Boston police report they walked in on a man-made staircase waterfall, underage drinking and an unlicensed nightclub when they checked out a wild party late Sunday night at a MIT frat house near Kenmore Square.Phi Delta Theta is licensed by the city as a dormitory with a maximum of 39 occupants; however, investigators report there was closer to 116 revelers present shortly before midnight Sunday before they shut the Labor Day weekend celebration down.