A railcar comprises a composite floor assembly. The composite floor assembly comprises a plurality of channels disposed on top of an underframe and longitudinally extending along a length of the composite floor assembly. Each of the plurality of channels forms a recessed portion to allow the flow of liquid. The composite floor assembly further comprises an integral drain pan integrated into the composite floor assembly such that the integral drain pan forms a recessed portion along the longitudinal end of the composite floor assembly. The integral drain pan is configured to accumulate the liquid flown from the plurality of channels.