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ANIBRIA The 2 year model predictions agree reasonably well with the actual groundwater analytical data collected from wells MW-1 and EW-1, located closest to the MTBE source, where the highest MTBE concentrations were observed 1 to 2 years following soil sample collection. Maximum MTBE concentrations were 160,000 microgram per liter detected in well MW-1 during 4 February 1999 and 440,000 pg(L detected in well EW-1 during August 1999. By comparison, the model predicts that after two years (July 15, 2000) the maximum MTBE concentration will be 158,703 µgd— r Remaining MTBE Mass: To assess the feasibility of MTBE mass removal from unsaturated zone soils in the vicinity of the southeastern,product island (CPT-1 and EW-1), soil vapor extraction testing was performed during Aly"1001 (Cambria, Soil Vapor Extraction Feasibility Test Report, June 22, 2001). SVE testing performed on wells MW-1 and EW-1 demonstrated that there is not a significant amount of MTBE remaining in soil above the groundwater table, even when thegrow water was depressed with groundwater extraction. Vapor analytical data indicated that parts per million by volume (ppmv) MTBE was detected in extracted soil '�1g1 vapor from well MW-1 (screened 13.5 to 33.5 fbg) and no MTBE was detected in well EW-1 (screened 22 to 42 fbg). To further assist with MTBE mass removal efforts, in March 2000, a GWE system was installed at the site extracting groundwater from well EW-1. The GWE system operated until July 2001, when it was shut-down due to low influent groundwater concentrations. An estimated 1.8 pounds of total hydrocarbons and 15.2 pounds of MTBE were removed at the site. During this period the MTBE plume was remediated to concentrations below the 0.5 µg/L reporting limit. Furthermore, groundwater analytical data collected since shutdown demonstrate no rebound in MTBE concentrations. (-rY'u e.4- To summarize: • The majority of the MTBE mass previously identified in soils at X-1, X-2, and CP17-1, appears to have attenuated as demonstrated by the VLEACH model and supported by the groundwater analytical data. • The SVE testing performed during April 2001, demonstrated that there was little to no remaining MTBE mass in the unsaturated zone soils in this area approximately 5 years ago. • Groundwater monitoring data collected atter the UWE system was shutdown tiuly LUUI) indicates that there has been no rebound in MTBE concentrations. 0324 4