2008-08-12_REVISION - M1980244

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 8/12/2008
• Doc Name: Review of Surface Mine Slope Design and Blasting Vibration Control Plan
• From: DRMS-acs
• To: DRMS-bmk
• Type & Sequence: AM9
• Email Name: BMK
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE: August 12, 2008
TO: Berhan Keffelew
FROM: Allen Sorenson
COLORADO
D I V I S 10 N OF
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
Governor
Harris D. Sherman
Executive Director
Ronald W. Cattany
Division Director
Natural Resource Trustee
RE: Review of Surface Mine Slope Design and Blasting Vibration Control Plan, CrippleCre k and
Victor Gold, Cresson Project, Amendment No. AM-09, Permit No. M-1980-244
The Division of Reclamation, Mining, and Safety (DRMS) engineering staff has reviewed the Surface Mine Slope
Design submitted as appendix 5 to volume IV of the AM-09 application. DRMS has also reviewed other potions of
AM-09 where mine slope designs are described and the drawings where the mine slopes are depicted. In order for
the rock slopes described in AM-09 to be stable, specialized blasting to create final pit walls is required. If the
DRMS were to reclaim the mine pits under bond forfeiture, substantial amounts of specialized blasting may be
required to stabilize mine slopes that have been subject to production blasting. There are no costs dedicated to this
required reclamation blasting in the cost estimates provided by the Applicant. An estimate of these costs must be
provided for DRMS review. The estimate must consider the point in the mine plan where the greatest surface area
of mine slope would require reclamation blasting, which is not necessarily at the point of full mine out of the pits.
If the Applicant wants DRMS to consider reclamation blasting completed concurrently with the mine pits reaching
the pit limits, then a plan for concurrent reclamation blasting that will be enforceable under the terms of the permit
must be provided. If the Applicant wants the DRMS to consider reclamation blasting to be unnecessary for
portions of the pits to be backfilled, then the language in AM-09 allowing essentially total flexibility in the
implementation of pit backfilling must be rescinded, and reclamation cost estimates to allow bonding for
backfilling, at the point in the mine plan when those costs would be maximized, must be provided.
The DRMS has reviewed the blasting vibration information provided in appendix 4 to volume III of AM-09, and
the description of blasting vibration controls to be implemented contained in section 5.4.4 of the project description
in volume I. Some of the language contained in these two portions of AM-09 could be interpreted as being
contradictory. For this and other reasons, the Applicant must commit to the following in order to make necessary
blasting vibration controls enforceable by the DRMS.
1. The blasting will be done using the following minimum scaled distances: 43.8 for blasting in the North
Cresson areas; 35 for all other blasting.
2. The distance input factor for the scaled distance equation will be the horizontal distance from the location
of any blast to the nearest manmade structure not owned or controlled by the Operator. Such structures
shall include the underground workings of the Molly Kathleen tourist mine.
3. Peak particle velocity (ppv) caused by blasting vibration measured at any of the monitoring locations
approved by the DRMS in excess of 0.5 inches per second (ips) shall be reported to the DRMS as soon as
possible after the Operator has knowledge of such measurements. Measurements from any two blasting
events that exceed 0.5 ips, wherefore neither event has the cause of the elevated ppv been investigated and
results accepted by DRMS, shall trigger complete cessation of blasting operations until authorization to
continue is granted by DRMS.
Office of Office of
Mined Land Reclamation- Denver • Grand Junction • Durango Active and Inactive Mines