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Workplan For Soil Investigation Page 2 Proposed El Dorado Apartments Development Stockton, California April 18, 2002 CTE Job No. 20-1232 Based on a review of available documentation the use of aboveground or underground storage tanks has not been documented at the site. We have reviewed historical topographic maps [1987, 1976, 1968, and 1952], aerial photographs [1993, 1970, 1966, and 19531 to determine the progression of site history. Based on this review it appears that the site has not been developed in the past with commercial structures (e.g. gasoline service stations, manufacturing facilities, etc.) that may have caused soil contamination to occur. However, from a review of the 1952 historical topographic map and 1953 aerial photograph it appears that a spur of the railroad came onto the southern portion of the site at that time. OBJECTIVE AND PROPOSED WORK The purpose of the proposed work is to assess the extent of possible groundwater contamination at this site. Four soil borings will be advanced by an appropriately license subcontractor. Drilling activities will be observed by a representative of Construction Testing and Engineering, Inc. ("CTE"). As shown on the attached Figure 2 the proposed borings will be drilled in the area of the suspected contamination. Before drilling soil boring permits will be obtained from the San Joaquin County, Public Health Services, Environmental Health Division(PHS/EHD). Soil samples will be collected,at five-foot intervals and at lithologic changes to a maximum depth of approximately 20 feet below grade(fbg). Soil samples will be logged in the field using the Unified Soil Classification System. Soil samples will be monitored for the potential presence of petroleum hydrocarbons as outlined below. Selected samples will be retained for potential laboratory analysis by capping them with a Teflon sheet liner and a plastic cap. Collected samples will be identified by boring number and depth. Monitoring of soil samples for the potential presence of petroleum hydrocarbons will occur visually and with a gas-monitoring detector (e.g. Gastech, PID, or FID) using the following procedure. Selected soil samples will be placed in Zip-Lock or similar plastic bags for combustible gas testing. The soil samples will be shaken to release volatile constituents, a small hole will be poked into the bag,and the sampling port of the gas-monitoring device will be introduced into the headspace above the soil sample. A sample of the headspace vapors will be withdrawn and analyzed for hydrocarbon vapors by the gas-monitoring device. Additionally,selected,soil samples will be submitted to a State of California-certified environmental laboratory for analytical testing. Soil sample identifications,including boring designation and depth, will be recorded on a chain-of-custody form before delivery to the laboratory.Soil samples delivered to the laboratory will be analyzed for total petroleum hydrocarbons-extended(TPH-ext.)and volatile aromatic hydrocarbons (by EPA Method 8020). In addition the sample with the highest TPH-ext.