Where to use the Maintenance Pump key in Marathon

TheMaintenance Pump key is one of many keys you can find throughout Marathon and Tau Ceti IV, and as keys often do, it opens a locked door. Problem is, other than knowing it’s somewhere in Maintenance on Dire Marsh, you don’t know exactly where said locked door is. It’s guaranteed to give you some decent loot inside, but it’s possible to spend ages wandering around Maintenance — it’s a big place — without finding the door.