Environmentalists are quick to point fingers of blame at petroleum companies when there’s a pipeline rupture and hundreds of thousands of litres of oil leak into waterways and onto agricultural land.More than 400 000 litres of oil spilled in Saskatchewan in two separate incidents in the past eight months. The damaged pipelines belonged to Husky Energy and Tundra Energy Marketing and each wore much venom from angry residents in several affected communities.
Mother Nature, though, received a free pass even though she was more to blame than anyone. Her unpredictable actions often ruin some of the best laid plans and designs from engineers and geoscientists.
Best Laid Pipelines Gang Aft Agley
Saskatchewan’s love affair with oil is no secret. Its production is vital to the economy and it’s an industry that employs thousands. But it also has its naysayers. Environmentalists argue loudly that pipelines that carry oil to port pose a significant threat to delicate ecological reserve lands like the Great Sandhills north of Maple Creek and the Nebraska Wetlands stateside.
“Slope stability, particularly at river crossings, is probably one of the most challenging aspects of maintaining our pipeline infrastructure.”
So when more than 225 000 litres of heavy oil leaked in the North Saskatchewan River in the summer of 2016, environmentalists had another “I told you so” moment. Communities like Melfort, North Battleford and Prince Albert and almost everywhere in between were forced to shut off their water intake from the river and find alternative water sources for nearly two months. The oil slick travelled 380 kilometres downstream.
The pipeline belonged to Husky. The petroleum giant said the cleanup job cost more than $90 million, not to mention the stresses it placed on communities and residents that were affected.
But before the finger of blame is pointed at Husky, take into consideration another culprit – Mother Nature. She is unpredictable. Ground movement was eventually tagged as the cause of the ruptures in the 19-year-old pipeline.
“The break was a sudden, one-time event in a section of the pipe that had buckled due to the force of ground movement,” read part of a post-incident report from Husky Energy.
Grant Ferguson, P.Geo., Eng.L., an associate professor of geological engineering at the University of Saskatchewan, echoed the findings from Husky.
“Slope stability, particularly at river crossings, is probably one of the most challenging aspects of maintaining our pipeline infrastructure. However, given the number of crossings and low frequency of incidents, I would suggest that this demonstrates that our geotechnical engineers have been rising to the challenge for the most part.”
Soil structures and perhaps seismic activity confound some of the best laid plans. Planning for so many unknown variables is nearly impossible.
Water You Going To Do?
Slope movement in Saskatchewan is very much tied to the hydrologic conditions. Over the past seven or eight years the province has been in a bit of a wet phase and groundwater levels monitored by the Water Security Agency show that levels are exceptionally high.
By contrast, Saskatchewan went through a low phase through the early turn of the century before it took off again, with some of these areas several metres higher than what they have been historically.
As a result, soils weaken and there’s a greater chance of a slope failure.
“I think that’s a lot of what is going on with (the Husky pipeline rupture),” Ferguson said.
Ferguson said the pipeline crossing near Maidstone, site of the Husky line, was installed at a time when the water table would have been lower than what it is right now.
“Certainly conditions have changed in the soils around there,” he said. “What would have been a more stable situation back in the 1990s is not because we’ve had changes in the pore water pressure.”
Husky maintained the majority of the leaked oil was recovered and that no water bodies were impacted. But Ferguson lamented that soils along the riverbanks and at river bottom likely wouldn’t be as fortunate. In addition, in some cases wells used for drinking water and agricultural purposes would be affected.
Catalyst for Concern
A second major oil leak in Saskatchewan was reported in January near Stoughton. This time, approximately 200 000 litres of oil spilled on low-lying agricultural land on a First Nation. Tundra Energy Marketing claimed responsibility for the spill, though the cause is still under investigation.
“The soils were such that we were seeing glacial tills throughout most of that area and low permeability. And so whatever migration of contaminants you’re going to have are not going to be that rapid,” Ferguson explained.
These most recent spills are what fuel the protests from pipeline detractors. The much talked about Keystone XL pipeline route has the potential to disturb Saskatchewan’s Great Sandhills region in the southwestern quadrant, in addition to slicing through the sensitive Nebraska Wetlands en route to the Texas gulf coast.
The Dakota Access line also has spurred controversy among many Native Americans in the Dakotas and Iowa who say the pipeline would impact sacred Indian burial sites and the quality of water in the area.
“If something did get into the ground, it would move quickly,” Ferguson noted. “Instead of it moving a few metres over the year it might be a few metres over weeks or months. It’s a major area for getting water into our groundwater systems and aquifers.”
Sinking Cities
Slope stability isn’t just a concern for pipelines in rural areas. It has long been an issue along the east bank of the South Saskatchewan River in Saskatoon, particularly near Saskatchewan Crescent and 16th Street. In this affluent neighbourhood, many landowners saw their backyards give way and crumble several metres down the riverbank.
Further bank movement in the spring of 2016 forced the City of Saskatoon to close park trails and sidewalks in that neighbourhood for safety concerns.
In an effort to curb the lagging riverbank, a geotechnical site investigation resulted in the decision to construct an H-pile and concrete lagging retaining wall, conduct further earthwork on the lower slope and installation of sub-drains.
Though it’s unclear what effect, if any, these projects will have on the stability and Mother Nature’s will.
Constantly Learning and Improving
Pipelines expansion appears to be very much in Canada’s and North America’s near future. Both the Keystone XL and Dakota Access lines have been approved after years of delay.
Perhaps a silver lining to the oil leaks is the fact that engineers are gaining a better understanding of which areas are more sensitive, as well as learning how the geology interacts.
Ferguson said, “A lot of questions still remain on how this will all play out. We’ve talked about the end of oil. What will that look like? But at least we’re learning about this now and asking the right questions, whereas before we would just lay down the pipe without considering the things we are now.”