Certified blaster Darrel Alan Winstead, 47, and blaster helper Samual Joe Lindsey, 23, were killed on October 28 at Armstrong Coal’s Equality highwall mine in Ohio County when the one-ton truck they were in was covered by rock and rubble in a highwall collapse.
Both the men were employees of contracting firm Mine Equipment and Mill Supply.
“The two miners were in the No.11 pit traveling to the area of the pit that had been prepared for the loading of explosives and the eventual blasting of material as part of normal mining activity when the highwall failure occurred,” the agency said in its final report released late Tuesday.
“Mine management failed to recognize a geologic anomaly, located in the portion of the highwall below the No. 14 coal seam and above the No. 13 coal seam, prior to the highwall failure.”
A Caterpillar 773 truck and Hitachi excavator were also struck by rock in the incident, though the operators of both escaped uninjured.
According to various witnesses of the collapse, there was no indication of any loose material in the highwall, nor had any material fallen in the pit that morning.
MSHA investigators determined the highwall failure occurred in the shale/siltstone zone between the No.14 and No.13 coal seams, about 1700 feet east of the western end wall.
“It was a wedge-type failure, where the rock mass between two intersecting [or nearly intersecting] discontinuities slid into the pit,” officials said.
“The rock mass slid along the northeast-facing geologic discontinuity and dropped approximately 30 feet onto the pit floor. The bulk of the slide debris on the pit floor was located east of the center of the failure area in the highwall and the volume of the material that slid into the pit was estimated to be approximately 9000 cubic yards; using 120lb/cu.ft, this would approximate over 14,000 tons of material.”
An MSHA review of the mine’s training plan was also found to be deficient.
An examination conducted for the No.11 pit the morning prior to the highwall failure was found to be inadequate too because the examiner failed to recognize the exposed geologic anomaly on the highwall.
“This anomaly was present for several days prior to October 28, 2011,” MSHA determined.
“Similar anomalies were also present in the highwall a few hundred feet to the west of the highwall failure at the same time as the fatal accident. The examination record book did not note the presence of the anomaly, nor the need for corrective actions to be taken by the mine operator.”
That very issue was at the center of the incident and its resulting deaths, investigators determined.
“The fatality occurred because of a geologic anomaly, located in the portion of the highwall below the No. 14 coal seam and above the No. 13 coal seam,” MSHA concluded.
“The area of the pit where this shows itself also had two intersecting [or nearly intersecting] discontinuities that slid into the pit [and] the absence of a substantial bench to prevent the massive failure from entering the active pit where miners were working contributed to the death of two miners.
“The failure by mine management and the mine examiners to examine the site adequately and to recognize the anomaly and its potential failure and the lack of recognition of hazards by the miners were also contributing factors.”
To rectify the issues, MSHA ordered the operator to revise its ground control plan, and train all miners in the changes.
The mine also retained an experienced geologist to provide evaluations of ground conditions as well as to instruct examiners in proper procedures to recognize anomalies in the highwall.
Finally, the operator incorporated in its approved training plan hazard recognition by a qualified professional, and all miners were trained on the revisions.
Armstrong received a total of five 104(a) citations for a violation of 30 CFR.
One of the most significant was for Section 77.1000 stemming from its failure to establish and follow a ground control plan.
Equality Mine near Centertown, Kentucky, employed 118 people and 14 contractor employees at the time of the incident and recorded daily production of about 13,500t.
A regular safety and health inspection by MSHA was in progress at the time of the accident.
The mine’s non-fatal days lost incidence rate for the mine in 2010 was 0.00, versus the national NFDL incidence rate of 1.12 for surface mines.
The incident was the only non-single fatality in US coal in 2011. All 2012 deaths to date have also been single deaths.