Having a blast in Coffs Harbour
Work on the $2.2 billion Coffs Harbour bypass has reached a major milestone, with the first of the controlled blasts for cuttings carried out successfully today between Bruxner Park and West Korora roads.
Transport for NSW Regional Director North Anna Zycki said parts of the bypass alignment contained very hard rock that could not be easily excavated using mechanical techniques like hammering, so needed to be blasted.
“After significant planning and preparation, we did a trial blast on 26 July that went well, and it was great to see this first blast go off as expected,” Ms Zycki said.
“Blasting means we can complete this work faster, more safely and efficiently, with less impact to nearby residents.
“We need to move about two million cubic metres of rock to build the bypass and using blasting to break rock in some locations will be of great assistance.”
Ms Zycki said blasting involved:
· drilling blast holes over multiple days
· placing explosives in the holes according to a set pattern and depth
· implementing safety measures across an exclusion zone including stopping traffic on roads if required
· detonating the blast.
“We use licensed specialists to plan and carry out controlled blasting and monitor vibration and blast noise to ensure we comply with our requirements,” Ms Zycki said.
“After breaking the rock, it is crushed and loaded into large trucks to be used on the project.
“Rock removed from the blast sites will be used to build up or ‘fill’ parts of the road that run through lower-lying areas and for processing to use as pavement material.”
Controlled blasting for cuts will be carried out between 9am and 5pm weekdays and 9am to 1pm on Saturdays, and is expected to take about a year to complete.
Blasting for tunnels will start later in the year.
A surface mining machine will also be trialled in some locations. The surface miner breaks and crushes rock in a single operation for improved efficiency.
How blasts are carried out
Safety is the utmost priority for all projects carried out by Transport for NSW and there are strict requirements in place for every blast. The Coffs Harbour Bypass project has developed and implements clear blast safety procedures, including working with emergency services and keeping them regularly informed of blasting activities.
Blasting and handling of explosives is conducted in accordance with all applicable NSW legislation.
• The shotfirer establishes a drilling and blast pattern, including blasthole lengths, type and quantity of explosives to be loaded into the blastholes and the initiation sequence
• Drilling of all holes required for the blast takes place to specified depths and locations and these are checked by the shotfirer before loading the explosives
• The blast holes are loaded with the required amount of explosive and detonators placed
• The shot is ‘tied’ to connect the detonators in the required sequence
• An exclusion zone is established using blast guards and, if required, traffic control on public roads prior to the blast countdown
• Initiation of the blast is conducted by the shotfirer only when they are satisfied that it is safe to do so. The shotfirer will have full discretion to terminate the blast sequence at any time if they determine it is not safe to proceed.
• Before firing the blast, there is a siren and final countdown
• Controlled blast is fired
• When it is determined safe, the shotfirer will inspect the blast location and confirm complete detonation. Upon confirmation that the area is safe to enter, the ‘all clear’ will be given by the shotfirer.