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Appendix B Advanced AGE Project No. 99-0559 Environmental Page 3 of 12 n.M 9 The general groundwater flow direction for HU1/HU2 was towards the west-northwest and the groundwater flow direction was calculated to be north or northwest in the lower flow units (HU3 to HU6). Approximately six inches or less of free-product has been intermittently observed in well MW-2 and lesser volumes have been detected in well MW-1 and MW-3. The highest concentrations of dissolved total petroleum hydrocarbons quantified as gasoline (TPH-g) and MTBE have been documented in the area of the former UST and approximately 75 feet southwest of the suspected release. The highest concentrations of MTBE have been detected in samples from well MW-2 at the former UST release area. TPH-g and benzene have been detected at concentrations as great as 870,000 microgram pre liter (pg/1) and 48,000 pg/I, respectively in May 2003. The last samples collected from each of the four shallow wells contain benzene above 6,000 pg/I and TPH-g at concentrations greater than 170,000 pg/l, further MTBE was detected above 2,200 pg/I. The highest concentrations of petroleum hydrocarbons detected in the CMT wells at the site were present in the groundwater samples collected from wells screened in HU1 and HU2 at the east edge of the UST area (MW-7). The well MW-8 also had detectable concentrations of BTEX compounds during sampling. Variable concentrations of low BTEX values were detected in well MW-5 and moderate concentrations of MTBE were also detected in the upper screen of the well. Low to moderate, yet stable concentrations of BTEX compounds were detected in well MW-6; also moderate concentrations of MTBE were also detected in the upper screen of the well MW-6 with lower concentrations detected in the lower screened wells of MW-6. The fuel additives TAME, ETBE and 1,2-DCA were detected in samples from the former UST area, and down-gradient of the UST area (MW-4/MW-6). The vertical extent of impacted groundwater, has been defined at the perimeter of the site; the vertical extent of impacted groundwater at the western and southern edge of the site are defined by well MW-5, and to a lesser degree by MW-6. The vertical extent of impacted groundwater, at the former UST area, has not been defined and extends beyond the vertical depth of well MW-7E. The lateral extent of shallow impacted groundwater towards the west and southwest, down-gradient of the UST area, has not been defined. INSTALLATION OF GROUNDWATER RECOVERY WELLS On 01 and 02 April 2003, four groundwater extraction well EW-1 through EW-4 were installed on the site. The wells were single-completed as groundwater extraction wells with a 4-inch diameter perforated well casing (60 to 80 feet) to a depth of 80 feet bsg.