As a general rule, when they exceeds a certain number of places, livestock farms are subject to a very restrictive ICPE authorization which mainly provides an environmental study and a public report. With this “immediately” applicable decree, when regrouping and modernizing livestock farms that fulfill certain conditions, those farms will be exonerated from the environmental impact study and the public report.
The simplified regimen will only be conceded to regroupings that do not cause a “global animal increase” of over 5% of the limit, which for swine and poultry, the European threshold was determined to be 2.000 fattening pigs, 750 sows or 40.000 birds. Regroupings, supervised by the prefect, must not cause any modification sensitive to the dissemination plan, assuring sufficient measures to control impact, such as damages to the vicinity and pollution of the air and aquatic environments.
http://agriculture.gouv.fr/le-president-de-la-republique