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FirITASCA:
<br /> Denver, Inc.
<br /> 4.0 HUMIDITY-CELL TESTING
<br /> 4.1 METHODS
<br /> Humidity-cell tests are designed to enhance the release of acidity/alkalinity, metals, and other
<br /> constituents from solid materials by providing conditions conducive to sample oxidation and then
<br /> leaching with a fixed volume of water on a weekly basis.
<br /> The tests were coordinated by Itasca and conducted by ACZ. For each HCT, approximately
<br /> 1 kilogram (kg) of rock was placed in a clear acrylic cell and flushed with 1,000 mL of deionized
<br /> water. Subsequently, cells were subjected to a weekly cycle composed of three days of dry air
<br /> followed by three days of water-saturated air and then a 1,000-mL flush with deionized water on
<br /> the seventh day.' Testing was conducted in a climate-controlled facility. The HCT effluent was
<br /> analyzed on a weekly basis for sulfate, iron, calcium, and magnesium concentrations; pH;
<br /> acidity/alkalinity; electrical conductance (EC); and oxidation reduction potential (ORP). Effluent
<br /> from Weeks 0, 1, 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, and 50 was also analyzed for aluminum,
<br /> antimony, arsenic, barium, beryllium, cadmium, chloride, chromium, copper, fluoride, lead,
<br /> manganese, mercury, nickel, nitrate plus nitrite, phosphorus, potassium, selenium, silver,
<br /> sodium, thallium, TDS, and zinc concentrations. Standard leachate sample parameter analyses
<br /> were performed according to HCT methodology (ASTM 2013). A blank sample (PBS) was tested
<br /> using the same methodology described above for laboratory quality assurance purposes.
<br /> Each of the HCTs was conducted for 53 weeks, when Itasca judged that the solute release rates
<br /> had stabilized enough that the HCT results could be used to assess the potential for acid
<br /> generation and solute release from Project waste rock.
<br /> 2 Tap water instead of deionized water was mistakenly added to each HCT during Week 33.The tap water contained
<br /> elevated concentrations of calcium, magnesium, and sulfate and was a higher pH than the deionized water.
<br /> Documentation regarding the incident is compiled in Appendix B with the other laboratory transmissions. The tap
<br /> water does not appear to appreciably affect the effluent quality subsequent to Week 33.
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