Reportage in Bergsäkert 2023#2
FROM 1500 METERS TO 1700 METERS
Sweden´s deepest mine becomes even deeper
Renström mine has long been Sweden’s deepest mine. Now it is becoming even deeper. From the current 1500-meter level, Bergteamet is developing the deep ramp to the new 1700-meter level on behalf of Boliden Mineral AB.
The ramp will mainly be used as an exploration site and is being built with several insertion chambers for drilling so that the ore body’s shape can be mapped in detail, making future mining production as efficient as possible.
“The test drilling is already underway with three drilling rigs,” says Per Lundgren, production technician for Boliden Mineral AB, in Renström mine.
Has existed for 70 years
Renström mine is located a few miles outside Boliden and is Sweden’s deepest mine. In January 2019, the depth of 1500 meters was reached, which corresponds to a little more than four Eiffel Towers stacked on top of each other. In the mine, which opened in 1952, ore containing zinc, copper, lead, gold, and silver is mined.
“The purpose of continuing deeper is that we have found mineable ore at this depth,” explains Per Lundgren.
High heat at depth
Bergteamet began the tunnelling project already in September 2022 and has currently reached 1583 meters.
The work has gone well, but one of the challenges is the temperature, which increases the deeper you go into the mine.
“At the deepest point, it is warm and humid. The temperature is around 25 degrees, and when the machines are running or when we have reinforced and the sprayed concrete is curing, it gets even warmer,” says Jörgen Olsen, Bergteamet’s Site Manager.
Transport times and ventilation
The great depth also brings long transport times. It takes about 40 minutes to get down or up, one way.
“The distance to reach the 1583-meter level is almost exactly 15 kilometers, and considering the driving time, it is important to plan the logistics so that we have efficient work,” says Jörgen.
Another challenge is ventilation. To solve this, there is a new ventilation shaft that goes from 1480 down to the 1502-meter level. The air is then led further via ventilation tubes running along the ceiling.
Good rock conditions despite the depth
“There is high rock pressure down here, but the rock is actually incredibly good despite being so deep. We also know from experience that there are difficult rock conditions in the nearby area where we are develop the ramp. We have kept a few blasts short, but otherwise, we have been able to keep the same pace as usual,” says Jörgen.
Safety is important, and adjustments are constantly made according to the conditions.
“We constantly monitor the rock. The rock mechanics continuously check for cracks in the rock or if any reinforcement bolts are loosening, and then we act together based on that,” explains Per Lundgren.
Close cooperation in production
The project to develop Renström mine to record depth is based on close cooperation.
“Per and I meet every day, and all foremen hold briefings where we go through if anything important has happened in terms of health, environment, and safety or if any special events are planned for the day,” says Jörgen Olsen.
The relationship between Bergteamet and Boliden is good and significant, according to Per Lundgren.
“We have known each other for many years, and Bergteamet is easy to cooperate with. We get quick help, and we solve everything together. Therefore, it is natural to continue the cooperation,” he says.
Has long experience
Per has worked at Boliden for 30 years, and 27 of them have been in Renström mine.
“When I started here, the deepest level was 1000 meters, and the plan was to close the mine within a few years, but that didn’t happen. Today, Renström mine is a successful mine with new discoveries,” he says.
The depth surprises many
Renström mine is the deepest in Sweden and probably the deepest mine in all of Scandinavia.
“It is fun that we get to develop the deepest mine and always be at the lowest point. We have gotten used to it ourselves, but when talking to outsiders, many are amazed when they hear about the depth. For us, it doesn’t really matter if it is 120 or 1700 meters. We work just as carefully and purposefully regardless of depth, but it does feel a bit extra fun anyway,” says Jörgen Olsen.
Finished in a year
The work to develop the ramp began in November 2022, and the plan is to be down to 1700 meters by the turn of the year 2024/2025.
Reportage in Bergsäkert 2023#2