EARTH PRESSURES..............................................................................................................................11 4.6 ON-SITE AND OFF-SITE IMPACTS........................................................................................................................11 5.0 ENGINEERING RECOMMENDATIONS..........................................................................................................12 5.1 BUILDING FOUNDATION RECOMMENDATIONS....................................................................................................12 5.1.1 Bearing Capacity........................................................................................................................................12 5.1.2 Settlement...................................................................................................................................................13 5.1.3 Concrete Slabs-on-Grade...........................................................................................................................13 5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS...........................................................................................13 5.2.1 Excavation..................................................................................................................................................13 5.22 Placement and Compaction of Native Soils and Engineered Fill.............................................................13 5.2.3 Retaining Wall Backfill..............................................................................................................................14 5.2.4 Wet Weather Considerations......................................................................................................................15 5.2.5 Building Pads.............................................................................................................................................15 5.3 BUILDING AND FOOTING SETBACKS....................................................................................................................15 5.4 SURFACE AND SUBSURFACE DRAINAGE...............................................................................................................15 5.5 VEGETATION BUFFER AND CONSIDERATIONS.....................................................................................................16 5.6 TEMPORARY AND PERMANENT EROSION CONTROL...........................................................................................16 5.7 SEPTIC DRAINFIELDS...........................................................................................................................................17 51.8 STRUCTURAL MITIGATION..................................................................................................................................17 6.0 CLOSURE...............................................................................................................................................................18 Appendix A-Site Plan Appendix B-Soil Information Appendix C-Slope Stability Appendix D—Erosion Control Appendix E—Drainage Details 1.0 INTRODUCTION Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned single family residence located at 21261 E State Route 3, identified as parcel number 12206-44- 02010, 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 August 28, 2018.It was determined that slopes in excess of 40%with a vertical relief of at least 10 feet were present within 300 feet of the planned development. Based on this site characteristic, the proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason County Resource Ordinance (MCRO) 17.01.100. During the site visit by Envirotech, surface and subsurface conditions were assessed. After completion of the field work and applicable project research, Envirotech prepared this geotechnical report which, at a minimum, conforms to the applicable MCRO. As presented herein,this report includes information pertaining to the project in this Introduction Section; observations of the property and surrounding terrain in the Surface Conditions Section; field methods and soil descriptions in the Subsurface Investigation Section; supporting documentation with relation to slope stability, erosion, seismic considerations, and lateral earth pressures in the Engineering Analyses and Conclusions Section; and, recommendations for foundation, settlement, earthwork construction, retaining walls, erosion control, drainage, and vegetation in the Engineering Recommendations Section. 1.1 Project Information Information pertaining to the planned development of the project was provided by the proponent of the property. The planned development consists of a 1- or 2-story single family residence, detached garage/shop, 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 Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 1 Parcel 1220644-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 1 I � references concerning slope stability, and review water well reports from existing wells near the project; • Collect bulk samples,as applicable,at various depths and locations; • Perform soils testing to determine selected index and/or engineering properties of the site soils; • Complete an engineering analysis supported by the planned site alterations, and the surface and subsurface conditions that were identified by the field investigation, soil testing,and applicable project research;and, • Establish conclusions based on findings, and make recommendations for foundations, drainage, slope stability,erosion control, earthwork construction requirements, and other considerations. r. � a s 0 Greek fdL:nr S. �' Project s ,F Lake F Vicinity Map from Mason County Website Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 2 Parcel 1220644-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 1 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the project was gathered on August 28, 2018 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, 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% appear to be within 300 feet of the planned development. The maximum critical slope is approximately 44% with a vertical relief of about 35 feet. Ascending grades are generally located to the east of the planned development. These slopes are relatively minor within 300 feet of the project,with no apparent slope grades of at least 15%. 2.2.1 Upslope Geomorphology The upland area of the property and beyond is generally situated on a hillside of glacial origin. 2.3 Surface Drainage Runoff originating upslope of the development is mostly diverted away from the property by accommodating topography. The ravine running through the property had typical erosion. However, 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,PLLC 21261 E State Route 3 PO Box 984 page 3 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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. Shallow sloughing was observed within the stream convergence. Indications of deep-seated slope problems were not observed during the site visit. r_ s 3 t i Aerial Photo from Google Website Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 4 Parcel 1220644-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 3.0 SUBSURFACE INVESTIGATION Information on subsurface conditions pertaining to the project was primarily gathered on August 28,2018 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 4 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 48 inches, and very dense soils from 48 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, 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. The "Geologic Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap and Pierce Counties, Washington" by Michael Polenz, Katelin Alldritt, Nicholas J. Hehemann, Isablle Y. Sarikhan, and Robert L.Logan,July 2009,provides the following caption(s)for the project area: Undifferentiated sediment older than V ashon tilt--Gravel,sand. fines. and diamicton older than Vashon till:compact:may include any pre-Lashon unit and units Qga and Qgas where those could not be differentiated from pre Vashon outwash_A map boundary mismatch with the Vaughn quadrangle to the south resulted where Logan and Walsh (2007)included narrow exposures of pre-lashon deposits along steep valley walls with V ashon till(unit Qgt). Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 5 Parcel 1220644-02010 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 October 5,2018 Vahon recessional outwash—Gravel and sand: locally includes silt or clay:tan to gray:rounding and sorting diverse, but most cornuuoniy subrounded and moderately sorted:stratified and loose;ranges from a fete feet to a few tens of feet duck but may locally exceed 100 ft along Mission Creek:deposited by Vashon meltwater in outwash channels or isolated bas-ms.generally less compact than advance outwash(unit Qga)_but in some exposures difficult to distinguish from unit Qga where not separated by till.stratigraphically overlies till.Most deposits of this unlit are ice-proximal and difficult to separate froin unit Qgic.locally resulting in gradational boundaries and poor distinction between units Qgic and Qgo (and subunits),This difficulty is illustrated, for instance.by a'leaping'" outwash channel(Fig.2)_Locally divided iuo: Landslide deposits—Gravel.sand.silt.clay.and boulders in slide bodv and toe,due to Wrap scale.includes exposure of underlying touts in scarp areas: angular to rounded clasts and grains:wnsorted: generally loose. jumbled,and unstratifned.but may locally retain prinary bedding: conuuonnty includes liquefaction features.Absence of a nipped slide does not imply absence of shding or hrazard as some slides are too small to show at map scale-Although the large Aiderwood landslide southwest of Belfair may have been triggered by seismicity about 1.1 ka(see Structure), review of aerial photographs also suggests historic movement for this slide.The unit post-dates t ashon ice and is predominantly Holocene but locally tuay include some late Pleistocene deposits. IFF Qpu Project QP u o �Y 1 Oaf Qgt ! , Qp l (/�1 �Rg' is 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 Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 6 Parcel 12206-44-02010 Belfair, Washington 98528 Mason County, Washington Ph. 360-275-9374 October 5.2018 locations. Soils for this project were primarily described utilizing the Unified Soil Classification System(USCS)and the Natural Resource Conservation Service(MRCS)descriptions. The project is currently composed of native soils without indications of fill. Within test pit locations, soils within the upper 4 feet of natural ground were generally observed to be moist, brown silty sand with gravel(SM). Soils below the upper 4 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 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 Alderwood Gravelly Sandy Loam,Ab, with 8% - 15%slopes Alderwood Gravelly Sandy Loam, A,,,with 15% - 30% slopes, and Everett Very Gravelly Sandy Loam, Eh, with 8% - 15% slopes The soil designations are depicted in the aerial photograph below, and descriptions are provided in Appendix B of this report. Soil Survey From USDA Natural Resources Conservation Service 3.3.1 Groundwater From 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. Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 7 Parcel 1220644-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 4.0 ENGINEERING ANALYSES AND CONCLUSIONS The following section includes slope stability, erosion, seismic considerations, and impacts to both on-site and oil 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 Resource Map from the Washington State Department of Natural Resources (DNR), the project is not within terrain labeled `highly unstable' relating to soils. DNR did not label 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: t � n M Project d 1V1 #F y y Ill P Resource Map from Washington State Department of Natural Resources Website Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 8 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 October 5,2018 SOILS-On Resource Maa on}y Hydric Sois Highly Unstable Highly-Erodible F 1ehiv Unstable& Highly Erodible No Data or Gravel Pits SLOPE—On Resource]lap only Meditun 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 used in the analysis, and are based on observed conditions, known geology, and/or published parameters: Upper 5 feet soil depth Soil unit weight: 132 pcf Angle of internal friction: 30 degrees Cohesion: 0 psf Soils below 5 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 1.8 and 1.4, respectively. See the slope stability information in Appendix C for a depiction of input parameters and example of outputs. Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 9 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 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 is a known fault beneath this project. The fault is labeled a Class `B' known as the Sunset Beach Scarp, Tacoma Fault Zone. 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 very low to 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 Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 10 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 indicated 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,PLLC 21261 E State Route 3 PO Box 984 page 11 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 13 inches(17 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 21261 E State Route 3 PO Box 984 page 12 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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. 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 Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 13 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 t FILL 1 I I UNDISTURBED SUBGRA)lP 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. 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 Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 14 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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. 5.2.5 Building Pads Building pads are not expected for this project. 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 20 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-I T�- 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 from the structures to an appropriate protected discharge area. Leakage of water pipes, both drainage and supply lines,shall be prevented at all times. Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 15 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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. 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 dispersion is located at least 25 feet from the top of all slopes exceeding 40%, conforming to the Mason County Small Parcel Stormwater Plan. Recommended dispersion locations are delineated on the Site Plan in Appendix A, and drainage details are provided in Appendix E of this report. 5.5 Vegetation Buffer and Considerations For this project, we believe that a detailed clearing and grading plan is not warranted unless Mason County thresholds are exceeded, and basic vegetation management practices should be adhered to. Vegetation Buffer—Vegetation shall not be removed from the face of the critical slope or within a distance of 10 feet beyond the top of the slope. However, any tree deemed hazardous to life or property shall be removed. If tree removal is necessary, then stumps and roots shall remain in place, and the underbrush and soil shall remain undisturbed as much as possible. Any disturbed soil shall be graded and re-compacted in order to restore the terrain similar to preexisting conditions and drainage patterns. See the Site Plan in Appendix A of this report for a depiction of the vegetation buffer. 5.6 Temporary and Permanent Erosion Control Erosion control during construction should include minimizing the removal of vegetation to the least extent possible. Erosion control measures during construction may include stockpiling cleared 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 Plan 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, Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 16 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 Drainfields The approximate location of the septic drainfield is presented on the Site Plan in Appendix A of this report. Based on the septic drainfield location with relation to the existing and proposed topography, the drainfields are not expected to adversely influence critical slopes. This is also based on compliance with all recommendations in this report. 5.8 Structural Mitigation With respect to landslide alleviation or slope improvements, structural mitigation is not necessary for this project. This determination is based on the anticipated improvements of the project, engineering conclusions,and compliance with all recommendations provided in this report. Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 17 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 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 14z=:;, .&0)6, Robert McNearny,E.I.T. Michael Staten,P.E. Staff Engineer Geotechnical Engineer Envirotech Engineering,PLLC 21261 E State Route 3 PO Box 984 page 18 Parcel 12206-44-02010 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 5,2018 APPENDIX A SITE PLAN 10' VEGETATED BUFFER TOP OF SLOPE EXCEEDING 10' VEGETATED BUFFER A 40% c3 , 1 20 C❑NSTRUCTION SETBACK 20' C❑NSTRUCTI❑N SETBACK fro\ 00 so (90 SCALE: 1'=120' SILT FENCE T 56± \� 0 30 60 120 CONSTRUCTION ENVELOPE P\ (� SILT FENCE L \ �,� inICONSTRUCTION A ENVELOPE I/' I rn DISPERSION TRENCH DISPERSION 0 TRENCH CD C:� rq �. ft- 536 EXISTING DRIVEWAY STREAM (TOE NOTES; OF SLOPE) PROPOSED SEPTIC PROJECT/ OWNER/ LOCATIONS ARE1. ROSION DEPIICTED, AN CONTROL D ALTERNA MAY BE IVESRMAYED FBE UTILI EOR THIS IDEAS EXEPLAI RAL EDCINIOTHE DRAINFIELD AREA NS SINGLE FAMILY RESIDENCE GEOTECHNICAL REPORT. GEOTECHNICAL REPORT 2. CONTOURS WERE NOT PREPARED BY A LICENSED LAND SURVEYOR. CAMPBELL CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND 21261 E STATE ROUTE 3 INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 12206-44-02010 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 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 EXISTING CONTOUR FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING TP TEST PIT SITE PLAN PROPERTIES. APPENDIX B SOIL INFORMATION VERTICAL AND HORIZONTAL SCALE. SILTY SAND W/ GRAVEL (SM) PROPOSED STRUCTURES EXISTING GRADE STREAM VERY DENSE VERY DENSE GLACIAL TILL GLACIAL TILL SECTI❑N A-A PROJECT/ OWNER/ LOCATION, SINGLE FAMILY RESIDENCE GE❑TECHNICAL REPORT CAMPBELL 21261 E STATE ROUTE 3 PARCEL 12206-44-02010 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: CampBell Geotechnical Report DATE OF LOG: 8/29/18 PROJECT NO: 18174 LOGGED BY: MCS CLIENT: Kevin Campbell EXCAVATOR: N/A LOCATION: Parcel 12206-44-02010 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 ILL PI CURVE AND TEST DATA DEPTH N 10 30 50 0 _ r 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. C. - 2 4 Light brown, dense Excavation terminated at approximately 4.0 feet 5 6 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. Map Unit Description:Alderwood gravelly sandy loam, 15 to 30 percent slopes—Mason County,Washington Mason County, Washington Ac—Alderwood gravelly sandy loam, 15 to 30 percent slopes Map Unit Setting National map unit symbol: 2t627 Elevation: 0 to 1,000 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 46 to 52 degrees F Frost-free period: 160 to 240 days Farmland classification. Farmland of statewide importance Map Unit Composition Alderwood and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting 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 Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A- 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2-21 to 30 inches: very gravelly sandy loam Bg-30 to 35 inches: very gravelly sandy loam 2Cd1 -35 to 43 inches: very gravelly sandy loam 2Cd2-43 to 59 inches: very gravelly sandy loam Properties and qualities Slope: 15 to 30 percent Depth to restrictive feature: 20 to 39 inches to densic material Natural drainage class: Moderately well drained Capacity of the most limiting layer to transmit water(Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low(about 2.7 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B usDA Natural Resources Web Soil Survey 10/5/2018 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description:Alderwood gravelly sandy loam, 15 to 30 percent slopes—Mason County,Washington Forage suitability group: Limited Depth Soils(G002XS301 WA), Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XN302WA) Hydric soil rating: No Minor Components Everett Percent of map unit: 5 percent Landform: Karnes, eskers, moraines Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope Down-slope shape: Convex Across-slope shape: Convex Hydric soil rating: No Indianola Percent of map unit: 5 percent Landform: Eskers, kames, terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: No Shalcar Percent of map unit: 3 percent Landform: Depressions Landform position (three-dimensional): Dip Down-slope shape: Concave Across-slope shape: Concave Hydric soil rating: Yes Norma Percent of map unit: 2 percent Landform: Depressions, drainageways Landform position (three-dimensional): Dip Down-slope shape: Concave, linear Across-slope shape: Concave Hydric soil rating: Yes Data Source Information Soil Survey Area: Mason County, Washington Survey Area Data: Version 14, Sep 10, 2018 usDA Natural Resources Web Soil Survey 10/5/2018 Conservation Service National Cooperative Soil Survey Page 2 of 2 Map Unit Description: Everett very gravelly sandy loam,8 to 15 percent slopes--Mason County,Washington Mason County, Washington Eh—Everett very gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting National map unit symbol: 2t62b 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: Karnes, eskers, moraines Landform position (two-dimensional): Shoulder, footslope Landfonn position (three-dimensional): Crest, base 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: 8 to 15 percent Depth to restrictive feature: More than 80 inches 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: Low(about 3.2 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A USDA Natural Resources Web Soil Survey 10/5/2018 ROVE Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description:Everett very gravelly sandy loam,8 to 15 percent slopes—Mason County,Washington Forage suitability group: Droughty Soils (G002XS401 WA), Droughty Soils (G002XF403WA), Droughty Soils (G002XN402WA) Hydric soil rating: No Minor Components Alderwood Percent of map unit: 10 percent Landform: Ridges, hills Landform position (two-dimensional): Shoulder Landform position (three-dimensional): 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 (three-dimensional): Riser 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 14, Sep 10, 2018 usDA Natural Resources Web Soil Survey 10/5/2018 Conservation Service National Cooperative Soil Survey Page 2 of 2 APPENDIX C SLOPE STABILITY STABLE Slope Stability Analysis System New User Project Campell Datafile: Dynamic : Bishop STABLE Version 9.03.00u Bishop xxtxttxtxxxxxxx+txtx+t++xtxxxtx+xxxxxxxxtxtxxtxtxxx+xxxt++ TITLE Dynamic x tt tx xxxxxxxt:xrttxxtttx+xxxxxxxxxxx+xxxxxtxxxtxxtx+xxtxxt UNITS (Metric/Imperial) - I x+xxxxxt+xx+x++*txttxxxtxtxttxxxxxxxxxxttx+xtxtxxxx+xtxxtx GEOMETRY DEFINITION POINTS NO. X Y 1 0.000 0.000 2 100.000 0.000 3 180.000 -35.000 4 190.000 -35.000 5 220.000 -10.000 6 300.000 -10.000 7 0.000 -4.000 8 100.000 -4.000 9 180.000 -39.000 10 190.000 -39.000 11 220.000 -14.000 12 300.000 -14.000 13 30.000 0.000 14 42.630 0.000 15 55.260 0.000 16 67.890 0.000 17 80.530 0.000 18 93.160 0.000 19 105.790 -2.530 20 118.420 -8.060 21 131.050 -13.590 22 143.680 -19.110 23 156.320 -24.640 24 168.950 -30.160 25 181.580 -35.000 26 194.210 -31.490 27 206.840 -20.960 28 219.470 -10.440 29 232.110 -10.000 30 244.740 -10.000 31 257.370 -10.000 32 270.000 -10.000 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 MZ Associates Ltd Printed on: 04/10/18 @ 11:22:38 Page: 1 STABLE Slope Stability Analysis System New User Project Campell Datatile: Dynamic : Bishop 9 10 2 10 11 2 11 12 2 SOILS SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT. 1 SM CONTINUOUS-BLACK 0.00 30.0 132.000 2 HP CONTINUOUS-BLUE 400.00 40.0 140.000 xxxxx*+*#x«**#**x*#****«*«xx*xx*xx+****x*+*xxxxx#**+#x+*+x 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 240.000 **#**##*#*#***# # * 30.000 * * 270.000 * * 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 Grid 5 Circles through point 17 Grid 6 Circles through point 18 STABLE82002 MZ Associates Ltd Printed on: 04/10/18 @ 11:22:38 Page: 2 -- - 1 _ o0 1 . 10 1 _ 2 O 1 _ 30 1 . 40 1 . so 1 _ 6 0 1 _ 7 0 1 _ 8 0 g 1 . 90 2 . 00 �... _i337 j = P r o j e c t _ C a m p e 1 1 Data£ile Static Analysis Si.stiop .:TABLE�20U3 N2 A� ocirte� LCC 1 . O O 1 . 1 O 1 . 2 O 1 . 30 1 . 40 1 . 50 1 _ 6 O 1 . 7 O 1 . 80 1 . 90 =2 O O O 932 P r o j e c t C-Am p e l 1 DataLEA- Dynamic A n a l y s i s B i s h o p JTAPL E�30o3 M'/. Awwocl.cew Lcd APPENDIX D EROSION CONTROL GEOTEXTILE FABRICS 2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC WRAP AROUND TRENCH OR EQUIVALENT OR BETTER AND WIRE MESH TO AT LEAST ENTIRE BOTTOM OF TRENCH 2 6 FT MAX, O.C. 6 FT —� 0.5 FT BEFORE PLACING GRAVEL 2'x2'x5' WOOD POST OR 12' DEEP, 8' WIDE TRENCH EQUIVALENT OR BETTER EXISTING FILLED WITH 3/4' TO 1 1/2'11 GROUND SURFACE WASHED GRAVEL or VEGETAT�N 2 T DIRECTION OF 2.SIFT 12' DEEP, 8' WIDE WATER FLOW 11 GROUND SURFACE EXISTING TRENCH FILLED WITH 1 T 12 }1 3/4' TO 1 1/2' 2.5 FT 251FT WASHED GRAVEL OR VEGETATION y g•f_ BOTTOM EXTENTS OF GEOTEXTILE FABRIC SILT FENCE - DETAIL SILT FENCE - CR SS SECTION 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 THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED. PERMANENT EROSION CONTROL NOTES, EMPORARY EROSION CONTROL NOTES, OR 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 STALES, LEVEL SPREADERS AND SEDIMENT BASINS. ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR. GRASS SEEDING 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE, LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH FOLLOWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS ACCROSS EPTEMBER. HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF OR PERPENDICULAR TO THE SLOPE. HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING 3. SEEDING RECOMMENDATIONS, AS SHOWN BELOW, AND SHOULD BE R OTHER APPROVED TREATMENT. 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 ARMORING OF THE SEED BED WILL BE NECESSARY, (e.g., TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL GEOTEXILIZE JUTE MAT, CLEAR PLASTIC COVERING). REAS CLEARED OR ❑THERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED RECOMM6, FERTILIZERS ARE TO BE USED ACCORDING IZ SUPPLIERS' HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS, ADJACEENDATIONS, AMOUNTS SHOULD T MINIMIZED, ESPECIALLY REE 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 OCT❑BER 1 WILL BE DONE WHEN PHYSICAL COMPLETION PROPORTIONS PURITY GERMINATION F THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE NAME BY WEIGHT(%) (%) <%) ❑ SATISFACTORY GROWTH. IN THE EVENT THAT PERANENT STABILIZATION IS NOT ❑SSIBLE, 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 RUBRA COM, S ADO CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE WHITE BANNER, SHADOW, K❑KET) WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION WHITE DUTCH EPENS)CLOVE 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 REMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED POUNDS PER ACRE. ❑ 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 24 (HORIZONTALNERTICAL). TRANSPORT OFF-SITE IS OBSERVED. 3. MULCHING SHOULD 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 ❑THERWISE 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 (EQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT EING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY IABILIZED 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/ LOCATION4 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 GEOTECHNICAL REPORT 2. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF EACH BARRIER TO AVOID USE OF JOINTS, IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED CAMPBELL TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT 21261 E STATE ROUTE 3 BOTH ENDS TO THE POST. PARCEL 12206-44-02010 3. STANDARD FILTER FABRIC SHALL BE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) 2 4 IN MASON COUNTY, WASHINGTON SPACING. 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 PO 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 APPENDIX E DRAINAGE DETAILS 1'-0 MIN 1'-0 MIN END CAP OR PLUG CLEAN OUT WYE FROM PIPE 4' OR 6' PERFORATED PIPE LAID FLAT/LEVEL FLOW TO SECOND TYPE 30 CB W/ DISPERSAL TRENCH NOTCHED SOLID COVER IF NECESSARY GRADE BARD (LOCKING) 2'X2' NOTCHES A A 18" 0,C,50, FD . _ TYPE 30 CB W/SOLID COVER p — —TYPE 1 CB CLEAN OUT WYE W/SOLID FROM PIPE COVER 4 PLAN FLOW TO OTHER N.T.S. 18' ❑C ASANECE NECESSARY NCHING S 2• 2' GRADE BOARD NOTCHES 1`0 MIN 2' 2'X12' GALVANIZE PRESSURE BOLTS 1'-0 MIN NOTES; TREATED toy MAX GRADE �_ L THIS TRENCH SHALL BE CONSTRUCTED S❑ BOARD AS TO PREVENT PINT DISCHARGE AND/OR z EROSION 4' OR 6' PERFORATED 2. TRENCHES MAY BE PLACED NO CLOSER M PIPE LAID THAN 50 FEET TO ONE ANOTHER, (100 FEET bL FLAT ALONG FL❑WLINE) LEAN (s5% 4' X 4' SUPPORT POST FINES) 3. TRENCH AND GRADE BOARD MUST BE Z FILTER lb'-j WASHED LEVEL, ALIGN TO FOLLOW CONTOURS OF SITE, FABRIC ROCK 4, SUPPORT POST SPACING AS REQUIRED BY �D SECTIDN A-A SOIL C❑NDITIONS TO ENSURE GRADE BOARD N.T,S, REMAINS LEVEL, PROJECT/ OWNER/ LOCATION, SINGLE FAMILY RESIDENCE GE❑TECHNICAL REPORT CAMPBELL 21261 E STATE ROUTE 3 PARCEL 12206-44-02010 MASON COUNTY, WASHINGTON ENGINEER, ENVIROTECH ENGINEERING PO BOX 984 BELFAIR, WASHINGTON 98528 360-275-9374 DRAINAGE GEO 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: hen Permit#: 1QIA1,01$" 0D04 0 'A1 Parcel#: I ?,n(o,q+ OLOID Date(s)of the Document(s)reviewed: D CT hi 1. (a) A discussion of general geologic conditions in the vicinity of the proposed development, OK?�`� Comment: (b) A discusson of specific soil type OK? I� Comment: (c) A discussion of ground wateTend' 'ons OK? Comment: 5( (d) A discussion of the upslope geomorphology OK?_X Comment: (e) A discussio of the location of upland waterbodies and wetlands OK?Xi Comment: (f) A discussion of history of landslide ktivity in the vicinity, as available in the referenced maps and records OK? X_Comment: 2. A site plan that identifies the im.porta t development and geologic features. OK? 4 Comment: 3. Locations and logs of exploratory holes or probes. OK? X Comment: 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. OK? /\ Comment: 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. OK? Comment: 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. OK? Comment: 1 7. (a) Appropriate restrictions on placement of drainage features OK? _Comment: r� (b) Appropriate r strictions on placemN f septic drain fields OK?I Comment:(c) Appropriate restrictions on placement of compacted fills and footings. OK? _Comment:��I Page 1 of 2 Form Effective June 2008 (d) Recommended buffers from th�aandslide hazard areas shoreline bluffs and the tops of other slopes. OK?�—Comment: (e) Recommended setbacks from thg landslide hazard areas shoreline bluffs and the tops of other slopes. OK? Comment: AG' — l� 8. Recommends ions 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 remov I. OK? 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 from erosion, landslides and harmful construction method OK? Comment: 10. An analysis of both on-site and off-site impacts of the proposed development. OK? Comment: 11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. OK? Comment: 12. Recommendations for the preparation of structural mitigation or details of other proposed mitigation. OK? Comment: 13. A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existin and proposed development on the site. OK? Comment: Are the Documents signed and stamped?X_ By whom? Fly License#: ��1�� License type: p� FIRST REVIEW 'Approved ❑ Need more info. If not approved, what is the next action/recommendation for further action? Reviewed by , on Time spent in review: Z 5 /1 l )k SECOND REVIEW/ UPDATE ❑ Approved ❑ Need more info. Reviewed by , on .Time spent in second review: THIRD REVIEW/UPDATE ❑ Approved ❑ Need more info. Reviewed by on .Time spent in third review: Disclaimer.- Mason County does not certify the quality of the work done in this Geotechnical Report. Page 2 of 2 Form Effective June 2008