Kim Chuan Depot is a train depot for the Mass Rapid Transit system in Singapore. The depot is constructed fully underground and provides maintenance, stabling and operational facilities for the Circle line. It is located in Hougang, along Upper Paya Lebar Road, and is accessible via Kim Chuan Road. It used to be the first depot in Singapore to serve two independently operated MRT lines, until the adjacent Tai Seng Facility Building, became operational with the revenue operation of the Downtown line Stage 3 on 21 October 2017. History To facilitate the construction of the depot, part of the Kim Chuan Village was acquired in September 2000 for the construction of the depot and the road viaduct. The Kim Chuan Road was permanently closed from Hougang Avenue 3 to Kim Chuan Drive on 27 June 2002. On 25 October 2002, part of the Hougang Avenue 3 was realigned and on 25 November 2002, part of the Kim Chuan Road was closed. The project cost S$297 million to construct and 2.1 million cubic metres of soil had to be excavated for its construction. Touted as the world's biggest underground depot, it officially opened on 4 March 2009, employing 300 staff members. The depot was used for the temporary storage and light maintenance of rolling stock for the Downtown line, before the completion of the Tai Seng Facility Building. It also provided a route in which Downtown line trains can be towed from the depot to its operational line via the Circle line tracks. Once the main depot, Gali Batu Depot was completed with stage 2 of the Downtown line, Kim Chuan Depot simply provides a route for newly delivered Downtown line trains to be transferred in to the Tai Seng Facility Building. Design The depot has a capacity to stable 70 trains and covers an area of more than 100,000 square metres, reaching a depth of 24 metres at some points. Specifically, the main depot floor is 800 metres in length, 160 metres in width and 23 metres in height. The facility contains the main operation control centre for the Circle line, maintenance facility, stabling areas, and ancillary facilities such as train wash and workshops. It also houses an automatic storage and retrieval system, a warehouse that stores spare parts for the rolling stocks and other equipments. The depot is connected to the adjacent Tai Seng Facility Building on the east