The development of a trona mine that could repay the city of Casper $5.5 million depends on the trona market, one expert said.

Dennis Kostick, a soda ash analyst with the U.S. Geological Survey said right now, soda ash, which is what producers make from trona, is "a very hot commodity."

Casper officials may vote to spend millions on a proposed civic auditorium and be repaid with royalties from a trona mine that does not yet exist.

John Wold, chairman of Wold Trona Co., sold his leases in the Green River Basin to FMC Corp. a couple of years ago but retained 1 percent of the production royalties.

Several years ago, Wold told the Citizens for a Civic Auditorium that the group could use the trona royalties for construction of a performing arts center.

If the council approves the proposal, 30 percent of Wold's possible trona royalties would be given to the city during a period of a decade or more to repay the $5.5 million. The rest of the royalties would be used for operations of the facility.

Some Casper City Council members recently questioned if the likelihood of a trona mine coming to fruition is high enough to warrant an investment of millions.

International demand for trona is high, Kostick said, but the international producers are also working hard.

"China has been very strong in their internal consumption of soda ash," Kostick said, in part because of the new buildings needed for the 2008 Olympics and also for drinking water treatment.

But, China, India and Europe have also invested in trona mines of their own, both in the U.S. and other countries.

The Green River Basin is one of the largest trona reserves in the world. It accounts for up to 35 percent of the world's soda ash made by five producers in the area.

The leases that FMC now holds will expire in 2016 unless the company begins mining the trona or asks the Bureau of Land Management for an extension.

Wold said he doesn't think BLM will give FMC an extension, which means the company needs to, "put in a mine or drop out."

Wold said it's "conceivable" that FMC will decide not to do anything with the leases, but "very, very unlikely because they paid a significant price for acquiring the leases."

When FMC will build the mine and how much it will produce is left to speculation, Wold said, because the company isn't "divulging" any information.

FMC officials did not return several messages left by the Casper Star-Tribune.

The leases are in a useful location in the Green River Basin, according to Kostick. In some areas the trona is fairly deep underground but Wold's former leases are in a shallow area, making mining easier.

Ken Barbe, president of the Citizens for a Civic Auditorium, said FMC plans to use in-situ mining, also known as solution mining, to collect the trona.

FMC has used this method in the past, Kostick said. Even though the system needs to improve, this type of mining reduces the problems and costs associated with underground mining.

Kostick said producers are currently "stretched to their limits," but they are also meeting the market demands.

Regardless of the current trona situation, Wold said he would like someone to be able to eventually use the possible royalties.

But, he said, it's been between two and three years and he wonders if the trona royalties wouldn't be better served going to another institution.

"I am very interested in higher education," Wold said. "It's been dragging out now for two to three years, and in the meantime, I have been approached by some schools who are very interested in the long-term financing that the royalties could provide."

The Citizens said the royalties could bring enough to pay back the city as well as help with operations, but Wold isn't sure how much the royalties could earn.

"It all depends on the actual stream of royalties," he said. "… There are a number of assumptions you will have to make."

In the mean time, the city will discuss the possible partnership in it's Monday work session and may hold a final vote on Sept. 16.

Contact city reporter Christine Robinson at (307) 266-0639 or christine.robinson@trib.com