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The following report addresses the concerns voiced in the July 18, 2000 Nonconcurrence letter <br /> from California Regional Water Quahty Control Board -central Valley Region (CRWQCB-CVR.) <br /> for site closure Former Regal Station R603, located at 6425 Pacific Avenue, Stockton, California <br /> 95207 <br /> CRWQCB-CVR concerns: <br /> 1 The off-site TPHg plume has not been laterally or vertically defined, <br /> 2 The concentrations of TPHg in off-sire monitoring well MW-12 are increasing, while TPHg in <br /> on-site wells are decreasing, <br /> 3 The status of a domestic water supply well southeast of the site has not been determined, <br /> 4 The groundwater has not been monitored for all fuel oxygenates and fuel additives, and <br /> S The quarterly groundwater monitoring has not been conducted since January 1999 <br /> Conclusions <br /> Staff recognizes the substantial effort Regal has made However, based on the high concentrations <br /> of TPHg and the lack of lateral and vertical definition off-site and dowwgradient of the site, we <br /> cannot concur with San Joaquin County's closure recommendation at this time For us to consider <br /> concurrence, Regal must submit a report which defines the lateral and vertical extent of <br /> groundwater contamination at their site, present an analysis of groundwater samples for all five <br /> fuel oxygenates, 1,2-dichloroethylene, ethylene dibromide, ethanol, and methanol by EPA Method <br /> 8260B, determine the status of the closest domestic water supply well, and complete a mass <br /> balance calculation of groundwater contamination using all monitoring well data <br /> Summary <br /> After reviewing Mr. Hartzell's letter, we offer the following comments for each of the CRWQCB- <br /> CVR concerns <br /> 2 R-603 Jan 2001 <br />