A Real-Time Control Strategy for Operating the Milwaukee Metropolitan Sewerage District (MMSD) Conveyance and Storage System

This paper describes the development of a revised wet weather operating strategy for the Milwaukee Metropolitan Sewerage District (MMSD) conveyance and storage system. The MMSD provides for the conveyance, storage and treatment of wastewater in a service area covering approximately 425 square miles in southeastern Wisconsin. The MMSD collects sewage generated in 28 municipalities and agencies and conveys it for treatment at one of its two treatment plants. Most of the municipal sewers in the service area are separate sanitary sewers. However, approximately 25 square miles of service area in the City of Milwaukee and the Village of Shorewood are served by combined sanitary and storm sewers. Under most circumstances, all collected sewage is conveyed directly to one of the treatment plants. During extreme wet weather, excess flows generated in both the combined and separate sewer areas can exceed the conveyance and treatment capacities of the existing facilities. Excess flows can be stored in the District's inline storage system (ISS) or discharged through overflow outfalls in the system. Wet weather conditions can include heavy rainfall, snowmelt, and rain during snowmelt or moderate rain with saturated soil conditions. Wet weather generates stormwater runoff in the combined sewer area and rainfall derived infiltration and inflow (RDII) in the separate sewer area.