Thousands have vowed to rally on the lawn of British Columbia’s legislature Monday to protest proposals involving oil pipelines and tankers on Canada’s West Coast.

The planned sit-in at the legislature in Victoria has been organized by the group “Defend Our Coast,” which describes itself as a coalition of environmental and social justice organizations from B.C.

More than 3,500 people have signed an online pledge to participate in the rally, according to Greenpeace Canada. Celebrities such as Mark Ruffalo, Pamela Anderson and Michael Moore are among those lending their support to the cause.

“There’s not a whole lot I can say besides the fact that this is going to be the largest act of civil disobedience against the tar sands in Canada’s history,” organizer Eric Nordal told CTV British Columbia.

For some, the Northern Gateway pipeline has become a source of discontent not only because of concerns over the expansion of the Alberta oil sands, but also the federal government’s recent sweeping changes to environmental laws.

The protests have garnered support from unions including the Communications, Energy and Paperworkers Union, the Canadian Auto Workers, the B.C. Teacher's Federation, the Canadian Union of Public Employees and the United Fishermen and Allied Workers' Union.

Demonstrators also have the backing of Greenpeace, ForestEthics, the Council of Canadians and several First Nations, and have been endorsed by high-profile activists such as David Suzuki and Stephen Lewis.

Representatives from northern B.C. aboriginal communities, some of the strongest voices opposing the projects, are also expected to attend Monday’s demonstration.

Event organizers say the sit-in will be carried out “in the same spirit” as similar anti-pipeline protests in front of the White House in Washington, D.C. and on Parliament Hill in Ottawa last year.

Actress Daryl Hannah was among dozens of environmental activists arrested in front of the White House last year for participating in a protest against TransCanada’s proposed Keystone XL pipeline, which was denied a permit by U.S. President Barack Obama’s administration. (Hannah, a long-time activist, was arrested again this year at a Keystone XL protest in Texas. She was released in early October.)

Organizers have told participants in Monday’s Defend Our Coast sit-in that, while the protest is intended to be peaceful, many could be risking arrest.

Participants were encouraged to attend an information session, or “protest boot camp,” in Victoria on Sunday in preparation for what organizers hope to be a massive show of force.

Among the participants were two Calgary residents who drove to B.C. to take part in the sit-in.

“There’s lot of Albertans against it, but only a brave few will actually say so in public spaces,” Mary Nokleby told CTV News.

Many B.C. residents fear the potential damage to the province’s coast if a spill were to occur.

“I live in White Rock so there’s a beautiful beach there and the idea of tanker spill demolishing that is just unbelievable to me,” said one demonstrator Sunday.

“While arrests are a potential outcome from this action, being arrested is not the goal,” reads a statement on the Defend Our Coast website.

Thus far, about 1,700 people participating in the protest have formally pledged a willingness to be arrested.

Well-known B.C. activist Tzeporah Berman, arrested 20 years ago during the Clayoquat Sound logging protests, has said she may make an appearance at Monday’s sit-in.

“We have a federal government that wants to push these pipelines down our throats, no matter the cost to British Columbians,” she said.

Meanwhile, hearings continue into Enbridge’s proposed Northern Gateway pipeline, intended to carry Alberta crude to British Columbia’s coast for eventual transport overseas.

Another pipeline, the Trans Mountain by Kinder Morgan, has also been the subject of impassioned debate. Kinder Morgan wants to twin the existing line -- which moves oil from Alberta to Burnaby, B.C. -- more than doubling its capacity.

With reports from CTV British Columbia’s Peter Grainger and Ed Watson and files from The Canadian Press