3.1    introduction

This section of the Final EIR describes the Trans Bay Cable Project (Project) as now 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. 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 Project as currently proposed. Refer to Appendix A of the Draft EIR for more information regarding Project component design, construction activities, operation and maintenance procedures, public safety, and alternatives considered. This section is intended to replace Section 3.0 provided in the Draft EIR.

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 53 miles through a proposed submarine and buried onshore HVDC cable installed undersea beneath 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.

As discussed previously in Section 1.1 (Introduction), two primary refinements to the proposed Project are considered in this Final EIR relative to the description of the proposed Project presented in the Draft EIR as issued in May of 2006. These two refinements are intended to avoid potentially significant Project impacts to cultural/historic resources in San Francisco and avoid or minimize potentially significant impacts to biological resources and water resources in Pittsburg. As summarized in Section 1.0 of this Final EIR, the proposed Project would not result in any potentially significant impacts that were not addressed in the Draft EIR, and no unavoidable adverse significant impacts would occur. These refinements are also intended, in part to address various comments received on the Draft EIR (refer to Section 12.0 of this Final EIR for more information).

In San Francisco, the previously proposed San Francisco HWC Converter Station site layout as assessed in the Draft EIR has been shifted to the western portion of the overall HWC site as a mitigating action to completely avoid the need to demolish two historic buildings on the eastern portion of the overall HWC site. The shifted site is referred to as the "HWC (Mitigated)" site in this Final EIR. Demolition of the two historic buildings on the eastern portion of the overall HWC site was identified as an unavoidable adverse significant impact in the Draft EIR and is not applicable to the HWC (Mitigated) site. The shifted layout is also located further away from the Bay and would not preclude or interfere with the possible future construction of a Bay Trail segment along the portion of the Bay waterfront to the east. The shifted layout is located between the western boundary of the HWC site assessed in the Draft EIR and Illinois Street. The previously proposed HWC site layout as assessed in the Draft EIR has been deleted from further consideration in this Final EIR.

In Pittsburg, the previously proposed Standard Oil Converter Station site and associated ancillary facilities have been deleted from further consideration and been replaced with the Pittsburg West Tenth Street Alternative 1 (E/W) site that was analyzed in Sections 5.4 and A‑8.2.3.1 of the Draft EIR. As discussed in Section 6.3 (Environmentally Superior Alternative) of the Draft EIR, the proposed West Tenth Street Alternative 1 site would avoid various potentially significant impacts associated with the previously proposed Pittsburg Standard Oil site (and associated onshore/offshore AC/DC cable routes and access road over Kirker Creek), including those to sensitive biological resources and water quality associated with dredging at two locations in New York Slough. The balance of this project description addresses the refined Trans Bay Cable Project.

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 of the Draft EIR.

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 sites in San Francisco and Pittsburg and the interconnecting submarine cable is presented on Figures 3-1 and 3-2.

3.4.1    Construction in San Francisco

The proposed 5.0-acre converter station site in San Francisco is known as the HWC (Mitigated) site, and is located on 23^rd Street, southwest of the existing Mirant Power Plant, south of the PG&E Potrero substation, and approximately 200 feet west of San Francisco Bay (refer to Figure 3-3). The site is currently developed and occupied by two businesses (Airgas and DHL) at 525 23^rd Street. The existing buildings would need to be demolished during site preparation. The site is currently zoned Major Industrial, which permits the proposed use. The site is located on fill material and currently contains subsurface contamination (soil and groundwater). Planned remediation prior to construction of the converter station is discussed in Section 4.A.14, Hazardous Materials and Waste Management, of this Final EIR.

An aerial view of the existing HWC (Mitigated) site is shown on Figure 3-3 of the Final EIR, with the proposed converter station site boundary 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 architecturally appropriate treatments to the buildings and the sound walls on the west, north, and south site perimeters in areas that are visible to the public. Access to the site would be via 23^rd Street, and no new offsite road construction would be required. The proposed HWC (Mitigated) Converter Station layout, elevation view, and two photosimulations are shown on Final EIR Figures 3-4 through 3-7.

The proposed onshore route for the HVDC entry into the San Francisco Converter Station from San Francisco Bay runs west along 23^rd Street before turning south 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 (refer to Figure
3-8 of the Final EIR).

The double-circuit 115 kV HVAC interconnecting cable would exit the proposed San Francisco Converter Station from the north side and cross 23^rd Street approximately 300 feet from the easterly line of Illinois Street, and then extend northward along the eastern boundary of the existing PG&E Potrero substation, where it would enter the substation and connect with the electrical grid (refer to Figure 3-3 of the Final EIR).

The proposed construction laydown area for the San Francisco site is south of the HWC site off of Cargo Way at Pier 94/96. This laydown area was identified as an alternate in the Draft EIR. The laydown area at Pier 94/96 is owned by the Port of San Francisco and designated as the "Pier 94/96" 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 Cargo Way. The site has no standing buildings or structures, and lies on land that was reclaimed from San Francisco Bay early in the twentieth century. The previously proposed (Draft EIR) laydown area at the Western Pacific site has been removed from consideration due to space constraints with pending development at this site.

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 53 miles from the now proposed HWC (Mitigated) Converter Station site in San Francisco to the West Tenth Street Alternative 1 Converter Station site in Pittsburg, California (refer to Figure 3-1 and Map
A.2-1 which has been revised and incorporated into Section 3.0 of this Final EIR). 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 3-9 of this Final EIR).

The proposed submarine cable would extend from San Francisco to Pittsburg below the floor of San Francisco Bay, San Pablo Bay, the Carquinez Strait, and Suisun Bay. 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 (or equivalent) 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 3-10 of this Final EIR) 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 the seabed materials by the use of water jets 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 now proposed 5.8-acre converter station site in the City of Pittsburg is the Pittsburg West Tenth Street Alternative 1 site which was evaluated as an alternative in the Draft EIR. The formerly proposed Standard Oil site and associated ancillary facilities (i.e., AC/DC cable routes, construction laydown areas, and access road) have been deleted from consideration in this Final EIR.

The Pittsburg West Tenth Street Converter Station Alternative 1 (E/W) site is located north of West Tenth Street and west of Beacon Street in close proximity to the PG&E 230 kV substation (refer to Figures 3-1 and 3-11 of this Final EIR). Use of this site would require leasing or procuring and reconfiguring several parcels in the northwest quadrant of the overall West Tenth Street group of parcels. Existing development on the West Tenth Street site includes light industrial businesses. The Alternative 1 site is in proximity to a new residential community on the south side of West Tenth Street. The City of Pittsburg is in the process of amending the existing CS-O (1171) zoning district (Service Commercial with Limited Overlay [Ordinance No. 00-1171]) for a group of parcels. The affected zoning district includes Assessor Parcels 085-270-016, 085-270-018, 085-270-019, 085-270-020, 085-270-022, 085-270-025, 085-270-026, 085-270-029, 085-270-032, 085-270-035, 085-270-036, 085-270-038, 085-270-039, and 085-270-040) and encompasses an area larger than that required for the converter station layout under consideration for the Pittsburg West Tenth Street Converter Station Alternative 1 site. The details of the proposed Overlay Zoning Amendment would be as follows with respect to allowable uses, setbacks, and height limitation:

"Utility, Major " with the additional land use regulations: "L39 Limited, as a permitted use, to electrical substations of 50 megawatts or less, or AC/DC power converter stations with electrical transformers. Any structures must be located a minimum of 35 feet from the right-of-way of West Tenth Street and a minimum of 600 feet from the right-of-way of Beacon Street, and with the maximum height of any building not to exceed 65 feet and/or any ancillary structure/tower not to exceed 80 feet in height. The site perimeter must be planted with a substantial screen of evergreen trees and other landscaping in order to minimize the impact of the size, height and bulk of the structures."

This revised text to the City of Pittsburg Zoning Ordinance is based on a Zoning Amendment proposed by the City in order to satisfy the needs of the Project proponent. The language above does not apply to land use on West Tenth Street as it exists today.

The Pittsburg West Tenth Street Converter Station Alternative 1 location (including ancillary facilities), layout under consideration, elevation views, and a photosimulation are presented on Figures 3-11 through 3-14 of this Final EIR. This site includes a proposed permanent access road that would connect to West Tenth Street (refer to Figure 3-12 of this Final EIR). Construction traffic would access this site via the existing access road to the Mirant Pittsburg Power Plant north of West Tenth Street on the west side of the site.

An aerial view of the existing West Tenth Street Alternative 1 (E/W) site is shown on Figure 3-11 of this Final EIR. 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.

The proposed construction laydown areas for the Pittsburg West Tenth Street Alternative 1 (E/W) Converter Station site are located on the adjacent Mirant Pittsburg property north of the site (refer to Figure 3-11 of this Final EIR). 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.

For the most part, the AC and DC cable routes for the now proposed Pittsburg West Tenth Street Converter Station Alternative 1 (E/W) site would be located on the Mirant Pittsburg Power Plant property. The AC cable would start from the north side of this proposed converter station site, enter the Mirant Pittsburg Power Plant property, travel north-northwest through the southern tank farm along Mirant's access road, loop east, and connect to the PG&E switchyard (refer to Figure 3-11 of this Final EIR).

The DC cable route would follow the AC cable route for most of the land portion of the distance between the proposed West Tenth Street Converter Station Alternative 1 (E/W) site and the DC cable entry point into Suisin Bay. At the point where the AC cable diverges to the PG&E switchyard, the DC cable would continue to the northeast to the edge of the Mirant Pittsburg Power Plant property before turning northwest into Suisin Bay. The transition from onshore to offshore would be completed via HDD (refer to Figure 3-15 of this Final EIR).

3.5    Operation

It is currently anticipated that the Project would become operational as early as 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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