As a GC who has had many dealings with County Health Dept. I would suggest you contact a Septic tank installer first, maybe ask a couple, and ask for suggestions.
Many years ago our local installers here could do minor repairs etc without a HD permit. Not any more. They can pump out w/o a permit, but any repairs etc. now w/o a permit means their license if caught.
I would contact HD as last resort. Once that ball gets rolling you can't stop it.
First be sure you are not violating any zoning laws by putting the RV there and living in it, then deal with the waste.
