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New West Petroleum #1003 2 - 3 April 2008 Lodi, San Joaquin County while the estimated MTBE mass in groundwater is 3.5 gallons. Due to the shallow depth to groundwater, soil vapor extraction has not been considered effective or feasible for treatment of soil, and was not evaluated in the FS. An Enhanced Leak Detection Test conducted in January 2006 confirmed the absence of leaks in the existing underground storage tanks system. The FS discussed the beneficial uses of groundwater under the Regional Board's Basin Plan, including Municipal and Domestic Supply, Agricultural Supply, and Industrial Supply. The FS proposes the following applicable water quality goals (WQGs): COPC WOGS Legal Authority MTBE 5 u /L Secondary MCL Benzene 1 u /L Prima MCL Toluene 150 u /L Prima MCL Eth (benzene 700 u /L Prima MCL Xylenes 1,750 u /L Prima MCL 1 -MCL = Maximum Contaminant Limit, Title 22 (see comments) California Code of Regulations (CCR). The Secondary MCL is the Taste and Odor Threshold, while the Primary MCL is the State and/or Federal limit for public water supplied by a purveyor. The FS evaluated the following technologies for final remediation: • Monitored Natural Attenuation (MNA), • Ozone Injection (03 Inj), and • Expanded Groundwater Pump And Treatment (GWP&7). Alternative 1: MNA consists of monitoring the MTBE groundwater plume until there is evidence of plume stability and declining concentrations in monitoring wells, combined with no evidence of vapor intrusion into buildings, to establish a recommendation for a low risk closure. MNA also looks for evidence of biodegradation of MTBE by microorganisms. The estimated cost for MNA lasting 20 years is $690,000. While MNA is feasible, the lack of hydraulic control of the MTBE plume and the continued migration threat towards the municipal supply wells negated this alternative. Alternative 2: 03 Inj involves construction of new injection wells connected by underground piping to an ozone generator. The 03 injected into the MTBE plume quickly breaks down into oxygen which reacts chemically with the MTBE, degrading it to byproducts tertiary butyl alcohol, 2-propenol, acetone, pyruvic acid and eventually to biomass, carbon dioxide, and water. The oxygen also dissolves into the water and aids in aerobic degradation by microorganisms. The estimated cost for 03 Inj was $570,000 over four years of operations and two years of post- treatment groundwater monitoring. As discussed above for MNA, 03 Inj does not provide hydraulic control of the MTBE plume, and was likewise rejected. Alternative 3: The expansion of the existing GWP&T also requires construction of new wells connected by underground piping to a treatment system, however the wells are groundwater extraction by submersible electric pumps and the treatment system is currently onsite and operational. Water would be pumped back to the existing onsite groundwater treatment system