The Canal & River Trust charity, which cares for Toddbrook Reservoir in Whaley Bridge, celebrates a significant milestone this month, with the installation of nearly 1,000 sheet piles forming the route of the new £15 million overflow spillway channel – a fundamental part of the design that will bring the reservoir back into use.
A new interactive fly-through 3D computer model showing how the finished structures will look now available on the Trust’s website, and members of the public are invited to see progress up close at two public open days hosted on-site on Friday, 7th and Saturday, 8 July.
The existing auxiliary spillway on the dam wall was damaged in the summer of 2019 after excessive rainfall, and the reservoir has been kept virtually empty ever since. Following two public consultations and a detailed planning application, work started on the chosen restoration scheme in the autumn of last year and is expected to take just over two years to complete. The northern end of the town’s Memorial Park has been temporarily closed to the public to make way for the site compound and spillway works.
The project, designed by Arup and delivered by principal contractor Kier, involves removing the damaged auxiliary spillway and replacing it with a new overflow spillway structure to the north of the dam. This will feature a side channel weir, tumble bay, spillway channel and stilling basin, which will link into the existing bypass channel flowing into the River Goyt in the town’s Memorial Park.
Now the sheet piles are in place; the ground can be excavated to form the new channel, which will be lined in concrete, forming a base and side walls for the new spillway. These will be constructed over the coming months, starting with the weir and tumble bay at the top of the reservoir, followed by the spillway chute, stilling basin and two cylindrical concrete turrets, which are an essential engineering feature to slow the water flow before it enters the open channel and River Goyt.
A further 500 concrete piles will be installed at the top of the dam crest and tumble bay, and at the stilling basin. This involves pouring concrete into cylindrical columns, which are then reinforced with steel to form the structure’s foundations. A few further short periods of sheet piling are also expected to occur from early August.
Julie Sharman, chief operating officer of the Canal & River Trust, said: “We have reached a significant milestone with the project, and it’s important to share the progress made on the construction work to restore the reservoir – particularly so everyone can now see the route of the new overflow spillway. We must restore the reservoir for the amenity value to the community in Whalley Bridge and its role in supplying water to the Peak Forest and Macclesfield canals.
“This month, we are also celebrating the significant role female engineers play in delivering the Toddbrook construction project, not only from the Canal & River Trust but also from our contractors Kier and engineering designers Arup. Leading up to International Women in Engineering Day on 23 June, my colleagues have visited several local schools to hopefully inspire a new generation of female students to pursue careers in science and engineering. It is fantastic that we lead by example on such a challenging, high-profile construction project.”
At the end of the leading construction works, concrete panels from the 1970s auxiliary spillway will be removed, and the dam will then be repaired and grassed over. A new playground will be rebuilt in the Memorial Park, which will also be re-landscaped with trees, wildlife habitats, additional paths and a new footbridge over the bypass channel. The sailing club will be relocated behind the new tumble bay, where it will feature a new slipway, clubhouse, boat storage and car park.
Temporary sheet piles will be kept in place at the dam crest throughout construction to maintain essential flood protection measures. High-volume pumps will also remain in the reservoir to manage water levels until the end of the restoration project.
The public can go behind the scenes of the project at two free public open days on Friday, seven and Saturday, 8 July. Places must be booked in advance through the Canal & River Trust website: https://canalrivertrust.org.uk/restoring-toddbrook-reservoir.