TABLE OF CONTENTS Jacques W. Delleur
School of Civil Engineering
Purdue University
West Lafayette, Indiana
Sediment deposits in sewers create negative effects on the hydraulic performance of the system and on the environment. Problems that arise include blockage, surcharge, early overflows, large pollutant discharges and costly removal. The erosion of sediments in sewers can release pollutants in concentration that exceed the levels found in the various contributing sources of the sediments and pollutants (Ashley et al., 1992). Solid particles constitute the support on which other pollutants are adsorbed, among them heavy metals and hydrocarbons. Intermittent discharges from combined sewer overflows often involve sediments and associated pollutants and are recognized as a major pollution source in urban receiving waters.
There are several recent reviews of literature: Bertrand-Krajewski et al. (1993), Ashley et al. (2000) and Delleur (2001).
The supply of sediments to the drainage system occurs primarily during storm events. The runoff washes off the particles accumulated on the tributary surfaces. Other sediment supply mechanisms include wind action and vehicle motion. Sanitary solids are also found in combined drainage systems and of course in sanitary sewers.
The sediment load from the upstream watersheds can be estimated using the Universal Soil Loss Equation, USLE (Wischmeier and Smith, 1965, 1978) or the more recent revised version, RUSLE (Renard et al., 1993). The RUSLE and USLE are multiplicative relationships of the form
where A = the average soil loss per unit of area
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