(This article was written in 2001 and stated the cleanup would last two years. It looks like it is still going on. At one time, it was one of the most heavily polluted bases in the nation. Cleanup started in the 1980s. As of 2005, it is still ongoing and expected to take at least another decade.)
Five stories high, two football fields long and wider than the state Capitol, the bright white polyester shell will encompass a long-abandoned grave of radioactive waste from a still-secret Cold War mission. The mammoth tent will be a compelling symbol of how big the business of environmental cleanup in the region has become.
The big top will be up for as long as it takes moon-suited workers to unearth, evaluate and ship off an estimated 1,000 corroding steel drums of waste from the 30-foot deep landfill on the west side of the decommissioned Watt Avenue base.
The job probably will take two years, according URS Corp., a global engineering company performing the $38 million cleanup for the McClellan Air Force Base Conversion Agency.
Unlike other toxic burial grounds on the 2,800-acre installation, this two-acre site is largely a mystery to environmental investigators. That's because it contains debris and chemical solutions from a top-secret analytical laboratory that operated nearly 50 years on the base without disclosing the full nature of its work or the substances involved.
"If these drums are crushed and opened, we don't know what will be released," said Ray Lidstrom, URS project manager.
Former lab workers, said Roxanne Yonn, a URS spokeswoman who interviewed several of the technicians, told cleanup officials only that they might uncover any amount of radioactive samples, solutions and tainted lab equipment at various degrees of potency.
Yonn said cleanup crews aren't taking any chances. "We're treating the whole site as radioactive," she said.
The dig will be much like an archaeological excavation. Front-loaders and excavators will gingerly remove dirt in 30-square-foot grids, one foot at a time, to avoid striking and damaging buried drums. Any barrels spotted will be removed carefully with hand shovels, and their contents will be analyzed and inventoried by a laboratory on site.
The $2 million shell of PVC polyester fabric and aluminium frames, which takes three weeks to erect, is designed to keep out wind and rain.
Workers will wear full containment suits equipped with oxygen tanks to avoid potential lethal inhalation of radioactive elements. Air in and around the shell will be monitored for contamination.
Nearly three-quarters of the project's $38 million cost goes toward the transportation and disposal of the waste, officials said. The unearthed soil and drums will be shipped to landfills in Andrews, Texas; Clive, Utah; Barnwell, S.C.; and the federal Department of Energy's Hanford nuclear reservation in Washington state.
The estimated time and cost of the cleanup mushroomed after URS crews made an unexpected discovery in an exploratory dig of the landfill last August.
Workers found a container of glass laboratory bottles labelled "Pu," for plutonium. Highly poisonous and radioactive, the metallic element is produced in nuclear reactors and is the primary fuel in nuclear weapons.
"Everything was placed on hold," Yonn said.
Air Force officials knew from earlier surveillance that the site contained low-level radioactive waste, presumably from the radium in paint once used to illuminate cockpit gauges and gun sights.
Plutonium, however, came as a complete surprise, Air Force spokesman Lt. Robert Firman said after the discovery.
Firman said the base had no records of the element's use at the military installation, where the chief mission was aircraft maintenance.
The McClellan Central Laboratory, however, had a different mission. That operation was staffed with nuclear scientists and technicians who are still sworn to secrecy about whom they worked for and their chief duties.
The plutonium find, which was locally televised, prompted some former lab workers to inform cleanup officials that the radioactive material probably came from their operation.
"When I first saw that picture (of the bottles), I chuckled, thinking, 'Gee, I wonder whether my fingerprints are still on them,' " said Mike Chinnock of Citrus Heights, a nuclear chemistry technician at the lab from 1966 to 1970.
Chinnock and other lab workers agreed to share certain details with Air Force officials in charge of the cleanup
after getting clearance from unspecified national defense authorities.
"Some workers won't talk at all," Yonn said. Those who did talk divulged enough to convince cleanup officials that the old landfill could contain material much more radioactive than previously thought.
"It made everybody pause," she said."