This multi-year, multi-disciplinary project included geochemical characterization of waste rock and evolved to include modified testing to evaluate the novel tailings management strategies at the Black Butte Copper Project. Enviromin’s design and implementation led to a defensible dataset and predictive water quality models to support continued mine permitting efforts. Using hydrologic, geochemical, and geologic data Enviromin developed geochemical models to predict water quality during operations and post-closure for underground workings as well as surface facilities (waste rock stockpile and cement paste tailings facility). Results from these models were used to assess compliance with non-degradation criteria and design of water treatment facilities for the Black Butte Copper Project.

Using geochemical data, and geologic and hydrologic models, Enviromin developed iterative predictive models of water quality for proposed pit lakes, underground mine workings, and heap leach dewatering ponds using PHREEQC and PHREEQ-Pitzer. The team also provided support for column testing and modeling of reactive transport of arsenic in groundwater. The Enviromin team assembled multiple sources of historical data, conducted gap analyses, and identified additional data needs using statistical analysis of existing data from nine pits and for 11 lithotype groupings. The extent of historical and recommended geochemical tests representing the scope of spatial and geologic variation of these projects required attentive data management, statistical analyses, and close coordination with site geologists and contract laboratories. Enviromin conducted relevant Acid Base Accounting (ABA) and Meteoric Water Mobility Procedure (MWMP), to supplement existing relevant data and adhere with Nevada Division of Environmental Protection (NDEP) and Bureau of Land Management (BLM) regulatory guidance. Enviromin used the results of this comprehensive static testing to select relevant samples for kinetic humidity cell test (HCT) work. Mineralogy analyses were also conducted, to validate MWMP and HCT results, using x-ray diffraction (XRD) and scanning electron microscopy (SEM) by a Nevada-certified laboratory. In support of the permitting process, Enviromin presented results to regulatory agencies for input and approval of kinetic test termination.

To support the Bonnie Expansion Project, Enviromin reviewed existing geochemical studies and conducted additional environmental geochemical testing. This work included careful review of the available data for potential use as analogs for the expansion area followed by a geochemical testing program to support the proposed expansion. Enviromin was able to conduct limited testing and use statistical techniques to generate confidence that the testing was sufficiently representative of the waste rock from the proposed project. The entire program, including initial comparison and final draft of the outcomes, was completed in less than two years, despite kinetic tests that ran for a full year. The Apex Expansion Project was subsequently identified as an underground alternative to the Bonnie Expansion Project. Enviromin was able to apply various statistical techniques to demonstrate that the geochemical data developed in support of the Bonnie Expansion Project sufficiently represented the rock to be mined from the Apex Expansion Project. Enviromin actively addressed agency comments with Barrick, resulting in regulatory approval of the Apex Expansion Project permit.