Canadian Consulting Engineer

Tar sands pits could turn into lakes

October 10, 2012
By Canadian Consulting Engineer

A group focused on dealing with the environmental impact of the Alberta oil sands mining has released a study on how to rejuvenate the landscape by turning the exhausted pits into lakes.

A group focused on dealing with the environmental impact of the Alberta oil sands mining has released a study on how to rejuvenate the landscape by turning the exhausted pits into lakes.

The 434-page “End Pit Lakes Guidance Document” provides technical and operational information for “end pit lakes.” The idea is that the toxic by-products of oil sands mining would sink to the bottom and be contained below the body of water in the lower depths. The document defines an end pit lake (EPL) as: “an engineered water body, located below grade in an oil sands post-mining pit. It may contain oil sands by-product material and will receive surface and groundwater from surrounding reclaimed and undisturbed landscapes.”

The document was produced and presented to the Government of Alberta on October 1 by a special committee of the Cumulative Environmental Management Association (CEMA). CEMA is a multi-stakeholder organization that includes oil sands companies as well as First Nations and Metis Groups, governments of all levels and environmental groups.

The document cost over a $1 million to research and develop, and was written and independently reviewed by experts from around the world, including Dr. Vivienne Wilson, a botanist with CH2M HILL. The introduction was written by Gord McKenna of BGC Engineering and James Hrynyshyn of West Hawk Associates.

There are no end pit lakes now, but there are proposals for 30 of them. CEMA says that the report is not intended to support or recommend their use, only to provide a “enough information to create a conceptual level EPL design, as well as a framework for the elements, should the application of this technology be approved by the Government of Alberta.” The report looks at the chemistry, geography and ecology factors, as well as the experiences of pit lakes in other types of mine such as coal and metals mines. It details the construction and operation of the mines, and draws up a 100-year timeline.

In trying to tread relatively neutral ground, CEMA’s memorandum to the Deputy Minister of Environment and Sustainable Resource Development notes some of the concerns that have been expressed with the end pit lake technology.

For example, EPL lakes have to be considered in the context of their larger watersheds, and that the planning of such lakes “are monumental tasks that involve all aspects of mining.”

They note that some Aboriginal and environmental groups are concerned that water-capped tailings may not be enough to contain the tailings’ toxicity. End pit lakes are an unproven technology in the area of oil sands, although they say “a sinificant body of work” has been done on the chemical processes involved.

At the same time CEMA can hardly conceal its hope that these lakes are a long term solution to the oil sands legacy: “If oil sands operators can successfully demonstrate the effectiveness of EPLs as a reclamation tool, the new lakes could also serve as a permanent alternative to the temporary tailings ponds that now store by-products of he oil sands extraction process.”

An article in the Globe and Mail took this idea one step further, and envisioned the area around Wood Buffalo becoming “Alberta’s very own Lake District, a recreational haven complete with campgrounds, boating, fishing — even swimming.”

CEMA has produced similar guidance documents for wetlands, soils, re-vegetation, and riparian areas.

To view the End Pit Lake Guidance Document or for more information click here.


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