Looking back at historic constructionーNHK WORLD-JAPAN NEWS

Key Concepts

• Tatayama Tunnel: A 3.7 kilometer tunnel under the Northern Japan Alps, completed in 1971.
• Tateyama Kurobe Alpine Route: A popular tourist route connecting Toyama and Nagano prefectures, attracting 840,000 visitors annually.
• Tunnel Construction Challenges: High altitude (2,400m), water inflows (up to 48 tons/minute), unstable soil leading to collapses, and low temperatures.
• AI Colorization: The use of Artificial Intelligence to restore color to archival footage of the tunnel’s construction.

The Historical Significance of the Tatayama Tunnel

The Tatayama Tunnel, a 3.7 kilometer passageway beneath the Northern Japan Alps, stands as a testament to engineering perseverance. Completed in 1971, it dramatically reduced travel time between Toyama and Nagano prefectures, previously a two-day journey on foot, to a mere 10-minute electric bus ride. The tunnel is a key component of the Tateyama Kurobe Alpine Route, which currently attracts approximately 840,000 visitors each year, contributing significantly to regional development. Construction commenced in 1966 with the explicit goal of spurring economic growth in the region.

Construction Challenges and Technical Difficulties

The construction of the Tatayama Tunnel presented numerous and significant challenges. Sat Ai, a former surveying team member who began working on the project at age 18, recounts the difficulties faced by the construction crews. The primary obstacles stemmed from the tunnel’s high altitude of 2,400 meters, resulting in substantial differences in air pressure and consistently low temperatures.

A major issue was the constant influx of water. Sato recalls his initial impression being “water was gushing out. Cold water.” At its peak, the tunnel experienced water inflows reaching a maximum of 48 tons per minute. This necessitated continuous pumping, and any interruption in the power supply – and therefore the pumps – resulted in flooding and a complete halt to work. As Sato explains, “When electricity stops, the pump stops. When the pump stops, it gets flooded. Then you won't be able to do anything.”

Beyond water, the geological conditions proved problematic. The soil was described as “soft,” and approximately one year into construction, a significant ceiling collapse occurred. Fortunately, no injuries were sustained, but the incident blocked the tunnel and forced a suspension of work for over two months.

Personal Experiences and Emotional Impact

Despite the harsh working conditions, Sato found solace in the surrounding mountainous landscape. He actively engaged in recreational activities like skiing and climbing in the Tatayama region, developing a strong personal connection to the area, stating, “I went skiing and climbing in Tatayyama and made this mountain my home.”

The completion of the tunnel in December 1969, after 3 years and 8 months of construction, was a deeply emotional moment for Sato and the entire team. He vividly remembers being “filled with emotion,” and reflecting on the risks taken, stating, “We risked our lives for the tunnel breakthrough. This is where my life began.”

AI Colorization of Archival Footage

NHK utilized Artificial Intelligence (AI) technology to colorize archival footage from the construction period. This process, highlighted in the video, significantly enhances the visual impact of the historical recordings. A comment within the footage notes, “That’s a good color. Faces become lively,” demonstrating the impact of colorization on bringing the past to life and making the experiences of the workers more relatable.

Legacy and Future Outlook

Fifty-five years after its completion, Sato expresses his hope that the Tatayama Tunnel will continue to attract tourists from around the globe. The tunnel remains a vital transportation link and a significant attraction within the Tateyama Kurobe Alpine Route, embodying the dedication and resilience of those who built it.