Sewer-Groundwater Interaction in Urban Coastal Areas

Fecal Indicator Bacteria (FIB) are the primary tools recommended by the U.S. EPA to monitor sewage contamination in waterways. Their concentration along one of the most populated area in the U.S. can exceed the EPA guidelines for water quality after a minor rain event or even in dry weather conditions. Here, we present a study to investigate the role of groundwater infiltration into damaged sewer pipes on combined sewer overflow (CSOs) after a minor rain event or even in dry weather. Groundwater and sewer modelling were combined with a statistical model accounting for weighted risk factors, such as, e.g., pipe material and size, and type of soil, for a coastal city (Hoboken, NJ) located in one of the most populated areas of the U.S. A risk map of groundwater infiltration was then determined. Preliminary simulations of the groundwater accounting for the tide show that the large parts of the sewer network of the city may be submerged always by groundwater. Parts of the network present also high risk of failure, suggesting that they may be affected significantly by infiltration and may require, therefore, renovation or upgrading.