Waste and Tailings

Waste rock is the mined rock that does not have economic value. It is managed on-site according to strict and detailed environmental regulations and industry standards. Wherever possible, it is reused as fill in underground operations and site rehabilitation.

Tailings are the finely ground rock, trace metals and process chemicals remaining after ore has been processed. Hudbay adheres to the Mining Association of Canada’s highly regarded TSM protocols for managing tailings. Where water is plentiful, tailings have historically been piped into secure engineered impoundments contained by tailings dams. TSM guidelines address best practices for the location, design, construction, operation and closure of tailings facilities so that structures are stable and comply with industry and government standards, and solids and water are properly managed. Independent reviews are conducted on our tailings management design and practices in Saskatchewan and Manitoba and at Constancia, in accordance with the TSM protocol.

In the Manitoba Business Unit, the Flin Flon Tailings Impoundment System (FFTIS) has been operating for more than 80 years and covers about 350 hectares. Approximately 1.3 million tonnes of tailings are added annually. Safety measures include the following:

• Daily, weekly and monthly inspections by trained Hudbay personnel. For example, daily water sampling ensures that effluent quality is achieved 100% of the time.
• Comprehensive annual inspection of the FFTIS (including assessments of dam stability) by third-party geotechnical engineering consultants.
• Deposition plans to manage projected tailings production are produced by third-party engineering consultants.
• Detailed geotechnical designs for annual construction on the dams, completed by third-party consultants, are submitted to both Manitoba and Saskatchewan regulators prior to construction. Tailings dams usually grow in height and size over time. They are designed and engineered to be raised in stages to accommodate an increasing volume of tailings, reflecting the continued production from the orebody.
• An independent quality assurance/control monitoring program is in place during construction of dam raises.
• Inspection and monitoring of construction activities are performed by independent geotechnical engineering consultants.
• Upon completion of construction, detailed as-built engineering drawings are produced by the geotechnical engineering consultant and provided to the regulators in an annual report.

Separate from the annual inspections, a dam safety review is conducted every five years as recommended by the Canadian Dam Association.

In consideration of the environmental conditions in Arizona, Rosemont plans to construct a state-of-the-art, dry-stack tailings facility, which would use significantly less water than traditional facilities, allow for better dust control, be significantly more stable and reduce the potential of environmental impacts to groundwater. The use of dry-stack tailings will also allow more effective and earlier rehabilitation of the tailings area (see Rosemont environmental case study).