Riverside, Calif., power reliability project advances with new underground transmission line
(UI) — The City of Riverside is advancing the Riverside Transmission Reliability Project (RTRP), a long-planned effort to add a second power connection to California’s electric grid and reduce the city’s reliance on a single transmission source.
The project is designed to provide redundancy and additional capacity for Riverside Public Utilities’ (RPU) electric system, which currently imports all outside power through a single connection from Southern California Edison’s (SCE) Vista Substation in Grand Terrace. That connection limits imports to 557 MW, constraining the city’s ability to meet growing demand during peak periods and emergencies.
RTRP would add a second transmission connection and a new substation, increasing the amount of power that can be imported into Riverside and improving system resilience for critical facilities, including hospitals, emergency services, schools, universities and traffic infrastructure.
While RPU has added local generation over the past decade to help meet peak demand, city officials say those facilities are not sufficient as a long-term solution to projected load growth. The new transmission infrastructure is intended to provide greater flexibility and reliability as energy needs continue to increase.
The California Public Utilities Commission approved the RTRP in March 2020, allowing the project to move into phased construction. Work includes multiple 69-kV subtransmission lines, substation upgrades across RPU’s system and a new Wilderness Substation. The project also includes both underground and overhead high-voltage transmission components to be built by SCE.
Construction on one segment of the 69-kV subtransmission lines connecting the Riverside Energy Resource Center to Freeman Substation is approximately 70% complete. Remaining work is expected to resume in January 2026, with additional installation planned along Indiana Avenue between Tyler Street and Gibson Street, which could result in temporary traffic impacts.
Substation upgrades at Freeman, Harvey Lynn, Casa Blanca and the Riverside Energy Resource Center are ongoing or complete, with remaining work at Orangecrest and Casa Blanca substations anticipated to wrap up by mid-2026. Grading, site preparation and street improvements for the Wilderness Substation and SCE’s Wildlife Switchyard are scheduled to begin in 2026.
SCE’s portion of the project includes a 230-kV underground transmission line and a 230-kV overhead line, both targeted for construction beginning in late 2028, along with a new Wildlife Substation expected to be completed in 2029.
Officials note that construction schedules remain subject to change and do not include design or pre-construction activities. Once completed, the RTRP is expected to strengthen Riverside’s electric transmission network and support long-term growth across the region.
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