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Home My WebLink AboutGeoTech Assessment Review for BLD2005-00004 - BLD Engineering / Geo-tech Reports - 3/2/2005 °N STArFo� MASON COUNTY o i z PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shelton,WeshiVon98594 r ti Y G) !_ y �0 1864 DATE: March 2Id, 2005 INTER-DEPARTMENTAL COMMUNICATIONS TO: Chuck McCoy,DCD- Planner FROM: Alan A. Tahja,P/W- Co. Hydr. Engr. WO#PLG-05 SUBJ: Geo-Tech Assessment Review NAME: Gipson-LeGault SFR 6-b Limerick BLD2005-00004 Tammi, The geotechnical assessment prepared for the proposed Jake LeGualt-Tracy Gipson Single Family Residence (SFR)to be constructed at 100 East Clonakilty Court, Shelton,has been received and reviewed by Public Works. The report appears to satisfactorily fulfill County requirements for geotechnical assessment reporting. The assessment's author indicates that, in his opinion,the completed development of the property will not cause stability problems for either the subject property or neighboring properties, and that a more detailed investigation(report) is not warranted. From the contents of the assessment,I recommend accepting the report as satisfying the County's requirement(s)for stability investigation and geotechnical reporting. Recommendations contained in the assessment should be incorporated into the site's development and made conditions for permit issuance. Adequate Erosion and Sediment(E&S) control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts. The migration or release of silty water or mud from the applicant's property will be considered a violation of County and State water quality protection regulations. In summary,the geotechnical assessment prepared for the proposed residence appears acceptable, and stability issues may be considered to have been adequately investigated and addressed. Please feel free to contact me at County extension 461 if you have any questions regarding these comments,or if you feel any features need further discussion or attention. Sincerely, 4ALA. Tahj a File: H: \WP\GEO\Assessments\LeGualt-Gipson.doc WORK ORDER -PUBLIC WORKS DEPT. CEIVEE W. Date: (q Work Order TY,6--06 PERMIT#: � Request !-4u c �y ed by: Number. �-- h� Authorized by: Date: 3 / I %,yU;aUNTY PUBLIC WORKS Type of Work: ---? CHARGE TO: NAME , �_a v AGENCY/COMPANY BILLING ADDRESS PHONE Pub.Works Person in Cha e: tot Projed Time Une: (from-to dates) %`"`" PMIW Stag dat: 3_Z-_OS E.anaW�h Oft. TO App w*rwte host: 3`l' �= ESTIMATED TOTAL i'S: COSTi:BTIMA 'E . ID) )Z3t4 Employee LEO. t simm. RAW* TOTAL S 3 Z�6s 647t7-4 35 — !�Q 7OTAL n EQUIPMENT USED: . MATERIAL USED: ---' —* (n Actual Cost = BARS: PROSE: DATE Employee I�BKEQ Name LBO Hom Fdnme TOTAL$ EQUIPMENT USED: ! Raft g� TOE MATERIAL,USED: TOTAL ALL (0) BILLED DATE_ INV yam_ PAID DATE REC.M CKX�_ EAl RECEIVED E B 2 E 2005 MCCD - PLANNING Geotechnical Assessment 100 East Clonakilty Court Shelton, WA Prepared for Tracy Gipson & Jake LeGault Lacey, WA by Geotechnical Testing Laboratory Olympia, Washington February 19, 2005 GEOTECHNICAL TESTING LABORATORY TRACY GIPSON& JAKE LEGAULT 1228 USA LANE, APT. 204, Box 16 LACEY, WA 98503 RE: GEOLOGICAL ASSESSMENT 100 EAST CLONAKILTY COURT SHELTON,WA 98584 PARCEL 321275400043 N470 16.818' W 123°02.523' 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 redeveloped with a single-family residence. Currently, a shed occupies the site. .Y C Emir l' SITE CONDITIONS The subject site is a lot located east of Lake Limerick, approximately 5 miles northeast of Shelton, Washington, (see attached vicinity map). The site is accessed from Clonakilty Court along the western property line. The subject site is located in an area of moderate residential development. From the proposed building location, the site slopes toward the west and toward the east. Historically, a residential structure occupied the central portion of the site. The steepest portion of the site, with slopes approaching 36 percent, is situated downhill and east of the proposed building location. Minimal grading is expected at the proposed building location. The lot is vegetated with fir, cedar, and madrone trees as well as salal, huckleberry, Scot's broom, bracken ferns, rhododendron, holly, Oregon grape, and grasses. 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) 7544848 GEOTECHNICAL TESTING LABORATORY GEOLOGIC CONDTTIONS The Soil Survey of Mason County, USDA Soil Conservation Service (1960) has mapped the southeast site soils as Alderwood gravelly sandy loam, 5-15 percent slopes (Ab). The report reads: The Alderwood soils typically formed from glacial advance outwash. They are described as having good natural drainage. Typically, there is no occurrence of a high water table. Internal drainage is described as �! f 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. The soils are not considered hydric. .r y ',t w � ��µ •��Jw� et, '��_ " r The Geologic Map of the Shelton PI 00,000 Quadrangle, Washington, by Logan(2003) describes the site as late Wisconsinan (Pleistocene)glacial deposits. The glacial till (Qgt) is described as: Unsorted, unstratifred, highly compacted mixture of clay, silt, sand, gravel, and boulders deposited by glacial ice of the Puget lobe; gray; may contain interbedded stratified sand, silt, and gravel, sand-size fraction is very angular and contains abundant polycrystalline quartz, which distinguishes this unit from alpine till, cobbles and boulders are commonly striated and(or)faceted; although unweathered almost everywhere, may contain cobbles or small boulders of deeply weathered granitic rock. 10011 Blomberg Street SW, Olympia,WA 98512 2 Phone#: (360) 7544612 Fax#: (360) 7544848 I GEOTEC14NICAL 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. 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. Depth to static groundwater is unknown, but is assumed to be beyond the scope of the proposed single-family residence. DEPTH TO COMPETENT SOIL Typically, dense gravelly sandy loam is found throughout the site. Competent soil can be expected approximately 8 inches below the ground surface. PAST SLOPE INSTABILITY Near 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. Ditch side slopes stand with little sign of erosion. L fy i. v 1 10011 Blomberg Street SW, Olympia,WA 98512 3 Phone#: (360) 7544612 Fax#: (360) 7544848 GEOTECHNICAL TESTING LABORATORY HISTORY OF LANDSLIDE ACTIVITY No historical landsliding was observed during our site investigation onsite or near the subject parcel. At the proposed building location, the slopes are compact and dense. Onsite trees are straight and vertical. The Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977) describes the site area as Class 1. Class 1 is expressed as: Areas believed to be stable. Slopes generally less than 15 percent, but may be greater locally in areas too small to be shown at the map scale. Largely comprises rolling uplands underlain by very stable material such as young glacial till, mantled in places by a thin layer of sandy gravel or other permeable material, also includes flood plains, deltas, alluvial fans, and some beach deposits. Class I areas immediately adjacent to steep slopes of class 3 areas may be threatened by potential landsliding. Normal,proper engineering practices generally are adequate to insure stability in these areas. POTENTIAL FOR LANDSLIDE ACTIVITY This site has very little potential for landslide activity. The proposed building location is located in an area where slopes are approximately 5 percent. To the east of the proposed building location, slopes are up to 36 percent. Since slopes are moderate and the building location relief is less than 10 feet, the potential for landslide activity is not a concern. 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 or soft rock. r L r _ e t r I�3 j A a 10011 Blomberg Street SW, Olympia,WA 98512 4 Phone#: (360) 7544612 Fax#: (360) 754-4848 . GEOTECHNICAII TESTING LABORATORY RECOMAUNDATIONS 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 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. Respectfully, GEOTECHNICAL TESTING LABORATORY � as �e of 4 .c. Harold Parks, L.G., L.E.G. � Senior Engineering Geologist ehaed G HAROLD F Zxf, 7 3/-�c1S' 10011 Blomberg Street SW, Olympia,WA 98512 5 Phone#: (360) 754-4612 Fax#: (360)754-4848 GEOTECI-INICAL TESTING LABORATORY Vicinity Map s Bo t Romp& 1-207 ''�� .• �` Bootfit Rnrhp ! f ti 4 ;�—. t � .rpm:- }• '; ,� � L,'►/ /� ;� . -"".�6 !/f� "c. • �_lt' • 4 wr 1-208 YET Figure 1 10011 Blomberg Street SW, Olympia,WA 98512 Phone#: (360) 754-4612 Fax#: (360) 754-4848