Based off of the mission Arbiter when the Gas Mine station is in free fall. Where you also fight the Heretic leader Sesa 'Refumee at the end of the mission.
I have the areas where they push the cargo on the energy belt things as teleporters at the end of the tunnel areas that will send you back at the top areas. They are color coded for map orientation.
Would like to thank NOBLE706 for letting me use the forge object: Halo Reach Type-31 Seraph. Did some modifications on it.