The construction of the subfluvial tunnel, the flagship project of the Provincial Council designed to connect the Right Bank and the Left Bank under the estuary, has generated significant controversy. This is particularly true among residents of the Antiguo Golf area, who believe they will bear the brunt of the noise and disruption from the works. With a budget exceeding 448 million euros, the project's execution is expected to last six years.

Organized as the Arpa (Artaza Parkeko Herritarrak) association, residents have filed a lawsuit with the Administrative Litigation Chamber of the High Court of Justice of the Basque Country. They are directly seeking the annulment of the infrastructure project. They argue that it was approved with «serious breaches of administrative and environmental legality», which, in their opinion, could even lead to its «nullity in full law».

Furthermore, they are immediately requesting the «precautionary suspension» of the works to prevent what they consider «irreversible» damage to citizens and the environment. They claim there are several «errors in the processing», such as the lack of a series of «mandatory authorizations». «The project has been approved without essential mandatory reports, such as those from the Basque Water Agency, Coasts, or Air Safety», they state.

The plaintiffs warn that the environmental impact study «does not justify that the only solution to connect the two banks is the construction of the tunnel». It does not provide other alternatives, and the effects of the pollution it will entail are not evaluated, even though the report already indicates that the construction will lead to an increase in traffic and emissions in the medium term. This, they point out, «contradicts European policies on sustainable mobility and the fight against climate change».