Letter to Thames Water regarding Controlled Sewage Overflows

Cllr Emily Smith, Leader of the Vale of White Horse District Council wrote a letter to Thames Water regarding Controlled Sewage Overflows (CSOs) into the River Thames.

Thames Water has provided the following response to Cllr Emily Smith’s letter:

Thames Water
Customer Relations
PO Box 436
Swindon
SN38 1TU

 20 January 2021

Sewer discharges into the River Thames

Dear Councillor Smith

Thank you for your letter of 4 January, addressed to our Chief Executive Officer, Sarah Bentley. As a Senior Case Manager from our Executive Office, Sarah’s asked me to reply on her behalf. I welcome the opportunity to address the concerns you’ve shared with us, in relation to controlled sewer discharges into the River Thames, particularly during 2019.

I completely understand what a worrying situation this is, and the impact this has on the villages, community, and the environment, including wildlife. Also, I appreciate the effect it has on swimmers who enjoy swimming in the river, particularly during the summer months, as well as other recreational activities that are enjoyed in and around the river.

I fully recognise any wastewater discharging into the River Thames is of course highly undesirable and I’d like to assure you, we don’t allow this to occur lightly. Unfortunately, the likely alternative is that homes may flood internally and externally with wastewater, which we of course need to prevent.

I’d like to assure you we work closely with our stakeholders across our region by way of meetings and open and honest correspondence to offer reassurance about our work in this field. With recognition from water companies, our regulators, and the government, that the current situation about discharges of untreated sewage into the environment is unsatisfactory and changes are needed. Though we must underline the resolution to minimise the discharges isn’t an immediate one. We work with the Environment Agency (EA) to identify, as swiftly as possible, any unsatisfactory CSO’s so that remediation can be included in our five-year business plan.

It may be worth noting, between October 2019 and March 2020, we experienced much higher-than-average rainfall, with several named storms. Following such exceptional levels of rainfall, even when the rain has ceased, the ground is saturated, and the water table is very high. In these circumstances, ground water infiltrates into our foul water sewer, through multiple small points of entry.

Our foul water network isn’t designed to accommodate all these additional flows, which then results in flooding, once the sewer is running at full capacity. It also means there’s extra flows for the Sewage Treatment Works (STW) to treat, beyond its design parameters, which can lead to additional discharges. We of course recognise and share the local concerns about the discharges from our STW’s. These discharges have occurred because of the inability of the works to fully treat all incoming flows, consequent of exceptionally wet weather and the aftermath of a very high-water table.

It’s important to clarify, we’re only, within our permit, allowed to release partly treated and/or screened storm sewage to the river, along with fully treated consented discharges. As mentioned, we work hard to prevent it from happening, however we have no reason to believe our actions have been unlawful. These permit conditions are in place to prevent pollution to the watercourse and harm to wildlife.

I’d like to assure you, in the short term, our operations team are working hard to minimise storm discharges, as far as possible through operational good practise. In the longer term, we’re developing our plans for addressing catchments such as the Thames Valley, which are affected by groundwater ingress into the sewers, increasing flows to the STW. This has started with local stakeholder workshops to capture local knowledge and evidence to ensure we have as complete an understanding as possible and can target our activity, as appropriate.

Separate to this, I’m liaising with our Environment Information Request (EIR) team to get a better understanding of how we may be able to publish real-time data regarding Controlled Sewer Overflows into the River Thames. I’ll keep you fully updated on the outcome of this suggestion.

I trust you’ve found this information helpful. I’ll contact you again on or before 15 February to provide a further update re the above. In the meantime, if I can be of any further assistance just let me know. Alternatively, you can call Maria on 0800 0093666. Our offices are open from 9am to 5pm, Monday to Friday and we’ll be happy to help.

Yours sincerely

Mari Long

Senior Case Manager – Executive Office