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Scammonden Dam
Scammonden Water, west of Huddersfield, West Riding of Yorkshire, UK
associated engineer
Peter Burgess Mitchell
Herbert Lapworth & Partners
Col Stuart Maynard Lovell
date  1st November 1966 - 31st October 1969
UK era  Modern  |  category  Dam/Reservoir  |  reference  SE051167
ICE reference number  HEW 215
Scammonden Dam carries the M62 motorway over Deanhead Valley in the Pennines. It is the first — and so far only — British reservoir embankment to carry a motorway, and combines the dual functions of water supply and highway infrastructure. Construction was hampered by terrible weather and the dam's location close to a peat bog.
The dam lies between junctions 22 and 23 of the M62, on the 10km stretch across the Pennines that separates Manchester and Leeds. Its unique status as the first motorway over a dam in the world required a Parliamentary Bill (Huddersfield Corporation Act 1965) to confer the necessary legal powers for the work, which was a collaborative venture between the Ministry of Transport and Huddersfield Corporation Waterworks.
Surveying for the new motorway began in November 1961 and in January 1962 nine weather stations were set up around the dam site to monitor visibility, temperature and snowfall. The data, and a 800m trial stretch of motorway built in October 1962 near the Brown Cow Inn, were used to determine the most suitable materials to withstand the harsh climate.
The route of the carriageway was set out in July 1963. The excavation of Deanhead Valley began in August 1964 and that for the dam two years later. However, it was the dam's progress that determined the completion of the whole section of motorway.
The soft peat overburden had to be removed — all 713,000 cubic metres of it — to get down to a sound foundation, 12.8m below ground level in the centre of the valley. Some 53,000 tonnes of clay from the Gildersome to Lofthouse cuttings on the M62 and 3.4 million cubic metres of rock from the Deanhead Valley excavations and elsewhere were used in the dam's embankment.
Scammonden Dam has a rolled clay core with graded sandstone fill on its upstream and downstream sides that constrains the core and allowed pore water pressure to dissipate during construction. Settlement occurred in three stages — elastic settlement, consolidation and sudden increases in settlement (when gradually increasing pressure on the fill led to over-stressing). New methods were developed on site to measure and monitor the stresses and strains within the 3.6 million cubic metre embankment during its construction.
The M62 crosses the 625m long embankment 63.1m above the original valley floor. The dam is 54.9m wide at the crest and 435.9m wide at the base. Slatted fencing on either side of the embankment, below carriageway level, provides effective wind breaks for vehicles emerging from the cuttings onto the exposed dam crest.
In addition to its direct catchment, the reservoir impounds water from an indirect area three times larger. Scammonden Water has a maximum depth of 51.8m. Normal draw-off is through a 2.5km tunnel driven southwards into the adjoining valley — the shortest route to Huddersfield. Its entrance within the reservoir basin is 7.9m below top water level. When the water level falls beneath the tunnel entrance a pumping station downstream of the dam embankment delivers water through a rising main into the tunnel, discharging into the next valley.
The lip of the overflow bellmouth, which discharges through a tunnel in the valley side, is more than 9.75m below the top of the embankment and 4m below the floor of an access underpass through the dam. It lies next to the valve shaft superstructure, which is connected to the reservoir’s east bank by a footbridge supported on a second tower.
Water started to fill the reservoir in July 1969 and by October it held 7.7 million cubic metres. Landscaping included tree planting, picnic areas, parking and other facilities. Most of the buildings in Deanhead village were either demolished or submerged to make way for the dam and reservoir. The church still stands and is used for worship, while the vicarage is now the Sailing Club centre.
The M62, including Scammonden Dam, was opened to traffic on December 20th 1970. The official opening took place on 14th October 1971, when HM Queen Elizabeth II unveiled a plaque near the valve tower of Scammonden Water.
County engineer (West Riding of Yorkshire): James Anthony Gaffney
Engineer (Huddersfield Corporation Waterworks): W.M. Jollans
Resident engineer: A.J.H. Winder
Main contractor: Sir Alfred McAlpine & Sons Ltd
Research: ECPK
"Motorways that take to the moors" by David Rowlands
in Design Journal, Issue 268, April 1971, available at http://vads.ahds.ac.uk
"Discussion: Observed and Predicted Deformations in a Large Embankment Dam during Construction" by A.D.M. Penman et al, ICE Proceedings, Vol.51, Issue 4, pp.729-755, London, April 1972
reference sources   CEH North

Scammonden Dam