Renovation Phase 2

The submission of the planned remediation phase to the state authorities (responsible under the ALSAG act) in April 2026 marked a decisive step toward the long-term containment of the contaminated site S23—the "firefighting training ground"—at Salzburg Airport. The goal of Phase 2 is to permanently prevent the leaching of PFAS from the contaminated subsurface into the groundwater.

The core of the planned measure involves constructing a U-shaped diversion wall using the narrow-wall method, covering an area of ​​approximately 19,000 m². This technical barrier encloses the contaminated zone and diverts the entire groundwater flow around the designated PFAS-contaminated site, thereby permanently preventing groundwater from flowing through the contaminated soil mass and leaching out PFAS.
Additionally, the surface of the designated PFAS-contaminated site will be sealed with a 2.5 mm thick HDPE geomembrane to prevent further mobilization of PFAS caused by infiltrating rainwater. Contaminated soil near the surface is to be excavated and disposed of in a regulated manner.

A hydraulic containment system for the groundwater will be implemented within the diversion wall. Groundwater will be pumped via 12 wells and routed through a groundwater treatment plant. The treated groundwater will then be returned to the aquifer in a controlled manner via an infiltration trench located outside the designated contaminated site. A separate infiltration system will be constructed to handle rainwater accumulating within the area enclosed by the diversion wall.

The remediation method now being adopted to secure the contaminated site was identified as the best implementation option following a comprehensive analysis of alternatives conducted in 2022 in collaboration with the Federal Environment Agency. From today’s perspective, Phase 2 entails securing the contaminated site. The hydraulic containment system will remain in permanent operation—likely for decades—following the completion of construction work, as will the groundwater treatment plant, the aforementioned cut-off wall, and the surface seal. Furthermore, monitoring to determine PFAS concentrations in the groundwater flow will continue. These measures are designed to prevent further PFAS from entering the groundwater, thereby facilitating a gradual reduction in groundwater PFAS concentrations. Consequently, the hydraulic containment system and the groundwater treatment plant will remain in operation for an extended period. As the reduction process is very slow, operations are expected to continue for decades.
Operational experience gained during Phase 1 has been directly incorporated into the design of the new groundwater treatment plant: given that the groundwater body in the eastern airport area exhibits unfavorable hydrochemical characteristics—specifically elevated iron and manganese concentrations—a key focus of the design is raw water treatment (involving iron and manganese removal and oxygen enrichment of the extracted groundwater) as a preliminary step to the actual PFAS removal process using activated carbon filters.

As is to be expected with a construction project of this magnitude, noise and vibration impacts will occur—particularly during the main construction phase, and especially in connection with the installation of the cut-off wall in 2028 and the surface sealing in 2029. Consequently, all construction activities will be continuously monitored and overseen by experts specializing in environmental medicine and noise and vibration control.

Local residents will be informed prior to the start of construction, and measures will be taken to document the condition of surrounding buildings. A central point of contact for affected parties will be established for the duration of the construction phase, supported by comprehensive documentation and continuous noise and vibration monitoring. Detailed information will be provided in a timely manner once the specific schedule has been finalized.