4.10.1 Regional Setting

In most areas, automobile and truck traffic are the major sources of environmental noise. Traffic activity generally produces an average sound level that remains fairly constant with time. Air and rail traffic, and commercial and industrial activities are also major sources of noise in some areas. Various noise sources are associated with utility operations including stationary sources, such as turbines, compressors, generators, cooling towers, and automatic safety release valves, and mobile sources, such as maintenance trucks.

Federal, state, and local agencies regulate different aspects of environmental noise. Federal and state agencies generally set noise standards for mobile sources such as aircraft and motor vehicles, while regulation of stationary sources is left to local agencies. Local regulation of noise involves implementation of General Plan policies and Noise Ordinance standards. Local General Plans identify general principles intended to guide and influence development plans, and Noise Ordinances set forth specific standards and procedures for addressing particular noise sources and activities. Each of the five power plants to be divested is governed by city or county ordinances.

General Plans recognize that different types of land uses have different sensitivities towards their noise environment; residential areas are generally considered to be the most sensitive type of land use to noise, and industrial/commercial areas are generally considered to be the least sensitive. Noise ordinances typically set forth standards related to construction activities, nuisance-type noise sources, and industrial property-line noise levels.

4.10.2 Local Setting

Some land uses are considered more sensitive to ambient noise levels than others, due to the amount of noise exposure (in terms of both exposure duration and insulation from noise) and the types of activities typically involved. Residential areas, schools, and hospitals generally are more sensitive to noise than are commercial and industrial land uses. Land uses near the power plants vary from industrial and commercial to residential and open space. Consequently, the following section discusses land uses and noise sources at the local level.

The Potrero Power Plant is located in an industrial section of the San Francisco Waterfront between Islais Creek Channel and Central Basin. Noise sources in this area are predominantly the result of vehicle traffic on 3rd Street, operations of the power plant and adjacent industrial uses north and south of the plant. The nearest residential land uses are across 3rd Street, approximately 2,000 feet west of the plant. The only other existing noise sensitive land use near the plant includes Warm Water Cove Park, approximately 500 feet southwest of the plant. Visitors to Warm Water Cove Park would not be considered sensitive to noise because the park is a day-use area located in an industrial zone and is used primarily for access to the bay. The Plant has not received complaints regarding operational noise (Lyons, 1998)

Noise monitoring of the Potrero plant was conducted on March 19, 1998. During the monitoring event, Unit 3, which is a fossil-fueled unit that is typically in operation, was operating at full capacity (210 MW). The three combustion turbine units are standby units, operated during peak usage, and were not in operation during the monitoring event (but are the same age and size as Unit 1 at the Hunters Point Power Plant, which was monitored to operate at 86 dBA at a distance of 20 feet from the turbine). Assuming simultaneous operation of all three combustion turbines, resultant noise at the nearest property line would be 68 dBA.

Noise levels at a distance of 20 feet from Unit 3 were monitored to be 93 dBA. Noise levels within the turbine housing were monitored to be 102 dBA. Ambient noise levels decline with distance from the plant. Noise levels at the southern property line nearest Unit 3 were monitored to be 79 dBA. Noise levels at the eastern property line were monitored to be 80 to 85 dBA. Noise levels at the northern property line were observed to be influenced by plant operation and were monitored to be 62 dBA. The western property line is approximately 1,200 feet from the power plant and is buffered from it by several structures of substantial height. Ambient noise levels monitored at the western property line, which is the property line nearest existing sensitive receptors, were monitored to be 64 dBA. At the western property line, noise from power plant operation was not detectable to the technician at the time of noise monitoring and monitored noise levels were generally the result of vehicle operations on Illinois Street and 3rd Street, as well as industrial operations along Illinois Street.

The Contra Costa Power Plant is located in an industrial area on the shore of the San Joaquin River in unincorporated Contra Costa County, just east of Antioch. Noise sources in this area are predominantly the result of vehicle traffic on Highway 160 and operations of the power plant and adjacent industrial uses east and west of the plant. The nearest residential land uses are over one mile south of the plant. Other existing noise sensitive land uses near the plant include Antioch Regional Shoreline Marina, approximately 1,000 feet east of the plant.

Due to the distance to sensitive noise receptors, noise from plant operations does not contribute substantially to the ambient noise environment of sensitive receptors. According to the Plant Manager for the Contra Costa Power Plant, plant operations have not resulted in noise complaints from the surrounding community (Gouveia, 1998).

Noise monitoring was conducted at the Contra Costa Power Plant on March 12, 1998. At the time of monitoring, Units 6 and 7 were not in operation and only the two synchronous condensers (Units 4 and 5) were in operation. The turbines for the synchronous condensers are located within a building enclosure. Interior noise levels were monitored to be 90 dBA at a distance of 20 feet from the condenser units. Exterior noise levels at the southern property line were not observed to be influenced by plant operations.

The Pittsburg Power Plant is located in an industrial area on the shore of the San Joaquin River in unincorporated Contra Costa County. The plant is adjacent to the City of Pittsburg, and is within its sphere of influence. Noise sources in this area are predominantly the power plant operations and adjacent industrial uses south of the plant. The nearest residential land uses are located within the City of Pittsburg, approximately 800 feet east of Units 1 through 4. Other existing noise sensitive land uses near the plant include Marina Park and Riverview Park, approximately 1,000 feet east of the plant.

At the northern property line adjacent to the San Joaquin River, noise levels were monitored to be 81 dBA across from Unit 7, and 79 dBA across from Unit 5. Plant operational noise was not noticeable to the technician at the western property line at the terminus of the canal, where wind and distant industrial forklift operations were the predominant noise source. At the southern property line, plant noise was not noticeable to the technician and was monitored to be 58 dBA.

According to the Plant Manager for the Pittsburg Power Plant, noise complaints from plant operations have primarily been the result of safety relief valves (Gouveia, 1998). Periodically, the automatic safety relief valves for the boilers are activated resulting in the release of high-pitched noise levels for a short period of time. Currently, safety relief valves are activated very infrequently (less than 10 days per year) (Gouveia, 1998).

The Geysers Power Plant consists of 14 operating units, two of which are in Lake County and 12 of which are in Sonoma County. The predominant land use within their location in the Mayacmas Mountains is exploration, development, and utilization of geothermal energy. In addition, surrounding land uses in the vicinity of the Geysers plant are primarily recreation and mining. Rural residential receptors are generally very distant from plant units and present at very low densities.

Noise related to power plant operation will occur nearly continuously for the estimated 30-year life of each unit. The major noise sources associated with unit operations are cooling towers, turbine generators, and pumping gear. The cooling tower, because of its large size and wide band frequency spectrum, is the most significant source of noise at distances greater than 200 feet from the perimeter of the unit. Noise related to pumps and the turbine/generator unit decreases more rapidly with distance than noise from a cooling tower due to their small radiating surface and high frequency content. Total noise from a single unit is estimated to be approximately 60 dBA at 500 feet based on measurements of Unit 11 (Lake County, 1981). Measurements conducted by ESA in March of 1998 indicated noise from cooling towers to range from 75 to 85 dBA at a distance of 50 feet. Accounting for attenuation of noise with distance, this recently monitored noise level is consistent with earlier estimates. Units are spaced apart to the degree that there is no overlap of typical operational noise.

4.10.3 Regulatory Framework

Article 29 of the San Francisco Police Code prohibits unnecessary, excessive, and offensive noises from all sources subject to its power. Section 2909 of the Code restricts noise levels generated by fixed noise sources, such as power plants. This section states that it is unlawful for any person to operate any fixed machinery or equipment, or similar mechanical device, in any manner so as to create any noise which would cause the noise level measured at the property line of the affected property to exceed the standards for a given zoning designation shown in Table 4.10-1.

Land uses adjacent to the Potrero Power Plant are located in M-2 zoning districts. Application of the San Francisco Noise Ordinance to the Potrero Plant results in a property line noise limit of 75 dBA at all property lines, at all times. Noise monitoring indicates that plant noise violated standards of the noise ordinance at the eastern property line (undeveloped bay-front) and southern property line (a vacant asphalt storage area of HMR Global Recycling).

Contra Costa County does not currently have a Noise Ordinance. Noise complaints within the County are addressed through application of peace disturbance sections of the County Police Code (Forsythe, 1998). Other than the Marina, sensitive land uses are not located within a one mile radius of the Contra Costa plant.

The Sonoma County General Plan cites a noise limit of 65 dBA at the boundary of each leasehold related to geothermal power plants, based on the absence of nearby residential areas near the geothermal plants (Sonoma County, 1989).

4.10.4 Significance Criteria

Based on the California Environmental Quality Act (CEQA) Guidelines (Governor’s Office, 1997), a project may be deemed to have a significant effect on the environment if it would increase substantially the ambient noise levels for adjoining areas. A change in noise levels of less than 3 dBA is not discernible to the general population; an increase in average noise levels of from 3 to 5 dBA is clearly discernible to most people (California Department of Transportation, 1991). An increase in the noise environment of 5 dBA or greater is considered to be the minimum required increase for a change in community reaction (U.S. Department of Transportation, 1990) and, for the purposes of this analysis, constitutes a significant noise impact. With temporary noise impacts, identification of "substantial increases" depends upon the duration of the impact, the temporal daily nature of the impact, as well as the absolute change in dBA levels.

For operational impacts, operational noise that would exceed the "normally acceptable" land use compatibility noise range of the General Plan in the jurisdiction where a project element is proposed would be considered a significant noise impact. If a land use already exists in a "conditionally acceptable" or "normally unacceptable" noise compatibility environment, as designated in the General Plan, then an increase in operational noise that would result in a change of land use compatibility category would be considered a significant noise impact. For land uses designated as within a "clearly unacceptable" noise compatibility environment, operational noise that would result in a 3 dBA or greater increase to the existing noise environment would be considered significant, if sensitive receptors are present that would be affected. If sensitive receptors would not be present but the land use is considered sensitive to noise, then a 5 dBA increase would be considered significant. Otherwise, an increase would only be considered significant if it violated a local noise ordinance or substantially contributed to an existing violation of a noise ordinance.

4.10.5 Impacts and Mitigation Measures

None.

None required.

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An important part of a noise analysis is the identification of noise-sensitive land uses that may be affected by a project. This would include any residential properties, schools, or other noise-sensitive land uses adjacent to the project site. As described under "Setting" above, one of the four power plants (Pittsburg) is located near a number of residential areas and other noise-sensitive land uses.

As a general rule, noise produced by a single generating unit is fairly constant over a range of loads (PG&E, 1996). This means that a unit operating at 25 percent, 50 percent, or 100 percent of its maximum capacity would produce a similar noise level whenever it is turned on. Consequently, changes in the load factor for a particular unit will not greatly affect noise levels, whereas increases in the hours per day a unit is operated and increases in the number of units operating could greatly affect a noise environment. The plants would have a tendency to operate at or closer to their analytical maximum capacities under new ownership. As a result, although noise levels from operating units are not expected to increase, individual units may operate more often, or the frequency of multiple units in operation simultaneously could increase, which would increase, to some degree, the overall noise environment near the power plants.

Night is the most sensitive time for noise effects. The expected result of potential increases in generation would be that multiple units are operated at night (two units would be expected to produce a noise level about 3 dBA higher than one unit). However, current information indicates that, sometimes, multiple boilers are left on at night, but at a somewhat lower capacity than during the daytime (which does not affect the noise levels). Steam boilers are generally started during daytime hours; nighttime start-ups are not expected as a reasonably foreseeable consequence of divestiture (Weatherwax, 1997). Because multiple units are operated at night under existing conditions at most locations within the applicable noise ordinance criteria, the operation of multiple units at night under divestiture would not constitute a significant impact (violate the noise ordinance). If multiple units operating at night operated at higher capacity, this would also not be significant because noise produced by a single unit is fairly constant over a range of loads.

On occasion (estimated at two to three occurrences per year by the plant manager at the Pittsburg plant), automatic safety relief valves, installed on boilers are activated, resulting in a high-pitched whistling sound that lasts for a short period of time. If operations at the Pittsburg plant increase as a result of divestiture, the frequency of these releases may increase. However, this would not be a constant occurrence and would not be anticipated to expose sensitive receptors to severe noise levels

Increased operations resulting from the project could result in relatively small noise level increases at some locations; these would not be significant. Accordingly, mitigation measures are not required to be incorporated into the project.

Typical operations at the Potrero Power Plant consist of operation of Unit 3. Units 4, 5, and 6 are two-engine combustion turbines with a maximum output of 52 MW, and each currently runs about 500 hours per year during peak electrical demand. Units 4, 5, and 6 are restricted by permit from operating more than 877 hours per year. Because of inefficiency factors in operation, increased operation of Units 4, 5, and 6 is not considered to be a probable result of divestiture. Modeling results of the expected capacity were the same for Units 4, 5, and 6 under both the 1999 Baseline and the 1999 Analytical Maximum scenarios. Consequently, the potential for increased operation at the Potrero plant would involve Unit 3 operating at a higher capacity factor. Modeling results found that the 1999 Baseline of 25 percent capacity could rise to an Analytical Maximum of 44 percent.

The Potrero plant is located over 2,000 feet east of the nearest residential receptors. Land uses south and north are all heavy industrial, while San Francisco Bay lies to the east. Warm Water Cove Park, which is located approximately 500 feet from the Potrero Plant would not be considered sensitive to noise because the park is a day-use area located in an industrial zone and is used primarily used for access to the bay. Noise monitoring at the western property line revealed the noise from power plant operations 1,800 feet away is not noticeable in the presence of vehicle traffic and other adjacent industrial operations of the area. Given the remote location of the plant with respect to sensitive receptors, increased operation of Unit 3 would not contribute appreciably to the noise environment at sensitive noise receptors, particularly given the presence of substantial intervening structures and the ambient noise levels of the urban environment. Consequently, potential increased operations by a new owner of the plant would not result in a significant impact to the noise environment.

The San Francisco Noise Ordinance regarding fixed-point noise sources allows for a property line noise environment of up to 75 dBA at anytime. Existing monitored noise levels at the northern (62 dBA) and western (62 dBA) property lines are consistent with the Noise Ordinance. Existing monitored noise levels at the southern property lines (adjacent to industrial uses) varies from 60 to 79 dBA, depending on the proximity to Unit 3. Monitored noise levels on the eastern property line (adjacent to the San Francisco Bay) vary from 65 to 85 dBA, also depending on the proximity to Unit 3. While these existing noise levels are inconsistent with the Noise Ordinance, there is currently no public access to these property lines.

The potential for increased operation at the Potrero plant would involve the increased frequency of operation of Unit 3 at or near capacity. This unit currently operates under typical operations.

Increased output of this unit would be unlikely to affect noise environments of the western and northern property lines, but could increase the frequency of existing excesses of the Noise Ordinance standard at the southern (industrial) and eastern (bayfront) property lines. However, given the fact that doubling of sound energy is required to raise a noise environment by 3 dBA, and further that the plant currently operates Unit 3 approximately 83 percent of the time, a 5 dBA increase in noise levels would not occur at these property lines due to increased frequency of operation under divestiture. Also, the public does not currently have access to these areas, and would not be affected by a potential increase in the frequency of high noise levels. Consequently, this impact would be less than significant and no mitigation would be required.

Operations at the Contra Costa Power Plant vary greatly during the year. The two synchronous condensers are typically always operating, while operation of Units 6 and 7 vary, but can occur at full capacity, particularly in summer months (Gouveia, 1998). The air permits for retired units (including the synchronous generators) have expired, and a separate environmental review would be required for any potential buyer who proposed to bring them back into operation. Consequently, the potential for increased operation at the Contra Costa Plant would involve the more constant operation of Units 6 and 7 throughout the year. Modeling results found the 1999 Baseline of 36 percent capacity could rise to an Analytical Maximum capacity of 79 percent. Existing noise levels at the plant boundaries were monitored to range from 41 to 48 dBA.

Because of substantial land buffers around the Contra Costa Plant (1,200 feet from Unit 7 to the nearest property line), it is not reasonably expected that noise levels would exceed the normally acceptable range. Consequently, potential increased operations by a new owner of the plant would not result in a significant impact to the noise environment.

Operations at the Pittsburg Power Plant vary greatly during the year. Any of the seven units may be operating at a given time, depending on region-wide power demand. Operation of all seven units at full capacity, can occur in summer months (Gouveia, 1998). Consequently, the potential for increased operation at the Pittsburg plant would involve more use of the seven units throughout the year.

Night is the most sensitive time for noise effects. The expected result of potential increases in generation would be that multiple units are operated at night (two units the same distance from a location would be expected to produce a noise level about 3 dBA higher than one unit). However, current information indicates that, sometimes, multiple boilers are left on at night, but at a somewhat lower capacity than during the daytime (which does not affect the noise levels). Steam boilers are generally started during daytime hours; nighttime start-ups are not expected as a reasonably foreseeable consequence of divestiture (Weatherwax, 1997). Because multiple units are sometimes operated at night under existing conditions within the applicable noise ordinance criteria, the operation of multiple units at night under divestiture would not constitute a significant impact (violate the noise ordinance). If multiple units operating at night operated at higher capacity, this would also not be significant because noise produced by a single unit is fairly constant over a range of loads. Modeling results found that the 1999 Baseline of 31 percent capacity could rise to an Analytical Maximum capacity of 68 percent.

Occasionally, "stacking" of steam within units occurs and it becomes necessary to vent pressurized steam accumulations to the atmosphere. These steam releases are partially mitigated by the use of rock filters that aid attenuation of the noise that results from the dispersion of the steam. Stacking can result in brief, yet substantial, noise events that can be heard up to six miles away. Operational techniques have reduced stacking events at the Geysers from as much as 39 events per year in 1986 to less than 7 events per year in 1988 (Lake County Air Quality Management District, 1991), mainly as the result of air quality related restrictions on blowdown events. Given that the Analytical Maximum capacity would not appreciably change from the existing Baseline, divestiture is not expected to increase the frequency of stacking events.

None.

None required.

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REFERENCES - Noise