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• 3.4 SURFACE DRAINAGE MODIFICATIONS. The surface drainage on the west side of the West Ridge pile will utilize the existing drainage system and no modifications to this side are proposed. The west side drainage system includes (from north to south) a 24-inch half culvert located on the west side ditch (on top of the crushing and screening level fill), and two 36-inch culverts located below the access road (see Figure 1). The west side ditch is routed into the West Ridge waste pile sedimentation pond (see Ref. 2). Modifications of the surface drainage system are proposed on the east side of the West Ridge pile. These modifications include routing of the surface runoff of an area of approximately 0.45 acres (see Figure 2), located on the northeast part of the West Ridge pile, into the main drainage separating the west and east ridges, and into the sedimentation pond # 3 as shown in Reference 2. In addition, the 4-inch diameter PVC sewage treatment plant effluent pipe, located in this area, will be removed and rerouted out of the construction zone. The above specified area to be routed to the Sedimentation pond # 3 is limited on the south side by the north end of the east ditch (point "A" in Figure 2). The remaining area of the modified pile will continue to drain to the West Ridge waste pile sedimentation pond, according to original design. • The West Ridge waste pile sedimentation pond located southeast of the West Ridge waste pile shall be routinely maintained during the mining operations as set forth in original specifications (Reference 1). These specifications set forth a minimum useable volume below the principal spillway crest of 0.67 acre-feet (29,200 cubic feet). An area of approximately 4.4 acres will contribute to the surface runoff into this pond (original design contributed around 4.85 acres). These drainage modifications are necessary because of the relatively steep slopes on both sides of the main drainage channel between he west and east ridges. These steep slopes make the routing and hydraulics of a drainage ditch very difficult. The overall effect of these modifications will be a slightly reduced sediment load being conveyed into the West Ridge waste pile sedimentation pond. An additional 0.48 acres (or 21,000 square feet) will be diverted into the main drainage, and the culvert "O" drainage area and eventually through ponds 3 and 4. These ponds also receive the discharge from the West Ridge waste pile sedimentation pond. • 3.5 UNDERDRAINS (ROCK DRAINS). Underdrains shall be constructed in both periphery drainages located within the footprint of the 3