On this job we were called out to correct a water problem that was misdiagnosed as a moisture problem. When I first looked under this home I noticed a very nice 12 mill reinforced vapor barrier that was covered in mud and floating. Apparently the homeowner hired an extremely well known, nation-wide termite company to deal with this problem and their solution was a vapor barrier.
In my experience I've noticed that vapor barriers are only good for moisture, not standing water. When standing water is present vapor barriers in most cases only worsen the problem and in many cases wind up being pulled out and trashed. Unfortunately this seems to be a big problem in central Tennessee as I'm seeing companies recommend vapor barriers to correct drainage problems on almost a daily basis. Hopefully the pictures here will speak for themselves.
Folks, if you've got a standing water problem, please don't be sold on the idea that putting some plastic down will fix this!