Performance assessment of a single-layer moisture store-and-release cover system at a mine waste rock pile in a seasonally humid region (Nova Scotia, Canada)
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Cover systems are commonly applied to mine waste rock piles (WRPs) to control acid mine drainage (AMD). Single-layer covers utilize the moisture “store-and-release” concept to first store and then release moisture back to the atmosphere via evapotranspiration. Although more commonly used in semi-arid and arid climates, store-and-release covers remain an attractive option in humid climates due to the low cost and relative simplicity of installation. However, knowledge of their performance in these climates is limited. The objective of this study was to assess the performance of moisture store-and-release covers at full-scale WRPs located in humid climates. This cover type was installed at a WRP in Nova Scotia, Canada, alongside state-of-the-art monitoring instrumentation. Field monitoring was conducted over 5 years to assess key components such as meteorological conditions, cover material water dynamics, net percolation, surface runoff, pore-gas, environmental receptor water quality, landform stability and vegetation. Water balances indicate small reductions in water influx to the waste rock (i.e., 34 to 28% of precipitation) with the diminished AMD release also apparent by small improvements in groundwater quality (increase in pH, decrease in sulfate/metals). Surface water quality analysis and field observations of vegetative/aquatic life demonstrate significant improvements in the surface water receptor. The WRP landform is stable and the vegetative cover is thriving. This study has shown that while a simple store-and-release cover may not be a highly effective barrier to water infiltration in humid climates, it can be used to (i) eliminate contaminated surface water runoff, (ii) minimize AMD impacts to surface water receptor(s), (iii) maintain a stable landform, and (iv) provide a sustainable vegetative canopy.
KeywordsAcid mine drainage Contaminant remediation Hydrogeochemistry Environmental monitoring Water balance Landform stability
This work was conducted under the CAPs Monitoring Project and funded by Enterprise Cape Breton Corporation (ECBC) which was later dissolved into Public Works and Government Services Canada (PWGSC). The authors wish to thank the anonymous reviewers for their helpful comments towards the improvement of this paper. Special thanks are given to Joseph MacPhee and Joseph Shea (PWGSC) and Devin MacAskill (Cape Breton Regional Municipality, CBRM) for their support during this study. The authors would also like to acknowledge Greg Meiers (O’Kane Consultants) for sharing his expertise, along with David Mayich, Fred Baechler (exp Consultants), and Jamie Tunnicliff (Stantec Consulting Ltd.).
- Ayres, B., Dirom, G., Christensen, D., Januszewski, S., O’Kane, M. (2003). Performance of cover system field trials for waste rock at Myra Falls Operations. In: T. Farrell, & G. Taylor (Eds.), Proceedings of the 6th International Conference on Acid Rock Drainage (ICARD), 12–18 July 2003, Cairns, QLD, Australia. ISBN: 1875776982.Google Scholar
- Barber, L. A., Ayres, B. K., Schmid, B. (2015) Performance evaluation of reclamation soil covers at Cluff Lake mine in northern Saskatchewan. In: A. B. Fourie, M. Tibbett, L. Sawatsky, & D. van Zyl (Eds.), Mine Closure 2015: Proceedings of the Tenth International Conference on Mine Closure, 1–3 June 2015, Vancouver, BC, Canada. Australian Centre for Geomechanics, Perth. ISBN 9780991790593.Google Scholar
- Benson, C. H., Thorstad, P. A., Jo, H., & Rock, S. A. (2007). Hydraulic performance of geosynthetic clay liners in a landfill final cover. Journal of Geotechnical and Geoenvironmental Engineering, 133(7), 814–827. https://doi.org/10.1061/(ASCE)1090-0241(2007)133:7(814).CrossRefGoogle Scholar
- Blowes, D. W., Ptacek, C. J., Jambor, J. L., Weisener, C. G., Paktunc, D., Gould, W. D., & Johnson, D. B. (2014). 11.5—The geochemistry of acid mine drainage. In: H. D. Holland, & K. K. Turekian (Eds.), Treatise on geochemistry, 2nd edn. (pp. 131–190). Oxford: Elsevier. https://doi.org/10.1016/B978-0-08-095975-7.00905-0.
- Bonstrom, K., Allen, G., O’Kane, M., Christensen, D. (2012). Evolution of cover system design and waste rock management at a mine in the Pilbara region of Western Australia. In: A. B. Fourie, & M. Tibbett (Eds.), Mine Closure 2012: Proceedings of the Seventh International Conference on Mine Closure, 25–27 September 2012, Brisbane, Australia. Australian Centre for Geomechanics, Perth. ISBN 9780987093707.Google Scholar
- INAP (The International Network for Acid Prevention). (2014). Global acid rock drainage guide. http://gardguide.com/images/5/5f/TheGlobalAcidRockDrainageGuide.pdf Accessed 22 June 2017.
- King, M., Check, G., Carey, G., Abbey, D., Baechler, F. (2003). Groundwater and contaminant transport modelling at the Sydney Tar Ponds. In: Canadian Geotechnical Society. Proceedings of 56th Annual Canadian Geotechnical Conference and 4th Joint IAH-CNC/CGS Groundwater Specialty Conference, September 29–October 1, 2003, Winnipeg, Manitoba, Canada.Google Scholar
- Krahn, J. (2004). Vadose zone modeling with VADOSE/W: an engineering methodology (1st ed.). Calgary: GEO-SLOPE International Ltd.Google Scholar
- Meer, S. R., & Benson, C. H. (2007). Hydraulic conductivity of geosynthetic clay liners exhumed from landfill final covers. Journal of Geotechnical and Geoenvironmental Engineering, 133(5), 550–563. https://doi.org/10.1061/(ASCE)1090-0241(2007)133:5(550).CrossRefGoogle Scholar
- MEND (Mine Environment Neutral Drainage). (2004). Design, construction and performance monitoring of cover systems for waste rock and tailings: volume 1—summary. Canadian Mine Environment Neutral Drainage Program, Project 2.21.4a, July 2004. http://mend-nedem.org/wp-content/uploads/2.21.4a-Cover-Design-Manual.pdf. Accessed 15 May 2017.
- O’Kane, M., & Ayres, B. (2012). Cover systems that utilise the moisture store-and-release concept—do they work and how can we improve their design and performance? In: A. B. Fourie, & M. Tibbett (Eds.), Mine Closure 2012: Proceedings of the Seventh International Conference on Mine Closure, 25–27 September 2012, Brisbane, Australia. Australian Centre for Geomechanics, Perth. ISBN 9780987093707.Google Scholar
- Power, C., Ramasamy, M., MacAskill, D., Shea, J., MacPhee, J., Mayich, D., Baechler, F., & Mkandawire, M. (2017). Five-year performance monitoring of a high-density polyethylene (HDPE) cover system at a reclaimed mine waste rock pile in the Sydney Coalfield (Nova Scotia, Canada). Environmental Science and Pollution Research, 24(34), 26744–26762. https://doi.org/10.1007/s11356-017-0288-4.CrossRefGoogle Scholar
- Power, C., Tsourlos, P., Ramasamy, M., Nivorlis, A., & Mkandawire, M. (2018). Combined DC resistivity and induced polarization (DC-IP) for mapping the internal composition of a mine waste rock pile in Nova Scotia, Canada. Journal of Applied Geophysics, 150 40–51. https://doi.org/10.1016/j.jappgeo.2018.01.009.
- Salinas Villafane, O. R., Igarashi, T., Harada, S., Kurosawa, M., & Takase, T. (2012). Effect of different soil layers on porewater to remediate acidic surface environment at a close mine site. Environmental Monitoring and Assessment, 184(12), 7665–7675. https://doi.org/10.1007/s10661-012-2526-z.CrossRefGoogle Scholar
- Sracek, O., Gzyl, G., Frolik, A., Kubica, J., Bzowski, Z., Gwozdziewicz, M., & Kura, K. (2010). Evaluation of the impacts of mine drainage from a coal waste pile on the surrounding environment at Smolnica, southern Poland. Environmental Monitoring and Assessment, 165(1–4), 233–254. https://doi.org/10.1007/s10661-009-0941-6.CrossRefGoogle Scholar
- Watzlaf, G. R., Schroeder, K. T., Kleinmann, R. L. P., Kairies, C. L., Nairn, R. W. (2004). The passive treatment of coal mine drainage. U.S. Department of Energy, DOE/NETL-2004/1202.Google Scholar