2019-09-09_PERMIT FILE - C1981019A ‎(6)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 9/9/2019
• Section_Exhibit Name: Exhibit 07 Methodologies & Assumptions for Sedimentation Pond Design Evaluations
• Media Type: D
• Archive: Yes

TABLE 6
COLOWYO COAL COMPANY
SEDIMENTATION POND SUMMARY PROPOSED PLAN
I
SECTION 16 EAST TAYLOR EAST TAYLOR
STREETER WORK AREA GOSSARD GULCH A STOKER SIDING RAIL LOOP PROSPECT WEST PIT POND POND POND
POND POND POND POND POND POND POND POND Post Mining Active Mining Post Mining
WATERSHED AREA(acres):
Disturbed 0.0 00 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Postmining Topsoiled and Seeded 310.8 108.3 25.9 364 14.5 5.7 103.8 875 21.9 106.2 82.2
Undisturbed-Phase III Released 136.2 13.2 0.0 697 0.0 0.0 236.8 23.2 125.6 49.8 70.4
1-2 Year Reclamation 109.9 0.0 0.0 462 0.0 0.0 231.4 0.0 81.1 76.6 166.2
3+Year Reclamation 821.2 0.0 0.0 5658 0.0 0.0 128.9 88.8 39.5 418.3 757.5
Total Area 1378.1 121.4 25.9 718.1 14.5 5.7 701.0 199.5 268.1 650.9 1076.3
POND PARAMETERS:
Bottom Elevation 6578.0 7146.0 6384.9 6605.0 6321.8 63440 6734.0 6821.0 7740.2 69300 6930.0
Principal Spillway Invert Elevation 6585.0 71558 6391.0 6617.5 6329.6 6351.5 6750.3 6837.0 77529 6952.0 6951.0
Emergency Spillway Invert Elevation 6588.0 7158.0 6392.7 6619.2 6332.0 6353.0 67520 6838.0 77545 6954.0 6953.5
Top of Embankment 6591.0 7160.0 6400.9 6621.0 6334.0 6355.0 67550 6841.0 7756.0 6956.0 6956.0
Storage Volume Below Emergency Spillway Invert(ac-ft) 11.2 23.2 4.3 6.7 3.2 1.5 61 13.8 5.4 9.1 8.6
Storage Volume Below Principal Spillway Invert(ac-ft) 5.2 17.0 3.0 5.7 1.9 1.0 51 12.6 44 7.5 6.7
Storage Volume Below Lowest Spillway Perforation(ac-ft) 2.63 1233 N/A 3.82 0.38 N/A 2.25 5.50 126 2.85 285
Principal Spillway Parameters:
Type Perf.Riser Perf.Riser Fixed Siphon Perf.Riser Perf.Riser Trickle Tube Perf.Riser Perf.Riser Perf.Riser Perf.Riser Perf.Riser
Riser Diameter(in) 12.0 12.0 N/A 120 120 N/A 12.0 18.0 12.0 18.0 18.0
Riser Height(ft) 3.7 5.1 N/A 3.5 5.7 N/A 8.7 11.6 9.2 10.0 10.0
Barrel Diameter(in) 180 12.0 6.0 12.0 12.0 8.0 120 18.0 12.0 18.0 18.0
Elevation of Perforation(s)(ft) 6583.0 7154.0 N/A 66155 6325.0 N/A 6744.0 6830.0 7746.0 6944.0 6944.0
Size of Perforation(s)(in) 4.0 4.0 N/A 3.0 4.0 N/A 4.0 4.0 4.0 4.0 40
Number of Perforations 2.0 3.0 N/A 2.0 10 N/A 2.0 3.0 2.0 2.0 20
Emergency Spillway Parameters
Type Trapezoidal Trapezoidal Trickle Tube Trapezoidal Trapezoidal Trapezoidal Trapezoidal Trapezoidal Trapezoidal Trapezoidal Trapezoidal
Diameter(in) N/A N/A 30.0 N/A N/A N/A N/A N/A N/A N/A N/A
Bottom Width(ft) 20.0 150 N/A 15.0 5.0 7.0 12.0 24.0 19.0 200 20.0
Length(ft) 50.0 140.0 155.0 30.0 40.0 150 200 21.0 17.0 20.0 20.0
Side Slopes'z'H.1V(ft) 15 1.5 N/A 15 2.0 2.0 1.5 1.5 2.0 2.0 2.0
HYDROLOGIC/HYDRAULIC PARAMETERS:
Base Flow Rates(cfs) 0.00 0.00 0.00 0.00 0.00 0.00 0.15 0.03 0.00 0.00 000
10-Year,24-Hour Storm Event:
Precipitation(in) 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1 80 1.80
Runoff Volume(ac-ft) 611 519 1.51 0.88 0.85 0.33 3.20 3.50 267 5.99 7.27
Principal Spillway Peak Discharge(cfs) 3.08 1 36 1.40 0.38 058 0.45 1.46 1.65 4.22 2.29 244
Emergency Spillway Peak Discharge(cfs) 0.00 0.00 0.00 000 0.00 0.00 0.00 0.00 0 0.00 0.00
Peak Surface Water Stage Elevation(ft) 6585.68 7155.17 6390.15 6616.17 6326.94 6351.93 6747.01 6831 71 7754.15 6951.03 6952.40
25-Year,24-Hour Storm Event-
Precipitation
ventPrecipitation(in) 2.30 2.30 2.30 2.30 2.30 2.30 2.30 2.30 230 2.30 2.30
Runoff Volume(ac-ft) 22.77 8.51 234 4.68 1.31 0.51 8.29 6.47 515 1283 18.48
Combined Principal and Emergency Spillway Peak Discharge(cfs) 21 03 1.88 1.53 2.75 0.72 0.62 4.00 2.38 24.69 1141 81.57
Peak Surface Water Stage Elevation(ft) 6588.38 7156.04 6390.94 6618.03 6327.91 6352.19 6751.43 6833.57 775500 6954.56 6954.69
Pond Freeboard(ft) 2.62 3.96 996 2.97 6.09 2.81 3.57 7.43 1.00 1.44 1.31
SEDIMENT LOADING PARAMETERS:
Storm Predicted Peak Settlable Concentration(ml/I) 0.04 0.00 0.00 0.00 0.00 000 0.00 0.00 0.00 000 000
SEDCAD estimated Annual Sediment Loading(ac-ft) 0.00 0.12 0.04 0.17 001 0.02 1 91 0.49 0.06 0.21 0.020
Available Sediment Storage Volume at max.sediment storage EI(ac-ft) 084 4.86 1.17 2.85 0.20 1.03 1.41 2.18 0.56 0.43 0.43
Maximum sediment storage elevation (ft) 6581.3 71507 6388.3 6614.0 6323.9 6351.5 6741.6 6825.4 7743.70 6935.00 6935.00
Predicted Number of Storage Years to Gate Valve Invert >50 40.2 26.6 17.2 28.4 45.0 1.4 4.4 8.7 2.0 218
Revision Date 8/13/19
Exhibit 7 Page 10 Revision No.: TR-132