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Home My WebLink AboutGEO2020-00072 - BLD Engineering / Geo-tech Reports - 3/14/2020 624)lzt) REC �r Str��t Geotechnical Report McClure Single Family Residence XXX E Baker Court, Belfair Parcel No. 12207-75-00120 Mason County, Washington March 14, 2020 Project#2035 PLANNING Prepared For: South Shore Construction PO Box 963 Belfair, Washington 98528 Prepared By: Envirotech Engineering PO Box 984 Belfair, Washington 98528 Phone: 360-275-9374 cLNDe 43045 "k �FCISTER�� sS��NAL��C` 3/14/2020 MASON COUNTY Submittal Checklist COMMUNITY SERVICES Geotechnical Report iaMnp 'Iwnnnp rmmrnrwiirMm irmminnirwim 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 Kimberly McClure Parcel# 12207-75-00120 Site Address XXX E Baker Court (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 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—Appendix A (3) Locations and logs of exploratory holes or probes. Located on Map(s) Site Plan and Soil Logs(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) 9 Page 1 of 38 (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) 17 (c) Appropriate restrictions on placement of compacted fills and footings, Located on page(s) 14 (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) 15 (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) 16 (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) 11 (11) Specifications of final development conditions such as,vegetative management,drainage,erosion control,and buffer widths. Located on page(s) 16 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) 17 (13) A site map drawn to scale showing the property boundaries,scale, north arrow, and the location and nature of existing and proposed development on the site. Located on 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 cuff dr Report,dated March 14,2020,and entitled McClure Single Family Residence, meets all the requirements of the Mason County Resource Ordinance, Geologically Hazardous Areas Section, is complete and true,that the assessment 43045 Y demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical 3/14/2020 design recommendations,and that all hazards are mitigated in Disclaimer:Mason County does not such a manner as to prevent harm to property and public certify the quality of the work done in health and safety. this Geotechnical Report. Page 2 of 2 TABLE OF CONTENTS 1.0 INTRODUCTION.................................................................................................................................1 1.1 PROJECT INFORMATION.................................................................................................................... 1 1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK........................................................................ 1 2.0 SURFACE CONDITIONS....................................................................................................................3 2.1 GENERAL OBSERVATIONS..................................................................................................................3 2.2 TOPOGRAPHY.....................................................................................................................................3 2.2.1 Upslope Geomorphology............................................................................................................3 2.3 SURFACE DRAINAGE..........................................................................................................................3 2.3.1 Upslope Water Bodies................................................................................................................3 2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4 3.0 SUBSURFACE INVESTIGATION.....................................................................................................5 3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5 3.2 GENERAL GEOLOGIC CONDITIONS...................................................................................................5 3.3 SPECIFIC SUBSURFACE CONDITIONS.................................................................................................7 3.3.1 Groundwater............................................................................................................................... 7 4.0 ENGINEERING ANALYSES AND CONCLUSIONS......................................................................8 4.1 SLOPE STABILITY...............................................................................................................................8 4.1.1 Slope 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.....................................................................................................11 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 5.2.2 Placement and Compaction of Native Soils and Engineered Fill...........................................14 5.2.3 Retaining Wall Backfill.............................................................................................................15 5.2.4 Wet Weather Considerations....................................................................................................15 5.2.5 Building Pads............................................................................................................................1 S 5.3 BUILDING AND FOOTING SETBACKS.................................................................................................15 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 Appendix E—Drainage Details 1.0 INTRODUCTION Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned single family residence located at XXX E Baker Court, identified as parcel number 12207-75- 00120, 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 March 9,2020. It was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were present within 300 feet of the planned development. Based on this site characteristic, the proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason County Resource Ordinance (MCRO) 17.01.100. During the site visit by Envirotech, surface and subsurface conditions were assessed. After completion of the field work and applicable project research, Envirotech prepared this geotechnical report which, at a minimum, conforms to the applicable MCRO. As presented herein,this report includes information pertaining to the project in this Introduction Section; observations of the property and surrounding terrain in the Surface Conditions Section; field methods and soil descriptions in the Subsurface Investigation Section; supporting documentation with relation to slope stability, erosion, seismic considerations, and lateral earth pressures in the Engineering Analyses and Conclusions Section; and, recommendations for foundation, settlement, earthwork construction, retaining walls, erosion control, drainage, and vegetation in the Engineering Recommendations Section. 1.1 Project Information Information pertaining to the planned development of the project was provided by the proponent of the property.The planned development consists of a 1-or 2-story single family residence,new on-site septic system, and other ancillary features typical of this type of development. Approximate building footprint and other proposed features with relation to existing site conditions are illustrated on the Site Map provided in Appendix A of this report. 1.2 Purpose of Investigation and Scope of Work The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the project in order to provide geotechnical recommendations that should be implemented during development. The investigation included characterizing the general project surface and subsurface conditions, and evaluating the suitability of the soils to support the planned site activities. In order to fulfill the purpose of investigation, the geotechnical program completed for the proposed improvements of the project include: • 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 Envirotech Engineering Geotechnical Report PO Box 984 page 1 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 and/ or cut banks, review geological maps for the general area, research published references concerning slope stability, and review water well reports from existing wells near the project; • Collect bulk samples,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. N i n I� y I 6 If I aw r. I w 1 Project ; - i E Aaa 0, Vicinity Map from Mason County Website Envirotech Engineering Geotechnical Report PO Box 984 page 2 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the project was gathered on March 9, 2020 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. Vegetation on and near the project consists primarily of secondary growth firs, cedars, 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 57% with a vertical relief of about 50 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. 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 Geotechnical Report PO Box 984 page 3 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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. N A Aerial Photo from Mason County Website Envirotech Engineering Geotechnical Report PO Box 984 page 4 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 3.0 SUBSURFACE INVESTIGATION Information on subsurface conditions pertaining to the project was primarily gathered on March 9, 2020 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 3 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 terminus. 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. Heheman, Isablle Y. Sarikhan, and Robert L.Logan,July 2009,provides the following caption(s)for the project area: Envirotech Engineering Geotechnical Report PO Box 984 page 5 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 Peat—O:g;mw and orgmte-nch wdtment.include-,peat.muck.silt.and Vas►oa till—Uzr:_we&ur a atafied(btu locally banded)mix of clan.:dt- clay.tvpwa%-in closed depression,include:all recognized upland :and.and paiv].typically supported by a sandy matrix,mostly gray bin wetland peas and flat surface:in clwAd depmssww.unless a different locally ranging to tin light brows or orange.typically unweathered. unit or standing water was spectfically identified(idennfinnon of some lodgment tall compact.with w•ell4t eloped face,resmblmg concrete. polTons t therefore tentatne).freshwater egmvaknt of unit Qm where but near the surface commonly hadJy and(or)looses and covered by I to field data were unavviable.mapped on the bast:of topography.aerial 6 8 of loose ablation ell;deposited directly by glacial are and commonly photos.ce print mapping—for example.peat beneath the runway at includes clasts at clumps phacked from underlying unit-..Clast•.we Bremerton National airport w•as noted on a I934 soil map(t:S Bureau of commonly striated and faceted with angular cc rounded edges Boulder. Chema ttv and Soils.1934)and in geotechmcal bonny-.drilled in 200E ate generally spare within the till but Lup(emnc)boulder of phuomc (Fred Sah bun'.Past of Bremerton.oral commum.2008)that suggested or metamorphtc rock are common on till surfaces Some exposures include some peat outside the area showy on the 1934 soils map.Thai discrepancy mterbands and kn es of sand and gtat^d.locally with shears and point and the absence of peat in the area according to a more recent soil-map Till forms a locally patchy and seemingly randomly distributed cover up to (Me furphy.1980)caused a to show the peat boundaries as inferred The a several tens of feet Chuck,with a dnckncs of 5 to 20 ft most common It unit postdate•.Vi•.hon ace and L predominantly Holocene but locally tvpicaih•dotn=tes,but is also locally dt-contimous on.fluted surfaces. includes some late Pleistocene deposits with indnidual dnmlmz measuring 0 1 to 0 3 m wide by 0.8 to 1.3 m long and the long axis aligned with the direction of ice flow Till tvpicalh• Laudslide deposits--Gravel sand.sth.clay.and boulder,in slide body t in sharp.unconfotmable contact with uimderhtng units.most commonly and toe.due to trap scale.includes exposure of underl}wg units in scarp advance outwash(unit Qga and m1 umrt) Unit Qgt he-,stranpaphically areas.angular to rounded cla:t--,and grains:unsorted.generally kw-w. below unit Qgo It may include unrecognized exposures of older till A jumbled and mstcatified but may locally retain primary bedding. may,boundary mismatch between unit Qgt an this map and unit Qgos on commonly mcludes liqu elarnon features Absence of a mapped slide does the Vaughn quadrangle to the south(Logan and Walsh.2007)may have not amply absence of shdtag or hazed as some slides are too small to resulted 6om a map-production error in the uotthwe-.t comet of the how at map gale Although the large Akkrwood landslide southwest of Vaughn map(Josh Logan.W asI Duvn of Geologv and Earth Fitsources. Beifam may have been tnggend by seismicity about I 1 ka(we Structure) oral cotnmun.-009) review of aerial photographs also suggest-hnstoric movement for this slide.The unit post-dates Vashan we and is predommamh-Holocene but locally may include ant late Pleistocene deposit lop Project ;''!,' ao''; w S mJ !1 /7 -. t tam.✓/ •. a� � 4u%-1.�� t �j Qed ; e, sir Q, QO Geological Map Department of Natural Resources Washington State Envirotech Engineering Geotechnical Report PO Box 984 page 6 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 fill. Within test pit locations, soils within the upper 3 feet of natural ground were generally observed to be poorly graded sand with some gravel and some silt(SP-SM). 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. The soil designations are depicted in the aerial photograph below,and descriptions are provided in Appendix B of this report. N s - d t 0 W Im dD al .♦i. F 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 150 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 Geotechnical Report PO Box 984 page 7 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 present 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 `Intermediate' 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: Watt oRlu N / IQTSAP J 1puan LA.5 P pJ 1` Project Go. ' u y;r+RHer .WNh�rW KTSAP ♦ .7 PIERCE l� a( J loll r , stable 1Awno[ltwC W- Intermediate 6 V Modified . .. .. y Unstable V Unstable(old slide) 0 1.5 31W y Unstable(recent slide) Map from Washington State Department of Ecology Website Envirotech Engineering Geotechnical Report PO Box 984 page 8 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 According to the Resource Map from the Washington State Department of Natural Resources (DNR), the project is not within terrain labeled `highly unstable' relating to soils. DNR labeled portions of this project as medium and high slope instability with relation to slopes. A Resource Map from the DNR Forest Practices Application Review System is provided below: NU ■ s■ all ■ Project .! 1 0 so 96 an ■ Soils �-' , • a-■ Hydnc Sods ■ ' Highly Unstable ■ ■ �'•; Highly Erodible No Data or Gravel Pits ■� ■ ■ r Slope Stability-West Moderate Slope Instability ' e- ■ High Slope Instability � a 0 150 300ft —Z Million� 1:4.514 Resource Map from Washington State Department of Natural Resources Website 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: Soil unit weight: 120 pcf Angle of internal friction: 36 degrees Cohesion: 0 psf Envirotech Engineering Geotechnical Report PO Box 984 page 9 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 at least 1.5 and 1.1, respectively. See the slope stability information in Appendix C for a depiction of minimum factors of safety away from the project. 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 The nearest Class `A' or Class `B' fault to this property is the Tacoma Fault Zone, which is mapped in the vicinity of this project. This information is based on the USGS Quaternary Fault and Fold Database for the United States. Potential landslides due to seismic hazards have been considered, and are addressed in the Slope Stability Analysis Section provided earlier in this report. Soils immediately below the expected foundation depth for this project are generally Type D, corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the regional seismic zone is 3 for this project. The estimated peak ground acceleration ranges from 0.50g to 0.60g.This estimation is based on the United States Geological Survey(USGS)National Seismic Hazard project in which there is an estimated 2% probability of exceedance within the next 50 years. Envirotech Engineering Geotechnical Report PO Box 984 page 10 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 4.3.1 Liquefaction The potential for liquefaction is believed to be low for this project. This is based,in part, on the subsurface conditions such as soil characteristics and the lack of a permanent shallow water table. Subgrade characteristics that particularly contribute to problems caused from liquefaction include submerged, confined, poorly-graded granular soils (i.e. gravel, sand,silt). Although gravel-and silt-sized soil particles could be problematic,fine and medium grained sands are typically subjected to these types of seismic hazards. No significant saturated sand stratifications are anticipated to be within the upper 50 feet of the subsoil for this project. 4.4 Landslide,Erosion and Seismic Hazards Conclusions DNR 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 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. A structural or geotechnical professional should design retaining walls based on specific conditions. Soil parameters for the structural design of retaining walls may be estimated as 134 pounds per cubic foot (pcf) and 118 pcf for engineered fill and native soils, respectively. The angle of internal friction may be estimated as 36 degrees and 32 degrees for engineered fill and native soils,respectively. These soil parameters are based on soil type and placement conforming to the Earthwork Construction Recommendations Section in this report. 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 Geotechnical Report PO Box 984 page 1 1 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 15 inches shall be placed at a minimum of 12 inches below the existing ground surface atop unyielding soils or atop engineered fill constructed per this report. 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 Envirotech Engineering Geotechnical Report PO Box 984 page 12 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 upon a site inspection by a geotechnical engineer after the foundation excavation is completed. 5.1.2 Settlement Total and differential settlement that a structure will undergo depends primarily on the subsurface conditions, type of structure, amount and duration of pressure exerted by the structure,reduction of pore water pressure, and in some instances, the infiltration of free moisture. Based on the expected native soil conditions, anticipated development, and construction abides by the recommendations in this report, the assumed foundation system may undergo a maximum of 1.0 inch total settlement,and a maximum differential settlement of 0.75 inch. 5.1.3 Concrete Slabs-on-Grade Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted coarse, granular material (Retained on U.S. Sieve #10 or greater) that is placed over undisturbed, competent native subgrade or engineered fill per the Earthwork Recommendations Section below. The recommendations for interior concrete slabs-on-grade as presented herein are only relevant for the geotechnical application of this project. Although beyond the scope of this report, concrete slabs should also be designed for structural integrity and environmental reliability. This includes vapor barriers or moisture control for mitigating excessive moisture in the building. 5.2 Earthwork Construction Recommendations Founding material for building foundations shall consist of undisturbed native soils to the specified foundation depths. Compacted engineered fill, or selective re-compacted native soils may be used to the extents provided in this Earthwork Construction Recommendations Section. The following recommendations include excavations, subgrade preparation, type of fill, and placement of fill for building foundations. 5.2.1 Excavation Excavation is recommended to remove any excessive organic content or other deleterious material, if present, beneath foundations and to achieve appropriate foundation depth. Additional sub-excavation will be required for this project if the soils below the required foundation depth are loose, saturated, not as described in this report, or otherwise incompetent due to inappropriate land disturbing, or excessive water trapped within foundation excavations prior to foundation construction.All soils below the bottom of the excavation shall be competent, and relatively undisturbed or properly compacted fill. If these soils are disturbed or deemed incompetent, re-compaction of these soils below the anticipated footing depth is necessary. Excavations shall be completely dewatered, compacted, and suitable before placement of additional native soil, engineered fill or structural concrete. Envirotech Engineering Geotechnical Report PO Box 984 page 13 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 t FILL 1 64-11sTURBED SUBGRA 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 Particle 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 Geotechnical Report PO Box 984 page 14 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 5.2.3 Retaining Wall Backfill Native soils may be used as retaining wall backfill for this project if the total wall height is 4 feet or less and the recommendations below are followed. Native soils for retaining walls exceeding 4 feet in height must be approved by the local authority or evaluated by an engineer.Backfill may consist of engineered fill, as presented in this report,or borrow material approved by a geotechnical engineer. Compaction of these materials shall be achieved in compacted lifts of about 12 inches. Each lift should be uniformly compacted to at least 85%, and no more than 90% of the modified Proctor maximum dry density (ASTM D 1557).If pavement or building loads are planned to be located within retaining wall backfill, then 90% compaction is required. In addition, heavy construction equipment should be at a distance of at least V2 the wall height. Over-compaction and limiting heavy construction equipment should be prevented to minimize the risk of excess lateral earth pressure on the retaining structure. Envirotech recommends that retaining wall backfill is compacted with light equipment such as a hand-held power tamper. If clean,coarse gravel soils are utilized as engineered fill, and surcharges will not influence the retaining wall, compaction may be achieved by reasonably densifying granular soils with construction equipment. 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 for this project, if utilized, shall be constructed per the fill placement and compaction recommendations as presented above. Both engineered fill and native soils may be used for building pads. Building pad slopes shall be no steeper than 2:1 for both compacted engineered fill and re-compacted native soils used as fill. Building pad fill shall be"keyed"into the existing subgrade to a depth of at least 2 feet below the existing ground surface. The term "keyed," as used here, implies that the interface between the building pad and subgrade is horizontally level. Alternatively, building pads may be keyed into the subgrade to the above specified depth,and stepped. Stepped fill should be keyed into the subgrade at a minimum width of 8 feet. All footings shall be located at least 5 feet away from the top of the engineered fill slope. 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 50 feet footing Envirotech Engineering Geotechnical Report PO Box 984 page 15 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 S_'._P[ SLOPE �ACE -� _ —1 I ' —I I 'I I SETBACK —I 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. If impervious thresholds are exceeded per the prevailing agency 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 infiltration is avoided in order to maintain slope stability, and that roof downspout dispersion on splash blocks are employed. Recommended 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 the prevailing agency 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 Envirotech Engineering Geotechnical Report PO Box 984 page 16 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 is 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 Drainfrelds Septic drainfields were considered in our geotechnical evaluation.This includes septic drainfields with relation to the observed soil conditions, expected vegetation removal, and existing and proposed topography. Based on the aforesaid parameters, the septic 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 Geotechnical Report PO Box 984 page 17 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 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 — Jessica Smith,M.S. Michael Staten,P.E. Staff Geologist Geotechnical Engineer Envirotech Engineering Geotechnical Report PO Box 984 page 18 Parcel 12207-75-00120 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 March 14,2020 APPENDIX A SITE PLAN SCALE, 1 INCH = 150 FEET 0 �5 1S0 10 O APPROXIMATE TIE OF •} �1�� CRITICAL SLOPE EXCEEDING 404 50 FT CONSTRUCTION A 2�' np O SETBACK FROM TOP 2 2M OF CRITICAL SLOPE 2� BUILDABLE AREA NQ, s � L i � i TPIe <' l APPROXIMATE TOP _ _ / ET 1411 OF CRITICAL SLOPE EXCEEDING 10 FT VEGETATION 40% REMOVAL BUFFER FROM TOP OF CRITICAL SLOPE NOIES- PROJECT/ OWNER/LOCATION- L EROSION CONTROL MAY BE REQUIRED FOR TH1S 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. MCCLURE CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND XXX E BAKER COURT INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 12207-75-00120 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 ENGINEER, ENGINEERING OF SLOOPES,WATER FEATURES,ETC.,WITH RELATION TO THE PROPERTY EN BOX ECH LINES MUST BE VERIFIED BY THE OWNER,RECOMMENDATIONS IN THE —� SLOPE INDICATOR BELFATR, WASHINGTON 96528 984 GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS,ETC. WITH BELL 75-9371 RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC EXISTING CONTOUR FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING TPI TEST PIT SITE PLAN PROPERTIES. APPENDIX B SOIL INFORMATION VNIMBIL 00 IaIZINTAL XALD B400M I PC" Y TCET PROPOSED HOUSE BAKER Cl %ISTING GRADE S ,_r Far ALA_ 13P RD 711 POORLY GRADED SAND WITH GRAVEL AND SILT (SIP - SM) SECTION A-A 1RLiST/�}/I.DTI�TION SING.F. FAMILY RESIDENCE GEO'ECHIML REPORT N AUME -40 TE!, -cmg.IMTDN 1)MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE (QI[ POSITIVE DRAINAGE b r/ 2) THE SOIL PROFILE IS ACCURATE FOR THE DEPTH Or WON Mpe THE OBSERVED TEST PITS AT THE SPECIFIEI LOCATI�6. LOVER DEPTHS ARE BASED IN SITE GEOLOGY, WELL LOG(S),AND/131 EXPERIENCE IN THE GENERAL AREA. 97I_ PROFILE TEST PIT LOG TEST PIT NUMBER TP-1 PROJECT: McClure Geotechnical Report DATE OF LOG: 3/9/2020 PROJECT NO: 2035 LOGGED BY: RJM CLIENT: Kimberly McClure EXCAVATOR: NIA LOCATION: XXX Baker Court DRILL RIG: None Mason County,Washington ELEVATION: N/A INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A STANDARD PENETRATION TEST SOIL STRATA, DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE AND TEST DATA DEPTH N 10 30 50 0 SM-SP Poorly graded SAND with GRAVEL and some SILT t 2 3 Excavation terminated at apprmarnatety 3 feet 4 5 6 7 8 9 10 No Groundwater Encountered ENVIROTECH ENGINEERING Ttw mbm bon pertains only to this bong and should riot be Geotechrucal Engineering interpreted as berg inAdatrve or the entee me Map Unit Description AlderNood gravelly sandy Win 8 to 15 percent slopes—Mason Counh. Washington Mason County. Washington Ab—Alderwood gravelly sandy loam. 8 to 15 percent slopes Map Unit Setting National snap unit symbol 211:626 Elevation 50 to 800 feet dlean annual precipitation 20 to 60 Inches Mean annual as temperature 46 to 52 degrees F Frost-free penod 160 to 240 days Farmland classification. Prime farmland if Irrigated Map Unit Composition Alderwood and sinldar 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) Shoulder Landform position(three-dimensional) Nose slope tall Down-slope shape Linear,convex Across-slope shape Convex Parent material Glacial drift and/or glacial oulwash over dense glaciomanne deposits Typical profile A-0 to 7 inches gravelly sandy loam Bw 1-7 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 2Cd 1-35 to 43 inches very gravelly sandy loam 2Cd2-43 to 59 inches very gravelly sandy loam Properties and qualities Slope 8 to 15 percent Depth to restrictive feature 20 to 39 inches to densic material Natural drainage class Moderately well drained Capacity of the most hinting layer to transmit water(Ksat) Very low to moderately low(0.00 to 0.06 mlhr) 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 27 inches) Interpretive groups Land capability classification(irrigated) None specified Land capability classification(nonirngated) 4s Hydrologic Sod Group. B I siA Natural Resources Web Sal Survey 3/13/2020 01111111111 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description Allenwood gravely sandy loam,8 to 15 percent slopes—Mason County, Washington Forage suitability group: Limited Depth Soils(GO02XN302WA), Limited Depth Soils(0002XS301 WA),Limited Depth Soils (GO02XF303WA) Hydric s ll rating: No Minor Componefrts Everett Percent of map unit 5 percent Lanrdform Kames,eskers,moraines Landform positron(two-dimensional): Shoulder,footslope Landform position(three-dimensional): Crest,base slope Down-slope shape, Convex Across-slope shape: Convex Hydre sdl 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 Larxfform: Depressions Landform position(three-dimensional) Dip Down-slope shape: Concave Across-slope shape: Concave Hydnc soil rating: Yes Norma Percent of map and 2 percent Landform: Depressions,dramageways 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 15,Sep 16,2019 usDA Natural Resources Web Soil Survey 3/13/2020 AM Conservation Service National Cooperative Sod Survey Page 2 of 2 247 F WATER WELL REPORT „OIW ,.D g AGE138 4) T� DOW sw' a/_a/ STATE OF WASHINOTON WSW RqM P-,, Nv WA- - Q' 0)OWNER: Name FREDAND-DMNN PAPS Aa6ew E0_&QXAfiLJ ELFAP_WA fts2s (2)LOCATION OF WELL: couny M�AMgQy -. __. �_—.. 8W IN NON 114 sac 7 T Wri (2a)STREET ADDRESS OF WELLt9rnwedaftrmb) _ u/ rn TAX PARCEL NO. 12207-7S4 201 L (3)PROPOSEDUSE: Zoafwb ❑Hamm ❑mmaicW (10)VALL LOG or011COMOSIOlNq�1tOC®IJt1E0pl#I710N: 0en9amse ❑Ad wetf Doom reneebw Deeme by erer,anac+r.a.al ffwww«++sea.« « ❑DNbdr keaw r eaaamsr b Mar rweaea arraara aan arrr«naywerseAar♦e O dbeeaaaraa erae0aereaawrea C (4)TYPE OF WORK: OwW%numor of ww(a more Oran onel - - — _ -. —� O mmmwdf tbedrod wTgy,L - -- - T 0 ❑D.aprw =Dw Bored BR 37 ]:Jfl rdaor ad Cable D.a GRHY`LAY-- E ❑Daoommbu0n X,, ta Rory J.rbd BROWN CLAY AND SLITS plummullom oYalYldaee a br va SEAMS Of SAW ADD GMY WW _1'fllmb 41m—lJj ib_ g R -- ` Uner innWied —_ OWL Dom R b it O Threaded _-- Dset lob Rb__ IL C Fe*wf- auonw LjYm UUNo Type of pwkrralor used - - - SIZE d parkramorr Yt my _In - � Os+lorasrs k9m � Rb_ k perkssorN►an - 0 parkrapar Rra— t b_ _R Ol Ilrwswwte (SYae Cab K9fW Mft M4 - - — -- -- ksalvNdna7 ww"AQKWXK « r" M�� mom sutl t1lmLftls mtta e,m t f91Nal��1t[)ytb mNm❑Obelmawafiamt --_--�_.® 6EaleAtlMaaafle7ait ib awn m to III )— t oatF. mr"QIY To 42 i 0 suwtat used in"m 61LINInom _ Z Dw any btreb conWn unueaalsaaYfl -Ya Nor N TypeofwateN Depfdamab-,_. _ al htrVW of seal"V sbatm off O -O (7)PUMP: 14—ect—e.Nerve — Type SUB KP.--�- --- — .—. .— - --— fll O C00V G (S)WATER LEVELS: und-budsoamem" mo. m e abn Bee Gael ft irk s S/?/2092_ 19 Compklt.d 8f72W2_ 19 _ V sbx i..r_ �— k loam oupofwd ode b/2Sp'1 WELL CONSTRUCTION CERTIFICATION: LLf Mes as praaese ebb per some inch Deb i conetrxud arlwor sooeor'ebpms'dnry for co W m of Nra wolf.nd iu N- An—wear A dara0sed by __ —. mnpaanu wtb,ax wasnrtpton we•�rarrwudon W hoards Miabnaib used O .61Cj end era iniornleion reported abo a are WA a my seer kndw/ed9e and bNe ((h WELL TESTS:OfeWdO er Ia amoW maw rnr re lowed below ert lerea Type or pmr Name NICHOLAS J._EBNBL_ LsOdirIas"° 2147 01 Wad a 00MO tad aaeat®Yea❑Nb a yee.M~?TDDC._ Dnarrmraeaea E VOW IS 9dAnb.wNr A dra mmm arw 4FIR fore Trynee Name Uoense No ` YW 9dJnen.amA 4 aawdOwn arm ...— rra -- ---- Ip YWK--,ydakm,*a _ R 6 mi~afW --- — ha Dn109 C—pany TOP DOG DRILLINGAM -.�Zmm _ O` �rlt S 4 came"O e c y �4 e TMW YAWL" T)om Wrs raw ik9Yff ftt a •a ----— —— — Aida �e�r�� ., a�. e i- x■dsacrs R.oasaeonNo TOPOODC054RA Dare sm=002 9 Doweled B Aer ted 16 SWANK saml_L%ayawdbanaft l_ his (USE ADDITIONAL SHEETS IF NECESSARY) wnett _— 9WArwt vif own sd d_ R tr _ hn. Eo*W is an Equd Opportunity&M ANmab.e Agrm er pbry F« .An—flow 9 0 In Deb OM2152 spwW aCMnrn10Mba f1•ds. the WNW Reammm Pmgrom at Temp.ratum or waar -Yes AND (390)407.41M. TAB TDD n~is(3W)407-a= APPENDIX C SLOPE STABILITY 1 . O O 1 . 1 O 1 . 2 O 1 . 3 O 1 . 40 1 . 5 O 1 . 60 1 . 70 1 . 80 1 . 90 2 . 00 voo P r o j e c t M c C 1 u r e A a p Datafile Dynamic Analysis Analysis Bishop 1 . O O 1. 1 0 1 _2 0 1. 3 0 1 . 40 1 . 50 1 60 1 _ 7 O 1 . 80 190 00 �.y 3 83 P r o j e c t Mc C 1 u r a R e p o r t Data£i 1® _ Static Analysis Analysi s Sishop APPENDIX D EROSION CONTROL GEOTEXTILE FABRIC WRAP AROUND TRENCH TO AT LEAST ENTIRE BOTTOM OF TRENCH BEFORE PLACING GRAVEL 2'x2'x5' WOOD POST OR 12' DEEP, B' WIDE TRENCH EQUIVALENT OR BETTER FILLED WITH 3/4' TO 1 1/2' WASHED GRAVEL OR VEGETATION \f 23 fT DIRECTIOK of - EXISTING WATER FLOW GROUND SURFACE >rT }� E7 R 1 g SILT FENCE — CROSS SECTION N.T.S. 2'x2' WOOD POST (TYR) GEOTEXTILE FABRIC OR EQUIVALENT OR BETTER AND WIRE MESH 2 6 FT MAX. O.C. I iR LL7R EXISTINGGROUND SURFACE 0 12- DEEP, W VIDE TRENCH FILLED WITH 3/4' TO 1 I/2' NEU Im Ff WASHED GRAVEL OR VEGE4TI BOTTOM EXTENTS OF GEOTEXTILE FABRIC SILT FENCE - DETAIL N.T.S. PROVIDE FULL WIDTH 3/4 IN TO 1 1/ INGRESS/EGRESS CRUSHED GRAVEL R PLACED AT 6 IN MINIMUM DEPTH WELL-DRAINED SOILS -0.02 IN/MIN F`'LL LEnGIN R=25 FT MIN 4 ACCESS Roan STABILIZED CONSTRUCTION ENTRANCE N.T.S. 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GEOLO'd-' - 06672- 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: /" '(.- `- Ly Permit#: U,10 20 2 0— C! I Z11Ll Parce Date(s) of the Document(s) reviewed: 12 4 2 d 1. (a) A discussjon of general geologic conditions in the vicinity of the proposed development, OK? Comment: �, Z (b) A discugsjon of specific soil types OK? Comment: (c) A discussion of ground water conditils OK? Comment: }� i (d) A discus i n of the upslope geomor bolo OK? Comment: 2 p (e) A discussion of the location of upland waterbodies and wetlands OK? Z Comment: Z , 3 , (f) A discus ' n of history of landslide c ivitX in the vicinity, as available in the referenced maps and records OK? K Comment: r I 2. A site plan that identifies the important development and geologic features. OK? x, Comment: 0 �I' A_ 3. Locations and logs of exploratory holes or probes. OK? Comment: l 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: Dew'q v 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: I (�O c` +0 V 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? Y Comment: L4 , l f ( 7. (a) Appropriate restrictions on placement of drainage features OK? X Comment: �;I q i (b) Appropriate restrictions on placement of ptic drain fields OK? ',,/ Comment: J ,-I (c) Appropriate restrictions on placement o�ompacted fills and footings. OK? Comment: J. 2- Page 1 of 2 Form Effective June 2008 (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes. OK? V Comment: (e) Recommended setbacks from the Ian slide hazard areas shoreline bluffs and the tops of other slopes. OK? Comment: 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. OK?1� Comment: V or ko ut'i ore— S-,5 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. t- OK?_ Comment: 10. An analysis of both on-site and off-site impacts of the proposed development. OK? `/ Comment: y r 11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. OK? �/ Comment: t� 12. Recomm ndations for the preparation of structural mitigation or details of other proposed mitigation. OK? ¢ Comment: J , �,�a YV� /k L(,A` 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. OK? Comment: 51` F-t- / tY Dc�✓��X Are the Documents/signed and stamped? By whom?q 36 ►C+�>7� S T� .�� License#: -r License type: Pt 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: 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