The major operation to pump water out of Toddbrook Reservoir in Whaley Bridge has continued at pace overnight, ahead of the anticipated arrival of storms later today.
Emergency response teams have been working around the clock to shore up a section of the damaged spillway and reduce water levels due to the "substantial threat to life" posed should the dam wall breach.
Around 1,500 residents were evacuated from their homes in Whaley Bridge on Thursday, and a further 55 properties in the Horwich End area were cleared on Saturday evening due to the potential increase in risk of adverse weather in the coming days.
The Met Office has issued a yellow weather alert for scattered heavy showers and thunderstorms during Sunday afternoon and evening, warning that more than 30mm of rain could fall in a short space of time where downpours occur.
More pumps have been brought in to speed up the removal of water from the reservoir, and an RAF Chinook, which dropped 400 tonnes of aggregate to reinforce the damaged dam wall and stop water from entering the reservoir, was back in action on Saturday. Grout has been poured around the bags to bind them to further strengthen the structure.
Deputy Chief Fire Officer for Derbyshire Fire & Rescue Service, Gavin Tomlinson, speaking on Sunday morning, said: “Crews have been faced with a massive challenge to pump water from the reservoir and this work continues.
"A total of 22 pumps have been working through the night and we have been successful in taking about 35 per cent of the water held in the reservoir out. This work will continue until engineers are confident that the water is at a safe level and the risk has been mitigated.
On the construction of the dam and the challenges that presented, Mr Tomlinson added: "The dam is like a bowl, it doesn’t have straight sides, so as the water level drops crews are having to relocate the pumps to ensure they are able to work as effectively as possible.
“Our priority remains the same, to pump as much water out of the reservoir as possible, to protect the Whaley Bridge community from the risk of the dam failing."
By Saturday afternoon, the Canal & River Trust had estimated the reservoir was at 83 per cent of its holding capacity, following the removal of 23 million gallons of water 12 hours.
A spokesperson for the trust said local people were being advised to plan to be away from their homes for up to seven days.
Also on Saturday, Environment Secretary Theresa Villiers met the emergency response teams at Whaley Bridge and also spoke to residents at the rest centre in Chapel-en-le-Frith.
She said: "My thoughts are with the people who have had to leave their homes. Having spoken today to some of those evacuated I know how difficult this situation is for them and I pay tribute to their patience and fortitude. It’s been wonderful to see the community support and spirit in Whaley Bridge.
"I want to thank all emergency services, military personnel, Environment Agency and volunteers for their continued hard work. I am confident that everything that can be done is being done and I’ve seen a reassuring amount of progress today."
Chair of the Environment Agency, Emma Howard Boyd added: "Real progress has been made, and after seeing our pumps and the RAF Chinooks at work today I am confident we are doing all we can to lower the water levels and secure the dam."
Roads in and around the area remain closed and rail services between Buxton and Hazel Grove, and through the Hope Valley towards Sheffield, are suspended.
A helpline number for residents, 01629 533190, is open between 9am and 10pm and there is an answerphone facility outside of these hours.
There is also an email address for anyone wishing to donate items or services: email@example.com.