国土交通省 関東地方整備局 江戸川河川事務所
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  • 首都圏外郭放水路

    Overview of Facilities

    Bank

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    "Inflow facilities" and "Banks" for taking water from the rivers

    Inflow Facility

    Inflow Facility

    The collection of flood waters heading towards the Metropolitan Outer Area Underground Discharge Channel will be dumped into the Overflow Levee located on the embankment of each river such as the Nakagawa River or the Kuramatsu River. When the water level rises above the dam, it will flow naturally into the inflow facilities. The entrances to the inflow facilities are fitted with dust collectors that catch trash and debris on a screen and continuously push them upwards in order to prevent any large debris from flowing in.

    Five Banks

    Bank

    All of the five banks are connected by the Metropolitan Outer Area Underground Discharge Channel. The depth of each bank is about 70 meters, and their interior diameter is about 30 meters, which is large enough to fit a whole space shuttle or the Statue of Liberty.
    Banks No.2 through No.4 are fitted with lids with electric opening and closing devices, allowing administrative vehicles to be brought in easily. In addition, if you take the elevator to the bottom of No.3 Bank, you will find double-layered watertight doors like those that you would find in a submarine. These watertight doors are installed to prevent the inflow of water from reaching the other side of the elevator, where there is mechanical equipment, including the elevator itself.
    Additionally, Banks No.3 through No.5 make use of a method called the “drop shaft,” in which water flows down along the walls. Utilizing this method prevents deformation of the influx port and softens the impact on the bottom of the bank due to water falling from a 60-meter height.

    Cross-sectional diagram of bank (No.2 bank)

    Cross-sectional diagram of bank (No.2 bank)

    No.1 bank

    No.1 bank

    Of the five banks, the No.1 Bank is located closest to the Showa Drainage Pump Station. Unlike the other four banks, this particular bank does not have drainage facilities. Its role is to send the water from each bank into the Pressure-Adjusting Water Tank. By the way, the banks are facilities for taking in water from the influx facilities.
    In addition to serving its purpose as a bank, the No.1 Bank also served as a working base for the construction of the tunnel while it was being built, and has also been useful in the maintenance and management of the discharge channel, as well as for importing administrative vehicles and ventilation equipment since its completion.

国土交通省 関東地方整備局 江戸川河川事務所
〒278-0005 千葉県野田市宮崎134 電話:04(7125)7311