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May, 1961
Boring for Water
A series of deep boreholes to provide water for essential services at the Consett Iron Co. Ltd., Co. Durham, is being drilled by William Coulson Ltd. of Rotherham and Durham.
The first of these holes has been sunk to a depth of 340 ft. to yield 1,200 gallons of water an hour to supplement cooling water wastage by evaporation and leakage at the new Hownsgill plate mill.
Using a Pilcon 650 mobile rotary drilling rig and tricone bits, Coulsons first drilled through the coal measures — consisting of strata of shales, post stones and coal seams — to a depth of 151 ft.
Difficulties were, however, encountered during this drilling period as existing plans had only indicated coal measures to a depth of 80 ft. Between that depth and 151 ft., coal workings, which had been mined perhaps several centuries ago and had not been anticipated, caused the hole to collapse, trapping the drill rods and bit. These were successfully recovered, the hole was reamed and a 7 in. outside diameter casing was inserted. Drilling was then continued with a diameter of 6¼ in. to the final depth through open sandstones and post stones.
Although the standing water level was 198 ft. deep, the very fine grain of the sandstone did not allow water to percolate sufficiently quickly to meet the requirements and there was a drawdown of about 100 ft. An airlift pumping test was tried at 340 ft. but there was insufficient submergence to give a satisfactory result.
A 6 in. electric submersible Pulsometer pump, capable of lifting 2,500 gallons an hour to a head of 350 ft., was installed at the bottom of the hole but, owing to the scarcity of water, was throttled down by 1,300 g.p.h to give the required delivery of 1,200 g.p.h.
The second hole has been sunk to a depth of 333 ft., similarly cased through the coal measures to 170 ft. and equipped with a 6 in. Pulsometer pump. The Pilcon mobile drilling rig used by Coulsons is mounted on a four-wheel drive Bedford vehicle which has been fitted with hydraulic jacks for quick setting up and levelling. It is equipped with an automatic high pressure control and is capable of continuous feeding of drill rods for open drilling — as at Consett — although it can also be used for core drilling.
Drawings and Photographs accompanying the article
Article reproduced from a copy of the magazine held at National Mining Museum Scotland, Newtongrange, Midlothian.
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