The Former Katayama Tunnel Upper Entrance: A Taisho-Era Waterworks Heritage in Kofu

Nestled in the mountainous landscape of Kofu City, Yamanashi Prefecture, the Former Katayama Tunnel Upper Entrance (平瀬浄水場旧片山隧道上口) stands as a compelling testament to Japan's early modern waterworks engineering. Built in 1913 during the Taisho era, this stone-constructed tunnel portal is part of the historic Hirase Water Purification Plant system — one of the oldest continuously operating water supply systems in Japan. Registered as a Tangible Cultural Property by the Agency for Cultural Affairs, this unassuming yet dignified structure offers visitors a rare window into the infrastructure that brought modern sanitation and clean water to the people of Kofu over a century ago.

A Brief History of the Hirase Water Purification Plant

The Hirase Water Purification Plant was originally constructed in 1909 (Meiji 42) and began supplying water to the city in January 1913 (Taisho 2), making Kofu the 26th city in Japan to establish a modern public water supply. Drawing water from the Arakawa River, which flows down from the 2,592-meter Mount Kunishi deep within the Chichibu-Tama-Kai mountain range, the plant has served the residents of Kofu and surrounding areas for well over a hundred years.

The Katayama Tunnel was a critical component of the system's water transmission route, carrying treated water through the mountainous terrain from the purification plant to the city below. The tunnel's upper entrance — the subject of this article — is the upstream portal located within the Hirase district, while its counterpart, the lower entrance, stands in the Haguro-cho Nashinoki area of the same city.

Why It Was Designated a Registered Tangible Cultural Property

The Former Katayama Tunnel Upper Entrance was registered as a national Tangible Cultural Property (Building) on October 9, 1998. The registration recognizes its significance as an essential piece of Kofu's waterworks history. Built from carefully worked stone, the portal features an arched opening fitted with an iron gate, measuring 4.6 meters wide and 3.4 meters tall. While slightly smaller than its lower counterpart, it shares the same architectural style, illustrating the consistency and craftsmanship of Taisho-era civil engineering.

The structure was also included in the Yamanashi Prefecture Survey of Modern Heritage Buildings, underscoring its broader importance within the region's industrial and architectural legacy. In 2020, it received further recognition when it was designated as a component cultural property of the Japan Heritage story "Koshu no Takumi no Genryu — Mitake Shosenkyo," linking it to the wider narrative of Shosenkyo Gorge's natural beauty, water culture, and craftsmanship traditions.

Architectural Features and Highlights

The charm of the Former Katayama Tunnel Upper Entrance lies in its honest, understated elegance. The stone masonry of the portal reflects the engineering standards of early 20th-century Japan, a period when the nation was rapidly modernizing its infrastructure while still drawing on traditional construction techniques. The arched opening, sealed with a sturdy iron gate, conveys a sense of purpose and permanence that has endured for more than a century.

Visitors familiar with the lower entrance of the Katayama Tunnel will notice the deliberate symmetry between the two portals. The upper entrance, while slightly more compact, maintains the same stone-constructed form and proportions. Taken together, the pair of tunnel openings create a compelling narrative of water's journey from mountain source to city taps — a journey that once passed through the very rock of these hillsides.

The Hirase Water Purification Plant complex also includes several other registered cultural properties that are worth exploring, including the Former Intake Gate Section, the Former Filtration Pool Regulating Well, and the Second Tunnel Upper Entrance, each with its own inscription plaque bearing classical Chinese characters that evoke the poetic relationship between water, clouds, and rain.

Connections to Shosenkyo Gorge and the Japan Heritage Story

The Former Katayama Tunnel Upper Entrance is one of six registered cultural properties at the Hirase Water Purification Plant that together form part of the Japan Heritage designation "Koshu no Takumi no Genryu — Mitake Shosenkyo: The Pulse of Crystal that Led to Faith, Craftsmanship, and Advanced Technology." This prestigious certification, awarded in June 2020, tells the story of how the Shosenkyo Gorge area — with its abundant water, crystal deposits, and mountain faith traditions — shaped the culture and industry of the Kofu region.

The water that once flowed through the Katayama Tunnel originated from the same pristine mountain streams that carved the spectacular Shosenkyo Gorge, a designated Special Place of Scenic Beauty and one of Japan's most celebrated valleys. Today, visitors can combine a trip to the tunnel entrance with a visit to Shosenkyo, enjoying both the natural grandeur of the gorge and the quiet dignity of these early modern waterworks structures.

Visiting the Site and Surrounding Attractions

The Former Katayama Tunnel Upper Entrance is located in the Hirase-cho district of Kofu City, within the grounds of the Hirase Water Purification Plant. The plant is situated approximately 8.5 kilometers northwest of JR Kofu Station. While the purification plant does offer guided facility tours on weekdays by advance reservation (approximately 90 minutes), the cultural property itself may be viewable during such visits. It is recommended to contact the Kofu City Waterworks and Sewerage Bureau in advance to confirm viewing arrangements.

The surrounding area offers several rewarding destinations for cultural and nature enthusiasts. The famous Shosenkyo Gorge is accessible by bus from Kofu Station (approximately 30 to 45 minutes depending on the stop). The gorge features a 5-kilometer walking trail along the Arakawa River, passing through breathtaking scenery of granite cliffs, unusual rock formations, and the spectacular 30-meter Senga Falls. The area is particularly stunning during autumn foliage season (mid-October to late November) and in spring when fresh green leaves illuminate the valley.

Other nearby points of interest include the Hirase Water Source Former Office (Suiko-an), a charming 1935 wooden building that now serves as a museum of water history, the Yumura Onsen hot spring district for relaxation, and the Kofu city center where visitors can explore Kofu Castle ruins (Maizuru Castle Park) and sample local specialties such as hoto noodles and Koshu wine.