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Fal estuary oysters under threat from contaminated mine at Baldhu near Truro

By WBMiles  |  Posted: November 29, 2012

Oysters from the Fal estuary

Oysters from the Fal estuary

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The UK's only wild oyster breeding ground is under threat from contaminated water from a disused mine shaft.

The contaminated mine water could flood into the Fal estuary due to rising water levels at an industrial site near Truro.

It is feared that water from the abandoned mine at Wheal Jane near Baldhu could spill out into the Carnon River and then the Fal Estuary, a designated marine Special Area of Conservation.

The Environment Agency said mine water levels in the shaft were continuing to rise faster than the seven pumps in operation could take the water out.

The  Fal estuary, in Cornwall, has one of the few remaining stocks of native  oysters in the United Kingdom, and the only one of wild oysters. A law dating to 1868 makes it illegal to gather them with mechanical means or from crafts  other than sail boats or row boats.

Mark Pilcher for the Environment Agency, said: "We are doing all we can to monitor the shaft water levels to understand if or when any spill might occur into the Carnon River.  The water is currently rising at a rate which is faster than the pumps can manage.

"With the ground saturated after this week's rain, there is a risk that mine groundwater will continue to rise over the next week. The bulk of the mine water will continue to be pumped and treated at the maximum rate but there is a risk that a smaller amount may be discharged and we are working with our partners to assess what the impacts might be."

Cornwall Fire and Rescue Service said it was asked to help pump water from the mine entrance into a dam to alleviate potential flooding and contamination into the Carnon Valley.

The Environment Agency was alerted to the danger by site operator Veolia Ltd.

In normal circumstances, mine water leaving the site is pumped and treated to control pollution.

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  • Phil_lip  |  November 29 2012, 4:36PM

    Hmmm Cadmium in our oysters, what about the rest of the food chain, better make sure the local fishermen know about this before they eat the nights catch.

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  • shagrats  |  November 29 2012, 2:38PM

    Some info from the last time it spewed ! The initial water had a very acidic pH (2.8) and had a high metal loading. To control this discharge it was treated with lime, the adit was plugged and the water was pumped from the mine into the existing Wheal Jane tailings dam. However pumping was stopped on the 4th of January 1992 for technical reasons and whilst an alternative treatment method was being investigated on January 13th there was the accidental release of approximately 50 million litres of acidic (pH 3.1) metal laden water (Younger, 2002). Fe hydroxides carried in suspension in the mine water formed a very visual orange plume which flowed out via Restronguet Creek into Carrick Roads. The water was also contaminated with some metals in solution, the most significant of which was the presence of more than 600 parts per billion (ppb) of cadmium. This mine water was less dense than the saline waters in the estuary and formed a buoyant plume flowing out to sea. The impact was extremely visual and public concerns relating to health effects and the impact of the mine waste discharge on tourism in the area caused significant public pressure for both an immediate and a long term solution to the incident. Initially pumping recommenced with the treated mine water discharge being allowed to settle in the tailings dam. Hunt and Howard (1994) examined the speciation of arsenic within the waters in the Carnon River and in Restronguet Creek following the Wheal Jane event and found that ****nite concentrations in the Carnon River below the tailings dam decreased significantly with time after the event, whilst the levels within the estuary remained relatively constant. In contrast the concentration of ****nate was low in both the river and the estuary following the initial discharge but increased significantly in the estuary in the following July. The implication of these observations are that the concentrations of ****nate and ****nite within the estuarine area is probably unrelated to the mine water discharge. Arsenic and cabmium are about as nasty as you can get. Measure the oysters before, and a week afterwards for any of this stuff and you should have your culprit. I can remember one Falmouth Oyster festival that was more like a fried egg festival, they were so loaded with Iron and other stuff. To say Arsenic levels are not related to one incident is probably right, but they can be related to a persistent release form that source.

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  • shagrats  |  November 29 2012, 10:24AM

    What mine and where, and what minerals did it contain ?. I'm sure we touched on this a few weeks back on here as regards to the balls up with, was it South Crofty (I can never remember) !

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