Tom Cook’s article in the Baton Rouge Business Report provides helpful insight on the meaning and application of FEMA’s “substantial damage” standard to Baton Rouge homeowners affected by the August floods. Cook explains that determining “substantial damage” is a bit of “a mystery,” and that online research of the term may prove bewildering.
In short,

The East Baton Rouge City-Parish government has launched the Private Property Debris Removal program, authorizing debris removal teams to collect flood debris extending 30 feet beyond the public right-of-ways and onto private properties. FEMA authorized the City-Parish to move forward with the program as long as homeowners sign a right-of-entry agreement. To participate, homeowners must