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SECO° R <br /> • SENSTIVE RECEPTORS <br /> In January 2003, SECOR performed a sensitive receptor survey which included a search '` <br /> of Department of Water Resources well logs, contact of the local water purveyor, and a r <br /> 500-foot door-to-door well search. Based on SECOR's receptor survey, 12 wells are <br /> Present within '/ mile of the site. Eight of the twelve well are upgradient or cross- r <br /> gradient. The four down-gradient wells (to the north) are located approximately 1,500 to <br /> 2,500 feet from the site. The Lathrop Grammar School irrigation well is located <br /> approximately 1,600 feet northeast of the site and is the closest of three wells identified <br /> during a 2000-foot radius receptor survey conducted at the site. F <br /> MONITORING AND SAMPLING <br /> TRC's Groundwater Monitoring Report dated November 8, 2005, is included as <br /> Attachment 1, including Tables 1- 3, Figures 1 - 5, plus field data sheets and - <br /> groundwater analytical reports. Currently MW-1 through MW-19 are monitored and <br /> sampled quarterly each year. Samples are analyzed for total purgeable petroleum <br /> hydrocarbons (TPPH), BTEX, and fuel oxygenates. <br /> During the fourth quarter 2005, groundwater flow was to the northeast at a gradient of <br /> 0.002 ft/ft. Maximum reported concentrations of TPPH, benzene, and MTBE during the x <br /> fourth quarter 2005 were reported at 22,000 pg/L (MW-9), 420 pg/L (MW-1), and 520 <br /> pg/L (MW-16), respectively. MTBE concentrations in wells appear relatively stable <br /> based on graphs of concentration vs. time proved in TRC's Groundwater Monitoring % <br /> Report dated November 8, 2005, included as Attachment 1. Based on benzene and <br /> 011 MTBE isoconcentration maps (Figures 4, and 5 in Attachment 1) the plume is delineated <br /> in all directions. TPPH is delineated in all directions except downgradient to the <br /> northeast. <br /> REMEDATION STATUS <br /> _5. <br /> No active remediation. y <br /> CHARACTERIZATION STATUS " <br /> i- <br /> Contamination in soil has been adequately delineated. Benzene, and MTBE in <br /> groundwater have been laterally delineated in all directions. TPPH in groundwater has <br /> been laterally delineated in all directions to below 100 ppb. Vertical delineation in <br /> groundwater has not been completed. <br /> WASTE DISPOSAL SUMMARY <br /> The volume of purged groundwater generated and disposed of during the quarterly �� <br /> groundwater monitoring event is reported in TRC's quarterly report. <br /> RECENT SUBMITTALS/CORRESPONDENCE <br /> No recent submittals or correspondence, n <br /> i <br /> %ik <br />