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First-Quarter 1992 Groundwater Monitoring Report � )ANA Tri-Valley Growers, Thornton, California ' April 8, 1992 W2102 (BTEX), and total petroleum hydrocarbons as gasoline (TPHG), by EPA methods 8020 and modified 8015, respectively In addition, the sample collected from monitoring well MW 1 was analyzed for total oil and grease (TOG) by EPA method 5520 B&F No dissolved gasoline hydrocarbon constituents were reported above detection limits in ' monitoring wells MW1, MW2, MW3, MW5 or MW6 Oil and grease was not reported above detection limits in MW1 (Table 2) ' Influent and effluent samples from the pumping well (MW4) were analyzed for BTEX and TPHG during the March 12 sampling event, the influent sample was also analyzed for TOG Analytical results indicate an decrease in TPHG and BTEX levels in the influent sample collected during this sampling round The influent sample recorded nondetectable levels of ' TOG Analytical results indicated no break-through in either carbon filter 1 (TVGT EFF1C) or carbon filter 2 (TVGT EFF2C) during this sampling round Influent BTEX and TPHG concentrations over time are plotted on Figures 6 and 7 Laboratory analyses were performed by RESNA Environmental Laboratory (DHS certification ' #1211) The analytical results are summarized in Table 2, the laboratory reports and chain-of- custody documentation are presented in Attachment 2 ' Based on nondetectable petroleum hydrocarbon results for the previous year, we request that wells MW3 and MW6 be placed on a biannual sampling schedule and that the total oil and grease (TOG) analysis of well MW 1 and the influent sample be discontinued RESNA personnel will continue with the quarterly monitoring program which will include a report detailing system performance We will continue to monitor system performance and adjust pumping rates as necessary 1 QM032792 SAY 2