Vista Gold Corp. (TSX, NYSEAMEX: VGZ) has completed the first phase of water treatment at the Mt Todd mine site in Northern Territory, Australia, and has received authorization to release treated water from the mine site into the Edith river, subject to stringent water quality and environmental standards.
In a press release the miner said that, as part of the water management plan to protect the nearby Edith River system, approximately 10.3 gigaliters of water affected by acid rock drainage is currently stored in the Batman pit.
The gold firm had undertaken laboratory, bench-scale and pilot-scale testing programmes to evaluate the effectiveness of the water treatment methods to be used at the Mt Todd gold project.
The water quality had rapidly improved with the pH rising from 3.3 to 6.4, with significant decreases in the concentrations of aluminium, copper, chromium, iron and lead as a result of to precipitation. Vista said it continued to add about 2 000 t of hydrated lime and believed water quality would continue to improve as the water approaches the pH target of 7.
Vista had a permit to release treated water only when flow rates were sufficient to ensure that Australian drinking water standards for health were achieved downstream of the mixing zone.
The company carries out daily water quality testing during periods of discharge, and yearly macro-invertebrate and sediment testing programmes in the Edith river to ensure that there is no long-term impact to the environment.
Based on historic flows in the Edith River, Vista estimates that two wet seasons would be required to complete the discharge of water from the pit.
To date, Vista had invested over $9 million in the water treatment programme and the construction of the automated management system.
Vista is currently working on completing a feasibility study for the Mt Todd gold project.