A number of changes in mine safety practices are needed to prevent underground coal mine explosions like the one that ripped through Massey Energy’s Upper Big Branch mine in April 2010, killing 29 miners, said the West Virginia Office of Miners’ Health Safety and Training.
The office has issued its report on the Upper Big Branch explosion and its causes. West Virginia Gov. Earl Ray Tomblin said in a Feb. 23 statement about the report: “Much like the other reports on the tragic explosion at the UBB mine – one common theme prevails; this disaster was preventable. I am committed to making sure that our laws are properly enforced and that we pass meaningful mine safety legislation. We simply cannot bear another mine disaster in West Virginia. I am working with the Legislature to make sure that my legislation, currently pending in the House of Delegates, passes so that we can work to prevent another mine disaster from occurring. I am confident that the Legislature will soon pass House Bill 4351 so that I can sign it and we can immediately begin its implementation.”
Incidentally, Massey Energy was taken over in June 2011, after the explosion, by Alpha Natural Resources (NYSE:ANR), which since then has been dealing with the legal aftermath of the explosion. Alpha promised a total revamp of Massey’s much-criticized mine safety program.
On April 5, 2010, an explosion tore through the underground workings at the Performance Coal mine. The explosion began after gas, mostly methane, was ignited by frictional impact as the shearer was cutting sandstone roof or by the rock colliding with steel supports or other rock while falling from the sandstone roof behind the longwall shields. The report said it is more likely that the longwall shearer ignited the methane.
The methane apparently was liberated from the mine floor behind the roof-supporting longwall shields, and, as this gas flowed to the return behind the shields, the airflow then became restricted by a recent roof fall across the #7 entry of the #21 Tailgate. This may have allowed the methane to accumulate near where the shearer was operating. This roof fall would not allow the air current to move directly toward the return at the tailgate corner of the gob, causing it to flow outby to an open crosscut. The shearer shut down just a few feet short of its normal stop position as it mined into the tailgate entry. About 1½ minutes later an explosion occurred in the gob behind the longwall shields, spreading quickly to the #21 Tailgate and from there tore through an extensive area of the mine.
This accumulation of methane was not detected by the required mine examinations or by the required machine-mounted methane monitors. The methane explosion morphed into a coal dust explosion, which severely damaged ventilation controls and other equipment in its path until the fuel was consumed and the explosion extinguished itself outby the track switch at the beginning of North Glory Mains.
Lack of rock dusting seen to be key issue
“Part of our investigation involved examining the sources of fine coal dust, both float dust from mining sections and conveyor belts, as well as sloughed material from friable coal ribs,” said the report. “We find that fine accumulations that can easily be dispersed into the air by the pressure wave ahead of a propagating flame are of primary concern and deserve increased attention. The amount of rock dust being maintained on mine surfaces at the time of the explosion was insufficient to stop a coal dust explosion. The region where the dust explosion started does not appear to have had rock dust periodically applied over the fine coal dust.”
The report added: “Periodic applications of rock dust over accumulating fine coal dust are necessary to render such dust harmless. The greatest defense against the hazards of fine coal dust is the proper application of rock dust. The way we currently sample and apply rock dust needs to be modernized, using the latest research knowledge and most appropriate sampling and analyzing methods available. Other strategies to arrest a dust explosion include explosion mitigation barriers, which have important applications in certain conditions. Investigators found evidence that a water barrier just west of #22 Cross-over stopped the explosion from propagating further inby in the #21 Headgate entries. Further research is needed to demonstrate the practical application of water barriers, rock rubble barriers and other explosion-mitigating strategies as supplemental protection with generalized rock dusting to prevent explosion propagations in the future. The data combined in the full report will serve as a resource for future research.”
The report said the removal of hazards and violations identified during required mine examinations were not corrected in a timely manner. There was no indication that the #21 Tailgate entries west of the #21 Cross-over had been rock dusted since the longwall began production in September 2009.
The West Virginia mine safety office currently has insufficient statutory language to regulate the way that coal mines are ventilated, the report added. Coal operators must take a more proactive approach to the ventilation of each coal mine under their authority and responsibility. The industry has taken a step back over the years in proper planning and preparation as long-term plans are developed.
“The operator must once again lead the way in doing the hard and extensive work necessary to properly ventilate each mine,” the report added. “Registered Professional Engineers can help bridge the gap between prudent planning and maintenance of mine ventilation. Mine managers and regulators must allow the Professional Engineer to do his/her job and should not be so quick to disregard the engineer’s professional judgment, which he/she is charged by charter to do in order to protect public safety.”
Also, a closer look must be taken concerning the use of belt air during longwall mining to assure that the most effective means are being utilized to maximize ventilation to the longwall face and the active gob areas including the tailgate T-Split (i.e., where the longwall face intersects its principle return air course). The T-split is a critical location where longwall ventilation can become blocked, which is what happened at UBB, the report noted.
The excessive use of airlock doors along the ventilating current must be minimized to assure that ventilation is not compromised. Although this is currently addressed in the West Virginia Code, it requires clarification with stricter guidelines for enforcement, the report said.
Critical air splits in the mine should be adequately monitored at strategic locations to give warning of unusual or dangerous amounts of methane, carbon monoxide or other harmful gases. This system should alert the operator if an air reversal or a drastic change occurs in the ventilating air volumes. These devices should give warning to a central location on the surface so workers in the affected areas can be alerted to hazardous conditions.
Mine management should review the mine ventilation, roof conditions and any other specific hazard to the mine, such as inundation potential, and organize and schedule mine examinations to ensure conformance to the law and regulations, being specifically attuned to the potential hazards at the mine, the report said.