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E <br /> Third-Quarter Groundwater Monitoring Letter Report January 15, 1992 <br /> y <br /> Tri-Valley Growers, Thornton, California W2102 <br /> petroleum hydrocarbons as gasoline (TPHG), by EPA methods 8020 and modified 8015, <br /> respectively. In addition, monitoring well MW 1 was sampled for total oil and grease(TOG)by <br /> EPA method 5520 B&F. <br /> No dissolved gasoline .yydroearbon constituents were reported above detection limits in <br /> monitoring wells MW 1,MW3,or MW6. Oil and grease was not reported above detection limits <br /> in MW 1 (Table 2). The zero line for total petroleum hydrocarbons in the groundwater is plotted <br /> on Figure 5. <br /> Influent and effluent samples from the pumping well (MW4) were also analyzed for BTEX, <br /> TPHG,and TOG on October 9 and Dumber 19, 1991. .Analytical results indicate an increase <br /> in TPHO and the gasoline constituents benzene; toluene,.and xylenes in the`Mue'nt:samples:' <br /> collected on December"19 from the'October 9 sampling round .:..Ethylbenzene levels are shown <br /> to have decreased since the October 9 sampling round. The influent sample recorded <br /> nondetectable levels of TOG. Analytical'*-milts indicated'break-through,-in carbon filter..1 <br /> �..� <br /> (Cl?l.C);`brat not in.carbon filter 2 (CF2C)during the.October.4 sampling round:'`Carbon filter <br /> 1 was replaced on November 11, 1991. No break-through from carbon filter 1 (EFFC1) or 2 <br /> r <br /> (EFFC2)was evident during the December 19 sampling round. <br /> Laboratory analyses were parformed by Applied Analytical Laboratory (DHS certification <br /> #1211). The analytical results are summarized in Table 2; the laboratory reports and chain-of- <br /> custody <br /> hain-ofcustody documentation are presented in Attachment 2. <br /> As previously approved, monitoring wells MW2 and MW5.have been changed to a biannual : <br /> sampling schedule. Sampling of wells MW2 and MW5 will be included in the next quarter's r <br /> activities. RESNA personnel will continue with the quarterly monitoring program which will <br /> include a report detailing system performance. The first quarterly monitoring event of 1992 will <br /> include analysis for BTEX and TPHG from all monitoring wells, and remediation system <br /> influent(MW4) and effluent. The sample from MW-1 and Influent will also be analyzed for <br /> TOG. We will continue to monitor system performance and adjust pumping rates as necessary. <br /> t <br /> QM010592.s,►Y 2 <br />