SOUTH West Water has said that storm overflow spills in the village of Altarnun are reducing following new engineering work.

In 2024, Altarnun Sewage Treatment Works on the edge of Bodmin Moor, was one of South West Water’s highest spilling storm overflows, seeing a huge 206 spills recorded.

South West Water says its engineers had found that during sustained downpours Altarnun’s treatment works could become overwhelmed, which would then trigger the storm overflow — a system designed to protect homes and streets from flooding by spilling waste into local rivers.

The water supplier has said that high levels of rainfall in areas such as this can put additional pressure on treatment works.

A spokesperson from South West Water explained: “In moorland areas like Altarnun, groundwater levels can fluctuate significantly, which can lead to more surface water and groundwater finding its way into local sewers.

“This extra water can put additional pressure on treatment works, especially during wet weather, and this was the case in Altarnun.”

However, in an effort to combat more water finding its way into the sewers and to help the treatment works cope with demand, South West Water’s engineers have taken action to improve its network.

Firstly, to keep water out of the sewers, engineering teams completed CCTV surveys along the local network to identify the sections of the pipe that were worst affected by infiltration.

They then installed a protective lining to 40 metres of sewer in the area and carried out repairs across the local network, including upgrades to six manholes.

Following this, teams installed a new storm storage tank at Altarnun Wastewater Treatment Works to increase capacity. This allows additional flows from heavy rain to be held at the treatment works when the site is at capacity, so it can be returned to the treatment process when flows reduce.

Following these improvements being installed, South West Water has reported that the number of spills in 2025 fell by 20 per cent.

Commenting on the news, Hazel Tranchant, head of tactical asset management at South West Water, has said that these sorts of improvements are what customers want to see, however, she has admitted that the organisation still has plenty of work to do in order to reduce the number of spills across the region.

She said: “Customers quite rightly want to see storm overflows operating less often.

“At Altarnun, we’ve focused on reducing the amount of extra water entering the sewer network and increasing storage for rainfall so the system can cope better.

“We know there is much more work to do to reduce spills across the region but it’s great to see how targeted improvements like this are making a difference and that we’re heading in the right direction.”

The improvement works at Altarnun formed part of South West Water’s £16-million Infiltration Reduction Programme. The initiative targeted 175 high-risk sites across the region following a review of performance at more than 1,600 storm overflows.