DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
Coal Mine Safety and Health
Report of Investigation
(Underground Coal Mine)
Fatal Fall of Roof Accident
February 18, 2002
Brimstone Mine # 1
Knott County Mining
Kite, Knott County, Kentucky
I.D. No. 15-16893
By
Darlas W. Day
Coal Mine Safety and Health Inspector
Harlan, Kentucky
Originating Office:
Mine Safety and Health Administration
District 7
3837 S. U.S. Hwy. 25 E, Barbourville, Ky 40906
Joseph W. Pavlovich, District Manager
Report Release Date: September 3, 2002
OVERVIEW
On Monday, February 18, 2002, at approximately 2:50 p.m., a 39-year-old roof bolting machine operator was involved in a roof fall accident. The victim was installing roof supports in the No. 6 heading when a large section of the mine roof failed, striking him, and resulting in fatal injuries.
It is the consensus of the investigation team that the accident occurred as a result of the victim working under unsupported roof.
It is the further consensus of the investigation team that the underlying cause of the accident was the positioning of the roof-bolting machine. During the roof bolting process, and contrary to the provisions of the approved roof control plan, the roof bolting machine was skewed at such an angle to the coal rib that the protection afforded by the ATRS system was negated, and therefore exposed the machine operator to unsupported roof.
GENERAL INFORMATION
Knott County Mining Co operates the Brimstone No. 1 Mine, located near Kite, Knott County, Kentucky. The mine extracts coal from the Elkhorn No. 3 coal seam, which averages about 38 inches in height. Overburden ranges up to a maximum of about 800 feet. Approximately 350 to 400 feet of interburden separates the Elkhorn No. 3 seam from the overlying Hazard No. 4 seam. Portions of the Hazard No. 4 seam have been mined on the property. The mine is accessed through five drift openings.
Two mining units produce coal, two shifts per day, at the Brimstone No. 1 Mine utilizing a 'supersection' layout. At the time of the accident, the 'supersection' was developing a barrier block between two previously developed sections. Six headings were being advanced on 47 foot centers with crosscuts on 55 foot centers. The approved roof control plan allows entries and crosscuts to be developed to a maximum width of 20 feet. Mining height typically ranged between 40 and 52 inches.
The roof was supported on development by Grade 60, 5/8 inch diameter, 42 inch long, fully grouted, headed rebar roof bolts. The bolts were installed with eight-inch square, grade 2, donut embossed plates. Maximum spacing between bolts was 4 feet.
The controlling company of Knott County Mining is:
A E I Resources 2000 Ashland Drive, Ashland Kentucky 41101.
Mine officials for the mine are:
John Swiney, Manager
Stewart Bailey, Safety Manager
The last regular Mine Safety and Health Administration (MSHA) Safety and Health Inspection (AAA) was completed on December 12, 2001.
An AAA inspection was on going at the time of the accident.
Description of the Accident
On February 18, 2002, the day shift crew, under the supervision of section foreman David Shepherd, entered the mine at their regularly scheduled starting time of 6:00 a.m. The crew traveled from the surface to the 003-0 working section (MMU) via battery powered rubber tired personnel carriers.
Production started on the section as usual. At approximately 2:00 p.m. the continuous mining machine had completed the cut in the No. 6 Heading and the roof bolting machine operator was installing roof bolts in the No. 6 Right Crosscut.
During this time, Shepherd examined the No. 6 Heading and reportedly did not observe any hazards. Shepherd reportedly spoke to Manual Ritchie, Roof Bolting Machine Operator (victim), who was installing roof bolts in the No. 6 Right Crosscut. Shepherd reportedly told him to install a couple of rows of roof bolts in the No. 6 Heading and then to get the scoop and to clean up some rock that had fallen earlier.
At approximately 2:30 p.m. the scoop operator, Charles E. Mitchell stated that the victim (Ritchie) stopped him and stated that he was going into No. 6 Heading to put up two rows of support and that he would need the scoop to clean up some rock in order for the roof bolting machine to enter the place and to maneuver. Mitchell reportedly started cleaning the No. 6 Crosscut when he heard the sound of falling rock. He called for Ritchie and when he did not get a response, he immediately traveled into the No. 6 Heading. Upon his arrival he saw Ritchie pinned under the fallen rock and called for help. Hearing his call, the section crew immediately came to his assistance.
As the crew began to recover the victim, wooden cribs were installed for purposes of safety, and lifting jacks were used to lift the rock in order to extract the victim. Shepherd examined the victim for vital signs. None were found.
The victim was immediately placed on a stretcher and transported to the surface. Upon his arrival, he was pronounced dead by Knott County Coroner Jeff Blair.
Investigation of the Accident
John Swiney, Mine Manager notified MSHA of the accident, on February 18, 2002 at 3:15 p.m.
MSHA Supervisor Dave M. Jones, of the Hindman Field Office, traveled to the mine and, together with representatives of the Kentucky State Department of Mines and Minerals (KDMM), traveled underground to the 003-0 working section and assisted with the recovery. Following the recovery an investigation of the accident was immediately begun. A 103(k) order was issued to ensure the safety of all persons until completion of the investigation.
Photographs and sketches of the accident scene were made by KDMM on February 18, 2002. Interviews were conducted on February 19, 2002 of seven persons considered to have knowledge of the facts surrounding the accident.
None of those interviewed requested that their statements be kept confidential. The onsite portion of the investigation was completed and the 103(k) order was terminated on February 21, 2002.
Training
Training records were reviewed and all required training was found to be complete.
Discussion
During the investigation the following physical factors were determined to be relevant to the occurrence of the accident:
1. The victim was operating a Roof Ranger I roof bolting machine (Model RR1-13-B C-F, Serial No. 90081) on the 003 section when the accident occurred. This machine was equipped with a safety-arm-type automated temporary roof support (ATRS) system. The dual safety-arm system used two, 6 inch wide by 42-inch long pads as the roof contact device. The machine was not equipped with a canopy.
2. At the time of the accident, the victim was in the process of drilling a hole approximately 33 inches from the right rib. It appeared that the operator had already installed 10 roof bolts in this cut. Two-hole straps had been installed in conjunction with several of these bolts apparently to provide additional support across several sub-vertical joints present at this location. The roof-bolting machine was positioned with the rear of the machine angled toward the left rib. The positioning of the machine placed the operator inby the last row of roof bolts and the support provided by the ATRS system. One roof bolt had been installed inby and an additional, partially drilled, hole was observed immediately adjacent (within approximately 6 inches) of the hole being drilled at the time of the accident.
3. The working section had been developed on 47 foot x 55-foot centers leaving a coal pillar approximately 27 feet by 35 feet in size. Overburden at the accident site was 400 feet. Assuming an in-situ coal strength of 900 p.s.i. and an average mined height of 4 feet, the estimated pillar stability factor for this area is 2.45. Pillar spalling was minimal on the section.
4. Portions of the overlying Hazard No. 4 coal seam have been mined. However, the overlying works are located approximately 400 feet vertically and 800 feet horizontally from the accident site.
5. Entry width near the outby edge of the roof fall measured 21 feet 07 inches and the mined height of the entry was 52 inches. Entry width was measured within the fall cavity after the fallen material was removed; the width was determined to be 21 to 22 feet. The MSHA approved roof control plan limits entry width to 20 feet.
6. The roof was supported with Grade 60, 5/8 inch diameter, 42 inch long, fully grouted, headed rebar roof bolts. The bolts were installed with 8 inch square, donut embossed Grade 2 plates. Outby the accident site, five bolts had been installed per row across the width of the entry. Spacing between bolts in these rows averaged 30.5 to 52.5 inches. The immediate roof at the accident site consisted of gray sandy shale with coal streaks. The first 13 to 16 inches of the immediate roof was composed of a competent shale unit with few coal streaks. Several coal streaks up to 1/8 inch were observed in the brow of the fall cavity above this unit. A substantial slab of the fallen material remained intact after impact. The largest piece measured 21 feet wide by 19 feet 11 inches long by 13 to 16 inches thick. The weight of the fallen material was estimated to be 40 tons.
7. Several sub-vertical joints were observed on the mining section. One such joint was present 2 � feet outby the fall and the outby edge of the fall was aligned in the same orientation. Two-hole straps placed on bolts adjacent to the fall extended across these features.
8. A single roof bolt had been installed within the volume of fallen rock. The bolt was observed to be intact and a cured resin column was present on the top 6 inches of the bolt. The bolt appeared to have pulled from the drill hole in which it had originally been installed. A portion of this drill hole measuring 11 � inches in depth was observed in the back of the roof fall cavity.
9. Roof bolts plates and resin were retrieved from the accident site for the purpose of evaluation and testing at the Pittsburgh Safety and Health Technology Center. Tests were conducted in the Roof Control Division laboratory on February 28 and March 1, 2002. Resin anchorage strength was evaluated by performing pull tests of 5/8 inch and � inch bolts anchored in 1 foot long, 1-inch diameter holes drilled in an Indiana limestone block. The results of these tests were within a range of values typical for the resin support system components tested. In addition, ultimate tensile strength of bolts, bolt elongation and plate deformations were evaluated utilizing a Tinius-Olsen Universal Testing Machine. Test results exceeded minimum values established for these parameters in ASTM F432-95 standards.
Of the physical factors observed during the investigation, Physical Factors Nos.1 and 2 were deemed to be most significant in the determination of causal relationships of the accident. Investigators determined, in the absence of any other information, that the positioning of the machine, with the alignment of the machine at such a skewed angle from the right rib, resulted in the victim's own position under unsupported roof and denying him the benefit of the protection of the ATRS.
An examination of the operator's roof control plan, which had been approved on September 15, 1998, revealed that the positioning of the roof bolting machine at the accident site was contrary to the provisions of the approved plan (Page 9). This was determined to be the major contributing factor to the accident and was cited accordingly (see Enforcement Actions).
Root Cause Analysis
A root cause analysis was performed on the accident. The following root cause was identified:
After viewing the accident scene, investigators made an evaluation of the machine's position relative to the fallen rock. Investigators determined that the skewed angle of the roof-bolting machine resulted in the protection of the machine operator being negated, exposing him to unsupported roof. Investigators also determined that the approved roof control plan contained additional safety precautions to insure protection by the ATRS system. These particular provisions of the approved plan were not being complied with at the time of the accident.
Conclusion
It is the consensus of the investigation team that the accident occurred as a result of the victim working under unsupported roof.
It is the further consensus of the investigation team that the underlying cause of the accident was the positioning of the roof-bolting machine. During the roof bolting process, and contrary to the provisions of the approved roof control plan, the roof bolting machine was skewed at such an angle to the coal rib that the protection afforded by the ATRS system was negated, and therefore exposed the machine operator to unsupported roof.
Enforcement Actions
(1) A 103(k) order, no. 7482746 was issued to Knott County Mining to ensure the safety of the miners until the investigation could be completed.
A 104(a) citation no. 7532813 was issued to Knott County Mining, for a violation of 30CFR, Section 75.220(a)(1) stating, "On February 18, 2002, a fatal fall of roof accident occurred in the No.6 entry on the 003 working section. The victim was operating a single head Fletcher roof bolting machine, S.N.90081, when the accident occurred. The investigation of this accident revealed that the sequence of roof bolt installation and the angle of the roof bolting machine, as positioned at the last row of installed permanent roof supports (roof bolts), resulted in the machine operator being positioned inby these supports and the automated temporary roof support (ATRS) system. This sequence and positioning was contrary to the provisions of the mine operator's approved Roof Control Plan dated September 15, 1998. "
Related Fatal Alert Bulletin:
FAB02C05
APPENDIX A
The following persons provided information and /or were present during the investigation:
Knott County Mining Officials
Coy Lane .......... PresidentKnott County Mining Employees
David Shepherd .......... Foreman
John Swiney .......... Manager
Stewart Bailey .......... Safety Manager
Charles E. Mitchell .......... Scoop OperatorKentucky Department of Mines and Minerals
James Huff .......... Continuous Mining Machine Operator
James S. Amburgey .......... Roof Bolting Machine Operator
Tony Amburgey .......... Roof Bolting Machine Operator
Tracy Stumbo .......... Chief Accident InvestigatorMine Safety and Health Administration
Johnnie Green .......... Inspector, Accident Investigator
Bobbie Sexton .......... Inspector
Keith Conley .......... Inspector
Freddie Moore .......... Inspector
Daniel Johnson .......... Supervisory Coal Mine Safety and Health Inspector
Darlas W. Day .......... Inspector/ Accident Investigator (CMS&H)
Ronald Honeycutt .......... Inspector (CMS&H)
Joseph Zelanko .......... Mining Engineer, MSHA Office of Technical Support