Abstract: At 6:45 a.m. on March 4, 2019, Employee #1, a carpenter employed by a civil engineering company, and Coworker #1, his supervisor, were engaged in the construction of an extension to a heavy rail system 80 feet below the surface, both tunnels and new stations. They were in a station and working on a set of vertical modular aluminum shoring frames, part of the process of building concrete forms for horizontal and vertical concrete segments in the stations. Employee #1 and his supervisor were measuring the elevations of a shoring frame to confirm the height required for a concrete deck. Employee #1 used the inside of the frame like a ladder and climbed to the desired height. He then latched his self-locking aluminum rebar hook onto the horizontal member of the frame to prevent his falling. He took measurements and performed needed work, twisting the screw jacks upward and/or downward according to the supervisor's directions. After completing work on that side of the shoring, he disconnected his self-locking rebar hook from the horizontal bar of the shoring frame and attempted to travel across the side cross-braces of the frame without fall protection. During this movement, Employee #1 lost his footing and fell from the cross-braces, striking the concrete floor and PVC pipes lying on the floor, a fall height of 13 feet. A complex emergency recovery was required to lift Employee #1 topside. He then was transported to the hospital and admitted for treatment of dislocated shoulders, a dislocated elbow, and multiple lacerations.