Mesa Substation Project


Southern California Edison (SCE) is proposing the Mesa Substation Project to ensure that the electric grid will continue to serve the needs of its customers in the region. Upgrading the existing Mesa Substation and connecting existing transmission lines to the substation will address future reliability concerns related to the projected retirement of older coastal power plants and the previous retirement of the San Onofre Nuclear Generating Station (SONGS), without requiring new transmission lines or substations.

Monterey Park, Montebello, Rosemead, South El Monte, Commerce, Bell Gardens, Pasadena, City of Industry, Santa Clarita, and portions of unincorporated Los Angeles County

The project will primarily consist of:

  • Upgrade the existing Mesa Substation in Monterey Park from 220 kilovolt (kV) to a 500 kV substation.
  • Replacement (removal and installation) and modification of transmission lines, subtransmission lines, and distribution structures to accommodate the new Mesa Substation layout.
  • New telecommunications lines and modifications to an existing line, mostly on existing poles and in existing ducts.
  • Temporary modifications to 220-kV equipment at several existing substations to prevent electrical outages during construction.
  • Relocation and replacement of an existing Metropolitan Water District 72-inch-diameter waterline with an 84-inch-diameter waterline through the substation site.
  • Electrical and/or telecommunications equipment upgrades at 28 existing substations, mostly in other nearby communities.

The California Public Utilities Commission (CPUC) approved the project on February 9, 2017.

  • 2014-February 2015: SCE conducted project planning and public outreach activities for the project
  • March 2015: SCE filed a project application with the California Public Utilities Commission (CPUC)
  • February 2017: The CPUC approved the project
  • Summer 2017: SCE anticipates a Notice to Proceed from the CPUC, which is required to begin construction-related activities
  • September 2017: SCE anticipates start of major construction
  • 2022: Targeted Operating Date.
Expose as Block

For general information about this project or to be added to our mailing list, please call our toll-free project hotline at 1-866-464-2005.