Laserfiche WebLink
THRIFTY OIL CO. <br /> March 17, 2009 0-95098 <br /> Mr. Mike Infurna, Jr. RWQCB #390652 <br /> Senior REHS 2 <br /> County of San Joaquin mIC,C� VEDD <br /> Public Health Services/Environmental Health Division <br /> 304 East Weber Avenue, 3rd Floor MAR 2 0 2009 <br /> Stockton CA 95202 <br /> ' ENVIRONMENT HEALTH <br /> RE: Former Best California Gas Ltd. Station #172 PERMIT/SERVICES <br /> Circle K Station #2705449 <br /> 7647 Pacific Avenue <br /> Stockton, CA 95207 <br /> Subject: Request to Reduce Groundwater Sampling Frequency in Selected Monitoring Wells <br /> Dear Mr. Infurna: <br /> This letter is written as a request to reduce the groundwater sampling frequency for several <br /> monitoring wells displaying non-detectable to trace hydrocarbon concentrations, at the above- <br /> referenced Best California Gas, Ltd. (Best) site in Stockton, California(Figure 1). The purpose of <br /> this request is to reduce costs and energy expenditure, so that more resources are available for higher <br /> priority tasks such as site remediation. <br /> It is proposed that five wells (MW-4, MW-5, MW-6, MW-7, and MW-9) be reduced from a <br /> quarterly to an annual sampling schedule. During the last eight quarters of sampling,generally trace <br /> to low hydrocarbon concentrations were observed sporadically in these wells. The current and <br /> historical groundwater sampling data is summarized in the Summary Table,Table 1,and Table 2; <br /> the sampling results of the wells proposed to be sampled on an annual basis are shaded in the tables. <br /> The fourth quarter 2008 groundwater elevation map and TPHg, benzene, MTBE, and TBA <br /> distributions in groundwater are presented in Figures 2, 3, 4, 5, and 6, respectively. As shown in <br /> these figures, most of these wells are distant from the core of the dissolved hydrocarbon plume,and <br /> thus concentrations in these wells are not expected to significantly change (as demonstrated by the <br /> past two years data). Adequate control of the dissolved hydrocarbon plume configuration is <br /> therefore expected through annual sampling of these peripheral wells, and quarterly monitoring of <br /> the remaining wells which display higher dissolved concentrations. By implementing these sampling <br /> reduction measures, a cost savings of approximately $4,000 per year is estimated for this site. <br /> QO <br /> 13116 Imperial Highway, Santa Fe Springs, CA 90670• (562)921-3581 <br />