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437 Miner Street, Stockton <br /> Page 3 <br /> commented that there was residual soil contamination in this area that should be evaluated as a <br /> potential continuing source for continuous leaching of the contamination to the groundwater as <br /> well as for potential vapor intrusion hazards for future site uses. A soil vapor study was <br /> conducted in November 2006. Total petroleum hydrocarbons as gasoline concentrations in the <br /> vapor samples exceeded the San Francisco Bay Regional Water Quality Control Board <br /> Environmental Screening Levels. There was discussion that the tracer gas may have caused <br /> false positives. ENSR has confirmed since the meeting that the vapor probes are still in place <br /> so additional sampling may be performed. A proposal for further evaluation of potential soil <br /> vapor intrusion and leaching of contaminants from the soil to groundwater is still <br /> required. Evaluation of feasible alternatives to remediate the concentrations of <br /> contaminants in the groundwater in the area of U3 is also required. These proposals <br /> should be submitted to EHD by December 10, 2007. <br /> In the recommendations included in the "Additional Site Assessment Report" dated June 27, <br /> 2007, prepared by ENSR for this site, there was discussion about the levels of total dissolved <br /> solids (TDS) in the water samples and evaluating salinity in the groundwater without explanation <br /> of the use of this evaluation. The EHD provided Chevron/ENSR a copy of the California State <br /> Water Resources Control Board Resolution 88-63 which states that surface and groundwater is <br /> potentially suitable for municipal or domestic water supply except if the TDS exceeds 3000 mg/L <br /> or doesn't supply a single well with a sustained yield of 200 gallons per day. The EHD informed <br /> Chevron/ENSR that the water at this site is considered to be of potential beneficial use and as <br /> such has to be cleaned up to the CVRWQCB water quality goals. <br /> If you have any questions contact me at(209)468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Margaret Lagorio, REHS <br /> Program Coordinator Unit IV <br /> C: Jim Barton — CVRWQCB <br /> David Irey—SJCADA <br /> George Forsythe - ENSR <br />