Poor design and intermittent maintenance behind collapse of Toddbrook Reservoir in Whaley Bridge

A section of the dam wall collapsed last August, leading to fears that the dam could collapse and flood the town.

More than 1,500 residents were forced to leave their homes for several day as emergency services, partner agencies and volunteers worked around the clock to pump water from the reservoir.

An independent report into the incident has today been published, which has found that: “The cause of failure at Toddbrook Reservoir on the 1 August 2019 was the poor

design of the spillway, exacerbated by intermittent maintenance over the years which would have caused the spillway to deteriorate. It has not been possible to say whether it was the poor design or the intermittent maintenance that was the primary cause of failure on the day.”

The report found several flaws in the design of the spillway which meant that it ‘was not fit for the purpose of conveying the probable maximum flood.’

Several days of heavy rainfall led to part of the dam wall collapsing, but the report said that ‘with consistent good quality maintenance over the years leading up to the event the spillway may not have failed.’

It added that if the spillway had been kept clear of vegetation, and maintenance carried out, the spillway may have survived.

Had the water level not been reduced, ‘catastrophic failure’ of the dam may have occurred, the report adds.

“This could have happened without warning and at night such that widespread evacuation would have been impossible,” it adds.

A series of recommendations have now been made by the report, which was produced by Professor David Balmforth, former President of the Institution of Civil Engineers.

Among the 22 recommendations, which have been accepted by the government, are:

The Environment Agency should urgently seek to identify any reservoirs with potentially similar spillway characteristics to those at Toddbrook. The Environment Agency commissions new guidance on the failure mechanisms of spillways and how to undertake spillway inspections. Inspecting Engineers and Supervising Engineers inspect spillways closely and by direct access during their visits, with a minimum of one year between Supervising Engineers’ spillway inspections.

Speaking after the report was published, lead reviewer Professor David Balmforth said: “This has been an extensive and detailed review of the incident. I am grateful for the excellent cooperation of the Environment Agency and the Canal & River Trust, and for the input from members of the public.

“Important lessons have been learnt and I have made a number of recommendations that will help to improve the way in which we ensure the safety of our reservoirs in the future.”

And Environment Secretary George Eustice said: “This review provides the whole reservoir industry with important lessons following the incident that took place at Toddbrook Reservoir last year, and I hope it also reassures the public that we remain committed to ensuring the safety of reservoirs across the country.

“There is nothing more important than the safety of our communities, and I expect the Environment Agency and reservoir owners to immediately take action on these recommendations in order to ensure the continued safety those living and working near reservoirs.”

2High Peak MP Robert Largan said: “I welcome this report. It’s only right that people are given answers as to what went wrong last year and that we take steps to make certain that nothing like this can ever happen again.

“I am pleased the Government have quickly confirmed they accept the recommendations of the report and will be acting on them as soon as possible.

I will be working closely with Ministers and the Canal & River Trust to learn the lessons and repair the dam. But I want to make certain this is more than just a repair job. We need to take this opportunity to make improvements for the whole community, such as potentially installing a circular path round the reservoir and looking at a hydro electric generator.”

A second part of the review has also been recommended, to look at how the Reservoirs Act and regulations are implemented and make any necessary recommendations to further ensure reservoir safety.