Current Conditions:
 

The waters of Berkeley Pit Lake are severely polluted.  The pH of the lake is roughly 2.5, with the high acidity due to the oxidation of pyrite and other sulfides that are exposed to water, O2, bacteria, and other elements that are released into solution by direct oxidation of sulfide minerals or by secondary reaction with acidic water1.  The lake contains high concentrations of As, Cu, Cd, Co, Fe, Mn, Zn, SO4, and other inorganics.  Environmentally, the concentrations of these metals are toxic.  Economically, however, they are not found in high enough concentrations to make recovery profitable.       FeII/Fe III cycling in the lake is dependant on O2 concentrations and the photo-catalytic effect of sunlight near the surface.  Fe and SO4 also precipitate as jarosite and other oxy-sulfate compounds.  The pit water contains deep and shallow zones with distinct properties.  The chemocline (zone of rapid physical and chemical change) is at about 50 feet of depth.  In the epilimnion (upper zone), pH is 2.5, and the water reaches 0 degrees C (surface freezing occurs) in winter and about 25 degrees C in summer.  Conductance is 7,900 uS, redox is 670 mV, and turbidity is 30 NTU.  Important dissolved ion concentrations are Cu: 140 mg/L, Zn: 540 mg/L, and the FeII/Fe III ratio is 0.36.  In the hypolimnion (lower level) the pH is 2.5, and temperature is consistent at 4.5 degrees C.  Conductance is measured at 8,600 uS, redox is 630 mV, and turbidity is 5 NTU.  Dissolved ion concentrations are Cu: 190 mg/L, Zn: 620 mg/L, and the FeII/Fe III ratio is 2.51.  The values of other heavy metal concentrations are also extremely toxic to plant and animal life.  In addition, there is no detectable organic carbon available to support the growth of organisms in the lake.

Workers board the S.S. Berkeley Pit to sample the water conditions1.     Sediment samlpling helps determine the dissolved chemical composition of the water1.