Of the below-ground obstacles, Arup director of construction David Caiden stated: "It's a spaghetti of tunnels, utilities, pipes and cables—I've never seen anything like it." Complicating the process, the project must go over, or under, subway lines, Amtrak railway lines, and the Queens-Midtown Tunnel linking Manhattan and Queens, in later phases. In addition, there were geological anomalies along the way of Phase 1. Manhattan's geology changes along the subway's length, passing through rock and soft ground, consisting of sands, silts, and clays over Manhattan schist, and there are faults and shear zones as well as fractured rock. Hard-rock TBMs in diameter, in length, and in weight were used to tunnel during the first phase, progressing at a rate of about per day. The tunnels near the 125th Street station would need to go through soft soil in addition to diving underneath the existing IRT Lexington Avenue Line. The soft-soil tunnels are in contrast to the hard-rock bored tunnels south of 92nd Street and the cut-and-cover tunnels north of that point (necessitated because Manhattan's rock profile drops sharply north of 92nd Street).