The Tri-City Herald reports about 130 workers were surveyed for contamination after the radioactive soil was detected Wednesday morning.
Todd Nelson, a spokesman for contractor Bechtel National Inc., says the amount of contaminated soil was small and the contamination level was low.
The vitrification plant is being built to treat 56 million gallons of highly radioactive and toxic waste. Waste is not being pumped there, but routine radiological surveys are conducted to monitor for contamination that could spread from other parts of the Hanford site.
Nelson says any contaminated areas at the site will be cleaned up. Employees will return to the construction site Thursday.