O'Kane, M, Meiers, G & McCombe, C 2006, 'Design, Construction and Performance Monitoring of the Large-Scale Waste Rock Cover System Field Trials at the Historic Mount Morgan Mine Site in Queensland, Australia', in AB Fourie & M Tibbett (eds), Proceedings of the First International Seminar on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 427-440, https://doi.org/10.36487/ACG_repo/605_35
The Mount Morgan Mine, in central Queensland, was in operation for over a hundred years and generated
134 Mt of waste rock and tailings. The last ten years of activity at the site involved re-treatment of historic
The Mount Morgan mine site is a significant source of Acid Rock Drainage (ARD) in the Dee River
catchment. The State of Queensland, Department of Natural Resources and Mines (NR&M) manages the
site, and in January 2000 NR&M developed the Rehabilitation Plan for the Mount Morgan mine site, Central
Queensland (Unger, 2003). The objectives of the plan are to: improve water quality downstream; avoid
managing ARD interception and treatment indefinitely; manage the site in accordance with its significant
mining heritage; and develop and apply best-practice rehabilitation and management at this site. A seepage
interception and pump-back system is currently in place, and the amount of ARD entering the groundwater
system and ultimately reaching the Dee River is being quantified.
A number of projects are in progress, or have been completed, towards achieving these objectives. One of
these projects is the development of a cover system for waste rock material at the mine site. This project
involved the construction of two large-scale cover system field trials in 2003 on acid-generating waste rock,
as well as installation of field performance monitoring systems (site-specific meteorological conditions, net
percolation, interflow, moisture content, matric suction, temperature, and surface runoff). In addition, a
monitoring system was installed at a “natural” site in order to compare performance of an undisturbed area,
in terms of storage and release of moisture, to the cover system field trials.
The two cover systems are designed to limit the infiltration of meteoric water to the underlying waste rock as
a means of controlling long-term acidic drainage from the waste rock dump. Test Plot 1 is referred to as a
“water-shedding” cover system with a nominal 1.0 m thick layer consisting of a compacted clay layer
overlain by a layer of non-compacted growth medium (weathered granodiorite), while Test Plot 2 which is
referred to as a “moisture store-and-release” cover system consists of a nominal 2.0 m thick layer of growth
This paper will briefly describe the design and construction of the field trials, as well as the field
performance monitoring system. Discussion and field performance monitoring data will be provided on the
difference in performance between the two cover system field trials. Emphasis will be placed on the impact
on performance of the two cover systems as a result of runoff volumes. In particular, it has been
demonstrated that runoff volumes negated the intended performance of the respective water-shedding and
moisture store-and-release cover design. A complete water balance for each field trial will be presented
illustrating the difference in performance between the cover system field trials.
Mine Closure 2006 ― Andy Fourie and Mark Tibbett (eds)
© 2006 Australian Centre for Geomechanics, Perth, ISBN 0-9756756-6-4
Mine Closure 2006, Perth, Australia 427
Mine Environment Neutral Drainage (MEND) (2004) Design, construction and performance monitoring of cover
systems for waste rock and tailings. Canadian Mine Environment Neutral Drainage Program, Project 2.21.4,
OKC (2002) Mount Morgan Rehabilitation Project – Design of Covers over acid generating waste rock (MM401),
Stage Two Final Report, Waste Rock and Potential Cover Material Characterisation, and Cover System Design
Soil-Atmosphere Modelling. OKC Report.
Penman, H.L. (1948) Natural evapotranspiration from open water, bare soil, and grass. Proc. Roy. Soc., London, Ser.
A. No. 193, pp. 120-145.
Unger, C. and Laurencont, T. (2003) Development of a Sustainable Rehabilitation Strategy for the Management of Acid
Rock Drainage at the Historic Mount Morgan Gold & Copper Mine, Central Queensland. In Proceedings of the
Sixth International Conference on Acid Rock Drainage, Cairns, Queensland, Australia, 14-17 July, 2003, pp.
Design, Construction and Performance Monitoring of the Large-Scale Waste Rock Cover
System Field Trials at the Historic Mount Morgan Mine Site in Queensland, Australia
M. O'Kane, et al.
440 Mine Closure 2006, Perth, Australia