Appendix — Alabama Power Co. v. Sierra Club

Office - Supreme

FILED

FEB 28 1964

: No. 83- ALEXANDER L. STEVAS.

— s 2 —__——

83-1499

IN THE

Supreme Court of the United States

OCTOBER TERM, 1983

ALABAMA POWER Co., et ai.,

Petitioners,

V.

SIERRA CLUB, et al.,

Respondents.

APPENDIX TO

PETITION FOR A WRIT OF CERTIORARI TO THE

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

HENRY V. NICKEL

(Counsel of Record)

F, WILLIAM BROWNELL

MICHELE POLLAK

HUNTON & WILLIAMS

P.O. Box 19230

2000 Pennsylvania Ave., N.W.

Washington, D.C. 20086

(202/955-1500)

Counsel for Petitioners

Alabama Power Co., et al.

February 1984

— —— ——— —_——__ __. . -

eee _

WILSON - Evrae Printing Co.. Inc. . 769.0096 . WasninaTow,. 0 C. 20001

APPENDIX

TABLE OF CONTENTS

Page

DECISION AND SUBSEQUENT ORDERS

OF THE COURT

Sierra Club v. EPA, 719 F.2d 486 (D.C. Cir.

PR Ne eS RE ne la

Order of December 13, 1983 [denying petition for

rehearing] . saiubadiiediesiiaeaeietemeasundereaencadaats 70a

Order of December 13, 1983 (denying suggestion

for rehearing en banc] .. 72a

Order of December 13, 1983 [denying motion for

clarification] . 74a

Order of January 6, 1984 (delaying issuance of

mandate through January 19, 1984] 76a

Order of February 9, 1984 [delaying issuance of

mandate through February 21, 1984] 200000000000... 78a

AGENCY DECISIONS, FINDINGS OF FACT

AND REGULATIONS

Environmental Protection Agency, Stack Height

Regulations, 47 Fed. Reg. 5864, et seq. (1982)... 80a

Environmental Protection Agency, Use of Supple-

mental Control Systems and Implementation of

porno Standards, 38 Fed. Reg. 25697, et seq.

(1978) .. aiana adigiade 108a

RELATED STATUTES

Clean Air Act §§ 101, 110(a) (1), 110(a) (2) (A)-

(J), 128, 42 U.S.C. §§ 7401, 7410(a) (1), 7410

(a) (2) (A)-(J), 7423 (Supp. V 1981) 20000000... 106a

RECORD MATERIALS

Excerpts from Environmental Research and Tech-

nology, Analysis of EPA Proposed Regulations

on Stack Height Limitation (March 1979) (sub-

mitted as Appendix C to Comments of the Utility

Air Regulatory Group (March 7, 1979) ) ............. 112a

Excerpt from EEA, Inc., Cost and Economic Im-

pact Analysis of the Proposed Stack Heights

Regulation (August 15, 1980) 0000 123a

la

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

No. 82-1384

SrerRA CLUR and NATURAL RESOURCES

DEFENSE COUNCIL, INC., PETITIONERS

Vv.

ENVIRONMENTAL PROTECTION AGENCY, RESPONDENT

ALABAMA POWER COMPANY, et al.,

KENNECOTT MINERALS Co.,

TENNESSEE VALLEY AUTHORITY,

STATES OF NEW YORK, et al.,

STATE OF VERMONT,

AMERICAN PETROLEUM INSTITUTE, et al., INTERVENORS

No. 82-1412

COMMONWEALTH OF PENNSYLVANIA, PETITIONER

v.

U.S. ENVIRONMENTAL PROTECTION AGENCY, and

ANNE M. GORSUCH, ADMINISTRATOR, RESPONDENTS

STATES OF NEW YORK, et al.,

ALABAMA POWER Co., et al.,

STATE OF VERMONT,

AMERICAN PETROLEUM INSTITUTE, et al., INTERVENORS

2a

No. 82-1845

SIERRA CLUB and NATURAL RESOURCES

DEFENSE COUNCIL, INC., PETITIONERS

v.

ENVIRONMENTAL PROTECTION AGENCY, RESPONDENT

ALABAMA POWER COMPANY, et al.,

AMERICAN PETROLEUM INSTITUTE, et al., INTERVENORS

No. 82-1889

COMMONWEALTH OF PENNSYLVANIA, PETITIONER

v.

U.S. ENVIRONMENTAL PROTECTION AGENCY, and

ANNE M. GORSUCH, ADMINISTRATOR, RESPONDENTS

ALABAMA POWER COMPANY, et al.,

AMERICAN PETROLEUM INSTITUTE, et al., INTERVENORS

Petitions for Review of Orders of the

Environmental Protection Agency

Argued April 18, 1988

Decided October 11, 1983

Richard E.. Ayres and Howard I. Fox, for petitioners in

Nos. 82-1384 and 82-1845.

Thomas Y. Au, Assistant Counsel, Commonwealth of

Pennsylvania, was on the brief for petitioners in Nos.

82-1412 and 82-1889.

Catherine A. Cotter, Attorney, Department of Justice,

of the bar of the Supreme Court of California, pro hac

vice by special leave of Court, and Christina Kaneen,

3a

Attorney, Environmental Protection Agency, of the bar of

the Supreme Court of Illinois, pro hac vice by special leave

of Court, with whom Carol E. Dinkins, Assistant Attorney

General, Department of Justice, Robert M. Perry, General

Counsel, and Charles S. Carter, Acting Assistant General

Counsel, Environmental Protection Agency, were on the

brief, for respondents. Barry S. Newman, Attorney, De-

partment of Justice, and Jesse Carrillo, Attorney, En-

vironmental Protection Agency, also entered appearances

for respondents in Nos. 82-1384, 82-1412, 82-1845 and

82-1889.

Henry V. Nickel, with whom F. William Brownell and

Michele Pollak were on the brief, for intervenors, Alabama

Power Co., et al., in Nos. 82-1384, 82-1412, 82-1845, and

82-1889,

Stark Ritchie and David T. Deal were on the brief for

intervenors, American Petroleum Institute, et al., in Nos.

82-1384, 82-1412, 82-1845, and 82-1889.

Alfred V. J. Prather and Kurt E. Blase were on the

brief for intervenor Kennecott Minerals Company in No.

82-1384.

James E., Fox was on the brief for intervenor Tennessee

Valley Authority in No. 82-1384.

Francis X. Bellotti, James R. Gomes, and Stephen M.

Leonard for Commonwealth of Massachusetts, Robert

Abrams and David R. Wooley, for State of New York,

and Dennis J. Robert, II, for State of Rhode Island, were

on the brief for intervenors, State of New York, et al., in

Nos. 82-1884 and 82-1412. Val Washington also entered

an appearance for State of New York in No. 82-1884.

Before EDWARDS, Circuit Judge, MCGOWAN and MAc-

KINNON, Senior Circuit Judges.

Opinion for the Court filed by Senior Circuit Judge

McGowan.

4a

McGowan, Senior Circuit Judge: This case concerns

the amount of credit electric power plants and other ma-

jor sources of air pollution may receive for the height of

their emissions stacks in calculating limitations on their

emission of pollutants.

Under the Clean Air Act as amended (“the Act”) and

its regulations, emissions limitations for each such source

are fixed on the basis of local, ground-level concentrations

of pollutants, which cannot exceed certain national stand-

ards or incremental increase limitations. Since taller

stacks tend to disperse pollutants over a greater area,

a utility or other source can lower the ambient pollution

concentrations not only by reducing the amount of pol-

lutants it emits into the air, but also by raising the height

of its stack. After the basic provisions of the Act were

passed in 1970, many chose the latter route. In 1977

amendments to the Act, Congress declared that such tall

stacks and other dispersion techniques were not to be

taken into account in calculating the limitations on emis-

sions imposed by the Act. 42 U.S.C. §7423 (Supp. V

1981). Rather, pollution standards were to be achieved

by direct limitations on emissions. The present case

brings before us final regulations issued by the Environ-

mental Protection Agency (EPA) to implement this

provision.

The regulations at issue are detailed and somewhat

complex. Generally speaking, under the 1977 amend-

ments credit for stack height in calculating emissions

limitations is limited to the height dictated by “good

engineering practice’ (GEP). Id. § 7428(a)(1). This

height was defined by Congress to be that necessary to

ensure against certain kinds of localized atmospheric dis-

turbance created by the source itself or nearby obstacles,

and resulting in excessive concentrations of pollutants in

the immediate vicinity of the source. Jd. § 7428(c). The

regulations under review define a number of the statu-

tory terms, such as “nearby” and “excessive,” provide

5a

various methods for determining GEP height and 4eter-

mine when each may be used, implement a statutory bar

on credit for use of “dispersion techniques” other than

stack height, define a statutory “grandfather” clause for

pre-1970 stacks, and provide a timetable for implementa-

tion of the regulations by the states, which are the pri-

mary enforcers of the Act.

We have reviewed carefully the specific provisions chal-

lenged here. Among them we find certain aspects of the

regulatory scheme to be contrary to the terms of the

statute and others to be arbitrary and capricious exer-

cises of the discretion conferred on the EPA by the Act.

These provisions must therefore be overturned. We re-

mand certain other provisions for further consideration

by the agency in light of our discussion here. The re-

mainder of the challenged regulations we uphold.

I

The events leading up to the enactment of the section

of the Clean Air Act Amendments of 1977 involved in

this case have been described in our opinion in Alabama

Power Co. v. Costle, 686 F.2d 328, 388-91 (D.C. Cir.

1979) ,' and in the House committee report accompanying

those amendments, H.R. REP. No. 294, 95th Cong.,

1st Sess. 81-92 (1977) [hereinafter cited as HousE RE-

PORT]. Briefly, under the drastic overhaul of the Clean

1 Alabama Power brought before this court regulations im-

plementing the Act’s prevention of significant deterioration

(PSD) program, intended to protect areas still having rela-

tively clean air, 42 U.S.C. §§ 7470-7491 (Supp. V 1981). See

43 Fed. Reg. 26,380, 26,888 (1978). Included was a provision

that in determining a source’s emissions limitations, both the

source and surrounding polluters would have their emissions

modeled as though they were emitted at GEP height. Indus-

trial petitioners urged that only the emissions from the source

itself should be modeled at GEP height; the surrounding fa-

cilities should be modeled with their actual stack heights. We

upheld the regulation. See 636 F.2d at 388-92. The instant

case concerns, inter alia, the method of setting GEP height

for each source.

6a

Air Act undertaken in 1970, EPA was directed to pre-

scribe national ambient air quality standards for various

pollutants. 42 U.S.C. § 1857c-4 (1976). Upon promulga-

tion of an air quality standard, each state was required

to adopt and submit to EPA a state implementation plan

providing for attainment and enforcement of the stand-

ard. Id. § 7410(a).

Initially, EPA approved state plans that authorized,

in place of direct limitations on emissions, the use of tall

stacks to meet air quality standards. EPA also allowed

the use of other dispersion techniques called supplemental

or intermittent control systems, which are programs that

vary the release of pollutants over time depending on

whether meteorological conditions favor dispersion. EPA’s

policy was overturned by the courts, which, led by the

Fifth Circuit, ruled that the Act allowed reliance on dis-

persion techniques only after implementation of “the

maximum degree of emission limitation achievable.”

NRDC v. EPA, 489 F.2d 390, 410 (5th Cir. 1974), rev’d

on other issues sub nom. Train v. NRDC, 421 U.S. 60

(1975) ; see Kennecott Copper Corp. v. Train, 526 F.2d

1149, 1151-60 (9th Cir. 1975), cert. denied, 425 U.S.

935 (1976) ; Big Rivers Electric Corp. v. EPA, 528 F.2d

16, 20-22 (6th Cir. 1975), cert. denied, 425 U.S. 934

(1976). “Informed as well as chastened by these ju-

dicial decisions,” Alabama Power, 636 F.2d at 390, EPA

in 1976 issued guidelines that, while placing primary

emphasis on emissions reductions, allowed the use of tall

stacks to meet ambient standards in two situations: (1)

where the source was already using “the best available

emission control technology,” or (2) where use of such

technology would be “economically unreasonable or tech-

nologically unsound.” Stack Height Increase Guideline,

41 Fed. Reg. 7450, 7451-52 (1976) [hereinafter cited as

1976 Guideline] .*

*The predecessor to this guideline was evidently issued

only after the initiation of a contempt proceeding for failure

7a

Congress emphatically rejected this approach in the

1977 amendment of the Act that is the subject of the

present controversy. In introducing the bill on the Senate

floor, Senator Muskie criticized the 1976 guidelines for

allowing any use of tall stacks whatsoever in meeting

ambient standards: “Far from prohibiting the construc-

tion of tall stacks or the use of intermittent controls, the

guidelines provide that once minimal emission control re-

quirements are met, polluters are encouraged to substi-

tute unlimited stack height for any further control of

emissions.” 128 Conc. REc. 18,027 (1977). The mood

in the House was the same, id. at 16,203 (remarks of Rep.

Waxman, a sponsor of the House bill) (“The committee

has unequivocally rejected the use of tall stacks and inter-

mittent controls as a final means of compliance with the

Clean Air Act’s requirements.”), and in section 123 of the

amended Act Congress banned virtually all reliance on

tall stacks or “any other dispersion technique” in achiev-

ing compliance with ambient air quality standards, 42

U.S.C. § 7423(a) (Supp. V 1981).

Congress did not, however, actually prohibit tall stacks

or limit their height; in fact, section 123 specifically en-

joins the EPA Administrator (“the Administrator’)

from prohibiting any increase in stack height or restrict-

ing the height of any stack in any manner. Id. § 7423(c).

Rather, the law limits the credit that may be obtained

for such stack height in determining whether the plant

will cause ambient air standards to be violated or in-

crease pollution by too large an increment. The credit

system is based on techniques of modeling whereby, via

to comply with the Fifth Circuit’s order in NRDC v. EPA.

See NRDC v. EPA, 529 F.2d 755, 760 (5th Cir. 1976) (“We

deny the [contempt] motions . . ., noting however, that such

motions apparently were necessary to compel the Adminis-

no al ti tet issued more than a year

ore,”).

8a

mathematical or small-scale physical demonstrations, a

plant’s emissions can be assumed to emerge from a cer-

tain stack height and then mapped as they fall to earth

in order to see their effect on ambient pollution. Thus,

section 123 is intended to eliminate any credit a plant

might receive for the dispersive effects of a tall stack

in the calculation of its emissions limitations, although

the stack itself remains in place.

There were essentially three reasons for Congress’s re-

fusal to allow reliance on tall stacks and intermittent con-

trol measures. First, dispersion techniques do not reduce

the amount of pollution in the air, but merely spread it

around, exporting it to other areas where it is too late

to control the problem, and exposing previously pristine

areas to contamination. See, e.g., HOUSE REPORT, supra

p. 5, at 84-85. Second, the long-range transport of cer-

tain pollutants was also linked to the formation of “acid

rain,” which is precipitation containing acidic derivations

of sulfur oxide and nitrogen oxide emissions. Acid rain

was thought responsible for reduced soil and water pro-

ductivity in certain areas, particularly the Northeast

and Canada. See, e.g., id. at 88-84, 85-86; 123 CoNG.

REc. 18,026 (1977) (remarks of Sen. Muskie). Third,

intermittent control systems, which are dependent on syn-

chronizing plant operation with weather conditions, were

thought to be unreliable and virtually impossible to en-

force. See, e.g., id.; HOUSE REPORT, supra p. 5, at 82-

83, 87.

In rejecting the limited permission to use dispersion

techniques contained in the 1976 guidelines, however,

Congress largely adopted the distinction drawn in those

guidelines, and in a 1973 stack height proposal, between

stack heights that would be allowed without question and

those that would be regarded as a dispersion technique.

See id. at 93 (statute “affirm[s]” the standard used by

the Administrator). This distinction is the main battle-

ground of the present litigation. The guidelines had

9a

based the distinction on “good engineering practice,”

wiich the preamble to the 1973 proposal defined as

follows:

[A] stack which conforms to good engineering prac-

tice is sufficiently tall that emissions from the stack

are not significantly affected by the atmospheric

downwash, eddies, or wakes created by the facility

or nearby structures and terrain. Emissions from

stacks which are shorter than required by good engi-

neering practice often can cause excessively high

ground level concentrations and nuisances within,

and in the immediate vicinity of, the facility.

Use of Supplementary Contro! Systems and Implementa-

tion of Secondary Standards, 38 Fed. Reg. 25,697, 25,700

(1973) (proposed rules) [hereinafter cited as 1973

Guidelines]. Congress appears to have taken the main

elements of this statement in its definition of good engi-

neering practice hsight. Section 123 defines that height as

the height necessary to insure that emissions from

the stack do not result in excessive concentrations of

any air pollutant in the immediate vicinity of the

source as a result of atmospheric downwash, eddies

and wakes which may be created by the source itself,

nearby structures or nearby terrain obstacles.

42 U.S.C. § 7423(c) (Supp. V 1981).

As the quoted language from the 1973 proposal sug-

gests, downwash, eddies, and wakes are caused by the

wind hitting structures or other obstacles near the stack.

The turbulence created in the wake of the obstacles tends

to suck a plume of emissions down to the earth before it

has had a chance to disperse, resulting in inordinately

high pollution concentrations near the plant. See also

House REpPoRT, supra p. 5, at 93 (“Without some provi-

sion for stack height, a plume released downwind of such

a structure might become engulfed by turbulent eddys

[sic] within the wake of the structure.”); 122 Cone.

Rec. 34,384 (1976) (remarks of Sen. Muskie) (“This is

10a

necessary in order to allow good plume rise without down-

washing the plume onto the local area.’’).

While the statute generally left the determination of

GEP stack height to regulations to be promulgated by

the EPA Administrator, it set an upper limit of two-and-

one-half times the height of the stack’s source. 42 U.S.C.

§ 7428(c) (Supp. V 1981). This, too, was taken from

the 1973 and 1976 guidelines. See 1976 Guideline, supra

p. 6, at 7451-52; 1973 Guidelines, supra p. 9, at 25,700,

25,701. The formula was seen as codifying “the stack

height-nearby structure relationship that has been looked

to historically as a responsible way of dealing with the

problem of aerodynamic downwash.” HOUSE REPORT,

supra p. 5, at 93. While the guidelines used the two-

and-one-half-times standard as the standard GEP stack

height, however, Congress was clear in its conference

report that the statutory formula was generally intended

to be an upper limit, and that if EPA found that the

problem of downwash, eddies, and wakes could be pre-

vented by stacks of less than two-and-one-half times fa-

cility height, it was to give credit only for the lower

height. 128 Conc. Rec. 27,071 (1977) (Clean Air Con-

ference Report (1977): Statement of Intent; Clarifica-

tion of Select Provisions). Nevertheless, like the guide-

lines, the statute provides that a plant operator can get

credit for a greater-than-formula height by demonstrat-

ing to the satisfaction of the Administrator that a greater

height is needed to prevent the downwash problem de-

scribed in the Act. 42 U.S.C. § 7423(c) (Supp. V 1981).

In barring any credit for tall stacks and other disper-

sion techniques, Congress believed it was merely reaf-

firming a command it had given in the 1970 Clean Air

Act amendments. It “intended to ratify the general

thrust, if not the specific holdings, of the three U.S.

courts of appeals” that had interpreted the earlier Act

to bar primary reliance on such techniques. House RE-

PORT, supra p. 5, at 91. As a result, the section’s grand-

lla

father clause provides an exemption only for stacks “in

existence” or dispersion techniques “implemented” before

the date of the 1970 amendments, and not for those built

between 1970 and the enactment of the 1977 amendments.

42 U.S.C. § 7423(a) (Supp. V 1981) ; see House REPORT,

supra p. 5, at 93.

Section 128 directs EPA to issue regulations imple-

menting these provisions by February 7, 1978, 42 U.S.C.

§ 7423(c) (Supp. V 1980) (“[n]ot later than six months

after August 7, 1977”), and the states are directed to

revise their applicable implementation plans, as neces-

sary, within nine months of the promulgation of EPA’s

regulations, id. § 7401 note (the later of one year after

enactment of the Act or nine months after promulgation

of EPA regulations). Proposed regulations were not is-

sued until January 12, 1979, however. Stack Height Reg-

ulations, 44 Fed. Reg. 2608 (1979). Under a court-

ordered timetable, Sierra Club v. Gorsuch, No. 81-0094

(D.D.C. June 22, 1981, modified Aug. 20, 1981, and

Feb. 17, 1982), EPA then issued a revised set of pro-

posed regulations on October 6, 1981, 46 Fed. Reg. 49,814

(1981), and finally issued final regulations on Febru-

ary 8, 1982, 47 Fed. Reg. 5864 (1982) (to be codified in

40 C.F.R. $$ 51.1, 51.12, 51.18). Petitioners NRDC and

Sierra Club filed motions for reconsideration on various

grounds, all of which were denied. Petitions for review

were then filed in this court under the Act’s sixty-day

review provision. 42 U.S.C. § 7607(b) (Supp. V 1981).

The core of the new regulations is the determination

of GEP stack height. The rules provide three methods;

a source operator may use whichever of the. methods

yields the greatest GEP height. First, a “de minimis

height” of sixty-five meters is permitted for all sources

regardless of the size or location of any structures or

terrain features. .47 Fed. Reg. at 5868 (to be codified at

40 C.F.R. § 51.1(ii) (1)). The Administrator stated that

this height represented “a reasonable estimate of the

12a

height needed to insure that emissions will not be af-

fected by common ground-level meteorological phenomena

which may produce excessive pollutant concentrations.”

Id. at 5865. The de minimis feature is not challenged in

this case.

Second, the regulations provide two mathematical for-

mulas, one to be used by stacks in existence on Janu-

ary 12, 1979, the date of publication of EPA’s original

proposed rules, and the other for stacks whose construc-

tion commenced after that date. The formula to be used

by the earlier stacks is what the Administrator termed

“the traditional engineering formula of two and one-half

times the height of the nearby structure” (hereinafter

called the 2.5 Rule). Jd. The second formula is a refine-

ment of the first that is intended to reflect the reduced

height needed to surmount the less severe downwash

effects produced by tall, thin structures. See 46 Fed. Reg.

at 49,815. The refined formula gives credit for the height

of the nearby structure plus one-and-one-half times the

lesser of the height or width of the structure (hereinafter

called the 1+1.5 Rule). 47 Fed. Reg. at 5868 (to be

codified at 40 C.F.R. § 51.1(ii) (2) (ii)). Under either

formula, only “nearby” structures may be used. “Nearby”

is defined as a distance from the stack of five times the

lesser of the height or width of the structure itself, up

to one-half mile. Jd. at 5869 (to be codified at 40 C.F.R.

§ 61.1(jj)).

The third method for calculating GEP stack height is

by a physical demonstration, either a fluid model or a

field study. This method must be used to obtain credit

for downwash produced by terrain features or by any

obstacle that is not “nearby.” The demonstration must

show that a greater-than-formula height is needed to

ensure that emissions from the stack do not result in

excessive concentrations of any air pollutant. Jd. at 5868-

69 (to be codified at 40 C.F.R. § 51.1(ii) (3)). “Exces-

sive concentrations” is defined as maximum concentra-

18a

tions of a pollutant at least forty percent in excess of the

maximum concentrations of the pollutant in the absence

of the downwash, eddy, or wake effects. 7d. at 5869 (to

be codified at 40 C.F.R. § 51.1(kk)).

We will describe other details of the challenged regula-

tions as needed in dealing with each of petitioners’ objec-

tions to the new rules. We will discuss first those objec-

tions going roughly to the formulation and operation of

the three methods, next those going to when the various

methods are applied, then objections to certain exemp-

tions from the regulations, then the various grandfather

clauses provided by the regulations, and finally an ob-

jection to EPA’s timetable for state implementation of

the regulations.

II

A. Definition of “Nearby”

As noted, the new regulations define “nearby” for

purposes of application of the formulas as five times the

height or width of the structure, up to one-half mile.

There is no specific limit on the distance that structures

and terrain obstacles may be from the stack in order to

be taken into account in a demonstration. NRDC and

Sierra Club argue that Congress intended to limit the

structures and terrain obstacles that may be said to

cause downwash to those within one-quarter mile of the

stack, so that the regulations are contrary to law with

regard to both the formulas and demonstrations.

The source of petitioners’ argument is certain language

in the House Report that they say indicates Congress’s

understanding that “nearby” meant no more than one-

quarter mile away. The Report’s discussion of the term

is as follows:

In affirming the 21 times standard used by the

Administrator, the committee referred to downwash

problems created by both manmade structures and to

terrain features located “nearby” the source. The

committee intends that the term “nearby” be strictly

l4a

construed, in keeping with the general policy of

statutory interpretation favoring strict construction

of exceptions and variances. If this term were con-

strued too broadly (that is, to apply to manmade

structures or terrain features one-fourth to one-half

mile away from the source or more), the result could

be an open invitation to raise stack heights to un-

reasonably high elevations and to defeat the basic

underlying committee intent.

House REPORT, supra p. 5, at 93 (emphasis added).

EPA apparently selected the one-half-mile limitation

solely in response to this expression of congressional in-

tent; it itself believed that downwash effects occur at

greater distances from the obstacles and that the five-

times-height-or-width rule was a better approximation

of the longevity of those effects than is the one-half-mile

limit. See 44 Fed. Reg. at 2610; 46 Fed. Reg. at 49,819.

We agree that the one-half-mile limitation is a suffi-

cient response to the congressional intent. The statute

specifically gives the EPA Administrator discretion to

promulgate regulations to determine GEP height and

the House report clearly indicates that that discretion ex-

tends to defining terms such as “nearby” as necessary,

presumably in light of the Administrator’s expertise. The

report standing alone is arabiguous on whether it was try-

ing to impose a specific limitation on the definition of

“nearby,” but when read in light of the statute’s broad

conferral of discretion it is most readily interpreted as

an attempt only to suggest the scale of magnitude that

the committee had in mind, and not to pick a specific fig-

ure. The one-half-mile limitation that EPA chose is at

or near the outer edge of the range Congress was think-

ing of, but it does not go beyond it. Thus, we find the

Administrator’s choice to be consistent with both the leg-

islative history and the statute.

The refusal to give any content to the statutory term

“nearby” when applied to demonstrations is quite a dif-

lba

ferent matter.’ The rationales offered were that (1) some

obstacles create downwash effects at distances of more

than one-half mile, (2) the fluid modeling methods would

accurately tell precisely when such effects were occurring,

and (3) the boundaries of many terrain features are not

always distinct and thus a specific distance limitation

would be difficult to apply. See 46 Fed. Reg. at 49,819:

sec also id, at 49,821 (accuracy of fluid modeling). Thus,

the Administrator believed that the statute was intended

to allow credit for the height needed to avoid the effects

of ony downwash that could cause excessive concentra-

tions of pollutants.

While such an approach might make a good deal of

sense, we do not think it is the approach commanded by

the statute. The primary support for the Administrator’s

reading is that the language from the House Report

quoted above, which places great emphasis on the word

“nearby” as a carefully imposed limitation on the de-

termination of GEP height, discusses the term only in

connection with the formula method, not the demonstra-

tion technique. The Report disevsses demonstrations in a

different paragraph and does not mention the word

“nearby” there at all. HOUSE REPORT, supra p. 5, at 93.

Moreover, applying the “nearby” limitation only to the

formula method and not to demonstrations would cer-

tainly be rational because, unlike demonstrations, the

formulas do not otherwise select the obstacles to be

taken into account. Without some limitation, the for-

* EPA somewhat lamely suggested that the new regulations

do in fact give some meaning to the word “nearby” as applied

to demonstrations: “Any terrain feature which is close

enough to a source to cause excessive concentrations must be

considered a ‘nearby’ feature.” 46 Fed. Reg. at 49,819. If this

were the statute’s command, it would be no different if the

word “nearby” did not apply to demonstrations. Thus, “near-

by” must effectively be read out of the statute in order to

reach EPA's interpretation.

l6a

mulas could conceivably be used to give credit for the

height of any obstacle upwind of the stack, even though

the turbulence created in the wake of those obstacles

could not possibly disrupt the plume. Demonstrations,

however, do select the obstacles that will be taken into

account, because they more accurately tell which will

actually cause downwash.

Nevertheless, the legislative history is not explicit

enough to refute the clear thrust of the statutory lan-

guage. In describing the demonstrations that are per-

mitted, the statute states that the operator may show

“that a greater height [than two-and-one-half times the

height of the source] is necessary as provided under the

preceding sentence.” 42 U.S.C. § 7423(c) (Supp. V 1981)

(emphasis added). The “preceding sentence’ defines

“good engineering practice” as the height necessary to

ensure that excessive concentrations will not result from

downwash created by the source, “nearby structures or

nearby terrain obstacles.” Jd. (emphasis added). Thus,

the statute explicitly applies the “nearby” limitation to

demonstrations.

If such a reading were utterly nonsensical, we might

be tempted, as a matter of interpretation of likely in-

tent, to strain the statutory language to arrive at a

more rational result. See, e.g., American Tobacco Co. v.

Patterson, 456 U.S. 63, 71 (1982) (“Statutes should be

interpreted to avoid . . . unreasonable results whenever

possible.”); 2A C. SANDS, STATUTES AND STATUTORY

CONSTRUCTION § 45.12 (4th ed. 1978) (same). But such

an approach to interpretation of statnies must be used

with utmost caution, for the line between irrationality

and mere bad policy is a wavering and uncertain one.

Here, sense can be made of a limitation on the stack-

height credit operators may receive in addition to the

requirement that the height be necessary to avoid ex-

cessive concentrations of pollutants in the immediate

vicinity of the plant. When EPA originally proposed

17a

these regulations in 1979, for example, it apparently in-

tended some version of the “nearby” limitation to apply

to demonstrations; it explained that it interpreted “the

Congressional guidance as a criterion to indirectly estab-

lish a reasonable upper limit on GEP stack heights.” 44

Fed. Reg. at 2610; see id. at 2611 (“As in the case of

GEP determinations using the empirical equation, the

definition of ‘nearby’ is integral to determine the extent

to which structures or terrain features may reasonably

influence the fluid modeling or field study based GEP

determination.”). That is, Congress may merely have

wanted to place an absolute cap on the credit a source

could receive for a tall stack, perhaps out of a distrust

of the political and scientific methods by which the

agency's determinations of stack height credit were to be

made.

In addition, as the Administrator’s rationale for elimi-

nating the “nearby” limitation suggests, that limitation

will primarily affect sources located in hilly terrain, since

it is unlikely that a manmade obstacle will be large

enough to create downwash problems at distances of

greater than half a mile. Yet there are strong indica-

tions in the legislative history that Congress specifically

sought to discourage utilities from locating in hilly ter-

rain, because such locations tend to require very tall

stacks, leading to greater dispersion of pollutants. For

example, the House report states that it was “the ex-

pectation of this committee that persons responsible for

siting new facilities will not locate them next to terrain

features which will produce . . . downwash.” HOUSE

REPORT, supra p. 5, at 98. See infra pp. 37-88 (other in-

dications of this intent). Applying the “nearby” limita-

tion to all methods of deriving GEP heights may be fur-

ther evidence of Congress’s lack of solicitude for utilities

located next to mountains (as opposed to those located

next to very local, and presumably smaller, terrain fea-

tures that may be surmounted with less stack height).

18a

Finally, even if there is an element of arbitrariness in

Congress’s applying the “nearby” limitation to demon-

strations, we note that the entire GEP stack height al-

lowance was already regarded as something of a conces-

sion from the strict command that dispersion not be used

to meet air quality standards. Congress may simply have

been unwilling to compromise further the predominant

purpose of reducing emissions in order to take account of

what it may have regarded as fairly attenuated claims

of downwash. There is frequently some arbitrariness

when a lawmaker says, “Thus far and no further,” but

such lines frequently must be drawn.

The statutory language must thus be interpreted to

apply “nearby” to demonstrations as well as to the for-

mulas as a limitation on the amount of downwash that

will be taken into account in giving credit for stack

height. We remand, therefore, for the EPA to include

new regulations that apply the same “nearby” limitation

to demonstrations as is applied to the formulas.

B. Definition of “Excessive Concentrations”

When a source owner seeks to obtain credit for stack

height greater than provided by the formulas, it must

demonstrate that downwash can be expected to cause

“excessive concentrations” of pollutants in the vicinity

of the plant. The regulations define “excessive concen-

trations” as a forty-percent increase over the levels in the

absence of the downwash-creating obstacle. 47 Fed. Reg.

at 5869 (to be codified at 40 C.F.R. § 51.1(kk)).

Petitioners NRDC and Sierra Club argue that such a

definition is arbitrary and capricious because it does not

measure any absolute amount of pollutant that is a

danger to health or welfare, but instead invokes a rela-

tive measure. They state that the forty-percent rule

would permit a source located in a very clean area to

raise its stack height credit, even if the downwash

avoided would only increase pollutant concentrations by

19a

a very small amount that would be of no harm to any-

one. They urge a return to a standard like the one

EPA originally proposed in 1979. Under that standard

a source would have had to show that downwash would

both increase pollutant concentrations by at least forty

percent and cause a violation of a national ambient air

quality standard or, in certain areas, an incremental in-

crease limitation. 44 Fed. Reg. at 2611.

EPA eliminated the second of these criteria—requiring

a violation of an air quality standard—in 1981. It said

that its air quality standards and incremental limitations

are unable to measure the high pollutant concentrations

of extremely short duration that are typical of down-

wash. 46 Fed. Reg. at 49,819. This is because the stand-

ards measure pollutants after they have dispersed in the

air, not in the concentrated doses caused by downwash.

Id, Also, the standards measure average concentrations

over time periods ranging from one hour to one year,

which is too long to measure accurately the peak con-

centrations of downwash pollutant. Jd. (In this court,

EPA states that it is currently reviewing its SO. stand-

ard to determine whether a short-term standard is neces-

sary to protect public health. Brief of Respondents at 35

n.27.)

Thus, only the forty-percent test was left. In this cir-

cumstance, the basis for, and derivation of, that test

become especially important.

The forty-percent figure was derived from a review

of the scientific literature on stack heights, including re-

ports of wind tunnel tests EPA itself conducted during

the rulemaking. EPA discovered a consensus in the liter-

ature that “the well established 2.5 times rule” was the

stack height necessary to avoid “significant effects” for

most buildings. The 1+1.5 Rule was found to be the

consensus for tall, thin buildings. See Guideline for De-

termination of Good Engineering Practice Stack Height

(Technical Support Document for Stack Height Regula-

20a

tions) (July 1981), Joint Appendix (J.A.) at 1086 [here-

inafter cited as Technical Support Doc.].

EPA then looked to the amount by which ground-level

concentrations of pollutant were increased when a 2.5

or 1+1.5 stack was in place. It found that these formulas

did not eliminate all effects of downwash but limited in-

creased concentrations to roughly forty to eighty percent

over the preexisting concentrations, with eighty percent

representing an unusually high amount. See id. at 1096.

EPA reasoned that if under traditional engineering prac-

tice the increase in concentrations was limited to about

forty percent, then increases over forty percent could be

regarded as excessive. See Draft Technical Support Docu-

ment for Determination of Good Engineering Practice

Stack Height (July 31, 1978), J.A. at 42 (Where range

of increases recorded at GEP height was 20% to 40%,

report concluded that “an increase in maximum concen-

trations less than 20% is less than expected for GEP

stack height while an increase in maximum concentra-

tions greater than 40% is excessive.”’).

The forty-percent figure is thus the lesson of history:

it is what the engineering community has regarded as

too much downwash. NRDC and Sierra Club argue that

this approach is all wrong, since Congress’s real concern

in encouraging stack heights high enough to prevent “ex-

cessive concentrations” of downwash was the protection

of human health. Therefore, they say, EPA must exer-

cise its own independent judgment and define the term

to allow enough height to prevent health-threatening

downwash, and no more. Because the forty-percent

standard is based on a relative value that varies with

background concentrations, NRDC and Sierra Club as-

sert, it does not measure the absolute levels of pollutant

that are a danger to health.

Our review of the statute and its legislative history

discloses sharply conflicting signals on whether Congress

intended to legislate the proexisting engineering practice

2la

or only so much stack height as would protect health or

welfare. On the one hand, the primary statutory stand-

ard was “good engineering practice,” suggesting an in-

tent to mandate whatever engineers had been doing.

Moreover, the entire purpose of the statute was to remedy

an abuse that had arisen whereby polluters were building

stacks solely to evade Clean Air Act requirements; Con-

gress may well have wanted to return to whatever en-

gineers would do in the absence of the Act. In addition,

the statute explicitly endorsed the standard—the 2.5 Rule

—that Congress thought was the traditional engineering

practice.

Nevertheless, Congress did not stop there, for it pro-

vided a very precise definition of what it regarded as

“good engineering practice,” suggesting that it did not

intend to leave the question of stack heights entirely to

professional standards. While the statutory term at the

center of that definition, “excessive concentrations,” is

ambiguous—it could be read as either in excess of the

previously recognized standard or in excess of some ab-

solute standard, such as safety—-the legislative history

points strongly in the direction of a meaning turning on

danger to public health. The House committee report

describes why downwash can be a problem in the follow-

ing terms: “When this [downwash] occurs even the

plume from a well-controlled source may cause air

quality standards (or other requirements) to be vio-

lated.” HOUSE REPORT, supra p. 5, at 93. We think it a

strain to refer to the previously recognized standard as a

“requirement”; it seems likely that the committee was

referring to other legal requirements, such as state nui-

sance law or the Clean Air Act’s prevention of significant

deterioration increments.

EPA’s 1973 stack height guidelines, which, as we have

said, appear to have been Congress’s main source for the

statutory language, also strongly suggest that the evil

sought to be avoided by good engineering practice was

22a

tied to some minimum level of Canger or inconvenience

to the community. They provided:

Emissions from stacks which are shorter than re-

quired by good engineering practice often can cause

excessively high ground level concentrations and nui-

sances within, and in the immediate vicinity of, the

facility. . . . The use of stack height up to the level

of good engineering practice is encouraged by EPA

in order to avoid local nuisances.

1973 Guidelines, supra p. 9, at 25,700; see also, e.g.,

Commonwealth v. South Covington & C. St. Ry., 181

Ky. 459, 463, 205 S.W. 581, 583 (1918) (“[A] common

or public nuisance is the doing of or failure to do some-

thing that injuriously affects the safety, health, or morals

of the public, or works some substantial annoyance, in-

convenience, or injury to the public... .”); United

States v. County Board, 487 F. Supp. 187, 148 (E.D.

Va. 1979) (“The term ‘nuisance’. . . includes everything

that endangers life or health, gives offense to the senses,

violates the laws of decency, or obstructs the reasonable

and comfortable use of property.’’).

What seems most likely is that Congress thought tra-

ditional engineering practice and protection of health

were the same thing. If that is the case, however, what

are we to do if it develops, as NRDC and Sierra Club

argue, that traditional engineering practice in fact dic-

tates a height that is in some cases much higher than

necessary to protect human health? We are saved from

the full rigors of this potential conundrum by the confer-

ence committee. Its report states:

[I]f it should be determined that downwash, eddies,

and wakes can be prevented by stacks of less than

21% times facility height, the Administrator’s rule

should give ‘credit’ only for the height needed to

avoid these conditions.

. . . In other words, it was not our purpose to

make a Congressional judgment about what stack

23a

height was needed to prevent downwash. We intend

EPA to make this judgment, subject only to the Con-

gressional prohibition on the excessively high stacks

of over 21% times building height.

123 ConG. Rec. 27,071 (1977).

What this passage suggests is that Congress wanted

the Administrator to determine the height necessary to

avoid excessive concentrations of downwash-caused pollu-

tion. Since Congress believed that the 2.5 Rule was in

fact the good engineering practice rule, see HOUSE RE-

PORT, supra p. 5, at 93 (“A stack height value produced

by reference to this historical relationship is referred to

as ‘good engineering practice’ stack height and has been

used by EPA in its regulations.”), the passage suggests

that the conference committee saw the possibility of a

distinction between its definition of the amount of down-

wash to be avoided and what engineers had been doing.

If that turned out to be the case, the committee was

clear that the statute’s definition would govern. Thus,

development of a standard governing the height of stacks

by refarence solely to what engineers had been doing,

with no regard for some real life values, was contrary to

the intent of Congress.

Reading the House committee report as a whole con-

firms this view. It begins its discussion of the details of

the bill with the observation that downwash is a prob-

lem because it causes air quality standards or other re-

quirements to be violated, and only then discusses the

“historically . . . responsible way of dealing with the

problem.” Jd. This suggests that meeting air quality

standards was primary in its mind and that good engi-

neering practice was merely a way to do so.

Finally, we are considerably bolstered in our view that

Congress was thinking primarily of dangers to health be-

cause that was the position originally taken by the Admin-

istrator. In the 1979 proposed regulations, primary re-

24a

liance was placed on the requirement that the downwash

in question cause a violation of air quality standards.

The forty-percent proviso was merely intended, EPA

wrote, “to establish a reasonable upper bound for credit-

able stack heights.” 44 Fed. Reg. at 2611.

When EPA dropped the air quality standards as one

of its criteria for measuring “excessive,” it did not ad-

dress whether the forty-percent test measured danger to

health or welfare. Neither EPA nor the utilities that

have intervened on its behalf have disputed the conten-

tion of Sierra Club and NRDC that the forty-percent

rule, because it measures relative changes in “pre-

existing concentration,” cannot measure the absolute

levels of pollutant that are a danger to health. See

Brief of Petitioners at 39. We agree that the level of

pollutant that is a danger to health is an absolute value:

the Act clearly envisions that the national ambient air

quality standards that are to protect health and welfare

will be defined in terms of maximum concentrations of

each pollutant, see, ¢.g., 42 U.S.C. § 7409(c) (1976) (re-

quiring promulgation of standard for “NO, concentra-

tions over a period of not more than 3 hours’’), and that

is the way the Administrator has consistently imple-

mented the Act, see, ¢.g., American Petroleum Institute

v. Costle, 665 F.2d 1176 (D.C. Cir. 1981) (approving

ozone standard of 0.12 parts per million), cert. denied,

455 U.S. 1084 (1982).

We disagree, however, with the petitioners’ interpreta-

tion of the present regulation, and thus with their conclu-

sion regarding the relation of the regulation to health.

NRDC and Sierra Club appear to assume that the forty-

percent increase in concentration is to be an increase over

the preexisting levels in the area including background

concentrations of pollutants. We believe, however, that

the increase is to be measured against the amount of the

source’s own plume that falls to the ground even without

downwash, regardless of preexisting or background con-

centrations of pollutant from other sources,

25a

Petitioners’ interpretation is arguably the most natural

reading of the language of the regulation itself, which is

as follows:

“Excessive concentrations” for the purpose of de-

termining good engineering practice stack height in

a fluid model or field study means a maximum con-

centration due to downwash, wakes, or eddy effects

produced by structures or terrain features which is

at least 40 percent in excess of the maximum con-

centration experienced in the absence of such down-

wash, wakes, or eddy effects.

47 Fed. Reg. at 5869 (to be codified at 40 C.F.R.

$51.1(kk)). The regulation does not specify whether

the “maximum concentration experienced in the absence

of such downwash” is to be measured with or without

pollutants generated by other sources. The 1979 proposal

was similarly ambiguous. See 44 Fed. Reg. at 2614

(maximum concentrations “due in part or whole to down-

wash, wakes, or eddy effects’’).

The preamble to the final regulations, however, is ex-

plicit that the forty-percent standard requires the source

to demonstrate that “maximum concentrations caused by

the source’s emissions from its proposed stack height,

without consideration of nearby structures or terrain

obstacles, will increase by at least 40 percent when the

effects of the structures or terrain obstacles are consid-

ered.” 47 Fed. Reg. at 5865 (emphasis added). Even

more important, we see no reason why, as a scientific

matter, one would rationally include background concen-

trations in the calculation.

Although this court’s knowledge of the operation of

downwash is admittedly rudimentary, it seems most likely

that the amount of additional pollutant that is brought

to the earth by means of downwash will somehow relate

to the amount of the original fallout, either because fall-

out is a process similar to downwash and therefore pro-

26a

duces proportionate amounts of grounded pollutants, or

because both relate proportionately to the density of the

plume. Presumably, therefore, the amount of a plume

that falls to earth near the plant even in the absence of

downwash is either an absolute number for all plumes

emitted at a certain height or, more likely, varies with

the density of the plume. Conversely, it seems unlikely

that the amount of downwashed pollutant from a given

stack height should vary with background concentrations

of that pollutant in the area. That would mean that the

eddies and whirlpools that bring the plume down to earth

would operate more effectively the dirtier the surround-

ing air becomes, which, even if possible, seems odd. We

conclude, therefore, that the forty-percent increase refers

to an increase in the amount of pollutants from the plume

that fall to the ground regardless of atmospheric con-

ditions.

We have not had any argument on whether the regula-

tion, so interpreted, in fact estimates dangers to health

and welfare. On the one hand, it seems likely that it was

such dangers to health and welfare that traditional engi-

neering practice, from which the forty-percent figure was

derived, sought to prevent, at least in a very rough way.

On the other hand, EPA has not made this argument,

relying instead on congressional approval of good engi-

neering practice per se. In addition, the EPA scientists

who derived the forty-percent figure did not describe it

as an accurate measure of danger to health or welfare.

It was rather a measure of what scientists conducting

wind tunnel experiments in the past had thought was “a

significant concentration difference” as they observed the

smoke pouring out of their model smokestacks, See Tech-

nical Support Doc., supra p. 20, at 1092. The EPA scien-

tists cautioned:

The visualized . . . studies can be strongly biased by

the observer's eye and are extremely sensitive to the

density of the smoke. The information from concen-

27a

tration profiles is influenced strongly by where the

traverse through the plume is made [to determine

the plume centerline] and the judgment in determin-

ing what constitutes a significant concentration

difference. ...

. . . Although the consensus opinion in the scien-

tific literature strongly supports using [the 1+1.5

Rule] to determine GEP stack height, actual studies

could show the need for a much taller or lower stack

depending on one’s interpretation of what is a sig-

nificant influence and on the effect of possible plume

rise.

Id, at 1089-92 (emphasis added).

Moreover, we note that EPA chose the forty-percent

figure from a range of increased concentrations produced

by a stack 2.5 times the height of the obstacle, and forty

percent was at the low end of that spectrum. The choice

of forty percent as the definition of “excessive” is more

consistent with an attempt to arrive at a reasonable

upper limit on stack height—i.e., to place a floor on the

amount of increased concentration that would justify an

increased stack height—rather than an attempt to dis-

cern the historical concept of safe levels of downwash.

Reliance on the lower figure alone also does not appear

to be consistent with the clearly expressed congressional

expectation that credit for stacks in excess of the 2.5 Rule

would “be highly infrequent and that the latitude given

the Administrator to allow full credit for such stack

height [would] be exercised with circumspection and ut-

most caution in those rare circumstances proven to justify

its use,” HOUSE REPORT, supra p. 5, at 93.

Finally, apart from the intention of EPA in develop-

ing the forty-percent rule, we think it unlikely that even

the reinterpreted present rule will measure an absolute

pollutant concentration that is dangerous to health, rather

than a range of concentration increases varying with the

density of the plume and other factors. Of course, it may

28a

be that, for all stacks large enough to be of concern, that

range of increases will be entirely above the threshold

of danger to health or welfare. EPA has not said so,

however, and our examination of the derivation of the

figure suggests strongly that that is not the case.

We think our best course is to remand the definition of

“excessive concentrations” to the Administrator with in-

structions to develop a standard directly responsive to the

concern for health and welfare that motivated Congress

to establish the downwash exception. We do not condemn

the historical approach EPA has taken to deriving that

standard, but we caution EPA to be aware that it is

writing under substantially different conditions from

those that faced the engineers who first developed the

rules of thumb for stack height. The engineers could be

satisfied with a conservative rule that was absolutely

sure to eliminate health hazards, but only local ones;

EPA must be more stringent, since any extra height will

mean increased emissions and longer transport of pol-

lutants, both of which Congress has instructed the agency

to minimize. Therefore, EPA must satisfy itself in some

way independent of history that the standard it derives in

fact fairly approximates the stack height level needed to

protect local health and welfare; in doing so, moreover,

it should err on the side of reducing stack height, in

keeping with Congress’s command that credit for stack

heights above the 2.5 Rule height be granted with “ut-

most caution.” These two precepts are the heart of our

holding on this issue.

C. Failure to Consider Plume Rise

Plume rise refers to the tendency of exhaust gases to

continue to rise after they leave the stack because of their

momentum and heat. Petitioners NRDC and Sierra Club

assert that in deriving the 1+1.5 and 2.5 Rules EPA has

ignored plume rise. They argue that the failure to con-

sider plume rise is arbitrary and capricious, because it

-will lead to the prediction, of excessive concentrations

where none wi!! occur since the “effective” height of the

stack will be much higher than the physical height. Thus,

they say, the GEP formulas will allow higher GEP height

than needed to ensure against excessive concentrations of

pollutant caused by downwash.

EPA admits that the formula does not take account

of plume rise, but asserts that “[u]nder the very high

wind cenditions that cause downwash, no plume rise

takes place near the source.”” Summary of Comments and

Responses on the October 7, 1981 Proposal of the Stack

Height Regulations (Dec. 1981), J.A. at 1190 [herein-

after cited as 1981 Responses]; accord Technical Sup-

port Doc., supra p. 20, at 1102 (“[T]he critical condi-

tions for determining GEP stack height for most sources

are considered likely to be high winds associated with

neutral atmospheric stability with little plume rise near

the sources.”) ; see also 46 Fed. Reg. at 49,820 (“[T]he

comments correctly pointed out that the technical support

document was based on studies which did not include

plume rise.’’).

NRDC and Sierra Club dispute this factual conclusion,

citing two pieces of evidence. First, they point out that

EPA’s own regulations for running the demonstrations

that operaturs may use to gain above-formula height re-

quire the inclusion of plume rise. See 46 Fed. Reg. at

49,820 (“Fluid models and field studies take into account

gas flow rates and temperature, in addition to stack

height. Accordingly, they will take into account some

plume rise in establishing the GEP stack height.”) ;

Draft Guideline for Use of Fluid Modeling to Determine

Good Engineering Practice Stack Height (June 1979),

J.A. at 677-78, 680 [hereinafter cited as Fluid Modeling

Guideline]. Second, they cite a report submitted by the

Tennessee Valley Authority in this rulemaking that es-

timates the plume rise above the top of the stack during

strong winds to be 99, 84, and 145 meters at 76, 91, and

80a

305 meter stacks, respectively. See An Analysis of

Terrain-Induced Aerodynamic Disturbances Near the

Kingston Steam Plant, Kingston, Tennessee, at 1-1, Rec-

ord at 77 app.

We view this as a factual dispute that we must re-:

view under the substantial evidence standard, see 5

U.S.C. § 706(2)(E) (1976). We side with EPA. Its

conclusion that plume rise is not significant rests pri-

marily on the wind tunnel studies cited in its technical

support document, which did not provide for plume rise,

-yet derived approximately the same formula as appar-

ently had arisen as “a practical formula” from years of

empirical observation, presumably including any plume

rise. Compare Technical Support Doc., supra p. 20, at

1080 (“This rule arose during the early part of this

century as a practical formula. [A 1955 study] report(s]

that the rule had been successfully used by the British

electricity generating industry during the previous 20

years.”) with id. at 1086 (“A review and evaluation of

the current literature . . . reveals a consensus that [the

2.5 Rule is) the stack height necessary to avoid signifi-

cant effects for buildings whose projected width is greater

than its height. . . . [Otherwise, the 1+1.5 Rule is ap-

propriate.]”). Since studies that do not account for

plume rise arrived at the same conclusion that was de-

rived from observations including: plume rise, it seems

fair to infer that at least the usual amount of plume

rise does not have a significant effect on downwash. In

response to concerns about the possibility of artificially

increasing plume rise beyond the normal amount, EPA’s

regulations prohibit as a dispersion technique installa-

tion of fans and heaters intended to enhance plume rise.

See 47 Fed. Reg. at 5868 (to be codified at 40 C.F.R.

§ 51.1(hh)); id. at 5867; 46 Fed. Reg. at 49,820; infra

pp. 50-57.

That EPA has allowed operators to account for plume

rise in demonstrations does not persuade us that the

8la

1+1.5 Rule is unprincipled, because we think it entirely

rational for EPA to be more concerned that even small

amounts of plume rise be accounted for when a source

is seeking greater height than provided by the formulas.

Congress specifically directed that such increased height

be allowed only “with circumspection and utmost caution

in those rare circumstances proven to justify its use.”

HOusE REPORT, supra p. 5, at 93. (The report was re-

ferring to heights in excess of the 2.5 Rule, but we think

it clear that its thinking applies equally to the more ac-

curate 1+1.5 Rule.) The formulas, on the other hand,

are intended to be easy to apply and, of necessity, some-

what rough rules of thumb. We think such a dual ap-

proach was within the contemplation of Congress and is

not a capricious use of EPA’s limited resources.

Petitioners’ citation of the significant plume rise re-

ported in the TVA study does not substantially under-

mine EPA’s assertion that plume rise is fairly insignifi-

cant under downwash conditions. The TVA report does

not contradict EPA’s finding that, particularly as wind

speed increases, plume rise near the stack, where down-

wash occurs, is generally small even though plume rise

further downwind may be significant. Such a phenome-

non is an expected consequence of high wind conditions,

and it is consistent with EPA’s view that plume rise

has little effect on downwash near the stack. See Fluid

Modeling Guideline, supra p. 29, at 666 (“Under such

conditions [high wind speed and neutral stability], plume

rise near the source where its rise is dominated by mo-

mentum flux, will be small while its rise farther down-

wind may be largely due to buoyancy [heat] flux.’).

We affirm the refusal to include plume rise in the

derivation of the formulas.

D. Inclusion of Plume Impaction

Plume impaction occurs when a plume of exhaust gases

emitted from a stack hits a higher hill or mountain down-

82a

wind of the stack. Under stable atmospheric conditions,

the plume can hit the mountain before it has dispersed,

causing high concentrations on the mountainside. See

1981 Responses, supra p. 29, at 1166.

In response to comments received after its 1979 pro-

posed regulations, EPA decided to allow credit for stack

heights needed to avoid violation of national air quality

standards on the elevated terrain. See 46 Fed. Reg. at

49,815-16. The new regulations allow a source to receive

credit for the amount of its stack necessary to ensure

that violations will not occur on the mountain as a result

of the amount of the mountain’s height that is above

GEP height. 47 Fed. Reg. at 5869 (to be codified at 40

C.F.R. § 51.12(1)).* Without plume impaction credit, the

* The operation of the plume impaction credit is difficult to

explain but, ultimately, ingeniously simple in conception.

Three steps are involved. See 47 Fed. Reg. at 5867.

First, the GEP stack height is calculated with regard to

downwash-causing obstacles. If a violation of air quality

standards is predicted by reason of the plume hitting a moun-

tain higher than GEP height, then the source may go to the

second step. If no violation is modeled, then the source can-

not claim impaction credit.

Second, an emission limitation is set by imagining that the

mountain is as tall as the GEP stack height calculated in step

one. Thus, it is assumed that the mountain is short enough

to permit the GEP stack height to throw the plume over the

mountain, and an emissions limitation is set so that no viola-

tion will occur on the truncated mountain.

source would have to reduce its emissions to prevent

modeled violations on the mountainside.

Petitioners NRDC and Sierra Club argue that section

123 does not permit EPA to give credit for stack height

necessary to avoid any phenomena other than “down-

wash, eddies and wakes,” and that plume impaction is

not one of these statutorily specified exemptions. Plume

impaction is caused by obstacles downwind of the stack,

rather than upwind of it, and generally occurs when

there is little wind to disperse the plume, rather than

when the wind is strong.

EPA admits that plume impaction is not the same as

downwash, eddies, or wakes, but argues that they are

sufficiently similar that the same rationale should apply

to it. 47 Fed. Reg. at 5866 (“In all of these events,

structures or terrain features interfere with plume dis-

persion.”); 1981 Responses, supra p. 29, at 1167-68

(“These conditions are similar but independent of each

other since they generally occur under different meteoro-

logical conditions.”). The agency relies on its general

authority under section 301 of the Act to “prescribe such

regulations as are necessary to carry out [its] functions

under [the Act].” 42 U.S.C. § 7601(a)(1) (Supp. V

1981).

EPA’s construction of the statute is condemned by the

general rule that when a statute lists several specific

exceptions to the general purpose, others should not be

implied. See, e.g., A.H. Phillips, Inc. v. Walling, 324

U.S. 490, 498 (1945) (“Any exemption from such hu-

manitarian and remedial legislation must . . . be nar-

emissions to precisely the amount needed to avoid violations

84a

rowly construed ... .”); Colorado Public Interest Re-

search Group, Inc. v. Train, 507 F.2d 748, 747 (10th

Cir. 1974) (“{WJhere the legislature has acted to except

certain categories from the operation of a

law, it is to be presumed that the legislature in its ex-

ceptions intended to go only as far as it did, and that

additional exceptions are not warranted.”).

Had we any doubts that this rule should apply to this

case, they are eliminated by the specific instruction in

the House committee report that the term “nearby”

should be “strictly construed, in keeping with the gen-

eral policy of statutory interpretation favoring strict

construction of exceptions and variances.” HOUSE RE-

PORT, supra p. 5, at 93; see also supra pp. 15-18 (discus-

sion of meaning of “nearby”). Not only the word

“nearby,” but the entire permission to give credit for

“good engineering practice” height constitute exceptions

or variances. Congress sought to prohibit reliance on

stack height to achieve air quality standards except in

certain cases that it very specifically defined.. The speci-

fied cases are where stack height is needed to prevent

excessive concentrations resulting from “downwash, ed-

dies and wakes.” We should be extremely chary of add-

ing any others.

EPA argues, however, that this rule should be softened

when it appears that Congress was not informed of the

problem and therefore did not deliberately omit it. EPA

asserts that this is such a case. See 47 Fed. Reg. at 5866

(“Section 123 does not mention impaction. However,

neither the language of the statute nor the legislative

history show that this omission was deliberate.”). We

35a

several factors, including fuel and fuel additives, that

affect automobile emissions suggests that at least some

members of Congress did not expect statutory term

“fuel” and “fuel additives” to include other potential

causes of pollution, such as motor oil). We conclude, how-

ever, that the obverse rule advanced by EPA—that if

there is no evidence that Congress knew of or considered

the other things, the presumption should be that they are

included in the statutory exception—would be contrary

to the strict construction of exceptions directed by judi-

cial doctrine and by the legislative history of this law.

Cf. Harrison v. PPG Industries, 446 U.S. 578, 592 (1980)

(“{I]t would be a strange canon of statutory construc-

tion that would require Congress to state in committee

reports or elsewhere in its deliberations that which is

obvious on the face of a statute.”).

In any case, there is some evidence in the legislative

history of the 1977 amendments that Congress was in

fact made aware of the problem of plume impaction in

hilly terrain. Representatives of electric utilities ap-

peared before the congressional subcommittees consider-

ing the amendments and discussed the deleterious effects

the new laws would have on utilities. They contended

that several provisions in combination would limit the

availability of plant sites in mountain areas. Among the

provisions raentioned were those that sought to prevent

the deterioration of clean-air areas, called prevention of

significant deterioration (PSD) provisions, and the tall

stacks section. Thus, a representative of the Edison Elec-

tric Institute, the principal national association of

adverse effect of the amendments:

(2) More coal-fired power plants would have to be

built in the mid-west and in eastern coastal plains

and less in the Appalachians and the West because

TPAD] ond tall otcch lito in'eneno ot ity tenet

{PSD} and tall stack limits in areas

36a

Clean Air Act Amendments of 1977: Hearing on S. 251,

S. 252, and S. 253 Before the Subcomm. on Environmen-

tal Pollution of the Senate Comm. on Environment and

Public Works, 95th Cong., Ist Sess. (pt. 2), at 231 (1977)

(written testimony of Donald G. Allen).

Moreover, these limitations on siting were linked spe-

cifically to plume impaction by the testimony of E. Allan

Hunter, president of the Utah Power & Light Co., before

the same subcommittee. Mr. Hunter proposed a variance

procedure for allowing certain plants to exceed the rele-

vant PSD limitations for five percent of the year to

account for those days on which plume impaction might

occur :

Our problem lies in the nature of the topography

out in Utah. Utah consists of narrow valleys, with

mountainous or hilly terrain on either side. The

mountainous terrain models [that] are now being

used to predict pollutant concentrations indicate that

perhaps a few days in the year under stagnant air

conditions the SO, concentration on the adjacent hill-

sides would exceed the allowable limits.

Id. at 37 (oral testimony) ; see also id. at 387 (written

statement of Mr. Hunter) (“What we here urge is an

alternative that would facilitate good plant siting... .”);

id. at 339 (same) (“This material [certain studies] does

indicate that without . . . some relief from the short term

plume impact on high terrain ..., we cannot build suffi-

cient capacity to supply the electric needs of our cus-

tomers in the next twenty years.”). Although these com-

plaints were heard and became part of the congressional

debate on the amendments, see, ¢.g., 122 Conca. REC.

34,405 (1976) (remarks of Sen. Tower, opponent of the

37a

Thus, although no one made explicit the link advanced

in the regulations between taller stacks and plume impac-

tion, these excerpts suggest that at least some members

of Congress were aware that (1) requiring short stacks

would somehow tend to preclude certain potential sites

for power plants in hilly terrain, and (2) plume impac-

tion was one reason that fewer such power plant sites

would be available. It may be too much of a leap to say

that Congress understood that taller stacks might help

to reduce the effect of plume impaction, and rejected such

an approach. But we think we may infer at least that

the problems created by plume impaction and by requir-

ing short stacks in hilly terrain were brought to Con-

gress’s attention, and Congress chose not to focus on,

and resolve, them. This suggests a relative indifference

to the problem of nearby mountains causing very strin-

gent emissions limitations, an indifference that is at odds

with the willingness to avoid the strict limitations that

would be required because of downwash, eddies, and

wakes, were it not for section 123.

Little more need be said to refute the argument raised

in this court by a number of utility intervenors that ex-

cluding plume impaction from the calculation of emission

limitations would result in much stricter limitations for

utilities located in mountainous terrain than for ones

located in the flatlands. Since this would mean a decline

in jobs and industrial activity in mountain regions, the

utilities argue, EPA has properly construed section 123

in light of the purpose stated in section 101 of the Act

“to protect and enhance the quality of the Nation’s air

resources so as to promote the public health and welfare

and the productive capacity of its population.” 42 U.S.C.

§ 7401(b) (1) (1976) (emphasis added).

88a

tain areas. Thus, the House committee report noted the

committee’s “expectation” that “persons responsible for

citing new facilities will not locate them next to terrain

features which will produce .. . downwash.” House Re-

PORT, supra p. 5, at 938. Moreover, it quotes EPA Ad-

ministrator Douglas Costle’s statement that the Adminis-

tration thought it “ ‘clearly preferable to require tighter

controls or more careful siting to solve our air quality

problems rather than disperse pollutants over greater

distances.’” Jd. at 92 (emphasis added). In his testi-

mony, Mr. Costle went on to state, “If we later learn that

tall stacks are essential for siting certain types of facili-

ties, we would consider asking Congress for authority to

allow tall stacks for such facilities in cases where public

health would not be affected.” Clean Air Act Amend-

ments of 1977: Hearings on H.R. 4151 & H.R. 4758 Be-

fore the Subcomm. on Health & the Environment of the

House Comm. on Interstate & Foreign Commerce, 95th

Cong., Ist Sess. (pt. 2), at 1679 (1977).

Thus, we do not think section 123 permits EPA to take

plume impaction into account in setting the degree of

emission limitation required for sources in hilly areas.

EPA’s reliance on its general authority to make rules

necessary to carry out its “functions” does not avail it,

because, as we pointed out in Lubrizol Corp. v. EPA, 562

F.2d 807, 815 n.20 (D.C. Cir. 1977), a specific statutory

directive “defines the relevant ‘functions’ of EPA,” so

that section 123 is the sole source of statutory authority.

We admit that there is much to commend EPA’s ac-

tion from a policy perspective. Without EPA’s plume

impaction provisions, the law discriminates harshly

against utilities located in mountainous terrain, for it

will require them to emit far less than their flatland

counterparts. The only cost of allowing EPA to mitigate

that discrimination by bringing flatland and mountain

emissions limitations closer together would be that moun-

89a

tain utilities would have to disperse their pollutants more

widely. See supra note 4.

We note, however, that Congress viewed tall stacks as

a problem not only because they did not decrease the

loading of emissions into the air, but also, and independ-

ently, because they served to disperse pollutants more

widely. Wide dispersion had been linked to the formation

of acid rain, tended to export pollution to previously pris-

tine areas, and made enforcement more difficult because

of the difficulty of tracing dispersed pollutants back to

their source. See House REPORT, supra p. 5, at 83-87;

see also An Assessment of the Potential Effect of Stack

Height on Sulfate Formation and Sulfur Deposition (De-

cember 1979), J.A. at 791 (“Tall stacks allow more sul-

fate formation and less [sulfur] removal than an equiv-

alent release at lower heights... .”). Of course, such

wider dispersion is permitted anyway by the Act, see 42

U.S.C. § 7428(c) (1976) (EPA may not restrict in any

manner the actual stack height of any source), but the

plume ‘impaction rules would encourage or, effectively,

require it. It is conceivable that Congress would decline

to encourage the very tall stacks no doubt needed to over-

come plume impaction in mountainous terrain. Thus, the

construction we place on the statute is harsh, but not

utterly irrational, and therefore we are constrained to

give the statutory exception the strict interpretation that

Congress specifically intended.

EPA's attempt to reduce efnissions limitations by s0

40a

provided by the formulas. Petitioners Sierra Club and

NRDC assert that it was an abuse of discretion for EPA

not to require demonstrations in two other cases: (1)

whenever local or federal pollution authorities believed

the formulas overestimated the height needed to prevent

excessive concentrations of downwash-caused pollution,

and (2) whenever a facility sought to raise an existing

stack. The latter argument is based on the theory that

stacks have historically been built to avoid downwash, so

that there is a presumption that existing height is suffi-

cient.

The first of these provisions was included in the 1979

proposed regulations, and the second—regarding existing

stacks—was mentioned then as a specific case in which

demonstrations might be required in particular instances.

44 Fed. Reg. at 2614; see id. at 2610. In 1980, in con-

nection with a request for approval of credit for stack

height increases at two existing power plants in Ohio,

EPA decided to require demonstrations in all cases where

a source sought to raise an existing stack height. 45 Fed.

Reg. 42,279, 42,281-82 (1980). The agency explained

that it had become increasingly concerned that current

emissions levels were “resulting in significant regional

air pollution problems, particularly acid rain.” Jd. at

42,281.

Since publication of EPA’s [1979] proposal, several

sources have requested relaxations of SO, emission

limitations in connection with stack height increases

up to the height permitted by the GEP formula. EPA

is concerned that allowing sources automatic credit

for GEP formula is roperly encouraging

emission limit relaxa and SO, emission increases

4la

pending consideration of the final rules. 46 Fed. Reg.

28,650 (1981).

Neither the 1981 reproposed regulations nor the final

regulations under review contain either provision. EPA

gave three reasons for the changes. First, it expressed

great faith in the formula as an accurate measure of

GEP height. In the 1981 reproposal, for example, EPA

stated, {W]e have established that the formula is the

best determination of good engineering practice stack

height based on nearby structures.” 46 Fed. Reg. at

49,820; see also 1981 Responses, supra p. 29, at 1172

(“(A)fter reviewing the facts and information available,

EPA believes that the formula provides a very good esti-

mate of the stack height necessary to avoid excessive

concentrations caused by downwash.’’).

Second, evidently as to the proposal that local authori-

ties be allowed to require demonstrations for below-

formula stack heights, EPA asserted that “inconsisten-

cies could result.” 46 Fed. Reg. at 49,820. This comment

is cryptic, but we suspect that it must refer to incon-

sistencies between lax and zealous state environmental

protection agencies, resulting in different requirements

for similarly situated plants in different states.

Third, EPA cited a passage from the House committee

report that it says indicates an intent to allow automatic

credit up to forraula height. 1981 Responses, supra p. 29,

at 1173. The passage is from the report’s discussion of

the PSD provisions, in which the committee argues that

those provisions will allow sufficient industrial develop-

ment in all but the cleanest areas. House REPORT, supra

p. 5, at 159-64. The report adds:

42a

stack heights up to 214 times, or more in some cases

under the bill.)

Id. at 162 (emphasis added) *

This last reason is easily neutralized. We agree that

the House committee, and perhaps the Congress generally,

"EPA also suggested that the 1980 decision to require

demonstrations for all increases of existing stacks was in-

tended as a response to a temporary problem, rather than a

permanent solution. It explained the decision as follows: “In

June 1980, faced with the requirement to approve or dis-

approve State Implementation Plan revisions for two Ohio

power plants and still in the process of evaluating its policy

on increase [sic] stack heights at existing facilities, EPA

established as stringent a policy as possible to handle the

issue.” 1981 Responses, supra p. 29, at 1172.

We note that EPA has at times attributed a good deal

more permanence to its 1980 decision than it now does. See

46 Fed. Reg. 28,650, 28,650 (1981) (withdrawing the policy)

proposal.”) (emphasis added). Nevertheless, we realize that

EPA issued the new policy without public comment and

hurriedly, in order to comply with a commitment it had made

43a

probably had in mind a system of determining GEP stack

height involving a generalized formula applicable to all

sources except those seeking greater height. This appears

to have been the general conception of the 1973 guidelines

upon which Congress drew in drafting section 123, see

1973 Guidelines, supra p. 9, at 25,700 (2.5 Rule produces

proper height in “fairly level terrain,” but “[(f]or more

complex situations, . . . detailed engineering and meteor-

ological investigations . . . should be conducted to deter-

mine the appropriate stack height”), and the House re-

port’s discussion of section 123 itself seems to make the

same assumption, see HOUSE REPORT, supra p. 5, at 93

(“affirming the 214 times standard” but recognizing need

to approve greater height when “aerodynamics of a

source” require it).

Nevertheless, the statute itself is carefully designed to

commit the determination of GEP height to “regulations

promulgated by the Administrator” and speaks of the 2.5

Rule only as an upper limit. The conference committee’s

report even more clearly evinces an intent to leave the

entire question of what method to use to determine GEP

height to the discretion of the Administrator (subject to

the requirement of demonstrations for any height above

21%, times the height of the source). The conference com-

mittee explicitly stated that the Administrator’s rule

“should give ‘credit’ only for the height needed to avoid”

the downwash problem, and suggested that that rule

might differentiate among various kinds of sources if it

was found that the height needed to avoid downwash so

varied. The report concluded, “In other words, it was

not our purpose to make a Congressional judgment about

what stack height was needed to prevent downwash. We

intend EPA to make this judgment ....” 123 Cone.

Rec. 27,071 (1977). The report does not depart from the

expectation that GEP height will usually be determined

by a formula, but it does make clear that the formula

up to the Administrator. Implicit in that discre-

power to decide when the formula must be

ay

z

44a

used. Therefore, our review here is not of an interpreta-

tion of specific congressional intent, but rather of the

agency’s exercise of its discretion.

In evaluating whether EPA acted arbitrarily and

capriciously in rejecting the two additional uses of dem-

onstrations it initially proposed, we are left, then, with

two explanations: an expressed belief in the accuracy

of the formulas, and a fear of inconsistent enforcement.

See generally SEC v. Chenery Corp., 382 U.S. 194, 196

(1947) (agency action must be judged solely on the

grounds invoked by the agency). Of the two explana-

tions, the central reason must be EPA’s confidence that

the formulas provide “a very good estimate of the stack

height necessary to avoid excessive concentrations caused

by downwash,” 1981 Responses, swpra p. 29, at 1172, for

if EPA had less confidence in the formulas, its view of

how much inconsistency in state enforcement it could

tolerate would surely change.

EPA’s confidence in the formulas developed under the

agency’s apparent view that “excessive” meant an amount

over the amount permitted by traditional engineering

practice. We have found this to be an inadequate defini-

tion of the term, however, because Congress intended the

agency to arrive at an independent conclusion regarding

the stack height needed to prevent dangers to health and

welfare resulting from downwash. See supra pp. 18-28.

The words “excessive concentrations,” from which we

45a

trations). We must remand for the agency to consider

how well the formulas protect against excessive concen-

trations and thus whether they are so accurate that dem-

onstrations need not be used to justify raising stack

heights in the two circumstances noted at the outset.

The Administrator’s second justification for the present

rule is also deficient, and we therefore caution him that

should he again propose the disparate use of demonstra-

tions, he must rely on something other than bald asser-

tions about inconsistency of enforcement. We are not in

a position to say whether a well-grounded fear of incon-

sistent state enforcement might conceivably justify not

providing states with discretion to require demonstrations.

We are certain, however, that it will not do for EPA

merely to assert that “inconsistencies could result.” In-

consistencies will always result from a regulatory scheme

that relies on some measure of state enforcement, but the

Act clearly envisions state implementation of generalized

directives from EPA. See, e.g., 42 U.S.C. § 7407(a)

(Supp. V 1981) (“Each State shall have the primary

responsibility for assuring air quality within the entire

geographic area comprising such State... .”); see also

Train v. NRDC, 421 U.S. 60, 68-70 (1975) (discussing

various states’ approaches to implementing 1970 amend-

ments to Act). At the least, EPA must specify why it

is that such “inconsistency” is especially likely and harm-

ful in this case, and that inconsistency must be weighed

against the harms to flow from allowing widespread over-

estimation of stack heights to go uncorrected.

We note two other considerations that were clearly

absent from EPA’s initial determination of the amount

to which demonstrations were to be used and that should

be considered pursuant to our remand. First, there is

virtually no evidence in the record supporting a conclusion

that the formulas err only in one direction. Although a

number of commentators suggested that the 2.5 Rule was

regarded as yielding a minimum height necessary to avoid

46a

downwash, see J.A. at 142-43 (comments of Rohm & Haas

Co.) ; id. at 389 (comments of The Southern Co.), the

data discussed by EPA scientists in their review of the

literature suggest no such bias. Some of the data in fact

suggest that the formulas overestimate the necessary

stack height in some circumstances, while virtually no

data indicates that they underestimate it. See Technical

Support Doc., supra p. 20, at 1087 (“The extent of sig-

nificant effects for rounded structures are likely not as

great as those for sharp-edged structures, although there

is very little information available.”) ; see also id. at 1083

(downwash less at rounded-edged than at sharp-edged

structures). The conclusion of EPA was that while there

was a consensus around the 1+1.5 Rule, “actual studies

could show the need for a much taller or lower stack de-

pending on one’s interpretation of what is a significant

influence and on the effect of possible plume rise.” Jd. at

1092.

In this light, EPA cannot use the inaccuracy in the

formulas to allow demonstrations to obtain credit for

height above that provided by the formulas but not to

limit credit below it. Rationality demands that if the

inaccuracy is neutral, the corrective device must be neu-

tral. The statute does not command otherwise. The pro-

vision for demonstrations for above-formula height does

not require the Administrator to provide for such demon-

strations if he believes they are unnecessary. That provi-

sion is part of the definition of good engineering practice

height, 42 U.S.C. § 7423(c) (Supp. V 1981), the deter-

mination of which the statute leaves to the Administra-

tor’s discretion, see id. § 7423(a) (1). The House com-

mittee report leaves no doubt that the provision for

demonstrations was a discretionary power, not a com-

mand. House REPORT, supra p. 5, at 93 (“In such in-

stances, the Administrator has been given discretion to

approve a State implementation plan which provides for

stack height greater than the 214 times standard.”).

47a

Second, EPA appears to have radically undervalued

the presumption raised by the fact that an existing stack

was built to less-than-formula height. The House com-

mittee recognized that “for many years, good air quality

management has meant building a stack sufficiently tall

to offset aerodynamic downwash created by structures in

the immediate vicinity of the stack.” House REPORT,

supra p. 5, at 93. It seems fair and logical to assume

that, particularly in the large plants governed by the Act,

good air quality management has been followed and that

dangers to health and welfare have not been tolerated.

There is, moreover, some data to support this assump-

tion, in that EPA, after its initial review of the several

applications for increased stack height credits for exist-

ing stacks that were filed after the 1979 proposed regula-

tions were issued, became convinced that some or all of

the increases were unjustified. See 45 Fed. Reg. at

42,281.

In the absence of a strong showing that this presump-

tion is mistaken, it may be rebutted in individual cases

only by a reliable indicator of the height needed to prevent

dangers to health or welfare caused by downwash. In the

present final regulations, EPA has severely undermined

its claim that the formulas are such an indicator by al-

lowing demonstrations to increase stack height above the

formula height without any special indication that that

was a class of sources for which the formulas were not

likely to yield the right result. Such inconsistency is the

hallmark of arbitrary action.

We remand for the EPA to reconsider whether, in light

of its new understanding of “excessive concentrations,”

demonstrations are necessary before stack heights may be

raised, even if the final height will not exceed formula

height.

F. Definition of “Stack” to Exclude Flares

A flare is a pipe used in the oil, natural gas, and chemi-

cal industries to vent combustible gases by burning them

48a

at the top. In its 1979 proposed regulations, EPA explic-

itly included “flare[s]” in its definition of the statutory

term “stack.” 44 Fed. Reg. at 2613. The affected indus-

tries, two government agencies, and the American Society

of Mechanical Engineers submitted comments arguing

that flares are different from stacks because flare height

is intended not to disperse pollutants but to allow for the

safe combustion of dangerous gases produced during mal-

functions in the industrial process. For this reason and

because it believed flare emissions were difficult to meas-

ure, EPA excluded flares from the definition of “stacks”

in its reproposed and final regulations. See 47 Fed. Reg.

at 5868 (to be codified at 40 C.F.R. § 51.1(ff)) (“ ‘Stack’

means any point in a source designed to emit solids, liq-

uids, or gases into the air, including a pipe or duct but

not including flares.”); 1d. at 5867; 46 Fed. Reg. at

49,817, 49,820. NRDC and Sierra Club argue that “flare

stacks” are essentially no different from stacks in that

they vent emissions into the atmosphere, and that their

height can be used to evade emissions limitations. There-

fore, they say, EPA’s exclusion of flares from the defini-

tion of “stack” is contrary to law.

We find that EPA’s definition of the term “stack” is a

reasonable interpretation of a more or less technical term

by the agency charged with implementation of the statute,

and therefore affirm its exclusion of flares. See generally

Zenith Radio Corp. v. United States, 487 U.S. 448, 450

(1978) (agency’s definition need not be the only reason-

able one, but must be “ ‘sufficiently reasonable’ to be ac-

cepted by a reviewing court”) (quoting Train v. NRDC,

421 U.S. 60, 75 (1975)); Lead Industries Ass’n v. EPA,

647 F.2d 1130, 1147 (D.C. Cir.) (“Where different inter-

pretations of the statute are plausible, so long as EPA’s

construction of the statute is reasonable we may not sub-

stitute our own interpretation for the Agency’s.”), cert.

denied, 449 U.S. 1042 (1980).

The record supports the conclusion that the engineering

community defines “stacks” to exclude flares, and that

49a

flare height is intended, under standard engineering prac-

tice, primarily to safeguard personnel and structures from

the heat, flames, and unburned toxic gases that emanate

during flaring, rather than to disperse the resulting con-

centrations of pollutants. See, e.g., J.A. at 200 (comments

of American Society of Mechanical Engineers); id. at

195-96 (comments of Monsanto Co.); id. at 203 (com-

ments of Shell Oil Co.) ; id. at 353-54 (comments of Chev-

ron U.S.A., Inc.). Some flares, if the release is small

enough or remote enough, burn the gases at ground level.

Id. at 358 (distinguishing “elevated flares” from “pit

flares” and “ground flares”). Moreover, in part because

of this primary purpose, flares are generally erected in

isolated areas where, unless there is a nearby terrain

obstacle, downwash is generally not a problem. Therefore,

the height demanded by safety might not be justifiable if

the sole aim were to prevent downwash. This seems un-

likely to have been Congress’s intent. Finally, there is no

mention of flares in the legislative history. We affirm

EPA’s definition of stack to exclude flares.

* Nevertheless, the pollutants produced by the combustion

that takes place at the top of flares are regulated under the

Clean Air Act just as the similar pollutants produced by the

combustion that occurs at the base of the stacks are. See, e.g.,

id, at 846-47 (comments of Michigan Dept. of Natural Re-

sources) (describing PSD limitations placed on ground level

sulfur dioxide impact of burning hydrogen sulfide derived

from natural gas). Therefore, there is presumably an incen-

tive for a source to raise its flare above the height dictated

by safety in order to be able to increase the dispersion of the

pollutants produced. See id, (80-meter limit on flare height

would reduce permissible SO, emissions from over 8000 to

about 2000 pounds per day). This is precisely the kind of dis-

persion usage that Congress sought to forbid.

While it may be impracticable to prevent this abuse via the

“good engineering practice” formulation developed by Con-

gress to deal with stack heights, excessive flare height still

might be a “dispersion technique” for which credit is barred

under section 128(a) (2), 42 U.S.C. § 7423(a) (2) (Supp. V

1981). We do not think it plain, as intervenor American

50a

G. Definition of “Dispersion Techniques”

Section 123 bars giving emission credit for tall stacks

and “other dispersion techniques.” EPA’s final definition

of “dispersion technique” includes, in addition to the tall

stacks and intermittent or supplemental control systems

mentioned in the statute, the “addition of a fan or re-

heater to obtain a less stringent emission limitation.” Ex-

pressly excluded from the definition are reheating the gas

stream to its original temperature after the use of a pollu-

tion control system, certain agricultural and silvicultural

uses of smoke, and “combining the exhaust gases from

several stacks into one stack.” 47 Fed. Reg. at 5868 (to

be codified at 40 C.F.R. § 51.1(hh)).

Sierra Club and NRDC object that the definition does

not include a number of dispersion techniques that should

Petroleum Institute asserts, that the term “any other disper--

sion technique” is directed at dispersion stratagems other than

height. The statute commands that the degree of emission

limitation required for “any air pollutant under an applicable

implementation plan” shall not be affected by either stack

height or any other dispersion technique. Since emissions of

flares are regulated by the applicable implementation plans,

and excess flare height is not excess “stack height,” it may

well be one of the “other dispersion techniques” regulated

under section 128(a) (2).

We make no ruling on this question. While NRDC and

Sierra Club have advanced the argument before this court, it

was apparently not put before the agency, and we do not

have its response. See J.A. at 911 (Sierra Club comments);

id, at 1217 (petition for rehearing); cf. United States v. L.A.

Tucker Truck Lines, 344 U.S. 33, 87 (1952) (“Simple fairness

to those who are engaged in the tasks of administration, and

to litigants, requires as a general rule that courts should not

topple over administrative decisions unless the administrative

body not only has erred but has erred against objection made

at the time appropriate under its practice.”). Moreover,

there is no suggestion that flare height above that required

for safety has ever been used as a dispersion technique or

that the problem is anything more than a theoretical one.

See generally infra p. 56.

5la

be barred: (1) the use of fans and reheaters to avoid a

more stringent emission limitation, rather than merely to

gain a less stringent one, (2) the addition of nozzles and

other devices to increase plume rise, (3) combining sev-

eral stacks into one for the purpose of increasing plume

rise, and (4) other such techniques polluters may devise

in the future.

EPA’s original proposal defined “dispersion technique”

far more broadly than its final rule, so that it included

“the manipulation of source process parameters, exhaust

gas parameters, stack parameters other than height, or

other selective handling of exhaust gas streams so as to

increase the exhaust gas plume rise.” 44 Fed. Reg. at

2613-14. It narrowed the definition in response to com-

ments that persuaded the agency that “many changes in

stack dimensions and exhaust gas characteristics are made

to improve the efficiency of the facility rather than to

enhance dispersion.” Response to Petitiors for Reconsid-

eration of the Stack Height Rules (May 1982), J.A. at

1225 [hereinafter cited as Reconsideration Decision]. In

its reproposed regulations, the agency added an explicit

test of a purpose to increase plume rise and provided that

combining stacks would not be deemed a dispersion tech-

nique unless there was manipulation of flow rates or tem-

perature for the purpose of enhancing plume rise. 46 Fed.

Reg. at 49,817; see id. at 49,816 (preamble says “for the

sole purpose of enhancing plume rise”). It commented

that “[tjhe significance of other dispersion techniques is

not well documented and the Agency intends to give fur-

ther consideration to the need for restrictions of this type

prior to promulgation.” Jd. at 49,816.

In its final regulations, as noted, EPA abandoned the

generic definition of “dispersion techniques” and limited

the term to specific equipment—fans and reheaters—in-

stalled for the purpose of obtaining a less stringent limi-

tation. It eliminated any test of intent in the permission

to combine several stacks into one. The agency explained

52a

that the change would “prevent only the installation of

equipment clearly intended to enchance [sic] plume rise.”

47 Fed. Reg. at 5867. It declined to prohibit other tech-

niques that were accompanied by such an intent because

such a test “would involve the Agency in subjective judg-

ments that could be difficult to support.” Reconsideration

Decision, supra p. 51, at 1225; accord id. at 1226 (“Such

subjective judgments would be difficult to make and to

enforce.”). “A test based on the installation of specific

equipment accompanied by a request for a relaxed emis-

sion limit was deemed to be more workable.” Jd. at 1225.

EPA did not dispute that all the techniques cited by peti-

tioners could be used in order to increase plume rise and

disperse pollutants so as to lower emissions limitations.

While somewhat less than ideally clear, EPA’s explana-

tions may be read to suggest that it weighed two factors

in deciding which of these techniques it would even at-

tempt to regulate: the likelihood that they would be used

as dispersion techniques, rather than as bona fide engi-

neering improvements (i.e., the “significance” of these

techniques), and the burden, both on enforcement agen-

cies and on industry, of attempting to differentiate legiti-

mate from illegitimate uses. EPA did not argue that use

of these techniques in order to increase plume rise would

not be a “dispersion technique” within the meaning of the

statute. Rather, it became convinced that few would use

such techniques and that the effort of catching those who

did would be great. In so doing, however, we think EPA

has created an exemption from the statute based upon its

perceptions of the costs and benefits of enforcing the law.

We find no source for such a power. See Alabama Power

Co. v. Costle, 686 F.2d 3238, 357 (D.C. Cir. 1979)

(“[T]here exists no general administrative power to cre-

ate exemptions to statutory requirements based upon the

agency’s perceptions of costs and benefits.”’).

' Although EPA has not argued to the contrary, we first

ascertain for ourselves that the techniques cited by peti-

58a

tioners are within the intended meaning of the statutory

term “dispersion techniques.” The language of the Act is

categorical—the amount of emission limitation “shall not

be affected in any manner by... any... dispersion

technique”—and a broad construction is appropriate to

achieve the remedial purpose intended. There is no help-

ful legislative history to shed light on the meaning of the

term. We think the words themselves, however, sweep

broadly enough to encompass at least the meaning urged

by petitioners: the use of devices, alterations to the stack,

or other techniques when they are significantly motivated

by an intent to gain emissions credit for greater disper-

sion. Were such techniques not included, they could be

used to enhance plume rise to such an extent as to make

the limitations on stack height illusory.

Since the regulations do not regulate all the techniques

contained in this definition, the regulations effectively cre-

ate an exemption not indicated in the statute itself. Such

categorical exemptions are generally not favored, Ala-

bama Power, 636 F.2d at 358, but there are two situa-

tioris in which they are allowed: cases of administrative

necessity and de minimis situations, id. at 358-61. EPA

has vaguely invoked both of these justifications. However,

both must be shown with greater rigor than EPA has

brought to bear here. See id. at 359 (agency bears “a

heavy burden to demonstrate the existence of an impossi-

bility”) ; id. at 360 (“Determination of when matters are

truly de minimis naturally will turn on the assessment

of particular circumstances, and the agency will bear the

burden of making the required showing.”’).

Apparently the only evidence concerning whether pro-

hibiting these techniques would yield a gain of trivial or

no value (in the sense of furthering the goals of the stat-

ute) consists of EPA’s finding that “many changes in

stack dimensions and exhaust gas characteristics are

made to improve the efficiency of the facility rather than

to enhance dispersion.” Reconsideration Decision, supra

54a

p. 51, at 1225, and like comments submitted by industry,

e.g., J.A. at 1029 (comments of Utility Air Regulatory

Group) (“Recombination of exhaust streams is typically

done for sound economic and engineering reasons, totally

apart from any environmental plume rise that might oc-

cur.”’) ; id. at 101-02 (comments of Stearns-Roger Inc.)

(listing engineering reasons for manipulating exhaust gas

velocity, temperature, etc.). Even these few, unspecific,

unquantified estimates do not attempt to establish that

use of these techniques in order to disperse pollutants

more widely would only trivially undermine the Act’s

command that emissions limitations be met by direct con-

trols. Neither the comments nor EPA’s responses suggest,

for example, that there is in fact no or little incentive to

implement these techniques because the potential reduc-

tion in emissions limitations would not be worth the cost.

Clearly, more is required to show that a technical viola-

tion is truly de minimis.

There is more evidence to support EPA’s claim of ad-

ministrative necessity, and that is where it has placed its

primary reliance. One local agency asserted that enforce-

ment of the original broad definition of dispersion techni-

ques would require scrutiny of “every possible aspect of

source construction, process flows, plant configuration and

siting,” which, it said, was beyond its capabilities. Jd. at

814 (comments of Allegheny Co. Bureau of Air Pollution

Control). Several states expressed less vehement concerns

about their ability to draw the lines required by the vari-

ous proposals. See id. at 965 (comments of Conn. Dept.

of Environmental Protection) (inquiring how a state

could establish with any certainty that enhanced plume

rise “was an intentional or an incidental result” of

changes to stack flow characteristics) ; id. at 236 (com-

ments of S.C. Dept. of Health & Environmental Control)

(seeking list of stack parameters for various source cate-

gories to be used in comparing changes proposed . by

sources). EPA found that discerning the subjective moti-

vation for stack and flow parameter changes, as required

55a

by its 1981 reproposal, would be “difficult.” Reconsidera-

tion Decision, supra p. 51, at 1225, 1226.

We do not see anything in the language, history, or

purpose of section 123 that “authorizes approaches that

deviate from the legislative mandate in response to con-

cerns about feasibility,” Alabama Power, 686 F.2d at 360.

The House committee report sternly cautions the Admin-

istrator to construe narrowly exceptions and permitted

variances from the bar on reliance on dispersion tech-

niques. See HOUSE REPORT, supra p. 5, at 93-94. Other

legislative history, ¢.g., 128 Conc. Rec. 18,027 (1977)

(remarks of Sen. Muskie) (quoted supra p. 7), as well

as the detailed cabining of the Administrator’s discretion

in the statute itself, suggest some distrust of the agency’s

prior flexibility towards industry.

In the absence of an authorization to take feasibility

into account in administering a particular statute, the

agency may avoid implementing a statute only by show-

ing that attainment of the statutory objectives is impos-

sible. See Alabama Power, 686 F.2d at 859 (“the agency

[bears] a heuvy burden to demonstrate the existence of

an impossibility” (footnote omitted)); NRDC v. Train,

510 F.2d 692, 718 (D.C. Cir. 1975) (“The sound discre-

tion of an equity court does not embrace enforcement

through contempt of a party’s duty to comply with an

order that calls him ‘to do an impossibility.’” (footnote

omitted) ). Especially in light of the fact that the ad-

forts at enforcement, see Alabama Power, 686 F.2d at

359 (“The agency's burden of justification in such a case

is especially heavy.”), the showing here falls far short.

Moreover, even if separately determining the intent of

56a

of plant improvements that are clearly legitimate or

clearly illegitimate. See id. at 358 (“Courts frequently

uphold streamlined agency approaches or procedures where

the conventional course, typically case-by-case determina-

tions, would, as a practical matter, prevent the agency

from carrying out the mission assigned to it by Con-

gress.”) ; see also J.A. at 236 (comments of S.C. Dept. of

Health & Environmental Control) (suggesting “list of

stack parameters for various source categories that can

be used in the comparative analysis”). It might be able

to quantify the amount of plume rise that could be pre-

sumed to have an engineering, rather than a dispersion,

rationale, in the manner that one commenter suggested.

Id. at 978-79 (comments of ASARCO Inc.) (proposing

to permit exit velocities of 1.5 times the 95th percentile of

local windspeeds raised to the fifth power). EPA might

also be able to select large classes of improvements that

may be exempted from regulation because their use as

dispersion techniques is no more than a theoretical possi-

bility or their impact on the goals of the Act is otherwise

trivial. By thus focusing enforcement resources narrowly

on the plant improvements likely to be undertaken for

the purposes of increasing dispersion, EPA should be able

to reduce substantially the number of cases in which a

full-scale examination of the motivation for the change

will be required.”

We see no evidence that EPA has adequately explored

these regulatory alternatives. Rather, when it appeared

that the definition of “dispersion techniques” would de-

pend on a question of intent, the agency simply cave. in

and allowed full credit for any plume enhancement tech-

57a

nique not involving fans or heaters. We overturn the

narrow definition of “dispersion techniques” and direct

EPA to develop rules disallowing credit for all “disper-

sion techniques” as that term is used in section 123, un-

less the agency can justify its failure under the standards

discussed in this opinion and in the opinion of this court

in Alabama Power, 686 F.2d at 857-61.

H. Definition of “Stack Height in Existence”

Section 123(a) contains a grandfather clause intended

to exempt pre-1971 stacks from the limitation on emis-

sion credit contained in the “good engineering practice”

provision. Other dispersion techniques implemented be-

fore the enactment of the Clean Air Amendments of 1970

are also exempted from emission credit limits. The clause

reads, “The preceding sentence shall not apply with re-

‘spect to stack heights in existence before December 31,

1970, or dispersion techniques implemented before such

date.” 42 U.S.C. § 7423(a) (Supp. V 1981).

EPA’s final regulations define a stack “in existence” to

mean that the owner or operator of the source had, by

December 31, 1970,

(1) begun, or caused to begin, a continuous program

of physical on-site construction of the stack or (2)

entered into binding agreements or contractual obli-

gations, which could not be cancelled or modified

without substantial loss to the owner or operator, to

undertake a program of construction of the stack to

be completed in a reasonable time.

47 Fed. Reg. at 5868 (to be codified at 40 C.F.R.

§ 51.1(gg)). Sierra Club and NRDC object that this def-

inition is contrary to the plain English meaning of the

statutory language, as well as to the legislative history.

They urge a definition like that contained in the 1979

proposed regulations: “ ‘In existence’ . . .. means that

stack heicht (of a stack) which has been constructed.” 44

Fed. Reg. at 2613. EPA adverts to the legislative history

58a

and clear purpose of the provision to grandfather sources

that before the 1970 amendments made good faith com-

mitments to use certain stack heights. In 1981 Responses,

supra p. 29, at 1164. An EPA study of the impact of the

stack height regulations stated that the change in the def-

inition of “in existence” would exempt stacks at four to

eight power plants from the requirements of section 128.

Impact Assessment Report for the Final Stack Heights

Regulations (Dec. 1981), J.A. at 1054, 1059 [hereinafter

cited as Impact Assessment Report].

The weightiest evidence in favor of the narrower 1979

definition is the fact that the 1977 amendments elsewhere

explicitly refer to facilities as to which construction con-

tracts had been awarded as of a certain date, suggesting

that “in existence” means some stage beyond the signing

of the contract. Section 128 itself in effect exempts the

stacks at a single power plant in Tennessee, known as the

Kingston Station, see 128 Conc. Rec. 18,480-81 (1977)

(remarks of Sen. Baker), in part by referring to stacks

“for which a construction contract was awarded before

February 8, 1974.” 42 U.S.C. § 7428(a) (Supp. V 1981) ;

see also id. §§ 7475(a), 7479(2) (PSD program applies

to facilities “on which construction is commenced after

August 7, 1977”; “commenced” defined to mean that the

operator has obtained all necessary permits and has be-

gun continuous program of construction or has entered

into binding agreements to do so, which cannot be modi-

fied without substantial loss). The distinction between

these provisions and the grandfather clause under review

was the primary basis for EPA’s original proposal that

“fin existence” be defined as physically constructed. See

44 Fed. Reg. at 2611 (“Since Congress in 1977 defined

‘commenced construction’ to include the acquisition of

permits, the beginning of actual construction or the enter-

ing into binding contracts, EPA believes the term ‘in ex-

istence’ must mean something more.”’).

NRDC and Sierra Club also cite language in the House

committee report that “sources which raised their stacks

59a

or constructed tall stacks after the date of enactment

should [not] be eligible for any credit,” House REPoRT,

supra p. 5, at 98, which they say indicates an intent to

include stacks under construction in section 123.

Nevertheless, we find EPA’s final definition of the

term to be a reasonable one and affirm it. See supra pp.

48-49. EPA’s interpretation is necessary to make the

clause equitable, which was undoubtedly Congress’s pur-

pose. Thus, the House committee report explained that the

committee “believe[d] that sources which in good faith

raised their stacks before the 1970 act limited dispersion

methods should not be penalized.” House REPORT, supra

p. 5, at 98. Clearly, a source that irrevocably and in

good faith contracted for a tall stack prior to the 1970

act may be penalized by application of the provision in

the same way that one that had completed construction

of the stack would be. Our emphasis on the words “in

good faith” and “penalized” in the language from the

House report is not contradicted by the passage cited by

petitioners. Petitioners emphasize in their passage the

words “raised their stacks or constructed tall stacks after

the date of enactment,” which they say means that any

stack that was not completed prior to the date of enact-

ment should be included in the statute. The two passages

appear close together and were evidently meant to refer

to the same distinction between stacks that were to be

included in section 123 and those that were not. Yet one

uses both the words “raised” and “constructed” and the

other uses just “raised,” which suggests that the words

were not written with the special emphasis petitioners

ascribe to them. In any case, there is no reason why the

terms “raised” and “constructed” should not be read to

mean the entire process of raising or constructing stack

height, from beginning to end.

Also, a similar grandfather clause in EPA’s 1976

stack height guidelines, which we have said were, along

with their 1973 predecessors, the source for much of the

6%a

detail in section 128, drew the line at commencement of

construction. 1976 Guideline, supra p. 6, at 7451 (“a

State may not take into account the dispersive effects of

an increased stack height for which construction com-

menced after January 31, 1972”). Moreover, the 1976

guidelines set out this grandfather clause in a section

headed, “Sources in Existence Prior to January $1, 1972,”

which might have been the origin of the statutory lan-

guage. Under the guidelines, a source that was under

construction in 1972 would be exempt from the stack

height limits, and thus “in existence,” if construction

of its stack height had commenced. Thus, the term “in

existence” in the guidelines could in some instances mean

“under construction,” the definition urged by EPA.

Further evidence that Congress did not mean the term

“in existence” to exclude stack heights contracted for or

under construction is that the use of that term in an-

other section of the 1977 amendments must be so read

to achieve Congress’s purpose. A section of the PSD

provisions requires certain sources “in existence on Au-

gust 7, 1977,” to install the best available retrofit tech-

nology to reduce visibility impairment produced by the

source’s emissions. 42 U.S.C. §7491(b)(2)(A) (Supp.

V 1981). The general permit provisions for new facili-

ties require more stringent protection of visibility for all

facilities ‘on which construction is commenced after Au-

gust 7, 1977.” Id. § 7475(a); see also id. § 7479(2) (A)

(definition of “commenced” to include “entered into bind-

ing agreements”). Thus, in order to provide some regula-

tion of visibility for sources under construction or con-

tracted for on August 7, 1977, “in existence” must be

read to mean “on which construction has commenced.”

EPA urges a parallel construction here. See Alabama

Power Co. v. Costle, 686 F.2d 328, 396 (D.C. Cir. 1979)

(“[Wle must assume that the meaning of a particular

term is to be consistent throughout the Act.’’).

The legislative history of the “Kingston exemption”

diminishes any inferences that may be drawn from the

6la

fact that it uses the phrase “for which a construction

contract was awarded” to mean essentially what EPA

urges as the definition of “in existence.” This provision

was added to the bill on the floor of the Senate at the

instance of Senator Howard Baker in order to exempt a

particular plant in his home state of Tennessee. See 123

Conc. REc. 18,480-81 (1977). It was thus drafted by a

different author, added late in the process when it was

too late to check it for consistency with other sections

of the Act, and debated without the benefit of a committee

report and with attention focused only on its purpose as

opposed to its details. Senator Baker may have seen

some ambiguity in the term “in existence” and used

more specific language to ensure that his purpose was

achieved. We do not think the possibility that one sen-

ator thought the statute’s grandfather clause was am-

biguous rebuts the other persuasive evidence of the rea-

sonableness of EPA’s interpretation of congressional

intent.

We affirm EPA’s definition of “in existence.”

Sierra Club and NRDC argue that the grandfather

clause is subject to abuse unless EPA bars sources from

receiving emission credit for emissions from new facili-

ties tied into their grandfathered tall stacks. Such a pro-

vision was included in the preamble to the 1979 proposed

regulations, 44 Fed. Reg. at 2612 (“credit only for emis-

sions from facilities that before December 31, 1970 were

committed to tie into a stack in existence as defined in

this Regulation”) but was deleted without explanation

in the 1982 final regulations. EPA admits that it: neg-

lected to respond to Sierra Club’s comment that the

provision be included in the final regulations themselves,

but argues that the failure was at most harmless error.

Since the failure to respond leaves us “to guess as to the

agency’s findings or reasons,” Greater Boston Television

Corp. v. FCC, 444 F.2d 841, 851 (D.C. Cir. 1970), cert.

denied, 403 U.S. 928 (1971), and we may not uphold

x

agency action on the basis of arguments advanced not

by the agency itself, but only by counsel during litiga-

tion, FPC v. Texaco Inc., 417 U.S. 380, 397 (1974), we

remand this issue to allow the agency to explain why it

refused to prohibit tying new sources into pre-1971 stack

heights.

I. Prospective Application of 1+1.5 Rule

As noted, EPA’s regulations provide two formulas for

the determination of GEP height: the 2.5 Rule for use by

stacks in existence (as defined in the regulations) on

January 12, 1979, and the 1+1.5 Rule for all other

stacks. 47 Fed. Reg. at 5868 (to be codified at 40 C.F.R.

§ 51.1(ii) (2)). The dividing date is the day on which

the agency published its 1979 proposed regulations, in

which it first proposed the 1+1.5 Rule. Retroactive ap-

plication of the new formula was eschewed because it

was thought to be unfair to sources that “in good faith

had constructed stacks in accordance with” the previously

accepted 2.5 Rule. Jd, at 5866.

Sierra Club and NRDC argue that the two-formula

approach is contrary to the Act, which allows credit

only for good engineering practice height, as determined

by the Administrator. Once EPA determines that the

relevant amount of downwash can be prevented by a

certain height, it must give credit only for that height.

Allowing application of the 2.5 Rule, the argument goes,

gives credit for stack height in excess Of GEP height.

In addition, petitioners cite the conference committee’s

report, which states the committee’s intention that “if

it should be determined that downwash, eddies, and wakes

can be prevented by stacks of less than 2% times facility

height, the Administrator’s rule should give ‘credit’ only

for the height needed to avoid these conditions,” 123

Conc. Rec. 27,071 (1977).

We hold that the statute does not prevent EPA from

allowing its past rule to be applied to stacks built be-

63a

fore its new formula was proposed, but that the agency

has erred in allowing sources that did not rely on the

old formula to use it. Congress was moved to enact

section 128 by evidence that during the 1970’s many

sources had built tall stacks far above the heights dic-

tated by sound engineering practice. To allow such

sources to claim credit for heights up to the 2.5 Rule

would be a windfall for them, unjustifiable under either

the statute or the equitable considerations that govern

retroactivity.

Although the conference committee directed that the

Administrator’s rule give credit only for whatever height

he determined was needed to prevent downwash, it did

not speak to whether that rule should be applied retro-

actively or only prospectively. The courts have addressed

the limits of an agency’s implied power to apply a rule

retroactively and have discerned a set of considerations

that limit that power. We think that these considerations

are also suggestive of the outlines of an agency’s duty to

apply a rule retroactively, although the weight of each

will be somewhat different. Among the considerations

that enter into the consideration of retroactivity are

{1] whether the new rule represents an abrupt de-

parture from well established practice or merely

attempts to fill a void in an unsettled area of law,

[2] the extent to which the party against whom the

new rule is applied relied on the formed rule, [3]

the degree of the burden which a retroactive order

imposes on a party, and [4] the statutory interest in

applying a new rule despite the reliance of a party

on the old standard.

Retail, Wholesale & Department Store Union v. NLRB,

466 F.2d 380, 390 (D.C. Cir. 1972) (retroactive applica-

tion of rule developed in adjudications); see Tennessee

Gas Pipeline Co. v. FERC, 606 F.2d 1094, 1116 n.77

(D.C, Cir. 1979) (same: “The relevant factors [concern-

ing the limitations on permissible retroactivity] include

64a

the degree of retroactivity, the need for administrative

flexibility, and the hardship on the affected parties.”),

cert. denied, 445 U.S. 920 (1980), 447 U.S. 922 (1980).

In this case, the new rule is a departure from both a

legal rule proposed in 1978 and in effect since 1976, and

an industry practice of much longer standing. See Tech-

nical Support Doc., supra p. 20, at 1080 (“[The 2.5

Rule! arose during the early part of this century as a

practical formula.”) ; cf. NLRB v. Majestic Weaving Co.,

355 F.2d 854, 860 (2d Cir. 1966) (Friendly, J.) (Every

case of first impression has a retroactive effect, “[b]ut

the problem of retroactive application has a somewhat

different aspect in cases not of first but of second im-

pression, where an agency alters an established rule

defining permissible conduct which has been generally

recognized and relied on throughout the industry that it

regulates.”). Moreover, for operators with tall, thin

buildings who have met air quality standards with a

stack height two-and-one-half times the height of the

building, the burden of retroactivity may include ex-

pensive retrofitting of control equipment and renegotia-

tion of contracts in order to purchase coal with lower

sulfur content. See J.A. at 926 (comments of Utility Air

Regulatory Group).

The statutory interest in applying the new rule despite

individual reliance is, of course, the crucial consideration

in the context of requiring an agency to apply one of its

rules retroactively. Here, any retroactivity detracts from

the intention to place maximum reliance on direct emis-

sions reductions rather than dispersion. But the objec-

65a

maintain a situation that Congress sought to end. Finally,

we do not think the conference committee report was

intended to allow only a single review of the state of

engineering knowledge in order to determine what stack

height is needed to prevent downwash, but rather that it

would tolerate refinement of the approach as knowledge

expanded. Likewise, we have noted that the technical

basis for establishing certain rules may be available only

after some experience in regulating the field is gained.

See supra pp. 55-56 & n.7. Yet, a rule that required that

every refinement of the GEP formulas or of demonstra-

tion techniques be applied retroactively would place the

natural reluctance to act unfairly or inequitably as an

obstacle to implementation of those developments. We do

not think the statute requires such a result, particularly

since retroactive application may frequently be quite

burdensome for particular sources.

Nevertheless, one of the factors to be considered in

determining retroactivity is the extent of reliance on the

old rule. In this case, there is persuasive evidence that

many sources built stacks in the relevant period without

in fact relying on the 2.5 Rule, but instead built their

stacks tall in order to obtain credit for dispersion. See

e.g., HOUSE REPORT, supra p. 5, at 81-82; 123 CoNG. REC.

16,203 (1977) (remarks of Rep. Waxman during intro-

duction of amendments) (“(Tjhe utility industry in

particular has tried to gain acceptance for operating

methods which only disperse harmful emissions over a

large area, which are unreliable in practice and which

mask each source’s contribution to a region’s air quality

problems. .. . I feel that the committee has finally, after

a half-dozen years, laid this argument to rest.”); Ala-

bama Power Co. v. Costle, 686 F.2d 328, 388 (D.C. Cir.

1979) (“A good many industrial facilities .. . [built]

taller-than-necessary stacks in order te achieve greater

dispersion of their emissions and thus comply with na-

tional ambient standards.”). Compare Impact Assess-

66a

ment Report, supra p. 58, at 1059 (eight plants built tall

stacks before 1971) with Identifying and Assessing the

Technical Bases for the Stack Height Regulatory Analy-

sis (Dec. 1979) (EPA consultant’s report), J.A. at 713

(171 stacks over 500 feet tall built since 1970). Putting

an end to this evasion of the act was, in fact, the primary

motivation for section 123. Thus although we would be

concerned by the burden caused by retroactive applica-

tion of the new rule against sources that actually relied

on the old rule, such concerns are rather attenuated when

there was no reliance whatsoever. In these circumstances,

both judicia! doctrine and congressional purpose command

that the agency limit the use of the 2.5 Rule to those

sources that actually relied on it.

We remand this provision to the agency to allow it to

reformulate its rule to take actual reliance into account.

J. Timetable for State Implementation

Section 406(d) (2) of the 1977 amendments provides:

Except as otherwise expressly provided, each State

required to revise its applicable implementation plan

by reason of any amendment made by this Act shall

adopt and submit to [EPA] such plan revision before

the later of the date—

(A) one year after the date of enactment of this

Act [Aug. 7, 1977], or

(B) nine months after the date of promulgation

by [EPA] of any regulations under an amendment

made by this Act which are necessary for the ap-

proval of such plan revision.

42 U.S.C. § 7401 note (Supp. V 1981). In the preamble

to its final regulations, EPA purported to carry out this

section via a two-stage implementation process. First,

the states would be allowed nine months from the promul-

gation of the regulations to draft and submit rules limit-

ing stack height credit. Then, presumably after a four-

month period of review by EPA, see id. § 7410(a) (2)

(“The Administrator shall, within four months after the

67a

date required for submission of a [state implementation

plan], approve or disapprove such plan or each portion

thereof.”), the states would have another nine months to

revise their emission limitations to make them consistent

with the state rules. 47 Fed. Reg. at 5865-66; Recon-

sideration Decision, supra p. 51, at 1227.

EPA’s two-stage process, allowing a total of twenty-

two months between promulgation of EPA’s regulations

and submission of revised emission limitations (followed,

presumably, by another four months for EPA approval),

is plainly contrary to section 406(d) (2). The “applicable

implementation plan” referred to in that section is the

state implementation plan required under section 110, 42

U.S.C. § 7410 (Supp. V 1981); the latter section ex-

plicitly requires that state implementation plans contain

“emission limitations, schedules, and timetables for com-

pliance with such limitations,” id.; see also id. § 7471

(requiring plan to contain “emission limitations and such

other measures as may be necessary . . . to prevent sig-

nificant deterioration of air quality”); id. § 7502(b) (8)

(same as to nonattainment provisions of Act). There is

thus no place in the statutory timetable for submission of

separate state regulations governing stack heights.

Moreover, we see no place for such state regulations in

EPA’s own final regulations. The regulations are detailed

and precise and do not mention alternative means of com-

pliance from which the states may pick and choose. Even

if states had to adopt stack height regulations, they

would probably merely mimic EPA’s version. In any case,

that process could not extend the time allowed by statute

for submission of implementation plans containing specific

emissions limitations.

In its brief before this court, EPA’s lawyers assert that

the agency “made a specific finding that it would be im-

possible for the states to completely revise their plans

within nine months.” Brief of Respondents at 68 (citing

68a

J.A. at 1233). We find no such specific finding on the

page cited by the brief nor in the other materials in the

record regarding the timetable for state implementation.

This conclusory statement certainly does not meet the

“heavy burden to demonstrate the existence of an im-

possibility” that is required by the law, Alabama Power

Co. v. Costle, 636 F.2d 328, 359 (D.C. Cir. 1979).

EPA’s two-stage implementation plan is reversed.

K. Timetable on Remand

Congress directed EPA to promulgate regulations to

carry out section 123 of the Act no later than six months

after it was passed in August 1977. EPA’s proposed regu-

lations were not issued until January 1979, seventeen

months after enactment. Its final regulations were

promulgated four-and-one-half years after the statute

was passed. We have now passed the sixth anniversary

of that date. During this time, polluters have not been

obliged to reduce their emissions rather than rely on dis-

persion, because the statute must be implemented by the

states, which have awaited EPA’s regulations.

Petitioners request that we direct EPA to promulgate

“without delay” regulations free of the violations we have

found. In light of the regulatory history set out above

and the now urgent need to implement Congress’s com-

mands, we think it best to quantify that obligation. We

note that many, though not all, of the flaws we have

found in EPA’s regulations were reversals of positions

taken in the 1979 proposed regulations, so that we have

some confidence that solutions are not beyond the realm

of imagination. Others will require the expenditure of

considerable effort to correct, but Congress thought EPA

could solve all problems in six months and the agency has

had six years. We think it appropriate to direct EPA

to promulgate new final regulations that remedy the de-

fects this court has found within six months from the

issuance of our mandate, the period originally specified

by Congress.

69a

Ill

The following provisions of EPA’s stack height regula-

tions are affirmed: (1) the definition of “nearby” as ap-

plied in the GEP formulas; (2) the failure to consider

plume rise in deriving the GEP formulas; (3) the ex-

clusion of flares from the definition of “stack”; and (4)

the definition of .“‘in existence.”

The following provisions are reversed as beyond the

agency’s statutory authority: (1) the inclusion of plume

impaction in the calculation of creditable stack height;

and (2) the two-step, twenty-two-month timetable for

state implementation of the regulations.

We remand the following provisions to the EPA for

further action not inconsistent with this opinion: (1) the

failure to apply a “nearby” limitation to GEP demonstra-

tions; (2) the definition of “excessive concentrations” ;

(3) the failure to require demonstrations before stacks

are raised up to formula height; (4) the definition of

“dispersion technique”; (5) the refusal to prohibit new

facilities from tying into pre-1971 stack heights; and (6)

the grandfather clause for application of the 2.5 Rule.

We direct EPA to promulgate new final stack height

regulations as to these issues within six months from the

date of issuance of this court’s mandate.

It is so ordered.

70a

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

September Term, 1983

No. 82-1384

SIERRA CLUB AND NATURAL RESOURCES

DEFENSE COUNCIL, INC.

Petitioners

Vv.

ENVIRONMENTAL PROTECTION AGENCY

Respondent

ALABAMA POWER COMPANY, et al.

KENNECOTT MINERALS Co.,

TENNESSEE VALLEY AUTHORITY

STATES OF NEW YORK, et al.

STATE OF VERMONT

AMERICAN PETROLEUM INSTITUTE, et al.

Intervenors

And Consolidated Case Nos. 82-1412,

82-1845 & 82-1889

[Filed Dec. 13, 1983]

Before: EDWARDS, Circuit Judge; MCGOWAN and MAc-

KINNON, Senior Circuit Judges

ORDER

On consideration of the Petition for Rehearing of In-

tervenor Alabama Power Co., et al, filed November 29,

1983, it is

71la

ORDERED by the Court that the aforesaid Petition is

denied.

Per Curiam

For The Court:

GEORGE A. FISHER

Clerk

By: /s/ Robert A. Bonner

ROBERT A. BONNER

Chief Deputy Clerk

72a

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

September Term, 1983

No. 82-1384

SIERRA CLUB AND NATURAL RESOURCES

DEFENSE COUNCIL, INC.,

Petitioners

Vv.

ENVIRONMENTAL PROTECTION AGENCY,

Respondent

ALABAMA POWER COMPANY, et al.

KENNECOTT MINERALS Co.,

TENNESSEE VALLEY AUTHORITY

STATES OF NEW YORK, et al.

STATE OF VERMONT

AMERICAN PETROLEUM INSTITUTE, et al.

Intervenors

And Consolidated Case Nos. 82-1414,

82-1845 & 82-1889

[Filed Dec. 13, 1983]

Before: ROBINSON, Chief Judge, WRIGHT, TAMM,

WILKEY, WALD, MIKVA, EDWARDS, GINSBURG,

BorK, SCALIA and STARR, Circuit Judges;

McGowAN and MACKINNON, Senior Circuit

Judges

ORDER

The suggestion for rehearing en banc of Intervenor

Alabama Power Co., et al, filed November 29, 1983, has

73a

been circulated to the full Court and no member has re-

quested the taking of a vote thereon. On consideration

to the foregoing, it is

ORDERED by the Court en banc that the aforesaid

suggestion is denied.

Per Curiam

For The Court:

GEORGE A. FISHER

Clerk

By: /s/ Robert A. Bonner

ROBERT A. BONNER

Chief Deputy Clerk

Cireuit Judges Wright, Wilkey and Bork did not partici-

pate in this Order.

74a

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Before:

September Term, 1983

No. 82-1384

SIERRA CLUB AND NATURAL RESOURCES

DEFENSE COUNCIL, INC.,

Petitioners

Vv.

ENVIRONMENTAL PROTECTION AGENCY,

Respondent

ALABAMA POWER COMPANY, et al.

KENNECOTT MINERALS Co. &

TENNESSEE VALLEY AUTHORITY

STATES OF NEW YORK, et al.

STATE OF VERMONT

AMERICAN PETROLEUM INSTITUTE, et al.

Intervenors

And Consolidated Case Nos. 82-1412,

82-1845 & 82-1889

[Filed Dec. 13, 1983]

EDWARDS, Circuit Judge; MCGOWAN and MAc-

KINNON, Senior Circuit Judges

ORDER

On consideration of the Motion of Alabama Power Co.,

et al. for Clarification of the Court’s Decision on “Nearby

Terrain Obstacles”, filed November 25, 1983, it is

75a

4

ORDERED by the Court that the aforesaid motion for

clarification is denied.

Per Curiam

For The Court:

GEORGE A. FISHER

Clerk

By: /s/ Robert A. Bonner

ROBERT A. BONNER

Chief Deputy Clerk

76a

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

September Term, 1983

No. 82-1384

SIERRA CLUB AND NATURAL RESOURCES

DEFENSE COUNCIL, INC.,

Petitioners

we

ENVIRONMENTAL PROTECTION AGENCY,

Respondent

ALABAMA POWER COMPANY, et al.

KENNECOTT MINERALS Co.,

TENNESSEE VALLEY AUTHORITY

STATES OF NEW YORK, et al.,

STATE OF VERMONT

AMERICAN PETROLEUM INSTITUTE, et al.,

Intervenors

And Consolidated Case Nos. 82-1412,

82-1845 & 82-1889

[Filed Jan. 6, 1984]

Before: EDWARDS, Circuit Judge, MCGOWAN and MACc-

KINNON, Senior Circuit Judges

ORDER

On consideration of the motion of intervenor for stay

of issuance of mandate, it is

17a

ORDERED by the Court that the Clerk is directed to

delay issuance of this Court’s mandate through Janu-

ary 19, 1984.

Per Curiam

For The Court:

GEORGE A. FISHER,

Clerk

By: /s/ Robert A. Bonner

ROBERT A. BONNER

Chief Deputy Clerk

78a

UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

September Term, 1983

No. 82-1384

SIERRA CLUB AND NATURAL RESOURCES

DEFENSE COUNCIL, INC.

Petitioners

Vv.

ENVIRONMENTAL PROTECTION AGENCY

Respondent

ALABAMA POWER COMPANY, et al.,

Intervenors

And Consolidated Cases No. 82-1412,

82-1845 & 82-1889

[Filed Feb. 9, 1984]

Before: EDWARDS, Circuit Judge, MCGOWAN and MAc-

KINNON, Senior Circuit Judges

ORDER

On consideration of the motion of Intervenors, Ala-

bama Power Company et al., to further stay mandate

and of the opposition thereto, it is

79a

ORDERED by the Court that the motion is granted

and the Clerk is directed to not issue the mandate of this

Court through February 21, 1984.

Per Curiam

For The Court:

GEORGE A. FISHER

Clerk

By: /s/ Robert A. Bonner

ROBERT A. BONNER

Chief Deputy Clerk

80a

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[AD-FRL 2010-1; Docket No. A-79-01]

Stack Height Regulations

AGENCY: Environmental Protection

Agency (EPA).

ACTION: Final rulemaking.

SUMMARY: Section 123 of the Clean Air Act requires

EPA to promulgate regulations to assure 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 exceeds good engineering practice (GEP) or by

any other dispersion technique. Regulations to implement

Section 123 were proposed on January 12, 1979 at 44 FR

2608 and repropesed October 7, 1981 at 46 FR 49814.

Today’s action incorporates changes to the reproposal and

finalizes these regulations.

DATE: These rules are effective March 10, 1982.

ADDRESS: Docket A-79-01, containing material rele-

vant to this action, is located in the Central Docket Sec-

tion (A-130), U.S. Environmental Protection Agency, 401

M Street, S.W., Washington, D.C. 20460.

FOR FURTHER INFORMATION CONTACT: Mr.

Bruce Polkowsky, MD-15, Office of Air Quality Planning

and Standards, U.S. Environmental Protection Agency,

Research Triangle Park, North Carolina 27711. Tele

phone: (919) 541-5540.

SUPPLEMENTARY INFORMATION:

Docket Statement

All pertinent information concerning the development

of these regulations is included in Docket No. A-79-01.

8la

The Docket is open for inspection by the public between

the hours of 8:00 a.m. and 4:00 p.m., Monday through

Friday, at the EPA Central Docket Section, West Tower

Lobby, Gallery One, 401 M Street, S.W., Washington,

D.C. Background documents normally available to the

public, such as Federal Register notices and Congressional

reports, are not included in the docket. A reasonable fee

may be charged for copying documents.

I. Background

A. Statute

Section 123 was added to the Clean Air Act by the

1977 Clean Air Act Amendments. It prohibits stacks

taller than good engineering practice (GEP) height and

other dispersion techniques from affecting the emission

limitations required to meet the national ambient air

quality standards (NAAQS) or prevention of significant

deterioration air quality increments (PSD increments).

Section 123 requires EPA to promulgate regulations

which define GEP stack height, and which restrict the use

of other dispersion techniques, including intermittent or

supplemental control techniques. This rulemaking fulfills

this requirement. In the near future, EPA also intends

to propose rules on the use of intermittent control tech-

niques.

B. Rulemaking

On January 12, 1979 (44 FR 2608), EPA published a

notice proposing limitations on stack height credit and

other dispersion techniques. The notice proposed specific

rules to be used in determining GEP stack height for any

source and specific requirements for State Implementa-

tion Plan (SIP) revisions. EPA provided an extended

period for the submission of public comments on these

proposed regulations. EPA held a public hearing on May

31, 1979 followed by a 30-day period for the submission

of additional comments (44 FR 24329, April 25, 1979).

82a

EPA provided for comments on additional technical in-

formation (44 FR 40359, July 11, 1979 and 46 FR 24596,

May 1, 1981). Finally, EPA recently reproposed the

regulations with changes made in response to the com-

ments received (46 FR 49814, October 7, 1981).

Forty individuals and groups commented on the Oc-

tober 1981 proposal. EPA has considered all comments

and has made a number of changes in the regulations in

response to these comments. Most of these changes sim-

ply clarify the proposed rules. The revisions are outlined

in Section IV: “Changes in the Regulations from the Oc-

tober 1981 Proposal.” In addition, EPA has prepared a

document entitled “Summary of Comments and Responses

on the October 7, 1981 Proposal of the Stack Height Reg-

ulations.” This document has been placed in Docket A-

79-01, and, depending upon available supplies, copies may

also be obtained from: EPA Library (MD-35), U.S. En-

vironmental Protection Agency, Research Triangle Park,

N.C. 27711. A copy of this document will be sent to all

persons who submitted comments on the October 1981

proposal.

C. Documents

In conjunction with the regulations, EPA developed sev-

eral technical and guidance documents. These served as

background information for the regulations and all are

included in Docket No. A-79-01. The following documents

have been placed in the National Technical Information

Service (NTIS) system and may be obtained by contact-

ing NTIS at 5285 Port Royal Rd., Springfield, Virginia

22161.

(1) “Guideline for Determination of Good Engineering

Practice Stack Height (Technical Support Document for

Stack Height Regulation),” July 1981, U.S. Environmen-

tal Protection Agency, Office of Air Quality Planning and

Standards, EPA-450/4-80-023. (NTIS PB82 145301)

83a

(2) “Guideline for Use of Fluid Modeling to Deter-

mine Good Engineering Practice Stack Height,” July

1981, U.S. Environmental Protection Agency, Office of

Air Quality Planning and Standards, EPA-450/4-81-003.

(NTIS PB82 145327)

(3) “Guideline for Fluid Modeling of Atmospheric

Diffusion,” April 1981, U.S. Environmental Protection

Agency, Environmental Sciences Research Laboratory,

EPA-600/8-81-009. (NTIS PB81 201410)

II. Program Overview

A. The Problem

There are two general methods for preventing viola-

tions of the NAAQS and PSD increments. Emission con-

trols 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 a source and to prevent high con-

centrations of pollutants near the source. The Clean Air

Act requires pollution sources to meet the NAAQS and

PSD increments by complying with emission limitations

instead of relying on dispersion techniques.' Section 123

defines stack height exceeding GEP as a dispersion tech-

nique.

Tall stacks and intermittent or supplemental control

systems (ICS or SCS) are the two basic types of disper-

sion techniques. Tall stacks enhance dispersion by releas-

ing pollutants into the air at elevations high above ground

level, increasing the volume of air through which pollu-

tants must travel to reach the ground. Releasing pollu-

1 See Sections 110(a) (2)(B), 128, 302(k), and 302(m) of the

Act, 42 U.S.C. 7410(a) (2) (B), 7428, 7602(k), and 7602(m). The

Notice of Proposed Rulemaking contains a more detailed discussion

of the Act’s prohibition of the use of dispersion techniques. See

44 FR 2608-2610.

84a

tants from a tall stack allows a source to reduce the am-

bient levels of its pollution as measured at ground level

without reducing the amount of pollution it releases. In-

termittent and supplemental control systems vary a

source’s rate of emissions to take advantage of meteoro-

logical conditions. When atmospheric conditions do not

favor dispersion and an NAAQS may be violated, the

source temporarily reduces its pollutant emissions. When

conditions favor rapid dispersion, the source emits pollu-

tants at higher rates.

Use of dispersion techniques instead of constant emis-

sion controls can result in additional atmospheric loadings

which may contribute to undesirable environmental ef-

fects. The use of tall stacks increases the possibility that

pollution will travel long distances before it settles to the

ground.

Although dispersion techniques may produce adverse

effects, some stack height is needed to prevent excessive

concentrations of pollutant emissions created by airflow

disruptions caused by structures, terrain features, and

ground-level meteorological phenomena. These excessive

concentrations result from interference with the plume.

Section 123 responds to this problem by allowing EPA to

give a source credit for that portion of its stack height

needed to prevent excessive concentrations near the source.

This height is called GEP stack height.

The regulations promulgated today define “excessive

concentrations,” “nearby,” and other important concepts.

They also establish methods for determining the GEP

stack height for all stationary sources to which these

regulations apply.

B. The Program

These regulations do not limit the physical stack height

of any source, nor require any specific stack height for

any source. Instead, they set limits on the maximum

85a

stack height credit to be used in ambient air quality

modeling for the purpose of setting an emission limita-

tion and calculating the air quality impact of a source.

Sources are modeled at the physical stack height unless

that height exceeds their GEP stack height. The regula-

tions apply to all stacks constructed and all dispersion

techniques implemented since December 31, 1970.

1. Methods of Determining GEP Stack Height. The

regulations establish three basic methods of calculating a

source’s GEP stack height.

(a) De minimis height—EPA is adopting 65 meters

as the minimum GEP stack height for all sources regard-

less of the size or location of any structures or terrain

features. Sixty-five meters represents a reasonable esti-

mate of the height needed to insure that emissions will

not be affected by common ground-level meteorological

phenomena which may produce execessive pollutant con-

centrations. Typical causes of these phenomena include

surface roughness and the temperature changes caused by

the solar heating and terrestrial cooling cycle (see page

26 of the Technical Support Document).

Virtually all significant sources of SO, can justify

stack height credits greater than 65 meters. Accordingly,

this de minimis height will have little effect on atmos-

pheric loadings of sulfur dioxide.

(b) Mathematical Formulas—Excessive concentrations

may be produced by downwash, wakes, and eddies caused

by structures located near the stack. EPA is adopting

two formulas with which to calculate the GEP stack

height: One for stacks in existence on January 12, 1979

(the date of publication of EPA original proposed rules),

and one for stacks constructed after that date.

For stacks in existence on January 12, 1979, EPA

has adopted the traditional engineering formula of two

and one-half times the height of the nearby structure

(H=2.5H) as the formula for determining the GEP

86a

stack height. For stacks constructed after January 12,

1979, EPA has established a refined formula of the height

of the nearby structure plus one and.one-half times the

height or width of the structure, whichever is less

(H=H+1.5L) as the formula for determining the GEP

stack height.

(c) Physical Demonstration—In some cases, a source

may need a stack taller than the height predicted by the

formulas to prevent excessive concentrations of a pollu-

tant due to downwash, wakes, or eddies created by struc-

tures or terrain obstacles. In such cases, Section 123 pro-

vides that a source may obtain credit for all of the stack

height necessary to avoid excessive concentrations pro-

vided it demonstrates to the satisfaction of the reviewing

authority that the additional height is necessary.

EPA is requiring such a source to demonstrate that

maximum concentrations caused by the source’s emissions

from its proposed stack height, without consideration of

nearby structures or terrain obstacles will increase by at

least 40 percent when the effects of the structures or ter-

rain obstacles are considered. This difference in concen-

trations must be shown either by a fluid model study con-

ducted in accordance with guidelines published by EPA

or by a field study which has been approved by the review-

ing authority.

Before a source can obtain credit for a GEP stack

height determined by a fluid modei or field study demon-

stration, Section 123(c) requires that the reviewing au-

thority must notify the public of the availability of the

source’s demonstration study and must provide an oppor-

tunity for a public hearing.

2. Method of Adjusting GEP Stack Height for Ele-

vated Terrain Areas. As traditionally defined, plume

impaction occurs when a plume emitted from a stack

interacts with terrain that is taller than the stack. The

contact between the plume and the terrain can produce

87a

high pollutant concentrations. EPA is establishing a pro-

cedure which will allow sources to adjust their GEP stack

height to avoid modeled plume impaction on elevated ter-

rain causing one to predict violations of the NAAQS or

applicable PSD increments which will not occur. (This

procedure is explained in Section IV.C.) The predicted

violations will not occur because the physical stack height

is sufficient to ensure that the plume passes over the ele-

vated terrain.

Before a source can obtain credit for a GEP stack

height based on allowances for terrain impaction, the re-

viewing authority must notify the public of the avail-

ability of the source’s demonstration study and must pro-

vide an opportunity for a public hearing.

8. Grandfathered Stack Height. The 1970 Clean Air

Act became effective on December 31, 1970. Prior to that

date some sources had constructed stacks taller than their

GEP height. In Section 123, Congress recognized this and

exempted those sources’ stack heights. Section 123 allows

credit for stack height in existence on December 31, 1970.

A source’s stack is considered to be “in existence” if that

stack was part of the design of a facility on which con-

struction commenced prior to December 31, 1970.

4. Other Dispersion Techniques. The regulations pro-

hibit the use of other dispersion techniques to attain or

maintain any NAAQS or protect a PSD increment. Those

techniques include major alteration of plume characteris-

tics such as the manipulation of exhaust flow rates or

temperatures for the purpose of enhancing plume rise.

The regulation defines three types of dispersion tech-

niques: (1) tall stacks, (2) use of ICS or SCS, and (3)

addition of a fan or reheater to obtain a less stringent

emission limitation. However, the regulations exempt (1)

reheating of a gas stream following the use of a pollutant

control system, (2) smoke management in agricultural or

silvicultural programs, and (3) combining exhaust gases

from several stacks into one stack.

88a

III. State Implementation Plan Requirements

EPA is establishing a two-stage process for the imple-

mentation of these regulations. All States must review

and revise, as necessary, their SIPs to include provisions

that limit stack height credits and dispersion techniques

in accordance with these regulations. Section 406(d) (2)

of the Clean Air Act Amendments of 1977 requires that

these SIP revisions be submitted within nine months of

promulgation of these regulations.

After EPA approves a State’s stack height rules, the

State must review existing limitations to determine

whether these limitations have been affected by stack

height credit above GEP levels or any other dispersion

technique. If so, the State must revise the emission limi-

tations to be consistent with its revised SIP.

IV. Changes in the Regulations From the October 7,

1981 Proposal

EPA has made several changes in the proposed regula-

tions as a result of the public comments on the reproposed

regulations. These changes are noted below.

A. Prospective Application of the New GEP Formula

On February 18, 1976 (41 FR 7450), EPA published

the “Stack Height Increase Guideline’ which provided

guidance on its policy for the use of tall stacks. The

guideline permitted credit for stacks up to two and one-

half times the height of the facility it served. On Novem-

ber 3, 1977, after passage of the Clean Air Act Amend-

ments of 1977, EPA promulgated a final rule on some

changes to its prevention of significant deterioration

(PSD) program (42 FR 57459). As part of the pre-

amble to that notice, EPA defined GEP as “two and one-

half times the height of the source” (2.5H).

On January 12, 1979 (44 FR 2608), EPA proposed

regulations to implement Section 123 which refined the

89a

two and one-half times rule by defining GEP stack height

as the height of a nearby structure plus one and one-half

times the lesser of the height or width of the nearby

structure (H+1.5L). That proposal and the reproposal

of that regulation on October 7, 1981 (46 FR 49814)

would have made the new formula retroactive to Decem-

ber 31, 1970.

Four commenters argued that EPA’s definition of GEP,

until January 12, 1979, had been based on two and one-

half times the building height and that sources in good

faith had constructed stacks in accordance with that defi-

nition. Applying the new formula retroactively would be

unfair to those sources. The commenters argued that the

new formula should be applied prospectively.

In response to these comments, EPA has developed two

formulas for determining GEP stack height: (1) For

stacks in existence on January 12, 1979, the formula is

H,=2.5H; (2) for all other stacks, the formula is

H—H+1.5L.

B. Definition of “in existence”

Section 123 does not affect stack heights “in existence”

on December 31, 1970. In October 1981, EPA praposed

to define “in existence” to mean that the owner or opera-

tor of a stack had obtained all necessary preconstruction

permits or approvals required by Federal, State or local

air pollution control agencies, and either (1) actually

commenced construction, or (2) entered into a binding

commitment for construction.

Comments on the reproposed definition stated that this

new definition would discriminate unfairly against sources

located in the few States or local jurisdictions which re-

quired construction permits for air pollution sources in

1970. (There were no Federal permit programs in 1970.)

EPA agrees that the reproposed definition might operate

unfairly. EPA has deleted the requirement for such ap-

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provals or permits in determining whether a source’s

stack is “in existence” as of December 31, 1970.

However, the regulations now apply the two and one-

half times formula for determining GEP only to stacks

“in existence” on January 12, 1979. Federal requirements

for preconstruction permits for air pollution sources were

effective well before 1979. Accordingly, EPA is retaining

the permit requirement for sources which want to claim

credit for stacks “in existence” as of January 12, 1979.

EPA has changed § 51.1(ii), which defines GEP, to re-

quire sources wishing to use the two and one-half times

formula to show that they had obtained, prior to Janu-

ary 12, 1979, all preconstruction permits required by 40

CFR Parts 51 and 52.

The remaining portions of the definition of “in exist-

ence” are identical to the October 1981 proposal.

C. Impaction Credit

Many comments on the January 1979 proposal asked

EPA to provide stack height credit for a source which

experiences plume impaction. Plume impaction occurs

when a plume emitted from a stack interacts with a ter-

rain feature that is taller than the stack. The contact

between the plume and the terrain feature can produce

high pollutant concentrations, especially under stable at-

mospheric conditions in which the plume disperses slowly.

EPA decided that sources should receive stack height

credit when impaction produces concentrations high

enough to violate an NAAQS or applicable PSD incre-

ment. EPA included in its October 1981 reproposal a

procedure for determining the amount of credit needed to

prevent plume impaction.

EPA has received three types of comments on the pro-

posed impaction credit. Environmental groups claimed

that Section 123 does not authorize impaction credits.

Several industrial commenters asked EPA to clarify the

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proposed procedures for impaction credits. Finally, some

industrial commenters asked EPA to modify a portion of

its proposed procedures. To respond to these comments,

EPA is presenting below a brief description of its ration-

ale and procedures for impaction credits. EPA is also

providing a brief explanation of its reason for declining

to make procedural modifications.

(1) Rationale

Plume impaction resembles downwash, wakes, and

eddies. In all of these events, structures or terrain fea-

tures interfere with plume dispersion. If the interfer-

ence occurs relatively close to the stack, before the plume

has had adequate opportunity to disperse, high concen-

trations of pollutants can occur.

In enacting Section 123, Congress decided that sources

should be allowed sufficient stack height credit to pre-

vent high pollutant concentrations caused by downwash,

wakes, and eddies. Congress called this height “good

engineering practice.” Any additional stack height was

to be regarded as a dispersion technique that might al-

low a source to relax its emissions limitations. Section

123 does not mention impaction. However, neither the

language of the statute nor the

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