Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Monday, March 17, 2014

Bernic Lake

I tried to be nice about this, but recent information about the unfolding situation at Tanco's Bernic Lake mine have really raised by ire.

Tanco has been mining caesium (pollucite) from under the lake. They had a permit that stipulated that they leave a certain thickness of rock (call it 'x') in support pillars, which hold up the roof of the mine (also the bottom of the lake). Presumably, company executives signed off on the specifications which led to the permit. Unfortunately, much of 'x' was ore, so the company began to extract it, with the result that the pillars are now smaller than originally proposed, and now are in danger of collapse (not my original source).

The original proposal was to drain a portion of the lake, block it off with a coffer dam, extract the remaining ore, fill the hole, and refill the lake. Which to my mind was doable, and a brief review of some of the environmental impact statements from interested parties suggested that this could be managed (aspects of the original proposal may be accessed here).

The trouble is that draining the lake and managing its environmental consequences is potentially costly. So apparently the company is considering a different proposal, which has been described (I have not seen original engineering documents) as continuing the underground mining operations, replacing the supporting rock as it is mined with some engineered structure.

The main difference between the new plan and the original plan is that the new plan is considerably cheaper, but risks the lives of the miners (especially given the company's operating record). But what do the lives of miners mean when almighty dollars are at stake?

No doubt there are subtleties that I have missed as I have not seen the original documents--and if I look at it completely dispassionately, it looks possible. But here we come to the history of the company. Considering how it has operated in the past with respect to engineering plans, I suggest the authorities in Manitoba should tell Tanco to fuck off.

Update:

Otto has reminded me that I was remiss not to mention that Cabot Corp. is the parent company of Tanco.

2 comments:

  1. Thanks for this post . I am trying to call attention to this situation. It is #2 on my global watch list of mines at risk of catatsrophic failure. Very similar situation at Gold Ridge Mine Solomon Islands..miners drove it to a level of risk where no matter what is done there will be a large public consequence. .(Lindsay Newland Bowker Bowker Associates Science & Research In The Public Interest)

    ReplyDelete
  2. This should not be #2 on anyone's list of potential catastrophic failures. The ground is strong, under low vertical stresses and extremely competent. The "drain the lake" plan was filled with red herrings about weakened pillars, all in an attempt to open pit the mine under the lake because the current engineers are open pit guys, not underground guys. They simply wanted to get 100% extraction and this was the only way. When environmental opposition to their plan became too much, they went back to plan B, which was safe, just not as economically friendly. And no, it is not cheaper to mine underground. Not even close. Just can't get 100% extraction.

    ReplyDelete