In 1998, the Department of Energy determined that a new facility to store highly enriched uranium materials at the Y-12 National Security Complex was needed. The new facility was intended to modernize security, improve operational efficiency, and consolidate highly enriched uranium materials. The originial design was patterned after a previously constructed facility at another Department site and consisted of a concrete bunker covered by and earthen berm on the top and three sides of the facility. In February 2000, the Department approved the berm design. The Y-12 Complex is now part of the Department's National Nuclear Security Administraton (NNSA).