asked the Secretary of State for Northern Ireland what is the chemical composition of the deposit which is removed by brushing the interior of the main pipeline from the Caugh Hill treatment works to Londonderry; and whether tests have shown the discharge resulting from such brushing to be within the legal limits for discharge into a watercourse.
The trunk main from the Caugh Hill water treatment works is scoured once a year. The main substances removed by scouring are small deposits of aluminium compounds and ferrous material formed by oxidation. Neither of these compounds is toxic, and no complaints have ever been received regarding their effect on the waterway.
asked the Secretary of State for Northern Ireland if tests have shown that the effluent from the Caugh Hill treatment works at present meets the legal requirement for discharge into a watercourse; on how many occasions it was tested at the point of exit from the treatment plant and at the point of discharge into the River Ovenreagh during the past two years; and what was the result of such tests.
During the past two years, eight tests have been taken of the effluent at the point of its exit from the Caugh Hill treatment plant and in addition 30 sludge samples have been taken. Monitoring of the River Ovenreagh indicates that the discharge from the treatment works has not had a harmful effect on the ecology of the river.