Innovative wastewater management system deployed for Littleborough flood defence works

Phase 1 of the Environment Agency’s Flood Risk Management Scheme which will reduce the risk of flooding to 1,000 properties and key infrastructure in Rochdale and Littleborough is underway in Littleborough, using an innovative ‘rain-ready’ system to handle polluted water created by construction activities.

The scheme includes the construction of a flood storage reservoir and sections of linear defences both upstream and downstream, as well as modifications to existing defences along the River Roch.

A rain-ready system of settlement ponds and silt capture channels was used by contractor VolkerStevin to manage and treat silty water before it could be discharged into the River Roch. Silt control products and design advice for the project were provided by Frog Environmental, a joint venture company with the RSK Group.

Richard Walsh, VolkerStevin senior project manager, said: “With increasing UK rainfall over recent years, the site was designed with a rain-ready mitigation system to tackle the inevitable surface water.”

He explained that the design reduces the need for continual pumping, with water left in the settlement pond as required. Pre-construction testing showed the soil particles are small and take over 24 hours to settle, which means the water could not be discharged without significant mitigation.

He said: “Water is pumped through a pipe reactor where it is treated with gel flocculant to reduce settlement time, then into settlement ponds and a final polishing pond, which runs over a series of biodegradable mats to remove any remaining silt.”

 

 

Frog Environmental project manager Gavin Beat said: “The rain-ready approach of using silt mats, settlement ponds and silt capture channels means the equipment remains in place year-round, ready for use whenever needed. Independent laboratory testing has shown that there is 99% reduction in total suspended solids and up to 99% reduction in iron. This means the water being discharged back into the river actually meets the threshold for drinking water standards.

“VolkerStevin contacted us early on in the process, giving plenty of time for discussion and review before the project’s critical works began. It really emphasises what can be achieved with early engagement towards water management.”

This approach to water management is one of several sustainability-focused approaches taken on-site for this second phase of works. Other approaches included the use of low-carbon sheet piling, biofuel and hybrid vehicles and the reuse of crushed concrete for the haul road. The project won the Building and Construction Flood Protection category – National Green Champion Award at the 2024 Green Apple Awards.

The Rochdale and Littleborough Flood Risk Management Scheme is being led by the Environment Agency in partnership with Rochdale Borough Council and has been supported by Network Rail, the North West Regional Flood and Coastal Committee, Transport for Greater Manchester, the Department for Education and the Department for Transport.

Once complete, the flood scheme will better protect 723 homes and 489 businesses from flooding. The Littleborough section will safeguard 337 homes and 185 non-residential properties. Additionally, the scheme aims to provide considerable environmental benefits, with 1.2 acres of woodland enhancement at Grove Lodge and over 130 trees and 160 metres of hedging to be planted.

Nick Pearson, Area Flood and Coastal Risk Manager at the Environment Agency, said: “We understand the devastating impact flooding can have, which is why reducing flood risk is our top priority.

“We are pleased with the success of the construction of this scheme to date and that hundreds of homes and businesses are set to benefit from improved protection.

“We can’t always predict where the rain will fall or where flooding will occur, but we do know which areas are at risk, so it’s essential we all do our part by checking our flood risk and signing up for flood warnings via www.gov.uk/prepare-for-flooding. By taking small steps today, you can immediately improve your own readiness.”

Councillor Tricia Ayrton, Deputy Leader and Portfolio Holder for Climate Change and Environment, said: “Our community understands first-hand the devastating impact that flooding has, so these works will have a lasting and very real impact on our many residents and businesses in these areas.”