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i Section 4 Feasibility Study This section describes preliminary alternatives for remediation of the fuel leak at the Del Monte former Disco tanks location in Stockton. Alternatives development consists of: • Reviewing the RI findings • identifying applicable remediation technologies • Developing and evaluating alternatives which will achieve the remedial action objectives • Selecting a cost-effective option { For the Disco location, remedial action alternatives were developed for groundwater containing dissolved petroleum hydrocarbons and for currently unsaturated soils that have been affected by vertical migration of fuel down to the water table and fluctuating water table elevations. l Summary of RI Findings Data and observations presented in the previous section are sufficient to identify the nature and general extent of contamination in the subsurface and to develop a remedial action plan. The following are the main findings that affect the evaluation of remedial options: 1. Soils underlying the site consist of subequal proportions of sand and silt. The soils are generally homogeneous, lacking obvious stratification, and extensive low-permeability layers are - absent. The soils are moderately to highly permeable. 2. The groundwater table presently occurs at about 75 ft bgs. Groundwater flow is generally north to northwestward, largely controlled by withdrawals from three onsite deep wells operated by Del Monte. Seasonal and year-to-year changes in water level are substantial; the water table appears to be near its historic lowest level. 3. Groundwater in the area is used for industrial supply and municipal potable- water supply. Several high-capacity wells exist within 1 mile of the site. These wells are typically more than 250 feet deep and obtain water from sand layers from 140 to more than 400 feet bgs. sF03160ARP1007.51 4-1