Several hazardous substances would be used in the operation of the proposed FMC Substation. One 115 kV - 21 kV, 45-MVA transformer could contain up to 9,500 gallons of mineral oil, which is used as an insulating medium and coolant. The mineral oil would not contain Polychlorinated Biphenyls (PCBs). To prevent the release of mineral oil in the event of damage to the transformer, PG&E proposes to mount the transformer on a pad with drainage directed to a SPCC collection system and pond that could hold 110% of the volume of oil from one transformer, plus rainwater runoff. A weir system with a manually operated gate valve would retain any oil in the SPCC pond for collection and disposal at an approved site. Environmental Protection Agency regulations require that the equipment and spill containment area be inspected at least monthly. During heavy storm periods, more frequent monitoring of the transformers and the SPCC pond would be conducted to prevent overflows of the pond. The operator would check the pond for evidence of an oil sheen, and any oil would be cleaned up before the valve would be manually opened by the operator to release rainwater that had accumulated in the pond.
Batteries would be used for emergency back-up power at the new substation. Similar to automobile batteries, these batteries would contain sulfuric acid in the electrolyte, which is in a gel, rather than liquid, form. The substationís three batteries would have 20 cells each for a total of 60 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 to the environment of material from the batteries in the event of a spill would be prevented by housing batteries in a dedicated metal-enclosed compartment in the switchgear building.
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.
Other hazardous materials are used in construction and maintenance of the substation and power lines, including petroleum products, paints, and adhesives, as well as those hazardous materials used in autos and trucks. The use of such materials is common and is regarded as posing less than significant risks to worker or public health or safety.
In the long term operation of the substation, and in the operation of the power and distribution lines, there is a finite risk of electrical arcing and short-circuits due to failure of the equipment or when a live phase conductor falls to the ground. The design of the substation, including the placement of the wires, equipment, and the seven-foot-high fencing around the substation, and the design of the power and distribution lines, are 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. The sensing and high-speed relay systems that sense a broken line and activate circuit breakers within about one-tenth of a second mitigate the risk of fire and other harm to the public from downed power lines.
If soil contamination werepresent within any construction areas, such contaminated soils disturbed or excavated during site preparation could pose a health risk to construction workers or the adjacent public. Contaminated waste soils must be handled and disposed of in accordance with local, state, and federal regulations. If soil contamination were present within any construction areas, all excavation would proceed according to worker safety requirements of the Federal and California Occupational Safety and Health Administrations (OSHA). If there were any site contamination that would require action, OSHA rules then 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 to dispose of construction-derived waste soil in accordance with local, state, and federal regulations. These effects would be less than significant.
PG&Eís proposed mitigation measures are consistent with those employed at other substations and power lines, and would be adequate to ensure a minimal risk of fire, accidental explosion or release of hazardous substances. Assuming implementation of the mitigation measures proposed as part of the project, additional mitigation is not required and the hazard would be less than significant.
To the extent that the construction and operation of the project would improve the reliability of the local electric power system, the proposed substation and related power lines would benefit local emergency response capabilities. Traffic interruptions due to construction activities would be coordinated with the cities of San Jose and Santa Clara. No interference with the emergency response plans or emergency evacuation plans of the City of San Jose or the City of Santa Clara is evident.
,d) The project will take high-voltage electricity from the two new PG&E 115 kV power lines, step-down the voltage to 21 kV, and distribute the electricity to local customers. By its nature, the project provides certain benefits and poses certain risks to the public. Because the project will alter the electric and magnetic fields (EMF) in the vicinity of the substation site and along the routes of the two new 115 kV power lines and the 21 kV distribution lines, concerns about potential health-related consequences of the EMF are addressed.
Some portions of the new power lines are located on the right-of-way of an existing PG&E 115 kV power line, an operating high-voltage electric power transmission facility, or along lower-voltage distribution lines. PG&E has not estimated the magnetic field strengths to be expected at the substation boundary or under the power lines. However, similar 115 kV power lines, under peak electrical load conditions, have been estimated to generate a magnetic field strength of roughly 150 milliGauss (mG) or less at the edge of the right-of-way. Also, other substations have been estimated to generate a magnetic field strength in the range of roughly 15 mG or less at the substation boundaries. These values represent, in effect, rough estimates of the maximum conditions at the boundaries of the substation and boundaries of the power line right-of-ways; directly under the power lines, the values could be higher.
Typically, it can be expected that the highest levels of magnetic field strengths at the boundaries of the substation would occur at the locations of the undergrounded 21 kV distribution lines or the locations of overhead 115 kV power lines. Similarly, the highest levels of magnetic field strengths would be expected to occur at the center of the power line right-of-way, under the lowest point of the power line.
Compared to present maximum contributions from the existing 115 kV power lines and other distribution lines, the project would add a contribution that would be similar to the existing magnetic field strength present under the existing lines.
Average annual electrical load conditions for the substation and the power lines 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.
Ultimately, up to nine underground 21 kV distribution circuits would connect the Nortech Substation to the existing electric distribution system. While not part of the proposed project, they would contribute to EMF at the site. These contributions would occur within the existing rights-of-way of the streets and power lines and not on surrounding industrial or commercial properties. Members of the public that would be exposed to these fields include anyone walking within the distribution line right-of-ways.
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 North San Jose Capacity Project includes the following "no cost and low-cost" EMF reduction measures:
1) Poles will be installed at a clearance to reduce EMF at ground level.
2) The phasing of the Trimble - Nortech 115 kV power line would be arranged to create the minimum magnetic field at the edges of the power line right-of-way. The phasing would be CBA (top, middle, bottom), to cross-phase with the phasing on the Newark -Trimble 115 kV power line.
3) Use compact equipment spacing at the substation, which reduces the site area used and allows equipment to be remain farther from the substation boundary. Providing more distance between the equipment and the property lines would reduce magnetic field strength at the property line.
The possible relationships between exposure to EMF and potential health-related effects have been investigated by many organizations, including 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; that committee concluded that the current body of evidence does not show that exposure to power-frequency EMF presents a human hazard.
Based on the results of the U.S. National Academy of Science study, there is no evidence that the EMF from the proposed substation, the 115 kV power lines and the 21 kV distribution lines presents a health hazard to those individuals who live and/or work in the vicinity of the substation site or power line routes. Further, there is no evidence that the additional EMF contributed by the proposed substation or the new power line circuit would create a health hazard or potential health hazard. The impact is less than significant and mitigation beyond that proposed as part of the project is not required.
Also accompanying the operation of the power lines are concerns about other phenomena such as corona discharge, electrical interference, and electric shock and currents induced by the power lines. Design standards for power lines use established standards to limit the effect of these phenomena to less than significant levels.
Operation of the proposed Nortech Substation would not greatly alter the number of people working on or using that site, since the substation will be operated remotely. Those who do work periodically at the substation site would be PG&E employees or contractors, acting in accordance with occupational health and safety requirements. As a result of these two factors, the substation would result in a small increase the total exposure of people to any existing sources of potential health hazards.
Operation of the proposed power lines would not change the number of people working within or using the power line route right-of-ways. No individuals would live or work within the right-of-ways, which could be used as open space or as public or private parking lots. As a result, operation of the power lines would result in very small increases in the total exposure of people to any existing sources of potential health hazards.
e) The substation site and the power line routes include substantial amounts of vegetation, ranging from native vegetation to landscape vegetation, including mature trees within the right-of-ways of the proposed power lines. See also the analysis of biological resources effects in this checklist.
The cleared and graded area within the substation would be maintained and kept free of shrubs or trees that might colonize the site; this would prevent any hazard of arcing leading to a fire that would spread to the landscaping trees on the perimeter of the site. There would be no increase in fire hazard on the substation site or adjacent areas.
Operation of the power lines carries a finite risk of electric arcing due to objects contacting the energized power line; that arcing, in turn, could lead to a fire. Where there are existing power lines over portions of the length of the two new power lines, the incremental increase in fire risk along those portions is likely very small. The project includes detailed measures to mitigate the fire risk along the routes of the two power lines, so even on those portions of the new lines where there are no existing power lines, the incremental increase in fire risk also is likely very small. The rigorous maintenance of right-of-way landscaping trees, in accordance with the power line tree clearance criteria and the maintenance schedule proposed (PG&E, 1998 NSJCP PEA), would be effective in reducing to acceptable levels the risk of fire due to tree contact with power lines. As a part of the construction of the two power lines, existing landscape trees within the right-of-ways would be removed and replaced with tree species with growth habits that are more suitable to locations under power lines. See also the project description for the criteria used to select and maintain trees within the power line right-of-ways.
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