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FYI
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If air pollution and visibility improve at the rate of one deciview per decade, it
would take between 130 and 150 years to obtain "pristine" views at the Class I areas in Texas -- Big Bend National Park and Guadalupe Mountains National Park.
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(Source: Data from IMPROVE monitors, National Park Service.)
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Visibility -- how far you can see on a clear day -- has become a major air quality
issue in cities and in rural and wilderness areas. Without the effects of pollution, the natural visual range in the eastern states would be 90 miles, while in the West it
would be approximately 140 miles.* However, soil dust, sulfates from sulfur dioxide,
carbon monoxide and nitrates from nitrogen oxide emissions, soot, ozone haze, and other contaminants, as well as natural events like volcanic explosions, have reduced
visual range to 14 to 24 miles in the East and 33 to 90 miles in the West.
In 1980 the EPA adopted visibility protection provisions under the Clean Air Act to
help protect 156 "Class I" areas nationwide -- major parks and wilderness areas over 6,000 acres -- where pristine air quality and scenic vistas are integral features.
In Texas the TCEQ and its predecessors have been charged by the EPA with coming up with a plan to protect visibility in Big Bend National Park and Guadalupe
Mountains National Park, the only two Class I areas in Texas. According to the
TCEQ's January 1995 visibility protection plan and 2001 Periodic Review and Report, the National Park Service must be
notified and given time to review the permit application of any new source located within 100 kilometers of either park * However, because no major sources are located within 100 kilometers of Big Bend, the document states that this
provision has not been utilized and a long-term strategy for visibility protection has not needed to be developed.
Nonetheless, studies have shown that sulfur dioxide emissions from sources more than 100 kilometers from Big Bend
are having adverse effects on visibility.* In fact, visibility within the parks and visual range in general in these parks has
plummeted. For example, while natural visibility in Big Bend should be roughly 150 miles, average visibility is now 60
miles (50 in summer months), according to recent averages. In fact, on some days the amount of particles in the air is
so bad that the health of visitors has been impacted. For example, between August 21 and 27, 1995, visual range in Big Bend averaged 23 miles (only 9 miles on August 22).* Similarly, visibility in the Guadalupe Mountains was reduced to 30 miles during the same period.
The complexity of the air visibility issue is evidenced by recent data from the Guadalupe Mountains. For example, the
lowest visibility measured in deciviews (a measurement of visual range) was recorded in October and November of
2002, where days averaged less than 1.0 deciview. Nonetheless, just one month earlier, on September 2, 2002, the measured deciview was 22.4, the second best day recorded since 1988*. Overally, data from 1994 to 1998 showed
that air visibility in Big Bend and Guadalupe remained relatively stable with no statistically significant decline.
Studies have linked visibility reduction in Big Bend to sulfur dioxide emissions from sources in West Texas, the Gulf
Coast of Texas and northern Mexico.* The largest sources of sulfur dioxide emissions in the area are from the Carbón I
and II coal-fired electric generating plants near Piedras Negras, Coahuila, Mexico. A 1996 study, conducted by U.S. and
Mexican authorities, suggested that visibility impairment was due to a variety of sources, including large coal-fired plants in Northeast Texas, as well as Mexican sources.* The Carbón I and II plants have been constructed and
operated without basic control-equipment technology for sulfur dioxide, which would be required for new plants in the United States but is not in Mexico.* This fact -- as well as Mexico's plans to build other electric generating plants in the
area -- has led to a series of meetings between the U.S. and Mexican governments, although no concrete actions other than the 1996 air quality study have been agreed upon.
In 1997 the EPA proposed revising the 1980 visibility rules by addressing visibility impairment due to regional haze in
Class I areas. Under the adopted 1999 regulations for regional haze, states must establish goals for improving visibility
in national parks and develop long-term measures to reduce emissions of pollutants that cause visibility impairment.
Under the rule, states are expected to work together to address these pollutants, many of which are transported
hundreds of miles. Texas has joined nine other states as part of the Central States Regional Air Partnership. Under the
proposals, states are given flexibility about designing programs that would improve visibility, although they are expected
to design programs that would reach natural background conditions within 60 years, and must improve visibility on the
20 percent of most-polluted days while maintaining current levels of visibility on the 20 percent of cleanest days. As
part of this program, states also need to monitor for PM2.5 -- fine particulate matter -- in the parks; identify old,
uncontrolled major pollution sources; and evaluate the need to install additional pollution controls such as Best
Available Retrofit Technology (BART) or design an emissions trading program at these older sites, as well as other sources of pollution.*
Still, whether as part of a regional approach or an individual approach, states will not have to submit their initial plans
until 2004 at the earliest, and in most cases won't have to submit final plans until 2008. The EPA estimates that the
regional haze rules will cost between $1 and $4 billion to implement, but will provide between $3.5 and $10.8 billion
per year in health and other benefits. In 2001, the Bush administration proposed amending the 1999 regional haze
rules by offering guidelines for the Best Available Retrofit Technology determinations. Under the proposed amendment,
states are given additional guidelines and more flexibility in determining whether BART will be required for these older sources of pollution or whether to enact an emissions trading program*.
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TOP 15 SULFUR DIOXIDE EMISSIONS SOURCES
NEAR BIG BEND PARK
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Source: TNRCC, State Summary of Emissions Database, 1998.
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Note: Total for Carbon I/II is an estimate.
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