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Secondary PM2.5 MERPs Demonstrations
Michael Moeller, Region 42019 EPA Regional/State/Local Modelers' Workshop
Seattle, WA
โข EPAโs 2017 revisions to the Guideline on Air Quality Models includes the following two-tiered demonstration approach for addressing single-source impacts on ozone and secondary PM2.5 (as detailed in Section 5):
โข Tier 1 demonstrations involve use of technically credible relationships between emissions and ambient impacts based on existing modeling results or studies deemed sufficient for evaluating a project sourceโs impacts.
โข Tier 2 demonstrations would involve case-specific application of chemical transport modeling (e.g., with an Eulerian grid or Lagrangian model).
โข Section 5 does not provide a requirement for chemical transport modeling
โข The EPA believes photochemical grid models are generally most appropriate for addressing ozone and secondary PM2.5, because they provide a spatially and temporally dynamic realistic chemical and physical environment for plume growth and chemical transformation.
Background: Single-Source Impacts on Ozone and Secondary PM2.5
โข April 30th 2019, the EPA released the final Guidance on the Development of Modeled Emission Rates for Precursors (MERPs) as a Tier 1 Demonstration Tool for Ozone and PM2.5 under the PSD Permitting Program or โMERPs Guidanceโ
โข Update to the draft MERPs Guidance that was released in December 2016โข Spreadsheet has also been posted to SCRAM that contains the underlying maximum impact and MERPs information (daily
PM2.5, annual PM2.5, and daily maximum 8-hr average O3 ) for each of the hypothetical sources.โข https://www3.epa.gov/ttn/scram/guidance/guide/illustrative_merps_epa_modeling_2018dec28version.xlsxโข Additional hypothetical sources were addedโข More examples were included
โข Cumulative Impact Analysesโข Source Impact analyses for Class I PSD Increment (discussed further later)
Background: Single-Source Impacts on Ozone and Secondary PM2.5
https://www3.epa.gov/ttn/scram/guidance/guide/illustrative_merps_epa_modeling_2018dec28version.xlsx
Tier 1 PM2.5 MERPs Demonstration Example
A step by step demonstration of how to apply Tier 1 MERPs to assess secondary PM2.5 impacts in PSD permits, including a refined analysis to
address long-range transport into Class I areas)
Step 1) Start with lowest, most conservative, illustrative MERPs for selected Climate Zone (Table 4-1, new to revised guidance):
Tier 1 Demonstration: Selecting an appropriate hypothetical MERPs
Step 2) Screen the closest hypothetical sources to the project facility and select the lowest, most conservative, MERPs
Tier 1 Demonstration: Selecting an appropriate hypothetical MERPs
Step 3) If selecting a nearby hypothetical source that is not the most conservative, the applicant should describe how the existing modeling reflects the formation of O3 or PM2.5 in that geographic area and is therefore most appropriate.
Information that could be used to describe the comparability of two different geographic areas include:โข nearby local and regional sources of pollutants and their emissions (e.g., other industry, mobile, biogenics) โข rural or urban nature of the area โข terrain โข ambient concentrations of relevant pollutants where availableโข average and peak temperatures โข humidity
Tier 1 Demonstration: Selecting an appropriate hypothetical MERPs
Table A-1. Complete list of EPA modeled hypothetical sources presented in this document. โMax Nearby Urban (%)โ column provides the highest percentage urban landcover in any grid cell near (within 50 km) the source.
MERP (tpy) =๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐ ๐ฃ๐ฃ๐๐๐๐๐ฃ๐ฃ๐๐ (๐๐๐๐๐๐ ๐๐๐๐ ๐ข๐ข๐ข๐ข๐๐๐
) โ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐ ๐๐๐ข๐ข๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐๐ก๐ก๐๐๐ฆ๐ฆ๐๐ ๐ก๐ก๐ก๐ก๐๐ ๐๐๐๐ ๐ข๐ข๐ข๐ข
๐๐๐ ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐
MERP (tpy) = 1.2 ๐ข๐ข๐ข๐ข๐๐๐
โ 1000 ๐๐๐ก๐ก๐ก๐ก๐.271 ๐ข๐ข๐ข๐ข
๐๐๐= 367 tpy MERP (tpy) = 1.0 ppb โ 500 ๐๐๐ก๐ก๐ก๐ก
1.1๐4 ๐ก๐ก๐ก๐ก๐๐= 441 ๐ก๐ก๐๐๐ก๐ก
Tier 1 Demonstration: Example MERPs Calculation
Class II Values
Metric Poll State County Emissions Stack Height Conc MERPDAILY SULFATE Florida Bay 1000 10 3.271 367
Metric Poll State County Emissions Stack Height Conc MERPO3 MDA8 NOX Florida Bay 500 10 1.134 441
FL Project Source
Tier 1 Demonstration: PM2.5 24-hr SIL ExampleExample: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐
๐๐๐๐modeled
concentration of Primary PM2.5 for the 24-hr Class II SIL.
NOX and SO2 precursor contributions to secondary PM2.5 are considered together, in addition to modeled primary PM2.5, to determine if the sourceโs air quality impact would exceed the PM2.5 SIL.
Equations to assess Project emission secondary impacts:
Project Impact as % of SIL = ๐ธ๐ธ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐๐ธ๐ธ๐๐๐๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐
* 100
Project Impact in ppb or ๐ข๐ข๐ข๐ข๐๐๐
= ๐ธ๐ธ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐๐ธ๐ธ๐๐๐๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐
โ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐ ๐ฃ๐ฃ๐๐๐๐๐ฃ๐ฃ๐๐ (๐๐๐๐๐๐ ๐๐๐๐ ๐ข๐ข๐ข๐ข๐๐๐
)
Project Impact in ppb or ๐ข๐ข๐ข๐ข๐๐๐
= ๐ธ๐ธ๐ธ๐ธ๐๐๐ธ๐ธ๐ธ๐ธ๐๐๐๐๐ธ๐ธ ๐๐๐๐๐ก๐ก๐๐ ๐ก๐ก๐๐๐ก๐ก ๐๐๐๐๐๐๐ธ๐ธ ๐๐๐๐๐๐๐๐๐๐๐๐๐ก๐ก โ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐ ๐๐๐ข๐ข๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐๐ก๐ก๐๐๐ฆ๐ฆ๐๐ ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐๐๐ข๐ข๐ฆ๐ฆ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ (๐๐๐ก๐ก๐ก๐ก) ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL Example
Is Primary + Secondary PM2.5 > SIL?
Step 1): Use lowest illustrative MERP from the Southeast Climate Zone:
Tier 1 Demonstration: PM2.5 24-hr SIL Example
PM2.5 24-hr SIL = 1.2 ๐๐๐๐๐๐๐๐
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐๐๐๐๐
modeled concentration of Primary PM2.5 for the 24-hr Class II SIL.
Tier 1 Demonstration: PM2.5 24-hr SIL ExampleExample: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐
๐๐๐๐modeled
concentration of Primary PM2.5 for the 24-hr Class II SIL.
Step 1): Use lowest illustrative MERP from the Southeast Climate Zone:
Project Impact as % of SIL =( 100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐1,94๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5๐๐๐ธ๐ธ๐๐๐๐
+ 100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐2 ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐๐67 ๐๐๐๐๐๐ ๐๐๐๐2 ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5 ๐๐๐ธ๐ธ๐๐๐๐
) * 100 = 32% of SIL
Project Impact in ๐ข๐ข๐ข๐ข๐๐๐
= ( 100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐1,94๐ ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5 ๐๐๐ธ๐ธ๐๐๐๐
+ 100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐2 ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐๐67 ๐๐๐๐๐๐ ๐๐๐๐2 ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5๐๐๐ธ๐ธ๐๐๐๐
) * 1.2 ๐ข๐ข๐ข๐ข๐๐๐
= 0.384 ๐๐๐๐๐๐๐๐
Primary + Secondary PM2.5 as % of SIL:1.0๐ข๐ข๐ข๐ข๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐
1.2๐ข๐ข๐ข๐ข๐๐๐ ๐๐๐๐๐๐+ 0.32 = 115% of SIL
Primary + Secondary PM2.5 in ๐ข๐ข๐ข๐ข๐๐๐
:
1.0 ๐ข๐ข๐ข๐ข๐๐๐
+ 0.384 ๐ข๐ข๐ข๐ข๐๐๐
= 1.384 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
Is Primary + Secondary PM2.5 > SIL?1.0 + 0.38 = 1.38 ๐ฎ๐ฎ๐ฎ๐ฎ
๐ฆ๐ฆ๐๐
If no, then total PM2.5daily is below the SIL and no Class II Increment or NAAQS analysis is necessary
Step 2: Select lowest MERP from nearby sources with similar stack height:
Step 1): Use lowest, illustrative MERP from the Southeast Climate Zone:
100 tpy NOx from source/1,943 tpy NOx daily PM2.5 MERP = 0.05100 tpy SO2 from source/367 tpy SO2 daily PM2.5 MERP = 0.27 Total Secondary PM2.5 = .05 + .27 = .32 * 100 = 32% or 0.32 * 1.2 ug
m๐= 0.384 ๐ฎ๐ฎ๐ฎ๐ฎ
๐ฆ๐ฆ๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL ExampleExample: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐
๐๐๐๐modeled
concentration of Primary PM2.5 for the 24-hr Class II SIL.
PM2.5 24-hr SIL = 1.2 ๐๐๐๐๐๐๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL Example
Step 2): Select lowest MERP from nearby sources with similar stack height:
-Florida, Bay (12EUS2):-Alabama, Tallapoosa (12EUS3):-Alabama, Autauga (12EU2):
Metric Poll State County Emissions Stack Height Conc MERPDAILY NITRATE Florida Bay 1000 10 0.618 1943DAILY NITRATE Florida Bay 500 10 0.283 2122DAILY NITRATE Alabama Autauga 500 10 0.178 3370DAILY NITRATE Alabama Autauga 1000 10 0.341 3514DAILY NITRATE Alabama Tallapoosa 500 10 0.092 6555
Metric Poll State County Emissions Stack Height Conc MERPDAILY SULFATE Florida Bay 1000 10 3.271 367DAILY SULFATE Alabama Autauga 1000 10 3.097 387DAILY SULFATE Florida Bay 500 10 1.366 439DAILY SULFATE Alabama Autauga 500 10 1.231 487DAILY SULFATE Alabama Tallapoosa 500 10 0.325 1844
Same MERPs from Step 1; therefore:
Total Secondary PM2.5 = 0.384 ugm๐
or 32% of SIL
Total PM2.5 = 1.0 + 0.38 = 1.38 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐๐๐๐๐
modeled concentration of Primary PM2.5 for the 24-hr Class II SIL.
Is Primary + Secondary PM2.5 > SIL?1.0 + 0.38 = 1.38 ๐๐๐๐
๐๐๐๐
Then Total PM2.5 Daily is below the SIL and no Class II Increment or NAAQS analysis is necessary
Step 2: Select lowest MERP from nearby sources with similar stack height:-Florida, Bay (12EUS2):-Alabama, Tallapoosa (12EUS3):-Alabama, Autauga (12EU2):
Same as Step 1:
Total Secondary PM2.5 = 0.384 ug/m3 or 32% of SILTotal PM2.5 = 1.0 + 0.38 = 1.38 ๐๐๐๐
๐๐๐๐
Step 3): Select most representative nearby source for similar scenario (500 tpy and L stack):
Step 1): Use lowest illustrative MERP from the Southeast Climate Zone:
100 tpy NOx from source/1,943 tpy NOx daily PM2.5 MERP = 0.05100 tpy SO2 from source/367 TPY SO2 daily PM2.5 MERP = 0.27 Total Secondary PM2.5 = .05 + .27 = .32 * 100 = 32% or 0.32 * 1.2 ug
m๐= 0.384 ๐๐๐๐
๐๐๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL ExampleExample: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐
๐๐๐๐modeled
concentration of Primary PM2.5 for the 24-hr Class II SIL.
PM2.5 24-hr SIL = 1.2 ๐๐๐๐๐๐๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL Example
Step 3): Select most representative nearby source for similar scenario (500 tpy and L stack):
-Florida, Bay (12EUS2):-Alabama, Tallapoosa (12EUS3):-Alabama, Autauga (12EU2):
Information that could be used to assess the comparability of two different geographic areas include:โข nearby local and regional sources of pollutants and
their emissions (e.g., other industry, mobile, biogenics)
โข rural or urban nature of the area โข terrain featuresโข ambient concentrations of relevant pollutants
where availableโข average and peak temperatures โข humidity
Metric Poll State County Emissions Stack Height Conc MERPDAILY NITRATE Florida Bay 500 10 0.283 2122DAILY NITRATE Alabama Autauga 500 10 0.178 3370DAILY NITRATE Alabama Tallapoosa 500 10 0.092 6555
Metric Poll State County Emissions Stack Height Conc MERPDAILY SULFATE Florida Bay 500 10 1.366 439DAILY SULFATE Alabama Autauga 500 10 1.231 487DAILY SULFATE Alabama Tallapoosa 500 10 0.325 1844
100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐6,555 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5 ๐๐๐ธ๐ธ๐๐๐๐
= 0.015
100 ๐๐๐ก๐ก๐ก๐ก ๐๐๐๐2 ๐๐๐๐๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐1,844 ๐๐๐๐๐๐ ๐๐๐๐2 ๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐2.5๐๐๐ธ๐ธ๐๐๐๐
= 0.05
Total Secondary PM2.5 = .015 + .05 = .065 * 100 = 7% of SILor 0.065 * 1.2 ๐ข๐ข๐ข๐ข
๐๐๐= 0.078 ๐๐๐๐
๐๐๐๐
Total PM2.5 = 1.0 + 0.078 = 1.078 ๐๐๐๐๐๐๐๐ โ
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐๐๐๐๐
modeled concentration of Primary PM2.5 for the 24-hr Class II SIL.
Is Primary + Secondary PM2.5 > SIL?1.0 + 0.38 = 1.38 ๐๐๐๐
๐๐๐๐
Then Total PM2.5 Daily is below the SIL and no Class II Increment or NAAQS analysis is necessary
Step 2: Select lowest MERP from nearby sources with similar stack height:-Florida, Bay (12EUS2):-Alabama, Tallapoosa (12EUS3):-Alabama, Autauga (12EUS2):
Same as Step 1:Total Secondary PM2.5 = 32% of SIL or 0.384 ๐๐๐๐
๐๐๐๐Total PM2.5 = 1.0 + 0.38 = 1.38 ๐๐๐๐
๐๐๐๐
Step 3): Select representative nearby source for similar scenario (500 tpy and L stack)-Florida, Bay (12EUS2):-Alabama, Tallapoosa (12EUS3):-Alabama, Autauga (12EU2):
NOx: 100 tpy/6555 MERP = 0.015SO2: 100 tpy/1844 MERP = 0.05Total Secondary PM2.5 = 7% of SIL or 0.078๐๐๐๐
๐๐๐๐Total PM2.5 = 1.0 + 0.078 = 1.078 ๐๐๐๐
๐๐๐๐
Step 1): Use lowest illustrative MERP from the Southeast Climate Zone:
100 tpy NOx from source/1,943 tpy NOx daily PM2.5 MERP = 0.05100 tpy SO2 from source/367 TPY SO2 daily PM2.5 MERP = 0.27 Total Secondary PM2.5 = .05 + .27 = .32 * 100 = 32% or 0.32 * 1.2 ug/m3 = 0.384 ๐๐๐๐
๐๐๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL Example
โ
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 1.0 ๐๐๐๐๐๐๐๐
modeled concentration of Primary PM2.5 for the 24-hr Class II SIL.
PM2.5 24-hr SIL = 1.2 ๐๐๐๐๐๐๐๐
Tier 1 Demonstration: PM2.5 24-hr SIL Example
Is Primary + Secondary PM2.5 > 100% or 1.2 ๐ข๐ข๐ข๐ข
๐๐๐?
Perform Cumulative Analysis
NAAQS Modeling:Modeled Primary PM2.5 + MERPs Secondary
PM2.5 + Background Monitor < NAAQS?
PSD Increment:Modeled Primary PM2.5 + MERPs Secondary
PM2.5 < Increment?
YES
PM2.5 24hr Analysis Complete
NO
Tier 1 Demonstration: Class I Analysis Example (Daily PM2.5) PM2.5 24-hr Class I SIL = 0.27 ๐๐๐๐
๐๐๐๐
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with ๐๐.๐๐๐๐ ๐๐๐๐๐๐๐๐
concentration of Primary PM2.5 at 50 km and the nearest Class I area is 150 km away
FL Source
Class I Area -Chassahowitzka
Use AERMOD to model primary PM2.5 at 50km in the direction of the nearest Class I area โChassahowitzka, 150km away
Primary PM2.5 at 50 km = ๐๐.๐๐๐๐ ๐๐๐๐
๐๐๐๐
Include Secondary PM2.5for Class I PM2.5assessments
Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 0.18 ๐๐๐๐๐๐๐๐
concentration of Primary PM2.5 at 50 km and the nearest Class I area is 150 km away
Step 2) Select lowest MERP from nearby sources (Florida, Bay) with similar stack height:
Same as Step 1Total Secondary PM2.5 = .05 + .27 = 0.32 * 1.2 ๐ข๐ข๐ข๐ข
๐๐๐= 0.384 ๐๐๐๐
๐๐๐๐
Step 3): Select representative nearby source (Alabama, Tallapoosa) for similar scenario (500 tpy and L stack)
NOx: 100 tpy/6555 MERP = 0.015SO2: 100 tpy/1844 MERP = 0.05Total Secondary PM2.5 = 0.065 * 1.2 ๐ข๐ข๐ข๐ข
๐๐๐= 0.078 ๐๐๐๐
๐๐๐๐
Step 1) Use lowest illustrative MERP from the Southeast Climate Zone:
100 tpy NOx from source/1,943 tpy NOx daily PM2.5 MERP = 0.05100 tpy SO2 from source/367 TPY SO2 daily PM2.5 MERP = 0.27 Total Secondary PM2.5 = .05 + .27 = 0.32 * 1.2 ๐ข๐ข๐ข๐ข
๐๐๐= 0.384 ๐๐๐๐
๐๐๐๐
Tier 1 Demonstration: Class I Analysis Example (Daily PM2.5)
Primary PM2.5 at 50km + Secondary PM2.5 = 0.18 + 0.384 = 0.564 ๐๐๐๐
๐๐๐๐
Primary PM2.5 at 50km + Secondary PM2.5 = 0.18 + 0.384 = 0.564 ๐๐๐๐
๐๐๐๐
Primary PM2.5 at 50km + Secondary PM2.5 = 0.18 + 0.078 = 0.258 ๐๐๐๐
๐๐๐๐
PM2.5 24-hr Class I SIL = 0.27 ๐๐๐๐
๐๐๐๐
โ
Tier 1 Demonstration: Class I Analysis Example (Daily PM2.5)Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 0.2 ๐๐๐๐
๐๐๐๐concentration of Primary PM2.5 at 50 km and the nearest Class I area is 150 km away.
Step 3): Select representative nearby source (Alabama, Tallapoosa) for similar scenario (500 tpy and L stack)
NOx: 100 tpy/6555 MERP = 0.015SO2: 100 tpy/1844 MERP = 0.05Total Secondary PM2.5 = 0.065 * 1.2 ๐ข๐ข๐ข๐ข
๐๐๐= 0.078 ๐๐๐๐
๐๐๐๐
Primary PM2.5 at 50km + Secondary PM2.5 = 0.2 + 0.078 = 0.278 ๐๐๐๐
๐๐๐๐
PM2.5 24-hr Class I SIL = 0.27 ๐๐๐๐
๐๐๐๐
What to do when neither Step 1 โ 3 will work and the nearest Class I area is significantly further than 50km?
The maximum predicted secondary concentrations are within 10 โ 50 km of the source and decrease substantially with distance. Taking the conservative, maximum values from the MERPs may not work for all projects, requiring a more refined approach.
Alabama, Tallapoosa: 500 tpy, L Height (From MERPs Guidance Modeling)
Conc
entr
atio
n (u
g/m
3)
Distance from Source (Km)
Source 19: Alabama, TallapoosaEmissions: 500 TPY
Stack Height: L
Maximum Impact โฅ 50 km from source (ug/m3)
24-hr AnnualSulfate 0.2031 0.0041Nitrate 0.0626 0.0012
Tier 1 Demonstration: Class I Analysis Example (Daily PM2.5)Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 0.2 ๐ฎ๐ฎ๐ฎ๐ฎ
๐ฆ๐ฆ๐๐concentration of Primary PM2.5 at 50 km and the nearest Class I area is 150 km away.
Refined Approach Step 1: Take the maximum impact โฅ 50 km from the hypothetical source and add to the primary PM2.5
Project Impact (๐ข๐ข๐ข๐ข๐๐๐
) = ๐ธ๐ธ๐ธ๐ธ๐๐๐ธ๐ธ๐ธ๐ธ๐๐๐๐๐ธ๐ธ ๐๐๐๐๐ก๐ก๐๐ ๐ก๐ก๐๐๐ก๐ก ๐๐๐๐๐๐๐ธ๐ธ ๐๐๐๐๐๐๐๐๐๐๐๐๐ก๐ก โ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐ ๐๐๐ข๐ข๐๐๐๐๐๐๐๐๐ก๐ก ๐๐๐๐๐ก๐ก๐๐๐ฆ๐ฆ๐๐ ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐๐๐ข๐ข๐ฆ๐ฆ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐ (๐๐๐ก๐ก๐ก๐ก) ๐๐๐๐๐๐๐๐ โ๐ก๐ก๐ก๐ก๐๐๐๐โ๐๐๐๐๐๐๐ฆ๐ฆ๐๐๐๐ ๐๐๐๐๐ข๐ข๐๐๐ฆ๐ฆ๐๐
PM2.5 Nitrate Daily: 100 ๐ก๐ก๐๐๐ก๐ก โ0.0626๐๐๐๐๐๐๐๐500 ๐๐๐ก๐ก๐ก๐ก
= .013 ๐ข๐ข๐ข๐ข๐๐๐
PM2.5 Sulfate Daily: 100 ๐ก๐ก๐๐๐ก๐ก โ0.20๐1๐ข๐ข๐ข๐ข๐๐๐500 ๐๐๐ก๐ก๐ก๐ก
= .041 ๐ข๐ข๐ข๐ข๐๐๐
Total Secondary PM2.5 = .013 + .041 = .054 ๐ข๐ข๐ข๐ข๐๐๐
Primary PM2.5 + Secondary PM2.5 = .20 + .054 = 0.254 ๐๐๐๐๐๐๐๐
PM2.5 24-hr Class I SIL = 0.27 ๐๐๐๐
๐๐๐๐
Tier 1 Demonstration: Class I Analysis Example (Daily PM2.5)Example: A small, surface-level source in central Florida with 100 tpy of NOx and 100 tpy of SO2 with 0.23 ๐๐๐๐
๐๐๐๐concentration of Primary PM2.5 at 50 km and the nearest Class I area is 150 km away.
What if Step 1 refined screening was not enough?
Step 2: Take the maximum impact โฅ the distance the project facility is from the nearest Class I area and add to the primary PM2.5
Distance (km)24-hr Impact (ยตg/m3)
Nitrate Sulfate10 0.0702 0.258420 0.0915 0.325330 0.0821 0.305240 0.0720 0.258450 0.0492 0.155360 0.0626 0.203170 0.0501 0.150080 0.0389 0.109490 0.0306 0.0880
100 0.0287 0.0787110 0.0266 0.0590120 0.0256 0.0667130 0.0206 0.0577140 0.0235 0.0572150 0.0201 0.0571
Maximum Impact โฅ 150km:
PM2.5 Daily Nitrate: 100 tpy โ 0.0201 ๐ข๐ข๐ข๐ข/๐๐๐500 ๐๐๐ก๐ก๐ก๐ก
= .004 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
PM2.5 Daily Sulfate: 100 tpy โ 0.0571 ๐ข๐ข๐ข๐ข/๐๐๐500 ๐๐๐ก๐ก๐ก๐ก
= .012 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
Total Secondary PM2.5 = .004 + .012 = .016 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
Primary PM2.5 + Secondary PM2.5 = .23 + .016 = .246 ๐ฎ๐ฎ๐ฎ๐ฎ๐ฆ๐ฆ๐๐
PM2.5 24-hr Class I SIL = 0.27 ๐๐๐๐
๐๐๐๐