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20 October 1998 AGE-NC Project No. 98-0470 Page 2 of 7 the highest possible impact to ground water calculated to be 1,670 ppb of xylene. LW 2.3. GROUND WATER DEPTH AND FLOW DIRECTION LW The estimated depth to ground water at the property is approximately 40 to 50 feet below surface grade(bsg),based on the map titled Lines.ofEqual Depth to Groundwater Spring 1996 published. 'y 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 1996 published by the San Joaquin County FCD&WCD,the site is in an area where ground water flows toward the northeast, but this may be modified by changing recharge and discharge patterns. . The prevailing ground water flow direction in south central Stockton is generally toward the northeast; however,localized ground water flow direction may vary during winter/summer cycles, and can be effected by tidal fluctuations and local recharge and discharge sources. Ground water is taw considered to be of beneficial use and is utilized for domestic, industrial and commercial purposes. ;., 3.0. PROCEDURES 3.1. DRILLING AND SAMPLING On 20 July 1998,soil boring MW-1 was advanced at the site,through.the:former UST excavation. f The boring location is illustrated on.Figure 2. Soil boring MW-1 was advanced to a depth of 65 feet bsg. Drilling was performed using a truck-mounted CME 75-HT drill rig:equipped with continuous flight, eight-inch,hollow-stem augers. The drill rig and two-man crew were supplied by Soils Exploration Services of Sacramento, California. Samples were collected at five-foot intervals in all borings;using a split-tube sampler loaded with three clean, 2-.by 6-inch brass sleeves. A 140-pound hammer was used to advance the sampler 18 inches;the number of blows required to advance the sampler in 6-inch increments was recorded on the boring logs.All sampling equipment was washed in an Alconox solution and rinsed twice with water prior to each sampling run. Auger returns were stored on-site in DOT rated 55-gallon drums pending laboratory analysis and disposal at a licenced facility. r - . Soil samples were preserved by covering both ends of the brass sleeve with Teflon sheets, capping and sealing with tape. Samples were stored in a chilled container and transported under chain-of- Advanced GeoEnvironmental,Inc.