Case Study: Hatch achieves on-time, on-budget delivery of a 3,500-meter Lake Ontario tunnel outfall with Bentley

Hatch Designs a Complex 3,500-meter-long Tunnel Under Lake Ontario to Replace Aging Outfall

Hatch was hired to design a new 3,500‑meter tunneled outfall for the City of Toronto’s Ashbridges Bay Treatment Plant to replace an aging 1947 outfall and increase hydraulic capacity. The project required sinking a deep shoreline shaft, mining a long tunnel beneath Lake Ontario, installing 50 diffuser risers, and managing complex geotechnical, environmental and coordination challenges across dispersed teams. To address these demands, Hatch used Bentley applications, including MicroStation, OpenRoads, ProjectWise, OpenBuildings and STAAD.

Using Bentley’s suite, Hatch created borehole‑derived surfaces, detailed 3D tunnel and shaft models, and a connected data environment for cross‑office collaboration, which optimized shaft depth, excavation methods and constructability reviews. Bentley’s tools helped Hatch deliver the 3,500‑m design ahead of schedule: 100% of issued‑for‑tender submissions were delivered a week early (saving CAD$25,000), staff hours were reduced by about 2,000 with roughly CAD$350,000 in labor savings plus CAD$35,000 in printing savings, and the detailed design was completed on time and within budget.

Hatch

Kevin Waher

Senior Project Manager Tunnels