The El Limón Guajes Mine Complex (ELG) is comprised of our El Limón, Guajes and El Limón Sur open pits, our El Limón Guajes Underground Mine (including zones referred to as Sub-Sill, El Limón Deep, Sub-Sill South, and El Limón Sur Deep), and our processing plant and related infrastructure. The processing plant operates around 13,000 tonnes per day (tpd) with gold recoveries of 89%, slightly higher than the original design recovery of 87%.
El Limón Guajes (ELG) MINE Complex
Following the release of a feasibility study in October 2012, construction on ELG started in October 2013, with commercial production declared in April 2016.
Most ore is sourced by the El Limón and Guajes open pits with a smaller portion from our El Limón Sur open pit. The open pits contained approximately 885,000 gold equivalent ounces in reserves at the end of 2022 at an average gold equivalent grade of 3.27 gpt (863,000 ounces of gold at an average grade of 3.20 gpt gold). Lower-grade ore is being stockpiled. Open pit mining is expected to cease in 2025 with the forecast depletion of reserves. The ELG Underground contained approximately 508,000 gold equivalent ounces in reserves at the end of 2022 at an average gold equivalent grade of 6.17 gpt (480,000 ounces of gold at an average grade of 5.83 gpt gold).
Efforts to enhance the contribution of ore from ELG Underground have been successful. Following a record average underground mining rate of 1,523 tpd in 2022 (including 1,685 tpd in Q4), we are targeting to exit 2023 at a mining rate of 1,800 tpd and exit 2024 at a rate of 2,000 tpd.
Logistics & Processing
Ore from the Guajes open pit is trucked directly to a crusher located near our processing plant. Ore from the El Limón open pit is crushed and then transported to our processing plant using an innovative conveyor system called RopeCon, a Doppelmayr product. The primary reason to employ RopeCon was to reduce the safety risk of driving loaded ore trucks down steep slopes. Another major benefit is that the RopeCon produces more than 60% of the energy it consumes, and with this investment, we save approximately 5,520 in tonnes of CO2e emissions annually.
Ore from our mining operations is then treated in our centralized processing plant, which utilizes carbon-in-pulp milling technology with an associated cyanide leach to produce gold doré. The processing plant treats approximately 13,000 tpd of ore, of which a majority of ore processed is from the open pits.
A SART plant (sulfidization, acidification, recycling, and thickening) was commissioned in 2018 to remove soluble copper from the leach circuit. The SART plant reduces consumption of our two most costly reagents (cyanide and metabisulfite) by 20-30%, or approximately $10M/year. It also decreases the cyanide content of our tailings by about 5x and produces a saleable by-product with revenues that more than offset the plant’s operating costs ($5.5M OPEX vs $6.9M revenue).1
1) Average based on 24 months of operation in 2019 and 2020
The processing plant will be utilized to treat ore from Media Luna, which will require the addition of copper and iron sulphide flotation circuits as well as other changes to the plant. Upgrades to the processing plant related to the Media Luna Project are expected to be tied-in to the existing plant in Q4 2024, at which time the throughput of the processing plant is expected to be 10,600 tpd. The tie-in of the upgrades will require approximately 4 weeks to complete, at which time the plant will not be in operation.
For any mining operation, tailings management is a key environmental focus. ELG discharges no water to the natural environment and uses industry best practices with respect to tailings management.
The Global Industry Standard on Tailings Management (GISTM), a global best-practice standard for the safe and effective management of tailings, was published in August 2020 by ICMM, the United Nations Environment Program (UNEP) and Principles for Responsible Investment (PRI). In 2022, our Board of Directors supported Management's recommendation to formally adopt the GISTM and achieve full conformance within the prescribed timeframe.
At our ELG Complex, we designed and constructed a filtered tailings storage facility (FTSF), which is one of the largest globally and one we believe to be best-in-class in the mining industry. As such, Torex has taken considerable care and expense to mitigate the potential for a tailings failure to negatively impact the surrounding environment, including the adjacent Balsas River and Presa Caracol reservoir.
Mitigating the risk to these waterways started with the design of a tailings storage facility to contain the material. In order to reduce the amount of water within the tailings, we filter our tailings in a process which reduces the moisture content to approximately 17%. The remaining water is collected and sent back to the processing facilities for re-use. This conserves water, eliminates the need for tailing embankments and essentially eliminates the risk of dam failure.
Tailings are conveyed and stacked within the storage facility. A buttress of rock on the downstream side of the storage facility adds additional stability and safety. We have internal technical teams dedicated to monitoring the area daily, and their work is audited by external experts who inspect the site twice a year in both the wet and dry seasons. The facility is also inspected annually by an independent, third-party consultant.