National Botanic Garden of Wales Regency Restoration

The Regency Restoration was a five-year project to restore features of a Regency period landscape at the National Botanic Garden of Wales. It was the largest project of its kind in Wales, and the first ecological and landscape restoration completed for a generation.

The landscape was originally created in the late 18^th century for Sir William Paxton MP, in what is now Waun Las National Nature Reserve.

As the central feature at the botanic garden, the restoration of the 200-year-old landscape brought significant benefits to the local community and for the wider tourism industry.

A community project

Extensive works included lake and reservoir creation, dam reconstruction and new water control infrastructure, six footbridges and extensive footpaths.

By engaging with the community and local schools during construction and beyond, people of all ages were inspired to volunteer their time, promoting the heritage and environmental importance, and raising the profile of civil engineering.

Successfully managing a project like this required a dedicated team of specialists working closely together, as well as the many volunteers from the local community.

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

Historical society and volunteer research assisted the design process, with local societies invited to create a vision for the project design brief, using photography and art to inspire the community.

Meanwhile, the construction enabled everyone to learn about historical and modern engineering in a historic landscape, as they took part in reducing the environmental impacts of construction with tree planting and moving plants.

The project promoted local procurement from the early planning stages, engaging with consultant ecologists, designers, and engineers during construction.

It also had support from local stonemasons, steel fabricators (bridges), timber bridge engineers, material suppliers (stone for cascade water features, roads and landscape paths), blacksmiths (railings), and tree surgeons (site clearance).

Innovative design

The project consistently used new ideas and innovative thinking in design to ensure modern reservoir safety regulations were met, while blending into the ecologically-sensitive heritage landscape.

Innovations in construction methodology included the water-filled ‘AquaDam’ used for temporary works during the concrete cascade construction. This helped to avoid the heavy construction that would have been needed with an earth dam, which would have damaged the landscape and posed a pollution risk to the water.

This massively reduced the risk to the local environment, the site ecology, and disturbance of unearthed heritage.

Using specialist machinery also improved efficiencies. A low ground pressure excavator was used for desilting works, and a wide track dozer was used to pull a sheepsfoot roller (a roller with many rectangular-shaped lugs, or ‘feet’) to compact the clay on the linear dam more effectively.

The new dam structures also offer important flood protection for the community downstream.

Sustainability throughout

Sustainability measures were taken across the project both in the design planning phases and during construction:

• A weir (a barrier across the width of a river) designed in a ‘cascade’ shape to reduce the amount of reinforcement and concrete needed, and therefore reducing carbon footprint.
• The route of new dam structure incorporated a special, dedicated bypass for eels to use. This prevents loss of elvers (baby eels) as they migrate.
• Bespoke bypass valve, designed to ensure flow remains even when reservoir isn’t full. This prevents the stream running dry, sustaining local wildlife and ecology.
• Sustainable use of materials, including: FSC-certified hardwood for bridges, extensive use of lime instead of cement, 25,000m³ clay for dam construction from on site borrow pits, and use of biodegradable hydraulic oils in machinery.
• Preservation/mitigation for wellbeing during construction of protected and significant species.
• Economic sustainability by using local construction labour and the finished project attracting tourism to the area.

Project milestones

• 2016 – early contractor involvement enabled early identification of risks to the programme and cost, including dam safety, access, environmentally sensitive location, work on live watercourses, and preservation of archaeology.
• June 2018 – works commence
• May 2020 – bridge replacement completed
• October 2020 – works completed

What engineering skills were used in the project?

• Flood management
• Water engineering
• Civil engineering
• Project management