North Sea power cable project sparks water and environmental fears on Langeoog

Plans to Route Power Cable Beneath North Sea Island of Langeoog Spark Environmental and Local Concerns

Environmentalists and residents of Langeoog are raising alarms over proposals to lay a high-voltage power line beneath the North Sea island. The Protection Association for the German North Sea Coast (SDN) has warned of "significant risks to nature, drinking water supplies, and tourism." The local council fears the island's underground freshwater reservoir could be jeopardized. Public consultation on the "BalWin5 Seaside" project documents will remain open until the end of April.

The initiative aims to transmit electricity from multiple offshore wind farms to the mainland. Grid operators Amprion and TenneT have selected a route passing beneath the eastern part of Langeoog.

Island's Freshwater Supply at Risk The crux of the issue for residents: the cable is set to be installed using controlled horizontal directional drilling, running just beneath—or potentially through—a critical freshwater lens under the island. Thanks to this natural reservoir, Langeoog has so far avoided relying on a pipeline from the mainland for its drinking water.

These lenses form when rainwater seeps into the island's sandy soil, collecting above denser saltwater that seeps in from the sea. The freshwater, being less dense, effectively "floats" on top of the saltwater below.

Expert Reports Deem Project Safe—But Locals Remain Skeptical Langeoog has multiple freshwater lenses: one is currently tapped via several wells for drinking water, while those in the east remain untouched. "At present, the eastern freshwater lenses play no role in the public water supply," confirms the Oldenburg-Ostfriesland Water Association. However, they could become vital if conditions for water extraction in the island's west deteriorate.

The water association is now demanding a documentation and monitoring program to record any impact the cable installation may have on the freshwater reserves.

Amprion and TenneT commissioned independent assessments to evaluate potential effects in advance. Engineering firm Burmeier concluded that the tunneling beneath Langeoog would have "no significant impact on the size of the freshwater lens or the chemical, physical, and biological properties of the groundwater."

That said, the report acknowledges that minor, localized changes to groundwater quality—caused by drilling fluid, filtrate water, or temperature increases near the cables—cannot be entirely ruled out. "However, since these effects are expected to be limited in scope and/or temporary, the freshwater lens as a whole will not be compromised," the engineers stated.

"These Are Just Model-Based Assessments" Langeoog's mayor, Onno Brüling (CDU), remains unconvinced. Drawing on his professional experience, he cautions that "such models often bear little resemblance to reality.""For us, the risks are unpredictable," Brüling argues. If Amprion and TenneT are so confident in their projections, he suggests, they should guarantee the island's water supply.

"Had the priority from the start been to minimize disruption to the Wadden Sea, alternative routes—such as near the Jade shipping channel—could have been chosen," says Ulrich Birstein, deputy chairman of the SDN. Though such a detour would substantially increase the cable's length.

Brüling stresses that the community is not opposed to climate action or the energy transition. "This is extremely important to us," he says. But a resource as vital as drinking water must not be put at risk. "If I didn't speak up, I'd be failing in my duty," the mayor asserts.

The SDN criticizes the planned cable route for cutting through the heart of the Wadden Sea UNESCO World Heritage Site, affecting core protected areas. "If the goal had truly been to disturb the Wadden Sea as little as possible, they would have explored other options from the outset," Birstein insists. The alternative, however, would mean a far longer cable.

Planners justified the wind farm grid connection by citing the "overriding public interest," arguing that it outweighed concerns about constructing in a sensitive and ecologically valuable natural area. "That's a killer argument," says Birstein, noting that many of the wind farms in question have yet to be developed.

Yet the expansion targets are ambitious, creating a sense of urgency. Installed offshore capacity along Germany's coast is set to rise from 9.7 gigawatts at the end of last year to 30 gigawatts by 2030—a push to reduce the country's reliance on fossil fuels.

The construction site where the power line comes ashore lies within the "Ostfriesische Seemarsch between Norden and Esens" bird sanctuary. Birstein warns: "Even a temporary intervention is still an intervention."

However, an expert assessment by Oldenburg-based environmental consultancy IBL-Umweltplanung, prepared for the planning approval process, concludes: "Any impairment of the area's conservation objectives and protective purpose can be ruled out." The bird sanctuary itself, it argues, will not be adversely affected.