Scammonden Water

Scammonden Water is 51.8 metres at its deepest point and water is drawn-off through a 2.5 kilometre tunnel driven southwards to supply Huddersfield. The overflow bellmouth, next to the valve shaft superstructure, discharges water to the valley below via a tunnel in the valley on the reservoir's eastern side. The reservoir started to fill in July 1969 and the area was landscaped and parking and other facilities were provided.

The motorway (M62), which was dependent on the completion of the dam, was opened to traffic on 20 December 1970.

http://en.wikipedia.org/wiki/Scammonden_Reservoir