The history of Box Tunnel, Wiltshire
At the time of opening, Brunel’s Box Tunnel was the longest railway tunnel ever built.
Controversial from the start, its problematic construction delayed the completion of the Great Western Railway’s London to Bristol route until June 1841. Today it is one of Isambard Kingdom Brunel’s most celebrated structures.
An impossible project
Originally proposed in the Great Western Railway Act of 1835, building a tunnel through Box Hill was considered an impossible and dangerous engineering project by its critics. Box Tunnel, located between Chippenham and Bath, was the most challenging engineering work on the entire London to Bristol route. It featured an unusually steep gradient of 1 in 100 over its length, which was steep by Brunel’s standards.
Bath Stone
Between 1836 and 1837, eight shafts were dug through the hill to study the rock. The tunnel, nearly two miles long, went through different types of rock, including Bath Stone, Inferior Oolite, Fuller’s Earth, and some Lias Clay at the western end. The tunnel was 9,636 feet (2,937 meters) long and 25 feet (7.6 meters) wide, and 247,000 cubic yards (189,000 cubic meters) of material were removed.
Two contractors built the tunnel. George Burge from Herne Bay handled 75% of the work from the west, while local contractors Lewis and Brewer did the rest. Construction started in December 1838.
Railway navvies
Working conditions during the construction of the tunnel were poor. The tunnel was divided into six isolated sections, and access to these sections was primarily through ventilation shafts, which were 25 feet (7.6 meters) in diameter and ranged from 70 to 300 feet (21.3 to 91.5 meters) deep. Blasting, which used 1 ton of explosives per week, occurred within these chambers while the workmen were present. The only illumination came from candles, with 1 ton of candles consumed each week.
During the early construction phase, workmen often had to evacuate quickly due to water gushing in from the Great Oolite strata. Pumping facilities had to be increased to manage the significant inflow of water.
The final piece
The delayed completion of Box Tunnel was holding up the opening of the entire line from London to Bristol. By August 1839, only 40% of the tunnel was built. By summer 1840, the sections from Paddington to Faringdon Road and from Bath to Bristol were done.
In January 1841, Brunel increased the workforce from 1,200 to 4,000 men. Thanks to their hard work, the tunnel was finished in April 1841. The tunnel was started from both ends in 1836, and when they met in 1841, the alignment was off by less than 2 inches (5 cm).
Brunel designed a grand entrance for the west end of the tunnel, while the east end was simpler. The tunnel opened for traffic on June 30, 1841, without any ceremony.
Did you know?
Legend has it that the rising sun shines through Box Tunnel on Brunel’s birthday, 9 April. Recent research has shown that unfortunately this is not the case, although the sun does shine directly through the tunnel on several other days throughout April and again in September.