Recent heavy rain and the threat of flooding have focused some residents’ minds on the prospect of a Royal Mail depot being built at Patcham Court Farm.

Among them is drainage expert David Harris who fears that plans for the derelict farm site could bring the potential to make flooding much worse in Patcham.

Mr Harris knows well the water systems coming off the Downs into Patcham. He started his career as a trainee road and drainage engineer in the surveyor’s department at Brighton Borough Council.

His concerns about the potential effects of the proposed Royal Mail depot at Patcham Court Farm are grounded in years of detailed knowledge. The scheme would mean more surface water flowing into the village.

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He shares a daily alert with Patcham residents, monitoring groundwater levels to warn people when their cellars are likely to flood – and excess water can rise high enough to cause surface flooding.

The Argus: Retired surveyor David Harris who monitors flooding in Patcham

The octogenarian said: “The infrastructure downstream can’t stand it. We are so close to flooding now across the whole year. It occurs in the winter but there are increased incidents of flooding.

“When the groundwater floods, it inundates the sewers, bringing sewage to the surface, creating a health risk. It’s not morally possible to develop that site. It cannot stand it.”

A flood risk assessment for the Royal Mail scheme by the engineering consultancy Mott MacDonald said that the “impermeable area” on the site would more than double if the scheme went ahead.

Mott MacDonald recommended that the site be developed as though it were greenfield land rather than a brownfield site with drainage routes.

Run-off generated by the scheme would need to be addressed at the planning stage, according to the report.

Mr Harris said that when he worked for the old borough council, it had its own engineers who had historic background knowledge of the issues facing Patcham rather than subcontracting specialist services as it does today.

He said “All the (former council) engineers knew the town because they had been in the town all their working life.

“I knew from one of the senior engineers that the surface water sewer from the Co-op southwards, down to the southern end of Old London Road was totally blocked with silt.”

Before the A23 was widened and the A27 Brighton bypass was built, Mr Harris said that Southern Water had upgraded the old brick Victorian drains which were blocked up with silt and tree roots.

Decades ago, borough council engineers opened up the brick sewer but, when it proved impossible to remove the silt and roots, they sealed it shut again.

Mr Harris said that his family had lived in the village since at least the 19th century, with knowledge of past floods passed down the generations.

When he was doing his “national service” in 1960, his father wrote to tell him about serious flooding in the village.

Before the sewer was upgraded, he said, the situation was worse than it is today.

Mr Harris said: “We used to flood from surface water three or four times a year into people’s cottages. My then-wife and I used to help an 80-year-old lady clean up her cottage.”

He was also concerned about the level of agricultural contamination at the former farm, warning that pollutants could be released into the groundwater if the site was disturbed by the proposed scheme.

Mr Harris said: “It’s very close to the Southern Water adits (underground channels) 50 metres beneath the surface. It’s a ‘source protection zone grade one’. There is nothing higher for the protection of our drinking water.

“We are already at the limit for (agricultural) contaminants. Any rise could put Patcham out of production. It could be at the limit. It is crucial for our drinking water.”

Royal Mail submitted a planning application to Brighton and Hove City Council in July 2022 although the scheme has yet to go before the Planning Committee.

More than 1,000 objections have been sent to the council – as have 12 letters of support – with the effects on groundwater among the key concerns.

Southern Water told the council that Patcham Court Farm was on the Brighton A and Brighton B “groundwater abstraction points” and that contamination would reach water sources within 50 days.

The site is within 150 metres of an adit connected to the Brighton A sources. People fear the risk that physical or chemical contaminants released on the surface could quickly reach the groundwater.

Conservative councillor Carol Theobald, who represents Patcham and Hollingbury, spoke out about her concerns at the council’s City Environment, South Downs and the Sea Committee in November.

She highlighted the flood risk and said that, in the 23 years since the November 2000 floods, it had become clear the sewer system was no longer sufficient for Patcham’s needs.

Labour councillor Tim Rowkins, who chairs the committee, said that the council was responsible for surface and groundwater flooding but not sewers. The council was, though, working with Southern Water on ways to reduce flood risks.

When groundwater levels start to rise, residents are having to play a waiting game. In July 2022, senior councillors were due to be asked to approve a land deal with the Royal Mail.

The deal would have meant granting a long lease on council land – Patcham Court Farm – in a move that would have led to the Royal Mail vacating two of its existing sites.

As a result of the proposed deal, the council would replace the two premises – at North Road in Brighton and Denmark Villas in Hove – with hundreds of homes.

But the immediate prospect of a deal was dropped. And now, as with the groundwater levels, the residents keep a watching brief, ready to flood the council and Royal Mail with more objections as they try to protect their homes.