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vx a p l�y-1 U 1� . 49 w4 A S S O C I A 7 E S I N C `e r f�✓ ��r� hydrocarbons from the soil and then circulates back through the DCC well After a period of time this rate of transfer from adsorbed to dissolved slows, due to a royrnum reduction A the residual adsorbed phase mass The dissolved phase mass removal occurs from both increased biological activity and >n-well air stripping during circulation through the DDC well casing ' Ma(d) The PZla(d) data for dissolved phase TPHg and benzene (Figure 12) shows initially decreasing concentrations followed by increasing concentrations This trend indicates transport and breakthrough of higher dissolved phase concentrations following approximately one month of pilot system operation It is likely that these higher concentrations were transported into the PZ1a(d) area through the circulation caused by ASI operation PZl b(d) The PZlb(d) data for dissolved phase TPHg and benzene (Figure 13) did not seem to increase or ' decrease by a significant amount during the air sparge pilot test Because the monitoring point 1s located a greater distance from ASI, the 30 day pilot test operational period was probably not long enough to allow for concentration reductions in the dissolved phase ATC expects the dissolved phase concentrations of TPHg and benzene to decline over the next few months if operation of the system continued General i Overall, the data for dissolved phase TPHg and benzene versus time indicate positive influences associated with DDC application at the site The data indicate circulation was occurring throughout the expected treatment zones, and the mass transfer from adsorbed phase to dissolved phase was taking place Different areas exhibited variation in data trends, however, without detailed adsorbed phase data from both the initial and ending periods of the pilot test, additional claims of the pilot system's success cannot be made ' 6.5 Air S ar c Pilot Test Results—Petroleum Hydrocarbon Mass Removal ' ATC used the well head air emission data to evaluate mass removal rates resulting from in-well air stripping As an initial step in the process, in-well stripping efficiency was calculated using influent, AS 1(d), and effluent, AS 1(s), dissolved phase petroleum hydrocarbon concentrations This calculation was made by dividing the effluent concentration from AS 1(s) by the influent concentration from AS I(d) and subtracting this ratio from 1 ' The average influent concentration of TPHg detected in AS 1(d) while the pilot test was in operation is shown below w U63931reportslnfs doc 14 1