MINE SAFETY AND HEALTH ADMINISTRATION
ROCKY MOUNTAIN DISTRICT
Metal and Nonmetal Mine Safety and Health
Accident Investigation Report
Underground Nonmetal Mine
Fatal Electrical Accident
FMC Trona Mine
Green River, Sweetwater County, Wyoming
August 28, 1998
Ronald J. Renowden
Mine Safety and Health Specialist
Joel T. Tankersley
Mine Safety and Health Inspector
Robert C. Boring
Rocky Mountain District
P.O. Box 25367, DFC
Denver, CO 80225-0367
Robert M. Friend
James Lee Fenton, underground water systems superintendent, age 53, was electrocuted at about 12:40 p.m. on August 28, 1998, when he contacted a damaged energized power cable. Fenton had a total of 35 years mining experience, 19 of which were at this mine, the last 3 years as a superintendent. He had received training in accordance with 30 CFR, Part 48.
MSHA was notified at 2:15 p.m. on the day of the accident by a telephone call from the safety supervisor for the mining company. He initially believed that Fenton had suffered a heart attack. An investigation was started the same day.
The FMC Trona Mine, an underground operation, owned and operated by FMC Corporation, was located 20 miles west of Green River, Sweetwater County, Wyoming. The principal operating officials were James M. Pearce, resident manager, and John V. Cora, mine manager. The mine was normally operated three, 8-hour shifts a day, seven days a week. A total of 1,060 persons was employed, of this number, 265 persons worked underground.
Trona was mined with continuous bore miners, a longwall machine, and in-situ solution mining. The material was conveyed by belt to the number 2 and 4 shafts, then hoisted to the surface. Mine development encompassed 36 square miles and contained over 2,500 miles of underground roadways. Six shafts provided access to the mine for materials/personnel and for ventilation. The finished products were caustic soda, sodium cyanide, soda ash, sesqui, sodium bicarbonate, and phosphates.
An MSHA inspection was ongoing at the time of the accident.
The accident occurred at the No. 7 shaft sump area between No. 1 crosscut and 598 west. The equipment involved was a flat, four conductor, No. 2 AWG power cable that carried 3-phase, 480 volts alternating current to a Joy shuttle car. The cable was manufactured by Amercable and was rated 600/2000 volts, MSHA P-184, type W. Approximately 240 feet of the power cable extended from a circuit center to the reel on the shuttle car. This section of cable contained 15 splices and repairs. The remaining cable, approximately 260 feet, was spooled on the car reel. The cable was damaged in the form of a puncture that penetrated the outer jacket and extended into a power conductor.
The shuttle car power circuit was protected at the local circuit center by the following equipment:
--- A KAM 225-amp, three-pole molded case, 600-volt AC, adjustable instantaneous trip circuit breaker. The magnetic trip setting range was 625 to 1250 amps. The breaker trip was set at 781 amps, which was within specifications. The breaker was equipped with an under voltage release coil for remote tripping.
--- A Femco GM1000A Ground Sentinel II provided continuity monitoring of the ground wire in the power cable. The unit was in the wireless application, where, the three-phase conductors carried a signal to the shuttle car and the equipment grounding conductor served as the return signal path to the GROUND SENTINEL II. Tests conducted after the accident revealed that the monitor was functioning properly.
--- A Sasser Electric and Manufacturing ground fault trip unit that operated on the "zero sequence" phase unbalance detection principle with a 300:5 current transformer. The trip "test" function revealed that the monitor tripped at about 3 amps, which was within specifications.
A 1,000 KVA/100KW, 4160/480 (wye) combination power distribution center provided 480 volts power to the circuit center in a resistance grounded wye configuration. The size of the neutral grounding resistor at the 480 volt transformer secondary was 18 ohms, limiting the ground fault current to a maximum of 15 amps. The victim contacted a voltage to ground of about 277 volts. His body completed a high impedance path through earth back to the power center. The current flow through the victim was less than three amps, most likely in the milliamp range. The ground fault detector did not open the circuit breaker.
Laboratory tests conducted by MSHA concluded that the cable had sufficient damage to cause the outer surfaces to become electrically conductive in the presence of tap water when energized at the voltage potentials expected during use. Current flows measured during testing were considered sufficient to pose a potential shock hazard. Trona dissolved in tap water was found to significantly increase the relative conductivity of the solution media and higher currents would be expected to occur on the cable's surfaces if the tests were repeated using this solution as the wetting agent.
On the day of the accident, James Fenton (victim) reported for work at the No. 8 Shaft at 8:00 a.m., his regular starting time. He went underground and traveled to the No. 5 shaft to check on various water projects, then continued on to No. 7 shaft sump project where he joined Bob Lester, mine production supervisor.
After lunch, shuttle car operator, Cory Doak, was returning to the sump mining area from the gob when the circuit breaker tripped on ground fault. Doak was not able to reset the circuit breaker, so he placed the switch in the off position.
When Doak did not return to the sump, Fenton and Lester assumed that a problem had occurred. Lester left to get a maintenance man and Fenton and Henry Lewis, miner operator, walked the haulage route. They encountered Doak, who informed them the car was down and the power was off. The three proceeded to the car.
Upon arriving at the car, they noticed that approximately 100 feet of unreeled cable was laying in ruts along the rib. Water had puddled in the ruts. Lewis suggested that they hang the cable on rib rollers. After hanging it, the loader operator was instructed to dump a couple of buckets of dry material on the roadway to eliminate the ruts and the water. After one load of material was dumped, Fenton asked Doak to reset the breaker. He reset the breaker and left it in the "ON" position.
Since the maintenance man had not yet arrived, Fenton, Lewis, and Doak walked along the rib kicking dry material into the ruts. Fenton checked the cable and made remarks about the poor condition of the cable and that it needed to be replaced. Fenton was showing Doak bad spots on the cable. Fenton suddenly turned his back against the rib with his hand on the cable and collapsed. Lewis turned to see what was happening and thought Fenton was having a heart attack. Edward Branson, maintenance man, arrived at about this time and Lewis yelled to him that Fenton was down. Branson turned off the circuit breaker. A faint pulse was detected and arrangements were made to transport Fenton to the surface.
Fenton was first taken to No.7 shaft, however, a hoist person was not on duty. A pulse could not be detected and CPR was started. Fenton was then transported to No.5 shaft and hoisted to the surface. An ambulance was waiting and Fenton was taken to a local hospital where he was pronounced dead at 2:05 p.m.
The direct cause of the accident was the poor condition of the trailing cable and failure to repair the damaged part before it was energized. A contributing factor was failure to protect the cable against mechanical damage.
Order No. 4351289 was issued on August 31, 1998, under provisions of Section 103(K) of the Mine Act:
A death on mine property was reported to MSHA at 2:15 p.m. on August 28, 1998, indicating that a possible heart attack had occurred. Preliminary investigation discovered a small cut in a trailing cable near where the victim was standing. This order is issued to assure the safety of persons at this operation until the affected area can be returned to normal operations as determined by an authorized representative of the Secretary. The mine operator shall obtain the approval of an authorized representative before entering or disturbing the affected area.
This order was terminated on September 1, 1998, after the investigation of the affected area was completed. All electrical equipment was checked and found to be safe for miners to return to work. The affected power cable to the shuttle car was removed from service.
Citation No. 7949802 was issued on September 30, 1998, under provisions of Section 104(a) of the Mine Act for violation of 30 CFR 57.12030:
An accident resulting in a fatality occurred at this operation on August 28, 1998, when a superintendent contacted a damaged spot on an energized 480 volt power cable for the No. 94 shuttle car. Prior to the accident a phase-to-ground fault tripped open the circuit breaker. After attempts to reset the breaker failed, the cable was hung along the rib out of the water. The circuit breaker was reset energizing the cable without repairing the damaged spot on the cable.
This citation was terminated on October 23, 1998, after the mine operator trained all underground employees, instructing them not to energize equipment when a potentially dangerous condition is suspected or exists. This edict will be reinforced during annual refresher training under the electrical hazards section of the company's training plan.
Citation No. 7949803 was issued on September 30, 1998, under provisions of Section 104(a) of the Mine Act for violation of 30 CFR 57.12004:
An accident resulting in a fatality occurred at this operation on August 28, 1998, when a superintendent contacted a damaged spot on an energized 480 volt power cable for the No. 94 shuttle car. The power cable had not been protected against mechanical damage in that it had been run over by the shuttle car, tied to the back by No. 9 wire, and tightly wrapped around a steel rib roller. A few days prior to the accident a section of cable had been dragged on the mine floor and spliced in to the cable feeding the shuttle car.
This citation was terminated on October 23, 1998. Management has and will continue to reinforce existing policies and retrain underground personnel that electrical conductors exposed to mechanical damage shall be protected. Shuttle car operators were instructed to "hug" the adjacent rib with the shuttle car when back-spooling to avoid running over the cable. Underground employees have been instructed not to wrap trailing cables around rib rollers. During annual refresher training the above issues will be reinforced under the section on electrical hazards.
Persons participating in the investigation were:
John V. Cora ..........mine manager
Richard L. Steenberg .......... mine superintendent
Ted K. Walker .......... mine maintenance superintendent
Gordon Christianson .......... mine maintenance electrical supervisor
Michael S. Bonomo .......... mine electrical engineer
Steven R. Schuyler .......... mine safety manager
David L. Thomas .......... mine safety supervisor
Joan K. Carpenter .......... manager-human resources
Rowdy Heiser .......... mine safety engineer
Edward C. Branson .......... class A maintenance man
Henry Lewis .......... continuous miner operator
Cory Doak .......... shuttle car operator
William Masters .......... special projects operator
Robert A. Lester .......... mine production supervisor
Michele Santos-Cranford .......... mining engineer
Brent Peterson .......... shop electrician-8 shaft
United Steelworkers of America Local 13214
Larry Patterson .......... miners' representative
Mine Safety and Health Administration
Ronald J. Renowden .......... mine safety and health specialist
Joel T. Tankersley .......... mine safety and health inspector
Robert C. Boring .......... electrical engineer
Related Fatal Alert Bulletin: