A NUCLEAR ISSUE: Both Rio Algom and Denison say they can

If mine decommissioning is Issue No. 1 for the mining industry, Rio Algom’s and Denison’s Elliot Lake, Ont. mines will likely become Reclamation Sites No. 1 in terms of public scrutiny.

Denison and Rio must render environmentally benign approximately 127 million tons of acid-generating, “mildly” radioactive tailings – at least to the satisfaction of the Atomic Energy Control Board (AECB) and in all likelihood, to a federally-appointed, five-member panel drawn from the judiciary, academia, perhaps even from the social sciences and divinity schools. Through public hearings, the panel, empowered through the Federal Environmental Assessment Review Office (FEARO), will hear submissions from intervenors of all stripes. It might become a lightning rod for environmentalists and anti-nuclear groups.

“You can take it to the bank that this will go to FEARO,” Said Ken Kay, Rio’s Manager, Environment, Decommissioning, Safety and Loss Control.

George Jack, AECB’s Manager, Waste and Impacts Division, told The Northern Miner Magazine the board “is considering” referring Rio’s closure plan to FEARO. “You can’t do a huge environmental assessment without public involvement,” he said. But even if the AECB is the sole review, that procedure is still “in full public view.” And, in the end, the AECB is the decision-maker. The FEARO panel, however, is “powerful and persuasive.”

Less controversy should attend the more prosaic elements of the closeout – the underground and surface plant. All equipment must be removed from underground and the shaft secured to prevent entry. On surface, the mill and surfact buildings will be removed. As well, any radioactivity above clean-up criteria on the plant site must be dealt with. This should not ose serious problems, although a full-blown FEARO hearing could prove otherwise.

In all probability, the tailings reclamation will be the key irritant. Both Denison (which submitted its plans in mid-May) and Rio (Which is well ahead of Denison) are seeking approval of a flooded tailings concept. This prevents acid generation and best minimizes rediation exposure – gamma and radon gas emissions. Various shallow and deep (3 m) sand cover concepts have been eliminated as possibilities by both Rio and Denison (acid generation is not stopped), as have two other options – pyrite removal and the addition of lime as a buffer. Underground disposal in the labyrinthine drifts and stopes of the abandoned mines is costly and, at best, a partial solution – only about 35% – 40% of the dailings would fit underground – and deep water dumping into a lake nearby would be extremely costly, up to $300 million, not to mention its severe effects on downstream waters, Rio says.

If accepted, the flooded tailings applications will be the first used in a comprehensive decommissioning program for a waste management area in Canada. The proposal of both companies must meet a whole raft of provincial and federal regulations. But chief among them are the AECB’s R90 policy, which states decommissionings must meet the interests of health, safety and security and the protenction of the environment according to AECB-approved plans. They also must ensure that wastes are dealth with to minimize the burden on future generations, and to protect the environment and human health, taking into account all social and economic factors. As well, the waste management systems must not rely on active human intervention.

For both Rio and Denison, effluent from the tailings for a time during the post-decommissioning period would be treated with lime, to maintain a pH balance of 6.5-9.5, and brium chloride to precipitate radium 226, the isotope of radium that is the key radiation concern. The radium would accumulate as sludge. Eventually, it is envisaged the need for treatment would be eliminated – Rio hopes that would accur 10 years after reclamation is complete – and only continuing monitoring would be necessary after that.

Rio Algom’s current reclamation plan covers the Panel and Quirke mines, roughly 16 km. north of the townsite. (The key consultants are Golder Associates, Senes Consultants, and Cumming Cockburn Ltd.) The Quirke tailings impoundment, separated by dykes into five cells, contains 42 million tonnes covering 190ha with a drainage basis of 292 ha. The nearby Panel tailings contain 15 million tonnes of material covering 115 ha with a total draining area of 281 ha.

Both sites are dammed by natural ridges and engineered structures consisting of till cores, grout curtains into bedrock and several layers of sand, gravel and boulders than can withstand seismic activity of 6.5-7 Richter magnitude abnd with epicentres 230 km away. Around the tailings perimeter of Quirke, seepage is expected at the rate of 100-150 gal. per min. This is uncollectable and, therefore, will not be treated. Eventually Rio expects acid draining to subside complete. However, ture “Walk-away” will not occur. “Some form of on-going monitoring and maintenance will have to be in place… in the short and long term,” concludes a case history compiled by Rio Algom. No one is certain what the phrase “long term” means, but up to 10,000 years is not out of the question.

Equipped with emergency spill-ways, the tailings and dam structure would be unaffected by a “probable maximum precipitation” storm of 424 mm in 12 hours. The worst regional storm ever recorded was in Timmins. It dumped 193 mm in 12 hours.

Natural precipitation will ensure a minimum 2 ft. of water will cover the tailings. In the event of extremely dry weather, a small lake adjacent to the Quirke tailings could easily replenish the tailings water cover, Kay pointed out during a tour. Flooding blocks oxygen and, therefore, the generation of acid. The tails contain between 4%-6% iron pyrite.

Flooding also assures negligible radon gas emissions. But the question of what are dangerous levels, relates to dosage, which, in turn, is a function of emission levles and duration of exposure. A long walk over the tails every day of the year now, unflooded, will not result is exposures that reach the allowable dosage levels for the general population of five millisieverts (mSv) per annum as set out by the AECB (New regulations would peg the allowable dosage as 1 mSv, independent of normal “background” exposure, of which every member of the public recieved in Canada on average 2 to 3 mSv per year.) However, camping on the tailings for an extended period of time could result in higher dosages.

“A passenger on a flight from Toronto to Vancouver is exposed to that much and more from a one-hour walk on our tailing.” said Kay. “When they’re flooded, the tails emit virtually no radon gas and little gamma radiation.”

Peter Townsend, Denison’s general manager agrees. “Everybody looks at Elliot Lake and thinks radioactivity. It’s not. It’s acid generation.” This is ture. Radon gas levels are generally low and radium 226 can be controlled. But the public might want assurances that at some point in the future, the threat of radioactive contamination will have been eliminated altogether.

This is precisely the point the AECB’s Jack makes. “The levels are not hazardous for inadvertent or casual occupany. But I would not build a house with a foundation in the tailings,” he said. Certain types of land use must be prevented for a long, long time.

And that, when the public hearings are convened, might form the nub of the argument from opponents. If Rio Algom and Denison can’t assure total radioactive abatement within some realistic time frame, how can they insist their plans are safe? In the year 21,000, let alone 2100, who or what will indicate to the denizens of the are that under this 2-ft. water cap rests up to 100 ft. of radioactive sand? Where other civilizations have collapsed and, in some cases, entirely vanished after only a few centuries will our civilization survive to post warnings?

Beyond such imponderables, however, it still remains to be seen wheter even the flooded tails option will be favored by the AECB and FEARO panel. “Wheter it is an acceptable long-term solution, we don’t know yet,” Jack said.

The panel could reject Rio’s $60 million flooded tails solution and request instead the $300 million deep-water option or perhaps something else not yet considered.

As Townsend put it: “We can’t reject an option out of hand because it’s expensive. We can’t reject some of the options just because we feel like it.” The bulk of Denison’s tailings (65 million tons) sits behind engineered structures similar to Rio Algom’s. (The one difference is that Denison has added a hypalon liner in its dams.) But Denison also owns the adjoining Stanrock property and its 6.5 million tons of tailings, which are impounded by dams made from tailings material.

“At Stanrock, we could move the tailings behind engineered structures,” Townsend said. For Denison the focus now is on its Denison impoundment. Stanrock demolition is set to begin in 1993.