The company that operates the 236-mile crude oil pipeline system that traverses southern Maine and parts of New Hampshire and Vermont has done a good job of moving billions of gallons over 70 years with few spills, federal records and news reports show.

Reports of notable incidents from the federal Office of Pipeline Safety since 2001 show only one spill on the Portland Pipe Line Corp. system, which runs from Portland Harbor to Montreal. It occurred in Harrison in 2003, and was attributed to natural Earth movement. The incident resulted in 12 barrels of spilled oil and $246,172 in cleanup costs.

More serious accidents have happened, including one that predates modern regulations and reporting requirements.

In 1960, a pipe break near a pumping station in Waterford sent oil running down a hill and into a small brook, according to news reports. The spill, estimated at 1,000 barrels, put an 8-inch coating of oil on the water. Crews built earthen dams to keep the oil from the nearby Crooked River.

In 1986, the pipeline spilled an estimated 84 gallons into the Israel River near Lancaster, N.H. The leak was blamed on a damaged exterior coating.

The pipeline’s safety record is of special interest now, as Canadian pipeline companies prepare to reverse longstanding westbound oil flows to move diluted bitumen east from the Alberta tar sands.

Portland Pipe Line Corp. says it has no current plans to reverse its flow of conventional crude oil and handle diluted bitumen, but environmental groups suspect those plans will change.

“It’s not really about them,” Glen Brand, director of the Sierra Club in Maine, said of Portland Pipe Line. “This is really about what’s in the pipe, and the risk to Maine.”

Environmental groups say the thick, tar-like oil, which is diluted with natural gas compounds to let it flow through pipelines, is more corrosive than conventional crude and more likely to damage pipes. They point to numerous spills from pipelines carrying diluted bitumen, including a major spill in 2010 in the Kalamazoo River in Michigan that’s still being cleaned up today.

The problems have caught the attention of Congress, which has directed the Pipeline and Hazardous Materials Safety Administration to study whether there’s an increased risk in transporting tar-sands oil. In March, the agency asked the National Academy of Sciences to do the study.

The Portland Pipe Line consists of two coated, steel pipes, 18 and 24 inches in diameter. The 18-inch pipe was installed in 1950; the 24-inch pipe was installed in 1965. Oil is off-loaded to a tank farm in South Portland and pumped through eight pump stations.

From Quebec, the system enters Maine and runs underground along Route 2 in the Bethel area, then dives southeast through the Oxford Hills area into Waterford, Casco, Raymond and Windham, following Route 302 along Panther Pond and Sebago Lake.

The possibility of a more-corrosive oil being pumped near the lake is of interest to the agency that supplies drinking water to 200,000 Greater Portland residents from Raymond to Yarmouth and Scarborough.

“We have been following the issue,” said Michelle Clements, a spokeswoman for the Portland Water District. “But at this point, there’s no formal plan or project to review or comment on.”

The district has taken part in spill-response exercises coordinated by the pipeline company, Clements said.

But the biggest efforts go into preventing a spill. The pipeline company monitors and tests pipe pressure to detect leaks. It moves special inspection tools through the pipes to clean them, and others that use sensors to check the wall’s thickness and detect potential flaws and corrosion.

The company summarizes its efforts in annual inspection reports filed with the Office of Pipeline Safety. The 2011 report, for instance, shows that three “immediate repair conditions” were identified based on in-line inspections.

The agency visits pipelines to do its own inspections. Along the Portland pipeline, it has done two field inspections and one systemwide inspection since 2006. It also did three “targeted” inspections of safety areas identified for special review.

“All pipelines are inspected at least every two to three years, in some sort of way,” said Damon Hill, a spokesman for the Office of Pipeline Safety.

Staff Writer Tux Turkel can be contacted at 791-6462 or at:

tturkel@pressherald.com