The locations where five new wetland sites could be created in the Norfolk countryside to help unblock a ban on new homes being built have been revealed.
The areas have been identified as potential solutions to a limbo which means councils have been blocked from approving plans for new housing for almost a year.
Experts hope the wetlands will 'soak up' - or 'neutralise' - harmful pollution generated by new housing, to prevent it ending up in Norfolk's rivers.
The sites are close to Kirby Bedon, near Norwich, Dereham, Gressenhall, Fakenham and Colkirk.
The areas have been offered up by landowners in response to an appeal from Natural England, which had imposed the ban on new housing unless the so-called 'nutrient neutrality' issue had been resolved.
The government's advisory body is concerned that nutrients in the wastewater from homes are ending up in the river Wensum and Norfolk Broads, where they reduce oxygen in the water and make it harder for aquatic species to survive.
Natural England issued a directive last March preventing councils from allowing housing in those catchment areas until mitigation was provided to offset the impact of the nutrients.
Under plans being drawn up, wastewater from housing will be directed towards the new areas of wetlands, where nutrients can be 'captured' in natural ways, rather than seep into rivers.
The five sites will be evaluated by experts, before decisions are taken on whether to develop them as constructed wetland areas.
Constructed wetland involves shallow ditches being dug out and filled with wetland plants.
The plants act as natural purifiers, with the water draining through them and the nutrients, such as nitrogen and phosphorus, removed.
They can vary in size, but may only take up a couple of acres.
The newly-constructed wetlands, on private land, are unlikely to be places the public would be able to visit.
Defra and the Department of Levelling Up, Housing and Communities are making up to £30m available to pay for the creation of the wetland.
Developers would buy "credits" for such wetland projects to mitigate their schemes.
Mike Burke, programme director of sustainable development at Natural England, said: "To deliver nature recovery and grow our economy we need to develop and deploy innovative tools.
"The new Nutrient Mitigation Scheme is a great example, showing how we can protect our natural assets and go further to achieve our socio-economic goals."
Councils in Norfolk have been working on their own credit mitigation scheme in the meantime, involving developers buying into other solutions, including via a joint venture with Anglian Water.
Decisions for thousands of new homes across Norfolk have been held up by the restrictions, including major schemes such as Norwich's Anglia Square revamp and the Long Stratton bypass scheme, which is linked to the construction of housing.
Phil Courtier, the lead planning officer at Broadland and South Norfolk councils, has previously warned there was a "significant risk" of building firms going bust unless there is a swift resolution to the issue.
He said the delays in being allowed to give housing the go-ahead was having "the biggest impact of anything, ever, on the growth of Norfolk".
He had previously said he hoped the first decisions on major Norfolk housing schemes in a year could be made from April.
South West Norfolk MP Liz Truss, during the campaign which led to her brief stint as prime minister, had signalled she would scrap the nutrient neutrality requirement.
But Michael Gove, now reinstated as levelling-up, housing and communities secretary, has shown no appetite to do so.
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