In a decision issued at the end of last year (OVG Niedersachsen, 12 December 2025 – 12 MS 43/24), the Higher Administrative Court of Lower Saxony (OVG Niedersachsen) commented on the requirements for decommissioning bonds (Rückbausicherheiten) to be provided for onshore wind turbines, as well as on the requirements for evidence of structural stability in permitting procedures for onshore wind turbines (Standsicherheitsnachweis). Both aspects are relevant in project development and, in also in a transaction context. We have therefore summarised below the court’s key statements.

Background: An environmental association brought legal proceedings against an emission control permit (permit under the Federal Emission Control Act, or Bundes-Immissionsschutzgesetz (BImSchG Permit)) for three onshore wind turbines. In addition to the amount of the decommissioning bond ordered in the BImSchG Permit, the association criticised, among other things, the requirements imposed with respect to the structural stability of the wind turbines. The court upheld the association’s claims on both points.

Decommissioning costs

The court held that the decommissioning obligation of the wind farm operator to be secured pursuant to section 35(5) sentence 3 of the German Federal Building Code (Baugesetzbuch (BauGB)) covers the wind turbine’s installations locatedbothabove ground and underground. This includes, where relevant also deep pile foundations (Pfahlgründungen). Accordingly, the decommissioningcosts likely required for that purpose must be included when calculating the amount of the security to be provided before the start of installation works.

This standard obligation does not apply only by way of exception if, in the individual case, removal of the piles after the end of operations would be disproportionate. However, according to the court, requirementsare high for such a finding. In the case at hand, the wind turbines were to be constructed in or near a water protection area (Wasserschutzgebiet). Against this background, the court decided that the potentially high efforts involved in proper removal are not sufficient to assume that removal would be disproportionate. Rather, the court stated that it must also be considered how permanently leaving the piles in place and their slow decomposition over the next 100 years would affect the soil or the groundwater.

To put the decision in a practical context: In the past, it was not always clear whether the statutory decommissioning obligation also covers the removal of pile foundations. For project developers, the decision of the court therefore means that going forward they will generally need to assume significantly higher decommissioning costs in case of pile foundations. Investors in projects should scrutinise the decommissioning costs assumed, as the amount of decommissioning security to be provided – and thus the costs of such security – may also increase accordingly.

Structural stability

By virtue of its concentrating effect (Konzentrationswirkung) under section 13 BImSchG, the BImSchG Permit generally also covers the review of a facility’s structural stability under state building law. As the procedure for the BImSchG Permit does not provide for a comprehensive delegation of tasks (e.g., to engineers), the Higher Administrative Court held that the permitting authority may not simply transfer the review of structural stability for statically/structurally complex construction measures to an engineer acting as a delegated public agent (Beliehener) and then adopt that review results in its decision without carrying out its own further review. Accordingly, while the permitting authority may rely on the results submitted by experts, it must also conduct a review of the expert reports, according to the court.

Furthermore, the Higher Administrative Court confirmed that structural stability must also be reviewed and established as part of the permitting decision. While in principle the BImSchG Permit may be issued subject to a condition (Bedingung), the permitting authority is generally obliged to verify the existence of all permitting prerequisites and to confirm them before granting the permit.

Accordingly, the permitting authority may not initially refrain from reviewing structural stability and shift the review that is actually required to a point in time after the BImSchG Permit has been granted (e.g., by way of an ancillary provision (Auflage) that the evidence of structural stability be submitted subsequently prior to the start of construction or commissioning). Under the Ninth Ordinance on the Implementation of the Federal Emission Control Act (9. Verordnung zur Durchffchrung des Bundes-Immissionsschutzgesetzes), this is permissible only by way of exception for documents whose details are not directly relevant to assessing the permissibility of any given facility. An order imposing a suspensive condition (aufschiebende Bedingung) regarding evidence of structural stability is therefore only possible if, at the time the permit is granted, at least a reliable prognosis that the missing prerequisite will be fulfilled within a foreseeable period is possible.

From a practical perspective, the decision once again underlines the importance of the permitting authority itself providing evidence of structural stability. Particularly in complex site conditions, such as pile foundations, the evidence of structural stability will generally need to be available already at the time the permit is granted. Project developers should take this aspect into account in the permitting process in order to obtain a legally reliable permit – and to address, at an early stage, risks arising from potential challenges to the BImSchG Permit and corresponding reservations by investors in the context of a transaction.