The Fire Road Mine coal mine in eastern Canada has been a source
of acid mine drainage since the mid 1980's. Lime neutralization treatment has
been ongoing and lime treatment costs and mine water acidity levels have
dropped significantly over time. Placement of the resulting treatment sludge back
onto and into the backfilled mine site may be a factor in reducing the mine water
acidity. One of the originally defined benefits of placing the sludge back into the
waste rock was that the sludge would fill up the void spaces and possibly
decrease the rate of oxygen diffusion to the waste rock that was above the
ground (mine) water elevation. This would possibly reduce the rate of acid
generation.
ERI results support the hypothesis that resistivity imaging can identify areas
where sludge is likely resident in the vadose zone. This information was beneficial
to determining the behaviour of the sludge in the vadose zone and initiated
discussions about the whether the benefits of sludge in this zone are temporary or
long term. Improving the mine water chemistry to "zero lime demand" is the
ultimate goal for mine water treatment at this mine.