Civil Engineering


M5 Oldbury Drainage


Carnell worked in collaboration with National Highways, Kier and Active Tunnelling to install a pioneering drainage system deployed underneath the M5 at Oldbury to filter water runoff.

The system is thought to be the largest of its kind in the country and will help to capture debris and pollutants before water runoff from the M5 is discharged into the water course.

Despite many challenges such as limited access from the local road network and restricted working space, our team worked hard to complete the scheme in April 2022.

The vortex separators varied in size up to 3m diameter and are installed inside caissons up to 8m deep. We also installed prefabricated valve chambers, a series of inspection chambers and pipework up to 750mm in diameter, with a civils team carrying out the finishing works afterwards.

Detailed planning and early engagement (ECI) prior to construction removed most of the commercial risk from the construction phase but a detailed and regularly reviewed risk management system incorporating delivered mitigation measures and realistic contingency plans helped deliver this scheme in budget.

Improving water quality to watercourses

The vortex separators remove fine and coarse particles, hydrocarbons and floatable debris from surface water 

There are 10 filters installed in the drainage pipework which is designed to capture debris and pollutants which can then simply be removed by specialists at regular intervals.

This is a real boost to the local canal network that runs underneath the M5 Oldbury viaduct.