By Stephen Weninger, P.Eng., Stantec
Changing the Model – Wandering River Regional PipelineWater & Wastewater pipelines
A design-build team completed the Wandering River Regional Pipeline across 88 kilometres of Northern Alberta, taking just over a year.
From the June-July issue, page 18
A complex and unique project, the Wandering River Regional Pipeline is the first regional water project in Alberta completed using a design-build delivery model. Completed by Graham Design Builders with Stantec as the prime consultant, the project is a textbook example of how cooperation, teamwork and communication between different stakeholders can have positive results. The 88-kilometre system was designed, constructed and put into operation in only 13 months.
The project won a 2014 Award of Excellence from Consulting Engineers of Alberta and won the 2013 Project of the Year from the Alberta Public Works Association.
Located in Athabasca County along Highway 63 to the oil sands in northern Alberta, the pipeline brings treated water north from the Aspen Regional Water system. The pipe extends from Boyle to Wandering River via Grassland. The project also involved building a new 550-cu.m potable water reservoir at Wandering River and modifications to a reservoir at Grassland.
Wandering River’s existing water treatment plant lay in the way of construction for twinning Highway 63, so the plant was scheduled for demolition in December 2012. With the new pipeline project awarded in July 2011, timelines were a concern. Without the pipeline the community would be left without potable water.
In anticipation of possible delays, the team sought regulatory approval concurrently for the 300+ crossings — utilities, highways and environmental features — along the line. Construction proceeded in locations where approvals were in place, even if approvals were still outstanding in nearby areas. This process meant that the alignment had to be moved several times during the early months of construction while approvals with long lead times trickled in.
Horizontal directional drilling
Using horizontal directional drilling (HDD) to install nearly the entire 88-km length of the system greatly reduced the project’s potential environmental impacts. Installing using the HDD method also allowed the project to be exempt from the requirement to obtain an approval under the Environmental Protection and Enhancement Act, which reduced the overall timeline by approximately six months. Also known as “trenchless” drilling, the HDD method allows pipe to be installed at a wide variety of depths with minimal disturbance to the surface. Excavations only occur at either end of a drilled section of pipe, often 300-500 metres apart. Once the desired depth of pipe is reached, a steering apparatus allows the drill head to manoeuvre horizontally through the ground before surfacing. Due to the depth of the frost line in Alberta, the pipe on this project was installed at a minimal depth of 2.7 metres with a depth of up to 6 metres in some areas.
The system consists primarily of fusible polyvinyl chloride pipe (FPVC) and represents the largest project by length of FPVC installed to date in North America. The FPVC allows the HDD contractors to fuse sections of the pipe together, enabling them to install greater lengths at one time. The FPVC pipe also gave cost savings since its larger internal diameter allowed the use of 150-mm diameter pipe. The HDPE pipe which is more commonly used for this application has thicker walls and would have required the use of 200-mm diameter pipe.
Muskeg and other difficult terrain
Throughout the construction teams encountered different terrains, which posed a threat to the timeline. Although much of the alignment paralleled roads, there were several stretches of private land, streams and a river to cross, as well as a 12-km section of undeveloped land. This land sat in muskeg, which meant that the installation had to be scheduled to proceed during frozen conditions otherwise the equipment would sink into the soils.
In some areas, unexpected gravel and boulders delayed the teams. On several occasions the drill was deflected below large boulders, but when the pipe was pulled back, the rock would settle and crush the pipe. Finding the offset rocks became a trial and error exercise of exposing the buried pipe. In areas where rocks and boulders were prevalent, the contractor shortened the drill lengths from 500 to 150 metres to minimize the production losses.
The most challenging crossing was under the Wandering River a few kilometres south of the community. The sandy soils required a conductor barrel to be installed to below the depth of the sand so that drilling mud pressure could be maintained.
The project was completed on budget and ahead of schedule and provides long term reliable clean and safe drinking water for the two communities and 70+ residences that lie along the pipeline. Despite Wandering River and Grassland being small communities, their relative remoteness along Highway 63 makes them of strategic importance to the 11,000 vehicles that travel to and from the Alberta oilsands region daily. The new waterline and reservoir provide the communities with the resources they need as they grow as service centres along this energy corridor. cce