Controversial Canadian regs. (Mining).
Modern mining techniques require millions of gallons of water, mixed with chemical "lixiviants," to strip specific metals from pulverized ore. Besides the target metals, however, this process also releases other metals such as arsenic, lead, and zinc. Before returning water to the environment, mining operations must remove these metals, usually. by adding lime and allowing the metals to settle in dammed areas. Like most Western governments, Canada regulates the amount of metal remaining in treated water that can be released into waterways.
Environmentalists were disappointed to learn that the proposed limits for dissolved arsenic, copper, lead, nickel, and zinc are no different from those adopted in 1977. "You can have standards that are five times stronger than is proposed and that are technically and economically feasible and achievable," says Burkhard Mausberg, executive director of the Canadian Environmental Defence Fund. No limits were set at all for mercury or cadmium, both of which have been officially designated as "toxic" under the Canadian Environmental Protection Act.
The limits in the proposed regulations are unchanged from existing law, says Chris Doiron, a senior specialist for standards development for Environment Canada, because "the physical mechanical separations and the technology for achieving that haven't changed substantially for some of the metals over the course of the past twenty years." But the proposed metal mining effluent regulations, which will fall under the federal Fisheries Act, offer significantly more environmental protection than the 1977 law, he says. The proposed regulations were developed through a consultation process involving representatives from industry, environmental groups, aboriginal groups, and federal and provincial departments.
The new rules will cover all of Canada's 93 metal mines, two-thirds of which are exempt from the current law. For the first time they set a limit for cyanide (1.0 ppm), which is used as a lixiviant in gold mining. They require that effluent pass an acute lethality test on juvenile trout. (A second test--on Daphnia magna, a species of water flea--is also required, but only for data collection.) They lower the allowable total suspended solids limit from 25 ppm to 15 ppm. And they require that mines conduct environmental effect monitoring.
"There have been incredible increases in technology since 1977 in the ability to measure smaller, minute amounts of dissolved metals," says Catherine Coumans, research coordinator for the environmental group MiningWatch Canada. She says that's why many countries are able to set limits lower than Canada's proposed limits. For example, Sweden, Ghana, South Africa, Vietnam, Indonesia, and Japan have limits that are half or less of the Canadian standard for lead; the United States and Sweden have limits that are one-half or less the Canadian limit for copper.
Industry representatives readily accept renewal of the current metal limits, but the lower total suspended solids limit is another matter, says Leonard Surges, manager of environment, safety, and health for Noranda, one of Canada's largest mining and smelting companies. Spring and fall runoff in mountainous areas is already laden with sediment, and that water must be stored and allowed to settle much longer than under current limits. That means building bigger dams. "The cost to do something which may not significantly reduce discharges to the environment, which may in fact increase the risks [for instance, a larger dam may be more likely to fail], which probably won't have a measurable benefit, can really be quite substantial," Surges says.
The trout lethality test requirement also concerns mining companies, says Elizabeth Gardiner, vice president of technical affairs for the Mining Association of Canada, because the industry hasn't found a way to consistently identify what in a given batch of effluent might cause the lethality test to fail. "What [the methodology] doesn't do is always provide a consistent answer as to why your effluent may be toxic," she says. But that's the whole point of the test, says Coumans, who adds, "It can be quite difficult to see how metals complex and what their actual effect is in biota. Even if you get all the individual limits right, you can still get mixes that are going to have a biological impact."
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|Publication:||Environmental Health Perspectives|
|Date:||Oct 1, 2001|
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