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MJ ZMV <br /> f=- <br /> Working To Restore Nature <br /> This study focuses on the water quality in the shallow water-bearing zone identified by Hotchkiss <br /> c <br /> and Balding (1971). Regional groundwater within this zone occurs less than 10 feet below grade <br /> f over most of the Tracy area. General groundwater gradient is to the north. The flood basin <br /> deposits of the shallow water bearing zone have well developed soil profiles and consequently <br /> poor permeability. The quality of the shallow groundwater in the Tracy area is generally poor. <br /> �+ During the period of investigation the depth to groundwater at the site has ranged from 5.64 feet <br /> to 9.24 feet below grade (Table 1). When groundwater levels were last measured in December <br /> 1993 the depth to water ranged from 8.13 to 8.66 feet. Gradient direction has consistently been <br /> to the north-northwest at a magnitude ranging from 0.003 to 0.005 ft/ft. <br /> 3.0 BACKGROUND <br /> The site is currently and has been operated in the past as a cement production plant. Three <br /> underground storage tanks were formerly located on the site (Figure 2). The tank capacities and <br /> i<{ contents were as follows: 1) one 2,000 gallon unleaded gasoline tank; 2) one 350 gallon leaded <br /> gasoline tank; and 3) one 1,000 gallon diesel tank. These tanks were used to fuel facility <br /> Ff: <br /> vehicles. <br /> }` 3.1 History of Soil and Groundwater Investigation <br /> On August 23, 1988 the three underground fuel storage tanks were removed from the site. <br /> r California Water Labs collected soil samples from the capillary fringe in both tank excavations <br /> as well as a groundwater sample from the diesel tank pit. The soil samples collected from the <br /> gasoline tank pit were analyzed for benzene, toluene, and xylenes (BTX) and total petroleum <br /> hydrocarbons as gasoline {TPHg)• One soil sample was also analyzed for total lead and ethylene <br /> err <br /> dibromide. The soil and groundwater samples collected from the diesel tank pit were analyzed <br /> for BTX and for total petroleum hydrocarbons as diesel (TPHd). <br /> OW01951REPORTMCL012594 TNL 2 <br /> vJ <br /> f <br />