Fly ash
From the start, the power stations' fly ash was dumped in the North Sea, and 800,000 tonnes of fly ash were dumped between the Stella and Blyth stations in 1976. By 1991, National Power's licence had been restricted to dumping only 50,000 tonnes of ash a year from the Stella power stations. By this point the North East coast was the only place in Europe to dump fly ash at sea. Fly ash dumping had been found to make sea bed inert, with much life being smothered and killed by the fly ash. It was also found to create problems for the fishing industry, when their trawlers caught large lumps of it. The licence for Stella was terminated in May 1991, with the stations' closure. Blyth power stations' licence was terminated by the end of 1992, ending fly ash dumping in the North Sea.