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These drifts were called the Lower Three Quarters Main Drift and the Lower Three Quarters Back Drift respectively, and it was in the former that the explosion occurred after they had been driven about 700 yards. During this period they had encountered several faults, including an 80 feet upthrow fault, a 150 feet downthrow fault and a downthrow fault of unknown throw, and had passed through small areas of the Broughton Moor Lickbank, the Upper Three Quarters and the Lower Three Quarters Seams, which were lying between intersecting faults. Output had been obtained from each of these seams and at the time of the explosion the Broughton Moor Lickbank and the Upper Three Quarters Seams were still being worked.

The drifts were driven at various gradients, depending upon the varying conditions, but since April, 1956, they had been advanced at a low gradient of 1 in 100/200 rising inbye. so to form roadways which later would be suitable for use in the working of the area when it was proved. Accordingly, they were supported by 12 feet by 8 feet steel arches generally set at 3 feet intervals. Stentons, supported by 8 feet by 7 feet steel arches, were driven at approximately 110 yards intervals.

About two weeks before the explosion the question of temporarily discontinuing the drifts arose so as to allow the labour to be concentrated on more promising and more immediate work elsewhere in the mine, and the management decided very rightly that as a first step another stenton, No. 5 Stenton, should be driven to provide through ventilation and eliminate the use of auxiliary fans during the period in which the drifts would be standing.

Organisation and Method of Work

The two drifts and the workings in the Upper Three Quarters Seam comprised a deputy’s district, in which 22 persons were employed. There was a deputy on each shift and except at week-ends he made the pre-shift inspection for the following shift. The deputies carried out the shotfiring in the drifts themselves, but a shotfirer was employed for this purpose in the Upper Three Quarters Seam workings.

Each drift was worked on a 24-hours cycle by three shifts, each with a team of three men, as under :–

Morning shift		6.10 a.m.		–		1.40 p.m.
Afternoon shift		2.10 p.m.		–		9.40 p.m.
Night shift		10.10 p.m.		–		5.40 a.m.

The deputies and the drifters changed shifts on a weekly rotation and, accordingly, each deputy always had the same drifters under his control.

Drivage was effected by firing rounds, each of about 35 shots, in holes drilled wet by compressed air boring machines, the debris being hand filled into tubs which in the Main Drift were hand drawn to a main and tail haulage system just outbye No. 4 Stenton. The shotholes were charged with unsheathed Polar Ajax explosive and No, 6 L.T. short delay detonators. The shotfiring appliance was a Beethoven Dynamo-Condenser Type Mark II 100-shot Exploder, Serial No. 820, which was used under an Instrument of Approval dated 16th March, 1956, in pursuance of Article 14 (2) of the Coal Mines (Explosives) Order, 1951. The Approval continued in force under the provisions of Section 191 of the Mines and Quarries Act, 1954.

Ventilation

The two drifts and the workings in both seams were served by one main ventilating split taken from the Loco Main Drift which was an intake airway, and according to the records the quantity of air passing in the Lower Three Quarters Back Drift at a point 10 yards outbye from No. 4 Stenton on 25th November, 1957, i.e., the day prior to the explosion, was 9,450 cubic feet per minute. Most of this air had already passed round the workings in the Upper Three Quarters Seam, from which the weekly output was 700 tons.

Each drift was ventilated by an electrically driven auxiliary forcing fan, that for the Main Drift being a 2 h.p. Aeroto fan situated in No. 4 Stenton and fitted with a combination of 18 inches diameter metal tubes and 20 inches diameter flexible tubing. The Back Drift was ventilated by 18 inches diameter metal tubes and 24 inches diameter flexible tubing fitted to a 5 h.p. fan at the outbye side of No. 4 Stenton.

According to analyses of the air samples taken by the management, the average methane content over a period of five months of the air passing at a point 10 yards from the face of the Main Drift was about 0.2 per cent. The highest content found was 0.4 per cent, in the last sample which was taken on 12th November, 1957. the previous highest being 0.33 per cent. on 9th July.

Upon occasion deputies have recorded in their statutory reports the finding of inflammable gas m the Upper Three Quarters Seam workings, but have never done so in regard to either of the drifts, including that for the pre-shift inspection made prior to the commencement of the shift during which the explosion occurred.

One of the two surviving deputies for the district said in examination during the investigation that about three weeks prior to the explosion he had found between 1½ per cent. and 2 per cent, of firedamp at the roof at the face of the Main Drift when it was about 10 yards back from its present position. He did not enter the fact in his report, however, being under the impression that he did not require to do so as at the time he found it he was testing during a stoppage of the auxiliary fan and was not making what he considered was a statutory inspection. He reported the matter, however, to an overman who was in charge of the drifting at the mine.

The overman stated that he remembered the occasion, but on testing carefully as high as he could reach in and around the face of the Main Drift. he found no inflammable gas.

Electrical Power Supply

A 550 v. 3-phase 50-cycle supply with earthed neutral point was derived from the secondary winding of a 150 k.v.a. 3,300/550 v. transwitch unit which was situated at the Loco Main Drift. It was fitted with a 3,300 v. oil circuit breaker equipped with over-current protection and earth leakage protection operated from the 550 v. system.

This system supplied the plant in the explosion area, including the two auxiliary fans, and also the workings in the Upper Three Quarters Seam in which coal cutting and conveying plant was in use, and the Loco Drifts in which power loading and two auxiliary fans were used. The total horsepower of the plant in the system was 627 h.p.

There was no evidence of frequent tripping of the switch on overload, although such a large amount of horsepower was connected to it.

Full details of the electrical plant in the explosion area are not relevant and accordingly are not given.