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�✓ .r/ 13 August 2002 AGE-NC Project No. 02-0950 Page 2 of 5 The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basin 5-22). The estimated depth to ground water at the site is 20 feet below surface grade (bsg) based on information from Lines of Equal Depth of Water Wells Fall 1999, published by the San Joaquin County Flood Control District and Water Conservation District- FCD&WCD. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1999 also published by the San Joaquin County FCD&WCD, the site is in an area where ground water appears to be traveling southwest. 2.2. UNDERGROUND STORAGE TANK REMOVAL It is our understanding that two underground storage tanks (USTs) were removed from the site in March 2002. The USTs were reportedly utilized for the storage and dispensing of gasoline and diesel. Concentrations of total petroleum hydrocarbons quantified as diesel (TPH-d), gasoline (TPH-g),volatile aromatics(benzene,toluene,ethyl benzene and xylenes;BTEX)and total lead were detected in soil samples collected from the UST excavation. Based upon the analytical results of soil samples collected during UST removal,the EHD required the preparation of work plan to define the lateral and vertical extent of contamination in soil and ground water. 3.0. SCOPE OF WORK AGE proposes to collect soil samples to determine ifpetroleum hydrocarbon and/or MTBE-impacted soil and/or ground water is present beneath the site.The preliminary site assessment will include the following tasks: • Permitting and pre-field work activities; • Soil and groundwater sample collection and analysis; • Report preparation. The preliminary site assessment tasks are discussed below. 3.1. PERMITTING AND PRE-FIELD WORK ACTIVITIES A site assessment boring permit will be obtained from the EHD for all on-site and off-site boring locations and encroachment permits will be obtained from the City of Stockton Public Work Advanced GeoEnvironmental,Inc.