Draft Appendix C of the TSD for the rule titled " Regional Haze: Revisions to 

Provisions Governing Alternatives to Source -Specific Best Available Retrofit 

Technology (BART) Determinations, Limited SIP Disapprovals , and Federal 

Implementation Plans" RIN 2060-AR05 

Phil Lorang to: Kymn, Christine J. 11/14/2011 11:47 AM

Cc: Brian Timin, Lea Anderson, Martha Keating, Paula VanLare, Rhea 

Jones

From: Phil Lorang/RTP/USEPA/US

To: "Kymn, Christine J." <Christine_J._Kymn@omb.eop.gov>

Cc: Brian Timin/RTP/USEPA/US@EPA, Lea Anderson/DC/USEPA/US@EPA, Martha 

Keating/RTP/USEPA/US@EPA, Paula VanLare/DC/USEPA/US@EPA, Rhea 

Jones/RTP/USEPA/US@EPA

Phil Lorang, Senior Policy Advisor

Air Quality Policy Division, OAQPS, EPA

919-541-5463
1

APPENDIX C

Sensitivity Analysis Accounting for Proposed Increases in Transport Rule 

Allowances

The Better than BART modeling analysis for this proposed rule was completed using the 

emissions totals from the final Transport Rule, and also assuming that the July 11, 2011 proposal 

regarding ozone-season NOx emissions in five states will be finalized.1 Recently, EPA 

proposed2 to make adjustments to the EGU SO2 and NOx allowances in several states. In all 

cases, the allowances are proposed to be increased. Table C-1 summarizes the proposed 

allowance increases.

Table C-1 Proposed increases in Transport Rule 2014 SO2 and NOx allowances

State 2014 SO2

Budget 

Increase (tons)

2014 NOx 

Budget Increase 

(tons)

Louisiana N/A 4231

Mississippi N/A 2136

Michigan N/A 5228

Nebraska N/A 3559

New Jersey N/A 112

New York 3527 3485

Texas 70067 1375

Wisconsin 7757 2473

Total Increase 81351 22599

The proposed SO2 and NOx allowance increases are relatively modest compared to the total 

modeled reductions from the Transport Rule. The modeled SO2 reductions from the Transport 

Rule are ~3.8 million tons per year and NOx reductions are ~125,000 tons per year. The only 

increase in emissions that is large enough to potentially affect the Better than BART analysis is 

the SO2 allowance increase in Texas. This is due to the relatively large increase in Texas SO2 

compared to other states, and the fact that SO2 emissions account for the majority of the PM2.5 

and visibility impacts from the Transport Rule. Therefore, we completed a more detailed 

sensitivity analysis of the potential impact from the Texas SO2 allowance increase. 

 1 The air quality modeling conducted for this analysis included in the CSAPR scenario the states 

addressed in the July 11 proposal. These states are Iowa, Kansas, Michigan, Nebraska, Minnesota, and 

Oklahoma.

2 Revisions to the Federal Implementation Plans to Reduce Interstate Transport of Fine Particulate Matter 

and Ozone, 76 FR 63860 (October 14, 2011)
2

Table C-2 shows the Texas SO2 emissions as modeled in the Better than BART analysis and the 

emissions that would occur if the allowances are increased as proposed.

Table C-2 Texas 2014 SO2 emissions and decreases compared to the 2014 modeled base 

case

2014 Base Case 

SO2 Emissions

2014 TR+ 

BARTelsewhere SO2 

Emissions

(estimate from 

IPM, used in air 

quality 

modeling)

2014 Proposed 

Allowance 

Increase

SO2 Emissions 

Decrease from 

TR (as modeled)

SO2 Emissions 

Decrease from 

TR with "extra" 

allowances

453,332 266,627 70,067 -186,705 -116,638

Table C-2 shows that the modeled SO2 reduction in Texas is ~186,000 tons per year. After 

accounting for the proposed increase in SO2 allowances in Texas, the SO2 emissions reduction 

is still ~116,000 tons per year. This would reduce the total SO2 reduction from the Transport 

Rule from ~3.8 million tons per year to ~3.7 million tons per year. 

It can be seen from Table C-2 that even with the increase in SO2 allowances in Texas, there is 

still a large SO2 reduction in Texas, compared to the 2014 base case. And, the impact on the 

total net SO2 reduction from the Transport Rule is minimal (< 2% decrease in SO2 reductions).

Given this information, we would still expect major visibility improvements at Class I areas in 

and around Texas from the Transport Rule. However, in order to better inform the process, we 

performed a very conservative sensitivity analysis to provide a limiting upper estimate of the 

worst case impact of increases in Texas SO2 allowances. 

Sensitivity Analysis of Better than BART with Increased Texas SO2 Allowances 

We identified the most likely “affected” Class I areas for Texas and then assumed that these 

areas would get zero benefit from the Transport Rule. Table C-3 shows the 9 Class I areas in and 

near Texas that were identified as the affected areas3. We identified these areas by looking at the 

regional haze analysis conducted by the CENRAP regional planning organization in support of 

the development of regional haze SIPs in Texas and surrounding states. 

 3 Affected Class I areas were identified by examining consultation letters from states surrounding Texas which were 

included in the Texas regional haze SIP submissions. The letters are included in Appendix 4-3 available here: 

http://www.tceq.texas.gov/airquality/sip/bart/haze_appendices.html. We included 6 areas which had a > 2 Mm-1

impact from Texas. These areas had much higher visibility impacts from Texas compared to other analyzed Class I 

areas. We also included the 3 Class I areas that are in Texas or are represented by an IMPROVE monitor that is 

located in Texas.
3

Table C-3 Class I areas most affected by Texas emissions and the modeled visibility 

improvement from the Transport Rule + BART-elsewhere case

Class I Area Name State

TR+BARTelsewhere 

20% Best days

TR+BARTelsewhere 20% 

Worst days

Big Bend NP TX -0.2 -1.1

Caney Creek Wilderness AR -0.4 -3.2

Carlsbad Caverns NP TX -0.1 -0.9

Guadalupe Mountains NP TX -0.1 -0.9

Hercules-Glades Wilderness MO -0.6 -2.5

Salt Creek NM -0.1 -0.7

Upper Buffalo Wilderness AR -0.5 -2.5

White Mountain Wilderness NM -0.1 -0.6

Wichita Mountains OK -0.2 -1.6

For this analysis, we assumed that the visibility benefits shown in Table C-3 would become zero 

as a result of the allowance adjustment for SO2 in Texas. This is a very conservative assumption 

because there would still be 116,000 tons per year of SO2 reductions in Texas and this also 

assumes that there would be no visibility benefits in these 9 Class I areas from the ~3.6 million 

tons of SO2 reductions from the other Transport Rule states. This is not a realistic assumption, 

but one that we use here in order to be conservative. 

Sensitivity Analysis Results

We recalculated the average visibility changes at the 60 Eastern and 140 nationwide Class I areas 

in the Better than BART analysis, assuming that the visibility change at the 9 Class I areas in 

Table C-3 would be zero. The first prong of the Better than BART test would still be passed 

because there will be no degradation in visibility at any Class I areas on either the 20% best or 

20% worst days. Table C-4 below shows the average visibility results and the re-calculated 

average visibility results for the Texas sensitivity case. 

Table C-4 Average visibility improvement on the 20% best and 20% worst days in the Better 

than BART analysis and the Texas sensitivity analysis

“Transport Rule + 

BARTelsewhere”

“Transport Rule + 

BART-elsewhere” 

Texas Sensitivity Case

“Nationwide BART”

60 Class I Areas in the Eastern 

Transport Rule Modeling 

Domain

20 percent Worst Days 1.6 1.3 1.0

20 percent Best Days 0.3 0.3 0.2

140 Class I Areas in the Western 

and Eastern Transport Rule 

Modeling Domains
4

20 percent Worst Days 0.7 0.6 0.5

20 percent Best Days 0.1 0.1 0.1

Table C-4 shows that the even with very conservative assumptions in this analysis, the Transport 

Rule+ BART-elsewhere case is still, on average, better than (or equal to) nationwide BART on 

both the 20% best and 20% worst days at the 60 Eastern Class I areas and at the 140 nationwide 

Class I areas.