When the operator does not wish to submit to his obligation to restore a site on which a classified facility was operating, the third-party applicant procedure allows him to transfer this responsibility, in whole or in part, to a third party. The latter will thus assume the costs of this remediation and will in fact become responsible for it for the Administration. It should be noted that, once the substitution is effective, it is enforceable against third parties and the Administration. Finally, the polluter pays principle is not necessarily affected by this substitution, since if the third party were to default and it were impossible to implement the financial guarantees of the latter, the liability of the last operator could be brought into play.

This procedure was created by the law n°2014-366 for access to housing and renovated urbanism of March 24, 2014, known as the ALUR law, and by its application decree n°2015-1004 of August 18, 2015. The purpose of this procedure is to allow the operator who wishes to get rid of his obligation to still fulfill it without appealing to the state services, it is to allow the rehabilitation to be done. This also allows the purchaser of the site who would like to change the use made of it to carry out the necessary work directly, thus avoiding an additional cost and a much longer procedure. Indeed, before this possibility of substitution, the last operator had to proceed to the rehabilitation measures required for an industrial use similar to his own before being able to sell the site to the purchaser who then had to carry out the work necessary for the change of use he wished to make. Finally, this possibility of transferring the rehabilitation to a third party depicts a certain willingness on the part of the State. Indeed, there is a scarcity of land available for quarrying and other ICPE sites, so many sites that were previously ICPE sites remain abandoned due to the industrial use similar to the previous one that was to be made. With this procedure, we will try to encourage the reconversion of these available grounds.
It should also be emphasized that this practice is mainly aimed at specialized companies with the technical and financial capacities necessary for these rehabilitation and redevelopment operations that not all operators necessarily have. The idea here is to help companies that would be suited to this type of work to take over from operators whose technical capacities may not necessarily be geared towards rehabilitation. This is in line with one of the legislator's wishes, i.e. to obtain the most complete rehabilitation possible in order to enable the site in question to be reconverted and to be able to use the land still available as much as possible.

The third-party substitution procedure contains six steps.
The third party must be voluntary; the transfer of the reclamation obligation cannot be imposed on him. The first step is therefore to ask the industrialist for his agreement to the transfer of the reclamation obligation, but also to the future use of the site.
It must then obtain the agreement of the owner of the land, if the latter is not the last operator, and of the competent planning authority if these agreements were not previously obtained during the procedure for the cessation of activity on the site that is the subject of the application. The owner and the authority have three months to give a response, if none is made, they are deemed favorable.
The third party will then submit its proposal for future use to the prefect, which will be accompanied by the agreements of the last operator, the owner and the competent planning authority. Following this submission, the prefect makes a decision, taking into account the use made of the land adjacent to the site and the town planning documents. The prefect has two months to give his opinion, after which time his lack of response will be considered as a refusal of the proposed future use.
Once the proposed future use has been accepted by the Prefect, the third party applicant may submit a request for substitution. The application shall include the rehabilitation brief, an estimate of the amount and duration of the work and a document presenting the technical and financial capacities of the third party applicant. The prefect has four months to decide on the request, after which time his silence is considered a rejection.
Once the request for substitution has been accepted, the prefect issues a substitution order defining the work to be carried out, the amount, the duration and the deadline for the third party to provide financial guarantees. This amount corresponds to the cost of the planned work.

Once the work has been carried out, it is recorded in a report by the inspector of classified installations, thus allowing the financial guarantees to be lifted.
However, it is not enough to determine who is responsible for the obligation, it is also necessary to legally define this responsibility in order to guarantee the application of the obligation to restore the site in a fair manner.