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January, 1952

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Coal has been worked in outcrops of south-west Durham for centuries, and a lease granted in 1687 by the Lord Bishop of Durham providing for the control of coal mines and seams in the neighbourhood of Evenwood, Ramshaw, Gordon, Morley and Toft Hill, indicates that by this period shafts had become necessary. These places lie to the east of the outcrop working and as time went on and the shallower deposits became worked out newer and deeper reserves had to be exploited towards the dip, thus inaugurating an almost imperceptible migration that has continued to the present. Unfortunately, water from surface streams was tapped by the shallower mines, which consequently, after exhaustion and abandonment, became flooded. If at that time those flooded areas had been effectively isolated from the rest of the coalfield the working of the eastern districts would have been very much simplified. They were not isolated, however, which in view of the state of mining knowledge then is not surprising. Indeed had the engineers responsible been armed with present day knowledge the task would have been formidable, for the area is intersected by several large faults and dykes running west to east, and many of the seams and much of the strata are porous.

Consequently, for more than 50 years collieries situated at a lower level to the east have been burdened with the cost of pumping large volumes of water coming from workings other than their own. Moreover, as the eastern collieries were deeper the pumping bead and resultant cost were greater than would have been the case had the water been handled in the west.

In 1936, at the initiation of the South-West Durham Reconstruction and Development Board, Arthur Morton Hedley, a prominent consulting mining engineer, conducted a survey of the area. He reported that the idea of establishing one central pumping station was quite impracticable, because of the work involved in driving roadways to conduct the water from the various accumulations to one point. Serious concern was recorded, however, on account of the disproportionate share of the general pumping cost that was being borne by those companies working properties to the east of the district for example, Dorman, Long & Co. Ltd., then producing approximately half of the district’s output were handling nearly 80 per cent. of the water being pumped.

Measures to alleviate this inequitable circumstance by forming a mines-drainage board were discussed in the report but there were many obstacles. Owners of collieries working in the western parts of the area had little or no underground water, and they pointed out that on account of their remoteness from the ports and industrial areas high transport charges made it difficult for them to compete with more favourably placed owners to increase their production costs by a share of the cost of a general pumping scheme would, they suggested, place them in an uncompetitive position. Probably the most effective argument against the scheme was put by those who stated that only about eighty per cent. of the potential output from the existing collieries was being marketed and so there was no object in liberating further areas of coal. In any event, by the outbreak of war very little had been done, and during the war all available plant and men were concentrated on producing coal from the workable collieries and any idea of a co-ordinated pumping scheme had to be shelved.

Post-nationalisation arrangements

On Vesting Date most of the district under consideration became the No. 4 area of the N.C.B. Northern Division, and as the majority of the senior mining engineers of the new Area had experienced many of the difficulties in working near accumulations of water, a co-ordinated dewatering plan was quickly put forward. At that time water from the flooded areas was being pumped at seven points.

Evidence available suggested that the water was held at three more or less separate levels, and that an appreciable quantity was overflowing from the higher levels and so had to be pumped against greater heads from the deeper accumulations. Consequently the first aim of the dewatering scheme was to pump out the water against the smallest possible bead, thereby preventing it from reaching the deeper workings to the east.

Extensive earthworks were completed in the area near the outcrops so as to minimise the amount of water finding a way underground in the first place, and pumping commenced at an old coalwinding shaft of the flooded West Auckland colliery (see Fig. 1). This particular shaft was chosen because it connected with the "pond" at the shallowest level and because it was known to be clear of debris to the level of the lowest seam — the Brockwell. Moreover, electrical power was available, and there were convenient means for water disposal at the surface.

Harland submersible pumps were used for the purpose and the first to be commissioned began to pump in May, 1950. It has four stages, runs at 2,910 r.p.m., and can handle from 1,160 to 900 gallons per minute against heads between 215 and 315 ft. The motor, which is water filled and sealed, is of squirrel-cage construction, has a 120 h.p. continuous rating, and works at 500 volts taking an amperage of 138.

Power for the cable is conducted along a B.I. multicore waterproof, rubber-insulated cable. This is entwined around the rising main, which is of 8 in. diameter, lap-welded mild-steel flanged pipes coated inside and out with bitumen solution, and clamped to the pipe joints at 15-ft. intervals. The submersible pump unit is situated 318 ft. down at the shaft bottom, the rising main being suspended from the surface. At the surface the water discharges into a rectangular notch measuring box and from there enters a concrete culvert, 100 yards long, which delivers into the river Gaunless.

A pressure gauge is fitted to the rising main at the surface and to ensure that the pump is in good working order the quantity and pressure are recorded hourly. For measuring the depth of water in the shaft a Harland waterlevel indicator, working on the compressed-air bell principle, is provided and there is also a workshop-made float-operated mechanical depth indicator.

The water-level indicator chart is mounted on the pump control gear which is situated in the surface engine room. and which was also supplied by the Harland Engineering Company. The pump control gear consists of a Korndorffer auto-transformer starter complete with isolating switches, overload releases, change over switches, and line contactor.

For lowering and raising materials in the shaft the Pickrose winch shown in Fig. 6 is used. It is of the two-speed type and is powered by a Mather & Platt squirrel-cage 20-h.p. motor rotating at 750 r.p.m. One drum is provided and this has a diameter of 22½ in. and a width of 16½ in. thus accommodating some 1,350 ft. of 2 3/8 in. circumference rope. With an average rope speed of 40 ft. per min. the winch exerts a vertical pull of 16,200 lb. and with the faster speed of 135 ft. per min. a vertical pull of 5,800 lb.

In the same engine room there is a small winder operating a 4 ft. 6 in. by 3 ft. inspection cage. The winder, which is of Tinsley manufacture, is geared and has a parallel drum 4 ft. in diameter and 4 ft. 6 in. wide. A multistrand, non-rotating rope 2 in. circumference is used and is driven at a maximum speed of 16 ft. per minute. The driving motor has a horsepower of 25 h.p., works on a 500 V 3-phase supply, and rotates at 730 r.p.m.; the Metropolitan Vickers Electrical Company are the manufacturers and a metallic controller is provided.

Electrical power is purchased from the B.E.A., the incoming voltage, 2,750, being stepped down through a Brush 300-kVA transformer to 500 V.

In June, 1950, a second pump, identical with the first respect of both construction and piping arrangements, was slung in the shaft. Since then the manufacturers have supplied a third pump intended to act as a standby, but to date performance from the working pumps has been so satisfactory that replacement has not been necessary. With the two pumps working, approximately 2,500 gallons per minute are being taken from underground at West Auckland colliery and by now well over a thousand million gallons have been extracted.

Results to date

In spite of heavy rainfall and power cuts the level of the water in the West Auckland shaft has been reduced something like 10 ft. each month since pumping commenced. The barrier between the old West Auckland property (see Fig. 1) and the take of St. Helens colliery is known to be breached at about 60 ft. above ordnance datum, and there is believed to be another connection through the old Brusselton colliery at 42 ft. above ordnance datum. In addition, the Shildon Lodge colliery water is connected to that just mentioned by a breach in the barrier at 250 ft. below ordnance datum. The reduction in water level has not therefore been confined to the West Auckland property only. Indeed, measurements show that the water level at Shildon Lodge shaft has reduced some 60 ft., thus lowering it to just over 100 ft. above ordnance datum. As the Shildon Lodge water was overflowing into the Eldon colliery property at a level approximately 150 ft. above ordnance datum this last result is particularly important, for it has meant that the amount of pumping east of the Middridge barrier (see Fig. 1) has been practically halved. Similarly, the pumping to the north of the Butterknowle fault has been reduced.

At the same time, reserves estimated at something like 5 million tons have already been dewatered and may be worked when the time is propitious. To the south of West Auckland one small drift mine — Bildershaw colliery — has already reopened and will shortly be producing about 100 tons per day.

The benefits mentioned so far, however, are only of a secondary nature. The reduction in head will help prevent water percolation into the collieries to the east and so lower the cost of development and exploitation there. At Dean and Chapter colliery (see Fig. 1) for instance, a main locomotive road is scheduled running in south-west by west direction. At present, this colliery is pumping some 600 gallons per minute, and were the working to approach the flooded areas the quantity could be excepted to increase considerably. Moreover, to lay out such a haulage road and then leave unextracted the large proportion of the coal in the vicinity would be unthinkable. Obviously, very little detailed planning can be done until either the extent of the water has been determined or it has been removed.

To dewater the rest of the flooded area the heaviest pumping will have to be transferred from West Auckland colliery. Either Eldon or Chilton colliery will be chosen for the site of the next pumping station, and study of the plan (Fig. 1) will suggest reasons for this choice. The transfer will not be made, however, until the responsible mining engineers are satisfied that all possible water has been taken out from the upper level. Definite information will then be available on the rate of flows that may be expected, and it is more than likely that pumping at a lower rate than at present will have to continue at West Auckland.

The initial cost of this useful project has not been excessive. Indeed, by reducing the heads against which the water is handled annual pumping costs have been more than halved, and less than three years’ operation will save considerably more than the capital cost involved. This calculation takes note of pumping costs only and does not consider the immeasurable benefit to both production and safety by rendering the flooded areas accessible. From all points of view an unqualified success may be claimed for the scheme, and the sponsors are to be complimented on their initiative and foresight.

Acknowledgments

For permission to publish this article we are indebted to the Durham Divisional Board of the N.C.B. and we gratefully acknowledge the help received from Mr. D. R. Brooks, Area General Manager, No. 4 Area, Durham Division, and his staff in the preparation of this article.

Drawings and Photographs accompanying the article