GENERAL50712

• Permit No: C1981034
• IBM Index Class Name: General Documents
• Doc Date: 7/29/1988
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN1
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

The area of surface disturbance at Red Canyon was previously mined
land, and as such, the revegetation success criteria of Rule
4.05.10 applies. Vegetative ground cover is the only success
criteria which can be applied on previously mined lands. In
general, the Division has assumed that the vegetative cover on
pre-disturbance native rangeland is "adequate to control erosion"
if signs of excessive erosion are not present. In this instance
the vegetation success standard is based on total vegetative cover
in the sagebrush community adjacent to the affected areas at Red
Canyon. Methods to measure herbaceous cover and production,
species diversity, and woody plant density are discussed in Section
2.05.4(2)(vi) of the permit application (starting on page 133 of
Volume 11, and in Appendix F). GMCC plans to use the line
intercept method. This method was used for sampling, and conducted
in order to set the revegetation success standard. Measurements
were made to the nearest centimeter along 10 meter randomly located
and oriented transects. Based on data collected in the summer of
1983, a vegetative success standard of 26% has been established.
The Division proposes to approve the use of this sampling technique
to demonstrate revegetation success. (4.15.7(1)).
VIII. Protection of Fish. Wildlife and Related Environmental Values
Grand Mesa Coal Company proposes to perform plant specific
application of herbicides if significant numbers of noxious weeds
threaten successful revegetation. The Division proposes to approve
this usage. (4.18(4)(9)).
Fish and wildlife habitat is a planned post-mining land use. The
applicant has selected appropriate plant species and distributions
to benefit fish and wildlife. (4.18(4)(1)).
IX. Subsidence Control
The applicant proposes a subsidence control plan in accordance with
Rule 2.05.6(6) to prevent material damage due to subsidence of the
undermined area. Extraction is to be limited to a maximum of 55%
of the in-place coal. Further, within "safety zones", beneath the
structures delineated within the area of potential influence,
extraction is to be limited to 50% of the in-place coal. Two
methods of pillar stability analysis are presented to demonstrate
the adequacy of the designed pillar sizes to bear existing
overburden loads. Safety factors are demonstrated to be sufficient
in all cases. "Safety zones" are delineated on Map
2.05.6(6)(f)(ii)(c)-1 for workings within both the "D" and "E"
seams. In addition, a South African analytical technique is
utilized to demonstrate that the mine design should preclude
interaction between extraction within the "E" and "D" seams. The
plan adopts all measures in order to reduce the likelihood of
subsidence, prevent material damage, or mitigate the effects. The
Division proposes to approve the plan. (4.20.1(2) and 4.20.3(1)).
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