Like many large North American cities, Montreal’s sanitary sewer systems were first established in the mid-1800s, with the bulk of the infrastructure built out in the decades following the Great Depression. Although the average age of Montreal’s water and wastewater infrastructure is 57 years, some of the sewer pipes date back as far as 1840.
In recent years, the City has been plagued by frequent water main breaks – which sometimes cause large sinkholes that disrupt traffic and utility service to the surrounding areas. In 2009, the City’s Service de l’Eau department recorded 29 water main breaks per 100 km, a rate that was double or even triple other major cities in Canada. Just this past August, a 26-ft x 16-ft sinkhole along Sainte Catherine Street – the City’s primary commercial artery – swallowed a backhoe, forcing a complete closure of the busy roadway for three weeks while the City worked to complete repairs.
According to Wilson Wong, ing. jr., project manager for Service de l’Eau, these water main breaks can at times have a significant impact on the area’s sewer infrastructure – after a water main failure, the soil surrounding nearby sewer pipes is destabilized, allowing the soil particles to migrate through any leaks in the sewer pipe and eventually lead to subsurface voids in the soil. Additionally, large amounts of clean water can infiltrate into the sewers – resulting in significant increases in volume and process costs at the water treatment facilities.
As a result, the City of Montreal is slating more than $1 billion to replace and rehabilitate its water and sewer infrastructure. “As of June 2013, over 80 percent of our 4,300 km (2,672 miles) of small diameter sewer lines have been inspected,” said Wong. “Of this amount, 473 km (294 miles) are in an advanced or highly advanced state of degradation.”
Between 2006 and 2012, the City’s Service de l’Eau department replaced or renewed more than 430,000 ft of sewer pipe, with approximately 50 percent of that work completed through rehabilitation methods such as the Inliner Technologies Cured-in-Place Pipe renewal system.
Ottawa-based Clean Water Works, an Inliner CIPP-certified installer, finished two of these contracts for Service de l’Eau earlier this year and subsequently began a third contract in July.
• The 2012 East Sector project encompassed 38,057 ft of pipe under a contract of $11.6 million.
• The 2012 West Sector project encompassed 35,104 ft of pipe, with a value of $11.1 million.
• The third contract, which began in July, is for 56,000 ft of pipe, with a value of $13.7 million.
Approximately 70 percent of the pipe being renewed by CWW is 24-in. x 36-in. egg-shaped brick sewer, with the remaining 30 percent consisting of concrete round pipe ranging from 12 to 72 in. diameter.
CIPP technology allows for the rehabilitation of damaged underground wastewater and storm sewer pipes without excavation. The process minimizes disruption to the public by reducing noise, traffic disturbance and road damage – and can be done within a far shorter timeframe, and usually for less cost than replacement. With Inliner CIPP, a felt tube saturated with resin, is inserted into the pipe via inversion or the pulled-in-placed method of installation. Hot water or steam is then circulated through the installed tube to cure the resin. This creates a new “pipe inside a pipe” and is designed to provide the conduit with a minimum 50-year service life.
For these projects, CWW uses air inversion and steam curing for small- and medium-diameter pipes (up to 41 in.) and water inversion and water curing for the larger diameter pipes. All lines are inspected via CCTV, cleaned and prepped prior to proceeding with the lining. In order to locate live service connections needing reinstatement after lining, lag-bolts are installed over live connections during the preparation process. The sewers are flushed and reamed of all debris and intrusions. Many concrete spot repairs are completed from the interior to fill voids prior to lining. The majority of these repairs are completed manually by confined-space man-entry crews.
The combined sewer pipes are located under arterial streets through major intersections in downtown Montreal, an area that is home to many hotels, bars and restaurants.
“There is a tremendous amount of coordination required with the community to ensure that disruptions are kept to a minimum,” said CWW project manager Nicolas Brennan. “We meet with all the local businesses to make sure we properly understand their needs and prepare case-specific bypass solutions – which in some cases includes using large submersible pumps and pumper trucks to transfer the effluent downstream or into vacuum tankers to be hauled to CWW’s treatment plant.”
CWW also prepares extensive traffic control plans, which are subject to City approval and obtains separate road occupation permits from more than a dozen city boroughs. “Working in urban settings such as these Montreal locations, each pipeline that you access services several businesses and each of these businesses service many patrons,” said Brennan. “The end result is that hundreds of residents and business owners are affected if the work does not go as planned.”
Rehabilitation of one 2,600-ft segment of pipe along Avenue du Parc was canceled twice over a two-year period due to intense opposition from the local business community, which was concerned about closures and disruptions. “Renewing the pipes in this area had been a political hot-button issue, but the pipe had major infiltration so it couldn’t be delayed any longer,” said CWW project manager Kyle Peori. “The mayor and representatives from several boroughs got involved – and after eight or nine meetings – we were able to agree on a plan for renewing the pipes with minimal disruption to the businesses.”
Internal coordination is carefully orchestrated, as well, with the crews installing an average of two liners per day. The tubes are wet out at CWW’s facility in Ottawa at night, then transported to the jobsite to begin the installation process in the morning. A night crew re-instates the service connections, then the process starts all over again the next day. Many busy streets require the lining to be performed at night, as with the Avenue du Parc segment.
“When you combine the liner transport, diversion pumping, pipe cleaning, traffic control and host of other details that need to take place, you really need to have your schedule nailed down and be communicating well across the board,” said CWW rehabilitation manager Sandy Campbell. “Once the project planning for each liner had been established and each member of the crew is made aware of the specific details, the hard part of the project is completed and we are just left to do what we do best – install liners in the ground.” After the sinkhole opened up in Sainte Catherine Street in August, CWW was charged with lining the major collection pipeline that ran perpendicular to the sewer that had collapsed. The active construction site, which was undergoing repairs from the sinkhole incident, meant access would be difficult – but it was critical to bolster the strength of the collector before it broke under the stress of the subsurface soil voids in the sinkhole. To minimize any interference with the sinkhole reparations, the CWW project management team decided to reverse the direction of the installation – staging the inversion, heating and supporting equipment and vehicles at the downstream end of the pipeline.
CWW had to quickly mobilize its teams and reschedule other coinciding projects, in both the wetout and installation divisions to accommodate the time constraints of this emergency lining effort. If the logistics of this emergency project weren’t complicated enough, the collector line was continuing to convey very heavy flows, which had to be diverted from the sinkhole area through a busy part of the city and back into the collector line downstream from the equipment staging area.
The three lining contracts also include lining of catch basin leads connected to the mainline sewers. In cases where the leads cannot be rehabilitated due to major defects such as major offset joints, sumps or breaks, the drains are excavated and replaced.
Despite the enormous complexity, these comprehensive lining projects are finishing on time and on budget. CWW credits the Inliner network as an important tool for the company’s success. “The ongoing collaboration within the Inliner network and focus on new processes and tools is critical to keeping us at the forefront of the industry,” said Brennan.
Geoff Yothers is director of Inliner Technologies LLC.
