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*awl � 1. 0 SITE DESCRIPTION The Stockton Scavenger operations facility is located on approxi- mately 4.5 acres of land at 1240 Navy Drive in Stockton, CA (Fig 1) . Geographically, it is situated one quarter mile west of the inter- section of Interstate 5 and Charter Way in township 1N-range 6E. Section numbers were not shown on USGS topographical maps. The work performed at the site was in response to leaks from two un- derground storage tanks which have been excavated and removed from the area. A generalized site base map is shown in Figure 2 which also shows the former locations of the tanks. The tanks contained hydraulic oil and diesel fuel used for fueling trucks and the oper- ation of equipment. The capacity of the hydraulic oil tank was 500 gallons while the diesel fuel tank held 1000 gallons. It is unknown how much liquid was released from either tank. A detailed soils investigation was initiated as a result of elevated levels of contamination found in samples taken from the walls of the excava- tion. Three groundwater monitoring wells have been installed at the site. The wells were required due to the close proximity of the base of the excavation to the water table (the excavation is approximately twenty feet deep with groundwater encountered at 25 feet) . 2.0 RESULTS OF PREVIOUS WORK 2. 1 Soil Sampling Procedure The initial investigative stage at the facility consisted of obtain- ing soil samples from various depths to determine the extent of con- tamination in the unsaturated substrate. Boreholes from which samples were obtained were drilled using a CME 75 hollow-stem auger rig. Sam- ples were taken pursuant to each five foot interval using an 18 inch California split spoon sampler. This process continued until ground- water was encountered or to a depth of 31.5 feet. The sampler was equipped with brass sleeves which were decontaminated prior to their reuse. Each brass sleeve containing a sample was field screened using a Pho- tovac TIP I-Photo Ionization Detector with 10.6 electronic volt lamp. The instrument was run past an end of the sleeve where the surface of the soil had been disturbed to allow for volatiles to be detected by the meter. Samples which registered a positive reading on the Photo- vac were capped and taped on both ends and placed in an iced cooler until their delivery to a California certified lab. Each sample was analyzed for the following constituents: Benzene Low to Med Boiling Pt. Hydrocarbons Toluene High Boiling Pt. Hydrocarbons (Diesel) Xylenes Petroleum Oil (Motor Oil) Ethyl Benzene (1)