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ENVIRONMENTAL HEALTH IJEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K. Heran, R.E.H.S. <br /> Director' <br /> 304 East Weber Avenue,Third Floor Carl Borgman,R.E.H.S. <br /> Laurie A. Cotulla, R.E.H.S. Stockton,California 95202-2708 Mike Huggins, R.E.H.S., R.D.1. <br /> • r Program Manager Telephone: (209)468-3420 Douglas W. Wilson, R.E.H.S. <br /> Margaret Lagorio,R.E.H.S. <br /> Fax: (209)464-0138 Robert McClellon, R.E.H.S. <br /> Website: www.,sjgov.org/ehd/ Jeff Carruesco, R.E.H.S. <br /> LORI SHIELDS FEB 2 2 2006 <br /> DIESEL PERFORMANCE <br /> 2804 FREMONT STREET <br /> STOCKTON CA 95205 <br /> RE: Diesel Performance SITE CODE: 1120 <br /> 2804 Fremont Street <br /> Stockton CA 95205 <br /> San Joaquin County Environmental Health Department (SJCIEHD) has reviewed <br /> Remedial Activities Summary Report(June 2005-October 2005) (Report) dated <br /> January 27, 2006, prepared on your behalf by ATC Associates Inc. (ATC) and has the <br /> following comments. <br /> In December 2001 a soil vapor extraction (SVE) pilot test was performed at this site. In <br /> their November 2002 report of this test, ATC concluded that SVE appeared to be a viable <br /> alternative for remediation of the soil contamination at this site. In correspondence dated <br /> January 27, 2003, July 8, 2003 and November 19, 2003 SJCIEHD directed submittal of a <br /> Corrective Action Plan (CAP) and feasibility study. They were finally submitted on <br /> February 17, 2004. In the CAP ATC recommended using a high vacuum dual phase <br /> extraction mobile remediation system to conduct individual five-day long remediation <br /> events, once a month for three months. SJCIEHD subsequently approved this proposal <br /> with the condition that the monthly events continue until it is determined that remediation <br /> of the soil contamination is complete. <br /> In the Report ATC makes two recommendations. First, ATC recommends conducting <br /> confirmation soil sampling and if analytical results indicate that remediation efforts have <br /> been successful, the site should be considered for closure. ATC previously made this <br /> recommendation in the first Remedial Activities Summary Report dated June 18, 2005. <br /> SJCIEHD's response to this recommendation is the same as previously given, which is <br /> that as long as the vapor extraction system is yielding high concentrations of <br /> contaminants and significant mass is being removed, which it is, remediation must <br /> continue. Average contaminant removal rates for the series of SVE events has been <br /> approximately 70 pounds per monthly event. Plotting the average monthly influent TPHg <br /> concentrations against time does not show steadily declining vapor concentrations; the <br /> average concentration of the last event of Test 2 is nearly as high as the average <br /> concentration for the first event of Test 1. <br /> Second, ATC recommends installation and operation of a full time SVE system, and <br /> provides a cost evaluation of two vapor destruction methods. ATC stated.that vapor <br /> destruction by catalytic oxidizer would be more cost effective than carbon canisters, and <br /> estimates that with implementation of full time remediation a significant proportion of the <br /> vadose zone contaminants will be removed in 4-6 months. SJCIEHD agrees with the <br />