Minimising noise and vibration from blasting activities
Blasting operations can cause excessive noise and vibrations. Noise from blasting is a significant factor and can be disturbing to neighbouring residents or other workers in the area. It is the leading element for blasting complaints in Queensland.
People can detect vibration at levels much lower than those that cause even superficial damage to susceptible structures. However, excessive structural vibration caused by ground vibration from blasting can severely damage a structure.
Therefore, only a competent person complying with best practice environmental management should conduct blasting to minimise the impacts of airblast overpressure and ground-borne vibration on the community.
Ensure that, if blasting noise does spread to a noise-sensitive place, the airblast overpressure:
- isn't more than 115dB (linear) peak for 9 out of any 10 consecutive blasts, regardless of the interval between blasts
- doesn't exceed 120dB (linear) peak for any blast.
Ensure that, if ground vibration does spread to a noise-sensitive place, the ground-borne vibration doesn't exceed a peak particle velocity of:
- 5mm per second for 9 out of any 10 consecutive blasts, regardless of the interval between blasts
- 10mm per second for any blast.
To minimise disruption to the public, blasting is to be conducted only between 9am and 3pm on Monday to Friday, and between 9am and 1pm on Saturdays (not on Sundays or public holidays).
Conduct blasting outside these times only when blasting during these times is impracticable or the site is so remote that no one will be affected.
When a temperature inversion or heavy, low cloud cover is present, airblast overpressure values will be higher than normal in surrounding areas. Therefore, avoid blasting if predicted airblast overpressure values in noise-sensitive places exceed acceptable levels. If this isn't practical, schedule the blasting to minimise noise annoyance, such as 11am–1pm.
Also, avoid blasting when strong winds are blowing from the blasting site towards noise-sensitive places.
Conduct monitoring and record the following:
- maximum instantaneous charge in kilograms
- location of the blast (including which bench level)
- airblast overpressure level, dB (linear) peak
- peak particle velocity (mms-1)
- location, date and time of recording
- meteorological conditions
- distances from the blast site to noise-affected buildings, structures or boundary of any noise-sensitive place.
If you can't access a property for monitoring, measure at the property boundary and extrapolate the results to reflect the impact at the receptor premises.
Measure blasting noise with measurement equipment with a lower limiting frequency of 2Hz (-3dB response point of the measurement system) and a detector onset time of no more than 100 microseconds.
Vibration instruments must be able to measure over a range of 0.1mms-1 to 300mms-1 with accuracy within 5% and a frequency response flat to within 5% over a frequency range of 4.5Hz to 250Hz.
Outdoor measurement of airblast overpressure
Measure airblast overpressure at a location that is:
- exposed to the direction of blasting
- at least 4m from any noise-affected building or structure, or within the boundary of a noise-sensitive place
- 1.2–1.5m above the ground.
Outdoor measurement of ground vibration
Attach the ground-borne vibration transducer (or array) to a mass of at least 30kg to ensure good coupling with the ground where the blast site and the measurement site can't be shown to be on the same underlying strata. Ensure the mass is buried so its uppermost surface is level with the ground surface.
Place the ground-borne vibration transducer (or array) at least the longest dimension of the foundations of a noise-affected building or structure away from it, and between that building or structure and the blasting site.
Only a qualified and experienced person or organisation should measure and report on airblast overpressure and ground vibration levels.
Record the details of measuring instruments, measuring procedure, location, date and time of recording, and weather conditions for each assessment.
Keep records of the results of all airblast overpressure and ground vibration levels and other required information for at least 5 years.