ENFORCE22856

• Permit No: C1981019
• IBM Index Class Name: Enforcement
• Doc Date: 10/29/2003
• Doc Name: Blast Review Summary
• From: Byron Walker
• To: Dan Hernandez
• Violation No.: CV2003013
• Media Type: D
• Archive: No

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DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: (303)832$106
Interoffice MEMORANDUM
Date: October 29, 2003
To: Dan Hernandez
STATE OF COLORADO
From: Byron G. Wal el~
Re: Blast Review Summary, Colowyo, C-1981-019
COLORADO
DIVISION OF
MIN ORALS
GEOLOGY
0.EC LAMATION•MINING
SAFETY•SCIENCE
Bill Owens
Governor
Greg E. Wakher
Executive Director
Ronald W. Cottony
Division Director
Natural Resource Trustee
As a result of a review of a record of a February 16, 2003, blast at the Colowyo Coal Mine, the
Division of Minerals and Geology (Division) concluded (theoretical reconstruction) that a
maximum of 9,135 pounds of explosives were detonated during an 8-millisecond time period.
The blast record indicated that 2,970 pounds was the maximum weight of explosives that had
been detonated during an 8-millisecond time period. The Colowyo Permit C-1981-019
designates use of a formula [Rule 4.08.4(]0(c)(i)] to determine the maximum pounds of
explosive allowed to be detonated during an 8-millisecond time period. This amount, for the
blast of February 16, 2003, was (at a distance of 3,161 feet from the nearest occupied dwelling)
3,303 pounds. Colowyo subsequently submitted a seismograph record that indicated that the
maximum allowable peak particle velocity of I.00 inch per second had not been exceeded during
this blast [Rule 4.08.4(10)]. The Division noted that the seismograph had been last calibrated on
December 13, 2001, and required a determination of applicability. The seismograph was
recalibrated on April 29, 2003, and was found to have drifted slightly during operation. The
acoustic drift equated to about 0.83%, and the seismic channels had drifted about 0.75%,
variances that were considered (by Instantel, Inc.) to be of low significance for the microphone
and negligible for the vibration sensors.
As a result of the review findings of the February ] 6, 2003, blast, the blast records of November
2, 2002; Februazy 2, 2003; February 3, 2003; February 6, 2003; February 12, 2003; February 13,
2003; and March 19, 2003 were checked with regard to accuracy of the total weight of
explosives detonated per hole and the maximum weight of explosives detonated per 8-
millisecond period [Rule 4.08.5(11)]. All of the records had entries for the information required
by Rule 4.08.5, plus additional information not required by the rules, though some of the
information was incomplete. Seismograph records of the blasts, except for the blast of February
3, 2003, were included in this review.
In lieu of providing the actual total weight of explosives used per hole, Colowyo's permit allows
its blast records to include hole depth information (drill reports) and a hole loading sheet. From
this information, the total weight in any hole can be determined. A summary of review findings
is as follows:
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey