Integrated Lining Solution Delivers Motorway Drainage Boost

Lanes Group has completed an innovative project to line over one kilometre of large diameter highway drainage pipe and associated access chambers on a section of the M3 motorway.

The work, carried out to seal the surface water drainage system against water ingress, was part of a wider project to counter voids that threatened the stability of the carriageway.

It is believed to be the first time substantial lengths of large highway drainage pipes and connecting access chambers have been lined together in this way on behalf of National Highways.

Sealed and strengthened

Lanes carried out the work for Jackson Civil Engineering on the northbound carriageway of the M3 near Camberley, Surrey, between January and May 2024.

Ben Forsyth, Head of Highways at Lanes, said: “This project delivered an integrated pipe and chamber lining solution for highway drainage that we believe is a rehabilitation first on a trunk route or motorway.

“The project has sealed and strengthened the motorway drainage system in an area that, because of ground conditions, made it more susceptible to water infiltration, increasing the risk of water pooling on the carriageway, creating a major hazard for road users.

“As climate change is making our weather more volatile, being able to safeguard the capacity of sections of highway drainage pipe that are particularly susceptible to groundwater infiltration is going to be increasingly important, to maintain optimum road safety and traffic flows.

“The success of this project has demonstrated the viability and cost-effectiveness of this drainage rehabilitation approach, and Lanes’ ability to implement it for our highway maintenance customers.”

Challenging project – difficult weather

The pipe and chamber lining project was integral to a larger project led by Jackson Civil Engineering to resolve voids forming under the motorway.

These were being caused by the interaction of sandy ground and a high groundwater table beneath the carriageway.

The lining work was carried out by Lanes’ sewer rehabilitation division, supported by jet vac tanker and CCTV drainage survey teams from the company’s Sevenoaks depot.

A total of 12 liners were installed, all but one over 90 metres long, in highway drainage pipes ranging in diameter from 600mm to 800mm.

Lanes Lining Project Manager Gary Carey said: “This was a challenging project, in part because it was carried out during in difficult weather conditions with periods of heavy rain.

“Each section of pipe being lined had to be isolated with over pumping of surface water run-off, and operational windows during which liners could be installed were constrained to minimise traffic disruption.”

1,000 watt ultraviolet lamps

Starting on 8th January 2024, 11 of the cured in place pipe (CIPP) liners were installed over two three-week periods, during both day and night shifts, with the final liner installed on 2nd May 2024.

Each section of drainage pipe to be lined was first cleaned using the jet vac tanker. A six-person team then pulled a liner into the pipe with a mechanical winch.

The liner was then inflated in 50mbar intervals until an optimum pressure was reached. This allowed the liner to stretch up to the pipe size and cause a tight fit.

A dual-core light train with eight 1,000 watt lamps was inserted into the inflated liner then pulled through at a computer-controlled speed. This hardened resin in the liner, making a tough and water-impervious new pipe within the pipe.

As an example, the light train had the power to cure a 95-metre-long 750mm-diameter pipe in four and a half hours.

The access chamber lining works were carried out in 10 shifts starting in the first week of February 2024, with a total of seven concrete ring chambers lined, each one 3.5 metres deep and 1.5 metres in diameter.

It was the first time Lanes had used the spray lining system. The Lanes team was trained in Germany to use the Hermes spray lining rig and was supported by a Hermes technician during the first installation.

Spray lining – long-term solution

Each chamber was first cleaned by a remotely-controlled high pressure water jetting system. Mortar was then injected into the concrete ring joints to seal them.

In a final process, another remotely-controlled rig was lowered into the chamber to automatically spray-line its walls with a specialist dry mortar to a thickness of 10mm.

Gary Carey said: “Combining CIPP pipe lining with chamber spray lining, which are both proven and highly effective technologies, creates a completely sealed drainage system with long-term integrity.

“The alternative, to excavate and replace defective pipes, would be much more costly, take longer and be hugely disruptive without providing any extra protection against water infiltration.

“So, we were pleased to be able to provide Jackson and National Highways with absolutely the most effective and sustainable solution to rehabilitate and protect the highway drainage system.”