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On Saturday, May 20, 2006, an explosion occurred at approximately 1:00 a.m. in the sealed A Left Section of the Kentucky Darby, LLC, Darby Mine No. 1, resulting in fatal injuries to five miners and injuries to one miner. At the time of the explosion, six miners were underground during a non-producing shift.
Prior to the explosion, four miners were on the B Left Section preparing to perform routine maintenance work on equipment. Two miners from the B Left Section who had worked the afternoon shift remained after their shift and traveled to the seals which were constructed to isolate the abandoned A Left Section from the active mine.
The two miners rode a non-permissible battery-powered personnel carrier (buggy) down the return airway with a set of oxygen – acetylene torches for the purpose of removing metal roof straps from the roof that intersected the No. 1 and No. 3 Seals. One of these miners was the afternoon shift section foreman.
A methane explosion occurred behind the seals at A Left, which was caused by the cutting of a metal roof strap that passed through the No. 3 Seal. The forces from the explosion resulted in fatal injuries to the two miners and complete destruction of the seals. Forces from the explosion also damaged conveyor belt structure, roof supports, and ventilation controls.
The four miners who were working in the B Left Section attempted to evacuate and encountered thick smoke approximately four crosscuts outby the section power center. At this point they donned their CSE SR-100 self contained self rescue (SCSR) devices and attempted to continue their evacuation. During the evacuation, at least two of the miners intermittently removed their SCSR mouthpieces to communicate. The miners eventually became separated from each other. One miner survived and three died due to carbon monoxide poisoning with smoke and soot inhalation.
The accident occurred because the operator did not observe basic mine safety practices and because critical safety standards were violated. Mine management failed to ensure that proper seal construction procedures were utilized in the building of the seals at the A Left Section. Mine management also failed to ensure that safe work procedures were used while employees attempted to make corrections to an improperly constructed seal. Furthermore, mine management failed to adequately train miners in proper SCSR usage and escapeway routes.
In addition to a 103(k) Order, the company was cited for six conditions and/or practices which contributed in some way to the accident. An additional thirtyseven citations and orders were issued during the investigation, but were not considered to have contributed to the accident.
Darby Mine No. 1 (Darby) is an underground coal mine located approximately 26 miles east of Harlan, Kentucky, on State Route 38. The mine is operated by Kentucky Darby, LLC, of Middlesboro, Kentucky, under contract with Jericol Mining, Inc., of Cumberland Gap, Tennessee. The Kentucky Darby, LLC articles of organization list Ralph Napier, John D. North, and Connie G. Napier as members of the limited liability company. The principal official at the mine is Ralph Napier, who is the superintendent and the person in charge of health and safety.
The mine began production on May 28, 2001, in the Darby coal seam, which has an average thickness of 56 inches. The Owl coal seam, which has an average thickness of 36 inches, is above the Darby seam and was mined with the Darby seam in various locations. The resulting mining height varied from approximately 40 inches to 144 inches. At the time of the last regular health and safety inspection, the daily methane liberation rate was 38,707 cubic feet.
Description of Accident
Approximately two months prior to the accident, the company completed mining in the A Left Section and built three seals, constructed of Omega 384 blocks, to seal off the worked-out area. The seals were built over the course of three working shifts under the supervision of Amon Brock, afternoon shift foreman, and Mark Sizemore, day shift outby foreman.
After construction, the seals were referred to as the "return seals" to differentiate them from another set of seals located off the intake air course. The return seals were also referred to by number, with the No. 3 Seal being the furthest inby of the three.
On May 19, 2006, the weekly examination for hazardous conditions was conducted on the day shift by Mark Sizemore. During this examination, Sizemore was accompanied by Mitchell (Tom) Lunsford, mine examiner, and the two traveled to the areas requiring examination by non-permissible batterypowered personnel carrier.
At approximately 9:00 a.m., they arrived at the No. 3 Seal in the return air course and Sizemore performed a visual examination and tested for methane with a hand-held instrument. The maximum methane concentration was reported to be 0.1 percent, and no hazards were noted by Sizemore.
At approximately 3:45 p.m., the afternoon shift crew entered the mine to begin the scheduled production shift. The crew consisted of Amon Brock; Jimmy Lee, shuttle car operator; Travis Blevins, shuttle car operator; Randy Fields, continuous mining machine operator; Jeff Coker, roof bolting machine operator; Clark Cusick, roof bolting machine operator; James Philpot, miner helper; and Patrick Cupp, belt attendant.
The shift progressed normally until the conveyor chain on the continuous mining machine broke. A new link was installed in the 5 conveyor chain and the crew continued mining throughout the remainder of the shift.
At approximately 11:00 p.m., the midnight (maintenance) shift began. The midnight shift crew consisted of George (Bill) Petra, foreman; Roy Middleton, electrician; Paris Thomas, mechanic; and Paul Ledford, roof bolting machine operator. Petra and Middleton traveled by battery-powered personnel carrier to the working section.
Shortly after this, Thomas and Ledford traveled underground on a separate personnel carrier to the No. 4 Belt Drive where they discussed the status of the conveyor belts with Cupp.
After this discussion, they separated to observe the conveyor belt drives for the remainder of the afternoon shift. Ledford traveled to the No. 3 Belt Drive and Cupp went to the No. 2 Belt Drive. Thomas remained at the No. 4 Belt Drive area.
At approximately 12:35 a.m., Ledford returned to the No. 4 Belt Drive. He and Thomas then traveled to the working section. Cupp concluded his activities at the No. 2 Belt Drive and exited the mine at approximately 12:40 a.m. At approximately 12:45 a.m., the afternoon shift crew, with the exception of Brock and Lee, boarded a battery-powered mantrip and traveled toward the surface.
They passed the oncoming midnight shift crew in the vicinity of the section power center. Brock and Lee boarded a personnel carrier loaded with an oxygen cylinder, an acetylene cylinder, a cutting torch, and other tools. They traveled in the return air course to the A Left Seals.
The physical evidence suggests that Brock and Lee arrived at the area of the return seals and commenced to cut metal roof straps that had been placed in the area as roof support but which had not been removed when the seals had been built.
The acetylene cylinder and cutting torch were found in the area as was a piece of roof strap that gave indications that it had been cut with a torch.
Brock had a methane detector with him but it is clear that it was not being used to check continuously for methane given that it was found in his pocket after the explosion. The detector was functional since it was giving off an alarm when the body was found.
There is no indication that any test for methane was made behind the seals before the cutting commenced. There was no means available to sample the atmosphere behind the No. 3 Seal. Therefore, a cutting torch should not have been used in the vicinity of the seals.
The afternoon shift crew arrived safely on the surface at approximately 1:00 a.m. A few seconds after exiting the mine, they were buffeted by a gust of air, dust, and debris coming out of the portals of the mine.
Initially they believed that either a massive roof fall or a collapse of the highwall had occurred. The crew 6 concluded that an explosion had occurred when the odor of burned coal reached the portals.
Meanwhile, after the afternoon shift crew departed from the working section, Petra began examining the face areas for hazardous conditions. Middleton, Ledford, and Thomas dispersed to perform other duties on the section. While on the working section, they also heard the explosion.
Petra gathered the crew together and informed them that an explosion might have occurred because Brock and Lee had taken tanks and a cutting torch into the return. The crew boarded two personnel carriers and began traveling in the outby direction in the intake travelway, which was the primary escapeway.
They encountered dense smoke approximately four crosscuts outby the section power center, at which point they stopped and donned SCSRs. They boarded a single personnel carrier and continued traveling in the outby direction. The crew did not have a detector capable of detecting carbon monoxide.
After traveling approximately 300 feet, the personnel carrier became lodged on debris from an overcast that had been extensively damaged by the force of the explosion. The crew got off of the vehicle and proceeded on foot until they reached the power center located one crosscut inby the No. 4 Belt Drive.
Somewhere near this point, Ledford and Middleton removed their SCSR mouthpieces and discussed how they should exit the mine. Ledford informed Middleton that he had located the high-voltage power cable and that he intended to follow it to the surface. Middleton told Ledford that he was going back to find the power center.
After another short discussion, Ledford began walking outby in the No. 5 Entry, using the high-voltage power cable as a guide. Ledford had no further contact with the other miners.
Ledford traveled approximately 1,050 feet in the No. 5 Entry until he reached a point just inby the No. 3 Belt Drive, where he collapsed and lost consciousness. Ledford regained consciousness at approximately 3:05 a.m. and crawled into the No. 6 Entry, where he was discovered by rescuers.
Ledford was taken out of the mine on a battery-powered personnel carrier. He was transported to Lonesome Pine Hospital in Big Stone Gap, Virginia, where he was treated.
Petra, Middleton, and Thomas attempted to escape but eventually succumbed to carbon monoxide poisoning at different locations in the mine. Petra was found in the No. 5 Entry approximately 500 feet outby the No. 4 Belt Drive power center. Middleton was found approximately 700 feet outby the No. 4 Belt Drive power center in the left crosscut off of the No. 5 Entry. Thomas was found 800 feet outby the No. 4 Belt Drive power center in the crosscut between the No. 2 Entry and No. 3 Entry in the return air course.
Brock and Lee were located at or near the No. 3 Seal in the return air course when the ignition occurred and were both fatally injured by the forces resulting from the explosion. Brock was found 240 feet from the No. 3 Seal in the crosscut between the Nos. 4 and 5 Entries. Lee was found in the No. 5 Entry, approximately 340 feet from the No. 3 Seal and 20 feet outby where Petra was found.
Rescue and Recovery Operations
Actions taken during the initial rescue and recovery operation did not follow accepted past practices that have been developed from previous rescue and recovery operations.
Though the intent of these actions was to expeditiously rescue trapped or injured miners, rescuers were also at times exposed to potential danger.
The following description of the rescue and recovery operations has been reconstructed based on individual recollections, testimonies, and logs which at times are in conflict.
Robert Rhea, MSHA District 7 Harlan, Kentucky, Field Office Supervisor, was notified of the explosion by Napier at approximately 1:05 a.m.
Rhea notified John Pyles, MSHA District 7 Assistant District Manager-Inspection Division, who notified Norman Page, MSHA District 7 District Manager, and MSHA headquarters personnel. Rhea notified MSHA Inspectors Kevin Doan, Dale Jackson and Brad Sears about the explosion.
Once Rhea arrived at the Harlan field office he notified MSHA Inspector Roger Wilhoit about the event. MSHA’s Mine Emergency Unit (MEU) was subsequently notified.
Doan arrived at the mine and verbally issued a 103(k) order at 1:54 a.m. The mine fan was operating. He took tests for carbon monoxide at the fan, as no one at the mine site at this time had a carbon monoxide detector.
Doan used a MSA Solaris multiple gas detector and detected 2.6 percent methane and over 500 ppm carbon monoxide at the fan, indicating that significant combustion from an explosion or fire had occurred underground. Doan then took an air sample at about 2:01 a.m. Air sample, D-7889, was later analyzed and found to contain 0.23 percent methane, 19.26 percent oxygen, and 6,162 ppm carbon monoxide. Rhea and Jackson arrived at the mine site at 2:00 a.m.
MSHA periodically monitored the fan for explosive and harmful gases. Jackson was informed that the underground mine power was disconnected.
Ronnie Hampton, Supervisor, Kentucky Office of Mine Safety and Licensing (KOMSL), arrived and along with MSHA and Napier, established a command center. Air quality readings were taken at the fan and in all mine openings.
The fan readings were 0.20 percent methane, 20.8 percent oxygen and over 500 ppm carbon monoxide. The intake entry had 13 ppm carbon monoxide with no methane and good oxygen.
A decision was made by the command center for the rescuers to walk one of the main intake entries barefaced until they encountered 50 ppm carbon monoxide, low oxygen, or an explosive atmosphere. Some of the rescue team members entering the mine were equipped with hand-held radios provided by KOMSL.
Rhea, Jackson, Doan, Inspector Todd Middleton (KOMSL), and Mark Sizemore (Kentucky Darby employee) entered the No. 5 intake entry barefaced at 2:32 a.m., leaving Napier and Hampton in the command center. J.J. White, mine rescue team member, KOMSL, was stationed at the intake portal to relay information from the team to the command center.
Using a MSA Solaris multiple gas detector, the rescuers traveled the No. 5 Entry taking carbon monoxide readings every crosscut and detected 12 to 18 ppm.
They arrived at the intake seals and examined all six seals. They took quality readings at all the seals and had 19.8 to 20.8 percent oxygen, 3 to 12 ppm carbon monoxide, and 0 percent methane.
At 3:08 a.m., John Pyles called the command center and was informed that nonmine rescue personnel were underground. Pyles gave instructions for those persons to be withdrawn from the mine. At about the same time, a light was observed in the intake entry, and the rescuers informed the command center that they saw a light and traveled towards it.
They found Paul Ledford (survivor) at about 3:10 a.m. with his SCSR donned (without goggles or nose clip in place) in the No. 6 intake entry one crosscut inby survey station No. 494. The rescuers talked to Ledford, who said that the other three miners were approximately three to four crosscuts behind him. Ledford was unable to walk so the rescue team called for a personnel carrier.
Jackson and Middleton advanced to crosscut No. 15 where the equipment door between the neutral and intake entries had been blown out by the explosion. Napier and Lunsford arrived with a personnel carrier. Napier transported Ledford outside while Lunsford remained underground.
Communication between the command center and the underground personnel was not always maintained.
Jackson, Middleton and Sizemore then walked to the No. 3 Belt Drive. Tests for methane indicated 0 percent. The phone line installed inby that location was disconnected. The mine phone located at the belt drive was then used to establish communications back to the command center.
Ventilation controls were damaged during the explosion at crosscut Nos. 17, 18, and 19 between the belt and return entries.
Jackson advanced inby the No. 3 belt entry for about three crosscuts when he encountered carbon monoxide ranging from 80 ppm to off scale. The rescuers retreated to the No. 3 Belt Drive area. A fresh air base (FAB) was established at survey station No. 507 in the No. 6 Entry in the main headings; Jackson advanced in the No. 5 neutral entry about three crosscuts until he encountered approximately 80 ppm carbon monoxide. The rescuers retreated to the FAB.
Communications were established to the command center from the FAB using the mine phone. The FAB was manned by Doan. The rescuers advanced in the No. 7 intake entry to crosscut No. 22 where three entries were mined from the Parallel Mains to connect the Mains.
At this time they encountered concentrations of 80 ppm carbon monoxide and retreated back to the FAB. Hampton and the Harlan KOSML mine rescue team arrived at the FAB. Team members went under oxygen and advanced inby the FAB.
The team traveled inby the No. 3 Belt Drive one crosscut and then crossed the belt to get to the return entries, intending to explore in an outby direction or "tie back" to connect to areas previously explored.
When the team reached the return air course, they observed a cap lamp light inby. They traveled toward the light and discovered Paris Thomas, Jr. at approximately 4:30 a.m. He was located one crosscut outby survey station No. 517 in the No. 3 Entry in the crosscut between Nos. 2 and 3 Entries.
The team found high concentrations of carbon monoxide (actual value not specified). Thomas was checked for vital signs and none were found. No call was made to the command center at that time to report the carbon monoxide concentration or the identification and location of Thomas.
Several members of the Lone Mountain mine rescue team, accompanied by an MSHA MEU team member, arrived at the FAB. Jim Vicini, Lone Mountain Mine Rescue Team Trainer, was informed by the command center to take charge of the FAB.
The FAB was moved from the No. 3 Belt Drive to a location two crosscuts inby survey station No. 506 in the No. 7 Entry of the Mains. Air-quality tests were made inby and the FAB was advanced to the third location at survey station No. 523.
The FAB could not be advanced any further due to high concentrations of carbon monoxide migrating out of the cut-throughs between the parallel mains and main entries. Vicini requested curtains be installed across the cut-through entries to advance the FAB.
The Lone Mountain team members that arrived first and an MSHA MEU team member donned apparatus and advanced inby toward the B Left section using 1,000 feet of communication hard line with headsets.
The remainder of the Lone Mountain team accompanied by an MSHA MEU team member arrived at the FAB. Until this time, mine rescue teams had been advancing inby the FAB without the presence of backup mine rescue teams at the FAB.
The first Lone Mountain team advanced toward the B Left section and observed one light outby in the No. 5 Entry and two lights inby toward the section. The team explored inby toward the two lights.
The tail captain traveled to the end of the communication line at the No. 4 Entry. A personnel carrier with its lights on was found on top of the debris from the destroyed intake overcast.
A search was made around the personnel carrier and no persons were found. End caps from two SCSRs were found on the personnel carrier. Footprints indicated someone may have traveled inby in the Mains toward the old works.
The first Lone Mountain team observed a second light inby. They advanced to and found a personnel carrier located at survey station No. 1193 in the No. 3 Entry on the B Left section.
An MX250 handheld detector was found in the deck of the personnel carrier and indicated over 20 percent oxygen. The end caps from two SCSRs, one pair of SCSR goggles, and footprints were found one crosscut inby the personnel carrier between the No. 3 Entry and the second room turned right. The footprints indicated someone had traveled into these rooms.
The team split up to travel the No. 3 Entry and three of the rooms on the right side to the faces of the B Left entries. The team reported detecting 480 ppm carbon monoxide at the section power center and 70 ppm carbon monoxide at the faces of the B Left entries. No one was found. One team member had approximately 900 psi of oxygen remaining so the team retreated back toward the FAB.
During their retreat, the first Lone Mountain team met Middleton, who was traveling inby. Middleton said that a team member from Harlan KOMSL was advancing inby in each of the seven entries of the Mains toward the B Left section. The first Lone Mountain team accompanied by Middleton then retreated to the No. 5 Entry where they had previously seen a light. The team advanced outby toward the light leaving the low man with the tail captain.
At approximately 5:16 a.m. they found George "Bill" Petra and another victim that could not be identified, located about 35 feet inby survey station No. 526. Petra and the second victim were checked for vital signs, and none were found. The team then retreated to the FAB, called the command center and informed them of the location of both victims, one of which was identified. At this time, three victims had been located.
The Barbourville KOMSL team arrived at the FAB with ventilation curtains. The Harlan team then returned to the surface. Vicini instructed the Barbourville team to install the ventilation controls in the three cut-through entries, at crosscut No. 17 (near survey station No. 505), and in the crosscuts inby, where stoppings had been damaged between the intake and neutral entries. The FAB was then advanced to the fourth location, one crosscut inby survey station No. 559 in the No. 7 Entry.
The Barbourville team advanced from the FAB to the A Left seals and found that the seals had been destroyed. Air quality readings were taken at the seal locations. The team reported readings for the No. 1 seal entry as 19.1 percent oxygen, 1.5 percent methane, and carbon monoxide over range. The team then explored the return entries inby to the mouth of B Left section. They reported what was thought to be a roof fall close to crosscut No. 21 in the belt entry. The Hazard team traveled underground to the FAB. The team was instructed to travel the return entry toward the surface and meet the Martin KOMSL team that traveled from the outside toward the sealed area.
Vicini instructed three members of the Lone Mountain team to travel outby in the belt entry to check on what was reported as a roof fall. The remaining members were instructed to travel inby in the Mains to the worked out areas.
The teams were instructed to check each crosscut as they advanced. The team traveling outby had two members in the belt entry and one member in the No. 3 return entry. What had been reported as a possible roof fall was actually the belt and structure deposited against the rib. They also found the personnel carrier that Brock and Lee had been using. The wreckage of the personnel carrier was located in the belt entry at survey station No. 525. During further exploration the team located the body of Paris Thomas for the second time.
The Lone Mountain team advanced to the No. 3 Belt Drive. They retreated in the No. 5 neutral entry and searched each crosscut for the remaining victims. At approximately 8:45 a.m. one team member found Roy Middleton in crosscut No. 21 between the Nos. 4 and 5 Entries. Middleton was checked for vital signs and none were found. Middleton had his SCSR on with the mouthpiece dislodged from his mouth. He was wearing his goggles, but it is not known if the nose clip was in place. The team retreated to the wreckage of the personnel carrier, examined the crosscut and at approximately 8:45 a.m. found the last victim, later identified as Amon Brock, in crosscut No. 23 between the Nos. 4 and 5 Entries. Vital signs were checked and none were found. At this time, all victims had been located.
The team retreated to the FAB and informed the command center of the location of both victims, one of whom was identified. The entire Lone Mountain team was then instructed to return to the surface.
Pat Turner, Mike Elswick, and Todd Middleton, KOMSL rescue team members, traveled underground to make a ventilation change. A regulator was installed one crosscut inby survey station No. 470 in the No. 7 Entry at the mouth of the Parallel Mains. The stopping line was examined and repaired up to the FAB. This was done to increase the quantity of air to the FAB.
The Pikeville KOMSL team arrived at the FAB. The Pikeville, Hazard, Barbourville, and Martin teams made the ventilation change and the FAB was relocated to survey station No. 523.
The area where the victims were located was then cleared of high concentrations of carbon monoxide. MSHA MEU team members placed the victims in body bags. KOMSL team members transported the victims back to the FAB, where they were transported to the surface. At approximately 10:55 a.m., the victims were brought to the surface and transported to the coroner’s office.
The command center made a decision to make another ventilation change. The James River mine rescue team and an MSHA MEU team member traveled underground to the FAB. The James River team advanced inby the FAB toward the second set of cut-throughs located at survey station No. 593 in the No. 7 Entry. Air quality readings were taken in the cut-throughs, in the Parallel Mains entries, and in the Mains inby the cut-throughs.
The team reported 0.2 to 0.4 percent methane, 20.0 to 20.3 percent oxygen, and 85 to 150 ppm carbon monoxide. The team retreated to the FAB. A decision was made to allow the mine to ventilate without an air change over the weekend. All mine rescue personnel returned to the surface.
On May 22, 2006 members from the MSHA MEU and Harlan KOMSL teams entered the mine. Quantity and quality readings were taken at specific locations to determine how to re-ventilate the mine.
On May 23, 2006 representatives from KOMSL, the operator, and MSHA traveled to the FAB. MSHA and KOMSL teams explored the A Left section. Air quality checks were made at every crosscut. The lowest oxygen reading obtained was 20.6 percent. The highest methane and carbon monoxide readings obtained were 0.4 percent and 14 ppm respectively. The A Left section was ventilated with approximately 30,000 cubic feet per minute (cfm).
MSHA, KOMSL, and company representatives traveled the worked out areas located in the northern section of the mine. Air quality readings were taken to assure the old works were ventilated. The team encountered 0.5 percent methane and retreated. Ventilation controls were examined and it was determined that the equipment doors located at the top end of the Parallel Mains had been blown out during the explosion. The team returned to the surface. A decision was made to install curtains at these doors and allow the mine to ventilate overnight.
On May 24, 2006, MSHA, KOMSL, and company representatives traveled to the FAB. MSHA and KOMSL explored the B Left section. Air quality checks were made at every crosscut. The lowest oxygen reading obtained was 20.7 percent. The highest methane and carbon monoxide readings obtained were 0.4 percent and 10 ppm respectively. The B Left section and rooms were ventilated with approximately 18,000 cfm.
The worked out areas located in the northern section of the mine were traveled again after the ventilation was established and air quality readings were taken. The lowest oxygen reading obtained was 20.7 percent. The highest methane and carbon monoxide readings obtained were 0.5 percent and 40 ppm respectively. At this point, temporary ventilation controls had been established throughout the entire mine.
Investigation of Accident
On May 23, 2006, MSHA commenced an investigation of the accident pursuant to Section 103 of the Mine Safety and Health of 1977. The Administrator for Coal Mine Safety and Health assigned an investigation team consisting of personnel from MSHA Coal Districts 2, 3, 4, 6, and 8; MSHA Pittsburgh Safety and Health Technology Center; MSHA Educational Field Services, and the Office of the Solicitor, Department of Labor. Thomas Light, Assistant District Manager for District 2, was assigned as the accident investigation team leader.
Preliminary information was gathered and records were obtained from the MSHA District 7 office in Barbourville, Kentucky; the MSHA Field Office in Harlan, Kentucky; and from the mine operator. The team conducted physical investigations at the mine from May 24 to August 17, 2006.
During the on-site investigations, team personnel were accompanied by representatives from Kentucky Darby LLC, the State of Kentucky, the United Mine Workers of America, and other designated miners’ representatives.
At the time of the accident, the miners were not represented by any labor organization. After the accident, several miners designated the United Mine Workers of America and other parties to act as their representatives.
Persons were identified for the purpose of interviews. Thirty-two interviews were conducted by the MSHA investigation team. The interviews were attended by representatives from Kentucky Darby LLC, the State of Kentucky, the United Mine Workers of America, and other designated miners’ representatives. The State of Kentucky also conducted interviews, which an MSHA accident investigation team member and an attorney from the Office of the Solicitor attended.
Other contacts were made and information was obtained from contractors and State and local authorities. Pertinent and relevant records were collected and reviewed during the investigation. Physical evidence such as methane detectors, cap lamp assemblies, cutting torch parts, and various electrical components from the battery powered mantrip were examined or tested as necessary at designated testing facilities. Interested parties were informed of, and allowed to attend, testing. Samples collected during the investigation were analyzed and evaluated through the various testing facilities.
The mine began production in the Darby Coal Seam on May 28, 2001, using the room and pillar mining method. Mining started in the A Left Section in middle to late October 2005. A Left was developed by three entries driven from the return side of the Mains starting at crosscut No. 21. At the first crosscut in A Left, one additional entry was added to each side of the section. An additional entry was added at the third crosscut on the north side for a total of six entries.
Starting at the fifth crosscut, rooms were driven to the left (south). The A Left Section was mined to a distance of approximately 1,130 feet from the Mains. Five entries were driven to the right (north) for rooms near the furthest extent of the section. Mining in the rooms was discontinued on March 3, 2006 and the A Left Section was sealed with three seals constructed between March 18 and 22, 2006. These seals were referred to as the "return seals." No retreat mining was conducted in the A Left Section.
On March 6, 2006, mining started in the B Left Section. B Left was developed by three entries driven from the return side of the Mains starting at crosscut No. 30. Starting at the second crosscut in B Left, rooms were driven on each side of the section. The section had advanced to a distance of approximately 665 feet from the Mains at the time of explosion.
The mine was ventilated by a single, exhaust fan installed on the surface and connected by corrugated ductwork to the No. 1 drift opening. The fan was a Vortex, Model No. 54D-1139, and was belt-driven by a 100 horsepower electric motor. Measurements during the investigation indicated the fan was exhausting 114,206 cubic feet per minute (cfm) of air from the mine at a pressure of 3.2 inches of water. The second return opening had an equipment door to provide access to the return air course and to serve as an explosion-relief door. Overall mine ventilation prior to the accident is depicted on the map in Appendix B.
Air entered the mine through the remaining three drift openings, including the belt entry. The intake, return, and belt air courses were separated by 8-inch hollow-core concrete block stoppings that were dry-stacked and coated with sealant on the high pressure side.
The only exception was in the sealed A Left Section where several stoppings were built of Omega blocks instead of concrete blocks. Overcasts were constructed using a combination of concrete blocks, steel plates, and steel beams. The only two overcasts in service in the mine were located at the intersection between the Mains and the B Left Section.
The mine had developed a sixth entry, common with the belt entry, at the second crosscut inside the mine. A seventh entry, utilized as a third return air course, was added near the intake split point for the Parallel Mains, about 1,500 feet into the mine.
In the Mains, a stopping line across the intake and belt entries directed air into the B Left Section. Three entries provided access to the B Left Section. From there, the section expanded into rooms on the left and right sides of the development starting at the third crosscut. On May 3, 2006, during an MSHA inspection, an air quantity of 18,600 cfm was measured in the last open crosscut for the B Left Section.
According to the approved Ventilation Plan, the airflow for the belt entry should have been coursed to the return air courses outby the section belt feeder for the B Left Section. The accident investigation team, however, did not find a regulator to direct the belt air to the return air course. The only regulator shown on the mine map was located in the return air course between the first and second crosscut for the B Left Section and consisted of an equipment door (constructed of two hinged panels) in a stopping.
The return air flow in the Mains ventilated the front of the seals for the A Left area. During the recovery of the mine, line curtain was used to replace some of the damaged ventilation controls to reestablish air flow throughout the mine, including directing the entire Mains return air flow into the formerly sealed A Left area. The accident investigation team measured 51,256 cfm of return air at the mouth of A Left.
An explosion occurred at approximately 1:00 a.m. on May 20, 2006, inby the A Left No. 3 Seal. The explosion resulted in the immediate deaths of two miners who were located at the seal. Three of four miners evacuating from the B Left Section succumbed to carbon monoxide poisoning with smoke and soot inhalation.
The accident occurred because the operator did not observe basic mine safety practices and because critical safety standards were violated. Mine management failed to ensure that proper seal construction procedures were utilized in the building of the seals at the A Left Section.
Mine management also failed to ensure that safe work procedures were used while employees attempted to make corrections to an improperly constructed seal. Furthermore, mine management failed to adequately train miners in escapeway routes and proper SCSR usage.
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