Climate change campaigners are protesting ahead of a meeting where councillors are due to pick the preferred route for the multi-million pound Norwich Western Link.
Norfolk County Council's cabinet is today set to agree the route for the mooted road, which would connect the A47 to the Norwich Northern Distributor Road.
Officers are recommending that the cabinet backs the £153m Option C. That is a 3.9-mile road from the A1067, halfway between Weston Longville and Ringland, linking to the A47 at a new junction at Wood Lane.
It would require a 720-metre-long viaduct over the River Wensum, but the council says discussions with the Environment Agency and Natural England have led them to understand an appropriately designed and built viaduct would be acceptable, even though the River Wensum is a special area of conservation and a site of special scientific interest.
But Extinction Rebellion, which occupied the council chamber in protest against the road at a previous meeting in February, leading to arrests, are urging the council not to back the road.
They staged a demonstration outside County Hall where they created a mocked-up river, complete with pink boat.
They sang protest songs and held placards and banners with slogans such as 'Protect The Wensum Valley', 'Vote Earth' and 'Toads Not Roads'.
The route would go through a county wildlife site and would lead to the loss of woodland - a move being opposed by owners of that land.
But the council says it would be mitigating that, planting trees and creating new habitats.
The council says it would aim to achieve biodiversity net gain - so the project would leave habitats in a better condition than before construction.
They say Option C offered the best balance in terms of environmental impact, value for money, support, transport benefits and impact on local communities.
Supporters include the Norfolk and Norwich University Hospital, Norfolk Chamber of Commerce, Norwich Airport, Norfolk Constabulary, Norfolk Fire and Rescue, the New Anglia Local Enterprise Partnership, Road Haulage Association, First buses, Konectbus and city and district councils.
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