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Archive for the ‘Tailings’ Category

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Today was a typical day in the life of a mining consultant.  One report was issued; one project put on hold; one request for proposals received; and a long discussion on how to deal with an obdurate client.

The project put on hold was in the prefeasibility stage–of deciding how to reopen a mine closed some fifteen years ago.  The pit designer had calculated that $75 million of prestripping was needed to get to the ore.  The pit stability analyist had decided the pits could not go much deeper without rock bolting.  The metallurgist said there was no equipment available to get the ore ready for heap leaching.  The heap leach pad designer had said the new heap leach pad was feasible but a long way from the mill—would it be economic to transport that distance?  And the groundwater guys had said there was not enough groundwater to support operations.  No wonder it was put on hold.

The report issued advised on how to deal with a sinkhole that had developed in the tailings over an area where the geomembrane liner had been torn and repaired during installation.  And how to deal with diversion channels designed for a mere twenty-five year precipitation event.

The obdurate client wants to relocate waste rock to a site where the groundwater becomes artesian in the wet season.   And they do not want perpetual water treatment although the rock is acid generating.  Imagine that!

Then the RFP to proposed to compile a mine closure plan came in.  Can we win?  Is it worth compiling and submitting?  Should we team?

Finally I did a dry run of the EduMine webcast for next week on Mine Water Management.  Please to say that Clint Strachan of MWH has agreed to join me and present on mine water management at the Marlin Mine in Guatemala.  it will be great to hear his presentation.  There is still time to join us on Tuesday.

Then home to a drink and an opera.  Tell you about that in the next posting.

 

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I was always healthy until I visited the doctor for a checkup.  Then they found all sorts of things wrong with me:  internal components not working; high levels of this and that and consequential concerns; indications of too much drink and smoking; blood pressure where it should not be;  weight too high; and so on.  Although I did loose some fifteen lbs on my recent trip to Peru and Chile. Maybe not enough alcohol,  lots of walking, and all that terrible Peruvian food.  How can you like raw fish in vinegar; black potatoes in squid ink; or slimy muscles in red pepper?  I cannot and probably ate too little.

No matter.  We get old and things go wrong.   I suppose it is all a matter of what will get me first.  As long as it is not an angry reader of this blog.  But the doctor laughed and told me to keep going for there are many years yet to write this stuff, she said.  When did the doctor become a lady younger than my daughters?  It is just not fare.

So instead I spent the day writing reports on tailings dam I have recently observed.  I am amazed at the low standard of stability analyses I have seen.  Fourteen analyses and not one of them is correct!  Here is a list of the most common mistakes.  At least I have set those so-called reputable consultants working again.

  • Failure to include foundation soils in the stability analyses.  Apparently they did no foundation drilling, so did not include foundation layers.  Subsequent drilling has shown there are liquefiable layers in the foundation.
  • Failure to include the phreatic line in the cross section.  Apparently they had not yet installed piezometers so had no water table.  Subsequent work has shown that there is a high phreatic line in the cross section.
  • Use of circular arc failure surfaces in cohesionless materials.  We all know that planar failure surface develop in such materials.
  • Failure to use planar failure surface to calculate stability analyses involving sliding along a weak foundation layer.  They used circular arcs which simply cut through strong and weak foundation layers.
  • Use of the pseudostatic coefficient for seismic stability analyses in high earthquake regions.  They should be doing deformation analyses in order to estimate deformation.
  • Failure to account for buildup of excess pore pressures as the tailings rises.  Too complex to do I suppose.
  • Incorrect use of strengths of materials:  UU for slow failure and CU for fast failure.

No wonder these things fail.  Not only are the stability analyses done by amateurs, the phreatic surfaces they calculate using standard programs are just simply wrong.  But that is another blog topic.

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This year I have visited at least sixteen tailings facilities from the far north of Canada to the far south of Chile.  Mainly I was there to see about the state, safety, and ongoing operation of the facilities.  But along the way I had an incredible opportunity to observe and photograph mine water management facilities and systems. In next week’s EduMine webcast on Mine Water Management, I will have a chance to distill these many observations into a coherent whole.  So come join us in the webcast next Tuesday, Wednesday, and Thursday.  But three hours a day each morning and I will update you on the many systems, practices, components, and ideas I have gleaned from these trips and observations.  Many new case histories courtesy of the mines I visited. (more…)

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At this link is an announcement that the BC regulators are seeking proposals from consultants to help them evaluate the independent dam safety analyses they have ordered be done by independent folk on all the tailings facilities in BC. Dam Safety Inspection Review is the heading.  Here is the full announcement — it is fascinating for what it tells and what it does not tell. (more…)

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Just home from a four-week journey that took me to  Peru, Chile, Keystone CO, Banff, and Ekati NWT.  It is good to be back in the house where you can throw off the formalities of travel, eat simple food, and get drunk in private. They say that Peruvian food is the best in the world.  Indeed it is if you are in a fancy, expensive place in Lima.  But go to a mine and eat what the miners eat, and it is terrible beyond belief.  Rice & beans and other unrecognizable substances of gooey texture.  I lost weight.  Maybe it was the altitude = 14,500 ft.  You walk slow and breathe deep in those conditions. (more…)

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The final keynote speech at the conference on Tailings and Mine Waste was from Craig Benson. He talked about mine waste facility covers.   He has promised me a pdf of his talk. But in the meantime there are many documents by him and his coworkers readily available on the web that deal with much the same material as was in his presentation. (more…)

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Today’s keynote address was by Tamara Johndrow of Freeport-McMoRan Mining Company. Her topic was FCX Tailings Stewardship Program. Let me note what I recall of her talk. Tamara heads a group of about ten engineers.  Their task is to look after, or steward, all of Freeport-McMoRan’s tailings facilities.  If I recall correctly that includes 18 operating facilities and over fifty closed facilities.  That is a large portfolio. They have a single objective:  NO FAILURES. (more…)

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