This posting is intended as a small contribution to the debate about the Pebble Mine in Alaska. This posting is prompted by the oil in the sea from those who prefer oil to uranium. That is the miner in me talking. Sorry to the oil and gas men. And to the birds and fishermen.
A contentious issue is the question of what is perpetual? A young mining father told me today that his youngest daughter said “It is as long as I shall live.” His elder daughter said “It is at least the next ten years.”
For the mining economist is at least thirty years, for that is the period after which Net Present Value is meaningless. Might as well pass it on to a daughter who will live longer than that.
I stirred the discussion pot by claiming perpetual is at least 10,000 years, the period of the Holocene, the period of the present geological age, and the period homo sapiens has been farming. If we were entering a new period of glaciation, I would be correct. Global warming may make me wrong and perpetual may be longer than that.
I was listening to the story of a mine waste disposal facility that failed during construction of closure works. The lawyers claimed it was a failure. I asserted the design succeeded. Afterall the closure works were designed, in accordance with state law, for the 100 year storm. And the storm occurred, as you would expect within 100 years and the closure works failed. Somebody forgot to tell the lawyers the probability of the 100 year event in 100 years is almost 67 percent.
Too many people equate design for a 100 year event as implying the structure will last for 100 years. As the story of the failure on the mine closure works illustrates, this too common assumption is grossly wrong. Is this just another failure of education in history and elementary statistics?
The assembled engineers burst into defence of various design lives for mine closure works. And the heated debate soon degenerated into confusion over design life and design event. It was all cultural and ethnic.
The young man from a First Nations group said his people think of forever as seven generations. Touching but not very long! Even with a universal health scheme.
I recounted the story of my time in Spain consulting to the equivalent of the Spanish Nuclear Regulatory Commission. My host, a wise Spanish civil engineer, took me one evening after supper to stand on an old stone bridge. He said: “Jack, two thousand years ago a Spaniard was Emperor of Rome. This bridge we are standing on was built sixteen hundred years ago, That tower over there was built two hundred years later and soon after construction the owner of the castle, in a jealous fit, threw his wife from the tower. Local folk here still consider the family a little eccentric. My point is that only in young nations like the United States and in the British colonies do people think of a thousand years as a long time. In reality it is nothing to the average Spaniard.”
Then I recalled the Cahokia Mounds near East St. Louis. The society collapsed, but the earth mounds they built in the 1200s survive as a tourist attraction. I visited them to see the erosion: deep gullies cut into the soil they so patiently carried up in grass baskets. In spite of “perpetual” mid-western rain, the mounds persist. If you seek to see how mining waste piles will perform in the next eight-hundred years, go see these American mounds.
I admitted his point. I pointed out that on the Uranium Mill Tailings Remedial Action Program (UMTRA) we had to design mine closure works to remain stable for 1,000 years–that is, the legislated design life of our closure works was 1,000 years. So we designed the closure works to remain stable in the event of the probable maximum precipitation and the maximum credible earthquake–that is the design event was essentially the event that has a potential recurrence interval a lot greater than 1,000 years–and extending in theory almost to perpetualality.
OK, so you do not believe mine closure works should or could ever be designed to be stable in perpetuity. It can be done, in my opinion, if you are prepared to spend enough money to countermand the forces of nature. The technology is there. It is simply that the Uranium Mill Tailings Remedial Action Program (UMTRA) was the only one I know of that had the law and money to attempt this.
Which of course raises the questions: Does Alaska have the law, and does Anglo American have the money to close the Pebble Mine waste facilities to remain stable for 1,000 years, a long time, or in perpetuity? If the state has not the law, and Anglo has not the money, it is only a matter of time before the wastes spill down the rivers to the sea, like the oil spills from the ground to the oceans. It is but a matter of history repeating and elementary statistics. That is unless Anglo can hold back the forces of nature forever.
Ans so, this quiet Friday evening after a busy week that involved going out to eat and drink every night, I will now end this tirade and go to couch-potato with this summary;
- Do not confuse design event and design life.
- The design event can occur very early on in the design life of a mine waste closure facility.
- In the fullness of time all mine waste disposal facilities will flow to the sea–the only issue is the rate at which they do so.
- Extreme accidents do occur–even to big companies who have statisticians to calculate the odds, but not money enough to pay the costs.
Have a good weekend.