Sankey Viaduct

The Sankey Viaduct (locally known as the Nine Arches) is a railway viaduct in Newton-le-Willows in North West England. The majority of the viaduct is located within the borough of St Helens, Merseyside, with approximately a third to west of Sankey Brook being located within the borough of Warrington, Cheshire. It is a designated Grade I listed building and has been described as being "the earliest major railway viaduct in the world".

In 1826, the Liverpool and Manchester Railway Company (L&MR) was authorised to construct the world's first intercity railway. One obstacle on the selected 31-mile (50 km) route between Liverpool and Manchester was the Sankey Valley. The company's principal engineer, George Stephenson, designed the Sankey Viaduct for the double-track railway to traverse the valley and Sankey Canal with sufficient clearance for the masts and sails of the Mersey flats that used the canal.

The viaduct was built between 1828 and 1830, although work on the structure did not finish until the middle of 1833. On 15 September 1830, the viaduct was opened along with the Liverpool & Manchester railway. During 2015, Network Rail installed overhead line equipment as part of a wider electrification programme.

In 1826, the Act for the Liverpool & Manchester Railway (L&MR), the world's first intercity railway, was passed by Parliament. George Stephenson was the company's principal engineer for the 31-mile (50 km) route between Liverpool and Manchester. The route required crossing the Sankey valley west of Newton-le-Willows, about halfway along the line.

The Sankey valley contained two obstacles, the Sankey Brook and the Sankey Canal that was constructed to link the St Helens coalfield to the River Mersey. The engineered waterway could be regarded as the first canal built in England since Roman times.

To traverse the Sankey Valley, Stephenson had to devise a route for the railway to pass without obstructing barges on the canals and maintain gradients for steam locomotives using the route. The Sankey Brook Navigation Company objected to the Liverpool & Manchester Railway's intended route and insisted that any structure across the valley must provide a minimum clearance of 60 feet (18 m) above the water to allow fully-rigged Mersey flats to pass underneath.

Stephenson's solution was to construct an embankment on the west side of the valley, roughly 900 yards (820 m) long, and then cross the brook and the canal on a viaduct that met a smaller embankment on the eastern side. Stephenson designed the viaduct in conjunction with Thomas Longridge Gooch, his chief draughtsman. Constructed from yellow sandstone and red brick, the viaduct is of nine round-headed arches carried on piers that incline sharply from the base towards the top. Its form is similar to the traditional designs of canal aqueducts.

Work commenced on the embankment for the western approach in June 1827. The embankment was constructed of more than 100,000 tons of clay, marl and moss, which was compacted with brushwood. The clay was excavated from the sides of the valley. On completion, trees were planted to provide a natural camouflage for the structure. During the first half of 1828, William Allcard (1809–61) was appointed resident engineer for the mid-section of the Liverpool & Manchester railway, which included the Sankey Viaduct and Kenyon cutting.