The Bonneville Salt Flats west of the Great Salt Lake are so flat that racers can drive at mind-boggling speeds that break the sound barrier. But the expanse of salty crust began rapidly receding in the 1980s and hasn’t stopped. In just 30 years, the salt flats shrunk from 50 square miles to 35 square miles. They lost a third of their volume.
The racing community pointed at nearby groundwater pumping for potash mining as the culprit, so in the late 1990s, land managers approved a process called “laydown” — mixing all the leftover mining salts with groundwater and flooding it across the flats in an effort to help the crust regrow.
But scientists now say the process could actually make things worse.
“We’ve come to believe it’s not a good solution,” said Bill Keach, the state geologist and director of the Utah Geological Survey.
In 2019, the racing industry successfully lobbied Utah lawmakers to appropriate $5 million and reverse their decline. They hoped the U.S. Bureau of Land Management (BLM), which manages the flats, would match those funds with another $45 million to ramp up the brine laydown efforts. Congress never appropriated the federal funds, so Keach’s division returned $4 million back to the state the following year. But he kept $1 million to study the salt flats and get to the bottom of their disappearance.
“We were trying to figure out if lay down really is the answer,” Keach said, “because the salt pan is still getting smaller.”
Turns out, groundwater extraction — including the pumping done for brine laydown — has dramatically changed the aquifer beneath the salt flats. The subterranean water that built up the salt pan over thousands of years is now flowing away from the flats, carrying the salt away with it. Researchers published their findings in the Utah Geological Association Journal on Jan. 14.
“One thing they weren’t thinking about when they designed this [laydown] project is the system as a larger whole,” said Jeremiah Bernau, a recently graduated Ph.D. student from the University of Utah who led the study.
The site the potash company used to pump water for the laydown process was on the edge of the flats, next to the Silver Island Mountains. Supporters of the project may not have realized the water it extracted was linked to the aquifer beneath the shrinking salt crust.
“The idea that if you add brine to the top of the salt and grow more salt makes sense,” said Brenda Bowen, a professor of Geology and Geophysics at the U. who co-authored and guided the study. “But ... folks didn’t appreciate the scale of the connections.”
The salt flats crust is also difficult to penetrate, so flooding it with brine doesn’t recharge the groundwater below. Instead, the aquifer formed through a long process of snowmelt and runoff that scoured minerals and salts from the surrounding mountains, then sank into the valley floor or evaporated.
“This is water that’s 10,000 to 20,000 years old, “ Bernau said, “so it’s not getting restored very quickly.”
The researchers said they didn’t have enough data to say whether the laydown experiment did more harm than good.
“But long term,” Bernau said, “it does indicate the current method is not sustainable.”
Stopping the laydown process isn’t going to fix the salt flat’s problems, Bernau and Bowen added. And the potash industry’s pumping isn’t entirely to blame either. The aquifer has seen all kinds of disruption from human activities, including construction of the interstate and racing cars across the salt surface.
“It’s a highly modified landscape,” Bowen said, “and those modifications have changed the way water flows and where it used to flow to salt flats.”
The racing community will likely be disappointed, Bowen acknowledged, to learn the solution it advocated for isn’t having the desired effect.
“My hope is this additional understanding doesn’t cause any resistance to the science,” she said. “This appropriation the state made toward understanding the sustainability of the salt flats was about bringing together researchers, land managers, and racers who value this place to work on solutions.”
Asked for comment on whether it will end its laydown program or rethink water pumping permits, a BLM spokesperson said the agency is still reviewing the research.
“The BLM has been proactive in looking for solutions for aquifer recharge for nearly three decades,” the spokesperson wrote in an email. “Once we have reviewed the report and consulted with stakeholders, we will be able to assess next steps in overall management of the Bonneville Salt Flats geological-hydrological system.”
Keach summarized the study’s findings for lawmakers during a natural resources appropriation subcommittee Thursday. He said he’s not seeking any additional funding for salt flats research — there’s still about $300,000 left in the bank from the Legislature’s initial $1 million investment, with more studies to release soon.
“It was a great use of the state’s money to solve a longstanding problem,” he said in an interview after the presentation. “I’m a big believer that good science leads to good policy.”