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Six known water supply wells are located within a 2,000-foot radius of the site. Additional research is necessary to identify the location and operational status of these wells. At this time, these wells do not appear to threatened by the dissolved hydrocarbons beneath the Apache site. 7.2 Discussion The primary source for impact to the soil and groundwater beneath the site has been removed. Operation of an SVE system appears to have reduced residual hydrocarbons from the soil in the vicinity of the former UST. Additional investigation into the lateral extent of impact in this area is not warranted. COCs identified at this site include TPHG, benzene, TBA, and 1,2-DCA. In the upper portion of the water-bearing zone, the lateral extent of TPHG and benzene impact have been adequately characterized. MTBE is not a COC in the upper portion of the water-bearing zone. The compound 1,2-DCA is not adequately characterized to the west, southwest, southeast, or east. Significant concentrations of 1,2-DCA downgradient of the Sunland site (well MW-2) suggest a off-site contribution (neither soil or groundwater samples from the Sunland site appear to have been analyzed for 1,2-DCA). Further assessment of the lateral extent of TPHG, benzene, MTBE, and TBA is not warranted. In the lower portion of the water-bearing zone, chemical analytical data suggest the TPHG and benzene plume configuration appears to be stable, but the monitoring well network in the lower zone does not completely characterize the lateral extent of impact. The plume boundary is delineated to the east (well MW-10) and south-southeast (well MW-12), but due to the fewer wells screened in this zone, it is not possible to completely characterize the plume to the southeast (between MW-10 and MW-12), south, southwest, or west. As in the upper portion of the plume, MTBE is not a COC in the lower portion of the water-bearing zone. The compound 1,2-DCA is characterized to the east and south-southeast, but further characterization on 1,2- DCA in this zone is necessary to the southeast, south, southwest, and west. The presence of TPHG, benzene, and 1,2-DCA in the grab groundwater sample from 152 feet bgs in boring CPT- 8 indicate the vertical extent of groundwater impact is not completely characterized vertically. In addition, if USTs are or were present on the Port Stockton Foods facility to the west of the subject site, lower zone wells downgradient of these USTs would be required to evaluate whether they too had contributed to the groundwater impact beneath the Apache site. Additional wells are also required on the Apache site to more accurately delineate the core of the dissolved plumes in both the upper and lower zones. • p:\Apache Plastics\Reports\Apache 5CM.doc Page 15 Stratus