The question of how an oil spill from the proposed Keystone XL pipeline might affect the Ogallala aquifer was raised again this month, in a report the U.S. State Department will use to help it decide whether to approve or reject the controversial project.

The report concluded that a spill would have little effect on Nebraska's primary source of drinking water, because the oil would spread less than a thousand feet within the High Plains/Ogallala aquifer. The impact on the Ogallala aquifer would be "local," not "regional," said the report, which was prepared by the Nebraska Department of Environmental Quality (DEQ) and HDR Engineering, an Omaha-based consulting firm.

Scientists interviewed by InsideClimate News agreed with the report's conclusions that an underground spill probably wouldn't travel far and that a single accident wouldn't damage the entire Ogallala aquifer. But they also said the report didn't take into account other important factors:

Some of the chemicals found in the primary type of oil the pipeline would carry are trade secrets, so it's impossible to know how they would behave in the Ogallala aquifer.

The report analyzed the effects of only a 42,000-gallon spill, even though far larger spills have plagued U.S. oil pipelines in recent years. A 2010 accident in Michigan dumped more than a million gallons of a type of oil known as dilbit into the Kalamazoo River. In 2011, a pipeline leaked 63,000 gallons of oil into Montana's Yellowstone River.

The DEQ's study was generic, rather than specific to Nebraska's geology and hydrology. The actual risks would vary, the scientists said, depending on where the spill occurs in the Ogallala aquifer, the location of nearby wells and other site-specific factors.

"The DEQ report provides a general and generic assessment of the potential impacts from a hypothetical spill," said John Stansbury, a civil engineering professor at the University of Nebraska-Lincoln who has pushed for detailed studies about the pipeline's environmental impacts.

"The bottom line is that a thorough and adequate study of the impacts has not been done [to date], and that includes the DEQ report."

The DEQ's conclusion that the impact of a spill would be localized didn't reassure local ranchers and farmers. More than 85 percent of Nebraskans rely on the Ogallala aquifer for their drinking water, and virtually everyone along the route depends on it for their families, crops and livestock.

"We have the cleanest, purest water in America," said Bruce Boettcher, who raises organic cattle in Holt and Rock counties. The land has been in his family for five generations and he intends to pass it down to his three children.

"People have a connection to the land and the water...because the water is so close to the top of the ground. We live in it. It's right here; we see it every day. We don't want it disturbed."

TransCanada, the company that hopes to build the pipeline, told the DEQ in a letter last October that it will "provide an alternate water supply for any well where water quality was found to be compromised by a spill." But landowners say that's simply not feasible.

Susan Luebbe has 1,200 head of cattle on her ranch, and each one drinks 15 to 30 gallons of water a day. Where would the "alternate" water source come from, she asks. How could TransCanada transport tens of thousands of gallons per day on rural roads that are often unpaved, through blizzards and harsh weather conditions?

"It's a total joke," Luebbe said. "They can throw that [offer] out there, but they don't know what ranching is like in Nebraska."

Richard Kilmurry said some of his cattle drink from streams that are connected to the Ogallala aquifer, but TransCanada hasn't offered to replace contaminated surface water. "If your water is never going to be useable again, it pretty much renders your land useless," he said.

TransCanada did not respond to requests for comment for this story. In a news report earlier this month, the company said it welcomed the DEQ's conclusions, and president and CEO Russell Girling called the report "a rigorous and comprehensive review."

The groundwater study is just a small part of the 2,000-page report, which was designed to examine how the pipeline would affect Nebraska communities and natural resources. It concluded that "Construction and operation of the proposed Keystone XL Pipeline, with the mitigation and commitments [TransCanada] has identified...could have minimal environmental impacts in Nebraska."

The authors said TransCanada would be responsible for any spill cleanup and the company's commitments "such as funding for a public liaison, liability insurance, and private well testing, provide for additional protection of Nebraska's interests."

Pipeline opponents say the study is incomplete and tainted by conflicts of interest: HDR, the consulting firm hired by the DEQ, has worked on previous TransCanada projects. DEQ spokesman Brian McManus said the agency reviewed HDR's record and doesn't believe it creates a problem.

The agency's report is one of the last hurdles TransCanada faces in its years-long effort to get the pipeline approved in Nebraska. The project originally was routed through the Nebraska Sandhills, a particularly sensitive region over the aquifer. Under pressure from landowners and environmentalists, TransCanada moved it out of that area in November 2011. But the project still faces opposition from landowners and environmental groups, who will hold their fourth large protest outside the White House on Feb. 17.

The company is now waiting for Gov. Dave Heineman—who supports the pipeline—to sign off on the route. Heineman has until February to submit the report, along with his comments, to the U.S. State Department. The federal agency has ultimate authority over the Alberta-to-Nebraska section of the Keystone project because it crosses an international border.

Groundwater Concerns

The Nebraska portion of the Keystone XL is now slated to pass through 12 counties and 163 rivers and streams. Ten of the counties have no oil pipelines at all. The southernmost counties—Saline and Jefferson—contain a Kinder Morgan pipeline and a TransCanada pipeline that began operating in 2010.

Although the new route avoids the Sandhills, it still crosses areas with permeable soils and shallow groundwater, the same features that make the Sandhills vulnerable to contamination. The groundwater along much of the 274-mile route through Nebraska lies 20-50 feet beneath the surface. And 13 miles of the line crosses land where the aquifer is less than 10 feet underground.

Boettcher said the fear of groundwater contamination is why he continues to oppose the pipeline, even though the new route is now 15 miles from his land. "This water is just as valuable for me as for my neighbor 15 miles apart...I'm staying in this fight because [Keystone XL] is still going through fragile soils, wet ground and wet lands, and is still crossing high water tables."

Groundwater experts say it's virtually impossible to restore a contaminated aquifer to pristine conditions, although it can be cleaned up to meet federal drinking water standards. The time and cost required for such a cleanup depends on the location of the spill, the composition of the spilled oil, the amount of oil released, the movement of the groundwater and the location of nearby water wells—details that the DEQ report didn't analyze.

TransCanada has told the DEQ that it will test drinking water and livestock wells within 300 feet of the route before operating the pipeline. In the event of a spill, that baseline data could help determine whether oil had seeped into nearby wells.

Landowners like Luebbe are wary of staking their futures on TransCanada's promise. "How do we know they're testing for what's actually in [the oil]?" she said, since some of the dilbit chemicals are trade secrets. "I just don't trust them."

One of the landowners' biggest concerns is that a slow leak would go undetected because so much of the Keystone XL runs through remote areas. TransCanada has run newspaper ads assuring Nebraskans that its leak detection technology will quickly alert the company's control center in Canada of any accidents. But InsideClimate News recently reported that the leak detection systems used on most of the nation's pipelines rarely detect spills smaller than 1 percent of the pipeline's flow, which for the Keystone XL would be hundreds of thousands of gallons per day. An analysis of federal data showed that smaller spills are more often detected by the general public or pipeline workers than leak detection systems.

What Happens to Dilbit in an Aquifer?

The lack of information about a major type of fuel the Keystone XL would carry—diluted bitumen, or dilbit—has been a sticking point for years. Although the Keystone XL would transport a small amount of conventional crude oil from North Dakota, the bulk of its contents would be bitumen, a particularly thick oil from Canada's oil sands region. Much of that oil will be shipped as dilbit, a combination of bitumen and light liquid chemicals used to dilute the bitumen so it can be transported in pipelines.

There have been no independent studies on how dilbit behaves when it spills into an aquifer.

Landowners fear that a dilbit spill would be more devastating than a spill from conventional crude oil, as was the case during the 2010 Kalamazoo River spill. There, the dilbit initially floated on top of the water, but as the light chemicals evaporated, the bitumen sank to the river bottom. Emergency responders had to improvise new cleanup methods, and that work still isn't done. In October, the Environmental Protection Agency asked Enbridge to dredge an additional 100 acres of the riverbed.

Barbara Bekins, a hydrologist with the U.S. Geological Survey and an expert on aquifer contamination, expects dilbit to behave much more like regular crude if it is spilled into an underground aquifer.

Bekins has spent years studying an aquifer near Bemidji, Minn., where 450,000 gallons of light crude oil spilled in 1979. Initial cleanup efforts removed about three-quarters of the oil. In 1983, the U.S.G.S. began using the Bemidji aquifer, which isn't used for drinking water, to study how oil is remediated through natural processes. Almost 80,000 gallons remain in the surrounding soil and aquifer more than 30 years later.

After the Kalamazoo spill, the light chemicals in the dilbit evaporated because the dilbit was exposed to sun and wind. In an underground aquifer, however, sun and wind aren't factors, so Bekins said the thick bitumen would stay close to the point of release, while the lighter chemicals slowly dissolve into the groundwater. In regions where the water table lies deeper underground, the light chemicals would initially remain stuck to the rocks and soil above the water table. But over time, rain would wash them down into the groundwater.

Nebraska's DEQ used a computer model to analyze how dilbit would affect the Ogallala. They chose to focus on benzene, a cancer-causing agent found in all crude oils.

Stansbury, the University of Nebraska civil engineer, said that was a reasonable decision because benzene dissolves readily in water. Other chemicals found in dilbit are unlikely to travel as far as benzene, though he cautioned that it's hard to be sure since some chemicals are considered trade secrets.

The DEQ's computer model showed that in the case of a 42,000-gallon spill, it would take about three years for a plume of benzene to move 1,000 feet. The plume would have a concentration of 5 parts per billion, the upper limit of the EPA's safe drinking water standards for benzene. The plume could continue to spread further than 1,000 feet, they wrote, but by then the benzene concentration would be less than 5 parts per billion.

Dave Miesbach, a Nebraska DEQ water specialist who worked on the report, said some people mistakenly assume that an aquifer acts like an underground river or lake. But water in the Ogallala aquifer moves only about 300 feet a year on average, because it is trapped in tiny empty spaces between rocks, sand and gravel, and is sometimes blocked by impermeable layers of clay.

Bekins said the DEQ's findings are similar to what scientists discovered at Bemidji. There, the benzene plume grew for the first 10 years, then stabilized. The total area impacted never reached more than 660 feet long, 490 feet wide and 33 feet deep.

The water outside that zone is safe to drink, she said, and benzene levels in the contaminated area continue to drop as the benzene is consumed by naturally occurring bacteria that feed on petroleum products.

Stansbury said the science from the Bemidji spill—along with the modeling the DEQ did on the impact of a 42,000-gallon spill—offers general insight into how an oil spill would impact the Ogallala. But he said the study would have been much more valuable if it had assessed the impact of a worst-case scenario spill, one much larger than 42,000 gallons—and if the agency had modeled the effects along specific parts of the route, taking into account the location of drinking wells, the local geology and other factors.

Stansbury's colleague at the University of Nebraska-Lincoln, Wayne Woldt, has tried for years to get funding for such a study. But Stansbury said it has become "harder and harder to get money from truly unbiased sources."

Funding from industry or environmental groups could be seen as tainted by conflicts of interest, he said. And the research needed for the Ogallala is too specific to attract funding from the National Science Foundation, which supports more general, big picture projects. The EPA sometimes supports such projects, he said, but its budget has been tightened in recent years due to budget cuts.

The EPA did not respond to questions about its funding.

Jane Kleeb, the director of Bold Nebraska and a prominent pipeline opponent, said that given the importance of the Ogallala aquifer, no decision should be made about the pipeline until scientists conduct a detailed study like the one proposed by Stansbury and Woldt.

"I don't think that's too much to ask given that agriculture [contributes] 17 billion dollars a year for our state's economy, which obviously needs water to exist," said Kleeb, whose group has led Nebraska's pipeline opposition. "We as American taxpayers pay EPA and other federal agencies. So [they] should be able to find the money in their budgets to fund these studies."