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Quarterly Ground-Water Monitoring January 8, 1990 <br /> Beacon Station No. 502, Lodi, California AGS 86091-7 ` <br /> isomers (BTEX) by :environmental Protection Agency Method 602. The results of these <br /> analyses and previous laboratory analyses are summarized in Table 2. Copies of the <br /> Laboratory Analysis Reports are attached. <br /> The results of the laboratory analyses indicate that hydrocarbon constituents were not <br /> detected in the groundwater samples collected from MW-2, MW-3, and MW-5 but were <br /> detected in the samples from MW-i and MW-4. TPH as gasoline was detected at 0.210 <br /> parts per million (ppm) in the sample from MW-4 and at 0.150 ppm in the sample from <br /> MW-1. Concentrations of the BTEX compounds decreased since the July 21, 1989, <br /> sampling, whin the exception of an increase in benzene detected in the sample from MW-4. <br /> Applied GeoSystems evaluated the groundwater gradient across the site on November 21, <br /> 1989. The elevation of the top of the casing in each well was evaluated bj Moldenhauer <br /> Engineering Company, a licensed land surveyor of Davis, California on November 27, 1989. <br /> Elevations were measured in feet relative to mean sea level using a local U.S. Geological <br /> Survey benchmark as a datum. The measurements of the depths to ground water were <br /> combined with the casing elevations to calculate the elevations of the groundwater surface. <br /> These data are summarized in Table 3 and were used to evaluate the gradient of the <br /> groundwater surface at the time of this quarterly monitoring event (Plate P•-3). The <br /> average ground-water gradient was evaluated to be 0.005, with a flow direction towards the <br /> southwest, .lie magnitude of the gradient appears to be greater on the northeast end of the <br /> site. The orientation of the groundwater gradient is similar to that evaluated in previous <br /> sampling events. <br /> Applied GeoSystems recommends that monitoring of ground water at the site be continued <br /> on a quarterly basis. The next sampling event has been scheduled for the week of <br /> December 18, 1989. <br /> I <br /> i <br /> 2 <br /> s4 lied �e�� �terr�s <br /> a <br />