La. Stat. tit. 19 § 102
Where a price cannot be agreed upon with the owner, any municipal corporation of Louisiana may expropriate property whenever such a course is determined to be necessary for the public interest by the governing authority of the municipality; provided, however, in case of the acquisition of any electric light, gas or waterworks property or plant, or of any railroad property, such determination shall not be conclusive as to whether the purpose of the taking is necessary, which, if contested, is a judicial question to be decided independently by the trial judge. Where the same person is the owner of gas, electric light, and waterworks plants, or of more than one of any one kind of plant, the municipal corporation may not expropriate any one of the plants without expropriating all of the plants within its jurisdiction owned by the same person.
La. R.S. § 19:102