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OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

42) ll-B-17 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:50:53 AM Sheet 42 of 276 
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NOTE: This item is missing attachments. 
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Office of Air Quality Planning and Standards ^^<Z % 

Research Triangle Park, North Carolina 277J4-^T\\ 3 , 

0 1 NOV 1985 

MEMORANDUM 

SUBJECT: Enforcement of New Source PerformanceJjtandards for Asphalt 

Concrete Plants ~ ""* 

FROM: 

TO: 

Jack R. Farmer, Direa 

Emission Standards and En ring Division (MD-13) 

Edward E. Reich, Director 

Stationary Source Compliance Division (EN-341) 

The Emission Standards and Engineering Division (ESED) has completed 

the second review of the new source performance standards (NSPS) for 

asphalt concrete plants. Our review included an assessment of the available 

compliance test data and four plants that were tested by ESED. The data 

obtained indicate that there are some aspects of the standard that deserve 

more attention with regard to enforcement. These are process operation, 

control equipment operation, visible emissions, and reciprocity waivers. 

There are several process parameters that should be noted during an 

NSPS performance test. These are: plant production capacity, production 

rate during the test, and type of product. Because uncontrolled emissions 

increase with an increase in production rate, plants that demonstrate 

compliance while operating below the normal production rate may be out of 

compliance when operated at higher production rates. This is especially 

true for scrubber-controlled plants. Our review of available compliance 

test data indicates that the majority of the tests were conducted while 

the plants were operating at less than 80 percent of their design capacity. 

We recommend that testing be conducted at the highest production rate at 

which the plant plans to operate. 

The type of mix produced during the performance test will also affect 

emissions. Our data indicate that the type of product with the greatest 

emissions potential is a virgin surface mix. Production of a recycled 

mix or a base mix during the test will result in lower uncontrolled 

oarticulate emissions and will not provide an indication of the performanc2 

capabilities of the plant. Therefore, we recommend that tests be conducted 

w^ile producing a virgin surface mix. This is especially critical for 

plants that use scrubbers for control--since scrubbers are mora sensitive 

to change in inlet loadings. 
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Control equipment operating parameters provide an indication of the 

performance of the equipment. In particular the liquid flow rate ar: 

pressure drop across venturi scrubbers is directly related to the scrubber 

performance. Most venturi scrubbers used in the asphalt concrete industry 

are designed to operate at a pressure drop of 15 to 20 inches water column 

and a liquid to gas ratio of 8 to 10 gallons per thousand actual cubic 

feet. During our review, we found that the scrubbers are typically 

operated at lower pressure drops and liquid to gas ratios. This --..-zees 

the efficiency of the scrubbers. We recommend that scrubber operr.ng 

parameters be noted during the compliance test so as to provide an indication of proper operation of the control device during later inspections. 

The NSPS for asphalt concrete includes a visible emissions 1ir t of 

20 percent opacity. Visible emissions readings are often difficult to 

maka at a scrubber-controlled plant due to the presence of an attached 

steam plume. A detached steam plume is sometimes observed at plants 

controlled by fabric filters. In addition, there is often a blue haze 

associated with the production of recycled asphalt concrete. The blue 

h*ze generally develops down wind of the plant rather than at the stack 

vertex. The EPA reference Method 9 specifies that visible emissions 

should be evaluated between the stack and steam plume for detached plumes 

or after disappearance of the steam plume for attached plumes. Method 9 

does not include observations of condensing emissions that develop down 

wind of the plant. We have been informed that visible emissions sometimes 

are observed incorrectly when a steam plume or blue haze is present. We 

recommend that observers of visible emissions be made aware of the correct 

procedures for observing emissions when a steam or condensing plume is 

present during an asphalt concrete performance test. 

During our review, we learned of several instances where an asphalt 

concrete plant applied ror a waiver of testing requirements based on the 

performance of another plant of the same make and model. Data collected 

during our review indicate that operating and maintenance factors, in 

addition to design parameters, affect the performance of an asphalt 

concrete plant and its associated air pollution control equipment. For 

this reason, two individual plants of the same make and model may not 

have the same emission level. We do not recommend that demonstration of 

compliance by a particular plant be used to justify waiving the require-

;.ient that a second plant of the same type conduct a performance test. 

We believe that more attention by enforcement personnel to tne areas 

aascrioed above is needed and will result in an increase in the level of 

compliance with the standard. I hope this information will be useful to 

you. Additional supporting data is available in the attached background 

information document. If you have any questions regarding ou~ findin-js 

or reco'nmendations, please call Ken Durkee at FTS 629-5595. 

Attachment 

cc: Tiob Ajax (w/o attach.) Stan Cuffe (w/o attach.) Earl Salo (w/o attach. 

J. Crenshaw (w/o attach.) G. Emison (w/o attach.) G. Walsh (w/o attach.)