PDS Net Emissions Increase

Joe Lierow asserted that, for particular unit for which utilization would increase due to a a physical or operational change at another unit and where the particular unit would not experience a physical or operational change, you calculate the net emissions increase using past actual and future actual emissions (assuming the 2002 NSR Reform rules do not apply).

I first found this from a policy memo referenced in the Advanced NSR Workshop Volume I book [Sept. 2010; pg. 179; Part 305 - NET EMISSIONS INCREASE--40 CFR 52.21(b)(3); Section 5 - Other Calculations (for modification to existing units); Actual to potential (presumptive approach under 1980 rule)]:

Question 3:

Is the approach of comparing new, allowable emissions to old, actual emissions still appropriate for determining PSD applicability?

Response:

Under the PSD regulations, whether a physical change or change in the method of operation at a source will result in a "net emissions increase" requires a comparison of the "actual emissions" of the source before and after the change. For an existing emissions unit at a source, "actual emissions" before the change equal the average rate in tons per year at which the unit actually emitted the pollutant during the 2-year period (or more representative period) which precedes the change [see 40 CFR 52.21(b)(21)(ii)]. Where the change will affect the normal operations of an existing emissions unit (as in the case of a change which could result in increased use of the unit), "actual emissions" after the change must be assumed to be equal to "potential to emit." [emphasis added] The PSD regulations are quite clear regarding such circumstances [40 CFR 52.21(b)(21)(iv)]:

For any emissions unit that has not yet begun normal operations on the particular date, actual emissions shall equal the potential to emit of the unit on that date.

Where "allowable emissions" are the same as or less than the "potential to emit" for an emissions unit, "allowable emissions" may be used to define the "actual emissions" of that unit after the change. Consequently, for determining PSD applicability, the comparison of prior "actual" versus new "potential" emissions (or "allowable" where appropriate) is the correct methodology to use.

The comparison of prior "actual" to future "potential" emissions is made on a unit-by-unit basis for all emissions units at the source that will be affected by the change. It is done for the emissions unit(s) undergoing the physical change or change in the method of operation and also for any other units at which normal operations could be affected by the change at the source. [emphasis added] This, for example, includes a review for possible emissions increases at process-related emissions units due to a physical change which removed a bottleneck at only one of the units.

1998 EPA Memorandum, pg 3 (4.42.pdf)

But then I found further in the book a section specifically on increased utilization [pg. 194; Section 7]. It references a few policy documents that support Joe's contention. Here's one of the quotes from a relevant policy document:

"...emissions increases should be calculated as the worst case increases that could occur at those existing units [presumably this means the units experiencing a utilization increase] if the new or modified units were to operate at their maximum permitted capacity."