Over 1,500 people were evacuated from picturesque Whaley Bridge in Derbyshire in August 2019, when the Toddbrook Reservoir spillway began crumbling during heavy rain, threatening to collapse and flood the town.
Now, 12 months after the 1 August 2019 emergency operation to shore up the dam, engineers have completed a temporary repair until a major rebuild begins in 2021.
On Thursday 1 August 2019, torrential rain caused a large section of the spillway to fall away, leading to fear the dam could collapse, and residents of Whalley Bridge were told to evacuate, with many unable to return to their homes for over a week.
A massive operation entailed, enlisting the help of the RAF and hundreds of police and firefighters, as Chinook helicopters became a regular sight, as they installed hundreds of tonnes of aggregate on the damaged spillway, while firefighters hastily drained the reservoir.
In a March review of the reservoir, by Professor David Balmforth 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.
The report stated that it was not possible to say whether it was the poor design or maintenance issues that were the primary causes of the spillway failure, but improved maintenance over the years could certainly have prevented the incident.
The temporary fix for the dam wall has now been completed. The waterproof core of the dam has been improved with the addition of a concrete ‘cut off beam’ and an enhanced crest wall along the top of the dam to protect it against extreme weather. The temporary repairs will remain in place until the end of the permanent reconstruction project.
The final plans for the permanent rebuild have yet to finalised, but engineers estimate it will cost £10 million and take three years to complete.
The Canal & River Trust, which cares for the reservoir and over 2,000 miles of waterways, has worked with contractors Kier through record winter rainfall and the coronavirus crisis to increase the resilience of the dam’s auxiliary spillway.
Excess rainwater falling in the reservoir continues to be removed by on-site pumps and the reservoir will remain drained until the permanent reconstruction project is finished in three years.
Daniel Greenhalgh, Canal & River Trust North West regional director, said: “We are currently examining a range of potential repair options and the views of local residents are a key part of the decision-making process. We are planning to host a public consultation event in late summer and then confirm the preferred option in the autumn.”
The permanent works are scheduled to begin in spring 2021 at the Todd Brook inlet channel at the head of the reservoir.
After the emergency in August 2019, the masonry weir was raised by the installation of mesh baskets filled with sandbags which will be replaced by a new flow management structure and a footbridge.
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