Executives from a TransCanada Corp., which is seeking to build a massive pipeline linking Alberta's oil sands to U.S. refineries, said Tuesday that the line will include safety features to prevent a spill like the one that fouled the Yellowstone River in July.
TransCanada executives were in Montana to shore up support for a $7 billion project that has been assailed by environmentalists as too risky. Opponents argue the Keystone XL pipeline could lead to spills like an Exxon Mobil Corp. pipeline rupture in July that spewed an estimated 1,000 barrels of oil into the Yellowstone.
That spill followed other pipeline accidents in Michigan, Utah, North Dakota and elsewhere that underscored problems within the nation's vast, buried network of lines carrying natural gas and hazardous liquids such as oil.
TransCanada's 36-inch pipeline would transport more than a half-million barrels of oil a day. That's equivalent to more than 21 million gallons.
Company president Alex Pourbaix said Keystone XL would incorporate pipeline technologies and construction techniques not seen on older lines. He added that the company would take precautions beyond what is required by federal regulation.
"We are going to build and operate the safest pipeline and protect the Yellowstone River and all the other crossings," Pourbaix said.
To lower the risk of spills into waterways, the line would be buried at least 25 feet beneath 11 major river crossings between the Canadian border and southern Nebraska, company officials said.
Pourbaix said regular inspections would be conducted along the line's entire 1,900-mile route. The company also will install a greater number of safety shut-off valves than usual.
The U.S. State Department planned to release its final analysis of the TransCanada pipeline this month.
Exxon Mobil's Silvertip pipeline had been at least five feet deep beneath the Yellowstone riverbed as recently last year. Although the cause of its failure remained under investigation, officials suspect floodwaters may have scoured the river bottom and exposed the 20-year-old line to damaging debris.
In addition to the major river crossings, Keystone XL would cross beneath several hundred smaller waterways, said Les Cherwenuk, TransCanada's director of pipeline development and construction.
The line would be buried at least five feet deep beneath many of those waterways and on dry ground at least four feet deep, Cherwenuk said.
A University of Nebraska-Lincoln professor who analyzed the potential for accidents along the pipeline said that TransCanada had significantly underestimated the potential for leaks and spills. Stansbury added that prior studies of the pipeline were overly optimistic about how often leaks or spills would occur.
John Stansbury, an associate professor of water resources engineering, said even if a Keystone XL pipeline failure leaked into a lesser tributary, that could harm a major river like the Yellowstone or the Missouri as spilled oil flowed downstream.
"If someone comes along and knocks a hole in the pipe beneath XYZ creek, it won't make much difference how deep it was beneath the Yellowstone," Stansbury said. "In my estimation, there's going to be spills and there will be some big spills, and they underestimated the frequency and underestimated the volume."