Edmonton Showcases Trenchless Technology
This Canadian City is a strong proponent of new cutting-edge technologies that will benefit its underground infrastructure
By Sharon M. Bueno Oct 08, 2013
Saying that the City of Edmonton is the trenchless technology capital of North America is not that much of a stretch and within some circles it is perhaps a definitive pronouncement. You just won’t hear it uttered by anyone (officially) within the City’s respected Drainage Services Design and Construction group, despite hearing them tick off their list of past and current trenchless projects.
A modest group indeed, but they realize the imprint trenchless technology has left on the City’s underground infrastructure and how vital it is to its continued well-being.
This Canadian city — known as a prairie city — in the province of Alberta boasts a population of more than 850,000 in the city proper and 1.2 million in the surrounding area. The sewer system has flourished through the use of inventive, innovative and cutting-edge technologies, dating all the way back to the early 1900s when the use of hand tunneling was first recommended to city officials as a way to construct the sewers for a small yet expanding city.
Tunneling served as the method for constructing Edmonton’s first sewers, built deep beneath the ground. As the use of tunneling and the city itself grew, officials turned to a new generation of construction technologies to meet its underground infrastructure needs: trenchless technology. Large diameter tunneling began in earnest during the 1950s and modern trenchless methods have been employed since the 1980s. You name it — cured-in-place pipe (CIPP), pipe ramming, pipe bursting, pilot tube microtunneling, grouting, horizontal directional drilling, tunneling — and Edmonton uses it today or at minimum has given it a true test to address its sewer system rehabilitation and new construction needs.
“From those early years of tunneling came an appreciation that we can do a whole lot of work without disrupting the ground or disrupting society and our customers,” says Drainage Services branch manager Chris Ward, who has worked for Drainage Services since 1993. “As new technologies came along, we liked to explore them, apply them and see where they could go. Not all of them have been successful for us. Where they have been successful, we need to continue to pursue them. The cost of social disruption is significant.”
Edmonton’s sewers are not unlike any other large cities’— they are feeling their age and require specific attention to extend their lifespan. The average age of the sewer lines is just 50 years old, even though a large portion of the system itself is more than a century old. The City pours in more than $40 million a year on the rehabilitation of the sewer network to address ongoing capacity issues, as well as aging and physical deterioration. Trenchless technology has been critical to the success of its work.
As prolific as Edmonton has become in its use of trenchless applications, it also adds this wrinkle to its toolbox: the City does the majority of its trenchless work in-house and has served as a primary or sub-contractor to outside construction firms and private developers, mainly on tunneling projects. This bit of work — such as on past tunneling projects in Calgary — demonstrates its expertise in carrying out trenchless methods.
Edmonton is definitely a city other North American municipalities can look to for how to expertly and smartly use trenchless technology as a means to keeping their underground infrastructure operating smoothly and efficiently in the 21st century.
It just may be the trenchless capital of North America.
Incorporated as a town in 1892 and a city in 1904, Edmonton is the capital city of Alberta and offers an expansive river valley, high-quality educational institutions and is the hub of government. The economy of Edmonton is driven by the oil patch, making its makeup similar those cities in the oil-rich state of Texas.
The City of Edmonton Drainage Services Design and Construction (DDC) group provides underground sewer infrastructure design and construction services and is recognized in North America for its expertise in the applications of trenchless technology and tunneling. In fact, the group serves as the primary or sub-contractor to construction firms and private developers on projects other than the City’s, providing project and contract management services to utility companies, other municipalities and contractors.
The DDC oversees Edmonton’s 5,500 km of storm sewer, sanitary sewer and combined sewer network — 2,365 km storm, 2,180 km sanitary and 946 km combined sewer. The system’s condition is described as “fair” by DDC officials, which given the state of many North American cities’ sewers, is to be considered a rave.
“We are a fairly young city, nowhere near the age of a city such as Boston,” Ward says. “But it’s in fair condition for a lot of reasons. We have done a great deal of rehabilitation over the years and have put a lot of effort and resources into it.”
Edmonton uses a point scale of 1 to 5 to classify the condition of its sewer system, with 5 being the best and 1 the worst. “We are working to bring the system up to 3.25,” says Siri Fernando, project engineering manager for Drainage Services. “Right now we have areas that are below 2 [on the scale] and those are areas that are being looked at and we have extensive plans in place to rehabilitate them and get them in the proper physical condition.”
The point system uses computer modeling to predict age condition from the time the sewers are installed, as well as deterioration curves. The second part of the equation is the physical assessment, which is done by using video inspection on small diameter pipe or firsthand observations of the large diameters (walking the pipe).
“We are looking at capacity issues, physical deterioration of the pipe, cracks, etc.,” says Fernando, who has been with the DDC for 28 years and has witnessed the system’s rehab evolution. “Through the computer modeling perspective and physical observations, we are able to develop a proactive program, instead of a reactive one.”
And the difference between implementing a proactive program vs. a reactive program can mean hundreds of thousands of dollars to the city. “It is always more costly to do rehabilitation on an emergency basis,” Fernando says.
The term trenchless technology has been a part of the lexicon for just 40 years or so but tunneling, specifically hand tunneling, has been around for more than 100 years. Hand tunneling was first used in Edmonton in 1910. Consulting engineer Alexander Potter was tasked with providing recommendations to lay out the City’s first sewer network, which would serve as the framework for the expanding city in the years to come. Potter recommended hand tunneling to construct the system, citing the height of the plateau above the North Saskatchewan River — the city is 200 m above it — as the main reason necessitating a deep sewer structure. The City employed coal miners to hand tunnel the system during the winter months (their “off-season”). From there Edmonton was on its way.
Boom time in construction came with the conclusion of World War II. In Edmonton, that resulted in construction of large diameter sewers within the city, built for huge capacity. During the 1950s, the City tried a different approach to sewer construction by doing the work in-house and realized how cost-effective this route was. “At that time, Edmonton was considered a northern city and it was hard to get contractors to come up here to do the work and the proposals the City received were very expensive,” says Ray Schneck, DDC general supervisor of equipment. “So the City started to do the work itself and along the way built up its expertise in tunneling.”
By the 1960s, Edmonton decided to purchase and operate its own open-faced tunneling machine and in 1969 bought its first shield tunnel machine. Today, the city owns seven TBMs and has cultivated a strong reputation for its expertise in tunneling. “Edmonton equals tunneling in western Canada,” Ward says.
Its approach to the technology of tunneling continued on the rehab side with the onset of rehab methods that didn’t require the ground or customers to be disturbed. CIPP technology was first used here in the early 1980s and remains a key part of its rehab program today. On average, 50 to 60 km are rehabilitated via pipe relining each year.
“In 2012, we did an extraordinary amount of CIPP work, about 100 km,” Fernando says.
Other trenchless applications that are part of the DDC’s arsenal include pipe bursting in 2008 and pipe ramming in 2009. Also in 2009, DDC started experimenting with pilot-tube microtunneling for its smaller diameter tunneling projects, a method that is still being learned.
“The learning curve for pilot-tube has been tight and we’ve had some problems with it,” says Ray Davies, DDC general supervisor of tunnels. “For starters, our weather is a problem as the technology is very fluid-oriented and with our very cold winters, it means we have to basically shut everything down and start it up in the spring. It’s like learning about the technology all over again, making the learning curve a little longer.”
But DDC continues to use pilot-tube microtunneling on projects where it is deemed the best option, such as a project in progress on 66th Street involving 27-in. clay pipe. That’s the thing about Edmonton: If it doesn’t work the first time, DDC doesn’t give up on it, giving it a fair shot to show its worth.
“We get a lot of help from our suppliers with pilot-tube and others who are much more educated about it than we are,” Fernando says, noting that he would like to see improved guidelines on how to use the technology to make pilot-tube microtunneling easier to employ.
The City of Edmonton is also an active participant in several trenchless and tunneling industry associations, such as NASTT, Trenchless Technology Center Municipal Forums, Tunneling Association of Canada, and the Canadian Society for Civil Engineering and Water Environment Federation. DDC believes it is important to Edmonton’s success with these technologies to stay involved.
“We work with anybody who has something to offer on trenchless technologies,” Fernando says. “We look for new methodologies and we look for the expertise these [associations] offer.”
He also noted that Edmonton does a great deal of research work related to trenchless, most recently working with TTC and its former director Ray Sterling on a CIPP project involving the evaluation of some of the City’s older CIPP installations.
“We share our knowledge and learn what is happening elsewhere,” Ward says. “By working with these groups, it enables us to gain understanding, gain knowledge, as well as allows us to help others by telling them what we are doing so they can learn from our experience.”
Trenchless technology is a driving force in the plans DDC has for its underground infrastructure in the short-term and long-term. Though open-cut still has a key role (especially in its outlying, less populated areas) in the City’s infrastructure programs, trenchless is the first option in many of its plans.
“We do have a business strategy for our design and construction group and that is to expand and grow trenchless technology in our construction practices in Edmonton and other contracts we pick up from other municipalities,” Ward says. “We also have an open-cut group and there is still a need for that — I don’t see a world where that will completely vanish. We do pursue [trenchless] and it is a part of our core business plan.”
Sharon M. Bueno is managing editor of Trenchless Technology.