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What is DigIndy?

The DigIndy Tunnel System is a 28-mile long network of 18-foot diameter deep rock tunnels being built 250-feet beneath the city. Along with other projects in the combined sewer system and at Citizens two advanced wastewater treatment plants, the $2 billion program is Indy’s solution to reducing combined sewer overflows into area waterways by up to 97 percent, and keeping the utility in compliance with a Consent Decree with the U.S. Environmental Protection Agency.


The Problem

Combined sewers convey both storm water and wastewater (sewage) in one piping system. Historically, more than 800 communities across the United States built combined sewers once indoor plumbing became commonplace in the late 1800s.

During normal rain events with ¼-inch of rainfall or more, the combined system capacity can become overwhelmed, resulting in a mixture of storm water and wastewater overflowing into area waterways. This is referred to as a combined sewer overflow (CSO) event, which causes a threat to public health and the environment.

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The Solution

At 250-feet below ground, the DigIndy Tunnel System will store more than 250 million gallons of combined sewage during and after wet weather, and then slowly release the sewage to the Southport Advanced Wastewater Treatment Plant, which will discharge clean water back to our waterways. When the project is complete, combined sewage overflows into Indiana waterways will nearly be eliminated, and water quality will be greatly improved.

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Tunnel System Map


The Benefits

Our water and wastewater investments will have enormous benefits on the quality of life and the local economy. Cleaner rivers and streams will lead to enhanced recreational opportunities and community revitalization across Central Indiana. At the same time, Citizens system investments will create thousands of good paying jobs.

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Job Growth


Tax Revenue



Under the U.S. Environmental Protection Agency (EPA) Clean Water Act, Indianapolis and other combined sewer communities must develop plans to reduce sewer overflows to protect human health and the environment. Ignoring these problems makes it more difficult to attract new businesses, jobs and residents to our world-class city. To address CSOs, Citizens is implementing a $2 billion Long Term Control Plan that is required to be completed by 2025 under a consent decree with the EPA and the Indiana Department of Environmental Management (IDEM).

Higher wastewater rates will be necessary over the next decade to finance the more than $2 billion in investments required to ensure safe drinking water, system reliability and protection of public health and the environment.

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