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THIRD QUARTER 1996
<br /> QUARTERLY MONITORING REPORT
<br /> USA STATION#65 - LODI
<br /> SEPTEMBER, 1996
<br />' 5,1 Groundwater Flow and Gradient
<br /> Groundwater data collected at the site on July 18, 1996 and August 19, 1996 indicate that the
<br />' depths to groundwater ranged from 43 04 to 45 41-feet bgs on July 18, 1996 and 43 44 to 45 96
<br /> on August 19, 1996 The groundwater elevations range from 7 53 to 6 04-feet below MSL on
<br /> July 18, 1996 and 8 08 to 6 45-feet below MSL on August 19, 1996 The directions of
<br />' groundwater flow have been calculated to be trending to the southeast with average hydraulic
<br /> gradients of approximately 0 0034-ft/ft across the site on July 18, 1996 and 0 0037-ft/ft on
<br /> August 19, 1996 Historic field data suggests that groundwater generally flows to the south with
<br /> minor fluctuations to the east and/or west, as shown on Figures 3 through 6
<br /> 5.2 Results of Groundwater Laboratory Analyses
<br /> Groundwater analytical results for
<br /> y the July 1$, sampling were not at all consistent with prior
<br /> quarterly results Park resampled the wells on August 19, 1996 All test results have been
<br /> presented for completeness, but the July results should be reviewed cautiously, because of several
<br /> anomahes The July 18, 1996 analytical results detected TPH G in five of the sampled
<br /> monitoring wells (MW-2, MW-3, MW-7, S-1, and S-2) Concentrations of TPH G for the July
<br /> 18, 1996 sampling event ranged from 53 micrograms per liter(µg/l) in MW-2 to 11,000 µg/1 in
<br /> MW-3 TPH G was non-detect at the method detection ltnut (ND) in wells MW-1, MW-4, MW-
<br /> 5, MW-6, and MW-8 for the July 18, 1996 sampling event The August 19, 1996 analytical
<br /> results report TPH G detected in four of the sampled monitoring wells (MW-3, MW-8, S-1, and
<br /> S-2) Concentrations of TPH G for the August 19, 1996 sampling event ranged from 780 µg/1 in
<br />' MW-8 to 11,000 9g/1 in S-2 TPH G was ND in wells MW-1, MW-2, MW-4, MW-5, MW-6,
<br /> and MW-7 for the August 19, 1996 sampling event
<br /> The July 18, 1996 analytical results report benzene detected in five of the sampled monitoring
<br /> wells (MW-2, MW-3, MW-7, S-1 and S-2) Concentrations of benzene for the July 18, 1996
<br /> sampling event ranged from 12 gg/l in MW-2 to 300 4g/l in S-1 and S-2 The August 19, 1996
<br /> analytical results report benzene detected in four of the sampled monitoring wells (MW-3, MW-8,
<br /> S-1, and S-2) Concentrations of benzene for the August 19, 1996 sampling event ranged from
<br /> 25 µg/1 in MW-8 to 260 µg/1 m S-1 Analytical results are summanzed in Table 2, and shown on
<br /> Figures 7 and 8 Copies of laboratory reports and COC documentation are included in Appendix
<br /> B
<br /> The results of the August 19, 1996 sampling event indicated that MW-7 and MW-8 returned to
<br /> previously reported levels The August 19, 1996 sampling event indicates that downgradient
<br /> wells have continued to be ND for TPH constituents However MW-3 continues to have unusual
<br /> results At this time Park recommends the monitoring be continued
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