Laserfiche WebLink
{ CM0001640 <br />f <br />Page 12 <br />data. Using these data, a drain may be sized to effectively treat the seep water. <br />3.1.5 Surface Water Diversion <br />A surface water diversion channel was evaluated to control surface water runoff in the upper <br />reaches of the ERV, near the No. I Tailing Dam. The location of the surface water diversion is <br />shown on Figures 3 and 4. <br />The surface water diversion was evaluated because a qualitative evaluation of surface water runoff <br />i pathways (Appendix A) indicated that surface water runoff from the No. 1 Tailing -Dam can reach <br />the Chalk Mountain Reservoir. This conclusion is somewhat supported by the water quality data <br />for the Chalk Mountain Reservoir. As noted in Section 2.0, the water quality in Chalk Mountain <br />Reservoir is generally good. However, manganese concentrations are slightly elevated compared <br />to runoff water in the Chalk Mountain Interceptor. The elevated manganese concentrations may <br />Ell be caused by surface water runoff from the No. 1 Tailing Dam which can enter the reservoir. <br />The surface water diversion will consist of a rock-lined ditch, approximately eight feet wide and <br />four feet deep, with a trapezoidal cross section. These dimensions were determined based on <br />anticipated surface runoff from the PMP for the ERV. The peak channel flow from a PMP event <br />is estimated to be 310 cubic feet per second. <br />The diversion will run adjacent to the county road and divert surface water runoff <br />from No. 1 <br />Tailing Dam toward the current West Tailing Delivery discharge point. From this point, the <br />surface water will report to Robinson Lake or be impounded if the No. 1 Tailing Dam seep <br />impoundment were constructed. <br />4 <br />I <br />U <br /> <br />46 <br />L