Poisonous hydrogen sulphide gas bubbles up in oilsands tailings pond during company reclamation efforts

Hanneke Brooymans, Edmonton Journal, February 21, 2010--The industry is working on ways to reduce the size of tailings ponds. Shown here is the Base Mine Lake tailings pond at Syncrude's extraction and upgrading facility at Mildred Lake, taken in 2008. Efforts to clean up one of northern Alberta's biggest environmental messes -- oilsands tailings ponds -- have created another problem: air pollution that includes a deadly poisonous gas. Air emissions monitors in the area around the Fort McMurray oilsands have been picking up a steady increase in sulphur-based pollutants, including poisonous hydrogen sulphide.

Officials from industry and Alberta Environment have many theories about why emissions are increasing, but by far the most surprising is the link to the ongoing reclamation of a Suncor tailings pond. "It's like when you step into a wetland, all these bubbles come up because you disturbed the bottom," says Preston McEachern, head of science, research and innovation for Alberta Environment.

The Journal recently checked the statistics for hydrogen sulphide emissions in the Fort McMurray area, and checked in with government, industry and affected residents about what is happening and how they feel.

Q: How did the increase in hydrogen sulphide emissions come to light?

A: In 2006, the monitoring network in the area started picking up spikes of hydrogen sulphide in the air that passed the concentration level the government considers acceptable. In the last five years, the number of times hydrogen sulphide levels have exceeded the guidelines has skyrocketed. The worst station counted four infractions of the province's daily concentration guideline five years ago. Last year, there were 76 days in which the air concentration broke the guideline. (For more details, see table that details the infractions.)

Q: Should this be a concern for the people working and living in the Fort McMurray area?

A: The provincial government and the companies in the area note the concentrations are well below occupational health and safety exposure limits. The guideline being broken is set at what's called a nuisance level, which is approximately the level at which the gas can be smelled. However, there continues to be a debate about the effects of long-term exposure to low concentrations of the gas.

Sheldon Roth, a neuroscientist in the University of Calgary's toxicology division, has studied hydrogen sulphide. "My bottom line," he says, "would be there's not enough information whatsoever. We just don't know. And there's not a lot of research in that area."

Alberta Health and Wellness has just started a review of the scientific literature investigating health effects associated with low-level, chronic hydrogen sulphide exposure. The ministry says it's doing the review in response to concerns expressed about low-level exposure.

Q: What do local residents think of the problem?

A: Fort McKay, a community of about 600, sits about 15 kilometres north of Syncrude and about 30 kilometres north of Suncor. More than half the time, the wind is blowing from the south-southeast, so people in the community smell odours on a fairly regular basis, said Lisa Schaldemose, executive director of Fort McKay's Industry Relations Corporation. She said community members noticed an increase in odour incidents last spring. One day this past summer her office received 60 calls from upset residents. "The community's very concerned about their air quality and particularly how it relates to their health and how it's relating to the health of the land, because these people are still, to some extent, living off the land." Schaldemose said though they have good relationships with companies in the area, the community has its own air quality expert analyzing data from monitors in the area. He will be giving the community a briefing on his findings this spring.

Q: What is being done about this issue?

A: The provincial government began investigating the issue in 2006 when it noticed the upward trend, says Al Montpellier, Alberta Environment's regional compliance manager for the northern region. "That's when we started to look at the different sources in the area and really started to work with the companies and say, 'Where is this coming from?' " he says.

In 2007, the province issued two environmental protection orders, one against Syncrude in August and one against Suncor in December, in an attempt to get hydrogen sulphide emissions under control.

Syncrude closed its order last year, says company spokeswoman Cheryl Robb. That order was related to hydrogen sulphide emissions that came from an effluent pond, not a tailings pond. The pond is used for waste water during an unexpected shutdown, not a tailings pond used during regular operations. Suncor's order is still open. Montpellier says the company handed in its report in January, but the ministry still has to go through it to decide if the company has done enough.

The federal government requires companies to report their emissions each year, but the actual regulation of air quality is in the hands of the province. However, the National Pollutant Registry Inventory, which is available to the public online, showed a dramatic increase in the amount of hydrogen sulphide emissions reported by Suncor -- from 31 tonnes in 2007 to 708 tonnes in 2008, the latest available year. Syncrude, on the other hand, reduced its hydrogen sulphide from 129 tonnes to 62 tonnes.

Q: Why is Suncor reporting so much more hydrogen sulphide?

A: There have been no actual increases in hydrogen sulphide emissions between 2007 and 2008 by the company, says spokeswoman Sneh Seetal. Instead, when the company took samples of emissions from the ponds and had them tested, it discovered it had previously under-reported the hydrogen sulphide emissions. What they previously thought was largely a group of compounds called volatile organic compounds turned out largely to be hydrogen sulphide.

Q: Why is Suncor allowed to emit that much more hydrogen sulphide than Syncrude?

A: Alberta Environment doesn't actually put a limit on hydrogen sulphide emissions in the approvals obtained by the companies. Instead, it relies on the air monitoring network to pick up problems with pollutants, and then it acts on that information. Suncor is not convinced the air monitors are picking up strictly hydrogen sulphide. It turns out that the monitors can be fooled by other chemicals that also contain sulphur.

Alberta Environment acknowledges this fact, but it says it's equally concerned about these other chemicals as well, since they also have unpleasant smells. The Wood Buffalo Environmental Association, which runs the air monitoring stations, says it had special equipment installed at one of the stations last October to help sort out how much hydrogen sulphide there is compared to other sulphur compounds. However, Montpellier, from Alberta Environment, says the majority of the odour issues related to sulphur compounds are Suncor's, based on wind direction and other meteorological conditions.

Q: How does tailings pond cleanup fit into all of this?

A: Both Suncor and Alberta Environment think these emissions, whatever their exact composition, are coming from a tailings pond that is being reclaimed. A tailings pond contains a mixture of water, fine tailings, heavy metals and other chemicals. Gas bubbles in this mixture are trapped by the pressure of the water on top. But once you start to remove the water cap, the pressure is released and the gas bubbles up into the air." And the kicker is that as you reduce the cap, wind starts to have a huge effect on turbulent mixing," says Preston McEachern, head of science, research and innovation for Alberta Environment. "It's like when you step into a wetland, all these bubbles come up because you disturbed the bottom."
Suncor says reclamation on one of its ponds began in earnest in 2007. The water cap was completely removed as of last November.

McEachern says removing the water cap is one step that has to happen to turn the pond back into a surface that can be replanted with vegetation. At the end of the day the government has to balance its concerns, he says. They want to get rid of the old tailings ponds, but they want to do it on days or periods when the possible implications of gas release will be low, he says.