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River Fal 5: The Questionable Colour of Water

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– Restronguet Point (where?)

Out in the middle of the Carrick Roads Mylor Church Haven’s hidden behind the marina’s white coppice of masts. The rotating arms of the Roscrow wind turbines can be seen waving in the distance between the dip of two headlands, and the Fal really does feel like sea not river. The water is wide and the land skirts round as though the coast is folding in on itself and we’re floating in a bay that might gradually be enclosed completely by land. There’s a salt tang on the lips. A seal’s back surfaces and sinks with the roll of a submerging rubber tyre. The shorelines are beaches not river banks, lined with strands of seaweed and scattered with the pale specks of gulls. A breeze is blowing, and for the moment it’s chilly as a cloud shifts across the sun. The shade turns a patch of  water deep indigo, looking like the shape and shadow of a reef beneath the surface as the sunlit section is turquoise green. Then the cloud shifts in the brisk coastal wind and so does the illusionary peril of underwater rocks.

Heraclitus said that nobody steps into the same river twice. You can’t even look at it twice, without each glance becoming a double take wherein even the colour plates will have changed. I keep thinking I see it as the colour I like best, but then glance back another day, another moment, and I’ve changed my mind as the water’s changed its hue. Cornflowers under a fresh June sky. The slate slabs in my garden in a thunderstorm. A duck’s head; a kingfisher’s wing. The hull of Largs Bay when the sort of rain descends that’s rain and cloud and sky all at once, and sky and water are one and the same both leaching into one another: an eye grey, a camouflage grey, when really it’s the reverse and the ship’s that shade to match the water not the water to match the ship. A new twenty pence piece catching the light. An old twenty pence piece catching the dark. An old penny, copper heavy: when the floodwaters burst from a network of mines and flowed like Heinz soup or paint swills down the Carnon Valley and out into the Fal from Restronguet Creek.

From mid-channel the emergence of that creek is hidden by a tree-covered bar that extends down from Harcourt to Restronguet Point, but a map reveals the branch of the tidal waters extending up past the village of Point to Devoran, where the rivers Kennal and Carnon join the tidal creek. Both of these rivers drain some of the most heavily industrialised landscapes in Cornwall. The Fal Estuary catchment covers 346km2, which includes a large part of the China Clay District and well over seventy documented mines, more than forty of which are within the Carnon River basin.

Today many holiday brochures praise the Fal Estuary area for its ‘unspoilt’ and ‘natural’ beauty, when the reality is that this area has always represented a combination of industrial and rural. In fact the area is markedly spoiled, quite literally, given the numerous ways in which mining waste has affected the local environment. Geographically the course of the Fal has been altered by the impact of the minerals industry, with increased sedimentation rates effectively causing a sea level fall: Tregony was considered a sea port back in mediaeval times but is now two and a half miles upstream from the Fal’s tidal limit, with the river a narrow and shallow channel far out of reach of the sea vessels that once moored up there. Metalliferous deposits suspended in waters running from adits to rivers to the estuary are so high that some tubeworms – which construct their protective outer pipes by cementing together sand and sediment particles – have been found with several different kinds of metals glued into the walls of their homes.

Though underground mining activity has now ceased in the area its influence is still felt, even if the effects are not always visible. Metalliferous deposits take years to break down and some can be highly toxic: with arsenic, copper and cadmium among the most common minerals found locally. They can also affect the water chemistry, making it very acidic. Acid Mine Drainage occurs when resource extraction exposes elements that would normally be contained within a body of rock to air, causing them to oxidise producing acidic compounds. If mining takes place below the water table the galleries are drained by pumps during active periods. If excavations become flooded these acidic compounds go into solution, causing tremendous problems if this leaks into the hydrological system. This is exactly what happened prior to January 13th 1992, when 50 million litres of acidic waters heavily laden with metals were accidentally released into the Fal Estuary after pumping ceased at the recently closed Wheal Jane near Bissoe.

The Wheal Jane incident garnered much media and public interest because the resulting orange plume staining the river was such a visual impact. The reality is that the most serious pollution in the estuary is much more long term and far less obvious. Flora and fauna in the area have become so acclimatised to the high levels of metals that have been flushing through the system during the hundreds of years of mining activity that they have adapted to their presence and were consequently very little affected by the additional minerals contributed by Wheal Jane. Experts consider the real problem to be the extremely high levels of metal deposits that have accumulated over the years in the river sediments, both in the intertidal areas of the creeks and on the bed of the estuary. However the sediments, whilst they remain sedentary, act as stabilisers for the contaminants. Where sulphide minerals are contained at some depth within the built-up sediments they are effectively ‘locked away’: conditions here are anoxic so there is no danger of them reacting with the oxygen in air or water unless the sediments are disturbed. Along with the potential disruption of maerl beds near the mouth of the Fal this is the other main environmental concern of the proposed expansion of Falmouth Docks: the deep dredging required could not only mobilise contaminants, but some of the material dredged will be considered toxic waste. Developers plan to use a mobile treatment plant to consolidate an estimated 100,000m3 of contaminated sediments dredged up during the project, which will then be taken away and disposed of at a secure landfill site, whilst the clean dredgings will be dumped offshore in Falmouth Bay.

Articles in this series form part of a longer piece on the tidal section of the River Fal in Cornwall. In it I imagine what it would be like to start at low tide at the river mouth, travelling upriver to the highest tidal point at high tide, and returning back to the sea, by exploring the locations on and around the river and making my own ‘tidal journey’ inland and back out to sea. There are thirteen parts to the series. They can of course be read in order, but you don’t necessarily have to start with part 1, it being a cyclical journey there is no definitive start and end point. Each section can also be read as a stand-alone piece.

 

More on this?

For a great overview of the Fal river catchment’s background, geology, conservation and industrial history, in addition to a comprehensive and in-depth look at the River’s mining contamination see 

Pirrie D, Power M R, Rollinson G, Hughes S H, Camm G S, Watkins D C (2004) Mapping and visualisation of historical mining contamination in the Fal Estuary, Cornwall. University of Exeter: Camborne School of Mines; which can be viewed here

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Author: Merryn

open the curtains and take a look out the window if you want to know what the weather's like

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