Document ID: EPA-R07-OAR-2020-0024-0016
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2020-02-04T05:00Z

Ms. Darcy Bybee
Director, Air Quality Control Program
Air Pollution Control Program
P.O. Box 176
Jefferson City, MO 65102-0176

Ms. Bybee,

The U.S. Environmental Protection Agency appreciates the opportunity to participate in the State's rulemaking process. The EPA is providing comments pursuant to the 60-day public notice of the following rules of which the Missouri Department of Natural Resources has indicated its intent to revise and submit to EPA for inclusion in the State Implementation Plan:

 10 CSR 10-2.205: Control of Emissions from Aerospace Manufacture and Rework Facilities
 10 CSR 10-2.230: Control of Emissions from Industrial Surface Coating Operations
 10 CSR 10-5.220: Control of Petroleum Liquid Storage, Loading and Transfer
 10 CSR 10-5.295: Control of Emissions from Aerospace Manufacture and Rework Facilities
 10 CSR 10-5.330: Control of Emissions from Industrial Surface Coating Operations
 10 CSR 10-6.045: Open Burning Requirements
 10 CSR 10-6.060: Construction Permits Required
 10 CSR 10-6.062: Construction Permits by Rule
 10 CSR 10-6.065: Operating Permits
 10 CSR 10-6.170: Restriction of Particulate Matter to the Ambient Air Beyond the Premises of Origin
 10 CSR 10-6.220: Restriction of Emission of Visible Air Pollutants
 10 CSR 10-6.261: Control of Sulfur Dioxide Emissions 
 10 CSR 10-6.330: Restriction of Emissions from Batch-Type Charcoal Kilns
 10 CSR 10-6.372: Cross-State Air Pollution Rule Annual NOx Trading Allowance Allocations 
 10 CSR 10-6.374: Cross-State Air Pollution Rule Ozone Season NOx Trading Allowance Allocations 
 10 CSR 10-6.376: Cross-State Air Pollution Rule Annual SO2 Trading Allowance Allocations 
 10 CSR 10-6.390: Control of NOx Emissions from Large Stationary Internal Combustion Engines

The EPA has reviewed the available information in the Draft Text document, the Regulatory Impact Report and the Rulemaking Report for each of the rule revisions. As discussed between the EPA and the Missouri Department of Natural Resources staff, EPA is providing these detailed comments to help improve clarity and to simplify the proposed rule changes where possible, in line with Missouri's efforts to streamline rules. 

The EPA is very encouraged by the improvement in air quality in Missouri and is committed to working with the State to help streamline rules and to ensure that when the rule revisions are submitted to the EPA as SIP revision submissions, the submissions contain the information required to meet the Clean Air Act requirements of Section 110(l) and are protective of the National Ambient Air Quality Standards.

                                    Sincerely,
							
                                    Michael Jay
                                    Branch Chief
                                    Air Planning and Development Branch

Enclosure

This enclosure includes comments on Missouri Department of Natural Resources' proposed rule revisions as provided on State's Regulatory Action Tracking System webpage and posted for 60-day public comment from 4/06/18 to 6/05/18.  The EPA's comments are based upon the available information for each rule including, the Draft Text document, Regulatory Impact Report and Rulemaking Report. These detailed comments are provided to help improve clarity and to simplify the proposed rule changes where possible, in line with MoDNR's efforts to streamline rules.
Rule Specific Comments:
10 CSR 10-2.205 Control of Emissions from Aerospace Manufacture and Rework Facilities and 10 CSR 10 CSR 10-5.295 Control of Emissions from Aerospace Manufacture and Rework Facilities
 There are two references in this rule to a different rule section, 10 CSR 10-6.030(22), however section (22) does not currently exist in 10 CSR 10-6.030 Sampling Methods. The EPA is aware that the MoDNR is proposing to add this section to 10 CSR 10-6.030 in a public comment period from May 15, 2018 to August 02, 2018. As such, EPA would not act on this submission until 10 CSR 10-6.030 was also submitted to EPA. 
 The EPA encourages the MoDNR to assess the need for adding a reference to 10 CSR 10-6.030(22) in subsection (5)(A) or (5)(C) of this rule because these sections already specify which test method to use (Method 24 and Methods 18, 25, and/or 25A respectively) and where the methods can be found (40 CFR Part 60, Appendix A). The draft rule text language for the potential revisions to 10 CSR 10-6.030, adding section (22) incorporates 40 CFR Part 60 by reference.  It may be unnecessary to divert the public to another state regulation which incorporates a federal regulation by reference and provides no additional clarity than what is already specified in the subsection (5)(A) and (5)(C) of this rule.
 In section (5) of the rule, the coatings referenced in the rule that are described as "waterborne" and "not waterborne" coatings have different requirements to determine the volatile organic compound content of the coating. "Waterborne" is followed by a parenthetical term "water-reducible." However, neither "waterborne," "not waterborne," nor "water-reducible" are included in the definitions section, 10 CSR 10-5.295(2), or in the state's 10 CSR 10-6.020 Definitions and Common Reference Tables.  The EPA recommends that the term "waterborne" be added to either 10 CSR 10-5.295(2) or 10 CSR 10-6.020. If the MoDNR does add the definition of "waterborne," we recommend that the MoDNR use the definition as codified in the CFR such as the definition of "waterborne" found in the National Emissions Standards for Aerospace Manufacturing and Rework Facilities, 40 CFR 63 Subpart GG.   Additionally, if the term "waterborne" is defined by the MoDNR in accordance with 40 CFR 63 Subpart GG, then the EPA recommends the removal of the parenthetical "water-reducible" as "water-reducible" is an incomplete description of "waterborne."
10 CSR 10-2.230 Control of Emissions from Industrial Surface Coating Operations
 The draft rule adds several new definitions. However, some of the new definitions (e.g., light-duty truck, side seam coating (three (3)-piece), topcoat) are different than what are currently in the rule, 10 CSR 10-6.020 Definitions and Common Reference Tables. For clarity, the EPA recommends that these definitions match. If definitions are purposefully different, then EPA recommends that the MoDNR explain which definition supersedes. 
 Where the MoDNR is introducing definitions not previously used (e.g., can coating), the EPA recommends that the MoDNR use already codified definitions found in the Code of Federal Regulations (CFR) or in the State Implementation Plan where available. 
 Eight terms, including (can coating, end exterior coating, exterior coating (two (2)-piece), extreme performance coating, fabric coating, interior body spray (two (2)- and three (3)-piece), side seam coating (three (3)-piece), and vinyl coating are defined in the draft rule text, however, only part of the term is used again in the rule text, primarily in tables with the words "coating" or "adhesive" used in the heading. The EPA recommends that the MoDNR refer to the complete term throughout the rule.
 The Rulemaking Report indicates that the MoDNR is making the rule consistent with a similar rule applicable to the St. Louis area, 10 CSR 10-5.330. In particular, the MoDNR is adding exemptions to 10 CSR 10-2.230 at subsection (1)(C).  The MoDNR will need to submit a demonstration showing how the added exemptions to the SIP submission meets the requirements of Clean Air Act section 110(l) and 193 of the also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA.
10 CSR 10-5.220 Control of Petroleum Liquid Storage, Loading and Transfer
 The draft rule text proposes to change the applicability of this rule in paragraph (3)(C)1. from tanks that are between 500 gallons up to 1,000 gallons to tanks that are 550 gallons up to 1,000 gallons. Because of the change in applicability, the MoDNR will need to ensure that MoDNR's State Implementation Plan submission meets the requirements of sections 110(l) and 193 of the Clean Air Act, also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA. 
 The draft rule text at part (3)(C)1.C.(III), proposes to add the ability for an equivalent pressure/vacuum valve to be used as approved by the staff director. The EPA recommends that the MoDNR add information to the rule explaining how the staff director will determine equivalency of the pressure/vacuum valve. For example, language could be added indicating that the staff director will determine that a pressure/vacuum valve is equivalent if it has met the alternative test method requirements in §63.7(f) as specified in 40 CFR Part 63.11120(a)(1)(ii).
 The draft rule text at subsection (3)(E) proposes to remove the state's Stage II vapor recovery requirements from Gasoline Dispensing Facilities. Since the EPA's 2012 determination that onboard refueling vapor recovery systems are in ``widespread use'' in the nation's motor vehicle fleet, states, such as Missouri, that were required to implement Stage II vapor recovery programs under CAA section 182(b)(3), can now remove the requirement from the SIP if doing so is consistent with the general SIP revision requirements of CAA section 110(l) and section 193.[,] The MoDNR will need to ensure that MoDNR's SIP submission meets the requirements of Section 110(l) and 193 of the Clean Air Act, also known as the "anti-backsliding" provisions.

10 CSR 10-5.330 Control of Emissions from Industrial Surface Coating Operations
 The draft rule text includes the insertion of several definitions. However, some of the new definitions (e.g., actual emissions, aerospace vehicle or component, antifoulant coating, as-applied, automobile, class I hardboard, class II finish, cleaning operations, electrodeposition, facility, flush cleaning, heavy-duty vehicle, high-performance architectural coating, light-duty truck, sealer, sheet basecoat, vacuum-metalizing coating, volatile organic compound) are different than what are provided in the state's 10 CSR 10-6.020 Definitions and Common Reference Tables. For clarity, the EPA recommends that these definitions match. If definitions are purposefully different, then EPA recommends that the MoDNR explain which definition supersedes. As such, the EPA recommends that MoDNR carry over definitions found elsewhere in the SIP into the proposed revisions to 10 CSR 10-5.330 Control of Emissions from Industrial Surface Coating Operations where applicable. 

 Where the MoDNR is introducing definitions not previously used, the EPA recommends that the MoDNR use already codified definitions found in the Code of Federal Regulations or in the SIP where available. For example, MoDNR is proposing to define "thinner" at paragraph (2)(T)3., but has not previously defined this term in its 10 CSR 10-5.330 Control of Emissions from Industrial Surface Coating Operations regulation or its 10 CSR 10-6.020 Definitions and Common Reference Tables regulation. The EPA recommends that MoDNR use the definition for "thinner" provided at 40 CFR Part 63 Subpart MMMM -- National Emission Standards for Hazardous Air Pollutants for Surface Coating of Miscellaneous Metal Parts and Products. 
      Other examples of definitions not previously used in this rule include but are not limited to, add-on control device, airless and air-assisted airless spray, as-received, bed liner, can coating, can end, capture system, cavity wax, cleaning material, cleanup solvent, coating line, purge, coating solids deposited, deadener, dip coating, enamel, end sealing compound, facility maintenance operations, final repair, flash-off area, flat wood paneling coating, floor covering installation adhesive, indoor, floor covering installation adhesive, outdoor, flow coating, gasket/gasket-sealing material, glass-bonding primer, hardwood plywood, ink jet technology, lubricating wax/compound, magnetic data storage disk coating, motor vehicle coatings, motor vehicle refinishing, over varnish, powder coating, pressure sensitive tape and label coating line, roller coating, sealant, surface preparation solvent, thinner, thin particleboard, trunk interior coating, two-component coating, two-piece can exterior coating, two-piece can exterior end coating, underbody coating, undersea-based weapons systems component, weather strip adhesive, web coating line. 
 The terms "Electrostatic spray application," "Flexible coating," "Flush cleaning," "Glass-bonding primer," "Perimeter bonded sheet flooring installation," "Silicone release coating," "Surface preparation solvent," and "Undersea-based weapons systems component" are defined in the draft rule text at section (2), however, they are not mentioned again in the rule. The EPA recommends the that MoDNR reassess the need for adding these definitions as they are not used in the rule.

 Thirty-two terms, including "Cove base installation adhesive," "Electric dissipating coating," "Extreme high-gloss coating," and "Floor covering installation adhesive, indoor" are defined in the draft rule text, however, only part of the term is used again in the rule text, primarily in tables with the words "coating" or "adhesive" used in the heading. The EPA recommends that the MoDNR refer to the complete term throughout the rule.

 The draft rule text provides definitions in the same format throughout the document except for the definition for the term "polyvinyl chloride plastic" or "PVC plastic." The EPA recommends that the MoDNR use a consistent format for definitions throughout the rule.
10 CSR 10-6.045 Open Burning 
 The draft rule text includes the insertion of several definitions. However, some of the new definitions (e.g., household waste, open burning, trade waste, untreated wood) are different than what are provided in the state's 10 CSR 10-6.020 Definitions and Common Reference Tables. For clarity, the EPA recommends that these definitions match.  If definitions are purposefully different, then EPA recommends that the MoDNR explain which definition supersedes.

 Where the MoDNR is introducing definitions not previously used in its rule (e.g. air curtain incinerator, vegetative waste, wood processing facility), the EPA recommends that the MoDNR use already published definitions found in the CFR or MoDNR's approved 111(d) state plans where applicable. 
      For example, MoDNR is proposing to define air curtain incinerator at 10 CSR 10-6.045(2)(A), but has not previously defined this term in its 10 CSR 10-6.045 Open Burning regulation or its 10 CSR 10-6.020 Definitions and Common Reference Tables regulation. The EPA recommends that the MoDNR use a previously promulgated definition such as the definition for air curtain incinerator provided at 40 CFR Part 60, Subpart CCCC- Standards of Performance for Commercial and Industrial Solid Waste Incineration Units (CISWI) (40 CFR § 60.2245), 40 CFR Part 60, Subpart DDDD- Emissions Guidelines and Compliance and Times for CISWI (40 CFR § 60.2810) or the state's 111(d) plan to implement the CISWI guidelines as approved at 40 CFR Part 62, Subpart AA, §62.6360. 
The definition of air curtain in subsection (2)(A) is different than the definition in subsection (3)(F). Since the definition at subsection (3)(F) more closely aligns with already promulgated definitions at 40 CFR Part 60.2245, 40 CFR Part 60.2810 and the state's approved CISWI 111(d) plan, EPA recommends that the MoDNR revise its proposed definition at subsection (2)(A) to match subsection (3)(F) and then cite to the new definition found in subsection (2)(A). 

 The draft rule text removes a reference to 40 CFR Part 60 Subpart CCCC which identifies that air curtain incinerators are CISWIs. EPA recommends that the MoDNR retain this reference, and the EPA encourages the MoDNR to add clarifying language that air curtain incinerators that meet the conditions of this rule are also required to meet the requirements of 40 CFR §§ 60.2242 (Title V permit obligations), 60.2250 (emission limitations obligations), 60.2255 (opacity monitoring obligations), and 60.2260 (record keeping and reporting obligations).

 The current draft rule text may inadvertently separate the emission limitation and the requirement that they be determined by the average of three 1-hour blocks consisting of ten 6-minute average opacity values. The emission limit is currently at paragraphs (3)(G)1. and (3)(G)2., and the determination by averaging three 1-hour blocks consisting of ten 6-minute average opacity values is not found until subsection (4)(D). The EPA recommends that the averaging requirement be added to section (3) of the draft rule text. 

 The draft rule text found at section (5) requires that an air curtain incinerator subject to the rule be "evaluated within sixty (60) days of the initial startup date and annually thereafter using Method 9 of Appendix A-4 to 40 CFR 60 as specified in 10 CSR 10-6.030(22)" however, section (22) does not exist in the state's 10 CSR 10-6.030 Sampling Methods. The EPA is aware that the MoDNR is proposing to add this section to 10 CSR 10-6.030 in a public comment period from May 15, 2018 to August 02, 2018. As such, EPA would not act on this submission until 10 CSR 10-6.030 was also submitted to EPA. 

 The EPA encourages the MoDNR to assess the need for adding a reference to 10 CSR 10-6.030(22) in subsection (5) of this rule because this subsection already specifies which test method to utilize (Method 9) and where it can be found (40 CFR Part 60, Appendix A-4). The draft rule text language for the potential revisions to 10 CSR 10-6.030, adding section (22), just incorporates 40 CFR Part 60 by reference. It may be unnecessary to divert the public to another state regulation, which then incorporates a federal regulation by reference and provides no additional clarity, when the requirement is already specified section (5) of this rule.

 The Regulatory Impact Report seems to indicate that the emission limitations in the rule would apply more broadly than what is specified by the rule. The RIR states, "facilities and operations that under the current rule are required to obtain an open burning permit may now open burn as long as they comply with the limits, conditions, and restrictions outlined in the rule." However, the draft rule text only provides emission limitations on those open burning operations that are required to use an air curtain incinerator. The EPA recommends that the MoDNR modify its draft rule text if its intent was to apply the emission limitations to open burners that are not using an air curtain incinerator or to modify its RIR text if its intent is to require emission limits only to those burners required to utilize an air curtain incinerator. 

 If the revisions to the rule would in fact change the requirement to comply with the emission limits from a broader applicability (i.e., all open burning operations required to obtain an open burning permit) to just those open burning operations that are using an air curtain incinerator, than the MoDNR will need to ensure that MoDNR's State Implementation Plan submission meets the requirements of Section 110(l) and 193 of the Clean Air Act, also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA.
10 CSR 10-6.060 Construction Permits Required
 The EPA recommends that the MoDNR move the information at subsection (1)(C) which establishes the need to obtain a permit to subsection (1)(A) to provide additional clarity to the public. 

 The EPA recommends that the MoDNR clarify the new criteria in paragraph (1)(A)3., for when a source is covered by the permitting rule, to provide clarity if these criteria are based on actual emissions, allowable emissions, or potential to emit.  It is also unclear if net emissions changes are allowed to be considered. 

 The EPA suggests the use of the term "begin actual" construction in lieu of "commence" construction to determine the deadline by which a permit must be obtained in paragraph (1)(C)1. As defined in the state's rule 10 CSR 10-6.020 Definitions and Common Reference Tables, "commence" means that a source has begun a continuous program of actual on-site construction or has entered into binding agreements or contractual obligations to undertake actual construction. Using this term could be confusing to companies, who often enter into contractual agreements to purchase equipment and services prior to submitting a permit application or receiving a permit.  

 The EPA suggests that the MoDNR add language to either subsection (1)(A) Covered Installations or subsection (1)(C) Prohibitions to make it clear that the major source nonattainment (e.g. NA-NSR), attainment (e.g. PSD) and HAP (e.g. 112(g)) permitting requirements found in sections (7), (8) and (9) apply independently of the "modification" test used to establish minor-NSR applicability. The EPA makes this suggestion because it is aware that the term "modification", found in the draft rule text at paragraph (1)(C)1., has been interpreted as a "gatekeeper" to the rest of the construction permitting rule. In other words, if a project is not a "modification", then the source is not obligated to read any further and no permits are required, and the EPA would disagree with this interpretation of the term. 

 Additionally, the MoDNR's definition of "modification" in section (2) seems to imply that a modification only occurs when there is a change in pre-project to post-project potential emissions. While EPA has approved the potential to potential applicability test for many state minor NSR programs, this test does not extend to the EPA's major source programs. For example, the major source permitting programs found in sections (7) and (8), for nonattainment and attainment areas, respectively, require a comparison of pre-project actual to post-project projected emissions to determine whether these requirements apply. 

 In the draft rule text, at subparagraphs (1)(C)2. and 3., a permit must be obtained before a source can "begin(ing)" operation. The term "begin" could be interpreted as a one-time event (e.g. the first day the project begins operating) and may be more limiting than the department intends. If the department means to prohibit a source from operating without a construction permit (which often contains many on-going operational conditions), then it would be appropriate to remove the word "begin(ing)."

 The EPA recommends that the MoDNR reconsider removing the following language from its draft rule text at subsection (1)(D), "The waiver is not available to sources seeking federally enforceable permit restrictions to avoid review under sections (7)  -  (9) of this rule." "Synthetic minor" permits issued to limit a source or project out of major source status, often involve substantive air quality review and includes a significant number of emissions limitations, along with monitoring, recordkeeping and reporting. By the time such permits are issued, which can take several months, the source may have significant equity in the ground and may be resistant to any design changes compelled by the MoDNR's review, despite the company's "liability waiver" declaration in subparagraph (1)(D)1. C. For this reason, the EPA believes that the above quoted language that the MoDNR proposes to remove from subsection (1)(D) should be retained. 

 Definitions for the terms "permanent shutdown" and "pilot plant" are being adding in the draft rule text, however the terms are not mentioned again in the rule. The EPA recommends the that MoDNR remove these definitions if not needed in the rule. 

 The terms "pilot trial(s)" and "pilot process(es)" are used in the draft text, but are not defined in this rule or the state rule, 10 CSR 10-6.020 Definitions and Common Reference Tables. The EPA recommends the that MoDNR add the definition for "pilot trial(s)" and "pilot process(es)". Alternatively, the MoDNR could replace the terms "pilot trial(s)" and "pilot process(es)" in the draft rule text by adding a definition for "pilot plant" if it makes sense to do so.

 The EPA recommends that the cross reference in part (3)(B)2.D.(II) be changed to (3)(B)2.D.(I) instead of (3)(B)2.(I). and that the cross reference in part (3)(B)2.D.(III) be changed to (3)(B)2.D.(II) instead of (3)(B)2.(II) because the draft rule text references are incorrect.

 The EPA recommends that title of subsection (3)(D) be changed to "Application Review Process and Permit Issuance" instead of "Application Review Process," because the section also includes procedures for final issuance of permits. 

 The EPA recommends that the last sentence in the introductory paragraph (3)(D)2. -- "Nothing in this rule limits the power of the permitting authority in this regard. The following condition examples are solely for illustration:"  -  be replaced with "Such conditions may include:". Describing the conditions as "illustrative" does not give the public regulatory certainty that these conditions are in fact true conditions. 

 The EPA recommends that the MoDNR add the words "relocation of portable plants" to the last sentence of subparagraph (3)(D)5.B. so the reader does not have the added step of finding that information in paragraph (4)(D)1. to see what type of projects it is referring to. 

 The EPA recommends that the MoDNR retain the existing applicability language for portable equipment in 10 CSR 10-6.060(4)(A)1. because the new language appears to allow very large expansions at existing installations. Since the focus of the applicability appears to be based on the size of "construction or modification" (e.g. the project) and not the size of the installation, the 250 ton per year applicability criteria for particulate matter could far exceed the de minimis thresholds if the existing source is already major for PM; potentially triggering Prevention of Significant Deterioration review. Since the air quality analysis in section (4)(E) is discretionary, very large sources of PM could potentially qualify for a portable permit in conflict with the requirement that any new construction or modification not cause or contribute to an air quality exceedance. If MoDNR proceeds with the expanded 250 tpy PM applicability threshold for portable projects, the MoDNR will need to ensure that MoDNR's State Implementation Plan submission meets the requirements of Section 110(l) and 193 of the Clean Air Act, also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA.

 The EPA recommends that the MoDNR review references to paragraphs (3)(L)4. through 7. made in subsection (4)(E), paragraph (5)(E)1. and subsection (10)(D) (regarding the discretionary requirement to conduct an air quality analysis for portable equipment) because paragraphs (3)(L)4. through 7. do not currently exist in the proposed rule.  

 The EPA recommends that the MoDNR consider relabeling section (5) "De Minimis Permits" to "Minor-NSR Permits" or a similar title that more fully conveys the scope of the permitting requirements since the draft rule text also applies to all non-portable, non-temporary and non-major source permitting actions.

 The EPA recommends that the MoDNR consider adding language to section (5) to "Unless otherwise required to obtain a permit under Sections (4), (7), (8), (9) or (10) of this rule, any construction or modification at a covered installation, for which a pre-project analysis shows a net emissions increase, shall obtain a permit under this Section." Without the addition of clarifying language, the addition of new terms like "changes" and "emission increases" which are not defined, and the elimination of existing terms like "net" emissions increase and "modification" to the applicability criteria, may potentially introduce uncertainty to the public on which projects must be permitted. 

 The EPA recommends that the MoDNR consider whether general permits issued under the new draft text language at section (6) also qualify for exclusion under section (5) since "general" permits, when available, commonly replace the need for case-by-case new source review. 

 For increased clarity, the EPA recommends that the MoDNR consider revising the draft text language at subsection (5)(B) to read "The submittal and review of each permit application and issuance of each permit will follow the procedures of section (3) of this rule and, when applicable, subsection (12)(A) of this rule."

 The EPA recommends the MoDNR consider adding definitions at section (2) of the undefined terms "screening model action levels" and "risk assessment levels" at subsection (5)(D) and at paragraph (5)(F)6. Additionally, because these terms are related to pre-construction hazardous air pollutant modeling, which is not considered part of the EPA's criteria pollutant pre-construction permitting program, the EPA would ask that, when the SIP submission is made for the rule's revision, that MoDNR be clear that it is not requesting that paragraph (5)(F)6. be included in the SIP. If the MoDNR has a desire to seek the EPA's approval of the HAP modeling requirements, it may be possible for MoDNR to do so under CAA 112(l). The EPA would welcome additional coordination on this matter. 

 There is a reference at paragraph (5)(F)1. to 10 CSR 10-6.030(21) however, section (21) does not exist in the state's 10 CSR 10-6.030 Sampling Methods. The EPA understands, from review of the MoDNR's Regulatory Action Tracker website, that the MoDNR is in the process of revising 10 CSR 10-6.030 Sampling Methods and that those potential rule changes will be made available for public comment from May 15, 2018 to August 02, 2018. As such, EPA would not act on this submission until 10 CSR 10-6.030 was also submitted to EPA.

 The draft text of 10 CSR 10-6.030(21) incorporates 40 CFR Part 51 by reference. It would be unusual for a state to incorporate 40 CFR Part 51 in whole.  If the federal definitions of 40 CFR Part 51 are absent or differ from those found in 10 CSR 10-6.020 Definitions and Common Reference Tables or 10 CSR 10-6.060(2), for clarity, EPA recommends that the full text of the definitions (e.g. major stationary source, major modification, net emissions increase and significant), are included at sections (2), (7) or even 10 CSR 10-6.020 rather than incorporate 40 CFR Part 51 in whole, by reference.

  The EPA recommends that the MoDNR evaluate the reference to paragraph (5)(A)1. at subparagraph (5)(F)7.B. as it appears to be an incorrect reference. The correct reference could possibly be paragraph (5)(F)7.

 The EPA recommends that the proposed removal of the following text found in section (7), "this section applies to the construction of any new major stationary source or any project at an existing major stationary source in an area designated as nonattainment,"  be included in subsection (7)(B). Under the applicability procedures in subsection (7)(B), the language refers only to projects at an existing major stationary source. Since major source nonattainment review applies to both new and modified major stationary sources, this language should be included in subsection (7)(B).

 The EPA recommends that the MoDNR clarify the reference at paragraph (7)(C)1. to 40 CFR 51.165(a)(3) and (9) as incorporated by reference in 10 CSR 10-6.030(21). This section refers to section 173(a)(1)(A) of the Clean Air Act, but the purpose of such reference is not clear. Generally, the rules as found in 40 CFR 51.165 fully implement the requirements of the CAA and it is not necessary and may not be appropriate to also adopt the Clean Air Act directly.

 The EPA recommends that the MoDNR consider removing the word application from subsections (7)(F) and (8)(C) since more than just the application is subject to public review, including but not limited to the application, draft permit, and the technical support document.

 The EPA would like the MoDNR to be aware that section (8)(A) proposes to adopt EPA's PSD program rules, found in 40 CFR 52.21, by reference as of July 1, 2018, however, portions of 52.21, like the exclusion for ethanol plants from the 100 ton per year "named" source list, may not be approvable into the SIP pending resolution of ongoing litigation. 

 The EPA recommends that the MoDNR consider adopting the relevant provisions in 40 CFR Part 63, Subpart B Requirements for Control Technology Determinations for Major Sources in Accordance with Clean Air Act Sections, Sections 112(g) and 112(j) by reference at section (9) of 10 CSR 10-6.060 to shorten eight pages of draft rule text. If the MoDNR adopts by reference, EPA recommends that they also update the incorporation by reference dates and internal cross-references to other portions of its permitting rules. 
      In the alternative, if the MoDNR opts to keep the draft rule text for section (9) as is, the EPA recommends that the MoDNR do the following to remove the adoption by reference of sections of the CAA and unnecessary adoption by reference of 40 CFR Parts 51,52, 71 and 70: 
 Remove the direct adoption of any portion of the CAA in section (9), paragraph(9)(B)7., section (9)(C) and part (9)(D)3.D.(II)(c) and instead substitute the relevant regulatory provisions found in 40 CFR Part 63, Subpart B.  
 Revise the adoptions of 40 CFR Parts 51 and 52 in subparagraph (9)(B)2.A. to include just those portions relevant to "lowest achievable emission rate (LAER)".
 Remove the adoption by reference of 40 CFR Part 71 in paragraph (9)(E)2.
 Replace the adoption by reference of 40 CFR Part 70 in paragraph (9)(E)2. with a reference to MoDNR's operating permit rules in 10 CSR 10-6.065.
 Replace any references to the Office of the Federal Register bookstore and National Technical Information Service in sections (9), paragraph (9)(A)7., subparagraph (9)(B)2.A., paragraph (9)(B)7., section (9)(C) and part (9)(D)3.D.(II)(c), and (9)(E)2. with a link to the on-line e-CFR at https://www.ecfr.gov.

 The EPA recommends that the MoDNR add the following text "for permits issued pursuant to section (7), a description of the amount of offsets..." to the draft rule text at part (12)(A)2.B.(IV) since offsets and LAER pertain to permits issued under section (7). The EPA also recommends that the MoDNR add "for permits issued pursuant to section (8), the degree of increment consumption..." to part (12)(A)2.B.(V) since increment consumption pertain to permits issued under section (8). 

 The EPA recommends that the MoDNR consider adding notification for any Indian Governing Body that might have interest in projects permitted in the southwestern part of the state to part (12)(A)2.D.(II)  since there are three tribes that border Missouri that have "treatment as state" status.

 The EPA recommends that the MoDNR consider switching the requirement, in Appendix B to 10 CFR 10-6.060, that a source provide notification to the state if it wants to opt-out of unified review to a requirement that a source provide notification to the state if it wants to opt-in to unified review instead. 

 Because "general" permits are more akin to permits-by-rule, and contain administrative requirements that apply directly to the MoDNR, the EPA recommends moving section (6) to its own rule (i.e., promulgating 10 CSR 10-6.063, General Construction Permit for example) so that sources can quickly evaluate any benefit they might gain from the streamlined permitting requirements, or not.  
10 CSR 10-6.062 Construction Permits by Rule 
 The EPA recommends that the MoDNR retain the language that it has proposed to delete from subparagraph (3)(B)2.E. that specifies the operational temperature of the second chamber of the incinerator. It would be unclear to the public what temperature is to be monitored and alarmed if this language is removed from the rule. 
10 CSR 10-6.065 Operating Permits
 Items 2. and 3. of the Regulatory Impact Report state, "removing the requirement to have a Basic State Operating Permit relieves the need for sources to have this permit but they are still required to meet any obligations contained in air program rules" and "sources that would have needed a Basic State Operating Permit must still meet the provisions found in other air program rules," respectively. The EPA recommends that the MoDNR provide additional information for the public on which sources specifically would no longer need to obtain a basic operating permit, how the MoDNR will be made aware of the presence of new sources if not requiring a basic operating permit, which "other air program rules" the source would need to follow and how compliance with "other air program rules" will be enforced. 

 If the MoDNR finalizes the revisions to 10 CSR 10-6.065 as proposed to remove the basic operating permit program, the EPA recommends that the MoDNR create separate standalone rules (e.g., promulgating 10 CSR 10-6.066 Intermediate State Permits to Operate and 10 CSR 10-6.067 Title V Operating Permits) to increase clarity to the public on the different permitting programs in the state and the permitting expectations of those programs. 

 The EPA recommends that the MoDNR remove part (4)(B)1. A. (I) which refers to initial notifications/applications which occurred in 1997 as they may no longer applicable.
 The EPA recommends that the MoDNR consider the continued need for the requirement for 40 CFR Part 70 installations to file initial applications on a schedule set up in a permit registry established in 1997 as found in part (5)(B)1.A.(I). as that registry may no longer be applicable.
 The EPA recommends that the MoDNR remove the requirement found at part (5)(B)1. A. (II) that a source file a complete application no later than twelve (12) months following the Administrator's approval of the operating permit program, as this approval occurred in 1997. Additionally, the EPA recommends that the MoDNR remove the requirement found at part (5)(B)1. A. (VI) that discusses submittal of initial phase II Acid Rain permits by January 1, 1996 for SO2 and by January 1, 1998 for NOx, as both dates have passed.
 The EPA recommends that the MoDNR consider switching the requirement, in subsection (5)(D), that a source provide notification to the state if it wants to opt-out of unified review to a requirement that a source provide notification to the state if it wants to opt-in to unified review instead.
 The EPA recommends that part (5)(E) 5.B.(iv) of the draft rule text be removed and reference to public participation per section (6) should be included as section (6) also provides the requirements for public participation. 
10 CSR 10-6.170 Restriction of Particulate Matter to the Ambient Air Beyond the Premises of Origin 
 The draft rule text and Regulatory Impact Report do not specify how compliance with this rule would be demonstrated or verified other than the sentence in paragraph (3)(A)2., "The nature or origin of the particulate matter will be determined to a reasonable degree of certainty by a technique proven to be accurate and approved by the director." The draft rule text currently says that section (5) Test Methods do not apply. Without the addition of provisions to the rule to make it clear what a "reasonable degree" is and which "techniques" the director might approve and how the director might make that determination, the EPA would consider this an approvability issue when submitted as a State Implementation Plan revision.
     
 The EPA recommends that the MoDNR provide regulatory language on what record keeping and reporting requirements would exist for a facility to determine compliance with the rule.
     
 The draft rule adds several new definitions. However, some of the new definitions are different than what are currently in the rule, 10 CSR 10-6.020 Definitions and Common Reference Tables. For clarity, the EPA recommends that these definitions match. If definitions are purposefully different, then EPA recommends that the MoDNR explain which definition applies to this section. 
10 CSR 10-6.220 Restriction of Visible Air Contaminants
 The draft text at subsection (1)(A) exempts internal combustion engines from the opacity rule. However, such engines, if fired with diesel, can have visible emissions that exceed the numeric opacity limits in section (3) of the draft rule text. The EPA recommends that the MoDNR consider limiting this exemption to internal combustion engines firing natural gas or other clean gaseous fuels to ensure that MoDNR's State Implementation Plan submission meets the requirements of Section 110(l) and 193 of the Clean Air Act, also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA. 
      
 The EPA recommends that if the MoDNR intends to exempt turbines from the opacity requirements, it should do so under section (1)(L) or create an additional exemption for turbines that burn clean gaseous fuels. Turbines are not IC engines and would not qualify for an exemption under section (1)(A) of the rule as such. 

 The draft rule text refers to "CMS", however, "CMS" is not defined in this rule or in state's rule, 10 CSR 10-6.020 Definitions and Common Reference Tables.  There are different types of CMS, including: continuous emission monitoring systems; continuous opacity monitoring systems, and; continuous parametric monitoring systems for example. Additionally, a stationary source may be required in federal rules, such as 40 CFR Part 63, subpart LLL, to conduct one or more of these types of monitoring, or a source may have the option of selecting which type of monitoring is appropriate for its processes and air pollution control system. As such the EPA recommends that the MoDNR provide a definition of CMS even if it is to specify that CMS may be applied broadly in the rule. 
      
 In the draft rule text at paragraph (3)(D)2., the requirement for portland cement calcining kiln operations to install a CMS is eliminated. The Regulatory Impact Report indicates that the revision was made because "Cement kilns are subject to strict particulate matter (PM) limits in 40 CFR Part 60, subparts LLL and EEE which prevent them from reaching an in-stack opacity close to the opacity limits of 6.220. They are also required to monitor PM emissions using PM continuous opacity monitoring systems (CEMS) which are more sensitive than COMS." Based on this information, the EPA recommends that the MoDNR consider exempting Portland Cement kilns from the rule altogether in section (1) as it has for Industrial, Commercial, and Institutional Boilers and Process Heaters subject to 40 CFR Part 63, subparts DDDDD, JJJJJ and UUUUU, if all of the Portland Cement plants in Missouri are subject to 40 CFR Part 63, subparts LLL and EEE. If the MoDNR exempts Portland Cement kilns, the MoDNR the MoDNR will need to ensure that MoDNR's State Implementation Plan submission meets the requirements of Section 110(l) and 193.

      It should be noted that visible emission limits in section (3)(A) seem to still apply to portland cement kilns even though the monitoring requirement has been removed. In some cases, portland cement operations have had difficulty with detached plumes or secondary formation of PM away from the stack which are often not detectable by a COMS or CMS at the stack location, so its possible MoDNR may be retaining the numerical portland cement kiln opacity limits at section (3)(A) for these types of instances. If so, the department may want to further explain its rationale in the regulatory impact report so the state can still act on opacity emissions exceeding the numerical thresholds which are otherwise met at the stack and verified through the continuous monitoring required by 40 CFR Part 63, subparts LLL and EEE.
 The EPA recommends that the MoDNR revise the RIR language to reference the correct CFR citation as follows, "strict particulate matter (PM) limits in 40 CFR 60 63 Subparts LLL and EEE."

 The EPA recommends that the MoDNR revise the RIR language to reference the correct term as follows, "required to monitor PM emissions using PM continuous opacity emissions monitoring systems (CEMS) which are more sensitive than COMS."

 Where the MoDNR is introducing new definitions not previously used (e.g., digester gas, existing emission unit, landfill gas, liquefied petroleum gas, natural gas, new emission unit, qualified observer, refinery gas), the EPA recommends that the MoDNR use already codified definitions found in the Code of Federal Regulations or the SIP where possible. 
      For example, the MoDNR is proposing to add a new definition for the term "qualified observer" at subsection (2)(X). The definition in the proposed state rule does not match the EPA's definition at 40 CFR Part 60, Appendix A, Method 9 section 3. 
 There are three references to the regulatory citation 10 CSR 10-6.030(22), however section (22) does not exist in the state's 10 CSR 10-6.030 Sampling Methods. The EPA understands, from review of the MoDNR's Regulatory Action Tracker website, that the MoDNR is in the process of revising 10 CSR 10-6.030 Sampling Methods and that those potential rule changes will be made available for public comment from May 15, 2018 to August 02, 2018.  As such, EPA would not act on this submission until 10 CSR 10-6.030 was also submitted to EPA.

 The EPA encourages the MoDNR to assess the need for adding a reference to 10 CSR 10-6.030(22) in sections (2), (3), and (5) of this rule because those sections already specify which 40 CFR Part 60 requirements apply.  The draft rule text language for the potential revisions to 10 CSR 10-6.030, adding section (22), incorporates 40 CFR Part 60 by reference.  It may be unnecessary to divert the public to another state regulation, which then incorporates a federal regulation by reference, and provides no additional clarity, when the requirement is already specified in sections (2), (3), and (5) of this rule. 
10 CSR 10-6.261 Control of Sulfur Dioxide Emissions
 The draft rule text at section (1) states that the rule applies to any source that emits SO2 except for individual units fueled exclusively with natural gas and liquefied petroleum gas, individual indirect heating units with a rated capacity less than or equal to 350,000 Btus, and individual units' subject to a more restrictive SO2 emission limit or restrictive fuel sulfur content limit. The EPA recommends that the MoDNR consider adding an exemption for units fueled by landfill gas because they also emit SO2 but the MoDNR may not intend to regulate these types of sources under this rule. 
 Based on the information provided in the Regulatory Impact Report and the Rulemaking Report, the EPA is concerned with the draft rule text proposal to remove "Table I  -  Sources with SO2 emission limits necessary to address the 2010 1-hour SO2 National Ambient Air Quality Standard" from section (3)(A) and to remove the requirement for owners or operators of sources subject to the rule in Jackson and Jefferson Counties to accept delivery of only ultra-low sulfur distillate fuel oil with a maximum fuel sulfur content of 15 ppm for use in unit(s) fueled, in whole or in part, by diesel, No. 1 fuel oil and/or No. 2 fuel oil, no later than January 1, 2017 from section (3)(D).  These provisions are specifically listed in the "Control Strategy" on page 35 of the MoDNR's 2015 Nonattainment Area Plan for the Jackson County 2010 1-hr SO2 nonattainment area as necessary for attainment of the NAAQS.[,]  By removing the limits from the SO2 rule, and not describing why the specific limit is no longer necessary or providing a citation to another document where the emission limit is duplicated (and both permanent and enforceable), the removal of Table I from 10 CSR 10-6.261, and the ultra-low sulfur distillate fuel oil requirement, introduces uncertainty as to how this will ensure protection of the NAAQS.  For the EPA to approve the 2015 Jackson County 1-hr SO2 Nonattainment Area SIP or to redesignate the area to attainment, the MoDNR would need to provide additional explanation for why the limits originally identified in Table I, and the requirement to burn ultra-low sulfur fuel in applicable units, are no longer necessary.  
 Section 3 in the RIR discusses the "environmental and economic costs and benefits of the proposed rulemaking."  While the section does seem to address the economic costs to industry by stating there are none, there is no discussion on the environmental costs or benefits of the proposal. For example, how does removing the provision in subsection (3)(D) that sources in Jackson and Jefferson counties only use ultra-low sulfur distillate fuel oil to allow sources to use a wider range of fuels impact attainment and maintenance of the NAAQS?  Does removing this fuel restriction that part of the 2015 Jackson County 1-hr SO2 Nonattainment Area SIP control strategy impact the environment or negatively affect SIPs that MoDNR has submitted for the EPA's approval?  At a minimum MoDNR should explain how the change in the limit of liquid fuel sulfur content in Jackson County from 15 ppm to 35,249 ppm (pre-1968 units) or 8,812 ppm (post-1968 units) would not impact the Jackson County nonattainment area's ability to attain and or maintain the NAAQS.
10 CSR 10-6.330 Restriction of Emissions from Batch-Type Charcoal Kilns 
 The draft rule adds several new definitions, such as "facility". However, some of the new definitions are different than what are currently in the rule, 10 CSR 10-6.020 Definitions and Common Reference Tables. For clarity, the EPA recommends that these definitions match. If definitions are purposefully different, then EPA recommends that the MoDNR explain which definition supersedes. 
10 CSR 10-6.372 Cross-State Air Pollution Rule Annual NOx Trading Allowance Allocations 
 The EPA recommends that the MoDNR consider replacing the term "CSAPR Annual NOX" at paragraph (3)(A)2. with "CSAPR NOX Annual" to be better aligned with name if the federal trading program in the remainder of the draft rule text. 

 The EPA recommends that the MoDNR change "40 CFR 97.405" in section (3) to "40 CFR 97.404" because the applicability provisions of the program start at 40 CFR § 97.404. 

 The EPA recommends that the MoDNR remove (II) from the citation of "part (3)(B)2.D.(II)," in part (3)(B)2.D.(I), because part (3)(B)2.D.(II) does not actually provide the types of notifications required by the rule; subparagraph (3)(B)2.D. includes the notifications required by the rule. 

 The EPA recommends that the MoDNR consider replacing the term "TR NOX Annual" in subparagraph (3)(B)3.I., to "CSAPR NOX Annual" (in both occurrences) to be better aligned with the terms used in the Code of Federal Regulations that the MoDNR is adopting in its rule.

 The EPA recommends that the MoDNR consider removing the column "Ozone Season NOX Program" in Table II, which provides the default capacity factors for new sources, as that column is unnecessary for a NOx Annual rule. 
10 CSR 10-6.374 Cross-State Air Pollution Rule Ozone Season NOx Trading Allowance Allocations

 The EPA recommends that the MoDNR change "40 CFR 97.805" in section (3) to "40 CFR 97.804" because the applicability provisions of the program start at 40 CFR § 97.804.

 The Regulatory Impact Report and the Rulemaking Report describing the MoDNR's proposed action to incorporate the Cross State Air Pollution Rule Federal Implementation Plan into the State Implementation Plan by reference include some inconsistencies with the FIP methodology for allocating CSAPR NOX Ozone Season Group 2 allowances.  
      The Rule Making Report lists the sections that the MoDNR does and does not propose to incorporate by reference.  Three sections (40 CFR 97.811(a), 40 CFR 97.811(b)(1), 40 CFR 97.812(a)) should not be included in the list of exclusions in the RMR.  Including these sections in the list of exclusions in the RMR is inconsistent with the draft rule text of 10 CSR 10-6.374. Contrary to the RMR, the draft rule text appropriately incorporates these sections by reference and thus incorporate the FIP methodology for allocating CSAPR NOX Ozone Season Group 2 allowances. 
      The Regulatory Impact Report language does not explain the differences between allocation methodologies of in the draft rule text for ozone season program compliance versus annual program compliance. Specific RIR language of concern is:
      "These alternative methods included removing the requirement that retired
      units lose their allowances permanently after 5-7 years of non-operation, eliminating the
      new unit set-aside and redistributing these allowances to all units, and reallocating
      allowances to new units based on their highest emissions in the last five years. However,
      the stakeholders preferred the method being proposed by these state rules."
      The EPA recommends that the MoDNR provide a description in the supporting materials that distinguishes the difference between the proposed allocation methodologies so that the intent to incorporate the FIP allocation methodology by reference into 10 CSR 10-6.374 is clearly understood.
10 CSR 10-6.376 Cross-State Air Pollution Rule Annual SO2 Trading Allowance Allocations
 The EPA recommends that the MoDNR consider replacing the terms "Annual SO2 Group 1" and "CSAPR SO2 Annual Group 1" with "CSAPR SO2 Group 1" to be better aligned with the name of the federal trading program. 

 The EPA recommends that the MoDNR change the phrase "and instead are replaced by section (3) of this rule" in paragraph (1)(B)2.  to "nor are they replaced by any provisions in this rule". 

 The EPA recommends that the MoDNR change "40 CFR 97.605" in section (3) "40 CFR 97.604" because the applicability provisions of the program actually start at 40 CFR § 97.604.

 The EPA recommends that the MoDNR remove (II) from the citation of "part (3)(B)2.D.(II)", in part (3)(B)2.D.(I), because part (3)(B)2.D.(II) does not actually provide the types of notifications required by the rule; subparagraph (3)(B)2.D. includes the notifications required by the rule. 

 The EPA recommends that the MoDNR consider removing the column "Ozone Season NOX Program" in Table II, which provides the default capacity factors for new sources, as that column is unnecessary for the SO2 Group 1 rule.
10 CSR 10-6.390 Control of NOx Emissions from Large Stationary Internal Combustion Engines
 The EPA recommends that the MoDNR list the specific compliance verification records at paragraph (4)(B)1. instead of the general statement of "all records necessary to demonstrate compliance." 

 Paragraph (1)(B)2. introduces two new terms, "combustion ignited" and "spark ignited," to the rule that are not defined in the rule at section (2)(C) or in the rule, 10 CSR 10-6.020 Definitions and Common Reference Tables. However, these terms are defined in the CFR and have specific meaning in the New Source Performance Standards for Stationary Spark Ignition Internal Combustion Engines and the New Source Performance Standards for New Source Performance Standards for Stationary Compression Ignition Internal Combustion Engines.  Where the MoDNR is introducing definitions not previously used, the EPA recommends that the MoDNR use already codified definitions found in the Code of Federal Regulations.

 The MoDNR will need to submit a demonstration showing how the added exemption for Spark Ignition engines to the exemption provided at paragraph (1)(B)2., to the State Implementation Plan submission meets the requirements of Section 110(l) and 193 of the also known as the "anti-backsliding" provisions. These sections relate to the EPA's authority to approve a SIP revision that removes or modifies control measure(s) in the SIP only after the state has demonstrated that such a removal or modification will not interfere with attainment of the National Ambient Air Quality Standards, Rate of Progress, Reasonable Further Progress or any other applicable requirement of the CAA.

 Additionally, since stationary internal combustion engines can only be either a compression ignition engine (diesel-fueled engines or dual fuel engines) or a spark ignition engine (gasoline and gas fueled engines) it seems unnecessary to introduce the terms in the exemption at paragraph (1)(B)2., as both types of engine are offered the potential for the exemption. The EPA recommends that the MoDNR consider revising the text to say "any stationary IC engine that began operation after September 30, 1997..." especially since the terms CI and SI engine are not used again until subsection (5)(B) of the proposed rule text. The EPA also recommends that the MoDNR consider revising the text of subsection (5)(B) to read "One (1) of the following emissions measurement approaches must be used to provide a demonstration of compliance with the twenty-five (25)-ton exemption threshold for stationary IC engines under paragraph (1)(B)2. of this rule."

 The EPA recommends that the new term "unit" at subsection (2)(C) be broadened to include duel fuel engine so that it is inclusive of the engine's named in paragraph (3)(A)2. Additionally, the word "unit" is only used in the term "unit-by-unit" in subparagraph (3)(1)B.(I) and (3)(1)B.(II) but elsewhere in the proposed rule revisions the word "unit" appears to have been replaced by the word "engine".  The EPA suggests that the term "unit-by-unit" be defined instead of "unit" at subsection (2)(C).

 The EPA recommends that the MoDNR consider replacing the phrase "particular engine" at subsection (3)(B) with "particular unit" to provide better alignment with the terms defined at subsection (2)(C).  

 There are three references to the regulatory citation 10 CSR 10-6.030(22), however section (22) does not exist in the SIP approved 10 CSR 10-6.030 Sampling Methods.  The EPA understands, from review of the MoDNR's Regulatory Action Tracker website, that the MoDNR is in the process of revising 10 CSR 10-6.030 Sampling Methods and that those potential rule changes will be made available for public comment from May 15, 2018 to August 02, 2018.  As such, EPA would not act on this submission until 10 CSR 10-6.030 was also submitted to EPA.

 The EPA encourages the MoDNR to assess the need for adding a reference to 10 CSR 10-6.030(22) to sections (4) and (5) of this rule.  These sections already specify that the requirements are for a Continuous Emissions Monitoring Station installed to meet the requirements of 40 CFR 60, Appendix B and F.  The draft rule text language for the potential revisions to 10 CSR 10-6.030, adding section (22), just incorporates 40 CFR Part 60 by reference.  It may be unnecessary to divert the public to another state regulation, which then incorporates a federal regulation by reference, and provides no additional clarity, when the requirement is already specified in sections (4) and (5).
 The EPA recommends that the MoDNR consider replacing the term "subject engine" at paragraph (4)(B)1. with "subject unit" to be better aligned with the terms defined at subsection (2)(C)

 The EPA recommends that the MoDNR consider replacing the term "engine" at paragraph (4)(B)3. with "unit" to be better aligned with the terms defined at subsection (2)(C).