2008-08-11_PERMIT FILE - C1992080A

• Permit No: C1992080A
• IBM Index Class Name: Permit File
• Doc Date: 8/11/2008
• Doc Name: Revised Permit Document
• Section_Exhibit Name: Abridged Permit Document
• Media Type: D
• Archive: Yes

• Particles coarser than fine sand would not be transported off of the terrace during a 10 -year, 24-
hour storm based on most particle size classes plotting within the area of no motion in Figure 4.6 of
OSM's publication "Design of Sediment Control Measures for Small Areas in Surface Coal
Mining", 1982 (assuming: roughness coefficient 1240, terrace slope 0.01, unit discharge from
terrace 0.008 cfs per foot of length). Discharge from the terrace would be filtered by the angular
rock on the slope immediately downhill from the terrace and by rock -lined ditches, and then would
be diluted by mixing with the runoff from the more than 10 acres of undisturbed areas through
which it would pass before leaving the permit area.
Stream Channel Reconstruction (Carbon .function Canyon)
Carbon Junction Canyon was reconstructed for use as a permanent diversion as detailed below.
The work involved a diversion of 1962 feet that was riprap lined and with one culvert crossing
under the main access road. The channel itself is 14' wide after lining and varies in depth from 1.9
feet to 2.8 feet for segment 6, including freeboard.
Exhibit N within Appendix 2.05 shows that the peak flow for the upper segment (above the junction
with the mine access road) is 346 cfs for the 100 year event for a drainage area of 188 acres. This
was verified to be correct. This flow was used to design the diversion channel.
As seen in the mine plan map and reclamation map, the total distance of the diverted channel is
1962 feet. The initial segment (Segment 1) starts at the tributary channel that is a side canyon to the
i Carbon Junction Canyon. Shortly downstream from this side canyon, the flows from the diversion
enters the main canyon. Also, the side canyon is sufficiently large and rock -lined so that no
armoring of this channel is needed.
The following table shows the design sections of the diversion channel. The Carbon Junction
Canyon Map contains the existing and design cross - sections as well as culvert details and concreted
section details.
Segment
Length (feet)
Grade ( %)
Comments
#1
333
7.3
Lined Section
92
436
2.19
Lined Section
#3
277
5.31
Lined Section
#4
84
16.14
Section in Culvert
#5
184
9.78
Lined Section
#6
648
2.15
Lined Section
Total
1962
•
Abridged Permit Document 5 -7 Feb 2008