At approximately 3.10am on July 24th 1991, three mineworkers were asphyxiated by gas released during an outburst at the working face in W12 Panel.
The outburst occurred shortly after restarting the cutting of coal after the miner had been stopped for the routine installation of roof supports. The Deputy, Bruce Corbett, had told Mr. Broughton to recommence the mining of coal and had then walked away to investigate a diesel man car that had entered the panel. This act probably saved his life.
The outburst occurred on a reverse thrust fault, previously unknown in spite of in-seam seismic exploration of the area.
The gas liberated by the structure consisted mainly of carbon dioxide with probably some methane.
Although Illawarra Bottom Gas (CO2 + CH4) had been detected on numerous occasions as this panel had progressed (as it had during the mining of W11 Panel), no gas had been detected on the shift that the outburst occurred nor for at least the previous six shifts. When previously detected it had been effectively handled as a ventilation problem, not as a precursor to an outburst.
South Bulli Colliery was not classified as an outburst prone mine with outburst mining procedures only being introduced when an outburst potential was detected. A two-week Coronial Inquest was conducted during July, 1992.
Recommendations
The mine should consider the development and application of an overall formally-documented "management system" which, in its entirety, appropriately deals with the outburst risk at the mine.
1.a) The document should address areas such as:
- the gathering of geological and geotechnical information,
- the assessment and review of that information,
- prediction,
- identification,
- planning,
- minimisation,
- protection,
- mining operations, etc.
b) In addressing the above areas, the document should identify the methodology and systems to be used in each of the specific areas.
e) The document should identify the relevant persons to which each area applies and should communicate to those persons their responsibility and accountability within each particular area.
2. The mine should consider reviewing the outburst mining procedures and equipment at the mine to bring them to an appropriate standard which is on a level with the risk of outburst as experienced in the accident.
3. The mine should consider reviewing the overall training program so that appropriate training is given in all aspects of the "Management System".
4. The mine should consider the design, construction and maintenance of panel ventilation systems to ensure that, as far as practicable, the system remains intact following an outburst.
5. The mine should consider reviewing all travelling access within a panel when there is a potential for an outburst. The information and direction should be included in the "Management System".
6. A consideration should be given to reviewing the type and availability of breathing apparatus so that it is suitable for effective escape and, if possible, for first response rescue. This is a requirement for all personnel in all possible breathing restricted environments in underground coal mines.
7. There is a need to consider reviewing the risks associated with carbon dioxide in coal mines. The areas for review are:
- Regulations
- Apparatus in general
- Mining methods
- Communication of the risks, etc
8. A consideration should be giyen to reviewing the Coal Mines Regulation Act, 1982 to ensure it recognises and deals with the outburst risk. Secondly, that it appropriately addresses the detection and recording of carbon dioxide in coal mines and also deals with this problem.