How To Improve Your Air Quality Analysis Report: Part 1- Report Structure

Having worked in a bureaucracy for 20+ years, there have been many times when I would ask someone, why is this done this way? A lot of the time the answer was,  “I don’t know” or “it’s just done this way because it has always been done this way.” Neither answer would set well with me, so I would look into the topic and try to come up with a better way.

Over the decades I have reviewed quite few air quality analysis (AQA) reports. Nearly all of them had the same format and structure. I asked myself, why are they all about the same? The answer is they all follow the order of items listed in the (TCEQ) guidance document referring to what should be included in the AQA report. To be honest, there has never been a requirement or even a suggestion that the order of the listed items be followed. The order is arbitrary.

Each agency modeler had their own reviewing style and reviewed the required items in a slightly different order from another modeler. Over the years, I discovered a certain order worked better and more efficiently.

Who Is the Audience?

Do you know who the AQA report if for? The agency modeler? The client? The public? Actually, the report is really for the permit reviewer. The permit reviewer is the hub for all information regarding an air quality permit application. The parts of the AQA report the permit reviewer is most interested in are:

  • What is the air quality permit number?
  • Which air contaminants are being evaluated?
  • Did the predicted concentrations demonstrate compliance?
  • What are the predicted concentrations to put into the Technical Review document?

The best way to speed up the review process is to put these item up front and in a prominent location. Once the permit reviewer has this information, the remainder of the application review can be carried out in parallel with the detailed reviewed of the AQA report.

Most importantly, if there is a problem with any of these items, it can be a show stopper. The sooner a vital problem can be found, the sooner it can be fixed. It serves no purpose for the review to go on for days or weeks, only for the whole AQA report and analysis to be completely re-done.

Who Else Reviews the AQA?

The details of the AQA report are reviewed by the dispersion modeling staff and toxicology staff, if air toxics are involved. The order of the details of the analysis will make a difference in the time required to complete the review, particularly if there are any problems, discrepancies, or omissions. The sooner a vital problem can be found, the sooner it can be addressed and fixed.

Global v. Local

The suggestions for the order of all the information that goes into an AQA report are based on the premise that rarely is a report perfect and any errors big enough to throw the whole report out need to be found as quickly as possible. The assumption made is the larger in scope an error is, the more likely it is to terminate the review process. For example, an inconsistent use of a stack exit temperature is an error, but it make not make much of a difference in the overall outcome (demonstration of compliance or not). If a site is located next door to a Class I area, and there is no Class I increment analysis, that omission will stop the review.

The suggestion is to address global issues first and then get more granular throughout the report.

Once you have provided the permit reviewer with the information they need, next provide the information that pertains to the entire AQA.

Where in the World is the Site In Question?

First, provide the information about where the site is located and everything pertinent in the vicinity. This information impacts the following issues:

  • Which Class I areas or other areas of special interest (Air Pollutant Watch List Areas (Texas), schools (Texas), tribal lands) are nearby and require additional analysis to be performed;
  • If you are performing a NAAQS analysis, are there any nonattainment areas that can be impacted
  • If you are performing a NAAQS analysis, which ambient air monitors are representative of where the site is located;
  • What meteorological datasets are representative of where the site is located;
  • Which elevation datasets are appropriate for the modeling domain;
  • Which land use dataset is representative of the modeling domain

Any significant error or omission at this point can end the review process early and quickly.

Explain What You Did

After you have described where the site is and defined the scope of the analysis, describe the methodology and list the tools, and datasets used to perform the analysis.  Tell the modeling reviewer what you did and what you used to arrive at the results and conclusions. As before, if there is a big problem with modeling approach, programs used (AERMOD, ISCST3, CalPUFF, etc.), or datasets (meteorological data), the review can end without agency staff getting into the nitty-gritty details. The details would be invalid.

At this point you are still defining the scope of the analysis. The modeling reviewer should have a good idea of what kind of information was relied upon to perform the analysis but has not seen any of it yet.

List the tools you used and version (dispersion, meteorological, terrain, and building downwash models) and what datasets (meteorological observations, land use datasets, and terrain datasets). If there were any special settings you selected for the various models or if there was any data substitution methodology for missing or questionable data, this is the place to mention and justify. It serves no purpose to show all the data you used first then mention where it came from and how you manipulated it. Describe what you did and used first, then show it all later in the report.

If there is a problem with the appropriateness of the models or the datasets, no time is wasted reviewing invalid information.

Show How You Did It

If all the information presented thus far has passed muster, now is when you start to lay out exactly what you did. Now is when you present all of your input data.

The first, and most important, input data to present is a listing of all the electronic files that contain the input data, e.g. dispersion model, meteorological model, building downwash, etc. input files. Without a listing of these files, the review cannot even start. As a reviewer, I gave up trying to decipher the dozens of cryptic file names I had before me to determine what each file was for. Too many times I assumed one thing only to discover, after several days, that I had used the wrong “encryption key” on the file naming convention. It only take a few minutes to document the files you are submitting to the reviewing agency. It is time well spent.

Next, list and describe the data related to the part of the project that triggered the permitting action. In most cases, the initial scope of the project includes only those sources and operations covered by the immediate permit application under review. If the initial results are below certain thresholds, such as the SILs, the analysis goes not further. If not, then the scope of the project widens. Describe the details of the initial scope first and thoroughly, before you start on the wider scope.

If there are problems with the initial scope of the project, no time is wasted reviewing the larger scope analysis as it may be invalid.

List the sources, buildings, and emission rates evaluated. Describe and justify each input value. Any correction of scaling factors should be mentioned. This is typically the largest portion of the AQA report.


The AQA report structure that has been adopted by applicants has not rhyme or reason. We have suggested an alternative to the status quo that does have a rationale: if something goes wrong, it will save time and effort on the part of the applicant and the regulatory reviewer.

Though most consulting companies have long established templates to compile AQA reports, the initial effort to make changes consistent with the suggestions made will be significant, however, the changes may save a significant amount of time and effort in the long run.

If you found this article informative, there is more helpful and actionable information for you.  Go to to see a list of past webinar mini-courses. Every Wednesday (Webinar Wednesday), NaviKnow is offering FREE webinar mini-courses on topics related to air quality dispersion modeling and air quality permitting. If you want to be on our email list, drop me a line at [email protected].

One of the goals of NaviKnow is to create an air quality professional community to share ideas and helpful hints like those covered in this article. So if you found this article helpful, please share with a colleague.