Summary

Air emissions from the proposed Metcalf Energy Center (MEC) are controlled through the use of the best available emission control technology. These controls will make the Metcalf Energy Center one of the cleanest power generation facilities in the United States.

The project is located in the Coyote Valley south of San Jose, where air quality levels are generally good and within most air quality standards. The air quality impacts of the Metcalf Energy Center were evaluated and shown to satisfy all state and federal air quality requirements. The Metcalf Energy Center obtained air emission credits which will more than offset plant emissions. Furthermore, by providing more efficient and lower-cost power, the project can displace older, less-efficient power plants.

The requirements applicable to the Metcalf Energy Center include new source review (NSR) and prevention of significant deterioration (PSD) requirements, as well as a number of prohibitory rules. The NSR and PSD programs apply to the facility as a whole, and are designed to ensure that new projects are developed in a manner that will not interfere with meeting health- and welfare-base ambient air quality standards.

Existing Air Quality

The U.S. Environmental Protection Agency (EPA) and California Air Resources Board have each established ambient air quality standards to protect public health and welfare.

Air quality standards have been set for ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, particulate sulfates and fine particulate matter (PM10). Ambient air quality data for all of these pollutants, except sulfur dioxide, are monitored by the Bay Area Air Quality Management District.

Ozone is formed in the atmosphere as a result of complex reactions between reactive organic gases and oxides of nitrogen in the presence of sunlight. Consequently, peak ozone levels are recorded during the summer months, when there is the most sunlight. Ozone levels in the San Jose area have been relatively constant, or declining slightly, over the last ten years despite the tremendous growth in the area.

Carbon Monoxide (CO) results from inefficient combustion, principally from motor vehicles and other mobile sources of air pollution. Peak CO levels arc usually seen during winter months. There have been no violations of state or federal CO standards measured in San Jose since 1991.

Nitrogen Dioxide (NO2) is formed primarily in the air from reactions between nitric oxides and oxygen or ozone. There have been no violations of state or federal nitrogen dioxide standards measured in San Jose during the last ten years.

Emissions of nitrogen oxides from all sources in Santa Clara County are about 44,000 tons per year. Emissions from the Metcalf Energy Center will be only 124 tons per year.

Fine Particulate Matter (PM10) in the air is caused by a combination of wind-blown fugitive dust; particles emitted from combustion sources, including wood stoves and fireplaces (usually carbon particles); organic, sulfate and nitrate aerosols formed in the air from emissions of gaseous pollutants and natural aerosols (such as salts from sea sprays). PM10 levels have been below the federal standards, but above the state standards, in the San Jose area over the last ten years.

Environmental Impacts

Air emissions result from the operation of the combined-cycle gas turbines, cooling tower and emergency equipment. Air emissions from the Metcalf Energy Center are shown in the table below. These emissions are calculated based on the maximum capacity of the equipment, consistent with operating limits expected to be imposed as permit conditions, and thus represent a worst case. Actual emissions during plant operation have been much lower than the levels shown below.

This table does not reflect the fact that the Metcalf Energy Center has obtained air emission credits that more than offset these emissions. Additionally, the table does not reflect the fact the energy center can displace older facilities that produce significantly more emissions. Emission comparisons between existing conventional plants and the Metcalf Energy Center are shown in the attached bar chart and clearly illustrate the reductions that the Metcalf Energy Center will achieve as compared to existing conventional power plants.

Regulatory Requirements

The project's emissions and air quality impacts are required to comply with various local, state and federal laws, regulations and standards. In addition to the California Energy Commission's review, the air quality impacts of the Metcalf Energy Center will be reviewed by the Bay Area Air Quality Management District.

The requirements applicable to the Metcalf Energy Center include new source review (NSR) and prevention of significant deterioration (PSD) requirements, as well as a number of prohibitory rules. The NSR and PSD programs apply to the facility as a whole, and are designed to ensure that new projects are developed in a manner that will not interfere with meeting health- and welfare-base ambient air quality standards.

For further information on the Metcalf Energy Center's emissions compliance, please refer to the Bay Area Air Quality Management District's website at www.baaqmd.gov (see the site index and click on the letter "M", then click "Metcalf Energy Center").