Sustainable Reuse of Mine Tailings and Waste Rock as Water-Balance Covers
Abstract
:1. Introduction
2. Materials and Methods
2.1. Soils and Mine Tailings
2.2. Water Balance Cover Design and Modeling
2.2.1. Storage Assessment
2.2.2. Water-Balance Modeling
2.2.3. Test Site, Vegetation Characteristics, and Meteorological Data
2.2.4. Boundary and Initial Conditions
2.3. Water-Balance Covers Composed of Mine Waste
3. Results
3.1. Fixed Storage Layer Thickness Composed of Mine Tailings
3.2. Fixed Storage Layer Thickness Composed of Tailings and Waste Rock
3.3. Adjusted Storage Layer Thickness Composed of Tailings and Waste Rock
3.4. Contribution to the Circular Economy and Mining Sustainability
4. Conclusions
- Percolation rates for WBCs simulated with hard rock mine tailings met the prescribed percolation rate of the Natural Cover (i.e., 4 mm/year). Lower percolation rates were representative of tailings with higher clay content and lower hydraulic conductivity (ks).
- Evapotranspiration and percolation increased and runoff decreased with an increase in ks of the storage layer. Storage layers with larger ks results in faster infiltration through the cover (percolation) and faster transfer of water out of the soil via evapotranspiration.
- Addition of waste rock to WBCs increased percolation when the storage layer thickness was fixed due to reduced storage capacity. The effect of waste rock addition was more pronounced in WBCs that included tailings with higher ks.
- Two methods were presented to redesign the storage layer thickness in a WBC that includes mixed WR&T: Method 1—redesign for the constant available storage and Method 2—redesign for the constant void volume. Both methods yielded similar WBC thicknesses and similar percolation rates that compared favorable to the percolation rate with no waste rock.
- Reuse of mixed WR&T in on-site WBCs provides an opportunity to enhance mine site sustainability via reduced costs associated the acquisition of raw materials required for closure as well as reduced waste volumes requiring storage.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Soil | θs | θr | α, 1/cm | n | Ψa (cm) | Sand (%) | Silt (%) | Clay (%) | ks (cm/s) (Actual) | ks (cm/s) (Modified) | Ropt |
---|---|---|---|---|---|---|---|---|---|---|---|
Top Soil | 0.50 | 0.00 | 0.0049 | 1.33 | 205.76 | -- | -- | -- | 2.8 × 10−6 | 2.8 × 10−5 | - |
Silty-Sand | 0.35 | 0.00 | 0.0142 | 1.27 | 70.27 | 34 | -- | -- | 6.0 × 10−5 | 6.0 × 10−4 | 2.01 |
Copper | 0.46 | 0.01 | 0.0196 | 1.453 | 50.99 | 69 | 30 | 1 | 7.6 × 10−5 | 7.6 × 10−4 | 2.43 |
Gold | 0.45 | 0.00 | 0.0163 | 1.33 | 61.18 | 23.5 | 71.5 | 5 | 4.3 × 10−5 | 4.3 × 10−4 | 2.38 |
Coal | 0.47 | 0.04 | 0.0054 | 1.249 | 183.50 | 35 | 39 | 26 | 1.2 × 10−6 | 1.2 × 10−5 | 2.49 |
Oil Sand a | 0.39 | 0.00 | 0.0167 | 1.34 | 61.18 | 67 | 24 | 9 | 2.7 × 10−7 | 2.7 × 10−6 | 2.16 |
Soil/Tailings | Waste Rock Content (%) | Modeling Condition | Storage Layer Height (mm) | Percolation Rate (mm/year) |
---|---|---|---|---|
Coal mine tailings | 0 | - | 1220 | 0.200 |
30 | Fixed height | 1220 | 0.260 | |
30 | Adjusted height-Method 1 | 1810 | 0.135 | |
30 | Adjusted height-Method 2 | 1740 | 0.135 | |
45 | Fixed height | 1220 | 0.830 | |
45 | Adjusted height-Method 1 | 2390 | 0.075 | |
45 | Adjusted height-Method 2 | 2220 | 0.075 | |
Copper mine tailings | 0 | - | 1220 | 3.17 |
30 | Fixed height | 1220 | 4.71 | |
30 | Adjusted height-Method 2 | 1770 | 3.36 | |
45 | Adjusted height-Method 2 | 2350 | 3.09 |
Simulated Water Balance Cover | Evapo- Transpiration (mm/year) | Runoff (mm/year) | Average Soil Water Storage (mm) | Average Saturation Degree (%) | Percolation (mm/year) |
---|---|---|---|---|---|
Natural Cover | 328.6 | 0.215 | 151.6 | 30.3 | 2.36 |
Copper Tailings | 327.4 | 0.185 | 91.1 | 18.3 | 3.17 |
Gold Tailings | 329.6 | 0.18 | 144.1 | 28.9 | 1.69 |
Coal Tailings | 325.6 | 0.18 | 303.7 | 60.9 | 0.20 |
Oil Sand Tailings | 314.9 | 2.17 | 120.4 | 24.1 | 0.00 |
Soil/Tailings | Waste Rock (%) | Runoff (mm/year) | Evapotranspiration (mm/year) | Percolation (mm/year) | Average Soil Water Storage (mm) | Average Saturation Degree (%) |
---|---|---|---|---|---|---|
Natural Cover | 33 | 0.215 | 328.6 | 2.36 | 151.1 | 30 |
48 | 0.170 | 328.1 | 2.69 | 139.4 | 32 | |
63 | 0.190 | 327.1 | 3.41 | 112.8 | 30 | |
Copper Tailings | 0 | 0.185 | 327.4 | 3.17 | 91.1 | 14 |
15 | 0.180 | 330.5 | 4.08 | 80.3 | 15 | |
30 | 0.180 | 325.9 | 4.71 | 75.3 | 16 | |
Oil Sand Tailings | 0 | 2.170 | 314.9 | 0.00 | 120.4 | 22 |
30 | 2.140 | 328.3 | 0.00 | 93.5 | 23 | |
45 | 1.040 | 301.0 | 0.00 | 71.8 | 24 | |
Coal Tailings | 0 | 0.180 | 321.7 | 0.20 | 303.7 | 47 |
15 | 0.190 | 333.9 | 0.32 | 274.0 | 49 | |
30 | 0.320 | 317.8 | 0.26 | 212.4 | 45 | |
45 | 0.265 | 328.9 | 0.83 | 215.0 | 55 | |
71.3 | 0.525 | 315.0 | 1.85 | 124.4 | 52 |
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Gorakhki, M.H.; Bareither, C.A. Sustainable Reuse of Mine Tailings and Waste Rock as Water-Balance Covers. Minerals 2017, 7, 128. https://doi.org/10.3390/min7070128
Gorakhki MH, Bareither CA. Sustainable Reuse of Mine Tailings and Waste Rock as Water-Balance Covers. Minerals. 2017; 7(7):128. https://doi.org/10.3390/min7070128
Chicago/Turabian StyleGorakhki, Mohammad H., and Christopher A. Bareither. 2017. "Sustainable Reuse of Mine Tailings and Waste Rock as Water-Balance Covers" Minerals 7, no. 7: 128. https://doi.org/10.3390/min7070128