The long-awaited £90M Boston Barrier has finally been approved by the government – but may not start on site for another two and a half years.
The project to protect 20,000 properties in the Lincolnshire town from tidal flooding was awarded the remaining chunk of its funding last week.
It was a major breakthrough for Boston, which many felt was sidelined by the government after a tidal surge flooded 579 homes in the area last winter.
But the town faces a further five-year wait before the barrier is ready.
Environment Agency project manager Nic Rowlinson said an application for a Transport and Works Act Order would be submitted to the transport secretary in autumn 2015.
“There will then an 18-month period where the transport secretary will consult over the proposals, which includes time for a public inquiry,” he said. “If everything goes to plan then we aim to begin construction of the barrier in mid-2017 and complete it by December 2019.”
The project will see a 25m wide ‘rising cill’ barrier installed in the tidal Boston Haven, to be raised to 7.55m above ordnance datum using hydraulic cylinders when needed.
Further work, outside the scope of this scheme, will include building flood walls to the same height as the raised barrier. Earth embankments downstream will later be raised in line with this work.
The government has spent about £6M to date preparing for the Boston Barrier – including surveys, planning and a 12-week period of ground investigations carried out by consultant WYG. Consultant Mott MacDonald is working on the Transport and Works Act Order application along with preliminary designs for the barrier.
A further £11M has been committed by Lincolnshire County Council, with the remaining £73M approved by Treasury chief secretary Danny Alexander last week.
Rowlinson denied that the scheme, which was named on last year’s National Infrastructure Pipeline, had been delayed by issues over funding.
“Delivery of the Boston Barrier was already underway before the December 2013 flooding,” he claimed.
“The high priority of the project has meant that flood risk management funding has not been an issue. The time taken to deliver the project has been dictated by its complexity – including the need to secure consent through a Transport and Works Act Order.”
Rowlinson warned that gaining this consent could prove a major hurdle.
“The Environment Agency has experience of securing these orders, for example for the Ipswich Tidal Surge Barrier, however they are complex pieces of legalisation which ideally require the support of affected parties and take considerable time to prepare and consent.”
Once underway in 2017, the project will involve building a cofferdam for construction works while allowing river traffic to pass.
Homes near to the site will have an impact on access, hours and methods of construction.
“We have been developing with our suppliers access routes, design and construction methods to enable the works to be cost effectively delivered,” said Rowlinson.
Environment Agency workers and contractors were forced to install temporary demountable flood defences after a 30m section of flood wall was damaged by last December’s surge.
In total, 60m of temporary defences were needed to tie in to the existing wall, along with other temporary repairs to damaged flood defences in the town.
Site workers installed steel piles to depths of 3m and placed 2,000t of stone to mend a 40m breach in a flood bank at Slippery Gowt.
Nonetheless, media and political attention last winter focused on the Somerset Levels, leaving a feeling that Boston had not received the same amount of help.
“The night Boston flooded, Nelson Mandela died,” said a spokesman for Boston Borough Council in February. “We have not had the sort of media coverage [that Somerset has].”
- You can view a video of how the Boston Barrier will work here.