5.5 PITTSBURG WEST TENTH STREET ALTERNATIVE 2 (N/S)

SECTION 5.0

ENVIRONMENTAL SETTING, IMPACTS, AND MITIGATION

PROJECT ALTERNATIVES

5.5 PITTSBURG WEST TENTH STREET ALTERNATIVE 2 (N/S)

5.5.1 Introduction

The Pittsburg West Tenth Street Converter Station Alternative 2 (N/S) site is located adjacent to and east of the Pittsburg West Tenth Street Alternative 1 (N/S) site described in Section 5.4.1 (refer to Figure 5.4-3). The information presented in Section 5.4 is generally applicable to this site as well, however, this site is oriented in a north-south configuration and is closer to West Tenth Street and the residences to the south of West Tenth Street. The fact that this alternative site is closer to the residences south of West Tenth Street influences the impact assessments for noise and vibration and visual resources. In addition, the onshore AC/DC cable routes for Alternative 2 have the potential to impact a wetland area north-northwest of the converter station site whereas the Alternative 1 cable routes would completely avoid this sensitive habitat. Access to the Pittsburg West Tenth Street Converter Station Alternative 2 site would be from West Tenth Street at the southern end of the site. The Pittsburg West Tenth Street Converter Station Alternative 2 location (including ancillary facilities), layout under consideration, elevation views, and a photosimulation are presented on Figures A.1-1 and A.8-24 through A.8-27 in Appendix A.

5.5.2 Air Quality

5.5.2.1 Environmental Setting

The environmental setting for air quality associated with the Pittsburg West Tenth Street Converter Station Alternative 2 site in Pittsburg is as described in Section 4.2.1.

5.5.2.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station, Alternative 2 (N/S) are as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measures AIR-1 (Fugitive Dust Controls) for Impact AIR-1 (Fugitive Dust Emissions)
Mitigation Measure AIR-2 (Exhaust Controls) for Impact AIR-2 (Equipment Exhaust Emissions)

Potentially significant impacts associated with installation of the offshore DC cable route (refer to Section 4.2.3.4) apply equally to this alternative converter station site. However, offshore cable installation for the proposed Pittsburg Standard Oil Converter Station would involve slightly more offshore cable installation with associated marine vessel emissions than this alternative converter station site. The emissions estimates presented in Section 4.2.3 and Appendix D are based on the proposed Standard Oil Converter Station site - i.e., selection of the Pittsburg West Tenth Street, Alternative 2 (N/S) site would result in slightly less emissions than accounted for in Section 4.2.3 for the proposed Standard Oil Project site.

5.5.3 Geologic Resources and Soils

Background geological resources and soils data for the proposed Project is presented in Section 4.3. This background information is also generally applicable to this alternative site.

5.5.3.1 Environmental Setting

Site-specific environmental setting and information for this alternative site are as discussed in Section 5.4.3.1 for the Pittsburg West Tenth Street Converter Station Alternative 1 site which are essentially the same site with respect to geologic conditions and soils.

5.5.3.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site, and Section 5.4.3 for the Pittsburg West tenth Street Converter Station Alternative 1 site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure GEO-1 (Design Project for Erosion Control) for Impact GEO-1 (Soil Erosion and Compaction)
Mitigation Measure GEO-3 (Design to Seismic Design Requirements) for Impact GEO-3 (Strong Ground Shaking)
Mitigation Measure GEO-4 (Design Project for Liquefiable Deposits) for Impact GEO-4 (Liquefaction)
Mitigation Measure GEO-5 (Design Project for Shrink-Swell/Subsidence) for Impact GEO-5 (Shrink-Swell/Subsidence)

5.5.4 Water Resources and Quality

5.5.4.1 Environmental Setting

The environmental setting for the Pittsburg West Tenth Street Alternative 2 site is as described in Section 5.4.4.2 for the Alternative 1 site, except that the Alternative 2 site is not located within a 100-year flood zone.

5.5.4.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 site are generally as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure WATER-1 (Erosion Control and Contaminant Source Control) for Impact WATER-1 (Erosion and Contaminated Runoff)
Mitigation Measure WATER-2 (Spill Prevention and Control Plan for HDD) for Impact WATER-2 (Surface Water Quality Impacts from HDD)
Mitigation Measure WATER-3 (Use of Pilot Hole and Reaming) for Impact WATER-3 (Groundwater Quality Impacts from HDD)

5.5.5 Terrestrial Biological Resources

5.5.5.1 Environmental Setting

The Pittsburg West Tenth Street Converter Station Alternative 2 site (N/S) includes Township 2 North, Range 1 East, in an undefined southeastern section of the Honker Bay 7.5-minute USGS Quadrangle with elevations ranging from 0 to 15 feet above mean sea level (see Sheet 10 of Map A.2-1 and Figure A.8-24). This location corresponds to the northwestern side of Pittsburg, near West Tenth Street and Willow Pass Road, and occurs within industrialized and previously disturbed landscapes. A small section of cleared and maintained field with planted horticultural trees and ruderal herbaceous weed species occurs along the Mirant Property entrance road adjacent to West Tenth Street, and one wetland ditch dominated by cattail (Typha sp.) wetland occurs near the entrance to the Mirant property (just before the security gate and north of the Pittsburg West Tenth Street Alternative 2 site). This ditch runs in a culvert under the Mirant entrance road.

5.5.5.2 Environmental Impacts

5.5.5.2.1 Construction-related Impacts.

Potential Impacts to Natural Communities and Wildlife Habitat. The majority of this site is dominated by previously developed and industrialized landscapes described in Section 4.5 as Disturbed/Developed habitats. A smaller section of the onshore cable route near the entrance to the Mirant Power Plant and West Tenth Street contains heavily disturbed California annual grassland series vegetation along the edges of a paved roadway (entrance road to Mirant) and one freshwater ditch that is vegetated with cattail wetland with a culvert under the entrance road to the Mirant property.

Impacts to Wetlands. One freshwater canal wetland dominated by cattail occurs along the cable route near the entrance to the Mirant property. Impacts to this wetland could occur from onshore cable trenching across this area associated with the Pittsburg West Tenth Street Converter Station Alternative 2.

Impacts to Potentially Occurring Special-status Species. Western pond turtle has the potential to be impacted by construction of the AC/DC of cable route near marshes and open water ditches associated with the Pittsburg West Tenth Street Converter Station Alternative 2.

Giant garter snake historically ranged throughout the Sacramento and San Joaquin valleys but is very scarce throughout its range due to the elimination of natural sloughs and marshy areas. This federally-listed threatened species is an active diurnal snake rarely found away from water. It is likely to feed upon introduced species such as mosquito fish, carp, and minnows, as native historic food sources are often unavailable. Potential habitat within the Project area is located within the open surface run-off ditch, and wetlands within portions of the Mirant property along the West Tenth Street Converter Station Alternative 2 onshore cable route.

Terrestrial Endangered, Rare, or Threatened Species. This alternative (cable route) has the potential to significantly impact, either directly or through habitat modifications, terrestrial endangered, rare, or threatened species, as listed in Title 14 of the California Code of Regulations (Sections 670.2 or 670.5) or in Title 50, Code of Federal Regulations (Sections 17.11 or 17.12).

Giant Garter Snake and Western Pond Turtle. This alternative has the potential to affect these species if they are present in the vegetated freshwater ditch near the entrance to the Mirant property within the proposed cable route for this alternative site. This surface run-off ditch provides potential habitat for these species, because it contains a continuous water supply and sufficient emergent vegetation. Western pond turtles are known from the immediate vicinity of the Project area while giant garter snake is expected from the region in these habitat types. Snakes and turtles could be incidentally harmed or harassed by construction activities if they were foraging within the Project area adjacent to the wetland or within the canal/ditch at the time of construction.

Impact TBIO-3: Disturbance or Fill of Wetlands and Streams. Potential jurisdictional wetlands exist in the Project area that may be filled or altered during construction, due to project trenching for onshore cables associated with the Pittsburg West Tenth Street Converter Station Alternative 2 site. This is a potentially significant impact.

Mitigation Measure TBIO-3e: Implement HDD or Comparable Technology Techniques to Avoid Impacts to Wetlands. The onshore cable routes for the Pittsburg West Tenth Street Converter Station Alternative 2 site shall incorporate HDD or comparable technology techniques from the converter station site to the north and west to the paved access road into the Mirant Pittsburg Power Plant to avoid impacts to the wetland area and associated habitat. This mitigation measure would also avoid potential impacts to giant garter snake and western pond turtle habitat as well as annual grassland vegetation. The HDD shall be drilled at a minimum of 15 feet below the bottom of the wetland area in order to avoid a "frac-out" (i.e., release of drilling mud). The temperatures associated with the buried AC cable are expected to be warmer than ambient soil temperatures over a limited area (refer to Appendix F for more information). The required minimum HDD depth shall also remove any potential for impacts to this wetland due to potential heating from the buried cable. Implementation of the HDD or comparable technology techniques would avoid impacts to the wetland within this portion of the onshore cable route.

Implementation Responsibility: Project proponent/construction contractor

Requirements and Timing: HDD operations shall be conducted as discussed above during the applicable portion of the construction phase.

Qualified biological monitors shall be required to be present during Project-related ground disturbance in this area.

Monitoring Requirements: City of Pittsburg to monitor and ensure compliance

Resulting Level of Significance. Implementation of Mitigation Measure TBIO-3e would reduce Impact TBIO-3 to a less-than-significant level.

With implementation of the following additional mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure TBIO-4a (Avoidance of Habitat and Timing of Construction), TBIO‑4b (Worker Training for Giant Garter Snake and Western Pond Turtle), TBIO-4c (Biological Monitoring for Giant Garter Snake and Western Pond Turtle), and TBIO-4d (Avoiding Impacts to Wetlands and Habitat) for Impact TBIO-4 (Potential Impacts to Giant Garter Snake and Western Pond Turtle)

5.5.6 Marine Biological Resources

5.5.6.1 Environmental Setting

Background information, including evaluation of marine biological resources with the potential to occur in the Project area, as well as the regulatory framework, are provided in Section 4.6.

5.5.6.2 Environmental Impacts

The Pittsburg West Tenth Street Converter Station Alternative 2 would eliminate the need for the HVAC installation in the Bay, and would reduce the length of the HVDC installation by approximately 4 miles relative to the proposed Standard Oil site. No cable installation would be needed in the channel between Winter Island and Browns Island and no dredging would be needed. This would result in incrementally lower construction and operational impacts relative to those described in Section 4.6. No construction or operation impacts would occur east of the Mirant Pittsburg property under this alternative.

5.5.7 Cultural Resources

5.5.7.1 Environmental Setting

The environmental setting for cultural resources for the Pittsburg West Tenth Street Converter Station Alternative 2 site is as described in Section 5.4.7.1 for the Alternative 1 site.

5.5.7.2 Environmental Impacts

The environmental impacts for Alternative 2 are as described for Alternative 1 in Section 5.5.6.2; no potentially significant impacts to cultural resources are anticipated associated with Alternative 2.

5.5.8 Land Use and Recreation

5.5.8.1 Environmental Setting

The environmental setting for land use and recreation for the Pittsburg West Tenth Street Alternative 2 is as described in Section 5.4.8.1 for Alternative 1, except that the Alternative 2 (N/S configuration) (refer to Figure A.8-20) site is located approximately 300 feet closer to the residences on the south side of West Tenth Street than Alternative 1.

5.5.8.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 site are as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site and in Section 5.4.8.2 for the Pittsburg West Tenth Street Alternative 1 site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure LU-2 (Height Allowance) for Impact LU-2 (Exceedence of Height Allowance)

5.5.9 Marine Transportation and Commercial Fishing

If the Pittsburg West Tenth Street Converter Station alternative was selected instead of the Standard Oil site, there would be no need to install the submarine AC and DC cables between the PG&E Pittsburg substation and the Standard Oil Converter Station site landfall on the east end of New York Slough. This alternative would therefore avoid the potential local impacts to commercial marine transportation and commercial fishing vessel operation east of the Mirant Pittsburg property. Selection of this alternative would also avoid the need to dredge the shipping channel in two locations on either end of New York Slough, thereby minimizing potential impacts relative to the proposed Standard Oil Converter Station site.

5.5.10 Traffic and Transportation

5.5.10.1 Environmental Setting

The environmental setting for traffic and transportation for the Pittsburg West Tenth Street Converter Station Alternative 2 is as described in Section 5.4.10.1 for Alternative 1.

5.5.10.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site and Section 5.4.10.2 for the Pittsburg West Tenth Street Converter Station Alternative 1. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure TRAFFIC-1 (Coordination to Reduce Cumulative Traffic Impacts) for Impact TRAFFIC-1 (Cumulative Traffic Impacts)
Mitigation Measure TRAFFIC-2 (Coordination of Oversized Loads) for Impact TRAFFIC-2 (Oversized Loads)

5.5.11 Noise and Vibration

5.5.11.1 Environmental Setting

The environmental setting for noise for the Pittsburg West Tenth Street Converter Station Alternative 2 is as described in Section 5.4.11.1 for Alternative 1, although the Alternative 2 site is oriented north-south and is much closer to the residences on the south side of West Tenth Street than Alternative 1.

5.5.11.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are generally as described in Section 4.11.3 for the proposed Pittsburg Standard Oil site and Section 5.4.11.2 for the Pittsburg West Tenth Street Converter Station Alternative 1 site, except as noted below for impacts due to pile driving.

5.5.11.2.1 Construction-related Impacts. Scheduled construction hours at the alternative Pittsburg West Tenth Street Converter Station site are consistent with those given for the proposed Standard Oil Project site in Section 4.11. Criteria are not set forth by the Pittsburg Noise Element or Noise Ordinance related to construction noise levels and times of operation. The anticipated noise sources would be the same as those outlined for the proposed Project site in Section 4.11.

Acoustical calculations were performed to estimate noise from construction activities at the closest residences with the same methodology as described for the Pittsburg Standard Oil Converter Station site. The closest offsite residential uses to the alternative West Tenth Street Converter Station Alternative 2 site (N/S configuration) consist of multi-family residences approximately 150 feet to the south and 600 feet to the east. Average sound levels at the closest residences to this alternative site would be 79 and 67 dBA, respectively, as summarized in Table 5.5.11-1.

TABLE 5.5.11-1
CALCULATED SOUND LEVELS FROM CONSTRUCTION OF THE
PITTSBURG WEST TENTH STREET CONVERTER STATION – ALTERNATIVE 2

Converter Station Site	Receptor Description	Distance to Receptors (Ft)	Calculated Sound Level from Construction (dBA)	Calculated Sound Level from Pile Driving (dBA)
				L_max	L_eq
Pittsburg West Tenth Street Alternative 2 (N-S Orientation)	Single-family residences (182 Builders Court)	150	79	95	90
	Single-family residences (900 Beacon Street)	600	67	83	78

Construction noise would be audible at the residential receptors south of West Tenth Street. Construction noise would be intermittent and limited to the hours of 7:00 a.m. to 7:00 p.m. Monday through Friday, thus there would be no significant impact.

Pile Driving. Calculations were performed to estimate sound levels from pile driving at the receptors (refer to Table 5.5.11-1). Direct line-of-sight sound levels at the residences from the Alternative 2 site were calculated to be 95 dBA L_max (90 dBA L_eq) at the residences 150 feet south and 83 dBA L_max (78 dBA L_eq) at the residences 600 feet east. Although pile driving is not subject to sound level restrictions in Pittsburg, it is limited to the hours of 7:00 a.m. to 10:00 p.m. However, because received noise levels from pile driving are calculated to be higher than 90 dBA at the closest receptors for Alternative 2, this is a potentially significant impact.

Impact NOISE-2: Construction Sound Levels. Sound levels from pile driving at the Pittsburg West Tenth Street Alternative 2 site are calculated to be 95 dBA L_max at the residences on the south side of West Tenth Street. This impact would occur over an estimated 4- to 5-month period. Pittsburg does not restrict sound levels from pile driving, however, the FTA recommends that hourly sound levels of 90 dBA from pile driving be considered a significant impact at residences (FTA, 1995). Accordingly, this impact is considered to be potentially significant.

Mitigation Measure NOISE-2: Construction Noise Control Measures. Mitigation Measure NOISE-2 shall be applied to the Pittsburg West Tenth Street Converter Station Alternative 2 site. The Project proponent shall submit and implement a noise reduction plan containing site-specific noise attenuation measures to ensure maximum feasible noise attenuation. The noise reduction plan shall be approved by the City of Pittsburg.

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. Noise mitigation measures (e.g., shrouding) for pile driving are difficult to implement and typically capable of reducing noise levels by 10 dBA at most. Although mitigation would reduce the severity of this impact, the impact remains significant. Approval of the Pittsburg West Tenth Street Converter Station Alternative 2 would require a Statement of Overriding Considerations by the City of Pittsburg.

Calculations were performed to estimate vibration from pile driving activities at the closest residences. Vibration from pile driving was assumed to have point source propagation characteristics. Vibration levels for impact pile drivers are typically 0.644 inches/second peak particle velocity (PPV) at 25 feet (FTA, 1995). Under normal propagation conditions, vibration levels at residences 150 feet from the pile driving for Alternative 2 would be less than 0.08 in/sec, which is well below the FTA threshold of 0.20 in/sec; resulting in a less than significant impact.

Construction Traffic. Construction traffic impacts for Alternative 2 are as described for Alternative 1 in Section 5.4.11.2.

5.5.11.2.2 Operations-related Impacts. Calculations were performed using linear octave band sound power levels as inputs from each noise source. Siemens conducted the noise analysis, the results of which are summarized here and provided in Appendix H. As summarized in Table 5.5.11-2, unmitigated sound levels at the alternative West Tenth Street Converter Station sites would exceed the City of Pittsburg 75 L_dn requirement. This is considered to be a potentially significant impact. With implementation of the following

TABLE 5.5.11-2
CALCULATED SOUND LEVELS FROM OPERATION OF THE
PITTSBURG WEST TENTH STREET CONVERTER STATION – ALTERNATIVE 2

Converter Station Site	Receptor Description	Calculated Sound Level (dBA)	Calculated Sound Level (dBA) With Mitigation
Pittsburg West Tenth Street Alternative 2 (N-S orientation)	North Property Line	78 L_dn	74 L_dn
	South Property Line	77 L_dn	66 L_dn
	East Property Line	76 L_dn	72 L_dn
	West Property Line	79 L_dn	72 L_dn
	Receptors	70 L_dn	60 L_dn

mitigation measures, this potentially significant impact would be reduced to a less-than-significant level:

Mitigation Measure NOISE-1 (Noise Barrier Installation for Alternative Converter Station) for Impact NOISE-1 (Converter Station Operations Sound Levels)

5.5.12 Public Services and Utilities

5.5.12.1 Environmental Setting

The public services and utilities discussions for the Pittsburg West Tenth Street Converter Station Alternative 2 site (including associated onshore cable routes) are consistent with the proposed Standard Oil site discussed in Section 4.12, except for the distances to certain facilities that are as discussed in Section 5.4.12.1 for the Pittsburg West Tenth Street Converter Station Alternative 1.

5.5.12.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are generally as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site, except as noted in Section 5.4.12.5 for the Pittsburg West Tenth Street Alternative 1 site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure PS-1 (Construction Fire Prevention) for Impact PS-1 (Construction-related Fire Hazards)
Mitigation Measure PS-2 (Utility Survey) for Impact PS-2 (Existing Onshore Underground Utilities)
Mitigation Measure PS-3 (Operations Fire Prevention) for Impact PS-3 (Operations Fire Hazards)

5.5.13 Visual Resources/Aesthetics

5.5.13.1 Environmental Setting

This alternative site is located in an industrial area of Pittsburg, south of the existing Mirant Pittsburg Power Plant property and the existing PG&E Pittsburg substation (Photo 1, Figure 5.4-1). The Pittsburg West Tenth Street Converter Station Alternative 2 is located in the central portion of the overall West Tenth Street property and is oriented in a north-south direction. The proposed site is set within the commercial frontage along West Tenth Street. It is opposite the entry to a new residential community that was recently developed (Photo 2, Figure 5.4-1) on the south side of West Tenth Street. The existing character in the area to the east and west is one of wholesale and service commercial business of a relatively modest scale. In the background is the larger scale series of fuel tanks and the Mirant Pittsburg Power Plant with its substantial stack visible in the photo at mid right. Traffic on West Tenth Street used to be predominantly commercial but recently, with the development of new housing tracts to the west of Pittsburg, there is an increasing amount of residential traffic as well.

5.5.13.1.1 Visual Quality. There is relatively low-density commercial clutter on the north frontage of West Tenth Street with a backdrop of heavy industrial as indicated by the tanks and stacks. There are no scenic vistas or natural features. The visual quality is lacking in harmony and coherence. Visual quality is classified as Low.

5.5.13.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are generally as described in Section 4.2.3 for the proposed Pittsburg Standard Oil site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level.

This Pittsburg West Tenth Street Converter Station, Alternative 2 (N/S) site is situated in a north-south configuration, connecting the abandoned railway corridor and to the frontage on West Tenth Street (Photo A, Figure 5.4-1). In this configuration, the large valve and DC halls with their ridgeline of 64 feet would be relatively close to West Tenth Street compared to Pittsburg West Tenth Street Converter Station Alternative 1 (E/W). At this time no supplemental architectural design has been proposed as part of the Project.

The present CS-O zoning district allows a maximum height of 35 feet. The converter station would not be allowed at this location with the current zoning. The visual analysis below assumes that this issue would be addressed via a pending amendment to the Zoning Overlay for the collective West Tenth Street parcels which will address acceptable uses, setbacks, and height limitations.

5.5.13.2.1 KOP P-3.2: West Tenth Street. Key observation points (KOPs) for this alternative site are shown on Map 5.4-1. Alternative 2 (N/S), unlike Alternative 1 (E/W), encroaches close to West Tenth Street with a proposed 35-foot setback (Photo B, Figure 5.5‑1). In this configuration, the 64-foot ridgeline would dominate the streetscape since the structure is almost three times as high as adjacent structures which are in the 20- to 24-foot range. A project at this location would also require a zoning and height limitation change by the City of Pittsburg. The City is currently processing a Zoning Overlay Amendment for a 35-foot setback and a 65-foot height limitation. While the alternative Project would meet this proposed criteria, the Impact Severity is classified as High given the great change in mass which would be obtrusive along this street frontage.

The Impact Susceptibility for the area is classified as Moderate given the residential project across the street with a resulting Impact Severity of Significant. There is the potential to reduce the impact level through mitigation (Photo C, Figure 5.5-2). The Project proponent has proposed a landscaping plan with multiple layers of landscape planting ranging from shrubs to clusters of trees selected from the City of Pittsburg's approved planting list (Photo C, Figure 5.5-2). The Project proponent determined that some potential mitigation measures (such as reducing the height of the DC/valve hall or increasing the setback from West Tenth Street) would not be possible given the technical constraints of the equipment size and layout as well as the constrained size of the property available.

Light and glare would be a concern with the recent residential development south of West Tenth Street. With implementation of the following mitigation measure, this potentially significant impact would be reduced to a less-than-significant level:

Mitigation Measure VIS-2 (Plan Submittal Requirements for Lighting) for Impact VIS-2 (Converter Station will Create Substantial Light and Glare)

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 level of impact, 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 shall 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 the 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

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. Approval of the Pittsburg West Tenth Street Converter Station Alternative 2 would require a Statement of Overriding Considerations by the City of Pittsburg.

5.5.14 Hazardous Materials and Waste Management

5.5.14.1 Environmental Setting

The Pittsburg West Tenth Street Converter Station Alternative 2 site (north-south configuration is located in a light industrial and service commercial business area of Pittsburg, south of the existing Mirant Pittsburg Power Plant property and the existing PG&E Pittsburg substation (refer to Figures A.1-1 and A.8-24). The Pittsburg West Tenth Street Converter Station Alternative 2 site is shown on Figure 5.4-3, which also shows the site parcel numbers and some of the current site activities. The environmental setting for this alternative site is as described in Section 5.4.14.1 for the Alternative 1 site, except as noted below.

The northern half of the overall West Tenth Street location (i.e., group of parcels) has more contamination than the southern half. Therefore, Alternative 2, the north-south converter station configuration, likely has less contaminated soil that would need to be disposed of than Alternative 1, the east-west converter station configuration.

Alternative 2, the north-south converter station configuration, does not include Parcel 40 of the West Tenth Street location. Parcel 40 was not investigated as part of the Phase II Soil and Groundwater Investigation because site access was not available. If Alternative 2 was selected and approved, Parcel 40 would not need to be investigated in a supplemental Phase II investigation.

5.5.14.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 site are generally as described in Section 4.14.3 for the proposed Pittsburg Standard Oil Converter Station site. With implementation of the following mitigation measures, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level.

5.5.14.2.1 Construction-related Impacts. Impacts HAZ-1 through HAZ-6 apply to construction activities at the Pittsburg West Tenth Street Converter Station Alternative 2 site.

With implementation of the following mitigation measures, potentially significant environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure HAZ-1 (Complete an ACM Abatement Plan and an LBP Abatement Plan) for Impact HAZ-1 (Removal of Potentially Hazardous Building Materials Resulting from Demolition)
Mitigation Measure HAZ-2 (Soil Removal Protocols) for Impact HAZ-2 (Contaminated Soil Removal)
Mitigation Measure HAZ-3 (Reduction of Hazards During Construction Phase) for Impact HAZ-3 (Construction-phase Hazardous Materials Use)
Mitigation Measure HAZ-4 (Management of Construction-phase Waste Streams) for Impact HAZ-4 (Construction-phase Waste Streams)
Mitigation Measure HAZ-5 (Construction-phase Spill Prevention, Control, and Countermeasure) for Impact HAZ-5 (Construction-phase Accidental Spills)
Mitigation Measure HAZ-6 (Reduction of Construction Dust and Volatilization of Contaminants) for Impact HAZ-6 (Construction-phase Dust and Volatilization of Contaminants)

5.5.14.2.2 Operations-related Impacts. Impacts HAZ-8 through HAZ-12 would apply to the operations phase at the Pittsburg West Tenth Street Alternative 2 site. Mitigation Measures HAZ-8 through HAZ-12 would be implemented to reduce potentially significant impacts to less-than-significant levels:

Mitigation Measure HAZ-8 (Control of Operations-phase Hazardous Materials) for Impact HAZ-8 (Operations-phase Hazardous Materials Usage)
Mitigation Measure HAZ-9 (Manage Waste Generation, Storage, and Disposal During Operations Phase) for Impact HAZ-9 (Operations-phase Waste Streams)
Mitigation Measure HAZ-10 (Operations-phase Spill Prevention, Control, and Countermeasure) for Impact HAZ-10 (Operations-phase Accidental Spills)
Mitigation Measure HAZ-11 (Reduction of Fire and Explosion Risk and Emergency Support During Operations Phase) for Impact HAZ-11 (Operations-phase Fire and Explosion Risk)
Mitigation HAZ-12 (Manage Seismic Activity) for Impact HAZ-12 (Impacts from Seismic Activity)

5.5.15 Paleontological Resources

5.5.15.1 Environmental Setting

No fossil localities have been identified within the footprint of the Pittsburg West Tenth Street Converter Station Alternative 2 site, including associated AC/DC cable routes. The Pittsburg West Tenth Street Converter Station Alternative 2 site and its associated onshore AC cable route components are assigned a high sensitivity rating, since excavations have the potential to penetrate into undisturbed Qal sediments which could contain significant fossil resources (refer to Figure 4.15-2). The nearshore DC cable route north of the Mirant Pittsburg Power Plant is assigned a low sensitivity rating, since excavations are not expected to penetrate into undisturbed Qal sediments where there would be a potential for significant paleontological resources. The associated construction laydown area is assigned a low sensitivity rating, as use of this area is not expected to penetrate into undisturbed Qal sediments.

5.5.15.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg West Tenth Street Converter Station Alternative 2 are as described in Section 4.2.3 for the proposed Pittsburg Standard Oil Converter Station site. With implementation of the following mitigation measure, potential environmental impacts associated with this alternative would be reduced to a less-than-significant level:

Mitigation Measure PALEO-1 (Potential Fossil Resources Protection) for Impact PALEO-1 (Disturbance of Fossil Resources)