MMG says it needs to develop a new tailings storage solution if the mine and its 500 jobs are to last beyond 2024.

A wave of protests against preparatory work at MMG's preferred South Marionoak tailings storage site led to a string of arrests.

MMG paused the roadworks following what it described as unwarranted legal threats from the environmentalist Bob Brown Foundation.

Federal Environment Minister Sussan Ley recently decided the project would need full assessment under environmental law.

MMG documentation sent to the Environment Department nominated an area south-west of the town called Natone Creek.

It said it was owned by Sustainable Timber Tasmania, was in a permanent timber production zone, included dense rainforest and was previously prospected and mined.

The Bob Brown Foundation on Wednesday confirmed it would oppose a tailings storage development at Natone Creek, although it was not clear if that would include protests and activists attaching themselves to machinery, as happened at South Marionoak.

"We oppose rainforest and native forest clearance for the tailings waste," foundation campaign manager Jenny Weber said.

"Obvious alternatives for such clearance are available.

"MMG could raise the walls and buttress two current dams.

"This would future-proof the existing dams.

"Companies around the world are lifting the walls on their tailings storage facilities.

"After catastrophic dam collapses in South America, there is a move to reach new global standards on dam safety.

"International companies are changing their ideas about managing their tailings facilities to ensure stability.

"Stability of tailings storage facilities depends on investment over time."

Rosebery Mine acting general manager Steve Scott recently said the company could not "just keep raising the walls" of the existing storages for safety reasons.

"You can only put walls so high before the engineering behind it doesn't stack up," he said.

Ms Weber said MMG had multiple options.

They also included building a paste-fill plant and pumping dewatered tailings back underground to fill the voids left by mining, reprocessing materials from the current tailings dams or a new tailings dam not involving rainforest clearance.

MMG said South Marionoak was the only current viable option for a tailings storage facility.

"MMG has been reviewing a number of possible sites since 2008 and done extensive work into maximising current facilities and other options available," it said.

"We have sought expert advice, conducted risk assessments and progressed the options that were deemed to offer the most balanced solution in terms of social and environmental impact.

"To date, the site that offers this is South Marionoak."

It said it continued to explore Natone Creek, but it was yet to be proven as a viable and safe location for a tailings storage facility and was of a similar landscape to South Marionoak.

"We reiterate there is no solution that has no impact," the company said.

"The two facilities we currently use for tailings storage are nearing their full and safe capacity.

"We have plans in place over the coming years to increase the capacity by raising walls and changing the way we deposit tailings."

It said that would only provide tailings storage until 2024.

"Making further changes beyond what we have planned to these facilities could diminish the safety and stability of the infrastructure," MMG said.

"Other alternatives previously considered have been ruled out because of their greater environmental impact or engineering and safety risks.

"Rosebery Mine needs a new tailings storage facility to be able to continue its operations beyond 2024.

"These decisions should be carefully studied and rigorously assessed.

"After consulting international experts in tailings design and management, we are pursuing the best solutions available.

"The Bob Brown Foundation has every right to have their views heard on conservation issues, but that should not extend to the safe design and management of tailings storage."

MMG told the Environment Department it considered four tailings storage options, with South Marionoak the preferred option and Natone Creek the "second potentially feasible option".

It said it considered putting tailings material in underground voids, but it was deemed unfeasible.

State Resources Minister Guy Barnett said: ``It is no surprise to hear that the radical BBF are as opposed to MMG's alternative tailing storage dam site as they are the current site."

``Despite previous rhetoric that the company should use an alternative site, the BBF has changed the goalposts to suit their extremist agenda.

``This is unfortunately par for the course for radical environmentalists and simply underlines their opposition to jobs and our regional communities.

``The tailings storage dam location is a matter for MMG and we have always said that any proposal should be subject to the appropriate assessment and approvals process.

"This position is unchanged.

``I call on the BBF and their fellow travellers to cease their attacks on regional Tasmania and our productive industries.''