Each year, more-and-more system owners are turning to trenchless technologies to address their underground infrastructure needs.
From installing new infrastructure, undergrounding existing aerial infrastructure or rehabilitating what is already underground, trenchless offers a less disruptive construction option to get these critical projects done. Also falling under the auspices of trenchless work include the locating and mapping, inspection and assessment and cleaning of these vast underground networks.
It appears Canada, and other countries across the globe, have been hit with a myriad of challenges in the last three years. The pandemic, labor shortages, supply chain challenges, price increases and record inflation have all impacted how, and how much, work a municipality can get done.
To help gauge the strength of the trenchless industry across Canada, look at the challenges being faced by system owners and to get an idea of where things might be headed, Trenchless Technology Canada presents its annual municipal roundtable.
Participating in this year’s roundtable are Canada’s capital city of Ottawa and two regional municipalities — Wood Buffalo in northeastern Alberta, which includes Fort McMurray, and York Region in southern Ontario, a part of the Greater Toronto and Hamilton Area.
Responding to our questions are:
Briefly describe your system and its condition. What is unique about your system and/or the way it operates?
Duclos: The City of Ottawa has approximately 6,200 km of separated, combined and partially separated sewer pipe networks, over 50 pumping stations as well as a sewage treatment plant. The city has piped infrastructure that is 150 years old and is still in service. The oldest infrastructure is in areas with the heaviest utility congestion, which can make renewal challenging. The city manages the performance of the combined and partially separated areas by utilizing modulating gates and a large central sewage storage tunnel. This enables maximizing the capacity of the system and minimizing potential sewage overflows and basement flooding.
Rabeau: The Regional Municipality of York is a two-tier municipality where the Region provides bulk water supply to nine local cities and towns for distribution and collects and conveys wastewater from local collection systems for treatment before discharging into receiving water bodies. York Region owns and operates approximately 300 km of trunk sewer systems and approximately 300 km of pressurized systems, including both sewage forcemains and watermains across a total area of 1,776 sq km. A large part of the Region’s trunk sewer, forcemain and watermain systems was constructed by the Ontario government in the early 1980s and transferred to the Region in the late 1990s. The system is also unique in that the Region is the only municipality of its size in the Greater Toronto and Hamilton Area (GTHA) without direct access to Lake Ontario. This lack of access to main water bodies required developing partnerships with Peel Region and the City of Toronto for drinking water, and Peel and Durham Regions for wastewater treatment. Notwithstanding these arrangements, the Region’s Water and Wastewater Master Plan updates continue to identify the need for new infrastructure to provide water and wastewater service for ongoing population growth.
Ross: The Fort McMurray Urban area has a combination of gravity sewers and force mains convey the sanitary waste across the community. All areas within the Urban service area send the untreated sewage to the wastewater treatment plant located 5km north of the downtown core. The infrastructure age ranges from vintage 1960s pipes to newly constructed infrastructure under our various urban infrastructure rehabilitation program. Most of the storm water in the urban area is managed via gravity sewers that drain to adjacent tributaries and watersheds. Most of the residential zones built prior to 2000s does not have storm ponds to help attenuate flows or address stormwater quality before discharging to the tributaries. Stormwater quality in these areas is addressed via storm treatment systems.
What are the main problems you are facing with your system?
Rabeau: While older infrastructure is mainly located adjacent to environmentally sensitive areas such as valleys and water courses, newer infrastructure is mainly located within the Region’s existing road corridors. Rehabilitation or new construction of this infrastructure can be challenging to overcome with stringent environmental constraints and minimizing impacts to communities such as traffic delays, noise and vibration. Additionally, areas with older infrastructure often require significant bypass pumping to facilitate rehabilitation and new construction, while maintaining the requisite level of service to customers. A significant portion of York Region’s wastewater infrastructure is concrete pipe (of varying manufacturing methods). Older concrete pipe (that has not been lined or manufactured with specific additives), is very susceptible to microbially induced corrosion, propagated by the liberation of H2S gas which can eat away at the concrete pipe walls. This is where our lining/rehabilitation programs come into play to ensure that we are mitigating/eliminating the impact of H2S.
Ross: Typical issues that we see with our underground systems include aging infrastructure within our residential areas, undersized and overwhelmed sewer pipes during high intensity rainfall events, undersized water distribution systems in our residential areas, pressure related issues when there are large differences in elevation across a pressure zone.
Duclos: The city has a large inventory of pipes with a broad range of conditions, thus requiring a significant level of effort in data management. The network routinely performs as expected day to day and week to week, and rapid development of new neighborhoods puts a strain on existing systems, including pump stations and collector pipes. Recent emergency flooding events have identified key improvements in areas adjacent to the Ottawa River. Climate change is also an emerging consideration in the city’s asset management plans and policies.
What specific trenchless technologies do you use?
Duclos: Ottawa chooses the most cost-effective method for renewal of its piped infrastructure; often choosing integrated renewal, where all assets within a road segment are replaced under a single project to minimize disruption. To replace older sections of piping in heavily populated and congested areas of the city, in-place trenchless rehabilitation is often the option chosen. Utilizing trenchless technologies minimizes the effort for significant coordination and lessens the disturbance disruption on businesses and residents. Some of these technologies include:
- An extensive cured-in-place pipe (CIPP) program as it is a cost-effective way to extend the useful life of piped infrastructure. CIPP rehabilitation is the most common renewal technique used at the city for small to medium size pipes.
- Lining or sliplining with different materials such as Corrugated Steel Pipe, panel-liner, shotcrete, fiberglass reinforced pipe systems, high-density polyethylene, PVC for large diameter pipes is often selected for renewal of larger diameter pipes.
- Jack and bore, directional drilling (watermains and forcemains), pipe ramming for replacement or new pipes may be selected based on site specific conditions and requirements. Trenchless tunneling methods were selected for the largest infrastructure projects such as the Central Sewage Storage Tunnel and the new Light Rail Transit tunnel under downtown Ottawa.
Rabeau: The Region continues to explore opportunities for using trenchless technologies for both rehabilitation and new construction projects. Sprayed-in-place pipe (SIPP), sliplining and CIPP have all been reviewed and selected for respective trunk sewer rehabilitation projects. Specifically, the Region has used geopolymer spray liner (for SIPP), centrifugally cast fiberglass-reinforced polymer mortar pipe (HOBAS) for sliplining and multiple incarnations of CIPP liner. For new trenchless installations, earth pressure balance machines (EPBM), microtunnelling, jack and bore and horizontal directional drilling (HDD) are commonly used. Given each project is unique in objectives and challenges, a thorough engineering evaluation of feasible construction technologies is required for recommending any construction technology.
Ross: The RMWB uses a wide variety of trenchless technologies across their capital projects. Technologies that I am aware of being used include HDD, auger boring, pipe bursting, CIPP, direct pipe, microtunnelling just to name a few.
How has your use of trenchless technologies changed?
Rabeau: Trenchless technologies have become increasingly more attractive and thus more widely used by the Region. The increased emphasis on managing environmental constraints, maintaining traffic flow, minimizing surface disruption and restoration, and maneuvering around existing underground utilities have made trenchless methods be top of mind for our projects, whether for rehabilitation or new infrastructure.
Duclos: The use of trenchless technology has grown and evolved with product advances and development, and as the city broadens its experience with these technologies. Initial use of CIPP in residential applications resulted in infiltration of odours to nearby residences and businesses. In response, the City of Ottawa has developed a risk-based approach which limits the use of high styrene-based polyester resins within heavily populated areas. The use of low VOC and UV-cured CIPP liners has also increased for many projects due to the environmental benefits and increased affordability. Over the past few years, The City has seen stronger competition between trenchless technology companies, which has driven even more innovative and cost-effective approaches. The level of service from trenchless companies has also improved, partly in response to more stringent requirements from owners such as the City of Ottawa.
Ross: Where we have been installing new large diameter trunk sewers to meet our infrastructure needs, we have begun to adopt more accurate guided boring methodologies such as microtunnelling and pilot tube guided boring. We rely heavily on our professional consultant’s expertise when selecting the most appropriate trenchless technology to meet our infrastructure installation and rehabilitation needs.
What impact, if any, have supply chain issues and cost increases had on your projects?
Rabeau: The Region is facing construction cost escalation and supply chain issues in most of our construction projects, especially with suppliers in the U.S.
Ross: Cost escalations due to the recent inflation in Canada has certainly driven cost up, sometimes by as much as 250 per cent depending on the project scope. Understanding that infrastructure improvements are needed to keep up with the growing demand of rehabilitating our aging infrastructure, the critical projects have still been moving ahead, while we have seen some of our more “want” type projects (park space improvement) being shelved.
Duclos: Supply chain issues and cost increases have impacted many projects. The increased demand and delivery times for low-VOC resins has resulted in schedule and cost impacts on some lining projects. The increased use of UV-cured liners as a substitute for low VOC liners on City projects has increased our supplier base and has helped offset some of these issues. This approach aligns with the overall response the City has adapted due to supply chain issues and cost increases across all types of infrastructure projects. Modifying project schedules, considering alternative products, and collaborating with the construction industry partners has helped accommodate these pressures.
How have you worked with contractors and suppliers to best navigate these hurdles?
Duclos: The City proactively monitors market conditions, and as a result, project estimates have been adjusted based on recent design and construction costs. While the pricing for CIPP has increased, it remains a preferred and cost-effective solution for many pipe rehabilitation projects. We continue to have regular liaison meetings with industry associations to ensure we stay informed of current pressures in the market. Considering all infrastructure projects, we have extended project schedules due to longer delivery times. We have also pre-purchased long-lead time equipment in advance and have considered product substitutions. Collaboration with contractors, suppliers and industry associations has been key to adapting to market conditions.
Rabeau: The Region considers supply chain issues in project planning and scheduling and may incorporate cost escalation provisions in individual tenders on a case-by-case basis to share the cost risk with contractors.
Ross: I personally had to navigate this issue yet. I would say that we take our engineering baseline cost estimates and apply a 30 per cent cost increase to the total anticipated project price to have a ballpark estimate of the anticipated project cost. While the market is still in a state of constant volatility, there is not much that can be done to plan around the pricing and supply chain issues. We have begun reviewing the option of purchasing materials ahead of time where we are aware that there may be long lead times. This helps to accelerate or at least keep the project on schedule while we work to select our contractors.
When it comes to trenchless projects, what other challenges are you facing?
Rabeau: One significant challenge is the availability of qualified contractors to perform trenchless work for both rehabilitation and new construction projects. This challenge has become apparent when investigating newer or less frequently used technologies such as SIPP or Spiral Wound pipe. Another technical challenge is providing adequate bypass systems for the Region’s large diameter infrastructure. Our larger systems tend to convey significant volumes of wastewater. Designing, constructing and maintaining adequate bypass systems can be challenging from a technical standpoint (in terms of location and staging areas) as well as a fiscal standpoint.
Duclos: Some challenges facing trenchless projects include odour concerns associated with (styrene-based) polyester resins. Ground conditions (variable rock elevations/ Leda clay/ high groundwater table) often create difficulty for tunnelling installations. Multiple public property owners (municipal/provincial/federal) can make project coordination challenging. And a lack of competition for medium-large pipe installation.
Ross: Contractor availability is one thing that I am concerned with currently. Understanding that the construction industry seems to be experiencing a labour shortage, we are aware that project schedules should expect to be impacted when contractors are able to meet the project needs.
Do you have any final thoughts?
Duclos: The City of Ottawa has a strong track record in the application of various trenchless technologies and is always looking to adopt these or alternative technologies, where it is considered advantageous to do so. The City is also undertaking a pilot program to identify new and emerging products and technologies, as well as reviewing innovative ways to monitor performance. This pilot project will allow us to better understand new products and technologies prior to adopting them.
Ross: Trenchless technologies in construction allow municipalities to construct and repair critical pieces of infrastructure while having far less impact on residents than traditional methodologies. Whenever possible, it’s always worthwhile to discuss trenchless options with industry experts to understand what benefits your projects can get from using trenchless methods. It has been a goal of mine to better understand the different trenchless technologies available in the industry so that I can be a better project manager and municipal engineer. Having a better understanding of the applicable applications, pipe materials that can be used among the different methods, and general limitations of each method, would help any engineer and project manager when deciding whether a trenchless technology may be right for your project.