PERMFILE45937

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 9/2/2004
• Doc Name: Attachment 1 to 9
• Section_Exhibit Name: Exhibit 7 East Taylor Pond - 010A
• Media Type: D
• Archive: Yes

COLOWYO COAL COMPANY
010A-EAST TAYLOR
SEDIMENTATION POND SUMMARY
/ '
J
/ ORIGINAL 1996 1998 2002 DIFFERENCE
CONFIGURATION STUDY STUDY DIFFERENCE STUDY 1998 T02002
ATERSHED AREA (acres):
Disturbed 0.0 0.0 0.0 0.0
Postmining Topsoiled and Seeded 100.0 126.0 26.0 188.5 62.5
Postmining Undisturbetl 300.0 148.3 -151.7 250.0 101.7
t-2 Year ReUamation 30.2 70.5 40.3 74.6 4.1
3+Year ReUamaeon 515.9 573.8 57.9 535.2 -38.6
Total Area 946.1 918.6 -27.5 1048.2 129.6
POND PARAMETERS:
Bottom Elevation 6930.0 6930.0 6930.0 0.0 6930.0 0.0
Principal Spillway Invert Elevation 6952.0 6950.0 6952.0 2.0 6952.0 0.0
Emergency Spilhvay Irnert Elevation 6954.0 6954.0 6954.0 0.0 6954.0 0.0
Top of Embankment 6956.0 6956.0 6956.0 0.0 6956.0 0.0
Storage Volume Below Emergenoy Spillway (ao-R) 8.58 8.58 8.58 0.00 9.1 0.5
Storage Volume Below Prncipal Spillway (ao-ft) 7.01 5.62 7.01 1.39 7.5 0.5
Principal Spillway Parameters:
Type Drop Inlet Drop Inlet Perf. Riser Pert. Riser
Riser Diameter (in) 18.0 18.0 18.0 0.0 18.0 0.0
Riser Height (R) 10.2 8.2 10.2 2.0 10.0 -0.2
Barrel diameter (in) 18.0 18.0 18.0 0.0 18.0 0.0
Elevation of Perforation(s) (R) N/A N/A 6944.0 6944.0
Size of Perforation(s) (in) N/A N/A 4.0 4.0
Number o(Perfora8ons N/A N/A 2 2.0
Emergency Spillway Parameters:
Type Trapezoidal Trapezoidal Trapezoidal Trapezoidal
Diameter (in) N/A N/A N/A WA
Bottom Width (ff) 20.0 20.0 20.0 0.0 20.0 0,0
Length (R) 20.0 25.0 20.0 -5.0 20.0 0.0
Side Slopes'i H:iV (R) 3.0 3.0 2.0 -1.0 2.0 0.0
HYDROLOGICRiVDRAULIC PARAMETERS:
Base Flow Rates (US) 1.00 0.03 -0.97 0.00 0.0
10-Year, 24•Hour Storm Event:
Precipitation (in) 1.8 1.8 0.0 1.8 0.0
Runoff Volume (ao-ft) 5.9 7.5 1.6 7.3 -0.2
Principal SpilNvay Peak Discharge (c(s) 15.9 4.0 -11.9 2.2 -1 8
Emergenry Spillway Peak Discharge (cfs) 0.0 0.0 D.0 0.0 0.0
Peak Surtace Water Stage Elevation (R) 6953.5 6952.3 -1.2 6950.7 -1.6
25-Year, 24-Hour Slortn Event:
Precipitation (in) 2.3 2.3 0.0 2.3 0.0
Runoff Volume (ao-R) 10.2 13.0 2.8 15.7 2.7
Prncipal Spillway Peak Discharge (c(s) 18.5 12.0 -6.5 10.1 -1.9
Emergenry Spilhvay Peak Discharge (cfs) 25.1 3.7 -21.4 0.0 -3.7
Peak Sudace Water Stage Elevation (R) 6954.8 6954.1 -0.7 6953.4 -0.7
Pond Freeboard (h) 1.2 1.9 0.7 2.6 0.7
SEDIMENT LOADING PARAMETERS:
Storm Predicted Peak Settlable Concentration (ml/l) 0.00 0.00 0.0 0.00 0.0
Predicted Annual Sediment Loading (acft) 0.37 1.13 0.76 0.90 -0.2
Available Sediment Storage Volume (ao-R) 1.88 1.88 0.00 2.13 0.3
Maximum Sediment Storage Elevation (R) 6941.8 6941.6 6941.8 0.0 6942.0 0.2
Predictetl Number of Storage Years 5.1 1.7 -3.4 2.4 u
0.7