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C A M B R I A wall, which contained 0.395 parts per million (ppm) methyl tertiary butyl ether (MTBE) by EPA Method 8260A at 13 feet below grade (fbg). The area was further excavated, later in February 1999, when Stockton Service Station Equipment Company, Inc. (SSSEC) of Stockton, California installed new, larger USTs, as discussed below. Soil beneath the northern two dispenser islands and associated piping contained residual benzene and MTBE at maximum concentrations of 0.962 and 60.4 ppm. These concentrations were at 12.5 fbg beneath the northwesternmost dispenser. Soil beneath the westernmost dispenser was excavated to non-detect concentrations. These activities are described in Cambria's June 11, 1999 Underground Storage Tank Removal Report, During February 1999, SSSEC installed a new gasoline UST, a new diesel UST, and five dispensers for the current station owner/operator in the same locations as the former USTs and dispensers. Based on the February 1999 soil over-excavation results, Cambria drilled four soil borings near the northern dispensers and associated piping during February 2000. One of these borings was converted into a monitoring well (MW-5). Total petroleum' hydrocarbons as gasoline (TPHg) and benzene were not detected in soil or groundwater during this investigation. MTBE was detected by EPA Method 8260A in groundwater from well MW-5 at a concentration of 10.3 parts per billion (ppb) during,the initial sampling event. Complete details of this investigation may be found in Cambria's September 8, 2000 Site Investigation/First Quarter 2000 Groundwater Monitoring Report. Cambria began implementing our approved October 23, 2000 Site Investigation Work Plan in November 2000. During this investigation, it was brought to our attention that our access agreement was invalid, and our work was immediately halted. Once Equiva and the site property owners negotiate a fully executed access agreement, this phase of investigation will be completed. Specifically, well MW-7 will be installed, wells MW-7 and MW-8 will be developed, and wells MW-5 through MW-8 will be sampled. These results will be included with those from the following proposed phase of work and reported by February 12, 2001. WORK PLAN Technical Rationale for Proposed Scope of Work A small amount of MTBE (32.4 ppb during.June 2000) has been identified .by EPA Method 8260 in groundwater from well MW-5, suggesting that additional investigation in this area is warranted. Results from the most recent monitoring 1346 2 I