Beneath the street

First of all, that's a cool machine. Second, this is a shot of the eternity that is road construction at Maiden Lane and Broadway. What I don't understand is what they're chipping through. Is the street seriously supported by 15 feet of solid stacked brick and mortar? There's so much underground in this neighborhood, not to mention how much has been burried and built upon over time. Still, it seems like a pretty blunt effort.