M62 and Scammonden Dam

Year:1970

Duration:6 years

Cost:Unknown

Country: Pennines, UK

What did this project achieve?

Build a dam that carries a motorway that links both sides of the Pennines.

Scammonden Dam is a multipurpose structure that creates a reservoir and supports a 10km stretch of the M62 motorway, between junctions 22 and 23.

The route, which lies on the area of the Pennines that separates Manchester and Leeds, sped up journey times between Lancashire (now Greater Manchester) and Yorkshire. It now takes just two hours – instead of five - to travel between Liverpool and Hull, for example.

Conditions in the Pennines are some of the harshest in the UK, and it was important to build a route that would be able to stay open in bad weather.

At the time the motorway was planned, Huddersfield Water Authority was looking at a proposal for a dam and reservoir.

The proposal suggested that by sitting the dam on the route of the motorway, across Deanhead Valley, it could be taller than planned at 76m. This would create a larger reservoir.

The result was a 4,200 sq metre dam, reservoir, motorway, and the largest single span fixed-arch bridge in the country, Scammonden Bridge.

The bridge carries the A6025 over the motorway at the Deanhead cutting. A cutting is another name for the excavation in a piece of high land for a road.

Scammonden Dam was a collaboration between the Ministry of Transport and Huddersfield Corporation Waterworks.

It was designed by Rofe, Kennard and Lapworth. The main contractor was Sir Alfred MacAlpine and Sons.

The motorway was opened to traffic in December 1970. The official opening, by Queen Elizabeth II, took place the following October.

The unique project is a great example of a multiple-use structure that solves two problems at once, making both economically viable.

Difference the project has made

The reservoir, owned by Yorkshire Water, has also become a place for leisure activities, with an active sailing club, activity centre and walks.

Travelling between Yorkshire and Greater Manchester, either sides of the Pennines, is now easier and faster.

How the work was done

The excavation of Deanhead Valley began in August 1964, and excavations for the dam started in 1966.

Around 713,000 cubic metres of peat bog were removed to reach a solid rock base, which was nearly 12.8m below ground level in the middle of the valley.

The dam’s embankment measures 625m long and is 63.1m above the original valley floor. It’s 435m wide at its base, and 55m wide at road level.

The embankment was built using material excavated during the building of the motorway, 53,000 tonnes of clay from cuttings between Lofthouse and Gildersome, and 3.4 million cubic metres from the valley excavations.

Water from the reservoir is routed through a 2.5km tunnel southwards to supply Huddersfield.

The reservoir has an overflow spillway, which is a structure that allows for release of water from a dam, to help prevent floods from destroying it.

Scammonden Water has a bellmouth spillway, which means it’s shaped like an inverted bell. This allows water to enter all around the perimeter. The water is released from the bellmouth to the valley below via a tunnel in the valley on the reservoir’s eastern side.

Water started to fill the reservoir in July 1969. By October, it held 7.7 million cubic metres.

The reservoir is 625m long, and when full, has a surface area of 4,200 sq metres. It is 73m deep at its deepest point.

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Many millions of people drive over it and don’t give a second thought to the technicalities behind building it

Alastair Harvey

Yorkshire Water countryside and recreation manager,14 Oct 2011 in ExaminerLive

Fascinating facts

The Scammonden Dam was the first in the world to carry a motorway – and still the only one in Britain - and needed the passing of the Huddersfield Corporation Act 1965.

Scammonden Reservoir supplies water to about 200,000 people in Huddersfield.

The village of Deanhead was submerged to create the reservoir. The village’s vicarage is now the reservoir’s sailing club centre.

People who made it happen

  • Client: Ministry of Transport and Huddersfield Corporation Waterworks
  • County engineer (West Riding of Yorkshire): James Anthony Gaffney
  • Dam engineer (Huddersfield Corporation Waterworks): WM Jollans
  • Resident engineer: AJH Winder
  • Main contractor: Sir Alfred McAlpine & Sons

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