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i T Monitoring Well Installation Report Speedy Mart,8200 N Highway 99 Page 7 of 8 ppb respectively Groundwater samples collected from the developed monitoring wells at the site also contained elevated levels of gasoline constituents TPHg ranged from 1,300 ppb downgradient well MW4 to 120,000 ppb in well MWl Benzene ranged from 27 ppb (MW4) to 17,000 ppb (MW1), and MTBE ranged from 6 1 ppb (upgradient well MW2) to 44,000 ppb (MW1) Groundwater analytical results summarized in Tables 4 and 5 Laboratory reports and chain-of-custody documentation are included in Attachment E Groundwater samples collected from the water supply well after the well survey contained non- detect to low levels of dissolved gasoline constituents, including benzene and MTBE The sample collected at a depth of 72 feet btc contained no detectable contaminants The sample collected from a depth of approximately 90 feet btc contained benzene at 0 7 ppb and MTBE at 86 ppb The sample collected at a depth of 222 feet btc contained benzene at 1 6 ppb, MTBE at 120 ppb, and TPHg at 63 ppb SUMMARY AND CONCLUSIONS • Relatively low levels of residual gasoline constituents remain in the unsaturated soil beneath the former USTs from approximately 30 feet bgs to groundwater at approximately 60 feet bgs . o Vadose zone soils in perimeter borings installed at the site are generally free of residual contamination However, soil samples collected from the capillary fringe zone in each bonng/well contained low levels of residual gasoline constituents including MTBE o Low level soil contamination in the saturated zone appeared to be limited to the depth interval between 60 feet bgs and approximately 75 feet bgs in the penmeter borings However, low level contarnmation, including benzene and MTBE were detected in soil at 95 feet bgs in well MW 1 • Groundwater beneath the site has been significantly impacted by gasoline constituents, including benzene and MTBE • The lateral extent of groundwater contamination has not been defined in any direction • The water supply well at the site is in poor condition and apparently has been impacted by dissolved contaminants RECOMMENDATIONS Based upon subsurface investigations conducted to date, Ground Zero makes the following recommendations • Install additional monitoring wells to further investigate the lateral extent of groundwater contamination groundzeltuieburghvelirpt doc