AGRU lining system supports an upgrade at a northern Nevada mine

Context

A northern Nevada mine and associated heap leach facilities began operations in 1986, utilizing a closed-circuit tertiary crushing system. By 2003, the system was replaced with an open-circuit crusher with higher throughput. In 2019, the system was upgraded to a single high-pressure grinding rolls (HDPR) crusher. With the transition to the new crusher, mine owners sought to take full advantage of the region’s low average annual precipitation. With about 13 inches of rain a year, mining operations could effectively operate 24/7.

However, the site’s fourth heap leach pad was nearing capacity and prompted the creation of a fifth, larger heap leach pad that would be able to help meet the requirements through the expected life of mine.

Challenge

Modern mining operations often rely on low-cost, high-efficiency technologies to keep the project profitable. Often, these mining operations utilize passive heap leaching to separate desired metals from crushed ores. Designing and implementing an effective heap leach pad requires careful planning as well as a strong, long-term design.

The mine described in this case study is the result of decades of iteration and improvements. The latest change saw the introduction of an HDPR crusher that supports year-round mining operations. The new crusher is expected to produce a finer product that facilitates cyanide heap leaching of silver and gold from ore, with an estimated 94% recovery for gold.

To achieve reliable, low-cost operations, both the heap leach pad and process pond required a durable and long-lasting containment system. Both would also need to be massive. And to further complicate matters, the expansion occurred during the global pandemic and a tumultuous time in the liner industry.

Solution

AGRU worked closely with the mine’s stakeholders to supply over 12.2 million square feet of high-density polyethylene (HDPE) liner for the leach pad and process pond despite industry shortages. AGRU manufactured 80 mil HDPE double-sided MICROSPIKE®, with about 10.8 million square feet going toward the new heap leach pad. AGRU also supplied about 600,000 square feet of 200 mil geonet for pond drainage as well as the geotextile specified for use under the riprap in the stormwater diversion channels and drainage outfall areas.

Because the fourth existing heap leach pad was fast approaching capacity, the mine owners set an aggressive schedule for completing the new pad. The contractor and installers worked with large crews to accommodate the schedule and have consistently beat milestones, thanks in part to AGRU’s liner having smooth edge seams that helped streamline installation.

MicroSpike also carries the benefit of being manufactured with highly consistent asperities that yield more reliable and predictable interface shear strength.

Outcome

The mine upgrade was completed on November 17, 2021, ahead of schedule.