Abstract

The City of New Haven and the New Haven Water Pollution Control Authority operate a wastewater collection and treatment system that serves over 200,000 residents in the cities of New Haven, Woodbridge, Hamden, and East Haven. The system contains twenty-four permitted regulating structures to relieve high flows associated with wet weather events. These structures permit overflows from the combined sewers to local receiving waters. To address the water quality impacts from these overflows, a facilities plan completed in 1981 recommended construction of separate sanitary and storm sewers on a city-wide basis. In 1997, the City started to re-evaluate this plan because of changes in regulatory requirements as well as advances in available technologies for the control or treatment of wet weather flows.

MOUSE, an Arcview-GIS based dynamic model, was selected to analyze the performance of the combined sewer overflow (CSO) system. Three-month, 6-month, I -y, and 2-y design storms were simulated to evaluate the performance of the system. In addition, An average rainfall year was simulated to determine the performance of the system under typical rainfall conditions. The statistics for overflow frequencies, overflow volumes, and overflow durations in this average rainfall year were calculated for each overflow regulator. The statistics were then organized according to receiving waters so that the level of impact caused by the CSOs to each receiving water and the priorities for control could be arranged. Color coding of percent utilization of the pipes and available freeboard at each manhole

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