Abstract: Contamination of the sampling portion of an observation well is avoided while providing axial float between the observation well cover and observation well liner by this observation well cover. The observation well cover includes a manhole ring that is set in a raised area of concrete. A manhole cover is fit on the ring and a liner cover fits underneath the ring. The liner cover has a trap to collect contamination. The walls of the screen cover slidingly mate with a wall and, of an 8-inch to 12-inch observation well liner and, respectively. The inner wall of the trap access hole slidingly mates with the outer wall of a 2-inch or a 4-inch observation well liner. This observation well cover provides axial float of the liner relative to the observation well cover while maintaining sealing integrity.