Two Hanford workers were sent to the hospital around noon Thursday as a precaution after developing respiratory symptoms that might be linked to chemical vapors from underground waste tanks.
About an hour earlier, two other workers smelled vapors and were sent to be checked out by the Hanford occupational medical provider.
The two workers sent to Kadlec Regional Medical Center in Richland with nose and throat irritation were doing routine radiological surveillance at the group of tanks called the BY Tank Farm. They were the only workers there, said John Britton, spokesman for Department of Energy contractor Washington River Protection Solutions.
The other workers, who smelled vapors, were at the C Tank Farm, where work is under way to empty waste from single-shell tanks into newer double-shell tanks until it can be treated for disposal. C Tank Farm was evacuated and workers were instructed to stay upwind.
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Restrictions at the BY Tank Farm, where a dozen 758,000-gallon tanks hold waste, were lifted about 4 p.m. Restrictions were lifted at the C Tank Farm about two hours later when results from chemical vapor sampling there came back negative. It has seven tanks that still hold waste.
The two workers taken to the hospital were released and Thursday evening were cleared to return to work, said Rob Roxburgh, spokesman for Washington River Protection Solutions.
Hanford’s underground tanks vent chemical vapors to the atmosphere, where they are dispersed by the wind. However, Thursday morning, there was virtually no wind at the tank farms and a low pressure system was moving over the area, Britton said.
Such weather conditions limit dispersal of the vapors, he said.
The vapors include about 1,800 chemicals, including nitrous oxide, mercury, ammonia and benzene. Hanford officials previously have said that chemicals are well below the occupational exposure limit in the air that workers breathe.
Workers have reported symptoms including headaches, scratchy throats and watery eyes after breathing the vapors, and some workers believe they have suffered serious illnesses as a result.
Tank farms are evacuated when workers smell the vapors, Britton said.
Exhaust stacks that emit fumes have been raised higher above the ground to keep vapors away from workers and help them disperse.
Industrial hygiene workers monitor for the vapors when work is done that can disturb tank waste, which increases vapors, such as the work being conducted in the C Tank Farm to empty tanks. In addition, one person in a work group wears an instrument to monitor for chemical vapors.
w Annette Cary: 582-1533; email@example.com; Twitter: @HanfordNews