Open Cut

Long Term Erosion & Water Quality Assessment from a Range of Coal Mine Rehabilitation Practices

Open Cut » Environment

Published: December 04Project Number: C10037

Get ReportAuthor: Chris Carroll, Les Pink, S Griffiths, A Tucker, P Burger, L Merton, D Cameron, | Department of Natural Resources, Mines and Energy

The initial field study at Curragh assessed runoff, erosion and water quality from rehabilitated land at two scales: field plot (0.01 ha) and contoured catchment (0.58, 0.41 and 0.91 ha). Three contoured catchments with an average slope gradient of 10% were monitored from 1994 to 2003. These represent current rehabilitation practices at Curragh mine. The plot study terminated after 1999 but the catchments were continued until 2003.

Similar to the plot study, the greatest window-of-erosion risk occurred in the early years after rehabilitation and before >50% vegetative cover was established. Most of the sediment lost during the study was due to a large proportion of surface area being exposed to the erosive forces of rain and runoff. Pasture growth reduced soluble salt concentrations at the surface of spoil material and reduced the risk of salt movement on-site and off-site.

In contrast to the spoil erosion plots, vegetative cover has progressively colonised the spoil on the catchments. The weathering and breakdown of spoil laid down in strips has enabled pasture species to colonise the spoil areas in the catchments. Soil migration from upslope and leaf litter expressed as organic carbon also improved the quality of the material, contributing to pasture growth and survival.

The 10-year study has provided a unique opportunity to monitor the condition and trend of rehabilitated catchments over 3 distinct climatic cycles. The first 3 years were dry, with well below Curragh's median rainfall of 565 mm, receiving an average of 315 mm. The following 3 years were relatively wet with an average of 686 mm experienced. This period saw buffel grass flourish and cover levels attain >80% of surface area. The final 4 years saw a shift back towards drier conditions - average rain was 335 mm. During this period buffel grass survived and showed its resilience during unfavourable rainfall conditions.

Oaky Creek
Long-term research into the success of rehabilitation at Central Queensland coalmines was conducted at Oaky Creek Coal Mine. The study measured wetter, dryer and median years of rainfall and recorded the performance of topsoils, spoils and landform designs. In 1993, field plots 0.1 ha in size, with slope gradients of 30% were established, measuring runoff, sediment loss and runoff water quality. From 2002, box-cut style slopes with 30% gradients, mid-slope berms or benches and sediment ponds were monitored using erosion pins. Rainfall was measured at the experimental sites using pluviometers connected to data loggers.

A major result from the long-term study was the importance of vegetative cover in rehabilitation. On steeper slopes - 30% gradients - it was found that the greatest window of erosion risk was before vegetation reached a minimum 80% surface cover.

Another important finding from the long-term study was the critical role topsoil played in reducing erosion. High vegetative cover levels were attained on topsoil treatments with spoil treatments performing poorly in regard to vegetative establishment.

Findings from box-cut study sites at Oaky Creek identified the need for these designs to be stabilised soon after establishment to control bench integrity and rill erosion. The effectiveness of benches or berms, designed to dissipate runoff velocity down a slope, was reduced due to low pasture establishment on spoil treatments. Benches exposed to rainfall and runoff, deteriorated rapidly and are now largely ineffective in fulfilling their design purpose. On the other hand, topsoil treated benches performed better with reasonable cover established, and significantly less erosion evident. .

The performance of the sediment pond designs on the modified box-cut sites featured at the new sites ranged from reasonable to poor. Ponds were formed from spoil and tended to have low hydraulic conductivity and permeability, resulting in sealing of the base thus preventing infiltration. Infiltration was further inhibited due to fine clays and silts deposited in the ponds reducing the ponds ability to capture subsequent runoff events. If sediment ponds are to be used in the future greater consideration on the permeability of their base is required. Successful design of sediment ponds requires taking into account the runoff coefficient of the material and catchment area. Pond wall and spillway design also needs to be considered to account for occasions when ponds overtop.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C29021Assessing The Impact Of Consecutive Night Shifts On Night-Time Alertness, Daytime Sleep And Timing Of The Circadian System

In the Australian coal mining industry, most guidelines for managing...

C33037Quantifying Recharge To Groundwater Systems In The NSW Coalfields (Sydney, Gunnedah And Gloucester Basins)

The purpose of this project was to estimate the rate of diffuse rec...

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook