MAI-2010-09
DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
METAL AND NONMETAL MINE SAFETY AND HEALTH
REPORT OF INVESTIGATION
Underground Metal Mine
(Gold)
Fatal Explosives Accident
May 28, 2010
Discovery Day Mine
Gold Run Enterprises LLC
Forks of Salmon, Siskiyou County, CA
Mine ID No. 04-05222
Investigators
James Fitch
Supervisory Mine Safety and Health Inspector
Brad Breland
Supervisory Mine Safety and Health Inspector
Tom Lobb
Physical Scientist
Originating Office
Mine Safety and Health Administration
Western District
2060 Peabody Road, Suite 610
Vacaville, CA 95687
Wyatt S. Andrews, Acting District Manager
OVERVIEW
On May 28, 2010, James S. Bennett, supervisor, age 62, died when an unplanned delayed initiation of explosives occurred. The victim and Michael Engelke, miner, entered a blast area to check it. When they were within 25 feet of the face, the misfire detonated and both miners were struck by fly rock from the blast. Engelke was injured, hospitalized, and later released.
The accident occurred because management failed to ensure that policies and procedures to protect miners in blast areas were followed. The procedures did not ensure that miners did not return to the blast site for at least one hour after the suspected burning stopped.
GENERAL INFORMATION
The Discovery Day Mine, an underground gold mine operated by Gold Run Enterprises LLC, is located near Forks of Salmon, Siskiyou County, California. The principal operating official is Patrick A. Fagen, manager. The mine normally operates one 10 hour shift per day, for 10 to 14 days, with one to two weeks between rotations. Total employment is 14 persons.
Gold bearing ore is drilled and blasted from stopes in the mine. The broken rock is transported by a haul truck to the primary crusher where it is crushed and processed. The finished product is sold to commercial industries.
The last regular inspection was completed at this mine on February 26, 2010.
DESCRIPTION OF THE ACCIDENT
On the day of the accident, James S. Bennett (victim) started work at 7:00 a.m., his normal start time. Bennett went to the 13 east drift with Ralph Kuntz and Michael Engelke, miners, to set up to drill the next round in the heading. The crew drilled the round before lunch.
After lunch, Bennett and Kuntz loaded the round. Kuntz then left the area. About 8:00 pm, Bennett lit the fuse and went to the inby bend in the 13 east drift to wait for the round to detonate. Engelke went further down the drift toward the 72 crosscut. After the blast detonated, Engelke walked to Bennett and they discussed that the blast did not sound right.
Bennett and Engelke waited for about 15 to 20 minutes before reentering the area. Bennett was walking in the center of the drift, slightly ahead of Engelke. When Bennett was about 20 to 25 feet from the face, several of the still loaded holes detonated. Both Bennett and Engelke were struck by broken rock and debris from the blast.
They left the 13 east heading and started out of the mine, with Bennett assisting Engelke. Bennett and Engelke met Kuntz in the B9 crosscut, who then walked with them out of the mine. The victims were treated and then life-flighted to a hospital in Redding, California, where Bennett died on May29, 2010. The cause of death was attributed to blunt force trauma. Engelke was hospitalized and later released.
INVESTIGATION OF THE ACCIDENT
On May 28, 2010, the Mine Safety and Health Administration (MSHA) was notified at 11:08 p.m. PST by a telephone call from manager Patrick Fagen to MSHA's emergency call center. Brad Breland, supervisory mine safety and health inspector, was notified and an investigation started the next day. An order was issued under the provisions of section 103(j) of the Mine Act to ensure the safety of the miners. A citation was issued for late reporting.
MSHA's accident investigation team traveled to the mine, conducted a physical inspection of the accident scene, interviewed employees, and reviewed conditions and work practices relevant to the accident. MSHA conducted the investigation with the assistance of the state of California Occupational Safety and Health, Mining and Tunneling Unit (Cal/OSHA), the Siskiyou County Sheriff's Bomb Squad, and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE).
DISCUSSION
Location of the Accident
The accident occurred at the face of the 13 east drift. The toe of the muck pile was approximately 17 feet from the face. The floor of the drift was wet and muddy. Individual rocks ranging up to approximately 6 inches wide by 6 inches long and 6 inches thick were observed on the floor past the toe of the muck pile. The upper 3 feet of the face was visible above the muck pile. The blasted face was deeper on the left side than the right. Shock tubes from the detonators, used when the face was loaded, were observed in two holes. Both of these holes were to the right of the center line of the face.
13 East Drift
The 13 east drift extended northeast off the 72 crosscut drift. It was being developed to intersect with the #1 and #2 veins which run northwest to southwest. The drift was 8 feet high and 8 feet wide. Ground control consisted of a mixture of timber, split set, point anchor bolts, and mats. Ground water had been encountered in the face when the lower holes were drilled.
Explosive Product Involved With the Accident
The explosives and detonators used in the blast were as follows:
ANFO (Ammonium Nitrate Fuel Oil) - Alpha Mix Explosives Blasting Agent 1.5D, EX-9311228 NA 0331
Powder - "Dyno." AP Plus 1 � X 8 inch emulsion based 1.1D explosive 18FE04J1-29611
Explosive Boosters - Dyno Nobel Red Stingers 10 gram cast boosters 1.1D
Detonation Cord - DYNO Special 25, UN0065 1.1D
Detonators - "DYNO LP." Nonelectric 1.1B 1 - 11 period delays with 12 foot lead-ins.
- #1 - 500mS delay time
#2 - 800mS delay time
#3 - 1100mS delay time
#4 - 1400mS delay time
#5 - 1700mS delay time
#6 - 2000mS delay time
#7 - 2300mS delay time
#8 - 2700mS delay time
#9 - 3100mS delay time
#10 - 3500mS delay time
#11 - 3900mS delay time
#12 - 4400mS delay time
Detonators - 'Non-Electric' blasting caps (unassembled for safety fuse) 1.4b UN0267, EX- 8511062
Safety Fuse - Red Plastic Coated 1.4S, UNK parameters (Burns at 40 seconds per foot)
Factors Relating to Blasting Practices
No stemming was used for this blast.
Number of caps used - 18 Non-Electric Shock Tube
Number of timing circuits - 1 series
Number of holes per delay period - 2 - 3
Maximum explosive weight used per delay - 10-15 pounds
Range of pounds of explosives used per hole- 4-5 pounds (0.5 lb/ft blast hole)
Type of firing circuit - Detonation Cord initiated Shock-Tube [w/in hole delays]
Blast initiating device - 1 Instantaneous Blasting Cap with 10 feet of Safety Fuse
Contributing Factors of the Explosion
ANFO (ammonium nitrate/fuel oil) is a non-ideal explosive, meaning that its explosive properties are dependent on the conditions of use. The steady state velocity of ANFO varies from approximately 8,000 feet per second (fps) in 1 � inch diameter blastholes to over 15,000 fps in 12 inch or larger blastholes1. This minimum detonation velocity of 8,000 fps is the advertised detonation velocity of a 1 � inch column of ANFO. Lesser velocities are considered a "Low-Order-Deflagration" which can result after or with burning.
The ALPHA ANFO had an expired shelf life and sat for a long period of time in moist conditions. Therefore it would not have been as sensitive to initiation from the primer as it was originally, because ammonium nitrate acts as a desiccant and readily adsorbs water. Another problem resulting from this extended storage is referred to as "Fuel Migration". Fuel Migration is a result of the fuel oil portion separating from the ammonium nitrate during extended storage. Portions of the ANFO become under fueled making the affected product less sensitive to detonation.
Two of the blastholes were reported to have been wet and muddy. The primer used in these two blastholes was the much smaller 10 gram DYNO Stinger instead of the recommended 1 � X 8 inch cartridge of Nitroglycerin Dynamite. The portions of "shock tube" observed remaining in the face at the time of inspection would have been consumed if these two blastholes detonated as planned.
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1 17th Edition ISEE Blaster's Handbook, pg 264
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Training and Experience
James Bennett (victim,) had 20 years of mining experience with 3 months and 2 weeks at this mine. He had received training in accordance with 30 CFR Part 48.
Michael Engelke had 20 years of mining experience with 4 years, 3 months and 2 weeks at this mine. He had received training in accordance with 30 CFR Part 48.
ROOT CAUSE ANALYSIS
A root cause analysis was conducted and the following root cause was identified:
Root Cause: Management failed to ensure that miners were clear of areas where burning explosives were suspected.
Corrective Action: The deteriorated explosives have been removed from the mine site. Management trained all miners in the proper time to wait for suspected misfires or burning explosives.
CONCLUSION
The accident occurred because management failed to ensure that policies and procedures to protect miners in blast areas were followed. The procedures did not ensure that miners did not return to the blast area for at least one hour after the suspected burning stopped.
ENFORCEMENT ACTIONS
Order No. 6398906 was issued on May 29, 2010, under the provisions of Section 103(j) of the Mine Act:
- A serious accident occurred at this operation on May 28, 2010, when two miners were injured by a detonated blast. This order is issued to insure the safety of all persons at this operation. Very little communication has occurred with the plant manager due to poor communications at the mine. A verbal order was issued to the mine manager during a brief telephone conversation at 8:25 a.m. All persons are prohibited from entering the mine.
Note: The inspector was delayed contacting mine management because the phone system was not operating at the mine.
The order was subsequently modified to a Section 103(k) order on May 29, 2010 The Section 103(k) order has not been terminated because the mine is closed and has not operated since the accident occurred
Citation No. 8564422 was issued on October 12, 2010, under the provisions of Section 104(d)(1) of the Mine Act for a violation of 30 CFR 57.6903:
- A fatal accident occurred at this operation on May 28, 2010, when two miners were reentering their work area after initiating a blast. A delayed detonation occurred and they were struck by fly rock and the concussion from the blast. The second miner received serious injures. Mine management engaged in aggravated conduct constituting more than ordinary negligence in that they knew the requirements of burning explosive material, were aware of multiple recent failures at this mine of charges to explode when expected, were aware of an obvious and improper audible report from this blast, and had reason to suspect burning explosives at the blast site, yet failed to ensure that miners waited the proper period of time before returning to the area. This is an unwarrantable failure to comply with a mandatory standard.
The mine is closed and has not operated since the accident occurred. Therefore, the citation has not been terminated.
Related Fatal Alert Bulletin:
FAB10M09
Fatality Overview:
PowerPoint / PDF
APPENDIX A
Persons Participating in the Investigation
Gold Run Enterprises LLC
- Patrick Fagen ............... Manager
Ralph Kuntz ............... Miner
Michael Engelke ............... Miner Bureau of Alcohol, Tobacco and Firearms
- Michael Briw ............... Investigator
Roger Root ............... Investigator State of California, Department of Industrial Relations
- Jarel Snapp ............... Associate Engineer, Mining and Tunneling
Siskiyou County Sherriff's Department
- Robert Buker ............... Bomb Squad Commander
Charles Pipkin ............... Deputy
Ronald Quigley ............... Deputy Mine Safety and Health Administration
- Brad Breland Supervisory Mine Safety and Health Inspector
Tom Lobb ............... Physical Scientist
James Fitch ............... Supervisory Mine Safety and Health Inspector
Steve Kidwell ............... Mine Safety and Health Inspector
