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<br />Mr. Joe Shoemaker September 9. 1993 <br />B. Hydrologic Balance (PHC Update) <br />1. CECs discussion of inflow volumes and wmparison with predicted levels is adequate. <br />2. Figures 12 through 24, illustrating water elevation and conductivity trends in the <br />bedrock ground water monitoring wells from 1986 through the present were updated <br />as requested in the Preliminary Adequary Review (PAR). However, graphs <br />illustrating water elevations in the Trout Creek Sandstone were not provided and <br />should be included in the PHC. The graphs provided in the AHR could be used in <br />the PHC. <br />3. Figure 24, illustrating conductivity trends in the alluvial wells was updated as <br />requested in the PAR. However, Figure 22, illustrating water level trends in the <br />alluvial wells was missing from the submittal and no water level data were provided. <br />CEC should submit Figure 22, updated to show water level trends through the <br />present. <br />4. An update of total dissolved solids (TDS) levels, with graphs showing trends from <br />1986 through the present was requested in the PAR. No graphs were submitted, and <br />TDS data were provided for 1991 only. CEC should provide a table showing <br />historical as well as current TDS data and graphs showing TDS trends as requested <br />in the PAR. <br />5. Lz the PAR, the Division requested an updated written narrative regazding the <br />current piezometric surface in the Middle Sandstone as compazed with the predicted <br />drawdowns. Although the original PHC predicted drawdown in the Middle <br />Sandstone associated with mining the E and F coal seams, the magnitude of the <br />drawdown was not predicted. Therefore, CEC compared measured drawdowns in <br />the Middle Sandstone with a calculated prediction of drawdown for the Twentymile <br />Sandstone and found good agreement between the observed and predicted <br />drawdowns. Although the practice of comparing observed drawdowns in one aquifer <br />to predicted drawdowns in another aquifer is questionable, the comparison appears <br />reasonable in this case because of the similarities in the aquifer properties and <br />thicknesses. Therefore, CECs response to this request is deemed adequate. <br />6. The PAR requested a comparison of actual effects of mining on the Twentymile <br />Sandstone with predictions from the PHC. CEC provided a discussion of water level <br />and water quality observations in the Twentymile Sandstone stating that neither <br />water levels nor water quality (based on conductivity) have changed significantly. As <br />the PHC did not predict a magnitude of impact, CEC presented calculations for a <br />worst-case prediction of future impacts to water levels in the Twentymile Sandstone <br />for 15 years of dischazge at 100 gpm using the Theis equation (incorrectly labelled <br />as the Theim equation in the narrative). CECs response regazding water level <br />impacts is adequate. However, a prediction of water quality impacts should also be <br />