22 October 2021
Flooding updates from Cirencester Town Council, Environment Agency and Thames Water

Please find below the latest flooding updates from Cirencester Town Council, the Environment Agency and Thames Water.

Cirencester Town Council: Update October 2021

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Environment Agency: Updated 29 June 2021

The following Environment Agency update provides an overview of its flood risk activities in the Cotswolds Constituency since the Cotswolds annual flood forum meeting on 5 March:

Maintenance overview

We continue to deliver our flood risk maintenance programme in the Cotswolds as planned and have completed some extra work that we received additional funding to deliver. This includes maintenance to all of the tributaries of the River Churn in the Preston & Siddington areas, reducing flood risk by removing some very large blockages and returning the flow back to those channels. Funding for this work will not be available every year so in the future it will fall to the riparian owners to be aware of the ongoing maintenance requirements through their stretch of the river and to undertake the maintenance that they deem necessary.


We continue to support Cirencester Town Council in relation the Memorandum of Understanding they have with local land owners to operate sluice gates in the town centre. An exercise to run through the operation of the Memorandum of Understanding with the Town Council is being planned.

We have received funding to complete routine river maintenance on behalf of the riparian owners this year and have completed river channel and bank clearance. In the autumn, we plan to remove trees which have fallen into the upper reaches of the River Churn.

We and other partners attended the recent Cirencester Flood Risk Management Group meeting which was led by Gloucestershire County Council. One of the key outputs of the meeting was to explore further the impact of groundwater levels on flooding in the area which will involve input from our hydrogeologists.

We have submitted a bid for government funding to improve the flood defences in Watermoor. Subject to the success of this funding bid, we will carry out an inspection to identify the remediation options available.


We and other partners have been involved in supporting the work of the Bledington Flood Group. We have provided technical input on flood risk activity permitting and further flood risk measures. We have also brought forward our maintenance work which is scheduled to start during the week commencing 2 August.

Thames Water: Updated October 2021

We are absolutely committed to protecting and enhancing our rivers and supporting the communities who love them. Putting untreated sewage into rivers is unacceptable to us, to our customers and to the environment. We're working hard to make discharges unnecessary, with the help of the government, Ofwat and the Environment Agency.  Our current business plan, spanning 2020-2025, will deliver environmental improvements to 745km of rivers across the region. The use of digital technology to create a more intelligent sewer network and enabling more proactive maintenance and repairs will help us to drive a reduction in untreated sewer discharges. 

Eliminating discharges is not going to be quick, easy, or inexpensive and we welcome the continued support of our customers and regulators, who are equally passionate about this topic, as well as extensive collaboration with local communities and other stakeholders, to achieve cleaner rivers.  

Specific questions regarding Apney St Peter (responding to development and recreational use of the river):

I’d like to reassure you we are significantly investing in Ampney St. Peter Sewage Treatment Works (STW). Ampney St. Peter STW has been upgraded numerous times over the years to comply with the new discharge permits and storm tank improvements. We are currently planning a ‘flow to full treatment upgrade’ which put simply means the treatment process will be increased to accept more flow for treatment and reduce the amount of untreated sewage going into our storm tanks or discharging to the environment. The project, alongside a number of other STW upgrades are being reviewed at the moment but we expect the upgrade to be completed no later than March 2025. In order to size the upgrade sufficiently we have also delivered some additional onsite flow monitoring this year which will allow us to better understand the volumes of flow coming in and out of the site.

In reference to the pumping arrangements. In 2017/18 we installed a second wet well (underground storage tank) adjacent to the original Ampney St. Peter pumping station and separated the two incoming sewer networks serving the STW. The original pump station now only serves the network from Ampney Crucis, whilst a new pump station serves Ampney St. Peter and Ampney St. Mary. This scheme substantially reduced the risk of flooding in the catchment.

We recognise more work needs to be done, particularly when it comes to infiltration. This occurs predominantly during winter/spring months when groundwater levels are high, resulting in clean water infiltrating into the sewer network or through manholes from surcharging highway/land drainage. Ampney St. Peter catchment suffers from this seasonal infiltration, and this affects the sewer network at the same time placing significant pressure on STWs. We are working to tackle some of the root causes and in the short term our operational teams have been working hard carrying out lift and look surveys & CCTV investigations to identify sources of water ingress. As a result, we have repaired sections of high risk sewers and sealed a number of manhole covers.

Looking further ahead we are developing a Groundwater Impacted System Management Plan (GISMP) for the Ampney St. Peter sewerage system. GISMPs are agreed with the Environment Agency and published on our website. They outline the short, medium and long term interventions to tackling infiltration in the sewerage system. https://www.thameswater.co.uk/about-us/regulation/drainage-plans. We are building evidence for a more strategic wholesale approach to sewer lining to line large portions of the network in the high-risk groundwater areas of the network for each system. We are not funded to deliver this level of lining in this period (2020-25), however, where interventions can be undertaken as part of routine sewer maintenance activities these will be communicated and progressed separately. 

Ampney St. Peter STW is also being assessed under the Environment Agency SOAF (Storm Overflow Assessment Framework) programme. The framework ensures that we are proactively monitoring and managing the performance of our overflows considering the pressures of growth and changing rainfall patterns. Stage 1 and 2 assessments which investigates the root cause of the spills and quantifies environmental impact is due to be complete for Summer 2022. Interventions identified as part of this process will be included in our next business plan (2025-2030).


We have a duty to provide maintain and extend our sewer network to accommodate new development. For STW upgrades we are funded through our 5 year business plan and for sewer enhancements we are funded via infrastructure charges from developers. To help us understand what development is coming forward we monitor local plans which give a longer-term view of development, up to 20 years, as well as planning applications which give a 1 – 5 year view. 

As you may be aware, Water and Sewerage companies are not statutory consultees in the planning process and have limited powers to prevent connection to our networks. We therefore work closely with developers and planning authorities to ensure any upgrades needed to serve a new development are delivered in line with the new development’s needs/timescales. When commenting on planning applications we undertake desktop assessments to calculate any potential impact on the existing infrastructure and in some cases we may seek an appropriately worded planning condition to ensure occupation of the development doesn’t outpace the delivery of the infrastructure. 

When assessing new development it is important to understand whether surface water flows are proposed to discharge into our system. Foul flows from new development are often very small in comparison to the existing sewerage systems – we often refer to 100 houses of foul flow being equivalent to one house with their roof drainage connected into the foul. Therefore when we undertake desktop assessments for foul flow the impact is often assessed as negligible in comparison to the existing situation, assuming new surface water flows are managed on site and not connected to our system. So discharges from Ampney St. Peter are a result of infiltration into the sewers, not from over development and our efforts in the catchment are to restore the headroom by reducing the infiltration flows.  

All discharges from STWs are regulated by the Environment Agency. We monitor spills from STWs over a long period of time (multiple years as weather patterns are varied) to understand the impact surface water/infiltration is having and if triggers are met we will instigate a STW study and plan upgrades as appropriate to remain compliant within our consent. We recognise the lag effect this causes, and we are working with WaterUk and DEFRA to challenge a developers right to connect.

Recreational use of the river

We fully appreciate just how well loved these rivers and stream are and why people want to use them for recreation.  However, we need to gently remind people that sewage discharges aren’t the only sources of pollutants, nor are water companies responsible for river quality generally. Animal faeces from livestock and wildlife, along with run-off from farms and roads, also contribute to the hazards. It really is up to individuals to make informed decisions based on numerous factors and we support the government’s advice on open water swimming: https://www.gov.uk/government/publications/swim-healthy-leaflet/swim-healthy

The wider health of the river concerns us, though formal assessments are part of the Environment Agency’s role.  We certainly recognise that real-time discharge notifications of sewage discharges play an important part in helping people make informed decisions about whether to use the river or not. We're currently trialling these notifications around Oxford to support an application for bathing water status. Details on this can be found here (www.thameswater.co.uk/riverhealth). We're looking to adopt a similar approach for our other wastewater catchments in the future. The Environment Agency are responsible for river health and undertake regular monitoring to better understand areas that require additional investment and interventions, either from water companies, councils or private landowners. Long term monitoring can be an expensive and resource intensive activity and as such is usually targeted to hotspot areas and for a finite period. Our Oxford trial will run for at least a year and will be the longest bacterial monitoring programme on a watercourse in England. The learnings from this will help us better understand the general health of the river and what proportion of the perceived poor water quality is linked to sewage spills/effluent, under a range of conditions.