4.A   SAN FRANCISCO HWC (MITIGATED) CONVERTER STATION

4.A.1   Introduction

As discussed in Sections 1.0 and 3.0 of this Final EIR, the previously proposed San Francisco HWC Converter Station site layout as assessed in the Draft EIR has been shifted to the western portion of the overall HWC site as a mitigating action to completely avoid the need to demolish two historic buildings on the eastern portion of the overall HWC site. The shifted site layout ("HWC [Mitigated]" site) is also further away from the Bay and would not preclude or interfere with the possible future construction of a Bay Trail segment along the portion of the waterfront to the east. The HWC (Mitigated) site layout would also avoid impacts to any portion of the historic Station A Complex on the adjacent Mirant property to the north associated with the alternating current (AC) cable interconnection to the Pacific Gas and Electric Company (PG&E) Potrero Substation. Accordingly, the previously proposed HWC converter station site layout assessed in the Draft EIR has been deleted from further consideration and has been replaced by the HWC (Mitigated) site layout.

The San Francisco HWC (Mitigated) Converter Station site is located on fill at the southeastern corner of the 23^rd and Illinois streets intersection. The site is bounded completely by industrial land uses. The Mirant Potrero Power Plant and PG&E Potrero Substation are directly northeast and north of the site, respectively. The AC cable would traverse 23^rd Street and the Mirant Potrero Power Plant property into the PG&E substation and the DC cable would run east-west along 23^rd Street. San Francisco Bay is located approximately 200 feet east of the site. The San Francisco HWC (Mitigated) site (refer to Figure 3-3) is located directly west of the previously proposed HWC site as assessed in the Draft EIR and is within the Central Waterfront area of San Francisco.

The overall HWC site is comprised of the buildings at 435, 525, and 555 23^rd Street, and is bounded on the north by 23^rd Street and the Mirant Potrero Power Plant, on the east by a small, undeveloped parcel owned by the Port of San Francisco and by San Francisco Bay, on the south by 24^th Street, and on the west by Illinois Street. The HWC (Mitigated) site is located on the portion of the overall HWC property at 525 23^rd Street which is currently occupied jointly by DHL and Airgas. The existing building (non-historic) on the HWC (Mitigated) site would need to be demolished to accommodate the proposed converter station at this location. The entire site is currently either covered with buildings or pavement. The site is known to have subsurface contamination (soil and groundwater) from historic activities and uses (refer to Section 4.A.14 for more information).

4.A.2   Air Quality

4.A.2.1   Environmental Setting

The environmental setting for air quality associated with the San Francisco HWC (Mitigated) Converter Station site in San Francisco is as described in Section 4.2.1 of the Draft EIR for the previously proposed HWC site.

4.A.2.2   Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the San Francisco HWC (Mitigated) Converter Station site layout in San Francisco are as described in Section 4.2.3 of the Draft EIR for the previously proposed San Francisco HWC site. Potentially significant air quality impacts associated with installation of the offshore DC cable route (refer to Section 4.2.3.4 of the Draft EIR and Table 1-1 in this Final EIR) apply to the San Francisco HWC (Mitigated) Converter Station. With implementation of the following mitigation measures, potentially significant impacts would be reduced to less-than-significant levels for the San Francisco HWC (Mitigated) Converter Station:

4.A.3   Geologic Resources and Soils

Background geological resources and soils data for the San Francisco HWC (Mitigated) Converter Station site are as presented in Section 4.3 of the Draft EIR for the previously proposed HWC site. This background information is also applicable to the San Francisco HWC (Mitigated) Converter Station site. Site-specific environmental setting and impact discussions for the HWC (Mitigated) site are presented below.

4.A.3.1   Environmental Setting

4.A.3.1.1   Site Geology. The San Francisco HWC (Mitigated) Converter Station site is shown on Figure 3-3 of this Final EIR and is located directly adjacent to and west of the previously proposed HWC site shown on Figure 4.3-3 of the Draft EIR. The geology of the San Francisco area, including the HWC (Mitigated) site, is shown on Figure 4.3-3 of the Draft EIR. Soil types are shown on Figure 4.3-4 of the Draft EIR. The site is underlain primarily by artificial fill over reclaimed tidal flats featuring Bay Mud and estuarine deposits. The artificial fill consist of gravels, sands, and clays. Serpentine bedrock may be present at depth although the mapped location of the ridge is to the east of the site.

Geologic Resources. The San Francisco HWC (Mitigated) Converter Station site does not have any identified unique geologic features or resources. Paleontological resources are discussed in Section 4.A.15 of this Final EIR.

Faults. No active or potentially active faults have been identified on the HWC (Mitigated) site. Figure 4.3-2 of the Draft EIR illustrates the major Quaternary faults in the site region. The closest known active faults are the San Andreas fault (9.5 miles to the west) and the Hayward fault (12 miles to the east). Table 4.3‑1 of the Draft EIR presents maximum earthquake magnitude estimates and indicates the closest distance from each fault to the previously proposed HWC site, which is also applicable to the HWC (Mitigated) site. Each fault zone is described in detail in Section 4.3.1.2 of the Draft EIR.

4.A.3.2   Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the San Francisco HWC (Mitigated) Converter Station site are as described in Section 4.3.3 of the Draft EIR for the formerly proposed HWC site. With implementation of the following mitigation measures, potential environmental impacts associated with the HWC (Mitigated) site would be reduced to a less-than-significant level:

4.A.4   Water Resources and Quality

4.A.4.1   Environmental Setting

The San Francisco HWC (Mitigated) Converter Station site is shown on Figure 3-3. The converter station site is located approximately 200 feet west of the Bay. There is no surface water on the site. Stormwater from the site is currently directed to the San Francisco combined stormwater and sanitary sewer system. As described in Section 4.4.1.5 (Drainage and Flooding) of the Draft EIR, the majority of San Francisco is served by a combined storm sewer system, where storm water, along with residential and commercial sewage, is directed to three wastewater treatment plants prior to being released to San Francisco Bay or the Pacific Ocean.

Based on the results of the Phase II investigation conducted at this site, site contaminants are generally similar to those described for the eastern portion of the overall HWC site as discussed in Section 4.14 of the Draft EIR. Groundwater was encountered at a depth of approximately 10-15 feet below ground surface (bgs). The pH of the groundwater is close to 7 or neutral. The groundwater is impacted with a variety of site contaminants as follows: heavy metals, heavy petroleum hydrocarbons, gasoline constituents including benzene, cyanide, and polynuclear aromatic hydrocarbons (PAHs). The groundwater does not exceed the hazardous waste criteria, but no fish bio-assay tests were conducted. It is unlikely that the groundwater is hazardous. The groundwater is not impacted with polychlorinated biphenyls or hexavalent chromium. The groundwater flow direction on the overall HWC site is split, probably because of the subterranean ridge that runs under the eastern portion of the overall HWC site. The groundwater flow direction on the HWC (Mitigated) site is to the southwest. In the eastern portion of the overall HWC site the groundwater flow direction varies from the southeast to the northeast. Refer to Section 4.A.14 for more information regarding groundwater conditions at the HWC (Mitigated) site.

The San Francisco HWC (Mitigated) Converter Station site is not located within the 100-year flood zone.

4.A.4.2   Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the San Francisco HWC (Mitigated) Converter Station site are generally as described in Section 4.4.3 of the Draft EIR for the previously proposed HWC site. Groundwater collected during groundwater dewatering during construction at the HWC (Mitigated) site (e.g., under the transformer bay where the planned excavation depth of approximately 15 feet would likely extend below the groundwater level of 10-15 feet bgs) would require treatment, follow-on sampling and analysis, and evaluation before it could be discharged to the combined San Francisco storm/sanitary sewer. Alternatively the groundwater could be sent offsite for treatment and disposal at a commercial water treatment facility. Refer to Section 4.A.14 (Hazardous Materials and Waste Management) for more information about potential contaminated groundwater-related impacts and associated mitigation (HAZ-7).

With implementation of the following mitigation measures, potential environmental impacts associated with the HWC (Mitigated) site would be reduced to a less-than-significant level:

4.A.5   Terrestrial Biological Resources

4.A.5.1   Environmental Setting

The HWC (Mitigated) site is located adjacent to and west of the previously proposed HWC site. The environmental setting for this site is consistent with the previously proposed HWC site, as described in Section 4.5 of the Draft EIR.

4.A.5.2   Environmental Impacts

This area is dominated by previously developed and industrialized landscapes described in Section 4.5 of the Draft EIR as Disturbed/Developed habitats. No potential impacts to natural communities, wetlands, or special-status species would be expected from development of the HWC (Mitigated) site.

4.A.6   Marine Biological Resources

4.A.6.1   Environmental Setting

Background information, including evaluation of marine biological resources with a review of special-status species with the potential to occur in the Project area, as well as the regulatory framework, are provided in Section 4.6 of the Draft EIR.

4.A.6.2   Environmental Impacts

The potential environmental impacts to marine biological resources associated with the San Francisco HWC (Mitigated) Converter Station and associated submarine High Voltage Direct Current (HVDC) cable system route in the Bay are as described in Section 4.6.3 of the Draft EIR. In summary, no potentially significant impacts to marine biological resources have been identified.

4.A.7   Cultural Resources

4.A.7.1   Environmental Setting

4.A.7.1.1   Archaeological Resources. Archival research indicates that the San Francisco HWC (Mitigated) Converter Station site (refer to Figure 3-3) is located in an area of potential archaeological sensitivity. Prior to the reclamation efforts initiated in the latter half of the 19th century, Potrero Point, upon which the HWC (Mitigated) parcel is situated, extended into the waters of San Francisco Bay from just south of 24^th Street to 23^rd Street and east to Delaware Street (U.S. Coastal Survey [USCS], 1852).

Although this places the San Francisco HWC (Mitigated) Converter Station site on lands once submerged beneath San Francisco Bay, the portion of this property where the converter station layout is now proposed was once bisected by the Tubbs Cordage Company ropewalk. A ropewalk consists of a long narrow building where strands of yarn were manually twisted into ropes.

The San Francisco Cordage Manufactory was constructed on the block bounded by present day Indiana, Tennessee, Tubbs, and 22^nd Streets by Alfred and Hiram Tubbs in 1856. Subsequently renamed the Tubbs Cordage Company, the facility included a ropewalk which at its longest reached a length of over 1,500 feet. Over much of its length, the ropewalk rested on piers just above the waters of the Bay. As mentioned above, strands of yarn were manually twisted into ropes atop the length of the ropewalk. Ropes manufactured in this process were considered superior to those manufactured in the then newly invented machine twisting process. Ropes manufactured at the Tubbs facility were utilized by California's burgeoning shipping and mining industries (Wirth Associates, 1979a:6-8, 96; 1979b:36-37).

The ropewalk is depicted on the USCS Maps of 1859, 1869, and 1884, extending southeastward into the Bay from roughly today's Kentucky Street just north of the intersection with 23^rd Street. Based on a review of the Sanborn Map of 1914, it appears that the historic feature bisected what is now the western portion of the overall HWC property at the corner of Illinois and 23^rd Street and passed through the parcel at a bearing of roughly 110 degrees.

Although the Sanborn Map of 1914 still depicts a portion of the ropewalk allowing for an accurate delineation of its route, by this date the feature is no longer depicted as extending over open water across the current Project area. The area is instead solid ground with the ropewalk terminating at Kentucky. This configuration of the ropewalk is still depicted on the Sanborn Map of 1952.

In addition to the archaeological inventory, boring logs of a recent soil-sampling program (URS, 2006) at the HWC (Mitigated) site were examined. These logs reveal that the current HWC (Mitigated) site is underlain by upwards of 20 feet of fill material. The fill, primarily sand or sandy soils, becomes coarser with depth and contains brick, gravel, concrete, wood, and other rubble down to depths of 20 feet below ground surface. Underlying the initial fill material is silty sand with gravel that also contains occasional brick and concrete fragments. Intact structural remains were not observed in any of the borings. The assortment of constituents observed in the fill is a common occurrence in San Francisco. It has been reported that a wide variety of material was used in the historical filling of the waters off San Francisco. Although sand was the primary constituent (Dow, 1973), household trash and structural debris was commonly deposited in the bay as fill material. For example, Captain Fred Klebingat (quoted in Olmstead et al., 1977:128) observed some of the materials used as fill for the area south of Folsom Street. He stated that they "dumped rubbish from buildings," including pulverized bricks and old concrete. He also witnessed the dumping of a cargo of hay bales and sacks of cement off the five-masted schooner W.H. Marston, as well as animal remains.

4.A.7.1.2   Historic Architectural Resources. The San Francisco HWC (Mitigated) Converter Station site completely avoids the historic buildings (two Western Sugar Refinery warehouses) on the eastern portion of the overall HWC property. The previously proposed HWC converter station layout would have required demolition of these two historic structures which would be considered an unavoidable adverse significant impact. In addition, the AC cable route to the PG&E Potrero Substation that was associated with the previously proposed HWC site would have resulted in an unavoidable adverse significant impact on the historic Station A Complex on the adjacent Mirant property. The onshore AC cable route associated with the HWC (Mitigated) site completely avoids this impact as well. The onshore AC cable route between the HWC (Mitigated) site and the PG&E Potrero Substation (refer to Figure 3-3 of this Final EIR) does traverse an area of potential archaeological sensitivity, including the portion on the Mirant property. The HWC (Mitigated) site contains buildings constructed after 1961 that have served various types of warehouse and transshipment purposes since that time. Their simple, one-story, utilitarian construction is typical of mid-20th century ground freight warehousing and shipping facilities. The buildings are less than 50 years old and as such, do not require further study or historical evaluation, nor are they considered historical resources for the purposes of the California Environmental Quality Act (CEQA). The land surrounding the San Francisco HWC (Mitigated) Converter Station site underwent a great deal of change during the 1950s and 1960s, further altering the setting of the site. These changes included construction of a shipping warehouse across Illinois Street to the west, closure of the manufactured gas facility to the north, and extensive construction and remodeling of the PG&E power plant property (Station A) to the north through 1983, when Station A was removed from service. The former sugar refinery to the east and north of the HWC (Mitigated) site was closed in 1949 and nearly all of its facilities were also removed during this time.

In conclusion, there are no historic architectural resources present within the footprint of the San Francisco HWC (Mitigated) Converter Station site or the proposed AC cable route to the PG&E Potrero Substation.

4.A.7.2   Environmental Impacts

4.A.7.2.1   Archaeological Resources. It is unknown whether or not the ropewalk described above was left intact during reclamation efforts. During San Francisco's reclamation efforts of the mid- to late-19th century, wharves were commonly used as platforms from which to dump fill material. It is in this manner that the numerous wharves that once extended out into Yerba Buena Cove became entombed along with ships, barges, and other vessels that were moored alongside. As such, it is possible that remnants of the Tubbs Cordage Company ropewalk might lay buried within the site of the San Francisco HWC (Mitigated) Converter Station site.

Given the potential archaeological sensitivity within the confines of the San Francisco HWC (Mitigated) Converter Station site and along the proposed AC cable route to the PG&E Potrero Substation, it is possible that with Project implementation on this site and AC cable route, archaeological resources might be exposed during construction activities. The same potentially significant impact on archaeological resources described in the Draft EIR is applicable to a portion of the HWC (Mitigated) site. With implementation of the following mitigation measures which are the same as those specified for the HWC site previously proposed on the eastern portion of the property (refer to Section 4.7.3.2.1 of the Draft EIR for more information), potential environmental impacts to archaeological resources would be reduced to less-than-significant levels for this Project site:

4.A.7.2.2   Historic Architectural Resources. Construction of the San Francisco HWC (Mitigated) Converter Station would not cause a significant adverse change because this site contains no historical resources. Construction of the San Francisco HWC (Mitigated) Converter Station would not cause direct or indirect significant adverse change to nearby resources or potential resources. This construction would not require demolition or physical alteration of historical resources, or any of the potential contributing elements of nearby historic district(s). The introduction of the proposed converter station facilities would be consistent with the types of industries that have operated in this area for nearly 130 years. In fact, this part of the Central Waterfront has long been utilized for various energy-related uses, including massive multi-story manufactured gas storage tanks (no longer extant), and a multi-story electric power generation plant. The remaining nearby historical resources (the Station A complex and the sugar warehouses) were constructed and operated in an area that was already surrounded by large-scale industrial utilitarian buildings and structures when they were completed. Construction of the San Francisco HWC (Mitigated) Converter Station site, therefore, would not cause a significant adverse indirect change to the sugar warehouses, or the Station A complex as individual historical resources. Nor would this action cause a significant adverse indirect change to the potential historic district(s) because it would not impair the ability of the potential district(s) to convey historic significance. This activity would not materially impair the significance of the potential district(s) and the impact to the potential historic district(s) would be less than significant.

Given the above, there are no historic architectural mitigation measures proposed for the San Francisco HWC (Mitigated) Converter Station site or associated onshore AC cable route to the PG&E Potrero Substation.

4.A.7.3   References Cited

Dow, Gerald Robert. 1973. Bay Fill in San Francisco: A History of Change. Unpublished M.A. Thesis, San Francisco State University.

Olmstead, R., N. Olmstead, and A. Pastron. 1977. Channel Outfalls Consolidation Project. Report submitted to the San Francisco Wastewater Management Program.

URS. 2006. Phase II Soil and Groundwater Site Investigation Report for HWC (Mitigated) Site, Western Portion of the Harrigan Weidenmuller Company Property at 435, 525, and 555 23^rd Street, San Francisco, California. September.

Wirth Associates, Inc. 1979a. Potrero 7: Phase I Cultural Resources Overview and Inventory. Submitted to Pacific Gas and Electric Company, San Francisco.

1979b. Potrero 7: Phase II Archaeological Test Excavations. Submitted to Pacific Gas and Electric Company, San Francisco.

4.A.8   Land Use and Recreation

4.A.8.1   Environmental Setting

The proposed San Francisco HWC (Mitigated) Converter Station site and onshore AC/DC cable routes are collectively referred to as the San Francisco HWC (Mitigated) site in this section, unless otherwise noted.

4.A.8.1.1   Existing Land Uses. The San Francisco HWC (Mitigated) site is located at the southeastern corner of the 23^rd and Illinois streets intersection. The site is bounded completely by industrial land uses. The Mirant Potrero Power Plant and PG&E Potrero Substation are directly northeast and north of the site, respectively. The AC cable would traverse 23^rd Street and the Mirant Potrero Power Plant property into the PG&E substation and the DC cable would run east-west along 23^rd Street. San Francisco Bay is located approximately 200 feet east of the site. The San Francisco HWC (Mitigated) site is located directly west of the previously proposed HWC site as assessed in the Draft EIR, and within the Central Waterfront area of San Francisco. Existing land uses within this area are described further in Section 4.8.1 of the Draft EIR.

4.A.8.1.2   Potentially Sensitive Land Uses. Table 4.A.8-1 lists potentially sensitive land uses near the San Francisco HWC (Mitigated) site. The current routing of the Bay Trail along Illinois Street is located directly adjacent to the HWC site, and Warm Water Cove Park is located approximately 200 feet east of the site. The nearest residences are located approximately 480 feet from the west edge of the alternative San Francisco HWC (Mitigated) Converter Station site. A church is located about 1,000 feet northwest of the HWC (Mitigated) Converter Station site. Additional potentially sensitive land uses within the area are consistent with those associated with the previously proposed HWC site, as discussed in Section 4.8.1 of the Draft EIR.

4.A.8.1.3   Zoning Designations. The San Francisco HWC (Mitigated) site is zoned M-2 Heavy Industrial. Permitted uses and development standards (including height restrictions and exemptions) are consistent with those associated with the previously proposed HWC site, as discussed in Section 4.8.1 of the Draft EIR.

4.A.8.1.4   Land Use Trends. Land use trends for the San Francisco HWC (Mitigated) site are consistent with the previously proposed HWC site, as discussed in Section 4.8.1 of the Draft EIR.

4.A.8.2   Environmental Impacts

The San Francisco HWC (Mitigated) Converter Station would not result in potentially significant impacts related to land use or recreation. The San Francisco HWC (Mitigated)

TABLE 4.A.8-1
POTENTIALLY SENSITIVE LAND USES NEAR
SAN FRANCISCO HWC (MITIGATED) CONVERTER STATION SITE

Converter Station site is completely bounded by industrial land uses. The Mirant Potrero Power Plant and PG&E substation are directly north and northeast of the site. The San Francisco HWC (Mitigated) Converter Station site represents further development of an area committed to industrial use rather than the introduction of industry to a non-industrial area.

The San Francisco HWC (Mitigated) Converter Station site is located within the same planning subarea (Central Waterfront) and zoning district (M-2) as the previously considered HWC site in the Draft EIR. Land use plans and policies pertaining to the San Francisco HWC (Mitigated) site are consistent with the previously considered HWC site. As such, public access to the shoreline and open space is emphasized. The HWC site is located adjacent to the Bay Trail, which is shown on Figure 4.8-1 of the Draft EIR. Temporary impacts to the Bay Trail are expected during construction, as discussed in Section 4.10, Traffic and Transportation, of the Draft EIR. Temporary impacts to the Bay Trail from construction would be mitigated by Mitigation Measure TRAFFIC-3. No permanent impacts to the Bay Trail are expected with operating the converter station at the HWC (Mitigated) site. Public access to the shoreline is provided by Warm Water Cove Park situated 200 feet east of the San Francisco HWC (Mitigated) site. Operations of the HWC (Mitigated) Converter Station would not affect public access to Warm Water Cove Park or lessen recreational opportunities along the Bay Trail.

As discussed for the previously considered HWC site, the Central Waterfront Area Plan stipulates maintaining and improving existing recreational improvements at Warm Water Cove and expanding to the north side of the cove as opportunities arise. The policy requires that public access be provided along the north side of the cove and a fishing quay be constructed at the Bay. The San Francisco HWC (Mitigated) Converter Station would not be affected by this policy, as the site is farther west of Warm Water Cove Park than the previously considered HWC site. The HWC (Mitigated) site is currently zoned Heavy Industrial and the converter station is consistent with permitted uses within this district.

The San Francisco HWC (Mitigated) Converter Station would be consistent with the existing uses of the site and surrounding area. The nearest residential development near the San Francisco HWC (Mitigated) site is approximately 480 feet to the northwest of the site. The San Francisco HWC (Mitigated) Converter Station would not require displacement of housing and would not have significant land use impacts on the community.

Established uses surrounding the alternative San Francisco HWC (Mitigated) Converter Station site are primarily industrial. Potentially sensitive land uses in the area include Warm Water Cove Park located 200 feet east and a church situated approximately 1,000 feet northwest of the site. The Potrero Power Plant and PG&E substation are directly northeast and north of the site. Pier 70 to the north and Pier 80 to the south are actively used for dry dock and container terminals.

Proposed future development plans outlined in the Draft Central Waterfront Neighborhood Plan would rezone the HWC (Mitigated) Converter Station site from M-2 to PDR (Production, Distribution & Repair) and the converter station is consistent with uses within the proposed PDR district. The Plan would also rezone the area west of Illinois Street, directly across the street from the HWC (Mitigated) site, from M-2 to mixed use residential. Although future residences may be located directly across the street from the converter station following commencement of operation of the facility, the Draft Plan specifically prohibits residential development on PDR districts and the HWC (Mitigated) site would be bounded on the north, east, and south by PDR districts. The character of the site would not change given that the site would continue to be industrial in nature and primarily bound by industrial properties. The Plan had not been finalized or approved at the time this Final EIR was prepared, and no specific development plans have been brought forward at this time. Thus, assessing potential conflicts requires a degree of speculation. Notwithstanding, potential noise and visual impacts to possible future residences are discussed in Section 12.0 (Response to Comments) of this Final EIR.

4.A.9   Marine Transportation and Commercial Fishing

The San Francisco HWC (Mitigated) Converter Station would not impact marine transportation or commercial fishing.

4.A.10 Traffic and Transportation

4.A.10.1 Environmental Setting

The environmental setting for traffic and transportation for the San Francisco HWC (Mitigated) Converter Station site is consistent with the discussion presented for the previously proposed San Francisco HWC Converter Station site in Section 4.10.1 of the Draft EIR.

4.A.10.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the San Francisco HWC (Mitigated) Converter Station site are as described in Section 4.10.3 of the Draft EIR.

4.A.10.2.1 Construction-related Impacts. Construction traffic impacts discussed for the previously proposed HWC Converter Station site (and laydown areas) in Section 4.10.3.2.1 of the Draft EIR are also applicable to the HWC (Mitigated) Converter Station.

Since this site is directly adjacent to the previously proposed HWC Project site in San Francisco and the local streets used for Project-related truck deliveries and work trips would remain the same, the construction-related transit, bicycle, pedestrian, rail, and parking impacts would be the same as described for the previously proposed HWC site.

With implementation of the following mitigation measures, potential traffic-related environmental impacts associated with the HWC (Mitigated) site would be reduced to a less-than-significant level:

4.A.10.2.2 Operations-related Impacts. No operations-related impacts to traffic or transportation have been identified.

4.A.11 Noise and Vibration

4.A.11.1 Environmental Setting

The San Francisco HWC (Mitigated) Converter Station site is directly adjacent to and west of the previously proposed HWC site assessed in Section 4.11 of the Draft EIR. Descriptions of the land use surrounding the site are the same as identified for the previously proposed HWC site. Ambient noise measurement locations utilized to assess the HWC (Mitigated) site are the same as those presented in Section 4.11 of the Draft EIR for the previously proposed HWC site. The results of the ambient noise measurements are summarized in Table 4.11-2 of the Draft EIR. The measurement locations are shown on Figure 4.11-1 of the Draft EIR.

Sensitive receptors in the HWC (Mitigated) site Project area are the same as those identified for the previously proposed HWC site in Section 4.11 of the Draft EIR. They consist of multi-family residences approximately 480 feet west at 2638 3^rd Street in between 22^nd and 23^rd Streets and multi-family residences approximately 1,150 west at 1423 Indiana Street. No residences have a direct line-of-sight to the Project due to intervening three- and four-story commercial buildings in between the residences and the site. In addition, both residences are within 500 feet of Interstate 280 to the west.

4.A.11.2 Environmental Impacts

4.A.11.2.1 Construction-related Impacts. Scheduled construction hours at the San Francisco HWC (Mitigated) Converter Station would be the same as those given for the previously proposed HWC Project site in Section 4.11 of the Draft EIR. The anticipated noise sources would be the same as those outlined for the previously proposed HWC site in the Draft EIR.

Acoustical calculations were performed to estimate noise from construction activities at the closest residences with the same methodology as described for the previously proposed HWC site. The closest offsite residential uses to the San Francisco (Mitigated) Converter Station site consist of multi-family residences approximately 480 feet west and 1,150 feet to the west. Average construction sound levels at the closest residences to the San Francisco HWC (Mitigated) Converter Station construction site would be 69 and 62 dBA (A-weighted sound level), respectively, as summarized in Table 4.A.11-1. Because of the intermittent nature of construction work and the intervening buildings, it is unlikely that noise from construction would be audible at the residences, much less increase the existing noise levels by 5 dBA; therefore, there would be no significant impact. During this time period, construction activity would be required to comply with the City's noise ordinance criteria (80 dBA at 100 feet) and would result in a less-than-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 were calculated to be 85 dBA maximum sound level (L_max) (80 dBA equivalent sound level [L_eq]) at the residences 480 feet west and 78 dBA L_max (73 dBA L_eq) at the residences 1,150 feet west. Due to the intervening buildings, received sound levels at the receptors would be substantially less than predicted, although it is likely that noise from the pile driving would still be audible at the receptors. Section 4.11.3.1.1 of the Draft EIR details pile driving restrictions to be followed in San Francisco. Pile driving would be required to comply with these requirements and would result in a less-than-significant impact.

TABLE 4.A.11-1
CALCULATED SOUND LEVELS FROM CONSTRUCTION OF THE
SAN FRANCISCO HWC (MITIGATED) CONVERTER STATION (dBA)

Calculations were performed to estimate vibration from pile driving activities at the closest residences, as detailed in Section 4.11.1.2 of the Draft EIR. 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 the closest residences 480 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. Construction traffic impacts discussed for the previously proposed San Francisco HWC Converter Station site in Section 4.11.3.1.1 of the Draft EIR are also applicable to the San Francisco HWC (Mitigated) Converter Station site.

4.A.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 previously proposed HWC Converter Station. As shown on Figures 3-4 and 3-5 of this Final EIR, the proposed Project design for the San Francisco HWC (Mitigated) Converter Station includes an approximately 12- to 14-foot-tall sound wall around the northern, western, and southern boundaries. A noise analysis was conducted for the HWC (Mitigated) site, and the results are summarized here and provided in Appendix H of this Final EIR.

As summarized in Table 4.A.11-2, hourly average sound levels from the San Francisco HWC (Mitigated) Converter Station layout would range from 63 dBA L_eq on the western property line to 71 dBA L_eq at the northern and southern property lines. Because sound levels are below the San Francisco 75 dBA L_eq requirement, there would not be a significant impact.

The L_dn are used by the State of California to define acceptable land use compatibility with respect to noise. Because of the time-of-day penalties associated with the L_dn descriptor, the L_eq for a continuously operating sound source during a 24-hour period will be numerically less. Thus, for a noise source operating continuously for periods of 24 hours, the L_eq will be

TABLE 4.A.11-2
CALCULATED SOUND LEVELS FROM OPERATION OF THE
SAN FRANCISCO HWC (MITIGATED) CONVERTER STATION (dBA)

6 dB lower than the L_dn value. Thus, the San Francisco noise ordinance requirement of 75 dBA L_eq (1 hr) at the property lines would be equivalent to 81 dBA L_dn.

4.A.11.2.3 Cumulative Impacts. The proposed San Francisco HWC (Mitigated) Converter Station site is located on the east side of Illinois Street between 23^rd and 24^th streets. As discussed in Section 7.2.3.4 (Central Waterfront Neighborhood Plan [Plan]) of the Draft EIR, the City and County of San Francisco is considering rezoning the location of the overall HWC site to PDR (Production, Distribution & Repair). In addition, the draft Plan envisions rezoning the west side of Illinois Street to mixed use residential. The compatibility (including operational noise impacts) of the proposed HWC (Mitigated) layout with the possible future mixed use residential development across Illinois Street is discussed in the Response to Comments in Section 12.0 of this Final EIR.

4.A.12 Public Services and Utilities

4.A.12.1 Environmental Setting

The public services and utilities discussions for the San Francisco HWC (Mitigated) Converter Station site and onshore cable routes are consistent with those for the previously proposed HWC site addressed in Section 4.12.1 of the Draft EIR.

4.A.12.2 Environmental Impacts

Potential impacts to public services and utilities from construction of the San Francisco HWC (Mitigated) Converter Station are consistent with the impacts discussed in Section 4.12.3 of the Draft EIR for the previously proposed HWC site. Mitigation measures include development of a Construction Fire Prevention and Protection Program and an Operations Fire Prevention and Protection Program. Furthermore, a survey shall be conducted prior to any excavation work at the converter station site or associated DC and AC cable routes to prevent conflict or disruption of existing underground utilities. With implementation of the following mitigation measures, potential environmental impacts would be reduced to less-than-significant levels for the San Francisco HWC (Mitigated) Converter Station site.

4.A.13 Visual Resources/Aesthetics

This section addresses the visual resources environmental baseline conditions and the potential for the proposed San Francisco HWC (Mitigated) Converter Station to cause significant visual impacts on those resources in the San Francisco study area.

4A.13.1  Environmental Setting

4.A.13.1.1 Concepts and Terminology. The concepts and terminology that comprise the visual resources analysis for the proposed HWC (Mitigated) site are as discussed in Section 4.13.1.1 of the Draft EIR, and include the concepts of Visual Quality, Viewer Sensitivity, Viewer Exposure, etc.

4.A.13.1.2 Methodology Overview. The methodology utilized in analyzing the HWC (Mitigated) site is the same as identified in Section 4.13.1.2 of the Draft EIR, and retains the use of Key Observation Points (KOPs) and simulations to analyze potential Project impacts.

Project Setting.

San Francisco HWC (Mitigated) Converter Station. The proposed HWC (Mitigated) Converter Station site would occupy an approximately 5-acre site between 23^rd Street and 24^th Street fronting on Illinois Street. The existing HMR warehouse structure to the east would remain. The proposed site is currently occupied by the large "L" shaped Airgas and DHL building and related warehouses and parking lots both adjacent to Illinois Street and to the rear that would need to be demolished for implementation of the HWC (Mitigated) converter station.

The KOPs selected for this assessment in San Francisco are shown on Map 4.13-1 of the Draft EIR. The same KOPs utilized for the Project analysis are retained but the actual views have been shifted to include the altered Project location which is west and somewhat south of the previously proposed Project site. A new KOP has been added at the intersection of Illinois Street and 24^th Street (KOP-SF-6).

The San Francisco HWC (Mitigated) Converter Station site is visible from Illinois Street and when viewing down both 23^rd and 24^th streets. All views are within the context of the existing Mirant Power Plant, the adjacent PG&E substation or the Sheedy construction site (see Context photographs 1 through 4, Figures 4.13-1 and -2 of the Draft EIR, and Figures 4.A.13-1 and 4.A.13-4 of this Final EIR). This is an existing industrial area both in terms of the visual context and the type of traffic traversing the area. The converter station site is also visible from the Potrero housing projects approximately 0.5 mile to the west. While the facility would be visible from a more birds-eye view, again it would be seen in the context of the larger industrial activity of the area and the primary focus of any viewer would be toward San Francisco Bay in the background (see Photo 5, Figure 4.13-3 in the Draft EIR). The third viewing area is from Warm Water Cove Park which is located approximately 200 feet east of the San Francisco HWC (Mitigated) Converter Station site. Existing views from this area are toward the Bay to the east and the existing industrial structures to the north, west, and south. In this context, the existing buildings to the west would be demolished and replaced by the proposed San Francisco HWC (Mitigated) Converter Station (see Baseline Photo A of KOP SF-3 shifted, Figure 4.A.13-3). The onshore AC cable connections would be from the proposed converter station site to the existing PG&E Potrero Substation and would not involve significant visual disturbance to this area. Similarly, the offshore HVDC cable connection would be underground from the proposed HWC (Mitigated) site into San Francisco Bay and would not involve significant areas of additional disturbance. The proposed laydown area (Pier 94/96) is currently used for truck parking and Port-related activities and would not require any construction that would affect the visual character of the area.

Visual Quality. The proposed San Francisco HWC (Mitigated) Converter Station site lacks visual coherence and harmony. While the Airgas/DHL structure is relatively cleanlined, it is large and exists within an atmosphere that is visually cluttered by the juxtaposition of materials storage, graffiti, uneven pavement, and overhead wires. There are no immediate natural landforms except for the water of Warm Water Cove which is degraded by debris, decaying docks, and industrial fences. San Francisco Bay at this location does not play a significant visual role when viewing the site from adjacent roads or even Warm Water Cove viewing toward the Project area. The visual quality of the site is classified as Low.

Viewer Sensitivity. This concern may also be categorized as the reason people would visit the area. In this case the area is industrial. Those that work there would have low expectations of the area in terms of its scenic content. City of San Francisco traffic counts along Illinois Street taken in September 2003 at 22^nd Street show an Average Daily Traffic (ADT) of 2,285 trips per day. The duration of travelers' view of the site would range in the area of 10 to 15 seconds given the frontage along Illinois Street. Warm Water Cove Park users may be there in part for the view of the water. However, the converter station site, which is to the west, does not really affect views of the cove or Bay. Given the overall context, viewer sensitivity is rated Low.

In addition to travelers, there are those that live in trailers parked along some of the streets or in homeless encampments. In addition to those living and working in the immediate area, there are those residents living in the housing project on Potrero Hill. Here the view is more expansive and does include San Francisco Bay (Photo A, Figure 4.A.13-2). For these residents, the sensitivity level would be Moderate, not as high as other portions of San Francisco with views of the Bay unaffected by heavy industrial structures in the foreground. The overall viewer sensitivity level is classified as Low to Moderate.

Therefore, the visual susceptibility index (meaning the probability that a given landscape will demonstrate a noticeable visual impact with Project implementation) is Low. Put another way, any proposed facility would have a low probability of disrupting the existing visual resources of the area as seen from roads and public places.

4.A.13.2 Regulatory Setting

With the exception of CEQA, there are no specific regulations by federal or state agencies that apply to this area.

The overall applicability of various visual resource-related laws, ordinances, regulations, and standards is presented in Table 4.13-1 of the Draft EIR. In summary, those of relevance are as follows: The proposed San Francisco HWC (Mitigated) Converter Station site is zoned M‑2 with certain height restrictions as outlined in the 40-X bulk district. However, the project is exempt from these restrictions under section 260 (b) (1) (M). Refer to Table 4.13-1 of the Draft EIR for more information.

4.A.13.3 Environmental Impacts

The thresholds of significance for the HWC (Mitigated) site are the same as identified in the analysis for the previously proposed HWC site in Section 4.13 of the Draft EIR.

The Environmental Setting presented above assesses the susceptibility of the site to potential impacts that might be generated by the HWC (Mitigated) site. In this section, the applicant-proposed design is simulated into the baseline photographs and evaluated for its severity. The Impact Severity of the Project from each KOP is determined based upon the same criteria as the previously proposed Project site. Does the project:

The response to these criteria determines the Impact Severity of a project. The integration of these two summary criteria determines the final impact. The impacts below are evaluated for the HWC (Mitigated) site from the four applicable KOPs. Where appropriate, relevant mitigation measures are identified and numbered in sequence.

Construction-related impacts include the process of erecting the converter station and related cable and infrastructure connections, which is projected to take 27 to 30 months. While there would be moving equipment and erecting cranes which certainly would be visible from the adjacent KOPs, these visual impacts are classified as short term and, therefore, less than significant and no mitigation is required.

Operations-related impacts are defined as those impacts that would be visible while the converter station is in operation and visible over the lifetime of the structure. The potential for impacts is discussed on a KOP-by-KOP basis.

4.A.13.3.1 San Francisco HWC (Mitigated) Converter Station. The proposed San Francisco HWC (Mitigated) Converter Station site is located on an approximately 5-acre site on the east of Illinois Street between 23^rd and 24^th streets. Use of this site as proposed would require removal of the existing Airgas/DHL warehouse and office structures. The most visible component would be the valve and DC hall structure, which has a ridgeline 64 feet in height and a building floor area of approximately 23,000 square feet. The electric switchyard includes a series of metal poles approximately 80 feet in height, which would be most visible from Illinois Street. An articulated 12- to 14-foot-high screening wall with vines (similar to those utilized by the California Department of Transportation (Caltrans) in the San Francisco Bay area) is included as visual screening along the Illinois, 23^rd and 24^th street frontages back to the main structures.

The proposed converter station is located within an M-2 zone which allows an exemption to the 40-foot height limitation. There is also potential concern about shadows cast by plant components into Warm Water Cove. However, in this case with the demolition of the existing warehouse and the additional half block setback for the new structure, the shadow conditions on the cove are improved over the present condition.

KOP SF-1: 23^rd Street at Illinois Street. From this location, the visual changes include the replacement of the large white masonry warehouse (Airgas/DHL) by the switchyard in the foreground and the valve and DC hall structure in the background. The 80-foot-high metal poles and portions of the switchgear are visible above the screening wall (Photo B, Figure 4.A.13-1). From this KOP, while the visual character is more cluttered than the existing condition, the Project structures would be neither out of scale with the adjacent buildings nor would they unfavorably contrast with the surrounding context; no scenic vista would be obscured. The Impact Severity is classified as Low.

Since the Impact Susceptibility for the area is also Low, the resulting impact per the guidance provided in Table 4.13-2 of the Draft EIR would be less-than-significant for this KOP.

KOP SF-2: Potrero Hill. There are glimpsed views of the Project site for residents of the housing projects on Potrero Hill. However, as can be seen (Photo B, Figure 4.A.13-2), the view is relatively distant and the converter station would replace structures of a similar size and character. The new structures would not project to a height that would significantly obscure views of the San Francisco Bay. They are neither out of scale nor unfavorably contrasting. The Impact Severity is classified as Low. Since the Impact Susceptibility for the area is Low to Moderate, the resulting impact would be less than significant.

KOP SF-3: Warm Water Cove Park. The replacement of the existing warehouse structures by the Project structures, generally of the same scale, would result in less visual clutter but would introduce a greater building mass near the west end of Warm Water Cove. (Photo B, Figure 4.A.13-3). While a portion of the view west towards Potrero Hill would be blocked, this is not considered a significant scenic vista. The increased visual impact of the building mass is considered somewhat offset by the reduced clutter and removal of the existing structures and related storage yards. The Impact Severity is classified as Moderate. The Impact Susceptibility for the area is also Moderate given that the views are from Warm Water Cove, a public place. The resulting impact would be considered adverse but less than significant.

KOP SF-5: 24^th Street at Illinois Street. From this location, the visual change would be the replacement of the large white Airgas/DHL warehouse office structure with the switchyard in the foreground and the converter station valve and DC hall structure in the background to the east. The 80-foot-high metal poles are visible at the top portions of some of the switchgear above the screen wall (Photo B, Figure 4.A.13-4). The existing PG&E Potrero Substation is visible north of 23^rd Street on the left portion of the photo. From this KOP, the Project structure would be neither out of scale with the adjacent buildings nor would it unfavorably contrast with the surrounding context; no scenic vista would be obscured. The Impact Severity is classified as Low. The frontage along 24^th Street to Warm Water Cove Park is classified as an improvement on the existing condition. Since the Impact Susceptibility for the area is also Low, the resulting impact per Table 4.13-2 of the Draft EIR would be less than significant for this KOP.

Impact VIS-1A: HWC (Mitigated) Converter Station Domination of View. Since the architectural design character of the building and the general character of proposed landscaping have not been identified in detail, there is the possibility of generating potentially significant visual impacts based upon the potential of the Project to dominate the scene or become obtrusive on views from Warm Water Cove Park. This condition may also be true of the landscape screening wall proposed along Illinois, 23^rd, and 24^th streets.

While this impact has been classified as less than significant without design controls, it may still be adverse. This adversity can be lessened through the application of Mitigation Measures VIS-1a and VIS-1b.

Mitigation Measure VIS-1Aa: Plan Submittal Requirements for Building Materials and Colors. All major Project features, including buildings, structures, fencing, and sign backgrounds (excluding electric switch gear and related wires and cables, etc. which shall be galvanized gray as shown in the simulations) shall be painted with neutral tan or gray colors that will minimize the size and height of the facility, blend with adjacent structures, and be compatible with natural landscapes where applicable. A specific painting plan shall be developed for approval by the agency with local jurisdiction to ensure that the proposed colors do not unduly contrast with the surrounding landscape colors. All treatments shall be in non-reflective colors. The painting plan shall be submitted sufficiently early to ensure that any pre-colored buildings, structures, and linear facilities shall have colors approved and included in bid specifications for such buildings or structures.

Implementation Responsibility:  Project proponent

Requirements and Timing:         Architectural design 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, in consultation with the City and County of San Francisco, to monitor and ensure compliance

Mitigation Measure VIS-1Ab: Plan Submittal Requirements for Landscaping. A specific landscaping plan shall be prepared showing the location of proposed landscaping, the varieties and sizes of plants to be planted, and the proposed time of maturity for each species. Plants shall be selected from the approved species list prepared by the agencies with jurisdiction. As practical, given space limitations, plant street trees along Illinois and 24^th streets to make these frontages more pedestrian-friendly. It is recognized that there is not adequate space for a full planter along these frontages. Planting additional trees along the western portion of Warm Water Cove within the park would also reduce the visual impact of the structure.

Implementation Responsibility:  Project proponent

Requirements and Timing:         Landscaping 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, in consultation with the City and County of San Francisco, to monitor and ensure compliance

Resulting Level of Significance. Application of Mitigation Measures VIS-1Aa and VIS-1Ab would further reduce Impact VIS-1A.

Impact VIS-2: Converter Station Will Create Substantial Light and Glare. There is potential for the Project to cast more ambient light into the immediate area than the existing conditions. There is also the possibility that the luminaries of some of the lighting fixtures may be seen directly by either residents of Potrero Hill or visitors to Warm Water Cove Park, which through the abrupt contrast of the fixtures' light with the surrounding general darkness, may create the effect of glare. While this impact has been classified as less than significant, without design controls it may still be adverse. This adversity can be lessened through the application of Mitigation Measure VIS-2.

Mitigation Measure VIS-2: Plan Submittal Requirements for Lighting. Except as required by security and worker-safety requirements, night lighting shall be hooded to direct illumination downward and inward toward the areas to be illuminated in order to minimize nighttime light and glare, backscatter to the nighttime sky, and visibility of lighting to public viewing areas. A specific lighting plan consistent with operational and safety needs and limiting the general lighting levels to a maximum reasonable level shall be submitted to each agency with jurisdiction for approval. The plan shall include provisions for timed and/or motion detection-controlled switches.

Implementation Responsibility:  Project proponent

Requirements and Timing:         A lighting plan shall be prepared by professionals qualified in the designated field of expertise; lighting plans and revised design shall be submitted prior to final planning approval

Monitoring Requirements:          City of Pittsburg, in consultation with the City and County of San Francisco, to monitor and ensure compliance

Resulting Level of Significance. Application of Mitigation Measure VIS-2 would further reduce Impact VIS-2.

4.A.13.4 Cumulative Impacts

The proposed San Francisco HWC (Mitigated) Converter Station site is located on the east side of Illinois Street between 23^rd and 24^th streets. As discussed in Section 7.2.3.4 (Central Waterfront Neighborhood Plan [Plan]) of the Draft EIR, the City and County of San Francisco is considering rezoning the location of the overall HWC site to PDR (Production, Distribution & Repair). In addition, the draft Plan envisions rezoning the west side of Illinois Street to mixed use residential. The compatibility (including potential visual impacts) of the proposed HWC (Mitigated) layout with the possible future mixed use residential development across Illinois Street is assessed in Section 12.0 (Response to Comments) of this Final EIR.

4.A.14 Hazardous Materials and Waste Management

4.A.14.1 Environmental Setting

The overall HWC site is comprised of the buildings at 435, 525, and 555 23^rd Street, and is bounded on the north by 23^rd Street and the Mirant Potrero Power Plant, on the east by a small-undeveloped parcel owned by the Port of San Francisco and by San Francisco Bay, on the south by 24^th Street, and on the west by Illinois Street, as described in Section 4.14 of the Draft EIR. The HWC (Mitigated) site is located on the portion of the overall HWC property at 525 23^rd Street.

Currently, the property at 435 23^rd Street is occupied by HMR Global Recycling (HMR), at 525 23^rd Street is occupied jointly by DHL and Airgas, and at 555 23^rd Street is an empty warehouse formerly occupied by the San Francisco Municipal Railroad (MUNI). A metal clad, roofed, open-sided storage shed is located on the south-central portion of the HWC site. The shed is approximately 230 feet long. Approximately 190 feet of the 230-foot-long shed is occupied by HMR and the other approximately 40 feet of the western portion of the structure is occupied by DHL. The two areas of the shed are separated by a chain link fence. HMR uses its portion of the shed to store computers, monitors, and other equipment on shrink-wrapped pallets for offsite shipment. DHL uses its portion of the shed to store excess packing materials and vehicle maintenance tools. There is a large parking area to the north and west of the "L"-shaped, DHL and Airgas building. Airgas stores gases in pressurized cylinders and has minimal parking spaces open for customers in its portion of the parking lot. The parking lot in front of DHL on the north side of the site is used for employee and customer parking and the parking of DHL company trucks and vans. A chain link fence separates the two parking lots. Two smaller parking areas connected by a driveway are located to the south and west of HMR. These parking areas are for customer and employee parking and parking company vehicles. The HMR parking areas are separated from the DHL parking lot by a chain link fence.

The proposed San Francisco HWC (Mitigated) Converter Station site would include the DHL and Airgas jointly occupied building and associated large parking lot, the two small parking lots to the south and west of HMR, and approximately half of the open-sided, metal clad storage shed (refer to Figure 3-3).

The proposed and alternative AC and DC cable routes associated with the proposed HWC (Mitigated) site are shown on Figure 3-3. The proposed underground direct current (DC) cable to the HWC (Mitigated) site would come from a location approximately 800 feet offshore in San Francisco Bay to the eastern end of 23^rd Street via an underground conduit installed with HDD or similar underground drilling methods. A drilling pit would be installed in the southern 23^rd Street ROW at a location 100-500 feet from the Bay to install the conduit for the cable. The purpose of using the underground drilling methods is to minimize contact with potentially contaminated nearshore Bay sediments. From the HDD drilling pit the cable would be installed using traditional trenching methods along the southern 23^rd Street ROW in a westerly direction to the northeast corner of the HWC (Mitigated) site. From the northeast corner of the converter station site the cable route would be trenched south to the connection point in the converter station. Excavated HDD drilling pit spoils, HDD drilling mud/drilling spoils, and soils excavated during cable route trenching that were not used in refilling the cable trench would be characterized and disposed of offsite in compliance with applicable regulations.

The proposed underground AC cable route from the HWC (Mitigated) site to the PG&E Potrero substation switchyard would start near the middle of the proposed HWC West Converter Station site on the north side and run northwest across 23^rd Street and onto the Mirant Potrero site, turn north along the property boundary between the Mirant Potrero site and the PG&E substation, turn west into the PG&E substation, and turn north to the connection with the PG&E substation (Figure 3-3). The AC cable would be installed by traditional trenching and backfill methods. Excess excavated soils that could not be returned to the cable trench would be characterized and disposed of offsite in compliance with applicable regulations.

According to the Environmental Data Resources, Inc. (EDR), report prepared for the Phase I Environmental Site Assessment (ESA) for the entire HWC site (EDR, 2005; URS, 2005a), no sensitive receptors (e.g., schools, hospitals, day-care facilities, or long-term health care facilities) are located within a 0.25-mile radius of the site. The closest park to the HWC site is Warm Water Cove Park, which is located southeast of the site.

The Phase I ESA identified Recognized Environmental Conditions (RECs) for the HWC (Mitigated) site that are provided in the Draft EIR and the Phase I conducted for the HWC Site.

Additionally, a Phase II investigation was recently performed at the HWC (Mitigated) site (URS, 2006). Twenty borings were advanced on the HWC (Mitigated) site to a depth of 20 feet below ground surface (bgs) for the Phase II Soil and Groundwater Investigation. These borings were advanced to conduct soil sampling for the purpose of characterizing the soil for disposal and onsite use, groundwater sampling to evaluate groundwater quality, and to evaluate groundwater flow direction. Transducers and data loggers were left in five of the temporary wells installed on the site for one week to evaluate groundwater flow direction.

The results of the Phase II investigation report can be summarized as follows:

4.A.14.2 Environmental Impacts

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the HWC (Mitigated) site are as described in Section 4.14.3 of the Draft EIR for the previously proposed San Francisco HWC site. With implementation of the following mitigation measures, potential environmental impacts would be reduced to less-than-significant levels for the HWC (Mitigated) Converter Station site:

4.A.14.3 References

State Water Resources Control Board. 1988. Resolution 88-63, Sources of Drinking Water.

URS. 2006. Phase II Soil and Groundwater Site Investigation Report for HWC (Mitigated) Site, Western Portion of the Harrigan Weidenmuller Company Property at 435, 525, and 555 23^rd Street, San Francisco, California. September.

4.A.15 Paleontological Resources

4.A.15.1 Environmental Setting

No fossil localities have been identified within the footprint of the San Francisco HWC (Mitigated) Converter Station site or the associated AC/DC cable routes. The proposed HWC (Mitigated) Converter Station site is 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 4.15-1 in the Draft EIR). The cable routes are assigned a low sensitivity rating, since typical excavations are not expected to penetrate into undisturbed Qal sediments where there would be a potential for significant paleontological resources.

4.A.15.2 Environmental Impacts

No fossil localities have been identified within the footprint of this Project component. However, construction excavations have the potential to penetrate into undisturbed Quaternary alluvium (Qal) sediments which have the potential to contain significant fossil resources. This would be a potentially significant impact.

The thresholds of significance, identification of potentially significant impacts, mitigation measure requirements, and residual impact findings for the proposed San Francisco HWC (Mitigated) Converter Station site are as described in Section 4.15.3 of the Draft EIR for the previously proposed HWC site. With implementation of the following mitigation measure, potential environmental impacts to paleontological resources associated with the HWC (Mitigated) site would be reduced to a less-than-significant level.

---

Return to the Table of Contents.

Open the Draft EIR in a new window.

On to the next section.