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Rock is in high demand

Friday, 8th January, 2016

By Michael Murphy

Mawsons blasted a section of its quarry just off Holten Drive earlier this week to keep up with increasing demand for its rock.

The quarry called in Orica to set the charge and it went off without a hitch about 9.30am on Wednesday, giving workers access to more “Broken Hill Gneiss” - a rock similar to granite used in concrete and sealing aggregate for roads.

The quarry supplies the Australian Rail Track Corporation, the company charged with managing Australia’s interstate rail network.

Mawsons usually supplies the ARTC with about 10,000 tonnes a year, but it is about to deliver another load to take the tally to over 12,000 tonnes in the last four months.

“We are changing the plant over on the weekend to make ballast which we supply to the ARTC,” said quarry manager Maurice Kerrins.

“We have got three trains to load in a fortnight.

“We loaded a train just before Christmas and it ended up in Kalgoorlie.

“After a derailment ... the carriages were sitting here, so they asked us to load it.”

Mr Kerrins said the quarry and concreting business was having a good run, particularly after picking up two major projects last year: the Solar Wind Farm and Essential Water’s Reverse Osmosis Plant.

Mawsons supplied about 30,000 tonne of spalls - basketball-sized rocks - for the drainage system at AGL’s Solar Farm just outside of Broken Hill, and about 7,000 tonnes of material for roads and dam walls around the RO plant.

Mawsons fires about four times a year, and weeks of preparation and planning go into a blast.

Orica designs the explosion using precision equipment.

“We show them where we want to blast, then they laser profile the whole front of the face and mark the holes out, the angle and depth, and then when we drill it,” Mr Kerrins said.

“There’s no guess work in it anymore.

“The days of rocks flying everywhere are gone. 

“Takes about six hours to load ... one bang and it’s all over.” 

Depending on where they are blasting, they sometimes have to block off Holten Drive - better known as the backtrack - and develop traffic management plans for City Council approval.

They also knock out communication plans to inform residents, particularly those nearby, and they let CBH know what is going on so they don’t think something is happening on their mine site.

And it can all be put off, if the wind is blowing in the wrong direction.

“If we get the wind coming in an easterly direction, when the wind is blowing into town, we can’t blast, we have to wait. 

“Before I started here, they had one shot in the ground ready to go for a month.”

Mr Kerrins said the quarry had 16 types of rock in it, so they had to be selective about how they extract it as some sections were not viable.

The quarry has an estimated “28-year life” and the company is beginning to plan rehabilitation works.

They have stockpiled topsoil from the quarry, and after getting some advice from the State Government, they will begin collecting seeds and growing plants and trees on the lease to help the land recover after the mining operation.

In the meantime, there’s still plenty of rock to be extracted from the quarry. 

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