£170M upgrade of M25 junction 28 continues with brook diversion to protect wildlife

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The M25 junction 28 connects the M25 with the A12, as well as providing local access to Brentwood in Essex and the A1023 Brook Street. At peak times up to 7,500 vehicles per hour pass through the junction. National Highways says it is “operating at capacity” and that traffic is expected to increase in the area by around 30% by 2037.

The roads operator is therefore undertaking junction upgrades to improve the flow of traffic. Graham was appointed as main contractor in a £124M contract signed in February 2021. The scheme was given the green light in May 2022 following planning delays and main construction work commenced in September 2022. 

It is expected to be open for traffic in summer 2025, with planting and landscaping continuing off network for a short time afterwards.

In recent days National Highways oversaw the relocation of 600 fish and other wildlife from one side of the M25 to the other ahead of work to temporarily divert Weald Brook from running through the junction 28 upgrade. Environmental specialists were engaged to move 12 species of fish, including a 50cm long European eel and Bullhead fish. The eel was among wildlife in the brook listed on the International Union for Conservation of Nature Red List of Threatened Species.

The brook diversion is part of preparatory work to National Highways to start installing the steel girders for two bridges. As well as the diversion of Weald Brook, the nearby Ingrebourne River is also being diverted to allow construction of the new slip roads.

National Highways has also worked with utilities companies to move cables out of the area. To enable this, a lane was closed from 17 July to 7 August on the A12 eastbound between Petersfield Avenue and the A12 slip road for M25 junction 28.

Planned improvements as part of the junction 28 upgrade include a new two-lane loop road with hard shoulder for traffic travelling from the M25 anti-clockwise onto the A12 eastbound towards Brentwood. This merges into a single lane to provide a smooth transition between the loop road and A12.

The scheme will also upgrade the A12 eastbound to allow traffic from the loop road to join into a dedicated lane. In addition, the A12 eastbound exit slip road will be reconfigured for traffic using junction 28. The M25 anti-clockwise entry slip road will also be reconfigured for traffic leaving junction 28, to accommodate the new loop road.

Other works include widening the M25 anti-clockwise carriageway to provide additional space for traffic leaving to join the A12. Two new road bridges are part of the project, one carrying the A12 eastbound exit over the loop road, the other to take the loop road over the M25 anti-clockwise entry.

The scheme also includes plans including the installation of specially designed culverts to take the loop road over the Weald Brook and Ingrebourne River. The culverts will ensure water flows freely under the road while allowing the movement of wildlife on the banks of the brook.

Three attenuation ponds, two within the loop road and one to the west, will also be constructed to enable surface water management of flow from the roads to reduce the risk of flooding. The scheme also includes landscaping, seeding, planting and measures to protect local wildlife including fences to keep deer, otters and other wildlife off the road.

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