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Home My WebLink AboutGeoTech Assessment Review for BLD2005-01353 - BLD Engineering / Geo-tech Reports - 9/15/2005 .STAT ON F y M MASON COUNTY ^ S u + DIRECTOR/COUNTY ROAD ENGINEER N PUBLIC WORKS= shekon waahmgton vasaa Z Ny y 1%4 DATE: September 15, 2005 INTER-DEPARTMENTAL COMMUNICATIONS TO: Chuck McCoy, DCD -Planner FROM: Robert A. Thuring, PE, Engr and Constr. Mgr. BLD2005-01353/ SUBJ: Geo Tech Assessment Review NAME: James Huskey, Parcel 22304-76-90120 I have reviewed the Geo Tech Assessment and find it satisfactory. The evaluation raises no issues or concerns, and appears acceptable for the level of reporting required. Recommendations contained in the report should be incorporated into the site's development. The applicant and his contractor to should be alerted to their responsibility to protect neighboring properties during and after construction, from adverse stormwater runoff impacts. Sincerely, Robert A. Thuring, PE Engineering and Construction Manager 06 Ser ECEI 'VED From: Jim Huskey SEP ,0 ] 2005 To: Charles Mead McCoy III (Land Use Planner) w MCCD - PLANNING Subj: GEOLOGICAL ASSESSMENT FOR CASE NO. BLD2005-013 NO. 223047690120/PROJECT DESC. 24X34 POLE BUILDING 1. The following geological assessment is provided to complete permit application (case no. BLD2005-01353)for proposed construction of a 24X34 pole building on parcel no. 223047690120. Please feel free to contact me at work(360)396-1894 from 08:00 AM to 4:00 PM or at home(360) 372-2608 for more information if required. 4e incerely, s .4Htiskke RECEIVED SEP yy 7 2005 MCCD - PLANNING Geological Assessment 270 NE Lake Ridge Drive Belfair, WA Prepared for James Huskey Belfair, WA by Geotechnical Testing Laboratory 1 Olympia, Washington September 2, 2005 rr GEOTECHNICAL TESTING LABORATORY .TAMES HUSKEY 270 NE LAKE RIDGE DRIVE BELFAIR,WA 98528 RE: GEOLOGICAL ASSESSMENT 270 NE LAKE RIDGE DRIVE BELFAIR,WA 98528 PARCEL 223047690120 N47030.688' W122056.692' PURPOSE The objective of the geological assessment is to assess the surface and subsurface conditions prevalent at the subject site according to Mason County Ordinance 17.01.100.E4. The parcel is to be developed with a pole building without a concrete floor. The existing structure and septic drainfield are not within the scope of this report. ,T SITE CONDITIONS The subject site is approximately 1.69-acres located 7 miles northwest of Belfair, Washington. The site is accessed from Lake Ridge Drive. The subject site is located in an area of moderate residential development �►:>. • � , . and is surrounded by residentially developed parcels. Currently the site has been prepared for construction. The steepest portion of the site has slopes approaching 38 percent along the eastern property line. The slopes are 1, well vegetated with native plant species. Rapid stream incision was not identified at the site. Slope instability was not discerned onsite or on adjoining parcels. 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone#: (360) 754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY GEOLOGIC CONDITIONS The Soil Survey of Mason County, USDA Soil Conservation Service (1960) has mapped the western site soils as Alderwood gravelly sandy loam(Ab). The survey describes the site soil as follows: The Alderwood soils typically formed from mixed gravelly glacial till dominated by acid igneous rock. It occupies undulating to rolling moraines. In undisturbed areas a 1-to 2-inch mat of very dark brown, acid organic matter is on the surface. This grades to a thin, dark grayish-brown, highly organic mineral soil. The surface soil consists of a friable, brown, medium acid gravelly sandy loam 8 to 13 inches deep. It has a weak granular structure and contains numerous rounded shot. Below the surface soil, to depths ranging from 18 to 24 inches, is a pale-brown gravelly sandy loam that is very friable, is single grained, and contains small to moderate amounts of shot. Between this layer and the cemented till is a 3- to 10-inch layer of very pale brown gravelly sandy loam. It contains no shot and is firmer but has the same texture as the layer above. However, it is faintly to distinctly spotted and horizontally streaked with brown and yellow. The cemented till consists of light-gray, gravelly sandy loam, and it normally occurs at depths ranging from 24 to 32 inches. It is impermeable to roots and very slowly permeable to water. The first few inches is usually laminated and streaked with reddish brown and yellow. Below this, to a depth of many feet, the till is uniformly cemented,fairly uniform light gray, and medium to strongly acid. A thin mat of roots often lies over the till. The cemented substratum tends to restrict the rapid downward movement of moisture. C{41 The Soil Survey of Mason County, USDA Soil Conservation Service(1960)has mapped the eastern site soils as an Alderwood gravelly sandy loam, 15 to 30 percent slopes(Ac). The Alderwood soil typically formed from glacial advance outwash. The soil is described as having good natural drainage. Typically, there is no occurrence of a high water table. Internal drainage is described as medium. An erosion hazard may exist if the vegetation is removed; otherwise, the soil has a low erosion hazard in its present condition. Cementation is usually present. 10011 Blomberg Street SW,Olympia,WA 98512 2 Phone#: (360) 754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY The Geologic Map of Washington — Northwest Quadrant (2002) has mapped the site geology as glacial till deposits(Qgt)of continental glacial origin. The report reads: Till— Unsorted, unstratified, highly.compacted mixture of clay, silt, sand, gravel, and boulders deposited by glacial ice; may contain interbedded stratified sand, silt, and gravel. Includes part of the Vashon Drift undivided. i; lava GROUNDWATER CONDITIONS Groundwater seepage was not observed at or near the proposed building location. No wetland vegetation was observed at or near the proposed building location. Minor wetland vegetation was observed along Erickson Lake. Depth to static groundwater is presumed deep and approximately at the level of Erickson Lake. may' x - DEPTH TO COMPETENT SOIL The proposed building location is underlain by glacially deposited gravelly sandy loam. Competent soil can be expected approximately 2 to 8 inches below the existing ground surface. 10011 Blomberg Street SW,Olympia,WA 98512 3 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY PAST SLOPE INSTABILITY East of the proposed building location,trees were found straight and vertical. No indication of past instability was discerned at the proposed building location or throughout the site. Adjoining parcels display similar signs of stability as the subject site. HISTORY OF LANDSLIDE ACTIVITY No historical landsliding was observed during our site investigation onsite or near F the subject parcel. At the proposed building location, the eastern slope is compact and dense. Onsite trees are straight and vertical. r sr POTENTIAL FOR LANDSLIDE ACTIVITY This site has no indication or record of old or recent landslide activity. Even though slopes approach 38 percent, the potential for landslide activity is not a concern for the proposed deve lopment. i 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. 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. Site class C is a very stiff soil. RECOMMENDATIONS There is no evidence of soil erosion or deposition onsite to suggest that the site should be included in the Erosion Hazard Area designation. Site conditions for the proposed development do not warrant a more comprehensive Geotechnical Report. We recommend no further action is needed unless areas of concern are unearthed during construction or damage ensues from vegetation clearing. To minimize erosion and sedimentation, we recommend that underbrush remain for areas outside the building location. If there are any changes it the loads, grades, locations, configurations or types of facilities to be constructed, the conclusions and recomm idations presented in this report may not be fully applicable. If such changes are made, we should be given ' opportunity to review our recommendations and provide written modifications or verifications,as appropi—ce. Respectfully, GEOTECHNICAL TESTING LABORATO Wash; Harold Parks, L.G., L.E.G. Senior Engineering Geologist 10011 BlombergStreet SW,Olympia, WA 98512 �j �I►*` YmP 827 Phone#: (360)754-4612 Fax#: (360)754-4848 c►e�sed Qeo�O HAROLD PARKS GEOTECHNICAL TESTING LABORATORY VICINITY MAP lip 7� U-) A, ri :7 4-11 if II !3* t ,llXA" aL 141 Ir ff, y ivs \)qQ it Im I Tj I, / 44 ,V 'I .". , f" te .10 1 OM' 10 V: 6;47 —iolATI, W 4� 41, rr Al +-V We 4: J7 t7 1 1,6 10011 Blomberg Street SW, Olympia, WA 98512 5 Phone#: (360)754-4612 Fax#: (360)754-4848