March 18, 2014
As the United States grapples with one of the worst winters on record, extremely low temperatures and Polar Vortex activity are common during the winter months for our friends to the north.
Extreme weather conditions in Canada typically make construction projects more challenging. But infrastructure will always need to be maintained, regardless of Mother Nature’s antics.
When Ottawa-based Clean Water Works was tasked with lining several storm culverts traversing Highway 30 in the Chateauguay area of the Province of Quebec, the remote location and lack of access to utilities were far bigger challenges than the weather, despite the fact that February was hit hard by several severe winter storms, causing saturated soils and hazardous driving conditions.
The owner, the Quebec Ministry of Transportation, selected cured-in-place pipe (CIPP) lining as a solution to enhance the structural strength of the pipes while mitigating the effects of corrosion.
Most of the installations were performed in relatively remote agricultural areas, so the site/staging areas and associated means of access had to be constructed as part of the project. Sources of fuel, water and power were not readily available onsite, so the logistics of managing these resources was an important part of planning the project.
“The biggest issue by far was the lack of water access near the staging areas and the weight and mass of the liners,” said Clean Water Works project manager Nicolas Brennan. “These were very large pipes so impregnating the tube with the resin then transporting them to the site was out of the question, due to excessive weight of the tubes.”
With the culverts ranging from 36 to 96 in. in diameter and up to 492 ft in length, the largest liner alone would require 180,000 gals of water to implement a traditional water inversion and cure of the liner. “We were talking about a minimum of 36 water tanker deliveries, just for the 96-in. tube,” said Brennan.
The 96-in. tube, with a required design thickness of at least 42 mm, would have created a unit weight of more than 275 lbs per linear foot of impregnated liner. Since this excessive weight prevented the liner and tube from being transported in a resin-impregnated state, an onsite wetout facility was required to complete the installation. Due to the roadside setup of the installation equipment and the spacing of the culverts, the equipment also had to be portable, requiring disassembly and re-assembly at each subsequent inversion site.
Realizing that the use of air inversion and steam cure would eliminate the logistics issue of water transport and significantly reduce the project’s overall water consumption, the team focused on how the installations could be completed with the air inversion method, which typically had not been used on liners of this size.
“A general guideline that we follow is 60 in. and under can be inverted by air and cured by steam, but thanks to our experience with cured-in-place pipe, and the creative innovation of the professionals at Clean Water Works, we were able to come up with a viable solution,” said Inliner Technologies director Geoff Yothers.
The first consideration was to design a solution that could accommodate the air pressure and force required to invert a 96-in., 37-mm liner. After analyzing the massive amount of weight of the tube, which would have to be dragged behind the inverting face, the Clean Water Works operations management team consulted with Inliner Technologies and Liner Products, the tube manufacturer, in developing a novel two-part solution.
Using an over-the-hole wetout setup, the team developed a plan to impregnate the liner, pulling the wetout liner into the pipe rather than inverting it. They then planned to impregnate a 95-in. by 9-mm calibration tube, which would be stacked at the end of the liner.
“Once the calibration hose was completely wet out, the crew would assemble an air inverter capable of inverting the calibration hose into the liner, which had been pulled into the line, inflating it and expanding the two liners as one,” explained Yothers. “Once expanded to the wall of the existing pipe with air pressure, the air would be replaced with steam to execute the cure.”
The end result was a cured 96-in. by 46-mm cured liner without the expense, logistics and consumption of 180,000 gals of water.
Over the span of the total project, the use of air inversion and steam cure resulted in a savings of 500,000 gals of water.
“We were very pleased to be able to develop a novel solution to this unique problem, and all installations were performed without any major issues,” said Brennan. “Once again, we were able to satisfy a client by demonstrating the flexible nature of cured-in-place pipe, even with the most challenging of environmental conditions.”
Michelle Sinning a principal of Sinning Communications.