Air Quality is essentially the measure of the cleanliness of air, a measure of how much smog there is, or of how much carbon dioxide is in the air. Motor vehicles, industries, construction equipment and some commercial operations are among the sources of air pollution in the San Antonio area. The main air pollutants emitted from motor vehicles are volatile organic compounds (VOCs), nitrogen oxides (NOx), carbon monoxide, carbon dioxide, particulate matter and a class of compounds called mobile source air toxics (MSATs). VOCs and NOx can react in the air in sunlight to form ground-level ozone. Because the reactions take place over several hours, maximum concentrations of ozone are often far downwind of the precursor sources. Thus, ozone is a regional problem and not a local condition or specific to a particular project.
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Source: AIRNow.gov
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By federal law, San Antonio must meet National Ambient Air Quality Standards. If a city meets the emissions standard then they are in 'attainment.' The opposite is also true, cities who fail to meet standards are declared in 'nonattainment.' The San Antonio area is currently in attainment, although not by much. In January 2010, the U.S. Environmental Protection Agency (EPA) proposed revising the air quality standard for ground-level ozone by lowering the ambient limit. The new threshold, scheduled to be announced by July 31, 2011, is intended to be more protective of human health and the environment. The EPA will subsequently designate communities around the country that fail to meet the revised standards. The consequences of failing to improve our air quality include health and mobility challenges and major impacts on the area's economic growth.
Emissions are divided into four different sources1:
- Mobile Sources: emissions from both on-road (combustion & evaporation of fuels in vehicles on public roadways) and off-road (internal combustion engines such as the engines found in trains, construction equipment, airplanes and lawnmowers)
- Point Sources: significant emissions from stationary equipment such as turbine engines, wood & pulp processors, industrial surface coating and petroleum storage tanks
- Non-Point Sources (or Area Sources): many small emissions that when clumped together have an effect such as residential fuel consumption, solvents, product storage & distribution (such as gas), waste management, forest fires and wind erosion
- Biogenic Sources: represent 30% of all volatile organic compound emissions in the eastern half of Texas. From sources such as oaks, pines, sweet gums, eucalyptus and poplars.
The National Environmental Policy Act (NEPA) of 1969 and the Clean Air Act of 1970 (as amended) require the consideration of the impact highway improvements may have on local air quality. This is accomplished by determining whether or not localized carbon monoxide concentrations would be adversely affected by the proposed improvement. In the Draft EIS for US 281 this will be accomplished in accordance with TxDOT's Air Quality Guidelines 2006. In the Draft EIS you will find a calculated air quality impact for carbon monoxide (CO) for each of the alternatives to determine the potential for impacts along US 281. An MSAT analysis will be completed and documented in the Final EIS for the preferred alternative.
The Alamo RMA is focusing on reducing mobile source emissions to improve overall air quality. As you may have noticed, the US 281 Super Street has improved congestion, but the US 281 EIS will develop a long-term solution to the transportation problems along US 281. To further improve mobility on US 281, each build alternative being considered in the EIS includes complementary elements such as bus service, park-and-ride facilities, bike and pedestrian facilities, growth management, transportation demand management and transportation system management.
For more information on air quality in San Antonio please visit the Alamo Area Council of Governments (AACOG) website. The Natural Resources Department at AACOG addresses air quality issues in this region by bringing together stakeholders from all interests to develop air pollution reduction plans that benefit our quality of life. Some of AACOG's projects to support this initiative include air pollution monitoring, data analysis, emission inventory development, modeling and reporting. To learn more about air quality and health in south Texas please visit CleanAirDrive.com.
Further Readings:
http://www.epa.gov/air/basic.html
http://www.tceq.state.tx.us/
http://www.aacog.com/air
http://airnow.gov/
http://www.cleanairdrive.com/Air/AQFactSheet.pdf
Regulatory Background:
National Environmental Policy Act 1969 (http://ceq.hss.doe.gov/nepa/regs/nepa/nepaeqia.htm)
1970 Clean Air Act and Amendments (http://www.epa.gov/air/caa/)
Sources:
1 Claxton, Greg. (11 December 2009). Community Inventory: Natural Environment.
Imagine Austin. Retrieved from http://www.imagineaustin.net/
