Environmental Impacts and Mitigation Measures

The DEIR includes summary impact statements, mitigation measures and residual levels of impact after the recommended mitigations are followed. For each significant impact there is a recommended mitigation measure and an indication of whether the impact would be mitigated to a less-than-significant level after implementation of the recommended mitigation. The EIR analyzes the environmental impacts, mitigation measures and significance after mitigation under the following categories: air quality; biological resources; cultural resources; geology, soil and paleontology; hydrology and water quality; land use and recreation; noise and vibration; public health and safety; public services and utilities; socioeconomics; transportation and traffic; and visual resources.

When the analysis presented in the EIR shows that a less than significant impact will occur as a result of the Project, that impact is generally not discussed further and no mitigation measures are identified in the EIR. When the EIR determines that the Proposed Project could potentially cause significant environmental impacts, the EIR identifies feasible mitigation measures to avoid or reduce the impact to a less than significant level.

The environmental impact assessments for the Proposed Project and alternatives are based on a classification system with the following four associated definitions:

Class I: Significant impact that can not be mitigated to a level that is less than significant.

Class II: Significant impact that can be mitigated to a level that is less than significant.

Class III. Less than significant impact, no mitigation required.

Class IV: Beneficial impacts.

No Impact: No impact identified.

In a number of instances, SDG&E proposed measures to reduce impacts to potentially affected resources or areas and these are termed Applicant Proposed Measures (APM) in the EIR. These actions are considered in the impact assessment as part of SDG&E's Proposed Project description and are different from CEQA mitigation measures described in the EIR.

In summary, the EIR findings are catalogued according to resource issue area, along with the Class I and Class II impacts that would be expected from the construction and operation of the Propose Project, and the comparative effects of the alternatives are presented.

Air Quality: The Proposed Project would generate localized pollutant emissions from construction equipment over the 24-month duration of the construction, but the APMs suggested by SDG&E would reduce these impacts to less than significant levels. The Design Option Alternatives and the Alternative 7PV1 would both have similar impacts to the Proposed Project.

Biological Resources: In regards to Sensitive Vegetation Communities, Sensitive Plant Species, Sensitive Animal Species, Invasive Plant Species, and Bird Electrocution and Tower/Line Collisions, the impacts would be less than significant,or mitigated to less than significant level. Mitigation along with APMs would reduce indirect impacts due to construction activities to less than significant. With the exception of the South Bay Power Plant to Sweetwater River Overhead Design Alternative, the other design alternatives would have no impact on biological resources. Although the Overhead Design Alternative would result in some impacts to biological resources, they would not be as great as from the Proposed Project.

Cultural Resources: Seventeen cultural resources have been recorded within or adjacent to the proposed OMPPA Project ROW. All of the recorded sites are either pre-historic or historical period archaeological sites and were determined to be ineligible for California Register of Historic Resources or to be non-unique archaeological resources. No Native American sacred sites are known to exist in the project area and none are expected. The likelihood of encountering undiscovered cultural resources during construction is low, except in the Old Town Substation Segment where the likelihood is considered high. APMs and mitigation measures provided would reduce potentially significant impacts to undiscovered cultural resources to less than significant. The cultural impacts under the alternatives are anticipated to be generally the same as the Proposed Project.

Geology, Soils, Palentology: Soil liquefaction is considered a potential seismic hazard along the entire underground cable alignment, Segments #4 and #6, however underground facilities are generally not subject to direct effects of shaking because they are confined by overlying soils. Mitigation has been provided to ensure that potentially significant impacts to geologic hazards and Paleontological resources would be mitigated to less than significant. Geological impacts from the design option alternatives and Transmission System Alternative 7 PV1 would not be different from the Proposed Project. Geologic impacts from the South Bay Power Plant to Sweetwater River Overhead Design Alternative would decrease from the Proposed Project as this alternative would primarily modify existing structures and would not require mitigation for geologic hazards.

Hydrology and Water Quality: Potential impacts from the Proposed Project would include: impacts from soil erosion and sedimentation from construction activity and access roads, potential degradation of water quality through spill of potentially harmful materials used in construction, and groundwater disturbance through project-related excavation and boring. The only potential significant impact was for flood or erosion due to placement of proposed underground cable within various stream channels. Proposed mitigation, along with APMs, is aimed at reducing all the impacts to hydrology and water quality to less than significant. Under the design option alternatives, the impacts to hydrology and water quality would either be the same as for the Proposed Project, or could be mitigated to less than significant. Under Alternative 7 PV1, impacts to hydrology and water quality are anticipated to be greater, but with APMs and provided mitigation, impacts would be less than significant.

Land Use, Agriculture and Recreation: The Proposed Project transverses numerous cities, unincorporated areas, MCAS, is adjacent to the U.S. Navel Station and the Sweetwater Marsh Natural Wildlife Refuge, follows an existing SDG&E ROW through rough foothills, mesas, steep valleys and ravines, and continues through residential and urban areas involving commercial and industrial uses as well as residential developments and parks. Short-term impacts from the project include disruption to the community associated with dust, noise/vibration, public health and safety, traffic and visual quality, and long-term impacts would result from precluding or conflicting with existing and/or planned land uses. These impacts are fully mitigable, and with implementation of all mitigation recommended in the EIR, all impacts to land use and recreation would be less than significant. With the exception of the South Bay Power Plant to Sweetwater River Overhead Design Alternative, the design option alternatives have been developed to reduce such land use impacts, and in particular, the undergrounding in Chula Vista would result in no conflicts or impacts to applicable land use plans and policies. The Overhead Design Alternative would conflict with the applicable land use plans and policies relevant to the City of Chula Vista Bayfront. Alternative 7 PV1 would reduce the long-term disruption of existing land uses and recreational facilities, but the additional construction activities this alternative requires would create greater impacts. However, mitigation measures provided would reduce such construction related impacts to less than significant.

Noise and Vibration: During the 24-month anticipated construction period, the intermittent construction noise and vibration impacts from the Proposed Project would be potentially significant, but using proper noise suppression techniques and following proposed mitigation measures would reduce the noise and vibration impacts to less than significant levels. The noise impacts from the construction of the design option alternatives would not be significantly different from the Proposed Project, except for the South Bay to Sweetwater overhead option which would reduce noise and vibration by the elimination of trenching and boring along the route, and that segment requires no mitigation. However, noise from the overhead line operation would slightly increase, but would be less than significant. Noise and vibration would be increased under Alternative 7 PV1 due to the increased duration and disturbance area. However, construction noise and vibration could be mitigated to less than significant and noise from operation of the Alternative would be the same as for the Proposed Project.

Public Health and Safety: Hazardous Materials and
Environmental Contamination Environmental contamination is likely to be encountered so mitigation measures have been developed related to project construction to supplement the APMs SDG&E proposed, so that potential contamination from spills during construction and project operation would be prevented, or removed and properly transported so that all impacts would be less than significant. The design option alternatives would either produce the same impacts as the Proposed Project, or if there were significant impacts, they could be mitigated to less than significant. The overhead design from South Bay to Sweetwater would reduce potentially significant impacts due to the possibility of encountering hazardous materials to less than significant since there would not be trenching or boring along the project segment that would have the potential of disturbing existing hazardous materials. Alternative 7 PV1 would create the potential for greater impacts from contamination and hazardous materials due to additional construction activities and larger disturbance area, but with implementation of mitigation measures they would be less than significant.

EMF Issues: TheThe EIR does not consider electro-magnetic fields in the context of CEQA. Presently there are no applicable regulations related to EMF levels from power lines since there is no agreement among scientists that EMF does create a potential health risk and there are no defined or adopted CEQA standards for defining health risks from EMF. Nevertheless, the EIR does present EMF general information as well as project-specific EMF information for the benefit of the public and decisionmakers.

Public Services and Utilities: Project construction has the potential to disrupt utility systems, conflict with planned utilities along the route and restrict access for emergency vehicles. Although the impacts are considered significant, with implementation of the APMs and mitigation measures provided, the impacts would be reduced to less than significant. The design option alternatives present either the same impacts as the Proposed Project, or if the impacts are increased, they can be mitigated to less than significant. Alternative 7 PV1 would produce greater public service and utilities impacts than the Proposed Plan, but the impacts could be mitigated to less than significant.

Population and Housing: Construction activity for the Proposed Project is considered short-term and it is anticipated that all construction personnel would be with-in a two-hour commute and would not impact the population levels and there would be no new regional growth, and no need for new housing. Because all project facilities would occur within SDG&E's existing ROW, no removal or relocation of units or businesses is required. The design option alternatives and Alternative 7 PV1 would produce the same anticipated impacts as the proposed Project.

Transportation and Traffic: Overhead line construction activities would have minimal impacts to area traffic or roadways because the route is in an existing SDG&E ROW. Some temporary land and road closures would be required. Construction related impacts on traffic would be more severe for the underground segment because of the roadway construction. The Proposed Project would result in short-term and permanent elimination of parking spaces, short-term disruption to public transit operations and conflicts with planned roadway improvements. Mitigation is provided to reduce these impacts to less than significant. Under the design option alternatives, some increase the impacts to traffic, others decrease it, and some require road closures. In total, however, with the mitigation provided, the impacts are either eliminated or reduced to less than significant. Under the Alternative 7 PV1 option, traffic related impacts would be greater than under the Proposed Project, but are mitigable, loss of parking spaces is reduced, and conflicts with planned roadway improvements would be the same.

Visual Resources: The Proposed Project presents visual impacts with long-term changes to the aesthetic environment by the addition of transmission structures and circuits. In particular, 21 of 24 key viewpoints in Segment #3 would experience significant Class I visual changes that could not be mitigated to less than significant levels. At four other key viewpoint locations, APMs and mitigation measures would reduce the impacts to less than significant. Under the design option alternatives, the visual impact would be similar to those of the Propose Project and would be minor and less than significant in these localized areas. Alternative 7 PV1, however, would result in additional beneficial visual changes, since the lattice towers, that are more industrial in character, are removed, and replaced with just the proposed monopoles. Depending on viewer location and conditions, the degree of overall change under this alternative would range from beneficial to slightly adverse when compared with the Proposed Project.

Other EIR Sections

As required by CEQA, the EIR also contains a section addressing the cumulative and growth-inducing impacts of the Proposed Project. For the most part, the EIR determines that the project has very little potential for resulting in cumulatively considerable effects as defined by the CEQA Guidelines, mainly because most of the Project's effects are temporary, and the long-term effects are either not additive to the effects of other projects or are so minor as to not be cumulatively considerable. However, from the Miguel Substation to I-5 the Proposed Project would have significant and unavoidable (Class I) visual impacts to views from a number of local residential neighborhoods, park and recreation areas, and public facilities. Cumulatively, the existing and proposed structures would create a visually dominant industrial corridor through residential areas of Chula Vista. The EIR considered this impact from the Miguel Substation to I-5 to be cumulatively considerable and significant.