What the Ozatogawa Power Plant Tailrace is
The Ozatogawa Power Plant Tailrace is a channel of 1925 in Tokudacho, Hitachiota, Ibaraki Prefecture, entered on Japan's list of Registered Tangible Cultural Properties on 8 November 2004. Its job is to carry water that has passed through the turbine from the powerhouse back to the Satokawa. It belongs to Tokyo Hatsuden Co., Ltd. and has been in use since the station started generating in February 1926.
The channel runs 142 metres. It does not run straight but bends partway along, giving a dogleg plan. The open concrete cut has a bed width of 2.7 metres, and the side walls are dry stone laid diagonally on a shallow batter. From the end of the channel, stone revetment continues into the Satokawa for a further 17 metres.
The channel is crossed by 3 reinforced concrete bridges giving maintenance access. Each springs a segmental arch, and the spandrel walls above are faced in coursed stone. Those bridges are much of the reason the Ozatogawa Power Plant Tailrace does not read as a drain.
Why it is a Registered Tangible Cultural Property
The criterion applied was contribution to the historic landscape of the country. That the channel was registered on the same day as the powerhouse, the intake and the spillway says a good deal about how the group was assessed: a hydro scheme is not a building but a sequence, and it is only complete when the water has been taken from the river, dropped, and given back.
What carries the Ozatogawa Power Plant Tailrace is the quality of the civil work. The channel walls are laid diagonally, the river revetment is coursed masonry, and the bridge spandrels are faced in yet another bond. Stone is handled differently according to what each part has to do, which makes this a legible example of how concrete and stonework were combined in the late years of the Taisho era.
In 2017 the stations along the Satokawa were recognised by the Japan Society of Civil Engineers as a Selected Civil Engineering Heritage, and the society's record singles out the precision of the stonework in these channel walls.
What to look for
Those 3 maintenance bridges hold the eye, and they are where the Ozatogawa Power Plant Tailrace stops looking utilitarian. Their arches are segmental rather than semicircular, so they sit low against the width of the cut, and the coursed facing above sets a run of horizontal joints against the curve below. These are working crossings for staff; nothing about them needed to be handsome. They were made handsome anyway.
The side walls repay a closer look. Stone set on the diagonal marches along the shallow batter in regular ranks, and across nearly 100 years of running water the joints have held over long stretches. The mason's skill survives in the wall itself rather than in any record of it.
Walk to the point where the channel meets the Satokawa and you can see the revetment turning to follow the riverbank. Channel and river defence were built as one piece of work, leaving the boundary between the two deliberately hard to place.
Seeing and reaching the Ozatogawa Power Plant Tailrace
The Ozatogawa Power Plant Tailrace is live and you cannot climb down into it. The land is managed by Tokyo Hatsuden Co., Ltd., and crossing the maintenance bridges is not permitted either. The channel does run open along the front of the powerhouse, so the water and the bridges can be seen from the road outside, and photography from there is unrestricted.
The site is in Tokudacho, Hitachiota. Take Route 349 as far as the Satomi district and turn off along the river. Allow about 1 hour by car from Hitachiota Station on the JR Suigun Line. Bus services are sparse and worth checking before you travel.
The concrete lip of the channel gets slippery in the wet and some stretches have no railing, so keep back from the edge and look from the road side. (Access information checked in September 2026.)
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Q&A
- What is the Ozatogawa Power Plant Tailrace?
- It is the channel that returns water from the powerhouse to the Satokawa after it has passed through the turbine. The open concrete cut runs 142 metres on a dogleg plan.
- Can I visit the Ozatogawa Power Plant Tailrace?
- The channel is in service and cannot be entered. You can look at the water and the maintenance bridges from the road outside the managed area.
- How many bridges cross the Ozatogawa Power Plant Tailrace?
- There are 3. All are reinforced concrete with segmental arches and coursed stone facing to the spandrel walls.
- When was the Ozatogawa Power Plant Tailrace built?
- In 1925. It became a Registered Tangible Cultural Property on 8 November 2004.
- How do I get to the Ozatogawa Power Plant Tailrace?
- It lies in Tokudacho, Hitachiota. The drive from Hitachiota Station on the JR Suigun Line along Route 349 takes about 1 hour.
Basic Information
| Name | Ozatogawa Power Plant Tailrace |
|---|---|
| Location | Tokudacho, Hitachiota, Ibaraki Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2004 (Heisei 16) |
| Quantity | 1 facility |
| Dimensions | Concrete, 142 metres long, with reinforced concrete bridges and 17 metres of stone revetment |
| Owner | Tokyo Hatsuden Co., Ltd. |
| Public Access | Exterior only; interior not open |
References
- National Cultural Properties Database, Ozatogawa Power Plant Tailrace (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00004314
- National Cultural Properties Database, Ozatogawa Power Plant Main Building (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00004313
- Registered Tangible Cultural Properties, Tokyo Hatsuden Co., Ltd.
- https://tokyohatsuden.co.jp/csr/cultural_property/
- Japan Society of Civil Engineers Kanto Branch, Satokawa River System Hydroelectric Power Stations
- https://www.jsce.or.jp/branch/kanto/04_isan/h29/h29_4.html
Last verified: 2026.09.05