Mandy Lake is a small and inactive lacustrine subaqueous tailings disposal site located near the town of Flin Flon, Manitoba, Canada. During 1943-1944, 73,000 metric tonnes of high-sulphur base metal tailings from the nearby Mandy Mine were discharged into the lake.
The Mandy Lake site has been the object of two monitoring campaigns since it ceased its activities. The first one, in 1975-1976, focused on characterizing tailings material, water and vegetation. The second investigation, in 1989-1990, addressed in detail water quality, sediments composition and biota. It also emphasized the geochemistry of tailings and tailings interstitial water.
Both studies arrived at similar conclusions, namely that despite high sulphide and metal contents in the tailings, water quality in the lake is good and there is diverse and abundant aquatic life. The lake has rehabilitated naturally and will probably continue to do so.
Reclamation works at Mandy Mine were restricted to the former pit, buildings and causeway. No reclamation was carried out on the lake.
A comparison with other Canadian lakes used as tailings disposal sites reveals that the major impact from this practice occurs during the actual depositional stage; once discharge has stopped, the ecosystems gradually recover. Future investigations should therefore pay special attention to the recovery rate of lacustrine ecosystems so as to fully document the return of such disposal facilities to natural conditions.
