I think we're done here. I finally found out who owns the ditch, which is in a utility/drainage easement. It's VDOT. And they required a permit to install a culvert. The contractor who put the culvert in front of my lot didn't get one, and I wouldn't be surprised if he had ever got one. It's not clear how the permitting is enforced. So up to last week we hadn't been able to actually talk to the owner of the company. My son who owns the lot had tried every way possible to communicate with the guy without luck. So I gave it a try and got him on the phone. To make a long story short, he said putting the culvert in front of our lot was no big deal and would cost $2K to remove it. He even had the gall to suggest the future homeowner of the modular could pay for it. I finally told him if he wouldn't take it out, we would.
So this past weekend we used an excavator to dig it up and put it in his front yard, along with a big pile of dirt. This Monday the dirt pile and culvert were gone. I'd like to get some money out of him for the excavator rental and our time, but not sure if it's doable and we don't really what to invest anymore time dealing with this loser.