1989-10-10_REVISION - M1988112 (12)

Home Browse Search

Dewatering of the tailings will occur through two • methods, underdrainage into a drain layer over the liner and through the main embankment to a lined collection pond, and evaporation and water reclaim from the free water pool on top of the tailings for reuse in the mill. Water within the drainage layer will be directed to a lined collection ditch at the downstream toe of the embankment. The ditch will route flows to a collection pond located downgradient of the main embankment. Because of the potential for continuous high hydraulic heads, the pond will be double-lined with a leak detection layer between the liners. From the double-lined storage pond, water will be recycled to the free water pool in the tailings disposal area using an automatic pump and pipeline system. The designs for the drainage layer are discussed in detail in Section D.6.5.2. The collection pond is discussed in detail in Section D.6.5.4. Two diversion systems around the southern and eastern • end of the disposal area have been designed to safely conduct the calculated flows from the 100-yr recurrence interval, 24- hr duration storm event. The runoff from the undiverted catchment area, and precipitation falling directly on the disposal area from the design storm event are accommodated in normal operation. The diversion design is discussed in Section D.6.5.5. The project water balance is contained in Section D.6.7. Two additional embankments will be constructed along the perimeter of the disposal area. The first embankment will be constructed as part of Phase I. The embankment, designated as the East Dike, will be constructed on the upper end of the disposal area on the east side to contain tailings and to divert storm flow from Catchment Area D. The second embankment, designated as the North Dike, will be constructed during Phase " :-~ 0-22