2008-05-13_REVISION - C1981008 ‎(5)‎

• Permit No: C1981008
• IBM Index Class Name: REVISION
• Doc Date: 5/13/2008
• Doc Name: Bond Release Application
• From: Greg Lewicki and Associates
• To: DRMS
• Type & Sequence: SL11
• Email Name: MLT
• Media Type: D
• Archive: No

• Cover Factor "C"
For rangeland and pastureland, the "C" factor is directly related to the percent of the
ground covered by vegetation and the type of vegetation that is present. Subsurface effects
such as root mass can also be considered. The type of vegetation is important because
herbaceous plants with a live cover of 25% will protect the soil much better than a site
that contains an equal cover but where the cover is primarily comprised of trees or shrubs.
Table 3 (from EPA 1977) shows the variation in "C" factors for varying range conditions.
From the 1987 study of the dryland pasture and irrigated pasture areas, the cover
breakdown is given below:
Pre-Mine Conditions
Dryland Pasture - 1987 Cover Data
The dryland pasture study area had 29 percent bare ground, 30.2 percent litter, 3.7 percent
rock fragments, 12.7 percent annual grasses, 7.3 percent perennial grasses, 2.6 percent
perennial fortis, 0.2 percent annual fortis, and 13.5 percent perennial shrubs for a total of
37 percent live vegetation. Note: The dryland pasture area transects were taken from the
Coal Mining Permit C-81-008 2005-2006 Mid Term Review.
• 0.2% Annual Fortis
12.7% Annual Grasses
7.3% Perennial Grasses
2.6% Perennial Fortis
13.5% Perennial Shrubs
30.2% Litter
Ground Cover (cover that contacts the surface) =Annual fortis + Annual Grasses +
Perennial Grasses + Litter
Ground Cover = 50.4%
Canopy Cover =Perennial Shrubs + Perennial Fortis
Canopy Cover = 16.1
Using Table 3 and a canopy of 0% (short brush 0.5 meter in height) and the "G" canopy
type, the chart of Figure 1 was developed. From this chart, a ground cover that contacts the
surface of 50.4% yields a "C" factor of 0.07. Since the actual canopy is 16.1 %, another
chart was developed from the data in Table 2 showing the change in "C" factor versus
ground cover for a canopy of 25%. This is Figure 2, and using a ground cover that contacts
the surface of 50.4%, gives a "C" factor of 0.06. Since the actual canopy is 16.1%, a
simple interpolation is required to give the correct "C" factor:
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