Developing a Framework for Effective Air Quality Management

3.7 Implementation of Air Quality Plans

3.7.9 Special Enforcement Issues Potential to Emit

An important consideration for enforcement agencies is the concept of “potential to emit.” A controlled source will produce a given amount of emissions based upon the emissions produced by the source and the effectiveness of the control equipment applied to that source. If the emissions control system fails, then the emissions from that source can increase by 100 times. Thus, sources are often rated by the potential emissions from that source if it operates twenty-four hours per day with no control equipment. This potential to emit is important because it tells the enforcement agency which sources should be more carefully watched. For example, a large particulate source of 1000 tons per year controlled by a baghouse might have an emission rate of only 10 tons per year. A moderate sized woodworking operation with no controls might also emit 10 tons per year of emissions. On the surface, these two sources might seem to deserve the same attention. However, since there are no controls at the woodworking shop, it is unlikely that the woodworking shop would increase its emissions significantly under any set of circumstances. At the same time, the emissions from the large particulate source could increase by up to 100 times if the controls were not properly managed. The source with the 1000 tons per year potential to emit should be given more attention in order to insure that emissions are kept to a minimum.

Thus, sources are often rated by their potential to emit rather than their actual emissions for purposes of assigning enforcement priorities. Upset Conditions

It is not possible to operate any industrial process without occasional malfunctions. Thus, the concept of upset conditions has become an important aspect of enforcement programs. Businesses are allowed to violate emission limits due to unforeseeable failures (breakdowns) in operating or control equipment if they take certain actions. A breakdown is defined in the Los Angeles air quality agency as “a condition caused by an accidental fire or non-preventable

mechanical or electrical failure.” The typical actions that are required are:

* The breakdown is immediately reported;

* The breakdown is not due to improper operation or maintenance;

* Steps are taken immediately to correct the condition;

* Steps are taken to mitigate emissions to the extent feasible; and

* Equipment is shut down by the end of an operating cycle. Variances

There are cases in which a source is found to be violating permit conditions or emission regulations but can not immediately get into compliance without shutting down and causing economic harm to the region that is greater than the air quality benefit. Most agencies have a process for addressing this type of situation to provide a variance to a rule. The South Coast Air Quality Management District sets forth six requirements for getting a variance.

1. The petitioner for a variance is, or will be, in violation of any rule, regulation, or order of the agency

2. Due to conditions beyond the reasonable control of the petitioner, requiring compliance would result in either: an arbitrary or unreasonable taking of property, or the practical closing and elimination of a lawful business.

3. The closing or taking would be without a corresponding benefit in reducing air contaminants.

4. The applicant for the variance has given consideration to curtailing operations of the source in lieu of obtaining a variance.

5. During the period the variance is in effect, that the applicant will reduce excess emissions to the maximum extent feasible.

6. During the period the variance is in effect, the applicant will monitor or otherwise quantify emission levels from the source, if requested to do so by the district, and report these emission levels to the district pursuant to a schedule established by the district.

There are cases when sources agree to mitigate their emissions impacts by reducing emissions from another source beyond regulatory requirements.

Variances are granted for periods as short as one day and can be extended to several years. In most cases, variances are given in 90 day or one year increments.

During the months of February and March 2002, the SCAQMD granted 16 variances and denied 2. Poor Atmospheric Ventilation

Many cities around the word have special geographical and resulting atmospheric considerations that impact air quality; cities such as Los Angeles, Mexico City, Bogotá, and Santiago, Chile are surrounded by mountains, which inhibit air flow. Under certain atmospheric conditions inversions form resulting in little or no atmospheric ventilation. This means that air pollution levels can become dangerously high very quickly.

In this case, a special enforcement solution that is generally recommended is to restrict the circulations of part of the vehicles fleet and to reduce industrial operations during these critical episodes.

In Santiago, Chile, these kinds of episodes are called pre-emergency or emergency; depending on how bad is the atmospheric situation. An atmospheric and emissions model predicts the air quality of the next day considering all the parameters. The Chilean episode levels are shown in table 3.7.9-1.
3.7.9-1 Chilean Air Quality Episode Levels for Particulate Matter