Scammonden Reservoir lies between junctions 22 and 23 of the motorway. It is the only structure of its type in Britain where the motorway forms the dam.
Permission for the construction was granted in 1965 where the Deanhead Valley was flooded to form the reservoir. The village of Scammonden was flooded, and many buildings were demolished.
Surveying began in November 1961 and the route of the carriageway was determined in mid 1963. Excavation in the Deanhead Valley commenced the following year and for the dam in 1966. This required the removal of 713,000 cubic metres of peat bog to reach the solid rock base nearly 13 metres below ground level. Material excavated elsewhere on the line of the motorway, clay from cuttings between Lofthouse and Gilderstone, and 3.4 million cubic metres from the Deanhead excavations was used to build the dam’s embankment which is 625 metres in length and 63.1 metres above the original valley floor. The 3.6 million cubic metre embankment is 435 metres wide at its base and 55 metres at road level.
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, which was dependent on the completion of the dam, was opened to traffic on 20 December 1970 and officially opened by HM Queen Elizabeth II who unveiled a plaque near the valve tower of Scammonden Water on 14 October 1971.
The picture shows the motorway and the reservoir under construction in August 1970.