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Giant Mine Roaster Complex Decontamination and Deconstruction Project

Giant Mine Roaster Complex Decontamination and Deconstruction Project - Yellowknife, Northwest Territories, Canada

Decontaminating and Deconstructing the Giant Mine Roaster Complex

The Giant Mine Roaster Complex deconstruction project is a critical element of the remediation at a large, abandoned gold mine on the edge of Great Slave Lake within the Yellowknife city limits, about 250 miles south of the Arctic Circle. The mine operated from 1948 to 2004 under a series of owners. At project inception, the roaster complex’s buildings and other structures were in various states of disrepair and contained large amounts of arsenic trioxide (a byproduct of the ore roasting) and asbestos. Other contaminants included acids, caustics, cyanide, polychlorinated biphenyls (PCBs), and mercury.

Public Works and Government Services Canada (PWGSC) hired Parsons on behalf of Aboriginal Affairs and Northern Development Canada (AANDC) to decontaminate and deconstruct the 10 major structures at the roaster complex, which will effectively address the associated public safety and environmental risks. By deconstructing some of the most contaminated structures in Canada, Parsons will render the Giant Mine site safer and more stable until performance of the full mine site remediation project.

One of many contaminated sites in Canada’s federal inventory, the Giant Mine remediation project is crucial because of the large volume of arsenic trioxide throughout the interiors of the roaster complex buildings and in underground storage. Actions are complicated by the need to address the overlapping jurisdictions of federal, territorial, municipal, and aboriginal rights and interests. In addition, all activities pertaining to the Giant Mine cleanup are heavily scrutinized by regulators, aboriginal and non-aboriginal community members, and the news media.

In the roaster complex, the highly toxic arsenic trioxide occurs throughout the structures in forms ranging from loose dust to rock-like scale—and all present a high risk to workers, the public, and the environment. All decontamination and deconstruction work is performed in Level B personal protective equipment (PPE), including full-face respirators. In addition, continuous air monitoring is performed in work areas and at the remediation area perimeter fence.

Parsons is managing five specialty contractors, providing comprehensive services to decontaminate and deconstruct the 10 aboveground structures to slab-on-grade while protecting workers and the public. These structures had a collective area of about 2.5 acres and included two roaster buildings, an electrostatic precipitator building, a calcine process building, a fan house, a weight scale building, a maze of interior and exterior ducts and flues throughout the complex, a baghouse building where arsenic trioxide was removed, a 60-ft-tall silo for arsenic trioxide storage, and a 150-ft-tall chimney that dominated the Yellowknife landscape for more than a half-century.

Arsenic and asbestos waste in TDG-compliant cubic-meter bags

Arsenic and asbestos waste in TDG-compliant cubic-meter bags

During the 2013 field season, Parsons removed more than 4.5 million pounds (2,250 tons) of highly toxic arsenic and asbestos wastes. Wastes were packaged in cubic-meter bags approved for the transportation of dangerous goods (TDG) and are stored onsite for eventual disposal within the former mine. In addition, about 5,000 pounds of non-arsenic and non-asbestos hazardous wastes were packaged, shipped, and properly disposed of offsite. The stack, roaster flues, fan house, weight scale building, and arsenic silo were deconstructed after the client confirmed their decontamination, and decontamination is nearly complete in three of the five remaining buildings. All structures will be decontaminated and deconstructed by the end of the 2014 field season.

Parsons ensures that all federal, territorial, and municipal regulations and requirements are met throughout the decontamination and deconstruction processes. We achieve this by preparing and implementing detailed plans for project management, mobilization and demobilization, logistical support, dust control and air quality management, environmental protection, decontamination, and deconstruction.

Maintaining a Safe and Healthy Working Environment


To keep the arsenic trioxide and asbestos from escaping and potentially creating hazardous conditions in the community, Parsons first seals each building. In some cases, this involves covering the exterior of the building with scaffolding and then with shrink-wrap. Negative air machines pull air in, and exhaust is vented through high-efficiency particulate air (HEPA) filters to remove all contaminants. The buildings are decontaminated within the containment system, and all remaining building components are sprayed with a glue sealant. After the arsenic trioxide and asbestos-containing materials are removed and all internal building surfaces are decontaminated and sealed, the containment systems, including the shrink wrap and scaffolding, are disassembled and the final building deconstruction takes place. Using this approach, we effectively protect citizens and the environment from any release of arsenic trioxide or asbestos fibers during decontamination and deconstruction activities.

Site of former stack, roaster flues, fan house, weight scale house, and arsenic silo

Site of former stack, roaster flues, fan house, weight scale house, and arsenic silo

Challenges

The remote, near-Arctic location of this project poses multiple challenges. Parsons’ approach to successfully maintain the aggressive schedule while ensuring the safety of workers and the community included the following:

  • Parsons extended the fall construction season by nearly 2 months by improving thermal and other protection for workers and water systems. Some solutions required innovative thinking, such as applying petroleum jelly to skin contact points on the full-face respirators to ensure a continued airtight seal as gaskets became stiff and to prevent the masks from freezing onto worker’s faces. As a result, Parsons safely continued decontamination and deconstruction in the unheated structures even when temperatures fell to -27°C (-17°F). A base course of scaffolding installed around the remaining structures in the fall will enable starting operations in the spring well before the snow melts and ground thaws.
  • Because the local workforce was not trained in this type of work, Parsons provided extensive informal and formal training, including a 2-day course that resulted in asbestos card certification for the entire workforce, which involved more than 30 local aboriginal workers. This training and experience substantially improves their employment prospects after completing this project.
  • To address the logistical difficulties of working in a remote location with limited services, Parsons developed a dedicated logistical coordinator role to assist the project team in planning and procuring critical supplies and equipment. We effectively mentored our First Nation partner to fill this key function. We also revised project planning and scheduling practices to account for logistics issues.
  • We maintained flexibility to overcome unanticipated conditions such as delays in the installation of critical safety monitoring equipment by others at project startup and the discovery of large volumes of rock-like arsenic trioxide encasing the interior of the entire electrostatic precipitator system. We revised the project schedule and labor loading to address each problem, and we used earned value to accurately track progress.

As a result, Parsons is ahead of schedule, having completed 58% of the total scope—well above the 2013 field season goal of completing 47% of the effort.

During this winter shutdown, all remaining structures are in a safer, more stable configuration than in previous winters and are inspected weekly, with maintenance as needed. Crews will be working onsite by April 1, 2014, and all work will be completed before the winter of 2014.

Parsons continues to be a leading provider of dismantlement, demolition, decommissioning, and decontamination services, and we have one of the best safety records in the industry. By completing the decontamination and deconstruction of the Giant Mine Roaster Complex, the once unstable and highly contaminated area will be made safe until the full-scale, decade-long remediation efforts are underway for the rest of the contaminated former mine site. Parsons’ contribution is expediting the return of the land to citizens of the surrounding communities, who can then pursue endeavors ranging from fishing and trapping to development.