2019-09-18_PERMIT FILE - C1981035 ‎(9)‎

• Permit No: C1981035
• IBM Index Class Name: PERMIT FILE
• Doc Date: 9/18/2019
• Doc Name: Hydrologic Designs
• Section_Exhibit Name: KI Appendix 11
• Media Type: D
• Archive: No

• 1. Scope and Purpose
In compliance with Colorado State reclamation regulations pertaining to hydrology of
mine sites, a design for the drainage system at National King Coal Mine in presented in
this document. Detailed hydrologic and hydraulic analysis of sedimentation ponds,
channels and pipes were performed as part of this study.
2. Mine Drainage Plan
The drainage plan for the National King Coal Mine has two components: 1) diversion
of uncontaminated water, originating upstream of the mine yard and waste pile, around
the yard to the discharge point at the north end of the site and 2) routing of water from
the mine yard, waste pile and some adjacent areas through sedimentation ponds. This is
achieved through a series of open channels and pipes. Figure 1 is a schematic diagram
of the drainage basin which shows the different subbasins. The large areas labeled east
and west basins are diverted around the mine. The area labeled mine yard (this includes
the waste pi(e) is the only area which generates contaminated runoff. The natural areas
adjacent to the mine yard on the west, as well as the natural area south of the waste pile
do not generate contaminated water but are routed to the sedimentation ponds in order
to simplify the drainage system.
2.1 Diversion of Uncontaminated Runoff
• Runoff from th
e east basin is intercepted above the coal waste pile in an open
channe! and routed through reach 1 as shown in Figure 2. Reach 1 terminates at a
junction with an armored open channel at the front and on top of the waste pile,
designated reach 2. This channel carries the uncontaminated runoff down the waste pile
face and to the clear water diversion channel behind the office, reach 5:
Because of the high flow velocity exi#ing the pipe, energy dissipation at the outlet is
required. Water from the channel~will discharge into a rock lined pool 5 ft wide by 10
feet long with a minimum depth of 3 ft before entering the downstream channel. The
outlet from the pool to the ditch should be at the same elevation as the invert of the
channel outlet. The rock lining should consist of two layers. The bottom layer should be
a'/~" to 2" gravel blanket at least 3" thick. This will prevent the erosion of soil from the
pool floor and sides due to surging flows. The second layer should be a graded material
with a minimum stone size of 8" and a D~ of 14". The outer rock lining should be at feast
two stones thick. This layer will resist the high velocity flow exiting the pipe. The
channel exit should be directed, at an angle toward the center and bottom of the pool.
Care should betaken to place large stones in the path of the exiting jet. As an
alternative-the pool can be constructed with rock filled gabions. In either case the rock
protection should extent one foot above the pool outlet opening elevation.