Jane Kleeb is a savvy activist who, Nebraska’s Republican governor once said, “has a tendency to shoot her mouth off most days.” A Florida native who moved to Nebraska in 2007 after marrying a rancher active in Democratic politics, she did as much as anyone to bring the massive Keystone XL crude oil pipeline to a halt last year.

James Goecke is a counterpoint to Kleeb. A hydrogeologist and professor emeritus at the University of Nebraska in Lincoln, he has been measuring water tables in Nebraska’s ecologically sensitive Sand Hills region since 1970 and has shunned the political limelight — until now. He recently appeared in an ad for the pipeline’s owner, TransCanada, rebutting some of the arguments against the project and its new route.

Under ordinary circumstances, Kleeb and Goecke would be natural allies. Democrats in a red state, they both care about preserving Nebraska’s unique environment. Instead, they are divided over Keystone XL, a 1,700-mile steel pipeline that would carry heavy, low-quality crude from Canada’s oil sands to refineries in Texas.

At the heart of their battle is whether the pipeline would pose a threat to the massive Ogallala Aquifer — one of the world’s largest underground sources of fresh water. By one calculation, it holds enough water to cover the country’s 48 contiguous states two feet deep. The Ogallala stretches beneath most of Nebraska from the Sand Hills in the west to the outskirts of Omaha. And it runs from South Dakota well past Lubbock, Tex.

Named after a Northern Plains tribe, the Ogallala provides water to farms in eight states, accounting for a quarter of the nation’s cropland, as well as municipal drinking wells. Though early white explorers who saw this apparently arid part of the Great Plains called it a “great American desert,” the aquifer has turned it into America’s breadbasket.

The spongelike aquifer formed more than 20 million years ago, when erosions of gravel and sand from the Rocky Mountains were washed downstream. It is replenished by rain and melting snow, but it gets just two to five inches of precipitation a year, according to a ­TransCanada filing to the Nebraska Department of Environmental Quality. Much of the water it holds was absorbed thousands or millions of years ago.

In some places the aquifer is buried 1,200 feet deep, but in many places it is at or very close to the surface, often less than five feet below ground. In these places, you can literally stick a stake in the ground and hit water. Extensive stretches of Nebraska’s plains require no irrigation; to keep cattle watered, ranchers just dig a hole and the water flows in.

That’s where concerns about the Keystone XL came in. Its original route traversed 92 miles of the Sand Hills and the Ogallala. TransCanada, which said it would bury the pipeline at least four feet underground, could in many places be putting it in water.

If the pipeline should spring a leak where it touches the aquifer or even above it, Kleeb and other opponents say, oil could quickly seep into and through the porous, sandy soil. The Ogallala, Kleeb said last year in a television interview, is “a very fragile ecosystem, literally made of sand. . . . To have a pipeline crossing that region is just mind-boggling.”

She cited University of Nebraska civil engineering professor John Stansbury, who drew on pipelines’ history and TransCanada regulatory filings to predict that during the projected 50-year life span of the pipeline, “there would be 91 leaks . . . that could potentially put 6.5 million gallons of tar sands oil in the Ogallala aquifer and essentially contaminate our drinking water.”

He maintained that a worst-case spill in the Sand Hills region could pollute 4.9 billion gallons of groundwater with a “plume” of contaminants 40 feet thick, 500 feet wide and 15 miles long.

The message rallied Nebraskans from ranches to cities, and it was what President Obama pointed to in January when he rejected the initial Keystone XL route. In May, TransCanada submitted a revised route to the State Department, bypassing the Sand Hills but still passing over some parts of the aquifer.

“The Ogallala aquifer is the greatest underground water source, I believe, in the world,” said Gerald E. Happ, whose ranch in Greeley the pipeline originally would have crossed. “And it’s the purest. . . . And we need the water, and maybe the water may be way more precious than the oil sometime in the future.”

Expert is ‘embarrassed’

All this offends Goecke, who even Stansbury calls “the number one expert” on the aquifer. Goecke says that many people have the wrong impression about the danger a pipeline leak would pose to the Ogallala. It’s not like dropping oil into a lake, he says; remember, the aquifer is more like a sponge.

He said people “were concerned that any spill would contaminate and ruin the water in the entire aquifer, and that’s just practically impossible.” To do that, the oil would essentially have to run uphill, he said. “The gradient of the groundwater is from west to east; 75 percent to 80 percent of the aquifer is west of the pipeline, and any contamination can’t move up gradient or up slope,” he said.

“Secondly,” Goecke added, “any leakage would be very localized. . . . A spill wouldn’t be nice, but it would certainly be restricted to within a half-mile of the pipeline.” He predicted that the varied layers of fine-grained seams of silt and clay would contain the flow of oil.

After TransCanada submitted a revised Keystone XL route that veered east of the Sand Hills, Goecke agreed to appear in a television ad for TransCanada.

“I’ve spent my career drilling holes to and through the Ogallala Formation. I’ve probably seen as much of the Ogallala as anybody,” he says on camera. “There’s a misconception that if the aquifer is contaminated, the entire water supply of Nebraska is going to be endangered, and that’s absolutely false. If people recognize the science of the situation, I think that should allay a lot of the fears.”

Kleeb sees the ad as a betrayal.

“Dr. Goecke . . . at one point was raising the same red flags many of us still are today,” said Kleeb. “In his original testimony to our state [legislature] in 2010, he said he actually does not know [the impact on the Ogallala] since he does not know how tar sands and the chemicals mixed with it will affect the aquifer. To say a spill will be ‘localized’ is just spin by TransCanada to try to ease the valid concerns we all have — the unknown risks.”

The full story about Goecke is a bit more complicated.

“I was embarrassed about the ad because I knew I would look like a shill for TransCanada,” said Goecke, who wasn’t paid for appearing in it. “But what I talked about was common sense.”

While Goecke thinks some threats have been exaggerated, he has his own worries about the pipeline. Where the revised route crosses Holt County, he says, the water table is so near the surface that leaks would go into it more quickly and directly “and foul stuff up.” According to TransCanada’s April 18 filing with Nebraska’s environment department, 10.48 miles of the new pipeline route would cross areas where the depth to groundwater is five to 10 feet.

Goecke also worries about the crossing of the broad, shallow Platte River, because if oil leaked there, “that could get downstream and foul the water supply for Omaha and Lincoln.”

But Goecke believes TransCanada has taken precautions. It plans to drill far under the riverbed to avoid the problem other pipelines have encountered when riverbeds change and trees or other debris swept downstream tear holes in the pipe. TransCanada, whose new Nebraska route includes 29 year-round water crossings, has also said it would make the pipeline thicker in sensitive areas.

TransCanada has tried to ease anxieties about leaks. At its Calgary headquarters, the company has a control room that monitors pipeline pressures throughout its network. There are 16,000 data points on the existing Keystone pipeline, completed last year, and they are refreshed every five seconds, the company says.

Quickly detecting a pressure drop that could indicate a leak is essential; the flow rate on the existing pipeline is about 410 barrels a minute, and the capacity of the new line would be about a third bigger. The company says that it can isolate a piece of pipeline and shut off the flow of oil in just 15 minutes.

TransCanada chief executive Russ Girling said in an interview, however, that in the event of a spill in the ground, “the oil doesn’t migrate from that spot. It doesn’t go anywhere. This notion that we have a plume of oil . . . that doesn’t occur.”

In Canada, the company has already drilled deep under the Red Deer River, one of the two biggest Canadian rivers the new line would cross. Using horizontal drilling pioneered in the oil industry, TransCanada has burrowed a 11 / 2-mile-long hole, 230 feet under the riverbed, and pulled the steel pipe through. A small piece of the pipeline, sealed, is visible on either side awaiting the next stage of construction.

But Stansbury says there still isn’t enough known. While he conceded in an interview that his worst-case scenario might be overstated, he added that “an adequate assessment of the risks hasn’t been made” and that TransCanada is required to analyze such a scenario as part of its environmental impact study.

Other environmental threats

Oil isn’t the only threat to the Ogallala.

Pipeline supporters accuse landowners who oppose it of being blind to the damage they themselves have done.

The aquifer has long been drained for irrigation and for industrial uses such as ethanol plants, which turn corn into motor fuel. From the time humans began extracting water from the aquifer through 2000, the volume of water in the aquifer fell by about 6 percent. Since then irrigation and industrial usage has accelerated.

The decline in the aquifer isn’t uniform. From 2007 to 2009, for example, there was an increase in water stored in the aquifer in Nebraska overall, according to Goecke, but in southwest Nebraska water levels are falling; by 2007, there were 41 / 2 times as many irrigation wells in the state as there had been in 1960. In north Texas and west Kansas, the Ogallala water levels are falling precipitously, more than 100 feet in 60 years, according to a University of Texas at Austin study.

And the use of pesticides on cropland has polluted parts of the formerly pristine aquifer.

But many environmentalists say that the pipeline poses special dangers: They say that ingredients of crude from oil sands make pipelines more prone to leaks. They argue that the diluted bitumen, or “dilbit,” from the oil sands can separate under pressure and temperature and create explosive natural gas, heavy compounds and corrosive acids.

Environmentalists also point to Enbridge, another Canadian pipeline company, which two years ago suffered a pipeline rupture that dumped at least 20,000 barrels into Talmadge Creek, ultimately fouling more than 40 miles of the Kalamazoo River near Marshall, Mich.

Unlike conventional crude oil, which floats in water, the bitumen in the oil sands crude sank to the riverbed, making it hard to recover. Higher levels of benzene in the pipeline mixture forced a temporary evacuation of the area.

“Just looking at the Kalamazoo spill, it does scare us as to what a spill could do in our state and water supply,” Kleeb said.

TransCanada has also suffered leaks, though not as dire. The company’s existing Keystone pipeline has had 14 leaks, all at pumping stations where they were controlled. The smallest was “a few drops,” the company says, but the biggest was about 400 barrels. The company has identified a piece of equipment at fault, a fitting that failed aboveground, and replaced them up and down the line.

“When people talk about the 14 spills . . . every one of them was a leak on our pump stations, and they’re minor,” said TransCanada’s Girling. “They are coming through seals. . . . Our pipe has not leaked once. It’s welded. And if it breaks underground, [the oil] doesn’t go anywhere. We shut the pipeline down.”

But Kleeb said: “TransCanada can not say they are building the ‘safest’ pipeline with the ‘best’ technology if . . . their line already had 14 leaks — and I don’t care if it’s only been on the pumping stations: Leaks are leaks, and 14 is not safe.”

“Jane Kleeb’s big political argument was ‘protect the aquifer,’ ” said a longtime Republican Party activist, who asked for anonymity to protect his business relationships. “You’ll get a sympathetic ear for that from people living in Lincoln or Omaha. Now with new route she’s still against it, which means she’s really just against fossil fuels.”

Indeed, the new route has not mollified Kleeb, who says it still runs over ecologically sensitive areas. Kleeb also doubts political arguments that the pipeline will enhance U.S. energy security; she says that much of the crude in the line would be refined in Texas and sold overseas.

“I hate bullies. I hate corporations who think because they have a lot of money and political officials in their pocket they can run all over landowners,” Kleeb said. “I also don’t like politicians saying we have to be ‘energy-independent’ and then allow an export pipeline to cross our land and water while pretending it is helping make our country energy-independent.”