A worst-case scenario spill from the proposed Keystone XL pipeline into the Platte River in Nebraska would form a plume of oil that could extend more than 450 miles, contaminating drinking water for people as far away as Kansas City, Mo., and threatening wildlife habitat, according to an independent analysis of the project released Monday.
The study by John Stansbury, a professor of water resources engineering at the University of Nebraska-Lincoln, also said a worst-case spill in the Sandhills region of Nebraska could pollute 4.9 billion gallons of groundwater with a plume of contaminants 40 feet thick, 500 feet wide and 15 miles long.
"This plume, and other contaminant plumes from the spill, would pose serious health risks to people using that groundwater for drinking water and irrigation," Stansbury said in the report.
The Keystone XL proposed by TransCanada would connect oil fields in Alberta with refineries along the U.S. Gulf Coast.
The pipeline has generated opposition, in part because it would go through the porous soils and high water tables in the Sandhills, which mark the northern boundary of the massive Ogallala Aquifer.
The project still must be approved by the U.S. State Department.
The federal Clean Water Act requires TransCanada to estimate the potential worst-case discharge from a rupture of the pipeline and to estimate how it would respond to a spill.
"It is widely recognized that the environmental assessment documents for the Keystone XL pipeline are inadequate, and that they do not properly evaluate the potential environmental impacts that may be caused by leaks from the pipeline," the report said.
TransCanada, for example, estimates the pipeline would have 11 so-called "significant spills" of more than 50 barrels of oil over its 50-year design life.
"However, TransCanada made several assumptions that are highly questionable in the calculation of these frequencies," the report said.
TransCanada spokesman Terry Cunha decried the report.
"As a pipeline operator across North America for over 60 years, safety is a top priority for TransCanada. We would not put our reputation or the public at risk by doing the things that this document ... suggests," he said.
Stansbury said TransCanada ignored some historical data regarding pipeline spills and assumed the Keystone XL would be built so well it would have half as many spills as other pipelines in service.
He also said the type of oil that would move through the pipeline is more corrosive than the conventional crude oil transported in existing pipelines.
"All of these factors tend to increase spill frequency ... resulting in 91 major spills over a 50-year design life of the pipeline," he said.
Stansbury said one main difference between TransCanada's calculation and his was the estimated time it would take to shut down the pipeline following a spill.
He said TransCanada estimated it would take 11.5 to 19 minutes.
Stansbury, who also is a risk-assessment instructor for the U.S. Army Corps of Engineers, pointed to a "very similar pipeline" that ruptured in 2010 and spewed 800,000 gallons of crude oil into the Kalamazoo River in Michigan.
"The time to finally shut down the pipeline was approximately 12 hours, and during those 12 hours, the pipeline pumps were operated for at least 2 hours," he said. "It is clear that the assumption of 19 minutes or 11.5 minutes is not appropriate.
"Therefore, worst-case spill volumes are likely to be significantly larger than those estimated by TransCanada," Stansbury said.
In a conference call with reporters, Stansbury said he did the study because he felt federal regulators who will make the decision whether to approve the pipeline needed unbiased information.
Documents prepared by TransCanada "painted what I thought was an unrealistically optimistic picture."
Anthony Swift, an energy policy analyst with the Natural Resources Defense Council, said the tar sands oil that would move through the Keystone XL poses unique hazards.
"Tar sands crude is a thick, corrosive mixture moved at higher pressures and temperatures than conventional crude oil ... that the U.S. pipeline system is designed for," he said. "Unfortunately, U.S. pipeline safety regulators have not evaluated these risks or considered the measures which would ensure the safe operation of tar sand pipelines."
While TransCanada's Cunha said the company still was analyzing the report, he pointed out several statements by Stansbury he said were wrong and which he clarified, including:
* Cunha said TransCanada's failure frequency for Keystone XL is based on "analyzing the applicable threats and then estimating the probability of failure based on those threats along with the risk reduction factors (design, construction and operations integrity programs). We use risk-based assessments that are industry leading methods to quantity failure frequency."
* The time to shut down Keystone XL "has been accurately reflected in the risk analysis and is consistent with the Keystone Pipeline record. We have established our own operating record that demonstrates prompt reaction time to any indication of an operational abnormality. This document does not address the differences in system design and operating characteristics (including single phase flow in Keystone) that make it unlikely that Keystone operators would have difficulty distinguishing a leak."
* Cunha said TransCanada "accurately represents historical data. TransCanada used a more detailed assessment of causes of historical pipeline incidents, evaluating Keystone against each of these threats to establish an accurate risk profile."
* As for the tar sands oil, Cunha said the company "has conclusively demonstrated that these oils are not corrosive to steel. Keystone XL will ship a wide variety of crude oil types including conventional oil, shale oil, partially upgraded synthetic oil and oil sands derived bitumen blends. None of these crude types create a risk of destroying the pipeline from within and causing leaks. Why would we construct a $13 billion pipeline system only to put something in it to destroy it?"
Cindy Myers, who lives two miles from the proposed pipeline route in Holt County, said she gets her drinking water from the Ogallala Aquifer.
"Pure drinking water is irreplaceable, and I strongly believe in protecting what we have," she said.
Jane Kleeb, of the anti-pipeline advocacy group Bold Nebraska, said the report is alarming.
"The report confirms one thing -- Nebraskans cannot take TransCanada at their word," she said. "While TransCanada is busy assuring elected officials that everything is fine and will be fine, Nebraska scientists and water experts are issuing warning signs over and over again.
"The report gives black and white evidence to county officials, state officials and federal officials that this pipeline is not ready to be laid because there are too many unanswered questions and safety risks."