Analysis of more than 40,000 hours of sewage discharge into the Solent during 2020

Solent Protection  Society (SPS) has analysed the Environment  Agency (EA) annual data for sewage overflow spills in 2020 and has extracted the spills that flow into the Solent either directly of from its tidal rivers and estuaries. This data is more comprehensive than the useful but limited information from Southern Water’s Beachbuoy web application

The data shows that there are some 300 overflow pipes into the Solent and they discharged diluted untreated sewage for over 42,600 hours in 2020. We know from other monitoring that these discharges usually occur after rainfall and it does not have to be heavy or extreme.

Further analysis has shown that 77% of these hours were related to 34 identified overflow pipes which we believe should be given priority for urgent action by Southern Water.

They are variously described as Combined Sewer Overflows (CSOs), Combined Emergency Overflows (CEOs) or Sanitary Sewer Overflows (SSOs) and collectively they discharged for an average of nearly 1000 hours each.

The worst area is from the eastern side of the Isle of Wight covering Ryde, Bembridge and Sandown, closely followed by Chichester/Langstone Harbour, the River Test, Portsmouth Harbour, Southampton Water and Cowes/Gurnard. All these areas either affect bathing beaches or marine leisure activities as well as environmentally sensitive marine protected areas.

In all SPS has divided the Solent into 15 areas and identified the 34 overflows in these areas that are most critical. The worst performing individual overflow was Chichester WTW 2 SSO with over 2600 hours of spilling; the equivalent of discharging continuously for over three and a half months in 2020.

Of the remaining 33 overflows 12 discharged for over 1000 hours each.

Many groups around the Solent are pressing Southern Water, the EA and OFWAT as well as our MPs and local councils to take action to reduce these overflows as the New Environment Bill now requires.

The Bill unfortunately did not specify a timescale or what scale of reduction should be achieved but SPS will be pressing for a significant reduction over a short timescale.

Initially SPS will press Southern Water to significantly improve the identified 34 overflows within 5 years.