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Metal and Nonmetal Mine Safety and Health

Report of Investigation

Surface Nonmetal Mine
(Sand and Gravel)

Fatal Powered Haulage Accident

October 29, 2001

Portable Crusher
Circle Paving
Riverton, Fremont County, Wyoming
ID No. 48-01326

Accident Investigators

John R. King
Mine Safety and Health Inspector

Dennis A. Jorgensen
Mine Safety and Health Inspector

Anita L. Goodman
Mine Safety and Health Specialist

Robert A. Johnen
Civil Engineer

Originating Office
Mine Safety and Health Administration
Rocky Mountain District
P.O. Box 25367, DFC
Denver, CO 80225-0367
Irvin T. Hooker, District Manager


On October 29, 2001, Sterling S. Middleton, laborer, age 36, was fatally injured when he became entangled in the discharge belt take-up pulley.

The accident occurred because maintenance was being performed on conveyor components that were in motion.

Middleton had a total of four weeks and two days mining experience all at this operation. Middleton received four hours of training on September 4, 2001, in accordance with 30 CFR, Part 46.


Portable Crusher, a surface sand and gravel operation, owned and operated by Circle Paving, was a mobile plant used to crush and screen sand and gravel at various locations. At the time of the accident, the plant was being operated near the Wind River on the west side of Riverton, Fremont County, Wyoming. The principal operating official was Dana L. Sims, president. The mine was normally operated one, 10-hour shift a day, five days a week. Total employment was six persons.

Material was extracted from the bed of the Wind River using a backhoe. Gravel was extracted from near the river's edge and then hauled by front-end loader to the plant. The material was then screened, crushed and stockpiled. The finished product was utilized for a paving project at the Riverton Airport.

The last regular inspection of this operation was completed on July 31, 2001. Another regular inspection was conducted at the conclusion of this investigation.


On the day of the accident, Sterling S. Middleton (victim) reported for work at 7:00 a.m., along with Mitchell K. Hornecker, superintendent; Charles R. Foreman, crusher operator; Sequoia L. Middleton, Joshua M. Brunner, Julie A. Hornecker, laborers; Thomas A. Lea and Edmund L. Tindall, front-end loaders operators. Hornecker directed all employees to change the screens on the screening units, perform maintenance, and cleanup spilled material.

The plant was started up around noon and operated for about an hour when problems were encountered. The screen decks started to build up with wet material and spillage occurred along the conveyors. Wet material had built-up on the pulley drums causing misalignment of the conveyor belt which allowed material to spill. Foreman shut down the plant and assisted the other employees in removing the material from the screen decks. After the clean-up, the plant was restarted a second time. Foreman again observed that the screens were building up with material so he sounded the siren to alert the employees that he was shutting down the plant. At this time, he observed Middleton standing near the cone crusher. Foreman stated that he looked away to watch the primary feed belt and when he looked back he saw the victim kneeling near the frame of the cone crusher between the feed and discharge belts. Foreman hand-signaled the victim to stay where he was and then looked away to check on the status of the primary belt and screen deck. Foreman then looked back toward the cone crusher area and saw that the victim had become entangled in the discharge belt take-up pulley. He immediately shut down all systems and used his radio to call for emergency assistance. Middleton was pronounced dead at the scene by a local coroner. Death was attributed to massive head and chest trauma.


MSHA was notified at 4:12 p.m., on the day of the accident by a telephone call from Robert Clyde, Circle Paving field agent, to Thomas L. Markve, special investigator. An investigation was started the next day. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of miners.

MSHA's accident investigation team traveled to the mine, made a physical inspection of the accident site and equipment involved, interviewed persons, and reviewed documents relative to the job being performed by the victim. The investigation was conducted with the assistance of mine management, mine employees and the State of Wyoming mine inspectors. The miners did not request nor have representation during the investigation.


� The accident occurred at the top drive/take-up pulley of the under cone crusher discharge conveyor, Company ID No. 17-81.

� The equipment involved in the accident was a Norberg portable cone crusher unit with a material feed conveyor and an under cone discharge conveyor. The machinery was mounted on an over-the-road trailer.

� The trailer was an open frame design with no bed, deck or platform on the framing. The framing consisted of various sizes and shapes of structural members, including beams, angles, channels, and structural tubing.

� The victim had accessed the top of the trailer between the feed conveyor and the discharge conveyor and was positioned on a 3-1/2-inch wide cross beam.

� The conveyor belt involved had a total length of 100 feet and transported material from the crusher to an elevated screen.

� The conveyor belt was not provided with a scraper to clean material from the underside of the belt.

� Mined gravel material was wet and had a tendency to stick to the conveyor.

� There were approximately ten separate conveyors that comprised the system. All conveyors were operated from a single elevated control booth and had to be shut down individually. The distance from the booth to the accident area was approximately 48 feet.

� There was no master cut-off switch for the entire system in the control booth nor were the conveyors equipped with emergency stop switches. The only shut down capability for the entire system was the master switch on the generator which was 100 feet from the control booth.

� The top drive/take-up pulley area would have to be accessed to clean wet material from the belt and drive/take-up pulley, to tighten the conveyor belt to eliminate slippage, or to adjust alignment of the belt.

� The take-up pulley was not guarded to protect persons. There was, however; no ladder, steps, working platform, walkway or scaffold to obtain access to the area.

� The victim had climbed up onto the framework from the ground and walked on the framing members that varied in width from 3-1/2 to 6 inches.

� The 3-1/2-inch beam where the victim had been standing was 63 inches above the ground.

� The distance above the beam where the victim had been standing to the pinch point at the top drive/take-up pulley was 34 inches.


The root cause of the accident was the failure to establish safe operating procedures for cleaning and removing material from machinery. The accident occurred because the equipment had not been deenergized or blocked against hazardous motion prior to the performance of maintenance tasks.


Order No. 6277368 was issued on October 29, 2001, under the provisions of Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on October 29, 2001, when an employee was attempting to remove mud from a take-up pulley under a conveyor belt. This order is issued to ensure the safety of persons at this operation and prohibits all activity at the crushing area until MSHA has determined it is safe to resume normal operations in this area. The mine operator shall obtain approval from an authorized representative of the Secretary for all actions to recover and/or restore operations to the affected area.
This order was terminated on November 1, 2001. The conditions that contributed to the accident no longer exist.

Citation No. 7935670 was issued on November 8, 2001, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.14105:
A laborer was fatally injured at this mine while attempting to conduct clean-up on a conveyor system that was in motion. The power on the system was not turned off nor was it blocked against motion.
This citation was terminated on November 8, 2001, when the operator conducted retraining for all employees with emphasis on lock out/tag out procedures.

Related Fatal Alert Bulletin:
Fatal Alert Bulletin Icon FAB00M06


Persons Participating in the Investigation

Circle Paving
Mitchell K. Hornecker ......... superintendent
State of Wyoming
Donald G. Stauffenberg ......... state inspector of mines
Tom McDonald ......... deputy inspector of mines
Mine Safety and Health Administration
John R. King ......... mine safety and health inspector
Dennis A. Jorgensen ......... mine safety and health inspector
Anita L. Goodman ......... mine safety and health specialist
Robert A. Johnen ......... civil engineer

Persons Interviewed

Circle Paving
Mitchell K. Hornecker ......... superintendent
Charles R. Foreman ......... crusher operator
Tom A. Lea ......... front-end loader operator
Edmund L. Tindall ......... front-end loader operator
Joshua M. Brunner ......... laborer
Julie A. Hornecker ......... laborer
Sequoia L. Middleton ......... laborer
Fremont County, Wyoming
Edward R. McAusland ......... coroner
Brady Patrick ......... deputy coroner
Faye Hill ......... assistant chief county ambulance technician