The integrity and performance of water and wastewater buried pipelines are growing issues across Canada.
Some municipal pipelines have been around for more than 100 years and, like every man-made infrastructure, have begun to wear out. As pipelines fail to meet regulatory requirements and performance standards, municipalities need to rehabilitate or replace them.
According to the 2016 Canadian Infrastructure Report Card, the total combined linear asset (i.e., distribution and transmission pipes) replacement value of potable water, wastewater, and stormwater is approximately $204 billion. Many municipalities and water utilities lack funds to rehabilitate or replace pipelines that are in poor condition. The current renovation/renewal rate is not enough, which means this infrastructure deficit will keep on growing.
Over the past two decades, innovative trenchless construction methods have been developed to repair, renew and replace pipelines, without the need for continuous excavations. These technologies not only provide direct cost-savings but also have lower social and environmental costs. Trenchless pipe rehabilitation techniques such as cured-in-place pipe, sprayed-in-place pipe, and slip lining, build new pipe using existing pipe as a form.
Utilizing trenchless rehabilitation techniques that reduce the construction footprint can have a huge impact on social, environmental and capital costs. For example, the City of Winnipeg has saved considerably on gravity pipeline renovation, by shifting from “cut and fill” replacement to trenchless lining techniques.
A study conducted in 2008 compared the costs of the open-cut method to pipe-bursting, which is an online pipeline replacement technique. It concluded that trenchless pipe bursting is less expensive than the open-cut method by about $4.70 per foot per inch of diameter. According to a 2005 study, restoration of existing surfaces and utilities, which were removed or damaged during trench excavation, equates to approximately 70% of the budget on open-cut projects.
By going trenchless, there is the potential to save millions of dollars. When compared to other technologies, savings of $130 million were made by Winnipeg from 1997 to 2012 by using cured-in-place-pipe for 145 km of sewer rehabilitation. The City can save a further $390 million when it rehabilitates another 433 km of its sewer infrastructure.
Pipeline rehabilitation and replacement decisions should consider direct, social and environmental costs. According to the 2013 Municipal Infrastructure Survey, approximately 71% of the respondents considered trenchless technologies to be cost-effective and efficient methods for installation and rehabilitation of deep pipelines and pipelines crossing roads, railway tracks, rivers, and other inaccessible and environmentally sensitive areas.
“By using trenchless techniques, municipalities can stretch their limited capital budgets and can do more pipeline rehabilitation with less money,” says Jonathan Pearce, past chair of the Centre for Advancement of Trenchless Technologies.