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Home My WebLink AboutGEO2009-00050 - GEO Geological Review - 6/19/2009 MASON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT Planning Division P O Box 279, Shelton,WA 98584 910 (360)427-9670 Geotechnical ReportReview Acceptance Letter June 19, 2009 JOHN BYERLY P O BOX 133 BELFAIR WA 98528 Case No.: GE02009-00050 Parcel No.: 123312390012 Proiect Description: Geo Report submitted for the Construction of Detached garage The Geotechnical Report for JOHN BYERLY has been received and reviewed by the Planning Department. The report was prepared by Curtis Cushman dated 6/15/2009. Based on the certification provided by the licensed engineer/geologist, the referenced Geotechnical Report was prepared in general accordance with the requirements in the Mason County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.5. Mason County considers the review valid until such time as scope of project, site conditions, and/or regulations change. Should the scope of work, site conditions, and/or regulations change after the original review, then an addendum from the original author of the report may be required to address these changes. The report would only be re-reviewed if a permit for development were submitted after these changes occur. Mason County does not certify the quality of the work done in this Geotechnical Report. Please contact me at (360) 427-9670, ext. 365 if you have questions. Sincerely, -Allan Borden Land Use Planner Mason County Planning Department Comments: 6/19/2009 Page 1 of 1 GE02009-00050 pN"STATE MASON COUNTY o P� A o N DEPARTMENT OF COMMUNITY DEVELOPMENT 0 A NUPlanning Division 7 N y y P O Box 279, Shelton, WA 98684 1864 (360)427-9670 NOTIFICATION OF INCOMPLETE APPLICATION May 19, 2009 JOHN BYERLY PO BOX 133 BELFAIR WA 98528 Parcel No.: 123312390012 Proiect Description: GARAGE/STORAGE Dear Applicant: You have submitted a permit application (case no. BLD2009-00384) for proposed construction or development in the county. Upon review of your application, I have determined that the contents of the application are incomplete or do not provide enough detail for review. Therefore, review of your application will not proceed until the necessary information is provided (see the comment section of this letter for details.) Once the information is submitted and the application is complete, I will continue to process your application accordingly. If the additional information is not provided to the County within 180 days of this request, the application shall expire and no further action on the proposed development shall take place. Please contact me at (360) 427-9670, ext. 365 if you have questions. Sincerely, /�A'Ilan Borden Land Use Planner Mason County Planning Department 5/19/2009 Page 1 of 2 BLD2009-00384 NOTIFICATION OF INCOMPLETE APPLICATION 5/19/2009 Case No.: BLD2009-00384 Comments: Your building permit request for a new garage did not include a completed geologic assessment as part of the review materials. A site inspection of the property by Allan Borden on Tuesday May 19, 2009 revealed that the existing manufactured home is setback very close to a 35 percent or greater slope and the staking for the proposed garage about 80 feet from the top of slope in the east area of the property. The geological study must be submitted to comply with the landslide hazard areas development standards. When the house was sited in July 1995, the 35 percent slope was noted but the home setback was permitted. The landslide hazard areas development standards have been updated several times since that date, and new development on this parcel and the parcel to the north (both owned by you) must have the geological study prepared to comply with these standards. A list of qualified geo study preparers is enclosed with this letter. Until the geological assessment and accompanying geo study checklist are submitted to this Department, further permit review cannot proceed by the Planning or Building Departments. Both departments must be assured that the new development will not affect slope stability conditions. 5119/2009 Page 2 of 2 BLD2009-00384 \�123312390080 1233123901\ 123312390093 1�0 123312390072 160 123312390011 223361490002 123310060010 1\ 123312390071 123312390120 i 123312390010 123312390070 / �Q 123312390012 123310060000 5� o Q` 223365300038 123315000017 ^p vP 123310060010 123313200080 T23NR1 W 0 123315000015 223365300039 123310060010 00 223365300040 123315000014 d / �o 123310060000 223369999999 rI 123310060000 4 /// 123315000013 123313190010 123313200020 223369999999 ryo 123315000012 123315000018 123315000011 123315000010 123313290090 123315000008 123315000009 t123315000008 123313290100 123315000007 N 1 inch = 100 feet W E 1 inch = 0.02 miles S i � Z � i � 5 � i I � I I i � I b. I -67 S `N ff � I f, .4 ZP I r 1 J I Ui t�i '1 CIO W `� �c8 Ind►'' �s 4 xc, lndv L4 --fiArRCEL FILL Mason County Department of Community Development Submittal Checklist For a 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 found to be not applicable, the report should explain the basis for the conclusion. Applicant/Owner JOHN BYERLY Parcel# 123312390012 F--RW %V O o q-o 0 3 S 4 Site Address 370 NE LARSON LAKE RD, BELFAIR, WA 98528 (1) (a)A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) 7 (ORIGINAL REPORT) (b) A discussion of specific soil types / Located on page(s) 7-8 (ORIGINAL REPORT) V (c) A discussion of ground water conditions Located on page(s) 8 (ORIGINAL REPORT) (d) A discussion of the upslope geomorphology Located on page(s) 5-6 (ORIGINAL REPORT) (e) A discussion of the location of upland waterbodies and wetlands Located on page(s) 1 (ADDENDUM) (f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records Located on page(s) 8-9 (ORIGINAL REPORT) V/ (2) A site plan, which identifies the important development and geologic features. Located on Map(s) FIGURE 2 a,e,,��/��ei:5�-fyZ (3) Locations and logs of exploratory holes or probes. Located on Map(s) FIGURE 2 (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)) onna�a geologic map of the site. Located on Map(s) FIGURE 2 'c'�ZC��.t t��'zwt (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. �p j Located on Map(s) FIGURE 4 4Z�'�Z7!'�'Zti eeeeOi_ If (6) A description and results of slope stability analyses performed for both static and seismic loading conditions. Analysis should examine worst-case failures. The analysis should include the Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5; the minimum seismic safety factor is 1.1 and the quasi-static analysis coeffients should be a value 0.15. Located on page(s) 14 (ORIGINAL REPORT) &2 (ADDENDUM) (7) (a)Appropriate restrictions on placement of drainage features Located on page(s) 14 (ORIGINAL REPORT) (b) Appropriate restrictions on placement of septic drain fields Located on page(s) NONE PROPOSED (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) 16-18(ORIGINAL REPORT) Page 1 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. / Located on page(s) 1 (ADDENDUM) (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) 1 (ADDENDUM) (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) 2 (ADDENDUM) (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) 15 (ORIGINAL REPORT) (10) An analysis of both on-site and off-site impacts of the proposed development. / Located on page(s) 22 (ORIGINAL REPORT) v (11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and buffer widths. Located on page(s) ADDRESSED IN POINTS 7 TO 10 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) NONE PROPOSED rf (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) FIGURE 2 J�-fz1 I, CURTIS D CUSHMAN hereby certify under penalty of perjury that I am a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. I also certify that the Geotechnical Report, dated APRIL 30, 2007, and entitled 370 NE LARSON LAKE RD, BELFAIR, WASHINGTON meets all the requirements of the Mason County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) 0 nglfmring Geologist `gyp 2439 ed Geo�o CUI3TIS DEAN CUNN10"' Page 2 of 2 Form Effective June 2008 Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report. GEOTECHNICAL REPORT 370 NE LARSON LAKE ROAD BELFAIR, WASHINGTON PREPARED FOR JOHN BYERLY BY GEOTECHNICAL TESTING LABORATORY OLYMPIA, WASHINGTON APRIL 30, 2007 SCOPE OF UNDERSTANDING JOHN BYERLY P.O.Box 0133 BELFAIR,WA 98528 RE: ADDENDUM 370 NE LARSON LAKE ROAD BELFAIR,WA 98528 PARCEL 123312390012 N47,26.440'W 122°51.787' 6-15-09 Mr. Byerly: As per your request, we have updated the original Geotechnical Report with this addendum and checklist for the project listed above. The original report, dated April 30, 2007, in combination with this updated addendum is expected to satisfy the most recent developments in the Landslide Hazard Areas requirements as set forth by Mason County. Please find attached to this addendum the revised site plan and a cross section. We have provided three copies for your review and distribution. A garage (26'X 24') is proposed at the southwest corner of the parcel. The proposed garage is well set back, 80 feet, from the limit of the Landslide Hazard Area. It is to be noted that the 50-foot vegetative buffer zone covers the existing building. These have been mapped on the site plan (figure 2). Based on available documents, the original report, and site slope models; it is our opinion that the proposed development poses no threat to the landslide hazard area and vice-versa. It is advised to follow all the recommendations as per the original report. No upland waterbodies and wetlands were observed upon review of available maps and documents. The surface and groundwater conditions are provided in the original report. In addition to the recommendations as per the original report, the following section is provided. VEGETATIVE MANAGEMENT These recommendations and the following are general and may be modified subject to approval. 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, septic drainfields and their associated drains, etc. Densely rooted evergreen shrubs are preferable than tree species on slopes of greater than 15% gradient. Tall trees may become unstable in wet soils under high wind conditions. Tall trees located on a steep slope may be taken out as long as the stumps remain in the ground. "No disturb" zones should be marked on final plans and flagged at the job- site. Exposed soils should be immediately revegetated with grass and local shrubs. # 07-0195 10011 Blomberg Street SW, Olympia, WA 98512 1 Phone#: (360) 754-4612 Fax#: (360) 754-4848 The owner may remove trees within 15 feet of structures that require future access as well as those with damaged roots from the construction procedures. A Certified Arborist should perform view clearing, branch thinning, and maintenance. Conifers should not be topped. We are also a full service laboratory that can meet all your building, testing (compaction, asphalt, concrete), and inspection needs. 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. o{ Wash, Respectfully Submitted, GEOTECHNICAL TESTING LABORATORY �07 ngineering Geologist S 2439 Curtis D Cushman, L.G., L.E.G. ed GB0 Senior Engineering Geologist # 07-0195 10011 Blomberg Street SW, Olympia, WA 98512 2 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEOTEOINICALTIMNGLAwRAToRy SLOPE MODEL SLOPE MODEL A •, STATIC - _ FoS: 1.84 . - 130 • 179 G a 90 - j N w 7o Name: Gravelly Sandy Loam Unit Weight: 128 S0 Cohesion: 300 Phi: 38 Phi-B:O 30 10 0 25 50 75 100 125 1s0 175 200 225 250 275 300 Distance(ft) sYERLABY s&oae A DYNAMIC - FOS Byerty Site--Slope A S A W Name:Glayelly Sandy Loam Unli Weight 129 Cohesion:300 Phi,38 Phi-B:0 # 07-0195 10011 Blomberg Street SW,Olympia, WA 98512 3 Phone#: (360) 754-4612 Fax#: (360) 754-4848 ' O stS Vo'` CD M CA) b CJf O 1' IV `. 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U); O O LO w � i C) OD V3NV(18VZ.VH �(Ills(]Nvl,=101INI-I ---------- ........................................................... ..................... .........................----------- 3NII 1:133ing 3AIIV!D. 3A IOOJ 09 cLo) . . ... . . . . . . . ... . . . . ... . . . . . .. . . ... . . - - - - - - Wan g F�CD ;j y Utz a C) a a a C) 0 0 U) N c) CD CD o CD O c) c) C) Ln rn Bu � F R • 'R. ♦ •-sue , ,- • t' x PW t♦ .#. ♦♦ MM, ` ,♦ ♦ i • a r p Ili��wd_1 .':. ♦, �•, • ♦ ♦ ♦_•♦ `♦♦ 14 ol w • �� - •� R R�!� •, .ice R♦✓ r,. Y J ♦• ♦ i d� R ♦ R ♦ ♦ i • • a ` • r V • ra t J a \ a ♦RJR ♦r' s • ♦ • a: • i • r � i ♦ • • • „ ♦ e + ; ♦ r J ♦ r ; r♦ ♦` •. i♦ ♦R+ i• ♦�•�♦ Ri ♦ ERR i• �' ♦. s .J . . • t i �, ♦ i J , i a♦` .. *fat ._ • . . i '♦R • • • �f,o w0c, - GEOTECHNICAL REPORT 370 NE LARSON LAKE ROAD BELFAIR, WASHINGTON PREPARED FOR JOHN BYERLY BY GEOTECHNICAL TESTING LABORATORY OLYMPIA, WASHINGTON APRIL 3012007 GEOTECHNIC'AL TESTING LABORATORY CONTACT INFORMATION PREPARER INFORMATION GTL PROJECT NUMBER: 07-0195 CONTACT: LANCE LEVINE ADDRESS: 10011 BLOMBERG STREET SOUTHWEST OLYMPIA,WASHINGTON 98512 TELEPHONE: (360)754-4612 FACSIMILE: (360)754-4848 EMAIL ADDRESS: GEOTESTLAB@COMCAST.NET CLIENT INFORMATION CLIENT: JOHN BYERLY TELEPHONE: (360)275-6230 BILLING ADDRESS: P.O.BOX 0133 BELFAIR,WASHINGTON 98528 SITE ADDRESS: 370 LARSON LAKE ROAD BELFAIR,WASHINGTON 98528 PARCEL: 123312390012 GPS LOCATION: N47,26.440'W122°51.787' 10011 Blomberg Street SW, Olympia, WA 98512 2 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEOTECHWAL TESTtNG LABORATORY SCOPE OF UNDERSTANDING JOHN BYERLY P.O.Box 0133 BELFAIR,WA 98528 RE: GEOTECHNICAL REPORT 370 NE LARSON LAKE ROAD BELFAIR,WA 98528 PARCEL 123312390012 N47°26.440'W122°51.787' Mr. Byerly: As per your request, we have conducted a soils exploration, foundation evaluation, and slope stability analysis for the above-mentioned parcel. The results of this investigation, together with our recommendations, are to be found in the following report. We have provided three copies for your review and distribution. Soil samples were submitted for laboratory testing from the project site. The data has been carefully analyzed to determine soils bearing capacities, footing embedment depths and building setback distances. The results of the exploration and analysis indicate that conventional spread and continuous wall footings appear to be the most suitable type of foundation for the support of the proposed structure. Some variability was encountered in comparing the soil profiles of the site. Net allowable soil pressures, embedient depth, and total expected settlements have been presented for the site later in the report. We are also a full service laboratory that can meet all your building, testing (compaction, asphalt, concrete), and inspection needs. 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, °� w�`4h GEOTECHNICAL TESTING LABORATORY y 0� Engineering Geologist �� 827 `g`` Harold Parks, L.G., L.E.G. Brj ° Senior Engineering Geologist S�'d Ge°� HAROLD PARKS t KIP lQES ?- 31-0'7 10011 Blomberg Street SW, Olympia, WA 98512 3 Phone#: (360) 754-4612 Fax#: (360) 754-4848 EOTECHNICAL TESTING LABORATORY TABLE OF CONTENTS CONTACTINFORMATION.....................................................................................................................................2 SCOPEOF UNDERSTANDING ...............................................................................................................................3 TABLEOF CONTENTS............................................................................................................................................4 INTRODUCTION.......................................................................................................................................................5 SITECONDITIONS...................................................................................................................................................6 SurfaceConditions..................................................................................................................................................6 SiteGeology............................................................................................................................................................7 SiteSoils................................................................................................................................................................. 7 SubsurfaceExplorations.........................................................................................................................................8 SubsurfaceConditions............................................................................................................................................8 SlopeStability.........................................................................................................................................................8 CONCLUSIONS AND RECOMMENDATIONS.................................................................................................... 10 General.................................................................................................................................................................. 10 GEOLOGICALLYHAZARDOUS AREAS............................................................................................................. 1 1 Landslide Hazard Classification........................................................................................................................... 1 1 Seismic Hazard Classification .............................................................................................................................. 1 1 Erosion Hazard Classification .............................................................................................................................. 12 SlopeStability....................................................................................................................................................... 12 BuildingSetback................................................................................................................................................... 13 Seismic—Liquefaction Hazard............................................................................................................................. 15 ErosionControl..................................................................................................................................................... 15 EARTHWORK......................................................................................................................................................... 16 SitePreparation..................................................................................................................................................... 16 StructuralFill........................................................................................................................................................ 17 Suitability of Onsite Soils as Fill.......................................................................................................................... 17 Cutand Fill Slopes................................................................................................................................................ 18 FoundationSupport............................................................................................................................................... 18 FloorSlab Support................................................................................................................................................ 19 RetainingWalls..................................................................................................................................................... 19 RetainingWall Alternatives..................................................................................................................................21 SiteDrainage.........................................................................................................................................................21 SepticImpact.........................................................................................................................................................21 LIMITATIONS.........................................................................................................................................................22 Figure1 Vicinity Map...........................................................................................................................................23 10011 Blomberg Street SW, Olympia, WA 98512 4 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEOTECHNIC'AL TESTING LA130 ATORY . 1 INTRODUCTION ' This report summarizes the results of our geotechnical consulting services for the proposed single-family residence. The site is located along the east-facing hillside overlooking the Hood Canal in Mason County. The ' site is approximately 1.5 miles southwest of Belfair, Washington. The location of the site is shown relative to the surrounding area on the Vicinity Map, Figure 1. A { :.� ' Our understanding of the project is based on our discussions with you and our explorations and review of the site. We understand that the parcel is to be developed by replacing the existing single-family residence within a similar footprint. The site will be accessed by an existing driveway from Larson Lake Road. In general, grading will consist of the excavation of the foundation and footings. The approximate layout of the site is shown on the Site ' Plan, Figure 2. The site slopes toward the east from the proposed building location. The steepest slope measured onsite was ' approximately 48 percent. Therefore, Mason County requires that a geotechnical report be prepared in accordance with the Critical Areas Ordinance. ' The purpose of our services is to evaluate the surface and subsurface conditions at the site as a basis for providing geotechnical recommendations and design criteria for the project and to satisfy the requirements of the Mason County Critical Areas Ordinance. Geotechnical Testing Laboratory is therefore providing geologic and hydrogeologic services for the project. Specifically, our scope of services for this project will include the following: 1. Review the available geologic,hydrogeologic,and geotechnical data for the site area. 2. Conduct a geologic reconnaissance of the site area and surrounding vicinity. 3. Investigate shallow subsurface conditions at the site by observing the exposed soil and reviewing published well logs. 4. Evaluate the landslide and erosion hazards at the site per the Mason County Critical Areas Ordinance regulations. 5. Provide geotechnical recommendations for site grading including site preparation, subgrade preparation, fill placement criteria(including hillside grading), temporary and permanent cut and fill slopes, drainage and erosion control measures. 10011 Blomberg Street SW,Olympia, WA 98512 5 Phone#: (360) 754-4612 Fax#: (360) 754-4848 1 GEOTECRNICAL TESTtNO LABORATORY - =7 V� .4. c r _ SITE CONDITIONS SURFACE CONDITIONS The proposed building site is located in an area of moderate residential development in the Puget Sound glacial upland along the northern hillside of the Hood Canal. The site has an eastern exposure. We conducted a reconnaissance of the site area on April 17,2007. Site elevations range from approximately 20 to 150 feet. The building area of the site has vegetation common to the Northwest. The vegetation includes fir, madrone, cedar, pine, dogwood, and maple trees as well as salal, Scot's broom, huckleberry, Oregon grape, bracken fern, blackberry, manzanita, and ' grasses. At the time of the site visit, we observed no evidence of active a surface erosion. No evidence of +� deep-seated slope instability was observed onsite. Minor raveling and - - sloughing was observed along the toe i of the eastern fill material. r ':'�•Y Surface water flow was not observed f onsite. The general topography of 1� 1 the site area indicates that drainage ' flows toward the east from the proposed building location. ' 1001 1 Blomberg Street SW,Olympia, WA 98512 6 Phone#: (360)754-4612 Fax#: (360) 754-4848 1 GEOTECHNICAL TESTING LABORATORY SITE GEOLOGY The site is generally situated within the Puget Sound glacial upland. The existing topography, as well as the surficial and shallow subsurface soils in the area, are the result of the most recent Vashon stade (stage) of the Fraser glaciation that occurred between about 9,000 and 11,000 years ago, and weathering and erosion that has occurred since. A description of the surficial soils is included in the"Site Soils"section of this report. In general, 6 the soils are composed of glacial outwash material. The Geologic Map of Washington—Northwest Quadrant(2002)has mapped the site geology as glacial outwash deposits(Qgo)of continental glacial origin. The report reads: Undifferentiated outwash — Recessional and proglacial stratified sand, gravel, and cobbles with minor silt and clay interbeds deposited in delta, ice-contact, beach, and meltwater stream environments; may include advance outwash. Includes part of the Partridge Gravel,part of the Everson Glaciomarine Drift, and part of the Vashon Drift undivided. 1 '•t . 1 Y-. c c. 1 SITE SOILS 1 The Soil Survey of Mason County, Washington, USDA Soil Conservation Service (1960) has mapped the eastern site soils as Everett gravelly loamy sand, 15 to 30 percent slopes(Ef). The survey describes the soil as follows: The Everett series consists of somewhat excessively drained, pale-brown gravelly soils. They ' occur as inextensive gravel ridges on the glacial moraines, or, more commonly, as fairly continuous outwash channels between ridges of Alderwood soils. They have developed upon assorted glacial till and outwash material. The rainfall is 45 to 60 inches a year. The vegetation ' is mainly drought-resistennt madrone, manzanita, and kinnikinnick. Everett soils are droughty because the loose gravel and sand subsoil and substratum offer little resistance to downward movement of water. The capacity of the surface soil to hold available moisture is low. Everett soils are in the eastern half of the country, in association with Alderwood soils. They also occur in intricate patterns with the Kitsap and Indianola soils. Compared to the Grove soils, the Everett soils have a paler surface soil and subsoil and, in development, were dominated more by ' acid igneous parent rock. Everett gravelly loamy sand, 15 to 30 percent slopes (Ef). Except for slopes, this soil is similar to Everett gravelly loamy sand, 5 to 15 percent slopes. Profile characteristics vary greatly from place to place, especially on the steeper slopes. The Soil Survey of Mason County, Washington, USDA Soil Conservation Service(1960) has mapped the western site soils as Everett gravelly loamy sand, 5 to 15 percent slopes(Ee). The survey states: This soil is similar to Everett gravelly loamy sand, 0 to 5 percent slopes, but its profile is more variable and the thicknesses of the surface soil and subsoil are slightly less. t 10011 Blomberg Street SW, Olympia, WA 98512 7 Phone#: (360)754-4612 Fax#: (360)754-4848 1 c• 4 r y }Sa+s r.' t"GEOTECHNICAL TESTING LABORATORY 5'r s y �/�rc t.`s { tSUBSURFACE EXPLORATIONS Subsurface conditions at the site were evaluated by observing the exposed building site soil and reviewing ' available well logs. Groundwater was not encountered at the proposed building location and is beyond the scope of this report(approximately 107 feet below ground surface). Depth to competent soil is approximately 12 inches throughout the proposed building location. ' SUBSURFACE CONDITIONS ' In general, dense Everett gravelly sandy loam was observed in the undisturbed portions of the site. Vashon Stade glacial material was observed below the Everett material. Groundwater was not observed or encountered. Groundwater seepage was not observed onsite. Based on the site topography and the nature of the near surface soil,seasonally perched groundwater conditions may be expected during periods of extended wet weather. 1 �k V . f ' SLOPE STABILITY The Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977)describes the site area as Class ' 2. Class 2 is described as: Areas believed to be stable under normal conditions, but may become unstable if disturbed by man's activities, if slope is oversteepened by erosion, or if subjected to strong seismic shaking. Slopes generally steeper than 15 percent, but may be less in some areas of weak geologic materials. Includes areas underlain by: well-drained sand and gravel, mostly on valley sides that lack known slope failures;glacial till with steep slopes:and bedrock. 10011 Blomberg Street SW, Olympia, WA 98512 8 Phone#: (360)754-4612 Fax#: (360)7544848 CEOTECHNICAL TESTING LABORATORY The Coastal Zone Atlas, volume 9, Mason County (MA-12) maps the site as Vashon Advance Outwash (Qva). The chance of flooding is less than one percent. Permeability is described as high, while runoff potential is low. Infiltration is moderate on natural slopes and high on cut slopes. Springs at the bases of slopes are common (springs or seeps were not observed during the site reconnaissance). The slope stability is described as "stable" at the proposed building location and"intermediate" in the eastern portion of the site. ' Slopes approximately 48 percent were observed Scott 1:z.. „ onsite. Since slopes of 40 percent or greater with 10 " feet or more of vertical relief occur near the site, Mason County requires that a geotechnical report be MER co The near-surface soils are in a dense to very densempleted according to the Critical Areas Ordinance. 1 �• . condition except at the ground surface. The surficial t M soils are generally in a medium dense condition. In general, the undisturbed native soils of the site - : 1 consist of a mixture of variable amounts of sand, silt, A and gravel. These soil materials are in a dense A condition except where they have been disturbed by -.. weathering activity. No evidence of deep-seated 1 9 landslide activity or significant erosion was observed onsite at the time of our investigation. `` Weathering, erosion, and the resultant sloughing and shallow landsliding are natural processes that can affect steep slope areas. Instability of this nature is ' typically confined to the upper weathered or disturbed zone, which has been disturbed and has a lower strength. Only minor raveling and sloughing were observed along the eastern fill material. Significant weathering typically occurs in the upper 2 to 3 feet and is the result of oxidation, root penetration, wet/dry cycles, and freeze/thaw cycles. Erosion in steep slope areas such as this can be reduced by encouraging vegetation and discouraging runoff from the steep slopes. Erosion control recommendations for the sloping areas are provided in the"Erosion Control"section of this report. AL AN �M 1001 1 Blomberg Street SW,Olympia, WA 98512 9 Phone#: (360)754-4612 Fax#: (360) 754-4848 1 ' GEOTECKNICAL TESTtNC LABORATORY] CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on the results of our site reconnaissance, subsurface observations, and our experience in the area, it is our opinion that the site is suitable for the proposed project. The proposed building location is stable relative to deep- seated instability and will not be affected by the proposed structure. The proposed structure will not undermine adjacent slopes. Proper drainage control measures will reduce or eliminate the potential for erosion in this area and improve slope stability. The hazards of the landslide area can be mitigated in such a manner as to prevent ' harm to property and public health and safety,and the project will cause no significant environmental impact. In general, the Everett soils observed at the site may be suitable for use as structural fill material. Saturated soil conditions are not associated with these soils during or following extended periods of rainfall. However, to ' reduce grading time and construction costs, we recommend that earthwork be undertaken during favorable weather conditions. ' Conventional construction equipment may be utilized for work at the site. Conventional spread footings may be utilized at the site for support of the structure. We do recommend that roof and footing drains be installed for the structure with conventional spread footings. A vapor barrier is recommended for all slab-on-grades. ' Pertinent conclusions and geotechnical recommendations regarding the design and construction of the proposed single-family residence are presented below. 1 y .s. 1 1 ' 10011 Blomberg Street SW,Olympia,WA 98512 10 Phone#: (360)754-4612 Fax#: (360) 754-4848 1 GEOTECHNICAL TESTING LABORATORY GEOLOGICALLY HAZARDOUS AREAS LANDSLIDE HAZARD CLASSIFICATION The Mason County Critical Areas Ordinance(17.01.100)defines a landslide hazard area as: The following shall be classified as Landslide Hazard Areas: a. Areas with any indications of earth movement such as debris slides, earthflows, slumps and rockfalls (see figure F.100). b. Areas with artificial oversteepened or unengineered slopes, i.e. cuts or fills. c. Areas with slopes containing soft or potentially liquefiable soils. d. Areas oversteepened or otherwise unstable as a result of stream incision, stream bank erosion, and undercutting by wave action. e. Slopes greater than 15% (8.5 degrees) and having the following.• i. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock(e.g. sand overlying clay); and ii. Springs or groundwater seepage. f. Any area with a slope of forty percent or steeper and with a vertical relief of ten or more feet except areas composed of consolidated rock. A slope is delineated by establishing its toe and top and measured by averaging the inclination over at least ten feet of vertical relief. SEISMIC HAZARD CLASSIFICATION The Mason County Critical Areas Ordinance(17.01.102)defines a seismic hazard area as: 1. Areas susceptible to ground failure including the following: a. Areas with Mapped geologic faults until proven inactive; b. Deep road fills and areas of poorly compacted artificial fill; c. Areas with artificially steepened slopes (i.e. old gravel pits); d. Postglacial stream, lake or beach sediments; e. River deltas; f. Areas designated as potential Landslide Hazard Areas; g. Bluff areas; and h. Areas underlain by potentially liquefiable soils 2. The following criteria may be used as a guide by the County to indicate areas that have a higher likelihood of meeting the classification criteria'above: a. Areas identified on the Coastal Zone Atlas of Washington, Volume 9, Mason County as Af, Qal, Qa2, Qvc, Qls, Qos and Qp. b. Areas identified on the Mason County Soil Survey Map as having slopes greater than 15 percent. c. Faults identified on "Map Showing Known or Suspected Faults With Quaternary Displacement in the Pacific Northwest", A.M. Rogers, T.J. Walsh, W.J. Kockelman and G.R. Priest, US Geologic Survev, 1996; or described in "Active Faulting Investigations on the Canyon River Fault, Southern Olympic Range, Washington", T.J. Walsh and KG. Neal, U.S. Geologic Survey, 1997. d. Areas underlain by potentially liquefiable soils as shown "Liquefaction Susceptibility Map of Mason County, Washington" by Stephen P. Palmer, Sammantha L. Magsino, James L. Poelstra, Eric L. Bilderback, Derek S. Folger, and Rebecca A. Niggemann, September 2004 This site does qualify as a seismic hazard area because the site is categorized as, "l.f. Areas designated as potential Landslide Hazard Areas" 10011 Blomberg Street SW, Olympia, WA 98512 Phone#: (360)754-4612 Fax#: (360) 754-4848 GE®TECHNICAL TESTING LABORATORY EROSION HAZARD CLASSIFICATION The purpose of the Erosion Hazard Section (17.01.104) is to identify areas that present potential dangers to public health and safety, and to prevent the acceleration of natural geological hazards, and to neutralize the risk to the property owner from development activities. Areas in Mason County underlain by soils which are subject to severe erosion when disturbed. Such soils include, but are not limited to, those for which potential for erosion is identified in the Soil Survey of Mason County, USDA Soil Conservation Service, 1960, ' or any subsequent revisions or additions to this source. These soils include, but are not limited to, any occurrence of River Wash ("Ra') or Coastal Beaches ("Cg') and the following when they occur on slopes IS%or steeper: a.Alderwood gravelly sandy loam ("Ac"and"Ad') b. Cloquallum silt loam("Cd') c. Harstine gravelly sandy loam ("Hb') d. Kitsap silt loam ("Kc') The soils at the site are mapped as Everett gravelly sandy loam (Ee and Ef). This site does not meet the technical criteria of an erosion hazard area. 1 t *f SLOPE STABILITY Based on our field observations, explorations and our experience with the soil types encountered on the property, we conclude that although natural slopes are approximately 48 percent,they are generally stable relative to deep- seated failure in their present configuration. The proposed building location is in an area where the slope is approximately 1 percent. Excavation and back-filling will occur based on appropriate engineering and earthwork recommendations found in the following"Earthwork" section. Grading in the building portion of the site should be conducted in accordance with geotechnical recommendations provided herein. 10011 Blomberg Street SW,Olympia, WA 98512 12 Phone#: (360) 754-4612 Fax#: (360)754-4848 1 i ' G '+®TIECHNICAL 'TESTING LABORATORY ' Slope stability was modeled using the GeoStudio 2004 program (version 6.20) in both static and dynamic conditions (ce = 0.15). Factors of safety were determined using Bishop's, Janbu, and the Morgenstern-Price methods. The site was modeled using a monolithic layer of gravelly sandy loam. The material was determined to have a unit weight of 128 pef, cohesion of 300 psf, and a shear angle (0) of 39°. Under static conditions, the slopes remained stable-to deep-seated and shallow failure (F.S. = 1.74). Under dynamic loading, the 3328 computations demonstrated that the slope is not susceptible to surficial raveling or large deep-seated failure. The ad following figure illustrates the moment factor of safety for slope "A" under the existing conditions. The critical slip surface factor of safety is equal to 1.31. Mason County code requires a factory of safety to be at least 1.1 at the proposed building location. This figure is the solution of greatest concern and exhibits the need for a building setback of 22-feet from the face of the eastern slope. No building setback will be required from the small western slope. All foundation elements shall be constructed on native material or engineered fill material. Byedy Site--Slope A 1 c 1 c ' o � G W m Description Gravelly Sanoy Loam y YUt 128 Cohesion:300 ' Phi.38 m a b 9 i6 tm iE 19, 1R a0 iE SI TI6 ]D � � Distance M ' As previously discussed, weathering, erosion and the resultant surficial sloughing and shallow landsliding are natural processes that affect slope areas. Minor surficial raveling and sloughing was observed along the eastern ' fill material. To manage and reduce the potential for these natural processes, we recommend the following: ➢ No drainage of concentrated surface water or significant sheet flow onto the sloped areas. ' ➢ No filling within the setback zone unless retained by retaining walls or constructed as an engineered fill. Re-establish vegetation on fill material. 10011 Blomberg Street SW, Olympia, WA 98512 14 Phone#: (360)754-4612 Fax#: (360) 754-4848 1 GEO'I ECHNIGAL TESTING LABORATORY SEISMIC—LIQUEFACTION HAZARD 1 According to the Seismic Zone Map of the United States contained in the 2003 International Building Code(IBC), the project site is located where the maximum spectral response acceleration is 45 percent of gravity(g). 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 very low liquefaction potential. 1 The Site Class Map of Mason County, Washington by Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggemann (September 2004) maps the site area as site class C to D. Site class C is a very stiff soil or soft rock and site class D is a stiff soil. Based on the subsurface conditions observed at the site,we interpret the site conditions to correspond to a seismic Soil Profile Type D, for Stiff Soil, as defined by Table 1615.1.1 (IBC). This is based on probing with a '/z-inch diameter steel probe rod. The shallow soil conditions were assumed to be representative for the site conditions ' beyond the depths explored. Based on our review of the subsurface conditions, we conclude that the site soils are only mildly susceptible to ' liquefaction. The near-surface soils are generally in a dense condition and the static water table is located well below the surface. Shaking of the already dense soil is not apt to produce a denser configuration and subsequently excess pore water pressures are not likely to be produced. c 'r• tEROSION CONTROL 1 It is our opinion that the potential erosion hazard of the site is not a limiting factor for the proposed development. Removal of natural vegetation should be minimized and limited to the active construction areas. Yard landscaping around the home is permissible, but understory growth on the slopes should be encouraged as much as possible as a deterrent to erosion. Hazard trees located on steep slopes may be removed only if the stumps ' remain to deter erosion. Temporary and permanent erosion control measures should be implemented and maintained during construction ' and/or as soon as practical thereafter to limit the additional influx of water to exposed areas and protect potential receiving waters. ' 10011 Blomberg Street SW,Olympia,WA 98512 15 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNicAL TESTING LABORATORY 8 Erosion control measures should include, but not be limited to, silt fences. berms, and swales with ground cover/protection in exposed areas. A typical silt fence detail is included on Figure 2. Any re-contouring of the site will create a need for erosion control measures as listed above. •, EARTHWORK SITE PREPARATION All areas to be excavated should be cleared of deleterious matter including any existing structures, debris, duff, J and vegetation. Based on our observations, we estimate that stripping on the order of 8 to 14 inches will be necessary to remove the root zone and surficial soils containing organics. Areas with deeper, unsuitable organics should be expected in the vicinity of depressions or heavy vegetation. Stripping depths of up to 3 feet may occur v in these areas. These materials may be stockpiled and later used for erosion control and landscaping. Materials that cannot be used for landscaping or erosion control should be removed from the project site. No foundation elements shall be constructed on fill material. Where placement of fill material is required, the exposed subgrade areas should be proof-rolled to a firm and unyielding surface prior to placement of any fill. We recommend that trees be removed with the roots, unless ` located on a slope. Excavations for tree stump removal in any building area should be backfilled with structural iY fill, compacted to the density requirements described in the"Structural Fill"section of this report. t If structural fill is needed, we recommend that a member of our staff evaluate the exposed subgrade conditions after removal of vegetation and topsoil stripping is completed. ' Any soft, loose or otherwise unsuitable areas delineated during foundation preparation or probing should be compacted, if practical, or over-excavated and replaced with structural fill, based on the recommendations of our report. w� 1 ti • � ' „OrPl nAp ! f ' 10011 Blomberg Street SW,Olympia, WA 98512 16 Phone#:(360) 754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY STRUCTURAL FILL All fill material should be placed as structural fill. The structural fill should be placed in horizontal lifts of appropriate thickness to allow adequate and uniform compaction of each lift. Fill should be compacted to at least 90 percent of MDD (maximum dry density as determined in accordance with ASTM D-1557)to within 2 feet of }'4 subgrade and 95 percent MDD in the upper 2 feet. The appropriate lift thickness will depend on the fill characteristics and compaction equipment used. We recommend that the appropriate lift thickness be evaluated by our field representative during construction. The suitability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines (material passing No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. During wet weather, we recommend the use of well-graded sand and gravel with less than 9 percent(by weight) passing the No. 200 sieve based on that fraction passing the 3/4-inch sieve. If prolonged dry weather prevails during the earthwork and foundation installation phase of construction, a somewhat higher(up to 10 percent)fines content will be acceptable. 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. v e ,I L� 1 + 1 SUITABILITY OF ONSITE SOILS AS FILL Onsite soils may be considered for use as structural fill if industry standards are satisfied. In general, the native ' soils (sand, silt, and gravel)encountered on the site must have less than 10 percent fines (material passing the US No.200 sieve)to be suitable for use as structural fill. 10011 Blomberg Street SW,Olympia, WA 98512 17 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY CUT AND FILL SLOPES ' All job site safety issues and precautions are the responsibility of the contractor providing services and/or work. The following cut/fill slope guidelines are provided for planning purposes. ' Temporary cut slopes will likely be necessary during grading operations. As a general guide,temporary slopes of 1.5 to 1 (horizontal to vertical) or flatter may be used for temporary cuts in the upper 3 to 4 feet of the glacially consolidated soils that are weathered to a loose/medium-dense condition. Temporary slopes of 1 to 1 or flatter may be used in the unweathered dense to very dense sands and gravel. ' These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the slope and that significant seepage is not present on the slope face. Flatter cut slopes will be necessary where significant raveling or seepage occurs. All foundation elements must be founded on ' native material or engineered fill material. Surface drainage should be directed away from all slope faces. All slopes should be seeded as soon as practical to facilitate the development of a protective vegetative cover or otherwise protected. FOUNDATION SUPPORT ' Where foundation elements are located near slopes between 5 and 30 percent, the footings should be located a minimum of 2 times the footing width from the slope face(horizontally), and founded in medium dense or denser native soils or properly prepared structural fill. We recommend a minimum width for isolated and continuous wall footings to meet IBC 2003. Footings founded as described above can be designed using an allowable soil bearing capacity of 2,000 psf(pounds per square foot) for combined dead and long-term live loads in areas of medium dense to dense soils. The weight of the footing and any overlying backfill may be neglected. The allowable bearing value may be ' increased by one-third for transient loads such as those induced by seismic events or wind loads. Lateral loads may be resisted by friction on the bases of footings and floor slabs and as passive pressure on the ' sides of footings. We recommend that an allowable coefficient of friction of 0.40 be used to calculate friction between the concrete and the underlying soil. Active pressure may be determined using an allowable equivalent fluid density of 250 pcf(pounds per cubic foot). ' 10011 Blomberg Street SW, Olympia, WA 98512 18 Phone#: (360) 754-4612 Fax#: (360)754-4848 1 GEOTECHNICAL TESTING LABORATORY We estimate that settlements of footings designed and constructed as recommended will be less than 1 inch, for the anticipated load conditions, with differential settlements between comparably loaded footings of % inch or r less. Pq Most of the settlements should occur essentially as loads are being applied. However, disturbance of the i foundation subgrade during construction could result in larger settlements than predicted. 1 FLOOR SLAB SUPPORT Slabs-on-grade should be supported on medium dense or dense native soils or on structural fill prepared as described in the "Structural Fill' section of this report. We recommend that floor slabs be directly underlain by a 1 minimum 6-inch thickness of coarse sand and/or gravel containing less than 5 percent fines (by weight). The drainage material should be placed and compacted to an unyielding condition. ' A synthetic vapor barrier may be used for the control of moisture migration through the slab, particularly where adhesives are used to anchor carpet or tile to the slab. A thin layer of sand may be placed over the vapor barrier and immediately below the slab to protect the liner during steel and/or concrete placement. The lack of a vapor barrier could result in wet spots on the slab,particularly in storage areas. r ' RETAINING WALLS Retaining walls may be utilized on the sloping portion of the site to retain fill material. The lateral pressures acting on the subgrade and retaining walls will depend upon the nature and density of the soil behind the wall. It ' is also dependent upon the presence or absence of hydrostatic pressure. If the adjacent exterior wall space is backfilled with clean granular, well-drained soil (washed rock), the design active pressure may be determined using an active pressure coefficient equal to 0.25 (Ka = 0.25). This design value assumes a level backslope and drained conditions as described below. Retaining walls located on or near the toe of a slope that extends up behind the wall should be designed for a ' lateral pressure, which includes the surcharge effects of the steep slope in proximity to the wall. Although not expected at this site,the following data is provided for planning purposes. 10011 Blomberg Street SW,Olympia, WA 98512 19 Phone#: (360) 754-4612 Fax#: (360) 754-4848 1 GEOTECHNICAL TESTING LABORATORY For an irregular or composite slope, the equivalent slope angle may be determined by extending a line upward from the toe of the wall at an angle of 1 to 1 (Horizontal to Vertical)to a point where the line intersects the ground 1 surface. The surcharge effects may be modeled by increasing the equivalent fluid pressure for flat ground by the percentage given in the following table: SLOPE INCLINATION:EQUIVALENT FLUID PRESSURE Slope Angle Percent Increase Equivalent Fluid Pressure Horizontal 0% 35 pcf 3H:1V 25% 44 pcf 2H:1 V 50% 53 pcf 1 H:1 V 75% 61 pcf If the walls are greater than 4 feet in height, exclusive of the footing, additional design considerations should be applied. F7 Positive drainage, which controls the development of hydrostatic pressure, can be accomplished by placing a zone of coarse sand and gravel behind the walls. The granular drainage material should contain less than 5 percent fines. The drainage zone should extend horizontally at least 18 inches from the back of the wall. The drainage zone should also extend from the base of the wall to within 1 foot of the top of the wall. The drainage zone it should be compacted to approximately 90 percent of the MDD. Over compaction should be avoided as this can lead to excessive lateral pressures. A perforated PVC pipe with a minimum diameter of 4 inches should be placed in the drainage zone along the base of the wall to direct accumulated water to an appropriate discharge location. We recommend that a non-woven geotextile filter fabric be placed between the drainage material and the remaining wall backfill to reduce silt migration into the drainage zone. The infiltration of silt into the drainage zone can,with time, reduce the permeability of the granular material. The filter fabric should be placed in such a way that it fully separates the drainage material and the backfill, and should be extended over the top of the drainage zone. ' Lateral loads may be resisted by friction on the bases of footings and as passive pressure on the sides of footings and the buried portions of the wall. We recommend that an allowable coefficient of friction of 0.40 be used to ' calculate friction between the concrete and the underlying soil. 1 J ' ' 10011 Blomberg Street SW, Olympia, WA 98512 20 Phone#: (360)754-4612 Fax#: (360) 754-4848 1 GEOTECHNICAL TESTING LABORATORY ' RETAINING WALL ALTERNATIVES Typically, block wall systems are more cost effective for long-term walls than the other options. Specific design criteria for these options can be provided at your request by the block manufacturers. J 4 SITE DRAINAGE 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 1 basins and tight-lined into the appropriate drainage facilities or to the base of the western slope. We recommend that conventional roof drains be installed. Footing drains shall be installed for the single-family residence. 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. We recommend that the collected stormwater runoff be directed into the appropriate drainage facilities by tight- line. Drainage control measures are included on Figure 3. Onsite irrigation to lawn areas should be closely monitored. We do not expect any adverse affects on the recharge condition of the groundwater system. ' SEPTIC IMPACT The existing septic drainfield will not be re-located from the southern portion of the site. The drainfield location ' setback is greater than 45 feet from the top of the eastern slope. We conclude the slope stability of the site will not be adversely impacted. 1 1 1 t � 10011 Blomberg Street SW,Olympia, WA 98512 21 Phone#: (360)7544612 Fax#: (360)754-4848 1 1 GEOTECHNICAL TESTING LABORATORY 1 LIMITATIONS 1 We have prepared this report for the use of John Byerly and members of his design team, to use in the design of a portion of this project. The data used in preparing this report, and this report, should be provided to prospective ' contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on data from others and our site reconnaissance, and should not be construed as a warranty of the subsurface conditions. This report is quantified as a micro-study and not a macro-study. Geotechnical Testing Laboratory and its personnel cannot be responsible for unforeseen and widespread geologic events (such as earthquakes, large-scale faulting, and mass wasting)beyond the scope of this project. ' Variations in subsurface conditions are possible and may occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient consultation should be made with our firm during construction to confirm that the conditions encountered are consistent with those indicated by the recommendations and for design changes should the conditions revealed during the work differ from those ' anticipated,and to evaluate whether earthwork and foundation installation activities comply with contract plans. If our analysis and recommendations are followed, we do not anticipate any on site or off site impact from the ' construction. It is our conclusion that potential landslide hazards from the landslide area can be overcome so as not to cause harm to property,public health and safety, or the environment. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures,except as specifically described in our report for consideration in design. � I If there are any changes in the loads, grades, locations, configurations or types of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate. Recent changes in the Mason County Code require our firm to revisit the site (after six months)to ensure the conditions are in agreement with our original report. 1 1 1 1 1 10011 Blomberg Street SW,Olympia, WA 98512 22 Phone#: (360)7544612 Fax#: (360) 754-4848 1 GEOTECHNICAL TESTING LABORATORY ORY FIGURE I VICINITY MAP `r 1. f2 _� �- J 3m a •`! 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