ARCHIVED REPORTS XR0000730 - Laserfiche WebLink

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SEC ® R . SENSTIVE RECEPTORS •5. In January 2003, SECOR performed a sensitive receptor survey which included a search of Department of Water Resources well logs, contact of the local water purveyor, and a 500-foot door-to-door well search. Based on SECOR's receptor survey, 12 wells are present within '/2 mile of the site. Eight of the twelve well are upgradient or cross- gradient. The four down-gradient wells (to the north) are located approximately 1,500 to 2,500 feet from the site. The Lathrop Grammar School irrigation well is located approximately 1,600 feet northeast of the site and is the closest of three wells identified during a 2000-foot radius receptor survey conducted at the site. MONITORING AND SAMPLING TRC's Groundwater Monitoring Report dated August 11, 2005, is included as Attachment 1, including Tables 1- 3, Figures 1 - 5, plus field data sheets and groundwater analytical reports. Currently MWA through MW-19 are monitored and sampled quarterly each year. Samples are analyzed for TPPH, BTEX, and fuel oxygenates. During the third quarter 2005, groundwater flowed radially away from well MW-12 at a gradient of 0.015 ft/ft. Maximum reported concentrations of TPPH, benzene, and MTBE during the third quarter 2005 were 59,000 ppb (MW-1), 1,500 ppb (MW-2), and 230 ppb (MW-16), respectively. MTBE concentrations in wells appear relatively stable based on graphs of concentration vs. time proved in TRC's Groundwater Monitoring Report dated August 12, 2005, included as Attachment 1. Based on TPPH, benzene, and MTBE isoconcentration maps (Figures 3, 4, and 5 in Attachment 1) the plume is delineated in all directions. REMEDATION STATUS No active remediation. CHARACTERIZATION STATUS Contamination in soil has been adequately delineated. TPPH, benzene, and MTBE in groundwater have been laterally delineated in all directions. Vertical delineation in groundwater has not been completed. WASTE DISPOSAL SUMMARY The volume of purged groundwater generated and disposed of during the quarterly groundwater monitoring event will be reported in TRC's quarterly report. RECENT SUBMITTALS/CORRESPONDENCE July 5, 2005 -- SECOR submitted Results of Additional Site Assessment and Site Conceptual Model. �• July 27, 2005 — Sart Joaquin County response letter to Results of Additional Site Assessment and Site Conceptual Model dated July 5, 2005.