Falling coal rib struck two workers - who are father and son - in the underground workings of the mine when the strata failed on  July 4. One of the workers suffered serious injuries.

 

The NSW Resources Regulator has started an investigation to determine the cause and circumstances of the incident.

 

It said rib conditions should be assessed as early as possible during the cutting of the development faces, continue through the formation of the pillars and while the pillars stand because there is often time-dependent movement, and during and after secondary extraction as stress abutments develop in pillar extraction.

 

"Competent geotechnical personnel should carry out assessment of rib stability should be carried out, which should consist of, at least, detailed rib mapping throughout the life of the workings and installation of pillar rib instrumentation such as extensometers and instrumented rib bolts," the Regulator said.