24 JULY 2022 WorldWide Drilling Resource® Lucky Friday Mine Demonstrates Success with New Method Adapted from Information by Hecla Mining Company Hecla Mining Company is the largest silver producer in the U.S. Founded in 1891, the company operates mines in Alaska, Idaho, and Quebec, Canada. The Lucky Friday mine in Mullan, Idaho, is one of Hecla’s operations which has been active since 1942. It is a deep underground silver, lead, and zinc mine located in the Coeur d’Alene Mining District in the northern part of the state. In 2021, Hecla began testing and implementing the Underhand Closed Bench (UCB) mining method at the Lucky Friday mine. This is a new, productive mining method developed in an effort to proactively control fault-slip seismicity in deep, high-stress, narrow-vein mining. The method uses bench drilling and blasting methods to fragment significant vertical and lateral extents of the vein beneath a top cut taken along the strike of the vein and under engineered backfill. It is accomplished without the use of drop raises or lower mucking drives, which could result in local stress concentrations and increased exposure to seismic events. Large blasts, using up to 35,000 pounds of pumped emulsion and programmable electronic detonators, fragment up to 350 feet of strike length to a depth of approximately 30 feet. These large blasts proactively induce fault-slip seismicity at the time of the blast and shortly after it. This blasted corridor is then mined underhand for two cuts. As these cuts are mined, little to no blasting is done to advance them. Dilution is controlled by supporting the hanging wall and footwall as mining progresses through the blasted ore. The entire cycle repeats and stoping advances down-dip, underfill, and in a destressed zone. The method allows for greater control of fault-slip seismic events, significantly improving safety. In addition, a notable 75% increase in silver production has been achieved by reducing seismic delays and utilizing bulk mining techniques. In 2021, 86% of the tons mined were produced through the UCB method. Hecla’s President and CEO Phillips S. Baker Jr. said, “The year also positions Hecla for future success with our exploration program delivering our highest silver reserves in more than 20 years and the Lucky Friday’s establishment of a new, innovative mining method that should be both safer and more productive. This method . . . will allow the Lucky Friday to increase projected production in 2022 by almost a million silver ounces over 2021, which was a million and half more than 2020.” Drilling and blasting operations at the Lucky Friday mine. EXB Looking for Events? Click on this box in our online issue worldwidedrillingresource.com
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