DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
ACCIDENT INVESTIGATION REPORT
(Underground Coal Mine)
Fatal Fall of Roof
SHOSHONE NO. 1 MINE (48-01186)
CYPRUS SHOSHONE COAL CORPORATION
Hanna, Carbon County, Wyoming
September 11, 1996
David W. Elkins
Originating Office - Mine Safety and Health Administration
P.O. Box 25367, Denver, Colorado 80225-0367
John A. Kuzar, District Manager
On September 11, 1996, at 12:05 a.m., a fall of roof occurred on the face of the 5 Right longwall section. The longwall was idle at the time of the accident. Four miners were standing in the panline, under roof supports, installing mesh in preparation for recovery of the longwall. Without warning, a slickensided piece of top coal, 3 feet thick by 5 feet wide by 8 feet long, fell. The top coal, which had cantilever support from the tips of shields 102 and 103, pivoted around the tips of the shields and landed on the panline, entirely under the roof supports. This resulted in the death, by crushing, of one miner and minor injuries to two other miners.
Shoshone No. 1 Mine is an underground coal mine that is located four miles north of Hanna, Wyoming, on County Route 291. The mine is operated by Cyprus Shoshone Coal Corporation, a subsidiary of Cyprus Amax Coal Company.
The mine has five drifts into the Hanna #80 coal seam, which has an average thickness of 20 feet. This mine was originally opened by Carbon County Coal Company, circa 1969. Cyprus Shoshone Coal Corporation purchased the mine in 1987. The mine has 2 active working sections. One working section uses a remote controlled Joy 12CM-12 continuous mining machine, two Joy 10SC shuttle cars, a Fletcher CHDDR-13 double boom roof bolter, and belt haulage. The other working section is a longwall that uses 140 Kloeckner- Becorit, 500-ton two-leg shields, an Anderson Mavor model 1000 shearer, and belt haulage.
The mine employs 90 underground miners and 21 surface workers, and has a daily production of approximately 5,700 tons of coal. The mine works two 10-hour production shifts per day, from Monday through Saturday. The mine has an extensive history of spontaneous combustion of the coal and liberates negligible amounts of methane. The mine has a petition for modification which allows 2 entry development of longwall panels. This petition was requested due to poor roof conditions and to reduce the possibility of pressure bumps.
In the area of the accident, the depth of cover was 600 feet. The immediate roof consisted of a 4-foot layer of top coal overlain by a main roof consisting of thinly stratified, weakly laminated shale, sandstone, siltstone, and claystone. The top coal was left in place to form a stronger immediate roof and to prevent deterioration of the main roof. The average mining height was 11 feet. Primary roof support along the longwall face was provided by 140 Kloeckner-Becorit, 500-ton two-leg shields. Most of the shields were equipped with face guards (a.k.a. face sprags). Primary roof support in the headgate and tailgate consisted of 6-foot long, 3/4-inch diameter, fully-grouted resin bolts installed on 4-foot centers crosswise by 5-foot centers lengthwise. Supplemental support in the tailgate consisted of two rows of cribs on 5-foot centers.
A regular safety and health inspection was ongoing at the mine prior to the accident.
The principal officials at the mine are:
Dewey Tanner........................General Manager
Ernal Shaw.............................Manager of Safety
DESCRIPTION OF ACCIDENT
On Tuesday, September 10, 1996, at 2:01 p.m., the preshift examination of the 5 Right longwall section was completed. The examiner did not observe any hazardous conditions. At 4:00 p.m., the swing shift production crew entered the mine. Eighteen miners and foremen traveled to the 5 Right longwall face, which was located 40 feet inby crosscut 4 of the 5th Right panel. The longwall was idle for this shift because the crew had to install mesh in preparation for recovery of the longwall equipment.
The work procedure for installing mesh during this shift consisted of hanging rolls of flexible synthetic mesh (Dywidag Fortrack 200/80-30 Geogrid) from the tops of the shields, parallel to the face. Installation of an 85 foot long roll of mesh proceeded as follows: First, the mesh was unrolled for approximately 2 feet. This length was placed between the tops of the shields and the roof. Then, one or two miners would hold the roll of mesh in place while a roof bolter operator stood under a shield and used a Gopher G350/3 hand-held roof drill with a telescopic leg to drill an angled hole in the roof near the tip of a shield. Next, a two-foot long resin bolt was passed through the mesh and installed in the hole. This bolt anchored the mesh in place. This procedure of installing bolts was repeated every 15 feet or so along the face for the entire length of the roll of mesh.
Once a roll of mesh had been installed, the above procedure was repeated until rolls of mesh had been installed for the entire length of the face. Then, the longwall would resume operation and advance for approximately 40 feet to the recovery room. The mesh would be unrolled as the longwall advanced. Since the mesh was anchored on one end by the roof bolts, advancement of the shields would cause the mesh to cover the tops of the shields entirely. This would help control the roof and gob when the shields were removed.
During this shift, the miners were divided into small groups at different locations along the longwall face. Each group was to install rolls of mesh. Near the end of the shift, all of the mesh had been installed along the face except for a length of approximately 100 feet. Two groups combined to finish this job. The combined group began to install a two-foot roof bolt near shield 103. Alan Vaughn was operating the hand-held roof drill with the assistance of Ed Buckendorf, while Loid D. Caleb (victim) and Jim Welch held the roll of mesh in place. All four men were standing in the panline under the shields. At approximately 12:05 a.m. on Wednesday, September 11, 1996, after the hole had been drilled approximately one-foot deep, a large piece of top coal fell from between the face and shields 102 and 103. Vaughn, Buckendorf, and Welch all saw the coal begin to fall and ran. Welch shouted for everyone to run. The top coal, which had cantilever support from the tips of shields 102 and 103, pivoted around the tips of the shields and landed on the panline, entirely under the roof supports. Loid Caleb was totally covered by the solid piece of coal, which measured 3-feet thick by 5-feet wide by 8-feet long. Alan Vaughn's lower left leg was pinned between the piece of top coal and the spill plate, and Ed Buckendorf's back was scratched by the hand-held roof drill as it fell.
All of the work groups along the longwall were summoned to help rescue and aid the victims. The miners moved the panline, via the double-acting conveyor push-ram on shield 103, in order to free Vaughn's leg. The miners used come-alongs and chains attached to the shields to lift the piece of top coal off of Caleb. It took approximately 20 minutes to extract him. An emergency medical technician examined Caleb at the scene and determined that he was dead. Nevertheless, Caleb was promptly removed from the mine, where he was formally pronounced dead by the Carbon County Coroner.
PHYSICAL FACTORS INVOLVED
- Five certified foremen and 3 miners examined the roof in the
area of the accident within 2 hours prior to the accident.
All of them considered the roof to be safe.
- Caleb, Welch, Buckendorf, and Vaughn were all positioned
under the location where the top coal fell. All but Caleb
were positioned near the outside edges of the top coal and
were able to jump out of the way when they noticed that the
roof was falling. Caleb, being positioned directly under
the middle of the top coal, was unable to escape.
- Vaughn and Buckendorf were standing in the panline
approximately one foot away from the spill plate while they
were drilling the angled hole. When the top coal began to
fall, Vaughn tried to climb over the spill plate, but his
leg became trapped between the top coal and the spill plate.
Whereas, Buckendorf ran in the panline away from the falling
top coal, but was hit in the back by the falling hand-held
roof drill. A tendon in Vaughn's left leg was bruised, but
no bones were broken. The scratches on Buckendorf's back
did not require treatment.
- The top coal that fell was heavily slickensided, and all
sides were smooth. Therefore, it is unlikely that there
were warning signs that the top coal was loose or could
- Slickensided coal is a geological anomaly for this coal
- All witnesses to the roof fall stated that there were no
audible or visible warning signs that the top coal was
likely to fall.
- The victim, Loid Caleb, had received training in accordance
with Title 30 of the Code of Federal Regulations, Part 48.
He had over 7 years of experience as a longwall miner.
- The forepoles on all of the shields in the vicinity of the roof fall were fully extended. The face guards on all of the shields in the vicinity of the roof fall were retracted. The face guards had to be retracted in order to install the mesh.
The accident occurred due to an undetected geological anomaly in the top coal, which resulted in a roof fall. This roof fall resulted in a fatality and two injuries despite the fact that all of the victims were positioned under roof supports at the time of the roof fall.
There were no violations of Title 30 of the Code of Federal Regulations that contributed to the accident.
Respectfully submitted by:
David W. Elkins
Assistant District Manager For Inspections
John A. Kuzar
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