I think you need to talk to an attorney. If you have a good case (I think you do), they may take the case on contingency which means if you don't win any money you don't owe them anything. You should be able to recover their fees as well.

As stated previously, my understanding is if their construction caused a drainage issue for you they are responsible to remedy it or pay you to do so.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.