2018-07-24_PERMIT FILE - C2010089 ‎(6)‎

• Permit No: C2010089
• IBM Index Class Name: Permit File
• Doc Date: 7/24/2018
• Doc Name: Pond NHN-001 East Ditch Extension Design
• Section_Exhibit Name: Appendix 2.05.3‎(4)‎-11
• Media Type: D
• Archive: No

Introduction
Pond NHN-001 at the New Horizon North Mine is designed to capture and contain the runoff
from the 10 -YR, 24 -HR storm event as part of sediment control at the mine. This pond has been
constructed as well as the entire associated Pond NHN-001 West Ditch. A majority of the Pond
NHN-001 East ditch has also been constructed. Designs presented herein for NHN-001 East
Ditch Extension are for a specific segment of the Pond NHN-001 East Ditch from station 0+00 to
10+79 as shown on Map 2.05.3(4)-11. Refer to Section 2.05.3(4) for design information on other
segments of the Pond NHN-001 East and West Ditches.
Stormwater Data
The stormwater runoff values modeled for the Pond NHN-001 East Ditch extension are the 10 -
YR, 24 -HR event that produces a rainfall depth of 2.0 inches.
Pond NHN-001 East Ditch Extension Design
Map 2.05.3(4)-11 shows the currently constructed sections of NHN-001 East Ditch from Station
27+11 at the pond inlet to Station 0+00 (this station 0+00 ends at the southern outlet of the West
Haul Road culvert). As -Built information for this portion of the Pond NHN-001 East Ditch can
be found in Appendix 2.05.4(3)-7. The stationing then resets on the north side (inlet) of the West
Haul Road culvert and the designs for Station 0+00 to 10+79 area contained in this appendix.
The East Ditch Extension is designed to utilize a trapezoidal cross section with a minimum
bottom width of 6 feet and side slopes no steeper than 2H:1 V on the east side and 3H:1 V on the
west side as shown on Table 2.05.3(4)-11-1.
Map 2.05.3(4)-11 provides the alignment of the Pond NHN-001 East Ditch extension, profiles
with anticipated grades and design details and criteria. No erosion causing velocities are
expected within the NHN-001 East Ditch Extension. The attached SEDCAD demonstration
shows the ditch design based on the appropriate sub -watersheds and channel characteristics.
Table 2.05.3(4)-11-1: NHN-001 East Ditch Extension Design
Ditch
Station
Cumulative
Slope
Minimum
Maximum
Maximum
Rip Rap
Section
Flow (cfs)
M
Bottom
East Side
West Side
D5o (in.)
Width (ft.)
Slope
Slope
(HAV)
(H:lV)
Segment 1
8+60 to
1.48
0-3
6.0
2.0
3.0
N/A
10+79
Segment 2
4+88 to
3.43
0-1
6.0
2.0
3.0
N/A
8+60
Segment 3
0+00 to
4.91
0-2
6.0
2.0
3.0
N/A
4+88
Appendix 2.05.3(4)-11 Page - 3 - June 2018 (TR -17)