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of the ventilating current previous to the explosion. This map also shows the probable point of origin of the explosion, the approximate area traversed by flame and the approximate area affected by violence. The map of the explosion area, appendix B, shows on a larger scale the course of the ventilating current previous to the explosion, the probable point of origin, the approximate area traversed by flame, and the approximate area affected by violence. In addition, this map shows the location of bodies of the victims of the disaster, the direction of major forces, the locations where dust and air samples were taken during the investigation, together with reference numbers thereto, and the points on the entries where the rock-dust zones terminated as of the day of the explosion.

METHANE AS A FACTOR IN THE EXPLOSION Very little methane was liberated in the mine during normal operations previous to the explosion. At the time of the last Federal inspection, the mine was liberating a calculated quantity of approximately 64,000 cubic feet of methane in 24 hours. Table No. II contains the analytical results of air samples collected during the investigation. It will be observed that the methane content of the face samples ranged from 0.04 to 0.09 percent and two samples in the return air current contained 0.07 and 0.06 percent methane. The face samples were collected at a time when the ventilation had been only partially restored and there was no perceptible movement of air at the faces. An air sample collected at the face of 1 west, where the explosion is believed to have originated, contained 0.09 percent. Although tests were made frequently in the returns and at the face of working places during recovery operations by shift loaders who used flame safety lamps, traces of methane were not found. These facts lead to the conclusion that methane was not involved to any appreciable extent in this explosion.

TABLE II.-Air analysis report
(Mine: No.5. Company: Centralia Coal Co. Collected: Apr. 1, 2, and 3, 1947)

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Four of the six working sections of the mine were affected by the flame and violence of the explosion. The remaining two sections were affected only by the afterdamp resulting from the combustion of coal dust. Forces were extremely violent in some portions of the explosion area, while in others the velocity of the explosion was so slow that little evidence to indicate the direction of forces could be observed. The direction of forces was determined wherever possible by the movement of material, such as timbers, shattered remains of wooden stoppings, cars and other equipment, debris, and by the bending of trolley wire hangers. From evidence of this nature, it was determined that the explosion probably originated at the face of 1 west and spread north and south through the first openings to the right and left. The forces in 20, 21, and 22 north 4 west were generally strong in the direction of 4 west throughout the entire

length of these entries, except the portion of these entries in the active working section near 1 west where the evidence of forces was not pronounced in any direction. The forces evidently traveled across and through the rooms off 21 north 1 west and there was evidence of strong forces toward the faces of 20 and 21 north. Evidence indicated that the explosion traveled outby on 1 and 2 west between 19 and 20 north and also in three of the air course rooms between 19 north and 20 north. While there was much evidence of intense heat and flame in the rooms off 18 and 19 north, there was little evidence of force in any general direction in these rooms. The forces, however, were definitely and strongly inby in 18 north and 19 north entries. Strong forces from 1 and 2 west entered 18 and 19 north 4 west and traveled toward 4 west for a distance of approximately 800 feet. Forces in 1 and 2 west were definitely outby between 18 north and a point about 200 feet inby 14 north where they died out completely.

FLAME

The area traversed by the flame of the explosion was determined by a careful examination of abandoned and active workings within the explosion area. In this examination, evidence of flame was indicated by deposits of coked particles on mine surfaces and timbers, bits of burned paper, burned explosives, and card. board explosives boxes, charred or burned sight strings, and charred or burned splinters on numerous timbers left standing throughout the explosion area.

Flame extended from the face of 1 west and the workings adjacent thereto to a point outby on 1 and 2 west approximately 800 feet from the faces of 1 and 2 west. Flame was present in 20, 21, and 22 north entries off 4 west, extending from 2 west a distance of approximately 800 feet toward 4 west on these entries. The active rooms off 20 and 22 north 4 west were also filled with flame during the explosion. Flame was present throughout 20 and 21 north 1 west and the active and abandoned rooms connected thereto. Flame traversed three of the air course rooms between 19 and 20 north 1 west, but failed to reach 19 north at the points where these rooms connected to 19 north. Flame traveled through the crosscuts in the rooms off 19 north and came out on 19 north entry through Nos. 17, 18, 19, and 20 rooms, crossed over to 18 north through the last two crosscuts, entered the rooms off 18 north through Nos. 17, 18, 19, and 20 rooms and traversed the active rooms off 18 north.

Special attention is invited to the fact that flame traveled through the crosscuts of all of the rooms off 19 north and a number of rooms off 18 north and failed to reach 18 and 19 north entries, except in the areas near the last three crosscuts.

FACTORS THAT PREVENTED THE SPREAD OF THE EXPLOSION

The explosion was localized and confined to four working sections of the mine; however, the two remaining sections into which the explosion failed to propagate were affected by afterdamp. The explosion failed to propagate further in every instance when it reached or as it approached the end of the rock-dusted zones on the entries. While the explosion traveled through all of the active rooms and some of the abandoned rooms in each section, none of which had been treated with rock dust, it failed to propagate through the old workings to any great extent because many of these were partially caved and in some instances filled with incombustible roof rash that had been transported there from adjacent entries by means of shuttle cars. While some of the back entries were not rockdusted, they were generally fallen in and the dust in them was largely covered by incombustible rock. A factor that retarded the development of high velocities as the explosion traveled outby was the existence of large areas of open abandoned workings which provided space for the relief of pressure. Unquestionably, the presence of rock dust in entries, even though somewhat deficient in quantity, was the most important factor in preventing the spread of this explosion throughout the mine and to the shaft bottom.

ACTIVITIES IN THE WORKING SECTIONS AT THE TIME OF THE EXPLOSION

A section of this report entitled "Explosives and Blasting" under the heading of "General information” describes in detail the blasting practices at this mine. It was established previously in this report that the explosion occurred at approx. imately 3:26 p. m. The official quitting time for the shift was 3:30 p. m. At the moment of the explosion, all face operations had ceased, except the igniting of shots which had been charged in the boreholes at various times during the shift. Nearly all electric equipment in the immediate explosion area had been withdrawn from the faces and parked. It was definitely determined that no face electric equipment was in operation at the time of the explosion. It is, therefore, believed that the only possible ignition sources present at the faces at the time of the explosion were the open lights of the shot firers and a few others, and the detonation of explosives. Most of the men comprising the working shift were at the man-trip stations on the entries where the man-trips were already made up and waiting for the shot firers to complete the ignition of shots, so that the shot firers could ride to the bottom of the shaft with the man-trips, all of which was customary practice.

To support the conclusion that the explosion originated at the face of 1 west entry, the condition of the working sections in the mine is discussed in detail. 13 and 14 north section, 1 west

This section was the first set of workings ventilated by the intake air current and it was not directly affected by the flame and violence of the explosion. The man-trip was in process of being loaded in 13 north when the explosion occurred. Evidently all of the working shift in this section, except a machine man, a driller, a trackman, and a trip rider, walked down 13 north entry after the explosion and encountered afterdamp at the intersection of 13 north 1 west where they were all killed. Sixteen bodies were subsequently found at this point by rescue crews. The machine man, driller, trackman, and trip rider followed these men down 13 north entry sometime later and after finding the bodies of their comrades at 1 west, they contacted the assistant mine superintendent at the shaft bottom by telephone. Subsequently, these men were met by rescue parties. All four of them survived the explosion and it is believed that their 16 fellow workmen would also have survived if they had remained in the 13 and 14 north working section or if they had been equipped with and had used miner's self-rescuers. 13 and 14 north section, 1 west

Two crews of men were working in this section; one crew worked in room Nos. 19, 20, 21, and 22 off the 23 and 24 south entries, and the other crew worked in a group of rooms inby and the entries. Blasting operations had been completed in this section and the men had boarded the man-trips. The explosion must have occurred before the trips started toward the bottom of the shaft. The concussion from the explosion apparently warned the men that something of a serious nature had occurred in some other part of the mine, and they left the man-trips and started to walk toward the 4 west haulage road. Pieces of cardboard and wood that the men used to sit on in the steel cars, and their lunch pails were still in the cars, indicating that they abandoned the cars hurriedly. The outby group of 13 men was found on 23 south about 200 feet inby 4 west and about 700 feet outby the man-trip. The 14 men who had worked inby the farthest apparently tried to find their way to 22 south entry through one of the rooms which had been connected between 22 and 23 south entries. This group of men was found at the face of room 8 off 23 south, and notes indicating the time of day were found chalked on pieces of slate at the face of No. 11 room. Various notes left by these men indicated that some of them were alive but weakening fast at 7 p. m. Rooms Nos. 6 and 15 off the 23 south were connected with rooms driven from 22 south, but it is extremely doubtful that these men could have saved themselves by traveling that way, as they would eventually bave to come onto the full return from the devastated areas. They could however, have retreated to the innermost point of the section and erected barricades. The doors and stoppings that were damaged by the explosion on the outby end of this section permitted the poisonous air to be short-circuited away from this isolated part of the mine.

The consensus of opinion of the men engaged in directing the recovery work was that these 27 men might have saved themselves if they had knowledge of barricading. 18 and 19 north section, 1 west

Room 13, 19 north: Fresh cut at face.

Room 14, 19 north: Face of room and crosscut cleaned up. Mining machine back from face, controller off, nips off.

Room 15, 19 north: Cleaned up.
Room 16, 19 north: Cleaned up. Loaded car at face.
Room 17, 19 north: Cleaned up.
Room 18, 19 north: Cleaned up.
Room 19, 19 north: Cleaned up. Loaded car at face.
Room 20, 19 north: Cleaned up.

Nineteen north entry: Face and crosscut to right cleaned up. Limit of flame 10 feet inby last open crosscut. Flame did not reach face.

Eighteen north entry: Face and crosscut to left cleaned up. Flame did not reach face.

Room 21, 18 north: Cleaned up. Flame extended about 30 feet into room, but did not reach face.

Room 20, 18 north: Face of room shot down. Top left rib shot misfired. Crosscut to left cleaned up, and loading machine parked out by crosscut switch. Flame extended 60 feet inside room, but did not reach face.

Room 19, 18 north: Old fall at face of room. Room had been idle for 30 days.

Room 18, 18 north: Left crosscut cut through to face of room 19. Cleaned up. Body found along left rib near face. Left rib of crosscut was shot to make connection with 19 room. Eight holes had been charged at the face of room 18. The top left rib shot had been exploded, resulting in a blown-out shot. Remaining holes were charged but not fired. Evidence of heat was present on the surfaces of all fuzes extending out of the holes. Flame extended to the face of the room. Four bodies, one of which probably was the shot firer, were found near the face. It was concluded that the top left rib shot was ignited by the explosion and blew out because the shots upon which it depended were not fired. A new crosscut was turned to the left near the face of room 18 and was in two cuts. Six holes had been charged at the face of this crosscut and the top left rib shot had been exploded, resulting in a blown-out shot. The remaining holes were charged but not fired. Evidence of heat was present on the surfaces of all fuzes extending out of the hole. It was concluded that the top left rib shot was ignited by the explosion and blew out because the shots upon which it depended were not fired.

Room 17, 18 north: Eight holes at the face charged and stemmed. Fuzes were not ignited but showed evidence of heat on surfaces extending out of holes. Flame reached the face. Positive evidence of coal-dust stemming was found in the holes. Crosscut to the left cleaned up.

Room 16, 18 north: Eight holes had been charged at the face. The top right rib hole and the third top hole from the right had exploded. The remaining holes were not fired but evidence of heat was present on the surface of all fuzes extending out of the holes. Flame extended to the face of the room. was concluded that the two exploded charges were ignited by the flame of the explosion. Right crosscut cleaned up.

Room 15, 18 north: Cleaned up. Room had not worked for about 6 weeks. Flame traversed this room.

Room 14, 18 north: Face of room stopped previous to explosion. Crosscut turned to left near face, driven two cuts. Face of crosscut shot down. Coal fall appeared normal. Flame reached the face of the room and crosscut. Sixty feet back from the crosscut, another crosscut had been turned to the left to pick up No. 15 room. This crosscut had been driven almost its full length. The face was shot down and the coal fall appeared to be normal. A body, presumed to be the second shot firer, was found along the right rib in this crosscut. Flame extended about half way through the crosscut but did not reach the face.

Room 13, 18 north : Face of room, coal shot down. Coal fall appeared normal. Crosscut to right cleaned up. Flame extended to the face but did not extend outby the second crosscut from the entry.

It is seen from the foregoing data, that blasting was not scheduled to be done in any of the rooms off 19 north, in the faces of 18 and 19 north entries, nor in rooms 15, 19, and 21 off 18 north. It appeared evident that the two shot firers started at opposite ends of the section to ignite shots and worked toward the center. It was, therefore, concluded that one shot firer ignited the shots in the face of room 20 and then proceeded to room 18 where a track crew was still working. At this juncture, the shot firer would have requested the track crew to go to the man-trip, but the explosion occurred before the men left the place and before the shot firer had an opportunity to ignite any of the shots in room 18. In the meantime, the other shot firer ignited the shots in room 13, then proceeded to room 14 and ignited the shots in the crosscut near the face, and then ignited the shots in the second crosscut from the face. The explosion must have occurred very soon after these shots were ignited, but before the shot firer had time to leave the crosscut. His body was found along the right rib of this crosscut.

No evidence of movement of materials or other evidence of force could be found in rooms 13, 14, or 20, nor in any other working places in 18 or 19 north that would indicate that the explosion might have originated in one of these places. The information herein presented with reference to 18 and 19 north, and the

workings thereof, leads to the conclusion that the explosion probably occurred
before any of the ignited shots were detonated and that the explosion did not
originate in any of these places.
20 and 21 north section, 1 west

Room 5, 20 north: Face of room and crosscut to right shot down.
Room 6, 20 north: Face shot down.

Room 7, 20 north: Face of room shot down. Crosscut to left undercut but not drilled. Drill truck in room 70 feet from room switch.

Room 8, 20 north : Face shot down.
Room 9, 20 north: Face shot down.
20 north entry : Face shot down.
21 north entry: Face cleaned up.
Room 9, 21 north: Caved at face prior to explosion.
Room 8, 21 north: Face shot down.
Room 7, 21 north : Room face and crosscut to left shot down.
Room 6, 21 north : Face of room partly loaded out.
Room 5, 21 north : Face cleaned up.
Room 4, 21 north: Face cleaned up.
Room 3, 21 north : Face cleaned up. Clean-up car at face.

From the foregoing data, it is known that blasting was not being done at the face of 21 north entry or in rooms 3, 4, 5, 6, and 9 off 21 north. Blasting was completed in 20 north entry, rooms 5, 6, 7, 8, and 9 off 20 north, and in rooms 7 and 8 ott 21 north. The coal falls in all places appeared to be normal and there was no definite indication of forces in an outby direction between the faces and the first crosscuts of any of these places. The bodies of the shot firers were found with a number of other men at the man-trip, approximately 250 feet outby the face of 21 north. The entire 20 and 21 north sections 1 west were traversed by flame during the explosion. No evidence was found that would indicate that the explosion may have originated in the workings of 20 and 21 north 1 west. 20, 21, 22 north section, 4 west

Room 36, 20 north: Face of room and crosscut on the left cleaned up. Room 37, 20 north: Face of room and crosscut on the left cleaned up. Room 38, 20 north: Face of room cleaned up. Room 39, 20 north: Face of room and crosscut to left clearned up. Room 40, 20 north: Face of room and crosscut to left cleaned up. Room 41, 20 north: Cutting machine sumped in and half way across face. Controller otr.

Room 36, 22 north: Face of room cleaned up. Crosscut to left partly cleaned up. Loading machine back from face, nips off.

Room 37, 22 north: Face cleaned up. Crosscut to left cut through and shot down.

Room 38, 22 north: Face and crosscut to left shot down.

Room 39, 22 north : Face of room shot down. Body of shot firer found 75 feet from face near last open crosscut. Shot firer's cap found at face.

Crosscut to the left driven in three cuts. Six shots charged at face. Three bottom shots and top-right shot were not ignited, but indicated heat on fuzes projeeting out of holes. Top-left shot and middle shot blown out.

From the foregoing data it is known that blasting was not being done in any of the rooms off 20 north or in room 36 off 22 north. Blasting was completed in rooms 37 and 38, 22 north; the coal fall in these places appeared to be normal. In room 39 off 22 north, the face of the room was shot down and the coal fall appeared to be normal, but the last crosscut on the left which had been driven three cuts contained four unexploded charges and there was positive indication that the right top hole and the top center hole had been ignited and had blown out. Fuzes attached to the undetonated charges showed positive indications of heat on the outer surfaces. Three of the charges which were not detonated were probed during the investigation and it was found that they had been stemmed with coal dust in paper dummy bags. The body of the shot firer was found 75 feet from the face near the last open crosscut.

It is customary for the two drillers who act as shot firers to ignite the shots as soon as possible after the men have left the working faces so that they will not delay the starting of the man-trip toward the shaft bottom. Accordingly, it is presumed that the two shot firers entered 38 room and one ignited the shots in the crosscut while the other ignited the shots in the face. One of the shot firers then proceeded to room 37 and ignited the shots in the face, after which he proceeded to the man-trip where his body was found. The other

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