Ref: 15/SW/01/11 Price: £25
ISBN: 184057 772 X
Many sewerage catchments in the UK suffer infiltration problems when groundwater levels rise. Groundwater enters sewers though various means including underground leaks and can overload a network, giving rise to sewer flooding and unusable sanitation. Mitigation approaches such as tankering or over-pumping to watercourses can be expensive and/or unpopular with local residents.
The industry frequently addresses infiltration by sealing assets against ingress, but this may not be the most economic approach, particularly where mitigation (such as prevention of inflows from other sources) is possible. This report describes and assesses options for the prevention, management and mitigation of infiltration, taking account of water company experience, stakeholder views and published literature.
A framework has been developed for the economic assessment of intervention options, and its use is demonstrated through application to two case studies. To support this framework, methodologies are proposed to estimate in advance the costs and benefits of an intervention. In addition, an approach has been developed to model the relationship between rainfall and infiltration-related sewer flooding. Where successful, this could be used to distinguish weather-related changes in performance from those that are due to infiltration prevention measures, to enable the benefits of these measures to be quantified following implementation.