Nova Scotia's environment minister says the owner of the province's only operating gold mine has not provided sufficient information about proposed changes at the site for him to make a decision whether or not to approve them.

Environment Minister Tim Halman sent a letter to Atlantic Mining NS Inc. on Wednesday informing the company that he needs more details about tailings disposal, historic tailings, and the project's impact on ground and surface water, wildlife, wetlands, a nearby wilderness area, and fish and fish habitat before he can determine the possible environmental impacts of the proposed changes.

In July, the company, better known by its corporate name, Atlantic Gold, submitted to the province its plans for changes at the mine in Moose River, N.S.

It wants to store the tailings — the material that remains after ore has been processed for gold — in the open mining pit because its current storage area is expected to run out of room in March.

The open pit, which will be finished being mined next year, would be allowed to fill with water and eventually seep out into the Moose River. The company says it would treat the water before it is discharged into the river.

The company's proposed changes also include expanding the designated storage area for waste rock, moving an access road and allowing the company to extract clay from more of its land.

Halman's request for additional information included questions about how permeable the open pit is, details of the water treatment plan, how the changes would meet the Fisheries Act and how the Moose River would be affected, among others.

In an emailed statement, Atlantic Gold spokesperson Dustin O'Leary said the mine's parent company, St Barbara Limited, will work with the government to provide more details.

"The province of Nova Scotia is making efforts to be thorough and provide Nova Scotians with comfort and clarity in the environmental assessment process," said O'Leary.

"St Barbara remains fully committed to demonstrating all the steps we are taking to protect the local environment."

He said the additional information will be provided "in due course," but did not provide a timeline.

O'Leary did not respond to a question from CBC News about what will happen to the mine's tailings once the tailings pond is full in March if the approval has not been granted.

Atlantic Gold has one year to submit the additional information. Once it is submitted, the environment minister will have 50 days to make a decision.

Public feedback on the proposed changes at the mine were accepted earlier this summer, and, along with responses from provincial and federal government departments, Mi'kmaw and environmental groups, total more than 450 pages.

Environment Department staff recently conducted tests on a rust-coloured substance at the Touquoy mine's tailings pond after the discoloured material was spotted and photographed by a pilot. The results of those tests are expected in about a week.