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Calculation sheets for the underdrain follow revised Figure A-2. <br />Equations and table data utilized in the discharge calculations for the <br />trench and sandstone portions of the underdrain were taken from the <br />Engineering and Design Manual for Disposal of Excess Spoil by CTL/Thompson, <br />Inc. for the Office of Surface Mining, 1982. That poction of the <br />CTL/Thompson text citing the sequence and use of the equations follows the <br />calculation sheets. The discharge equation used to calculate fill <br />discharge was taken from Groundwater Hydrology by Herman Bouwer, 1978. <br />The surface of the underdrain will serve as the Eaet F111 and Terrace <br />Sandstone Downdrain (ED) as it will still be a topographic low with a <br />positive drainage gradient. The topographic dimensions of the underdrain <br />exceed the designed cross-sectional area of the ED, and the gradient is <br />similar. Aa pit and fill development progresses, the ED will be moved to <br />[he east, away from the underdrain until its final position is similar to <br />that illustrated on Map 5-1. Position of the ED will always be west of the <br />WC. <br />3 <br />