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South Carolina State Implementation Plan

                         SOUTH CAROLINA
         DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROL
               AIR POLLUTION CONTROL REGULATIONS
                     REGULATION NUMBER 62.7
             GOOD ENGINEERING PRACTICE STACK HEIGHT



Section I  GENERAL

The purpose of this regulation is to prevent the use of tall
stacks or other dispersion techniques from affecting the
emissions limitations required to meet National Air Quality
Standards (NAAQS) or Prevention of Significant Deterioration
(PSD) increments.  This Regulation does not, in any manner,
restrict the actual physical stack height nor the actual use of
dispersion techniques at any source.  Rather, it sets limits on
the maximum CREDIT for stack height and other dispersion
techniques which can be used in ambient air quality modeling for
the purpose of setting an emission limitation and calculating the
air quality impact of a source.  Sources requiring modeling must
use Good Engineering Practice (GEP) Stack Height.  Credit for
dispersion techniques is prohibited.

Section II  APPLICABILITY

This regulation applies to all stacks excluding flares which were
not "in existence" before December 31, 1970.  The regulation also
applies to stack heights or dispersion techniques at sources
which were reconstructed or under major modification after
December 31, 1970.

Section III DEFINITIONS AND CONDITIONS

For the purpose of determining GEP stack heights and other
parameters applicable to modeling, the following definitions and
conditions apply.

A. Stack "in existence" - A stack on which the owner or operator
had (1) begun, or caused to begin, a continuous program of
physical on-site construction or (2) entered into binding
agreements or contractual obligations which could or modified
without substantial loss to the owner or operator to undertake a
program of construction to be completed in a reasonable time.

B. "Dispersion Technique"

1. Any technique which attempts to affect the concentration of a
pollutant in the ambient air by:

     a. Using that portion of a stack which exceeds good
engineering practice stack height;

     b. 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
stack; or other selective handling of exhaust gas streams so as
to increase the exhaust gas plume rise.

2. Paragraphs 1a, b, and c above do 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 source
generating the gas stream;

b. The merging of exhaust gas streams where:

          (i) The source owner or operator demonstrates that the
     process was originally designed and constructed with such
     merged gas streams;

          (ii) After July 8, 1985, such is part of a change in
     operation at the plant 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" applies only to
     the emission limitation for the pollutant affected by such
     change in operation; or

          (iii) Before July 8, 1985, such merging was part of a change
     in operation at the plant 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 Department 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 such intent, the
     Department shall deny credit for the effects of such merging
     in calculating the allowable emissions for the source;

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

d. Episodic restrictions on residential woodburning and open
burning; or

e. Techniques which increase final exhaust gas plume rise where
the resulting allowable emissions of sulfur dioxide from the
plant do not exceed 5,000 tons per year.

C. "Good Engineering Practice" (GEP) Stack Test Height - The
greater of:

1. 65 meters, measured from the ground-level elevation of the
base of the stack;

2.  Hg = H + 1.5 L,
    where

     Hg = good engineering practice 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,
      L = lesser dimension, height or projected width of nearby
          structure(s)

The Department or EPA 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 Department and EPA 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.

D. "Nearby" -

1.  For the purpose of applying the formula provided in paragraph
C.2. above, nearby means that distance up to five times the
lesser of the height or the width of a structure, but not greater
than 0.98 km (1/2 mile), and

2. For conducting demonstrations under paragraph C.3. above,
nearby means not greater than 0.8 km (1/2 mile), except that a
PORTION of a terrain feature may be considered "nearby" when:

a. at a distance of 0.8 km (1/2 mile) from the stack the height
of the feature is at least 40% of the GEP (as determined by the
formula in paragraph C.2. above) or 26 meters, whichever is
greater; and,

b. the portion of the terrain feature must be within 10 times the
maximum height of the feature, but not more than 2 miles, from
the stack.

All heights are measured from the ground-level elevation at the
base of the stack.

E. "Excessive Concentration" - For the purpose of determining
good engineering practice stack height under C.3, above.

1. For sources seeking credit for stack height exceeding that
established under C.2. above, excessive concentration means a
maximum ground-level concentration resulting from stack emissions
which are due in whole or part to downwash, wakes, and eddy
effects produced by nearby structures or nearby terrain features
which is at least 40 percent in excess of the maximum
concentration experienced in the absence of such downwash, wakes,
or eddy effects and which contributes to a total concentration
due to emissions from all sources that is greater than an ambient
air quality standard;

2. For sources seeking credit for stack height exceeding that
established under C.2. above, and where such sources are subject
to the Prevention of Significant Deterioration program, excessive
concentration means a maximum ground-level concentration
resulting from stack emissions which are due in whole or part to
downwash, wakes, or eddy effects produced by nearby structures or
nearby terrain features which is at least 40 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.

3. The allowable emission rate to be used in making
demonstrations under E.1 or E.2 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 Department, alternative emission rate shall be
established in consultation with the source owner or operator;

4. For sources seeking credit after October 11, 1983, for
increases in existing stack heights up to the heights established
under paragraph C.2. above, excessive concentration means either:

a. a maximum ground-level concentration due in whole or part to
downwash, wakes or eddy effects as provided in E.1. or 2. above,
except that the emission rate specified by any applicable
Regulation (or, in the absence of such a limit, the actual
emission rate) shall be used; or

b. The actual presence of a local nuisance caused by the existing
stack as determined by the Department; and

5. For sources seeking credit after January 12, 1979 for a stack
height determined under C.2. above where the Department requires
the use of a field study or fluid model to verify GEP stack
height, for sources seeking stack height credit after November 9,
1984 based on the aerodynamic influence of cooling towers, and
for sources seeking stack height credit after December 31, 1970
based on the aerodynamic influence of structures not adequately
represented by the equation in C.2. above, excessive
concentration means a maximum ground-level concentration due in
whole or part to downwash, wakes or eddy effects that is at least
40 percent in excess of the maximum concentration experienced in
the absence of such downwash, wakes, or eddy effects.

SECTION IV  PUBLIC PARTICIPATION

For any source whose emission limitation is based on a GEP stack
height which exceeds that allowed by Section III C.1 or 2 above,
the public will be notified of the availability of the
demnstration study and the opportunity for a public hearing will
be provided.
________________________________________________________________

THIS IS THE FEDERALLY APPROVED REGULATION AS OF MAY 28, 1987

               Date Submitted      Date Approved    Federal
               to EPA              by EPA           Register

Original Reg:  JUN 11, 1986        MAY 28, 1987     52 FR 19859


END


For information about the contents of this page please contact Sean Lakeman



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