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� � � .. - li .3 ..� ' '` gym..-• :: - _' - - Fir <br /> r s" <br /> .ayR -.T�::. 'its :ju �b•.P '� <br /> AW, 42 .` ,, ��4~ iw �r�se'""£,., "'"''�<r' R.4� � �.�;"�'' y '`4",� M1+,� � 1��, g- ,�k ��� M'"k' .�• <br />;rte= <br /> Nlr. Chuck Carmel <br /> July 11, 1991 <br /> Niac 9 <br /> The Slow rate 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 saturated aquifer(b)that was tested is about 20 ft. Tltereforc,the hydraulic conductivity(1C) <br /> is about 45 feet/day or. <br /> Hydrocarbon Data <br /> Figure 7 shows the estimated extent of benzene, ethylbenzene, toluene, and xylene (BETX) <br /> compounds in the shallow groundwater beneath the site. The numbers refer to the sum,or total, <br /> of benzene, toluene,ethylberrzene and xylenes from the February 1991 groundwater sampling. <br /> Modeling Analysis <br /> A capture 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 were made <br /> to make the model user friendly and to provide better graphics support. <br /> Figure 8 shows the capture zone resul-ing from pumping R-13 at a constant discharge rate of 12 <br /> gpm. Model. parameters.included the hydraulic conductivity (45 ft/day), aquifer thickness (20 <br /> ft), hydraulic gradient (0.002) and direction of flow. The model is based on two-dimensional, <br /> steady-state, uniform flow conditions with continuous pumping. <br /> Twelve individual streamlines (groundwater pathlines) appear on Figure S. The bold line on <br /> Figure 8 is the location of the capture zone boundary. Note that the capture zone boundary on <br /> Figure 8 envelops the BETX plume. Therefore, the plume will be captured by pumping the <br /> recovery well (R-13)at a constant discharge rate of approximately 12 gpm. <br /> Figure 9 presents the results for calculations ruade with a flow rate of 10 gpm. Although 10 gpm <br /> is sufficient to capture most of the plume, hydrocarbons hear the capture zone boundary may <br /> migrate downgradient. Currently the recovery well is pumping at an average rate of <br /> approximately 10.8 gprn. <br /> Brawn and Caldwell <br />