Mino Water Purification Plant No. 1 Water Source Intake

What Is the Mino Water Purification Plant No. 1 Water Source Intake?

The Mino Water Purification Plant No. 1 Water Source Intake (三野浄水場第一水源取水口) on the right bank of the Asahi River in Mino, Kita-ku, Okayama City, is a river intake built in 1905 for Okayama's first waterworks, and it was registered as a Registered Tangible Cultural Property on February 9, 2005.

This is where Okayama's water supply begins. Set into a stone embankment at the northeast corner of the plant are two intakes of different ages: the northern one dates from the opening of the waterworks in 1905, and the southern one was added in 1926 during the second expansion. The Agency for Cultural Affairs lists the structure as concrete and reinforced concrete, 33 meters long, dated 1905 with alterations in 1926.

Why It Was Registered

The No. 1 intake was registered for contributing to the historic landscape of the country. The Agency's description draws attention to the carefully laid stone revetment, built to a steep batter, and to the pairing of a plain concrete intake from 1905 with a reinforced concrete one from the 1920s. Two generations of construction sit side by side on one stretch of riverbank.

The names of the engineers behind the later work are on record: the 1926 intake was built by Ikeda Tokusaburō under the direction of Ōi Seiichi.

The Okayama City Waterworks Bureau adds a technical detail. The northern intake first worked as a siphon, drawing river water through a pipe into a pump suction well (a sand-settling well). When the southern intake was added in 1926, the northern one was rebuilt so that water entered by gravity, and that is the arrangement you see today.

What to Look For

Start with the stonework. The embankment rises at a batter of one in ten, meaning it leans back only 10 centimeters for every meter of height, so the wall facing the river stands nearly upright. The two intake openings are cut into it.

Then compare the two intakes. They do the same job but belong to different eras: Meiji-period concrete to the north, Taishō-period reinforced concrete to the south. The northern intake also carries the story of its conversion from siphon to gravity flow.

Water taken in at the Mino No. 1 intake passes through settling basins and on to the slow sand filter beds about 260 meters to the west. Standing here with the plant layout in mind, you are at the first step of a journey the city's water has been making since 1905.

Visiting

The intake is part of a working water facility. You cannot walk onto the intake or the embankment, and there is no public interior. The Waterworks Bureau does not say how much of it can be seen from public roads or from the opposite bank of the Asahi, and it gives no guidance on photography, so follow any signs on site.

Directions to the plant, Water Museum hours, and the conditions for group plant tours are covered on the Mino Water Purification Plant page.