Sleeping of blasting shots in mining and quarrying

Background

Blasting operations in Victorian mines and quarries typically involve 'load & shoot' operations where blasting is conducted immediately after loading or on the same day.

Recently, an increase in blasting delays have been reported which results in the loaded bench being slept (charged explosives remaining loaded in the blasting holes or loaded above ground) for an extended duration. These delays often occur due to breakdown of specialist vehicles, adverse weather or misfire events.

Blasting delays increase the risk to employees' and other persons' health and safety due to the explosives security, for example from uninitiated or unintentional detonation, deterioration or theft of the explosives.

Increased planning can both reduce the likelihood of blasting delays and reduce the severity of hazards if delays occur.

Safety issues

If blasting is delayed and the shot is to be slept, operators need to adjust blast management plans (BMP) at short notice and may not have adequate resources on hand to ensure that the site is under positive control.

Common hazards whilst sleeping a shot include:

• the safety and security of the sleeping shot(s)
• unconsumed explosives, loaded blast holes and initiating systems exposed above ground
• cracked or unstable ground, presenting a risk to employees and vehicle traffic in the area
• changes in the ground conditions including:
  • ground temperature (hot ground) that can cause the explosive to degrade, premature or uninitiated detonation
  • ground water can interact and affect the explosive which can degrade the explosives, cause inconsistency in the performance of the explosives, etc
• adverse weather events, for example electrical storms or heavy rain, can lead to the unintentional detonation, degrading the explosives
• hazards introduced by any remediation options chosen, for example clearing and re-loading blast holes, re-drilling or heavy earthmoving plant to mechanically clear the broken ground
• increased post-blast fume or flyrock as a result of changes in the explosive composition

Recommended ways to control risks

• When responding to a blasting delay, reduce time pressures (for example, from noise restrictions, incremental weather) to ensure priority is given to safe and controlled blasting. This may mean blasting is further delayed by one or more days to ensure blasting can occur safely.
• Include provisions for extended sleep time when preparing the BMP.
• Film each blast using video and/or drone footage to assist the identification of full or partial misfires, unauthorized site access, unplanned rock fall or other hazards during blasting operations.
• Maintain complete and correct records of drilling, blast hole loading sheets, mobile processing unit (MPU) operating checks and explosive quality checks.
• Review and revise the BMP, and any risk assessments.
  • Ensure any new hazards are identified and communicated to relevant persons.
  • Ensure any hazards associated with the control for the blasting delay are also assessed, controlled and communicated.
• Secure and control the site. Review the exclusion zone and sentry locations. Ensure sentries have adequate welfare provisions and communication. Consider the use of mobile lighting, earth mounding for temporary roadblocks and security cameras.
• Ensure the nominated blast controller is trained and appropriately licensed.
• Control all explosives at the site, including any that have not been loaded. Consider whether the initiation system can be unhooked or other means of preventing unplanned initiation. Consult the explosives provider for technical support with blasting products and systems.
• Update notifications including local police, Earth Resources Regulations, WorkSafe Victoria, sensitive receptors and other relevant stakeholders.

• Conduct a post-incident investigation to identify the contributing factor(s) for the blasting delay and implement preventative measures for the future.

Legal duties

Under the Dangerous Goods Act 1985 and Dangerous Goods (Explosives) Interim Regulations 2021, duty holders (licensee, shotfirer, or persons in control or persons who uses explosives) must:

• comply with Part 8 Use of Blasting Explosives, and in particular with requirements in Australian Standard  2187.2 Explosives-Storage and Use, Part 2: Use of explosives (AS 2187.2) including:
  • prevent access to explosives by persons who are not authorized to have access
  • report incidents involving an injury or immediate risk to a person’s safety, property damage or other dangerous incidents
• comply with relevant requirements of the Australian Explosives Code
• arrange for the safe disposal or return of explosives that are damaged or defective or that show signs of deterioration
• prepare a BMP in accordance with AS2187.2 which includes a plan for dealing with any misfire, and commensurate with the size, location, nature and complexity of blasting operations
• comply with the instructions of the shotfirer when charges are being prepared and fired and until the ‘all clear’ signal is given on completion of blasting
• ensure that all blast holes which are charged are fired as one round and fired without undue delay. Any charge fired and not exploded is to be treated as a misfire in accordance with the BMP

Under the Occupational Health and Safety Act 2004, employers must:

• so far as is reasonably practicable, provide and maintain a working environment that is safe and without risks to the health of employees and independent contractors
• provide or maintain plant or systems of work that are safe and without risks to health, so far as is reasonably practicable
• provide employees with the necessary information, instruction, training or supervision to enable them to do their work in a way that is safe and without risks to health
• ensure, so far as is reasonably practicable, that people other than employees are not exposed to risks to their health or safety arising from the employer's conduct

Australian Standard

Australian Standard 2187.2: Explosives – Storage, Handling and Use. Part 2: Use of explosives section 5 clause 6.1.9 Section 10.3 'Treatment of Misfires'

Australasian Explosives Industry Safety Group

Code of Good Practice: Blast Guarding in an Open Cut Mining Environment

Code of Good Practice: On-Bench Practices for Open Cut Mines and Quarries