The Air and Waste Management Association (AWMA) held a conference entitled Guideline on Air Quality Models: Next Generation of Models in Raleigh, NC from October 28 - 30, 2009. During the conference representatives from U.S. EPA's Air Quality Modeling Group (AQMG) announced that they would be releasing new versions of AERMOD preprocessors AERMET and AERSURFACE in the not-too-distant future. AERMOD is U.S. EPA's preferred air dispersion model for evaluating impacts up to 50 kilometers from the source. AERMET is the preprocessor to AERMOD that processes meteorological data for input into AERMOD. Some new features of the updated version of AERMET include the ability to average sub-hourly onsite meteorological data and the use of the station elevation for pressure calculations. In addition, a separate processor to calculate hourly meteorological data from 1-minute Automated Surface Observing System (ASOS) data will be included. AERSURFACE, which is used to calculate micro-meteorological variables from land use patterns, is being updated to allow it to process 2001 National Land Cover Data (NLCD). There also may be the option to incorporate aerial photography data into AERSURFACE for areas in which the 2001 NLCD is not representative of current land use patterns. U.S. EPA also indicated that a release of the AERMOD screening tool AERSCREEN would also be coming soon. AERSCREEN could be used as a screening tool to calculate ambient pollutant concentrations when no meteorological data is available. The screening tool uses a matrix of worst case meteorological conditions in the place of collected meteorological data to calculate ambient concentrations. When released, these updated programs will be available here.

At the same conference, a representative of the National Park Service (NPS) announced that the final 2009 Federal Land Managers Air Quality Related Values Work Group (FLAG) document would be released in the very near future. FLAG is comprised of the NPS, the U.S. Forest Service (USFS), and the U.S. Fish and Wildlife Service (USFWS). The FLAG document outlines procedures to follow when completing an Air Quality Related Values (AQRV) Analysis in Federal Class I air quality areas as part of an air construction permit application. Some key updates contained within the final 2009 FLAG document will be the recommendation to use Method 8 for visibility modeling, the annual average background visibility data instead of 20% best day background visibility, and the 98th percentile values instead of peak predicted values. When the updated FLAG document is released, it will be available here.

Please contact ALL4's Dan Dix at 610.933.5246 x18 (ddix@all4inc.com) should you have any questions about how these modeling program changes could affect future air permitting efforts at your facility.