Attn: Docket ID No. EPA-HQ-OAR-2006-0888

Page 3

WESTERN STATES AIR RESOURCES COUNCIL

July 7, 2006

Air and Radiation Docket and Information Center

U.S. Environmental Protection Agency

Mail Code 6102T

1200 Pennsylvania Ave., NW

Washington DC 20460

Attn: Docket ID No. EPA-HQ-OAR-2005-0175

Dear Sir or Madam:

The Western States Air Resources (WESTAR) Council, an association of 15 western state air quality managers, appreciates the opportunity to comment on the Proposed Rule titled Prevention of Significant Deterioration New Source Review: Refinement of Increment Modeling Procedures, published on June 6, 2007. WESTAR’s concerns about the ineffectiveness of the current approach ….are well known to EPA. In May 2005, WESTAR provided 14 “Recommendations for Improving the Prevention of Significant Deterioration (PSD) Program to EPA, several of which are cited in EPA’s proposal. We welcome EPA’s proposed rule as an important first step in reforming PSD.

WESTAR’s comments are organized to follow the outline of EPA’s proposal, with specific references to our May 2005 recommendations. While we recognize that the scope of this rulemaking is limited to the refinement of modeling procedures, our expectation is that EPA will address other important deficiencies in the current PSD program in subsequent rulemaking. WESTAR’s comments on this proposal assume EPA will follow up this rule with “a separate rulemaking to address additional concerns that WESTAR and others have raised”. Quoting from WESTAR’s letter to Jeffrey Holmstead transmitting our recommendations:

“The enclosed recommendations represent a unanimous agreement between all of the state and federal land management agency participants, an agreement achieved by carefully balancing the needs of the participating agencies over the past 18 months. Implementing these recommendations will improve the effectiveness and efficiency of the PSD program to protect air quality in attainment areas and in the nation’s parks and wilderness areas. We encourage EPA to consider these recommendations in total, thereby maintaining the balance represented in the recommendation package.”

In summary, while the primary focus of this proposal is on preconstruction review and new source permitting, prevention of significant deterioration will not be achieved by focusing on this element of the program alone. To be effective, the overall program must address all sources that contribute to significant deterioration through the implementation of an integrated air quality management program that includes, but is not limited to major new sources. WESTAR urges EPA to address these related elements of the PSD program promptly in future rulemaking.

General Comments

Generally ok. High on flexibility, falls short on requested clarification.

Comments on Section II: Background

Footnote 4 on page 31377 describes how significant impact levels (SIL) are currently being used to define the extent of the impact area where an increment analysis must be performed, but there is no commitment on EPA’s part to adopt the SILs, as specifically recommended by WESTAR in Recommendation 1: “WESTAR recommends that EPA promulgate the significant impact levels for Class I, II, and III areas that are contained in EPA’s 1996 proposed PSD rule.” EPA should commit to adopting the significant impact levels as originally proposed in 1996.

Comments on Section IV: Proposed Clarifications Regarding the Effect of the Draft New Source Review Workshop Manual

Comments on Section V: Proposed Refinements to Increment Modeling Procedures

Section A. This section describes the emission sources that are to be included in a PSD increment consumption analysis.

* from table: Workgroup members were ok with how EPA addressed the sources to be included in an increment analysis (all, with specific, listed exceptions).>

* <acknowledge that this section includes a discussion on variances, and the proposed rule includes new language on this, but WESTAR does not have a consensus and individual members are expected to provide comments>

* <note discussion about states that did not include mobile sources in increment analyses will not be required to go back and recalculate inventories, and suggest that they extend this philosophy to address our recommendation 11>

Section B. This section describes how emissions are estimated for use in cumulative increment analyses. The underpinnings of EPA’s proposal are summarized in subsection 1, wherein EPA compares the difference in rigor needed to estimate emissions for increment consumption analyses versus that needed for an analysis used to determine compliance with a NAAQS. WESTAR agrees with EPA’s summary. Our May 2005 recommendations were in large part based on the notion that the rigor of the analysis should be proportional to risk that an increment will be exceeded or that there could be an adverse AQRV impact. WESTAR supports EPA’s proposal to give reviewing authorities discretion in choosing the most appropriate emissions estimates, provided that the choice is justified based on standards of reliability, consistency, and representativeness of the data.

* <note that our comments sought a balance between flexibility and the need for consistency between jurisdictions. Our suggestion was to limit choice to a permissible list of options. In the absence of the menu, it is critical that EPA clearly define the standards of reliability, consistency, and representativeness.>

* <provide specific references to our recommendations regarding this balance>

* <Excerpt from recommendation 12 that monitoring data can play an important complementary role, and that the definition/standards of reliability, consistency and representativeness in the first bullet should apply to monitoring data as well>

* <EPA requested comment on WESTAR’s 2-step menu approach. Do we defend? Or do we suggest how the same underlying goal is achieved if EPA provides the standards noted in first bullet?>

* <Should we comment on each sub bullet, 1-5, or do we simply support the idea of state discretion guided by EPA standards?>

Section C. This section discusses how meteorological data are used in increment analyses. The proposal discusses the use of meteorological data used for modeling purposes, and in particular how that data may be considered to be used in an assessment of increment consumption. Most of the discussion relates to clarifying the EPA's consideration of using prognostic meteorological data in an increment assessment. However, very little discussion is provided for steady-state models, beyond a generic discussion of the factors already identified in Appendix W (theGuideline on Air Quality Models) to judge the appropriateness of a given set of meteorological data to a specific modeling application (e.g. spatial and temporal representativeness, terrain factors, surface characteristics, and land use characteristics).

Historically, the EPA has required that all increment assessments, which are based on a two-step model process (i.e. a baseline set of model results and a "current" year set of model results, subtracted from each other), use the same set of meteorological data to evaluate both modeling scenarios. The discussion in the preamble does not address the EPA's desire to continue this practice nor offer any accepted alternatives.WESTAR believes that, consistent with the discussion in the preamble for the emission inventory and the "representative" period for emissions, EPA should also discuss the viability of alternatives to the standard modeling practice of "paired-in-time and paired-in-space" modeling evaluations using the same set of meteorology.

WESTAR Alternative Meteorology Proposal

The PSD regulations define "baseline concentration" as "that ambient concentration level that exists in the baseline area at the time of the applicable minor source baseline date." (empashsis added) The determination of the baseline concentration (via modeling) then should be affected by both emissions (and associated information such as location and stack parameters) and meteorology representative of the baseline period.The proposed regulatory changes already discuss the emission inventory component needed to perform an analysis thatcontributes to a determination of baseline concentration. However, if current modeling practices arefollowed, the baseline concentration would be based on model results that areaffected by anemission inventory represtative ofthe baseline period, and meteorological data representative of someother time period (usually more contemporary). This is inconsistent with the definition of baseline concentration.

A common sense reading of this definition implies that an appropriate evaluation of the baseline concentration should consider both emissions and meteorology, whichare representative of the baseline period. WESTAR proposes that EPA include a discusssion (and implement rule changes if needed), that also allow for the consideration of meteorology from the baseline period to determine the baseline concentration. WESTAR recognizes that many baseline dates may be too aged to implement this approach. If the data is not available, the standard meteorological approach should still be employed. If, however, the baseline date is more recent, useable data for the baseline period should be allowed to be used in the baseline modeling, if it exists. This approach has two distinct advantages. First, it is consistent with the definition of baseline concentration. Second, in future modeling assesments, as new meteorological data becomes available in an area, it does not force the permitting authority to re-assess (during a periodic review)the baseline concentration utilizing the more recent meteorological data. In essence, the baseline concentration remains the baseline regardless of futuremeteorlogical developments.Of course, the standard modeling approach using the same meteorological data would continue to be availble to a permitting authority at its discretion or if no suitable baseline meteorology is available.

We urge EPA to work with the states and other interested parties to d

If you have any questions, please do not hesitate to contact Dan Johnson, WESTAR Executive Director, at 206-254-9145, .

Sincerely,

Brian Gustafson, President

Western States Air Resources Council

500 Union Street, Suite 640, Seattle, WA 98101 (206)254-9142