February 15, 2008

Demolition/Environmental Engineering

Terrasan Environmental Solutions finds Corus project a down-to-earth remediation

Firm scores LEED points by treating, re-using contaminated soil

PETER KENTER

correspondent

The construction of the new $130-million home of Corus Entertainment on Toronto’s waterfront is underway, with soil remediation efforts continuing through the coldest months of winter to keep pace with an ambitious construction schedule.

The Aecon Group was retained to build the structure by the Toronto Economic Development Corporation (TEDCO) with Terrasan Environmental Solutions tapped to clean up contaminated soils. TEDCO’s environmental consultant, Trow Associates Inc. is overseeing the overall co-ordination of remediation work. The site is located south of Queen’s Quay Blvd., near the Jarvis St. slip.

“Our role on the project is to complete the bulk and detailed excavation work for the project and completing the remediation of the building site,” says Doug Dolby, a project engineer with Terrasan.

“The site covers about 7,000 square metres in area and is made up of a hodgepodge of historical imported fill, including deleterious building materials, assorted rubble, brick, concrete, wood, silt and fly ash.”

Extensive environmental investigations determine that the soil at the site is marginally impacted.

The major contaminants on-site include pockets of polycyclic aromatic hydrocarbons (PAH) and petroleum hydrocarbon compounds (PHC).

The building design is aiming for Gold certification under Leadership in Energy & Environmental Design (LEED) and some of the expected points are associated with soil recycling and remediation.

WILLIAM CONWAY/PROGRESS PHOTOGRAPHY

A team of excavators work on removing soil at the site of the Corus Entertainment complex on Toronto’s eastern waterfront. Much of the contaminated soil on site is being chemically remediated and reused in construction.

“We’re assisting TEDCO with recycling the soil,” says Dolby.

“That means that, instead of transporting the contaminated soil that exceeds Ministry of the Environment (MOE) Table 3 criteria for coarse textures to an MOE waste-recovery facility, much of the soil is being remediated and reused in construction.” All clean Table 3 soil that meets industrial/commercial MOE criteria from the site is taken by truck to nearby 51 Commissioners Road, another TEDCO site that will also earn LEED points for diverting the potential soil from landfill. The remediated soil confirmed by Trow, is reused for clean, inert fill.

The excavation depth of the site is 3.7 metres below grade. “They’ve already installed the caissons and rebar, so we were also chipping down the concrete so they could tie the building into those caissons,” says Dolby.

The remediation project began on January 2, with 12 remediation workers on site, not including drivers. The entire project is slated to be completed in just seven weeks. “It’s a quick turnaround for the project,” says Dolby. “We put extra people on the contract to ensure it’s finished on time.”

Workers on the site are following a detailed health and safety protocol, developed by Trow and Aecon.

Although atypically cold weather has frozen the ground, part of the remediation effort involves applying a dilute form of hydrogen peroxide to the soil to break down PAHs and PHCs into oxygen vapour and carbon dioxide vapour, with the remaining simple acids left for bio-degradation by the native microbial population of the soil.

Because the solution has a lower freezing temperature than water, it essentially defrosts the frozen soil on contact, making it more pliable and easy to manipulate. “Diluting the hydrogen peroxide with water in cold temperatures is a bit tricky,” adds Dolby.

The building, which will house 1,300 media and entertainment sector workers, is expected to be completed by 2010.

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