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other upstream disturbances as long as a partially completed pond can contain about 2 acre-feet. <br />It should also be noted that all of the coal stockpile area has been modeled at a curve number of <br />85 as with all other disturbances, while in reality a much lower curve number would be <br />appropriate once coal is actually stockpiled in that location. <br />In total, there are about 346 acres included in the models, which includes about 135 acres of <br />disturbances. As shown in the attached modeling outputs, it is demonstrated that the two pond <br />system is adequate to adequately treat the runoff from all of the disturbances. <br />For the first SEDCAD model, it can be seen that the 10 year, 24 storm event with 1.8 inches of <br />precipitation resulted in a peak water surface elevation of 7,119.65 in the Section 36 Pond and a <br />peak water surface elevation of 7,061.64 in the Middle Pond. Both of these elevations are well <br />below their respective pond's emergency spillway. It can be further seen that the outfall of the <br />Middle Pond has an effluent concentration of 0.00 mUl for the Volume weighted 24 hour <br />outflow, below the required limit of 0.50 ml/1. <br />For the second SEDCAD model, which assumes that the Coal Stockpile Pond is not yet <br />completed, it can be seen that the 10 year, 24 storm event with 1.8 inches of precipitation <br />resulted in a peak water surface elevation of 7,121.37 in the Section 36 Pond and a peak water <br />surface elevation of 7,062.90 in the Middle Pond. Both of these elevations are well below their <br />respective pond's emergency spillway. It can be further seen that the outfall of the Middle Pond <br />has an effluent concentration of 0.22 ml/1 for the Volume weighted 24 hour outflow, below the <br />required limit of 0.50 ml/l. <br />For the third SEDCAD model, the 25 year, 24 hour storm event of 2.3 inches of precipitation <br />resulted in the peak water surface elevation of 7,121.44 in the Section 36 Pond. The emergency <br />spillway elevation for this pond is set at 7,125.0, and under this condition the emergency <br />spillway is not even engaged. For the Middle Pond, the peak water surface elevation is 7,063.13, <br />about 1.9 feet below the emergency spillway. Again, the emergency spillway is not engaged. <br />This analysis, while it describes a temporary condition, demonstrates that the two pond system <br />can adequately handle the expected disturbances as outlined on Exhibit 7-23, Figure J1. <br />Exh. 7-23J-2 Revision Date: 3/3/17 <br />Revision No.: TR -108 <br />