Where the River Water Arrives
The Sanjo City Waterworks Bureau Osaki Water Purification Plant Receiving Well (Transmission Well) (三条市水道局大崎浄水場着水井（送水井）) is a 1933 cylindrical well at the Osaki waterworks in Nakashin, Sanjo City, Niigata Prefecture, that receives raw water pumped from the river intake, and it was listed as a Registered Tangible Cultural Property on October 28, 2011. It sits at the northeast corner of the slow sand filters.
It is reinforced concrete, 3.6 meters across inside and 1.8 meters deep, with an area of 10 square meters. The double name reflects a double job: it is a receiving well that takes in water from the river, and a transmission well that sends that water on into the filters.
The Niigata branch of the Japan Society of Civil Engineers explains that as a receiving well it steadies the pressure of the water pumped up from the intake. Water arriving with force is calmed here before it is let gently into the beds.
Why a Small Well Matters
The Agency for Cultural Affairs counts the Sanjo City Waterworks Bureau Osaki Water Purification Plant Receiving Well (Transmission Well) with the filters as the core of the plant's function. Every drop pumped from the riverside, about 350 meters away, passes through it before reaching the filters. It is among the smallest of the twelve listed structures, but in the process it is the front door.
Slow sand filtration depends on water moving gently through sand. Water rushing in would churn up the bed, so its pressure has to be tamed first. Combining the receiving and transmission functions in one well does that job over the shortest possible distance.
The design is purely functional, in line with the city's account that the plant's process structures carry no ornament. The outline of the cylinder is the whole of its form.
Where to Look From
The city's reference photograph of the Sanjo City Waterworks Bureau Osaki Water Purification Plant Receiving Well (Transmission Well) is taken from the north, with the cylinder at the corner of the filters and the water of the beds beyond. That angle shows best how well and filters relate.
Only the top of the well shows above ground. Picture the 1.8-meter-deep cylinder set into the corner of the filter beds and you can trace the path the water takes from well to bed.
Visiting
The well is inside the working plant, which is normally closed. During the spring opening, look for it at the northeast corner of the slow sand filters. It handles raw water, so keep back from the rim and do not lean over it.
Directions and opening conditions are collected on the Sanjo City Waterworks Bureau Osaki Water Purification Plant page.
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Q&A
- What does the receiving well at the Osaki Water Purification Plant do?
- It takes raw water pumped from the river intake, steadies its pressure, and sends it on into the slow sand filters, serving as both receiving well and transmission well.
- When was the Osaki plant receiving well built?
- It was built in 1933 and listed as a Registered Tangible Cultural Property on October 28, 2011.
- How big is the receiving well of the Osaki Water Purification Plant?
- It is a reinforced concrete cylinder 3.6 meters across inside and 1.8 meters deep, with an area of 10 square meters.
- Where is the receiving well within the Osaki plant?
- At the northeast corner of the slow sand filters.
- Can you see the Osaki Water Purification Plant receiving well?
- The grounds are normally closed, but it can be seen from outside when the city opens the grounds in cherry blossom season.
Basic Information
| Name | Sanjo City Waterworks Bureau Osaki Water Purification Plant Receiving Well (Transmission Well) |
|---|---|
| Location | 4420-3 Nakashin, Sanjo City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Building) |
| Year Designated | Registered 2011/10/28 (Heisei 23) |
| Quantity | 1 structure |
| Dimensions | Reinforced concrete cylinder, 3.6 meters inside diameter, 1.8 meters deep, area 10 square meters |
| Owner | Sanjo City Waterworks |
| Public Access | Normally closed as a working waterworks; the grounds may open to walkers in cherry blossom season |
References
- Cultural Heritage Database: Sanjo City Waterworks Bureau Osaki Water Purification Plant Receiving Well (Transmission Well) (Agency for Cultural Affairs, in Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00008840
- Registered Tangible Cultural Property: Sanjo City Waterworks Bureau Osaki Water Purification Plant (Sanjo City, in Japanese)
- https://www.city.sanjo.niigata.jp/soshiki/shimimbu/shogaigakushuka/bunkazai/bunkazai/1740.html
- Sanjo City Waterworks Bureau Osaki Water Purification Plant (Japan Society of Civil Engineers, Niigata branch, in Japanese)
- https://jsce-niigata.com/introduction/article/049/art049.html
Last verified: 2026.09.25
