Bobbi No-Nose brought in several workers to dig through the ground to the Diamond City strongroom, as part of the operation. She was looking for a faster way to dig through the ground after her workers were driven out by mirelurks. Luckily, she had managed to get in contact with a mechanic named Mel, who is skilled in robots. He was working on a tunneling robot named Sonya that could quickly dig through loose ground with a powerful electromagnetic pulse.
Imprisoned for a small-time misdemeanor revolving around the robotic waiter Wellingham, Bobbi hired the Sole Survivor to bust Mel out of jail. He brought Sonya along to the Dig to take over from the workers. Her EMP blasts were put into good use for boring through the Boston underground.