Highways England constructs eco tunnel under busy main road without disruption


As part of a pioneering scheme to cut pollution, Highways England (HE) has been able to construct a tunnel under a busy main road without any interruption to traffic flow.

HE’s trial project involves installing underground drainage pipes, tunneled under the A38 at Dean Burn in Devon, and a filtration pond filled with engineered soil to trap oil and metal residue that are carried in the water running off the busy road. The area is particularly important because right next to the road sits Potter’s Wood, a protected Site of Special Scientific Interest (SSSI), and as well as improving water quality, earth excavated from the pond and tunnel is being used to create bug hotels, butterfly scrapes and bee banks to benefit biodiversity.

The scheme, enabled by HE’s Environmental Designated Funds, has been designed by contractors Kier and delivered by South West Highways, and if successful, the system could be rolled out at other locations around the country’s major A roads and motorways. The project used special small-scale tunneling equipment to dig the modified drainage channel under the A38 while vehicles travelled above unaffected. The Dean Burn scheme started in July and with KJ Thulborn undertaking landscaping and environment features, project is scheduled to be completed by the end of October.

HE’s £225m (US$275m) Environmental Designated Fund has been set up to improve the environmental performance of the country’s Strategic Road Network (SRN). It is to be used for projects that are ‘beyond business as usual’ which will help achieve benefits for one, or preferably a combination of areas including: cultural heritage, biodiversity, landscape, flooding and water quality, carbon emissions, and noise pollution.

“We’re very excited to be trialing this new and innovative environmental system and if it’s successful we could be rolling it out across the country. Our Designated Funds program was developed so that we can invest in projects beyond our traditional road build and maintenance, and this is a glowing example of how this funding can have a positive impact on people and communities,” said HE’s A38 project manager, Michelle Reed. “The filtration system provides a physical barrier to polluted water, then chemical and biological mechanisms work in combination to break down even more pollutants. It also has the advantage of taking up far less space than other treatment systems, which makes it very cost effective.”

Reed said, “When completed, this work should significantly improve the quality of water running into Dean Burn and help to support the local environment and its wildlife. This is the first time we have used this machinery in the South West and it’s been such a success we have completed the tunneling ahead of schedule and only two overnight lane closures have been needed.”

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Adam joined the company in 1994, and has been News Editor of TTT since 2009. In his other role as Circulation Manager, he helped create the original Traffic Technology International distribution list 23 years ago, and has been working on it ever since. Outside of work, he is a keen fisherman, runs a drumming band, and plays an ancient version of cricket.