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3 0 WORK PLAN, GROUNDWATER EXTRACTION Groundwater in six of the monitoring wells continues to contain concentrations of MTBE Concentrations of MTBE in the wells nearest the former UST source area (VW-2, MW-2 and MW- 3) have declined significantly, However, as shown on the Charts of MTBE in Groundwater (Appendix B), the MTBE concentration trends in the wells downgradient of the source area (MW-5, MW-6 and MW-7) are increasing Given the increasing MTBE concentration trend in the downgradient wells, EHD and RWQCB have declined requests to consider the case for regulatory closure EHD and RWQCB indicated that they would reconsider case closure once the MTBE concentration trend could project the natural attenuation of MTBE to below water quality goals ' As such, the objective of this proposed scope of work is to establish a declining MTBE concentration trend in the downgradient wells, so that the case can be considered for regulatory closure To achieve this objective Ramage Environmental proposes to extract groundwater from the downgradient wells (MW-5 and MW-7) on a monthly basis for at least six months Monthly, groundwater will be extracted for approximately four hours from MW-5, and for approximately four hours from MW-7 Groundwater will be extracted using a 5,000-gallon capacity vacuum truck capable of generating a vacuum of between 25 and 29 inches of mercury, and a one- inch diameter, semi-rigged, clear, PVC, downhole stinger Based on the historical groundwater analytical results, the vacuum truck will be used to transport the extracted groundwater as non- hazardous waste to a licensed facility for recycling IDuring the initial groundwater event, the drawdown and sustainable extraction rates will be measured in MW-5 and MW-7, and changes ;n depth-to-groundwater will be monitored in the surrounding monitoring wells These groundwater yield and radius of influence data may be used to modify future groundwater extraction efforts ' During the extraction of groundwater from MW-5 and MW-7, groundwater samples will be collected to evaluate the hydrocarbon mass removal The groundwater samples will be transported in an iced cooler with chain-of-custody documentation to a state of California certified hazardous waste testing laboratory, and will be analyzed for TPH-as-gasoline and BTEX by EPA Method 802018015M or 82606, and for MTBE, DIPE, ETBE, TAME, TBA and 1,2-DCA by EPA Method ' 82606 The results of the monthly groundwater extraction will be documented in subsequent quarterly groundwater monitoring reports 7 r r