Sue Water Purification Plant No. 3 Slow Filtration Sedimentation Basin

The Northern End of the Row

The Sue Water Purification Plant No. 3 Slow Filtration Sedimentation Basin (末浄水場三号緩速沈澱池, Sue Jōsuijō Sangō 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 lies north of the No. 2 basin, closing the row of three, and covers 2,848 square metres.

The three basins share one design. The Kanazawa City Public Enterprise Bureau dates them to December 1930 and gives a depth of 5.5 to 5.85 metres. This one is farthest from the main gate, close to the axis that runs north from the pavilion in the front garden.

From the Mountains to the Basin

In its entry for the Sue Water Purification Plant No. 3 Slow Filtration Sedimentation Basin, the Agency for Cultural Affairs traces how the water gets here.

It starts in the upper Sai River, which gathers its water from the mountains running up to the Hakusan range. Drawn off from there, it enters the plant through a main buried beneath the road outside the main gate. The main feeds the receiving well beside the gate at the southern tip of the site, then a raw-water treatment unit, and from the east side of the basins the flow is divided evenly among them.

The main is about 1.8 kilometres long, and the intake sits on the middle course of the Terazu Canal, an Edo-period irrigation channel. Mountain water, farm canal, buried pipe, gateside well, three basins: the entry for No. 3 fits the whole route into the description of one basin.

The even split matters. If one basin took more than its share, water would move through it too fast and carry silt on to the filters. Dividing the flow equally from the east lets all three basins work as intended.

Reading the Basin East to West

Registered for its contribution to the historic landscape, the basin finishes off the broad band of water the three make along the east of the site.

On a tour, look at the eastern edge. That is where water comes in, and the inlets and the movement of the surface show how the distribution works. At the western edge the water leaves for the filters on lower ground. One basin holds the before and after of this stage of treatment.

Clay pipe beneath the basin drains groundwater, and the basin is divided into sections against expansion; the Agency treats both as common to all three.

Seeing It

The Sue Water Purification Plant No. 3 Slow Filtration Sedimentation Basin is shown only on the plant's pre-booked group tours, which include the sedimentation basins and filters and take about 40 minutes. Applications are due two weeks ahead.

The front garden, open without booking, lies west of the basins, but how much of the northernmost basin can be seen from there is not stated in published sources.

Nothing is published on photography, so ask the guide. Directions and garden hours are on the Sue Water Purification Plant page.