March 30, 2009

CITY OF CALGARY

The 55-hectare Nose Creek landfill site is adjacent to the Bow River and Nose Creek, a small tributary. Operational from the 1920s, the landfill was the destination of choice for construction and residential waste until the city closed it in 1967.

Calgary plans minimal disruptions during clean-up of Nose Creek landfill site

SAUL CHERNOS

correspondent

Old landfills may be an eyesore and environmentally sensitive, but sometimes it’s best to let sleeping dogs lie.

That’s the approach the City of Calgary took with its decommissioned Nose Creek Landfill.

Looking to clean up the site, which already has some overlying development and is slated for more, the city decided to leave as much of the old waste in place as possible.

The 55-hectare site is adjacent to the Bow River and Nose Creek, a small tributary.

Operational from the 1920s, the landfill was the destination of choice for construction and residential waste, until the city closed it in 1967.

Jasna Hundal, manager of disposal and treatment with the City of Calgary’s waste and recycling services department, said crews removed waste where appropriate and feasible, and used caps and vapour controls to manage the rest, as they head into the final stages of the multi-year project.

A decade ago, in an initial cleanup of the northern section of the landfill, crews installed clay caps to contain non-hazardous construction debris found underneath.

The area, adjacent to the Calgary Zoo, was then converted to parkland.

Activity resumed two years ago.

With further development slated, including an expansion of the zoo, relocation of the Telus World of Science and an extension of the city’s light-rail transportation system, the city decided to finish the job.

The city undertook health and environmental risk assessments.

Through borehole samples, they confirmed the contents as household and construction waste, and the cleanup began.

On the south portion of the landfill, which abuts the zoo, crews plan to increase an existing network of passive collection wells and venting systems to handle methane gas, which is a natural byproduct of decomposing food and other organics.

It can be volatile if released in large amounts.

Because the zoo wants to expand its parking lot and house additional animal-care facilities, it’s important to ensure any methane is under control.

“The waste is pretty old, so not much gas is being produced anymore, but we still want to make sure it’s kept away from any cars,” he said.

Work on this section of the landfill should be completed later this year, as Calgary’s construction season generally runs from May through November.

The central part of the site has also undergone remediation.

“There was a bit of municipal garbage there, but it was mostly construction waste and a lot of old fill – soil mixed with gravel,” Hundal said.

Crews used screens to separate larger debris from the soil, which was then used as backfill, and caps were installed as needed.

So far, industrial and other hazardous wastes have not been found.

“I guess we were lucky, because with old construction material from that time , one would potentially expect asbestos and other things,” he said.

One section, less than 10 percent of the total area, has yet to be fully scoped.

Because the area is already substantially developed, a major exploratory excavation is considered impractical.

However, initial indications were reassuring.

Borehole tests came up dry, indicating no apparent liquids, and sampling indicates clean groundwater.

“At this point we’re only really looking at landfill gas management,” he said, adding that if anything imminently dangerous is found, the city would address it.

Overall there have been few technical hurdles.

One challenge has been working with the large number of stakeholders.

“It was not just a couple of city departments,” he said, listing the zoo and science centre as two of the parties involved.

A CP Rail right-of-way is adjacent to the site, so the railway needed to be consulted and plans to extend light rail through the area also required consideration.

The landfill remediation has also occurred partly in tandem with the city-led restoration of Nose Creek.

The creek was straightened a number of years ago.

“The city and science centre management want to restore the old creek bed to a more natural state,” Hundal said.

Though incomplete, the Nose Creek project earned top spot in the 2008 Canadian Urban Institute Brownie Awards under a category addressing sustainable remediation technologies and technological innovation.

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