2004-09-02_PERMIT FILE - C1981019A

• 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 Section 16 Pond - 009A
• Media Type: D
• Archive: Yes

COLOWYO COAL COMPANY
009A -SECTION 16
SEDIMENTATION POND SUMMARY
ORIGINAL 1996 1998 2002 DIFFERENCE
CONFIGURATION STUDY STUDY DIFFERENCE STUDY 1998 TO 2002
ATERSHED AREA (acres):
DisiuNed 0.0 0.0 0.0 0.0
Postmining Topsoiled and Seeded 25.0 80.3 55.3 17.6 -62.7
Postmining Untlisturbetl 36.0 32.9 -3.1 53.7 20.8
i-2 Vear Reclamation 33.5 27.1 -6.4 47.7 20.6
3+Vear Reclamation 78.0 59.9 -18.1 146.4 86.5
Total Area 172.5 200.2 27.7 265.5 65.3
POND PARAMETERS:
Bottom Elevation 7740.2 7740.2 7740.2 0.0 7740.2 0.0
Principal Spillway Invert Elevation 7752.9 7752.0 7752.9 0.9 7752.9 0.0
Emergency Spillway Invert Elevation 7754.5 7754.5 7754.5 0.0 7754.5 0.0
Top of Embankment 7756.0 7756.0 7756.0 0.0 7756.0 0.0
Storage Volume Below Emergency Spillway (ac-f0 5.31 5.31 5.31 0.00 5.4 0.1
Storage Volume Below Principal Spillway (ao-ft) 4.35 3.87 4.35 0.48 4.4 0.1
Principal Spillway Parameters:
Type Drop Inlet Drop Inlet Pert. Riser PeA. Riser
Riser Diameter (in) 12.0 12.0 12.0 0.0 12.0 0.0
Riser Height (ft) 9.2 8.3 9.2 0.9 9.2 0.0
Barrel Diameter (in) 12.0 12.0 12.0 0.0 12.0 0.0
Elevation of Perfomgon(s) (ft) N/A N/A 7746.0 7746.0
Size of Perforetion(s) (in) N/A N/A 4.0 4.0
Number of Pertorations N/A N/A 2 2.0
Emergency Spillway Parameters'.
Type Trapezoidal Trapezoidal Trapezoidal Trapezoidal
Diameter (in) N/A N/A N/A N/A
Bottom Width (ft) 20.0 20.0 19.0 -1.0 19.0 0.0
Length (ff) 15.0 15.0 17.0 2.0 17.0 0.0
Side Slopes'z'H:1V (tt) 2.0 3.0 2.0 -1.0 2.0 0.0
HYDROLOGIC/HYDRAULIC PARAMETERS:
Base Flow Rates (cfs) 3.00 0.03 -2.97 0.00 0.0
10-Year, 24-Hour Storm Event:
Precipitation (in) 1.8 1.8 0.0 1.8 0.0
Runoff Volume (aoft) 1.5 4.7 3.2 0.4 -0.3
Principal Spillway Peak Discharge (cfs) 5.2 2.2 -3.1 0.4 -1.8
Emergency 6palway Peak Discharge (cfs) 0.0 O.D 0.0 0.0 0.0
Peak Surface Water Stage Elevation (ft) 7753.9 7752.4 -1.5 7746.2 -6.2
25-Year, 24Hour Stonn Event
Pre~pitation (in) 2.3 2.3 0.0 2.3 0.0
Runoff Volume (aok) 2.7 7.6 4.9 1.9 -5.7
Principal Spillway Peak Discharge (cfs) 6.0 4.8 -1.2 1.1 -3.7
Emergency SpilNvay Peak Discharge (cfs) 2.3 2.4 0.1 0.0 -2.4
Peak Surface Water Stage Elevation (ft) 7754.6 7754.6 D.0 7747.6 -7.0
Pond Freeboard (H) 1.4 1.4 0.0 8.4 7.0
SEDIMENT LOADING PARAMETERS:
Storm Predicted Peak Settlable Concentration (mVl) 0.00 0.00 0.0 0.00 0.0
Predicted Annual Sediment Loading (ac-ft) 0.17 0.24 0.07 0.12 -0.1
Available Sediment Storage Volume (acts) 0.54 0.54 0.00 0.56 0.0
Maximum Sediment Storage Elevation (ft) 7743.7 7743.7 7743.7 0.0 7743.7 0.0
Predicted Number of Storage Years 3.2 2.3 -0.9 4.7 2.5
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