On Friday, Sept. 4, crews from the Kenny/Obayashi joint venture marked hole-though on the OSIS Augmentation and Relieve Sewer (OARS) for the City of Columbus, Ohio. The $265 million project comprises 23,300 lf 20-ft ID tunnel. Also included is the construction of three shafts, one that will be finished as a screen chamber with a screen building on top of it, one that will be finished as a pump station; and the last shaft that will pick up flow from an existing relief sewer via a new relief structure and tangential inlet structure.
The project is located within the limits of Columbus running under and adjacent to the Scioto River from Neil Ave. and Vine St. to the Jackson Pike Wastewater Treatment Plant. The tunnel is being built approximately 170 ft below ground, reducing risks associated with construction at more shallow levels. This will require special drop structures (or vertical shafts) to direct flow from existing shallow sewers to the new deep tunnel. In addition, the drop structures will dissipate energy and minimize air entry into the tunnel. The tunnel shafts are designed to handle hydraulic surges which will prevent impacts on upstream sewers.
This project is the largest capital improvement project undertaken by the City of Columbus to date.