(SUMMIT) A worker died Monday afternoon at a southwest suburban reservoir under construction as part of the Deep Tunnel project.

Robert Ellison, 55, was pronounced dead at the McCook Reservoir worksite in the 7700 block of Canal Bank Road in Summit at 2:20 p.m., according to the Cook County medical examiner’s office. He lived in the 39300 block of Hickory Street in far northwest suburban Spring Grove.

The federal Occupational Health and Safety Administration is investigating along with Summit police, according to the medical examiner’s office. Representatives could not immediately be reached for more details.

An autopsy was scheduled for Tuesday.

The McCook Reservoir is one of two in the suburbs being completed in the Deep Tunnel project to improve flood control and prevent water pollution, according to the Metropolitan Water Reclamation District of Greater Chicago.