APPCOR11247

• Permit No: C1981047
• IBM Index Class Name: Application Correspondence
• Doc Date: 7/23/1982
• Doc Name: REVIEW OF SUPPLEMENTAL SUBMITTALS FOR THE BLUE RIBBON MINE
• From: MLR
• To: RICH DOMINGUE
• Media Type: D
• Archive: No

I II lllllllllllll III
STATE OF COLORApO qif RAgp D. ~AMM. Gnvcrn o•
D EPAflTMENT OF NATURAL RESOURCES
D. Monte Pascoe, Execu true Director
A'ILiVED LAND REf,LA~11A'TiON
423 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
David C. Shelton
July 23, 1982 DlfeCtOf
T0: Rich Domingue '•
/7 (1 n
FROM: Jim Pendleton y`~%~~-'~
RE: Review of Supplementa'Z Submittals for the Blue Ribbon Mine
~_~ %
Pursuant to your request, I have reviewed the supplemental materials submitted
by [destern Associates, Inc., in response to your draft findings document
For the Alue Ribbon Mine. The applicant submitted several revisions to the
• operation facilities sections and to the reclamation plan sections of the
original application. In addition, the applicant submitted a stability
analysis for the haul road at the Blue Ribbon !Sine. I forward the following
comments for your consideration.
Aline Facilities
The applicant has amended this section of the application to describe the
geologic setting of the haul road, The applicant observes that the cut
slopes do not attain the normally required static slope safety factors (Rule
4.03,1(3)(c) along those portions of the road cut into non-bedrock colZuvial
material. The applicant further observes, in response to requirements of
Rule 4.03.1(3)(c)(i), that this inadequacy should not result in significant
environmental harm because sliding is not expected to occur. If landslides
occur, the applicant proposes to repair the damage and remove the slide debris.
The applicant observes that "the disturbed area is small and that reclamation
will provide a final slope with an adequate stability." The applicant refers
the reader to Appendix D for support of these contentions.
Haul Road Stability Analysis
This stability analysis, prepared by Rocky hfountain Geotechnical, Inc.,
consultant to the operator, appears to be in keeping with the state-of-the-art
in those techniques which it describes. It is, however, inadequate to
completely satisfy our regulatory requirements.
The stability analysis uses material strength properties derived during an
earlier analysis by the same consultant of a landslide problem occurring at
the neighboring portal facilities. Utilizing these peak and residual material
shear strengths, the consultant performed a sensitivity-type analysis of
several representative road cross-sections; (I) completely colluvial road
cut, (2) partial bedrock/colZuvial road cut, and (3) total bedrock road cut.
This anaZUSis demonstrates that the road cut slopes are marginally stable in
all conditions. The analysis suggests that cuts c~ihich penetrate a thickness
of colluvium greater than 8.5 to 10.5 feet may not achieve the required
static slope safety factor in excess of 1. 5. The consultant's report concludes