GeoInsighter Summer/Fall 2006 Newsletter

"PTE" - AN INCONVENIENT TRUTH

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With apologies to the former Vice President, I decided to appropriate the title of his recent movie to focus attention on an issue that defies easy definition - the dreaded "Potential to Emit" (more commonly referred to within the "in" crowd as "PTE"). And, in an unintended way, the title conveys a connection to the general regulatory rationale for dealing with PTE in the first place, a desire to limit emissions to the atmosphere that, over the long run, could exacerbate global warming.

"Potential to Emit" is a core component of the federal regulatory program that was created to address emissions sources of pollutants to the air - the Clean Air Act (CAA). In certain states, the federal government has delegated authority for regulating and permitting sources under the CAA to the state government. Massachusetts, New Hampshire, and Connecticut have all been granted authority by Region 1 of the United States Environmental Protection Agency (USEPA) to manage the CAA permitting process.

The air permitting process governs operations that could emit pollutants to the air. The pollutants that are most commonly regulated under the CAA for the majority of typical business operations include volatile organic compounds (VOCs) and particulate matter. The CAA specifies several classes of air permits that are generally tied to the quantity of emissions that a facility or operation could theoretically emit. Each category (or level) of permit has associated requirements for record keeping, annual documentation, and possibly the need for emission controls. In general, the associated recordkeeping and possible need for control technologies increases as the theoretical quantity of pollutants for a facility or operation increases. It is this theoretical quantity of pollutants that a facility or operation could generate that has come to be referred to as the "Potential to Emit."  

The "inconvenient truth" about "Potential to Emit" is that it has nothing to do with current facility operations and actual air pollutant emissions from those operations. PTE is a calculation of the theoretical maximum quantity of emissions that could be generated by a certain facility or business. By using a "theoretical maximum" as the basis for a permit, the regulatory community assumed that the business community would then be able to self implement the permit requirements - as long as equipment and process changes were not implemented at a permitted facility, it could be assumed that the operation would not exceed its permitted emission limits.

Therefore, PTE calculations are typically completed assuming that facilities/equipment operate 24 hours per day, 7 days per week, 365 days per year. You and I know that this is rarely the case, but the regulations require that PTE calculations be made using this assumption. For instance, if I have a piece of equipment that is currently being used to manufacture 1 widget per day (and I currently operate my business with one 8-hour shift because that is my current level of business orders), but the equipment has the capacity to produce 10 widgets in a 24-hour day, the PTE calculations will be based upon a production rate of 10 widgets per day. However, I am allowed to consider "rate-limiting" steps in the manufacturing process. If I paint these widgets using an automatic spray booth that can only accommodate 5 widgets per 24-hour day, then I am allowed to base my PTE calculations on this limitation, and, consequently, I would only calculate potential emissions from the widget making equipment using a rate (i.e., throughput) of 5 widgets per day. I am also allowed to consider local government restrictions, such as ordinances that limit "hours of operation."

As you probably realize, the development of PTE calculations is often a very collaborative process between the consultant and the facility operations folks. The more process-specific and equipment-specific information that is available, the "tighter" the PTE calculations become. And, although it is not always readily apparent, there are often "rate-limiting" steps in the manufacturing process that result in production/capacity limitations that can be incorporated into the PTE evaluation. A word of caution, however, these rate limiting steps or factors are typically incorporated as conditions in the air permits and can become a constraint in growing production capacity. To go back to the earlier example, if I get a new paint spray booth that can accommodate 10 widgets per 24-hour day, I may be in violation of my permit limitations if I install and use it.

We have noticed an increase in CAA permit enforcement activities within Massachusetts this year. The revenues that are being generated in associated fines (i.e., tens of thousands of dollars per fine; the CAA allows up to $27,500 per day per violation) may prove a strong motivator for other New England states to take similar actions regarding CAA air permitting requirements. If you are a business that has never really looked at PTE, or are a facility that has an existing permit, it may be wise to revisit PTE, especially if you have recently added new equipment, production lines, or made changes to process chemicals. Complete an evaluation so that you know where you stand with regard to PTE. With regard to CAA permitting requirements, the "Convenient Truth" is that having your house in order and the necessary information available when the state inspectors come knocking is an extremely effective environmental management tool. When it comes to air permitting, "An ounce of prevention is worth a pound of cure!"

Michael J. Webster, P.G., L.S.P.

Jarrod P. Yoder, P.G.

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