With the lack of headroom due to a build up of bed materials, and the potential for scour damage during flood conditions; flood elevation and scour protection measures were urgently required.
Due to the susceptibility of the River Calder to respond quickly to rainfall and consequently rise in river level, it was imperative that the weather conditions were checked and monitored prior to and during any activities where personnel are working in the watercourse.
To allow semi-dry access below the bridge structure, the river was diverted through two twin wall pipes each 35m in length.
Once the river flows were diverted, the river bed materials required reducing down to formation level beneath the bridge and for 6m upstream and downstream of the structure to allow placement of the Proserve scour protection Mattresses. Due to the high flood protection walls on either side of the river, it was necessary to lower the excavator and micro excavator into the river using a crane from the road adjacent.
120t of mobile bed materials was moved from below the bridge to increase the headroom and achieve the formation levels for the design. Care had to be taken not to undermine the bridge foundations or the footings of the adjacent retaining walls.
Scour protection was achieved and the project was completed on time and to budget.