In December, Trenchless Technology magazine, a publication devoted to smaller-diameter underground technologies such as horizontal directional drilling (HDD) and microtunneling, announced its annual list of the Top 50 engineering firms in North America for trenchless technology, and we were thrilled to learn that WSP was ranked fifth for 2022.
This was a significant jump from the firm’s 14th place ranking only one year earlier — an indication of the growth and commitment that WSP is making in this important market.
What Is Trenchless Technology?
Trenchless technology covers a variety of construction techniques used to install or rehabilitate underground infrastructure — primarily pipelines — that allows for minimal disruption to surface traffic, businesses, residents and the environment.
This technology creates many benefits for both clients and communities, and what’s so exciting to me about trenchless technology is its minimal impact to our communities and the environment. When performed properly, this technology offers sustainable improvements to our communities with minimal impact relative to our daily lives.
Trenchless technology methods strive to:
- minimize disturbances to the existing environment;
- limit traffic and social impacts within urban areas;
- reduce the need for new space underground and problems associated with pipe routing;
- require less overall space underground, which minimizes the chances of interfering with existing utilities or abandoned pipes;
- require less exposed work area and is therefore safer for workers, communities and the environment;
- reduce or outright eliminate the need for excess spoil removal; and
- minimize damages to pavement and disturbances to other utilities and infrastructure.
Is Trenchless Technology Cost Prohibitive?
The biggest objection we face when discussing trenchless technology with clients is cost. It is often perceived to be more expensive than open-cut construction, because while the installation cost is similar at small diameters, it’s more costly on a cost-per-foot basis, especially at larger diameters.
But when the full social costs are considered, such as community and environmental costs, trenchless technologies are less impactful and usually more favorable — than open-cut installation methods. There are also significant advantages to both cost and schedule when using trenchless technologies for crossing wetlands, roadways, railroad tracks, streams, rivers and other obstacles or sensitive environmental areas.
The technology is also continuously developing based on previous project experiences and innovations in the methods, which leads to continuous improvements and efficiencies that continue to make trenchless technology competitive with open-cut installation methods.
So when the full spectrum of costs and potential community and economic impacts are considered for the full life span of a project, the additional construction expense is often offset by the social and environmental benefits to make it the more viable option to consider for a variety of pipeline and utility projects.
Trenchless Technology Capabilities
WSP’s earliest tunnelling achievements can be traced back more than a century to the late 1800s and includes substantial work designing and constructing the first New York City Subway. To this day, we honor that heritage by striving to lead in every aspect of tunneling – from large-diameter to small, which includes the use of modern trenchless technology techniques.
WSP’s capabilities in trenchless technology includes planning, program management, risk management, detailed design and onsite services during construction. Our in-depth understanding of local geology, ground-structure interaction and construction technologies — combined with the systematic application of investigative, scientific, engineering and risk management techniques — provide practical solutions for all trenchless projects.
This technology is inherently preferred by organizations that are committed to developing Future Ready® projects because its methods of installation are resilient and environmentally sensitive. They often reduce the carbon footprint of the construction project by minimizing impact and reducing spoil removal, while also being capable of dealing with various constraints and challenges.
Microtunnelling Using Trenchless Technology
WSP recently used trenchless technology to help Indiana and North Carolina construct their first curved microtunnel projects. Microtunneling includes the use of remotely controlled microtunnel boring machines, which are commonly used to install pipelines less than 96 inches in diameter, and usually too small for manned tunnelling machines.
While using trenchless technology for these projects is not uncommon, curved microtunneling is relatively new within North America and poses greater difficulties that we are now able to overcome. Compared to more conventional straight microtunneling, curved microtunneling imposes non-uniform axial loading conditions on the jacking pipe, which has inhibited its adoption until fairly recently.
WSP designed two offsite gravity drainage storm sewers for Indiana’s State Road (SR) 37 Improvements Project and recommended using trenchless construction methods. This project culminated from years of collaboration between the cities of Fishers and Noblesville, Hamilton County and the Indiana Department of Transportation and was part of a concentrated effort to address traffic congestion and public safety challenges along the SR37.
This construction team used two methods: two-pass tunneling and microtunneling for installation of the 54-inch diameter storm sewers. The project included the installation of 6,500 feet of storm sewer, which successfully navigated difficult conditions for the 2,650-foot-long south drainage line and the 4,700-foot-long north drainage line. The tunneling and trenchless technology used on the project benefited residents in Hamilton County immensely as SR37 was able to stay open throughout the entirety of this critical project.
Challenging boulders and groundwater obstacles were overcome to successfully install a record-breaking 2,304-foot long curved microtunnel, and the project won Trenchless Technology magazine’s 2020 Project of the Year, New Installations Honorable Mention; and American Council of Engineering Companies’ 2021 Indiana Engineering Excellence Honor Award.
In North Carolina, WSP was the engineer of record working with Charlotte Water, Sanders Utility Construction Company and Bradshaw Construction Corporation for several one-pass sanitary sewer tunnels. The 3,587-foot long, 48-inch diameter reinforced concrete utility pipe was installed within extremely variable subsurface conditions that consisted of granitic rock with strengths up to 30,000 pounds per square inch, as well as soft alluvial deposits.
Construction was complete in late 2020 and included a 1,170-foot-long curved microtunnel, which was the first planned direct-jack curved sanitary sewer in North Carolina. Trenchless technology was selected to help ease permit negotiations on behalf of Charlotte Water and benefited the area by significantly reducing construction impact to the surrounding community.
Between Stewardship and Infrastructure
I firmly believe that we should all be good stewards of the environment and recognize that reliable and sustainable infrastructure is critical to society and protecting our way of life. Using trenchless technology construction methods is one of the small ways we can commit to that goal.
The ability of trenchless technology to navigate environmentally sensitive areas with minimal to no impact is a major benefit for society and helps reconcile our goals of environmental stewardship and infrastructure development. I am pleased that WSP is a leader and partner providing these solutions to our clients, developing new innovations with this technology to provide even greater benefits for the communities our clients serve.
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