On Aug. 29, a Robbins Crossover XRE tunnel boring machine (TBM) crossed the finish line at the Ohio Canal Interceptor Tunnel (OCIT) in Akron. The OCIT Project consists of the construction of a conveyance and storage tunnel system to control combined sewer overflows (CSOs) for several regulators in the downtown Akron area. The EPA-mandated project includes the 1.17 mile conveyance and storage tunnel, as well as drop shafts, diversion structures, consolidation sewers, and related structures.

Dubbed “Rosie” in honor of Rosie the Riveter, the Crossover XRE is 30.4 feet in diameter and was designed for the projects transitioning geology, from soil, to partial face shale, and full face shale rock. Standing for a crossover (X) between rock (R) and earth pressure balance (E), the XRE has been designed and deployed by Robbins on multiple projects that feature sections of both hard rock and soft ground in the tunnel alignment.

A crew member cleans the cutterhead of the Robbins Crossover TBM.
The Robbins Comany A crew member cleans the cutterhead of the Robbins Crossover TBM.

The machine includes a versatile cutterhead that can be configured for hard rock or soft ground. While in soft ground and mixed face conditions it operated in closed mode, but once it hit solid rock crews switched excavation to open mode. Once in full-face shale rock, advance rates reached a high of 111 feet in two 10-hour shifts. Muck removal was completed using a Robbins continuous conveyor.

“One of the most challenging aspects of this job was that we launched right into the most difficult part. We had 200 feet of soft ground, a very short reach, and then from there we went right into a mixed face for 600 ft,” says David Chastka, Project Manager for Kenny Construction, a joint venture contractor on the project with Obayashi Corp. “It took everybody we had in the industry, everybody from Robbins, to fight through that first 800 feet.”

Now that tunneling is complete, the machine will be disassembled and removed from its retrieval shaft this fall. The OCIT is the largest public improvement project in the city’s history and a significant investment in environment and infrastructure that will benefit Akron residents and businesses.