For the Birds - Gold Mining stories

When I went to work at a gold mine in NV in 1988, they were having trouble with migratory birds. It seems that my mine was killing more birds in the cyanide reclamation ponds (at $1000 per incident) than all other gold mines in NV. Very shortly thereafter it was discovered that this was because we were reporting honestly.

We tried Nets, we tried Cannons, we tried Shotguns, we tried Owls both real and mechanical.

Some father, while theoretically babysitting at McDonalds, noticed the play place balls.
They are a matte surface, not shiny like water, they form a 'solid' cover if you have enough of them, and if the sides of your pond are steep, they adapt well to changing water levels.

After the local McDonalds threw them out for stealing too many play place balls, the guys took their idea to management. "If the birds cannot see any water, they will not land on it". While play place balls tend to be red, yellow and blue, our ideal balls would be black to retain heat (the ponds freeze in the winter, limiting production) Management was impressed but had two problems: Where can you buy place place balls, and how do we mend fences with the local McDonalds so our employees do not have to drive 240 miles to the next one.

Humility was the answer, our management went to the local MickyD's and volunteered to replace all the balls with brand new ones if the McDonalds would just give them the name and address of the company they bought them from.

I retired 11 years ago, and you could look out over a vast sea of play place balls and still see one in a thousand that were red or yellow. (Face it, you cannot return the balls once they have been exposed to cyanide, that would be wrong!)

Now they are all black.



And by a decade later, this is common:Silver Lake Reservoir - Wikipedia, the free encyclopedia

 

I worked for 14 years at a gold mine (7000 feet long, 4000 feet wide and 3000 feet deep) The gold (very slowly) accumulates there as the hot water coming in contact with the magma intrusion cools rapidly due to many faults in the rock there. Gold falls out of suspension when water goes below 140 degrees F. (obviously, water is not liquid at 140 degrees C) Since the site has a great quantity of 140 degree water (they are trying to keep a 3000 foot hole dry) all our 'cold' water is really waste water from the dewatering. (drinking water is in 5 clear gallon bottles or we would have to be a water district in the eyes of the EPA)

It really is odd at first to flush.

The fault lines are visible in this example but never named:


A side effect of the many faults, is that the pit is prone to slides, we need a fairly shallow slope, and you can still see slides where the rock slides obscure the steps:

 

Sometimes you find answer, sometimes you find all new problems.

In the winter, the pit would fill up with diesel fumes, as the cold air on top 'capped' the warmer air near the bottom. Since the trucks could only pull 7 MPH when going uphill under load, they burned a lot of diesel.

We found a guy who could make our diesel to AC electric trucks run on trolley lines. We built substations, and wired the trucks up for trolley use. We needed supports for large Pantographs and prisms from Tanks so the driver could see if s/he was on Trolley.

Besides polluting less, the trucks could go 11 MPH on trolley, so there were both environmental and productivity rewards. Once on level ground, the truck went back to diesel, but not being under load, it could do 35 MPH. Or so the theory went.

It only took the drivers 24 hours to discover that if they were on full throttle in diesel AND on trolley, they could do 13 MPH uphill out of the pit.


This still pollutes almost half as much per trip, as each truck gets out in half the time as just diesel. EXCEPT, these drivers will just make more trips! So as an environmental technique it was not very well received by the EPA. Mind you it increased productivity and the diesel cloud was reduced. (more of the trip was on level ground, since the uphill run was quicker)

Sadly by the time we got trolley all sorted out, Komatsu had a bigger truck, and it was DC electric not AC. Converting as much power as we used from AC to DC is not trivial. (The Prius has a separate cooling system just for it's inverter)

So now they run much larger trucks (compare the ladder up to the cab to the top picture for scale)

 

For a higher grade ore, conveyor belts are cost effective.
The ore we move is about 0.10 ounces of gold per ton. To mine a million ounces of gold a year you move a lot of ore.
Worse, due the low angle of our pit wall, we move a lot of rock that is NOT ore, just overburden.
One downside of a conveyor is that it fails all at once. If one truck fails, you still move ore.

And it should have occurred to me, when 16,000 feet up the Andes, conveyers works just as well as ever, but diesel is gasping for air.

Barrick Gold Corporation - Operations - South America - Veladero


Barrick Gold Corporation - Operations - South America - Pierina


Barrick Gold Corporation - Operations - Australia Pacific - Kanowna
(pictures)