A dam of china clay sludge waste in Cornwall, UK, has dropped approximately 0.9m, releasing thousands of tonnes of the material into the river

Fal and turning it thick with sludge. The river is reportedly a milky brown colour and discoloured around 10km from the incident.

The 500m long Kernick Mica dam is located downstream from Tregony. It is a retention dam for clay and is owned by Imerys, formerly English China Clay. It is not known what caused the dam to drop 0.9m, but investigations are currently under way at the site.

‘We are monitoring the river, taking samples and advising on measures needed to stop further drainage of the china waste into the Fal,’ said Rob Torr of the Environment Agency. Checks are also being made for dead fish, although none have been found so far.

The material formed a yellow slick in the estuary and the Environment Agency was concerned about the levels of metal contaminants in the mica which was released. However, initial tests taken from the river and estuary have shown that the slick has not caused a rise in metal levels in the water. Monitoring will continue for as long as the river remains polluted with the clay sludge and until all the debris and waste have been removed.

The most serious concern now is the high levels of silt and solids in the water. This blocks out natural sunlight, smothers spawning beds and can clog fish gills, killing fish. ‘Even though the tests bring us some good news, the shear scale of silt and sludge that entered the river could pose a serious problem for the river and its wildlife for some time to come,’ said Torr.