Work on the damaged dam in Whaley Bridge will take years and cost “millions”, the project manager has said.
More than 1,500 people were evacuated from the Derbyshire town from August 1 due to fears that the dam wall at the Toddbrook Reservoir would collapse after heavy rain.
But the Canal and River Trust, which is responsible for maintaining the dam, have now said it is “happy” with how it was originally built – describing the incident as an “anomaly”.
Project manager for the trust, Rob Jowitt, said there are other dams with a similar construction but there will be no change and no increase in cost for monitoring them.
He told the PA news agency: “There are other dams of similar construction – earth embankment dams – obviously this was built over 200 years ago.
“The investigations we have done, I’m guessing, will be spread around because there are over 2,000 other dams around the country and the lessons we have learned here will be spread around other organisations who look after and maintain dams.
“We look after 72 dams, some are operational and some aren’t. We’ll carry on with our regulated inspections – weekly and daily inspections – so there may be a few lessons learned in terms of maybe we add some processes in to our inspections, but the investigation may come back and say we were doing everything to the letter.
“There are obviously dams with similar spillways but each dam is slightly different – different size, different width, depending on how many cubic metres of water they are holding back.”
Mr Jowitt said there would be no cost increase for monitoring the other dams of a similar design because the same inspections would be carried out.
He said: “There will be no increase in cost unless the investigation into what happened here says we need to start doing other types of investigation but at the minute we are doing everything to the book as the Reservoir Act stipulates.”
Questioned about the future of the dam at Toddbrook Reservoir, Mr Jowitt said: “I wouldn’t like to speculate on the scale of the rebuild and repair, but it’s going to be major and potentially two to three years worth of work.
“The scale of the cost could vary massively, so until we get the designs back… we don’t know if we can self-fund it or ask the Government for input.”
Speaking about the cost of a rebuild, Mr Jowitt said: “It will certainly be in the millions – I’m not sure whether it’ll be in the tens or hundreds or thousands of millions.
“Until we get those designs done, and all the investigation done, I couldn’t put a figure on it.”
Commenting on how long the trust would be working on the dam repairs, Mr Jowitt said: “It will easily be two years. Obviously any longer than that is going to be down to the scale of the construction and scale of the work they are going to have to do.”
Mr Jowitt told PA there were weekly and daily inspections of the dam at Toddbrook Reservoir before it was damaged despite vegetation growing in between the concrete slabs.
He said: “We had regular inspections of the dam, we had periodic, principal inspections – and then weekly inspections and possibly daily inspections.
“As far as why this happened, the investigation is still going on. We have surveyed everything, we have left no stone unturned – at the minute we know the position of every stone around here with the amount of surveys we have had done.
“The daily and weekly inspections were visual – and obviously we have stringent checks we have to do during these inspections.
“Everything happened suddenly. There was no warning that it was going to fail.”
Asked if it was fair to describe the damaged dam in Whaley Bridge as an anomaly, Mr Jowitt said: “Yes, definitely. It came as a surprise – there were no tell-tale signs that anything was going to happen.
“It was just with the amount of rainfall we had over that period, it’s very rare to see it over the top of the auxiliary spillway because usually the primary spillway will take all the flow away – so it was just the freak weather we had.”
Questioned on whether he was confident the trust would be able to deal with another period of “freak” weather, Mr Jowitt said: “We have got everything place to be able to deal with that and shift the water as and when we need to.
“With the weather we had on Friday, which was obviously quite a big weather event, we turned eight of the 11 pumps on so we still had three sat there and we managed the water levels perfectly fine.”
Speaking of the safety of the dam, Mr Jowitt said: “With the management we have got at the minute, we know that if we do get heavy rainfall that we can manage that. We can manage a one-in-200-year flood event.
“We are happy that the reservoir, at its drawn down state, can take a huge influx of water and we can manage those levels so we don’t have to start evacuating residents again.”