ARCHIVED REPORTS XR0006610 - Laserfiche WebLink

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• Corrective Action flan—Tosco(76) Service Station No 11192, Stockton, California March 13,2002 4. The potential effects of residual contamination on nearby surface water, wetlands, and groundwater: In April of 2001, GR conducted a well search and SRS in the vicinity of the subject site The well search was conducted within a '/2-mile radius around the site Based on the available data supplied by the DWR, three municipal wells were identified within the '/2-mile radius of the study area, the closest well is located approximately 1,000 feet north-northwest of the site The depths of all three municipal wells were reported to exceed 550 feet bgs and contain screened intervals beginning at a minimum of 350 feet bgs The SRS was conducted within a 500-foot radius centered around the Subject site The SRS involved distributing questionnaires to all residences and businesses within the study area, requesting information about potential groundwater receptors GR distributed 141 questionnaires via the U S Post Office and a total of 49 questionnaires (35%) were returned to GR None of the returned questionnaires identified the presence of a well within the SRS study area Based on the information presented in subsections 2 and 3 above, the potential effects of residual contamination on nearby surface water and wetlands is considered to be minimal However, based on the analytical results of the groundwater samples collected from the monitoring wells to date, the first aquifer beneath the site has been impacted by petroleum hydrocarbons Although GR has identified municipal wells that are potentially located downgradient from the site, the distance to the nearest municipal well (1,000 feet) and the screened interval depth (350 to >550 feet) make it • unlikely that groundwater from beneath the site will reach the municipal well 32 Feasibility Study The responsible party shall conduct a feasibility study to evaluate the alternatives for remedying or mitigating the actual or potential adverse effects of the unauthorized release. Each alternative shall be evaluated for cost effectiveness, and the responsible party shall propose to implement the most cost-effective corrective action: GR has reviewed various proven and recent remedial options that are available for use at the site The following is a brief description and comparison of those options OPTION #1 - NO REMEDIAL ACTION/LONG TERM MONITORING COST Low TIME FRAME Long term ADVANTAGES 1) Low annual cost 2) Minimal disruption of station operations 14024508 $