Highways Agency

• Designing to minimise environmental impacts
• Education initiative

Designing to minimise environmental impacts

Designing to minimise environmental impacts

Integral to reducing the long-term environmental impact of a road is developing an 'intelligent' design – one that takes full account of local conditions and requirements, and that is creative and considerate in its solutions.

For the A10 Wadesmill Bypass particular areas of concern were protecting wildlife habitats, dealing with water run-off, and managing the large volume of earthworks.

Wildlife habitat and movement

It was clear from the surveys the Highways Agency commissioned, and studies undertaken by the environmental consultants, that something needed be done to ensure that the new road would not destroy the habitats of any key mammal populations. It would, however, sever a number of their travelling routes.

Underpasses have been provided suitable for small mammals and deer. Mammal ledges at suitable heights have been incorporated within all culverts and underpasses, with the larger ones having softer edging to encourage deer movement. One culvert, which accommodates a large stream, was shortened as it was considered to be too long and dark to convince the deer to use it.

Water

Run-off' from roads is frequently a headache for designers, and often requires the use of huge interceptors to trap heavy metals and oils emitted by vehicles and prevent them from entering the watercourse.

Bearing in mind the environmental aims of this project, the contractor was able to implement a far more ecofriendly solution. Water running off of the road is directed to specially designed balancing ponds that contain vegetation (such as reeds) to act as a natural filter.

Environmental consultant, Kara Millen explains:

"The series of ponds, large and shaped to reduce flow, allow nature to gently do its work as the toxins are removed from the water by microbial action,"

"by the time the run-off leaves the ponds it is as clean as the river or stream it is joining."

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Bypass environmental enhancement features

We were determined to explore every opportunity for making the A10 Bypass an environmentally successful scheme. In addition to protecting the existing flora and fauna - including deer, badgers, newts and others - we wanted to see what else they could be brought to the project that would benefit the area.

Local ecology was investigated to discover which species had once inhabited the area, but which for one reason or another, had left. The research revealed that these included otters, bats, certain butterfly species (such as the Grizzled Skipper), and other invertebrates.

In an effort to encourage these species back, the aim was to provide a safe and suitable environment. Initiatives have included retaining woodland tree stumps for use in the creation of refuges for reptiles; building large numbers of bat caves and boxes; constructing an otter holt by the river; and giving the ditches a more 'natural' feel to encourage voles.

Another key biodiversity concern has been the wetlands. These provide a very special habitat, and one that has been decreasing over the past decade. By creating new wetlands at the pond areas, and by cleaning up the ponds themselves, the Team is helping to establish habitats that will grow into rich ecosystems and that will be attractive to a number of species, including the Great Crested Newt. The Great Crested Newt is a protected species found in the local area, but the numbers of this species are declining.

Other initiatives implemented include carefully storing stripped woodland topsoil, which has its own micro-ecosystem, for reinstatement within the new woodland planting areas. This also applies to hedgerows.