I have a similar issue currently, although it's a much larger area. I was concerned about the dreaded "Wetlands" designation.I contacted our companies law firm which has a permitting / environmental lawyer. He advised me to contact an environmental engineer to take a look at it to see what advice he would have. The engineer was very helpful but he took one look at it and said he is 99% sure that it would be considered a wetland. He did give me a contact at the Army Corps of Engineers that he said would be helpful and also be happy if I contacted them before I did anything. The engineer also didn't charge me anything for coming out and taking a look. Now I am on the fence on contacting the Corps. I was advised that I might only need a simple national permit or it might get much more involved for what I want to do.

BTW.. The biggest issue I have come up with concerning a wetland is adding fill, which is a big no no.