The project, 12 years in the making, started Tuesday when crews at the long-closed uranium plant started pumping highly radioactive waste out of two concrete storage silos and into temporary metal tanks, which will hold the material until it is mixed with concrete and shipped across country for disposal.

In addition to the pipes used to pump the material from the silos into the tanks, a separate pipe system continuously cleans the air inside the silos because of the huge amounts of radon gas the waste generates.

There are three "silos" at the sprawling, 1,050-acre Fernald site. Silos 1 and 2 hold the most dangerous waste. A third silo holds radioactive powder.

Crews began pumping water into the two silos with the clay-like waste last week.

Jeff Wagner, a spokesman for the government's contractor performing the work, said the work on the $400 million silos project will ultimately define the success or failure of the entire cleanup.

"This is the most significant step we've taken in the project," Wagner said. "The silos will define when the site will ultimately be closed. Today is a big step in completing not only the silos, but ultimately taking those final steps we need for closure."

The government has set a 2006 deadline to finish the entire cleanup, which includes removing millions of tons of radioactive dirt, building debris, cleaning underground water and removing waste from the three silos. That deadline is in jeopardy because Nevada has threatened to sue to keep the waste from being buried in the desert near Las Vegas. That issue is still unresolved, but it will take about four months to empty the two silos.

Lisa Crawford, a nearby resident of the plant and long-time observer of the cleanup for a citizen's group that sued to get the cleanup started, said it's a scary project.

"This is the worst stuff out there," Crawford said. "So we're all a little nervous. We want them to do this cautiously, and we'll be paying very close attention."

The work of emptying the powdery waste from Silo 3 was supposed to begin months ago, but has been delayed because of the threatened lawsuit.

E-mail dklepal@enquirer.com