Open Cut » Environment
The aim of this project was to develop a practical methodology, based on computer modelling and field monitoring, for predicting the hydrology and water quality of final spoil-void systems, primarily for use in on-site planning of final spoil-void systems and in gaining regulatory approvals.
As part of the original BHP Spoil Hydrology Project (PPK, 1997) the Spoil Hydrology Lumped Parameter Model (SHLPM) was presented at an informal meeting attended by representatives of regulators, BHP Coal and PPK.
The outcome was a general agreement that the modelling approach was appropriate, but there was a need for field data to further validate the model and to allow for calibration for specific applications. This agreement led to the current ACARP Project C7007, based on field monitoring.
The project activities included establishing a network of eight test sites representing individual spoil-void catchments. The monitoring sites include six from Queensland (Peak Downs, Saraji, German Creek, Blackwater, South Blackwater and Moura mines) and two from New South Wales (Ravensworth East and Hunter Valley Number 1 mines).
The characteristics of open-cut spoil heaps result in a distinctive hydrology. These characteristics can be classified into two main groups: spoil materials and spoil structure.
Spoil materials that contain fresh sedimentary or basalt sequences will have a different hydrology and quality from natural surface materials (soils). The spoil structure is a consequence of the methods used for placing and reshaping spoil and topsoil.
Spoil structure is the more significant of the two factors because of the challenges it presents for quantifying spoil hydrology processes, and hence for developing reliable models predicting spoil hydrology outcomes.
There is a need to understand the nature of spoil hydrology processes, primarily to identify or develop appropriate models to simulate the hydrological behaviour and water quality, and secondarily to plan field data collection for model validation and calibration. Research to satisfy these needs is being carried out in collaborative programs funded by the coal mining industry, with the aim of developing objective, reliable and practical methods for simulating the hydrological behaviour of spoil-void systems.
Major research studies already completed include this ACARP project, on the hydrology and water quality of final spoil-void systems, the Spoil Hydrology Project (SHP) funded by BHP Coal from 1993 to 1997 (both managed by PPK Environment & Infrastructure), the ACARP projects on Postmining Landscape Parameters for Erosion and Water Quality Control (PLPEWC), and investigations by individual mining companies, for example MIM.