2014-04-09_REVISION - M1977493 (2)

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Ray Lazuk March 19, 2014 Page 13 6.0 CONCLUSIONS The following conclusions have been garnered from this analysis: 1. The interceptor systems at the Climax Mine have served their intended function for many years by reducing the volume of unimpacted surface runoff that enters the industrial area. 2. Except for the 36 -inch CMP culvert crossing under the road to the Observatory near Station 95 +00, the Chalk Mountain Interceptor can pass the 10 -year rainfall event. 3. The East Interceptor can pass both the 10 -year rainfall and 10 -year rain -on -snow events in its current configuration. 4. The West Interceptor does not currently have adequate capacity to pass the 10 -year rainfall event without overtopping when the gates into the interceptor at the overflow structures are fully open. Climax operators have the ability to reduce flow into downstream reaches of the West Interceptor by partially or fully closing the interceptor gates at the Kokomo and Searle diversion structures. As a general observation, the slope of the West Interceptor is very flat, which promotes slower velocities and deeper water depths. Water that overtops the West Interceptor upstream of 5Dam would discharge into and be fully contained by Tenmile TSF and Mayflower TSF. 7.0 REFERENCES 1. U.S. Department of Agriculture (USDA), Soil Survey of Holy Cross Area, Colorado, White River National Forest, 2003. 2. U.S. Bureau of Reclamation (USBR), Flood Hydrology Manual, 1989. 3. Resource Engineering, Inc., Clinton Canal Flow Release Test, Glenwood Springs, Colorado, 1996. 4. U.S. Department of Agriculture (USDA), National Engineering Handbook Part 630, Chapter 9, 2004. 5. U.S. Army Corps of Engineers (USACE) HEC -RAS River Analysis System, User's Manual, 2010. 6. U.S. Army Corps of Engineers (USACE) HEC -HMS Hydrologic Modeling System, User's Manual, 2010.