HALIFAX -- The owners of a large Nova Scotia pulp mill are suggesting the operation will be forced to shut down -- threatening 300 jobs -- unless the province extends a legislated deadline for closing the highly polluted waste water facility at Boat Harbour.

The existing deadline is one year away -- Jan. 31, 2020. The company was originally given five years to design and build another treatment facility to replace the fetid lagoons near the Pictou Landing First Nation.

The lagoons contain nearly 50 years worth of toxic waste, which former Nova Scotia environment minister Iain Rankin has called one of the worst cases of environmental racism in Canada.

Speaking at a news conference Thursday, Northern Pulp spokeswoman Kathy Cloutier said the company got bogged down in the industrial approval process and it needs about another year to get the job done.

"Some will say they have heard this before, and look where we are now. We recognize this, and relish the opportunity to be the exception rather than the rule," she said, referring to the fact that the mill's previous owners routinely made cleanup promises they did not keep.

"We want to bring about a positive legacy that addresses environmental concerns. Despite best intentions, we have not always gotten it right in the eyes of the Mik'maq or in the eyes of our stakeholders."

Cloutier said if the province rejects the request, the mill will not break the law by continuing to dump effluent into Boat Harbour past the deadline. That means the mill would almost certainly be forced to shut down, at least temporarily.

However, she said the company is moving ahead with building its new $130-million treatment facility and pipeline, even if the province fails to grant an extension.

Premier Stephen McNeil has consistently said his government has no intention of extending the deadline in the Boat Harbour Act, legislation that was drafted in 2015 after a serious effluent spill at the Pictou Landing First Nation.

McNeil confirmed Thursday he had spoken with company officials, but he said he had not changed his mind.

"The deadline is the deadline," he said after a cabinet meeting. "We gave them five years."

However, the premier also said he would be open to hearing proposals from residents of the Pictou area, including the local Tory members of the legislature. He said if a consensus was reached on amending the act, that could be debated on the floor of the legislature.

Cloutier said a temporary shutdown is not a realistic option, especially in the winter months.

The premier said the province is already looking into a Plan B, which would involve dealing with the fallout from a permanent closure.

The chief of Pictou Landing First Nation, Andrea Paul, has said the deadline must not be extended. The 600 members of the band marked the beginning of an official one-year countdown during a ceremony Thursday morning.

Paul said the company should not have held its news conference on the same day as the First Nation's event.

"Northern Pulp has just shown us what their new era of improved Indigenous relations will look like," she said in a statement released late Wednesday.

Durney Nicholas, a fisherman from Pictou Landing First Nation, said he wasn't impressed with what he heard at the news conference on Thursday.

"I'm not going to accept what they are saying," he said afterwards. "We're going to still say no. We're going to keep fighting, too ... Enough is enough."

P.E.I. Premier Wade MacLauchlan and other critics have said the project should be subjected to a more rigorous federal environmental assessment.

Cloutier said the company would welcome such scrutiny, but only if the shutdown deadline is extended.

Ronnie Heighton, president of the Northumberland Fishermen's Association, said his group has no reason to trust the company.

"As far as we're concerned, the date is the date," he said in an interview. "They just wasted time away."

The association is opposed to Northern Pulp's plan to build a pipeline that would dump more than 60-million litres of treated waste water daily into the Northumberland Strait.

The company has insisted the water will be largely unaffected within two metres of the pipeline's discharge point.

Heighton doesn't buy that.

"The stuff will still be there," said Heighton, whose group represents about 600 fishermen who fish for lobster, herring, crab, scallops and oysters. "We're talking about ... tonnes of solids per day. After about 30 years, the stuff will be on the surface."

The company confirmed Thursday it had submitted an environmental assessment application to the province for its new treatment and pipeline plan, which will include the use of a so-called Activated Sludge Treatment system.

Cloutier has said that of the 131 kraft pulp mills operating in North America, about 20 per cent use that system. The remaining 80 per cent use the lagoon system now in use at Boat Harbour. No other treatment system is used, she said.

The company has said the treated effluent it plans to pump into the Strait will meet federal regulations for emissions, but opponents say there's a lack of scientific evidence regarding how the waste will affect the long-term health of the waterway.

The 10 kilometre pipeline will travel from Abercrombie point, where the mill is located, across Pictou Harbour and then overland to the west of Pictou before extending into the Strait north of Caribou, N.S.

Built in 1967, the mill manufactures 280,000 tonnes of Northern Bleached Softwood Kraft pulp every year. Most of it is exported to make toilet paper and other paper products.