2004-09-02_PERMIT FILE - C1981019A ‎(5)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 9/2/2004
• Doc Name: Attachment 1 to 9
• Section_Exhibit Name: Exhibit 07 Rail Loop Pond - 006A
• Media Type: D
• Archive: Yes

COLOWYO COAL COMPANY
O06A -RAIL LOOP
SEDIMENTATION POND SUMMARY ~

ORIGINAL 1996 1996 2002 DIFFERENCE
CONFIGURATION STUDY STUDY DIFFERENCE STUDY 1998 TO 2002
WATERSHED AREA (aer¢s):
Disturbed 5.7 5.7 0.0 0.0
Postmining Topsoiletl and Seeded 0.0 0.0 0.0 5.7 5.7
Postmining Undisturbed 0.0 0.0 0.0 0.0 0.0
1-2 Year ReGamation 0.0 0.0 0.0 0.0 0.0
3+Vear ReGamation 0.0 0.0 0.0 0.0 0.0
Total Area 5.7 5.7 0.0 5.7 0.0
POND PARAMETERS:
Bottom Elevation 6344.2 6344.2 6344.2 0.0 6344.0 -0.2
Principal Spilhvay Invert Elevation 6351.5 6351.5 6351.5 0.0 6351.5 0.0
Emergency Spilhvay Invert Elevation 6353.0 6353.0 6353.0 0.0 6353.0 0.0
Top of Embankment 6355.0 6355.0 6355.0 0.0 6355.0 0.0
Storage Volume Below Emergency Spillway (ac-ft) 1.41 1.41 1.41 0.00 1.5 0.1
Storage Volume Below Principal Spillway (aoft) 0.97 0.97 1.09 0.12 1.0 -0.1
Principal Spillway Parameters:
Type Trickle Tube Trickle Tube Trickle Tube Trickle Tube
Riser Diameter (in) N/A N/A N/A N/A
Riser Height (ft) N/A N/A N/A N/A
Bartel Diameter (in) 8.0 8.0 8.0 0.0 8.0 0.0
Elevation of Perforation(s) (H) N/A N/A N/A N/A
Size of Pertoration(s) (in) N/A N/A N/A N/A
Number of Perforations N/A N/A N/A WA
Emergency Spillway Parameters'.
Type Trapezoidal Trapezoidal Trapezoidal Trapezoidal
Diameter (in) N/A N/A N/A N/A
Bottom width (ft) 7.0 7.0 7.0 0.0 7.0 0.0
Length (ft) 15.0 25.0 15.0 -10.0 15.0 0.0
Side Slopes'z'H:iV (ft) 2.0 2.0 2.0 0.0 2.0 0.0
HYDROLOGIC/HYDRAULIC PARAMETERS:
Base Flow Rates (GS) 0.0 0 0 0.0 0.00 0.0
t0-Vear, 24-Hour Storm Event:
Preupitation (in) 1.8 1 8 0.0 1.8 0.0
Runoff Volume (ao-H) 0.5 0.5 0.0 0.3 -0.2
Principal Spillway Peak Discharge (cfs) 0.9 0.9 0.0 0.4 -0.4
Emergency Spillway Peak Discharge (ds) 0.0 0.0 0.0 0.0 0.0
Peak Surtace Water Stage Elevation (ft) 6352.3 6352.3 0.0 6351.9 -0.4
25-Vear, 24-Hour Storm Event:
Precipitation (in) 2.3 2.3 0.0 2.3 0.0
Runoff Volume (ao-H) 0.7 0.7 0.0 0.5 -0.2
Principal Spilhxay Peak Discharge (GS) 1.1 1.1 0.0 0.6 -0.5
Emergency Spillway Peak Discharge (cfs) 0.0 0.0 0.0 0.0 0.0
Peak Surface Water Stage Elevation (ft) 6352.7 6352.7 0.0 6352.2 -0.5
Pond Freeboard (ft) 2.4 2.4 0.0 2.8 0.5
SEDIMENT LOADING PARAMETERS:
Storm Pretlicted Peak Settlable Concentration (mV0 0.00 0.00 0.0 0.00 0.0
Predicted Annual Sediment Loading (ac-H) 0.02 0.02 0.00 0.02 0.0
Available Sediment Storage Volume (ac-ft) 0.64 0.64 0.00 1.03 / 0.4
Maximum Sediment Storage Elevation (ft) 6351.5 6351.5 6351.5 0.0 6351.5 0.0
Predicted Number of Stora a Vears 32.0 32.0 0.0 45.0 13.0