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Interim Remediation Plan and Second Quarter 2001 Groundwater Monitoring Report Moore Petroleum Bulk Plant,5491 F Street,Banta,California Page 9 • VEW-2: Overall, detected concentrations increased this quarter(with the exception of benzene) and VEW-2 was the only well with a concentration of methanol at slightly above the detection limit. • RW-2: All detected concentrations decreased this quarter. This well was sampled at the conclusion of the pumping test (March 29, 2001) and it appears the groundwater concentrations were diluted. Based on groundwater level data recorded during the pumping test, it appears that one extraction well is not enough to hydraulically control the potentiometric surface to halt the off site migration of MTBE. However, dewatering the former tank basin area with one recovery well (RW-2) did influence the down gradient, sentinel well (MW-12) suggesting that installing three wells, as originally proposed, should provide the necessary hydraulic control. Based on groundwater analytical data recorded during the pumping test, it appears that dilution, not capture of the groundwater plume was occurring. Concentrations of TPHg reduced dramatically after extracting only 500-gallons of water from recovery well RW-2. A review of groundwater concentrations presented on Table 5 shows that MTBE is influencing groundwater at sentinel well MW-12 which provides early warning for the domestic Rhodes well located at 5451 F Street(just 20-feet further down gradient). MTBE concentrations in groundwater at well MW-12 have remained relatively constant during the last three quarterly monitoring events. Furthermore, MTBE has not been detected at the Rhodes well since October 27, 2000. MTBE has been below detection limits for the last five monthly sampling events at the Rhodes well. In fact,the October 27, 2000 detection of MTBE has been the only constituent detected during any of the eight monthly sampling events conducted at that well. It appears as if TPH diesel was reported as motor oil for several wells during this quarter. Apex recommends sampling for napthalene next quarter. Napthalene is an additive in diesel and not motor oil,therefore if napthalene is sampled, TPHd and motor oil can be separated Recommendations Apex recommends not utilizing groundwater extraction at the site at this time for the following reasons. 1) Due to low hydraulic conductivity at the site, groundwater radius of influence during pumping is small, 2)Low petroleum concentrations in groundwater during groundwater pumping suggest poor performance and negative cost effectiveness, and 3) currently MTBE is not influencing groundwater at the Rhodes domestic well.