More polluted debris — this time slag — found buried atop Kenilworth drinking water reservoir

Add contaminated slag to the growing pile of pollution the city is paying $5 million-plus to remove from atop the Kenilworth drinking water reservoir.

A contractor found soil laced with benzo(a)pyrene, a common but cancer-linked industrial pollutant, while digging ahead of repairs to the 57-year-old reservoir above the Kenilworth Access. Council voted to spend up to $5 million to truck away 16,000 tonnes of polluted soil to ensure it could never leach into Mountain drinking water.

The good news is that soil is now gone - but the bad news is the work uncovered 3,200 cubic metres of contaminated slag stuck to the top of the water storage tank. City staff are recommending it also be removed as a safety precaution.

We don't want to have any risk that (the pollutants) migrate through the joints in the reservoir roof," said city water planning director Mark Bainbridge, who emphasized there is no evidence" to suggest any contaminants from the polluted soil or slag have thus far breached the aging drinking water reservoir.

The unwelcome discovery means pollution removal and other work atop the reservoir will continue until the end of this year and cost an extra $400,000, although most of the cost should be covered by the project contingency budget.

Slag is the waste rock separated from metal during steelmaking. In this case, city tests found some of the material is contaminated with polycyclic aromatic hydrocarbons, chemicals commonly found in coal, oil and gas.

Slag has often been reused for road building and cement manufacturing, noted Coun. Lloyd Ferguson, who questioned why the material posed a risk worth removing.

Bainbridge acknowledged slag can be found buried underground all over the city, including under many roads, but added we don't have storage of treated drinking water beneath roads."

Council is expected to sign off on the updated pollution removal project and cost next week.

Matthew Van Dongen is a transportation and environment reporter at for The Spectator. mvandongen@thespec.com