What is DigIndy?

The DigIndy Tunnel System is a 28-mile-long network of 18-foot-diameter tunnels built 250-feet beneath Indianapolis. Originating from a federal consent decree in 2006, its purpose is to protect local waterways and public health by diverting at least 95% of sewer overflows—about 5 billion gallons annually—into Citizens Energy Group’s treatment facilities. “Sewer overflows” refers to wastewater from homes and businesses in Indianapolis which historically would have spilled over into local waterways due to the original design of the sewer system. Key project benefits include cleaner rivers and streams, improved public health, associated green infrastructure, and long-term environmental sustainability.

360 Virtual Tour

Art Project

Future & Legacy

Beyond 2025, the DigIndy Tunnel System will continue to operate under a federally mandated monitoring period through 2030, ensuring it consistently diverts billions of gallons of wastewater from local waterways. This will significantly improve the health of the White River and its tributaries, making them safer for recreation and wildlife. While no new tunnels are planned, Citizens will maintain and optimize the system in perpetuity. The project also enables regional growth by improving water quality and infrastructure reliability—key factors in attracting development. DigIndy's legacy includes community-focused programs like the Citizens Art Project and environmental education partnerships, which will continue to connect residents to their waterways.

Construction

While construction on various facilities to prepare for what would eventually be the DigIndy Tunnel System began as early as 2003, the mining of the various tunnels began in 2013 with the initial Deep Rock Tunnel Connector segment. Mining continued through 2022 with associated construction to connect the near-surface and deep-rock sewer systems. Major milestones include the opening of the Deep Rock Tunnel Connector in 2017, the White River and Lower Pogues Run tunnels in 2022, and the completion of all construction in 2025. The total construction cost was approximately $2 billion, with efficiencies gained by standardizing tunnel diameters and using a single tunnel boring machine (TBM). Funding for design, construction, and ongoing maintenance came via sewer rate adjustments approved originally by the City-County Council and subsequently by the Indiana Utilities Regulatory Commission after Citizens Energy Group acquired the wastewater utility in 2011. The tunnels were mined through bedrock and designed to store and convey massive volumes of wastewater for treatment. One mile of the tunnel system holds about 10 million gallons of sewage.

Regulation & Water Treatment

The requirement for the DigIndy Tunnel System was mandated by a 2006 federal consent decree between the City of Indianapolis, the U.S. Environmental Protection Agency, and the Indiana Department of Environmental Management, requiring compliance with the Clean Water Act through a Long-Term Control Plan. This plan outlined dozens of control measures, including tunnel construction and treatment upgrades. The Belmont and Southport Advanced Wastewater Treatment Plants were expanded to handle increased capacity—Belmont’s upgrades concluded in 2012, and Southport’s in 2017.

Environmental Impact & Sustainability

A primary DigIndy project requirement was to divert at least 95% of combined sewer overflows (and at least 97% of overflows within the Fall Creek watershed), a goal now being met with the system capturing approximately 5 billion gallons annually. As of mid-2025, more than 7 billion gallons had already been diverted by portions of the systems that were operational. This ongoing diversion of wastewater dramatically reduces pollution in local waterways and aligns with long-term sustainability goals for Indianapolis. The 10 Thousand Trees initiative, launched during the construction period in partnership with Keep Indianapolis Beautiful and the Indianapolis Department of Public Works, was implemented to complement the work of the tunnel system by introducing more than 10,000 trees that will absorb increasing amounts of stormwater runoff as they mature.

Community Impact

Citizens Energy Group engaged neighborhoods throughout the DigIndy construction process via public art, education, and environmental partnerships. The DigIndy Art Project, in collaboration with Big Car Collaborative, brought local artists and residents together to tell stories about their communities and waterways—resulting in murals and public art which can now be seen in neighborhoods along the city’s waterways. DigIndy Legacy projects include continued investment in environmental education and improvements to public spaces with partners like Indy Parks; the Friends of the White River; and the Blueways Initiative at Frank’s Paddlesports Livery. By improving water quality and infrastructure, DigIndy also paves the way for private development along the riverfront.

Communications

Citizens Energy Group worked to keep the community informed regarding progress on the many facets of the DigIndy Tunnel System across a decade and a half of construction. Wide-ranging communications included information about road closures; pictures of project milestones and community projects; interactive assets (such as this Google map of the various tunnels); and educational videos explaining the need for the DigIndy project, such as the video below.