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VZ1 INC i 72 Site Hydrogeology Groundwater level measurements were made at each monitoring well on June 2, 1989, after a minimum 12-hour equilibration period following construction of monitoring wells MW-9 and MW-10 (McLaren, 1989a) A second sounding round was performed on June 19, 1989, allowing over two weeks for equilibration following well construction The depth to water in each well was measured with an electric sounder Tables 5 and 6 tabulate groundwater surface elevations across the site Maximum groundwater surface elevations were reported to vary by up to one foot (McLaren, 1989a) The normal limit of vertical accuracy for this method of measurement is 0 02 feet 7,3 Estimated Extent of Petroleum Hydrocarbon Contamination Exhibits 7, 8 and 9 depict the estimated horizontal and vertical extent of petroleum 4& hydrocarbon contamination in soils and groundwater at the site The extent of the soil petroleum hydrocarbon contamination has been depicted based on levels of TPH-G greater than 100 mg/kg The extent of groundwater hydrocarbon contamination has been depicted based on the presence of TPH-G and VOCs in concentrations above regulatory agency established drinking water standards Soil Petroleum Hydrocarbon Contamination Exhibit 7 depicts the locations of soil borings and monitoring wells where soil samples have been collected for analyses Exhibit 7 also presents the soil sample analytical results adjacent to the soil borings or monitoring wells where they were collected The petroleum hydrocarbon-contaminated soil pattern extends from the former tank location at a depth of seven feet bgs to a horizontal distance of up to 35 feet from the tank The areal extent of soil hydrocarbon contamination is estimated to be approximately 1,750 square feet, based on the map pattern depicted on Exhibit 7 19150011 005 23