The Range of Environmental Concerns - Mining and the Environment: From Ore to Metal - page 531

For compliance with regulatory efl uent discharge standards, dei ning the i nal dis-
charge point is important ( Case 13.6 ).

For compliance with regulatory
effl uent discharge standards,
defi ning the fi nal discharge point
is important

Acid Rock Drainage

The most serious and pervasive environmental problem related to mine waste manage-
ment is arguably acid rock drainage (ARD), further detailed in Chapter Seventeen. ARD
is commonly associated with gold, copper, and other metal sulphide mining projects. It is
also common at coal mines where sulphide minerals may occur on partings in the coal or
in interbedded shales. However, there are many mining projects where there is no poten-
tial for ARD. These include most laterite mining projects for nickel, iron and alumina,
many uranium projects, diamond and placer tin mines. Acid generation occurs when mine
openings, pit walls, and sulphide-rich materials in waste rock and tailings are exposed to,
and react with, oxygen and water to form sulphuric acids. Sulphuric acid, which is gener-
ated easily, dissolves metals such as iron, copper, aluminium, and lead ( Figure 13.7 ) . This is
a natural process, occurring over thousand of years as sulphide-bearing rocks are subjected

CASE 13.6
Where to Measure Compliance?

Mining differs from manufacturing and other industries in
that mining activities are embedded into the natural envi-
ronment. The ultimate boundary of legal responsibility for
the mine operator is the boundary of the mine property

or assigned mining lease. In any given mine water man-
agement system there may be several water compliance
points, e.g. tailings slurry outlet at the thickener, decant
outlet at the tailings pond, water outlet at the polishing

pond, discharge point into the fi rst signifi cant surface
water body, or exit point at the mining lease
boundary.

CONTRACT OF WORK BOUNDARY

Creek

Final Discharge Point

Polishing
Pond

Settling
Pond

Mine Water

Tailings
Basin

Mine Water Ponds

Tailings
Pipeline

Process
Water

Mine & Mill

Possible Compliance Point