Collaborative working in Great Yarmouth to protect homes, businesses and infrastructure

Background

JBA Bentley has been working on the award-winning Great Yarmouth Flood Defence Scheme, a multi-partner project led by the Environment Agency since 2019, with works due to be completed in 2023. JBA Bentley, a joint venture between JN Bentley and Jeremy Benn Associates (JBA), brings together the specialist skills and expertise of the two firms: JN Bentley as a civil engineering contractor, and JBA Consulting as a water and environmental consultant and designer.

The scheme consists of 22 packages of work, which vary from raising the height of some of the existing walls, installing cathodic protection, installing plating to existing steel sheet piles and constructing new setback flood defence walls. The environmental team are fully integrated into this multi-disciplinary project and site team, which has enabled a full understanding of the scope of works, and appreciation from all involved of the scheme’s environmental constraints.

Collaborative working in Great Yarmouth to protect homes, businesses and infrastructure
Welding back the cut-out section.

For each works package, there have been appropriate environmental and ecological assessments undertaken to guide the works, from Environmental Risk Assessments to Water Framework Directive Scoping Assessments and bat surveys. Once the initial assessments were completed, all necessary licenses and consents were acquired. This includes successfully covering all works packages within one overarching scheme Habitats Regulations Assessment, resulting in the successful granting of assent from Natural England.

Whilst obtaining consent for works that required a full marine license, we sub-contracted technical work to a specialist marine sub-consultant which resulted in supporting evidence that the proposed piling method (Silent piling) and the programme would not be detrimental to migratory fish. The site team also consulted the environmental team on the use of coatings and resins.

To date, twenty environmentally compliant work packages have been delivered on programme.

Collaborative working

In the early stages of the scheme, there was a change in methodology from the installation of new piles to plating the existing piles. This change met the design life requirements, whilst also removing the need for a cofferdam which results in intrusive temporary works. A cofferdam would have involved piling into the river bed and pumping water out, creating an obstruction within the port of Great Yarmouth.

In addition, during the construction, the site teams have used innovative processes to control concrete when used in close proximity to the river. A window was cut out of the full-length steel plate and a grout sock was placed inside and weighed down to the base of the river with paving slabs. Concrete was then pumped into the grout sock below the window. Once set, the sock was cut off and then welded back to the cut-out section.

Collaborative working in Great Yarmouth to protect homes, businesses and infrastructure

Works to repair the quay wall capping beam were adjacent to mudflat and, therefore, to minimise disturbance to the mudflat and adjacent salt marsh, a working platform was welded onto the quay wall. This had the additional benefit of allowing works to proceed unrestricted by the tide, resulting in a greater working window.

Collaborative working in Great Yarmouth to protect homes, businesses and infrastructureThe environmental team undertook optioneering for how the neglected riverbank could be enhanced. The accepted proposal was to reprofile the riverbank and install brushwood fascines, rock rolls and reclaimed timber fenders from the quay walls to create an intertidal terrace, encouraging suspended sediment from the tidal river to accumulate and form mudflat. Monthly monitoring of the silt accumulation was undertaken for a year after completion and showed that silt was gradually depositing within the features. This works package contributed to the Great Yarmouth scheme being awarded “Winner of the Environmental and Sustainability Initiative of the Year British Construction Industry Awards 2021”.

Want to know more?

Contact Dave.Sargent@jbaconsulting.com for more information about this project and work in Environmental Services.



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