Environmentalists and others say it is a real possibility that corrosive tar sands could be transported from Canada through Maine, threatening the Androscoggin and Crooked rivers, Sebago Lake and Casco Bay with an environmental disaster.

Enbridge, a Canadian mega-oil-pipeline company, filed an application Friday to reverse its pipeline to bring corrosive tar-sands oil eastward to Montreal. If approved, environmentalists in Maine say it would open the door to bringing tar sands through New England for export.

“It’s very clearly the last shoe to drop before the tar sands head through your part of the state,” said Dylan Voorhees of the Natural Resources Council of Maine.

But that’s “just not the case,” Enbridge spokesman Graham White said Thursday. “We have no plans to ship any of our product through the Portland to Montreal pipeline.” While the company had a plan in 2008 that could have resulted in the transport of tar sands through the pipeline in Maine, that project was scrubbed because it was not economically viable, he said.

Ted O’Meara, spokesman for the Portland Montreal Pipeline Co., which is based in South Portland and has no affiliation with Enbridge, confirmed Thursday that there is no current plan with Enbridge or any other company to ship tar sands down the pipeline.

“It’s a pipeline that exists to ship product between South Portland and Montreal,” O’Meara said. “Obviously, we’re continuing to explore possibilities to use the pipeline. We have no secret agenda here.”

The Portland-to-Montreal pipeline is a 62-year-old pipeline that transports conventional crude oil 236 miles from tanker ships in South Portland harbor to Montreal.

The pipeline runs along and traverses some of Western Maine’s most critical lake and river watersheds, said Lee Dassler of the Western Foothills Land Trust. It crosses the Androscoggin River twice, the Crooked River six times and passes within 1,000 feet of Sebago Lake, Portland’s reservoir. The pipes were lain across the riverbed at the crossings, rather than buried.

The pipeline is composed of three pipes, set at or above the frost line, ranging from a 12-inch-deep pipe built in 1945 to a 48-inch-deep pipe built in 1965, Dassler said. One pipe is exposed on the Crooked River near Bolsters Mills in Otisfield.

That river’s Class AA water quality is home to a genetically unique landlocked Atlantic salmon fishery protected by the Maine Department of Inland Fisheries and Wildlife. It has been designated as one of Maine’s Outstanding Rivers under state legislation.

NRCM has called on the U.S. State Department to require a full environmental review of any proposal to bring tar sands through the pipeline. This is not required by the United States on cross-border oil pipelines, except through a Presidential Permit, which can be granted by the U.S. State Department, Voorhees said.

“A tar-sand spill varies from a crude-oil spill,” Dassler said Wednesday. “The diluent (often benzene) will rise to the surface and ignite, while the caustic bitumen will sink to the bottom.”

If polluted, river and lake bottoms would have to be scoured out, Dassler said.

Tar sands (also referred to as oil sands) are a combination of clay, sand, water and bitumen, a heavy, black viscous oil. Tar sands can be mined and processed to extract the oil-rich bitumen, which is refined into oil.

While agencies such as the Natural Resources Council of Maine and other environmental groups have initiated action to stop the tar sands from coming through Maine, local communities are also trying to stop it.

“Every town along the pipeline is organizing to draft and pass ordinances or resolutions,” Dassler said. “Volunteers in all the communities have begun conversations with our local elected representatives and will be taking that work to the federal level. The oppositions to this proposal will reach the president’s ear.”

In November, 256 of the 1,437 Harrison voters signed a petition that calls for the adoption of a resolution to “protect the health and safety of local citizens, water bodies and other natural resources in relation to possible transport of tar-sands oil through Maine.” They are among more than 2,000 petition-signers from Harrison, Casco and Portland.

Selectmen will decide sometime in February or March whether to place it on the June town meeting ballot, Harrison Town Manager George “Bud” Finch said.

[email protected]