Chichester Sewage Works Gets £25m to Add 57% Capacity

Southern Water has begun a £25m scheme to increase the treatment capacity of Chichester wastewater treatment works by around 57%. The company says the work started this month and will not finish until spring 2029.

The plant is the one the district council’s own planning factsheet calls “Apuldram (Chichester) Wastewater Treatment Works”, and the same factsheet says it is already “at environmental capacity”. That single phrase is why this scheme matters more here than a routine utility upgrade would.

The scheme, as Southern Water describes it, involves:

• new tanks and additional pipework on the Apuldram site
• an increase in treatment capacity of around 57%
• work carried out by the company’s infrastructure partner Galliford Try
• a stated aim of reducing the risk of storm overflows in heavy rain

The company’s statement carries no publication date. It says the work is “due to begin this month”, with completion “expected in spring 2029”.

Why Apuldram is different

Chichester Harbour has three Southern Water treatment works discharging directly into it: Apuldram, Bosham and Thornham. The council names all three in its factsheet on managing water quality and wastewater.

Apuldram has a specific problem, and it is not really a sewage problem. It is groundwater.

The council sets it out plainly. The Chichester catchment has high levels of groundwater getting into the sewer network. When the water table is high, that water leaks into the sewers. The extra volume pushes the works past what it can treat, and the storm overflow runs. In winter, the council says, heavy rainfall and high groundwater “frequently leads to the prolonged use of storm discharges”. That is the reason it gives for classing the works as being at environmental capacity.

The regulatory history goes back further than most residents will realise:

• 2013. An enforcement notice was served on Southern Water requiring further investigation of the flows reaching Apuldram.
• 2014. Those requirements were written into the site’s environmental permit as improvement conditions, aimed at schemes to cut infiltration and storm discharges.
• 2014. UV disinfection was installed on the storm overflow itself, which the council says limits the impact on water quality in the harbour when the overflow runs.

Southern Water has also named Apuldram a priority for long-term investment in its 25-year Drainage and Wastewater Management Plan, on the basis of storm overflow performance and nutrient risk.

What it means for building in Chichester

This is the part that touches anyone hoping to build, extend or buy new here.

Because Apuldram is treated as being at capacity, the council’s Local Plan, adopted in August 2025, carries a policy specifically about it. The council summarises policy NE17 as limiting new residential connections to Apuldram, and requiring any new development of ten or more dwellings to demonstrate that there will be no net increase in flow to the treatment works. Before the plan was adopted, the council says the same requirement was applied through a position statement agreed between Southern Water and the Environment Agency.

So a bigger works sounds like it should unlock housing. Be careful with that assumption, for three reasons.

1. The capacity is not there until 2029. Southern Water’s own completion date is spring 2029. Nothing about the constraint changes on the day the diggers arrive.
2. Nutrient neutrality is a separate lock. Natural England’s assessment in 2019 and 2020 found more than 3,000 hectares of the intertidal parts of Chichester Harbour in an “unfavourable, declining” condition. The council says it can now only grant permission where it is certain nutrient levels will not increase, even slightly. That is a Habitats Regulations test, and treating more wastewater does not by itself satisfy it.
3. Sewage is not the main nitrogen source. The council’s own factsheet puts the treatment works’ share of nitrogen pollution in the harbour at around 10%. The rest comes from farmland and urban runoff, private treatment plants, livestock and ditches.

Neither the council nor Southern Water has published anything saying NE17 will be relaxed when the works reopens at its new capacity. If that changes, it will show up in the council’s Local Plan monitoring, and we will cover it on the planning news page.

The rest of the harbour programme

The Apuldram scheme is not standing on its own. Southern Water says it sits alongside:

• a programme to seal 16km of sewer in the Lavant Valley, which feeds Chichester Harbour
• separate schemes to cut storm overflows at Thornham and Bosham
• the Three Harbours Partnership, a joint effort across Langstone, Chichester and Pagham harbours on water quality, biodiversity and carbon

Sealing the Lavant Valley sewers is the one to watch, because it goes at the actual cause the council identifies. Groundwater gets into the pipes; seal the pipes and less of it arrives at Apuldram in the first place.

George Taylor, Southern Water’s Director of Wastewater Operations, said in the company’s statement: “This is a significant investment that will make a real difference to the amount of wastewater we can treat and will help us play our part in improving the health of Chichester Harbour.”

What it means for you

If you swim, sail, paddle or walk dogs in the harbour. Nothing changes this year. Southern Water runs a free alert service, Rivers and Seas Watch, which notifies subscribers when there has been an untreated discharge into the harbour. The council recommends recreational users sign up to it. It also recommends basic hygiene: cover cuts with a waterproof plaster, wash hands after contact with the water, and keep hands away from your mouth until you have.

If you want to know the water quality where you go in. Chichester Harbour Conservancy samples at twelve locations around the harbour, twice a month in summer and once a month in winter, and publishes the results. The council warns those results are indicative only: they are specific to the date and time of sampling, there is no targeted sampling after a storm discharge, and quality varies across the harbour.

If you see or smell a pollution incident. Southern Water’s emergency reporting line is 0330 303 0368. The council has no enforcement powers over discharge permits. The Environment Agency is the body to raise permit concerns with.

If you are building. If your scheme is ten dwellings or more and it drains to Apuldram, expect to have to show no net increase in flow, on top of the nutrient neutrality calculation. That is the council’s stated position, and this upgrade does not change it today.

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