Facts
The CEVA project (Cornavin-Eaux-Vives-Annemasse rail link) provides for a new station at Eaux-Vives, on the site of the former station, whose square is the subject of major works.
On 24 July 2015, the Transports publics genevois (TPG), appellants, asked the Federal Office of Transport (FOT) to approve the plans for a new tramway stop on the route de Chêne, at the level of the Eaux-Vives station, and a new tramway turnaround loop for operational incidents, running through the rue de Savoie, replacing the existing loop on the avenue de la Gare des Eaux-Vives. The project is located on the public domain of the Commune of Geneva and concerns tram line 12, Roches-Amandolier section.
Put to public inquiry from 2 to 31 October 2015, the project gave rise to the objection of several residents (hereinafter: the objectors or [A.] et consorts), who did not contest the new tramway stop but the turnaround loop planned in the rue de Savoie.
The cantonal opinion of the General Directorate of Transport of 17 December 2015 was favourable, notably on the basis of the Service de l'environnement et des risques majeurs (SERMA), which noted the need for coordination with the City of Geneva, owner of the rue de Savoie, whose mandatory remediation had to take place no later than 31 March 2018. The Federal Office for the Environment (FOEN) considered on 17 February 2016 that the project constituted a modification of an existing fixed installation, with no measures to be provided other than those integrated into the project.
By decision of 6 December 2016, the FOT approved the project with conditions and dismissed the objections. It considered that only the noise of the chemin de Granges-Canal was to be remediated by the Commune of Chêne-Bougeries, and not that of the rue de Savoie. It held that releasing the esplanade and maintaining the functionality of the TPG network constituted important public interests, that no other option was realistic, that the immission limit values (ILV) were exceeded but not the alarm values (AV), and that the additional nuisances did not reach the perception threshold within the meaning of the Ordinance on Protection against Noise (NAO).
On 23 January 2017, the objectors appealed to the Federal Administrative Court (FAC). During the investigation, the TPG produced a corrected version of annex 5.2.6 b of the environmental impact statement, and the effect of the phono-absorbent surfacing planned on the rue de Savoie was added. By interlocutory decision of 24 January 2019, the suspensive effect was partially lifted.
By judgment of 30 April 2019, the FAC partially upheld the appeal and remitted the case to the FOT. It held that the ILV were exceeded in the rue de Savoie and that the modification of the installation had to be classified as notable; the FOT should therefore have examined whether the simultaneous remediation of the street was feasible so that road noise complied with the ILV by day and by night, and, failing that, verified the conditions for granting exemptions. For the remainder, the appeal was dismissed.
The TPG appeal to the Federal Supreme Court by way of public law appeal and request the annulment of the FAC judgment and the confirmation of the FOT approval decision of 6 December 2016. The FAC waives submitting observations. The FOT concludes that the appeal be upheld, the FOEN considers that the FAC applied the criteria of ATF 141 II 483 (Grünau judgment) too strictly, and the cantonal Department of Infrastructure and the City of Geneva adhere to the TPG submissions. The respondents conclude that the appeal be dismissed.
Considerations
As to admissibility, the Federal Supreme Court notes that the contested judgment, which remits the case to the lower authority, has an interlocutory character and is admissible only under the conditions of art. 93 para. 1 let. a or b FSCA. It holds let. b applicable: upholding the appeal would immediately end the proceedings and avoid a lengthy and costly evidentiary procedure, since the remittal would require examining the remediation of the rue de Savoie in connection with a City remediation project at the scale of the district, requiring new studies, new intervention by the authorities and a supplementary public inquiry, with considerably higher costs.
The Federal Supreme Court accepts the TPG's standing to appeal within the meaning of art. 89 FSCA. Although an institution governed by public law, the TPG do not act in the exercise of public authority but are affected in the manner of a private party by the implementation of a rail project falling within the exercise of their concession, and the contested judgment directly concerns their project.
On the merits, the Federal Supreme Court recalls the legal framework: new installations must comply with planning values (art. 25 EPA), existing installations must be remediated (arts. 16 and 17 EPA), and notably modified installations are subject to simultaneous remediation under art. 18 EPA and art. 8 NAO, with compliance with the ILV and not only the alarm values. The qualification of a notable modification rests on an overall approach, taking into account the foreseeable increase in immissions, the impact on the substance of the structure, costs, the duration of works and the extension of the installation's lifespan, reconstruction always being notable (ATF 141 II 483).
The Federal Supreme Court notes that the modification will not result in higher immissions, that the purpose of the street does not fundamentally change, that the road structure remains similar and that the works are in substance maintenance. It distinguishes the Grünau judgment, where the entire structure was to be replaced on a motorway section of more than one kilometre, whereas here the rue de Savoie measures only about 100 m, forms part of a broader rail project and constitutes a…