Abstract : The Northeast Ohio Regional Sewer District (NEORSD, Cleveland, OH) serves over one million citizens through the operation of three waste water treatment plants. NEORSD provides this service through combined and separated sewer systems, which, during rainfall events, are known to deliver large volumes of untreated wastewater containing high concentrations of Escherichia coli (E.coli), ammonia nitrogen, and phosphorus. NEORSD is currently investing $3 billion over the next 25 years to mitigate its combined sewer overflows and plans to allocate additional funds to improve remaining pollutant sources related to its system, e.g. separated sewers. A suite of PC-SWMM pollutant loading models have been confirmed for their ability to represent the environmental impacts of NEORSD's sewer system. The environmental benefits associated with infrastructure improvements are then predicted by the models to assist NEORSD in most efficiently spending financial resources.