Abstract: A hatch cover assembly for an access port includes a hatch which is adapted to cover the access port and a mechanism for applying a generally vertically-directed force to the hatch to raise it upwardly off the port, while maintaining the hatch in a generally-horizontal attitude. The assembly also includes a mechanism for mounting the hatch on the access port so that the hatch may be rotated about a generally vertical shaft from a closed position which covers the port to an open position which exposes the port, while avoiding any non-pivotal horizontal movement of the hatch with respect to the access port.