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OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

30) ll-B-15 

Docket Number: 

A-90-37 

Printed 11/4/2008 10:22:19 AM Sheet 30 of 147 
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/ £% \ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

I t^W ? 3 Office of Air Quality Planning and Standards 

\^y|£r / Research Triangle Park, North Carolina 27711 

* • ,o -

pISJLO^

 rt APR 051988 

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\ . - • • • • • • . ; 

MEMORANDUM - '•• — • 

SUBJECT: Note to New Source Review (NSR) Task Force Members 

FROM: Gary McCutchen, ChairmanJ^fr/ 

TO: See Below 

As you are aware, we are currently working on developing guidance 

material on the implementation of "top-down" best available control 

technology (BACT). Building on our discussions at the last Task Force 

meeting in Denver, we have prepared a brief draft outline of the "topdown" process. The outline contains the major elements and concepts 

behind a "top-down" BACT determination and is attached for your review 

and approval. 

The final outline will serve as the basis of a pending contract 

effort to develop more detailed guidance on the subject. Until the final 

guidance is issued, the outline may also be useful to the Regions and 

State and local agencies as a guide through the "top-down" process. 

Please submit your comments by April 15 to David Solomon of the New 

Source Review Section at FTS 629-5375 (USEPA, Mail Drop 15, Research 

Triangle Park, NC 27711). 

Attachment 

Addresees: 

New Source Review Task Force 

Ed Li 11 is 

John Calcagni 

cc: Chief, Air Branch, Regions I-X 
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Determining Best Available Control Technology (BACT): 

The "Top-down" Approach 

What is a BACT Determination ? 

The BACT determination, on a case-by-case basis, tak'ng into account 

energy, environmental and economic impacts results -in the maximum 

degree of reduction achievable by the source for each pollutant 

subject to a BACT analysis. 

What Pollutants are Subject to BACT Analysis ? 

Pollutants regulated under the Clean Air Act are subject to a BACT analysis 

if they are emitted in significant quantities by a major new source or if 

their emissions are significantly increased as a result of a major modification. 

This includes both criteria pollutants (for which the area in which the 

source plans to locate is designated either attainment or unclassifiable) 

and noncriteria pollutants. 

What is "Top-down" BACT ? 

The first step in this approach is to determine, for the emission source 

in question, the most stringent control available for a similar or 

identical source or source category. If it can be shown that this level 

of control is technically or economically infeasible for the source in 

question, then the next most stringent level of control is determined and 

similarly evaluated. This process continues until the BACT level under 

consideration cannot be eliminated by any substantial or unique technical, 

environmental, or economic objections. 

How is BACT Determined ? 

Of all the New Source Review processes, BACT determinations are perhaps 

the most misunderstood and the least correctly applied. Currently, BACT 

alternatives, if presented by the applicant at all, are often poorly 

documented or biased to achieved the decision the applicant desires. 

Existing EPA guidance on BACT requires an evaluation of control options 

for the source compared against a base case. The base case reflects the 

level of control option that would have been either required or chosen in 

the absence of BACT decisionmaking. In practice this is either the New 

Source Performance Standard (NSPS) or State Implementation Plan limit for 

the source. The base case is then reviewed against the more stringent 

alternate control options which have been demonstrated to operate on 

identical or similar sources. The control option with the lowest cost 

per ton removal is generally considered BACT, which in most cases is the 

base case. The structure of the analysis is biased against choosing a 

more stringent, albeit more costly, but affordable control alternative as 

BACT. Consequently, many BACT decisions inappropriately default to the 

least stringent control alternative regardless of the real viability of 

better controls. The use of "top-down" in the BACT determination would 

result in significantly greater consistency and more appropriate levels 

of control in BACT determinations nationwide. 
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An Outline of the "Top-down" Process 

I. Identification of the Most Stringent Technically Viable Control 

Alternatives 

A. Categories of Control Alternatives 

- Existing Control Technology -

Control technology which has been proven in practice or 

required by a permit for the category of source. 

- Technically Feasible Alternatives (technology transfer) -

Control technology which has been demonstrated in practice on 

other sources categories but has not been demonstrated in 

practice on the class or category of source under review. 

- Innovative Control Technology -

Control technology that has never been applied to any source 

on a full scale, continuously operating basis, but nevertheless 

could be technically applied to the source under review. The 

technology may be considered on the basis of pilot scale operations 

or short term testing. 

- Production Processes, Fuels and Materials (e.g., coatings, solvents) 

that are Inherently Less Polluting -

These options may be evaluated alone or in combination with other 

control options (e.g., flue gas treatment). 

B. Sources of Information on Potentially Viable Control Alternatives 

- The BACT/LAER Clearinghouse 

- The EPA Control Technology Center 

- Federal/State/Local Agency New Source Review Permits 

- Federal/State/Local Agency Permit Engineers 

- Control Technology Vendors 

- Environmental Consultants 

- Inspection/Performance Test Reports 

- Technical Journals 

- Air Pollution Control Seminars 
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II. Choosing BACT 

A. Most Stringent control Option is Assumed to be BACT, unless: 

- The applicant demonstrates via a case specific analysis 

the infeasibiity of the control option based on unique 

project specific mitigating factors (see Section III). 

B. If Most Stringent Control Option is Chosen by the Applicant 

the BACT Evaluation Process Stops except for an unregulated (toxic 

and hazardous) pollutant evaluation. 

III. Justifying a Less Stringent Control Option 

A. Rank Control Options in Terms of Stringentness 

B. Control Options are Listed with Most Stringent on Top 

- All control options must be at least as stringent as any applicable 

New Source Performance Standard 

C. Listing Compares Various Impacts of Each Control Option 

- Control efficiency (both capture and collection efficiency) 

- Economic 

- Environmental 

- Energy 

- Control of toxics and hazardous pollutants 

D. The Most Stringent Control Alternative is Assumed to be BACT 

Unless the Applicant Can Demonstrate that it is an Infeasible 

Control Option. 

- When an acceptable demonstration is made regarding the infeasibility 

of the most effective control option, the next most effective option 

is assumed tc be BACT. The process continues until a control 

option can noc be rejected on the grounds of its infeasibility. 

IV. Examples of Unique Factors Appropriate for Consideration in Evaluating 

the Infeasibility of the Most Stringent Control Option 

A. Technical Infeasibility 

- Control system cannot be transfered to (or used by) the specific 

source (e.g., transfer of a catalyst control device to a process 

gas from natural gas, or lack of water for a scrubber). 

B. Environmental Impacts 

- Less effective control option for criteria pollutant of concern 

provides greater overall control of the other pollutants (e.g., 

other criteria and/or toxic pollutants). 
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- Unique nonair impacts (e.g., sludge, water quality/availability) 

- Unacceptable imparment of visibility from more stringent option 

C. Energy 

- Significant energy penalties and bonuses for various control 

options 

E. Economic 

- Costs, relative (to other sources/areas) and absolute, as compared 

to the industry as a whole: 

-- Unit product price costs (dollar/percent increase per unit cost) 

of control option 

— Cost of control option as a percent of total project costs 

-- Cost in dollars per ton of pollutant removed 

-- Actual rate of return or investment compared to typical rate 

for industry 

- If applicable, cost comparison of control option for different 

source category versus this source category 

IV. Factors Which are Not Normally Acceptable for Consideration in 

Evaluating the Feasibility of the Most Stringent Control Option 

A. Environmental 

- At a less effective control level, neither the the PSD increments 

nor National Ambient Air Quality Standards would be violated. 

- A less effective control option models no significant impact. 

- The "alternate build" scenario (e.g., even at the higher emission 

rate, the project is less polluting than the power plant capacity 

it would replace). 

B. Energy 

- There is a energy penalty associated with the more effective 

option (unless a showing can be made that in this specific 

case it represents a "unique" burden not common to the industry). 

C. Economic 

*- Artificially low allocation of funding for effective pollution 

control. 

* These factors are never acceptable 
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- Amount source can borrow for project. 

- Individual financial capability of company to fund the 

proposed project. 

- Specific rate of return desired by the source (if not 

within the norm for the industry). 

- A depressed local economy. 

V. The BACT Determination Must be Enforceable 

A. For each subject pollutant The BACT determination must result 

in an emissions unit/point specific emissions limitation. 

- If technological or economic limitations on the application of 

measurement methodology to a particular emissions unit whould 

make the imposition of an emissions standard infeasible, a 

design, equipment, work practice, operational standard, or 

combination thereof, may be prescribed. 

- The BACT limits must be included in the PSD permit 

-- Emissions unit/point specific and enforceable