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Chirk Canal Tunnel
Shropshire Union Canal, Chirk, near Wrexham, Wales, UK
Chirk Canal Tunnel
associated engineer
Thomas Telford
William Jessop
date  25th November 1801
UK era  Georgian  |  category  Tunnel  |  reference  SJ285374
ICE reference number  HEW 162
photo  © John Charlton and licensed for reuse under this Creative Commons Licence
Telford’s Chirk Canal Tunnel is the longest of three tunnels on the Llangollen branch of the former Ellesmere Canal. The canal was refurbished in the 1980s and 1990s, and is well used by leisure craft. It is now part of a UNESCO World Heritage Site.
On 30th April 1793, a Parliamentary Act authorised construction of the Ellesmere Canal, with Thomas Telford (1757-1834) "appointed Sole Agent, Architect and Engineer" and William Jessop (1745-1814) as consulting engineer. Chirk Canal Tunnel lies just inside the Welsh border, midway between Ellesmere and Llangollen, on a branch that was constructed in 1795-1805 and opened on 26th November 1805.
Telford was probably responsible for the general design of the canal and its structures between Pont Cysyllte and Chirk Bank. In early 1794, work started on this section and Chirk Basin (SJ286374) at the southern end of the tunnel opened in 1801. On 25th November 1801, the 420m long Chirk Tunnel was completed "except for a final proportion of towing-path". By June 1802, the 174m long Whitehouse Tunnel (SJ286399 to SJ286401) had been completed and the Llangollen Canal was open as far as the southern end of Telford's famous Pontcysyllte Aqueduct (SJ270418 to SJ270421).
Chirk and Whitehouse tunnels were the first British canal tunnels to have towpaths. To save money, earlier canal tunnels had narrow bores and no towpaths. Boats were propelled through by leg power — boatmen or hired labourers would lie on the cargo and 'walk' along the tunnel wall.
Chirk Tunnel is founded at a relatively shallow depth — maximum 14m below ground level — and was constructed using mostly cut and cover technique. The central section was excavated from two shafts, and the tunnel roof still shows the remains of one shaft up to the ground.
The tunnel lining is brick. To make it waterproof, and prevent damage through water ingress from the surrounding ground, a clay sealant was put over the brickwork vault and topped with "loose stones".
The waterway is 2.9m wide and the towpath 1.5m. The underside of the brickwork is 3m above water level. The arched tunnel portals are of stone with ashlar voussoirs and raised keystones. They make the tunnel appear deceptively large as the bore flares out at the ends.
The towpath is supported on brick arches, which allow water to flow below and reduce drag on passing vessels. While the towpath enabled faster passage of boats its width restricted the tunnel to one-way traffic. However, the tunnel is so straight that a boat entering one end can be seen from the other end.
Around 1846, the Ellesmere Canal became part of the Shropshire Union Canal after a group merger between several canal and railway companies.
In about 1992, repairs were completed to the canal between Llangollen and Chirk. The tunnel and its portals have been Grade II* listed since July 1998.
In July 2009, the 17.7km of canal between Gledrid Bridge (SJ298368) and Horseshoe Falls (SJ195433), which includes Chirk Canal Tunnel, became a UNESCO World Heritage Site.
Research: ECPK
"The Canals of Britain: A Comprehensive Guide" by Stuart Fisher, Adlard Coles, 2nd edition, December 2012
reference sources   CEH W&WCEH WalesBDCE1

Chirk Canal Tunnel