Rhos on Sea coastal defence improvements, Wales

NEC has been used to procure the latest phase of a 15-year waterfront project at Colwyn Bay in north Wales. Conwy County Borough Council let contracts for the Rhos on Sea coastal defence improvement phase worth a total of £20 million to Alun Griffiths and Boskalis Westminster using the NEC4 Engineering and Construction Contract (ECC) Option A (priced contract with activity schedule) in May 2022. Mott MacDonald was appointed designer and NEC project manager under an NEC4 Professional Service Contract (PSC).

The Colwyn Bay Waterfront Project was started in 2011 to address historic beach erosion which had left coastal defences exposed and reduced the area’s appeal to visitors and residents. The latest phase (2b) at Rhos on Sea included placing 1 Mt of sand in front of the existing seawall, extending sewage outfalls, modifying a rock groyne next to the harbour, widening the promenade to provide more space for pedestrians and cyclists, and upgrading street furniture and lighting. 

Completed in May 2025, the scheme has transformed the area into a vibrant public space for visitors and the local community, bolstering the local economy and enhancing quality of life. It achieved a Breeam Infrastructure sustainability score of 92.5%, the highest in the UK to date, and won the Placemaking Project Award in the 2025 British Construction & Infrastructure Awards.

Carbon saving

Natalie Haines, associate at Mott MacDonald, says a design for resource efficiency workshop was held at the outset of the Rhos on Sea scheme. ‘This resulted in a 46% reduction in embodied carbon, totalling nearly 4,000 t, between the concept and detailed design stages’. 

For example, she says the beach recharge design was optimised in areas with less sensitivity to reduce overall material requirements. ‘The beach management plan provided trigger levels so sand levels could be proactively managed, reducing material loss offshore and saving operational carbon. Existing pavement surfacing was also left in situ and we reused 9,500 m³ of rock revetment.’

Haines says in line with the NEC requirement on the parties to act in a ‘spirit of mutual trust and co-operation’, the project team worked closely to develop a collaborative programme. ‘This provided protection against unforeseen delays and gave confidence that milestones, such as Welsh Government funding deadlines, would be met.’

She says all project risks were notified through NEC early warnings and discussed and mitigated at early warning meetings. ‘This fostered a collaborative approach to problem solving. NEC also incentivised value engineering, with rewards being fairly shared between the contractor and client.’ 

Haines concludes, ‘We are proud of our work on the Rhos on Sea scheme. It is so much more than flood defence – it has completely transformed the area to a vibrant place and improved the quality of life for visitors and residents alike.’

Simple administration

Benjamin Poulton, manager of the Colwyn Bay waterfront project, says NEC4 ECC Option A was chosen for the final phase due to its simplicity to administer. ‘Working from an activity schedule significantly reduced the work burden for all parties when it came to agreeing payments.’

He says NEC’s inherent transparency was also a factor. ‘Just as important as simplicity was that the contract also made it much more straightforward for the client organisation and the grant funder’s audit teams to understand what was happening throughout the project.’

Poulton says NEC’s collaborative processes such early warnings, revised programmes and compensation events were all discussed and recorded at weekly meetings using the cloud-based Thinkproject (formerly Cemar) management system. ‘This allowed us to discuss each issue, review progress and proposals and record decisions, providing a regularly updated ongoing narrative that was agreed by all parties.’ 

Benefits of using NEC

• NEC early warning process ensured that all project risks were notified and discussed, fostering a collaborative approach to problem solving.
• NEC incentivised value engineering, with rewards being fairly shared between the contractor and client. 
• NEC4 ECC Option A activity schedule reduced the workload for all parties when it came to agreeing payments.
• NEC’s inherent transparency made it easy for the client and grant funder to understand what was happening throughout the project.