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' A total A42 ORC' socks were emplaced in the source wells on April 3 P ► 1995. The system was monitored for 3, 5, 9, 12, 20, 30, 47, 60, 75, 93, 200, 288, and 365 days after ORC` emplacement to determine changes in DO and BTEX concentrations in the ground water. Morutor points were attached at three ' depths (2.1 m, 4 3 m, and 6 4 m) to the exterior of the source well screens dunag installauon so that DO and BTEX levels could be monitored at the barter with auiumal disturbance of the ORC*in the source wells. Additional up-gradient and ' down-gradient monitor points and monitor wells were sampled to determine both the horizontal and lateral distribution of DO througbout the aquifer, and the biodegradation of BTEX in the aquifer as a result of the increase of DO. ' ANALYTICAL METHODS Temperature, pH, conductivity, and DO were monitored on site A Hydae ' water meter was used for meawnng the pH, conductivity, and temperature of all ground water samples collected in the field. To provide accurate information at a reasonable cost; field screening procedures were used for monitoring DO and BTEX ' concentrations throughout DO levels were measured in the field using the Hach- Modified Winkler digital titration method Ground water samples were collected in ' 4C�-ml VOA vials, preserved with mercuric chloride, placed on ice, and transported back to the office where BTEX concentrations were measured using Ohinicrorn Total BTEX RaPID Assays®immunoassay Test Kits Duplicate samples, collected ' for laboratory analysis of BTS and TPH using EPA Methods 8020 and 8015 Modified, were collected in 40-m1 VOA vials, preserved with mercuric chloride, placed on ice, and transported directly to the laboratory. RESULTS OF ANALYSIS The collected data were analyzed to deterriune interactions between the ' added ORCand the BTEX plume The change in DO concentrations was determined by contouring the distribution of uutlal oxygen and the increase in total ' oxygen These calculauons were performed to determine background conditions and conditions at monitoring events for operating the full-scale system The same approach was used for estimating change in the total BTEX in the aquifer. ' Anal Analysis. The volume of DO was calculated using Surfer for Windows, a contouring and three-dimensional surface mapping software (Golden Software ' 1994). The values for the three methods, Trapezoidal Rule, Simpson's Rule, and Simpson's 3/8 Rule, were averaged and then used for determining trends. The same procedures used for the analysis of the DO concentrations were used for ' BTEX A porton of each plot upgradient of the source wells was blanked out during the calculations to determine a more realistic area of consideration. The bla iltang set the values for the upgradient concentrations to zero. This prevented ' values to be extrapolated into areas without monitoring points (no data to support). In a previous publication (Odencrantz et al , 1996) the blaming was not performed ' which showed a considerable different `macroscope' behavior of the system 'The source well monitor points at 4 3 m below ground level were used 1 90 " d dGZ = 90 66-tit-7Da❑