Acid drainage, heavy metals and the North Mara mine

I’m going to post another link to an article from The Daily News which is a popular English-language national daily newspaper in Tanzania. This article takes on a bit of a different twist from the last ones but is also related to the incident at the North Mara mine.

Barrick Gold’s explanation of what happened at the North Mara mine is that water from a waste rock storage area was released to the environment. Waste rock is rock that must be removed in order for a mine to operate, but which cannot be processed for economic benefit [1]. The problem is that rock, when disturbed and broken up and allowed to interact with the elements, can release toxins. If we’re dealing with large amounts of rock of the right (or should I say wrong) composition, this can become a serious problem. Now if we read the report titled Submission to the Standing Committee on Foreign Affairs and International Development by Barrick Gold Corporation, dated November 26, 2009, then we can find the following statement [2]:

In May 2009, an environmental incident occurred when water seeped from a mine rock storage facility into the Tigithe River. The situation was caused by high rainfall during the spring rainy season, which resulted in run-off from a temporary mine rock storage facility located on the property, near the river. The run-off water passed through rock that contained an elevated amount of naturally occurring sulphur, making the water acidic – a process known as acid rock drainage (ARD).

Now on to the newspaper article. It begins with the explanation that Barrick Gold has spent somewhere around a million dollars (1.4 billion Tanzanian shillings) to replace liners that were allegedly stolen from a waste rock storage site and that it was allegedly this theft that gave rise to the release of acidic water to the environment. So we’re aware right from the get-go that we’re dealing with this issue of ARD (which in the context of mining is also sometimes referred to as acid mine drainage or AMD).

The article quotes Teweli Teweli who is in charge of public relations at Barrick Gold Tanzania:

[Mr. Teweli] also refuted claims by activists that the mine had polluted River Tigite with heavy metals, saying that the mines including North Mara did not use mercury which is likely to be the source of heavy metals allegedly found in the river.

“There is no a single mine using mercury. We are using cyanide. How come that the activists were accusing us of polluting River Tigite with heavy metals when we don’t use mercury”, Mr Teweli argued.

Mr. Teweli then blames the possibility of heavy metal pollution in the area on artisanal miners, and the article mentions that Barrick is contributing to a program to support artisanal miners.

It makes a lot of sense to consider that artisanal gold mining can contribute to pollution, but there’s still a very crucial point that needs to be made here. People are concerned that Barrick Gold may be polluting the area with heavy metals for a simple reason. I’ll quote the U.S. Environmental Protection Agency which I think does a good job of explaining what that reason is [3]:

In addition to the acid contribution to surface waters, AMD may cause metals such as arsenic, cadmium, copper, silver, and zinc to leach from mine wastes. According to the Forest Service, the metal load causes environmental damage, and is of greater concern than the acidity in environmental terms.

I don’t know how to explain the fact that Mr. Teweli did not seem to be aware that ARD is readily associated with heavy metal pollution. The newspaper article was published at the end of October 2009, and according to Barrick they observed pollution from the spill (water with a low pH downstream of the mine) in May of 2009. Even assuming that there was no briefing on environmental hazards before May of 2009, there was still a period of five months that went by during which Barrick Gold Corporation had the opportunity to inform their head communications representative in Tanzania that ARD is readily associated with heavy metal pollution.

The Daily News article can be found here. It’s titled Barricks spends 1.4bn/- for rehabilitation of linners and was published on October 29, 2009.

[1] For example, National Resources Canada defines it in their Mining Information Kit for Aboriginal Communities here.

[2] This is one of the reports that I referred to in my email to the Minister of International Trade.

[3] In a document titled Technical Document: Acid Mine Drainage Prediction, December 1994, from the U.S. Environmental Protection Agency, which is available here


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