PERMFILE113861

• Permit No: M2004067
• IBM Index Class Name: Permit File
• Doc Date: 11/21/2005
• Doc Name: Exhibits 131-133
• From: City of Black Hawk
• To: DMG
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215 C O L O RA D O
Denver, Colorado 80203 O I v I S l O N O F
M 1 N
RA L$
Phone: [phone] s
FAX: [phone]$106 G E O L O G Y
RE CIANAT ION•NIN ING

DATE: January 25, 2005 UFFTY•S Qf NGE
Bill Owens
TO: Tom Schreiner eovemor
Greg E. Walther
FROM: Allen Sorenson ~ Executive Direaa
Ronald W. ranany
Division DirecYOr
RE: Review of the Geotechnical Aspects of the Application, Clear Creek Natural Resource Trustee
District Water Providers, I.LC, MMRR Quarry, File No. M-2004-067
The Division of Minerals and Geology (DMG) engineering staff have completed a review of the
MMRR Quarry application. In accordance with your request, the review was limited to those portions
of the application related to blasting, rock mechanics, and slope stability. The following issues were
identified and must be addressed by the Applicant before that DMG can recommend approval of the
application.
1. Ettastine Plan
The application provides a very generalized discussion of mitigation measures to be employed to
control offsite impacts that maybe caused by development and production blasting. Importantly, the
application states that blasting will "comply with the Office of Surface Mining (OSM) Guidance
Manual and other regulatory requirements." Adherence to OSM guidelines is satisfactory to meet the
DMG requirement to prevent offsite damage from ground vibration, air overpressure, and flyrock.
However, DMG will require submittal of a concise blasting plan prior to the DMG date for
consideration of the application, or a commitment to gain approval of a blasting plan through the
technical revision process prior to the initiation of blasting at the site. The only problem identified in
the genera] discussion of blasting included in the pending application is the proposal to control ground
vibration with a standard of 2 inches per second (ips) peak particle velocity at the permit boundary.
Since the development and production blasts will generate a ]ow frequency (less than 40 hertz)
component of ground vibration, DMG will require that peak particle velocity be less than 0.75 ips at
any structures not owned or controlled by the quarry operation and less than 0.5 ips at any older
structures with plaster-on-lath walls that may be within the zone of influence of quarry blast ground
vibrations.'
2. Cut Slopes in Access Road Corridor and Processing_Area
The cut slopes proposed are largely in excess of 50 feet in height and up to 150+ feet in height, but no
benching is proposed. These slopes should be benched to allow for revegetation of bench surfaces and
to provide catchments for rock fall. The Applicant must either provide a benching plan for the access
road and process plant cuts, or provide a justification for not installing benches.
3. Highwall Stability and Reclamation Costs
The application commits to benching of the quarry walls to a stable configuration at the perimeter of
the proposed "ten-yeaz"mining area. However, if the reclamation bond were to forfeit prior to
completion of the "ten-year" mine plan, and the final benching configuration were not in place at the
Offrce of Office of Exhibit 131 Colorado
Mined Lard Reclamation Active and Inactive Mines Geological Survey