2021-04-05_PERMIT FILE - C1981019 ‎(46)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 4/5/2021
• Doc Name: South Taylor Erosion Control And Sedimentation Plan
• Section_Exhibit Name: Exhibit 07 Item 20 -ST
• Media Type: D
• Archive: No

COLOWYO COAL COMPANY
SEDIMENTATION POND SUMMARY PROPOSED PLAN-SOUTH TAYLOR MINE PLAN
SECTION 28 WEST TAYLOR WEST TAYLOR
POND POND POND
Active Mining Post-mining
WATERSHED AREA(acres):
Disturbed 00 684 00
Postmining Topsoiled and Seeded 00 00 747
Undisturbed 2586 80.5 2191
1-2 Year Reclamation 525 53 1567
3+Year Reclamation 69 0.0 3787
Total Area Draining to Pond 31800 1542 8292
Excluded 00 6749 00
Total Watershed Area 318.00 829 10 82920
POND PARAMETERS:
Upstream Toe Elevation Original Ground 70580 74560 74560
Principal Spillway Invert Elevation 70710 7471.0 7471 0
Emergency Spillway Invert Elevation 70770 74758 74758
Top of Embankment 70820 7481 0 7481.0
Storage Volume Below Emergency Spillway Invert(ac-ft) 831 564 564
Storage Volume Below Principal Spillway Invert(ac-ft) 3.65 290 290
Storage Volume Below Lowest Spillway Perforation(ac-ft) 1 67 1 77 1 77
Principal Spillway Parameters
Type Perforated Riser Perforated Riser Perforated Riser
Riser Diameter(in) 180 180 180
Riser Height(ft) 66 105 105
Barrel Diameter(in) 18.0 180 180
Elevation of Lowest Perforation(s)(ft) 70645 74680 74680
Size of Perforation(s)(in) 30 30 30
Number of Perforations per Elevation 20 20 20
Emergency Spillway Parameters
Type Trapezoidal Trapezoidal Trapezoidal
Diameter(in) N/A N/A N/A
Bottom Width(ft) 300 30.0 300
Crest Length(ft) 300 300 300
Side Slopes'z'H 1V(ft) 20 20 20
HYDROLOGIC/HYDRAULIC PARAMETERS:
Base Flow Rates(cfs) 000 000 000
10-Year,24-Hour Storm Event
Precipitation(in) 1 80 1 80 1.80
Runoff Volume(ac-ft) 1 23 434 7.51
Principal Spillway Peak Discharge(cfs) 3.80 1.61 1406
Emergency Spillway Peak Discharge(cfs) 000 000 000
Peak Surface Water Stage Elevation(ft) 707002 7471.16 7473.74
Spillway Design Storm 25 yr/24 hr 25 yr/24 hr 25 yr/24 hr
Precipitation(in) 2.30 230 230
Runoff Volume(ac-ft) 238 1 44 1654
Combined Princ and Emer Spillway Peak Discharge(cfs) 774 426 5557
Peak Surface Water Stage Elevation(ft) 7070.64 7471 41 747652
Pond Freeboard(ft) 11 36 9.59 448
SEDIMENT LOADING PARAMETERS(10-Year,24-Hour Event):
Storm Predicted Peak Sediment Concentration(in,mg/1) 45,093 702,476 78,287
Storm Predicted Peak Settl Solids,(out,mi/1) 0.0 00 0.00
Predicted Annual Sediment Loading(ac-ft) 0.05 01 002
Max.sediment storage elevation (ft) 705600 7468.0 74680
Available Sediment Storage Volume(ac-ft) 1 71 2.02 202
Predicted Number of years to max sed stor EI 342 161 839
Revision Date: 01/28/19
Exh. 7-20-2 Revision No.: TR-131