Light work.
When I first began working in the mine I often stayed back to help with the loading of the shot with the blast crew.
The Mt Gunson Mine office up till the late1970s sat near the rim of the eastern part of the pit. Over time the mining operation had moved the pit a little closer.
A regular blast in the North Eastern corner of the pit one day caught every one a little by surprise when after checking the results and declaring the pit safe we arrived back in the office to discover one rock, about the size of a bowler hat had crashed through the roof of the office leaving quite an impressive hole in the roof and lay on the floor after having also passed with little effort, through the drawing office light table, destroying it on the way through.
The entire office complex, crib-room and toilets were soon after relocated much farther back and well out of harms way.
Protective Rubber:
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| CAT 769B |
Until the construction of Brownies Bunker ( after Warren Brown the mine manager ) a heavy steel plate box lined on the outside with railway sleepers, and supported on heavy steel skids which made the task a little easier. Previously all electric initiations were done simply by parking one of the 40ton dump trucks with the rear of the truck toward the shot, close but not too close, with the heavy steel tray raised.
The shot firer simply positioned himself in front of the rear dual wheels and fired the shot while pressing him self up close to the tires.
The successful shot was quickly followed by an impressive number of sizable rocks whizzing past, rebounding and pinging off the large tires.
Saturday Morning.
Jimmy Drain, one of the driller / shot firers on site, careful and confident.
Exactly what was needed when regularly letting off 10 or more ton of explosive on a daily basis.
I often found myself helping Jim, either loading shot or assisting him with loading or unloading the truck for a shot.
It was a Saturday morning, also a down weekend so the site was reduced to just a hand full of people mainly fitters or maintenance personnel, the two of us had loaded a shot in a new second pit after the company became interested in exposing an area of shallow ore quite near the surface in the original mine workings, in an area called, The Main Open Cut, cica 1920 / 50's, this work area was about three km east of the Mt Gunson, Cattle Grid Mine.
We had completed loading the shot an hour earlier than expected and had cleaned up the site in preparation for an early departure. We sat in the vehicle waiting for the advertised blast time to arrive so we could fire the shot, despite there being only a few people about and we were not expecting any visitors we stuck to procedure and the advertised blast time.
With a quarter hour before the blast Jim set off in his ute to do a safety and clearance inspection of the pit and general area making sure all was clear and no "unexpected visitors" had strayed into the area.
I remained in my vehicle parked across the only access road effectively blocking it to all traffic when Jim called me on the radio simply to check no one had passed by, then advised he was about to light the safety fuse before joining me parked seven hundred meters down the road and well away from the 5 ton of explosive we were about to detonate.
Less then a minute later Jim's ute appeared as he joined me at the road block.
As my vehicle was facing the blast he simply pulled up alongside and climbed out of his vehicle to join me in mine as we waited.
I cut the fuse about a minute longer than normal he said as the two of us waited.
He checked his watch, 30 seconds he said.
Then, a short time later the ground shook and rumbled as the delays fired, although we couldn't see directly into the small pit we could easily see the rock and dust rising as the noise of the blast arrived.
We waited in silence for the dust to clear.
A good twenty seconds past when we both became aware of a strange whooshing noise.
We both sat in silence listening, as the noise grew louder.
"Incoming" Jim warned as we both realized a rock of unknown size, weight and velocity was fast approaching from some where high above.
We could only sit and listen as the noise grew louder hoping we weren't included as part of it's landing area.
A rock, about the size of a bread basket weighing in at ten or more kilograms landed with a definitive thump just meter behind Jim's Ute and less than three meters from where the two of us sat.
Hmm, he said, then after a pause, it missed.
The Last Overburden Blast in the Cattle Grid. 1986.
After a third nine month extension to the Cattle Grid Pit EMECO decided it was time to end the mining operation, this was forced in them not by the exhaustion of the ore body, but simply by the boom in the Australian Mining industry in general. EMECO were associated with a new mining company in Western Australia, AWP (Mr. Alexander, Walker & Piper, who later went on to become Walker & Piper,) This new group had originally been the interested buyers of the CSR Mt Gunson Mining equipment, almost three years earlier.
They had a contract to open up a new gold mine near Laverton in Western Australia. At the time Australia was in the beginning of the mining boom, all forms of mining equipment were becoming hard to get, any new machines had a minimum of a two year waiting list.
The owners of this new Western Australian mine called ((Austwhim Resources NL, then, Austwhim, then Dominion mining) Cork Tree Well mine were becoming anxious for the operation to start.
The last Mt Gunson Mine overburden shot was a slightly bigger one than usual, in an attempt to help run down the stock of explosives we had on site.
News of the last shot spread far and wide, soon visitors from nearby stations rang asking if it was possible to watch, high ranking military and people from Woomera began to join the requests to attend.
We prepared and graded a suitable viewing area, decorated with pegs and coloured tape along with helpful staff to help look after the hundred or so visitors.
The pit and access roads were all graded and tidied.
The shot had been drilled and almost forty tons of explosives loaded and made ready, toward the end of the day the crowd began to grow in numbers.
Finally as the advertised time approached we performed the usual safety checks of the pit, both in and the surrounding roads and country side for any visitors.
The main road was blocked at the cattle grid and all was made ready.
I stood in the crowded observation area as the safety vehicle drove past tooting to indicate all was ready before he took up position by blocking off the assess road into the pit.
The shot firer was the only person in the pit and could be seen standing next to Brownies Bunker waiting for the signal to fire.
The crowd stood quiet and watching to see what happens next.
I checked the time then at the exact time advertised I took off and waved my hard hat over my head slowly side to side. This signal was repeated by the shot firer almost a half a km away in the bottom of the pit who then disappeared into the brown square box.
Two or three seconds later I watched as the down line flash across the top of the shot at somewhere near 2280ft pr/sec initiating all the detonators. Milli seconds later the first of the front holes went off the rest quickly followed in 15mill second delays later.
The ground shook in response as each 21mtr long 150mm diameter column of explosive detonated pushing a wall of rock dirt and dust into the air quickly obscuring the shot from further view.
From the growing wall of dust a large 15 or so ton rock appeared, it floated upward instantly causing me to question how something the size of a volkswagon could have survived the violence going on and yet remained intact and how it could have been kicked out of the shot.
The rock continued to rise as though powered by some invisible jet engine as it drew closer and larger rotating backward indicating it had somehow been booted from below and low down.
Still some way off the rock continued to rise easily passing the level of the gathered group of visitors, with insufficient forward velocity I noted it would fall well short of our location as it continued upward unexpectedly splitting in two almost equal halves both continuing to rotate in perfect formation as they began their descent, eventually landing with a dull double thud in the bottom of the waste dump some way below.
Curios I thought still puzzled by its appearance, while my mind ran through the maths of how much explosive would be needed to propel something with a 1500kg mass almost 100 meters into the air.
Turning I discovered I was the sole person still standing at the edge of the viewing area, every else one for some reason having moved well back.
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