A Herrenknecht Mixshield tunnel boring machine 13.5m in diameter broke through into its target shaft on 26 October 2026, completing the first tunnel built under the Panama Canal with a TBM, Ground Engineering reported on 9 November. Herrenknecht announced the breakthrough in a release dated 4 November.

From the start of tunnelling in September 2024 to the final breakthrough, the crews excavated 4.5km of tunnel for Metro Line 3, passing under the canal at a depth of up to 65m below sea level. The Tunnelling Journal reported that the machine, named Panamá, made its final breakthrough at Albrook. The tunnelling crews came from the HPH consortium of Hyundai Engineering & Construction, Posco Engineering & Construction and Hyundai Engineering.

Panama’s president, José Raúl Mulino, said at the celebrations marking the completion of the drive: “This remarkable feat of engineering offers us a groundbreaking solution to the challenges we take on.”

A drive in two stages under a working waterway

Tunnelling began on the western shore of the canal in September 2024, according to a Herrenknecht release published on 12 February 2026. The crossing under the canal was completed without any problematic incidents, the manufacturer said, and the machine reached a breakthrough at the future Balboa metro station, east of the canal, on 2 February 2026.

That left about 1.5km to the final breakthrough in October. Jürgen Hoss, head of project management at Herrenknecht, said the last stretch ran through ground conditions “that are rather atypical for a Mixshield” and “did not present our client with any major challenges”.

Peak performance on the drive reached 150 segment rings, or 300m, in a month. The teams achieved that rate in October 2025, Herrenknecht said.

The ground along the route includes sandstone, siltstone, tuff, clay and sand, breccias, mudstone, pyroclastic rocks, basalt and andesite. Herrenknecht said the specifications stipulated that the tunnel construction must not compromise the operational safety of the Panama Canal at any time, and that the HPH consortium chose a Mixshield in view of the complex geology and high groundwater pressure over 60m below sea level.

Over 4,500 sensors and an accessible cutting wheel

The machine has a diameter of 13,460mm, cutterhead drive power of 5,600kW and torque of 26,616kNm. Herrenknecht said the large diameter was planned so the metro could run through the tunnel on two tracks, and described the machine as the largest of its kind in Latin America.

Herrenknecht engineers fitted the machine with an accessible cutting wheel for the canal crossing, which allows the cutting tools at the front of the wheel to be changed from the rear under atmospheric pressure. Hoss said the concept “has once again proven its worth”, and that the Mixshield type had been developed “to such an extent that even a project like the one in Panama can be carried out safely and efficiently”.

“The TBM alone is equipped with over 4,500 sensors,” Hoss said in the February release. “Keeping track of their data and using them to control processes is a challenge. The tools and dashboards from Herrenknecht.Connected are the solution. This gives everyone involved in the project access to real-time data from the ongoing tunnelling – from the client and partners in the international joint venture to our team in Germany.”

Francisco Avila, chief executive of the Herrenknecht national company in Panama, said the company supplied equipment and services alongside the machine: “In the end, it was a large package that we offered and put together specifically to meet the customer’s requirements. For example: formwork for the segments to line the bored tunnel, a separation plant for processing the excavated soil, three multi-service vehicles for tunnel and construction site logistics, and systems for precise navigation of the huge machine.”

The line the tunnel belongs to

Metro Line 3 will connect the western suburbs of Panama City with downtown, and the 4.5km tunnel is the key structure of the line. Herrenknecht said in February that 150,000 people commute across a bridge every morning and evening on a 25km journey that can take up to several hours in traffic. Ground Engineering reported in November that the line will serve 250,000 commuters who until now have relied on a congested bridge.

César Pinzón, director of Metro de Panamá, said: “Residents of the western suburbs, in particular, will benefit from safer and faster transportation, which will save them hours stuck in traffic.” At the ceremony at Balboa station in February he said: “For thousands of residents, this first section is a concrete sign that the promised future is approaching, with fast and safe mobility.”

Dr.-Ing. E. h. Martin Herrenknecht, founder and chief executive of the manufacturer, placed the drive in a run of underwater crossings going back to the fourth Elbe Tunnel tube in Hamburg, bored with the TRUDE machine from 1997 to 2000. “Since then, our machines have crossed, among other places, the Yangtze River in China, the Port of Miami, the Bosporus, the Suez Canal, and an estuary in Hong Kong—where we even set a world record with a diameter of 17.63 meters,” he said.

Herrenknecht’s experience is also being incorporated into studies for a possible tunnel under the Strait of Gibraltar, according to Martin Herrenknecht. “Whether a nearly 40km long railway tunnel at a depth of up to 500m below sea level will one day become a reality remains to be seen. However, projects like Panama show how the boundaries of what is technically feasible can be pushed step by step.”