In Southern Ontario, Canada, immediately east of Toronto in Durham Region, is the growing area of Markham/Pickering. This area is designated to receive more development and population in the coming years, straining the current sanitary sewer resources. To handle the upcoming growth, a trunk sewer was contracted to accommodate the additional sanitary sewer flows projected from the future growth.

The goal of this sewer project is to carry 100 percent of the 2036 design sanitary sewers flows projected from future growth. The new SEC trunk sewer is approximately 14 km in length. The sewer is to be constructed at depths of 5m to more than 40m below the ground surface.

A major challenge of this project was to ensure that the pipeline stayed within the Newmarket Till soil stratum, which is more conducive material for tunnel construction. To do so, a substantial drop in elevation of the pipeline over its length was needed. The use of an Earth Pressure Balance Machine as a tunnel boring machine allowed for different modes of operation to accommodate the changing soils conditions.

Custom Formwork Solution

Doka was able to secure this project due to their expertise in 3D engineering design and custom built formwork solutions. Strabag, the contractor, relied on Doka to meet extremely tight project deadlines and to deliver high quality custom built formwork panels ready-to-use on site.

Doka supplied the custom benching formwork for 13 ventilation shafts in total, ranging between 10 to 60m depth. The custom formwork panels allowed Strabag to pour the “U-shaped” benching at the bottom of each ventilation shaft connecting the newly drilled tunnel openings with each other.

These custom formwork panels were based on Doka’s Large Area Formwork Top 50, including wooden gussets and custom splices. Each custom formwork element was highly complex and diff erent in shape and size, but the Doka pre-assembly team of Toronto rose to the challenge and met all customer needs. Every single formwork element was hand built and assembled to the highest possible standards in the formwork industry.

Doka’s local engineering department, together with the Competence Centre in Austria, played a key role in successfully designing this challenging custom formwork solution for Strabag.

Meeting Town Requirements

The final concrete finish was also extremely important to the client. The town of Markham required the use of Zemdrain, a form liner to be installed on every formwork element prior a concrete pour. Doka’s custom formwork panels were epoxy coated during the assembly process and shipped to site ready to use. The achieved concrete finish was of high standard, comparable to Zemdrain, and was therefore accepted by the client. Doka’s custom formwork solutions and the good teamwork between Doka and Strabag made this project an overall success.