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8 of the greatest Welsh civil engineering projects of all time

01 March 2022

To celebrate St. David's Day, ICE has pulled together examples of great infrastructure in Wales that have had a positive impact on the country and its local communities.

8 of the greatest Welsh civil engineering projects of all time
The Menai Suspension Bridge, designed by Thomas Telford, was the first bridge to cross the Menai strait. Image credit: David P/Shutterstock

Wales is home to incredible infrastructure, some designed by civil engineering legends such as Thomas Telford and Robert Stephenson.

For St David's Day, when Wales celebrates its patron saint, we've pulled together a list of civil engineering projects that have shaped local communities across the country by improving transport, restoring the environment, boosting tourism, among other positive effects.

1. National Botanic Garden of Wales Regency Restoration

National Botanic Garden of Wales Regency Restoration
Image credit: WM Longreach

The Regency Restoration was a five-year project that restored a Regency period landscape at the National Botanic Garden of Wales. It was the largest project of its kind in Wales, and won ICE's People's Choice Award 2021.

The community and local schools were involved in the project, during construction and beyond, as people of all ages volunteered and promoted the landscape’s heritage as well as its environmental importance.

Local historians, ecologists, archaeologists, architects, and civil, structural, geotechnical and hydraulic engineers worked with environmental contractors to sympathetically restore the landscape.

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2. Colwyn Bay Waterfront Project Phase 2

Image credit:
Image credit:

Colwyn Bay's waterfront was once the town’s biggest asset. This project restored the promenade to its former glory and provided a more modern, accessible, and inclusive waterfront that can draw visitors back to the seaside town.

The Victorian promenade had fallen into disrepair, with poor lighting often hosting anti-social behaviour and uneven surfacing and crumbling shelters becoming a common feature.

A key element of the wider regeneration within the town, the project has created a space that represents the best elements of the town’s past but is also a vision of the town’s future.

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3. Cardiff Bay Barrage

Image credit: Philip Bird LRPS CPAGB/Shutterstock
Image credit: Philip Bird LRPS CPAGB/Shutterstock

In the early 1980s, secretary of state for Wales, Nicholas Edwards, suggested a project to revitalise Cardiff Bay and create a development that included new shops, homes and, as a centrepiece, an opera house on the waterside.

However, the tidal nature of Cardiff Bay exposed mudflats for much of the day and was viewed as an unappealing backdrop to the scheme. To remedy the background, they built a barrage, or a low-level dam, across the mouth of the bay, which created a more scenic setting.

As one of the biggest civil engineering projects in Europe at the time, it became the catalyst for the regeneration of Cardiff Bay.

The barrage saw its millionth visitor less than five years after it opened - a golden retriever called Henry, in October 2005.

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4. Conwy crossings

Image credit: Steve Allen/Shutterstock
Image credit: Steve Allen/Shutterstock

The Conwy crossings include: Conwy suspension bridge (1826), Conwy railway bridge (1848), Conwy road bridge (1958), and Conwy road tunnel (1991).

Engineer Thomas Telford designed the suspension bridge (pictured above) to match the nearby Conwy Castle. The towers on each end were castellated – made to look like battlements.

Engineer Robert Stephenson's Conwy railway bridge was the first – and only surviving – tubular bridge in Britain.

Apart from enabling easier transportation, the crossings have had other positive effects, as soil dug out from the Conwy tunnel were used to build a bird sanctuary on the east bank of the river: the Glan Conwy Nature Reserve.

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5. Pontcysyllte Aqueduct

Pontcysyllte Aqueduct
Image credit: Travellite/Shutterstock

Pontcysyllte Aqueduct is the longest and highest aqueduct in the UK. Crossing the Dee Valley, it's a grade 1 listed construction and part of a World Heritage Site.

It was designed by Thomas Telford as one of his first major projects. It included a cast-iron trough that carried water and boats across the valley.

The project was viewed as ambitious and ground-breaking when work started in 1795, since it would be more than three times the height of existing aqueducts.

The structure was built during the 20 years of so-called 'canal mania' between 1790 and 1810. Over 1,180 miles (1,900km) of canal were completed over this period.

The area has become known for its wildlife – otters have been spotted in the canal!

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6. Menai Suspension Bridge

Image credit: David Pimborough/Shutterstock
Image credit: David Pimborough/Shutterstock

The Menai Suspension Bridge was the first to cross the Menai Strait – a fast-flowing stretch of tidal water that was 1,300ft (400m) wide at its narrowest point.

Before the bridge went up the only way across the channel was by ferry. Thomas Telford recommended a suspension bridge as high banks and fast-moving currents meant it would be difficult to build on the seabed.

The bridge made it quicker and safer to get people and goods from Anglesey to Wales, including cows. The main source of income on Anglesey at the time was cattle farming. Getting cows from the island to markets on the mainland meant swimming them across the river. Valuable animals were often swept away or drowned in strong currents!

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7. Severn Crossings

Severn tunnel with trees
Image credit: John Corry/Shutterstock

The Severn crossings include the Severn tunnel, Severn bridge and the second Severn crossing. At the times they were built, the crossings considerably reduced journey time and congestion when travelling from England to Wales.

The Second Severn Crossing is now the main road link between England and Wales and is used by more than 80,000 vehicles a day. It has won numerous construction industry awards.

The Second Severn bridge was the longest river crossing in the UK when it opened in 1996. It has been designed to withstand an earthquake or a ship crashing into it.

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8. Dinorwig Power Station

Dinorwig power station
Image credit: Gail Johnson/Shutterstock

Dinorwig Power Station was built in caverns inside Elidir Fawr (a mountain in north Wales) to provide rapid response to sudden demands for electricity. The power station also stores cheap energy produced at night for use during peak times of demand.

The scheme was constructed in the abandoned Dinorwig slate quarry. To preserve the landscape in Snowdonia National Park, engineers built the power station inside the mountain itself.

Opened in 1984, Dinorwig was the biggest civil engineering project ever commissioned by the UK government at the time.

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  • Ana Bottle, digital content editor at ICE