1 Technical Support Document For the Modeling and Weight of Evidence (WOE) Portions of the Document Entitled “Cecil County , Maryland 8

- Hour Ozone State Implementation Plan and Base Year Inventory

SIP Revision: 07

- 05 June 15, 2007

TSD Prepared June , 2012 Todd A. Ellsworth Office of Air Monitoring and Anal ys is, 3AP40 U.S. Environmental Protection Agency , Region 3

1650 Arch Street Philadelphia, Pennsylvania 19103

/S/

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

June 22, 2012

_________________ Date Signed2 

## Technical Support Document **For the Modeling and Weight of Evidence (WOE)**  **Portion s**  **of the Document Entitled**  **“ Cecil County, Maryland** 

**8 -**  **Hour Ozone State Implementation Plan**  **and Base Year Inventory**

**SIP Revision: 07**  **- 05**  **June 15, 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 W OE portions of Maryland ’s State Implementation Plan (SIP) entitled “ Maryland State Implementation Plan for Attainment of the 8

- Hour Ozone National Ambient Air Quality Standard Reasonable Further Progress and Attainment Demonstration, June 2007 ” , hereafter referred to as the Maryland SIP. Maryland 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. Classified as a “moderate” nonattainment area, the Philadelphia area is required to attain the NAAQS by 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 Maryland SIP
. **Introduction to the**  **Maryland State Implementation Plan fo**  **r Ozone** The Maryland SIP includes plans to reduce ozone

- causing emissions for Maryland ’s portion of the Philadelphia Area. The Plan also includes modeling that will predict whether the area will meet the ozone standard b y the due date. This TSD reviews modeling and WOE portions of the Maryland SIP
. This TSD reviews Maryland ’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 c ooperated via the Ozone Transport Commission ’s (OTC) Modeling Committee to prepare the modeling that was performed b y the New York State Department of Environmental Conservation (NY S DEC) and supporting organizations. Maryland believes that their SIP model ing when combined with additional supporting anal ys es (Weight of Evidence) (WOE) “Demonstrates that the entire Philadelphia

Wilmington

- Atlantic City, PA

-NJ
- DE
- MD moderate non

- attainment area will attain the 8

- hour ozone NAAQS in 2009”.3

**W hat**  **Are The Com**  **ponents Of A**  **Modeled Attainment Demonstration ?**  **M odeling**  **P rocess**  **Overview** The OTC Modeling Committee used the Commun ity 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 ye ar ozone 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 sati sfactory . Once the model performance was determined to be adequate, 2009 ozone concentrations were modeled by

running the model with projected emissions for 2009 and the original 2002 meteorology

. The meteorolog y was held constant so that the results o f changing the emissions would not be influenced b y changing meteorology . T he EPA modeling guidance 1 recommends that states use the modeled ozone concentrations in a relative sense and not rely

solel y on the concentrations the model predicts for the attai nment 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

- hour daily maximum predictions in the future to the mean of the 8

- hour dail y maximum predictions with baseline e missions, over all relevant day s. The base ye ar ozone design values at each monitor are then multiplied by

the monitor

- specific RRF to produce an attainment ye ar design value. If the result is less than or equal to 84 ppb, at all locations, the modeling s ys tem will have predicted attainment of the ozone air quality standard. **The Regulatory Framework** Section 110 (a) (2) (k) of the Clean Air Act requires 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 Administrator to be at least as effective to demonstrate attainment of the ozone health

- based standard by the requ ired 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, 2004, 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 att ainment date is June 2010 for moderate areas, states must achieve emission reductions b y the ozone season of 2009 in order for ozone concentrations to be reduced, and show attainment , during the last complete ozone season before the 2010 deadline. The m odeling 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 Quali ty Goals for Ozone, PM 2.5 , and Regional Haze, EPA **-** 454 /B

- 07

- 002 , April 20074

1. Develop a conceptual description of the problem to be addressed. 2. Develop a modeling/analy sis protocol. 3. Select an appropriate model to suppo rt 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 con ditions 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. Perfor m 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 Maryland**  **Address All Of The Components Of A Modeled Attainment Demons**  **tration?** The Maryland SIP addresses each of the elements of a model ed attainment demonstration as follows: **Conceptual description of the problem** A conceptual model describes how weather patterns affect the formation and transport of ozone, accounting for emissions and photochemistry

. The Maryland SIP 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, emissions 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 locally. A complete co nceptual description of the ozone problem in the Philadelphia area is contained in Section 12

. 1 of the Maryland SIP. **Modeling/analysis protocol** The Ozone Transport Commission’s (OTC’s) Modeling Committee developed a protocol for modeling the ozone problem in the northeastern United States. The modeling protocol is located in Appendix H
- 1 of the Maryland SIP. 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**  **emonstratio n**  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 Maryland

. 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 12.2 of the Maryland SIP.5

**M eteorological**  **T ime**  **P eriods**  **U sed in the**  **M odeling**  Section 12

. 2 of the Maryland SIP notes that the OTC Modeling Committee agreed to model the entire ozone season of 2002. Using the entire ozone season of 2002 covers many different kinds of ozone episodes and exceeds EPA’s recommendations for episode selection. 2002 was a go od year to model because it was the base ye ar 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 Committe e 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 Center for Atmospheric Research Mesoscale Meteorological Model (MM5) version 3.6 w as 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 contained in Section 12.2 of the Maryland SIP
. **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 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 area is included in the 12 kilometer grid cell area. The OTC Modeling Committee used a 12

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

- hour ozone attainment modeling that indicated that m odeling at finer resolutions than 1 2 kilometers would not result in increased model accuracy

. 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. The grid resolution , modeling domain and boundary conditions are described in Section 12.2 of the Maryland SIP
. Vertical resolution is the number of layers and the size of each layer in the model. The layers in the photochemical grid model were set up to be compatible with the model that produced weather conditions for the photochemical grid model. The vertical grid resolution used in the modeling is described in Section 12.2 of the Maryland SIP
. T he vertical resolution used in the modeling exercise followed EPA’s modelin g guidance and therefore adequatel y represent s the atmosphere where ozone forms and is transported. **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

-6

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 , develo ped the necessary growth and control factors and applied to the 2002 inventory

. E missions 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 provid ed 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 Model (IPM) to develop the state and unit

- level emissions. These inventories are identified as 2009 on the way (2009OTW), s ince they

reflect all emission control measures that were promulgated or would become effective on or before 2009. Details of emissions processing are provided in Appendices H
- 10 of the Maryland SIP. **B ase**  **C ase**  **R un**  **Model P**  **erformance E**  **valuation** NY DEC perf

ormed 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 in cluded performance statistics for all monitors inside the Philadelphia nonattainment area. The model performance evaluation results are presented in included in Appendix H
- 12 the Maryland SIP. The anal ys is indicates the modeling s ys tem does an adequate j ob of estimating the eight

- hour surface ozone concentrations throughout the Philadelphia area. **2009 C**  **ontrol C**  **ase M**  **odeling and the Modeled A** **ttainment T**  **est** The photochemical grid model used with projected emissions for 2009, including emission changes due t o 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 in states’ emissions to be determined without being influence d by ye arl y fluctuations 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 year7

design values at each monitor to produce projected future ye ar design values (2009). The projected 2009 design values represent design values that should result from emissio n controls Maryland 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 n ot pass the attainment test since design values are projected to be over the 84 ppb standard (see Table 1 below)

. **Table 1 Modeled Design Value** 

Monitor ID Site Name County State DVC (ppm) RRF

OTB/OTW V4 2009

Model DV (ppm) 2009

Monitored (ppm)
1000100 02 Killens Pond Kent DE 88 0.8934 78 75 100031007 Lu ms Pond New Castle DE 91 0.8462 77 75 100031010 Brandywine New Castle DE 93 0.8781 81 78 100031013 Bellefonte New Castle DE 89 0.8759 77 74 100051002 Seaford Sussex DE 90 0.8462 76 76 100051003 Lewes Sussex DE 86 0.8956 77 76 240150003 Fair Hill Cecil MD 98 0.8336 81 84 340010005 Nacote Creek Atlantic NJ 88 0.8762 77 72 340070003 Camden Camden NJ 98 0.8996 88 87 340071001 Ancora State Hospital Camden NJ 100 0.8733 87 81 340110007 Millville Cumberland NJ 94 0.8486 79 78 340150002 Clarksboro Gloucester NJ 98 0.9004 88 83 340210005 Rider College Mercer NJ 97 0.8908 86 81 340290006 Colliers Mills Ocean NJ 107 0.8703 9 1 80 420170012 Bristol Bucks PA 99 0.8976 88 88 420290100 New Garden Airport Che ster PA 94 0.8387 78 77 420450002 Chester Delaware PA 91 0.8705 79 77 420910013 Norristown Montgomery PA 92 0.8861 81 79 421010004 AMS Lab Philadelphia PA 72 0.9081 65 64 421010014 Roxboro Philadelphia PA 91 0.9070 82 81 421010024 NE Airport Philadelp hia PA 97 0.9035 87 84 421010136 Elmwood Philadelphia PA 84 0.9070 76 82

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 recomm ends supplementary analyses in all cases, and specifically recommends a WOE analysis if modeled ozone is greater than or equal to 82 ppb.8

**Summary of Photochemical Grid Modeling Results** In summary , the basic photochemical grid modeling presented in the Maryland SIP meets EPA’s guidelines and when used with the meth ods 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

Wilmington

- Atlantic City, PA

-NJ
- DE
- MD ozone nonattai nment 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, Maryland decided to use WOE to demonstrate attainment of the ozone standard in the Philadelphia area. **Weight of Evidence Demonstration** EPA ’ s modeling guidance d escribes how to use 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 determine if the results of the photochemical mode ling sy stem are correctly (or not correctly) predicting future air quality

. The WOE portion of the Maryland SIP describe s the anal ys es performed, databases used, key assumptions and outcomes of each anal ys is, and why the evidence, viewed as a whole, supp orts 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

- hour ozone standard. Table 2 outlines under what circumstances a WOE demonstrati on 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 demons tration. 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 EPA guidance. The Roxboro monitor is excluded from the WOE analysis since its current design value is significantl y lower than the eight

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

 A comparison of model

- predicted 2009 ozone design values and mon itored design values for 2006 and 2009  An anal ys is of recent ozone trends in the Philadelphia nonattainment area,  Alternative methods for calculating the 2009 ozone design value

.9

**Table 2. EPA**  **Guidelines for Supplemental Analyses and Weight of Evidence D**  **eterminations**

Results of Modeled Attainment Test Supplemental Analyses Future Design Value < 82 ppb, all monitor sites Basic supplemental analyses should be completed to confirm the outcome of the modeled attainment test Future Design Value 82

- 87 ppb, at one or mo re sites/grid cells A weight of evidence demonstration should be conducted to determine if aggregate supplemental analyses 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 mo deled attainment test. **Modeled Concentrations vs.**  **Monitored De**  **sign Values** Table 3 b elow lists the OTC modeled 2009 design values and the 2006

- 20 11 monitored design values. Maryland did not have access monitored ambient ozone data from 2007

- 201 1 ambient data when it wrote its SIP. Because the m odeled 2009 and projecte d 2006 design values are surprisingl y close to one another with most modeled concentrations only slightl y lower than the monitored 2006 design values , Maryland SIP suggest s that 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 attainment by the attainment date. C lassified as a “moderate” nonattainment area, the Philadelphia area is required to attain the NAAQS by June 2010, in effect, by end of 2009 o zone season . As shown in Table 3 b y the end of the 2009 o z o ne season only two ozone monitors (Bristol & Camden) were still monitoring nonattainment. However the 4 th high monitored 8

- hour values in 2009 were less than or equal to 84 ppb, the level needed to qualify for a one ye ar extension of the attainment date. As a result, the EPA granted the Philadelphia area a one ye ar extension of the attainment date to June 2011 or effectivel y b y the end of the 2010 ozone season. Additionally , the 2009 data presented Table 3 and earlier in Table 1 show that the model is over predicting the monitored design values b y any where from 1

- 13 ppb in 19 out of the 22 cases.10

**Table 3. Modeled vs. Monitored Design Values**

**Des ign Value Trends**  T he Maryland SIP 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 NOx 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 cooler 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 that occurred while the NO x SIP Call was implemented. However additional emission reductions have continued to occur due mostl y local controls in each nonattainment area and a few reductions in major sources due to States’ initiatives in the Ozone Transport Region. As Table 4 s hows, the monitored ozone design values for each of the Philadelphia area monitors continued to decline and now show attainment beginning in 2010 and continue to show attainment in 2011. Moni tor Site ID Number 2009 Modeled DV 2006

Monitored DV 2007

Monitored DV 2008

Monitored DV 200 9

Monitored DV 20 10

Monitored DV 20 11

Monitored DV Fairhill

- CECIL CO, MD 240150003 81 90 93 90 84 80 81 Colliers Mills

- OCEAN CO, NJ 340290006 91 93 92 87 80 81 81 Rider College

- M ERCER CO, NJ 340210005 86 87 91 87 81 78 78 Ancora State Hospital

- CAMDEN CO, NJ 340071001 87 89 88 86 81 80 80
Camden

- CAMDEN CO, NJ 340070003 88 84 88 87 87 83 Clarksboro

- GLOUCESTER CO, NJ 340155001 88 86 91 87 83 81 82
Bristol

- BUCKS CO, PA 42 0170012 88 86 92 92 88 83 80 Northeast Airport

- PHILADELPHIA CO, PA 421010024 87 90 91 89 84 82 8311

**Table 4. Recent Ozone Design Value Trends**  **for Philadelphia A rea Monitors**  Monitor ID Site Name 2003 2004 2005 2006 2007 2008 2009 2010 2011 100010002 Killens Pond 0.089 0.084 0.080 0.080 0.081 0.081 0.075 0.074 0.071 100031007 Lums Pond 0.093 0.084 0.080 0.078 0.082 0.080 0.075 0.075 0.075 10 0031010 Brandywine 0.093 0.089 0.082 0.082 0.083 0.083 0.078 0.076 0.075 100031013 Bellefonte 0.090 0.085 0.082 0.081 0.081 0.078 0.074 0.075 0.077 100051002 Seaford 0.091 0.085 0.082 0.080 0.082 0.081 0.076 0.077 0.076 100051003 Lewes 0.088 0.085 0.084 0.082 0.082 0.079 0.076 0.077 0.075 240150003 Fair Hill 0.100 0.094 0.088 0.090 0.093 0.090 0.084 0.080 0.081 340010005 Nacote Creek 0.091 0.085 0.092 0.079 0.077 0.074 0.072 340070003 Camden 0.101 0.093 0.085 0.084 0.088 0.087 0.087 0.083
34007100 1 Ancora State

Hospital 0.101 0.095 0.091 0.088 0.089 0.086 0.081 0.080 0.080
340110007 Millville 0.095 0.89 0.084 0.083 0.083 0.081 0.078 0.076 0.071 340150002 Clarksboro 0.099 0.095 0.088 0.086 0.087 0.087 0.083 0.081 0.082 340210005 Rider College 0.1 00 0.092 0.086 0.087 0.091 0.087 0.081 0.078 0.078 340290006 Colliers Mills 0.109 0.102 0.094 0.093 0.092 0.087 0.080 0.081 0.081 420170012 Bristol 0.100 0.093 0.086 0.086 0.092 0.092 0.088 0.083 0.080
420290100 New Garden

Airport 0.100 0.094 0.087 0.08 6 0.085 0.082 0.077 0.076 0.074
420450002 Chester 0.093 0.089 0.082 0.083 0.085 0.083 0.077 0.074 0.073 420910013 Norristown 0.094 0.089 0.086 0.085 0.086 0.084 0.079 0.078 0.077 421010004 AMS Lab 0.075 0.068 0.063 0.062 0.068 0.067 0.064 0.066 0.068 4 21010014 Roxboro 0.093 0.086 0.081 0.078 0.080 0.078 0.081 421010024 NE Airport 0.097 0.095 0.090 0.090 0.091 0.089 0.084 0.082 0.083 421010136 Elmwood 0.083 0.079 0.070 0.074 0.077 0.081 0.082 **Alternative Baseline Design Value** Se ven 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 (2002). Thus the baseline concentration is the average of the 2002, 2003 and 2004 eight

- hour ozone design values. Many States in the Philadelphia area believe that by using the US EPA recomme nded method for calculating a monitor’s baseline concentration , und ue weight is placed on the 2002 ozone season, one of the worst ozone seasons since the late 1990s. As alternative to the US EPA’s baseline concentration calculation, a straight average of the 4 th highs over12

the same years (2000

- 2004) was used to calculate the baseline concentration . This approach weighs each ye ar equall y. EPA guideline method baseline = 10 5.7 ppb Maryland ’s alternative baseline = 104 .2 ppb 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 the model is still over predicting the actual monitored 2009 design values in six out of the seven cases. **Table 5**  **. Alternative Baseline Concentration Analysis**  **Site Nam e**  **State Alternative**  **Baseline OTW/OTB V4** 

**RRF Alternate 2009**  **2009 Monitored Design Value**  Camden NJ 94.0 0.8996 84 87 Ancora S.H. NJ 98.6 0.8733 86 81 Clarksboro NJ 96.4 0.9004 86 83 Rider College NJ 95.6 0.8908 85 81 Colliers Mills NJ 104.2 0.8703 90 80 Bristol PA 96.6 0.8976 86 88 NE Phila PA 94.6 0.9035 85 84 **Alternative RRF** Maryland calculated 2009 modeled ozone design values 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 ye ars. RRFs were calculated for several different ozone levels; 2002 baseline model concentrations  85 ppb, 2002 baseline model concentrations  90 ppb and 2002 baseline model concentrations  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. T he projected modeled 2009 design values were recalculated using the most beneficial alternative RRFs

. This reduces the modeled 2009 values slightl y but the model is still over predicting the actual monitored 2009 design values in six out of the seven cases.13

**Table 6**  **. Alternative Projected 2009 Modeled Values Using Alternative RRFs**  **Site Alt RRF**  **DV Base Alt Projected 2009**  **2009 Monitored Design Value**  Camden 0.8915 98.0 87 87 Ancora S.H. 0.8723 99.7 86 81 Clarksboro 0.8875 98.0 86 83 Rider 0.8908 97.7 86 81 Colliers Mills 0.8703 105.7 91 80 Bristol 0.8892 99.0 88 88 NE Airport 0.8991 96.7 86 84 **Combining Alternative Baseline Concentrations and Alternative RRFs** Tab le 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. This reduces the modeled 2009 values slightl y but the model is still over predicting the actual monitored 2009 design values in five out of the seven cases. **Table 7**  **. Combined Effects of Alternative Baseline Concentrations and Alternative**  **RRFs Site**  **Alt RRF Alt DV Base**  **Alt Projected 2009**  **2009 Monitored**

**Design Value** Camden 0.8915 94.0 83 87 Ancora S.H. 0.8723 98.6 86 81 Clarksboro 0.8875 96.4 85 83 Rider 0.8908 95.6 85 81 Colliers Mills 0.8703 104.2 90 80 Bristol 0.8892 96.6 85 88 NE Airport 0.8991 94.6 85 84 In summary , with the benefit of having the 2009 monit ored design values, it’s obvious that the model is over predicting the actual concentrations, even when model adjustments are made to account for model over prediction. **Summary of EPA’s Evaluation**  **Maryland ’s**  **WOE Analysis** Maryland ’s photochemical grid modeling results predict a 2009 projected design value well above the air quality health standard for the Philadelphia ozone nonattainment area

. However, after taking into account WOE arguments regarding model over prediction of the 2009 monitored des ign values and recent ozone design value trends, which show attainment of the standard by 20 10 , the Maryland SIP has demonstrated attainment of the ozone standard b y the extended attainment date of June 201 1

.14

**Summary of EPA’s Technical Findings**  The res ult of the photochemical grid modeling analy sis 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, a number of WOE arguments have b een made that when taken together with recent air quality trends show attainment of the ozone standard b y the extended date of June 2011. EPA’s review of the attainment demonstration portion of the Maryland SIP determined the following :

 The Maryland SIP modeling us es an appropriate photochemical grid model and follows EPA’s guidance methods and d oes not predict attainment in 2009.

 The Maryland SIP relies on emission reductions resulting from a commitment to adopt and implement a number of regulations pri or 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

. Maryland ’s own anal ys is shows that Maryland must adopt all these measures, and additional measures as well to show attainment by 2009

.

 In order to insure attainment, Maryland refers to additional measures which were not included in the original phot ochemical modeling analy sis. M ost of these measures are not contained in the SIP and are not committed to by Maryland as part of its attainment demonstration. While EPA encourages Maryland to continue to promote these worthwhile and important emission re duction programs, the amount of tangible air quality benefit is difficult to estimate with any

degree of certainty

. However, implementing these measures will move the State’s nonattainment areas closer to attainment.

 An evaluation of recent air quali ty data indicates that the Philadelphia area has attained the 1997 8

- hour ozone standard by the applicable attainment date of June 2011

. **Recommendation of A** **pproval of the**  **Attainment Demonstration** EPA has carefull y evaluated the information provided by Maryland and other information it deems relevant to help understand what the air quality was likel y to be by the extended attainment date of June 2011 or effectivel y b y the end of the 2010 ozone season. EPA conclude s that Maryland ’s SIP satisf ies the Cle an 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. Based on EPA’s review of the technical information provided in the Maryland SIP , EPA concludes that the SI P demonstrates attainment of the ozone standard by the June 2011 attainment date and EPA should approve the attainment demonstration portion of the SIP
.