A Small Brick Tunnel Built to Flush Away Silt
Not every cultural property is grand. Midway along the Nagara River Power Station's waterway, at the base of the drainage channel of its second settling basin, sits a structure barely wider than a person: the Second Settling Basin Drainage Culvert, built in 1910. It is a short segmental-arch tunnel of brick and stone, two point three metres long, ninety centimetres wide and eighty-five centimetres high. Modest in size, it does a job the whole plant depends on.
A run-of-river station draws raw river water, and river water carries sand. Left alone, that grit would wear the turbines and clog the channel, so the water first passes through settling basins where the sediment drops out. This culvert sits where the collected silt is flushed back out. At the tunnel's end a portal is built up, its voussoirs cut from granite, and inside sits an iron sand-flushing gate connected to a winch. Open the gate and the trapped sand is washed clear.
Why an Overlooked Structure Was Worth Protecting
The culvert was registered as a Tangible Cultural Property in 2001, protected alongside the more photogenic parts of the same power station. Its value lies less in beauty than in completeness. When the Nagara River Power Station began operating in March 1910, built by the Nagoya Electric Light Company as its first plant, it was among the largest hydroelectric stations in the country, and it survives with an unusually full set of its original working parts: the main building, the aqueduct bridges, the intake, and small service structures like this one.
The scheme itself had a long gestation. First conceived by Kobayashi Shigemasa, whose early company failed in the recession of the late 1890s, it was revived by the engineer Noguchi Shitagau and carried through by Nagoya Electric Light, which imported German turbines and generators to complete it. The station passed to Chubu Electric Power in 1951 and still runs today. Because pieces like the drainage culvert were kept, later generations can read the plant not just as architecture but as a working system, sediment control included.
The Craft in a Utilitarian Object
For all its plain purpose, the culvert was not built carelessly. The commentary that accompanies its listing describes it as small in scale yet heavy and dignified in appearance, and the description fits. The granite voussoirs of the portal give a hard, precise edge to the brick behind them, and the segmental arch is a shape chosen for strength in a low, wide opening. Someone decided that even a silt outlet deserved to be made properly.
Be realistic about visiting. This is a functioning part of a live power station, tucked into the middle of the conduit, and it is not a place laid out for sightseers. If the machinery of a Meiji power plant interests you, the accessible starting point is the station's red-brick main building in Tachibana, where the exterior and the retired original turbine can be seen. Understanding what the culvert does adds depth to that visit, even if the culvert itself stays out of easy reach.
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Q&A
- What is a settling basin drainage culvert for?
- Settling basins let sand carried by the river drop out of the water before it reaches the turbines. This culvert is where that collected sediment is flushed back out of the system.
- How does the flushing actually work?
- An iron gate inside the tunnel, linked to a winch, is raised to release the trapped sand. The granite-fronted portal marks the end of the short brick-and-stone arch.
- Why register something so small?
- Because it helps preserve the power station as a complete working system. Keeping the service structures, not just the grand ones, shows how the 1910 plant was designed to run.
- Can visitors see it?
- Not readily; it is operational infrastructure within the conduit. The main building in Tachibana is the practical place to experience the station up close.
Basic Information
| Name | Nagara River Power Station Second Settling Basin Drainage Culvert |
|---|---|
| Location | 168-8 Suhara, Mino City, Gifu Prefecture |
| Designation | Registered Tangible Cultural Property (registered 2001) |
| Built | 1910 (Meiji 43) |
| Structure | Brick and stone segmental-arch culvert, length 2.3 m, width 0.90 m, with iron sand-flushing gate |
| Owner | Chubu Electric Power Co., Inc. |
| Access | Operational conduit structure; not open to visitors |
References
- Agency for Cultural Affairs, National Cultural Properties Database — Nagara River Power Station Second Settling Basin Drainage Culvert
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00002248
- Mino City — Nagara River Power Station Main Building and Eight Related Structures
- https://www.city.mino.gifu.jp/docs/1174.html
- Wikipedia — Nagara River Power Station
- https://ja.wikipedia.org/wiki/長良川発電所
Last verified: 2026.07.03