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Pond E was constructed so that the primary outlet device (Riser) is <br />located as far away as practical from the major point of inflow. In <br />order to prevent a vortex from being formed by water entering the <br />pipe, the riser has drain holes set in a vertical pattern. <br />Dense clay was used as fill material in pond embankments. Under no <br />circumstances was coal processing waste used. All fill material was <br />selected to exclude the presence of sod, large roots, or other large <br />vegetation matter and frozen material. <br />The placement and spreading of fill was started at the lowest part of <br />the foundation and was brought up in lifts of less than 3 feet to <br />facilitate compaction and to meet the design requirements of Rule <br />4.05.6. Each lift was compacted so that the density of the materia] <br />is adequate to meet design criteria for stability and safety. See the <br />construction plans and specifications in Exhibit 8, Sedimentation Pond <br />Design. <br />The design specifications for embankment height provided for a minimum <br />of 1.0 foot freeboard between the emergency spillway design flow level <br />and the top of the embankment, plus a five percent factor to offset <br />settling. The emergency spillway is designed to safely discharge the <br />runoff from a 25-year, 24-hour event as documented in Exhibit 8, <br />Sedimentation Pond Design. Flow velocities are designed to be non- <br />erosive, and channel lining is provided where appropriate. <br />The embankment specifications provide far combined upstream and <br />downstream side slopes of the settled embankment not less than lv:5h <br />with neither slope steeper than lv:2h. Slopes have been designed to <br />be stable in all cases. Pond embankments were stabilized with respect <br />to erosion immediately after construction by seeding one of the <br />perennial seed mixtures on the outslopes and top of the dam and on all <br />areas disturbed by construction. The upstream face of the embankment <br />has been stabilized against erosion with vegetation, gravel, or by <br />• <br />2.05-17 <br />