Flood resilience improved on A421 as National Highways completes pumping station upgrade

National Highways has completed a £1.5m upgrade of the pumping station at Marston Moretaine to help minimise disruption from flooding on the A421.

The scheme was prompted by severe flooding last September, when more than 160 millimetres of rain fell in just over a day, overwhelming existing pumps and leaving the carriageway under water for an extended period.

At the time, more than 72 million litres of water – around 30 Olympic-sized swimming pools – had to be removed using temporary equipment, pipes and a fleet of tankers.

As part of the upgrade, the control system has been redesigned and relocated several metres above the road to protect it from future flooding, while new pumps and monitoring technology have also been installed.

Simon Amor, Head of Scheme Delivery at National Highways, said: "This has been a crucial piece of work to improve journey reliability on one of the region’s key strategic roads.

"This has been a crucial piece of work to improve journey reliability on one of the region’s key strategic roads.

"The main issue we saw last year was that water levels rose above the electrical components within the station, irreparably damaging the equipment and leaving us unable to pump water away from the carriageway.

"We have now moved equipment to well above the local flood level, replaced the pumps and installed new technology to give us more reliable data from the station."

Martin Fellows, Regional Director for National Highways in the East of England, said the flooding last year was the result of a combination of factors.

He said: "It wasn’t just the very intense rainfall that we had in a short space of time, it was the fact that that rainfall fell on what was already highly saturated ground and that the level of runoff from the fields alongside the A421 also contributed to extreme amounts of water being retained on the road.

"We are confident that the solution we’ve put in place, whilst it won’t remove the risk of flooding happening, will enable us to clear that water quickly should there be excessive rainfall on already saturated land.

"What it can do is clear that water as quickly as possible."

The new system also includes remote monitoring, allowing National Highways staff at its South Mimms control room to track pump performance in real time and send engineers if problems arise.

Mr Fellows said the project was not part of long-term plans but was carried out in response to last year’s exceptional conditions.

"We weren’t planning to upgrade the pumping station. There was no reason to suggest that it hadn’t worked effectively in the past. It was as a consequence of that particular set of unique circumstances that all came together," he said.

National Highways said it is continuing to review the resilience of its infrastructure in light of climate pressures and thanked drivers and local residents for their patience during the works.