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ENVIRON-4ENTAL HEALTH JEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Donna K. Heian, R.E.H.S. <br /> Uodl Supervisors <br /> Director 304 East Weber Avemle,Third Floor Carl Borgman,R.E.H.S. <br /> Laurie A. Ciptulla, R.E.H.S. Stockton,California 95202-2708 Mike Huggins, R.E.H.S., R-DI <br />' •`z., .P Progrom Manager Douglas W. Wilson, R,EJI.S. <br /> Telephone: (209)468-3420 Margaret Lagorio, R.E.H.S. <br /> Fax: (209)464-0138 Rohert McClellon, R.F.H.S. <br /> Website:www,sjgov.org/ebd/ Jeff Carruesco, R.E.H.S. <br /> TOM BARBOUR RECEIVED APR 10 2006 <br /> 206 <br /> 2382 DEREK AVENUE APR I 40 <br /> " <br /> ATWATER CA 95301-9212 <br /> RE: Bob's Muffler Shop SITE CODE: 2247 <br /> 466 Moffat Blvd. <br /> Manteca CA 95336 <br /> San Joaquin County Environmental Health Department(SJCIEHD) has reviewed Soil <br /> Vapor Extraction Pilot Test Report(Report) dated December 22, 2005, and Quarterly <br /> Report— Fourth Quarter 2005 submitted to Geotracker on March 15, 2006, both <br /> prepared on your behalf by Advanced GeoEnviron mental, Inc. (AGE) and has the <br /> following comments. <br /> The Report documents an 8-hour soil vapor extraction (SVE) pilot test that was <br /> conducted at your site on September 16, 2005. One vapor extraction well was installed <br /> to conduct the test. Results of the test indicate that an effective radius of influence of <br /> approximately 80 feet would be achieved at vacuum of 0.10 inches of water. PID <br /> readings during the test ranged from 78-162 parts per million total petroleum <br /> hydrocarbons (TPH). However, analytical results from four air samples collected during <br /> the test were non-detect for all constituents analyzed. The Report recommends <br /> conducting another SVE test of longer duration. Soil contamination is present across the <br /> site, concentrated at 20-25 feet below surface grade (bsg), which is just at and below the <br /> groundwater surface. This critical location is the likely reason the air samples collected <br /> during the SVE test were non-detect. The soil contamination is located mostly below the <br /> vadose zone. SJC1EHD has discussed this proposal with AGE.and noted that it was <br /> unlikely another test of longer duration would be approved without a modification(s) that <br /> may increase the likelihood of a successful test, such as the addition of groundwater <br /> extraction to lower the groundwater level and expose the contaminated soil to the <br /> influence of the SVE system, or provision of a technical reason why a longer test is likely <br /> to be successful. <br /> Groundwater contamination at this site has been documented in all shallow onsite <br /> monitoring wells, wells MW-1 through MW-5. A deep, discretely screened onsite <br /> monitoring well, MW-6, is non-detect for the constituents analyzed. Concentrations of <br /> detected contaminants fluctuate; currently only MW-2, MW-3 and MW-5 have <br /> concentrations above the detection limit. AGE recommends in the most current <br /> quarterly monitoring report.that the site be considered for closure. <br /> Per the 2003 Corrective Action Plan, an estimated 212 gallons of gasoline remains in the. <br /> soil and.0.29 gallons remains in the groundwater. However., the calculations for the <br /> contaminant mass remaining in the groundwater used the reported concentrations from <br /> just one monitoring event. SJCIEHD directs recalculation of the estimated dissolved <br /> mass in order for it to be more representative of the overall historical concentrations of <br /> TPH reported in the groundwater at this site. <br />