The city of Indianapolis signed a consent decree with the U.S. Justice Department and U.S. Environmental Protection Agency (EPA) to make more than $1.86 billion in improvements to curb overflows from its sewer system. According to the EPA, the settlement will be the third highest-cost Clean Water Act settlement addressing combined sewer overflows (CSO), and will ultimately reduce the volume of Indianapolis’ untreated CSO discharges by 7.2 billion gallons in an average year.

Indianapolis agreed to make the improvements over 20 years to reduce the overflows-which currently occur approximately 60 times per year-down to four or fewer per year. The city will also pay penalties of $588,900 each to the United States and Indiana, and spend $2 million on a project to eliminate failing septic systems. The city may offset up to 90 percent of the state’s penalty by spending an additional $1,050,020 on the septic system project.

Under the consent decree, Indianapolis has specifically agreed to implement a Long Term Control Plan designed to greatly reduce overflows from its combined sewer system and will implement another plan designed to eliminate overflows from its sanitary sewer system (SSOs), and perform various other remedial measures.

The city’s municipal wastewater and sewer system currently discharges approximately 8 billion gallons of untreated sewage each year into the White River and its tributaries from approximately 133 CSOs, and a lesser number of SSO and bypass locations, the EPA says. Indianapolis owns two large municipal, advanced wastewater treatment plants, as well as nearly 246 square miles of sewers that feed into the treatment plants. The sewer system serves approximately 866,000 people.