The Tokyo Metropolitan Government is upgrading the sewerage system to clean the water in the moats of the outer garden of the Imperial Palace as part of its bid to host the 2016 Olympic Games.

Its plan is aimed at improving the sewerage system to reduce the amount of polluted water flowing into the moats after heavy rainfall and to stop deterioration of the water quality by fiscal 2015.

The International Olympic Committee is scheduled to meet in Copenhagen on Oct. 2 to choose the games site. The candidates are Tokyo, Chicago, Madrid and Rio de Janeiro.