Air Pollution
Estimated Emissions from Two New Mexicali Power Plants Are Low, but Health Impacts Are Unknown Gao ID: GAO-05-823 August 12, 2005Power plants emit pollutants that have been linked to various negative health effects. In 2003, two new power plants, owned by Sempra Energy and Intergen, began operations 3 miles south of the U.S.-Mexico border near Imperial County, California. The county does not meet some federal and state air quality standards and may be further impacted by the emissions from these plants. Although these plants export most of the electricity they produce to the United States, they are not currently required to meet any U.S. or California emissions standards. GAO was asked to determine (1) how emissions from the two plants compare with emissions from recently permitted plants in California and emissions from sources in Imperial County, and what emissions standards they would be subject to if they were located in Imperial County; (2) the health impacts of emissions from the plants on Imperial County residents; and (3) options available to U.S. policymakers to ensure that emissions from these plants do not adversely affect the health of Imperial County residents. In commenting on a draft of this report, DOE disagreed with our characterization of the limitations of their assessment of the health impact of pollution from the Sempra and Intergen power plants. We believe we have portrayed the limitations of this assessment accurately.
The estimated emissions from the Sempra and Intergen power plants near Mexicali are comparable with similar plants recently permitted in California and are low relative to emissions from the primary sources of pollution in Imperial County, California, which are dust and vehicles. However, if the plants were located in Imperial County, they would be required to take steps to improve air quality by reducing emissions from other pollution sources in the region, such as paving dirt roads, because the county is not meeting certain U.S. air quality standards. Although emissions generated from the Sempra and Intergen plants may contribute to various adverse health impacts in Imperial County, the extent of such impacts is unknown. The Department of Energy (DOE) estimated that emissions from these plants may increase asthma hospitalizations by less than one per year. However, DOE did not quantify any other asthma-related impacts, such as emergency room visits or increased use of medications, which, although less severe, are likely to occur more often. In addition, DOE did not determine whether increased emissions would cause other respiratory or cardiovascular problems and the impact of particulate matter on particularly susceptible populations. Finally, the potential health impacts associated with ozone could be greater than DOE estimated because some important data needed for modeling were not available. Existing laws and international agreements may not provide adequate mechanisms to address adverse health impacts resulting from power plant emissions. Policymakers could take some actions, such as requiring plants that seek to export electricity to the United States to use specified emission controls. While this action would have benefits, it would also have costs, such as possibly reducing energy supplies available to Southern California. Long-term policy options include the development of a binational pollution reduction program or a trust fund to provide grants and loans to support air quality improvement projects. However, substantial efforts on both sides of the U.S.-Mexico border would be required to establish the legal and management framework necessary for such programs to be effective.
GAO-05-823, Air Pollution: Estimated Emissions from Two New Mexicali Power Plants Are Low, but Health Impacts Are Unknown
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Report to Congressional Requesters:
United States Government Accountability Office:
GAO:
August 2005:
Air Pollution:
Estimated Emissions from Two New Mexicali Power Plants Are Low, but
Health Impacts Are Unknown:
GAO-05-823:
GAO Highlights:
Highlights of GAO-05-823, a report to congressional requesters:
Why GAO Did This Study:
Power plants emit pollutants that have been linked to various negative
health effects. In 2003, two new power plants, owned by Sempra Energy
and Intergen, began operations 3 miles south of the U.S.-Mexico border
near Imperial County, California. The county does not meet some federal
and state air quality standards and may be further impacted by the
emissions from these plants. Although these plants export most of the
electricity they produce to the United States, they are not currently
required to meet any U.S. or California emissions standards.
GAO was asked to determine (1) how emissions from the two plants
compare with emissions from recently permitted plants in California and
emissions from sources in Imperial County, and what emissions standards
they would be subject to if they were located in Imperial County; (2)
the health impacts of emissions from the plants on Imperial County
residents; and (3) options available to U.S. policymakers to ensure
that emissions from these plants do not adversely affect the health of
Imperial County residents.
In commenting on a draft of this report, DOE disagreed with our
characterization of the limitations of their assessment of the health
impact of pollution from the Sempra and Intergen power plants. We
believe we have portrayed the limitations of this assessment
accurately.
What GAO Found:
The estimated emissions from the Sempra and Intergen power plants near
Mexicali are comparable with similar plants recently permitted in
California and are low relative to emissions from the primary sources
of pollution in Imperial County, California, which are dust and
vehicles. However, if the plants were located in Imperial County, they
would be required to take steps to improve air quality by reducing
emissions from other pollution sources in the region, such as paving
dirt roads, because the county is not meeting certain U.S. air quality
standards.
Although emissions generated from the Sempra and Intergen plants may
contribute to various adverse health impacts in Imperial County, the
extent of such impacts is unknown. The Department of Energy (DOE)
estimated that emissions from these plants may increase asthma
hospitalizations by less than one per year. However, DOE did not
quantify any other asthma-related impacts, such as emergency room
visits or increased use of medications, which, although less severe,
are likely to occur more often. In addition, DOE did not determine
whether increased emissions would cause other respiratory or
cardiovascular problems and the impact of particulate matter on
particularly susceptible populations. Finally, the potential health
impacts associated with ozone could be greater than DOE estimated
because some important data needed for modeling were not available.
Existing laws and international agreements may not provide adequate
mechanisms to address adverse health impacts resulting from power plant
emissions. Policymakers could take some actions, such as requiring
plants that seek to export electricity to the United States to use
specified emission controls. While this action would have benefits, it
would also have costs, such as possibly reducing energy supplies
available to Southern California. Long-term policy options include the
development of a binational pollution reduction program or a trust fund
to provide grants and loans to support air quality improvement
projects. However, substantial efforts on both sides of the U.S.-Mexico
border would be required to establish the legal and management
framework necessary for such programs to be effective.
Map of the U.S.-Mexico Border Region Near the Sempra and Intergen Power
Plants:
[See PDF for image]
[End of figure]
www.gao.gov/cgi-bin/getrpt?GAO-05-823.
To view the full product, including the scope and methodology, click on
the link above. For more information, contact John B. Stephenson at
(202) 512-3841 or stephensonj@gao.gov.
[End of section]
Contents:
Letter:
Results in Brief:
Background:
Emissions from the Mexicali Plants Are Comparable to New Plants in
California, but Offset Requirements Would Apply in Imperial County:
Emissions Generated by the Sempra and Intergen Power Plants May
Contribute to Various Adverse Health Impacts in Imperial County, but
the Extent of Such Impacts Is Unknown:
Policymakers Have Limited Options to Ensure That Emissions from the
Sempra and Intergen Power Plants Do Not Adversely Affect the Health of
Residents in Imperial County:
Conclusions:
Agency Comments and Our Evaluation:
Appendix I: Objectives, Scope, and Methodology:
Appendix II: Comments from the Department of Energy:
GAO Comments:
Appendix III: GAO Contact and Staff Acknowledgments:
Tables:
Table 1: Key Power Plant Pollutants and Potential Health Impacts:
Table 2: Average Emissions from the Sempra and Intergen Power Plants
Based on Third-party Testing:
Table 3: Comparison of Estimated Sempra and Intergen Plant Emissions
and the Emission Limits of Recently Permitted Power Plants in
California:
Table 4: Summary of Annual Emission Estimates for the Sempra and
Intergen Power Plants Using Three Alternative Operating Assumptions
(Tons per Year):
Table 5: Estimated Annual Average Emissions in 2004 for Imperial
County, California (Tons per Year):
Table 6: Comparison of NOx Emission Rates from the Sempra and Intergen
Plants and Power Plants in Imperial County and Baja California:
Table 7: Potential Offsets in Imperial County, California, Identified
by the Imperial County Air Pollution Control District:
Table 8: Imperial County Air Quality Compared with National Standard
for PM10 (1997-2003):
Figures:
Figure 1: Map of the Sempra and Intergen Power Plants and the
Associated Transmission Lines:
Figure 2: Electrical Production at the Sempra and Intergen Power
Plants:
Figure 3: Relative Emissions Contributions by Source Assuming the
Sempra and Intergen Plants Operated at Maximum Allowable Emissions and
All Emissions Reached Imperial County:
Figure 4: Pyramid of Potential Health Impacts for Asthmatics:
Abbreviations:
BLM: Bureau of Land Management:
CO: carbon monoxide:
DOE: Department of Energy:
EPA: Environmental Protection Agency:
NAAEC: North American Agreement on Environmental Cooperation:
NAFTA: North American Free Trade Agreement:
NOx: nitrogen oxides:
NH3: ammonia:
PM: particulate matter:
PPM: parts per million:
VOC: volatile organic compounds:
United States Government Accountability Office:
Washington, DC 20548:
August 12, 2005:
The Honorable Hilda Solis:
Ranking Member:
Subcommittee on Environment and Hazardous Materials:
Committee on Energy and Commerce:
House of Representatives:
The Honorable Bob Filner:
House of Representatives:
In 2003, two new power plants owned by American-based corporations,
Sempra Energy and Intergen, began operations 3 miles south of the U.S.-
Mexico border near Mexicali, Mexico, and Imperial County, California.
These modern natural gas-fired plants use advanced pollution control
technologies; nevertheless, they emit some pollutants such as nitrogen
oxides and airborne particles, known as particulate matter. Some health
studies have found that even the smallest incremental increase in the
amount of particulate matter in the air corresponds with an increase in
adverse health effects.
The U.S.-Mexico border region is experiencing significant economic,
industrial, and population growth, and that growth is expected to
continue. Imperial County is one of the fastest growing counties in
California and is expected to double in population by 2025. The county
does not currently meet some federal and state air quality standards
and has one of the highest asthma prevalence rates for children ages 1
through 17 in the state. The increased demand for energy to meet the
needs of the border region could lead to the construction of additional
power plants, with the associated potential for increased air pollution
and negative impacts on public health.
In the United States, the Clean Air Act establishes the principal
framework for federal, state, and local efforts to protect air quality.
Under this act, the Environmental Protection Agency (EPA) establishes
health-based air standards that the states must meet.[Footnote 1] EPA
has issued air quality standards for six primary pollutants--carbon
monoxide, lead, nitrogen dioxide,[Footnote 2] ozone, sulfur dioxide,
and two categories of particulate matter (PM2.5 and PM10)[Footnote 3]-
-that have been linked to a variety of health problems. Agencies
collect data on the levels of these pollutants to determine if air
quality is meeting the federal standards. Areas that do not meet these
federal standards are designated as "nonattainment" areas and are, as a
result, generally subject to more stringent emission control
requirements. Imperial County is currently designated as a
nonattainment area for PM10 and ozone.[Footnote 4] New facilities being
built within a nonattainment area that are expected to generate
emissions above a certain threshold may be required to provide
mitigation measures in the form of emission offsets. These offsets are
designed to improve air quality in nonattainment areas by reducing
emissions from other pollution sources in the region. They could
include, for example, providing funds to update diesel engines or to
pave dusty dirt roads.
The Sempra power plant has a single power-generating unit with the
capacity to produce a total of 650 megawatts of electricity per hour,
all of which are designated for export to the United States.[Footnote
5] The Intergen facility, which has a total capacity of 1,060
megawatts, is composed of two units: one that produces power
exclusively for the United States and a second that exports up to one-
third of its power to the U.S. market. Because the plants are located
in Mexico, Mexican agencies have the exclusive authority to regulate
the permitting and construction, as well as the emissions resulting
from their operation. Mexico regulates the emissions of several
pollutants from its power plants but requires natural gas-fired plants,
such as Sempra and Intergen, to report emissions of only nitrogen
oxides. In part, because of the advanced technology and control
equipment these plants are using, their estimated emissions of NOx are
significantly lower than the established emission limit in Mexico.
The electricity generated by these plants is transmitted into the
United States over electric transmission lines authorized by
presidential permits issued by the Department of Energy's (DOE) Office
of Fossil Energy.[Footnote 6] These permits are required before
electric transmission facilities are constructed, operated, maintained,
or connected at the U.S.-Mexico border.[Footnote 7] DOE is responsible
for reviewing permit applications and conducting an environmental
evaluation as part of this review. DOE issued a final environmental
impact statement on the Sempra and Intergen transmission lines in
December 2004 that included an assessment of the potential health
impacts associated with emissions from the power plants.
In this context, you asked us to determine (1) how emissions from the
Sempra and Intergen power plants compare to emissions from recently
permitted plants in California and emissions from sources in Imperial
County, and what emissions standards the plants would be subject to if
they were located in Imperial County; (2) the health impacts of
emissions from the power plants on Imperial County residents; and (3)
what options exist for U.S. policymakers to ensure that emissions from
these power plants do not adversely affect the health of Imperial
County residents.
To address these objectives, we visited the Sempra and Intergen plants
near Mexicali, Mexico; interviewed plant representatives, various
federal, state, and local air quality officials, and other key
stakeholders; and reviewed relevant documents and studies. To address
how emissions from the Sempra and Intergen power plants compare to
emissions from recently permitted plants in California, we used data
from emissions tests conducted at the plants by third-party
contractors. We did this because Mexico does not require the plants to
report actual emissions of pollutants other than nitrogen oxides. We
assessed the reliability of the data by (1) reviewing documentation of
test objectives and quality control procedures provided by the third-
party contractors who conducted the tests, (2) talking with Sempra and
Intergen officials to determine the scope and generalizability of the
tests, and (3) reviewing reports of actual NOx emissions submitted to
the Mexican government to verify consistency with the test results. We
determined that the data were sufficiently reliable for the purposes of
this report. We also obtained the permissible emission limits for
comparable plants in California. Comparable plants were selected by
identifying all natural gas power plants of similar size and
specifications to the Sempra and Intergen plants that were permitted in
California between 2000 and 2004. Because all California power plants
are permitted on a case-by-case basis, emissions limits may vary with
each project. Therefore, we used the entire range of emission limits
for the 23 plants that were identified during our selection process. To
determine how the emissions from the Sempra and Intergen power plants
compared to emissions from sources in Imperial County, we utilized the
2004 estimated annual average emissions inventory for the county
developed by the California Air Resources Board, among other things. To
address what emissions standards the plants would be subject to if they
were located in Imperial County, we reviewed federal and California
regulations for new power plants, interviewed EPA, state, and Imperial
County air quality officials, and reviewed the emission limits and
selected permitting conditions for power plants located in California.
To identify the potential health impacts from plant emissions, we
reviewed the health assessment methodology DOE used in its
environmental impact statement, reviewed relevant studies, and met with
health experts. To determine available policy options, we reviewed the
Clean Air Act; environmental and trade agreements among the United
States, Mexico, and Canada; and academic research. See appendix I for
additional details on our scope and methodology. We conducted our work
between September 2004 and August 2005 in accordance with generally
accepted government auditing standards.
Results in Brief:
The emissions from the Sempra and Intergen power plants near Mexicali
are comparable to emissions from similar plants recently permitted in
California and are low relative to emissions from the primary sources
of pollution in Imperial County--dust and vehicles. However, if the
plants were located in Imperial County, they would be required, among
other things, to offset their emissions to help improve regional air
quality. Our review of emissions test data obtained from Sempra and
Intergen indicates that estimated emissions from these plants generally
fall within a range of allowable emission limits identified from 23
plants of comparable size and specifications permitted in California
between 2000 and 2004. Although the Sempra and Intergen plants will
cause some increase in regional emissions of PM10 and nitrogen oxides
(which contribute to ozone formation), the primary sources contributing
to PM10 and ozone in Imperial County are various forms of dust and
motor vehicles. In addition, based on the amount of energy produced per
pound of NOx emissions, these plants are cleaner than other major fuel-
fired plants operating in Imperial County or the border region of Baja
California, Mexico. Nevertheless, if the plants were located in
Imperial County, they would be required to offset their emissions
because the county is a nonattainment area for PM10 and ozone. More
specifically, Imperial County air quality rules would require that the
operators of each plant provide emissions offsets of at least 1.2 tons
for every ton of emissions released by the plant that contribute to
area nonattainment status.
Emissions generated by the Sempra and Intergen power plants, like any
other source of emissions, may contribute to adverse health impacts in
Imperial County, but the full extent of such impacts is unknown. In its
December 2004 final environmental impact statement, DOE estimated an
increase in asthma hospitalizations in Imperial County of less than one
per year as the result of increased emissions from the two plants.
However, DOE did not fully assess the plants' health impact because it
did not quantify other asthma-related health impacts, such as emergency
room visits, physician visits, and increased use of asthma medication,
which, although less severe than hospitalization, are likely to occur
more often, according to health experts. Also, the DOE study did not
address the extent to which increased emissions of particulate matter
would cause other adverse health impacts, such as other respiratory or
cardiovascular conditions. In addition, DOE did not analyze the health
impacts from increased power plant emissions on particularly
susceptible populations, such as asthmatic children and low-income
asthmatic adults. Imperial County is one of the poorest counties in
California and low-income asthmatics adults are more susceptible to
health problems, in part, because they have less access to health care.
Finally, EPA officials are concerned about the accuracy of DOE's
modeling of estimated ozone increases for its final environmental
impact statement because comprehensive data on some key factors, such
as temperature and relative humidity, were not available. According to
EPA officials, if the modeled estimates of increased ozone are not
correct, the impacts on air quality from these two plants could be
significant, resulting in some adverse health impacts that were not
reported by DOE.
Policymakers have limited options to ensure that emissions from the
Sempra and Intergen power plants do not adversely affect the health of
residents in Imperial County. The Sempra and Intergen plants are not
subject to the federal Clean Air Act or the California Clean Air Act
and, therefore, are not required to offset their emissions. In
addition, relevant agreements among the United States, Canada, and
Mexico may not provide adequate mechanisms to address adverse health
impacts resulting from emissions from these plants because they only
require the countries to enforce their own environmental laws, not to
implement specific pollution control requirements. Nevertheless,
policymakers could take some actions. For example, the Congress could
enact legislation restricting the importation of electricity generated
by these plants if they do not meet certain U.S. emission and offset
requirements. While this action would have benefits to air quality and
health, it would also have costs, such as possibly reducing energy
supplies available to Southern California. Similarly, DOE could modify
its regulations to require permit applicants seeking to import
electricity into the United States from Mexico to employ specified
emission controls and obtain offsets. However, these two policy options
may raise trade issues under the North American Free Trade Agreement. A
third option would be to develop programs that provide economic
incentives to reduce pollution in the U.S.-Mexico border region. Market-
based programs, such as EPA's program to reduce emissions that
contribute to acid rain, have proven successful elsewhere in the United
States in reducing emissions. Finally, another potential option is the
development of a binational clean air trust fund that could provide
grants and loans to support air quality improvement projects for cities
along the U.S.-Mexican border. However, developing the legal and
regulatory framework needed to create these binational programs is
likely to require substantial time and effort.
DOE commented on a draft of this report and generally disagreed with
our characterization of the limitations of the health risk assessment
done as a part of the environmental impact statement for the Sempra and
Intergen power plants. Specifically, DOE did not agree with our
assertion that it did not analyze all of the likely asthma-related and
other health impacts of increased pollution from the power plants.
However, DOE's environmental impact statement analyzed adverse health
effects only for asthma hospitalization, which is just one in a
continuum of adverse health impacts. DOE also disagreed with our
assertion that it did not analyze the potential health impacts of
pollution from the Sempra and Intergen power plants on susceptible
populations in Imperial County. Although DOE said that its
environmental impact statement included children in its asthma
hospitalization estimates, asthmatic children are not the only
susceptible population and asthma hospitalization is not the only
potential health impact. Finally, DOE did not agree that health impacts
from ozone formation may be larger than it estimated in its final
environmental impact statement because of limitations in its ozone
modeling analysis. However, in its comments on the final environmental
impact statement, EPA said that it continues to support off-site
mitigation efforts to ensure that there is no net increase in air
pollution in Imperial County because of the ozone modeling limitations.
For these reasons, we believe the report accurately characterizes the
limitations of DOE's health assessment and have made no changes to the
report in response to these comments. DOE's specific comments and our
detailed responses are presented in appendix II of this report.
Background:
The Sempra and Intergen plants are located in close proximity to each
other near Mexicali, Mexico--an area 3 miles south of the U.S.-Mexican
border and Imperial County, California (see fig. 1). Final permitting
and construction for both of the plants and the associated transmission
lines to the United States began in 2001, and commercial operations
commenced in July 2003. Fuel for the plants is provided by a 145-mile
cross-border natural gas pipeline built by Sempra Energy, which began
operating in September 2002.
Figure 1: Map of the Sempra and Intergen Power Plants and the
Associated Transmission Lines:
[See PDF for image]
[End of figure]
The Sempra plant, known as Termoelèctrica de Mexicali, consists of one
natural gas-fired, combined-cycle power-generating unit with a total
capacity of 650 megawatts. In this type of plant, electricity is
produced by a combination of gas turbines and steam turbines. Heat from
the gas turbine exhaust, which would otherwise be released to the
atmosphere with exhaust gases, is captured and used by a heat recovery
steam generator to produce steam, which in turn is used by the steam
turbine to generate additional electricity. The Sempra plant operates
with an export permit from the Mexican government and produces
electricity exclusively for export to the United States. The facility
is equipped with the latest pollution control technologies, including
selective catalytic reduction systems to reduce NOx emissions and an
oxidizing catalyst system to reduce carbon monoxide (CO)
emissions.[Footnote 8]
The Intergen plant, which consists of two natural gas-fired combined-
cycle units (collectively known as the La Rosita Power Complex), has a
total capacity of 1,060 megawatts. The first unit provides two-thirds
of its 750 megawatt capacity to Mexico, with the remaining one-third
available for export to the United States. The second unit has a
generating capacity of 310 megawatts, all of which is designated for
export to the U.S. market. (See fig. 2.) Originally, only the second
unit was designed to include a selective catalytic reduction system,
but as of April 7, 2005, all four of the combustion turbines within the
two units have been equipped with these systems to control NOx
emissions.
Figure 2: Electrical Production at the Sempra and Intergen Power
Plants:
[See PDF for image]
[End of figure]
Although no U.S. emissions requirements apply to these plants, Sempra
and Intergen required a presidential permit to construct and connect
the new transmission lines needed at the U.S.-Mexican border to export
electricity into the United States. Because of the similarities of the
proposals submitted by the companies, DOE decided to consider them
together in a single environmental assessment, required as part of the
permitting process.[Footnote 9] In December 2001, DOE completed the
environmental assessment and issued a finding of no significant impact
and presidential permits for both of the proposed projects. Following
these decisions, Sempra and Intergen constructed the transmission lines
and began commercial operations. However, as a result of subsequent
litigation, on July 8, 2003, the U.S. District Court for the Southern
District of California instructed DOE to prepare a more comprehensive
environmental review, which included an assessment of the health
impacts from the power plants as part of its analysis. DOE's
environmental impact statement was issued in final form in December
2004. DOE found that the proposed power plants presented a low
potential for environmental impacts and published a record of decision
in the Federal Register on April 25, 2005, authorizing presidential
permits to be granted for both transmission lines to the respective
power plants as presently designed.
The operation of any fuel-fired power plant results in a variety of air
pollutants. However, because natural gas is a relatively clean fuel,
the primary emissions of concern from these plants are generally
limited to nitrogen oxides (which contribute to ozone formation);
particulate matter; and, in some cases, carbon monoxide. Nitrogen
oxide, or NOx, is the generic term for a group of highly reactive
gases, all of which contain nitrogen and oxygen in varying amounts.
Ground level ozone, another primary pollutant, is not emitted from the
plants directly but is formed in the presence of sunlight by a chemical
reaction between NOx and various air pollutants known as volatile
organic compounds (VOC). Particulate matter refers to dust, dirt, soot,
smoke, and liquid droplets directly emitted into the air by various
sources. Secondary formation of PM can also take place by the
combination of NOx and ammonia (NH3).[Footnote 10] Carbon monoxide is a
colorless and odorless gas that is formed when carbon in fuel is not
burned completely. These four pollutants have been linked to a variety
of negative health effects, including, but not limited to, aggravated
asthma, reduced lung function and other respiratory illnesses, and
aggravation of heart disease, as well as premature deaths (see table
1). While emissions of sulfur dioxide are also a significant concern at
some power plants, the use of natural gas at the Sempra and Intergen
facilities greatly reduces sulfur dioxide emissions compared with other
fuels such as coal or oil. For example, U.S. coal contains an average
of 1.6 percent sulfur, and oil burned at electric utility power plants
ranges from 0.5 percent to 1.4 percent sulfur; comparatively, natural
gas has less than 0.0005 percent sulfur.
Table 1: Key Power Plant Pollutants and Potential Health Impacts:
Pollutant: Nitrogen oxides;
Potential health impact:
* Can irritate the lungs, cause bronchitis and pneumonia, and lower
resistance to respiratory infections;
* Contribute to the formation of ozone.
Pollutant: Ozone;
Potential health impact:
* Triggers a variety of health problems, including aggravated asthma,
even at very low levels;
* Can cause permanent lung damage after long-term exposure;
* Can contribute to premature death.
Pollutant: Particulate matter;
Potential health impact:
* Can aggravate asthma;
* Can cause increases in respiratory problems like coughing and
difficult or painful breathing;
* Can lead to chronic bronchitis or decreased lung function;
* Can contribute to premature death.
Pollutant: Carbon monoxide;
Potential health impact:
* Can cause harmful health effects by reducing oxygen delivery to the
body's organs (like the heart and brain) and tissues;
* Can cause chest pains in those with heart disease and other
cardiovascular effects after repeated exposures;
* High levels can lead to vision problems, reduced ability to work or
learn, reduced manual dexterity, and difficulty performing complex
tasks.
Sources: EPA and the Southwest Consortium for Environmental Research
and Policy.
[End of table]
Emissions from the Mexicali Plants Are Comparable to New Plants in
California, but Offset Requirements Would Apply in Imperial County:
The emissions from the Sempra and Intergen power plants in Mexicali are
comparable to emissions from similar plants recently permitted in
California and are low relative to emissions from the primary sources
of pollution in Imperial County, which are various forms of dust and
motor vehicles. However, if the plants were located in Imperial County,
they would be required, among other things, to offset their emissions
by reducing emissions from other pollution sources in the region.
Estimated Emissions from the Sempra and Intergen Plants Are Comparable
to Emissions from New California Plants:
Power plants in Mexico are not required to report to federal agencies
in the United States on actual emissions of key pollutants generated
during plant operations. Therefore, we believe that the best data
available to estimate emissions from the Sempra and Intergen power
plants comes from emission performance tests conducted by independent
third-party contractors hired by the power plants. The average
emissions from the Sempra and Intergen plants based on the results of
the third-party testing are presented in table 2.
Table 2: Average Emissions from the Sempra and Intergen Power Plants
Based on Third-party Testing:
Pollutant: NOx (ppm);
Sempra results[A]: Turbine 1: 2.33;
Sempra results[A]: Turbine 2: 2.08;
Intergen results[B]: Turbine 1: 15.33[C];
Intergen results[B]: Turbine 2: 13.37[C];
Unit 1: Turbine 3: 2.41;
Unit 2: Turbine 1: 3.14.
Pollutant: PM10 (lbs/hr);
Sempra results[A]: Turbine 1: 12.80;
Sempra results[A]: Turbine 2: 11.86;
Intergen results[B]: Turbine 1: 7.73;
Intergen results[B]: Turbine 2: 3.18;
Unit 1: Turbine 3: 3.09;
Unit 2: Turbine 1: 7.10.
Pollutant: CO (ppm);
Sempra results[A]: Turbine 1: 0.00;
Sempra results[A]: Turbine 2: 0.00;
Intergen results[B]: Turbine 1: 0.71;
Intergen results[B]: Turbine 2: 1.24;
Unit 1: Turbine 3: 0.86;
Unit 2: Turbine 1: 0.73.
Pollutant: NH3 (ppm);
Sempra results[A]: Turbine 1: 0.45;
Sempra results[A]: Turbine 2: 0.41;
Intergen results[B]: Turbine 1: [D];
Intergen results[B]: Turbine 2: [D];
Unit 1: Turbine 3: 1.24;
Unit 2: Turbine 1: 1.73.
Pollutant: VOC (lbs/hr);
Sempra results[A]: Turbine 1: [E];
Sempra results[A]: Turbine 2: [E];
Intergen results[B]: Turbine 1: 0.07;
Intergen results[B]: Turbine 2: 0.11;
Unit 1: Turbine 3: 0.83;
Unit 2: Turbine 1: 0.86.
Legend: NOx = nitrogen oxides; ppm = parts per million; PM10 =
particulate matter; lbs/hr = pounds per hour; CO = carbon monoxide; NH3
= ammonia; VOC = volatile organic compounds.
Sources: Sempra and Intergen.
[A] These tests were conducted on June 4-6, 2003, and July 8-9, 2003.
[B] These tests were conducted between September 20 and September 28,
2004.
[C] Selective catalytic reduction systems were installed on these
turbines in March and April 2005, after these tests had been completed.
These turbines have been emitting NOx at a level below 2.5 ppm since
the installation of the new equipment.
[D] NH3 is a by-product of selective catalytic reduction control
technology and was not emitted by these turbines at the time the tests
were conducted because the control technology had not yet been
installed.
[E] VOC emissions were undetectable at the plant during these tests.
[End of table]
We were not able to compare emissions data from the Sempra and Intergen
plants with emissions data from an individual plant in Imperial County
to determine whether the plants would likely meet emissions
requirements because no similar natural gas-fired power plant has
recently been permitted for construction in the county. Therefore, we
evaluated the Sempra and Intergen data against a range of allowable
emission limits from the 23 natural gas-fired power plants of similar
size and specifications that were given permits to operate elsewhere in
California by the California Energy Commission between 2000 and 2004.
These 23 plants are among the cleanest fuel-fired plants in the United
States. We found that the levels of emissions for major pollutants
(NOx, PM10, CO, NH3, and VOC) from the Sempra and Intergen plants are
generally comparable to the range of emissions limits for the recently
permitted California plants (see table 3).
Table 3: Comparison of Estimated Sempra and Intergen Plant Emissions
and the Emission Limits of Recently Permitted Power Plants in
California:
Pollutant: NOx (ppm)[C];
Range of CA emission limits[A]: 2.0 - 2.5;
Sempra average[B]: 2.2;
Intergen average[B](US Export): 2.8;
Intergen average (Mexico): 14.4.
Pollutant: PM10 (lbs/hr);
Range of CA emission limits[A]: 3.0 - 18.5;
Sempra average[B]: 12.3;
Intergen average[B](US Export): 5.1;
Intergen average (Mexico): 5.5.
Pollutant: CO (ppm);
Range of CA emission limits[A]: 2.0 - 10.0;
Sempra average[B]: 0.0;
Intergen average[B](US Export): 0.8;
Intergen average (Mexico): 1.0.
Pollutant: NH3 (ppm);
Range of CA emission limits[A]: 5.0 - 10.0;
Sempra average[B]: 0.4;
Intergen average[B](US Export): 1.5;
Intergen average (Mexico): [D].
Pollutant: VOC (lbs/hr);
Range of CA emission limits[A]: 1.6 - 6.6;
Sempra average[B]: [E];
Intergen average[B](US Export): 0.8;
Intergen average (Mexico): 0.1.
Legend: NOx = nitrogen oxides; ppm = parts per million; PM10 =
particulate matter; lbs/hr = pounds per hour; CO = carbon monoxide; NH3
= ammonia; VOC = volatile organic compounds.
Sources: GAO analysis of data from the California Energy Commission,
Sempra, and Intergen.
[A] The range of emission limits is based on best available control
technology requirements for 23 similar plants permitted in CA between
2000 and 2004. Although these limits are based primarily on the use of
modern emissions control equipment, best available control technology
is determined on a case-by-case basis and may take into consideration
factors such as potential economic impacts, as well as design or
operational standards.
[B] Sempra and Intergen emissions data are based on the average of
emissions from the individual turbines recorded during testing.
[C] ppm for the California plants are based on a 1 or 3-hour average,
depending on the testing method required by the local air pollution
control agency. NH3 levels are computed based on a 1, 3, or 24-hour
average.
[D] NH3, or ammonia, is a by-product of selective catalytic reduction
control technology and was not being emitted at this unit at the time
of the tests because the control technology had not yet been installed.
[E] VOC emissions were undetectable during tests conducted at the
plant.
[End of table]
As shown in table 3, the average NOx emissions from the Intergen power
plant were the only emissions that exceeded the range of emissions from
recently permitted plants in California. This was the case, in part,
because the plant was not originally designed to meet California
requirements. However, as of April 7, 2005, all combustion turbines at
the Intergen plant had been equipped with the selective catalytic
reduction control technology for nitrogen oxide that is common in the
newer California plants. With the exception of one turbine, which will
continue to operate at a maximum NOx limit of 3.5 ppm, all other
turbines are expected to emit NOx at a level below 2.5 ppm. According
to Intergen plant officials, the last two turbines to be equipped with
selective catalytic reduction systems have been meeting these levels
since the systems became operational in March and April 2005,
respectively. Data provided by plant officials, based on continuous
monitoring of all emissions from these turbines over a 1 week period,
also indicate that both turbines are achieving the expected NOx
reductions.
Estimated Annual Emissions from the Sempra and Intergen Plants Are Low
Relative to Emissions from Sources in Imperial County:
One way to assess the environmental impact of emissions from power
plants is to examine the tons of pollutants they emit on an annual
basis. The third-party performance tests discussed above provide the
best available data to estimate annual emissions likely to occur during
actual operations at the Sempra and Intergen plants because the data
are based on observations of the actual equipment in operation. Other
options for estimating annual emissions from these plants include using
(1) the maximum allowable emissions levels for similar plants in
California and (2) the emissions estimates that DOE developed during
its environmental impact assessment of the Sempra and Intergen plants.
Table 4 presents annual emissions estimates based on each of these
three alternative operating assumptions.
Table 4: Summary of Annual Emission Estimates for the Sempra and
Intergen Power Plants Using Three Alternative Operating Assumptions
(Tons per Year):
Pollutant: NOx;
Third-party testing: 374;
Maximum allowable emissions levels in California: 610;
DOE's environmental impact statement: 610.
Pollutant: PM10;
Third-party testing: 200;
Maximum allowable emissions levels in California: 352;
DOE's environmental impact statement: 1,210.
Pollutant: CO;
Third-party testing: 919;
Maximum allowable emissions levels in California: 1,897;
DOE's environmental impact statement: 3,089.
Pollutant: NH3;
Third-party testing: 86;
Maximum allowable emissions levels in California: 518;
DOE's environmental impact statement: 646.
Pollutant: VOC;
Third-party testing: 57;
Maximum allowable emissions levels in California: 105;
DOE's environmental impact statement: 1,026.
Source: GAO analysis of data from Sempra, Intergen, the California
Energy Commission, and DOE.
[End of table]
Under the first scenario, annual emissions levels were estimated using
the values determined by third-party contractors during turbine
performance tests at the Sempra and Intergen plants. For the two
Intergen turbines that did not have selective catalytic reduction
systems installed when the testing was conducted, we estimated annual
NOx emissions using the testing values recorded for the similar turbine
that was operating with such equipment. We did so because these two
turbines are now equipped with selective catalytic reduction systems
and their future emissions are likely to be similar to those from the
turbine that was using this technology during the tests. These
estimates do not take into account start-up and shutdown operations of
the plant, which may contribute to increased plant emissions for
approximately 1 to 2 hours. However, the total annual estimate is based
on the conservative assumption that the plants are operating at maximum
emission levels, 24 hours a day, 365 days a year. The actual operation
of the plants, and the resulting emissions, would be less than this
because of scheduled maintenance, forced outages, and varying
electrical demand in California.
The second estimates of annual emissions were based on maximum
allowable emissions determined during the permitting process for
similar California plants. These maximum allowable emissions are higher
than the estimates based on third-party testing data. California grants
permits to construct power plants on a case-by-case basis. As a
condition of receiving a permit, the state places limits on emissions
of individual pollutants. These limits are based on the use of best
available control technology and take into consideration energy,
environmental, and economic impacts. Under this estimating scenario,
the annual estimates also account for short term variations in
emissions levels that may occur during start-up and shutdown operations
and are based on the conservative assumption that the plants are
operating at maximum emissions levels, 24 hours a day, and 365 days a
year.
The final, and highest, emissions estimates are based on the values DOE
used in its environmental impact statement. DOE's estimates are based
on either the maximum emissions allowable by permit from the Mexican
government or the vendor guarantee limits, which are the maximum
emissions levels specified by the manufacturer that a piece of
equipment is likely to produce. These values tend to be much higher
than the levels that typically occur during normal power plant
operations. For example, the vendor guarantee limit of PM10 for
turbines at the Intergen plant is 52.3 pounds per hour. However, the
actual emissions of PM10 at plants using similar equipment are
typically below 10 pounds per hour. In addition, DOE's estimates also
assume that the Sempra and Intergen plants are operating at these
levels 100 percent of the time, 365 days per year. Averaged on an
annual basis, these estimates are likely to be significantly higher
than the actual emissions resulting from operations at these plants.
According to DOE's environmental impact statement, emissions from the
Sempra and Intergen power plant would result in increases of ambient
concentrations of NOx, PM10, and CO in Imperial County. However, it is
difficult to determine the actual percentage of plant emissions that
will reach Imperial County annually. For most of the year, the winds in
the vicinity of the Sempra and Intergen plants travel predominantly
from the United States to Mexico. However, during the months of June,
July, and August, this trend reverses and the winds travel
predominantly from Mexico to the United States. Even assuming the
plants operate at the maximum emissions levels allowed in California,
and that all of those emissions reach Imperial County, annual emissions
from the plants are low compared with various forms of dust and
emissions from motor vehicles--the primary sources contributing to
nonattainment of the standards for PM10 and ozone in Imperial County
(see fig. 3).
Figure 3: Relative Emissions Contributions by Source Assuming the
Sempra and Intergen Plants Operated at Maximum Allowable Emissions and
All Emissions Reached Imperial County:
[See PDF for image]
Note:
Emissions contributions of less than 0.5 percent were not included in
this figure. In the PM10 category, mobile sources (0.5 percent), the
Sempra and Intergen power plants (0.4 percent), and fuel combustion
(0.2 percent) emissions were omitted.
[A] The "mobile sources" category includes emissions from sources such
as on and off-road motor vehicles, airplanes, trains, boats, and farm
equipment.
[B] The "fuel combustion" category includes other stationary sources,
such as electric utilities, manufacturing, food and agricultural
processing, and service and commercial operations.
[C] The "other sources" category includes all subcategories identified
by the California Air Resources Board, such as farming, fires, waste
burning, and mineral processing that contribute emissions not included
in the other categories listed.
[End of figure]
According to 2004 California emissions inventory estimates, road and
windblown dust constituted almost 89 percent of total PM10 emissions
within Imperial County. Mobile sources, which include both personal and
commercial vehicles, accounted for 79 percent of total NOx emissions in
the county. Even if they were located in Imperial County and operated
at maximum allowable California emissions levels 24 hours per day, the
plants would emit 352 tons per year of PM10, compared with nearly
77,000 tons per year from road and windblown dust, and 610 tons per
year of NOx, compared with almost 10,000 tons per year from mobile
sources (see table 5).
Table 5: Estimated Annual Average Emissions in 2004 for Imperial
County, California (Tons per Year):
Stationary sources:
Emissions sources: Fuel combustion[A];
NOx: 2,537;
PM10: 150;
CO: 325.
Emissions sources: Other stationary sources;
NOx: 11;
PM10: 1,011;
CO: 22.
Subtotal;
NOx: 2,548;
PM10: 1,161;
CO: 347.
Area-wide sources:
Emissions sources: Paved and unpaved road dust;
NOx: 0;
PM10: 13,647;
CO: 0.
Emissions sources: Fugitive windblown dust;
NOx: 0;
PM10: 63,068;
CO: 0.
Emissions sources: Waste burning and disposal;
NOx: 106;
PM10: 799;
CO: 4,395.
Emissions sources: Other miscellaneous;
NOx: 37;
PM10: 7,194;
CO: 252.
Subtotal;
NOx: 142;
PM10: 84,709;
CO: 4,647.
Mobile sources:
Emissions sources: On-road motor vehicles;
NOx: 5,143;
PM10: 139;
CO: 25,831.
Emissions sources: Other mobile sources;
NOx: 4,847;
PM10: 252;
CO: 8,629.
Subtotal;
NOx: 9,990;
PM10: 391;
CO: 34,460.
Total;
NOx: 12,680;
PM10: 86,260;
CO: 39,454.
Legend: NOx = nitrogen oxides;
PM10 = particulate matter;
CO = carbon monoxide.
Source: GAO analysis of California Air Resources Board data.
[A] The Fuel Combustion subcategory includes stationary sources such as
existing electric utilities, manufacturing, food and agricultural
processing, and service and commercial operations.
[End of table]
Another way to examine the environmental impact of a power plant is to
evaluate the amount of pollution emitted per unit of electricity
produced. This calculation has been used within the energy industry to
measure how efficiently power plants produce electricity. As
illustrated in table 6, the Sempra and Intergen plants produce much
lower emissions of NOx for each megawatt of energy generated than do
other power plants operating in Imperial County and the border region
of Baja California, Mexico. For example, Sempra's estimated emission
rate for NOx of .04 pounds per megawatt of electricity is over 35 times
lower than that rate at El Centro, the only major fuel-fired plant
operating in Imperial County in 2002.[Footnote 11]
Table 6: Comparison of NOx Emission Rates from the Sempra and Intergen
Plants and Power Plants in Imperial County and Baja California:
Mexicali plants (2004):
Power plants: Sempra;
NOx emissions rate (lbs/MW): 0.04;
Annual NOx emissions (lbs): 89,668;
Net annual energy generation (MW): 2,389,549.
Power plants: Intergen;
NOx emissions rate (lbs/MW): 0.30[A];
Annual NOx emissions (lbs): 1,309,422;
Net annual energy generation (MW): 4,306,690.
Imperial County (2002):
Power plants: El Centro;
NOx emissions rate (lbs/MW): 1.45;
Annual NOx emissions (lbs): 610,674;
Net annual energy generation (MW): 421,736.
Baja California (2002):
Power plants: C.C.C. Presidente Juarez (Rosarito);
NOx emissions rate (lbs/MW): 2.38;
Annual NOx emissions (lbs): 4,942,713;
Net annual energy generation (MW): 2,077,250.
Power plants: C.TG. Presidente Juarez (Tijuana);
NOx emissions rate (lbs/MW): 4.15;
Annual NOx emissions (lbs): 2,694,021;
Net annual energy generation (MW): 648,420.
Legend: NOx = nitrogen oxides;
lbs/MW = pounds per megawatt.
Sources: GAO analysis of data from Sempra, Intergen, and the Commission
for Environmental Cooperation.
[A] Intergen's values represent emissions produced in 2004 before the
installation of selective catalytic reduction technology on two of the
four units. Future NOx emissions rates will likely be comparable to
those at the Sempra plant.
[End of table]
If the Plants Were Located in Imperial County, California, among Other
Things, Standards Would Require Them to Offset Their Emissions:
If the Sempra and Intergen plants were located in Imperial County, to
help improve air quality, California regulations would require, among
other things, offsets for all emissions from the plants that contribute
to nonattainment of the PM10 and ozone standards in the county. Under
the specific offsetting rules established by the Imperial County Air
Pollution Control District, the operators of each plant would be
required to reduce emissions from other pollution sources in Imperial
County by at least 1.2 tons for every ton of emissions the plants
released.[Footnote 12] In addition to offsetting emissions of PM10 and
NOx generated by the plant, Sempra and Intergen would also be required
to offset all emissions of VOC, which, in combination with NOx,
contribute to the formation of ozone.[Footnote 13]
As shown in table 7, potential offsets identified by the Imperial
County Air Pollution Control District in DOE's environmental impact
statement include (1) paving roads, (2) retrofitting emission controls
on existing power plants in Imperial County, (3) funding projects
designed to increase the use of natural gas in motor vehicles, (4)
controlling Imperial County airport dust, and (5) retrofitting diesel
engines for off-road heavy duty vehicles. According to the Air
Pollution Control District, repaving approximately 23 miles of roads
could reduce PM10 emissions in Imperial County by about 650 tons per
year--more than the estimated annual PM10 emissions from both plants
based on the maximum allowable emissions levels in California. The
District estimated the paving project would cost approximately $430,000
per mile for a two-lane road, bringing the total cost to about $9.9
million.
Table 7: Potential Offsets in Imperial County, California, Identified
by the Imperial County Air Pollution Control District:
Potential offset: Paving roads;
Description of project:
* Pave 50 road segments in Imperial County, totaling 23 miles;
Estimated cost: $9,890,000;
Estimated emission reduction: 650 tons per year (PM10).
Potential offset: Enhancing use of natural gas in motor vehicles;
Description of project:
* Fund maintenance of El Centro natural gas facility; Estimated cost:
$150,000;
* Fund natural gas facility to be constructed at the Calexico Unified
School District; Estimated cost: $250,000;
* Acquire land in Brawley, California, for construction of a new
natural gas facility; Estimated cost: $250,000 to $500,000;
* Replace/update fleet of fifteen Imperial Valley buses; Estimated
cost: $4 million to $5 million;
Estimated emission reduction: 0.1 tons per year[A] (PM10).
Potential offset: Controlling Imperial County Airport dust;
Description of project:
* Begin treatment of bare desert soil with chemical dust retardants or
cover soil with crushed rock in the most sensitive areas;
Estimated cost: $150,000;
Estimated emission reduction: 15 tons per year (PM10).
Potential offset: Retrofitting diesel engines;
Description of project:
* Update the diesel engines of off-road vehicles used in agriculture,
earthmoving, or construction;
Estimated cost: $250,000;
Estimated emission reduction: 3.3 tons per year (PM10).
Potential offset: Retrofitting emission controls on existing power
plants;
Description of project:
* Install selective catalytic reduction technology on one main unit of
the existing steam plant at the Imperial Irrigation District, as well
as all of the smaller units used only during periods of peak
electricity demand;
Estimated cost: Not Estimated;
Estimated emission reduction: The main unit is already scheduled to be
retrofitted in 2007-2008 (NOx).
Legend: NOx = nitrogen oxides;
PM10 = particulate matter.
Source: DOE.
[A] Estimated emission reduction applies only to the bus replacement
project. Emission reductions from the other projects were not
quantified.
[End of table]
In addition to the potential offsets identified above for Imperial
County, according to DOE, mitigation measures may be even more abundant
and cost-effective if applied on the Mexican side of the border. Some
potential projects include paving roads in Mexicali, Mexico;
replacing older automobiles and buses with newer, less polluting ones;
and converting brick kilns to run on natural gas. However, according to
DOE, it does not have the authority to impose or enforce offsets in
Mexico.
Finally, if the power plants were located in California, the Intergen
plant would likely be required to make additional equipment
modifications to be consistent with other plants recently constructed
in California. These modifications would include installing additional
carbon monoxide control equipment and achieving a small reduction in
NOx emissions in one of the plant's four combustion turbines. Although
emissions testing data indicate that Intergen's carbon monoxide levels
are generally comparable to those of California plants without this
equipment, nearly all of the plants recently permitted in California
have installed oxidizing catalyst systems to control carbon monoxide
emissions. In addition, the Intergen plant would likely be required to
lower the maximum NOx emissions in one turbine by 1.0 ppm--from 3.5 ppm
to 2.5 ppm. Although this turbine is currently equipped with a
selective catalytic reduction system to control NOx emissions, Intergen
has stated that certain technical aspects of the design of the turbine
prevent it from attaining emissions levels of 2.5 ppm.
Emissions Generated by the Sempra and Intergen Power Plants May
Contribute to Various Adverse Health Impacts in Imperial County, but
the Extent of Such Impacts Is Unknown:
Emissions from the Sempra and Intergen power plants may contribute to
adverse health impacts in Imperial County, but the extent of those
impacts is unknown for several reasons. First, in its environmental
impact statement, DOE did not calculate the total health impacts in the
county because it did not analyze all the likely asthma-related or
other health impacts from the increased pollution caused by the Sempra
and Intergen plants. Second, DOE did not analyze the health impacts
from increased power plant emissions on particularly susceptible
populations, such as asthmatic children and low-income populations.
Finally, because of uncertainty in DOE's modeling of ozone increases
due to emissions from the power plants, the health impacts related to
ozone may be larger than DOE estimated.
DOE Did Not Analyze All the Likely Asthma-Related and Other Health
Impacts of Increased Pollution from the Sempra and Intergen Power
Plants:
In its December 2004 final environmental impact statement, DOE
estimated that emissions from the Sempra and Intergen power plants
would result in increased concentrations of NOx, PM10, and CO in
Imperial County. DOE used EPA's "significant impact levels" to help
assess the impact of these emissions increases on the residents of
Imperial County. Generally, significant impact levels are thresholds
below which the environmental and health impacts of air pollution are
not viewed as significant; however, EPA designed them to be used only
in areas that meet air quality standards.[Footnote 14] Although the
plants will add more pollution to an area already violating the
national standards for PM10 and ozone, DOE reported that because all
pollution increases would be below EPA's significant impact levels,
emissions from the plants would not produce any significant air quality
impacts in Imperial County. Specifically, DOE calculated that emissions
from the power plants would be expected to increase asthma
hospitalizations in the county by less than one case per year. However,
DOE's analysis did not quantify all of the health impacts from the
increase in PM10 emissions.
Health experts told us that the potential impact on asthmatics would be
broader than the minimal increase in hospitalizations described in the
environmental impact statement because hospitalization occurs only in
the most acute asthma cases. According to these experts, an increase in
PM10 pollution could exacerbate the underlying condition of anyone
suffering from asthma. According to data from the 2003 California
Health Interview Survey, 21,000 Imperial County residents, or 14
percent of the county's population, have been diagnosed with
asthma.[Footnote 15] Approximately 13,000 of these asthmatics
experienced asthma symptoms during the previous year. The health
experts we spoke with agreed that hospitalizations and other adverse
health effects are part of a pyramid of potential adverse health
effects. While the number of hospitalizations is represented at the top
of the pyramid, other adverse health impacts such as emergency room
visits, physician visits, asthma medication use, and increased asthma
symptoms are layered vertically downward, with the number of people
increasing in each subsequent group as you move to the bottom of the
pyramid (see fig. 4).
Figure 4: Pyramid of Potential Health Impacts for Asthmatics:
[See PDF for image]
[End of figure]
In addition, the DOE study did not address the extent to which
increased emissions of particulate matter would cause other adverse
health impacts, such as other respiratory or cardiovascular problems.
These impacts could include chronic obstructive pulmonary disease,
pneumonia, cardiovascular disease, as well as increased symptoms of
upper and lower respiratory disease, decreased lung function, or
premature death. According to the project manager of DOE's analysis,
the expected incidence of other adverse health effects resulting from
PM10 exposure has not been quantified because of a lack of data.
DOE Did Not Analyze the Health Impacts on Particularly Susceptible
Populations in Imperial County:
Studies funded by EPA, the Health Effects Institute,[Footnote 16] and
others have concluded that certain groups are likely to be more
susceptible to particulate matter than others, and therefore experience
more adverse health effects. For example, these studies identified
asthmatics, especially children, as a potentially susceptible
subpopulation. According to data from the 2003 California Health
Interview Survey, approximately 19 percent of Imperial County children
ages 1 through 17 have been diagnosed with asthma, or about 9,000
children. In addition, the relationship between socioeconomic factors
and asthma exacerbation has been documented in various studies.
Imperial County is ranked as one of the poorest counties in California,
with some of the highest poverty and unemployment rates in the state.
An estimated 22 percent of the overall population lives below the
national poverty level, in comparison with 13 percent statewide.
Results from a 2001 California asthma report indicate that asthmatic
adults with family incomes below the national poverty level are nearly
twice as likely to experience symptoms every day or every week as those
with incomes three times the poverty level, in part, because they have
less access to health care.[Footnote 17]
Finally, residents of Imperial County are currently exposed to airborne
particulate pollution exceeding the Clean Air Act's health-based
National Ambient Air Quality Standard for PM10. For instance, in 2003,
Imperial County residents were exposed to an annual average
concentration of PM10 that was 30 micrograms, or 63 percent higher,
than the national standard of 50 micrograms per cubic meter of air, as
shown in table 8. As a result, Imperial County residents can be
expected to have higher incidence of adverse health effects caused by
airborne particulate pollution than residents living in areas with less
of that contaminant.
Table 8: Imperial County Air Quality Compared with National Standard
for PM10 (1997-2003):
PM10: Maximum 24 hour concentration;
Micrograms per cubic meter of air: National standard: 150;
Micrograms per cubic meter of air: Imperial County: 1997: 532;
Micrograms per cubic meter of air: Imperial County: 1998: 176;
Micrograms per cubic meter of air: Imperial County: 1999: 227;
Micrograms per cubic meter of air: Imperial County: 2000: 268;
Micrograms per cubic meter of air: Imperial County: 2001: 647;
Micrograms per cubic meter of air: Imperial County: 2002: 373;
Micrograms per cubic meter of air: Imperial County: 2003: 840.
PM10: Calculated days over national standard;
Micrograms per cubic meter of air: Imperial County: 1997: 12;
Micrograms per cubic meter of air: Imperial County: 1998: 12;
Micrograms per cubic meter of air: Imperial County: 1999: 32;
Micrograms per cubic meter of air: Imperial County: 2000: 38;
Micrograms per cubic meter of air: Imperial County: 2001: 18;
Micrograms per cubic meter of air: Imperial County: 2002: 21;
Micrograms per cubic meter of air: Imperial County: 2003: 25.
PM10: Annual average;
Micrograms per cubic meter of air: National standard: 50;
Micrograms per cubic meter of air: Imperial County: 1997: 77.7;
Micrograms per cubic meter of air: Imperial County: 1998: 66.1;
Micrograms per cubic meter of air: Imperial County: 1999: 77.8;
Micrograms per cubic meter of air: Imperial County: 2000: 95.2;
Micrograms per cubic meter of air: Imperial County: 2001: 86.2;
Micrograms per cubic meter of air: Imperial County: 2002: 81.3;
Micrograms per cubic meter of air: Imperial County: 2003: 80.
Legend: PM10 = particulate matter.
Source: DOE.
[End of table]
In its environmental impact statement, DOE acknowledges that there are
preexisting conditions of concern in Imperial County, such as asthmatic
children and low-income populations, both of whom are particularly
susceptible to health problems from pollution, and the fact that the
county is a Clean Air Act nonattainment area for PM10. However, DOE did
not fully explore these conditions to determine their potential health
impacts. DOE believes that because the increases in emissions from the
plants are below EPA's significant impact levels any health impacts
will be negligible. However, some health studies have found that even
the smallest incremental increase in particulate matter air pollution
increases the incidence of adverse health effects.
Health Impacts from Ozone Formation May Be Larger Than Estimated by
DOE:
DOE conducted air dispersion ozone modeling for the Imperial Valley-
Mexicali air basin to determine what impact emissions from the Sempra
and Intergen plants would have on the formation of ozone. DOE
concluded, based on its modeling, that there would be no meaningful
change in ozone levels as a result of the operation of the Sempra and
Intergen power plants. Consequently, DOE concluded that the health
impacts from ozone formation as a result of plant emissions would be
minimal. However, if the modeling is not accurate, then the health
impacts could be larger than DOE estimated.
EPA officials have raised concerns about the accuracy of DOE's modeling
of estimated ozone increases. In its comments on DOE's draft
environmental impact statement, EPA stated that it is difficult to
quantify the impact of a small number of facilities (i.e., the two
power plants) on the maximum ozone concentration in an air basin. The
lack of area-specific information, such as temperature, relative
humidity, and levels of volatile organic compounds (an ozone
precursor), in the Imperial County-Mexicali air basin makes modeling
ozone formation particularly difficult. Because these data were not
available, DOE used surrogate values from Phoenix, Arizona.[Footnote
18] Furthermore, DOE's analysis relied on air monitoring data and the
EPA ozone model to determine the potential influence of NO2 emissions-
-the primary pollutant emitted from the Sempra and Intergen power
plants--on ozone concentrations in Imperial Valley. DOE concluded that
increased NOx emissions from the plants could produce a decrease in
ozone concentrations. In its comments on the draft environmental impact
statement, EPA stated that peak ozone concentrations generally occur in
areas away from sources of high NOx emissions, not at the monitor where
high NO2 concentrations are measured. They emphasized that if modeled
ozone projections are not correct, impacts to air quality from the
plants' emissions could be significant. Recent research funded by EPA
and others has found that increases in ozone pollution raise the risk
of premature death. Finally, EPA recommended that DOE require Sempra
and Intergen to implement mitigation measures to ensure that increased
concentrations of ozone do not occur in the air basin.
In response to EPA's comments, in its December 2004 final environmental
impact statement, DOE presented a sensitivity analysis that indicated
that power plant emissions could result in either increases or
decreases in peak ozone concentrations depending on model input
assumptions. However, DOE again concluded that its modeling of ozone
formation did not indicate any meaningful change in ozone levels as a
result of the operation of the Sempra and Intergen power plants and
therefore chose not to require any mitigation requirements in its
record of decision. According to DOE officials, although the record of
decision states that mitigation of emissions is the preferred option,
the sum total of emissions from the plants is so minimal that it is not
cost-effective to require mitigation measures in the United States.
However, DOE has not conducted any analysis to support its claim that
mitigation measures are not cost-effective. Furthermore, DOE said that
it does not have the resources needed to conduct a comprehensive
monitoring program to ensure that mitigation projects are completed
satisfactorily. Finally, DOE acknowledged in the environmental impact
statement that mitigation measures may be more abundant and cost-
effective in Mexico. However, DOE told us that while it has the
authority to require the plants to take mitigation measures in the
United States, it does not have the authority to require or enforce
such measures in Mexico.
Policymakers Have Limited Options to Ensure That Emissions from the
Sempra and Intergen Power Plants Do Not Adversely Affect the Health of
Residents in Imperial County:
Because the Sempra and Intergen power plants are not subject to either
the federal Clean Air Act or the California Clean Air Act, they are not
required to provide offsets for their emissions. In addition, relevant
agreements among the United States, Canada, and Mexico may not provide
adequate mechanisms to address adverse health impacts resulting from
emissions from these plants. As a result, policymakers have limited
options to ensure that emissions from these plants do not adversely
affect the health of residents in Imperial County.
Existing Laws and Agreements May Not Provide Effective Mechanisms to
Address Adverse Health Impacts:
Existing U.S. law provides few options to ensure that emissions from
the Intergen and Sempra plants do not adversely affect the health of
residents in Imperial County. Because the Intergen and Sempra plants
are not located in the United States, federal and California
environmental agencies do not have authority over the plants. The
federal Clean Air Act contains no language extending the statute's
coverage to pollution sources that are located outside of the United
States. Similarly, the text of the California Clean Air Act limits its
application to pollution sources that are located in California.
Because neither of these laws applies to the Sempra or Intergen plants,
U.S. environmental agencies have no authority under existing law to
require the plants to implement pollution control measures.
Similarly, existing international agreements provide few options to
ensure that emissions from the Sempra and Intergen plants do not
adversely affect the health of residents of Imperial County. The
governments of the United States and Mexico have ratified two
agreements that are of particular importance to environmental
conditions in the border region. The first was signed at La Paz,
Mexico, in 1983. The La Paz Agreement creates a framework for promoting
cooperation between the United States and Mexico on issues of
environmental protection in the border region. For example, the
agreement states that the United States and Mexico will "cooperate in
the solution of the environmental problems of mutual concern in the
border area," and that high officials from the two countries will meet
annually to review the agreement's implementation. The agreement does
not require either government to implement specific pollution control
requirements or provide a course of action for either country to pursue
if a particular project in the border region harms the health of border
region inhabitants.
The other environmental agreement, the North American Agreement on
Environmental Cooperation (NAAEC), also provides few options to ensure
that emissions from the Sempra and Intergen plants do not adversely
affect the health of residents of Imperial County. The United States,
Canada, and Mexico signed the NAAEC in 1993 to supplement the
provisions of the North American Free Trade Agreement. The NAAEC
provides a dispute resolution procedure under which the United States,
Mexico, or Canada may request consultation with another party to the
agreement regarding whether there has been a persistent pattern of
failure by that other party to effectively enforce its environmental
law. The parties must make every attempt to resolve the matter through
the consultative process. However, if consultation fails to lead to a
satisfactory resolution, then either party may take a series of steps
that may culminate in the meeting of an impartial, five-member
arbitration panel. This panel can determine whether the party
complained against has persistently failed to enforce its environmental
law. If the panel issues a decision finding such a persistent failure,
it may formulate an action plan to remedy the enforcement failure and
may ultimately impose monetary penalties if the enforcement failure
persists. Thus, the NAAEC dispute resolution procedure provides an
option for U.S. policymakers, but only if the Mexican government
persistently fails to enforce the Mexican environmental laws that apply
to the two plants. The NAAEC dispute resolution procedure does not
provide a useful option for U.S. policymakers if the Intergen and
Sempra plants comply with Mexican law, even if the plants adversely
affect the health of the residents of Imperial County.
Policymakers Have Limited Options to Protect Imperial County Residents
from Adverse Health Impacts:
There are some actions policymakers could take to protect Imperial
County from increased emissions from the Sempra and Intergen power
plants. For example, the Congress could enact legislation restricting
the importation of electricity generated by power plants whose
electrical output is dedicated exclusively to the United States if they
do not meet certain U.S. emission and offset requirements. While this
action would have benefits to air quality and health, it would also
have costs, such as possibly reducing energy supplies available to
southern California. In 2003 a bill was introduced in the Senate and
House that would have prohibited the exportation of natural gas from
the United States to Mexico for use in power plants near the U.S.
border if the plants do not provide air quality protection that is at
least equivalent to the protection provided by air quality requirements
applicable in the United States. Each chamber referred the bill to
committee; neither the Senate nor the House committee reported the bill
to the full chamber for consideration.
Similarly, DOE could modify its regulations that apply to applicants
for presidential permit seeking to build new international transmission
lines to import electricity into the United States from Mexico. The
modified regulations could require that the lines connect to plants
that employ specified emissions controls and obtain offsets in the
United States. However, limiting the import of electricity from Mexico
into California could jeopardize some electricity supplies for parts of
southern California, which could be problematic especially during peak
consumption periods. According to the California Independent System
Operator, the demand for energy in California is growing at nearly 4
percent annually. During the summer of 2004, the peak demand record set
in 1999 was broken seven times, and the California Independent System
Operator believes that the record will likely fall again during the
summer of 2005.
Moreover, both of the above options would need to be assessed to
determine if they are compliant with the North American Free Trade
Agreement (NAFTA). The agreement allows either the U.S. or Mexico to
restrict energy imports for a range of reasons, including protection of
human life or health. However, such import restrictions must meet a
variety of conditions. For example, though NAFTA recognizes a country's
right to license imports and exports of energy, any such licensing
system must be consistent with NAFTA and not frustrate its overall
objectives of eliminating trade barriers, promoting fair competition,
and increasing investment opportunities. NAFTA also requires energy
regulatory agencies to minimize disruptions to contractual
relationships in applying their regulations.
A third option would be for the United States and Mexico to expand
cooperation under the existing binational initiative to address
transboundary air pollution in the U.S.-Mexico border region by
providing economic incentives, such as emissions trading, to reduce
pollution. Such programs have proven successful in the United States in
reducing emissions that contribute to acid rain. At the international
level, the United States and Canada have developed an air pollution
agreement that could possibly serve as a model for a similar agreement
between the United States and Mexico. However, based on the Canadian
example, developing the legal and regulatory framework needed to create
a binational emissions trading program with Mexico is likely to take a
significant amount of time. The United States and Canada initiated
cooperative efforts in 1980 through a memorandum of understanding, and
11 years later the 1991 U.S.-Canada Air Quality Agreement identified
market-based mechanisms, including emissions trading, as areas for
further discussion. In April 1997, the United States and Canada agreed
on a joint plan of action for addressing transboundary air pollution,
expanding the initial focus on acid rain to also examine ground-level
ozone and particulate matter. In 2000, the Air Quality Agreement was
formally expanded to address transboundary ground-level ozone issues.
In 2004, the United States and Canada initiated a joint study to
examine the feasibility of establishing a binational emissions trading
program. Issues being addressed include the legal authority and the air
pollution monitoring, assessment, and reporting system that would be
needed to implement such a program.
At the state level, Texas passed legislation in 2001 that authorized
the state's environmental agency to accept reductions in emissions from
brick kilns in Ciudad Juarez, Mexico, to satisfy new state emission
control requirements passed by the Texas Legislature in 1999. In return
for air emission allowances under Texas law, the local utility, El Paso
Electric, arranged the destruction of older, high-polluting, open-top
kilns and replaced them with less polluting closed-top kilns. This
emission control project serves the Paso Del Norte air basin, which is
officially recognized in the La Paz Agreement, and includes El Paso,
Texas, and Ciudad Juarez, Mexico.
Finally, another potential option is the development of a binational
clean air trust fund that could provide grants and loans to support
projects that would improve the air quality of U.S. and Mexican cities
that share air basins in the border region. Implementing such a program
could help offset emissions generated by a variety of sources,
including power plants in Mexico that are not required to offset their
emissions. Funds from a variety of sources, such as appropriations from
both nations' legislatures, fast-lane fees for cars and trucks at ports
of entry, and fees from airports and railroads operating along the
border, could be held in a joint U.S.-Mexican trust fund for
distribution to states, counties, cities, or local air pollution
control districts along the shared border.[Footnote 19] The binational
clean air trust fund could also potentially obtain funds from power
plants located in the U.S.-Mexico border region that are looking for
opportunities to offset their emissions, although they are not required
to do so by law. Both Intergen and Sempra have shown an interest in
supporting projects aimed at improving the air quality in the border
region. For example, Intergen supports an applied research grant
program to improve air quality in the California-Mexico border
region,[Footnote 20] and Sempra is developing a fund to support the
implementation of environmental projects, such as road paving, in the
border city of Mexicali, Mexico, that it expects to implement before
the end of 2005.
Conclusions:
The Sempra and Intergen plants near Mexicali, Mexico, are modern power
plants that use advanced air pollution control technologies. As a
result, the pollution they emit is comparable to that emitted by
similar plants that have recently received permits to operate in
California and is low relative to dust and emissions from vehicles, the
primary sources of pollution in Imperial County. Nevertheless, the
plants emit some pollutants into an air basin that already does not
meet some air quality standards and is home to many asthmatic children
and a low-income population that may be particularly susceptible to
adverse health consequences from any level of pollution increase. DOE
concluded in its environmental impact statement that pollution from the
plants would not result in significant health impacts in Imperial
County and therefore did not require the plants to offset their
emissions. However, the DOE analysis did not fully examine several
issues that could have led to an assessment of a larger adverse health
impact in Imperial County. In addition, if the plants were located 3
miles north in Imperial County, California, they would be required to
fund projects to reduce pollution from other sources to offset their
emissions regardless of whether there was a documented adverse health
impact. However, now that DOE has determined that no offsets are
required, options available to U.S. policymakers in the short term to
directly address the existing health concerns are limited. In the long
term, the United States and Mexico could implement an emissions trading
program or a clean air trust fund to address pollution in the border
area, but such programs are likely to take years, and require
significant binational effort to develop.
Agency Comments and Our Evaluation:
We provided draft copies of this report to the Department of Energy
(DOE) and to the Environmental Protection Agency (EPA) for their review
and comment. We received a written response from DOE's Director, Office
of Electricity Delivery and Energy Reliability. EPA provided technical
comments which we incorporated in the report.
DOE disagreed with our assertion that it did not analyze all of the
likely asthma-related and other health impacts of increased pollution
from the Sempra and Intergen power plants. Specifically, DOE stated
that the environmental impact statement for the two plants (1) notes
the full range of respiratory effects associated with exposure to
airborne particulate matter (PM10) and (2) uses the number of potential
additional asthma hospitalizations in Imperial County as a
representative estimate of the number of potential health effects cases
associated with power plant emissions of PM10. While DOE's
environmental impact statement acknowledges that increases in PM10
concentrations could have adverse health impacts such as increased
asthma symptoms and chronic bronchitis, up to hospitalization and
death, DOE did not quantify or report quantified estimates for any
adverse health effects other than asthma hospitalizations. For example,
DOE did not quantify the extent to which asthma sufferers would have
increased doctor visits or medication use related to increased
pollution. Furthermore, while asthma hospitalizations are one measure
of potential adverse health impacts from increased emissions of
particulate matter, there are many other adverse health effects that
have been documented, such as chronic lung disease, chronic bronchitis,
pneumonia, and cardiovascular disease that DOE did not quantify. For
these reasons, asthma hospitalizations do not represent the "full
range" of potential adverse health impacts in Imperial County.
DOE also disagreed with our assertion that it did not analyze the
potential health impacts of pollution from the Sempra and Intergen
power plants on susceptible populations in Imperial County. According
to DOE, because the environmental impact statement's estimate of
increased asthma hospitalizations is based on data that include
children ages 14 and under, it accounts for health impacts on
susceptible populations. However, asthmatic children are not the only
susceptible population mentioned in our report, and asthma
hospitalization is not the only potential health impact. Moreover,
DOE's analysis does not differentiate among different population
subgroups in terms of their susceptibility to the effects of air
pollution but instead characterizes potential adverse health effects
for the population as a whole. Consequently, we continue to believe
that DOE's environmental impact statement did not address the full
range of potential health impacts on susceptible populations in
Imperial County.
Finally, DOE does not agree that the health impacts from ozone
formation may be larger than it estimated in the environmental impact
statement. DOE said that it addressed EPA's concerns regarding the
uncertainty in the ozone modeling in the final environmental impact
statement. However, while EPA acknowledged in its comments on the final
environmental impact statement that the document clarified the
limitations of the ozone modeling analysis, it also reiterated its
support for off-site mitigation efforts to address these limitations to
ensure that there is no net increase in air pollution in Imperial
County. As a result, we continue to believe that ozone formation may
have larger health impacts than estimated in the final environmental
impact statement. DOE's specific comments and our detailed responses
are presented in appendix II of this report.
We are sending copies of this report to the Secretary of Energy, and
the Administrator of the Environmental Protection Agency, and
appropriate congressional committees. We will also provide copies to
others upon request. In addition, the report will be available at no
charge on the GAO Web site at http://www.gao.gov.
If you or your staffs have any questions about this report, please
contact me at (202) 512-3841 or stephensonj@gao.gov. Contact points for
our Offices of Congressional Relations and Public Affairs may be found
on the last page of this report. GAO staff who made major contributions
to this report are listed in appendix III.
Signed by:
John B. Stephenson:
Director, Natural Resources and Environment:
[End of section]
Appendix I: Objectives, Scope, and Methodology:
The objectives of this report were to determine (1) how emissions from
the Sempra and Intergen power plants compare to emissions from recently
permitted plants in California and emissions from sources in Imperial
County, and what emissions standards the plants would be subject to if
they were located in Imperial County; (2) the health impacts of
emissions from the power plants on Imperial County residents; and (3)
what options exist for U.S. policymakers to ensure that emissions from
these power plants do not adversely affect the health of Imperial
County residents. To address all three of these objectives we visited
the Sempra and Intergen plants in Mexicali, Mexico; interviewed plant
representatives, various U.S. federal, state, and local air quality
officials, and other stakeholders; and reviewed relevant documents and
studies.
To determine emissions from the Sempra and Intergen plants we obtained
data from emissions performance tests conducted at the plants by third
party contractors (GE Mostardi Platt and Air Hygiene). These tests were
designed to document the average emissions of selected pollutants
(nitrogen oxide, particulate matter, carbon monoxide, volatile organic
compounds, and ammonia) from the combustion turbines at each of these
plants. The results of these tests were reported in standard units of
measurement, namely parts per million or pounds per hour. According to
the contractors, they completed the tests according to Environmental
Protection Agency and California-approved methods and conducted quality
assurance activities related to their test results. We assessed the
reliability of the data by (1) reviewing documentation of test
objectives and quality control procedures provided by the third party
contractors, (2) conducting interviews with plant officials to
determine the scope and generalizability of the tests, and (3)
reviewing reports of actual NOx emissions submitted to the Mexican
government to ensure consistency with the test results. Based on this
assessment, we determined that the data were sufficiently reliable for
the purposes of this report.
To determine annual emissions estimates from these plants, we used the
results from the emissions tests to calculate the annual tonnage that
these plants would be likely to emit. We computed these values based on
the conservative assumption that these plants would be operating 24
hours a day, 365 days a year. In addition to the estimates obtained
from the testing results, we also used the maximum allowable emission
limits of comparable plants in California to develop a more
conservative estimate of annual emissions from these plants. For
Sempra, we utilized the Elk Hills power plant as the primary basis for
developing comparative estimates. This natural gas-fired power plant is
partially owned by Sempra Energy and utilizes very similar equipment
and pollution control technology as the Mexicali plant. For the
Intergen plant, we used a combination of comparable estimates because
no similar, Intergen owned facilities were recently constructed in
California. To estimate nitrogen oxide (NOx) and ammonia (NH3), we used
vendor guarantee limits, which are the maximum emissions levels
specified by the manufacturer that a specific piece of equipment is
likely to produce (e.g. selective catalytic reduction systems).
Particulate matter (PM10) was estimated using the average allowable
emissions limit from all comparable plants in California permitted
between 2000 and 2004. Because the Intergen plant is not equipped with
an oxidation catalyst, carbon monoxide (CO) was estimated using a
specific plant in California, permitted in 2000, that was the only one
licensed without such control equipment. Finally, because some
California permits establish volatile organic compounds (VOC) limits in
parts per million and others do so in pounds per hour, we were not able
to develop an average for all recently permitted plants in California.
For this reason, we used emissions limits from the Elk Hills power
plant to estimate annual emission levels of VOC at the Intergen plant.
To determine how estimated emissions from the Sempra and Intergen
plants compare to recently permitted plants in California, we developed
a range of maximum allowable emission limits for all natural gas-fired
power plants in California with similar specifications, licensed
between 2000 and 2004. This time frame was chosen because it
corresponded to the dates that the Sempra and Intergen plants in
Mexicali were designed, permitted, and began commercial operations.
Because all California power plants are permitted on a case-by-case
basis, emissions limits may vary with each project. Therefore, we used
the entire range of emission limits for the 23 plants that were
identified during our selection process. We then compared the range of
emission limits from the 23 plants that we identified with the third
party testing results we obtained from the Sempra and Intergen plants.
To determine how the emissions from these plants compare to emissions
from sources in Imperial County we utilized the 2004 estimated annual
average emissions inventory for Imperial County developed by the
California Air Resources Board. We also met with officials from the
California Air Resources Board and reviewed emissions reports for
stationary sources obtained from the Imperial County Air Pollution
Control District. To determine the levels of nitrogen oxide emissions
from the Sempra and Intergen plants in relation to existing plants in
Imperial County and Baja California, Mexico, we obtained reports
developed for the Mexican government that included annual emissions of
nitrogen oxides based on data from the continuous emissions monitoring
system on each turbine. Comparable data for the El Centro plant in
Imperial County and the two Baja California plants were obtained from a
report produced by the Commission for Environmental Cooperation of
North America.[Footnote 21] To assess the reliability of these data
sources we (1) spoke with officials at the California Air Resources
Board and reviewed documentation related to data collection and quality
control procedures used to develop the annual emissions inventory, and
(2) corroborated the emissions data related to the El Centro plant with
the EPA Clean Air Markets database. Based on these assessments, we
determined that the data were sufficiently reliable for the purposes of
this report.
To determine what emissions standards the plants would be subject to if
located in Imperial County we reviewed the principal federal
regulations applicable to new power plants located in the United States
and the emission limits of similar plants recently permitted in
California. The primary federal regulations we reviewed were those
established under EPA's New Source Review program for new or modified
major pollution sources. We reviewed selected state and local air
pollution regulations because state and local agencies have
responsibility for implementing specific permitting activities as part
of the federal program. The state and local regulations we reviewed
included the permitting conditions of several power plants licensed by
the California Energy Commission to determine the standard permitting
criteria and the air quality rules established by the Imperial County
Air Pollution Control District for sources located in Imperial County.
To identify the potential health impacts from emissions generated by
the Sempra and Intergen power plants, we reviewed the health assessment
in DOE's environmental impact statement. We met with the project
manager of DOE's health assessment to gather additional information
about the assessment methodology. We reviewed EPA's comments on the
environmental impact statement, and interviewed EPA officials and
health experts regarding DOE's health assessment methodology. In
addition, we reviewed relevant EPA reports, and other health studies
regarding the impacts of particulate matter and ozone on human health.
Finally, we reviewed a recent California health survey to obtain
current information on asthmatic populations in Imperial County and
other California counties.
To determine the policy options available to ensure that emissions from
the Sempra and Intergen plants do not adversely affect the health of
Imperial County residents, we reviewed the federal Clean Air Act, the
California Clean Air Act, key provisions of the North American Free
Trade Agreement, as well as environmental agreements between the United
States and Mexico, such as the La Paz agreement, and a trilateral
agreement between the United States, Mexico, and Canada--the North
American Agreement on Environmental Cooperation; and academic research.
We also participated in a transboundary air quality management
conference where officials from various federal, state, and local
agencies in the United States and Mexico met to discuss strategies to
address binational air pollution.
We conducted our work between September 2004 and August 2005 in
accordance with generally accepted government auditing standards.
[End of section]
Appendix II: Comments from the Department of Energy:
Note: GAO comments supplementing those in the report text appear at the
end of this appendix.
Department of Energy:
Washington, DC 20585:
July 29, 2005:
Mr. John B. Stephenson:
Director, Natural Resources And Environment:
U.S. Government Accountability Office:
441 G Street, N.W., Room 2T23A:
Washington, DC 20548:
Dear Mr. Stephenson:
Thank you for the opportunity to comment on the Government
Accountability Office's (GAO) draft report entitled, "Air Pollution:
Estimated Emissions from Two New Mexicali Power Plants Are Low, but
Health Impacts Are Unknown." The Department of Energy (DOE) has
reviewed the draft and offers comments in the following three areas of
the report.
The GAO report noted on Page 27 that: DOE Did Not Analyze All the
Likely Asthma-Related and Other Health Impacts of Increased Pollution
from the Sempra and Intergen Power Plants.
DOE Response: The environmental impact statement (EIS) notes the full
range of respiratory effects associated with exposure to airborne
particulate matter (PM10), ranging from asthma symptoms, chronic
bronchitis, and lower respiratory effects, up to hospitalizations and
death, and assumes a general 3% across-the-board increase in all such
effects for each 10-mu g/m3 increase in PM10 as reported in Pope and
Dockery (1999). This factor is based on a summary of results of
epidemiological studies of acute exposures to particulate matter. The
EIS uses the number of potential additional hospitalizations (less than
one per year) in Imperial County as a representative estimate of the
number of potential health effects cases associated with power plant
emissions of PM 10. DOE used this measure of health effects rather than
any of the other levels in GAO's "Pyramid of Potential Health Impacts
for Asthmatics" (Figure 4 in GAO's draft report) because DOE considered
hospitalizations to be the best parameter for representing impacts on
asthma for two reasons. First, the actual number of baseline
hospitalizations is well documented (compared to other parameters such
as doctor visits or use of rescue inhalers). Second, hospitalizations
are a measure of one of the most severe impacts and, thus, of high
interest to stakeholders and decision makers.
While the "Pyramid" is a useful tool for expressing the general idea
that less severe effects have higher frequency, we think that it is not
a useful model for computing actual numbers of effects. Take, for
example, the 2003 report "Asthma in California, Findings from the 2001
California Health Interview Survey," which GAO cites in its report. The
report notes that the frequency of asthma symptoms is reduced by timely
and regular use of medication, regular consultation with physicians,
and education regarding the recognition of the onset of symptoms.
Therefore, as the frequency of use of medication and physician visits
increases, the frequency of asthma symptoms, emergency room visits, and
hospitalizations would be expected to decrease and impacts from PM10 on
one level of the "Pyramid" are not expected to be directly related to
impacts on the next level in a simple and quantifiable way. DOE instead
relied on verifiable baseline rates of hospitalizations to calculate
additional cases of this representative health effect of PM10.
Regarding the potential relationship between PM10 and increased
cardiovascular effects, including coronary obstructive pulmonary
disease, which the EIS does not discuss, DOE notes that the observed
association for these diseases is relatively recent in the literature
of impacts and is based on far fewer studies than the association
between PM 10 and respiratory effects (Pope and Dockery 1999).
Sufficient facts and research have not yet been published from which
DOE can draw the inference that a statistically linear relationship
exists between the small increase in PM 10 attributable to the power
plants and an increased incidence of these cardiovascular diseases.
The GAO report noted on Page 29 that: DOE Did Not Analyze the Health
Impacts on Particularly Susceptible Populations in Imperial County.
DOE Response: The EIS acknowledges such populations in the estimate of
additional hospitalizations. The baseline hospitalization rate in
Imperial County is the highest in the state and is nearly twice the
state average computed from actual discharge rates in Imperial County
over a three-year period (CDHS 2003). The EIS presents hospitalization
rates for 0-14 year olds (p. 4-103) as well as for all ages to
highlight the susceptibility of children to asthma. The EIS contains a
computation (p. 4-104) of the estimate of additional hospitalizations
in the county using the all-ages baseline rate, which implicitly
accounts for contributions from all groups. The estimated impact in
terms of additional hospitalizations accounts for susceptible
populations because they are included in the baseline rate.
The GAO report noted on Page 30 that: Health Impacts from Ozone
Formation May be Larger Than Estimated by DOE. The section of the
report goes onto discuss EPA's comments on the draft EIS in which it
did raise concern about the uncertainty in ozone modeling.
DOE Response: EPA's concerns regarding the uncertainty in ozone
modeling in the draft EIS were addressed in the final EIS. Indeed, DOE
included in the final EIS the results of sensitivity analysis to
respond to EPA's comments. That analysis showed that the production of
ozone was insensitive to changes in input assumptions for model
parameters for which estimated values were used. These results reduce
the uncertainties associated with the ozone modeling and support the
conclusion reached that impacts to air quality would be minimal. That
is, emissions from the power plants would be expected to have very
little impact on the ozone levels in Imperial County.
On page 30 of its report, GAO cites EPA's comment that "peak ozone
concentrations generally occur in areas away from sources of high NOx ,
not at the monitor where high NO2 concentrations are measured." In
response to the EPA comment, all references to air monitoring data with
respect to ozone formation were removed in the final EIS. Therefore,
citing the EPA comment regarding the location of peak ozone
concentrations is not relevant since the ozone model (OZIPR) that DOE
used estimates peak ozone concentrations, wherever they would occur.
DOE appreciates the opportunity to comment on this draft report and
looks forward to receipt of the final version.
Sincerely,
Signed for:
Kevin M. Kolevar:
Director:
Office of Electricity Delivery and Energy Reliability:
GAO Comments:
The following are GAO's comments on DOE's written comments provided in
their letter dated July 29, 2004.
1. While DOE's environmental impact statement acknowledges that
increases in PM10 concentrations could have adverse health impacts such
as increased asthma symptoms and chronic bronchitis, up to
hospitalization and death, DOE did not quantify any potential adverse
health effects other than asthma hospitalizations. Instead, the EIS
relies solely on comparisons to significant impact levels to gauge the
magnitude of potential adverse impacts on human health. In doing so,
DOE determined that emissions from the two plants were below
significant impact levels, and therefore, these emissions would not
produce any significant air quality or adverse health impacts in
Imperial County. As we stated in our report, significant impacts levels
were designed to be used only in areas that meet air quality standards;
Imperial County is currently designated as a nonattainment area for
PM10 and ozone because it does not meet air quality standards for these
two pollutants.
2. Asthma hospitalizations are just one measure of potential adverse
health impacts from increased emissions of particulate matter. While
asthma hospitalizations are more severe and likely to occur less often
than doctor visits or increased medication use for asthma, they cannot
be considered representative of the "full range" of potential adverse
health impacts associated with asthma in Imperial County. In addition
to asthma-related adverse health effects, numerous studies have linked
increased exposure to particulate matter to other non-asthma-related
adverse health effects, such as chronic bronchitis, chronic lung
disease, pneumonia, and cardiovascular disease.
3. We disagree with DOE that hospitalizations are the best parameter
for representing impacts on asthma. While asthma hospitalizations in
Imperial County may be well documented, the 2003 California Health
Survey provides information on other asthma-related health impacts in
Imperial County. For example, the survey contains information on the
number of Imperial County residents who take medication to control
asthma. In addition, the survey presents information on the number of
Imperial County residents who had asthma symptoms within a specified
time frame and who visited an emergency room or urgent care facility
for asthma-related health problems during that time frame. Such
information could have been used, along with information on
hospitalizations, to create a more complete estimate of the potential
asthma-related health effects from increases in pollution from the
power plants.
4. The report does not use the health effects pyramid, or suggest it
should be used, to compute instances of potential health effects from
air pollution. However, we believe that the health effects pyramid is
useful for understanding the variety of ways in which increased
pollution can aggravate asthma suffering in Imperial County. In so
doing, it also highlights the full range of potentially quantifiable
effects related to asthma.
5. During our review of the health effects literature, we identified a
number of studies that support a linear relationship between increases
in particulate matter pollution and increased incidence of
cardiovascular diseases.
6. Asthmatic children are not the only susceptible population mentioned
in our report, and asthma hospitalization is not the only potential
health impact. Consequently, we continue to believe that DOE's
environmental impact statement did not address the full range of
potential health impacts on susceptible populations in Imperial County.
DOE's quantification of just one adverse health impact for the entire
population of Imperial County masks the differential effects that can
beset more susceptible subpopulations in the County.
7. In commenting on the final environmental impact statement, EPA
acknowledged that DOE had clarified the limitations and uncertainties
of the ozone modeling analysis. However, in its comments EPA said it
continues to support and encourage off-site mitigation efforts to
address the limitations in the ozone modeling to ensure that there is
no net increase of air pollution in Imperial County.
8. We believe that EPA's comment regarding peak ozone concentrations is
relevant because it is presented in the context of EPA's comments on
the draft environmental impact statement. We also note in the report
that DOE took action in response to EPA's comment.
[End of section]
Appendix III: GAO Contact and Staff Acknowledgments:
GAO Contact:
John B. Stephenson (202) 512-3841:
Acknowledgments:
In addition to the contact named above, Leo G. Acosta, Charles Bausell,
Nancy Crothers, Brandon Haller, Ryan Lambert, Omari Norman, Kim Raheb,
and Stephen Secrist made key contributions to this report.
FOOTNOTES
[1] The standards are known as the National Ambient Air Quality
Standards.
[2] Nitrogen dioxide (NO2), a common air pollutant, is one of a group
of gases collectively known as nitrogen oxides, or NOx. The term NOx is
used commonly in both the United States and Mexico to describe these
gases, but NO2 is sometimes monitored to report on the levels of all
nitrogen oxide emissions in general.
[3] PM2.5 and PM10, also known as fine and coarse particulate matter,
respectively, refer to the size of the airborne particles measured at
the diameter (in micrometers).
[4] Ozone is formed at ground level by a chemical reaction of various
air pollutants, including NOx, combined with sunlight. Ozone is a key
ingredient in urban smog.
[5] Independent of such factors as time of day, time of year, and
geographical location, in general, one megawatt of electricity is
sufficient to meet the needs of 750 to 1,000 households for 1 hour.
[6] On April 13, 2005, the Secretary of Energy transferred the
authority to grant presidential permits to the Office of Electricity
and Energy Assurance. That office has subsequently been renamed the
Office of Electricity Delivery and Energy Reliability.
[7] Exec. Order No. 10485, 18 Fed. Reg. 5397 (Sept. 9, 1953) amended by
Exec. Order No. 10238, 43 Fed. Reg. 4957 (Feb. 3, 1978).
[8] Selective catalytic reduction is a post-combustion cleaning
technology whereby NOx emissions chemically react with ammonia (NH3) to
produce ordinary nitrogen and water vapor. An oxidizing catalyst is
similar in concept to catalytic converters used in automobiles. The
catalyst, normally coated with a metal, such as platinum, is used to
promote a chemical reaction with the oxygen present to convert carbon
monoxide into carbon dioxide and water vapor.
[9] Because the proposed lines traverse land managed by the U.S.
Department of the Interior, Bureau of Land Management, they also
participated in the environmental assessment.
[10] For this reason, ammonia (NH3) is often included in the review of
potential impacts from power plants and is subject to emission limits
as part of the permitting process conducted in California. NH3
emissions, typically referred to as ammonia-slip, are released from
power plants as a byproduct of selective catalytic reduction control
technology.
[11] North American Power Plant Air Emissions, Commission for
Environmental Cooperation of North America, 2004.
[12] Imperial County Air Pollution Control District, Rule 207, Section
C.3 (Revised Sept. 14, 1999).
[13] The border city of Calexico, California, is also in violation of
the state ambient air quality standard for CO. Therefore, if the plants
were located in Imperial County close enough to Calexico to impact the
city's air quality, the plants would also be required to offset their
emissions of CO.
[14] EPA has established significant impact levels for NO2, SO2, CO,
and PM10 in the context of permitting a major source or major
modification to an existing pollution source in the United States. 40
C.F.R. § 51.165(b)(2).
[15] The California Health Interview Survey--maintained at the UCLA
Center for Health Policy Research in Los Angeles, California--is the
state's largest health survey. The telephone survey of adults,
adolescents, and children is a collaborative project of the UCLA Center
for Health Policy Research, the California Department of Health
Services, and the Public Health Institute, and is conducted every 2
years.
[16] The Health Effects Institute (HEI) is an independent, nonprofit
corporation chartered in 1980 to provide impartial research on the
health effects of air pollution. Supported jointly by the U.S.
Environmental Protection Agency and industry, HEI has funded over 170
studies and published over 100 research reports. HEI supported research
has produced findings on the health effects of a variety of pollutants,
such as carbon monoxide, nitrogen oxides, ozone, and most recently,
particulate air pollution.
[17] UCLA Center for Health Policy Research, Asthma in California:
Findings from the 2001 California Interview Health Survey, November
2003.
[18] DOE used data from Phoenix, Arizona because it is one of the 10
cities that was already built into the EPA ozone model (OZIPR)
database, and they believe Phoenix, Arizona is the most representative
proximate city in terms of climate, latitude, and physiography.
[19] Richard Ryan, "Financing Clean Air on the Border: Establishing a
Binational Clean Air Trust Fund (BiCAT)" (paper presented at the Border
Institute VII, Transboundary Air Quality Management conference, in Rio
Rico, Ariz., April 2005).
[20] The program, known as the Border Ozone Reduction and Air Quality
Improvement Program, is administered by a Harvard University-affiliated
nonprofit organization, LASPAU: Academic and Professional Programs for
the Americas.
[21] The Commission for Environmental Cooperation of North America was
established by the North American Agreement on Environmental
Cooperation--one of the two side agreements to the North American Free
Trade Agreement.
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