A Project Office located in Chatham County, North Carolina, colloquially known as "Big Hole", came online in the mid 1960s and was described by area residents and persons employed in the construction of the site as being "department-store sized" with walls "several feet thick" covered in copper, buried 30 feet underground on large shock-absorbing springs, constructed with plumbing made out of rubber, and outfitted with tropospheric scatter antennas.