Laserfiche WebLink
1 <br /> A <br /> In February 1991, Roy F Weston, Inc (Weston) performed an additional <br /> assessment of the site that included drilling four soil borings and completing each as <br /> ' monitoring wells (MW-4, MW-5, MW-6, and MW-7) Low levels of toluene and lead <br /> were detected in soil samples from all four borings while xylenes were detected in <br /> ' soil samples from three of the four bonngs. Benzene, xylenes, and total petroleum <br /> hydrocarbons in the gasoline range (TPH-g) were detected in groundwater from <br /> ' MW-1. No petroleum hydrocarbons in excess of detection limits were found in the <br /> groundwater from any other wells <br /> ' Weston performed quarterly monitoring of the groundwater monitoring wells for <br /> the second and third quarters of 1992 and the first quarter of 1993 Benzene, <br /> toluene, xylenes, and TPH-g were detected in only MW-1 during these sampling <br /> events The results of the Weston assessment and monitoring are presented in <br /> Appendix C, Tables C-1 and C-2. <br /> ' In 1993, the District contracted Black & Veatch to perform an additional site <br /> assessment and remediation at the site To further define the nature and extent of <br /> the contamination, Black & Veatch drilled seven hydropunches in the vicinity of the <br /> former USTs and collected one groundwater sample from each hydropunch Two <br /> monitoring wells (MW-8 and MW-9) were then installed using the results of the <br /> ' hydropunch samples to locate the wells MW-8 was placed near the center of the <br /> plume in an area suspected to have the highest concentration of petroleum <br /> ' hydrocarbons MW-9 was placed downgradient of MW-8 at the estimated edge of <br /> the plume. Soil samples were collected and the hthology was characterized during <br /> ' the drilling of the monitoring well bonngs Groundwater samples were collected <br /> from each of the seven hydropunch locations (HP-1, HP-2, HP-3, HP-4, HP-5, HP-6, <br /> and HP-7) and from all nine monitoring wells (MW-1, MW-2, MW-3, MW-4, MW-5, <br /> MW-6, MW-7, MW-8, and MW-9) Samples were analyzed for BTEX, TPH-g, and <br /> lead. <br /> ' The assessment indicated the presence of petroleum hydrocarbons in excess of <br /> the detection linuts in the soil sample collected at 15 feet bgs (in the saturated zone) <br /> ' from MW-8. No petroleum hydrocarbons were detected in the soil from MW-9 <br /> Lead was not detected in either the soil or groundwater. BTEX and TPH-g were <br /> detected at concentrations in excess of detection limits in samples from MW-1, MW- <br /> 8, HP-1, HP-4, and HP-5. The highest concentrations of BTEX and TPH-g were <br /> detected in MW-8 and HP-4 The results of the additional site assessment are <br /> I� reported in the Additional Assessment and Remedial Options Report, Black & Veatch <br /> ' 96R7 East Bay Municipal Utility District <br /> 40429700 fcr 10 Final Closure Report <br />