The Bonneville racing community believes that potash mining is most responsible for the salt flats’ degradation. Potash is a component of the brine that bubbles up in the spring and thickens the salt layer. But since the federal Bureau of Land Management first issued mining leases in 1963, mining companies have been pumping the brine into facilities across Interstate 80, south of the salt flats.

There, potash is precipitated out of the brine. The common salt is left behind and stored on the mining company’s property. Bonneville proponents have long argued that the salt should be returned to the racecourse once the potash has been extracted.

Today, surface mining of the brine has largely ceased, but it is still being pumped out of wells on the mining company property by Intrepid Potash, current holder of the mining lease. That lowers the aquifer below the salt flats and reduces the amount of brine that rises to the surface, so natural restoration is minimal.

The racers have regularly complained to the mining companies over the years, but according to Louise Ann Noeth , an author of Bonneville motorsports books and the public relations representative for Save the Salt, they were complaining to the wrong entity. The Bureau of Land Management is at fault, Ms. Noeth said. “The lease basically says the mining companies can wreak havoc and only have to repair it when mining activity has concluded. The language in the lease was meant for other kinds of mines where damage can’t be repaired until mining has ceased.”

Brenda Bowen , the director of the Global Change and Sustainability Center at the University of Utah, has studied the salt flats. “Everything that happens on and around the salt crust has some kind of impact on this ephemeral landscape,” Ms. Bowen said. However, it is difficult to pin the degradation on any single activity, she added: “A century of extraction has certainly changed the landscape, but so has the racing.”

At times, mining companies have been mindful of the need to preserve this natural treasure and have mixed some of the waste salt with water and pumped it back onto the salt flats.

In recent years, Intrepid Potash has been returning 0.6 million tons or less of salt brine to Bonneville’s surface. According to a document published by Save the Salt, Intrepid’s effort has helped stabilize the salt but is not sufficient to expand it.