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The case

The FirstLight Power Resources hydro-electric plant lies deep inside a mountain in Northfield, USA. Here, Mammoet had to deliver a 255-ton transformer from its factory in Austria on the other side of the Atlantic. At 215 meters underground, the transformer had to be moved down through a steep and narrow tunnel. To make absolutely sure it would fit, a test run was carried out inside the mountain with a full-scale wooden mock-up of the transformer. By leaving nothing to chance, Mammoet successfully completed the precarious task, keeping downtime for the plant to an absolute minimum.


The biggest challenge of the Northfield project was the delivery of the transformer to its foundation bed in the heart of the mountain. The powerhouse where the transformer had to be installed was 215 meters underground at the end of a tight, steep 760-meter tunnel. Looking to avoid the worst-case scenario of getting stuck halfway at all costs, Mammoet needed a watertight plan to safely deliver the cargo to its extraordinary destination. But before it came to the grand finale, the colossus first had to be picked up at the inland port of Linz, Austria - some forty days earlier.

Managing the entire transport chain to deliver to the heart of a mountain.

FirstLight Power Resources plant Northfield, USA

From Linz, Mammoet transported the transformer on a barge via the River Rhine to the port of Zeebrugge, where it began its cross-Atlantic journey to Newark, USA. Once the transformer arrived at the American port, it was transferred from ship to a specialized railcar and then carried across three states. Using a purpose-built railway siding which was constructed on the jobsite, Mammoet then moved the transformer from the railcar onto the trailer. To doublecheck that the last leg through the treacherous tunnel could be successfully completed, Mammoet had created a life-size wooden model of the transformer. Once the dry-run with the mock-up had been executed without incident, Mammoet proceeded to move the real transformer through the narrow tunnel to safely place it onto its foundation.

day 25 Life-size mock-up of transformer

day 38 Arrival of transformer at Northfield

day 39 A tight fit through the 760 meter tunnel

day 39 Arrival at the underground powerhouse

Getting stuck in the tunnel or missing any of the many hand-over points along the way would have resulted in significant delays that would have disrupted the change-out schedule of the old transformer. In turn, this would have lead to unwanted downtime of the plant. But through careful planning and managing the entire transport chain, Mammoet safely delivered the transformer within the available timeframe.

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