2018-09-04_REVISION - C1980007 ‎(11)‎

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 9/4/2018
• Doc Name: Proposed Decision and Findings of Compliance
• From: DRMS
• To: CAM Mining, LLC
• Type & Sequence: PR15
• Email Name: LDS
• Media Type: D
• Archive: No

55

In order to judge the credibility of MCC's statements regarding slope stability, the
Division requested the submittal of supporting information. MCC responded by
submitting a report prepared by Geo-Hydro Consultants, Inc., entitled "Landslide Study,
Geo-Hydro Consultants, Mt. Gunnison No. 1 Mine," included within the permit
document in Exhibit 14. This report, prepared in conformance with the current
state-of-the-art, includes design recommendations for the surface facilities to be
constructed within the landslide deposit delineated in the surface facility area of the
West Elk Mine site. One of the design recommendations forwarded within the report is
the installation of a dewatering system consisting of horizontally inclined dewatering
wells installed throughout the affected area, specifically within the portal bench and
access road. Specific engineering design plans for this system have been included
within the permit document. In addition, intricate bin-wall retaining structures were
subsequently included within the design documents in the permit section.

The area of the surface facilities has been the focus of historic and recent landslide
activity. The Division required MCC to demonstrate, through appropriate geotechnical
analyses, that the proposed backfilled surfaces would satisfy the required static slope
safety factor of 1.3. Merrick and Company prepared a "Report of Stability Analyses
and Recommendations for Reclaimed Surface Facilities at the West Elk Coal Company,
Mt. Gunnison No. 1 Mine." The report presents the results of the required stability
analyses and recommendations for reclamation of the affected area.

MCC proposes to return all surface disturbed areas to approximate original contour,
with the exception of the waste disposal sites.

XI. Revegetation

Information regarding the vegetation in the West Elk Mine permit area is found in
Sections 2.04.10 and 2.05.4; Exhibits 31, 32 and 33; and Maps 42, 43 and 44 of the
PAP. No threatened and/or endangered plant species were found anywhere within the
permit area.

Success of revegetation efforts was originally based on reference areas established in
July 1980 and enlarged in 1981. Reference areas were established for mixed shrub and
dry meadow communities and were shown on Map 44.

MCC proposed replacing the two reference areas with the use of a historic reference
area, the Historic Records Study Area (HRSA), for evaluating revegetation success.
Vegetation in the HRSA resembles the expected post-mining vegetation community.
The HRSA is located in a former agricultural and pasture area southwest of the facilities
area as shown on Map 53. Use of the HRSA was approved with PR-7 and is presented
in Section 2.05, page 2.05-69 of the PAP.

The following technical standards were established with TR-125 (approved in 2011) as
the standards that will be used for determining revegetation success on disturbed areas
of the West Elk Mine: minimum live vegetation cover of 53.04 %, minimum herbaceous
production of 180.38 grams per cubic meter, and at least three perennial species of
which two are cool season perennial grasses and one is a cool season perennial forb. No