MEETING WITH KIER AND CANAL & RIVER TRUST
21 March 2025
Kier Group plc is one of the biggest businesses we have welcomed to Business Club with a group revenue over £4bn, some 10,000 employees and a current portfolio of over 400 live projects across the UK. They started as specialists in pouring concrete and are a leading provider of infrastructure services and construction, with the UK government as a big customer, so it was no surprise that Kier won the contract to repair and restore Toddbrook Dam.
The dam was erected in the first years of Queen Victoria’s reign to provide water for the Peak Forest and Macclesfield canals as Combs reservoir quickly proved inadequate. Like hundreds of other similar clay core dams, it has stood the test of time – till recently. In late July 2019 days of endless rain, with flooding downstream in Bramall and Poynton and overflowing reservoirs through the Goyt Valley, culminated in one terrifying morning (1 August) when it looked like the dam might actually disintegrate. Horrified residents watched as water blown across the top crashed down on the spillway concrete plates, breaking several; in the now unprotected earth core, a slurry quickly formed and began to hollow out the upper part of the dam. Thank heaven this was spotted early, with emergency plans enacted and a full evacuation of 1,500 people underway by mid-afternoon. Everyone in Whaley Bridge knows that had this happened at night and not been spotted, the dam would have given way resulting in huge damage and loss of life.
We have an excellent record on dams in this country; it’s the first time in almost a century that one of Britain’s many dams has been at risk of collapse. The 2020 Balmforth Inquiry which followed blamed poor maintenance allowing weeds and even small trees to weaken the integrity of the concrete; but “inadequate” redesign decades ago didn’t help. A severe rainfall event had damaged the original spillway, leading to the construction of an auxiliary spillway between 1969 and 1970. But.. it’s hardly good practice to put your risk reliever (the spillway) right on top of your original risk (the dam) – if one fails the whole structure is compromised. It’s also not a great idea to protect the core with relatively thin concrete sheets. An accident waiting to happen.
Our wonderful speakers Tess Smith, Stakeholder Manager for Kier, and Dilwyn Parry, Project Manager from the Canal & River Trust, owners of the reservoir and dam, outlined what is now happening, and why, and when completion is expected. They both bring a wealth of experience to their jobs. For Tess, Yorkshire Water, Amey, Jarvis, Balfour Beatty and Transport for Greater Manchester feature on her CV; though not an engineer herself, she has worked with them for decades and her role includes engagement with schools, politicians, local authorities and the public. Dilwyn is a qualified engineer with 17 years with the CRT before widening his experience, who returned to manage this important project a year ago.
One issue which quickly emerged in 2019 was how hard it was to reduce the reservoir level. Ancient systems meant that, with the spillway unavailable, water could flow in four times faster than it could be released; the main flow to the canals has to be carefully controlled, while the flood capacity of the relatively small Todd Brook is quite limited. Hence the massive pumps, brought in from all over the country. The new design looks odd to us, though it would have been familiar to the Victorians, as the spillway is relocated once more to the side. There will be huge new concrete silos mainly underground to store storm water, allowing release once flooding danger has diminished. Hence the power-driving we’ve heard here for months – some 270 piles have been driven down into the mud to hold the structure of the entire new spillway “to secure it against land movement, old mineshafts, even earthquakes.” A stylish new downflow is intended to reduce turbulence. Far more sluice pipes with multiple valves are being installed. Eleven high-volume pumps are still on constant standby, to keep the water level low while repair continues, and will be almost the last item to disappear.
The dam itself will be repaired once all this complex reconstruction is completed. Then the “Reservy,” as the old maps call it, will slowly fill, hopefully from early next year. While that’s going on, sports and playground areas will be restored and a new yacht clubhouse created. A tricky decision has to be taken soon, Dilwyn said – the order of £50,000 worth of fish for restocking. The last bit is the football pitch where the current project offices are sited. That won’t be ready till the end of 2026. Fingers crossed.
The project was originally signed off in 2022 at about £15 millions and a timetable of about 2 years, so the reservoir should have been filling up by late 2024. That obviously has not happened. Why not? Partly because of increased safety standards, so some work can only be done when the reservoir is not filling up – that means, a clear interval of 5 dry days. Not a common event in our corner of the world.
And we know, if it is going to take twice as long, the overrun cost will be eyewatering. That’s dealt with, Tess explained, by a “contract of shared risk.” Whereas a straightforward short-term project might be a fixed cost offer, that would be unsuited to a complex and changing environment like this.
We asked, why are there no plans for hydro-electric power from the outflow? “Because it is too intermittent,” Dilwyn said. The Todd Brook is a low flow stream – that’s why it’s excellent for the canals, and also why a big reservoir is needed. Combs actually holds more water, but checks have shown that its pipes also need replacing, so the work continues. So why leave all the silt in Toddbrook, so the capacity is less than 200 years ago? Because the volume of water is greater at the top, not the V-shaped bit at the base – it’s not worth the effort of digging it all out. Basic maths. Of course.
This was a fascinating presentation, with many questions; we could have heard far more. I was left with admiration for the original engineers, who understood the power and value of water, and got the design basically right two centuries ago. And for their modern counterparts wrestling with heightened safety concerns, eye-watering costs, the added challenges of climate change, and the need to leave a legacy for another 200 years.