SECTION 9.0

UNAVOIDABLE ADVERSE SIGNIFICANT IMPACTS

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9.1    INTRODUCTION

This section discusses unavoidable significant adverse impacts that would be expected to occur if the proposed Trans Bay Cable Project (Project), including alternatives, was implemented. Unavoidable significant adverse impacts are those which cannot be reduced to a less-than-significant level. Approval and implementation of a project that involves unmitigable significant impacts typically requires a Statement of Overriding Considerations by the Lead Agency for CEQA compliance (i.e., City of Pittsburg for this Project). Unavoidable significant adverse impact findings are summarized in the following sections, by proposed converter station site, and alternative converter station site, as applicable.

9.2    PROPOSED PROJECT

9.2.1    San Francisco HWC Converter Station

See Section 4.7, Cultural Resources, for details regarding the nature of buildings addressed in the following impact discussions.

9.2.1.1    Cultural Resources

Impact CUL-2: Disturbance of Historical Architectural Resources. The construction of the converter station would require demolition of historical resources. This action would cause a significant adverse change to these historical resources under CEQA. This is considered a significant impact.

Mitigation Measure CUL-2a: Recording Architectural Resources. Recording would ensure a permanent record of the present appearance and context of the historical resources. Under this mitigation proposal, the Project proponent would ensure that the historical resources to be demolished would be recorded to Historic American Buildings Survey (HABS) and Historic American Engineering Record (HAER) standards prior to any construction activities. The HABS/HAER documentation would be filed with the State Historic Preservation Officer (SHPO), the HABS/HAER collection in the Library of Congress, the University of California Bancroft Library, the San Francisco Landmarks Preservation Advisory Board files at the San Francisco Planning Department, the Foundation for San Francisco's Architectural Heritage (FSFAH), and the San Francisco Public Library.

Although recording eliminates one adverse impact of demolition (the loss of historical information), it does not prevent the physical loss of historically significant resources. Therefore, additional mitigation measures should be developed and could include Mitigation Measures CUL-2b and CUL- 2c:

Mitigation Measure CUL-2b: Architectural Resource Interpretive Display and/or Interpretive Material. The Project proponent would develop a display or interpretive material for public exhibition and dispersal. The display or interpretive material, such as a printed brochure, could be based on the photographs produced in the HABS/HAER documentation, and the historic archival research previously prepared for the resources in and near the Project. This display and/or interpretive material would be provided to the City of San Francisco.

Mitigation Measure CUL-2c: Architectural Resource Salvage Opportunities. After recording and at least 30 days prior to demolition, the interested parties would have the opportunity to salvage architectural elements for re-use or curation. Items selected would be removed in a manner that minimizes damage to those items.

Resulting Level of Significance. Mitigation Measures CUL-2a through 2c are intended to be part of the overall consideration of impacts to historical resources as part of this Project. While implementation of Mitigation Measures CUL-2a through CUL-2c would lessen Project impacts, demolition of historical resources is a significant adverse change that cannot be mitigated to a less-than-significant level. These proposed mitigation options, therefore, will be discussed and refined by the Project proponent and other responsible agencies in conjunction with preparation of a Statement of Overriding Considerations. Mitigation measures will be set forth in the Mitigation Monitoring Reporting Program (MMRP), which will include input from other responsible agencies.

No other unavoidable significant adverse impacts have been identified for the proposed Project.

9.3    PROJECT ALTERNATIVES

9.3.1    San Francisco Mirant Converter Station Alternative

9.3.1.1    Cultural Resources

See Section 4.7, Cultural Resources, for details regarding the nature of buildings addressed in the following impact discussions.

Impact CUL-2: Disturbance of Historical Architectural Resources. The impact findings and discussion, including proposed mitigation measures, presented in Section 9.2.1.1 for the proposed HWC Converter Station also apply to the San Francisco Mirant Converter Station Alternative (all three sites/layouts).

9.3.2    Pittsburg West Tenth Street Converter Station Alternative 2 (N/S)

9.3.2.1    Noise and Vibration

Impact NOISE-2: Construction Sound Levels. The construction sound levels hazard (Impact NOISE-2) described in Section 5.11.3.2.1 applies to the Pittsburg West Tenth Street Converter Station Alternative 2 site. Sound levels from pile driving at the Pittsburg West Tenth Street Alternative 2 site would be 95 dBA L_max (90 dBA L_eq) at the residences 150 feet south. Although Pittsburg does not restrict sound levels from pile driving, the FTA recommends that hourly sound levels of 90 dBA from pile driving be considered a significant impact at residences (FTA, 1995).

Mitigation Measure NOISE-2: Construction Noise Control Measures. Mitigation Measure NOISE-2 described in Section 5.11.3.2.1 shall be applied to the Pittsburg West Tenth Street Converter Station Alternative 2 site.

Implementation Responsibility:  Project proponent/construction contractor

Requirements and Timing:         Submit plans and obtain approval from City of Pittsburg Planning Department during Design Review

Monitoring Requirements:          City of Pittsburg to monitor and ensure compliance

Resulting Level of Significance. The City of Pittsburg noise ordinance prohibits pile driving between the hours of 10 p.m. and 7 a.m. While implementation of Mitigation Measure NOISE-2 would lessen noise impacts from pile driving at the sensitive receptors (residences) in proximity to this site, this impact cannot be reduced to a less-than-significant level. Accordingly, a Statement of Overriding Considerations would be required for this impact.

9.3.2.2    Visual Resources

Impact VIS-5: Converter Station Domination of View. This impact is similar to Impact VIS-1 described previously for the other converter station sites under consideration. However, given the size and height of the converter station at the West Tenth Street Converter Station Alternative 2 (N/S), the Project would generate a potentially significant impact and more intensive mitigation would be required. While in this circumstance it is not possible to reduce the impact to a less-than-significant level, CEQA does call for identification of mitigation measures which may reduce the adversity of the impact. This design effort would be concerned with the selection of appropriate architectural design and building colors as well as the landscape design in the street yard setback area.

Mitigation Measure VIS 5a: West Tenth Street Converter Station Alternative 2: Street Yard Setback. The Project proponent shall work with the City of Pittsburg to rezone the property to provide a front yard setback of 35 feet and increase the height restriction to 65 feet for all buildings and 80 feet for ancillary structures.

Implementation Responsibility:  Project proponent

Requirements and Timing:         Comply with setback and height limitations in final design plans and obtain approvals prior to construction

Monitoring Requirements:          City of Pittsburg to monitor and ensure compliance

Mitigation Measure VIS 5b: Street Yard Landscape. The Project proponent shall work with the City of Pittsburg to provide a secure and extensive landscape plan for the street yard along the frontage of West Tenth Street to partially reduce the adverse and significant visual impact of the converter station at this location. Specific elements in this plan include:

• Multiple layers of vegetative screening shall be selected from the City of Pittsburg-approved planting list. This screening shall be generally located to create the visual effect simulated in Photo C, Figure 5.5-2. The intent is to soften and obscure the physical form and mass of the DC/valve hall as seen from residences across the street and travelers along West Tenth Street, not completely screen the structure. Various heights, colors, and textures of vegetation shall be selected and the trees shall be clustered to avoid the effect of a rigid soldier row. The tree selection shall include species which would be expected to reach 45 feet in height within five years.

• The perimeter security fence/wall shall be set back from the rear of the sidewalk by a minimum of 15 feet. Chain link fencing shall not be used. If fencing is selected then it shall be of wrought iron or steel pickets. If a solid wall is preferred, the surface material shall be a split face block or stucco compatible with the residential development across West Tenth Street. No visible barbed wire shall be allowed to meet security requirements.

Implementation Responsibility:  Project proponent

Requirements and Timing:         All plans shall be prepared by professionals qualified in the designated field of expertise; plans and revised design shall be submitted prior to final planning approval to ensure that the identified mitigation measure is satisfied

Monitoring Requirements:          City of Pittsburg to monitor and ensure compliance

Mitigation Measure VIS-5c: Architectural Design and Building Colors. The Project proponent shall work with the City of Pittsburg to design a structure that is compatible in materials with the neighborhood and select colors that will minimize visual impacts with the adjacent community. While this effort will partially reduce the adverse and significant impact of the converter station at this location, the significant impact would remain. Specific elements in this plan shall include:

• Work with the City of Pittsburg architectural review process to select a building design that effectively reduces the street façade to the minimum consistent with the technical requirements of the equipment housed within the structures

• Select building surface materials, such as stucco, that are compatible with the adjacent community<

• Select muted light colors that will minimize apparent bulk and height of the DC/valve hall and other structures

Implementation Responsibility:  Project proponent

Requirements and Timing:         All plans shall be prepared by professionals qualified in the designated field of expertise; plans and revised design shall be submitted prior to final planning approval to ensure that the identified mitigation measure is satisfied

Monitoring Requirements:          City of Pittsburg to monitor and ensure compliance

Resulting Level of Significance. Application of Mitigation Measures VIS-5a, 5b, and 5c would help reduce the Impact VIS-5, but would not mitigate the impact to a less-than-significant level. Accordingly, a Statement of Overriding Considerations would be required for this impact.

No other unavoidable significant adverse impacts have been identified for the Project alternatives.