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1.2 Hydrolo�Y • The subject property is situated in the north-central portion of the San Joaquin County Groundwater Basin Groundwater elevations at the site have dropped approximately 20 feet since the beginning of the site investigation program in 1987 The most recent depth to groundwater measurements taken at the site indicate groundwater is currently found at approximately 60 feet below ground surface (bgs) This depth corresponds with the depth indicated on the San Joaquin County Flood Control District Map entitled "Lines of Equal Depth to Water in Wells, Spring 1993 " As noted in Section 1 1, groundwater gradient data collected from the site in 1987 indicated a north-northeast flow direction However, based on the recent San Joaquin County Flood Control District Map entitled "Lines of Equal Elevation of Water in Wells, Spring 1993," the groundwater flow direction at the site is shown to be regionally to the south Given the hydrogeological changes that have occurred between 1987 and 1993 and the differences that are commonly observed between regional and site specific groundwater flow directions, there is currently uncertainty as to which direction (northeast or south) the groundwater flows at the site ' 2.0 PROPOSED SITE INVESTIGATIONS ACTIVITIES The proposed field investigation activities will consist of installing and sampling four soil borings Maround the former gasoline tank location and a one-time sampling of groundwater beneath two existing well locations (MW-2 and MW-3) which have been dry since December 1991 Groundwater sampling at the two proposed locations will provide coverage to address either ' groundwater flow direction currently present at the site All soil and groundwater samples will be analyzed for TPH-G and BTEX parameters 2.1 General Re iiirements ' This work plan has been developed to conform to the Tri-Regional Recommendations and is structured to address the concerns of the San Joaquin County EHD All work described below will be completed under the direction of a California Registered Geologist and all analytical ' work will be conducted by an analytical laboratory certified by the State of California to conduct the required analyses ' 2.2 Soil Borings Four soil borings will be installed in positions surrounding the former gasoline UST excavation ' area as shown on Figure 2 Each boring will be drilled to a maximum depth of 60 feet or the current groundwater level Soil samples will be collected at 5-foot intervals from each boring starting at 35 bgs All samples will be evaluated and three samples from each boring will be submitted for chemical analyses at WESTON's Analytical laboratory in Stockton, California Additional procedural details are provided in Section 3 2 1 ;MNkPITS15JCMVCr)WP 3 ��'�