SECTION 5.0

ENVIRONMENTAL SETTING, IMPACTS, AND MITIGATION

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PROJECT ALTERNATIVES

5.6    PITTSBURG MIRANT CONVERTER STATION ALTERNATIVE

5.6.1    Introduction

The Pittsburg Mirant Converter Station Alternative site is located in unincorporated Contra Costa County within the larger Mirant Pittsburg Power Plant site (refer to Figures A.1-1 and A.8-28 in Appendix A) on the east-central portion of the overall site. The Pittsburg Mirant Converter Station Alternative site is located east of the PG&E Pittsburg Substation and west of a north-south oriented tank farm on the Mirant Pittsburg Power Plant site (refer to Figure A.8-28 in Appendix A). The alternative converter station site is industrial and currently has an oil tank and several wooden and metal frame buildings, which would need to be demolished prior to installation of a converter station on this site. The layout, plan view, elevation view, and a photo simulation for the Pittsburg Mirant Converter Station Alternative are shown on Figures A.8-29 through A.8-31 in Appendix A. The proposed temporary construction laydown areas and onshore cable routes for this alternative (as well as the Pittsburg West Tenth Street Converter Station Alternatives 1 and 2) are also located on the Mirant Pittsburg Power Plant site (refer to Figure A.8-28 and Map A.2-1, Sheet 10 of 10).

If this alternative were to be approved and selected for implementation, the specific location and layout of the Pittsburg Mirant Converter Station Alternative (and associated temporary laydown areas) might be subject to minor modification to accommodate Mirant's future plans for the site areas.

As discussed above, the Pittsburg Mirant Converter Station Alternative site is currently (at the time this Draft EIR was prepared) located in unincorporated Contra Costa County. The site is within the City of Pittsburg's Sphere of Influence and is included in the Planning Area of the City's General Plan. The Pittsburg City Council has initiated the process to pre-zone an area that includes the alternate site to IG (General Industrial), which is consistent with the City's General Plan Land Use designation of "Industrial" for that area. A Mitigated Negative Declaration is in preparation for the pre-zoning and an application for annexation has been submitted to the Contra Costa Local Agency Formation Commission (LAFCO). Upon annexation, the Laws, Ordinances, Regulations, and Standards (LORS) of the City of Pittsburg would be applicable to the Pittsburg Mirant Converter Station Alternative site.

5.6.2    Air Quality

5.6.2.1    Environmental Setting

The environmental setting for air quality associated with the Pittsburg Mirant Converter Station Alternative site is as described in Section 4.2.1 for the proposed Standard Oil Converter Station site. This Pittsburg alternative converter station site has a unique air quality aspect. St. Peter Martyr School (425 West Fourth Street) is located within 1,000 feet of the Mirant Pittsburg site. This will invoke BAAQMD Rule 2-1-412 which requires that BAAQMD notify the school families in writing of the proposed project at least 30 days prior to issuing the air permit. The BAAQMD must review, consider and respond to any comments received before taking action on the permit. This is a notification requirement only and it does not incorporate any more restrictive air quality standards or health risk criteria.

5.6.2.2    Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are as described in Section 4.2.3 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:

• Mitigation Measure 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 Mirant site would result in slightly less emissions than accounted for in Section 4.2.3 for the proposed Standard Oil Project site.

5.6.3    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. Site-specific environmental setting and impact discussions for this alternative site are presented below.

5.6.3.1    Environmental Setting

The Pittsburg Mirant Converter station site location is shown on Figure 4.3-5.

5.6.3.1.1    Site Geology. The Pittsburg Mirant Converter Station and laydown areas are located approximately 400 feet from Suisun Bay. The geology of the Pittsburg area is shown on Figure 4.3-5. Soil types are shown on Figure 4.3-6. The site is underlain by flatland soils (soils with slopes between 0 and 20 percent) (City of Pittsburg, 2001) consisting of Pleistocene fluvial and alluvial deposits. Portions of the site are underlain by artificial fill.

Geologic Resources. The converter station site does not have any identified unique geologic features or resources. Paleontological resources are as discussed in Section 4.15 for the proposed Standard Oil site.

Faults. Figures 4.3-2 and 4.3-5 illustrate the location of the site with respect to the major Quaternary faults in the site region. Table 4.3-1 presents maximum earthquake magnitude estimates for faults in proximity to the site.

As shown on Figure 4.3-5, the mapped location of the Pittsburg-Kirby Hills Fault Zone runs in a southeasterly direction from Suisun Bay, immediately west of the Mirant (formerly PG&E) power plant, through the West Tenth Street residential neighborhoods to the intersection of Harbor Street and the Pittsburg-Antioch Highway. The mapped location of this fault zone is directly adjacent to the Pittsburg Mirant Converter Station site. As discussed in Section 4.31.2.10, a recent fault rupture hazard investigation (Terrasearch, 2005) found no evidence that the Pittsburg-Kirby Hills Fault Zone is active in the Project Vicinity.

5.6.3.2    Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are generally as described in Section 4.3.3 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 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)

5.6.4    Water Resources and Quality

5.6.4.1    Environmental Setting

The alternative Pittsburg Mirant Converter Station site is shown on Figure 4.4-5. The converter station and laydown sites are located approximately 400 feet south of Suisun Bay. There is no surface water on the site. Some storm water at the site is captured in oil-water separators before the clear-well water (clean water) is discharged to Suisun Bay. Prior to use, existing structures (e.g., tankage) would be demolished and removed and the site would be graded and paved as necessary.

As shown on Figure 4.4-4, the alternative Pittsburg Mirant Converter Station site and associated laydown areas and onshore cable routes are within the Lawlor Creek Watershed. The Pittsburg Mirant Converter Station site is located within the 100-year flood zone (refer to Figure 4-4).

As described in the groundwater section for the proposed Standard Oil Site (Section 4.4.1.6.2), the site is located within the Pittsburg Plain Groundwater Basin. The water-bearing units in the Basin are Pleistocene to recent alluvial deposits of sand, gravel, and clay. Groundwater tends to flow northerly, toward Suisun Bay.

The Pittsburg Mirant Converter Station site is underlain by artificial fill near the Bay, where the shallower, tidally influenced groundwater may be encountered. Groundwater levels in the Pittsburg area vary from a few feet below ground surface (bgs) near Suisun Bay, to 28 feet bgs in the upland areas of the Pittsburg Plain (City of Pittsburg, 2001). Shallower groundwater (2 to 7 feet bgs) can be found in low-lying areas near Suisun Bay and in ravines and creek channels. Groundwater is tidally influenced and tends to be saline with high mineral concentrations (City of Pittsburg, 2001). Intense pumping for industrial uses in the 1930s through 1950s resulted in overdraft and seawater intrusion. Limited amounts of water drawn from the underground aquifer are now blended with raw water from the Contra Costa Canal before treatment and distribution to the City of Pittsburg.

Groundwater at the site is contaminated with TPH and metals. Groundwater contamination at the site is discussed further in Section 5.6.14.

5.6.4.2    Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are generally as described in Section 4.4.3 for the proposed Pittsburg Standard Oil site, except as noted below for Impact WATER-8. 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)

Flooding. Some areas along the shoreline and drainages leading to the Suisun Bay and San Francisco Bay are potential floodplains. Risks associated with building in a floodplain include threats to life and property. Local city or county government agencies regulate floodplain development through land use controls, based on determinations of flood elevations. FEMA maintains maps of 100-year flood areas in the Bay counties. A "100-year flood" refers to a flood level with a 1 percent or greater chance of being equaled or exceeded in any given year.

As shown on Figure 4.4-4, the Pittsburg Mirant Converter Station Alternative site (including ancillary facilities) is located within the Lawlor Creek watershed within the 100-year flood zone. Impacts due to flooding of the site are considered potentially significant. With implementation of the following mitigation measure, this potentially significant environmental impact would be reduced to a less-than-significant level:

• Mitigation Measure WATER-8 (Flood Mitigation) for Impact WATER-8 (Flooding)

Refer to Section 5.4.4.2 for more information regarding this potential impact and associated mitigation.

5.6.5    Terrestrial Biological Resources

5.6.5.1    Environmental Setting

The Pittsburg Mirant Converter Station sites include 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 20 feet above mean sea level (see Sheet 10 of Map A.2-1 in Appendix A). This location corresponds to an area in unincorporated Contra Costa County just outside the northwestern side of the City of Pittsburg, near Suisun Bay and occurs within industrialized and previously disturbed landscapes.

5.6.5.2    Environmental Impacts

The area encompassed by the Pittsburg Mirant site is dominated by previously developed and industrialized landscapes described in Section 4.5 as Disturbed/Developed habitats. No impacts to natural communities, wetlands, or special-status species would be expected to occur from this alternative. In addition, no operations phase related impacts have been identified for terrestrial biological resources associated with this alternative.

5.6.6    Marine Biological Resources

5.6.6.1    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.

5.6.6.2    Environmental Impacts

The Pittsburg Mirant Converter Station Alternative 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 Pittsburg Standard Oil site. No cable installation would be needed in the channel between Winter Island and Browns Island and no dredging would be needed where the AC/DC cable routes cross New York Slough. 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.

5.6.7    Cultural Resources

5.6.7.1    Environmental Setting

5.6.7.1.1    Archaeological Resources. No archaeological resources were identified within the Mirant Pittsburg Converter Station Alternative site, onshore AC/DC cable routes, or laydown areas during any phase of the investigation. The route of the offshore DC cable has not been subjected to a geophysical inventory. As such, it is unknown if submerged and/or sub-bottom archaeological resources occur within the footprint of this portion of this alternative.

5.6.7.1.2    Historic Architectural Resources. No historic architectural resources were identified within the Mirant Pittsburg Converter Station Alternative site, cable routes, or laydown areas during any phase of the investigation.

5.6.7.2    Environmental Impacts

5.6.7.2.1    Construction-related Impacts.

Archaeological Resources. No archaeological resources have been identified within the alternate Pittsburg Mirant Converter Station, onshore AC/DC cable routes, or construction laydown areas. As such, significant impacts to archaeological resources would not be anticipated with the construction of this Project component.

Historic Architectural Resources. No historic architectural resources have been identified within the Pittsburg Mirant Converter Station, onshore AC/DC cable routes or construction laydown areas. As such, significant impacts to historic architectural resources would not occur with implementation of this Project component.

5.6.8    Land Use and Recreation

5.6.8.1    Environmental Setting

The alternative Pittsburg Mirant Converter Station site, onshore AC/DC cable routes, and construction laydown areas are collectively called the Mirant Pittsburg site here, unless otherwise noted.

5.6.8.1.1    Existing Land Uses. The Pittsburg Mirant site is completely encompassed within the Mirant Pittsburg Power Plant site, and the PG&E Pittsburg Substation. The site is located within unincorporated Contra Costa County, just northwest of annexed areas within the City of Pittsburg. The site is located within Pittsburg's Sphere of Influence and Planning Area, and as such, is addressed in the Northwest River Planning Subarea in Pittsburg's General Plan. The Mirant Power Plant encompasses much of this subarea, in addition to a small portion occupied by the Concord Naval Weapons Station. The remainder of the Northwest River consists of marshland (CPPD, 2004).

5.6.8.1.2    Potentially Sensitive Land Uses. Table 5.6.8-1 lists potentially sensitive land uses near the alternative Pittsburg Mirant site. Residential development is located approximately 460 feet from the site, just west of the Pittsburg Marina. Additional residential development occurs farther southeast of the site along Linda Vista Avenue. A church (Stewart Memorial) is located at the north terminus of Linda Vista Avenue, approximately 500 feet from the site. Marina Park and St. Peter Martyr School are situated 650 feet and 900 feet, respectively, southeast of the site.

TABLE 5.6.8-1
POTENTIALLY SENSITIVE LAND USES NEAR
PITTSBURG MIRANT CONVERTER STATION ALTERNATIVE

 

5.6.8.1.3    Zoning and General Plan Designations. The Pittsburg Mirant site is currently located within unincorporated Contra Costa County. The site is within the City of Pittsburg's Sphere of Influence and is included in the Planning Area of the City's General Plan. The site is designated as Industrial in the Pittsburg General Plan and is currently zoned HI (Heavy Industrial) by Contra Costa County. The Mirant site is currently subject to development regulations in Contra Costa County Zoning Ordinance Section 84-62. There are no regulations or limitations on lot area, height, or side yard in the HI district (Section 84-62.602). Heavy industrial manufacturing uses "of all kinds" and all other industrial or manufacturing products are permitted in the HI district.

The Pittsburg City Council recently initiated pre-zoning an area that includes the Mirant Converter Station site to IG (General Industrial). This new zoning for the site would be consistent with the General Plan land use designation of Industrial for that area. A CEQA Initial Study is currently being prepared for the pre-zoning.

5.6.8.1.4    Land Use Trends. The Mirant Pittsburg site is located in the general area of the West Tenth Street site. Land use trends associated with the Mirant Pittsburg site are discussed in Section 5.4.8.1.4.

5.6.8.2    Environmental Impacts

The alternative Mirant Pittsburg Converter Station is completely bounded by the existing Mirant Pittsburg Power Plant and PG&E Pittsburg Substation. The alternative Mirant Pittsburg Converter Station would represent further development of an area committed to industrial use rather than the introduction of industry to a non-industrial area.

Land use plans and regulations applicable to the Mirant Pittsburg site include the Pittsburg General Plan, Pittsburg Municipal Code, and Contra Costa County Zoning Ordinance. The Mirant Pittsburg Converter Station Alternative is located in the City of Pittsburg's Northwest River Planning Subarea. The Mirant Power Plant encompasses much of this subarea, in addition to a small portion occupied by the Concord Naval Weapons Station. The remainder of the Northwest River subarea consists of marshland. Pittsburg's General Plan Policy 2-P-96 for the Northwest River subarea stipulates maintaining the Mirant Pittsburg power plant site in the Industrial designation and pursuing annexation of the power plant and adjacent properties to ensure land use control of these areas. The General Plan states that opportunities for non-industrial uses should be explored in the unlikely event that the plant is decommissioned in the future. The General Plan also indicates that expansion of the power plant or related industrial uses to the west of the facility should be regulated by the City of Pittsburg.

The site is currently zoned HI, (Heavy Industrial) by Contra Costa County. The Pittsburg Mirant site is currently subject to development regulations in the Contra Costa County Zoning Ordinance Section 84-62. There are no regulations or limitations on lot area, height, or side yards in the HI district. Heavy industrial manufacturing uses "of all kinds" and all other industrial or manufacturing products are permitted in the HI district. The Pittsburg Mirant Converter Station Alternative site is currently within the City of Pittsburg's Sphere of Influence and is included in the Planning Area of the City's General Plan. The Pittsburg City Council has initiated the process to pre-zone an area that includes the Alternate site to IG (General Industrial), which is consistent with the City's General Plan Land Use designation of "Industrial" for that area. A Mitigated Negative Declaration is in preparation for the pre-zoning Upon annexation, the Laws, Ordinances, Regulations, and Standards (LORS) of the City of Pittsburg would be applicable to the Pittsburg Mirant Converter Station Alternative site. No conflicts with current zoning or future re-zoning of the site are anticipated with development of the Mirant Converter Station.

The alternative Mirant Pittsburg Converter Station would be consistent with the existing uses of the site and surrounding area. The nearest residential development near the site is approximately 460 feet to the east. The Mirant Pittsburg Converter Station Alternative would not require displacement of housing and would not have significant impacts on the community.

The site is completely bounded by the existing Mirant Power Plant and PG&E Pittsburg Substation. The nearest potentially sensitive land uses are located beyond the power plant boundaries, and include residences located approximately 460 feet to the east, an existing church 500 feet to the northeast, and a park and school 650 feet and 900 feet to the southeast, respectively. The Mirant Pittsburg Converter Station Alternative would be consistent with established and proposed land uses of the area.

In summary, no potentially significant land use or recreation related impacts have been identified for the Pittsburg Mirant Converter Station Alternative.

5.6.9    Marine Transportation and Commercial Fishing

The Pittsburg Mirant Converter Station Alternative would not impact marine transportation or commercial fishing.

If the Pittsburg Mirant Converter Station Alternative site was selected instead of the proposed Standard Oil site, there would be no need to install the submarine AC/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 site. Selection of this alternative site 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.

5.6.10  Traffic and Transportation

5.6.10.1  Environmental Setting

Roadways near the alternative Mirant Pittsburg Converter Station site in Pittsburg and unincorporated Contra Costa County, respectively, are discussed in Section 4.10.1 based on the onshore portion of the proposed cable routes to the PG&E Pittsburg Substation associated with the proposed Standard Oil Converter Station site. The environmental setting for traffic and transportation for the Mirant Pittsburg Converter Station Alternative is consistent with the discussion presented for the proposed Standard Oil Converter Station in Section 4.10.1, with the exception of the items noted below.

• The Pittsburg Mirant Converter Station Alternative site has controlled access and, as such, offers parking to those allowed through the Mirant's gate. On-street parking is permitted on the residential streets to the east of this site.

• The Pittsburg Mirant Converter Station site is served by public transit, including Tri Delta Transit Service, which operates the north-south Route 70 Pittsburg-Marina to Buchanan Loop and the east-west Route 387, which connects the Pittsburg Bay Point BART Station with the centers of Pittsburg and Antioch. Service on these routes operates weekdays with Route 387 extending into evening hours at frequencies ranging from 45 to 90 minutes.

• In Pittsburg, the General Plan identifies bicycle routes planned for the study area including Railroad Avenue, Third Street, Harbor Street, North Parkside, West Tenth Street, Loveridge Road, and Herb White Way. The West Tenth Street and Herb White Way bicycle routes are near the site.

• Construction traffic would utilize the existing access road to the Mirant site. The access road to the Mirant site would remain on the private road.

5.6.10.2  Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are generally as described in Section 4.10.3 for the proposed Pittsburg Standard Oil Converter Station site, and in Section 5.4.10.2 for the Pittsburg West Tenth Street Converter Station Alternative 2. 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)

5.6.11  Noise and Vibration

5.6.11.1  Environmental Setting

The alternative Pittsburg Mirant Converter Station site is located within the Pittsburg Mirant Power Plant property, adjacent to the PG&E Pittsburg Substation. This site is industrial and currently has an oil tank on it; in addition, multiple oil tanks oriented in a north-south configuration are located to the east of the site. This site is not located within the City of Pittsburg; therefore, the applicable jurisdiction is currently the County of Contra Costa. As discussed in Section 5.6.1, the City of Pittsburg has initiated the process to pre-zone an area that includes the Pittsburg Mirant site to IG (General Industrial), and an application for annexation of this area has been submitted to the Contra Costa LAFCO. Upon annexation, the LORS of the City of Pittsburg, including those related to noise, would be applicable to the Pittsburg Mirant site.

A series of sound level measurements were conducted on September 13 through 14, 2005 to quantify the existing acoustical environment at the alternative Pittsburg Mirant Converter Station site as well as at sensitive receptors near this alternative site. The same methodology identified in Section 4.11.1.2. for the proposed San Francisco HWC site sound level measurements was used. The results of the measurements are summarized in Table 4.11-3. The measurement locations are shown on Figure 4.11-2. The following summarizes the property line measurements.

ST7     Thirty-minute measurements were conducted during the daytime and nighttime at the southeast property line of the alternative Pittsburg Mirant Converter Station site. This alternative site is bounded by a single-family residential subdivision to the east, Marina Park to the southeast, and industrial uses to the west and north. Marina Park is the site of a recently approved residential development (Mariner Walk Project). The daytime measurement was taken between 4:20 p.m. and 4:50 p.m. on September 13 and the nighttime measurement was taken between 10:56 p.m. and 11:26 p.m. on September 13. The daytime noise sources included aircraft overflights, barking dogs, birds vocalizing, faint sirens, infrequent automobile honking (faint), and vehicular traffic. The loudest noise sources were the leaves rustling and humming from the power plant. The nighttime noise sources included industrial hum, vehicular traffic from West Tenth Street, rustling leaves, and a helicopter overflight. The daytime one-hour L_eq was 47.9 dBA and the nighttime one-hour L_eq was 50.6 dBA.

Sensitive receptors in the project area consist of single-family residences approximately 460 feet to the east on Linda Vista Avenue, Marina Park approximately 650 feet to the southeast, and single-family residences approximately 1,500 feet to the south. The residences to the east and Marina Park to the southeast are separated from the Pittsburg Mirant site by three storage tanks associated with the Mirant Pittsburg Power Plant, although there is direct line-of-sight in between the tanks. There is also a 6-foot-tall embankment on the western property line of the residences. The residences to the south do not have a direct line-of-sight due to the intervening buildings on Beacon Street. The following describes the measurements conducted at the closest residential receptor.

ST8     Thirty-minute measurements were conducted during the daytime, evening, and nighttime at the intersection of West Second Street and Linda Vista Avenue. The meter was setup next to the rear yard of the residence, facing the Pittsburg Mirant power plant between 204 and 196 Linda Vista Avenue. Surrounding land uses were residential to the north, east, and south and industrial to the west. The daytime measurement was taken between 10:35 a.m. and 11:05 a.m. on September 14, the evening measurement from 9:00 p.m. and 9:30 p.m. on September 13, and the nighttime measurement was taken between 23:30 and 24:00 on September 14. Noise sources during the daytime were distant vehicular traffic, aircraft overflights, train whistles, people talking, music from residences, and birds vocalizing. Noise sources for the evening were the power plant, vehicular traffic on surface streets and SR 4, train whistles, and leaves rustling. Noise sources at night included vehicular traffic on surface streets and SR 4, aircraft and helicopter overflights, train whistles, and automobile horns. The daytime one-hour L_eq was 44.8 dBA, the evening one-hour L_eq was 45.3 dBA, and the nighttime one-hour L_eq was 46.9 dBA. The calculated L_dn was 53 dBA.

The existing noise environment and sensitive receptors for the onshore DC/AC cable routes and laydown areas would be the same as that identified for the Pittsburg Mirant Converter Station Alternative site, above.

5.6.11.2  Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are generally as described in Section 4.11.3 for the proposed Pittsburg Standard Oil site, except as noted below.

5.6.11.2.1  Construction-related Impacts. Scheduled construction hours at the alternative Pittsburg Mirant 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 generally the same as to those outlined for the proposed Project site.

Acoustical calculations were performed to estimate noise from construction activities at the closest residences with the same methodology as described for the proposed Standard Oil Project site. The closest offsite residential uses to the alternative Pittsburg Mirant Converter Station consist of single-family residences approximately 460 feet east and single-family residences approximately 1,500 feet southeast. Average sound levels at the closest residences to the Pittsburg Mirant Converter Station Alternative construction site would be 70 and 59 dBA, respectively, as summarized in Table 5.6.11-1. Because of the intermittent nature of construction work and intervening structures and roads, construction noise would not be audible at the receptors. Furthermore, because construction would be limited to the hours of 7:00 a.m. to 7:00 p.m. Monday through Friday, there would be no significant impact.

Pile Driving. Calculations were performed to estimate sound levels from pile driving at the receptors. Direct line-of-sight sound levels at the residences 460 feet east were calculated to be 86 dBA L_max (81 dBA L_eq) and 74 dBA L_max (69 dBA L_eq) at the residences 1,500 feet southeast. 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. Pile driving would be required to comply with the requirements of Pittsburg. These noise levels are below the 90 dBA threshold of significance (FTA, 1995) and, thus, would result in a less-than-significant impact.

TABLE 5.6.11-1
CALCULATED SOUND LEVELS FROM CONSTRUCTION OF THE
PITTSBURG MIRANT CONVERTER STATION ALTERNATIVE

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 460 feet from the pile driving would be 0.008 in/sec, which is well below the FTA threshold of 0.20 in/sec; resulting in a less than significant impact.

Construction Traffic. Impacts identified for the Pittsburg West Tenth Street Alternative 1 site in Section 5.4.11.2 are applicable to the Pittsburg Mirant Converter Station Alternative. No significant construction traffic-related noise impacts are anticipated.

5.6.11.2.2  Operations-related Impacts. Calculations were performed using linear octave band sound power levels as inputs from each noise source with the same equipment as the proposed Project site. Siemens conducted the noise analysis, the results of which are summarized here and provided in Appendix H. Sound levels during the operations phase would not exceed the 60 dBA L_dn standard at the closest sensitive receptor and would not result in a significant impact. As summarized in Table 5.6.11-2, unmitigated sound levels at the alternative Pittsburg Mirant Converter Station site would exceed the City of Pittsburg 75 L_dn requirement. This is considered to be a potentially significant impact. With implementation of the following mitigation measure, this potentially significant impact would be reduced to a less-than-significant level:

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

TABLE 5.6.11-2
CALCULATED SOUND LEVELS FROM OPERATION OF THE
PITTSBURG MIRANT CONVERTER STATION ALTERNATIVE

5.6.12  Public Services and Utilities

5.6.12.1  Environmental Setting

The public services and utilities discussions for the alternative Pittsburg Mirant Converter Station Alternative site (including associated onshore cable routes) are consistent with the proposed Standard Oil site discussed in Section 4.12.1, except for the distances to certain facilities that are addressed below.

CCCFPD Station No. 84 (300 East Sixth Street) is located 0.6 mile to the southeast of the Pittsburg Mirant site. Station No. 85 (2555 Harbor Street) is located 2.3 miles to the southeast. Fire and Hazardous Materials Response Unit response times to the Pittsburg Mirant site are consistent with the response times to the proposed Standard Oil site, addressed in Section 4.12.3.3.2.

The closest clinic to the Pittsburg Mirant site is the Pittsburg Health Center (2313 Loveridge Road), located approximately 3 miles to the southeast. The closest full service hospital is Sutter Health (3901 Lone Tree Way) in Antioch, located approximately 7 miles to the southeast. The schools closest to the Pittsburg Mirant site are St. Peter Martyr (425 West 4^th Street), located 1 mile to the east, and Parkside Elementary (985 West 17^th Street), located approximately 1.5 miles to the south.

5.6.12.2  Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are generally as described in Section 4.12.3.3 for the proposed Pittsburg Standard Oil site, except as noted below.

Several fire hydrants are present along West Tenth Street; however, the fire department is not able to provide information on fire hydrants within the Mirant Power Plant property. The Contra Costa Fire Code Section 903.2 stipulates that a fire hydrant may need to be added if the site is located more than 150 feet off of a main public street. A fire flow test in addition to an access and water supply review are typically recommended where fire hydrants are not in the general vicinity of the site. Mitigation measures would include performing a flow test with the fire department to ensure that access and water supply can accommodate the proposed Project facilities. 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)

• Mitigation Measure PS-4 (Water Service) for Impact PS-4 (Water Service)

5.6.13  Visual Resources/Aesthetics

5.6.13.1  Environmental Setting

The alternative Pittsburg Mirant Converter Station site is located within the Mirant Pittsburg Power Plant property east of the PG&E Pittsburg Substation. The site is industrial in character and is currently utilized primarily for parking at the Mirant Pittsburg Power Plant. There is a series of large storage tanks, as well as other small metal and wood supporting structures in the immediate area. Marina Park, which includes a series of recreation fields, is located to the east of the site and is somewhat screened by a windrow of trees (Photo 1, Figure 5.6-1). Beyond the park there is an older residential neighborhood (Photo 2, Figure 5.6-1). An approved development plan would relocate Marina Park to the northwest corner of Herb White Way and East Eighth Street. A new subdivision of single family homes (Mariner Walk) is planned and approved for development at the site of the present park.

5.6.13.1.1  Visual Quality. The alternative Pittsburg Mirant Converter Station site is classified as heavy industrial as it is adjacent to the Mirant Pittsburg Power Plant, the PG&E Pittsburg Substation, and the large storage tanks. There are no scenic features or landmarks in the vicinity. Views toward the site from the park and residential area are screened by the existing trees which somewhat soften the industrial character. The visual quality of the site itself is low but the scene as viewed from the adjacent areas is improved by the tree screen.

Visual Quality is rated as Moderate.

5.6.13.1.2  Viewer Sensitivity. Given that the viewers are from developed residential and recreation areas, their general sensitivity is rated as moderate. There are relatively few viewers since there are no major arterial roads in the area. The duration of views from the park is classified as long (defined as more than three minutes) given that people will be using the park for significant amounts of time. In the future when residences replace the park, there will be fewer viewers but with a projected higher level of sensitivity. These two factors are considered to equalize each other.

Viewer sensitivity, therefore, is classified as Moderate. The visual susceptibility index is classified as Moderate, meaning any proposed facility would have a moderate probability for disrupting the existing visual resources of the area as seen from roads and public places assuming that the screening trees remain in place.

5.6.13.2  Environmental Impacts

The alternative Pittsburg Mirant Converter Station site is located internally on the existing Mirant Pittsburg Power Plant. The PG&E Pittsburg Substation is located to the west, the Mirant Power Plant to the north, and a series of large tanks to the south and east. The only visual access to this location occurs from Marina Park to the east (Photo 1, Figure 5.6-1).

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are as described in Section 4.13.3 for the proposed Pittsburg Standard Oil site.

5.6.13.2.1  KOP P-4: Marina Park. Key observation points (KOPs) for this alternative site are shown on Map 5.4-1.The addition of the alternative Pittsburg Mirant Converter Station is simulated and contributes almost no visible change to the views from Marina Park Area whether it is the current park or the approved single family residential area (Photo B, Figure 5.6-2). This is true because the facility would be seen in the context of the existing power plant and related fuel tanks. The existing tree screen is relatively mature and would also shield the project at this location. Therefore, there are no issues of visual dominance or contrast of character, and no scenic vista is blocked. The Impact Severity is Low.

Since the Impact Susceptibility for the area is Moderate, the resulting impact would be less than significant. The view from the Marina Park area could be slightly improved by planting additional trees and shrubs adjacent to the existing screen. Although this potential impact is less than significant, with implementation of the following mitigation measures, this potential impact would be reduced further:

• Mitigation Measure VIS-1a (Plan Submittal Requirements for Building Materials and Colors) and Mitigation Measure VIS-1b (Plan Submittal Requirements for Landscaping) for Impact VIS-1 (Converter Station Domination of View).

5.6.14  Hazardous Materials and Waste Management

5.6.14.1  Environmental Setting

The Pittsburg Mirant Converter Station Alternative site is located within the larger Mirant Pittsburg Power Plant property (refer to Figure A.1-1 and A.8-19 in Appendix A). The Mirant Pittsburg Power Plant property and the PG&E Pittsburg Substation are located at 696 and 696-B West Tenth Street. The Mirant Pittsburg Power Plant property has an area of approximately 2,100 acres, of which a 280-acre parcel on the eastern end is used for power generation and its associated activities. The PG&E Pittsburg Substation is approximately 37.5 acres in area and is located within the Mirant Pittsburg Power Plant property to the south of the power generation units. The two sites are known collectively in this section of the EIR as the Mirant Pittsburg Power Plant/PG&E substation property. The section considers the combined Mirant parcel and the PG&E substation areas as they relate to the properties' common history and because the proposed AC cable route would utilize portions of the PG&E switchyard property.

The proposed DC cable route would extend from the proposed converter station site (at the current location of Tank 7) along the Main Road, run between the closed-air preheater wash pond and Tank 1, exit the Mirant Pittsburg Power Plant property at its northeastern end, and extend into New York Slough.

The proposed AC cable route would extend from the proposed converter station site along the Main Road, enter the PG&E substation property at its southern boundary, and terminate at the PG&E substation.

The Mirant Pittsburg Power Plant property is bordered to the north by New York Slough, to the south by Willow Pass Road and the BNSF railroad tracks, to the east by residential/commercial properties, and to the west by PG&E non-power generation property. The Mirant Pittsburg Power Plant property consists of an office building, seven power generating units, a cooling water canal, two cooling towers, 16 ASTs containing fuel oil and constructed within concrete/diked berms, several chemical and oil ASTs, a hazardous waste storage area, solid waste management units (SWMUs), four closed Class I surface impoundments, and one active Class II surface impoundment. The PG&E substation consists of a control building, a hazardous waste storage area, and a mobile tank trailer. The substation consists of a 230-kilovolt (kV) transmission unit and a 115-kV transmission unit.

According to the EDR report prepared for the Phase I ESA for the Mirant Pittsburg Power Plant property (URS, 2005e), one sensitive receptor is located within a 0.25-mile radius: St. Peter Martyr parochial school, a Kindergarten through eighth grade school that is located to the southeast of the Mirant Pittsburg converter station site. The Mirant Pittsburg Power Plant property is identified as an RCRA facility with existing soil and groundwater contamination. A Remedial Feasibility Investigation was conducted at the site and stabilization measures were implemented in 1999. The stabilization measures primarily involved source removal activities and in situ and off-site treatment. Groundwater monitoring of contamination at the Mirant Pittsburg Power Plant property is required to evaluate subsurface plume control. The Mirant Pittsburg Power Plant property is also listed in the Toxic Pits Control Act (TPCA) Database and is known to have five active toxic pits. In addition, the EDR report identified a total of 43 USTs at the Mirant Pittsburg Power Plant property, some of which may have been sumps rather than tanks. These tanks appear to have been installed between 1952 and 1981 and were used to store product and waste. The status of these USTs is not known.

The URS Phase I ESA for the Mirant Pittsburg Power Plant property identified the following RECs based on conditions at the Mirant Pittsburg Power Plant property:

• REC 1, ASTs (at the proposed converter station site and immediately east of the site; also near to the DC cable route): The Phase I investigation of the Mirant Pittsburg property identified a number of issues regarding these tanks:

• The Phase I file review and previous ESAs for the Mirant Pittsburg Power Plant property indicate that several chemical and fuel oil releases have occurred near the fuel ASTs and the diked containment areas where the spills were contained. Although impacted soils from the AST releases were removed and disposed of offsite on a case-by-case basis, data gaps in the records documenting the investigations, the remediation of the residual sources, and the impacted areas were noted.

• In the early 1980s, electrical equipment was cleaned outside of Units 1 through 7 with solvents containing trichloroethene (TCE) within a concrete-covered and bermed area. Subsurface impacts from this practice are expected to have occurred in these areas. VOCs were detected above the preliminary remediation goal (PRG) level around these units during a Phase II investigation in 1997.

• A 1997 Phase II investigation reported maximum detections of TPH and PAHs in soil at concentrations of 11,000 mg/kg and 32.83 mg/kg, respectively, north of Tank 1 near the proposed boring pit location for the DC cable route. Also, a maximum TPH concentration of 690 mg/L was detected in groundwater collected closer to the north side of Tank 1. URS found no evidence of subsurface remediation activities in this area in the files reviewed for the Phase I ESA for this site. Although groundwater in this area is monitored as part of a groundwater monitoring program for the previously regulated air preheater wash pond, the wells in this area are not being sampled for TPH or PAHs. Therefore, the current TPH and PAH concentrations in groundwater remain unknown.

• Interviews conducted during a previous Phase I in 1997 investigation indicated several releases of no. 6 fuel oil in and around Tanks 1 through 6 (along the DC cable route). Although some of these releases were cleaned up, it was suspected that the subsurface soils might have been affected. Further, a Phase II investigation in 1997 identified metals and VOCs in groundwater as a remedial issue at this location. Again, URS found no evidence documenting subsurface remediation of this area in its Phase I ESA for the Mirant Pittsburg property.

• REC 2, power-generating units (north and east of the converter station site): Several contamination issues were identified for the power-generating units at the Mirant Pittsburg Power Plant property:

• Previous investigations of the Mirant Pittsburg Power Plant property reported detections of PCBs around the power generating units (Units 1 through 6) at a maximum concentration of 0.03 mg/kg in soil. No records were found to document whether this contamination was remediated in the Phase I ESA for this site.

• A 1996 PG&E memorandum indicated that before 1971, some wastewater from the cleaning of vehicles and large turbine parts as well as drainage from degreasers and steam cleaners may have been directed to the riverbanks between Units 6 and 7. Also, some previous fuel spills had flowed into Willow Creek. No information was found on the locations of these discharges in the Phase I ESA for this site.

• A Phase II investigation in 1997 identified TPH and PAH concentrations in groundwater and TPH concentrations in soil (no information was available on the specific concentrations) in the areas between Units 6 and 7. No documentation was found regarding remedial efforts in the Phase I ESA for this site.

• The integrity of several underground pipelines, including a fuel oil supply line, was not verified. Records were found documenting subsurface wastewater spills from the pipelines connecting the generating units to the Class I surface impoundments.

• The integrity of several sumps, including the oily sludge/condensate collection sump beneath Units 1 through 6, a storm water transfer sump, and a catch basin sump located south of Unit 6, was not verified. A potential for releases from these underground pipelines and sumps exists.

• REC 3, unknown locations: Rectangular basins at the Mirant Pittsburg Power Plant property were subject to unauthorized dumping by local residents. The exact locations of these basins are unknown. To confirm that the materials dumped at these locations did not create an REC, further research would be needed to identify these areas for further investigation and potential remediation.

• REC 4, unknown location: A PG&E memorandum indicated that before 1970, accumulated wastes from the former clarifier sludge pond and oily water treatment system were disposed of somewhere on-site, but the location of the on-site disposal is unknown. The memorandum also indicated that PG&E was conducting an investigation to identify this area. This former onsite disposal area may need further investigation and remediation, depending on the results of that investigation.

• REC 5, Tank 16 (in the far southern part of the Mirant Pittsburg Power Plant property): A previous Phase I investigation reported that soil saturated with no. 6 fuel oil was discovered northeast of Tank 16 outside of the containment basin and south of the railroad tracks. A significant amount of fuel oil was encountered up to a depth of 5 feet in the trenches that were excavated. Also, a 1997 Phase II investigation identified TPH and PAH contamination in groundwater and TPH contamination in soil near Tank 16. In the URS Phase I ESA, no documentation was found of subsurface remediation in this area. Therefore, the contamination in this area may remain in the subsurface or may have migrated along the railroad tracks.

• REC 6, unknown location: Until 1989, painting material was stored at the Mirant Pittsburg Power Plant site on a 7-inch-thick concrete pad and unpaved surface. A Phase I investigation identified stains and cracks on the concrete pad. Although the area received closure from DTSC, it is noted that the soil samples were not analyzed for VOCs. Hence, this area may require further investigation and potential remediation.

• REC 7, liquid waste storage area (northwest of Tank 1): In 1997 a Phase II investigation identified metals in groundwater near the previously operated liquid waste storage area. Thus, this area may represent an REC to the Mirant Pittsburg Power Plant property and to the proposed DC cable route.

• REC 8, throughout Mirant Pittsburg Power Plant site: A 2004 chemical inventory reported under EPCRA indicated that the asbestos-containing waste insulation material was handled at the Mirant Pittsburg Power Plant property. Given the age of the buildings at the site, it is likely that the buildings and equipment on the property are insulated with asbestos-containing material. These materials should be tested if demolition is conducted as part of the redevelopment of the property.

• REC 9, west of Main Road: Between the late 1970s and early 1980s, a portable turbine power generator located to the west of the main road was operated using kerosene. The unit reportedly leaked routinely. Since no documentation exists about spill cleanup and subsurface remediation, contaminated soil may still exist in this area. This is an REC for the Pittsburg Mirant site and also could be an REC for the AC cable route.

• REC 10, throughout Mirant Pittsburg Power Plant site: Given the age of the buildings on the Mirant Pittsburg Power Plant site, lead-based paint was likely used in building construction and maintenance.

• REC 11, north and south of the power-generating units: The proposed converter station site is located near the current hazardous waste storage area, the hazardous materials storage buildings, and the former asbestos and paint storage area. Based on the types of materials stored and handled at these locations, the potential for contamination exists. Soil staining at the former asbestos and paint storage area was noted during RCRA inspections. Also, a Phase II investigation conducted in 1998 (by Fluor Daniel GTI) identified TPH in soil and TPH and PAH in groundwater in this area. Remediation of this area was not reported in any of the files reviewed. Hence, the potential for VOC, TPH, and PAH contamination in this area still exists for the converter station site and both the AC and the DC cable routes.

• REC 12, demineralizer and neutralization pond: Quarterly groundwater monitoring conducted to monitor the previously regulated demineralizer and neutralization pond (DNP) indicates potassium and fluoride Upper Confidence Limit (UCL) exceedances in groundwater for the DNP unit. The fluoride exceedance is attributed to upgradient minor sources such as the shower and eye wash station. The exceedance of potassium is still being investigated. This is an REC for the Pittsburg Mirant site and the DC cable route.

• REC 13, PG&E substation (along AC cable route): The Phase I investigation of the Mirant Pittsburg property identified a number of issues regarding the PG&E substation:

• In previous Phase I investigations at the PG&E substation, TPH was detected in soil at concentrations of 30 mg/kg and in water at concentrations of 3,000 micrograms per liter (µg/L). Arsenic was also detected in groundwater at 90.2 µg/L. These areas may potentially need remedial action, as no records were found documenting remediation in these areas in its Phase I ESA.

• Before 1970, cleaning compounds and spills or leaks of transformer oil were discharged to the rock blotter surrounding the base of the transformers at the PG&E substation. Because the cleaning compounds contained hazardous chemicals, the spills potentially impacted the Pittsburg Mirant site.

• Underground piping was used to transfer dielectric fluid from the PG&E substation oil-containing circuit breakers and main bank transformers to two former ASTs located west of the PG&E substation. Integrity of this piping does not appear to have been investigated, and hence potential for polychlorinated biphenyl (PCB) release from these pipelines exists.

The Phase I ESA identified the following RECs for the Mirant Pittsburg Power Plant site from surrounding properties:

• REC 14, 701 Willow Pass Road (south-southwest of Mirant Pittsburg Power Plant property): Greif Fiber Drum, originally Sonoco Fiber Drum, which operated at 701 Willow Pass Road, is located upgradient and 2,669 feet south-southwest of the Mirant Pittsburg Power Plant property. The site is listed in the Comprehensive Environmental Response, Compensation and Liability Information System (CERCLIS) and Voluntary Cleanup Program (VCP) Databases. Soil and groundwater contamination is known to exist at the site. TCE, dichloroethene (DCE), and vinyl chloride have been identified as the primary contaminants. Monitoring wells installed by Sonoco Fiber Drum are known to exist at the site to identify the extent of the contamination. Due to the proximity of this site to the Mirant Pittsburg Power Plant property and the migration potential of the contamination, this site is identified as a REC to the Mirant Pittsburg property.

5.6.14.2  Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative site are generally as described in Section 4.14.3 for the proposed Pittsburg Standard Oil site.

5.6.14.2.1  Construction-related Impacts. Impacts HAZ-1 through HAZ-6 apply to the alternative Pittsburg Mirant 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:

• 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)

5.6.14.2.2  Operations-related Impacts. Impacts HAZ-8 through HAZ-12 would apply to the operations phase at the Pittsburg Mirant Converter Station Alternative 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)

5.6.15  Paleontological Resources

5.6.15.1  Environmental Setting

No fossil localities have been identified within the footprint of the alternative Pittsburg Mirant Converter Station site. The Pittsburg Mirant Converter Station and its associated onshore AC/DC 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 cable route associated with this alternative 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 laydown areas are assigned a low sensitivity rating, as use of these areas is not expected to penetrate into undisturbed Qal sediments.

5.6.15.2  Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the Pittsburg Mirant Converter Station Alternative are as described in Section 4.15.3 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 PALEO-1 (Potential Fossil Resources Protection) for Impact PALEO-1 (Disturbance of Fossil Resources)