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Ms. Laurie Cotulla V %00 July 25, 1989 Page 7 y,, Analytical results for the soil samples indicate that EPA Method 8020 constituents exceeding the California Regional Water Quality Control Board (RWQCB) designated levels in waste or soils for the protection of groundwater [(designated levels) as presented in "The Designated y Level Methodology for Waste Classification and Cleanup Level Determination" Marshack, Jon B., April 1987] were only identified in sample ATR-4B from 10.5 to 11.0 feet in borehole ATR-4. Sample ATR-4B contained 2.2 parts per million (ppm) benzene. With a laboratory .L. detection limit of 10 ppm, three of the seven soil samples contained identifiable amounts of petroleum hydrocarbons with EPA Method 8015, modified. Samples ATR-2B (10.0 to 10.5 feet), ATR-313 (10.0 to 10.5 feet), and ATR-4B contained 710 ppm, 1,300 ppm, and 1,700 ppm petroleum hydrocarbons, respectively. With a detection limit of 0.01 ppm, no EPA Method 8010 constituents were identified in any of the soil samples. In April 1987, EPA Method 602 identified benzene, toluene, and xylene exceeding DHS action levels (Marshack, 1987) in groundwater samples collected from wells ATR-3 and ATR-4. Xylene was identified in well ATR-1 and toluene was identified in well ATR-2; however, the concentrations were well below DHS action levels. Lead was identified in the groundwater samples from the four wells. It exceeded the RWQCB primary drinking water standard for lead of 0.05 ppm in wells ATR-2 and ATR-3. Petroleum hydrocarbons were identified (EPA Method 8015) in wells ATR-3 and ATR-4 at concentrations of 17 and 21 ppm, respectively. Petroleum hydrocarbons were not identified in wells ATRA and ATR-2 based on a detection limit of 1.0 ppm. With the exception of 1,2-Dichloroethane, none of the EPA Method 602 constituents exceeded RWQCB primary drinking water standards. Groundwater from wells ATR-2 and ATR-3 contained 1,2-Dichloroethane at concentrations of 5.9 and 20 ppm, respectively. The RWQCB primary drinking water standard for 1,2-Dichloroethane is 5.0 ppm. 4.0 In Brown and Caldwell's September 28, 1987 PAR, the following conclusions were presented: 1. No floating product was found at this site. La 2. The lateral extent of hydrocarbon contamination in soil and groundwater was not defined. 3. It is unlikely that a nearby municipal well would be affected by hydrocarbons in groundwater at this site because the well is approximately 114 miles away, not t. downgradient from the ARCO site, and draws water from a deeper aquifer. 4. The soils at the locations of the on-site wells do not contain significant levels of hydrocarbons. Therefore, excavation, on-site soil aeration, soil venting, off-site soil treatment, and landfilling are unnecessary. 5. From the hydrocarbon levels identified in the groundwater and the fact the tanks and lines appear to be structurally sound, it is thought the hydrocarbons originated from overfilling the tanks. 4+ La _ BROWN AND CALDWELL V 723 S STREET SACRAMENTO,CALIFORNIA 95814-7092•(916)444-0123