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h A considered for closure at a future date. The ozone injection system is expected to +- eliminate nearly 100% of the hydrocarbon contamination in the soil and groundwater. L.• 3.1 Mass Balance of Contaminants in Groundwater The mass quantity of TPH gasoline and diesel in the upper groundwater zone was calculated using the inferred water contamination levels and plume size as indicated in the Quarterly Groundwater Monitoring and Sampling Report, Third Quarter, 2002 Sampling Event. The areal extent of the contaminated groundwater at the water table is estimated to be 8000 square feet for the gasoline plume and 1000 square feet for the more limited diesel plume. The vertical extent of the highly contaminated groundwater in the upper saturated zone is estimated to be ten feet for a interstitial volume of 24,000 cubic feet or 680,000 liters (L) of water with gasoline contamination and 3,000 cubic feet or 85,000 L of water with diesel contamination in the upper water zone, assuming an average soil porosity of 30% 'r The extent of the gasoline plume was broken down into three concentric rings representing decreasing contaminate values as you move from the center outward. The inner ring with an estimated volume of 110,000 L was given an average gasoline +� contaminant value of 40,000 µg/L. The second and third rings were estimated at 230,000 L and 340,000 L with average contaminant values of 5,000 µglL and 500 µg/L, ` respectively. These values calculate out to a mass of 5.7 kilograms (kg) of TPH gasoline �,. in the upper, most contaminated, groundwater zone. The gasoline mass below the upper ten feet is expected to be much less since gasoline is a LNAPL. LN The smaller diesel plume with an estimated volume of 85,000 L was given an average diesel contaminant value of 400 µglL. These values calculate out to a mass of 0.034 kg of TPH diesel in the upper groundwater zone. The diesel mass below the upper ten feet is L. expected to be much less if not zero. 3.1.1 Calculations: 3.1.1.1 TPH-gasoline Areal extent of groundwater }glume from figure 7: 8000 square feet (ft2) 1 TPH-gasoline `' Estimated thickness of highly contaminated groundwater: 10 feet (ft) Presumed porosity (interstitial space): 30% 1 cubic foot (W) = 28.5 liters (L) L. thus, (8000 ft2)(10 ft)(0.30)(28.5 L 1 W) = 680 000 L of highly impacted groundwater LW The groundwater plume in figure 7 is divided in half, into an outer ring (50%) and inner ring. The inner ring was further divided into the center one-third (16% of the total) highly contaminated zone and the moderately contaminated two-thirds (34% of the total) outer L. zone of the inner ring, yielding three concentric rings. From the quarterly analytical groundwater results and figure 7, the innermost ring (16%), LN middle ring (34%), and outer ring (50%) have average contaminant concentrations of gasoline of 40,000 micrograms/litter (kg/L) , 5000 µg/L, and 500 µg/L respectively. LO No JJW GEOSCIENCES InC.