1989-10-10_REVISION - M1988112 (12)

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4. An internal collection and drainage system to • enhance tailings dewatering and convey the water through a lined ditch to alined collection pond downstream of the disposal site; 5. A lined collection pond and associated ditches downstream of the tailings disposal area with a pump and pipeline system for return of water to the free water pool; and 6. A 100 year 24 hour stormwater diversion ditch system around the tailings disposal area. A main embankment will be constructed tco contain the tailings solids as shown on Figure C-1. The main embankment will consist of material which is permeable relative to the tailings product. The drainage of water from the tailings into the embankment will promote consolidation of the tailings adjacent to the embankment allowing construction of subsequent raises. The tailings disposal area behind the main embankment will be developed in two phases. Phase 1 will consist of two disposal areas, referred to as the upper disposal area and lower disposal area, separated by a splitter embankment. The splitter embankment is located as shown on Figure C-3. By splitting the disposal area into two segments during the initial disposal period when the disposal area approximates the valley floor and is at the narrowest point. the rate of rise of each part of the disposal area can be minimized thereby allowing the maximum amount of tailings consolidation to occur between deposition of lifts. In order to operate each area of tailings disposal during the Phase 1 operations, the volumes of tailings deposited in each area will differ. On average approximately 33 percent of the total tailings volume will be placed in the upper area with the remainder placed in the lower area. In this manner the relative elevations of the two areas will be equal at the end of Phase 1 operations. D-2D