MAP15: Waste Disposal is the fifteenth level of Icarus: Alien Vanguard. The level is set within the waste management facility of the exploration cruiser, Icarus, and it was designed by Ken Simpson and Jim Kennedy. It uses the music track "Heart of the Hive" by David "Tolwyn" Shaw.
After leaving the closet you started the map in, ride up the barrier that drops on approaching. The northern wall has brown borders; you can walk through this wall to find a light amplification visor (sector 272). Doing so causes the barrier to lower again. Note that if you end up west of the barrier when it rises, it will be impossible to obtain this secret.
Beyond the barrier from secret #1, descend the southern stairway. Its southern wall has two misaligned portions that can be opened, revealing alcoves: While the western one hides a rocket launcher, the eastern one (sector 268) contains a teleporter. Enter it to get to the cage in the southwest of the map, where you can obtain a partial invisibility. Use the right (western) teleporter to return to this secret or the left (eastern) one to be teleported to the room east of the processing area (the large room with a pool and a rocket launcher on a pole in the center), where two sergeants await you.
Descend the northern stairway beyond the barrier mentioned in secrets #1 and #2 and follow the passage to the north, where you see a soul sphere behind bars. Follow the branch to the west where you find a recess in the eastern wall with a light at the bottom. Push it to find a chaingunner in a small room (sector 125), where you open the northern piping to reach the soul sphere.
In the room with the bloodfall "stairway," there is a closet (sector 52) containing a shotgun that is impossible to access except through the idclipcheat.
Before passing the barrier mentioned in official secret #1, lower the waterfall to gain a blue armor.
Secret exit: In the stone room where you acquire the red keycard, the northern side of the teleport out of the room has a different texture than the rest. After grabbing the keycard, step onto the teleporter from this side and you will be taken to a different-looking exit hall with a simulation portal marked "RESTRICTED" and "TOP SECRET". Open the barrier and step into the portal to go to the secret level, MAP31: Great Balls of Fire.
Due to a secret being impossible to reach, you can only obtain 75% Secrets on this level.