L. Preston Bryant, Jr. 

Secretary of Natural Resources 

COMMONWEALTH a/VIRGINIA 

DEPARTMENT OF ENVIRONMENTAL QUALITY 

Street address: 629 East Main Street, Richmond, Virginia 23219 

Mailing address: P.O. Box 1105, Richmond, Virginia 23218 

Fax (804) 698-4500 TDD (804) 698-4021 

www.deq.virginia.gov 

APR 04 Z008 

Ms. Judith M. Katz, Director 

Air Protection Division (3APOO) 

U.S. Environmental Protection Agency, Region III 

1650 Arch Street 

Philadelphia, Pennsylvania 19103-2029 

David K. Paylor 

Director 

(804) 698-4000 

1-800-592-5482 

Reference: Plan to Improve Air Quality in 

the Washington DC-MD-V A 

Region: SIP for the PM2.5 

NAAQS 

Dear Ms. Katz: 

Pursuant to the requirements of Section 110 of the Clean Air Act, we are officially 

requesting approval of a revision to the Commonwealth of Virginia State Implementation Plan 

(SIP) approved under the authority of § 10.1-1185 of the Code of Virginia and submitted in 

accordance with the requirements of 40 CFR Part 51 (Requirements for Preparation, Adoption, 

and Submittal of Implementation Plans). As provided in Section 174 of the Clean Air Act, the 

plan was prepared by the Metropolitan Washington Air Quality Committee (MWAQC). This 

revision is effective March 7, 2008. 

This revision consists of a demonstration of the progress being made to improve air 

quality in the Washington nonattainment area and the efforts underway to assure that all 

necessary steps are taken to reach the national ambient air quality standard for PM2.5 by 2009. 

The revision includes (i) the attainment plan, (ii) analysis of reasonably available control 

measures, (iii) attainment demonstration, (iv) contingency plans for failure to attain the air 

quality standard, (v) mobile source budgets, and (vi) the base year 2002 air pollutant emissions 

inventory. 
Enclosed are the following: 

1. State Implementation Plan (SIP) for the Annual Fine Particulate (PM2.S) Standard 

and the 2002 Base Year Inventory for the Washington, DC-MD-V A 

N onattainment Area. 

2. Certification of Public Participation Activities and Compliance with State 

Administrative Procedures 

3. Record of Hearing and Summary of Testimony 

If you have any questions or need additional information, please let us know. 

DKP\RAM\kgs 

TEMPLATES\SIP-PLAN\PLNOO 

SIP\NONATTN PLANS\2008\NV Apm-SIP.DOC 

Enclosures 
ENCLOSURE 2

CERTIFICATION OF PUBLIC PARTICIPATION ACTIVITIES

AND COMPLIANCE WITH

STATE ADMINISTRATIVE PROCEDURES

As required by 40 CFR 51.102(f) and Section 2.1(b) and (d) through (g) of Appendix V 

of 40 CFR Part 51, the following information regarding public participation activities and 

compliance with state administrative procedures is provided.

PUBLIC PARTICIPATION ACTIVITIES

As required by 40 CFR 51.102(a), a hearing to accept public testimony concerning a 

proposed revision to the Commonwealth of Virginia State Implementation Plan was 

held at the George Mason High School, 7124 Leesburg Pike, Falls Church, Virginia, at 

7:00 p.m. on January 28, 2008.

In the National Capitol Interstate Air Quality Control Region, the public was given notice 

of the hearing in the Washington Times on December 28, 2007 (copy attached). As 

required by Section 2.1(g) of Appendix V of 40 CFR Part 51, the hearing was held in 

accordance with the information found in the public notice, and according to the state's 

laws.

The Regional Administrator for the U.S. Environmental Protection Agency was notified 

of the hearing, as was each local air pollution control agency which will be significantly 

affected by the revision and is located in the affected Air Quality Control Region. In 

addition, the District of Columbia and Maryland, which share affected interstate Air 

Quality Control Regions with Virginia, were notified of the hearing. These notifications 

follow the requirements of 40 CFR Part 51.102(d).

The complete record of the hearings, along with any testimony received and responses 

thereto, is located at the Office of Air Regulatory Development of the Department of 

Environmental Quality. The department contact to access this information is the 

Director, Office of Air Regulatory Development. A summary of the testimony received 

and responses thereto is attached.

COMPLIANCE WITH STATE ADMINISTRATIVE PROCEDURES

As required by § 2.2-4031 of the Code of Virginia, notice of the hearing was given to the 

public in the Virginia Register on January 21, 2008 (copy attached).

TEMPLATES\SIP-PLAN\PLN02

SIP\NONATTN PLANS\2008\NVApm-SIP-2.DOC
FRIDA Y. DECEUBER 18, 1007 * 

AD810177_ 
General Notices/Errata 

Volume 24, Issue 10 

DEPARTMENT OF ENVIRONMENTAL QUALITY 

Air Quality Plan 

Notice of action: 1be Department of Environmental Quality 

(DEQ) is announcing an opportWlity for public comment on a 

proposed plan to attain and maintain the national ambient air 

quality standard for PM2 5 in the metropolitan Washington, 

D.C. area, which includes the northern Virginia jurisdictions 

of Loudoun County, Prince William County, Fairfax County, 

Arlington COWlty, the City of Falls Church, the City of 

Alexandria, the City of Manassas, the City of Fairfax, and the 

City of Manassas Park. If adopted, the Commonwealth 

intends to submit the plan or portion thereof as a revision to 

the Commonwealth of Virginia State Implementation Plan 

(SIP) in accordance with the requirements of §110(a) of the 

federal Clean Air Act. The SIP is the plan developed by the 

Commonwealth in order to fulfill its responsibilities W1der the 

federal Clean Air Act to attain and maintain the ambient air 

quality standards promulgated by the U.S. Environmental 

Protection Agency (EPA) tI1der the Act. 

Purpose of notice: DEQ is seeking comments on the overall 

plan, including (i) the attainment plan, (ii) the analysis of 

reasonably available control measures, (iii) the attainment 

demonstration, (iv) the contingency plans for failure to attain 

the air quality standard, (v) mobile source budgets, and (vi) 

the baOle year 2002 air pollutant emissions inventory. 1be 

base year 2002 air pollutant emissions inventory has been 

prepared in response to the emission inventory requirements 

W1der §172(c) of the federal Clean Air Act in accordance with 

40 CFR 51.915. 

Public comment period: December 28, 2007, to January 30, 

2008. 

Public hearing: George Mason High School, 7124 LeesbtIg 

Pike, Falls Church, Virginia (within walking distance of the 

West Falls Church Metro Station) at 7 p.m. on January 29, 

2008. 

Description of proposal: The proposed revision, "State 

Implementation Plan (SIP) for the Annual Fine Particulate 

(PM25) Standard and the 2002 Base Year Inventory for the 

Washington, DC-MD-VA Nonattainment Area," was 

prepared by the :Metropolitan Washington Air Quality 

Committee (MW AQC), which consists of elected officials 

from the affected localities and repreOlentatives of state 

transportation and air quality planning agencies. The plan is 

intended to show the progress being made to improve air 

quality in the Washington nonattainment area and the efforts 

W1derway to assure that all necessary steps are taken to reach 

the federal health standard for PM25 by 2009. MWAQC 

prepared the plan to comply with the Clean Air Act 

Virginia Register of Regulations January 21, 2008 

1318 
Amendments of 1990 and with federal implementation 

guidance. 

Federal infonnation: This notice is being given to satisfy the 

public participation requirements of federal regulations (40 

CPR 51.102). The proposal will be submitted as a revision to 

the Commonwealth of Virginia SIP W1der §110(a) of the 

federal Clean Air Act in accordance with 40 CPR 51.104. All 

provisions of the proposal are planned to be submitted as a 

revision to the Commonwealth of Virginia SIP. 

How to comment: DEQ accepts written comments by email, 

facsimile transmission, and postal mail. In order to be 

considered, written comments must include the full name, 

address, and telephone nwnber of the person commenting and 

be received by DEQ by 5 p.m. on the last day of the comment 

period (January 30, 2008). Due to problems with the quality 

of facsimile transmissions, commenters are encouraged to 

provide the signed original by postal mail within one week. 

Both oral and written comments are accepted at the public 

hearing. DEQ prefers that comments be provided in writing, 

along with any supporting docwnents or exhibits. All 

testimony, exhibits, and docwnents received are part of the 

public record. Please note this proposed plan is being 

conclIrentiy reviewed by the U.S. EPA. 

To review proposal: 1be proposal and any supporting 

docwnents are available on the DEQ Air Public Notices for 

Plans website: 

http://www.deq.virginia.gov/air/permittingfplanotes.html. The 

docwnents may also be obtained by contacting the DEQ 

repreOlentative named below. 1be public may review the 

docwnents between 8:30 a.m. and 4:30 p.m. of each business 

day W1til the close of the public comment period at the 

following locations: DEQ Main Street Office, 8th Floor, 629 

E. Main Street, Richmond, Virginia, 804-698-4070; and DEQ 

Northern Virginia Regional Office, 13901 Crown Court, 

Woodbridge, Virginia, 703-583-3800. 

Agency Contact: Doris Mcleod, Air Quality 

Plannerillepartment of Air Data Analysis and Planning, 629 

East Main Street, P.O. Box 1105, Richmond, VA 23218, 

telephone (804) 698-4197, FAX (804) 698-4510, or email 

damcleod@deq.virginia.gov. 

Volume 24, Issue 10 Virginia Register of Regulations 

1319 

General Notices/Errata 

January 21, 2008 
1

ENCLOSURE 3

RECORD OF HEARING AND SUMMARY OF TESTIMONY

As required by 40 CFR 51.102(e), the complete record of the hearing, along with a list 

of witnesses and the text of the written presentations or summary of the oral 

presentations, is located at the Office of Air Regulatory Development of the Department 

of Environmental Quality. The department contact to access this information is the 

Director, Office of Air Regulatory Development.

As required by Section 2.1(h) of Appendix V of 40 CFR Part 51, below is a summary of 

the testimony received and responses thereto. Included is a brief statement of the 

subject, the identification of the commenter, the summary of the comment and the 

response (analysis and action taken). Each issue is discussed in light of all of the 

comments received that affect that issue. All comments have been reviewed and 

responses developed based on an evaluation of the issues raised in consideration of 

the overall goals and objectives of the air quality program and the intended purpose of 

the document under review.

1. SUBJECT: Air quality analysis for PM2.5 emissions.

COMMENTER: Mirant Corporation

TEXT: The commenter objects to the inclusion of the requirement for Mirant 

Potomac River Generating Station (PRGS) to submit an air quality analysis for PM2.5

emissions once methodologies for such an analysis are finalized. The requirement is 

found in Section 9.4.3 of the draft PM2.5 SIP. No technical or legal basis exists for the 

inclusion of this requirement in the PM2.5 SIP, actual monitoring data do not support the 

conclusion that such an analysis is necessary, the air quality analysis required to be 

submitted by PRGS has no relationship to the PM2.5 attainment SIP, and PM2.5

emissions from PRGS are well-controlled.

RESPONSE: The technical and legal basis for the PRGS PM2.5 ambient air 

quality analysis requirement is supported by law and regulation. 9 VAC 5-20-180 I 

gives the State Air Pollution Control Board authority to shut down a facility to prevent 

violations of the NAAQS: “Regardless of any other provision of this section, the owner 

of any facility subject to the Regulations for the Control and Abatement of Air Pollution 

shall, upon request of the board, reduce the level of operation at the facility if the board 

determines that this is necessary to prevent a violation of any primary ambient air 

quality standard...” 9 VAC 5-20-160 A provides the board authority to request 

information from registered facilities: “The owner of any stationary source to which 

permits are issued under 9 VAC 5 Chapter 80 (9 VAC 5-80-10 et seq.) or for which 

emission standards are given in 9 VAC 5 Chapter 40 (9 VAC 5-40-10 et seq.), 9 VAC 5 

Chapter 50 (9 VAC 5-50-10 et seq.), and 9 VAC 5 Chapter 60 (9 VAC 5-60-10 et seq.) 

shall, upon request of the board, register such source operations with the board and 

update such registration information. The information required for registration shall be 
2

determined by the board and shall be provided in the manner specified by the board.” 9 

VAC 5-40-50 H requires facilities to provide various reports at the request of the board: 

“Upon request of the board, the owner of an existing source subject to the provisions of 

this chapter shall provide notifications and report, revise reports, maintain records or 

report emission test or monitoring result in a manner and form and using procedures 

acceptable to the board...” §172(c)(1) of the federal Clean Air Act (Nonattainment Plan 

Provisions) requires that plans shall “...provide for attainment of the national primary 

ambient air quality standards.” §172(c)(1) also requires that plans contain emission 

limitations and other such control measures, means, or techniques as may be 

necessary or appropriate to provide for attainment.

Although the actual monitoring data currently available may not necessarily indicate the 

presence of a NAAQS violation for PM2.5 attributable to PRGS, these data are 

inconclusive to a certain extent. Violations of the NAAQS depend on numerous factors, 

including meteorology, facility stack configuration, local area topography, emissions 

from other facilities, and regional load being transported into the area. Emission rates 

from any facility are dependent upon fuel type, demand, limitations placed on the facility 

by a variety of permits, and other operational and economic factors.

There are also several uses of air quality data in evaluating the impacts from a facility 

such as PRGS. One of the most important, identified in the EPA’s Guideline on Air 

Quality Models, is the use of air quality measurements “in a complementary manner to 

dispersion models, with due regard for the strengths and weaknesses of both analysis 

techniques.” While air quality measurements are particularly useful in assessing the 

accuracy of model estimates, such measurements do not eliminate the need to apply a 

model to assess an individual facility’s impact. Although it is possible to use air quality 

measurements alone to assess NAAQS compliance, this approach would not likely be 

preferred unless available models are found to be unacceptable, and monitoring data 

have sufficient spatial and temporal coverage.

Therefore, the presence of local monitoring data showing no NAAQS violation does not 

obviate the need for a specific facility analysis using a model.

The PM2.5 air quality analysis does indeed have a relationship to the PM2.5 attainment 

plan. The facility operates within the boundaries of the nonattainment area and is 

considered to be upwind of many other nonattainment areas such as Baltimore and 

Cecil County in Maryland.

The federal reference monitoring program for PM2.5 in the metropolitan Washington 

area is one of the most robust monitoring networks in the United States. Based on the 

data from this federal reference monitoring program, the nonattainment area has 

demonstrated compliance with the annual PM2.5 standard of 15.0 μg/m3. However, 

attainment plans often focus on specific facilities as well as the overall regional air 

quality. For instance, facility-specific RACT requirements may be enumerated within 

attainment plans, and facility-specific requirements may also be used for contingency 

measures in attainment plans as well as maintenance plans. An important part of the 
3

attainment plan is the assumptions made for growth in various emissions categories 

and how such growth is incorporated into the attainment plan. To take into account 

growth in emissions, the state may examine specific facilities or types of facilities to 

determine likely growth rates. Therefore, specifying requirements or specifying facility 

data for a particular facility is not a deviation from past or current attainment planning 

practices. Ascertaining whether or not a facility—particularly one that has engendered 

enforcement actions and significant public comment--does not cause or contribute to a 

PM2.5 ambient air quality violation in an area that currently does not contain a federal 

reference monitor, via an approved analysis methodology, is clearly an appropriate 

topic for the PM2.5 attainment plan.

Whether or not the description of “well-controlled” should be applied to the existing 

PM2.5 control devices at PRGS (electrostatic precipitators) is unclear. A comparison of 

tested emission rates, as provided by the commenter in a different submittal, to those 

required by the existing source regulations in 9 VAC 5-40 (Existing Stationary Sources)

indicates that PRGS appears to operate at well below 0.12 lb PM/mmbtu. However, a 

comparison of those same emission rates, and emission limitations in the draft PRGS 

permit, to limitations placed on new coal-fired boilers through the Best Available Control 

Technology (BACT) process shows that the limitations on new coal-fired boilers may be 

somewhat more stringent.

Regardless of whether or not the facility is “well-controlled,” other factors often affect 

ambient air quality impacts, including facility and local topographical configurations, as 

discussed above. Therefore, the existence of PM2.5 control devices does not make the 

requirement for an ambient air quality analysis moot.

2. SUBJECT: PM2.5 impacts from the PRGS power plant.

COMMENTER: City of Alexandria

TEXT: The attainment plan does not contain a detailed description of how 

existing permit programs will be specifically implemented, or enhanced, in regard to 

PM2.5. The attainment plan should contain more rigorous monitoring, permitting, and 

enforcement programs

RESPONSE: For the purposes of determining attainment of a NAAQS by a 

regional area, federal reference monitoring (FRM) data must be used to show 

compliance or noncompliance with the standard. The existing FRM network in the 

metropolitan Washington area consists of 14 PM2.5 monitors and is one of the most 

robust monitoring networks in the country. For years 2003-2005 as well as for years 

2004-2006, this monitoring network has demonstrated compliance with the 1997 PM2.5

standards of 15.0 μg/m3 on an annual basis and 65 μg/m3 on a 24-hour basis. FRM 

data for the year 2007 are not currently available for Maryland and Washington, D.C. 

However, DEQ has completed quality assurance reviews and has certified the Virginia 

2007 PM2.5 data. These data show that the highest measurements in northern Virginia 

reflect PM2.5 design values of 14.1 μg/m3 on an annual basis and 34.0 μg/m3 on a 24-
4

hour basis, well beneath both 1997 standards.

This draft attainment plan is designed to address the 1997 standards. In 2006, new 

standards were promulgated that lowered the 24-hour requirement to 35 μg/m3 PM2.5. 

The attainment demonstration process for the new standard will be undertaken at a 

later date. The attainment planning process for the 1997 standard must occur prior to 

and independently from the process needed for the 2006 standards. The main purpose 

of this attainment plan therefore continues to be demonstrating compliance with the 

1997 standards.

Section 8.2 of the draft attainment plan discusses the changes made to the major 

stationary source permitting program in regard to PM2.5. Section 8.4 notes the intention 

by the state agencies to adopt further PM2.5 nonattainment permitting requirements, 

including requirements for precursor emissions, controls, and offsets, when these 

regulations are finalized by EPA.

In the 2008-2010 Grant Work Plan, of which both EPA Region III and DEQ are parties, 

DEQ has a grant commitment to submit a draft NSR SIP for PM2.5 nonattainment areas 

no later than 6 months after EPA finalizes the PM2.5 NSR implementation rule. This 

commitment is found under Objective 1.1-Healthier Outdoor Air, Sub Objective 1.1.1 –

More People Breathing Cleaner Air, Work Plan Component – NAAQS NSR.

It is therefore clear that Virginia intends to adopt the EPA’s finalized version of 

nonattainment permitting requirements when they become available. To include in the 

draft attainment plan an outline of these requirements prior to publication of a final 

version would be premature, since EPA has published little regarding these new 

regulations, and since changes are always likely between proposed and final versions.

Additionally, including in an attainment plan specific requirements of the new source 

review permitting program would be duplicative. The new source review permitting 

program is published under a separate chapter of the Regulations for the Control and 

Abatement of Air Pollution and is thus subject to the Administrative Process Act, 

including that statute’s public participation requirements. Modeling requirements that 

may be necessary for the program are generally guidelines published by EPA and used 

by many states across the country. If such details were included in the attainment plan, 

any changes made to modeling guidance or the new source review program would also 

necessitate a revision of the attainment plan, which is a time-consuming, resourceintensive process. Therefore, it is not appropriate or necessary to include additional 

detail about the permitting program within the attainment plan.

3. SUBJECT: Implementation of existing permit programs.

COMMENTER: City of Alexandria

TEXT: The existing permitting program and regional/national control programs 

alone are insufficient to accomplish the SIP goal. The goals must be accomplished as 
5

expeditiously as possible, mindful of 2006 standards. Rigorous monitoring programs 

and more severe limitations are necessary due to model uncertainty. Lax permitting, 

monitoring, and compliance programs allow increases of emissions over this attainment 

plan’s emissions inventories and caps.

RESPONSE: The programs outlined within the attainment plan are in fact 

sufficient to accomplish the SIP’s goals. FRM data show that the region has already 

attained the 1997 standards of 15.0 μg/m3 on an annual average and 65 μg/m3 on a 

daily average. These accomplishments are attributable to many of the control 

programs implemented in previous attainment plans for ozone. Additional federal, 

state, and supplemental control programs, as outlined in the draft attainment plan, will 

continue to reduce precursor and direct emissions of PM2.5. This attainment plan will 

continue to improve air quality.

It is indeed important to be mindful of the 2006 PM2.5 NAAQS standard on a regional 

basis. For years 2004-2006, only one regional FRM located in Washington, D.C. 

showed a 24-hour design value above 35 μg/m3

. The data for all states have not yet 

been certified for years 2005-2007. However, Virginia’s data have been certified for 

these years, and these data show all monitors in northern Virginia have 24-hour 

averages of no more than 34.0 μg/m3

. On a regional basis, these data show that air 

quality is improving and appears to be attaining or nearly attaining the 2006 standard.

Modeling uncertainty does exist and is documented as part of the modeling evaluation 

report. However, EPA has recognized the fact that PM2.5 models have intrinsic 

uncertainties due to many factors, including but not limited to the complex nature of 

PM2.5 formation and the current state of the science of PM2.5 modeling. To address 

these uncertainties, EPA requires the use of the modeling results in a relative sense 

rather than an absolute sense. Virginia must make comparisons between modeling 

outputs for 2002 and 2009, then use these ratios with actual FRM data to predict future 

design values. Direct model output results for 2009 may not be used to show future 

attainment status. The use of the modeling outputs in a relative sense, coupled with 

the current improved air quality in the metropolitan Washington D.C. area, does not 

support the development of more stringent permitting requirements than those that will 

be published for implementation of the PM2.5 nonattainment permitting program.

It is important to note differences between regional modeling protocols and facilityspecific point source modeling that is performed for new and modified units under the 

Prevention of Significant Deterioration (PSD) major new source review permitting 

program. Modeling performed within the PSD permitting program to determine if a 

facility causes or contributes to a NAAQS violation is performed when guidance for 

such analyses is available. Additionally, such analyses are typically performed at the 

facility’s potential to emit or permitted levels to ensure that all levels of operation by the

new facility will not have an impact on the NAAQS.

Regional modeling inventories are based on actual emissions and projected emissions. 

A facility’s projected emissions are rarely as high as its potential to emit. Projected 
6

emissions are generally extrapolated using a base year’s actual emissions inventory 

and applying a conservative growth factor, as required by EPA. In some instances, 

projected emissions are adjusted based on control estimates. However, projected 

emissions are almost never based on potential to emit of a facility. Using such a 

methodology region-wide would drastically inflate the point source emissions inventory 

of an area. Such inflation of the projected emissions inventory could result in the 

implementation of costly and unnecessary regional control measures. Such mitigation 

efforts cannot be supported if there is every reasonable expectation that PM2.5 air 

quality is good and getting better, as indicated by the FRM data. Therefore, it is not 

appropriate to set projection year emission inventories equal to permitted limits or 

potential to emit.

Virginia’s permitting, enforcement, and monitoring programs are far from lax. Facilities 

that trigger major new source review permitting in the northern Virginia PM2.5

nonattainment area, either as new or modified sources, must install technology deemed 

to meet lowest achievable emission rates (LAER). This technology determination does 

not allow the cost of a control device to be considered in feasibility studies, making it a 

very stringent hurdle. Additionally, offsets must be obtained to ensure that emissions 

increases will not adversely affect regional air quality. These permitting requirements 

are quite stringent and will continue to be applied in PM2.5 nonattainment areas.

The Commonwealth clearly enjoys a strong, capable enforcement and monitoring 

program at both the regional and state level. The air compliance and enforcement staff 

at DEQ’s Northern Regional Office conducted 209 full compliance evaluations of 

facilities, reviewed 55 stack tests, and conducted 96 Stage II inspections in 2007. A 

total of 83 enforcement follow-ups were conducted in 2007 as well. Additionally, in 

2007, the northern Virginia Inspection and Maintenance Program performed 463 overt 

inspections and 177 covert inspections. These inspections resulted in 138 inspectors 

and/or stations being fined, losing licenses, or otherwise being prohibited from 

operating. Across the Commonwealth, DEQ conducted over 8,500 full compliance 

evaluations, more than 200 stack tests reviews, and over 390 enforcement follow-ups.

4. SUBJECT: RACT/RACM

COMMENTER: City of Alexandria.

TEXT: The attainment plan does not discuss additional RACT/RACM in enough 

detail.

RESPONSE: 40 CFR 51.1010, which delineates requirements for reasonably 

available control measures (RACM) and reasonably available control technology 

(RACT), predicates the implementation of a suite of measures on whether those 

measures can collectively advance the attainment date of a nonattainment area by one 

year. Since the metropolitan Washington area is currently attaining the 1997 PM2.5

NAAQS, based on FRM data for 2003-2005 and 2004-2006, it is not possible for any 

suite of measures to advance attainment. This explanation is provided in section 8.3 of 
7

the draft attainment plan. No further requirements or discussions of RACT/RACM are 

necessary for the plan to be approved. Therefore, the RACT/RACM requirements for 

this attainment plan are satisfied.

5. SUBJECT: Monitoring and opacity standards.

COMMENTER: City of Alexandria.

TEXT: U.S. EPA’s Clean Air Fine Particulate Implementation Rule suggests the 

use of more stringent monitoring and opacity standards. Virginia’s current opacity 

standard of 20% allows PM2.5 emission increases without adequate review. Opacity 

limitations should be strengthened to no more than 10%.

RESPONSE: How the current opacity standard for large boilers allows 

emissions increases above a baseline is unclear. However, the justification for

examining monitoring and opacity standards as discussed in EPA’s Clean Air Fine 

Particulate Implementation Rule (72 FR 20586, April 25, 2007) is that of RACT/RACM. 

The commenter is referencing language found in 72 FR 20617 which is in the context of 

observations on control opportunities when examining requirements for RACT/RACM. 

As noted in the response to comment 4, RACT/RACM requirements are predicated on 

advancing the attainment date, which is not possible for the metropolitan Washington 

area. Therefore, unless a facility undergoes a major modification as part of the new 

source review major permitting process (in which case LAER must be applied), or 

undergoes a minor modification (in which case BACT must be applied), there currently 

is no basis for reviewing source-specific opacity standards applied to major stationary 

sources.

6. SUBJECT: CMAQ analysis.

COMMENTER: City of Alexandria

TEXT: CMAQ generally over-predicts during winter months and under-predicts 

during summer months. This aspect of model performance cannot be considered 

acceptable. Statistical metrics such as fractional error and bias do not provide 

assurance that the model predictions meet the modeling performance goals on either a 

24-hour or an annual basis. There is no observed error in model performance on the 

end model result in the target year of 2010. The design value calculations should 

include columns of maximum predicted values that reflect the model’s worst-case 

performance for this modeling domain. The analysis relies too heavily on the trend in 

observed PM2.5 levels.

RESPONSE: A critical component of every air quality modeling study is the 

model performance evaluation (MPE) in which the modeled estimates for the current 

year base case are compared against observed values to assess the model’s accuracy 

and provide an indication of its reliability.
8

The first step in the modeling process is to verify the model’s performance in terms of 

its ability to predict PM2.5 and its individual components (i.e., sulfate, nitrate, 

ammonium, organic carbon, elemental carbon and other PM2.5) in the right locations 

and at the right levels. To do this, the model predictions for the base year simulation are 

compared to the ambient data observed in the historical episode.

The MPE included in the metropolitan Washington attainment plan was developed 

based on input from several regional planning groups such as the MidAtlantic/Northeast Visibility Union, the Ozone Transport Commission, and the 

Association for Southeastern Integrated Planning. Specifically, all elements of the 

modeling platform, including the emissions, meteorology, and air quality model, have 

undergone an evaluation. The MPE consists of a combination of statistical and 

graphical evaluations recommended by EPA in its guidance. After review of the MPE, if 

the model appears to be producing PM2.5 in the right locations for the right reasons, 

then the model can be used as a predictive tool to evaluate various control strategies 

and their effects on PM2.5.

The issue of model performance goals for PM2.5 is an area of ongoing research and 

debate. Performance goals refer to targets that a well-performing model should 

achieve, whereas performance benchmarks are based on historical model performance 

measures for the best performing simulations. Performance goals are necessary in 

order to provide consistency in model applications and expectations across the country 

and to provide standardization in how much weight may be accorded modeling study 

results in the decisionmaking process. The model performance goals and criteria are 

not regarded as a pass/fail test but rather as a basis of inter-comparing model 

performance across studies, sensitivity tests, and models.

The results of the MPE for the metropolitan Washington area for PM2.5 and its individual 

species indicate that the CMAQ model performance for surface PM2.5 is good, with 

acceptable bias and error. The MPE was consistent with EPA guidance and includes 

the proper statistical performance metrics.

EPA and DEQ recognize that although good model performance remains a prerequisite 

for use of a model in an attainment demonstration, problems posed by less than ideal 

model performance on individual days are reduced through the use of the model results 

in a relative sense. Furthermore, starting with an observed concentration as the base 

value reduces problems in interpreting model results. It is recognized that model 

results and projections will continue to have associated uncertainty. The attainment 

demonstration that EPA recommends recognizes this by including modeling plus other 

supplemental analyses such as air quality trends to determine whether all available 

evidence supports a conclusion that a proposed emission reduction plan will suffice to 

meet the NAAQS.

In summary, the issues identified by the commenter are not regulatory requirements 

and are not appropriate for inclusion in the attainment demonstration, since attainment 

tests are based on the application of relative response factors. The regional and local 
9

model performance is acceptable for PM2.5 and was evaluated using EPA-approved 

procedures. While there are some differences between the spatial data between subregions, there is nothing to suggest a tendency for the model to respond in a 

systematically different manner between regions. Examination of the statistical metrics 

by sub-region confirms the absence of significant performance problems arising in one 

area but not in another, building confidence that the CMAQ modeling system is 

operating consistently across the full modeling domain. This confidence in the 

modeling results allows for the modeling system to be used to support the PM2.5

attainment plan.

7. SUBJECT: Unmonitored areas.

COMMENTER: City of Alexandria

TEXT: The proposed SIP provides no assurance that attainment with the 

NAAQS will be achieved in unmonitored areas where local-scale modeling is the only 

means for determining compliance. Alexandria is an unmonitored area. Detailed 

special purpose monitoring data show time periods when concentrations at Marina 

Towers approached or exceeded the NAAQS. These data present a clear indication 

that the regional monitors are not representative of concentrations in Alexandria and 

that an unmonitored area analysis must be conducted.

RESPONSE: The information presented by the commenter compares all 

monitoring data to the 2006 daily 35 μg/m3 standard. This attainment plan is directed at 

the 1997 standards, for which the daily standard is 65 μg/m3

. Data provided do not 

exceed 65 μg/m3.

Additionally, use of exceedence periods is not particularly helpful in comparisons to the 

NAAQS. Each NAAQS standard contains both a numerical limitation and a statistical 

methodology for computing that standard from monitoring data. The statistical 

methodology, for example an annual average or a fourth highest, three-year average, is 

partly due to concerns of exposure time and rates. To violate a NAAQS, the standard 

must be surpassed using the appropriate statistical approach. The Clean Air Act 

concerns itself with violations of the NAAQS, not exceedences. Exceedences must 

therefore be considered data variability, not actionable violations.

In regard to the inclusion of an unmonitored area analysis, the regional modeling 

attainment demonstration does not address future air quality at locations where there is 

no PM2.5 monitor nearby. To guard against the possibility that air quality levels could 

exceed the standard in areas with limited monitoring, EPA suggests that additional 

review is necessary, particularly in nonattainment areas where the PM2.5 monitoring 

network just meets or minimally exceeds the size of the network required to report data 

to the Air Quality System. This review is intended to ensure that a SIP control strategy 

leads to reductions in PM2.5 and its constituent pollutants at other locations that could 

have baseline (and future) design values exceeding the NAAQS were a monitor 

deployed there. The test is called an unmonitored area analysis (UAA).
10

The UAA uses a combination of the 12-km gridded model output and ambient data. 

The analysis should include, at a minimum, all nonattainment counties and counties 

surrounding the nonattainment area. Based on DEQ’s initial review of the gridded 

model output and ambient data, the UAA is unlikely to reveal any areas where future 

design values would exceed the NAAQS in the metropolitan Washington area.

EPA stresses that due to the lack of measured data, the examination of concentrations 

as part of the UAA is more uncertain than the monitor-based attainment test. EPA’s 

guidance recommends that predicted violations of the unmonitored area analysis be 

carefully scrutinized to determine whether they are likely to exist in the ambient air or 

whether they may be caused by an error or uncertainty in the modeling system. At a 

minimum, it may be appropriate to commit to additional deployment of ambient monitors

in areas where the UAA predicts future violations. This monitoring would allow a better 

assessment in the future of whether the NAAQS is being met at currently unmonitored 

locations. In fact, in many ways the analysis of PRGS using special purpose monitors 

has already fulfilled the goal of the UAA. The PRGS should not be considered an 

“unmonitored area” based on the fact that there is a continuous PM2.5 monitor operating 

on the southeast property line and an FRM located on the roof of Marina Towers. The 

Marina Towers FRM monitor site is located in the area of expected maximum impact 

from PRGS. PRGS remains one of the best monitored sources in Virginia.

Predicted violations of the UAA should be handled on a case-by-case basis. As such, 

additional analyses and tracking requirements may be needed depending on the nature 

of the problem and the uncertainty associated with the potential violations. EPA also 

stated at its June 2007 PM2.5 modeling workshop that the UAA was not designed to 

look for unmonitored PM micro-scale hot-spot issues. This would preclude the use of 

the UAA as a useful technique in evaluating impacts from an individual source such as 

PRGS.

DEQ is currently in the process of conducting the UAA for the metropolitan Washington

area. DEQ is also part of the test group for the recently released beta version of EPA’s 

Model Attainment Test Software (MATS), which is the tool required to conduct the UAA. 

Unfortunately, this tool is limited and does not have the spatial field feature necessary 

to complete the UAA. EPA expects that this component will be added in the next 

version of MATS and DEQ will complete the analysis upon release of the updated 

software.

The metropolitan Washington area currently has a network of 14 PM2.5 monitors. 

Several of these monitors were established as State and Local Air Monitoring Stations 

(SLAMS). These SLAMS monitors were selected based on specific monitoring 

objectives (background concentration, area of highest concentration, high population, 

source impact, transport, and rural impact) as required by EPA and siting scales (micro, 

middle, neighborhood, urban, and regional) established by EPA. It is believed that the 

density of the monitoring network relieves the necessity of applying the UAA. Despite 

being confident that the monitoring network is robust for the metropolitan Washington
11

area, once the final version of the MATS tool has been released, and after sufficient 

peer review and proper guidance for the analysis of the results is provided, DEQ will 

complete the UAA.

8. SUBJECT: Modeling analysis.

COMMENTER: City of Alexandria

TEXT: No FRM monitor exists in Alexandria. Additionally, monitoring alone, 

especially within the impact area of a large source, is insufficient to demonstrate 

NAAQS compliance. Only through a modeling analysis that includes a robust receptor 

network can NAAQS protection be assured. DEQ should immediately address primary 

impacts of PM2.5 in the local areas surrounding PRGS. Modeling tools are available.

RESPONSE: DEQ is examining the possibility of installing either a special 

purpose PM2.5 monitor or a PM2.5 FRM within Alexandria. Whether or not such a 

monitor can be sited and operated within Alexandria depends on a number of issues, 

including personnel and monetary resources as well as locating an appropriate site for 

such a monitor. If at all possible, DEQ would prefer to gather necessary monitoring 

data to determine air quality within Alexandria’s city limits. DEQ is also exploring the 

possibility of PRGS continuing to operate at least one of the two PM2.5 monitoring 

stations they currently are using to gather air quality data.

The statement that NAAQS protection can be assured only through a modeling analysis 

is inaccurate. As stated elsewhere, there are several uses of air quality data in 

evaluating the impacts from a facility such as PRGS. One of the most important uses 

identified in the EPA’s Guideline on Air Quality Models is the use of air quality 

measurements “in a complementary manner to dispersion models with due regard for 

the strength and weaknesses of both analysis techniques.” While air quality

measurements are particularly useful in assessing the accuracy of model estimates, 

these measurements do not necessarily eliminate the need to apply a model to assess 

an individual facility’s impact. Although it is possible to use air quality measurements 

alone to assess NAAQS compliance, this approach would not likely be preferred unless 

available models are found to be unacceptable, and monitoring data has sufficient 

spatial and temporal coverage.

Additionally, for certain pollutants, such as SO2, conservative EPA-approved modeling 

analyses are indeed available and can be used for such a purpose. However, this is 

not the case for all pollutants. For example, there is no source-specific, EPA-approved 

modeling approach for ozone from facilities that emit VOC and NOX; nor do appropriate 

modeling methodologies exist for estimating direct PM2.5 impacts. A few states have 

published guidance for estimating impacts from new or modified sources using statespecific significant impact levels. No federal guidance has yet been finalized on such 

protocols. Currently, it is unclear what type of analyses EPA will require in regard to 

source-specific PM2.5 emissions. Modeling may not be a part of such analytical 

guidance. Adoption of other states’ guidance, which was intended for use on new and 
12

modified facilities and not existing facilities, would set a precedent for use in other areas 

of the Commonwealth. Due to its highly conservative nature, use of such guidance may 

unjustifiably prohibit the construction or modification of facilities within the 

Commonwealth. Use of such guidance, as applied to existing facilities, may 

unjustifiably require source curtailment or other expensive operational changes.

Section 9.4.3 requires an analysis be performed after an analytical approach is finalized 

by EPA and peer reviewed. This analysis may or may not involve Gaussian modeling 

of some type. Regardless, the analysis will be performed to ensure PM2.5 NAAQS 

compliance by PRGS.

9. SUBJECT: Modeling analysis.

COMMENTER: City of Alexandria

TEXT: In Section 9.4.3, DEQ defers any modeling analysis of the PRGS facility 

until an appropriate implementation methodology for PM2.5 is established, which 

appears to be an acknowledgement that the proposed SIP is deficient and that a more

appropriate implementation plan is necessary.

RESPONSE: Section 9.4.3 was in no way added to address any “deficiency.” It

was included to address Alexandria’s concerns regarding PM2.5 air quality even though 

the special purpose monitors in the city do not show violations of either the 1996 or the 

2006 PM2.5 NAAQS standard. Including such requirements to address concerns is an 

appropriate use of the attainment plan. However, it is not a requirement of the PM2.5

planning process to address any particular facility, and the plan would be complete and 

approvable without this language. Generally, such facility concerns should be 

addressed within the normal state permitting processes. In this case, the language in 

Section 9.4.3, much of which is also included in the recent draft permit for PRGS, was 

added to the draft attainment plan in part to help build a consensus with Alexandria’s 

participants in the planning process and to help provide assurances to the citizens that 

air quality it being protected.

10. SUBJECT: Local area analysis.

COMMENTER: City of Alexandria.

TEXT: Alexandria strongly recommends that a local area analysis (LAA) be 

conducted.

RESPONSE: The LAA uses dispersion models to address observed primary 

PM2.5 contributions at monitors. Specifically, in areas with large spatial gradients of 

primary PM2.5, dispersion models are best suited to characterizing the change in 

primary PM2.5 in the future. Areas that are relying on local primary particulate matter 

controls to reach attainment should submit a LAA as part of the primary attainment 

demonstration. In other areas, a LAA may be useful as a supplemental analysis.
13

EPA also states in its guidance that the dispersion modeling results should be 

evaluated to ensure adequate model performance. Similar to photochemical grid 

modeling, the dispersion model results should be compared to ambient data to ensure 

that the model is working well. Many of the same statistical calculations used for 

photochemical grid modeling are recommended for evaluating primary PM2.5 and PM2.5

components predicted by a dispersion model.

The LAA is used to determine the actual (or typical) contribution from sources at a 

monitor, and the model results are used in a relative sense. Therefore, it is only 

appropriate (and in fact conservative) to use actual emissions in the base year and 

projection year emissions inventories. Using actual emissions should lead to a 

reasonable estimate of air quality improvements from reducing emissions at the 

contributing sources. Using allowable emissions might lead to an overestimate of 

benefits from emissions controls.

The LAA appears to be an optional element of the SIP modeling demonstration, and 

the need for this analysis is considered on a case-by-case basis. The LAA is likely not 

required by EPA as part of the metropolitan Washington attainment planning process. 

This is due to the fact that the monitoring network does not have any observed spatial 

gradients of primary PM2.5 and that the attainment plan does not need to rely on local 

primary PM2.5 controls to reach attainment.

Based on its review of existing monitoring data, EPA initially did not invite DEQ to 

participate in a LAA workshop that was conducted in October 2007. However, due to 

concerns expressed by stakeholders, DEQ requested and was granted approval by 

EPA to attend this workshop. The focus of the workshop centered on areas that have 

elevated primary PM2.5 concentrations in their core urban areas or that contribute to 

their highest FRM. At this time, no monitors within the metropolitan Washington area

are projected to exceed the NAAQS so it does not appear to be a necessary 

requirement in this circumstance to conduct the LAA. All of the regional monitors are 

projected to reach attainment with the PM2.5 NAAQS in 2009. The future year inventory 

projections have significant decreases in primary PM2.5 and PM2.5 precursors resulting 

from various control programs throughout the region. Furthermore, existing monitoring 

data suggest a uniform regional pattern with respect to PM2.5 concentrations. No 

monitor’s data appears significantly different, on average, than data gathered at other 

monitors within the FRM network. For these reasons, no LAA is necessary.

11. SUBJECT: Proposed permit for PRGS.

COMMENTER: City of Alexandria

TEXT: DEQ’s proposed permit for PRGS is contradictory to SIP goals. The 

inventory used in the attainment plan regional modeling exercise is less than proposed 

permit limits and therefore underestimates emissions.
14

RESPONSE: The proposed permit is not contradictory to SIP goals. The goal 

of the attainment plan is to demonstrate compliance by 2009 with the 1997 PM2.5

NAAQS standards. Current FRM data show, as discussed in other responses, that the 

region is indeed meeting the 1997 PM2.5 NAAQS standards. The proposed PRGS 

permit reduces emissions from the baseline year for this facility. The proposed permit 

will improve air quality and is not contrary to the goals of the PM2.5 attainment plan.

As noted elsewhere, there are differences between regional modeling protocols and 

facility-specific point source modeling that is performed for new and modified units 

under the PSD Major NSR permitting program. Modeling performed within the PSD 

permitting program to determine if a facility causes or contributes to a NAAQS violation 

is performed when guidance for such analyses is available. Additionally, such analyses 

are typically performed at the facility’s potential to emit or permitted levels to ensure that

all levels of operation by the facility will not have a negative impact on the NAAQS.

Regional modeling inventories are based on actual emissions and projected emissions, 

partly due to the fact that the model is regional in nature. Projected emissions are 

rarely, if ever, as high as the potential to emit of a facility. To assume that projected 

emissions equal potential to emit for every facility in the point source inventory over an 

entire region would drastically inflate emission estimates in the projection year, 

especially considering the conservative nature of the other projection estimates. For 

instance, the emission factors for area source categories are generally highly 

conservative. These estimates are further inflated, since many grow in relation to 

population increases, which in the northern Virginia area are quite high. Additionally, 

transportation budgets in the projection year do not take into account transportation 

emission reduction measures, which account for many tons of emission reductions and 

are withheld for use in rare conformity situations. Transportation emissions also do not 

take into account emission reductions achieved through DEQ’s on-road emissions 

testing program, which monitors the tailpipe emissions of vehicles to locate and repair 

polluting automobiles between required station inspections. Therefore, the 2009 

projection year inventory is very conservative. As noted in the response to comment 8, 

inflation of the projected point source emissions inventory may result in the 

implementation of costly and unnecessary regional control measures. Such mitigation 

efforts cannot be supported if there is every reasonable expectation that PM2.5 air 

quality is good and getting better, as indicated by the FRM data. Therefore, projection 

year emission inventories will not be set to be equal to permitted limits or potential to 

emit.

12. SUBJECT: PRGS reduced operational loads.

COMMENTER: City of Alexandria

TEXT: The SIP does not address the reduced operational loads of PRGS that 

were important events in relation to the downward 24-hour design level trends between 

2002-04 and 2003-05. Chapter 9 should include a thorough discussion, along with a 

timeline that matches the implementation of the regional programs with the FRM 
15

monitoring results and include the effects of various actions concerning PRGS on the 

decline in regional values.

RESPONSE: Detailed discussions of every facility’s operational changes 

between 2002 and 2009 are not necessary. The goal of the attainment plan is to 

demonstrate compliance with the 1997 PM2.5 NAAQS by 2009 on a regional basis. The 

attainment plan discusses the enforceable limits of the Virginia CAIR caps, to which 

PRGS is subject, as well as a variety of other control measures and their expected 

overarching effect on air quality, such as the Maryland Healthy Air Act and a coal-tonatural gas conversion made at a nearby power plant. None of these descriptions 

include greatly detailed accounts of each measure or strategy since the sum total of all 

the reductions are used to show that PM2.5 regional air quality in northern Virginia and 

metropolitan Washington is good and getting better. Additionally, providing in Chapter 

9 a discussion of various control strategy and programs implementation schedules as 

they correspond to FRM monitoring results would be an incredibly lengthy process, 

given the number and variety of control programs that have gone into or are scheduled 

to go into effect between 2002 and 2009. Such an analysis would have to include 

reductions from such significant source sectors as the power industry, the 

transportation sector, the petroleum fuel sector, auto body refinishing, surface coating, 

and many others. Such an analysis is unnecessary in any event due to the regional 

context of the attainment plan.

13. SUBJECT: PM10 as a surrogate for PM2.5.

COMMENTER: City of Alexandria

TEXT: DEQ should not rely on PM10 as a surrogate for PM2.5 in the permitting 

process for PRGS. EPA has suggested, in May 31, 2006, correspondence from Mr. 

Donald Welsh to Congressman James Moran that the PM2.5 SIP is an appropriate place 

to address the issue of PRGS’ air quality issues.

RESPONSE: The PM2.5 attainment plan is not an appropriate arena in which to 

discuss federal permitting guidance, adopted by DEQ, in regard to the use of PM10 as a 

surrogate for PM2.5. Such permitting concerns are more appropriately addressed 

through the many significant public participation opportunities afforded the public during 

the permitting process. In any event, the current permitting guidance is appropriate 

since it reflects recommended federal guidance on the issue of PM2.5 in permits.

Regarding the EPA documentation sent to Congressman Moran, the draft PRGS permit 

satisfies the suggestions made in this letter regarding enforcement of the PM2.5

NAAQS. Page 3 of the addendum provided by Mr. Welsh notes that “Even following 

approval of the SIP for PM2.5, it may be that the only enforceable restrictions on Mirant 

are a general, statewide provision limiting PM2.5 emissions, or a specific PM2.5 permit 

limit given to the PRGS through the normal Virginia permitting process. A permit limit 

for PM2.5 is the most likely mechanism; however, at present Mirant is not subject to any 

such permit limits.”
16

PRGS air quality issues are being addressed through the normal permitting process. 

Requirements of the permit and of the draft attainment plan as listed in Section 9.4.3 

mandate an ambient air quality analysis after methodologies for such analyses are 

finalized. Use of the normal permitting process is appropriate for addressing specific 

facility concerns.

14. SUBJECT: Ambient air quality analysis.

COMMENTER: City of Alexandria

TEXT: Language in Section 9.4.3 requiring an ambient air quality analysis is 

deficient since it fails to insure that the analysis will be done in a timely manner. It also 

suggests that methodology to conduct such an analysis is not available at the present 

time, which is contrary to existing EPA guidance. The language should be revised to 

read: “Using an available Gaussian dispersion model, such as AEROMOD, for 

stationary sources, which has been approved by USEPA to model primary PM2.5

impacts, DEQ shall conduct an ambient air quality analysis of the emissions of PM2.5

from the Mirant Potomac River Power Generating facility. DEQ shall complete this 

analysis within 120 days of adoption of the SIP by MWAQC.”

RESPONSE: The language suggested by the commenter is not appropriate. As 

noted elsewhere, it is not certain that Gaussian dispersion modeling will be a 

requirement of PM2.5 ambient air quality analyses. EPA has not yet published modeling 

guidance for PM2.5 pollution. Use of published guidance for other pollutants, such as 

SO2, is not prudent given that the highly complex nature of PM2.5 chemistry may not 

make the use of guidance for other pollutants applicable. If Gaussian dispersion 

modeling is eventually required, no federal guidance currently exists explaining the 

application to PM2.5 of this technique, which is multi-faceted and highly complicated.

DEQ is committed to working with the public, regulated community, and other 

stakeholders in the development of appropriate PM2.5 guidance. DEQ has formed a 

PM2.5 Implementation Workgroup, which was announced on the Virginia Regulatory 

Town Hall on January 2, 2008. This announcement solicited participation in a 

workgroup responsible for the development of a draft policy to evaluate both new and 

existing sources that have the potential to emit of PM2.5 in quantities that could have 

possible significant adverse health and environmental impacts. This approach goes 

beyond that of other states that have developed procedures that evaluate new and 

modified facilities only. DEQ seeks membership from environmental and health 

organizations, academia, the legal profession, and industry or trade associations that 

have a background in air quality modeling, policies, or programs to serve on this 

workgroup. The first meeting will likely take place in March 2008. Due to the 

exploratory nature of the workgroup, no estimation of a time frame for project

completion can be made. However, DEQ will be providing the board periodic updates 

on the progress of workgroup efforts.
17

The language included in Section 9.4.3 states that the timeline for submitting the 

analysis will be determined by DEQ. This language was included to account for the fact 

that the requirements of the ambient air quality methodology are not known so that a 

reasonable timeframe cannot currently be fixed. However, it is reasonable for DEQ to

require that PRGS submit a protocol once the final methodologies are approved by the 

board within a certain time frame. DEQ will also commit to publishing this document on 

the DEQ website so that citizens may review the contents. Section 9.4.3 has been 

updated to reflect this change and now reads as follows:

Based on a schedule and protocol to be established by DEQ after US EPA promulgates final rules 

for PM2.5 analysis, or UE EPA promulgates revised implementation guidance or policy for PM2.5

analysis, or DEQ establishes a more appropriate implementation methodology for PM2.5, Mirant 

Potomac River Power Station shall conduct an ambient air quality analysis for the emissions of 

PM2.5 from the facility. No later than 60 days after approval of the implementation methodology by 

the Virginia State Air Pollution Control Board, Mirant Potomac River Power Station shall provide to 

DEQ a detailed protocol outlining how the facility will implement the approved methodologies. 

DEQ will make this document available to the public by publishing this protocol on the DEQ

website.

Even without these changes, the language in Section 9.4.3 clearly indicates DEQ’s

intention to require an analysis, once methodologies are determined, within a 

reasonable period of time.

15. SUBJECT: Voluntary measures.

COMMENTER: City of Alexandria

TEXT: Alexandria requests the inclusion of various measures that the city funds 

and oversees in the attainment plan, as these measures are directionally correct and 

improve air quality.

RESPONSE: The supplemental measures as listed by the commenter have 

been added to the plan.

16. SUBJECT: PRGS impacts on PM2.5 concentrations in the City of Alexandria.

COMMENTER: Fairfax County Federation of Citizen's Associations

TEXT: The commenter requests that the Community Multi-scale Air Quality 

(CMAQ) model be re-run to calculate a design value for a model node point 

representative of downtown Alexandria.

RESPONSE: The CMAQ modeling results cannot be run as requested by the 

commenter and still conform to EPA guidance on how CMAQ results should be used. 

As noted in elsewhere, EPA recommends the use of CMAQ results in a relative sense 

when calculating future design values. In other words, CMAQ is run for both 2002 and 

2009, and estimated concentrations for PM2.5 for each year are used to create a ratio. 
18

This ratio may be thought of as 2009 divided by 2002; however, this explanation is 

somewhat oversimplified since PM2.5 is a composite of a variety of different chemical 

compounds that must be factored into the equation. The calculated ratio of 2009 to 

2002 is then applied to actual 2002 monitored design values at FRMs to calculate the 

projected 2009 design values for each monitoring site. EPA recommends the use of 

CMAQ in this manner for many reasons. One reason such methodology is 

recommended is the state of the science of PM2.5 modeling, which is really in its 

infancy. EPA recognizes that the model does not account for many physical and 

chemical properties of PM2.5 and therefore believes using the model in a relative sense 

provides more certain results. Another reason such methodology is recommended is 

the belief that actual monitoring data should play a significant role in the projected 

design value calculations. Using the CMAQ results in the relative sense ensures that 

the design value projections have a strong basis in actual monitoring results.

Since no FRM monitor exists in Alexandria, this modeling exercise cannot be performed 

according to EPA guidance. Note that in the response to comment 8, consideration is 

being given to locating a special purpose PM2.5 monitor or a PM2.5 FRM in the city.

17. SUBJECT: PRGS impacts on PM2.5 concentrations in the City of Alexandria.

COMMENTER: Fairfax County Federation of Citizen's Associations

TEXT: The attainment plan should include a Gaussian dispersion model for 

PRGS of direct fine particulate emissions with downwash. Data from the model should 

not be added to background concentrations to address the issue that background 

concentrations may include the effects of PRGS’s emissions.

RESPONSE: Specific facility concerns, including results of any air quality 

analysis performed on PRGS or any other facility, do not belong in a regional 

attainment plan. Due to significant facility concerns, Section 9.4.3, which reiterates the

requirement in the draft permit for PRGS, requires an ambient air quality analysis be 

performed on PRGS’s emissions when methodology for such an analysis is finalized. 

Including the results of the Gaussian dispersion model performed by the City of 

Alexandria on this facility as part of the attainment plan would not make the plan any 

more approvable. The draft attainment plan is fully approvable in its current state. 

Including the results of the Gaussian dispersion model may also be premature since it 

is unclear what methodology will be recommended for PM2.5 ambient air quality 

analyses. If the recommended methodology is something other than a Gaussian 

dispersion model, including the results of such modeling in the attainment plan could be 

misleading. Lastly, it is unclear what purpose including the results of Alexandria’s 

Gaussian dispersion model with the background concentration removed would serve. 

The following table below shows Alexandria’s calculated impacts by PRGS in the 

Gaussian model:
19

PRGS Modeled PM2.5 Impacts

(Case ID - 5 units operating at mid-range load for 24 hours per day)

24-hour

(μg/m3)

Annual

(μg/m3)

Stack Impacts on Elevated Receptors:

3-year avg. of 8th-highest, stacks alone, among all 

Marina Towers rooftop receptors.

6.5 0.9

Coal and Ash Yard Impacts on Ground-level 

Receptors:

3-year avg. of 8th-highest, ground-level, from coal and 

ash yard sources only.

8.2 2.6

Background

3-year avg. of 8th-highest, closest monitor.

34.1 14.1

NAAQS 35 15.0

Not including the background concentrations would demonstrate a maximum impact of 

8.2 μg/m3 on a 24-hour basis, far less than either the 1997 24-hour standard of 65 

μg/m3 or the 2006 24-hour standard of 35 μg/m3

. The maximum impact of 2.6 μg/m3 on 

an annual basis is far less than 15.0 μg/m3

. Including this information does not provide 

any additional insight to the regional air quality issues of the metropolitan Washington 

area.

18. SUBJECT: Clarifying text, technical details, and growth rates for area source 

emissions inventories.

COMMENTER: Fairfax County Federation of Citizen's Associations

TEXT: (a) Figure 2-5 does not include data for March through September of 

2005. (b) Text in Section 2.2.4 does not appear to support the figure. Perhaps different 

plots should be used. (c) Figure 2-10 needs more explanation, especially concerning 

the reasons for not considering ammonia emissions for control purposes in the SIP. 

Also, terms on the figure need more explanation. (d) Figure 2-11 is misleading. The 

axis should be changed to reflect zero or should contain a jog to indicate that the axis 

doesn’t begin at zero. (e) The plan needs to clarify the difference between area “non 

stationary” sources and mobile sources. A definition for “county-equivalent” should be 

provided. Non-road airport vehicles need to be mentioned in Section 3.2.2. (f) The 

commenter suggests examining certain sectors of the area source emissions inventory 

to determine if appropriate growth factors have been used. The specific sectors 

mentioned are residential fuel combustion, open burning, municipal landfills and 

incineration, and fugitive dust emissions.

RESPONSE: (a) This figure has been updated to include information through 

December 2005. (b) An updated figure and additional information within the text of the 

section have been added. (c) Figure 2-10 has been updated to better explain the 

content and terms of the figure. However, the reasons why ammonia is not considered 

a significant precursor to PM2.5 are explained thoroughly in the plan, including Section 

2.8. (d) The range of the y axis in Figure 2-11 was defined from 14.0 to 17.5 in order to 

clearly demonstrate a declining design value trend line. Extending the y axis to zero 

instead of 14.0 creates a trend line that is nearly flat. A flat trend line does not clearly 
20

indicate the significant level of air quality improvement measured by the FRM network. 

Also, data are labeled for design values for different years, and the annual PM2.5

standard line is clearly delineated in the graph. The figure is quite clear in its meaning.

(e) A sentence has been added to Section 3.2.3 to define what constitutes a mobile 

source. Section 3.2.2 provides details about area sources, and the discussions in 

these two sections make clear distinctions between area and mobile sources. 

Examples have been added to illustrate the differences between area “non stationary” 

and mobile sources. Since the MWAQC area inventory is calculated at county level, 

the term “county-equivalent” is not relevant and has been deleted. Non-road airport 

vehicles are included in the non-road inventory. (f) DEQ has examined the open 

burning emissions category and found updated guidance for determining emissions 

from this source sector. However, for the other mentioned sectors, growth surrogates 

for different area and nonroad source categories were decided in consultation with the

state air agencies’ staff and the Emissions Inventory Sub-Committee of the Technical 

Advisory Committee. These factors are the most appropriate factors available to 

inventory staff and have therefore been employed in inventory development. As EPA 

provides additional guidance on how these emissions inventories should be developed, 

such guidance will be examined for use in future inventories.

19. SUBJECT: Health effects of PM2.5.

COMMENTER: Ms. Crenshaw-Van Fleet, citizen and member of the Air Quality 

Public Advisory Committee (AQPAC)

TEXT: The attainment plan makes no mention that the reductions, 

contingencies, or controls as documented will cause a reduction in the occurrences of 

the health conditions and problems caused by PM2.5. Will health problems and 

conditions associated by the Department of Energy with PRGS in its SEA decrease with 

the application of this attainment plan? Results from a study done by the Agency for 

Toxic Substances and Disease Registry are due sometime in late winter or early spring 

of 2008. This study should be carefully reviewed.

RESPONSE: Language has been added to the attainment plan to indicate that 

attainment of the PM2.5 NAAQS, as well as further air quality improvements, will have a 

positive influence on the health and well-being of the citizens of the Commonwealth.

The attainment plan requires that PRGS perform an ambient air quality analysis when 

the methodology for such an analysis is finalized. The results of this study may show 

that additional controls on PRGS are needed to ensure the PM2.5 NAAQS is met. The 

purpose of the attainment demonstration is to ensure that the region meets the NAAQS 

in a timely manner. The plan also ensures that further air quality improvements will be 

enjoyed by the citizens of the metropolitan Washington area. However, the federal 

Clean Air Act does not mandate that a study demonstrating health benefits from each 

control program as applied within each separate nonattainment area be provided to 

create an approvable plan. While such information would certainly be interesting and 

noteworthy, DEQ does not have the resources to undertake such an endeavor. Such 
21

an endeavor is also not a necessary requirement of the PM2.5 attainment planning 

process.

The study from the Agency for Toxic Substances and Disease Registry will be reviewed 

by DEQ.

20. SUBJECT: PM2.5 monitors located near large PM2.5 sources

COMMENTER: Ms. Crenshaw-Van Fleet, citizen and member of AQPAC

TEXT: Current PM2.5 monitors at PRGS do not meet siting criteria and thus 

cannot be used for this SIP. Are there other point sources in the Metropolitan 

Washington Region that would benefit from properly sited PM2.5 monitors? Any and all 

locations that are considered sources of PM2.5 emissions should have PM2.5 monitors 

properly sited under EPA criteria.

RESPONSE: One monitor located near PRGS (on top of Marina Towers) uses

federal reference measurement methods to collect data on that site. The location does 

not meet the criteria for FRM monitoring sites, since FRM siting criteria include 

limitations on the height of the sampling probe. The criteria suggest that appropriate 

heights for probes should be approximately equal to the level at which an average 

person breathes.

However, data from this site have not been discounted. Since the FRM testing 

methodology requires the use of a laboratory to analyze filters, FRMs are not real time 

monitors. In other words, there is a lag between the sample collection time and when 

the results of the laboratory analyses are received. For the FRM on the top of Marina 

Towers, at the time the draft SIP was being written, DEQ had 10 months of 2007 data, 

January through October. To calculate an annual average, 12 months of data are

needed. As a place holder, data from November and December of 2006 were used to 

examine the annual average at that monitoring site. The data indicate an annual 

average for one year of 13.7 μg/m3

, well below 15.0 μg/m3. This information was not 

included in the draft attainment plan because using November 2006 through October 

2007 data is an irregular method of calculating an annual average; because three years 

of data were not available from this monitoring site, as required by the statistical 

methodology for the NAAQS; and because the calculated annual average was well 

beneath the 15.0 μg/m3 standard. In early February of 2008, the final months of PM2.5

data for 2007 at the Marina Tower monitors became available. For January through 

December 2007, the Marina Towers monitor measured an annual average of 13.5 

μg/m3 and a 24-hour average of 31.3 μg/m3. DEQ will continue to examine the data 

gathered from this monitoring site.

As discussed elsewhere, DEQ is considering locating a PM2.5 monitor within the City of 

Alexandria due to concerns raised about PRGS. To summarize, PM2.5 FRMs are 

resource intensive (installing a PM2.5 FRM costs approximately $13,000 each with an 

annual operations cost of approximately $15,000), and DEQ must operate within its 
22

resource constraints. Adding additional monitors to the already robust monitoring 

network in the area would be quite costly without showing any great deviation from the 

measurements made at the current FRM sites. To date, the FRMs in the metropolitan 

Washington area do not appear to show a great deal of data deviation, indicating that 

the PM2.5 air quality in the metropolitan Washington area is more a regional issue than 

it is a localized issue. It is not necessary or cost effective to locate FRMs near every 

major point source of PM2.5 emissions in the metropolitan Washington area.

21. SUBJECT: Emissions from PRGS.

COMMENTER: Ms. Julie Crenshaw-Van Fleet, citizen and member of AQPAC

TEXT: Mirant Potomac River Generating Station is a point source considered to 

be a high polluter by EPA. High polluters should be considered hot spot problem 

locations. The use of TRONA at PRGS, and its effects on PM2.5 emissions and human 

health, should be discussed in the attainment plan.

RESPONSE: EPA does not define a “hot spot” within regional modeling 

guidance. The current EPA guidance for regional modeling to support attainment plans 

notes that LAAs are required for areas within a region that show elevated monitored 

PM2.5 concentrations at monitors within the federal reference monitoring network when 

compared to data from other federal reference monitors in the region. There is no 

identified gradient in PM2.5 concentrations in the FRM network in the metropolitan 

Washington region. Therefore, by EPA’s definition, there is no requirement to conduct 

a local area analysis. DEQ is aware of highly conservative micro-scale modeling that 

indicates the possibility of a hot spot in the City of Alexandria even though current data 

from the monitors located in the modeled area show that concentrations are well 

beneath the NAAQS. Additionally, FRM monitoring data at the nearby monitoring 

station in Arlington show compliance with the NAAQS. Regardless, the attainment plan 

does include requirements for further actions to address the concerns regarding 

emissions from PRGS through additional analyses, when methodologies become 

available, as required by Section 9.4.3.

Regarding the use of TRONA injection for SO2 control at the PRGS, the attainment plan 

is not an appropriate place to enumerate details about a specific facility’s operational 

considerations. Such details are routinely examined and incorporated into permits 

through the normal permitting process. Such details have been and continue to be the 

subject of scrutiny by DEQ permitting staff in the ongoing PRGS permitting process. 

The PRGS permitting process has included many public comment opportunities for

citizens to examine and comment on the drafts.

In regard to specific concerns about PM2.5 increases from the use of TRONA injection 

at PRGS, the May 31, 2006, letter from Mr. Welsh to Congressman Moran provides an 

enclosure that addresses the issues of full scale evaluations of TRONA use and 

particulate increases due to TRONA injection. The enclosure states, “EPA believes 

there is sufficient evidence that TRONA is a suitable absorbent for injection into a 
23

power plant flue gas stream for the purpose of removing sulfur dioxide. ... The Material 

Safety Data Sheet (MSDS) for TRONA identifies is as a relatively non-toxic compound. 

...” The enclosure also summarizes the effect of TRONA at PRGS as, “TRONA was 

demonstrated to remove 80% of SO2 emissions, while not impacting opacity and 

significantly decreasing the PM10 emission rate.”

PM2.5 tests were performed using EPA’s Conditional Test Method 40 (CTM-40) at 

PRGS on December 14 through 17, 2006. These tests confirmed that TRONA injection 

did not increase PM2.5 emissions from the boilers.

22. SUBJECT: PM2.5 impacts of the PRGS in Alexandria, Virginia

COMMENTER: Sierra Club

TEXT: PRGS is the single largest source of PM2.5 in northern Virginia. PM2.5

monitors at Marina Towers measured concentrations above the 35 μg/m3 24-hour 

NAAQS on several occasions in 2007. EPA scientists have recommended an annual 

PM2.5 NAAQS limit that is lower than 15.0 μg/m3. The City of Alexandria’s dispersion 

modeling to date, including downwash, demonstrates that a “hot spot” exists. PRGS 

contributes significantly to PM2.5 nonattainment in Alexandria and the metropolitan 

Washington areas.

RESPONSE: While PRGS is indeed a large emitter of PM2.5, it is not the largest 

point source emitter in the metropolitan Washington area, nor is it the largest emitter in 

northern Virginia, when all segments of the point, area, non-road, and transportation 

inventories are considered.

As stated elsewhere, short-term excursions above the 35 μg/m3 standard are not 

actionable violations. Violations are based on statistical methodologies to take into 

account exposure rates. Occasional exceedences of the 35 μg/m3 standard must be

treated as data variability unless a violation of the PM2.5 NAAQS occurs. Additionally, 

this attainment plan is designed to address the 1997 PM2.5 NAAQS, which sets the 

standards at 15.0 μg/m3 on an annual average and 65 μg/m3 on a 24-hour average. 

Since the NAAQS standard is based on three years of data, only a partial evaluation 

can be made of the Marina Towers monitoring data. As previously noted, for January 

through December 2007, the Marina Towers monitor measured an annual average of 

13.5 μg/m3 and a 24-hour average of 31.3 μg/m3. DEQ will continue to examine the 

data gathered from this monitoring site.

The purpose of this attainment plan is to address the 1997 standards as finalized. 

These standards are 15.0 μg/m3 on an annual average and 65 μg/m3 on a 24-hour 

average. Certainly it is important to be mindful of the 2006 standard revision to 35 

μg/m3 on a 24-hour basis as well as other information such as scientific 

recommendations. However, this document, which shows that air quality has improved 

and currently meets the 1997 standards at all FRM monitors and that air quality is 

predicted to meet the 2006 standards at all FRM monitors by 2009, is fully approvable 
24

as written.

See the response to comment 21 for a discussion of “hot spots.” As noted in the 

response to comment 10, the current EPA guidance for regional modeling to support 

attainment plans requires LAAs for areas within a region that show elevated monitored 

PM2.5 concentrations at monitors within the federal reference monitoring network when 

compared to data from other federal reference monitors in the region. EPA does not, 

within the context of SIP attainment planning, have a definition for the term “hot spot.” 

The monitoring network shows similar results for various monitoring sites.

To ensure that PRGS is not causing a NAAQS violation, the attainment demonstration 

requires that an ambient air quality analysis of PRGS emissions be provided once such 

methodology is finalized. Alexandria’s modeling exercise of PRGS emissions does not 

use a methodology that has been peer reviewed and finalized by EPA. The 

methodology may doublecount PRGS emissions since it adds background 

concentrations from nearby PM2.5 FRMs even though PRGS, as an existing facility, 

contributes to these concentrations. The methodology adopted by Alexandria has been 

used by other states, but only for new and modified sources, not existing sources. 

Therefore, Alexandria’s methodology and results are inappropriate for inclusion in this 

attainment demonstration.

23. SUBJECT: Non-road emissions.

COMMENTER: Metropolitan Washington Airports Authority

TEXT: The commenter requests confirmation that the attainment plan intends 

to account for airport construction equipment emissions. Additionally, the commenter 

requests that construction emission budgets for airports can be derived from the plan 

as percentages of county construction equipment emissions, based on employment at 

the airports relative to county employment.

RESPONSE: County level construction emissions are intended to account for 

construction emissions at the airports as well as other facilities within each county. 

DEQ agrees that past methodologies have used a percentage of employment by the 

airport, as compared to county employment data, to demonstrate the inclusion of these 

emissions in the implementation plan. However, it is not appropriate to include this 

methodology in the attainment demonstration narrative. Future guidance from EPA 

may provide other acceptable ways in which to apportion these emissions so that 

inclusion in the attainment plan of any particular way may require a future SIP revision, 

a time and resource intensive process.

24. SUBJECT: Corrections and clarifications.

COMMENTER: U.S. EPA, Region III

TEXT: The plan must address both the annual and 24-hour 1997 NAAQS 
25

standards; that much of the guidance for this plan is also relevant to both the annual 

and 24-hour standard; that the appropriate level of precision for the annual standard is 

15.0 μg/m3. Clarifying language in regard to the status of the nonattainment area 

emissions caps within the Virginia CAIR rule should be added; and that a typographical 

mistake was located in Section 9.3.1.

RESPONSE: These comments are acceptable, and the proposal has been 

revised accordingly.

TEMPLATES\SIP-PLAN\PLN03

SIP\NONATTN PLANS\2008\NVApm-SIP-3.DOC