One of the longest-running Robbins TBMs is launched for the second of five deep-level CSO tunnels in Indianapolis, USA.
The 6.2m diameter main beam machine, operated by the Shea/Kiewit Joint Venture (SKJV) on behalf of the project owner Citizens Energy Group, was launched on 20 September for excavation of the 8.5km White River Tunnel.
This is the first of four tunnels, which together run to 28km, included in the US$500 million build-only contract awarded to SKJV in June this year (2016) for TBM excavation of the second phase of the DigIndy wastewater tunnel project. The same joint venture successfully completed excavation of the project’s 12.2km-long Deep Rock Tunnel Connector (DTRC), using the same machine, in July 2014. On that drive the machine achieved world records in its size class of 6–7m including Best Daily Advance (124.9m); Best Weekly Advance (515.1m); and Best Monthly Advance (1,754m).
Once the White River Tunnel is completed the machine will go on to excavate the Lower Pogues Run, Fall Creek, and Pleasant Run Tunnels, all through a predominant geology of limestone and dolomite rock.
“It is nice to start the job with a machine that has already been proven and successful,” said Stuart Lipofsky, Project Manager for SKJV.
However the DRTC is far from being the TBM’s first job. Originally built in 1980, it has been used on New York City’s Second Avenue Subway, as well as projects in Massachusetts and Canada. Once the machine completes the DigIndy network of tunnels it will have bored more than 51km, an achievement that will make it one of the hardest working Robbins TBMs ever put into service. “The age of the machine was not a concern for us, it was a positive. We knew it could perform in harder, abrasive rock,” said Lipofsky.
The machine was launched from the 67m deep White River shaft following a refurbishment that included new motors, gearboxes, electronics, and other elements. As of the last week of September, the TBM had already advanced 300m. About 1,600m into the White River Tunnel the drive will bifurcate eastwards to bore the 2.7 km Lower Pogues Run Tunnel in front of Lucas Oil Stadium in downtown Indianapolis. The machine will then be backed up to the bifurcation point before continuing north for completion of the White River Tunnel.
As the machine advances, Robbins continuous conveyors remove muck in an extensive system that was proved highly successful during excavation of the DRTC. Much of the conveyor structure remains the same for the new tunnels, with new horizontal and conveyor belting provided. The conveyors will wind through curves as sharp as 300m in radius, as the tunnels follow the path of the White River overhead.
The SKJV has until 2021 to complete the White River and Lower Pogues Run tunnels for local owner Citizens Energy Group, and until 2024 to complete all the tunnels. The use of a single TBM for all 40km of the project was seen as a positive: “The use of one machine was more efficient for our crews,” said Dan Martz, Vice President of J.F. Shea. “The schedule allowed us to run with one TBM and we feel we can do it with one machine. It also was a less costly option than running two machines in terms of the owner funding the project.”
Once complete, the EPA-mandated deep tunnel project will reduce the amount of raw sewage overflows and clean up tributaries along the White River.