What if our job is a pipeline job, what would be used as the legal property description? Their could be over 100 land owners where the pipe is to be installed.
Louisiana's Notice of Contract rules are laid out at § 4811 of the Private Works Act (lien statute). Notably, at that section - the legal description of the land where work is being done isn't what's required. Rather, § 4811(2) states that the Notice of Contract shall contain "a complete property description of the immovable upon which the work is to be performed and the name, if any, of the project." Still, since more than a street and mailing address is required, it makes sense that most parties generally include a legal description.
As for how, exactly, to provide a legal description for a series of properties that will be home to a pipeline - that's a bit tougher. Mechanics lien laws don't always make it easy to comply for work that spans a vast number of properties. If there's an easement or other document providing a singular description of the land that the project will span - perhaps within the agreements with the numerous land owners or some other party, or within financing documents for the agreement - that may be sufficient.
But, ultimately - as long as the description of the land where work is being done is more specific than a mailing address (such as the inclusion of a number of addresses, coupled with a more distinct description of the land), it may well be sufficient.
Finally, because this is such a complex and unique issue, it would likely be useful to consult a Louisiana construction lawyer and ask them to provide legal advice on the issue. With all of the relevant documents in hand, they might have a good plan of action for succinctly describing the work.