HomeInDepthDigIndy Project Featured in TBM Magazine

DigIndy Project Featured in TBM Magazine

Brierley served as the owner’s Third-Party Consultant to address challenging conditions

Tunnel Business Magazine DigIndy Article

Indianapolis’ $2 billion DigIndy program is mitigating CSO discharges by building large diameter tunnels to capture and store wastewater that would otherwise discharge into the environment. The six-tunnel project comprises a network of 28 miles of 18-ft inside diameter tunnels, in addition to other sewer system and treatment plant improvements. When complete, the tunnel system will store more than 250 million gallons of wastewater that will be conveyed and treated at the Southport Advanced Wastewater Treatment Plant.

Citizens Energy Group has administered the project since it acquired the water and wastewater systems in Indianapolis in 2011. Citizens Energy Group recognized opportunities to increase project delivery efficiency by restructuring how work was awarded. This included negotiations with Shea-Kiewit Joint Venture to complete all the tunneling work. Having this long-term contract enabled Shea-Kiewit JV to keep a skilled tunnel workforce. All six tunnels were mined using a refurbished 20-ft, 2-in diameter Robbins hard-rock TBM, reconfigured for the Indianapolis geology.

Brierley Associates got involved in 2017, when a section of weaker rock was encountered on the Lower Pogues Run Tunnel.  Groundwater inflow through this reach was adverse and significantly different from all other sections constructed up to that time. Brierley was engaged by Citizens Energy Group as the owner’s third-party consultant to identify and assess the conditions causing excessive water inflow and evaluate risks for the yet-to-be-constructed Fall Creek and Pleasant Run tunnels.

“Brierley assessed the geotechnical data for the Lower Pogues Run Tunnel, and used the results to evaluate the Fall Creek and Pleasant Run Tunnels, one of which we found to possess a similar ground structure,” stated Brierley’s Project Manager, Ike Isaacson. “Based on our analysis we were able to predict that groundwater conditions within these structures wouldn’t pose a significant challenge for the construction of the remaining two tunnel segments. This analysis helped Citizens Energy Group keep the project on schedule for completion by 2025.”

The project is detailed in the February 2023 issue of Tunnel Business Magazine. Click here to download the article.


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