Sierra Madre Gains SEMARNAT Approval for Guitarra Mine Upgrades

Sierra Madre Gold and Silver announced that SEMARNAT approved modifications to the existing operating permit for the Guitarra mine and mill complex in the State of Mexico. These modifications include the implementation of dry stack tailings deposition, the construction of a tailings filter plant, and the use of backfill tailings, among others. The company considers this modification to be essential, as it could help it restart mining operations at La Guitarra. 

The approved modifications include the implementation of dry stack tailings deposition at the active tailings facility site, TSF 1-3. This will be complemented with the construction of a tailings filter plant adjacent to the existing mill. Additionally, Sierra Madre will employ paste backfill using tailings in the La Guitarra underground mine, while 58 surface drilling pad locations have been approved to support further exploration and development activities.

The approval for dry stack tailings deposition marks a significant milestone for Sierra Madre as it progresses toward potentially restarting operations at the Guitarra Mine. This modern system will replace conventional tailings deposition, allowing for more process water to be recycled and enabling more tailings to be deposited within the existing footprint of TSF 1-3. This method is considered more environmentally responsible and enhances long-term safety and security, the company noted.

TSF 1-3, which comprises two conventional tailings deposition sites, has a remaining capacity of 230,000t. The company plans to utilize this capacity during initial startup operations. Construction on one of these sites commenced in April 2024 and is expected to be completed before the rainy season begins in June. Construction includes building a dam, in 30cm compacted lifts, with the inner dam face and bottom covered by a high-strength HDPE liner.

At the processing plant's operating capacity of 500t per day, these expansions will support at least 15 months of operations. This timeframe will allow Sierra Madre to design and construct a combined dry stack and paste backfill tailings disposal system.

Sierra Made notes Stantec Consulting International and Ingenieria y Construcción de Presas conducted high-level studies indicating that TSF 1-3 could potentially accommodate at least 500,000t of dry stack tailings. Sierra Madre plans to conduct additional geotechnical drilling and studies during the upcoming rainy season to gather more high-water saturation data before finalizing the layout and design. The company noted this data will aid in making informed operational decisions.

The approval for using tailings for paste backfill is another crucial development. This process involves removing a portion of process water from the tail product of the plant, pumping it as a slurry to mined-out areas, mixing it with cement, and using it to fill open voids. This method enhances mine stability, increases process water recycling, reduces potential acid generation on the surface, and saves space in TSF 1-3. Initially, paste fill will be utilized in stopes below the main San Rafael haulage level, 10m above the processing plant, which minimizes initial pumping requirements and potentially reduces capital and operating costs.

SEMARNAT also approved 58 surface drill pad sites for testing various vein systems near existing La Guitarra mine workings and other areas north of the existing underground workings. These sites will enable the company to test the Progresso, Perdida Guitarra, and 350 veins, as well as the Las Palmas-Inca and Santa Teresa vein systems, which have never been drill-tested and have a combined surface strike length exceeding 9km. Historic mine workings and surface samples from these systems have shown economically interesting silver and gold values.