Employees were putting in the helical foundation to install a PTC tower when they hit rock and stopped work. An employee took the boom truck remote control and climbed onto the boom truck bed and proceeded to disconnect the foundation adapter plate from the helical foundation. The employee then lifted the boom to remove the helical foundation from compression and pushed the foundation over toward the ground at the back of the boom truck. At that time, the injured employee came around the back of the boom truck and was struck by the falling foundation, resulting in a fracture to the right foot and a tendon injury to the right knee.