PERMFILE124595

• Permit No: C1984062
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 24 RILL & GULLY PLAN
• Media Type: D
• Archive: No

A = cross-sectional of flow area in square feet.
n = Manning's roughness coefficient.
• R = hydraulic radius in feet
= area (A) / wetted perimeter (P).
5 = slope of the energy gradient (usually equal r,c: the slope of the
channel).
Design velocities for the channel will not exceed 3 fps for bare soil
ditches or 5 fps for grass-lined or rip-rapped channels. Channel slope will
be primarily dictated by the slope of reclaimed drainage located above the
permanent drainageway. Generally, channels will be seeded to promote
vegetation growth, and increase stability and reduce erosion potential. The
cross-section shape of the channel will typically be trapezoidal, with side
slopes of 3: 1. The channel bottom will typically be 10-12 feet for
calculated peak runoff flows above / cfs. Wide flat-bottomed channels are
observed to be stable in undisturbed areas and vegetation may become
established relatively easily. Channel sides and bottoms will be scarified,
channel sides and possibly channel bottoms will be broadcast seeded. The
seed mixture used for stabilization is the same as the currently approved
• pastureland seed mix.
Diversion ditch construction will follow the same guidelines outlined
above. However, ir, some cases, diversion ditches will be V-bottom rather
than flat-bottom for ease of snow removal. Past experience of Colorado
Yampa Coal Company has shown V-bottom ditches can be more easily cleared of
snow than flat-bottom ditches.
It is not possible to accurately designate the location of all
diversion ditches at this time. Generally, diversion ditches will be
constructed in areas where slopes exceed eight (8) percent and in headwater
areas where reclamation is not complete. In the latter situation, water
generated from spoil would be prevented from causiny excessive erosion
within down-slope reclamation.
•
24-9