The multi-million pound scheme to revamp one of the busiest junctions on the A47 in Norfolk will only be able to take place after water voles are moved, it has been revealed.

The Thickthorn junction, on the edge of Norwich, is due to be changed as part of the £300m scheme for the A47 between Peterborough and Great Yarmouth.

But the changes involve diverting a stream near Hethersett, which is a habitat for water voles – a species which is protected by law under the Wildlife and Countryside Act 1981.

Peter Havlicek, the A47 Programme Manager, revealed the presence of the voles when he gave county councillors an update on the scheme at a recent meeting, reports the Eastern Daily Press.

He said: “The interesting thing with this scheme, on the ecological front, is that we have got the presence of water voles. With the diversion of the Cantley Lane stream, where the Cantley Lane link joins in with Cantley Lane, we’ve got to make sure that these water voles are moved south of the Cantley Lane link and there is licensed work we will need to do to make sure.

“All the ecology surveys need to be complete before we are in a position to determine the number of water voles and also suitable receptor sites for the translocation of the water voles. Identification and enhancement of the receptor sites to provide local conservation benefit will be determined through engagement with Natural England.

“It will also be necessary to apply to Natural England for a protected species licence in order to undertake any conservation work relating to the water voles prior to any construction works taking place.”

Norfolk County Council will also need to give consent before the section of the Cantley Stream can be diverted.

The Norfolk Wildlife Trust said it would be looking closely at the situation, with water voles having faced serious decline across the country in recent years.

Mike Jones, conservation officer at the trust, said: “We are aware of the potential impacts of the Thickthorn proposals but are waiting to see the full results of the surveys in the application, which we understand will be made early next year.

“Water voles have faced serious declines across the whole country over the last few decades and it is vital that these works ensure the local water vole population and their habitat is secured and enhanced.”

The proposals on the A47 include a new slip road off the A11 northbound, before the roundabout, which will take motorists beneath both roads before rejoining traffic on the A47 heading towards Great Yarmouth.

The complete overhaul of the roundabout will also see a segregated left-hand turn added to those travelling eastbound on the A47, a new footbridge added and a fourth lane on the southern part of the junction.

An application to get a development consent order for the Thickthorn work is due to be lodged in March next year, with Highways England saying that, if consent is granted, work could start in 2023, with the new junction open in 2024.