2013-10-07_PERMIT FILE - C1981025A ‎(6)‎

• Permit No: C1981025A
• IBM Index Class Name: Permit File
• Doc Date: 10/7/2013
• Doc Name: Final Engineering Calculations
• Section_Exhibit Name: 4.0 Appendix 4-B
• Media Type: D
• Archive: Yes

_• APPENDIX 4-B
NARRATIVE, EXPLANATION AND CERTIFICATION
The majority of the information contained in Appendix 4-B is no
longer applicable to the reclaimed North Thompson Creek mine sites
or unit train loadout haul road. The following narrative will
explain the current status of the drainage control at the mine
sites and unit train loadout haul road.
No. 3 Mine Site
The reclaimed No. 3 Mine does not have any design ditches or
culverts within the reclaimed area. The drainage control features
presented on Map D-4-7 including ditch D-1 and culverts C-7 and C-8
have been reclaimed. The only ditch associated with the reclaimed
No. 3 mine site is ditch D-2A. Ditch D-2A conveys run-off from the
reclaimed No. 3 mine area and the undisturbed area above (drainage
area 10) to the east.
Water Tank Area
The water tank disturbance does not have any design ditches or
culverts within the reclaimed area. The drainage control features
presented on Map D-4-7 including ditch D-3, culverts C-3, C-5, C-9,
C-10 and pond P-2 have been reclaimed. Ditch D-2B conveys runoff
• from the water tank reclaimed area and the undisturbed area above
(drainage area 7 and ~ of 6) to the east.
No. 1 Mine Area
The reclaimed No. 1 Mine does have a few design ditches and
culverts within the reclaimed area. However the drainage control
features presented on Map D-4-8 including culverts C-11 and C-12
have been reclaimed. Ditch D-4 collects water along the south
boundary of the reclaimed site and conveys the water to pond P-9.
The basis for the design flow for this ditch is the design flow for
the emergency spillway for pond P-9 which is presented in this
appendix on page P-9-2.
Ditches D-6 and D-7 convey the run-off from the undisturbed areas
above the mine site to pond P-4 where it is conveyed under the
county road by culvert C-6. Ditch D-7 is the upper diversion ditch
for the refuse pile so it is designed to handle the run-off from
the 100-year event (drainage areas 3A, 3B and 4). Ditch D-6 is
designed to handle the run-off from the 10 year event (drainage
areas 3A, 3B, 4, SA, SB and ~ of 6). The design for ditches D-6
and D-7 is presented on pages 4-B:5 & 6.
Ditches D-9 and D-10 convey the run-off away from the refuse pile.
The design for these ditches is presented in a section of this
• appendix titled; Snowmass Coal Company, Mid-Term Review Response,
4-B:1 October 1994