DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
OFFICE OF THE ADMINISTRATOR
COAL MINE SAFETY AND HEALTH
REPORT OF INVESTIGATION
FATAL FALL OF ROOF ACCIDENT
BOWIE MINE #2 - I.D. NO. 05-04591
BOWIE RESOURCES, LTD.
PAONIA, DELTA COUNTY, COLORADO
DECEMBER 14, 1998
by
BILLY G. FOUTCH
SUPERVISORY COA MINE SAFETY AND HEALTH SPECIALIST, NORTON, VA
CHARLES H. GRACE
CONFERENCE AND LITIGATION REPRESENTATIVE, BARBOURVILLE, KY
GARY E. SMITH, P.E.
MINING ENGINEER, HUNKER, PA
JOSEPH C. ZELANKO, P.E.
PITTSBURGH SAFETY AND HEALTH TECHNOLOGY CENTER
MINING ENGINEER, PITTSBURGH, PA
JOHN R. COOK
PITTSBURGH SAFETY AND HEALTH TECHNOLOGY CENTER
MINING ENGINEER, PITTSBURGH, PA
Originating Office - Mine Safety and Health Administration
Office of the Administrator - Coal Mine Safety and Health
4015 Wilson Boulevard, Arlington, Virginia 22203
Robert A. Elam, Administrator
Release Date: April 22, 1999
OVERVIEW
At approximately 11:35 p.m. on December 14, 1998, a roof fall occurred on the 002-0 working section located in the First East Submains, First Right, Number 8 Room of Bowie Resources, Ltd.'s Bowie Mine #2. The fall resulted in the deaths of Rocky Gallob, a 38-year-old continuous mining machine operator with over 11 years of mining experience and Hector Camacho, a 35- year-old continuous mining machine helper with over 5 years of total mining experience.
The roof fall occurred at the No. 22 coal pillar of the No. 71 Crosscut as the final lift of the pillar was being mined. The diesel ram-car operator, R. J. Wist, was waiting to load his car. He was signaled by Camacho to retreat and while doing so, the mine roof inby him completely collapsed. The roof fall extended from the No. 22 coal pillar into the outby intersection, crushing the remainder of the coal pillar, covering the continuous mining machine, and fatally injuring both the machine operator and his helper. The ram-car operator escaped, uninjured, his life being saved by the attentiveness of his co-worker.
Statements obtained during interviews indicated that ground conditions had deteriorated over the last two shifts prior to the accident. During this period, unusual amounts of heaving in the mine floor had been observed and some timbers had been dislodged or broken and been re-set. At least once during each of these last two shifts, the continuous mining machine and crew had retreated for safety to an outby location.
Despite these conditions, mining was resumed without installing additional or supplemental support. The section foreman was present during earlier mining activity, however had left the area immediately prior to the accident. As the final cut was taken from the coal pillar, the mine roof fell, extending from the No. 22 pillar continuing into the outby intersection.
Mine management failed to take appropriate action to support the mine roof or to otherwise protect persons from hazards related to falls of the mine roof where they were required to work or travel. Despite increasing evidence of deteriorating ground conditions, mining was resumed in the No. 22 coal pillar without the installation of additional support. Appropriate actions by mine management, based upon prevailing conditions, would have been to direct the installation of additional support or to discontinue mining at that location.
The Bowie Resources Ltd., Bowie #2 Mine, located near Paonia, Delta County, Colorado, began operation on or about November 4, 1997. The mine is developed and serviced through three portals consisting of drift openings into the Upper D or D-2 Coal Seam. According to the Approved Roof Control Plan, the coal seam ranges from 120 to 204 inches in thickness.
The principal management officers at the mine at the time of the roof fall were:
William Bear, Jr.........................................Vice President of Operations
Brad Hanson..............................................Mine Manager
Ernal Shaw.................................................Safety Manager
Barry Schreckengost..................................Mine Foreman
Jim Abshire................................................Mine Engineer
On January 29, 1998, Bowie Resources, Ltd., a Colorado corporation, and a subsidiary of AEI
Holding Company, Inc. (AEI), 1500 N. Big Run Road, Ashland, Kentucky 41102, filed a Legal
Identity Report with the Mine Safety and Health Administration (MSHA) listing the following
corporate officers:
Donald P. Brown........................................Director-Chairman
Keith Seiber................................................Director-President
Shoji Nakano..............................................Director
William Bear, Jr..........................................Vice President of Operations
John Baum..................................................Director-Secretary
According to representatives of the mine operator, the portal area, mineral, and overlying surface area are owned, in fee, by AEI.
The mine employs a total of 150 miners and produces coal on one shift per day, seven days per week, utilizing swing and weekend crews. Equipment maintenance is performed on a separate non-producing shift.
Coal is mined by remote-control-operated continuous mining machines, which load directly into diesel powered ram cars which haul the product to the respective loading points where it is dumped onto 48-inch conveyor belts and transported to the surface. Coal is processed to final size on the surface and stockpiled, after which it is loaded into trucks and then transported to nearby silos. From the silos, the product is loaded directly into railcars and shipped to market.
The mine has two sections, comprised of one advancing and one retreating section. The advancing 001-0 section utilizes a three to seven entry system developing headings and gate roads for a planned longwall section. The retreating 002-0 section utilizes a four to eight entry system and develops rooms to the right or south of the panels. The pillars developed from these rooms and accompanying crosscuts are subsequently partially extracted, leaving only bleeder pillars needed for ventilation and examination purposes.
The mining equipment on the 002-0 working section included a Joy Model 12CM12 Continuous Mining Machine, three Jeffrey Model 4116 Diesel Ram Cars, one Jeffrey Model 4115 Ram Car, a Wagner LST5S Scoop, and a Fletcher Model DDR-17 Roof Bolting Machine.
The last MSHA regular Safety and Health inspection (AAA) was completed on December 11, 1998.
THE ROOF FALL
On Monday, December 14, 1998, at approximately 4:10 p.m., the 002-0 working section's evening shift crew traveled underground via diesel-powered pick-up truck. Arriving on the section at approximately 4:20 p.m., the crew, consisting of Keith McFarland, Dennis Linman, Richard Ungaro, Greg Gerhard, Robert Cowie, Eric Neal, R.J. Wist, Hector Camacho and Jeffrey Bagwell, gathered at the section's supply location or "kitchen" outby the active pillar line where retreat mining was scheduled to resume. Rocky Gallob, the continuous mining machine's regular operator, was late in arriving to work.
McFarland, the section foreman, conducted a safety talk. One of the topics discussed during the talk concerned hazards and safety practices related to pillar extraction. Also, reportedly discussed, were problems which had been encountered on the previous shift, including deteriorating roof conditions. These conditions had forced the prior shift's continuous mining machine crew to discontinue and later to resume mining, while extracting the coal pillar immediately inby where the accident was later to occur.
McFarland then issued instructions to the section crew. These instructions included work assignments, pre-operational checks of mobile equipment, and clean-up of the area.
The continuous mining machine was undergoing repairs and was not immediately available for production at the start of the shift. After evaluating the progress of repairs on the machine, McFarland and Hector Camacho, the continuous mining machine helper proceeded to the pillar line to examine the area and to plan the placement of the machine's cable and the mining of the No. 22 pillar. Upon their examination, McFarland reported observing a substantial amount of heaving in the mine floor. After completing repairs on the machine at approximately 5:00 p.m., McFarland instructed members of the crew to "grade" the area of floor heave to allow proper access for mining to commence on the first cut from the No. 22 pillar.
McFarland reported that at 6:00 p.m., mining commenced on the initial cut or lift into the No. 22 coal pillar of the No. 8 room. Hector Camacho, normally the machine operator's helper, operated the machine on the first cut, assisted by Richard Ungaro, whose normal occupation was as a roof bolting machine operator. Shortly thereafter, Gallob arrived and assumed his normal duties and mined the second cut as the machine's operator, with Camacho as helper.
Barry Schreckengost, mine foreman, had also arrived on the working section. According to his statement obtained in interviews, he traveled to the pillar line where he and McFarland observed the mining of the first and second cuts. McFarland stated that the crew experienced some difficulty in mining the first two cuts from the pillar, having to retreat to safety due to falling cap rock. McFarland described what he termed "bouncing noises" as Camacho mined the third cut. The fourth cut was reportedly mined by Gallob without incident. As Gallob continued to operate the machine on the fifth and final cut, McFarland reported hearing falling rock in the interior of the gob. The continuous mining machine crew, Gallob and Camacho, were again forced to retreat to safety as the mine roof showed signs of instability. Approximately fifteen to twenty minutes later, conditions had reportedly stabilized. McFarland stated that he and Gallob discussed the on-going conditions and decided that mining should resume, to complete the mining of the pillar. McFarland stated that both he and Schreckengost then left the pillar line and proceeded back toward the "kitchen" area. McFarland stated that he intended to travel to the surface to check the status of an injured family member and to take Schreckengost with him. Schreckengost reportedly was to examine the roadway on his way out and had just stopped to sign the posting board provided for that purpose.
Mining was in progress to extract the final lift from the fifth cut, when at approximately 11:35 p.m., the roof failed.
Dennis Linman, roof bolting machine operator, and Richard Ungaro, scoop operator, had been assigned to position themselves in the outby crosscut between the No.'s 21 and 22 coal pillars in which "breaker posts" had been previously installed. From this position Linman and Ungaro could look directly into the gob area immediately inby the continuous mining machine crew. Their instructions were to signal the crew by means of the sound from a whistle, or to utilize the light beam from their cap lamps in a "waving" or "flagging" fashion to alert the crew to possible or impending danger. In his interview statement, Linman stated that as he was observing the continuous mining machine, he heard a timber break and some roof material fall in the gob area. To alert the crew members, he immediately began to sound the whistle, but just as the whistle sounded, the roof rock fell in the area of the continuous mining machine. Hearing the whistle sound, Ungaro reported that he observed the machine and crew immediately begin their retreat. He then turned, leaving his position, to assist the crew in handling the machine's trailing cable. The roof collapsed as he rounded the outby pillar corner preventing him from witnessing the event.
At the same time, R. J. Wist, a ram-car operator, had just positioned his machine under the boom of the continuous mining machine and was in the process of loading his car. According to Wist, as he was looking forward from his operator's compartment toward the machine and crew, he heard the whistle blow and saw the signal from a cap lamp, indicating that he should retreat quickly. He further stated that Camacho, the machine helper, yelled at him to back up. Camacho then reportedly turned and took two or three steps inby, in the direction of Gallob and the continuous mining machine. Wist immediately proceeded to leave the area in his ram-car as the roof began to fail. Wist stated that he had only cleared the outby intersection by a narrow margin as the area behind him collapsed, with a portion of the falling mine roof striking the rear of his ram-car. Wist stated that he traveled approximately 50 feet outby, stopped, turned his machine off, and proceeded back, on foot, toward the location of the continuous mining machine, finding it completely covered with rock and debris.
The force of the roof fall was heard and the resulting concussion was felt by the section foreman and other employees located on the working section. They immediately gathered at the scene and called for their missing co-workers. Their calls were unanswered.
RECOVERY OPERATIONS
Following the roof fall, Robert Cowie, one of the ram-car operators, ran for help. Cowie met McFarland, who was in the process of returning to the area after hearing and feeling the concussion from the roof fall. Cowie called to McFarland, telling him that a roof fall had covered the continuous mining machine and that Rocky Gallob and Hector Camacho were missing. McFarland called to Schreckengost, requesting that he travel to the mine telephone to obtain additional personnel to assist in the rescue.
Arriving at the scene, McFarland stated he observed the magnitude of the roof fall and the continuous mining machine's trailing cable leading underneath. A scoop, located approximately two crosscuts outby was immediately trammed to the scene. McFarland instructed Wist, who had remained at the scene following the roof fall, to travel outby to the power center to insure that power to the continuous mining machine had been deenergized. McFarland next instructed Linman, who had rushed to the scene after observing the fall, to travel to the mine telephone and obtain more scoops, in order to speed the work of loading the fallen rock. The crew then began setting additional timbers in the area.
As the work progressed and additional scoops were brought up to the area, additional timbers were set, in succession, leading up to the location of the missing miners. During this period, Schreckengost returned to the scene after coordinating the acquisition of additional personnel, equipment, and supplies. Danny Carter, section foreman on the 001-0 section, also arrived, bringing with him additional equipment and personnel to assist in the recovery effort. Among the additional personnel was Pete Milner, a scoop operator on the 001-0 section. McFarland instructed Milner to assist him in the removal of the fallen rock. McFarland and Milner began their efforts, proceeding with caution. During the work, Jeff Bagwell arrived on the scene. Bagwell, the 002-0 section mechanic, had been attending to work outby the section. Bagwell asked McFarland if power to the area had been disconnected. McFarland told him that Wist had previously attended to it, but requested that Bagwell travel outby to confirm it. Bagwell complied, also shutting off the machine's water supply, and returned to the scene of the accident.
Carter and McFarland next cut the machine's power cable to gain better access to the area. Pulling the cut cable back, McFarland stated that he observed a respirator filter in the rubble, leading him to believe that at least one of the missing miners was close at hand. Milner returned with the scoop to assist. The two cautiously proceeded to roll the fallen rock out of the way. At that point, McFarland reported finding Gallob in a prone position, in close proximity to the outby brow, suggesting to McFarland that the victim had been "running out."
McFarland then called for Danny Carter, the 001-0 section foreman, who was working nearby. The two proceeded to remove the rock by hand until they were impeded by a large section of rock which required the use of a chain. Schreckengost and one of the other miners came up and assisted in removing the rock. Finishing the removal of the rock from Gallob, McFarland immediately checked for vital signs but found none. The crew removed Gallob from the immediate area and continued their search for Camacho, attempting to ascertain his position.
McFarland directed the 002-0 crew to exit the mine. The crew reluctantly left and traveled to the surface. Schreckengost then instructed Carter to remove another of the miners, Jeff Wilson, who was reportedly inexperienced and who had arrived with the other 001-0 crew members to help in the work. Carter complied and returned to the accident scene. Upon his return, Carter told McFarland that the 002-0 crew refused to leave the surface. While the search for Camacho continued under the supervision of Carter and Schreckengost, McFarland returned to the surface, reportedly to console his crew. McFarland stated that upon his arrival on the surface he was met by Ernal Shaw, safety manager and MSHA's Gary Frey and Danny Cerise, who had just arrived from the Delta, Colorado Field Office. McFarland spoke with his crew members. He then briefed the MSHA inspectors, discussing the progress of the recovery.
MSHA had been notified of the accident at 12:27 a.m. on December 15, 1998, by Jim Abshire, mine engineer. Gary Frey, Supervisory Inspector for the Delta Field Office reported that Abshire had contacted him at his home, approximately an hour after the occurrence. Frey contacted MSHA District 9 personnel in Denver, Colorado advising them of the accident and briefing them with information which was available at the time. Frey then contacted Danny Cerise, federal coal mine inspector at his home, instructing him to travel to his duty station in Delta, Colorado where Frey would meet him. While awaiting Cerise's arrival, Frey contacted Abshire, for an update of developments at the mine. At approximately 1:00 a.m., Abshire informed him that one of the miners had been located, but not yet recovered. Frey maintained intermittent contact with the mine and with MSHA district personnel until Cerise's arrival, when they immediately traveled to the mine. They were met by Ernal Shaw, safety manager who briefed them on the on- going recovery, stating that one of the victims had been recovered, and was dead. During the briefing by Shaw and McFarland, a call from underground at 3:17 a.m. announced that Gallob was being transported to the surface. Camacho had not yet been located. Gallob's body arrived on the surface at approximately 3:35 a.m. During this period, Brad Hanson, mine manager, and William Bear, Jr., vice president of operations, arrived at the mine.
After the briefing, the MSHA inspectors immediately traveled underground with Hanson and Bear, leaving the surface at 3:45 a.m. and arriving on the 002-0 working section at approximately 4:00 a.m. Upon their arrival at the accident scene, they were met by Schreckengost who announced that Camacho had just been found and was now partially uncovered. Hanson and Frey quickly examined the area, finding that additional support would be needed. With the installation of the additional support, the work steadily progressed under Hanson's supervision. Camacho's body was recovered at approximately 4:38 a.m. No vital signs were found. At approximately 4:55 a.m., Camacho was transported from the section, arriving on the surface at approximately 5:15 a.m., followed by the MSHA inspectors.
At approximately 5:30 a.m., Frey returned to the surface and contacted Richard Gates, MSHA Acting Assistant District 9 Manager, who advised him of the pending arrival of the investigation team. Frey remained at the mine to obtain preliminary information and documents, and then left the mine at 8:20 a.m. on December 15, 1998.
Billy G. Foutch, Supervisory Coal Mine Safety and Health Specialist, was appointed as leader of MSHA's investigation team. The primary focus of the investigation was to determine the cause(s) and extent of the roof fall and to assess the nature of geologic conditions in the area. The members of the investigation team arrived in Delta, Colorado at approximately 12:00 a.m., on the morning of December 16, 1998, approximately 24 hours following the occurrence of the accident. The team began its investigation the same morning.
MSHA personnel from the Delta and Denver, Colorado offices provided information regarding mine conditions, practices, and plan requirements. A pre-investigation conference and briefing was held at MSHA's Delta Field Office. During this conference, mine and accident information was principally provided to the investigation team by Billy Owens, MSHA District 9 Supervisory Mine Safety and Health Specialist (Roof Control), and by Gary Frey, MSHA Delta Field Office Supervisor.
The on-site portion of the investigation began in the afternoon of the same day, December 16, 1998. Preceding the underground portion of the investigation, mine records were examined in order to determine preexisting conditions and practices. The mine employees did not designate a representative of the miners to participate in the on-site portion of the investigation. The investigation team entered the mine accompanied by company personnel. The accident investigation was organized with personnel assigned to map the accident area, to evaluate the roof control system and conditions, to assess geologic conditions, to determine the extent and magnitude of the roof fall, and photograph, videotape, and collect information. In addition, roof conditions and roof control practices in other areas of the mine were evaluated in order to determine any correlation to similar conditions and practices which may have existed on the 002-0 working section prior to the accident. The first day's investigative assignments were completed within several hours, and the investigators exited the mine. Subsequent examinations of the precise scene of the accident were made during the following days by selected team members to further assess the area as recovery of the continuous mining machine proceeded.
On December 18, 1998, MSHA investigators began conducting interviews of persons with knowledge of the facts and circumstances surrounding the accident. Interviews were conducted with twenty-one mine employees between December 18, 1998, and December 21, 1998. The interviews were held at the MSHA Delta Field Office and at the Bowie # 1 mine complex located near Paonia, Colorado. Two additional interviews were conducted by telephone on January 7, 1999.
Several hourly employees designated Brad Hanson, mine manager, as their personal representative during the interviews. Hanson also served as a personal representative of several officials and agents of the mine operator. However, no hourly employees, officials or agents of Bowie Resources, Ltd. were represented by attorneys. Further, no person interviewed requested that their interviews be kept confidential.
DISCUSSION
General Mine Geology
According to the Keystone Coal Manual, Maclean Hunter Publishing Company, pp. S-47, 1991, coal bearing strata of Colorado are apportioned into eight regions and twenty-one coal fields. The Bowie #2 mine is located within the Somerset field of the Uinta region. This field encompasses the mines operating along the North Fork of the Gunnison River in Delta and Gunnison counties. Six coalbeds are discernable within the region; these coalbeds are designated letter names from A to F (A being the lowest stratigraphic seam).
The Bowie #2 mine operates in the D (or Upper D) seam. The seam is accessed via three drifts at a surface elevation of approximately 6900 feet above sea level. The seam dips toward the northeast (strike south 80 degrees east) at a rate of 5% and topographic highs exceed 8000 feet in elevation in the area. A stratigraphic dip and topographic increase combine to provide a rapid rise in overburden height. According to the approved roof control plan, maximum overburden is 2000 feet above the D-2 seam. The coalbed ranges in thickness from 10 to 17 feet with bony coal present at both the upper and lower contacts. Interbedded shales, sandstones, and coal form the immediate roof while the floor is composed primarily of shale.
The B seam lies about 270 feet beneath the D seam on the Bowie #2 mine property. Reportedly, the King mine was opened near the turn of the century and operated for many years in this lower seam. The mine is now abandoned. Available maps indicate that areas were mined beneath the current Bowie #2 mine workings.
Mine Development and Roof Control History
The Bowie #2 mine development started in late 1997. Three initial drifts were extended to form the five to seven entry wide North Mains. These parallel entries were driven approximately 4700 feet toward the northwest. Two sections were driven eastward off the mains. The 001-0 working section is currently developing entries for a longwall gate road in the area referred to as the D1 Tailgate. The 002-0 working section developed the First East Submains eastward for a total of 81 crosscuts. At this point, development ceased and the section began driving rooms southward and commenced retreat mining activities.
Prior to the roof fall accident, the operator had reported no unintentional falls of the mine roof. Slickensided geologic features occur locally and are controlled through proper scaling and roof support practices. Difficult conditions of a more pervasive nature are present adjacent to "burn" areas. Burn areas are portions of the coalbed, typically near the outcrop, which have been altered through combustion. At the Bowie #2 mine the extent of these areas was estimated using a geophysical technique and the estimates were delineated on the mine map as the B seam and D seam "burn lines". Poor roof conditions were encountered adjacent to the D seam burn line near crosscut No. 61 in the First East Submains. While sandstone roof appeared to be prevalent across the eastern end of the section, observations of test holes drilled in the mine roof adjacent to the burn line indicated the presence of clay beds (1 to 4 feet in thickness). Fractured roof conditions encountered near crosscut No. 81 were also attributed to the presence of a burn line. In this case it was presumed that pronounced vertical roof fractures resulted from ground displacements associated with a burn line in the underlying B seam rather than in the D seam. Mining induced seismic events, referred to as "bounces," "bumps" or "thumps," were other phenomena reported at the Bowie #2 mine. A Dictionary of Mining, Mineral, and Related Terms, Bureau of Mines, 1968, provides one definition of a "bounce" as, "a sudden spalling off of the sides of ribs and pillars due to excessive pressure; a bump. Zern." The apparent correlation between the term "bounce" and the term "bump" was generally confirmed by most of those interviewed. However, although most classified this occurrence as 'normal' in this mine, not all those interviewed indicated that they had experienced "bounces" in the mine. "Thumps" were generally characterized as rock noise, distinguishable from bumps or bounces.
Ground Conditions on the 002-0 Section
According to statements obtained during interviews, ground conditions had been deteriorating in the area prior to the accident. Retreat mining had begun the previous shift on the No. 21 pillar, immediately adjacent to the scene of the accident. Statements obtained during interviews indicated that mining had been completed with difficulty, including the retreat of the continuous mining machine and crew due to unstable roof conditions at that location.
On the first cut taken from the next or No. 22 coal pillar, Keith McFarland, section foreman, stated that the crew reported difficulty, having to retreat to safety "a couple of times" due to falling cap rock. McFarland subsequently reported having to retreat to safety "a couple of times" and some rock falling during the extraction of the second cut.
During the mining of the third cut, McFarland described "bouncing noises." He described a "bounce" as "when the pillar actually yields, you can feel the floor give." McFarland also stated that he had experienced some previous problems with the coal ribs spalling. He attributed the spalling to the coal's "cleat," or main joint in the coal seam, not to the effects of the release of energy as a result of increasing pressure. Richard Ungaro, who had been assigned to observe the mine roof inby the No. 22 pillar, also confirmed that he heard a bump or bounce during the mining of the third cut.
The fourth cut was reportedly mined by Gallob without further incident. Gallob continued to operate the machine on the fifth and final cut. At approximately 11:15 p.m., McFarland reported hearing falling rock on the interior of the gob. The continuous mining machine crew, Gallob and Camacho, were again forced to retreat to safety as the mine roof showed signs of instability. Approximately ten minutes later, Gallob reportedly stated to McFarland that he thought "it" (the roof rock falling) had stopped and asked if he should proceed back in to complete the mining of the pillar. McFarland replied in the affirmative. McFarland stated that, at that point, he and Barry Schreckengost, the mine foreman who had arrived earlier, left the area and proceeded back to the "kitchen" area. The roof fall occurred at approximately 11:35 p.m., only minutes later.
In his interview, McFarland further stated that at the beginning of the shift he had observed that the mine floor, in the crosscuts leading into the subject pillar, had heaved extensively. He estimated that the floor had heaved "3 � to 4 feet between the floor and roof." He further stated that as a result of the heaving, several timbers had broken and required re-setting, including the "turn row," which he described as "pretty much gone." McFarland stated that he had instructed Dennis Linman, a roof bolting machine operator, to assist in bringing the continuous mining machine up to the pillar line, to "grade" the mine floor. As the "grading" of the mine floor progressed, the foreman described its condition as "real soft."
In interviews, Linman, also an eyewitness to the accident, confirmed that at the start of the shift he had been assigned to "clean up" the section. During this work he stated that he had likewise observed the results of an unusual amount of heaving in the mine floor. He stated that he had cleaned up the heaved floor material and had also re-set some timbers in the area. Linman also confirmed the deteriorating ground conditions in the area by stating that he had hoped that more complete caving would occur and relieve the pressure. (It was noted by the investigators that the approved roof control plan submitted by the operator, which was subsequently approved by MSHA, specified only partial pillar extraction, indicating that complete caving of the mine roof was not intended.)
Barry Schreckengost, mine foreman, described the deteriorating conditions on the 002-0 section immediately prior to the accident. He indicated that, prior to the actual mining, he was acutely aware that in this area, the pillars "would be tough to mine." Schreckengost confirmed the floor heave in the area and that no additional support had been installed at the location of the accident.
Norman Wallace, maintenance foreman, had completed the pre-shift examination approximately one hour prior to the miners' arrival on the working section. Wallace stated in his own interview that he had observed nothing unusual during the course of his examination, as evidenced by the Pre-shift Mine Examiner's Report.
Subsequent to the accident, MSHA investigators examined the area. The discovered conditions of roof, rib, and mine floor were documented on the pillar line and in the entries and crosscuts outby the scene of the accident. Measurements indicated that entry height across the section averaged 9 feet. Coalbed thickness reportedly averaged 12 feet. The upper portion of the coalbed was mined to a gray sandstone immediate roof and approximately 3 feet of coal was left in the bottom. Entries were reportedly mined to an 18-foot width. The measured width of the entries averaged 18.5 feet. Rib sloughage at several locations had increased the width by as much as 4 feet, as measured from the deepest point on opposing rib lines. During the development of the First East Submains test holes had been drilled into the mine roof at varying intervals. Rock type and thickness were determined along the length of each hole and the location of any detected fractures was noted. Data from these holes indicated that the immediate roof in the area surrounding the accident scene is predominantly sandstone as well. Available information indicates that there were 15 documented test holes drilled within a 600 foot radius of the accident location. Three of the fifteen holes show a layer of shale in the immediate roof. Two holes contained shale at the 7.5 to 8 foot depth, while the other was a 7 foot hole showing 1 foot of shale at the 6 to 7 foot depth. The remaining holes all show sandstone for the entire length of the hole. Two of these were 11 feet deep while the remaining 10 holes were 8 feet deep. No cracks were noted for any of the 15 holes.
During the investigation, several instances of cutter roof were observed on and outby the pillar line. Roof strata adjacent to several pillar ribs had failed and had fallen away to form a guttered cavity above the rib line. In some instances, nearer the active pillar line, the failures were pronounced. Farther away from the pillar line the condition lessened. Several cutters (two to three feet wide and deep) were observed to have been previously supplemented with additional roof bolts at some point after the guttering had taken place. The most pronounced cutters were located adjacent to pillar numbers 23, 24, and 25. Cutter roof conditions are usually associated with high vertical and/or horizontal stress conditions.
The 002-0 working section was initially developed in an East-Northeast direction which paralleled the direction of the coal cleat at North 75 degrees East. Reportedly, difficult rib conditions prompted a change in orientation to an East-Southeast direction. Although the well- developed cleat system continues to affect opposing pillar corners, the change in orientation improved spalling along the sides of most pillars. As part of the investigation, the degree of rib sloughage present on the 002-0 section was assessed and documented. Conditions ranged from virtually no sloughage to those of severe perimeter sloughage on the section. In general, sloughage was most pronounced along pillars immediately adjacent to the subject pillar line. At these locations the entire periphery of the pillars was sloughed to a high degree. Outby the pillar line the rib conditions varied considerably. Ribs in these areas tended to show a higher degree of sloughage along pillars running in a line to the Northwest from the pillar line. The severity of rib sloughage is most likely attributed to the level of vertical stress acting in a particular location.
At the time of the investigation, floor heave conditions were observed only in the No. 2 entry of the First East Submains inby the active pillar line between crosscuts 72 and 73. However, it was reported that substantial heave conditions had been present on the 002-0 section immediately prior to the accident. As previously pointed out, statements obtained during interviews indicated that floor heave between pillars No. 22 and No. 23 required that the floor be graded with the continuous mining machine. It is possible that additional floor heave could have occurred on the working section but had gone unnoticed during the conduct of the investigation. These features could have been obscured by the movement of equipment in affected roadways. Floor heave is also normally associated with weak floor strata and high vertical and/or horizontal stress.
The Roof Control Plan in effect at the time of the accident was originally approved on August 5, 1997, and had been amended to incorporate or delete various provisions since that date. The plan provides for full overhead support in all advancing roof spans, including entries and crosscuts.
Fully grouted, 3/4 inch diameter, headed, rebar bolts are used on the advancing sections. The minimum bolt length is 72 inches with installation on a maximum of 60 inch centers. The plan also provides for the installation and types of supplemental support to be utilized in addition to the fully grouted bolts, should conditions warrant.
The plan was further amended on November 19, 1998, to incorporate a plan for partial pillar recovery. Roof support on the retreating 002-0 section is maintained with full overhead support in the entries and crosscuts with breaker timbers and radius timbers installed on no more than 5 foot centers. A single row of breaker posts, referred to by company personnel as a "danger row," is also specified by the approved plan, however, no additionally installed supports were indicated in the pillar lifts or splits. The pillars were mined utilizing a remotely operated continuous mining machine. The roof control plan amendment further stipulated that pillar lifts and splits were not to exceed 20 feet in width and when the remotely operated continuous mining machine was used the maximum perpendicular depth of the pillar lift would not exceed 40 feet.
Neither the original plan, nor any of the subsequent amendments submitted by the mine operator, specified the drilling of test holes as a safety precaution or as a prerequisite to roof bolt installation. Statements obtained during interviews indicated that, as an operational company policy, test holes were routinely drilled in the panel entries of both working sections. Test holes were not, however, routinely drilled in the rooms developed for the 002-0 working section, possibly due to immediately planned pillar extraction at that location.
Mining Method and Roof Control (002-0 Section)
The 002-0 section (First East Submains) had been advanced as a five entry panel on 85 foot by 90 foot centers to within approximately 300 feet of the property boundary leaving average minimum size coal pillars of 67 feet by 72 feet in dimension. Entries were mined approximately 18 feet wide and a barrier pillar, approximately 700 feet in width, separated the end of the panel from the previously described "burn-line."
Following development of the First East Submains panel which ended near the "B Seam Burnline," the 002-0 section had advanced 8 rooms to the right (south) of the panel entries. The room entries were developed on 85 by 90 foot centers, using an average crosscut and entry width of 19 feet. After the room pillars were developed, twenty of these were subsequently extracted, leaving bleeder pillars for ventilation and examination purposes and also leaving the last row of room pillars. This last row of room pillars is commonly referred to as the "standing row" and is extracted after the adjacent set of rooms is developed and connected.
The normal retreat mining method used on the 002-0 section was to develop a set of five to seven rooms to the outcrop barrier pillar, mine the "sump-cuts" in the barrier at the rear of the gob, and then to partially extract the developed coal pillars in succession moving down dip in each row.
The standard roof bolting practice placed four bolts per row across the entry. These bolts were typically 6 foot long, 3/4 inch diameter, Grade 60, fully grouted rebar bolts, installed through 8 inch wide, 15 foot long steel straps. Rib side bolts were typically installed within 2 feet of the rib while the inside bolts were installed four to five feet apart. Rows of bolts were typically spaced on 5 foot centers. Additional bolts had been installed in areas affected by sloughage, particularly on pillar corners. Also noted was one area affected by cutter roof where 8 foot long fully grouted rebar bolts had been installed and another area where resin-anchored cable bolts had been utilized due to poor roof. Pillar extraction had resumed the previous shift on the No. 21 coal pillar, located in the "standing row" immediately adjacent to the No. 22 coal pillar where the accident occurred.
Breaker and turn posts, as required for pillar extraction, appeared to have been installed in accordance with the minimum provisions of the approved Roof Control Plan. However, despite deteriorating ground conditions, mining was resumed on the No.22 coal pillar without the installation of additional or supplemental support.
Description and Extent of the Roof Fall
The exact dimensions of the material which comprised the December 14 roof fall could not be determined since the inby area was inaccessible. It was apparent that the area included supported entries to the north and west of the No. 22 pillar being extracted and much of the unsupported span between them. However, as estimated by mapping, the fall measured at least 85 feet in width by 50 feet in length.
Observations confirmed that the roof had fallen to a height near the top of the 6 foot fully- grouted resin roof bolts used to support the development entries. The brow of the mine roof at the recovery site measured 6 feet in height and the tops of several roof bolt holes were visible in the roof above the fallen material. The immediate mine roof contained at least 6 feet of gray sandstone with shale streaks. Although individual beds were identifiable, the strata was not highly laminated. Unit thicknesses appeared to range between 3 and 16 inches. The weight of the fallen material is estimated at 1900 tons.
Conditions of remnant pillars, breaker posts, and turn rows associated with pillars numbered 21 and 22 were observed from locations immediately adjacent to the pillar line. Portions of the larger, inby pillar remnants were visible in both locations as were rows of breaker and turn posts. As previously described, breaker and turn posts appeared to have been installed in accordance with the minimum provisions of the approved roof control plan. In most cases the posts were in contact with the mine roof and floor although a number were buckled or broken. The mined interior of pillar No. 21 appeared to have been partially filled with several feet of rock which had fallen from the immediate roof. However, portions of the remnants of the pillar were visible. In contrast, only a portion of the largest remnant was visible at the No. 22 pillar location. A two to three-foot wide space observed over the outby pillar remnant, referred to by mine personnel as the "safety pillar," indicated that this coal block had collapsed. Fallen roof and broken timbers adjacent to the other outby remnant suggest that this pillar failed as well. No safe vantage point was available to assess the condition of the smaller inby remnant. Significant pillar sloughage was observed outby the subject pillar line in Room 8 and the entries between Rooms 8 and 9.
Contributory Factors to the Roof Fall
Panel geometry and mining sequence likely contributed to increased stress and deterioration of pillars on the active retreat line. During retreat mining, approximately 65 percent of the original coal pillar was extracted, yielding an overall recovery rate of approximately 78 percent. The remaining coal in each pillar was comprised by four pillar remnants left at the four original pillar corners. The largest remnant was located on an inby (southeast) corner and contained 65 percent of the remaining coal. The "safety pillar" was located on the northwest corner, immediately adjacent to the location of the continuous mining machine during the fifth and final cut. This smaller remnant contained, by comparison, approximately 17 percent of the remaining coal. The other 18 percent was evenly divided between the two opposite remnants. The relative strength of the larger remnant may have resisted caving of the mine roof while allowing the immediate roof to deteriorate in the large span between it and the intact outby pillars.
As retreat mining progresses, loads generated by overlying strata are concentrated in the remaining coal and transferred to adjacent pillars. In this case, it appears that as the fifth and final cut was being taken from Pillar No. 22, the load concentrated in the outby remnant (safety pillar) exceeded its load-carrying capability. With the failure of this remnant, the unsupported span in the mining zone increased substantially and may have become unstable. Although overburden loads were transferred to adjacent pillars, the larger inby remnant, and perhaps the gob, the weight of unstable rock in the immediate roof relied largely on the support of the outby remnant pillar.
Rib sloughage, floor heave, and cutter roof are consistent with high stress levels which could have resulted from several factors present on the 002-0 working section. First, yielding and/or failure of pillar remnants within the gob area may have created stress abutments at the pillar line boundaries. As the area of the panel grew, it is likely that the degree of remnant yielding and the magnitude of the abutment grew as well. Second, as mining progressed farther outby, overburden height also increased fairly dramatically. Both dip and topography acted to increase the vertical stress on each successive pillar removed. Third, prior mining in the underlying B Seam appears to have created the potential for vertical stress concentrations above B Seam pillar remnants. Several substantial barriers cross beneath the 002-0 section. The relative significance of each of these factors is difficult to assess. For example, remnants underlying the panel fall along a northwest trend. At the same time, overburden increases in that direction.
Overburden on the 002-0 section increased from a low of less than 500 feet near Crosscut No. 77 to over 900 feet near Crosscut No. 69 in the First East Submains (see Appendix H). As retreat mining progressed outby, nearly each successive pillar was recovered under slightly deeper cover. The No. 1 Pillar was overlain by approximately 500 feet of cover, while cover overlying Pillar No. 22 approached 750 feet at the location of the accident.
The underlying B Seam workings appear to have affected the distribution of stress across the 002-0 section. Portions of the working section located above the B Seam gob areas exhibited generally less rib sloughage than areas associated with underlying abutment zones. Though the interaction was masked somewhat by the influences of overburden height variations and retreat abutment stresses in the area, there appears to be a general correlation between the degree of sloughage and undermining.
SUMMARY AND CONCLUSION
Cause of the Accident
When questioned by MSHA investigators in regard to the probable cause(s) of the accident, responses from interviewees were mixed. While some attributed the probable cause to increased pressures as a result of failing to achieve adequate falls on adjacent pillars, others felt that the mine roof was simply defective at that location. Also notable was the mixture of responses as to what may be done to prevent a similar occurrence. Some stated simply that pillar extraction should be discontinued entirely at this mine. Others contended that either more, or a different type of, support should have been used. Contrastingly, several of the interviewees stated that to have installed additional support in this instance would have made the continued mining of the pillar either impractical or impossible due to the tight clearances available for the passage of the mining machinery.
Statements obtained during interviews indicated that ground conditions had deteriorated over the last two shifts. During this period, unusual amounts of heaving in the mine floor had been observed and some timbers had been dislodged or broken and re-set. At least once during each of the last two shifts prior to the accident, the continuous mining machine and crew had retreated for safety to an outby location. Despite these conditions being present, mining was resumed without installing additional or supplemental support.
Mine management failed to take appropriate action to support the mine roof or to otherwise protect persons from hazards related to falls of the mine roof where they were required to work or travel. Despite increasing evidence of deteriorating ground conditions, mining was resumed in the No. 22 coal pillar without the installation of additional support. Appropriate actions by mine management, based upon prevailing conditions, would have been to direct the installation of additional support or to discontinue mining at that location.
CONTRIBUTORY VIOLATION
30 CFR 75.202 (a)
The mine roof was not adequately supported to protect persons from hazards related to falls of roof in the Number 22 coal pillar and outby intersection of the 002-0 MMU, an active working section where persons worked and traveled.
On the evening of December 14, 1998, retreat mining was in progress on the No. 22 Coal Pillar. Statements obtained during the accident investigation revealed that ground conditions had been deteriorating over a period of two separate working shifts. During this period, unusual amounts of heaving in the mine floor had been observed, some timbers had dislodged or broken and been re-set, however no additional support was added. At least once during each of the last two shifts prior to the accident, the continuous mining machine and crew had retreated for safety to an outby location.
Despite these conditions being present, mining was resumed without installing additional or supplemental support. The section foreman was present during earlier mining activity, however had left the area immediately prior to the accident. As the final cut was taken from the coal pillar, the mine roof fell, extending from the Number 22 pillar continuing into the outby intersection, crushing the remainder of the coal pillar, covering the continuous mining machine, and fatally injuring both the machine's operator and his helper.
This violation was determined to be a contributing factor to the occurrence of the fatal accident.
Submitted by:
Billy G. Foutch
Supervisory Coal Mine Safety and Health Specialist
Charles H. Grace
Conference and Litigation Representative
Gary E. Smith, P.E.
Mining Engineer
Joseph C. Zelanko, P.E.
Mining Engineer
John R. Cook
Mining Engineer
Approved by:
Robert A. Elam
Administrator
for Coal Mine Safety and Health
Related Fatal Alert Bulletin: 
FAB98C27