RICHLAND — Workers recently completed clean-up work on 140 acres of the Hanford nuclear reservation where liquid waste from the making of nuclear bombs was poured into trenches in the ground.

The Tri-City Herald reported nearly 500,000 tons of contaminated soil — 20,000 large dump truck loads — were dug up and buried in a lined landfill at Hanford for low-level radioactive waste.

John Price of the state Energy Department said it was pleased with the completion of the work by CH2M Hill Plateau Remediation in the core of the BC Control Area, Hanford’s largest waste site by area.

The trenches were built in 1955. They were covered with sand and gravel in 1969 to protect them from wind and animals.