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### Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania’s Fine Particulate Matter State Implementation Plan (SIP) Entitled “ State Implementation Plan Revision: Attainment Demonstration and Base Year Inventory Pennsylvania Portion of the Philadelphia - Wilmington, PA -NJ - DE Fine

Particulate Nonattainment Area April 2010”
TSD Prepared October, 2011 by Todd A. Ellsworth Office of Air Monitoring and Analysis, 3AP40 U.S. Environmental Protection Agency, Region 3

1650 Arch Street Philadelphia, Pennsylvania 19103

/s/

____________________________________________ Reviewed by Andrew Hass, Acting Associate Director, Office of Air Monitoring and Analysis (3AP40)

October 11, 2011

_________________ Date Signed2

**Purpose of the Technical Support D ocument**  This Technical Support Document (TSD) describes the Environmental Protection Agency ’s (EPA’s) evaluation of the modeling and WOE portion of Pennsylvania ’s State Implementation Plan (SIP) revision entitled “ State Implementation Plan Revision: Attainment Demonstration and Base Year Inventory Penns ylvania Portion of the Philadelphia - Wilmington, PA -NJ - DE Fine Particulate Nonattainment Area April 2010 ”. This SIP revision will h ereafter be referred to as the Philadelphia Area PM 2.5 SIP . InApril 2005 the Environmental Protection Agency ( 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 F ine Particulate Nonattainment Area (NAA). The Philadelphia Wilmington, PA -NJ - DE Nonattainment Area (Philadelphia Area) is comprised of 9 counties in Pennsylvania, New Jersey and Delaware. Th e Penns yl vania counties included in this NAA are : Bucks, Che ster, Delaware, Montgomery and Philadelphia counties (five - county Philadelphia area) . 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. Figure 1 displays a map of the Philadelphia Area.

**F igure 1: Map of**  **the Philadelphia -**  **Wilmington, PA -**  **NJ -**  **DE**

PM 2.5 **Nonattainment Area**

1 Environmental Protection Agency, Clean Air Fine Particle Implemen tation Rule , 40 CFR Part 51, March 29, 2007.3

The purpose of this TSD is to provide more detailed information than can be contained 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 Philadelphia Area PM 2.5 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 annu al 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 th at serious health effects are associated with exposures to PM 2.5 . F ollowing promulgation of a new or revised NAAQS, EPA is required by the CAA to designate areas throughout the United States as attaining or not attaining the NAAQS; this designation proces s is described in section 107(d)(1) of the CAA. In 1999, EPA and state air- quality agencies initiated the monitoring process for the 1997 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 - 03. On April 14, 2005, EPA published a final supplemental rule amending the agency ’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, comprising 208 counties within 20 states (and the District of Columbia) nationwide, with a combined population of about 88 million. The Philadelphia- Wilmington, PA -NJ - DE PM 2.5 Nonattainment Area , which is the subject of this proposed rulemaking, is included in the list of areas not attaining the 1997 PM 2.5 NAAQS . 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 states to submit attainment plans for areas designated as nonattainment for the revised 24 - hour PM 2.5 NAAQS. Therefore the Philadelphia Area 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 d esignations 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 Ph iladelphia - Wilmington, PA -NJ - DE PM 2.5 Nonattainment Area i s designated as attaining the 1997 24 - hour PM 2.5 NAAQS.4

**Introduction to the**  **Philadelphia Area PM**  **2.5 State Implementation Plan for**  **the Annual Average**  PM **2.5 Standard**  On July 1 8, 1997 the US Environmental Protection Agency ( EPA) established a health based fine particulate matter (PM 2.5 ) National Ambient Air Quality Standard (NAAQS) at 15.0 micrograms per cubic meter (μg/m3), annual average. The Penns ylvania counties of Bucks, Chester, Delaware, M ontgomery and Philadelphia counties w ere designated by the EPA as being in non**-** attainment for th e annual PM 2.5 NAAQS in April 2005 2

. The Philadelphia Area PM 2.5 SIP includes plans to reduce PM 2.5 emissions within the Philadelphia - Wilmington, PA -NJ - DE P M 2.5 Nonattainment Area . The Plan also includes modeling that will predict whether the area will meet the PM 2.5 standard by the attainment date. This TSD reviews Pennsylvania’s documentation of modeling that show s attainment of the annual average PM 2.5 s tandard by the 2 010 attainment date. All of the states 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 (NY S DEC) and supporting organizations. Pennsylvania believes that the Philadelphia Area 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 Philadelphia - Wilmington, PA -NJ - DE PM 2.5 Nonattainment Area 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**  Pennsylvania 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 used by the MA NE - 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 ben chmark run to ensure accurate results. The MANE - VU RPO used the Community Multi - scale Air Quality

model (CMAQ) versio n 4.4 as its photochemical grid model . The model use s simulations of chemical 2 70 FR 944 , January 5, 20055

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 the 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 determin e if the model performance was satisfactory . Once the model perform ance was determined to be adequate, 2009 PM 2.5 concentrations w ere modeled by

running the model with projected emissions for 2009 and the original 2002 meteorology . The meteorology was held constant so that the results of changing the emissions would n ot be influenced b y changing meteorology . The EPA modeling guidance 3 recommends that states use the modeled PM concentrations in a relative sense and not rely solel y on the concentrations the model predicts for the attainment year (2009 in this case ). A modeled attainment test is an exercise in which an air quality

model 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 11 . EPA’s rec ommended test is one in which model estimates are used in a “relative” rather than “absolute” sense. Ratio s 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 concentrations 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 el emental 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). E ach 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 “component specific design value”. This l atter quantity is estimated using measured site - specific 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 ye ar values of the seven PM 2.5 compo nents. If all future site - specific PM 2.5 design values are less than or equal to 15.0 3 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Go als for Ozone, PM 2.5 , and Regional Haze, EPA **-** 454 /B - 07 - 002 , April 20076

micrograms per cubic meter (μ/m 3 ) at all locations, the test is passed and the modeling sy stem 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. 2. Develop a modeling/analysis protocol. 3. Select an appropriate model to support the demonstration. 4. Select appropriate meteorological time perio ds 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 model. 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 a pply the attainment test. **H ow**  **Did Pennsylvania**  **Address All Of The Components Of A Modeled Attainment Demonstration?**  The Philadelphia Area PM 2.5 SIP addresses each of the el ements 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 Philadelphia Area PM 2.5 SIP is described in 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

) , Novemb er 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 NSCAUM 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 c oncentrations 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. Episod es 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 by long range transport of sulfur emissions from industrialized areas within and outside the area.7

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 urban contribution to wintertime sulfate levels is significant relative to the 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 o f the MANE - VU region 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 the winter, urban organic carbon ( OC ) and sulfate each account for about a third of the ov erall PM 2.5 mass concentration observed 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 ni trate in urban areas can be twice 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**  **emonstration** By agreement of the OTC, NY S DEC ran the Community Multi - scale Air Quality

Model version 4.4 (CMAQ) for the states in the northeast ozone transport region, that includes Pennsylvania . CMAQ is an acceptable model, listed in the photochemical modeling guidance 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 V of the Philadelphia Area PM 2.5 SIP . **Meteorologic al**  **T ime**  **P eriods**  **U sed in the**  **M odeling**  The Philadelphia Area 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 s election. 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” ye ar to be used for an annual model simulation. Two factors were used in selecting 2002 as the “representative” ye ar : 1. 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 2. the pattern of quarterl y mean values is similar to the pattern of quarterl y mean concentrations averaged over 3 years. **Meteorological 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 mo del . The P ennsylvania State University /National Center for Atmospheric Research Mesoscale Meteorological Model (MM5) version 3.6 was chosen for the modeling analy sis . The MM5 model provide s a reasonable representation of weather conditions at the surface and aloft.8

**Domain of the M**  **odel, H**  **orizontal/ V**  **ertical R**  **esolution 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 (see Figure 2 below) . 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 by

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 cells . The Philadelphia Wilmington, PA -NJ - DE PM 2.5 Nonattainment Area i s 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 adequately 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 mode l that produced weather conditions for the photochemical grid model. The vertical resolution 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 .

**Figure 2**  **. OTC Modeling Study Domain**

**Outer grid at 36 -**  **kilometer resolution, inner grid at 12 -**  **kilometer resolution**9

**Emissions U**  **sed in the A** **ir Q**  **uality M**  **odel** The emissions data for 2002 were generated b y individual states 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 provide 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 , contracted 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 states , developed 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 provided 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 “gridded temperature” information . As for the emissions from the EGU sector, the inter- RPO work group utili zed the Integrated Planning Model (IPM) to develop the state and unit - level emissions. These inventories are identified as 2009 on the way (2009 OTW), since they reflect all emission control measures that were promulgated or would become effective on or b efore 2009. Emission inventory

details are provided in Sections III and IV of the Philadelphia Area 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 determine how well CMAQ reproduced 2002 PM 2.5 con centrations. 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 sub stantial 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.10

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 p erformance 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 model to respond in a sy stematically different manner between regions. E xamination of the st atistical 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 modeling 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. **2009 C**  **ontrol C**  **ase M**  **odeling and the Modeled A** **ttainment T**  **est** As previousl y mentioned, the Philadelphia - Wilmington , PA -NJ - DE PM 2.5 NAA has an attainment date of April 5, 2010. The PM 2.5 NAAQS 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 strategie s currentl y being implemented (“on the books”) will lead to attainment of the annual average NAAQS for PM 2.5 by 2 009. The modeling is applied in a relative sense, similar to the 8 - hour ozone 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 Results** Table 1 presents the results of the annual SMAT results for the PA -NJ - DE non attainment 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 PM 2.5 NAAQS.

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

**Table 1**  **: Annual**  **SMAT Results**  **for Philadelphia**  **- Wilmington,**  **PA -**  **NJ -** **DE PM**  **2.5 No nattainment Area**  **On -**  **The -**  **Books -**  **On -**  **The -** **Way Control Measures**

**Summary of Photochemical Grid Modeling Results** In summary , the basic photochemical grid modeling , presented in the Philadelphia Area PM2.5 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 1 3 . 5 μg/m 3 in the Philadelphia - Wilmington, PA -NJ - DE PM 2.5 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, 2010. **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 limited 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 Qu ality 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 th ere. 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. **AIRS ID**  **Site Name**  **County State**  **2000 -**  **2004 DVB 2009**  **Q1 Q2**  **Q3 Q4**  **DVF** 420170012 Bristol Bucks PA 14.14 13.69 14.73 13.85 12.1 420290100 New Garden Chester PA 14.39 14.73 16.36 13.76 12.4 4204500 02 Chester Delaware PA 15.07 15.96 16.34 13.74 13.3 420910013 Norristown Montgomery PA 12.68 13.62 13.96 12.34 11.3 421010004 AMS Lab Philadelphia PA 15.99 14.01 15.95 13.82 12.9 421010024 NE Airport Philadelphia PA 13.58 13.63 14.95 12.96 11.9 4210100 47 Broad Street Philadelphia PA 16.59 16.45 15.80 15.37 13.5 421010136 Elmwood Philadelphia PA 15.70 14.20 15.27 12.99 12.7 100031003 Bellefonte New Castle DE 14.87 15.16 15.50 13.13 12.6 100031007 Lums Pond New Castle DE 13.16 14.37 16.05 10.66 11.3 1 00031012 Newark New Castle DE 15.27 14.91 16.53 13.14 12.6 100032004 MLK New Castle DE 16.41 15.40 17.61 14.04 13.3 340070003 Camden Camden NJ 13.99 14.54 15.76 12.47 12.3 340071007 Pennsauken Camden NJ 13.99 14.00 14.75 13.59 12.3 340155001 Gibbstown Gloucester NJ 13.92 13.43 15.08 11.39 11.712

It is important to note that the Philadelphia - Wilmington, PA -NJ - DE PM 2.5 NAA currentl y has an operating network of fifteen PM 2.5 monitors . EPA believes that the density o f the monitoring network in NAA relieves the necessity of applying this additional anal ys is. **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 Philadelphia - Wilmington, PA -NJ - DE PM 2.5 NAA are projected to exceed the annual PM 2.5 NAAQS so it does not appear to be a necessary requirement in this circumstance to conduct the local area anal ys is. PADEP h as observed enhancement of PM 2.5 concentrations at the Chester monitor by l ocal sources. U sing emissions to distance ratios (Q/d) and local predominant wind directions; seven (7) sources were identified for possible anal ys is with a dispersion model to gauge the effect of local direct PM 2.5 emissions on the North Braddock monitor. Al ocal area anal ys is using a dispersion model, however, was not conducted since the modeled concentrations for the Chester monitor currently

w ould attain the PM 2.5 NAAQS. This does not preclude the Department from conducting a dispersion modeling anal ys is as part of a local area anal ys is in the future for the EPA’s revised 24 - hour PM 2.5 standard. **Supplemental Analyses and Weight of Evidence (WOE) Determination** EPAs 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 anal ys es in all cases. EPAs modeling guidance d escribes how to use a photochemical grid model and additional anal ytical methods to complete a WOE analysis to estimate if emissions control strategies will lead to attainment . A WOE anal ys is is a supporting analy sis that helps to determine if the results of the photochemical modeling system are correctly (or not correctly) 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.13

Due to the fact that the model ing results presented in Table 1 fall below the aforementioned “weight of evidence” thresholds established by EPA, a limited supplemental anal ys is was deemed necessary to support the 2009 attainment demonstration. **PM 2.5**  **Design Values** Table 2 (see below) show s the 2009 annual PM 2.5 design value for all monitors in the Philadelphia - Wilmington, PA -NJ - DE PM 2.5 NAA . Iti s clear from this figure that all the monitors are currentl y attaining the NAAQS. All the monitors continue to attain in 2010. 

### Table **2: 200**  **8 -**  **2010 Philadelphia**  **- Wilmington, PA**  **- NJ**  **- DE PM**  **2.5 NAA**  **Monitored PM**  **2.5 Design Values**  **A IRS**  **ID Site Name**  **County Sta**  **te 200**  **8 2009**  **2010 Annual**  **PM 2.5**  **DV Annual** 

**PM 2.5**  **DV Annua** 

**l PM** **2.5 DV**  420170012 Bristol Bucks PA 12.6 12 .2 11.3 420290100 New Garden Chester PA 13.4 13.9 13.8 420450002 Chester Delaware PA 14.1 13.7 13.1 420910013 Norristown Montgomery PA 12.3 11.7 10.5 421010004 AMS Lab Philadelphia PA 13.4 12.5 11.5 421010024 NE Airport Philadelphia PA 12.4 11.6 10.5 421010047 Broad Street Philadelphia PA 14.5 13.0 11.9 421010136 Elmwood Philadelphia PA 13.2 13.3 X 100031003 Bellefonte New Castle DE 12.9 12.2 11.1 100031007 Lums Pond New Castle DE 11.8 11.3 10.5 100031012 Newark New Castle DE 12.9 12.2 11.2 10003 2004 MLK New Castle DE 14.2 13.0 11.7 340070003 Camden Camden NJ 12.9 13.3 12.9 340071007 Pennsauken Camden NJ 12.7 11.7 10.3 340150004 Gloucester NJ 11.6 11.4 10.0 421010055 24 th and Ritner Philadelphia PA 13.5 12.4 12.0 421010057 Fire Admin

Buildin g Philadelphia PA 12.7 12.1 11.714

**Summary of EPA’s Evaluation**  **Pennsylvania ’s**  **WOE Analysis** Th e reduction in PM 2.5 precursor emissions, c oupled with current annual PM 2.5 design values that show attainment of the annual NAAQS, confirms the Commonwealth’s assertion that the Philadelphia - Wilmington, PA -NJ - DE PM 2.5 NAA will be in compliance with the annual PM 2.5 NAAQS by the attainment date.
**S ummary**  **of EPA’s Technical Findings** The result of the photochemical grid modeling analysis using EPA’s recommended methods predicts that the Philadelphia - Wilmington, PA -NJ - DE PM 2.5 NAA w ill attain the annual PM 2.5 standard by the attainment date of April 5, 2010. This result is confirmed b y the 2010 air quality data presented in Table 2. **Recommendation of A** **pproval of Attainment Demonstration** EPA has carefull y evaluated the information provided by Philadelphia Area PM 2.5 SIP . EPA conclude s that Philadelphia Area 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.15

**Attachments :**  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
.