Trans Bay Cable

Until recently, San Francisco had two power plants within city limits to support local demand: Hunters Point Power Plant (shut down in 2006) and Potrero Generating Station (shut down in 2011); the remaining electric load for the city is supplied through the grid. Located at the northern tip of San Francisco Peninsula, the city was connected to the rest of California's grid through a single transmission path, including the San Mateo Substation near Coyote Point Recreation Area. On December 8, 1998, a disturbance at that substation tripped it offline; the resulting chain reaction also would knock the transmission lines out of service and shut down both Hunters Point and Potrero electric generating stations, causing a power outage covering most of the city for eight hours.{{cite news |url=https://www.sfgate.com/news/article/PG-E-Blackout-Cost-S-F-A-Pretty-Penny-2973867.php |title=PG&E Blackout Cost S.F. A Pretty Penny |author=Epstein, Edward |date=December 10, 1998 |newspaper=San Francisco Chronicle |access-date=8 March 2021}}{{cite news |url=https://www.sfgate.com/bayarea/article/Backups-Should-Have-Stopped-Blackout-in-Its-2973761.php |title=Backups Should Have Stopped Blackout in Its Circuits / PG&E lapses did more harm than crew, PUC says |author=Howe, Kenneth |date=December 15, 1998 |newspaper=San Francisco Chronicle |access-date=8 March 2021}}

Following the prolonged outage, the utility (Pacific Gas and Electric), the City and County of San Francisco, and the California Public Utilities Commission formed the San Francisco Stakeholder Study Group (SFSSG) to determine immediate transmission solutions to ensure electric reliability, which led to the upgrading of PG&E transmission lines and towers paralleling Interstate 280 under the Jefferson-Martin transmission line project to diversify the path.{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=C: CAISO Documents |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/TBC-AppC.pdf}} After the Jefferson-Martin project was complete, PG&E decommissioned Hunters Point in 2006.{{cite news |url=https://www.sfgate.com/news/article/Big-victory-for-Hunters-Point-activists-As-PG-E-2534998.php |title=Big victory for Hunters Point activists / As PG&E closes its old, smoky power plant, the neighborhood breathes a sigh of relief |author=Fulbright, Leslie |date=May 15, 2006 |newspaper=San Francisco Chronicle |access-date=9 March 2021}}

{{OSM Location map

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|mark-title1 =Pittsburg converter site

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|caption=Key sites of Trans Bay Cable, which runs west from Pittsburg through Suisun and San Pablo Bays, then south through San Francisco Bay to San Francisco

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The SFSSG also studied projects to enhance long-term reliability, which included an evaluation of several proposals for transmission lines across San Francisco Bay. In September 2005, the California Independent System Operator (CAISO) identified the Trans Bay Cable (TBC) project as the preferred option over alternatives from PG&E, which had proposed building AC lines to Potrero from East Bay substations in Moraga or Fremont. The capital costs of the alternatives were approximately equal, but the HVDC technology proposed for the TBC project would have reduced transmission losses.{{cite report |url=http://www.caiso.com/14cd/14cd7bd415cb0.pdf |title=San Francisco Peninsula Phase 2 Long-Term Electric Transmission Planning Technical Study |date=November 14, 2005 |publisher=California Independent System Operator |archive-url=https://web.archive.org/web/20060508235658/http://www.caiso.com/14cd/14cd7bd415cb0.pdf |archive-date=May 8, 2006 |url-status=dead}}{{rp|16}} The submarine route also avoided siting concerns for high-voltage overhead transmission lines and towers in residential neighborhoods; in addition, adding the new transmission line could obviate the need to build peaking power plants within city limits,{{cite news |url=https://www.sfgate.com/business/article/Transbay-electric-connection-300-million-2622926.php |title=Transbay electric connection / $300 million project would send power through buried cables |author=Baker, David R. |date=July 10, 2005 |newspaper=San Francisco Chronicle |access-date=8 March 2021}} including the removal of the Potrero Generating Station.{{cite web | url=https://www.eenews.net/stories/1059942594 | title=POLITICO Pro }}

Babcock & Brown (B&B) executed a development agreement with the City of Pittsburg in January 2004, and introduced the project to CAISO in February. The original intent was for B&B to develop the cable project and finance it, then transfer ownership to the city's municipal utility (Pittsburg Power) and convey transmission rights to CAISO. The San Francisco Board of Supervisors voted 9–2 to approve the TBC project in August 2007{{cite news |url=https://www.sfgate.com/politics/article/Supes-approve-53-mile-Trans-Bay-power-cable-2512080.php |title=Supes approve 53-mile Trans Bay power cable |author=Buchanan, Wyatt |date=August 8, 2007 |newspaper=San Francisco Chronicle |access-date=9 March 2021}} and the final discretionary permit was granted by the San Francisco Bay Conservation and Development Commission on August 16, 2007.{{cite web |url=https://ceqanet.opr.ca.gov/2004082096/8 |title=Trans Bay Cable Project, SCH Number 2004082096 |publisher=State of California, Governor's Office of Planning and Research, California Environmental Quality Act |access-date=9 March 2021}}

Construction on the TBC officially began on December 15, 2007.{{cite news |url=https://www.bizjournals.com/eastbay/stories/2007/12/17/story7.html |title=Trans Bay Cable officially breaks ground |author=Scanlon, Mavis |date=December 16, 2007 |work=San Francisco Business Times |url-access=subscription |access-date=8 March 2021}} A joint venture between Siemens Energy and Prysmian Construction Services (formerly Pirelli Cable) were responsible for building the turnkey project;{{cite web |url=https://www.ptd.siemens.de/artikel1012_low.pdf |title=Trans Bay Cable Project |publisher=Siemens |access-date=9 March 2021}} the Siemens/Prysmian joint venture subcontracted electrical equipment installation to Cupertino Electric.{{cite web |url=https://www.cei.com/our-work/transbay-cable |title=TransBay Cable |website=Cupertino Electric Inc. |access-date=9 March 2021}} After B&B declared bankruptcy in 2009, the management of B&B partnered with John Hancock Life Insurance Company, creating SteelRiver Infrastructure Partners to complete the cable.{{cite news |url=https://www.spglobal.com/marketintelligence/en/news-insights/trending/qgv8zjnv3oen-k2ound3ig2 |title=Trans Bay transmission asset could be headed for NextEra yieldco |author=Tsarouhis, Fotios |date=November 20, 2018 |work=S&P Global Market Intelligence |access-date=8 March 2021}}

Cable laying operations began on October 11, 2009 using the cable vessel Giulio Verne and the barge Manson 73 for the shallower eastern approaches. The starting point for both vessels was just west of the Benicia–Martinez Bridge. By November 6, Giulio Verne had laid cable to the north side of the San Francisco–Oakland Bay Bridge and Manson 73 had completed its {{convert|24|km|adj=on|abbr=on}} segment to Pittsburg; a total of {{convert|78|km}} of cable had been placed. Another Manson Construction Company barge, Hagar, was used to perform post-lay burial activities, including placing flexible concrete mats for protection.{{cite web |url=https://www.waterboards.ca.gov/sanfranciscobay/board_info/agendas/2009/november/4_EOrpt.pdf#page=6 |title=Executive Officer's Report |date=November 10, 2009 |publisher=California Regional Water Quality Control Board, San Francisco Bay Region |access-date=9 March 2021}} The cable was laid, buried, and connected at each end by December 3, 2009, and a preliminary test was conducted on January 15, 2010, successfully transmitting 400 MW to the San Francisco grid. However, during subsequent testing, the converter modules failed at a higher than expected rate. Final testing was completed on November 3, 2010, with substantial completion declared a week later; the Trans Bay Cable entered revenue service on November 23.{{cite web |url=https://www.nfma.org/assets/documents/asfeb11boyle.pdf |title=An Introduction to Trans Bay Cable |date=February 2011 |author=Boyle, Jason |publisher=SteelRiver Infrastructure Partners |access-date=8 March 2021}} After the Trans Bay Cable was completed, Potrero (then owned by Mirant) was decommissioned in 2011.{{cite news |url=https://www.sfgate.com/news/article/SF-shutting-down-power-plant-Jan-1-2452695.php |title=SF shutting down power plant Jan. 1 |author=Coté, John |date=December 21, 2010 |newspaper=San Francisco Chronicle |access-date=9 March 2021}}

TBC was damaged in September 2014 after {{ship|MV|Ocean Life}} dropped anchor after losing power near the Benicia–Martinez bridge;{{cite report |url=https://bopc.ca.gov/wp-content/uploads/sites/41/2016/08/Board-Minutes-9-25-14.pdf |title=Minutes |date=August 2016 |publisher=The Board of Pilot Commissioners for the Bays of San Francisco, San Pablo, and Suisun |access-date=9 March 2021}} repairs took four months to complete.{{cite news |url=https://www.potreroview.net/trans-bay-cable-pumps-pittsburg-power-into-san-francisco/ |title=Trans Bay Cable Pumps Pittsburg Power into San Francisco |date=November 2016 |author=Iacuessa, Michael |work=The Potrero View |access-date=9 March 2021}} In 2018, Siemens upgraded the control system, allowing black start capability, which enables the TBC to support critical infrastructure needs in San Francisco as the sole source of power, without relying on the local grid. Under black start conditions, up to 300 MW electric can be supplied through the TBC; normally, the TBC can transmit up to 400 MW, which is approximately 40% of the total load for San Francisco under peak demand.{{cite news |url=https://www.modernpowersystems.com/features/featureblack-start-upgrade-for-the-san-francisco-bay-cable-6245877/ |title=Black start upgrade for the San Francisco bay cable |date=July 18, 2018 |work=Modern Power Systems |access-date=9 March 2021}} SteelRiver sold its interest in the cable to NextEra Energy Transmission in July 2019 for a reported $1 billion.{{cite web |url=https://www.steelriverpartners.com/trans-bay-cable/ |title=Trans Bay Cable |publisher=SteelRiver Infrastructure Partners |access-date=8 March 2021}}{{cite press release |url=http://newsroom.nexteraenergy.com/2019-07-16-NextEra-Energy-Transmission-completes-acquisition-of-underwater-transmission-cable-system |title=NextEra Energy Transmission completes acquisition of underwater transmission cable system |date=July 16, 2019 |publisher=NextEra Energy |access-date=8 March 2021}}

In the original plan, there were five major components in the Trans Bay Cable project:{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=A.1 Detailed Project Description: Introduction |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/Appendix-A-1.htm}}{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/0-TOC.htm |title=Addendum to the Final Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=2007 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=2.0 Project Description |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/2-ProjDescription.htm}}

1. {{convert|57|mi}} of submarine and underground HVDC cable bundle
2. New {{convert|5.4|acre|adj=on}} converter station in Pittsburg, converting AC grid power to DC
3. New {{convert|6.8|acre|adj=on}} converter station in San Francisco, converting DC to AC
4. {{convert|5.5|mi}} of single-circuit 3-phase 230 kV AC lines connecting converter station with PG&E substation in Pittsburg
5. {{convert|0.3|mi}} of double-circuit 3-phase 115 kV AC lines connecting converter station with PG&E substation in San Francisco

The original design for the HVDC cable bundle included a 400 kV transmission line (approximately {{convert|114|mm|in|order=flip|abbr=on}} in diameter), a 12 kV metallic return (ground) cable ({{convert|86|mm|in|order=flip|abbr=on}} diameter), and a fiber optic communication cable ({{convert|1|in}} diameter); the total bundle was {{convert|10|in|mm|abbr=on}} in diameter.{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=A.3 Detailed Project Description: Project Component Design |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/Appendix-A-3.htm}} With the adoption of HVDC Power Link Universal System (PLUS) technology, two cables of identical size were used instead for the transmission line, along with the fiber optic cable. Each cable is energized to 200 kV (one positive, one negative). The HVDC converter for HVDC PLUS uses a half-bridge topology; the system is rated to carry up to 400 MW of electric power in a symmetrical monopole configuration.{{cite web |url=https://assets.siemens-energy.com/siemens/assets/api/uuid:83dc80ed-cbd6-4027-9e48-83a87eab8e0b/263_160390_ws_hvdcplususlowres.pdf#page=15 |title=HVDC PLUS – the decisive step ahead |date=December 2016 |publisher=Siemens Energy |access-date=9 March 2021}}

Prysmian Group manufactured the HVDC and terrestrial AC cables in its Arco Felice (Naples) factory and laid the submarine HVDC cable using its own ship, the Giulio Verne ({{IMO|8302014}}).{{cite press release |url=https://www.prysmiangroup.com/en/en_2007-Trans-Bay.html |title=Prysmian Secures 125 Million $ Contract With Trans Bay Cable Llc For A New Submarine Power Link In San Francisco (USA). |date=2007 |publisher=Prysmian Group |access-date=8 March 2021}}{{cite news |url=https://www.ecmag.com/section/your-business/trans-bay-cable-completed-under-san-francisco-bay |title=Trans Bay Cable Completed Under San Francisco Bay |date=January 2011 |author=Breslin, Mike |work=Electrical Contractor |access-date=8 March 2021}}

Each converter station consists of a valve hall originally designed to be {{convert|64|ft}} high, a DC hall, and a control building; the total area for the buildings is {{convert|23000|ft2}}; in addition, a switchyard will handle the connection to the existing grid after conversion. With the update to HVDC PLUS, the building height and size were reduced:{{cite report |url=http://www.caiso.com/Documents/070418_BriefingonTransBayCableProject_Presentation_Originalpresentation_.pdf |title=Trans Bay Cable Project: Presentation To Board of Governors, California Independent System Operator |date=April 18, 2007 |author=Babcock & Brown |publisher=California Independent System Operator |access-date=8 March 2021}} height was reduced to {{convert|35|ft}} and the required footprint is reduced by approximately 25 percent.{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/0-TOC.htm |title=Addendum to the Final Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=2007 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=1.0 Executive Summary |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/1-ExecSummary.htm}}

The original route for the AC lines connecting the Pittsburg substation with the converter site (near the Delta Energy Center) were mainly underwater, running approximately north from the substation, east around the northern end of Browns Island, southeast along the slough between Browns and Winter islands, east to the southern tip of Winter Island, then south and back on land to the converter site.{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=Figure A.1-3 Proposed Converter Site/Standard Oil |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/figures/Figure-A.1-3.jpg}} However, the Pittsburg converter station later was moved to a site near West Tenth Street, just south of the existing PG&E substation,{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/0-TOC.htm |title=Addendum to the Final Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=2007 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=Figure 2.6-2: Pittsburg Converter Station Plan View (West Tenth Street HVDC PLUS) |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/Figures/Fig2.6-2.jpg}} reducing the AC interconnect lines to less than {{convert|1|mi}} and shortening the HVDC cable bundle to {{convert|53|mi}}. The San Francisco converter station is near the intersection of 23rd and Illinois, between Piers 70 and 80.{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=Figure A.1-2 Proposed Converter Site/HWC |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/figures/Figure-A.1-2.jpg}}{{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/0-TOC.htm |title=Addendum to the Final Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=2007 |publisher=City of Pittsburg |access-date=8 March 2021 |chapter=Figure 2.5-2: San Francisco Converter Station Plan View (HWC mitigated HVDC PLUS) |chapter-url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc_addendum/Figures/Fig2.5-2.jpg}}

The submarine HVDC cable is buried at a depth of {{convert|3|to|6|ft}} below the floor of the Bay to protect it from anchor strikes. In certain locations, such as where the cable crosses existing utilities, it is unable to be buried, and flexible concrete mats were placed atop the cable for protection.{{cite web |url=https://www.spn.usace.army.mil/Missions/Regulatory/Public-Notices/Article/1650122/spn-2004-285120-trans-bay-cable-maintenance-regional-general-permit/ |title=SPN-2004-285120 Trans-Bay Cable Maintenance Regional General Permit |date=October 1, 2018 |publisher=Department of the Army, San Francisco District, Corps of Engineers |access-date=9 March 2021}}

{{reflist}}

• [http://www.transbaycable.com/ transbaycable.com]
• [http://www.usa.siemens.com/energy-efficiency/energy-efficiency.html?tab=Transmission-and-distribution HDVC Plus Technology provided by Siemens]
• {{cite report |url=http://www.ci.pittsburg.ca.us/pittsburg/pdf/tbc/index.htm |title=Draft Environmental Impact Report for the proposed Trans Bay Cable Project |author=URS Corporation |date=May 2006 |publisher=City of Pittsburg |access-date=8 March 2021}}

Category:HVDC transmission lines

Category:San Francisco Bay

Category:Energy in the San Francisco Bay Area

Category:2010 establishments in California

Category:Energy infrastructure completed in 2010

Category:Pittsburg, California