Technical Support Document (TSD) for
AERMOD-Based Assessments of Long-Range
Transport Impacts for Primary Pollutants
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EPA-454/B-15-003
July 2015
Technical Support Document (TSD) for AERMOD-Based Assessments of Long-Range
Transport Impacts for Primary Pollutants
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Analysis Division
Air Quality Modeling Group
Research Triangle Park, North Carolina
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Preface
This document provides the results and interpretation of AERMOD simulations for typical PSD sources.
The focus of the analysis is to determine the impact of a range of source types on pollutant
concentrations in the near and far field.
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Contents
Preface 4
Contents 5
Tables 6
Figures 7
1. Introduction 8
2. Background 8
3.0 Approach to evaluating near-source and long-range impacts 10
3.1 Source Types and Characteristics 10
3.2 Modeling Assessment of Various Facility Types 11
4. Summary of results 14
4.1 NO2 and SO2 screening 14
4.2 Refined analyses for NO2 and SO2 17
4.3 Refined analyses for PM10 and PM25 20
5. Conclusions 21
6. Additional information 21
References 22
Appendix A 23
Plots from NO2 and SO2 screening analysis 23
Appendix B 34
Plots from NO2 and SO2 refined analysis 34
Appendix C 47
Plots from PM refined analysis 47
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Tables
Table 1 - Significant Impact Levels (SILs) for Criteria Pollutant by Class 1, 2, and 3 Areas 9
Table 2 - PSD Increment for Criteria Pollutants by Class 1, 2, and 3 Areas 10
Table 3 - Summary of Modeling Scenarios by Source Type from AERMOD Implementation Workgroup
(AIWG) 11
Table 4 - Results for Phase 1 screening modeling for NO2 and SO2 by Facility type5 15
Table 5 - Results for Phase 1 screening modeling for NO2 and SO2 by Facility type, continued 16
Table 6 - Summary of NO2 and SO2 emissions for the coal EGU facility 17
Table 7 - Results from the Phase 2 refined analysis for NO2 18
Table 8 - Results from the Phase 2 refined analysis for SO2 19
Table 9 - Summary of 2011 NEI emission data used in refined modeling analysis 20
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Figures
Figure 1 - Location of receptors for screening and refined runs 13
Figure 2 - Results from the screening analysis for the asphalt plant 24
Figure 3 - Results from the screening analysis for the biomass plant 25
Figure 4 - Results from the screening analysis for the cement kiln 26
Figure 5 - Results from the screening analysis for the coal EGU 27
Figure 6 - Results from the screening analysis for the ethanol plant 28
Figure 7 - Results from the screening analysis for the flare 29
Figure 8 - Results from the screening analysis for the fuel oil turbine 30
Figure 9 - Results from the screening analysis for the landfill gas turbine 31
Figure 10 - Results from the screening analysis for the natural gas compressor station 32
Figure 11 - Results from the screening analysis for the pulp and paper plant 33
Figure 12 - Refined NO2 and SO2 results, ASX, max and design values, 1-hr NAAQS 35
Figure 13 - Refined NO2 and SO2 results, DHT, max and design values, 1-hr NAAQS 36
Figure 14 - Refined NO2 and SO2 results, OAK, max and design values, 1-hr NAAQS 37
Figure 15 - Refined NO2 and SO2 results, SMQ, max and design values, 1-hr NAAQS 38
Figure 16 - Refined SO2 results, ASX, 3 & 24-hr increment 39
Figure 17 - Refined SO2 results, DHT, 3 & 24-hr increment 40
Figure 18 - Refined SO2 results, OAK, 3 & 24-hr increment 41
Figure 19 - Refined SO2 results, SMQ 3 & 24-hr increment 42
Figure 20 - Refined NO2 & SO2 results, ASX, annual NAAQS 43
Figure 21 - Refined NO2 & SO2 results, DHT, annual NAAQS 44
Figure 22 - Refined NO2 & SO2 results, OAK, annual NAAQS 45
Figure 23 - Refined NO2 & SO2 results, SMQ, annual NAAQS 46
Figure 24 - Refined PM25 results, ASX, 24-hr annual increment 48
Figure 25 - Refined PM25 results, DHT, 24-hr annual increment 49
Figure 26 - Refined PM25 results, OAK, 24-hr annual increment 50
Figure 27- Refined PM25 results, SMQ, 24-hr annual increment 51
Figure 28 - Refined PM25 results, ASX, 24-hr NAAQS 52
Figure 29 - Refined PM25 results, DHT, 24-hr NAAQS 53
Figure 30 - Refined PM25 results, OAK, 24-hr NAAQS 54
Figure 31 - Refined PM25 results, SMQ, 24-hr NAAQS 55
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1. Introduction
For long-range transport (LRT) applications of distances of more than 50 km from a source, the proposed
revisions to EPA's Guideline on Air Quality Models (published as Appendix W to 40 CFR Part 51) include
recommendations of a screening approach for addressing PSD increment and removal of CALPUFF as an
EPA preferred model for such applications. While there is no proposed replacement refined model =for
LRT applications under Appendix W, the information provided in this report indicates that the need for
LTR assessments for NAAQS and PSD increment violations for inert pollutants is rare thereby mitigating
the necessity for a preferred model for regulatory LRT assessments. This document provides technical
details of an EPA modeling assessment that supports this proposed change, including summarizing the
model scenarios and approach used to determine the impact of a range of source types on pollutant
concentrations in the near and far field.
2. Background
The permitting process for the Preventions of Significant Deterioration Program (PSD) requires that a
new or modifying source demonstrate that the additional emissions will not cause or contribute to a
violation of the NAAQS or PSD increment. The traditional approach for demonstrating compliance is a
multi-step process. As described in Section 9 of the proposed version of Appendix W, this two-stage
process entails:
1. Conduct a single-source impact analysis where only the new or modifying source is considered
in the analysis. The new or modifying source will model its own emissions to determine the
appropriate impacts for each applicable pollutant and each averaging time. The predicted
impacts from the single source are compared to the Significant Impact Level (SIL) for each
averaging time and pollutant.
a. If all single source impacts are less than the SIL, then the new or modifying source is
generally not expected to cause or contribute to a violation of a NAAQS or PSD
increment and the compliance demonstration is considered complete.
b. If the single source impacts are greater than the SIL anywhere, then there is a chance
that the source will cause or contribute to a violation of a NAAQS or PSD increment and
then a cumulative impact analysis should be undertaken.
2. The cumulative impact analysis takes into account all sources affecting the air quality in an area
including the project source impact and consideration of background, which includes
contributions from natural, nearby, and unknown sources. The cumulative modeling
demonstrations for NAAQS and PSD increment are different:
a. For a NAAQS compliance demonstration, the emissions from the new or modifying
source must be added to the background concentrations and the resulting "design
concentration(s)" are compared to the specific NAAQS to determine compliance. When
modeled violations are evident, the contribution from the new or modifying source to
the modeled violations can be compared to the SIL to determine if the source is causing
or contributing to the modeled violation(s).
b. For a PSD increment compliance demonstration, the total increase in concentrations
from all permitted sources is compared to the 'baseline' concentration. The total
increase in concentrations is not allowed to be greater than the applicable PSD
increment.
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As indicated above, the SIL is used as demonstration tool to determine the culpability of a new or
modifying source to any NAAQS or PSD increment violations. Table 1 shows the SIL levels for PM2.5,
PM10, SO2, NO2, and CO, while Table 2 shows the PSD increment levels of fine particulate matter
(PM2.5), coarse particulate matter (PM10), sulfur dioxide (SO2), and nitrogen dioxide (NO2). In 1996, a
rulemaking was proposed with Class I specific SILs for NO2 (annual: 0.1 ug/m3), SO2 (annual: 0.1 ug/m3,
24-hr: 0.2 ug/m3, 3-hr 1.0 ug/m3) and PM10 (annual: 0.2 ug/m3, 24-hr: 0.3 ug/m3) (U. S. EPA, 1996).
While this rule never went final, such that these Class I SILs have never been promulgated, it is our
understanding that they have been used in practice by some states and regions for a screening analysis
to eliminate the need for increment analysis are longer transport distances.
Pollutant
Class 1
Class 2
Class 3
Source
Fine Particulate Matter (PM2.5)
Annual mean
24-hr maximum
0.061
0.07
0.3
1.2
0.3
1.2
40CFR51.165(b)(2)
Particulate Matter (PMio)
Annual arithmetic mean
24-hr maximum
*
*
1
5
*
*
Carbon Monoxide (CO):
8-hr maximum
1-hr maximum
*
*
500
2000
*
*
40 CFR 52.21 (k)(2)
40CFR51.165(b)(2)
Sulfur Dioxide (SO2)
Annual mean
24-hr maximum
3-hr maximum
1-hr maximum
*
*
*
*
1
5
25
3 ppb (~7.8 ug/m3)
*
*
*
*
40CFR51.165(b)(2)
(U. S. EPA, 2010b)
Nitrogen Dioxide (NO2):
Annual mean
1-hr maximum
*
*
1
4 ppb (~7.5 ug/m3)
*
*
40CFR51.165(b)(2)
(U. S. EPA, 2010a)
Table 1 - Significant Impact Levels (SILs) for Criteria Pollutant by Class 1, 2, and 3 Areas.
For most PSD compliance demonstrations, the near-source impacts (e.g., those occurring within 50 km
of the new or modifying source) are the controlling factor in successfully meeting Clean Air Act
requirements. For the inert criteria pollutants, these near-source impacts are assessed with the EPA's
preferred dispersion model, AERMOD (Cimorelli, et al, 2005). Due to variations in meteorology that is
expected to occur beyond 50 km and the time required for a plume to travel this distance, steady-state
plume models like AERMOD are expected to be overly conservative in the far-field. Thus, when long
range transport (LRT) is expected to be important (i.e., impacts beyond the nominal distance of 50 km),
1 The annual and 24-hr Class I SILs were remanded and vacated by request from the EPA in January 22, 2013. These
values are currently under review and the EPA is developing a proposed rule to update the PM25 SILs. See the
PM25 modeling guidance for more discussion on this issue (U. S. EPA, 2014).
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an alternative model is necessary for assessing impacts for those distances with the current Appendix W
recommending the use of the CALPUFF modeling system (U. S. EPA, 2003). Section 6.2.3 of the current
version of Appendix W, published in 2005, discusses the regulatory needs for LRT impact assessments.
The focus in section 6.2.3 is the need to protect Class I areas and in particular, Class I PSD increments are
identified as the most stringent regulatory benchmarks in the PSD program. While refined LRT modeling
could also be needed for NAAQS, it is uncommon that a facility can demonstrate compliance for a
NAAQS and not also comply with applicable PSD increment(s).
Pollutant
Class 1
Class 2
Class 3
Fine Paniculate Matter (PM2.5)
Annual mean
24-hr maximum
l
2
4
9
8
18
Particulate Matter (PMio)
Annual arithmetic mean
24-hr maximum
4
8
17
30
34
60
Sulfur Dioxide (SO2)
Annual mean
24-hr maximum
3-hr maximum
2
5
25
20
91
512
40
182
700
Nitrogen Dioxide (NO2):
Annual mean
1-hr maximum
2.5
NA
25
NA
50
NA
Table 2 - PSD Increment for Criteria Pollutants by Class 1, 2, and 3 Areas.
3.0 Approach to evaluating near-source and long-range impacts
In order to assess the nature of long range transport aspects of a PSD compliance demonstration, a
variety of facility types were modeled across several inert criteria pollutants for a range of meteorology
conditions to improve our understanding of the source impacts in the near-field (i.e., within 50 km) and
far-field (beyond 50 km).
3.1 Source Types and Characteristics
Table 3 provides a summary of the source types that were included in a modeling study conducted by
EPA state agencies under the AERMOD Implementation Workgroup (AIWG). In 2011, EPA re-instituted
the AIWG with a focus on the new 1-hour NO2 and SO2 NAAQS. The purpose of the workgroup was to
provide insights into challenges being brought forward by stakeholders regarding modeling as part of
compliance demonstrations for the new standards (Snyder & Thurman, 2012). The workgroup focused
on modeling of "real world" examples utilizing existing and newly formed guidance for the NO2 (U. S.
EPA, 2010a) and SO2 NAAQS (U. S. EPA, 2010b). The AIWG workgroup was composed of EPA staff from
the Regional offices and the Office of Air Quality Planning and Standards (OAQPS) as well as modelers
from state, territorial, and local air quality agencies. The workgroup compiled a list of source types or
facilities that were of interest to various state and local agencies.
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For each modeled facility, emissions and source characteristics were based on actual facilities from past
permitting experiences but were modified to be generic facilities. AIWG participants conducted several
modeling scenarios across multiple regions of the country that reflected changes stack height, addition
of controls, and modifications of facility boundaries reflecting changes in ambient air. Also for NO2
sources, the modeling scenarios involved comparing the use of available Tier 3 methods under Appendix
W: Plume Volume Molar Ratio Method (PVMRM) and Ozone Limiting Method (OLM). For complete
details of the AIWG modeling study and results, the full report is available
at:http://www.epa.gov/ttn/scram/10thmodconf/review material/AIWG Summary.pdf and
http://www.epa.gov/ttn/scram/10thmodconf/review material/AIWG Summary v2.pdf.
Table 3 - Summary of Modeling Scenarios by Source Type from AERMOD Implementation Workgroup
(AIWG)
Pulp & paper plant
Base emission (tpy)
NO2/SO2
Stack heights (m)2
Fuel oil turbine
Landfill gas turbine
NG compressor
104/6083
1184/417
80/45
90/0.01
9657/3403
25, 25, 25, 253, 253, 253, 251, 61, 61, 61
13,13,13,10
11, 11, 11, 11, 53
30, 30 ,29, 85, 85, 72, 72, 76, 8, 67, 67
3.2 Modeling Assessment of Various Facility Types
The goal of this modeling assessment is to determine what types of facilities may have significant
impacts, as defined as modeled concentrations above the SIL, at distances greater than 50 km from the
source. There are fundamentally 4 parameters that affect this result: 1) the source configuration (e.g.,
stack height), 2) the emission rate, 3) the meteorology in the geographic area, and 4) the terrain in the
geographic area. The source configurations and meteorology are closely tied when determining
maximum impacts from a facility. These two aspects of a modeling compliance demonstration under
PSD are more constrained than the possible range of emissions. Any facility, whatever source
configuration and meteorology, can have significant impacts at any distance if the emissions are high
2 Primary stacks for NO2, for SO2, for both
3 NO2 only, no SO2 emissions at this stack height.
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enough. Thus, it is essential to have emissions that reflect reality with respect to the facility type, which
makes the AIWG modeling scenarios ideal for this evaluation.
Each original AIWG scenario was evaluated with a limited number of meteorological scenarios, which
generally originated in the vicinity of the physical location of the facility that the scenario was based
upon. However, to expand the usefulness of these scenarios for the purposes of this assessment and to
more efficiently evaluate maximum potential impacts, a three-phased analysis of was used here:
1. In the first phase, screening meteorology, generated by the MAKEMET tool included in
AERSCREEN (U. S. EPA, 2011), was used to evaluate a source's maximum 1-hour concentration
impacts that could occur across these "worst-case" meteorological datasets. The screening
meteorology includes conditions ranging from low wind & high stability cases, which would give
highest concentrations for near-surface releases, to high wind and highly unstable conditions,
which would give the highest concentrations for elevated release, with tall stacks. In addition to
using screening meteorology, this initial phase used the SCREEN option in AERMOD, which
determines plume centerline concentrations, regardless of the wind direction and
source/receptor spatial relationships. When using this option with multiple sources in a single
AERMOD run, the estimated concentrations are biased to be higher because each receptor will
see the plume centerline from each source, which generally could not occur regardless of the
wind direction. For these model simulations, receptors were placed at distances ranging from
100 m to 60 km. Multiple receptor heights were used in order to evaluate the potential
presence of terrain downwind, with receptor heights including 0, 25, 65, 100, 150, and 200 m
(Figure 1). Due to the plume centerline option being used, only a single receptor at each
distance and height was required. Thus, the results from this initial phase represent an
extremely conservative estimate of plume impacts. If the results from a facility showed impacts
less than the SIL under this initial phase, then it is not expected for it to have impacts greater
than the SIL for a refined single-source analysis.
2. The second phase of more refined modeling was pursued for those facilities whose predicted
impacts from the first phase were above the SIL at 50 km. For this phase, AERMOD's CO SCREEN
option was not used and several sets of actual meteorology were used instead of screening
meteorology. One set of the actual meteorology selected was known to cause higher
concentrations in surface releases, while one was known to cause higher concentrations with
elevated releases. Additional meteorological data sets were used to provide more complete and
robust findings. Since the plume centerline concentrations were not calculated in this phase, a
polar receptor grid was used with 1-degree radial spacing through 360 degrees. Receptor
distances and heights matched those from phase 1. For this second phase, we calculated 1-hour,
3-hour, 24-hour and annual concentrations to compare to the SILs for various averaging periods.
3. The third phase was pursued if results from the second phase still indicated impacts above the
SIL at 50 km, wherein the facilities were evaluated against the relevant NAAQS for each
averaging period. If the facility's impact was above the NAAQS in the near field, then the
emissions were scaled down such that the source's impact satisfied the NAAQS in the near-field
and its impacts at 50 km and beyond were evaluated and compared to the SIL for the
appropriate averaging periods. This phase was based off the modeling in phase 2 by linearly
scaling concentrations rather than scaling emissions and rerunning model simulations.
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60000
-60000
Receptor locations
-60000 -30000 0 30000
Distance from center, m
60000
200
150'
,100'
(L>
X
50
4.
Receptor locations
-•—o—•
-•—o—•
-B-
0 _ 20000 40000 60000
Distance from center along each radial, m
Figure 1 - Location of receptors for screening and refined runs/
4 Panel A shows the x and y locations, with refined receptors colored in black and screening receptors in red. Panel
B shows the x and z locations for all receptors along any x/y radial.
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The AIWG scenarios included NO2 and SO2 emissions only, with NO2 using full conversion. However,
PSD increments exist for CO, PM10, and PM2.5. Since CO air quality levels and emissions are currently so
low, this pollutant is rarely an issue in PSD permitting and therefore were not evaluated in this
assessment. However, PM10 and PM2.5 are necessary to include in this assessment and evaluated along
with NO2 and SO2. Since PM emissions were not included in the original AIWG scenarios, an analysis of
the EPA's 2011 National Emissions Inventory (NEI,
http://www.epa.gov/ttn/chief/net/2011inventory.html) was conducted to determine scaling factors for
PM emissions, based on the NO2 and SO2 emissions for a particular facility type. Additional details on
this analysis are provided in the next section.
4. Summary of results
4.1 NO2 and SO2 screening
The first phase of screening analysis was conducted for NO2 and SO2 only. The results are summarized
in Table 4 and Table 5 and in multiple figures are provided in Appendix A. For these screening runs, the
maximum concentration for both NO2 and SO2 at each receptor was recorded. In addition, the 8th high
1-hour concentration for NO2 and the 4th high 1-hour concentration for SO2 were also recorded at each
receptor. The 8th and 4th high 1-hour concentrations are the concentrations typically used for
determining compliance in a refined cumulative modeling analysis. While results are conservative given
the plume centerline concentrations calculated in the screening analysis, they give some sense of the
distribution of the highest concentrations and provide valuable perspective on the maximum
concentrations.
Several of the facility impacts were below their respective 1-hour SILs at the 50 km distance. The flare
was below the SIL for NO2 and the asphalt plant and biomass burning plant were below the SIL for SO2.
The landfill gas turbine and natural gas (NG) compressor were below the SIL at 50 km for both NO2 and
SO2. Several other facilities were very close to the SIL at 50 km or had some receptors above and some
below the SIL, depending on the receptor height. Only the NG compressor was compliant with any
NAAQS, which has negligible SO2 emissions. While several facilities were close to the NAAQS, most were
orders of magnitude higher than the NAAQS for both the highest concentration and the associated ranks
concentration.
The focus of the evaluation here is to determine if source impacts are above the SILs at 50 km. However,
as noted in Table 4 and Table 5, most of the facilities are fairly close to the applicable SILs at 50 km but
well above the NAAQS in the near field. While the analysis of the SILs at 50 km is largely within the
context of the PSD increment, an analysis of PSD increment would be completed in conjunction with an
analysis of NAAQS. Thus, it is reasonable to assume that NAAQS compliance in the near field would need
to be met before considering the source impacts at 50 km and comparing to the applicable SIL,
particularly if the concentrations in the near field are orders of magnitude above the NAAQS (i.e.., the
NAAQS is the controlling standard). When the emissions from these facilities are scaled back to meet the
NAAQS in the near field, the impacts from most of the facilities at 50 km fall well below the applicable
SILs. For example, for the fuel oil turbine, the equivalent of the design value from the screening runs for
NO2 (the 8th maximum 1-hr average) was 1115 ppb (not shown), while the standard is 100 ppb and the
maximum impact at 50 km was 12.5 ppb. The emissions would need to be reduced by a factor of 11 to
pass a NAAQS demonstration. This reduction would also apply to the impact at 50 km, resulting in an
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Table 4 - Results for Phase 1 screening modeling for NO2 and SO2 by Facility type5
Facility
Asphalt
plant
Biomass
Cement
kiln
Coal
EGU
Ethanol
plant
Receptor
Elevation
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
NO2 NAAQS (impacts in ppb)
Maximum 1-
hour impact
291.0
856.8
884.7
408.3
181.1
129.8
17.5
17.7
548.5
899.4
534.6
243.7
148.7
149.1
150.4
152.2
1468.9
6771.0
232.8
970.7
434.3
222.1
517.2
1572.6
391.4
811.9
1735.2
1746.1
1871.6
1109.3
Impact at 50 km
(SIL4ppb)
5.7
6.2
4.4
2.3
1.6
1.4
1.0
1.0
1.7
5.5
2.8
1.5
12.6
12.7
12.7
12.7
12.7
21.7
5.0
6.0
3.8
3.8
3.8
6.1
6.4
6.4
7.4
15.6
13.7
6.0
SO2 NAAQS (impacts in ppb)
Maximum 1-
hour impact
96.1
115.4
50.0
49.7
49.3
49.0
11.2
11.3
351.4
576.2
342.5
156.1
60.8
61.0
61.5
62.2
567.6
2397.5
74.8
74.9
75.8
77.3
1328.8
4388.2
32.2
175.6
1091.4
1223.5
1311.5
777.3
Impact at 50 km
(SILSppb)
0.7
0.7
0.2
0.2
0.1
0.1
0.7
0.7
1.1
3.5
1.8
1.0
5.2
5.2
5.2
5.2
5.2
8.8
6.9
6.9
6.9
6.9
6.9
16.7
3.0
3.0
4.7
11.0
9.6
4.2
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Table 5 - Results for Phase 1 screening modeling for NO2 and SO2 by Facility type, continued5
Facility
Flare
Fuel oil
turbine
Landfill gas
turbine
NG
compressor
Pulp&
paper plant
Receptor
Elevation
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
NO2 NAAQS (impacts in ppb)
Maximum 1-
hour impact
4.0
17.2
95.8
132.3
150.8
90.2
78.3
212.4
770.3
808.5
1126.0
907.9
28.1
110.5
230.5
174.0
75.5
42.4
92.6
835.8
351.9
181.9
59.9
43.1
303.0
290.6
815.1
9733.0
10313.8
8546.9
Impact at 50 km
(SIL4ppb)
0.3
0.3
0.7
1.5
1.2
0.6
3.2
3.2
5.8
10.8
12.5
7.4
1.0
1.1
1.9
1.1
0.5
0.4
3.2
3.7
1.8
1.2
1.0
1.0
26.7
26.8
26.8
43.7
85.8
65.6
SO2 NAAQS (impacts in ppb)
Maximum 1-
hour impact
207.2
897.8
5014.2
6924.3
7888.0
4718.9
22.0
64.1
275.6
231.8
403.9
325.1
13.0
65.7
136.9
104.0
45.1
25.3
0.0
0.1
0.1
0.0
0.0
0.0
452.9
603.3
3438.1
2718.0
2542.2
2235.4
Impact at 50 km
(SILSppb)
16.4
16.4
37.7
77.3
60.9
29.9
0.9
0.9
1.4
3.5
4.5
2.7
0.4
0.5
1.0
0.6
0.3
0.2
0.0
0.0
0.0
0.0
0.0
0.0
11.3
11.3
18.0
12.0
21.8
18.4
5 The screening runs have several layers of conservatism built into them. Firstly, the screening meteorology is
designed to pick the meteorology that will result in the worst case concentrations for any facility configuration.
Secondly, plume centerline concentrations have been calculated, giving the highest concentration possible from
along a cross section of a plume. Thirdly, the plume centerline concentrations are occurring for each source
simultaneously. While there is some physical possibility of the worse-case met occurring and directing a plume
such that a receptor is along the plume centerline, the third case is generally not possible.
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impact of 1.4 ppb at 50 km, which is well below the SIL of 4 ppb. The pattern that emerges from this
adjustment to emissions indicates that facilities with emissions from the taller stacks (e.g., the cement
kiln and the coal EGU) are the only ones that still have some impacts above the applicable SIL at 50 km.
Facilities with the lower release points have their maximum impacts in close proximity to the fence line
so their impacts at 50 km are much lower after the adjustment to meet the NAAQS. Facilities with
emissions concentrated at tall stacks do not see their maximum impacts until much farther downwind
because the plumes need more time to impact the surface. Of course, this pattern is significantly
influenced by including receptors that are close to stack height. When looking at only the elevated
receptors, the emissions scaling necessitated to bring the elevated receptors to NAAQS levels replicates
the pattern of maximum near field impacts for facilities with lower release heights.
The findings from the screening results is that most types of facilities in most terrain will have their
maximum impacts relatively close to the source. When the emissions from these facilities are adjusted
to meet the NAAQS, the far-field impacts are unequivocally less than the SIL such that no assessment of
LRT would be necessary. While terrain is a complicating factor, the results also show that the only facility
type that could pass a NAAQS assessment in the near-field but still have impacts above the applicable
SIL at distances of 50 km or greater are those with very tall stacks.
4.2 Refined analyses for NO2 and SO2
Based on the findings from the initial screening analysis, the second phase of refined modeling, which
uses 5 years of actual meteorology and computes NAAQS and increment appropriate modeled design
values, focuses solely on those facility types with tall stacks. Both the coal EGU and the cement kiln fit
this profile, but we focused only on the coal EGU because its SO2 emissions were concentrated at the
tallest stack and its NO2 emissions were distributed to the two tallest stacks (150 m and 100 m stack
heights), thereby providing the most insightful test case for refined modeling. Table 6 shows the specific
emissions for each stack at the coal EGU scenario for NO2 and SO2.
Table 6 - Summary of NO2 and SO2 emissions for the coal EGU facility
Stack height (m
NO2 emissions (tpy)
SO2 emissions (tpy)
For the refined modeling analysis, we used four meteorological datasets consisting of 5 years of
meteorological data from 2006 to 2010, reflecting National Weather Service (NWS) stations located at
JFK airport in Ashland, Wl (ASX), Somerset airport in Somerville, NJ (SMQ), Dalhart airport in Dalhart, TX
(DHT), and Oakland airport in Oakland, CA (OAK). These datasets were selected based on prior usage of
a large set of meteorological datasets regularly used by the EPA and are known to represent a range of
meteorological conditions. These data sets also provide spatial variability in the refined modeling
analyses. The airports are all ASOS sites, with 1-minute observations processed through AERMINUTE and
AERMET using the beta u* adjustment option (U. S. EPA, 2014). The maximum 1-hour concentration (5-
year average), NAAQS specific design value (5-year average of 98th percentile and 99th percentile daily 1-
1564
4867
174
87
104
4.3
10.4
.7
10.4
.3
' The 150 m stack is above GEP height, but was modeled at this height anyway.
17
-------
hour maximum concentrations), annual average (5-year average of each annual average), and 24-hour
and 3-hour increment levels (highest first and second values) for SO2. As noted above, a polar grid was
used with 1-degree separation and 360 degrees (receptor distances and heights matched those used in
the screening analysis).
Table 7 - Results from the Phase 2 refined analysis for NO2
Met
scenario
Receptor
Elevation
Maximum 1-hr impact
(ppb, 1st high)
All receptors
50km(SIL4ppb)
98th percentile 1-hr impact
(ppb, 8th high)
All receptors
50km(SIL4ppb)
ASX
DHT
SMQ
25
65
100
150
200
25
65
100
150
200
25
65
100
150
200
25
65
100
150
200
546.81
505.18
373.36
301.35
311.18
286.22
357.80
340.30
269.71
216.93
199.68
239.83
417.98
397.27
312.91
250.09
245.54
212.50
443.30
425.08
302.98
243.67
253.43
250.14
1.50
1.66
1.34
1.27
1.39
1.60
1.38
1.45
1.32
1.28
1.35
1.50
1.62
1.75
1.53
1.52
1.56
1.91
1.15
1.22
1.20
1.09
1.19
1.32
366.15
344.43
270.46
217.27
217.01
191.64
235.82
210.89
129.94
118.30
128.86
127.65
318.30
302.32
239.16
191.94
146.20
138.62
344.51
370.58
227.72
183.29
189.48
184.82
0.94
1.04
0.97
0.85
0.99
1.15
0.75
0.76
0.77
0.73
0.80
0.96
1.16
1.17
1.15
1.12
1.14
1.19
0.72
0.81
0.81
0.72
0.94
1.08
Plots summarizing the refined modeling analysis for NO2 and SO2 are presented in Appendix B and the
results are summarized in Table 7 and Table 8. The most striking difference from the screening and
refined analysis is the decrease in the maximum 1-hour values. For NO2, the maximum from the
screening (with unsealed emissions) was 1572 ppb, while the maximum from the refined runs was
around 546 ppb (again, with unsealed emissions). For SO2, the maximum concentrations decrease even
18
-------
Table 8 - Results from the Phase 2 refined analysis for SO2
Met
scenario
Receptor
Elevation
Maximum 1-hr impact
(ppb, 1st high)
All receptors 50 km (SIL 4 ppb)
99th percentile 1-hr impact
(ppb, 4th high)
All receptors 50 km (SIL 4 ppb)
ASX
DHT
OAK
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
0
25
65
100
150
200
23.65
23.69
24.08
34.60
68.70
262.24
23.39
23.60
23.97
49.53
87.43
652.11
28.98
29.01
29.23
43.59
82.33
394.67
25.57
25.63
25.75
34.85
49.22
177.58
2.58
2.57
2.57
2.56
2.56
3.20
2.47
2.46
2.46
2.46
2.46
3.15
3.01
2.99
2.97
2.96
2.95
4.04
2.08
2.07
2.06
2.05
2.04
2.40
14.22
14.31
14.68
24.57
57.76
200.78
12.04
12.07
12.40
42.82
53.61
454.48
21.36
21.52
21.75
28.06
67.46
329.24
16.24
16.35
16.47
24.03
38.58
139.80
1.98
1.97
1.96
1.95
1.95
2.47
1.81
1.80
1.78
1.77
1.76
2.28
2.65
2.64
2.63
2.63
2.62
2.97
1.63
1.63
1.62
1.62
1.62
2.12
further from 4388 ppb to 454 ppb. For NO2, the maximum 1-hour concentrations at 50 km from the
refined modeling (with unsealed emissions) are now well below the 1-hour SIL at X to Y. However, the
SO2 concentrations are still above the SIL at 50 km with the unsealed emissions, ranging from F to G. If
the SO2 emissions are scaled such that the near-field results meet the NAAQS, then the impact at 50 km
are below the 1-hour SIL at W to V. However, the maximum impacts in the near-field for SO2 are driven
by results at the 150 and 200 m receptors, i.e., elevated receptors reflective of terrain features in vicinity
of the facility. The elevated receptors were included to evaluate the potential impacts of terrain on the
modeling results. However, realistically, a facility with a 150 m stack with large emissions is not likely to
be built in the immediate vicinity of terrain near or above stack height, as the facility would not be able
to pass a NAAQS compliance demonstration. Thus, it is somewhat unrealistic to consider these elevated
receptors at the closest distances. If these elevated receptors are not considered in the near-field, then
19
-------
the EGU would pass the NAAQS in the near-field, but be above the SIL in the far-field. Thus, the near-
field concentrations would not indicate a NAAQS violation because there would be no receptors near
stack height and that a source of this type could indeed have significant impacts at 50 km or greater and
need an LRT assessment. For the other averaging times, the maximum concentrations or estimated
increment contributions are well below the SILs and increments at 50 km, even with the unsealed
emissions. If emissions were scaled to pass the 1-hour NAAQS, then the concentrations at 50 km for the
other averaging periods would be even farther below the benchmarks being considered here. In general,
these results show that the longer the averaging period, the less likely that there will be significant
impacts at distances of 50 km and greater.
4.3 Refined analyses for PM10 and PM25
Since the AIWG facilities did not include PM10 or PM2.5 emissions, we derived these emissions by
scaling from the emission rates for SO2 and NO2 based on emission ratios of these pollutants for EGUs
listed in the NEI. The ratios of PM10 and PM2.5 emissions to NOx emissions for all EGUs with NOx
emissions greater than 40 tons were calculated. Similarly, emission ratios were computed for EGUs with
SO2 emissions greater than 40 tons. PM emissions were significantly lower than NOx and SO2 emissions.
The results are summarized in Table 7. On average, the PM10 emissions were about 22% of NOx and
SO2 emissions, while PM2.5 emissions were around 19% of NOx and SO2 emissions. The facilities with
the greatest PM10 and PM2.5 emission ratios resulted in PM10 and PM2.5 being 50% of NOx and 38% of
SO2. Given how close PM10 and PM2.5 emission ratios were, this assessment focused on PM2.5
emissions only, as the PM2.5 standard are more stringent than the PM10 standards. Since both PM10
and PM25 would be modeled as inter pollutants, the model would treat each pollutant equally with
respect to dispersion, so modeling both PM10 and PM25 with the approximately the same emission
rates would result in roughly the same modeled concentrations. The average emission ratios (20%) were
used to scale the PM emissions for the PM analysis.
Table 9 - Summary of 2011 NEI emission data used in refined modeling analysis
NOx ratios
PMlOmax
8.0%
PMlOmin
49.4%
PMlOmean
22.9%
PM25 max
4.8%
PM25 min
49.2%
PM25 mean
19.5%
SO2 ratios
PMlOmax
3.1%
PMlOmin
37.7%
PMlOmean
22.6%
PM25 max
2.7%
PM25 min
37.6%
PM25 mean
18.7%
Plots summarizing the refined modeling analyses for PM2.5 are presented in Appendix C. The results
from the annual average are well below the annual SILs at 50 km. For the 24-hour concentrations, it is
difficult to draw specific conclusions from the results, given the uncertainty in the applicable SIL. The
maximum concentrations are certainly well below the increment and below some of the 24-hr Class I
SILs that are available. For the NO2-scaled emissions, the NAAQS near-field concentrations are slightly
above the NAAQS (16 ug/m3) and right at the lowest PM25 SIL option. The SO2-scaled emissions have
slightly higher maximum impacts (20 ug/m3) but are in between the two lowest PM25 SIL options. For
the NO2 case, when emissions are scaled down to meet the NAAQS, the 50 km impacts become solidly
below the SIL, while the SO2 50 km impacts are still higher than the lowest PM25 SIL option.
20
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5. Conclusions
The results from this analysis indicate that for most facility types, if the facility can confirm compliance
with the short-term standards in the near-field, then there are not likely to be significant impacts at 50
km. Thus, for most facilities that show compliance in the near-field, no evaluation of LRT would be
needed. There are indications, however, that for a select class of facilities, mainly those that have very
tall stacks (greater than 100 m), there is a possibility of having an impact that is significant with respect
to the short-term NO2, SO2 and PM25 SILs. These types of facilities have their maximum impact much
farther from the facility than most, which means a higher emissions rate would be acceptable. The
results also indicate that terrain features can be important for these types of facilities, as elevated
terrain, near stack height, can see higher plume impacts much closer to the source. When this occurs,
the compliance with the short-term standard may be sufficient to decrease long-range impacts and
eliminate the potential need for an LRT assessment. Conversely, elevated receptors in the far-field can
increase the need for LRT assessments, as these receptors would experience impacts closer to the
plume centerline. Given the GEP restrictions on stack heights, there are not likely to be many facilities
with stacks tall enough to pass the near-field NAAQS requirement while still having significant impacts at
50km.
6. Additional information
Data for the analyses described in this TSD can be obtained by contacting:
Chris Owen, PhD
Office of Air Quality Planning and Standards, U. S. EPA
109 T.W. Alexander Dr.
RTP, NC 27711
919-541-5312
owen.chris@epa.gov
21
-------
References
Cimorelli, et al. (2005). AERMOD: A Dispersion Model for Industrial Source Applications. Part I: General
Model Formulation and Boundary Layer Characterization. J. App. Meterol, 682-693.
Snyder, E., & Thurman, J. (2012). AERMOD Implementation Workgroup NO2 & SO2 modeling. 10th
Conference on Air Quality Modeling. U. S. EPA, RTP, NC.
U. S. EPA. (1996). 40 CFR Parts 51 and 52: Prevention of Significant Deterioration (PSD) and
Nonattainment New Source Review (NSR). FR, Vol. 61, No. 142, July 23,1996, 38249 - 38344.
U. S. EPA. (2003). Guideline on Air Quality Models. 40 CFR Part 51 Appendix W (68 FR 18440).
U. S. EPA. (2010a, June 29). Guidance Concerning the Implementation of the 1-hour NO2 NAAQSfor the
Prevention of Significant Deterioration Program.
U. S. EPA. (2010b, August 23). Guidance Concerning the Implementation of the 1-hour SO2 NAAQSfor
the Prevention of Significant Deterioation Program.
U. S. EPA. (2011, March). AERSCREEN User's Guide, pp. EPA-454/B-11-001.
U. S. EPA. (2014, May). Addendm to User's Guide for the AERMOD Meteorological Preprocessor
(AERMET), EPA document number EPA-454/B-03-002. Retrieved from RTP, NC.
U. S. EPA. (2014). Guidance for PM2.S Permit Modeling, EPA report number EPA-454/B-14-001. RTP, NC,
May.
22
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Appendix A
Plots from NO2 and SO2 screening analysis
For all figures in this section, the NO2 SIL is shown in blue and the SO2 SIL is shown in red.
23
-------
-
CL-
Q.
CM
O
NO2 asphalt, max results
10
20 30 40
downwind dist, km
50
-••o
-± 25
» 65
-+- 100
-& 150
60 ^200
halt, eiqth hiqh results
20 30 40
downwind dist, km
eo e 200
SO2 asphalt, max results
to
20 30 40
downwind dist, km
50
60 e 200
SO2 asphalt, fourth high results
to
20 30 40
downwind dist, km
50
Figure 2 - Results from the screening analysis for the asphalt plant.
25
65
+- 100
& 150
60 e 200
24
-------
NO2 biomass, max results
10
20 30 40
downwind dist, km
50
60
- 25
» 65
-+- 100
a 150
200
CM
O
NO2 biomass, eigth high results
to
20 30 40
downwind dist, km
50
60
- 25
» 65
-+- 100
a 150
r 200
SO2 biomass, max results
to
20 30 40
downwind dist, km
50
25
65
100
150
60 e 200
SO2 biomass, fourth high results
to
20 30 40
downwind dist, km
50
60
- 25
» 65
-+- 100
a 150
200
Figure 3 - Results from the screening analysis for the biomass plant
25
-------
NO2 cement kiln, max results
ic
20 30 40
downwind dist, km
50
-••o
-± 25
» 65
-+- 100
-& 150
60 ^200
.
CL
Q.
CM
O
NO2 cement_kiln, eigth high results
:
20 30 40
downwind dist, km
50
- 25
» 65
-+- 100
-& 150
60 ^200
SO2 cement kiln, max results
ic
20 30 40
downwind dist, km
50
•A 25
*• 65
-+- 100
-& 150
60 ^200
SO2 cement_kiln, fourth high results
ic
20 30 40
downwind dist, km
50
25
65
100
150
60 200
Figure 4 - Results from the screening analysis for the cement kiln
26
-------
NO2 coal_egu, max results
ic
20 30 40
downwind dist, km
^- 25
» 65
-+- 100
•a 150
60 ^200
NO2 coal_egu, eigth high results
:
20 30 40
downwind dist, km
25
65
+- 100
150
60 e 200
jQ
Q.
CL
CM
O
to
ic
SO2 coal_egu, max results
20 30 40
downwind dist, km
50
•A 25
*• 65
-+- 100
S 150
60 ^200
SO2 coal_egu, fourth high results
ic
20 30 40
downwind dist, km
50
- 25
» 65
-+- 100
-& 150
60 ^200
Figure 5 - Results from the screening analysis for the coal ECU
27
-------
NO2 ethanol, max results
ic
20 30 40
downwind dist, km
25
65
+- 100
150
60 e 200
NO2 ethanol, eigth high results
:
20 30 40
downwind dist, km
50
25
65
+- 100
150
60 e 200
SO2 ethanol, max results
ic
20 30 40
downwind dist, km
50
60 e 200
SO2 ethanol, fourth high results
ic
20 30 40
downwind dist, km
50
60 200
Figure 6 - Results from the screening analysis for the ethanol plant
28
-------
NO2 flare, max results
10
20 30 40
downwind dist, km
50
60 e 200
NO2 flare, eigth high results
20 30 40
downwind dist, km
- 200
1C
SO2 flare, max results
20 30 40
downwind dist, km
50
-••o
-± 25
-M- 65
-+- 100
•a 150
60 ^200
SO2 flare, fourth high results
:
20 30 40
downwind dist, km
50
-•- o
-± 25
» 65
-+- 100
-a 150
60 ^200
Figure 7 - Results from the screening analysis for the flare
29
-------
NO2 fuel oil turbine, max results
1C
20 30 40
downwind dist, km
50
60 e 200
NO2 fuel_oil_turbine, eigth high results
:
20 30 40
downwind dist, km
150
60 e 200
SO2 fuel oil turbine, max results
to
20 30 40
downwind dist, km
50
25
• 65
+- 100
& 150
60 e 200
SO2 fuel_oil_turbine, fourth high results
to
20 30 40
downwind dist, km
50
25
65
+- 100
150
60 200
Figure 8 - Results from the screening analysis for the fuel oil turbine
30
-------
NO2 landfill_gas_turbine, max results
10
20 30 40
downwind dist, km
50
^- 25
» 65
-+- 100
a 150
60 ^200
NO2 landfill_gas_turbine, eigth high results
to
20 30 40
downwind dist, km
50
60
- 25
» 65
-+- 100
-& 150
r 200
SO2 landfill_gas_turbine, max results
to
20 30 40
downwind dist, km
50
-••0
-± 25
*• 65
-+- 100
-a 150
60 ^200
SO2 landfill_gas_turbine, fourth high results
to
20 30 40
downwind dist, km
50
-* 25
» 65
H- 100
a 150
60 ^200
Figure 9 - Results from the screening analysis for the landfill gas turbine
31
-------
CM
O
NO2 ng_compressor, max results
10
20 30 40
downwind dist, km
50
60
- 25
» 65
-+- 100
-& 150
200
NO2 ng_compressor, eigth high results
to
20 30 40
downwind dist, km
50
-•• 0
-± 25
» 65
-+- 100
-& 150
60 ^200
SO2 ng_compressor, max results
20 30 40
downwind dist, km
50
•A 25
-M- 65
-+- 100
•a 150
60 ^200
SO2 ng_compressor, fourth high results
20 30 40
downwind dist, km
50
-* 25
» 65
-+- 100
-a 150
60 ^200
Figure 10 - Results from the screening analysis for the natural gas compressor station
32
-------
.a
Q.
Q.
8
NO2 pulp_paper, max results
:
20 30 40
downwind dist, km
50
Z_hill
-••o
-± 25
» 65
-+- 100
a 150
60 ^200
iqth hiqh results
:
20 30 40
downwind dist, km
50
-•-o
-± 25
» 65
-+- 100
-& 150
60 ^200
CL
CL
CM
O
CO
SO2 pulp_paper, max results
ic
20 30 40
downwind dist, km
50
-••o
-± 25
*• 65
-+- 100
•a 150
60 ^200
S02 pul
er, fourth high results
ic
20 30 40
downwind dist, km
50
- 25
» 65
H- 100
-a 150
60 ^200
Figure 11 - Results from the screening analysis for the pulp and paper plant
33
-------
Appendix B
Plots from NO2 and SO2 refined analysis
For all figures in this section, the NO2 SIL is shown in blue and the SO2 SIL is shown in red.
34
-------
NO2 ASX_NAAQS, max results
T
20 30 40
downwind dist, km
-•- 65
-+- 100
•& 150
60 200
NO2 ASX_NAAQS, eigth high results
20 30 40
downwind dist, km
60 200
so2 ASX NAAQS, max results
20 30 40
downwind dist, km
60 200
SO2 ASX_NAAQS, fourth high results
i:
T
20 30 40
downwind dist, km
50
25
65
100
150
60 ^200
Figure 12 - Refined NO2 and SO2 results, ASX, max and design values, 1-hr NAAQS
35
-------
NO2 DHT_NAAQS, max results
20 30 40
downwind dist, km
5C
60 200
NO2 DHT_NAAQS, eigth high results
20 30 40
downwind dist, km
50
Z hill
60 200
so2 DHT NAAQS, max results
20 30 40
downwind dist, km
60 200
SO2 DHT_NAAQS, fourth high results
i:
20 30 40
downwind dist, km
50
z_mn
-•- o
25
60 200
Figure 13 - Refined NO2 and SO2 results, DHT, max and design values, 1-hr NAAQS
36
-------
NO2 OAK_NAAQS, max results
i
20 30 40
downwind dist, km
5C
60
150
200
NO2 OAK_NAAQS, eigth high results
20 30 40
downwind dist, km
50
Z hill
60 200
so2 OAK NAAQS, max results
20 30 40
downwind dist, km
25
60 200
SO2 OAK_NAAQS, fourth high results
i:
20 30 40
downwind dist, km
50
z_mn
-•- o
25
60 200
Figure 14 - Refined NO2 and SO2 results, OAK, max and design values, 1-hr NAAQS
37
-------
NO2 SMQ_NAAQS, max results
20 30 40
downwind dist, km
5C
60 200
NO2 SMQ_NAAQS, eigth high results
20 30 40
downwind dist, km
50
60 200
so2 SMQ NAAQS, max results
20 30 40
downwind dist, km
60 200
SO2 SMQ_NAAQS, fourth high results
i:
20 30 40
downwind dist, km
50
z_mii
-•- o
25
60 200
Figure 15 - Refined NO2 and SO2 results, SMQ, max and design values, 1-hr NAAQS
38
-------
so2ASXH1H,3hr
20 30 40
downwind dist, km
to
so2 ASX H2H, 3hr
20 30 40
downwind dist, km
50
•-0
200
to
so2ASXH1H,24hr
20 30 40
downwind dist, km
50
Z hill
60
200
to
so2ASXH2H,24hr
20 30 40
downwind dist, km
50
Z hill
60
200
Figure 16 - Refined SO2 results, ASX, 3 & 24-hr increment
39
-------
so2DHTH1H,3hr
20 30 40
downwind dist, km
5C
Q- 50
CM
so2 DHT H2H, 3hr
20 30 40
downwind dist, km
50
100
150
200
so2DHTH1H, 24hr
20 30 40
downwind dist, km
6G
i:
so2 DHT H2H, 24hr
20 30 40
downwind dist, km
50
Z hill
100
150
200
60
Figure 17 - Refined SO2 results, DHT, 3 & 24-hr increment
40
-------
so20AKH1H,3hr
20 30 40
downwind dist, km
5C
Z hill
50
so2 OAK H2H, 3hr
20 30 40
downwind dist, km
Z hill
50
10
so2OAKH1H,24hr
20 30 40
downwind dist, km
Z hill
6G
200
i:
so2 OAK H2H, 24hr
20 30 40
downwind dist, km
50
Z hill
6C
200
Figure 18 - Refined SO2 results, OAK, 3 & 24-hr increment
41
-------
8
10
so2 SMQ H1H, 3hr
20 30 40
downwind dist, km
5C
: 50
- 100
|- 150
200
to
so2 SMQ H2H, 3hr
20 30 40
downwind dist, km
50
Z hill
50
10
so2SMQH1H,24hr
20 30 40
downwind dist, km
Z hill
6G
200
1 3
so2 SMQ H2H, 24hr
20 30 40
downwind dist, km
50
60
200
Figure 19 - Refined SO2 results, SMQ, 3 & 24-hr increment
42
-------
NO2 ASX ANN, max results
o
20 30 40
downwind dist, km
0
50
100
150
200
so2 ASX ANN, max results
1C
20 30 40
downwind dist, km
50
6C
Figure 20 - Refined NO2 & SO2 results, ASX, annual NAAQS
43
-------
2.0
1.5
1.0
Q.
CL
8
-z.
NO2 DHT_ANN, max results
20 30 40
downwind dist, km
50
100
150
200
so2 DHT ANN, max results
1C
20 30 40
downwind dist, km
50
6C
Figure 21 - Refined NO2 & SO2 results, DHT, annual NAAQS
44
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NO2 OAK_ANN, max results
10
20 30 40
downwind dist, km
100
150
200
so2 OAK ANN, max results
1 3
20 30 40
downwind dist, km
50
60
Figure 22 - Refined NO2 & SO2 results, OAK, annual NAAQS
45
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o
NO2 SMQ_ANN, max results
20 30 40
downwind dist, km
50
so2 SMQ ANN, max results
20 30 40
downwind dist, km
Figure 23 - Refined NO2 & SO2 results, SMQ, annual NAAQS
46
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Appendix C
Plots from PM refined analysis
For all figures in this section, the PM25 increment is indicated on each plot. For the NO-scaled emissions,
this is shown in blue and the SO2-scaled emissions are shown in red.
47
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E10
so2-scaled ASX_PM25 H1H, 24hr
10
20 30 40
downwind dist, km
50
Z hill
50
CO
no2-scaled ASX PM25H1H, 24hr
20 30 40
downwind dist, km
50
Z hill
50
60
CO
no2-scaled ASX_PM25, ann avg
1C
20 30 40
downwind dist, km
50
Z hill
so2-scaled ASX_PM25, ann avg
20 30 40
downwind dist, km
•-0
50
Figure 24 - Refined PM25 results, ASX, 24-hr annual increment
48
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co
CD
so2-scaled DHT_PM25 H1H, 24hr
20 30 40
downwind dist, km
5C
Z hill
100
150
200
no2-scaled DHT PM25H1H,24hr
20 30 40
downwind dist, km
50
CO
no2-scaled DHT_PM25, ann avg
20 30 40
downwind dist, km
50
Z hill
100
150
200
6G
so2-scaled DHT_PM25, ann avg
1C
20 30 40
downwind dist, km
50
6C
Figure 25 - Refined PM25 results, DHT, 24-hr annual increment
49
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so2-scaled OAK_PM25 H1H, 24hr
co
20 30 40
downwind dist, km
5C
no2-scaled OAK PM25H1H,24hr
20 30 40
downwind dist, km
50
no2-scaled OAK_PM25, ann avg
20 30 40
downwind dist, km
50
Z hill
100
150
200
6G
so2-scaled OAK_PM25, ann avg
1C
20 30 40
downwind dist, km
50
Z hill
100
150
200
6C
Figure 26 - Refined PM25 results, OAK, 24-hr annual increment
50
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so2-scaled SMQ_PM25 H1H, 24hr
20 30 40
downwind dist, km
5C
no2-scaled SMQ PM25H1H,24hr
20 30 40
downwind dist, km
50
60
no2-scaled SMQ_PM25, ann avg
20 30 40
downwind dist, km
50
6G
so2-scaled SMQ_PM25, ann avg
20 30 40
downwind dist, km
50
Figure 27 - Refined PM25 results, SMQ, 24-hr annual increment
51
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so2-scaled ASX_PM25_24HR_NAAQS 8th high, 24hr
20 30 40
downwind dist, km
50
no2-scaled ASX_PM25_24HR_NAAQS 8th high, 24hr
1 3
20 30 40
downwind dist, km
50
6C
Figure 28 - Refined PM25 results, ASK, 24-hr NAAQS
52
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so2-scaled DHT_PM25_24HR_NAAQS 8th high, 24hr
20 30 40
downwind dist, km
50
no2-scaled DHT_PM25_24HR_NAAQS 8th high, 24hr
1C
20 30 40
downwind dist, km
50
Figure 29 - Refined PM25 results, DHT, 24-hr NAAQS
53
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so2-scaled OAK_PM25_24HR_NAAQS 8th high, 24hr
20 30 40
downwind dist, km
50
no2-scaled OAK_PM25_24HR_NAAQS 8th high, 24hr
1 3
20 30 40
downwind dist, km
50
6C
Figure 30 - Refined PM25 results, OAK, 24-hr NAAQS
54
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so2-scaled SMQ_PM25_24HR_NAAQS 8th high, 24hr
100
150
200
20 30 40
downwind dist, km
no2-scaled SMQ_PM25_24HR_NAAQS 8th high, 24hr
1 3
20 30 40
downwind dist, km
50
6C
Figure 31 - Refined PM25 results, SMQ, 24-hr NAAQS
55
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56
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United States Office of Air Quality Planning and Standards Publication No. EPA- 454/B-15-003
Environmental Protection Air Quality Analysis Division [July, 2015]
Agency Research Triangle Park, NC
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