Part of the Three Mile Island Unit 1 Steam Generator Replacement Project, the OSGSF was built to provide long-term storage to two original steam generators and portions of the RCS hot leg piping. Approximately 5,400 square feet and approximately 30 feet in height, it was designed to minimize any chance of radiation exposure at its perimeter. Jingoli used approximately 1,500 CY of concrete to construct the cast in place concrete structure.