首都圏外郭放水路 - Shutoken Gaikaku Hosuiro

Metropolitan Area Outer Underground Discharge Channel - G-Cans Project

Useful Information

Location:	720 Kamikanasaki, Kasukabe city, Saitama 344-0111. Kasukabe, Saitama Prefecture. 2nd floor at Ryukyukan, Showa drainage pump station (Reception). (35.997390, 139.811442)
Open:	Online reservation system one month in advance. [2023]
Fee:	Underground Temple Course: Adults JPY 1,000. Shaft Experience Course: Adults JPY 3,000. Pump Proficiency Course: Adults JPY 2,500. Impeller Exploration Course: Adults JPY 4,000. [2023]
Classification:	Sewage System
Light:	Incandescent Electric Light System helmet and headlamp provided
Dimension:	L=6,300 m.
Guided tours:	Underground Temple Course: Max=50, D=55, St=100, MinAge=6. Shaft Experience Course: Max=20, D=110 min. Pump Proficiency Course: Max=20, D=100. Impeller Exploration Course: Max=20, D=110 min.
Photography:	allowed
Accessibility:	The staircase into the tank has 100 steps
Bibliography:
Address:	Metropolitan Area Outer Discharge Channel Tour, 720 Kamikanasaki, Kasukabe city, Saitama 344-0111, Tel: +81-48-747-0281.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then. Please check rates and details directly with the companies in question if you need more recent info.

History

1993	project started.
2002	tunnel ready for use.
JUN-2006	system in full operation.

Description

The Tokio Sewer system is an impressive series of vast underground chambers and vaults. The climatic conditions require enormous sewers to drain the huge amounts of water rainfall might bring. The eastern part of Saitama Prefecture has always been prone to floods. The flood control system is actually separated from the normal sewers and does not contain waste water. It is intended to swallow floods, store them for some time and then release the water controlled into rivers. It also allows the transport of huge amounts of water from one part of the city to another.

The operator of the whole sewer system is the government, or better the Edogawa River Office under the Land, Infrastructure and Transport Ministry. They now offer regular public tours into the flood control tunnel in Kasukabe, Saitama Prefecture. The 6.3 km long conduit is located 50 meters below national road 16 and connects the Otoshifurutone and Edo rivers. If the Otoshifurutone River or the nearby Naka River flood, the excess water may be channeled into the tunnel from five different locations. It is stored in an underground chamber and released into the Edo River over the next days.

The huge water chamber called Underground Palace or Underground Temple is big enough to store 670,000 m³ of water. The 25 m high ceiling of the chamber is supported by 59 columns. The official name is 首都圏外郭放水路 (Metropolitan Area Outer Discharge Channel).

The tours are actually not a tourist venture. It is a public service to give citizens a chance to see how their millions were spent. And while they have an English website, they offer tours only in Japanese. For security reasons it is necessary that visitors understand the guides, so visitors who do not speak Japanese must bring someone to translate. And as it is a working facility, there are several restrictions. Obviously the place may not be visited in the weather conditions which might result in a flood. The tours are held on workdays only and children under five are not allowed, children under 16 must be accompanied by an adult. It is also necessary to be there at least 30 minutes before the tour starts for the security instructions.

They started with a single tour, which soon became so popular, they now offer four different tours. 地下神殿コース (Underground Temple Course) is the original tour which shows the huge cistern with its pillars. 立坑体験コース (Shaft Experience Course) shows the massive shaft 1, includes walking on a passageway which is approximately 70 m above ground. Participants must sign a waiver and wear a safety belt and helmet. ポンプ堪能コース (Pump Proficiency Course) shows the pump room and the pressurization water tank explaining the involved technology. This is the only such pumping facility open to the public. The tour is cancelled when the pumps are working. インペラ探検コース (Impeller Exploration Course) shows the giant impeller in the innermost part of the pressure regulation water tank, which has finally been opened after many requests by visitors. Again its necessary to sign a waiver and wear special equipment, which are hip wader boots and helmet with headlamp.