Managing Ecological, Community and Bathing Water Quality Aspects in Design and Construction: Runswick Bay Coastal Protection Scheme, UK

Abstract

The Runswick Bay Coastal Protection Scheme consisted of repairs and installation of concrete toe protection to the existing seawall and the placement of approximately 9,500 tonnes of imported rock armour to form a new revetment totaling 250m length. The historic concrete seawall had reached the end of its serviceable life with a predicted failure within the next ten years. The newly constructed scheme offers an enhanced standard of protection to 96 residential and 17 non-residential properties, including 6 listed buildings and infrastructure such as access roads and utilities, from coastal erosion for the next 100 years. Tourism, the foremost revenue stream of the community has also been safeguarded by the works. The scheme was achieved through collaboration across the project team with a focus on long term coastal protection alongside consideration for minimising the impact to the site given its sensitive status, i.e. designated for its ecological, landscape, heritage and bathing water quality. An emphasis during both the design and construction work was given to reducing disruption to the local community and visitors along with seeking opportunities for ecological enhancement. The project involved the local community as much as possible to help steer the project’s design and construction. The programme for the construction phase was developed to minimise disruption to the area during peak visitor periods. Construction works commenced in February 2018 and the programme included a two-week suspension of activity over the school Easter holiday period, with completion scheduled for the end of June 2018, prior to the start of the school Summer holidays. During construction, water quality was monitored through regular sampling and laboratory testing to ensure the works did not adversely affect bathing water quality. A sampling regime was developed which incorporated eleven sampling points across the wider bay to determine potential pollution sources. These data augmented the existing information collected by the Environment Agency and provided useful verification for future intertidal rock off-loading and stockpiling operations. To mitigate environmental impact from the works, workforce and machinery movements were limited to previously confirmed access routes and working areas to avoid ecologically sensitive locations. Existing foreshore boulders heavily colonised with marine flora were carefully set aside to allow construction. These were then placed against the toe of the new rock structure as ‘seed rocks’ to encourage rapid colonisation of the new material. The engineered rock structure was modified to provide improved textural complexity and water retention through the creation of artificial rockpools and surface scoring. At this time, the scheme represents the largest application of this type of ecological enhancement in the UK and represents a combination of leading-edge coastal engineering practice and innovation in ecological design. The scheme designs will be monitored through links between public and private sectors and academia.