Located about 160 km north of London, the town of Boston in Lincolnshire is in a flood risk area due to its proximity with the River Witham. To assure protection of 17,000 properties, a 25-metre wide rising gate was installed on the river. The project was achieved using 5,900 tonnes of sheet piles produced by ArcelorMittal Europe – Long Products.
An urgent need for flood defence
Boston is a port and market town in Lincolnshire, on the east coast of England. Crossed by the River Witham, the region has suffered from several floods these past years. To ensure the protection of 17,000 homes and businesses in case of future storm surge flooding, the Boston Barrier partnership was created between the Environment Agency, Lincolnshire County Council, Boston Borough Council and Black Sluice Internal Drainage Board. Company BAM Nuttall was commissioned by the Environment Agency to design and build a tidal flood defence gate. Once the project completed, the town will be protected from forecast sea level rises for 100 years.
A 100-year protection thanks to our sheet piles
There are three main installations on the left bank of the river:
Regarding the construction of the quay wall, the preferred option was to use an anchor wall but this couldn’t be achieved due to the existing concrete quay wall with anchor blocks. Consequently, a 740-metre long quay wall composed of 19-metre long HZ®/AZ® sheet piles was built, with tubular piles with ties were used onto the back.
The sheet piles were supplied by ArcelorMittal Europe – Long Products and are part of our EcoSheetPile™ range, meaning they were produced through the electric arc furnace (EAF) route. Produced in our mills of Belval and Differdange, Luxembourg, the sheet piles, as well as fully finished sheet pile elements, were supplied to customer BAM Nuttall, with whom we have been working for many years. Deliveries were a challenge for the teams involved as they had to be just-in-time to be closely coordinated with the ongoing construction works and piling progress.
The 100-year design life was also another challenge for the design team as it needed to resist the risk of accelerated low water corrosion. Different solutions were explored, such as thickening the sheet piles but, in the end, the engineers opted for the Impressed Current Cathodic Protection (ICCP), a system used to control the corrosion using anodes connected to a direct current (DC) power source.
The gate is already fully operational and can be raised in just 20 minutes. The Boston Barrier project is expected to be fully completed in 2022.