October 18, 2014Shawinigan is a small town in the Mauricie region of the province of Quebec, Canada. Like most small North American towns, the town was established near a river in the early 1900s, in this case, for its abundant wood that traveled down the rapids to Trois-Rivières, a renowned pulp and paper hub in the province. These rapids also made Shawinigan an interesting site for powerful hydroelectric installations that once powered the entire City of Montreal.
As the industrial sector rapidly grew in the area due to the proximity of the energy, the small town slowly became a city and was granted that status in 1958, long after the first underground infrastructures were built.
More than 55 years later and after close to 100 years of quick expansion, underground infrastructure problems started appearing. City officials decided to tackle this problem by placing a bid for close to a mile of lower lateral repairs using lining as a pilot for further work.
Laterals in Shawinigan — like most cities in Quebec, with the exception of Montreal — are the property of the homeowner, down to the property line. From that line to the main sewer, it is the City’s responsibility. Since there are no cleanouts at the property line and expensive equipment was not available, laterals were inspected from inside the houses to prevent disruption for cleanout installation.
Working from existing accesses upstream has saved the City of Shawinigan a great deal of money, but has also presented some challenges.
First, this type of work has proven to be a logistic challenge for the contractors. Since everything related to the laterals was done from inside the houses, appointments with the homeowners had to be taken. This went surprisingly well, considering the City is working from private property. Workers have heard multiple times from homeowners that they preferred giving access inside the house through an existing cleanout than digging one on their front lawn. Collaboration between the two parties was an example to follow.
Since the contractor did the inspection from the homeowners’ side, their part of the pipe was inspected and cleaned for free and they were offered to line their own part of the lateral with mobilization and travel fees paid by the City. Only the material had to be covered by the homeowner.
Technical challenges were also present, such as 90-degree drops and difficult cleanout accesses. These challenges aren’t unexpected in a lining project so the contractor had these situations covered. However, the most daunting challenge was traveling. Imagine having to inspect, clean but also line more than 60 laterals in a remote location with only one team. It is a time-consuming and resource-consuming exercise.
Main line lining has the advantage of lining long sections at a time in a location that allows you to work early and late. Therefore, a whole neighborhood could be lined by a crew in just a few days. Therefore, the crew leaves for 10 to 12 days of continuous work and the project is done.
Lateral lining is an entirely different ball game: You can only clean and CCTV seven or eight lines per day as homeowners won’t allow you in their house after an eight-hour work day, and rightly so — it is private property after all. Therefore, time management and appointments are key to the success of such a project to ensure no more time is wasted. Also, considering this is a workload of more than a month, the project was not done all at once to spare the crew and the families so a small mistake could delay an install for more than a week.
This is why the contractors decided to line the pipes using an epoxy with an extreme shelf-life at an ambient temperature. Crews used a Formadrain lining system along with its proprietary Durapox resin, which has a 60-day, open-time resin. Durapox can stand mixed in a pail for more than two months, preventing a lot of material waste on problematic jobs and allowing the liners to be prepared in advance without the need of a refrigerated truck and a third crewmember. Having this flexibility made the project flow smoother, knowing that whatever delays the crew could be facing that the liner curing before the insertion was never going to be an issue — which is rather unusual for lining crews. It did have to cure a bit longer than standard steam curing epoxies as a tradeoff; however it did not take much more time than any ambient cure system. Absolutely no waste was created and no expensive shipping had to be done to get the liners to the crew. The crew could leave the shop with all the liners they needed in a pickup bed.
The project spanned from the end of April to the end of July, with crews working every other week. Of the 60 houses initially visited for CCTV inspection and cleaning, approximately 40 of them ended up being lined from the property line to the main connection and approximately 10 homeowners took the opportunity to line their own part of the lateral in the process.
Carl Marc-Aurele, P. Eng., is a chemical engineer at Formadrain Inc., which is based in Montreal, Canada.