By Robynn Andracsek, P.E., Burns & McDonnell and Contributing Editor
How do you know if the air around your facility is “clean”? And what are the consequences if it is not clean enough?
As one of its basic tenets, the Clean Air Act (CAA) directs the U.S. Environmental Protection Agency to establish National Ambient Air Quality Standards (NAAQS) as federal health standards for outdoor air. Ambient air monitors operated by each state measure the actual air quality in each area. These measurements are then compared to the numeric NAAQS limits. The CAA’s goal is for every part of the country to meet these standards. Attaining and sustaining NAAQS compliance is the driver behind the New Source Review, Acid Rain program, emission inventories and almost every other air regulation that applies to a power plant. (Okay, there are a few other regulations that deal with hazardous air pollutants like mercury.)
Of the six criteria pollutants for which EPA has established NAAQS, ground-level ozone is the one with the most non-attainment areas. Ozone is almost entirely a secondary pollutant formed when volatile organic compounds (VOCs) and nitrogen oxides (NOX) react under conditions of high temperatures and direct sunlight. With ozone, it’s all about location: ground-level ozone (smog) can adversely affect human lungs and plant life while upper air ozone protects life from the sun’s harmful rays. However, it sometimes takes a degree in statistics to know if an area is in attainment or not. Compliance with the 8-hour ozone standard is based on the 3-year average of the 4th-highest daily maximum 8-hour ozone reading from each monitor. What’s more, non-attainment is divided into five categories: marginal, moderate, serious, severe and extreme.
Let’s say you are in an ozone non-attainment area. Your state must develop a State Implementation Plan (SIP) to bring the area back into attainment. Since both NOX and VOC are precursors to ozone, the SIP can address one or both. Reducing NOX or VOC emissions to the atmosphere removes the ingredients required for ozone formation. The consequences for a SIP failing to achieve attainment can be stifling as well as costly. If the EPA thinks a SIP is not sufficiently strict, responsive or timely it will impose a Federal Implementation Plan. Sanctions can include loss of federal highway dollars and EPA funds. Worse yet, the area can be reclassified to a worse category of non-attainment. The most common non-attainment classifications (marginal, moderate or serious) put the area at risk for limitations on projects such as new road construction.
One of the biggest concerns to existing power plants is the imposition of Reasonably Available Control Technology (RACT). Here, specific facilities and operating units are identified and required by the SIP to install retrofit controls. This is costly for power plants and other large emitters such as refineries, glass manufacturers and steel mills.
The story doesn’t end once an area achieves attainment. Safeguarding is required to ensure the area doesn’t slip back into non-attainment. Designating an area as being “in attainment” requires that emissions be less than or equal to NAAQS, that a fully approved SIP be in place, that substantial proof exists the air quality has improved due to permanent and enforceable emission reductions and that an EPA-approved “maintenance plan” is in place. Within three years of the redesignation, the state must submit a 10-year maintenance plan detailing plans to preserve the attainment status.
In March 2008, EPA lowered the ground-level ozone standard from 80 parts per billion (ppb) to 75 ppb over an 8-hour period. Based on estimates from 2004 to 2006 data, 345 monitored counties violate the 2008 8-hour ozone standard of 75 ppb. This included 74 counties that were in attainment with the 80 ppb standard. EPA will likely designate areas as non-attainment based on data from 2006 to 2008 or later, which is expected to show improved air quality.
In January 2010, EPA proposed to lower ozone even further, to 60 70 ppb, “to ensure they are clearly grounded in science” since 75 ppb was “not as protective as recommended by EPA’s panel of science advisors.” This is yet another step back from Bush-era EPA policy.
Additionally, EPA is proposing new 1-hour NAAQS for both SO2 and NO2. Adding this 1-hour standard will work against the ability of power plants to recover from short-term emission upsets. EPA is proposing the NO2 1-hour standard at 0.080 to 0.100 ppm and the SO2 1-hour standard at 0.050 to 0.100 ppm.
These proposed changes in NAAQS for ozone, SO2 and NO2 will lead to even more areas designated as non-attainment and even more power plants called to task.
Thanks to Whitney Smith, Burns & McDonnell, for her input to this column.