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r <br /> Third Quarter 1992 Groundwater Monitoring Report <br /> Tri-Valley Growers, Thornton, California <br /> October 2, 1992 <br /> W2102 <br /> ethylbenzene, xylenes (BTEX), and total petroleum hydrocarbons as gasoline (TPHG), by EPA <br /> methods 8020 and modified 8015, respectively <br /> No dissolved gasoline hydrocarbon constituents were reported at or above detection limits in <br /> monitoring wells MW 1, MW2, MW3, MW5 or MW6 <br /> Influent and effluent samples from the pumping well (MW4) were analyzed for BTEX and <br /> TPHG during the September 4 sampling event Analytical results indicate a decrease in TPHG <br /> levels and an increase in BTEX levels in the influent sample collected during this sampling <br /> round Analytical results indicated minor break-through (toluene detected at 1 5 ppb) in carbon <br /> filter 1 (TVGT EFF1C) The sample collected from carbon filter 2 (TVGT EFF2C) did not <br /> contain any detectable analytes during this sampling round Influent BTEX and TPHG <br /> concentrations over time are plotted on Figures 5 and 6 <br /> Laboratory analyses were performed by RESNA Environmental Laboratory (DHS certification <br /> #1211) The analytical results are summarized in Table 2, the laboratory reports and chain-of- <br /> custody documentation are presented in Attachment 2 <br /> On September 9, 1992, RESNA personnel performed a maintenance visit to repair influent <br /> carbon filter 1 The system was functioning properly and pumping at a rate of 2 8 liters per <br /> minute <br /> RESNA personnel will continue with the quarterly monitoring program which will include <br /> reports detailing system performance We will continue to monitor system performance and <br /> adjust pumping rates as necessary <br /> QRTRRLYIQM092192 FNL 2 <br />