A BTR controller witnessed an SOP violation when a supervisor working position failed to follow local procedures during an opposite direction operation.

Narrative

Aircraft X was inbound on visual approach to Runway 13 from the Southwest. A PC12 was cleared for takeoff from Runway 31 with a turn to 360. Aircraft X intercepted the final at four miles and was told that traffic was taking Runway 31 for departure. Our local SOP states that opposite direction departures must be airborne and established in a turn prior to the inbound aircraft being established on a five mile final. The SOP specifically states that visual may not be used. When it became apparent that this was going to be very close; I expected the PC12 to be turned further to the East so they would have had more room between them; but I just heard the FLM (Flight Line Manager) switch the aircraft to departure. At no time did I ever hear him say that he had both the aircraft in sight on the frequency; nor do anything to comply with the SOP; nor try to take any action that would have made it less close. We should not let Supervisors who have had no previous Tower experience check out at minimum qualification times. They need to be more knowledgeable about the rules because they are certifying officials.