There is a lesson for us all in the failure of the heap leach pad at the Bellavista mine. Here is an edited version of the first news report I saw:

Glencairn Gold Corp. suspended operations at its Bellavista Mine in Costa Rica, citing the risk of a cyanide spill and ground movements that may compromise containment of cyanide used to dissolve gold from crushed ore. The earth movement - up to one centimeter a day in some parts of the leach pad and waste pile - is attributed to years of unusually heavy rain.

“Based on earth movement patterns in Costa Rica, the geological structure at the site and the opinions of its experts, the company does not believe that there is a risk of sudden earth movement at this time,” Glencairn stated. “However, continued small movements could compromise the sub-liner, liner and drain system.”

Glencairn said the mine closure is a “precautionary measure until a full technical analysis has been completed and required remedial action has been implemented.”

Gray said the company first noticed earth movements as early as May. “Monitoring since then has revealed that the movements have been identified in the range of one centimeter per day,”

“We are taking a conservative approach with our valuation and are assuming that the ground movement problems will take one year to resolve and mining will not restart until August 2008.”

A few weeks later, this (edited) news report appeared:

Glencairn Gold Corp. shares were trading near a six-year low, a day after the company warned that its Bellavista mine in Costa Rica may remain closed indefinitely and that the Toronto-based company needs cash urgently.

All mining and leaching operations at the gold heap leach mine in Costa Rica were suspended last month after ground movements raised concerns about risk of a cyanide spill.

The company said last month that massive ground movements - first noticed in May - had caused cracks at two corners of a leach pad which contains cyanide used to dissolve gold from crushed ore.

Another report states:

President and CEO Peter Tagliamonte said "We have suspended mining operations and application of cyanide at Bellavista and are expending every effort to find a permanent solution and get the Company back on track. While this solution is sought, Bellavista will have a significant negative impact on the Company."

This story is fraught with questions. The technical part simply does not hang together.

As the first reported indicated, the rate of movements clearly gives reason to be concerned about the integrity of the liner, which if breached and torn would let seepage from the pad pass to the ground beneath and presumably the groundwater. Suspending all operations won’t do a thing to address the problem. Good that they have stopped applying cyanide, but that won’t stop what is in the heap leach pad getting out if the liner is torn.

A heap leach pad should have a series of drains at the base of the pad. Theoretically these drains should be able to accept any seepage down through the heap leach pad materials. The drains of a conventionally designed heap leach pad ensure that seepage through the pad is vertically downwards. At Bellavista this does not appear to be happening. Are the drains blocked? Are they inadequate? Have they been rendered inoperative by the reported movement? Is this what their month-long technical evaluation indicated?

Presumably in the period between the first and second report, they completed a “full technical analysis” and decided to “close indefinitely.” Not that the second report tells us much: only that there are cracks at two corners. Funny but the corners of piles of rock tend to be the most stable part of piles. If you look at the three-dimension geometry, the corners are the parts with the flattest slope inclinations. Makes me wonder what other problems and deficiencies there are in this heap leach pad.

They are still “expending every effort to find a permanent solution.” I do not know the mine or the site, but the obvious solutions include: a berm to stabilize the sliding mass; toe drains to dewater the perched water table in the heap; vertical dewatering wells from the top of the pad; a layer of plastic over the pad to limit further ingress of rainwater; removal of material from the crest of the slope to lighten the load on the failing mass.

I cannot understand how company can spend a month studying a failing heap leach pad that could well be polluting the mine site and beyond, and then issue a casual statement that they will probably never restart mining. No information about what they have done, what the problem is, what the long-term environmental impact is or what it will cost to clean up the mess: polluted groundwater; impacted surface water; failed masses of cyanide-saturated rock; and so on.

I managed to access the Glencairn 2006 Annual Report. On page 6 is a picture of the heap leach pad, presumably sometime in early 2006. Here is that picture. In their 2005 report they said they would be mining for seven years: did they sort of plan to sit and leach for five more without actually adding to the pad once it was a pyramid.

The picture above shows an amazing scene. I guess the heap leach pad is about 100-ft high; those lifts look to be about 10 ft each. Then it looks as though the foundation material has been cut away over about a 25-ft height (the grassed embankment at the toe.) The grassed embankment looks steep; I would guess 1.75H:1V. So we have a tall and steep rock pile on a foundation, probably of saturated in-situ soil without toe support.

Here is another picture that, I think, shows the heap leach pad (notice the same little pump shed besides the pregnant solution ponds). This shows an even more amazing situation: the whole hillside has to be loaded with the ponds, pad, and heap materials.

I cannot see space to build a stabilization toe berm; I cannot see how they can readily flatten the slope.  I would guess that if there is a failure plane it starts on the top deck and cuts down through the rock of the heap leach pad, passes through the liner, and continues on down and out through saturated foundations soils. 

The other thing that amazes me is that if this is the heap leach pad in 2006, how much longer could they continue to use it even if it were not failing.  Pretty soon it would be a pimple or pyramid with a sharp point at the top.  Surely the life of this heap leach pad was limited as a result of geometry even before they shut it down due to failure.  Don’t they have another one under construction?

Here is a picture from the Glencairn 2005 Annual Report.  It has the heading “Bellavista Mine achieves commercial production” splashed across it, so this is presumable part of Bellavista.  Notice how extraordinarily high and steep the outer embankment of what appears to be a water dam.  They clearly like things high, steep, and wet in Costa Rica.  Is it not illegal in that country to have such high, steep water retention structures?

Did nobody explain to them the basic fact that the hills around there are, to use that funny term, meta-stable, i.e., being eroded back continuously by natural processes. Did nobody have the courage to tell somebody that steepening a natural hillslope could only result in failure? What is their “closure plan” for this heap leach pad and water pond? It is inconceivable that you can stabilize these things in the long term.