Award-winning project ‘future proofs’ Scilly Isles’ harbour

TVO St Mary's Harbour

An award-winning harbour improvement project successfully completed by Team Van Oord partner Kier, will be the subject of a presentation at the forthcoming ICE Coasts, Marine Structures and Breakwaters 2017 Conference* to be held in Liverpool next month.

The design and build harbour improvement works at St Mary’s harbour, carried out by Kier on behalf of Cornwall Council, has previously been the recipient of a ‘Gold’ Green Apple Environmental Award*, and a CEEQUAL ‘Gold’ Outstanding Achievement Award*.

The works consisted of a quay extension and widening to form a new 40m long quay and wave wall.

The project future proofed the harbour for a proposed new passenger vessel and increased the capacity of the quay for both passengers and freight.

St Mary’s Harbour is a private harbour operated by the Duchy of Cornwall. The harbour is the traffic hub for the Isles of Scilly and because of their reliance on tourism, the existing quay had to remain operational throughout the project. This included a daily 400+ passenger ferry service from spring to autumn and three weekly freighter deliveries year round, as well as other passenger services during the spring and summer months.

TVO St Mary's Harbour 2

For the quay extension Kier proposed the construction of a modular caisson gravity structure as this required the use of less marine plant and yielded the best environmental outcome. This solution required minimal disruption of the seabed to secure the extension into position, with considerably less risk to programme and improved safety of the workforce.

In the quay widening area high levels of contamination within the marine sediments were found, requiring a radical rethink of the construction methodology.

Dominic Primmer, Senior Design and Construction Manager at Kier Construction, said:

“Traditional encapsulation using close-centred piles topped with precast concrete slabs proved expensive and timely, with the piling generating high levels of hazardous waste.

“Instead of this approach, in what was a UK ‘first’, we pioneered a solidification methodology within the tidal zone.

“This alternative approach to eliminate piling and the subsequent reduction in the volume of contaminated waste was estimated to have resulted in a 42% reduction in carbon emissions, while saving £1.8m and six months on programme in comparison with the piling solution.

“The project was completed without any major safety or any lost time incidents – a significant achievement considering the challenging working environment and weather conditions.”

Since project completion, Kier has received a ‘Gold’ Green Apple Award for the in situ stabilisation of marine sediment and environmental protection work on the project.

The project has also been awarded a CEEQUAL Gold Outstanding Achievement Award, in recognition of its drive towards sustainability in civil engineering and infrastructure in public spaces.

Since 1982, the ICE Coasts, Marine Structures and Breakwaters Conference has shaped the marine engineering sector, by unveiling innovative technologies, assessing techniques, making formal recommendations and providing in-depth technical analyses.

CEEQUAL is the evidence-based sustainability assessment, rating and awards scheme for civil engineering, infrastructure, landscaping and public realm projects. The scheme promotes and celebrates the achievement of high environmental and social performance. The CEEQUAL Outstanding Achievement Awards are presented at an annual ceremony in London.

The Green Apple Environment Awards scheme is an annual international campaign which recognises, rewards and promotes environmental best practice around the world. The Green Apple Awards were launched in 1994 by The Green Organisation and have since become one of the world’s most recognised environmental awards schemes.

29 August 2017