The proposed Talon Metals mine in Tamarack is an underground mine. Ore extracted from the mine is planned to be shipped to a new processing plant in North Dakota (announced by Talon in October 2022).
The mine will have multiple shafts down to the mineral deposits. The main shaft will provide primary access for personnel and materials will be a decline ramp from the surface. This shaft will also serve as the main fresh air intake for the mine and the main conduit for mine services. The main shaft will be approximately 1700 feet deep with a 12" concrete liner.
In addition, a multi-purpose shaft will be driven in close proximity to the surface based storage area. This shaft will act as the main exhaust for the mine and will house a vertical conveyor for the materials handling system (hauling material up to the surface for storage and transport to North Dakota), secondary egress and redundant services, where required.
Once down to the level of the deposit, lateral tunnels are created around and into the mineral deposits to extract the ore.
Stopes (large underground rooms) are created as the ore is brought to the surface for storage and shipping. It is expected that the mine will extract
approximately 3,600 tons of material per day. At approximately 85 tons per rail car, this equates to about 43 rail cars per day.
Underground blasting is likely used to release ore from bedrock. We note that at the Eagle Mine in Michigan, people can feel the blasts at all hours often twice a day from MANY miles away. Dust created by the blasting underground is vented to the surface via the main exhaust vertical shaft. Mine operations generate significant air borne pollution vented directly into the atmosphere and as such, Talon needs to filter the main exhaust shafts with industrial air filters capable of removing potentially toxic dust from blasting. These filters are not currently in the Talon mine plan. Talon will also need to implement dust mitigation for normal material handling (loading and transfer of ore and rock) as well as covering the storage areas and rail cars to prevent wind blown propagation of toxic dust.
Originally, an on site processing plant was planned to process the extracted ore. This plant would have produced a significant quantity of high sulfide tailings. The original plan was to backfill the fully mined stopes (the large underground rooms left by removing the ore) using a cement based paste backfill mixed with high sulfide tailings and development waste rock. If the mined out stopes can no longer be filled (there are no tailings to create the paste backfill) there could be a large increase of water flowing from the acquifers into the mine from exposed water features and thus creating a significant amount of additional water that must be pumped out.
There are two main sources of water that must be removed from the mine, service water needed for underground operations and mine water entering from all of the aquifers above via what Talon calls "water bearing features" in the exposed rock.
Relative to mine service water, the Eagle Mine report and tour information, the 2020 Talon PEA and the 2021 PEA all talk about how much water is needed for underground operations. You need to pump water down into the mine for:
Generally, when Talon adds up all of the above water needs, they estimate about 330,000 gallons of water per day for underground mine operations (see page 227 of the Talon 2021 PEA - link in the footer of this page). This is based on the known water needs for each piece of equipment and use. And of course, this is all consistent with what the Eagle mine reports. And these pumping requirements are fairly consistent between the 2020 to the 2021 PEA. This water does not soak into rock, it needs to be pumped out, thus dewatering of the mine is required and becomes a part of the total mine pumping requirements.
In addition, both the 2020 and 2021 PEA conclude that there will 9.9 gallons / minute per water bearing feature coming in from the aquifer with an average of one water bearing feature per 216 meters of drill data as measured through past data logging. This is a scientifically supportable level of water inflow based on Talon facts and of course, this inflow increases as the mine surface area increases. This is well documented on page 228 of the 2021 PEA. Here Talon estimates between 2.3-2.6 million gallons of water per day must be pumped out of the mine based on an average inflow noted above. However, if the stopes are no longer filled with the paste backfill, one could expect the number of water bearing features to increase dramatically. This raises the question, How much beyond the 2.6 million gallons a day must now be pumped? Will it be 5 million gallons? More?.
Or will will Talon ship in gravel and sand to be used for filling the stopes? Talon plans to extract 3600 tonnes (metric) of material per day (per their PEA). That's about 4000 US tons. To replace that material, logically, you would need to fill with about 4000 tons per day of gravel (mixed with a bit of cement for the paste fill). That's another 40-50 large train cars of sand and gravel per day that most be shipped into the facility from someplace, everyday, 365 days a year for 12 plus years. It is not clear where they might get this material.
The 2.6 million gallons of water is dirty water (contaminated by sulfide dust as well as direct contact with the sulfide ore) but Talon has not committed to treating this water in their documentation. Treatment of this water would require large, energy intensive industrial filters that change the water chemistry impacting local lakes, wetlands and aquifers when the water is released into the environment. In addition, where does Talon release this water? Will a new lake be created? Can the aquifers be replenished? How much will lake and wetland water levels drop? All unanswered questions.
The Michigan Eagle Mine is an underground nickel-copper mine similar to what is being proposed for Tamarack (See www.michigan.gov/-/media/Project/Websites/egle/Documents/Reports/OGMD/2020-ogmd-eagle-mine-annual-report.PDF for details related Eagle Mining monitoring anomalies). At Eagle Mine monitor point QAL023B, the mean water level readings from 10/2019 – 9/2020 indicated a maximum of 1.7 feet (ft) below the calculated minimum background baseline level. The mine attributed this drop in water levels pumping of the mine services well and groundwater infiltration into the mine. This drop in water levels is due to an average pumping requirement of 80,000 to 150,000 gallons a day – but the Talon Tamarack site must pump potentially much more than 2,600,000 gallons per day!
In addition, the Eagle mine listed at least 17 monitoring events that show levels of pollution and water chemistry changes outside the planned benchmark range – some with sulfate levels that exceed Minnesota's wild rice standards by a factor of 1500.
There will likely be multiple storage facilities on site at the mine. Development rock excavated from the tunnels that descend into the mine and connect the various mineral deposits will generally be stored on the surface. This rock can be used later to fill mined out stopes to some extent. This rock may also be contaminated with sulfide and other toxic minerals. The Eagle Mine report (referenced above) lists 33 toxic substances being monitored. In addition, ore must be stored prior to transport to North Dakota. These storage areas must be lined to prevent contamination from seeping into the ground water. We note that Eagle Mine TDRSA (Temporary Development Rock Storage Area) is lined with both a primary and secondary lining. A leak detection system is installed between the liners to monitor primary lining integrity. A total of approximately 55 gallons of water was purged from the leak detection sump in 2020, a larger volume than 2019. Thus we see that the lining system does leak after only a few years of operation. The leak levels are currently very small at this point but as noted in the Eagle Mine report, increasing slightly over time.