A joint venture between Balfour Beatty and Zen Pacific is about to start excavating underground station concourses for Nam Cheong station on Hong Kong's West Rail mega project. The work is complicated by the fact it will have to take place under live Airport Express railway tracks and around the foundations for the busy elevated West Kowloon Expressway. Airport Express and the viaduct both have to remain open during the work. When complete, Nam Cheong will form an interchange between West Rail's central Hong Kong terminus and new platforms for the Tung Chung mass transit railway line. At the moment the Tung Chung line shares Airport Express track as it passes through the site.