The presence of these pits, particularly given the uncertainty of their precise location and number, should give great pause to development—with its corresponding digging and trenching—on the McClellan site until the issue is resolved.
Capping McClellan toxics safe, military says
By Chris Bowman - Bee Staff Writer
Published 12:00 am PDT Tuesday, August 21, 2007
As it promotes a proposal to cap, rather than remove, long-lived radioactive waste at the former McClellan base, the Air Force is issuing assurances that well-maintained seals can hold for thousands of years.
To prevent human contact with the waste, generations of caretakers would have to routinely maintain and periodically rebuild the barriers.
"It's a legacy," said Steve Mayer, who heads the Air Force cleanup. "This remedy is something that will have to be maintained in perpetuity."
The proposal must be approved by the U.S. Environmental Protection Agency.
Air Force officials say they are confident the caps will work and allow for some commercial development at the old waste dumps.
They point to one such cap site, constructed 22 years ago, that covers a series of unlined industrial waste trenches at the northwest corner of McClellan. Wells puncture the cap, extracting toxic vapors from the soil and contaminated groundwater 100 feet below. Yet the barrier has held firm.
"It's been trouble-free," Mayer said. "This has been a good test bed for us."
Still, state health officials wonder whether the barriers can stand the test of centuries.
The pits likely contain long-lived radioisotopes, predominantly radium-226 from luminescent aircraft instruments. McClellan was a major aircraft repair depot and supply base from 1936 through June 2001.
Radium-226 has a half-life of 1,600 years, the time it takes the substance to lose 50 percent of its radioactivity by decay. Plutonium-239, found in one unearthed drum at McClellan, has a half-life of about 24,000 years…
… Interviews with former McClellan workers and documents of historic base operations have given cleanup managers "a good understanding of what could be in those pits," said Dave Green, radiation safety officer for the Air Force Real Property Agency at McClellan.
At the same time, the agency states in its capping proposal, "There is significant uncertainty on the type and levels of radioactive wastes that may be present in the pits."…
… The Air Force says burial of radioactive waste was common in the 1950s through early 1960s. Cleanup officials have relied mostly on interviews with retired McClellan workers to locate the sites.
