The East-Sullivan Mine Site: from Abandonment to Restoration
The East Sullivan mine was closed in 1966, leaving 15 Mt of acid-generating tailings free to contaminate the environment. An experimental wood waste cover was implemented in the early 80's in order to prevent sulphide oxidation. Contaminant production and dispersion were investigated in the 90's to validate that concept and guide later actions. Ligneous wastes stop oxygen, and also favour infiltration, rise the water table and allow a rapid flushing of pre-cover, acid-prone, groundwater. These are replaced by reducing and alkaline waters that favour sulphate reduction and base metal precipitation. The initial restoration strategy was modified to take advantage of these properties. An innovative treatment of acid effluents, based on the recirculation of water discharging around the impoundment through the organic cover, was implemented in 1998. Thanks to these unconventional approaches, the restoration budget could be cut by several M$, compare to the amounts required by standard, early 90's, techniques.