The Plodder seam lies in the lower part of the productive Coal Measures. In the area being worked it has a total thickness of 5 feet 1 inch, including two bands of dirt, 3 inches and 4 inches thick respectively; it is the practice to leave up 7 inches of top coal. The roof is shale of medium strength whilst the floor is a strong warrant or fireclay. The seam, which dips at the general gradient of 1 in 5 in a direction approximately due south, is not of first class quality but the large coal finds a ready market as locomotive fuel.

Serious development in the seam (the final one to be exploited at the colliery) began in 1956, though a short proving heading had been driven and abandoned in 1928-29. This heading, 50 yards long, had been reached by a cross measure drift, or tunnel, started from a road in the Haigh Yard seam at a point some 350 yards from and approximately level with the bottom of No. 1, the downcast shaft. When the project was abandoned, a brick stopping was built across the bottom of the stone drift.

Early in 1956 it was decided to re-open the Plodder seam and the brick stopping at the foot of the stone drift was removed. Firedamp was encountered behind the stopping but was cleared by the installation of a fan, placed outbye of the foot of the drift, and appropriate tubing. The stone drift was found to be in good condition but the heading in the seam was almost completely closed. It was cleaned up and a drivage to prepare a face 110 yards long to advance to the dip and another to be used as a return airway (known as Gibfield Stret) were started; this work can be seen on inset B, Plate I.

During the development period the narrow places were ventilated by a fan placed on the Haigh Yard level outbye of the foot of the stone drift; firedamp was never detected. The coal was conveyed along a system of conveyors and ultimately to the foot of the drift, where it was loaded into tubs. When the drift had been driven originally, a brick wall had been built up the middle for ventilation purposes. The conveyor was laid in the right hand passageway thus formed (going uphill) whilst a tub track for the taking in of supplies was laid up the left side. The haulage for the supplies was an electrically driven 10 h.p. Pikrose engine fixed in a recess at the side of the roadway on a short level piece of road at the top of the drift in the area where the Plodder seam had been exposed by the driving of the drift. The roads leading from the short level roadway had a dipping gradient in both an inbye and an outbye direction. The drum of the engine faced inbye but the placing of a pulley appropriately in the floor a few feet away enabled the haulage to be used both on the coal heading dipping towards the face and on the stone drift outbye.

The development programme was carried out without serious difficulty. A ventilating circuit was established on 12th September, 1956, when Gibfield Stret made a connection with an existing roadway in an old district of the Plodder seam workings of the neighbouring Gibfield colliery.

After this connection had been made, another drivage in the coal was started back towards the pit bottom from a point approximately half way along the dip development face, to serve as a loader gate and second intake airway. This heading joined up with a new stone drift (No. 1) set off from the Haigh Yard level some 120 yards inbye of the foot of the 1929 drift (henceforth called No. 2), see Plate I.

Towards the end of October the Plodder development face to the dip was started, as an orthodox double unit face, with two face belts delivering on to a centre loading belt in No. 1 drift intake, the coal being loaded into tubs at the foot of the drift. There was no urgency for the dip face to move away quickly and an average advance of no more than one cut of 4 feet 6 inches was made each week. Preparations for the opening out of a flank face to work towards Gibfield proceeded apace, however, and at a later date the enlarging of Gibfield Stret, with a view to providing a new return to Chanters No. 2 shaft, was started. In connection with this scheme, a start was made, about the beginning of February, 1957, with the ripping of the bottom ten yards of No. 2 drift in preparation for the building of an air crossing over the Haigh Yard level. The 10 h.p. Pikrose hauler at the high point of No. 2 intake, which had been in action to a limited extent only after No. 1 drift had been completed, was used to deal with the dirt made at this ripping.

The Haigh Yard seam at Chanters is being worked in an area some 3,500 yards from the Chanters shafts; since the main haulage road and the return airway for the Haigh Yard workings passed quite close to the shafts of St. George's colliery, the opportunity was taken to use these shafts, both upcast and downcast, to ventilate the Haigh Yard workings.

The stone drifts to the Plodder district were set off from a road in the Haigh Yard seam in an area remote from the present Haigh Yard workings; in fact, as already mentioned, within a distance of less than 500 yards from the foot of Chanters No. 1 downcast shaft. A quantity of 95,000 cubic feet per minute of fresh air passed down this shaft into the Trencherbone inset, at the depth of 375 yards, to ventilate the Victoria and Five Quarters seams. Below the Trencherbone inset there was no consistently measurable flow of air in the shaft, and the Plodder district had to rely upon a split of 9,500 cubic feet of air per minute from Bedford No. 3 downcast shaft (via the old No. 1 Engine brow) and another of 8,660 cubic feet of air per minute from St. George's downcast shaft, by way of the Haigh Yard haulage road, which is also known at St. George's clip brow. Both these splits reached the Haigh Yard level independently, some distance inbye of Chanters No. 1 shaft. Just before reaching the Plodder, about 8,000 cubic feet per minute of this quantity leaked away to ventilate a man riding brow and some connections leading to Chanters No. 2 shaft, leaving a quantity of just over 10,000 cubic feet per minute to circulate in the Plodder district.

The air for the Plodder district thus came from St. George's and Bedford downcast shafts and returned to Gibfield upcast shaft. In the district itself intake air travelled up both Nos. 1 and 2 drifts, along the face advancing to the dip, and returned up Gibfield Stret and the newly developed flank face into Gibfield No. 1 East old district. Air measurements on 22nd February, 1957, showed that a quantity of 3,182 cubic feet of air per minute was entering the face at the left hand intake, one of 3,996 was entering the face at the centre intake and a quantity of 2,422 was leaking from No. 1 intake through the connection between it and the return. This amount of leakage was due to the fact that a gate belt was installed in the connection. Statutory sampling showed that the air at both the intake and return ends of the dip face contained 0. 1 per cent. methane.

When the return air reached the old Gibfield district, two paths were available to it, the first by the bottom road of Gibfield No. 1 East district (on which a loosely built stopping which acted as a regulator was built, through which it was possible to travel and close to which the board indicating the dividing line between Chanters and Gibfield was placed), and the second via a length of old face and the untravellable middle road of the same district. The first of these currents, a quantity of 6,000 cubic feet of air per minute, passed straight into the return of Gibfield Plodder whilst the second, which contained 4,000 cubic feet of air per minute, joined the intake to Gibfield 21's Plodder district and went round a length of slowly-moving coal face before entering the return. These were the arrangements when, following an inspection at Gibfield by certain officials on 22nd February, it was decided to divert some of the 6,000 cubic feet of air per minute current, by the installation of an 80-yards length of tubing, from the loosely built stopping on the bottom road of No. 1 East district through some ventilation doors to 21's intake. This was in an endeavour to lower the temperature of 21's district, not on account of the finding of inflammable gas there (see inset A, Plate I).

The installation of the air tubes, which were partly of metal and partly of canvas, was completed on 27th February. No attempt was said to have been made to force air through the pipes by restricting the amount of air passing through the loose stopping straight into the return, and a measurement of the air coming out of the pipes, on 28th February, showed that a quantity of 1,581 cubic feet of air per minute was passing through them into 21's intake.

The electrical apparatus in the Plodder district was supplied from a 150 KVA 2,000/600 volts transformer in No. 2 Plodder substation, situated some 340 yards from No. 1 pit bottom. The neutral point of the transformer was earthed and a flameproof oil-immersed section switch in this substation controlled the 600 volts supply to the district. This switch was fitted with time-lagged overload trips set at 100 amperes and an instantaneous earth leakage device arranged to trip when 7½ amperes flowed from phase to earth. On the occurrence of an earth fault, this earth leakage device was arranged to trip out the switch and lock it out mechanically, with an indicator flag to show that it had operated.

The 0.075 square inches paper insulated lead covered double wire-armoured 600 volts feeder cable from the above switch passed up No. 1 drift to a flameproof gate-end switchboard in the connecting road between Nos. 1 and 2 drifts, controlling the conveying and cutting apparatus on the face. A similar cable was looped from the busbars of this gate-end switchboard outbye to supply the switch controlling the 10 h.p. Pikrose haulage in No. 2 drift. This control switch and the haulage motor, both of flameproof type, were interconnected with a four-core pliable wire armoured cable with bolted type connectors at each end. The haulage motor was also fitted with an integral three-pole line switch. This haulage unit and its control switch were some 90 yards from the section switch in No. 2 Plodder substation.