Citizens Energy Celebrates Completion of DigIndy Program

On Oct. 9, Citizens Energy Group and its partners celebrated the completion of the DigIndy project, an underground tunnel system in Indianapolis, Indiana. The project aims to divert billions of gallons of wastewater annually from Hoosier rivers and streams, and fulfills plans to address nearly all combined sewer overflows in Central Indiana.

“DigIndy stands as one of the most ambitious infrastructure projects in Indiana’s environmental history,” said Clint Woods, commissioner of the Indiana Department of Environmental Management. “Its completion marks a major milestone in our long-term, best-in-the-country efforts to protect Hoosier waterways and safeguard public health.”

DigIndy, comprising 28 miles of tunnels, was completed after a 14-year construction process and will bolster Indiana’s already significant progress in reducing sewage overflow events in Indiana’s waterways. A combined sewage overflow (CSO) is a utility wastewater discharge that occurs when rainfall or snowmelt exceeds the system’s capacity, causing it to be overwhelmed and discharge untreated sewage into rivers and streams, potentially posing a threat to human health and the environment. In 2008, more than 35 billion gallons of untreated sewage were released from CSO events across Indiana. By 2024, that figure dropped to 10.2 billion gallons, a 71.3% reduction.

The DigIndy program includes:

• Deep Rock Tunnel Connector: 39,362 lf of tunnel; 3 CSO connecting structures/deaeration chambers and adits.
• Eagle Creek Tunnel: 9,175 lf of tunnel (added as a change order to the Deep Rock Tunnel Connector project); one CSO connecting structure/plunge drop.
• White River Tunnel: 30,628 lf of tunnel; 2 bifurcations; 7 CSO connecting structures/deaeration chambers and adits.
• Lower Pogues Run Tunnel: 10,182 ft, bifurcates from White River Tunnel; 2 CSO connecting structures/deaeration chambers and adits.
• Fall Creek Tunnel: 20,244 lf of tunnel; 10 CSO connecting structures/deaeration chambers and adits.
• Pleasant Run Tunnel: 41,472 lf of tunnel; eight CSO connecting structures/deaeration chambers and adits.

All tunnels were built using the same 20-ft, 2-in. OD refurbished Robbins hard-rock tunnel boring machine, originally manufactured in 1980, reconfigured for the Indianapolis geology. The tunnels are lined using Everest forms with a 1-ft thick cast-in-place concrete lining for a finished diameter of 18 ft.

Project Team

Owner: Citizens Energy Group
Tunnel Contractor: Shea–Kiewit
Designers: AECOM (Deep Rock Tunnel Connector, Eagle Creek Tunnel); Black & Veatch (Lower Pogues Run Tunnel, White River Tunnel, Fall Creek Tunnel, Pleasant Run Tunnel)
Construction Manager: AECOM
Owner’s Third-Party Consultant: Brierley Associates
TBM Manufacturer: Robbins
Combined Consolidation Sewer Contractors: F.A. Wilhelm, Bowen Engineering Corp.