Evolutionary Transition of Stormwater Pump System in Tokyo

One of the roles of sewerage is to effectively discharge stormwater and protect urban areas from inland flooding, but there are several challenges to overcome. Urban development is progressing in Tokyo, and the amount of stormwater flowing into the sewers is increasing. In order to respond to the increase in the frequency of heavy rainfall in recent years, it is necessary to improve the capacity of stormwater pumps. The Bureau of Sewerage Tokyo Metropolitan Government has been working on the technological development of higher-performance stormwater pumps since the 1950s, when initial-type stormwater pumps were installed. The technological development history of stormwater pumps in Tokyo can be broadly divided into four periods. The first period spanned approximately 30 years when initial-type pumps, which start to operate after stormwater flows into the pump station, were active. In the second period, which spans approximately 20 years from 1980, two types of pumps were developed; a non-water supply pump that could operate reliably even in an earthquake, and a standby operation pump that could respond to sudden stormwater inflow during torrential rains. The third period spans approximately 15 years from 1999, when the waterless standby pump, which integrated the features of the two pumps developed in the second period, was developed and introduced. The fourth period is the era of pumps with higher performances than third period pumps developed after 2015. Currently, these stormwater pumps are operated together with a rainfall radar system that accurately grasps the rainfall situation and protects the citizens of Tokyo from inland flooding.