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Work Plan—PEA Page 4 Former Haley Flying Service GPE Project 474.2 possibly penetrate. The area immediately adjacent to the washout pit is unpaved and consists of bare ground. The property was formerly the site of a 1,000-gallon regular unleaded gasoline tank and a 5,000-gallon aviation fuel tank. These tanks were removed in 1990 under County supervision. As a part of the tank closure, one confirmation soil sample was collected from beneath the 1,000-gallon tank and two soil samples were collected from under the 5,000-gallon tank. The sample from beneath the 1,000-gallon tank and one of two samples from beneath the 5,000- gallon did not contain detectable gasoline hydrocarbons or BTEX compounds. The other soil sample from beneath the 5,000-gallon tank contained 610 parts per million (ppm) of total gasoline hydrocarbons. It also included 6.5 ppm of benzene, 62 ppm of toluene, 41 ppm of ethylbenzene and 169-ppm of xylene. Due to the very shallow groundwater, the tank pit contained native groundwater, which was also sampled. The groundwater did not contain detectable gasoline hydrocarbons (<10ppm), but 3.9 parts per billion (ppb) of benzene were detected as were 18.4 ppb of toluene, 7.5 ppb of ethylbenzene and 32 ppb of xylene. Based on these sample results, the San Joaquin County Environmental Health Department issued a "notice of unauthorized release" in 1994. Information pertaining to mitigation of the release has been misplaced from the County files, but based on the LUST list maintained by the RWQCB, the site was adequately mitigated and officially closed. The ESA identified several environmental issues that were deemed to represent ongoing "recognized environmental conditions" as follows: • The soil in the vicinity of the mobile building is stained with oil in some areas. If the oil has penetrated more than a short distance into the soil, it could represent an adverse environmental condition. • A surface release in front of the westerly hangar of two drums of water, oil and diesel fuel in 2001 was the subject of an emergency response call by County agencies. The spill was cleaned up, but the San Joaquin County Environmental Health Department indicated that additional work would be needed to investigate the extent of impact to the soil in the area of the spill. • A surface release of what probably was pesticide impacted the soil in the vicinity of the washout area in 1982. The incident was the subject of a report by the California DTSC. The agency indicated that additional work is needed to investigate the impact to the soil, but to date it does not appear that such work has been completed. • The operation of the concrete-lined washout-pit was not in compliance with applicable regulations and there is a possibility that the use of the pit could have impacted the soil in the area around the pit and adjacent concrete pad. 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209) 569-0293 Modesto, Ca 95356 Fax: (209) 569-0295