SOUTH PORTLAND The South Portland Planning Board determined Tuesday that a controversial proposed ordinance aimed at blocking the flow of so-called Canadian tar sands oil through Maine to Portland Harbor is not consistent with the city’s comprehensive plan.

The vote not to endorse the ordinance was 4-2, with one member absent, said Tex Haeuser, South Portland’s planning and development director.

“It wasn’t any one single thing, it was based on all the testimony,” Haeuser said.

In a previous meeting, opponents and supporters of the measure turned out in force to argue their cases before the board.

The Planning Board recommendation, which is not binding, is a first step toward a citywide referendum on the proposal.

The City Council is expected to take up the proposal Aug. 19. Voters could make the final decision at the ballot in November.

South Portland sits at the eastern end of a 236-mile-long pipeline that shuttles crude oil from Portland Harbor to Montreal.

Environmentalists fear the pipeline could be reversed and used to carry Canadian tar sands oil from Alberta, through Maine to Portland Harbor to be exported around the world.

Opponents trying to block Canada’s exports of the oil say its use will accelerate climate change and increase the risk of costly and damaging spills.

Portland Pipe Line Corp., which operates the pipeline and says it has no immediate plans to reverse its flow, has said that tar sands oil would not carry any more risk than other crude.

Tar sands oil critics petitioned to change South Portland’s zoning ordinance to prohibit the export of tar sands oil by restricting certain uses of the city’s oil terminals.

Although petitioners say existing activities won’t be affected, some of the city’s terminal operators have argued that the change would have broader impacts beyond the tar sands debate, limiting their ability to expand or modernize.

Matt Byrne can be contacted at 791-6303 or at:

mbyrne@mainetoday.com