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event. MW-1 continues to have the highest concentration of gasoline contamination for TPHg at 118,000 ppb. which is higher than 107,000 ppb. of the last sampling event. The groundwater • hydraulic gradient was calculated at S=0.003 with the down slope in the northeast direction,which matches the historical data for this site. The gradient is determined by the first ground water elevation data of MW-1, MW-2, and MW-3 (see a site map attached). Analysis for oxygenates during this event indicate the presence of both MTBE and 1,2 DCA in moderate amounts in MW-1,MW-2 and EW-1.MW-1 had the highest concentration ofboth MTBE and 1,2 DCA (see attached recap sheets). The monitoring wells that were damaged by others were developed and sampled. Monitoring well MW-S appears to have been impacted by the damage.TPHg has jumped from non-detect,when last sampled, to 5730 ppb. during this event. Conclusions The hydraulic gradient for this monitoring event has returned to the traditional hydraulic gradient flow direction of northeast from the northwest direction of the last event. In general, all of the monitoring well groundwater samples, with the exception of MW-1 and MW-2, yielded lower concentrations of TPHg than last quarter. The MW-1 groundwater sample results were lower in concentrations than last years first quarter monitoring event. MTBE was detected in MW-1,MW- 1R, MW-2 and EW-1. Low concentrations of 1,2-DCA were detected in MW-1,MW-7S, MW-3, and EW-l. Low concentrations of EDB were analyzed in MW-1 and EW-1. The extraction well EW-1 produced the highest concentrations of TPHg and 1,2 DCA and is positioned in the best location to remove the highest concentrations of gasoline contamination in the sand aquifer at 50' below the surface. Recommendations The author recommends that monitoring well sampling be continued on a quarterly basis with analysis for TPHg,BTEX,and oxygenates.MW-8S should be developed again for the next sampling event. Work in Progress The present work plan calls for mobilization of a 21,000 gallon tank and pump installation for the pump test. This work will be started when the UST Fund is current on reimbursement for this site. At the present time, funds for the completion of this work plan are not available. Spoil removal and site maintenance is planned for the near future. Please curt Ervin Rifenburg of this office at (209)368-9381 if you have any questions on this report. Respectfully submitted, O�ApFESs�pN 1 64 tithi gineerin r cc 1 S7 Ervin Ri cc: Michael D. Sharon Scotts Ave. Stockton, Ca. 3