With a finished diameter of 18ft (5.5m), the Lucky Friday #4 Shaft was sunk to a final depth of 9,587ft (2,922m) below surface. The project is moving into the furnishing construction phase where shaft steel and the final conveyances will be installed. Project completion is scheduled for late 2016.
Justin Oleson, president of Cementation USA, said: “The sinking of the Lucky Friday #4 Shaft is truly a world class achievement. Each of the many Hecla and Cementation employees, suppliers, and subcontractors that worked toward this moment should be very proud of what has been accomplished. Special thanks go to our client, Hecla Limited, for the tremendous safety and project support we’ve received. This support was integral to the incredible safety and shaft sinking records that have been achieved.”
The Cementation group, which is currently sinking 15 shafts worldwide, stated that it has sunk the deepest single lift shaft in the world at the South Deep mine in South Africa, the deepest shaft in Canada at Kidd Mine D No.4 shaft, the deepest single lift shaft in the US at the Resolution copper project, and now the deepest shaft in the US.
George Sturgis, vice president – project development at Hecla Mining, commented: “Our partnership with Cementation to reach the bottom of #4 Shaft goes much deeper than 9,587ft below the surface. We share the value of safety that has come before the changing priorities for the work, and the secure planning foundation provided by thorough engineering. Hecla’s 125th anniversary will be celebrated in many ways this year, reaching the bottom of #4 Shaft with Cementation is surely one of the best.”
Eric Smith, general manager of operations at Cementation USA, said: “Reaching the bottom of #4 Shaft is an accomplishment that the Hecla/Cementation project team should be very proud of. The project team not only overcame many technical and logistical challenges, but also maintained an ethos of continuously identifying ways to enhance safety and project performance.”
Completion of this shaft is a major milestone for the historic Lucky Friday mine, which has been in operation for over 74 years. The shaft provides access to lower mining levels which increases operational flexibility and extends the life of the mine by 23 years. This milestone occurs in the same year that Hecla Mining is celebrating its 125th anniversary.
The Lucky Friday #4 Shaft is a vertical shaft that begins underground, which makes it a winze - an internal shaft which requires the equivalent of a shaft headframe and hoisting system to be installed underground before the excavation activities can occur.
Hecla selected Cementation USA to sink the shaft, excavate accesses, stations and pockets, and install the related infrastructure, which include a state-of-the-art fully automated ~180t/h material handling system, a 500 gallon per minute (1,893L/min) water pumping system, a centralised refrigeration system with 886t of cooling capacity, a batch plant, and other systems.