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16 August 2001 AGE-NC Project No. 01-0852 Page 5 of 7 The concentrations of hydrocarbons and ethanol detected in samples T2-5 and T3--4 are below the I levels that would normally be of regulatory concern as long.as the data are not suggestive of an unassessed major release. AGE believes the data collected to date do.not indicate major releases in t the assessed areas. The lack of detectable concentrations of the target hydrocarbons in samples T12-5,T9-6 and HA14 minimizes the likelyhood of a significant releases of the hydrocarbons from the suspected former ASTs in the three areas. It should be noted that the actual locations of the suspected ASTs are not precisely known. The possibility of major unauthorized releases of the target hydrocarbons to the new pond or the old ponds was not favored by the lack of detectable concentrations of the hydrocarbons in NP 1 and OP 1. These results do not indicate that no release has occurred in these large receptors, but the samples obtained do not appear to have been impacted. Due to subsurface access limitations in the area of T7, the sampling locality is not'ideal'to demonstrate that no release has occurred from the sump; the sampling point was approximately I 1 � feet away from the sump,but was 14 feet below surface grade(bsg),below the bottom of the sump which was at approximately 10 feet bsg. The sample obtained was a poorly sorted sand.. The lack of detectable concentrations of the target hydrocarbons in the sample do not support the possibility of a significant subsurface release from the sump,but do'inot prove that such a release has not occurred. The detection of hexavalent chromium in all of the samples collected at approximately.l �oot-bsg around the initial samples collected.at each of the two known cooling towers show-that the. hexavalent chromium is,fairly widespread in the areas (Figure 4); the lack 6f detectable concentrations in the sam�les collected at'5 feet bsg(T4-5 and T8-5) indicates tot the hexavalent chromium-impacted soil in the areas closest to the suspected points of release does not extend as much as 5 feet into the subsurface. The detected distribution of hexavalent chromium is suggestive . of deposition by wind-blown spray from the cooling towers impacting the shallow soil.The Available data does not appear to indicate a significant subsurface release of the contaminant. Cross Sections A=A' and B=B' (Figure 5) show the vertical distribution of the hexavalent chromium suggested by the available data. The concentrations detected in the 10 shallow samples collected do not exceed f Federal EPA Region IX Preliminary Remediation Goals for residential soil(30 mg/kg)or industrial soil(64 mg/kg),but would exceed the California-modified PRG for residential soil (0.2 mg/kg) if applicable. As the site is anticipated to continue in industriat/commercial use, the California- modified PRG would not appear to-be applicable. The Introduction to the EPA Region IX PRGs states: `The Region 9 PRG table combines current EPA toxicity values.with"standard" exposure factors to estimate contaminant concentrations in enviromnental media (soil, air, and water) that are Advanced G"Environmental,Ina'