PERMFILE47451

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 51 Lower Refuse Pile
• Media Type: D
• Archive: Yes

Mountain Coal Company, L.LC. Exhibit 51
West Elk Mine ~ Lower Refuse Pile

~;

Phase I Phase Phase Phase
11 III IV'
Total yield (ft') for cleanout period '_8,742 27,931 32.099 68.34.4
sedimentvieldand 10-vear.24-hour
~ -
storm
Elevationofpoolassumingtotal 6108.1 6108.0 6108.6 6104.14
sediment yield for cleanout period
and 10-vear.24-hours[orm
Total elevation difference(feetbelow 0.9 I.0 0.4 2.4
spillway) between spillway (elevation
6117.7)and pool for l0-year. 24-hour
storm with cleanout period sediment
vield
' Note that these numbers are only for [he Phase IV Lower Refuse Pile portion of the drainaee entering pond MB-'R
and do not reflect the overall pond desien.
Table 12 - 25-Year, 24-Hour Storm Peak Discharge'
Phase Peak Discharge (cfs)
I 82
11 9.4
111 1 1
I V 34.09
' From LRP only
The outfall works are composed of a 48-inch corrueated metal pipe drop riser structure at 6117.7 feet of
elevation. There is an 8-inch dewa[ering valve at an invert elevation of 6103 feet. The upper emergency
spillway consists of an 8-foot wide trapezoidal channel at an elevation of 61 18.7 with 2:1 sideslopes. The
final dike elevation is 6120 feet. The emergency spillway has a capacity of 15.39 cfs at elevation 61 18.95
fee[. The pond can safely pass the discharge from a 100-year 24-hour storm event.
6.3.2 Phase V Effects on Sediment Control Pond
Surface water runoff for the LRP will continue to be controlled through sedimentation pond MB-2R.
Surface water runoff volume, peak flow, and sediment load quantities were computed for the Phase V
reconfiguration to determine effects of the design modification and ensure compliance with the CMLRB
Regulations. Results indicate the e~is[ing runoff controls have adequate capacity to manage the LRP
Phase V modification.
31