Cover System Performance Monitoring:
The objectives of field performance monitoring are to:
- Develop an understanding for key processes and characteristics that control performance;
- Obtain a complete water balance for the cover system;
- Develop credibility and confidence with respect to performance of the proposed cover system from a closure perspective; and
- Develop a database to calibrate numerical modelling tools, which can then be used to predict long-term cover system performance.
O'Kane Consultants design and install field monitoring systems to monitor various parameters that influence the performance of dry cover systems.
Critical parameters to measure include the net percolation of meteoric water and the ingress of atmospheric oxygen into the underlying waste material, with the former related to the other water balance components as follows:
PERC = DS + NSI, and NSI = PPT - AET - RO
where:
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PERC is net percolation into the underlying waste material from the base of the cover;
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DS is change in moisture storage within the cover layers;
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NSI is net surface infiltration;
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PPT is precipitation;
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AET is actual evapotranspiration; and
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RO is runoff.
In general, the design and installation of lysimeters to monitor evaporative fluxes as well as net infiltration is well understood and implemented in the soil science discipline. However, the design of lysimeters for dry cover system monitoring programs in the mining industry have typically not included fundamental lysimeter design aspects established in the soil science discipline. O'Kane Consultants use saturated-unsaturated seepage numerical models to design lysimeters installed in the field to ensure they will provide an accurate assessment of net percolation quantities under a variety of precipitation events. Further details on the key aspects of properly designing a lysimeter can be found in the following paper.
O'Kane, M. and Barbour, S.L., 2003. Field Performance of Lysimeters used to Evaluate Cover Systems for Mine Waste. Proceedings of 6 th International Conference for Acid Rock Drainage, Cairns, Qld., Australia, July 2003.
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