Mine Openings – Underground Workings and Open Pits

Overview of BC Law

Under BC law, miners must “take all practicable measures to prevent inadvertent access to mine entrances, pits and openings that are dangerous by reason of their depth or otherwise, by unauthorised persons and ensure that the mine workings and fixtures remain secure.”²³⁹

Specific legal requirements for decommissioning underground mine workings in BC are as follows:

• All underground mine openings (shafts, raises, stope openings, adits, or drifts) must be “capped with a stopping of reinforced concrete or filled with material so that subsidence of the material will not pose a future hazard;”²⁴⁰
• For shafts or raises, the stopping must be “secured to solid rock or to a concrete collar secured to solid rock” and capable of supporting a specified uniformly distributed load;²⁴¹
• “Where there is evidence or a potential for use by wildlife, mine openings may be fitted with a barrier that allows wildlife passage but prevents human entry;”²⁴²
• A permanent and effective drain must be installed when mine openings are permanently closed and there is a risk that mine water may build-up dangerous pressures that could cause a blow-out of the fill or concrete.²⁴³

Specific legal requirements for decommissioning open pits in BC are as follows:

• Pit walls constructed in overburden must be reclaimed in the same manner as dumps;²⁴⁴
• Pit walls do not need to be re-vegetated;²⁴⁵
• Pit floors must be re-vegetated where they are free from water and safely accessible;²⁴⁶ and
• Where pit floors will impound water, but not form part of the permanent water treatment system, the water body that is created in the pit must achieve use and productivity objectives.²⁴⁷

Provincial policy also recommends that geotechnical stability assessments be completed for the sealing of mine openings.²⁴⁸

Issue

BC law lacks specific, enforceable legal provisions regarding the marking and rehabilitation of mine openings.

Recommended Solutions

Clarify the legal requirements for fencing and warning signs around mine openings

[Tags: Enforcement; Monitoring; Health and Safety]

Under BC law, there are no explicit legal requirements to install fencing and warning signs around mine openings. Conversely, this is a mandatory legal requirement in other jurisdictions. For example, in Quebec, specific legal requirements for fencing are specified for the mine worksite.²⁴⁹ In addition, warning signs must be placed at the entrance to the mine access roads and at set intervals.²⁵⁰

Enact specific legal requirements for rehabilitating open pits

[Tags: Pit Flooding; Closure Plans]

In Ontario, legal provisions specify preferred methods for rehabilitating open pits. Greatest preference is given to pit backfilling, followed by flooding “if fully justified in the closure plan”.²⁵¹ Where flooding is the chosen method, “a professional qualified in hydrogeology shall predict the water elevation within the pit to provide an assurance of the continuing effectiveness of flooding as a protective measure”.²⁵² Sloping may only be used if proven to be “more appropriate than backfilling or flooding”.²⁵³ Finally, where sloping is also deemed impracticable, boulder fencing or berming may be employed if fully justified in the closure plan.²⁵⁴