VolkerStevin, working with subsidiary companies VolkerBrooks and VolkerGround Engineering, have together successfully completed stabilisation works to the bank of the River Don in Doncaster.
The built embankment separating the South Yorkshire canal and River Don at Wheatley Cut, has a long history of instability. Over the end of 2012 and early 2013, rapid slope movement compromised the crest of the flood embankment which raised concern regarding the immediate stability of a 600m stretch of embankment. If this failed it could have resulted in the canal emptying into the River Don and potentially flooding around 700 properties in north Doncaster.
In April 2013, the Environment Agency (EA) awarded VolkerStevin the contract for the stabilisation works to the river bank and to construct an emergency steel sheet piled wall, 650m in length to resolve the short term stabilisation issues. Following further designs, to resolve long term structural instability, VolkerStevin was also contracted to install a further 650m of toe piles and regrading of the embankment.
Due to the restricted width of the embankment between the river and canal and lack of road access, piling work was completed from a floating platform of Linkflote pontoons, which had a 70 and 80 tonne crawler crane mounted on top. The platform was mobilised by VolkerBrooks and moved down the canal daily, as work progressed. VolkerBrooks also supplied the waling beams consisting of twinned ‘H’ section steel beams totalling around 235 tonnes.
The sheet piles were driven 12m below crest level using a vibratory hammer and then completed by back driving with a hydraulic impact hammer, when more resistant clay soils were encountered, by VolkerGround Engineering. The toe piles were driven by use of vibratory and hydraulic impact Movax type excavator mounted hammers. The two pile lines were joined with tie rods to provide long term stability. Throughout the work all piling equipment and materials were transported on pontoons with tugs to the works location.
The team also re-profiled the earth embankment to a sufficiently shallow angle, to reduce future slippage and provide safe access for the EA, the Canal and River Trust and the public.
The embankment now provides a complete barrier through the river bank which will stabilise the existing material and prevent any further deterioration of the area between river and canal for the next 50 years.
Alice Hearne, senior user representative for the EA commented: “The embankment at Arksey Slips was actively moving at the start of the project and had been for some weeks. Because the site is in accessible by road it was not possible to install temporary defences, so quick and efficient works were essential. I have been very pleased with the way the project has progressed with VolkerStevin. The compressed design period and thoughtful, well managed construction works have meant that the site has progressed rapidly, and the immediate risk to flooding relieved quickly, prior to total failure and associated flood incident, which I am fairly certain would have occurred given a little more time. I’d like to congratulate VolkerStevin for their efforts.”
Rob Coupe, managing director for VolkerStevin said: “This project has been a great example of how VolkerStevin, working with VolkerBrooks and VolkerGround Engineering, execute exemplary flood prevention works.”