Question
I live in South Louisiana and the Federal govenment has been doing a lot of clean up with machine on wetlands that I own from Katrina. I have a huge live oak in the back of my lot that is about 60" in diameter and about 35' tall. One of the bush clearing machines they were using ground on two of the main roots extending out from the tree. The damage to them is about 3 inches deep and about 2 feet long. Will this damage kill the tree and or what can I do to help it recover.. Thanks for your help.

Answer
Live oaks are real hardy trees and not subject to much rot diseases. The root system are in the first 18 inches of the soil so if the damage was only in the top three inches there will be plenty of roots left not damaged. This amount of damage will not kill the tree and it will recover with little effect. just recover the exposed roots and you should see no health problems from this damage.
If the "clean up" changed the soil and lowered the water table near the tree this may have an effect this summer when the tree needs water.
The general rule is keep work away from the tree twice the distance of the dripline of the foliage. (the dripline is the outer most edges of the limbs and foliage).
I do not think from what you described there will be a problem.