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B.17

IV.B. TECHNICAL FEASIBILITY ANALYSIS (STEP 2)

In step 2, the technical feasibility of the control options identified 

in step 1 is evaluated. This step should be straightforward for control 

technologies that are demonstrated--if the control technology has been

installed and operated successfully on the type of source under review, it is

demonstrated and it is technically feasible. For control technologies that

are not demonstrated in the sense indicated above, the analysis is somewhat

more involved. 

Two key concepts are important in determining whether an undemonstrated

technology is feasible: "availability" and "applicability." As explained in

more detail below, a technology is considered "available" if it can be

obtained by the applicant through commercial channels or is otherwise

available within the common sense meaning of the term. An available

technology is "applicable" if it can reasonably be installed and operated on

the source type under consideration. A technology that is available and

applicable is technically feasible.

Availability in this context is further explained using the following

process commonly used for bringing a control technology concept to reality as

a commercial product:

! concept stage;

! research and patenting;

! bench scale or laboratory testing;

! pilot scale testing;

! licensing and commercial demonstration; and

! commercial sales. 
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OCTOBER 1990

B.18

A control technique is considered available, within the context

presented above, if it has reached the licensing and commercial sales stage of

development. A source would not be required to experience extended time

delays or resource penalties to allow research to be conducted on a new

technique. Neither is it expected that an applicant would be required to

experience extended trials to learn how to apply a technology on a totally 

new and dissimilar source type. Consequently, technologies in the pilot scale

testing stages of development would not be considered available for BACT

review. An exception would be if the technology were proposed and permitted

under the qualifications of an innovative control device consistent with the

provisions of 40 CFR 52.21(v) or, where appropriate, the applicable SIP.

Commercial availability by itself, however, is not necessarily

sufficient basis for concluding a technology to be applicable and therefore

technically feasible. Technical feasibility, as determined in Step 2, also

means a control option may reasonably be deployed on or "applicable" to the

source type under consideration.

Technical judgment on the part of the applicant and the review authority

is to be exercised in determining whether a control alternative is applicable

to the source type under consideration. In general, a commercially available

control option will be presumed applicable if it has been or is soon to be

deployed (e.g., is specified in a permit) on the same or a similar source

type. Absent a showing of this type, technical feasibility would be based on

examination of the physical and chemical characteristics of the pollutantbearing gas stream and comparison to the gas stream characteristics of the

source types to which the technology had been applied previously. Deployment

of the control technology on an existing source with similar gas stream

characteristics is generally sufficient basis for concluding technical

feasibility barring a demonstration to the contrary.
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OCTOBER 1990

B.19

For process-type control alternatives the decision of whether or not it

is applicable to the source in question would have to be based on an

assessment of the similarities and differences between the proposed source and

other sources to which the process technique had been applied previously. 

Absent an explanation of unusual circumstances by the applicant showing why a

particular process cannot be used on the proposed source the review authority

may presume it is technically feasible.

In practice, decisions about technical feasibility are within the

purview of the review authority. Further, a presumption of technical

feasibility may be made by the review authority based solely on technology

transfer. For example, in the case of add-on controls, decisions of this type

would be made by comparing the physical and chemical characteristics of the

exhaust gas stream from the unit under review to those of the unit from which

the technology is to be transferred. Unless significant differences between

source types exist that are pertinent to the successful operation of the

control device, the control option is presumed to be technically feasible

unless the source can present information to the contrary.

Within the context of the top-down procedure, an applicant addresses the

issue of technical feasibility in asserting that a control option identified

in Step 1 is technically infeasible. In this instance, the applicant should

make a factual demonstration of infeasibility based on commercial

unavailability and/or unusual circumstances which exist with application of

the control to the applicant's emission units. Generally, such a

demonstration would involve an evaluation of the pollutant-bearing gas stream

characteristics and the capabilities of the technology. Also a showing of

unresolvable technical difficulty with applying the control would constitute a

showing of technical infeasibility (e.g., size of the unit, location of the

proposed site, and operating problems related to specific circumstances of the

source). Where the resolution of technical difficulties is a matter of cost,

the applicant should consider the technology as technically feasible. The

economic feasibility of a control alternative is reviewed in the economic

impacts portion of the BACT selection process.
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OCTOBER 1990

B.20

A demonstration of technical infeasibility is based on a technical

assessment considering physical, chemical and engineering principles and/or

empirical data showing that the technology would not work on the emissions

unit under review, or that unresolvable technical difficulties would preclude

the successful deployment of the technique. Physical modifications needed to

resolve technical obstacles do not in and of themselves provide a

justification for eliminating the control technique on the basis of technical

infeasibility. However, the cost of such modifications can be considered in

estimating cost and economic impacts which, in turn, may form the basis for

eliminating a control technology (see later discussion at V.D.2).

Vendor guarantees may provide an indication of commercial availability

and the technical feasibility of a control technique and could contribute to a

determination of technical feasibility or technical infeasibility, depending

on circumstances. However, EPA does not consider a vendor guarantee alone to

be sufficient justification that a control option will work. Conversely, lack

of a vendor guarantee by itself does not present sufficient justification that

a control option or an emissions limit is technically infeasible. Generally,

decisions about technical feasibility will be based on chemical, and

engineering analyses (as discussed above) in conjunction with information

about vendor guarantees.

A possible outcome of the top-down BACT procedures discussed in this

document is the evaluation of multiple control technology alternatives which

result in essentially equivalent emissions. It is not EPA's intent to

encourage evaluation of unnecessarily large numbers of control alternatives

for every emissions unit. Consequently, judgment should be used in deciding

what alternatives will be evaluated in detail in the impacts analysis (Step 4)

of the top-down procedure discussed in a later section. For example, if two

or more control techniques result in control levels that are essentially

identical considering the uncertainties of emissions factors and other

parameters pertinent to estimating performance, the source may wish to point

this out and make a case for evaluation and use only of the less costly of

these options. The scope of the BACT analysis should be narrowed in this way
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OCTOBER 1990

B.21

only if there is a negligible difference in emissions and collateral

environmental impacts between control alternatives. Such cases should be

discussed with the reviewing agency before a control alternative is dismissed

at this point in the BACT analysis due to such considerations.

It is encouraged that judgments of this type be discussed during a 

preapplication meeting between the applicant and the review authority. In 

this way, the applicant can be better assured that the analysis to be

conducted will meet BACT requirements. The appropriate time to hold such a

meeting during the analysis is following the completion of the control

hierarchy discussed in the next section.

Summary of Key Points

In summary, important points to remember in assessing technical

feasibility of control alternatives include: 

! A control technology that is "demonstrated" for a given type or class

of sources is assumed to be technically feasible unless

source-specific factors exist and are documented to justify technical

infeasibility. 

! Technical feasibility of technology transfer control candidates

generally is assessed based on an evaluation of pollutant-bearing gas

stream characteristics for the proposed source and other source types

to which the control had been applied previously. 

! Innovative controls that have not been demonstrated on any source

type similar to the proposed source need not be considered in the

BACT analysis. 

! The applicant is responsible for providing a basis for assessing

technical feasibility or infeasibility and the review authority is

responsible for the decision on what is and is not technically

feasible.