The Challenge:

Kier were appointed to undertake improvement works to St Mary’s Harbour on the Isles of Scilly. Located within environmental and ecological protection areas, the scope of works included:

  • Demolition of existing sea wall and construction of a 23 metre quay extension. This included removal of existing features, preparation of the seabed and finishes
  • Reclamation to widen the freight yard access
  • New/improved freight and passenger facilities
  • Re-surfacing to improve the freight handling area and parking around the harbour-side building Protecting the environment was considered throughout the design process

Management of the construction phase followed the same environmental standards. The concrete and steel used contained high levels of recycled materials without compromising on structural integrity. The quay walls design included opportunities for colonisation by marine species and birds.

The Solution:

We pioneered new methods to reduce carbon and improve efficiency during the improvement works.During investigation our team became aware of previously unidentified contaminants within the sediments.The engineering design for the quay wall extension involved the re-use of excavated sediments within the project. The discovery of contaminants rendered this approach non-viable.

We worked with the Marine Management Organisation, Cornwall Council, the Environment Agency and our supply chain to propose alternative solutions. Our team investigated lower carbon solutions. Developing a method for solidifying the marine sediments by mixing them with a blend of high-strength cement as binder. We understand this is the first time this method has been employed within the UK within a tidal zone.

The Impact:

This solution yielded the best environmental outcome and also delivered a 42% reduction in carbon.

It was six months faster than other solutions and provided £1.8m (82%) cost saving in comparison to other solutions.

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