Environmental Risks of Soluble Hydrolic Oil in Mine Water Discharge

Underground » Environment - Subsidence and Mine Water

Published: January 00Project Number: C7034

Get ReportAuthor: Steven Riley, Chris McQuade, Sam Adeloju | University of Western Sydney Nepean

Soluble oil produced from underground coal mines is not an environmental risk unless there is a substantial spill.  Soluble hydraulic oil is an integral component in all longwall coal mining operations and is typically used as a five percent solution with water. The daily quantity used in longwall mining can vary from as little as 50L to more than 1200L, depending on the age, technology and maintenance of the equipment.

After prolonged and repeated contact with the skin, many soluble oil concentrates and some of their aqueous emulsions can remove the natural oil from the skin, irritate the skin and cause skin damage.

When discharged from a mining operation, soluble oil may also impact on aquatic ecosystems. As a result, environmental authorities have become increasingly interested in the potential environmental effects of soluble oil produced from mining operations.


Project Objectives

The objectives of this research were to establish:

  • Whether mine water discharges which may have been contaminated with soluble hydraulic oil emulsions are toxic to aquatic species and detrimental to the receptor stream environment
  • The level of soluble oil at which environmental risk of discharge is unacceptable.

The study was undertaken at a Western Coalfields mine in NSW.


The research involved risk analysis, toxicity and chemical testing of water discharged at the pit head. Some initial problems occurred because fine-grained sediment in the background stream waters draining a relatively undisturbed catchment was toxic to the test organisms.   The research found:

  • Manufacturer's claims that biodegradation decreased soluble oil concentrations decreased by 90 to 95 percent over 28 days were correct
  • In normal mine operations, soluble oil appears to biodegrade before it reaches the surface
  • Soluble oil is not a risk to the environment unless there is a substantial spill
  • The incorporation of some risk abatement strategies would dramatically reduce the risk of the impact of these spills on the environment.

Where To From Here

This research project has highlighted the lack of previously published data on the impact of soluble mine oil on the local environment. Mine water evaluation has predominantly focused on acid mine drainage and heavy metal contamination.

The variable nature of the pit head discharge water from underground mines requires long-term sampling and analysis. Further analysis of the wetland treatment process is also desirable.

Analysis of sediment samples from the settling pond would provide useful information on the accumulation of organic and inorganic contaminants and potential future management issues.


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