Odour mitigation works by the Sherford Consortium to try and alleviate the notorious Plympton Pong have been successful, independent testing has shown, despite residents reporting ongoing issues.

Works were completed in July at the new town of Sherford where wastewater is pumped directly to the Marsh Mills sewage treatment works run by South West Water.

It follows campaigning by local councillors to get to the bottom of the intense pong which has plagued residents and businesses in the area for years.

They feared that the new Sherford development, where more than 5,000 homes are being built, was contributing to the stink.

The works have included switching the pumping station from three active pumps to two and reducing the dual rising main to a single pipe, which has “significantly increased the speed at which wastewater moves through the system, alongside chemical solution dosing to neutralise the odour”.

Independent specialists were appointed to run tests in July and August, placing gas monitoring equipment, taking samples, and carrying out analysis at both Sherford’s pumping station and at the chamber by Merafield Road.

Multiple visits were undertaken to build a thorough picture of conditions throughout the system.

The Sherford Consortium, which is a partnership of housebuilders leading the one billion development of Sherford, said the report confirmed that the changes made to the foul water pump station were performing as intended and “demonstrates that Sherford is not contributing to the ongoing odour issues affecting the Plympton area”.

It continued: “Sherford’s pumping station is being monitored around the clock by a specialist maintenance contractor and this will continue. The consortium will continue to monitor septicity levels, altering the dosing volumes if required, and maintain the facilities until South West Water takes over responsibility for the pumping station.”

The consortium said the report has been shared in full with South West Water with whom it had maintained close communication throughout.

Independent Plympton councillors Terri Beer and Andrea Loveridge have been having regular meetings to push for improvements.

They are continuing to ask questions of South West Water following several complaints from residents over the last two weeks regarding strong odours affecting the Merafield area, particularly during the early hours of the morning.

“Residents have reported that the smell has been so severe on several occasions that they have had to close their windows, and in some cases, it has been disturbing their sleep,” said Cllr Beer.

One responding to Cllr Beer’s Facebook post said if anything the pong had got worse: “It’s usually in the early hours of the morning, it’s been that bad it’s even woke me up, I’ve lived here for 40 years and it’s about as bad as it’s ever been.”

Cllr Beer said: “Whether the source is the pumping station, the treatment centre, or another facility, this issue remains unresolved and continues to have a significant impact on local residents’ quality of life. I would like the issue identified and resolved. Plympton has suffered too long.”

South West Water upgraded its Marsh Mills site last year in a bid to reduce the smell and limit the risk of sewage spills during heavy rainfall. It has previously improved the plant to cope with extra capacity and installed fans to deal with odour.