recent key projects
bear creek mining corp, peru
GRE has been involved with the +300 million ounce silver, lead, zinc bulk tonnage open pit project since 2011. The project is located at an elevation of 5,000 meters in challenging terrain. GRE’s initial responsibilities included geotechnical, hydrogeologic, and environmental drilling and site investigation programs for the project Feasibility Study (FS) and Environmental Social Impact Assessment (ESIA) permitting (in Spanish) in 2012. In 2014-2015, GRE completed a project optimization study of mine, process, tailings, and hydrologic aspects of the project, followed by a FS update that included the resource estimate, mine plan, and geometallurgical model, with input on process design. The geometallurgical model utilized state of the art non-parametric statistical methods to create a multivariate adaptive regression model that greatly improved the spatial understanding of metallurgical response, allowing GRE to optimize the mine plan, significantly enhancing project economics. In 2017, GRE provided Qualified Persons oversight of the Phase 1 Front End Engineering Design Study involving geology, resource, reserve, hydrology, geochemistry, mining, marketing, and project economic models.
amulsar project feasibility study
lydian armenia, armenia
GRE supported the 3.5 million ounce Amulsar gold project through the performance of a series of FSs. The Amulsar Gold Project is currently under construction. GRE’s contribution to the FSs included: design and stability evaluation of the barren rock storage facility, pit dewatering predictions, acid rock drainage (ARD) management, and closure planning related to water quality management issues. The barren rock storage facility design required waste blending and waste encapsulation to mitigate ARD risk. This exercise involved the careful management of acid generating and non-acid generating waste streams from the pit to allow for the creation of encapsulation cells without the need for doublehandling of the waste. Due to the encapsulation design and other elements of GRE’s ARD management plan, the site is able to consume all ARD-impacted leachate during operations, or is able to treat ARD-impacted water using affordable passive treatment alternatives. Using GRE’s approach to barren rock management and ARD management, Lydian was able to realize ~$65M in projected savings in comparison to prior ARD management plans and barren rock storage facility designs.
luna gold, brazil
For the Pre-Feasibility Study (PFS), GRE performed the following: waste rock storage facility design, pit dewatering predictions, surface water management plan, geochemical characterization, pit slope stability, and acid rock drainage (ARD) management plan. Key challenges to the project included the remote location, the management of saprolitic soils, the management of extreme seasonal precipitation, and the close proximity of the Atlantic Ocean to the pit (which ultimately will be significantly below sea level). The GRE team performed multiple rounds of hydrogeologic, geotechnical, and geochemical field characterization. The team created an integrated slope-stability model and hydrogeologic model for the pit that allowed for an optimized pit slope angle (thus saving waste rock production). In addition, GRE saved significant capital by optimizing the existing water management infrastructure from the prior mine operation. The end result of the effort was a PFS with a positive economic outcome that permitted rapid financing.
anfield gold, brazil
GRE has been involved with the narrow vein gold Coringa project since 2009, including the initial resource, at the Preliminary Economic Analysis (PEA), and FS stages, with overall project responsibility for the PEA. The most recent work included developing a surface water management plan, groundwater management plan, waste rock dump design, environmental monitoring plan, and acid-rock drainage management plan for the development of the Coringa for the FS. Key challenges of the project included the management of extreme tropical rainfall, the management of saprolitic soils, and environmental management in a sensitive tropical rainforest ecosystem. GRE performed hydrogeologic, geotechnical, and environmental field work to collect the necessary data, and GRE has created predictive models for the following: water balance, dewatering, tailings storage facility seepage, geochemical water quality, and waste rock dump stability. These predictive models form the key sections of the FS and Environmental Impact Assessment. Prior work (2009-2015) included two resource estimations, two PEAs, a scoping acid rock drainage characterization, and the initial hydrogeologic characterization. The Coringa project is currently under construction.
NEW CASTLE GOLD, CALIFORNIA
GRE has been retained by Newcastle Gold to perform the open pit mine optimization, mine design, and capital and operating cost estimates for the previously producing, 4.0 million ounce Castle Mountain gold project in Southern California. Key features of the project include land and water constraints that required innovative solutions. The study is expected to be finalized in the first half of 2018.
GOLD SPRINGS PROJECT
PRELIMINARY ECONOMIC ASSESSMENT
TRI METALS MINING, UTAH/NEVADA
GRE provided structural geologic mapping support, metallurgical test work support, completed several mineral resource estimates, and PEA of the nearly million ounce Gold Springs heap leach gold/ silver project. The work consisted of numerous pit sizes and production rates identifying various viable scenarios. The results were further analyzed to determine the most robust economic scenario to advance to the next level of study. GRE is continuing its involvement in the project as it advances to the PFS stage.
GRE evaluated numerous mining and processing options for the moderately refractory multimillion ounce green fields gold project. Both open pit and underground mining were considered in combination with a series of processing options including: flotation and ultra-fine grinding with cyanidation, pressure oxidation of flotation concentrates and whole ore, and bio leaching of low grade ore and flotation concentrate. Preliminary mine plans and production schedules were developed, including capital and operating costs for each scenario. The study involved review of historic metallurgical testing and the development of metallurgical balances, design criteria, and cost estimations. The study also included preliminary analysis of the ARD potential, and permitting and closure requirements, along with water management.
PEA, OPERATIONS SUPPORT, TAILINGS CONSTRUCTION DESIGN
ECI EXPLORATION & MINING, MEXICO
GRE completed a PEA for expanding a currently producing 150 tpd silver-gold-lead-zinc underground mine and mill operation to rates up to 1,500 tpd. The PEA considered multiple production rates and mining sequences, and cutoff grades, to determine the optimum economic expansion scenario. We also assisted in the review and refurbishment plans for the entire operation including the mine, mill, and tailings facility. The mining work involved detail mine planning, development sequencing, estimating manpower, equipment, and material requirements. The plant review included oversight of a comprehensive metallurgical program involving different ore types to maximize recovery of gold and silver. GRE also provided recommendations for expansion of the flotation plant, and a review of the partially constructed oxide circuit identifying the additional equipment required prior to commissioning. The tailings work included review and redesign of a partially designed and constructed tailing storage facility. The design updates of the TSF included a liner system, seepage and stability evaluations, updates to the staging of the upstream raises, and compliance with groundwater monitoring. GRE also assisted on the preparation of tailings design documents used for permitting, including translation to Spanish. GRE’s work was used to create a detailed 18-month operating budget for the existing mine using productivities, consumption rates, and current unit costs. GRE also played a key role in updating the cost accounting system to better track operating and capital costs for management and to support due diligence review of potential partners.
HEAP LEACH DESIGN &
ALACER GOLD, TURKEY
GRE completed the construction level design for the Phase 4 leach pad which will allow the stacking of up to 68 million tonnes of ore on the ultimate pad. The design included a benched foundation and stability buttresses to maximize ore storage within the facility. Staged construction has been ongoing since 2015 and is scheduled to be completed in 2018. Alacer has now asked GRE to perform the Phase 5 work. GRE has actively supported the construction by reviewing daily construction reports, verifying manufacturer certificates for materials meet specification and answering operational questions. GRE also provided recommendations for stability monitoring for a Hydro-Jex heap injection program design to liberate entrained leach solution and extract additional gold from the heap through a series of pressure injection wells. Alacer is contemplating a Phase 5 expansion for the leach pad, where GRE is assisting them in the preliminary evaluation and study plans.
ARD MITIGATION &
GRE is assisting a 20,000 tonne per day operating copper mine with ARD characterization, and mitigation. In addition, GRE is conducting a geotechnical and hydrogeologic investigation of the existing tailings storage facility (TSF). GRE’s work includes performing on-site geochemical kinetic cell tests on potentially acid generating (PAG) waste rock. The work is designed to characterize ARD kinetics under ambient climate conditions. Additional testing will determine the effectiveness of microbial controls designed to suppress the microbes that catalyze ARD-forming chemical reactions. The ARD mitigation effort also includes a large scale ARD waste rock trial encapsulation test with long term monitoring using lysimeters. The goal of this work is to develop a strategy to manage long ARD development in waste rock and pit walls and to reduce future water quality management costs. GRE designed and executed a geotechnical investigation of the exiting tailings storage facility. GRE oversaw the installation of geotechnical monitoring instruments and an extensive Cone Penetration Test (CPT) program to characterize the subsurface conditions. Along with the CPT investigation, samples were collect to depth and from surface material for laboratory analysis. Piezometers and Vibrating Wire Piezometers were also installed to better understand the phreatic conditions and pore pressures within the dam. All of the data collected was used to develop the database required to analyze and predict seepage behavior and geotechnical stability within the dam.