Red7Marine developed the scheme with its chosen designer, Robert Leeds Structural Design, starting late last year, with work on site commencing early August 2022.
Red7Marine's 250t deck capacity Haven Seariser 3 jack-up barge carried out a proof dig in September at the design locations of the pile wall. The barge was equipped with a 35t excavator from W M Plant Hire.
The team carried out two dive surveys and extensive digging, several timber piles were removed as well as concrete and metal. All design sheet pile locations were also probed to highlight that the sheet piles could be installed safely and without risk of obstruction.
Following the final proof dig and dive survey, Red7Marine began piling activities.
Red7Marine was responsible for the on‐site sheet pile wall installation which comprised of a continuous sheet piled wall formed using approx. no.100 sheet pile pairs spanning a length of 140m.
To carry out the piling activities, Red7Marine utilised its Haven SeaStabler as a flat top barge and the Haven Seariser 3 jack-up barge. Both barges and a piling gate were secured and fixed into position in each pile location. Piles were lifted from the flat top material barge into the piling gate on the jack-up barge, and then were vibrated into the riverbed using a variable frequency piling hammer, this allowed for a slow start method, which is a requirement for ecological preservation.
Pile installation progressed from north to south and required several barge moves on the northern side of Sladdens Pier.
The barge was also positioned on the inside of the Trawl Dock for the final section of pile wall to reduce impact on the main navigational channel into Lowestoft. When all sheet piles were installed to design level, capping beams were installed across the top of the recently driven sheet pile wall.
Kristen Branford, MD at Red7Marine said: "This has been a great contract for our team to be involved with and highlights our capabilities as a design and construct contractor.
"We are utilising several pieces of our own plant, as well as working with our specialist supply chain partners to ensure the successful delivery of this project."
Rob Page, divisional project manager for Wales & Short Sea Ports at Associated British Ports, said: "This is an important project for ABP that protects our asset and ensures continuing support of our offshore wind providers that are berthed within the Trawl Dock as well as ABP infrastructure.
"We are pleased to be working with Red7Marine as a local contractor supporting the local economy. The Port of Lowestoft plays a vital role in enabling offshore energy generation in the East of England and ABP is investing to develop the outer harbour and the wider Port, playing a key role in the region's success."
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