The First of Three Settling Basins
The Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin (末浄水場一号緩速沈澱池, Sue Jōsuijō Ichigō Kansoku Chindenchi) is a reinforced concrete settling basin built in 1930 at the Sue Water Purification Plant in Suemachi, Kanazawa City, Ishikawa Prefecture, and was registered as a national Registered Tangible Cultural Property on 28 August 2001. It is the southernmost of the three basins serving the slow-filtration line and covers 2,848 square metres.
A sedimentation basin holds water still long enough for the heavier silt to drop out before filtration. Slow sand filters have a fine bed that clogs quickly if muddy water reaches it, so this basin does the rough work first. Water leaves from its western end and runs down to the filters on lower ground.
The Kanazawa City Public Enterprise Bureau dates the completion of the basins to December 1930 and gives their depth as 5.5 to 5.85 metres. More than ninety years on, the basin is still part of the working process.
Registered as Part of a Landscape
The criterion for registration was contribution to the historic landscape. The basin was valued less as an object than as one piece of the scene the plant makes.
Raw water enters at the main gate, passes the receiving well and is shared evenly among the three basins from their eastern side. The Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin lies closest to the gate. All three have the same area and construction, and set side by side from south to north they form a broad band of water along the eastern side of the site.
That arrangement was planned together with the garden at the front of the site. With the pavilion of the front garden as the pivot, the route the water takes by gravity, from basins to filters to collecting well, is the plan of the whole site.
Sloping Walls and an 8-Metre Stair
The Agency for Cultural Affairs singles out the basin's cross-section. The lower part of the side walls, about 4 metres, is not vertical but raked at a slope of 1.5 horizontal to 1 vertical, so the basin widens gently toward the top.
In one corner a stair about 8 metres long follows the same slope down to the floor. It gives access for cleaning and inspection; settled sludge has to be removed from time to time, and this is the way down.
The basin is divided into sections to cope with expansion, and the joints are sealed with asphalt and other materials to keep it watertight. Beneath it runs clay pipe to carry off groundwater seeping up from below. Much of the care that keeps the basin sound is invisible once it is full.
Seeing It
The Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin can be seen only on the plant's pre-booked group tours, which the bureau says cover the treatment process and the sedimentation basins and filters, and last about 40 minutes. Tours are for groups such as local governments and community associations.
The front garden, open without booking, lies just west of the three basins, but published sources do not say how much of the water surface can be seen from there. Plan on getting close only with a tour.
The bureau says nothing on photography, so ask the guide. Directions and garden hours are on the Sue Water Purification Plant page.
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Q&A
- When was the Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin built?
- In 1930. The Kanazawa City Public Enterprise Bureau dates the completion of the basins to December 1930.
- How big is the No. 1 sedimentation basin at Sue Water Purification Plant?
- It is a reinforced concrete tank of 2,848 square metres, 5.5 to 5.85 metres deep. The three basins are the same size.
- What is distinctive about the Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin?
- The lower 4 metres or so of its side walls are raked at a slope of 1.5 to 1, and a stair about 8 metres long runs down one corner at the same slope.
- Can visitors see the sedimentation basins at Sue Water Purification Plant?
- Yes, on pre-booked group tours that include the basins and filters. Applications are due two weeks before the visit.
- When was the No. 1 sedimentation basin at Sue Water Purification Plant registered?
- On 28 August 2001, as registration number 17-0043, for its contribution to the historic landscape.
Basic Information
| Name | Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin (末浄水場一号緩速沈澱池) |
|---|---|
| Location | 1-1 Suemachi, Kanazawa City, Ishikawa Prefecture |
| Designation | Registered Tangible Cultural Property (structure), registration number 17-0043; criterion: contribution to the historic landscape |
| Year Designated | Registered 2001/08/28 (Heisei 13) |
| Quantity | 1 structure |
| Dimensions | Reinforced concrete, area 2,848 m² |
| Owner | Kanazawa City |
| Public Access | Shown on booked group tours only (front garden open without booking) |
References
- National Cultural Properties Database, Agency for Cultural Affairs — Sue Water Purification Plant No. 1 Slow Filtration Sedimentation Basin
- https://kunishitei.bunka.go.jp/heritage/detail/101/00002231
- Kanazawa City Public Enterprise Bureau — Registered Tangible Cultural Properties at Sue Water Purification Plant
- https://www2.city.kanazawa.ishikawa.jp/about_us/facility_tour/water02/water04/
- National Cultural Properties Database, Agency for Cultural Affairs — Sue Water Purification Plant Garden (detailed description)
- https://kunishitei.bunka.go.jp/heritage/detail/401/00003666
- Kanazawa City Public Enterprise Bureau — Sue Water Purification Plant Facility Tours (booking required)
- https://www2.city.kanazawa.ishikawa.jp/about_us/facility_tour/water01/
- Kanazawa City Public Enterprise Bureau — Sue Water Purification Plant Front Garden (no booking required)
- https://www2.city.kanazawa.ishikawa.jp/about_us/facility_tour/water02/
Last verified: 2026.09.24
