Scour protection delivered by Stobart Rail & Civils
Stobart works to protect bridge from water erosion using its extensive knowledge.
Ongoing climate change is increasing the frequency of flood events around the country, resulting in ever changing challenges for asset managers. This is a particular concern for bridge structures crossing rivers where accelerating erosion to the supporting elements – abutments, piers and wing walls – can quickly cause damage that requires major intervention to repair.
Stobart Rail & Civils are specialists in environmental protection programmes, and are the Environment Agency’s partner on their Major Incident Response programme providing emergency flood resilience for communities around the country. This in-depth knowledge of environmentally challenging projects and the key stakeholders involved in their mitigation ensures that Stobart can plan and deliver innovative solutions, supported with their extensive plant fleet that includes numerous excavators, dump trucks and rock handling equipment suited to any job.
Stobart are supporting Network Rail LNE on a programme of scour protection schemes that are adding resilience to structures and ensuring that more significant remedial works do not become necessary. These projects all use solutions including rock armour, stone filled reno mattresses, and concrete filled blankets that Stobart design to provide long-lasting and sustainable protection.
One particularly challenging project for 2020 is at Rainbow Bridge that carries the PED5 Mexborough East Junction to Doncaster line across the River Don near Doncaster. This is at the heart of the major floods that caused so much devastation towards the end of 2019. The five span structure has two piers within the watercourse and recent Network Rail inspections had revealed scour to the faces along with undermining of the foundations.
Access to the bridge is a key challenge with no suitable route available from the adjacent land, and with the river being navigable it isn’t possible to construct a temporary causeway to enable plant access. Stobart’s solution uses a specialist barge to carry their twenty tonne excavator directly to the workface. A nearby jetty at an industrial site downstream is the ideal location to load the barge with the rock armour that Stobart will place in a 900mm layer beneath the bridge. Stobart will first excavate the existing riverbed material down to the design level then will regrade this material back on top once the rock is in position. As well as maintaining the habitat in the river this will return the level of the riverbed back up to its optimal profile to reinstate the damage caused by the scour.
Where erosion has extended beneath the foundations, Stobart will complete underpinning using concrete filled bags packed into the voids. A permeable membrane surrounds each bag to allows water to enter to start the curing process, but does not allow any of the concrete to wash out, ensuring there is no environmental damage.
Projects like these are just a few of the schemes that demonstrate Network Rail’s proactive commitment to managing the impact of climate change to provide a resilient railway, and Stobart’s capability and experience ensures that cost-effective solutions are readily available that achieve great results and maximise value for money.