SOUTH PORTLAND, Maine — A group of South Portland residents announced on Thursday a citizens’ initiative to prevent Portland Pipe Line Corp. from being able to pump oil sands, also known as tar sands, from Canada to its facility on South Portland’s harbor.

At a rally outside South Portland City Hall Thursday morning, the group Concerned Citizens of South Portland launched the “Waterfront Protection Initiative,” which might appear on the November ballot if enough signatures are collected.

The rally involved roughly 40 adults and children holding colorful signs that declared, “Leave the tar sands in the ground” and “No tar sands in Casco Bay.” The group began the rally with the chant, “South Portland stands against tar sands.”

By using the citizens initiative process, the group wants to change the city’s zoning ordinances to prohibit Portland Pipe Line Corp. from making upgrades to its pier near Bug Light that would be necessary if it decides to pursue the reversal of its pipeline so it could pump tar sands from Montreal to South Portland.

The 236-mile pipeline has pumped crude oil from South Portland to Montreal for 70 years.

The company explored reversing its pipeline in 2008, but did not follow through on the project. At the time, it filed a plan for necessary upgrades on the pier that included two 70-foot tall smokestacks that would burn off what opponents say are dangerous chemicals as the oil sand crude is loaded onto ships that would take it to refineries around the world.

The ordinance change would preserve the company’s current use of the pipeline and importing activities on its pier, according to Robert Sellin, a South Portland resident and co-chair of the citizens group.

“We don’t threaten the pipeline, the jobs or anything, but what we do want to prevent is reversing the pipeline flow,” Sellin said, “and thereby prevent them from offloading here in our port and then burning off all the vapors.”

In order to qualify the initiative for the ballot, the group will need to collect 950 signatures from South Portland registered voters.

Sellin is confident the group will succeed because the community is behind the effort. He said 67 South Portland businesses have already gone on the record opposing any future proposal to ship oil sand crude out of South Portland.

“At its heart, this campaign is about protecting our community,” said Sellin, a retired businessman who became a permanent resident of South Portland in 2011.

Portland Pipe Line Corp. has not officially announced plans to reverse the pipeline to carry oil sand crude to South Portland, but CEO Larry Wilson told the Bangor Daily News in February that the company is “aggressively looking for every opportunity,” including a reversal, to help the company remain viable as global energy markets change.

Because of inexpensive oil sand crude coming out of western Canada, the Canadian refineries that have traditionally been Portland Pipe Line Corp.’s customers are buying less crude oil from other sources around the world that are imported through South Portland.

“The economy is difficult … it’s impacted these refineries that we serve, and the market is changing,” Wilson said in February. “If we do nothing, it’s going to be a very difficult environment for this company.”

Wilson was not immediately available for comment on Thursday.

The company, though, released a statement that said it was “disappointed in this latest attack on our company, our reputation and the benefits we provide to South Portland and the region.”

It said it has paid $25 million in property taxes to the city over the past 30 years and currently grants public access to five acres of Bug Light Park that it owns.

“We are not currently proposing to construct facilities at our marine terminal, but should we desire to develop our facilities further we have every confidence that the City of South Portland and other agencies would treat us fairly and consistently as they have in the past,” the statement reads. “In the meantime, we ask that the community not discriminate against one of the top taxpayers and job creators in the city.”

Sellin and the other speakers in their press conference referred to the company as ExxonMobil by virtue of its ownership stake in the parent company of Portland Pipe Line Corp.

Portland Pipe Line Corp. is a wholly owned subsidiary of Montreal Pipeline Ltd., which itself is owned by three Canadian companies: Imperial Oil, Shell and Suncor Energy, according to Wilson. ExxonMobil owns 69.6 percent of Imperial Oil, according to Imperial’s most recent management proxy statement.

“So as the campaign heats up in the coming weeks and months remember it will be ExxonMobil trying to defeat our Waterfront Protection Initiative,” Sellin said at the rally.

Sellin said any increased industrial use at Portland Pipe Line Corp.’s pier would be inconsistent with the city’s comprehensive plan, which was adopted last October.

The group’s ordinance claims the comprehensive plan “envisions a transition to more of a mixed use area preserving the opportunity for traditional marine uses while accommodating recreational, business, and even residential uses,” for the area on the waterfront where the company’s pier is located.

The plan does not preclude the expansion of industrial uses of the land, however. It states that “the city’s development regulations should continue to allow existing marine and oil facilities to upgrade or expand on parcels that are already used for this purpose.”

The group is attempting to collect signatures by Mon., June 17, according to Sellin. But missing that deadline won’t put an end to the initiative. South Portland Assistant City Clerk Karen Morrill said that deadline is not one mandated by law, and that signatures for a citizens’ initiative could likely be turned in as late as mid-September and still make it on the November ballot.

If the initiative is successful, Sellin said the group expects a strong pushback from Portland Pipe Line Corp. and a potential court battle.

“The pipeline or ExxonMobil may well try to challenge us in court,” he said. “It has to do with land use and the ability to control land use within our community, and that’s very defensible. We feel that if we do face a legal challenge we will certainly prevail.”

Whit Richardson is Business Editor at the Bangor Daily News. He blogs about Maine business, entrepreneurs and the economy.