Air Quality in the Capital Area Planning for a More Stringent Ground-level Ozone Standard

Transcription

1 Air Quality in the Capital Area Planning for a More Stringent Ground-level Ozone Standard Written by Bill Gill, Kristin Hebert, and Faith Melgaard, CAPCOG Air Quality Staff August 2008 Air quality in the Austin Area is generally considered good most of the time, so it may surprise you that we are on the verge of being designated as a nonattainment area for the new federal ozone standard. We have been put in this position by the U.S. Environmental Protection Agency s (EPA s) action to strengthen the National Ambient Air Quality Standard (NAAQS) for ground-level ozone to 75 parts per billion (ppb). If you have been keeping up with air quality issues over the years, you are most likely aware that the Capital Area is no stranger to dealing with the ozone NAAQS. Through various regional planning efforts, local governments, community and business leaders, environmental groups, and concerned citizens in the Capital Area have been working towards maintaining compliance with the ozone NAAQS since the 1997 standard of 84 ppb was put in place. Throughout the efforts to comply with the ozone standard, CAPCOG s air quality group has been involved with providing technical assistance to area businesses, government entities, and community groups. The technical assistance provided by the air quality group is aimed at compiling and analyzing information that assists in the effort to gain a better understanding of the sources of ozone in the Capital Area. Over the years, CAPCOG s air quality group has been able to provide assistance to local air quality planning efforts by operating air monitoring stations, estimating and modeling emissions, and developing regional planning strategies that include emissions reduction measures. The data that results from these air quality assessments is an important asset for the Capital Area and will be vital to analyzing where the region stands with compliance of the new ozone NAAQS. Monitoring CAPCOG s air quality group, through a contractor, operates and maintains six continuous ozone monitoring stations located in the CAPCOG planning region. As shown in Figure 1, five of the CAPCOG monitors are located within the contiguous five-county area that makes up the Austin-Round Rock MSA (A-RR MSA). Additionally, CAPCOG operates and maintains an ozone monitor at an LCRA site in Fayette County. The objective of operating these monitors is to collect data on ozone and ozone precursor concentrations (Nitrogen Oxides [NOx]) as well as meteorological data such as wind direction, speed and temperature, which compliments existing TCEQ monitoring data for the A-RR MSA. The two regulatory monitors referenced in Figure 1 are operated by the TCEQ, and are used to determine compliance with the ozone NAAQS.

2 Air Quality in the Capital Area (Page 2 of 6) Figure 1 Location of ozone monitors in the Austin area. The data collected at these monitors is integrated into the TCEQ data collection and archiving system. This system, known as LEADS (Lockheed Environmental Analysis and Display System), controls all routine measurement functions, including calibrations. The monitoring data for each monitor is posted on the TCEQ s website at The ozone levels monitored at the two TCEQ regulatory monitors (Audubon and Murchison) are used to determine if the area surrounding the monitors is in compliance with the ozone NAAQS. Attainment of the ozone NAAQS is based on the 3- year average of the fourth-highest daily maximum 8-hour average ozone concentrations measured annually at each regulatory monitor. This 3-year average is called the design value. Figure 2 shows design value trend and fourth-highest readings at the two regulatory monitors in the A-RR MSA. The A- RR MSA is currently designated in attainment of the 1997 NAAQS for ozone. The attainment designation was based on the design value of 80 ppb (calculated as an average of the 4th highest reading from 2005, 2006 and 2007).

3 8-hr Ozone (ppb) August 2008 Air Quality in the Capital Area (Page 3 of 6) Design Value and Monitored Ozone Concentrations Austin-Round Rock MSA th highest Audubon 4th highest Murchison hr Ozone Standard hr Ozone Standard Austin Round Rock MSA Design Value Design value and O 3 readings as of 7/25/ Year Figure 2 - Austin-Round Rock MSA 8-hour ozone design value historic trend. As of July 25, 2008, the 4th highest ozone readings for the Audubon and the Murchison monitoring sites were 66 ppb and 71 ppb, respectively. Based on these readings, the design value is at 76 ppb, which exceeds the 2008 NAAQS. This design value is likely to increase as there are potentially more high ozone days that will occur during the remainder of the 2008 ozone season. Based on this projection, the A-RR MSA is at risk for being out of compliance with the ozone NAAQS. To assess ozone generation and transport over a larger area than can be done by ground-based monitoring stations, CAPCOG has contracted with the Baylor Institute of Air Sciences (BIAS) to conduct airborne sampling of ozone under various meteorological scenarios. The results of these airborne flights show that transported emissions often come from heavily polluted upwind areas, many of which are already ozone nonattainment areas. Figure 3 demonstrates the extent to which an urban ozone plume emanating from a large nonattainment area can impact areas far downwind of the source region.

4 Air Quality in the Capital Area (Page 4 of 6) Figure 3 Houston urban ozone plume. Airborne sampling data acquired by Baylor University on September 17, 2007 Modeling The use of computer models to estimate and project future emissions of air pollutants is a key component to providing technical assistance on air quality issues. Because ground-level ozone is formed by the chemical reaction between NOx, VOCs, and sunlight, photochemical models are important tools in ozone air quality planning. Photochemical models have become widely recognized for use in demonstrating compliance with the ozone NAAQS, and for their ability to assess impacts from local emission reduction measures and various control strategies. The Comprehensive Air Quality Model with Extensions (CAMx) photochemical grid model, most commonly used, simulates the physical and chemical processes significant in the formation and transport of ground-level ozone based on meteorological, emissions, landuse, and other geographic inputs. In 2001, CAPCOG s air quality group collaborated with San Antonio, Victoria, Corpus Christi, and TCEQ to develop a multi-day high ozone episode for photochemical modeling. The Austin and San Antonio areas used the episode to analyze the emission reductions from various control strategies being considered in the development of regional planning initiatives. Sensitivity analyses were run using photochemical modeling to evaluate both potential control strategies and potential sources of emissions growth. Figure 4 demonstrates the emission reductions predicted by the vehicle Inspection and Maintenance program. Similar modeling analyses were conducted to investigate the impact from potential and new sources in the locations upwind from Austin-Round Rock MSA. Figure 5 shows potential ozone impacts related to emissions from a proposed coal-fired power plant with meteorological conditions similar to those occurring on September15,

5 Air Quality in the Capital Area (Page 5 of 6) Figure 4 - Difference in predicted daily maximum 8-hour averaged ozone concentrations on September 17 between the 2007 Future Case with no local controls applied but with I&M programs in Travis and Williamson Counties. Figure 5 - Difference in predicted daily maximum ozone concentrations (ground-level) averaged over 8 hours on the 4-km CAMx domain on September 15 between Run 7 (Modified 2007 Future Case) and Run 4 (New Power Plant Only).

6 Air Quality in the Capital Area (Page 6 of 6) In anticipation of the need to demonstrate where the A-RR MSA stands with compliance of the EPA s new ozone standard, CAPCOG and the Alamo Air Council of Governments (AACOG) are working together to develop a preliminary CAMx model to project the region s air quality status in To improve the photochemical modeling from 2001, CAPCOG contracted work with the University of Texas at Austin (UT) to further develop a model for the A-RR MSA that will consider future control measures such as: federal, state, and local controls for non-road, mobile and non-point (area) sources, voluntary controls on local point sources, and the Inspection and Maintenance (I/M) program in Travis and Williamson Counties. The results from this modeling will be available for use to analyze future air quality trends for the region. Regional Planning Strategies Regional air quality planning strategies play an important role in working towards attainment of the ozone NAAQS. Government officials from counties in the A-RR MSA participate in several regional air quality improvement initiatives through their involvement with the Clean Air Coalition (CAC). The CAC is a voluntary, unincorporated association which became linked with CAPCOG by resolution in The CAC consists of elected officials from the A-RR MSA who are representatives of the governmental entities that agreed to participate in the Central Texas 8-hour O3 Flex Agreement (8-O3 Flex). In support of regional planning strategies, the CLEAN AIR Force of Central Texas, a nonprofit organization made up of representatives from local businesses, governments and environmental groups, provides a forum on air quality issues of regional interest and conducts outreach activities to inform the community on air quality alerts and ways to improve air quality. The 8-O3 Flex is the latest in a series of regional initiatives and builds on the region s previous plans: the 1-hour O3 Flex program and the Early Action Compact. The 8-O3 Flex program is a voluntary agreement between local governments within the MSA, the TCEQ, and EPA that allows local governments to implement measures to reduce ozone emissions in order to maintain compliance with the 1997 ozone NAAQS. The emissions reductions measures in the 8-O3 Flex include, but are not limited to: a Regional Web-based Rideshare Matching Program (River Cities Ride Share); Expanded Clean Air Coalition; Ozone Watch and Warning System; Primary Transportation Emission Reduction Measures (TERMS); AirCheck Texas Local Initiative Project (Currently only available in Travis and Williamson Counties); Paving of Unpaved Roads; Maintenance for Growth Offset Measures. Voluntary initiatives, such as those outlined in the 8-O3 Flex, have allowed the region to address ozone problems proactively rather than wait to address them through the prescribed federal nonattainment process. These initiatives have been instrumental in keeping the region in compliance with the 1997 ozone NAAQS. Future Planning Initiatives As we look towards demonstrating compliance with the new federal ozone standard, access to air quality data will continue to be an important asset for the Capital Area. The ability to compile and analyze air quality data has been an effective tool in implementing air quality planning initiatives, and will continue to be utilized by stakeholders, elected officials, and air quality groups in determining compliance with the new ozone NAAQS.