Jeremy's Blog 14th June 2024: Flooding Can Bring a Dark Legacy
This article by Jeremy Moody first appeared in the CAAV e-Briefing of 13th June 2024
We can often overlook how much our landscape has been affected by mining. It is not just coal or Cornish copper and tin. Mining has left a history from the Neolithic flint mines at Grimes Graves and copper mines at Great Orme to today’s great underground granite aggregate quarry at Glensanda in the Highlands and the massive Woodsmith polyhalite mine being hewn under the North Yorkshire Moors. Our varied geology sees old limestone mines tunneled under Dudley and Bradford on Avon, salt mines in Cheshire, copper mines at Alderley Edge, fluorspar in the Peak District, antimony in Dumfries, arsenic in Devon, wolfram in the Lake District and Cornwall, and slate, gold and more in Wales.
The old, often forgotten, mines leave a legacy, troubling conveyancing and giving rise to subsidence claims, often because of coal. Sometimes a forgotten Cornish copper mine opens up under a house. Old mining waste tips can be toxic with heavy metals. More insidiously, old metal mines, that often needed pumping when working, have filled with water that leaches out. Whether from minewater or waste, old risks are given force by the greater flooding with climate change. A study of three Welsh mines has found excessive metal concentrations in watercourses now 90-115 years after they had been abandoned.
The legacy of lead workings is emerging as one of our greater challenges. We worked lead for two millennia. The Romans took it from the Mendips, Derbyshire, Shropshire (where Snailbeach is said to have produced more lead per acre over 2,000 years than any other mine in Europe) and elsewhere. In 1815, William Smith, the “father of British geology”, knew of 132 lead mines from Lanark southwards. It was not environmentally friendly. New veins were found in upper Swaledale, a lead mining landscape for centuries, by unleashing pent-up water to scour soil from rock. Smelting as well as ore-washing was often on site.
Lead has been very useful, from pipes, weights and shot to roofs and flashings, from old pewter to cosmetics. Lead tablets were used to leave curses in waters at Bath and in neighbouring counties. As known in classical times, it is so toxic that we have now removed it from plumbing (derived from the Latin for lead), petrol and paint and are moving towards steel and bismuth for shot pellets. Left in mine waste tips, flooding can take it downstream, leaving it in sediment on flood plains. There are occasional reports of livestock poisoning from grazing and silage (echoes of the 1990 issue of lead in imported cattle feed), especially after flooding – though fly-tipping is also a cause.
Parliament’s Welsh Affairs Committee took evidence on this last month. NRW had assessed that 9 of the 10 catchments most polluted by metal mines were in Wales with threats to health and ecosystems. The BBC reports on concerns in north Ceredigion over lead in eggs and horses. Last Thursday’s Financial Times reported a North Yorkshire farm, tested after ewes miscarried and failed to thrive, finding 2,129ppm of lead in soil, over ten times the US acceptable threshold.
The stories of asbestos and tobacco show that risks were known to science long before being more widely accepted. In such cases, the valuer can be caught out afterwards. In the present state of awareness and knowledge and with the increased incidence of severe flooding, it seems prudent to be cautious and, at least in relevant areas, review the valuation disclaimer for contamination where flood-borne sediment with lead (or other heavy metals) has not been assessed – as for asbestos.
If conversation on a farm that might be affected suggests relevant symptoms, urge veterinary advice which might lead to soil testing. This Foods Standards Agency leaflet gives some advice on reducing risk from lead and other metals, principally by managing pastures to avoid grazing grass too short. The longer term answer is remediation of the worst waste tips and tailings. Abandoned mines are for government action; DEFRA has an environmental target to halve the length of English rivers polluted by harmful metals from abandoned mines by 2038, against a baseline of around 1,000 miles.
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When an increasingly litigious age finds it so easy to be wise with hindsight, producing the old scientific papers, it seems sensible to take care in valuation reports and other work. More broadly, this problem offers one illustration of the pollution and damage that flooding can bring to land.