SITE INFORMATION AND CORRESPONDENCE

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Mr. Joseph Mello, CHG - 2 - 23 January 2013 2. NuStar concludes that MNA is an appropriate remedy for the Site based on the following: • Monitoring wells at the edge of the plume show stable or decreasing concentration trends. • Previous assessments demonstrate that both aerobic and anaerobic biodegradation is occurring. • More active remedial alternatives are not feasible because the Site is an active bulk terminal, which inhibits implementing most on-site active remediation methods. Additionally, active remediation will not likely significantly reduce the remedial time over the time required for MNA. • There are no domestic or municipal uses of the groundwater in the Site vicinity. 3. NuStar prepared isoconcentration contours for total petroleum hydrocarbons as gasoline (TPHg), TPH as diesel (TPHd), benzene, and methyl tert butyl ether (MTBE) from 2004 and 2012. Petroleum hydrocarbon concentration contours demonstrate that the extent of hydrocarbons in groundwater have decreased over the eight years without the addition of active remediation. 4. NuStar currently analyzes groundwater samples for TPHd with and without a silica gel cleanup procedure. TPHd groundwater results following the silica gel cleanup procedure were either below laboratory detection limits or significantly less than those analyzed prior to the silica gel cleanup procedure. NuStar concludes that TPHd concentrations in groundwater are being influenced by naturally-occurring biogenic interferences or organic breakdown products. I concur with the recommendation to collect groundwater samples for TPHd analysis both with and without silica gel cleanup. The reduction of TPHd concentrations following the use of the silica gel cleanup procedure may be a further indication of the natural attenuation occurring at the Site. 5. NuStar evaluated the Site in accordance with California State Water Resources Control Board Low Threat Underground Storage Tank (UST) Case Closure Policy Resolution No. 2012-0016 (LTCP) and states the Site meets the following general criteria: • The unauthorized release is within the service area of a public water system. • The unauthorized release consists only of petroleum. • The unauthorized release was stopped. • Free product has not been observed in Site monitoring wells since 2006. • A conceptual site model was submitted. • Secondary sources have been removed to the extent practicable. NuStar excavated contaminated Soil to the extent possible given the Site is an active bulk fuel terminal. • Groundwater has been tested for MTBE. • Nuisance conditions do not exist at the Site. Nustar concludes that the criteria in the LTCP for direct contact with vapor and soil have been met and the objectives for closure will be to meet the groundwater specific criteria outlined in the LTCP. The Site has met the following groundwater criteria for Scenario 4: • Plume exceeding WQOs is less than 1,000 feet • There is no free product