Okaya Viaduct Monument
Heading north on the Nagano Expressway from Okaya City, the first rest stop is Midoriko Parking Area (down lane).
In mid-August, I noticed a monument here. I’d used this spot before but never paid it any mind.
Though the surrounding grass is a bit overgrown, it’s right near the parking lot.
Approaching it, I saw it was the Okaya Viaduct Monument.
They probably built it at the nearby parking area because we can’t stop to see a monument right next to a highway bridge.
An explanatory plaque was attached to the top of the monument.
It’s difficult to make out in the photo, so here is a translation of the text.
“Okaya Viaduct
The Okaya Viaduct is located approximately 8 km east of this point at the junction of the Chuo Expressway and Nagano Expressway. It spans the JR Chuo Main Line, Tenryu-gawa River, and Okaya city center with a length of 922 m and a height of 55 m.
This bridge employs a prestressed concrete continuous box girder bridge design, integrating piers and girders. High-strength steel bars introduce compressive forces into the concrete girders. With a maximum span length of 148m between piers, the structure branches into girders in four directions, creating an elegant curve.
This bridge pioneered new frontiers in concrete bridge construction and was recognized for its outstanding aesthetic appeal, earning it the 1986 Tanaka Award (Project Category) from the Japan Society of Civil Engineers.
The Tanaka Award was established to commemorate the achievements of the late Dr. Tanaka Yutaka (1889–1964), who dedicated his life to advancing bridge engineering in Japan. It is awarded for contributions that enhance bridge technology."
(The missing characters were filled in based on my best guess, so there might be some slight differences.)
In the center foreground is a circular plaque inscribed “Tanaka Prize 1987.”
Although Showa 61 corresponds to 1986, since the award appears to be given by fiscal year, the actual decision to award it was likely made in 1987.
Tanaka Yutaka was an engineer and Doctor of Engineering from Nagano City. As the chief bridge designer during the reconstruction following the Great Kanto Earthquake, he worked on bridges like the Eitai Bridge and Kiyosu Bridge over the Sumida-gawa River. He introduced new technologies, laying the foundation for the modernization of bridge construction.
On the right side is a table detailing materials and structure, but parts of the surface are damaged and illegible.
Considering the monument was erected in 1987, it’s perhaps inevitable that it’s in this condition after over thirty years.
Personally, I wish something could be done about the problem of text not lasting on monuments and explanatory panels standing in public spaces.
The photo embedded in the center is also partially peeling off. I suspect most of the other plates were damaged naturally by flying debris from typhoons, hail, or freezing in winter, but I suspect the lower right part of the photo was intentionally damaged.
Finally, I’ll share photos of the viaduct taken this past May.
This is the viaduct seen from the intersection in front of Okaya Station.
The viaduct viewed from a nearby road looking up.
The Okaya Viaduct is currently undergoing improvement work. It’s a six-year project involving not just the Okaya Viaduct, but also improvements to several bridges at the junction.
Details about the improvement work are posted on the NEXCO Central Japan website, so I recommend checking there for the latest status. (Link provided at the end)
I wonder how they set up the scaffolding. I’m afraid of heights, so just imagining it makes my legs go weak.
Work was suspended during the first half of August but resumed on August 20th.
Due to the construction, traffic jams are occurring near the Okaya Junction, and rear-end collisions have increased. Please be careful when passing through.
[Reference] (written in Japanese)
“Nagano Expressway Okaya Viaduct Improvement Project” (NEXCO Central Japan website)