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.11 W1_ 'I Emmi <br /> Mr. Chuck Carmel <br /> July 11. 1991 <br /> Page 9 <br /> r <br /> The flow rai_ and time-drawdown data were both hand- and computer-analyzed by the <br /> generalized straight-line method of Cooper and Jacob(1946). A simple correction was applied ' <br /> to the. discharge data to account for well storage effects. Analysis of the data is shown on <br /> Figure 6. Data analysis indicates an aquifer transmissiviry (T) of 900 ft`/day. The thickness of <br /> the satusatsdd aquifer(b)that was tested is about 20 ft. Therefore,the hydraulic conductivity(K) <br /> is about 45 feet/day or. <br /> Ic=7 <br /> r <br /> Hydrocarbon Data <br /> Figure 7 shows the estimated extent of benzene, ethylbenzene, toluene, and xylene (B=) <br /> compounds in the shallow groundwater beneath the site. 'The numb:rs refer to the sum,or total, <br /> cf benzene,toluene,ethylbenzene and xylenes from the February 1991 groundwater sampling. <br /> t , Modeling Analysis <br /> A caiture zone modeling analysis was performed using RessgM(O'Neill, 1990). RessgM is a <br /> modified version of the popular Ressq model (Javandel et al., 1984). Modifications v--re made <br /> to make the model user friendly and to provide better graphics Support. <br /> I <br /> Figure 8 shows tate capture zone resulting from pumping R-13 at a constant discharge rate of 12 <br /> gptn. Model parameters included the hydraulic conductivity (45 ft/day), aquifer thickness (20 <br /> i <br /> ft), hydraulic gradient(0.02) and direction of flow. The model is based on two-dimensional, <br /> steady-state, uniform flow conditions with continuous pumping. <br /> e <br /> Twelve individual streamlines (groundwater pathlines) appear on Figure 8. The bold line on <br /> Figure 8 is the location of the capture zone boundary. Note that the capture zone boundary on i <br /> Figure 8 envelops the BETX plume, Therefore, the plume will be captured by pump ng the <br /> recovery well (R-13) at a constant discharge rate of approximately 12 ,Spm. <br /> Figure 9 presents the results for calculations made with a flow rate of 10 gem. Although 10 gem <br /> is sufficient to capture most of the plume, hydrocarbons near the capture zone boundary may <br /> migrate downgradient. Currently the recovery well is pump ng at an average rate of <br /> approximately 10.8 gpm. <br /> t� <br /> Brown anti Caldwyell <br /> i,onsu�[r�nts <br /> 5 <br />