2004-09-02_PERMIT FILE - C1981019A ‎(3)‎

• 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 Gossard Pond - 003A
• Media Type: D
• Archive: Yes

COLOWYO COAL COMPANY
003A-GOSSARD
SEDIMENTATION POND SUMMARY
r

ORIGINAL 1996 1998 2002 DIFFERENCE'
CONFIGURATION STUDY STUDY DIFFERENCE STUDY 1998 T02002
ATERSHED AREA (acres):
Disturbed 25.9 25.9 0.0 0.0
Postmining Topsoiled and Seeded 0.0 0.0 0.0 25.9 25.9
Postmining Undisturbed 0.0 0.0 0.0 0.0 0.0
1-2 Year ReUamation 0.0 0.0 0.0 0.0 0.0
3+year Reclamation 0.0 0.0 0.0 0.0 0.0
Total Area 25.9 25.9 0.0 25.9 0.0
POND PARAMETERS:
O
~' ~ 6
Bottom Elevation 6384.9 6384.9 6384.9 0.0 6384.9 0.0
Principal Spillway Invert Elevation 6388.3 6390.3 6389.3 -1.0 6391.0 / 1.7
Emergency Spillway Invert Elevation 6392.7 6392.7 6392.7 0.0 6392.7 0.0
Top of Embankment 6400.9 6402.0 6400.9 -1.1 6400.9 0.0
Storage Volume Below Emergency Spillway (ac-ft) 4.33 4.33 4.33 0.00 4.3 r/ 0.0
Storage Volume Below Principal SpilAVay (ac-n) ~ 1.24 2.54 1.76 -0.78 3.0 1.2
Principal Spilkvay Parameters:
Type Trickle Tube Drop Inlet Drop Inlet Fixed Siphon
Riser Diameter (in) N/A 6.0 6.0 0.0 N/A
Riser Height (H) N/A 2.0 1.0 -1.0 N/A
Bartel Diameter (in) 6.0 8.0 6.0 -2.0 6.0 0.0
Elevation of Perforation(s) (R) N/A NIA N/A N/A
Size of Pedoration(s) (in) N/A N/A N/A N/A
Number or Perforations N/A N/A N/A N/A
Emergency Spillway Parameters:
Type Trickle Tube Trickle Tube Trickle Tube Trickle Tube
Diameter (in) 30.0 30.0 30.0 30.0
Bottom Width (H) N/A N/A N/A N/A
Length (ft) 155.0 100.0 155.0 55.0 155.0 0.0
Side Slopes'i H:N (!t) N/A N/A N/A N/A
HVDROLOGIClHVDRAULIC PARAMETERS:
Base Flow Rates (cfs) 0.0 0.0 0.0 0.00 0.0
10-Year, 24-Hour Storm Event:
Precipitation (in) 1.8 1.8 0.0 1.8 0.0
Runoff Volume (ac-ft) 2.1 2.1 0.0 1.5 -0.6
Principal Spillway Peak Discharge (cfs) 2.0 1.2 -0.8 1.4 0.2
Emergency Spillway Peak Discharge (cfs) 0.0 0.0 0.0 0.0 0.0
Peak Surface Water Stage Elevation (ft) 6391.9 6391.2 -0.7 6390.2 -1.1
25-Year. 24-Hour Storm Event:
Precipitation (in) 2.3 2.3 0.0 2.3 0.0
Runoff Volume (ac-ft) 3.1 3.1 0.0 2.3 -0.8
Principal Spillway Peak Discharge (cfs) 2.6 1.3 -1.3 1.5 0.3
Emergency Spillway Peak Discharge (cfs) 0.0 0.0 0.0 0.0 0.0
Peak Surface Water Stage Elevation (ft) 6392.7 6392.2 -0.5 6390.9 -1.2
Pontl Freeboard (R) 9.3 8.8 -0.5 10.0 1.2
SEDIMENT LOADING PARAMETERS:
Storm Predicted Peak Settlable Concentration (mN) 0.00 0.00 0.0 0.00 0.0
Predicted Annual Sediment Loading (ac-R) 0.08 0.08 0.00 0.04 0.0
Available Sediment Storage Volume (ac-k) 1.55 / ~ 1.55 0.00 1.17 -0.4
Maximum Sediment Storage Elevation (ft) 6388.3 6388.3 6388.3 0.0 6388.3 0.0
Predicted Numher of Storage Years 19.4 19.4 0.0 26.6 7.2
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