UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX AIR DIVISION

Technical Support Document 

for

EPA’s Proposed Rulemaking

for the

California State Implementation Plan

Imperial County Air Pollution Control District, Rule 425, Aerospace Coating 

Operations

Prepared by: Adrianne Borgia

Reviewed by: Andrew Steckel

January, 2011
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RULE IDENTIFICATION - 

Agency: Imperial County Air Pollution Control District (ICAPCD)

SIP Approved Rule: Rule 425 – Aerospace Coating Operations 

Adopted – May 18, 2004; Submitted – July 19, 2004

EPA Approved – May 19, 2005 (70 FR 28826)

Subject of this TSD: Rule 425 – Aerospace Coating Operations 

Adopted – February 23, 2010; Submitted – July 20, 

2010

RULE SUMMARY -

Rule 425, Aerospace Coating Operations, is a rule designed to reduce VOC 

emissions at industrial sites engaged in coating airplanes, space craft and their 

component parts. VOCs are emitted during the preparation and coating of the 

parts, as well as the drying phase of the coating process. The provisions of this 

rule apply to any person who applies, specifies the use of, or supplies coatings for 

the surface preparation and coating of metal parts. Section A defines the 

Applicability of the rule, including exemptions and the ROC limit table. Section B 

covers requirements, including storage, disposal, transfer efficiency and maximum 

quantities and vapor pressure of solvents, the ROC limit for maskants and 

strippers, application methods and cleaning methods of electrostatic spray gun 

cleaning. Section C outlines the recordkeeping requirements, reporting schedule 

and content. Finally, Section D indicates the test methods necessary for this 

coating operation. Changes from the approved SIP rule include:

1. In section A.4, the reference to deleted Section A.3c, was removed.

2. The references to non-existent subsections of A.2 were removed.

3. Record retention denoted in Section C.2 was increased from two to five 

years.

EPA EVALUATION - The following criteria were used to evaluate the submitted 

rule. 

1. Enforceability - The Bluebook (Issues Relating to VOC Regulation 

Cutpoints, Deficiencies, and Deviations, EPA, May 25, 1988) and the Little 

Bluebook (Guidance Document for Correcting Common VOC & Other Rule 

Deficiencies, EPA Region 9, August 21, 2001) were used to help evaluate 

compliance with the CAA §110(a)(2)(A) requirement for enforceability. 

2. RACT – EPA’s Control Technique Guideline (CTG) titled, “Surface Coating 

Operations at Aerospace Manufacturing & Rework Operations” (EPA453/R-97-004, December 1997), and other state and local rules for this 

category were used to help evaluate the RACT requirements of CAA 

§182(b)(2).
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3. SIP Relaxation - Where previous versions of rules have been SIP approved, 

new submittals must comply with CAA §110(l) and §193 regarding SIP 

relaxations.

The monitoring, recordkeeping, reporting and other requirements generally ensure 

that the submitted rule can be enforced. 

ICAPCD regulates a serious nonattainment area for Ozone and therefore needs 

reasonably achievable control technologies (RACT). However, as noted in their 

RACT SIP, “Draft 2009 Reasonably Available Control Technology State 

Implementation Plan,” Imperial County Air Pollution Control District, dated July 13, 

2010, no aerospace coating sources exist in the district. As a result, ICAPCD is 

not required to adopt RACT requirements for this source category. Nonetheless, 

we have still reviewed Rule 425 for potential RACT issues and identified these in 

the recommendations section below. 

The submitted rule does not relax the SIP and complies with §110(l) and §193. 

RULE DEFICIENCIES – We have identified no deficiencies with Rule 425 

sufficient for EPA to propose less than full approval. 

ADDITIONAL RECOMMENDATIONS FOR THE NEXT RULE REVISION - The 

following revisions are not currently the basis for rule disapproval, but are 

recommended for the next time the rule is amended. 

 

1. Table 425-1 lists ROC limits for various types of coatings that have not 

been defined. For clarity and enforceability, please define the following:

a. Adhesive, Structural Autoclavable

b. Adhesive, Structural Epoxy

c. Adhesive, Non-autoclavable

d. Adhesive, Elastomeric

e. Radiation–effect Coating 

f. Solid-film Lubricant; Fasteners and Non-fastener lubrication

g. Dip coat

2. Table 425-1 lists ROC limits for coatings that are not specifically included in 

the CTG. These higher limits should be removed or justified for: 

a. Adhesive, Structural Epoxy

b. Adhesive, Elastomeric

3. Section B.9 lists several application techniques that have not been defined. 

For clarity and enforceability, please define the following:

a. Dip coat

b. Airless spray application for use with Maskants and Temporary 

Protective Coatings
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4. Please verify, per the CTG Model Rule in appendix B, B.3 (b) (1), that the 

airless spray application, specified in Section B.9.e, achieves emission

reductions equivalent to HVLP or electrostatic application methods.

5. To comply with the Little Bluebook recommendations for EPA-approved 

ASTM test methods (page 13, #4) please provide the title of ASTM 

Method D 2369 referenced in Section D.2 Please use only the version 

approved by EPA listed in 40 CFR 60.17, which is 1995 for ASTM D2369.

Similarly, EPA methods, listed in Sections D.1, D.7, D.8 and D.9, should 

include the full title. 

6. Both ASTM D1639 and ASTM D2306 referenced in Section D.3 and D.4, 

respectively, had been withdrawn by ASTM in 2005 and 2006,

respectively, with no replacements. EPA Method 18, Measurement of 

Gaseous Organic Compound Emissions by Gas Chromatography, is an 

approved method that replaces ASTME D2306.

EPA ACTION - The submitted Rule 425 strengthens the SIP and the rule largely 

fulfills the relevant CAA §110 and part D requirements. EPA staff recommends a 

full approval of Rule 425 pursuant to CAA §110(k) (3) and §301(a).

ATTACHMENTS -

1. ICAPCD Rule 425, Aerospace Coating Operations, 

as submitted on July 20, 2010

2. ICAPCD Rule 452, Aerospace Coating Operations, 

as submitted on July 19, 2004 into the SIP on May 19, 2005. 

ADDITIONAL REFERENCES -

1. “Issues Relating to VOC Regulation Cutpoints, Deficiencies, and 

Deviations,” (a.k.a., Bluebook) EPA OAQPS, May 25, 1988. 

2. “Guidance Document for Correcting Common VOC & Other Rule 

Deficiencies,” (a.k.a., Little Bluebook), EPA Region 9, August 21, 2001. 

3. “Surface Coating Operations at Aerospace Manufacturing & Rework 

Operations,” EPA-453/R-97-004, December 1997. 

http://www.epa.gov/ttn/naaqs/ozone/ctg_act/199712_voc_epa453_r-97-

004_aerospace_rework.pdf

4. “Draft 2009 Reasonably Available Control Technology State 

Implementation Plan,” Imperial County Air Pollution Control District, July 

13, 2010.