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World Heritage Sites in North Wales

Event organised by ICE

18 April 2024
18:15 - 19:15 BST (GMT+1)

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North Wales has a very rich heritage of engineering works extending back through history to Roman times and before that the mining of copper in the Bronze Age. That heritage includes the three very distinct and diverse World Heritage Sites. They include 4 Edwardian Castles, Pontcysyllte Aqueduct and Canal and the Slate Landscape of North West Wales. These sites extend across North Wales from Chirk to Harlech. 

Slate represented a major industry in North Wales, dating back in history for centuries, but developing dramatically from the end of the 17th century through to the 19th century and 20th century. Quarries at Penrhyn near Bethesda and Ffestiniog continue in production now. Although gaining the slate was by traditional quarrying and mining, the infrastructure necessary to process, transport and export the slate products involved considerable amounts of engineering. 

Transporting the slate to the ports and harbours was undertaken using narrow gauge railways, some of which survive as for example the Padarn Lake Railway and the Ffestiniog Railway. 

Jessop and Telford worked together to create several ground breaking structures. Seen originally as a means of providing a more direct route to Ellesmere Port the scheme was never to be completed ending at Trefor Basin with a feeder from Llnagollen.

Driven in part by an earlier failure suffered by Jessop, firstly Chirk Aqueduct changed the way such structures were designed and built. A departure from an aqueduct carrying a clay lined canal. The formality of chirk with its masonry walls and cast iron invert proved to be a far more efficient and effective solution to span the valley of the River Ceriog. Passing through Chirk Tunnel with its innovative design of towpath and on to Pontcysyllte, the Dee valley presented and even more daunting obstacle. The decision was made to use cast iron to form the trough, dispensing with the masonry.

This revolutionary concept led to the building of the iconic Pontcysllte Aqueduct, designed and built with the assistance of Hazledine. Water was to be provided from the River Dee upstream at Horseshoe Falls and the navigable feeder extends as far as Llangollen.

Hear from William Day, former director of Arcadis, who will present how these three sites provide an insight into the period in which each was developed and also the development of the civil engineering industry.


William Day

William Day


Former director

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William Day

William Day has been involved with forensic engineering and historic structures for many years.  

Initially working on the design and construction of bridges he became deeply involved in infrastructure management and the restoration and conservation of bridges of many types. Moving to North Wales to work on Menai Suspension Bridge. His interest has widened to include castle and canal structures among others. Although retired, he continues his interest in historic structures.