About 1,000 workers in central Hanford took cover Wednesday afternoon until a false alarm was declared.
About 2 p.m. a chlorine alarm at the 238W Water Treatment Plant sounded and workers in the 200 West Area were ordered to take cover as a precaution.
No chlorine leak was detected and the alarm was discovered to have malfunctioned, said Geoff Tyree, a Department of Energy spokesman. Maintenance had been done on the alarm earlier in the day.
The take cover order was lifted at about 3:40 p.m. and swing shift workers reported to central Hanford as usual Wednesday evening.
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Chlorine is the only hazardous substance at the 238W Water Treatment Plant, which treats water from the Columbia River for use at Hanford, Tyree said. The water is used for drinking, fire protection, irrigation and processing, primarily in central Hanford.