Report blasts ‘intermittent maintenance’ of reservoir
A MAJOR independent report has found ‘poor design’ and ‘intermittent maintenance over the years’ led to the failure of the dam at Toddbrook Reservoir in Whaley Bridge.
More than 1,500 people were evacuated from the picturesque town in Derbyshire when the spillway wall at the reservoir began crumbling during heavy rainfall in early August last year.
A ‘danger to life’ warning was issued and unprecedented scenes followed.
The spillway’s failure led to a huge emergency operation involving the
RAF and hundreds of firefighters and police officers, which saw the wall shored up with hundreds of tonnes of aggregate and the reservoir drained.
Professor David Balmforth, a reviewer of reservoir safety, published the independent report.
The Balmforth Report called the intermittent maintenance of the spillway ‘particularly concerning,’ as it occurred ‘despite repeated requests from supervising engineers.’ “With consistent good quality maintenance over the years leading up to the event the spillway may not have failed,” it said.
The report’s findings and recommendations said: “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.
“With consistent good quality maintenance over the years leading up to the event the spillway may not have failed. However, it would have been unlikely to survive the probable maximum flood which is many times greater than the flood in which it failed.”
The report went on: “The intermittent maintenance of the spillway at
Toddbrook reservoir is particularly concerning. This occurred despite repeated requests from Supervising Engineers.”
In his executive summary he indicated, for the first time, what actually happened. He said that on the morning of August 1, a single slab of the dam’s spillway chute collapsed into a large void that had formed underneath.
Brown ‘slurry’ was then seen pouring from under the slabs, which are said to have failed and lifted, further down the spillway chute. The reservoir is owned by the Canal and River Trust.
In response, the Trust said the Balmforth report, and a separate independent report by expert reservoir engineer Dr Andrew Hughes, commissioned earlier by the Trust, ‘identified serious hidden design flaws, inherent in the concrete auxiliary spillway from the time of its installation in 1970.’
Richard Parry, chief executive, said: “Keeping people safe is always our top priority; we welcome any steps that reduce risks to local people and are fully committed to acting on all the lessons learnt from this incident and taking the actions arising from both these reports.”
The government said it accepted a series of recommendations to further strengthen reservoir safety. A huge engineering project to repair the dam at Toddbrook started in January.