London & South East

Refurbished sea defence will protect thousands of homes

High Knock The High Knocke to Dymchurch High Knocke  Sea Defence – Frontage A project is now complete, offering peace of mind to the thousands of residents who live directly behind it.

The Environment Agency funded refurbishment scheme has ensured that the standards of protection provided by the sea defence are significantly higher than those of the previous defence, which required frequent repair. Taking into account the anticipated sea level rise for the next 100 years, the project will offer substantial protection for the next century.

Works commenced on site in February 2009 and were completed in June 2011. Under the £29m project, a new wave return wall and primary defence wall have been created, along with a stepped revetment to provide easy visitor access to the seaside.High Knock

The sea defence was constructed using reinforced concrete and stands at approximately 2.2km long and 8m high. Although some of the concrete was cast-in-situ by the main contractor, Birse Coastal, most of it (around 44,000 tonnes) was precast by Macrete in Northern Ireland and then transported by sea on a three-week delivery schedule from Belfast to Rye Harbour.

Interestingly, precast concrete access step units at the town centre and in-situ concrete promenade surfaces have a deliberately exposed aggregate finish to provide extra grip underfoot. This effect was achieved by applying a retarder to the finished surfaces and washing out unset laitance the next day.High Knock

The project team has received various awards for their efforts. This includes a British Construction Industry Award in September, with the team being successful in winning in the Civil Engineering £3-£50m range. In addition, they have won an ICE South East Excellence award, and their engagement with the community led them to win a Considerate Constructor Gold Award.

Peter Richardson, Environment Agency Project Manager, said: “Because we were working close to a residential development, this made building extremely difficult.High Knock

“Effectively, we ended up having to build a haul road along the seaward side of the existing defences, which ultimately became encapsulated within the permanent works to provide a lower promenade. The promenade now exists over two levels: the high level, which has always been there but is now greatly improved; and the lower level promenade, which was used as a haul road and crane platform during the construction process.

“We undertook constant noise and vibration monitoring throughout the entire process. We were set some extremely stringent standards and, as a team, were able to meet these throughout the course of the project.

“It was a very interesting project to be involved with, particularly due to the difficult environment and the fact that access was restricted. We were also working in a busy tourism area and so had to ensure that this industry was not impacted by the works that were being carried out. As a result, we made every effort to keep as much of the area open as possible.High Knock

“During the project, we built up very strong relations with the local parish council, district council and local community groups and we are extremely grateful for their support. Everyone is delighted with what we’ve achieved, and the awards speak for themselves.”


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