1 

### Technical Support Document**— Area Designations for the**  **Washington -**  **Baltimore**   ** Northern Virginia, DC** **- MD**  **- VA**  **- WV Combined Statistical Area**  **(CSA)**

**2008 Ozone National Ambient Air Quality Standards Scope:**  This Technical Support Document (TSD) is for designation of the final nonattainment and “ unclassifiable/ attainment” areas and the establishment of the boundaries thereof within the Washington - Baltimore - Northern Virginia, DC - MD - VA - WV CSA (hereafter the Wash ington - Baltimor e NV CSA or just “this/the CSA”). 

### Summary: Maps of Final Nonattainment Areas : Washington, DC

- MD - VA area Figure 1 a is a map of the Washington, DC - MD - VA nonattainment area under the 2008 ozone NAAQS . The map provides other relevant information including the locations and design values of air quality monitors, county

and other jurisdictional boundaries, the CSA boundary , prior nonattainment area boundaries for 1997 ozone NAAQS, and major transportation arteries . It also shows the attaining/violating status for 2008 - 2010 for the remainder to the remainder of the Washington Baltimore - Northern Virginia, DC - MD - VA - WV CSA as well as all or parts of the York - Hanover, PA CBSA, Lancaster, PA CBSA, Chambersburg, PA CBSA, Hagerstown - Martinsburg MD - WV CBSA, Richmond, VA CBSA, Philadelphia - Camden - Vineland CSA as well as other counties in Penns yl vania, Maryland, and Virginia .2

**Figure 1a. The Washington ,**  **DC -**  **MD -**  **VA Nonattainment Area**

The boundary

for the Washington , DC - MD - VA nonattainment area under the 2008 ozone NAAQS for the 2008 ozone NAAQS consists of: (1) The Counties of Arlington, Fairfax, L oudoun, and Prince William, and the Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park in Virginia; ( 2) The entire District of Columbia; and (3) The Counties of Calvert, Charles, Frederick, Montgomery , and Prince George ’ s in Maryland. Figure 1b is a map of the Baltimore MD nonattainment area under the 2008 ozone NAAQS. The map provides other relevant inf ormation including the locations and design values of air quality monitors, county and other jurisdictional boundaries, the CSA boundary , prior nonattainment area boundaries for 1997 ozone NAAQS, and major transportation arteries . It also shows the attaining/violating s tatus for 2008 - 2010 for the remainder to the remainder of the Washington - Baltimore - Northern Virginia, DC - MD VA - WV CSA as well as all or parts of the York - Hanover, PA CBSA, Lancaster, PA CBSA , Chambersburg, PA CBSA, Hagerstown - Martinsb urg MD - WV CBSA, Richmond, VA CBSA, Philadelphia - Camden - Vineland CSA as well as other counties in Penns yl vania, Maryland, and Virginia .3

Baltimore Area **Figure 1b. The Baltimore ,**  **MD Nonattainment**  **Area**

The boundary

for the Baltimore , MD nonattainment area under the 2008 ozone NAAQS consists of Anne Arundel, Baltimore, Carroll, Harford, and Howard Counties and Baltimore City . Tables T able s 1a to 1c below identifies the areas and associated counties or parts of counties in the District of Columbia, State of Maryland **and** Commonwealth of Virginia that EPA has determined must be designated as nonattainment for the 2008 ozone national ambient air quality standards (“2008 ozone NAAQS” or “2008 NAAQS”) and the nonattainment areas in which each will be plac ed. In accordance with section 107(d) of the Clean Air Act (CAA), EPA designates an area (county or a part of a county) “nonattainment” if it is violating the 2008 ozone NAAQS or if it is contributing to a violation of the 2008 ozone NAAQS in a nearb y are a. The technical anal ys es supporting the boundaries for the individual nonattainment areas are provided below. **Table 1a. Nonattainment Areas in District of Columbia .**  Area The District of Columbia’s Recommended Nonattainment EPA’s Nonattainment Counties4 Counties Washington, DC - MD - VA* District of Columbia: District of Columbia: **Table 1b. Nonattainment Areas in Maryland.** Area Maryland’s Recommended Nonattainment Counties EPA’s Nonattainment Counties Washington, DC - MD - VA* Calvert County Charles County Frederick Count y Montgomery

Count y Prince George ’ s Count y Calvert County Charles County Frederick Count y Montgomery

Count y Prince George ’ s Count y Baltimore , MD Anne Arundel County Baltimore City Baltimore County Carroll County Harford County Howard Count y Anne Arundel County Baltimore City Baltimore County Carroll County Harford County Howard Count y **Table 1c. Nonattainment Areas in Virginia.** Area Virginia’s Recommended Nonattainment Counties EPA’s Nonattainment Counties

Washington, DC - MD - VA* Alexandria City Arlington County Fairfax City Fairfax County Falls Church City Loudoun Count y Manassas City Manassas Park City Prince William County Alexandria City Arlington County Fairfax City Fairfax County Falls Church City Loudoun Count y Manassas City Manassas Park City Prince William County *The Washington, DC - MD - VA nonattainment area is a multi - state nonattainment area. **Remainder of the Washington -**  **Baltimore -**  **NV CSA:** The remaining Counties and Cities in the Maryland, Virginia and West Virginia that are part of the Washington - Baltimor e - NV CSA are designated “unclassifiable/attainment .” 

### Back**ground –**  **State Recommendations , EPA’s Proposed Modifications and State**  **Responses :**  The District of Columbia’s Recommendations:5

March 2009: On March 11, 2009, the District of Columbia recommended the entire District of Columbia be designated nonattainment as part of a nonattainment area which includes at a minimum the entire “W ashington DC - MD - VA MSA” but the District also supported using larger combined statistical areas based upon sound science. The District supported its recommendation with air quality data that showed monitors in the District were violating the 2008 ozone NAAQS and an analy sis of emissions showing that the District itself contributed less than 10 percent of 2002 ozone precursor emissions within the “ Metropolitan Washington Area” and thus would need reductions in a broader area than just the District to attain the 2008 ozone NAAQS. 1 In response to EPA ’s December 9, 2011, letter to the Mayor of the District of Columbia2 regarding EPA’s proposed modifications to the District’s recommendations, on March 12, 2012, the District replied to EPA’s December 9, 2012 lett er. 3 Maryland’s Recommendations: The March 2009 recommendations: On March 10, 2009 4 , Maryland recommended retention of the current nonattainment boundaries “if EPA is confident that strong national rules would be in place three ye ars in advance of attai nment dates for nonattainment areas in Maryland.” These nonattainment areas included the current Baltimore nonattainment area and boundaries, the Maryland portions of the current Washington DC - MD - VA nonattainment area, and Cecil County as part of a Philad elphia based nonattainment area. With these recommendations, Maryland also recommended that Washington County be part of a nonattainment area based upon Hagerstown, Maryland, and an “Eastern Shore” nonattainment area comprising Kent and Queen Anne’s Count ies. In the alternative, Maryland supports the “implementation of a large regional nonattainment area encompassing a significant portion of the U.S. East Coast” “if EPA is not confident that strong national rules will be in place” in order to “force reg ional controls and reductions in transported pollution” in an time frame appropriatel y related to the dates b y which areas in Maryland are required to attain the 2008 NAAQS. Under this alternative, Maryland would support a nonattainment designation for al l counties and cities in the State. Maryland noted that most of the State is already heavily regulated due to existing ozone and fine particle requirements. Maryland stated that its scientific research, which uses airplanes, ozone - measuring balloons, and laser measuring techniques, shows that air transported into Maryland often carries levels of ozone already exceeding the standard. Maryland concluded that it will need to rel y heavily on reductions in transported pollution to meet the 2008 NAAQS. Maryland concluded that because of “incoming” ozone levels above the standard, strong national rules will be needed for areas like Maryland to attain the 2008 NAAQS. Maryland provided a map which represented the spatial extent of 2008 1 The District cited the 2002 emissions inventory contained within its State Implementation Plan (SIP) revision dated May 23, 2007 for the Washington DC - MD - VA Nonattainment Area. This 2002 emissions inventory was for the Washington DC MD - VA nonattainment area under the 1997 ozone NAAQS (of 40 CFR 50.9) and thus covered an area smaller than the current Washington - Arlington - Alexandria Metropolitan Statistical Area. Refer to 76 FR 58116 , September 20, 2011. 2 Letter dated December 9, 2011, from S hawn M. Garvin , Regional Administrator, EPA Region III, to the Honorable Vincent C. Gray, Mayor of the District of Columbia. 3 Refer to Letter dated March 12, 2012, from Christophe A. G. Tulou, Director District department of the Environment, to Shawn M. Garvin, Regional Administrator, EPA Region III. 4 March 10, 2009 Letter from the Honorable Martin J. O’Malley, Governor of Maryland, to William T. Wisniewski, Acting Regional Administrator, EPA Region III.6

ozone levels in Maryland, Delaware, New Jersey and southeastern Penns yl vania to show that large areas outside of Maryland have levels above the 2008 NAAQS. Maryland also provided a summary table of modeled 2009 design values for Delaware and Maryland based upon work performed by th e Bureau of Air Quality Anal ys is and Research, Division of Air Resources, New York State Department of Environmental Conservation. In a December 9, 2011 letter to the State of Maryland, 5 EPA propose d to modify and respond to Maryland’s recommendations as follows: (1) EPA would not designate Kent, Queen Anne’s and Washington Counties as nonattainment for the reasons provided in our cover letter. (2) EPA would retain the current nonattainment area bound aries for portions of Maryland current**ly** designated nonattainment under the 1997 ozone NAAQS for the reasons provided in Parts Iand II to the “Technical Anal ys is” below. (3) EPA intended to modify Maryland’s recommendations for Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles, Frederick, Harford, Howard, Montgomery , and Prince George ’ s Counties and Baltimore City

insofar as EPA decline d to base its decisions upon the likelihood that additional “strong national rules” will be in - place at some ti me in the future. (4) EPA believe d it cannot concur with a recommendation to designate as nonattainment a large portion of the East Coast of the U.S. due to transport from such an area and that EPA did not intend to designate a large nonattainment area as suggested b y Maryl and. EPA noted that Maryland’s support of its recommendations is dated (as a recommendation made two ye ars ago will be) because it relied upon 2008 and 2009 design value data and projections. As EPA noted previously , EPA must conside r the best information available at the time EPA promulgates designations. Because the 2010 design values are available, EPA must consider this information and based upon this information believes that the extent of areas still violating the 2008 NAAQS is less than it was two years ago. March 7, 2012: In response to EPA ’s December 9, 2011, letter to the Governor of Maryland regarding EPA’s proposed modifications to Maryland’s recommendations, on March 7, 2012, Maryland reaffirmed as its recommendation for a multi - state nonattainment area. 6 Maryland specifically recommended the following 17 States for inclusion in such an area: The District of Columbia 7 , Maryland, Delaware, New Jersey , New York, Pennsylvania, Virginia, West Virginia, Ohio, North Carolina, Tennessee, Missouri, Illinois, Indiana, Kentucky, Michigan and Wisconsin. Maryland provided a “5 - factor analy sis” in support of this recommendation. As an alternative to the 17 - State nonattainment area, Maryland recommended that at a minimum the entire Washington - Baltimore - NV , DC - MD - VA - WV CSA be designated nonattainment . Maryland provided a “5 - factor anal ys is” in support of this recommendation. After March 7, 2012:

5 Letter dated December 1, 2011 from the Honorable Martin J. O'Malley, Governor of Maryland, to Shawn M. Garvin, Regional Administrator USEPA Region 3, Recommending Revised area Designations for Maryland for the 2008 Ozone NAAQS , item number EPA - HQ - OAR - 2008 - 0476 - 0492 in the docket for this action. 6 Letter dated March 7, 2012, from Robert M. Summers, Ph.D., Secretary, Maryland Department of the Environment to Shawn M. Garvin, Regional Administrator, EPA Region III. 7 Under CAA section 302(d) the District of Colum bia is considered a “State” for the purposes of Title I and other Titles of the CAA. Hereafter in these responses to Maryland’s submittal, the term “State(s)” will refer to any “State” or the District generically whereas the term “District of Columbia” or just “the District” will refer to the District of Columbia itself.7

Subsequent to March 7, 2012, the Maryland Department of the Environment provided materials to supplement its “5 - factor anal ys es” supporting its March 7, 2012 recommendations. These were: (1) “Where does the air pollution in the OTR come from and what do we need to do to fix it?,” Tad Aburn, Director, Air and Radiation management Adm inistration, presented at the OTC Annual meeting June 9 and 10, 2010. 8 This document discussed the “elevated reservoir,” the NLLV, long - range transport, the correlation between ozone reductions and the number of EGUs installing controls due to the NOx SIP call, the “leeside” trough, linkage between all emissions in the 1997 Washington DC - MD VA Nonattainment area , and a call for controls throughout the eastern part of the country . (2) “ Moving Forward to Address Regional Transport ,” Tad Aburn , Air Directo r, MDE , February 8, 2012 , MARAMA Science Meeting . 9 This document discussed recent ozone data for the ten monitors in the OTR (2011 data), remaining possible local controls, the relative ratio of Baltimore emissions to other areas, emissions of top four S tates contributing to Maryland ozone, the “elevated reservoir,” the NLLV, long - range transport, Washington DC - MD - VA Nonattainment area contribution and the “bay

breeze,” city

to cit y transport, aloft measurements of up to 0.070 to 0.080 ppm after 2004, loc al emissions estimated to contribute 10 to 20 percent, the need for “super - regional” NOx controls, results of OTC scenario 4 modeling and with 5 percent additional beyond scenario 4 controls result in little ozone reductions, a call for Federal NOx measure s on six source categories that represent 75 percent of the NOx left to regulate. 10 (3) “ Making Progress on Cleaner Air, What We’ve Achieved Under the Clean Air Act Amendments of 1990, and Where We Need to Go , Getting to the New Ozone Standards , A Pathw ay Forward,” November 10th, 2010 . 11 This November 10th, 2010 presentation : discussed trends in regulatory measures and ozone levels since 1990 ; predicted probable nonattainment areas under the 2008 ozone NAAQS, concluded that additional controls within the OTR are still critical but may onl y reduce about 1/3 of the ozone problem in most OTC cities ; and concluded that n ational/super - regional controls are now essential because incoming ozone is already measured at levels above a 60 - 70 ppb standard and thus contribution from outside the OTR represents approximately 2/3 of the ozone problem in most OTC cities . OTC identified priority source categories from the June 2010 OTC Resolution urg ing EPA to adopt national rules to reduce interstate NOx emissio ns from EGUs , from more stringent On - Road Vehicle Standards , from IC I Boilers , Cement Kilns , Marine Engines and Locomotives because these categories represent 75 percent of the NOx left to regulate , models of transport westerl y and NLLJ, the “elevated res ervoir,” the NLLJ, long - range transport, and reductions in ozone concentrations in both the “elevation reservoir” and at ground level attributable to the NOx SIP call. (4) “ Modeling Committee Update ,” OTC Air Directors’ Meeting , April 24th, 2012 .” Th is document discussed 8 - hour ozone trends, how design values changed (based upon 2011 preliminary data), potential nonattainment areas under the 2008 ozone NAAQS, h ypothetical 2012 design values discounting 2009 data, and schedules for OTC air quality mode ling. 8 Also available on - line at http://www.otcair.org/upload/Do cuments/Meeting%20Materials/ConceptualModel_20090602%20TAD%20FOR%20OTC% 20Final.pdf . 9 Also available on line at http://www.marama.org/presentations/2012_Sci ence/Aburn_Science2012#542,1,Slide . 10 Subsequent to the State’s March 7, 2012 letter Maryland also submitted in a separate 4 - page document which consisted solely of pages 33 through 36 of this document. 11 Also available on line at http://www.otcair.org/upload/Documents/Meeting%20Materials/OTC%20Overall%20Progress%20Report%20 - %20Fall%202010.pdf

.8

EPA considered these document s as they related to elements of Maryland’ s March 7, 2012 response to EPA. Most of the salient points of these presentations were also discussed in Maryland’s March 7, 2012 letter. Maryland also submitted a docum ent estimating reasonable further progress reductions in a nonattainment area with the borders of the 1997 Baltimore nonattainment area (that under the 1997 ozone NAAQS) and a nonattainment area comprised of the entire Washington - Baltimore - NV CSA and a doc ument of a “ Aspirational Conformity Regulation .” EPA did not base its decisions on the former but rather used the 5 - factor analy sis to determine which portions of this CSA should be designated nonattainment. As to the latter, EPA did not base its decisi on on it because it represents a control regulation not yet implemented whereas the CAA requires EPA to base its decisions on current contribution. Regarding a 17- State Nonattainment area: In letters discussed previously in this document, Maryland and the District of Columbia recommended that EPA designate the entire State as part of a large multi - state nonattainment area including all or portions of 17 other states, and the District of Columbia. EPA d oes not believe that creation of a super regional nonattainment area to address pollution transport is the appropriate approach. As an initial matter, section 107(d)(1) provides that areas designated nonattainment should include any “nearb y” area contribut ing to a violation of the NAAQS. We believe that broad super - regional areas go beyond this by including areas that are not necessaril y “nearb y” but contribute to nonattainment through long - range transport. The CAA has separate provisions to address this p henomenon. Section 110(a)(2)(D) requires states to address ozone transport that contributes to a violation of the NAAQS in another State. In addition, section 184, creates the northeast ozone transport region and also grants EPA authority to establish add itional transport regions, as appropriate. Finall y, we note that the approach taken b y EPA is consistent with the approach Congress specified for serious and above areas for the 1 - hour NAAQS, where in section 107(d)(4)A), Congress set the CMSA boundaries a s the presumptive boundaries of the nonattainment area. In Catawba Co. v. EPA 12 [1] , the Court upheld that “contribute” under §107(a)(1)(A) of the CAA does not necessaril y mean “an y contribution” to nonattainment but rather a degree of contribution suffici ent to deem an area nonattainment, that is, sufficient enough to warrant designation as nonattainment. “Section 107(d) is ambiguous as to how EPA should measure contribution and what degree of contribution is sufficient to deem an area nonattainment ...” Cata wba County v. EPA , 571 F.3d 20 (D.C. Cir. 2009) (Internal citation omitted but with emphasis added) . “Thus, reasonabl y exercising the discretion that Congress delegated to it, EPA interpreted “contribute” to mean “sufficientl y contribute,” and then applie d the C/MSA presumption and nine - factor test precisel y to identify those areas that meet that definition.” Virginia’s Recommendations: March 2009:9

On March 11, 2009 13 , Virginia recommended the four areas in Virginia for nonattainment. These were a Hampton Roads area, a Fredericksburg area, a Richmond area and a Northern Virginia area consisting of only a portion of Virginia within the “Washington DC - MD - VA” Metropolitan Statistical Area (MSA). Virginia supplied a “5 - factor anal ys is” in support of its recommendations. November 2011 and later: On November 21, 2011 14 , Virginia updated its prior recommendations. Virginia specifically noted that of the four areas Virginia recommended for a nonattainment designation in 2009 two

– the Hampton Roads and Fredericksburg areas

– had come into attainment based upon 2008 to 2010 air quality monitoring data. In addition, Virginia noted that the Richmond area was in attainment of th e 2008 ozone NAAQS based upon 2009 - 2011 air qualit y data and requested that the Richmond area not be designated nonattainment. Virginia did not send a reply in response to EPAs December 9, 2011, letter to the Governor of Virginia 15 which did not propose t o modify an y of Virginia’s recommendations, Subsequent to EPAs December 9, 2011 letter, the Virginia Department of Environmental Quality provided a supplemental anal ys is in response other States’ revised recommendations for a combined Washington - Baltimore - NV CSA . Comm on elements of Recommendations: All the recommendations are based upon 2008 to 2010 air quality data to identify

the violating monitors. 16 These data are from FRM monitors or FEM monitors sited and operated in accordance with 40 CFR part 58. 

### Technical Analysis for the Washington **- Baltimore**  **- Northern Virginia CSA**  **– the**  **Washington, DC -**  **MD -**  **VA and Baltimore Areas: Factor Assessment**  EPA’s anal ys es below provide the basis for the final nonattainment area boundaries. It relies on our anal ys is of whether and which monitors are violating the 2008 ozone NAAQS, based on certified air quality monitoring data from 2008 - 2010, and an evaluation of whether nearby areas are contributing to such violations. EPA has evaluated contribution s from nearb y areas based on a weight of evidence anal ys is considering the 5 - factors identified below. EPA issued guidance on December 4, 2008 that

13 A letter dated March 11, 20 09 from David K. Paylor, Director, Virginia Department of Environmental Quality, to William T. Wisneiwski, Acting Regional Administrator, EPA region III. 14 Letter dated November 21, 2011, from Michael G. Dowd, Air Quality Division Director, Virginia Department of Environmental Quality, to Diaina Esher, Director, Air Protection Division, EPA Region III. 15 Letter dated December 9, 2011, from Shawn M. Garvi n, Regional Administrator, EPA Region III, to the The Honorable Robert McDonnell, Governor of Virginia. 16 Although Virginia certified air quality data for all their monitors for the 2011 ozone season, Virginia’s November 21, 2011 revised recommendation referred to use of the 2011 data with respect to the Richmond VA area. With respect to the Virginia’s portion of the Washington - Baltimore -NV CSA, the 2011 data does not alter the numbers of monitors violating of attaining the 2008 ozone NAAQS and therefor e does not materially affect the decisions regarding the baoundaries of nonattainment areas within this CSA.10

identified these factors as ones EPA would consider in determining nonattainment area boundaries and recomm ended that states consider these factors in making their designations recommendations to EPA. 17 1. Air quality

data (including the design value calculated for each Federal Reference Method (FRM) monitor or Federal Equivalent Method (FEM) monitor in the area) ; 2. Emissions and emissions - related data (including location of sources and population, amount of emissions and emissions control , and urban growth patterns); 3. Meteorology

(weather/transport patterns); 4. Geograph y and topography (mountain ranges or other basin boundaries); 5. Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, Indian country , metropolitan planning organizations (MPOs)). Ground - level ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Because NOx and VOC emissions from a broad range of sources over a wide area t ypically contribute to violations of the ozone standards, EPA believes it is important to consider whether there are contributing emissions from geographic area s near the violating monitor . In EPA’s designations guidance for the 2008 ozone NAAQS EPA recommended examining CSA/CBSAs because certain factors used to establish CSAs and CBSAs are similar to the factors EPA is using in this technical analy sis to determine if a nearby area is contributing to a violation of the 2008 ozone NAAQS. EPA used the same basic approach in the designation process for the 1997 ozone NAAQS. Where a violating monitor is not located in a CSA or CBSA, EPA’s guidance recommended using the boundary

of the county

containing the violating monitor as the starting point for considering the nonattainment area’s boundary . **The Composition of the Washington -**  **Baltimore -**  **Northern Virginia, DC -**  **MD -**  **VA -**  **WV CSA:** The Washington, DC - MD - VA and Baltimore nonattainment areas are part of the Washington Baltimore - Northern Virginia, DC - MD - VA - WV CSA . This consists of the following CBSAs: 18 (1) The Baltimore - Towson, MD Metropo litan Statistical Area (MSA) 19 , 20

- Anne Arundel, Baltimore, Carroll, Harford, Howard, and Queen Anne ’ s Counties and Baltimore C ity in Maryland; (2) The Culpeper, VA Micropolitan Statistical Area (Culpeper, VA CBSA)

– Culpeper County in Virginia; (3) The Lexington Park, MD Micropolitan Statistical Area (Lexington Park, MD CBSA) - St. Mary ’ s County in Maryland; (4) The Washington - Arlington - Alexandria, DC - VA - MD - WV MSA (Washington D C - MD - VA - WV CBSA) : The Maryland Portio n: the Counties of Frederick, Mo ntgomery, Calvert, Charles , and Prince George ’ s; the entire District of Columbia; the Virginia Portion: the Counties of Arlington, Clarke, Fairfax, Fauquier, Loudoun, Prince William, Spotsylvania, Stafford , and Warren, an d the Cities of

17 The December 4, 2008 guidance memorandum “Area Designations for the 2008 Revised Ozone National Ambient Air Quality Standards” refers to 9 facto rs. In this technical support document we have grouped the emissions - related factors together under the heading of “Emissions and Emissions - Related Data,” which results in 5 categories of factors. 18 Source: OMB Bulletin No. 10 - 02, December 1, 2009. 19 Metropolitan and Mircopolitan Statistical Areas are each types of CBSAs. Hereafter, MSA will refer to only to a Metropolitan Statistical Area, and, CBSA will refer to both Mircopolitan and Metropolitan Statistical Areas generally and also be used in lie u of Mircopolitan Statistical Area and Metropolitan Statistical Area when referring to a specific area.. 20 Generally hereafter the “Baltimore - Tow son, MD CBSA.”11

Alexandria, Fairfax, Fall s Church, Fredericksburg, Manassas, and Manassas Park; and the West Virginia Portion: Jefferson County . (5) The Winchester, VA - WV MSA - Frederick County and Winchester City

in Virginia and Hampshire County in West Virginia. Core Cities/Counties in this CSA: Under OMB’s December 27, 2000 (65 FR 82228), Notice of decision “Standards for Defining Metropolitan and Micropolitan Statistical Areas” a CBSA is built around either an urbanized area or urbanized cluster with central counties and outl yi ng counties. A central county is associated with the urbanized area or urban cluster that accounts for the largest portion of the county ’s population. The central counties associated with a particular urbanized area or urban cluster are grouped to form a single clust er of central counties for purposes of measuring commuting to and from potentially qualifying outlying counties. A county qualifies as an outlying count y of a CBSA if it meets the following commuting requirements: (a) at least 25 percent of the employed r esidents of the count y work in the central count y or counties of the CBSA; **or** (b) at least 25 percent of the employ ment in the count y is accounted for b y workers who reside in the central county or counties of the CBSA. The counties included in a CBSA **must be contiguous**  . Two adjacent CBSAs will merge to form one CBSA if the central count y or counties (as a group) of one CBSA qualify as outlying to the central county or counties (as a group) of the other CBSA using the measures that define an outl yi ng county of a CBSA. An y two adjacent CBSAs will form a Combined Statistical Area (CSA) if the employment interchange measure 21 between the two areas is at least 25; **or,** if the adjacent CBSAs that have an employ ment interchange measure of at least 15 and less than 25 they will combine if local opinion, as reported b y the congressional delegations in both areas, favors combination. See , 65 FR 82228 at 82236 - 82237. In this TSD the following central cit y/ counties in the Baltimore - Towson MD CBSA will be considered to be “core counties/cit y” of the 1997 Baltimore Nonattainment area : Anne Arundel, Baltimore, Howard Counties and Baltimore City . Likewise, the following central cities/counties of the Washington - Arlington - Alexandria, DC - VA - MD WV CBSA will be considered to be the ”core cities/counties” in the 1997 Washington DC - MD - VA Nonattainment area : the District of Columbia, DC ; Prince George ’ s County, MD ; Arlington County , VA ; Fairfax County , VA ; Lo udoun County , VA ; Prince William County , VA ; Alexandria City , VA ; Fairfax City , VA ; Falls Church City , VA ; Manassas City , VA ; and Manassas Park City , VA . 22 EPA Guidance and Historical Approaches: The December 4, 2008 guidance memorandum “Area Designations for the 2008 Revised Ozone National Ambient Air Quality Standards” recommended for CSAs that the anal ys is should start with the CSA boundary associated with violating monitors . The Washington - Baltimore - NV CSA consists of five CBSAs comprising 34 counties and independent cities plus the District of Columbia. 23 As will be discussed under Factor 1 in a following section of this document, the monitors violating the 2008 NAAQS are located in two areas still designated nonattainment under the 1997 ozone NAAQS

–

21 The e mp loyment interchange measure is a measure of ties between two adjacent entities. T he employment interchange measure is the sum of the percentage of employed residents of the smaller entity who work in the larger entity and the percentage of employment in the smaller entity that is accounted for by workers who reside in the larger entity . 65 FR 82228 at 82238. 22 This is the CBSA core less Stafford County, VA. 23 Under section 302 (d) of the CAA, the District of Columbia is considered a state. In this analysis the terms “state,” a “county” and/or an “independent city” when used in a broad sense may also refer to the District of Columbia when required by context.12

the current Baltimore nonattainment area and the current Washington DC - MD - VA nonattainment area. (Further details of the designation of areas under the 1997 ozone NAAQS are discussed under Factor 5 “ Jurisdictional boundaries. ”) EPA used the same basic app roach in the designation process for the 1997 ozone NAAQS as EPA is using for the 2008 ozone NAAQS. Therefore, EPA has previousl y considered the same factors for setting the boundaries of the current Baltimore and Washington DC - MD - VA nonattainment areas. For purposes of analy sis, a reasonable step is to break the area into smaller pieces that reflect the boundaries used to designate areas under the 1997 ozone NAAQS. In other words, start with a presumption that the boundaries of the current Baltimore and Washington DC - MD - VA nonattainment areas include the counties and independent cities which contribute to the currently violating monitors , and then apply the five factors to see if the current Baltimore and Washington DC - MD - VA nonattainment areas should be contracted, expanded, realigned , or even merged based upon differences in current conditions as opposed to conditions as of 2004 when areas were designated for the 1997 ozone NAAQS. **Grouping of Areas for Presentation:**  For the purposes of **the presentation of**  this analysis, the Washington - Baltimore - NV CSA will be broken into the following subcomponents: (1) The Baltimore Nonattainment Area as it was defined under the 1997 ozone NAAQS 24 ( 1997 Baltimore nonattainment area) consisting of Anne Arundel, Baltimore, Carroll, Harford, and Howard Counties and Baltimore City in Maryland. 25 This is the Baltimore - Towson, MD CBSA less Queen Anne’s County

in Maryland. (2) The Washington DC - MD - VA Nonattainment Area as it was defined under the 1997 ozone NAAQS ( 1997 Washington DC - MD - VA nonattainment area) 26 consisting of: the Maryland Portion: Frederick, Montgomery , Calvert, Charles, and Prince George ’ s Counties ; the entire District of Columbia ; and the Virginia Portion: Arlington, Fairfax, L oudoun, Prince William C ounties, and the Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park. (3) Fredericksburg, VA Area consisting of Fredericksburg City and Spotsylvania and Stafford Counties in Virginia. 27 (4) The Frederick County , VA Area consisting of Frederick Count y and Winchester City in Virginia. 28 (5) Eight other counties: Queen Anne ’ s County in Maryland (which was a portion of the Kent County and Que en Anne ’ s County Area under the 1997 ozone NAAQS ) 29 ; St. Mary ’ s County in Maryland; Clarke, Culpeper , Fauquier, and Warren Counties in Virginia; and Hampshire and Jefferson Counties in West Virginia. As will discussed under the Factor 1

– Air Quality Data section of this TSD below, the 1997 Baltimore area and the 1997 Washington DC - MD - VA nonattainment ar ea contain all the monitors within the entire CSA that area violating the 2008 ozone NAAQS.

24 Codified at 40 CFR 50.9. 25 Sources: 40 CFR 81.321 and to 69 FR 23838, April 30, 2004. 26 Sources: 40 CFR 81.09, 81.321 and 81.347and to 69 FR 23838, April 30, 2004. 27 This was a separately defined nonattainment and later maintenance area under the 1997 ozone NAAQS. Sources: 40 CFR 81.347 and 69 FR 23838, April 30, 2004. 28 This was a separately defined attainment/unclassifiable area under the 1997 ozone NAAQS. Sour ces: 40 CFR 81.347 and 69 FR 23838, April 30, 2004. 29 Sources: 40 CFR 81.321 and to 69 FR 23838, April 30, 2004.13



### EPA’s overall assessment of the factors for the Washington **- Baltimore**  **- NV CSA**  **is as**  **follows :**  

### Factor Assessment **Factor 1**  **: Air Q**  **uality D**  **ata** For this factor, EPA considered 8 - hour ozone design values in parts per million (ppm) for air qualit y monitors in counties in the Washington - Baltimore - NV CSA area based on data for the 2008 - 2010 period, that is, based upon a monitor’s 2010 design value, which are the most rec ent ye ars with fully certified air quality

data. A monitor’s design value is the metric or statistic that indicates whether that monitor attains a specified air quality standard. The 2008 ozone NAAQS are met when the annual fourth - highest dail y maximum 8 - hour average concentration, averaged over 3 years is 0.075 ppm , or less. A design value is only valid if minimum data completeness criteria are met. See , 40 CFR part 50 Appendix P. Where several monitors are located in a county (or a designated nonattainment area or maintenance area), the design value for the county or for an area (which in general can be an y grouping of counties or be some currentl y defi ned area such as a CBSA, CSA or current or former nonattainment area) is determined b y the monitor in that county /area with the highest design value. The 2010 design values for the ozone NAAQS for counties in the Washington - Baltimore - NV CSA are shown in Ta

bles 2 . The “AQS ID No. ” is the identification number assigned to the monitor in EPA’s Air Quality

S ys tem (AQS). The “short name” is a semi - descriptive name often used in various State and/or EPA records. Note that o nly counties in the Washington - Baltim ore - NV CSA that have ozone monitors are included in Table 2 . **Table 2**  **. Monitor data for the Washington**  **- Baltimore**  **- NV CSA**  **.** County (Co.) /City, State Monitor AQS ID N o . Short Name State Recommended Nonattainment? 1997

Nonattainment (NA)/ attainment Area 8 - hr Ozone

Design Values, 2008 - 2010 (ppm) District of Columbia Monitors in the Washington - Baltimore - NV CSA: District of Columbia 110010025 110010041 110010043 Takoma

River Terrace McMillan Reservoir Yes Washington NA Washington NA Washington NA 0.075 0.077 0.079 Maryland Monitors in the Washington - Baltimore -NV CSA: Anne Arundel Co., MD 240030014 Davidsonville Yes Baltimore NA 0.079 Baltimore Co., MD 240051007 240053001 Padonia

Essex Yes Baltimore NA Baltimore NA 0.077 0.078 Calvert Co., MD 240090011 Calvert Co. Yes Washington 0.077 Carroll Co., MD 240130001 South Carroll Yes Baltimore NA 0.076 Charles Co., MD 240170010 Southern Maryland Yes Washington NA 0.075 Frederick Co., MD 240210037 Frederick Co. Yes Washington NA 0.075 Harford Co., MD 240251001 240259001 Edgewood

Aldino Yes Baltimore NA Baltimore NA **0.089** 0.07814

Montgomery Co., MD 240313001 Rockville Yes Washington NA 0.074 Prince George ’ s Co., MD 240330030 240338003 Howard

University

– Beltsville Prince George ’ s Co unty Equestrian C enter 30 Yes Washington NA Washington NA 0.078 0.077 Baltimore City, MD 245100054 Furley E.S.Rec Center Yes Baltimore NA 0.067 Virginia Monitors in the portion of the Washington - Baltimore -NV CSA: Arlington Co., VA 510130020 Arlington Yes Washington NA 0.079 Fairfax Co., VA 510590030 Franconia Yes Washington NA 0.081 Fauquier Co., VA 510610002 Sumerduck No Fauquier Co. Attainment 0.065 Frederick Co., VA 510690010 Butler Manuf. Co Near Rest No Frederick Co. (VA) Attainment 0.068 Loudoun Co., VA 511071005 Ashburn Yes Washington NA 0.075 Prince William Co., VA 511530009 James S. Long Park Yes Washington NA 0.070 Stafford Co., VA 511790001 Widewater No Fredericksburg NA/maintenance 0.070 Alexandria City, VA 515100009 Alexandria Yes Washington NA 0.074 West Virginia has no monitors in this CSA. Note: Data Source: ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html ). A county or cit y that shows a violation of the 2008 ozone NAAQS must be included in a nonattainment area. See , section 107(d)(1)(A) of the CAA which requires designation of nonattainment for an y area that does not meet a NAAQS. A county (or partial county) must also be designated nonattainment if it contributes to a violation in a nearb y area. Each county without a violating monitor that is located near a county with a violating monitor has been evaluated based on the weight of evidence of the five factors and other relevant information to determine whether it sufficientl y contributes to a nearb y violation. Identification of Violating Monitors: Nine counties within the Washington - Baltimore - NV CSA contain a monitor violating the 2008 Ozone NAAQS. These moni tors are contained solel y within the boundaries of those areas designated nonattainment under the 1997 Ozone NAAQS; these are the 1997 Washington, DC - MD - VA nonattainment area and the 1997 Baltimore nonattainment area. ( See , 40 CFR 81.309, 81.321 and 81.34 7.) All other monitors within the CSA , but outside the boundaries of designated nonattainment areas under the 1997 ozone NAAQS are attaining the 2008 Ozone NAAQS. Therefore , the following jurisdictions must be designated by operation of law as nonattainm ent , 31 within one or more nonattainment area(s) within the Washington - Baltimore - NV CSA : (1) The District of Columbia ; (2)

30 Due to the length, may be shortened to “Pr. George’s Co Eq Ctr” at time hereafter. 31 EPA would expand the boundaries of nonattainment to include the whole county or the District of Columbia containing a violating monitor because the States or the District of Columbia so recommended.15

Anne Arundel, Baltimore, Calvert, Carroll, Harford, Prince Geor ge’s Counties in Maryland; and (3) Arlington and Fairfax Counties in Virginia. Analy sis of the Concentrations as indicated b y Design Values within the Washington - Baltimore - NV CSA: The highest concentrations within the Washington - Baltimore - NV CSA are found at the Edgewood site (or Edgewood monitor) in Harford County , MD and the Franconia site in Fairfax County , VA which have design values of 0.089 and 0.081 ppm, respectively . T he fact that the Edgewood site has a high value is not surprising because this monitor was located for the objective of measuring highest concentratio ns on an urban scale. One can reasonably infer that this monitor was sited to be downwind of Baltimore Cit y and other parts of the Baltimore - Towson , MD CBSA . See , Table 3 - 2a . in “ Ambient Air Monitoring Network Plan For Calendar Year 201 1 , ” by the Ambient Air Monitoring Program, Air and Radiation Administration Management, Maryland Department of the Environment, May 2 7 , 201 0 . 32 Appendix 1 of this analysis contains a summary of relevant regulatory

and guidance documents related to selection of sites for ozone monitors and to monitoring objectives. In the 1997 Washington DC - MD - VA nonattainment area , the Howard University - Beltsville site has a dual monitoring objective of population exposure and highest concentration. This site would fulfill the requireme nt that the Washington - Arlington - Alexandria, DC - VA - MD - WV Metropolitan Statistical Area have such a site. Refer to Appendix 1 of this analysis . See , Table 3 - 2a. in “Ambient Air Monitoring Network Plan For Calendar Year 201 1 ,” b y the Ambient Air Monitoring Program, Air and Radiation Administration Management, Maryland Department of the Environment, May 27, 2010 . One can reasonabl y infer that that this monitor was sited to monitor the expected highest concentrations downwind of the densel y populated urban c ore surrounding the District of Columbia. In their 5 - factor anal ys es submitted with the State’s March 7, 2012 letter, 33 Maryland supplied ex tensive information and data to show why the Edgewood monitor had a higher design value than other monitors in the CSA. This information related to transport of ozone and its precursors on various scale and the effect that the Appalachian Mountains and the Chesapeake Bay have on transport or on the concentration of ozone at monitors in Maryland and in particular at th e Edgewood monitor. Generally , within the Washington - Baltimore - NV CSA the highest design values occur in two separate areas : (1) the first of these areas of peak design values is centered on the monitors in Fairfax County, the District of Columbia and Anne Arundel County with design values of 0.079 to 0.081 ppm; (2) the second areas of peak ozone concentrations is northeast of Baltimore City and centered on the Edgewood monitor in Harford County with a design value of 0.089 ppm. These two areas are “ circled ” with a red, solid line in Figure 2a below. Near each of these areas of peak ozone concentrations are monitors each with a design value of 0.077 ppm or 0.078 ppm. Near the F airfax County - District of Columbia - Anne Arundel County group are the two monitoring sites in Prince George’s Count y, MD. Inclose proximity to and northeast of the Edgewood site are the Aldino monitor site in Harford County and the two monitoring sites (E ssex and Padonia) in Baltimore County . Outside these areas, the design values fall off to attaining monitors. Monitors attaining the 2008 ozone NAAQS are found north, northwest, west, southwest and south of the curve formed b y the Calvert County, MD

—Fair fax County , VA

— Carroll

—Baltimore (Padonia)

— Harford Counties, MD monitors. ( The curve of the Calvert County , MD

—Fairfax County , VA

— 32 Source: MDPlan2010.pdf (Downloaded 12/9/2011 from http://www.epa.gov/ttn/amtic/plans.html). 33 Letter dated March 7, 2012, from Robert M. Summers, Ph.D., Secretary, Maryland Department of the Environment to Shawn M. Garvin, Regional Administrator, EPA Region III.16

Carroll

—Baltimore (Padonia)

—Harford Counties, MD monitors is shown in Figure 2b below with a solid, pink line .) Just outs ide this curve of violating monitors are three monitors each with a design value of 0.075 ppm (just attaining the 2008 NAAQS)

– the ones in Charles County , MD, Loudoun County , VA and Frederick Count y, MD. These attaining monitors are joined b y a red, dash ed line in Figure 2b. Adjacent States: South, southwest, west, and northwest of these three monitors are a number of monitors generall y 0.005 ppm below the 2008 NAAQS. These are the monitors in Fauquier, Frederick, Prince William and Stafford Counties in Virginia. (These three are joined by a dotted, green line in Figure 2b.) There are also attaining monitors in the northern tip of Caroline County , VA, Berkeley County , WV and Washington County , MD. Table 3 provides basic data for these other monitor s: **Table 3. Three Attaining Monitors Outside the Washington -**  **Baltimore -**  **NV CSA.** County/City, State Monitor AQS ID

No. Short Name State Recommended Nonattainment? 8 - hr Ozone

Design Values, 2008 - 2010 (ppm) EPA final

designation Caroline County, VA 510330001 Corbin No 0.073 Attainment Berkeley County, WV 540030003 Martinsburg Ball Field No 0.070 Attainment Washington County, MD 240430009 Hagerstown Yes or no 34 0.072 Attainment Note: Data Source: ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html ). The District of Columbia and Maryland both recommended a very large, 17 - State nonattainment area. Maryland in particular questioned why States immediately

adjacent to the Washington - Baltimore - NV CSA did not meet the geographic close proximity prong of CAA section 107(d)(1)(A). While EPA believes that the entire States of Delaware, Penns ylvania, Virginia and West Virginia do not meet section 107(d)’s requirements to be considered areas “contributing” to nonattainment in “nearb y areas,” EPA’s reasoning for entire States does not necessarily suffice for adjacent CBSAs or counties not in a CBSA. EPA therefore considered ozone design value concentrations in other ad ja cent counties and CBSAs. The basic air quality data for such areas is provided in Table 4 below: **Table 4. Other Monitors in Adjacent Areas Outside the Washington -**  **Baltimore -**  **NV CSA.** CBSA or County/City, State Monitor AQS ID

No. 8 - hr Ozone

Design Values, 2008 - 2010 (ppm) EPA final

designation New Castle County, DE 1000 - 1007 or

100031013 0.075 Nonattainment Note 4 - 2 Chester County, PA 420290100 0.076 Nonattainment Note 4 - 2 Cecil County, MD 240150003 0.080 Nonattainment Note 4 - 2 Dover CBSA (Kent Co.), DE 100010002 0.074 Attainment Chambersburg (Franklin Co.), PA CBSA 420550001 Attainment

34 Only if all of Maryland was part of a 17 State nonattainment area did Maryland recommend non attainment.17

York - Hanover CBSA (Adams and York Cos.),PA 421330008

421330011 420010002 0.071

0.074 0.073 Attainment Lancaster County/CBSA, PA 420710007

420710012 0.077

0.075 Nonattainment Kent County, MD 240290002 0.075 Attainment Page County, VA 511390004 0.066 Attainment Madison County, VA 511130003 0.073 Attainment Hanover County, VA Note 4 - 1 510850003 0.075 Attainment Notes: Sources: Data Source: ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html ). 4 - 1: Part of the Richmond, VA CBSA. 4 - 2: As part of the Philadelphia - Wilmington - Atlantic City, PA -NJ - MD - DE nonattainment area These patterns of ozone design values suggest that there could be two separate areas with a linkage between high emissions of ozone precursors in within some geographic region such as the core of the Baltimore - Towson CBSA or Washington CBSA and peak ozone design values in that geographic region such as at the Edgewood monitor or the Franconia. One such geographic region might be the area northwest of Baltimore City centered on the Edgewood monitoring site in Harford County , MD. The Edgewood monitoring site is circled (in red) in Figure 2a below , the north - easternmost county in the Washington - Baltimore - NV CSA. The peak ozone area for the second such geographic region might be the group of monitors consisting of the monitors in Fairfax County , VA, the District of Columbia , and possibly the monitor in Anne Arundel Count y, MD. These are also “circled” in Figure 2a below with a s urrounding red solid line.1819

Design Value Changes – 2003 to 2010: Table 5 shows the 2003 design values used to designate and classify areas under the 1997 ozone NAAQS, the 2008 design values used b y the States to make their 2009 recommendations for th e 2008 ozone NAAQS and the 2010 design values. The first and second highest design values in the Washington - Baltimore - NV CSA are emphasized in bold, underlined ty pe; design values within 0.002 ppm of the second highest value are emphasized in bold ty pe. **T able**  **5 . Air Quality Data**  **– Design Values for 2003, 2008 and 2010.**  County State Recommended Nonattainment for 2008 NAAQS? 2003 8 - hour

ozone design value (ppm) 35 2008 8 - hour

Ozone design value (ppm) 36 2010 8 - hour

Ozone design value (ppm) 37 Baltimore nonattainment area: Anne Arundel Co., MD Yes **0.098 0.087**  **0.079** Baltimore Co., MD Yes 0.093 0.085 0.078 Carroll Co., MD No 0.089 0.083 0.076 Harford Co., MD Yes **0.103 0.091**  **0.089** Baltimore City, MD Yes 0.082 Inc. D 0.067 Washington DC - MD - VA nonattainment area District of Columbia, DC Yes 0.094 **0.087 0.079**  Calvert Co., MD No N/D 0.079 0.077 Charles Co., MD No 0.094 0.082 0.075 Frederick Co., MD No 0.088 0.082 0.075 Montgomery Co., MD No 0.088 Inc. D 0.074 Prince George ’ s Co., MD Yes 0.093 **0.087** 0.078 Arlington Co., VA Yes **0.099** 0.085 0.079 Fairfax Co., VA Yes 0.097 **0.087 0.081**  Loudoun Co., VA Yes 0.092 0.083 0.075 Prince William Co., VA Yes 0.087 0.078 0.070 Alexandria City, VA Yes 0.092 0.081 0.074 Frederick Co., VA Area Frederick, VA No 0.085 0.073 0.068 Fredericksburg, VA Area Stafford, VA No 0.088 0.081 0.070 Other Counties Fauquier, VA No <0.085 0.071 0.065

35 “Chapter 2 8 - Hour Ozone Nonattainment Designations and Classifications” docket item EPA - HQ - OAR - 2003 - 0083 - 1812 in docket EPA - HQ - OAR - 2003 - 0083 (downloaded November 15, 2011) and available on - line at Regulations.gov. 36 Data Source: dv_ozone_20 06_2008.xls (downloaded on 11/29 /2011 from http://www.epa.gov/airtrends/values.html. 37 Data Source: ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html.20

Note: “N/D ” means no data; “ Inc. D ” means there was incomplete data to calculate a design value; “< 0.085” means the design value was under the 1997 ozone NAAQS and the county was designated attainment. For designations under the 1997 ozone NAAQS, the Edgewood site in Harford County had a design value (for the peri od 2000 - 2002) of 0.103 ppm, and all othe r monitored counties in the 1997 Baltimore nonattainment area except that in Baltimore City violated the 1997 ozone NAAQS with a design value of 0.085 ppm or more. 38 Likewise, for designations under the 1997 ozone NAAQS, Arlington County, VA had the highes t design value of 0.099 ppm for the period 200 1 - 200 3 ; for the 200 1 - 200 3 period, all other counties currentl y having monitors in the current Washington DC - MD - VA nonattainment area except Calvert County

(which did not have a monitor with 3 years of valid data for 2000 - 2002) violated the 1997 ozone NAAQS with a design value of 0.085 ppm or more. 39 For the designations under the 1997 ozone NAAQS, the design value for the 1997 Baltimore nonattainment area was 0.004 ppm gr eater than the design value for the 1997 Washington DC - MD - VA nonattainment area. Both areas were classified as moderate nonattainment areas. 40 For their 2009 recommendations, the States generally relied upon 2008 design values. Three monitors in the 1997 Washington DC - MD - VA nonattainment area had a design value of 0.087 ppm (for 2006 - 2008) which set the design value within the 1997 Washington DC - MD - VA nonattainment area at 0.087 ppm. The Edgewood site in Harford County , M D had a design value for the same period of 0.091 ppm which set the design value within the 1997 Baltimore nonattainment area at 0.0 91 ppm. The difference in 2008 design values between these two nonattainment areas designated under the 1997 ozone NAAQS was still 0.004 ppm. Currently , for the period 2008 - 2010, the difference in design values for these two monitors has grown to 0.008 ppm. The trend in design values has been downward since 2003. In 2008, no monitor in the current Baltimore and Washington DC - MD - VA nonattainme nt areas were attaining the 2008 NAAQS of 0.075 ppm; nor was the monitor in the Fredericksburg, VA Area. Now some of the counties and cities on the edge are attaining the 2008 NAAQS, and some interior areas, such Alexandria City , VA and Montgomery County , MD, are as well. Admittedly , due to ye ar to year fluctuations in weather from one ozone season to the next, the design values will also fluctuate in response , but over longer periods of time a definite overall trend will be apparent if there is progress. The counties and cities in the Washington - Baltimore NV CSA saw a decrease in design values of 0.006 to 0.014 ppm over the period 2003 to 2008. Most counties and cities in the Washington - Baltimore - NV CSA over the last two years (2008 to 2010) saw design value decreases of 0.006 to 0.011 ppm; however, during the last two years, two saw decreases of only 0.002 ppm. These were the monitors in Harford and Charles Counties in Maryland. Of particular note are the design values in Frederick and Charles Counties in Maryland. These are within 0.002 ppm of attaining the 2008 NAAQS. As such, these counties might be classified as marginal nonattainment areas if each were a separate nonattainment area. The CAA contains a presumption that marginal areas are expected to attain the relevant ozone NAAQS without any additional controls beyond those already promulgated; currentl y promulgated federal mobile source measures are one source of reductions available for marginal areas to attain the 2008 NAAQS and continue to oc cur as the fleet of older highway motor vehicles and other mobile source engines are

38 “Chapter 2 8 - Hour Ozone Nonattainment Designations and Classifications” docket item EPA - HQ - OAR - 2003 - 0083 - 1812 in docket EPA - HQ - OAR - 2003 - 0083 (downloaded November 15, 2011) and available on - line at Regulations.gov ( http://www.regulations.gov ). 39 Ibid. 40 Ibid. See also, 69 FR 23858, April 30, 2004 .21

replaced b y new highway motor vehicles and other mobile source engines required to meet newer, more stringent emission standards. Also of note is the apparent trend at the Davidsonville monitoring site in Anne Arundel Count y, MD. The trend at this monitor seems to track that of the current Washington DC - MD - VA nonattainment area. In 2003, this monitor’s design value was 0.001 ppm less than the design value of 0.099 p pm for Arlington County , VA and 0.005 ppm of that in Harford Count y, MD (which establishe d the design value for the 1997 Baltimore nonattainment area). In 2008 this monitor’s design value was equal to that for the 1997 Washington DC - MD - VA nonattainment ar ea and 0.004 ppm less than that of Harford County . For 2010, this monitor’s design value was 0.002 ppm less than the design value of 0.081 ppm in Fairfax County , VA , 41 and 0.010 ppm of that in Harford County , MD. This monitor seems to track (that is, is alway s equal or less than) the peak in the current Washington DC - MD - VA nonattainment area and, as with the peak in the current Washington DC - MD - VA nonattainment area, has diverged from the trend in the Harford County , MD. Such a result might suggest that the air quality data at the monitor in Anne Arundel County is more influenced by

emissions in the current Washington DC - MD VA nonattainment area than emissions in the rest of the current Baltimore nonattainment area. 42 The 2008 to 2010 air quality data stro ngl y suggest that there are two main peak points of ozone concentrations in the Washington - Baltimore - NV CSA. The first is in Harford County , Maryland in the northeast of the Washington - Baltimore - NV CSA. The second peak area is located at the Fairfax County monitor in Virginia and this peak extends into Arlington County , VA, the District of Columbia and possibly into Anne Arundel County Maryland. A similar situation existed in 2004 when EPA designated areas for the 1997 ozone NAAQS. Harford County had the highest design value (0.103 ppm) of any monitor in the current CSA. Arlington County had the highest design value (0.099 ppm) in the 1997 Washington DC - MD - VA nonattainment area; Fairfax County , VA and Anne Arundel County , MD both had design values clos e (0.097 and 0.098 ppm, respectivel y) to that in Arlington County, VA. For 2008, the pattern was repeated. Harford County had the highest design value (0.091 ppm) of any monitor in the current CSA. Fairfax County , VA, the District of Columbia and Prince George’s County , MD all had the highest design (0.087 and 0.098 ppm, respectivel y) in the 1997 Washington DC - MD - VA nonattainment area and Anne Arundel County , MD had the same design value. All monitors in the 1997 Washington DC - MD - VA nonattainment area ar e showing currentl y attainment of the 1997 ozone NAAQS. Except for the monitors in Harford County , MD all other monitors (including that in Anne Arundel County , MD) in the 1997 Baltimore MD nonattainment area are currentl y showing attainment of the 1997 o zone NAAQS. The design values in this CSA over the last 7 years suggest ed that there are two central peak areas of nonattainment within the Washington - Baltimore - NV CSA. The first is in Harford County , MD in the far northeast portion of the Washington - Ba ltimore - NV CSA. The second is in the vicinity of Fairfax and Arlington Counties in Virginia and extends into the District of Columbia, and into Anne Arundel and Prince George’s Counties in Maryland. See Figure 2a.

41 The Preliminary TSD for the December 9, 2011 letters sent to the States incorrectly stated this Davidsonville monitor was 0.002 ppm less than the design value in Arlington County. 42 As will be discussed under Factor 3

– Meteorology

– consideration of prevailing winds on exceedance days support a conclusion that this monitor is more closely tied to the rest of the Baltimore area but also in part to Montgomery and Prince George’s Counties in Maryl and.22

Detailed Analysis based Upon Exceedance Day Values: E PA received comments from Maryland, the public and others regarding the adequacy of s urface wind roses to represent wind patterns o n day s the 2008 ozone NAAQS is exceeded . 43 As a result of such comments, EPA re - evaluated the five - factors for this CSA in light of meteorology data resulting from use of the National Oceanic and Atmospheric Administration’s (NOAA) Hy brid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model to supplement the Factor 3 Meteorology portion of the anal ys is of the Preliminary TSD. 44 To allow consideration of air movement above the surface layer we ran the HYSPLIT model to obtain trajectories for three heights

– 100 meters, 500 meters and 1 ,000 meters. We ran the HYSPLIT to obtain 1,000 meter runs in order to better understand aloft movement of air that can be expected to mix down as the night - time inversion breaks - up. EPA considered 5 ye ars, 2006 through 2010 inclusive, of exceedance day data of complete, certified data for the current monitors in the CSA. Due to the number of monitors and exceedance day s (over 980 monitor - day combinations) EPA did not (and could not due to time constraints) run trajectories for each exceedance day at eac h monitor in the CSA. To narrow down the level of effort, EPA examined the air quality data (Factor 1) in more detail. We examined the 2006 to 2010 8 - hour ozone concentrations for the monitors in the “violating center” 45 of the CSA and grouped the data by day s when the 2008 ozone NAAQS was exceeded. When selecting monitors for which to run the HYSPLIT model EPA had to consider the density of the monitoring network and the following issues: (1) a needed decision to designate all or a substantial portion of this CSA as one nonattainment area as recommended b y two States or split the CSA into more than one nonattainment and attainment areas as recommended b y two States; (2) the need to develop a conceptual model of the relationship between meteorology (win d directions on exceedance day s) and ozone concentrations within the CSA in light of Maryland’s (and other parties’) comments on meteorology ; (3) the observation that the design value for the current Washington DC - MD - VA nonattainment area by the Davidsonvi lle monitor in Anne Arundel County “tracks” that in the 1997 Washington DC - MD VA nonattainment area indicating this county may be linked to emission in this area; (4) comment by

the States that EPA’s preliminary analy sis 46 appeared to indicate that counties forming the borders between the Baltimore - Towson and the Washington DC - MD - VA - WV CBSAs, such as, Anne Arundel County , Prince George’s Count y and others coul d be placed in more than one nonattainment area and thus the CSA should contain one nonattainment area ; 47 (5) Maryland’s comment that the uniformity of design values across the CSA for all monitors except the Edgewood monitor demonstrates that the two regions should be designated as one nonattainment area ; and,

43 For example, refer to documents EPA - HQ - OAR - 2008 - 0476 - 0405 and EPA - HQ - OAR - 2008 - 0476 - 0456 and to the Response to Public Comments Document] in the docket for this action. 44 “Preliminary Technical Support Document, December 2011, entitled, Maryland Are a Designations for the 2008 Ozone National Ambient Air Quality Standards, prepared by the Region 3 USEPA” document number EPA - HQ - OAR - 2008 - 0476 - 0235 in the docket for this action. 45 Basically all monitors in the CSA were considered except the monitor in F rederick County, VA. 46 For example, refer to Preliminary Technical Support Document, December 2011, entitled, “Maryland Area Designations for the 2008 Ozone National Ambient Air Quality Standards,” prepared by US EPA Region 3 which is document number EPA - HQ - OAR - 2008 - 0476 - 0235 in the docket for this action. Similar TSDs were prepared for EPA’s December 9, 2011 responses to the District of Columbia and to Virginia

– refer to document numbers EPA - HQ - OAR - 2008 - 0476 - 0231 and EPA - HQ - OAR - 2008 - 0476 - 0237.23

(6) Maryland’s extensive information on met eorological and related geographical factors regarding transport in general and frequency and severity

of exceedances at the Edgewood monitor. **To consider these issues and State submitted data, EPA therefore needed to examine the air quality**  **data in vast**

**ly more detail than in the case of many other areas in the country where perhaps there is only one violating monitor, perhaps the relationship between a few counties’ emissions and one or**  **only one or two monitors are at issue, or where substantial geograph ic barriers constrain air**  **movement.** EPA obtained the 2006 through 2010 (inclusive) air quality monitoring data for each monitor b y day for the Baltimore CBSA and for the Washington DC - MD - VA - WV CBSA. This data provides the 2006 through 2010 data for all the violating monitors currentl y in the CSA. This data was downloaded on February 1, 2012, from http://www.epa.gov/airdata/ad_data_daily .html by selecting “Ozone” for the “Pollutant,” “2006, 2007, 2008, 2009 or 2010” (as applicable) for the “Year,” “Baltimore - Towson , MD” or “Washington - Arlington - Alexandria DC - MD - VA - WV” for “Select a City (defined as a CBSA),” and “All Sites” for the “Monitor Si te” (with exceptional events data). A cop y of the downloaded spreadsheet files has been placed in the docket for this action. This 2006 through 2010 (inclusive) data also includes daily

8 - hour maximum ozone concentrations for the monitors in the CSA clos e to exceeding the 2008 ozone NAAQS such as those in Charles, Frederick and Montgomery Counties in Maryland, Loudoun County and Alexandria City

in Virginia, the Takoma monitor in the District as well as many monitors with design values at or below 0.070 pp m. The only monitor within the CSA for which EPA did not obtain daily 8 - hour maximum ozone concentrations for 2006 through 2010 was that in Frederick County , VA . 48 Inthe 2006 to 2010 (inclusive) period for the monitors examined, EPA identified over 980 d istinct instances of monitor - day s. Extraction and G rouping by Episodes: EPA extracted for each monitor the date and the maximum 8 - hour ozone concentration and grouped these by “episode.” In this document an “exceedance day” is for a monitor a day or date on which that monitor recorded a maximum 8 - hour ozone concentration at or above 0.076 ppm. For the CSA or a CBSA, an exceedance day is a day or date on which at least one monitor in that CSA or CBSA, respectivel y, recorded a maximum 8 - hour ozone concentration at or above 0.076 ppm. An “episode” is a period of at least one day or more than one consecutive day s on which at least one monitor in the CSA or a CBSA recorded a maximum 8 - hour ozone concentration at or above 0.076 ppm. Summary data for each epis ode in the years 2006, 2007, 2008, 2009 and 2010 is provided in Table A2 - 1 of Appendix 2 of this document . For each exceedance day for the CSA, the maximum 8 - hour ozone concentration is provided for each monitor exceeding the 2008 ozone NAAQS (that is, a value of 0.076 ppm or more) for each monitor EPA has provided the following subset of data: the date, the AQS ID No. (expressed with hy

phens, e.g., 24 - 025 - 1001 versus 240251001), the maximum 8 - hour ozone concentration, the units of measure (ppm), the cor responding daily

Air Quality

Index (AQI) value the number of dail y 1 - hour ozone readings (“Daily Obs Count”) and percent completeness (“Percent Complete”) for that day , the AQS parameter code and description (“Descript”), the name of the State and the name of the County or City in which the monitor is located. The data is arranged b y ye ar, by date and grouped b y episode. The data in this Table A2 - 1 is only for those monitors in place as of 2008 48 EPA did not obtain this due to the parameters EPA used to filter the data; EPA filtered the AQS data by specifying by “Select a City (defined as a CBSA).” EPA did not intend to examine the air quality on a day by day basis for monitors with a design value at or below

0.070 ppm because these were w ell below the NAAQS and because EPA obtained the day by day data for the purpose of identifying the days the ozone NAAQS was exceeded for those monitors violating the 2008 ozone NAAQS. Therefore, EPA did not exclude the data for Frederick County, VA but rather incidentally obtained the day by day data for the other monitors with a design value well below the 2008 ozone NAAQS.24

to 2010 because these are the monitors the design values of which were used to determine which monitors and counties contained a violating monitor. Table A2 - 2 in Appendix 2 to this document contains a subset of the episode day s listed in Table A2 - 1 for the three year period 2008 to 2010. EPA chose episodes from 200 8 to 2010 because this was the most recent three year period of certified data available. Unlike Table A2 - 1 which provides data for only monitors that exceeded 0.075 ppm on a day , Table A2 - 2 also has the maximum 8 - hour ozone concentration for all monitors in the Baltimore - Towson and Washington DC - MD - VA - WV CBSAs. For each monitor EPA has provided the following subset of data: the date, the AQS ID No. (expressed with hy phens, e.g., 24 - 025 - 1001 versus 240251001), the maximum 8 - hour ozone concentration, the units of measure (ppm), the corresponding daily Air Quality

Index (AQI) value , the number of dail y 1 - hour ozone readings (“Daily Obs Count”) and percent completeness (“Percent Complete”) for that day , the AQS parameter code and descripti on (“Descript”), the name of the State and the name of the County or City in which the monitor is located. The data is arranged by year, b y date and grouped b y episode. EPA chose episodes that represented a variety of wind patterns as predicted by the HY SPLIT model and chose episodes that represented the worst conditions based upon length of the episodes in day s, the number of different monitors recording an exceedance on at least one day of the episode, and the maximum concentrations recorded b y monitors . 49 EPA also cho se other episodes during which the Edgewood monitor recorded an exceedance because Maryland presented extensive data regarding meteorological - topographical factors that disproportionately affect that monitor. EPA therefore obtained HYSPLIT model back - trajectories predictions for virtually all (if not all) exceedance day s for this monitor. The purpose of examining a subset of all the episodes was to examine the concentration gradients occurring within the CSA and the concentrations measured on the ground at the monitors predicted to be on the up - wind boundary of the CSA. EPA examined these to see if the Edgewood monitor was aty

pical in that it might record higher concentrations than other monitors in close proximity and to see how ozone con centrations waxed and waned in relation to the more densel y populated/higher emissions counties and cities within the CSA and in relation to upwind - edge and downwind - edges of the CSA. EPA performed these anal ys es because a simple design value plot across the CSA does not represent daily , peak, 8 - hour ozone concentration gradients except only on a very gross level of resolution as a design value represents a three - ye ar average of onl y one value per ye ar for each monitor. Maryland also submitted its analy s is of transport of ozone across various boundaries

– CBSA and, State

– and scales

– city - to - city and from Missouri to Maryland (discussed further under Factor 3

– Meteorology). Maryland provided its anal ys is of the “elevated reservoir” and cited three mo nitors in close proximity

that are located at high - elevations (relativel y to monitors within the CSA). 50 These monitors are the “Piney

Run” monitor (AQS ID No. 24 - 023 - 0002 ) in G arre tt County , MD, the “Big Meadows” monitor (AQS ID No. 51 - 113 - 0003 ) within th e Madison County portion of Shenandoah National Park (SNP) , and the “Methodist Hill” monitor (AQS ID No. 42 - 055 - 0001 ) in Franklin County , PA. EPA therefore examined 2008 to 2010 data for these monitors and placed the entire 2008 to 2010 monitoring data in the docket for this action. A subset of this data is provided in Table A2 - 3 in Appendix 2 of this document. This subset is for the episode day s of the 2008 to 2010 episodes listed in Table A2 - 1 and in cases for the day before the start of the episode. For each monitor EPA has provided the following subset of data: the date, the AQS ID No. (expressed with h yp hens, e.g., 24 - 025 - 1001

49 In some respects these criteria are all inclusive in that examination of the episode d ata in Table A2 - 1 will show that the largest number of different monitors exceeding 0.075 ppm and the higher concentrations are found on days during multi - day episodes. Extra weight was given to an episode if a monitor recorded a concentration that was among the four - highest for that monitor during that year. 50 For example, refer to page 17 of “ Moving Forward to Address Regional Transport, ” Ta d Aburn - Air Director, MDE, February 8, 2012 - MARAMA Science Meeting , a copy of which has been placed in the docket.25

versus 240251001), the maximum 8 - hour ozone concentration, the units of measure (ppm), the AQS parameter code and descriptio n (“Descript”), the name of the State and the name of the County or City in which the monitor is located. The data is arranged b y date. **In past designations, EPA has rarely considered this level of detail for every designation decision, but to reiterate** 

**, the decisions for this CSA are not typical due to: the State submitted information regarding meteorology and its effects on the Edgewood monitor; the differing recommendations**  **by two States seeking a single nonattainment area for the CSA and another**  **two seeking retention of the**  **1997 Washington DC**

**- MD**  **- VA nonattainment boundaries.**  Design value and exceedance day trends for the 2006 to 2010 period: As noted in Tables 2 and 5, the highest design value for the Washington - Baltimore - NV CSA is and has been set by

the Edgewood monitor in Harford County , MD. The same monitor sets the design value (DV) for the 1997 Baltimore nonattainment area . For the 1997 Washington DC - MD - VA nonattainment area , the location of the design value monitor has shifted over time . For 2008 - 2010, the Franconia monitor in Fairfax County , VA has a DV of 0.081 ppm. Based upon the 2008 - 2010 DVs, other monitors in this CSA with a DV close to the Franconia monitor are the Davidsonville, McMillan Reservoir and Arlington monitors , each w ith a DV of 0.079 ppm. Close behind are the Aldino, Howard U.

–Beltsville and Essex monitors each with a DV of 0.078 ppm. Table 6 provides the DVs for these monitors and a few others since the 2006 to 2008 period: **Table 6 .**  **Design Values for Select Moni tors**  Design value (ppm) State Monitor AQS ID No. 2006 -

2008 2007 - 2009 2008 - 2010 District of Columbia McMillan

R es 110010043 0.087 0.080 0.079 Anne Arundel Davidsonville 240030014 0.087 0.080 0.079 Baltimore Essex 240053001 0.085 0.078 0.078 Harford Edgewood 240251001 0.091 0.087 0.089 Harford Aldino 240259001 0.089 0.082 0.078 Prince George ’ s HU - Beltsville 240330030 0.083 0.078 0.078 Prince George ’ s Pr Geo. Eq.

Ctr. 240338003 0.087 0.078 0.077 Arlington Arlington 510130020 0.085 0.079 0.079 Fairfax Franconia 510590030 0.085 0.080 0.081 Data Sources: dv_ozone_2006_2008.xls (downloaded on 11/29/2011 from http://www.epa.gov/airtrends/values.html ). Ozone_DesignValues_20072009_FINALr03dec10.xls (downloaded on 3/30/2012 from http://www.epa.gov/airtrends/values.html ) ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html

. For the same set of monitors, Table 7 provides the approximate number of exceedances of the 0.075 ppm standard per ye ar .26

Table 7 . Approximate Number of Exceedance Day s per Year for Sel ect Monitors 51 Monitor AQS ID No. 2006 2007 2008 2009 2010 McMillan R es. 11 - 001 - 0043 22 14 8 2 16 Davidsonville 24 - 003 - 0014 14 20 13 0 12 Essex 24 - 005 - 3001 19 13 11 1 15 Edgewood 24 - 025 - 1001 21 24 15 9 27 Aldino 24 - 025 - 9001 17 22 13 2 8 HU Beltsville 52 24 - 033 - 0030 22 14 9 1 16 Pr Geo. Co. Eq. Ctr. 24 - 033 - 8003 16 17 10 0 9 Arlington 51 - 013 - 0020 17 19 8 2 13 Franconia 51 - 059 - 0030 18 14 6 1 13 Table 8 provide s the approximate number of exce edances for the 3 - ye ar periods 2006 to 2008, 2007 to 2009, 2008 to 2010 and grand total for 2006 to 2010: **Table 8. Approximate Number of Exc**  **e edances for Select**  **Monitors** 53 Approximate Number of Exceedances Monitor AQS ID No. 2006 - 2008 2007 -

2009 2008 - 2010 2006 -

2010 McMillan R es. 11 - 001 - 0043 44 24 26 62 Davidsonville 24 - 003 - 0014 47 33 25 59 Essex 24 - 005 - 3001 43 25 27 59 Edgewood 24 - 025 - 1001 60 48 51 96 Aldino 24 - 025 - 9001 52 37 23 62 HU - Beltsville 24 - 033 - 0030 45 24 26 62 Pr Geo. Co. Eq. Ctr. 24 - 033 - 8003 43 27 19 52 Arlington 51 - 013 - 0020 44 29 23 59 Franconia 51 - 059 - 0030 38 21 20 52 **Data Sources:** 51 Derived by manual sorting and compiling of the data in Table A2 - 1 in Appendix 2 to this document. Numbers may therefore be approximate only. 52 Short for Howard University

– Beltsville. 53 Derived by manual sorting and compiling of the data in Table A2 - 1 in Appendix 2 to this document. Numbers may therefore be approximate only.27

(1) Files Balt - Tow CBSA 2006 ad_viz_plotval_data.csv, Balt - Tow CBSA 2007 ad_viz_plotval_data.csv, Balt - Tow CBSA 2008 ad_viz_plotval_data.csv, Balt - Tow CBSA 2009 ad_viz_plotval_data.csv and Balt - towson CBSA 2010 ad_viz_plotval_data.csv downloaded from http://www.epa.gov/airdata/ad_data_daily.html by selecting “Ozone” for the “Pollutant,” “2006, 2007, 2008, 2009 or 2010” for the “Year,” “Baltimore - Towson, MD” for “Select a City (defined as a CBSA),” and “All Sites” for the “Monitor Site” (with exceptional events data). (2) Files Wash - AADC CBSA 2008 ad_viz_plotval_data.csv, Wash - AADC CBSA 2007 ad_viz_plotval_data.csv, Wash - AADC CBSA 2008 ad_viz_plotval_data.csv, Wash - AADC CBSA 2009 ad_viz_plotval_data.csv and Wash - AADC CBSA 2010 ad_viz_plotval_data.csv downloaded from http://www.epa.gov/airdata/ad_data_daily.html by selecting “Ozone” for the “Pollutant,” “2006, 2007, 2008, 2009 or 2010” for the “Year,” “Washington - Arlington - Alexandria DC - MD - VA - WV” for “Select a City ( defined as a CBSA),” and “All Sites” for the “Monitor Site” (with exceptional events data). (3) All files downloaded February 1, 2012 . A few conclusions that can be drawn from Tables 6, 7 and 8 are: (1) From Table 7

– 2009 had an at ypicall y low number of exceedances. (2) From Table 6

– As a result of the 2009 ozone season data the design values dropped at all monitors for the period 2007 t o 2009 from those in 2006 - 2008. (3) From Table 6

– The differenc e between the Edgewood monitor and the highest de s ign values in the Washington DC - MD - VA - WV CBSA grew from 0.004 ppm (0.091

– 0.087) for the 2006 to 2008 period to 0.008 ppm (0.087

– 0.080) for the 2007 to 2009 period. (4) From table 7

– The number of excee dances per monitor in 2010 retur ned to levels somewhere between the levels of 2007 and 2008 except for the Edgewood monitor which had more exceedances in 2010 than any

other year in the period before 2009. (5) From Table 6

– Except for the Franconia and Ed gewood two monitors, in spite of the increase in number of exceedances in 2010, design values for the period 2008 to 2010 remained stable or dropped in comparison to the period for 2007 to 2009. The Franconia monitor saw an increase of 0.001 ppm; for the Edgewood monitor the increase was 0.002 ppm. (6) From Table 6

– The difference between the Edgewood monitor and the highest design value(s) in the Washington DC - MD - VA - WV CBSA grew from 0.007 ppm (0.087

– 0.080) for the 2007 to 2009 period to 0.008 ppm for the 2008 to 2010 period. ( 7 ) From Table 7

– Prior to 2009, the Edgewood monitor was ranked first or second in number of exceedances per ye ar and had a comparable number of exceedances per ye ar to the next lower or higher ranked monitor (21 versus 22; 24 ve rsus 22, and 15 versus 13). ( 8 ) From Table 7

– For 2009 and after, the Edgewood monitor had far more exceedances b y a factor of 4.5 (9 versus 2) times for 2009 and 1.6 times (27 versus 16) of the next highest monitor. (8 ) From Table 8

– For an y three - ye ar period during 2006 through 2010, the Edgewood monitor has alway s had the most exceedances over an y three - year period; one might expect the monitor with the higher design values to have more exceedances but this does not alway s hold up. For the 2007 to 2 009 period, all the monitors within the Washington DC - MD - VA - WV CBSA listed in Tables 6 through 8 and the Davidsonville monitor had more exceedances in this period but had equal or lower design values for 2007 to 2009 than the Franconia monitor. For 2008 t o 2010, the Franconia monitor had fewer aggre gate ex ceedances than all but one 54 of the monitors within the Washington DC - MD - VA - WV CBSA and the Davidsonville monitor but still had a higher design value. (9) The Edgewood monitor did not respond the same to whatever affected the design values and number of exceedances in 2009 and 2010 at other monitors. By all accounts 2009 was a mild year insofar as conditions for ozone formation as shown by the number of exceedances recorded at various monitors. But the Edgewood monitor is the only one which recorded over four concentrations over 0.075 ppm during the 2009 ozone season .

54 That being the Prince George’s County Equestrian Center monitor.28

In the current Baltimore - Towson CBSA as well as the CSA, the Edgewood monitor stands apart in both its current design value and number o f exceedances in any three year period It has one and one - half times as many

exceedances over the five - ye ar period 2006 to 2010. In the current Washington DC - MD - VA - WV CBSA, the Franconia monitor current ly sets the DV for this area but has not alway s don e so as shown in Table 6 and has not had the most exceedance day s in any ye ar nor any

3 - or 5 - ye ar period. Basic Statistics for the Edgewood monitor in Harford County, MD: The number of exceedance day s for the Edgewood monitor was counted to be 96 for th e 5 - year period 2006 through 20 10 . EPA decided that these should be grouped somehow to make displaying the back trajectories for more than one day easier to understand because for th e 5 - ye ar period 2006 through 2010 there would be 288 (96 x 3) back - trajec tories if all three altitudes for all day s were displayed in one overlay . One way

to analyze the exceedance data is to perform some basic statistical analyses on the data. Using the five years of data for the Edgewood monitor the mean, the median and the standard deviation were determined. The mean value of the exceedances is 0.0858 ppm, the median 0.085 ppm and the standard deviation is 0.008066 ppm 55 (8 ppb). The distribution is somewhat skewed in that 50 values are below the mean and 46 are above the mean. The highest value, 0.113 ppm, is over 3 standard deviations from the mean whereas the lowest values, 0.076 ppm, lay only about 1.2 standard deviations off the mean. 56 However, 14 values are greater than the mean value plus 1 standard deviation (a va lue of 0.0939 ppm), and, 14 values are less than the mean value minus 1 standard deviation (a value of 0.077 ppm). Placing the data into quintiles 57 , the values would be as follows: **Table 9. Quintiles for the Edgewood monitor.** Group Ozone concentration range 1. Bottom Quintile 0.0 76 - 0. 078 ppm 2. L ower Quintile 0.0 79 to 0.082 ppm 3. Middle Quintile 0.082 to 0.087 ppm 4. Upper Quintile 0.087 to 0.090 ppm 5. Top Quintile 0.091 ppm or more Because several quintiles would contain concentrations of 0.082 and 0.087 ppm, the data was split into the following five groups such that each group was defined b y a unique range of concentrations. The final grouping selected was as follows: **Table 10. Quintiles for the Edgewood monitor.**  Group Number Ozone concentration range Number of values in Group 1. Bottom Quintile 0.0 76 - 0. 078 ppm 19 2. L ower Quintile 0.0 79 to 0.082 ppm 16 3. Middle Quintile 0.082 to 0.087 ppm 21

55 Using the Microsoft® Office Excel® “STDEV()” function. 56 No doubt this fact could be due who lly or in part to fact that the mean and standard deviation were computed for only those values above the fixed value of 0.075 ppm of the entire set of ozone concentration readings. 57 When distributed in groups of 19, 19, 20, 19 and 19.29

4. Upper Quintile 0.087 to 0.090 ppm 21 5. Top Quintile 0.091 ppm or more 19 The data for this section was manuall y extracted from the data in Table A2 - 1 of Appendix 2 to this document. The full listing of Edgewood exceedance day s upon which the statistics were based can be fo und in Tables A2 - 4 in Appendix 2 to this document. Numbers may therefore be approximate only. Episodes per Year and Length of Episodes As defined earlier in this document, an exceedance day is an y da y during which at least one monitor in the CSA recorded an 8 - hour ozone concentration of 0.076 ppm or more. An ozone episode is a period of one or more consecutive day s during which at least one exceedance was recorded in the CSA. The following table provides some summary statistics for exceedance day s and episodes for the CSA for the period 2006 - 2010 (all data approximate). **Table 11. Episodes and Exceedance Days per Year 2006 to 2010 58**  Year Number of

Epis odes Number of

Exceedance day s Length of

Longest Episode(s) Dates of Longest

Episode(s) 2006 15 38 5 day s 5/28 - 6/1; 7/17 to 7/21 and 8/22 to 8/26 2007 16 51 8 day s 7/31 to 8/7 2008 16 25 4 day s 7/15 to 7/18 2009 8 10 2 day s 6/25 to 6/26 2010 20 42 7 day s 8/28 to 9/3 Totals 2006 to 2010 65 166 8 day s - - - - Severity of Episodes: If exceedances of or greater than 0.095 ppm (the mean plus more than one standard deviation for the Edgewood data) are considered to be “especially high,” then the monitors in the CSA recorded the following during the period 2006 to 2008: **Table 12. Epis odes with Any Exceedance Day over 0.094 ppm**  59 Year Dates Peak Concentration At Monitor

(AQS ID #) Number of

exceedances > 0.095 ppm during the ye ar Number of

Different Monitors recording Value > 0.095 ppm 58 Derived by man

ual sorting and compiling of the data in Table 2A - 1 of Appendix 2 of this document. Numbers may therefore be approximate only. 59 Derived by manual sorting and compiling of the data in Table 2A - 1 of Appendix 2 of this document. Numbers may therefore be ap proximate only.30

2006 5/28 - 6/1 0.116 Widewater (51 1790001 ) 12 11 2006 6/21 - 6/22 0.096 Pr. Geo. Co. Eq. Ctr 60 (240338003) 2 2 2006 7/17 - 7/21 0.118 Alexandria (515100009) 16 10 2006 8/22 - 8/26 0.098 Essex (240053001) 2 2 Totals for 2006 32 ---- 2007 5/29 - 6/1 0.100 Aldino (240259001) 1 1 2007 6/7 - 6/8 0.108 Aldino (240259001) 2 2 2007 6/18 - 6/19 0.103 Davidsonville (240030014) 3 3 2007 7/7 - 7/10 0.113 (2 monitors) Aldino &

Edgewood (240259001 &240251001) 2 2 2007 7/14 - 7/17 0.095 Arlington (510130020) 1 1 2007 7/31 - 8/7 0.118 Davidsonville (240030014) 4 4 Totals for 2007 13 2008 6/10 0.099 Padonia (240051007) 1 1 2008 6/12 - 6/14 0.097 Padonia (240051007) 3 3 2008 7/11 - 7/12 0.100 Edgewood (240051001) 1 1 2008 7/15 - 7/18 0.104 Arlington (510130020) 6 6 Totals for 2008 11 2009 6/25 - 6/26 0.109 Edgewood (240051001) 1 1 Totals for 2009 2010 7/3 - 7/8 0.100 McMillan Reservoir (110010043) 4 4 2010 7/23 0.101 Edgewood (240051001) 1 1 2010 8/9 - 8/11 0.115 Essex (240053001) 6 5

60 Short for Pr. Georges Co. Equestrian Ctr .31

2010 8/28 - 9/3 0.098 Calvert Co. (240090011) 2 2 Totals for 2010 13 Totals 2006 to 2010 70 19 different monitors Of these 70 exceedances over 0.094 ppm, Edgewood monitor recorded 14 (20%). Prince George’s Co. Equestrian Center and Davidsonville each recorded 6; McMillan, Essex and Arlington each recorded 5; Aldino and Fairfax each recorded 4; Howard U.

–Beltsville and Widewater 61 each recorded 3; nine other monitors each recorded 2 or 1. 62 Comparing Tables 11 and 12 the highest recorded value often occurs during the longest episode of the ye ar. The longer episodes often have th e largest number of monitors recording “especiall y high” concentrations. Once again, based upon the Tables 11 and 12, 2009 would seem to have been a mild ye ar insofar as conditions for ozone formation. Conversel y, there were around 17 single day episo des where only one monitor within the entire CSA recorded an exceedance of the 0.075 ppm standard. The highest concentration recorded on such day s was 0.083 ppm with most recorded exceedances at or below 0.079 ppm. Eight of such day s were at the Edgewoo d monitor. 63 In addition there were around five single day episodes where onl y a pair of monitors “close” to each other each recorded an exceedance. Such parings are Edgewood - Padonia, Edgewood - Aldino, Edgewood - Essex, Southern Maryland - Calvert Co. and Davi dsonville - Prince George’s Co. Equestrian Center. The air qualit y data shows that the CSA averages 13 episodes per ye ar and 33.2 exceedance day s per ye ar for the period 2006 to 2010. The maximal length of the episodes ranges from 4 to 8 day s (2009 excluded) and around four episodes per ye ar where concentrations in excess of 0.094 ppm can be expected (2009 excluded). The air qualit y data also shows that the Edgewood monitor is atypical; while it may not record the highest value in an y given episode or ye ar it is more likely to record an “especiall y high” value as reflected b y its 2008 - 2010 DV of 0.089 ppm and its 20% share of “excessively high” values. This monitor also is more likely to record an exceedance and more likel y to be the only monitor to re cord an exceedance during a single day episode. Episode Day s and Extent of Exceedances: Examination of this data suggests that the CSA is subject to various regimes that result in varying patterns of ozone levels within the CSA: On some day s only

one or a few monitors exceeded 0.075 ppm; on other day s, the extent of exceedances was more widespread or extremely widespread with higher levels across most if not all of the CSA. On some day s the highest readings were found at one end

– either the North easternmost portion clustered around the monitors North and East of Baltimore City or around the District of Columbia’s and Arlington and Fairfax Counties’ monitors.

61 None in 2008 or later. 62 These were: South Carroll, Rockville, Southern Maryland, Alex andria, Pad onia, Calv ert Co., James S. Long Park , Asburn and Furley E.S. Rec Center . 63 The only pother monitors with two such days were Aldino and Rockville; the Franconia, River Terrace, Howard U

— Beltsville, Fred erick County and Widewater monitors each had one.32

Some other conclusions can be reached: generall y, especiall y high con centrations ( in this case using Edgewood monitors’ “top quintile” threshold those over 0.091 ppm 64 ) are often recorded on day s which are part of a multi - day

episode (that is, two or more consecutive day s with at least one exceedance recorded at least one mo nitor within the CSA); there are exceptions such as on July 23, 2010 where “Edgewood” recorded a concentration of 0.101 ppm, and July 10, 2008, (0.099 ppm at the “Padonia” monitor in Baltimore County), The Edgewood Monitor May be Atypical The “Edgewood” monitor does appear to be out of the ordinary besides in other way s besides its design value: This monitor does not necessaril y record the highest 8 - hour concentration of an y CSA monitor for an ozone season but clearl y has had a 4 th high value each seaso n that is greater than on average than other nearb y monitors. For the period 2006 to 2008, this monitor did not have a number of exceedance day s that stood apart from other monitors

– in 2006 “Edgewood” recorded 21 exceedances versus the maximum of 22 els ewhere, 65 in 2007 Edgewood recorded 24 exceedances versus the next highest number of 22, and in 2008 “Edgewood” recorded 15 exceedances versus the next highest number of 13 66

. 67 After 2008, the “Edgewood” monitor did start to record a higher number of exceed ances – 9 in 2009 68 versus a maximum of 2 at three other monitors and in 2010 “Edgewood” recorded 27 exceedances versus a maximum of 16 elsewhere. 69 This monitor represented about 20% of the day s where onl y one monitor within the CSA exceeded 0.075 ppm. Th ere are many day s where this monitor recorded a peak 8 - hour concentration 10, 20 or even 30 ppb (0.010, 0.020 and 0.030 ppm) higher than other close monitors such as the “Essex,” “Aldino” and “Padonia” monitors in Harford and Baltimore Counties. Maryland in their March 7, 20102 five - factor anal ys es presented evidence that a related topographical - meteorological phenomenon combine at the Edgewood location to result in higher levels of daily ozone concentrations at the Edgewood monitor than otherwise might oc cur. These phenomenons are discussed under Factor 3 Meteorology below. T he results presented in this paragraph would suggest that Maryland’s conclusion could be is correct under certain conditions . However, as stated previously in this document, a county /independent cit y (or partial count y) must also be designated nonattainment if it contributes to a violation in a nearb y area. Each count y without a violating monitor that is located near a county wi th a violating monitor has been evaluated based on the weight of evidence of the five factors and other relevant information to determine whether it contributes to the nearb y violation. In a CSA where counties with violating monitors are adjacent to each other and where EPA in the past concluded that there were two separate nonattainment areas, even a count y with a violating monitor needs to be evaluated to see if that county sufficientl y contributes to violations at another nearb y, violating county . Such an evaluation can guide a decision on grouping counties with violating monitors to set the boundaries of a nonattainment area (or areas) containing more than one violating monitor. 

## Factor 2: **Em issions and Em**  **issions -**  **Related Data**

64 In the aggregate, all monitors in the CSA recorded around 986 exceedanc es during 2006 - 2010 with the top 197 (essentially the top quintile) concentrations being 0.088 ppm or higher. 65 At the “McMillan Reservoir” monitor in the District of Columbia and the “Howard University - Beltsville” monitor in Prince George’s County, MD. 66 At the “Davidsonville” and “Aldino” monitors in Anne Arundel and Harford Counties, Maryland, respectively. 67 At the “Aldino” monitor also in Harford County, MD. 68 2009 was a y ear where a low number of exceedances were generally seen. 69 At the “McMillan Reservoir” and the “Howard University - Beltsville” monitors.33

EPA evaluated emissions of ozone precursors (NO x and VOC) and other emissions - related data that provide information on areas contributing to violating monitors. 

### Emissions Data All Emissions Aggregated at the County /City L evel: EPA evaluated count y - level emission data for NO x an d VOC derived from the 200 8 National Emissions Inventory (NE I), version 1.5 . This is the most recently available NEI. ( See , http://www.epa.gov/ttn/chief/net/2008inventory .html ) . Sufficiently high emissions levels in a nearby area indicate the potential for the area to contribute to monitored violations . We will also consider any additional information we receive on changes to emissions levels that are not reflected in recent inventories. These changes include emissions reductions due to permanent and enforceable emissions controls that will be in place before final designations are issued and emissions increases due to new sources. Table 13 shows emissions of NO x and VOC given in tons per year (tpy) for violating and potentiall y contributing counties in the 1997 Baltimore MD and Washington DC - MD - VA nonattainment areas and other portions of the Washington - Baltimore - NV CSA . **Table 13**  **. Total 2008 NO x**  **and VOC Emissions** . County /City State

Recommended Nonattainment? NO x

(tpy) VOC

(tpy) Baltimore MD Nonattainment Area : Anne Arundel County Co., MD Yes 30,541 14,423 Baltimore City, MD Yes 18,621 11,397 Carroll County, MD Yes 6,617 3,948 Harford County, MD Yes 5,854 6,396 Howard County, MD Yes 9,219 7,848 Baltimore County, MD Yes 29,392 16,807 Baltimore Subtotal: 100,244 60,819 Washington DC - MD - VA Nonattainment Area: District of Columbia, DC Yes 11,332 11,362 Calvert County, MD Yes 2,797 2,406 Charles County, MD Yes 5,823 3,939 Frederick County, MD Yes 9,389 6,460 Montgomery County, MD Yes 21,097 20,426 Prince George ’ s County, MD Yes 24,043 18,882 Arlington County, VA Yes 5,264 4,329 Fairfax County, VA Yes 21,403 25,603 Loudoun County, VA Yes 6,948 7,331 Prince William County, VA Yes 7,698 8,603 Alexandria City, VA Yes 3,349 2,625 Fairfax City, VA Yes 326 79434

Falls Church City, VA Yes 138 324 Manassas City, VA Yes 553 1,020 Manassas Park City, VA Yes 92 285

Washington DC - MD - VA Subtotal: 120,252 114,389

**Table 13**  **(continued). Total 2008 NO x**  **and VOC Emissions .** 

County State

Recommended Nonattainment? NO x

(tpy) VOC

(tpy) Fredericksburg, VA Area: Spotsylvania County, VA No 3,539 4,226 Stafford County, VA No 3,377 3,516 Fredericksburg City, VA No 859 1,007

Fredericksburg, VA Subtotal: 7,775 8,749 Frederick County, VA Area: Frederick County, VA No 2,838 4,714 Winchester City, VA No 508 1,006

Frederick Co., VA Area Subtotal: 3,346 5,720 Other counties: Queen Anne ’ s County, MD No 2,725 2,402 St. Mary ’ s County, MD No 3,475 4,038 Clarke County, VA No 941 949 Culpeper County, VA No 1,726 2,109 Fauquier County, VA No 3,383 3,389 Warren County, VA No 1,463 1,773 Hampshire County, WV No 734 2,078 Jefferson County, WV No 1,566 1,481

All other counties subtotal: 16,013 18,218

CSA Total: 247,630 207,894 **Data sources:** (1) NOx emissions (tpy

) - NEI08v1.5

– Total NOx emissions include Nonpoint, Nonroad, Onroad and Facilit y NOx emissions from ftp://ftp.epa.gov/EmisInventory/2008_nei/v1.5_GPR (May 19, 2011). (2) VOC emissions (tpy) - NEI08v1.5

–Total VOC emissions include Nonpoint, Nonroad, Onroad and Facilit y VOC emissions from ftp://ftp.epa.gov/EmisInventory/2008_nei/v1.5_GPR (May 19, 2011)35

In their March 7, 2012 submittal, Maryland supplied an amended inventory for certain Maryland counties to reflect the 2009 EGU emissi on caps imposed under the Maryland Health y Air Act and implementing regulation. 70 The following Table 14 shows the effects that Maryland claimed. **Table 1**  **4 . Total 2008 NO**  **x and VOC Emissions**  . County /City State

Recommended Nonattainment? NO x

(tpy) VOC

(tpy) Baltimore MD Nonattainment Area : Anne Arundel County Co., MD Yes **22,110** 14,423 Baltimore City, MD Yes 18,621 11,397 Carroll County, MD Yes 6,617 3,948 Harford County, MD Yes 5,854 6,396 Howard County, MD Yes 9,219 7,848 Baltimore County, MD Yes **25,736** 16,807 Baltimore Subtotal: **88,157** 60,819 Washington DC - MD - VA Nonattainment Area: District of Columbia, DC Yes 11,332 11,362 Calvert County, MD Yes 2,797 2,406 Charles County, MD Yes 5,823 3,939 Frederick County, MD Yes 9,389 6,460 Montgomery County, MD Yes **18,415** 20,426 Prince George ’ s County, MD Yes **19,793** 18,882 Arlington County, VA Yes 5,264 4,329 Fairfax County, VA Yes 21,403 25,603 Loudoun County, VA Yes 6,948 7,331 Prince William County, VA Yes 7,698 8,603 Alexandria City, VA Yes 3,349 2,625 Fairfax City, VA Yes 326 794 Falls Church City, VA Yes 138 324 Manassas City, VA Yes 553 1,020 Manassas Park City, VA Yes 92 285

Washington DC - MD - VA Subtotal: **113,320** 114,389 Fredericksburg, VA Subtotal: 7,775 8,749 Frederick Co., VA Area Subtotal: 3,346 5,720 All other counties subtotal: 16,013 18,218

CSA Total: **228,611** 207,894

70 Refer to regulation COMAR 26.11.27.01 through .04, and .06 “Emission Limitations for Power Plants” in the codification of the Maryland SIP at 40 CFR 52.1070(c) and also to 73 FR 515 99, September 4, 2008 .36

The net overall effect is minimal in that the rankings by NOx overall emissions drop Montgomery County out of the top five and raises Baltimore City , MD from sixth to fifth as shown in Table 15 . **Table 15. Ranking and NOx emissions of the Top Six NOx Emissions Counties** Area Maryland Adjusted Value (tp y) New

Rank 2008

NEI Value (tpy) Prior

Rank Baltimore County , MD **25,736** 1 29,392 2 Anne Arundel County

Co., MD **22,110** 2 30,541 1 Fairfax County , VA 21,403 3 21,403 4 Prince George ’ s Count y, MD **19,793** 4 24,043 3 Baltimore City , MD 18,621 5 18,621 6 Montgomery

Count y, MD **18,415** 6 21,097 5 For NOx emissions, in the following discussion the 2008 NEI value or ranking will be in braces “{}”. The 1997 Washington DC - MD - VA nonattainment area contains 49.6 % { 48.5% } of the Washington Baltimore - NV CSA’s total NOx emissions and 55% of the Washington - Baltimore - NV CSA‘s total VOC emissions. The 1997 Baltimore nonattainment area contains 38.6% { 40.5% } of the Washington - Baltimore - NV CSA’s total NOx emissions and 29% of th e Washington - Baltimore - NV CSA’s total VOC emissions. Together the 1997 Washington DC - MD - VA and Baltimore nonattainment areas contain 88.1% { 89% } of the Washington - Baltimore - NV CSA’s total NOx emissions and 84% of the Washington - Baltimore NV CSA’s total VOC emissions. In the Washington - Baltimore - NV CSA , Anne Arundel, Baltimore, Prince George ’ s and Montgomery Counties in Maryland , Baltimore City , MD and Fairfax County in Virginia comprise the “ top six ” 71 when ranking b y VOC or by NOx emissions (with first being highest) . Using the 2008 NEI data an area was in the “top five” within the Washington - Baltimore - NV CSA if it has NOx emissions of more than 20,000 tpy

or VOC emissions of more than 14,000 tpy . Using Maryland’s revised values, the diffe rence between fifth and sixth for NOx emissions is insubstantial

– only 1.1% of 18,415 tons per y ear. A ll of these areas contain a violating monitoring or are adjacent to at least one county with at least one monitor violating the 2008 ozone NAAQS . The f ollowing comprise the next five highest ranked (that is, numbers 7 through 11 within the Washington - Baltimore - NV CSA ) for VOC or NOx emissions (not listed in order of ranking) : Frederick

71 The groupings by ranking were set to divide the 34 jurisdictions into four groups. To some extent the groups fell out naturally and are composed as follows: The same five jurisdictions ranked first to fifth for both NOx and VOC emissions and thus defined the “top five.” The same six jurisdictions fell within a rank of sixth through eleventh for both NOx and VOC emissions and thus defined the second group of sixth through eleventh. A “middle group” of those ranked between 12 th and 23 rd inclusive included the same twelve jurisdictions where: Calvert County, MD ranked at 22 nd for both NOx and VOC emissions; and Queen Anne’s County, MD ranked at 23 rd for both NOx and VOC emissions. Jurisdictions with less than approximately 2,500 tpy NOx or 2,200 tpy VOC re present less than one per of the CSA total emissions and comprise those areas ranked 24 th or lower.37

and Howard Counties in Maryland, the District of Columbia, and, L oud oun and Prince William Counties in Virginia . An area ranking 7 th through 11 th within the Washington - Baltimore - NV CSA needed to have NOx emissions of between 6,900 and 11,332 tpy or VOC emissions of between 6,400 and 14,000 tpy . Of these, only the District of Columbia has two of three monitors violating the 2008 ozone NAAQS. Lo udoun County , VA and Frederick County each has a monitor with a design value of 0.075 ppm which is only

one ppm from violating the 2008 ozone NAAQS. All are adjacent to one or more counties or the District of Columbia which contain at least one monitor violating the 2008 ozone NAAQS. Of these “top 11” counties for emissions , Frederick, Montgomery , Prince George ’ s Counties in Maryland, the District of Columbia, and, Fairfax and L oudoun Counties in Virginia are clustered around the Fairfax County

monitor which has a design value of 0.081 ppm. Of the top eleven, o nl y Baltimore County , MD is adjacent to Harford County , MD which contains the Edgewood monitor which has a design value of 0.089 ppm. The low emissions of the Cities of Fairfax, Falls Church, Manassas and Manassas Park in Virginia result in low ranking for emissions when the jurisdictions in the Washingto n - Baltimore - NV CSA are rank ed by emi ssions from highest to lowest. The Cities of Fairfax, Falls Church, and Manassas Park rank 32 nd , 33 rd , and 34 th (of 34) in the Washington - Baltimore - NV CSA . Manassas City ranks 28 th for VOC and 30 th for NOx within the W ashington - Baltimore - NV CSA . However, these are cities with very small land areas and are entirely surrounded or wedged in between larger counties . Table 16 compares the emissions and emission density of these cities with th ose jurisdictions that entirely surround these cities. Data for Alexandria City and with the District of Columbia are also presented to provide emissions densities for other highl y urbanized areas . **Table 16**  **. Total 2008 NO x**  **and VOC Emissions Densities of Selected Cities and Counties.**

County State Recommended Nonattainment? NO x

(tpy) VOC

(tpy) Land Area (sq. mi.) Emissions

Density NO x (tpy/sq. mi.) Emissions

Density VOC (tpy/sq. mi.) District of Columbia Yes 11,332 11,362 67.9 166.89 167.34 Fairfax Co., VA Yes 21,403 25,603 405.9 52.73 63.08 Fairfax City, VA Yes 326 794 6.1 53.37 130.21 Falls Church City, VA Yes 138 324 2.0 68.80 162.14 Arlington Co., VA Yes 5,264 4,329 25.8 204.04 167.78 Prince William Co., VA Yes 7,698 8,603 348.9 22.06 24.66 Manassas City, VA Yes 553 1,020 10.1 54.74 100.98 Manassas Park City, VA Yes 92 285 1.5 61.25 190.25 Alexandria City, VA Yes 3,349 2,625 15.2 220.35 172.70 Notes: “sq. mi.” means square miles. As can be seen from this table, the Cities of Fairfax, Falls Church, Manassas and Manassas Park have emissions densities in tons per year per square mile equal to or greater than the surrounding count y in the cases of the Cities of Fairfax, Manassas and Manassas Park . In the case of Falls Church City , Falls Church has emissions densities greater than Fairfax County but less than Arlington County . Due to38

Virginia’s sy stem of governance, these cities are inventoried separatel y ; i n most other states (Baltimo re City in Maryland being one exception) , such high density areas such as cities are not. The Cities of Fairfax, Falls Church, Manassas and Manassas Park can be considered to be high emissions areas on the basis of their emissions densities as opposed to their absolute emissions. As for Arlington County

and Alexandria City

in Virginia, these rank , respectively , 14 th and 21 st for VOC emissions and 15 th and 20 th for NOx , respectively . These jurisdictions are small in absolute land area but the emissions densities are the highest in the both the DC - MD - VA nonattainment area and the Washington - Baltimore - NV CSA. Both are adjacent to other areas containing a monitor violating the 2008 NAAQS. Of the remaining two counties, Charles and Calvert in the 1997 Washington DC nonattainment area, these two rank in the “ middle group” (between 12 th and 23 rd inclusive) : Calvert County , MD ranks low in this “middle group ”

– 22 nd within the Washington - Baltimore - NV CSA for both NOx and VOC , respectivel y ; Charles County , MD ranks higher than Calvert in this “middling” group

– 18 th and 14 th for VOC and NOx emissions, respectivel y. Both are adjacent to counties with violating monitors. Of the two, Charles is more likely to be upwi nd of a violating monitor because it is southeast of the Fairfax County , VA monitor, west - southwest of the monitor in Calvert County , MD and south - southwest of the Equestrian Center monitor in Prince George’s County , MD; Calvert County is due south of the monitor in Anne Arundel Count y, MD and south - southeast of the Equestrian Center monitor in Prince George’s County , MD. Of the remaining two counties, Harford and Carroll in the 1997 Baltimore nonattainment area, these two rank in the middle (between 12 th and 23 rd inclusive): Carroll County , MD ranks in the middle or high in this “middling” group – 17 th and 12 th for VOC and NOx emissions, respectively ; Harford Count y, MD ranks higher than Carroll in this “middling” group

– 1 2 th and 1 3 th for VOC and NOx emissions, respectivel y. Both are adjacent to counties with violating monitors. Of the two, Carroll County is more likely to be upwind of a violating monitor because it is west - southwest to west of the Padonia monitor in Baltimore County , MD. Harford County , MD is adjacent to Baltimore County , MD but one can expect that it is unlikely

to be upwind of either violating monitor in Baltimore County because both monitors in Harford County

were sited to be downwind of the urbanized core of bo th Baltimore City and County . In general, the counties and cities in the 1997 Baltimore and Washington areas likely sufficientl y contribute to nonattainment at one or more monitors in at least one of these two nonattainment areas because the County

has a violating monitor, because the count y or cit y is adjacent to a count y with a violating monitor or the small city has emissions densities comparable to or higher than surrounding or adjacent areas. Of the other areas or the counties listed under “other co unties” in the preceding table most have low emissions and are remote from areas containing a monitor violating the 2008 NAAQS: (1) The Frederick County , VA Area contains 1.5% { 1.4% } and 2.8% of the Washington - Baltimore - NV CSA NOx and VOC emissions, resp ectivel y. As a whole this area would rank 18 th for NOx emissions and 13 th (the actual rank for Frederick County, VA alone) for VOC emissions. If the Frederick County , VA Area was included with the 1997 Washington DC - MD - VA nonattainment area, the emissio ns of the Frederick Count y, VA Area would be about 2.9 { 2.7 } and 4.8 percent of such an area’s NOx and VOC emissions, respectivel y. (For example, for VOC emissions, 2.7% = 3,346/(3346+120,252) * 100.) This area is remote from an y counties with violating monitors and is separated from the 1997 Washington DC - MD - VA no nattainment area by the sparsel y populated Clarke and Warren Counties in Virginia. (2) Hampshire Count y (emissions rankings within CSA: 25 th for VOC & 29 th for NOx) is remote from any violating monitor in the Washington - Baltimore - NV CSA and likewise has l ow emissions (1 percent39

or less of the Washington - Baltimore - NV CSA’s total for either NOx or VOC) in spite of its size (644 square miles). If included with the 1997 Washington DC - MD - VA nonattainment area, its emissions would be about 1.8 percent or less o f such an area’s NOx or VOC emissions, respectivel y. The nearest monitors in the Washington - Baltimore - NV CSA or elsewhere are those in Frederick Count y, VA and Berkeley County , WV. These have a design value well less than the 2008 NAAQS of 0.075 ppm. Th e design values are 0.068 ppm for Frederick County , VA and 0.070 ppm for Berkeley County , WV (Data source: Table 5 to ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html ). (3) Clarke (emissions rankings within CSA: 27 th for VOC & 31 st for NOx) and Warren (emissions rankings within CSA: 26 th for both VOC for NOx) Counties in Virginia each comprise less than one percent of CSA total for either NOx or VOC emissio ns. If either were included with the 1997 Washington DC - MD - VA nonattainment area , the emissions of either would be less than 1.6 percent of such an area’s NOx or VOC emissions, respectively . The nearest monitors within the CSA are attaining the 2008 NAAQ S. ( 4) Queen Anne’s County MD (emissions rankings within CSA: 23 th for both VOC & NOx) is at the bottom of the “middling” group (12 th through 23 rd inclusive) in the Washington - Baltimore - NV CSA. Its emissions are 1.1 to 1.2 percent of the Washington - Baltimore - NV CSA’s total for NOx or VOC. If included with the 1997 Baltimore nonattainment area, its emissions would be about 3.0 { 2.9 } and 3.5 percent of such an area’s NOx and VOC emissions, respectivel y. Its emissions would add about 2.7 to 3.8 percent. Queen Anne’s County is in close proximity

(that is separated from adjacent counties in the Washington - Baltimore - NV CSA by stretches of the Chesapeake Bay) to several violating monitors, namely the Essex monitor in Baltimore Count y and the monitor in Anne Arundel County . Because Queen Anne’s County

is in the Ozone Transport Region (OTR), section 184 of the CAA requires many sources of VOC and major stationary sources of NOx be controlled by reasonably

available control technology

(RACT) pursuant to sections 182(b)(2) and 182(f) and requires major stationary sources of VOC and NOx be subject to nonattainment new source review (NSR) requirements at the OT R major stationary source thresholds. Also motor vehicles in Queen Anne’s County are subject to enhanced inspection and maintenance program (enhanced I/ M) as required b y section 184 of the CAA. 72 (5) Jefferson Count y, WV (emissions rankings within CSA: 2 7 th for VOC & 25 th for NOx), if included with the 1997 Washington DC - MD - VA nonattainment area, would comprise about 1.4 { 1.3 } percent of such an area’s NOx or VOC emissions, respectively . (6) Fauquier Count y, VA emissions rankings within CSA: 20 th for VO C & 18 st for NOx is in the “middling” group (ranks 12 th through 23 rd inclusive) of the Washington - Baltimore - NV CSA. If included with the 1997 Washington DC - MD - VA nonattainment area, its emissions would be about 2.9 { 2.7 } and 2.9 percent of such an area’s NOx and VOC emissions, respectively . However, Fauquier County is not adjacent to a count y containing a monitor violating the 2008 NAAQS. Both the geographically

nearest monitors (in Stafford and Prince William Counties, VA) have a design value of 0.070 p pm well below the 2008 NAAQS. (7) Culpeper Count y, VA (emissions rankings within CSA: 24 th for both VOC & NOx) is just below the “middling” group. If included with the 1997 Washington DC - MD - VA nonattainment area, its emissions would be about 1.5 { 1.4 } and 1.8 percent of such an area’s NOx and VOC emissions, respectivel y. 72 See , 61 FR 56183 at 56185, October 31 , 1996 for details on the OTR enhanced I/M requirements in Maryland. The relevant provisions that define the geograp hic scope of Maryland’s enhanced I/M program can be found in Code of Maryland Regulations (COMAR) 11.14.08.02B (19) and 11.14.08.03 in the approved Maryland SIP

– see 40 CFR 51.1070(c). Copies of COMAR 11.14.08.02B(19) and 11.14.08.03 are available on - li ne via http://yosemite.epa.gov/r3/r3sips.nsf/SIPIndex!OpenForm40

Culpeper County

is even more remote than the adjacent Fauquier Count y from any county containing a monitor violating the 2008 NAAQS.

. (8) St. Mary ’ s County , MD ranks in the “midd le” within the Washington - Baltimore - NV CSA (17 th for NOx and 16 th for VOC) for NOx and VOC emissions. If included with the 1997 Washington DC - MD VA nonattainment area, its emissions would be about 3.0 { 2.8 } and 3.4 percent of such an area’s NOx and VOC em issions, respectivel y. St. Mary ’ s County is adjacent to Calvert County which does contain a monitor violating the 2008 NAAQS. (9) The Fredericksburg, VA Area contains the following areas: Stafford County (emissions rankings within CSA: 19 th for both VOC & NOx); Spotsylvania County (emissions rankings within CSA: 16 th for NOx and 15 th for VOC); and Fredericksburg City (emissions rankings within CSA: 28 th for NOx and 29 th for VOC). The total emissions in the Fredericksburg, VA Area are about 6.5 and 7.7 pe rcent of the 1997 Washington DC - MD - VA nonattainment area’s NOx and VOC emissions, respectivel y. Alone, Spotsylvania County ’s emissions are about 3.4 { 2.8 } and 3.1 percent of the 1997 Washington DC - MD VA nonattainment area’s NOx and VOC emissions, respectivel y; the nearest monitors to Spotsylvania County are those in Fauquier and Stafford Counties in Virginia and Charles County in Maryland. The former two monitors are easily attaining the 2008 NAAQS. All of these three monitors are interposed between Spots yl vania County and violating monitors in the Washington - Baltimore - NV CSA. (Another monitor in an adjacent county is that in Caroline County , VA which is attaining the 2008 NAAQS with a design value of 0.073 ppm [Data source: Table 5 to ozone_dv75_20082010.xls (downloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html) ]). I f Spots yl vania County contributes to ozone l evels in other counties its highest contribution is likely to an y one of these three counties. If Spotsylvania and Stafford Counties were included in a nonattainment area encompassing the 1997 Washington DC - MD - VA nonattainment area or one consisting of bo th the 1997 Baltimore and Washington DC - MD - VA nonattainment areas, then Fredericksburg Cit y should also be included because although its absolute emissions are low its emissions densities exceed that of each of the two surrounding counties. If added to the 1997 Washington DC - MD - VA nonattainment area, the total emissions of Stafford County alone would be about 2.9 { 2.8 } and 3.0 percent of the combined area’s NOx and VOC emissions, respectivel y. For the case where a combination of Stafford County and Fred ericksburg City are included in such an expanded nonattainment area, their combined emissions would be about 3.7 { 3.4 } and 3.8 percent of such an area’s NOx and VOC emissions, respectively . The monitor in Stafford County is in the northeast corner of the count y and is interposed between much of the county’s (or the combined emissions of the count y plus Fredericksburg Cit y) and the violating monitor in Fairfax County . The attaining monitor in Charles County , MD is interposed between Stafford Count y and the violating monitor in Calvert County , MD. Likewise, the attaining monitors in Stafford and Fauquier Counties in Virginia and the attaining monitor in Charles County Maryland are interposed between Spotsylvania County

and Fredericksburg Cit y and the violat ing monitors in Calvert County , MD and Fairfax County , VA. Finally , of the cit y and two counties in the Fredericksburg Area onl y Stafford County is in the OTR. 73 Section 184 of the CAA requires that in attainment areas within the OTR many sources of VO C and

73 The OTR was defined in 1990 by section 184 of the CAA to include the statistical area that included the District of Co lumbia. In 1990, only Stafford County was part of the statistical area that included the District of Columbia. EPA has always interpreted the scope of section 184(a) to include only those states specified by name, the District of Columbia and41

major stationary

sources in the OTR of NOx be controlled by reasonabl y available control technology (RACT) pursuant to sections 182(b)( 2 ) and 182(f) and requires major stationary sources of VOC and NOx be subject to nonattainment NSR requirements at the OTR major stationary source thresholds. Also motor vehicles in Stafford Count y are subject to enhanced I/M as required by section 184 of the CAA. 74 Mobile Source Emissions: Both Maryland and the District expressed concern about the effects of mobile s ource emissions on nonattainment within the CSA in their March 7, 2012, and March 12, 2012, responses to EPA’s December 9, 2011 letters,. Maryland ’s comment was that the mobile source NOx emissions become the largest source of NOx emissions “post Maryland’s Healthy Air Act.” Maryland commented that the split between the Baltimore and Washington “areas” is approximately 40% and 60%, respectivel y. The District urged EPA to weight mobile source emissions more heavil y than was done in the Pr e liminary TSDs. EPA examined the 2008 emissions data used for the anal ys is for EPA’s preliminary TSD. EPA broke out the on - road mobile sources NOx emissions data for the CSA and found that the split between the aggregate on - road mobile source emissions of the current Washington and Baltimore Nonattainment area s is 61.6% in the current Washington DC - MD - VA Nonattainment area and 38.4% in the current Baltimore Nonattainment area . For the CSA , Table 17 provides a summary of the on - road mobile sources VOC and NOx emi ssions broken down by areas. **Table 17. Mobile Source Emissions in the Washington -**  **Baltimore -**  **NV CSA:** NO x VOC Area NOx (tpy) Percent of CSA Total Area VOC (tpy) Percent of CSA Total Baltimore Area 37,192 32.9% Baltimore Area 20,836.7 30.9% Washington Area Washington Area Maryland Portion 29,960 26.5% Maryland Portion 18,418.2 27.3% Virginia portion 23,476 20.8% Virginia portion 14,464.6 21.5% DC Portion 6,333 5.6% DC Portion 4,041.3 6.0% Washington Area sub - total 59,768 52.9% Washington Area sub - total 36,924.2 54.8% Fredericks b urg, VA CBSA 5,431 4.8% Fredericks b urg, VA CBSA 3,387.0 5.0% Frederick Co., VA area 1,675 1.5% Frederick Co., VA area 921.1 1.4% those porti ons of other States which shared the same statistical area as the District as of November 15, 1990 . See for example, 40 CFR 51.120 (60 FR 4712, Jan. 24, 1995) which related to a SIP call on all the OTR States . 74 See 61 FR 57343 at 57346, November 6, 199 6 for details on the OTR enhanced I/M requirements for Virginia. The relevant provisions that define the geographic scope of Virginia’s enhanced I/M program can be found in 9 VAC 5 - 91 - 20 and 9 VAC 5 - 91 - 30 in the approved Virginia SIP

– see 40 CFR 51.2420(c). Copies of 9 VAC 5 - 91 - 20 and 9 VAC 5 - 91 - 30 are available on - line via http://yosemite.epa.gov/r3/r3sips.nsf/SIPIndex!OpenForm .42

Other Virginia CSA Counties 4,978 4.4% Other Virginia CSA Counties 2,918.4 4.3% O ther Maryland CSA Counties 3,101 2.7% O ther Maryland CSA Counties 1,728.8 2.6% West Virginia Counties 918 0.8% West Virginia Counties 714.3 1.4% CSA Total 113,063 100.0% CSA Total 67,430.4 100.0% A full listing is provided in Table 3 - 1 of Appendix 3 to this TSD. It provides county /city specific values for the CSA counties as well as some outside counties. Maryland’s on - road NOx emissions are 62.1% of the CSA total and 69.3% of the aggregate on - road mobile source NOx emissions in the cur rent Washington and Baltimore nonattainment areas . The two nonattainment areas under the 1997 ozone NAAQS account for 85.8 % of the NOx emissions and 85.7 % of the VOC emissions. On March 1, 2012, Virginia Department of Environmental Quality (VA DEQ) submitted a presentation 75 regarding the CSA. One slide shows how mobile source emission s declined since 2002 ; another slide noted that mobile source emissions are projected to continue to decline b y 2017 with federal and state measures already in place. On one slide VA DEQ claimed that an analy sis of transportation control measures undertaken for the Washington, DC transportation planning estimated that an expenditure of $85 million (annually) would reduce N O x emissions by

only 220 tons per year. EPA does not disagree that highway , mobile source emissions in the Washington DC - MD - VA n onattainment area (under the 1997 ozone standard) could well be 1.5 times those in the 1997 Baltimore ozone nonattainment area. However, mobile source emissions are well contro lled by federal and state programs. Significant reductions can be expected in the coming ye ars. **Population density and degree of urbanizatio n**  EPA evaluated the population and vehicle use characteristics and trends of the area as indicators of the probable location and magnitude of non - point source emissions . These include ozone - creating emissions from on - road and off - road vehicles and engines, consumer products, residential fuel combustion, and consumer services. Areas of dense population or comm ercial development are an indicator of area source and mobile source NO x and VOC emissions that may contribute to ozone formation. Table s 1 8 and 1 9 show the population , land area, population density (in thousands of persons per square mile) , and populatio n growth information for each count y /cit y in the Washington - Baltimore NV CSA . **Table 1**  **8 . Population and Growth in the Baltimore and Washington DC**  **- MD**  **- VA Nonattainment**  **Area Portions of the Washington**  **- Baltimore**  **- NV CSA**  **.** County State Recommended Nonattainment? 2010

Population Land Area

(sq. mi.)* 2010

Population Density (1000 pop/sq mi) Absolute

change in population (2000 - 2010) Population

% change (2000 - 2010) Baltimore MD Nonattainment Area: Anne Arundel Co., MD Yes 537,656 452 1.19 46,325 +9% 75 A copy of which has been placed in the docket.43

Baltimore City, MD Yes 620,961 87 7.14 (27,626) - 4% Carroll Co., MD Yes 167,134 453 0.37 15,557 +10% Harford Co., MD Yes 244,826 460 0.53 25,362 +12% Howard Co., MD Yes 287,085 253 1.13 37,565 +15% Baltimore Co., MD Yes 805,029 624 1.29 49,037 +6% Baltimore Subtotals: 2,662,691 2,330 1.14 146,220 +6% Washington DC - MD - VA Nonattainment Area: District of Columbia, DC Yes 601,723 68 8.86 30,000 +5% Calvert Co., MD Yes 88,737 237 0.37 13,573 +18% Charles Co., MD Yes 146,551 473 0.31 25,347 +21% Frederick Co., MD Yes 233,385 666 0.35 36,884 +19% Montgomery Co., MD Yes 971,777 506 1.92 94,282 +11% Prince George ’ s Co., MD Yes 863,420 493 1.75 60,213 +7% Arlington Co., VA Yes 207,627 26 8.05 18,045 +10% Fairfax Co., VA Yes 1,081,726 406 2.67 106,808 +11% Loudoun Co., VA Yes 312,311 521 0.60 138,440 +80% Prince William Co., VA Yes 402,002 349 1.15 118,206 +42% Alexandria City, VA Yes 139,966 15 9.21 10,626 +8% Fairfax City, VA Yes 22,565 6 3.70 929 +4% Falls Church City, VA Yes 12,332 2 6.17 1,940 +19% Manassas City, VA Yes 37,821 10 3.74 2,466 +7% Manassas Park City, VA Yes 14,273 2 9.52 3,934 +38%

Washington DC - MD - VA Subtotals: 5,136,216 3,779 1.36 661,693 +15% **Table 1**  **9 . Population and Growth**  **in Other Portions of the Washington -**  **Baltimore -**  **NV CSA .**  County State Recommended Nonattainment? 2010

Population Land

Area (sq. mi.)* 2010 Population Density (1000 pop/sq mi) Absolute

change in population (2000 - 2010) Population

% change (2000 - 2010) Fredericksburg, VA Area: Spotsylvania Co., VA No 122,397 412 0.30 30,891 +34% Stafford Co., VA No 128,961 280 0.46 35,437 +38% Fredericksburg City, VA No 24,286 11 2.29 4,922 +25% Fredericksburg, VA Subtotals: 275,644 702 0.39 71,250 +35% Frederick County, VA Area: Frederick Co., VA No 78,305 415 0.19 18,725 +31% Winchester City, VA No 26,203 9 2.82 2,510 +11%

Frederick Co., VA Area Subtotals: 104,508 425 0.25 21,235 +26% Other counties: Queen Anne ’ s Co., MD No 47,798 395 0.12 7,031 +17% St. Mary ’ s Co., MD No 105,151 402 0.26 18,631 +22%44

Culpeper Co., VA No 46,689 382 0.12 12,215 +35% Clarke Co., VA No 14,034 178 0.08 1,333 +10% Fauquier Co., VA No 65,203 651 0.10 9,615 +17% Warren Co., VA No 37,575 216 0.17 6,025 +19% Ham pshire Co., WV No 23,964 644 0.04 3,673 +18% Jefferson Co., WV No 53,498 212 0.25 11,059 +26% All other counties subtotals: 393,912 3,080 0.13 69,582 +21%

CSA Totals: 8,572,971 10,315 0.83 969,980 +13% * Values are rounded to nearest whole number; sub - totals and CSA total may not add - up due to rounding. Sources: U.S. Census Bureau population estimates for 2010 as of August 4, 2011 ( http://factfinder2.census.gov/faces/tableservices/jsf/pages/productview.xhtml?pid=DEC_10_PL_GCTPL2.STO5&prodType =table ). Subsequent to its March 7, 2012 letter Maryland supplied growth data for counties and cities in the CSA. A copy

of this data has been appended to this TSD as Appendix 4. For th e most part Maryland’s data compared 2000 against 2007 or 2009 to compute the population change. These data were from either Maryland’s MD Statistical Handbook or from a Virginia government source s . The exceptio ns were for Fairfax, King George’s and Loudoun Counties in Virginia for which Maryland cited U.S. Census Bureau as the source. For Fauquier County , VA Maryland submitted data posted on - line at “ http://www.fauquiercounty .gov/government/departments/commdev/ index.cfm?action =demographics ” which provided a July

1, 2010 population estimate. The difference s between Maryland’s values for Fairfax, Fred erick (VA) and L oudoun Counties and those in Tables 18 and 19 are apparently revised C ensus Bureau values for 2000. **Table 20. Maryland’s data for four Virginia Counties: County**  **Population Data 2010**  **2000 Change 2000**  **- 2010**  **Percent change, 2000**

**to 2010**  King George ’ s Co. VA 23,584 16,803 6,781 40.4% Fairfax County , VA 1,081,726 969,749 111,977 11.5% Frederick Count y, VA 78,305 59,209 19,096 32.3% Loudoun Not provided Not provided 142,712 84.1% EPA notes Maryland’s submission but is not going to use Maryland’s data for most areas because EPA would like to compare like periods to like periods (2000 to 2010) and use the most recent data (2010). EPA does note Maryland’s data for Fairfax, Frederick (VA) and Loudoun Counties but notes the differences reall y do not change the comparisons: for instance, whether Loudoun County ’s growth rate was 80% or over 84% still makes its growth rate far larger than any other county or city in the CSA. Fairfax County ’s rate is still between 11 and 12 % which is also well above the average growth rate for the entire CSA. Frederick County ’s rate is still well over the CSA average and is essentially unchanged when in relation to other counties as it retains its relat ive ranking in relation to other counties

– that is, it is st i ll ahe a d of Jefferson County , WV and behind Spotsylvania County , VA. For the Fauquier County data, the population given by Maryland is apparently

a July 1, 2010 estimate.45

The following discussion will therefore use the data from Tables 18 and 19 to allow “like to like” comparisons. The 1997 Washington DC - MD - VA nonattainment area contains 59.9% of the Washington - Baltimore NV CSA’s total population and 68.2% of the Washington - Baltimore - NV CSA’s total absolute change in population. The Cities of Fairfax, Falls Church, Manassas and Manassas Park once again have lower absolute populations and change in population but these areas are generall y more densel y populated than the surrounding count y or nearb y counties. The exception is Falls Church City which has a density

less than Arlington Count y on one side (6.17 versus 8.05) but twice as high as Fairfax County (6.17 versus 2.67) on its other side. Some densel y populated cities had low growth r ates less than the area’s overall rate while others such as Falls Church were slightly greater than the area’s overall rate while Manassas Park’s was over twice the area’s overall rate. Of the other portions, those with the highest population densities gr ew at a rate less than the area’s overall rate, and, conversely those with population densities less than the area’s overall average grew more quickly . The fastest growing areas are in Virginia (L oudoun and Prince William Counties) both of which border Fa irfax County which has a monitor violating the 2008 NAAQS. Just over half (55%) of the population live in the areas

– the District of Columbia and Fairfax, Arlington Charles, Prince George’s and Calvert Counties

– that contain one or more monitors violati ng the 2008 NAAQS. Adding in those who live in areas adjacent to these areas with violating monitors (that is the entire 1997 Washington DC - MD - VA nonattainment area less Frederick Count y Maryl and) encompasses 95 percent of the 1997 nonattainment area’s po pulation; Frederick Count y however is adjacent to Carroll County , MD that contains a monitor violating the 2008 NAAQS. The 1997 Baltimore nonattainment area contains 38.1% of the Washington - Baltimore - NV CSA’s total population and 15.1% of the Washington - Ba ltimore - NV CSA’s total absolute change in population. Of the areas in the 1997 Baltimore nonattainment area , Howard and Harford Counties had growth rates appreciably

higher than the area’s overall rate. Carroll County is the least densely

populated area in the nonattainment area and had a growth rate greater than the area’s overall rate. Well over half (63%) the area’s population lives in Harford and Baltimore Counties, and, Baltimore City and thus are in close proximity to the Edgewood monitor with the highest design value in the Washington - Baltimore - NV CSA’s and the 1997 Baltimore nonattainment area. Well over half (64%) the area’s population lives in Howard and Baltimore Counties and Baltimore City , and thus are in close proximity to the monitors in B altimore County . Anne Arundel County is adjacent to the heavil y populated Prince George’s County, MD and Howard County , MD the latter of which had the highest growth rate in the Baltimore nonattainment area and had a growth rate comparable to the faster growing 1997 Washington DC - MD VA nonattainment area. Together the 1997 Washington DC - MD - VA and Baltimore nonattainment areas contain 91.0% of the Washington - Baltimore - NV CSA’s total population and 83.3% of the overall change within the Washington - Baltimore - NV CSA. Most of the areas within these two 1997 nonattainment areas are moderatel y to very densely populated. In general, the counties and cities in the 1997 Baltimore and Washington nonattainment areas likel y sufficiently contribut e to nonattainment at one or more monitors in at least one of these two areas because the County has a violating monitor, because the county or city is adjacent to a count y with a violating monitor or the small city has a population density

comparable to o r higher than surrounding or adjacent areas. Of the other areas or the counties listed under “ other counties ” in the preceding table most are relatively sparsel y populated or remote from areas containing a monitor violating the 2008 NAAQS:46

(1) The Frede rick County , VA Area still contains only 1.2% of the Washington - Baltimore - NV CSA’s population in spite of its growth rate of twice the overall rate in the Washington - Baltimore - NV CSA. This area is remote from any counties with violating monitors and is separated from the 1997 Washington DC - MD - VA nonattainment area by the sparsel y populated Clarke and Warren Counties in Virginia. This area’s total population is less than the absolute population change in Fairfax County , Loudoun Count y or Prince William County in Virginia. (2) Hampshire Count y is remote from an y violating monitor in the Washington - Baltimore - NV CSA and is likewise sparsel y populated. It growth rate is not appreciabl y greater than that of the Washington Baltimore - NV CSA as a whole and its ab solute population change is one - tenth that of Frederick County , MD which has a similar land area and growth rate. (3) Clarke and Warren Counties in Virginia are sparsel y populated and their absolute change in population is small in comparison to areas with in the 1997 Washington DC - MD - VA nonattainment area. Clarke County

has a population that is less than all other areas in the Washington - Baltimore - NV CSA except the very

small Falls Church City . (4) Queen Anne’s County MD has a growth rate nearl y three ti mes that of the 1997 Baltimore nonattainment area but both the absolute change and the absolute population are small. It is still sparsel y populated. (5) Jefferson Count y, WV had a growth rate twice the overall rate in the Washington - Baltimore - NV CSA. It is still sparsely

populated and is not adjacent to a count y containing a monitor violating the 2008 NAAQS. In addition , Jefferson County ’s total popu lation is half the absolute population change in the adjacent Loudoun County , VA. (6) Fauquier Count y, VA had a growth rate comparable to that of the 1997 Washington DC - MD - VA nonattainment area (17% versus 15%) but its absolute change was small

– around 9, 600 which is one one - hundredth of the Washington - Baltimore - NV CSA’s overall change or 1.5% of that for the 1997 Washington DC - MD - VA nonattainment area. Fauquier County is still sparely

populated and is not adjacent to a count y containing a monitor violati ng the 2008 NAAQS. ( 7 ) The situation for Culpeper Count y, VA is similar to that for Fauquier County , VA. Culpeper had a growth rate of 35 percent. Inaddition , it is still sparel y populated and has a smaller population than Fauquier Count y. However, Cu lpeper Count y is even more remote from any count y containing a monitor violating the 2008 NAAQS.

. (8) St. Mary ’ s County , MD is the most populous and most densely populated of the “other counties.” Even so, its total population is less than the absolute population change in Fairfax County , Loudoun County or Prince William County in Virginia. St. Mary ’ s County is less densely

populated than any county or city in either the Washington DC - MD - VA or Baltimore nonattainment areas. It s absolute population is greater than Calvert County , MD which is smaller in size. St. Mary ’ s County is adjacent to Calvert County

which does contain a monitor violating the 2008 NAAQS. (9 ) The Fredericksburg, VA Area had not insubstantial growth. Its individual jurisdict ions grew at a rate from about two to three times faster than the Washington - Baltimore - NV CSA’s overall rate and overall at a rate twice that of the 1997 Washington DC - MD - VA nonattainment area. In terms of land area and population density

it is somewhat c omparable to Frederick Count y, MD , but it had an absolute change in population almost twice Frederick County. Unlike Fredrick Count y, MD, the Fredericksburg, VA Area is not adjacent to an y county with a monitor violating the 2008 NAAQS.47



### Traffic and comm **uting patterns** EPA evaluated the commuting patterns of residents in the area, as well as the total Vehicle Miles Traveled (VMT) for each county . In combination with the population/ population density

data and the location of main transportation arteries (s ee Figure 1 a or 1b above) ; this information helps identify the probable location of non - point source emissions. A county with high VMT and/or a high numb er of commuters is generally

an integral part of an urban area and indicates the presence of motor vehicle emissions that may

contribute to ozone formation. Table 20 shows the total vehicle miles traveled (VMT) and total number of commuters for each county within the Washington - Baltimore - NV CSA . **Table 21**  **. Traffic and Commuting Patterns .**  County State Recommended Nonattainment? 2008 VMT (million miles) Total

Commuters Baltimore MD Nonattainment Area: Anne Arundel Co., MD Yes 5,759 255,425 Baltimore City, MD Yes 3,619 249,125 Carroll Co., MD Yes 1,272 77,394 Harford Co., MD Yes 2,324 111,398 Howard Co., MD Yes 3,793 134,596 Baltimore Co., MD Yes 8,227 373,013 Baltimore Subtotals: 24,994 1,200,951 Washington DC - MD - VA Nonattainment Area: District of Columbia, DC Yes 3,685 260,296 Calvert Co., MD Yes 764 37,355 Charles Co., MD Yes 1,260 61,504 Frederick Co., MD Yes 2,932 102,033 Montgomery Co., MD Yes 7,443 454,680 Prince George ’ s Co., MD Yes 8,718 396,948 Arlington Co., VA Yes 1,634 115,614 Fairfax Co., VA Yes 10,484 526,655 Loudoun Co., VA Yes 1,567 92,040 Prince William Co., VA Yes 3,094 150,274 Alexandria City, VA Yes 793 76,811 Fairfax City, VA Yes 177 11,753 Falls Church City, VA Yes 62 5,803 Manassas City, VA Yes 290 18,077 Manassas Park City, VA Yes 27 5,415

Washington DC - MD - VA Subtotals: 42,929 2,315,258 Fredericksburg, VA Area: Spotsylvania Co., VA No 1,256 45,132 Stafford Co., VA No 1,698 48,202 Fredericksburg City, VA No 363 9,564

Fredericksburg, VA Subtotals: 3,317 102,898 Frederick Co unty, VA Area:48

Frederick Co., VA No 542 30,167 Winchester City, VA No 135 11,865

Frederick Co., VA Area Subtotals: 677 42,032 Other counties: Queen Anne ’ s Co., MD No 923 20,736 St. Mary ’ s Co., MD No 822 43,101 Clarke Co., VA No 300 6,438 Culpeper Co., VA No 520 15,951 Fauquier Co., VA No 1,055 28,103 Warren Co., VA No 435 15,286 Ham pshire Co., WV No 216 8,255 Jefferson Co., WV No 388 20,937 All other counties subtotals: 4,659 158,807 CSA Totals: 76,576 3,819,946 * MOBILE model VMTs are those inputs into the NEI version 1.5. ** U.S. Census Bureau estimates for 2000 County - to - County Worker Flow http://www.census.gov/hhes/commuting/data/commuting.html . Together the 1997 Washington DC - MD - VA and Baltimore nonattainment areas contain 88.7 percent of total VMT and 92 percent of the total commuters within the Washington - Baltimore - NV CSA. As stated pre viousl y in this document, EPA recommended examining CSA/CBSAs because certain factors used to establish CSAs and CBSAs are similar to the factors EPA is using in this technical anal ys is to determine if a nearby area is contributing to a violation of the 20 08 ozone NAAQS. These similar factors include degree of urbanization which is used to define a “central county (or counties)” in a CBSA and certain employ ment related commuting indices which are used to join “outlying counties” to “central county

(or counties)” to form a CBSA. One or more CBSAs are alway s joined if the “employ ment interchange rate” 76 is 25 percent and may be joined to form a CSA if the “employ ment interchange rate” is at least 15 percent between these two CBSAs. 77 Therefore, there is so me degree of urbanization and commuting within the CBSAs comprising the Washington - Baltimore - NV CSA and some degree of commuting between CBSAs within this CSA. However, when a county’s number of commuters or VMT are a significant fraction of another county’s, such a county cannot indicate the presence of as much motor vehicle emissions that may contribute to ozone formation as the county with the higher VMT or number of commuters. The 1997 Washington DC - MD - VA nonattainment area contains 56.1% of the total VMT and 60.6% of total commuters within the Washington - Baltimore - NV CSA. There is a vast disparity in the absolute VMT values within the 1997 Washington DC - MD - VA nonattainment area: excluding such ph ys ically small areas as the Cities of Fairfax, Falls Church, Manassas and Manassas Park, the VMT of Fairfax County , VA is over 13 times that of Calvert County , MD. The top three in terms of absolute VMT are 76 The “employment interchange rate” between two areas is defined as the sum of the percentage of employed residents of the area with the smaller total population who work in the area with the larger total pop ulation and the percentage of employment in the area with the smaller total population that is accounted for by workers residing in the area with the larger total population. See, 64 FR 56628 at 56643, October 20, 1999 . 77 See “ Section 8. Combining Adjac ent Core Based Statistical Areas ,” 65 FR 82228 at 82237, December 27, 2000. These current standards came into use starting 2003 (65 FR 82228 at 82235 - 82236) and will be replaced in 2013 w hen the 2010 standards come into force (75 FR 37246 at 37249 , June 2 8, 2010) .49

Fairfax County , VA and Montgomery and Prince George’s Counties in Maryland. Together they comprise 26,6 44 million (62%) of 42,929 million VMT for the 1997 Washington DC - MD - VA nonattainment area. Together they contain or enclose all the violating monitors within the 1997 Washington DC - MD - VA nonattainment area except that in Calvert County , MD. The next thr ee areas in terms of VMT are the District of Columbia, Prince William County , VA and Frederick County , MD which comprise 9,711 million (22.6%) of 42,929 million VMT for this 1997 nonattainment area. Filling out 95 percent of the VMT in the 1997 Washington DC - MD - VA nonattainment area are the combined VMT of Loudoun and Arlington Counties in Virginia and Charles Count y, MD with 4,461 million (10.4%) of 42,929 million. With respect to the Cities of Alexandria, Fairfax and Falls Church, these are a ll adjacent to an area that contains a violating monitor. With respect to the Cities of Manassas and Manassas Park, these two cities under this factor might or might not sufficiently contribute to nonattainment within the Washington - Baltimore - NV CSA but s hould be included in a nonattainment area if the surrounding county of Prince William County is. As far as VMT is concerned, Calvert County is on the edge of the Washington - Baltimore - NV CSA and has the lowest VMT of an y area within the 1997 Washington DC - MD - VA nonattainment area exclusive of the smaller independent cities in Virginia. Calvert County is adjacent to two counties (Prince George’s and Anne Arundel) in Maryland containing a violating monitor. The 1997 Baltimore nonattainment area contains 32. 6% of the Washington - Baltimore - NV CSA’s total VMT and 31.4% of the Washington - Baltimore - NV CSA’s total commuters. Of the areas in the 1997 Baltimore nonattainment area , all except Baltimore City and Howard contain a violating monitor. Baltimore and Anne Arundel Counties rank one and two for total VMT and for total number of commuters within the 1997 Baltimore nonattainment area. Carroll County has the lowest VMT and number of commuters within the 1997 Baltimore nonattainment area . As far as absolute VMT , the ratio of the highest to the smallest value is about 6.5 to 1 . Carroll and Harford Counties are at the bottom. Carroll County ’s VMT comprises about 5% of 1997 Baltimore nonattainment area’s VMT. Harford County likely contributes to the ozone violat ion at the two monitors located within Harford Count y . B ecause these monitors were located to be downwind of the main urbanized core surrounding Baltimore City , Harford County

might not be a contributor to violations at other monitors in the Washington Ba ltimore - NV CSA but rather more a receptor of ozone and precursor emissions from within the Washington - Baltimore - NV CSA. In general, the counties and cities in the 1997 Baltimore and Washington nonattainment areas likely sufficiently

contribute to nonattainment at one or more monitors in at least one of these two areas because in most cases commuting patterns and VMT favor inclusion and most are adjacent to a county cont aining a violating monitor . Of the other areas or counties listed under “ O ther counties” in the preceding table, all but one has less than 1,000 million VMT . Together these eight “other” counties comprise 6.1 percent of the Washington - Baltimore - NV CSA’s total VMT and comprise 4.2 percent of the Washington - Baltimore NV CSA’s total commuters . Of these “ O ther counties,” St. Mary ’s and Queen Anne’s in Maryland , and Fauquier in Virginia , comprise most of the VMT and total commuters of the se eight “other” counties. Table 13 shows the share (as a percentage of the Washington - Baltimore - NV CSA’s total) of Fauquier, Queen Anne’s, and St. Mary ’s Counties of the VMT and total commuters and compares these three with the remaining five “ O ther” counties: **Table 22**  **. Traffic and Commuting Patterns**  **– Fauquier, Queen Anne’s and St. Mary’s Counties as**  **a Percentage of CSA Totals .** 50

County , State 2008 VMT

( % of CSA total) Number

commuting to any violating counties (% of CSA total) Total Commuters

(% of CSA total) Fauquier Co., VA 1.4% 0.3% 1.1% St. Mary ’s Co., MD 1.1% 0.3% 1.1% Queen Anne’s Co., MD 1.2% 0.3% 0.5%

Subtotal: 3.7% 0.9% 2.8% Subt otal for Clarke, Culpeper, & Warren Counties, VA and Hampshire & Jefferson Counties, WV 2.4% 0.4% 1.4% Total eight “other” counties 6.1% 1.3% 4.2% Share of Fauquier, Queen Anne’s, and St. Mary ’s Counties 60.1% 72.1% 67.3% (1) The Frederick County , VA Area contains less than 1 percent of the Washington - Baltimore - NV CSA ’s VMT or those “commuting to or within any violating counties.” The area’s VMT (677 million) is less than any

other area within the 1997 Washington nonattainment area (independent cities excepted). The total number of commuters is 1.1 percent of the tot al number of commuters in the Washington - Baltimore - NV CSA . This area is remote from an y counties with violating monitors and is separated from the 1997 Washington DC - MD - VA nonattainment area by Clarke and Warren Counties in Virginia. (2) Hampshire Count y is remote from an y violating monitor in the Washington - Baltimore - NV CSA and likewise has low VMT (216 million). The VMT is less than all but the three smallest independent cities in the 1997 Washington nonattainment area. (3) Clarke and Warren Counti es in Virginia have low VMT which is only greater than some of the small independent cities of comparable population (Manassas Park City and Manassas City , respectivel y) in the Washington - Baltimore - NV CSA . (4) Queen Anne’s County MD has 20,576 total commuters which is less than one - third the number of the next lowest county

( Carroll County with 77,394 ) in the Baltimore - Towson, MD CBSA but only one half percent (0.5%) of the Washington - Baltimore - NV CSA’s total or 1.7 percent of the total for the 1997 Baltimore nonattainment area. Queen Anne’s County is only connected to the rest of the CBSA by the Chesapeake Bay

Bridge (U.S. Routes 50 and 301) across the Chesapeake Bay to Anne Arundel County (see Figure 1 a or 1b which shows a road crossing the Chesap eake Bay from Queen Anne’s to Anne Arundel). Queen Anne’s has 923 million VMT (1.2% of the Washington - Baltimore - NV CSA’s total or 3.7% of the 1997 Baltimore nonattainment area) which is comparable to that of Carroll County ((1,272 million) even though Qu een Anne’s population is roughl y one third of Carroll’s (47,798 versus 167,134).51

(5) Jefferson Count y, WV has low VMT (388 million) which is only greater than some of the small independent cities of comparable population (Manassas Park City and Manassas City

combined) . Jefferson County

is not adjacent to a count y containing a monitor violating the 2008 NAAQS. (6) Fauquier Count y, VA has the most VMT of these “other counties” at 1,055 million (1.4% of the Washington - Baltimore - NV CSA’s total or 2.5% of the total for the 1997 Washington - DC - MD - VA nonattainment area) . Fauquier is comparable to Charles County , MD (1,260 million) which has twice the population (146,551 versus 65,203) but is greater than that of Calvert County , MD (764 million VMT) , which has a slightly greater population. Fauquier County has fewer commuters than either Charles or Calvert Counties. Fauquier County is separated from the nearest counties with violating monitors by

L oudoun and Prince William Counties in Virginia. (7) The situ ation for Culpeper Count y, VA is similar to that for War r en County , VA. It s VMT is slightly greater at 520 million (versus 435) than Warren’s . The number s of commuters are similar, at 15, 951 versus 15,286 , respectivel y. However, Culpeper Count y is even more remote from any county containing a monitor violating the 2008 NAAQS. Culpeper County is separated from the nearest counties with violating monitors by Fauquier, Loudoun and Prince William Counties in Virginia.

. (8) St. Mary ’ s County , MD has a VMT of 822 million (1.1% of the Washington - Baltimore - NV CSA’s total or 1.9% of the total for the 1997 Washington - DC - MD - VA nonattainment area). This is more than Calvert County , MD. The total number of commuters at 43,101 (1.1% of the W ashington - Baltimore NV CSA’s total or 1.9% of the total for the 1997 Washington - DC - MD - VA nonattainment area) is between that of Calvert and Charles Counties , which is not surprising because St. Mary ’s population falls between that of these other two. St. Mary ’s comprises the CBSA of the Lexington Park MD micropolitan statistical area , whereas Charles County is part of the 1997 Washington DC - MD - VA nonattainment area ; the 1997 Washington DC - MD - VA nonattainment area is within a different CBSA

– the Washington - Arlington - Alexandria, DC - VA - MD - WV Metropolitan Statistical Area

– than St. Mary ’s . Because St. Mary’s Count y is in a separate CBSA from the 1997 Washington DC - MD - VA nonattainment area, that is, is not part of the Washington - Arlington - Alexandria, DC - VA - MD - WV Metropolitan Statistical Area, one can infer that the degree of integration between St. Mary ’s County and the 1997 Washington DC - MD - VA nonattainment area is likel y less than that of either Charles or Calvert County . St. Mary ’ s Count y is adjacent to C alvert County which does contain a monitor violating the 2008 NAAQS. (9) The Fredericksburg, VA Area as a whole has 3,317 million VMT which is 4.3% of the Washington Baltimore - NV CSA’s total or 7.7% of the total for the 1997 Washington - DC - MD - VA nonattainment area. The total number of commuters is 22,124 ; this is 2.7 percent of the Washington - Baltimore - NV CSA’s total or 4.4 percent of the total for the 1997 Washington - DC - MD - VA nonattainment area. The total VMT and total number of commuters for the Fredericksburg, VA Area are comparable to that of Prince William County , VA. Unlike Prince William County , VA , the Fredericksburg, VA Area is not adjacent to an y count y with a monitor violating the 2008 NAAQS. The Fredericksburg, VA Area is within the Washingt on - Arlington - Alexandria, DC - VA - MD - WV Metropolitan Statistical Area which contains the 1997 Washington DC - MD - VA nonattainment area. Of the three jurisdictions within the Fredericksburg, VA Area, Stafford County has the largest VMT and total number of commuters. **With Regards to Counties in the CSA and Mobile Source Emissions:** C ounties included as part of an y CSA indicates ties to the core urban area. As discussed under “ Core Cities/Counties in this CSA ” elsewhere in this document , inclusion in a CBSA or combination of two or more CBSAs indicate s commuting linkages above various thresholds.52

Just because a count y is located in a CSA , this fact does not fully reflect the amount of VMT and hence emissions commuting puts within any pa rticular counties of a CSA. The obvious factors are: whether or not the county

or cit y i s a core city

or count y within its parent CBSA or is an outlying count y or city of a CBSA; its proximity to the core count y/ counties of its parent CBSA; its proximity to core counties and cities of an adjacent CBSA , and so on. The Washington - Baltimore - NV CSA consists of: the Baltimore - Towson CBSA; the Culpeper, VA Micropolitan Statistical Area (Culpeper CBSA); the Lexington Park MD (St. Mary ’s Count y), Micropolitan Statistical Area (Lexington Park CBSA); the Washington - Arlington - Alexandria, DC - VA MD - WV Metropolitan Statistical Area (Washington CBSA); and the Winchester, VA - WV Metropolitan Statistical Area (Winchester CBSA). Anne Arundel and Prince George’s Countie s are core counties (see “ Core Cities/Counties in this CSA” elsewhere in this document) of their respective “parent” CBSAs

– the Baltimore - Towson CBSA and the Washington CBSA. They are adjacent to each other. EPA does not doubt that there is cross - commut ing between the two. Likewise, as Maryland noted, Washington Beltway facilitates travel in the Washington CBSA; this roadway as well as other such as Interstate - 95 and its offshoots facilitate commuting among the core counties/cities of the Washington CBS A such as the District of Columbia, Fairfax Co., VA, and Montgomery and Prince George’s Counties in Maryland. Conversel y, Hampshire County, WV is an outlying count y in the Winchester CBSA. The Winchester CBSA is part of the Washington - Baltimore - NV CSA. For the Winchester CBSA to be part of the CSA, the percentage of workers in the Winchester CBSA commute to the Washington CBSA plus of the percentage of the emplo yment in the Winchester CBSA is of residents from the Washington CBSA that is at least 15 percent but might be at least 25 percent. 78 By virtue of its status as an outlying count y, one knows at least 25 percent of the employ ment in Hampshire is from residents of Winchester City and Frederick Count y, VA or 15 percent of the commuters in Hampshire County reside in Virginia. That the Winchester CBSA is part of the Washington - Baltimore - NV CSA onl y means there is employment related commuting interchange between it and the larger Washington CBSA. Warren and Clarke Counties in Virginia are outlying counties in the Washington CBSA and adjacent to the Winchester CBSA (namel y Frederick County , VA). Itwould seem that the commuting ties among these counties alone could tie the Winchester area to the Washington CBSA and hence to the greater Washington Baltimore - NV CSA. Likewise, Warren and Clarke Counties in Virginia are each an outlying county in the Washington CBSA. This means at least 25 percent of those workers of either work in the central counties and cities of the Washin gton CBSA or 25 percent of the employ ment in either is from persons from the central counties and cities: the nearest central county to Clarke County

is the adjacent L oudoun Count y; in the case of Warren Count y the nearest adjacent central county is Prince William with part of the outlying county of Fauquier in between; however, Interstate 66 runs through Warren County into Prince William County and to Fairfax County

and no doubt facilitates commuting. The CSA delineation does not necessaril y connote on - r oad vehicular travel , only the interchange of employ ment. Thus, a portion of the commuting within some of the CBSAs or between CBSAs constituting the Washington - Baltimore - NV CSA could be b y rail using the various subway and light rail sy stems within the C SA.

78 Refer to OMB’s December 27, 2000 (65 FR 82228), Notice of decision “Standards for Defining Metropolitan and Micropolitan Statistical Areas” for how OMB determines CBSAs and CSAs and refer to the discussion under the heading “ The Composition o f the Washington - Baltimore - Northern Virginia, DC - MD - VA - WV CSA ” elsewhere in this document.53

EPA recommended starting the boundary determination process at the boundaries of a CSA/CBSA because the factors used to establish the CBSAs and CSAs are similar to some of the factors EPA considers in determining whether a nearb y area is contributing t o the violation(s) of the standard. But EPA determines whether an area is contributing to the violation(s) of the standard at a nearby monitor only after consideration of all five factors. Conversely , EPA believes the fact that a count y or city is not in a CBSA/CSA is noteworthy because the level of employ ment interchange and hence commuting is usually less than the criteria levels used by OMB. 

### Factor **3 : Meteorology (weather/transport patterns)**  Background: EPA received comments that s urface wind roses are not the best technical tool to assess prevailing winds because surface wind roses do not represent the three - dimensional flow of air in the atmosphere; transport patterns based solely on surface wind speed and direction ignores aloft winds and regular vertical mixing such as occurs dail y; three - dimensional wind fields provide a more realistic presentation of the origins of air during ozone exceedance day s. 79 As a result of such comments, EPA re - evaluated the five - factors for this CSA in light of meteorology data resulting from use of the National Oceanic and Atmospheric Administration’s (NOAA) Hy brid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model for this Factor 3 Meteorology portion of this document. 80 This analy sis supplements and to a great extent supplants the Factor 3 anal ys is in “ Technical Anal ys is for the Washington, DC MD - VA and Bal timore Areas 81 ” by improving EPA’s understanding of prevailing winds . To allow consideration of air movement above the surface layer , we ran the HYSPLIT model to obtain trajectories for three heights

– 100 meters, 500 meters and 1,000 meters. We ran the HYSPLIT to obtain 1,000 meter runs in order to better understand aloft movement of air that can be expected to mix down as the night - time inversion breaks - up. Due to the number of monitors and exceedance day s EPA did not (and could not due to time constr aints) run trajectories for each exceedance day at each monitor in the CSA. To narrow down the level of effort, EPA examined the air quality data (Factor 1) in more detail. We examined the 2006 to 2010 8 - hour ozone concentrations for the monitors in the “violating center” 82 of the CSA and grouped the data b y da ys when the 2008 ozone NAAQS was exceeded. When selecting monitors for which to run the HYSPLIT model EPA had to consider the density of the monitoring network, the need to decide whether to desi gnate all or a substantial portion of this CSA as one nonattainment area or split the CSA into more than one nonattainment area, and the need to develop a conceptual model of the relationship between meteorology (wind directions on exceedance day s) and ozo ne concentrations within the CSA in light of Maryland’s (and other parties’) comments on meteorology , and comments noting that the “tracking” of the design value for the 1997 Washington DC MD - VA nonattainment area b y the Davidsonville monitor in Anne Arund el County indicates there should be only

one nonattainment area within the CSA . 79 For example, refer to documents EPA - HQ - OAR - 2008 - 0476 - 0405 and EPA - HQ - OAR - 2008 - 0476 - 0456. 80 “ Preliminary Technical Support Document, December 2011, entitled, Maryland Area Designations for the 2008 Ozone National Ambient Air Quality Standards, prepared by the Region 3 USEPA ” document number EPA - HQ - OAR - 2008 - 0476 - 0235 in the docket for this action. 81 Refer to in d ocket item numbers EPA - HQ - OAR - 2008 - 0476 - 0235, EP A - HQ - OAR - 2008 - 0476 - 0405 and EPA - HQ - OAR 2008 - 0476 - 0456 in the docket for this action. 82 Basically all monitors in the CSA were considered except the monitor in Frederick County, VA.54

Normally when we are developing a conceptual model understanding of what yields ozone exceedances in an area we will evaluate 5 to 10 years worth of meteorological data. In s ome areas where the meteorology

is well known, where the design value monitor statistically dominates the data in terms of design value and number of exceedances , or where there is onl y one violating monitor in the area, we might need to examine the wind p atterns on day s the 0.075 ppm standard was exceeded at that violating monitor. However, in the case of the Washington - Baltimore - NV CSA, there we re several determinations to be made or factors to consider: F irst EPA had to determin e whether the CSA should contain one nonattainment area enclosing all the violating monitors within the CSA as recommended by two States or be split into two n onattainment area s (and some attainment areas) as recommended by two States . S econd, the patterns of exceeding monitors on exceedance days shows that parts of the area might be exceeding on certain day s while other parts not recording exceedances on the same days . Third , especially high values can occur at different monitors . F ourth, on multi - episode day s portions of the area record exceedances or especially high values on some day s while other parts record exceedances or especially high values on other days of the same episode . There is also the need to examine ozone concentration gradients and the need to correlate concentration levels across the CSA with model predicted wind directions . These determinations and factors would support performance of a more extensive meteorology analysis than most areas in the country . **In past designations, EPA has rarely considered this level of detail for every designation decision, but**  **to reiterate, the decisions for this CSA are not typical due to: the State submitted information regarding meteorology and its effects on the Edgewood monitor**  **and the differing rec**  **ommendations of**  **two States seeking a single nonattainment area for the CSA and another two States**  **seeking retention of the 1997 Washington DC**  **- MD**  **- VA nonattainment boundaries.**  About HYSPLIT generally: We used the National Oceanic and Atmospheric Administration Hy brid Single Particle Lagrangian Integrated Trajectory

Model (NOAA HYSPLIT or just “HYSPLIT”) to develop a conceptual model of the meteorological transport conditions within the regional area within and around the CSA. We evaluated 24 - hour back tra jectories for the 2006 - 2010 time period using the NOAA HYSPLIT model. We evaluated trajectories for 100, 500 and 1000 meter heights to gain an understanding of where air may “mix down” as the nighttime inversion breaks - up. Several factors need to be kep t in mind: HYSPLIT back - trajectories are depicted as a relatively thin line, which can be taken to represent the center of an air parcel of some width. An area traversed by the line is considered traversed by the air parcel. HYSPLIT back - trajectories used in ozone designations are based upon meteorological fields at a 40 km (about 24.8 miles) resolution. HYSPLIT back - trajectories are produced at various end heights to capture the behavior of air parcels at various heights within the mix ed layer of the atmosphere. Lower - level trajectories may be affected by terrain. HYSPLIT back - trajectories end at the monitoring site in question; therefore, if one starts at the monitor the further a point is on the curve is away from the monitor (the en d point) , the location of the air mass is further back in time. Selection of Monitors: We aimed to develop an understanding of what wind patterns were conducive to ozone formation throughout the area. However, to develop three (100, 500 & 1000 m) back trajectories for every exceedance day

for every monitor would produce hundreds of results that might not materiall y provide more information than a fewer number. Clearly , data for the Edgewood monitor in Harford Count y, MD55

is critical because this monitor has the highest design value of any monitor in the CSA and by far experiences more exceedance day s. The Franconia monitor in Fairfax County , VA is also important because it is the current design value monitor in the Washington DC - MD - VA n onattainment area and is the violating monitor furthest from the Edgewood monitor. (Franconia is in the far southwest of the CSA, and, Edgewood is in the far northeast.) However, the Franconia monit or did not have as man y ex ceedance day s as several other monitors in th e southwest , being surpassed b y the McMillan Reservoir monitor in the District of Columbia and the Arlington monitor in Arlington County , VA. See Table s 6, 7 and 8 elsewhere in this document . For this reason , the Arlington and McMillan Reservoir monitors were also considered. The Davidsonville monitor in Anne Arundel County was selected based upon its design value history (at times equal to that in the current Washington DC - MD - VA Nonattainment area ), number of “especially high” exceedances over the 2006 to 2010 period and its location close to the border of the two nonattainment areas designated under the 1997 ozone NAAQS . Initiall y, the Howard U

—Beltsville monitor was likewise selected over the monitor at Prince George’s Equestrian Center because Howard U

—Beltsville monitor is closer to the border of the two nonattainment areas designated under the 1997 ozone NAAQS , currentl y has a higher design value and has recorded more exceedance day s over the 2006 - 2010 period. By using the data for the Davidsonvi lle and Howard U

—Beltsville monitors EPA could correlate the ground level ozone concentrations with the back - trajectory

results to gain an understanding of air movement patterns and measured ozone values in that portion of the two current n onattainment area ’s common border. Finally , HYSPLIT back - trajectories for certain other monitors were considered when necessary to gain an understanding of wind directions on those day s for which the main monitors did not exceed the 2008 ozone NAAQS. For other mo nitors, we examined the back - trajectories for some monitors as surrogate s for other close monitors. For example, the McMillan, Arlington and Fairfax monitors are close to the Takoma and River Terrace monitors in the District. Therefore, on day s for which we had back trajectories for one or more of the three former monitors we inferred that these represented the prevailing winds at the other two monitors in the District. L ikewise, comparing the trajectories available for an episode day , we could gain an o verall sense of the prevailing winds for that day . For 2006 and 2007, certain other monitors were examined as well. These were certain days for outlying monitors such as those in Carroll (South Carroll), Calvert (Calvert Co.) and Charles (Southern Maryland) Counties in Maryland and Stafford County (Widewater) in Virginia. Grouping: EPA categorized the back - trajectory results into roughl y five quintiles b y the concentration measured at the monitor. The concentration ranges for these “quintiles” were based upon the results of the analy sis for the Edgewood monitor. Refer to Table 10 e lsewhere in this document for the ranges of each “Group.” Some General Observations: Review of the HYSPLIT predicted trajectories actually occurred in two batches. Our first review looked at the 2008 - 2010 predictions. Our second review considered the 2007 and 2008 predictions. Our evaluation considered all the 2006 to 2010 predicted back - trajectories. The back - trajectories for different monitors suggest that 2006 and 2007 featured more episodes featuring southerly or southwesterl y winds than 200 8 and 2010 (2009 had so few episodes no general conclusion would seem warranted). Even so, 2006 to 2010 contained a considerable number of exceedance day s featuring56

winds from the northeast, north and northwest which corresponded to higher concentrations (say in Group 4 or higher

– that is, over 0.087 ppm) or “especiall y high” concentrations (that is, 0.095 ppm --- see under Factor 1 under “ Severit y of Episodes ” and Table 12 elsewhere in this document) recorded at the Edgewood monitor . Sample Results: Figures on the following pages provide examples of the HYSPLIT results. An electronic cop y of all the HYSPLIT results has been placed in the docket for this action due to the voluminous nature of all the outputs (1807 single pages in Adobe ® Acrobat ® 83 port able data file (PDF) format which when zipped are over 50 megab yt es in size). Figures 4 a through 4 d show sample 100 , 500 and 1000 meter Results for the Edgewood Monitor for July 6, 2010 . Figures 5a through 5d show sample 100 , 500 and 1000 meter Results for the Edgewood Monitor for August 10 , 2010 .

83 Trademarks of Adobe Systems Incorporated .57

**Figure 4a**  **All Levels**  **– 100, 500, 1000 meters** 58

**Figure 4 b**  **-- 100 Meters (Above)**  **Figure 4 c**  **– 500 meters**  **(above)**

**Figure 4d .**  **1000 meter Results (above)** 59

**Figure 5a.**  **All Levels**  **– 100, 500 and 1000 meters** 60 **Figure 5 b 100**  **meters (above)**  **Figure 4 c 500 meters (above)**  **F**

**Figure 5**  **d 1000 meter Results (Above)** 61 

### Analyses: **1. Does the current Washington DC -**  **MD -**  **VA Nonattainment area**  **contribute to nonattainment in the current Baltimore MD**  **Nonattainment area**  **?** For the 2008 to 2010 time period, the HYSPLIT trajectories support the conclusion that the Edgewood monitor is downwind of the 1997 Washington DC - MD - VA Nonattainment area . The trajectories for just the 100 and 500 meter heights suggest the Edgewood monitor is downwind of the 1997 Washington DC - MD - VA Nonattainment area on the following day s when the Edgewood monitor exceeded 0.075 ppm: **Table 23**  **.** Day s by

Year the Edgewood Monitor is Downwind of the 1997 Washington DC - MD VA Nonattainment area : YEAR Trajectory

Height 2008 2009 2010 100 meters 6/7, 6/13 - 14, 7/3,

7/12, 7/29, & 9/4 6/26, 7/15 - 7/16, 8/16

& 8/18 5/21, 6/22, 6/26 - 6/27,

7/3 - 7/4, 7/16, 7/23, 8/9, 8/29, 9/1 - 9/2, 9/24 500 meters 4/19, 6/13; 7/3, 7/18,

7/29, & 9/4 7/15 6/22, 6/26 - 6/27, 7/16, 7/23, 7/31, 8/9, 9/1, 9/2 & 9/24. The air at 100 and 500 meters height are likel y the first to mix when the night - time inversion breaks up. These day s represent 25 of the 51 2008 - 2010 exceedance day s for the 100 meter height and 17 of 51 day s for the 500 meter height. The HYSPLIT back - trajectories indicate that many other areas are also upwind of this monitor on many day s. On some day s the winds come from the east or northeast. On other day s the winds come from the south but the trajectory

does n ot cross the core of the Washington CBSA 84 but does cross outlying counties (such as Calvert or Charles) of the 1997 Washington DC - MD - VA nonattainment area. Likewise, on some day s when the predicted directions are from the northwest, the trajectories might only cross an outlying Frederick Count y, MD and not the core of the Washington CBSA. When the predicted winds are from the west, northwest, southwest and south - southwest, the trajectories almost alway s cross the core of the Baltimore nonattainment area. 85 Figures 5 A - 1 to 5 A - 10 86 of Appendix 5 “ Appendix 5: HYSPLIT Trajectories for Edgewood b y Group and Exceedance Day s Over 0.100 ppm ” show the HYSPLIT results overlaid on a map. They are 84 Refer to “ The Com

position of the Washington - Baltimore -Northern Virginia, DC - MD - VA - WV CSA” elsewhere in this document. 85 The Baltimore - Tow son CBSA and Baltimore nonattainment area share the same “core” as discussed in “ The Composition of the Washington - Baltimore - Northe rn Virginia, DC - MD - VA - WV CSA” elsewhere in this document. 86 The following nomenclature is used for the figures in the appendices to this document: The first number is the appendix number, the “A” indicates that the figure is in an appendix, and the number after the hyphen is the figure number within that appendix. Thus Figure 5A - 1 refers to the first figure in Appendix 5 of this document.62

grouped b y the “Groups” defined in Table 10 elsewhere in this document. For each “Group” there is a map for 2008 to 2010 exceedance day s and one for 2006 to 2007 exceedance day s. Analy sis of the full set of data for the Edgewood monitor counted the back - trajectory for each altitude for each day . Thus each exceedance day would contribute three to the aggregate sum . The trajectories were placed in one of three exclusive categories: “Not any part of the Washington CBSA,” “Onl y the Charles, Frederick or Calvert Counties portion of the Washington CBSA” or the “ Washington CBS A except Calvert/Charles/Frederick Counties in MD .” A trajectory was counted under the “Not an y part of the Washington CBSA” only when the trajectory

never crossed an y area in the. A trajectory was counted under the “Onl y the Charles, Frederick (MD) or Ca lvert Counties portion of the Washington CBSA” if the only portion of the CBSA it crossed was in Charles, Frederick and/or Calvert counties. Likewise if the trajectory

crossed any

where in the Washington CBSA it was counted under the “ Washington CBSA except Calvert/Charles/Frederick Counties in MD” unless it only crossed Charles, Frederick (MD) or Calvert Counties. The gross results of this analy sis are found in Table 24 : **Table 24**  **. Trajectory Counts for Edgewood Monitor:** Geographic area Number of Trajectories Counted 87 Percent of Total Not Washington CBSA 126 46.32% Only Frederick (MD), Calvert, and/or Charles Co. of 1997 Washington DC - MD - VA nonattainment area 56 20.59% Washington CBSA except Calvert/Charles/Frederick Counties in MD 90 33.09% 272 EPA does agree that air masses arriving at the Edgewood monitor on exceedance days can arrive from the West - Northwest, from the Northwest, from the Southwest and even from the North and Northeast as well as day s where the air mass stayed locall y – essentia lly circulated within the CSA boundaries

– for a 24 - hour period. EPA acknowledges that there are exceedance day s when the Edgewood monitor records concentrations of 0.087 ppm and higher (as well as day s when the concentration is less than 0.087 ppm) and the air masses came to Edgewood via the core CBSA counties and cities of the Washington CBSA and the southern outer counties/CBSAs (such Calvert, Charles and St. Mary ’s) , or the westerl y outer counties/CBSAs (such as the Winchester, VA area or Clarke (VA), Warren (VA) or Jefferson (WV)). For instance, on July

3, 2008 (a single day

episode), the trajectories at all three levels were from the Southwest and arrived via the core CBSA counties and cities of the Washington CBSA and passed through Baltimore C ity

before arriving at Edgewood. Yet, he onl y two monitors in the CSA that recorded exceedances were at Edgewood at 0.089 ppm and at Aldino at 0.079 ppm. L ikewise, on July 18, 2008 (the second day of a 2 - day episode) the back - trajectories suggest Edgewoo d was directl y downwind of much of the core CBSA counties and cities of the Washington CBSA and recorded an

87 These counts were made off Figures 4A - 1 to 4A - 10. Some trajectories may have been missed. Even so, a general se nse of exceedance day prevailing winds can be inferred overall.63

exceedance of 0.102 ppm. 88 Similarly , on July 23, 2010 (a single day

episode), the back - trajectories from Edgewood were similar to those on July 3, 2 008. The Edgewood monitor recorded an exceedance of 0.101 ppm as did the Aldino (at 0.086 ppm) and Essex (at 0.082 ppm) monitors. 89 Examining the back - trajectory results for the Edgewood monitor, EPA does not dispute that the “core CBSA counties and cit ies” of the 1997 Washington DC - MD - VA Nonattainment area is upwind of the Baltimore CBSA on many day s the 2008 ozone NAAQS is exceeded. 90 Li kewise, based upon the back trajectories , EPA cannot exclude the outlying counties of the Baltimore and Washington CB SAs and the adjacent CBSAs of Culpeper and Winchester in Virginia and Lexington Park, MD, from further consideration regarding contribution. However, based upon the back - trajectories for some day s when the concentration recorded at the Edgewood monitor wa s 0.087 ppm or higher, the back - trajectories predicted that the bulk of the air did not travel over most portions of the Washington CBSA (excepting at time s Frederick County , MD) but came from the Northwest, the North - northwest, the North and even from the Northeast. Table 25 provides a listing of such day s for just 2008 to 2010 alone. **Table 25 .**  **Days by Year the Edgewood Monitor is Not Downwind of the 1997 Washington DC**  **- MD**  **- VA**  **Nonattainment area :**  YEAR Trajectory

Height 2008 2009 2010 Edgewood Monitor: 100 meters

– 22 of 51 day s 4/18, 6/12, 7/16 - 17 &

7/28/ 4/26, 6/25, 7/13 & 8/27/ 5/5, 5/27, 6/2, 6/23,

6/25, 7/17, 7/31, 7/5 - 7/7, 8/19 & 8/30 - 31 500 meters

– 27 of 51 day s 4/18, 6/12, 7/11 - 12,

7/16 - 17 & 7/28 4/26, 6/5 , 6/25 - 6/26,

7/13 , 8/16 & 8/27/2009 5/5, 5/21, 5/27, 6/2,

6/23, 6/25, 7/31, 7/5 - 7/7, 8/10, 8/19 & 8/30 - 31 At the Edgewood monitor on some of the day s with higher ozone readings (“Groups 4 & 5”

– measured concentration > 0.087 ppm) the HYSPLIT trajectories suggest the winds came from the 1997 Washington DC - MD - VA Nonattainment area on some day s but came from elsewhere on other day s. Refer to Figures 4 A - 1 to 4A - 5 in Appendix 4. On the “Group 2 and 3” days (between 0.079 through 0.086 ppm inclusive), the predominant directions seem to be from the South to Southwest , that is, often through the Washington CBSA . For other day s (“Group 1” < 0.078 ppm) the winds come from a variety of directions. When trajectories end at the Edgewood monitor , these trajectories pass through the “core” (say Fairfax County , VA, the District, Prince George’s and Montgomery Counties in Maryland) of the 1997 Washington DC - MD - VA Nonattainment area , and they also cross Anne Arundel County , Maryland and

88 The back - trajectories suggest that the Howard University - Beltsville monitor in Prince George’s County, MD was directly dow nwind of the Arlington (VA), Fairfax (VA) and Montgomery (MD) and Prince George’s (MD) Counties as well as the District of Columbia; this monitor had an exceedance of 0.097 ppm. 89 The difference between the values at Aldino and Essex might be due to Aldino likely being immediately downwind of the high emissions areas of Baltimore City and Baltimore County as well as the ore of the Washington CBSA and Howard and/or Anne Arundel Counties in Maryland. 90 As defined by OMB these would be: Montgomery and Prince George's Counties in Maryland; the District of Columbia; an d, Arlington, Fairfax County, Loudoun, Prince William and (to a lesser extent) Stafford Counties plus the Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park in Virginia . Refer to OMB Bulletin No. 10 - 02, “Update of Statistical Area Definitions and Guidance on Their Uses,” December 1, 2009 .64

skirt the Southeastern fringes of Baltimore City and County

or pass through Baltimore City and parts of Baltimore County

and through Howard Count y. So while the 1997 Washington DC - MD - VA Nonattainment area is often upwind of the Edgewood monitor, there are a considerable number of day s were this monitor recorded an ozone concentration considerabl y over the NAAQS (say 0.087 ppm or more, i.e., “Groups 4 and 5” day s) when the trajectories (of an y height) did not pass through the 1997 Washington DC - MD - VA No nattainment area . This happened on the following dates: June 7, June 14, July 11 and July

17, 2008 ; May

5, June 2, June 25 and 26, July

5 through 7, August 10, August 19 and the period August 29 and 30, 2010 . For instance, on July

11, 2008 (the first day

of a two day

episode), the trajectories of the air masses arriving at Edgewood did not cross the core CBSA counties/cities of the Washington CBSA but came from the Northwest via Washington, Frederick (MD) , Carroll , Howard and Baltimore Counties. The c oncentration at Edgewood was 0.100 ppm as well as 0.084 ppm at Essex to the Southwest and 0.079 ppm at Aldino to the Northeast of Edgewood . 91 On June 25, 2009 (the first day of 2 - day episode), the back - trajectories from Edgewood came from the North, and this monitor recorded an exceedance of 0.109 ppm. The only

other exceedances observed that day were 0.079 ppm at Aldino, 0.086 ppm at Essex and 0.076 ppm in Calvert County , MD. 92 Li kewise, on May 27, 2010 (single day

episode), the back - trajectories from Edgewood came from the Northeast; Edgewood recorded an exceedance of .089 ppm. For the period July 3 through 7, 2010 (the first 5 day s of a 6 - day episode) , the 100 meter level back - trajectories passed through the core CBSA counties and cities of the Washington CBSA before arriving at Edgewood on the first two day s. On these first two day s, the 500 and 1000 meter back trajectories did not pass through the core CBSA counties and cities of the Washington CBSA because they arrived via Harford and/or Baltimore County or via Baltimore City only . For the next three day s all back - trajectories passed through Harford, Cecil and/or Baltimore Counties befo re arriving at Edgewood. Edgewood recorded the following exceedances (by date from the 3 rd to the 7 th ): 0.082 ppm, 0.090 ppm, 0.097 ppm, 0.092 ppm and 0.088 pm. EPA believes that it is quite possible or likely that the readings on the 5 th to the 7 th wer e affected b y the return of the ozone precursors emitted at ground level (from under 100 meters) in the Washington CBSA on the 3 rd and the 4 th , but higher level winds apparently never passed through much of the Washington CBSA on these day s. These resul ts suggest that the 1997 Washington DC - MD - VA nonattainment area and even the Washington CBSA as a whole are upwind of the Edgewood monitor on some day s the 2008 ozone NAAQS is exceeded at the Edgewood monitor. However, there are a considerable number of d ay s when the HYSPLIT back - trajectories crossed no part of the Washington CBSA or just a portion of Fredrick County , MD only . This latter result say s the Washington CBSA is not the only cause of high levels of ozone at the Edgewood monitor. **2. Placement of Anne Arundel and Prince George’s Counties**  EPA also examined in some detail back - trajectories for the Davidsonville (AQS ID No. 24 - 003 - 0014) and Howard Universit y - Beltsville (Howard U - B

– AQS ID No 24 - 033 - 0030) monitors in Anne Arundel and Prince George ’s Counties, respectivel y, in Maryland. 91 The only other monitor in the CSA recording an exccedance was Davidsonville at 0.076 ppm. The back - trajectories to Davidsonville passed through the core of the Washington CBSA. 92 On June 26, 2009, the back - trajectories ending at Edgewood” were from the west crossing the West Virginia “panhandle”, northern Loudoun County, VA, Washington, Frederick, and/or Carroll Counties (MD) and finally as they must Baltimore City and/or County. The Edgewood mo nitor recorded an exceedance of 0.091 ppm while the Aldino monitor recorded an exceedance of 0.081 ppm. The only other exceedances recorded in the CSA were at Arlington, VA and the District of Columbia each with a maximum of 0.080 ppm.65

Anne Arundel County: Figures 6 A - 1 to 6 A - 10 of Appendix 6 “ HYSPLIT Trajectories for the Davidsonville, Prince George’s Equestrian Center and Howard University

—Beltsville by

Group ” show the HYSPLIT results overlaid on a map. They

are grouped by

the “Groups” defined in Table 10 elsewhere in this document. For each “Group” there is a map for 2008 to 2010 exceedance day s and one for 2006 to 2007 exceedance day s. The Davidsonville m onitor likewise can receive air from man y directions on episode days. Given the close proximity

of Prince George’s, Calvert and Charles Counties to the Davidsonville site, many trajectories from the Northwest cannot help but graze the northern portion of Prince George’s; likewise, when the trajectories are from the South or Southwest, the trajectory may not cross the core of the 1997 Washington DC - MD - VA nonattainment area but only cross the outlying Calvert and/or Charles Counties. Maryland has full abil ity to regulate these 3 counties regardless of what nonattainment area they are placed. On some day s the trajectories could not only skim Prince George’s, Calvert and Charles Counties, but they also crossed a portion of the 1997 Baltimore nonattainment area and later the Washington area and vice versa. Analy sis of the full set of data for the Davidsonville monitor counted the back - trajectory for each altitude for each day . Unlike the anal ys is for the Edgewood monitor for which a trajectory was placed in an exclusive category , a trajectory that passes through both the Washington CBSA and the 1997 Baltimore nonattainment area was counted twice since both areas were implicated. Thus each exceedance day

would contribute three or in some case six to the aggre gate sum. The categories used were “19 97 Baltimore nonattainment area ” which means no part of the Washington CBSA was crossed and some other portion of the 1997 Baltimore nonattainment area except Anne Arundel Count y was crossed ; 93 the “Washington CBSA ex cluding Charles and/ or Calvert Counties only” which means that no part of the Washington CBSA was crossed except Charles and/or Calvert Counties, “Charles or Calvert County

onl y” which means no other part of the Washington CBSA was crossed except one or bo th of these counties , “Prince George’s Count y only” which means the only portion of the Washington CBSA crossed was Prince George’s County and then into the rest of the 1997 Baltimore nonattainment area, and “Other” which means no part of a trajectory pass es through an y portion of the 1997 Baltimore nonattainment area (except Anne Arundel Count y) or the Washington CBSA. The gross results of this anal ys is are found in Table 2 6 . **Table 26**  **. Trajectory Counts for Davidsonville Monitor: 94**  2008 to 2010 2006 to 2010 Geographic area Number of Trajectories Counted Percent of

Total Number of

Trajectories Counted Percent of

Total Washington CBSA excluding Charles and/or Calvert Counties only 14 19.7% 58 38.6 %

93 Given the lo cation of the Davidsonville monitor all trajectories must pass through some portion no matter how short. 94 These counts were made off Figures 5A - 1 to 5A - 10. Some trajectories may have been missed. Even so, a general sense of exceedance day prevailing w inds can be inferred overall.66

Calvert and/or Charles County only 2 2.8% 16 10.5% Prince George’s Count y only 13 18.3% 7 4.6% 1997 Baltimore nonattainment area 40 56.3% 64 42.1% Other 2 2.8% 11 7.2% Total 71 166 Over the five years, the data slightl y favors the Washington CBSA as being predominantly upwind of the Davidsonville monitor though trajectories through Calvert and/or Charles only are passing through lower emissions area. Over the last three years, the data more heavil y favors the 1997 Baltimore nonattainment area as b eing predominantly upwind of the Davidsonville monitor . Of the day s with exceedances above 0.078 ppm, the counts are: **Table 2 7**  **. Trajectory Counts for Davidsonville Monitor –**  **Exceedance Days over 0.078 ppm: 95**  2008 to 2010 2006 to 2010 Geographic area Number of Trajectories Counted Percent of

Total Number of

Trajectories Counted Percent of

Total Washington CBSA excluding Charles and/or Calvert Counties only 8 18.2% 32 36.4% Calvert and/or Charles County only 0 0.0% 11 9.3% Prince George’s Count y only 9 20.5% 7 5.9% 1997 Baltimore nonattainment area 27 61.4% 44 43.2% Other 0 0.0% 6 5.1% Total 118 Review of Figures 6A - 4 through 6A - 5, and 6A - 9 through 6A - 10, corresponding to exceedance day s of 0.08 7 ppm or higher

– substantially over 0.075 ppm by

over 15 percent

– suggest that the Davidsonville monitor records its highest exceedances when it is downwind of the 1997 Washington and Baltimore nonattainment areas. Over the five years, the data slightl y favors placement of the Davidsonville moni tor with the core of the Washington CBSA though trajectories through Calvert and/or Charles only are passing through lower emissions area. Prince George’s County

– Howard - University -Beltsville (Howard U -Beltsville): For the Howard U - B eltsville monitor the reverse is true. For a preponderance of the day s where an exceedance of 0.079 ppm or more was recorded , the back - trajectories passed through the core CBSA

95 These counts were made off Figures 5A - 1 to 5A - 10. Some trajectories may have been missed. Even so, a general sense of exceedance day prevailing winds can be inferred overall.67

counties and cities of the Washington CBSA as well as at time s Calvert, Charles, Frederick and St. Mary ’s County

in Maryland and through Fauquier and other outl yi ng Counties in Virginia. For days with an exceedance of 0.078 ppm of less, there was no clear pattern; the trajectories were from various directions though none passed through the Baltimore CBSA other than Carroll County . For these reasons, based upon reception of ozone and ozone precursors, EPA believes that the Howard University

– Beltsville monitor should be placed in a nonattainment area that includes the core CBSA counties and city of the Baltimore CBSA. Naturall y all trajectories must pass through Prince George’s County and thus would count as passing through the Washington CBSA. However, some trajectories at some point looped into Prince George’s County before traversing the 1997 Baltimore nonattainment area. Some also skimmed the border of Montgomery

and Howard Counties. The categories used were : (1) “Washington CBSA (except Prince George’ s County

and skims) ” which means the trajectory crossed some portion of the Washin gton CBSA (except Prince George’s), did not skim the Montgomery - Howard border, and crossed no portion of the 1997 Baltimore nonattainment area ; (2) “Direct to 1997 Baltimore nonattainment area” which means the trajectory

crossed from Prince George’s County into the 1997 Baltimore nonattainment area without a loop within Prince George’s; (3) “ Loop Prince George’s and Howard; ” (4) “Washington plus Baltimore” which means the trajectory at some point crossed both the Washington CBSA (except only a crossing of P rince George’s County) and the 1997 Baltimore nonattainment area : and (5) “Skimmed Montgomery

and Howard” which counted those skimming the border of Montgomery and Howard Counties and did not cross any other portion of the Washington CBSA (excepting Prince George’s) . The gross results of this anal ys is are found in Tables 28 and 29. **Table 2 8**  **. Trajectory Counts for Howard U**  **- Beltsville**  **Monitor: 96**  2008 to 2010 2006 to 2010 Geographic area Number of Trajectories Counted Percent of

Total Number of

Trajectories Counted Percent of

Total Washington CBSA (except Prince George’s Count y and skims) 35 59.3% 66 65.4% Loop Prince George’s and Howard 3 5.1% 3 2.9% Skimmed Montgomery

and Howard 6 10.2% 6 5.9% Direct to 1997 Baltimore nonattainment area 15 25.4% 23 22.8% Washington plus Baltimore 0 0.0% 3 2.9% Total 59 101 **Table 2 9**  **. Trajectory Counts for Howard U**  **- Beltsville**  **Monitor –**  **Exceedance Days over 0.078 ppm:**  **97** 2008 to 2010 2006 to 2010 Geographic area Number of Percent of Number of Percent of 96 These counts were made off Figures 5A - 1 t o 5A - 10. Some trajectories may have been missed. Even so, a general sense of exceedance day prevailing winds can be inferred overall. 97 These counts were made off Figures 5A - 1 to 5A - 10. Some trajectories may have been missed. Even so, a general sense of exceedance day prevailing winds can be inferred overall.68 Trajectories Counted Total Trajectories Counted Total Washington CBSA (except Prince George’s Count y and skims) 34 63.2% 49 69.0 % Loop Prince George’s and Howard 3 5.9 % 3 4.2 % Skimmed Montgomery

and Howard 2 5.3 % 2 2.8% Direct to 1997 Baltimore nonattainment area 9 23.7 % 23 22.8% Washington plus Baltimore 0 0.0% 3 4.2 % Total 38 71 This monitor is located such that air masses have to pass through the “core” counties and cities of both the 1997 Baltimore and Washington nonattainment areas. Most of Prince George’s County lies to the south and Southeast, Anne Arundel and/or Howard Counties are immediately east, north and north northwest, Montgomery

County is northwest, the District is directly to the southwest. For the Howard U - B monitor , for a preponderance of the day s where an exceedance of 0.079 ppm or more or, of less than 0 .078 ppm was recorded, the back - trajectories passed through the Washington CBSA. For these reasons, based upon reception of ozone and ozone precursors, EPA believes that the Howard University

– Beltsville monitor should be placed in a nonattainment area that includes the core CBSA counties and cit y of the Washington CBSA. Prince George’s County

– Prince George’s Equestrian Center: For the Prince George’s Equestrian Center (Pr. G. Eq. Ctr.) monitor, the pattern ought to be a mix between the situations f

ound at Davidsonville and Howard - U

—Beltsville monitors for 2008 - 2010 . Because 2006 to 2007 exhibited a different bias towards winds from the south than 2008 to 2010, we examined some trajectories for 2006 and 2007 , particularly to capture day s where Anne Arundel and Howard U - Beltsville did not exceed 0.075 ppm. These are displayed on Figure s 6A - 11 through 6A - 14 . These suggest that the monitor exceeds on day s when the winds pass through Prince George’s County form the Northwest, West, Southwest and then p ass through other portions of the 1997 Washington DC MD - VA nonattainment area and other core counties and cities of the Washington CBSA. However, on day s where it recorded an exceedance of 0.087 ppm or more (“Groups” 4 and 5 day s – refer to Figure 6A - 14 in Appendix 6 ) many trajectories pass through the Baltimore CBSA before turning back and passing through either the core of the 1997 Washington Nonattainment area (including the northwest portion of Prince George’s itself) o r through Charles County . Pr ince George’s County - Conclusion: The meteorology

assessment strongl y favors placement of the Howard U - Beltsville monitor in the nonattainment area containing the core the Washington CBSA which is the core of the 1997 Washington nonattainment area. To a lesser extent, the meteorology assessment favors placement of the Prince George’s Equestrian Center monitor in the nonattainment area containing the core the Washington CBSA which is the core of the 1997 Washington nonattainment area.69

Because the H oward U - Beltsville monitor is so strongl y linked to the Washington CBSA and because the Prince George’s Equestrian Center monitor is also linked to this CBSA more than the 1997 Baltimore Nonattainment area , the meteorology assessment strongl y favors placem ent of Prince George’s County in the nonattainment area containing the core of the Washington CBSA which is also the core of the 1997 Washington nonattainment area. **2. Does the current Baltimore MD Nonattainment area**  **contribute to nonattainment in the current**  **Washington DC**

**- MD**  **- VA**  **Nonattainment area ?**  EPA also investigated if the Baltimore CBSA or 1997 nonattainment area also may contribute to the monitors in the Washington CBSA namel y the McMillan Reservoir (DC), Arlington and Franconia (VA) monitors

– “ the 3 - central monitors” in this CBSA . In the previous part of this document , we looked at the two monitors in Prince George’s County , MD and concluded that meteorology favors placement with the nonattainment area containing the core of the Washington CBSA which is also the core of the 1997 Washington nonattainment area. Figures 7A - 1 to 7A - 10 of Appendix 7 “ Appendix 7: HYSPLIT Trajectories for Arlington, Franconia & McMillan Res. Monitors by Group ” show the HYSPLIT results overlaid on a map. They are gr ouped by the “Groups” defined in Table 10 elsewhere in this document. For each “Group” there is a map for 2008 to 2010 exceedance day s and one for 2006 to 2007 exceedance day s. Once again geographic location dictates the sort of trajectories that are possible. The trajectories can be placed into 5 categories: (1) on some exceedance day s are prett y much straight from the north or northeast into Montgomery of Prince George’s Counties before ending at one of the three monitors ; (2) some sweep through only Anne Arundel County

of the 1997 Baltimore Nonattainment area ; (3) some cross only

Howard and/or Carroll Counties in the 1997 Baltimore Nonattainment area ; (4) some cross over both portions of both the 1997 Baltimore Nonattainment area as well as the 1997 Washington area; and, finally , (5) some pass over no part of the Baltimore nonattainment area. Due to the geographic location of these monitors, most trajectories that cross some portion of the 1997 Baltimore Nonattainment area must also cross the core CBSA counties of Montgomery and Prince George’s in Maryland and Fairfax in Virginia as well as the District of Columbia on days where the trajectories run straight from Baltimore Ci ty to the Arlington and Franconia monitors. Note that each of these three monitors did not necessarily record a value in the range for the same group on the same day s as the others; for example, on “Group 5” day s (values > 0.091 ppm) all three recorded a value over 0.092 ppm on 7/17/2008 (0.095, 0.100 and 0.104 ppm) and 7/7/2010 (0.092, 0.095 and 0.100 ppm) but only

two recorded values over 0.092 ppm on 6/12/2008 (0.093 & 0.096 ppm with the 3 rd at 0.085 ppm) and only

Franconia recorded a value of 0.091 pp m or more on 8/30/2010 (but the other exceeded 0.075 ppm). And note that one monitor might have an exceedance on a day that falls within one “Group” while another has an exceedance on the same day that falls into another group. For example, on 8/10/2010 , Arlington recorded a concentration of 0.088 ppm (in “Group 4”) while Franconia recorded a concentration of 0.082 ppm (within “Group 3”). Refer to Table 2A - 1. These trajectories are presented in Figures 7A - 3 and 7A - 4 in Appendix 7 . The gross results o f this anal ys is are found in Table 30 . Because these monitors may exceed on the same day s, the gross counts overstate the results. Therefore because there are three monitors the gross70

results are divided b y three to allow some sort of absolute numbers to numbers comparison with the Edgewood monitor and the others discussed in the preceding part of this document. **Table 30**  **. Trajectory Counts for the Franconia, McMillan Res. And Arlington Monitors: 98**  **Category Gross**  **Count Adjusted (Gross/3)**  **Percentage** 2006 - 2010 Data (1) Straight

– Baltimore 80 26.7 18.2% (2) Anne Arundel County onl y 28 9.3 6.4% (3) Howard and Carroll 47 15.7 10.7% (4) Baltimore and Washington 11 3.7 2.5% (5) No part of 1997 Baltimore area 266 86.7 60.6% 439 146.3 2008 - 2010 Data onl y (1) Straight

– Baltimore 54 18.0 23.8% (2) Anne Arundel County onl y 2 0.7 0.9% (3) Howard and Carroll 38 12.7 16.7% (4) Baltimore and Washington 8 2.7 3.5% (5) No part of 1997 Baltimore area 108 36.0 47.6% 227 75.7 Examination of the back - trajectory results for these three monitors in the Washington CBSA, EPA also concludes that the “core CBSA counties and city” of the Baltimore CBSA are upwind of these three violating monitors in the Washington CBSA. Many of the day s for which an ex ceedance of 0.087 ppm or more was recorded at any one (or more) of the monitors in Arlington and Fairfax Counties (VA) and the District of Columba, the back - trajectories implicate some portion of the core CBSA counties and city of the Baltimore CBSA. Of c ourse, air from the core CBSA counties and city of the Baltimore CBSA to one of these monitors has to pass through Prince George’s and/or Montgomery Counties in Maryland as well. 99 **4. Monitors and Counties** Gen e rally : Examination of available data has shown that every county, the District, and Baltimore City are likely upwind of one or more violating monitors at times. Examination of the figures in Appendices 5, 6 and 7, also show that on average the closer a county /ci ty is to a monitor the more likely it has more trajectories to that monitor crossing it. As for the count y or city containing a violating monitor, it has to be designated nonattainment but all back - trajectories from that monitor must pass over the count y in which a violating monitor is located . Of course, size is a factor. Classic examples are those in Prince George’s County , MD: The Howard U Beltsville monitor sees many trajectories from the south cross its north - south axis. L ikewise, the Prince

98 These counts were made off Figures 5A - 1 to 5A - 10. Some trajectories may have been missed. Even so, a general sense of exceedance day prevailing winds can be inferred overall. 99 And through the District of Columbia most time as well in the case of monitors in Arlington and Fairfax Counties in Virginia.71

Ge orge’s Equestrian Center monitor sees man y trajectories cross its southern half and man y cross its north - south axis. Some relatively

small areas with violating monitors such as that in Arlington County or perhaps even the District of Columbia are hard t o anal yz e in this respect. At most the air mass spends a brief period of time in the small entity during the period immediately before the air mass reaches the monitor. These two monitors are located in a region of high emissions and emissions density. Contribution to ozone at these monitors may

result from emissions from the larger adjacent areas as well as from mixing from the layers of air above the nocturnal inversion and from other long - range transported ozone and precursors. Carroll Co., MD and Calvert County Maryland: Examination of the trajectories for surrogate monitors on specific day s when either of the Calvert County or the South Carroll monitors recorded an exceedance for the period 2008 to 2010 suggest these two monitors record exceedance s when downwind of the urbanized cores of the 1997 nonattainment areas. We ran the HYPLIT for these monitors for 2006 and 2007 once we discerned that the 2006 and 2007 wind patterns for other monitors showed that the wind patterns for 2008 and 2010 might not represent a good sampling of exceedance patterns. The back - trajectories for 2006 and 2007 also suggest these two monitors record exceedances when downwind of the urbanized cores of the 1997 nonattainment areas. For the South Carroll monitor, the principal local upwind areas are the District, Montgomery , Howard, Prince George’s, Fairfax, Prince Will iam, Anne Arundel and Charles Counties , with Frederick and Baltimore Counties plus Baltimore City being occasionally upwind. There can be day s when the back - trajectories suggest Carroll County is upwind of the CSA ; examples included September 4, 2008 . For Calvert County , the principal local upwind areas are the Anne Arundel, Howard, Prince George’s, Baltimore Counties plus Baltimore City , and to a lesser extent, Carroll County , with the District , Harford and Montgomery Count ies being occasionally upwind . There can be day s when the back trajectories suggest Calvert County is upwind of the CSA; examples include September 4, 2008. . The 2006 and 2007 trajectories are found in Figures 9A - 1 and 9A - 2 of Appendix 9 to this document. Outlying Counties: Figures 9A - 3 to 9A - 11 show the trajectories crossing counties in various areas. The areas are: (1) the western CSA counties and areas of Clarke, Culpeper, Fauquier, Warren in Virginia, of Jefferson and Hampshire in West Virginia, and the Frederick County Are a in Virginia; (2) Queen Anne’s Count y, MD, (3) St. Mary ’s County , MD, and (4) the Fredericksburg area in Virginia. For the first three, there are two figures

– one with trajectories to violating monitors in the 1997 Washington area and one to violating m onitors in the 1997 Baltimore area. For the last, the 1997 Washington area has been broken into two slides

– one for violating monitors in Virginia and one for violating monitors in the District and Maryland. Western CSA counties and areas of Clarke, Cul peper, Fauquier

, Warren in Virginia, of Jefferson and Hampshire in West Virginia, and the Frederick County Area Figures 9A - 3 to 9A - 4 show the trajectories crossing these areas. One cannot directly compare the figures directly

in that the back - trajectories from the 1997 Washington area represent 5 monitors versus two in the 1997 Baltimore area. Figures 9A - 3 to 9A - 4 suggest that these areas are upwind of both the 1997 Baltimore an d Washington nonattainment areas. However, Figure 9A - 3 suggests that Culpeper, Fauquier, Warren and Jefferson Counties are more often upwind of monitors in the 1997 Washington72

nonattainment area than Clarke and Hampshire Counties and the Frederick County Area in Virginia . Figures 9A - 1 and 9A - 2 suggest these areas are rarely upwind of the monitors in Carroll and Calvert Counties. Queen Anne’s County, MD Figures 9A - 5 to 9A - 6 show the trajectories crossing Queen Anne’ s . One cannot directl y compare the fi gures in that the back - trajectories from the 1997 Washington area represent 5 monitors versus two in the 1997 Baltimore area. Figures 9A - 5 and 9A - 6 suggests that Queen Anne’s County is upwind of violating monitors in both the 1997 Baltimore and Washington nonattainment areas . Figures 9A - 1 and 9A - 2 suggest Queen Anne’s is rarely upwind of the monitors in Carroll and Calvert Counties. St. Mary’s County, MD Figures 9A - 5 to 9A - 6 show the trajectories crossing St. Mary ’s. Comparing Figures 9A - 5 and 9A - 6 sugg ests that St. Mary ’s County is more often upwind of violating monitors in the 1997 Baltimore Nonattainment area because many more trajectories from the two monitors cross the count y than those from the five monitors in the 1997 Washington Nonattainment are a . Figures 9A - 1 and 9A - 2 suggest St. Mary ’s is rarel y upwind of the monitor in Carroll County ; on day s when Calvert County receives winds from the south, St. Mary ’s is likely upwind of Calvert County . The Fredericksburg area in Virginia Figures 9A - 7 to 9A - 9 show the trajectories crossing the Fredericksburg area in Virginia. One cannot directl y compare Figure 9A - 8 to the other two because it represents 3 monitors in the District’s and Maryland’s portions of the 1997 Washington area , whereas the other two figures results from only two other monitors. Figure 9A - 9 is for the Davidsonville and Edgewood monitors the latter of which had far more exceedances than an y other monitor in the CSA. The other four are comparable in number of exceedance day s – in th e range of 52 to 62. That Figure 9A - 9 shows fewer trajectories than the other two suggests the Fredericksburg Area is more often upwind of the 1997 Washington Nonattainment area . Figures 9A - 7 and 9A - 8 suggest that when the Fredericksburg Area is upwind o f these monitors the air mass moves through this area and then to the northwest over the Arlington , Franconia, McMillan and Howard U - Beltsville monitors in turn. Figures 6A - 11 to 6A - 14 suggest this area is at time s upwind of the Pri nce George’ s Equestrian Cent er monitor as well . Figures 9A - 1 and 9A 2 suggest this area is rarely upwind of the monitor in Calvert County but is upwind of Carroll County ’s monitor about one - third of the time. Linkage Table for Violating Counties: Examining the available info rmation, EPA has updated the linkage tables over those used previously. 

### Table 31 **. Meteorological Linkages** Location of Violating Downwind Receptor Monitor Adjacent Upwind Possible Contributing Area(s Close Upwind Possible Contributing Area(s)

– Counties, Cities or CBSAs Harford County Baltimore County , adjacent CBSAs in Maryland and Pennsylvania. Baltimore City , Anne Arundel , How ard, Montgomery , Prince George’s , Fairfax 100 , Arlington 101 , Frederick (MD) ,

100 Wherever Fairfax County is indicated also includes at times Fairfax City and Alexandra City. 101 Wherever Arlington County is indicated also includes at times Falls Church City73 The District 102 , and CBSAs in Delaware , Maryland and Penns yl vania adjacent to the Washington - Baltimore - NV CSA and to a lesser extent, Calvert , Charles , Prince William , 103 Lo udoun . Baltimore County Anne Arundel, Carroll, Harford, & Howard Counties; Baltimore City ; and adjacent CBSAs in Pennsylvania. Frederick (MD), Prince George’s and Montgomery , Fairfax , Arlington , the District , CBSAs in Delaware, Maryland and Pennsylvania adjacent to the Washington - Baltimore - NV CSA a and to a lesser extent, the Calvert , Charles , Prince William , Lo udoun . Carroll County Howard and Montgomery Counties ; to a l esser extent, Baltimore and Frederick, (MD) Cos. And Baltimore City. Arlington, Anne Arundel and Prince George’s , Fairfax, the District , County , VA. Prince George’s, Fairfax, and Charles, and to a lesser extent Lo udoun , Calvert, Frederick (MD), Prince William, and Baltimore Counties plus Baltimore City . Anne Arundel County Baltimore Co., Calvert, Prince George's , and Howard. Fairfax, Charles, the District, Baltimore City , Montgomery , and to a lesser extent, Loudoun, Prince William, Arlington, and Frederick (MD). Fairfax County , VA Arlington, Charles, Loudoun , Montgomery , Prince George’s, the District, Alexandria and Fairfax C ities and to a lesser extent Prince William. Anne Arundel, Howard, Calvert , Carrol l , plus Baltimore Co. and City and to a lesser extent Frederick (MD) , Prince William and the Fredericksburg area. Arlington County , VA Fairfax, the District, and Falls Church City . Anne Arundel, Charles, Howard, Loudoun , Montgomery , Calvert, Prince George’s, Prince William , Alexandria and Fairfax Cities plus Baltimore Co. and City and to a lesser extent: Prince William, Frederick (MD) , and the Fredericksburg area. D istrict of Columbia Montgomery , Prince George's Arlington, Fairfax, and, Alexandria and Falls Church Cities. Charles, Howard, plus Baltimore Co. and City , the Fredericksburg area and to a lesser extent: Calv ert , Carroll, Prince William L oudoun , Frederick (MD) Prince George’s County , MD District of Columbia, Anne Arundel, Charles Fairfax, Montgomery , Howard ; and to a lesser extent: Calvert. Arlington, Prince William, Baltimore Co. and City , and to a lesser extent: the Fredericksburg area, Loudoun, and Fr ederick (MD) .

102 Wherever the District is indicated also includes at times Alexandra City. 103 Wherever Prince William County is indicated also includes at times also Manassas and Manassas P ark Cities.74

Calvert County , MD Prince George’s and Anne Arundel, and possibl y to a lesser extent: Saint Mary ’s, and Charles. Baltimore Co. and City , Howard, and to a lesser extent: Fairfax, Montgomery , Frederick (MD) , Carroll, and Harford . 

### 5 **. Other Meteorological Analyses**  Regarding Transport on L arger Scales , the Nocturnal L ow Level Jet (NLLJ) the “ Bay Breeze” and “Lee side” trough 104 : EPA does not disagree with Maryland that transport of ozone and its precursors from other States such as those of the Ohio River Valley and Penns yl vania, Virginia , North Carolina and others affects ozone levels at monitors in Maryland. As discussed elsewhere in this document, EPA believes that large scale transport is to be addressed under other provisions of the CAA and not section 107(d)(1)(A) designations. For the reasons discussed in section 3.1.2 of “Responses to Significant Comments on the State and Tribal Designation Recommendations for the 2008 Ozone National Ambient Air Quality Standards (NAAQS),” Docket Number EPA - HQ - OAR - 2008 - 0476, U.S. Environmental Protection Agency , April 2012 , EPA believes that the CAA requires the nonattai nment designation process under section 107(d)(1)(A) requires contribution to be of a level sufficient to warrant a nonattainment designation and such contribution must be to violating areas that are “nearby;” the longer range transport that is not address ed under section 107(a)(1)(A), the CAA prohibits “significant” contribution , not any contribution. EPA does not dispute Maryland’s data regarding aloft levels of ozone entering Maryland. However, EPA notes that these aloft levels do not seem to be causin g violations at ground level ozone monitors between Maryland’s borders and most of the States that Maryland has identified: Kentucky , North Carolina, Ohio, Michigan, Indiana, West Virginia and others. All monitors in West Virginia are currentl y attaining the 2008 ozone NAAQs. This is based upon the fact that many of these are attaining the 2008 ozone NAAQS at this time. Of note are those closest to Maryland such as that in Monongalia, Greenbrier and Berkeley

Counties as well as those along the Penns yl vania - West Virginia border. The monitors in Virginia south of the Washington - Baltimore - NV CSA , in particular those in Frederick, Caroline, L oudoun, Fauquier, Stafford, Albemarle, Page, Madison and all in the Richmond, VA CBSA are currentl y attaining the 200 8 ozone NAAQS. 105 The monitor in Madison County , VA is located on a ridge of the mountains within the border of Shenandoah National Park. So are the monitors in Garrett and Washington Counties in Maryland. The same is true for all monitors save a couple i n Pennsylvania located west of the Lancaster, Reading, Allentown - Bethlehem - Easton and Philadelphia - Camden Wilmington CBSAs in Pennsylvania. Most are attaining with the onl y exception s are in the Pittsburgh area ; so are many

in Eastern Ohio along the Penns yl vania - Ohio border. 106 Also, on many

day s that EPA examined by comparing the HYSPLIT back - trajectories and monitored ozone concentrations for particular episode day s. In addition to the monitors in the CSA, EPA examined measured ozone concentrations at three higher elevation monitors near the CSA for 2008 - 2010 episode 104 Maryland’s March 7, 2012, letter in response to EPA’s December 9, 2011, letter discussed portions of these topics under various factors; EPA is consolidating the responses here. 105 Richmond had a design value of 0.076 ppm based upon 2008 t o 2010 data but because Virginia certified its 2011 data early, EPA considered the 2009 to 2011 design value of 0.075 ppm as the most current design value upon which to base a attainment/unclassifiable - nonattainment decision. 106 Data Source: ozone_dv75 _20082010.xls (dow nloaded on 9/22/2011 from http://www.epa.gov/airtrends/values.html ).75

day s. These monitors were the Shenandoah National Park (SNP) monitor (“SNP”) (AQS ID No. 51 - 113 - 0003) located in Madison County , VA, the monitor in Garrett County , Maryland (“Piney Run,” A QS ID No. 24 - 023 - 0002) and the monitor in Franklin County , PA (“Methodist Hill,” AQS ID No. 42 - 055 - 0001). 107 Refer to the data in Table A2 - 3: Air Quality Data

– “Three ‘Higher Elevation Monitors’ Episode Day s for 2008 through 2010 ” in Appendix 2. In some cases where our HYSPLIT results suggested one or more of these monitors could be upwind of the CSA, EPA did indeed find one of these monitors recording an ozone concentration above the 0.075 ppm NAAQS. 108 These day s were often on the second or later day

of a multi - day

episode. However, EPA found that on other day s the measured ozone concentrations at one or more of these monitors was 0.010 ppm (10 ppb) below the NAAQS and more day s where the measured ozone concentrations at one or more of these monitors was well below 0.065 ppm. For instance, on April 18, 2008, the Methodist Hill monitor recorded a 0.074 ppm while both the Davidsonville and Edgewood monitors recorded 0.087 and 0.086 ppm, respectivel y. The SNP monitor recorded a concentration of 0.071 p pm on September 2, 2010 and the Methodist Hill monitor a 0.077 ppm while the Padonia (North of Baltimore) and Edgewood monitors recorded 0.092 and 0.82 ppm, respectivel y. 109 On the previous day , the Edgewood monitor recorded a 0.090 ppm while the SNP monito r recorded onl y a 0.062 ppm. 110 High levels of o zone at these three higher elevation monitors did not alway s correspond to the worst levels of ozone measured within the CSA. For example, on June 26, 2009, the Edgewood monitor recorded a 0.091 ppm; on the same day , the Piney Run and Methodist Hill monitors recorded 0.059 and 0.047 ppm, respectivel y. L ikewise, on July 23, 2010, the Piney

Run monitor recorded a 0.047 ppm while the Edgewood monitor recorded 0.101 ppm. Finally , on June 14, 2008, the Piney Run, Methodist Hill and SNP monitors recorded 0.041, 0.052 and 0.069 ppm, respectivel y, while the Edgewood monitor recorded 0.093 ppm. This data set to correlate the possible “aloft reservoir” with the back - trajectories is limited by the number of higher - elevation monitors in close proximity to the CSA. EPA did not attempt to identify one of these three higher elevation monitors as a good surrogate for each ozone exceedance day within the CSA and on a number of day s could not do so because the back - traje ctories predicted the prevailing winds blew from the Northeast for which none of these three higher - elevation monitors could be considered an adequate surrogate. Instead, EPA could only examine back - trajectories for a number of episodes focusing on those with higher concentrations measured within the CSA or those with higher concentrations measured at one of these three higher elevation monitors to gain a sample of what this data might reveal.

107 Maryland identified these three as examples of higher elevation monitors which might provide an indication of the levels in an elevated reservoir. Refer to http://www.otcair.org/upload/Documents/Meeting%20Materials/ConceptualModel_20090602%20TAD%20FOR%20OTC% 20Final.pdf which Maryland sent to EPA subsequent to their March 7, 2012, response and copy of which has been placed in th e docket. 108 EPA did not necessarily require the back - trajectory to cross the county; if one of these three higher elevation monitors wa s between back - trajectories at different elevations or close enough to be a reasonable indicator, EPA considered the data. 109 The HYSPLIT back - trajectories for the 500 and 1000 meter levels were geographically offset; the 1000 meter trajectory wa s more northerly than the 500 meter one. That the Padonia monitor recorded a higher concentration than Edgewood could be due t o its location dow nw ind of the heavy emissions areas of Baltimore CBSA core. The Back - trajectories for the 100 meter level for bth the Howard - University - Beltsville and Edgewood sites indicated a southerly wind in the CSA. 110 These two days in September 2 010 were near the end of a seven - day (8/28 to 9/3/2010) episode.76

Gradients within the Washington - Baltimore - NV CSA: EPA examined a number of episodes to determine what sorts of ozone gradients are observed within the CSA. EPA examined the back - trajectories to gain some understanding of the prevailing winds on the particular episode day

and considered the ozone concentratio ns at all monitors within the violating center of the CSA. EPA considered a variet y of episodes with emphasis on the longer episodes, those with highest ozone readings, and those with the most widespread extent of measured exceedances. 111 Some single day episodes were considered as well , such as July 23, 2010 on which the Edgewood monitor recorded 0.101 ppm with only two other monitors in the CSA exceeding at 0.082 ppm. EPA considered the peak ozone concentrations at monitors for which the HYSPLIT ba ck - trajectories predicted were on the upwind edge of the CSA for that day of the episode and examined the ozone concentrations across the CSA. In most instances the monitors on the predicted upwind edge were below the 0.075 ppm NAAQS. Sometimes the value s were below 0.060 ppm (60 ppb ) b ut at other times often between 0.070 and 0.074 ppm (70 to 74 ppb). L ower upwind values often correlated with lower peak values and vice versa. For some episodes the HYSPL I T predicted trajectories showed that the prevail ing winds drastically shifted direct by

around 180 degrees. Examples included September 3 and 4, 2008 and April 18 and 19, 2008 where the winds on the first day were northerl y and on the second day were predicted to be southerly . On the first day the northern, upwind monitors for the Washington CBSA were generall y below 0.075 ppm

– sometimes well below at 0.053 to 0.068 ppm

– and the peak values occurred downwind of the core CBSA counties and cities of the Washington CBSA. On the second day , the southern monitors were now predicted to be on the upwind edge; these recorded exceedances in the 0.076 to 0.081 ppm range. In the Baltimore CBSA, on April 18, 2008, both the Aldino and Edgewood monitors recorded values of 0.085 - 0.086 ppm when on the predicted upw ind edge; on the second day

they recorded lower values

– 0.082 ppm at Edgewood and less than 0.075 ppm at Aldino. The high values on April 18 th when both the Aldino and Edgewood monitors were on the predicted upwind edge could be due to these monitors bei ng downwind of the Lancaster and York CBSAs. In the September 2008 episode, both were less than 0.065 ppm when on the predicted upwind edge, and onl y Edgewood recorded an exceedance of 0.080 ppm on September 4 th . Based upon examination of the predicted upwind, ground level concentrations, EPA can conclude that incoming aloft ozone levels do not seem to cause appreciable numbers of exceedances at monitors located at the predicted, upwind edges of the CSA. EPA found that often the monitor at the Equestrian Center in Prince George’s County , 112 the monitors in Anne Arundel (Davidsonville), Charles and Calvert Counties record their highest concentrations when these monitors are downwind of the core CBSA counties and cities of the Washington and/or Baltimor e CBSAs. However, on other day s, these monitors recorded exceedances when they seemed to be on the upwind edge of the CSA, but on these days the exceedances were generall y low in the 0.076 to 0.079 ppm range. The Howard University - Beltsville monitor in P rince George’s County , MD is located between the core CBSA counties and cities of the Washington CBSA and the Baltimore CBSA. As noted elsewhere, EPA found that for a preponderance of the day s where an exceedance of 0.079 ppm or more was recorded at the H oward University - Beltsville monitor that trajectories passed through the core

111 Needless to say, quite often the longest episodes produce the highest concentrations and the widest extent of measured exceedances. 112 this is located essentially east of the District of Columbia as opposed to the Howard U - Beltsville Monitor in the same county which is essentially on a line between Baltimore City and the District; the latter monitor is located near Beltsville, MD between Interstate 95 and the Baltimore - Washington Parkway.77

CBSA counties and cities of the Washington CBSA as well as at time Calvert, Charles, Frederick and St. Mary ’s County

in Maryland and through Fauquier and other outl yi ng Counties in Virginia. EPA did not expend much effort to determine when the monitors in Fauquier, Prince William and Stafford Counties in Virginia recorded high values because the design value at these monitors is comfortabl y below (0.070 ppm or less) the 2008 NAAQS. L ikewise, EPA could not discern definitive trends for the monitors Frederick and Carroll Counties in Maryland because these monitors did not have many exceedances

– 10 and 12, respectivel y, -- in the time period examined. Also, the design values of these monitors are barel y above the 2008 ozone NAAQS at 0.075 or 0.076 ppm. EPA did note that the gradients around the Edgewood monitoring site in Harford County, MD might well be steeper on some day s than elsewhere in the CSA on high exceedance day s. In the Washington CBSA plus the Davidsonville monitor in Anne Arundel County that is close to the border of the Washington CBSA, steep gradients can also occur. EPA considered these two groups separatel y for several reasons: (1) These two sets of monitor s sets are separated b y considerable distance between being literally

at opposite ends of the region of violating monitors in the CSA; (2) Maryland’s persuasive evidence that the Edgewood monitor is affected b y meteorological - topographi cal factors in a manner different from other monitors in the CSA. These observations were made b y comparing the concentration of one monitor with those close to the first and computing the difference. The minimum difference for each exceedance day examined was noted. The monitors in Harford (Aldino) and Baltimore (Essex and Padonia) Counties were considered to be close to the Edgewood monitor. For the Washington CBSA plus Davidsonville site, close monitors might include those in the District, Fairfax and Arlington Counti es in Virginia, those in Prince George’s County , MD plus the Davidsonville monitor in Anne Arundel County , MD. For both sets, the difference could be as low as zero or often as high as 0.010 to 0.011 ppm. For the Washington CBSA/Davidsonville case, the h ighest values were 0.014 ppm. One such day was August 20, 2010; monitors in the District and Arlington County , VA recorded concentrations in the range of 0.077 to 0.081 ppm and the Howard university - Beltsville monitor, for which the HYSPL I T back - trajectories predicted was immediately upwind, recorded a concentration of 0.066 ppm. This value differs from the other two close monitors’ concentrations by 0.011 to 0.015 ppm. Another case was August 30, 2010; The Franconia monitor recorded 0.091 ppm while on e in the District recorded 0.077 ppm for a difference of 0.014 ppm; on the same day the monitors in Calvert and Charles Counties in Maryland recorded 0.098 and 0.087 ppm, respectivel y. In contrast, the Edgewood monitor and on occasion the Essex monitor in Baltimore County , MD record similar concentrations that are appreciabl y higher than other nearb y monitors. The highest differences are shown in Table 3 2 . **Table 3 2**  **. Edgewood**  **and Essex Exceptional Gradients** Date High Monitor Concentration (ppm) Next highest

Concentration (ppm) At location Difference (ppm) 7/11/2008 Edgewood 0.100 0.084 Essex 0.016 6/25/2009 Edgewood 0.109 0.086 Aldino 0.023 7/6/2010 Edgewood 0.092 0.072 Padonia 0.020 7/6/2010 Essex 0.090 0.072 Padonia 0.018 8/10/2010 Edgewood 0.110 0.086 Padonia 0.024 8/10/2010 Essex 0.115 0.086 Padonia 0.029 8/29/2010 Edgewood 0.096 0.066 Aldino 0.030 On July 6 th and August 10, 2010, the HYSPLIT back - trajectories predicted the prevailing winds were from the Northwest. Refer to Figures 4a to 4d and 5a to 5d. In which case, any “bay breeze” effect78

might well affect the concentrations recorded at the Essex monitor in a manner similar to the Edgewood monitor. The Essex monitor is similarly sited to the Edgewood monitor in that it is on a peninsula and close to the Chesapeake Bay ; however, for winds from the Northwest, the Essex monitor is likely downwind of more local emissions because it is closer to Baltimore City within the core of the Baltimore CBSA. EPA concludes that the greater extremes in concentration gradients around the Edgewood monitor than that found in other parts of the CSA could well be an indication that the “Bay Breeze” and/or convergence of southwest and the lee - side winds do in fact result in more extreme exce edances at the Edgewood monitor (and perhaps the Essex monitor at times) than would be otherwise seen. Maryland’s Modeling Results: Subsequent to the State’s March 7, 2012 letter Maryland also provided various summaries of the results of the OTC modeling, or of Maryland modeling including the results summarized in the State’s March 7, 2012 letter. These were:

“ Using CMAQ to Evaluate the Impact of the Washington DC Area on the Baltimore Area , A Series of Sensitivity

Runs to look at Contribution and Culpability , Additional Information for EPA ” MDE and the UMCP , April 7, 2012 And its attachment “ Attachment Baltimore NAA and Maryland Zero Emissions Modeling, and Washington DC NAA Only Emissions Modeling Results , Modeling Completed by Universit y of Maryland College Park (UMD) for the Maryland Department of the Environment (MDE) ” This document included the same summary informat ion as that in Appendix C of the State’s March 7, 2012 letter but also included sensitivity anal ys is for the emissions in the 1997 Washington DC - MD - VA Nonattainment area . A copy of these documents have been placed in the docket for this final action. EPA does not dispute that the 1997 Washington DC - MD - VA Nonattainment area may contribute to ozone concentrations in the 1997 Baltimore Nonattainment area . EPA’s own meteorological assessment resulted in the same conclusion that the prevailing winds on some o zone exceedance day s in Baltimore are such that emissions in the 1997 Washington DC - MD - VA Nonattainment area contribute to ozone levels in the 1997 Baltimore Nonattainment area . However, the issue is , when considered in light of all five factors , whether the 1997 Washington DC - MD - VA and Baltimore nonattainment areas should be one area under the 2008 ozone NAAQS. Generally , the “ Washington DC Area ” case, predicts maximum concentrations that are compatible with EPA’s HYPL T back - trajectories. EPA and Maryland’s data sets do not match up perfectl y; EPA did not run the HYSPLIT model for August 5 th and 8 th due to the low number of exceedances on these two days (two at 0.079 ppm on the 5 th at an attaining monitor and an outside monitor and none on the 8th). Likewise, Maryland did not submit a summary of the results for August 13 th , 16 th and 17 th which were likewise day s with few exceeding monitors (one at 0.076 ppm on the 13 th , one at 0.076 ppm on the 15 th , and three exceedances (0.080, 0.086 and 0.086 ppm) on the 17 th . On August 1 st and 4 th , the HYSPLIT model predicted the prevailing winds were from the Northeast to the Northwest (depending on day and altitude). The Maryland “ Washington DC NAA ” runs predicted the maximum effects south of the District in r oughl y the Southeastern portion of Fairfax County , VA, the Southwest portion of Prince79

George’s County , MD and Northern Charles County . Likewise on August 2 nd , 3 rd , 6 th , 12 th and 15 th , which were day s when the HYSPLIT model predicted the prevailing winds were from the southwest to west - southwest at lower levels (100 and 500 meters), the Maryland model predicted the maximum effects for the Washington DC Area (identified as the “only DC” case in Maryland’s submittal) were northeast of the District of Columb ia along a line between the District and Baltimore City . EPA reviewed the information and only has a few comments. On some day s the base case modeling results suggest widespread non - attainment through the 1997 Washington DC - MD - VA and Baltimore Nonattainment area s when in fact the monitors recorded few exceedances. For example, on August 14, 2007, the results suggested the area of highest concentration was centered on Charles County , MD which in fact was where the only exceedance was recorded (a 0.077 ppm). However, for areas just north and west of the Charles County ’s two Peninsulas , mainly in Fairfax County , VA and Prince George’s County , MD the base case results suggest values well above 0.076 ppm (colored red on the map in Maryland’s submitt al ) , but the Franconia monitor recorded an 8 - hour concentration of 0.071 ppm, and, the Prince George’s Equestrian Center monitor recorded a 0.069 ppm. Similarly , on August 3, 2007, the base case results predicted high values on a line between roughl y the District through northern Prince George’s County

(near the Howard Universit y - Beltsville site)/Montgomery County , MD (home of the Rockville monitor) to Baltimore City and central and North Baltimore County with values much closer to 0.095 ppm than 0.076 ppm (colored red to dark red on the map in Maryland’s submittal ). In fact, a monitor in the District and the one at Rockville, MD both recorded a 0.084 ppm (highest in the CSA); the Edgewood and Aldino monitors in Harford County recorded 0.078 and 0.081 ppm , respectivel y; the Howard - Universit y - Beltsville monitor recorded a 0.077 ppm; and, the Padonia and Essex monitors in Baltimore County

recorded a 0.062 ppm and 0.072 ppm respectivel y. However, for August 4, 2007, a day on which 19 of the current monitors in the CSA recorded exceedances , the base case results predicted a wide area of high values. On that day, the Davidsonville and Prince George Equestrian Center recorded the highest concentrations at 0. 118 and 0.110 ppm, respectively . About 12 monitors re corded concentrations at or more than 0.085 ppm. L ikewise on 7/7/2007, the base case predicted exceedances over a wide portion of the CSA whe n in fact 12 of the current monitors recorded exceedances. EPA acknowledges Maryland noted that for such sensitiv ity runs the exact ppb projections are much less important than the relative (small, medium, large) size and directions of the ozone benefit or disbenefit. Regarding Maryland’s Modeling Results for July 9, 2007: Maryland cited research and modeling per formed by the University

of Maryland (UMD). This includes high resolution (0.5 kilometer (km) domain) WRF (meteorological) and CMAQ (photochemical) modeling in an effort to learn how the bay breeze dy

namics work and if pollution from the Washington area i s transported towards the Edgewood monitor. This high resolution meteorological modeling shows westerl y winds transport ozone and ozone precursors from the Washington region to over the bay starting in the earl y morning hours (7 AM). Refer to Figure 3 - 3 ( of the Maryland submittal) for these meteorological modeling results of the Maryland submittal . Later in the morning, at around 9 AM (EST) meteorological modeling shows winds over the bay become northerl y and stagnation in the northern end of the Chesapeake Bay causes pollutants to accumulate. Refer to Figure 3 - 4 (of the Maryland submittal) for these meteorological modeling results. High resolution CMAQ modeling illustrates how earl y morning stagnation over the Chesapeake Bay allows high pollution concentr ations at the bay breeze convergence zone to buildup and then be lofted and transported downwind towards the Edgewood monitor. Maryland provided summary results in form of map overlay s for the 0.5 km grid and coarser grids for July 9, 2007. One such res ult compared the model - predicted ozone concentrations80

to the actual measured values for July 9 th for 0.5, 1.5, 4.5 and 13.5 km grid resolutions. The higher the resolution (that is, the smaller the grid size) the better the model - predicted values matched the measured value near the Edgewood monitor. EPA acknowledges that Maryland has investigated use of a finer grid around the Edgewood monitoring site for modeling ozone concentrations . EPA does not dispute that such modeling shows that emissions from the Washington CBSA or portions thereof contribute to concentrations in excess of the 2008 ozone NAAQS at the Edgewood monitor. However, using the HYSPLIT model generated back - trajectories, EPA has identified around 15 day s in the last three years where the H YSPL I T predicted prevailing winds did not arrive via the 1997 Washington DC - MD - VA Nonattainment area or even from the Washington CBSA at large ye t the Edgewood monitor recorded exceedances of 0.082 ppm or higher. On around 11 of those day s the recorded co ncentration was 0.087 ppm or higher. The HYSPLIT results predict that Chester, Lancaster and York Counties in Pennsylvania, Cecil and Washington Counties in Maryland, and New Castle County , DE are upwind on some of such day s. All of these counties are p art of other CBSAs and most are designated nonattainment under the 2008 ozone NAAQS. EPA compared the back - trajectories predicted b y the HYSPLIT model to the results Maryland submitted for July 9, 2007. Refer to Figure 5A - 11 in Appendix 5 of this TS D; the July 9, 2007 trajectories are specially indicated. The HYSPLIT back - trajectories showed the winds turning from a northwesterly flow to a flow running to the northeast parallel to the shore of the bay between Anne Arundel County and the Edgewood monitoring site. The 100 meter back trajectory was closest to the bay

and the 1000 meter trajectory

was furthest away

with the 500 meter trajectory in between. The recorded concentration at the Edgewood monitor on July 9 th was 0.0113 ppm which was the h ighest concentration recorded at this monitor in the 5 years 2006 through 2010, inclusive. In the 5 year period 2006 through 2010, inclusive, the Edgewood monitor has recorded five additional concentrations in excess of 0.100 ppm. These occurred on Augu st 10, 2010 (0.110 ppm), June 25, 2009 (0.109 ppm), May 30, 2006 (0.103 ppm), July

18, 2008 (0.102 ppm) and July 23, 2010 (0.101 ppm). The HYSPLIT predicted 15 back - trajectories for these day s of which eight do not pass any where near the 1997 Washington - DC MD - VA nonattainment area or the Washington DC - MD - VA - WV CBSA at all. Refer to Figures 5A - 11 and 5A - 12 in Appendix 5 of this document. Of the remaining seven back - trajectories, three pass through the core CBSA counties and cities of the Washington DC - MD - VA_WV CBSA; two graze either the extreme corner of Montgomery or Prince George’s Counties in Maryland and pass through the outer counties of either Calvert or Frederick (MD); one starts in Pennsylvania then heads southeast through Frederick, Carroll, H oward and Anne Arundel Counties before looping abruptly through Prince George’s and finishes in a northeasterly direction via Anne Arundel towards Edgewood, and, the last passes in a northeasterl y direction through the Winchester Virginia CBSA and the Hage rstown Martinsburg MD - WV CBSA and grazes the northwest corner of Frederick County , MD, then arches through Adams County , PA, and finishes in a southeasterl y direction through Carroll and Baltimore Counties. EPA does not dispute that such modeling shows th at emissions from the Washington CBSA or portions thereof could contribute to concentrations in excess of the 2008 ozone NAAQS at the Edgewood monitor. However, EPA’s anal ys es implicate areas other than portions of the Washington DC - MD - VA - WV CBSA or 1997 Washington DC - MD - VA ozone nonattainment area on day s when particularl y high ozone concentrations have been recorded at the Edgewood monitor. EPA cannot concur with Maryland’s conclusion that mobile source emissions in the 1997 Washington DC - MD - VA ozone no nattainment area or even the Washington DC - MD - VA - WV CBSA are the sole cause of the higher ozone concentrations measured at Edgewood based upon the results of a single episode day .81

**4. Notes on**  **Fredericksburg, VA Area, Frederick County, VA Area, and the “ other counties:”**  The closest monitors to the “outer rim” Virginia and West Virginia counties in the Washington Baltimor e - NV CSA are attaining the 2008 ozone NAAQS. These “outer rim” counties are the Counties of Frederick, Warren, Clarke, and Culpeper and Winchester City in Virginia, and Jefferson County , WV. The most relevant attaining monitors are those in Frederick County, MD and in L oudoun, Prince William, Fauquier, and Stafford Counties in Virginia. Of these “outer rim” counties, Clarke County , VA and Jefferson County , WV are adjacent to Frederick Count y, MD or Loudoun County, VA , both of which contain a monitor with a design value of 0.075 ppm. The monitors attaining the 2008 ozone NAAAQS in Frederick County , MD or Loudoun County , VA are located be tween Clarke County , VA and/or Jefferson Count y, WV, and the violating monitors in Carroll County , MD and/or Fairfax County , VA. In contrast, Culpeper County , VA is adjacent to Fauquier Count y which contain s a monitor with a design value of 0.070 ppm or l ower. Prince William County , VA is interposed between Fauquier, and Stafford Counties , and thus between Culpeper County and the violating monitor in Fairfax County . To the extent Clarke County, VA and Jefferson County , WV are upwind of the monitors in Frederick County , MD or Loudoun County , VA their contribution to air quality in Frederick Count y, MD or Loudoun Count y, VA does not result in a violation of the 2008 NAAQS. In the case of Culpeper County , VA, to the extent it is upwind of the monitors in to Fauquier, Prince William , and Stafford Counties Culpeper County ’s contribution to air quality in the latter three counties does not result in a violation of the 2008 NAAQS. The case of Frederick or Warren Counties and Winchester City in Virginia is the same as the case for Clarke County , VA and Jefferson County , WV. **5. Original Wind Roses:** The original wind roses in Factor 3 anal ys is in “ Technical Anal ys is for the Washington, DC - MD - VA and Baltimore Areas” in Docket item numbers EPA - HQ - OAR - 2008 - 0476 - 0235 are reproduced in Appendix 8 . 

### Factor **4 : Geography/topography (mountain ranges or other air basin boundaries)**  The geograph y/topography anal ys is evaluates the phy sical features of the land that might affect the airshed and, there fore, the distribution of ozone over the area. Warren and Clarke C ounties are separated from the rest of the Washington - Baltimore - NV CSA by the easternmost portion of the Appalachian Mountains. 113 The Frederick County , VA area is west of these two counties and thus is also separated from the major, urbanized portions of this CSA by the easternmost portion of the Appalachian Mountains. Jefferson County , WV is adjacent to Clarke County , VA and also is so separated. Oth er than Warren and Clarke Counties discussed in the preceding paragraph, the Washington Baltimore - NV CSA area generall y does not have any geographical or topographical barriers appreciably

113 Page 3 - 593 of “Chapter 3 Justifications in Support of EPA's 8 - hour Ozone Des i gnation s & Classifications” docket item EPA - HQ - OAR - 2003 - 0083 - 1813 in docket EPA - HQ - OAR - 2003 - 0083 (dow nloaded May 27, 2011) and available on - line at Regulations.gov (http://www.regulations.gov/#!home;oldLink=false).82

limiting air pollution transport within its air shed. Therefore, there are no barriers to transport elsewhere in this CSA . Maryland agreed with the EPA conclusion that the Washington - Baltimore - NV CSA generall y does not have an y barriers appreciably limiting air pollution within its air shed. The Appalachian Mountains are a barrier to surface transport but not to aloft transport of ozone and ozone precursors. Maryland states that the following geographical features create meteorological phenomenon that function in a role similar to geographical barriers: (1) The Chesapeake Bay

“breeze” play s a role similar to a geographical barrier by preventing pollution from blowing out to sea and channeling it back toward the Baltimore area, and especially at the Edgewood monitor. (2) Maryland also said that the position of the Appala chian Mountains enables formation of a meteorological phenomenon called a “leeside trough.” According to the American Meteorological Association Glossary (2010), a leeside trough is “a pressure trough formed on the lee side [opposite the wind] of a mountai n range in situations where the wind is blowing with a substantial component across the mountain ridge; often seen on United States weather maps east of the Rocky Mountains, and sometimes east of the Appalachians.” Maryland said that the leeside trough us ually develops over Maryland, this phenomenon results in pollutants from the Ohio River Valley and Western PA veering (or turning northward) into Maryland and at the same time allows ozone and ozone precursors to be transported from Virginia and North Caro lina into Maryland too. (3) Another meteorological phenomenon that results from the location of the Appalachian Mountains to the west and the Atlantic Ocean to the east is the nocturnal low level jet (NLLJ). The NNLJ is a fast moving stream of air that is ty pically observed between the Appalachian Mountains and the Atlantic Ocean during the late night and early morning hours. This fast moving stream of air can reach speeds of 40 mph and stretches from North Carolina to Maryland and further. EPA has cons idered certain geographical - topological related phenomenon which affects air movements under the Factor 3 Meteorology response. EPA acknowledges that the “leeside” trough and the “bay breeze” could well act as barriers to air movement and tend to concentrate ozone levels at the Edgewood monitor site more than elsewhere. To the extent the “leeside” trough and NLLJ relate to transport from other States beyond the scale of intra - CSA or transport from adjacent CBSAs, EPA considers such transport to be within the scope of the prohibitions of sections 110(a)(2)(D) and/or 176A. EPA has addressed Maryland’s comments in sections 3.1.2 and 3.2.3.1 of “Responses to Significant Comments on the State and Tribal Designation Recommendations for the 2008 Ozone National Ambient Air Quality Standards (NAAQS),” Docket Number EPA - HQ - OAR - 2008 - 0476, U.S. Environmental Protection Agency , April 2012. EPA has reviewed Maryland’s information on the NLLJ and concludes that by Maryland’s own data

– winds travelling 200 miles overn ight

– the NLLJ is indicative of long - range transport not to be addressed when designating nonattainment areas under section 107(d). **Factor 5**  **: Jurisdictional boundaries** EPA consider s existing jurisdictional boundaries for the purposes of providing a clearl y defined legal boundary and carrying out the air quality planning and enforcement functions for nonattainment areas.83

Examples of jurisdictional boundaries include existing/prior no nattainment areas for ozone or other urban - scale pollutants, counties, air districts, townships, metropolitan planning organizations (MPOs) , state lines, Reservations, urban growth boundary , etc. Where existing jurisdictional boundaries are not adequate t o describe the nonattainment area, other clearl y defined and permanent landmarks or geographic coordinates are used . For the 1997 ozone NAAQS, the Washington - Baltimore - NV CSA is was broken down as shown in Table 33 :84

**Table 3**  **3 . Breakdown of the Washing**  **ton -**  **Baltimore -**  **NV CSA by Area under the 1997 Ozone NAAQS.**  Area Name Constituent Counties and Cities: Status (as of November 22, 2011) (40 CFR 81.309, 81.321, 81.347 and 81.349) 1997 Baltimore Nonattainment Area: Anne Arundel, Baltimore, Carroll, Harford, and Howard Counties and Baltimore City in Maryland. Nonattainment - Serious 114

1997 Washington DC - MD - VA Nonattainment Area: Maryland Portion: Frederick, Montgomery , Calvert, Charles and Prince George ’ s Counties. The entire District of Columbia . Virginia Portion: Arlington, Fairfax, L oudoun, Prince William Counties, and, the Cities of Alexandria, Fairfax, Falls Churc h, Manassas, and Manassas Park. Nonattainment - Moderate 115

Frederick Count y , VA Area : Frederick Count y and Winchester City

in Virginia . Attai nment Fredericksburg, VA Area : City of Fredericksburg and Spotsylvania and Stafford Counties in Virginia. Attainment (Maintenance) Queen Anne ’ s County

portion of the Kent County

and Queen Anne ’ s County

Area: Queen Anne ’ s County in Maryland Attainment (Maintenance) Other Attainment Counties: In Maryland: St. Mary ’ s County In Virginia: Clarke, Culpeper, Fauquier, and Warren Counties. In West Virginia: Hampshire and Jefferson Counties . Attainment Attainment Attainment “Attainment (Maintenance)”signifies an area initially designated nonattainment effective June 15, 2004 ( 69 FR 23858 , April 30, 2004) and later redesignated to attainment subject to a maintenance plan under section 175A of the CAA. “Attainment” signifies an area initi all y designated attainment effective June 15, 2004 ( 69 FR 23858 , April 30, 2004) or April 15, 2008 ( 73 FR 17897 ) .

114 EPA reclassified the area on February 1, 2012. Refer to 77 FR 4901. 115 EPA determined that the area attained by its statutory, applicable attainment date and remains in attainment. Refer to 77 FR 11739 , Feb. 28, 2012.85

The boundaries of the Baltimore severe nonattainment area under the 1 - hour ozone NAAQS were the same as those for the 1997 ozone NAAQS shown in the preceding table. (56 FR 56694 , November 6 , 1991) The boundaries of the Washington DC - MD - VA severe nonattainment area under the 1 - hour ozone NAAQS included those shown for the 1997 ozone NAAQS shown in the preceding table plus Stafford County , VA ( 56 FR 56694, November 6, 1991 ). Queen Anne ’ s County

in Maryland was part of the Kent County and Queen Anne ’ s County 1 - hour attainment (maintenance) area under the 1 - hour ozone NAAQS. All other portions of the Washington - Baltimore - NV CSA were designated attainment for the 1 - hour ozone NAAQS ( 56 FR 56694 , November 6 , 1991) . As far as transportation planning is concerned , the Baltimore and Washington DC - MD - VA nonattainment area s are served b y different MPO s . T he N ational Capital Region Transportation Planning Board (TPB) is the MPO for much of the Washington - Arlington - current Washington DC - MD VA nonattainment area . TPB ’ s planning area covers the District of Columbia and surrounding jurisdictions. In Maryl and these jurisdictions include Frederick County , Montgomery Count y, and Prince George ’ s Count y and the St. Charles urbanized area of Charles County , plus the cities of Bowie, College Park, Frederick, Gaithersburg, Greenbelt, Rockville, and Takoma Park. In Virginia, the planning area includes Alexandria, Arlington County , the City of Fairfax, Fairfax County , Falls Church, Loudoun Count y, and the Cities of Manassas and Manassas Park, and Prince William County . 116 T he Baltimore Regional Transportation Board consists of 11 members of the Baltimore Regional Transportation Board are made up of elected officials from the cities of Annapolis and Baltimore, the counties of Anne Arundel, Baltimore, Carroll, Harford and Howard . 117 Likewise, the Fredericksburg VA Are a is covered by its own MPO

– the Fredericksburg Area Metropolitan Planning Organization (FAMPO). FAMPO’s region includes the City of Fredericksburg and counties of Spotsylvania and Stafford. 118 The air qualit y planning for the Washington DC - MD - VA area has been a multi - jurisdictional area since before 1990. Section 107 (d)(4)(A) of the CAA set the presumptive boundaries for serious and higher classified ozone nonattainment areas at the larger of the CBSA or Consolidated Metropolitan Statistical Area (CMSA) area subject to certain alterations allowed by section 107 (d)(4)(A) . In addition, the Metropolitan Washington Air Quality Committee (MWAQC), a multi - state air qualit y planning organization comprised of : (1) elected officials of the Council of Governments (COG) member jurisdictions plus members from Charles, Calvert, and Stafford counties; (2) the air management and transportation directors of the District of Columbia, Maryland, and Virginia; (3) members of the Maryland and Virginia General Assemblies; and (4) the chair of the TPB . 119 The principal mandates of MWAQC are to prepare plans demonstrating attainment of the federal ozone standards and “rate of progress” reductions in criteria pollutants and prep are inventories and budgets of emission s for the current Washington DC - MD - VA nonattainment area. No other area (nonattainment or otherwise) has such a group. Past practice dictates against splitting the relevant portions of the current Washington DC - MD - VA nonattainment area along state lines.

116 http://www.mwcog.org/transportation/tpb/ , last checked November 28, 2011. 117 “ BRTB Members ,” http://www.baltometro.org/transportation - planning/brtb - members last checked November 28, 2011. 118 “About FAMPO,” http://www.fampo.gw region.org/ last checked November 28, 2011. 119 "BYLAWS of the Metropolitan Washi ngton Air Quality Committee" as amended through October 27, 2004. http://www.mwcog.org/environment/air/downloads/MWAQC_bylaws.PDF downloaded November 28, 2011.86 

### Summary of the 5 **- Factor Analysis:**  **Individual Count y**  **/City Summaries: Harford County:**  Harford County must be designated nonattainment due to the presence of two monitors violating the 2008 ozone NAAQS. It contains the monitor with the highest design value within the Washington - Baltimore - NV CSA as well as the 1997 Baltimore nonattainment area. Harford County has total emissions which are neither at the low or high end

– it ranks in the middle (that is between 12 th through 23 rd inclusive when ranked from largest to smallest) within the Washington - Baltimore - NV CSA; likewise, its mobile source emissions are also ranked 11 th for both VOC and NOx; its population is one tenth of that in the 1997 Baltimore nonattainment area and not exceptionally large or small; its population density

is half the overall average for the 1997 Baltimore nonattainment area; commuting patterns indicate it is linked to the Baltimore CBSA as an outl yi ng county ; traffic patterns merit no special attention one way or another; meteorology indicates its total emissions may contribute to nonattainment in Baltimore County (as well as to its own nonattainment). Meteorology indicates it is downwind of Baltimore County , adjacent CBSAs in Maryland and Penns ylvania, Baltimore Cit y , the Counties/Cities/States of Anne Arundel, Howard, Montgomery , Prince George’s, Fairfax 120 , Arlington 121 , Frederick (MD), The District 122 , and to a lesser extent, the Counties of Calvert, Charles, Prince William, L oudoun. Factors th at favor placement of this county in a nonattainment area containing Baltimore County and hence as part of a Baltimore Area with the same or similar boundaries as for the 1997 Baltimore nonattainment area are jurisdictional boundaries and meteorology which indicates it is often downwind of all the other counties in the Baltimore CBSA . It is upwind of other many violating monitors in the CSA though rarel y that in Carroll county. It is also often downwind of CBSAs in Delaware, Maryland and/or Pennsylvania a djacent to the Washington - Baltimore - NV CSA. **Baltimore County:** Baltimore County must be designated nonattainment due to the presence of two monitors violating the 2008 ozone NAAQS. Baltimore County is among “top six ” counties for total emissions in the W ashington - Baltimore - NV CSA. It s mobile source emissions are ranked 3rd for VOC and 2nd for NOx. It is adjacent to Harford County which has the highest design value in the Washington - Baltimore - NV CSA and the 1997 Baltimore nonattainment area. It has the highest population in the 1997 Baltimore nonattainment area. Its growth rate is well below the Washington Baltimore - NV CSA’s average, but equal to the 1997 Baltimore nonattainment area average rate. Ithas the highest VMT within the 1997 Baltimore nonatt ainment area and third highest within the Washington - Baltimore - NV CSA. Its VMT is about one - third the total for the 1997 Baltimore nonattainment area and about one - ninth of the total for the Washington - Baltimore - NV CSA. Commuting patterns link it to the Baltimore CBSA as a core count y. Meteorology indicates it is upwind of Harford County ’s Edgewood and Anne Arundel’s Davidsonville monitor s much of the time and is upwind of other monitors in the CSA though rarely that in Carroll County. Meteorology indicates it is downwind of Harford County , Baltimore City , and the Counties/Cities/States of Anne Arundel, Howard, Montgomery , Prince George’s, Fairfax 123 , Arlington 124 , Frederick (MD), The District 125 , and to a lesser

120 Wherever Fairfa x County is indicated also includes at times Fairfax City and Alexandra City. 121 Wherever Arlington County is indicated also includes at times Falls Church City 122 Wherever the District is indicated also includes at times Alexandra City. 123 Wherever Fairfax County is indicated also includes at times Fairfax City and Alexandra City. 124 Wherever Arlington County is indicated also includes at times Falls Church City 125 Wherever the District is indicated also includes at times Alexandra City.87

extent, the Counties/Cities/States of Calvert, Charles, Prince William, L oudoun. It is also likel y downwind of CBSAs in Delaware, Maryland and/or Pennsylvania adjacent to the Washington Baltimore - NV CSA. Factors that favor placement of Baltimore County in a nonattainment area containing Harford and Anne Arundel Counties , that is, as part of the Baltimore Area with the same or similar boundaries as the 1997 Baltimore nonattainment area , are its total emissions , jurisdictional boundaries , commuting patterns, and meteorology

which indicates it is upwind of a violating monitor s in Harford and Anne Arundel Counties . We weigh the factors as supporting placement in a Baltimore Area with the same or similar boundaries as the 1997 Baltimore nonattainment area. **Baltimore City:** This city does not have violating monitor. It ranks in the “top six ” counties for total emissions within the Washington - Baltimore - NV CSA and third (of six) in the 1997 Baltimore nonattainment area. Its mobile source emissions are ranked 7th for VOC and 8th for NOx. Itis densely populated, but experienced a population decline over the past 10 ye ars. Its VMT is about one - eighth that of the 1997 Baltimore nonattainment area. Meteorology indicates it is upwind of Harford County’s Edgewood monitor and likely those in Baltimore County at times and of Anne Arundel’s Davidsonville monitor much of the time and is upwind of other monitors in the CSA though rarel y that in Carroll County . Commuting patterns link it to the Baltimore CBSA as a core county . Factors that favor designation of Baltimore City as nonattainment based upon contribution are total emissions , commuting patterns, jurisdictional boundaries, and possible contribution to Anne Arundel, Harford and Baltimore Counties. These factors support placement in a Baltimore Area with the same or similar boundaries as the 1997 Baltimore nonattainment area. **Howard County:** Howard County does not have a violating monitor. It ranks in the “top 11” counties for total emissions within the Washington - Baltimore - NV CSA and fourth (of six) in the 1997 Baltimore nonattainment area. Its mobile source emissions are ranked 8th for VOC and 7th for NOx. Itis densely populat ed. Its growth rate is about equal to the Washington - Baltimore - NV CSA’s average but over twice that for the 1997 Baltimore nonattainment area average. Its VMT is not exceptional. Commuting patterns link it to the Baltimore CBSA as a core county . Meteorology

indicates it is upwind of violating monitors throughout the CSA especiall y those around the District - Arlington - Fairfax - Prince George’s Counties/States, those in Anne Arundel, Baltimore and Harford Counties and that in Carroll County . Meteoro logy suggests it has about equal influence on nonattainment in the 1997 Baltimore nonattainment area and in the 1997 Washington DC - MD - VA nonattainment area. Factors that favor designation of Howard County as nonattainment based upon contribution are its t otal emissions , jurisdictional boundaries, and meteorology indicating contribution to violating monitors in Harford, Baltimore and Carroll Counties. Factors that favor placement with Prince George’s County and other 1997 Washington area monitors are its possible contribution. That it is part of the Baltimore - Towson CBSA and not the Washington CBSA suggests that it is more linked to the former b y commuting and hence mobile source emissions. Factors that favor designation of Howard County as nonattainment based upon contribution are total emissions , commuting patterns, jurisdictional boundaries, and possible contribution to Anne Arundel, Harford and Baltimore Counties. These factors support placement in a Baltimore Area with the same or similar boundarie s as the 1997 Baltimore nonattainment area.88

**Carroll County:** Carroll County must be designated nonattainment due to the presence of a monitor violating the 2008 ozone NAAQS. It is adjacent to one other county with a violating monitor

– Baltimore County . It has total emissions which are neither at the low or high end

– it ranks in the middle (12 th through 23 rd inclusive) within the Washington - Baltimore - NV CSA. It s mobile source emissions are ranked 17th for VOC and 18th for NOx. Ithas the lowest population and population density within the 1997 Baltimore nonattainment area with a growth rate less than the Washington Baltimore - NV CSA’s average but twice that for the 1997 Baltimore nonattainment area. L ikewise, its VMT and number of commuters are at the lower end for the Washington - Baltimore - NV CSA and the 1997 Baltimore nonattainment area. Commuting patterns link it to the Baltimore CBSA as an outl yi ng county . That it is part of the Baltimore - Towson CBSA and not the Washington CBSA suggests that it is more linked to the former by commuting and hence mobile source emissions. Meteorology

indicates that it is upwind of the violating monitor s in Harford and Balt imore Counties as well as violating monitors throughout the CSA , especiall y those around the Arlington - Fairfax - Prince George’s Counties/States, those in Anne Arundel, Baltimore and Harford Counties and to a lesser extent the District. It is downwind of the Counties /Cities/States of Howard , Montgomery , Arlington, Anne Arundel, Prince George’s, Fa irfax, the District of Columbia, and Charles, and, to a lesser extent Loudoun , Calvert, Frederick (MD), Prince William, and Baltimore Counties plus Baltimore City . Its monitor has a design value w ithin 0.001 parts per million (ppm ) of attaining the 2008 ozone NAAQS. This air quality

consideration suggests that the monitor in Carroll County will likely

be attaining the 2008 NAAQS within a few y ears without further controls and will not be the key monitor needed for attainment withi n the Washington - Baltimore - NV CSA or in an area containing Harford County. Factors favoring including it as part of a Baltimore Area with the same or similar boundaries as for the 1997 NAAQS: (1) jurisdictional boundaries; (2) possible contribution to mon itors in the Baltimore CBSA, (3) contribution from the Baltimore area; and ( 4 ) commuting patterns. Factors favoring inclusion with the 1997 Washington DC - MD - VA nonattainment area counties are meteorology supporting contribution from th is area to Carroll C ounty and vice versa. The possible contribution to the violating monitor in Carroll County from Anne Arundel, Frederick (MD), Prince George’s and Montgomery Counties in Maryland is likely more than the possible contribution from the closest areas in oth er States

– the District plus Arlington, Fairfax, and Lo udoun Count ies because the total (NOx plus VOC) emissions from these Maryland counties (53,000

– 69,000) are somewhat greater that of the out - of - State areas (44,000

– 48,000) and because the Maryland counties are more proximate. EPA has determined that these out - of - State areas should be designated nonattainment , and, to the extent that emissions from these out - of - State areas may

contribute ozone concentrations in Carroll County , that contribution wil l be lessened b y emission controls already in place in those out - of

- State areas . Overall the factors support placement in a Baltimore Area with the same or similar boundaries as the 1997 Baltimore nonattainment area since placement of Carroll County will not affect the probable needed controls for attainment at the South Carroll monitor. **Anne Arundel County:** Anne Arundel County must be designated nonattainment due to the presence of a monitor violating the 2008 ozone NAAQS. It is among the “top six” in total emissions in the Washington - Baltimore - NV CSA and the top two in the 1997 Baltimore nonattainment area. Its mobile source emissions are ranked 5th for VOC and 5th for NOx. Itis more densely populated than the either the average for the Washingto n - Baltimore - NV CSA or the 1997 Baltimore nonattainment area. Its growth rate is less than the Washington - Baltimore - NV CSA’s average but higher than that for the 1997 Baltimore nonattainment area. Its VMT is about one - fifth the total for the 1997 Baltimor e89

nonattainment area and about one - thirteenth of the total for the Washington - Baltimore - NV CSA. Commuting patterns link it to the Baltimore CBSA as a core county . That it is part of the Baltimore Towson CBSA and not the Washington CBSA suggests that it i s more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of many monitors in the CSA but in particular Edgewood in Harford County . Meteorology

indicates it is downwind of the Counties /Cities/ States of Baltimore Co., Calvert, Prince George's , Howard, Fairfax, Charles, the District, Baltimore City , Montgomery , and to a lesser extent, L oudoun, Arlington, Prince William, and Frederick (MD). Factors that favor inclusion of Anne Arundel County in a nonattainment area based upon contribution are its total emissions , jurisdictional boundaries, commuting patterns and meteorology in that it is proximate to and a possible contribut or to Edgewood in Harford Count y. Factors that favor inclusion with a nonattainment area including the District, Fairfax, Calvert , Arlington and Prince George’s Counties are meteorology and total emissions . Factors that favor inclusion with Baltimore City and County

and Harford County

are jurisdictional boundaries. Air quality

considerations suggest that the monitor in Anne Arundel County might likely be attaining the 2008 NAAQS within a few ye ars without further controls and will not be the key monitor needed for attainment within the Washington - Baltimore - NV CSA or in an area containing Harford County . For these reasons, the factors weigh in favor of grouping Anne Arundel County with the rest the Baltimore nonattainment area. **Fairfax County, VA:** Fairfax County must be designated nonattainment due to the presence of a monitor violating the 2008 ozone NAAQS. It contains the monitor with the second highest design value within the Washington - Baltimore - NV CSA as well as the 1997 Washington DC - MD - VA nonattainment area. However, its de sign value is only 0.002 ppm more than other monitors in the District of Columbia and Arlington County . The monitors in Arlington and Fairfax Counties and in the District of Columbia are clustered in a relatively small area at the core of the Washington - A rlington - Alexandria, DC - VA MD - WV MSA. Fairfax County is among the “top six” counties for total emissions in the Washington Baltimore - NV CSA. It s mobile source emissions are ranked 1st for VOC and 1st for NOx. Ithas the highest population in the Washington - Baltimore - NV CSA. Its growth rate is slightly below the Washington - Baltimore - NV CSA’s average rate and the 1997 Washington DC - MD - VA nonattainment area’s average rate. It has the highest VMT and number of commuters within the 1997 Washington DC MD - VA nonattainment area and highest within the Washington - Baltimore - NV CSA. Its VMT is about one - fourth the total for the 1997 Washington DC - MD - VA nonattainment area and one - seventh of the total for the Washington - Baltimore - NV CSA. Commuting patterns link it to the Washington CBSA as a core count y. Meteorology

indicates it is upwind of violating monitors in Arlington County , VA and the District of Columbia and in Prince George’s County as well as those in Anne Arundel, Prince George’s, Baltimore and Harford Counties. Meteorology indicates it is downwind of the Counties /Cities/States of Arlington, Fairfax City , Loudoun, Alexandria City , Prince George's , Ch arles, the District, Montgomery , Baltimore Co., Calvert, Howard, Baltimore City , and to a lesser extent Frederick (MD) , Prince William and the Fredericksburg area.90

Factors that favor inclusion in a nonattainment that includes Arlington County and the District of Columbia, that is, as part of a Washington - DC - MD - VA nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS are its total emissions , meteorology , commuting patterns, the close proximity

of Arlington and Fairfax Counties’ and the District of Columbia’s monitors with design values of 0.079 to 0.081 ppm at the Arlington - Fairfax - District core, jurisdictional boundaries and Virginia’s recommendation. Factors that favor inclusion in a nonattainment that includes Ann e Arundel , Harford, and Baltimore Counties , that is, as part of a Baltimore nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS , are its total emissions , meteorology , For these reasons, the factors weigh in favor of inclusion of Fairfax County in a nonattainment area that includes Arlington County and the District of Columbia, that is, as part of a Washington - DC - MD - VA nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS **Prince George’s County, MD:**  Prince George’s County must be designated nonattainment due to the presence of two monitors violating the 2008 NAAQS. It is among the “top six” counties for total emissions in the Washington - Baltimore - NV CSA and essentiall y tied for second wi th Montgomery County , MD within the 1997 Washington DC - MD - VA nonattainment area. It s mobile source emissions are ranked 2nd for VOC and 3rd for NOx. Itis more densel y populated the either the average for the Washington - Baltimore - NV CSA or the 1997 Washi ngton DC - MD - VA nonattainment area. Its growth rate is slightl y less than that in the Washington - Baltimore - NV CSA and 1997 Washington DC - MD - VA nonattainment area averages. Itis the third most populous area in the Washington - Baltimore - NV CSA and 1997 Wash ington DC - MD - VA nonattainment area. Ithas the second highest VMT and third highest number of commuters within the Washington - Baltimore - NV CSA. Commuting patterns link it to the Washington CBSA as a core county. That it is part of the Washington CBSA an d not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. It s VMT is about one - fifth the total for the 1997 Washington DC - MD - VA nonattainment area and about one - ninth of the total fo r the Washington - Baltimore - NV CSA. Meteorology

indicates it is upwind of violating monitors in Calvert, Arlington and Fairfax Count ies and the District of Columbia as well as those in Anne Arundel, Baltimore and Harford Counties and to a lesser extent, Carroll County . Meteorology

indicates it is downwind of the Counties /Cities/States of Arlington, District of Columbia, Anne Arundel, Charles , Fairfax, Montgomery , Howard , Prince William, Baltimore Co. and City , and to a lesser extent: L oudoun, Calvert , and Frederick (MD) and the Fredericksburg area. M eteorology

favors including Prince George’s County as part of a nonattainment area with either Anne Arundel County or with Fairfax and Arlington Counties plus the District Factors that favor inclusion i n a nonattainment that includes Arlington County and the District of Columbia, that is, as part of a Washington - DC - MD - VA nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS , are its jurisdictional boundaries, commuting patte rns, total emissions , meteorology , and commuting patterns .91

Factors that favor inclusion in a nonattainment area that includes Anne Arundel, Harford, and Baltimore Counties , that is, as part of a Baltimore nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS are its total emissions , and meteorology . Therefore, the factors favor grouping Prince George’s County with the Fairfax County , VA and the District of Columbia monitors as part of a Washington - DC - MD - VA Area with the same or similar boundaries as for the 1997 ozone NAAQS. **Montgomery County, MD:** Montgomery County does not have a violating monitor, but has a monitor with a design value of 0.074 ppm. It is among the “top six” counties for total emissions in the Washington - Baltimore - NV CSA and essentially tied for second with Prince George’s County , MD within the 1997 Washington DC - MD - VA nonattainment area. Its mobile source emissions are ranked 4th for VOC and 4th for NOx . Itis more densel y populated the either the average for the Washington Baltimore - NV CSA or the 1997 Washington DC - MD - VA nonattainment area. Its growth rate is slightl y less than the Washington - Baltimore - NV CSA and 1997 Washington DC - MD - VA nonattainment area averages. It is the second most populous area in the Washington - Baltimore - NV CSA and 1997 Washington DC - MD - VA nonattainment area. It has the fourth highest VMT within the Washington Baltimore - NV CSA and third highest number of commuters within the Washington - Baltimore - NV CSA. Its VMT is about one - sixth the total for the 1997 Washington DC - MD - VA nonattainment area and about one - tenth of the total for the Washington - Baltimore - NV CSA. Commuting patterns link it to the Washington CBSA as a core count y . That it is part of the Washington CBSA and not the Baltimore Towson CBSA suggests that it is more linked to the former CBSA b y commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/States of Baltimore, Harford, Arlington Fairfax, Calvert, Prince George’s, and Anne Arundel Count ies and the District of Columbia and to a lesser extent Carroll. The monitor in Carroll County has a design value is within 0.001 ppm of attai ning the 2008 ozone NAAQS. This air quality consideration suggests that the monitor in Carroll County

will likely

be attaining the 2008 NAAQS within a few years without further controls and will not be the key

monitor needed for attainment within the Wash ington - Baltimore - NV CSA or in an area containing Harford County . Factors that favor inclusion in a nonattainment area that includes Arlington County and the District of Columbia, that is, as part of a Washington - DC - MD - VA nonattainment area with the sam e or similar boundaries as for the 1997 ozone NAAQS are its jurisdictional boundaries, commuting patterns, total emissions , meteorology to some extent , and commuting patterns . Factors that favor inclusion in a nonattainment area that includes Anne Arun del, Harford, and Baltimore Counties , that is, as part of a Baltimore nonattainment area with the same or similar boundaries as for the 1997 ozone NAAQS are its total emissions , and meteorology to a fair extent. Therefore, the factors favor grouping Princ e George’s County with the Fairfax County , VA and the District of Columbia monitors as part of a Washington - DC - MD - VA Area with the same or similar boundaries as for the 1997 ozone NAAQS. **Frederick County, MD:** Frederick Count y does not have a violating monitor, but has a monitor with a design value of 0.074 ppm. It ranks in the “top 11” counties for total emissions within the Washington Baltimore - NV CSA and fifth in the 1997 Washington DC - MD - VA nonattainment area. It is sparsely92

populated. Its mobile source emissions are ranked 10th for VOC and 9th for NOx. It s growth rate is a little more than the 1997 Washington DC - MD - VA nonattainment area average but over 1.5 times that of the Washington - Baltimore - NV CSA’s average. Its VMT is not excep tional. Commuting patterns link it to the Washington CBSA as an outlying count y. That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in Baltimore and Harford Counties and to a lesser extent the Counties/Cities/States of Arlington , Fairfax, Calvert, Prince George’s, Carroll and Anne Arundel Count ies and the District of Columbia . M eteorology slightl y favors for including Frederick County as part of a nonattainment area with Baltimore and Harford Count ies. Factors that favor inclusion in a nonattainment area containing Baltimore and Harford Count ies are meteorology and e missions. F actors that favor inclusion with a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are jurisdictional boundaries as part of the 1997 Washington DC - MD - VA nonattainment area , and commuting patte rns. Therefore, the factors favor grouping Frederick County , MD with the Fairfax County , VA and the District of Columbia monitors as part of a Washington - DC - MD - VA Area with the same or similar boundaries as for the 1997 ozone NAAQS. **Calvert County, M D:**  Calvert County must be designated nonattainment due to the presence of a monitor violating the 2008 ozone NAAQS. It ranks in the “middle group” (between 12 th and 23 rd inclusive) for NOx and VOC total emissions within the Washington - Baltimore - NV CSA. Its mobile source emissions are ranked 23rd for VOC and 24th for NOx. Ithas the smallest population of any county (and even less than Alexandria City , VA) in the 1997 Washington DC - MD - VA nonattainment area (some cities in Virginia are smaller). It has the lowest VMT of an y county (but those of most cities in Virginia are smaller) within the 1997 Washington DC - MD - VA nonattainment area. Its growth rate is one and one half times the Washington - Baltimore - NV CSA’s average but the overall change is low. Its population density

is low at less than one third that of the 1997 Washington DC - MD - VA nonattainment area. Commuting patterns link it to the Washington CB SA as an outl yi ng county . That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities /States of Arlington , Fairfax, and Anne Arundel Counties and to a lesser extent the Counties/Cities/States of Prince George’s, Baltimore, Harford, Carroll and the District of Columbia . Meteorology indicates it is downwind of the Counties/Cities/States o f Prince George’s, Anne Arundel, Baltimore Co. and City , Howard, and to a lesser extent: Fairfax, Montgomery , Frederick (MD), Carroll, Harford plus possibly Saint Mary ’s, and Charles. Air quality

considerations suggest that Calvert and Prince George’s and Anne Arundel Counties will attain the 2008 NAAQS within about the same time period without further controls and th at none of the monitors in these counties will be the key monitor needed for attainment within the Washington Baltimore - NV CSA or in an are a containing Fairfax County .93

Factors that favor inclusion in a nonattainment area containing Anne Arundel or Harford Count y as part of a Baltimore Area with the same or similar boundaries as the 1997 Baltimore nonattainment area are meteorology

which in dicates that at times Calvert County is upwind of Anne Arundel and Harford at times. Factors that favor inclusion in a nonattainment area containing Prince George’s and Fairfax Counties are: meteorology

which indicates Calvert County could contribute to and could receive contribution from counties which are part of the 1997 Washington - DC - MD - VA nonattainment area , commuting patterns and jurisdictional boundaries. Therefore, th e factors favor grouping Calvert County with the Fairfax County , VA and the District of Columbia monitors as part of a Washington - DC - MD - VA Area with the same or similar boundaries as for the 1997 ozone NAAQS. **Charles County, MD:** Charles County does not have violating monitor but has a monitor with a design value of 0.075 ppm. It ranks in the “middle group” (between 12 th and 23 rd inclusive) for NOx and VOC total emissions within the Washington - Baltimore - NV CSA. It s mobile source emissions are ranked 18th for VOC and 19th for NOx. It s population is smaller than any county in the 1997 Washington DC - MD - VA nonattainment area except Calvert County (but those of cities in Virginia are smaller). Its growth rate is around one and one half times both the Wa shington - Baltimore - NV CSA and 1997 Washington DC - MD - VA nonattainment area averages but the overall change is lower than any other count y except Calvert County within the 1997 Washington DC - MD - VA nonattainment area. Its population density

is low at less than one third that of the 1997 Washington DC - MD - VA nonattainment area. It has the lowest VMT of an y count y except Calvert County (but those of the cities in Virginia are smaller) within the 1997 Washington DC - MD - VA nonattainment area. The overall number of commuters is but a tiny

fraction of that for the 1997 Washington DC - MD - VA nonattainment area. Commuting patterns link it to the Washington CB SA as an outlying count y. That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/States of Arlington , Fairfax, Prince George’s, Carroll, and Anne Arundel Counties and the District of Columbia , and, to a lesser extent the Counties/Cities/States of Baltimore, and Harford plus possibly Calvert. Air quality considerations suggest that Calvert , Anne Arun del and Carroll Counties will attain the 2008 NAAQS within about the same time period without further controls and that none of the monitors in these counties will be the key

monitor needed for attainment within the Washington - Baltimore - NV CSA or in an are a containing Fairfax or Prince George’s County , or, the District . Factors that favor inclusion in a nonattainment area containing Anne Arundel, Baltimore and Harford Count ies are meteorology . Factors that favor inclusion with a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are jurisdictional boundaries, and commuting patterns. Therefore, the factors favor grouping Charles County with a Washington - DC - MD - VA Area with the same or similar bo undaries as the 1997 Washington - DC - MD - VA nonattainment area.94

**Loudoun County, VA:** Loudoun Count y does not have a violating monitor but has a monitor with a design value of 0.075 ppm. It ranks in the “top 11” counties (10 th for VOC and 11 th for NOx) for total emissions within the Washington - Baltimore - NV CSA and ties for sixth (with Frederick County , MD) in the 1997 Washington DC - MD - VA nonattainment area. Its mobile source emissions are ranked 15th for VOC and 16th for NOx. Its population is near the median for counties in the 1997 Washington DC MD - VA nonattainment area and its densit y is one - half that of the 1997 Washington DC - MD - VA nonattainment area. Its growth rate was 80 percent and the absolute change in population was greater than the entire population of all the cities in Virginia except Alexandria and even some of the counties in the 1997 Washington DC - MD - VA nonattainment area. Its growth rate is around one and one half times both the Washington - Baltimore - NV CSA and 1997 Washington DC - MD - VA nonattainment area averages but the overall change is lower than an y other count y except Calvert County within the 1997 Washington DC - MD - VA nonattainment area. Commuting patterns link it to the Washington CB SA as a core count y. That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA b y commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/S tates of Arlington and Fairfax, and, to a lesser extent the Counties/Cities/States of Baltimore, Prince George’s, Anne Arundel, Carroll, and Harford and the District of Columbia . Air quality considerations suggest that Anne Arundel and Carroll Counties w ill attain the 2008 NAAQS within about the same time period without further controls , and , that none of these monitors in these counties will be the key monitor needed for attainment within the Washington - Baltimore - NV CSA or in an area containing Fairfax o r Prince George’s County , or, the District . Factors that favor placement of Loudoun County in a nonattainment area Fairfax and Arlington Counties as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington DC - MD - VA n onattainment area are its closer proximity to Fairfax and Arlington Counties, emissions, growth rate, commuting patterns, and jurisdictional boundaries. Factors that favor inclusion of L oudoun Count y in a nonattainment area containing Anne Arundel, Baltim ore and Harford Count ies are meteorology , emissions, and growth rates . Factors that favor inclusion with a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are meteorology , are its closer prox imity to Fairfax and Arlington Counties emissions, Virginia’s recommendation, jurisdictional boundaries, and commuting patterns. Therefore, the factors favor grouping Loudoun County with a Washington DC - MD - VA Area with the same or similar boundaries as th e 1997 Washington - DC - MD - VA nonattainment area. **Arlington County, VA:** Arlington County must be designated nonattainment due to the presence of a monitor violating the 2008 ozone NAAQS. Its design value is similar to those in part of the District of Columbia and only

0.002 ppm less than that in Fairfax County . These monit ors are clustered in a relativel y small area at the core of the Washington - Arlington - Alexandria, DC - VA - MD - WV MSA. It ranks high in the “middle group” for total emissions within the Washington - Baltimore - NV CSA. It s mobile source emissions are ranked 14th for VOC and 13th for NOx. While its absolute total emissions and population are not exceptional, its total emissions and population densities are both high which is indicative of an urban core area. Population growth was slightly less than the averages f

or the Washington - Baltimore - NV CSA and the 1997 Washington DC - MD - VA nonattainment area. Its VMT95

is less than one - twent y - fifth of that even for the 1997 Washington DC - MD - VA nonattainment area. Commuting patterns link it to the Washington CB SA as a core co unt y. That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA b y commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/C ities/States of Baltimore, Prince George’s, Harford, Fairfax and Carroll and the District of Columbia , and, to a lesser extent the Counties/Cities/States of Anne Arundel. Meteorology indicates it is downwind of the Counties/Cities/States of Fairfax, th e District, Falls Church City , Anne Arundel, Charles, Howard, Loudoun , Montgomery , Calvert, Prince George’s, Prince William , Alexandria and Fairfax Cities plus Baltimore Co. and City and to a lesser extent: Prince William, Frederick (MD), and the Frederick sburg area. The factors somewhat favor a designation of nonattainment based upon contribution: these are its total emissions and population densities, meteorological indications of possible interstate contribution to and from the District of Columbia , and jurisdictional boundaries. Factors that favor inclusion of Arlington Count y i n a nonattainment area containing Anne Arundel, Baltimore and Harford Count ies are meteorology and emissions . Factors that favor placement of Arlington County in a nonattainment area with Fairfax County and the District as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are its closer proximity to Fairfax and Arlington Counties, em issions, Virginia’s recommendation, commuting patterns, and jurisdictional boundaries. Therefore, the factors favor grouping Arlington County with the Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainme nt area. **Prince William County, VA:** Prince William County does not have violating monitor. It ranks in the “top 11” counties (8 th for VOC and 10 th for NOx) for total emissions within the Washington - Baltimore NV CSA and ties for fourth (VOC) and fifth (NOx) in the 1997 Washington DC - MD - VA nonattainment area. Its mobile source emissions are ranked 9th for VOC and 10th for NOx. It s population is fifth within the 1997 Washington DC - MD - VA nonattainment area and its population density is a little less than that of the 1997 Washington DC - MD - VA nonattainment area. Its growth rate was 42 percent, and, the absolute change in population was second highest in the 1997 Washington DC - MD - VA nonattainment area. Its VMT is not exceptional. Commuting patterns link it to the Washington CB SA as a core count y. That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/States of Prince George’s, and, to a lesser extent the Counties/Cities/States of Baltimore, Anne Arundel, Harford, Fairfax and Carroll and the District of Columbia . Factors that favor inclusion of Prince William County in a nonattainment area containing Anne Arundel, Baltimore and Harford Count ies are meteorology , and emissions .96

Factors that favor placement of Prince William County in a nonattainment area with Arlington and Fairfax Counties and the District as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are its closer proximity to Fairfax and Arlington Counties, emissions, Virginia’s recommendation, commuting patterns, growth and jurisdictional boundaries. Therefore, the factors favor grouping Prince William County with the Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area. **Alexandria City, VA:** Alexandra City doe s not have violating monitor. It has total emissions which are neither at the low or high end

– it ranks in low end (21 st VOC and 20 th NOx ) of the middle (12 th through 23 rd inclusive) within the Washington - Baltimore - NV CSA. It s mobile source emissions ar e ranked 25th for VOC and 25th for NOx. It s population is not exceptional, but it is densely populated

– about 7 times the 1997 Washington DC - MD - VA nonattainment area average. Its growth was less than the 1997 Washington DC - MD - VA nonattainment area avera ge. It s VMT is not exceptional. Its emission densities are high. Commuting patterns link it to the Washington CB SA as a core cit y . That it is part of the Washington CBSA and not the Baltimore - Towson CBSA suggests that it is more linked to the former CB SA by

commuting and hence mobile source emissions. Meteorology

indicates this city is likely upwind of violating monitors in the same counties and the District as the District of Columbia Arlington County and perhaps Fairfax County . The factors favor a designation of nonattainment based upon contribution: these are possible contribution to the monitors in Arlington , Fairfax and Prince George’s Counties and the District of Columbia, total emissions and population densities, commuting patterns, Virginia’s recommendation and jurisdictional boundaries. While it may possibly contribute to monitors in Anne Arundel, Harford and other Counties, its close proximity and high emissions densities favor merging for boundaries purposes with the surrounding jurisdictions of Fairfax County and the District of Columbia. The factors favor placing this county in the same nonattainment area as Fairfax and Arlington Counties and the District of Columbia. Factors favoring this placement are jurisdictional boundari es, commuting patterns, possible contribution to Fairfax and Arlington Counties, and Virginia’s recommendation. No factors compel placement in a different nonattainment area. **Fairfax, Manassas, Manassas Park, and Falls Church Cities, VA:** Fairfax, Mana ssas, Manassas Park, and Falls Church Cities do not have a monitor. Fairfax and Falls Church Cities are in close proximity to the violating monitors in Fairfax and Arlington Counties. All are small

– ten square miles or less (for comparison: Alexandria C ity is 26, the District of Columbia is over 60 and Frederick County , MD the largest is over 650 square miles). Generally all have low absolute total emissions , VMT, and number of commuters. All are ranked 29 th or lower for mobile source emissions. All are densely populated with a density just under 3 to 7 times the overall CSA density . The total emissions densities are high which is likely ty pical for urban core areas. Their total emissions and population densities are comparable to or higher than the adjacent/surrounding counties and thus these cities are indistinguishable from these adjacent/surrounding counties. Commuting patterns link it to the Washington CB SA as a core cit y . That it is part of the Washington CBSA and not the Baltimore Towson CBSA suggests that it is more linked to the former CBSA b y commuting and hence mobile source emissions.97

Meteorology

indicates th ese cities are likel y upwind of violating monitors in the same counties and the District as the applicable adjacent/enclosing juri sdictions

– the District of Columbia, Arlington, Fairfax and/or Prince George’s Counties. While each of these may possibly contribute to many

monitors in the CSA, their close proximities and high emissions densities favor merging for boundaries purposes w ith the enclosing/adjacent jurisdictions of the District of Columbia, Arlington, Fairfax and/or Prince George’s Counties. The factors that favor designation of nonattainment for contribution are mainly their total emissions densities , commuting patterns, jurisdictional boundaries, Virginia’s recommendations and population densities which are comparable to or higher than the adjacent/surrounding counties. Fairfax City should be in a nonattainment area that includes Fairfax and Arlington Counties and the Di strict of Columbia as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington DC - MD - VA nonattainment area. Falls Church City should be in a nonattainment area that includes Fairfax and Arlington Counties and the District of Columbia, for the same reasons as for Arlington and Fairfax Counties between which Falls Church is located. Manassas and Manassas Park Cities should be in the same nonattainment area as Fairfax and Arlington Counties for the same reasons as for Pri nce William County , which encloses both. **The District of Columbia:** The District of Columbia must be designated nonattainment due to the presence of monitors violating the 2008 ozone NAAQS. Its design value is similar to those in part of the Arlington Co unty

and only 0.002 ppm less than that in Fairfax County . These monitors are clustered in a relativel y small area at the core of the Washington - Arlington - Alexandria, DC - VA - MD - WV MSA. It ranks in the “top 11” counties (at 7 th for both NOx and VOC) for tot al emissions within the Washington Baltimore - NV CSA and fourth in the 1997 Washington DC - MD - VA nonattainment area. It s mobile source emissions are ranked 6th for VOC and 6th for NOx. Itis densely populated (8 times the average for the 1997 Washington DC - MD - VA nonattainment area) and has the sixth highest population within the Washington - Baltimore - NV CSA and the fourth within the 1997 Washington DC - MD - VA nonattainment area. Its growth rate is well less than

– about one - third

– of the 1997 Washington DC M D - VA nonattainment area and CSA averages. Its VMT is not exceptional at one - twelfth that of the 1997 Washington DC - MD - VA nonattainment area. Commuting patterns link it to the Washington CB SA as a core cit y . That it is part of the Washington CBSA and n ot the Baltimore - Towson CBSA suggests that it is more linked to the former CBSA by commuting and hence mobile source emissions. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/States of Prince George’s, Baltimore, Anne Ar undel, Harford, Fairfax and Carroll. Meteorology indicates it is downwind of the Counties/Cities/States of Montgomery , Prince George's Arlington, Fairfax, Charles, Howard, plus Baltimore Co. and City , the Fredericksburg area and Alexandria and Falls Church Cities , and , to a lesser extent: Calvert, Carroll, Prince William L oudoun , and Frederick (MD). The District of Columbia’s initial recommendation was for nonattainment. The District of Columbia’s anal ys is suggested that its total emissions were a s mall (7% NOx and 9% VOC) part of those in the 1997 Washington DC - MD - VA nonattainment area and suggested the need for additional controls on on - road and off - road mobile and disperse area sources and stricter controls on large industrial sources and power pl ants to curtail transported pollution . At this point in the designation process, EPA does not disagree with the District of Columbia that an appreciable part of the air quality problem within the District of Columbia is due to total emissions outside its borders. This decision is based in part upon the District of Columbia’s evaluation and in part upon EPA’s evaluation contained within this document. The District of Columbia is surrounded by three of the “top six” counties for total emissions in the Wash ington -98

Baltimore - NV CSA. These are: Fairfax County , VA (4 th NOx, 1 st VOC); Montgomery Count y, MD (5 th NOX, 2 nd VOC); and Prince George’s Count y, MD (3 rd for NOx and VOC). These three counties comprise the top three within the 1997 Washington DC - MD - VA non attainment area. The District is a densely populated area at the core of the Washington - Arlington - Alexandria, DC - VA - MD - WV CBSA . The District’s mobile source emissions rank 6 th ( for both NOx and VOC) overall in the CSA. Around the District are three of the top five jurisdictions in the CSA for mobile source emissions

– Fairfax, Montgomery

and Prince George’s Counties. The factors that favor the placement of the District of Columbia in the same nonattainment area as Prince George’s, Fairfax and Arlington Counties as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD - VA nonattainment area are: jurisdictional boundaries; commuting patterns; meteorological indications of possible contribut ion to and from the District of Columbia and counties in the 1997 Washington - DC - MD - VA nonattainment area; and the close proximity

of violating monitors in Arlington , Prince George’s and Fairfax Counties as well as the District of Columbia’s monitors with d esign values of 0.079 to 0.081 ppm at the Arlington - Fairfax District core. Likewise, the high emissions in surrounding areas favor the placement of the District of Columbia in the same nonattainment area as Prince George’s, Fairfax and Arlington Counties as part of a Washington - DC - MD - VA Area with the same or similar boundaries as the 1997 Washington - DC - MD VA nonattainment area . No factors compel placement in a different nonattainment area. **The Frederick County, VA Area (Frederick County and Winchester C ity in Virginia)**  This area does not have a violating monitor, but has a monitor with a design value of 0.070 ppm. In total, this area has aggregate total emissions about equal to Arlington County , VA for NOx and less than Frederick Count y, MD for VOC. As such, the area would rank 13 th VOC and 15 th NOx within the Washington - Baltimore - NV CSA. Li kewise, the total area’s mobile source emissions would rank 1 3 th for VOC and 18 th for NOx . Individuall y each cit y/ county in this area ranks lower. The total popul ation is less than Alexandria City and would exceed onl y Calvert County , MD (and the other cities in Virginia). The growth rate was not quite twice the Washington - Baltimore - NV CSA average but the absolute change is less than most counties in the Washingto n - Baltimore - NV CSA. Total VMT is less than Alexandria City . The area is separated from the main parts of the Washington - Baltimore - NV CSA by the easternmost portion of the Appalachian Mountains. The area is not adjacent to any count y with a violating mon itor. Meteorology suggest this area is upwind of violating monitors within the CSA but the closest monitors are attaining the 2008 ozone NAAQS. Available meteorological information does not favor 1997 Baltimore or 1997 Washington nonattainment areas . Co mmuting patterns indicate that this area is a separate CBSA thus has less interchange with the Washington CBSA than adjacent counties within the Washington CBSA have with the core of the Washington CBSA. The geographic remoteness, middling emissions, juri sdictional boundaries and Virginia’s recommendation are factors favoring a designation as “unclassifiable/attainment” due to the remoteness of this area from violating monitors and its low population density , and the presence of a monitor attaining the 200 8 ozone NAAQS. **Fredericksburg, VA Area (City of Fredericksburg, Spotsylvania and Stafford Counties)** Stafford County

does not have violating monitor but has a monitor with a design value of 0.070 ppm. For total emissions , Spotsylvania and Stafford Counties rank between 15 th and 19 th for total emissions

– within the “middle group” (between 12 th and 23 rd inclusive)

– within the Washington - Baltimore - NV CSA. As for mobile source emissions, Spotsylvania is ranke d 12th for VOC and 12th for NOx, and, Stafford is ranked 13th for VOC and 14th for NOx. Their populations, VMT and number of commuters are not exceptional. They are relativel y sparely populated , having a population density less than even99

the Washington - B altimore - NV CSA average. In total the Fredericksburg, VA Area would have total emissions about equal to Prince William County , VA, a population less than L oudoun Count y, VA, an absolute population growth between Montgomery and Prince George's Counties in Maryland, VMT about 110 percent of Prince William’s. Commuting patterns link it to the Washington CB SA as: a core county n the case of Stafford County ; and as outl yi ng cit y/ count y in the case of Spotsylvania and Fredericksburg Cit y. Meteorology

indicates it is upwind of violating monitors in the Counties/Cities/States of Fairfax, Arlington and the District of Columbia as well as the Counties/Cities/States of Prince George’s Baltimore, Anne Arundel, and, Harford,. Meteorology

indi cates that the Fredericksburg, VA Area is upwind of violating monitors in Arlington County , VA about 22 percent of the time and of the monitor in Prince George’s County , MD about 18 percent of the time. Meteorology and total emissions indicate the possibi lity of contribution to Arlington and Prince George’s Counties. However, as the tip of the Fredericksburg, VA Area closest to violating monitors in the Washington - Baltimore - NV CSA, Stafford County is more remote from these violating monitors than Charles County , MD or Prince William County , VA over which total emissions from Stafford Count y have to travel to reach a violating monitor. Charles County, MD or Prince William County , VA are adjacent to Stafford County and are attaining the 2008 ozone NAAQS. The factors that favor designation of “unclassifiable/attainment” would seem to outweigh those for another designation are : the better than the NAAQS air quality in Stafford County , this area’s lack of close proximity

to areas with a violating monitor, jurisdictional boundaries and Virginia’s recommendations. **Queen Anne’s County, MD:** Queen Anne’s County does not have violating monitor. For total emissions it ranks at the bottom (23 rd for both NOx and VOC) within the “middle group” (between 12 th and 23 rd inclusive) within the Washington - Baltimore - NV CSA. Its mobile source emissions are ranked 20th for VOC and 17th for NOx. It s population is low

– about one fourth of the count y within the 1997 Baltimore MD nonattainment area (Carroll Co.) with the lowest population. Its growth rate is about three times that of the 1997 Baltimore MD nonattainment area, but the absolute change is less than half that of Carroll County , MD. Its VMT is low and less than that of even Carroll County , MD. Commuting patterns link it to the Baltimore CBSA as an outl yi ng county . Meteorology

indicates it is upwind of violating monitors in both the 1997 Baltimore and Washington nonattainment areas. This county

is in the OTR an d is subject to Maryland’s enhanced I/M program. The meteorology

favors designation as nonattainment based upon contribution, and, the total emissions related factors are not compelling for a nonattainment designation given that the county is in the OTR , the low emissions related factors and given the limited access for commuting to the rest of the Washington - Baltimore - NV CSA. T he jurisdictional boundaries factor would seem to favor designation of “unclassifiable/attainment” and outweigh factors favorin g a nonattainment designation. The factors favor a designation of “ attainment/unclassifiable” would seem to outweigh those for another designation .100

**St. Mary’s County:** St. Mary ’s County does not have violating monitor. For total emissions it ranks 16 th VOC and 17 th NOx

– within the “middle group” (between 12 th and 23 rd inclusive) of the Washington - Baltimore - NV CSA. It s mobile source emissions are ranked 19th for VOC and 21st for NOx. It s population is lower than all other jurisdictions within the 1997 Washington DC - MD - VA nonattainment area. Its growth rate is about one and one - half times that of the 1997 Washington DC MD - VA nonattainment area, but the absolute change is less than half that of Carroll County , MD. Its VMT is low and less than that of A lexandria City and less than one and one - half times that of Calvert County . Commuting patterns indicate that this area is a separate CBSA thus has less interchange with the Washington CBSA than adjacent counties within the Washington CBSA have with the co re of the Washington CBSA. Meteorology

indicates St. Mary ’s County is upwind of violating monitors in both the 1997 Baltimore and Washington nonattainment areas and suggests that it is more often upwind of violating monitors in the 1997 Baltimore nonatt ainment area. St. Mary ’s Count y is in the OTR. Its total emissions related factors are not compelling for a nonattainment designation given that the county is in the OTR. Its possible contributions to nonattainment at the Edgewood monitor are solel y i ntrastate. Because this possible contribution to violating monitors involves only intrastate contribution , Maryland will primarily be responsible for mitigating an y such intrastate contribution. T he low emissions - related factors and that of jurisdictional boundaries favor an “ unclassifiable /attainment ” designation. **Fauquier County, VA:** Fauquier Count y does not have violating monitor but has a monitor with a design value of 0.065 ppm. For total emissions it ranks 15 th VOC and 20 th NOx within the Washington Baltimore - NV CSA

– within the “middle group” (between 12 th and 23 rd inclusive). It s mobile source emissions are ranked 16th for VOC and 15th for NOx. It s population is low, and, it is sparel y populated. Its growth rate was abo ut one and one - half times that of the Washington - Baltimore - NV CSA as a whole, but the absolute change is low. Its VMT is low in comparison to most other areas within the 1997 Washington DC - MD - VA nonattainment area. Only 27 percent of its commuters travel into an area with a violating monitor. Meteorology

indicates it is upwind of violating monitors in both the 1997 Baltimore and Washington nonattainment areas . Factors that favor designation as nonattainment for contribution are possible contribution to Fairfax and Arlington Counties. Factors that favor designation as “unclassifiable/attainment” are Virginia’s recommendation (possible contribution to the closest violating monitors is intrastate ), low population, jurisdictional boundaries, and the pre sence of a monitor attaining the 2008 NAAQS in Fauquier, Stafford and Prince William Counties . The factors that favor designation as “unclassifiable/attainment” seem to outweigh factors for a nonattainment designation. **Culpeper, Clarke, and Warren Counti es in Virginia and Hampshire and Jefferson Counties in**  **West Virginia:** None of these counties have a violating monitor. Both states recommended that these counties within their State be designated attainment. For total emissions , each ranks 24 th or lower in the Washington - Baltimore - NV CSA. Culpeper’s mobile source emissions are ranked 21s t for VOC and 23rd for NOx AND Warren’s rank 24 th and 22 nd . The West Virginia Counties each rank far lower 27 th101

or less . The population of each is low, and, each is sparel y populated. The VMT of each is low. For all but Jefferson County , the total number of commuters is less than that of Manassas City . The total number of commuters in Jefferson County is not appreciabl y greater than that of Manassas Cit y (20,937 versus 18,077, respectively). The total emissions of each are 1 percent or less than the total for the Washington - Baltimore - NV CSA. Commuting patterns link Culpeper, Clarke, Jefferson and Warren Counties to the W ashi ngton CBSA as outlying counties . Commuting patterns link Hampshire County to the Winchester VA, CBSA as an outl yi ng county . Because the Winchester , VA CBSA is a separate CBSA form the Washington and Baltimore - Towson CBSAs Hampshire has less interchange with the Washington CBSA than adjacent counties within the Washington CBSA have with the core of the Washington CBSA. Some of these counties separated from the main parts of the Washington Baltimore - NV CSA by

the easternmost portion of the Appalachian Mountains. These “outer rim” counties in the Washington - Baltimore - NV CSA in Virginia and West Virginia are closest to attaining monitors to the extent they are upwind of any

monitors in the Washington Baltimore - NV CSA. These “outer rim” areas are the Co unties of Frederick, Warren, Clarke, and Culpeper and Winchester City in Virginia, Jefferson County , WV. The relevant attaining monitors are those in Frederick County , MD and in L oudoun, Prince William, Fauquier, and Stafford Counties in Virginia. Of the se “outer rim” counties, Clarke County , VA and Jefferson County , WV are the ones more likely

to sufficient contribute to a violating monitor because the closest monitors within the Washington - Baltimore - NV CSA just attain the 2008 ozone NAAQS. No factors w ould seem to support designation as nonattainment; the factors that favor designation as “attainment/unclassifiable” are the States’ recommendations, remoteness from violating monitors, low total emissions related factors, and jurisdictional boundaries. **N onattainment Areas:**  As discussed above, EPA has determined that certain counties/cities can be formed into a Baltimore , MD nonattainment area consisting of Anne Arundel, Baltimore, Carroll, Harford, and Howard Counties and Baltimore Cit y in Maryland and, that certain counties/cities can be formed into a Washington, DC MD - VA nonattainment area consisting of: The Counties of Frederick, Montgomery , Calvert, Charles, and Prince George ’ s in Maryland; The entire District of Columbia ; and , The Countie s of Arlington, Fairfax, L oudoun, and Prince William and the Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park in Virginia. One area or two: As discussed under Factor 3, EPA believes that the Edgewood monitor could well be affected on a substantial number of days b y emissions in CBSAs adjacent to the Washington - Baltimore - NV CSA in Pennsylvania, Delaware and even Maryland as well as by emissions in the Washington, DC - MA - VA nonattainment area under the 2008 ozone NAAQS. L ikewise, EPA does not discount the effects of mobile source emissions throughout the Washington - Baltimore - NV CSA but can conclude that the majority of these are in Maryland and that the mobile source emissions in the Washington, DC - MD - VA nonattainment area are not the sole cause of high exceedances at the Edgewood monitor. Mobile source emissions will decline throughout the CSA and the other nonattainment and attainment areas surrounding this CSA. Numerous EPA regulations for new motor vehicles and other on - road and n on -102

road mobile source engines will continue to produce reductions in ozone and ozone precursors before the Baltimore area ’s attainment date. See , 77 FR 8197 at 8202, February 14, 2012. As Maryland noted, States have limited ability to regulate mobile sour ce emissions. 126 EPA sees little reason to designate areas nonattainment due solely to emissions sources which will decline substantially due to already promulgated Federal rules and which the States involved will have little ability to regulate. As for the CBSAs adjacent to the Washington - Baltimore - NV CSA in Pennsylvania, Delaware and even Maryland, these are in the ozone transport region (OTR) formed under section 184 of the CAA. The Washington, DC - MD - VA ozone nonattainment area and Stafford Count y, VA is also in the OTR and thus is subject to the same minimum section 184 requirements which include reasonabl y available control technology

requirements, enhanced vehicle inspection and maintenance programs, and major source permitting requirements at least as stringent as an area classified as moderate nonattainment as these other CBSAs. EPA therefore concludes that there would be limited benefit in combining Baltimore , MD nonattainment area and the Washington, DC - MD - VA nonattainment area to address mobi le source emissions in the Washington CBSA that would not offset consideration of jurisdictional boundaries by involving additional MPOs in the Baltimore, ND area planning process. EPA has determined that it is appropriate to keep two nonattainment areas in this CSA. **Conclusion s**  **:** Based on the assessment of factor s described above , EPA has concluded that the following counties and independent cities listed below meet the CAA criteria for inclusion in the two nonattainment area s indicated below : A Baltimore , MD nonattainment area consisting of Anne Arundel, Baltimore, Carroll, Harford, and Howard Counties and Baltimore City in Maryland . A Washington, DC - MD - VA nonattainment area consisting of: The Counties of Frederick, Montgomery , Calvert, Charle s, and Prince George ’ s in Maryland; The entire District of Columbia ; and , The Counties of Arlington, Fairfax, L oudoun, and Prince William and the Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park in Virginia.

126 “ Emissions from mo bile sources, including onroad, nonroad, marine, air, and rail, also continue to contribute significantly to NOx and VOC emissions levels, but the setting of mobile emissions standards is outside the authority of most states to regulate. “ Refr to “APPENDIX A 5 (9)

– FACTOR ANALYSIS FOR THE 16 STATE NONATTAINMENT AREA,” to a Letter dated March 7, 2012, from Robert M. Summers, Ph.D., Secretary, Maryland Department of the Environment to Shawn M. Garvin, Regional Administrator, EPA Region III.103



### A **ppendix 1**  **: Pertinent Background on Monitoring Objectives and Scales**  Objectives: EPA has identified three major objectives for air quality monitoring: (1) Provide air pollution data to the general public in a timely manner. (2) Support compliance with ambient air quality standards and emissions strategy development. EPA and others will be used data from monitors for NAAQS pollutants to compare an area ’ s air pollution levels against the NAAQS. (3) Support for air pollution research studies. EPA has specified that to support these three basic air quality monitoring objectives, a network must be designed with a variety

of ty pes of monitoring sites. Monitoring sites must be capable of determining among other things the peak air pollution levels, typical levels in populat ed areas, air pollution transported into and outside of a cit y or region, and air pollution levels near specific sources. The six general site t ypes are: (1) Sites located to determine the highest or maximum concentrations expected to occur in the area cov ered b y the network. (2) Sites located to measure “population exposure,” that is, ty pical concentrations in areas of high population density . (3) Sites located to determine the impact of substantial sources or source categories on air quality . (4) Sites lo cated to determine general background concentration levels. (5) Sites located to determine the extent of regional pollutant transport among populated areas; and in support of secondary

standards. (6) Sites located to measure air pollution impacts on visibility , vegetation damage, or other welfare based impacts. See , section 1.1 of Appendix D to 40 CFR Part 58 “Ambient Air Qualit y Surveillance” (Appendix D hereafter). Regarding Regulatory Compliance and Maximum Concentration Sites: For regulatory

compl iance, the principle objective is to measure the ozone concentration in the high population density

areas and the maximum downwind concentration from the urban region. It is important to be careful when selecting the high population sites because, particul arl y in dense urban areas, the greatest concentration of people may be in an area with heavy automobile traffic, which may result in low ozone concentration due to nitric oxide titration. See , section 4.2 of Guideline On Ozone Monitoring Site Selection, E PA - 454/R - 98 - 002, August 1998 (1998 Guideline hereafter). Within an ozone monitoring network, at least one ozone site for each CBSA , or CSA if multiple CBSA s are involved, must be designed to record the maximum concentration for that particular metropolit an area (section 4.1(b) of Appendix D to 40 CFR Part 58). Based upon a review of meteorological and air quality data, the prospective maximum concentration monitor site should be selected in a direction from the city that is most likely

to observe the highest ozone concentrations, more specificall y, downwind during periods of photochemical activity . In man y cases, these maximum concentration ozone sites will be located 10 to 30 miles or more downwind from the urban area where maximum ozone precursor emissi ons originate (see , section 4.1(f) of Appendix D).104

Regarding Scales: Section 4.1 (c) of Appendix D defines “urban scale” as “an area of city - like dimensions, on the order of several kilometers to 50 or more kilometers or more.” “Urban - scale sites can al so be used to measure high concentrations downwind of the area having the highest precursor emissions.” See , section 4.2 of Guideline On Ozone Monitoring Site Selection, EPA - 454/R - 98 - 002, August 1998 (1998 Guideline). Section 4.1 (c) of Appendix D to 40 CFR Part 58 (“Ambient Air Qualit y Surveillance”) defines “Neighborhood scale” as some reasonably homogeneous urban sub - region, with dimensions of a few kilometers. Homogeneit y refers to pollutant concentrations. Neighborhood scale data will provide valuable information for developing, testing, and revising concepts and models that describe urban/regional concentration patterns. These data will be useful to the understanding and definition of processes that take periods of hours to occur and hence inv olve considerable mixing and transport. Under stagnation conditions, a site located in the neighborhood scale may also experience peak concentration levels within a metropolitan area. Section 4.1 (c) of Appendix D to 40 CFR Part 58 (“Ambient Air Qualit y Sur veillance”) defines “Regional scale” as a scale of measurement will be used to ty pify concentrations over large portions of a metropolitan area and even larger areas with dimensions of as much as hundreds of kilometers. Such measurements will be useful for assessing the O 3 that is transported to and from a metropolitan area, as well as background concentrations. In some situations, particularl y when considering very large metropolitan areas with complex source mixtures, regional scale sites can be the maximum concentration location.105 

# Appendix 3 to **Te chnical Support Document** **— Area Designations for the Washington**  **- Baltimore**  **- Northern Virginia, DC**  **- MD**  **- VA**  **** **WV Combined Statistical Area (CSA) 2008 Ozone National Ambient Air Quality Standards** 106



### Population growth rates From 2000 to 2010, Loudoun County VA grew at a rate of 84.1%, the 5 th highest growth rate in the US 127 . There were no Maryland counties in the top 10 US growth rates for counties of 10,000 or more. Virginia statewide populatio n increases were also higher than Maryland’s increases from 1980 to 2010 128 . The Virginia County data are located in the footnoted web page 129 . Maryland count y data are from MDP’s Maryland Statistical Handbook 130

. **State % chg 1980**  **- 1990**  **% chg 1990 -**  **2000 % chg**  **2000 -**  **2010** Maryland 13.4 10.8 9.0 Virginia 15.8 14.4 13.0 Northern VA 16.3 (2000 - 2007) **County (Baltimore, DC**  **and Ex -**  **urban) Growth Rate in**  **Percent G**  **rowth in absolute**  **pop .**  **change Data Year** **s Virginia counties**  Washington DC region Loudoun 84.1 142,712 2000 - 2010 Loudoun 62.5 105,997 2000 - 2007 Fairfax 11.5 131 42,763 2000 - 2007 Prince W illiam 32.5 91,126 2000 - 2007 Fauquier 132 18.3 65,460 2010 Fredericksburg area Spots yl vania 32.6 29,512 2000 - 2007 Stafford 30.2 27,941 2 000 - 2007 King George 133 40.4 2 000 - 2010 Wi nchester area Frederick 32.3 134 13,740 2 000 - 2007 **Ma ryland counties**  GR > 15% in **bold** Baltimore region Anne Arundel 6.4 31,545 2000 - 2009 Baltimore County 4.7 35,506 2000 - 2009 Baltimore City - 2.1 - 13,736 2000 - 2009 Carroll 12.7 19,192 2000 - 2009 Harford 10.9 23,924 2000 - 2009 Howard 13.7 34,035 2000 - 2009

127 US Census link to a PDF for Population Distribution and Change: 2000 to 2010 (page 9), http://2010.census.gov/2010census/ 128 http://www.census.gov/compendia/statab/cats/population.html -- #14 : State Population -- Rank, Percent Change, And Population Density (link to a P DF document) 129 http://vaperforms.virginia.gov/extras/profileSummary.php -- links to a PDF report 130 MD Statistical Handbook linked from the following web page: http://planning.maryland.gov/msdc/S2_Estimate.shtml 131 http://quickfacts.census.gov/qfd/states/51/51059.html 132 http://www.fauquiercounty.gov/government/departments/commdev/index.cfm?action=demographics 133 http://quickfacts.census.gov/qfd/states/51/51099.html 134 http://quickfacts.census.gov/qfd/states/51/51069.html107

Washington DC region Montgomery 11.3 98,254 2000 - 2009 Prince George’s 4.1 33,044 2000 - 2009 Frederick **16.7** 32,704 2000 - 2009 Calvert **19.6** 14,649 2000 - 2009 Charles **18.0** 21,680 2000 - 2009 Washington County EAC Wa shington 10.6 13,987 2000 - 2009 Attainment

/exurban St. Mary’s **19.4** 16,767 2000 - 2009 Kent/Queen Anne’s Maintenance Area Queen Anne’s **18.2** 7,398 2000 - 2009 Kent 5.5 1,047 2000 - 2009 Philadelphia region Cecil **17.3** 14,845 2000 - 2009108 

# Appendix **8 to**  **Te chnical Support Document** **— Area Designations for the Washington**  **- Baltimore**  **- Northern Virginia, DC**  **- MD**  **- VA**  **- WV Combined**  **Statistical Area (CSA)**



### 2008 Ozone **National Ambient Air Quality Standards 30 Year Average Wind Rose Data**  This is reprinted from “ Technical Anal ys is for the Washington, DC - MD - VA and Baltimore Areas” 

### in Docket item number s EPA - HQ - OAR - 2008 - 0476 - 0235 , EPA - HQ - OAR - 2008 - 0476 - 0405 and EPA - HQ OAR - 20 08 - 0476 - 0456. The anal ys is in “Factor 3: Meteorology (weather/transport patterns)” elsewhere in this document supplements and to great extent supersedes this data. The 30 - ye ar average summer surface - level wind directions for the design value count y in eac h of the areas is shown in Figures 3a through 3 d. For Harford Count y (Figure 3a), MD in the in the Baltimore nonattainment area the winds are from the west - northwest through the south - southeast about 62 percent of the time.

Map Legend: WNW means from the west - northwest; NNW means from the north - northwest; NNE means from the north - northeast; ENE means from the east - northeast; ESE means from the east southeast; SSE means from the south - southeast; SSW means from the south - southwest; and, WSW means from the west - southwest. For Fairfax County

(Figure 3b), VA in the Washington DC - MD - VA nonattainment area the winds are from the west - northwest through the southeast about 64 percent of the time. 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% NNE ENE

ESE

SSE SSW WSW WNW NNW 

## Figur **e 3a. Harford Co., MD**

Harford Co., MD109

For Stafford County

(Figure 3c) in the Fredericksburg, VA Area the winds are from the south - southwest through the south - southeast about 39 percent of the time and from other directions more or less equally .

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% NNE ENE

ESE

SSE SSW WSW WNW NNW 

## Figur **e 3b.**  **Fairfax County ,**  **VA**

Fairfax County, VA

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% NNE ENE

ESE

SSE SSW WSW WNW NNW 

## Figur **e 3c. Stafford County ,**  **VA**

Stafford County, VA110

For Frederick Count y (Figure 3d) in the Frederick County, VA Area the winds are from the south southw est through the south - southeast about 37 percent of the time and from other directions more or less equally

with the exception of west - northwest which occurs a little over 15 percent of the time.

Figures 3e and f show the data for all the counties in the Baltimore and Washington DC - MD - VA nonattainment areas, respectivel y. The patterns are essentiall y the same for all counties and cities in the Washington DC - MD - VA nonattainment area and the same fo r all counties and cities in the current Baltimore nonattainment area.

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% NNE ENE

ESE

SSE SSW WSW WNW NNW 

## Figur **e 3d. Fr**  **ederick County ,**  **VA**

Frederick County, VA111 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% NNE ENE

ESE

SSE SSW WSW WN W NNW Anne Arundel Co., MD Baltimore Co., MD Carroll Co., MD Harford Co., MD Howard Co., MD Baltimore City, MD

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% NNE ENE

ESE

SSE SSW WSW WN W NNW Arlington Co., VA District of Columbia Fairfax Co., VA Fauquier Co., VA Loudoun Co., VA Prince William Co., VA Calvert Co., MD Charles Co., MD Frederick Co., MD Montgomery Co., MD Prince George's Co., MD 

### Figure 3f. Washington DC **- MD**  **- VA NA Area**  **Figure 3e. Baltimore Nonattainment Area**