UThe past is polluted orange: the future’s brighter
Adrian Fox, Principle Engineer with Atkins Mining, discusses the practical problems of cleaning up past industrial pollution while keeping an eye on the future.While today’s industries are having to tighten procedures ever more diligently to control and recycle industrial effluent, there is also a job to be done in cleaning up the legacy of past processes.
When abandoned collieries are closed, the pumps are switched off and water starts to rise.
In numerous cases this water, polluted by iron and often turning a telltale vivid orange, reaches the surface and can then discolour existing watercourses – a case of industrial effluent with historic roots.
The Coal Authority has an extensive national programme to remediate the environmental impacts arising from the mine waters’ question and currently has identified 110 discharges across Scotland, England and Wales for priority attention.
There are numerous remedial measures to purify the ochreous discharges before allowing it back into the water system, including cascades to aerate it, lagoons and various filters, with the Coal Authority favouring sympathetic environmental solutions including reed beds.
South Wales, and the archetypal mining communities of the Valleys, provide a microcosm of the problems UK-wide, and consultants Atkins Mining, a term contractor to the Authority, are working on a number of schemes in the area.
At Corrwg, near Glyncorrwg, three minewater discharges have turned the nearby Afon Corrwg orange. Because of the scale of the project, the planned £500,000 scheme will eventually involve 11 wetland ponds full of reeds to remove iron and the narrow steep-sided site has caused logistical problems.
One of the discharges is on the opposite side of the river to the planned ponds, necessitating the need for a steel bridge to take it across the river. Even reaching the site can be a headache because it is accessible only through 3.5 miles of forest track.
Until the advent of the Water Bill, gaining access to sites could prove problematic to the Authority, but they now have the power to gain access to land to perform emergency works and have compulsory purchase powers where appropriate.
The Corrwg site is typical of the work which is going on – albeit on a smaller scale – at Goytre, near Port Talbot where an Environment Agency report claimed the discharge was visible up to 2,000m downstream in the Ffrwd Wyllt, Glyncastle, near Resolven, Mountain Gate, near Ammanford, and Tan-y-Garn.
One of the first steps in cleaning historical industrial effluent is to consult all the available records dating back to the height of the industrial revolution to gather as much information as possible.
But as the team discovered at Lathallan Mill, Scotland, things are not always that simple.
At Lathallan, near Fife, the consultants came up with a sympathetic sustainable solution to the discolouration of the Den Burn watercourse. But when they were first called in the team could find no records of mining at the remote site.
The only evidence we had to go on was anecdotal, there were no records of the workings we believed were causing the pollution. Anecdotal evidence indicated the problem could date back to medieval times when monks from a nearby monastery are believed to have worked coal up to 30m below the surface – at a time when environmental concerns were somewhat less stringent than today.
But the bad habits of the monks in question meant more headaches for the consultants on a very constricted, heavily wooded site containing hostile vegetation in the form of Japanese Knotweed.
The first step of the treatment process involved a simple cascade made from local stone remaining from demolished farm buildings.
Some tree felling – for access – was unavoidable but the larger logs were recycled to line the access track and the smaller branches chipped and mulched to aid organic matter on the site.
A landscaped settlement pond filled the dual purpose of removing sediment and attracting wildlife, and three reed beds completed the purification process. Other features like soil nailing, straw and gravel filters and a bulk order of mushroom fertiliser from a grateful farmer in Auchtermuchty kept the sustainable theme of the scheme as well as providing a boost to the local economy.
Building on the success of its term contract with the CA, Atkins Mining is turning its gaze to the Emerald Isle where there are similar mine waters problems to be addressed.
The Coal Authority’s UK programme is a huge task. It demonstrates the importance of addressing the historic legacy of Britain’s former industries as well as the need to keep tight reign on industrial effluent in ongoing processes, to ensure future generations do not have to pick up the tab.
By Adrian Fox, Principle Engineer, Atkins Mining.