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### Technical Support Document for the Modeling and Weight of Evidence (WOE) Portions O f the State of Delaware’s Ozone State Implementation Plan (SIP)

Entitled “ D elaware S tate I mplementation P lan F or Attainment of the 8 - H our O zone N ational A mbient Air Q uality S tandard Reasonable Further Progress and Attainment Demonstration , June 2007” Purpose of the Technical Support Document This Technical Support Document (TSD) describes the Environmental Protection Agency ’s (EPA’s) evaluation of the modeling and WOE porti ons of Delaware’s State Implementation Plan (SIP) revision entitled “ Delaware State Implementation Plan for Attainment of the 8

- Hour Ozone National Ambient Air Quality Standard Reasonable Further Progress and Attainment Demonstration, June 2007 ” (Delaware SIP revision for the Philadelphia area). Delaware is part of the Philadelphia

- Wilmington

- Atlantic City ozone nonattainment area (Philadelphia area). The Philadelphia area is comprised of 18 counties in Pennsylvania, New Jersey , Delaware and Maryland. Cl assified as a “moderate” nonattainment area, the Philadelphia area is required to attain the NAAQS b y June 2010, in effect, b y the ozone season of 2009. 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 Delaware SIP revision for the Philadelphia area. Introduction to the Delaware State Implementation Plan for Ozone The Delaware SIP revision for the Philadelphia area includes plans to reduce ozone

causing emissions for Delaware ’s portion of the Philadelphia Area. The Plan also includes modeling that will predict wheth er the area will meet the ozone standard b y the due date. This TSD reviews modeling and WOE portions of the Delaware SIP revision for the Philadelphia area
. This TSD reviews Delaware ’s documentation of modeling and WOE that attempts to show attainment of the eight

- hour ozone standard b y the 2009 ozone season. 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 b y the New York State Departme nt of Environmental Conservation (NY S DEC) and supporting organizations. Delaware believes that their SIP modeling when combined with additional supporting anal ys es (Weight of Evidence) (WOE) “Demonstrates that the entire Philadelphia

Wilmington

- Atlantic C ity, PA

-NJ
- DE
- MD moderate non

- attainment area will attain the 8
- hour ozone NAAQS in 2009”.2

W hat Are The Components Of A Modeled Attainment Demonstration ? M odeling P rocess Overview The OTC Modeling Committee used the Community Multi

- scale Air Quality model (CMAQ) version 4.4 as its photochemical grid model . The model use s simulations of chemical reactions, emission of ozone precursors and a sophisticated meteorological model to produce ozone concentrations over the eastern United States. The meteorological data used in the meteorological model was for the base year ozone season of 2002. The photochemical grid mode l was run with the base year meteorology and base year emissions to determin e 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 e missions for 2009 and the original 2002 meteorology
. The meteorolog y w as held constant so that the results of changing the emissions would not be influenced b y changing meteorology. T he EPA modeling guidance 1 recommends that states use the modeled ozon e concentrations in a relative sense and not rely solel y on the concentrations the model predicts for the attainment year (2009). The relative response factor (RRF) used in the modeled attainment test is computed by taking the ratio of the mean of the 8

- h our daily maximum predictions in the future to the mean of the 8

- hour dail y m aximum predictions with baseline emissions, over all relevant day s. The base year ozone design values at each monitor are then multiplied by the monitor

- specific RRF to produce an attainment year design value. If the result is less than or equal to 84 ppb, at all locations, the modeling sy stem will have predicted attainment of the ozone air quality standard. The Regulatory Framework Section 110 (a) (2) (k) of the Clean Air Act r equires states to prepare air quality modeling to show how they will meet ambient air quality standards. EPA determined that areas classified as ‘moderate’ or above must use photochemical grid modeling or any other anal yt ical method determined by the Adm inistrator to be at least as effective to demonstrate attainment of the ozone health

- based standard b y the required attainment date (40 CFR 51.908, published at 70 FR 71612 on November 29, 2005). In 40 CFR 51.903, published at 69 FR 23951 on April 30, 200 4, EPA specified how areas would be classified with regard to the eight

- hour ozone standard set by EPA in 1997. At 69 FR 23858, on April 30, 2004, EPA followed these procedures and classified the Philadelphia

- Wilmington

- Trenton, PA
-NJ
- DE
- MD and ozone nonattainment area as moderate, so they must attain the 1997 eight

- hour ozone standard by June 2010. Since the attainment date is June 2010 for moderate areas, states must achieve emission reductions b y the ozone season of 2009 in order for ozone concentratio ns to be reduced, and show attainment , during the last complete ozone season before the 2010 deadline. The modeling guidance lists nine steps for preparing modeling to demonstrate attainment of the ozone standard.
1 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 20073

1. Develop a conceptual description o f the problem to be addressed. 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 model. 7. Generate emissions inputs to the ai r 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) an d a pply the attainment test.
H ow Did Delaware Address All Of The Components Of A Modeled Attainment Demonstration? The Delaware SIP revision for the Philadelphia area 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 ozone, accounting for emissions and photochemistry. The Delaware SIP revision for the Philadelphia area describes the climatology that produces high ozone concentrations in the Philadelphia area. On warm sunny day s, winds from the southwest and west blow emissions from sources of ozone

- forming chemicals both at the surface and aloft toward the Philadelphia area. In addition, emiss ions from large combustion sources in the Ohio Valley and other areas are brought eastward b y upper level winds to the east coast, augmenting the ozone formed locall y. A complete conceptual description of the ozone problem in the Philadelphia area is cont ained Delaware explains this in Section 7.7 of their SIP revision for the Philadelphia area
. Modeling/analysis protocol The Ozone Transport Commission’s (OTC’s) Modeling Committee developed a protocol for modeling the ozone problem in the northeastern Uni ted States. The modeling protocol is located in Appendix 7

- 1 of the Delaware SIP revision for the Philadelphia area . It adequatel y describes how the photochemical grid model will be used in the ozone attainment plans. 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, including Pennsylvania
. CMAQ is an acceptable model, listed in the photochemical modeli ng guidance as a currentl y u sed 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 SIP revision for the Philadelphia area
.4

Meteorological T ime P erio ds U sed in the M odeling Section 7.3 of the Delaware SIP revision for the Philadelphia area notes that the OTC Modeling Committee agreed to model the entire ozone season of 2002. Using the entire ozone season of 2002 covers man y different kinds of ozone ep isodes and exceeds EPA’s recommendations for episode selection. 2002 was a good year to model because it was the base year for the attainment plans and as a whole is representative of meteorological conditions conducive to elevated concentrations of ozone . 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 provid es life

- like meteorological inputs to the photochemical grid model
. The P ennsylvania State University /National Cent er 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. A summary of the MM5 application is cont ained in Section 7.4 of the Pennsylvania SIP revision for the Philadelphia area. 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 . The size of the modeling domain was made large enough to include all emission sources that affect ozone formation in the northeastern United States
. Even this boundary is defined b y a larger photochemical mo del ing domain th at cover s much of North America
. Over the northeastern United States, the model used 12 kilometer grid cells . The Philadelphia area is included in the 12 kilometer grid cell area. The OTC Modeling Committee used a 12

- kilometer grid size f or the areas in and near its states to provide a fine enough grid resolution to adequatel y capture the ozone patterns experienced in the ozone transport region (OTR). The OTC Modeling Committee chose to use a 12 kilometer grid resolution b ased on its stat es’ experiences with the one

- hour ozone attainment modeling that indicated that m odeling at finer resolutions than 12 kilometers would not result in increased model accuracy
. Outside the local area s the grid resolution used in the modeling is 36 kilometer s . The selection of model domains and horizontal grid resolution was deemed acceptable to EPA. The grid resolution, modeling domain and boundary conditions are described in Appendix 7

- 2 of the Delaware SIP revision for the Philadelphia area
. Vertical re solution 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 grid resoluti on used in the modeling is described in Appendix 7

- 2 of the Delaware SIP revision for the Philadelphia area
. T he vertical resolution used in the modeling exercise followed EPA’s modeling guidance and therefore adequatel y r epresent s the atmosphere where oz one forms and is transported.5

Emissions U sed in the A ir Q uality M odel The emissions data for 2002 were generated b y i ndividual 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 by 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 RPO s 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
. E missions for mobile sources and the electric energy ge nerating 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 the Northeast States for coordinated Air Use Management (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 utilized the Integrated Planning Mod el (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. Details of emission s processing are provided in Appendices 7

- 7, 7
- 8 and 7

- 9 of the Delaware SIP revision for the Philadelphia area
. B ase C ase Run Model P erformance E valuation NY DEC performed a model evaluation for the OTC to determine how well CMAQ reproduced the Philadelphia nonattainment area’s 2002 ozone season concentrations. Model evaluation followed performance statistics outlined in EPA modeling guidance. The OTC’s evaluation included performance statistics for all monitors inside the Philadelphia nonattainment area. The model performance evaluation results are presented in included in Appendix 7

- 6 the Delaware SIP. The anal ys is indicates the modeling s ys tem does an adequate job of estimating the eight

- hour surface ozone concentrations throughout the Philadelphia area. 2009 C ontrol C ase M odeling and the Modeled Attainment T est The photochemical grid model used with projected emissions for 2009, including emission changes due to regulations the states are planning to implement and expected growth by the 2009 ozone season. Meteorological conditions from 2002, the same as the base ye ar modeling , were used in the 2009 modeling. Using the base case meteorology allows the effect of changes in6

states’ emissions to be determined without being influence d by ye arl y fluc tuations in meteorology and is consistent with EPA guidance
. As described earlier in this T S D, the attainment test used in the Philadelphia area modeling demonstration involved the application of model

- based RRFs to base year design values at each monitor to produce projected future year design values (2009). The projected 2009 design values represent design values that should result from emission controls Delaware and other states planned to have in place in 2009. The 2009 design values should be less than or equal to 84 ppb at all monitoring stations to meet the attainment test2

. The SIP modeling predicts that in 2009 , Philadelphia area will not pass the attainment test since design values are projected to be over the 84 ppb stan dard (see Table 1 below)
. Table 1 Modeled vs. Monitored Design Value

Summary of Photochemical Grid Modeling Results In summary , the basic photochemical grid modeling presented in the Delaware SI P revision for the Philadelphia area meets E PA’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 ozone design value is predicted to be 9 1 ppb in the Philadelphia

- Wilmingto n - Atlantic City, PA
-NJ
- DE
- MD ozone nonattainment area. Thus, based on EPA’s modeled attainment test , Philadelphia area has not demonstrated that it will reach attainment of the ozone standard in the 2009 attainment year with the modeled emission reduction strategies committed to by the OTC states. To make a case for attainment, Delaware decided to use WOE to demonstrate attainment of the ozone standard in the Philadelphia area.

2 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, and specifically recommends a WOE analysis if modeled ozone is greater than or equal to 82 ppb. Monitor Site ID Number 2009 Modeled DV
Fairhill

- CECIL CO, MD 240150003 81 Colliers Mills

- OCEAN CO, NJ 340290006 91 Rider

- MERCER CO, NJ 340210005 86 Ancora State Hospital

- C AMDEN CO, NJ 340071001 87 Camden

- CAMDEN CO, NJ 340070003 88 Clarksboro

- GLOUCESTER CO, NJ 340155001 88 Bristol

- BUCKS CO, PA 420170012 88 Northeast Airport

- PHILADELPHIA CO, PA 421010024 877

Weight of Evidence Demonstration EPA = s modeling guidance d escribes how to u se a photochemical grid model and additional anal yt ical methods to complete a WOE anal ys is to estimate if emissions control strategies will lead to attainment of the eight

- hour NAAQS for ozone. A WOE anal ys is is a supporting analy sis that helps to determi ne if the results of the photochemical modeling system are correctly (or not correctly) predicting future air quality
. The WOE portion of the Delaware SI P revision for the Philadelphia area describe s the anal ys es performed, databases used, key assumption s and outcomes of each anal ys is, and why the evidence, viewed as a whole, supports a conclusion that the Philadelphia nonattainment area will attain the NAAQS despite the model prediction th at some monitors’ future design values exceed the current eight

- ho ur ozone standard. Table 2 outlines under what circumstances a WOE demonstration is needed. Model

predicted design values are summarized above in Table 1 . Of the twenty- two (22) ozone monitors in the Philadelphia nonattainment area only eight ( 8 ) exceed the threshold (82 ppb) where the EPA modeling guidance recommends a WOE demonstration. Three of the monitors fall within the 82

- 87 ppb threshold outlined in Table 1 and four others fall within the last category listed in the WOE table included in the US E PA guidance. The Roxboro monitor is excluded from the WOE analysis since its current design value is significantl y l ower than the eight

- hour standard (modeled 82 ppb, actual monitored 78 ppb). The WOE anal ys is for the remaining seven monitors include s th e following:

· A comparison of model

- predicted 2009 ozone design values and monitored design values for 2006, · An anal ys is of recent ozone trends in the Philadelphia nonattainment area, · Alternative methods for calculating the 2009 ozone design value, · An analy sis of model

- predicted regional transport, · University of Maryland’s anal ys is of model sensitivity to emission changes. Table 2. EPA Guidelines for Supplemental Analyses and Weight of Evidence Determinations Results of Modeled Attainment Test Supplement al Analy ses Future Design Value < 82 ppb, all monitor sites Basic supplemental anal yses should be completed to confirm the outcome of the modeled attainment test Future Design Value 82

- 87 ppb, at one or more sites/grid cells A weight of evidence demons tration should be conducted to determine if aggregate supplemental analy ses support the modeled attainment test Future Design Value > 88 ppb, at one or more sites/grid cells More qualitative results are unlikely to support a conclusion differing from the outcome of the modeled attainment test.8

Modeled Concentrations and Current Design Values Table 3 b elow lists the OTC modeled 2009 design values and the 2006 and 2007 design values and 2008 preliminary design values. The m odeled 2009 and projected 2006 d esign values are surprisingl y close to one another with most modeled concentrations slightly lower than the projected 2006 design values
. The Delaware SIP revision for the Philadelphia area state s that the 2006 design values suggest additional reductions over the next three ozone seasons might bring several of the monitors that are currently just over the eight

- hour ozone standard into compliance
. If this is true, air monitoring data from 2007 and 2008 should support Delaware ’s conclusion, but it does not. Table 3 . Modeled vs. Monitored Design Values

Delaware did not have access to 2 007 ambient data or preliminary 2008 ambient data when it wrote its SIP revision for the Philadelphia area . However, even at that time, information was availab le that showed a comparison between a 2006 design value with modeled 2009 results was biased toward an optimistic result because the summer of 2004 was a much cooler than normal (according to the National Climatic Data Center, the summer of 2004 was ranked as the 20 th coolest of the last 110 years in the Northeast)
. D ata from 2005 and 2006 show ed that the number of 4th high values over the ozone standard was much higher in 2005 and 2006 than 2004 ’s in the Philadelphia nonattainment area
. (See F igure below ) We also know , based on the 2007 design values and the preliminary 2008 design values , that the 2 006 design values were biased low due to the extremely low values measured in 2004 due to cool weather conditions in 2004
. Monitor Site ID Number 2009 Modeled DV 2006 Monitored DV 2007 Monitored DV Preliminary 2008 Monitored DV Fairhill

- CECIL CO, MD 240150003 81 90 93 90 Colliers Mills

- OCEAN CO, NJ 340290006 91 93 92 87 Rider

- MERCER CO, NJ 340210005 86 87 91 87 Ancora State Hospital

- CAMDEN CO, NJ 340071001 87 89 88 86 Camden

- CAMDEN CO, NJ 340070003 88 84 88 90 Clarksboro

- GLOUCESTER CO, NJ 340155001 88 86 91 87 Bristol

- BUCKS CO, PA 420170012 88 86 92 92 No rtheast Airport

- PHILADELPHIA CO, PA 421010024 87 90 91 899

Based on the 2007 and prelim inary 2008 ambient data, the modeled 2009 modeled design values now appear to be either reasonable or maybe even too low in some cases
. When the 2007 and preliminary 2008 design values (92 ppb ) and the preliminary 2008 4 th high ozone value (90 ppb) are e xamined, it is not reasonable to assume the Philadelphia area will be in attainment of the ozone standard after the 2009 ozone season. The 2008 design values also suggest that the 2009 model

- predicted design values are very reasonable and d o not seem to b e over - predicted by the model. Design Value Trends T he Delaware SIP revision for the Philadelphia area states that there have been significant declines in the Philadelphia nonattainment area’s eight

- hour ozone design values over the last several decades. Significant declines did occur after enactment of the NO x SIP Call in the 2003/2004 period
. The data in Table 4 show that ozone design values have decreased sharply after 2003. EPA’s study of the effect of the NOx SIP Call has documented the beneficial effects of the NOx SIP Call emission reductions that were in place b y the 2004 ozone season across the eastern United States Since 2004, design values have not continued to decrease as sharpl y for several reasons. First, the 2004 ozone season was cool er than normal, so the decreases in ozone due to additional controls have been offset somewhat b y higher concentrations as the areas have returned to more typical summertime conditions. Second, current reductions in ozone and precursors transported from the Midwest are not as large as the decreases that10

occurred while the NOx SIP Call was implemented. Even if EPA’s Clean Air Implementation Rule (CAIR) is implemented, most of the ozone season reductions due to CAIR are not likel y t o be implemented until af ter 2009. Any additional reductions in ozone in the 2008 and 2009 ozone seasons will be limited to mostly local controls in each nonattainment area and a few reductions in major sources due to States’ initiatives in the Ozone Transport Region. While th e observed design values for 2007 are only 1 to 3 ppb higher than the model

predicted value for 2009, an ozone reduction of 9 ppb would be needed to reduce design values to attainment by 2009 and 6 ppb to reduce the 4 th high value to less than or equal to 84 ppb (level needed to qualify for a one year extension of the attainment date)
. Unless emission reductions that will occur between now and 2009 are to equal to , or more effective than the reductions from 2002 to 2007 when ozone decreased by up to 10 ppb , the Philadelphia nonattainment area will not reach attainment by the 2009 ozone season . Even if local controls in 2008 and 2009 could reduce emissions by the amount of local reductions observed during the NOx SIP Call implementation years, comparable red uctions in ozone needed to attain the standard in 2009 will not happen since the present ozone trends will be not be assisted by the large reductions in transported ozone and precursors that occurred before 2005. The recent trend in 8

- hour ozone concentrations at the Philadelphia area ozone monitors presented i n Table 4 indicate that attainment of the 8

- hour ozone standard b y the end of the 2009 ozone season is unlikely
.11

Table 4. Recent O zone Design Value Trends

Alternative Baseline Des ign Value Seven monitors within the Philadelphia area are projected to exceed the current eight

hour ozone standard following the US EPA’s recommended method. The recommended baseline concentration used in the attainment demonstration is the average of the three eight

- hour ozone design values that include the emission base year (200 2). Thus the baseline concentration is the average of the 2002, 2003 and 2004 eight

- hour ozone design values. Delaware asserts that by using the US EPA recommended method for calculating a monitor’s baseline concentration , und ue weight is placed on the 2 002 ozone season, one of the worst ozone seasons since the late 1990s. As alternative to the US EPA’s baseline concentration calculation, Delaware took the straight average of the 4 th highs over the same years (2000

- 2004). This approach weighs each year equall y. EPA did not recommend this method as it is not as robust as EPA’s recommended method. The Delaware method gives equal weight to the 2004 ozone season that has the advantage of emission reductions resulting from the NOx SIP Call
. Additionally , i n 2004 the Philadelphia area had the fewest number of day s with eight

- hour ozone 85 ppb or above during the period 1980 to 2007. According to the National Climatic Data Center, the summer of 2004 was ranked as the 20 th coolest of the last 110 years in the Northeast. In the Midwest, upwind from the northeast and a significant source of ozone precursors, 2004 was ranked 5 th coolest. 2004 was significantly cooler than normal, which means 2004 was not ty

pical according to the conceptual model described in th e SIP revision for the Philadelphia area . With a cooler than usual summer and lower concentrations due to implementation of the NOx SIP Call, including 2004 in a pre

- control strategy baseline Site 2003 2004 2005 2006 2007 Preliminary 2008 Camden 101 93 85 84 88 88 Ancora S.H. 101 95 91 89 88 86 Clarksboro 98 94 88 86 91 87 Rider 99 91 86 87 91 87 Colliers Mills 106 99 94 93 92 87 Bristol 100 93 86 86 92 92 NE Airport 97 95 90 90 91 89 Fairhill 98 92 89 90 93 9012

creates a low bias for an y averaging method that includes it eq ually with other years. An examination of the recent design value trends presented earlier in Table 4 shows that the extraordinary decrease in ozone in 2004 does not continue i n the following years, when increasing ozone occurred while emissions did not i ncrease. For these reasons , EPA believes the recommended method for calculating the baseline design value provides more stability to the baseline design value and better represents the meteorology and emissions of the 2002 emissions baseline year. Method s (see below) equally as reasonable as Delaware ’s method that were not evaluated in the Delaware SI P revision for the Philadelphia area produce baseline design values the same as EPA’s recommended method or even higher for the peak ozone site of the Phila delphia area ozone nonattainment area at Colliers Mills
. EPA guideline method baseline = 10 5.7 ppb Delaware ’s alternative baseline = 104 .2 ppb 2002 design value used by EPA and the State for designation purposes = 113 ppb 2003 design value, centered on 2002 = 106 ppb. The baseline value calculated using EPA’s recommended method is well within the range of values cal culated b y other methods, so using EPA’s recommended method is reasonable and does not produce an anomalous value. Table 5 lists the alternative baseline value and the projected 2009 concentration for the seven monitors that are projected to exceed the current eight

- hour ozone standard in 2009. This reduces the modeled 2009 values slightly but still leaves them close to the preliminary 2008 design values. Even with this adjustment the 2009 Colliers Mills monitored design value (90 ppb) still remains ab ove the highest concentrations listed in EPA’s WOE cut
- offs. Table 5 . Alternative Baseline Concentration Analysis Site Name State Alternative Baseline OTW/OTB V4

RRF Alternate 2009 Camden NJ 94.0 0.8996 84 Ancora S.H. NJ 98.6 0.8733 86 Clarksboro NJ 96.4 0.9004 86 Rider College NJ 95.6 0.8908 85 Colliers Mills NJ 104.2 0.8703 90 Bristol PA 96.6 0.8976 86 NE Phila PA 94.6 0.9035 8513

Alternative RRF Delaware calculated 2009 modeled ozone design valu es by multiplying the modeling baseline design values with a relative response factor (RRF) as recommended by EPA’s photochemical modeling guidance. At each monitoring site, the state calculates the RRF associated with the maximum eight

- hour ozone concentration in the nine grid cells nearest with the monitoring site on high ozone day s. L ower RRF s produce larger decrease s in ozone between the base and future years. The Delaware ozone Plan recalculates RRFs for several different ozone levels; 2002 base line model concentrations 3 85 ppb, 2002 baseline model concentrations 3 90 ppb and 2002 baseline model concentrations 3 95 ppb. The idea is to see if the air

- quality model predicts more reductions on day s with higher ozone concentrations (more benefit on the worst day s). Table 6 contains the different RRFs based on the 2002 baseline model concentrations. Delaware then recalculat ed the projected modeled 2009 design values using the most beneficial alternative RRFs . This lowered the projected modeled des ign values at nearl y all seven monitors by 1 ppb, except Bristol and Colliers Mills which were unchanged. Despite the use of alternative methods for calculating the RRF, the resulting future year concentrations for the Bristol and Colliers Mills monitors still exceed EPA’s recommended WOE cut
- off concentrations (see above in Tabl e 2). Table 6 . Alternative Projected 2009 Modeled Values Using Alternative RRFs Site Alt RRF DV Base Alt Projected 2009 Camden 0.8915 98.0 87 Ancora S.H. 0.8723 99.7 86 Clar ksboro 0.8875 98.0 86 Rider 0.8908 97.7 86 Colliers Mills 0.8703 105.7 91 Bristol 0.8892 99.0 88 NE Airport 0.8991 96.7 86 Combining Alternative Baseline Concentrations and Alternative RRFs Table 7 contains the projected 2009 modeled design values from combining the alternative baseline concentrations and the alternative RRF calculations described in the previous two sections. The combination of these two alternative approaches lowers the projected 2009

- modeled concentrations significantly , but still leaves the Colliers Mills monitor above the highest concentrations listed in the U.S. EPA’s WOE chart. Five of the other six monitors still remain above the levels needed for attainment of the ozone standard.14

Table 7 . Combined Effects of Alternative Baseline Concentrations and Alternative RRFs Site Alt RRF Alt DV Base Alt Projected 2009 Camden 0.8915 94.0 83 Ancora S.H. 0.8723 98.6 86 Clarksboro 0.8875 96.4 85 Rider 0.8908 95.6 85 Colliers Mills 0.8703 104.2 90 Bristol 0.8892 96.6 85 NE Airpo rt 0.8991 94.6 85 Regional Transport Analysis The NO x SI P Call reduced ozone precursor emissions over a large region of the eastern US. These reductions reduced regional transport from the large power plants along the Ohio River into the Philadelphia n onattainment area. Penns yl vania maintains an elevated monitoring site (Methodist Hill) on South Mountain in south

- central Pennsylvania approximately 40 miles southwest of the City of Harrisburg. Methodist Hill sits at approximately 1900 ft above mean

- sea level and is in a go o d position to sample ozone concentrations entering the eastern ozone transport region ( OTR). The Delaware SIP revision for the Philadelphia area contends that o ne way to gauge how well the OTC air quality m odel is simulating regional transport is to examine how well the modeled 2009 eight

- hour ozone design value compares to the 2006 actual design value. Table 8 contains the modeled 2009 concentration and the actual 2006 ozone design value. The model appears to be over predicting Me thodist Hill’s design value by approximately 6 ppb. This seems to indicate the model may not be adequately characterizing the effects of the NO x SI P Call on upwind sources (under predicting the benefit). Delaware contends that the 6 ppb difference repres ents an overestimation of background (regional) concentrations entering the eastern OTR and suggests the modeled 2009 design values may be overestimated b y as much as 6 ppb within the Philadelphia Nonattainment Area. This may be true for this particular m onitor, but it is inappropriate to generalize this statement to the entire Philadelphia area based on one monitor. Additionally , when a comparison is made using the 2007 and preliminary 2008 design value s for the Methodist Hill monitor, the difference is o nly 4 ppb, which is closer to the projected 2009 model

- predicted design value and not nearl y enough of a reduction to reduce modeled 2009 modeled ozone design values to levels need ed to demonstrate attainment.15

Table 8 . Modeled 2009 vs. Monitored Ozone Design Values at Methodist Hill EPA Baseline RRF

OTB/OTW V4 Modeled

2009 2006 DV 2007 DV Preliminary 2008 DV 90.6 0.8488 76 70 72 72 Analysis of Air - Quality Model Sensitivity to Emission Changes The Delaware SIP revision for the Philadelphia are a cites a study of the 2003 Northeast Blackout ( Marufu et al., 2004 ) that shows that the blackout caused a drop of at least 7 ppb ozone, and likely considerabl y m ore, and a modeling study of the same event ( Hu et al., 2006 ) that used CMAQ to predict ed onl y a 2.2 ppb change. The modeled reduction in ozone due to the blackout on August 14, 2003 was compared to the difference in aircraft measurements of ozone made by the University of Maryland at Selinsgrove PA on the blackout day and on reference non

- blacko ut day s with similar meteorology
. Modeled ozone reductions due to the large number of power plant shutdowns during the blackout were on the order of 2.2 ppb while reductions of up to 7 ppb were noted in the aircraft data when measurements made on the blac kout day were compared to measurements made on non

- blackout day s ( August 4, 2002 and August 3, 2005 ) that had meteorology thought to be similar to the meteorology on the blackout day . T he University of Maryland concluded air

- quality models such as CMAQ may be under predict ing ozone reductions due to control programs such as the NO x SI P Call by up to a factor of two
. To be conservative , the University of Maryland lowered the i r estimate of mode l under

- prediction of ozone reductions from 100% to 50%
. Appli cation of the 50 % under prediction results in adjusted modeled 2009 design values of less than 85 ppb for all WOE monitors inside the Philadelphia Nonattainment Area ( se e T able 9 below). Given the CMAQ 2009 design value predictions and the 2007 and preli minary 2008 monitored 2008 design values shown earlier in Table 3 , it appears that the model is doing a good job predicting the future year design values in the Philadelphia area. CMAQ predicted a ~10

- 13 percent ozone reduction for the 2002

- 2009 time pe riod which is very close to the measured ozone reductions for the same period. For this reason and for other reasons detailed below, we believe the 50 % adjustment to the 2009 design values discussed earlier to be inappropriate. Table 9. Modeled Design Value Adjustments Due To Model Under - Prediction of Benefits
SITE BASELINE

DV MODE LED

2009 DV ∆ PPB 1.5 x ∆ PPB ADJUSTED 2009 DV Camden 98.0 88
- 10.0
- 15.0 83.0 Ancora S.H. 99.7 87
- 12.7
- 19.0 80.7 Clarksboro 98.0 88
- 10.0
- 15.0 83.0 Rider 97.7 87
- 10.7
- 16.0 81.7 Colliers Mills 105.7 91
- 14.7
- 22.0 83.7 Bristol 99.0 88
- 11.0
- 16.5 82.5 NE A irport 96.7 87
- 9.7
- 14.5 82.216

Analysis of the Blackout Study Adjustments Measured changes in ozone at Selinsgrove PA during the August 14, 2003 blackout are us ed to argue that CMAQ does not respond adequately to upwind emissions reductions. In order to determine what ozone should have been if the blackout had not occurred, the University of Maryland (UM) paper compared ozone measurements on the blackout day with ozone measurements on meteorologicall y s imilar day s. As a result of this comparison, the UM paper concludes that ozone should have been reduced by twice as much as the amount predicted by photochemical grid modeling done b y G eorgia Tech ( Hu et al., 2006 ) for the blackout day
. T he vast majority of emissions reductions from the August 14, 2003 Northeast blackout were from NY and Ontario (not the Midwest). The ozone and ozone precursors were likely reduced in central PA, but the emissions reductions were g enerally not coming from the locations that transport ozone into the Baltimore or Philadelphia Area s . Even if the blackout had a large impact in central PA, there is no way to translate that impact on ozone to the entire Philadelphia area. EGU emissions likely account for a large fraction of the ozone in rural PA, but a much smaller fraction of ozone in the urban Northeast corridor
. In the urban corridor, transported ozone may be important, but NOx from mobile sources is still the biggest source of ozone in the Philadelphia area (See Tables 3
- 4, 6
- 10, 6
- 11 and 6

- 12 in the Delaware SI P revision for the Philadelphia area)
. . Th is is not the case in rural PA
. The only modeling of the blackout study was done by Georgia Tech ( Hu et al., 2006 ). The Georg ia Tech paper argues that because the emissions reductions were coming from NY and Ontario (and not the Midwest), they would not expect a large ozone reduction in the urban areas
. Georgia Tech's modeling only saw a 2.2 ppb ozone reduction in the Selinsgro ve PA area . . Additionally , the Georgia Tech modeling used the SAPRC chemistry
. No additional modeling was performed by the University of Maryland to support their conclusions from the blackout study. No effort was made to separate out the impacts of transported ozone and precursors from local sources
. As mentioned above August 4, 2002 and August 3, 2005 were the reference days with ostensibly similar meteorology to the August 15, 2003 blackout meteorology that the University of Maryland used in the ir anal ys is. EPA understands that comparing different day s with similar weather conditions is only an approximation as no two weather patterns are exactl y alike. It is almost impossible to find a period with identical meteorological conditions, much less the same chemical state of the air parcels entering the regions as occurred on August 15, 2003. Furthermore, the weather on the day s used to compare with the blackout day was significantl y different because the wind trajectories on the blackout day were mostly from Western New York and Northern Ontario, as opposed to northern Ohio and Western Pennsylvania on the comparison day s. The reduction in ozone on the blackout day would be less than if the blackout occurred on the comparison day s since the blackout day ’s emissions came from an area with lower emissions than the comparison day s. For these reasons, and other discussed in the Georgia Tech paper, the modeling may not be wrong when it predicts onl y a 2.2 ppb decrease in ozone on the17

blackout day in the area upwind of the northeast corridor’s ozone nonattainment areas. Also, the studies compared the model with observations in central Pennsylvania, not the northeast corridor. Central Pennsylvania is not representative of ozone impacts affecting the urban areas of the northeast corridor, where mobile source NOx emissions dominate (see Tables 3

- 3, 3
- 4 , 6
- 11 and 6

- 12 in the Delaware SIP revision for the Philadelphia area) . Mobile source emissions were not significantly affected during the blackout. Monit ored ozone on the reference day s was used to reach the conclusion that the model is under

- predicting the benefits of upwind NOx reductions. E ven though the recent measurements don’t support the claim of an underestimate of ozone reduction from the model , there may still be a valid issue with regard to underestimation of upwind ozone reductions
. If the model underestimates the impact of upwind NOx reductions, then there may be a compensating error which overestimates the ozone reductions from other sourc es . Therefore it is possible that the modeling s ys tem overestimated the benefits of low level NOx reductions
. This makes it inappropriate to make an y a cross the board adjustments to the DV. Any reductions in DV from transport may need to be compensated by increases to the DV from other (local low level) sources Given all of the facts, there is no technical basis for the adjustment factor that is used to adjust the design values
. In creasing the modeled ozone reduction by 50% is not conservative and is no t supported b y the current modeling contained in the Delaware SI P revision for the Philadelphia area and ambient measurements. The Effect of 2007 - 2009 and 2008 - 2009 Emission Reductions Any measures that reduce emissions that cause ozone pollution, even if not committed to by Delaware will help the Philadelphia area meet the Cle an Air Act’s requirement in section 172 (c) that all nonattainment areas reach attainment as soon as practicable . Even if Delaware ’s attainment plan does not conclusively show attainment by 2009 and this portion of th eir SIP revision for the Philadelphia area is not approved, attainment must still occur as soon as possible. Table 10 below contains NOx and VOC emission reductions that are expected to occur between 2007

- 2009 and 2008

- 2009 in the Philadelphia area. A detailed discussion of how EPA estimated these emission reductions is contained in Attachment 1 of this TSD. Using the sensitivity of the CMAQ modeling contained in the Delaware SIP revision for the Philadelphia area to reductions in emissions, EPA estimated the potential reduction in ozone conc entration that might be expected from emission reductions that will occur between 2007

- 2009 and 2008

- 2009 in the Philadelphia area. The modeled ozone reduction factor ( 0 .021 ppb/ton) is estimated by dividing the average model predicted ppb reduction in d esign values for all the Philadelphia area monitors b y the total 2002

- 2009 Philadelphia area emission reductions that were included in the modeling. If both VOC and NOx contribute proportionally to ozone reductions (not necessaril y true, but used here as a simplifying assumption), then EPA’s modeled ozone reduction factor is multiplied by the total expected 2007

- 2009 emission reduction (VOC +NOx) expected to occur in the Philadelphia area. The result is a 2.25 ppb reduction in ozone for the 2007

- 2009 peri od. When this concentration is subtracted from the 2007 design value (93 ppb)18

and the 2007 4 th high ozone value (102 ppb) for the Philadelphia area, the result is 91 ppb and 99 ppb respectivel y, which does not show attainment
. When a similar process is ap plied to the emission reductions expected to occur between 2008 and 2009 using the preliminary 2008 design value (92 ppb) and the preliminary 2008 4 th high ozone value (90 ppb), the result is projected 2009 design value of 90 ppb and a projected 2009 4 th h igh ozone level of 88 ppb which again does not show attainment. Additionally , the potential 2.25 ppb and 1.21 ppb reductions in ozone are probabl y over estimates of the actual ozone reductions that could result from 2007

- 2009 and 2008

- 2009 emission reduct ions. Emission controls between 2007 and 2009 may have the potential to reduce ozone concentrations in 2009, however; the actual ozone reduction will most likely be less than the ozone reduction predicted from the model based ozone reduction factor. The 2007
- 2009 emission reductions will not be assisted by the large reductions in transported ozone and precursors that occurred before 2005 due to the NOx SIP Call that are accounted for in the modeling. Any additional reductions in ozone in the 2008 and 200 9 ozone seasons will be limited to mostly local controls in the nonattainment area and a few reductions in major sources due to States’ initiatives in the Ozone Transport Region.19

Table 10. Estimated Ozone Benefit from 2007 - 20 09 and 2008 - 2009 Emission Reductions
Ar ea Name Major NOx

Emission Reduction I

n SIP Revision NOx

Emission Reduction (TPD) (2007

- 2009) NOx Emission

Reduction (TPD) (2008

- 2009) Major VOC

Reductions in SIP Revision VOC Emission

Reduction (TP D) (2007

- 2009) VOC Emission

Reduction (TPD) (2008

- 2009) Ozone Benefit

(PPB) ( .021 ppb/tpd) x (tpd reduction) (2007

- 2009) Ozone Benefit

(PPB) (.021 ppb/tpd) x (tpd reduction) (2008

- 2009)
Philadelphia Fleet Turnover 43.3 20.31 Fleet Turnover 30.88 14.29 DE Multi

- P 13.01 to

19.01 9.394 to 11.23 Certain Categories of IC I Boilers 2 (NJ

estimate ) 2 (NJ

estimate ) The below

are all 2008 to 2009 Refinery Enforcement Initiative 0.3 (NJ

estimate ) 0.3 (NJ

estimate ) Refinery

Enforcement Initiative 0.9 (NJ

estimate ) 0.9 (NJ

estimate )
NOx RACT rule 2006 2.1 (NJ

estimate ) OTC
- Consumer Products Phase 2 0.02 ( MD

estimate ) 0.02 ( MD

estimate )
OTC
- PFC Phase 1 0.06 (MD

estimate ) 0.06 (MD

estimate ) OTC
- PFC Phase 2 0.03 (MD

estimate ) 0.03 (MD

estimate ) OTC

– Industrial Adhesives 0.10 (MD

estimate ) 0.10 (MD

estimate ) EPA MACT Standards 1.1 (NJ

estimate ) 1.1 (NJ

estimate ) Consumer Products 2009 Am endments 0.4 (NJ

estim ate ) 0.4 (NJ

estimate ) Adhesives and Sealants 2.2 (NJ

estimate ) 2.2 (NJ

estimate ) Asphalt Paving (Cutback and Emulsified Asphalt) 1.5 (NJ

estimate ) 1.5 (NJ

estimate )
Portable Fuel Containers (2005 + 2009) 0.8 (NJ

estimate ) 0.8 (NJ

estimate ) Regulation 1124 Section 46, Crude Oil Li ghtering Operations 2.58 ( DE

estimate ) 2.58 ( DE

estimate )
Totals .... 66.71 33.84 Totals .... 40.57 23.98 2.25 1.21
In summary , for ozone reductions to continue as they have since 2002, then e mission reductions would have to continue as they have in the past. Even if r eductions in local emissions continue to be about the same as past years, reductions in transported emissions will not be at the same level seen during the implementation of the NOx SIP C all in the 2003

- 2004 period. Therefore, we should not assume that a continuation of local emission reductions per the rate achieved during the earlier part of this decade will20

mean the same reduction in ozone now, as transported ozone will not be reduced at the same rate as in previous years. States have not provided quantitative information about how much emissions in the Ozone Transport Region outside the Philadelphia nonattainment area will be reduced compared to earlier years. To make an est imate of reductions, EPA used information in Delaware SIP revision for the Philadelphia area and those of surrounding states to calculate the amount of emission reductions in states’ plans for the P hiladelphia nonattai nment area. O zone design valu es in the past five years have decreased enough to get the Philadelphia ozone nonattainment area more than halfway to attain ing the standard by 2009. However, that large drop in ozone concentration was aided b y the NOx SIP Call
. The expected e mission red

uctions over the next two years are less than the past five year period. There will be no comparable reduction in long

- range transported pollutants scheduled to occur in the next two years , even if the Clean Air Interstate Rule ( CAIR) program was implemented on schedule. EPA believes that the arguments presented above indicate that it is not likely that planned emission reductions between 2007 and 2009 are sufficient for the Philadelphia area to attain the ozone standard
. Summary of EPA’s Evalu ation Pennsylvania ’s Delaware ’s WOE Analysis Delaware ’s photochemical grid modeling results predict a 2009 projected design value well above the air quality health standard for the Philadelphia ozone nonattainment area
. Even after accounting for the potential ozone benefits from additional measures not included in the modeling, attainment of the ozone standard b y 2009 for Philadelphia area is not likely
. The Delaware SI P revision for the Philadelphia area makes a possible, but ultimately , not convincing argument to show that ozone will be less than or equal to 8 4 ppb in 2009. With the modeled result at least 7 ppb away from attainment, EPA’s modeling guidance reasonably points out (see Table 2 above) that Delaware need s to supply a very substantial amount of evidence that the model is significantl y over estimating future ozone concentrations. Modeling studies give conflicting results as to whether Delaware will get more reductions in ozone than predicted by the model. Current air quality data seem to i ndicate that the model is not significantly over predict ing ozone concentrations in 2009. Recent air quality data also confirm the large gap between present air quality and attainment by 2009. Air quality data through 2007 and preliminary data for 20 08 are so far above the level needed for attainment that it is doubtful if those states in the Philadelphia area will able to implement enough emission controls to reach the standard b y 2009. The present air quality also does not support the hy pothesis that the models are incorrect. Present air quality concentrations should be closer to the standard since the Philadelphia area is only one ye ar from when it should be attaining the standard . Instead, present air quality is21

very similar to the 2009 model

- p redicted air quality
. Emission r eductions anticipated to occur between now and 2009 are also not enough to close th e ambient air quality gap. T he information and calculations provided in the Delaware SI P revision for the Philadelphia area emphasizes me thods or data that support their claims that is reasonable to assume the Philadelphia nonattainment area could attain the ozone standard b y the deadline. EPA’s review of the WOE anal ys es must evaluate a spectrum of likely alternative calculations, not onl y those that tend to enhance arguments that the area could attain the ozone standard. As noted before, the method recommended b y E PA’s guidance and other reasonable variations on EPA’s methods predict the area will not attain the ozone standard b y 2009. Delaware has not provided convincing evidence that the proposed adjustments to the photochemical grid model’s attainment year forecast will give a more accurate answer than the calculations based on EPA’s recommendations in its modeling guidance. Additionally , recent air quality trends when combined with an anal ys is of ozone benefits from emissions controls expected to come online between now and the start of the 2009 ozone season do not support the case for attainment. Impact of the Vacatur of EPA’s Clean Air Interstate Rule (CAIR) On June 11, 2008 the United States Court of Appeals for the District of Columbia Circuit issued an opinion vacating the Clean Air Interstate Rule (CAIR) in its entirety . This opinion did not become final before Decemb er 23, 2008, when the Court reconsidered its June 11 decision and issued an opinion remanding CAIR to EPA without vacating. North Carolina v. EPA , Docket No. 05

- 1244 (D.C. Cir. Dec. 23, 2008). The Court stated in its December 23 opinion that EPA was still under an obligation to remedy wh at the Court characterized as “fundamental flaws” with CAIR, though the Court declined to impose a deadline for EPA to finalize that remedy
. Whether or not CAIR and its associated emissions reductions remain in effect does not alter EPA’s analy sis of the approvability of the attainment demonstration. The modeling and WOE anal ys is in the proposed SIP revision took into account the anticipated CAIR reductions. EPA has determined that the Area is not likely to attain the standard even with these reductions. If additional proceedings were to result in vacatur of CAIR, our conclusion that the Area us unlikely to attain the NAAQS would not change; however, loss of the CAIR reductions would further increase the odds of the Area reaching attainment by the applicable June 2010 deadline. Summary of EPA’s Technical Findings The result of the photochemical grid modeling analysis using EPA’s recommended methods predicts that the Philadelphia area ozone nonattainment area will not attain the standard in the attainment year of 2009. In response to this, Delaware has offered a number of WOE arguments that whe n taken together present an outside chance of truly22

attaining the ozone standard. However, EPA’s review of the attainment demonstration portion of the Delaware SIP revision for the Philadelphia area determined the following :

· The Delaware SIP revision for the Philadelphia area modeling us es an appropriate photochemical grid model and follows EPA’s guidance methods and d oes not predict attainment in 2009.

· The Delaware SIP revision for the Philadelphia area relies on emission reductions resulting from a commitment to adopt and implement a number of regulations prior to the start of the 2009 ozone season. Some of these were included in the photochemical grid modeling. These regulations would provide for additional reductions from boilers, refineries, power generation, consumer products and portable fuel containers. Delaware ’s own anal ys is shows that Delaware must adopt all these measures, and additional measures as well to show attainment by 2009
. Delaware must adopt these measures as soon as possible to insure that these e mission reductions occur by the start of the 2009 ozone season to have an y chance of attaining the standard in 2009.

· Regardless of the issues raised by Delaware regarding the performance of EPA’s recommended air quality models, the 2007 air quality data and preliminary 2008 air quality data continue to exceed the ozone standard b y a significant margin. Even a linear comparison of the percentage of additional emission reductions planned by the state with the needed improvement in air quality between 2007 and 2009 indicates it is unlikely that air quality will improve enough for the Philadelphia area to meet the ozone standard or qualify the area for a one year extension of the attainment date in 2009.

· When comparing the measured ozone co ncentrations in 2007 to the ozone concentrations predicted for 2009 b y using EPA’s recommended application of the photochemical grid modeling, the photochemical grid model does not exhibit the magnitude of inaccuracies suggested in the Delaware SI P revisio n for the Philadelphia area
.
· In order to insure attainment, Delaware refers to additional measures which were not included in the original photochemical modeling analysis. M ost of these measures are not contained in the SIP revision for the Philadelphi a area and are not committed to by Delaware as part of its attainment demonstration. While EPA encourages Delaware to continue to promote these worthwhile and important emission reduction programs, the amount of tangible air quality benefit is difficult t o estimate with an y degree of certainty. Based on EPA’s estimates of the ozone benefits that the proposed additional measures could provide, it is not likely that the additional ozone benefit will be sufficient for the Philadelphia area to demonstrate att ainment of the ozone standard or qualify for a one year extension of the attainment date in 2009. However, implementing these measures will move the State’s nonattainment areas closer to attainment.23

· The Philadelphia area attainment demonstration relie d on adjustments to the baseline design values and on adjus tments to the model predicted relative response factors form the basis of the photochemical modeling anal ys is. These adjustments to the base year starting value and the amount of reduction in ozone from 2002 to 2009 differ from EPA’s modeling guidance and, more importantly , are not sufficiently justified and are artificially weighted toward a conclusion that Philadelphia area will attain the ozone standard in 2009
.
· The Philadelphia area attainment demonstration relied on research which evaluated the impact of a widespread power blackout to develop an alternative approach to estimating anticipated air quality i mprovements from upwind power plants. While EPA believes that this approach provides some insight into the transport of ozone precursors, a critical review of all the research available to EPA and Delaware leads EPA to disagree with the premise that the air quality modeling results should be adjusted using Delaware ’s alternative approaches.

· EP A encourages Delaware to implement all of its planned measures as soon as possible to meet the Clean Air Act’s requirement that all nonattainment areas reach attainment as soon as practicable. Recommendation of Disapproval of Attainment Demonstration E PA has carefull y evaluated the information provided by Delaware and other information it deems relevant to help understand what the air quality is likely to be by the 2009 ozone season. EPA conclude s that Delaware’s SIP revision for the Philadelphia does not satisfy 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. For the Delaware SIP revision for the Philadelphia area to show attainment o f the air quality standard , several factors would have to coincide. The photochemical grid model would have to be under

- predicting the change in ozone by at least 40 percent. All of the measures Delaware committed to implement as part of its SIP revision for the Philadelphia area as well as measures not committed to as WOE would have to be implemented by the beginning of the 2009 ozone season. To expect all of these factors to occur is not realistic. In addition, based on recent air quality data, Delaware and its surrounding states would have to reduce emissions by levels equaling perhaps 50 percent of the total emission reductions contained in the SIP revision for the Philadelphia area
. These emission reductions would have to occur between 2007 and the beginning of the 2009 ozone season. Based on EPA’s evaluation of Delaware ’s rate of progress plans for the Philadelphia area , it is unlikely that more than 20 percent of the Philadelphia area’s emission reductions will occur in the next few years, making it implausible that ozone in the Philadelphia area will be reduced from 2007 design value of 93 ppb or the preliminary 2008 design value of 92 ppb to 84 ppb by 2009.24

Based on EPA’s review of the technical information provided in the Pennsylvania SIP re vision for the Philadelphia area , EPA concludes that the SIP revision for the Philadelphia area does not show attainment of the ozone standard by 2009 and EPA should disapprove the attainment demonstration portion of the SIP
.25

Attachments : Attachment 1