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Rc�:JIl:1 Oti:ce INTERNATIONAL 4555 Pate Bcu eac; TECHNOLOGYMa 2, 1996 Martinez caiL'0=;45512233 CORPORATION Y 510-372-9':c� _ Fm 9i0-372522= IT Project NO: 765748 Mary Maeys San Joaquin County Public Health Services Environmental Health Division PO Box 2009 Stockton, California 95201 Planned Overexcavation Activities Pacific Bell Tank Replacement Project 2300 Eight Mile Road; Stockton, California Dear Ms. Maeys: IT Corporation (IT) was retained by Pacific Bell to conduct oversite and verification sampling activities during the removal of two underground storage tanks from the above referenced Pacific Bell Property. The tanks consisted of one 4,000 gallon diesel fuel tank and one 10,000 gallon unleaded gasoline tank, which were removed on May 2, 1996 by representatives of Aronson Engineering. Two separate excavations (one for each tank) were dug, with two verification soil samples being collected beneath the diesel tank and three verification soil samples being collected beneath the unleaded gasoline tank. A mobile lab operated by Sparger Technology was onsite to analyze the verification samples. Analytical results indicated the presence of unleaded gasoline _ in two of the three samples collected from the gasoline tank excavation (the sample collected at the east end and the sample from the center of the excavation floor possessed the gasoline concentrations. Petroleum contaminants were not encountered in the diesel tank excavation. It is the intention of IT to conduct overexcavation and a second round of verification sampling activities in the areas found to contain fugitive petroleum concentrations. A track excavator will be delivered to the site on May 2, 1996 in preparation for overexcavation efforts to begin on May 3, 1996 at 0700. IT anticipates extending the depth of the excavation a maximum of 5.0 feet to (resulting in a maximum excavation depth of 20.0 feet below grade). The excavation side walls (east, and possibly north and south) may be extended a maximum of 2.0 feet beyond current limits, in the areas adjacent to the impacted soils. Overexcavation activities will be continued until no further visual, olfactory or field screening indications of petroleum contamination exists or the limits of the excavating equipment have been reached. Overexcavation activities will also be halted if it appears that any onsite structure may be undermined. A mobile laboratory will be onsite to analyze the second round of verification soil samples. Samples will be collected from the center of each new wall or floor excavated at a rate of 1/20 yd' of soil removed. The samples will be analyzed for total petroleum hydrocarbons (TPH) as gasoline and benzene, toluene, ethyl benzene and xylenes (BTEX) using detection limits of 1.0 ppm for the TPH as gasoline and 0.005 ppm for the BTEX constituents. All results will be