Groundwater Development & Dewatering Support for the Collahuasi Mine

In addition to developing large-scale, sustainable groundwater supplies for mining operations for over 20 years, M&A designed and implemented groundwater flow models to evaluate mine dewatering and support geotechnical stability analyses at two open pits.

Overview

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.

Services

Mine Water Supply

  • Characterized regional hydrogeologic conditions and developed baseline data
  • Characterized the hydrogeology and developed a water balance in the pit and surrounding areas to support and preserve mine water rights
  • Used the results of aquifer testing to demonstrate well capacities for water rights applications and evaluate alternative locations for production wells
  • Designed a program for monitoring impacts to groundwater and spring flow from pumping associated with mine operations

Mine Dewatering

  • Analyzed data to characterize hydrogeologic / pit conditions
  • Designed 61 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

Wellfield Services

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

Groundwater Modeling

M&A developed the following hydrologic models for this project:

  • A regional groundwater flow model using FEFLOW to support dewatering operations for the Rosario Pit
  • A 3D subregional groundwater flow models for the Rosario and Ujina pits to support geotechnical stability analyses for pit designs
  • A 3D pit-scale model to predict pore-pressure distributions in the wall rock of the Rosario pit to support geotechnical stability analyses for short-term operations
  • A groundwater flow model for the Coposa and Michincha basins to optimize wellfield design and simulate the long-term impacts of pumping
  • 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
  • A particle-tracking model to evaluate the capture of groundwater potentially containing elevated concentrations of dissolved constituents