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Work Plan For a Limited Subsurface Investigation - Former Chevron Service Station #9-5775 November 24, 1998 PREVIOUS ENVIRONMENTAL WORK The five former USTs, former hydraulic hoist, former dispenser islands and associated product piping were removed on August 24, 1998. Soil samples were collected from beneath the USTs and product piping. Very low to non-detectable concentrations of petroleum hydrocarbons were detected in all the soil samples from beneath the waste oil USTs, the product lines, the hydraulic hoist, and five of the six samples from the gasoline UST pit. The sample from 14.5 feet below ground surface (bgs) beneath the eastern end of the middle gasoline UST contained 14,000 parts per million (ppm) of Total Petroleum Hydrocarbons as gasoline (TPHg), 84 ppm of benzene and 56 ppm of methyl tert-butyl ether (MtBE). Based on field screening data, the area beneath the eastern end of the middle gasoline UST was excavated from 14.5 to 16 feet bgs, and a second sample collected. This sample contained 880 ppm of TPHg and 11 ppm of MtBE. Benzene was not detected in this sample. The area beneath the eastern end of the middle gasoline UST was overexcava ted from 16 to 22.5 feet bgs on August 31, 1998. Soil samples were collected from the base and the eastern wall of this excavated area. The base sample contained 2,300 ppm of TPHg, 4.1 ppm of benzene and 330 ppm of MtBE. The wall sample, collected at 1805 feet bgs, contained 290 ppm of TPHg, 0.35 ppm of benzene and 22 ppm of MtBE. Groundwater was not encountered during this investigation. Based on information supplied by Mr. Harlin Knoll (SJCPHS), groundwater in the vicinity of the subject site should be encountered at approximately 40 feet bgs. Based on data from monitoring wells in the vicinity, the historic groundwater low appears to be approximately 65 feet bgs. Mr. Knoll indicated that groundwater flow in the site vicinity should be toward the south. SCOPE OF WORK Soil sampling during the UST removal identified high concentrations of petroleum hydrocarbons beneath the eastern end of the middle gasoline UST at a depth of 22.5 bgs. SJCPHS has requested a work plan to define the full extent of gasoline and fuel oxygenate impact in both soil and groundwater. GR proposes to drill one exploratory soil boring (SB -1) to a depth of 65 feet bgs. This boring will be drilled through conductor casing previously installed in the overexcavated area beneath the eastern end of the former middle gasoline UST during backfilling. Three groundwater monitoring wells will be installed at the property boundary along W. Kettleman Lane (well MW -1), S. Pleasant Avenue (well MW -2) and S. Lee Avenue (well MVV -3). A fourth well (MW -4) will be installed in the location of the former waste oil USTs. To evaluate the vertical extent of hydrocarbon impact, all borings will be drilled to a depth of 65 feet bgs. To fully evaluate subsurface conditions, the exploratory soil boring (SB -1) and three of the well borings (MW -1, MW -2 and MW -3) will be logged continuously to total depth. Locations of the proposed soil boring and monitoring wells are shown on Figure 2. GR Field Methods and Procedures are included in Appendix A. In addition, GR will conduct a search to locate domestic and municipal wells in the site vicinity. Where possible, GR will obtain the construction details for the wells. 346341.04-1 2