2023 Trenchless Technology Project of the Year Rehab Runner Up: Rehabilitating Twin Water Mains on the Pont de la Concorde

When the two water mains providing potable water and fire protection to Saint Helen’s and Notre Dame islands started showing signs of deterioration, the City of Montreal began looking at potential repair options.

City officials knew going into the process that whatever the method selected, it needed to be minimally invasive to the activities going on above ground.

Saint Helen’s and Notre Dame islands in Montreal are well-noted recreational areas for Montreal residents, as well as the many visitors who come to the region. Given that it is a tourist destination location, any form of construction on or around the island is a thoroughly thought-out process.

The water mains connect to St. Helen’s Island via the Pont de la Concorde (Concordia Bridge). More precisely the twin water mains are inside steel caissons that extend the length of the bridge. The pipes were installed as part of Expo 67 in 1966 and are part of the City of Montreal’s main drinking water system. The existing drinking water pipes are made of steel and concrete lining with welded joints.

The pipes have an internal diameter of 425 mm and each span approximately 700 m across the river. Given that the pipes are over 50 years old and have been subjected to harsh conditions including the cold Montreal winters, breaks began to occur on the pipes. Spot repairs were made, but it was clear that a permanent fix was needed before a catastrophic failure occurred on either line.

The City evaluated several options for the rehabilitation of the pipes. The structural repair needed to meet the fire protection needs of the sector, work within the constraints of the steel pipe and be able to be installed with limited access.

Because these are potable water pipes, the rehab materials must meet Bureau de normalization du Québec (BNQ) certification. BNQ is a standardization organization for Quebec, and the products used on this project had to meet BNQ3660-950, “Safety of Products and Materials in Contact with Drinking Water.”

Though not specifically tendered as an ultraviolet-cured project, Lévis, Québec-based Lafontaine Inc., inquired if the work could be completed using the UV CIPP method, particularly the Saertex-Liner H2O. The contractor won the project marking its first UV CIPP installation for a water main.

It’s important to note that, not only was this installation a first for Montreal, but this is the first documented use of UV CIPP for a water main in Canada.

Why This Project is Outstanding

Before this challenging installation could get under way, Lafontaine had to make sure its crews were properly equipped to complete the project. This required close coordination with Saertex MultiCom LP in Germany – where Saertex’s liners for pressure applications are manufactured.

This included several meetings with Saertex through the planning process, sending Lafontaine technicians to Germany for training and having a Saertex technician onsite for the work.

This pre-project work also included getting the process BNQ certified. Lafontaine is now the first company in Canada to be BNQ certified for UV CIPP lining in potable water mains.

For the project, Lafontaine handled digging the trenches on both ends of the bridge to tie-in the lined portion to the existing off-bridge infrastructure; its team; its work also included the installation of a bypass system for both lines over the bridge. Subcontractors were used for the pre-installation cleaning, as well as additional electrical work inside of the bridge.

Because these are the only water mains feeding potable water to the islands, Lafontaine had to build a bypass system to handle the constant flow of water. The bypass ran along the topside of the bridge and required special end connections on either side that would accommodate any of the natural expansion and contraction of the bridge as temperatures fluctuated.

One of the benefits of using the UV-cured liner vs. traditional felt is that the footprint of the installation is smaller. This was key considering the only access to the water mains were at either end of the bridge or through 700-mm diameter access points on the bridge. Those access points to the steel caissons were spaced every 25 m in the steel walls.

While the UV CIPP process made installing the liner easier, it was not without its challenges.

Because of the size and location of the access points on the bridge, Lafontaine’s crews could not carry the liner onto the bridge. As part of the bid process, the City required prospective bidders to physically visit the site and the inside of the steel caissons.

After looking at the site conditions, Lafontaine determined that the liner section needed to be pulled into the bridge using a temporary piping system they built. This system ensured that the liner would not tear as it made its way into the bridge.

In terms of their tools and curing light trains, those had to be carried onto the bridge and lowered into the access points for each section of the project. Given the project site constraints, the installation of the liners went smoothly with no issues.

Lafontaine along with team members from Saertex and UV equipment supplier Prokasro, began the installation in October 2022. Over the course of three weeks, four sections – eight total segments of liner – were installed.

All told the pre-installation work, bypassing, post-installation disinfection and return to service was completed from June to December 2022.

Owner: City of Montreal
Engineer: Marie-Pier Simard, ing., City of Montreal
Contractor: Lafontaine Inc.
Equipment and Suppliers: Saertex MultiCom LP, ProKASRO
Value of Trenchless Project (US$): $6,120,000