Drilling mud sump with a small lake in the background. Image courtesy of Michael Pisaric (Brock University).

A couple of Brock researchers are part of a collaborative research team whose recent findings suggest that the legislated method for disposing of land-based drilling wastes associated with oil and gas exploration in Canada’s Arctic is no longer effective.

Their findings are based on the group’s latest research on the cumulative impact of climate warming and oil and gas exploratory activities during the 1970s and 80s on lake ecosystems in the Mackenzie River Delta region of the Northwest Territories.

“Lakes in the region are undergoing warming, they’re being impacted by permafrost thaw, and now on top of that, there’s also the impact of hydrocarbon exploration,” says Joshua Thienpont, a post-doctoral fellow in Brock’s Geography Department working under the supervision of associate professor Michael Pisaric.

Large drilling sump near Mackenzie Delta lake. This large sump is perched above and close to the edge of a small lake. The gravel road created during drilling is still visible. Image courtesy of Joshua Thienpont (Brock University).

Hydrocarbon exploration industries in Northern Canada dispose of their drilling wastes into pits called “drilling sumps.” These are Olympic pool-sized craters dug into the permafrost and filled with industrial wastes – primarily cuttings and drilling fluids.

“Only 30 or 40 years ago, it was assumed that these sumps were a permanent disposal mechanism – that this material would be locked in the permafrost forever,” Thienpont says. “But we now know the permafrost is not as permanent as we had originally thought.”

Based on the research, he also notes, “Sumps are probably not the perfect disposal method in regions of warm permafrost, which is not only likely to thaw, but already thawing.”

Thienpont and his colleagues analyzed the aquatic biology of more than 100 lakes in the Mackenzie River Delta, Canada’s largest and longest river system. They found that some lakes with nearby “sumps” contained high levels of salts, particularly chloride, a main component of drilling waste fluids. Arctic drilling rigs use a saline solution of concentrated potassium chloride to keep them from freezing in the extreme cold.

The research team then compared the data from these sites against undisturbed pristine lakes and naturally disturbed lakes that have been transformed by “thaw slumps,” a spectacular form of permafrost degradation.

Large, active retrogressive thaw slump. This spectacular form of permafrost degradation is common in the Mackenzie Delta uplands region. Image courtesy of Joshua Thienpont (Brock University).

“We wanted to compare the modern water chemistry of these lakes that have sumps in their vicinity, to other lakes in the region,” says Thienpont.

“So we looked at lakes that had no impact on them, no local disturbances,” he says, “and we also compared them to sites with active permafrost thaw, which we know are highly disturbed, so we could put any changes from drilling sumps in the context of other lakes in the region undergoing chemical changes.”

Thienpont preparing a sediment corer. Image by Linda Kimpe (University of Ottawa).

In one of the lakes researchers examined with a nearby “sump,” they discovered a change in lake biology at the time the pit was constructed in 1972. They noticed the appearance of a species of invertebrate known to be tolerant of high salinity, so they could infer there was some impact on the lake when the “sump” was constructed.

Paleoecological methods, which use lake sediment cores to better understand past environmental conditions, were used in order to draw historical comparisons between lake ecosystems from before and after the appearance of drilling sumps in the area.

Thienpont and a colleague in a sediment corer canoe. Image by Linda Kimpe (University of Ottawa).

“In the Arctic there’s not a lot of monitoring going on in any environment, so you have to reconstruct the environment using proxy records such as lake sediments,” says Thienpont.

“We looked at the biological indicators, the remains of algae and small invertebrates in the sediments, to see if there had been any impact on the aquatic biology over time,” he says. “We’re often looking at the remains of organisms, which have a particular affinity for different environmental conditions, such as high salinity.”

Click here for a copy of the study “Exploratory Hydrocarbon Drilling Impacts to Arctic Lake Ecosystems“