By Mary Hauner-Davis, Burns & McDonnell, and Robynn Andracsek, P.E., Burns & McDonnell and contributing editor
|Mary Hauner-Davis, Burns & Robynn Andracsek|
We’ve reached that time of the decade when EPA changes the ozone National Ambient Air Quality Standard (NAAQS). Normally, a change to a NAAQS has substantial impacts on a limited area; however, the proposed new ozone NAAQS would have significant effects to many areas of the country (and we’re not just talking urban areas anymore.)
The current ozone NAAQS is an 8-hour standard of 75 ppb (0.075 ppm) based on a 3-year average. In January of 2010, the EPA issued a proposed new NAAQS for ozone at 60 ppb. In that instance, President Obama cancelled that rulemaking in September 2011 because he “did not support asking state and local governments to begin implementing a new standard that will soon be reconsidered.” Four years later, the revised proposed standard has come back a little less stringent than that proposed in 2010. The current proposal is an ozone limit between 65-70 ppb based on the annual fourth-highest daily maximum 8-hour concentration, averaged over 3 years. (Yes, the statistics really matter.)
Figure 1 shows the areas of the country that would be out of attainment if the NAAQS were set at different levels. The number of rural areas that could be classified as non-attainment is quite dramatic. State officials have stated that they are very concerned about how to write their State Implementation Plans (SIP) because the normal RACT items are not items that are appropriate for rural areas, such as vehicle exhaust testing.
You need to know if you are in an area that is changing to may be nonattainment after the ozone NAAQS is lowered. Ozone is formed in the atmosphere when NOx and VOC react in sunlight. Therefore, ozone is regulated by its precursors (NOx and VOC). If there is ozone NAAQS exceedance, the state agency will figure out if it is NOx or VOC limited and will reduce emissions from either or both sources of these pollutants.
Nonattainment Counties Under Different Ozone Standards
If your plant is in a county that will be changing to nonattainment after the NAAQS is lowered, you may have to reduce emissions as required by the SIP. This could mean add-on NOx or VOC controls for your plant. Further this could affect proposed modification/expansions. The level of nonattainment (marginal, moderate, serious, severe or extreme) determines the emissions threshold that makes your plant major or minor for nonattainment new source review (NNSR) applicability. For example, if you are in an area that is deemed severe nonattainment then any project that has emissions over 25 tons per year of NOx or VOC will be subject to NNSR. Not only does this mean the installation of Lowest Achievable Emission Rate (LAER) (which does not take into account costs like Best Available Control Technology does in attainment areas) but it also means obtaining offsets at a ratio of 1.1 to 1 (marginal) up to 1.30 to 1 (severe). Clearly this will increase the project costs. In the near future, as the new NAAQS is implemented, there will not be many offsets available (generated) so finding these precious emission credits will be just another headache to endure. Similarly, if you are planning to construct a new greenfield power plant, be aware of the areas that switch to nonattainment, so you can avoid NNSR if possible.
The final 2015 ozone NAAQS is expected to be published in October 2015, after which follows several years of implementation. It is unclear if new projects will have to comply with the revised standard before the final designations are made in October 2017. The EPA has stated that in-the-pipeline permit applications might be required to consider project impacts on the 2008 NAAQS but not the 2015 NAAQS but this has not been finalized either. There are lots of uncertainties related to new ozone NAAQS. Plant owners are forewarned to keep a close eye on this rule and its implementations as it will affect a lot of new-to-the-nonattainment-world areas.