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Thunder Bay's infamous "blob," an enormous toxic puddle that sat on the floor of Lake Superior, is finally getting cleaned up.

Originally thought to occupy an area of about 13,000 cubic metres, the blob was an underwater dump for a succession of nearby industries, and consists mostly of creosote. When broken down into its various components, creosote contains harmful chemicals that seriously compromise the harbour's health.

It's anyone's guess how long the blob took to develop, but by 1986 things were so bad that the Great Lakes Quality Agreement of the same year declared it to be an "area of concern." Since then, past and present landowners have worked with Environment Canada, the Ontario Ministry of the Environment and local representatives and formed a complex remedial action plan (RAP) whose best cleaning agents are turning out to be such humble life forms as marsh grasses, algae and snails.

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The site is owned by Northern Wood Preservers Inc., but it's just the last of many owners that include Abitibi-Consolidated and CN Rail. It's only in the past 20 years that such industrial pollutants as creosote have been considered harmful. Used to preserve wood in railway ties and hydro poles, creosote "drippings" have accumulated on the lake floor for more than 50 years. The drippings contain all manner of nasty substances, among them polycyclic aromatic hydrocarbons, chlorophenols, dioxins and furans.

Golder Associates, an engineering firm that specializes in environmental clean-up projects, has supervised the construction of a 1,000-metre-long rockfill containment berm that runs parallel to Thunder Bay harbour's shipping channel. The berm connects an unused ore dock with one corner of the Northern Wood Preservers site and contains the toxic core of the blob -- a total of 13,000 cubic metres of contaminated sediment.

The sediment has been placed in what environmental experts call an engineered bioremediation cell for biological treatment. This is essentially a cement-lined pit which prevents the spread of contaminants into the soil while the company determines the best animal organisms (usually microscopic in size) and plants to leach the pollutants from the dredged material.

In principle, the system is similar to sewage treatment where waste water is channelled through a succession of pools and marshes which remove elements harmful to the natural environment. In the case of industrial pollutants, certain plants such as reeds and marsh grasses have the ability to "pull" pollutants from the soil. Working in combination with algae and even snails, the plants are eventually harvested and can be stored in smaller, more safely contained areas until they -- and their toxic contents -- can be safely disposed of. With luck, engineers expect treatment to be completed some time between 2001 and 2003.

To prevent movement of contaminants into the harbour, an isolation barrier is being built of clay along the north side of a pier owned by Northern Wood Preservers. To minimize the migration of sediment disturbed during dredging, an impermeable polyethylene silt curtain is anchored to the harbour bottom.

Willard Carmean, Professor Emeritus of Forestry at Lakehead University and a member of the Public Advisory Committee (PAC), remains guarded about the progress of the cleanup. "I was told there was more creosote there than they had anticipated."

Prof. Carmean says the PAC is willing to continue working with the consortium for the time being. At least the owner of the land is playing an active role.

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In the past, the land had several owners, says Prof. Carmean. "Everyone could say, 'somebody else did it,' or 'it wasn't the law at the time' and only the lawyers would benefit."

However, according to John Davis of Golder Associates, the project is proceeding steadily. He estimates that roughly two-thirds of the work is complete.

The newly reclaimed land, consisting of rockfill in the dredged area, still requires storm-water controls; that stage is scheduled for completion this autumn. While the south side of the harbour will likely be used for wood storage, the reclaimed land will take the shape of a healthy, treed marsh. Linda Turk is a freelance writer who lives in Kakabeka, Ont.

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