@Phoenixshade35 So it appears that not only has this design been done before, but after some research on my end it's quite the popular design. However, to save you some time, these are the inner workings of the base.
1. Zombies dash across corridor and over the powered garage doors. Any zombies that fall into the trench around the base end up pathfinding up to the ramps adjacent to the base's entrance/exit.
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2. On the other side, you watch the zombies approach. Above or beside you would be a lever where you power/unpower the garage doors. Behind you would be a room/compartment where the generator bank sits, and in front of you sits a vault hatch door to keep the brain-eating undead at bay.
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3. You flick the switch and send the zombies back to the underworld from whence they came... Or at the very least, a very deep, dark pit with an array of traps lined at the bottom.
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4. You flick the switch to seal the zombies to their unfortunate fate, and rinse and repeat.