During the 5th major maverick uprising, the massive Eurasia colony collided with Earth. This spread a massive amount of the Zero Virus and caused significant damage to the environment by spreading scrap/debris and contaminants around.
For weeks after the colony crashed teams of reploids worked tirelessly to clean up the area. Though the leftover Zero Virus instigated another problem dubbed the Nightmare Incident. After the resolution of the Nightmare Incident, they returned to cleaning up the area.
After the area was cleaned, they installed several environmental control systems to help the area regrow life and sealed the area off to prevent tampering.