21st Century Sheet Pile Solution for Victorian Dams
‘Are these Victorian dams still safe after over 150 years of use?’
This was the question many asked after August’s Whaley Bridge, Toddbrook Reservoir crisis. For water companies realising the potential risk, but believing they lack the budget to carry out dam repairs, Sheet Piling (UK) Ltd has a reservoir stabilisation and repair solution.
Whilst Toddbrook Reservoir’s damage story may be recent, Sheet Piling (UK) Ltd has carried out major dam and reservoir stabilisation projects in recent years. In 2017, innovative repairs to Island Barn Reservoir, managed by Thames Water, were implemented. Last year, we delivered a sheet pile solution to make-safe Redmires Reservoir, Sheffield, for Yorkshire Water. We have expert solutions that can make Victorian dams safe and stable.
Cost-effective dam repair solution
Many UK dams were constructed in the 19th century or early 20th century. Island Barn Reservoir was built in 1911, Redmires in 1836 and Toddbrook in 1830. As Dr Yurui Fan, lecturer in Flood and Coastal Engineering at Brunel University said after Toddbrook, “this raises concerns for dam safety in future.”
The glare of publicity on Toddbrook has fast-forwarded dam repairs-planning in the utilities sector. Water companies recognise that, despite budget constraints, there is no time to delay. 1500 residents’ lives were at risk in Whaley Bridge. Solutions to the repairs’ conundrum, the seepages from Victorian dams, and the issues arising from soil-based embankment dams, which can wash away rapidly if defences are breached, simply has to be sought.
The cost-effective dam stabilisation solution, as Island Barn and Redmires found, lies in the installation of a sheet pile cut-off wall, as detailed in a technical paper published by the British Dam Society for its Biennial Conference, and as installed by Sheet Piling (UK) Ltd.
Embankment Leakage Remedial Works
Embankment leakage is becoming a real issue with reservoirs and dams. At both Island Barn and Redmires, Sheet Piling (UK) Ltd installed an impermeable barrier of steel sheet piles, to form a contiguous cut-off wall, to prevent the leakage. At Island Barn, we had to address three separate leakage points and were one of two possible solutions considered.
Our watertight sheet pile solution was selected in preference to a cement-bentonite cut-off wall because the latter would have required extensive enabling works, to support large and heavy equipment, as well as causing a significant volume of arisings and spoil, and a risk of water pollution due to slurry entering the reservoir.
Our sheet pile solution has a relatively short installation duration requiring limited excavation of the embankment crest for a platform and only a shallow trench, to allow the use of walking press-in piling machinery. This unique sheet pile solution is not only extremely sympathetic to the existing reservoir embankment in ensuring stability is maintained during the works but is cost and programme effective when compared to other solutions. By using silent, vibration-less Giken piling equipment, we also minimised environmental impacts.
Additional Dam Repair Innovation: Island Barn
At both Island Barn and Redmires, Sheet Piling (UK) Ltd’s design experts introduced innovative elements that made the projects even more successful. At Island Barns, we created a pontoon-based solution. This relieved what could have been a fragile crest of the dam, of any unnecessary pressure. The pontoon carried equipment and acted as a lifting platform to feed piles to the Giken walking press. A jetty was constructed to enable plant to be loaded on to the pontoon, facilitating the installation of piles from the water. Sheet Piling (UK) Ltd designed the jetty as a rectangular cofferdam of sheet piles, filled with graded granular material.
The piles used in the Island Barn project were 18.3m-long, Arcelor GU32 sheet piles, with a design life of 100 years. Using the Giken pile pressing method allowed us to mitigate any potential liquefaction of granular reservoir embankment shoulders. Whilst there had been concerns about the use of water during water jetting – to install piles into the stiff London clay soils – we actually performed the operation without water jetting.
Following installation, we reinstated the clay core to its original condition, after pitch, tenacity and elongation tests, completing a hugely successful project on behalf of our clients, Costain, Atkins and Black and Veatch JV.
Innovative sheet pile solution: Redmires Reservoir
On behalf of client, Mott McDonald Bentley, we installed another dam repair solution in puddle clay, in the form of another sheet pile cut off wall, consisting of Arcelor Mittel PU32 sheet piles, to lengths between 16 and 20 metres in length.
Here, the Upper reservoir is retained by an earthfill embankment of puddle clay core, sitting on top of Glacial Till. We installed a sheet pile cut off wall consisting of 668 sheet piles, using a Giken F201silent vibration-less pile press with tracked power pack and again avoided any unnecessary pressure on the reservoir crest, by siting a crawling crane on a working platform constructed on the bottom of the drained Upper Reservoir.
Once again, we installed the piles without the need for water jetting, enuring there was no damge to the puddle clay.
Reservoir repairs – the 21st century way
Sheet Piling (UK) Ltd has proved it has a highly successful solution for reservoir stabilisation projects and repairs that need not cost the earth in embankments and puddle clay soils. With the Toddbrook Reservoir plight having accelerated the repairs programmes for many dams, such a solution could be the answer many stakeholders and water companies are seeking.
To find out how Sheet Piling (UK) Ltd could assist your project, please call +44 (0)1772 79 41 41.- Ends -
NOTES TO EDITORS
Sheet Piling (UK) Limited is one of the UK's leading piling contractors. Owning and operating a comprehensive range of specialist piling equipment Sheet Piling (UK) Ltd also carry extensive stocks of new and used piles enabling rapid reaction to any urgent requirements or emergency situations.