'Rock armour' to boost Sunderland's sea defences

Around 27,000 tonnes of ‘rock armour’ is set to be ordered by Sunderland City Council which has prepared a tender for the works and allocated a contingency budget of around £2.42million.

The works will create new rock revetment walls to update and improve the port’s Stonehill Wall and Hendon Foreshore Barrier sea defences.

Altogether, the new rock armour revetments will measure around 390 metres in length.

The city council’s cabinet agreed the next steps for the project at a meeting at Sunderland Civic Centre.

This included starting the process to procure the rock armour through open tender and the future appointment of a contractor to install it.

Councillor Graeme Miller, leader of the council, said the project aimed to “help prolong the lifespan of each structure” while continuing to protect the functionality of Hudson Dock within the Port of Sunderland.

Cllr Miller told the meeting:“Not undertaking the emergency works will leave the council at risk from the likelihood of further damage due to natural storm events and the increase of climate change and may lead to progressive failure of each structure with likely severe impacts including loss of functionality of the Port of Sunderland in terms of the navigation channel and Hudson Dock.

“[The project also] allows the council to comply with its statutory duties under the Coastal Protection Act 1949 and Sunderland Corporation Act 1972.”

Repairs to decking at the Stonehill Wall sea defences, that were damaged in the winter and spring storms of 2018, have already been completed.

However, the structure now requires 18,900 tonnes of rock for its 215-metre updated revetment – with the rocks weighing between one to three tonnes and six to ten tonnes.

Meanwhile, works for the Hendon Foreshore Barrier, which helps protect the Northumbrian Water treatment works, require 8,000 tonnes of rock armour for its 175-metre revetment with rocks weighing between three and six tonnes.

As part of the tender, it has been outlined how the rock will be delivered by ship or barge to the Port of Sunderland and transported to the works areas for land-based placement.

The council previously said that bringing rock to the port by sea has a lower carbon footprint than hundreds of HGV journeys from UK quarries and is less disruptive.

At this week’s cabinet meeting, councillors heard that the estimated costs of the sea defence project had the potential to increase due to factors such as weather.

Cllr Miller explained: “Councillors must be aware that these cost estimates [in the cabinet report] are based on information available at the time of writing.

“There is a risk however of price fluctuations due to inflation impacting on the cost of raw materials and weather risk."

He added: “A 10% risk contingency has been allowed for the supply of the rock armour due to weather delays.

“Depending on the prevailing weather conditions the outturn costs, due to any delays, could be significantly more.”

Following the cabinet decision, procurement of the rock armour is expected to start this month with rock deliveries anticipated to be no later than May 2022.

If everything goes to plan, construction activity would commence around May 2022 for Stonehill Wall and some time during 2022/23 for Hendon’s Foreshore Barrier.

Works on the port’s New South Pier have also been completed following damage in 2018 and last year, these works were project winners at the Institution of Civil Engineering North East ‘Robert Stephenson Awards.’

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