Short and Long Term Environmental Effects of Marine Tailings and Waste Rock Disposal from a Lead I Zinc Mine in Greenland

During its active operation from 1973 to 1990 the Black Angel Mine in West Greenland disposed its tailings in seawater slurry to a fjord. During the disposal between 10 and 30 tons of lead and between 30 and 55 tons of zinc dissolved annually in the receiving sea water. This resulted in a significant pollution of the surrounding marine environment. Other pollution sources, particularly waste rock dumps and dust from the ore crusher and concentrate handling, also were important. After closure of the mine in 1990 a waste rock dump was excavated and partly deposited on top of the tailings on the fjord bottom below 60 m water depth. The heavy metal pollution at the site has been monitored while the mine was operating, but also after mine closure in 1990, after which significant improvements of the environment has been observed in sea water and marine organisms. Analyses of the sea water after mine closure indicate that from the undisturbed tailings and waste rock deposited on the fjord bottom 0.1 tons lead and 5 tons zinc dissolve annually. The experience from this operation is that marine disposal of mining waste, which in some cases seems to work satisfactory, also can be a risky operation. Systematic testing of the waste is important before a decision is made to dispose mine