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Posts Tagged ‘Tailings’

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While we in BC have been preoccupied by the Mt Polley situation, yet another tailings failure has occurred.  This time in Mexico.  That brings the number of failures this year to three:  Duke Energy, Mt Polley, and Cananea.  Just the right number if the probability of failure is one in five thousand.

Reporting on the failure is sparse.  Here from the Mexico News Daily:

Negligence on the part of a copper mine in Cananea, Sonora, has been blamed for the spill of 40 million litres of copper sulphate into the Sonora River last week.

An earlier report by the environmental agency Profepa said it was sulfuric acid that was released by the Buenavista del Cobre mine, owned by Grupo Mexico. Arturo Rodríguez Abitia, assistant prosecutor of industrial inspection at Profepa, said the copper sulphate will have an environmental impact for its acidity. It is corrosive but will mix with the river water and become diluted and neutralized, he explained.

The tailings pond spill also contained heavy metals in concentrations that exceed health standards but are within those for environmental protection.

Residents of several municipalities are using potable water supplied by the government since their water systems, which draw from the Sonora River as well as the Bacanuchi, another river affected, have turned off the pumps.

Rodríguez said the mine acted in a negligent manner for not having monitored the release of the contents of the tailings pond. He said Profepa will be looking to apply the highest penaly possible, which is about 3 million pesos.

Monitoring of the mining industry is reported to be insufficient because three different agencies are responsible: Profepa, the Environmental and Natural Resources Secretariat (Semarnat), and the Economy Secretariat all have a role to play.

In saying the mine was at fault, Rodríguez said there should be control and emergency systems in place should a toxic spill occur, and the waste materials would be trapped by another pond to avoid being released into the river.

Detection systems to warn of a problem should also be in place.

Local officials said last week that the mine made no attempt to notify authorities of the incident. The water commission was advised by a municipal president.

Another mine in Durango was also faulted, in this case for a cyanide spill. Proyecto Magistral in El Oro released 2 million litres of water containing the compound, but it was reported to have been neutralized.

The Arizona Daily Star fills in a few details:

On Aug. 7, about 10 million gallons of mining acid spilled into the Sonora River, which supplies Hermosillo — Sonora’s capital — and tens of thousands of residents in various towns with drinking water. Sonoran state officials said residents alerted authorities to the spill while Grupo México, the mine’s owner, did not notify the state.

Tucson attorney Jesus Romo, who also lives in Banámichi, one of the affected towns, said the spill portends potential future damage from larger tailing ponds near the river.

“If they burst, it can mean the end of people living along the river,” he said.

The tailing pond that broke was more then 1.4 million cubic feet (40,000 cubic meters), but the others have have billions of cubic feet, he said.

The Sonoran government announced Monday that it has provided about $38,000 to each of the seven municipalities affected by the spill: Arizpe, Banámichi, San Felipe de Jesús, Baviácora, Aconchi, Ures and Hermosillo.

The World Socialist Web Site talks of a spill from a holding tanks, so this may not be a tailings falure after all.  Here is what they write:

Over 10 million gallons of toxic wastewater leached from a copper mine near the town of Cananea in northern Mexico spilled into the nearby Bacanuchi River on August 6. Reports indicate that copper waste tailings containing sulfuric acid and heavy metals leaked for more than a day from a holding tank into the river after heavy storms hit the region.

Hopefully we can get more definitive information.

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We are heartened by today’s announcements re the Mt Polley tailings facility failure.   I particular we applaud the choice of experts retained to do the engineering review. (more…)

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Subaqueous disposal means placement of tailings into or beneath a water cover. Deposition of tailings into a lake is the most common subaqueous method. In many instances the embankment dam is constructed as a water retaining structure and the impoundment is filled with water into which the tailings are discharged. (more…)

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Mike Jacobs of Goldcorp presented the keynote address today at Paste 2014 in Vancouver.  His topic:  Where mining meets the public–and why water is so important? He told us that Goldcorp annually publishes the statistics of the use of water at all its mines.  Commendable. Then he told us of the First Nations prayer ceremonies at the opening and closing of water seasons at their mines.  Incredible. (more…)

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The first official day of conference sessions at the Paste 2014 conference here in Vancouver.  Sean Wells, Director of Research for Suncor presented the opening keynote address. I cannot possibly here recount all he said.  All I can do is note a few points that he made that stuck with me.  In due course, his PowerPoint presentation will be available through InfoMine.  Get it and take deep thought over it, for his points are provocative, timely, and scary. He noted that the problems of oil sands tailings management are all about scale.  They oil sands produce so much tailings that the shear volumes and areas needed introduce problems not encountered in conventional tailings management.  I have heard it said that the two oil sands mines, Suncor and Syncrude, produce more tailings per day than the combined total of all the other mines worldwide.  His point is made. (more…)

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Day one of the  conference Paste 2014.   Actually the actual conference begins tomorrow.  Today there were short courses and meeting of friends and fellow travellers on the mining journey.  The most beautiful was a lovely lady from Brazil who is studying at the university of British Columbia for a semester and will be a mining engineer in a year or two.  We chatted over lunch and if she is, as I believe she will be, the future of mining, the profession is in good and beautiful hands. (more…)

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Lesson learnt: in all O&M tailings management manuals put in a requirement to observe the penstock more carefully when tailings discharge water is not going through it—look carefully to see if water from another source is exiting the pipe and find out why.

This is a new lesson learnt. This is something I had not before now thought of.  But on the basis of what I saw and did today, a necessary action.

Add it to your O&M manual.

Here are some pictures of this situation:

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If you have a penstock and seek to know more, contact me.

 

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This week we held a successful EduMine webcast on Advanced Tailings Topics. Four good speakers; many good attendees; and interesting presentations. Here is my summary of one of the issues in tailings management that we argued.

Forty years ago, the best geotechnical engineer and dam builder I have ever worked with warned me not to construct outward curving embankments. “They get pressure from the inward curving part where the tailings is, and so they move or creep outward. As the embankment soil or rock is not good in tension, it will crack and you dam will fail.”

Ever since I have managed to heed his advice. But we still see many cavalier designs of outward curving tailings facility embankments. Or worse square or rectangular plans. Recall that terrible failure at the corner of the facility that poured tailings into the Danube.

Of course I was attacked for these ideas—easier to attack than to solve.

My advice is to look very hard at flatter slopes, buttresses, and the effects of long-term creep outwards. Oh and install thick filters and drains that are self-healing.

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These past two days I have had to deal with that knotty subject, computer modeling for mines. I proposed a series of 2D runs in order to get a feel for how groundwater flows into an open pit and from the tailings facility. The younger generation cried in horror at my simplicity.  “We need 3D models to truly replicate the situations,” they protested. I protested: “We are not modeling things on the computer in order to replicate reality and create an electronic simulacrum of what is in nature.” (more…)

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There is still time to join us for the upcoming EduMine webcast Advanced Tailings and Mine Waste Facility Design, Operation, and Closure.  Here is the link to the course. Even if you have taken other courses before conferences, or the other EduMine webcast on Introduction to Tailings, or our previous Advanced Tailings courses, I know you will find interesting and exciting information, perspectives, practices, and case histories in this new course. (more…)

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