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r.. In February 1991, Roy F. Weston, Inc. (Weston) performed an additional assessment of the site that included drilling four soil borings and completing each as �.. monitoring wells (MW-4, MW-5, MW-6, and MW-7). Law levels of toluene and lead were detected in soil samples from all four borings while xylenes were detected in soil samples from three of the four borings. Benzene, xylenes, and total petroleum 160 hydrocarbons in the gasoline range (TPH-g) were detected in groundwater from MW-1. No petroleum hydrocarbons in excess of detection limits were found in the w.r groundwater from any other wells. Weston performed quarterly monitoring of the groundwater monitoring wells for the second and third quarters of 1992 and the first quarter of 1993. Benzene, toluene, xylenes, and TPH-g were detected in only MW-1 during these sampling events. The results of the Weston assessment and monitoring are presented in Appendix C, Tables C-1 and C-2. In 1993, the District contracted Black & Veatch to perform an additional site r.. assessment and remediation at the site. To further define the nature and extent of the contamination, Black & Veatch drilled seven hydropunches in the vicinity of the L former USTs and collected one groundwater sample from each hydropunch. Two monitoring wells (MW-8 and MW-9) were then installed using the results of the hydropunch samples to locate the wells. MW-8 was placed near the center of the plume in an area suspected to have the highest concentration of petroleum hydrocarbons. MW-9 was placed downgradient of MW-8 at the estimated edge of i.0 the plume. Soil samples were collected and the lithology was characterized during the drilling of the monitoring well borings. Groundwater samples were collected 16. from each of the seven hydropunch locations (HP-1, HP-2, HP-3, HP-4, HP-5, HP-6, and HP-7) and from all nine monitoring wells (MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-8, and MW-9). Samples were analyzed for BTEX, TPH-g, and lead. The assessment indicated the presence of petroleum hydrocarbons in excess of �. the detection limits in the soil sample collected at 15 feet bgs (in the saturated zone) from MW-8. No petroleum hydrocarbons were detected in the soil from MW-9. Lead was not detected in either the soil or groundwater. BTEX and TPH-g were detected at concentrations in excess of detection limits in samples from MW-1, MW- 8, HP-1, HP-4, and HP-5. The highest concentrations of BTEX and TPH-g were detected in MW-8 and HP-4. The results of the additional site assessment are reported in the Additional Assessment and Remedial Options Report, Black & Veatch aL.. 96R7 East Bay Municipal Utility District 40429700.fcr 5 Final Closure Report V