Vacuum System Reduces Pump Station Power Consumption

The Natomas Mutual Water Company's (NMWC) Sankey Diversion Project included a 434 cfs fish screen and pump station (Diversion) to divert water from the Sacramento River into an abovegrade irrigation canal on the landside of the Sacramento River levee. The pump station's five 48-in.-diameter welded steel discharge pipes are routed over the top of the river's flood protection levee at an elevation substantially higher than the canal water surface (discharge point). A complementary vacuum system was installed to reduce the pressure in the pipeline at the top of the levee and thereby reduce the total dynamic head and power consumption for the pump station. Early testing shows a 48% reduction in power use due to the vacuum system—a considerable savings because at least one 400 HP pump (and often three) runs 24-7 for months at a time. This paper presents the design concepts and components of a vacuum system with emphasis on vacuum piping requirements and mechanical systems integration. Design, installation, and startup of the vacuum system and associated piping at the Sankey Diversion Project will be reviewed, including operational control strategies.