The aqueduct carries the Llangollen Branch of the Ellesmere Canal in a graceful iron trough, 3.6m wide, over the River Dee. The trough is supported by four arched ribs that run between each of the 18 masonry piers. The span between piers is 13.6m and the total length of the aqueduct is 307m. At the lowest point of the valley, the trough is 36.9m above the river.

The slender tapering piers are hollow from a height of 21.3m upwards, which relieves the lower portions of excessive weight. The walls of the hollow parts are 1.2m thick with internal bracing.

The embankment at the south end of the aqueduct was one of the greatest earthworks undertaken at the time.

The towpath overhangs the channel on the east side — the area under it providing channel width for dealing with displaced water without narrowing the clear width of the aqueduct, which is 2.4m.

The building of this aqueduct is important historically because of the people it brought together: Thomas Telford, William Jessop (the Ellesmere Canal engineer, who approved the design), Mathew Davidson (who supervised), William Hazeldine (local iron master) and the two master masons John Wilson and John Simpson. Members of this team worked on many famous engineering works, including the Menai Bridge.

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Pontcysyllte Aqueduct, literally translated as “the bridge that connects the river”, could not be less understated if it tried. At 38m high, 305m long, nearly 3.7m wide and over 1.5m deep, Thomas Telford’s navigable aqueduct is a magnificent piece of Georgian engineering.

Unlike Telford’s contemporary James Brindley, whose earlier canals usually followed the contours of the land, Telford took a far riskier and direct approach by taking to the skies.

The aqueduct forms part of the Llangollen Canal, sailing over the River Dee across the Vale of Llangollen in north Wales. The Grade I listed structure was originally designed to link Wrexham’s ironworks and collieries with Chester and Shrewsbury, although it ended up providing water to north west England. Today the aqueduct is still in use as a major tourist attraction navigated by over 1,000 narrow boats a year.

Construction began in 1795 following convoluted exchanges with the Ellesmere Managing Committee and William Jessop, an eminent canal engineer who worked with Telford throughout the project. The primary construction materials were cast iron and stone, with the aqueduct’s cast iron plated trough supported on 18 stone piers. The piers taper from 6.4m wide at their base to 5.1m wide at their top, creating the delicate form of the aqueduct.

Telford’s planning and care with work on the project resulted in just one death during the 10 year construction period — a major feat given the enormity of the task. The aqueduct was opened in 1805 with Royal salute from the Royal Artillery Company as the first six narrow boats successfully crossed the valley. But that did not end Telford’s interest. For 30 years following its construction, he biannually visited and examined the aqueduct to ensure its structural integrity remained.

Unlike the earlier canal engineer John Rennie, who was university trained, Telford’s beginnings as the son of a shepherd and stonemason apprentice makes his achievement even more remarkable.

Amongst his peers Telford’s genius was also recognised as he was made the first president of the Institution of the Civil Engineers (ICE) in 1820, a post he held until his death in 1834. A portrait of Thomas Telford by Samuel Lane, commissioned by the Institution has a single structure in its background – the Pontcysyllte Aqueduct.

Drained and refurbished in 2003/4 prior to its 200th birthday, in 2007 the aqueduct was nominated for World Heritage Site status — a worthy testament to its ongoing success and Telford’s vision, in this his 250th anniversary year.

Supervising engineer: Mathew Davidson
Resident engineer: Thomas Denson
Masonry: John Wilson, John Simpson
Ironwork: William Hazledine