GENERAL33122

• Permit No: C1981033
• IBM Index Class Name: General Documents
• Doc Date: 3/31/1982
• Doc Name: PROPOSED DECISION and FINDINGS OF COMPLIANCE
• From: Mine No. 1, No. 2 & No. 3
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

_79_
XVI. Backfillinq and Grading - Rules 2.05.3(6), 2.05.3(9), 2.05.4(2)(a),
2.05.4(2)(c), 4.09. 4.13, and 4.14
The applicant has correctly observed; "In the canyon areas of the North Fork of
the Gunnison River, the steep topography resembles in many places what could be
called a 'natural highwaZl'.' The existing portals for the Bear No. I and No. 2
mines both occupy "steep slope mining" situations. The proposed portals for the
Bear No. 3 mine are proposed to be developed within the existing portal area of
the abandoned Edwards Mine, which has existed in unreclaimed condition for approximately
50 years. This proposed portal area also occupies a "steep slope mining" situation.
In each of these cases the applicant proposes to seal tree portals in compliance
with the MSHA regulations and partially backfill and grade the portal face-up area.
The applicant proposes to reclaim the portal areas of the Bear No. 1 and No. 2 mines
as depicted in Figure 1 and 2, included on pages 18 and 19 in the supplemental
submittal dated February 17, 1982. In the case of the Bear No. 1 portals, the
entire high-wall will be covered, but the fill will be graded to a lower slope
angle than the original topographic surface. This configuration will allow the
attainment of a static slope safety factor of 1. 3, in conformance with the permanent
program requirements. The backfill and grading plan proposed for the Bear No. 1
mine portal area is, therefore, judged by the Division to be in compliance with
the permanent program regulations.
In the case of the Bear No. 2 mine portals, the applicant proposes to partially
backfill the face-up cut to an elevation roughly half that of the existing high-wall.
In response to comments included in the Division's Preliminary Adequacy Review, the
applicant has completed a geotechnical investigation and stability analysis of the
Bear No. 2 portal area. This analysis was prepared by Rocky Mountain Geotechnical,
Incorporated, in accordance with the prudent state-of-the-art of slope stability
analysis. This analysis, contained in Volume 2 of 2 of the application revision,
dated May 15, 1981, presents a selection of alternatives for backfilling and grading
of the Bear No. 2 mine portal area. The preferred alternative, which the applicant
proposes to implement, relies upon the assumption of a value of the internal angle
of friction for the high-wall materials which exceeds the tested laboratory values
presented with the report. However, Rocky Mountain Geotechnical presents a plausible
rationale for field conditions exceeding normal laboratory-derived values, based
upon observed performance of the existing portal high-wall. To verify t1~e stability
of the proposed backfill and grading configuration, and in response to comments in
the Division's Preliminary Adequacy Review, the applicant has proposed to establish
three monitoring stations on the backfilZed material, to be monitored on a semi-annual
basis for a period of two years. In order to alleviate remaining inadequacies, the
Division finds that the following stipulations are necessary to find compliance with
the permanent program regulations;