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1 <br /> v1117 Lone Palm Avenue, Suite B <br /> LTCModesto, CA 95351 <br /> http://www.atcassociates.com <br /> 209.579.2221 <br /> A a s o c I w r e a I w o . <br /> Fax 209.579.2225 <br /> June 22, 2005 D <br /> 54.26823.0001 <br /> ' J'JL - 81 <br /> Ms. Lori Duncan E p IRONA4EIVT �� <br /> ' San Joaquin County ERMITjE'RV,� LTH <br /> Environmental Health Department <br /> 304 E. Weber Street, Third Floor <br /> Stockton, California 95202 <br /> ' Subject: First Quarter 2005, Combined Groundwater Monitoring and Remediation Systems <br /> Operations and Monitoring Report, Jamar Service Station, 4075 East Main Street, <br /> Stockton, California ' <br /> Dear Ms. Duncan: <br /> ' This report presents the results of quarterly groundwater monitoring and sampling performed <br /> between March 16-17, 2005 at the Jamar property located at 4075 East Main Street, Stockton, <br /> California (Figure 1) by ATC Associates Inc. (ATC). It also reports the operations and <br /> maintenance (O&M) of the remediation system performed on January 28, 2005 and February 22, <br /> 2005 in addition to that performed during the March 16-17, 2005 groundwater monitoring event. <br /> ' Quarterly groundwater monitoring and sampling was performed to assess the distribution of <br /> petroleum hydrocarbons in groundwater and to evaluate the groundwater flow direction and <br /> ' hydraulic gradient in the impacted aquifers. O&M of the remediation system was performed to <br /> evaluate the effectiveness of the ozone air sparge system at remediating petroleum impacted soil <br /> and groundwater. <br /> ' 1.0 SITE HISTORY <br /> ' In 1995, one 500-gallon waste oil underground storage tank (UST) and one 500-gallon kerosene <br /> UST were removed from the site. <br /> ' In December 1998, two 6,000-gallon and one 10,000-gallon gasoline USTs were removed from <br /> the site. Soil samples were collected from the tank pit and analyzed for petroleum hydrocarbons. <br /> Lab analyses indicated the samples collected from the tank pit contained detectable <br /> concentrations of petroleum hydrocarbon constituents.. _ The excavation was_..subsequently <br /> backfilled and a 20,000-gallon UST was installed. <br /> In September 1999, John P. Cummings & Associates (JPCA) advanced three soil borings, MW1, <br /> MW2, and MW3 to depths ranging from approximately 74 to 78 feet below ground surface (bgs). <br /> The borings were completed as monitoring wells. <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />