• Hatch

    Ashbridges Bay Treatment Plant Outfall

    Toronto, Ontario, Canada

Project Summary


Upgrading Toronto’s Largest Water Treatment Plant

Located east of downtown Toronto on the shore of Lake Ontario, the city’s Ashbridges Bay Treatment Plant, built in 1910 and operational in 1917, is one of Canada’s largest and oldest water treatment plants. However, the existing outfall had insufficient capacity for discharging treated water into the lake, as it was constructed in 1947. The outfall also did not meet current regulatory standards and was nearing the end of its service life. With team members in Canada, Australia, and the United Kingdom, Hatch was responsible for the design and construction of a new tunneled outfall that will send treated wastewater from the treatment plant into Lake Ontario. The estimated CAD$ 350 million project included sinking a shaft adjacent to the shoreline and then mining a tunnel through rock directly beneath the lakebed. The treated water would then flow by gravity from the plant through connecting conduits to the shaft and tunnel out into the lake. The location, complexity, and scale of the project all presented major challenges.

Advancing Beyond Traditional Software for Better Design, Analysis, and Communication

Hatch realized early on that they needed software that combined computer-aided design with engineering analysis to ensure the success of this project. Besides overcoming the multiple, complex challenges around the project’s construction, they also needed to minimize costs while considering the underwater soil and environmental features. Also, as the treatment plant services about 1.5 million residents, the final result needed to ensure an enhanced quality of life for the community, as well as any future residents as the city grows and expands. Coordination would be key to ensuring the successful delivery of this project; and with the team scattered throughout various offices, they would need to develop digital collaboration workflows for efficient communication.

Designing a Complex Shaft and Tunnel

Hatch was already familiar with Bentley, having used the software during this project’s initial design phase in 2015. Using Bentley’s OpenRoads, their engineers created surfaces from borehole logs, including the lake’s water level and the anticipated tunnel invert. Therefore, they were able to predict the geological boundary conditions below the lake to steer significant design decisions. With MicroStation, Hatch modeled all elements of the shaft and tunnel, allowing them to complete the tunnel rings and determine the proper rotation of each ring to help with possible connection problems. Hatch also used ProjectWise’s connected data environment so that the team could collaborate across several time zones, ensuring that the project was on time and under budget. They coordinated all CAD work, engineering analysis, and design in the platform, allowing the team to continue working on CAD drawings while PDFs were created on a separate server.

Delivering a High-quality Design that Exceeded Expectations

By using Bentley applications for this project, Hatch delivered a high-quality design to their client ahead of schedule. They designed a 3,500-meter-long tunnel with an internal diameter of 7 meters. The software’s advanced CAD capabilities allowed them to reduce staff hours by 2,000 hours, resulting in CAD$ 350,000 savings. With MicroStation 3D models used for review workshops, 100% of issued-for-tender submissions were delivered to the client a week in advance, saving CAD$ 25,000 in CAD staff hours. Also, because the project was paperless due to using ProjectWise’s connected data environment to share all documents and information, Hatch saved over CAD$ 35,000 in paper and printing costs. The new outfall is a critical element of the city’s expansion of its wastewater treatment capacity, and it is anticipated that it will help improve the city’s shoreline and beaches, as well as Lake Ontario’s water quality.

Project Playbook: MicroStation, OpenBuildings Designer, OpenRoads, ProjectWise, STAAD

  • Located along Lake Ontario, Ashbridges Bay Treatment Plant is one of Canada’s largest and oldest water treatment plants.
  • Its existing outfall was insufficient, did not meet current standards, and was nearing the end of its service life.
  • By using Bentley applications, Hatch delivered a 3,500-meter-long tunnel design to their client ahead of schedule.
  • “Bentley’s suite of software was implemented on the ABTPO project to build practical solutions that solve unique engineering challenges, to facilitate a connected and collaborative work environment, and to deliver a cost-effective and efficient project.”

    Kevin Waher Senior Project Manager Tunnels Hatch