Chipping Sodbury Tunnel

Chipping Sodbury Tunnel is a railway tunnel that sits on the South Wales Main Line in England.

Ventilation shaft near Badminton

The tunnel was constructed around 1897-1903 for the South Wales and Bristol Direct Railway.[1] It runs under the Cotswold Hills some 2 ¹⁄₂ miles (4.0 km) west of Badminton railway station and Chipping Sodbury Yard.

The tunnel is constructed with an arch brick lining and measures some 27'6" across and 20'9" high. The bricks were made from clay excavated from the tunnel.[2] It slopes at a 1:300 gradient from Badminton falling in a westerly direction towards Chipping Sodbury. Above the tunnel are a series of six ventilation shafts, which were used during construction to remove soil. The places where they reach the surface are circular brick vents between 4 metres (13 ft) and 8 metres (26 ft) high with castelations around the top. They are all Grade II listed buildings.[3] The brick built east and west portals of the tunnel are also listed.[4][5]

The tunnel cuts through major water conduits and springs and is therefore prone to flooding.[6] The route via the tunnel is closed on a regular basis, resulting in the cancellation and diversion of passenger and freight services.[7] Various plans have been drawn up to improve the flooding situation and pipes to achieve a gravity dranage system involving 6.5 kilometres (4.0 mi) of pipes was chosen.[8]

As part of the modernisation of the Great Western main line, the route through the tunnel closed from 19 August to 15 September 2017 to allow work to fit overhead electrification equipment via 4,064 holes in the roof,[9] and reduce the risk of flooding.[10][11][7] This included the expansion of the stormwater lagoon to hold 11,000,000 litres (2,400,000 imp gal; 2,900,000 US gal).[12]