By Gina Harris
With construction causing traffic snarls on Elgin Street, major repairs to the watermain on Gloucester Street come at a bad time.
But the region will limit the disruption to traffic and businesses by finding a new use for some old technology.
Instead of removing the 82-year-old cast iron pipe which supplies water from Bronson Avenue to the Rideau River, and from the Queensway north to the Ottawa River, a new polyethylene pipe will be inserted inside the old casing.
The process, known as slip lining, is new to the water industry, although it has been used elsewhere in Europe and North America in smaller sizes, and in this size in a rural environment.
“Yeah, we’re breaking new ground,” says project manager Mike Willmets. “I’ve had people call from Quebec, and many from the Toronto area, and we have a delegation of people coming from Halifax to witness portions of the installation.”
He says he believes this is the first time a pipe this large has been used for a watermain slip lining project in a high traffic, downtown area.
In October, a robotic camera was sent through the pipe to determine the condition of the watermain. The amount of deterioration in the pipe led to the immediate scheduling of the rehabilitation project.
“It’s not the sort of pipe you want to fool around with,” says Willmets. “If you can imagine a garden hose 36 inches in diameter flowing at 60 psi (pounds per square inch), that’s a tremendous amount of water. When it does break, the damage is enormous.”
An external consultant was hired to design the project.
“There was more technical expertise required because it is a new application and the region wanted to ensure that all avenues had been looked at to ensure it was a safe, economical and constructable design,” says Derek Potvin, who headed the design team. He says one of the biggest challenges the team faced was physically assembling the pipes while minimizing impact on traffic.
“When you assemble a long pipe in a downtown urban environment, you’ve got to give close consideration as to how this is going to be inserted into the pipe so that you don’t end up blocking the critical north-south links into the downtown core,” says Potvin.
Twelve to 14 pits will be dug at several locations over the 1.3 kilometre construction site. After cleaning the old pipe, a hose, similar to a large garden hose, will be inserted into a pit and pulled through the pipe a block at a time.
“To pull the pipe we need a big winch. It’s a diesel winch. And it’s noisy,” says Willmets.
“It’s brutally heavy, this pipe, and it’s strung out like a giant piece of spaghetti.”
The pipe comes in sections which are fused together using a giant hotplate. New lengths are added as the winch keeps pulling. High-density cement injected between the pipes will hold the new pipe in place.
This approach saves digging up the entire road.
“Every time you dig a hole it’s just nothing but dollar signs,” says Willmets. The project will cost $1.7 million but it will save the region approximately $1 million because of the new construction methods.
Using trenchless technology means the project, which began at the end of March, will be completed by mid-June. The work will be done one block at a time, beginning at Bronson Avenue.
“By the time people get wound up [over the noise and inconvenience] we’ll be finished, and move on to the next block,” says Willmets.
The shorter construction time and minimal excavations mean fewer traffic delays, fuel expenses, and mud run-off getting into the water.
The innovative project has caught the attention of the National Research Council Canada, which is helping fund a three-year study to measure the stresses and strain responses of the pipe.
“What we did was to assess how this pipe will interact with the host pipe, and how long this pipe will last,” says Jack Zhao, a research officer at the Institute for Research in Construction.
According to Zhao, data from the study will help both municipal engineers and researchers evaluate the performance of the pipeline in a real situation.