The Regional Municipality of Wood Buffalo (Alberta, Canada) has identified sewer construction as one of the key drivers of development according to its 2009 Wastewater Master Plan. One such project was an upgrade of the sanitary sewer system in the heart of Fort McMurray.

The Gregoire Sanitary Sewer project offered significant challenges, however, including a route that would pass underneath a developed urban area, a playground, a soccer field and busy Highway 63, and close to the environmentally sensitive Saline Creek valley. With the path of the sewer line cutting through oil-rich soils, disposal of excavated material was also a potential concern.

RMWB worked with the Alberta offices of Associated Engineering and drilling contractor, Direct Horizontal Drilling, to develop a plan that would limit the impact of installing a mile-long section of 600 mm steel pipe using trenchless, horizontal directional drilling. The path of the excavation included a complex curve underneath the Saline Creek and one section of sewer pipe that would have to be buried more than 160 feet deep under an actively sliding slope.

The public soccer field was selected as the project staging area. With the use of noise-reducing equipment and extensive sound barriers, the project was granted a 24-hour construction permit.

The overhead route

Rather than shut down Highway 63 during pullback of the continuous length of pipe, the project partners arranged for staging above the highway using industrial cranes and steel A-frames erected along the road.

While the drilling mud from the operation could be disposed of at sites used by resource drilling projects in the area, the project partners identified an old cement plant that could use the drilling fluid as part of a site remediation project.

The $16 million Gregoire Sanitary Sewer project was completed in 2012, on time and more than a million dollars under budget. The project has since earned a number of awards, including a 2014 Award of Excellence from the Consulting Engineers of Alberta and runner-up for the 2012 Trenchless Project of the Year from the Northwest Chapter of the North American Society for Trenchless Technology.