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Toronto's Port Lands stretches from the inner harbour to Leslie Street south of Lake Shore Blvd.Michelle Siu/The Globe and Mail

The numbers are staggering. Over the next decade, Waterfront Toronto expects to excavate two million cubic metres of contaminated soil and bring in another million of clean fill as the agency and its developers begin to revitalize the Port Lands. It's a process that will continue for decades, according to newly released real estate studies commissioned by the city.

That's enough to cover everything from Yonge to Spadina and the waterfront north to Queen in a metre of dirt. "The scale," said WT chief executive John Campbell, "is enormous."

To deal with all that dirty dirt in a sustainable way, the agency has awarded Green Soils, a North York firm, with a contract to set up a large-scale soil cleaning facility on the Port Lands, so those mountains of contaminated dirt don't need to be shipped off to dump sites up to 50 kilometres away. The decision follows a two-year WT pilot project on Unwin Avenue, and a tendering process that attracted four bidding groups.

Environmental groups and some GTA municipalities have stepped up pressure on Queen's Park to clamp down on firms that dump huge quantities of untreated, and possibly contaminated, construction soil in quarries north of the city. Last week, Toronto council also voted 34-3 to ask city staff to look at ways of tightening soil-testing rules for local developers.

Under the terms of its agreement with Green Soils, WT and its partners will send contaminated Port Lands soil to the new facility, provided the company offers rates competitive with the tipping fees charged by GTA landfills and other firms that offer soil remediation, including Direct Line Environmental in Pickering. Direct Line Environment is owned by GFL, which last fall won Toronto's curbside waste outsourcing contract and also has close ties to trucking companies that haul massive quantities of Toronto construction fill out to Durham Region.

Green Soils CEO Ashley Herman said the company plans to test various emerging soil cleaning technologies licensed from other firms. "For the first little while, it's going to be a bit of a world's fair."

The potential environmental impact is significant. According to Mr. Campbell, a study done for the agency found that if waterfront construction crews relied exclusively on the "dig and dump" approach to disposing of contaminated soil excavated from the Port Lands, they will generate 50 million kilometres of truck traffic on GTA highways. The estimated cost: $65-million for road wear and tear, accidents, fuel and tipping fees. A typical dump truck costs $125 an hour to operate.

"Taking soil from a construction site to a landfill isn't the best way of doing things," said Toronto environmental consultant Gordon Onley. "As we go forward, there's going to be a breaking point."

By Canadian standards, the WT project is a novel approach to dealing with brownfield sites. But other countries have plenty of experience in this field, especially the Netherlands; indeed, WT consulted with Dutch firms as it developed the soil cleaning strategy. Quebec, in turn, has landfill taxes designed to encourage construction companies to find other uses for excess soil.

According to Mr. Herman, there are two major categories of soil contaminants: oil and gas residue, often from leaking fuel tanks; and heavy metal residue, which often shows up beneath old factories and downtown development sites that have been built on landfill that includes long-buried deposits of coal ash.

Green Soil's North York facility currently cleans soil contaminated with fuels using a "bioremediation" technique that involves spraying dirt with bacterial compounds that can digest hydrocarbons.

For soil laced with trace metals, soil washing can isolate the contaminated material because it tends to adhere to small clay and silt particles. The residue is separated out and sent to a hazardous materials landfill.

At present, said Mr. Herman, there are no facilities in the GTA that are licensed to treat non-hazardous excavated soil laced with metal residue. The certificate of approval for GFL's rapidly expanding Pickering facility specifies that it is only permitted to offer bioremediation services.

David Harper, a managing partner at Kilmer Brownfield Equity Fund, said his firm has been investigating emerging technologies to clean excess contaminated soil to a level where it can used for road beds, flood barriers and berms to provide soundproofing for housing projects near rail or highway corridors.

Engineering consultant Paul Bowen, of Terraprobe Inc., said some contaminated soils can also be bound into a cement-like product, rendering them inert. Cement and construction firms are looking at this technique as a potentially economic alternative to increasingly expensive tipping fees.

Special to The Globe and Mail