by World War I. A contract was eventually awarded in 1923 to S. Pearson & Son and work continued until 1933. The third stage was planned to be another storage reservoir in Annalong to impound the Annalong River. However, after the difficulties encountered in building the Silent Valley dam the second dam was not built. Instead, a tunnel was driven under Slieve Binnian between 1947 and 1951 to bring water from the Annalong river to the Silent Valley reservoir. Between 1953 and 1957, a second dam was built further up the Kilkeel river valley to create Ben Crom Reservoir. The Mournes catchment area is surrounded by the Mourne Wall, built entirely by hand. Started in 1904, it took 18 years to complete. Naming An old name for the valley was Glen Setanta from a legend that the young Cú Chulainn spent time there. In the 1800s it was called Happy Valley apparently due to the jollity of prospecting Cornish miners. The name Silent Valley is supposed to derive from the absence of bird life during the long construction project. The Binnian Tunnel Between 1947 and 1951 over 150 men drove a tunnel underneath Slieve Binnian. The tunnel was built to carry water from the Annalong valley to the Silent Valley Dam, which had been completed in 1933, 14 years earlier. This was to further supply the growing demands of Belfast's water supply. Two work squads began at each end of the tunnel, and met half way almost 800 metres under the mountain. The technology in the day was lacking in every standard, and was lit by candlelight. When the two squads met, they were mere inches off. The tunnel measures square – and long. Its entry is at Dunnywater and its exit is on the roadside, a short distance from the visitor's centre. The Binnian Tunnel was officially opened on Thursday, 28 August 1952. References External links Northern Ireland Water Limited Department of Regional Development Newry and Mourne tourism Northern Ireland coast and countryside Reservoirs in County Down Tourist attractions in County Down