Tailings dam

Hi. Let’s talk about an important topic in primary industries around the world. You’ve probably heard of tailings dams by now with the rash of failures they’ve had, like the 2015 Bento Rodrigues disaster in Brazil.

Let’s back up a bit, though. You may have heard of these things but don’t actually know much about them. So what’s a tailings dam?

Mining companies build these large water-filled structures to store waste from their mines. These dams act as permanent containment, making them basically gigantic dump sites. Everything that goes in stays in, with no more processing or disposal. True story. You can find these dams in  mining for resources like copper, gold, and uranium. Yeah, that too.

Tailings dam
Courtesy of southdakotaprogressive.blogspot.de

As an interesting side note, Canada has the largest tailing dam in the world, at 18 kilometers long and 40 to 88 meters high. Imagine the volume of product you can leave in that. You could drop several small villages in there!

Worldwide, we have almost 3,500 active tailings dams, according to a report from infomine.com. The same report also notes research suggesting that tailings dams fail 10 times as often as conventional dams.

The need

Let’s go back to the failure of the dam in Brazil. It killed 17 people and released 60 million cubic meters of iron waste into the Bento Rodrigues district and the Doce River.

The waste contaminated 80 km of river, creating multiple grave socioeconomic and environmental impacts. For example, the IBAMA (Brazilian Institute of Environment and Renewable Natural Resources) reported that the changes in water quality (turbidity, suspended solids, and iron content) poisoned and asphyxiated numerous animals.

Tailings dam
Courtesy of Globo

And before the events in Brazil, incidents occurred in Canada, New Guinea, Hungary, and other countries. That means we need to improve their monitoring, right?

Constant monitoring may help avert problems in a tailing dam. While high-quality, secure monitoring involves many factors, here we’ll address the instrumentation solutions needed to provide data for a tailing dam.

The tools

In a dam, you can usually monitor displacement, strain, level, pressure, and flow. Most companies check these manually, sending operators to the field to pull the values, then add them to a spreadsheet later. An antiquated method but standard, sad to say.

However, smart instrumentation now exists that can send data throughout the day directly to a monitoring or control system. These tools can reduce or even eliminate human error from the readings. They can also provide more data in one day than an operator checking the dam two or three times a week.

Some dams may have different needs, but most should have level and flow measurement at least. You’ll also need two level measurements, one for the water table and one for the dam.

Tailings dam
Courtesy of Endress+Hauser

For the water table, you can install a hydrostatic level sensor in a PVC tube within a water well. You should make sure the sensor has enough cable, but otherwise it’s a fairly simple setup. You can collect this data using a wireless device, which provides good accuracy for a decent price. The device can provide regular updates, like every 15 minutes, and still have a long battery life.

Tailing dam
Real tailing dam level monitoring

For the tailings dam, you can use an ultrasonic level transmitter. It can monitor the dam’s surface and send the data wirelessly as well, saving more money and time with its easy and minimal setup.

Finally, for the flow, another ultrasonic will do the job in a Parshall flume. As a standard solution in the instrumentation world, you should have no trouble installing it and reaping the same benefits as the other solutions.

The key to success

It’s not a cliche when I say that standardized protocol is the key to success. For tailings dam monitoring, wireless devices provide great solutions to avoid high costs in structure. They also give a ton of process data, not to mention remote access to sensor status and configuration.

However, keep in mind that while you may want a cheap solution, you might not want it too cheap. The cheapest devices use private wireless protocols, requiring all devices in the network to come from the same company. That may work for you if all goes well. Of course, we know that only lasts so long. As soon as you have an issue with a device or network, you have only one vendor you can call.

And guess who calls the shots on how much it costs to fix? Yup.

Courtesy of FieldComm Group

If you can afford more, go for a standardized protocol like wirelessHART or ISA 100. That way if you need a new device, then you have a range of good options. You should also consider security. A mesh network will give you stable network conditions if set up correctly. It’ll also encrypt all the data in the network to keep your information safe.

Always remember that a cheap solution today may cost more in the long run.

Courtesy of giphy

We can’t see into the future, but we can think ahead and plan for the possibilities.

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