BGC Engineering

A Geology and Subsidence Workgroup (Workgroup) was convened as part of the Resolution Copper Project Environmental Impact Statement (EIS) team. The purpose of the Workgroup was to review Resolution Copper Mining’s (RCM) procedures, data, and geologic and geotechnical baseline documents.

The scope of this memo includes a critical evaluation of the setup, calibration, application and predictions of the M&A (2020a) Skunk Camp TSF groundwater flow and transport model, including the related inputs from the KCB (2020) seepage model.

This report summarizes the Groundwater Modeling Workgroup evaluation of the model construction and approach for the groundwater model used to evaluate future groundwater conditions at and surrounding the proposed Resolution Copper panel cave mine.

Background information on subsidence in Arizona, followed by a summary of the potential volumes of water to be withdrawn by Resolution Copper at the Desert Wellfield and current and historic water levels at the Desert Wellfield. Potential subsidence is estimated from the proposed water withdrawal based on observed subsidence in the Hawk Rock Area, which is located northwest of the Desert Wellfield.

The purpose of this memorandum is to summarize the available information supporting this approach, some considerations in managing pyrite tailings, the available guidance and best practice, other examples of subaqueous tailings disposal, and to generally comment on the applicability for this Project.

This memorandum provides a summary of relevant state regulations and guidelines for assessing seismic hazard and estimating design ground motions as well as a summary assessment and any review comments pertaining to the objectives listed above.

This technical memorandum summarizes and evaluates Montgomery & Associates’ (M&A’s) use of the ADWR Salt River Valley model for pumping from the Desert Wellfield.

This memorandum is intended to provide BGC’s third party evaluation and expert opinion on each of the issues raised by Malach, through a review of Malach’s report and cited references and based on data and reports from RCM and their consultants, and discussions within the Workgroup.

The objectives of this memorandum are to summarize the information provided by RCM and reviewed by BGC and the Workgroup, describe key considerations, as well as available guidance and best practice in the industry for subaqueous disposal of reactive tailings, comment on the applicability of subaqueous disposal in an arid environment.

This memorandum provides a summary of relevant state regulations and guidelines for assessing seismic hazard and estimating design ground motions as well as a summary assessment and any review comments pertaining to the objectives listed above.