Abstract: A lid assembly for a rectilinear bin includes two lid panels independently movably mounted to the bin such that when the lid assembly is in a fully-closed position, inner longitudinal edges of the panels abut each other so as to give the closed lid assembly an arched configuration. In the open position, each lid panel lies vertically along the exterior of a corresponding bin sidewall. Each lid panel is movable along tracks provided in the bin structure longitudinally outboard of the lid assembly by means of track wheels provided at each end of the panel's inner longitudinal edge. Each lid panel is movable between its open and closed positions by means of actuating arms each pivotably mounted at one end to the panel's outer longitudinal edge, and rigidly mounted at the other end to a rotatable horizontal lid actuation shaft mounted on the exterior of a corresponding bin sidewall.