Mine Waste Dumps – Waste Rock, Ore and Other Stockpiles

Overview of BC Law

Mining activities inherently disturb large volumes of soil and rock. As a result, waste rock, ore and other soils are generally stockpiled on the mine site during operation. At closure, BC law requires these stockpiles (dumps) to be reclaimed in a manner that ensures:²⁵⁵

• long-term stability (to meet the criteria provided in the Interim Guidelines of the British Columbia Mine Waste Rock Pile Research Committee)²⁵⁶
• long-term erosion control;²⁵⁷ and
• re-contouring that is consistent with the approved end land use.²⁵⁸

The material inventory maintained during operation of materials having ARD/ML potential must also be submitted to the regulatory authority at closure.²⁵⁹

Issue

The critical nature of slope stability requires clear legal provisions to govern decision-making.

Recommended Solutions

Mandate an engineering analysis of stockpile slope stability

[Tags: Slope Stability; Impoundment]

An understanding of slope stability is necessary for the safe and economic design of waste rock, ore and other stockpiles. Absent such understanding, stockpiles can pose a serious threat to local downstream communities.

BC law, however, does not explicitly require engineering analyses of final slope stability. Instead, it merely provides that “the long-term stability of exposed slopes of major impoundments shall meet the criteria provided in the Canadian Dam Association, Dam Safety Guidelines at the time of permitting or as amended by the chief inspector”. ²⁶⁰ It is also left to the Chief Inspector’s discretion as to whether a licensed professional will be required to prepare the closure plans. Conversely, this requirement is mandatory in other jurisdictions. For example, in California, final slope angles must be flatter than the critical gradient for the type of material involved. Furthermore, when final slopes approach the critical gradient an engineering analysis of the slope stability is required.²⁶¹

Mandate the stockpiling of mine wastes in a manner that facilitates phased reclamation

[Tags: Reclamation; Waste Dumps]

Progressive reclamation of mine waste dumps is also an important consideration for reducing reclamation at closure. This need is recognized in California, where legal provisions mandate that mine waste must be stockpiled in such a manner as to facilitate phased reclamation. These mine wastes must also be segregated from topsoil, topsoil substitutes and growth media salvaged for use in reclamation.²⁶²