Chapter 1 - INTRODUCTION

1996 Emission Inventory for the Alamo Area Council of Governments Region

 

Summary Information

 

Since the promulgation of the Clean Air Act (CAA) by the United States Congress some forty years ago, the impetus nationwide to maintain high air quality standards has only increased. For most of the intervening time, the San Antonio region has enjoyed the clear skies and clean air associated with the high standards of air quality known to many of the less densely populated areas of the country.

In 1997, air quality monitors began to compile the three-year set of eight-hour average ozone readings required by the amended National Ambient Air Quality Standards (NAAQS). The publication of this emissions inventory appears at the close of that three-year period and with the understanding that those ozone readings may be used to support redesignation of nonattainment for our region by the U.S. Environmental Protection Agency under the eight-hour ozone NAAQS. Perhaps never before in the history of the city have air quality considerations been as important as they are at this moment.

The compilation of the 1996 Emissions Inventory for the Alamo Area Council of Governments has required many thousands of man-hours of careful research and analysis. This Emissions Inventory (EI) provides a vast database of the many regional pollution sources, their emissions and emission rates. By understanding these many sources that together create air pollution, our planners, political leaders and common citizens can also work together to better manage them. Understanding and management skills are the tools we have at our disposal to ensure the quality of the air in our region.

The category names in the EI reflect much about the emissions sources that fall within each of the six categories. The "Point Sources" are those stationary emitters individually producing enough pollution that a description of each singular source is warranted. The state of Texas, through the agency of the Texas Natural Resource Conservation Commission, keeps records of these sources. By contrast, the "Area Sources" are those stationary sources that are so numerous and produce such low levels of contaminants that identification of individuals and their emissions is typically unwarranted. The "On-Road Mobile Sources" category is a self-descriptive name referring to the many vehicles traveling the regional roads and highways of Texas. The "Non-Road Mobile Sources" accounts for the emissions of those perhaps less obvious vehicles on farms, in the construction trades, and wherever else powered locomotion leaves the road. Because of the importance of the military in the San Antonio metropolitan area, the importance of aircraft within that military presence, along with the many similarities of military and airport emissions inventory techniques, the 1996 EI presented here includes a single category for both, "Airport and Military Sources." The airport and military source category includes area, non-road, non-road equipment, and on-road base emissions. Finally, the "Biogenics Sources" lists the pollutants due to the presence of plants and their biology.

Bexar County and the additional 11 counties in the AACOG Region are located in South Central Texas and the Hill Country. Bexar County contained five active military installations in 1996 and no major industries. San Antonio, the seat of Bexar County, occupies an area of 1,256.76 square miles. In 1996, the population of Bexar County reached 1,358,865 people. The San Antonio Metropolitan Statistical Area (MSA) is comprised of Bexar, Comal, Wilson, and Guadalupe Counties and has a population of 1,530,182 people. The entire AACOG region had a population of 1,712,331 people in 1996.

Since Bexar County is primarily an urban area with a large population that comprised 80% of the 1996 AACOG population, the primary contributors of NOx and VOC emissions in the county differed from those of the surrounding counties. For example, on-road sources contributed 35% of the total VOC emissions generated in Bexar County, whereas these sources were responsible for only 11% of the VOC emissions of the eleven surrounding counties. In contrast, biogenic sources contributed 15% of the total VOC emissions in Bexar County, while these sources produced 68% of the VOC emissions in the remaining counties. The VOC, NOx and CO emissions generated in the AACOG region, in tons per day and by source category, are illustrated in pie charts found on the Emissions By County Aggregates webpage and in a series of tables found on the Emissions By County, By Source Category, 1996 webpage.

The following chapters describe in detail the methodology used to determine emissions from the numerous sources of NOx and VOC. In addition, the chapters provide the results of the emission calculations for each source category in tons per year and tons per day.

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