On March 5, 2015, a Robbins 20.2-ft diameter Main Beam TBM finished boring a 9,175 lf extension tunnel, known as the Eagle Creek Tunnel, for the Indianapolis Deep Tunnel System. The contractor, Shea/Kiewit (S-K) JV, had much to celebrate: “I’m proud of our world records, and most of all our men and the hard work they have done as a team, working together to accomplish a project of this size,” explained Stuart Lipofsky, Project Manager, for S-K. “We finished the first 12.5-km (41,000-ft) [of the main tunnel] almost a year ahead of schedule. The extension added time but what is remarkable is that we were still able to finish within the original contractual dates,” continued Lipofsky.
The completion of the first leg of a much larger tunnel system targets three critical CSOs that flow into the nearby White River, and will go online in 2017. The completed tunnels bring the city one step closer to achieving its consent decree with the U.S. Environmental Protection Agency (EPA), set to be achieved by 2025, to eliminate overflows into the city’s rivers.
The rebuilt Robbins hard rock TBM was first used on the 7.8-mile long main tunnel, called the Deep Rock Tunnel Connector (DRTC). The new cutterhead arrived onsite in November 2012, and the machine was launched from a 250-ft deep shaft to bore through limestone and dolomite. The TBM achieved world records in its size class of 6 to 7 m (20 to 23 ft), including “Most Feet Mined in One Day” (124.9 m/409.8 ft); “Most Feet Mined in One Week” (515.1 m/1,690 ft); and “Most Feet Mined in One Month” (1,754 m/5,755 ft).
According to Tim Shutters, Construction Supervisor for project owner Citizens Energy Group, there were two main factors for the TBM’s high performance: “The first one is the very nice cutterhead provided by Robbins. It has performed very well. [Second], rock conditions are favorable for mining operations and optimal for fast production.”
Another important element that helped the record pace was, as Lipofsky put it, “one of the most complex continuous conveyor systems in North American tunneling construction.” The custom-built Robbins system, consisting of 82,000 ft of belt, included horizontal and vertical conveyors for efficient muck removal. The system was the first built by Robbins to go through sharp curves: “The belt is going through two 90-degree curves in opposite directions and S-curves in other places. It’s very unusual and amazing to see a belt system perform as well as this one did,” Lipofsky said.
Once complete, the deep tunnel project will reduce the amount of raw sewage overflows and clean up tributaries along the White River. Shutters describes the environmental benefits the project will provide the Indianapolis community: “I’ve lived in Indy all of my life, and the White River has never been a focal point for the city as there is a lot of pollution. I really think that once it has been cleaned up, people will want to visit, they will swim and fish, and property values along that body of water will go up. Being able to finally utilize the river is key for us.”
After the early completion of the Eagle Creek Tunnel, the project will be moving into its next two tunneling phases. The White River Deep Tunnel will continue 5.3 miles north of the completed DRTC and pump station. The Lower Pogues Run Deep Tunnel will split off 1.7 miles from the White River Deep Tunnel heading east. Two additional tunnels, including Fall Creek and Pleasant Run, are anticipated to be built in 2020, and the project (17miles of tunnels in total) is expected to be fully completed by the end of 2025.