If all work really is to take place within the bounds of the already designated easement, then there should be no "affected landowners." You already have an easement.  However, 25 feet does not leave you a lot of room to work with.  If the slope is going to encroach on anyone's lawn, or if people do not realize the extent of the right of way and have planted their lawn to the edge of the traveled way, or if water will run from the ditch onto anyone's land, or if you need to replace culverts under driveways, then it would be wise to try to get a drainage easement.  If someone is unwilling to grant you such an easement, then you know you have to be extra-careful not to affect their land.

We had one situation where we discovered it appeared a culvert under a side road had been intentionally blocked with a boulder when a house was built, so as to avoid having water run where the contractor would then need to put a culvert under the driveway.  Then the person's driveway used to flood every year.  When they told us they were going to have a culvert installed under their driveway, we told them about the blocked culvert, and they happily took care of that at the same time to help solve their flooding problem.

But not everyone is that cooperative!  Contrary to the belief that "It's easier to ask for forgiveness than to get permission," you will need to get along with your neighbors in the future.  It's better to ask politely than to make assumptions or bully your way through and end up with festering resentments.

Does anyone else have experience with this?