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South Nottinghamshire Coalfield.

November 1st, 2017 in News by admin

In 1998 the Coal Authority was offered the use of the pumping arrangements that operated at Annesley Bentinck Colliery by Midlands Mining if the mine closed. They were offered the same opportunity again in November and December 1999 with the knowledge that the mine would cease operations on Christmas Eve. Midland Mining the owner of the colliery saw the writing on the wall with respect to deep mining in the UK and decided that the time was right to close operations down. The management were also aware of the unique position of the mine and its strategic importance in the dewatering of the coalfield and the value of its unique water management infrastructure.

Instead of considering it the Coal Authority turned down the offer and stated publically that minewater in the South Nottinghamshire Coalfield from the shaft at Calverton Colliery when the time came. Calverton closed in 2000. The Coal Authority had commissioned research from British Geological Survey (BGS) to assess the minewater impacts on South Nottinghamshire, Nottingham and Erewash valley when deep mining ceased.

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BGS reported to the Coal Authority, Dti, Department for Energy and the Environment Agency (various papers on the same theme were published between 1998 and 2008) that when mining ceased in the region the minewater within workings would build at the deepest workings down dip of the coal strata. Flow of water coming from the outcrop and finding its way to Calverton. The work that backed up this hypothesis included modelling with all the data available in the Coal Authority and BGS itself. It all seemed rather simplistic at the time but also a little sad when the view was shown to be inaccurate. The mineshaft at Calverton was not developing in the time scale that was expected and by 2011 the Coal Authority advertised for tenders for putting down a borehole close to the Linby Colliery shaft so as to look at water within the workings between Newstead and Calverton. This bore has demonstrated that water would appear to be building in the area of Newstead and Annesley. The minewater monitoring point at Langton Colliery, a long time closed shaft that has been a monitoring point for many years confirmed this.

The failure of Calverton to act as the ‘sump’ for the South Nottinghamshire Coalfield has proved to have been caused by a cross section of issues that might have been picked up by the computer modelling. The strata, including the coal seams do not just run at an even slope from the outcrop of coals in the western Nottinghamshire/Derbyshire borders dipping to the east but they ripple, however slightly and lean towards the north. This has allowed some alteration of flow towards the north and even allowed some backflow at varied levels due to different coal horizons. Alongside the natural ground conditions issues that have stopped flow include goaf, the fall of roof material and the blocking of apparent water flow routes.

The water egress into the workings around Linby and Annesley has also developed differently to what might have been expected as water is not flowing from the northern and southern parts of the exposed coalfield. Rather it appears to be coming via Langton and the due western outcrop. Before the Annesley Bentinck Colliery closed the waters entering the colliery were channelled to one point. The gathered mine drainage entered a pumping lodge that also managed water vented via a stopping between the lodge and Langton. The total volume managed being 1.2 million gallons per day. At closure the managing valve at the stopping was closed so allowing the water backing up from Langton to be managed at A Winning pumping Station that had been put in place some years prior to the reprivatisation of the mining industry in 1994. Figures of pumping rates show that A Winning is now having an increase of water needing to be pumped but greater volumes are building away from the outcrop region.

These water developments are now demonstrating why the Coal Authority were offered the site at Annesley for the management of water from the coal measures. The water within the mine workings are a problem in that they will be polluting when they arrive at the surface. At Annesley the 1.2 million gallons of water each day was rich in iron and many more times saltier than sea water. In the 1980s it used to be discharged via the River Lean but the water chemistry coming to the pumping lodge became acidic, this acidity and chloride destroyed a woodland that the water passed through and polluted the river.

The solution was a set of lagoons and ponds that removed the high iron content and the chloride rich water then passed through a 17.5 kilometre pipeline running along beside railway lines south to the River Trent. This allowed the chloride water to be diluted by the river’s flow. The regulator permitted this option as at the time it was the only answer whilst the colliery was operational. When the colliery at Annesley closed the pipeline was abandoned and the pump house demolished.

When the colliery handed back their discharge consent to discharge chloride a similar consent was issued to National Power, the then operators of Ratcliffe on Sour Power Station. The future of minewater treatment in South Nottinghamshire is now in crisis. The need to manage the water before it reaches the level where it will appear in the above ground environment around the western edges of Nottingham, the Erewash Valley or out of the ground around the old Radford Colliery site, all are likely and there are now only a year or two before this may occur. There is also the other concern, the water rising into the aquifer above the coal measures. The infiltration is likely to take place where subsidence has taken place and that could be anywhere across the region.

It is time for these concerns to be addressed swiftly and publically.

Author: admin

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