Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, what assessment has he made of the effect of stormwater releases into Langstone Harbour on the health of the local environment; and what recent estimate he has made of the frequency of untreated sewage being discharged in storm overflows in that area in the latest period for which figures are available.

Storm overflows allow excess surface water and sewage to be directed away from homes during rainfall events. They are operating more frequently across the country due to housing growth and climate change. In 2019, storm overflows across the country spilled an average of 35 times each and nearly one in ten spilled more than 100 times.

Langstone Harbour is designated as a transitional waterbody under the Water Framework Directive (WFD). The Environment Agency (EA) monitors the harbour for water quality and ecology. Since the 1990s, there has been an improving trend in nutrients within the harbour. This is due in part to the transfer of the Budds Farm discharge from the north of the harbour to a long sea outfall 5 kilometres offshore. The improvement in nutrients has led to the substantial reduction in macroalgae and Langstone Harbour now consistently achieves WFD Good status for nitrogen and macroalgae.

Langstone Harbour is also a designated shellfish water under WFD. It fails the stringent WFD microbial standard in shellfish flesh. Discharges from Combined Surface water Outfalls (CSOs) are likely to be one of the sources of shellfish contamination, as sewage contains bacteria and other material that shellfish feed on which can contaminate the shellfish for a period of time. Upgrades to reduce CSO spills were proposed in Southern Water’s latest Asset Management Plan (AMP). However, this is unlikely to go ahead, as it will not be cost beneficial. The cost of infrastructure upgrades is likely to be far greater than the commercial value of harvested shellfish.

Southern Water provides the EA with a record of its storm water discharges annually, detailing frequency and duration. The most recent data for Langstone Harbour that has been fully assessed and is supplied below. The EA may request specific information at any time.

The data shows that, in 2019, the majority of storm water discharges into Langstone Harbour came from Budds Farm sewage treatment works, with 57 spills that year, totalling 617 hours.

Table 1: Storm water discharges into Langstone Harbour from Southern Water Assets 2019