1-1 1.0 INTRODUCTION

On 6 July 2005, the U.S. Environmental Protection Agency (EPA) published final amendments to its 1999 Regional Haze Rule (RHR) in the Fe deral Register, including Appendix Y, the final guidance for Best Available Retr ofit Technology (BART) determ inations (70 FR 39104-39172). The rule applies to any BART-eligible source that ‘‘e mits any air pollutant which may reasonably be anticipated to cause or contribute to any impairment of visibility” in any mandatory Class I federal area (Figures 1-1 through 1-4). States retain the authority to exempt cer tain BART-eligible sources based on dispersion modeling demonstrati ng that the source cannot reasonabl y be anticipate d to cause or contribute to visibility impairment in a Class I area. States also have the authority to define the modeling procedures used to establish BART emissi ons limits on those sources for which controls are required. To assist the states, the EPA has o ffered guidelines for how BART modeling should be conducted (EPA, 2005). Although the Fe deral regulations implementing the BART requirement afford States latitude in establishing criteria for BART -exemptions and for determining levels of BART controls required on specific sources, the disper sion modeling analyses must either conform to established EPA guidance for regulatory modeling or demonstrate, through an acceptable modeling protocol, that alternative modeling methods are equally consistent wi th the overall aim of the RHR.

States have the responsibility for preparing m odeling protocols that de scribe both the modeling analyses for the ‘subject to BART’ test and the visi bility improvement analyses as part of the BART determination. In developing modeling protocols, states are expected to collaborate with all stakeholders including Tribes, EPA, Federal Land Managers (FLMs), Regiona l Planning Organizations (RPOs) and the various source operato rs. Ultimately, EPA has the auth ority to approve or disapprove a state’s State Implementation Plan (SIP). A fl awed BART modeling analys is, including deviations from an agreed upon protocol, would be c onsidered in the SIP approval process.

At least three CENRAP States (Iowa, Minneso ta, and Texas) have already developed BART modeling protocols:

> “CALPUFF Modeling Protoc ol in Support of Best Ava ilable Retrofit Technology

Determinations”, (Johnson, 2005). Prepared by the Iowa Department of Natural Resources, Air Quality Bu reau, Des Moines, IA

> “Best Available Retrofit Technology (BART ) Modeling Protocol to Determine Sources Subject to BART in the State of Minnesota”, (MPCA, 2005), prepar ed by the Minnesota Pollution Control Agency, St. Paul, MN.

> “Screening Analysis of Potentially BART-eligible Sources in Texas”, (ENVIRON, 2005), prepared for the Texas Commission on Air Quality, Austin, TX.

Protocols may be under development in other States as well. To promote consiste ncy between states in the development of BART modeli ng protocols and to harmonize the approaches between adjacent RPOs, CENRAP commissioned the deve lopment of the BART Modeling Guidelines set forth in this document. These guidelines are intended to assist CENRAP states and source operators in the development of state-wide and s ource-specific modeling protocols sp ecifically tailored to the needs and requirements of a given f acility and Class I area(s).

In addition to the Iowa, Minnesota, and Texas protocols, the states of Colorado (CDPHE, 2005) and North Dakota (NDDH, 2005), VISTAS (VIS TAS, 2005), the Midwest RPO (Baker, 2005;1-2 LADCo, 2005) have also develope d BART protocols. Since they all address a common subject, there is substantial overlap in the discussions of nume rous topics such as Federal requirements, EPA guidance, CALMET/CALPUFF mode l descriptions, and recommended modeling procedures. Differences among the protocols exis t, of course, due to local mete orology, topography, the location of Class I areas, the mix of BART-eligible sources, and established modeling proced ures within the state, local and FLM groups. For consistency in BART m odeling applications acro ss the central U.S., in preparing these CENRAP Guidelines we have utilized relevant elements of each of these protocols.

The VISTAS protocol deserves special mention. It was prepared by members of the VISTAS Technical Analysis Work Group led by Ms. Pat Brewer, VISTAS’s Technical Advisor Dr. Ivar Tombach and Mr. Joe Scire of Earth Tech, Inc. The VISTAS BART protocol represents the

culmination of several draft versi ons and considerable public discussi on and input. At least two public workshops were convened in the autumn of 2005 to solicit comments and sugges tions on draft versions and to receive input from EPA and FLM staff on e volving agency guidance. See full comments at: http://www.vistas-sesarm.or g/BART/BARTComments.asp . Thus, element of the VISTAS protocol, reflecting the work of a very large number of organizations, were inco rporated as appropriate into the CENRAP modeling recommendations.

The guidelines presented in this document therefore represent the integrated writing efforts of many groups, especially the modelers and regulatory decision-makers instrumental in developing the VISTAS, MRPO, Iowa, Minnesota, Colora do and North Dakota protocols.

1.1 Overview

EPA’s BART requirements (70 FR, 39104-39172) are mandatory for electric generation units (EGUs) > 750 MW capacity. States are not required to follow the EPA BART guidelines for all sources, but are encouraged to apply the guideline concepts to all sources . States have the authority to make any or all aspects of the EPA BART guide lines mandatory for all BART determinations.

Sources are BART-eligible if they meet three specific criteria in cluding (a) emissions of at least 250 tons per year of a visibil ity-impairing pollutant, (b) begin operation between 7 August 1962 and 7 August 1977, and (c) are listed as one of the 26 listed source catego ries in the guidance. BART controls are required for any BART-eligible source that can be reasonably expected to “cause” or “contribute” to impairment of visibility in any of the 156 federal parks and wilderness (Class I) areas protected under the regional haze rule. Air quality mode ling is an important tool available to the States in determining whether a source can be reasonably exp ected to contribute to visibility impairment in a

Class I area.

A “BART-eligible emission unit” is defined as any single emission unit that meets the BART

criteria described above. A “BAR T-eligible source” is defined as the total of all BART-eligible emission units at a single facilit y. If a source has seve ral emission units, only those that meet the BART-eligible criteria are included in th e definition “BART-eligible source”.

1.2. Objectives of These Guidelines

Overall compliance with RHR visibility improveme nt goals in the CENRAP region entails four phases of visibility modeling:1-3 > Single-source modeling to determine wh ich BART-eligible sources are ‘subject to
BART’;

> Single-source modeling to determine the degr ee of visibility impr ovement attributable to proposed BART controls for each source subject to BART;

> Cumulative modeling to determine the combin ed effect of proposed BART controls for sources subject to BART in each CENRAP state; and

> Regional-scale modeling to determine if the combined effect of proposed BART

controls for all CENRAP states ultimatel y satisfy the RHR visibility improvement goals.

The responsibility for the first th ree modeling analyses belong to th e individual states. CENRAP’s mandate is to assess the aggregate effects of contro ls on progress toward attaining the visibility goals

across the domain. Tables 1-1 a nd 1-2 identify the Class I areas in and adjacent to the CENRAP domain. Figures 1-2 through 1-4 indi cate the location of Class I areas by federal land manager. Figure 1-5 identifies where visibility monitoring is currently occu rring in the CENRAP region.

This document applies only to the first tw o phases involving single-source modeling (i.e., screening to determine which BART-eligible sources are subject to BART, a nd single-source modeling to determine the degree of improvement related to the proposed BART control). The third phase will be addressed by the states in thei r Regional Haze SIPs due in 2008 and will most likely use the same or similar full-science modeling tools (CAMx or CMAQ) being used by the various RPOs dealing with the fourth phase. Individual CENRAP states will mo st likely conduct most, if not all, visibility modeling to determine which BART-eligible sources are subject to BART. Operators of sources determined to be ‘subject to BART’ may wish to conduct their own single-source modeling to determine the degree of visibility improvement, as they consider a variety of BART control options. The division of BART modeling be tween state and source operators wi ll likely vary widely across the CENRAP states. Ultimately, it is the state’s res ponsibility to review and verify all single-source visibility modeling analyses. Note that all BART modeling for sources in the CENRAP states must follow a written and approved protocol either developed by the state for general application or by the source operator for a source- specific analysis. Thus, depending upon the state in which they operate, BART-eligible sources may or may not have to deve lop individual protocols. This issue must be worked out with the state and cognizant FLM.

Given the focus on the first tw o visibility assessment phases , these guidelines focus on common procedures for air quality modeling in support of BART determ inations, consistent with the EPA guidelines and harmonized with the methods em ployed by other RPOs. (Figure 1-6 depicts this process). The guidelines are intended to pr ovide a common understanding among the organizations performing or reviewing BART anal yses – CENRAP state and local ai r agencies, EPA, FLMs, source operators, and contractors. Each state retains res ponsibility for the processes and procedures it will follow in satisfying the requirements of the RHR. Nothing in the CENRAP process replaces States’ responsibility to determine BART controls. Ther efore, this document describes suitable BART modeling systems and their app lication to two situations:

> Air quality modeling to determine whether a BART-eligible source is “subject to BART” and therefore the BART analysis proc ess must be applied to its operations.1-4 > Air quality modeling of emissions from s ources that have been found to be subject to BART, to evaluate regional haze benefits of alternative control options and to document the benefits of the preferred option.

These guidelines incorporate EPA final guidance and results of extensive public comments on BART modeling procedures recently propos ed by several organizations.

1.3 Overview of Recommended BART Modeling Procedures

States must determine whether a source in th eir jurisdiction emits any air pollutant (SO 2 , NO

x , PM, VOC) that “may reasonably be anticipated to cause or contribute to any im pairment of visibility” in a Class I area. EPA identifies three options for the states to consider. First, a state might conclude that all BART-eligible sources are subject to BART. Alternatively, a state might demonstrate that all BART-eligible sources together do not cause or contribute to any vi sibility impairment. Finally, a state may seek to determine if the impact from each individual BART-eligible source on any day is greater than a threshold value. If so , then the source is subject to BART.

The CENRAP states intend to pursue the third op tion, utilizing dispersion modeling to calculate impacts from individual sources with respect to a prescribed visibility threshold in Class I areas. This section discusses how the CALPUFF modeling system can be used to: (a) evaluate whether a BARTeligible source is exempt from BART controls, or to (b) quantify the visibili ty benefits of control options for sources that are determined to be subject to BART.

1.3.1 Three BART Modeling Approaches

The visibility modeling methods de scribed in these guidelines are grouped into th ree categories:

> Screening Modeling : The screening analysis uses the CALP UFF modeling system in default mode with pre-prepared modeling domains and model-ready meteorological inputs. This simple methodol ogy, described in detail in Chapter 6, is intended to quickly distinguish between sources that have no significant impacts on Class I area visibility and those sources for which imp acts are demonstrable or for which sourcespecific analyses are warranted.

> Source-Specific Modeling : A source-specific CALPUFF analysis (the subject of Chapter 7) is intended to remove some of the conservatism of the screening approach and bring more realism to bear in the analysis of a specific BART-eligible source. Here, the state or source operator may elect to in troduce greater source specificity into the modeling through the use of variable backgr ound ammonia, ozone, and visibility levels; puff-splitting; finer horizontal grid meshes in the meteorological and air quality modeling, and so on.

> Alternative Modeling : Refined full-science modeling is available to states or source operators on a case-by-case basis. Described in Chapter 8, this entails the application of a state-of-the-science regional modeling system and readily available RPO visibility data bases for either single source or cumulative source impact assessments.

For most sources in the CENRAP region, the use of the screening or source-sp ecific approaches will satisfy the BART regulatory requirements. Separate ch apters of this protocol are devoted to each of1-5 these BART modeling approaches. Re gardless of the approach, exemp tion modeling is the initial task at hand, followed if necessary by visibility impact modeling.

1.3.2 Exemption Modeling

Exemption modeling is intended as a definitive test of whether a source is subject to BART. A state and/or source operator may use one or more of three modeling approaches just introduced in performing exemption modeling. For most sources, an initial scr eening assessment with CALPUFF

should be considered to assess whet her a BART-eligible source is subj ect to BART. As described in Chapter 6, a screening CALPUFF di spersion modeling analysis is performed to assess whether a particular source is exem pt from BART, obviously ‘subject to BA RT’, or should consider additional source-specific modeling analyses to explore further its exemp tion status. Assumptions for the screening assessment are purposefully conservative so that a source that contributes to visibility impairment is not inadvertently exempted. If a source is shown not to contribute to visibility impairment using the CALPUFF screening assessmen t, the state may choose to exempt the source from BART or to require additiona l source-specific modeling to confirm it is not subject to BART.

If a source is shown to contribut e to visibility impairment in the screening assessment, the source has the option to undertake source-specific CALPUFF modeling to evaluate further whether it is subject to BART (see Chapter 7). Source-specif ic exemption modeling analysis can be used for sources that do not pass the screening analysis above or for which a more detailed modeling investigation is warranted. These analyses woul d typically include exerci sing CALPUFF with finer grid resolution (e.g., 1-2 km), more realistic estimates of background pollutant concentrations, sitespecific estimates of background natural visibility conditions, and so on.

In some circumstances, a state or source oper ator may wish to apply full-science modeling

methods to overcome CALPUFF’s inherent limitations (see Chapter 8). For exam ple, sources close to Class I areas, sources located in proximity to ot her large industrial or ur ban source complexes, or sources located great distances from a Class I ar ea may be better treated by a comprehensive fullscience modeling system. If alternative modeling is pursued, the requirements of the modeling protocol are increased. An alternative modeling protocol mu st justify the need for more advanced modeling methods, identify the availability of pertinent data sets, address model selection and configuration issues, and describe the methods to be used in applying the model to estimate visibility impacts. Discussions with state, EPA and FLM representatives should be conduc ted prior to development of an alternative modeling protocol to en sure all of the relevant issues are addressed in the document.

1.3.3 Modeling the Effects of BART Controls on Visibility

For sources determined to be ‘subject to BART’, the next step involves es timating the visibility benefits of possible BART control measures. Th ese benefits are determined by re-running the dispersion model using the screening modeling procedures or more resolved source-specific inputs. A key difference from the exemption modeling is th at the source terms and/or emissions data are

modified to reflect the BART control measures being evaluated. The ba se case to which the effectiveness of BART controls is compared is the “current emissions” scenario for which the exemption modeling analysis was performed. The pos t processing steps and procedures are the same. Side-by-side comparison of the visibility impacts provi des a direct estimate of the effectiveness of each

control scenario relative to the base case.1-6 1.3.4 Modeling Protocols

Regardless of the BART modeli ng approach (e.g., screening, sour ce-specific, or alternative modeling), a formal modeling protocol is require d. A modeling protocol should be submitted for all modeling demonstrations re gardless of the distance from the BART-e ligible source to the Class I area. The protocol is typically written by the state or the source operator an d then reviewed with state, EPA, and the FLM. EPA’s role in the development of th e protocol is advisory only as the “States better understand the BART-eligible source configurations” a nd factors affecting their particular Class I areas (70 FR 39126).

A protocol consists of many elements but mainly serves as a means for planning and communicating how a BART mode ling study will be performed before it occurs. Examples of required elements in the modeling protocol:

> The meteorological and terrain data that will be used;

> The source-specific information (stack hei ght, temperature, exit ve locity, elevation, and emission rates, speciation and size fractioni zation of applicable pollutants); and

> Receptor data from appropriate Class I areas.

The protocol guides the technical details of a modeling study and pr ovides a formal framework for reviewing technical assumptions , operational details, commitment s and expectations of the participants. It also provides means for resoluti on of potential differences of technical and policy opinion in an open process within pres cribed time and budge t constraints.

Modeling protocols all too often fa ll short of providing sufficient de tail in the description of the modeling assumptions and procedures to be employed (Roth et al., 2005). To assist the states and source operators in development of a protocol specific to a particular facility, protocol templates are given in Chapters 6 and 7 containing key elements that should be include in screening and sourcespecific applications, respectively. Of course, each protocol will have some unique features depending on the nature of the sources(s) and the Class I area(s) of interest. Also, the requirements for technical detail escalate from a screening a pplication to sour ce-specific application and this should be reflected in the content of the protocol.

1.4 Organization of this Document

The remainder of this document describes available models and data bases and the recommended procedures for their a pplication. Chapter 2 reviews EP A’s guidance for regional haze BART analysis modeling, as outlined in the 6 July 2005 Federal Register notice. Readers already familiar with the BART Rule may wish to skip to Chapter 3 where the CALPUFF model, EPA’s preferred tool for BART analyses , is introduced and its characteri stics and limitations discussed. EPA’s guidance allows for the use of appropriate al ternative models and Chapter 4 gives an overview of pertinent state-of-science regiona l photochemical/aerosol models and cu rrently available data bases. However, these CENRAP guidelines focus prim arily on the applicati on the CALPUFF modeling system. Chapter 5 identifies ex isting data bases developed by CENR AP and others to support BART modeling. Then, Chapters 6, 7 and 8 presen t the three BART modeling approaches.1-7 Chapter 6 discusses the specific steps needed to determine whether a BART-eligible source is subject to BART using th e CALPUFF model in the screening mode using pre-compiled regional meteorological modeling data sets and CALPUFF run in a conservative mode. Procedures are also identified for evaluating the effects of BART controls on those sources that are identified as ‘subject to BART. For sources determined to be subject to BART based on screening analyses, additional sourcespecific CALPUFF modeling might be performed as descri bed in Chapter 7. In a limited number of cases, it may be appropriate to use a full-science modeling system to develop more accurate estimates of a sources’ BART eligibility and/or to assess the effects of BART controls. Chapter 8 discusses the applications of state-of-science alternative models for this purpose. For each modeling approach described in Chapters 6 through 8, information re garding protocol development is provided as a template. Finally, a quality assurance me thodology for CALMET/CALPUFF BART modeling is outlined in Chapter 9.

Figure 1-1. Federal Class I A reas in the United States.1-8 Figure 1-2. U.S. Forest Service Class I Areas.1-9 Figure 1-3. National Park Service Class I Areas.1-10 Figure 1-4. Fish and Wildli fe Service Class I Areas.1-11 Figure 1-5. Location of Vi sibility Monitoring Site s in the CENRAP Domain.1-12 Figure 1-6. CANRAP BART Modeling Flow Chart. Screening CALPUFF Application (2001-2003 at 6 km)

High ∆ dv

> 0.5

Source-Specific CALPUFF Application (2001-2003 at 1-6 km)

98% ∆ dv

> 0.5



## Source subject to BART controls Source not subject

to BART controls

Source not subject

to BART controls 

# CENRAP BART Modeling Flow Chart

NO

Y ES

NO Y ES

Y ES1-13 Table 1-1. Federally Mandated Class I Areas in the CENRAP States.

U. S. Forest Service Caney Creek Wilderness (AR) Upper Buffalo Wilderness (AR) Boundary Waters Canoe Area (MN) Hercules - Glades Wilderness (MO)

National Park Service Big Bend National Park (TX) Guadalupe Mountains National Park (TX) Voyageurs National Park (MN)

U.S. Fish and Wildlife Service Wichita Mountains Wilderness (OK) Mingo Wilderness (MO) Breton Wilderness (LA)

Table 1-2. Federally Mandated Class I Areas Near the CENRAP States.

U.S. Forest Service Eagles Nest Wilderness (CO) Rawah Wilderness (CO) Pecos Wilderness (NM) Wheeler Peak Wilderness (NM) White Mountain Wilderness (NM) Sipsey Wilderness (AL) Rainbow Lakes Wilderness (WI)

National Park Service Arches National Park (CO) Bandelier National Monument (NM) Carlsbad Caverns National Park (NM) Chiricahua National Monument (NM) Great Sand Dunes National Monument (CO) Rocky Mountain National Park (CO) Badlands National Park (SD) Isle Royale National Park (MI) Theodore Roosevelt National Park (ND) Wind Cave National Park (SD) Mammoth Cave National Park (KY)

U.S. Fish and Wildlife Service Bosque Del Apache Wilderness (NM) Salt Creek Wilderness (NM) Seney Wilderness (MI) St. Marks Wilderness (FL) Lostwood Wilderness (ND)