Sewer infiltration/exfiltration and interactions with sewer flows and groundwater quality

Inflow/infiltration (I/I) and infiltration/exfiltration (I/E) are interactive processes which dynamically affect sewer and groundwater performance. The incidence and condition of "critical" sewers in the UK are identified together with methods of quantifying I/I and I/E as well as their impact on wet weather sewer performance and on urban groundwater pollution. Whilst the impacts of sewer trench I/I upon peak sewer flow conditions can be severe, the impacts of I/E appear to be of less concern although some caution is advocated in respect of long term sewer sustainability.