Substation Relocation and Expansion
The new Silvergate Substation will be approximately five acres in size, and will be located on the other side of Harbor Drive and a set of railroad tracks from the existing Main Street Substation, in the Barrio Logan neighborhood of the City of San Diego. The site for the Silvergate Substation is currently occupied by SDG&E's decommissioned Silvergate power plant, an industrial building, SDG&E's former 12 kilovolt (kV) Sampson Substation, and a parking lot, all of which would be replaced by the new substation. According to SDG&E, the new substation will be able to support four 230 kV circuits and 11 69 kV circuits, but initially will include three 230 kV circuits and seven 69 kV circuits.
The existing Main Street Substation is a 138 kV/69 kV substation. According to SDG&E, the Main Street Substation is over 40 years old, and all of the substation's equipment is obsolete, beyond its useful life and predicted life span, and spare parts are difficult to obtain. "So the equipment is falling apart as we speak." (SDG&E Witness Yari, Transcript v. 2, pp. 18-19.)1
In addition to the age of the equipment, the load on the Main Street Substation is forecast to increase from its current level of approximately 336 megawatts.2 According to an internal SDG&E load forecast, the expected load on the SDG&E substation will be about 420 megawatts in 2008 and closer to 440 megawatts (MW) in 2010.3 (Id., pp. 15-16.) SDG&E states that if the existing Main Street Substation is not replaced, by 2008 SDG&E would be in violation of the reliability criteria of the North American Reliability Council (NERC), the Western Electric Reliability Council (WECC), and the California Independent System Operator (Cal ISO). (Id., p. 17.)
SDG&E recognized the need to replace the aging equipment at Main Street Substation and initially looked at rebuilding the existing facility. (Id., pp. 25-26.) However, after the rebuild was publicly proposed in August 2000, SDG&E encountered significant community opposition from the residents of the neighborhood adjacent to the existing substation. The community expressed a desire for SDG&E to relocate the substation on the opposite (west) side of Harbor Drive. (Id.)
By mid-2004, SDG&E had exhausted its discussions with the community, and had determined that it was not desirable to rebuild at the existing site. (Id., pp. 26-27.) Also at about this time, SDG&E realized that as part of its Otay Mesa Power Purchase Agreement Transmission Project ("Otay Mesa Project," Application (A.) 04-03-008), it was going to have a new 230 kV source going by the site of its decommissioned Silvergate Power Plant (and adjacent 12 kV Sampson Substation), and that it could build a 230 kV substation on the old power plant site. (Yari, supra, pp. 27-28.)4
The site proposed for the new Silvergate Substation is larger than the existing Main Street Substation, and with the acquisition of an adjacent property, can accommodate an air-insulated 230 kV substation, increasing the capacity of the substation serving downtown San Diego and nearby areas. In addition, by connecting to a 230 kV line running between two other substations (Old Town and Miguel, either of which can supply power to the new substation even if the supply from the other one is interrupted) reliability is further increased in comparison to the present configuration, which has Main Street Substation being fed from only one direction. (Id., pp. 21-24.)
The new location is west of Harbor Drive, as requested by the community opposing SDG&E's proposal to rebuild the Main Street Substation. Finally, based on the record of this proceeding, including a public participation hearing, there appears to be no community opposition to the relocation of the substation.5
Overall, the relocation and capacity expansion of the substation appears to be an excellent approach to addressing the age of the Main Street Substation and the expected growth of load in the area served, while making good use of the old Silvergate Power Plant site and the adjacent new 230 kV transmission line. Our main concern is that it took SDG&E so long to recognize what appears to be an obvious answer. Neither the age of the Main Street Substation nor the continued growth in downtown San Diego should have come as a surprise to SDG&E. Community opposition to rebuilding on the existing site has existed since 2000, and SDG&E began planning the route for its 230 kV line some time ago. Yet SDG&E did not recognize the currently-proposed solution until 2004, while the Main Street Substation continued to deteriorate.
SDG&E was considering leasing or selling the Silvergate site to a company that hoped to build a desalination plant (id., pp. 27-28), and this may have delayed SDG&E's consideration of the Silvergate site for a substation. It concerns us that SDG&E appears to have put this venture ahead of its duty to reliably serve utility customers. We wish to remind SDG&E that reliable utility service should be its first priority.
1 The typical expected life of the electrical equipment is around 30 years. (Id.)
2 The Main Street Substation serves downtown San Diego and adjacent areas, including Coronado, National City, and Navy facilities located on San Diego Bay. (Id., p. 15.) The new Silvergate Substation would serve the same area.
3 SDG&E's Proponent's Environmental Assessment (PEA) forecasts a load of 502 MW by 2010, based on a forecast approved by the Commission in Decision (D.) 04-12-048. (Id., p. 61; PEA, p. 2-4.)
4 This timing is confirmed by the appearance of the Silvergate Substation Project in the environmental documents prepared in the Otay Mesa Project proceeding (A.04-03-008). The Silvergate Substation was not mentioned in the March 2004 PEA in that proceeding, but is discussed in the March 2005 Draft EIR. According to SDG&E, the first mention of the Silvergate Substation Project in the Otay Mesa proceeding was the October 2004 Memorandum of Understanding between SDG&E and the City of Chula Vista (filed in the Otay Mesa proceeding in November 2004), marked as Exhibit 6 in this proceeding. (SDG&E Counsel Barnes, Transcript v.2, p. 62.)
5 There is support from the City of Chula Vista for the portion of the project (discussed below) involving removal and undergrounding of transmission lines.
