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Capacity Assessment Framework

Working with the Environment Agency and other stakeholders, we commissioned HR Wallingford to develop a new capacity assessment framework – a standard way to assess how much capacity is available in drainage systems now, and what capacity might be available in the future, to enable investment to be targeted more effectively.

The initial framework focuses on capacity in the foul and combined sewer network; the framework could be extended to surface water sewers in the future.

To provide information for different audiences, there is an executive summarythe full report, a supplementary appendix on climate change, and a guidance document for practitioners.

Companies throughout the UK have been putting the new framework into practice, supported by HR Wallingford, to produce an assessment of the available capacity in companies’ foul and combined sewer networks.

This assessment gives an indication of sewer capacity and overflow performance, showing an index of risk, providing an extra tool to help companies prioritise investment.

Where there are higher risks, companies investigate further, including detailed computer modelling and monitoring, to understand the risks better and identify what action is needed.

To investigate the potential for the capacity assessment framework also being used to assess the capacity of surface water drainage assets, Water UK and Defra commissioned HR Wallingford to trial using the framework to assess the capacity of surface water sewers.