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Home My WebLink AboutGEO2020-00085 and Addendum for BLD2020-01486 - BLD Engineering / Geo-tech Reports - 8/17/2020 RECEIVED LANNING n c r o 2 ZOZo �-- 15 W�/�/ Alder Street MASON COUNTY Submittal C�eckfist COMMUNITY SERVICES Geotechnical Report Building,Pta ming,Environmental Health,Community Health Instructions: This checklist must be submitted with a Geotechnical Report and completed,signed,and stamped by the licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclusion. Note:Unless specifically documented, this report does not provide compliance to the International Residential Code Sections Section R403.1.8 for R403.1.7 for foundations on or adjacent to slopes,S expansive soils or section 1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes. ApplicanUO caner RJ Ana 9 Parcel# /2, 3 D Site Address ��,, o1.P �� 2 /1 9, Z1 I., (1) (a) A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) h - (b) A discussion of specific soil types, Located on page(s) :�Z-r? (c) A discussion of ground water conditions, Located on pages) 8 (d) A discussion of the upslope geom hology, Located on page(s) (e) A discussion of the location of upland waterbodies and wetlands, Located on pages) (f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records. Located on page(s) 4-2 (2) ' A site plan which identifies the important development and geologic features. Located on Map(s) q 1:4 J✓r Z (3) Locations and logs of exploratory holes or probes. Located on Map(s) 17 (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) 9 (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) 17 (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) 5 -// (7) (a) Appropriate restrictions on placement of drainage features, Rev.February 2018 Located on page(s (b) Appropriate restrictions on placement of septic drain fields, Located on page(s) I Z (c) Appropriate restrictions on placement of compacted fills and footings, Located on page(s) 1 2— (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes. Located on page(s) (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) 12 (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) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) /y (11) Specifications of final development conditions such as,vegetative management, drainage, erosion control,and buffer widths. Located on page(s) (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation./ Located on page(s) I? (13) A site map drawn to scale showing the property boundaries,scale, north arrow, and the location and nature of existing and proposed developmt on the site. en Located on Map(s) l -1 1 v.,v L rW ( sae Lt), 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 S�� fo - -- --� Geotechnical Report, dated O Z O and entitled II the re uirements of the Mason County Reaouroe Ordinance„7 / meets a q f� Geologically Hazardous Areas Section, is complete and true,that the ngineeri 39Geobgist assessment demonstrates conclusively that the risks posed by the ce7sed Geo�o landslide hazard can be mitigated through the included geotechnical design recommendations,and that all hazards are mitigated in such a Curtis Dean Cushman (Signature and Stamp) 's. manner as to prevent harm to property and public health and safety. Page 2 of 2 Disclaimer.Mason County does not certify the quality of the work done in this Geotechnical Report. -6qd 2020- O 1 qe)Lp ED 2020 M)85 RECEIVED GEOTECHNICAL REPORT OCT 0 2 2020 615 W. Alder Street RESIDENTIAL DEVELOPMENT SITE BEARDS COVE Div 2 TR 9 LARSEN LAKE ROAD BELFAIR, WASHINGTON PLANNING PREPARED FOR RJ PEABODY, INC. BY ALL AMERICAN GEOTECHNICAL OLYMPIA, WASHINGTON AUGUST 17, 2020 CONTACT INFORMATION PREPARER INFORMATION AAG PROJECT NUMBER: AAG20-068 CONTACT: CURTIS D.CUSHMAN ADDRESS: 8947 BUTTONWOOD LANE NE OLYMPIA,WASHINGTON 98516 TELEPHONE: (360)491-5155 CELL/TEST: (360)481-6677 EMAIL ADDRESS: CURTIS.CUSHMAN@COMCAST.NET CLIENT INFORMATION CLIENT: RJ PEABODY,INC. TELEPHONE: (360)895-3235 BILLING ADDRESS: RJ PEABODY,INC. P.O.BOX 565 BURLEY,WA 98322 SITE ADDRESS: BEARDS COVE Div 2 TR 9 BELFAIR,WASHINGTON EMAIL RJREALESTATE@MSN.COM PARCEL NUMBER 12330-53-00019 GPS LOCATION: 47.454 -122.848 AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 2 Phone#:(360)491-5155 Cell#: (360)481-6677 ALL AMENC AN GROTECHNICAL SCOPE OF UNDERSTANDING RJ PEABODY,INC. P.O.BOX 565 BURLEY,WASHINGTON 98322 RE: GEOTECHNICAL REPORT PROPOSED RESIDENCE BEARDS COVE DIv 2 TR 9 BELFAIR,WASIM'4GTON 47.438 -122.864(DD) PARCEL: 12331-50-00009 AUGUST 17,2020 Dear Sirs: RJ Reynolds (client) hired All American Geotechnical, Inc. (AAG) in June 2020 to do a geotechnical report for a residential property on a lot in Mason County, Washington. The following is the report written to comply with the Mason County Requirements in the Critical Areas Ordinance in accordance with the Submittal Checklist For a Geotechnical Report for the above property near the city of Belfair in Mason County, Washington. The site is to be developed with a single family residence. As per client request, we did a relevant site visit and a search of public documents. A copy will be provided to the client by PDF. Landslide hazards will be noted and analyzed in text. Other geotechnical information is likewise included. We appreciate this opportunity to be of service to you and we look forward to working with you in the future. If you have any questions concerning the above items,the procedures used,or if we can be of any further assistance please call us at the phone number listed below. Respectfully Submitted, ALL AMERICAN GEOTECHNICAL,INC. �e°f Wash�n ��a Quo Engineering Geologist �iO 2439 •�5�' erased Ge°�° Curtis D.Cushman,L.G.,L.E.G. Senior Engineering Geologist Curtis Dean Cushman AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 3 Phone#:(360)491-5155 Cell#:(360)481-6677 EYN GV6()TECHNICAL TABLE OF CONTENTS SCOPE OF UNDERSTANDING 3 INTRODUCTION 5 1) SITE CONDITIONS 5 SURFACE CONDITIONS 5 A) SITE GEOLOGY 6 B) SOIL TYPES 7 C) GROUND WATER CONDITIONS 8 D) UPSLOPE GEOMORPHOLOGY 8 E) UPSLOPE WATERBODIES AND WETLANDS 8 F) LANDSLIDE ACTIVITY 8 2) SITE PLAN 9 3) EXPLORATORY HOLES OR PROBES 9 4) PROPOSED DEVELOPMENT 9 5) CROSS SECTION 9 6) SLOPE STABILTY ANALYSIS 9 SEISMIC LIQUEFACTION HAZARD 10 GFOSEISMIC SETTING 1 I LATERAL EARTH PRESSURES 11 CONCLUSIONS AND RECOMMENDATIONS 14 PROVISIONS 14 READ THESE PROVISIONS CLOSELY 15 APPENDIX 16 REFERENCES 17 2015 AASHTO DESIGN SPECIFICATIONS 19 SLOPE MODELS 21 STATIC MODEL A-A' 21 DYNAMIC MODEL A-A' 22 STATIC MODEL B-B' 23 DYNAMIC MODEL B-B' 24 FIGURE 1 VICINITY MAP 25 FIGURE 2. SITE PLAN 26 FIGURE 2A. INSET 27 FIGURE 3. EROSION CONTROL NOTES 28 AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 4 Phone#:(360)491-5155 Cell#:(360)481-6677 ALL AMERIC.AN GROTWRNICAL INTRODUCTION This report summarizes the results of our geotechnical study of the parcel herein described. The parcel is a narrow near-rectangle long to the east-west with the eastern base somewhat wider than the western. The parcel is currently undeveloped. The west parcel line is just off Larson Lake Road, and the eastern line is near State Route 300. In general, the property descends to the east with its steepest slope beginning approximately 200 feet from the western property line. The property is covered with fairly heavy second-growth trees and common underbrush. The elevation ranges from 135 feet at its western end to approximately 35 feet at State Route 300. Our understanding of the project is based on materials sent by the client. The client plans to develop the property with a residence. Access to the parcel is on a short access road off NE Larson Lake Road near Belfair, Washington. NE Larson Lake Road is accessed directly from State Route 300. This geotechnical report and the checklist for Mason County involves the following: 1. A review of the available geologic, hydrogeological and geotechnical data for the site area. 2. A detailed geologic reconnaissance of the site area and surrounding vicinity. 3. Investigation and identification of shallow subsurface conditions at the site by characterizing the exposed soil, septic test pits, sampling, and reviewing published well logs. 4. Comparison of the site to published geologic maps, previous field investigations, and open file reports. Inspection of aerial photographs to determine the geomorphology of the site. 5. Evaluation of the landslide,erosion, and seismic hazards at the site per the Mason County Critical Areas Ordinance regulations(as of January 1,2007). 6. Slope modelling. The slope on the eastern part of the parcel exceeds of 40% and is greater in height than 10 feet. This is considered a Landslide Hazard Areas (LHA) Therefore, Mason County requires that a geotechnical report be prepared in accordance with the Mason County Resource Ordinance Sections 17.01.100 through 17.01.104. 1) SITE CONDITIONS SURFACE CONDITIONS The proposed location for the residential development is on the westernmost part of the lot on a low slope. This slope increases in pitch as it descends to the east. The property overall is basically covered with second-growth maturing trees, deciduous and conifers. There is undergrowth with a few open patches. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 5 Phone#:(360)491-5155 Cell#: (360)481-6677 ALL AUMCAN G OTECH ICAL Curtis D Cushman, L.E.G. and Blaise Jelinek E.I.T. of AAG conducted a site reconnaissance on July 14, 2020. Mr. Jelinek did a site revisit on August 13, 2020 to review the property. The purpose of a site visit is to physically observe the property and adjacent properties in order to identify any recognized geologic conditions. Visual observations were documented. The parcel is currently undeveloped. The trees are generally straight and vertical showing little or no signs of slope movement. A) SITE GEOLOGY The entire parcel is mapped as Qgic-Vashon Stade glacial ice-contact deposits on the Washington Geologic Information Portal which is taken from the Bel.fair 7.5-minute Quadrangle, Mason County, Washington;by Polenz, Michael, et al.; 2009; DNR Open File Report 2009-07. Geologic Unit Label:Qgic Publisher:WGS Publication Number:OFR 2009-7 Quadrangle Name:Belfair Symbology:Pleistocene continental glacial drift Geologic Unit Age: Pleistocene Geologic Unit Name: Vashon Stade glacial ice-contact deposits Unit Description: Sand, gravel, lodgment till, and flow till; minor silt and clay beds; tan to gray; variably sorted: loose to compact; massive to well stratified; locally includes over-steepened beds that typically reflect sub-ice flow, but their dip may, along with small-scale shears, also have developed as collapse features or due to glaciotectonic and tectonic deformation; formed in the presence of meltwater alongside ice, generally toward the end of the glaciation, and is thus commonly accompanied by stagnant-ice features, such as kettles and less-orderly hummocky topography, eskers (also separately mapped as subunit Qge), and subglacial or subaerial outwash channels. The deposits seen on site are likely SP Poorly graded gravelly sand using the ASTM classification. The nearest water well is at 390 NE Larson Lake showing a gravelly and sandy material profile in the column. The nearest identified displacement feature is the Sunset Beach scarp—Tacoma fault on the south side of Lynch Cove, which extends several miles southwest-northeast and is approximately 1114 miles to the southeast of the parcel at its closest point. This is apparently a feature of the Tacoma Fault system which is prominent in the.Allyn, Washington area. Seismic acceleration is important in modelling the slope stability as the Puget Sound area is in an active tectonic zone and although this scarp/fault trench does not pose an immediate hazard to the proposed building project, low levels of seismic activity are not uncommon and there is always the possibility of a major shock. The part of the parcel that will be developed is mapped on the Coastal Zona Atlas as Stable. AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 6 Phone#:(360)491-5155 Cell#: (360)481-6677 ALL AmmcAN onctL B) SOIL TYPES The soils in the areas of the proposed development are described by the USDA Web Soil Survey as: Ee—Everett gravelly loamy sand, 5 to 15 percent slopes Map Unit Setting • National map unit symbol: 2hk7 • Elevation: 50 to 500 feet • Mean annual precipitation: 55 to 90 inches • Mean annual air temperature: 48 to 50 degrees F • Frost-free period: 160 to 180 days Description of Everett Setting • Landform: Terraces • Parent material: Glacial outwash Typical profile • H1 - 0 to 7 inches: gravelly ashy loamy sand • H2 - 7 to 21 inches: extremely gravelly sand • H3 - 21 to 60 inches: very gravelly sand Properties and qualities • Slope: 5 to 15 percent • Depth to restrictive feature: More than 80 inches • Drainage class: Somewhat excessively drained • Capacity of the most limiting layer to transmit water (Ksat): High to very high (5.95 to 19.98 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: Very low (about 2.5 inches) Ib—Indianola loamy sand, 5 to 15 percent slopes Map Unit Setting • National map unit symbol: 2t635 • Flevation- n to 9R0 feet • Mean annual precipitation: 30 to 81 inches • Mean annual air temperature: 48 to 50 degrees F • Frost-free period: 170 to 210 days • Farmland classification: Prime farmland if irrigated Description of Indianola Setting • Landform: Eskers, kames, terraces AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 7 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL AMKRAN CAOTILCHNICAL • Landform position (three-dimensional): Riser • Down-slope shape: Linear • Across-slope shape: Linear • Parent material: Sandy glacial outwash Typical profile • Oi - 0 to 1 inches: slightly decomposed plant material • A - 1 to 6 inches: loamy sand • Sw1 - 6 to 17 inches: loamy sand • Bw2 - 17 to 27 inches: sand • BC - 27 to 37 inches: sand • C - 37 to 60 inches: sand Properties and qualities • Slope: 5 to 15 percent • Depth to restrictive feature: More than 80 inches • Drainage class: Somewhat excessively drained • Capacity of the most limiting layer to transmit water(Ksat): High to very high (5.95 to 99.90 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: Low (about 3.9 inches) The soil difference between these two is roughly in the gravel and loam content of the soils. Both are well drained with a deep water table (-109 feet as per a nearby drill log). The Everett soil appears to be the most common where seen on site. Soil is generally removed to the underlying glacial deposits. C) GROUND WATER CONDITIONS There was no ponding, springs, seeps or other water seen. There was no evidence of active surface erosion. There was no natural drainage channels on the parcel. D) UPSLOPE GEOMORPHOLOGY The slope flattens to the north and west,then rises to a 190-foot elevation ridge over 900 feet to the north. This does not constitute a geotechnical hazard to the parcel. E) UPSLOPE WATERBODIES AND WETLANDS There are no upland water bodies or wetlands F) LANDSLIDE ACTIVITY The 7.5-minute quadrangle shows numerus landslides in the mapped quadrangle,but there are none on or near the client property and there are none along the slope above Highway 300. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 8 Phone#:(360)491-5155 Cell#:(360)481-6677 ALL AMERICAN GROTItHNICAL LiDAR from the Mason County GIS shows no evidence of any landslides on or in the area around the site. There was no evidence of current on-site landslide activity. 2) SITE PLAN Please see Figure 2 in the appendix. 3) EXPLORATORY HOLES OR PROBES The site was surface examined along the access road, in exposures on the property,and as sampled as located on Figure 2. 4) PROPOSED DEVELOPMENT This will be a single family residence. 5) CROSS SECTION Four cross-sections are in the appendix are in the Appendix. They are along line A-A' and 13-13`. 6) SLOPE STABILTY ANALYSIS The Slope Stability Analysis is as follows following the Mason County Resource Ordinance of 2009: 17 01.100E5(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 Bishops Method of Circles The minimum static safety factor is IS, the minimum seismic [dynamic] safety factor is 1.1 and the quasi static analysis coefficients should be a value of 0.15. Slope stability was modeled using the GALENA 6.1 program in both static and dynamic conditions (ca= 0.301). "Static" condition refers to an "as is" state of a given slope. "Dynamic" puts seismic acceleration into the model for earthquake conditions. The factor for ground acceleration (ca) was determined from the Peak Ground Acceleration from the USGS Seismic Design Maps, included in the Appendix. The surface soil was field classified in the range of a SP, a very gravelly poorly graded sand. These units are consistent with the description of the Qgic Vashon Stade glacial ice-contact deposits. The site was modeled as monolithic unit. Groundwater was not included in the model. Parameters used for the subsurface material are presented in the table on the following page. AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 9 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL MN G ! (CAL Table 1.Modeling Parameters for Subsurface Material Geologic Unit i Unit Weight Cohesion Phi Angle Qgic-Vashon Stade Ice Contact Deposits 120 4(>D ; 35 (Pleistocene) 1 Factors of safety were determined using the Bishop (semi-circular) method. A ground water table was not included in the model,as there was no evidence of any. Under static conditions, the slopes did not show susceptibility to deep-seated failure that would cause damage to the existing development. See Appendix for model output and cross-sections. Under dynamic loading (Ca=0.301), the computations demonstrated that the development is safe and not susceptible to a deep-seated movement. The following are the Factors of Safety (FoS) attained for the sections with respect to their current topographical representation. General information for the slope profiles and the initial positions for analysis is presented in the following table. Table 2. Initial Positions,Variance,and Findings Analysis Loading Across JAnalysis Initial Positions(Analysis Range) Configurations Factor of Number Building Area IType ILower JUpper Radius JAnalyzed Safety Cross-Section A-A' __ _ _ Analysis 1 _ 1500# 343-390 ;Static ;63(50) __ �;342(5) ;406(50) _- 125,001 __ _ 2.77• Analysis?._- _1500#_343-390 _',Dynanvc_63(50)____:342(5)_____:406(50) ____125,001 1.33__ Cross Sirs -B' Analysis 3 1500# 342-381 :Static :109(50) :341 (5) 1420(50) 125,001 : 4.02 Analysis 4 _ 1500# 342-381 :Dynamic _109(50) _34l (5) :420(5-- : 125.--- 1.66 These calculated Factors of Safety (FoS) meet or exceed code standards. Thus, based on our slope models representing critical slopes at the subject site, it is apparent that the modelled sites are not susceptible to damage by deep-seated movements or instability The values input were selected to be as conservative as possible so the FoS are likely higher. The graphic output of these data is presented in the appendix,pages 21-24. SEISMIC LIQUEFACTION HAZARD The Liquefaction Susceptibility Map of Mason County, Washington by Palmer, Magsino, Poelstra, Bilderback, Folger, and Niggemann (September 2004) maps the site area as having a Low liquefaction potential. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 10 Phone#:(360)491-5155 Cell#: (360)481-6677 The Site Class Map of Mason County, Washington by Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggemann (September 2004) maps the area as site Class C to D. Site class C is a very stiff soil or soft rock and class D is stiff soil. GEOSEISMIC SETTING According to the Seismic Zone Map of the United States (Figure 1613.3.1(1)) contained in the 2015 International Building Code (IBC), the project site is located where the maximum spectral response acceleration is greater than 60 percent of gravity(g). We recommend following seismic factors for design purposes. • Site Class: D (stiff soil/soft rock) • Spectral response acceleration, short period(SMs): 1.452g (Fa= 1.05) • Spectral response acceleration, 1-second period(Smi): 0.874g(F„= 1.55) • Peak Ground Acceleration 0.602 LATERAL EARTH PRESSURES Lateral loads may be resisted by friction on the bases of footings and floor slabs and as passive pressure on the sides of footings. An allowable coefficient of friction of 0.40 may be used to calculate friction between the concrete and the underlying native soil. We recommend the following be used to determine the lateral earth pressures considering the onsite SP: • � (soil friction angle) 35degrees • Ko (at rest earth pressure coefficient) 1.428 • Ka(active earth pressure coefficient) 0.271 • Kp(passive earth pressure coefficient) 3.69 • y(soil unit weight) 120 pcf 7) RESTRICTIONS A) PLACEMENT OF DRAINAGE FEATURES All ground surfaces, pavements and sidewalks should be sloped away from the residence and associated structures. Surface water runoff should be controlled by a system of curbs, berms, drainage swales, and/or catch basins and tight lined into the appropriate drainage facilities. We recommend that conventional roof drains be installed. Footing drains shall be installed for the proposed structure. The roof drain should not be connected to the footing drain. For footing drains, the drain invert should be below the bottom of the footing. Typical drainage control measures are included on Figure 3 in the appendix. The soil will accept downspout and other drainage located at least 5 feet from the edge of the footing of the residence. (Figure 3 shows recommendations for a tightline system that is not applicable to this parcel.) Drainage should be such that there is no flow onto the steep slopes to the east. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 11 Phone#:(360)491-5155 Cell#:(360)481-6677 ALL AN GILOTIECHNWAL B) PLACEMENT OF SEPTIC DRAIN FIELDS The drain field is located as mapped on Figure 2. The drainfields will be outside the LHA but encroach the 50-ft vegetation buffer. Domestic water is from an off-site common source. C) PLACEMENT OF COMPACTED FILLS AND FOOTINGS RECOMMENDATIONS FOR SITE PREPARATION The area is forested and the trees shall be cleared as needed for construction. All areas to be excavated should then be cleared of deleterious matter including any debris, duff, and vegetation. All deleterious material will be removed and sub-soils reached for the footings for the construction of slab and/or footings. Any material that is excavated may be stockpiled and later used for erosion control and/or landscaping. Surficial material unsuitable for these tasks should be removed from the project site. No foundation elements shall be constructed on"untested"fill material. If demonstrated to be acceptable, the sand/gravel sedimentary material on site may be suitable for re-use as structural fill. Where placement of fill material is required, the exposed subgrade areas should be compacted to a firm and unyielding surface prior to placement of any fill. Over-excavation in any building area should be backfilled with structural fill, compacted to the density requirements described in the "Structural Fill" section of this report. RECOMMENDATIONS FOR STRUCTURAL FILL All fill material should be placed as structural fill. In general, the structural fill should be placed in horizontal lifts of 8 inches to allow adequate and uniform compaction of each lift. Fill should be compacted to at least 95 percent of MDD (maximum dry density as determined in accordance with ASTM D-1557)to grade. The final appropriate lift thickness will depend on the fill characteristics and compaction equipment used. Material placed for structural fill should be free of debris, organic matter, trash, and cobbles greater than 6 inches in diameter. The moisture content of the fill material should be adjusted as necessary for proper compaction. Onsite soils may be considered for use as structural fill only if industry standards are satisfied. Fill material requirements are found on page 9-26 to 9-30 of the WSDOT Standard Specifications 2010. In general, a native soil (sand, silt, and gravel) encountered on a site must have less than 10 percent fines (material passing the US No. 200 sieve)to be suitable for use as structural fill. Footing design will be by the Engineer of Record. AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 12 Phone#: (360)491-5155 Cell#:(360)481-6677 ALL AMERICAN GTCNICAL D) BUFFERS The construction area will be outside the 50 foot vegetation buffer. The slopes are such that erosion should not be a limiting factor. The LHA,which is on the downslope to the east shall not be disturbed. E) SETBACKS The site is outside of the acceptable hazards as defined by the slope stability model and the resultant Factors of Safety. The geotechnical setback is seen on Figure 2. 8) CLEARING AND GRADING PLAN Timber clearing will be needed. No grading is anticipated except to develop the foundations of the residence. "No Disturb" zones will not be required. No formal plan should be needed as long as safe procedures are employed with the clearing in keeping with Mason County regulations. All job site safety issues and precautions are the responsibility of the contractor providing services and/or work. 9) EROSION CONTROL PLAN It is our opinion that the potential erosion hazard of the site is not a limiting factor for the proposed development. Simple erosion control methods will reduce or eliminate any potential erosion risk. Trees and understory growth on the LHA slope itself will not be disturbed. Revegetation as needed should occur immediately following construction. No hazard trees appear to be present near the LHA. The possibility of down-slope contamination is highly unlikely if proper control methods are employed. A silt fence may be installed as shown on Figures 2 and 3 and other control methods, such as swales and baled straw are practical. No re-contouring of the site will occur. Surface drainage should be directed away from all slope faces. Straw, hay, or jute matting shall be used to cover the exposed soils until permanent vegetation is established. All slopes should be seeded as soon as practical to facilitate the development of a protective vegetative cover,or otherwise protected. Surface water should not flow toward or over any steep slopes. Drainage pipes should not daylight on any steep slopes. A revegetation plan should not be required. When residential plantings or any plantings on the periphery of the residential area and the slopes are planned, native species should be considered as the primary vegetation in areas away from lawn and ornamental plantings. Shallow rooted species, such as grass, should be planted closer than 10 feet from underground drainages. Densely rooted evergreen shrubs are preferable than tree species on slopes greater than 15% gradient. Tall trees may become unstable in wet soils under high wind conditions. In general,the steep sides of the ravine should be left in a natural condition unless erosion or sloughing eventually pose a hazard to the residence. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 13 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL AIN GEOTCHNIL 10) ON AND OFFSITE IMPACTS There should be no notable on- or offsite impacts if the project is completed according to the recommendations of this report and in accordance with all regulations and to the high standards and practices of the building contractor. No geotechnical impact is anticipated in the construction of the residence at either location. 11) FINAL DEVELOPMENT CONDITIONS All final conditions will follow the design by the Engineer of Record and compliance with all regulatory agencies. If this and the above recommendations are followed, final development conditions will be achieved. 12) STRUCTURAL MITIGATION There is no structural remediation to be done. 13) SITE PLAN Please see Figure 2. CONCLUSIONS AND RECOMMENDATIONS Based on the results of the site reconnaissance, subsurface observations, and our experience in the area, it is our opinion that the proposed site is suitable for the proposed development. As located, the proposed structure would not undermine adjacent slopes. Disturbance of vegetation within the parcel may be managed to avoid possible erosion. PROVISIONS GENERAL We have prepared this report for the exclusive use of RJ Peabody, Inc and their authorized agents for the proposed improvements in Mason County, Washington. Site inspections, research, and mapping have culminated in this report. This report is intended to meet the requirements of the Mason County Resource Ordinance. This report does not specify setbacks for: line-of-sight setbacks, FWHCA setbacks, eagle tree setbacks,wetland setbacks, or property line setbacks. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, expressed or implied, should be understood. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 14 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL AN GROTILCHNICAL Clients and property owners must understand that, while a slope may be found to have an acceptable Factor of Safety related to deep-seated mass wasting, surficial failure and landslides can and do occur on steep slopes. The property owners should monitor the stability of their property following construction. Moreover, acceptable Factors of Safety do not guarantee there cannot be failures. It is the responsibility of the property owners to understand that there are always risks in building on or near steeply sloped areas. CONTRACTORS ARE RESPONSIBLE FOR SITE SAFETY ON THEIR OWN CONSTRUCTION PROJECTS Our geotechnical recommendations are not intended to direct the contractor's procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to onsite personnel and to adjacent properties. READ THESE PROVISIONS CLOSELY Some clients, design professionals, and contractors may not recognize that the geoscience practices (geotechnical engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. All American Geotechnical includes these explanatory "limitations"provisions in our reports to help reduce such risks. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 15 Phone#:(360)491-5155 Cell#: (360)481-6677 ALL AMERICAN GROTECHNICAL APPENDIX References USGS Seismic Design Specifications Slope Models Figure 1.Vicinity Map Figure 2. Site Plan Figure 3. Erosion Control Notes. AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 16 Phone#:(360)491-5155 Cell#:(360)481-6677 ALL Aumcm GaoTacmicAL REFERENCES MAPS DeLorme 3-D TopoQuads(2002),Source Data USGS,Yarmouth,Maine. Dragovich, Logan, Walsh, and Schasse(2002),Geological Map of Washington—Northwest Quadrant(Geological Map GM- 50),published by Washington State Department of Natural Resources. Palmer, Magsino, Poelstra, Bilderback, Folger, and Niggemann (September 2004), The Liquefaction Susceptibility Map of Mason County, Washington, published by Washington State Department of Natural Resources. Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggemann (September 2004), The Site Class Map of Mason County, Washington,published by Washington State Department of Natural Resources. Polenz, Michael et al., (2009); Geologic Map of the Belfair Lake 7-5-minute Quadrangle, Mason County, Washington; DNR Open File Report 2009-07 Rogers, A. M., Walsh, T. J., Kockelman, W. J., and Priest, G. R. (1996), Map showing known or suspected faults with quaternary displacement in the Pacific Northwest, published by U.S. Geological Survey OFR 91-441-0, Plate 1, scale 1:2,000,000. PUBLICATIONS ASTM International(2005),Annual Book of Standards 2015,Section 4, Volume 4.08,published by ASTM International,West Conshohocken,Pennsylvania. Bloom(1991),Geomorphology,published by Prentice-Hall,Inc.,Upper Saddle River,New Jersey. Kollmorgen Instruments Corporation (1994), Munsell Soil Color Charts (1994 Revised Edition), published by Macbeth Division of Kollmorgen Instruments Corporation,New Windsor,New York. McCarthy(1993),Essentials of Soil Mechanics and Foundations,published by Prentice-Hall, Inc.,Upper Saddle River,New Jersey. Ness,Fowler,Parvin(1960),The Soil Survey of Mason County, Washington, USDA Soil Conservation Service, in cooperation with the United States Department of Agriculture, and Washington Agricultural Experimental Station, and the Soils Conservation Service. Parks, Neal, Koloski, Laprade, Molinari, Butler, and Lorentson (November 2006), Guidelines for Preparing Engineering Geology Reports in Washington, published by Washington State Geologist Licensing Board,Olympia,Washington. AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 17 Phone#: (360)491-5155 Cell#:(360)481-6677 ALL AMMCAN GROTECHNICAL WEBSnES Mason County Government Information Services (http://www.co.mason.wa.us) Mason County Codes,Ordinances,and Regulations (http://www.co.mason.wa.us/code) Puget Sound Lidar Consortium (http://pugetsoundlidar.ess.washington.edu/lidardata/index.htmi) Slope Stabilization Erosion Control Using Vegetation A Manual of Practice for Coastal Bluff (http://www.ecy.wa.govfbiblio/9330.htmi) Vegetation Management Guide for Puget Sound Bluff Property Owners (http://www.ecy.wa.gov/biblio/9331.html) United States Department of Agriculture Natural Resource Conservation Service (http://soildatamart.nres.usda.gov) Washington Administrative Code (http://apps.leg.wa.gov/wac/) Washington Department of Ecology (http://apps.ecy.wa.gov/welllog) (https:flfortress.wa.gov/ecy/coastalatlas/viewer.htm) AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 18 Phone#: (360)491-5155 Cell#:(360)481-6677 ALL AMERICAN ,OTECHNI L 2015 AASHTO DESIGN SPECIFICATIONS OTCHazards by Location Search Information National Park Redmond Coordinates: 47.439,-122.864 141 ft Seattle Elevation: 141 ft Q Olympic Timestamp: 2020-08-14T18:41:40.469Z National Forest Kent 0 Hazard Type: Seismic Tacoma e;W9 O Reference IRC-2015 - Puyaiiup Document: GO tjlt nt m e naP Report a map ertor Risk Category: l Site Class: D MCER Horizontal Response Spectrum Design Horizontal Response Spectrum Sa(g) Sa(g) 1.40 1.20 0.80 1.00 0.60 0.80 0.60 0.40 0.40 0.20 0.20 OM 0.00 0 5 10 15 Period(s) 0 5 10 15 Period(s) Basic Parameters Name Value Description SS 1.452 MCER ground motion(period=0.2s) S1 0.583 MCER ground motion(period=1.Os) 9h1s 1.452 Site-modified spectral acceleration value Sim 0.874 Site-modified spectral acceleration value SOS 0.968 Numeric seismic design value at 0.2s SA Sol 0 583 Numeric seismic design value at 1.0s SA -Additional Information Name Value Description SDC D Seismic design category Fa 1 Site amplification factor at 0.2s F„ 1.5 Site amplification factor at 1.0s CRy 0.973 Coefficient of risk(0.2s) CR1 0.934 Coefficient of nsk(1.0s) 8/14/2020,11:41 AM AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 19 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL AmEwcAN GtortcHNIcAL PGA 0.602 MCEG peak ground acceleration FpcA 1 Site amplification factor at PGA PGAM 0,602 Site modified peak ground acceleration Tt 16 long-period transition period(s) SsRT 1,452 Probabilistic risk-targeted ground motion(02s) SsUH 1.492 Factored uniform-hazard spectral acceleration(2%probability of exceedance in 50 years) SsD 2.614 Factored deterministic acceleration value(0.2s) S 1 RT 0.583 Probabilistic risk-targeted ground motion(1.0s) S1 UH 0.624 Factored uniform-hazard spectral acceleration(2%probability of exceedance in 50 years) SID 0.85 Factored deterministic acceleration value(1.0s) PGAd 0.934 Factored deterministic acceleration value(PGA) The results indicated here DO NOT reflect any state or local amendments to the values or any delineation lines made during the budding code adoption process.users should confirm any output obtained from this tool with the local Authority Having Judscliction before proceeding with design. Disclaimer Hazard loads are provided by the U.S.Geological Survey Seismic Design Web Services. While the information presented on this webshe is believed to be correct,ATC and its sponsors and contributors assume no responsibility or liability for its accuracy.The material presented in the report should not be used or retied upon for any specific application without competent examination and verification of its accuracy,suitability and applicability by engineers or other licensed professionals.ATC does not intend that the use of this Information replace the sound judgment of such competent professionals,having experience and knowledge in the field of practice,nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the report provided by this website.Users of the information from this website assume all liability arising from such use.Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by labludellongitude location in the report. f✓14/2020.11.41 AM AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 99516 20 Phone#:(360)491-5155 Cell#:(360)481-6677 Material Keys � sVasM SledeteCon6dDeposls N TA 035g:t20) n250 . O ON 00 d L17 r 200 y 150 CD w 100 o � ZZ �. 00 50 r n � Analvs�s 1 t� =° Multiple StabilRy Analysis ^ Melhe BishopSimplifed cSeffwe: Cireular Results �^ 100 Crft!Factor of Safety: 2.77 ON J 0 50 100 150 200 250 300 350 400 450 GALENA womuo Farm•taAug2o2o Prmeawd: 14AUC2020 Pr • g A Peobody,Larson Lake Analysis I Static A-A'Line Fk CAM American 0eoachdcaf&"FIbA1 JN Peabody Lamm Lake SFaUc A gM All American Geolech nbl,Inc. N Y Material Keys C ' ty � beGonhdDeposils y N (%DVO oa5 911 o � O CN 00 O tC Crl 200 += 150 0 00 cab � �. 100 w � o � � o 50 � r C�7 0 O Analysis 1 :'. Multiple Stability Analysis method- Bishop Sirnplilied Surface: Circular v, oy �o Results °.—° 00 vA 100 CYikkal Factor oySarety: 1.33 J 0 50 100 150 200 250 300 350 400 450 GALENA w sw Edled.14Aug2D20 Processed: 14Ae92020 P*g JR Peobody,Larson Lake Malys S 2 Dynamic A-N Line File:C AJI American GeotechrkaWakra Fiks12,A Peabody Larson Lake DYWIC Agmt All American Geotech nical,Inc. N i N yMaterial Keys a �o•yasMnSfleCon6d0epos6 :400 e35 JI C� O 00 250 t7 117 L' tz 2D0 150 O 0 N o. CD O 0 `�� Analyss 1 *:S Multiple Stability Analysis Method.. Bishop Simplified cSulase: Circular 0000 00 Results CN os -100 CYdicalFactaofSa�ety: 4.02 0 50 100 150 200 250 300 350 400 450 pew GALENA vo ft o E6kd:14 Aug 2020 Prows+ed 14 Aug 2020 Prdect JR Peabody,Larson Lake Andysis 3 Static B-B'Line File:QWIAmedwGeotech gGalersFWAURPeabodyLarsonLakeSlatice.grd All American Geotechnical,Inc. N � W I Y Material Keys C + M gvasM teconhcloeprA � 250 Ay O° a O C7 r 200 bd 150 00 ,soo W 100CN L4Y K Q O f... 0 l� r 50 z 0 Analyss 1CD Multiple Stability Analysis v✓ MelW. Bishop Simplified w Surface: Circular o > 00 Results 14 •10o Critical FactaolSafety: 1.66 ONCN 0 50 100 150 200 250 300 350 400 450 GALENA 1@r4mvo t:dipd 14Aug2020 Rocessed 14Aug2020 Prorecf JR Peobody,Larson Lake Analysis 4 Dynamic B-9 Line File:CAM American GeolechnicalkGalena Hasl4 JR Peabody Larson Lake Dynamic B.gmf All Ame dean Geoteeh niea 1,In C. N ALL AMRIN GTCHNIL FIGURE I VICINITY MAP 122`54.000'W 122153.000'w 122152.000-W 122"51.00T W WGS84 122'50.000'W ��, D 1/ 1q �C- a •I r o_ t� 1 � �, a - _- n 1C 1'U � s s UNI RIVER O AR r` 7 J e1ihirdy�.Inca ;r 1/ '� f� �'�� l �• , Residentul Dei4elu neirt.Siie 1�Ea rds(_'Ove DI TR 9 t l4J f, :. 12331-50-00009 4 y' v �• e�u.sa �+�' .r. � 'e+ f '`....• �.y Ce pOt.,ras � � J ` J PA j � .: y i. y, ! �'�'' S'K�r�P��v��A�T d��k�'Rx•j�`•x $ � t�/^ .-' `�t'. t s`'v`� by � .-r^� s �.'1t� as 4 '"'"ut �` •T`'�>i yR�� aE+ itp � -E•°' P' em' ^^ t`- tea s /r i Zsw z arth f Sk Al, 122*54,000'W 122-53.000,W '_22`52.000 W 122-51.000'W WGS84 122-50.000'W AV ° 5 WE 16YJ Q ,om fEtt 0 MRl O Printed Gam TOPO!C:A01 Not W Geap Uc Hd&n.o t%x topo.cm; AAG20-068 8947 Buttonwood Lane NE,Olympia, WA 98516 25 Phone 4: (360)491-5155 Cell#: (360)481-6677 ALL AMRRICAN GROTECRNWAL FIGURE 2. SITE PLAN AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 26 Phone#:(360)491-5155 Cell#: (360)481-6677 NOTES i This is not a survey. This trap is a presentation of information from county,state,and federal agencies,client provided information,and onsite observations;for discussion purposes of v �� the report with which this map is included. Water is from a �� ~ �N community source. A oQ o Site Geology Qsk Vashon Stade ice contact deposits �~ (Pleistocene) Silt Fe e�✓ Site Soils as Neede CEverett gravelly loamy sand, cl 5 to 15 percent slopes h Ef�-Everett gravelly loamy sand, �- 15 to 30 percent slopes Indianola loamy sand, --^—� 5 to IS percent slopes C.I.=5' of Wash'n o / m / / zaas �5 I - Q�Sed Geo�o Curtis Dean Cushman i I All American Geotechnical,Inc. Project tea,Br Site Plan Permit Number: parcel Number: 12331-50-00009 Figure 8947 Buttonwood Lane NE Number: BWJ Proposed Home 8/17/?A Propd H Olympia,Washington 98516 AAG20-068 Belfair,Washington Applicant JR Peabody 180 Larson Lake Revisions: PP Name: Site Address: 2 ALLAUMCANGEOTWBNICAL FIGURE 2A. INSET AAG20-068 8947 Buttonwood Lane NE,Olympia,WA 98516 27 Phone#: (360)491-5155 Cell#: (360)481-6677 ALL AMERICAN GROTECHN1CALL FIGURE 3. EROSION CONTROL NOTES AAG20 068 8947 Buttonwood Lane NE,Olympia,WA 98516 28 � Phone#:(360)491-5155 Cell#: (360)481-6677