A report affirming the shoreline of Lake Huron as the best place to bury radioactive waste failed to provide information the government had requested, federal environmental authorities say.

In a detailed letter and document sent to Ontario Power Generation, the Canadian Environmental Assessment Agency criticizes the utility's report as inadequate and asks it to try again -- much to the delight of project opponents.

The impugned OPG report came after Environment Minister Catherine McKenna asked the utility in February last year for information on, among other things, the feasibility of burying the low or moderately radioactive waste elsewhere.

In response, OPG insisted the Bruce nuclear plant near Kincardine, Ont., was the best location for its proposed deep geologic repository -- a massive underground rock bunker about 1.2 kilometres from Lake Huron.

Among other things, OPG said in its report in December that it would be cost-prohibitive and more dangerous to truck the hazardous waste elsewhere.

Critics, however, were quick to argue the analysis was simplistic, saying OPG had done no in-depth studies of other sites. The assessment agency appears to have agreed.

In a 15-page request for information, the federal agency calls OPG's analysis of other sites vague and superficial. The utility should have "objectively and rigorously" analyzed potential problems with other locations -- from construction of the repository to its ultimate closure, the document states.

"These alternative locations should be reasonable, conceivable, and realistic within the context of developing a deep geologic repository," according to the information request. "Candidate locations should be developed to a point where meaningful evaluations of the concepts can be made."

Among other things, the agency faults OPG for using inconsistent terminology and approach in discussing potentially harmful environmental impacts. It notes the report makes no mention of hazards related to other locations beyond the potential for crashes while trucking the waste to them, and asks for information on using trains to move the waste.

The document also contains substantive requests for information on the potential effects on the Great Lakes and the water supply -- an issue of huge concern to project opponents.

The agency also takes issue with OPG's assertion that choosing another location could potentially add billions to the project -- or possibly save money -- saying a detailed discussion of the wide range in cost estimates is needed.

OPG spokesman Kevin Powers said the request was an "expected" part of the process related mainly to "clarification and elaboration" of a few elements of the proposed project.

The utility, which has previously responded to 585 requests for additional information, would produce a timeline in the coming days for responding to the 23 new requests, Powers said.

What does seem clear is that McKenna's decision on the deep geologic repository, now slated for late this year or early next, will be pushed back. Either way, opponents are thrilled.

"They have done a good job of taking OPG to task," said Jill Taylor with the group SOS Great Lakes. "The featherweight quality of the OPG report and the many errors and misrepresentations have started to come to roost for OPG."

Scores of Great Lakes communities have passed resolutions or otherwise expressed opposition to the proposed repository, currently estimated to cost about $2.4 billion. The plan calls for about 200,000 cubic metres of low and intermediate nuclear waste to be stored in bedrock up to 680 metres underground starting in 2026.

American Congressman Dan Kildee, a project critic from Michigan, said he was hopeful Ottawa would reject the project.

In May 2015, an environmental review panel approved the repository but the federal government has since delayed its decision.

In addition, a feasibility study for disposing of highly radioactive spent nuclear fuel is currently underway and the assessment agency wants OPG to analyze how the two projects might interact environmentally.