Inside the city limits of Lancaster, Ca. you mat NOT leave a trailer unhooked from the tow vehicle on the street. You may NOT park your boat, trailer of anytype, or motorhome beside your house unless....you have a PERMITTED concrete driveway added to park on.
No grass or dirt or gravel parking allowed.
Good thing about the concrete is, when the professional installs it for the intended purpose of parking a heavy RV, it won't sink.
From lots of experience, I can say this: parking ANY heavy wheeled vehicle on grass or dirt or gravel that will allow water to penetrate into it will cause sinking.
Best thing to do is do the work necessary to keep as much water out of the area. This means sprinkler water, AND incedental run off that flows there.
And guess what happened to my PCV sprinkler pipes one time !
I like these little facey things.