The Rosebery gold, zinc, copper and lead mine is 100% owned by MMG and has been operating for more than 85 years.
However, plans to expand the underground mine and develop a tailings dam with associated infrastructure have been met by complete hostility from locals.
MMG made a final investment decision on the expansion in February with its tailings storage facility at capacity.
"To maintain Rosebery Mine, jobs and the local economy and to provide the storage capacity to invest in Rosebery's next stage of growth, we will need to construct a new tailings storage facility," MMG Rosebery mine general manager Rob Walker said.
The expansion will extend the mine's life by 40 years.
Locals have not welcomed the proposal, with the Bob Brown Foundation calling on MMG to abandon its plans, claiming the region's Tarkine rainforest will be destroyed.
The group has been organising regular protests on site to prevent geotechnical drilling and road construction.
Last week, protests heated up after a young activist allegedly assaulted a worker onsite.
According to the group's media statements the young man pushed a gate, which allegedly hit a security guard twice.
Billy Rodwell, 23, was arrested on Friday by police and charged with assault.
He was among 10 activitists to be arrested but was the only one to spend more than four days in Launceston jail after being denied bail.
The Bob Brown Foundation condemned the arrest, claiming police "overreached" their duty of care and falsified allegations.
"The Gutwein government is using workers as fodder to cover up for this multinational company's push to dump its toxic waste in the Tarkine rainforest," Bob Brown said.
"We will not be coerced this way.
"MMG admits it has other places to put its toxic wastes."
The recently returned Tasmanian Liberal government condemned the alleged violence, dubbing it "disgraceful" and an act of aggression from "radical protestors".
It comes as Tasmania looks to introduce laws that make it a crime to obstruct the use of a public thoroughfare with intent to "impede" business activity.
A previous version of the same laws was voted down in the Legislative Council.
The High Court of Australia has also struck down previous attempts to pass the legislation as an "unlawful restriction on Australians' freedom of pollical communication".
However, protests over mining activities in the region have ramped up over recent months.
Venture Minerals was repeatedly forced to call police to its Riley Creek iron ore project in Tasmania's southwest after protesters locked themselves to machinery and an access gate to stop site works over the past three months.