The contractor will be performing a mix of directional drilling and pipe bursting. Directional drilling is when the contractor digs a large hole (called a pit) at the starting point and ending point. Then they use a drilling machine to push the pipe underground from the starting point to the ending point. After the pipe is in the end pit they connect it to the rest of the system. Example images and a diagram are provided below.
Pipe bursting is when the contractor digs a large hole (pit) at a starting point and ending point (typically a gate valve, where gate valves are points in the watermain where it can be turned off). They lay down large metal rods in the existing pipe and connect these rods to a large machine at the end pit. In the starting pit they attach the pipe to the metal rods and the large machine pulls the rods and the pipe through, breaking the old pipe and installing the new pipe concurrently. Illustrations of pipe bursting operations are shown in the diagrams below.