The funding was designed to accelerate environmental cleanup programs that otherwise would have taken up to six years longer to complete, while creating about 3,000 mostly temporary jobs at the site.

Jim Giusti, a DOE spokesman, said most of the remaining $600 million will be spent by the time the stimulus program expires this fall, with the possible exception of the transuranic waste project, which involves packaging and shipping nuclear waste to a disposal site in New Mexico. That program could continue through fiscal year 2012.

The work financed by the extra money was already in the planning stage, but completing those cleanup efforts earlier has helped reduce the site's footprint by 122 square miles through closing, cleaning up or consolidating facilities into smaller areas.

The eventual goal is to reduce the footprint by 75 percent, or 233 square miles, Giusti said.

The projects that received stimulus funding included decommissioning two defunct reactors, packing and shipping of nuclear waste, demolishing an old cooling tower and removing obsolete buildings and facilities.

Employment through the program peaked last April, when the site's contractor -- Savannah River Nuclear Solutions -- had about 2,200 stimulus workers on the site. The number has since declined.

Giusti said that most of the jobs created by the program are not permanent.

"We had two categories of people under Recovery Act: jobs created, and jobs saved," he said. "Most jobs were temporary and not part of the regular contracts at SRS."

In recent months, Savannah River Nuclear Solutions was given DOE clearance to reduce its work force by as many as 1,400 positions by this fall.

So far, 328 employees have volunteered to leave and 342 more were affected by layoffs implemented last week. As many as 730 additional layoffs could occur by September.

Giusti said those cuts are mostly unrelated to the departures created by the completion of Recovery Act projects, although in theory, the stimulus money enabled the site to retain about 800 workers whose positions otherwise could have been eliminated long before now.

Savannah River Site's $1.615 billion stimulus allocation was the second-largest among 18 DOE facilities that shared $6 billion in stimulus funds. Hanford, in Richland, Wash., received $1.633 billion.