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The Harrington No. 10 Colliery (at the time of the explosion belonging to the United Steel Companies Ltd.) is situated at Lowca Village about six miles from Workington and three miles from Whitehaven. The shafts known as No. 10 (downcast) and No. 9 (upcast) and of 20 feet and 16 feet diameter respectively, are sunk on high ground within a few hundred yards of the sea under which are most of the workings. The pit bottom is in the Six Quarters Seam at a depth of 648 feet from the surface, and the Main Band Seam at the shafts lies at a depth of 350 feet.

The colliery output which was 5,000 tons per week in 1938 fell to 2,300 tons in 1943 and rose to about 3,000 tons per week in December 1946.

In 1946, altogether 770 persons were employed; 240 (of whom 30 were women) were employed on the surface ; 195 were engaged at the coal face and 335 as haulage and oncost workers. The average number employed underground on the day shift was 250, but on the day of the explosion there were 208 at work of whom 53 were in the Main Band Seam, the seam in which the explosion occurred.

Mr. J. A. Nimmo was the General Mining Manager of the Company’s Cumberland collieries, Mr. T. J. Hughes was the Agent, and Mr. Frank Graham the manager of the Harrington Colliery. At the date of the explosion Mr. John McCracken was the undermanager, having been transferred three months before from a similar position at No. 5 pit owing to the illness of the regular undermanager.

Supervision in the No. 2 district of the Main Band Seam was by two overmen (day and afternoon) and by one deputy on each shift.

The Main Band Seam, which is overlain by a thick sandstone roof, has a total thickness of 12 feet of coal and thin dirt partings, but the roof coal (2½ feet thick) is not worked; the floor is of fireclay and then a thick hard shale.

In this seam four units or districts were being worked, entered from the Main Band engine plane which starts at the Lickbank Junction off the North Plane haulage road at 1½ miles from the shaft and runs west for about a mile.

At this point mechanised mining was begun in 1943 in an endeavour to increase output, four parallel levels (numbered 1 to 4) being started off the Main Band engine plane as development roads and advanced by Joy Loaders and a M. & C. Arc Shearer. Later a trunk belt conveyor was installed in No. 3 level and also chain conveyors. Auxiliary fans were then introduced to ventilate the levels.

From these levels the No. 2 district, in which the explosion occurred, was opened out by five headings at right angles to the levels as shown on Plans Nos. 1 and 2, these headings being commenced in November 1944; shuttle cars were then introduced. The headings were driven at 50 feet centres, with thirlings at 150 feet, and were 15 feet wide by 10 feet high. As the headings advanced pillar workings were opened out to the left (later known as the shuttle car section), but the shuttle cars were withdrawn and this section abandoned a short time prior to the explosion, and supports were being withdrawn from it.

The area comprising the No. 2 district was very wet, water raining from the roof in the headings, and it was decided to advance the Nos. 2 and 3 headings (which were rising at about 1 in 18) rapidly to the boundary – fixed by a limiting minimum cover of 240 feet – so as to drain the water from the area, Duckbill loaders with Goodman shortwall coalcutters and Victor drills for simultaneous shotfiring being installed. These headings were reduced to a height of 6 to 7 feet at a point about midway between Nos. 5 and 6 left thirls, and continued at that height, the rate of advance being about 40 yards per month.

No. 1 heading was stopped at No. 4 left thirl, and No. 5 heading having struck a fault was discontinued, the intention being to drive back from the No. 5 right thirl to establish a connection.

No. 3 heading was the haulage road and intake airway in which was installed a belt convey or fed by a scraper chain conveyor in No. 6 left thirl between Nos. 2 and 3 headings and a similar conveyor in No. 5 right thirl.

At the date of the explosion Nos. 2 and 3 headings were some 40 yards in advance of the last (No. 7) thirl, these workings being about 3 miles distant from the shafts.

When no longer in use the thirls were sealed off by corrugated sheeting covered by brattice cloth. The undermanager said there was a shortage both of bricks and bricklayers and that was the reason brick stoppings had not been erected, but he considered the corrugated sheeting efficient.

Ventilation was produced by a Capell double inlet fan, electrically driven, situated at No. 9 shaft with a capacity of 200,000 cubic feet per minute at a water gauge of 8 inches. On the North side of the pit the North Plane haulage road (in the Six Quarter Seam) is the main intake; at the Lickbank Junction about 1½ miles from the shaft the air splits, that to the Main Band seam going west by way of the Main Band Engine Plane. From this separate splits are taken to the No. 4, No. 3 and then the No. 2 units, the remainder passing further inbye to ventilate the No. 1 unit.

The total quantity entering the North Plane as measured on 7th November, 1946, was 61,870 cubic feet per minute. The quantity entering the Main Band on the same date was 41,750 cubic feet. No measurements of the quantities in the separate splits in the Main Band were recorded in the statutory Air Measurements Book (M. & Q. No. 37), but readings for No. 2 District taken from a notebook showed 17,017, 16,744 and 17,876 cubic feet per minute for September, October and November, 1946, respectively.

Plan No, 2 shows the system of ventilation in the No. 2 unit, the district in which the explosion occurred. It will be seen that three auxiliary fans were in use, all of them electrically driven.

No. 1 fan fixed in No. 2 road was of the "Aerex" type (made by Walker Bros.) 19 inches diameter, driven by six half-inch belts (only four in use) with a total capacity of 8,750 cubic feet per minute. Adjustable louvres were fitted on the intake end for air regulation. This fan had approximately 300 feet of 24 inches diameter Meco canvas tubing attached to it for ventilating part of the old shuttle car section of workings recently abandoned and being drawn off.

No. 2 fan fixed in No. 3 road was of the "Aeroto" screw type (made by Davidson & Co.) direct driven at a motor speed of 2,900 r.p.m. Capacity 5,000 cubic feet per minute with 540 feet of tubing 24 inches diameter. Used for ventilating No. 4 heading and the No. 5 thirl extension. No. 3 fan also in No. 3 road was a duplicate of No. 1 and was used for ventilating Nos. 2 and 3 headings.

All the auxiliary fans were kept running continuously when men were at work in the area they served. Normally Nos. 2 and 3 ran constantly from Sunday midnight until about mid-day on the following Saturday. They were re-started on the Sunday morning at about 6.45 and run for some 5 or 6 hours – usually the maintenance engineers were on duty during this period – after which they again stood until re-started by the night shift deputy before making his pre-shift examination for the Monday morning shift.

No measurements were at any time taken of the quantity of air circulated by these fans, and for the reason stated later in this report the quantity in the intake at 100 yards from the working face was not measured as required by General Regulations.

Firedamp. – The Main Band seam is regarded as a fairly gassy one. During the six months preceding the explosion the statutory reports showed the presence of firedamp in No. 2 district to have been reported as follows :–

Back shift of same day, "2½ per cent, of gas in Nos. 2 and 3 Rises auxiliary fan under repairs."

Later on same back shift timed 8.15 p.m. to 9.10 p.m. "Nos. 2 and 3 Rise clear. Fan repaired."

No inspection on behalf of the workmen had been made in this district during this period.

Electrical Layout in No. 2 District. – Plan No. 3 shows the arrangement of the electrical cables and apparatus in this district.

The apparatus was supplied by a 100 kva Transwitch Unit [(1) on plan] 3,300/550 volts, situated in a substation on the low side of No. 3 Level. The oil circuit breaker on the 550 volt side of the transformer was fitted with earth leakage protection and controlled the main cable passing up No. 3 heading.

This main cable passed through the busbars of a number of switches before dividing into several sub-circuits. No. 2 switch, at the foot of No. 3 heading controlled the main trunk belt conveyor in that heading and was operated by an adjacent push button. Nos. 6 and 7 switches, situated near No. 3 left thirl, controlled a Mono pump in No. 3 heading and No. 1 fan respectively. The main and tail haulage in No. 2 heading was supplied by a cable teed off from the main cable just on the inbye side of No. 7 switch.

The main cable terminated at two section switches, Nos. 10 and 11, a little below No. 4 right. No. 10 switch controlled the coalcutter and drilling machine in No. 5 right and No. 2 fan; No. 11 switch controlled the two scraper chain conveyors feeding on to the No. 3 heading belt conveyor, one in No. 5 right and the other in No. 6 left, and the two duckbills in Nos. 2 and 3 headings. From No. 11 switch a pilot cable ran down No. 3 heading back to a push-button switch at the transfer point on No. 3 level, enabling the starting and stopping of the branch conveyors to be controlled, in relation to the movement of the main belt conveyor, from this point.

Just outbye of Nos. 10 and 11 switches a branch cable led further up No. 3 heading to supply No. 3 fan and the section switch, No. 19, controlling the supply to the coalcutters and drills in the headings.

The whole of the electrical apparatus in the district was of certified flameproof type, with the exception of the two shortwall cutters, two duckbills and the scraper chain conveyor in No. 5 right, which were of American design and manufacture.

The main and branch roadway cables were paper-insulated, lead-sheathed and double wire armoured, the short lengths of cable between the duckbills and their gate end switches were pliable wire armoured, as were the conveyor pilot cables ; the coalcutter and fan cables were screened trailing cables, and the drill cables were unscreened.

A certified bell and approved dry battery were used on the bare wire signalling system associated with the 30 h.p. main and tail haulage, the bare wires extending inbye as far as the return wheel at No. 5 left, and outbye to the bottom of No. 2 supply road.

A similar dry battery signalling system was installed in No. 3 heading, the bare wires extending from the transfer point at the outbye end of the heading to about 20 yards inbye of No. 4 right, beyond which up to No. 6 left there was a pull wire by which signals could be transmitted outbye.