The Mt Todd mine site is located within the Edith River catchment and is currently a significant source of Acid and Metalliferous Drainage (AMD). Downstream from the mine the Edith River flows into the Fergusson River, which ultimately flows into the Daly River system. During the wet season (December to April), runoff from the Mount Todd site drains either directly to the Edith River or indirectly through Horseshoe and Batman Creeks, that flow into Stow Creek and then into the Edith at the south east of the site.
For the remainder of the year, runoff does not occur from the site. At the time that mining operations ceased in July 2000, there had not been any significant remediation works undertaken. This left the site with a legacy of large volumes of mining wastes with the potential to generate AMD. Over the past few years, Batman Pit (RP3) has been used to store contaminated water primarily from RP1 and the Heap Leach Pad. This pumping combined with the Batman pit’s own catchment means that it is a net accumulator of water. A recent review of pit water levels, rainfall data and pumping records indicated that the storage capacity of Batman Pit is likely to be exhausted in the 2012-13 wet season.
The Department of Resources (DoR) requested that Water Technology Pty Ltd develop a water balance model of the mine to assist with mine site planning. In particular, the water balance model was to be used to determine the probability of uncontrolled releases from the pit and all mine site retention ponds during the 2012-13 wet season and to investigate the efficacy of various management options. This report describes the development of the water balance model.