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I ' Coca-Cola Enterprises - West USTEC job No 90054 03 to 33 ppb) Gasoline TPH concentrations have remained below detection limits in groundwater monitoring wells MW-2, MW-4, MW-5 and MW-6 I Benzene concentrations have increased in groundwater well MW-1 (below detection limits to 40 ' ppb) which is above the State of California recommended action limit of 0 7 ppb Benzene concentrations have remained below analytical detection limits for groundwater monitoring wells MW-2 through MW-6 The distribution of TPH and benzene concentrations for the fourth quarter 1991 are shown on Figure 4 Total lead concentrations have increased ing roundwater monitoring wells MW-3 (below ' detection limit to 0 030 ppm) and MW-4 (below detection limit to 0 0055 ppm) In a plot of historical TPH gasoline concentrations compared to historical groundwater elevations for MWA, an inverse relationship is suggested (Figure 5) TPH as gasoline levels peak at tunes of lowest groundwater elevations suggesting that decreases in concentration are the result of water elevation increases I 6 0 SUMMARY AND CONCLUSIONS Four vapor extraction wells were drilled and installed during this quarter at the Stockton site Six groundwater monitonng wells were measured and sampled in November 1991 by USTEC personnel Groundwater measurement results indicate that the groundwater flow is generally Ito the northeast which is consistent with previous monitoring results TPH gasoline and BTEX concentrations have increased in groundwater monitoring wells MWA and MW-3 The Ipresence of TPH as gasoline in these wells may be due to changes in the groundwater elevations Concentrations of TPH as diesel have decreased in all six wells since in the previous quarterly sampling Lead was detected in groundwater monitoring wells MW-3 and MW-4 7 I