Renaturation of an unauthorised landfill site gets off to a flying start

9 mars 2022

Site clean-up, a key step in healing the landscape

In Boissy l’Aillerie and Puiseux Pontoise, in the Val d’Oise, clean-up operations have begun. This is an essential step in moving to the landscape restructuring phase. The disposal of the 14,000m3 of waste started at the end of January 2022. This should last between 4 and 6 months. ECT bears the cost of this disposal and treatment. 

A look back at the creation of one of the largest unauthorised dumps in the Ile-de-France

  • December 4, 2017: Start of illegal land occupation and intensive dumping activities.
  • May 5, 2018: The Prefecture puts an end to illegal dumping. The entrance to the site is secured by the installation of concrete blocks at the entrance to the farm road.
  • In 6 months: 6,000 tonnes / 14,000 m3 of waste was deposited on the site.

The unauthorised landfill site that has developed in the municipalities of Boissy-l’Aillerie and Puiseux-Pontoise has caused a lot of damage. It could lead to irreparable degradation of the site if no action is taken.

Municipalities helpless in the face of illegal dumping

« The amount of illegal dumping has degraded the site. I would like to thank the Val d’Oise prefecture for taking charge of the case and finding a solution with ECT to restore the site. The fight against this scourge must be based on prevention, by strengthening surveillance and cooperation with law enforcement. Our small communes have no means of reacting to the treatment of unauthorised dumping, which is why it should be considered at the level of the inter-municipalities
Thierry Thomassin, Mayor of Puiseux-Pontoise

« 300 people were occupying the premises in this case. The illegal dumping activities started very quickly, without any intervention to stop the waste traffic. The illegal dump lasted five months and the extensive degradation of the site left the municipality and the owner with thousands of tons of waste. »
Michel Guiard, Mayor of Boissy-l’Aillerie

Inert soil inputs for an ambitious project

A broad consultation was carried out: 

  • The private owner.
  • Cergy-Pontoise Agglomeration.
  • The municipalities of Boissy-l’Aillerie and Puiseux-Pontoise.
  • The Val d’Oise department.
  • The decentralised services of the State.

Thus, it was determined that the site had sufficient available surface area to provide an adequate volume of inert soil. The purpose? To carry out a qualitative, agricultural and landscape project. The reuse of inert soil provides ECT with financial capacity for the project. The challenge is precisely to balance the costs of waste disposal and treatment and the renaturation of the site with the volume of land received.

ECT has several tasks to carry out in the rehabilitation of the illegal dump:

  • Support in taking into account urban planning and environmental constraints related to the PLU (the local urban plan). In consultation with the Val-d’Oise (CD 95) and the State services.
  • Financial and technical responsibility for the removal and processing of waste.
  • Quality redevelopment of the site through a development permit. The development permit is examined by the municipalities. It is accompanied by an environmental authorisation request (Water Law in France) examined by the State services.
  • The disposal and treatment of this waste.

An ambitious landscape restructuring project

  • The project provides for the reconstitution of agricultural areas and the recreation of a mosaic of natural environments (grassy, shrubby and wooded).
  • It takes into account, on a scale-up basis, the land, heritage and environmental constraints specific to the site and the NRP framework.
  • Given the current instability of the slope, the project proposes to consolidate it by filling it in, while at the same time restoring suitable hydraulic management.


An ECT site becomes a favourable environment for the Eurasian stone-curlew bird


ECT teams and DiRiF ecologists have recreated a nesting area for the Eurasian stone-curlew bird on the ECT site in Villeneuve.


The former landfill site will give way to an agricultural, landscape and hydraulic renewal project within the framework of the Parc Naturel Régional du Vexin Français.