SNC-Lavalin Engineers and Constructors, Toronto, is the general contractor for a two-year, $24-million, lump-sum management-fee decommissioning of the Teck Cominco zinc-lead mine. The mine is 100 kilometers northwest of Resolute in Nunavut Territory. Operating since 1981, 280 meters below sea level, it produced a million tonnes of zinc-lead annually until it was closed in August 2002. Nunavut-based Qikiqtaaluk Corp. is earthworks subcontractor. Équipements Industriels Robert Ltée., Shawinigan, Quebec, is the demolition subcontractor. Montreal-based Tower Arctic Ltd. is removing a 300-ft-long cell-style dock and restoring the shoreline.
Nonhazardous debris will be placed in a rock quarry with an engineered limestone cap. Hazardous material will be placed within the mine, which has steel gates. The gates then will be covered with a 60-ft-deep concrete fill mixture that will freeze in the permafrost conditions, says John Knapp, Teck Cominco site manager.
The work force peaked this summer at approximately 150, including 15 professional staff, trades and 25 local Inuit working as equipment operators, camp catering staff, maintenance staff and polar-bear monitors. Polar-bear monitoring is extremely important because bears have become quite familiar with the site activities and could pose a threat to the workers safety, says Kevin Larmondin, SNC site construction manager.
The project began in late August 2002 when a freighter docked at the island with heavy equipment specially equipped for subzero temperatures with low-temperature lubricants, hardened cleats on track units and radiator covers.
Round-the-clock darkness begins the first week of November, says project manager Ray Venter. After two brief months, work shifted inside with the dismantling of the mines 90,000-sq-ft concentrator. Demolition of the steel superstructure started in May 2003, using excavators with hydraulic shears.
|SHEARED Cut-up debris is buried in a rock quarry.|
Its lower section was a barge, on which tugboats had brought the entire concentrator building to the site. It was also the mines 10-million-litre diesel-fuel storage container. That fuel had to be pumped out and the tanks remediated. Mississauga, Ontario-based Smits Tank Cleaning worked for six weeks on the remediation, which included using an explosion-proof industrial truck to vacuum the hull tanks. Waste fuels and sludge were incinerated in a custom-designed dual-stage incinerator. Demolition of the barge started in July and finished in mid-September.
Dismantling the 122,330-sq-ft storage facility was easier. Six Caterpillar excavators and bulldozers, a D8N, a 365, a D10 and three 345s, used chains to pull down the steel frame A-style building after cuts were made in the steel.
It took about 15 seconds, says Venter.
Next spring will see dock removal, shoreline restoration and demolition of the 200-room accommodation building where the work force stays. Power lines will have to be rerouted to a temporary camp where a remaining 20-person crew will live as the project draws to a close.
By October we hope to be out of there and leave the site in a virgin state, says SNC Construction Vice President Gary Mockler.
(Photos courtesy of SNC-Lavalin Engineers and Constructors)