Is there a danger of acid rock drainage into the Lake or Boundary Waters?
Franconia will minimize the possibility of acid mine drainage leaving the site. About half of the waste rock and tailings, which will have sulfur levels about that of everyday rock, will be stored underground, to provide structural strength in mined out sections of the mines. The balance will be placed in a surface facility engineered to collect and treat, as required, water from the facility. On closure, the facility will be capped to minimize exposure to air and water, both of which must be present for acid mine drainage to occur.
