Alberta health officials are worried that a proposed new method for sizing emergency response zones for sour gas-well blowouts and other accidents involving the toxic gas will fail to protect the public.
But the Alberta Energy and Utilities Board (EUB) and an industry representative argue that changing how the size of emergency zones is calculated, by making the process more scientific, will better protect people from being exposed to poisonous hydrogen sulphide gas (H2S).
The debate comes as efforts continue to stem a sour gas leak from a well west of Edmonton.
The EUB is also preparing for a scheduled Jan. 11 public hearing on Compton Petroleum Corp.'s application to drill six critical sour gas wells just over a kilometre from Calgary's southeast city limits.
The debate is over what levels of hydrogen sulphide exposure should be used in calculating the size of emergency planning zones (EPZ) in Alberta. EPZs are the areas in which oil and gas companies have to prepare written plans to evacuate people and take other measures in case of a sour gas-well blowout or other accident involving H2S.
Dr. Brent Friesen, the Calgary Health Region's medical officer of health, says the region's health officials oppose the higher H2S exposure levels that the EUB is considering in a new model for calculating the size of EPZs.
The EUB is looking at using gas exposure levels of either 251 parts per million or 447 ppm for three minutes, which are two to four times greater than the current standard of 100 ppm averaged over three minutes, Friesen says.
"Our assessment of the scientific literature is that either of those (higher) exposures is unacceptable and is likely to result in either fatalities occurring or serious irreversible health effects," he says.
The higher levels could expose people caught out in the open to enough hydrogen sulphide gas to literally knock them down and quickly render them unconscious, Friesen says.
But Geoff Granville, a toxicologist with Shell Canada Ltd., says the H2S levels represent only a theoretical exposure to sour gas that's used to calculate the size of an EPZ and a company's ability to manage the emergency response.
In the event of a gas-well blowout or some other accident involving hydrogen sulphide, Alberta guidelines require the public to be evacuated from the area as soon as H2S concentrations reach 20 ppm for three minutes, Granville notes.
That means an evacuation would be carried out long before gas concentrations reach the levels currently used or being proposed to calculate EPZs, he says.
People can also take shelter from the gas inside their homes, which gives emergency responders another 24 hours to reach them, Granville says.
"If we didn't have a 20-ppm, three-minute evacuation guideline, the argument would be different. But we do have that guideline.
"I do not believe this new model will negatively compromise public safety at all," Granville adds.
Gary Nielson, senior adviser to the EUB's public safety team, says the single-model approach for calculating the size of emergency planning zones (EPZ) was recommended four years ago by the Advisory Committee on Public Safety and Sour Gas.
The EUB formed the committee to review Alberta's sour gas industry and recommend ways to make it safer.
The committee was concerned that several models were being used to calculate EPZs, and that arguments over these models at public hearings were eroding people's trust in the entire process.
"To make an informed decision, you need to have some kind of standard," Neilson says, adding the goal is to establish a single model or regulatory standard for EPZs that every company would have to use.
Even though the H2S levels being considered for this new model are higher than gas concentrations used in previous models, "you wouldn't expose anybody to those levels because one of the actions you would take is you get indoors, shut your doors and stay there until help arrives," Neilson says.
The higher H2S levels are based on studies of animals exposed to sour gas, as well as a review by Alberta Health and Wellness of the scientific literature on H2S exposure. This information indicates the higher gas levels more accurately reflect the health risks of potential exposure than the 100 ppm-over-three minutes concentration that has been used since 1990 to calculate the size of EPZs, Neilson says.
However, the ultimate size of each EPZ will also depend on several site-specific factors, he adds. They include the well's estimated H2S concentrations, the well's size, the predicted flow of the gas including fluctuating gas concentrations, the topography and whether the well would be immediately ignited to burn the escaping H2S in the event of an accident.
"I absolutely think it (the new model) is going to be safer for the public" than the comparatively crude approach now being used to determine the circular EPZ zones, Neilson says.
"What we're doing is putting science into picking (an EPZ) which is smaller for valid scientific reasons."
Compton Petroleum has applied to the EUB to reduce the size of the EPZ for its proposed six critical sour gas wells from a 15-kilometre radius to four kilometres.
This would remove nearly 250,000 southeast Calgary residents from the emergency planning zone and leave fewer than 200 homes within the EPZ.
But Neilson notes that the EUB's new model isn't being developed to make EPZs smaller or cheaper to manage for industry. The single model won't be approved by the regulatory board in time to be considered at the Compton hearing in mid-January, he points out.
Neilson says when the new model is implemented, he expects the size of some EPZs will shrink but the size of others could grow, depending on the site-specific factors that are plugged into each case.
Friesen, however, says Calgary health officials believe the H2S levels used to calculate EPZs are crucial, because these figures define the size of the area where a company has to plan for and actively manage the emergency response.
The CHR has recommended that the EUB either keep the 1990 standard of 100 ppm over three minutes, or implement a similarly protective health standard used by the U.S. Environmental Protection Agency.
The EUB's attempt to resolve the debate, by inviting medical experts and other stakeholders to a meeting in Calgary in late November, ended with Alberta's leading researchers on sour gas disagreeing over which H2S levels should be used, according to a transcript of that meeting.
Alberta environmentalist Martha Kostuch, who participated in the meeting, says she's not convinced the new model with its higher H2S levels will better protect people from a sour gas accident.
The less conservative the model is in terms of potential health risks, she says, "the smaller the emergency response zone is going to be and the fewer people that are going to be subject to whatever emergency plan there is."
However, Kostuch says it also doesn't make sense to have a model where the EPZ is so large - encompassing 250,000 people in southeast Calgary, for example - that mass panic and evacuation might cause more harm than a sour gas leak.
"But I also want an emergency response zone that makes sure the public's health is protected."
Kostuch urges the EUB, before it makes the switch to a single model for calculating EPZs, to find a process whereby medical experts and other stakeholders can agree on the H2S levels and other factors to be built into the model.
However, EUB adviser Nielson says he has carefully considered everyone's views and will now write a report - including his recommendations on what H2S levels should be used to calculate EPZs - for the regulatory board.
Nielson adds he hopes to have a draft report ready for input from all stakeholders by February, consider their feedback and then submit a final report to the EUB in April for its decision.
(Mark Lowey can be reached at mark@businessedge.ca)
