Yes, there is a pond nearby. It probably came from there.It's too hard to tell from just looking at the shell, but it's most likely some sort of slider or painted turtle. They are an aquatic species. Do you have a pond near your house where it may have come from?
It actually left the other day from the container it was kept in.Please post a pic of the underside and head and legs if possible. If it turns out to be a native turtle, then it should be let go. If there is a pond/lake/River near the home it was found, then that would be a good spot to let it go.