Two gas and coal dust explosions, the first at about 1:05 p.m. and the second at about 1:25 p.m., occurred on Thursday, December 6, 1962, in the 4 mains right area of Robena No.3 mine, United States Steel Corporation, Coal Division, Frick District, Carmichaels, Greene County, Pennsylvania. Thirty-seven men, all of those working in the 8 left section of the explosion area, are believed to have died as a result of the first explosion, as attested by the fact that some of the watches, including the watch on the body of the outermost victim, had been stopped between 1:03 and 1:05, while two other men who approached the area after the first explosion were knocked down but not injured by the forces of the second explosion. The other 133 men in the Robena No.3 mine at the time were withdrawn without mishap.
Bureau of Mines investigators believe that the first explosion originated in the face area of 8 left inby 90 crosscut between Nos. 4 and 8 entries when a mixture of methane and air was ignited by one of four possible sources: A nip station just outby 90 crosscut on No. 6 entry, a car puller activated by an open-type electric motor located on intake air at the inby right comer of No. 6 entry at 90 crosscut, friction sparks from bits of a continuous miner being operated at the face of the slant place between Nos. 7 and 8 entries inby 91 crosscut, or an auxiliary fan in operation and in nonpermissible condition in 91 crosscut between the slant and No. 8 entry.
The second explosion originated somewhere in 8 left section when gas and/or dust was ignited by residual fires or by an electric arc, since the main fan had been restarted and the mine power system had been reenergized soon after the first explosion. Coal dust assisted in the propagation of both explosions.
The Robena mine, operated as one unit, consists of three interconnected mines, Nos. 1,2, and 3, located at Greensboro and Carmichaels, Greene County, Pennsylvania, which are served by barges on the Monongahela River.
The 4 mains section consisted of 11 entries which had been developed about 1,800 feet inby 8 left junction. Entry development in 4 mains had been stopped and the section was idle at the time of the explosions.
Development in 8 left 4 main section consisted of driving 10 entries on 75-foot centers with crosscuts at 90-foot intervals. The 8 left entries had been turned off 4 mains and driven about 5,500 feet, at which point it was necessary to change the direction of development to intersect a recently sunk shaft (Kirby) located about 4,300 feet to the right of the active faces.
At this point the customary system of development, which was to advance entries from the return-air side of the split toward the intake or from left and right toward the center, a very commendable system from a ventilation standpoint, was temporarily discontinued, and the center or intake entries of both the right and left splits were advanced to get the radii driven and expedite the construction of overcasts in the section to permit splitting the air when the 900 turn would be made toward Kirby shaft. Apparently the fact that this rather drastic deviation from the usual development system would adversely affect ventilation of the faces was overlooked, and areas with sluggish ventilation inviting gas accumulation as well as reversal of airflow direction resulted.
Evidence brought out during the official hearings on the disaster disclosed that blasting was not done on the construction shift on December 6, and there was no indication during the investigation of the disaster that blasting had been done on the shift on which the explosions occurred.
The mine is classed gassy by the State and the Bureau of Mines. Preshift examinations for gas and other hazards were made by certified officials before the first operating shift of each day, and preshift examinations for succeeding shifts were made by the onshift certified official during his regular tour of duty. Onshift examinations for gas and other hazards were made by assistant foremen, mine foremen, safety inspectors, certain equipment operators, and shot firers. Gas wells penetrating the property were protected by blocks of coal left in place. An abandoned and plugged gas well was situated about 1,150 feet to the right of the faces in 8 left section.
At the time of the February 1962 Federal inspection of the Robena mine, the mine surfaces were generally dry. Dangerous accumulations of loose coal or coal dust were not observed.
Further testimony during the hearings revealed that 53 loaded cars and one partly loaded car of coal were in the section (2 loaded and a partly loaded car near the loading ramp between 89 and 90 crosscuts, 10 cars in 84 crosscut, 36 cars extending inby from 45 crosscut, and 5 on the right side pickup at 72 crosscut). Sixty-three tons of coal were swept from these cars by the forces of the explosions, and that portion smaller than 20 mesh would have been fuel to propagate the explosions. This tonnage figure was determined by comparing the average weight of coal in cars loaded before the disaster with the average weight of coal in the cars in the disaster area.
Testimony also revealed that it was believed that the explosion originated from an ignition of gas in the face area of 8 left and was propagated by the abovementioned coal dust in addition to 1,400 or more pounds on the mine floor resulting from timber hitches cut in the ribs between 76 and 77 crosscuts No. 5 entry and other coal dust in the entries.
Observation in the explosion area revealed that the boring-type continuous miner leaves rather smooth roof and rib surfaces to which rock dust does not readily cling, but coal dust does because the surfaces are wet when the coal dust is produced and possibly dry when rockdusted.
The electric equipment in 8 left section was examined during the investigation, and permissibility defects were found in the permissible-type equipment.
These deficiencies in the permissible-type equipment indicated general substandard inspection and maintenance of such equipment.
Illumination and Smoking
Permissible electric cap lamps were used for portable illumination underground. Smoking was not permitted or observed underground during any Federal inspection, and searches for smokers' articles were conducted frequently. Smoking material was not found in the section or among the personal effects of the victims, which is substantial proof of strict compliance with a no smoking requirement.
Story of Explosions and Recovery Operations
Mining Conditions Immediately Prior to the Explosion The mine was operating normally on the day of the
explosions, and the weather was cold and stormy.
The barometric pressure dropped from 30.04 at 6:00 a.m. December 4, to 29.35 at 1:00 p.m. December 6, 1962. The temperature ranged from a high of 61°F to a low of 27°F during the same period. It is the opinion of the Bureau investigators that the variation in atmospheric pressure did not contribute materially to the explosions.
The reports of the examinations by the fire boss and assistant mine foreman made on the last production shift (4:00 p.m. to 12:00 midnight on December 5, 1962) in the 8 left section prior to the explosions indicated that gas had not been detected in the affected section. However, during the official hearings on the explosions, a continuous miner operator on that shift stated that he had found gas at the intersection of the No. 5 entry and the inby radius from No. 5 to No. 6 entries, and that the air movement in this area was sluggish. He stated also that the section foreman was present when the gas was found and ordered a check curtain erected to improve the ventilation. The foreman insisted that gas was not found on this shift, and that he had never found gas during his 2 months' supervision of the section.
Evidence of Activities and Story of Explosions
The day shift entered the mine about 7:00 a.m. December 6, 1962, and those working in the 8 left 4 main butts area arrived at the work area about 7:30 a.m., according to the pre-shift examiner (construction foreman) who met and conversed with the foreman of the oncoming shift. The 37 persons in the 8 left area consisted of two production crews, comprised of a continuous mining machine operator and two shuttle car operators each and two roof bolters who worked wherever bolting was necessary; thus the bolters may be with either machine.
These 13 men were under the supervision of the production foreman. Others in the area were 14 construction men and a foreman, 2 repairmen and a foreman, 3 engineers, and 2 mainline transportation men. Since all persons in the section perished in the first explosion, it can only be presumed what work was in progress when the explosion occurred.
The first indication of trouble in the mine was noted by two repairmen, who had just completed repairing a compressor in the combination fanhouse and compressor station. According to John Syrek, repairman, the compressor was started at 1:00 p.m., and the two repairmen went to the lamp section of the service building about 50 feet from the compressor station. Soon after entering the lamp area, Syrek was apprised by Paul Honseker, his helper, that the audible fan signal was sounding an alarm. Looking out the window, Syrek said that he saw a white cloud of dust issuing from the nearby elevator shaft. He immediately went to the fan and found it stopped and was soon joined by Honseker and Ernest Benchek, the lampman. He told Benchek not to start the fan but to call the mine superintendent and Robert Rennie, surface maintenance foreman, whose headquarters was at Colvin shaft (Robena No. 1) and who was in charge of all fans. He also asked Honseker to check the air line leading to the shaft, as he thought it might have ruptured causing the white dust cloud.
In the meantime, Donald Sherrow, an electrician, upon telephoned instructions from Rennie, had arrived from the nearby Blaker shaft, checked the fan and, fmding nothing wrong, started it.
One might conjecture at this point that the fan should not have been started, since neither a power failure nor mechanical difficulty was indicated by the various safety devices on the fan.
According to Rennie, the mine was only partly reenergized (not all of the 13 substations were restored) when the Frosty Run fan stopped again and the mine was again deenergized by the hoisting engineer.
After this second fan stoppage Wydo, superintendent of No.3 mine, recognizing an unusual occurrence, called Rennie via the superintendent's clerk at No. 1 mine to keep the power off.
After the second fan stoppage, at which time Wydo was at Frosty Run giving various instructions and had observed the emergence of black dust from the downcast (elevator) shaft, other officials arrived and plans were made to cope with the underground trouble.
Soon after the second explosion, recovery operations were started and mine rescue teams were summoned. It was soon discovered that the forces of the explosions had destroyed stoppings, the air was short circuited about 4,000 feet from Frosty Run shaft bottom, and explosive and noxious gases permeated the atmosphere inby this point. Thus it was necessary to explore all entries leading to 8 left with self-contained oxygen breathing apparatus to ascertain the presence of and extinguish any fires before ventilation was reestablished.
The recovery was a long and tedious operation, taking from about 3:00 p.m. December 6 until the morning of December 11, 1962, when the face area was fmally ventilated.
The body of the first victim was found at 3:15 a.m. December 8 and the last was brought to the surface at 2:04 p.m. December 11, 1962.
Discussion of Evidence and Special Tests
The actual cause of the disaster can only be presumed, since all persons in the area encompassed by the first explosion were killed. Knowing the extent to which the places were advanced during the previous production shift and the general method of face ventilation from the testimony of both the last production shift foreman and the preshift examiner just prior to the shift on which the explosion occurred, coupled with the position and condition of men and machines after the explosions, the following conjectural pattern of activities just prior to the first explosion was established. The pertinent points follow:
The continuous miner in the radius near the junction with No. 6 entry was stopped, having cut through to No. 6 and advanced about 16 feet beyond No. 6 entry. This is substantiated by the controls being in the "off" position and the operator's body being found at the junction of No. 7 entry and 91 crosscut with the bodies of the section foreman and engineers.
The auxiliary fan between Nos. 3 and 4 entries, used to circulate air through the upper radius from No. 4 to No. 6 entry, was stopped with the controls in the "off" position.
The continuous miner at the face of the slant place between Nos. 7 and 8 entries off 91 crosscut was operating, as attested by the controls being in the "on" position, a partly loaded shuttle car under the miner conveyor boom with the conveyor control in the "on" position, coal on the conveyor, the shuttle car operator on the seat, and the continuous miner operator near the shuttle car operator as if fleeing from the face. The auxiliary fan installed in 91 crosscut between the slant and No. 8 entry was presumed to be operating, since it coursed air circulation through the slant place.
It was also known that a permanent stopping was being built across No. 7 entry between 89 and 90 crosscuts during this shift, since the masons were in the section, the lower course of blocks was in place, other blocks displaced by the explosions had mortar adhering to them, and the mortar marks appeared on the roof.
Having the foregoing established, it was assumed that when the auxiliary fan between Nos. 3 and 4 entries was stopped, air movement through the upper radius between Nos. 4 and 6 entries would be sluggish and gas might accumulate in this area. Actual tests on January 15, 1963, disclosed that, when the inby radius cut through to No. 6 entry, the auxiliary fan that was used to ventilate the radius received all its air from the No. 6 entry and thus made the radius between Nos. 4 and 6 entries virtually a dead air space where methane accumulated. The same tests also showed that, with the auxiliary fan stopped, the air would move toward the loading ramp on No. 6 entry. Even though the 8 left face area had been ventilated since December 11, 1962, gas started to accumulate near the face of No 6 entry and backed up at least 20 feet from the face within the 15 minute test period.
Assuming that the stopping in No. 7 entry between crosscuts 89 and 90 was completed after the gas had accumulated in the radius between Nos. 4 and 6 entries, a test was made to determine what action the air might take as a result of this entry being closed. This test disclosed that any gas accumulated in the radius would be moved to the face of the radius, down No. 6 entry toward 91 crosscut and splitting here with a part going toward No. 7 entry through 91 crosscut and another part traveling toward the ramp and nip station at 90 crosscut, thence through 90 crosscut to No. 7, thence back through No. 7 entry to 91 crosscut and joining the air and gas which had passed through No. 7 entry.
In passing down No. 6 entry to the ramp this gas could also pass over the open type motor of the car puller and the nip station. The total volume of air in 91 crosscut containing the aforementioned gas split at the slant. Five thousand cfm of this air ventilated the face of the slant place where the continuous miner was cutting a hard clay vein, which could emit sparks capable of igniting methane. The remaining 30,000 cfm of this air passed across the auxiliary fan which was not in permissible condition.
The special tests on January 15 disclosed that the auxiliary fan between Nos. 3 and 4 entries exhausted only 3,300 cubic feet of air a minute, which may not have been enough to keep the long radius and face properly ventilated.
Cause of the Disaster
This disaster was caused by the ignition of a body of methane by friction sparks or electric arc. The methane had accumulated in a portion of the face development that was not ventilated for a short period of time and was moved over operating equipment when completion of a permanent stopping in the section resulted in a reversal of face airflow.