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BLD2024-00928 Geotechnical Report SFR - BLD Engineering / Geo-tech Reports - 11/30/2023
PLANNING Geotechnical Report Harvey Residence 51 N Hidden Cove Lane, Lilliwaup Parcel No. 32424-22-00040 Mason County, Washington November 30, 2023 Project#23347 Prepared For: Barbara Harvey 2673 NW Nordeen Way Bend, Oregon 97703 Prepared By: Envirotech Engineering, PLLC PO Box 984 Belfair,Washington 98528 Phone: 360-275-9374 4 cLvn� 43b45 SS/FINAL 11/30/23 MASON COUNTY Submittal Ci COMMUNITY SERVICES Geotechnical Report 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 Barbara Harvey Parcel#32424-22-00040 Site Address 51 N Hidden Cove Lane, Lilliwaup (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) Geotechnical Site Plan—Appendix A (3) Locations and logs of exploratory holes or probes. Located on Map(s) Geotechnical 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) Geotechnical Site Plan (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which incorporates the details of proposed grade changes. Located on Map(s) Soil Profile (Appendix B) (6) A description and results of slope stability analyses performed for both static and seismic loading conditions.Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of Circles.The minimum static safety factor is 1.5,the minimum seismic safety factor is 1.1,and the quasi-static analysis coefficients should be a value of 0.15. Located on page(s) 10 Page 1 of42 (7) (a) Appropriate restrictions on placement of drainage features, Located on page(s) 19 (b) Appropriate restrictions on placement of septic drain fields, Located on page(s) 20 (c) Appropriate restrictions on placement of compacted fills and footings, Located on page(s) 14 and 16 (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) 19 (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) 18 (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) 19 (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) 13 (11) Specifications of final development conditions such as,vegetative management,drainage,erosion control,and buffer widths. Located on page(s) 14-20 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) 20 (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) Geotechnical 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 cL)np s Report,dated November 30, 2023 ,and entitled �� �`• 1 Harvey Residence meets all the requirements of the Mason County Resource Ordinance, Geologically Hazardous Areas Section, is complete and true,that the assessment demonstrates conclusively that the risks posed by the landslide l l/30/23 hazard can be mitigated through the included geotechnical Disclaimer:Mason County does not design recommendations,and that all hazards are mitigated in certify the quality of the work done in such a manner as to prevent harm to property and public this Geotechnical Report. health and safety.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 TOPOGRAPHY.....................................................................................................................................3 2.1.1 Upslope Geomorphology............................................................................................................3 2.2 SURFACE DRAINAGE..........................................................................................................................3 2.2.1 Upland Water Bodies.................................................................................................................3 2.3 SLOPE AND EROSION OBSERVATIONS...............................................................................................3 3.0 SUBSURFACE INVESTIGATION.....................................................................................................5 3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5 3.2 GEOLOGIC CONDITIONS....................................................................................................................5 3.3 SPECIFIC SUBSURFACE CONDITIONS.................................................................................................6 3.3.1 Groundwater............................................................................................................................... 7 4.0 ENGINEERING ANALYSES AND CONCLUSIONS......................................................................8 4.1 SLOPE STABILITY...............................................................................................................................8 4.1.1 Slope Stability Analysis.............................................................................................................. 9 4.2 EROSION............................................................................................................................................10 4.2.1 Shoreline Recession..................................................................................................................11 4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION..............................................................................11 4.3.1 Liquefaction..............................................................................................................................11 4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS........................................................12 4.5 LATERAL EARTH PRESSURES...........................................................................................................12 4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................13 5.0 ENGINEERING RECOMMENDATIONS........................................................................................14 5.1 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................14 5.1.1 Bearing Capacity.......................................................................................................................14 5.1.2 Settlement..................................................................................................................................15 5.1.3 Concrete Slabs-on-Grade..........................................................................................................15 5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................15 S.2.1 Excavation.................................................................................................................................15 5.2.2 Placement and Compaction of Native Soils and Engineered Fill...........................................16 5.2.3 Retaining Wall Backfill.............................................................................................................17 5.2.4 Wet Weather Considerations....................................................................................................17 5.2.5 Building Pads............................................................................................................................18 5.3 BUILDING AND FOOTING SETBACKS.................................................................................................18 5.4 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................18 5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................19 5.6 TEMPORARY AND PERMANENT EROSION CONTROL.......................................................................19 5.7 SEPTIC DRAINFIELDS........................................................................................................................20 5.8 STRUCTURAL MITIGATION...............................................................................................................20 6.0 CLOSURE.............................................................................................................................................21 Appendix A-Geotechnical Site Plan Appendix B-Soil Information Appendix C-Slope Stability Appendix D-Erosion Control Appendix E-Drainage Details 1.0 INTRODUCTION Envirotech Engineering, PLLC. (Envirotech) has completed this geotechnical report for a property located at 51 N Hidden Cove Lane, Lilliwaup, identified as parcel number 32424-22-00040 in Mason County, Washington. 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. An initial geotechnical evaluation of the project was conducted by Envirotech on November 21, 2023. 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) 8.52.140. 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. 1.1 Project Information Information pertaining to the project was provided by the proponent of the property, and observations from a field visit by Envirotech. The proposed development is expected to consist of a single family residence, and other ancillary features typical of this type of development . Approximate site development footprint with relation to existing geological site features are illustrated in the Geological Site Plan in Appendix A of this report. 1.2 Purpose of Investigation and Scope of Work The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the project in order to provide geotechnical recommendations that should be implemented during development. The investigation included characterizing the general project surface and subsurface conditions, and evaluating the suitability of the soils to support the planned site activities. In order to fulfill the purpose of investigation, the geotechnical program completed for the proposed improvements of the project include: Envirotech Engineering Geotechnical Report PO Box 984 page 1 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 • Review project information provided by the project owner and/ or owner's representative; • Conduct a site visit to document the site conditions that may influence the construction and performance of the proposed improvements of the project; • Define general subsurface conditions of the site by observing subsoils within test pits and/ or cut banks, review geological maps for the general area, research published references concerning slope stability, and review water well reports from existing wells near the project; • Collect bulk samples, 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. -------------------- - ------------------------------------- i i i i 1 i ,i Project r ! L------------------------------ Vicinity Map from Mason County Website Envirotech Engineering Geotechnical Report PO Box 984 page 2 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 2.0 SURFACE CONDITIONS Information pertaining to the existing surface conditions for the project was gathered on November 21, 2023 by a representative with Envirotech. During the site visit, site features were documented that may reveal potential geological hazards. This Surface Conditions Section provides information on topography, drainage and slope/ erosion conditions for the project and surrounding areas. An aerial photo of the project and immediate vicinity is provided on the following page. 2.1 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 Geological Site Plan in Appendix A for an illustration of the general slope indicators with respect to the planned development. Maximum sloping grades within 300 feet of the proposed development area with a vertical relief in excess of at least 10 feet were observed to be 91%. 2.1.1 Upslope Geomorphology The landform that is upland from property is considered a hillside knoll, and crest of volcanic origin with centuries of weathering overburden. Additional geomorphology that is pertinent to both upslope and downslope areas are provided in the Subsurface Investigation Section of this report. 2.2 Surface Drainage The majority of the stormwater runoff originating upslope from the anticipated development is expected to be minimal to moderate . Significant scour, erosion and sediment transport was not apparent near the project. 2.2.1 Upland Water Bodies There are no apparent water bodies or wetlands located upslope from the planned development that would significantly influence the project. 2.3 Slope and Erosion Observations The existing moderate slopes near the project signal a potential landslide or erosion hazard area. Some indicators that may suggest past slope movements include: Envirotech Engineering Geotechnical Report PO Box 984 page 3 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 November 30, 2023 • Outwash of sediments near the bottom of the slope, • 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. These slope instability indicators or other significant mass wasting on the property or within the general vicinity of the project were not observed. Indications of past landslides, current unstable slopes, deep-seated slope problems, or surficial slope failures were not observed during the site visit. 45 N HID DEN'COVE LN ^ky 51 N FIIDDEN COVE LN 4 Aerial Photo from Mason County Website Envirotech Engineering Geotechnical Report PO Box 984 page 4 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 3.0 SUBSURFACE INVESTIGATION Information on subsurface conditions pertaining to the project was gathered during research and a site reconnaissance. The site visit was accomplished on November 21, 2023 by a representative 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. See Appendix B for a soil profile cross-sections, soil logs, and other appropriate information as necessary. 3.1 Field Methods,Sampling and Field Testing Information on subsurface conditions for the project was accomplished by probing anticipated foundation areas with hand tools, and observing soils within test pit excavations and/ or earth cuts. Information on subsurface conditions also included reviewing geological maps within the project vicinity, and water well reports originating from nearby properties. No soil samples were collected for this project. Envirotech measured the relative density of the in-situ soils by gauging the resistance of hand tools. 3.2 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. More specifically for the project location, a caption from the Washington State Department of Natural Resources is as follows: Map Unit: Ev(c) Age: Eocene GeoMaterial: Extrusive igneous material Description: Tholeiitic basalt flows, basaltic flow breccia, filled tubes, and volcaniclastic conglomerate; gabbro dikes and sills; locally contains thin interbeds of basaltic tuff, chert, red argillite, limestone, and siltstone; rare andesite, dacite, and rhyolite; marine, pillow-dominated lower part grades into flow-dominated, partially non-marine near top with local columnar jointing;altered to palagonite, chlorite, zeolite, or epidote. Envirotech Engineering Geotechnical Report PO Box 984 page 5 Parcel 32424-22-00040 Betfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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. The project is primarily composed of undisturbed, native soils, without indications of substantial fill. Within native, undisturbed areas, competent bearing soils were encountered at 12 inches below the existing ground surface in locations where the ground was probed. For engineering purposes, these native soils consist of distinguishable layers, as presented below. Soils within the upper 2 feet of natural ground were observed to be primarily moist, brown silty sand with gravel (SM) . Soils below this upper soil strata were observed to be weathered basalt bedrock. The bedrock is believed to extend to depths of at least 50 feet. This is based on nearby well reports, site geology, and/or knowledge of the general area. Not withstanding the potential for any old fill, the relative densities are suitable for foundations as provided above. Expanded and specific subsurface descriptions, other than what is provided in this section, are provided within additional soil information 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 (SCS), the site soils are described as Grove gravelly sandy loam with 5% - 15% slopes. See the soil map below. Envirotech Engineering Geotechnical Report PO Box 984 page 6 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 R„ r s .,aix'.',• .6 Soil Survey From USDA Natural Resources Conservation Service 3.3.1 Groundwater From the water well report(s) and knowledge of the general area, permanent groundwater is at least 50 feet below the current ground surface. 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 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 `Unstable' regarding potential landslide activity. Descriptions of these mapping units may be found in the aforesaid Atlas. A Stability Map from the Coastal Zone Atlas for the general area of this project is provided below: Project Map from Washington State Department of Ecology Website Envirotech Engineering Geotechnical Report PO Box 984 page 8 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 According to the Resource Map from the Washington State Department of Natural Resources (DNR), the project is not within terrain labeled `highly unstable' relating to soils. DNR did not label portions of this project as medium and high slope instability with relation to slopes. A Resource Map from the DNR Forest Practices Application Review System is provided below: Project if r ar 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: Envirotech Engineering Geotechnical Report PO Box 984 page 9 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 Upper 4 feet soil depth Soil unit weight: 132 pcf Angle of internal friction: 30 degrees Cohesion: 200 psf Soils below 4 feet in depth Soil unit weight: 140 pcf Angle of internal friction: 40 degrees Cohesion: 400 psf Based on the slope stability analysis, unacceptable factors of safety could be present on and near the critical slope, but do not reflect conditions where development is expected to occur. For this project, at the location of the proposed development, minimum factor of safeties for static and dynamic conditions were estimated to be 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 Envirotech Engineering Geotechnical Report PO Box 984 page 10 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 Management Manual for Western Washington," prepared by the Washington State Department of Ecology Water Quality Program. 4.2.1 Shoreline Recession Due to the close proximity of a shoreline, an evaluation of the shoreline recession rate for this project was completed. This was accomplished by interviewing property owners within the vicinity of the project, and/or carefully reviewing and comparing historical aerial photographs of the project. Historical aerial photograph sources may be found in the 1951 aerial for the Soil Survey of Mason County, aerials from the Washington State Department of Ecology, and from the Washington State Department of Natural Resources website. Based on available information, we conclude that the past shoreline recession for this project is less than 5 feet in 50 years. 4.3 Seismic Considerations and Liquefaction There are no known faults beneath this project. The nearest Class `A' or 'B' fault to this property is the Hood Canal Fault Zone , which is not located on the property or adjacent properties. This information is supported by the USGS Quaternary Fault and Fold Database for the United States. Potential landslides due to seismic hazards have been considered, and are addressed in the Slope Stability Analysis Section provided earlier in this report. Soils immediately below the expected foundation depth for this project are generally Type D, corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the regional seismic zone is 3 for this project. The estimated peak ground acceleration ranges from 0.50g to 0.60g. This estimation is based on the United States Geological Survey (USGS) National Seismic Hazard project in which there is an estimated 2% probability of exceedance within the next 50 years. 4.3.1 Liquefaction The potential for liquefaction is believed to be low 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. Envirotech Engineering Geotechnical Report PO Box 984 page 1 l Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 4.4 Landslide,Erosion and Seismic Hazards Conclusions DNR did not indicate historic landslide activity near the project. Mapped slope conditions, as delineated by the Departments of Ecology and/or Natural Resources, were considered in our slope stability assessment. Based on the proximity and severity of mapped delineations with respect to the proposed development, results of the aforesaid slope stability analysis, observed surface conditions, and other pertinent information, it is our opinion that the proposed development may occur in accordance with the recommendations in this geotechnical report. 4.5 Lateral Earth Pressures Retaining walls may be utilized for this project. The lateral earth pressures exerted through the backfill of a retaining wall are dependent upon several factors including height of retained soil behind the wall, type of soil that is retained, degree of backfill compaction, slope of backfill, surcharges, hydrostatic pressures, earthquake pressures, and the direction and distance that the top of the wall moves. An equivalent fluid unit weight used for structural design may be estimated as the product of the backfill soil unit weight and the earth pressure coefficient for at-rest pressures. Retaining walls should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of the following: At-Rest Active Native Soils 49 pcf 32 pcf Engineered Fill Soils 45 pcf 28 pcf The values provided above shall be increased by 1 pcf for every 1 degree of backfill/ natural slope angle. These equivalent fluid unit weight values do not include lateral earth pressures induced by earthquakes, groundwater, or surcharges from live loads. Earthquake pressures should be added to the wall analysis, and treated as an inverted pressure triangle where the resultant pressure is located at 2/3 of the wall height, or other method approved by a structural engineer. The following resultant earthquake pressures as a function of the wall height(H) may be utilized: At-Rest Active Native Soils 15AH psf 9.8H psf Engineered Fill Soils 13.6H psf 8.211 psf Envirotech Engineering Geotechnical Report PO Box 984 page 12 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 November 30, 2023 See the Earthwork Construction Recommendations Section for details concerning the use of native soils, engineered fill and placement of backfill. 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 13 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 The recommended allowable bearing capacities and settlements as presented below, consider the probable type of construction as well as the field investigation results by implementing practical engineering judgment within published engineering standards. Evaluations include classifying site soils based on observed field conditions and soil testing for this project. After deriving conservative relative densities, unit weights and angles of internal friction of the in-situ soils, the Terzhagi ultimate bearing capacity equation was utilized for determining foundation width and depth. Foundation parameters provided herein account for typical structural pressures due to the planned type of development. A structural analysis is beyond the scope of a geotechnical report, and a structural engineer may be required to design specific foundations and other structural elements based on the soil investigation. Stepped foundations are acceptable, if warranted for this project. Continuous, isolated, or stepped foundations shall be horizontally level between the bottom of the foundation and the top of the bearing strata. The frost penetration depth is not expected to extend beyond 12 inches below the ground surface for this project under normal circumstances and anticipated design features. 5.1.1 Bearing Capacity Existing in-situ soils for this project indicates that the structure can be established on shallow, continuous or isolated footings. Foundations shall be established on relatively undisturbed native soil that is competent and unyielding. Alternatively, foundations may be constructed on selective re-compacted native soil or compacted engineered fill as described in the Earthwork Construction Recommendations Section of this report. For a bearing capacity requirement of no more than 1500 psf, a minimum continuous footing width of 12 inches shall be placed at a minimum of 12 inches below the existing ground surface atop unyielding soils and away from any potential old fill or disturbed soils. If setback encroachment is necessary, deeper Envirotech Engineering Geotechnical Report PO Box 984 page 14 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 foundation depths are required as outlined later in this report. Foundation recommendations are made available based on adherence to the remaining recommendations that are provided in this report. Alterations to the aforementioned foundation recommendations may be completed upon a site inspection by a geotechnical engineer after the foundation excavation is completed. 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, old fills/ disturbed soils 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, Envirotech Engineering Geotechnical Report PO Box 984 page 15 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 November 30, 2023 saturated, not as described in this report, or otherwise incompetent due to inappropriate land disturbing, or excessive water trapped within foundation excavations prior to foundation construction. All soils below the bottom of the excavation shall be competent, and relatively undisturbed or properly compacted fill. If these soils are disturbed or deemed incompetent, re-compaction of these soils below the anticipated footing depth is necessary. Excavations shall be completely dewatered, compacted, and suitable before placement of additional native soil, engineered fill or structural concrete. 5.2.2 Placement and Compaction of Native Soils and Engineered Fill For engineered fill or disturbed native soils that will be utilized as fill material directly beneath foundations, observation and/ or geotechnical testing is required prior to 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 _III I UNDISTURBED SUBGRA)lE 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 Envirotech Engineering Geotechnical Report PO Box 984 page 16 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 and permanent earth cuts and fill slopes exceeding 4 feet in height should be limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined excavations exceeding 4 feet should conform to OSHA safety regulations. Permanent cut and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an engineer. 5.2.3 Retaining Wall Backfill 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 '/2 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 Envirotech Engineering Geotechnical Report PO Box 984 page 17 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 10 feet. All footings shall be located at least 5 feet away from the top of the engineered fill slope. See the diagram below for a depiction of fill pads for structural support. 5.3 Building and Footing Setbacks Provided that assumptions relating to construction occur and recommendations are followed as presented in this report, the factor of safety for slope stability is sufficient for a 20 feet footing setback from the face of the nearby descending slopes exceeding 40%. See the figure below and the Site Plan in Appendix A for an illustration of the setbacks. STRUC'ruRE TOP ❑F S"OPE - SLOP - - -- -- - FACE._-j X _ _ - - - SETBACK I -- FOOTING Structures may be located closer to the top of slope by extending the portions of the foundation that encroaches the setback to depths provided herein. For setback encroachments of no closer than 10 feet from the top of slope, foundations should extend to the underlying bedrock. For setback encroachments between 5 feet and 10 feet from the top of critical slope, foundations should penetrate the upper layer of weathered bedrock, and bear on hard, sound bedrock. Setback encroachment of 5 feet should not be permitted. Weathered bedrock was tested to be 2 feet deep in one location, and could be deeper within the planned structural footprint. Weathered bedrock is typically 6 inches to 18 inches in thickness. 5.4 Surface and Subsurface Drainage Envirotech Engineering Geotechnical Report PO Box 984 page 18 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 if the total new structural footprint is less than 1000 sf. Recommended drainage details are provided in Appendix E of this report for this case. If roof areas add up to over 1000 sf, then runoff should be tightlined to the toe of slope with an approved energy dissipator. Any roof area located more than 50 feet from the top of slope only requires splash blocks. 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 5 feet beyond the top of the slope. However, any tree deemed hazardous to life or property shall be removed. If tree removal is necessary, then stumps and roots shall remain in place, and the underbrush and soil shall remain undisturbed as much as possible. Any disturbed soil shall be graded and re-compacted in order to restore the terrain similar to preexisting conditions and drainage patterns. See the Site Plan in Appendix A of this report for a depiction of the vegetation buffer. 5.6 Temporary and Permanent Erosion Control Erosion control during construction should include minimizing the removal of vegetation to the least extent possible. Erosion control measures during construction may include stockpiling cleared vegetation, silt fencing, intercepting swales, berms, straw bales, plastic cover or other standard controls. Although other controls may be used, if Envirotech Engineering Geotechnical Report PO Box 984 page 19 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 Drainfields 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 including maintaining drainfields behind the geotechnical setback without further geotechnical considerations. 5.8 Structural Mitigation Unless setbacks are encroached as provided earlier in this report, 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. Setback encroachments require deeper foundations per Section 5.3 of this report. Envirotech Engineering Geotechnical Report PO Box 984 page 20 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 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 i1� 5 Michael Staten, P.E. Geotechnical Engineer Envirotech Engineering Geotechnical Report PO Box 984 page 21 Parcel 32424-22-00040 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 November 30, 2023 APPENDIX A GEOTECHNICAL SITE PLAN SCALE. Vl--'H=67 FEET PC' BUILDINC. SETBACK FROM TOP OF SLOPE EXCEEDING 407 ',WITHOUT MITIZATION, MAY ENCROACH SETBACK 'ER GEOTECHNICAL REFOR7. 5' VEGETATION BUFFER FROM TO� OF SLOPE EXCEEDING 40% APPROXIMATE TOE 'IF SLOPE EXCEEDING 40% 42 070 51 N HIDDEN COVE LIN F-FRO)KIY4TE TOF OF 2 4748"see g, "LOPE F'X(:EEI)IN(, IC:/ -PROPOSED ('AFIl\ (TY') 91 N HIDDEN COVE LN 413 L ETXE3LZlM --DNTNOL MAY BE R=UIRED FOR lH:S SITE,t04ERAL LOCA72OWS ARE DEpirrEt, ANE ALTERNATIVES MAY BE J71LIZEL AS EXPLAMI)N T}E GE13TECHN3C-L REPOQ- -COVTORS WERE %0T PRE)lxrEI) By 4 LEC04SED LAND aR,EyaR cavmim: MERE Fx-;iApj3Li%TEv FRa4 A FLIBLY. Ljr.AR SOLRCE,AMP INCERP[144TEC FIELD MEASLJFEREVTS AS E-XPLAINEt EN THE UEEITEZHNILAL LEGEND 3. DO-NDARIES WERE NOT KEPAQED 01 OL LI'ENSED SURVEYOR LOCArMNS T`E ENGINEER, OF SITE FEATLRES THAT ARE SHOWN FERE.SU-N AS TIP CF SLOPES, TOE + -WCRARY 0 OF rLOOPE.S,vAm; rEATLRE.'.ME- WITH RELA710% To THE -iopog- EROSID4 cONrR ENV7OTF-rH OsGINECRIlk- L]Nr-s 4-sr BE VER IF3ED BY THE OVNER. REZ13HIENDA73ONS (N THE po FOX W4 c,r -ROV3EE SET A-KS. R-FFERS, CEPTHS, ETI- WITH W-U-L INDX,4mR DELFAIR, VASHINGTON %�i28 RrETTECHN'CAL -EPERIC 0 _LA7rO% TO GEOLD: FEAP-RES.NOT PROPEQT' LINES.THESE C&OLILIC --oc ExiSTIN:i :D%T[RJZ. FE-TURES, -A- BE LOCATES 01 THE SLI)JECT PROPERTY EP -ENKE(OREm- -pie TEST-I- SITE PLAN PROPERTIES. I I APPENDIX B SOIL INFORMATION WX-a:FFET lL c- EXISTING GRADE DR❑P❑SED HOUSE WEATHERED AND STRONG h❑❑D BASALT BEDROCK CANAL SECTION A-A wrcz EN.'SIEZR• U •3hOk GR-ME CHMGES REAUECE➢IN DRIER TO ACHIEVE ''OS(TIVE DapIMGE --Q BOX E984 ENCS>EfRING 'E FAI ?84 7� OBSERVED TEST ]i A&I THE FOR 'HE rEPIHICA E ➢f-27: vFSHEv'TON 905sv THC kDEPTHS ARE " sT THE SCaLO*.L LL7::AT[LA S' -�?g9774 LO•rEk DEPTHS ARE b)d ON iITE oFaO:r, WELL LOGtS>. NNMR EXPEkEEN=E EN THE M-,EkAL-Rr-, S❑IL ! ROFILE TEST PIT LOG TEST PIT NUMBER TP-1 PROJECT; Harvey Geotechnical Repor. DATE OF LOG: 11/21Y2023 PROJECT NO: 23347 LOGGED BY: MCS CLIENT; Barbara Harvey EXCAVATOR: NIA LOCATION; 51 N Hidden Cove Lane DRILL RIG; None Mason County,WashlnTJton ELEVA I ION: NiA INITIAL DEPTH OF WATER: NIA FINAL DEPTII OF WATER; NIA SOIL STRATA., FANP ,AR7Pr NETRATIoN TEST ULI, Ft SAMPLERS ItsCS DESCRIPTION -'I CURVE AIND TEST DA-rA ULI'I I fJ 10 30 +,n .................................................. SVI 10edlun,t rnvm,molst,loose to medlum ;. dense SII_l Y SAN-)valth gravel.Sand IF. mostly medlum,Gravel Is pdmadly course and subrcurced.No plasticlp(. Basalt bedrock Excavatlon terminated at aoproxlmately 4 feet e 7 No GroundwaterEncountereo ENVIROTLCH LNGINLLRING 1Ns^:ra mar,'Feaams m.r/rc "Is to—q ssd novae Gcotochnlcal E^glnocring I.'IrC(1lCICL Hi Me APPENDIX C 0 0 o 0 0 0 0 0 0 0 -1 (7 1 L w l` CD Ili O r • r i t 0 0 0 0 0 0 0 0 0 0 0 -4 N M w wr% 0 0 O -i *i -4 r{ -1 ^I -i ^I ri (I I v i f 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, 8' WIDE TRENCH EQUIVALENT OR BETTER FILLED WITH 3/4' TO 1 1/2' WASHED GRAVEL OR VEGETAT�N 23 FT DIRECTION OF — EXISTING WATER FLOW GROUND SURFACE 1 23 FT SILT_FENCE — CROSS SECTION N.T.S. 2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC OR EQUIVALENT OR BETTER AND WIRE MESH @ 6 FT MAX. O.C. I {-- y FT I F -- EXISTING — GROUND SURFACE 12' DEEP, 8' WIDE z TRENCH FILLED WITH 3/4' TO 1 1/2' 1 zs FT WASHED GRAVEL OR VEG TI 11 BOTTOM EXTENTS OF GEOTEXTILE FABRIC SILT FENCE — DETAIL N.T.S. PROVIDE FULL WIDTH 3/4 IN TO 1 1/2_�[N,� _ INGRESS/EGRESS CRUSHED GRAVEL PLACED AT 6 IN MINIMUM DEPTH WELL—DRAINED SOILS —0.02 IN/MIN FuLL LENGTH R=25 FT MIN 4 — ACCETS RrUD STABILIZED CONSTRUCTION ENTRANCE N.T.S. PERMANENT EROSION CONTROL NOTES. ENERAL NOTES, SEEDING FOR RAW SLOPES SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON .ESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR 1, BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL MALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES, .ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE SWALES, LEVEL SPREADERS AND SEDIMENT BASINS. INSPECTED DAILY AND IMMEDIATELY MAINTAINED,IF NECESSARY. 2.THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE, 3.ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN FOLLOWING SURFACE ROUGHENING,PERFORM ALL OPERATIONS ACCROS LACE UNTIL THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED, OR PERPENDICULAR TO THE SLOPE, 3,SEEDING RECOMMENDATIONS,AS SHOWN BELOW, AND SHOULD BE EMPORARY EROSION CONTROL NOTES. APPLIED AT THE RATE OF 120 POUNDS PER ACRE. 4, SEED BEDS PLANTED BETWEEN MAY 1 AND BETOBER 31 WILL OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A FOSTER AND PROTECT THE ROOT STRUCTURE. ERIOD EXCEEDING THE LISTED CRITERIA BELOW,ALL DISTURBED AREAS MUST BE 5.SEED BEDS PLANTED BETWEEN NOVEMBER i AND APRIL 30, MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED ARMORING OF THE SEED BED WILL BE NECESSARY, (e4}, ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR. GRASS SEEDING GEOTEXTILES, JUTE HAT, CLEAR PLASTIC COVERING). LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH 6.FERTILIZERS ARE TO BE USED ACCOIRDING TO SUPPLIERS' EPTEMBER. HOWEVER. SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF RECOMMENDATIONS, AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING. NETTING ADJACENT TO WATER BODIES AND WETLANDS. R OTHER APPROVED TREATMENT. USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION RY SEASON(HAY 1 TWU SEPTEMBER 30) --THE CLEARING OF LAND. INCLUDING THE CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER,MUST BE LIMITED TO WILY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE PROPORTIONS PURITY GERMINATION THERVISE STABILIZED,AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , NAME BY VEIGHT(Y.) (Y) I%) Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR,UNLESS IMMEDIATE TABUZATI134 IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL REDTOP (AGROSTTS ALBA) 10 92 90 REAS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ANNUAL RYE(LOLIUM MULTIFLORUM) 40 98 90 ROUGH THE USE OF MULCHING,NETTING, PLASTIC SHEETING,EROSION BLANKETS, CHEWING FESUE 40 97 80 FEE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED (FESTUCA RUBRA COMMUTATA) LAN OF ACTION UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, (JAMESTOWN, BANNER, SHADOW, KOkET) ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE WHITE DUTCH CLOVER 10 96 90 ERFORMED DURING THE FOLLOWING PERIODS.MARCH 1 TO MAY 15,AND AUGUST 15 TO (TRIFOLIUM REPENS) CTOBER L SEEDING AFTER OCT13BER 1 WILL BE DONE WHEN PHYSICAL COMPLETION F THE PROJECT 1S IMNINENTT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE MULCHING 0 SATISFACTORY GROWTH IN THE EVENT THAT PERANENT STABILIZATION IS NOT OSSIBLE, AN ALTERNATIVE METHOD CF GROUND COVER, SUCH AS MULCHING, NETTING,1,MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD LASTIC SHEETING. EROSION BLANKETS. ETC., MUST BE INSTALLED BY NO LATER THAN FIBER CELLULOSE. AND SHOULD BE APPLIED AT A RATE OF 1000 EPTEMBER 30. POUNDS PER ACRE. 2,MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES N THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT GREATER THAN 2,1 (HORIZONTAL-VERTICAL). CTIVIT/ES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE 3,MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN VNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON,ALL ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1, EAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. TOPSOILING ET SEASON (OCTOBER 1 THRU APRIL 30)--ON SITES WHERE UNIINTERUPTED 1. TOPSOIL SHOULD BE USED FOR THIS PROJECT DUE TO HIGHLY ONSTRUCTION ACTIVITY IS IN PROGRESS.THE CLEARING OF LAND, INCLUDING THE DENSE EXPOSED SOILS. EMQVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED 2, TOPSOIL SHOULD BE PLACED ON SLOPES NOT EXCEEDING 2.1. 0 AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN I STRIPPING AND STOCKPILING ON-SITE SOILS SHALL ONLY BE HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT PERMITTED IF TOPSOIL IS FRIABLE AND LOAMY (LOAM, SANDY LOAM, RANSPORT OFF-SITE IS OBSERVED, SILT LOAM, SANDY CLAY LOAM, CLAY LOAM), L CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE 4. STRIPPING SHALL BE CONFINED TO THE IMMEDIATE CONSTRUCTION AVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC AREAS. A VA TO SIX INCH STRIPPING DEPTH IS COMMON, BUT MEETING. EROSION BLANKETS, FREE DRAINING MATERIAL,ETC., WITHIN 5 DAYS AFTER DEPTH MAY RUNOFF DEPENDING RU THE S SHALL BE SOIL. ALL AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED, SURFACE RUNOFF CONTROL STRUCTURES SHALL BE IN PLACE BEFORE ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS,ETC., WILL NOT BE VIEWED AS STRIPPING. DEOUATE COVER IN AND OF THEMSELVES, IN THE EVENT THAT ANY LAND AREA NOT 1NG ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY TABILIZED 5 DAYS AFTER HAVING BEEN CLEARED,ALL CONSTRUCTION ACTIVITY ON HE SITE,EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL MMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN PPROPRIATELY PROTECTED OR STABILIZED. STaKPIE NANAGCMENT L STOCKPILE SWILL BE STABILIZED(VITM PLASTIC COVERING OR OTHER APPROVED DEVICE)DAILY BETWEEN NOVEMBER 1 AND MARCH 31. 2.IN ANY SEASON, SEDIMENT LEACMOHG FROM STOCK PILES MJST BE PREVENTED. 31 TOPSOIL SMALL NOT BE PLACED WHILE IN A FRIZEN OR MUDDY CONDITION,WHEN THE SUBGRADE IS FxCESSIVELY WET,ON vwE [1NpITIONS FxIST THAT MAY OTHERWISE BE DETRIMENTAL TO PROPER GRADING OR PROPOSED SODDING OR SEEDING, 4,PREVIOUSLY ESTABLISHED GRADES ON THE AREAS 70 BE 713PSOILED SHALL BE MAINTA➢ED ACCORDING TO THE APPROVED PLAYS, STABILIZED CONSTRUCTION ENTRANCE 1. MATERIAL SHALL BE 4 INCH TO B INCH QUARRY SMALLS (4 TO 6 INCH FOR RESIDENTIAL SINGLE FAMILY LOTS)AND MAY BE TOP-DRESSED WITH 1 INCH TO 3 INCH ROCK (STATE STANDARD SPECIFICATIONS, SECTION 8-15.) 2.THE ROCK PAD SHALL BE AT LEAST 12 INCHES THICK AND 50 FEET LONG <20 FEET FOR SITES WITH LESS THAN 1 ACRE OF DISTURBED SOIL). WIDTH SHALL BE FULL WIDTH OF THE VEHICLE INGRESS AND EGRESS AREA. SMALLER PADS MAY BE APPROVED FOR SINGLE-FAMILY RESIDENTIAL AND SMALL COMMERCIAL SITES. 3.ADDITIONAL ROCK SHALL BE ADDED PERIODICALLY TO MAINTAIN PROPER FUNCTION OF THE PAD. 4.IF THE PAD DOES NOT ADEQUATELY REMOVE THE MUD FROM THE VEHICLE WHEELS. THE WHEELS SHALL BE HOSED OFF BEFORE THE VEHICLE ENTERS A PAVED STREET.THE WASHING SHALL BE DONE ON AN AREA COVERED WITH CRUSHED ROCK AND WASH WATER SHALL DRAIN TO A SEDIMENT RETENTION FACILITY OR THROUGH A SILT FENCE. ILT FENCE GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL OR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS RELL CUT TO THE LENGTH OF H BARRIER TO AVOID USE OF JOINTS,IF JOINTS ARE NECESSARY.FILTER FABRIC SHALL BE SPLICED OGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT OTH ENDS TO THE POST. .STANDARD FILTER FABRIC SHALL BE FASTENED USING V STAPLES OR TIE WIRES (HOG RINGS) B 4 IN PACING. POSTS SMALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET, AND IVEN SECURELY INTO THE GROUND. WIRE MESH SHALL BE 2'X2'X14 GAUGE OR EQUIVILENT, THE WIRE MESH MAY BE ELIMINATED IF IRA-STRENGTH FILTER FABRIC (MONOFILAMENT),AND CLOSER POST SPACING IS USED. .A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS DN THIS SHEET ALONG THE LINE CF THE UST$ AND UPSLOPE FROM THE SILT FENCE, .SILT FENCES SHALL BE LOCATED DOVNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT, APPENDIX E DRAINAGE DETAILS HOUSE ROOF DOWNSPOUT SERVES UP TO 700 SF OF ROOF 50 FT MIN VEGETATED FLOW PATH DOWNSPOUT EXTENSION ROOF DOWNSP❑UT AND SPLASH BLOCK DETAILS N,T,S. Permit No: MASON COUNTY RECEIVED COMMUNITY DEVELOPMENT Permit Assistance Center,Building,Planning J U L 3 0 2024 BUILDING PERMIT APPLICATION W Alder Skeet ■� PROPERTY OWNER INFORMATION: CONTRACTOR INFORMATION: NAME:BARBARA HARVEY NAME:GREENPOD FABRICATORS MAILING ADDRESS:2873 Nw Nordeen way MAILING ADDRESS:WO Roo—"sL CITY:8ENO STATE:OR ZIP:97703 CITY:Port Tow nd STATE:WA ZIP:98368 Z PHONE#l:--233A520 PHONE:(360)301-9eas CELL: NIA PHONE#2: EMAIL:ANNOGREENPOD.DESIGN Z EMAIL:babsinmaine@gmad.conl L&I REG#aGREENFLas300 EXP.01 29 2026 PRIMARY CONTACT: OWNER❑ CONTRACTOR❑ OTHER❑ Z NAME u1C ROEDER EMAIL LUC&GREENPOD.DESIGN MAILING ADDRESS 242012THAVE SE CITY OLYMPIA STATE— —ZIP--' PHONE 919.49.9093 CELL wA PARCEL INFORMATION: PARCEL NUMBER 112 Digit Number)32424-22-00040 ZONWO RR-5 LEGAL DESCRIPTION(Abbreviated)TR 4 GOVT LOT 1&TAX 687-D S 34240 S 4011 FIRE-DISTRICT 17 SITE ADDRESS 51 N.HIDDEN COVE LANE CITY LILLIWAUP DIRECTIONS TO SITE ADDRESS FROM SHELTON:NORTH US HWY 101 NORTHBOUND TURN RIGHT ON N.HIDDEN COVE LANE PARCEL ON LEFT IS THE PROJECT WTI LEN 300 FT OF SLOPE(s)GREATER THAN 14%: YTS© NO❑ SNOW LOAD: sf IS PROPERTY T11 THEN 200 FT OF THE FOLLOWING: Ich Mk rn,hm<vt nt: SALTWATER E] LAKE❑ RTvTR'CREEK❑ POND❑ WETLAND❑ SEASONAL RUNOFF❑ STREAM❑ TYPE OF WORK: NEW p ADDITION❑ ALTERATION❑ REPAIR❑ OTHER A USE OF STRUCTURE(R.sid.nr.,Ga V,Cantu. W Bldg,E..)RESIDENCE IS USE: PRIMARY❑ SEASONAL[f NUMBER OF BEDROOMS'_ __ NUMBER OF BATHROOMS 1 HEATED STRUCTURE? YES Im,at.Bldg,❑ YES(Pn(,1 gfB1dg)A NO❑ DESCRIBE WORK NEW-SFR-SINGLE STORY RESIDENCE ABOVE UNHEATED STORAGE SQUARE FOOTAGE:,p-p...d, IST FLOOR 400 sq.ft. ?ND FLOOR sq.ft. 3RDFLOORO sq.tL BASEMENTO sq.ft. DECK 15 sq.ft. COVERED DECK 80 sq.ft. STORAGE 280 sq.ft. OTHER sq.ft. GARAGED sq.1Z Attached❑ Detached❑ CARPORT O sq.ft. Attached❑ Detached❑ MANUFACTURED HOME INFORMATION: *4 COPIES OF THE FLOOR PLAN REQITIRF.D* MAKE MODEL YEAR _LENGTH WIDTH BEDROOMS BATHS SERIAL NUMBER ENVIRONMENTAL HEALTH: SEWAG&'SEWER SOURCE: SEPTIC© SEWER❑ 1 NEW© EXISTING❑ PLUMBING IN STRUCTURE? YES I] NO❑ Ijyes,attach completed Water-Adequacy Fonn PERIMETER/FOUNDATION DRAINS PROPOSED? YES [ NO[] EXISTING SQ.Fr. EXISTING BEDROOMS D PROPOSED BEDROOMS 1 TOTAL BEDROOMS 1 OWNER acknowledges that submission of inaccurate information may result in a stop work order or permit revocation.Acknowledgement of such is by I signature below.1 declare that I am the owner and I further declare that I am entitled to receive this permit and to do the work as proposed.I have obtained permission from all the necessary parties.Including any easement holder or parties of Interest regarding this project The owner or legal nepresentalive,represents that the information provided is accurate and grants employees of Mason County access to the above described property and structure(s)for review and inspection.This pernitlapprication becomes null&void ff work or authorized construction is not commenced within 180 days or if construction work is suspended for a period of 180 days. PROOF OF CONTINUATION OF WORK ON THIS PERMIT IS BY MEANS OF INSPECTION. INACTIVITY OF THIS PERMIT APPLICATION OF 0 DAYS OF MORE WILL CAUSE THE APPLICATION TO BE EXPIRED.(MASON n0 WC COUNTY CODE 14.08.42) X 07/28/2024 Signature of OWNER(Must be sinned by[he OWNER) Date DEPARTMENTAL REVIEW APPROVED DATE DENIFD DATE TAGS/NOTES/CONDITIONS BUILDING DEPARTMENT PLANNING DEPARTMENT FIRE MARSHAL PUBLIC HEALTH