Environment Minister Catherine McKenna has dealt a setback to Ontario Power Generation's plan for a nuclear waste burial site on the shores of Lake Huron.

In a letter to the provincially-owned utility Thursday, Ms. McKenna delayed a decision on whether to approve its proposed deep repository for low– and medium-level radioactive waste.

Instead, she told OPG to submit additional studies, including assessments on possible alternatives to the currently proposed site at the Bruce nuclear station in Kincardine, Ont., and on the cumulative impacts of siting other nuclear waste facilities in the region.

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The additional work will take several months to complete.

The Canadian Environmental Assessment Agency concluded last May that the deep geological repository was not likely to cause any adverse environmental impacts. OPG intends to excavate a chamber 680 metres underground in impenetrable rock to bury waste that is now stored at surface at the Bruce site.

While local municipalities supported the project, some local residents mounted fierce opposition. Cities and town on both sides of the Great Lakes passed resolutions to argue no nuclear waste should be buried so close to the source of drinking water for 50 million North Americans. The Michigan state senate passed a resolution opposing the project.

In a statement, OPG said it understands the sensitivity around the burial of nuclear waste and respects the minister's desire for more information to inform her decision.

Ontario recently committed to extending the life of its Bruce and Darlington nuclear stations but still has no permanent plan for disposing of the nuclear waste. An arm's-length federal agency is also working on a plan to bury high-level radioactive waste, but has not selected a site.

OPG said it is confident further study will confirm "that a deep geologic repository is the right answer for Ontario's low and intermediate level waste, and that the Bruce site is the right location."

Beverly Fernandez, founder of the Stop the Great Lakes Nuclear Dump group, said the government should have simply killed the proposal rather than delay a decision.

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"No matter what process is followed, burying and abandoning radioactive nuclear waste in the Great Lakes Basin will always be a bad idea," Ms. Fernandez said. "The Trudeau government's environmental credibility is on the line."

Editor's note: A previous version of this story incorrectly stated the waste is now buried at nuclear plants across the province.