GENERAL48692

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Name: Proposed Decision & Findings of Compliance
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

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Colowyo has proposed that on regraded surfaces which are flatter than 4:1,
mulch:wi~Dl not be used. Mulch has been shown to be useful, and under
certain conditions critical, for reclamation of disturbed Lands. The
two basic purposes which a mulch serves are to buffer temperature extremes
and shade the soil surface, and to provide erosion protection mainly
through the deflection of raindrop impact. Asa result, a mulch is
most effective and necessary on steep slopes where erosion is a~concern,
in arid climates, or on slope exposures where the reduction in evaporation
is critical to obtaining sec~I germination and sesrlling establishment.
Past research conducted by the Soil Conservation Service has indicates
that, in areas where precipitation is between 18 and 25 inches, mulches
are generally not needed except on steep slopes (Ashley A. Thornburg,
Plant Materials for use on Surface Mined Land in Arid and Semi-Arid
Regions, SCS-TP-I 57, 1979}.
Precipitation at CoZowyo is near the lower end of this range, but
revegetation trials conducted by Colorado State University indicate that
mulching does not result in significantly higher vegetative cover of
reseeded stands. A number of mulching treatments, including straw,
wood shavings, chipped serviceberry and chipped sagebrush were compared
to a control (no mulch) treatment. Total vegetative cover after two
years was 38% for the control plots and 40% for the straw mulched plots.
Precipitation during the period was described as below normal (braves,
R.W., and W.A. Berg, 1979).
Given tha above considerations, the Division, in this instance, is suspending
the requirement for mulch on slopes which are flatter than 4:1. Erosion
control prior to vegetation establishment will be provided by contour
furrows. The following stipulation is imposed.
Stipulation No. 4
IF, IN THE FUTURE, ON-SITE INSPECTION BY THE DIVISION OR INFORMATION
COLLECTED BY COLOWYO INDICATE THAT THE SUSPENSION OF THE MULCHING
REQUIREMENT. IS DETRIMENTAL TO S~IEGETATION ESTABLISHMENT OR CONTRIBUTES
TO EXCESSIVE EROSION, MULCHING WILL BE RESUMED.
Several concerns regarding determinations of revegetation success were
identified during the review,~and are summarized below.
CoZowyo had originally located the reference area for the sagebrush
community in an area that will be disturbed by mining. Anew reference
area was selected and sampled in July, 1982. Comparisons of cover and
production were made between the existing and the new reference area.
The new reference area was shown to be comparable to the original
reference area. Sampling data is included in Colowyo's August 2, 1981
response to the Division's Adequacy Letter of July 9, 1981.