Challenge: To establish baseline geochemistry and hydrogeology in support of a Preliminary Feasibility Study (PFS) and Environmental Impact Assessment (EIA) for a remote site with limited access.

Solution: INTERA completed a PFS-level baseline environmental and hydrogeological investigation for the San Matias Copper-Silver-Gold Project (San Matias) in northwest Colombia.  In collaboration with a local consulting partner, INTERA developed and performed a baseline investigation of site hydrogeology, hydrology, and mine-waste geochemistry designed to meet industry best practices and the requirements for a Colombian EIA. This work included characterization of the surface water (flow and chemistry) within the regulatory required hydrologic “area of influence”, as well as for the San Pedro River basin to inform the water supply trade off study.  To inform the surface and groundwater water balances as well as the numerical groundwater modeling, we conducted geophysical surveys, performed spring and water usage census; installed piezometers, and designed, installed and operated surface water flow measurements networks.  The aquifer testing program required a creative approach that integrated packer, injection, slug, and pumping tests due to limited access. Five of the electrical resistivity tomography lines for groundwater characterization were performed using pack animals in one area of the site and other wells required access by horseback. A geochemical characterization program that included standard static and kinetic testing was developed and implemented for the proposed waste rock, tailings, and condemnation area soils. The geochemical program also included a characterization of the geochemical properties, metal content and extent/volume of artisanal tailings deposited in streams for an evaluation of remedial options. Data from the hydrogeologic program were used to develop conceptual and numerical models of groundwater flow for a preliminary evaluation of mine pit inflows and the impacts of river withdrawals. 

Results: Data and analyses from the investigations were consolidated into a NI 43-101 Pre-Feasibility Study Technical report that will inform the upcoming Environmental Impact Assessment for the national regulatory agency (ANLA).