SITE INFORMATION AND CORRESPONDENCE

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V threaten to affect, current or anticipated future beneficial uses of water. in addition, the level of site cleanup is consistent with the maximum benefit to the people of the state and will meet the applicable objectives in the Central Valley RWQCB Basin Plan within a reasonable time frame. The County's contentions are not supported by the facts in the record. As explained below, the facts show that both aerobic and anaerobic biologic degradation of residual petroleum hydrocarbon constituents is occurring at the site. The facts further show that all down-gradient monitor wells extend to and below the depth interval where the highest documented concentrations of dissolved phase hydrocarbons have been detected at the site. The primary sources of the release (the USTs, dispenser, and associated piping) have been removed as well as a substantial volume of affected soil from the immediate vicinity of the former USTs. Free product has never been observed in any site monitor wells and SVE has removed a substantial mass of residual petroleum hydrocarbons in the vicinity of the former pump island. With regard to affected groundwater and its potential to adversely impact current or anticipated fixture beneficial uses, substantial evidence in the record indicates that concentrations of dissolved phase hydrocarbons are decreasing, the plume is stable, MTBE is not present as a consequence of the release, and attenuation and biologic degradation of residual petroleum hydrocarbons in site soil and groundwater is occurring. Further, available data indicate that the affected groundwater monitored by site wells, in addition to being of inferior quality, is not hydraulically connected to the deeper groundwater aquifers that are used locally for municipal, industrial or-agricultural supply. The highest documented concentrations of petroleum hydrocarbons detected in site groundwater are in samples from monitor well MW-2 (this well is completed to a depth of 50 feet at the location of the former pump island where the release occurred). Concentrations of TPH-g and benzene typically ranged from-100,000 to 200,000 ppb and 6,000 to 25,000 ppb, respectively, from 1988 through 1994; concentrations of these constituents have declined to about 80,000 and 2,400 ppb, respectively, as demonstrated by the monitoring results of the past year. Reported concentrations of TPH-g and benzene in groundwater samples from the monitor well MW-4 (immediately down-gradient of MW-2 and completed to a depth of 54 feet) have ranged from 69 to 460 ppb and "non-detect" to 2.0 ppb, respectively' (32 sampling events over nine years). Other down-gradient wells, MW-5 (completed to a depth of 55 feet) and One sample,collected in August 1992,had a reported TPH-g concentration of 3,000 ppb. 9