Abstract

The purpose of this chapter is to discuss the methods and issues related to modelling and monitoring the inflow reduction programs currently being implemented by the City of Portland as part of its Combined Sewer Overflow (CSO) Facilities Plan. The inflow reduction programs consist of the disconnection of roof downspouts from the combined system and the installation of infiltration sumps for residential stormwater runoff. The Storm Water Management Model (SWMM) is used to track the performance of the sump and downspout disconnection programs. This chapter describes the modelling of these sumps and downspout disconnections in SWMM, current monitoring and modelling practices for the City, concerns and limitations of modelling and monitoring, and recommendations for further monitoring. There are several concerns and limitations in modelling and monitoring these conditions accurately. The primary concern of this effort is to be certain that the inflow reduction technologies are performing as expected.

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