GUIDELINES FOR DETERMINING
BEST AVAILABLE CONTROL TECHNOLOGY (BACT)
DECEMBER 1978
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
U S. Environmental Protection Agency

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GUIDELINES FOR DETERMINING BEST AVAILABLE
CONTROL TECHNOLOGY (BACT)
INTRODUCTION
The 1977 Clean Air Act Amendments establish more restrictive
conditions for the approval of pre-construction permit applications under
the Prevention of Significant Deterioration (PSD) program. One of the
new requirements is for best available control technology (BACT) to be
\ *
installed for all pollutants regulated under the Act. Under the revised
Act, BACT is to be determined on a case-by-case basis rather than auto-
matically applying an applicable Federal New Source Performance Standard
(NSPS), as was the case under the previous regulation. Concern has been
expressed that these determinations should be consistent *ron area to
area. In the context of case-by-case BACT, consistency does not ne-
cessarily mean that a new facility in one area will have an identical
emission limit as the same type of facility in another area. Consis-
tency means that a consistent approach is used in determining BACT and
that the impacts of alternative emission control systems are measured by
the same set of parameters, although evaluation of specific parameters
is done on a case-by-case basis.
PURPOSE
This guideline is intended for use by (1) EPA Regional Offices in
determining BACT during the interim period before the States adopt
*Pollutants subject to National Ambient Air Quality Standards, Standards
of Performance for New Stationary Sources, National Emission Standards
for Hazardous Air Pollutants, and Emission Standards for Moving Sources

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State Implementation Plan (SIP) provisions for implementing the PSD
program, (2) by States in writing PSD regulations or determining BACT
and (3) by individual sources in preparing PSD permit applications.
The purpose of the guideline is to provide the framework for a con-
sistent approach to determining BACT. The emphasis is on the types
of data which should be required in a pre-construction permit applica-
tion and how the data should be used in order to determine BACT. The
guideline addresses the technological question of whether the emission
control system proposed in the permit application represents BACT or
whether a more stringent level of emission control is appropriate
considering available technology and economic, energy, and environmen-
tal impacts. The guideline assumes accomplishment of all other air
quality review requirements including, for example, the requirement
that air quality standards and appropriate PSD increments are met,
stack heights are appropriate, and siting is acceptable.
In accomplishing this purpose, the guideline lists a number of
factors which can be considered in assessing energy, environmental, and
economic impacts. While the full list represents the magnitude of the
analysis that could be required for a very large and complex source, many
of these factors will not be relevant to the typical BACT review. The
inclusion of any factor should be based on its relative merit consid-
ering such influences as source size, nature of the process and control
options, and local conditions. It is the clear intent of EPA not to
require an analysis of the full proportion described herein for small
sources or for the use of conventional control equipment whose impacts

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are well established. In short, the BACT analysis should be held to a
minimum with the depth of analysis being dependent on the difficulty of
the decision.
PHILOSOPHY OF SACT
The primary purpose of BACT is to optimize consumption of PSO air
quality increments thereby enlarging the potential for future economic
growth without significantly degrading air quality. The Act places the
responsibility of determining BACT with the State once a PSD SIP revision
is approved. The BACT decision is to take into account energy, environ-
mental, and economic impacts and other costs associated with application
of alternative control systems. This case-by-case approach allows
adootion of improvements in emission control technology to become widespread
more rapidly than would occur through the uniform Federal new source or
hazardous emission standards. In setting the NSPS, for example, emission
limits are selected which can reasonably be met by c.11 new or modified
sources in an industrial category, even though some individual sources
are capable of lower emissions. Additionally, because of resource
limitations in EPA, revision of new source standards must laq somewhat
behind the evolution of new or improved technology. Accordingly, new or
modified facilities in some source categories may be capable of achieving
lower emission levels that NSPS without substantial economic impacts.
The case-by-case BACT approach provides a mechanism for determining and
applying the best technology in each individual situation Hence, NSPS
and NESHAPS are Federal guidelines for BACT determinations and establish
minimum acceptable control requirements for a BACT determination.

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Where Federal standards do not exist, guidance on well-control led sources
is available through the OAQPS clearinghouse (discussed later).
A critical decision in the BACT analysis is the relative weight
assigned to the energy, environmental, and economic impacts. Congress
implied that this decision should be made by the State, thus allowing
some flexibility in emission control requirements depending on local
energy, environmental, and economic conditions and local preferences.
For example, in an area with unusually high unemployment, the economic
impacts may be weighted more heavily if the application of a strict BACT
emission requirement would reduce production or jobs. On the other
hand, if visibility protection is a major value of the area, then
environmental impacts could be weighted more heavily. This flexible
approach allows the oermitting authority to consider a number of local
factors (for example the sue of the plant, the amount of the air
quality increment that would be consumed, and desired economic growth
in the area) in deciding on a weighting scheme. State judgment and
the Federal emission standards are the foundations for the BACT deter-
mination. Accordingly, EPA does not consider it appropriate to assign
nationally applicable weighting factors in this guideline.
GENERAL GUIDELINES
The recommended approach to determining BACT is to place on the
applicant the responsibility for presenting and defending the technology
selection.* This approach recognizes that the applicant is best
suited for assessing the costs, environmental residuals, and energy
*Preliminary meetings between the applicant and the permitting authority
are encouraged as a means of promoting efficiency in the review process

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penalties associated with alternative control options as they apply
to his processes. The permit application should contain the following
elements relative to BACT:
(1)	Proposal of a control system representing BACT. 3ACT should
address control of each emission point at a facility, including fugi-
tive process, fugitive dust, and stack emissions. Technology selection
should consider application of flue gas treatment, fuel treatment, and
processes or techniques which are inherently low-polluting. In no
*
circumstance should a system be proposed for any emission point unless
it is at least as stringent as the applicable SIP or Federal emission
requirement (whichever is more stringent). In cases where technolog-
ical or economic limitations on the application of measurement techniques
would make the imposition of an emission standard infeasible, a design,
operating, or equipment standard may be established
(2)	Presentation of alternative systems that could achieve a
higher degree of emission control. For each pollutant, the BACT permit
application should present control alternatives which have greater control
capabilities than the system proposed as BACT and which have been used or
proposed for the same or similar applications. In some cases, the BACT
decision may require a trade-off of control among pollutants. That is,
a technology may do slightly worse in controlling one pollutant, but do
significantly better in controlling another air, water, or solid waste
residual. Such alternatives should not be excluded from consideration,
but in justifying BACT for a given pollutant only those alternatives
which have greater control capabilities for that pollutant need be
presented in the permit application.

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If no better control technology is available for an emission point,
then such finding should be stated and supported, and no further analysis
is required. Other equipment with similar control capabilities need not
be presented (e.g., a baghouse versus an equivalent ESP at a particulate
emitter). Unrealistic alternatives need not be presented such as placing
in series control equipment which is normally used alone (e.g., an ESP
followed by a baghouse). In some cases, a better control technology may
be available for a general type of operation, but unique processing
equipment or procedures may create a valid technical reason which would
preclude its selection as BACT. Such situations should be fully supported.
(3) Defense of the BACT selection. The BACT selection for a parti-
cular pollutant is defended by demonstrating that each alternative control
system (representing a more stringent level of control for that oollutant)
would cause unreasonably adverse energy, environmental, or economic impacts
The rationale for rejecting each alternative should be oresented in the
form of an incremental analysis of the impacts of each alternative
system relative to the proposed BACT system. Relevant energy, environmental
and economic irrroacts are described below.
IMPACT ANALYSIS
This section outlines the types of impacts that should be recognized
by the permitting authority as relevant issues in assessing the energy,
environmental, and economic impacts of alternative control systems. For
instance, if en applicant wishes to reject an alternative control system,
he would do so by demonstrating the adverse impacts which would result
from the selection of that alternative system. This section lists

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specific energy, environmental, and economic impacts which may be addressed
in this impact analysis and explains the data requirements for documenting
an adverse impact. Each of the factors discussed below need not be
addressed in every permit application. Rather this guideline presents a
set of potential impacts any number of which may be addressed in a
permit application depending on the individual situation. For example,
even though a control system may produce solid waste by-products, such
impacts need not be presented in the PSD permit application unless the
applicant wishes to use solid waste impact as an argument against selection
of a particular control alternative as BACT.
In general, the BACT analysis should focus on the direct (on-site)
impacts of alternative control systems. Indirect energy or environmental
impacts are not required but may be considered where such impacts are found
to be significant ar.d well quantified. Indirect energy impacts include
such impacts as energy to produce raw materials for construction of
control equipment, increased use of foreign oil, or increased oil use in
the utility grid. Indirect environmental impacts include such consider-
ations as pollution at an off-site manufacturing facility which produces
materials needed to construct or operate a proposed control system.
Indirect impacts will generally not be considered in the BACT review
since the complexity of consumption patterns in the economy makes those
impacts difficult to quantify. For example, since manufacturers purchase
capital equipment and supplies from many suppliers, who in turn purchase
goods from the other suppliers, accurate tracing of indirect impacts may not

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be possible. Raw materials may be needed to operate control equipment,
and suppliers of these resources may change over time. Similarly, it
generally will not be possible to determine specific power stations and
fuel sources which would be used to satisfy electrical demand over the
lifetime of a control device.
Duplicative analyses will not be required in preparing the BACT
permit application. Any studies previously performed for Environmental
Impact Statements, water pollution permits, State Hew Source Review, or
other programs may be used when appropriate to demonstrate an adverse
energy, environmental, or economic impact.
These guidelines are applicable to both new and modified sources
Where approoriate, however, the review may consider any special economic
or physical constraints which might limit the application of
certain control techniques to a modification project. That is, the level
of control required for a process undergoing modification or reconstruction
may not be as stringent as that which would be required if the same pro-
cess were being constructed at a grass-roots facility. Such findings,
however, must be made on a case-by-case basis by the permitting authority
considering the relevant economic and environmental impacts.
The following discussion, under each of three headings of energy,
environmental, and economic impacts, lists and briefly describes a number
of factors which may be addressed in the respective impact analyses. These
factors are guidelines only and are not intended as an exclusive list of
considerations for 3ACT Some of these factors may not be appropriate

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be possible. Raw materials may be needed to operate control equipment,
and suppliers of these resources may change over time. Similarly, it
generally will not be possible to determine specific power stations and
fuel sources which would be used to satisfy electrical demand over the
lifetime of a control device.
Duplicative analyses will not be required in preparing the BACT
permit application. Any studies previously performed for Environmental
Impact Statements, water pollution permits, State New Source Review, or
other programs may be used when appropriate to demonstrate an adverse
energy, environmental, or economic impact.
These guidelines are applicable to both r.ew and modified sources
Where approDriate, however, the review may consider any special economic
or physical constraints which might limit the application of
certain control techniques to a modification project. That is, the level
of control required for a process undergoing modification or reconstruction
may not be as stringent as that which would be required if the same pro-
cess were being constructed at a grass-roots facility. Such findings,
however, must be made on a case-by-case basis by the permitting authority
considering the relevant economic and environmental impacts.
The following discussion, under each of three headings of energy,
environmental, and economic impacts, lists and briefly describes a number
of factors which may be addressed in the respective impact analyses. These
factors are guidelines only and are not intended as an exclusive list of
considerations for BACT. Some of these factors may not be appropriate

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in all cases, while, in other instances, factors which are not included
here may be relevant to the 8ACT determination. The guideline does not
address the evaluation of each factor nor the weighting of any factor
relative to another. Such determinations should be made on a case-by-
case basis by the permitting authority. For purposes of this discussion,
terms such as "emission control system" or "BACT system" refer to design,
equipment, or operating standards and non-polluting processes as well as
flue gas control equipment.
I. Energy Impact
Energy impacts should address energy use associated with a control
system and the direct effects of such energy use on the facility and the
community. As noted earlier, indirect energy impacts (such as energy to
produce raw materials for construction of control equipment) are not
required but may be considered if the permitting authority determines, based
on a showing by the applicant, that the impact is significant and that
the impact can be well quantified. Some specific considerations for
energy impacts are presented below.
A. Energy Consumption
The amount, type (e.g., electric, coal, natural gas), and source
of energy required by each alternative emission control system should
be identified and compared to the quantities and types of energy re-
quired by the proposed BACT system. In analyzing for energy consumption,
various alternatives can be compared in terms of a) energy consumption
per unit of pollution removed (for example, Btu/ton hydrocarbon removed)

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and b) energy consumption versus the portion of the remanmnq PSD
increment which is preserved for future growth. If such comparisons are
made, they should be computed on both an overall and an incremental basis.
B.	Impact on Scarce Fuels
The type and amount of scarce fuels (e.g., natural oas, distillate
oil) which are required to comply with each alternative control require-
ment should be identified and compared with the BACT requirement. The
designation of a scarce fuel may vary from area to area, but in general
a scarce fuel is one which is in snort suooly locally and can better be
used for alternative purposes, or one which may not be reasonably
available to the source either at present or in the future.
C.	Impact on Locally Available Coa:
"1ternatives which require the use of a fuel other than locally or
regionally available coal should be discouraged if such a requirement
causes significant local economic disruDtion or unemDloyment.
D.	Energy Production Impacts (electnc utilities)
The 1977 Act Amendments imposed more stringent BACT requirements,
which may affect electric utility units that were well along in the
planning process prior to adoption of EPA regulations in June 1978.
Where the start-up of the more stringent PSD program would result in
construction delays for these units, the BACT determination may consider
such impacts. The impact of delay plant operation should be assessed
in terms of reserve capacities, system reliability, and additional costs
implied by such delays.

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11. Environmental In.pact
The net environmental impact associated with each alternative
emission control system should be determned. Both beneficial impacts
(e.g., reduced emissions attributed to a control system) and adverse
lrciDacts (e.g., exacerbation of another pollution problem through use of
a control system) should be discussed and quantified. As pointed out
above, indirect environmental impacts (such as pollution impacts at an
off-site plant which manufacturers chemicals for use in pollution control
equipment) normally need not be considered. The analysis should be
presented in the form of the incremental impact of alternative control
systems relative to the system proposed as BACT in the permit application.
Some specific considerations are presented below
A. Air Pollution Impact
The impact of air pollutants emitted from a gas stream or a
fugitive emission source can be assessed terms of quantity of
emssions, modeled effects on air quality, or both. If application of a
control system directly removes or releases other air pollutants (or
precursors to other air pollutants), then the pollutants affected ar.d
the impact of these emission changes should be identified The analysis
can consider any pollutant affecting local air quality including pollutants
which are not currently regulated under the Act, but which may be of
special concern locally.
In the absence of a more systematic technique (e.g., market-type
systems, etc ) for allocating PSD increments, BACT determinations are
important for executing such allocations. PSD programs which depend on BACT
aeterminations to implement the allocation of increments should orcject

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desired levels of growth in an area so that BACT determinations for each
source will serve to insure that the total air impacts of future growth
are no greater than the available increments. In the first years of
the PSD program, many areas may have neither a functioning market system
for allocating increments nor accurate projections of desired growth.
During this initial period, it is important that such areas use the BACT
determinations to conserve the remaining increments as much as possible
until more systematic allocation mechanisms are put in place.
B.	Water Impact
Relative quantities of water used and water pollutants produced
and discharged as a result of use of each alternative emission control
system should be identified. Where possible, the analysis shoula assess
their effect on ground water and such local surface water quality
parameters as pH, turbidity, dissolved oxygen, salinity, toxic chemical
levels and any other important considerations. The analysis should
consider whether applicable water quality standards are met and the
availability ana effectiveness of various techniques to reduce potential
adverse effects.
C.	Solid Waste Disposal Impact
The quality and quantity of solid waste (e.g., sludges, solids) that
must be stored and disposed of or recycled as a result of the applica-
tion of each alternative emission control system should be compared
with the quality and quantity of wastes created if the emission control
system prooosed as BACT is used. The composition and various other
characteristics of the solia waste (such as permeability, water retention,
rewatering of dried material, compression strength, leachability of
dissolved ions, bulk density, ability to support vegetation growth and

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hazardous characteristics) which are significant with regard to potential
surface water pollution or transport into and contamination of sub-
surface waters or aquifers should be considered. All practicable solid
waste management options (such as sanitary landfill, incineration, ana
recycling) should be investigated and the relative advantages and
disadvantages discussed.
D.	Irreversible or Irretrievable Commitment of Resources
The BACT decision may consider the extent to which the alternative
\ -
emission control systems may involve a trade-off between short-term
environmental gains at the expense of long-term environmental losses
and the extent to which the alternative systems may result in irrever-
sible or irretrievable commitment of resources (for example, use of
scarce water resources).
E.	Other Environmental Impacts
Incremental differences in noise levels, radiant heat, or dis-
sipated static electrical energy should be considered where appropriate.
III. Economic Impact
This analysis should address the economic impacts associated with
the incremental costs of installing and operating alternative control
systems above the economic impact associated with the system proposed
as 3ACT. The review should include a complete explanation of pro-
cedures for assessing economic impacts and any supporting data. As
outlined below, economic considerations can address direct economic
impacts on the firm and impacts on local economic growth.
A. Direct Economic Impacts on the Plant
Direct economic impacts on the plant should be examined through
evaluation of the following:

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1. Direct Costs
The direct cost for each control alternative should be presented
both on an incremental and on an overall basis. Investment costs,
operations and maintenance costs and annualized costs should be presented
separately. Annualized costs are ooerations and maintenance costs plus
depreciation and interest cnarges on the investment Costs should be
itemized and explained. Credit for tax incentives should be included
along with credits for product recovery costs and by-product sales
generated f*~om the use of control, systems. The lifetime of the invest-
ment should be stated. Where possible, costs should be broken down
into Drocess change costs (costs of less polluting production process)
and direct pollution abatement costs (cost of pollution control equipment).
The costs of air treatment, water treatment and solid waste disposal
should be presented separately. The analysis should also include the
total investment cost of the rev/ facility
£s a guide in determining when control costs Decome excessive,
alternative control systems can be compared in terns of certain cost
effectiveness ratios. Such ratios may include the following*
0 ratio of total control costs to total investment costs
° cost per unit of pollution removed (for example, dollars/ton)
0 cost versus additional portion of remaining PSD increment
preserved for future growth.
- unit production costs (for example, mill/kw-hr, dollars/ton
of steel).
In some cases, the unit of production output may be difficult to determine,
as in the case of a plant producing many different products. In such
cases. unit production costs can be expressed as cost per dollar 0*
total sales

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2. Capital Availability
Capital availability addresses the difficulty that some sources
may face in financing alternative control systems. Proof of such
claims should be fully documented.
B. Local Economic Impacts
Local economic impacts address the economic feasibility of al-
ternative BACT requirements and the impact of the production decisions
of the firm in response to alternative levels of control. For example,
a BACT alternative may alter the economics of a project to the point
where the decision would be made to cancel the construction or expan-
sion of a facility, to relocate a plant, to reduce the scale of opera-
tion, or to change the production mix. The local economic impacts of
sucn decisions should be assessed in terms of local employment effects
including number of jobs, dollars paid in salaries, and changes in
employee skill levels required. The guideline does not imply that the
BACT decision should force new projects to the brink of cancellation.
The BACT decision must be based on sound judgment, balancing environment
benefits with energy, economic, and other impacts.
Local economic impacts also can address the effect of various BACT
alternatives on air quality increment consumption and the subsequent
impact on future growth potential in the surrounding area. The BACT
decision should reflect policy decisions to conserve the available air
quality increment for future growth.
!V Other Costs
Other costs associated with alternative emission control systems
nay be considered where appropriate

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-ss:s-,-ncz	sac~
Assistance tc v.e states arc :sr;o".= " l"ices ~r ='.a" ^acc cort-'c"
tecrnelo:> ».¦''' continue to be p^ovicec tircjcr tne I-lr5 ,_=i. so^'-ce
¦"ev.s'.j cl£=•"ng,noose -jcust 1. 15"" Tierc, i.c'ils*" I. Ba-re" :c ^eg-oia"
v-"-ces. "OACPS -ssistance for BAC'/^AC" LAE?. leteTiiir.ati ens ' _rirOucn
its reoository of information on past 3ACT/RACT/L^E? decisions, tne
c" ear-ngnot,se crovidss a corrLmcaticn "inf. -or acv-sing reverinc
a.tncnties O" eacr ctner's ceteT-inat"c^s, t^e^eo ¦ zo t~ cor.^" stent*
%
ir BACT determinations. The degree to wmcn tne c learma.nouse \n 1" oe
£"*ect've as a consistency-improving too1 i" 1 deoerd o** tie cecree tc
i men tne z-Z~ cete'^'^ations are reocrtec to Z-",zl	recior.a" Sf'ices
a^e reo'-ejtec to s^otit BAG" fincings t: :.ne :lea ¦:rgncuse :r eccitic".
to tne -e?03"to1".'. tre c"ear1 nonouse. sister a'sc fences a -"oca! ccv't
¦	—	p	•
-"or answering Questions re'stec to cci-.:; -ss„es =oz centre 1 tecnpc'oc.
.."tr '¦esoect to control tecnnclogy, jA~-5 car assist in estab": snnc tne
ran:e z~~ alternative controls rc>" a carticu'ic'- c^ocess, out cannot
evaluate case-by-case energy, envT-onr.enta 1, and economic ""act; or
se'ect B^CT eTissicn "levels. In s'ne-t, tne c'.earmcnojse : = r oe ar
i-.Dortant incut to tne reviei-.inc 5utr.cnt.15 cecis'c-, r^t "t carnot
suostKute fo>" the case-by-case ar.a'ysis reouired tc se'ect tne aco^c--"atr
control technology

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