Water company bosses have been told they must spend millions in upgrading Norfolk sewage works to help get thousands of new homes built in the county.
Anglian Water has been ordered by environment secretary Steve Barclay to upgrade wastewater treatment works in catchment areas covering the River Wensum and parts of the Broads by 2030.
The company will spend £138m at 19 Norfolk sites to reduce nutrient levels.
The government's demand is part of efforts to tackle the issue of nutrient neutrality, which has stopped decisions from being made on thousands of new homes in parts of Norfolk.
Government advisors Natural England told councils in March 2022 that they could not grant permission for new homes until it could be proven wastewater from new developments would not increase pollution and harm species.
Council bosses scrambled to find solutions to unlock housebuilding, with South Norfolk and Broadland councils leading a joint venture to allow decisions to be made.
The Norfolk Environment Credits scheme means developers can buy credits to fund mitigation measures to prevent pollution, such as wetland.
The scheme has even been used to compensate a farmer on land on the edge of Norwich, near the A47, in return for him no longer farming pigs, which create a lot of nutrients that flow into rivers.
During a visit to Hethersett last year, prime minister Rishi Sunak and local government secretary Michael Gove outlined the government's plan to ditch nutrient neutrality rules.
But the House of Lords voted against scrapping them, so the government is targeting water companies to make improvements.
An Anglian Water spokesperson said: "In line with the government’s guidance on nutrient neutrality, we’ve proposed £138m of investment in our business plan for 2025-30 to reduce nutrient levels at 19 of our sites, where population growth is predicted to cause an impact on local ecology.
"At the three largest sites, we will be delivering this work early, thanks to Ofwat approving our advanced infrastructure delivery programme.
"These investments will protect wildlife and ecological quality in Norfolk’s precious Broads and the River Wensum and mean developers need to find fewer credits to build much-needed housing."
Wastewater works in Aylsham, Fakenham, Coltishall, Reepham, Belaugh, Foulsham, Hindolveston, Swanton Morley, Sculthorpe, Stibbard, Wymondham and Mattishall are among those in line for improvement work.
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