A joint venture of Kenny/Obayashi received notice to proceed on the phase 1 September 2010. The USD 264.5M contract included the entire 20ft-diameter tunnel; Shafts 1, 2 and 6; OSIS Relief Structure at Shaft 6, Screen Building over Shaft 2, West Gate Chamber. Phase 2 began in August 2011 and involves construction of three more shafts, a pump station, pump electrical building, river overflow structure and other infrastructure. The overall project is currently scheduled to be completed in late summer 2017.
The OARS tunnel will include three relief structures that will divert wet weather combined sewer flow from the OSIS to the OARS tunnel. The OARS project will control all of the relief structures where the sewers currently overflow to the river in the downtown riverfront area.
The tunnel is being built approximately 170ft below ground, reducing risks associated with construction at more shallow levels.
