#copper mining

Excerpt from this story from the Associated Press (AP):

The transfer of federal forest land in Arizona to a pair of international companies that plan to mine one of the largest copper deposits in North America is complete, but a group of Apache women is asking the U.S. Supreme Court to intervene as a last-ditch effort to stop the project.

The title to the land was conveyed by the federal government to Resolution Copper on Friday after an appeals court denied requests by the San Carlos Apache Tribe and environmentalists seeking to block the move.

The appeals court determined that the plaintiffs’ legal claims likely would not succeed and lifted an emergency injunction that was put in place last summer.

The land includes Oak Flat — an area used for centuries for religious ceremonies, prayer and gathering of medicinal plants by the San Carlos Apache people and other Native American tribes. The tribe, the activist group Apache Stronghold and other plaintiffs have been fighting for years to save what tribal members call Chi’chil Bildagoteel.

Alexander Agassiz – Scientist of the Day

Alexander Agassiz, a Swiss-American zoologist, died Mar. 27, 1910, at age 75.

I wondered if this was a tailings dam and wanted to combat the copious misinformation in the reddit comments, so I did a little digging!

The Rosia Poieni mine in Romania is owned by the Romanian Government, operated by CupruMin S.A., started by the communist party in 1978 and ongoing today. It's a Copper open pit mine producing copper concentrate, using the flotation method, which is generally environmentally neutral and causes minimal damage; which makes this pond... unusual. I also realized the poster didn't know what he was talking about because he kept saying cyanide leaching. This is neither a leach heap, nor cyanide-prominent because sulfuric acid is the most common byproduct of copper mining, not cyanide (used for gold mining).

I initially searched for acid mine drainage from the Rosia Poieni pit and got a very helpful study from 2002 on Acid Mine Drainage into the Muscanilor brook that drains the mine site, passes their ore dump, and drains into a river further downstream. The paper details the type of minerals and alteration present at the mine (extremely helpful), and mentions that there's little to no carbonates present in the deposit, which makes it hard to neutralize the acid the mine generates.

However, this is to the south of the mine, and when I started looking at Google Maps, the laz decantare Valea Sesii is to the north. They don't process their copper concentrate onsite in their own smelter, so there was still minimal explanation for why there was so much acid in the pond. (Or what the pond was since "laz decantare" translates to decant pond in English, which is just a basin for solids to settle out.)

Searching for the smelter that processes their copper, I found the Zlatna Smelter from a USGS log. This says it's north of the mine, but Zlatna is actually south; I searched for a smelter north of the mine but couldn't find one, and in Zlatna you can see the smelter stack from the road; so I'm pretty sure this is just a typo. [Also, 45% recovery is insanely low. Even for 1992!]

So! Since the smelter (which would produce sulfuric acid) is out of the picture, we're back to wondering why this pond is so toxic.

I started doing searches on decant ponds, to see if there was a reason it was called a decant pond, and turned up a Romanian webpage from 2013 protesting the potential Rosia Montana mine. While a bit cumbersome, the pictures and write-up were the most insightful on what the hell is going on in Valea Sesii.

Link to the Blog

The Valea Sesii, via a mine contact, is an open valley tailings pond. This is Insanity #1. Tailings ponds can be acidic and it's what I thought the lake was in the first place. You usually line them, or place them on an impermeable rock/clay layer so acid doesn't leak into the water table. This valley could be on an impermeable rock layer; I don't have enough information; but it's very clear it's unlined. You also usually keep your ore and waste heaps near each other and on or close to the pond so all the acid drainage is in one spot. Their ore heap, according to the first paper, is all the way on the other side of the mine, so you have two points of drainage, and one just flows down the slope.

Insanity #2.

THEY STEPPED ON THE TAILINGS BEACH. THIS IS SUCH A BAD IDEA. I CANNOT EMPHASIZE ENOUGH HOW BAD AN IDEA THIS IS. THE FACT THEY WERE ABLE TO WALK AROUND A TAILINGS DAM OF THIS PH WITH NO SUPERVISION IS MENTAL. IT'S SO INSANE. YOU HAVE NO IDEA.

PLEASE DO NOT DO THIS. SULFIDES AND ACID DRAINAGE OFTEN CREATE A FOAM CRUST THAT LOOKS SOLID BUT IS INCREDIBLY UNSTABLE AND DECEPTIVE. THIS SAND IS ALSO <75um AND ACTS AS QUICKSAND. DO NOT WALK ON IT.

The author writes, "The tailings continue to be discharged consistently and the level of the pond rises every year. That's why the people from Cupru Min raise the dam year after year." (I still have to research Cupru Min.) But yes, this is how tailings dams work. Usually they're properly sequestered, lined, and don't eat up towns, but as tailings are deposited, they pump the largest sand grains onto a dike a few hundred feet thick and continuously deposit sand into the impoundment/valley, and the dike, keeping the water away from the dike walls. You can see this here, in the upper right corner:

Here we encounter Insanity #3 on the blog:

I cannot emphasize enough how insane this is. I'm sure they wanted to make a better way and couldn't because tailings are so unstable you can't make a path out to the deposition point, but someone has to walk out there and move these pipes, and turn them on and off manually. This picture makes me want to scream about safety. Also, let me just point out that water HAS to be a pH of <2 from the color. If someone falls in, you will be very, very badly burned. Begging whoever has to manage these pumps to be safe.

HOWEVER. None of this answered WHY the dam is so acidic if it's only used as a tailings pond, until the author reminded me, "the tailings mess is discharged through a system of pipes that ... allow the discharge to be directed to various areas on the contour of the pond."

This is also fairly normal; most mines have three to four basins they rotate deposition in, allowing them to dry out so they can compact the sand. But looking at the areas of deposition on the Valea Sesii, and putting the time into context, things make a lot more sense. Obviously this is only pieced together with my experience, pictures, and google maps, but it seems very likely.

The Rosia Poleni mine creates an incredible amount of acid due to its mineralogy and rock composition, and the rocks around it aren't able to neutralize the acid. In the 1970s, nobody cared about this, especially the USSR, and said Build It Anyway. So they simply allowed the acid to run into the valley. This is Insanity #4.

I'm sure it was either planned, or quickly realized that the acid would take over the valley, so the mine planned a dam to the northwest, and used it to contain deposition.

The tailings are from the concentrator. Concentrator tailings are usually low in sulfide content, because all the sulfides have copper and other metals, and get floated away. For example, another tailings pond I know of, with the same process as the Rosia Poieni mine, has a pH of ~6-7. (Water has a pH of 7.0.)

But their concentrator is about a mile away! They have to pump/direct their tailings sand a mile away to the pond! This, in its own way, is a minor insanity, just for the logistics. I think having your tailings pond >1mi is normal though.

And FINALLY, almost everything made sense. I would put five dollars on the acid shown in other areas of the pond being acid mine drainage pumped directly from low areas in the mine into the tailings pond. Better it go in the tailings pond than the river.

So that is the most likely operational history of the Rosia Poieni! If you're going to be angry at anyone, this mine is STATE OWNED. The Romanian government is IN CHARGE OF THIS MINE, although they do not operate it, THEY FUNDAMENTALLY PROFIT OFF OF IT. They are also allowed to MAKE THE ENVIRONMENTAL RULES. This is the downside of having state-run facilities. The government is now fundamentally a corporation and WILL NOT reign themselves in.

Now go, be free! And remember that cyanide is not used or a byproduct from copper mining, it's from gold mining.

-=-