The mine closure conference is underway in one of those tourist towns in the Rockies of Alberta. I am not there; somehow the event snuck up on me and I just could not bring myself to go to another conference where I would snooze unceasingly through dull talks in hushed and dark rooms. It is a liberating feeling to know that you have absolutely no desire to go to yet another conference.
But conferences on mine closure have a way of finding you. Andy Robertson sent me the slides of his address TOP 10 THINGS THAT GO WRONG WITH PLANS FOR MINE CLOSURE. (The link is good, but slow, so be patient.) Like all Andy’s talks it is full of interesting ideas and dire warnings. He tackles some holy grails of closure and demolishes them. The sad part is that we knew all this thirty years ago on the UMTRA Project, but then were derided. Maybe we were just not as entertaining as Andy nor were our meeting venues as beautiful. More likely, fewer mines had had to face the truths that Andy reiterates. Here are some of them.
The first to strike me is Andy’s statement that mine closure is a process, not an event. These days you need to plan for, prepare for, and actually mine for closure from the first glimmer of the mine’s birth to the last day of the last ton of ore extracted. And then you have to be prepared to be around forever to do something to try to limit the devastating forces of nature which laugh at your puny attempts to halt change.
The second point Andy hammers home is that mines are getting bigger and bigger; tailings impoundments are getting higher and higher; and thus the risks are every increasing. One of his slides notes that by the 2030s, the maximum height of tailings dam embankments will be nearly 480 meters ( I would settle for a round 500 m in predicting thus far ahead, but maybe he has a particular facility in mind.) Can you imagine the task of perpetually caring for a 500-m high earth embankment that generates no cash flow? Or defining the consequences of failure of such a structure? They will have to do that if ever they mine the Pebble Mine in Alaska.
The third point in Andy’s presentation that jolts us awake is his prediction of the consequences of proactive planning for mine closure:
- Increasingly risk-averse-based decision will control mine closure.
- Closure conditions (requirements) will dictate mine technology.
- Slurry tailings, high dams, and the use of geosynthetics will join the endangered list.
- “Closure Liability” will be as significant as “ore reserves.”
He proceeds to list and discuss the following things that go wrong in mine closure planning and implementation (best download the presentation to get the details.)
- Planning for incorrrect objectives: To avoid this anticipate trends in other jurisdictions and build in flexibility.
- Planning with flawed science. To avoid this at least recall that wetlands do not work, tailings are not impermeable and do not prevent infiltration, clay covers are fallible, and lime is not the answer to acid drainage. Keep in mind that extreme events do occur–the biggest earthquake, the largest storm, low strength layers in the foundation are real and will control in the long term.
- Planning for an event, when closure is a process. Face it, somebody will have to take custodial care of the closed mine and they will have to spend money forever looking after the site.
- Planning with inadequate financial provisions. Under-estimation is all too common. Have the estimate done by those with no conflict of interest, i.e., by those not seeking to maximize the value of the mine in the “selling” phase.
Andy recommends that if you cannot get it right the first time, you should plan to fix it the second and third time around. Soon enough we will have conference devoted to the failure of mine closure works. Rue the day!
My own thoughts prompted by looking at the presentation and writing the above: There are just some places we should not mine, because there are some places where we just cannot close the mine successfully or economically. And if we truly need the resources from a mine in a given place, we must, as a society, accept that some mined areas will have to be viewed as sacrifice zones—places forever degraded in the interests of resource development.
On a more positive note, we recall the Witwatersrand where we grew up on a mine. They have closed the mines in the sense that the headgear is gone and the slimes dams removed to be reworked and consolidated in giant new impoundments. But the mine workings are still there and groundwater is and will perpetually be different. What was once barren veld is now a sea of humanity living and working in dense urban areas that cling to the line of mines that once were along the edge of the vast basin of gold. Had the Boers or the British of 1890 talked of mine closure, they would have had no way to predict what did develop. And if they had had the ability to predict what is today the Witwatersrand, they would have had to conclude that this was destined to become a new place, a new way of life, and they would have had to face the reality of sacrifice of the loneliness of the veld for the roar of cities.
So too today, societies and places where there are vast ore bodies should debate changes of so great a scale as the change of the Witwatersrand from veld to city. Can you imagine an Alaska where six million people cluster in the dense urban settlements that develop around the long-forgotten mine? Anglo did it once; they could do it again in a different place. All the while branding closure as a process and not an event.