5 Colo. Code Regs. § 1001-5-A-VIII

Current through Register Vol. 48, No. 1, January 10, 2025

Section 5 CCR 1001-5-A-VIII - Technical Modeling and Monitoring Requirements

VIII.A. Air Quality Models

VIII.A.1. All estimates of ambient concentrations required under this Regulation Number 3 shall be based on the applicable air quality models, databases, and other requirements generally approved by U.S. EPA and specifically approved by the Division. If a non-U.S. EPA approved model, such as a wind tunnel study, is proposed, the nature and requirements of such a model should be outlined to the Division at a pre-application meeting. The application will be deemed incomplete until there has been an opportunity for a public hearing on the proposed model and written approval of the U.S. EPA has been received.

VIII.B. Monitoring

VIII.B.1. All monitoring must be performed in accordance with U.S. EPA accepted procedures as approved by the Division.

VIII.B.2. An owner or operator may submit a monitoring program for a proposed source or modification to the Division for review. Within sixty days after such submittal, the Division shall:

VIII.B.2.a. Approve the monitoring program; or

VIII.B.2.b. Specify the changes necessary for approval; otherwise, the monitoring program shall be deemed approved.

VIII.C. Stack Heights

This regulation sets limits for the maximum stack height credit to be used in ambient air quality modeling for the purpose of setting an emission limitation and calculating the air quality impact of a source. It does not limit the actual physical stack height for any source. The following shall not be considered in determining whether an emission limitation is met:

VIII.C.1. Stack height in excess of good engineering practice; or

VIII.C.2. Any other dispersion technique except that the provisions of this Section VIII.C. shall not apply to stack heights in existence or dispersion techniques implemented before December 31, 1970. Sources that were constructed, reconstructed, or for which major modifications were carried out after December 31, 1970, and that are emitting pollutants from such stacks, or using such dispersion techniques, shall be subject to the provisions of this section.

VIII.D. Definitions as used in Section VIII.C.

VIII.D.1. Stack in existence means that the owner or operator had:

VIII.D.1.a. Begun, or caused to begin, a continuous program of physical on site construction of the stack; or

VIII.D.1.b. Entered into binding agreements or contractual obligations that could not be cancelled or modified without substantial loss to the owner or operator, to undertake a program of construction of the stack to be completed in a reasonable time.

VIII.D.2. Dispersion Technique means any technique that attempts to affect the concentration of a pollutant in the ambient air by using that portion of a stack that 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 by increasing final exhaust gas plume rise by manipulating source process parameters, exhaust gas parameters, or combining exhaust gases from several existing stacks into one stack; or other selective handling of exhaust gas streams so as to increase the exhaust gas plume rise. The preceding sentence does not include:

VIII.D.2.a. 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 facility generating the gas stream;

VIII.D.2.b. The merging of exhaust gas streams where:

VIII.D.2.b.(i) The source owner or operator demonstrates that the facility was originally designed and constructed with such merged gas streams;

VIII.D.2.b.(ii) After July 8, 1983, such merging is part of a change in operation at the facility that includes the installation of pollution controls and is accompanied by a net reduction in the allowable emissions of a pollutant. This exclusion from the definition of dispersion techniques shall apply only to the emission limitation for the pollutant affected by such change in operation; or

VIII.D.2.b.(iii) Before July 8, 1985, such merging was part of a change in operation at the facility 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 emissions limitation or, in the event that no emission limitation was in existence prior to the merging, the reviewing agency shall presume that merging was significantly motivated by intent to gain emissions credit for greater dispersion. Absent a demonstration by the source owner or operator that merging was not significantly motivated by such intent, the reviewing agency shall deny credit for the effects of such merging in calculating the allowable emissions for the source;

VIII.D.2.c. Smoke management in agricultural or silvicultural prescribed burning programs;

VIII.D.2.d. Episodic restrictions on residential wood burning and open burning; or

VIII.D.2.e. Techniques that increase final exhaust gas plume rise where the resulting allowable emissions of sulfur dioxide from the facility do not exceed five thousand tons per year.

VIII.D.3. Good Engineering Practice Stack Height means the greater of:

VIII.D.3.a. 65 meters; or

VIII.D.3.b. For stacks in existence on January 12, 1979 and for which the owner or operator had obtained all applicable pre-construction permits or approvals required, Hg = 2.5H, provided the owner or operator produces evidence that this equation was actually relied on in establishing an emission limitation; and

VIII.D.3.c. For all other stacks, Hg = H + 1.5L where:

VIII.D.3.c.(i) Hg = good engineering practice stack height measured from the ground level elevation at the base of the stack;

VIII.D.3.c.(ii) H = height of nearby structure(s) measured from the ground level elevation at the base of the stack;

VIII.D.3.c.(iii) L = lesser dimension (height or projected width) of nearby structure(s) provided that the reviewing agency may require the use of a field study or fluid model to verify Good Engineering Practice stack height for the source; or

VIII.D.3.d. The height demonstrated by a fluid model or a field study approved by the reviewing agency, 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, structures, or terrain obstacles.

VIII.D.4. Nearby as applied to good engineering practice is:

VIII.D.4.a. For purposes of applying the formulae provided in Sections VIII.D.3.b. and VIII.D.3.c. in the definition of good engineering practice stack height means that distance up to five times the lesser of the height or the width dimension of a structure, but not greater than 0.8 kilometers (1/2 mile), and

VIII.D.4.b. For conducting demonstrations in Section VIII.D.3. in the definition of good engineering practice means not greater than 0.8 kilometers (1/2 mile), except that the portion of a terrain feature may be considered to be nearby that falls within a distance of up to ten times the maximum height of the feature, not to exceed two miles if such feature achieves a height 0.8 kilometers from the stack that is at least forty percent of the good engineering practice stack height determine by the formula or twenty-six meters, whichever is greater.

VIII.D.5. Excessive concentrations for the purpose of determining good engineering practice, stack height in a fluid model or field study, means:

VIII.D.5.a. For sources seeking credit for stack height exceeding that established by the formulae, a maximum ground level concentration due to emissions from a stack due in whole or part to downwash, wakes, and eddy effects produced by nearby structures or nearby terrain features that individually is at least forty percent in excess of the maximum concentration experienced in the absence of such downwash, wakes, or eddy effects and that contributes to a total concentration due to emissions from all sources that is greater than an ambient air quality standard.

For sources subject to the prevention of significant deterioration program, an excessive concentration alternatively means 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 that individually is at least forty percent in excess of the maximum concentration experienced in the absence of such downwash, wakes, or eddy effects and greater than a prevention of significant deterioration increment. The allowable emission rate to be used in making demonstrations shall be prescribed by the new source performance standard that is applicable to the source category unless the owner or operator demonstrates that this emission rate is infeasible. Where such demonstrations are approved by the Division, an alternative emission rate shall be established in consultation with the source owner or operator;

VIII.D.5.b. For sources seeking credit after October 1, 1983 for increases in existing stack heights up to the heights established by the formulae, either:

VIII.D.5.b.(i) A maximum ground level concentration due in whole or part to downwash, wakes or eddy effects as provided in Section VIII.D.5.a. except that the emission rate specified by any applicable state implementation plan (or, in the absence of such a limit, the actual emission rate) shall be used; or

VIII.D.5.b.(ii) The actual presence of a local nuisance caused by the existing stack, as determined by the Division; and

VIII.D.5.b.(iii) For sources seeking credit after January 12, 1979 for a stack height determined using the formula, where the Division requires the use of a field study or fluid model to verify good engineering practice stack height; for sources seeking stack height credit after November 9, 1984 based on the aerodynamic influence of cooling towers; and for sources seeking credit after December 31, 1970 based on the aerodynamic influence of structures not adequately represented by the formulae: a maximum ground level concentration due in whole or part to downwash, wakes or eddy effects that is at least forty percent in excess of the maximum concentration experienced in the absence of such downwash, wakes or eddy effects.

5 CCR 1001-5-A-VIII

37 CR 18, September 25, 2014, effective 10/15/2014

37 CR 24, December 25, 2014, effective 1/14/2015

39 CR 04, February 25, 2016, effective 3/16/2016

39 CR 21, November 10, 2016, effective 11/30/2016

41 CR 21, November 10, 2018, effective 11/30/2018

43 CR 02, January 25, 2020, effective 2/14/2020

44 CR 02, January 25, 2021, effective 2/14/2021

46 CR 02, January 25, 2022, effective 2/14/2023

46 CR 12, June 25, 2023, effective 7/15/2023

47 CR 06, March 25, 2024, effective 4/15/2024

47 CR 12, June 25, 2024, effective 7/15/2024