Work began on 23 May to demolish the last two buildings at the US gaseous diffusion uranium enrichment facility at Oak Ridge in Tennessee. Buildings K-131 and K-631, constructed in 1945, are the most contaminated structures still standing on the 890 hectare site, which hosted facilities constructed to support the Manhattan Project. Oak Ridge, which also produced enriched uranium for the commercial nuclear industry from 1945 to 1985, has been undergoing deactivation and decommissioning since the US Department of Energy (DOE) ended uranium enrichment in 1987. The site was then closed and re-named the East Tennessee Technology Park (ETTP). K-131 was built to provide uranium hexafluoride to the uranium enrichment cascade, while K-631 was used to withdraw gaseous depleted uranium from the cascade, convert it to liquid and transfer it into transport cylinders. Demolition has already begun on the five-story K-131, and the two-story K-631 will follow. The buildings, which are connected to one another and have a combined floor space of more than 83,000 square feet, are the most contaminated structures remaining at the site, the DOE Office of Environmental Management (OEM) said. Demolition of the two buildings by Oak Ridge Office of Environmental Management (OREM) and clean-up contractor UCOR is scheduled for completion this summer. All demolitions at ETTP are expected to be completed in 2020, when the site will be converted into a multi-use industrial park.