DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
COAL MINE SAFETY AND HEALTH
REPORT OF INVESTIGATION
Surface Coal Mine
Fatal Fall of Highwall Accident
February 20, 2002
Black Thunder Mine
Thunder Basin Coal Company, L.L.C.
Wright, Campbell County, Wyoming
ID No. 48-00977
Accident Investigators
David W. Elkins
Mining Engineer
Donald T. Kirkwood
Supervisory Civil Engineer
Stanley T. Schaeffer
Civil Engineer
Billy D. Owens
Supervisory Mining Engineer
J. Stephen Miller
Training Specialist
Originating Office
Mine Safety and Health Administration
District 9
P.O. Box 25367
Denver, Colorado 80225-0367
Allyn C. Davis, District Manager
Release Date: July 25, 2002
On February 20, 2002, Allen E. Greger, age 49, a bulldozer operator with 21 years of mining experience, drove a Caterpillar 834B rubber-tired bulldozer (also known as a wheel dozer) into the West Pit to perform routine cleanup work near a Marion 351M coal shovel. While Greger was pushing spilled coal toward the coal face near the base of a 230-foot high highwall, a large slab of mudstone fell from the highwall. The slab struck the bulldozer and completely crushed the operator's cab, causing fatal injuries to Greger. The slab was large enough to crush the operator's cab, even though the bulldozer was equipped with a rollover protective structure (ROPS) and a falling object protective structure (FOPS).
The accident occurred when a large slab of mudstone fell from the highwall directly onto the cab of the rubber-tired bulldozer, causing fatal crushing injuries to the operator. The root cause of the accident was the lack of safety procedures to restrict work near the base of highwalls. A contributing factor was that the bulldozer was being operated in a potentially hazardous location near the base of the highwall.
The Black Thunder Mine is a surface sub-bituminous coal mine located 12 miles southeast of Wright, Campbell County, Wyoming. The mine opened in 1977 and is currently operated by Thunder Basin Coal Company, L.L.C., a subsidiary of Arch Coal, Inc. of St. Louis, Missouri. This mine is the second largest surface coal mine in the United States, with an average production of 175,000 tons per day. The mine produced 67.6 million tons of coal in 2001, with 586 employees, 335 of which worked in the pits. The mine works two 12-hour shifts per day, seven days per week.
The overburden ranges from 100 to 230 feet thick, and consists primarily of unconsolidated, discontinuous lenses of clay, silt, sand, mudstone, and sandstone. The Wyodak coal seam has an average thickness of 68 feet and dips one degree to the west-southwest.
The mine has three continuously active pits and one occasionally active pit. Different ground control pit designs are used at the mine depending on whether the pit is a dragline pit, a truck and shovel pit, a boxcut, an entry extension, or an endwall development. Both the overburden and the coal are blasted. Four draglines and one to three shovels are the primary equipment used for removing the overburden. Four to six shovels are the primary equipment used for removing the coal. The shovels load the coal into haul trucks, which transport the coal to truck dumps, where it is crushed, and then conveyed to two train loadout facilities. These facilities load an average of 14 unit trains per day.
The last regular safety and health inspection at the mine was completed by the Mine Safety and Health Administration (MSHA) on January 11, 2002. The Non-Fatal Days Lost (NFDL) injury incidence rate, excluding office and contract workers, for the mine in 2001 was 0.00 compared to a National NFDL rate of 2.13.
The principal officials at the mine are:
Paul Lang .......... General Manager
Jerry Marshall .......... Mine Superintendent
Kevin Hampleman .......... Mine Manager
Michael Hannifan .......... Safety Manager
The 12-hour day shift on Wednesday, February 20, 2002, started at 7:00 a.m. Allen E. Greger, bulldozer operator and victim, was assigned his normal task of operating a Caterpillar 834B rubber-tired bulldozer, company number RT86. Greger's assignment, as usual, was to travel to all of the active pits (three pits were active that day) to clean up coal on the pit floor and to level the pit floor when needed. The normal procedure for cleaning the pit floor was to use the bulldozer blade to push the material toward the coal face, i.e. in a direction perpendicular to the coal face and parallel to the highwall. Greger usually performed cleanup work in each pit several times per shift, with some pits receiving more cleanup work than others, as conditions dictated.
Greger spent most of the shift performing cleanup work in the pits throughout the mine. At approximately 6:00 p.m., at dusk, he entered the West Pit via the 4-West Ramp. John Japp, shovel operator, was operating a Marion 351M shovel (company number 008) in the West Pit, excavating coal and loading it into haul trucks. He saw Greger approach his shovel to clean the pit floor, and he swung the shovel so that the front of the machine faced away from the highwall. Japp deactivated the shovel and waited for Greger to notify him when cleanup had been completed. From his position in the parked shovel, Japp could not see Greger working.
As Greger began his cleanup work, Todd Chatfield, equipment operator, drove toward the number 008 shovel in a Wiseda 240-ton haul truck (company number 223). At the same time, a grader was traveling away from the shovel on the travelway side of the pit. Chatfield pulled his truck slightly out of the travelway and stopped to allow the grader to pass. At this location, Chatfield was approximately 100 yards from the shovel. He observed Greger's bulldozer facing toward the coal face and working between the shovel and the highwall. He watched the bulldozer push material toward the face, back up, and begin to make another push toward the face. At that moment, Chatfield observed a few pebble-sized rocks fall near the bulldozer. A split-second later, a huge slab of mudstone fell off the highwall. The slab struck and completely crushed the operator's cab downward and toward the left side of the bulldozer. The slab also broke the rear axle of the bulldozer, pushing the frame into the ground.
Immediately, at 6:09 p.m., Chatfield called a "Mayday" on his radio to summon the Surface Mine Rescue Team (SMRT). Chatfield ran toward the bulldozer. He could not see Greger inside the smashed operator's cab, nor did he get a response from Greger when he called to him. Frank Myers, pit operations supervisor, arrived at the scene within two minutes of the "Mayday" call. He tried to reach the cab of the bulldozer, but had to retreat because rocks continued to fall from the highwall. Myers called on the radio to request that the life-flight helicopter be dispatched. Shortly thereafter, members of the SMRT arrived. Dan Nelson, the SMRT captain, could not get a response from Greger, and, due to the condition of the cab, determined that there was no room to survive inside the cab.
Japp swung the bucket of the shovel over the bulldozer, to protect rescue personnel from additional debris that was falling from the highwall. The rescue team attached a choker cable between the bulldozer and a Caterpillar 24H grader that had been brought to the scene. The grader had insufficient power to pull the damaged bulldozer. A Caterpillar 657E scraper was then connected to the bulldozer with the choker cable. The scraper pulled the bulldozer to a safe location in the middle of the pit and away from the highwall. Lance Wheeler, a licensed EMT-I, checked Greger and found severe trauma and no pulse. Also, Denny Bohne, a paramedic with the Wright Emergency Medical Service, examined Greger and found no signs of life. Consequently, the life-flight helicopter was canceled.
Working under light from portable light plants that had been brought to the scene, miners cut off the roof of the bulldozer's cab and removed it with a crane. This work proceeded slowly because, on impact, the large slab of mudstone had disintegrated into tightly compacted, silt and clay-sized material which completely filled the cab. This material had to be slowly excavated by hand to provide access for the cutting torches and to uncover Greger. At approximately 10:00 p.m., Greger's body was removed from the bulldozer.
The accident was reported to Larry Keller, MSHA Gillette, WY field office supervisor, at 7:12 p.m., on February 20, 2002. Keller promptly drove to the mine, secured the accident scene, and issued a Section 103(k) order to ensure the safety of the miners.
On February 21, 2002, members of MSHA's accident investigation team arrived at the mine. The team consisted of David W. Elkins, mining engineer and lead investigator from the District Office; Billy D. Owens, mining engineer and supervisor of the Ground Support Group in the District Office; Donald T. Kirkwood, supervisory civil engineer with Technical Support from Pittsburgh, Pennsylvania; Stanley T. Schaeffer, civil engineer with Technical Support from Pittsburgh, Pennsylvania; and J. Stephen Miller, training specialist with Educational Field Services from Denver, Colorado.
Miners were interviewed, the accident scene was examined, records were reviewed, and all the other mine pits and highwalls were examined. No other hazardous conditions were observed during these examinations.
The Section 103(k) order was terminated on February 23, 2002, based on the operator's submittal of two ground control plan revisions dated February 23, 2002. MSHA reviewed these revisions in accordance with 30 CFR 77.1000-1. One revision addressed specific procedures for hazard elimination and coal removal in the West Pit where the accident occurred. The second revision addressed specific procedures for hazard elimination and coal removal in the other areas of the mine. It required rubber-tired machines, operating on the pit floors, to maintain a minimum distance of 30 feet between the operator's cab and the base of the highwall. To ensure that equipment operators maintain a safe distance from the highwall, this revision also required that a berm be constructed between the highwall and the coal haulage roadways on the floor of the South and West pits.
- The ground control plan, dated October 15, 2001, which was in effect at the time of the accident, stated that dragline pit highwalls are generally scaled with the dragline bucket or a drag chain attached to a bulldozer traversing the length of the highwall crest. Highwalls are routinely scaled soon after they are created. The area of the highwall where the accident occurred had been excavated by the dragline less than 6 days prior to the accident and had been scaled.
- At the time of the accident, the Marion coal loading shovel was located adjacent to the area of the highwall where the fall occurred. As it was parked, the back of the shovel was estimated to be approximately 30 feet from the highwall. The bulldozer, which is 12 feet wide, was working between the highwall and the shovel at the time of the accident. The coal face was just past where the fall occurred. The 69-foot thick coal seam in this area had been recently loaded out during the shift.
- The highwall at the accident site consisted of 161 feet of overburden and 69 feet of coal. The overburden sloped back at an effective angle of approximately 57o. No benches were constructed in the overburden. The ground control plan did not require benches on highwalls in dragline pits.
- The overburden consisted primarily of unconsolidated, discontinuous lenses of clay, silt, and sand, which were deposited via a complex system of ancient meandering braided streams. In some places, these materials consolidated to form mudstone lenses with streaks and pockets of sand, sandy mudstone, and sandstone. This sand material tends to convey water more effectively than the surrounding clay and mudstone. When exposed by mining, water from these sandy materials tends to drain from the highwall. The amount and duration of the water flow varies greatly due to the variable nature of the sand pockets. Several intermittently located water seeps were visible on the highwall above the accident site. These were located directly below the mudstone lense from where the mudstone slab fell. It could not be determined conclusively that the seeps caused or contributed to the fall.
- An active overburden de-watering system was in use in the West Pit. It consisted of vertical holes drilled in the overburden in advance of mining. These holes were used to remove groundwater to reduce water seeps on the highwall face. The holes were located in rows that were parallel to the highwall. The spacing between the rows was variable, and the spacing between the holes within a row was approximately 500 feet.
- It is estimated that the mudstone slab that impacted the bulldozer fell from a paleo-channel in the highwall that was approximately 130 feet above the pit floor. Todd Chatfield, who very briefly saw the mudstone slab as it was falling from the highwall, roughly estimated that the rock slab was about the same length and width of the bulldozer (29 feet by 12 feet) and about 3 feet thick. Upon impact with the bulldozer, the slab broke apart, with most of it disintegrating into small silt and clay-sized particles.
- Temperatures for February 20, 2002, as recorded by the mine operator, were:
- The accident occurred at dusk. Sunset at that time of the year was at 5:38 p.m. Lighting in the area consisted of the machine mounted lights on the bulldozer and the shovel.
- Frank Myers, pit operations supervisor and certified Wyoming Surface Mine Foreman, was in charge of supervising and examining all active pits at the mine during the shift that the accident occurred. He stated that he usually examined each pit three or four times each shift. He estimated that he examined the West Pit three or four times on the day of the accident, with the last examination occurring at approximately 4:15 p.m. Other miners stated that they had seen Myers in the West Pit several times that day, as usual. Myers said he had not observed any highwall hazards or unusual highwall conditions in the West Pit. He considered the highwall in the accident area to be safe.
- At approximately 10:00 a.m., on the day of the accident, the West Pit was inspected by Donald G. Stauffenberg, Wyoming State Inspector of Mines, and Robert Solaas, Wyoming State Deputy Inspector of Mines. Both inspectors considered the highwall to be safe at that time.
- During the week preceding the accident, daily inspections of the mine were performed and recorded in accordance with 30 CFR 77.1713. During that time period, including the day of the accident, no hazardous highwall conditions were reported.
- Chad Kalpin, grader operator, was operating the grader in the West Pit at the time of the accident. He said he did not witness the accident because he was driving the grader away from the coal face at the time. He said the area of the highwall from where the mudstone slab fell had not shown any signs of instability prior to the accident.
- Routinely, shovel operators advise rubber-tired bulldozer operators to avoid working near the base of the highwall when potential problems exist. John Japp, shovel operator, stated that, prior to the accident, he considered the highwall where the accident occurred to be safe.
- Todd Chatfield spent most of his shift on the day of the accident operating a haul truck in the West Pit. He said that, prior to the accident, he considered the highwall where the accident occurred to be safe.
- Company policy allows any miner who detects a hazardous highwall condition to report that condition so that it can be remedied. During the 11 hours of the day shift preceding the accident, none of the miners who entered the West Pit reported any hazardous highwall conditions.
- The bulldozer involved in the accident was a 1998 Caterpillar 834B rubber-tired bulldozer, (also known as a wheel dozer), serial number 7BR00554 and company number RT86. It was equipped with a rollover protective structure (ROPS), which also met the applicable criteria for a falling object protective structure (FOPS). The ROPS/FOPS were installed by the equipment manufacturer. According to Caterpillar, the ROPS met the following criteria: SAE J394, SAE J1040c, and ISO 3471. The FOPS met the following criteria: SAE J231 Jan81 and ISO 3449-1984. The ROPS/FOPS met the MSHA requirements of 30 CFR 77.403 and 77.403(a). Due to the severe damage to the operator's cab of the bulldozer, the condition of the ROPS and FOPS could not be examined and evaluated. According to records and testimony, there was no indication that the ROPS and FOPS were in a state of disrepair prior to the accident.
- Greger's pre-operational "Equipment Check List" was not retrieved from the damaged bulldozer. The check list for the previous night shift did not indicate any defects. Greger's checklist for his previous day shift on February 19, 2002, did not indicate any safety defects, but noted that the hook on the back was broken off and the metal ripped open on the back bumper.
- During 2001, Greger spent considerably more time operating the rubber-tired bulldozer that was involved in the accident than any other piece of equipment at the mine.
- Greger received annual refresher training as required by 30 CFR 48.28(b)(4) on January 3, 2002. The Part 48 Training Plan, approved November 13, 1997, required annual refresher training in "Ground Control: Working in areas of highwalls, water hazards, pits and spoil banks, illumination and night work."
- In addition to an MSHA official, representatives from the Wyoming Office of the State Inspector of Mines, the Campbell County Sheriff's Department, the Campbell County Coroner's Office, the Wright Fire Department, and the Wright Emergency Medical Service responded to the accident.
- On January 22, 2002, a fall of highwall accident occurred in the east/west boxcut linking the West Pit with the Rail Boxcut. This accident, which occurred 4,625 feet from the February 20, 2002, accident site, caused severe injuries to a miner. This boxcut pit was 272 feet high with a 20-foot wide catch bench located 69 feet above the pit floor. Unlike the highwall for Greger's accident, which was excavated with a dragline, the highwall in this boxcut was excavated with a shovel using trucks to haul the material out of the pit. The miner was operating a Terragator cable reel vehicle located near the middle of the pit, approximately 53 feet from the highwall. The accident occurred when a rock fell from the highwall and rolled across the bench, which projected it to the middle of the pit where it struck the Terragator. A Section 104(a) citation (S&S) was issued for a violation of 30 CFR 77.1000, and cited an inadequate boxcut pit design. The citation required revisions to the ground control plan to be submitted to MSHA, and set a termination due date of February 25, 2002. After the accident, the operator removed equipment from the boxcut and blocked the area off. Coal extraction from the area was stopped, and steps were taken to blast the south highwall of the boxcut and raise the roadway in the boxcut to the top of the coal seam level. Revised ground control plans pertaining to boxcut design were being prepared to abate the citation at the time of the February 20, 2002, accident.
- In order to terminate the Section 103(k) order that was issued on the day of the fatal accident, the operator submitted two ground control plan revisions on February 23, 2002. These provided interim safety measures to protect miners until a new ground control plan could be developed. MSHA reviewed these revisions in accordance with 30 CFR 77.1000-1 and accepted them. One revision addressed specific procedures for hazard elimination and coal removal in the West Pit where the fatal accident occurred. The second revision addressed specific procedures for hazard elimination and coal removal in other areas of the mine. The second revision required rubber-tired machines, operating on the pit floors, to maintain a minimum distance of 30 feet between the operator's cab and the base of the highwall. To ensure that equipment operators maintain a safe distance from the highwall, this revision also required that a berm be constructed between the highwall and the coal haulage roadways on the floor of the South and West pits.
- Thunder Basin Coal Company submitted a new ground control plan on April 17, 2002, with highwall design and construction modifications addressing the safety concerns involved in the recent fall of highwall accidents. This plan was accepted by MSHA on May 2, 2002. It superceded all previous plans.
| Time | Temp(oF) | Time | Temp(oF) |
| 0049 | 24 | 1347 | 48 |
| 0200 | 26 | 1400 | 37 |
| 0400 | 26 | 1600 | 38 |
| 0600 | 27 | 1800 | - |
| 0800 | 31 | 2000 | 27 |
| 1000 | 41 | 2200 | 28 |
| 1200 | 41 | 2400 | 32 |
The low temperature for the day was 24oF and the high was 48oF. There was no precipitation during the day. For the six days prior to the accident, nightly low temperatures ranged from 17oF to 33oF. Daily highs ranged from 32oF to 57oF. No precipitation was reported for this period.
ROOT CAUSE ANALYSIS
A root cause analysis was performed on the accident. The following root cause was identified:
There was no procedure in place to limit or restrict working close to highwalls, and the bulldozer involved in the accident was being operated a few feet from the highwall. The base of a highwall is a potentially hazardous location due to the possibility of rocks and materials spalling from the highwall. Even though the bulldozer involved in the accident was equipped with falling object protection, it was not designed to withstand the impact of the large slab that hit it. Management did not take steps to address this hazardous situation by implementing safety procedures to restrict work near the base of highwalls.
The accident occurred when a large slab of mudstone fell from the highwall directly onto the cab of the rubber-tired bulldozer, causing fatal crushing injuries to the operator. The root cause of the accident was the lack of safety procedures to restrict work near the base of highwalls. A contributing factor was that the bulldozer was being operated in a potentially hazardous location near the base of the highwall.
A Section 103(k) order, Number 3563241, was issued on February 20, 2002, following the accident to ensure the safety of the miners.
A Section 104(a) citation, Number 7608575, was issued on January 28, 2002, following the fall of highwall accident that occurred on January 22, 2002, in the east/west boxcut linking the West Pit with the Rail Boxcut. This violation cited 30 CFR 77.1000 and stated in part that the ground control plan filed October 19, 2001, did not provide safe working conditions for the miners in the pits. It also stated that an inadequate boxcut design, including highwall bench widths and pit dimensions, allowed falling highwall material to strike an equipment operator working in the center of the pit floor. The citation required the ground control plan to be revised and set a termination due date of February 25, 2002.
At the time of the February 20, 2002, fatal accident, a revision to the ground control plan had not been completed. Citation Number 7608575 had not been terminated and was still in effect. Because of this, the citation was modified on February 23, 2002, after the fatal accident to "allow sufficient time for the mine operator to obtain expertise to develop a long term ground control plan that incorporates prudent engineering design in order to provide highwall stability, control loose highwall debris, and ensure safe working conditions for miners in the mining pits." Since Citation Number 7608575 was already in effect and was modified to require ground control plan revisions following the fatal accident, additional enforcement action regarding 30 CFR 77.1000 and the ground control plan was not taken.
Related Fatal Alert Bulletin:
FAB02C07
Persons furnishing information and/or present during the investigation were:
THUNDER BASIN COAL COMPANY, L.L.C. OFFICIALS
Paul Lang ............... General ManagerTHUNDER BASIN COAL COMPANY, L.L.C. EMPLOYEES
Kevin Hampleman ............... Mine Manager
Michael Hannifan ............... Safety Manager
Gregg Bierei ............... Engineering/Environmental Manager
Steve Beil ............... Operations Engineering Supervisor
Tom Skinner ............... Training Coordinator
Frank Myers ............... Pit Operations Supervisor
Larry Lane ............... Miners' RepresentativeARCH COAL, INC.
Ronald Holmes ............... Mechanic/Rescue Team Captain
Dan Nelson ............... Shovel Operator/Rescue Team Captain
John Japp ............... Shovel Operator
Todd Chatfield ............... Haul Truck Operator
Chad Kalpin ............... Grader Operator
Charles B. Russell, III ............... Director - Corporate SafetyJACKSON & KELLY PLLC, ATTORNEYS AT LAW
(Representing Arch Coal, Inc.)
L. Joseph Ferrara ............... AttorneyWYOMING DEPARTMENT OF EMPLOYMENT
OFFICE OF THE STATE INSPECTOR OF MINES
Donald G. Stauffenberg ............... State Inspector of MinesMINE SAFETY AND HEALTH ADMINISTRATION
Robert Solaas ............... State Deputy Inspector of Mines
David W. Elkins ............... Mining Engineer, Lead InvestigatorAPPENDIX B
Scott A. Markve ............... Coal Mine Safety & Health Inspector
Larry L. Keller ............... Supervisory Coal Mine Safety & Health Inspector
Billy D. Owens ............... Supervisory Mining Engineer, Ground Control Group
Donald T. Kirkwood ............... Supervisory Civil Engineer, Technical Support
Stanley T. Schaeffer, Jr. ............... Civil Engineer, Technical Support
J. Stephen Miller ............... Training Specialist, Educational Field Services
Persons interviewed during the investigation were:
THUNDER BASIN COAL COMPANY, L.L.C. OFFICIAL
Frank Myers ............... Pit Operations SupervisorTHUNDER BASIN COAL COMPANY, L.L.C. EMPLOYEES
Ronald Holmes ............... Mechanic/Rescue Team CaptainWYOMING DEPARTMENT OF EMPLOYMENT
Dan Nelson ............... Shovel Operator/Rescue Team Captain
John Japp ............... Shovel Operator
Todd Chatfield ............... Haul Truck Operator
Chad Kalpin ............... Grader Operator
OFFICE OF THE STATE INSPECTOR OF MINES
Donald G. Stauffenberg ............... State Inspector of Mines
Robert Solaas ............... State Deputy Inspector of Mines