SITE INFORMATION AND CORRESPONDENCE

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v Former TAOC Pump Station -4 _ 880 Beechnut 24 February 2004 Tracy, San Joaquin Co. Soil Stockpiles Eight borings were advanced to 3 feet in the soil stockpiles to collect samples. Composite samples were obtained from the smaller soil mounds. Concentrations of TPH-c in stockpiles ranged from 53 to 28,000 mg/kg and ND for BTEX. PAHs were detected in all soil samples. However, the minimum detection limit for PAHs was increased to accommodate the dilution factor required because of the elevated TPH concentrations. Groundwater During the investigation, groundwater samples were obtained from the existing monitoring wells. TPH-g, BTEX, and PAHs were not detected in the two downgradient wells (E and F). Consistent with previous analysis, TPH-d at 280 pg/L and 190 pg/L, was detected in samples from wells E and F respectively, and no analytes above lab reporting limits were detected in upgradient well REW-1. Product thickness in the two onsite wells was 2.0 and 4.5 feet, and approximately two to three gallons of floating product was removed from each well this quarter. Commercial businesses are present to the east, another ChevronTexaco site under investigation and residential properties are located to the west, and north beyond the downgradient wells the railroad right- of-way and beyond that is occupied by residences. CONCLUSIONS Except for the southeast portion of the site, the majority of the property has been impacted by significant concentrations of TPH compounds including PAHs. The extent of impacted soil, within the piles as well as extending from approximately 20 to 48 feet, has been adequately delineated. According to the soil sample analyses, concentrations of TPH compounds are present throughout the soil piles. Even though the property is fenced, the site is within a residential area and reportedly has been accessed by residents. The site needs to contain appropriate signage and notification and fencing needs to be maintained to prevent any unauthorized access. Impacted groundwater has not been delineated to the north-northwest beyond the northernmost locations sampled during the recent investigation. A plan and schedule needs to be submitted addressing potential future site use. The plan and schedule should address the remaining environmental issues with respect to the impacted soil in the near surface and in the piles. Based on the historical and recent investigative reports, a land-use deed restriction should be recorded for this site, limiting future development to non-residential. Board staff will wait to make a final determination regarding the site until the DTSC completes an evaluation of the human health risk assessment and the additional groundwater sampling has been completed.