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. 11 July 2003 AGE-NC Project No 03-1055 Page 2 of 5 The estimated depth to ground water at the property is approximately 10 feet below surface grade (bsg),based on the map titled Lanes of Equal Depth to Groundwater Spring 1996 published by the San Joaquin County Flood Control District and Water Conservation District(FCD&WCD) Based upon a previous investigation performed by AGE,ground water depth at the site ranges between 10 and 12 feet bsg It is inferred from the map titled Lanes of Equal Elevation of Groundwater Spring 1996, also published by the FCD&WCD, that ground water flows toward the northwest in the general area of the site, but this may be modified by changing recharge and discharge patterns Ground water is considered to be of beneficial use and is used for domestic, industrial and commercial purposes 2 2 UNDERGROUND STORAGE TANK REMOVAL A UST gasoline system reportedly operated on the site for approximately thirty years from 1940 until 1970 The UST system is assumed to have been removed after 1970, however, no records of the UST removal are available with the Tracy Fire Department, Tracy Building Department or the PHS-EHD 23 PREVIOUS SUBSURFACE INVESTIGATION On 04 May 2000, five soil probe borings were advanced at the site under observation by a representative of the PHS-EHD The probe borings were advanced in the former USTs excavation and the southern and central dispenser islands and two locations which are in the assumed hydrogeologic down-gradient location All borings were advanced to depths of 20 feet bsg A`grab' ground water was collected and analyzed from each soil boring TPH-g was detected in soil samples in the former dispensers area and to a lesser degree in the former UST excavation The depth limits of hydrocarbon-impacted soil was approximately 15 feet bsg and above 20 feet bsg Table 1 summarizes the analytical data of the soil sample analyzed TPH-g was detected in all grab ground water samples at concentrations ranging from 370 µg11 in sample B 1-H2O to 55,000µg/1 in sample B3-H20 Excluding sample B5-H2O,benzene was detected in the remaining samples at concentrations ranging from 0 54 µg/l in sample Bi-H2O to 160 µg11 in sample B3-H20 Toluene was detected in all five ground water samples at concentrations ranging from I 1 to 25 µg/1 Ethylbenzene was detected in sample B3-H20 at 58 µg/1 and sample B4-H2O at 2 5 µg/1 Xylenes were only detected in samples B2-H20,B3-H20 and B4-H20 at concentrations of 230 µg/l, 120 µg/1 and 1 9 µg/l, respectively MTBE was not detected in any of the ground water samples In addition, the remaining fuel oxygenates were not detected in sample B3-H20 Advanced GeoEnvaronmental,Inc