In addition to the one that came all the way to the surface, the Seattle Post Globe reports Sound Transit has found an additional six underground voids above the bored tunnel on the East side of the hill. Six of the seven total found voids have now been filled with concrete at a cost so far of about $1 million. Keep an eye out for more shifting soil!
Update: KOMO reporter (and Beacon Hill resident) Travis Mayfield has a video report on this story.
Thanks for the link!