A project to create a vast new underground stormwater storage tank in a Pendle town has reached a major milestone as engineers have now installed the lid.

The tank on Lindred Road, Nelson, in the Lomeshaye Industrial Estate, is 20m deep and 15m wide and holds almost two million litres of water – equivalent to around 25,000 bathtubs.

When operational in early 2024, the tank will give Pendle’s sewer system additional capacity during times of heavy rainfall and will play an important role in helping United Utilities improve water quality for nearly Pendle Water, as it will reduce the need for sewers to overflow in times of heavy rainfall.

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Senior project manager Tony Elliott said: “The tank will act as a ‘holding area’ for the extra rainwater that enters the sewer network during times of heavy rainfall. Holding it back means it isn’t all hitting our wastewater treatment works at the same time and the system is less likely to be overwhelmed.”

The wastewater upgrade in Nelson is part of a wider £75m investment programme to deliver improvements to Pendle Water and the River Calder.

As well as the new storm tank, work is also well underway to upgrade Burnley Wastewater Treatment Works. This includes a new plant where air is injected into raw sewage to encourage bacteria to ‘feed’ on it.

Additionally, an innovative technology called Biomag where iron oxide particles are added to reduce phosphorous levels is also being introduced.

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Tony added: “By increasing sewer capacity across the local area network, upgrading Burnley Wastewater Treatment Works, and carrying out improvements at Hyndburn Wastewater Treatment Works this investment will improve water quality in Pendle Water and the River Calder.

“We are acutely aware that these large projects can bring inconvenience and we are very grateful to the ongoing patience of site neighbours. For the Lindred Road tank we were able to make some modifications to the design so we could minimise the work needed in the road itself.”

During the last two years, United Utilities has reduced storm overflow operation by almost 40%, and is on track to improve almost 200km of rivers by 2025.

The company has just been granted approval to make an early start on £900m of investment which means that similar storm water storage projects across the region can get underway before 2025.