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1.0 INTRODUCTION Upgradient Environmental Consultants (Upgradient) assumed the responsibility for assessment and monitoring of groundwater contamination at the Chilies Trucking facility in Stockton, California in September, 1994 Upgradient submitted Quarterly Reports in October 1994, February 1995, August 1995, September 1995, January 1996, and May 1996, describing the progress of the investigation through the second quarter of 1996 The main purpose of this report is to present the results of the completed assessment of soil and groundwater contarrunation at the site This includes presenting the results of work performed during the third quarter of 1996 2.0 BACKGROUND INFORMATION 2.1 Site Location and Description The project site is located at 3931 Newton Road, in an industrial area on the northeast outskirts of Stockton near U S Highway 99 The location of the site is shown in Figure 1, and the site facilities are shown in Figure 2 Originally agricultural property, the site was developed as a commercial truck terminal in 1973 The property occupies an area of about 3 5 acres Topography in the area is generally flat, although the protect site is elevated a few feet above the adjacent parcels There is a maintenance building and office fronting Newton Road, with a large, unpaved storage yard/parking lot in the rear A diesel and gasoline fueling facility, consisting of two underground storage tanks (UST's), was formerly present on the east side of the storage yard (Figure 2) This facility was removed in 1989 and replaced with an above-ground fueling facility, which is located to the southwest of the abandoned facility 2.2 Previous Work Soil samples that were collected during the UST removal in 1989 contained petroleum hydrocarbons in the gasoline and diesel ranges, prompting assessment of the extent of soil contamination Contaminated soil was excavated to a depth of 35 feet by SEMCO in July, 1990, but residual hydrocarbons were detected in eleven of the fifteen samples collected from the floor and sidewalls of the excavation Clean soil was excavated from the west end of the property and placed into the open excavation The contaminated soil was then treated with bacteria and stored at the west end of the property It was later sampled and approved for disposal by San Joaquin County Public Health Service, Environmental Health Division (PHS/EHD) The soil was then spread out and the area was graded Due to the failure of the excavation work to completely remove all of the contaminated soil in the vicinity of the UST facility, further assessment of the extent of contamination was requested by PHS/EHD The firm of Richesin & Associates of Danville, California was retained in July, 1990 1