Course Overview

Combined Sewer Overflows (CSOs) operate as a pressure valve in our sewerage sewer systems designed to protect properties from sewers that when overwhelmed by rainfall can cause sewage to back up into our streets and properties causing flooding. CSOs are used to spill excess sewage into watercourses and the bathing water. The environmental risks as a consequence of CSO spills are likely to grow as a result of urbanisation, climate change and the ageing of our sewerage infrastructure. CSO spills can be associated with poor quality rivers and bathing waters and have recently attracted public and media scrutiny and outrage.

Subsequently the government released a Stormwater Overflow Discharge Reduction Plan in August 2022 and approaches to reduce CSO spills are a key part of the Water Industry National Environment Programme (WINEP) and the first round of the Drainage and Wastewater Management Plans (DWMPs). The management of CSOs are going to be a key feature of the industry’s investment plans for years to come and are likely to be one of the most significant areas of future investment for the water industry. Approaches to managing CSO spills include optimisation of the sewer system, building additional storage, reducing the amount of rainfall entering the drainage system through approaches like retrofitting Sustainable Drainage and sewer separation. Effectively and sustainably tackling CSO spills will require collaboration between water companies, local authorities, highway authorities and those managing urban drainage, surface water infrastructure and our places and spaces.

Course Details

  • Two half days (9:30-13:00)
  • £60 (VAT Incl.)

Combined Sewer Overflows – from challenge to opportunity

CIWEM’s Urban Drainage Group has developed training (split over two half days) that provides an accessible and engaging overview of CSOs and practical design exercises to discuss potential approaches to manage CSO spills. The training includes presentations from industry experts, with plenty of time for group discussion, reflection and exercises and it has been designed for those working in the water industry, local government and regulators.

[This training is now full. Registration is closed]

Click to view the Agenda

Learning Outcomes

Upon successful completion of the training, attendees will...

  • Gain a shared understanding of the purpose of CSOs both at the treatment works and in the network
  • Have a broad understanding of approaches to monitor and regulate CSO spills
  • Understand and describe some options for managing CSO spills and the benefits to be achieved
  • Appreciate collaborative approaches to planning and delivering solutions to manage CSO spills

Attend as a delegate

Online: Dial in from the comfort of your own desk, for only £60 (VAT Incl) you will benefit from virtual presentations from industry experts, lively discussion, and the sharing of ideas and good practice with peers through facilitated online breakout groups.

Hubs: Closer to the date, we will release the location of a series of regional in person hubs. All online delegates are invited to register to attend the face to face surgery hubs, hosted by friends of CIWEM and the CIWEM Urban Drainage Group where discussions will take place in person, alongside the virtual presentations and if you’re really lucky, some of the presentations may even take place onsite. Places at the hubs will be strictly limited and on a first come first served basis. Anyone who has registered to attend virtually will be sent a booking link for the hubs on release day…be ready to beat the rush.

For group bookings, please contact

The first round of Learning Hubs have been released!

Our face-to-face learning hubs are hosted by CIWEM friends and our Urban Drainage Group. Discussions will take place in person alongside the virtual presentations, and if you're lucky, some of the presentations may even take place at your site.

  • Only registered delegates will be invited to join a local hub, so register now.
  • Invitations to local hubs will be circulated the week of 13th March.
  • Space at the hubs is strictly limited and will be assigned on a first come, first served basis.
  • More hubs may be released in response to demand.

Sponsor the UDG Training Day

Are you working in urban drainage and surface water management, do you want to raise awareness of your company and the great work you are doing? Do you feel passionately about supporting the sector’s early career professionals, promoting good practice and delivering thought leadership? We are seeking partner organisations to sponsor the training content and help CIWEM and CIWEM UDG deliver valuable training to the industry.


Click to view Benefits of Sponsorship

Investment: £975.00+VAT

Contact Us

If you have any questions please email our team at or call 020 7831 3110.

Latest News and Events 


Whether you are studying, actively looking to progress your career, or already extensively experienced, our membership will add value and recognition to your achievements.

Read more


We organise a wide portfolio of UK and international thought leading events, providing an industry recognised forum for debate.

Read more


Our market-leading technical excellence training modules are delivered via online and classroom-based courses.

Read more