Whittier Narrows Water Reclamation Plant

The Whittier Narrows Water Reclamation Plant (WRP) is located at 301 N. Rosemead Boulevard in the City of El Monte. The plant occupies 27 acres south of the Pomona (60) Freeway. The plant was originally constructed for the purpose of demonstrating the feasibility of large scale water reclamation. The original plant was placed in operation on July 26, 1962, and consisted of primary sedimentation and secondary treatment with activated sludge. Click on the diagram to read about the wastewater treatment and water reclamation process.


The Whittier Narrows WRP was the first reclamation plant built by the Sanitation Districts. It provides primary, secondary and tertiary treatment for 15 million gallons of wastewater per day (see flow diagram below). The plant serves a population of approximately 150,000 people. All of the reclaimed water is reused at the plant, at the Upper San Gabriel Valley Municipal Water District, and as groundwater recharge into the Rio Hondo and San Gabriel Coastal Spreading Grounds. To learn more about the Sanitation Districts' reclaimed water programs, browse the Sanitation Districts' water reuse program and the resources and information.