-------
IjUihl^iiilMMimnf i lint j t !!l
1*1! if!:«!»»
!*'l* .Kf ii**i
?;i:!l!:i?lfi
JWJH
MiMlJ"
'pl-lHslH*1iH
•|«j|s«IfS|I|s;
s Ifs »l?iil«l
M
fillifl ]l! * !
iilSlijiiS 5= = ^
-------
8 so
ll^sl'M
t *«! 5sf s u-s-.-c »:?-_.* aa&3«-«2
aiiiifciiiliji'siffifiiii
j|l:H1i|j|
M.lfii'lii
»•«:;:
ilslSli
pi'ijc*ii!HUH
Vfl^illlliit I
-------
Monday
July 8, 1985
Part II
Environmental
Protection Agency
40 CFR Part 51
Stack Height Regulation; Final Rule
-------
27892
Federal Register / Vol. SO. No. 130 / Monday. July 8. 1985 / Rules and Reaulationj
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Pirt 51
Stack Height Regulation
AOIMCY: Environmental Protection
Agency (EPA).
ACTtOM: Final rulemaking.
•UMMAftv: Section 123 of the Clean Air
Act. as amended, requires EPA to
promulgate regulations to ensure that
the degree of emission limitation
required for the control of any air
pollutant under an applicable State
implementation plan (SIP) is not
affected by that portion of any stack
height which exceed* good engineering
practice (CEP) or by any other
dispersion technique. A regulation
implementing section 123 was
promulgated on February & 1982. at 47
FR 5604. Revisions to the regulation
were proposed on November 9. 1964. at
49 FR 44678. Today's action incorporates
changes to the proposal and adopts this
regulation IB final form.
Wltrivi DATE This regulation
becomes effective on August 7, 1985.
•on narrHBjH wpotniATtON CONTACT:-
Eric O. Ginsburg. MD-15, Office of Air
Quality Planning and Standards. EPA.
Research Triangle Paik. North Carolina
27711. Telephone (919) SO-IMsX
r Ajrr MMMSATIOW
Docket SketaaeeBl
Pertinent information concerning this
regulation is included in Docket Number
A-83-49. The docket is open for public
inspection between the aowra of MO
a.m. and 4:00 p.m.. Monday through
Fnday. at the EPA Central Docket
Section. West Tower Lobby, Gallery
One. 401 M Street SW.. Washington.
D.C. Background documents normally
available to the public, such as Federal
Register notices snd Congressional
reports, are not included in the docket
A reasonable fee may be charged for
copying documents.
Background
Statute
Section 123. which was added to the
Clean Air Act by the 1977 Amendments.
regulates the manner in which
techniques for disperson of pollutants
from a source may be considered in
setting emission limitations. Specifically.
section 123 requires that the degree of
emission limitation shall not be affected
by that portion of t stack which exceeds
CEP or by "any ether dispersion
technique." It defines CEP. with respect
to stack haagtas as:
the height necessary to insure that eanssions
from tht stack do not result in excessive
concentrations of any sir pollutant la the
immediate vicinity of the source a* a result ef
atmospheric downwash. eddies or weaes
which msy be crested by tht source ft
nearby structures or nearby terrain <
. . . (Stctioa 123(c)|.
Section 123 further provides that CEP
stack height shall not exceed two asvi
one-half times the height of the soorcx
(2.5H) unless a demonstration is
performed showing that a higher stack is
needed to avoid "excessive
concentrations." As the legislative
history of section 123 makes clear, deal
reference to a two and one-half •nsee
teat reflects the established practice of
using a formula for determaitng aee GBP
stack height needed to avert exeaaatve
downwash. Finally, sectioa 123 pronidea
that the Administrator shalllaaloss
only stack height credits flies) n, tea
portion of the stack height used to
calculating an emission limitation—
rather than actual stack heights.
With respect to "other disper
techniques" for which emission
limitation credit It restricted the statute
is lesa specific. It states only that net
term saall indado intermittent anal
supplemental control systems (ICS.
SCS), but otherwise leaves the definition
of that term to the discretion of the
cevt decision is provided later in this
ace.
Than flat statute delegates to ate
Administrator the responsibility for
oafaant loqr phraaes. including
"exceeatve concentrations" and
"aaarby," with respect to both
structures and tasrain obstacles, and
"other dispersion techniques." Tin
ArttasnanTatnr mast slso define the
requirements of an adequate
demonstration justifying stack baajat
credits in excess of the 2.5H fonMsU.
RuJemaJung and Litigation
On February 8.1982 (47 FR 58M). EPA
promulgated final regulations liaoiting
stack height credits and other diauetanau
techniques. Information concerning (&e
development of the regulation wea
included in Docket Number A-78-OI and
is available for inspection at the EPA
Central Docket Section. This regulation
was challenged in the U.S. Court of
Appeals for the D.C. Circuit by the
Sierra Club Legal Defense Fund. lac: tan
Natural Resources Defense Council, Inc;
and the Commonwealth of Penneylvantn
in Sierra Club v. EPA. 719 F. 2d 436. Oa
October 11.1983. the court issued its
decision ordering EPA to reconsader
portions of the stack height regulation.
reversing certain portions and uphotriing
other portions. Further discussion of the
Administrative Proceedings Subsequent
ic the Court Decision
On December 19.1983. EPA held a
patiic meeting to take comments 10
aswist the Agency in implementing the
mandate of the court. This meeting was
ed in the Federal Register on
• S. 1983. at 48 FR 54999.
Comments received by EPA are
included in Docket Number A-63-49. On
February 28.1984. the electric power
industry filed a petition for a writ of
eartiorari with the U.S. Supreme Court.
Waila Iha petition was pending before
dea ooen. the mandate from the U.S.
Court ef Appeals was stayed. On July 2.
MM. the Supreme Court denied the
petition (104 S.Ct. 3571). and on |uly IB.
19M. the Court of Appeals' mandate
W formally issued, implementing the
camrt's decision and requiring EPA to
promulgate revisions to the suck height
mulations within 4 months. The
promulgation deadline was ultimately
extended to June 27.1985. in order to
provide additional opportunities for
pafcu'c comment to allow EPA to hold a
pefalic hearing on January 8.1985. and to
provide additional time for EPA to
csBBplete its analysis of rulemaking
alternatives.
Documents
fa conjunction with the 1982
laajoBUfcon and this revision. EPA
developed several technical and
gaudance documents. These served as
background information for the
regulation, and are included in Dockets
A-79-01 and A-83-49. The following
documents have been or will be placed
as the National Technical Information
Service (NTIS) system and may be
obtained by contacting NTIS at 5285
Pert Royal Road, Springfield. Virginia
am.
n) "Guideline for Use of Fluid
Modeling to Determine Good
Bagineering Stack Height" July 1961,
H»A. Office of Air Quality Planning and
liamfrrria EPA-450/4-81-003 (NTIS
PBK145527),
(2) "Gvdeline for Fluid Modeling of
Atmospheric Diffusion." April 1961.
EPA. Environmental Sciences Research
Laboratory. EPA-dOO/8-81-009 (NTIS
PB81 201410).
(3) "Guidance for Determination of
Good Engineering Practice Stack Height
(Technical Support Document for the
Suck Height Regulation)." June 1985.
EPA. Office of Air Qualify Planning and
ftt—^—A, EPA-150/4-60-023R.
(4) "Determination of Good
Engineering Practice Slack Height—A
-------
Federal Register / Vol. 50. No. 130 / Monday, fuiy 8. 1985 / Rules and Regulations
,•893
Fluid Model Demonstration Study fcr a
Power Plant." April 1983. EPA.
Environmental Sciences Research
Laboratory. EPA-600/3-83-024 (NTIS
PB83 207407).
(5) "Fluid Modeling Demonstration of
Good-Engineering-Practice Stack Height
m Complex Terrain.'' Apn) 1983. EPA
Atmospheric Sciences Research
Laboratory. EPA/600/3-85/022 (NTIS
PB8S 203107).
In addition, the following documents
are available in Docket A-83-49.
"Economic Impact Assessment for
Revisions to the EPA Stack Height
Regulation." June 1985.
"Effect of Terrain-Induced Down wash
on Determination of Good-Engintnng-
Practice Stack Height" July 1984.
Program Overview
General
The problem of air pollution can be
approached in either of two ways:
through reliance on a technology-based
program that mandates specific control
requirements (either control equipment
or control efficiencies) irrespective of
ambient pollutant concentration*, or
through an air quality baaed system that
relies on ambient air quality levels to
determine the allowable rate* of
emissions. The Clean Air Act
incorporates both approaches, but the
SIP program under section 110 uses an
air quality-based approach to establish
emission limitations for source*.
Implicitly, this approach acknowledges
and is based on the normal dispersion of
pollutants from their points of origin into
the atmosphere prior to measurements
of ambient concentrations at ground
level.
There are two general methods for
preventing violations of the national
ambient air quality standards (NAAQS)
and prevention of significant
deterioration (PSD) increments.
Continuous emission controls reduce on
a continuous basis the quantity, rate, or
concentrations of pollutants released
into the atmosphere from a source. In
contrast, dispersion techniques rely on
the dispersive effects of the atmosphere
to carry pollutant emissions away from
the source in order to prevent high .
concentrations of pollutants near the
source. Section 123 of the Clean Air Act
limits the use of dispersion techniques
by pollution sources to meet the NAAQS
or PSD increments.
Tall stacks, manipulation of exhaust
gas parameters, and varying the rate of
emissions based on atmospheric
conditions (ICS and SCS) are the basic
types of dispersion techniques. Tall
stacks enhance dispersion by releasing
pollutants into the air at elevations high
above ground level, thereby providing
greater mixing of pollutants into the
atmosphere. The result is to dilute the
pollutant levels and reduce the
concentrations of the pollutant at ground
level, without reducing the total amount
of pollution released. Manipulation of
exhaust gas parameters increases the
plume rise from the source to achieve
similar results. ICS and SCS vary a
source's rate of emissions to take
advantage of meteorologic conditions.
When conditions favor rapid dispersion.
the source emits pollutants at higher
rates, and when conditions art adverse.
emission rates are reduced. Use of
dispersion technique* in lieu of constant
emission controls results in additional
atmospheric loadings of pollutants and
can increase the possibility that
pollution will travel long distances
before reaching the ground
Although overrtiiance on dispersion
techniques may product adverse effects.
some use of the dispersive properties of
the atmosphere has long been an
important factor In air pollution control.
For example, some stack height is
needed to prevent excessive pollutant
concentrations near a source. When
wind meets an obstacle such as a hill or
a building, a turbulent region of
downwash. wakes, and eddies is
created downwind of the obttadt as the
wind passes ovtr and around it This
can fore* a plume rapidly to the ground.
resulting in excttaivt concentrations of
pollutants near the source. A* discussed.
previously, section 123 rtcofoiZM mttt
phenomena and responds by allowing
calculation of emission limitations with
explicit consideration of that portion of
a source's stack that is needed to ensure
that excessive concentrations due to
downwash will not bt created near the
source. This height is called CEP stack
height
Summary of tht Court Decision
Petitions for review of EPA's 1962
regulation were filed is the D.C Circuit
within tht statutory time period
following promulgation of the regulation.
On October 11.1983. tht court issued its
decision ordering EPA to reconsider
portions of the suck height regulation.
reversing certain portions and upholding
others. The following is a summary of
the court decision.
The EPA i 1982 rule provided three
ways to ctrermine CEP stack height
One way was to calculate the height by
using a formula based on tht
dimensions of,nearby structures. Tht
other two were a de minim is height of 85
meters, and the height determined by a
fluid modeling demonstration or Reid
study. The court endorsed the formula
as a starting point to determine CEP
height. However, it held thdt EPA has
not demonstrated that the formula was
an accurate predictor of the stack
needed to avoid "excessive
concentrations of pollutants due to
downwash. Accordingly, the court
directed EPA to re-examine in three
ways the conditions under which
exceptions to the general rule of formula
reliance could be justified.
First the 1982 rule allowed a source to
justify raising its stack above formula
height by showing a 40-percent increase
in concentrations due to downwash.
wakes, or eddies, on the ground that this
was the percentage increase that the
formula avoided. Tht court found this
justification insufficient and remanded
tht definition to EPA with instructions
• to make it directly responsive to health
and welfare considerations.
Similarly, tht 1982 rule allowed a
source that built a stack to less than
formula height to raise it to formula
htight automatically. Once again, the
court required more notification that
such a step waa needed to avoid
advent health or welfare effects.
Finally, the court directed EPA either
to allow tht authorities administering
tht suck htight regulations to require
modtling by sources in other cases as a
check on poasibla error in the formula.
or explain why the accuracy of the
formula made such a step unnecessary
Tht 1982 rule provided two formulae
to calculate CEP suck htight For
source* conatructed on or before
January 12.1979. the data of initial
propoeei of tht stack htight regulations.
tht applicable formula waa 2.5 tunes the
height of tht source or other nearby
structure. For sources conatructed after
that date, the nde specified a newer,
refined formula, the height of the source
or other nearby structure plus l-S times
tht height or width of that structure.
whichever is leas (H-H1.5L). The EPA
baaed Its decision- to include rwo
formulae on the unfairness of applying
the new formula retroactively. In its
examination of this issue, the court
specified four factors that influence
whtthtr an agency has a duty to apply «
rule retroactively. They are:
1. Whether th« new rule reprmnta an
abrupt departure from wtU titabaahtd
practice or manly aiumpta to fill a void .n ;n
unsettled area of law.
i The extent to which tht party against
whom the new rule it applied rtiitd on me
former rule.
3. Tht dtfTM of burdtn which a retro»c::it
order impoMJ on a party, and
4. Tht itamtory inttreit in applying i new
ruJt dtapitt tht rehanc* of a party on :f.t :.d
itandard.
-------
27ifl4 Federal Raystac / Voi SO. No. 13O / Monday, frifr a. 19B5 I R»fe» and Regulations
719 t2d at 46? (citations omitted).
Applying this «nalyu» to the two
formulae, the court upheld EPA'i basic
decision.
However, the court also held that
sources constructed on or before
January IZ 1979. should not be
automatically entitled to fu»l credit
calculated under the 2.5H formula unless
they could demonstrate reliance on that
formula. The court remanded this
provision- for revision to take actual
reliance on the 2.5H formula tmo
account.
The slarate limits slack height eredW
to that needed to avoid excemiv*
concentration* dv* to downwaen caused
by "nearby" stnctune or terrein
feature*. TB* 19*2 regulation defined
"nearby" far GEP fonnoia epaKcatfoM
as Eve tines the leaver of either the
height or projected width of the
structure --•nrng dowowtak Dot to
exceed one self nik, No suck dietuc*
limitation we* placed oa struclwrea or
terrain features waa*a effect* wen
being considered in Quid -"•*•*-».
demonstrations or field studies. The*
court held that section 123 explicitly
applies the "nearby" limitation to
demonstrations and studies u weU aa
formula applications, and *y*»~m the
rule to ETA to apply the limitation in
both contexts.
The 198? rule defined 'dispersion
techniques" ae those techniques which
attempt to affect poQutant
coneentnttom bywmg that purtfun of a
stack exceedJnf GEP. by verywf
emission niee accordi** te> amiuspfteik.
condition* or pollutant eoncentrettene,
or by the eddirfo* el a fan or feheeiei to
obtain e lees stringent enuefen
• limitation. Th* court fbwnd this
definition too narrow because enp
techniow •sierBficamiy Motivate*) ey an
intern to gjun enusaions credit for
greater dispersion" shocJd be baited
"19 F.2d 462. As a resale the covt
directed EPA to develop iuh»»
disallowing credit for ail SMC*, diaperran
techniques oniess the Agency
adequately im&fied excapataae oa the
basis of administrative necaeeny or m «e>
rr:nimi3 result.
The CEP formulae established in in*
1982 rule do not consider peaaae nsa.«*
the ground that plume nse is not
significant under downwash conditions.
In its review of thti provision, the court
affirmed this judgment by EPA.
The 1982 rule addressed pnJIutant
concentrations estimated to occur whan.
a plume impacts efevated terrain by
auowini credit for stack height
necessary to avoid ait quality vtoLuiana
..i such cases. However, the court ruied
•.hat secijoo 123 did not allow EPA to
grant credit for plume irrptcnon in
setting auction liauti. tod nwernd tkta
part of the regulation.
Tb« prcjeabk (0 tha 1942 nfMkben
provided a 22 aoota proceaa fat Stale
iBipiaBcntation of the refuUtwo. The>
couct found this penod to ba> coBtrary to>
secnon 406(d)(2> of the CUaa Air Ac*
and rrrersed tL
The reguUtJoa. foUcwinf toe statute.
excluded stack* "in existence" oa or
before Oecenber tt. 1870. froei th* GEP
requirements. However, the reguUtoej
did not praiubit sourcee coaetracled
after Oeceaber 11. IBTtt rreat lecatviBg
credit for tying into pr*-19Jl stacks.
Although the court upbeM EPA's
definition of "ia existence," it aot«d> tbe4
EPA had tailed to eddies* taa> tte-ia)
issee.
this issue to EPA for juatifiatiem.
One other BfovieMi of the leaxiiannai
was challenged is th* Siarro CU> svifc
The sxriusiofi of flare* {ream th*
defiant? ol "sUck." IA Ua review el that
pmvtswv ih* court h«4d th*t BPA haei
acted properly.
Other provisions of th* nark height
regulation, euch aa. th*. a* nintmm stack
height attaMahed, under i 41.U»JMD.
were noi cneilcaged in tae> suit said t*e»
reman ia effect.
Summary of ttnt Mj*mitm ft
Notict ofFtopoiKfflaJmaicxnt
In th* Novamfaar 9t IflOa. notica.
responding to the court dadaun, EPA
proposed to redaflne a. aumbar of
specific tacns. "y['"^i«a "exceasiva.
coocaniraiiona*" k*ditepeie4ttii
tefhnimiaa." "nearby." aaaiothe*
unpoctanLconcapei* andi oraattaad u>
of the h**ea> tst
nft GEP StACk hfli^L TW
following ia. a auaaaacy of th* Mviaiaau
that wan proposed
The Court of Appeals held that EPA
erred in defixnae "ewceeai*1*
concentratian*" d«« u> «a%vmwe**w la*
purpoMe of jwatifyiaf a, slack pee tea
than formui*. height a* nothiag DMT*
than a 40-pejcent mcreaa* t* pnlUlaajt
coaceotratzoea over wh*l weoid eccur
in the ihetnrt of dowvweak k
remaadeck thia. veua to, EPA us r«We th*
dtfimnae, 10 son* ebeokt* k«ei ef ear
polludoa that could be in*sr»«eted to
endanger health and wellac*. and
to be "exenssiv*."
The EPA proposed two. aitomativt
approach** to defining "exceaene
concentrations." Fit*. EPA reqnantad
commcot oo whether th* eJVeeron*
appraeck adopted a* p*et of in* MM
reguiajtam HI tact pen* en* eejaiaal rhn
dangers to aetlrii end w«inue>
envisaoned by Coaejree* when it
section 129. In tns> rreat that seen •
showing catfd not b* made. EPA
proposed a two-part dcfettioa at*
excessive coacntnbaoe. re^uinnf ths (
the downwvaA. wakas. oreddws
induced by nearby structure* or terrain
feeturee reaeal ia inaieees in gtewnd-
levil poUmtant concmfritioos than
(*) Ceuee or ce»tribote to an
exceedaner of e NAAQS or appflnbfe
PSO mcrenwnt and
(b) Are at least 40 percent in excess of
concentration* projected to occur in the
absence of such structures or terrain.
features.
Definition of CEP Stack Hfigfit
EPA piaajoaed to find that th*
traditional (iSH) „* refined (H-M.5L)
formulae remained proper methods for
calculating CEP stack bvtgnt except EPA
proposed to revise its regulation to
allow EPA, the State or local air
pollution eon trot agency discretion to
require a farther demonstration using a
field study or Quid model to
demonstrate CEP stack height for a
source to a case where, it waa believed
that the fbnmria may not rettably predict
GEP height to the case of structures that
are porous ot aerodynamicaHy smoother
than block-shaped structures, it would
require a source to demonstrate the
downwash effect* of such structures
using a flefd study or fluid model before
receiving credit for stack height based
on the structures. EPA also proposed
generally to aJow saunas to nis*
existing stacks up to Cbnaula t-^v height
without further demonstration*, with the
exceptfoo no^a/j shove fiu dSacntiAnary
Rilianc* oa th* 23H Formula
In its 1982 ittie* EP A attawed sowce*
buik befew January U. MV9, th* date OB
which it propeeed m* reftaed H-t-l^L
formulae, to cakaUt* thwir enueswak
liout* e*Md ea UM tradetteMi UH
formui* thai existed, peamoueky. Ta*
court apfvoved this dia*neao«t bwl
ruled thai U should- be uouted to sowrces
that "reaVed" oa ta* Bediboaai fonmfa.
nimasrm. fat axaaxiie. that sources
that bad ci*i*ied o«Mt for stack* \*e
taller them th%fana»i* provideat etmid
not b* said t* a*** "reksd" am it
b respenv* to me eoert decwea EPA
propovad is revuw rte Hgalertnai »
requve thai fcr T*t fls euateace 00
January 12, 1979. source* deaMOBtrace
that their aetnaJty relied OB the S.SH
formal ia> I*** dsMgsi of their steci0
before recerraag credtt for ta«t an*M '»
propose*. EPA ispiseia' CBBXBMK on
eaarier •* ecceauseie
etf andl rs4i
-------
*
F*daw»J RagJatar / Vol. 5ft No. 130 / Monday. July a 198S / Rules and Regulation.
27895
DtfiniUtmof'Wtortrr"
In iti 1982 rule*, EPA allowed source*
that modeled the effects of terrain
obstacle* on downwash to include any
terrain features in their model without
limiting their distance from the stack.
The court though persuaded that this
was a sensible approach, since it
allowed the model to best approximate
reality, ruled that Congress had
intended a different result namely that
terrain features beyond H mile from the
stack should not be included in the
model.
In respoBM. EPA proposed to revise
i 51.1(ii)(3) o/it* regulation to limit the
consideration of downwash. wake*, and
eddy effects of structure* and terrain
feature* to thoae feature* «-J*««ifUH M
being ••nearby" aa defined ia | SLlfjj).
Under this propoaal structure* and
terrain feature* would be considered U>
be "nearby"*!/ they occur within a
distaaca of not more than O3 km (V4
mile): terrain features that extead
beyond 04 km could be cooatdered it at
a distance of &4 lea. they achieved a '
height greater than or equal to 40-
percent of th* CEP stack height
calculated by applying the CEP formula
to actual nearby structure*. In other
word*, a terrain feature would be said to
"begin" within tt mil* if it reached at
least the height of nearby building*
within that distance. Suoh feature* could
be considered only out to a distance"
equal to 10 time* the •»•»»"""« K^W»M gf
the feature, not to *xca*d 2 mile*.
The EPA propoeed two option* for
distinguishing bvtweea source*
constructed before and a/tar th* date ol
promulgation of the** revisjoae. Th*
first opboa wodd treat both categori**
of SOUTCM th* sam*. The second option
would unit th* coasio*r*tion of terrain
for new source* to only due* pordosu of
terrain feature* that fail entirely withia
0.8 km. thereby removing the poaaihilltj
of including feature* extending bcyood
Finally, EPA propoeed I
alternative* for conducting Aetd
modeling to evaluate th* dow*na*ali
effect* or nearby tetrem feaaesa*, Th***
alternative* described vanoa*,w*r* at
Iinuting terrain m the modd beyond th*
proposed distsnr* limitation*.
To establish a baaeiin* for
comparison, two alternative* would
initially modd the stack on a flat plan*
with no structure or terrain influence*.
To anaiyu downweeh effect*, the first
approach would then insert nearby
terrain, with ell terrain beyond th*
distance limrt "rat off" horizontally The
second eporoech would gradually
smooth and slope the terrain beyond the
distance limit down to th* elevation of
the base of the «fack.
The third approach would proceed in
a somewhat different manner. A
baseline would b* established by
modeling all terrain beyond the di»t*nce
limit waootaing aad *loping neerby
terrain to minima* it* influence. To
analyze downwaah effect*, th* nearby
terrain would than b* inserted into the
model end th* difference ia effect
rneesured to d*t*rrain* appropriat*
downwaah credit for stack height
Definition of "Ditpenitui Technique*"
Ia th* 1082 rale*. EPA identified two
practices, ia addition to ataeka above
CEP and 1CS/SCS, aa having ao pvpo**
other thaa ta obtaia a l*ee strtngnt
cmi*noa limitatioa. te so doing. It
allowed credit for any other practice
that had tb* raaolt of increasing
dispersion. Th* court concluded that
Congress h*d intended at a "inlm-if
to forbid any dispersion enhancement
practice that was significantly
motivated by aa intent to obtaia
additional credit for greater dispersion.
and remanded th* question to EPA for
^examination,
Tb* EPA proposed to revise it*
definition of "dispersion techniques"
generally to iadad*. ia *ddrboa to ICS.
SCS aad stack hctgnta ia *xc*a* of CEP.
any tadmkraa* that hav* IB* effect of
enhaactaaj cxhavat fa* atoaa* ria*.
Combining **v*reJ existing rtack* Into
on* a*w *teck can hav* each an effect
However, sue* oacabiaattoa* aieo oftea
hav* rnriensiiJent •economic an*)
anguMeftng juaHncatioo. Aooordingry.
combining of g*a •tnaca* snauM a*4 b*
ta allow eoufLes to tak* unlit
taattatfoae for N
w*w ortgin*iOjr dtsi^Md
•IFWUU W tVIMfV QW QMf^Of OOCQTB
with tb* iactallatioa of *ddKtonai
ooatfoie ywidiag * net redvcooa ia total
entt**iOB* of ta* effected pouotaat The
EPA retained exerottoa* from it*
definition or* prohibited dl*p*r*iea
tecaaipva* for *aiok* p*nag*fli*nt ia
egneurroral and aihricuiranl prescribed
bunung proejram* and also proposed to
exciude episodic restrictions oa
residential woodbuming aad debris
New Sources Tied into Pre-l&l Stack*
Section 123 exempts stacks "in
existence" at th* end of iflTO from it*
requirements. EPA's generel approach to
implementing this language was upheld
by the court However, tr its :982 rule
EPA had also allowed thif credit to
source* built after mat date that had
tied into stack* built before that date
EPA failed to respond to comments
objecting to this allowance, and so the
court remanded the question to EPA lot
the agency to address.
Upon ^examination. EPA saw no
convincing justification for granting
credit to these sources. Consequently.
for sources constructed after December
31.1970. with emissions ducted into
graadfathered stack* of greater than
CEP height and for sources constructed
before that date but for which major
modification* or reconstruction have
ben carried out subsequently. EPA
proposed to limit suck height credit to
only so much of the actual suck height
as conforms to CEP. Sources
constructed prior to December 31.1970,
for which modifications are earned out
that are not classified as "major" under
40 CFR Sl.ia(j}(i). 5U4(6N2)(i). and
51Jl(e)(2)(i) would be allowed to retain
fail credit for their existing stack
height*.
Plume Impocuon
In it* 1982 rule*. EPA illowed stack
height credit for "piome impacrion." a
phauueanon tnet is distinct from
downwash. wakes aad eddies. The
court though sympathetic to EPA's
policy position, reversed this judgment
as beyond tb* scop* of the statute.
Accordingly, EPA propoead to delete the
allowance of plum* impaetioa credit
from, it* regulation ia compliance with
the court i*~if*"' However. EPA also
recogaawd that soarca*. in complex
terram fee* addltioaai analytical
^rn^jt^. wam 4UI*«pCB*t to conduct
modeling ta deteeBiaa appevemate
e*ai*aioa liamitatiaaa. Coaaaaaently. EPA
r*qu**l**l TV"*"* oa whether eny
aliowaac* saooid be mad* for
impiaauatattoai probletM that may
molt from th* application of revised
CEP stack height assumptions end. if so.
how such ellowance should b* made.
State ImpiemetaSJoa Plan Reqummru
EPA's 19RZ nde* gave state* a total of
22 month* to revise their rules and to
establish source emission limitations
based on new stack height credits. The
court found this, too, to go beyond the
language of the statute. In response.
EPA suted in th* proposal that Slates
would b* required, pursuant to section
408(d)(2Kb) of the Clean Air Act. to
review their nriee and existing emission
limiUUona. revising them as na*ded to
comply with th* new regaiaoee within 9
months of the da to of IB
-------
27896 Federal Register / Vol. 50. No. 130 / Monday. July 8. 1965 / Rules and Regulations
Response to Public Comments on the
So vember ft 1984. Proposal
The EPA received over 400 comment!
during the public comment period and at
the public hearing, addressing a number
of aspects of the proposed
regulation.These comments have been
consolidated according to the issues
raised and are discussed, along with
EPA's responses, in a 'Response to
Comments" document included in the
rulemakmg docket. Certain comment*
can be characterized at "major" in that
they address issues that art
fundamental to the development of the
final regulation. These comments an
summarized below, along with EPA's
responses. Additional discussion of the
issues raised and further responses by
EPA can be found in the "Response to
Comments" document
I. Maximum Control of Emissions in Lieu
of Dispersion
A central legal and policy question
addressed in this rulemaking waa raised
in the comments of the Natural
Resources Defense Council (NROC) and
the Sierra Club. They contend that
section 123 requires ail sources to install
the maximum feasible control
technology before receiving any credit
for the dispersive effects of a stack of
any height or for other practices that
may enhance pollutant dispersion.
The NRDC argument is summarized
fully in the Response to Comments
document together with EPA'* response.
Very briefly, NRDC contends that
litigation prior to the 1977 Clean Air Act
Amendments had eatablished that
dispersion can never be used aa aa
alternative to emission control and that
this understanding was carried forward
and strengthened in the 1977 Clean Air
Act Amendment*. Accordingly, no rule
that doe* not require full control of
emissions a* a prerequisite to any stack
height credit would be consistent wife
Congressional intent
EPA disagrees. During the a yean
between 1977 and NRDC* comment*, a
period covering two Administrations
and three Administrator!. NRDCs
position has never been either adopted
by EPA or seriously advocated before it
The pre-1977 cases cited by NRDC-do
not bar all stack credit but only credit
for stacks beyond the historical norm.
Finally, the text and legislative history
of section 123 contain essentially no
support for NRDCs "control first"
position.
II. Discussion of Other Major Issue*
The EPA i position on the "control
first" comment* provide* the necessary
background against which the remaining
major issues in this rulemaking are
discussed. These issues are: the
definition of "excessive concentration*"
due to downwash. wake*, and eddie*;
the definition of "nearby:" and the
definition of "dispersion technique." A
question that affect* several of the**
decisions, and that i* addressed where
it arise*, concern* the extent to which
any change* made in the stack height*
regulation* should be applied
prospectively rather than retroactively.
This discussion of "excessive
concentration*" i* in turn divided into a
discussion of the physical characteristic*
of downwash. followed by a discussion
of the significance of those
characteristic* a* they pertain to the
CEP formulae, to stack* above formula]
height to *t*ck» being raited to formula
height and to stacka at formula height
being modeled at the choice of the
administering authorities.
Definition of "Excessive
Concentrations"
Tht Physical Natun of Downwash. A
number of commenter*. including the
Utility Air Regulatory Croup (UARC),
have argued that the court decision doe*
not obligate EPA to revise the definition
adopted in the 1982 regulation, but only
direct* EPA to ensure that the «K
percent criterion protect* againat
concentration* due to downwaah that
could be related to health and welfare
concern*. They point out that when
emiition* from a source become trapped
in the wake region produced by the
source itself or upwind structure* and
terrain feature*, tho*e auiaaiona an
brought rapidly to earth, with little
dilution. Thia. the coaunaatan argue,
can produce short-term peak
concentrations at groundlevel that an
many time* greater that the
concentration level* of the NAAQS.
BecauM their duration is relatively
short averaging theee concentration*
over the time* specified by the NAAQS
doe* not reault in NAAQS violation*.
Nonetheless, the-commenter* argue thai
the** concentration* should be regarded
as nuisance* that section 123 waa
specifically enacted to avoid
Accordingly, the commenter* held that
EPA would be justified in retaining the
40-percent criterion without requiring
that such increases result in
exceedance* of the NAAQS
These same commenters argued that
severe hardship* would result if EPA'*
second proposed definition of
"excessive concentrations" is adopted.
and that by limiting stack height credit
to that just necessary to avoid
exceedance of NAAQS or PSO
increment*, die definition would set to
limit actual stack design and
construction in a way that would
increau the likelihood of NAAQS or
PSD exceedance*. Thi* would occur.
they argue, because, by building only so
tall a *tack a* they can receive credit
for. sources would be eliminating a
"margin of safety" that would normally
be provided otherwise. Furthermore, it
waa argued that due to the changing
nature of background air quality.
inclusion of absolute concentrations
such as the NAAQS or PSD increments
in the definition would render
determination* of CEP stack height
constantly subject to change.
NRDC argued on the other hand that
only a violation of air quality standards
can be conaidered the type of
"cxccMivt concentration" for which
downwaah credit can be justified, the
EPA had failed to specify the health or
welfare significance of the short-term
peak* that it might consider as meeting
this deteription. and that in any event
UARG's attempt to show that short
stack* could cause a large number of
short-term peaks was technically flawed
in several different way*.
Response. Extensive discussion of the
downwash phenomenon, as well ss the
aerodynamic effect* of buildings and
terrain feature* on wind/low patterns
and turbulence, i* contained in the
technical and guidance document*
previously listed in this notice. To
.iimmjMa briefly, numerous studies
have shown that the region of
turbulence created by obstades to
windflow extend* to a height of
approximately iS time* the height of the
obstacle. Pollutant* emitted into this
region can be rapidly brought to the
ground, with limited dilution. Though
thia tendency decrease* the higher
vertically within dM downwaah region
that the plume i* released, because of
the highly unpredictable nature of
downwaah and the lack of extensive
quantitative data, it is extremely
difficult to reliably predict plume
behavior within the downwash region.
Aa noted in the comments submitted.
the distinguishing features of downwash
do not show up well over an averaging
time aa long aa 1 hour or more. Pollutant
concentration* resulting from
downwaah can erica and subside vary
quickly aa meteorological conditions.
including wind speed and atmospheric
stability vary. Thia can result in inort-
term peak*, lasting up to 2 minutes or so.
recurring intermittently for up to several
hour*, that significantly exceed the
concentrations of the 3- end 24-hour
NAAQS. Uttle quantitative information
la available on the actual levels of these
peak*, or on the frequency of their
occurrence since moat stacks have been
-------
Federal Register / Vol. so. No. 130 / Monday. JuJy 8. 1985 / Rules and Regulations
designed to. a void downwash and
because downwash monitoring it not
typically conducted.
A number of modeling and monitoring
studies in the record assess the
significance of downwash when plumes
are released into the dowmvash region.
The most important of these are a
number of studies cited m the November
9 proposal showing that for sources with
sulfur dioxide (SOi) emission rate* of 4
to 5 rounds per million British Thermal
Units (Ib./mmBTU), stack* releasing th«
plume into the downwash region can
significantly exceed the 3-hour NAAQS.
The utility industry submit ted
monitoring result* from four site*
showing that facilities with *hort sucks
(ranging from 23 to 80 percent of formula
height) generated many short-term
peaks in the vicinity of the plant at
concentration* at least 2 time* the
highest concentration of the 3-hour SOi
standard. i.a» 1 ppm for up to 10
minutes. Those concentration* are the
maximun that could be recorded by the
monitors used. There is no way to
determine from these data the true peak
ground-level concentration*.
The NRDC. in commenting on this
subject ha* argued that downwash- • '
related concentration* are largely
theoretical since stack* have generally
been built to avoid downwash. and that
actual concentration* occur under other
meteorological conditions auch as
"inversion breakup fumigation*" and
"looping plums," that can equal these
"theoretical" concentrations predicted
under downwash,' The NRDC also
en tinted the utility data on numeroos
technical grounds,
EPA'* itudie* indicate that, whee
stacks are significantly less than GBP
formula height high short-term
concentrations can indeed occur doe to
downwash that are in the range of the
values reported by the utility industry.
Concentrations produced by the other
conditions cited by NRDC, though high.
may be lower by an order of magnitude.
and occur less frequently by a* much a*
two orders of magnitude, than tho*e
produced by downwash.' A* (tack .'
' In 'mvtmon brufcup fuoiiftuon,' la in»
layer diuipcttt du* to fli«uo| of Kit ground. Itmaf
tne poiluiiiui ilui weft tripped in » 0*Ktad
suddenly 10 pound Itvel. in "toopini plumm." •
p.'uine ii broufht down ta ih« frouad do** w (S»
lourci m the form ol uiMfmiiMM pWfs vuuor *«*y
unstable itmovphtne eondjoaw.
'' Commend on P»ik Creund-Uvel
Concintri tiom Ou« to Buildinf Downwiia ReUuvi
>o Pejfc Conccnmiioni Under Aimoipnene
0 joeoton proceiiet." Aim H. Hub«r ind Princu
»oo'er ,'f JUM 10. 19B*.
height approaches the height determined
by the CEP formula, the expected
frequency and severity of short-term
peaks due to downwash becomes less
certain. This is to be expected since it is
the purpose of a formula height stack to
avoid excessive downwash. While it
might theoretically be possible for EPA
to revise the CEP formula-downward
(e.g.. from H+1JL to H+13L or some
other value), such a revision would hava
little purpose. By moving the release
point further into the downwash region.
such a change would increase the
probability of high down wain-caused
peaks. On the other hand such
relatively snail change* in stack height
are not likely to appreciably affect the
emission limitation for the sooro*. This
i* because emission limitations are
calculated based on physical stack
height and associated plume rise under
atmospheric conditions Judged meet
controling for the source. Increasing or
decreasing stack height by a email
fraction will not greedy change the rate
or extent of dl*penion and thus will not
affect the ground-level concentration.
Moreover, as EPA noted in its
November 9 proposal, no data presently
exist on which to base a revision to the
formula.
The NRDC submitted data to EPA
which It believed to support the
conclusion* that it urged EPA to adopt
concerning short-term peak
concentrations under other
meteroiogical conditions.'However,
these data were not presented la a form
that could be readily interpreted and
EPA ha* thus far been unable to draw
any conclusion* from then.4
In reviewing NRDC* coeaments OB
building downwash. EPA agrees that
there is greet uncertainty about oar
present understanding of thi»
phenomenon, and this is supported by
the range and variation of downwasa
effects ubseind la recent stadias.
However, no information has been
presented which would convince EPA to
abandon the present CEP formulae IB
favor of any alternative.
The health and welfare significance of
downwash concentrations that result in
violations of the ambient standard* are
documented end acknowledged in the
standards themselves. The significance
of short-term peaks at the levels that
EPA'* analyse* predict is more
judgmental. However, a number of
studies cited in EPA's "Review of the
National Ambient Air Quality Standard*
for Sulfur Oxides: Assesimem of jeb
Scientific and Technical Informatioi^H
f.EPA-wo/3-82-007. November 1982™
indicate that concentration* of one ppm
sustained for duration* of 5 minutes or
more can produce bronchoconstnction
in asthmatics accompanied by
symptom* such a* wheezing and
coughing. Such concentrations are well
within the range of concentrations that
can result from downwash. When
sources meet the ambient standards, the
frequency of occurrence for these
concentration* under the other
conditions cited by NRDC Is
substantially lower than for downwash
whan stacks an less than CEP.
GSP Formula Stack Height Some
coaaaatara. '•"•''"*'«$ NRDC stated
that EPA cannot justify retention ol the
traditional (1SH) and refined (H-rl.SL)
CEP formula* baaed aimply on their
relationship to the 40-percent en tenon.
and argued that the formulae provid*
too much credit in many or moat caies.
This, they argue, results in allowing
sources to obtain unjustifiably lament
emission limitations.
Other cosmmentar* argued that
Cftngree* explicitly reaffirmed the
traditional CEP formula, and that EPA
should allow """H«»"n reliance on it
(and by implication, OB the refined
formula that vraa rabaequendy denned
from it).
Response. The use of EPA's refined
formula as a starting Point for
determining GBP was not called Into
question by any litigant m the Sierra
flub ease. The court1* opinion Ukewite
does not question tne use of the formula
as a starting point A detailed discussion
of the court's treatment of the formula.
showing bow it endorsed the formula s
presumptive validity, la contained in the
Response to Comments document
Despite this limited endorsement ETA
might need to revisit the formula on it*
own if it* reaxamination of the
"excessive concentratien" and modeling
issues indicated that me formula dearly
and typically misstated the degree of
stack height needed to avoid downwatb
concentrations that caoaa taaaJth or
welfare
' Mtmercntfya from Oind C. Hiwkmi. NtOC M
Williim F Pederacn. jr. Office ol GtfwrmJ CaunML
L'SBPA. Mi? 2*. ISO,
• M*mor»n*im from A)in H Hubw ASM. to
Oivid Sionefleis. OAQPS. Ion* n. :*SS
However, no such result has emerged
frost our reexaminatioa. Stacks below
formula height are associated with
dowBwaaa-reiatad violations of the air
quality standard* themselves where
emission rates significantly exceed the
levels specified by NSPS, Even where
emissions are low. downwash
conditions at stack* below formula
height can be expected unlike other
condition*, to generate nianerou* ihorf-
term peak* of air pollution « high leveii
-------
27896 Federal Register / Vol. 50. No. 130 / Monday. July a. 1965 / Rules and Regulations
that raise a real prospect of local health
or welfare impacts.
As EPA stated in the proposal, it is
impossible to rely primarily on fluid
modeling to implement the stack height
regulations, particularly under the
timetable established by the court. 49 FR
44883 (November 9.1984). No
commenter other than NROC even
suggested a different formula that in
their eyes would be better, and NRDCs
suggestions were premised on their
"control first" position, which EPA has
found inconsistent with the statute and
has rejected. EPA considers the refined
formula to be the state-of-the-art for
determining necessary suck height
Given the degree of presumptive
validity the formula already poss*sa«a
under the statute and the court opinion.
we believe that this record amply
supports its reafftrmation.
Stack* Abon CEP Formula Height.
The EPA's 1979 stack height guidelines
[cite] imposed special conditions on
stacks above formula height—the
installation of control technology—that
were net imposed on lower stacks.
Similarly. EPA's 1973 proposal had
made credit above formula height
subject to a vaguely defined "detailed
investigation" (38 FR 25700). The
legislative history of the 1077 dean Air
Act Amendments cautioned that credit
for stacks above formula height should
be granted only in rare cases, and the
Court of Appeals adopted this aa oaa of
the keystones of its opinion. The court
also concluded that Congress
deliberately adopted very strict
requirements for sources locating in
hilly terrain.
For these reasons. EPA la requiring
sources seeking credit for stacks above
formula height and credit for any stack
height justified by terrain effects to
show by field studies or Quid modeling
that this height is needed to avoid a 40-
percent increase in concentrations due
to down wash and that such an increase
would result in exceedanca of air
quality standards or applicable PSD
increments. This will restrict stack
height credit in this context to cases
where the downwash avoided ia at
levels specified by regulation or by act
of Congress as possessing health or
welfare significance.
To conduct a demonstration to show
that an absolute air quality
concentration such as NAAQS or PSD
increment will be exceeded, it la
necessary to specify an enusaion rate for
the source in question.' The EPA
conecnvioaw" ln»o will
continue to result in excessive
concentrations when the source-
emission rate ia consistent with NSPS
requirements, additional stack height
credit may be justified through fluid
modeling at that enuseion rat*.
A source, of course, always remain*
free to accept the emission rate that ia
associated with a formula height stack
rather than relying on a demonstration
under the conditiona described here.
The third alternative mentioned in the
proposal—using the actual emission
limit for the source—has been rejected
because, to the extent that limit relied
on greater than formula height it would
amount to using a tall stack to justify
itself.
The EPA's reliance on exceedance*,
rather than violations of the NAAQS
and PSD increments, ia deliberate. Fluid
modeling demonstrations are extremely
complicated to design and carry out
even when the most simple
demonstration criteria—that is, a
percentage increase in concentrations.
c*uMd by downwua it independent of
mio.
'Ttw EPA wul raiy on IU Bnt Aviilabto lUtroflt
Tteftnotogy CiudcHiM la r*vwwut« wjr rvbwult
wtd ilt«m*Dv« miMioa 'tnuution*.
with no consideration of absolute
values—are assumed. Adding
consideration of an absolute
concentration such as a NAAQS or PSD
increment substantially complicates this
effort further and introduces the
scientific uncertainties associated with
predicting an exceedancc of a 3-hour or
24-hour standard based on 1 hour or less
of modeling data. Using an hour or less
of modeling values, based on one set of
meteorological data, to draw the
distinction between only one
exceedance of the standard during the
S700 hours in a year, and the two or
more that constitute a violation pushes
that uncertainty beyond reasonable
limits. EPA therefore does not find the
additional difficulties that would be
created by requiring violations instead
of exceedances to be warranted. That is
particularly so here, given that the
regulations require sources seeking
credit above the formula to be well-
controlled as a condition of obtaining
such credit
Use of an absolute concentration m
the test of "excessive concentrations"
can leed to problems of administering
the program, in that it can have a
"zoning" effect Since a source can only
get stack height credit to the extent that
it is needed to avoid a PSD Increment or
NAAQS exceedance. an emissions
increase in the area of that source may
increase concentrations beyond the
controlling limit thereby making it
difficult for new sources to locate in the
area, or for sequential construction of
additional emitting units at the source in
question.
This effect cannot be avoided under
any teat for "excessive concentrations"
that is tied to absolute concentrations.
However, that effect will be mitigated
by the fact that the use of this approach
is voluntary and limited to sources
wishing to rely on fluid modeling to
justify stack height credit Moreover, the
effects of downwash tend to occur very
near the source, usually on fenced .
company property. Since concentrations
measured at such locations sre not used
to evaluate NAAQS attainment or PSD
increment consumption, new sources
wishing to locate in the area are less
likely to be affected.
Sources planning sequential
construction «f sew emitting units at
one location or contemplating future
expansion can reduce the uncertainties
noted above by initially obtaining
permits for the total number of units
anticipated and by planning for
expansion in the calculation of
necessary physical stack height. In the
latter instance, only the allowable stack
height credit would be revised as
-------
Federal Register / Vol. 50. No. 130 / Monday. July 8. IMS / Rules and Regulations
27899
expansion is earned out—not actual
stack height
An additional theoretical
complication is presented when an
absolute concentration is wed where
meteorological conditions other than
downwash result in the highest
predicted ground-level concentrations in
the ambient air. In such cases, a source
that has established CEP at a particular
height, assuming a given emission rate.
may predict a NAAQS violation at that
stack height and emission rate under
some other condition, e.g.. atmospheric
stability Class 'A.' Reducing the
emission rate to eliminate the predicted
violation would result in stack height
credit greater than absolutely necessary
to avoid an excessive concentration
under downwash. Howevtr. reducing
stack height places the source back in
jeopardy of a NAAQS violation under
the other meteorological condition, and
to on. "ratcheting" stack height credit
and emission rates lower and lower. The
EPA has eliminated this "ratcheting"
potential in the CEP guideline by
providing that once CEP is established
for a source, adjusting the emission rate
to avoid a violation under other
conditions does not require
recalculation of a new CEP stack height
EPA is making this part of the
regulations retroactive to December 31.
1970. In the terms of the court's
retroactivtty analysis, stacks greater
than formula height represent a situation
that Congress did affirmatively "intend
to alter" in section 123. Moreover. EPA
regulatory pronouncements since 1970
have placed a stricter burden on source*
raising stacks above formula height than
on others.
N.o source is precluded from building
a stack height greater than formula
height if such height is believed to be
needed to avoid excessive downwash.
However, the design and purpose of
section 123 prohibit SIP credit for that
effort unless a relatively rigorous
showing can be made.
Given the ability of sources to avoid
modeling and rely on validity of the CEP
formulae and requirement for further
control of emissions in coniunctioa with
stack heights in excess of formulae
height, the result predicted by UAKC—
exceedances of the NAAQS or PSD
increments due to inadequate stack
height—is highly unlikely.
The potential effect of changes in
background air quality on stack height
credit is not substantially different from
the effect that such changes in
background can have on source
emission limitations in nonattainment
areas. In the first case, however, sources
may be able to address these effects
through greater stack height if such
changes affect the concentrations under
downwash. Moreover, the possibility
that shifting background air quality can
yield different calculations of CEP is
significantly limited by the feet that
consideration of background in CEP '
calculations is restricted to those cases
where credit for greater than formula
height is being sought or source* are
seexing to raise stacks to avoid
excessive concentration*.
Raising Stackt Below Formula Height
to Formula Height In response to EPA'a
proposal to allow automatic credit for
CEP formula height seven! commentera
have argued that EPA hea failed to
adequately respond to the court's
directive to "reconsider whether, in light
of its new understanding of 'exceaaive
concentrations,' demonstrations an
necessary before stack height* may be
raised even if the final height will aot
exceed formula height"
Re$ponM9, F using a stack below
formula heigi to formula height is not
in EPA's judgment subject to the sea*
statutory reservations as building stack*
greater than formula height However.
as the court has cautioned, it may still
be necessary for these sources to show
that raising stacks is necessary to avoid
"excessive concentrations" that raise
health or. welfare concerns.
For these reasons, sources wishing to
raise stacks subsequent to October 11.
1963. the date of the O.C Circuit
opinion, must provide evidence that
additional height is necessary to avoid
downwash-related concentration*
raising health and welfare concern*.
These rules allow source* to do mi* in
two way*.
The first way is to rebut the
presumption that the short stack we*
built high enough to avoid dewnwash
problem*: L*» to show, by tita-epecific
information such a* monitoring data or
dtixea complaint*, that the short stack
had in fact caiued a toeal nuisance tad
mnat be rai*ed for thi* reason. The EPA
believe* that both the historical
experience of the industry and the data
on short-term peaks discussed earlier
show that short stack* can cau*e local
nuisance* due to downwash. However,
where a source has built a short stack
rather than one at formula height it ha*
created a presumption that thi* i* not
the case. General data on saort-term
peak* may not be strong enough to
support by themselves and IB the
abstract a conclusion that the stack
must be raised (eravoid local advene
effect*. Instead, that proposition must be
demonstrated for **ch particular source
involved. .
In the event that a source cannot
make such a showing, the second way to
justify raising a stack is to demonstrate
by fluid modeling or field study an
increase in concentration* due to
downwaih that in at least 40-percent in
excess of concentration* in the absence
of such downwash and in excess of the
applicable NAAQS or PSD increments.
In making this demonstration, the
emission ret* in existence before the
•tack is raised must be used.
Since raising stacks to formul* height
i* not subject to the same extraordinary
reservation* expre**ed by Congress and
the court with respect to stacks being
rai*ed above formula height EPA doe*
not believe that the use of presumptive
"well-controlled" emission rat* is
appropriate hen. Aa discussed in EPA's
ntponae to NRDCs "control first"
argument the back: purpo** of section
123 was to take source* a* it found them
and bated on thoae drcumstaace*. to
a**ura that they did not avoid control
requirement* through additional
disiperefoa. Use of a source's actual
emiMion rate in thin Instance is
consistent with that b'asic purpose and
abeent special indications of a different
intent *nould be u*ed in stack height
The EPA believe* that it i* most
unlikely that any source with • current
emiaeioa limitation ha* failed to claim
full formula credit for a stack of formula
height Accordingly, the question
whether a source can receive stack
height credit op to formula height will
involve only source* that want to
actually raise their physical suck, not
source* that amply went to claim more
credit for a stack alnady in existence. A
source will presumably not go to me
trouble of raiting aa existing stack
without *ome reaeoa. If a source cannot
•how that the rea*oa waa in fact the
desire to avoid a problem caused by
downwash. then the Inference that it
waa inatead a deeire for more dispersion
credit i* hard to avoid A nuisance
caueed by downwashed emissions could
include citizen or employee complaints
or property damage. A source would be
expected to (how that complaint* of this
nature wen reasonably widespread
before getting credit under this section.
The EPA doe* aot intend to make taw
rule retroactive to stack* that
"commenced construction" on
modification* that would raise them to
formula height prior to October 11. 1963.
Applying the court's ntroactivity
analyst*. it appear*:
1. The aew rule doe* depart from prior
practice. The SPA'* 1873 proposed rule
affirmatively encouraged sources with
shorter stack* to raise them to formula
-------
27900 Federal Register / Vol. sa No. 130 / Monday. July 8. 1965 / Rules and Regulations
height.'Though EPA'i 1976 guideline
can be read u imposing a "control first"
requirement on some stack height
increases. Us general thrust gave
automatic credit for all stacks that met
the "2.5" times formula.'Automatic
permission was similarly set forth in the
1979 proposal, in the 1981 reproposal.
and in the 1982 final rule. Only a notice
published in 1980. but later withdrawn.
departs from this trend, requiring the use
of field studies or fluid modeling
demonstrations to justify stack height
increases up to CEP formula height*
Even then, the notice would have made
this policy prospective in its application.
2. Sources that raised stacks in
reliance on this paat EPA guidance
assuming the availability of dispersion
credit cannot be distinguished from the
sources, in the example approved by the
court that built stacks to the traditional
formula in an identical expectation of
dispersion credit
3. It cannot be said that the raising of
stacks to formula height is a practice
that Congress "affirmatively sought to
end." It is not mentioned in the text of
the statute or its legislative history.
Further, as the court haa already noted,
the statute attributes a degree of
presumptive validity to the formula on
which sources that raise their stacks
will have relied.
DnentioH to Rfquin Fhifd Modt/lng.
Several ceonenten argued thai EPA's
proposal to allow egenaea to require the
use of fluid modeling wu anneressary.
since EPA had already doconeated tao
validity of the GEP tennis*.
Furthermore, these conaentara argoe
that this allowance would make (tad
modeling the rule, rather thaa the
exception. This would result, the
commanten state, became it wee their
expectation that agendes or
environmental groups would nearly
always call for fluid m~<«n«g
demonstrations during the permit
application and review process.
Other commentsrs stated that
providing the discretion to require fluid
modeling was appropriate, since EPA
had failed to demonstrate that the CEP
formulae represented the m^mnm
height necessary to avoid excessive
concentrations.
Reiponn. The Court of Appeals -
directed EPA to reexamme whetfier its
rules should silow States, as a matter of
discretion, to require even sources that
planned to rely on the formula to show
instead by fluid modeling that a stack
this high wu required to avoid danger*
to health and welfare caused by
downwash. The court suggested that
EPA should include such a provision
unless it could find that the formula was
so accurate, or tended so much to err on
the low side, as to make discretionary
authority to adjust formula height
downward unnecessary.
The EPA believes that the court wes
mistaken in its conclusion that a stack
at formula height is likely to generate
downwash concentrations as great as 40
percent only in uncommon situations. In
fact EPA's observations indicate that
when sucks an built to GEP formula
height an increase in concentrations
due to downwash can still be expected
to occur that ia between 20 and 80
percent greater than the concentratioa
that would occur in the absence of
building influences. '*
Never,.' . ess. in response to the
court's r«. Jid. EPA is including in this
final rule a provision for the authority
adminiataring these rules to require field
studies or fluid modeling
demonstrations, evea for stacks built to
formula height ia caaea where U
believes that the foraoU mey
significantly overstate the appropriate
stack height credit11
While BPA believes the formula to a
reasonable rule of thnsnb inchesting the
stack height needed to avoid sosae
probability of a etududa violation tad
a significantly greater probability «* •
local nuieonoa, acfcul reaan* la any
given ose- may vary sonewnet beeesi
on specific circumstances. The BPA haa
attempted to •«•*••*•• tola possibility
withia the limits of available data by
identifying two particular siftsanons) la
which it believes thai the fomaJae mmy
not be ranabie tadksrtors of C» Poroee
strueanes and frHMpgr wages shapes
are aendyasuniceUy smoother tfaea the
simple block-shaped strecturee en
which the fonnelae are beted.11
Tfatoto
•• tJw mim» onUiiMd or om
OC UOf9 InWBt
ef MctM ns «f dM Q«u Air A*.
wMrvio0nB •toGMt lev MovnQp it uw foieflSs
ohM tppttt* M rauadad, tmcnav. >lln««< ito M»
for c*n«ln upend itruaum tad eeoUoa I
-
' Tbt UM of *«Mk )M«fiM «p • *« Ivrvl of i«o4
enfmwnnt pnetie* n tncoui«f>d by IPA • *nMr
10 tvaid local otuuacm' (3* Fl U70B).
• 41 PR 7481 (Ftbnuuy is. UPSk "inrf-'-r
s*ttwi» 8.1. aim tan
• O F* 4ZP» ff«M M. USBfc **afc lUfiimtiam W
•tick hoe* cndlt tt rhir»»«d «t <
Mr Mt
tar M*
•tructum IMI WOT* gnnud prior w NuniifcaS.
i»4. Sinct EPA puduuM to* M«r tl\mt4 cr»dt>
for ponu* rmenm. itx mtneti<« la thl« rai* for
tuc* tovcnrm •<**•• M *U ••<*»
i, no* OMBBOV n. ISTa
However. EPA acknowledges thai other
situations, of which the Agency is not
presently aware, may anse wherein the
formulae may not be adequate.
The EPA intends to "grandfather" any
source that relied on the formula in
building its stack before the date of
EPA's 1B79 proposal bom the effect of
this discretionery ^examination
requirement
Only in that proposal did EPA first
suggest that such a discretionary
reexamination provision might be
included In the final rule. The
retroactivity analysis set out earlier
therefore supports exempting stacks
built In reliance on EPA guidance before
that data, from discretionary
reexamination. Indeed, a failuct to
"grandfather" these sources would lead
to the paradoxical result that a source
that had built a GEP stack under the
traditional EPA formula would have its
direct reliance interests protected by the
"grandfather" provision previously
upheld by the cowl but could then lose
that ••graadfatbered" credit through a
rsse specific desnonstration rsqasrement
showing that the traditional formeia was
somewhat inaccurate— ** MMtaB MS
-------
Federal Register / Vol. SO. No. 130 / Monday. JuJy 8. 1983 / Rules and Regulations
2T901
If such sources had to show that use
of a formula height stack was needed to
avoid exceedances of the NAAQS or
PSD increments, that might prove
difficult for many of them. The
likelihood of such exceedances tends to
decrease as the emission rate for the
source decreases. By the same token.
the incremental emission reductions
available from the sources that are at
issue here tend to be small and among
the most expensive available. In terms
of emission reductions, little is at stake
where these sources are concerned.
Accordingly, the rules will require
such sources, if a reviewing authority
calls for a demonstration, to the rules
show that the use of a formula stack
height is needed to avoid a 40-percent
increase in concentrations due to
downwash. This will provide • rough
check on whether the formula, as
applied in the particular case at issue,
produces the result it was designed to
produce.
The EPA is not providing here for
sources to justify their formula height
stacks by arguing that the height in
excess of that needed to avoid NAAQS
violations is needed to avoid a local
nuisance. The discretionary modeling
requirement is designed for application
to stacks before they were built Beyond
that, there is no way to determine based
on the-absence of a local nuisance that a
formula height stack is not too tail in
the way that At presence alt nuisance
shows that a stack under formula height
in fact is too short Accordingly, there
will be no way. as there was with short
stacks being raised, to determine from
actual experience whether a local
nuisance would occur at a shorter stack
height Though avoiding local nuisance
is a legitimate purpose for which stacks
are built, it would be very difficult to
show by modeling what stack height
was needed to avoid it,
Some commenters have
misunderstood EPA's allowance of
discretion to require fluid modeling as
requiring such modeling whenever any
individual or entity called forsucb a
demonstration. This discretion rests
explicitly with the reviewing aftncies
who have always had the prerogative to
.-•quire more stringent analyses in thr
S!P process.-and no obligation is implied
for rnese agencies to require fluid
modeling simply because it has been
:*'Aed tot by some individual during the
permit review process. It is EPA's
expectation that technical decisions to
require such additional demonstrations
wouid be based on sound rationale and
valid data to show why the formulae
may not be adequate in a given
situation. In any case, given the burden
of reviewing a fluid modeling
demonstration, an agency it not likely to
exercise this option abiant sufficient
justification. Consequently. EPA
disagrees with the commenters'
contention that fluid modeling will
supplant the use of the CEP formulae.
except in what EPA believes will be
unusual instances.
Reliance on the 2.SH Formula. In
limiting the applicability of the 2.SH
formula to those cases where the
formula was actually relied upon, the
November 9 proposal defined such
reliance in terms of suck design. A
number of comments indicated that
actual stack design and construction
may ultimately be control not by the
2.5H engineennf rule, but by
construction materials specifications.
Consequently, while 2JH rule may have
provided an initial starting point in
stack design, the rule may not have
dictated final stack height In other
cases, it was argued that a number of
source owners may have constructed
their stacks in excess of what was
determined to be minimum CEP for
precautionary reason*, for process
requirements, or in anticipation of
additional growth in the ana
surrounding the facility, even though
emission limitations for theee sources
would have been limited then. M now.
to formula height Consequently, it we*
argued that EPA should allow source* to
demonstrate reliance on the formula in
the calculation of emiaaion limits a* well
as in the design of the stack.
In response to EPA's requeet for
comments on what evidence should be
considered acceptable in determining
reliance on the &5H formula, sane
commenttrs urged EPA to consider
reconstructed evidence, t.g, affidavits
from design engineers or copies of
correepondeace indicating past reliance
on EPA guidance. Other eoouaentan
stated that "reliance" should be very
strictly construed, that EPA should be
circumspect in its review of reliance
demonstrations, and that only
contemporaneous documentary
evidence, such as blueprints and facility
design plans, be accepted as evidence.
Response. The EPA is in genera]
agreement with the view that reliance
should be considered in relation to the
emission limitation for the source, not
the design. Since section 123 specifically
prohibits EPA from regulating actual
stack heights and rather regulates stack
height credits used in setting emission
limitations, it would be illogical to
require that sources demonstrate
reliance on the 2.5H formula for actual
stack design. Moreover, such an
approach would contradict principles of
sound planning, in that it would
those source* that have built taller
Hacks in anticipation of facility
expansion or other growth in the area
that could influence CEP
determination).
If a stack has been built taller than
2.5H formula provides, while the
emission limitation has been calculated
assuming 2.5H credit a convincing
demonstration has been made that the
source properly relied on the formula.
Conversely, if die emission limitation for
the source it based on some other stack
height credit such as 24H. 3.SH or some
other number, it would be difficult to
show that the CEP formula had in fact
been relied on.
In some caees the emission limit
information may be unavailable or
inconclusive, la such cases. EPA will
allow reliance on reconstructed
evidence of construction intent
In comments submitted during the
public comment period and in response
to questions raiaod by EPA at the public
hearing held on January & 1385, industry
repreaantadvae repeatedly stated that
contemporaneouii evidence of reliance
on the 2JH formula, such as facility
design plans, dated engineering
calculations, or decision records an
rarely. If ever, retained for more than a
few yean after construction of the
facility it completed. Consequently, they
arfued that moan cases of legitimate
reliance would be denied if
contemporaneous evidence ware
required to order to retain for the 2.5H
formula.
The EPA agree*. Additionally, credit
afforded by the 2JH formula in excess
of that resulting from the use of the
H+1JL darivativ* is likely to be small
except when the building on which
stack height credit It baaed is
subatantially taller than it is wide.
Finally, it is EPA'a view that the court
did not intend mat sources be subject to
a rigorous or ovarry stringent of reliance,
but only that they be accorded a
reasonable opportunity to show reliance
on the 2.SH formula. For these reasons.
EPA will allow the iiubmission of
reconstructed, l.a- noncontemporaneous
documentary evidence to demonstrate
reliance on the Z5H formula.
Definition of "Nearby". Comments
wen submitted by UARG and others.
arguing that effectively, no limitation
should be placed on the consideration of
terrain-induced downwash.
Alternatively, some of these
commenters argued that the court
decision requires that a limitation be
adopted that does not apply any
distance restriction of H mile in
moaeiing terrain effects such as is
-------
27M2 Fadatai Ragbtar / Vol. 5ft No. 130 / Monday. luiy 8. 1988 / Rule* tad Regulation!
applied to structure* in the UM of CEP
formula*, but rather allows
consideration of all terrain that'result*
in the tame downwash effect as those
structures within Vi mile of the stack.
Other commenters have argued that
the court decision snd legislative history
preclude EPA from allowing
consideration of any terrain beyond a
distance of H mile, regardless of where
it begins.
Response. For the reasons
summarized below. EPA does not accept
either the interpretation that the court
decision authorizes EPA to adopt a
definition based solely oa effect or that
it limits consideration exclusively to
terrain features falling entirety within H
mile.
When Congress dJacaaeed tb*
allowance of credit for stack height to
addreea dowawaah. It stated that th*
term "nearby wa* to be "strictly
construed" noting that If the tenm ware
to be interpreted "to apply to maa-nada
structure* or terra/n/eeairs* * to Vfc
mil* away fran the source* or more, the
result could be aa opea invitation to
raise itack heights to unreasonably high
elevations and to defeat the basic
underlying oomnuttee intent" »«
In its opouon, thceoort held that EPA,
could not give unlimited credit when
meuuitmg lamia f««tm» because that
would conflict with the Cimajeeaionsl
intention to imao** artificial Units oa
that credit The court waa not presented
with, and did not addreea, the question
of what to do about terrain feature* that
"bssjaa" witk4& V*. sail* and *xaiad*d
outside it The approach adopted by
EPA carried out doe rmigreaeinsiel
purpoae to impoaa aa artificial limit hot
at the same time reflects tha real facts
more doaely than aa absolute V4 miia
limitation.
Unlike man-made, structure*, tazraia
feeturea do not have readily definable
dimenaioae other than height For thia
reason. EPA has defined "nearby" aa
generally allowing inclusion of
consideration of terrain feature* that fafl
within a distance of % mil* of the stack,
EPA's definition wiO peanft
consideration of such tannin that
extends beyond the tt mile Omit if the
terrain begins within % mile, allowing
that portion within 10 time* the -
maximum height of the feature, dot to
exceed 2 miles, ai described in tha
proposal
To define when a terrain feature
"begins" within H mile. EPA has related
terrain height et the H mile distance to
the maximum stack height that could be
justified under the other two methods
for determining CEP. Accordingly. EPA
will require that terrain featurea reach a
height at tha ft milt di'Mnca limit of
either 28 maters (Le. U maters divided
by 2.5) or 40 percent of tha stack height
determined by the CEP formula* applied
to nearby buildings.
Treatment of New venui Butting
Source* Under the Definition of
"Nearby". In the proposal, EPA
requested comment on whether new
sources should be treated differently
from existing sources and presented two
options for addressing them.
Few comments were received on
these options. Several questioned the
logic of distinguishing between new and
existing sources in the regulations. One
coffimeater argued that new and existing
sources should both b* subject to the
strict 7% mile limit proposed under oa*
option for aew eoureee onry. This hat
already b**n discussed under EPA's
response to comments on the general
definition of "nearby" and I* not
addressed further here.
Reeponee. New sources ere initially
subject to more stringent control
requirements than many existing
source*. Consequently, it ia lee* likely
that tha emission limitation* and stack
height credits for the** source* will b*
affected by terrain feature*.
Furthermore, EPA believe* that tb*
effect of applying a more restrictive
antatioa will b*
and will result only ia mine* change* ia
siting, ratnar man suoetantia. raJocaOoa
of sosnesv For this reason. EPA ha*
selected the second option, treating i
and existing soon** IdttticaMjr <
to* definition of "nearby."
EPA ia giving thia definition of
"nearby" retroactive; application to
December 31 1870, Th* court's d*d*ie*
main* clear it* coooUieion that Conaraea
affirmatively focused on this iaeue and
aa of
(1977).
the enactment data) proper.
Definition of Othet Daaeniaa
recAiuaiM*. The EPA received many
comments oa tha proper scope of th^
definition of "dispersion tachmquas,"
and perhaps more oifthe appropriate
tm«if»/H« of the exclusions. Industry
commentars generally argued that EPA
had improperly proposed to deny
consideration for plume-enhancement
effects that are "coinddeataT with
techniques and practices routinely
carried out for sound «"g<"Mri''g and
economic reason*. They argued that
EPA should prohibit credit only when a
technique or practice was decisively
motive ted by e desire for dispersion
credit Such an approach would create a
"but for" test using tha intent of the
source owner or operator as tha basis
for EPA't decisions.
Other commenters argued thai EPA
must osa a tett baaed purely on »ffacu
prohibiting credit where a technique «
practice has the effect of enhancing
dispersion, regardles* of any other
justification.
Ruponte. In tha final regulation. Eft
has rejected tha polar positions
discussed above. Th* argument that
dispersion effects are forbidden
regardless of motive Is discussed and
rejected as a pan of the general
response to the argument that only
"well-controlled" sources can receive
any dispersion credit
Conversely, a pure "but for" test runs
the risk of Greeting exclusions that
effectively swallow the rule itself. The
EPA (udges that few, if any,
(0 STiM in
which some other benefit or justification
cannot b* assarted aa the basis for s
practice, and therefor* for such an
exclusion*
Where prospective evaluation of
merged gas streams, or combined
stacks, ia concerned, there is no reason
to assume the serious administrative
burdens investigating such ^*<"<* might
entail Th* court directed EPA to eppiy
an mrftt test "at a >«<»ttminn " «n«< Left it
free to take an approach that may be
less generous toward credit for
stack*. ^|r"~f sources in the
future wiU b* able to plan against the
background of rules that define
penmaeibie credits pntiMly, little
unfairn*** results from a restrictive
approach*
Wham ratmepectiv* application ia
""n^wrt^L however, the retroactiviry
analysts spaded out by tha court directs
that aa intent-baaed taat be employed u
described later. '
record en the** matters. EPA has
determined \Q take a "middle-ground"
approach to this queation. Tha final
regulation retains the same bread
prohibition found In the proposal on
increasing, exhaust gaa plume rise by
manipulation of parameters, or the
combining of exhaust gases from several
existing, stacks into one stack, with
several classes of exclusions. These
exclusion* recognize the existence of
independent Justifications based on
engineering and/or economic factors.
and include:
(1) Demonstration of original faculty
design and construction with merged
gaa stream*;
[2] Demonstration that merging after
July a, 196S ia part of e change in
operation that includes the install* non
of pollution controls and results in t net
reduction tn allowable emisaioos of the
pollutant for which credit is sought cr
-------
Federal Resists* / V0j. sa No. 130 / Monday. July a. 1965 / Ruje9 ,nd Radiations
(3) Demonstration that merging before
July 8.1905 writ pert of • change, uo
operation that included the installation
of control equipment or wit camad out
for lound economic or engineering
reason*. An allowable emissions
increaM creates the presumption that
the merging was not earned out for
sound economic or engineering
reasons."
Of these exclusions, the first is identical
to the proposal, and the second and
third are modifications of the second
exclusion included in the proposal with
a refinement based on prospective/
retroactive application.
The first exclusion was retained for
the reasons stated in the proposal After
reviewing the comments submitted. EPA
determined thet its previous
conclusion—that standard practice in
designing and coostntctiag facilities
routinely includes venting emissions
from several units into a common or
multiflued stack—is correct Sound
engineering and economic reasons.
based on costs of constructing and
maintaining separate stacks, availability
of land and cost savings for pollution
control equipment support facility
design and construction considerations.
Even if air pollution requirements did
not exist at ail sources would have
incentive* to use as few stacks as
poasible.
Since sacntuwg plume rise, rather
than phune rise itselt is a "dispersion
technique" and original design and
construction define the Initial base, such
original design aad construction of
merged gas streams is not considered a
dispersion technique. Moreover, In
designing the facility, a source can
usually choose to build one larger unit
rather than sevenl smaller units.
Therefore, prohibiting credit for ortgina/
design generally only effect the design
of units and not the phune rise.
Objections have been raised to
applying this logic to sources which are
constructed orer e period of time, bat
use a single stack. However, the same
factual arguments just listed would
apply is the same, if the original design
included provision for the additional
units in the plans for the facility, and in
the design and construction of the stack.
In such a ease, the later units merged .
into the stack would be included within
the exclusion.
In addition, it would be logically very
difficult to apply a rule* denying credif to
s.-final design stacks. EPA or the State
would have to assume how many stacks
Uatt tuod far •
if an M
would have been built absent a desire
for dispersion credit where they wodd
have been located and bow high they
would have been. Since these
alternative stacks would be portly
hypothetical then wodd be no clear
way of answering these questions: the
answer would simply have to be
selected arbitrarily from the wide rug*
of possible answers. This problem is
absent when existing stacks have been
combined
In contrast EPA finds change* from
the ongmal design of a facility in order
to include merged stacks to require •
narrower judgment The EPA cooduded
that where prospective application ia
concerned the exclusion should be
available only to sources that -^fpHifft
stacks reduces allowable •miftfrmt of
the pollutant tot which the credit is
granted There art obnoui
advantages in combining stacks to
reduce the number o/enuaaio* oomtrol
units that must be purchased la
addition, the installation of pollution
control for die pollutant ia question
provides fuhetantial assurance '**?* the
purpose of the combination ia not to
receive a more lenient tnusaioo limit
However, given past EPA gvfr^Ftf? OB
merging of stacks. EPA has concluded
that retroactive application of this tear
would not be proper. The EPA guidance
documents uniformly teak the view that
merging of separata stacks into a singia
stack "Is generally not considered a
dispersion technique'' absent other
factors such as excessive use of fans or
other devices.'* Each document
provided guidance to a source of a
Regional Office retarding the proper
treatment of merged sucks ia
calculating emission limitations. •
Considering these statements, EPA must
consider the standards expressed by the
court as previously discussed ia this
notice, ia judging the propriety of a
differing standard for retroactive
application. Given the nature aad
applications of the guidance which it
issued in the past EPA judges the first
two criteria—that la. whether the new
rule represents an abrupt departure from
well-estabtished practice, and whether
the parties against whom the aew rule ia
spplied relied on the former rule—to be
satisfied m addition, applying the
prospective criteria to past practice
would require significant change* in fuel
and/or control equipment for parties
whose emission limits were based on.
previous guidance. Finally, and
particularry where source* have not
been allowed to increase their
emissions as a result of the combining
stacks, EPA doe* not judge the statuto
interest to be overriding in this instan
since the rale even in its retrospective
version only exempts sources that can
show e reasonable non-dispersion
enhancement ground for combining
stacks, and thereby implements the
"intent" test suggested by the court. On
the other hand; EPA has never suggested
that combined stacks that cannot meet
such a test are proper. Sources whose
actual emissions an increased, or
whoee emission limitations are relaxed
in connection with the combining of
stacks create a strong presumption that
tat combination waa carried oat in
order to avoid me installation of
controls. Soch conbtnations would
indeed ran counter to die statutory
purpoe*. aad retrospective application
of a test thsit forbids them is therefore
proper.
Sxtmptiont from tht Definition of
Duptnian Ttchivqutt. The EPA
recalfwl maaereu* comments in
response) to its request for input on what
consideration, if any, should be given to
exciudBf aowcm from the definition of
TJtipanfoB Techniques" whose
•"ri*T*TPt are below a specified level or
whoee stacks an less than the dt
atiniaat height These commenters
argued that combining gis streams in
particular often had aa economx
Justification independent of its effect!
oa dispeietea. aad therefore should not
be geoienirf ftgpMUen. Other comments
stated tot m considering any such
exduatea. BPA should consider the
effect on tetol etmoepheric loadings.
Response. Some limitation on the
number of sources affected by the
deflaitiaa at "dispersion techniques'
necessary (or EPA to carry out the itack
height program. There are currently
estimated to be over 23JOO sources of
SO, m the United States with actual
emisaiona exceeding 100 tons per year. It
would not be possible for EPA or States
to review the emission limits of even a
significant friction of this number
within a reasonable lime period
Twenty-two thousand of these sources
have emietions lees than 5.000 tons per
year aad contribute a total of less than
13 percent of the to taJ annual SO»
emtsswo.lf For dais reason, and for
reasons of administrative necessity
discomed carter. EPA is adopting en
exemption from prohibitions on
manipolatifif plume rise for facilities
with allowable SOt emissions below
•Mcaonadwa fra Ouryl Tyter w
•otbbl«R. A«WI A rasa SM tito (MOT tai Wift
Butar Inm Hav** Ota. Oewtor » II
D««4 StoiMtatt » *MC* PUM. tarn 9.IMS,
MS. mi tnm D«nd!
to* lite ciM(xn. OAQPS
•*r»ttflc«eiao of SO, Poun
-------
27B04 Fed***1 Regutar / Vol. 50. No. 130 / Monday. July 8. 1965 / Rule* and Regulations
5.000 tons per year. Tbt EPA believe*
the effect of thi* exemption on total SOt
emissions to be de minima in nature.
Even if these sources wen able to
increase their emission rates as the
result of an exemption from the
definition of dispersion techniques, their
combined effect would not be
significant. Indeed, because these
sources are exempt on the basis of their
annual emissions, there exists an upper
limit to the extent to which they may
obtain relaxed emission limitations, Le,
to maintain an. exemption, the annual
emissions of a source may never exceed
5.000 tona per year. For these reason*.
the 5.000 ton limit passes a rV aunimit
test even more dearly than _« aft-malar
limit included without challenge in the
prior version of this role. Moreover, EPA
believes that a large majority of the**
sources would not be inclined to seek
lese stringent emission limitations. IB
part because a substantial portion of
them en baited by SUM and local fuel
useratee.
The EPA believe* at this time that a
d*mmimii state exemption is justified
only for sources of SOi and that the
number of small sources for which
emlsekm limitations for other pollutants
are a eiaBiflcant coocarn would not
support a similar exemption. The EPA
will (anrtaii* to review the need tor soca
exemption* and, if deemed appropriate.
will propose them for review and
comment at a ataixtat*.
Pfuaiflntpoction. The EPA received •
Dumber of comments pt^wf**"* chat
credit far piume uapacttoa be retained
on the (rounds that •itm*n»Hng fach
credit would have severe 'T***? OB
existing sources. Several approach**
were offered for overcoming plume
impaction effects in ">«dr%g to
determine omission limitations baaed on
CEP stack height Generally, thea* «
approaches focused on modifying thet
stack-terrain relationship repieeantad •
the models. Several commanter* argued
along these Unas that th* court
recognized and approved*** IRA's
attempt to avoid the efajcts-ef phnna
impaction. but only illesgoiiinil of
EPA's regulatory msthaj In allowing
sources to avoid impac ~~
commanters argued that the court did
not preclude EPA from allowing credtt
to avoid plume impactioa. but eauy from
allowing credit for stack height is
excess of CEP; this, it was argued, could
be remedied in a way that waa
consistent with the court decision by
incorporating impactioa avoidance
within the definition of CEP. It
suggested that EPA give its "later*!
approval* to the use of certain refined'
complex terrain models, in particular the
Rough Terrain Display Model (RTDM).
to calculate emission limitations for
sources affected by changes to the stack
height regulation.
Response. The.EPA agrees that the
court was cognizant of the problem of
plume impacooo and noted that there
was much to recommend EPA's
allowance of credit for impactioa
avoidance. However, the allowance of
credit for plume impactioa was not
remanded to EPA for revision or
reconsideration, but was reversed by
the court es exceeding EPA's authority.
The EPA doee nor agree that it would
be possible to redefine CEP in a manner
that allowed credit for avoiding
impactioa. since CEP it explicitly
denned in terms of preventing excessive
concentrations dae to down wash.
wakes, and eddies. Pram* impactioa is a
phenomenon completely unrelated to
dcrwnwash and. rather, is a consequence
of effluent gase* being emitted at aa
insuffldeat height to avoid their striking
downwind hillsides, cliffs, or
mountainaides prior to dilution.
Manipulation or "adjustment" of
modeling parameters to avoid predicting
theoretical plume impactioa where
actual stacks have bean constructed
above CEP would be tantamount to
granting the same impactioa credit that
was Invalidated by the court.
Furthermore. EPA believes that the
manipulation of modeling paremetan
for no other reason than to avoid aa
undesirable result la tfotoacally.
The EPA is In the peocees of revising
lt« "(Adeline oa Air Quality jabdel*7
A number of iadtviduaJe emamaotiBg oa
the guideline haw taojiaeiad that EPA
approve the us* of m* CIX7M modal aa a
of this iaeue caa oe food m documeata
associated with EPA's action oa the
modeling guideline (Docket Wo. A-«B-
46). With respect to (he revised stack
height regoiatioa. EPA has not refected
the use of KTDM,To ta* extent that
appropriate and complete data bases
and information on modal accuracy are
available. EPA may approve the aae of
RTOM oa a. ca**-by-ca** basis when
executed m accordance with th*
guideline requirements. Sponsors of
RTDM and presently developing more
extensive support for broader
applications of the model Wbea such
support 1* received and reviewed by
EPA. consideration will be given to
allowing more genera] use of RTDM in
regulatory activities such aa compliance
with the suck height rale.
TlaiftabJf for Stuff lapltatatation.
A cumber of commenten suted that it
was not possible to conduct the
necessary analyse*, prepare and
revised State rules and source-ipecific
emission limitations within the 9-mont.
tiaefraaie referred to in the November
proposal A variety of alternative
schedule* wen proposed by these
commenten for consideration by EPA.
ResponM. A* with EPA's previous
allowance of credit for plum* impactioi
the timetable for preparation and
submittal of revised SIP'S was not an
issue remanded by the court The EPA i,
in agreement that these revisions to the
suck height regulation will require
significant efforts by Sute and local
agencies, individual emission source
owners and EPA Regional and
Headquarters offices in order to comply
within the 0-aoam ttmefranu required
by section 40B(d)W of the 1977 Clean
Air Act Amendment!. It was based on
this concern that EPA originally
provided'a two-etap process for Sutes
to follow m revising their plans and
submitting them to EPA for approval
However, the court found that this effort
was explicitly contrary to section
406(dK2fand ordered EPA to follow the
••month schedule provided in the dean
Air Act
Afar SOvrctt Tl»d into Pr9-187fk
Stacks. A* indicated earlier, in response
to the coot opinion. EPA proposed to
deay "graadfathered" sutus to post-
1970 source* tying into pre-1971 stacks.
Some commentan stated that EPA wac
in no way prohibited from allowing
credit lor new source* ducted Into pre-
1971 stack* exceeding CEP height
Rather, they indicated that EPA simply
had to provide Justification for such
allowance.
Other oosnmeatan indicated general
support tar EPA'* proposal with respect
to aew source* tying into graadfathered
•tack*, bat enggiiM that several
expansion* or dexStcatioB* be
provided moat notably that la additioa
to raw and major modified sources.
reconstructed sources not be allowed
greater than CEP stack height cadi*
when tying into gieatar than CEP stacks.
Aavpona*. In further review of this
Issue. EPA caa find no convincing
rationale to allow eswcas constructed
after December 31. ttTOi to «v«4d CEP
restrictions simply by dacang their
imlsslnns iato a stack that is
-grandfathered" under section 123. On
the contrary, m* iataat of section 123 to
limit credit Cor stack height in excess of
CEP suggests that EPA should not allow
credit for such stack height sxeept to
honor financial commitments mad* prior
to the end of 1970. Source* In existence
after that date should be treated equally
under the regulation and not allowed ta
avoid legitimate control requirement*
-------
FadajraJ Reystar / V0L 50. No. 130 / Monday. July a. 1965 / Rules M(2)(E) hss bera added
to exclude from the definition of
prohibited "dispersion techniques" the
use of techniques affecting final exhaust
gas plume ns« where the resulting total
allowable emissions of SO» from the
facility do not exceed 5.000 tons per
year.
Section 51. l(ii)(11 has been revised to
specify that the 65 meter de minims'
height i« to be measured, as in other
aetenmaations of CEP stack height.
from '£e ground-level elevation at the
base s' the stack. This does not
represent a substantive change in the
rule :: in its application relative to past
practices, but rather a simple
clarification.
Section St.l(ii)(2) has been revised to
require that source owners demonstrate
that the 2.3H formula was relied on in
establishing the emission limitation.
Section 51.1(ii)(3) has been revised a*
discussed elsewhere in this notice to
specify that an emission rate equivalent
to NSPS most be met before a source
may conduct fluid modeling to Justify
stack height credit in excess of that
permitted by the CEP formulae.
Section 51.1(jj) now defines "nearby"
for purposes of conducting field studies
or fluid modeling demonstrations as OJ
km (H mile), but allows limited
consideration of terrain fsatuns
extending beyond that distance If such
features "begin" within 04 km, aa
defined in the regulation.
Section Stl(U) hss been revised to
provides separate discussions of
"excessive concentrations" for the
separate situations discussed earlier in
this preamble. As that discussion makes
clear. EPA believes that the differing
categories of sources subject to this rale
an best addressed by requirements tiiat
vary somewhat with those
circumstances. This definition embodies
that approach.
Section 51,12(k) has been corrected to
provide that the provisions of I 51.12(0
shall not apply to rtodr AsujgAo; in
existence before December ft. 107& The
proposal had mconettly stated that
". . . I 51.12 shall not apply to itoda
existence.. . ."
This regulation dots not Hmrt the
physical stack height of any source, or
the actual ose of dispersion technique*
st a source, nor dose it require any
specific stack height for any soarca.
Instead, it seta limits on the aaxtsma
credit for stack height and othar
dispersion techniques to be used in
ambient air modeling for the purpose of
setting an emission limitation and
calculating the air quality impact of a
source. Sources an modeled at their
actual physical stack height unless Out
height exceeds their CEP stack height
The regulation applies to all stacks in
existence and all dispersion techniques
implemented since December 31.1970.
State hnpiacoeatadon Plan
Requirements
Pursuant to section 406(dK2) of the
dean Air Act Amendments of 1997,
EPA is requiring that all States (1)
review and revise, as necessary, their
SIP'S to include provisions that limit
stack height credits and dispersion
techniques in accordance with this
regulation and (Z) review all existing
emission limitations to determine
whether any of these limitations have
been affected by stack height credits
above CEP or by any other dispersion
techniques. For any limitations that
have been so affected. States must
prepan revised limitations consistent
with their revised SIPs. All SIP
revisions and revised emission
limitations must be submitted to EPA
within 9 months of promulgation of this
regulation.
Interim Guidance
In its proposal. EPA stated that it
would use the proposed regulation to
govern stack height credits during the
period before promulgation of the final
regulation. Thai EPA further stated that
any stack height credits that an granted
based on this interim guidance would bt
subject to review against the final rules
and may seed to be revised.
Consequently, with these final rules.
EPA is requiring that any actions that
wen taken on Hack heights and stack
height credits during this intern penod
be reviewed and revised as needed to
be consistent with this regulation.
HsfoLatory neodbtBry Analysis
Pursuant to the provisions of 5 U&C.
606(b). I hereby certify that the attached
rule will not have "g"'fr^m economic
impacts on a substantial number of
snail entities. This rule is structured to
apply only, to Una) sources; La- those
with stacks above 06 maters (213 feet).
or with annual SOk emissions in excess
of MOO tons, a* further noted in the rule.
Based on aa analysis of impacts, electric
utility plants and several smelters and
pulp •"** paper mills will be
significantly afflicted by this regulation.
Exacatfv* Older 122*1
Under Executive Order 12291. EPA
must Judge whether a regulation is
"major" and therefore subject to the
requirement of a regulatory impact
analysis. EPA's analysis of economic
impacts predicts a potential cost to
emission source owners and operators
exceeding StOO million: therefore, this is
a major rale under Executive Order
12291. However, due to the promulgation
deadline imposed by the court. EPA did
not have sufficient time to develop a full
analysis of costs and ber.efits as
rrcmnd by the Eixscut:ve Order.
Consequently, it is not possible to judge
the annual effect of ih:s rale on the
economy. A pnttminarv economic
impact analysis and s ^ejuent revision
wen prepared and a:- i ie docket.
For any facility, the a .• r:alify and
economic impact of Lk.<; siack height
regulation genersJly de^tr.it on ths
extent to which the scv;d! stack at that
facility conforms to CE? s^dc height.
-------
27906
Federal Register / Vol. 50. No. 130 / Monday. July 8. 1965 / Rules and ReguJe lions
Thus, when tht regulation it applied to
large sources. ie~ those with itaek
height gnater than CEP and emissions
greater than 5.000 tons per year, it will
have the potential for producing
emission reductions and increased
control costs.
A preliminary evaluation of the
potential atr quality impacts and a cost
analysis of the regulation was
performed at the time of proposal. The
impacts identified were established in
isolation of other regulatory
requirements. The report predicted a
range of impacts, from a "low impact"
scenario that presumed that many
potentially affected source* would be
able to justify their existing suck
heights, configurations, and emission
limitations to a "high impact" scenario
which assumed that all of the potentially
affected sources would be required to
reduce their emissions to some degree.
In the development of its final
rulemaking action, EPA refined its-
evaluation of potential impacts,
producing revised estimates of the
probable coets of the changes to the
regulation and expected reductions in
SOi •missions. As a result of this
refinement EPA estimates that the nrie
will yield reductions in SQt emissions of
approximately 1.7 million tons per year.
The annualizad cost of achieving these
reductions will be aproximateiy $790
million, and the capital coat is expected
to be approximately S700 million.
This regulation waa reviewed by the
Office of Management and Budget, and
their written comments and any
responses are contained in Docket A-
83-48.
Judicial Review
The EPA believes that this rule is
based on determinations of nationwide
scope and effect Nothing in section 123
limits its applicability to a particular
locality, State, or region. Rather, section
123 applies to sources wherever located.
Under section 307(b)(l) of the dean Air
Act [42 U.S.C 7607(b)(l)i, judicial
review of the actions taken by this
notice is available only by the filing of a
petition for review in the United States
Court of Appeals for the District of
Columbia and within 60 days of the date
of publication.
List of Subjects in 4fl CFR Part 51
Air pollution control Ozone, Sulfur
dioxide. Nitrogen dioxide. Lead,
Paniculate matter. Hydrocarbons.
Carbon monoxide.
Dated: June 27.1915.
UeMTheaua,
Adminntntor.
PAP/T 51-freOUMCMENTS POH
PREPARATION, ADOPTION, AMD
SUBMrTTAL OP IMPLEMENTATION
PUNS
Part 51 of Chapter L Title 40 of the
Code of Federal Regulations is amended
as follows:
1. The authority citation for Part 51
continues to read as follows: j
Authority: Sec. 110. 301 ft), and 123. Oeaa
Air Act is amended (42 VAC. 7410, 7*n(»)
•ad 7429 J.
2. Section 51.1 is amended by revising
paragraphs (hh). (U), Oft and (kk) as
follows:
(hfe'fi) "Dispersion technique" means
any ( onique which attempts to affect
the concentration of a pollutant in the
ambient air by:
(i) Using that portion of a stack which
exceeds good engineering practice stack
height:
(ii) Varying the rate of emission of*
pollutant according to atmospheric
conditions or ambient concentrations of
that pollutant or
(iii) Increasing fl"fl exhaust gaa
plume rise by manipulating source
proceee parameters, exhaust gas
parameters, stack parameters, or
cftffihin'Be •'*^>"fft gases from several
existing sucks into on* stack; or otaee
selective handling of exhaust gat
streams so aa to increase the exhaust
gas plume tie*.
(2) The preceding sentence doe* not
include:
(i) The reheating of • gas stream.
following use of a pollution control
system, for the purpose of returning the
gu to the temperature at which it waa
originally discharged from lite facility
generating the gaa stream:
(ii) The merging of exhaust jaa
streams when:
(A) The source owner or operator.
demonstrates that the facility waa
originally designed and constructed with
such merged gas streams;
(B) After July S. 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
•ffectec- by such change in operation: or
(C) Be/ore July & IMS. such merging
was part of a change in operation at the
facility that included the installation of
emissions control equipment or wai
carried out for sound economic or
engineering reasons. When there wai
an increase in the emission limitation o
in the event that no emission limitation
was in existence prior to the merging, ai
increase in the quantity of pollutants
actually emitted prior to the merging, thi
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:
(iii) Smoke management in
agricultural or stlvicultural prescribed
burning programs;
(iv) Episodic restrictions on
residential woodbuming and open
burning; ee
(v) Techniques under I Sl.l(hh)(i)(iii)
which increase final exhaust gaa plume
rise where the resulting allowable
•missions of sulfur dioxide from the
facility do not exceed 5400 tons per
year.
(ii) "Good engineering practice" (CEP)
suck height means the greater of:
(1) 65 meters, measured from the
ground-level elevation at the base of the
aUdc
(2) (i) For sucks in existence on
Janoary 12, 1978, and for which the
owner or operator had obtained all
applicable permits or approvals required
under 40 CFR Parts 51 and 52,
H.-13H
provided the owner or operator
produces evidence that this equation
was actually relied on in establishing an
cmisMoa limitation:
(ii) For all other sucks.
H.-H+1JL. »
whore
H,-r»od •nemMrtaf practice Mick height
measured from the ground-level
•levstioa »r the base of the luck.
H - height of nearby •tructur*(i) tMMurcd
from the srouod-kvei eleveuon it tht
hue of the ttack.
L-lnMT Hi«»««»«*"«t height or protected
width, of nearby §trucnirtd)
provided that the EPA, State or local
control agency may require the use of •
field study or fluid modal to verify CEP
suck height for the source: or
(3) The height demonstrated by a fluid
model or a field study approved by the
EPA State or local control agency. *n'cil
ensures that the emissions from a itacic
do not result in excessive
-------
Federal Register / Vol. 50. No. 130 / Monday. July 8. 1985 / Rules and Regulations
2790'
concentrations of any nr pollutant as a
result of atmospheric downwaah. wakes.
or eddy effects created by the source
itself, nearby structures or nearby
terrain features.
(jj) "Nearby" as used in | Jl.l(ii) of
this part is defined for a specific
structure or terrain feature and
(1 j for purposes of applying the
formulae provided in i 5M(n)(2) 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 km (H
mile), and
12) for conducting demonstrations
under | 31.1(ii)(3) means not greater '
than 04 km (H mile), except that the
portion of a terrain feature may b«
considered to be nearby which fails
within a distance of up to 10 times the
maximum height (H,) of the feature*, not
to exceed 2 miles if such feature
achieves a height (HJ 04 km from the
stack that is at leest 40 percent of the
GEP stack height determined by the
formulae provided in f 51.1(ii)(2)(ii) of
this part or 28 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.
(kk) "Excessive concentration" la' '
defined for the purpose of determining
good engineering practice stack height
under f Sl.l(ii)(3) and mean*:
(1) for sources seeking credit for stack
height exceeding that established under
I 51.1(ii)(2), a "»•*'"""» ground-level
concentration due to emissions from a
suck due in whole or put to downwash,
wakes, and eddy effects produced by
nearby structures or nearby terrain
features which individually is at least 40
percent in excels of the maximum
concentration experienced in the
•b»ence of such downwash. wakes, or
eddy effects and which contributes to a
total concentration due to emissions
from all sources that is greater then an
ambient air quality standard. For
sources subject to the prevention of
significant deterioration program (40
CFR SIJ4 end 52.21). 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
which individually is at least 40 percent
in excess of the maximum concentration
experienced in the absence 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 "r*Mnt demonstrations
under this pert 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 authority
administering the State implementation
plan, an alternative emission rate shall
be established in consultation with the
source owner or operator;
(2) for sources seeking credit after
October 11063, for Increases in existing
stack heights up to the heights
established under } 3Ll(ii)(2), either (i)
a ***TT»"r> ground-level concentntioo
due in whole or part to downwaah.
wakes or eddy effects as provided in
paragraph (kkXl) of this section, except
that the emission rate specified by any
applicable State implementation plan
(or. in the absence of each a bait the
actual emission rate) shall be used, or
(ii) the actual presence of a local
nuisance caused by the existing stack.
as determined by the authority
administering the State iapleaastatfoa
plan: and
(3) for sources seeking credit after
January 12.1979 for a stack height
determined, under f SLl(ii)(2) where the
authority administering the State
implementation plan require* the use of
e field study or fluid model to verify
CEP stack height for sources seeking
stack height credit after November 9.
1984 based on the aerodynamic
influence of cooling towers, and/or
sources seeking stack height credit a/
December 31.1970 based on the
aerodynamic influence of structures not
adequately represented by the equations
in 151.1(10(2), a maximum ground-level
concentration due in whole or part to
downwash. wakes or eddy effects that
is et least 40 percent in excess of the
maximum concentration experienced m
the absence of such downwash. wakes.
or eddy effects.
3. Section 91.1 Is further emended by
removing paragraphs (11) and (mm).
fltlj (Amende*)
4. Section 31.12 is amended by
removing paragraph (1).
9. Section fll.!2(J) is amended by
removing "and (1)" from the first
sentence.
& Section 91.1200 to revised as
follows?
(k) The provisions of i 51.12(j) ihail
not apply to (1) stack heights in
existence, or dispersion technique*
Implemented on or before December 31.
1970. except where pollutants are being
emitted from such stacks or using such
dispersion techniques by sources, as
defined la section lll(e)(3) of the Clean
Air Act which were constructed or
reconstructed or for which major
modifications, as defined in
f I 9L18«XlMvWaJ, 91J4(bK2Ki) and
9Z2I(bM2)fl). wan carried out after
December 91 J97tt or (2) coal-fired
steaa electric generating units subject
to the provisions of Section 118 of the
Clean Air Act which commenced
operation before July 1.1887, and who*e
stacks were constructed under s
construction contract awarded before
February *. 1974.
7. Section 91.13(1) is amended by
moving "and (1)" from the first
|F* Deo. aa-taOM filed f-4-8* • « •m]
-------
EPA-450/4-80-023R
Guideline for Determination of Good
Engineering Practice Stack Height
(Technical Support Document for the
Stack Height Regulations)
(Revised)
US ENVIRONMENTAL PROTECTION AGENCY
Office of Air ana Radiation
Office of Air Quality Planning ana Standaras
Research Triangle Park. NC 27711
June 1985
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
•sffi*;
OCT 2 8 1985
MEMORANDUM
SUBJECT: Implementation of Stack Height .Regulations - Presumptive NSPS
Emission Limit for Fluid Modtfffng StacK'Above Formula GEP Height
FROM: Darryl D. Tyler, Director /
Control Programs Development Division (MD-15)
TO: Director, Air Management Division
Regions I-X
The following guidance is provided to explain the general emission
control requirements for sources conducting fluid modeling to justify stack
height in excess of that provided by the GEP formulae. While some of the
discussion and examples contained herein focus on utility sources, the
procedures outlined in tnis memorandum are generally applicable to all
stationary source categories. Please note that this 1s guidance. States
may present any other demonstrations that they may feel are warranted in
individual circumstances.
Background
.The revised stack height regulations published on July 8, 1985, define
three methods for determining good engineering practice (GEP) stack
height. These methods include:
1- a 65 meter de mini mis GEP height;
2- the height determined by using an applicable formula based on the
dimensions of nearby buildings; and
3- the height necessary to avoid excessive concentrations due to
downwash as shown using a field study or fluid modeling
demonstration.
As the preamble to the regulations points out, the revised definition
of "excessive concentrations," a 40-percent Increase in concentrations
due to downwash resulting in a NAAQS or PSD increment exceedance,
necessitates that an emission rate be specified for purposes of evaluating
fluid modeling. The regulations require that a presumptive emission rate
equivalent to the new source performance standards (NSPS) be established
for the source in question before modeling may be conducted to determine
-------
stack height needed to avoid excessive concentrations due to downwash.*
This emission nte is described as "presumptive" because it is EPA's
presumption that all sources seeking to justify stack heights exceeding
those provided by the GEP formulae are capable of controlling their
emissions to NSPS levels. However,, the regulations also allow source
owners or operators to rebut this presumption, establishing an alternative
emission rate that represents the most stringent level of control that
can feasibly be met by that source in excess of the NSPS level. In the
preamble to the regulations, EPA Indicated that 1t will rely on the
"Guidelines for Determination of Best Available Retrofit Technology for
Coal-Fired Power Plants and other Existing Stationary Facilities,
EPA-450/3-80-009b" (SART Guidelines) whan reviewing these rebuttals.
If it is infeasible for a source to control Its emissions to NSPS
levels, then an alternative limit representing the lowest feasible emission
limit must be met before obtaining credit for stack height in excess of
GEP formula height. Sources may consider such factors as remaining plant
life and the cost of modifyin; existing equipment when determining NSPS
feasibility.
Procedures
The general procedure that is described in the BART Guidelines for
analyzing control alternatives should be followed to identify and evaluate
alternatives for sources seeking credit for stack heights in excess of
those produced by the applicable GEP formulae. Because the guidelines
were originally written to address visibility Impairment, however, not all
of the analytical steps or applicability criteria—such as analysis of
visibility impairment or exemptions for power plants below 750 megawatts—
will be appropriate, and need not be addressed.
General steps in the analysis described in Section 2.0 of the
guidelines can be summarized as follows.
1. Identify a range of control alternatives, including both pre- and
post-combustion controls. In this regard, several fuel substitution and
alternative fuel blends should be considered, as well as technological
alternatives, such as coal c'eaning and flue gas desulfurization.
2. Calculate tie cssi, emissions, and other environmental and energy
impacts of the alternatives ^including those meeting NSPS objectives).
3. Select the alternative that represents the most stringent level
of emissions control feasible.
*Where the HS?S ias been subject to revision, and the source in
question is not subject to the revised NSPS, the earliest standard will be
applied; e.g., for po*er plants a rate of 1.2 Ib/mm3tu would be used.
-------
In performing these analyses, it is important to keep in mind that
EPA's presumption is that the NSPS emission limit is feasible unless
demonstrated otherwise. When carrying out evaluations, source owners or
operators may consider such factors as remaining useful plant life, the
remaining life of any equipment affected by revised emission rates
(including any control equipment), the cost of modifying boilers, control
equipment, and fuel handling facilities, and the cost of modifying or
cancelling existing fuel supply contracts (remaining useful plant life,
if a significant factor in determining NSPS feasibility, may necessitate
restrictions on the period of applicability of less stringent emission
limits). Finally, it is important to analyze, not only a range of alter-
native controls, but several combinations of alternatives, since such
combinations may yield a greater and more cost-effective degree of
emissions control.
Since determinations of the adequacy of any rebuttals of the NSPS
emission limit and the reasonabl* "ess of control alternatives considered
must be made on a case-by-case bs-is, and will be subject to public review
and comment during the rulemaking process, all technical and economic
analyses, as well as any claims of infeasibility, must be fully documented
and supported by any information that may be available.
If you have any questions regarding the application of this guidance
in a particular set of circumstances, please contact Eric Ginsburg at
(FTS) 629-5540 or Sharon Reinders at (FTS) 629-5526.
-------
\
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
AP??
Mr. John P. Proctor
Bishop, Cook, Purcell and Reynolds
Law Offices
1400 L Street, N.W.
Washington, D.C. 20005-3502
Dear Mr. Proctor:
Your letter of February 23, 1989 to Administrator Reilly was
referred to roe for response. The issues you describe were
previously raised to the attention of the Environmental
Protection Agency's (EPA's) Region III Office. You now question
Region Ill's rejection of your position that the best available
retrofit technology (BART) emission rate used in determining the
creditable stack height can be ignored for purposes of setting
the facility's operating rate as long as the operating rate is
consistent with the national ambient air quality standards
(NAAQS). The response provided to you by Region III on October
6, 1988 was extensively discussed with this office and with the
Office of General Counsel, and we fully endorse Region Ill's
conclusions and supporting rationale.
In your letter you stated that the sole basis for conducting
a fluid modeling study is to justify credit for stack height
above formula height, and that nothing requires States to rely on
the BART emission rate to determine the appropriate operating
rate. Actually, as noted by Region III, before such credit may
be considered, the preamble to the stack height regulation is
clear that the operating rate must be limited to the BART or new
source performance standards (NSPS) rate. The preamble to the
stack height regulation also notes that an emission limit more
stringent than BART/NSPS may be needed because the sources must
also meet the NAAQS and prevention of significant deterioration
requirements.
We agree with Region Ill's conclusion that NRDC v. Thomas.
838 F.2nd 1224 (D.C. Cir 1988), does not support your position.
In your February 23, 1989 letter to Administrator Reilly, you
raise a new argument not presented to Region III. You argue that
the court recognized that operating emission limitations are to
be determined after stack height credit has been calculated,
based on the court's acknowledgement that Congress imposed
technology-based limits in some situations, and EPA has authority
to mandate such limits for modeling demonstrations to determine
stack height credit. From this you conclude that a technology-
based emission rate used for fluid modeling is relevant only to
rhat modelina.
-------
In response, we point out first that the court's discussion
of technology-based emission limitations (838 F.2d at 1241) was
in reference to NRDC's control-first position and not related to
fluid modeling as you suggest. We believe that the opinion
indicates clearly that the court regarded the presumptive NSPS
emission limit as a limit that must be complied with once the
fluid modeling was completed ("We find the attempt of industry to
bar control-first no stronger than NRDC's effort to require it in
the within-formula context." 838 F.2d at 1241; "... industry
petitioners assert that in order to use the NSPS presumption, EPA
must be able to point to substantial evidence that it is attain-
able by most of the affected sources. But as EPA allows any
source to use a higher emissions rate when NSPS is infeasible,
there is no need for any sort of generic demonstration that it is
normally so." id at 1242).
Second, in quoting EPA's statement about the significance of
fluid modeling demonstrations, the court was merely citing with
approval EPA's rationale for refusing to grandfather demonstra-
tions undertaken and approved prior to adoption of the 1985
regulations. This in no way implies a finding by the court that
the presumptive NSPS requirement (or higher BART limit) is not
the constraining limit. Neither of these references provides
support to your position.
In conclusion, we are in full agreement with the position
taken by Region III that sources seeking credit above formula
height must meet an emission rate consistent with BART/NSPS.
While final action as to any particular source would necessarily
await a State implementation plan revision, I hope the above
responds to your inquiry. Staff in our Region III Office are
available to assist you and your client, and I suggest that you
contact them directly if you have further questions.
Sincerely,
Gerald A. Emison
Director
Office of Air Quality Planning
and Standards
cc: Charles Carter. OGC
Thomas Maslany, Region III
Marcia Mulkey, Region III
bcc: Robert Bauman, AQMD Pat Embrey, OGC
Jesse Baskerville, Region III Eric Ginsburg, AQMD
John Calcagni, AQMD Doug Grano, AQMD
SDPMPB:DGrano:DataTech/PROCTOR2:PFinch:RTP(MD-15) -.629-5255: 4-4-89
Control Number OAQP5--5- Due Date: 4-3-89
-------
i_*w crriCES
BISHOP, COOK, PURCELL & REYNOLDS
L STREET.- N W
WASHINGTON. DC 2OOO5-35O2
(202) 37I-570O
WHITER s OIPCCT oi»i_ February 23, 1989 TELEX *»os7i INTLAW ui
TELECOPIER (2OJ) 371 S95O
William K. Reilly
Administrator
United States Environmental
Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Dear Mr. Reilly:
The purpose of this letter is to request EPA's
concurrence with a conclusion reached by this firm
pertaining to the setting of emission limitations for
existing sources that receive credit for stack height above
Good Engineering Practice ("GEP") stack height.
Specifically, I am seeking your concurrence with the
following conclusion: that a facility which uses a Best
Available Retrofit Technology ("BART") emission rate in a
fluid model to determine GEP stack height may ultimately
receive a different operating emission rate as long as that
rate is demonstrated by a dispersion model as being
consistent with the National Ambient Air Quality Standards
("NAAQS"). EPA's consideration of this issue and response
is extremely important since the Agency's position will have
an immediate and long-term economic impact on one of our
client's operations. As pertinent here, our client must
make a major business decision regarding equipment
purchases, a possible shutdown of operations and technical
operating requirements. That decision is inextricably
linked to the stack height issues; it will be primarily
determined and affected by your response to this query.
For purposes of this discussion and request, I am
setting forth our analysis and position below as to what
legally appropriate procedures must be followed in
establishing operating emission rates pursuant to
Section 110 of the Clean Air Act for facilities receiving
credit for stack height above GEP formula height. In brief,
I believe this analysis supports our position that a
facility is not required to conduct a dispersion modeling
study that uses the same emission rate for a particular
pollutant that was used by the facility in justifying st^'jk
*."• ,
V'' '"
-------
winiam K. Re illy
February 23, 1989
Page 2
height above GEP formula height; i.e., fluid and dispersion
modeling emission rates are to be developed and applied
independently. Thus, a state may authorize an emission rate
for a particular pollutant at a facility as long as the
emission rate is demonstrated by a dispersion model as being
consistent with the attainment and maintenance of the NAAQS.
Our analysis follows:
(a) In order to receive credit for stack height above
GEP formula height, a facility must conduct fluid modeling
studies to analyze the effects of terrain obstacles on
downwash, and to show that the additional height is needed
to avoid "excessive concentrations"; i.e., a 40 percent
increase in concentrations due to downwash that cause or
contribute to an increase or.an exceedance of air quality
standards or PSD increments.
(b) To complete the fluid modeling studies and to show
that there will be excessive concentrations, a facility must
obtain a BART emission rate from tne applicable state agency
for each source. Although EPA's stack height regulations
initially require a source seeking to conduct a fluid
modeling study to use an emission rate equivalent to that
New Source Performance Standards ("NSPS") applicable to the
industrial source category ("presumptive NSPS emission
limit"), a source is permitted to rebut the applicability
of the presumptive NSPS emission limit.
(c) The sole basis for conducting a fluid modeling
study, and for obtaining an alternative emission rate to
complete the study, is to.justify credit for stack height
above GEP formula height. The rate is but one aspect of
justifying stack height above GEP formula height, and GEP
stack height is but one aspect in determining an appropriate
operating emission rate. See Section 123(a)(1) of the Clean
Air Act, 42 U.S.C. § 7423(a)(1). In short, there is
nothing in either the Clean Air Act or the implementing
regulations that requires or advises the states to use or
rely upon the BART emission rate, used for a fluid modeling
U 40 C.F.R. § 51(kk).
2/ 50 Fed. Reg. 27892, 27898 (July 8, 1985).
3/ 50 Fed. Reg. 278?2, 27898 (July 8, 1985).
I/ In this section, Congress limits the degree to which tall
stacks may be considered in setting emission limitations. As
is apparent from the statutory language used in Section 123,
Congress intended to allow the states to consider other
factors, in addition to stack height, in setting emission
limitations.
-------
William K. Reilly
February 23, 1989
Page 3
study, in conducting a dispersion study to determine an
appropriate operating emission rate.
(d) States are required to ensure the attainment and
maintenance of the NAAQS by establishing emission
limitations for facilities within their boundaries.
Moreover, with respect to existing sources, states have the
discretionary authority to determine and enforce whatever
mix of emission limitations it deems best for these sources,
as long as the overall effect is compliance with the NAAQS.
Train v. N.R.D.C.. 421 U.S. 60,79 (1974).
We believe our analysis and conclusion are supported by
the District of Columbia Circuit Court of Appeals' recent
decision in N.R.D.C. Inc. v. Thomas. 838 F.2d 1224 (D.C.
cir. 1988) in which the court reviewed EPA's stack height
regulations and the NRDC's argument that a source must apply
all available emission controls before it may justify a
stack height above GEP formula height. The Court of Appeals
rejected NRDC's "control-• vrst" argument fid, at p. 1235)
because it recognized tha^. BART (stack height) emission
rates and source-related emission limitations have
independent purposes: "Although the record does not allow
us to infer exactly the impact of the baseline emissions
rate on the emissions rate that would emerge (after the
stack height credit were calculated and then used to
determine the permissible emissions), all parties agree that
the impact is substantial. Indeed, that is what the issue
is all about. If Congress in Section 123 prescribed the use
of such a baseline emissions rate, with all its implications
for ultimate emission ceilings, it did so in a remarkably
cryptic way." Id. at p. 1236.
As is evident, the Court of Appeals recognized that
operating emission limitations are to be determined after
stack height credit has been calculated pursuant to
Section 123 of the Act. This conclusion is supported by the
Court's consideration of the following facts. First, the
Court observed that Congress imposed technology-based
emission limitations (including NSPS, BACT, LAER, RACT and
BART) in a variety of situations, and that EPA has the
authority to mandate a specific technology-based emission
limit (e.g., the presumptive NSPS limit) for GEP fluid
modeling demonstrations (id. at p. 1241) used for
calculating stack height credit. Second, the Court noted
that a "* * * xfluid modeling demonstration has no
significance apart from showing whether the source qualified
for credit under the stack height guidelines than in
effect.'" (emphasis in original). Id. at p. 1249. As
pertinent here, the Court's analysis supports the conclusion
that a specific technology-based emission rate used by a
facility in a fluid modeling demonstration is significant
only to the extent that it demonstrates whether a source
-------
william K. Reilly
February 23, 19S9
Page 4
should receive credit for stack height above GEP formula
height. A different conclusion; i.e., that the emission
rate used to calculate stack height (either a BART rate or
the presumptive NSPS rate) should be used by a facility,as
its operating emission rate, is contrary to the Court's
holding which rejected the "control-first" argument.
Please be advised that an EPA staff person, contacted by
our firm, appears to have reached a different conclusion.
Specifically, we have been advised by this staff member that
an existing source is required to operate at the lowest
emission rate resulting either from the -stack height
demonstration or dispersion study — even though another
(i.e., higher) emission rate will assure compliance with the
NAAQS.
It is our opinion that this position is inconsistent
with Sections 110 and 123 of the Clean Air Act, the stack
height regulations, and existing case law. Therefore, we
are requesting EPA's analysis of this issue and official
agency position. We would appreciate your prompt review of
tnis issue due to the impact that your response will have on
our client's operations and financial planning.
If you have any questions regarding this issue, please
feel free to contact me directly. Also, I have enclosed an
extra copy of this letter and a stamped, self-addressed
envelope. Would you please stamp this extra copy and return
it to me for our files.
JPP:cas
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park. Nortn Carolina 27711
OCT 1 0 1985
MEMORANDUM
SUBJECT: Questions and Answers on Implementing the
Revised Stack Height Regulation
FROM: G. T. Helms, Chieff' L U**—*
Control Programs Operations Branch (MD-15)
TO: Chief, A1r Branch, Regions I-X
A number of questions have arisen in several areas of the revised
stack height regulation since its promulgation on July 8. The following
answers have been developed in response. The questions and answers are
arranged under the general topic headings of interpretation of the regula-
tion, State implementation plan (SIP) requirements, and modeling analyses.
Please continue to call Sharon Relnders at 629-5526 if you have further
comments or additional questions.
Interpretation of the Regulation
1. Q: What criteria should be used to determine when a stack was "in
existence" with respect to the various grandfatherlng dates in the
regul ation?
A: The recent promulgation of revisions to the stack height regulatic
did not change the definition of "in existence." The definition is provic
in 40 CFR Sl.l(gg) and includes either the commencement of continuous
construction on the stack or entering into a binding contract for stack
construction, the cancellation of which would result 1n "substantial
loss" to the source owner or operator. The definition of what constitutes
a "substantial loss" will be the subject of future guidance.
2. Q: What "source" definition should be used in determining whether tie
ins to grandfathered stacks should be permitted or prohibited?
A: The term "source" in this instance means a single emitting unit.
Thus, credit for tying a single post-1970 unit(s) Into a grandfathered
stack serving a number of old units is prohibited under the regulation.
-------
-2-
3. Q: What is meant in the regulation by "facility"?
A: For purposes of this regulation, the definition contai-ned in
40 CFR 51.301(dj should be used. That definition essentially defines the
term as the entire complex of emitting activities on one property or
contiguous properties controlled by a single owner or designee.
4. Q: Must good engineering practice (SEP) stack height be established
separately for each pollutant? If not, how should it be determined?
A: It is not necessary to calculate a separate 6EP stack height for
each pollutant. Since "SEP* is defined by Section 123 of the Clean Air
Act as the height necessary to ensure against excessive concentrations of
any air pollutant, it follows that GEP should be established for each
source based on the pollutant requiring the greatest height to avoid
excessive concentrations.
5. Q: How should "reliance" on the 2.5H formula be determined?
•
A: First, "reliance" on the 2.5H formula applies only to stacks in
existence before January 12, 1979. Credit for "reliance* on the 2.5H
formula, can be granted under the following cases: (a) Where the stack
was actually built to a height less than or equal to 2.5H; (b) Where the
stack was built taller than 2.5H and the emission limitation reflects
^
use of 2.5H in the SIP modeling analysis; or (c) Where evidence is proviaB
to show "reliance" as discussed in the following paragraph. If no model™
was used to set the emission limitation for the source, then it cannot b€
argued that there was "reliance" on the formula, since EPA's guidance was
specifically aimed at using stack height credit in establishing emission
limitations. Once it is determined that the emission limitation was in
fact based on estimates of dispersion from the stack, then the source can
be said to have properly "relied" on .the 2.5H formula. In the event that
it cannot be determined that the emission limit is based on "reliance" on
the 2.5H formula, then the refined H + 1.5L formula must be used.
Where a clear relationship between a 2.5H stack height and the
emission limitation cannot be shown, where the emission limitation was
not calculated based precisely on the 2.5H height, or where the stack
height used in modeling cannot be verified, then additional evidence will
be needed. Preferred would be written documentation, such as copies of
the original engineering calculations or correspondence between the State
or the emission source owner and EPA indicating that the 2.5H formula
should be used to derive the emission limitation. However, recognizing
that such evidence is often not retained for more than a few years,
"reconstructed" documentation may be considered, but should only be used
as a last resort. This evidence should include explanations by those
individuals who were involved in designing the facility, calculating
emission rates, and who represented the facility in dealings with the
-------
-3-
State and EPA on how the emission limit was derived, including a discussion
of how the formula was originally used in deriving the source emission
limitation, a discussion of the analytical method applied, and a listing
of any contacts or discussions with EPA during that period. This listing
will aid EPA in searching its own files to find any records of communication
or correspondence that may bear on the Issue.
In no case should a source be allowed after January 12, 1979, to
obtain a relaxation in the emission limitation by arguing that 1t "relied"
on past EPA guidance endorsing the 2.5H formula. In cases where a relaxation
based on GEP formula height is sought 1n the future, the refined H + 1.5L
formula must be used.
6. Q: The preamble specifically discusses cooling towers as structures to
which the formula should not be applied. Will the Office of Air Quality
Planning and Standards be specifying other structures that are not well
represented by the formul a?
A: The discussion in the preamble and SEP guideline is not intended to
be all-inclusive; judgment should be used 1n determining when fluid
modeling should be used to estimate the effects of structures with rounded,
domed, or tapered shapes. Water towers and storage tanks are additional
examples of such structures. As additional Information becomes available
on the aerodynamic effects of specific building shapes and configurations,
we will evaluate the need to revise the GEP guidance. However, at present,
there are no plans to issue a "laundry 11st" of structures to which the
formulas do not apply.
SIP Requirements
7. Q: Should a compliance averaging-time be explicitly stated in a
SIP revision for sulfur dioxide (S02) emission limits that are revised to
meet the stack height regulation?
A: A compliance averaging time need not be specified as an enforceable
SIP provision as long as a stack test compliance method is in place in the
underlying federally approved SIP. EPA's current national policy requires
that SIP's and permits contain enforceable "short-term" emission limits
set to limit maximum emissions to a level which ensures protection of the
short-term national ambient air quality standards (NAAQS) and prevention
of significant deterioration (PSD) Increments. EPA relies upon a short-term
stack test provision in the SIP as the method of determining compliance
with the emission limits. In lieu of a stack test, EPA has accepted fuel
sampling and analysis and continuous emission In-stack monitors (CEM's).
When compliance is to be determined from information obtained by fuel
sampling and analysis and CEM's, short-term averaging times should be
specified.
-------
-4-
8. Q: Are all States required to have "stack height regulations"?
A: Limitations on creditable stack height and dispersion techniques
impact the SIP program in two areas— SIP emission limits for existing
sources and SIP provisions covering new source review (NSR)/PSD permitting
procedures. For existing sources, State regulations limiting credit 'for
stack height and other dispersion techniques (stack height regulations)
are not necessary as long as the SIP emission limits are not affected in
any manner by so much of the stack height as exceeds SEP, or any other
dispersion technique. Where a State has stack height regulations, those
regulations must be consistent with EPA's regulation. Where a SIP contains
regulations that are inconsistent with EPA's regulation, the State must
either adopt a stack height regulation that is consistent with EPA's or
incorporate the EPA regulation Sy reference.
For the NSR/PSD programs, it is essential that the plan contain
limitations on the amount of creditable stack height and other dispersion
techniques. The following cases have been developed to Illustrate what
action(s) may be required of the State since promulgation of the stack
height regulation.
CASE All): A fully or partially delegated PSO program that references but ^
does not define 6EP where the delegation agreement does not con tall
a date to define which version of the PSO rule is being
ACTION: Notify the State that all permits Issued henceforth must be
consistent with EPA's stack height regulation. All permits
previously issued must be reviewed and revised as necessary
within 9 months.
CASE A(2): A fully or partially delegated PSO program that references
but does not define GEP where the delegation agreement
does contain a date to define which version of the PSD rule
is being delegated.
ACTION: Update the delegation agreement to reflect agreement with EPA's
stack height regulation as of July 8, 1985. Notify the State
that all permits issued henceforth must be consistent with
EPA's stack height regulation. All permits previously Issued
must be reviewed and revised as necessary within 9 months.
CASE 8: The current federally approved SIP for NSR/PSD does not
contain a reference to SEP or cispersion techniques, i.e.,
provisions assuring that emission limitations will not be
affected by stack height 1n excess of SEP or any prohibited
dispersion techniques do not exist in the current SIP.
-------
-5-
ACTION: Notify the State that such provisions must be adopted and
submitted as a SIP revision within 9 months. This can be
accomplished by adopting stack height regulations at the
State level or by adopting the appropriate reference and
commitment to comply with EPA's stack height regulation as
promulgated on July 8, 1985. Interim permitting should be
consistent with EPA's stack height regulation.**
CASE C: The current federally approved SIP for NSR/PSD contains
references to, but does not define, GEP or dispersion techniques.
ACTION: Notify the State that a coranrftjnent to comply with EPA's stack
height regulation as promulgated on July 8, 1985, is required.
If a State is unar* to make such a commitment, State regulations
must be revised tc je consistent and submitted to EPA as a SIP
revision within 9 months and interim permitting should be
consistent with EPA's stack height regulation. No "grace
period" will be allowed for sources receiving permits between
July 1985 and April 1986.**
CASE D; The current federally approved SIP for NSR/PSD contains stack
height regulations that are inconsistent with EPA's regulation.
ACTION: Notify the State that such regulations must be revised to be
consistent and submitted as a SIP revision within 9 months
and that interim permitting should be consistent with EPA's
stack height regulation.**
CASE E(l): A SIP for NSR/PSO has been submitted to EPA, or will be
submitted to EPA before the due date for stack height revisions.
The submittal contains provisions that conflict with EPA's
stack height regulation.
ACTION: Notify the State that EPA cannot approve the submittal until
it is revised pursuant to EPA's July 8, 1985, regulation.
**In the event that a State does not have legal authority to comply with
EPA's regulation in the interim (e.g., because 1t must enforce State
rules that are inconsistent with EPA's regulation) and is compelled to
issue a permit that does not meet the requirements of the EPA revised
stack height regulation, then EPA should notify the State that such
penrits do not constitute authority under the Clean Air Act to commence
construction.
-------
-6-
CASE E(2): As in Case £(1), a SIP for NSR/PSD has been submitted to EPA
or will be submitted to EPA before the due date for stack
height revisions. The submittal is not Inconsistent with
EPA's stack height regulation, but portions of the existing
approved SIP that relate to the submittal are inconsistent^
ACTION: Approve the SIP submittal based on a coranrittaent by the State
to correct the inconsistencies in its existing SIP to comport
with EPA's July 8 regulation and submit the corrections as a
SIP revision within 9 months. Interim permitting should be
consistent with EPA's stack height regulation.** If th« exist-
ing SIP is ambiguous, i.e., the SIP references but does not
define terms relating to SEP or dispersion techniques, the
action steps outlined in Case C above should be followed.
CASE F: In nonattalnment areas, emission limits or permits do not always
Include modeling, but rather are based on lowest achievable
emission rate (LAER) and offsets.
ACTION: If no modeling is used 1n the Issuance of a permit, the emission
requirements for the source are not "affected" by stack heights
or dispersion techniques, and no action is needed. However, 1 f
modeling was used 1n the process of preparing and issuing a
permit, such as cases where offsets were obtained offsite, that
modeling must be reviewed for consistency with the stack height
regul ation.
9. 0: What must all
promulgated?
States do now that EPA's stack height regul ation is
A: States must review and revise. their SIP's as necessary to include or
revise provisions to limit stack height credits and dispersion techniques
to comport with the revised regulations, and, in addition, review and
revise all emission limitations that are affected by stack height credit
above GE? or any other dispersion techniques. In accordance with Section
AQ6(d)(2) of the Clean A1r Act, States have 9 months from promulgation to
sunmit the revised SIP's and revised SIP emission limitations to EPA.
In an August 7, 1985, memo titled "Impl anentation of the Revised
Stack Height Regulation — Request for Inventory and Action PI a/i to Revise
SIP's," Regional Offices were requested to begin working with each of
tneir States to develop States' Action Plans. Each Action Plan should
include the following: (l) An Inventory of (a) all stacks greater than
65 meters (m), (b) stacks at sources which exceed 5,000 tons per year
total allowable $03 emissions; and (2) A reasonable schedule of dates for
significant State actions to conform both State stack height rules and
emission limitations to EPA's stack height regulation. Schedules should
include increments of progress. Regional Offices should be satisfies
that each of their States provide schedules for completion of the tasks
-------
-7-
as outlined in the August memo and report the status of schedule commitments
to them on a monthly basis. Regional Offices have been asked to forward
monthly status reports to the Control Programs Development Division on
the States' progress to meet scheduled commitments and also report the
results of followup with the States on schedules that are not met. In
order to facilitate tracking the States monthly progress, guidance on a
standardized format will be issued shortly.
Modeling Analyses
10. Q: Is there any restriction or prohibition against, or demonstration
required for, raising an existing (or replacing) stack up to 65 m?
A: No, as long as prohibited dispersion techniques are not employed.
11. Q: Are flares considered to be stacks?
A: No, flares are excluded from the regulation.
12. Q: What load should be used for a fluid modeling demonstration?
A:- One hundred percent load should generally be used unless there
is a compelling argument otherwise..
13. Q: Can new or modified sources who have agreed to a case-by-case
best available control technology (BACT) emission rate be required to use
this rate for fluid modeling rather than a less stringent new source
performance standard (NSPS) emission rate?
A: As set forth in 40 CFR 51.1 (kk), the allowable emission rate to
be used in making demonstrations under this part shall be prescribed by
the NSPS that is applicable to the source category unless the owner or
operator demonstrates that this emission rate is infeasible.
14. Q: Must tne exceeddnce of NAAQS or PSD increment due to downwash, wakes,
or eddies occur at a location meeting the definition of ambient air?
A: No, the exceedance may occur at any location, including that to
which the general public does not have access.
15. Q: Is a source that meets NSPS or BACT emission limits subject to
restrictions on plume merging?
A: Yes. However, in a majority of such cases, there will be no practical
effect since 3ACT or NSPS limits will be sufficient to assure attainment
without credit for olume rise enhancement.
-------
-8-
Q: What stack parameters are to be used in modeling when the actual
stack neicnt is greater than GE? height?
A: Where it is necessary to reduce stack height credit below what is in
existence, for modeling purposes, use existing stack gas exit parameters--
temperature and flow rate--and existing stacic top diameter and model at
GE? neight.
17. Q: How should a stack that 1s less than GEP height be modeled when
dispersion techniques are employed?
A: In order to establish an appropriate emission limitation where a
source desires to construct less than a GEP stack but use dispersion
techniques to make up the difference in plume rise, two cases should be
tested. First, conduct a modeling analysis Inputting the GEP stack
height without enhanced dispersion parameters, then conduct a second
analysis inputting the less than GEP stack height with the increased
plume rise. The more stringent emission limitation resulting from each
of the two runs should be the one specified as the enforceable limitation.
18. Q: How are the effects of prohibited dispersion techniques to be excludes
for modeling purposes?
A: Where prohibited dispersion techniques have been used,, modeling to
exclude their effects on the emission limitation will be accomplished by
using the temperature and flow rates as the gas stream enters the stack, and
recalculating stack parameters to exclude the prohibited techniques
(e.g., calculate stack diameter without restrictions 1n place, determine
exit gas temperatures before the use of prohibited reheaters, etc.).
19. Q: How are single flued merged stacks and multiflued stacks to be
treated in a modeling analysis?
A: This is a mul Vistep process. First, sources with allowable S02
emissions below t.OOO tons/year may be modeled accounting for any plume
merging that has been employed. For larger sources, multi flued stacks
are considered as prohibited dispersion techniques in the same way as
single flued merged gas streams unless one of the three allowable conditions
has been met; i.e., (1) the source owner or operator demonstrates that
the facility was originally designed and constructed with such merged gas
streams; (2) after date of promulgation, demonstrate that such merging is
associated with a change in operation at the facility that includes the
installation of pollution controls and results in a net reduction in the
allowable emissions of the pollutant for which credit 1s sought; or (3)
before date of promulgation, demonstrate that such merging did not result
in any increase in the allowable emissions (or, in the event that no
emission limit existed, actual emission level) and was associated with a
change in operation at trie facility that included the installation of
-------
-9-
CTissions control equipment OP was carried out for sound economic or
engineering reasons, as demonstrated to EPA. Guidelines on what constitutes
sound economic or engineering justification will be issued shortly.
If plume merging from multiflued stacks is not allowable, then each
flue/liner must be modeled as a separate source and the combined impact
determined. For single flued merged stacks where credit is not allowed,
each unit should be modeled as a separate stack located at the same
point. The exit parameters, i.e. velocity and temperature, would be the
same as for the existing merged stack conditions and the volume flow rate
based on an apportionment of the flow from the Individual units.
20. Q: What stack height for point sources should be Input to air quality
dispersion modeling for the purpose of demonstrating protection of the
NAAQS and PSD increments?
A: A discussion of the maximum stack height credit to be used in modeling
analyses is provided in the "Guideline for Determination of Good Engineering
Practice Stack Height" and provides that the SEP stack height should be
used as input to the model assessment. If a source is operating with a
less than GEP stack height, then the actual stack height should be input
to the "model.
21. Q: What stack height should be used for background sources in
modeling analyses?
A: The GEP-stack height for each background source should
be input to the model assessment. If a background source is operating
with a less than GEP stack height, then the actual stack height should be
input to the model.
22. Q: Can credit for plume merging due to installation of control
equipment for total suspended particulate (TSP) matter be allowed when
setting the SOj 1imit?
A: To state the question another way, the concern is what impact
the merging and installation of control equipment have on the emission
limit for another pollutant, and whether the merging occurred before or
after July 8, 1985. After July 8, 1985, any exclusion from the definition
of "dispersion techniques" applies only to the emission limitation for
the pollutant affected by such change in operation and 1s accompanied by
a net reduction in allowable emissions of the pollutant. For example, a
source tears down two old stacks and builds one new GEP stack with an
electrostatic precipitator (ESP). This results in a net reduction in TS?
emissions. This source could model using stack gas characteristics
resulting from merging the two gas streams in setting the TSP emission
limit, but may not so node! and receive the credit for stack merging wnen
evaluating the Sty emission limit.
-------
-10-
Before July 8, 1985, installation of TSP pollution control equipment
generally justifies the merging of the stacks for TSP. However, if a
source's emission limitation for SOj increased after the merging, then
credit would generally not be allowed since it is presumed that the
merging was to increase dispersion.
A source with no previous SOj emission limit that merges stacks and
installs an ESP for TSP control may consider the effects of merging on
compliance with the TSP NAAQS but may not use merging to justify setting
an S02 emission limit less stringent than its actual emission rate before
the merging.
23. Q: If, after determining SEP stack height by fluid modeling,
dispersion modeling under other than "downwash" meteorological conditions
shows that a lower emission limit than that from the fluid model SEP
analysis is necessary to meet ambient air quality constraints, should a
new stack height be defined for the source?
A: No. GEP stack height 1s set. Ambient air quality problems
predicted by dispersion modeling at the fluid modeled height means that a
more stringent emission limit is necessary.
24. Q: Does EPA intend to issue additional guidance on fluid modeling
demonstrations?
A: See the attached memo from Joseph A. Tikvart, Chief, Source
Receptor Analysis Branch, to David Stonefield, Chief, Policy Development
Section, on guidance for a discussion of existing and additional guidance
on fluid model demonstrations.
Attachment
cc: Stack Height Contacts
Gerald Emison
Ron Campbel 1
B. J. Steigerwald
-------
PN 123-85-09-19-006
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
y* Research Triangle Park. North Carolina 27711
September 19, 1985
MEMORANDUM
SUBJECT: Guidance on Fluid Model Demonstrations for Determining GEP
Stack Height in Complex Terrain
FROM: „ Joaeph A. Tikvart, Chief
Source Receptor Analysis Branch, MDAD
TO: David Stonefield, Chief
Policy Development ;ction, CPDD
The recently promulgated stack height regulation requires that a source
that wishes to receive credit for the effects of vakes, eddies and dovnvash
produced by nearby terrain for the purpose of calculating GEF stack height
must conduct a fluid model demonstration or a field study. Recent guidance
for fluid modeling these terrain effects is contained in Section 3.6 of the
"Guideline for Determination of GEF Stack Height (Reviaed)," EFA 450/4-80-023R,
June 1985, available from NTIS as PB 85-225-241. In addition, the report
"Fluid Modeling Determination of Good Engineering Practice Stack Height in
Complex Terrain," EPA 600/3-85-022, available from NTIS PB 85-203-107,
provides an actual case of how EPA conducted a GEP determination, short of
performing the "excessive concentration" criteria test. Requests to conduct
field studies in lieu of fluid modeling demonstrations* will be evaluated on
a case-by-case basis; refer to pp. 46-47 of' the GEP Guideline.
Previously, EPA published three documents which form the basis for
conducting fluid model demonstrations, particularly in flat terrain
situations: (1) "Guideline for Fluid Modeling of Atmospheric Diffusion,"
EPA 600/8-81-009, April 1981, available from NTIS as PB 81-201-410; (2)
"Guideline for Use of Fluid Modeling to Determine Good Engineering Practice
Stack Height," EPA 450/4-81-003, July 1981, available from NTIS as PB 82-145-
327; and (3) "Determination of Good-Engineering-Practice Stack Height: A
Fluid Model Demonstration Study for a Power Plant," EPA 600/3-63-024, April
1983, available from NTIS as PB 83-207407.
Lastly, EPA conducted a 4-day work shop on fluid modeling and GEP
determination at the Fluid Modeling Facility at RTF in February 1981,
attended by staff from each Regional Office. Although some attendees are
no longer with the Agency, we believe at least one person in each Region
who attended is still "on board," except for Regions II and VIII, and could
serve as a resource person. At the Regional Workshop on the Stack Height
Regulation next month, we will poll the attendees concerning the need for
-------
another fluid modeling workshop for Regional Office and State technical
•taff. If a need is expressed and specific attendees can be identified, we
will request the Meteorology and Assessment Division, ASRL, to present such
a workshop at RTF within the next few months.
The above documents together with staff that have some knowledge of
fluid modeling should enable most Regions to provide initial technical
assistance to the States and enable the States to increase their own level
of expertise. Note that document (2) contains a report checklist in Section
5, outlining what a fluid model report should contain, additional items
explicitly related to complex terrain studies may be required on a case-by-
case basis, especially after reviewing EPA's example study carefully. Hore
detailed procedures for implementing the excessive concentration criteria
calculations, using data from a fluid model demonstration, are being developed
and will be provided at the upcoming Regional Workshop.
Should technical questions arise regarding CEP determinations or fluid
model demonstrations, please contact Jim Dlcke or Dean Wilson of my staff,
FTS 629-5681. We assume the Regional Office staffs will attempt a first-cut
resolution of technical issues before requesting our assistance.
cc: S. Relnders
R. Rhoads
F. Schiermeier
D. Wilson
-------
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/4-81-003
July 1981
Air
Guideline for Use of
Fluid Modeling to Determine
Good Engineering Practice
Stack Height
ENVIRONMENTAL PROTECTION
AGENCY
OCT 30 1981
UBRARY SERVICES OFFICE
-------
&EFK
Pwk MC 27711
EPA-600/3-83^2
April 1983 ^2
Determination of
Good-Engineering-
Practice Stack
Height
•
A Fluid Model
Demonstration
Study for a Power
Plant
-------
EPA-450/2-78-027R
SUPPLEMENT A
JULY 1987
SUPPLEMENT A
TO THE
GUIDELINE
ON
AIR QUALITY MODELS (REVISED)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office Of Air And Rodiotion
Office Of Air Qualify Planning And Standards
Research Triangle Park. North Carolina 27711
-------
PN iic-85-0i-O'-::
\ UN/TEO STATES ENVIRONMENTAL PROTECTION AGENCY
9 Offict of Air Quality Planning and Standards
V IX fl«s«arch Triang/e Park. North Caro/ina 2777 1
*' «»•*
January 2, 1985
MEMORANDUM
SUBJECT: Regional Implementation of Modeling Guidance
FROM: Joseph A. Tilcvart, Chief
Source Receptor Analysis Branch, MDAO (MO-14)
TO: Regional Modeling Contact, Regions I-X
Attached for your use is information on the implementation of modeling
guidance. Attachment 1 is an excerpt of a memorandum from J. tfilbum to 0. Tyler
(dated November 13, 1984) which identifies several issues. Attachment 2
provides our response to these issues.
It is our intent that the response merely reiterate the way in which we
understand modeling guidance to be routinely implemented by all Regional Offices.
however, having formalized that understanding, we believe that its circulation
is desirable. If you have any questions, please call me.
Attachments
*
cc: Chief, Air Programs Branch, Regions, I-X
B. Turner
yo. Wilson
-------
Attachment 1
(Excerpt of Memorandum from J. Wilburn to D. Tyler, Dated November 13, 1984)
As discussed in this memo, we are quite concerned as to our credibility
regarding the development and approval of SIP revisions and bubbles which
consider complicated and involved modeling. While our Armco experience may
be viewed by some as atypical, we feel that the problem is real enough to the
point that we request guidance on the following three .questions:
1. When do changes in EPA modeling procedures become official Agency
policy? Do such forms as informal modeling protocols and consensus
opinions developed at meteorologist meetings and workshops constitute
official Agency policy? If so, how is management at the regional
division and branch level informed of those decisions (i.e., are such
decisions communicated by policy memorandum or must regional manage-
ment be dependent upon regional participants at such meetings and
workshops to accurately convey OAQPS's policy decisions)?
Z. How do changes in Agency modeling policy affect in progress modeling
analyses? Do policy changes in modeling procedures invalidate
modeling protocols which accurately reflected modeling policy at the
initiation of ongoing modeling analyses? If so, we would appreciate
copies of all policy memorandums which communicated such policies.
3. Will it be necessary in order for Armco1s bubble application to be
concurred with by OAQPS, for Region IV to require Armco to submit a
fourth revision to their modeling procedures which would provide an
analysis of the 46 days with more than 6 hours of calm which have
thus far been deleted for the submittal pursuant to the original
protocol? If so, we would like an explanation of the rationale for
this requirement in light of our discussion in this memo.
-------
Attachment 2
•
(Excerpt of Memorandum from R. Rhoads to J. Mil burn, Dated December 24, 1984)
Regarding your first question: Changes 1n EPA modeling procedures
become official Agency guidance when (1) they are published as regulations
or guidelines, (2) they are formally transmitted as guidance to Regional
Office managers, (3) they are formally transmitted to Regional Modeling
Contacts as the result of a Regional consensus on technical issues, or
(4) they are a result of decisions by the Model Clearinghouse that effec-
tively set a national precedent. In the last case, such issues and deci-
sions are routinely forwarded to all of the Regional Modeling Contacts.
In order for this system to work, the Regional Modeling Contacts must be
actively Involved in all Regional modeling Issues and they must be con-
sulted on modeling guidance as necessary by other Regional personnel.
Regarding your second question: The time at which changes in
modeling guidance affect on-going modeling analyses is a function of the
type of agreement under which those analyses are being conducted. On-going
analyses should normally be "grandfathered" if (1) there is a written pro-
tocol with a legal or regulatory basis (such as the Lovett Power Plant) or
(2) the analysis is complete and regulatory action 1s Imminent or underway.
If the analysis is based on a less formal agreement and Is underway, the
Regional Office should Inform the source operators of the change and deter-
mine whether the change can be implemented without serious disruption to
the analysis. If for some reason any previous analysis must be redone,
then it should be redone in accordance with current modeling guidance. In
any event, consequences of falling to Implement current guidance should be
discussed with the OAQPS staff (Helms/11kvart) to ensure that Inappropriate
commitments are not made by the Regional Office.
Regarding your third question: As previously discussed with your
staff, the recent Armco modeling analysis 1s technically inadequate and
not approvable so long as the approximately 46 days with calms are
ignored. At the time the original protocol was developed, the deletion
of calms was common practice because we had no consensus on technically
valid procedures for addressing calms. However, (largely due to the
assistance of RO IV staff 1n developing a technical solution to the
calms issue) this practice was discontinued by consensus of the Regional
Modeling Contacts who recommended'immediate Implementation of the new
procedures (see Joe Tikvart's June 13, 1983, memo to Regional Modeling
Contacts). The subsequent Armco analysis which ignored calms was, there-
fore, deficient since there is no rationale for "grandfathering" an analy-
sis which was initiated after the new calms guidance was disseminated.
This Issue is no longer an issue since Armco has already submitted a
reanalysis that addresses the calms issue.
-------
June 7, 1988
MEMORANDUM
SUBJECT Revised Model Clearinghouse Operational Plan
FROM: Joseph A. Tikvart, Chief
Source Receptor Analysis Branch (MO-14)
TO: Chief, A1r Branch, Region VII
Chief, Technical Support Branch, Region I
Chief, Air and Radiation Branch, Region V
Chief, Air Programs Branch, Regions II, III, IV, VI, VIII, IX, X
On February. 9, 1988 I notified you of the expansion of the Model
Clearinghouse to include all criteria pollutants. That memorandum
explained briefly how the expanded Clearinghouse would operate and
identified individuals in the Technical Support Division and in the Air
Quality Management Division who would be involved in resolving Agency
regulatory modeling issues. The memorandum also promised that we would
be revising the 1981 Operational Plan for the Model Clearinghouse to reflect
the current operation. Attached is a copy of that revised plan.
To highlight major functions of the operational plan which you should
become most familiar with, please note the structure of the Clearinghouse
contained in Section 3, particularly Figure 1. Also you should become
familiar with the procedures for referring modeling issues to the
Clearinghouse, described in Section 4. Appendix B identifies the contacts
in the Regions for various types of modeling problems. Please check over
these lists for accuracy and keep us informed of any changes of these
personnel in your Region.
It should be remembered that the Model Clearinghouse is a service
we provide to the Regional Offices. We do not normally deal directly with
the State/local agencies or with industry since this would compromise our
function as second level reviewers and would interfere with your function.
However we have discussed access by States to Clearinghouse expertise
through the Regional Offices. Where a State wishes such a contact, we
urge your staff to work closely with their State counterparts to establish
a mutally agreed-upon position on the issue-.
Finally, for purposes of responding to questions from States and local
agencies about the Clearinghouse and its operation, we have no problem if
you wish to furnish them with a copy of this plan. For questions from the
public we would prefer that you instead provide them with a copy of Appendix C,
a separate copy of which is attached. This Appendix is a revised version
of a flyer we have distributed for a number of years at the EPA booth at
the annual APCA meeting.
-------
EPA Model Clearinghouse
Summary
The Model Clearinghouse is the single EPA focal point for reviewing the use of
modeling techniques for criteria pollutants in specific regulatory applications.
The Clearinghouse also serves to compile and periodically report for Regional
Office benefit Agency decisions concerning deviations from the requirements of the
"Guideline on Air Quality Models (Revised)."
Need for the Model Clearinghouse
The Guideline states that when a recommended model or data base is not used,
the Regional Administrator may approve the use of other techniques that are demon-
strated to be more appropriate. However, there is also a need to provide for a
mechanism that promotes fairness and consistency in modeling decisions among the
various Regional Offices and the States. The Model Clearinghouse promotes this
fairness and uniformity and also serves as a focal point for technical review of
"nonguideline" techniques proposed for use/approval by a Regional Administrator.
Functions of the Model Clearinghouse
The major function of the Clearinghouse 1s to review specific proposed actions
which involve interpretation of modeling guidance, deviations from strict interpre-
tation of such guidance and the use of options in the guidance, e.g., Regional
Office acceptance of nonguideline models and data bases. This is handled in two
ways: (1) the Clearinghouse, on r jest from the Regional Office, will review the
Region's position on proposed (specific case) use of a nonguideline model for tech-
nical soundness and national consistency, and (2) the Clearinghouse will screen
Federal Register regulatory packages for adherence to modeling policy and make
recommendations for resolution of any Issues identified.
A secondary function of the Model Clearinghouse is to communicate to regu-
latory model users in EPA significant decisions involving the interpretation of
modeling guidance. This is accomplished through an annual "Clearinghouse Report"
which itemizes the significant decisions that have been made and the circumstances
involved. This report serves to improve consistency in future decisions and as
a source of technical information for the Regional Offices. In addition to the
annual report the Clearinghouse informs users on a contemporary basis of signi-
ficant decisions through copies of written decisions and briefings at various
meetings and workshops.
Structure of the Clearinghouse
The Clearinghouse is formally located in the Source Receptor Analysis Branch
(SRAB) of OAQPS. However, the Air Quality Management Division (AQMD) also parti-
cipates in Clearinghouse matters involving SIP attainment strategies and other
regulatory functions.
The primary responsibility for managing the Clearinghouse and ensuring that
all of its functions are carried out is performed by a person full-time within
SRAB. The responsibility for responding to requests for review of modeling
issues is assigned, on a pollutant/program basis to three SRAB individuals. In
addition, AQMD supports the Clearinghouse with staff who are also knowledgeable in
modeling policy. These individuals are responsible for screening SIP submittals
and related documents, referring modeling issues to SRAB through the Clearinghouse
and documenting the final (and any significant interim) decision on disposition of
tne issues.
Communi cati on Chai n
The Model Clearinghouse functions within the organizational structure of EPA.
As such the Clearinghouse serves the EPA Regional Offices. It coordinates with
and communicates decisions to the Regional Offices. Any coordination with State
and local agencies and individual sources on Clearinghouse activities is a function
of t.^e EPA Regional Offices.
Cl
-------
REFERENCES FOR SECTION 4.3
-------
EPA-450/2-78-027R
Guideline On Air Quality Models
(Revised)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park. NC 27711
July 1986
-------
.-,
£1 \ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
February 15, 1989
MEMORANDUM
SUBJECT: Modeling Requirements for Pennsylvania Power and Light
(PP&L), Martins Creek, Pennsylvania
FROM: Robert D. Bauman, Chief
SO,/Particulate Matter Programs Branch (MD-15)
TO: Joseph Tikvart, Chief
Source Receptor Analysis Branch (MD-14)
This is in response to a memorandum dated January 4, 1989 from
Al Cimorelli, Region 3, to Dean Wilson of your branch. Since this
appears to be more of a policy than a technical issue, my branch
agreed to prepare a response.
Region 3 is asking if EPA policy would allow PP&L's modeling
analysis to address only the designated nonattainment area in
Warren County, New Jersey. If so, it might be possible to
reclassify the warren county area to attainment without an
evaluation of PP&L's impact outside the Warren County nonattainment
area. Additionally, the Region has asked if a redesignation for
Warren County could proceed independent of any revision to the
Pennsylvania SIP, in the event the modeling analysis shows warren
County to be attainment but shows a modeled violation in
Pennsylvania.
The Guide, j-ine on Air Quality Models ( Revised^ ( guide lir|e^ on
page 1-3 states that the current guidance should be followed in all
air quality analyses relative to State implementation plans and in
analyses required by EPA, State and local agency air programs. This
policy is consistent with stack height implementation policy and
general guidance found in a January 2, 1985 memorandum from SRAB
to the regional modeling contacts. Guidance contained in the
Guideline recommends on page 9-8 that "all sources expected to
cause a significant concentration gradient in the vicinity of the
source or sources under consideration for emission limit (s) should
be explicitly modeled." On page 8-4, the Guideline states that
"Receptor sites for refined modeling should be utilized in
sufficient detail to estimate the highest concentrations and
possible violations of a NAAQS or a PSD increment."
-------
I believe that application of guidance noted above does not
allow a partial modeling analysis. If a modeling analysis is
required for any reason, that analysis Bust meet the requirements
of the Guideline.
Redesignation policy is generally contained in the April 21,
1983 memorandum from Sheldon Meyers to the Regional Air Directors.
That policy includes requirements for a modeling analysis
demonstrating attainment and evidence of implementation of the
approved SIP. As noted by Region 3, PP&L's analysis may show
violations at locations outside of the designated nonattainment
area, while demonstrating an absence of violations within the
nonattainment area. In such an event, the existing SIP may be
judged adequate to demonstrate attainment in Warren county and an
action to redesignate the area to attainment could proceed before
the State completes the necessary effort to resolve the violations
outside the nonattainment area. While separate rulemaJcing actions
are possible, it may be more efficient to consolidate the
redesignation and SIP revision actions whenever possible.
I trust that this memorandum is responsive to Region 3's
concerns. If you need any additional information, please call me.
cc: A. Cimorelli, Region 3
vJH'Ginsburg, OAQPS/AQMD
D. Grano, OAQPS/AQMD
S. Sambo1, Region 2
D. Wilson, OAQPS/TSD
-------
REFERENCES FOR SECTION 4.7
-------
EPA-450/2-78-027R
Guideline On Air Quality Models
(Revised)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
July 1986
-------
REFERENCES FOR SECTION 5.1
-------
2T8S2
Federal Register / Vol. SO. No. 130 / Monday. |uly 8. 1985 / Rules and Regulations
ENVIRONMENTAL PROTECTION
AGENCY
40CFRPartS1
IAD-FRL-2S47-6)
Stack Height Regulation
AGENCY: Erv. .ror.nerr ,! Protection
ABC?.C> (EPA).
ACTION: Find! rulemaking
SUMMARY: Section 123 of the Clean Air
Art. as amended, requires EPA to
promulgate regulations to ensure that
;.-.e aegree of emission limitation
reared for tne control of any air
pollutant under an applicable State
implementation plan i.SIP] is not
affected by that portion of any stack
height which exceeds euod engineering
practice (GEP; or by any other
dispersion technique. A regulation
implementing section 123 was
prorr.^is-ite^ on February a. 1982. at 47
FR 5864. Revisions to the regulation
M ere proposed on November 9.1964. at
49 FR 44878. Today's action incorporates
changes to the proposal and adopts this
regulation in final form.
f wtcnvt DATE This regulation
becomes effective on August 7.1985.
POM PUMTHtft INFORMATION CONTACT:
Enc O. Gmsburg. MEM5. Office of Air
Quality Planning and Standards. EPA.
Research Triangle Park. North Carolina
27711. Telephone (919) 541-5540.
IMPOMMATIOM:
Docket Stat
Pertinent information concerning this
regulation is included in Docket Number
A-83-49. The docket it open for public
inspection between the hours of 8.-00
a.m. and 4.00 p.m.. Monday through
Friday, at the EPA Cential Docket
Section, West Tower Lobby. Gallery
One. 401 M Street. SW.. Washington.
D C. Background documents normally
a-, ailable to the public, such as Federal
Register nonces and Congressional
reports, are not included in the docket
A reasonable fee may be charged for
copying uocumenis.
Background
SfO.'l'.'S
Section 123. which was added to the
Clean Air Act by the 1977 Amendments.
regulates the manner in which
techniques for disperson of pollutants
from a source may be considered in
setting emission limitations. Specifically.
section 123 requires that the degree of
emission limitation shall not be affected
by that portion of a stack which exceeds
GEP or by "any other dispersion
technique." It defines GEP. with respect
to suck height* as.
the height necusMry to insure that emissions
from the suck do not result in excesMve
concentrations of any air pollutant in the
immediate vicinity of the source i> a revuli of
atmospheric downwash eddies or wakes
which m*> b« crtnted &> the source ittelf.
nearby structures or nearby terrain obstacles
. . . (Section 123|c||
Section 123 further provides that CEP
stack height shall not exceed two and
one-halt times the height of the source
(2.SH) unless a demonstration is
performed showing that a higher stack is
needed to avoid "excessive
concentrations." As the legislative
history of section 123 makes clear, this
reference to a two and one-half times
test reflects the established practice of
using a formula for determining the GEP
stack height needed to avoid excessive
downwash. Finally, section 123 provides
that the Administrator shall regulate
only stack height credits—that is. the
portion of the suck height used in
calculating an emission limitation—
rather than actual stack heights.
With respect to "other dispersion
techniques" for which emission
limitation credit is restricted, the statute
is less specific It state* only that the
term shall include intermittent and
supplemental control system* (ICS.
SCS). but otherwise leaves the definition
of that term to the discretion of the
Administrator
Thus the sutute delegates to the
Administrator the responsibility for
defining key phrases, including
"excessive concentrations" and
-nearby." with respect to both
structures and terrain obstacles, and
"other dispersion techniques." The
Administrator must also define the
requirements of an adequate
demonstration justifying stack height
credits in excess of the 2.5H formula.
Ruiemaking and Litigation
On February 8.1982 (47 FR 5864). EPA
promulgated final regulations limiting
stack height credits and other dispersion
techniques. Information concerning the
development of the regulation w«t
included in Docket Number A-79-01 and
is available for inspection at the EPA
Central Docket Section. This regulation
was challenged in the U.S. Court of
Appeals for the D.C. Circuit by the
Sierra Club Legal Defense Fund. lac; the
Natural Resources Defense Council. Inc.:
and the Commonwealth of Pennsylvania
in Stem Club v. EPA. 719 F. 2d 438. On
October 11.1983. the court issued it*
decision ordering EPA to reconsider
portions of the stack height regulation.
reversing certain portions and upholding
other portions. Further discussion of the
court decision is provided later in th:s
notice.
Administrative Proceedings Subscqun-t
to tne Court Decision
On December 19.19S3. EPA held a
public meeting to take comments to
assist the Agency m implementing trie
mandate of the ecu".. This meeting was
announced in the Federal Register on
December 8.1983. at 48 FR 54999
Comments r*ce-ved by EPA are
included in Docket Nurr.r.nr A-83-49 On
Februar. 2a.1984. the e.ect:: power
industry filed a petition fjr a \\n\ of
certiorar. with the U.S Si-prerr* Court
While the petition was pen .':r.g before
the court, the mandate frj.- tne U.S.
Court of Appeals Mas staved. On juiv 2.
1984. the Supreme Cour denied the
petition (104 S.Ct. 3571). and on ful> 18
1984. the Court of Appeals mandate
was formally issued, implementing the
court's decision and requiring EPA to
promulgate revisions to the stack height
regulations within 6 months. The
promulgation deadline was ultimate*;
extended to June 27.1985. in order to
provide additional opportunities for
public comment to allow EPA to hold a
public hearing on January 8.1985. and to
provide additional time for EPA to
complete its analysis of rulemaking
alternatives.
Documents
In conjunction with the 1982
regulation and this revision. EPA
developed several technical and
guidance documents. These served as
background information for the
regulation, and are included in Dockets
A-79-01 and A-43-49. The following
documents have been or will be placed
in the National Technical Information
Service (NTIS) system and may be
obumed by contacnng NTIS at 5283
Port Royal Road. Springfield. Virginia
22161.
(1) "Guideline for Use of Fluid
Modeling to Determine Good
Engineering Stack Height." July 1981.
EPA. Office of Air Quality Planning and
Standard*. EPA-4SO/4-81-003 (NTIS
PB62 145327).
(2) "Guideline for Fluid Modeling of
Atmospheric Diffusion." April 1981.
EPA. Environmental Sciences Researc.*:
Laboratory. EPA-600/8-01-009 (NTIS
PB81 201410).
(3) "Guidance for Determination of
Good Engineering Practice Stack Height
(Technical Support Document for the
Stack Height Regulator.)." June 1985
EPA. Office of Air Quality Planning and
Standards. EPA-«50'4-*0-0:3R.
(4) "Determination of Good
Engineering Practice Stack Height—A
-------
Federal Register / Vol. SO. No. 130 / Monday, fuiy 6. 1983 / Rules and Regulations 2?893
Fluid Model Demonstration Study for a
Power Plant." April 1983. EPA.
Environmental Sciences Research
Laboratory. EPA-600/>«3-024 (NTIS
PB83 207407).
(5) "Fluid Modeling Demonstration of
Cood-Engineenng-Practict Stack Height
in Complex Terrain." Aphl 1985. EPA
Atmospheric Sciences Research
Laboratory. EPA/600/3-85/022 (NTIS
PB85 203107).
In addition, the following documents
are available in Docket A-83-48.
"Economic Impact Assessment for
Revisions to the EPA Stack Height
Regulation." |une 1981
"Effect of Terrain-Induced Downwash
on Determination of Good-Enginering-
Practice Stack Height" July 1984.
Program Ovarviaiw
Central
The problem of air pollution can be
approached in either of two ways:
through reliance on a technology-baaed
program that mandates specific control
requirements (either control equipment
or control efficiencies) irrespective of
ambient pollutant concentrations, or
through an air quality baaed system that
relies on ambient air quality levels to
determine the allowable rates of
emissions. The .dean Air Act
incorporates both approaches, but the
SIP program under section 120 uses an
air quality-based approach to establish
emission limitations for sources.
implicitly, this approach acknowledges
and is based on the normal dispersion of
pollutants from their points of origin into
the atmosphere prior to measurements
of ambient concentrations at ground
level
There are two general methods for
preventing violations of the national
ambient air quality standards (NAAQS)
and prevention of significant
deterioration (PSD) increments.
Continuous emission controls reduce on
a continuous basis the quantity, rate, or
concentrations of pollutants released
into the atmosphere from e source. In
contrast, dispersion techniques rely on
the dispersive effects of the atmosphere
to carry pollutant emissions swey from
the source m order to prevent high .
concentrations of pollutants near the
source. Section 123 of the Clean Air Act
limits the use of dispersion techniques
by pollution sources to meet the NAAQS
or PSD increments.
Tall stacks, manipulation of exhaust
gas parameters, and varying the rate of
emissions based on atmospheric
conditions (ICS and SCS] are the basic
types of dispersion techniques. Tall
stacks enhance dispersion by releasing
pollutants into the air at elevations high
above ground level, thereby providing
greater mixing of pollutants into the
atmosphere. The result is to dilute the
pollutant levels and reduce the
concentrations of the pollutant at ground
level without reducing the total amount
of pollution released. Manipulation of
exhaust gas parameters increases the
plume rise from the source to achieve
similar results. ICS and SCS vary a
source's rate of emissions to take
advantage of meteorologic conditions.
When conditions favor rapid dispersion.
the source emits pollutants at higher
rates, and when conditions are advene.
emission rates are reduced. Use of
dispersion techniques in lieu of constant
emission controls results in additional
atmospheric loadings of pollutants and
can increase the possibility that
pollution will travel loaf distances
before reaching the ground.
Although overreUance on dispersion
technique • may produce edverse effects.
some us* -f the dispersive properties of
. the atmosphere has long been an
important factor in air pollution control
For example, some stack height is
needed to prevent excessive pollutant
concentrations near a source. When
wind meets an obstacle such as a hill or
a building, a turbulent region of
downwaah. wakes, aad eddies is
created downwtnd of the obstacle aa the
wind passes over aad around it Thia
can force a plume rapidly to the ground,
resulting in excessive concentrationa of
pollutants near die source. As discussed
previously, section 123 recognizes these
phenomena aad responds by allowing
calculation of emission limitations with
explicit consideration of that pardon of
a source's stack that is needed to ensure
that excessive concentrations dae to
dowawash will not be created near the
source. This height is called CEP stack
height
Summary of th» Court Oteiuon
Petitions for review of EPA's 1982
regulation were filed in the D.C Circuit
within the statutory time period
following promulgation of the regulation.
On October 11.1983. the court issued its
decision ordering EPA to reconsider
portions of the stack height regulation.
reversing certain portions and upholding
others. The following is a summary of
the court decision.
The EPA's 1982 rale provided three
weys to determine CEP stack height
One way was to calculate the height by
using a formula based on the
dimensions of^nearby structures. The
other two were a dt minimi* height of SS
meters, and me height determined by a
fluid modeling demonstration or field
study. The court endorsed the formula
as a starting point to determine CEP
height However, it held that EPA has
not demonstrated that the formula was!
aa accurate predictor of the stack heighr
needed to avoid "excessive
concentrations of pollutants due to
downwash. Accordingly, the court
directed EPA to re-examine in three
ways the conditions under which
exceptions to the general rule of formula
reliance could be justified.
First the 1962 rule allowed a source to
justify raising its stack above formula
height by showing a 40-percent increase
in concentrations due to downwash.
wakes, or eddies, on the ground that this
was the percentage increase that the
formula avoided. The court found this
hiatifieatioa iaaufficieat aad remanded
the definition to EPA with instructions
• to make It directly responsive to health
aad welfare considerations.
Similarly, the 1982 rule allowed a
source diet built a stack to less than
formula height to raise it to formula
height automatically. Once again, the
court required more justification that
such a step wan needed to avoid
adverse health or welfare effects.
Finally, the court directed EPA either
to allow the authorities administering
die stack height regulations to require
modeling by sources in other cases as »
check oa possible error in the formula.
or explain why the accuracy of the
formula made such a step unnecessary.
The 1982 rule provided two formulae
to calculate CEP stack height For
sources cosuuractad oa or before
laaoary 12,197ft the date of initial
proposal of the stack height regulations.
the applicable formula was 2J times tht
height of die source or other nearby
structure. For sources constructed after
that data, the nde specified a newer.
refined formula, the height of the sourct
or other nearby structure plus 1.5 times
die height or width of that structure.
whichever is lew (H+UL). The EPA
baaed its decision- to include two
formulae oa that unfairness of applying
the new formula retroactively. In its
examination of this issue, the court
specified four factors that influence
whether aa agency has a duty to apply *
rule retroactively. They are:
t Whether the new rule represent! in
abrvpt departure from well established
practice or merely attempt* to fill a void m an
unsettled area of lew.
2. The extent to which the party against
whom me new rale is applied relied on the
former rule.
3. The d*trw at burden which a reireictivi
order tmpoeea on a party, and
4. The statutory interest la applying t new
rule dttpite the riihance of e party on tht oid
standard.
-------
27M4 Federal JUeJster / Voi 50. No. 130 / Monday, hjfr a. 19B& / Rries and Regulations
TO F-Zd at 467 (citation* omitted}.
Applying this snalysis to tit two
formulae the court upheld EPA'* basic
decision.
However, the court also held that
sources constructed on or be/on
January 12.1979. should not be
automatically entitled to fuQ credit
calculated under the 2.5H formula unless
they could demonstrate reliance on that
formula. The court remanded this
provision- for revision to take actual
reliant* on the 2.5H formula into
account.
The statute limits stack hetgnt credit
to that needed to aveid excessive
concentrations da* t* Ju*n»esh caused
by "nearby" suuuura* or terrain
features, Tb* 19*2 leeuletfaui defined
"nesrhy" for GEPforsnola epancelfoas
as five tina* the, lesser of either tb*
height or projected width of th*
structun --"^-fl dowawash. aot te>
exceed oaa halt nit*. Na such djetaaca
limitation was pieced am structures or
terrain feature* whose effects warn
being considered ia Quid ^^^Htt
demonstrations or field srariies Tha>
court held that section 123 explicitly
applies tha "aaarby" limitation to
demonstrations and studies as watt aa
formula applications, and •••^•H*'* tha
rule to EPA. to apply the Umiatfra ia
both contexts.
The 1982 rule defined "dispersion
techniques" a* those techniques which
attempt to affect poButant
coDcentrstfans by effing met portfoii of a
stack exceeding GEP. by vuryinf
emission rate* accordta* te> attuuepaeih.
condition* or* pollutant concentration*.
or by th* eddttfoa ol a ran or refceatar ta>
obtain a tees strmgewi sBusvtew
limitation. Th* court found this
definition too aarrow because an*
technique "sianHlcairtrr eionvuted by aa)
intent to gain emissions credit for
greater dispersion" should be barred.
719 F.2d 462. As a reseJU (he court
directed EPA to develop ruses
disallowing credit for all each dUpenwa
techniques unless tb* Agency
adequately justified excacesuua on th*
basis of adamistrative necessity or ee*>
minimis result
The CEP formulae established in the.
1982 rule do not consider paeaae rise.**
the ground that plume nse is aot
significant under downwaah candltiana,
In its review oJT this provision, tha court
affirmed this judgment by EPA.
The 1982 rule addressed pollutant
concentration* estimated to occur whan.
a plume impacts elevated terrain by
allowing, credit Cor stack heighi
necessary to avoid air quality violations
in such cases. However, the court ruled
that section 123 did not allow. EPA to
grant credit for plume impaction ia
setting esMseic* units, sad ravened thta
part ol tk» regulation.
The praaaabktaifa* 1982 refMklMn
provided a 22 DMBXB pinnies tar Stele
iaaplaaentation ol th* refuiatiea Tbe
court found this period ta becoatrery t»
section 4i)6(d)(2> of the. dee* Air Act
and reversed it
The regukboav foilawiat *• stehrfaw
excluded stack* "i» austnce" ea of
before Oecesnber 3L iva from the CEP
requirements. However, the regvktMet
did not prohibit source* coaatncted
after Oecaaber 31.1000. freaa raceiviacj
credit for tying into pr*-19Xl stacks.
AJthougft th* court uobaid EPA's
defiaiaonaf"iBexiataQc*.-UBa4cdthe4
EPA bad hiiad to addtesa (k* oe-te,
issa*. AfiGOidasfM tee emit!
this issue to SPA fa* justificsttesv
On* othar Btonatosi of tbe i
was challenged! in the Siena C/uo suit:
Th* exclusion ol flare* frost the)
defiaiatan ol "suck," la. Us review el tkte
previaieo. th* court h*4d thai BPA bed-
acted properly.
Other provJausBsof th* stack haisjbt
regulation, such a* the d* mim'ssie stack
height esasbliahed uadat | SLKuMlk
were not challenged in tha suit sad the*
reaaia in affect.
Summary of ttio thvwuittr at J99i.
m the November a, Iflai, node*
responding, <" ta* court daaaioa EPA
praposed tn redefine asumbar of
specific teems. i*f'f'"fi"t "exeassUv*
technique*." "ttearfau." and other
important, ranatpss. and prnpnaeri ta
oftfanbaacafat
£,Th*
foOowutiaa
that were, proposed.
JThe Court of Appeals held that EPA
erred IB defirnaij ^SMoessrVe
concentrations" ea* tn enwawaah tea
purpose* of jmtifyiag a stack
than formuia, beiahu ea aothiasj i
than a OVoarcee tinaee.
coaceBtntsooa over whet weaid <
in the absence ol dowsvaak ft
remanded this, MSUS to EPA let reieAe th*
dafiataon to sosa* aoeoMtt* l*w*i ol ear
pollution that could be inta rate tad to
endanger health and weilere* a*d tea
to be •••xceaawe.-
The EPA pronoeed tw* sltarnefl^*
appcMcha* to denaiat "exe*a*i»*
concentration*," Fin*. EPA requested
conunsat oa whether the 4O>|
aperMch adcptvd a* pest i
reguUdoa ia lacs BRMee
dangert •» heaMi end wekmr*
envtaaaaad by Cooate**
section 123. hi ta* sweat that raeh *
showing eonid itot be made. EPA
proposed a two-part definition of
excessive ceaceetrsnaae, requiiiM* that
the dnwnwusa, wakes, or eddies
induced by nesrby structure* or terrain-
feature* result in inaesees in grewid-
level p^hler* conceesratioas that:
(sj Cause or eesriribule to sn
exceedanee of * NAAQS or applicable
(b) Are at least 40 percent in excess of
concentrations projected to occur in the
absence of such structures or terrain
features.
Definition of CEP Stock Htig/it
EPA proposed to find that tha
traditional (2JH1 and refined (H4-1JL)
formulae remained proper methods for
calculating CEP stack betgnf except SPA
proposed to revise its regulation t»
allow EPA. the Slat* or local air
pollution control agency discretion to
require c farmer demonstration using s
fieU study or fluid model to
demonstrate GZPstsck height for a
source tea case where it was believed
that the formats may not rsBaaly predict
CEP height In the case of structures that
are porous or aerodyaamicaJIy smoother
than block-shaped structures. R would
require s source to demonstrate the
downwaah effects of suck structures
using s field study or fluid model before
receiving credit for stack height based
on the structures. EPA also proposed
generally to aBow sources to raise
existing, stacks up to formula GEP height
without further demonstrations with tha
sxoptton anted above far rfismtinnary
Ae/jone* on t/t* iSH Formula
rnial9sttiuia>gA*Mn»iuii sources
bnik be/at* (aauary 12. un. the det* on
which it proposed marsneedH+VSL
formulae, tn i*Ti*nlitT t>*w eraiesMa
limits based ea the trerfhlanel XJ5H
forssui* that existed previously. Th*
court approved this dise'nerino but
ruled met it should be uautad t* sources
that "rehsd" oa the trsdibeaai foreMia.
sngaaeting, tor exasspie. that sources
that bad claimed credil for stacks aw
taller thea thaioramla psvnded«
not be. eaki ta bava "ratted" oa it
IB reepoasB to the coast deoawa, EPA
propaaeatsei
reejuvethas for stacks ini
January 12,1979, i
that thar aemaJtf raUsd ea th* Z3H
tormakt m the deatga of thesr stecst>
before recsavaag oedtl far that s«*hi»
proposes. EPA r*ea***»d i
whataahnuldi
ittfi