| SECTION 3.0 | PROJECT DESCRIPTION |
3.1 introduction
This section of the EIR describes the Trans Bay Cable Project (Project) proposed by Trans Bay Cable LLC (an affiliate of Babcock & Brown, which is a Sydney, Australia-based company with its major overseas office in San Francisco), in cooperation with the City of Pittsburg and Pittsburg Power Company (a municipal utility). Babcock & Brown would provide the financing for the Project. A consortium of Siemens Power Transmission & Distribution, Inc. and Prysmian Cavi e Sistemi Energia S.r.L would provide the converter station and cable technology, Project engineering, procurement and installation, and construction management. The Project is intended to be a cost-effective, energy-efficient solution addressing San Francisco's need for additional energy, while improving transmission grid reliability and load serving capability. The following discussion summarizes the Detailed Project Description (refer to Appendix A of this EIR for more information).
The Project as proposed would involve the installation of a submarine High Voltage Direct Current (HVDC) transmission cable and associated onshore facilities that would transmit electrical power and provide a dedicated connection between the East Bay near Pittsburg (which currently has transmission grid congestion and is fed by sufficient generating and transmission capacity) and the electrical transmission and distribution facilities serving the northern San Francisco peninsula. Figure 3-1 illustrates the general location of the facilities and the route of the transmission cable system. Use of a submarine HVDC cable allows for transmission of power over a very long distance with minimal energy loss.
Existing electrical power at a Pacific Gas and Electric Company (PG&E) substation near Pittsburg is provided as alternating current (AC). The proposed Project would involve drawing AC power from this existing Pittsburg PG&E substation and converting it to direct current (DC) at a proposed converter station in Pittsburg. The DC power would then be transmitted approximately 57 miles through a proposed submarine and buried onshore HVDC cable installed undersea beneath New York Slough, Suisun Bay, the Carquinez Straits, San Pablo Bay, and San Francisco Bay to a proposed converter station in San Francisco, where it would be converted back to AC power. This AC power would then be transmitted to the existing Potrero PG&E substation for release to the electrical grid.
3.2 PROJECT OBJECTIVES
The California Independent System Operator (CAISO) is a not-for-profit public benefit corporation that acts as the impartial operator of the state's wholesale power grid, maintaining reliability and directing the electricity traffic on the transmission grid that connects energy suppliers with the energy providers that serve over 30,000,000 Californians. The CAISO management and Board of Governors, in their decision of September 8, 2005, determined that the Trans Bay Cable Project is required to ensure reliable operation of the transmission system serving the San Francisco Bay Area. In keeping with the CAISO determination, the basic objectives of the Trans Bay Cable Project are discussed in greater detail in Section 2.3.
3.3 PROJECT COMPONENTS
The proposed Project consists of the following major components:
3.4 Construction
The proposed Project has major components in three distinct locations:
Overall Project construction would be expected to take approximately 27 to 30 months from the Notice to Proceed, including approximately 4 to 5 months to install the submarine cable, and 3 to 6 months for demolition of existing structures on the two proposed converter station sites. Construction activities at the converter station sites would overlap and would include grading and site preparation, foundation construction, erection of major equipment and structures, and installation of electrical and control systems. Connection of HVAC and HVDC transmission cables, switchyards and substations would also occur. A general overview of the three sites, and how they connect to one another, is presented on Figures 3-1 and 3-2.
3.4.1 Construction in San Francisco
The proposed 6.8-acre converter station site in San Francisco is known as the HWC site, and is located on 23rd Street, south of the existing Mirant Power Plant, southeast of the PG&E Potrero substation, and adjacent to San Francisco Bay. The site is currently developed and occupied by several businesses. The site is currently zoned Major Industrial, which permits the proposed use. The site currently contains subsurface contamination. Planned remediation prior to construction of the converter station is discussed in Section 4.14, Hazardous Materials and Waste Management.
An aerial view of the existing HWC site is shown on Figure 3-3, with the proposed converter station overlaid. The converter station buildings would occupy approximately 23,000 square feet at the site, and range in height up to 64 feet. Outdoor air-cooled radiators, transformers, AC switchgear, filters, and other equipment would occupy the balance of the site. The site would receive an architecturally appropriate treatment in areas that are visible to the public on the south and west sides, and would have a chain link fence on the north and east sides. Access to the site would be via 23rd Street, and no new offsite road construction would be required.
The proposed onshore route for the HVDC entry into the San Francisco Converter Station from San Francisco Bay would parallel the southern fence line of the HWC site for approximately 1,000 feet, to enter the DC hall at the proposed converter station site (refer to Figure 3-3). To avoid aquatic habitat and protect the cable at the shore crossing, the proposed cables would enter the Bay floor through casings placed by horizontal directional drilling (HDD). The casings would terminate offshore, and burial in the Bay floor would begin at the exit of the casings.
The double-circuit 115 kV HVAC interconnecting cable would exit the proposed San Francisco Converter Station from the north side and cross 23rd Street approximately 900 feet from the easterly line of Illinois Street, then run west along 23rd Street for approximately 600 feet. The HVAC cable would then extend along the eastern boundary of the existing PG&E Potrero substation for approximately 375 feet, where it would enter the substation and connect with the electrical grid.
The proposed construction laydown area for the San Francisco site is just south of the HWC site. The laydown area covers approximately 11 acres that is owned by the Port of San Francisco and designated as the "Western Pacific" site. The area would be devoted to equipment and materials laydown, storage, parking of construction equipment, small fabrication areas, and office trailers supporting construction at the San Francisco converter station site. Access to the proposed laydown area would be via 25th Street. The site has no standing buildings or structures, and lies on land that was reclaimed from San Francisco Bay early in the twentieth century. An alternate laydown area south of the proposed laydown area (Pier 94-96) is also shown on Figure 3-3.
3.4.2 Construction in San Francisco Bay and Adjoining Waterways
The submarine and onshore cable portion of the proposed Project would consist of an HVDC transmission cable system that would run approximately 57 miles from the HWC Converter Station site in San Francisco to the Standard Oil Converter Station site in Pittsburg, California (refer to Figure 3-1). The proposed HVDC transmission cable system would include a high voltage transmission cable, a separate medium voltage (MV) metallic return cable, and a fiber optic communication cable (refer to Figure 3-4).
The proposed submarine cable would extend from San Francisco to Pittsburg below the floor of San Francisco Bay, San Pablo Bay, the Carquinez Strait, Suisun Bay, and New York Slough. The cable route was selected to avoid shipping channels, anchorages, dredge disposal areas, Regional Water Quality Control Board-listed toxic hotspot areas, and other known obstacles.
The submarine cable would be put in place using Prysmian installation technology. Cable lay would be performed using a combination of the cable ship (C/S) Giulio Verne (or comparable vessel) and a barge equipped to lay the cable. The southern portion of the submarine cable would be installed using the Giulio Verne, and the eastern portion would be installed using a barge.
The cable would be buried in a bundled configuration (as shown on Figure 3-5) using the Hydroplow burial machine (or equivalent technology) towed by either the C/S Giulio Verne or by the barge. The working principle for the Hydroplow is to gently fluidize by the use of water jets the seabed materials in a narrow path and to a typical target depth of 3 to 6 feet, with the potential for local burial to greater depths if required, without displacing the majority of the material and minimizing the suspension of sediment in surrounding waters. The method effectively places cables at a consistent required depth of embedment in jettable bottom conditions.
3.4.3 Construction in Pittsburg
The proposed 7.5-acre converter station site in the City of Pittsburg is known as the Standard Oil site (this name reflects the site's proximity to the former Standard Oil Avenue; no portion of this site was connected with previous oil processing or storage). It is located within a developed area with a mix of existing and former industrial uses. The only existing structures on the site are two abandoned concrete wastewater storage tanks and a small dilapidated building. The remainder of the site was previously occupied first by a wastewater treatment facility and then intermittently by an automobile storage yard. The site would be cleared of all structures and stored materials prior to construction of the proposed converter station. There is no vegetation on the site except for a few scattered patches of ruderal (i.e., weedy plants, growing in rubble) species. The relatively flat site is surrounded by a berm, and contains no waterways or wetlands. The site is zoned IG (General Industrial), which permits the proposed use.
An aerial view of the existing Standard Oil site is shown on Figure 3-6, with the proposed converter station overlaid. The converter station buildings would occupy approximately 23,000 square feet at the site, and range in height up to 64 feet. Outdoor air-cooled radiators, transformers, AC switchgear, filters, and other equipment would occupy the balance of the site. The site would receive an architecturally appropriate treatment in areas that are visible to the public on the south and west sides, and would have an acoustical barrier on the north, and portions of the east and west sides, as shown on Figure A.3-8 in Appendix A. Access to the proposed Standard Oil Converter Station site and adjacent laydown area would be from a proposed new permanent access road that would run south from the site to the Pittsburg-Antioch Highway, or from an existing access road that runs west from the site to Loveridge Road.
The construction laydown area for the Pittsburg site is proposed for an approximately 7-acre area of vacant property adjacent to and north of the site. The area would be devoted to equipment and materials laydown, storage, parking of construction equipment, small fabrication areas, and office trailers supporting construction of the Pittsburg converter station. Temporary construction parking, staging, and storage areas would be developed by clearing/grubbing/removing topsoil from unimproved areas that would receive vehicular traffic and laydown. In addition to the proposed new access road, the existing access to the proposed converter station site and adjacent laydown area off Loveridge Road south of the existing railroad right-of-way (ROW) would likely be used to transport heavy loads during the construction phase (e.g., transformers).
The proposed HVAC and HVDC cable routings from the Standard Oil site would begin at the Pittsburg Standard Oil Converter Station site, as shown on Figure 3-1, which shows the HVDC cable that connects to the San Francisco Converter Station in blue, and the HVAC cable that connects to the PG&E substation in red. Both the HVDC and HVAC cable bundles run approximately 0.2 mile to the northeast to an existing paved access road associated with the Delta Energy Center (south of the BNSF Railroad ROW). This initial section of the buried cable routes would be installed via a horizontal directional drill (HDD). The route would then follow the existing paved access road in an easterly direction for a distance of approximately 0.25 mile, then turn north for approximately 0.5 mile along the Delta Diablo outflow access road before ending at a splice box between 100 and 500 feet south of New York Slough on Dow Chemical property. The submarine cable would be drawn in from the bay side, and would be joined to the underground cable in a splice box.
To avoid aquatic habitat and protect the cable at the shore crossing, the proposed cables would enter the bay floor through casings placed by HDD. The casings would terminate offshore, and direct burial in the bay floor would begin at the exit of the casings.
The proposed 230 kV HVAC interconnect between the PG&E substation and the proposed Pittsburg converter station would exit from the southernmost bay of the 230 kV switchyard, bearing west-northwest for approximately 850 feet, and then on a north-northeast bearing for a distance of 650 feet to a bore pit approximately 200 feet from the shoreline on Mirant property. The proposed HVAC would enter New York Slough approximately 500 feet west of Mirant's Pittsburg Power Plant Unit 7 and would be placed parallel to the HVDC cable. HVDC and AC cable would exit parallel to each other, as shown on Figure 3-6.
3.5 Operation
It is currently anticipated that the Project would become operational in 2009. The HVDC system transmission control activities would be performed under the direction of the CAISO. The HVDC technology proposed for the Project is highly reliable and requires minimal maintenance. The converter stations at each end of the submarine cable route (in San Francisco and Pittsburg) would normally operate with a minimal staff and/or be remotely operated. Personnel would support the stations by performing periodic inspections and routine maintenance.
The converter stations would use proven AC/DC conversion technology of thyristor valves, allowing the rapid control of power transfers and a fast response to changing system conditions. All critical auxiliary equipment, controls, protections, metering, and communications would use redundant systems to maximize system availability and reliability.
Automatic computer control systems would adjust operating parameters to maintain system operation within input settings directed by the CAISO. The fiber optic communications component of the submarine cable would allow direct communication between computer control systems at both of the converter stations. This would facilitate rapid response to changes in the AC transmission grid, converter station equipment, and/or the HVDC cable. The operators and/or computer systems would alert needed staff in the event that an incident requiring attention was detected.
At the commencement of system commercial operation, maintenance procedures and critical spare parts would be in place to ensure that reasonably foreseeable problems with the cable or converter stations could be remedied quickly.
3.5.1 Converter Station Maintenance
The proposed electrical equipment and electronic controls at the converter stations would be expected to require a minimal amount of routine maintenance on a periodic basis. Planned routine maintenance activities include: general visual inspections for signs of external damage, leakage, and overheating; checks of insulating fluids levels and properties; lubrication of cooling fans; and electrical checks that are beyond those performed automatically by the station computer systems. Some of the proposed equipment would be expected to operate indefinitely, without maintenance, while other components have limited life expectancies and would require periodic service or replacement. Approximately 5 planned outage days would be required every year.
The station control systems would be designed to automatically alert on-call personnel if problems were detected with the cable or converter stations. Contractual arrangements would be in place for specialized services that may be required to perform repairs on short notice.
3.5.2 Cable Repair
The proposed transmission cable is expected to require no scheduled maintenance for the proposed operational life of the Project (at least 40 years). If substantial damage to the cable were to occur, the repair might require a new section of cable to be added to the cable by splicing. A spare length of cable would be stowed on a boat or barge moored at the Pittsburg Marina or other suitable local facility, or in a nearby onshore storage area, specifically for making emergency repairs. Contractual arrangements would be in place for specialized services that may be required.
3.6 Decommissioning
Once the Project had reached the end of its useful life, Project facilities would be decommissioned in accordance with applicable regulations in place at that time. It is currently envisioned that the submarine and onshore-buried cable segments would be abandoned in place, that the converter stations in San Francisco and Pittsburg would be removed, and that those sites would be prepared for the subsequent land use appropriate for each site at that point in time.
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