Sandfire has designed Black Butte Copper for quick reclamation at the end of mine life with no need to treat water in perpetuity on site. We have chosen a dry cemented tailings facility (CTF) because it offers the highest environmental protection and quickest reclamation of any tailings facility designs we studied. Because the CTF will have no pond of standing water during operations, once the mine closes Sandfire will cover the facility with a 100 mil HDPE liner, weld it to the lower double liner, and cover the liner with 4 or more feet of fill, top soil, and grass. A sump will remain in the CTF to allow recovery of the small amount of water that may seep until the facility for monitoring, testing and treatment until the Montana DEQ determines that the system has stabilized and no further monitoring is needed.

No, our system of cemented paste backfill underground ensures none of the rock walls stay exposed to oxygen long enough to allow a release of metals. Once the cemented paste backfill is placed underground water movement returns to pre-mining levels. All water from underground will be either used in the mill process or treated within the Reverse Osmosis Water Treatment Plant prior to release back to the environment through the underground infiltration system.

We measure the pH of several different types of water. In the future mine area, surface water pH ranges from 6.9 to 8.5 (neutral to slightly alkaline), and ground water pH ranges from 6.2 to 7.1 (near neutral). Water from the reverse osmosis water treatment plant will have a pH between 6 and 9 (slightly acidic to moderately alkaline), a range that is similar to surface waters. The small amount of water that may be pumped from the cemented tailings facility could have a pH as low as 2, but it will be pumped into the much larger volume of water in the process water pond with a pH of 9 to 10, where it will be neutralized.

There are sulfide minerals present in copper mining which can create acid when they oxidize. Fortunately, the Johnny Lee deposit is completely encased by rocks having a high concentration of carbonate, which acts as a buffering (or neutralizing agent) against acid. In our intensive test work, these minerals have successfully neutralized the acidity that has been produced by sulfide oxidation. Tintina is taking every measure to minimize acid production, and the large volumes of carbonate in the mined rock and its host rocks are expected to be a great help in managing potentially acid generating rock (PAG). Mine operations around the world developed in carbonate host rocks are very successful in protecting the environment.

Potentially Acid Generating rock (PAG) rock is rock that when oxidized by surface weathering may form acid which can then leach metals. Leached metal ions can be harmful to fish and other aquatic life. PAG must and will be managed to inhibit oxidation in order to minimize any possible acid production. As an added precaution, all left over rock, PAG and NAG (non-acid generating rock) will be stored in the Cemented Tailings Facility.

Non-Acid Generating rock (NAG) is rock that in surface weathering/oxidizing conditions produces no acid. Our current test results show that most of the excess rock resulting from mining at Black Butte is non-acid generating. This is good news as this rock contains sufficient carbonate minerals to neutralize any potential acid generation from mineralized material. However, Tintina is placing all NAG rock from mining with the PAG (Potentially acid generating) rock into its cemented tailing facility where they will be secured with the tailings inside a sealed 100-mil liner and buried. No NAG or PAG rock will be left outside the CTF facility.

Based on extensive testing of the surface and groundwater of the area, which naturally leach metals from the surrounding rock, and the results of humidity cell tests on waste rock and cemented tailings, the most persistent elements exceeding groundwater and surface water standards are arsenic (As), selenium (Se), thallium (Tl), and strontium (Sr). Other elements, including copper (Cu), lead (Pb), nickel (Ni), mercury (Hg), cadmium (Cd), and zinc (Zn), could be of concern if waste rock were not properly managed. Fortunately, responsible management minimizes the amount of leaching of these elements into site water during the operation, and reverse osmosis water treatment removes all of them.