Crews at the Hanford vitrification plant have finished installing the Pretreatment Facility's fifth elevation of concrete walls.

The walls now stand about 97 feet tall.

To place the latest walls, crews used a specialized concrete pumping truck with an extendable arm that reaches about 200 feet vertically or horizontally.

The Pretreatment Facility, the largest of the vit plant's four major buildings, will have six elevated concrete sections and more than 113,000 cubic yard of concrete. Work on the sixth and final elevation has begun, and only four small wall sections remain before all concrete walls are complete.

When complete, the building's walls will stand 109 feet high. Steel columns and roof trusses will extend beyond the walls to an overall height of 120 feet.

The vitrification plant is required to begin operating in 2019 to treat radioactive waste now stored in underground tanks at Hanford. The waste is left from the past production of plutonium for the nation's nuclear weapons program.

The Pretreatment Facility will divide waste into high level and low activity radioactive waste, which will be separately turned into glass for disposal.