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Ms Marla Guensler Exxon Company, U S A August 25, 1995 Page 2 Dissolved oxygen content of the ground water was monitored in the test well, and in each observation well in the field Analysis of the DO data indicates that DO in the test well (MW-3) increased significantly during the test from 0 S ppm at the beginning of the test, to between 2 5 and 12 0 ppm later in the test The DO in the observation wells did show significant increases on some dates compared with the initial measurements, however, there does not appear to be any general trend in any of the observation wells with the possible exception of MW-5, which increased steadily through May 31, 1995, but then dropped back off in June and July 1995 Dissolved oxygen data is summarized in Table 1 located in Enclosure A Soil vapor carbon dioxide content above the ground water table was monitored in the test well, and each observation well by drawing an air sample into a tedlar bag and measuring the carbon dioxide content using a Drager tube An increase in the carbon dioxide level of the air above the ground water table indicates that there is increased biodegradation in the ground water, presumably due to an increase in available DO in the ground water Analysis of the carbon dioxide data indicates that there was a significant increase in each of the observation wells An increase in biodegradation in the ground water should aid in the remediation of dissolved petroleum hydrocarbons as the microbes use the petroleum hydrocarbon constituents as a food source. During the test, the most obvious changes in carbon dioxide were in observation wells MW-1 and MW-6 MW-1 initially contained 0 5 percent carbon dioxide and increased to 4.0 percent after 8 days of operation This initial increase stabilized and varied from 2.0 to 5 0 percent over the remainder of the test. MW-6 initially contained 0 0 percent carbon dioxide and increased to 1 0 percent after 8 days The level then varied from 0 0 percent to 3 0 percent during the remainder of the test The other two observation wells (MW-4 and MW-5) also showed increases in carbon dioxide during the test period These increases in all of the observation wells mdicate that the sparging in MW-3 increased the biodegradation of petroleum hydrocarbon constituents in the ground water at the site during the test period, with a radius of influence of more than 110 feet. Carbon dioxide data is summarized in Table 2 located in Enclosure A Pressure data was collected at each of the observation wells using a magnahelic gauge. An increase in pressure in the observation wells would indicate that the air being sparged into the ground water at the test well is increasing the air pressure in the interstitial voids in the soil away from the test well Analysis of the pressure data collected from the observation wells indicates that the spargmg of air into the ground water at MW-3 did not affect pressures in the observation wells There was some pressure influence seen in observation well MW-1 during the first month of the test, however, this influence dissipated later in the test for unknown reasons Reasons for the absence of pressure influence in the observation wells may have been due to the distance between the test well and the observation wells, or the fact that the sparging was not operating continuously due to problems with the air compressor Pressure data is summarized in Table 3 located in Enclosure A Ground water samples were collected from the wells on March 31, 1995, as baseline data for the air spargmg test The ground water samples were analyzed for benzene, toluene, ethylbenzene, total xylenes, and total petroleum hydrocarbons (TPH) as gasoline. The concentration of TPH as gasoline in the ground water in the test well MW-3 on March 31, 1995, was 1,300 micrograms per liter (,ug/L), and benzene was at 490 µg/L The concentrations of petroleum hydrocarbon constituents in the observation wells (MW-1 and MW-4 through MW-6) were below the laboratory detection limits.