Installing door on crawlspace access
Your photo doesn't show much of the area to the left of the opening, but from what is visible, this opening seems a perfect fit for a sliding door. The framing would be above and below the opening, perhaps a stop plate to the right of the PVC, but the door would have a slot to engage the pipe. If extreme sealing is required, weather stripping applied to the stop plate and around the door cut out should give a good closure. 

The bottom support framing could contain a long door slide to provide reduced friction, or simply wax the slot in which the door slides and the mating edge of the door. Moisture may come into play if the wood swells after time and should be considered when constructing the assembly.