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

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

Technology Category

Actuators - Hydraulic Actuators
Sensors - Temperature Sensors

Applicable Industries

Cities & Municipalities
Mining

Applicable Functions

Logistics & Transportation
Product Research & Development

Use Cases

Smart City Operations
Time Sensitive Networking

Services

Testing & Certification
Training

About The Customer

The customer in this case is the City of Toronto, specifically Toronto Water. The city is home to the Ashbridges Bay Treatment Plant, one of Canada's largest and oldest wastewater treatment plants. The plant, which was built in 1910 and became operational in 1917, has a peak hydraulic capacity of 3,300 megaliters of wastewater per day. However, the existing outfall had insufficient capacity for discharging treated effluent into Lake Ontario and was nearing the end of its service life. The plant services about 1.6 million residents, so the upgrade was crucial to ensure an enhanced quality of life for the community, as well as any future residents as the city grows and expands.

The Challenge

The Ashbridges Bay Treatment Plant Outfall (ABTPO) project in Toronto, one of Canada’s largest and oldest wastewater treatment plants, was in dire need of an upgrade. The existing outfall, constructed in 1947, had insufficient capacity for discharging treated effluent into Lake Ontario and was nearing the end of its service life. Hatch, a team based in Canada, was tasked with the design and construction of a new tunneled outfall to send treated wastewater from the plant into the lake. The CAD$ 300 million project involved sinking a shaft adjacent to the shoreline and mining a tunnel through rock directly beneath the lakebed. The project's location, complexity, and scale presented significant challenges. Additionally, the treatment plant services about 1.6 million residents, so 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.

The Solution

Hatch realized that traditional engineering delivery methods would be insufficient for this project. They needed software that combined computer-aided design with engineering analysis. Bentley applications, which Hatch had used during the project’s initial design phase in 2015, were ideal for this next phase. Using Bentley’s OpenRoads, Hatch’s engineers created surfaces from borehole logs, including the lake’s water level and the anticipated tunnel invert. This approach enabled the prediction of geological boundary conditions below the lake to steer significant design decisions. They used MicroStation to model 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.

Operational Impact

The use of Bentley applications allowed Hatch to deliver a high-quality design to their client ahead of schedule. The software’s advanced CAD capabilities enabled them to employ one full-time and two part-time team members, reducing staff hours significantly. The 3D models were used for technical peer and constructability review workshops, ensuring that all issued for tender submissions were delivered to the client a week in advance. The project was paperless due to the use of ProjectWise’s connected data environment for sharing all documents and information, which saved significant costs. ProjectWise’s collaborative environment also ensured connectivity across time zones, improving team efficiencies and enabling Hatch to complete the detailed design on time and within budget. The new outfall is a critical element of the city’s improvements to the plant’s hydraulic capacity, and it is anticipated that the ABTPO project will help improve the city’s shoreline and beaches, as well as Lake Ontario’s water quality.

Quantitative Benefit

Reduced staff hours by 2,000 hours, resulting in CAD$ 350,000 savings.
100% of issued for tender submissions were delivered to the client a week in advance, saving CAD$ 25,000 in CAD staff hours.
Saved over CAD$ 35,000 in paper and printing costs due to the use of ProjectWise’s connected data environment for sharing all documents and information.