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2.04.7 Hydrology Description <br />xylenes (BTEX), polycyclic aromatic hydrocarbons (PAH), and methyl <br />tertiary butyl ether (MTBE). <br />The groundwater sample collected from Well No. RW -2 revealed a low <br />level of toluene during the first quarter 2010 (estimated at 0.2 ppb by <br />ACZ). Methyl -tert-butyl ether (MTBE) was found at a level of 20.6 and 20.1 <br />ppb in Well No. RW -4, which is slightly above the State - defined maximum <br />contaminant level of 20 ppb for MTBE in groundwater. The concentration <br />of all other contaminants were below detection limits in all four alluvial <br />wells. <br />As discussed in section 2.04 -3, the site and adjacent lands were part of <br />refinery operations beginning in 1957 by the American Gilsonite Company. <br />The refinery originally processed gilsonite (i.e., bitumen: a naturally - <br />occurring solid or semi -solid hydrocarbon) ore into liquid products and <br />petroleum coke. The refinery was later converted to process conventional <br />crude oils into liquids and coke. Gary Energy Corporation purchased the <br />operation in December 1973 and produced gasoline and diesel fuel, jet <br />fuel, naphtha, vacuum gas oil, heavy fuel oil, calcined petroleum coke and <br />liquefied petroleum gas. <br />The acid - sludge waste cell is a mounded and soil- capped square area, <br />about 7 acres in size, near the site's northeast corner. The waste cell <br />contains approximately 85,000 cubic yards of solidified acid sludge. <br />The 39 -acre landfarm area consists of former evaporation ponds. <br />There are several areas in the northeast part of the site where coke <br />particulate -matter was disposed in a series of excavated and unlined <br />trenches. The material apparently originated from baghouses connected <br />to the former boiler exhaust stacks. In 1985, it was reported that at least <br />10,000 cubic yards of coke fines were landfilled. The landfill appears to <br />have a cap of native soils. <br />Any of the uses mentioned above could be the reason for detectable <br />levels of the aforementioned hydrocarbon contaminants. A spill at the <br />refinery is considered the most likely source of the contamination. <br />Hydraulic properties for the alluvial aquifer are unavailable. <br />Permit Application 2.04 -16 07/11 <br />