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£34m over next four years to avoid "catastrophic failure" of sewerage network

£34m over next four years to avoid

Wednesday 03 May 2023

£34m over next four years to avoid "catastrophic failure" of sewerage network

Wednesday 03 May 2023


Upgrading the island’s aging and increasingly struggling sewerage network will cost more that £34m over the next four years, a new study predicts.

The Government’s ‘Bridging Liquid Waste Strategy’ concludes that “significant investment over an extended period” is required to “avoid catastrophic failures and help battle against climate change and population growth”.

In particular, the network of 109 sewage pumping stations and rising mains – which carry sewage under pressure – are at “a critical point” because they were designed when the island’s population was a fraction of its current 103,000.

Without investment in the network, the strategy – which runs up to the end of 2026 – concludes that the island will be unable to meet its housing goals.

Already, plans to build 179 affordable homes in St. Peter are on hold because the drains in the area cannot cope.

A £83.3m new Sewage Treatment Works will open at Bellozanne at the end of this year. 

Although it has been built with extra capacity to cope with a predicted rising population, the total flow it can accommodate will be limited by the network’s capacity to deliver sewage to it.

Airport pumping station.jpg

Pictured: There are 109 pumping stations around the island, some of which need upgrading.

The Bridging Waste Strategy has been aligned with the aims of the Bridging Island Plan, which was passed by the States last year and provides for 4,300 homes to be built by 2025 with a further 3,600 homes required by 2030.

It is 'bridging' because the Infrastructure and Environment Department plans to develop a full liquid waste strategy covering 2026 to 2035.

The department's waste strategy states: “Clearly, house building on this scale and programme is a challenge in itself in the context of Jersey but the impact of large estates on the existing liquid waste system with its existing limitations is potentially catastrophic. 

“The locations of these houses have only been identified in the loosest terms to date which means detailed assessments of upgrades and reinforcement works cannot be completed for specific schemes to be included in this Bridging Liquid Waste Strategy. 

“However, the Bridging Island Plan has identified sites to the North and West of the Island, as well as St Helier, as the most likely to proceed in the short term. 

“These are around St Peter and Les Quennevais and this information has been used to identify concept solutions which have been named ‘Emerging Projects’. 

“I&E will work with the Planning Team to agree what size of developments need to be allowed for and then the specific local and downstream infrastructure upgrade projects at St Peter, St Brelade and Beaumont will be progressed to suit.”

When it comes to funding, the £83.3m capital cost of the new Bellozanne works has already been secured. Extra related projects include £1.5m, set aside for ‘odour mitigation’, and £1m for ‘outfall rehabilitation’. 

£4.5m will also be spent between now and the end of 2026 on ‘biosolids management’.

Infrastructure projects to avoid the “potentially catastrophic” failure of the network total more than £34m over the next four years.

They include replacing the First Tower ‘rising main’ and Bonne Nuit sewage treatment works, upgrading the north and east sewerage networks, and building new rising mains at Le Dicq.

Sewage Treatment Works Bellozanne.jpg

Pictured: A £83.3m new Sewage Treatment Works will open at Bellozanne at the end of this year. 

Once the new sewage treatment works opens towards the end of this year, replacing assets there will cost between £500,000 and £750,000 per year. The pumping stations will cost around £1.35m a year in ‘replacement assets and minor capital works’.

Although the treatment works is yet to open, having been delayed by the collapse of the main contractor in October 2021, Infrastructure is already planning for its replacement when it reaches its capacity.

The study finds: “Space is available for additional treatment to achieve a higher quality effluent and a larger population could be served if significant surface water separation works are completed. 

“However, the available data suggests that it is inevitable that the hydraulic capacity of Bellozanne STW will be exceeded at some point in the next ten to 30 years, even if the treatment capacity is not reached, and this will require a further treatment site to be created.

“Based on the ongoing Bellozanne STW project, the time required to complete the preliminary studies and enabling works required to deliver a new STW is fully recognised. 

“This is complicated by the fact that there is no existing site available and that this could potentially mean land must be reclaimed or purchased.

“It is therefore proposed to begin a pre-feasibility / needs study for a new STW as soon as the population models are released in 2023. This should provide a more defined timeline for treatment capacity on the island. 

“Depending on the findings of this study it may be necessary to immediately start detailed investigations such as site selection within the Bridging LWS period or this may be more appropriate within the 2025-35 Liquid Waste Strategy period.”

The full Bridging Liquid Waste Strategy 2023-26 can be read online.

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