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Home My WebLink AboutGEOtech Addemdum - GEO Geological Review - 2/25/2005 --— -- -- Michael MacSems - scan0003.bmp Page 1 { GEOTECHNICAL TESTING LABORATORY FEBRUARY 25,2005 BRAD SCHAUER P.O.Box 429 BELFAIR,WA 98528 ATTN: BRAD SCHAUER RE: GEOLOGICAL ASSESSMENT ADDENDUM 25491 NE STATE ROUTE 3 BELFAIR,WA 98528 PARCEL123211400040 N47028.214'W 122048.213' As requested verbally by Mason County,we have reviewed the offsite impact of the proposed logging project. Due to the nature and slope of the parcel,we do not anticipate offsite impact from logging. Respectfully, GEOTECHNICAL TESTING LABORATORY A/ �m4j& Harold Parks,L.G.,L.E.G. Senior Engineering Geologist 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone#:(360)754-4612 Fax#:(360)7544848 rvnunaei iviacoems-scanwUs.om GEOTECHNICAL TESTING LABORATORY FEBRUARY 25,2005 BRAD SCHAUER P.O.Box 429 BELFAIR,WA 98528 ATTN: BRAD SCHAUER RE: GEOLOGICAL ASSESSMENT ADDENDUM 25491 NE STATE ROUTE 3 BELFAIR,WA 98528 PARCEL123211400040 N47028.214'W 122048.213' As requested verbally by Mason County,we have reviewed the offshe impact of the proposed logging project. Due to the nature and slope of the parcel,we do not anticipate offsite impact from logging. Respectfully, GEOTECHNICAL TESTING LABORATORY Harold Parks,L.G.,L.E.G. Senior Engineering Geologist 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone k(360)7544612 Fax#:(360)754-4848 °ter. Geotechnical Assessment 25491 NE State Route 3 Belfair, WA Prepared for Brad Schauer Belfair, WA by Geotechnical Testing Laboratory Olympia, Washington February 21 , 2005 GEOTECHNICAL TESTING LABORATORY BRAD SCHAUER P.O. Box 429 BELFAIR, WA 98528 RE: GEOLOGICAL ASSESSMENT 25491 NE STATE ROUTE 3 BELFAIR,WA 98528 PARCEL123211400040 N47028.214' W 122°48.213' 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 currently developed with commercial structures. Forested land is scheduled for logging. A proposed structure will be located near the northwest property corner, see photo below. 1 M L. SITE CONDITIONS The subject site is a lot located along State Route 3, approximately 1 mile north of Belfair, Washington, (see attached vicinity map). The site is accessed from a gate off State Route 3 at the southeastern property corner. The subject site (12.12 acres) is located in an area of moderate commercial development and forestland. The site has virtually no slopes greater than 5 percent. The existing commercial structures occupy the central eastern portion of the site. The steepest portion of the site, with slopes approaching 5 percent, is situated downhill and southwest of the proposed building location. Minimal grading is expected at the proposed building location. The lot is vegetated with fir trees as well as salal, blackberry, and Scot's broom. 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 .4R -ryy: GEOLOGIC CONDITIONS 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 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. N t. �� .,� t {x �► . G �T ..� iYt. 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. 10011 Blomberg Street SW, Olympia,WA 98512 2 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY 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 structure. DEPTH TO COMPETENT SOIL Typically, dense gravelly sandy loam is found throughout the site. Competent soil can be expected approximately 12 inches below the ground surface. t � 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. 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 cemented, 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. 10011 Blomberg Street SW, Olympia,WA 98512 3 Phone#: (360) 7544612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY 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 2 percent. Since slopes are moderate and the building location relief is less than 5 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. a i b 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, ive recommend that underbrush remain for areas outside the proposed 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 modific:o� $h! cations, as appropriate. o' Respectfully, GEOTECHNICAL TESTING LABORATORY Ens nwng Geol* 827 ~� ed Ge°�° Harold Parks, L.G., L.E.G. Senior Engineering Geologist 3/a 1 Blomberg Street SW, Olympia,WA 98512 4 hone#: (360) 754-4612 Fax#: (360) 7544848 GEOTECHNICAL TESTING LABORATORY Vicinity Map • 'J 7 1 ri v I• ,f SCH U SITE z I Qr a]lb ( 1 t{ ' Fi cure 1 10011 Blomberg Street SW, Olympia,WA 98512 Phone#-. (360) 754-4612 Fax#-. (360) 7544848