It’s May 2, 2018 and the graduating mining engineering class from UBC was up bright and early to make it to their first mine tour. After a quick coffee in the lobby of Los Portales Hotel in Tarma, the group boarded the bus at 05:30 to leave Tarma and by 08:30 had arrived at the Yauliyacu mine. Right away, the class was greeted with the utmost hospitality. As the mine is located close to 4,200 m above sea level, the first order of business was to have vitals checked, and blood pressure, heart rate, and O2 levels were compared to baseline results taken two days ago back in Lima. Once everyone was cleared fit to function at the high altitude, management gave a warm reception and took the UBC students through a presentation outlining the site’s operations.
Introduction and welcome to the Yauliyacu Mine
The location has over 130 years of mining operation history. It was first used by the ancient Peruvians and later by the Spanish to mine silver. In 1887, Cia Backus and Johnston initiated exploration and development of the region. By 1905, a smelter had been built and the site began producing metal. Cia Backus and Johnston sold the operation to Cerro de Pasco in 1921. In 1974, the Peruvian government nationalized the operation and created Centromin to operate the mine. In 1997, the project was sold to Glencore, the current owner. Yauliyacu was Glencore’s first mining operation in Peru. Empressa Minera Los Quenuales operates the mine as a subsidiary of Glencore.
The mine is an underground polymetallic operation that produces zinc, lead, copper, and silver concentrates. The mine aims to produce 1.4 million tonnes of ore this year (up from 1.3 in 2017). Average metal grades over the course of Glencore’s ownership are 2.7 wt% zinc, 1.1 wt% lead, 0.25 wt% copper, and 3.4 oz/t silver.
The deposit exists in the highlands mineralization region of Peru, where many base metal deposits have been found among volcanic sedimentary settings. The mineralization at Yauliyacu is made up of narrow veins which are folded around the local anticlines and synclines. There is also regional disseminated mineralization around these vein systems caused by hydrothermal fluids with low sulphide content. This creates two distinct types of ore zones: high grade zones consisting of small, narrow veins, and larger bodies of ore made up by low grade disseminated mineralization.
The bulk zones are mined using a mechanized sub-level stoping mining method. Most of the zinc occurs in these zones, and the current amount of production provided by sub-level stoping is as high as 95 percent. Narrow vein mining is carried out using conventional cut & fill methods and shrinkage stoping, and represents approximately 5 percent of total production. Higher silver grades occur in these narrow veins, and Yauliyacu plans to increase production from the narrow veins to 15 percent of total production. This will enable recovery of the high-grade silver mineralization.
After mining, stopes are backfilled with waste rock, and tailings from the plant are deposited in the tailings pond contained by the Chinchan dam. The underground operation currently is made up of seven sections. Sections 1 to 4 are shallower and are accessed by ramp using trolley-powered railcars, while Sections 5 to 7 are deeper and are accessed through a shaft located at the base of the trolley. Ore is moved via conveyor and hauled by a skip from the deeper sections.
While the technical elements of the operations where described, safety was ever-present in the orientation. Specific concerns were the high elevation and the mine’s seismically active environment. Micro-seismic events are an almost-daily occurrence, and the mine is built to account for these. Los Quenuales and Glencore maintain close communication regarding safety and implementation of new initiatives. One such initiative is the “12 Safety Priorities”, which were prominently displayed throughout the mine. The mine uses an integrated management system that maintains up-to-date certifications in both the Occupational Health and Safety Assessment Series (OHSAS) and the International Organization for Standardization (ISO).
The orientation could have easily extended much later into the day with the number of questions and level of engagement from the UBC students. Conscious of time, the group broke for breakfast. Here the staff at Yauliyacu truly outdid themselves, providing omelets, cheese, bread, meat, fresh fruit, juice, and hot drinks.
Following breakfast, brand new complete sets of Personal Protective Equipment (PPE) were provided to everyone. The group then loaded up in the rail cars and headed underground for the tour. The rest of the morning was spent walking ramps and touring areas of Section 4. The group visited some narrow vein stopes, seeing the sulphide mineralization in these veins. Bruno Chunga, the safety program manager, was UBC’s tour guide and did an excellent job showcasing the mine’s workings. Paths were well marked, and safety signage was extensive, making it very clear for the tour group to know where they were going and where they should not go.
UBC Mining students about to head underground by rail
One surreal moment that showcased just how much history exists at Yauliyacu occurred when students were crossing a walkway and noticed through the guarding a very narrow long stope with no visible back or floor. Wondering who could have possibly made this, students were informed by miners that this stope was mined 200 to 300 years ago by men working with hand tools in the opening. The miners talked about occasionally finding remnants of antique colonial mining tools left behind by the Spanish.
Students walk towards the current production faces underground
The tour group eventually worked its way back towards the railcars and shaft headframe where lunch was taken underground in the offices. Lunch was provided by the Yauliyacu staff, and was every bit as satisfying as breakfast had been. Following lunch, the tour group loaded into the shaft cage and descended deeper into the mine. At the bottom a fleet of Toyota diesel pickups transported students to Section 5, around 1,600 metres below surface.
Students arrive at the lowest section of the mine, via shaft
In Section 5, UBC students saw development and working stopes for some of the bulk production sections. Here the mine was active with miners scaling, drilling, and going about their working shifts. Bruno did a wonderful job of engaging the miners with the tour group and getting them to answer questions the students had about the sequencing and planning of their production operations. Bruno also challenged students to share their own feedback on the operations, particularly regarding safety, to help create a dialogue that would draw from the underground mining work experience students had gained in many different countries. Around 16:30, the group returned to surface via the shaft cage and railcars, and called an end to the full day’s tour.
Drilling in an active face was stopped so that students could ask questions
The graduating mining students from UBC are incredibly thankful for the thought and care the Yauliyacu staff demonstrated in hosting the class for a tour. It was an excellent start to the Graduate Research Trip, and everyone at UBC would like to express their utmost thanks to everyone for helping to make it happen.
¡Muchas Gracias, y esperamos volver a verte pronto!
UBC Mining students in front of the portal at Yauliyacu