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DATE Pounds TPHg in Soil Pounds Benzene in Soil <br /> February 1989 62434.5 729.8 <br /> June 1997 212.9 <1 <br /> Percent removed 99.66% X99.86% <br /> The January 1, 1990 sample round was used to calculate the amount of dissolved gasoline range <br /> originally at the site after the tank pull and prior to the start up of vapor extraction, see Figure 7A. <br /> The January 1, 1990 sample was chosen because it is the first sampling round in which all of the <br /> onsite wells M W I-M W 10 were sampled. <br /> DATE Pounds TPHg in Water Pounds Benzene in Water <br /> January 2, 1990 298.5 143.5 <br /> June 1997 90.4 1.0 <br /> Percent removed 69.74% 99.30% <br /> DATE Total Pounds TPHg Total Pounds Benzene <br /> 62733 873.3 <br /> June 1997 303.3 1 <br /> Percent removed 99.52% 99.89% <br /> The site is being remediated through a combination of airsparging and vapor extraction. <br /> The removal rates associated with airsparging augmented biodegradation can not be directly <br /> measured, although evidence of its effects can be seen in the vapor extraction with the continued <br /> presence of the biodegradation end product Carbon Dioxide (CO2). All of the carbon found in the <br /> carbon dioxide may not have as its source the decomposition of gasoline, but sites with hydrocarbon <br /> contamination show significant increases in carbon dioxide levels due to biodegradation. <br /> In addition to the hydrocarbons removed as CO2, vapor extraction removed 75,088 pounds of TPHg <br /> as of 7/2/98. <br /> The Initial amounts of TPHg hydrocarbons after the tank pull prior to starting vapor extraction <br /> 62435 in the soil and 298 pounds in the water for a total of 62733 pounds. <br /> From the confirmation soil borings in June 1997, the soil presently contains approximately 213 <br /> pounds of TPHg , and the latest water samples , May 28, 1998, the water presently contains 90 <br /> pounds of TPHg for a total of 303 pounds of TPHg. <br /> Vapor extraction removed 75,088 pounds of TPHg, this is greater than the 62,132 pounds calculated <br /> to have been removed from the beginning and ending mass calculations. <br /> 7. Remediation equipment used to clean the site, see item 6 above and section report. <br /> 8. Zone of influence, see Figure 14. <br /> 9. Site has reached the isotopic phase and further active remediation will probably not hasten the <br /> further cleanup significantly. <br /> 10. See RBCA Tier Two below. <br /> I I 8603 Update #52/CLOSURE RV 7198 <br />