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SITE INVESTIGATION WORKPLAN MTBE in the subsurface soil. As of the date of this workplan, the San Joaquin County Environmental Health Division (SJCEHD) had not yet reviewed this case nor had it placed the. site into the Local Oversight Program(LOP). SITE HISTORY Site land use history was derived from the underground storage tank removal documentation and closure report completed in April 2000.1 The UOP moved its main campus to its present location in Stockton in approximately 1924. The UOP has owned the site for many years and has used it as a part of its educational facilities. STRUCTURES The underground storage tank was removed from a parking lot for the former UOP Physical Plant facilities. A gasoline pump was also located in the parking lot to the southwest of the former 1 tank. The former Physical Plant building, Central Receiving Building, Electric Shop, Custodial Warehouse and shed are located south and east of the former underground storage tank location. Underground Storage Tanks One 4,400 gallon unleaded gasoline underground storage tank was removed at the site on April 7, 2000 under permits issued by San Joaquin County Environmental Health Division (#022179) and the City of Stockton Fire Department (#00-91). The tank removal was conducted by Deltech Geotechnical Support, and soil sampling was conducted by Ground Zero Analysis, Inc. All ' removal and soil sampling activities were observed by Mr. Michael Kift and Mr. Vidal Pedraza of SJCEHD. The date of installation of the gasoline tank and pump and its period of use is unknown. No other underground storage tanks were identified on the site. ■ PREVIOUSLY DETECTED PETROLEUM HYDROCARBONS IN SOILS AND GROUNDWATER Ground Zero Analysis, Inc. conducted soil sampling and analysis immediately following the underground storage tank removal on April 7, 2000. The soil sampling locations were beneath the northern end of the tank at 13 feet below ground surface and beneath the southern end of the tank at 13 feet below ground surface. Additional soil samples were obtained from stockpiled soil. No groundwater was encountered in the tank excavation. Excavated soil from the tank pit (primarily pea gravel) was used as backfill. The locations of the soil sampling conducted on April 7, 2000 are provided in Figure 3 attached to this document. Documentation received from Ground Zero Analysis, Inc. associated with the tank removal and soil sampling, as well as the analytical reports are attached to this document as Attachment A. 1 Laboratory analysis of the soil samples indicated concentrations of MTBE beneath the tank and in 1 Underground Storage Tank Closure Report, 1081 W.Mendocino Ave.,Stockton,California,April 25,2000, prepared by Ground Zero Analysis, Inc. ' Environmental Science Associates 2 University of the Pacific Site Investigation Work Plan June 2000 200252