Toronto Ashbridges Bay Treatment Plant Outfall – Special Contract Provisions for Large Tunnelling Projects

摘要

The Toronto Ashbridges Bay Treatment Plant Outfall (ABTPO) project includes detailed design and construction management services for a new tunnelled outfall that will convey treated effluent from the Ashbridges Bay Treatment Plant (ABTP) into Lake Ontario. Once the new outfall is constructed, and additional ABTP improvements are complete, flow from the plant will be directed to the new outfall. The new outfall will convey up to 3,923 MLD (1036 MGD). Outfall components include an onshore shaft, approximately 85 m deep with an outer diameter of 16 m (52 ft); a 3,500 m (2.1 mile) long tunnel, with a 7 m (23 ft) internal diameter tunnelled through rock beneath the lakebed and risers constructed in line with the tunnel along the diffuser length extending from the tunnel horizon to the lakebed.