Unique Design, Manufacturing, and Installation Challenges for the CW System at the Ninemile Unit 6 CCGT Project

Ninemile Point plant was built in the 1950s to accommodate the growing energy demands for a booming New Orleans population. The 550-MW Ninemile Unit 6 CCGT project was proposed to replace the aging units 1 and 2 and provide New Orleans with very clean and efficient electricity generation. To reduce overall project costs, existing infrastructure was utilized wherever possible, including the circulating water system. The project would require some new circulating water lines installed near the building and tie-ins to existing concrete intake and discharge piping. Due to space limitations, certain utilities' corridors could not be relocated to accommodate the new circulating water lines. As a result, it was decided to transition to abovegrade steel pipe to transverse these utility corridors. The new circulating water system was required to be designed for seismic conditions and wind loadings due to hurricanes. In addition, manufacturing and installation schedules were limited as a result of hurricane season. Due to the station's proximity to the Mississippi River, groundwater conditions also had to be considered during design, manufacture, and installation phases of the project. Prestressed concrete cylinder pipe (PCCP) was chosen for below-grade piping (more than 1,500 ft of 72 in.) and steel pipe was utilized (more than 450 ft of 72 in) for abovegrade piping. Materials were delivered on schedule, and the pipe was able to be installed as required to the satisfaction of the design engineer and owner. Consequently, unit 6 will be able to begin operations in mid-2015 and provide long-term and reliable power to the New Orleans area.