During a Q&A session at the First International Oil Sands Tailings Conference currently underway in Edmonton, somebody asked Ed McRoberts of AMEC “Please comment on seepage and leakage from the tailings impoundments.” This morning the Globe and Mail wrote about a report from Environmental Defence that states that leakage from the oil sands tailings impoundments is estmated to be about 11 million liters a day.
Ed McRoberts answered most profeesionally that as a geotechnical engineer he controlled seepage from the impoundments so that the seepage does not affect the stability of the embankments and dikes impounding the tailings and entrained water. But he noted that he could not comment on leakage, as that is an issue for groundwater hydrologists. So far, so good.
As I wish to leave Edmonton unscathed, I too, as a geotechnical engineer, will not comment on leakage from oil sands tailings impoundments. But before anybody gets hot and bothered about leakage from a tailings impoundment, I urge them to read the many reports on leakage from the Uranium Mill Tailings piles that we remediated and closed in the early 1990s. The reports are readily available on the U.S. Department of Energy’s UMTRA website.
What it all boils down to is that gravity will make entrained tailings waters leak downwards in the fullness of time, unless you have a perfect liner beneath the tailings. And such exfiltrating water, as I prefer to call it in the interests of technical precision, will move on downwards to the groundwater and, depending on the topography, to surface waters. But if these groundwaters and surface waters are already affected by the radioactivity already in the ground and its waters, then in reality there is no detrimental impact.
Regulations that governed UMTRA demanded that we limit resultant changes in groundwater constituent concentrations to less than background or less than pre-set maximum concentration limits. Those regulations recognized the obvious fact that if you seek to walk away from the reclaimed tailings impoundment and be sure it will perform as designed in the long term, you do not put a liner beneath the tailings, for no liner can be relied on and it only serves to direct tailings exfiltration to an outlet point where you will have to collect it and treat it in perpetuity.
In the long term, the only way to limit exfiltration from tailings is to limit infiltration. And that can only be done with a cover, a cover that limits infiltration to such an extent that the resulting exfiltration does not result in an exceedance of background water quality or pre-set maximum concentration limits.
Thus, I submit the issue is not the quantity of water that exfiltrates. The issue is the impact of the exfiltrating leakage on groundwater and surface water quality. So before you go getting hot and bothered, I plead that we get the facts and adjudicate the issue in reasonable technical and scientific terms. More screaming about filling Toronto’s Rogers Center stadium every year with leakage from the oil sand tailings impoundments (as the Globe and Mail does) is silly, irresponsible, incendiary, and plain bad journalism.
I have not read the report as I cannot find a Google link to the report. If you can direct me, I will read it and undertake to comment on its veracity, accuracy, and relevance to more screaming and shouting.
PS. An update. Here is the link to the report. I have read it, and am no more informed than I was before. I grew to maturity under the scrutiny of the Nuclear Regualtory Agency (NRC) in the United States and learned early that the U.S. Environmental Protection Agency (EPA) has teeth and uses them. Both have lapsed, but I suspect their response to this issue would have been different. But then Canada is a small country of rugged individuals living in a harsh climate. Maybe they just do things differently and are proud of it.