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PART 1 -EXISTING FACILITIES • FAN LEVEL: Drainage of surface water runoff on the Fan Level appears to have a limited impact on the stability of this fill. However, it should still be adequately main- tained and controlled. The upper diversion ditch is intended to divert all flows generated in the undis- turbed upstream basin around the surface facilities of the mine. It is designed to prevent upstream basin flows from reaching the fan level fill. Our surveys indicate that the diversion ditch, as constructed, still has the capacity to carry the design flows from the upstream basin. Velocities at the maximum design flows will probably result in some minor erosion of the ditch, but the erosion should not compromise the stability of the fill. The grade of the upper diversion ditch, approximately 3%, is sufficient to insure that even the smallest flows are quickly diverted away from the fan level. This should significantly reduce the saturation of the ditch lining by minimizing the amount of surface storage which must be filled before flow begins. Existing instabilities have been observed in the cut slopes above the diversion ditch. A reoccurance oP these failures could result in material filling in the diversion channel and rendering it inoperable. Two methodologies have been identified to alleviate this concern: • 1. Stabilize the slopes. Geo-Hydro Consulting, Inc. has recommended two alternatives for stabilizing the existing instabilities of the soil cuts. The soil slopes could either be flattened to 1.SH:1V or a buttress could be added at the toe of the slope. Existing rock instabilities could be corrected by either flattening the slopes or by rock bolting the slope. 2. Construct an auxiliary diversion channel to divert flows away from fill areas on the site in the event oP a failure on the cut slopes above the existing diversion ditch. We recommend a combination of the aforementioned methodologies. The principle area of instability along the diversion channel is in the soil cut directly above the fan level bench. Two other small farZures have been identified in the rock cuts to the east of the fan level bench. We recommend constructing an auxiliary diversion ditch on the fan level below the soil cut. We also recommend stabilizing the rock slopes in accordance with Geo-Hydro's recommendations as the steep nature of these areas make en auxiliary ditch impractical. No failures have been observed in the rock cut to the west o[ the fan level bench consequently no improvements are proposed for this area. The auxiliary diversion ditch recommended herein should follow the alignment shown on the enclosed drawing and should be constructed to the grades shown on the pages labeled "Proposed Profile Auxiliary Diversion Ditch" in accordance with the "Typical Cross Sections Auxiliary Diversion Ditch."