After completing Steps 1 and 2, the players must wait for Excavator Pi to breach Tunnel 6. It should be noted that this can happen at any time in the game, and it is not a guarantee that this will occur after the completion of the first two steps. In fact, it can take many rounds before it happens.
When the automated voice notifies you that Excavator Pi will breach Tunnel 6, ignore the alarms until it has been breached. After the tunnel has been fully breached, head for the Retrieving Bay to hack the Excavator's terminal in order to regain access to the tunnel. The Excavator will now go away, making Tunnel 6 accesible again.
Proceed to Step 4