Montgomery & Associates - Water Resource Consultants
Montgomery & Associates

In 2011, the Collahuasi Mine recognized M&A for achieving 2 million hours without accidents or lost time.

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Groundwater Management for the Collahuasi Mine

For over 25 years, M&A helps an Andean mine develop and manage its groundwater resources in an arid, ecologically sensitive environment.

  • M&A Project DescriptionsClient: Compañía Minera Doña Inés de Collahuasi SMC
  • Time frame: 1990s–present
  • Location: Andean Highlands of Chile

The Collahuasi Mine is located within the Coposa and Michincha basins — an extremely arid, ecologically sensitive area of Chile that lies at an elevation of about 4,400 meters (14,400 feet) above sea level. The estimated groundwater demand for this mine is about 1,000 liters per second.

M&A has provided a range of services for this client. In addition to developing large-scale, sustainable groundwater supplies for mining operations at Collahuasi, we have conducted modeling, monitoring, and satellite image analyses to understand the potential impacts that would result from pumping. Recent services include developing groundwater models to support geotechnical stability analyses at two mine pits — Rosario and Ujina.

Services

Groundwater Development & Management

  • Characterized regional hydrogeologic conditions

  • Summarized baseline hydrologic data

  • Designed a program for monitoring impacts to groundwater and spring flow from pumping associated with mine operations

  • Constructed weirs and installed electronic monitoring equipment

  • Used the results of aquifer testing to demonstrate well capacities for water rights applications and to evaluate alternative locations for production wells

Pit Dewatering Analysis

  • Analyzed data to characterize regional hydrogeologic and local pit conditions

  • Designed exploration and dewatering wells in the Rosario and Ujina pit areas and supervised their construction and testing

  • Designed and installed cemented-in transducers in both vertical and horizontal boreholes to measure pore pressures

  • Evaluated hydrogeologic conditions in surrounding areas that might support future pit expansion

  • Supervised the construction of in-pit horizontal drains

  • Designed and conducted packer tests in diamond drill holes; conducted aquifer tests in dewatering wells

Wellfield Services

  • Designed, tested, and supervised the construction of 5 pilot production wells and 13 exploration wells

  • Design and supervision of construction and testing of 13 production water wells

Hydrologic Modeling

  • Developed a regional groundwater flow model using FEFLOW to simulate and help manage dewatering operations for the Rosario Pit

  • Developed three-dimensional, sub-regional groundwater flow models for the Rosario and Ujina pits to predict water table positions to support geotechnical stability analyses for long-term feasibility pit designs

  • Developed a three-dimensional, pit-scale groundwater flow model predict pore-pressure distributions in the wall rock of the Rosario pit to support in geotechnical stability analyses for short-term operations

  • Developed a groundwater flow model for the Coposa and Michincha basins to optimize wellfield design and simulate the long-term impacts of pumping

  • Developed a flow and transport model to evaluate the potential for dissolved chemical constituents to migrate away from waste rock and tailing impoundment areas and impact downgradient groundwater resources

  • Developed a particle-tracking model to evaluate the capture of groundwater potentially containing elevated concentrations of dissolved constituents

Satellite Imagery Analysis

  • Analyzed 28 Landsat 5 satellite images for the period February 1986 – July 2005 for the Salar de Coposa, Salar del Huasco, and Salar de Michincha basins

  • Selected high-quality, cloud- and noise-free images; georeferenced them to facilitate comparison; and corrected them for differences in sun angle, satellite position, and atmospheric haze

  • Determined the vegetation and surface water areas and assigned vegetation indexes (abundance and health)

  • Compared results for basins with and without groundwater pumping

  • Identified potential correlations with precipitation and groundwater pumping

  • Developed a satellite image monitoring system to establish an historic environmental baseline for surface water and vegetation within the region's salar basins

Outcome

Work on this project is ongoing.