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GEOTech for BLD2008-00170 - GEO General
ALKAI CONSULTANTS, LLC. Environmental Engineering • Geotechnical Engineering • Wetland Consulting April 30,2008 Job# 10145 Mason County Department of Community Development P.O. Box 279 Shelton,WA 98584 Attn: Mr. Scholz Geotechnical Report Review Permit#BLD 2008-00170 Applicant: Scott At your request, we have reviewed a Geotechnical Report for the above referenced permit. The report was prepared by Envirotech Engineering dated March 27, 2008. The report was signed and stamped by Michael Clyde Staten,PE(License#43045). The report contains the information required in the Mason County Code, Landslide Hazardous Areas 8.52.140.E. Further, it is ALKAI's opinion that the report was prepared to at least the typical standard of practice for geotechnical engineering in this area. We therefore recommend that Mason County accept the geotechnical report. Should you have any questions or concerns, or if we may be of additional assistance, please call our office at (360)613-2407 or contact us by e-mail at Jim@alkai.net. Sincerely, Donald Balmer,L.G. James ar ng,E.I.T Senior Hydrogeologist -{ Project Engineer Hydra,ogeologist w. 'c+ 1950 �44 �pQ r a e dG e _ Donald K 9aitr>.er $o 4&- Attachments: Geo Tech Work Order Geotechnical Report: Envirotech Engineering p g g Mason County Requirements Checklist l 9465 Provost Road NW, Suite 202 •Silverdale,Washington 98383 • (360) 613-2407 • Fax: (360) 613-2408 Projects 1 Z —� 17 ALKAI CONSULTANTS 5/2/2008 Mason County Requirements For Geotechnical Reports Mason county code 8.52.140 section 5(E) X❑ 1) A discussion of general geologic conditions,specific soil types,ground water conditions,the upslope geomorphology and location of upland waterbodies and wetlands, and history of landslide activity in the vicinity X❑ 2)A site plan which identifies the important development and geologic features. X❑ 3) Locations and logs of exploratory holes or probes. X❑ 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. X❑ 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. X❑ 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. X❑ 7) Appropriate restrictions on placement of drainage features,septic drain fields and compacted fills and footings, including recommended buffers and setbacks from the landslide hazard areas. X❑ 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. X❑ 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. X❑ 10)An analysis of both on-site and off-site impacts of the proposed development. X❑ 11) Specifications of final development conditions such as,vegetative management, drainage,erosion control,and buffer widths. X❑ 12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. X❑ 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. i 0 ' 1 ' Geotechnical Report for Jim Scott Single Family Residence 681 NE Mission Wood Drive Parcel 12307 34 90043 Mason County, Washington 2 March 27 008 Project#0827 f: I Prepared For: Jim Scott �, 5371 North Shore Rd CLYDg� `�` wnsy,sT9T ' Belfair, Washington 98528 ��ti Prepared By: 3! 06 Envirotech Engineering 064 SM-�� w� 74 NE Hurd Road SJ�NALV; ' Belfair, Washington 98528 Phone: 360-275-9374 F EXPIRES JAN 10,2009 Fax: 360-275-4789 TABLE OF CONTENTS 1.0 INTRODUCTION...........................................................................................................................1 1.1 PROJECT INFORMATION............................................................................................................... 1 1.2 PURPOSE OF INVESTIGATION........................................................................................................ 1 1.3 SCOPE OF WORK........................................................................................................................... 1 2.0 SURFACE CONDITIONS..............................................................................................................3 L 2.1 GENERAL OBSERVATIONS............................................................................................................3 2.2 TOPOGRAPHY...............................................................................................................................3 2.2.1 Upslope Geomorphology.......................................................................................................3 2.2.2 Downslope Geomorphology 2.3 SURFACE DRAINAGE.....................................................................................................................3 2.4 SLOPE AND EROSION OBSERVATIONS...........................................................................................4 i 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.............................................................................................5 3.31 Groundwater......................................................................................................................... 6 € 3.4 SoIIs TESTING.............................................................................................................................6 E3.4.1 Visual Classification............................................................................................................. 6 4.0 ENGINEERING ANALYSIS,CONCLUSIONS AND RECOMMENDATIONS..........................7 4.1 BUILDING FOUNDATION RECOMMENDATIONS.......................... t 4.1.1 Bearing Capacity.................................................................................................................. 4.1.2 Settlement............................................................................................................................. 7 4.2 LATERAL EARTH PRESSURES........................................................................................................8 4.3 EARTHWORK CONSTRUCTION RECOMMENDATIONS....................................................................8 4.11 Excavation............................................................................................................................8 4.3.2 Placement and Compaction of Nadve Soils and Engineered Fdl..........................................8 4.13 Retaining Wall BaciffM........................................................................................................9 4.3.4 Wet Weather Considerations................................................................................................. 9 4.4 SLOPE STABILITY AND EROSION CONTROL................................................................................ 9 4 41 Septic➢rainfield Impacts.................................................................................................... 12 4.4.2 Building and Footing Setbacks.................................................................. 4.4.3 Temporary and Permanent Erosion Control....................................................................... 12 4.4.4 Surface and Subsurface Drainage..................................................................................... 13 4.4.5 Vegetation Considerations.................................................................................................. 13 4.4.6 O fie impacts................................................................................................................... 14 4.5 SEISMIC CONSIDERATIONS AND LIQUEFACTION......................................................................... 14 ' ........... 5.0 CLOSURE..................................................................................................................... .....15 ' Appendix A-Site Plan Appendix B-Geologic Map Appendix C-Soil Information t Soil Profile Soil Logs Well Reports ' Appendix D-Slope Stability Input&Output Appendix E—Erosion Control r w , ' 1.0 INTRODUCTION Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a property Wood Drive identified as parcel number 12307 34 90043, Mason located at 681 NE Mission Wo County, Washington(Project). 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; and, recommendations for foundation, settlement, earthwork construction, lateral earth pressures, slope stability, erosion control, drainage and vegetation considerations in the Engineering Analysis and Recommendations Section. An initial geotechnical evaluation of the Project was conducted by Envirotech with the property owner, Jim Scott, on March 17, 2008. 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. Consequently, the proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason County Resource Ordinance 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. 1.1 Project Information Information pertaining to the Project was provided by the property owner with general assumptions by Envirotech that are typical of this type of development. The Project is accessed from NE Mission Wood Drive, a dirt road, linking NE Sand Hill Road. See the vicinity map on the following page of this report. The property is currently developed land consisting of a mobile home, septic system and other ancillary buildings. The planned development consists of a 1-or 2- story single family residence. Foundation construction is expected to consist of continuous strip footings with a crawl space beneath the home. Approximate building footprint with relation to site features are illustrated in the Site Map in Appendix A. 1.2 Purpose of Investigation The purpose of this geotechnical investigation was to evaluate the Project in order to provide geotechnical recommendations relating to the development of the property. The investigation included characterizing the general Project surface and subsurface conditions, and evaluating the suitability of the soils to support the planned site activities. 1.3 Scope of Work 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; • Define the general subsurface conditions of the site by observing subsoils extending to a ' depth of up to 8 feet below the natural ground surface, review geological maps for the general area, research published references concerning slope stability, and review water j Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 1 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County. Washington March 27,2008 ' well reports from existing wells near the Project; • Collect bulk samples at various depths and locations; • Perform soils testing to determine selected index properties of the soils that include 2 visual classifications; • 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. d ME�F$ i s s •� Pc 15 13 a1 i8 17 14 fi Such/Pond b � T23 6 f Projects —. 2� 23 �/ 24 % 19 m 28 25 =� 8 LLI = 28 1� W 0 7094ft Vicinity Map from Mason County Website Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 2 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the Project was gathered on March 17, 2008 by Michael Staten, geotechnical engineer with Envirotech. During the site visit,the type of geotechnical investigation was assessed, site features were documented that may influence construction and slope stability, soil samples were collected from selected locations, and near- surface soils were visually classified. This Surface Conditions Section provides information on general observations, vegetation, topography, drainage and slope/ erosion conditions for the Project and surrounding areas that may impact the Project. 2.1 General Observations The Project is currently developed land as previously mentioned. The location of the planned single family residence is to the south of the existing mobile home. Clearing and grading has taken place as part of the building pad preparation. Mission Road Drive runs near the north ' property line, and Mission Creek flows through the southern portion of the property. Beyond the property lines exists rural residential development with low density. Vegetation on and near the Project consists primarily of 2°a or 3rd growth pines, 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 Project is situated within and near slightly to steep sloping terrain. The planned building envelope location appears to be primarily on slightly sloping terrain of approximately 2%. The topographic information provided in this section was extrapolated from a public lidar source, and incorporated observations and field measurements. Slope verification included measuring slope lengths and inclinations with a cloth tape and clinometer. See the Site Map in Appendix A and the Geological Map in Appendix B in this report for an illustration of general topography with respect to the planned development. 2.2.1 Upslope Geomorphology Ascending grades are located to the north of the planned development. This slope is slightly sloping with apparent grades of less than 3%, and extends nearly 300 feet. There are no apparent water bodies or wetlands located upslope from the planned development. 2.2.2 Downslope Geomorphology Descending grades of up to approximately 56% exist to the south of the planned development with a vertical relief of approximately 34 feet. This grade decreases to about t15%between the above mentioned 56%grade and the slope toe. 2.3 Surface Drainage Stormwater runoff originating upslope from the anticipated development is expected to be minimal. Sheet flow is expected down the slightly sloping grades towards the south and west, and ' will mostly bypass the proposed residence towards the west. Sheet flow down the steep slopes on the property can be expected, as the runoff travels towards Mission Creek. Mission Creek flows I ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 3 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 in a southwesterly direction through the southern portion of the property. A 50 feet path of sediment accumulation and damaged vegetation was observed between Mission Creek and the toe of the 15% slope. Moderate streambank erosion was observed on the south bank of Mission Creek. Other than areas near the creek, excessive scour, erosion or other indications of past drainage problems were not observed at or near the planned development. 2.4 Slope and Erosion Observations The existing steep slopes near the Project signal a potential landslide or erosion hazard area. ' Some indicators that may suggest past slope movements include: • Fissures,tension cracks or naturally 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. 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. Accumulation of sediments near the slope toe is an apparent result from upstream bank erosion at a different location than the critical slope near the Project. i ' 1 Aerial Photo,from Mason County Website ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 4 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County,Washington March 27,2008 3.0 SUBSURFACE INVESTIGATION ' Information on subsurface conditions pertaining to the Project was gathered on March 17, 2008 by Michael Staten,geotechnical engineer with Envirotech. Specific information on field methods, sampling, field testing, subsurface conditions, and results from soil testing are presented in this section of the report. Appendix C of this report includes pertinent information on subsurface conditions for the Project, such as subsoil cross-sections, test pit log(s) representative of the bearing soils of the planned building, and water well report(s). Applicable test pit and well log ' locations are depicted on the Site Plan and Geologic Map provided in the appendix of this report. 3.1 Field Methods,Sampling and Field Testing ' Information on subsurface conditions for the Project was accomplished by examining soils within test pits extending to depths of up to 8 feet below the existing ground surface. Information on subsurface conditions also included reviewing water well reports originating from nearby ' properties. One bulk sample was collected at the Project site at approximately 18 inches below the existing ground surface near the anticipated building location. The soil sample collected was secured and transported for possible laboratory testing. 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 6 to 12 inches,and dense soils to depths of 24 to 40 inches.Very dense soils were encountered at 24 inches within the building pad, and 40 inches near the top of slope. 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 eP Y eP P� � eP J 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. 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 described utilizing the Unified Soil Classification System (USCS). Using the USCS in conjunction with estimated relative densities and other anticipated engineering properties of the soil, susceptibility for potential landslides, erosion and seismic ' hazards may be assessed. ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 5 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 The Project is composed of native soils with no indications of borrowed fill. For engineering purposes,these native soils consist of distinguishable layers,as presented below. Soils within the upper 8 feet of natural ground were observed to be low moisture, brown poorly- graded sand with gravel and poorly-graded sand with silt and gravel(SP, SP-SM)with a trace of cobbles. The relative densities of this soil are provided in Section 3.1 of this report. Gravels are primarily fine, and subangular to subrounded. Sand content was primarily coarse. The fines content exhibited no plasticity. Soils below the upper 2 to 3 feet of soils to a depth of at least 8 feet consisted of brown,very dense soils,locally known as `hardpan.' According to the well reports and knowledge of the general area, soils below the observed 8 feet in depth are dense to very dense hardpan, extending to a depth greater than 90 feet below the ' ground surface. 3.3.1 Groundwater ' From the water well report,permanent groundwater is almost 400 feet directly below the property at the building pad location. Perched groundwater at shallow depths was not ' observed on-site. However, groundwater was reported at depths of 67 feet, 180 feet and 246 feet below the ground surface. 3.4 Soils Testing The soil samples obtained at the Project site during the field investigation were preserved and transported for possible laboratory testing. Visual classification of soils was performed in the field. The following soil tests were performed in accordance with the American Standards for Testing and Materials(ASTM): 2 Visual Classifications(ASTM D2488) 3.4.1 Visual Classification The results from the visual classification are presented above in the Subsurface Conditions Section at depths of up to 8 feet below the natural ground surface. Specifically, soils within the upper 8 feet near the top of the slope consisted of approximately 25%gravel, 65%sand-sized soils, and less than 10%silt. Soils within the building location consisted of approximately 40%gravel, 55%sand-sized soils, and less than 5% silt. Minor variations observed during the visual classification of particle size ' content (i.e. gravel, sand, fines), or isolated pockets within the soil stratification were insignificant in relation to the overall engineering properties of the soil. ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 6 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 4.0 ENGINEERING ANALYSIS,CONCLUSIONS AND RECOMMENDATIONS The following sections present engineering analysis and 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; and, soil conditions that were identified from the geotechnical investigation that is summarized in the Subsurface Investigation Section. Engineering analysis and recommendations for the Project that is provided herein, includes pertinent information for building foundations, earthwork construction, slope stability/erosion control,drainage,vegetation and seismic considerations. 4.1 Building Foundation Recommendations Recommendations provided in this section account for the site development of a typical one- or two-story,single family residential structure. Below the upper 12 inches of Project soils,there are ' apparently two distinguishable layers of soil that will influence the bearing capacity and settlement of the structures. 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, and deriving probable relative densities, unit weights and angles of internal friction of the m-situ soils based on observed field conditions and soil testing for this Project. 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. The soils on-site have low to moderate frost susceptible characteristics and should be used only to the extents provided in this report. 4.1.1 Bearing Capacity For the existing site conditions, bearing values should increase with depth. Existing in- situ soils for this Project indicates that the structure can be established on shallow, continuous or isolated footings. Foundations shall be established on relatively undisturbed native soil. Alternatively, foundations may be constructed on selective re- compacted native soil or compacted engineered fill as described in the Earthwork Construction Recommendations Section of this report. Footing width and depth recommendations shall be adhered to,and are based on 1500 pounds per square feet(psf) maximum structural bearing pressure. For a bearing capacity requirement of no more than 1500 psf, a minimum footing width of 15 inches shall be placed at a minimum of 18 inches below the existing ground ' surface. Foundation recommendations are made available based on adherence to the remaining recommendations that are provided in this report. 4.1.2 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 ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 7 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 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. 4.2 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. ' 4.3 Earthwork Construction Recommendations Founding material for building foundations shall consist of undisturbed native soils. 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. 4.3.1 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,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. It is suggested that foundation excavations are inspected by a geotechnical engineer or qualified 1 professional in order to assess the bearing material prior to the placement of structural footings. 4.3.2 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 recommended 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 Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 8 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27.2008 re-compacted fill shall extend laterally from the bottom edge of the foundation at a rate of one foot for each foot of compacted or re-compacted fill beneath the foundation. See the illustration below. COMPACTED &HOOTINGNATIVE S❑ILS ❑R ENGINEEREDFILL II U ISTURBED SUBGRADE Both engineered fill and native soils used as compacted fill should be free of roots and other organics, rocks over 6 inches in size, or any other deleterious matter. Engineered fill should consist of 60%to 100%gravel-sized material(particles between 3/16-inch and 3 inches),and less than 10%fines(particles passing#200 standard sieve)by weight. I Compaction shall be achieved in compacted lifts not to exceed 8 inches and 12 inches for I native soils and engineered fill, respectively. Each lift should be uniformly compacted to j 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. 4.3.3 Retaining Wall Backfill As previously mentioned, significant retaining structures are not anticipated for this Project. However, if used, native soils may be used as retaining wall backfill for this Project. Backfill may also consist of engineered fill or borrow materials approved by a geotechnical engineer. Placement, compaction and extents of retaining wall backfill should also be specified by a geotechnical engineer or qualified professional. 4.3.4 Wet Weather Considerations Although the subsoil characteristics do not pose a great risk in regards to saturation, additional provisions may be required during prolonged wet weather. Every precaution should be made in order to prevent free moisture from saturating and ponding within excavations. If the bottom of excavations used for footing placement changes from a moist and dense characteristic as presented in this report to loose, saturated conditions, then these soils become unsuitable for foundation bearing material. If this situation occurs, a geotechnical engineer should be notified, or these soils should be completely removed and replaced with suitable compacted material as presented above. a 4.4 Slope Stability and Erosion Control 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 n ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 9 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 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. These factors of safeties are based on engineering standards such as defining engineering properties of the soil,topography,water conditions,seismic acceleration and surcharges. Surface sloughing or other types of surficial slope movements usually do not affect the deep- seated structural capability of the slope. However, excessive and/or repeated surficial slope movements, if not repaired, may represent a threat to the structural integrity of the slope. With appropriate drainage and erosion control provisions for this Project during and after construction, it is unlikely that this Project will experience excessive surficial movements. However, maintenance of the slope must be completed if the situation does arise 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' or `highly erodible' relating to soils. In addition, DNR did not indicated previous landslide activity near the Project. DNR labeled a very small portion of this projects' critical slope as medium and high slope instability with relation to slopes. This delineation is primarily dependent upon slopes and convergence. Secondly, lithology and precipitation are modeled within this delineation. In summary, this designation is based on mapping without field observations or knowledge of the specific site geology or soils. The Simplified Bishop Meth utilizing `STABLE' software was used to analyze the static P oP �, g � Y stability of the site slopes. 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 f values were used in the slope stability analysis in regards to topography, surcharges, water content, 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: ' Top 4 feet of weathered soils • Soil unit weight: 132 pcf • Angle of internal friction: 32 degrees • Cohesion: 0 psf Soils below upper 4 feet • Soil unit weight: 138 pcf • Angle of internal friction: 38 degrees • Cohesion: 0 psf ' 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. i ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 10 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27.2008 Anticipated building loads,building pad cuts, or impacts from septic drainfields are not expected to have any detrimental influence on the global stability of the slopes, provided that the setback requirements, drainage and all other recommendations in this report are adhered to. Based on the aforementioned Project criteria, observations, slope stability analysis, and the recommendations in this report, the Project has an acceptable factor of safety of over 1.5 relative to deep-seated, static slope failures. Furthermore,an acceptable factor of safety of over 1.1 for seismic conditions was also concluded for this Project. See the slope stability information in Appendix D for input parameters and example of outputs. For this project potential slip planes are naturally confined to the face of the steep descending slope. Because of the soil classifications, slopes are usually considered stable for grades at or less than the angle of repose. Currently,this slope grade is most likely less than the angle of repose. Minimum factor of safeties for static and dynamic conditions at the planned residential location were both estimated to be over 2.0. COD � .rL f• 1 � 111 •y i �r r h.l'■_ L ti 34 ° r7 if r L J �'• r' r: • 6'. ' • 11 17 17 { i t4■ ' 9 f Project v- ' Map from Washington State Department of Natural Resources Website ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 11 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27, 2008 i 4.4.1 Septic Drainfield Impacts The approximate location of the existing 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 the structures near the critical slope. 4.4.2 Building and Footing Setbacks Conservative surcharges from the anticipated site development were used in the slope stability analysis. 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 setback from the face of the nearby descending slopes exceeding 40%. See the figure below and the Geologic Map in Appendix B for an illustration of the setbacks. STRUCTURE TOP OF SLOPE SLOPE FACE I IL—I �— 50 FT MIN —� FOOTING 4.4.3 Temporary and Permanent Erosion Control Based on the USCS description of the Project soils,the surface soils are considered low to moderately erodible. Temporary and/ or permanent erosion control measures may be 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. Erosion control measures may need to be employed if excessive erosion occurs or required by the County or other prevailing agencies. Erosion control during construction should include minimizing the removal of vegetation to the least extent possible. If necessary, erosion control measures during construction may include stockpiling cleared vegetation,silt fencing,intercepting swales,berms,straw ' bales, plastic cover or other standard controls. Silt fencing is presented in this report as the first choice for temporary erosion control. However, multiple erosion control alternatives are provided that may be used for this Project.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 E for sketches and general notes regarding selected erosion control measures. The Site Map in Appendix A depicts ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 12 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 the recommended locations for erosion control facilities to be installed,if necessary. Permanent erosion control may also be necessary if substantial vegetation has not been established within disturbed areas upon completion of the Project. Temporary erosion control should remain in place until permanent erosion control has been established. Permanent erosion control may include promoting the growth of vegetation within the exposed areas by mulching,seeding or an equivalent measure. Selected recommendations for permanent erosion control are provided in Appendix E. 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. Sedimentation control should be adequate when utilizing the erosion control recommendations as presented herein together with implementing appropriate erosion controls with the degree of care as expected from a licensed contractor. Erosion control information and specifications in addition to what is provided in this report may be found in the current "Stormwater Management Manual for Western Washington,"prepared by the Washington State Department of Ecology Water Quality Program. 4.4.4 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 water mitigation will be required. This may include a combination of swales, berms, drain pipes, infiltration facilities, or outlet protection in order to divert water away from the structures. From a geotechnical perspective, both perimeter footing drains and roof drains are optional for the single family residence. If roof drains are not utilized, splash blocks should be placed at all downspouts. If footings are established at depths greater than 2 feet below final grade, then perimeter footing drains are recommended. If utilized, subsurface water intercepted in the perimeter footing drains, and stormwater collected from roof drains shall be tight-lined to an appropriate infiltration area or outlet protection area located downslope and at least 10 feet from any structure. In addition, drainage outlets shall not be within any of the recommended building setbacks or vegetation buffers that are provided in this report. 4.4.5 Vegetation Considerations Vegetation is an excellent measure to minimize surficial slope movements and erosion on slope faces and exposed surfaces. By removing trees, the root strength is decreased over time, thereby lowering the `apparent' cohesion of the soil. Transpiration is decreased, which results in additional groundwater,increased pore water pressure and less cohesion/ ' friction of the soil particles. Stormwater runoff also increases, and, fewer plants will create less absorption of the force from raindrops, thereby creating the potential for erosion hazards. Vegetation shall not be removed on the face of the steep slope, beyond the slope toe, or Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 13 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27,2008 I within 50 feet from 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 Geologic Map in Appendix B of this report for a depiction of the vegetation buffer. 4.4.6 Off-site impacts From a geotechnical position,it is Envirotech's opinion that the adjacent properties to the proposed development should not be significantly impacted if all recommendations in this report are followed. This is based on the expected site development, existing topography,land cover,and the recommendations presented in this report. 4.5 Seismic Considerations and Liquefaction Soils immediately below the expected foundation depth for this Project are generally Type D, corresponding to the International Building Code(IBC)soil profiles. Soils below a depth of 3 feet from the existing ground surface may be considered Type C. 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. There are no known faults beneath this Project. The nearest Class `A' or Class `B' fault to this ' property is the Tacoma Fault Zone, in which is approximately 8 miles to the south of this Project. This information is based on the USGS Quaternary Fault and Fold Database for the United States. ' The potential for liquefaction and other earthquake induced hazards are believed to be low for this Project. This is based, in part, on the slope stability analysis utilizing seismic considerations in addition to 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. 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. ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 14 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County, Washington March 27, 2008 I 5.0 CLOSURE Based on the project information 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. Therefore, it is recommended that a qualified engineer observes and documents the construction, or Envirotech is promptly notified if project and subsurface conditions found on-site are not as presented in this report so that we can re-evaluate our recommendations. 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 protect life and property. Semantics such as `suggested' or `optional' refer that the associated design or specification may or may not be performed. 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 ordinances or regulatory codes, or broadening of accepted geotechnical standards may affect the 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, ' Envrirotech Engineering Michael Staten,P.E. ' Geotechnical Engineer ' Envirotech Engineering Geotechnical Investigation Ph. 360-275-9374 page 15 Parcel 12307 34 90043 Fax: 360-275-4789 Mason County. Washington March 27.2008 0 u e 0 e SCALES 1 INCH = 80 FEET NE MISSION WOOD ROAD 330FT* XISTING DRIVEWAY SEPTI RAINFIELD AREA EXISTING PERTY LINE MOBILE ROPOSED DRIVEWAY �O PROPOSED A TP2 SILT FENCE OR ALTERNATIVE EROSION CONTROL, IF NECESSARY 44 >� TPl 9 D r N, IAtSS1� ��K PROJECT/ OWNER/ LOCATION; ' SINGLE FAMILY RESIDENCE GEOTECHNICAL REPORT JIM SCOTT PARCEL 12307 34 90043 ' NOTES, LEGEND MASON COUNTY, WASHIN GTON 1. EROSION CONTROL MAY BE REQUIRED FOR THIS SITE. GENERAL LOCATIONS, ENGINEERi BE UTILIZE ENXPLAINDINT THE GEOTECHNIVES TO SILTICAL ENCES SILT FENCE ENVIROTECH ENGINEERING REPORT. 74 NE HURD ROAD 2. CONTOURS WERE NOT PREPARED BY A LICENSED LAND SLOPE DIRECT'M BELFAIR, WASHINGTON 98328 ' SURVEYOR. CONTOURS WERE EXTRAPOLATED FROM A PUBLIC ��p� EXISTING CONTOUR 360-275-9374 LIDAR SOURCE, AND INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL REPORT. TPle TEST PIT SITE PLAN APPENDIX B GEOLOGIC MAP APPROXIMATE WATER WELL LOCATION (ADJACENT SCALE- 1 INCH 80 FEET PROPERTY TO NORTH) NE MISSION WOOD ROAD 3 T3 XISTING DRIVEWAY PTI AINFIELD AREA EXISTING OPERTY LINE MOBILE ROPOSED d DRIVEWAY O PR ED A TP2 SOILS] GLACIAL TILL. MEDIUM DENSE SILTY SAND WITH GRAVEL (SM) OVERLYING VERY DENSE SM SOFT ILDING SETBACK AND * VEGE TIVE BUFFER FROM TOP 0 40X+ SLOPE c (SEE OTECHNICAL REPORT) a -- sob I ' TOP OF 40%+ SLOPE Pl 9 TOP OF SLOPE MISSI� LREEK PROJECT/ OWNER/ LOCATIONS t SINGLE FAMILY RESIDENCE GE❑TECHNICAL REPORT JIM SCOTT PARCEL 12307 34 90043 LEGEND MASON COUNTY, WASHINGTON ' ENGINEER] —BUFFER/SET BACK ENVIROTECH ENGINEERING NOTESs 74 NE HURD ROAD L CONTOURS WERE NOT PREPARED BY A LICENSED LAND SLOPE DIRECTION BELFAIR, WASHINGTON 985M SURVEYOR. CONTOURS WERE EXTRAPOLATED FROM A PUBLIC 360-275-9374 t LIDAR SOURCE, AND INCORPORATED FIELD MEASUREMENTS AS --W— EXISTING CONTOUR EXPLAINED IN THE GEOTECHNICAL REPORT. tPt TEST PIT GE❑L❑GIC MAP 0 0 e 0 0 0 0 e B 1 1 1 1 1 1 � 2 § Ze § ■ �im BLiQ� a § d � § 0- ) Ld 0- § »kƒ -� $ -j k LL.U � ` 8� 0 .-J a � o §§§»■ LO Q o�© a� 2 o #� § ■� �® AC$ §k1*1 I k� � � � >� k IM o � � � �d Xj . �L Ll g § IL2 Ge Ge W - k § �§ z & �(■� § m ■ �� x ae ■ z0^Kk o- - � � � TEST PIT LOG TEST PIT NUMBER TP-1 CUENTt, NM,9wU EXCAVATM WA ': ♦ ' • • E • MIT AL DEPTH OF WATER WA RN&DE13TH OF WATM WA - • 1- ©© I molls ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ _ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ mommmm ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ ■■■■■■ c. a • M t C c _ . TEST PIT LOG TEST PIT NUMBER TP-2 PRDJECr. 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HA 96528 fA rrwroMM 4M n 90150"Ic blurt o wr�.I o r4 W LL Los or 4SA/oO�f 13 PAOCEDUFA CEscmgm O DaIA~tm 8wwts O Orrr O wdme OIISMI►awr.d�,�e WM tMwrrrs, *w, M—�rl,�.w�rbdgrb� ad�ttid ar/adM I dr aaMro,r w aa+lAt�owwvftd.�,d baa,as wy br soot C tp YrPeOFwc�c: Rwiaai#memod.d � s.,,,.,.b,.,,,,s AYwtdmudO %WSW 0 , MOW OV13 Otma t wldl 10 0 al"da wd o albry O dMbd OO O I B1 ORi[1 to (SI 0■A�INONEe drttUraaoi Eo,.Ia 450 r ` -- otpwamdpwtdwa� 4 a OONSIM CTIM Davaft � � ` 3 2 ��,r dbml"l ' abs iow t b t� Said & with meter 33 1M�ttYd prw yea, �,b R i p�IIII vb❑ tb a iBrown te TMdPwbrtltrand f S�dOnu,aNmr in by M prMdmMbdn N b sand 180 184 /Mbate„tbew 8 b • prbabm,a but 4 b rObH1 I d MtAdle,..w a... 1 I ha 2.46 ow+_await - wdr Ib Sand 8 _ k6 C Dew.—ammo iamtlpd,td vm Ib[Q &Mal wd i c - � o.ddrbt.dbttt �t. � 264 345 atrbt.d.d ,.. Ma a ltsbdd�p.,� bbdMMatdhatd _ nsita ' � � !—' 1 With water • O CId tnr tbabam,bw aaatlob atd�It rat❑ eb 0 I - Z 'ype°Im^ o.,wd..,t.� 1 n 360 420 fM puw. rr,rr crt.rawtt. j wiith eater 420 450 w VAUM LaV&* Adltbwi__ 4Z.At.r.a...wbi r bbog,dwit ova 1 N.ssbatl a Cww+� O N a pasm Mw.ap�wy Drb`_' V ="*%W ct�N t .d ue�OMMOOM a�W. w odt:Q a d MUTWM orb.ns..wdwwtwtl.Iwwneodwam ," I .aannpabdwdr.a.ru.bwprutlrtt.Itgp«de.rd wraaprpbtta,adfi ri,a❑ Ib® ■Ps 4trroat� ` Msd srMra ws1 R,r.ads.w.r. MAE Dayi AdMe t Belfaix WA 98528 r lFd.a.ta.a.o.b.r0,wpb.dtaev"awl"Mm wdtom...r •ow" Ltant.Ib 1884 Twb MAWLwd Two NabrLs,od am 1MRLad conwcb ft ' �Io�►yDI1100A c,.bi May s 98 . Drrdl.al - IUBE Mdt10N11L SFIEETS IF NECESSMi'Yy . %ftl" .15 _w/sw �t,w� •r•..t.r abw w ac a br Iw s�Equd OppalY.�r end Aefom an�ploydr~ �` IerHtsosrpss pe- Fa..• Dtb i n pan a rd" T..p.abtr.d.rw Nba a aw..pt aadlt,t umw vbt❑ Ib®I 4MIM Tht T=nlmbw is(208)4o7.6M , 12307- oofq-, i APPENDIX D SLOPE STABILITY I I ' STABLE Slope Stability Analysis System New User ' Project : Scott Datafile: Static Bahop #####++***##++**###+*++#*##*+***#+**+*###+++*###++*####**+ SOILS SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT. 1 upper CONTINUOUS-BLACK 0.00 32.0 132.000 2 lower CONTINUOUS-BLUE 0.00 38.0 138.000 PORE PRESSURE SPECIFICATION SOIL PIEZO RU EXCESS Y/N/P Value Value 1 N 0.000 0.000 2 N 0.000 0.000 PIEZOMETRIC SURFACE POINT POINT PORE PRESSURES POINT PRESSURE SLIP DIRECTION (+/- X) _ SLIP-CIRCLES AUTOMATIC Circle Centre Grid Extremities 305.800 # + 32.600 * * 293.400 ' 45.000 X spacing -- no. of cols (max 10)= 10 Y spacing -- no. of rows (max 20)= 20 Grid 1 Circles through point 11 ' Grid 2 Circles through point 12 Grid 3 Circles through point 13 Grid 4 Circles through point 14 Grid 5 Circles through point 15 ' Grid 6 Circles through point 16 Grid 7 Circles through point 17 Grid 8 Circles through point 18 ' Grid 9 Circles through point 19 i 0 0 0 0 0 0 0 0 0 0 0 i I } t + U 02 U D V) J ' •• N r` U Q� ' O 4 >,o s 0DDw LUC: m ' � OQ � 00000000000 0 N �') 1 0 �0 r m m 0 i i U D 0 0 j U) om�o N .. N E 4-1 U — ()o m D� D� � Dca ) P G i 1 1 1 i 1 1 APPENDIX E EROSION CONTROL 1 1 1 1 1 i ' GEOTEXTILE FABRIC 2'x2' MOOD POST CTYP) GEOTEXTILE FABRIC WRAP AROUND TRENCH OR EQUIVALENT OR BETTER AND VIBE MESH TO AT LEAST ENTIRE e 6 FT MAX. OU:. 03 FT BUTTON OF TRENCHBEFORE PLACING GRAVEL 2'x2'x5' WOOD POST OR �-- 6 FT --� ' 12' DEEP. 8' VIDE TRENCH EQUIVALENT OR BETTER EXISTING FILLED WITH 3/4' TO 1 1/2' GROUND SURFACE 2 WASHED GRAVEL OIHECTION W -b 2.5 FT 12' DEEP, 8' VIDE 1 EXISTING TRENCH FILLED WITH WATER FLOW GROUND SURFACE 3/4' TO 1 1/2' Pry FT T &5 FT WASHED GRAVEL BUTTON EXTENTS IF �iLr FENCE - DETAn GEOTEXTILE FABRIC - ' CI TL FENCE C HITS. N-TS- PERMANENT EROSION CONTROL NOTESi GENERAL NOTES, SOD PLACEMENT L SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON L SOD FOR GRASS SWALES SMALL BE MACHINE CUT AT A ' THESE PUGS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR 3/4-INCH UNIFORM THICKNESS AT THE TIME OF CURDa SHALL INSTALL ADDITIONAL. EROSION AND SEDIMENT CONTROL FACILITIES. MEASUREMENTS FOR THICKNESS SHALL EXCLUDE TOP GROWTH AND 2. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE THATCH. INSPECTED DAILY AND IMMEDIATELY MAINTAINED, IP NECESSARY. 2. STANDARD SIZE SECTIONS O' SOD FOR GRASS SWALES SHALL 3. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN BE STRONG ENOUGH TO SUPPORT THEIR OWN WEIGHT AND RETAIN PLACE UNTIL THE UPSLO'E AREAS HAVE BEEN PERMANENTLY STABILIZED. THEIR SIZE AND SHAPE WHEN SUSPENDED BY THE END OF A 3 FOOT SECTION. TEMPORARY EROSION CONTROL NOTES, 3. SOD FOR GRASS SWALES SHALL NOT BE HARVESTED OR ' TRANSPLANTED WHEN EXCESSIVELY DRY OR WET MOISTURE FOR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND CONTENT MAY ADVERSELY AFFECT ITS SURVIVAL- DISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A 4. SOD FOR GRASS SWALES SHALL BE HARVESTED, DELIVERED PERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE AND PLACED WITHIN A PERIOD OT 36 HOURS. IMMEDIATELY STABILIZED WITH MULCHING. GRASS PLANTING OR OTHER APPROVED EROSION CONTROL TREATMENT APPLICABLE TO THE TIME O" YEAR. GRASS SEEDING SEEDING FOR RAW SLOPES ALONE VILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH SEPTEMBER- HOWEVER, SEEDING NAY PROCEED WHENEVER IT IS IN THE INTEREST OF L BEFORE SEEDING, INSTALL HEEDED SURFACE RUNOFF CONTRO THE OWNER/CONTRACTOR. BUT MUST ALSO BE AUGMENTED WITH MJLCKM NETTING MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DICES, OR OTHER APPROVED TREATMENT. SWALES, LEVEL SPREADERS AND SEDIMENT BASINS4 2 THE SEED BED SWILL BE FIRM WITH FAIRLY FINE SURFACE, DRY SEASON (NAY 1 THRU SEPTEMBER 30> -- THE CLEARING IF LAND, INCLUDING THE FilLIM G SURFACE ROJGHEMIM PERFORM ALL OPERATIONS REMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO ACr mg OR PERPENDICULAR TO THE SLOPE ONLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE 3. SEEDING RECOMENDATMNS. AS SHOWN BELLOW, AND SHOULD BE OTHERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , APPLIED AT THE RATE IF LED POUNDS PER ACRE. BY NO LATER THAN SEPTEMBER 30 OR A GIVEN YEAR, UNLESS IMMEDIATE 4. SEED BEDS PLANTED BETWEEN NAY 1 AND OCTOBER 31 WILL STABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO AREAS CLEARED OR OTHERWISE DISTURBED MIST BE APPROPRIATELY STABILIZED FOSTER AND PROTECT THE ROOT STRUCTURE. THROUGH THE USE O" MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS. 5. SEED BEDS PLANTED BETWEEN NOVEMBER 1 AND APRIL 30, FREE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED ARMORING OF THE SEED BED WILL BE NECESSARY, (to, PLAN OF ACTION UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING. GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING)- FERTILIZING AND MULCHING 13F CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE 6- FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS' PERFORMED DURING THE FOLLOWING PERIODSI MARCH I TO MAY 15, AND AUGUST 15 TO RECOMMENDATIONS. AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY OCTOBER L SEEDING AFTER OCTOBER 1 VILL BE DOE WHEN PHYSICAL COMPLETION ADJACENT TO WATER BODIES AND WETLANDS- OF THE PROJECT IS IMMINENT AND THE ENVIRONENTAL CONDITIONS ARE CONDUCIVE TO SATISFACTORY GROWTH- IN THE EVENT THAT PERAMENT STABILIZATION IS NOT USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION POSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER. SUCH AS N LCHING, NETTING, CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE. PLASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY NO LATER THAN SEPTEMBER 30. PROPORTIONS PURITY GERMINATION IN THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT NA14E BY WEIGHT (X) C)D ACTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE co OWNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION AND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT REDTOP (AGROSTIS ALBA) 10 92 LEAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR 90 THE MAINTENANCE AND REPAIR [IF ALL EROSION AN SEDIMENT CONTROL FACILITIES. ANNUAL RYE CLO_IlM MLTIFLORUN) 40 98 WET SEASON (OCTOBER I THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED 90CHEWING FESUE 40 97 CONSTRUCTION ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE 80 REMOVAL O* EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED (FESTUCA RUBRA COMMUTATA) ' M AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN (JAMESTOWN, BANNER, SHADOW, KOCET) THE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT WHITE DUTCH CLOVER 10 96 TRANSPORT OFF-SITE IS OBSERVED. 90 (TRIFOLIUM REPENS) ALL CLEARED ON DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE COVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING. NETTING. PLASTIC MULCHING SHEETING, EROSION BLANKETS, FREE DRAINING MATERIAL. ETC., WITHIN 5 DAYS AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED 7 NOT BEING ACTIVELY WORKED. L MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD SILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC- WILL NOT BE VIEWED AS FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000 ADEQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT POUNDS PER ACRE- BEING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY 2- MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED STABILIZED 5 DAYS AFTER HAVING BEEN CLEARED, ALL CONSTRUCTION ACTIVITY ON SLOPES GREATER THAN 2d (HORIZONTAUVERTICAL). THE SITE. EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL 3. MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN IMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN AREAS WHICH CANNOT BE SEEDED BECAUSE OT THE SEASON. ALL APPROPRIATELY PROTECTED OR STABILIZED. AREAS REQUIRING MULCH SHALL BE COVERED BY MOVEMBER I. SILT FENCE PROJECT/ OWNER/ LOCATB?F L GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE FOR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS 2. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GEOTECHNICAL REPORT EACH BARRIER TO AVOID USE OR JOINTS, IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED JIM SCOTT TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT PARCEL 12307 34 90043 BOTH ENDS TO THE POST. MASON COUNTY, WASHINGTON ' 3 STANDARD FILTER FABRIC SHALL BE FASTENED USING I' STAPLES OR TIE WIRES (HOG RINGS) e 4 IN SPACIWA 4. POSTS SMALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET, AND ENGIMEERs DRIVEN SECURELY INTO THE GROUND. ENVIROTECH ENGINEERING 5. WIRE MESH SWILL BE 2'X2'X14 GAUGE OR EQUIVILENT. THE WIRE MESH MAY BE ELIMINATED IF 74 ME HURD ROAD EXTRA-STRENGTH FILTER FABRIC (MOOFILAMENT), AND CLOSER POST SPACING IS USER BELFAIR, WASHINGTON 98528 6- A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LIME OF THE 360-275-9374 POSTS AND UPSLORE FROM THE SILT FENCE. 7. SILT FENCES SHALL BE LOCATED DOVNSLOPE FROM THE CLEARING LB4ITS OF THE PROJECT. EROSION CONTROL 'I MASON COUNTY PLANNING GEO TECH WORK ORDER CONSULTANT ALKAI CONSULTANTS,LLC 9465 PROVOST ROAD NW, SUITE 202 SILVERDALE,WA 98383 PERMIT # 9 - 00 t-7 0 APPLICANT DATE MAILED. ' d PLANNER C---4 c,Z- AMOUNT BILLED ADDITIONAL COMMENTS "Please fill out the cost of the review and return this form and the report to us with your recommendations.