Letter from Environment Agency on Southern Water and wastewater discharges into Chichester Harbour
Our recent enforcement action against Southern Water was in response to their failure to meet permitted flow rates to full treatment prior to discharging storm effluent at a number of their assets during historic storm events. Compliant storm discharges are permitted by our permits and will continue to take place in response to heavy rainfall events. We are not seeking to eliminate them altogether but to ensure that where they do occur, they meet the stringent terms of our environmental permits, which are designed to minimise harm to the environment.
Southern Water operate several assets with Environmental Permits which authorise the discharge of dilute storm sewage into Chichester Harbour and surrounding areas during times of heavy rainfall. These storm sewage discharges are unavoidable at times because England has a ‘combined’ sewerage system in many urban centres which extends for hundreds of thousands of kilometres. This is a legacy of the past, with some sewers dating back as far as the Victorian era. Combined sewerage systems convey clean rainwater and wastewater from toilets, bathrooms and kitchens within the same pipes to a waste water treatment works (WwTW). During heavy, prolonged rainfall the capacity of these pipes can be exceeded many times over. Storm discharges act as relief valves which prevent the system from overloading, which would otherwise result in sewage backing up and flooding people’s homes, workplaces and neighbourhoods. Regulated discharges of diluted sewage during heavy rainfall are not a sign that the system is faulty.
To completely separate foul and surface water flows into two systems would not be possible without causing massive disruption and expense to homeowners and businesses, requiring thousands of kilometres of sewers to be dug up and replaced, the cost of which would have to be borne by bill payers. The Water Industry estimates the total projected cost of this to exceed £100 billion.
Chichester WwTW accounts for the majority of the storm discharges into Chichester Harbour during a typical year. In the most part this is due to the high groundwater levels, which in wet years can rise above the level of public sewers and private drains within a large part of the city. This results in infiltration of clean groundwater into the sewerage system, diluting wastewater and significantly increasing the volumes arriving at the WwTW for treatment. This has at times led to the WwTW operating its storm overflow for significant periods of time following rainfall.
Storm effluent is not discharged without some form of prior treatment – our permits typically require 6mm 2-dimensional screening to remove solids plus retention within a storm tank to allow settlement of polluting sediment prior to discharge. Our environmental permit for Chichester WwTW is more stringent still, requiring Southern Water to disinfect storm and treated final effluent with ultraviolet light prior to discharge, this affords protection to harbour users and shellfish beds by killing bacteria and viruses in the effluent.
To address the groundwater infiltration issue, we required Southern Water to investigate the sewer network within the city and then to produce and follow an Infiltration Reduction Plan. They continue to follow this plan and to take action to reduce groundwater infiltration and subsequent discharges from the WwTW but this will not result in a rapid resolution as there are many hundreds of kilometres of public sewer and private drains which are contributing to the problem.
On a national level the Environment Agency have introduced a requirement for water companies to monitor and report on their storm discharges (Event & Duration Monitoring or EDM), which has been pivotal in gaining a better understanding of the performance of storm overflows, and in holding water companies to account for compliance with their permits. Through EDM, the EA is now gathering intelligence on over 80% of the sewerage network – an increase of 14-fold over the last five years. Water companies are expanding their monitoring, having committed to accelerate work to install monitoring devices to create a complete picture of storm overflow impact by December 2023.
We have also agreed that water companies will make real-time data on sewage discharges from storm overflows at designated bathing waters available all year round. This data will be made available to help surfers, swimmers and other recreational water users to check the latest information all year round and make informed choices on where to swim.
EDM monitoring evidence has already been used to drive around £1.1billion of water company investment, which will see 800 investigations and nearly 800 improvements to storm overflows over the next four years. The same data assessments that brought about this investment will now be applied to the 2020 data for the next round of water company environmental improvements between 2025-2030.
A Storm Overflows Taskforce has been convened – made up of the Department for Environment, Food & Rural Affairs (Defra), the Environment Agency (EA), Ofwat, Consumer Council for Water, Blueprint for Water and Water UK. The Taskforce has agreed to set a long-term goal to eliminate harm from storm overflows. The Taskforce will jointly review the current Water Industry National Environment Programme in advance of the Price Review 2024. More information can be found on the Government website https://www.gov.uk/government/news/taskforce-sets-goal-to-end-pollution-from-storm-overflows
In addition, the Government are also introducing further measures into legislation based upon Philip Dunne’s Bill to reduce sewage discharges from storm overflows. Three key duties will be made law:
* A duty on government to publish a plan by September 2022 to reduce sewage discharges from storm overflows and to reduce their impact.
* A duty on government to report to Parliament on progress on implementing the plan.
* A duty on water companies and the Environment Agency to publish data on storm overflow operation on an annual basis.
You ask about the review of Southern Water’s consents (permits), this will take place as part of the wider Solent review of permits, which is a long and complex piece of work in its very early stages. The Environment Agency is currently defining the scope, resourcing and timescales for the review.
On the subject of agricultural pollution to Chichester harbour, improvements in farming practices have reduced polluting inputs over recent years, particularly nutrients. Our work has helped drive these improvements, most recently we have secured funding from Defra to undertake some targeted investigatory work in the Solent, specifically focussing on impacts from farming practices. We have created an independent team solely focussing on agriculture. Over the next year and beyond we will work alongside partners to install good practices and ensure improvements to infrastructure are made on specific farms as required.
