Stack Height Considerations

Stack Height Considerations. A. Definitions (1) “Emission limitation” and “emission standard.” A requirement established which limits the quantity, rate, or concentration of emissions of air pollutants on a continuous basis, including any requirements which limit the level of opacity, prescribe equipment, set fuel specifications, or prescribe operation or maintenance procedures for a source to assure continuous emission reduction. (2) “Stack.” Any point in a source designed to emit solids, liquids, or gases into the air, including a pipe or duct but not including flares. (3) “A stack in existence.” The owner or operator had either: (a) Begun, or caused to begin, a continuous program of physical on-site construction of the stack, or (b) Entered into binding agreements or contractual obligations, which 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. (4) “Dispersion technique.” Any technique which attempts 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 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 stack; or other selective handling of exhaust gas streams so as to increase the exhaust gas plume rise. The preceding sentence does not include: (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: (b) The merging of exhaust gas streams where: (1) The source owner or operator demonstrates that the facility was originally designed and constructed with such merged gas streams; (2) After July 8, 1985, 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 (3) 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 emission limitation or, in the event that no emission limitation was in existence prior to the merging, an increase in the quantity of pollutants actually emitted prior to the merging, the reviewing agency shall presume that merging was significantly motivated by an 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; (c) The use of smoke management in agricultural or silvicultural prescribed burning programs; or (d) Episodic restrictions on residential wood burning and open burning; or (e) Techniques under Rule 1.9.A.(4) which increase final exhaust gas plume rise where the resulting allowable emissions of sulfur dioxide from the facility do not exceed 5,000 tons per year. (5) “Good engineering practice (GEP) stack height.” The greater of: (a) 65 meters measured from the ground-level elevation at the base of the stack; (b) (1) For stacks in existence on January 12, 1979, and for which the owner or operator had obtained all applicable preconstruction permits or approvals required, Hg = 2.5 H, provided the owner or operator produces evidence that this equation was actually relied on in establishing an emission limitation; (2) For all other stacks, Hg = H + 1.5L, where Hg = good engineering practice 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 nearby structure(s), provided that the U. S. Environmental Protection Agency or the Commission may require the use of a field study or fluid model to verify GEP stack height for the source; or (3) The height demonstrated by a fluid model or a field study approved by the U. S. Environmental Protection Agency or the Commission, 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. (c) “Nearby.” As used in Rule 1.9.A.(5)(b)(2) is defined for a specific structure or terrain feature and means: (1) For purposes of applying the formulae provided in Rule 1.9.A.5(b) that distance up to five times the lesser of the height or the width dimension of a structure, but not greater than 0.8 km (1/2 mile), and (2) For conducting demonstrations under Rule 1.9.A(5)(c) that distance not greater than 0.8 km (112 mile), except that the portion of a terrain feature may be considered to be nearby which falls within a distance of up to 10 times the maximum height (Ht) of the feature, not to exceed 2 miles if such feature achieves a height (ht) 0.8 km from the stack that is at least 40 percent of the GEP stack height determined by the formulae provided in Paragraph 1.9.A(5)(2) of this part or 26 meters, 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. (d) “Excessive concentration.” For the purpose of determining good engineering practice stack height under Rule 1.9.A(5)(c) excessive concentration means: (1) For sources seeking credit for stack height exceeding that established under