National Emission Standards for Hazardous Air Pollutants for Source Categories: Aerospace Manufacturing and Rework

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[AD-FRL-4891-8]

National Emission Standards for Hazardous Air Pollutants for

Source Categories: Aerospace Manufacturing and Rework

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule and notice of public hearing.

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SUMMARY: The proposed standards would limit emissions of hazardous air

pollutants (HAP) from new and existing commercial, civil, and military

aerospace original equipment manufacturing (OEM) and rework facilities

that are major sources of HAP emissions. A major source is defined in

section 112(a) of the Clean Air Act as amended in 1990 (Act) as a

source that emits, or has the potential to emit, considering controls,

10 tons per year (tpy) or more of any individual HAP or 25 tpy or more

of any combination of HAP. The proposed standards implement section

112(d) of the Act, which requires the Administrator to regulate

emissions of the HAP listed in section 112(b) of the Act. Many of these

pollutants are emitted from cleaning, primer, topcoat, depainting, and

chemical milling maskant operations. These operations are being covered

in the proposed rule. The intent of the proposed rule is to protect the

public health by requiring new and existing major sources to control

HAP emissions to the level attainable by the maximum achievable control

technology (MACT). The EPA is also proposing Method 309 with the

standards. Method 309 would be used to determine the rolling material

balance period for carbon adsorbers.

A public hearing will be held, if requested, to provide interested

persons an opportunity for oral presentation of data, views, or

arguments concerning the proposed standards.

DATES: Comments: Comments must be received on or before August 5, 1994.

ADDRESSES: Comments: Comments should be submitted (in duplicate, if

possible) to: Air and Radiation Docket and Information Center (6102),

ATTN: Docket No. A-92-20, U.S. Environmental Protection Agency, 401 M

Street, SW., Washington, DC 20460. Public Hearing: If anyone contacts

the EPA requesting a public hearing, the hearing will be held at the

EPA Office of Administration Auditorium in Research Triangle Park,

North Carolina. Persons wishing to present oral testimony must contact

Ms. Julia Latta, Standards Development Branch (MD-13), U.S.

Environmental Protection Agency, Research Triangle Park, North Carolina

27711, telephone number (919) 541-5578 by July 1, 1994.

Background Information Document: The background information

document (BID) may be obtained from the U.S. EPA Library (MD-35),

Research Triangle Park, North Carolina 27711, telephone number (919)

541-2777. Please refer to ``National Emission Standards for Hazardous

Air Pollutants for Source Categories: Aerospace Manufacturing and

Rework--Background Information for Proposed Standards,'' EPA-453/R-94-

036a.

Docket: Docket No. A-92-20, containing supporting information used

in developing the proposed rule, is available for public inspection and

copying between 8:30 a.m. and 3:30 p.m., Monday through Friday, at the

EPA's Air and Radiation Docket and Information Center, Waterside Mall,

room 1500, 1st Floor, 401 M Street, SW., Washington, DC 20460. A

reasonable fee may be charged for copying.

FOR FURTHER INFORMATION CONTACT: For information concerning the

proposed rule, contact Ms. Vickie Boothe at (919) 541-0164, Standards

Development Branch, Emission Standards Division (MD-13), U.S.

Environmental Protection Agency, Research Triangle Park, North Carolina

27711.

SUPPLEMENTARY INFORMATION: The information presented in this preamble

is organized as follows:

I. Background

II. Summary of the Proposed Rule

A. Applicability

B. Proposed Standards for Affected Sources

C. Compliance Dates

D. Compliance Extensions

E. Compliance Testing and Monitoring

F. Recordkeeping and Reporting Requirements

III. Summary of Environmental, Energy, and Economic Impacts of the

Proposed Rule

A. Emission Reductions

B. Secondary Environmental Impacts

C. Energy Impacts

D. Cost Impacts

E. Economic Impacts

IV. Process Descriptions and Control Technologies

A. Process Descriptions

B. Control Techniques

V. Rationale for the Proposed Rule

A. Regulatory Development Process for NESHAP

B. Determining Maximum Achievable Control Technology (MACT)

``Floors''

C. Selection of Pollutants and Source Category(ies)

D. Selection of Emission Points Covered by the Proposed Rule

E. Selection of the Basis for the Proposed Rule

F. Selection of the Format of the Proposed Rule

G. Selection of Emission Test Methods and Monitoring

Requirements

H. Selection of Recordkeeping and Reporting Requirements

I. Selection of Compliance Deadlines

J. Operating Permit Program

K. Solicitation of Comments

VI. Administrative Requirements

A. Public Hearing

B. Docket

C. Executive Order 12866

D. Paperwork Reduction Act

E. Regulatory Flexibility Act

F. Clean Air Act Section 117

G. Regulatory Review

VII. Statutory Authority

The proposed regulatory text is not included in this Federal

Register notice, but is available in Docket No. A-92-20 or by written

or telephone request from the Air and Radiation Docket and Information

Center (see ADDRESSES). This notice with the proposed regulatory

language is also available on the Technology Transfer Network (TTN),

one of EPA's electronic bulletin boards. The TTN provides information

and technology exchange in various areas of air pollution control. The

service is free, except for the cost of a phone call. Dial (919) 541-

5742 for up to a 14,400 bps modem. If more information on TTN is

needed, call the HELP line at (919) 541-5384.

I. Background

The Act requires, under section 112, that EPA evaluate and control

emissions of HAP. The control of HAP is to be achieved through

promulgation of emission standards under sections 112(d) and (f) for

categories of sources that emit HAP. Pursuant to section 112(c) of the

Act, EPA published in the Federal Register the initial list of source

categories that emit HAP on July 16, 1992 (57 FR 31576). This list

includes major and area sources of HAP that the EPA intends to regulate

before November of the year 2000.

For the purposes of the proposed rule, aerospace industries refers

to all facilities that manufacture aerospace vehicles or components and

all facilities that rework (including repair) these aerospace vehicles

or components. Aerospace vehicle or component is defined as any

fabricated part, processed part, assembly of parts, or completed unit

of any aircraft including, but not limited to, airplanes, helicopters,

missiles, rockets, and space vehicles.

Section 183(b)(3) of the Act requires the Administrator to issue

control techniques guidelines (CTG) for volatile organic compound (VOC)

emissions from aerospace coatings and solvents to such levels as the

Administrator determines are achievable through adoption of best

available control measures (BACM). The EPA is required to take into

account the applicable requirements of section 112 in developing the

guidelines.

The organic HAP emissions limitations described in the remainder of

this notice also address the VOC emissions from aerospace coatings and

solvents. Thus, the control techniques evaluated for the MACT standard

are also applicable to VOC emissions.

The EPA traditionally issues a draft CTG containing recommended

control levels for public comment. Rather than issue a separate draft

CTG in this case, the EPA is using this notice to request public

comment on a draft BACM, which is the same as the proposed MACT for

coatings and solvents. Comments received on the proposed MACT rule will

also be considered in formulating a final BACM.

The information described here will also serve to provide guidance

to the States for developing VOC rules to meet other Clean Air Act

requirements.

Certain low-usage coatings were not addressed in the NESHAP. These

coatings are adhesives, sealants, and 30 specialty coatings which

represent less than 6 percent of the total HAP emissions from the

industry. Also, the EPA data analyses indicate that the MACT floor for

these coatings would be no control. The EPA is requesting public

comment on the need for a separate CTG providing guidance for the

control of these coatings.

II. Summary of the Proposed Rule

Table 1 provides an overview of the proposed rule, including

applicability; the standards for each affected source; test methods and

procedures; and monitoring, recordkeeping, and reporting requirements.

Table 1. Summary of Subpart GG of 40 CFR Part 63--National Emission Standards for Aerospace Manufacturing and

Rework Facilities

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Affected source Requirement Description

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Aerospace Facilities............ Applicability: General This rule applies to facilities engaged in

Information. original equipment manufacture and rework

of aerospace components and assemblies and

that are major sources as defined in 40 CFR

part 63. Specific operations are covered by

the rule. (63.741)

Estimated Number of Facilities.. Over 2,800 facilities are expected to be

affected by the rule. Applicable SIC codes

include 3720, 3721, 3724, 3728, 3760, 3761,

3764, 3765, and 4581.

Permit Requirements............. 1. Major sources required to obtain

operating permit in State where facility is

located according to procedures in 40 CFR

part 70 and applicable State regulations.

(63.741(d))

All Affected Sources............ Standards....................... 1. Comply with Secs. 63.4 through Sec. 63.6

of the General Provisions of 40 CFR part

63, Subpart A.\1\ (63.743(a))

2. Submit an operation and maintenance plan.

(63.743(b))

3. Obtain approval to use control device not

listed in this subpart. (63.743(c))

4. Wastes subject to RCRA are exempt from

the waste storage and handling requirements

of this subpart. (63.741(e))

Compliance Dates................ As provided for in the General

Provisions,\2\ within 3 years after the

effective date for existing sources and no

later than the standards' effective date or

upon startup, as appropriate, for new and

reconstructed sources. (63.749(a))

Test Methods and Procedures..... See individual affected sources. Also,

comply with Sec. 63.7 of the General

Provisions. (63.750(q))

Monitoring Requirements......... See individual affected sources. Also,

generally same as in Sec. 63.8(f) and (g)

of the General Provisions. (63.751(e) and

(f))

Recordkeeping Requirements...... Comply with Sec. 63.10 of the General

Provisions.\3\ (63.752(a))

Reporting Requirements.......... 1. Comply with Secs. 63.9 and 63.10 of the

General Provisions.\4\ (63.753(a)(1) and

(3))

2. Operating permit application can be used

for initial notification. (63.753(a)(2))

Cleaning Operations............. Standards....................... Housekeeping measures for all cleaning

operations at a facility subject to this

subpart. Measures address placing solvent

laden cloth or paper in closed containers,

storing fresh and used cleaning solvent in

closed containers, and minimizing losses

during handling and transfer. (63.744(a))

Test Methods and Procedures..... None.

Monitoring Requirements......... None.

Recordkeeping Requirements...... The name, HAP content of each cleaning

solvent, and supporting documentation.

(63.752(b)(1))

Reporting Requirements.......... Semiannual

1. New cleaning solvents that contain no

HAP. (63.753(b)(1)(i))

2. Discontinued cleaning solvents.

(63.753(b)(1)(ii))

Hand-Wipe Cleaning Operations... Standards....................... 1. Except for spray gun cleaning, all hand-

wipe cleaning solvent must meet either a

composition requirement or have a vapor

pressure less than 45 mm Hg. (63.744(b))

2. List of cleaning operations exempt from

composition and vapor pressure

requirements. (63.744(e))

Test Methods and Procedures..... 1. Composition determination through

manufacturer's data. (63.750(a))

2. Vapor pressure determination through

readily available sources if single

component; ASTM E 260-85 for multiple

component solvents. (63.750(b))

Monitoring Requirements......... For enclosed spray gun cleaners, visual

inspection for leaks at least once per

month. (63.751(a))

Recordkeeping Requirements...... 1. If complying with composition

requirements, name, data/calculations, and

annual volumes. (63.752(b)(2))

2. If complying as result of vapor pressure,

name, vapor pressure, data/calculations/

test results, and monthly volumes.

(63.752(b)(3))

3. For ``non-compliant'' cleaning solvents

used in exempt operations, daily volumes by

operation, and parts/assemblies cleaned.

(63.752(b)(4))

Reporting Requirements.......... Semiannual

1. Noncompliant solvent usage.

(63.753(b)(1)(iii))

2. New solvents and vapor pressure or

composition. (63.753(b)(1)(iv))

Annual

3. Everything is in compliance.

(63.753(b)(2))

Spray Gun Cleaning.............. Standards....................... 1. Use one of four specified techniques or

an equivalent. (63.744(c))

2. For enclosed spray gun cleaners, repair

as soon as practicable, but within 15 days.

(63.744(c)(1)(ii))

Test Methods and Procedures..... None.

Monitoring Requirements......... None.

Recordkeeping Requirements...... Record all leaks, including source

identification and dates leaks found and

repaired. (63.752(b)(5))

Reporting Requirements.......... Semiannual

1. Noncompliant spray gun cleaner used.

(63.753(b)(1)(v))

2. Leaks of enclosed spray gun cleaners not

repaired within 15 days of detection.

(63.753(b)(1)(vi))

Annual

3. Everything is in compliance.

(63.753(b)(2))

Flush Cleaning.................. Standards....................... Operating procedures specify emptying into

enclosed container or collection system or

equivalent. (63.744(d))

Test Methods and Procedures..... None.

Monitoring Requirements......... None.

Recordkeeping Requirements...... None.

Reporting Requirements.......... Annual

Everything is in compliance. (63.753(b)(2))

Primer and Topcoat Application Standards....................... Uncontrolled Primers

Operations. 1. Organic HAP content limit: 350 grams/

liter (2.9 lbs/gallon)(less water) as

applied. (63.745(b)(1))

2. VOC content limit: 350 grams/liter (2.9

lbs/gallon) (less water and exempt

solvents) as applied. (63.745(b)(2))

Uncontrolled Topcoats

3. Organic HAP content limit: 420 grams/

liter (3.5 lbs/gallon)(less water) as

applied. (63.745(b)(3))

4. VOC content limit: 420 grams/liter (3.5

lbs/gallon) (less water and exempt

solvents). (63.745(b)(4))

Uncontrolled Primers and Topcoats

5. Primers and topcoats can achieve

compliance through: (1) being below limit

in themselves or (2) average with compliant

primers. (63.745(d))

6. Primers and topcoats cannot be averaged

together. Controlled and uncontrolled

coatings cannot be averaged together.

(63.745(d)(2)(ii) and (d)(2)(iii))

Controlled Primers and Topcoats

7. If control device is used, must be

designed to capture and control all

emissions from the application operation

and must achieve an overall control

efficiency of at least 81%. (63.745(c))

All Primers and Topcoats

8. Specific application techniques must be

used. If alternative is sought, can only be

used if emissions are less than or equal to

HVLP or electrostatic spray application

techniques as demonstrated under actual

production conditions. (63.745(e)(1))

9. All application equipment must be

operated according to manufacturer's

specifications. (63.745(e)(2))

10. Exemptions from 8 above provided for

certain situations. (63.745(e)(3))

11. Operating requirements for the

application of primers that contain

inorganic HAP, including control with

either particulate filters or waterwash and

shutdown if pressure falls outside

manufacturer's specified operating limits.

(63.745(f)(1) through (4))

12. Exemptions from 11 provided for certain

application operations. (63.745(f)(5))

Performance Test Periods and 1. Test Periods For compliant coatings: each

Tests. 30-day period. For ``averaged'' coatings:

each 24-hour period. For ``controlled''

coatings, non-carbon adsorber: three 1-hour

runs. For ``controlled'' coatings, carbon

adsorber: each rolling period.

(63.749(d)(1))

2. Performance tests. Initial performance

test for all control devices to demonstrate

compliance with overall control efficiency

requirement. (63.749(d)(2))

Test Methods and Procedures..... 1. Organic HAP level determination

procedures. (63.750(c) and (d))

2. VOC level determination procedures.

(63.750(e) and (f))

3. Overall control efficiency of carbon

adsorber determined using mass balance

calculation in 40 CFR 60.433; for other

control devices, determine capture

efficiency and destruction efficiency. For

capture efficiency, use Procedure T in

Appendix B to 40 CFR 52.741 for total

enclosures and 40 CFR 52.741(a)(4)(iii)

procedures for all other enclosures.

(63.750(g) and (h))

4. For alternative application methods,

first determine emission levels for initial

90-day period using only HVLP or

electrostatic. Then use alternative

application method for period of time

necessary to coat equivalent amount of

parts with same coatings. Alternative

application method may be used when

emissions generated during the test period

are less than or equal to the emissions

generated during the initial 90-day period.

Dried film thickness must be within

specification for initial 90-day period.

(63.750(i))

Monitoring Requirements......... 1. Temperature sensors with continuous

recorders for incinerators, and install,

calibrate, maintain, and operate

temperature monitors according to

manufacturer's specifications. (63.751(b))

2. Continuously monitor pressure drop across

filter or waterwash. (63.751(c))

Recordkeeping Requirements...... 1. Name and organic HAP and VOC contents for

all primers and topcoats. (63.752(c)(1))

2. For ``compliant'' coatings, organic HAP

and VOC contents as applied, data/

calculations used to determine them, and

monthly usage. (63.752(c)(2))

3. For ``averaged'' coatings, daily values

of HAP and VOC contents (Ha and Ga) and

data calculations used to calculate Ha and

Ga. (63.752(c)(3))

4. For ``controlled'' coatings

(incinerator), overall control efficiency

and incinerator temperature(s).

(63.752(c)(4))

5. For ``controlled'' coatings (carbon

adsorber), overall control efficiency and

length of rolling period and all supporting

data/calculations. (63.752(c)(5))

6. Pressure drop across filters/waterwash

once per shift, and acceptable limits.

(63.752(d))

Reporting Requirements.......... Semiannual

1. All instances where organic HAP/VOC

levels were exceeded. (63.753(c)(1)(i) and

(ii))

2. Control device exceedances (out-of-

compliance). (63.753(c)(1) (iii), (iv) and

(v))

3. Periods when operation not immediately

shut down due to pressure drop being

outside limits. (63.753(c)(1)(vi))

4. New control devices. (63.753(c)(1)(vii))

Annual

5. Number of times the pressure drop limits

were exceeded. (63.753(c)(2))

6. Everything is in compliance.

(63.753(c)(2))

Depainting Operations........... Applicability................... Applies to the entire aerospace vehicle.

Does not apply to parts or units normally

removed. Wings and stabilizers always

covered. (63.746(a))

Standards....................... 1. Unless exempted, no organic HAP are to be

emitted from depainting operations. (63.746

(b)(1), (b)(3))

2. Requirement to minimize HAP during

periods of non-chemical based equipment

malfunction. (63.746(b)(2))

3. Use of organic HAP-containing strippers

for spot stripping and decal removal

limited to 26 gallons per aircraft per year

for commercial aircraft and 50 gallons per

aircraft per year for military aircraft.

(63.746(c))

4. Operating requirements for depainting

operations generating airborne inorganic

HAP, including control with particulate

filters that are at least 99% efficient.

(63.746(d))

Performance Test Periods and 1. For no organic HAP emissions: each 24-

Tests. hour period. (63.749(f)(1))

2. For spot stripping and decal removal

usage limits: each calendar year.

(63.749(f)(1))

3. Initial performance test to demonstrate

compliance with percent reduction

efficiency requirement for particulate

filters. (63.749(f)(2))

Test Methods and Procedures..... 1. Use manufacturer's data (or approved

alternative) to determine organic HAP

content. (63.750(j))

2. Procedures provided for determining

gallons of HAP containing stripper used for

aircraft. (63.750(k))

3. Use EPA Method 5 to determine particulate

filter control efficiency. (63.750(l))

Monitoring Requirements......... Continuously monitor pressure drop across

filter. (63.751(d))

Recordkeeping Requirements...... 1. Name, organic HAP content and supporting

documentation, and monthly volume of all

organic HAP-containing chemical strippers.

(63.752(e)(1))

2. List of parts/assemblies normally

removed. (63.752(e)(2))

3. For non-chemical based equipment, name

and type, and malfunction information

including dates, description, and

alternative methods used. (63.752(e)(3))

4. For spot stripping and decal removal,

annual volume used, annual average volume

per aircraft, and all data/calculations

used to calculate volume per aircraft.

(63.752(e)(4))

5. The pressure drop across the filter once

per shift, pressure drop limits specified

by manufacturers, and control efficiency

including test results/data/calculations.

(63.752(e)(5))

Reporting Requirements.......... Semiannual

1. Emission of organic HAP from nonexempted

depainting operations. (63.753(d)(1)(i))

2. New and reformulated chemical strippers

and HAP contents. (63.753(d)(1) (ii), (iii)

and (iv))

3. New non-chemical based depainting

techniques. (63.753(d)(1)(v))

4. Malfunction information on non-chemical

based techniques including dates,

description, and alternative methods used.

(63.753(d)(1)(vi))

5. Periods when operation not immediately

shut down due to pressure drop being

outside limits. (63.753(d)(1)(vii))

6. List of new/discontinued aircraft models

and, for new models, list of parts normally

removed for depainting.

(63.753(d)(1)(viii))

Annual

7. Exceedances of average annual volume

limits for spot stripping and decal

removal. (63.753(d)(2)(i))

8. Everything is in compliance.

(63.753(d)(2)(ii))

9. Number of times the pressure drop limits

were exceeded. (63.753(d)(2)(iii))

Chemical Milling Maskant Applicability................... Applies only to operations using Type II

Application Operations. chemical milling etchants (63.747(a))

Standards....................... Uncontrolled Maskants

1. Organic HAP emissions: 160

grams/liter (1.3 lbs/gallon) (less water)

as applied. (63.747(c)(1))

2. VOC emissions: 160 grams/liter

(1.3 lbs/gallon) (less water and exempt

solvents) as applied. (63.747(c)(2))

3. Maskants can achieve compliance through:

(1) being below limits by themselves or (2)

averaging with compliant maskants.

(63.747(e))

4. Both controlled and uncontrolled maskants

cannot be averaged together.

Controlled Maskants

5. If control device is used, must be

designed to capture and control all

emissions from maskant operation and must

achieve an overall control efficiency of at

least 81%. (63.747(d))

Performance Test Periods and 1. Test Periods. For compliant maskants:

Tests. each 30-day period. For ``averaged''

maskants: each 24-hour period. For

``controlled'' coatings, carbon adsorber:

each rolling period. For ``controlled''

coatings, non-carbon adsorber: three 1-hour

runs. (63.749(g)(1))

2. Initial performance test required for all

control devices to demonstrate compliance

with overall control efficiency

requirement. (63.749(g)(2))

Test Methods and Procedures..... Procedures provided essentially identical to

those for primers and topcoats for organic

HAP and VOC content levels. Use of Method

309 for determining rolling period for

carbon adsorber. (63.750(m)-(p))

Monitoring Requirements......... Same as for primers and topcoats if

incinerators are used.

Recordkeeping Requirements...... Same as for primers and topcoats.

(63.752(f))

Reporting Requirements.......... Semiannual

1. Exceedances of organic HAP/VOC levels.

(63.753(e)(1)(i) and (ii))

2. Control device exceedances (out of

compliance). (63.753(e)(1)(iii))

3. New maskants. (63.753(e)(1)(iv))

4. New control devices. (63.753(e)(1)(v))

Annual

5. Everything is in compliance.

(63.753(e)(2))

Waste Handling and Storage Applicability................... Wastes that are subject to RCRA are exempt

Operations. from the requirements of this subpart.

(63.741(e))

Standards....................... Unless subject to RCRA, work practice

requirements to minimize spills during

handling and transfer and storage in close

containers. (63.748)

Test Methods and Procedures..... None.

Monitoring Requirements......... None.

Recordkeeping Requirements...... Identification of each waste stream, whether

or not it is subject to RCRA, and

supporting documentation. (63.752(g))

Reporting Requirements.......... Semiannual

1. Any change in RCRA status of waste

stream, any new waste stream, and its RCRA

status. (63.753(f)(1))

Annual

2. No new waste streams and no change in

RCRA status of existing waste streams.

(63.753(f)(2))

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\1\The EPA promulgated regulations for subpart A of 40 CFR 63, which were published in the Federal Register on

March 16, 1994 at 59 FR 12408.

\2\Ibid.\3\Ibid.\4\Ibid.

A. Applicability

1. Description of the Source Category

The proposed rule would apply to each aerospace manufacturing and

rework facility that is a major source, as defined under section 112(a)

of the Act. A major source is one that emits or has the potential to

emit, considering controls, 9.1 megagrams per year (Mg/yr) (10 tpy) or

more of any hazardous air pollutant or 22.7 Mg/yr (25 tpy) or more of

any combination of hazardous air pollutants for all activities

conducted at the facility. An aerospace facility is defined as a

facility that produces in any amount an aerospace vehicle or component,

or a facility that reworks (or repairs) these vehicles or components.

Aerospace operations at any major source that conduct both aerospace

and non-aerospace work would be subject to the proposed standards,

regardless of the relative proportion of aerospace and non-aerospace

work at the facility.

While the proposed rule applies only to major sources, the EPA

requests comment on whether all or some of its requirements should be

applied to non-major sources. The Agency solicits available information

from state and local air pollution control agencies and others on the

nature, number and location of non-major aerospace facilities, the

quantities and types of hazardous air pollutants they emit, the impact

of these emissions on health and the environment, and the extent to

which these emissions already are controlled. Comments also are

requested on the economic and other impacts that would result from

applying requirements of the proposed rule to these smaller sources.

In general, aerospace facilities are covered by the SIC codes

listed in Table 2. However, facilities classified under other SIC codes

may be subject to the proposed standards if the facility meets the

definition of a major source and the definition of an aerospace

facility.

Based on information obtained through the Federal Aviation

Administration and the U.S. Department of Commerce--Bureau of the

Census, there are an estimated 2,869 aerospace facilities that will be

subject to the proposed standards. Of this number, 1,395 manufacture or

rework commercial products, and 1,474 manufacture or rework military

products. The combined HAP emissions from these facilities are

estimated to be over 189,000 Mg/yr (208,000 tpy).

In addition to these facilities, there are numerous subcontractors

that manufacture or rework aerospace vehicles or components. The

subcontractors may work directly for the

Table 2.--Aerospace Manufacturing SIC Codes

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SIC Code Description

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3720 Aircraft and Parts.

3721 Aircraft.

3724 Aircraft Engines and Engine Parts.

3728 Aircraft Parts and Equipment.

3760 Guided Missiles, Space Vehicles, and Parts.

3761 Guided Missiles and Space Vehicles.

3764 Space Propulsion Units and Parts.

3769 Space Vehicle Equipment.

Aerospace Rework SIC Code

4581 Airports, Flying Fields, and Services.

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OEM or rework facilities, or indirectly through first line

subcontractors. Since many of these subcontractors perform various

types of work, they are often classified under non-aerospace SIC codes.

Consequently, an estimate of the number of subcontractors cannot be

made. One company alone, however, employs the services of over 5,000

subcontractors.

2. Affected Sources

The proposed rule would limit organic HAP emissions from the

following sources at aerospace facilities: cleaning operation, primer

application operation, topcoat application operation, depainting

operation, chemical milling maskant application operation, and the

handling and storage of waste. The proposed rule would also limit

inorganic HAP emissions from primer, topcoat, and depainting

operations.

Organic HAP emissions from primer, topcoat, and chemical milling

maskant application operations occur from the evaporation of the

solvent contained in the coatings. These emissions occur during the

application of the coatings on aerospace vehicles or parts, which may

take place in large open areas, such as hangars, or in partially or

fully enclosed spaces, such as within spray booths.

Organic HAP emissions from cleaning and depainting operations occur

from the evaporation of the volatile portion of the cleaning solvents

or chemical strippers. Cleaning emissions are nearly always fugitive in

nature and occur at essentially every processing step. Emissions from

depainting are typically fugitive in nature since the operation is

carried out within a large hangar or in open tanks.

Organic HAP emissions from waste occur from evaporation of the

volatile portion of the waste while it is being handled or stored.

These emissions are fugitive in nature, occurring from each waste

container.

Inorganic HAP emissions from primer and topcoat application

operations occur during the application of the primer or topcoat. These

inorganic HAP emissions are paint particulates, commonly referred to as

``overspray,'' that do not adhere to the surface being coated. Like the

organic HAP emissions from the operations, the emissions of the

inorganic HAP occur in large open areas, such as hangars, or in

partially or fully enclosed spaces, such as within spray booths.

Inorganic HAP emissions from depainting operations occur from most

non-chemical methods, such as plastic media blasting, used to strip an

aerospace vehicle. (Chemical stripping techniques do not release

inorganic HAP.) These emissions occur as particulates generated during

the blasting process. The operation is typically carried out within a

large hangar equipped with a ventilation system and particulate

filtration device (e.g., a baghouse). The inorganic HAP that are

released from the depainting operations are primarily found in the

paint being stripped, although some stripping media may contain trace

amounts of inorganic HAP.

B. Proposed Standards for Affected Sources

In addition to the standards for affected sources as discussed

below, the proposed rule contains general standards. The general

standards stipulate that all affected sources subject to the proposed

rule are also subject to, as appropriate, Sec. 63.4, Sec. 63.5, and

Sec. 63.6 of subpart A of 40 CFR part 63.1 However, certain time

frames specified in these sections have been changed in the proposed

rule as follows:

---------------------------------------------------------------------------

\1\The EPA promulgated regulations for subpart A of 40 CFR part

63, which were published in the Federal Register on March 16, 1994

at 59 FR 12408.

---------------------------------------------------------------------------

(1) All affected sources shall submit any request for an extension

of compliance not later than 12 months before the affected source's

compliance date regardless of whether sources are included in emissions

averaging or not, rather than not later than 18 months before the

affected source's compliance date for sources that are including

emission points in an emissions average as provided for in

Sec. 63.6(i)(4)(i)(B),

(2) The Administrator (or the State with an approved permit

program) will notify the owner or operator in writing of his/her

intention to deny approval of a request for an extension of compliance

submitted under either Sec. 63.6(i)(4) or (i)(5) within 60 calendar

days after receipt of sufficient information to evaluate the request,

rather than notifying the owner of his/her approval or intention to

deny approval of a request for an extension of compliance within 30

calendar days as provided for in Sec. 63.6(i)(12)(i) and

Sec. 63.6(i)(13)(i). In addition, if the Administrator does not notify

the owner or operator in writing of his/her intention to deny approval

within 60 calendar days after receipt of sufficient information to

evaluate a request for an extension of compliance, then the request

shall be considered approved,

(3) The Administrator (or the State) will notify the owner or

operator in writing of the status of his/her application submitted

under Sec. 63.6(i)(4)(ii) (that is, whether the application contains

sufficient information to make a determination) within 30 calendar days

after receipt of the original application and within 30 calendar days

after receipt of any supplementary information that is submitted,

rather than 15 calendar days as provided for in Sec. 63.6(i)(13)(i). In

addition, if the Administrator does not notify the owner or operator in

writing of the status of his/her application within 30 calendar days

after receipt of the original application and within 30 calendar days

after receipt of any supplementary information that is submitted, then

the information in the application or the supplementary information is

to be considered sufficient upon which to make a determination,

(4) Each owner or operator is to be provided 30 calendar days to

present additional information to the Administrator after he/she is

notified of the intended denial of a compliance extension request

submitted under either Sec. 63.6(i)(4) or Sec. 63.6(i)(5), rather than

15 calendar days as provided for in Sec. 63.6(1)(12)(iii)(B) and

Sec. 63.6(i)(13)(iii)(B),

(5) Each owner or operator who has submitted an extension request

application under Sec. 63.6(i)(5) is to be provided 30 calendar days to

present additional information or arguments to the Administrator after

he/she is notified that the application is not complete, rather than 15

calendar days as provided for in Sec. 63.6(i)(13)(ii), and

(6) A final determination to deny any request for an extension

submitted under either Sec. 63.6(i)(4) or Sec. 63.6(i)(5) will be made

within 60 calendar days after presentation of additional information or

argument (if the application is complete), or within 60 calendar days

after the final date specified for the presentation if no presentation

is made, rather than 30 calendar days as provided for in

Sec. 63.6(i)(12)(iv) and Sec. 63.6(i)(13)(iv).

In addition, the proposed rule requires each owner or operator who

uses a control device or equipment to control HAP emissions to prepare

an operation and maintenance plan in accordance with Sec. 63.6 of

subpart A of 40 CFR part 63.2 In addition to the information

required in Sec. 63.6, the proposed rule requires that the owner or

operator of the control device or equipment include the following

information: (1) The operation and maintenance criteria for each air

pollution control device or equipment, including a standardized

checklist to document the operation and maintenance of the equipment;

(2) a systematic procedure for identifying malfunctions and for

reporting them immediately to supervisory personnel; and (3) procedures

to be followed to ensure that equipment or process malfunctions due to

poor maintenance or other preventable conditions do not occur.

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\2\Ibid.

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The general standards also state that an owner or operator who uses

an air pollution control device or equipment not listed in the proposed

rule must submit to the Administrator for approval a description of the

device, test data verifying the performance of the device or equipment

for HAP and/or VOC emissions, appropriate operating parameters that

would be monitored to establish compliance with the proposed standards,

and a copy of the inspection and maintenance plan required under

Sec. 63.6 of 40 CFR part 63.

Finally, Sec. 63.6(g) of subpart A of 40 CFR part 63 allows an

owner or operator of an affected source to use alternative means of

compliance. This allows the development and use of new technology not

known or not demonstrated at the time the rule was promulgated.

The affected sources for the proposed standards are defined as

follows: (1) Each cleaning operation (all hand-wipe cleaning operations

constitute an affected source, each spray gun cleaning operation

constitutes an affected source, and all flush cleaning operations

constitute an affected source); (2) each primer application operation,

which includes all primer applications at the facility; (3) each

topcoat application operation, which includes all topcoat applications

at the facility; (4) each depainting operation, which includes all

depainting of the outer surface of aerospace vehicles at the facility;

(5) each chemical milling maskant application operation, which includes

all chemical milling maskant applications at the facility for

subsequent use in Type II chemical milling etchants; and (6) each waste

storage and handling operation, which includes all waste handling and

storage at the facility.

The proposed standards also specify that HAP-containing waste that

is subject to the provisions of RCRA would not be subject to the waste

handling and storage requirements of the proposed standards. The EPA

included this provision so that the proposed standards would not

require less strict handling and storage of waste than the RCRA

requirements.

The following paragraphs summarize the proposed standards for each

affected source.

1. Cleaning Operation

The proposed standards for the cleaning operation, including those

specific to hand-wipe, spray gun, and flush cleaning operations, would

apply to all new and existing affected sources. The proposed standards

would require that all fresh and spent cleaning solvents be stored in

closed containers and that solvent-laden cloth, paper, or other

material be placed in bags or other closed containers immediately after

use. The bags or containers would be required to be kept closed at all

times (except when depositing or removing material) and of such design

so as to contain the vapors of the cleaning solvent. In addition, the

proposed standards would require the owner or operator to implement

handling and transfer procedures to minimize spills during filling and

transferring the cleaning solvent to or from enclosed systems, vats,

waste containers, and other cleaning operation equipment that holds or

stores fresh or spent cleaning solvents. The above requirements are

known collectively as housekeeping measures.

The proposed standards for the hand-wipe cleaning operation would

require the use of a cleaning solvent that conforms to the approved

composition list detailed in Table 3 or a cleaning solvent that has a

vapor pressure less than or equal to 45 millimeters of mercury (mm Hg)

at 20 deg.C (24.1 in. H2O at 68 deg.F).

Table 3.--Composition Requirements for Approved Cleaning Solvents

----------------------------------------------------------------------------------------------------------------

Cleaning solvent type Composition requirements

----------------------------------------------------------------------------------------------------------------

Aqueous.......................... Cleaning solvents in which water is the primary ingredient (80

percent of solvent as applied must be water). Aqueous solvents must be non-

flammable, non-combustible, and 100 percent soluble in water. Detergents,

surfactants, and bioenzyme mixtures and nutrients may be combined with the

water along with a variety of additives such as organic solvents (e.g., high

boiling point alcohols), builders, saponifiers, inhibitors, emulsifiers, pH

buffers, and antifoaming agents.

Hydrocarbon-Based................ Cleaners that are composed of a mixture of hydrocarbons and oxygenated

hydrocarbons and have a maximum vapor pressure of 7 mm Hg at 20 deg.C (3.75

in. H2O at 68 deg.F). These cleaners also contain no HAP or ozone depleting

compounds.

----------------------------------------------------------------------------------------------------------------

The EPA is proposing a work practice standard for the cleaning of

spray guns at all new and existing affected sources. The proposed rule

would require all spray guns to be cleaned by one or more of the

following methods (or their equivalent): (1) Use of an enclosed spray

gun cleaning system that is kept closed when not in use, (2)

nonatomized discharge of solvent into a waste container that is kept

closed when not in use, (3) disassembly of the spray gun and cleaning

in a vat that is kept closed when not in use, and (4) atomized spray

into a waste container that is fitted with a device designed to capture

atomized solvent emissions. In addition, the EPA is proposing that

leaks from enclosed spray gun cleaners be repaired as soon as

practicable but no later than 15 days from when the leak is first

discovered. The EPA is also proposing a work practice standard for the

flush cleaning of parts, assemblies, and components of a coating unit.

Under the proposed rule, each time a part, assembly, or component of a

coating unit (with the exception of spray guns) is flush cleaned, the

spent cleaning solvent would be emptied into an enclosed container or

collection system that is kept closed when not in use.

The following cleaning operations, which would still be required to

comply with the proposed housekeeping requirements, would be exempt

from the proposed cleaning solvent composition and vapor pressure

requirements:

(1) Cleaning during the manufacture, assembly, installation, or

testing of components of breathing oxygen systems that are exposed to

the breathing oxygen,

(2) Cleaning during the manufacture, assembly, installation, or

testing of parts, subassemblies, or assemblies that are exposed to

strong oxidizers or reducers (e.g., nitrogen tetroxide, liquid oxygen,

hydrazine),

(3) Cleaning and surface activation prior to adhesive bonding,

(4) Cleaning of electronics and assemblies containing electronics,

(5) Cleaning of aircraft fluid systems that are exposed to the

fluid,

(6) Cleaning of fuel cells, fuel tanks, and limited access spaces,

(7) Surface cleaning of solar cells, coated optics, and thermal

control surfaces,

(8) Cleaning during fabrication, assembly, installation, and

maintenance of upholstery, curtains, carpet, and other textile

materials used on the interior of the aircraft,

(9) Cleaning of metallic and non-metallic materials used in

honeycomb cores during the manufacture of these cores, and cleaning of

the completed cores used in the manufacture of aerospace vehicles or

components,

(10) Cleaning of polycarbonate substrates, and

(11) Cleaning and solvent usage associated with production,

research, development, quality control, and laboratory testing.

2. Primer and Topcoat Application Operations

The proposed standards for primer and topcoat application

operations would be the same for all new and existing affected sources.

Standards are being proposed to limit organic and inorganic HAP

emissions from these operations.

a. Organic HAP and VOC emissions. The standards being proposed

would limit the organic HAP emissions from primer application

operations to an equivalent organic HAP content level of 350 grams of

organic HAP per liter (2.9 pounds per gallon (lb/gal)) of primer (less

water) as applied, and from topcoat application operations to an

equivalent organic HAP content level of 420 grams of organic HAP per

liter (3.5 lb/gal) of topcoat (less water) as applied. In addition to

the organic HAP limits, the proposed standards would limit VOC

emissions from primer application operations to an equivalent VOC

content level of 350 grams of VOC per liter (2.9 lb/gal) of primer

(less water and exempt solvents) as applied, and from topcoat

application operations to an equivalent VOC content level of 420 grams

of VOC per liter (3.5 lb/gal) of topcoat (less water and exempt

solvents) as applied. Equivalent organic HAP and VOC content level

means the calculated organic HAP (or VOC) content of coatings that when

multiplied by the usage of the coatings yields the amount of organic

HAP (or VOC) actually emitted to the atmosphere by the use of the

coatings. Exempt solvents are those organic compounds that have been

determined by the EPA to have negligible photochemical reactivity.

The EPA has received information indicating that the organic HAP

and VOC content limits for topcoats do not represent demonstrated

technology for exterior commercial topcoats. Consequently, the EPA is

soliciting comments on whether a separate category should be developed

for exterior commercial topcoats with HAP and VOC content levels higher

than the proposed levels for topcoats. These comments should provide a

technical justification for a higher limit, including why currently

available commercial topcoats cannot be used by all sources.

Sources would be allowed to comply with the proposed organic HAP

and VOC content levels by one or both of the following means: (1) Use

coatings that individually comply with the organic HAP and VOC levels

or (2) use any combination of uncontrolled coatings such that the daily

volume-weighted average organic HAP and VOC contents of these coatings

comply with the organic HAP and VOC levels for that category (averaging

of primers and topcoats together is prohibited). Averaging between

uncontrolled coatings and controlled coatings is prohibited under the

proposed rule.

Instead of complying with the proposed organic HAP and VOC content

levels through compliant coatings or averaging, the proposed standards

allow the use of control devices provided each control device used for

the control of organic HAP or VOC emissions from primer or topcoat

application operations has an overall control efficiency, taking into

account capture and removal efficiency, of greater than or equal to 81

percent. In addition, except for incidental emissions that may escape

from the capture system, the control device cannot be used to control

only a portion of emissions from a coating operation.

Compliance with the proposed organic HAP and VOC content level

standards would be shown on a monthly basis for compliant coatings, and

on a daily basis for coatings complying by averaging. Compliance for

control devices other than carbon adsorbers would be shown on a

continuous basis based on a specific operating parameter or parameters,

such as temperature for incinerators. When a carbon adsorber is used to

comply with the proposed standard, compliance with the 81 percent

overall control efficiency requirement must be demonstrated for each

rolling material balance period. The length of the rolling period will

vary from source to source and is determined by the procedure specified

in proposed Method 309 in the proposed rule. The minimum rolling period

is one day, and the maximum rolling period is 30 days.

The EPA is also proposing an equipment standard for the application

of primers and topcoats. The proposed standard would require the use of

flow coat, roll coat, brush coat, dip coat, electrostatic attraction,

or high volume low pressure (HVLP) spray guns other than for the

exemptions listed below. All application equipment would be required to

be operated and maintained according to manufacturer's specifications

at all times.

The EPA is proposing to allow other application equipment that is

demonstrated to achieve emission levels equivalent to HVLP or

electrostatic spray guns. Compliance must be demonstrated by comparing

the emissions generated by the alternative application method to the

emissions generated by HVLP or electrostatic application methods under

actual production conditions. The alternative method must generate

emissions less than or equal to that generated by HVLP or electrostatic

spray methods.

During the alternative application method test period, the owner or

operator must ensure that the coating dried film thickness is

equivalent to that applied during the initial 90-day test period. This

is required to ensure that the owner or operator does not bias the test

results by applying an excessive amount of coating during the initial

90-day period and applying a minimal amount of coating during the

alternative application method test period. The EPA is requesting

comments on whether the requirements of the proposed standards are

sufficient to ensure that this situation does not occur. Specifically,

comments should address whether detailed recordkeeping should also be

required in order to determine that equivalent dried film thicknesses

were applied.

The EPA is proposing to exempt the following situations and

operations from the proposed equipment standards for the application of

primers and topcoats, although whatever application equipment is used

would still be required to be operated and maintained according to

manufacturers specifications at all times: (1) Any situation that

normally requires the use of an extension on the spray gun to properly

reach limited access spaces, (2) the application of coatings that

contain fillers that adversely affect atomization with HVLP spray guns

and cannot be applied by any of the specified application techniques,

(3) the application of coatings that normally have a dried film

thickness of less than 0.0005 inch and cannot be applied by any of the

specified application techniques, (4) the use of airbrush application

methods for stenciling, lettering, and other identification markings,

and (5) touchup and repair operations.

b. Inorganic HAP emissions. The standards being proposed for

inorganic HAP emissions from primer and topcoat application operations

would apply to those operations that spray apply coatings that contain

inorganic HAP (usually chromium, cadmium, and selenium). Such

operations would be required to be performed in a booth or hangar in

which the air flow is directed across the part or assembly being coated

and exhausted through one or more outlets. This air stream would be

required to pass through either dry particulate filters or a waterwash

system to remove the particulates before exhausting to the atmosphere.

In addition, the pressure drop across the filter or waterwash would

have to be continuously monitored. If the pressure drop moves outside

of the limits specified by the manufacturer to maintain proper

performance of the dry particulate filters or waterwash system, then

the operation must be shut down immediately and corrective action

taken. The process cannot resume until the pressure drop is returned to

the limits specified by the manufacturer.

The EPA is requesting comments on whether pressure drop is an

appropriate parameter on which to make continuous compliance

determinations with the inorganic HAP emission standards. The

possibility exists that different filter or waterwash manufacturers may

specify different pressure drop limits for products with essentially

the same performance. Since the proposed standards rely on pressure

drop as the basis for making compliance determinations, such a

difference would result in different requirements from one facility to

another. Thus, the EPA is requesting comments specifically on whether a

standardized pressure drop limit can be established, or if another

operating parameter exists on which to make compliance determinations

that would be consistent and enforceable for all types and brands of

filters and waterwash systems.

If pressure drop is selected as the parameter to be used to

determine continuous compliance, then a violation of the standards

could occur under one of the following conditions: (1) Whenever the

pressure drop moves outside the limits specified by the manufacturer or

(2) when the pressure drop is found to be outside the specified limits

when monitored and recorded once per operating shift. As the proposed

rule is currently written, a violation would occur in the latter

situation. The EPA is requesting comments on which of these options, or

another option, is most appropriate.

The EPA is proposing to exempt the following list of operations

from the proposed standards for inorganic HAP emissions from primer and

topcoat application operations:

(1) Touch-up of scratched surfaces or damaged paint,

(2) Hole daubing for fasteners,

(3) Touch-up of trimmed edges,

(4) Coating prior to joining dissimilar metal components,

(5) Stencil operations performed by brush or air brush,

(6) Section joining, and

(7) Touch-up of bushings and other similar components.

3. Depainting Operation

Standards are being proposed for both organic HAP emissions and

inorganic HAP emissions from depainting. With the exception of the

proposed standards for spot stripping and decal removal, as discussed

below, the standards being proposed for depainting would be the same

for all new and existing affected sources. The proposed standards would

apply only to the depainting of the outer surface of entire aerospace

vehicles, including the fuselage, wings, and horizontal and vertical

stabilizers of the aircraft, and the outer casing and stabilizers of

missiles and rockets. Standards for the depainting of parts,

subassemblies, radomes, and parts normally removed from the completed

vehicle before depainting are not being proposed at this time. However,

wings and stabilizers would always be required to comply.

a. Organic HAP emissions. The proposed standards would require that

there be no organic HAP emissions from the depainting operation. These

standards could be achieved through the use of (1) chemical strippers

that contain no organic HAP or (2) media blasting equipment, high

intensity ultra-violet light blasting, or any other non-chemical

depainting technique. However, the proposed rule would allow the use of

organic HAP-containing chemical stripper for spot stripping and decal

removal. The proposed rule would limit this use of organic HAP-

containing chemical stripper to an average of 26 gallons per aircraft

for commercial aircraft and 50 gallons per aircraft for military

aircraft, calculated on an annual basis.

Non-chemical-based depainting equipment would be required to be

operated and maintained according to manufacturer's specifications.

During any period of malfunction, the owner or operator would be

allowed to use a substitute material to depaint the vehicles. Unless

the substitute material does not contain any organic HAP, the

substitute material would not be allowed to be used for more than 14

consecutive days.

The proposed rule does not contain an annual limit on the number of

days a source may use HAP-containing chemical strippers during periods

of malfunction of non-chemical-based depainting equipment. The EPA is

requesting comments on whether an annual limit should be imposed and,

if so, technical justification for the number of days specified by the

limit.

b. Inorganic HAP emissions. The proposed rule for inorganic HAP

emissions would apply to those depainting methods (typically blasting

methods) that generate airborne particulate emissions, such as dust and

paint particles, that contain inorganic HAP. The proposed standards

would require that the depainting operation be carried out in an

enclosed hangar and that any air stream removed from the depainting

area be directed through a particulate filter (e.g., panel-type filter

or baghouse) before exhausting to the atmosphere. This filtration

system must have a particulate removal efficiency greater than or equal

to 99 percent, and the pressure drop across the filter must be

continuously monitored. If the pressure drop moves outside of these

limits as recorded each operational shift, then the operation must

immediately be shut down and corrective action taken. The process

cannot resume until the pressure drop is within the limits specified by

the manufacturer.

As described above for primer and topcoat application operations,

the EPA is requesting comments concerning the appropriateness of using

pressure drop to make compliance determinations and what action should

be taken when the pressure drop moves outside of the specified limits.

4. Chemical Milling Maskant Application Operation

The proposed standards for the chemical milling maskant application

operation would be the same for all new and existing affected sources

and applies only to those operations utilizing a Type II chemical

milling etchant. The proposed standards would limit organic HAP

emissions to an equivalent organic HAP content level of 160 grams of

organic HAP per liter (1.3 lb/gal) of chemical milling maskant (less

water) as applied, and limit the VOC emissions to an equivalent VOC

content level of 160 grams of VOC per liter (1.3 lb/gal) of chemical

milling maskant (less water and exempt solvents) as applied.

Alternatively, as for primer and topcoat application operations,

control devices that achieve an overall control efficiency of at least

81 percent and control all emissions (except for incidental emissions)

may be used.

Compliance with the organic HAP and VOC content level standards

would be allowed using one or both of the following means: (1) Use

chemical milling maskants that individually comply with the organic HAP

and VOC content levels or (2) use any combination of chemical milling

maskants such that the daily volume-weighted average organic HAP and

VOC content levels of these chemical milling maskants used in the

chemical milling maskant operation comply with the organic HAP and VOC

content levels. Averaging uncontrolled chemical milling maskants with

controlled chemical milling maskants, however, is prohibited under the

proposed rule.

Compliance with the proposed organic HAP and VOC content level

standards would be shown on a monthly basis for compliant chemical

milling maskants and on a daily basis for chemical milling maskants

complying by averaging. Compliance for control devices other than

carbon adsorbers would be shown on a continuous basis based on a

specific operating parameter or parameters, such as temperature for

incinerators. When a carbon adsorber is used to comply with the

proposed standard, compliance with the 81 percent overall control

efficiency requirement must be demonstrated for each rolling material

balance period. The length of the rolling period will vary from source

to source and is determined by the procedure specified in proposed

Method 309 in the proposed rule. The minimum rolling period is one day,

and the maximum rolling period is 30 days.

5. Handling and Storage of Waste

The proposed standards for handling and storage of waste would be

the same for all new and existing facilities. The proposed rule would

require that the handling and transfer of HAP-containing waste to or

from containers, tanks, vats, vessels, or piping systems be conducted

in such a manner that minimizes spills. In addition, all HAP-containing

waste would be stored in closed containers.

C. Compliance Dates

The proposed rule would require all existing sources to comply no

later than three years after the effective date of the standards. In

addition, the proposed rule adopts the compliance dates specified in

Sec. 63.6(b) and Sec. 63.6(c) of the General Provisions, 40 CFR part

63, subpart A.\3\

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\3\Ibid.

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D. Compliance Extensions

During development of the aerospace national emission standards for

hazardous air pollutants (NESHAP), the EPA received comments from the

regulated community regarding the process that would be used to comply

with the rule and certain difficulties that were anticipated,

particularly with the facilities' selection and approval of product

substitutions for coatings and hand-wipe cleaning solvents. Because of

the large number of product substitutions that may have to undergo

testing and qualification at each facility, some facilities may need to

request a compliance extension.

Section 63.6(i) of 40 CFR part 63 provides the requirements for

requesting an extension of compliance with a relevant standard

established under part 63.\4\ Specifically, Sec. 63.6(i)(4) allows the

issuance of a permit granting an extension of up to one year to comply

with the standard, if such additional period is necessary for the

installation of controls. Section 63.6(i)(4)(i)(B) requires requests

for compliance extensions to be submitted no later than 12 months

before the affected source's compliance date.

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\4\Ibid.

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The EPA is seeking comment on the significance of the potential

difficulties of complying with the proposed aerospace NESHAP in the

allotted 3 years (or 4 years if the one-year extension described above

is applied for and approved). In addition, the EPA is seeking comment

regarding how these difficulties can be addressed within the confines

of the statutory requirements of sections 112(d) and 112(i) of the Act.

Specifically, the EPA is seeking comment on what types of activities,

such as technical assistance, can be provided to assist sources

attempting to come into compliance with the aerospace NESHAP.

E. Compliance Testing and Monitoring

In addition to the specific testing and monitoring requirements

specified below for each affected source, the proposed rule adopts the

testing requirements specified in Sec. 63.7 of the General Provisions,

40 CFR part 63, subpart A.\5\

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\5\Ibid.

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1. Test Methods and Procedures

a. Cleaning operation. For multi-component cleaning solvents,

compliance with the proposed vapor pressure specifications would be

determined using E 260-85 to quantify the amount of each organic

compound in the cleaning solvent. The vapor pressure of each organic

compound would be determined from the manufacturer's data, standard

engineering reference texts, or other equivalent methods. The total

composite vapor pressure would then be calculated by summing the

partial vapor pressure of each component according to Raoult's Law.

For single component cleaning solvents, the EPA is proposing that

vapor pressure data supplied by the manufacturer of the cleaning

solvent, standard engineering reference texts, or other equivalent

methods be used for compliance determinations.

Owners or operators seeking to comply with the cleaning solvent

approved composition list would have to show compliance using data

supplied by the manufacturer of the cleaning solvent. The data must

identify all components of the cleaning solvent and demonstrate that

one of the approved composition definitions is met.

b. Primer and topcoat application operations. As noted earlier, the

proposed standards for organic HAP and VOC emissions would require

compliance with an equivalent organic HAP content level (pounds of

organic HAP per gallon of coating (less water) as applied) and an

equivalent VOC content level (pounds of VOC per gallon of coating (less

water and exempt solvents) as applied) for primers and for topcoats.

Compliance with these organic HAP and VOC content levels may be

accomplished by using compliant coatings, averaging between compliant

and non-compliant coatings, control devices, or any combination of

these methods. In addition, the proposed standards would require the

use of certain application techniques for the application of primers

and topcoats.

Test methods and procedures have been identified for compliance

with the organic HAP and VOC content levels. No test methods or

procedures have been identified for the application equipment

requirements; however, a test method has been identified for the

qualification of alternative application methods.

Method 24 in appendix A to 40 CFR part 60 would be used to

determine the VOC content of each primer and topcoat as applied.

Alternatively, manufacturer's data may be used to determine the VOC

content of these coatings. However, in the event of any inconsistency

between manufacturer's data and Method 24 test results, the Method 24

test results will take precedence.

The facility may rely on manufacturer's data to determine the

organic HAP content level of each coating. The total organic HAP weight

fraction and density of each coating as received would be determined

using the manufacturer's data. The volume of each primer and topcoat

used would be determined using company records. If diluent solvents or

other ingredients are added to a primer or topcoat prior to

application, then the total organic HAP and VOC weight fractions,

density, and volume must be adjusted appropriately to account for such

additions. These values would be required for each 24-hour period;

however, only changes in formulation would require re-determination of

total organic HAP and VOC weight fractions and density.

The proposed standards would then require the owner or operator to

calculate the volume-weighted average mass of both VOC and organic HAP

in coatings emitted per volume of coating (less water and exempt

solvents for VOC; less water for HAP) as applied. This calculation

would be performed for each 24-hour period.

If an owner or operator is seeking to comply by using compliant

coatings, the owner or operator would need to determine the organic HAP

content (less water as applied) and VOC content (less water and exempt

solvents as applied). If no changes in formulation as applied occurred,

then a re-calculation of the organic HAP and VOC content levels would

not be required. Where compliant coatings are used, the proposed rule

would require the determination of the organic HAP content using

manufacturer's data and VOC content using Method 24 or manufacturer's

data.

If a control device is used, the proposed standards require the

owner or operator to conduct an initial performance test to demonstrate

compliance with the overall control efficiency requirement of at least

81 percent. The percent reduction achieved by a control device may be

determined based either on total organic compounds (TOC) minus methane

and ethane or on total organic HAP.

For a carbon adsorber, the overall control efficiency would be

determined using a mass balance. The mass balance calculation would be

made every rolling period (the length of the rolling period will vary

from facility to facility and will range from 1 to 30 days).

For control devices other than carbon adsorbers, the overall

control efficiency would be based on capture efficiency and destruction

efficiency. Capture efficiency would be determined based on the

procedure specified in Sec. 52.741(a)(4)(iii) of 40 CFR subpart O,

unless the operation is performed within a total enclosure. An

enclosure that meets the requirements of a total enclosure as specified

in Sec. 52.741, appendix B, Procedure T of 40 CFR subpart O would have

a capture efficiency of 100 percent.

The destruction efficiency of a control device other than a carbon

adsorber would be determined using the following methods. Method 1 or

1A of 40 CFR part 60, appendix A, as appropriate, would be used for

selection of the sampling sites, and the gas volumetric flow rate would

be determined using Method 2, 2A, 2C, or 2D of 40 CFR part 60, appendix

A, as appropriate. Method 18 of 40 CFR part 60, appendix A, would then

be used to measure either TOC minus methane and ethane or total organic

HAP at the inlet and outlet of the control device. Also, any other test

methods or data that have been validated according to the applicable

procedures in Method 301 of 40 CFR part 63, appendix A, may be used.

The proposed standards would also allow the use of alternative

application methods provided that they generate organic HAP and VOC

emissions less than or equal to the emissions generated by HVLP or

electrostatic spray guns. The emission levels of the alternative

application method must be determined under actual production

conditions. This test would first involve determining the organic HAP

and VOC emissions for the 90-day period immediately preceding the

implementation of the alternative application method. During this

initial 90-day period, only HVLP or electrostatic spray guns would be

used. The alternative method would then be used on actual production

parts or assemblies for a period of time sufficient to coat an

equivalent amount of parts and assemblies as coated in the initial 90-

day period. Coatings used during the test period must be the same as

those used during the initial 90-day period. In addition, the dried

film thickness must be equivalent to that applied during the initial

90-day period.

The organic HAP and VOC emissions for the period of time where the

alternative method was used would then be calculated. Where the organic

HAP and VOC emissions after implementation of the alternative method

are less than or equal to the emissions for the initial 90-day period,

the alternative application method is in compliance.

The South Coast Air Quality Management District (SCAQMD), in

conjunction with the California Air Resources Board (CARB), is

currently developing a test protocol to measure the transfer efficiency

of spray application equipment. This test protocol would represent an

alternative method of qualifying application equipment for use under

the proposed standards. Since this test protocol is still under

development, the EPA is requesting comments from those familiar with

this test protocol or any other transfer efficiency laboratory test

method concerning the ability of these procedures to accurately and

repeatedly measure the transfer efficiency of spray application

equipment. In addition, the EPA is requesting comments on other methods

that may be used to measure the transfer efficiency of spray

application equipment.

c. Depainting. For the organic HAP emissions portion of the

proposed standards for depainting, the only test method or procedure

that would be required is the determination of the organic HAP content

of each chemical stripper. The proposed standards would require the use

of information supplied by the manufacturer to determine the organic

HAP content. If the organic HAP content of the chemical stripper cannot

be determined from manufacturer's data, then the owner or operator

would submit an alternative procedure for determining the organic HAP

content for approval by the Administrator.

For the annual limit on the gallons of organic HAP-containing

chemical stripper used for spot stripping and decal removal, the total

annual volume as applied of organic HAP-containing chemical stripper

and the number of aircraft depainted would be determined from company

records. The proposed standards would then require the owner or

operator to calculate the gallons of organic HAP-containing chemical

stripper used per aircraft. This calculation would be performed for

each annual period.

The proposed standards require inorganic HAP emissions from

depainting operations to be reduced by 99 percent using particulate

filters such as baghouses, cartridge filters, or dry filter media. The

EPA is proposing the use of Method 5 in appendix A to 40 CFR part 60 to

determine removal efficiency. The proposed standards would require

retesting whenever the particulate filter or supplier of the filter

media changes, or whenever modifications are made to the emission

collection system.

d. Chemical Milling Maskants. The same basic test methods and

procedures identified for primer and topcoat application operations are

also being proposed for chemical milling maskants, requiring the

determination of total organic HAP weight fraction, density, and volume

of chemical milling maskants as applied. Simpler procedures are being

proposed, as for primer and topcoat application operations, to

demonstrate compliance where only compliant chemical milling maskants

are being used.

As for primer and topcoat application operations, any control

device, including a carbon adsorber, used to control emissions from

chemical milling maskant application operations must have an overall

control efficiency of at least 81 percent and must control, except for

incidental emissions, all of the emissions from the maskant operation.

Test methods that would be used to determine the overall control

efficiency are identical to those given previously for primer and

topcoat application operations.

e. Handling and storage of waste. No test methods are being

proposed.

2. Monitoring Requirements

Monitoring is required by the proposed standards to determine

whether a source is in continuous compliance. This can be accomplished

by continuously measuring site-specific operating parameters, the

values of which are established by the owner or operator during the

initial compliance test. The operating parameter value is defined as

the minimum or maximum value established for a control device or

process parameter that, if achieved by itself or in combination with

other operating parameter values, determines that an owner or operator

is complying with the applicable emission limitation or standards. This

type of enhanced monitoring would be required for those emission points

for which the standards are expressed as a percent control. In

addition, the owner or operator is expected to install and operate the

equipment properly. For owners or operators complying with the proposed

standards for spray gun cleaning through the use of enclosed spray gun

cleaners, compliance would be demonstrated through recordkeeping (see

section II.F).

The proposed rule would require temperature to be monitored, using

a continuous recorder, for incinerators. For catalytic incinerators,

temperature monitors would be placed immediately before and after the

catalyst bed. For other incinerators, the temperature monitor would be

placed in the firebox or in the ductwork immediately downstream of the

firebox and before any substantial heat exchange occurs. All monitoring

equipment would be installed, calibrated, maintained, and operated

according to manufacturer's specifications.

Section 63.6(g) of 40 CFR part 63, subpart A, allows an owner or

operator of an affected source to request the use of alternative

methods of emission reduction for complying with design, equipment,

work practice, or operational emission standards, or combination

thereof, established under this part.6 Under the proposed rule, an

owner or operator of an affected source may also use control devices

other than those specifically identified in the proposed rule as a

means for achieving compliance with any portion of the rule. If devices

other than those identified are used, the proposed standards would

require the owner or operator to submit the parameters to be monitored

to the Administrator for approval.

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\6\Ibid.

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The proposed standards would require each owner or operator to

establish a range of values for each of these monitored parameters

during the initial performance test. As long as the control device is

operated within the established ranges, the proposed emission standards

are considered to be met. Consequently, exceedances of these parameters

would be considered a violation of the standards since operating the

control device outside of the parameters may reduce the efficiency of

the control device.

a. Cleaning operations. The proposed rule would require enclosed

spray gun cleaners to be visually inspected at least once per month for

leaks. The inspections would occur while the enclosed cleaner is in

operation.

b. Primer and topcoat application operations. Where an incinerator

or other control device is used to control organic HAP and VOC

emissions from primer and topcoat application operations, the

monitoring requirements specified above would be required.

For control of inorganic HAP emissions from primer and topcoat

application operations, the proposed standards would require that the

pressure drop across the particulate filters or waterwash be monitored

on a continuous basis.

c. Depainting. No monitoring requirements for organic HAP emissions

are being proposed. For inorganic HAP emissions, continuous monitoring

of the pressure drop across the filter, as for primers and topcoats, is

being proposed.

d. Chemical milling maskant application operations. Where a control

device is used to control organic HAP and VOC emissions from chemical

milling maskant application operations, the monitoring requirements

specified above would be required.

e. Handling and storage of waste. No monitoring requirements are

being proposed.

F. Recordkeeping and Reporting Requirements

The proposed rule proposes to adopt the requirements contained in

Sec. 63.9 (a) through (e) and Sec. 63.9 (h) through (j) and Sec. 63.10

(a), (b), (d), and (f) of 40 CFR part 63, subpart A.7 The proposed

rule, however, contains additional or clarifying elements and changes

certain time periods allowed for submitting or responding to certain

reports and requests required in Sec. 63.10. These elements and changes

are summarized below for each of the operations for which standards are

being proposed.

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\7\Ibid.

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1. Recordkeeping Requirements

a. Cleaning operations. For each cleaning solvent used at the

facility, the proposed rule would require a record of the name of the

cleaning solvent and documentation that shows the organic HAP

constituents of the cleaning solvent. For each cleaning solvent used in

hand-wipe cleaning operations that conforms to the approved composition

list, the records that would be maintained are the name of each

cleaning solvent, documentation demonstrating compliance to the

approved composition list, and annual purchasing records showing the

annual volume purchased of each. For each cleaning solvent used in

hand-wipe cleaning operations that does not conform to the approved

composition list but does conform to the vapor pressure requirement,

the information required to be recorded would be the name of each

cleaning solvent, the monthly usage of the cleaning solvent at each

operation, the composite vapor pressure, the manufacturer's data sheets

or other documentation of the vapor pressure, and any test reports and

calculations performed to determine the composite vapor pressure.

For cleaning solvents that do not conform to either the composition

or vapor pressure requirements and are used for the exempt cleaning

operations, daily records must be maintained of the name and volume of

each cleaning solvent at each operation at which it is used, and the

parts, assemblies, or subassemblies cleaned at these operations.

In addition, a record of all leaks from spray gun cleaners would be

kept, including source identification, the date that the leak was

discovered, and the date that the leak was repaired.

b. Primer and topcoat application operations. For all primers and

topcoats used at the facility, records must be maintained of the name

of each primer and topcoat and its organic HAP and VOC content as

received. In addition, the EPA is proposing different levels of

recordkeeping requirements depending on how the organic HAP and VOC

content levels are met. For primers or topcoats that are individually

compliant with the organic HAP and VOC content limits, records would be

required of the organic HAP and VOC content as applied, all data,

calculations, and test results (including Method 24 results taken

during an enforcement inspection) used in determining the organic HAP

and VOC contents as applied, and the monthly usage of each coating

formulation within each coating category.

If averaging among compliant and non-compliant coatings is used to

achieve compliance, then the proposed standards would require that up-

to-date records of daily volume-weighted average mass of organic HAP

and VOC contained in the coatings as applied be maintained. This

information would include all data and calculations used in determining

these daily values, such as manufacturer's data certifying the organic

HAP content of each coating as applied and Method 24 test results

(including those taken during an enforcement inspection) or

manufacturer's data that show the VOC content as applied.

If a control device is used to comply with the organic HAP or VOC

content limit for primers or topcoats, up-to-date records must be kept

on the control device. Each owner or operator would be required to keep

records of the equipment monitoring parameter measurements specified in

the proposed rule. For an incinerator other than a catalytic

incinerator, continuous records must be maintained of the firebox

temperature (or temperature in the ductwork immediately downstream of

the firebox). For a catalytic incinerator, continuous records must be

maintained of the gas stream temperature immediately before and after

the catalyst bed. For both types of incinerators, records must be

maintained of the overall control efficiency and all test results,

data, and calculations used in determining the overall control

efficiency.

For carbon adsorbers, records must be maintained of the overall

control efficiency, all test results, data, and calculations used in

determining the overall control efficiency, and the length of the

rolling material balance period and all of its supporting data and

calculations used to determine the rolling period.

For inorganic HAP emissions from primer and topcoat application

operations, either particulate filters or waterwash spray booths would

be used to achieve compliance. Records must be maintained of the

manufacturer's recommended limits for the pressure drop and readings of

the pressure drop across the filters or waterwash that are taken once

each shift during which the coating processes are in operation.

c. Depainting operation. Each owner or operator of a depainting

operation would be required to keep up-to-date records of the name of

each chemical stripper used, the organic HAP content of each stripper

and its supporting documentation, and the monthly volume usage of each

chemical stripper that contains organic HAP.

For non-chemical depainting methods, such as media blasting, owners

and operators would be required to maintain records of the type of non-

chemical-based equipment used and a description of any malfunctions

that occur. If a malfunction occurs, the information to be kept would

be the dates the malfunction occurred and was corrected, the methods

used to depaint the aerospace vehicles during the malfunction, and the

dates that these methods were begun and discontinued.

The proposed standards for depainting contains exemptions for parts

stripping, spot stripping, and decal removal, each of which requires

certain records to be maintained. For parts stripping, records must be

maintained for each model of aerospace vehicle of the parts normally

removed from the vehicle. For spot stripping and decal removal, annual

records must be maintained of the number of aircraft stripped, the

volume of organic HAP-containing chemical stripper used for spot

stripping and decal removal, the average number of gallons of organic

HAP-containing stripper used per aircraft, and all supporting data and

calculations.

For inorganic HAP emissions from depainting operations, either

particulate filters or baghouses (equipped with either bag or cartridge

filter media) would be used to achieve compliance. Records must be

maintained of the filter manufacturer's recommended pressure drop

limits and the readings of the pressure drop across the filter taken

once each shift during which the depainting process is in operation.

Also, records must be maintained of the particulate control efficiency

of each filter and all test results, data, and calculations used to

determine the control efficiency.

d. Chemical milling maskant application operation. The EPA is

proposing different levels of recordkeeping requirements depending on

how the organic HAP and VOC content levels are being met. For chemical

milling maskants that are individually compliant with the organic HAP

and VOC content levels, records of the volume-weighted average masses

of organic HAP and VOC emitted as applied must be kept. In addition,

all data and calculations used to determine these values and the

monthly volume of each chemical milling maskant formulation used each

month must be maintained.

If averaging among compliant and non-compliant chemical milling

maskants is used to achieve compliance, then the proposed standards

would require that up-to-date records of daily volume-weighted average

mass of organic HAP and VOC contained in the chemical milling maskants

as applied be maintained. This information would include all data and

calculations used in determining these daily values, such as

formulation data and Method 24 test results.

As for primer and topcoat application operations, if a control

device is used, up-to-date records must be kept on the control device.

Each owner or operator would be required to keep records of the

equipment monitoring parameter measurements specified in the proposed

rule. For an incinerator other than a catalytic incinerator, continuous

records must be maintained of the firebox temperature (or temperature

in the ductwork immediately downstream of the firebox). For a catalytic

incinerator, continuous records must be maintained of the gas stream

temperature immediately before and after the catalyst bed. For both

types of incinerators, records must be maintained of the overall

control efficiency and all test results, data, and calculations used in

determining the overall control efficiency.

For carbon adsorbers, records must be maintained of the overall

control efficiency, all test results, data, and calculations used in

determining the overall control efficiency, and the length of the

rolling material balance period and all of its supporting data and

calculations used to determine the rolling period.

e. Handling and storage of waste. Each owner or operator would be

required under the proposed standards to keep an up-to-date record of

each waste stream generated at the facility, identification of which

wastes are subject to RCRA and which are not, and documentation

supporting those determinations.

2. Reporting Requirements

The proposed rule would require four basic types of reports: (1)

Initial notification, (2) notification of compliance status, (3)

periodic reports, and (4) other reports. In addition, the proposed rule

would require that the results of any performance test required under

Sec. 63.7 of the General Provisions to 40 CFR part 63, subpart A, be

reported no later than 30 days after the completion of the test.8

A permit application as required under 40 CFR part 70 may be used in

lieu of the initial notification provided the same information is

contained in the permit application as required for the initial

notification.

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\8\Ibid.

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As stated above, the proposed standards adopt the reporting

requirements contained in Sec. 63.9(a) through Sec. 63.9(e) and

Sec. 63.9(h) through Sec. 63.9(j) and 63.10 (a), (b), (d), and (f) of

40 CFR part 63, subpart A. However, the time period allowed for the

Administrator to notify the owner or operator in writing of approval or

disapproval of the request for an adjustment to a particular time

period or postmark deadline submitted under Sec. 63.9(i) has been

changed to within 30 calendar days of receiving sufficient information

to evaluate the request, rather than 15 calendar days as provided for

in Sec. 63.9(i)(3).

Sections 40 CFR 63.9 and 63.10 of the General Provisions identify

the type of generic information to be included in the initial

notification, notification of compliance status, and other reports and,

therefore, this information is not repeated in this preamble. The

following paragraphs summarize the additional information specific to

the aerospace rule that should be included in the notification of

compliance status and the type of information to be included in the

periodic reports.

a. Cleaning operation. The notification of compliance status should

include an identification of each cleaning solvent used at the

facility, a description of the procedures to be used to ensure that

bags and containers are kept closed when not in use and that cleaning

solvents are stored in closed containers, the name of each cleaning

solvent that does not conform to the approved composition list, and the

vapor pressure test results of each.

Specific to spray gun cleaning, the notification of compliance

status should also contain a detailed description of all methods used

to clean spray guns and an explanation as to how each cleaning method

complies with the proposed standards.

Information to be included in the semiannual report covers all

noncompliance situations such as using a hand-wipe cleaning solvent

that does not conform to the approved composition list or vapor

pressure requirements used in a non-exempt operation. In addition, the

semiannual report includes information on new cleaning solvents used

for hand-wipe cleaning in the previous six months, as well as

previously reported cleaning solvents no longer in use. The information

to be provided is a list of any new cleaning solvents used in the

previous six months, a list of new non-HAP cleaning solvents, if any,

used, and, for new cleaning solvents used in hand-wipe cleaning

operations, the composite vapor pressure of each.

If the cleaning operation has been in compliance for the annual

period, then an annual report would be required occurring every 12

months from the date of the initial report stating that the cleaning

operation has been in compliance with the applicable standards.

b. Primer, topcoat, and chemical milling maskant application

operations. For primer, topcoat, and chemical milling maskant

application operations, the notification of compliance status should

identify the combination of compliant coatings, averaging, and control

devices that were used to demonstrate that the facility was in

compliance, and, for control devices, what operating parameters were

identified for continuous monitoring in order to ensure continuous

compliance with the proposed standards.

Owners and operators complying with the organic HAP and VOC content

levels for primer, topcoat, and chemical milling maskant application

operations would be required to report each exceedance of the organic

HAP or VOC content level, as well as any time a primer or topcoat

application operation was not immediately shut down when the pressure

drop across the filters or waterwash was out of range. These reports

would be submitted on a semiannual basis.

If control devices are used, semiannual reports would be required

that contain information on all days when the average values of the

parameters required to be monitored were outside the ranges established

in the operating permit.

For incinerators, this would be whenever each 3-hour average

temperature was below the average temperature established during the

most recent performance test during which compliance was demonstrated.

If no exceedances occur, each owner and operator would submit

annual statements indicating that each affected facility has been in

compliance. The annual reports for primer and topcoat application

operations would also identify the number of times, if any, the

pressure drop limits for each filter or waterwash system were exceeded.

c. Depainting operation. The notification of compliance status for

depainting operations should identify each chemical stripper used at

the facility to depaint aerospace vehicles and the organic HAP content

of each. Each chemical stripper that contains organic HAP and is used

for decal removal, depainting of parts, and spot stripping would also

be identified. In addition, the types of non-chemical depainting

methods and techniques used at the facility and the manufacturer's

recommended pressure drop across the filters for the particulate

removal system, if applicable, would be identified. Finally, each owner

or operator would be required to describe the depainting methods to be

used during periods of malfunction of the non-chemical depainting

methods.

Information to be included in the semiannual report would include

the name of any new chemical strippers used during the previous six

months and the organic HAP content of each. For each chemical stripper

used for depainting operations that undergoes reformulation, its

organic HAP content after reformulation would be submitted with the

semiannual report. The report would also be required if the owner or

operator used any new non-chemical depainting technique at the facility

since the initial report or any subsequent semiannual report. The

semiannual report would be required to identify each 24-hour period

where organic HAP were emitted from the depainting operation except

from the exempt operations, any periods of malfunction of non-chemical

depainting methods and techniques, and any periods where the non-

chemical depainting operation was not immediately shut down when the

pressure drop across the filters was out of range. For each malfunction

that occurs, the following information would be reported: (1) The piece

of equipment that malfunctioned, (2) the date the malfunction occurred

and the date it was corrected, (3) a description of the malfunction,

(4) the alternate methods used to depaint the aerospace vehicles during

the malfunction period, and (5) the dates that these methods were begun

and discontinued.

Finally, the semiannual report would be required to identify all

changes in the type of aircraft depainted at the facility and to

identify the parts normally removed for depainting separate from the

aircraft for each new type of aircraft depainted.

For spot stripping and decal removal, an annual report would be

required whenever the average volume per aircraft of organic HAP-

containing chemical strippers used exceeds the limits specified in the

proposed rule for the annual period.

If the depainting operation has been in compliance for the annual

period, then an annual report would be required every 12 months from

the date of the initial report stating that the depainting operation

has been in compliance with the applicable standards. This annual

report would also detail how many times the pressure drop limits for

each filter system were exceeded and report when the calculated annual

average volume of organic HAP-containing strippers used per aircraft

for spot stripping and decal removal exceeded the applicable limits.

d. Handling and storage of waste. The notification of compliance

status would identify each waste stream and identify whether it is RCRA

or non-RCRA regulated. The notification would also include a

description of the procedures to be used to ensure that spills are

minimized during handling and transfer operations. Also included would

be the procedures to be used to ensure that waste is stored in closed

containers.

Semiannual reports are required to identify any waste stream whose

RCRA or non-RCRA classification has changed. The semiannual report

would also identify any new waste streams and whether each is RCRA or

non-RCRA regulated. An annual report would be required if no changes

occurred in the RCRA status to the existing waste streams and if no new

waste streams were generated.

III. Summary of Environmental, Energy, and Economic Impacts of the

Proposed Standards

A. Emission Reductions

1. Existing Facilities

For the existing aerospace OEM and rework facilities (approximately

2,869 facilities in the base year 1991), the nationwide baseline HAP

emissions are estimated to be 189,000 Mg/yr (208,000 tpy).

Implementation of the proposed regulation would reduce these emissions

by approximately 112,600 Mg/yr (123,700 tpy), or 59 percent.

2. New Facilities

For the aerospace industry, no net growth is expected over the next

five years; therefore, no net emission reduction due to new facilities

is anticipated during this period.

B. Secondary Environmental Impacts

Secondary environmental impacts are considered to be any air,

water, or solid waste impacts, positive or negative, associated with

the implementation of the proposed standards. These impacts are

exclusive of the direct air emission reductions discussed in the

previous section. All of the impacts discussed below reflect the

maximum increase or decrease, as appropriate, that would occur if all

of the affected sources converted to the control option described.

Some product reformulations that may be used to comply with the

proposed standards for hand-wipe cleaning, primers, and topcoats may

contain organic HAP or VOC not present in the original product. In

these cases, different organic HAP or VOC may be emitted as a result of

the proposed rule, but the overall level of these compounds that are

emitted will decrease. Chemical strippers that do not contain organic

HAP used for depainting may result in increased VOC emissions when used

to replace methylene chloride-based chemical strippers (methylene

chloride is a HAP, but not a VOC).

There is a potential for an impact on water quality resulting from

some of the prescribed control measures. Under baseline conditions for

chemical milling maskant operations, no wastewater is generated;

however, some of the sources may install a carbon adsorber to control

solvent emissions. If all affected sources use carbon adsorbers, the

amount of water needed to create regenerating steam for these systems,

which will add to the wastewater burden from these sources, is

estimated to be 447 million gallons per year nationwide. For depainting

operations, there are two options available for meeting the proposed

rule, both of which will result in a decrease in the amount of

wastewater generated compared to baseline, which is 251 million gallons

per year. The decrease in wastewater nationwide is estimated to be 251

million gallons and 86 million gallons if all affected sources use dry

media blasting or chemical strippers that do not contain organic HAP,

respectively.

Sources installing a carbon adsorption system on their chemical

milling maskant operations would generate additional solid waste due to

the necessity of periodically disposing of spent activated carbon. If

all affected sources use carbon adsorbers, this added nationwide solid

waste burden is estimated to be 4,500 tons per year, compared to the

baseline of 21,200 tons per year. Rework facilities that presently use

a methylene chloride-based paint stripper must dispose of 3,469 tons

per year of paint/solvent sludge created by depainting. A total

conversion to dry media paint removal would produce an increase in the

amount of solid waste composed of dry paint chips and spent blasting

media. This increase in solid waste is estimated to be 13,280 tons per

year on a nationwide basis. The proposed standards for the control of

inorganic HAP emissions from primer and topcoat application operations

would result in the increase in solid waste generation from the

disposal of used dry filter media. The increased solid waste burden is

estimated to be 640 tons per year, compared to the baseline solid waste

generation of 3,540 tons per year.

C. Energy Impacts

Some of the control measures proposed for aerospace manufacturing

and rework operations would lead to increases in energy consumption.

Both of the control options for chemical milling maskant operations,

operation of a carbon adsorber or conversion to waterborne chemical

milling maskant, would involve increased electricity usage (waterborne

chemical milling maskants must be cured at elevated temperatures). The

total additional energy needed if all affected sources operate new

carbon adsorbers is estimated to be 1.7 billion kilowatt-hours (kWh)

per year, and the energy increase for all affected sources to operate

new curing ovens for waterborne chemical milling maskants is estimated

at 324,700 kWh per year. Baseline energy consumption for chemical

milling maskant operations is considered to be negligible since the use

of solvent-based chemical milling maskants does not directly require

the use of electricity.

The dry media paint removal systems that would be installed at

rework facilities consume additional energy compared to the solvent

stripping method. Baseline energy consumption for solvent stripping is

considered to be negligible since the use of these strippers does not

directly require the use of electricity. The increase in energy

consumption involved in operating dry media blasting systems is

estimated to be 51 million kWh per year. The use of chemical strippers

that do not contain organic HAP is essentially the same as the baseline

solvent stripping operation; therefore, no energy impact will result

from their use.

The proposed standards for the control of inorganic HAP emissions

from primer and topcoat application operations would require some

facilities to install additional spray booths. These spray booths,

whether equipped with dry filters or waterwash, will increase the

energy consumption of the affected sources. This increase in energy

consumption is estimated to be 5.9 million kWh per year, compared to

the baseline energy consumption of 117.4 million kWh per year.

D. Cost Impacts

The total capital and annualized control costs (1992 dollars),

including recovery credits, attributable to compliance with the

proposed standards have been estimated for both existing and new

facilities. The following two subsections summarize the results of this

cost analysis.

1. Existing Facilities

a. Capital costs. Capital costs would be incurred with the

implementation of control measures for chemical milling maskants (both

solvent-based chemical milling maskants with a carbon adsorber and

waterborne chemical milling maskants), dry media blasting for

depainting, spray gun cleaning, and control of HAP emissions from

primer, topcoat, and depainting operations. With the exception of dry

media blasting for depainting, the nationwide capital costs listed

below represent the maximum costs that would be incurred assuming that

all facilities implemented the specific control option. For dry media

blasting, it is not reasonable to assume that all commercial and

military rework facilities (a total of 2,026 facilities) depaint the

outer surface of aerospace vehicles. Therefore, it was assumed that

only 5 percent of the small and medium size rework facilities and all

of the large rework facilities perform outer surface depainting.

For carbon adsorbers used in conjunction with solvent-based

chemical milling maskants, the nationwide capital cost is estimated to

be $500 million, and for waterborne chemical milling maskants it is

estimated to be $289 million. The implementation of dry media blasting

systems for depainting would require a nationwide capital cost of $61

million. It should be noted that other control measures exist for

depainting other than dry media blasting, such as chemical strippers

that do not contain organic HAP, that require no capital investment.

Selection of chemical strippers that do not contain organic HAP by all

affected sources instead of dry media blasting would decrease the total

nationwide capital investment by approximately 10 percent. The proposed

rule would also require capital costs for high transfer efficiency

application equipment and spray gun cleaning equipment totalling $130

million and $10 million, respectively. The control of inorganic HAP

emissions from primer and topcoat application operations would require

the installation of spray booths and filter systems at a capital cost

of $13 million.

Total nationwide capital costs range from $503 million to $714

million, depending on which chemical milling maskant control option is

used.

b. Annual costs. All of the control options will result in some

annual costs being incurred by the affected sources. However, the

annualized cost figures presented below reflect the net cost to

implement the control options after taking into account the costs that

would have been incurred for baseline. This net cost (MACT cost minus

baseline cost) resulted in net annual savings for primers, topcoats,

and high transfer efficiency application methods; spray gun cleaning;

and the use of chemical strippers that do not contain organic HAP. All

other options resulted in net annual costs to the affected sources. The

net cost (or savings) for all control options reflects the maximum cost

(or savings) that would be incurred assuming all affected sources

implemented the specific control option.

Only one cost analysis was completed for primers, topcoats, and

high transfer efficiency application methods due to the

interrelationship between these operations. For example, high transfer

efficiency application methods will result in a lower volume of primers

and topcoats being applied. In addition, the organic HAP and VOC limits

on primers and topcoats will, due to higher solids content, also result

in a lower volume of the coatings being applied. The reduction in

coating usage due to the lower organic HAP and VOC content had to be

taken into account first, then the reduction in coating usage due to

high transfer efficiency application methods was applied to this

reduced coating volume to obtain the true overall reduction in coating

usage. After factoring in the annualized cost of the coating equipment,

the analysis showed a nationwide savings of $71 million for commercial

sources and $18 million for military sources.

The savings for primers, topcoats, and high transfer efficiency

application methods are due primarily to labor savings that would

result from the reduced volume of coatings to be applied. For example,

if it would have taken 15 gallons of primer under baseline conditions

to coat an aircraft and only 12 gallons under MACT conditions, then the

cost analysis assumes a labor savings for the 3 gallons of primer that

were not applied. The EPA has received some evidence, however, that the

labor stays the same or may even increase with the use of high transfer

efficiency application methods (specifically HVLP spray guns). The EPA

requests comments from facilities that have converted from conventional

spray guns to HVLP spray guns regarding the labor hours per gallon of

coating applied for each application method.

For spray gun cleaning, the proposed standards would result in a

nationwide savings of approximately $56 million. This is due primarily

to reduced solvent usage and associated spent solvent disposal.

The use of chemical strippers that do not contain organic HAP would

result in a nationwide savings of approximately $2 million. While the

cost of non-HAP strippers is generally higher than the cost of

conventional strippers, this cost is offset by the reduced disposal

costs incurred with non-HAP strippers. Since non-HAP strippers do not

contain methylene chloride, they can typically be treated on-site. This

eliminates the disposal costs incurred with the conventional strippers,

which are typically shipped off-site for disposal.

Nationwide annual costs are estimated to be $14 million for hand-

wipe and flush cleaning, $111 million for waterborne chemical milling

maskants, $2 million for inorganic HAP emissions from primer and

topcoat application operations, and $0.3 million for inorganic HAP

emissions from blast depainting operations.

Total nationwide costs, taking into account both the savings and

costs detailed above, are estimated to be a savings of $20 million.

Sources subject to the proposed rule would be required to perform

certain monitoring, recordkeeping, and reporting tasks. These

information collection requirements will create a burden on the

affected sources in terms of resources needed to comply with these

requirements (see section VI.D.). The total nationwide costs of the

manpower requirements to complete these tasks are estimated to be $36.7

million.

Total nationwide costs are estimated to be $16.7 million, which is

the sum of the annualized costs (a total nationwide savings of $20

million) and the costs due to monitoring, recordkeeping, and reporting

requirements (a total nationwide cost of $36.7 million).

2. New Facilities

For the aerospace industry, no net growth is expected over the next

five years; therefore, no net costs (or savings) due to new facilities

are anticipated during this period.

E. Economic Impacts

Due to the low total compliance costs associated with the proposed

regulation, the discussion of the economic impacts is presented in a

qualitative manner. The low costs of the proposed regulation are in a

large part due to cost savings expected to be achieved by some model

plants. The economic impact analysis discussed in a qualitative manner

the primary impacts (the direction of price and output changes in the

aerospace industry), as well as secondary impacts (the direction of

changes in the demands for inputs such as coatings) associated with the

proposed regulation.

Cost estimates indicate that the total annual compliance costs are

approximately $16.7 million. In 1990, revenue for this industry

equalled approximately $118.9 billion. Using revenue data as a proxy

for production costs, the costs of the proposed regulation are only

0.01 percent of the total production costs for the industry. This

increase in production cost is expected to have minimal impact on the

current prices and outputs of the aerospace industry.

Secondary impacts refer to changes in factor demand by all

aerospace producers. For example, while the primary impact of the

regulation on spray gun cleaning is a decrease in the cost of

performing this task, the actual cause of the decrease in the cost is a

reduction in the use of methyl ethyl ketone and other solvents.

Although compliance with the proposed regulation is expected to reduce

consumption of coatings and solvents in general and, therefore,

negatively impact the producers of these products, compliance with the

proposed regulation is also expected to increase product substitution

so that demand for non-HAP strippers, waterborne maskants, and low

vapor pressure solvents will increase. Lack of economic data on a

product-specific basis prevents quantification of the indicated

impacts.

IV. Process Descriptions and Control Technologies

A. Process Descriptions

Aerospace manufacturing and rework operations consist of the

following basic operations: Chemical milling maskant application,

chemical milling, adhesive bonding, cleaning (e.g., hand-wipe, spray

equipment, and flush), metal finishing, electrodeposition, coating

application (e.g., primers, topcoats, sealants, and specialty

coatings), depainting, and composite processing. In addition, most

aerospace manufacturing and rework facilities generate waste and

wastewater, and some facilities have storage tanks for hand-wipe

cleaning solvents. An aerospace facility may conduct all of these

processes in its operations, such as an OEM facility that produces the

entire aircraft. However, an aerospace facility may conduct only a

subset of these operations, such as a facility that produces a single

component or assembly, or a facility that provides a service such as

chemical milling.

1. Chemical Milling Maskant Application and Chemical Milling

Chemical milling uses etchant solutions to reduce the thickness of

selected areas of metal parts in order to reduce weight. The process is

typically used when the size or shape of the part precludes mechanical

milling or when chemical milling is advantageous due to shorter

processing time or its batch capability.

Chemical milling maskants are typically rubber- or polymeric-based

coatings applied to an entire part or subassembly by brushing, dipping,

spraying, or flow coating. After the chemical milling maskant is cured,

it is removed from selected areas of the part where metal is to be

removed during the chemical milling process. The chemical milling

maskant remaining on the part protects those areas from the etchant

solution. Chemical milling maskants typically contain either a toluene/

xylene mixture or perchloroethylene as its solvent constituents.

Organic HAP emissions occur through evaporation of the solvent as

the chemical milling maskant is applied and while it cures.

2. Adhesive Bonding (Adhesives and Adhesive Bonding Primers)

Adhesive bonding involves the joining together of two or more metal

parts, such as the parts of a honeycomb core. This process is typically

performed when the joints being formed are essential to the structural

integrity of the aircraft. The surfaces to be bonded are first coated

with an adhesive bonding primer to promote adhesion and protect from

subsequent corrosion. Structural adhesives are applied as either a thin

film or as a paste, and can be oven cured or cured in an autoclave.

Organic HAP emissions occur from the evaporation of solvents contained

in the adhesive bonding primer and adhesive during their application,

as well as during the curing step.

3. Cleaning Operations

a. Hand-wipe and flush cleaning. Aerospace components are cleaned

frequently during manufacturing to remove contaminants such as dirt,

grease, and oil, and to prepare the components for the next operation.

Cleaning is typically performed by a hand wiping process using a wide

variety of cleaning solvents. Assemblies and parts with concealed or

inaccessible areas may be flush cleaned by pouring the cleaning solvent

over or into the part. The cleaning solvent is then drained from the

part and the procedure is repeated as many times as necessary to ensure

the required cleanliness.

Organic HAP emissions from hand-wipe and flush cleaning operations

occur from the evaporation of cleaning solvents during the cleaning

process, including evaporation of the solvent from open containers and

from solvent-soaked cloth and paper. Organic HAP emissions also occur

from storage tanks used to store cleaning solvents.

b. Spray gun cleaning. Spray guns and other components of coating

units must be cleaned when switching from one coating to another and

when they are not going to be immediately reused. The cleaning of spray

guns can be performed either manually or with enclosed spray gun

cleaners. Manual cleaning involves disassembling the gun and placing

the parts in a vat containing an appropriate cleaning solvent. The

residual paint is brushed or wiped off the parts. After reassembling,

the cleaning solvent may be sprayed through the gun for a final

cleaning.

Enclosed spray gun cleaners are self-contained units that pump the

cleaning solvent through the gun within a closed chamber. After the

cleaning cycle is complete, the guns are removed from the chamber and

typically undergo some manual cleaning to remove coating residue from

areas not exposed to the cleaning solvent, such as the seals under the

atomizing cap.

Organic HAP emissions from spray gun cleaning occur from the

evaporation of cleaning solvents during the cleaning cycle, such as

while hand cleaning the guns in an open vat. Organic HAP emissions also

occur from enclosed spray gun cleaners when they are opened to remove

the guns.

4. Metal Finishing and Electrodeposition

Metal finishing processes are used to prepare the surface of a part

for better adhesion, improved surface hardness, and improved corrosion

resistance. Typical metal finishing operations include conversion

coating, anodizing, desmutting, descaling, and any operation that

chemically affects the surface layer of a part.

Electrodeposition, or metal plating, is an additive process for

metal substrates in which another metal layer is added to the substrate

in order to enhance corrosion and wear resistance necessary for the

successful performance of the component. The two types of

electrodeposition typically used are electroplating and plasma arc

spraying.

HAP emissions from metal finishing operations occur in the form of

gases or vapors that evaporate from the surface of processing

solutions. Evaporation of solution also occurs from the parts as they

are removed from the processing tanks.

5. Coating Application

A coating is a material that is applied to the surface of a part to

form a decorative or functional solid film. The most common coatings

are the broad categories of non-specialized primers and topcoats. There

are also numerous specialty coatings ranging from temporary protective

coatings to radiation effect coatings designed to shield aircraft from

radar detection.

Coatings are applied to aerospace vehicles and components using

several methods of application. The methods most commonly used are

spraying, brushing, rolling, flow coating, and dipping. Spray

application systems include conventional air spray, airless spray, air-

assisted airless, electrostatic, and high volume low pressure (HVLP)

spray. These latter two methods are generally accepted as having better

transfer efficiency than other spraying methods and are gaining

increased use as a means of using less coating and, hence, reducing

emissions.

Nearly all aerospace coatings contain a mixture of organic

solvents. Organic HAP emissions from coating application occur from the

evaporation of the solvents during mixing, application, and drying.

Inorganic HAP emissions of metal compounds (e.g., chromium and cadmium)

also occur from overspray, which is exhausted from spray booths or

paint spray hangars.

6. Depainting

The depainting operation involves the removal of coatings from the

outer surface of aircraft. The two basic depainting methods are

chemical depainting and blast depainting. Chemical depainting agents

are applied to the aircraft, allowed to degrade the coating, and then

scraped or washed off with the coating residue. Blast depainting

methods utilize a media such as plastic, wheat starch, carbon dioxide,

or high pressure water to remove coatings by physically abrading the

coatings from the surface of the aircraft.

Organic HAP emissions from chemical depainting occur from

evaporation of the solvents in the stripping solution. The amount of

emissions from the process is directly related to the surface area

being stripped, the type and thickness of coating to be removed, and

the effectiveness of the stripper. Inorganic HAP emissions occur from

the various blast depainting methods. The inorganic HAP are contained

in the coatings being removed (trace amounts of inorganic HAP may also

be found in some blast media) and are emitted as particulates.

7. Composite Processing

Composite processing consists of seven basic operations: Layup,

thermal forming, debulking, curing, break-out, compression molding, and

injection molding. Layup is the process of assembling the layers of the

composite structure by positioning composite material in a mold and

impregnating the material with a resin. Thermal forming is the process

of forming the layup in a mold, which usually takes place in an

autoclave. During the thermal forming process, debulking also may

occur, which is the simultaneous application of low-level heat and

pressure to the composite structure to force out excess resin, trapped

air, vapor, and volatiles from between the layers of the composite

structure. The curing step, which is the process of changing the resin

into a solid material through a polymerization reaction, also occurs in

the autoclave. After curing and removal from the autoclave, the break-

out process removes the composite structure from the molds or curing

fixtures.

Two other methods of forming composite structures are compression

molding and injection molding. Compression molding is the process of

filling one half of a mold with a molding compound, closing the mold,

and applying heat and pressure until the material is cured. Injection

molding uses a closed mold, where the molding compound is injected into

the mold, maintained under pressure, and then cured by applying heat.

Organic HAP emissions from composite processing occur from

volatilization of a small portion of the solvent components during

curing, because the majority of these solvents are consumed in the

curing reaction of the resin.

8. Wastewater

Nearly every aerospace manufacturing and rework operation has the

potential to generate wastewater. For example, metal finishing

operations use water to rinse parts after each processing step. These

rinse steps are typically carried out in large tanks with either a

continuous or intermittent water flow. The wastewater generated is

usually treated to some extent at the facility, then discharged.

HAP emissions from wastewater result from the evaporation of

volatile components in the water. Evaporation may occur in open

trenches, storage tanks, and treatment operations.

9. Handling and Storage of Waste

Waste is produced primarily from cleaning, coating, and depainting

operations. Cleaning operations produce solvent laden cloth and paper

and spent solvent which can emit organic HAP from the evaporation of

the solvents. Coating operations produce waste paint and waste solvent

thinner that also emit organic HAP through evaporation. Depainting

operations can produce either a liquid or solid waste stream depending

on the type of process used. Chemical depainting processes produce a

liquid sludge that consists of the stripper solution and paint residue.

Emissions occur from the evaporation of the solvent from the stripper

solution. Blast depainting processes produce a solid waste stream that

consists of paint chips and spent blasting media. Emissions do not

directly occur from this waste stream, although particulate emissions

are generated during the blasting process.

10. Storage of Hand-Wipe Cleaning Solvents

Many large aerospace facilities use storage tanks for hand-wipe

cleaning solvents. According to data obtained through responses to EPA

questionnaires under section 114 of the Act (section 114

questionnaires), these tanks are primarily above ground, fixed-roof

type ranging in size from 350 to 6800 gallons in size. Emissions from

these tanks occur from evaporation of the cleaning solvents, as well as

breathing and working losses.

B. Control Techniques

The principal techniques used by the aerospace industry to control

organic HAP emissions are preventative measures and control devices.

For the control of inorganic emissions, control devices such as filters

and waterwash are used. Preventative measures are any action, product

modification, process modification, or equipment change designed to

eliminate or reduce the generation of emissions. Control devices do not

prevent the generation of emissions, but rather capture or destroy the

emissions generated by a source.

Preventative measures are usually the most desirable method to

reduce emissions since they eliminate or reduce the actual generation

of pollutants. Typically, the emission reduction is obtained using less

energy and producing less waste than using a control device to achieve

the same emission reductions. Preventative measures used by the

industry are: (1) Product reformulations that replace products

containing high levels of HAP and VOC with products containing less HAP

and VOC or that eliminate the HAP or VOC content completely, such as

chemical strippers that contain no organic HAP for depainting; (2)

product reformulations, such as higher solids content coatings, that

reduce the amount of the HAP- and VOC-containing product used; (3)

equipment changes that result in emission reductions, such as replacing

conventional spray guns with HVLP spray guns; and (4) work practice

standards, such as housekeeping.

Control devices are typically used where product reformulation is

not feasible or where the concentration of the exhaust stream is

sufficiently high to warrant their use. Control devices may destroy the

HAP and VOC, as with an incinerator, or capture the HAP and VOC, as

with a carbon adsorber. Often, the compounds captured by a control

device can be recovered for reuse. Control devices in predominant use

by the industry for the reduction of organic HAP emissions are: (1)

Carbon adsorbers, (2) incinerators, and (3) ultraviolet oxidation.

Activated carbon fiber adsorbents to concentrate VOC emissions are

frequently used in conjunction with incinerators. For inorganic HAP

particulate emissions, reduction is achieved predominantly through the

use of filtration devices.

1. Preventative Measures

a. Product reformulation. HAP and VOC emissions may be controlled

by replacing products containing high concentrations of HAP and VOC

with ones that have reduced or eliminated HAP and VOC entirely. Each

individual facility must evaluate the ability of the new product to

maintain standards of quality and performance. In addition, the

potential overall environmental benefit of the reformulated products

must be carefully evaluated.

(1) Product reformulation--coatings. Product reformulations for

coatings can be generally classified as waterborne, higher solids,

powder, and self-priming topcoats. Each category is discussed below.

(a) Waterborne coatings. Waterborne coatings utilize a resin system

that is dispersible in water. A portion of the organic solvent is then

replaced with water. The organic solvent may be 5 to 40 percent by

weight of the waterborne coating, compared to a conventional organic

solvent-based coating containing as much as 80 percent by weight

solvent.

In addition to the lower solvent content, waterborne coatings have

other advantages over solvent-based coatings. Less overspray and

improved spray transfer efficiency may be achieved with waterborne

coatings than with conventional coatings that utilize solvents with a

density less than that of water. Additionally, because of the reduced

solvent content, waterborne coatings may be less toxic and present a

reduced fire hazard.

Waterborne coatings have limitations such as requiring spray guns

with specific materials of construction, protection from freezing, and

better control of temperature and humidity during application. In

addition, waterborne coatings generally require longer drying times,

are more sensitive to substrate material and cleanliness, and have

lower salt spray resistance.

(b) Higher solids. Higher solids coatings are solvent-based coating

formulations that have been modified to lower the solvent-to-solids

ratio. The coatings usually contain 50 to 65 percent by volume solids,

compared to conventional solvent-based coatings that may contain up to

40 percent by volume solids. The increased solids content gives greater

surface area coverage per gallon of coating, which reduces the total

volume of coating required. Consequently, solvent emissions are also

reduced when higher solids coatings are used to apply the same volume

of solids that are applied with a conventional solvent-based coating.

Higher solids coatings generally have higher viscosities and longer

drying times than conventional solvent-based coatings. The higher

viscosity tends to make spray application more difficult because it is

harder to control gloss and film thickness, and may require the coating

to be heated before application. Higher solids coatings typically are

not used as dip coatings due to the difficulty in maintaining a uniform

dispersion of solids in the dip tank.

(c) Powder. Powder coatings are a class of coatings applied

electrostatically in dry form and then baked to cure. The coatings

consist of fine, dry particles of paint solids. During the curing step,

the particles fuse to create a continuous film. Use of powder coatings

requires that the substrate must be able to withstand the high

temperatures (typically greater than 121 deg.C (250 deg.F) and

frequently greater than 177 deg.C (350 deg.F)) necessary to cure the

paint.

The major advantage of using powder coatings is greatly reduced

solvent emissions. The lack of a solvent base also reduces fire hazard,

toxicity, and the make-up air requirements of the spray booth.

Powder coatings must be applied electrostatically, so they cannot

be used on non-conductive parts such as composites. Other reported

disadvantages of powder coatings are the difficulty in obtaining a high

quality appearance, production must be shut down for color changes, the

powder must remain dry at all times prior to application, and higher

energy costs. As noted above, the high curing temperatures of powder

coatings precludes their use on temperature-sensitive substrates.

(d) Self-priming topcoats. Self-priming topcoats eliminate the need

to apply a primer coat between the substrate and the topcoat. Self-

priming topcoats have the adhesion and corrosion characteristics of a

conventional primer and the environmental resistance and functional

fluid resistance of a conventional topcoat. These coatings also

eliminate the need for chrome-containing primers.

(2) Product reformulation--hand-wipe cleaning solvents. Product

reformulations for hand-wipe cleaning that are prevalent in the

aerospace industry can be classified as aqueous, hydrocarbon-based, and

non-chemical. Each category is discussed below:

(a) Aqueous. Aqueous cleaners contain at least 80 percent water,

are non-flammable and non-combustible, and are completely soluble in

water. Other components may include corrosion inhibitors, alkalinity

builders, organic surfactants, and bioenzyme mixtures and nutrients

depending on the desired soil removal properties. Aqueous cleaners have

been used in non-critical areas where strict cleanliness requirements

do not have to be met, or where there are no confined spaces that may

trap residues of the cleaner.

(b) Hydrocarbon-Based. Hydrocarbon-based cleaners are nonsemi-

aqueous cleaners that are composed of a mixture of hydrocarbons and

oxygenated hydrocarbons. These cleaners have a maximum vapor pressure

of 7 mm Hg at 20 deg.C (3.75 in. H2O at 68 deg.F) and contain no

HAP or ozone depleting compounds.

(c) Non-chemical. Several aerospace facilities have demonstrated

the viability of using non-chemical methods such as dry media blasting

for cleaning operations. These methods are typically used to remove

dry, scale-like deposits such as carbon residue on engine components.

Dry media blasting can usually be used only on components that can

withstand the force of blasting without deformation.

b. Equipment changes. The aerospace industry has implemented

several equipment changes that directly reduce the level of HAP

emissions. While there are equipment changes that affect emissions from

every process, the three changes predominantly used in the industry are

high transfer efficiency spray guns, enclosed spray gun cleaners, and

proportional paint mixers. Each of these equipment changes are

discussed below.

(1

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