Estimating Infiltration and Inflow in Sanitary Sewers Using Flowmeter Data

This paper presents and demonstrates a method for extracting groundwater infiltration during dry periods and rainfall-driven infiltration and inflow during wet periods from sanitary sewer flowmeter data and related hydrologic measurements. The method is novel because it explicitly relates groundwater infiltration and peak rainfall-driven flow rates to easily accessible data such as rainfall and water-table elevation. Using data from 78 ultrasonic flowmeters in a large sewer system, together with rainfall and water-table records, the method identifies these relationships along with their associated confidence limits. In practice, the method can be used to estimate the magnitudes of extraneous-flow components under both dry- and wet-weather conditions.