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San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> Donna Heran, REHS <br /> 600 East Main Street <br /> c Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Robert McClellon,REHS <br /> i• - - - --- - - - -- Jeff Carruesco,REHS.RDI <br /> Website: www.sjgov.org/ehd Kasey Foley,REHS <br /> 9<iFo Rte` <br /> Phone: (209) 468-3420 <br /> Fax: (209) 464-0138 <br /> April 16, 2010 <br /> Mr. Charles Skobrak <br /> 9947 East Highway 26 <br /> Stockton, California 95215 <br /> Subject: Larry's Auto <br /> 308 North Grant Street <br /> Stockton, California 95202 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed In-Situ Air <br /> Sparging & Soil Vapor Extraction Feasibility Pilot Test Report — Fourth Quarter 2009 dated <br /> March 10, 2010, prepared and submitted by Advanced GeoEnvironmental, Inc. (AGE) on your <br /> behalf for the above-referenced site. By letter dated October 26, 2009, the EHD had <br /> approved the in situ air sparging/soil vapor extraction (IAS/SVE) pilot test and directed that the <br /> SVE system, initially installed and intermittently in operation at this site since May 2008, <br /> continue operating uninterrupted once the pilot test had been completed. <br /> In the report, AGE states that the IAS and the SVE pilot tests were performed simultaneously <br /> to evaluate air sparging as a remedial method to remove groundwater contamination at this <br /> site. AGE injected air into vapor well VW-5C and extracted soil vapor from extraction well <br /> EW-1, and vapor wells VW-2A, VW-2B, VW-3, VW-4, VW-5A and VW-5B. The initial <br /> dissolved oxygen measurements in groundwater at extraction wells EW-1 and EW-2, <br /> monitoring wells MW-1 through MW-3, and vapor wells VW-2A, VW-2B, VW-3, VW-4 and <br /> VW-5B indicate that oxygen was not detected in any of the wells; however, AGE believes this <br /> anomaly is "normal based on the historically elevated dissolved petroleum hydrocarbon <br /> concentrations near the pilot study area." Dissolved oxygen concentrations increased during <br /> the initial twenty-four hours of air sparging, then decreased in most of the wells. What is <br /> unclear to the EHD is how the oxygen was measured. Were oxygen measurements taken <br /> inside the wells, and if so, were the measurements taken prior to or following the purging of <br /> the wells? Or were these measurements taken from groundwater samples collected from the <br /> wells? The EHD believes that prior to sparging the wells, background dissolved oxygen <br /> measurements need to be taken over a period of several days while recording the oxygen <br /> readings two to three times per day from every well included in the study to establish a <br /> baseline that incorporates some natural fluctuation. <br /> Based on the information provided in this report, the EHD does not believe that enough <br /> information was presented to evaluate the effects of air sparging. Although AGE has <br /> recommended IAS/SVE for remediating both soil and groundwater at the northwest corner of <br /> the property near former Tank A, the EHD will not approve the submittal of a work plan to <br /> install and operate an IAS system until additional information is provided concerning the <br />