Technical Support Document (TSD)

For the Modeling and Weight of Evidence (WOE) Portions of the Document Entitled

“Delaware State Implementation Plan For Attainment of the PM 2.5 Annual National Ambient Air Quality Standard,” January 3, 2008

TS D Prepared May , 2010 Todd A. Ellsworth Office of Air Monitoring and Anal ys is , 3AP40 U.S. Environmental Protection Agency , Region 3

1650 Arch Street Philadelphia, Pennsylvania 19103

/s/

____________________________________________ Reviewed b y Walter Wilkie, Associate Director, Office of Air Monitoring and Anal ys is (3AP40)

June 15, 2010

_________________ Date Signed2



### Technical Support Document for the Modeling Portion Of the State of **Delaware’s Ozone State Implementation Plan (SIP) Entitle d “**  **Delaware**

**State Implementation Plan For Attainment of the PM**  **2.5** 

### Annual National Ambient Air Quality

**Standard, January 3, 2008” Purpose of the Technical Support Document**  This Technical Support Document (TSD) describes the Environmental Protection Agency ’s (EPA’s) evaluation of the modeling and weight of evidence (WOE ) portion of Delaware’s State Implementation Plan (SIP) revision entitled “ Delaware State Implementation Plan For Attainment of the PM 2.5 Annual National Ambient Air Quality Standard , January 3, 2008 .” This SIP revision will hereafter be referred to as the Delaware PM 2.5 SIP . In April 2005, EPA designated 126 areas of the country a s “non - attainment” under the annual fine particle (PM 2.5 ) National Ambient Air Quality S tandard (NAAQS). Among those non - attainment areas is the Philadelphia
- Wilmington, PA -NJ - DE PM 2.5 Non Attainment Area (NAA). This NAA includes : New Castle County Delaware, Burlington and Camden Counties in New Jersey and Bucks, Chester, Delaware, Montgomery and Philadelphia Counties in Pennsylvania. According to the federal Clean Air Act (CAA) and the EPA Implementation Rule 1 , this entire NAA must attain compliance with the annual PM 2.5 NAAQS by 2010. The purpose of this TSD is to provide more detailed information than can be c ontained in the official notice published in the Federal Register . Readers who need more information than we provide in this TSD or want to review the modeling in more detail should read the above referenced Delaware SIP. **The Regulatory Framework**  On July 18, 1997 (62 FR 36852), EPA established PM 2.5 NAAQS, including an annual standard of 15.0 μg/m 3 based on a 3
- ye ar average of annual mean PM 2.5 concentrations, and a 24
- hour (or dail y) standard of 65 μg/m 3 based on a 3
- year average of the 98th percentile of 24
- hour concentrations. EPA established the standards based on significant evidence and numerous health studies demonstrating that serious health effects are associated with exposures to PM 2.5 . F ollowing promulgation of a new or revised NAAQS, EPA is required b y the CAA to designate areas throughout the United States as attaining or not attaining the NAAQS; this designation process is described in section 107(d)(1) of the CAA. In 1999, EPA and 1 Environmental Protection Agency, Clean Air Fine Particle Implementation Rule , 40 CFR Part 51, March 29, 2007.3

State Air
- quality

A gencies initiated the monitoring p rocess for the 1997 PM 2.5 NAAQS , and , by January 2001 , established a complete set of air
- quality monitors. On January 5, 2005, EPA published initial air
- quality designations for the 1997 PM 2.5 NAAQS (70 FR 944), based on air
- quality monitoring data for calendar years 2001 - 20 03. On April 14, 2005, EPA published a final supplemental rule amending the A gency ’s initial designations (70 FR 19844). EPA did not consider modifications made in this rule to be “re - designations ” because the changes were made before April 5, 2005, the effective date of the initial designations. As a result of the final supplemental rule, PM 2.5 nonattainment designations are in effect for 39 areas, com prising 208 counties within 20 S tates (and the District of Columbia) nationwide, with a combined population of about 88 million. The Delaware portion of the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA which is the subject of this proposed rulemaking, is included in the list of areas not attaining the 1997 PM 2.5 NAAQS . The onl y Delaware C ounty included in the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA is New Castle County
. On October 17, 2006, EPA strengthened the 24
- hour PM 2.5 NAAQS to 35 μg/m 3 , and retained the level of the annual PM 2.5 standard at 15.0 μg/m 3 (see 71 FR 61144). On November 13, 2009, EPA designated areas as either attainment/unclassified or nonattainment with respect to the revised 24
- hour NAAQS (see 74 FR 58688). In th e November 2009 designation action , EPA established a deadline of December 14, 2012, for S tates to submit attainment plans for areas designated as nonattainment for the revised 24 - hour PM 2.5 NAAQS. Therefore the Delaware PM 2.5 SIP does not address the current 24 - hour PM 2.5 NAAQS. Of relevance to the proposed rulemaking herein, 74 FR 58688 clarified designations for the 1997 PM 2.5 NAAQS by relabeling the existing designation tables to identify designations for the annual NAAQS, and b y providing a separate table identifying designations for the 1997 24
- hour NAAQS (i.e., 65 μg/m 3 ). In that table, the P hiladelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA i s designated as attaining the 1997 24 - hour PM 2.5 NAAQS. **Introduction to the Delaware**  **State Implementation Plan for the Annual Average**  **PM 2.5 Standard** On July 1 8, 1997, EPA established a health based PM 2.5 NAAQS at 15.0 micrograms per cubic meter (μg/m3), annual average. New Castle County , Delaware was designated by the EPA as being in non**-** attainment for this annual PM 2.5 NAAQS in April 2005 2

. Kent and Sussex Counties were designated as attainment; however, sources within these counties emit PM 2.5 and PM 2.5 precursors which contribute to PM 2.5 non - attainment in New Castle County
. The PM 2.5 SIP includes plans to reduce PM 2.5 emissions for Delaware’s portion of the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA . The SIP also includes modeling that 2 70 FR 944 , January 5, 20054

will predict wh ether the area will meet the PM 2.5 standard b y the attainment date. This TSD reviews Delaware’s documentation of modeling that shows attainment of the annual average PM 2.5 standard by the 2010 attainment date. All of the S tates in the northeastern United States cooperated via the Ozone Transport Commission’s (OTC) Modeling Committee to prepare the modeling that was performed by the New York State Department of Environmental Conservation (NYSDEC) and supporting organizations. Delaware believes that their PM 2.5 SIP demonstrates that all of the CAA and Rule requirements associated with the annual PM 2.5 NAAQS have been met; and that Delaware and the entire Philadelphia
- Wilmington
- DE - PA -NJ NAA w ill attain compliance with the annual PM 2.5 NAAQS as expeditiously as practicable, and not later than 2010. **W hat Are The Components Of A Modeled Attainment Demonstration?**  **Modeling Process Overview** Delaware is a member of the Mid
- Atlantic/Northeast Visibility Union (MANE
- VU) Regional Planning Organization (RPO) . The MANE
- VU RPO was tasked with the assignment of preparing a PM - 2.5 modeling platform that all member states could use to demonstrate compliance with the 1997 PM 2.5 NAAQS. The New York State Department of Environmental Conservation (NYSDEC) was the lead agency

for coordinating and running the modeling platform use d by the MAVE
- VU RPO. Modeling centers responsible for running the platform included the NYSDEC, the University

of Maryland at College Park (UMD), the Northeast States for Coordinated Air Use Management (NESCAUM), the New Jersey Department of Environmental Protection (NJ DEP), and the Virginia Department of Environmental Quality (VA DEQ). Each modeling center was responsible for installing the modeling platform, conducting diagnostic tests and completing a benchmark run to ensure accurate results. The MANE
- VU RPO used the Community Multi
- scale Air Quality

model (CMAQ) version 4.4 as its photochemical grid model. The mo del uses simulations of chemical reactions, emission of PM 2.5 and PM 2.5 precursors and a sophisticated meteorological model to produce PM 2.5 concentrations over the eastern United States. The meteorological data used in the meteorological model was for th e base ye ar PM 2.5 season of 2002. The photochemical grid model was run with the base year meteorology and base year emissions to determine if the model performance was satisfactory. Once the model performance was determined to be adequate, 2009 ozone concentrations were modeled by

running the model with projected emissions for 2009 and th e original 2002 meteorology
. The meteorology was held constant so that the results of changing the emissions would not be influenced b y changing meteorology
.5

The EPA mo deling guidance 3 rec ommends that S tates use the modeled PM concentrations in a relative sense and not rel y solely on the concentrations the model predicts for the attainment year (2009). A modeled attainment test is an exercise in which an air quality

mod el is used to simulate current and future air quality. If future estimates of PM 2.5 concentrations are less than the NAAQS, then this element of the attainment test is satisfied. EPA’s recommended test is one in which model estimates are used in a “relative” rather than “absolute” sense. Ratios of the model’s future (2009) predicted PM 2.5 concentrations to base year (2002) predictions are calculated for all PM 2.5 monitor locations. These ratios are called relative response factors (RRF)
. Future PM 2.5 c oncentrations are estimated at existing monitoring sites b y multiplying a modeled relative response factor at locations “near” each monitor by the observation
- based, monitor
- specific, “baseline” design value. The resulting predicted “future concentrations ” are compared to NAAQS. The PM 2.5 attainment test is complicated and reflects the fact that PM 2.5 is a mixture species. Therefore, the attainment test for PM 2.5 is called the Speciated Modeled Attainment Test (SMAT). In the test, ambient PM 2.5 is divided into major components. These are:

- mass associated with sulfates

- mass associated with nitrates

- mass associated with ammonium

- mass associated with organic carbon

- mass associated with elemental carbon

- mass associated with particle bound water

- mass associated with “other” primary inorganic particulate matter

- and passivel y collected mass A separate RRF is calculated for each of the PM 2.5 components (except passive mass). Each of these site
- specific ratios are called component
- specific RRFs. Future PM 2.5 design values are estimated at existing monitoring sites by multiplying modeled relative response factors “near” each monitor times the observed “c omponent specific design value.” This latter quantity is estimated using measured site
- specif ic design values for PM 2.5 in concert with available measured composition data. Future site
- specific PM 2.5 design values at a site are estimated by adding the future year values of the seven PM 2.5 components. If all future site
- specific PM 2.5 design valu es are less than or equal to 15.0 micrograms per cubic meter (μ/m 3 ) at all locations, the test is passed and the modeling system will have predicted attainment of the PM 2.5 annual air quality standard. **Steps Required in a Modeled Attainment Demonstration** The modeling guidance lists nine steps for preparing modeling to demonstrate attainment of the PM 2.5 standard. 1. Develop a conceptual description of the problem to be addressed. 3 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM 2.5 , and Regional Haze, EPA **-** 454 /B
- 07 - 002 , April 20076

2. Develop a modeling/analy sis protocol. 3. Select an appropriate model to support the demonstration. 4. Select appropriate meteorological time periods to model. 5. Choose an appropriate area to model with appropriate horizontal/vertical resolution and establish the initial and boundary conditions that are suitable for the application. 6. Generate meteorological inputs to the air quality m odel. 7. Generate emissions inputs to the air quality model. 8. Run the air quality

model with base case emissions and evaluate the performance. Perform diagnostic tests to improve the model, as necessary
. 9. Perform future year modeling (including additional control strategies, if necessary) and appl y the attainment test. **How Did Delaware**  **Address All Of The Components Of A Modeled Attainment Demonstration?**  The Delaware PM 2.5 SIP addresses each of the elements of a model ed attainment demonstration as follows: **Conceptual description of the problem** A conceptual model describes how weather patterns affect the formation and transport of PM 2.5 , accounting for emissions and photochemistry. The conceptual model for the Delaware PM 2.5 SIP is described in the Attachment 1 entitled: The Nature of the Fine Particle and Regional Haze Air Quality Problems in the Mid
- Atlantic Northeast Visibility Union ( MANE
- VU

) Region: A Conceptual Description (NESCAUM

) , November 2006
. This document was prepared b y Northeast States for Coordinated Air Use Management (NESCAUM ) for use b y the OTC member States, and it provides the conceptual description of the fine particle issues in the OTC states, consistent with the EPA’s guidance
. The NESCAUM document contains a conceptual description that explains how elevated regional PM 2.5 peak concentrations in the summer differ significantl y from the largel y urban peak concentrations observed during winter. On average, summertime concentrations of sulfate in the northeastern United States are more than twice that of the next most important fine particle constituent, organic carbon (OC), and more than four times the combined concentration of nitrate and black carbon (BC) constituents. Episodes of high summertime sulfate concentrations are consistent with stagnant meteorological flow conditions upwind of the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA and the accumulation of airborne sulfate (via atmospheric oxidation of SO 2 ) followed b y long
- range transport of sulfur emissions from industrialized areas within and outside the area. National assessments have indicated that in the winter, sulfate levels in urban areas are higher than background sulfate levels across the eastern U.S., indicating that the local urb an contribution to wintertime sulfate levels is significant relative to the7

regional sulfate contribution from long
- range transport. A network anal ys is for the winter of 2002 suggests that the local enhancement of sulfate in urban areas of the MANE - VU reg ion ranges from 25 to 40% and that the long
- range transport component of PM 2.5 sulfate is still the dominant contributor in most eastern cities. In th e winter, urban OC and sulfate each account for about a third of the overall PM 2.5 mass concentration obs erved in Philadelphia and New York City areas. Nitrate also makes a significant contribution to urban PM 2.5 levels observed in the northeastern United States during the winter months. Wintertime concentrations of OC and nitrate in urban areas can be twic e the average regional concentrations of these pollutants, indicating the importance of local source contributions. This is likely because winter conditions are more conducive to the formation of local inversion layers which prevent vertical mixing. Under these conditions, emissions from tailpipe, industrial and other local sources become concentrated near the Earth’s surface, adding to background pollution levels associated with regionally transported emissions. **The M**  **odel Used in the Attainment D**  **emonst ration**  By agreement of the OTC, NYSDEC ran the Community Multi
- scale Air Quality

Model version 4.4 (CMAQ) for the S tates in the northeast ozone transport region, including Delaware
. CMAQ is an acceptable model, listed in the photochemical modeling guidan ce as a currentl y used photochemical grid model. EPA agrees CMAQ is appropriate for this modeling demonstration. The inputs to the model are described in Section 7 of the Delaware PM 2.5 SIP. **Meteorological T**  **ime P**  **eriods U**  **sed in the M**  **odeling** The Delaw are PM 2.5 SIP notes that the OTC Modeling Committee agreed to model all days in 2002. Modeling an entire ye ar covers many different kinds of PM episodes and exceeds EPA’s recommendations for episode selection. Due to the fact that the attainment demonstration is being conducted using a resource intensive photochemical grid model, EPA accepts the use of a single, recent “representative” year to be used for an annual model simulation. Two factors were used in selecting 2002 as the “representative” ye ar - the observed annual mean concentrations of PM 2.5 are close to the 3 - ye ar observed design value at all, or most monitoring sites, and the pattern of quarterl y mean values is similar to the pattern of quarterly m ean concentrations averaged over 3 ye ars. **Mete orological**  **D ata**  **U sed in the**  **A ir**  **Q uality**  **M odel**  The OTC Modeling Committee decided to use a prognostic meteorological model that provides life
- like meteorological inputs to the photochemical grid model
. The P ennsylvania State University /National Center for Atmospheric Research Mesoscale Meteorological Model (MM5) version 3.6 was chosen for the modeling analy sis
. The8

MM5 model provide s a reasonable representation of weather conditions at the surface and aloft. **Domain of the M**  **odel, H**  **orizontal/ V**  **ertical R**  **e solution and the**  **I nitial and**  **B oundary**  **C onditions**  The model ing domain extends from Maine to Florida and out in the Atlantic Ocean on the east and west to the Mississippi River . The size of the modeling domain was made large enough to include all emission sources that affect PM 2.5 concentration in the northeastern United States
. Even this boundary is defined b y a larger photochemical model ing domain th at cover s much of North America
. Over the northeastern United States, the model used 12 kilometer grid ce lls . The Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA is included in the 12 kilometer grid cell area. The OTC Modeling Committee used a 12
- kilometer grid size for the areas in and near its states to provide a fine enough grid resolution to adequatel y capture the PM patterns experienced in the ozone transport region (OTR). Outside the local area s the grid resolution used in the modeling is 36 kilometers . The selection of model domains and horizontal grid resolution was deemed acceptable to EPA. Vertical resolution is the number of layers and the size of each layer in the model. The layers in the photochemical grid model were set up to be compatible with the model that produced weather conditions for the photochemical grid model. The vertical resolutio n used in the modeling exercise followed EPA’s modeling guidance and therefore adequatel y represent s the atmosphere where PM 2.5 is emitted, forms and is transported. **Emissions U**  **sed in the A** **ir Q**  **uality M**  **odel** The emissions data for 200 2 were generated b y individual S tates within the OTR and assembled and processed through the Mid
- Atlantic Northeast Visibility Union (MANE
VU), a Regional Planning Organization (RPO). These emissions were then processed b y NYSDEC using the SMOKE emissions processor to provi de CMAQ compatible inputs. The 2002 emissions for the non
- OTR areas within the modeling domain were obtained from the corresponding RPOs and were processed using SMOKE, in a manner similar to that of the OTR emissions. The OTR states, through MANE
- VU, c ontracted MACTEC Federal Programs (called Contractor) to develop 2009, 2012 and 2018 inventories based upon 2002 inventories that the states had previousl y developed for use in the base
- ye ar model work. The Contractor, in consultation with the S tates, dev eloped the necessary growth and control factors and applied to the 2002 inventory
. Emissions for mobile sources and the electric energy generating units (EGUs) was not part of the Contractor’s effort. To generate on - road mobile emissions, the states prov ided the Virginia Department of Environmental Quality (VADEQ) and NESCAUM with appropriate MOBILE 6 input files along with the projected vehicle miles traveled (VMT), which was coupled with hourly “gridded9

temperature” information. As for the emissions fro m the EGU sector, the inter
- RPO work group utilized the Integrated Planning Model (IPM) to develop the state and unit
- level emissions. These inventories are identified as 2009 on the way (2009OTW), since they reflect all emission control measures that were promulgated or would become effective on or before 2009. Emission inventory

details are provided in Sections 3, 4 and 6.3.5 of the Delaware PM 2.5 SIP . **B ase**  **C ase**  **R un**  **Model P erformance**  **E valuation**  NY DEC performed a model evaluation for the OTC to deter mine how well CMAQ reproduced the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA 2002 PM 2.5 concentrations. CMAQ was employed to simulate PM 2.5 for the calendar ye ar 2002. Ar eview of PM 2.5 and its individual species was conducted for the study domain. The CMAQ model performance for surface PM 2.5 is good with acceptable bias and error. Several observations can be made with respect to model performance, including the following: 1. Approximately

80 - 90% of organic mass ( OM ) is in the primary fraction. Observed OM has distinct maximum during summer when secondary formation is highest; CMAQ exhibits substantial under
-prediction in secondary organic aerosols (SOA). The predicted primary OM is highest during the winter. 2. CMAQ captures seasonal variation in SO 4 well. 3. CMAQ appears to overestimate primary PM 2.5 components (EC, soil, primary OM), especially

during colder months. 4. CMAQ appears to underestimate secondary OM during the summer. These issues are not of great regulatory c oncern since attainment tests are based on the application of relative response factors. In summary , the regional and local model performance is acceptable for PM 2.5 . While there are some differences between the spatial data between sub
- regions, there is nothing to suggest a tendency f or the m odel to respond in a sy stematically different manner between regions. Examination of the statistical metrics by

s ub
- region confirms the absence of significant performance problems arising in one area but not in another, building confidence that the CMAQ m odeling system is operating consistentl y across the full OTC domain. This confidence in the modeling results allows for the modeling sy stem to be used to support the State Implementation Plan to meet the 24
- hour and annual PM 2.5 NAAQS.10

**2009 C**  **ontrol C**  **ase M**  **odeling and the Modeled A** **ttainment T**  **est** As previously

mentioned, the PA
-NJ - DE PM 2.5 nonattainment area has an attainment date of April 5, 2010. The PM 2.5 NAA QS include an annual standard of 15 μg/m 3 based on the 3
- ye ar average of annual mean PM 2.5 concentrations
. The purpose of a modeling assessment is to determine if control strategies currentl y being implemented (“on the books”) will lead to attainment of th e annual average NAAQS for PM 2.5 by 2 009. The modeling is applied in a relative sense, similar to the 8 - hour oz one attainment test. H owever, the PM 2.5 attainment test is more complicated and reflects the fact that PM 2.5 is a mixture. In the test, ambient PM 2.5 is divided into major components, with a separate relative response factor (RRF) and future design value (DVF) calculated for each of the PM 2.5 components. Since the attainment test is calculated on a per species basis, the attainment test for PM 2 .5 is referred to as the Speciated Modeled Attainment Test (SMAT) 4

. The following sections outline the process to determine that 2009 projections of PM 2.5 will meet the NAAQS from regional modeling, as suggested in EPA’s modeling guidance. **Annual SMAT R esults**  Table 1 presents the results of the annual SMAT results for the PA
-NJ - DE nonattainment area. The SMAT results demonstrate that the projected average annual arithmetic mean PM 2.5 concentration calculated at each FRM monitor attains the annual PM 2.5 NAAQS. Specificall y, all future design value (DVF) calculations are less than15 μg/m 3

. T able 1 presents the results of the annual SMAT results for a suite of regional modeling runs conducted by

O TC each representing OTB/OTW

– “On the Books, On the Way” control measures. All runs demonstrate compliance with the annual NAAQS. **Table 1**  **: Annual SMAT Results for PA -**  **NJ -** **DE Nonattainment Area**

**2009 On -**  **The -**  **Books -**  **On -**  **The -** **Way Control Measures AIRS ID**  **Site Nam e**  **County State**  **2000 -**  **2004 DVB 2009**  **Q1 Q2**  **Q3 Q4**  **DVF 10**  **- 003**  **- 1003**  **Bellefonte New Castle**  **DE 14.91**  **15.54 15.45**  **13.02 12.3**  **10 -**  **003 -**  **1007 Lums Pond**  **New Castle DE**  **13.30 14.49**  **15.69 11.10**  **11.4 10**  **- 003**  **- 1012**  **Newark New Cas**  **tle DE**  **15.56 15.00**  **15.75 13.57**  **12.5 10**  **- 003**  **- 2004**  **ML K**  **New Castle DE**  **16.79 15.60**  **16.66 14.26**  **13.3 34**  **- 007**  **- 0003**  **Copewood E Davis Camden**  **NJ 13.5**  **14.3 16.6**  **12.7 12.1**  **34 -**  **007 -**  **1007 Pennsauken TWP**  **Camden NJ**  **14.0 14.0**  **15.7 13.6**  **12.2 34**  **- 015**  **- 0001**  **Gibbstown Municipal Bldg.**  **Gloucester NJ**  **13.9 13.4**  **16.0 11.4**  **11.7 42**  **- 017**  **- 0012**  **Bristol Bucks**  **PA 14.14**  **13.68 14.70**  **13.82 12.4**  4 The guidance also states that additional analyses are recommended to determine if attainment will be likely, even if the modeled attainment test is “passed”. The guidance recommends supplementary analyses in all cases.11

**AIRS ID Site Nam**  **e County**  **State 2000**  **- 2004 DVB**  **2009 Q1**  **Q2 Q3**  **Q4 DVF**  **42 -**  **029 -**  **0100 Belm**  **ont Avenue Chester**  **PA 14.44**  **14.07 16.72**  **14.12 12.8**  **42 -**  **045 -**  **0002 Chester**  **Delaware PA**  **15.07 15.96**  **16.35 12.63**  **13.3 42**  **- 091**  **- 0013**  **Norristo wn**  **Montgom ery**  **PA 13.61**  **13.77 14.90**  **12.71 12.0**  **42 -**  **101 -**  **0004 Philadelphia AMS**  **Philadelphia PA**  **14.13 13.86**  **16.20 12.83**  **12.5 42**  **- 101**  **- 0020**  **Philadelphia Belm ont Ave**  **Philadelphia PA**  **14.0 14.4**  **15.4 13.1**  **12.0 42**  **- 101**  **- 0024**  **Philadelphia North East Philadelphia**  **PA 12.**  **43 12.37**  **15.56 11.45**  **11.0 42**  **- 101**  **- 0047**  **Philadelphia Broad Street Philadelphia**  **PA 15.54**  **14.88 16.89**  **13.25 12.8**  **42 -**  **101 -**  **0136 Philadelphia Elm** **wood Philadelphia**  **PA 13.75**  **13.04 15.75**  **11.93 11.5**  **Summary of Photochemical Grid Modeling Results** In summary , the basic photochemical grid modeling , presented in the Delaware PM 2.5 SIP , meets EPA’s guidelines and when used with the methods recommended in EPA’s modeling guidance, is acceptable to EPA. When EPA’s attainment test is applied to the modeling results, the 2009 annual
- average PM 2.5 design value is predicted to be 13.3 μg/m 3 in the Phil adelphia
- Wilmington, PA
-NJ - DE NAA . Thus, based on EPA’s modeled attainment test, the Philadelphia
- Wilmington, PA
-NJ - DE PM 2.5 NAA will reach attainment of the annual average PM 2.5 standard in 2009 before the attainment date of April 5, 201 0. **Unmonitored Area Analysis** The modeled attainment test does not address future air quality at locations where there is not a PM 2.5 monitor nearby. T o guard against the possibility that air quality

l evels could exceed the standard in areas with limit ed monitoring, EPA suggests that additional review is necessary , particularl y in nonattainment areas where the PM 2.5 monitoring network just meets or minimally exceeds the size of the network required to report data to Air Quality S ys tem (AQS). This review is intended to ensure that a control strategy leads to reductions in PM 2.5 and its constituent pollutants at other locations that could have baseline (and future) design values exceeding the NAAQS were a monitor deployed there. The test is called an “unmonitored area analysis”. The purpose of the anal ys is is to use a combination of model output and ambient data to identify areas that might exceed the NAAQS if monitors were located there. It is important to note that Delaware currentl y operates a netw ork of six PM 2.5 monitors. Four of these monitors are in New Castle County , which is part of the PA -NJ - DE nonattainment area. S ome of these monitors were established as State and Local Air Monitoring Stations (SLAMS). These SLAMS monitors were selected b ased on specific monitoring objectives (background concentration, area of highest concentration, high population, source impact, transport, and rural impact) as required by E PA and siting scales (micro, middle, neighborhood, urban, and regional) establishe d by EPA.12

EPA believes that the density of the monitoring network in New Castle County relieves the necessity of appl ying this additional analysis. **Local Area Analysis** EPA modeling guidance recommends that a l ocal area anal ys is be performed for those areas where local primary P M 2.5 sources are thought to be contributing to a monitor and causing non - attainment of the NAAQS. At this time, no monitors within the PA -NJ - DE nonattainment area are projected to exceed the NAAQS so it does not appear to be a ne cessary r equirement in this circumstance to conduct the local area analysis. Furthermore, existing monitoring data suggests a uniform regional pattern with respect to PM 2.5 concentrations rather than any “hot spot” monitor s . **Supplemental Analyses and We ight of Evidence (WOE) Determination**  EPA = s modeling guidance states that additional analyses are recommended to determine if attainment will be likely , even if the modeled attainment test is “passed
. ” The guidance recommends supplementary analyses in al l cases. EPA = s modeling guidance describes how to use a photochemical grid model and additional anal ytical methods to complete a WOE anal ys is to estimate if emissions control strategies will lead to attainment. A WOE analysis is a supporting anal ysis that helps to determine if the results of the photochemical modeling s ys tem are correctly (or not correctl y) predicting future air quality
. All models, including the CMAQ, model have inherent uncertainties. Over or under prediction may

r esult from uncertainties associated with emission inventories, meteorological data, and representation of PM 2.5 chemistry in the model. Therefore, EPA modeling guidance provides for other evidence to address these model uncertainties so that proper assessment of the probability to attain the applicable standards can be made. EPA modeling guidance states that those modeling anal ys es that show that attainment with the NAAQS will be reached in the future with some margin of safety ( i.e., estimated concentrations below 14.5 μg/m 3 for annual PM 2.5 and 62 μg/m 3 for 24 - hour PM 2.5 ) need more limited supporting material. Due to the fact that the modeling results presented in Table 1 fall well below the aforementioned “weight of evidence” thresholds established by EPA, a limited s upplemental anal ys is was deemed necessary to support the 2009 attainment demonstration.13

**Trends in**  **PM 2.5**  **Design Values** Figure 1 below show s the annual PM 2.5 design value trends for the period 2000 - 200 9 for all monitors in the PA -NJ - DE PM 2.5 NAA inc luding the monitors in Kent and Sussex Counties. It is clear from this figure that all the monitors show a downward trend in the annual PM 2.5 design value. It is noteworthy that from 2008 and after the design values at all monitors are in compliance with the annual PM 2.5 standard. Please note that the 2009 PM 2.5 design value s represented in Figure 1 are preliminary values. 

### Figure 1 **PM 2.5 A nnual A** 

**vg . Design Value Trend at Each Monitor in**  **the PA -NJ-DE PM2.5 NA**  **A**

**10 11**  **12 13**  **14 15**  **16 17** 
**2002 2003**  **2004 2005**  **2006 2007**  **2008 2009** 



### Years**C o** **n c** **e n** **t r** **a t** **i o** **n (** **u g** **/ m** **3 )**  **100031003 100031007**  **100031012 100032004**  **340070003 340071007**  **340155001 420170012**  **420290100 420450002**  **420910013 421010004**  **421010020 421010024**  **421010047 421010136**  **421010057 340150004**  **421010055 h** 

**Summary of EPA’s Evaluation**  **Delaware ’s**  **WOE Analysis** Design values at all monitors have trended downward since the ye ar 2000. This information coupled with current annual average PM 2.5 design all below the annual average PM 2.5 standard since 2007 support the demonstration of attainment by the 2010 attainment date.14

**Summary of EPA’s Tech nical Findings**  The result of the photochemical grid modeling analysis using EPA’s recommended methods predicts that the PA -NJ - DE PM 2.5 NAA will attain the annual average PM 2.5 standard by

the attainment date of April 5, 2010. **Recommendation of A** **pproval of Attainment Demonstration**  EPA has carefull y evaluated the information provided by Delaware PM 2.5 SIP . EPA conclude s that Delaware PM 2.5 SIP satisf ies the Clean Air Act’s requirement that State Implementation Plans provide for attainment of the N ational Ambient A ir Q uality S tandard by

the applicable attainment date.
Attachment : Attachment 1: The Nature of the Fine Particle and Regional Haze Air Quality Problems in the Mid

- Atlantic Northeast Visibility Union ( MANE
- VU) Region: A Conceptual Description (NESCAUM), November 2006.