Batteries would be used for emergency back-up power at the substation. Similar to automobile batteries, these batteries would contain sulfuric acid in the electrolyte. The substation’s two batteries would have 20 cells each for a total of 40 cells, and would provide an output of 125 volts (in comparison, an automobile battery has 6 cells and provides an output of 12 volts). Release of material from the batteries in the event of a spill would be prevented by housing them in a building with a concrete floor and without drains.
Nitrogen gas (N2) and Sulfur Hexafluoride gas (SF6), both inert and non-toxic gases, would be used at the substation. N2 would be used to slightly pressurize oil-filled equipment, while SF6 would be used as an insulator and arc suppresser in circuit breakers. SF6 would not be released under normal conditions; PG&E usually recycles the SF6 gas in the breakers during maintenance. When SF6 is exposed to electric arcs, a small quantity of solid residue forms that is highly toxic and must be removed to prevent exposure hazards to PG&E personnel working with the circuit breakers. Vacuuming with a heavy duty shop vacuum and/or cleaning of the equipment surfaces with dry, lint-free rags and proper disposal of the material is adequate to control potential hazards from this residue.
The only potential hazard to the public involved in the use of either the N2 or SF6 is a physical hazard involving the high pressure of the gases in the storage cylinders. The likelihood of a cylinder explosion is low; distance between the cylinders and any public access makes the risk of injury remote.
In the long-term operation of the substation, and in the operation of the power transmission and distribution lines, there is a finite risk of electrical arcing and short-circuits due to failure of the equipment. The design of the substation, including the placement of the wires, equipment, and the fencing around the substation, as well as the design of the power and distribution lines, is intended to prevent public access to high-voltage equipment and to minimize the risk to the public of shock or injury in the event of equipment failure.
Soils on the project site have no firm documentation of contamination with fuels, metals, volatile organic compounds, and phenol. One well log record (Well No. 7) indicates the possible presence of gasoline at a depth of 6 – 6 _ feet, as indicated by gasoline odor (Geomatrix Consultants, 1998). That well log is near the site of a former underground storage tank, located southerly of the proposed substation area. Nearby borings, including Boring No. 1 which is closest to the substation site, had no detected gasoline odor. Thus it may be surmised, that contamination, if present, probably is localized to the area near the tank. Although unlikely, if present within the substation construction area (poles and foundation structures), contaminated soils disturbed or excavated during site preparation could pose a health risk to construction workers. Little hazard likely would occur to the adjacent public. Additionally, contaminated waste soils would need to be handled and disposed of in accordance with local, state, and federal regulations. Risk-based analysis of on-site contamination indicates that on-site soil contamination is below target levels that would identify further investigation. However, the California Department of Toxic Substances Control (DTSC, the lead agency) has not categorically accepted risk-based assessment, and the case has not been closed. Consequently, the potential exists for site remediation to be required by the regulatory agency (DTSC). As the placement of the transformers requires a large, continuous concrete pad foundation, the soil would be effectively sealed below the substation. Construction of the foundation would require excavation, which would proceed according to worker safety requirements of the Federal and California Occupational Safety and Health Administrations (OSHA). If DTSC determines that site contamination requires action, OSHA rules than would require a site-specific Health and Safety Plan (HASP) to be prepared and implemented by PG&E and its contractors to minimize exposure of construction workers to potential site contamination, and properly dispose of construction-derived waste soil in accordance with local, state, and federal regulations.
The project is located near the right-of-way of a PG&E 115 kV power line, an operating high-voltage electric power transmission facility. The power line, under peak electrical load conditions, is estimated to generate a magnetic field strength of not more than 150 milliGauss (mG) at the edge of the right-of-way (PG&E, 1997). This value represents, in effect, a maximum baseline condition for the substation site, along the boundaries of the power line right-of-way; directly under the power line, the value would be higher.
PG&E calculated the magnetic field strength that would be created by the operation of the substation at the proposed substation property boundaries. Based on ultimate build-out of the substation with two 30-MVA transformer banks, up to eight 12 kV distribution feeders (four from each of the two banks), it was determined that the strength of the magnetic field at the property boundary would range from 0.1 mG to 21 mG (PG&E, 1997). The calculations include magnetic field strength contributions from the 115 kV power line, but exclude contributions from the existing 20-MVA transformer bank or the stand-by generator. Although connections to the power line are necessary, the power line is a part of the proposed project.
Under the maximum electrical load conditions, the contribution of the project to the magnetic field strength at the property boundaries would range from 0.1 mG to 21 mG, as follows: along the western boundary, 0.1 mG to 0.5 mG; along the northern boundary, 3.0 mG to 21 mG; along the eastern boundary, 0.1 mG to 3.0 mG; and along the southern boundary, 0.1 mG. Typically, the higher levels of magnetic field strengths at the boundaries of the substation correspond to the locations of the undergrounded 12 kV distribution lines.
Average annual electrical load conditions for the substation would be less than the maximum load, and the contribution of the project to the magnetic field strength at the property boundaries would be about correspondingly decreased. Further, typical magnetic field strengths at the edge of power line rights-of-way would be 10 mG to 90 mG (PG&E, 1997).
Ultimately, up to eight underground 12 kV distribution circuits would connect the Corona Substation to the existing electric distribution system. While not part of the proposed project, they would contribute to EMF at the site. The undergrounded feeds to the 12 kV distribution lines would exit the substation site on the Corona Road frontage.
These contributions would occur within the existing rights-of-way of the streets and power lines and not on surrounding residential or commercial properties. Members of the public that would be exposed to these fields include anyone walking within the rights-of-way or along the Corona Road frontage.
In response to public concern about possible health effects of EMF from electric utility facilities, the CPUC opened an investigation of the hazards. On November 2, 1993, the CPUC issued Decision 93-11-013, which recognized the public concern, but which declined to "adopt any specific numerical standard in association with EMF until we have a firm scientific basis for adopting any particular value." However, in that decision, the CPUC did direct all publicly-owned utilities to take "no cost and low-cost" EMF reduction steps on transmission, substation, and distribution facilities to reduce exposure of the public to magnetic fields.
In accordance with that requirement, the proposed design of the Corona Substation includes the following "no cost and low-cost" EMF reduction measures:
The PEA (PG&E, 1997) contains summary discussions about possible relationships between exposure to EMF and potential health-related effects, summarizing information from the U.S. National Academy of Sciences, American Medical Association, American Cancer Society, California Department of Health Services, National Institute of Environmental Health Sciences, U.S. Department of Energy, and the CPUC (PG&E, 1997). The U.S. National Academy of Sciences study (NAS, 1996) is the most recent comprehensive evaluation of the topic. The committee concluded that the current body of evidence does not show that exposure to power-frequency EMF presents a human hazard.
In conclusion, there is no evidence that the existing EMF from the substation or the 115 kV power line (and the 12 kV distribution lines) presents a health hazard to those individuals who live and/or work in the vicinity of the site. Further, there is no evidence that the additional EMF contributed by the proposed Corona Substation or the new power line circuit would create a health hazard or potential health hazard. The impact is less than significant and additional mitigation is not required.
Operation of the proposed Corona Substation would not substantially change the number of people working on or using the site, so the project would not increase the total exposure of people to any existing sources of potential health hazards.
Operation of the power tap line carries a finite risk of electric arcing due to objects contacting the energized power line; that arcing, in turn, could lead to a fire. Given that the new power tap line leading to the substation is short, and that the project includes measures to cut and replace trees that could be too close to the new extension, the incremental increase in fire risk is likely very small. Rigorous maintenance of right-of-way landscaping trees would be effective in reducing the risk of fire due to tree contact with power lines.
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