Fears over Sandown’s water treatment plant

By Press Release Sep 28, 2021

Serious concerns of sewer collapse and flooding in the water waste system at Sandown have been raised.

Sandown the only Island treatment plant assessed as a high level of concern by Southern Water. The water company, however, say the problems could be fixed if surface water run-off was dealt with differently, enabling it to eliminate water discharges into the Solent.

Answering questions from the Isle of Wight Council’s corporate scrutiny committee, Southern Water’s area manager, Keith Herbert, gave an overview after recent flooding devastated properties across the Island.

Hydraulic overload of the public sewers — or too much water in the system — was found to be a ‘not so hypothetical scenario’, said Mr Herbert. He said that flooding was a problem shared among agencies, including the Isle of Wight Council and the Environment Agency.

Cllr Peter Spink highlighted six significant concerns at the Sandown treatment works, which has a forecasted growth increase of 25 per cent by 2050. They are risks of pollution, sewer collapse and flooding, storm overflow, dry weather flow compliance and nutrient neutrality.

Mr Herbert said, as part of its £50m plans for the Island in the next 40 years, £9m would be used to address some of the concerns as ‘proactive intervention’. He said: “A lot of those problems would be resolved by removing surface water connections from the public foul sewer. If surface water connections were not plumbed into the foul sewer we would not flood as much and we would not discharge. It is fair to say we could eliminate almost all discharges by removing that surface water run-off.”

One recommendation is to completely separate surface and foul water, as surface water could overwhelm the capacity of public foul sewers.

The company is working towards a full rationalisation of water supplies on the Island as 20 works and 30 reservoirs serve the population which Mr Herbert described as too elaborate.

When questioned on new developments and housing adding to the pressures, Mr Herbert said newer properties were more water-efficient, with older housing stock causing more problems.

Cllr Chris Jarman said one of the outcomes was future developments would need to have complete separation of sewage from surface water.