The right bank of the River Don between Mile Thorn Sidings and Long Sandal Lock on the north east outskirts of Doncaster has a long history of instability. The Environment Agency had noted a failure of the river bank on a section between the River Don and the adjacent Stainforth and Keadby canal which had been caused by a combination of erosion of the river bank toe and high water pressures due to high river levels and leakage from the canal.
In the late spring of 2013, the Environment Agency awarded a contract for the stabilisation works to the river bank through the construction of a steel sheet piled wall 1.2km in length through the existing embankment.
VolkerGround Engineering's sub contract commenced in June 2013, and was completed in January 2014. Due to the restricted width of embankment between river and canal and lack of road access, piling works were completed from floating plant, mobilised by sister company VolkerBrooks, within the River Don. Plant and materials were floated down river from the main work site to suit the progress of the works.
The ground conditions underlying the river bank were predominantly soft clays to the full extent of the maximum 12m length of AZ 12 - 700 sheet piles. The upper embankment comprised sandy fill material for an initial depth of 2m. Piles were driven with a vibratory hammer and then completed by back driving with a hydraulic impact hammer when more resistant clay soils were encountered. All piling plant was crane suspended from a 70 tonne machine mounted on VolkerBrooks Flexiflote pontoon units.
The works will provide 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.