2011-05-03_PERMIT FILE - M2011015

• Permit No: M2011015
• IBM Index Class Name: PERMIT FILE
• Doc Date: 5/3/2011
• Doc Name: Proposed Blasting Plan Review
• From: DRMS-bmk
• To: DRMS-jle
• Email Name: JLE
• Email Name: BMK
• Email Name: AJW
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources ?vV
COLORADO
1313 Sherman St., Room 215 D I V I S I ON OF
Denver, Colorado 80203 RECLAMATION
Phone: [phone] MINING
FAX: [phone]
SAFETY
Bill Ritter, Jr.
MEMO Governor
Mike-King---
Executive Director
May 3, 2011
Loretta Pineda
Director
/To: Jared Ebert
)From: Berhan Keffelew
v
Re: MV2011-015, Silver Cliff Pit, proposed blasting plan review.
As you requested, I have reviewed the proposed blasting plan for M-2011-015, Silver Cliff Pit.
The only reference to the proposed blasting is mentioned in Exhibit D, mining plan. The operator stated,"
Blast hole drilling will be performed with hole sizes 2.5" - 4.0" diameter and bench height 20'-30'. Blasting will
be performed by a licensed blaster utilizing best non-electrical blasting techniques to minimize ground
vibrations and air blast and each shot will be monitored via seismic recorders placed between the blast and
nearest residence, approximately 2000 feet southeast of the mining area. Mining will progress to the north,
west, and east from the existing mining face located in the north central portion of the property. Typical shot
volumes will be in the range of 2000-3000 tons per round".
The information provided is inadequate for the Division to properly analyze the potential impacts from the
proposed blasting operations at the Silver Cliff Pit. Rule 6.5(4) requires, "sites where blasting is part of the
proposed, mining and reclamation, the Applicant shall demonstrate through appropriate blasting,
geotechnical and structural engineering analyses, that-off site areas will not be adversely affected by blasting"
Therefore the operator must address and answer the following concerns prior to application approval.
1) Given the close proximity of houses and structures to the proposed m.ining-arf-lasting area, the
operator should conduct a per-blast survey of these houses or structures. The pre- blast monitoring
could be in the form of a video, or photograph of existing cracks and visible damages to these
properties. The operator should send a letter to the nearby structure owners, to see if they would
allow the operator access to conduct the pre-blast survey of their structures.
2) The parameter normally used to assess the ground vibration is Peak Particle Velocity (PPV) expressed
in millimeters per second or feet per second (mm/sec. or ft/sec.). Most probable adverse impacts to
structures from a blast occur, from the vibration energy that is released after each blast. Rule 6.5(4)
requires the operator to demonstrate using appropriate blasting, vibration, gcotechnical and structural
engineering analyses to show, adverse impacts to nearby structures will not occur from the proposed
blasting events. Adverse impacts from air blasts, unless the structures are very close to the blast
location, are very rare.
3) In lieu of such a demonstration and in order to protect structures from adverse impacts from vibration
energy, the Division normally places, as a permit condition, the most protective (PPV) that must not be
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Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines