A novel solution has stabilised a new washwall at Diglis Basin on the River Severn in Worcester. The original wall failed three years ago when the basin accidentally drained and boats moored to the wall pulled it down as they dropped with the water level.
Galliford Try, through its Morrison Construction Omnibus Partnership with British Waterways, installed a new washwall from a row of 7.5m long sheet piles driven into Mercia Mudstone to a 4m depth.
The contractor welded I-beams to the inside of the piles from which a row of 11, 9m metal tie-rods were bolted and fixed to a second row of piles 9m back from the washwall in front of a grade II-listed lock-keeper's cottage.
'To start with we were going to secure the tie-rods to a reinforced concrete block anchor built in the ground in front of the cottage, ' says project manager Andy Shaw.
'A better solution though, was to use the passive pressure of the soil in between the new washwall and a second row of piles to achieve the necessary 200kN of loading. We estimate that not building a concrete anchor saved about £15,000, which will be shared with the client.' Access to site was a major issue.
The main approach road was shared with another contractor, which is building flats around the inner basin as part of the regeneration of Worcester's riverside.
The restricted site is surrounded on three sides by water; the canal, the outer basin and a finger wharf which connects to a boatyard, so site workers erected pedestrian and plant bridges across the wharf.
Part of the contract also involved Morrison Construction removing, and now restoring, two swing bridges that will be craned back into position later this summer.
Worth £275,000, the project was on course for completion at the end of July.