Technical Support Document

for the Proposed

Ozone NAAQS Regional Impact Analysis

Preliminary Analysis Conducted in Selecting the 

Policy Case for EGU Sources

(Description and Analysis)

EPA Docket number:  EPA-HQ-OAR-2007-0225

July 2007

U.S. Environmental Protection Agency

Office of Air and Radiation

EPA’s current regional strategies such as the NOx SIP Call and Clean
Air Interstate Rule (CAIR) are designed to reduce air pollution that
moves across state boundaries. Existing state and regional strategies
have resulted in substantial reductions of ozone, and further reductions
are projected to take place until 2020 under the current Ozone NAAQS. 
With the Proposed Ozone NAAQS, it is projected that there will be areas
of nonattainment.  To address ozone in these nonattainment areas, EPA
investigated other strategies, such as direct controls, sub-regional
caps, and enhanced energy efficiency.  The baseline and base case (as
explained in Chapter 3 of the Proposed Ozone NAAQS RIA) is the 2006
Final PM NAAQS RIA. 

Current analysis is based solely on ozone season strategies.  Possible
EGU reduction strategies (beyond CAIR/CAMR/CAVR for 2020) are as
following:

Local controls at all non-attainment counties (application of SCR and
SNCR in all coal units above 25MW)

Combination of sub-regional caps (in OTC and MWRPO where most of
nonattainment areas are) and local controls in the nonattainment
counties within CAIR region that are outside of the OTC and MWRPO.

Improved energy efficiency/clean distributed generation based emission
reductions (this is addressed in another TSD titled: Energy Efficiency
Approach to Reducing NOx Emissions for EGU Sources)

High Energy Demand Day strategies: Demand Response and Emissions
controls or performance standards on peaking units (This will be
addressed in the Final Ozone NAAQS RIA)

In order to select an EGU control strategy for the Proposed Ozone NAAQS
RIA to help bring projected nonattainment areas into attainment, EPA
conducted a series of IPM runs with various level of controls and
sub-regional caps with and without reducing the current summer season
CAIR cap (listed in 1 and 2 above). EPA analyzed the results for
emission levels and costs, and for other impacts for a number of
scenarios.  The following list describes the preliminary IPM runs
executed and Table 1 summarizes the results. 

Run 1: Base case, 2006 PM NAAQS RIA Control Strategy Case

Run 2: Applied regional (nested) caps in OTC and MWRPO for the ozone
season only.  Lower regional caps are calculated as a function of
percentage of (50%) the maximum possible reduction (through installation
of SCR and SNCRs in coal units above 25 MW) available from uncontrolled
coal units that were not projected to have previously installed
post-combustion controls in the base case. 

Run 3: Same as Run 2, with corresponding reduction in ozone season CAIR
cap.

Run 4: Same as Run 2, with 75%.

Run 5: Same as Run 4, with corresponding reduction in ozone season CAIR
cap.

Run 6: Same as Run 2, with 100% 

Run 7: Same as Run 6, with corresponding reduction in ozone season CAIR
cap.

Run 8: “Command and control” local controls: Applied SCR and SNCRs
to all uncontrolled coal units at all nonattainment counties. 

Run 9: Same as Run 8, with corresponding reduction in ozone season CAIR
cap.

Table 1 Comparison of Preliminary IPM Runs

Run #	NOx Emissions (Ozone Season, MTons)

(numbers in parentheses are the % change)	Marginal Costs ($/ton)
Incremental Cost (million 1999$)

	OTC	MWRPO	Rest of the CAIR Region	Total Emissions

In CAIR Region	CAIR Region Cap	OTC	MWRPO	Rest of the CAIR	Rest of the
CAIR

(annual)

	1	63	214	168	445	484.5	$0	$0	$0	$1,339	(Total Annualized Cost = $115.5
billion)

2(50%)	58

(-8%)	193

(-10%)	185 (10%)	436	484.5	$1,068	$2,764	$0	$1,014	$11.3

3 (50% w/ lower CAIR)	58

(-8%)	193

(-10%)	185 (10%)	436	437.0	$1,068	$2,764	$0	$1,014	$11.3

4 (75%)	55

(-13%)	177

(-17%)	193 (13%)	425	484.5	$1,877	$4,794	$0	$859	$15.9

5 (75% w/ lower CAIR)	55

(-13%)	177

(-17%)	193 (13%)	425	417.1	$1,748	$4,677	$128	$856	$15.8

6 (100%)	53

(-16%)	168

(-21%)	199 (18%)	420	484.5	$3,631	$7,003	$0	$735	$22.0

7 (100% w/ lower CAIR)	53

(-16%)	161

(-25%)	204 (22%)	418	397.3	$3,595	$6,937	$279	$659	$29.8

8 (local controls)	57

(-10%)	189

(-12%)	189 (13%)	436	484.5	$0	$0	$0	$847	$72.3

9 (local controls w/ lower CAIR)	57

(-10%)	189

(-12%)	189 (13%)	436	443.8	$0	$0	$0	$847	$72.3



                    Figure 1. Comparison of emission levels for the
preliminary IPM runs

An examination of spatial distribution of emissions suggested that 75%
reduction provides the most cost-effective way of reducing emissions at
the targeted nonattainment areas, considering transport, with the most
air quality impacts.  We have combined this scenario with application of
SCR and SNCRs in all uncontrolled coal units in the projected
nonattainment areas within CAIR outside of the OTC and MWRPO regions. 
This scenario has been modeled as the control strategy case in the
Proposed Ozone NAAQS RIA for air quality and economic impacts. 

