MEMORANDUM 
 
SUBJECT: 	Technical Support Document for Approval of a Missouri State Implementation Plan Revision relating to Restriction of Emissions Credit for Reduced Pollutant Concentrations from the Use of Dispersion Techniques
 
FROM: 		Steven Brown 
                  ARD/AQPB/CPPS 
 
TO: 			EPA-R07-OAR-2022-0285; MO-433 
 
THROUGH:  	Andy Hawkins, Branch Chief 
                  ARD/AQPB
                  
SUMMARY:  
The Environmental Protection Agency (EPA) is proposing to approve revisions to the Missouri State Implementation Plan (SIP) received from the Missouri Department of Natural Resources (MoDNR) as a SIP revision submission on January 30, 2020.
  
Specifically, the revisions are to the existing rule, Title 10, Division 10 of the Code of State Regulations, (10 CSR 10-6.140) "Restriction of Emissions Credit for Reduced Pollutant Concentrations from the Use of Dispersion Techniques", with a restructured version of the same rule. The rule was SIP approved in 40 CFR § 52.1320(c) on March 31, 1989 (54 FR 13184). The purpose of the state regulation is to limit the use of dispersion techniques rather than emission reductions to meet ambient air quality standards in the vicinity of major sources of air pollution. The use of certain dispersion techniques is prohibited by Section 123 of the Clean Air Act. 

These proposed revisions restructure the rule to the MoDNR standard rule organizational format, amend the applicability section by adding a new reference, add definitions
specific to this rule and remove unnecessary words. 

RULE REVISIONS: 
Below is EPA's description of the changes made to each rule section and the text of the revised rule. 
Revisions that are additions to MoDNR's existing approved SIP rule text are bold. Revisions that are deletions to the existing approved SIP rule text are stricken through. The rule text with changes is listed first and is followed by a summary of the EPA's review of the changes. In some sections there may be an EPA notation at the beginning of the section explaining rearrangement of language.
 
      10 CSR 10-6.140 Restriction of Emissions Credit for Reduced Pollutant
      Concentrations from the Use of Dispersion Techniques
 
(1) Applicability. 
 
(A) This rule shall apply applies to the procedures to account for emission dispersion techniques used in the calculation of any emission limitation or any revision of any limitation to be established by the director or to be considered for establishment by the Missouri Air Conservation Commission (MACC). This rule also requires that all emission limitations established by the director or by the MACC after December 31, 1970 be reviewed for compliance with this rule.

(B) 40 CFR 51, Appendix W, promulgated as of July 1, 2017 shall apply and is hereby incorporated by reference in this rule, as published by the Office of the Federal Register. Copies can be obtained from the
U.S. Publishing Office Bookstore, 710 N. Capitol Street NW, Washington DC 20401. This rule does not incorporate any subsequent amendments or additions.

(C) Exemptions. The provisions of section (3) of this rule do not apply to emission limitation credits from -- 

 Stack heights on which construction commenced on or before December 31, 1970, except where pollutants are being emitted from the stacks by source operations which were constructed, reconstructed, or on which major modifications were carried out after December 31, 1970; or

 Dispersion techniques implemented before December 31, 1970, except where these dispersion techniques are being applied to source operations which were constructed, reconstructed, or on which major modifications were carried out after December 31, 1970.

EPA Analysis:  The revisions to section (1) (A)(B)(C) are administrative in nature and do not affect the stringency of the SIP.  See below for explanation of changes.

Applicability (A): This revision is a minor word change from shall apply to applies. 

Applicability (B):  This revision adds a reference to the provisions of 40 CFR 51, Appendix W- Guideline on Air Quality Models.

Applicability (C)1-2:  The unchanged language was removed from the "Exemptions" section (3)(A)(B) in the SIP approved rule and placed in the "Applicability" section (C)1 (C)2 in the revised rule.


EPA Notation (addresses the following section): The "General" provisions text in section (2), are stricken through and removed from this section, but the unchanged language is moved down to section (3) in this revised rule. Due to this move, section (2) now becomes, the "Definitions" section.

(2) General

(A) The degree of emission limitation required of any installation for control of any air pollutant must not be affected by that portion of any installation's stack height that exceeds good engineering practice (GEP) or by any dispersion technique, except as provided in section (3) of this rule.

(B) Before the director or the MACC establishes an emission limitation that is based on a GEP stack height that exceeds the formula GEP height allowed by 10 CSR 10-6.020(2)(G)3.B., the director must notify the public of the availability of the demonstration study
and must provide opportunity for public hearing on it.

(C) This rule does not restrict the actual stack height of any installation or the use of any dispersion technique by any
installation.

(2) Definitions.

  Commence -- For the purposes of major stationary source construction or major modification, the owner or operator has all necessary preconstruction approvals or permits and -- 
 Began, or caused to begin, a continuous program of actual on- site construction of the source, to be completed within a reasonable time; or
 Entered into binding agreements or contractual obligations, which cannot be canceled or modified without substantial loss to the owner or operator, to undertake a program of actual construction of the source to be completed within a reasonable time.

   Dispersion technique -- 
 Any technique designed to affect the concentration of a pollutant in the ambient air by -- 
 Using that portion of a stack which exceeds good engineering practice stack height;
 Varying the rate of emission of a pollutant according to atmospheric conditions or ambient concentrations of that pollutant; or
C. Increasing final exhaust gas plume rise by manipulating source process parameters, exhaust gas parameters, stack parameters, or combining exhaust gases from several existing stacks into one (1) stack; or other selective handling of exhaust gas streams so as to increase the exhaust gas plume rise; and
       This definition does not include:
                 The reheating of a gas stream, following use of a pollution control system, for the purpose of returning the gas to the temperature at which it was originally discharged from the installation generating the gas stream;
                 The merging of exhaust gas streams where -- 
 The installation owner or operator demonstrates that the installation was originally designed and constructed with the merged gas streams;
 After July 8, 1985, the merging is part of a change in operation at the installation that includes the installation of emissions control equipment and is accompanied by a net reduction in the allowable emissions of a pollutant. This exclusion from the definition of dispersion technique shall apply only to the emission limitation for the pollutant affected by a change in operation; or
                   Before July 8, 1985, the merging was part of a
change in operation at the installation that included the
installation of emissions control equipment or was carried out for sound economic or engineering reasons. Where there was an increase in the emission limitation or in the event that no emission limitation was in existence prior to the merging, the director shall presume that merging was significantly motivated by an intent to gain emissions credit for greater dispersion. Without a demonstration by the source owner or operator that merging was not significantly motivated by that intent, the director shall deny credit for the effects of merging in calculating the allowable emissions for the source;

 Smoke management in agricultural or silvicultural prescribed burning programs;
 Episodic restrictions on residential woodburning and open burning; or
 Techniques under subparagraph (2)(B)1.C. of this rule which increase final exhaust gas plume rise where the resulting allowable emissions of sulfur dioxide from the installation do not exceed five thousand (5,000) tons per year.

 Emission limitation -- A regulatory requirement, permit condition, or consent agreement which limits the quantity, rate, or concentration of emissions on a continuous basis, including any requirement which limits the level of opacity, prescribes equipment, sets fuel specifications, or prescribes operation or maintenance procedures for an installation to assure continuous emission reduction.

       Excessive concentration -- 
 For installations seeking credit for reduced ambient pollutant concentrations from stack height exceeding that defined in paragraph (2)(E)2. of this rule, an excessive concentration is a maximum ground-level concentration due to emissions from a stack due in whole or part to downwash, wakes, or eddy effects produced by nearby structures or nearby terrain features which are at least forty percent (40%) in excess of the maximum concentration experienced in the absence of the downwash, wakes, or eddy effects, and that contributes to a total concentration due to emissions from all installations that is greater than an ambient air quality standard. For installations subject to the prevention of significant deterioration program as set forth in 10 CSR 10-6.060(8), an excessive concentration means a maximum ground-level concentration due to emissions from a stack due to the same conditions as mentioned previously and is greater than a prevention of significant deterioration increment. The allowable emission rate to be used in making demonstrations under this definition shall be prescribed by the new source performance regulation as referenced by 10 CSR 10-6.070 for the source category unless the owner or operator demonstrates that this emission rate is infeasible. Where demonstrations are approved by the director, an alternative emission rate shall be established in consultation with the source owner or operator;
 2. For installations seeking credit after October 11, 1983, for increases in stack heights up to the heights established under paragraph (2)(E)2. of this rule, an excessive concentration is either -- 
 A maximum ground-level concentration due in whole or part to downwash, wakes, or eddy effects as provided in paragraph (2)(D)1. of this rule, except that the emission rate used shall be the applicable emission limitation (or, in the absence of this limit, the actual emission rate); or
 The actual presence of a local nuisance caused by the stack, as determined by the director; and
 3. For installations seeking credit after January 12, 1979, for a stack height determined under paragraph (2)(E)2. of this rule where the director requires the use of a field study of fluid model to verify good engineering practice stack height, for installations seeking stack height credit after November 9, 1984, based on the aerodynamic influence of cooling towers, and for installations seeking stack height credit after December 31, 1970, based on the aerodynamic influence of structures not represented adequately by the equations in paragraph (2)(E)2. of this rule, a maximum ground level concentration due in whole or part to downwash, wakes, or eddy effects that is at least forty percent (40%) in excess of the maximum concentration experienced in the absence of downwash, wakes, or eddy effects.

 Good engineering practice (GEP) stack height -- The greater of -- 
 Sixty-five meters (65 m) measured from the ground-level elevation at the base of the stack;
 For stacks on which construction commenced on or before January 12, 1979, and for which the owner or operator had obtained all applicable permits or approvals required under 40 CFR 51 and 52,

                         Hg = 2.5H

 provided the owner or operator produces evidence that this equation was actually relied on in establishing an emission limitation; and for all other stacks,

                         Hg = H + 1.5L

             Where:
 Hg = GEP stack height, measured from the ground-level elevation at the base of the stack;
 H = height of nearby structure(s) measured from the ground-level elevation at the base of the stack; and
 
 L = lesser dimension, height, or projected width of the nearby structure(s). Provided that the director may require the use of a field study or fluid model to verify GEP stack height for the installation; or
 3. The height demonstrated by a fluid model or field study approved by the director, which ensures that the emissions from a stack do not result in excessive concentrations of any air pollutant as a result of atmospheric downwash, wakes, or eddy effects created by the source itself, nearby structures, or nearby terrain features.

 Major modification -- Any physical change or change in the method of operation at an installation or in the attendant air pollution control equipment that would result in a significant net emissions increase of any pollutant. A physical change or a change in the method of operation, unless previously limited by enforceable permit conditions, shall not include:
 Routine maintenance, repair, and replacement of parts;
  Use of an alternative fuel or raw material by reason of an order under sections 2(a) and (b) of the Energy Supply and Environmental Coordination Act of 1974, a prohibition under the Power Plant and Industrial Fuel Use Act of 1978, or by reason of a natural gas curtailment plan pursuant to the Federal Power Act;
  Use of an alternative fuel or raw material, if prior to January 6, 1975, the source was capable of accommodating the fuel or material, unless the change would be prohibited under any enforceable permit condition which was established after January 6, 1975;
  An increase in the hours of operation or in the production rate unless the change would be prohibited under any enforceable permit condition which was established after January 6, 1975; or
  Use of an alternative fuel by reason of an order or rule under section 125 of the Clean Air Act.

 Nearby -- Nearby, as used in the definition good engineering practice (GEP) stack height in paragraph (2)(E)2. of this rule, is defined for a specific structure or terrain feature -- 
  For purposes of applying the formula provided in paragraph (2)(E)2. of this rule, nearby means that distance up to five (5) times the lesser of the height or the width dimension of a structure, but not greater than one-half (1/2) mile; and
 For conducting fluid modeling or field study demonstrations under paragraph (2)(E)3. of this rule, nearby means not greater than one-half (1/2) mile, except that the portion of a terrain feature may be considered to be nearby which falls within a distance of up to ten (10) times the maximum height of the feature, not to exceed two (2) miles if feature achieves a height one-half (1/2) mile from the stack that is at least forty percent (40%) of the GEP stack height determined by the formula provided in paragraph (2)(E)2. of this rule, or twenty-six meters (26 m), whichever is greater, as measured from the ground-level elevation at the base of the stack. The height of the structure or terrain feature is measured from the ground-level elevation at the base of the stack.

 Stack -- Any spatial point in an installation designed to emit air contaminants into ambient air. An accidental opening such as a crack, fissure, or hole is a source of fugitive emissions, not a stack.

 Definitions of certain terms in this rule, other than those
specified in this rule section, may be found in 10 CSR 10-6.020.
 
EPA Analysis: The revisions to section (2) by adding definitions specific to this rule are administrative in nature. EPA reviewed these definitions and concluded they do not substantively change any existing statutory or regulatory requirement or impact the stringency of the SIP or air quality, nor do they impact the State's ability to attain or maintain the National Ambient Air Quality Standards.

EPA Notation (addresses the following section): The "Exemptions" provision text in section (3) are stricken through and removed from this section, but the unchanged language was moved to the "Applicability" section (1)(C) in this revised rule. Due to this move, section (3) now becomes, the "General Provisions" section.

(3) Exemptions. The provisions of section (2) of this rule shall not
apply to:
     (A) Emission limitation credits from stack heights on which construction commenced on or before December 31, 1970, except where pollutants are being emitted from such stacks by source operations which were constructed, or reconstructed, or on which major modifications were carried out after December 31, 1970; or

     (B) Emission limitation credits from dispersion techniques implemented before December 31, 1970, except where such dispersion techniques are being applied to source operations which were constructed or reconstructed, or on which major modifications were carried out after December 31, 1970.

       General Provisions.

  The degree of emission limitation required of any installation for control of any air pollutant must not be affected by that portion of any installation's stack height that exceeds good engineering practice (GEP) or by any other dispersion technique, except as provided in section (1).

 Before the director or the MACC establishes an emission limitation that is based on a GEP stack height that exceeds the formula GEP height allowed by this rule, the director must notify the public of the availability of the demonstration study and must provide opportunity for public hearing on it.

 This rule does not restrict the actual stack height of any installation or the use of any dispersion technique by any installation.

(4) Reporting and Recordkeeping. (Not applicable)

(5) Test Methods. (Not applicable)

EPA Analysis:  The revisions to section (3)(A)(B)(C) are administrative in nature and do not affect the stringency of the SIP. 

General Provisions (3)(A)(B)(C):  The unchanged language was moved from section (2) "General" to section (3) in the SIP approved rule.  Section (3) now becomes the "General Provisions" section.
