In October 1960 The Engineer reported that Ernest Marples, the minister of transport, had invited tenders for construction of the foundations and substructure of the Severn suspension bridge, plus access roads to the site.
The announcement marked the start of works on what we now call the M48 Severn Bridge, a project that would eventually connect England and Wales via the building of the Aust Viaduct, the Severn road bridge itself, a viaduct on the Beachley peninsula and a bridge across the River Wye.
“Erection of the [Severn] bridge superstructure and the building of the Wye Bridge and eastern and western approach roads will be carried out by further contracts, timed to enable the whole scheme to be completed within five to six years,” The Engineer said, adding that the project was being phased with the construction of the Forth road bridge in Scotland.
“The proposed suspension bridge, which will cross the Severn between Aust and Beachley where a motor ferry now operates, will have a main span of 3240ft,” the report added. “It will cost about £11,000,000, while the Wye bridge viaduct, and approach roads linking the bridges with the A.38 at Almondsbury on the east and the A.48 at Crick on the west will cost a further £5,000,000.”
All that was missing was ownership of the land on which to build, but our reporter noted that ‘negotiations were near completion’.
The contract out to tender involved construction of the two main piers forming the bases of the steel towers; the anchorages for the main cables; the approach viaduct on the Aust side, and the access road to it.
The east main pier (on the Aust side) and the east anchorage were both to be constructed on the tidal foreshore of the river, using hollow precast concrete blocks. These were to be placed in position at low tide and joined together with steel reinforcement and concrete filling placed in situ.
“The pier will be 140ft long, 42ft wide and 63ft high, and will be solid,” said The Engineer. “The anchorage will be a pair of massive blocks 145ft long, 40ft wide and 120ft high, separated by an enclosed space; each block will contain some hollow chambers and galleries.
The Engineer continued: “On the Welsh side of the river, the west main pier will be similar to that opposite, but will be supported on caissons. The west anchorage will be similar to the east, but constructed on dry land. The east approach viaduct will run from the Aust Cliff to the east anchorage in three spans of 170ft each.”
It was observed that the Severn bridge was to be a steel suspension bridge on concrete piers with steel towers about 470ft high. The main span was to be 3240ft - slightly less than the 3300ft span of the Forth road bridge - and each of the two side spans would be I000ft long. The road level would be approximately 130ft above high-water mark of ordinary tides at the piers, and 150ft in the centre.
“Under conditions of maximum temperature and loading the minimum clearance for navigation at the centres of the span will be 120ft. The width between parapets of the bridge will be 118ft. Twin 24ft carriage ways will be constructed, and provision made for cycle tracks and footpaths.
The bridge over the River Wye would be 1340ft long with twin carriageways, cycle tracks and footpaths. It was estimated that 40,000 tons of steel and 120,000 tons of cement would be required for the two bridges and approach viaducts.
“The new approach roads will be restricted to motor traffic, though cycle and pedestrian traffic will be allowed to use the bridges,” The Engineer said. “Access to the road over the bridge, apart from terminal junctions on A.38 to the east, and A.48 on the west, will be limited to two junctions with existing major roads.”
The early works for bridges over the Severn and Wye, plus approach roads, were prepared by Messrs. Mott, Hay and Anderson, as consulting engineers, in association with Messrs. Freeman, Fox and Partners. Sir Percy Thomas was employed as the consulting architect and the final design of the Severn bridge went on to be considered by the Royal Fine Art Commission.
Messrs. Mott, Hay and Anderson traded until 1989, when it merged with Sir M MacDonald & Partners to form Mott MacDonald.
Messrs. Freeman, Fox and Partners merged with John Taylor & Sons in 1987 to become Acer Consultants. The company was acquired by Welsh Water in 1993 and renamed as Hyder Consulting in 1996, a multi-national design and engineering consultancy.
Sir Percy Thomas formed the Percy Thomas Partnership and after 2004 was bought by Capita who formed Capita Percy Thomas, which specialises in cultural, defence, education, healthcare, industrial and science and technology projects.
The Royal Fine Art Commission existed between 1922-1999 and served as the government’s independent adviser on ‘matters affecting public amenity and aesthetics in England and Wales’.
The Severn bridge, and its cousin the M4 Prince of Wales Bridge, were toll crossings until 2018.