> Now he is demanding that we pay $2400 to have the driveway re-surfaced or he'll sue us.
Work to turn an instance of conflict, into a collaboration. Take the emotion out of the conversation. But do try to talk this out first.
On this subject, Stuart Diamond is brilliant > https://vimeo.com/43817099
Sounds like you need to add some kind of arbitration clause to your service contract. Also, If you've been paying premiums for 10 years I don't see why you would at least talk to your agent.
Do not take legal advice from HN (or anyone else on the internet). Ask your business's lawyer (and your insurance company).
What about bleach or hydrogen peroxide? No idea if that would work?
Consider it 2400 spent on learning how not to fuck up a driveway--just make them sign an agreement say "Hey, after this, you forfeit further claims to compensation".
And now, in the future, you know to put down a tarp or whatever to keep this from happening.
If your usage of chemical solvents was not legal (given that the waste going down a driveway would generally flow to a storm drain in most driveway scenarios) you may have other vulnerabilities here.
An engineer's solution:
One can of white spray paint.
found this stuff:
http://www.clean-rite.com/purplepower_driveway_and_concrete_...
Here's the thing... It's a "driveway" and it's unreasonable to expect no wear or discoloration on untreated concrete (ask any concrete company if that is reasonable and they will tell you "No").
If he was concerned about that he should have moved his car to a place on his property where this could not occur.
If he did not tell you that was a concern before you started, and especially if he parked the car there and told you to clean it there, I don't see how he has a case.
I would check to see if he's done this kind of thing before (and I'd be surprised if he hasn't) because that is evidence that he purposely set you up. If he has bring those records to court with you there's a good chance a judge would toss his case.