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Although the existing drainage control features will, with few exceptions, be removed, this <br />demonstration uses the ditch col]ectio^ system (see Map 8, Drainage Control, x/2/96, <br />submitted under Exhibit 7 Midterm Review, revised 8 May 1996) to compare pre-mining and <br />reclaimed areas runoff quality at the inlet of the existing Sediment Trap A and detention <br />ponds (the functions of the existing Sediment Trap A and detention ponds are not material <br />to this demonstration and are not described). Probable runoff discharge locations, both pre- <br />mining and after reclamation of drainage control features, are described under the <br />"Configuration" section of area discussions below. <br />From the small-scale, pre-mining topography information available (Map 1, Permit, and <br />USGS Topographic Map 7.5 Minute Chimney Rock Quadrangle), present land forms, with <br />some exceptions, are similar to pre-mining land forms. Pre-mining ridges and slopes of the <br />Barren Ridge and Revision 1 area are comparable to the present reclaimed land forms. The <br />before-mining and reclaimed configurations of the AVF are virtually identical. The existing <br />East Pit, North Flat, and East Slope knoll represents apre-mining remnant hill in the va]ley <br />door. Although the pre-mine landscape was likely different from the current groomed and <br />terraced slopes, the terraces likely limit the lengths of sheet and rill overland flow to those <br />of pre-mining conditions (as observed in adjacent undisturbed areas). As a consequence, <br />pre-mining and reclaimed topography are considered equivalent in this demonstration. The <br />exceptions are that post-mining plans call for retention of the facilities area (handstand and <br />buildings) and road access to and about the East Pit, North Flat, and East Slope. These <br />exceptions are addressed in site-specific discussions below. <br />This demonstration is made using the Sediment, Erosion, Discharge by Computer Aided <br />Design (SEDCAD+ Version 3) developed by Ms. Pamela J. Schwab of Civil Software <br />Design and Dr. Richard C. Warner, Agricultural Engineering Department, University of <br />Kentucky. <br />2. SEDCAD+ INPUT PARAMETERS <br />2.1 Storm <br />The Storm Type was selected as SCS Type II. The rainfall depth was selected as 2.10 <br />inches. The storm duration is the 10-year, 24-hour event. The SEDCAD+ model <br />(hydrograph convolution interval) time increment was selected as 0.1 hour. <br />2.2 Soils <br />Reference is made to Map 5, Soils, of the Permit. Original soils of the AVF (alluvial valley <br />floor) area were Nunn Loam, and this review and analysis considers salvaged Nunn Loam <br />as the material used to reclaim AVF disturbed areas. Nunn soils appear in the runoff <br />analyses for the Industrial Area and portions of the East Pit in so far as flows from these <br />areas cross Nunn soil to reach Sedimentation Trap A and Pond 2. Nunn Loam has been <br />assigned a soil group "C" (moderately high runoff potential) hydrologic characteristic by the <br />Page 2 of 34, 7 Oct 96 <br />