Scour valve house etc, Silent Valley Reservoir, Head Road, Kilkeel, Newry, Co Down, BT34 4PU

An integral part of Silent Valley Reservoir, this complex comprises three distinct elements forming possibly the most architecturally interesting of all the structures associated with the scheme. The overflow and outlet tunnel arches are particularly impressive, executed to the highest standards, and their appearance is enhanced by the landscaped grounds below the dam. The structures are historically significant as part of the second phase of the Mourne Scheme (the first being the impounding and diversion of the Kilkeel River to Belfast in 1901), and they form part of a larger grouping of contemporary water-related buildings.

The Scour Valve House

A small one-storey rectangular building sited on an island in the middle of the overflow channel. Two 36-inch diameter outlet pipes from the dam run into the basement; their flow is controlled at the adjacent valve tower. At the scour house, the pipes make a right-angle turn into the screening rooms. Valves at this abrupt turn can be opened to flush accumulated silt into a short length of tunnel which opens into the discharge channel.

The building is constructed of rock-faced granite blocks in irregular courses over a projecting base, with a flat concrete roof. It is embellished with stepped quoins and oversailing copings, all in ashlar granite. Two windows are placed in the north and south walls, and one in the west wall; all are 1/1 wooden-framed with plastic security sheeting. A metal roller door is positioned on the east wall with an ashlar granite surround. The building is accessed via footbridges from the east and west sides. These footbridges are of concrete faced with rock-faced granite. The arches have brick soffits, rusticated granite voussoirs and ashlar granite stringing over. The parapets have rusticated copings and terminal piers.

The Outlet Tunnel

Water discharging from the scour valves enters a short length of horseshoe-profiled brick-lined tunnel which emerges into the discharge channel through a pedimented arch of classical design. The arch voussoirs are of ashlar granite with a keystone, stepped into rock-faced granite spandrels in regular courses with an ashlar pilaster on either side and an entablature over. A stone in the pediment is inscribed '1932', the year the dam was completed. Immediately above this arch is a sloping grassed area enclosed by granite walls leading up to the scour valve house.

The Discharge Channel

The subterranean overflow tunnel from the bellmouth intake emerges into the open discharge channel just above the scour valve house. It exits through a horseshoe-shaped arch of similar design to the outlet tunnel arch. The arch spandrel continues up to a parapet embellished with rusticated copings and ashlar stringing. Just below the tunnel, the channel bifurcates around the scour valve house emplacement. The bed of each channel is pitched and stepped granite. The channels reunite below the scour valve outlet tunnel as a sloping channel which eventually continues as the Kilkeel River. The vertical sides of the 45-foot-wide channel are of concrete faced with rock-faced granite blocks in irregular courses with rusticated copings over.

Historical Development

The complex was erected by Belfast City & District Water Commissioners as part of the Silent Valley reservoir scheme, with Messrs S. Pearson & Son of London acting as contractor. According to historical records, the outlet tunnel was completed by 1926. The overflow tunnel, arch and channels either side of the scour valve house were built only after it was decided to insert a bellmouth overflow instead of a weir. These elements were completed, along with the dam, in 1932 and opened in 1933. The parapet at the head of the discharge channel dates from 1954.