Design details for the engineering structures which will be built as part of the Preston Western Distributor Road have been given the green light.
Members of Lancashire County Council’s development control committee approved plans for a total of eight features, including two viaducts – one across the Lancaster Canal at Lea and the other crossing Savick Brook. Both were described in papers presented to the committee as “major pieces of civil engineering which will have a significant visual impact”.
However, the design of each of the structures has been drawn up to ensure they are as “appropriate” as possible for their rural locations on the two-and-a-half mile stretch of dual carriageway, which will link north west Preston with a new junction on the M55.
“The bridges are in rustic steel, which is a bare face of material which, over time, acquires an ochre brown colour,” the authority’s principal planning officer Jonathan Haine explained.
“It has been chosen for its ease of maintenance and also [the fact that] the colour of it is fairly in-keeping with the natural environment, rather than stark white concrete material.”
The committee was told that the Lea Viaduct had been designed to “reflect the undulating topography in the area” and will include curved beams and slim supporting piers to “reduce the mass of the bridge as much as possible and limit [its] effect on views”. The Savick Brook viaduct will have similar minimising design features.
Meanwhile, two constructions at a less isolated location - a bridge and underpass at Bartle – will be faced in a red brick which matches some of the other buildings in those areas. Retaining walls at Bartle will be made up of a reinforced earth bank to “provide a grassed finish rather than an engineered material”, Jonathan Haine said.
An underpass at Darkinson Lane will be created from concrete arches with grass banks and surrounding hedges, while a bridge over the M55 at Becconsall will be constructed in a style which reflects other motorway bridges in the area, designed to minimise its impact.
Members heard that additional soundproof fencing of around 3m in height is set to be installed to reduce the noise experienced by households in Lea Town.
Landscaping of the route will take place along its entire length, with the seeding of embankments, planting of trees and hedgerows and an assurance that only those existing natural features which have to be removed for the road’s construction are lost.
While a “considerable” number of hedgerows and tress will be removed, the replacement planting is expected to mitigate its loss. A number of replacement ponds are also proposed to provide natural habitats.
Measures will be taken to compensate for a loss of flood plain around the Savick Brook where the new viaduct will be built - the deck of the bridge will be above the one in a hundred year flood level, with an allowance for climate change factored in.
A plan has also been submitted which will limit the use of construction vehicles to certain roads, while processes have been approved on how to deal with any archaeological features or contaminated land which may be discovered during the works.
The committee was told that several public footpaths will be diverted to allow the road to be built.
Work is set to begin on the route later this year and is due to be completed in March 2023.