Silent Valley Reservoir, Head Road, Kilkeel, Newry, Co Down, BT34 4PU

Earth gravity dam across headwaters of Kilkeel River between Slieve Bignian and Slievenaglogh impounding 11350 million litres (2500 million gallons) of water. Dimensions of dam are: 496 m (1627ft) long, basal width 210 m (700ft)/ top width 6.1m (20ft), height above former river bed 27m (88ft). Equal slopes on both sides: that on wet side pitched with granite blocks to minimise erosion, grassed on air side. Puddled earth core, with 1.8m (6ft) wide concrete water cut-off trench in underlying bedrock. Pitching continues for a short distance around sides of reservoir. A road runs across the top, 2.5m (8ft) above high water level. It has an irregularly-coursed roughly-dressed granite block wall with rusticated copings on its reservoir side. On the slope above the west end of the dam is the quarry from which stone was obtained. Valve tower (HB16/02/022) and bell mouth overflow (HB16/02/023) at south-east corner of reservoir, and scour valve house/ overflow channel (HB16/02/024) a short distance below embankment.