Comprehensive Monitoring And Modeling Program Reveals True Impact of CSO Discharges and Allows River Community to Focus Funds on Original System

Under the CSO Control Policy, small communities have the flexibility to perform less comprehensive monitoring and modeling. However, in the case of Ottawa, Illinois, a thorough monitoring and modeling program was beneficial in both developing a cost-effective CSO control plan and obtaining regulatory approval. The monitoring and modeling of the collection system helped Ottawa better understand its system, identify easily separated areas, and develop a solution without costly storage options. The water quality monitoring and modeling helped demonstrate that Ottawa CSOs have a modest impact on the high-flow Fox and Illinois Rivers, and that under the preferred control plan, CSOs would cause exceedances of the 400 cfu/100 mL fecal coliform criterion less than 1% of recreation season hours (water quality standards allow exceedances for 10% of samples). The additional upfront study allowed Ottawa to reinvest in its existing sewage collection system and secure a better financial future for the City.