ARCHIVED REPORTS XR0001738 - Laserfiche WebLink

Home Browse Search

Quarterly Ground-Water Monitoring June 30, 1989 Beacon Station No. 1-502, Lodi, California AGS 86091-6 The ground-water samples were sent to the Applied GeoSystems' analytical laboratory in Fremont, California, (California Hazardous Waste Testing Laboratory Certificate No. 153) , and analyzed for total petroleum hydrocarbons (TPH) as gasoline by modified Environmental Protection Agency (EPA) Method 8015; and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) by EPA Method 8020. Copies of the laboratory analysis reports are attached to this letter report, and results of these and previous laboratory analyses are presented in Table 2 . The results of the laboratory analyses indicate that the BTEX concentrations in ground-water samples collected from wells MW-1, MW-2, and MW--4 have decreased since the December 1988 sampling (except for the benzene concentration in the sample from MW-4, which increased slightly) . In contrast to the two previous samplings, BTEX constituents were detected in the sample from well 14W-3 . The concentration of TPH increased in samples from ground-water monitoring wells MW-1, MW-3, MW-4, and MW-5; however, the concentration of TPH decreased in the sample from ground-water monitoring well MW-2. The concentrations of benzene, toluene, and ethylbenzene in the sample collected from ground-water monitoring well MW-5 remained below the detection limits of the analytical methods used; xylene isomers were present in detectable concentrations. The ground-water gradient across the site was evaluated by combining measurements of the static water level with the relative elevation of the top of the casing in each monitoring well. The relative elevation of the top of the casing in each well was previously evaluated with a Lietz/Sokkisha C3E Automatic Level. The static water levels were adjusted using the top of the casing in well MW-3 as a common datum. These data are summarized in Table 3, and were used to evaluate the gradient of the static ground-water surface at the time of this quarterly monitoring (Plate P-3) . The evaluated ground-water gradient was 0.0024, and the flow direction is evaluated to be toward the southwest. The orientation of the ground-water gradient is similar to that in previous samplings. Applied GeoSystems recommends that quarterly monitoring at the site be continued; the next sampling event has been scheduled for the week of June 4, 1989. 3