The high-stakes relationship between blasting, environment and community

Atlantech Senior Mining Engineer David Shirley is extremely familiar with the real-world implications between drilling and blasting operations at mine sites and the impacts on the community and environment. As David explains, it is a close and intertwined relationship where all aspects must be carefully managed to minimise the impact on the environment and local communities.

Blasting effects

The process of blasting is integral in mining operations, particularly in open-cut mines due to visibility. A single blast at a mining operation using modern, bulk explosives can produce hundreds – or sometimes even thousands – of gigajoules of energy, all within a handful of seconds.

Understandably, as with most industrial processes where there is high energy output, not all the blasting energy is confined to the vicinity of the rock we aim to break. Extreme forces targeting rock in the explosives’ area does not simply dissipate at the mine’s lease boundary. Blasting energy produces other potential environmental and community outcomes kilometres away, including vibration, dust, noxious fumes, airblast overpressure, and flyrock (to a lesser, but still critical, extent).

Mine responsibilities

Miners have a duty and obligation to minimise the environmental impacts of blasting. All people, including miners and professionals working in and surrounding mining operations, need to act in the best interests of our families, friends, neighbours, businesses, and the environment.

Even before a mine is granted approval to begin development and operations, mining companies must start the consultation process early – collaborating closely with stakeholders to develop robust and practical limits and expectations for blasting-induced environmental impacts.

At first glance, ‘limits’, such as an airblast overpressure limit of 115dB to protect nearby buildings, may appear to be hard boundaries for productivity, constraints on performance, or restrictions on efficiency. In fact, regulatory developmental consent limits, in the form of a Blast Management Plan (BMP), are quite liberating. Objective environmental blasting limits empower mining engineers, shotfirers and managers by removing subjectivity and the grey areas of decision making when it comes time to fire a blast.

Even with the most thorough blast plans in place, there are reasons why blasting may be postponed on the planned firing day, including:

• Wind direction is towards a public area, community, or near-neighbour.
• Wind speed is over a threshold.
• Or a combination of the two variables above.
• Applicable in certain jurisdictions, the presence of an inversion layer in the atmosphere:

1. Prevents the adequate dispersion of blast fumes and dust and;
2. Reflects airblast overpressure back down to earth, effectively amplifying the sound.

Day of blasting

Before the day of firing, there are many design and execution inputs that are carefully planned by drill and blast engineers and shotfirers. The engineer must have a comprehensive understanding of the sensitive receivers’ surrounding the blast area, such as nearby infrastructure, buildings, or tailings dams for example.

They must consider the size of the blast bench and of the individual charges in the blast holes with relation to the distance to the receiver to model the expected vibration outcomes. Modelling the expected vibration outcomes involves a delicate balance of blast size, charge weight and timing sequence, all in relation to the distance to the receiver. If a nearby sensitive receiver is a building or some kind of infrastructure, it may have resonant frequencies which are to be avoided, thereby influencing the engineer’s initiation and detonation timing.

If a blast is near community or business infrastructure or a culturally significant artefact site, design parameters are closely engineered and modelled to limit the flyrock’s potential trajectory to within the pit limits.

Shotfirers and blast crew technicians collaborate closely with engineers to provide practical influence in the design process. Geological abnormalities in the rock are highlighted and design parameters altered so that operators may correctly execute the design as intended. Strictly adhering to bulk explosive weights and stemming heights are essential to ensuring that the blast is safe, effective, and productive whilst maintaining compliance with the BMP’s environmental and community limits. High standards of quality assurance in the ‘explosives loading’ and ‘record-keeping’ phases feed back into the engineering phase to refine predictive models and improve confidence levels.

We are here to help

Atlantech’s team of highly experienced Senior Mining Engineers collaborate with our in-house Environmental and Compliance Engineers regarding drill and blast design services. Our team of environmental engineers also assist with regulatory matters including development consent and environmental protection licences.

With excellent communication skills and engineering disciplines that work in alignment with one another, Atlantech is uniquely positioned to efficiently solve clients’ problems.

Get in touch with our experienced multidisciplinary team to find out more > atlantech.com.au/contact-us.