At a major new gold mine project in the Andes of Chile and Argentina, ARCADIS and ARCADIS Geotecnica completed a premine assessment of natural acid rock drainage (ARD) conditions. The work included recommendations for active control options during mine operation, which will be designed to mitigate potential impact to downstream agricultural land uses. ARD is the most significant water-related problem facing sulfide metal mining operations throughout the world, and a great deal of time and effort is expended in the western United States to control these impacts from historic mining activities.

The purpose of the Pascua Mine project was to:

• Establish baseline water quality conditions at the mine site.
• Collect site-specific data to assess the potential for stockpiled ore, waste rock, and tailings to generate ARD.
• Identify potential mitigative measures to reduce the formation of ARD and/or the environmental impacts from ARD.

We documented existing natural ARD conditions by field measurements of surface water and groundwater quality, conceptual and analytical groundwater modeling, comparison with historic data, and correlation with structural geology. Also evaluated was the potential for ARD generation from rock disposed as tailings. This study represents an emerging environmental responsibility on the part of the mining industry.

Client Benefits:

• Pro-active approach to emerging environmental issues and regulations.
• Able to use the premine development period to document natural conditions and potential impacts to downstream receptors.