2. Background and Procedural History

By Decision (D.) 08-12-031 the Commission granted Southern California Edison Company (SCE) a permit to construct (PTC) certain electrical facilities known as the El Casco System Project (El Casco Project). As approved, the El Casco Project, which is located entirely within Riverside and San Bernardino Counties, includes the following major components:

· construction of a 220/115/12 kilovolt (kV) substation (El Casco Substation), associated 220 kV and 115 kV interconnections, and new 12 kV line getaways on an approximately 28 acre site located within the Norton Younglove Reserve in Riverside County, California;

· upgrade of a total of approximately 15.4 miles of 115 kV subtransmission lines and associated structures within existing SCE rights-of-way in the Cities of Banning and Beaumont and unincorporated Riverside County;

· rebuilding of 115 kV switchracks within SCE's existing Zanja and Banning substations in the Cities of Yucaipa and Banning, respectively; and

· installation of fiber optic cables within public streets and on or through existing overhead and underground structures and conduits within the Cities of Redlands and Banning.

D.08-12-031 granted a PTC for the El Casco Project pursuant to General Order (GO) 131-D, which requires that the Commission review and approve the project in compliance with the California Environmental Quality Act (CEQA) and that the project complies with the Commission's electromagnetic field (EMF) guidelines. Consistent with lead agency responsibilities under CEQA, the Commission certified the Final Environmental Impact Report (EIR) and Recirculated Final EIR.

SCE's petition for modification of D.08-12-031, filed August 29, 2011, asks the Commission to modify certain aspects of the conceptual design for the approved El Casco Project to conform to final engineering. The design changes affect Segments 2 and 4 of the project, which has not been built yet; other segments of the project are under construction at present or have been completed. As discussed in greater detail below, the nature of the proposed changes required additional environmental review of Segments 2 and 4.

No protests or responses to SCE's petition for modification were filed. Pursuant to CEQA Guidelines § 15163(a), the Commission determined to prepare a Supplemental EIR for the El Casco Project. The Commission released the Supplemental Draft EIR for public review on November 30, 2011 and issued the Supplemental Final EIR on February 17, 2012.