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April 25, 2007

Environment

Ten years to clean up Tar Ponds

TORONTO

It’s taken more than 100 years to create the toxic stew of the Tar Ponds in Sydney, N.S. The federal and Nova Scotia governments hope to have it cleaned up in 10, at a cost of $400 million.

The Tar Ponds, the marshy estuary of Muggah Creek where it flows into Sydney Harbour, contain the heaviest concentration of contaminants on the 250-acre site of the former steel mill that, in the early years of the 20th century, produced close to half Canada’s steel. The mill closed in 2001.

Considerable work has been done elsewhere on the site in recent years. Smoke stacks and derelict buildings have been removed, an engineered containment system has transformed a former municipal dump into a grass-covered hill, and a new primary sewage treatment plant has diverted millions of litres of raw sewage from Muggah Creek.

GRANT YOUNG/SYDNEY TAR PONDS AGENCY

Over the winter, drilling was carried out as part of a geotechnical investigation of the bedrock underlying the Sydney Tar Ponds. Information gathered from the drilling will help determine the design and construction of the sheet pile wall of the clear channel which will be built to allow two fresh-water brooks to pass through the Tar Ponds without becoming contaminated. Bart Longyear did the work under contract to Maritime Testing.

Also, a barrier has been built across the mouth of Muggah Creek to prevent contaminants from flowing into Sydney Harbour during the upcoming cleanup.

This year marks the start of work on the ponds themselves

Contaminants in the 77 acres of the Tar Ponds include about 700,000 tonnes of contaminated sediment, mainly heavy metals and polycyclic aromatic hydrocarbons (PAHs) — both byproducts of coke production — as well as about 3.8 tonnes of polychlorinated biphenyls (PCBs) that were dumped there over the years.

After several costly false starts dating back to the early 1980s, the federal and provincial governments agreed the best solution to clear up the site would be a combination of stabilization and solidification. Stabilization makes the contaminants less mobile, less soluble and less toxic while solidification mixes cement and other hardening agents with the sludge to harden it and contain the contaminants.

While officials are confident the solution will work, environmentalists have expressed misgivings about what they view as an unproven technology.

An environmental review panel also had some questions about the process and there will be more pilot testing than planned to make sure the system works.

By mid-May, Earth Tech and CBCL Ltd. are scheduled to present their completed plan for carrying out the cleanup. While working on the plan, they have been drawing up tender documents for work to go out for tender later this year.

Among this year’s projects are creating new channels for Coke Ovens Brook and Muggah Creek as they pass through the Tar Ponds; construction of a new decontamination facility, originally planned to be open but now planned to be contained in a steel building and building a second-generation landfill, a lined site that has facilities to deal with water infiltration and landfill gases.

The first step for the rechannelization projects will be installation of sheet piling. The project is still awaiting environmental approvals to begin excavation but the piling does not require environmental approval, said John Chesal, communications officer with the Sydney Tar Ponds Agency.

Plans for the landfill were also affected by regulations.

“We had planned to use the CFB landfill site,” Chesal said, “but the provincial regulations changed Jan. 1 and we were required to build a second-generation landfill.”

Chesal said the agency has made significant efforts to keep contracts to a size that local contractors can handle. One of the largest was the $7-million realignment of Coke Ovens Brook, elsewhere on the site, carried out by Riverside Developments Ltd., and the construction of the barrier at the mouth of Muggah Creek carried out by J. & T. Van Zutphen Bros. Construction. Both projects were on-time and under budget.

Chesal said the work started this year is expected to be complete in this construction season. The work on the contaminants in the rest of the ponds — the largest part of the cleanup — will get under way next year.

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