As a result, by Korea’s independence from Japan in 1945, the Cheonggyecheon was severely contaminated with wastes from flimsy shacks built alongside of the stream. It had a fetid smell as well. In terms of Seoul's appearance and sanitation, the then Cheonggyecheon was a serious problem. The easiest way of solving this promblem was covering over the stream with concrete. In 1958, finally, the work to cover it up with concrete started as quickly as possible by August 1958. In addition, a 5.6 km-long, 16 m-wide elevated highway was completed over the stream in August 1971 after four working years.