SITE INFORMATION AND CORRESPONDENCE

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Mr. Sheldon Heckman - 2 - _ 12/27/01 Mr. Richard Calone,`Esq., Richard Calone, Inc. The Work Plan provides a chronological list of site activities in the warehouse/truck bays building over the years, which included: service facilities for fork lifts (1947-94), commercial tires (1970-present), and commercial lubrication (1988-94). A commercial diesel and gasoline fueling facility also occupied a portion of the site, which utilized Underground Storage Tanks (USTs). San Joaquin County Public Health Services-Environmental Health Division provides oversight of the USTs investigation activities. Ten groundwater monitoring wells are currently sampled for the separate USTs investigation (San Joaquin County). Other areas of concern that are described in the Work Plan include several above-ground storage tanks (AGTs) located inside of the warehouse/truck bays building. The Work Plan suggests that the AGTs were actually reused USTs. One additional AGT, half full of waste oil, is located outside of the warehouse/truck bays building.. Visual observation (stained surface) suggests that the AGT has leaked inside and outside of the concrete containment structure. Previous investigations also suggest that past operation of the facility may have involved the use of solvents (TPH-SS and VOCs), which are now detected at the site in groundwater and soil. The Work Plan also provides a schedule of activities and reports, which include: installing monitoring wells (after Board concurrence), conducting a thirty day feasibility pilot study, and submitting two reports (Problem Assessment Report and Final Remedial Plan). Please address the following comments in a revised Work Plan. General Comments: 1. The geologic cross-sections show a lithology of clay and silty clays at the site. The proposed SVE extraction system will include 25 foot spacing between the extraction wells. We are concerned that the radius of influence of the SVE wells may not be very significant because of the lithologic conditions at the site. This could result in a lack of response in the SVE test observation wells. Please design the SVE system with additional monitoring points closer than the current 25-foot spacing, taking into account the site soil lithology. 2. The SVE test observation wells, screened at 50 feet below ground surface (bgs), are very close to the water table, which has varied in depth at the site (35 to 54 feet bgs). Well completion depths may need to be modified to accommodate variations in the water table depth. The SVE pilot test should be redesigned to include several completion depths for the SVE observation wells, in order to evaluate if the detections of soil gas constituents are actually from the soil, and not the result of offgassing of constituents from the groundwater. 3. The request for an additional 30 days past well installation, to conduct a 10-hour SVE test, appears excessive. Excluding weather delays, one week past the well installation should be sufficient to conduct the pilot tests.