Technical Support Document (TSD) for
AERMOD-Based Assessments of Long-Range
Transport Impacts for Primary Pollutants
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EPA- 454/B-16-007
December, 2016
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 Assessment Division
Air Quality Modeling Group
Research Triangle Park, North Carolina
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Preface
This document provides the results and interpretation of AERMOD screening and refined model
simulations to estimate the pollutant concentration impacts in the near-field (i.e., less than 50km from
source) and far-field (i.e., greater than 50km from source) for a wide range of source types for the
purposes of informing the 2016 revisions to EPA's Guideline on Air Quality Models (published as
Appendix W to 40 CFR Part 51). This document is not intended to demonstrate methods to assess facility
impacts for NAAQS or PSD increment nor is it intended to provide any guidance on the usage of
screening for long-range transport or any other regulatory analyses.
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Contents
Preface 5
Contents 6
Tables 8
Figures 9
1. Introduction 10
2. Background 10
3.0 Approach to evaluating near-source and long-range impacts 13
3.1 Source Types and Characteristics 13
3.2 Modeling Assessment Overview 14
4. Summary of results 16
4.1 Phase 1: N02 and S02 NAAQS screening 16
4.2 Phase 2: Refined analyses for N02 and S02 23
4.2.11-hour NAAQS Results 24
4.2.2 3-hour, 24-hour, and annual PSD increment results 27
4.3 Phase 2: Refined analyses for PMio and PM2 5 28
4.3.1 24-hour NAAQS results 29
4.3.2 Annual NAAQS and PSD increment results 29
4.3.2 24-hour PSD increment results 30
5. Conclusions 31
6. Additional information 31
References 32
Appendix A 33
Plots and tables from the N02 and S02 NAAQS screening analysis 33
Appendix B 45
Plots from N02 and S02 refined analysis 45
B.l Comparisons against the 1-hour N02 and S02 NAAQS 45
B.2 Comparisons against the 3 and 24-hour S02 PSD increment 50
B.3 Comparisons against the annual N02 and S02 PSD increment 54
Appendix C 58
Plots from PM refined analysis 58
C.l Comparisons against the PM2.5 24-hour NAAQS 59
C.2 Comparisons against the annual PSD increment and NAAQS 63
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C.3 Comparisons against the PM2.5 24-hour PSD increment
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Tables
Table 1 - Significant Impact Levels (SILs) for NAAQS by Criteria Pollutant 11
Table 2 - PSD Increment and associated SILs for Criteria Pollutants by Class I, Class II, and Class III Areas.
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Table 3 - Summary of Modeling Scenarios by Source Type from AERMOD Implementation Workgroup
(AIWG) 14
Table 4 - Phase 1 Screening Modeling Results for N02 and S02 by Facility type: Maximum Impact Results
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Table 5 - Phase 1 screening modeling results for N02 and S02 by Facility type: Maximum Impact Results
at 50 km scaled to Reflect Near-Field NAAQS Compliance 22
Table 6 - Summary of N02 and S02 emissions for the coal EGU facility 23
Table 7 - Phase 2 Refine Modeling Results for N02 by NWS Station 25
Table 8 - Phase 2 Refine Modeling Results for S02 by NWS Station 26
Table 9 - Scaling factors from NAAQS refined analysis for use in PSD increment refined analysis 27
Table 10 - Phase 2 refined modeling results for N02 and S02 PSD increments by NWS station 28
Table 11- - Summary of 2011 NEI emission data used in refined modeling analysis 29
Table 12 - Phase 2 refined modeling results for 24-hour PM2.5 NAAQS by NWS station 29
Table 13 - Phase 2 refined modeling results for annual PM2.5 NAAQS and PSD increment by NWS
station 30
Table 14 - Phase 2 refined modeling results for 24-hour PM2.5 PSD increment by NWS station 30
Table A.l - Phase 1 screening modeling results for N02 and S02 by Facility type: 8th and 4th high results
from screening analysis 30
Table A.l - Phase 1 screening modeling results for N02 and S02 by Facility type: 8th and 4th high results
from screening analysis (continued) 31
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Figures
Figure 1 - Location of receptors for screening and refined runs 17
Figure 2 - Results from the screening analysis for the asphalt plant 35
Figure 3 - Results from the screening analysis for the biomass plant 36
Figure 4 - Results from the screening analysis for the cement kiln 37
Figure 5 - Results from the screening analysis for the coal EGU 38
Figure 6 - Results from the screening analysis for the ethanol plant 39
Figure 7 - Results from the screening analysis for the flare 40
Figure 8 - Results from the screening analysis for the fuel oil turbine 41
Figure 9 - Results from the screening analysis for the landfill gas turbine 42
Figure 10 - Results from the screening analysis for the natural gas compressor station 43
Figure 11 - Results from the screening analysis for the pulp and paper plant 44
Figure 12 - Refined N02 and S02 results, ASX, max and design values, 1-hour NAAQS 46
Figure 13 - Refined N02 and S02 results, DHT, max and design values, 1-hour NAAQS 47
Figure 14 - Refined N02 and S02 results, OAK, max and design values, 1-hour NAAQS 48
Figure 15 - Refined N02 and S02 results, SMQ, max and design values, 1-hour NAAQS 49
Figure 16 - Refined S02 results, ASX, 3 & 24-hour PSD increment 50
Figure 17 - Refined S02 results, DHT, 3 & 24-hour PSD increment 51
Figure 18 - Refined S02 results, OAK, 3 & 24-hour PSD increment 52
Figure 19 - Refined S02 results, SMQ 3 & 24-hour PSD increment 53
Figure 20 - Refined N02 & S02 results, ASX, annual NAAQS 54
Figure 21 - Refined N02 & S02 results, DHT, annual NAAQS 55
Figure 22 - Refined N02 & S02 results, OAK, annual NAAQS 56
Figure 23 - Refined N02 & S02 results, SMQ, annual NAAQS 57
Figure 24 - Refined PM25 results, ASX, 24-hour NAAQS 59
Figure 25 - Refined PM25 results, DHT, 24-hour NAAQS 60
Figure 26 - Refined PM2 5 results, OAK, 24-hour NAAQS 61
Figure 27 - Refined PM2 5 results, SMQ, 24-hour NAAQS 62
Figure 28 - Refined PM2 5 results, ASX, annual PSD increment and NAAQS 63
Figure 29 - Refined PM2 5 results, DHT, annual PSD increment and NAAQS 64
Figure 30 - Refined PM25 results, OAK, annual PSD increment and NAAQS 65
Figure 31 - Refined PM2 5 results, SMQ, annual PSD increment and NAAQS 66
Figure 32 - Refined PM2 5 results, ASX, 24-hour PSD increment 67
Figure 33 - Refined PM2 5 results, DHT, 24-hour PSD increment 68
Figure 34 - Refined PM2 5 results, OAK, 24-hour PSD increment 69
Figure 35 - Refined PM2 5 results, SMQ, 24-hour PSD increment 70
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1. Introduction
For long-range transport (LRT) applications at distances of more than 50 km from a source, the final
revisions to EPA's Guideline on Air Quality Models (published as Appendix W to 40 CFR Part 51) include
recommendations for a screening approach for addressing the NAAQS and Prevention of Significant
Deterioration (PSD) increment and removal of CALPUFF as an EPA preferred model for such applications.
In supporting these final revisions, the purpose of the modeling assessment detailed in this document is
to demonstrate what types of facilities may have significant impacts for NAAQS or PSD increment at
distances greater than 50 km from the source. While EPA has not determined a replacement refined
model for LRT applications under the revised Guideline, the information provided in this report indicates
that the need for LTR assessments for NAAQS and PSD increment violations for inert pollutants is
limited, thereby mitigating the necessity for a preferred regulatory model for LRT assessments. This
document provides technical details of the modeling assessment, including summarizing the model
scenarios and approach used to determine the air quality impact of a range of source types on pollutant
concentrations in the near-field (i.e., within 50 km) and far-field (beyond 50 km).
2. Background
The permitting process for the PSD program 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 two-stage approach, as recommended in section
9.2.3 of the Guideline, and has been applied in the PSD program for more than 25 years. Under this two-
stage approach, permitting authorities have issued PSD permits based on a demonstration that the air
quality impacts of a proposed source are below levels of impact considered to be significant. In this
document, significant impact levels (SILs) are used for illustrative purposes as a demonstration tool to
determine the culpability of a new or modifying source to any NAAQS or PSD increment violations. In
this context, a modeled ambient impact from a proposed new or modified source that is determined to
be less than the applicable SIL is generally considered not to "cause or contribute" to any modeled
violations of the relevant NAAQS or PSD increment.
Table 1 shows the SIL levels for NAAQS by criteria pollutant (i.e., PM25, PM10, S02, N02, and CO), while
Table 2 shows the PSD increment levels and associated SIL levels of PM25, PM10, S02, and N02. In 1996, a
rulemaking was proposed with Class I specific SILs for N02, S02, and PM10 (U. S. EPA, 1996). Please note
that these SILs for Class I PSD increments have never been promulgated; however, the values shown in
Table 2 have been used in practice under the PSD program over the past 20 years.
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 (CAA)
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 are
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 conservative in the far-field. Thus, when LRT is expected
to be important (i.e., impacts beyond the nominal distance of 50 km), an alternative model is necessary
for assessing impacts for those distances with the previous Guideline recommending the use of the
CALPUFF modeling system (U. S. EPA, 2003). Section 6.2.3 of the 2005 version of the Guideline discusses
the regulatory needs for LRT impact assessments. The focus in section 6.2.3 is the need to protect Class I
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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).
Table 1 - Significant Impact Levels (SILs) for NAAQS by Criteria Pollutant.
Pollutant
Class 1
Class II
Class III
Source
Fine Particulate Matter (PM2.5)
Annual mean
*
0.2 (0.3)1 ug/m3
*
40 CFR 51.165 (b)(2)
(U.S. EPA, 2016)
24-hour maximum
*
1.2 ug/m3
*
Particulate Matter (PMi0)
Annual arithmetic mean
*
1 ug/m3
*
40 CFR 51.165(b)(2)
24-hour maximum
*
5 ug/m3
*
Carbon Monoxide (CO)
8-hour maximum
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500 ug/m3
*
40 CFR 51.165(b)(2)
1-hour maximum
*
2000 ug/m3
*
Sulfur Dioxide (S02)
Annual mean
*
1 ug/m3
*
40 CFR 51.165(b)(2)
24-hour maximum
*
5 ug/m3
*
3-hour maximum
*
25 ug/m3
*
1-hour maximum
*
3 ppb (~7.8 ug/m3)
*
(U. S. EPA, 2010b)
Nitrogen Dioxide (NQ2):
Annual mean
*
1 ug/m3
*
40 CFR 51.165(b)(2)
1-hour maximum
*
4 ppb (~7.5 ug/m3)
*
(U. S. EPA, 2010a)
On August 1, 2016 the EPA released draft guidance with new PM2.5 SILs based on a new technical analysis (U.S.
EPA, 2016). The draft guidance recommended the most conservative values from either 51.165 and the new
technical analysis, which is 0.2 ug/m3 for the annual standard and 1.2 ug/m3 for the 24-hour standard.
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Table 2 - PSD Increment2 and associated SILs for Criteria Pollutants by Class I, Class II, and Class III
Areas.
Pollutant
Class 1
Class II
Class III
Source
Fine Particulate Matter (PM2.5)
Annual mean ug/m3
1 (0.05)
4(0.2)
8 (0.2)
(U.S. EPA, 2016)3
24-hour maximum ug/m3
2 (0.27)
9(1.2)
18 (1.2)
(U.S. EPA, 2016)
Particulate Matter (PM10)
Annual mean ug/m3
4(0.2)
17(1)
34(1)
61 FR 38338 (July, 23 1996)4
24-hour maximum ug/m3
8(0.3)
30 (5)
60 (5)
61 FR 38338 (July, 23 1996)
Sulfur Dioxide (S02)
Annual mean ug/m3
2(0.1)
20(1)
40 (1)
61 FR 38338 (July, 23 1996)
24-hour maximum ug/m3
5 (0.2)
91(5)
182 (5)
61 FR 38338 (July, 23 1996)
3-hour maximum ug/m3
25(1)
512 (25)
700 (25)
61 FR 38338 (July, 23 1996)
1-hour maximum
NA
NA
NA
Nitrogen Dioxide (N02)
Annual mean ug/m3
2.5 (0.1)
25(1)
50(1)
61 FR 38338 (July, 23 1996)
1-hour maximum
NA
NA
NA
2 PSD Increments for all pollutants listed here are set in 40 CFR 52.21 (c).
3 The draft EPA guidance includes new PM2.5 SILs for PSD increment. The prior PM2.5 SILs for PSD increment from
the 2010 rule were vacated. See (U.S. EPA, 2016) for more information.
4 The EPA published an NPRM in 1996 that included adding SILs for PSD increment for SO2, PM10, and N02 to the
CFR. This proposed rule was never went finalized. However, the proposed SILs for PSD increment have been used
by states and industry permit applicants for PSD increment in the absence of any other guidance or rulemaking.
These proposed SILs are thus used here in this analysis as a benchmark for the facility impacts.
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3.0 Approach to evaluating near-source and long-range impacts
In order to assess the nature of LRT aspects of a PSD compliance demonstration, inert criteria pollutant
emissions from a wide variety of facility types were modeled across 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 N02 and S02 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 N02 (U. S.
EPA, 2010a) and S02 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.
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 in stack height,
addition of controls, and modifications of facility boundaries reflecting changes in ambient air. Also for
N02 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.eov/ttn/scram/10thmodconf/review material/AIWG Summarv.pdf
and
http://www.epa.gov/ttn/scram/10thmodconf/review material/AIWG Summary v2.pdf.
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Table 3 - Summary of Modeling Scenarios by Source Type from AERMOD Implementation
Workgroup (AIWG)
Facility
Base emission (tpy)5
NO2/SO2
Stack heights (m)6'7
Asphalt plant
188/13.2
6, 3, 0.3
Biomass
244/174
55, 9, 9
Cement kiln
7140/3129
160, 160, 90s, 908
Coal EGU
1863/4959
150, 100, 6, 5, 5
Ethanol plant
1180/890
11, 11, 2, 43, 25
Flare
104/6083
25
Fuel oil turbine
1184/417
25, 25, 25, 258, 258, 258, 258, 68, 68, 68
Landfill gas turbine
80/45
13,13,13,10
NG compressor
90/0.01
11, 11, 11, 11, 58
Pulp & paper plant
9657/3403
30, 30 ,29, 85, 85, 72, 72, 76, 8, 67, 67
3.2 Modeling Assessment Overview
The goal of this modeling assessment is to determine what types of facilities may have significant
impacts in terms of NAAQS and PSD increment, as defined in this analysis as modeled concentrations
above the applicable SIL, at distances greater than 50 km from the source. There are fundamentally four
aspects that affect source impacts: 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 air quality impacts from a facility.
These two aspects of a 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 enough. Thus, it is essential to have emissions that
reflect all possible realities with respect to the facility type, which makes the AIWG modeling scenarios
ideal for this evaluation.
5 The analysis is based on annual emissions, which is what was available from the original AIWG databases.
However, annual emissions may not fully represent impacts for NAAQS or PSD increment from short term
emissions that can be evaluated separately for some facilities.
6 Primary stacks for NO2 are colored blue, for SO2 are colored red, for both are colored purple
7 Since the facilities were modeled in flat terrain, the stack heights here are a combination of the stack height and
the stack elevation.
8 NO2 only, no SO2 emissions at this stack height.
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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 two-phased analysis was used here:
1. Screening modeling for NAAQS: The first phase consists of a screening analysis using worst-case
meteorology generated by MAKEMET and AERMOD's SCREEN option (which calculates only
plume-centerline concentrations). The results from this screening analysis generate the
potential maximum 1-hour concentration from a particular source type in the near-field and at
or about the 50km distance. Since the screening analysis only generates 1-hour concentrations,
we limited this screening analysis to the 1-hour NAAQS for N02 and S02. To provide a more
appropriate basis in assessing the significance of source impacts in the far-field, we assessed the
source impacts at the 50km distance assuming NAAQS compliance in the near-field (i.e., scaling
factors developed that reflect adjusting predicted near-field concentrations to comply with
NAAQS). As such, source types with predicted impacts notably above the applicable NAAQS SIL
at 50 km from this phase were considered for further analysis in the second phase.
2. Refined modeling for NAAQS and PSD Increment: The second phase consisted of a refined
analysis based on 5-years of meteorology from 4 regionally varying NWS stations and AERMOD
version 14134. For this second phase, the 1-hour, 3-hour, 24-hour and annual concentrations
were computed for comparison to the appropriate SILs under more realistic modeling scenarios.
Similar to the screening modeling, predicted impacts at the 50km distance were assessed
assuming NAAQS compliance in the near-field. Since the screening analysis indicated that only
facilities with tall stacks might comply in the near-field and still have significant impacts at 50
km, the refined analysis focused on a single tall-stack facility (i.e., coal EGU) that serves as a
representative example of these source types.
The original AIWG scenarios included N02 and S02 emissions only, with N02 using full conversion.
However, PSD increments exist for CO, PMio, 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 was not evaluated in
this assessment. However, PMio and PM2 5 were necessary to include in this assessment and were
evaluated along with N02 and S02. 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/2011inventorv.html) was conducted to determine scaling factors to
generate PM emissions based on the N02 and S02 emissions for a particular facility type.
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4. Summary of results
4.1 Phase 1: NO2 and SO2 NAAQS screening
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
from 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/highly unstable conditions, which would give the highest concentrations for
elevated releases (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, regardless of the wind direction. For these model
simulations, receptors were placed at distances ranging from 100 m to 60 km. Figure 1 illustrates the
multiple receptor heights that were used to evaluate the potential presence of terrain downwind, with
receptor heights including 0, 25, 65, 100, 150, and 200 m. Due to the plume centerline option being
used, only a single receptor at each distance and height was required. The results from this initial phase
represent an extremely conservative estimate of plume impacts. For N02, full conversion was used, i.e.,
the emissions were 100% N02, and the half-life option in AERMOD was not used for S02.
The screening analysis was conducted for N02 and S02 only. The results are summarized in Table 4 and
in Figures 2 through 11 in Appendix A. For these screening runs, we estimated the maximum
concentration for both N02 and S02 at each receptor. In addition, the 8th high 1-hour concentration for
N02 and the 4th high 1-hour concentration for S02 were estimated at each receptor. The 8th and 4th high
1-hour concentrations are the concentration metrics typically used for determining compliance in a PSD
demonstration. While the 8th and 4th high results are conservative (due to the plume centerline
concentrations calculated in the screening analysis mentioned earlier), these metrics give some sense of
the distribution of the highest concentrations and provide valuable perspective on the maximum
concentrations.
As shown in Table 4, several of the facilities have predicted impacts below the respective 1-hour NAAQS
SILs for both N02 and S02 at the 50 km distance. The landfill gas turbine and natural gas (NG)
compressor were below the NAAQS SIL at 50 km for both N02 and S02. The flare was below the NAAQS
SIL for N02 and the asphalt plant and biomass burning plant were below the NAAQS SIL for S02. Several
other facilities were very close to the NAAQS SIL at 50 km or had some receptors above and some below
the SIL, depending on the receptor height. When the conservative nature of the screening modeling is
taken into account, it is apparent that the predicted impacts that are slightly above the NAAQS SIL in the
screening analysis (e.g., the asphalt and biomass plant have impacts just above the SIL at 50 km) can be
expected to be below the NAAQS SIL under a refined modeling analysis with representative
meteorological inputs. That said, there are still some source types that have impacts at the 50 km
distance well above the NAAQS SILs, including the cement kiln, coal EGU, ethanol plant, flare, fuel oil
turbine, and pulp and paper plant.
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60000
E 30000
MM*
> <
~ i
> <
» • <
> » i
~
0 20000 40000 60000
Distance from center along each radial, m
- Location of receptors for screening and refined runs.9
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While the results of the source impacts at 50 km compared to the appropriate SILs shown in Table 4 are
insightful, these screening modeling results do not reflect the fact that a PSD compliance demonstration
necessitates demonstrating compliance with the NAAQS in the near-field. 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 for NAAQS and/or PSD increments, particularly if
the concentrations in the near field are orders of magnitude above the NAAQS (i.e., the NAAQS is the
controlling standard). While the screening results are not equivalent to a NAAQS demonstration (which
would calculate 8th and 4th high values for N02 and S02, respectively, averaged over 5 years of
modeling with actual meteorology), the results for many of the facilities suggest that the sources would
need to reduce their emissions such that near-field compliance is achieved. Thus, the results in Table 5
present the 'scaled-back' results in that the predicted near-field concentrations have been used to
estimate adjustments required to meet the NAAQS, and the resulting adjustment factors were used to
then "scale back" the predicted 50km source impacts to yield estimates that reflect near-field NAAQS
compliance. The adjustments are made according to the following equation:
Equation i
NAAQS
Scaled 50 km impact = Original 50 km impact * (- —— -)
(.Representative near field impact)
Table 5 shows estimates of the 'scaled-back' source impact at 50 km based on meeting the NAAQS in the
near-field. The representative near-field impact is determined as the average of the 8th and 4th high
results for N02 and S02, respectively, across the six receptor heights from the screening results (See
Appendix Table A.l, see next paragraph for more discussion on this selection). The 50 km scaled impact
is the maximum impact at 50 km (as opposed to the 8th or 4th high) from all receptor heights scaled
back such that the representative near-field concentration meets the NAAQS. That is, the highest 50 km
impact from Table 4 has been reduced by a factor necessary for the percentile results to meet the
NAAQS. For example, for the fuel oil turbine, the representative near-field concentration from the
screening analysis for N02 (the average of the 8th maximum 1-hour averages shown in Appendix Table
A.l) was 639.4 ppb, while the standard is 100 ppb and the maximum impact at 50 km was 12.5 ppb
(Table 4). Even without considering background levels or contributions from nearby sources, the
emissions would need to be reduced by a factor of 6 to satisfy a NAAQS compliance demonstration (i.e.,
the 639.4 ppb impact would need to be less than or equal to 100 ppb, equating to roughly a reduction
factor of 6). This reduction would also apply to the impact at 50 km, resulting in an impact of 1.4 ppb at
50 km, which is well below the SIL of 4 ppb. When the 50 km impacts are scaled-back from these
facilities to meet the NAAQS in the near field, the predicted impacts from all the facilities at 50 km fall
below the applicable 1-hour SILs for the N02 and S02 NAAQS.
While this analysis is insightful, the nature of the screening modeling, with multiple levels of receptors at
each distance, can make the results somewhat difficult to interpret, particularly when determining
which near-field concentration is indeed "representative". The receptor grid was designed to reflect a
variety of terrain possibilities, but certain combinations of receptors can also result in virtual terrain that
is unrealistic. Thus, it is not an easy choice to select a near-field receptor to use in determining the near-
field NAAQS compliance scaling discussed above. For example, the asphalt plant, which has the majority
of the N02 emissions at 31 m, has the smallest impacts at the receptors with an elevation of 200 m. This
is reasonable, as the plume from a 31 m stack has the farthest to travel to a 200 m receptor from the
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potential receptor heights. However, if a hypothetical domain had terrain that had the facility at an
elevation of 0 m with a stack of 31 m (as we modeled here) and some downwind receptor at a 200 m
elevation, then this domain would out of necessity need to have receptor elevations between 0 m and
200 m. Thus, there should be receptors at intermediate elevations in between the source and the 200 m
receptor that would see higher concentrations than the concentration at the 200 m receptor. Therefore,
the concentration from the 200 m receptors is not representative as the domain-wide controlling
concentration. However, the concentrations from the receptors at 65 m, which are close to the stack
height, may not be representative either. This is because the maximum impacts at these receptor
heights occur immediately at the fence line, which implies a terrain in which the facility fence line is
located immediately adjacent to the base of some sort of cliff, such that the ground-level receptors are
at an elevation of 65 m above the facility (which has a base elevation of 0 m). This is unlikely and thus
the maximum impact from the 65 m receptors may not be representative either. This unlikely "cliff"
scenario is exaggerated even more with taller stack facilities. For example, the coal EGU has its N02
emissions distributed between a 120 m and 172 m stack, with the maximum impacts occurring at the
200 m receptors. Again, these maximum impacts would be at fence line receptors, implying a significant
terrain feature of 200 m immediately at the fence line of the facility. Conversely, it is unlikely that the
terrain over the entire domain of almost 40,000 square km is flat (i.e., all elevations are only 0 m) or that
there is a plateau, such that all receptors are at an elevation of 25 m over the entire domain. Ultimately,
no single concentration from Appendix Table A.l can be considered representative of the near-field
impacts from a variety of potential terrain arrangements. Thus, the average of the 4th high and 8th high
near-field concentrations were chosen as the "representative" near-field concentration.
In general, when complex terrain, such as the cliffs and plateaus discussed above, is not a major factor in
the compliance demonstration, the expectation is that most receptor elevations are not significantly
different from the baseline elevation of the facility. In such cases, facilities with the lower release points
(shorter stacks) have their maximum impacts in close proximity to the source such that their impacts at
50 km are much lower after the adjustment to meet the NAAQS. Conversely, 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 (or for the terrain to raise to the plume centerline). As a
result, the impacts at 50 km are not reduced as much as they are with short stacks when the NAAQS
compliance is taken into account. As the discussion of receptor heights and near-field impacts highlights,
the considerations of stack heights and receptor elevations are an important consideration in
determining what kind of facilities can potentially have significant impacts at 50 km. Based on these
considerations and the adjustments to reflect near-field NAAQS compliance indicates that facilities with
emissions from the taller stacks are most likely to still have some impacts above the applicable SIL at 50
km.
19
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Table 4 - Phase 1 Screening Modeling Results for N02 and S02 by Facility type: Maximum Impact
Results
Facility
Receptor
Elevation
I\I02 NAAQS (impacts in ppb)
S02 NAAQS (impacts in ppb)
Maximum 1-hour
Impact at 50 km
Maximum 1-
Impact at 50 km
impact
(SIL 4 ppb)10
hour impact
(SIL 3 ppb)10
0
291.0
5.7
96.1
0.7
25
856.8
6.2
115.4
0.7
Asphalt
65
884.7
4.4
50.0
0.2
plant
100
408.3
2.3
49.7
0.2
150
181.1
1.6
49.3
0.1
200
129.8
1.4
49.0
0.1
0
17.5
1.0
11.2
0.7
25
17.7
1.0
11.3
0.7
Biomass
65
548.5
1.7
351.4
1.1
100
899.4
5.5
576.2
3.5
150
534.6
2.8
342.5
1.8
200
243.7
1.5
156.1
1.0
0
148.7
12.6
60.8
5.2
25
149.1
12.7
61.0
5.2
Cement
65
150.4
12.7
61.5
5.2
kiln
100
152.2
12.7
62.2
5.2
150
1468.9
12.7
567.6
5.2
200
6771.0
21.7
2397.5
8.8
0
232.8
5.0
74.8
6.9
25
970.7
6.0
74.9
6.9
Coal
65
434.3
3.8
75.8
6.9
EGU
100
222.1
3.8
77.3
6.9
150
517.2
3.8
1328.8
6.9
200
1572.6
6.1
4388.2
16.7
0
391.4
6.4
32.2
3.0
25
811.9
6.4
175.6
3.0
Ethanol
65
1735.2
7.4
1091.4
4.7
plant
100
1746.1
15.6
1223.5
11.0
150
1871.6
13.7
1311.5
9.6
200
1109.3
6.0
777.3
4.2
10 SILs used in the analysis are described in Section 2 above.
20
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Table 4 - Phase 1 Screening Modeling Results for N02 and S02 by Facility type: Maximum Impact
Results (continued)
Facility
Receptor
Elevation
I\I02 NAAQS (impacts in ppb)
S02 NAAQS (impacts in ppb)
Maximum 1-
hour impact
Impact at 50 km
(SIL 4 ppb)10
Maximum 1-
hour impact
Impact at 50 km
(SIL 3 ppb)10
0
4.0
0.3
207.2
16.4
25
17.2
0.3
897.8
16.4
Flare
65
95.8
0.7
5014.2
37.7
100
132.3
1.5
6924.3
77.3
150
150.8
1.2
7888.0
60.9
200
90.2
0.6
4718.9
29.9
0
78.3
3.2
22.0
0.9
25
212.4
3.2
64.1
0.9
Fuel oil
65
770.3
5.8
275.6
1.4
turbine
100
808.5
10.8
231.8
3.5
150
1126.0
12.5
403.9
If)
•
-------
Table 5 - Phase 1 screening modeling results for NOz and SOz by Facility type: Maximum Impact
Results at 50 km scaled to Reflect Near-Field NAAQS Compliance
Facility
NOz NAAQS
NAAQS: 100
SIL: 4
(ppb)
S02 NAAQS
NAAQS: 75
SIL: 3
(ppb)
Asphalt plant
Representative near-field impact (unsealed)11
445.7
68.212
50 km scaled impact13
1.4
0.7
Biomass plant
Representative near-field impact (unsealed)
351.4
231.1
50 km scaled impact
1.6
1.5
Cement kiln
Representative near-field impact (unsealed)
1452.3
531.6
50 km scaled impact
1.5
1.6
Coal EGU
Representative near-field impact (unsealed)
545.9
812.1
50 km scaled impact
1.1
2.1
Ethanol plant
Representative near-field impact (unsealed)
1238.9
765.5
50 km scaled impact
1.3
1.4
Flare
Representative near-field impact (unsealed)
76.7
4201.6
50 km scaled impact
1.5
1.8
Fuel oil turbine
Representative near-field impact (unsealed)
639.4
214.8
50 km scaled impact
1.9
2.1
Landfill gas turbine
Representative near-field impact (unsealed)
104.1
62.9
50 km scaled impact
1.8
1.0
NG compressor
Representative near-field impact (unsealed)
253.4
0.0
50 km scaled impact
1.5
0.0
Pulp & paper plant
Representative near-field impact (unsealed)
36836.8
11993.1
50 km scaled impact
0.9
0.6
11 The representative near-field impact is calculated as the average of the "Maximum 1-hour impact" shown in
Appendix Table A.l across each receptor elevation.
12 For several facilities, the representative near-field impact is below the level of the NAAQS. In these cases
(highlighted in red), the 50 km impact is not scaled as described in the next footnote. Instead, the original result
from Table 4 is taken directly for Table 5.
13 The 50 km scaled impact is calculated as the maximum of the "Impact at 50 km" values in Table 4 across each
receptor elevation multiplied by the ratio of the level of the NAAQS to the representative near-field impact shown
in this table. See Equation 1.
22
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4.2 Phase 2: Refined analyses for NO2 and SO2
The second phase of the analysis focused on characterizing impacts from tall stack sources using a more
refined approach to determine modeled source-level impacts. For this phase, AERMOD version 14134
was used with representative meteorological inputs from several sets of NWS stations across the nation
(described further below). A variety of meteorological data sets were used to provide more complete
and robust findings that better represent source impacts across the nation. 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 screening
analysis as shown in Figure 1. For this second phase, 1-hour, 3-hour, 24-hour and annual concentrations
were calculated to compare to the SILs for various averaging periods.
This refined modeling approach will generate less conservative estimates of the impacts at 50 km from
the various facilities relative to the screening analysis that indicated the potential for source impacts
above the SIL at 50 km. As discussed above, when NAAQS compliance is considered, it appears that only
facilities with tall stacks have the potential to show compliance in the near-field assessment for the
NAAQS and still have impacts at 50 km near the SIL. The coal EGU and the cement kiln had the tallest
stacks with the cement kiln emissions mainly at the 160 m stacks, while the coal EGU emissions are
mainly at the 150 and 100 m stacks. While the screening analysis indicated that the pulp and paper
facility had the highest near-field and 50 km impacts, the tallest stacks at this facility were roughly half
the height of the primary stacks at the cement kiln and coal EDU. Therefore, we focused only on the coal
EGU because its S02 emissions were concentrated at the tallest stack while its N02 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 N02 and S02.
Table 6 - Summary of N02 and S02 emissions for the coal EGU facility
Stack height (m)
17514
120
51
50
50
N02 emissions (tpy)
1564
174
104
10.4
10.4
S02 emissions (tpy)
4867
87
4.3
.7
.3
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-
14 The 150 m stack is above GEP height, but was modeled at this height for illustrative purposes.
23
-------
year average), NAAQS specific design value (5-year average of 98th percentile and 99th percentile daily 1-
hour maximum concentrations), annual average (5-year average of each annual average), and 24-hour
and 3-hour PSD increment levels (highest first and second values) for S02. 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).
4.2.1 1-hour NAAQS Results
Plots summarizing the refined modeling analysis for N02 and S02 are presented in Appendix B and the
results are summarized in Tables 7 and 8 for each 1-hour NAAQS. The most striking difference from the
screening and refined analysis is the decrease in the maximum 1-hour values for both pollutants. For
N02, 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 S02, the maximum
concentrations decrease even further from 4388 ppb to 454 ppb. For N02, the maximum 1-hour
concentrations at 50 km from the refined modeling (with unsealed emissions) are now well below the 1-
hour NAAQS SIL at 50 km. However, the S02 concentrations are still above the SIL at 50 km with the
unsealed emissions. If the S02 emissions are scaled such that the near-field results meet the NAAQS,
then the impact at 50 km are below the 1-hour NAAQS SIL. However, the maximum impacts in the near-
field for S02 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, it is not likely that a large emitting facility with a
150 m stack would be built in the immediate vicinity of terrain near or above stack height because the
facility would likely have issues providing a successful 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 the EGU source type would satisfy the NAAQS
compliance demonstration in the near-field, but be above the NAAQS 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 possibly have significant impacts at 50 km or greater
and need an LRT assessment.
24
-------
Table 7 - Phase 2 Refine Modeling Results for N02 by NWS Station
Met station
Receptor
Elevation
Maximum 1-hour impact
(ppb, 1st high)
98th percentile 1-hour impact
(ppb, 8th high)
All receptors
50 km (SIL 4 ppb)
All receptors
50 km (SIL 4 ppb)
0
546.81
1.50
366.15
0.94
25
505.18
1.66
344.43
1.04
Ashland, Wl
65
373.36
1.34
270.46
0.97
(ASX)
100
301.35
1.27
217.27
0.85
150
311.18
1.39
217.01
0.99
200
286.22
1.60
191.64
1.15
0
357.80
1.38
235.82
0.75
25
340.30
1.45
210.89
0.76
Dalhart, TX
65
269.71
1.32
129.94
0.77
DHT
100
216.93
1.28
118.30
0.73
150
199.68
1.35
128.86
0.80
200
239.83
1.50
127.65
0.96
0
417.98
1.62
318.30
1.16
25
397.27
1.75
302.32
1.17
Oakland, CA
65
312.91
1.53
239.16
1.15
OAK
100
250.09
1.52
191.94
1.12
150
245.54
1.56
146.20
1.14
200
212.50
1.91
138.62
1.19
0
443.30
1.15
344.51
0.72
Somerville,
NJ
SMQ
25
425.08
1.22
370.58
0.81
65
302.98
1.20
227.72
0.81
100
243.67
1.09
183.29
0.72
150
253.43
1.19
189.48
0.94
200
250.14
1.32
184.82
1.08
25
-------
Table 8 - Phase 2 Refine Modeling Results for S02 by NWS Station
Met
scenario
Receptor
Elevation
Maximum 1-hour impact
(ppb, 1st high)
99th percentile 1-hour impact
(ppb, 4th high)
All receptors
50 km (SIL 3 ppb)
All receptors
50 km (SIL 3 ppb)
0
23.65
2.58
14.22
1.98
25
23.69
2.57
14.31
1.97
Ashland, Wl
65
24.08
2.57
14.68
1.96
(ASX)
100
34.60
2.56
24.57
1.95
150
68.70
2.56
57.76
1.95
200
262.24
3.20
200.78
2.47
0
23.39
2.47
12.04
1.81
25
23.60
2.46
12.07
1.80
Dalhart, TX
65
23.97
2.46
12.40
1.78
DHT
100
49.53
2.46
42.82
1.77
150
87.43
2.46
53.61
1.76
200
652.11
3.15
454.48
2.28
0
28.98
3.01
21.36
2.65
25
29.01
2.99
21.52
2.64
Oakland, CA
65
29.23
2.97
21.75
2.63
OAK
100
43.59
2.96
28.06
2.63
150
82.33
2.95
67.46
2.62
200
394.67
4.04
329.24
2.97
0
25.57
2.08
16.24
1.63
Somerville,
NJ
SMQ
25
25.63
2.07
16.35
1.63
65
25.75
2.06
16.47
1.62
100
34.85
2.05
24.03
1.62
150
49.22
2.04
38.58
1.62
200
177.58
2.40
139.80
2.12
26
-------
4.2.2 3-hour, 24-hour, and annual PSD increment results
For the N02 and S02 PSD increment analysis, the results from the refined analysis presented in Section
4.2.1 have been used to scale down the impacts in the 3-hour and 24-hour S02 PSD increment and the
annual N02 and S02 PSD increment calculations. The scaling factors are given in Table 9. As shown in
Table 10 for the 3-hour and 24-hour S02 PSD increment, the scaled down impacts at 50 km are below
the Class II PSD increment SILs and slightly above the respective Class I PSD increment SILs for three of
the four meteorological data sets (Section B.2). However as shown in Table 10 for the annual N02 and
S02 PSD increment, the source impacts at 50 km are well below both Class I and Class II PSD increment
SILs for all cases (Section B.3). In general, these results show that the longer the averaging period, the
less likely that there will be significant source impacts at distances of 50 km and greater.
Table 9 - Scaling factors from NAAQS refined analysis for use in PSD increment refined analysis
Meteorological dataset NO2 scaling factors SO2 scaling factors
ASX
0.27
0.37
DHT
0.42
0.17
OAK
0.31
0.23
SMQ
0.27
0.54
27
-------
Table 10 - Phase 2 refined modeling results for N02 and S02 PSD increments by NWS station
ASX
DHT
OAK
SMQ
Elev.
Max
50
Max
50
Max
50
Max
50
domain
km
domain
km
domain
km
domain
km
PSD Increment SILs: CI -1; C2 - 25
(ug/m3)
3-hr S02
H1H
100
25.1
1.11
8.0
0.55
10.2
1.23
26.3
1.77
150
51.0
1.11
34.8
0.56
42.1
1.22
50.1
1.77
200
223.6
1.32
214.9
0.90
193.2
1.20
221.1
1.79
3-hr S02
H2H
100
15.4
1.05
6.6
0.50
9.6
1.07
21.6
1.71
150
43.9
1.05
27.0
0.50
40.6
1.07
46.6
1.70
200
199.4
1.21
200.5
0.69
169.6
1.07
210.9
1.77
PSD Increment SILs: CI - 0.2; C2 - 5
(ug/m3)
24-hr S02
H1H
100
5.0
0.24
2.4
0.10
3.1
0.35
8.5
0.54
150
23.6
0.27
12.2
0.10
16.7
0.35
22.6
0.53
200
120.8
0.34
79.3
0.13
76.3
0.35
158.4
0.53
24-hr S02
H2H
100
4.7
0.24
2.3
0.09
2.9
0.33
8.0
0.42
150
17.2
0.25
8.5
0.10
15.1
0.33
20.2
0.43
200
101.8
0.29
73.2
0.13
60.4
0.33
108.7
0.52
PSD Increment SILs: CI - 0.1; C2 -1 (ug/m3)
100
4.1
0.01
1.3
0.00
3.5
0.02
8.7
0.02
Annual N02
150
4.0
0.01
1.2
0.00
3.7
0.02
8.2
0.02
200
4.6
0.01
1.5
0.00
4.6
0.02
7.7
0.02
100
0.4
0.02
0.7
0.01
0.7
0.07
0.6
0.02
Annual S02
150
0.9
0.02
2.2
0.02
2.2
0.07
1.4
0.03
200
4.3
0.03
10.3
0.02
9.5
0.07
3.9
0.03
4.3 Phase 2: Refined analyses for PMio and PM2.5
Since the AIWG facilities did not include PM10 or PM25 emissions, we derived these emissions by scaling
from the emission rates for S02 and N02 based on emission ratios of these pollutants for EGUs listed in
the NEI. The ratios of PM10 and PM25 emissions to NOx emissions for all EGUs with NOx emissions
greater than 40 tons were calculated. Similarly, emission ratios were computed for EGUs with S02
emissions greater than 40 tons. PM emissions were significantly lower than NOx and S02 emissions. The
emissions data used in the refined modeling analysis are summarized in Table 11. On average, the PM10
emissions were about 22% of NOx and S02 emissions, while PM2 5 emissions were around 19% of NOx
and S02 emissions. The facilities with the greatest PM10 and PM2 5 emission ratios resulted in PM10 and
PM2.s being 50% of NOx and 38% of S02. 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 PM2 5 would be modeled as inert pollutants, the model would treat each
pollutant equally with respect to dispersion, so modeling both PM10 and PM2 5 with the approximately
the same emission rates would result in roughly the same modeled concentrations. The average
28
-------
emission ratios (20%) were used to scale the PM emissions for the PM analysis, based on the original
N02 and S02 emissions presented in Section 3.1.
Table 11- - Summary of 2011 NEI emission data used in refined modeling analysis
NOx ratios
PM10 max
PM10 min
PM10 mean
PM2.5 max
PM2.5 min
PM2.5 mean
8.0%
49.4%
22.9%
4.8%
49.2%
19.5%
S02 ratios
PM10 max
PM10 min
PM10 mean
PM2.5 max
PM2.5 min
PM2.5 mean
3.1%
37.7%
22.6%
2.7%
37.6%
18.7%
4.3.1 24-hour NAAQS results
Plots summarizing the refined modeling analyses for PM2.5 are presented in Appendix C, broken out by
averaging time and form. The comparison against the PM2.5 24-hour NAAQS are presented in Section
C.l. As shown in Table 12, the results for both the S02-scaled and N02-scaled emissions for all 4
meteorological data sets are generally below the 24-hour NAAQS SIL of 1.2 ug/m3 within the first 5 km
from the source and are an order of magnitude below the SIL at 50 km.
Table 12 - Phase 2 refined modeling results for 24-hour PM2.5 NAAQS by NWS station
ASX
DHT
OAK
SMQ
Elev.
Max
domain
50
km
Max
domain
50
km
Max
domain
50
km
Max
domain
50
km
NAAQS SIL: 1.2 (ug/m3)
PM2.5 24-hr NAAQS
N02-scaled, 8th high
100
10.7
0.03
7.4
0.02
11.5
0.07
13.5
0.04
150
10.6
0.04
6.8
0.03
11.5
0.07
12.3
0.04
200
10.7
0.04
9.0
0.03
14.8
0.07
12.4
0.05
PM2.5 24-hr NAAQS
S02-scaled, 8th high
100
1.5
0.07
1.8
0.05
1.7
0.17
1.8
0.09
150
4.5
0.08
5.5
0.06
5.5
0.17
3.9
0.09
200
21.6
0.09
27.2
0.07
29.1
0.18
14.9
0.11
4.3.2 Annual NAAQS and PSD increment results
The comparisons against the annual NAAQS (0.2 ug/m3) and PSD increment (0.05 ug/m3) SILs is
presented in Section C.2. As shown in Table 13, similar to the 24-hour NAAQS results, the refined
modeling results for all 4 meteorological data sets are generally below the annual NAAQS SIL within the
first 10 km and are below the annual PSD increment SIL within the first 20 km. The modeled impacts are
again an order of magnitude below both SILs at 50 km.
29
-------
Table 13 - Phase 2 refined modeling results for annual PM2.5 NAAQS and PSD increment by NWS
station
ASX
DHT
OAK
SMQ
Elev.
Max
50
Max
50
Max
50
Max
50
domain
km
domain
km
domain
km
domain
km
NAAQS SIL: 0.2 | PSD Increment SILs CI - 0.05; C2 -
0.2 (ug/m3)
PM2.5 annual
N02-scaled
100
2.2
0.01
1.5
0.00
3.1
0.01
3.2
0.01
150
2.2
0.01
1.4
0.00
3.2
0.01
3.0
0.01
200
2.5
0.01
1.7
0.00
4.0
0.01
2.9
0.01
PM2.5 annual
S02-scaled
100
0.3
0.01
0.4
0.01
0.5
0.04
0.5
0.02
150
0.6
0.01
1.0
0.01
1.4
0.05
1.0
0.02
200
3.2
0.02
4.9
0.01
6.2
0.05
2.9
0.02
4.3.2 24-hour PSD increment results
The comparisons against the 24-hour PSD increment (0.27 ug/m3) SILs is presented in Section C.2. As
shown in Table 14, unlike the results for the 24-hour NAAQS and the annual NAAQS and PSD increment,
the refined modeling impacts are not clearly below the SIL at 50 km. For the S02-scaled results, the
impacts at 50 km are slightly above the SIL in all cases, while the N02-scaled results are slightly below
the SIL in all cases. The results from the 24-hour and annual NAAQS analysis did not as clearly indicate
issues with NAAQS compliance in the near-field (the maximum 24-hour results were around 10-12
ug/m3, while the maximum annual results were around 3-4 ug/m3). Thus, there is no clear suggestion
that the emissions would need to be reduced to meet the NAAQS in the near-field such that the 24-hour
PSD increment impacts would be reduced. Nonetheless, the impacts are fairly close to the 24-hour PSD
increment SILs without emissions adjustments.
Table 14 - Phase 2 refined modeling results for 24-hour PM2.5 PSD increment by NWS station
ASX
DHT
OAK
SMQ
Elev.
Max
50
Max
50
Max
50
Max
50
domain
km
domain
km
domain
km
domain
km
PSD Increment SILs: CI
-0.27; C2-1.2 (ug/m3)
PM2.5 24-hr N02-
scaled H1H
100
18.1
0.07
12.5
0.05
16.8
0.12
25.9
0.08
150
19.3
0.07
12.3
0.06
16.7
0.12
27.9
0.09
200
21.0
0.08
30.0
0.06
23.8
0.12
24.2
0.09
PM2.5 24-hr S02-
scaled, H1H
100
2.7
0.13
2.8
0.11
2.7
0.30
3.1
0.20
150
12.8
0.15
14.3
0.12
14.5
0.30
8.4
0.20
200
65.3
0.18
93.3
0.15
66.3
0.31
58.7
0.20
30
-------
5. Conclusions
While this analysis did not necessarily capture all occurances of possible Class I area increment concern,
the results indicate that for most source types, if NAAQS compliance with the short-term standards can
be demonstrated in the near-field, then there are not likely to be significant source impacts at 50 km.
Thus, for most facilities that show compliance in the near-field, no evaluation of LRT would seem to be
necessary for NAAQS. 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 N02, S02 and PM2.5 PSD increment. These types of facilities
may have their maximum impact much farther from the facility than most. The results also indicate that
terrain features can be important for these types of facilities, as elevated terrain at or near stack height,
can result in higher plume impacts much closer to the source. When this occurs, NAAQS compliance
with the short-term standard may be sufficient to decrease long-range impacts and eliminate the
potential need for an LRT assessment for NAAQS or PSD increment. Conversely, elevated receptors in
the far-field can increase the need for LRT assessments, as these receptors may experience impacts
closer to the plume centerline.
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
31
-------
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 N02 & S02 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 N02 NAAQSfor the
Prevention of Significant Deterioration Program.
U. S. EPA. (2010b, August 23). Guidance Concerning the Implementation of the 1-hour S02 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.
U. S. EPA. (2016). Guidance on Significant Impact Levels for Ozone and Fine Particles in the Prevention of
Significant Deterioration Permitting Program. RTP. NC: Office of Air Quality Planning and
Standards.
32
-------
Appendix A
Plots and tables from the NO2 and SO2 NAAQS screening analysis
For all figures in this section, the N02 SIL is shown in blue and the S02 SIL is shown in red.
Table A.l - Phase 1 screening modeling results for N02 and S02 by Facility type: 8th and 4th high
results from screening analysis
N02 8th high (ppb) S02 4th high (ppb)
Facility
Receptor
Elevation
Maximum domain
wide impact
Impact at 50 km
(SIL 4 ppb)
Maximum domain
wide impact
Impact at 50 km
(SIL 3 ppb)
Asphalt
plant
0
290.98
5.01
96.09
0.67
25
834.55
5.86
115.35
0.70
65
884.69
3.89
50.03
0.24
100
355.51
2.00
49.72
0.16
150
178.68
1.45
49.32
0.14
200
129.77
1.30
48.96
0.14
Biomass
plant
0
15.84
0.95
10.70
0.66
25
15.96
0.95
10.79
0.66
65
478.56
1.62
330.84
1.05
100
826.66
4.76
538.14
3.18
150
531.36
2.57
342.52
1.64
200
239.94
1.26
153.73
0.87
Cement
kiln
0
131.36
10.22
60.18
4.75
25
132.24
10.25
60.42
4.75
65
132.04
10.26
60.98
4.75
100
132.31
10.27
61.85
4.75
150
1468.85
10.28
567.58
4.75
200
6716.97
17.61
2378.44
7.77
Coal
EGU
0
232.76
4.96
74.15
6.50
25
876.53
5.53
74.34
6.51
65
425.18
3.33
75.22
6.52
100
212.36
3.33
75.24
6.52
150
517.19
3.32
1328.82
6.51
200
1011.55
5.70
3244.59
15.27
Ethanol
Plant
0
391.43
6.15
31.80
2.95
25
789.49
6.13
174.55
2.95
65
1735.24
6.26
1091.40
4.27
100
1702.15
14.10
1206.21
10.40
150
1706.04
13.23
1311.49
9.27
200
1109.31
5.92
777.34
4.20
33
-------
Table A.l - Phase 1 screening modeling results for N02 and S02 by Facility type: 8th and 4th high
results from screening analysis (continued)
Facility
N02 8th high (ppb) S02 4th high (ppb)
Receptor
Elevation
Maximum
domain wide
impact
Impact at 50
km (SIL4 ppb)
Maximum
domain wide
impact
Impact at 50
km (SIL 3 ppb)
Flare
0
3.96
0.29
207.24
15.71
25
17.16
0.29
897.76
15.72
65
90.49
0.64
4962.82
34.24
100
123.43
1.28
6534.81
67.90
150
134.97
1.13
7888.02
60.57
200
90.19
0.56
4718.89
29.92
Fuel oil
turbine
0
78.29
3.03
22.03
0.85
25
212.39
3.03
64.14
0.85
65
770.30
5.15
275.63
1.39
100
760.16
10.01
226.57
3.28
150
1115.39
11.06
375.08
4.20
200
899.59
7.29
325.10
2.63
Landfill gas
turbine
0
28.07
0.85
13.04
0.40
25
109.57
1.03
65.11
0.45
65
202.29
1.69
125.04
0.96
100
168.51
1.02
104.05
0.61
150
74.95
0.47
44.81
0.31
200
41.34
0.41
25.33
0.21
NG
compresso
r
0
92.64
3.02
0.01
0.00
25
804.09
3.51
0.12
0.00
65
348.38
1.60
0.05
0.00
100
179.34
1.18
0.03
0.00
150
55.66
0.98
0.01
0.00
200
40.27
0.96
0.01
0.00
Pulp &
paper
plant
0
279.81
23.97
423.68
10.58
25
276.14
24.06
603.28
10.63
65
815.05
24.12
3438.12
16.32
100
9282.87
39.86
2624.44
11.39
150
9242.13
80.56
2377.23
21.30
200
7811.38
60.86
2235.38
18.24
34
-------
N02 asphalt, max results, SIL 4
1000
_Q
CL
CL
CM
O
1000
_Q
CL
Q_
CM
O
20 40
downwind dist, km
N02 asphalt, eigth high results, SIL 4
20 40
downwind dist, km
S02 asphalt, max results, SIL 3
20 40
downwind dist, km
S02 asphalt, fourth high results, SIL 3
20 40
downwind dist, km
Z hill
150
Z hill
Figure 2 - Results from the screening analysis for the asphalt plant.
35
-------
N02 biomass, max results, SIL 4
Z h
M 150
20 40
downwind dist, km
N02 biomass, eigth high results, SIL 4
Z hill
O 10
M 150
20 40
downwind dist, km
S02 biomass, max results, SIL 3
z hill
iod
M 150
20 40
downwind dist, km
S02 biomass, fourth high results, SIL 3
Z hill
M 150
20 40
downwind dist, km
Figure 3 - Results from the screening analysis for the biomass plant
36
-------
.a 1000 -
CL
CL
CM
100-
10-
1000-
-Q
Q.
CL
CM
O
CO
100-
10-
N02 cement_kiln, max results, SIL 4
Z h
_Q 1000
M 150
20 40
downwind dist, km
N02 cement_kiln, eigth high results, SIL 4
/
\
f \l/ \
/ \l/
20 40
downwind dist, km
S02 cement_kiln, max results, SIL 3
downwind dist, km
S02 cement_kiln, fourth high results, SIL 3
20 40
downwind dist, km
60
1000
L
/
60
Z_h i 11
o
-A- 25
¦ 65
100
¦g- 150
200
Z hill
M 150
Z_h i 11
o
~ 25
¦ 65
100
® 150
^ 200
Figure 4 - Results from the screening analysis for the cement kiln
37
-------
N02 coal_egu, max results, SIL 4
1000
.o
Q_
Cl
CM
o
100
7 h
M 150
downwind dist, km
N02 coal_egu, eigth high results, SIL 4
Z hill
Q_ 100
m 150
20 40
downwind dist, km
S02 coal_egu, max results, SIL 3
z hill
1000 —^
CM 100
M 150
20 40
downwind dist, km
S02 coal_egu, fourth high results, SIL 3
Z hill
M 150
20 40
downwind dist, km
Figure 5 - Results from the screening analysis for the coal EGU
38
-------
N02 ethanol, max results, SIL 4
1000
.O
Q_
Cl
CM
O
Z h
M 150
100
20 40
downwind dist, km
N02 ethanol, eigth high results, SIL 4
Z hill
M 150
20 40
downwind dist, km
S02 ethanol, max results, SIL 3
z hill
1000
Q_ 100
M 150
20 40
downwind dist, km
S02 ethanol, fourth high results, SIL 3
Z hill
cl 100
M 150
20 40
downwind dist, km
Figure 6 - Results from the screening analysis for the ethanol plant
39
-------
N02 flare, max results, SIL 4
Z h
a- ID
M 150
10000
10000
20 40
downwind dist, km
N02 flare, eigth high results, SIL 4
Z hill
Q- '0
M 150
20 40
downwind dist, km
S02 flare, max results, SIL 3
z hill
C1 100
M 150
20 40
downwind dist, km
S02 flare, fourth high results, SIL 3
Z hill
M 150
20 40
downwind dist, km
Figure 7 - Results from the screening analysis for the flare
40
-------
Z_h i 11
o
~ 25
¦ 65
100
S" 150
"/^r 200
Z_h i 11
o
-A- 25
¦ 65
100
¦g- 150
200
Z_h j 11
• o
A 25
¦ 65
100
¦& 150
7^200
Z_hill
~ o
-A: 25
¦ 65
100
150
^200
1000
N02 fuel_oil_turbine, max results, SIL 4
Q_
Cl
CM
O
100
J2
CL
CL
CM
O
100
20 40 60
downwind dist, km
S02 fuel_oil_turbine, max results, SIL 3
0 20 40 60
downwind dist, km
S02 fuel_oil_turbine, fourth high results, SIL 3
20 40
downwind dist, km
N02 fuel_oil_turbine, eigth high results, SIL 4
20 40
downwind dist, km
Results from the screening analysis for the fuel oil turbine
Figure 8 -
41
-------
N02 landfill_gas_turbine, max results, SIL 4
20 40
downwind dist, km
N02 landfill_gas_turbine, eigth high results, SIL 4
20 40
downwind dist, km
S02 landfill_gas_turbine, max results, SIL 3
20 40
downwind dist, km
S02 landfill_gas_turbirie, fourth high results, SIL 3
20 40
downwind dist, km
Z h
M 150
Z hill
M 150
Z hill
M 150
Z hill
M 150
Figure 9 - Results from the screening analysis for the landfill gas turbine
42
-------
N02 ng_compressor, max results, SIL 4
20 40
downwind dist, km
N02 ng_compressor, eigth high results, SIL 4
20 40
downwind dist, km
S02 ng_compressor, max results, SIL 3
Q.0 100
20 40
downwind dist, km
S02 ng_compressor, fourth high results, SIL 3
20 40
downwind dist, km
Z h
M 150
Z hill
O 10
M 150
Z hill
M 150
Z hill
ClO 100
M 150
Figure 10 - Results from the screening analysis for the natural gas compressor station
43
-------
10000 -
_Q
Q_
CL
CM
O 100-
10000 -
-Q
CL
Q.
CM
O 100-
N02 pulp_paper, max results, SIL 4
-1
¦
1
gill
3 — T.
¦
1
¦=i
r
—
1-
20 40
downwind dist, km
N02 pulp_paper, eigth high results, SIL 4
20 40
downwind dist, km
S02 pulp_paper, max results, SIL 3
downwind dist, km
S02 pulp_paper, fourth high results, SIL 3
20 40
downwind dist, km
60
—i
¦
L
1
|g^
kr—i
==§
^
3 TVl J
1
ril Bi
¦ 11
r
—
—
60
1000
Z_h i 11
0
¦A- 25
¦ 65
100
150
$ 200
Z_h i 11
o
-A- 25
¦ 65
100
M 150
200
Z hill
M 150
Z hill
r\l 100
M 150
Figure 11 - Results from the screening analysis for the pulp and paper plant
44
-------
Appendix B
Plots from NO2 and SO2 refined analysis
For all figures in this section, the N02 SIL is shown in blue and the S02 SIL is shown in red.
B.l Comparisons against the 1-hour NO2 and SO2 NAAQS
-------
N02 ASX_NAAQS, max results; SIL of 4
100-
.Q
Q.
CL
-------
N02 DHT_NAAQS, max results; SIL of 4
.Q
Q-100-
CL
-------
N02 OAK_NAAQS, max results; SIL of 4
-Q 100
20 40
downwind dist, km
N02 OAK_NAAQS, eigth high results; SIL of 4
o 10
20 40
downwind dist, km
so2 OAK_NAAQS, max results; SIL of 3
-9 100
20 40
downwind dist, km
S02 OAK_NAAQS, fourth high results; SIL of 3
_Q 100
co 10
20 40
downwind dist, km
Z hill
150
Z hill
150
Z hill
150
Z hill
150
Figure 14 - Refined N02 and S02 results, OAK, max and design values, 1-hour NAAQS
48
-------
N02 SMQ_NAAQS, max results; SIL of 4
-Q 100
100-
Q.
CL
j
M —
20 40
downwind dist, km
S02 SMQ_NAAQS, fourth high results; SIL of 3
downwind dist, km
60
O 10
Z hill
150
Z hill
150
Z_hill
o
25
¦ 65
100
-g- 150
200
Z hill
150
Figure 15 - Refined N02 and S02 results, SMQ, max and design values, 1-hour NAAQS
49
-------
B.2 Comparisons against the 3 and 24-hour SO2 PSD increment
S02 ASX H1H, 3hr; SIL of 1 (C1); 5 (C2)
Z hill
200
20 40
downwind dist, km
S02 ASX H2H, 3hr; SIL of 1 (C1); 5 (C2)
Z hill
20 40
downwind dist, km
S02 ASX H1H, 24hr; SIL of 0.2
downwind dist, km
S02 ASX H2H, 24hr; SIL of 0.2
200
Z hill
200
Z hill
200
downwind dist, km
Figure 16 - Refined S02 results, ASX, 3 & 24-hour PSD increment
50
-------
CO
100
O)
CM
o
co
CO
100
O)
CNI
o
co
100
S02 DHT H1H, 3hr; SIL of 1 (C1); 5 (C2)
Z hill
20 40
downwind dist, km
S02 DHT H2H, 3hr; SIL of 1 (C1); 5 (C2)
Z hill
20 40
downwind dist, km
S02 DHT H1H, 24hr; SIL of 0.2
Z hill
20 40
downwind dist, km
S02 DHT H2H, 24hr; SIL of 0.2
Z hill
20 40
downwind dist, km
Figure 17 - Refined S02 results, DHT, 3 & 24-hour PSD increment
51
-------
S02 OAK H1H, 3hr; SIL of 1 (C1); 5 (C2)
CO
100
a>
3
CM
O
co
CO
a>
3
CM
O
co
100
20 40
downwind dist, km
S02 OAK H2H, 3hr; SIL of 1 (C1); 5 (C2)
20 40
downwind dist, km
S02 OAK H1H, 24hr; SIL of 0.2
20 40
downwind dist, km
S02 OAK H2H, 24hr; SIL of 0.2
20 40
downwind dist, km
Z_h
nil
#
0
~
50
¦
100
-4-
150
M
200
Z_h
nil
•
0
~
50
¦
100
I
150
200
Z_h
nil
#
0
~
50
¦
100
150
200
Z_h
nil
•
0
~
50
*
100
-j-
150
200
Figure 18 - Refined S02 results, OAK, 3 & 24-hour PSD increment
52
-------
S02 SMQ H1H, 3hr; SIL of 1 (C1); 5 (C2)
CO
100-
cn
^ 10-
O
co
1
jpbi
K
20 40
downwind dist, km
S02 SMQ H2H, 3hr; SIL of 1 (C1); 5 (C2)
downwind dist, km
S02 SMQ H1H, 24hr; SIL of 0.2
downwind dist, km
S02 SMQ H2H, 24hr; SIL of 0.2
downwind dist, km
60
CD 10
Z_h
nil
#
0
~
50
«
100
-j-
150
a
200
Z_h
nil
•
0
~
50
¦
100
|
150
a
200
Z_h
nil
#
0
~
50
*
100
-j-
150
a
200
Z_h
nil
•
0
~
50
*
100
-j-
150
a
200
Figure 19 - Refined S02 results, SMQ, 3 & 24-hour PSD increment
53
-------
B.3 Comparisons against the annual NO2 and SO2 PSD increment
N02 ASX_ANN, max results; SIL of 0.1
z hi
200
20 40
downwind dist, km
S02 ASX_ANN, max results; SIL of 0.1
200
20 40
downwind dist, km
Figure 20 - Refined N02 & S02 results, ASX, annual NAAQS
54
-------
N02 DHT_ANN, max results; SIL of 0.1
o 0.10
20 40
downwind dist, km
S02 DHT_ANN, max results; SIL of 0.1
Z_h
ill
~
100
A
150
¦
200
Z_h
ill
~
100
A
150
¦
200
20 40
downwind dist, km
Figure 21 - Refined N02 & S02 results, DHT, annual NAAQS
55
-------
N02 OAK_ANN, max results; SIL of 0.1
20 40
downwind dist, km
S02 OAK_ANN, max results; SIL of 0.1
100
150
200
100
150
200
20 40
downwind dist, km
Figure 22 - Refined N02 & S02 results, OAK, annual NAAQS
56
-------
N02 SMQ_ANN, max results; SIL of 0.1
1.00-
co
E
O)
3
CM
O
0.10-"
0.01 ¦
(
»
1
1
1
I
1
I
i
¦
—
tss)
\
20 40
downwind dist, km
S02 SMQ_ANN, max results; SIL of 0.1
downwind dist, km
60
Z_h
ill
~
100
A
150
a
200
Z_h
ill
~
100
A
150
¦
200
Figure 23 - Refined N02 & S02 results, SMQ, annual NAAQS
57
-------
Appendix C
Plots from PM refined analysis
For all figures in this section, the PM2.5 PSD increment is indicated on each plot. For the NO-scaled
emissions, this is shown in blue and the S02-scaled emissions are shown in red.
-------
C.l Comparisons against the PM2.5 24-hour NAAQS
S02-scaled ASX_PM25_24HR_NAAQS 8th high:SIL of 1.2
10.0
CO
D)
3
Z hill
200
20 40
downwind dist, km
N02-scaled ASX_PM25_24HR_NAAQS 8th high:SIL of 1.2
10.0
CO
E
"5>
3
Z hill
200
20 40
downwind dist, km
Figure 24 - Refined PM2.s results, ASX, 24-hour NAAQS
59
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S02-scaled DHT_PM25_24HR_NAAQS 8th high:SIL of 1.2
10.0-
co
D)
3
1.0-
0.1
20 40
downwind dist, km
60
N02-scaled DHT_PM25_24HR_NAAQS 8th high:SIL of 1.2
<2 1.0
20 40
downwind dist, km
Z_h i 11
100
150
¦ 200
Z_h i 11
100
150
¦ 200
Figure 25 - Refined PM2.5 results, DHT, 24-hour NAAQS
60
-------
S02-scaled OAK_PM25_24HR_NAAQS 8th high:SIL of 1.2
20 40
downwind dist, km
N02-scaled OAK_PM25_24HR_NAAQS 8th high:SIL of 1.2
Z_h i 11
100
150
¦ 200
Z_h i 11
100
150
¦ 200
20 40
downwind dist, km
Figure 26 - Refined PM2.s results, OAK, 24-hour NAAQS
61
-------
S02-scaled SMQ_PM25_24HR_NAAQS 8th high:SIL of 1.2
10.0-
ft
CO
O)
3
1.0-
0.1
20 40
downwind dist, km
60
N02-scaled SMQ_PM25_24HR_NAAQS 8th high:SIL of 1.2
10.0
CO
E
"5>
3
20 40
downwind dist, km
Z_h i 11
100
150
¦ 200
Z_h i 11
100
150
¦ 200
Figure 27 - Refined PM2.s results, SMQ, 24-hour NAAQS
62
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C.2 Comparisons against the annual PSD increment and NAAQS
N02-scaled ASX_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
1.00
CO
O)
=s
0.10
0.01
20 40
downwind dist, km
Z_h i 11
o
-A 50
¦ 100
150
S 200
S02-scaled ASX_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
Z hill
200
20 40
downwind dist, km
Figure 28 - Refined PM2.s results, ASX, annual PSD increment and NAAQS
63
-------
N02-scaled DHT_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
20 40
downwind dist, km
S02-scaled DHT_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
Z_h i 11
100
^ 150
¦ 200
Z_h i 11
100
^ 150
¦ 200
20 40
downwind dist, km
Figure 29 - Refined PM2.s results, DHT, annual PSD increment and NAAQS
64
-------
N02-scaled OAK_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
1.00
CO
O)
0.10
0.01
20 40
downwind dist, km
Z_h i 11
100
^ 150
¦ 200
S02-scaled OAK_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
1.0
Z hill
CO
100
150
200
0.1
0
20
40
60
downwind dist, km
Figure 30 - Refined PM2.s results, OAK, annual PSD increment and NAAQS
65
-------
N02-scaled SMQ_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
1.00-
00
O)
=s
£ 0.10-
0.01
1
1
1
1
1
1
4
\
V
1
20 40
downwind dist, km
60
S02-scaled SMQ_PM25, ann avg; SIL of 0.05 (C1); 0.2 (C2)
1.0-
00
O)
=s
0.1
T
1
1
I
TT
A1 T""hi
20 40
downwind dist, km
60
Z_h i 11
100
^ 150
¦ 200
Z_h i 11
100
^ 150
¦ 200
Figure 31 - Refined PM2.s results, SMQ, annual PSD increment and NAAQS
66
-------
C.3 Comparisons against the PM2.5 24-hour PSD increment
S02-scaled ASX PM25 H1H: SIL of 0.27
Z hill
200
10.0
CO
E
"o>
20 40
downwind dist, km
N02-scaled ASX PM25 H1H: SIL of 0.27
Z hill
200
20 40
downwind dist, km
Figure 32 - Refined PM2.s results, ASX, 24-hour PSD increment
67
-------
S02-scaled DHT PM25 H1H: SIL of 0.27
100
CO 10
O)
3
10.0
CO
E
"5>
3
1.0
20 40
downwind dist, km
N02-scaled DHT PM25 H1H: SIL of 0.27
20 40
downwind dist, km
Z_h i 11
100
150
¦ 200
Z_h i 11
100
150
¦ 200
Figure 33 - Refined PM2.s results, DHT, 24-hour PSD increment
68
-------
S02-scaled OAK PM25 H1H: SIL of 0.27
10.0
CO
CD
3
20 40
downwind dist, km
N02-scaled OAK PM25 H1H: SIL of 0.27
Z_h i 11
# 100
150
¦ 200
Z_h i 11
# 100
150
¦ 200
20 40
downwind dist, km
Figure 34 - Refined PM2.s results, OAK, 24-hour PSD increment
69
-------
S02-scaled SMQ PM25 H1H: SIL of 0.27
20 40
downwind dist, km
N02-scaled SMQ PM25 H1H: SIL of 0.27
Z hill
100
150
200
Z_h i 11
100
150
¦ 200
20 40
downwind dist, km
Figure 35 - Refined PM2.s results, SMQ, 24-hour PSD increment
70
-------
71
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United States Office of Air Quality Planning and Standards Publication No. EPA- 454/ B-16-007
Environmental Protection Air Quality Assessment Division December, 2016
Agency Research Triangle Park, NC
72
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