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Rock Blasting FAQ’s

Do you have public liability insurance?

Yes, we have a $10,000,000 public liability policy with Lloyds of London that lists Rock Drilling and Blasting as our primary activity.

Can you blast close to our existing home without causing damage (eg for a swimming pool)?

Blasting back yard pools is generally no problem. However, the closer the pool is to the house, the smaller the explosive charge must be so as not to exceed a safe vibration level - smaller blasts mean more of them which equates to more time and higher costs. In some cases non explosive rock splitting options can be used.

How do I know that you are not going to land rocks on my roof or crack my house?

We have all heard horror stories like this, thankfully most of these events occurred in times gone by when explosives were easily available to anybody who could demonstrate a genuine need. Back then, just about every builder, plumber and earthmover did their own blasting, often without any training and plenty of things went wrong. In recent years the tightening of controls over the supply and use of explosives has pretty much pushed out all but the drill and blast specialists.

The contemporary drill and blast specialist contractor should have a good understanding of blast vibration management methods including prediction and measurement as well as an understanding how to manage blasted rock to prevent it becoming airborne.

One good way to assess your potential contractors level of experience is to ask to see proof of insurance as if they have a bad record they will not be able to get cover and if they have not done much blasting they will not be able to afford the astronomical cost of public liability insurance for using explosives.

Our company is very serious about OH&S compliance, can you meet our needs?

We also take safety very seriously. We have a comprehensive Safety and Environmental Management Plan. Every job gets a site specific SWMS / JSA, and a blast management plan. All blasts are logged according to AS2187.2 and videoed. A precision seismograph records the vibration and sound levels for compliance verification if required.

The last guy that blasted for us covered the site in stone dust from his drilling, can you do something to prevent this?

Airborne stone dust is very dangerous and as such we go to a lot of extra trouble to capture it with a state of the art multistage HEPA Vacuum dust extractor system. This way all stone dust is safely contained and removed from the site.

 

What is the maximum number of holes that you can fire in one shot?

Common question that deserves a good answer. In the old days shots were fired one hole at a time using safety fuse. The next improvement to come along was Detonating Cord, this product allows many holes to be fired together – a big time saver… however this has a VERY big drawback in that because all of the holes fire at exactly the same time the resultant ground vibration can be very large. This is no problem if you are blasting out in a paddock but in a back yard you are very limited on the number of holes depending on the total mass of explosive and the distance to the nearest structure that may be affected. Lack of understanding on this point or the careless use of detonating cord has broken many homes in the past!

Modern blasting techniques utilise a process called millisecond delay blasting, this is a system where special detonators are used that have a built in time delay element so that every hole has different delay period and they all fire in very fast succession, typical time delay spacing is 25mS per hole. The huge advantage in using this system is that it does not matter whether you fire 3 holes or 300 holes, the peak vibration level is the same.

We always use millisecond delay detonators when working near buildings as part of our blast vibration management strategy.

When I’m asked “how many holes can you fire together”, my answer is “as many as we can safely cover.” Every job is different but it would not be uncommon to fire 30-40 holes in one shot using millisecond delay detonators.

If you are shopping for a blasting contractor for a sensitive project ask if he has the licence endorsement for millisecond delay detonators.

Can you sell me some explosives?

NO we do not have a license to sell.