The mine is classed gassy by the Pennsylvania Department of Mines and Mineral Industries. Air samples collected in split returns from the two working sections and the main returns during the inspection completed in December 1969 contained 0.35 to 0.49 percent methane, and those collected in the main returns indicated that methane was being liberated from the mine at a calculated rate of 1,180,000 cubic feet in 24 hours at that time. Preshift examinations for gas and other hazards were made by certified persons before the first operating shift each week, and preshift examinations for succeeding shifts were made by the on-shift officials during their regular tours of duty. On-shift examinations for gas and other hazards were made by certified foremen. Weekly examinations for gas and other hazards were made and recorded. During a hearing conducted after the underground investigation, testimony indicated that methane was detected in the mine with flame safety lamps on a number of occasions, but these findings were not recorded. Methane monitors were not used on the continuous-mining machines. Gas or oil wells were not on the property.

Air measurements taken in the crossover mains and recorded by the section foreman on the shift prior to the explosion indicated that 21,000 cubic feet of air a minute was passing through the last open crosscut between Nos. 6 and 7 entries. This foreman stated during the hearing that he had detected what he estimated to be 2 percent of methane in No. 4 entry during his shift, and this finding also had not been recorded. Analyses of air samples collected in the area during the investigation indicated methane ranging from 0.12 to 0.77 percent, see table 1. Methane could be detected with permissible flame safety lamps and electrical methane detectors at the faces in the section where the explosion occurred and in other sections at various times during the investigation in concentrations ranging from 1 to in excess of 3 percent. From tests made in the face areas after production of coal had been resumed, methane was emitted rather freely from the roof strata when breaks in the roof occurred.

Reportedly, a gas ignition that caused no injuries or property damage occurred in the crossover mains section approximately 3 weeks prior to this explosion. The flame from this ignition was confined to the immediate face area. It was not recorded in the record books at the mine, nor was it reported to the Bureau of Mines.

Dust

During the Federal inspection completed on December 2, 1969, the mine surfaces varied from wet to dry and were free from accumulations of loose coal and coal dust. Dust surveys with sampling points at 200-foot intervals were made in the two areas being developed during the inspection, and analyses of the 50 samples collected during the surveys indicated that

incombustible content of the mine dust ranged from 81 to 100 percent. The continuous-mining machines were equipped with water sprays which appeared to be effective while coal was being mined. The continuousmining machine involved in the explosion was equipped with 19 water sprays to allay dust. Reportedly, the sprays were being used at the time of the explosion; however, the valve for the sprays was found closed after the explosion, the presence of water was not observed in the face area, and testimony indicated that none of the workmen had turned the valve off after the explosion.

During the investigation, the rock-dust applications were found to be 49 to 94 feet from the faces in six working places in the south and crossover mains sections. Dust survey samples were collected at 50-foot intervals in the crossover mains and at 100- to 200-foot intervals in the remainder of the mine. Six dust samples were also collected at spot locations in the mine. Of the 135 samples collected, 36 (26.6 percent) which were collected in areas in which the dust was not disturbed to any appreciable extent contained less incombustible material than required. Six dust samples collected in the explosion area contained traces to large amounts of coke indicating that coal dust was a factor in the explosion. See Appendix H.

Transportation

Permissible-type cable-reel shuttle cars were used in the crossover mains section to transport the coal from the face areas. The coal was discharged into coal feeders at the belt-conveyor tailpieces, then transported by belt conveyors to the surface. The men were lowered into and hoisted from the 2,500-foot slope in special man cars. Mine cars pulled by trolley locomotives were used to provide transportation for the workmen between the slope bottom and the disembarking point at the end of the track haulage road. Supply cars pulled by permissible-type batterypowered tractors provided transportation for men to the working faces. Electricity

Electric power from the public utility system was transformed to 13,200 volts on the surface and conducted underground over nonmetallic sheathed cable. The high-voltage cable entered the mine through the slope portal. Underground, the high-voltage system supplied combination a.c.-d.c. power centers for five continuous-mining machine units, two 150-kv.-a. transformers for conveyor drive motors in 2 right and crossover mains, an 800-kv.-a. transformer for conveyor drive motors at the slope bottom, and a 300-kilowatt silicon diode rectifier along south mains that furnished 250 volts d.c. power for the trolley system. Short circuit, overcurrent, ground fault, and lightning protection was provided for the resistance grounded high-voltage power circuit which was

equipped with a fail-safe ground check circuit. A disconnecting switch was installed in the circuit near the entrance to the mine, and steelenclosed switch houses with vacuum switches were installed in the system underground near the slope bottom and in all branch circuits.

Electric face equipment in use in the right side of crossover mains at the time of the explosion consisted of a Joy 11CM-LAKK continuous miner, Bureau Approval 2G-2230-A, and National Mine Service Company 30S1234 shuttle car, Bureau Approval 2F-1323-13 in No. 7 entry, and a Galis 300 roof drill, Bureau Approvals 2F-2070A-1 and 25B1471 in No. 6 entry. The continuous miner and roof drill were operated with 3-phase 550 volts a.c., and 250 volts d.c. was supplied the shuttle car by a 150 kw. rectifier in the 600-kv.-a., a.c.-d.c. power center located approximately 400 feet outby the face of No. 7 entry. Short-circuit protection for trailing cables on the face equipment was by circuit breakers in the 13.200/550-volt power center. Ground fault protection was provided for trailing cables on the a.c. equipment.

A thorough examination of this equipment during the investigation disclosed no defects in permissibility or defective trailing cables. The continuous miner and roof drill were effectively frame-grounded through type G trailing cables and the shuttle-car frame was grounded by properly installed diodes. Tests for stray current between the frames of the continuous miner and shuttle car in No. 7 entry and between the equipment frames and earth disclosed a maximum of 7 volts and 4.5 milliamperes with the equipment in operation. Lesser values were obtained when the machines were not being operated. Results of studies made of intrinsic safety of circuits and equipment show that the measured value of current is considerably less than the minimum value of igniting current for methane.

Further examinations revealed that the continuous-miner control switches, with the exception of the conveyor switch, were in the on or running position. The water valve for the spray system was closed. Soot and dust deposits on the controls indicated that they had not been disturbed in the interim following the explosion and the time that they were examined.

Approximately 20 percent of the tungsten-carbide tipped bits in the drums and ripperveyor chain of the continuous-mining machine were worn to a point where only about 50 percent of their original cutting length remained.

During the inspection completed in December 1969, tests for methane were made frequently while electrical equipment was being operated in the face areas and just prior to the time such equipment was taken inby the last open crosscuts. Tests were made with permissible flame safety lamps and, according to testimony given during the investigation, these were generally made with walking flames. After the explosion, classes in the safe use and care of permissible flame safety lamps were begun at the mine by the Bureau of Mines. Instructions were also given in the maintenance and use of electrical methane detectors.

Illumination and Smoking

Permissible electric cap lamps were used for portable illumination underground. Smoking was not permitted underground or observed during preceding Federal inspections. Searches for smoker's articles were conducted periodically, but a record of the searches was not kept.

Mine Rescue and Firefighting Facilities

Some of the workmen at the mine have been trained in mine rescue and recovery; however, mine rescue equipment was not available at the mine. Properly equipped and trained mine rescue teams were available at a nearby mine. Self-rescuers were available for the underground personnel and some of the workmen wore self-rescuers during the rescue and recovery operations after the explosion. During the spot inspection made following the completion of the investigation, it was found that direction signs were not posted in the emergency escapeways in the mine and the shart emergency facilities were not maintained to allow persons to escape quickly.

Firefighting equipment consisted of waterlines paralleling the south mains and slope belt lines with outlets at suitable intervals. Water hose was provided at the belt tails and along some portions of the south mains belt line. Chemical fire extinguishers and supplies of rock dust were provided at belt drives and tailpieces, electrical installations, and oil-storage locations. A high-pressure rock-dusting machine with ample supplies of rock dust was available.

STORY OF EXPLOSION AND RECOVERY OPERATIONS

Activities of Bureau of Mines Personnel

Donald W. Huntley, subdistrict manager, Coal Mine Health and Safety District A, was notified of the occurrence about 4:20 a.m., April 10, 1970, by a telephone call from Thomas Musick, vice president and general manager. Huntley notified Harry Thompson, Warren Lewis, and Clyde Turner, coal-mine inspectors. Huntley, Thompson, and Turner arrived at the mine at 5:55 a.m., and Lewis arrived at 6:15 a.m. W. Dan Walker, Jr., district manager, was notified and arrived at the mine at 9:30 a.m.

A Withdrawal Order was issued under Section 104(a) of the Federal Coal Mine Health and Safety Act of 1969 on April 10, 1970, debarring all persons from the entire mine, except those needed for exploratory and recovery work. Before this Order was issued, the workmen had been removed from the mine, except the men engaged in restoring ventilation to the affected area.

Mining Conditions Immediately Prior to the Explosion

The mine was being operated normally on the day of the explosion. The main fan was operated continuously, and the fan-pressure recording chart indicated normal operating pressure until about 3:40 a.m. when abrupt changes occurred resulting in a drop in pressure of 0.25 inch. See Appendix D. The pressure remained at that level until ventilation facilities in the explosion area were repaired. The records of examinations by the mine examiners on April 9 and testimony of the employees indicated that conditions were normal and that there were no significant changes made in the ventilation pattern.

Evidence of Activities and Story of Explosion

Production of coal from the right side of crossover mains section ceased at about 11:15 p.m., on the 4 p.m. to 12 midnight shift, Thursday, April 9, 1970, when No. 6 entry and a crosscut between Nos. 6 and 7 entries had been driven to the depth permitted for advance beyond supported (bolted) roof. The continuous-mining machine was moved from the face and parked near the entrance to No. 6 entry at the end of the shift. The roof-bolting machine was in No. 7 entry where roof bolts were being installed until about 11:20 p.m., the normal quitting time.

The crossover mains section coal-producing crews for the 12 midnight to 8 a.m. shift arrived on the section about 12:30 a.m., April 10, 1970. The crews consisted of 15 workmen, including Harold Brindle, section foreman. One crew of 10 men proceeded to the left side of the section to start producing coal in No. 4 entry. The other crew of five men, which included a serviceman from the Joy Manufacturing Company who was checking the performance of a new Joy 11CM miner that had been taken underground on March 30, 1970, proceeded to the right side of the section.

Thomas G. Burkley, miner operator's helper, and Delmont Douglas, Joy serviceman, started to service the miner and change some dull bits; Francis Rethi, shuttle-car operator, went to his shuttle car and checked the trailing cable on the car and cleaned up around the belt feeder; and Andy Lazeration, roof bolter, proceeded into No. 7 entry, checked the condition of the roof and made a test for methane near the face with a flame safety lamp using a walking flame. Lazeration did not detect methane and started to install roof bolts. After he had installed several bolts, his brother, Pete Lazeration, miner operator, came into the place to assist him.

In the meantime, Brindle, section foreman, had started his fire-boss examination at the beginning of the shift and made his way from No. 2 entry right toward No. 7 entry. Brindle arrived in No. 7 entry and examined the place about 1:30 a.m. just as the last roof bolt had been installed and the bolting machine was being taken out of the entry to start bolting in No. 6 entry and crosscut. Methane was not detected during this examination.