Beyond the region's tallest pier, the team also maintains the Yuanchi Railway Bridge. A 235.8-meter fully enclosed sound barrier — the first of its kind on a high-speed railway in Northeast China — shields the habitat of a rare duck, the nationally protected Chinese merganser, acting like a silent coat for passing trains and minimizing noise impact on the surrounding ecosystem.

On subzero nights, with headlamps cutting through the darkness, the young inspectors move methodically along the bridge.

Chen Boyu, who has been on the job for less than two years, still recalls team leader Wang's advice: "The lighting at night is poor, so you need to inspect even more carefully." Every column, panel unit, and bolt is scrutinized, ice buildup and wind damage carefully noted, as the team balances precision with speed in the freezing wind.

"Most of what we maintain serves passengers," Jiang says. "But this sound barrier protects wildlife and the environment. That feels different."

Their work blends endurance with technology. Drones rise from snowy embankments, scanning towering piers, slopes, and tunnel entrances, while rebar detectors and crack-measurement instruments complement hands-on inspections. Real-time images stream back to handheld controllers, revealing hairline cracks and subtle defects that would be nearly impossible to spot with the eye alone.

"Subtle cracks or hidden defects that are difficult to see with the naked eye can now be quickly detected using drones," Chen explains.

Even before the railway opened, this team of post-2000s workers helped build a "bridge and tunnel gene database", collecting nearly 50,000 structural parameters. That data now serves as a benchmark, sharpening inspection efficiency and accuracy, and ensuring that every train gliding across the valley does so under the vigilant eyes of a generation that guards both infrastructure and the environment with equal care.

By day, they scale piers; by night they patrol sound barriers. Their work remains largely unseen. Even family members struggle to describe exactly where they work — somewhere in the wind and snow of Changbai Mountain, somewhere 100 meters above a frozen river, somewhere inside a dim concrete cavity long after midnight.

Yet every early departure, every careful tap of a hammer, every bolt rechecked is part of a quiet discipline. The trains that glide across the valley at dawn carry tourists, commuters and opportunity. Beneath them, in the cold and darkness, a generation born after 2000 keeps watch — measuring safety in footsteps, and guarding the line with patient precision.