Sound Transit awarded the construction contract for Mount Baker station and the Beacon Hill Tunnel to Japanese general contractors Obayashi Corporation in June 2004 for $280 million, the costliest component of the Central Link project. Construction began in September 2005 with the permanent closure of Stevens Street and utility relocation to clear the station site. By the following April, Obayashi completed erection of columns that would be used to support the elevated guideway and station. Mount Baker station was declared substantially complete in June 2009, excluding work on the elevators and escalators.