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i 27 September 1999 AGE-NC Project No 95-0167 f Page 2 of 9 ! Results of laboratory analysis of additional `grab' ground water samples collected from up-gradient and down-gradient locations indicated a limited ground water impact, however, hydrocarbon- impacted water has migrated east and northeast from the dispenser area The highest concentrations of dissolved hydrocarbon compounds are in the area east of the former UST and dispenser locations near P6 Hydrocarbons have been encountered in a down-gradient direction from the former dispenser, at the location of boring P5 and further down-gradient at the location of boring PI Based on the data from the grab water sample collected from boring P7, TPH-g concentrations in ground water decrease westward of the former fuel dispenser, under the building on the site 23 GROUND WATER DEPTH AND FLOW DIRECTION The estimated depth to ground water at the site is approximately 10 to 15 feet bsg, based on the map titled Lines of Equal Depth To Groundwater, Fall 1997 published by the San Joaquin County Flood Control District and Water Conservation District,and information obtained from the PHS-EHD from . monitoring wells at surrounding sites Furthermore, PHS-EHD records indicate that the highest observed ground water elevation at the property was 10 feet bsg,measured in 1986 During the initial site assessment conducted in September 1995, ground water was measured at approximately 25 feet bsg During the site assessment of April 1997, ground water was measured at approximately 15 feet bsg The prevailing ground water flow direction in central Stockton is generally toward the northeast, however, ground water flow direction may vary locally, seasonally and possible due to tidal fluctuations Ground water is considered to be of beneficial use and is utilized for domestic, industrial and commercial purposes 3 0. SCOPE OF WORK The site investigation was conducted to assess the lateral and vertical extent of petroleum hydrocarbon impact to soil and ground water beneath and surrounding the former gasoline dispenser location at the site The scope of work conducted during the site investigation activities include • Advancement of four soil borings, • Collection of soil samples from each soil boring, • Installation and development of four ground water monitoring wells, • Collection of ground water samples from each of the monitoring wells, AdiancedGeoEmironmental,Inc