That's what U.S. environmentalists are trying to avoid, said Dave Chambers, a geophysicist with the Center for Science in Public Participation, which also helped prepare the brief.
"You're ahead of us," he said. "The lesson there is that if this happens at Kensington, stand by, because there are going to be dozens of proposals to do the same thing.
"It's the cheap way to go, and that's what you're seeing in Canada."
But Gordon Peeling, chief executive of the Mining Association of Canada, defends Canada's regulations. He says the changes actually put tailings disposals under more environmental scrutiny.
Any such proposal must be examined by federal regulators and the local community, he said from Ottawa. The destruction of any fish habitat must be offset by improving other water bodies or through a cash payment.
Storing tailings under water minimizes leaching of contaminants from the ore, Peelings said. But steep terrain or geological risks sometimes make tailings ponds unfeasible, while lakes can act as natural containers.
"In certain geographic circumstances (a tailings pond) may result in greater terrestrial disturbance than comparative environmental impact on the lake."
Chris Doiron, chief of Environment Canada's mining and minerals section, said the new rules are actually tougher than the regulations they replace because they remove the decision from the fisheries minister's discretion and bump it up to the Treasury Board.
But Coumans remains skeptical.
"Once they've already made all their decisions they bring us in so they can say they've consulted nationally."
She says environmentalists believed the regulations were altered to legally grandfather five existing natural tailings ponds - not sanction new ones.