United States Environmental Protection Agency, Region 9

Air Division

Technical Support Document

for

EPA’s Notice of Proposed Rulemaking

for the

California State Implementation Plan

South Coast Air Quality Management District’s

Rule 1146, Emissions of Oxides of Nitrogen from Industrial, Institutional, and Commercial 

Boilers, Steam Generators and Process Heaters

Prepared by: Idalia Perez

June 2011
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South Coast Air Quality Management District (SCAQMD)

Submitted Rule

SCAQMD Rule 1146, Emissions of Oxides of Nitrogen from Industrial, Institutional, and 

Commercial Boilers, Steam Generators and Process Heaters:

 Adopted: September 5, 2008

 Submitted: July 20, 2010

 Determined complete: August 25, 2010

Previous Rule Submittals

There are no outstanding submittals of Rule 1146.

SIP-Approved Rule

 Adopted: November 17, 2000

 Approved by EPA: April 8, 2002 (67 FR 16640)

Rule Summary

Rule 1146 limits NOx and CO emissions from boilers, steam generators and process heaters with 

a total rated heat input larger than 5 MMBtu/hour with the exception of:

- boilers used by electric utilities; and

- boilers larger than 40 MMBtu/hour used in refineries; and

- sulfur plant reaction boilers.

As per Section (j) of Rule 2001, the provisions in Rule 1146 applicable to NOx emissions do not 

apply to facilities subject to SCAQMD’s RECLAIM program.

Rule Amendments 

Rule 1146 was amended to strengthen the NOx emission limits. Section (c)(1) has the new 

“Standard Compliance” limits and schedule. Section (c)(2) contains “Enhanced Compliance”

limits and schedule; these emission limits are lower than the “Standard Compliance” limits and 

the compliance deadlines are later than the “Standard Compliance” deadlines. Section (c)(7) 

states that certain units complying with the applicable BACT limit of 12 ppm can defer 

compliance with new limits until the units’ burners are replaced.

Section (d) contains provisions related to compliance determination. Language was added 

prohibiting tuning or servicing of units before source tests, except for unscheduled repairs. 

Additional tests methods were added to this section. The frequency of required compliance 

testing was decreased in Section (d)(6). Section (d)(8) was added to require periodic 

measurements of NOx and CO with portable analyzers. Section (d)(10) indicates that emissions 

that are determined to be in excess of the emission limits during a source test or a portable 

analyzer test are not to be considered violations if they are corrected within 72 hours. 

Other changes were done to the Rule language to improve clarity.

Effects on Emissions
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SCAQMD’s staff report estimates that the amendments to Rule 1146 will reduce NOx emissions 

by approximately 1.2 tons per day beginning in 2015 (see page 3-1). This reflects a 65% 

reduction of NOx emissions from this source category. 

Rule Evaluation

Generally, SIP rules must be enforceable (see § 110(a) of the Clean Air Act, hereafter CAA); 

must require Reasonably Available Control Technology (RACT) for major sources in certain 

ozone nonattainment areas (see CAA §182(b)(2) and (f)); must not interfere with any applicable 

requirements concerning attainment and reasonable further progress (RFP) or any other 

applicable requirement of the Act (see CAA § 110(l)); and must modify, in a nonattainment area, 

any SIP-approved control requirement in effect before November 15, 1990 (see § 193). Section 

172(c)(1) of the Act also requires implementation of all reasonably available control measures 

(RACM) as expeditiously as practicable in nonattainment areas.

Because the area regulated by the SCAQMD is designated nonattainment for the fine particulate 

matter (PM2.5) National Ambient Air Quality Standards (NAAQS) and designated and classified 

as extreme nonattainment for the ozone NAAQS (see 40 CFR 81.305), Rule 1146 must ensure 

RACT. Additionally, the RACM requirement in CAA section 172(c)(1) applies to this area. 

Guidance and policy documents that we used to help evaluate enforceability, RACT and RACM

requirements include the following:

Issues Relating to VOC Regulation, Cutpoints, Deficiencies, and Deviations (the "Blue 

Book"), US EPA, OAQPS (May 25, 1988).

Guidance Document for Correcting Common VOC and Other Rule Deficiencies, EPA 

Region IX (August 21, 2001, the “Little Bluebook”).

State Implementation Plans; General Preamble for the Implementation of Title I of the 

Clean Air Act Amendments of 1990, 57 FR 13498 (April 16, 1992); 57 FR 18070 (April 

28, 1992).

State Implementation Plans; Nitrogen Oxides Supplement to the General Preamble; 

Clean Air Act Amendments of 1990 Implementation of Title I; Proposed Rule, (the NOx 

Supplement), 57 FR 55620, November 25, 1992.

Clean Air Fine Particle Implementation Rule, 72 FR 20586 (April 25, 2007)

Determination of Reasonably Available Control Technology and Best Available Retrofit 

Control Technology for Industrial, Institutional, and Commercial Boilers, Steam 

Generators, and Process Heaters, CARB (July 18, 1991). 

http://www.arb.ca.gov/ractbarc/boilers.pdf

Alternative Control Techniques Document-- NOx Emissions from 

Industrial/Commercial/Institutional (ICI) Boilers, US EPA 453/R-94-022 (March 1994). 

http://www.epa.gov/ttn/catc/dir1/icboiler.pdf

Alternative Control Techniques Document-- NOx Emissions from Utility Boilers, US 

EPA 452/R-93-008 (March 1994). http://www.epa.gov/ttn/catc/dir1/utboiler.pdf

Credible Evidence Revisions; Final Rule, 62 FR 8314 (February 24, 1997). 

Review of State Implementation Plans and Revisions for Enforceability and Legal 

Sufficiency; Memorandum from J. Craig Potter, Thomas L. Adams Jr., Francis S. Blake 

(September 23, 1987). 

http://www.epa.gov/compliance/resources/policies/civil/caa/stationary/review-enf-rpt.pdf
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State Implementation Plans (SIPs): Policy Regarding Excess Emissions During 

Malfunctions, Startup and Shutdown from Steven A. Herman, Assistant Administrator for 

Enforcement and Compliance Assurance, and Robert Perciasepe, Assistant Administrator 

for Air and Radiation, September 20, 1999.

Discussion of RACT and RACM Criteria

Submitted Rule 1146 is only applicable to sources that are not subject to RECLAIM, as per 

Table 1 in SCAQMD Rule 2001, which cover all major NOx sources. Thus, Rule 1146 is not 

required to fulfill RACT requirements. Even if RACT were required, we believe SCAQMD Rule 

1146 likely implements RACT for NOx emissions for reasons including:

- Rule 1146 meets or exceeds requirements in analogous NSPS (40 CFR Part 60, 

Subparts D, Db, Dc);

- Emission limits in Rule 1146 are comparable to emission limits in Sacramento Metro 

Air Quality Management District (SMAQMD) Rule 411 and in San Joaquin Valley 

Unified Air Pollution Control District (SJVUAPCD) Rule 4306, the other large 

California ozone nonattainment agencies. These generally have among the most 

stringent stationary source requirements nationwide, and we are not aware of other 

reasonably available technological or operational controls likely to significantly 

reduce additional emissions from this activity.

- Both 1994 ACT documents mentioned above provide technical information including 

control techniques and achievable controlled NOx emission levels from boilers. Rule 

1146 requirements are comparable to the ACT. 

- The submitted rule is as stringent as CARB’s RACT/BARCT guidance.

Since no CTG has been issued recently for this activity, we do not have clear national guidance 

defining presumptive RACT. However, we believe the analysis summarized above sufficiently 

demonstrates that Rule 1146 implements RACT. 

CAA §172(c)(1) requires implementation of all reasonably available control measures (RACM) 

for Ozone and PM2.5 as expeditiously as practicable in SCAQMD. Because boilers emit NOx, 

SCAQMD must implement RACM for these activities if they will advance attainment of the 

PM2.5 or Ozone NAAQS when considered collectively with other measures. Therefore, 

additional control measures may be required pursuant to CAA §172(c)(1) if both: (1) additional 

measures are reasonably available; and (2) additional reasonably available measures (considered 

collectively with other measures) will advance attainment in the area. As described above, we 

believe that the NOx emission limits in the submitted rule implement RACT for NOx. We 

believe that this demonstration is sufficient to determine that the rule requires all measures that 

are “reasonably available” within the meaning of RACM under CAA § 172(c)(1). In separate 

rulemakings, EPA will take action on the State’s RACM demonstration for PM2.5 and Ozone 

based on an evaluation of the control measures submitted as a whole and their overall potential to 

advance the applicable attainment dates in the South Coast area.

Discussion of Enforceability

Per §110(a) of the Act, SIP rules must be enforceable. In 1987, EPA laid out enforceability 

criteria that SIP rules must meet to be both enforceable as a practical matter and within the
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statutory authority of the promulgating agency (see “Review of State Implementation Plans and 

Revisions for Enforceability and Legal Sufficiency,” from J. Craig Potter, Thomas L. Adams Jr., 

Francis S. Blake). Some of the criteria essential in practically enforceable rules include clear 

statements of applicability, specificity of the standard that must be met, explicit statements of 

compliance time frames, explicit statements of size and periodic event exemptions, and inclusion 

of record keeping requirements. We believe the submitted rule revisions adequately fulfill most of 

the relevant criteria identified above. Specifically, the Rule:

is generally clear and has clear applicability;

includes adequate recordkeeping and other compliance provisions; 

has testing and compliance timeframes.

Some of the recent Rule 1146 revisions were designed to increase rule compliance after a four 

year emission testing study revealed a 31% noncompliance rate for units regulated by the rule

(see page 2-8 of the Staff Report). The requirements for periodic monitoring of NOx and CO 

with portable analyzers that were added to section (d) increase the frequency of monitoring of 

units subject to this rule to monthly, with the required frequency dropping to quarterly if the unit 

is found to be in compliance for three consecutive emission checks. SCAQMD also added a 

provision (Section (d)(2)) prohibiting tuning or servicing of units before source testing. Although 

these two additions are designed to increase compliance, we are concerned with potential 

impacts to overall rule enforceability.

Section (d)(8) was added to the Rule to incorporate requirements for periodic monitoring of NOx 

and CO with portable analyzers. The language in (d)(8)(C) states: 

An owner or operator shall not be considered in violation of the emissions limits of this rule 

or in permit conditions if the owner or operator complies with requirements specified in 

paragraph (d)(10). Any emission check conducted by District staff that finds excess 

emissions is a violation.

Section (d)(10) states: 

A source test specified under paragraph (d)(6) or an emission check conducted under the 

requirements specified in paragraph (d)(8) that finds emissions in excess of those allowed by 

this rule or a permit condition shall not constitute a violation of this rule if the owner or 

operator corrects the problem and demonstrate (sic) compliance with another source test or 

emission check within 72 hours from the time the owner or operator knew of excess 

emissions, or reasonably should have known, or shut down the unit by the end of an 

operating cycle, whichever is sooner.

These provisions preclude the use of both source test data obtained during compliance testing 

required by the rule and emission data obtained from portable analyzers from being used to 

prove a violation of the emission standard. This contradicts the national credible evidence rule

from 1997 which removes what some construed to be a regulatory bar to the admission of nonreference test data to prove a violation of an emission standard (62 FR 8314). Revisions include 

changes to 51.212(c):

...For the purpose of submitting compliance certifications or establishing whether or not a 

person has violated or is in violation of any standard in this part, the plan must not preclude 

the use, including the exclusive use, of any credible evidence or information, relevant to 
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whether a source would have been in compliance with applicable requirements if the 

appropriate performance or compliance test or procedure had been performed. 

and 52.12(c):

For purposes of Federal enforcement, the following test procedures and methods shall be 

used, provided that for the purpose of establishing whether or not a person has violated or is 

in violation of any provision of the plan, nothing in this part shall preclude the use, including 

the exclusive use, of any credible evidence or information, relevant to whether a source 

would have been in compliance with applicable requirements if the appropriate performance 

or compliance test procedures or methods had been performed.

Prohibitory rules for other nonattainment areas do not include language that exempts testing 

results to be used for compliance determinations. For example, SJVUACPD Rule 4320, which 

covers similar sources and has similar emission limits, requires a CEM or an APCO approved 

Alternate Monitoring System that allows for periodic testing of exhaust emission concentrations 

(Section 5.4.2). Rule 4320 does not include language excluding either the CEM or the periodic 

monitoring from being used to show violations. Additionally, Rule 4320 requires source testing 

once every twelve months, with the period between source tests able to be extended to 36 months 

following two consecutive 12-month sources tests that show that the unit is in compliance. 

Consistent with EPA guidance, Rule 4320 Section 6.3.1.4 states that 

“any source test results that exceed the applicable emission limits in Sections 5.1 or 5.2.3 

shall constitute a violation of this rule”.

SCAQMD staff have explained that language in (d)(4):

“Emissions determined to exceed any limits established by this rule through the use of any of 

the above-referenced test methods shall constitute a violation of this rule.”

and language in (d)(8)(C):

“Any emission check conducted by District staff that finds excess emissions is a violation.”

act as a back-stop, not-allowing exceedances on portable monitors or source tests to be exempted 

in every situation. Additionally, they believe the increase in overall testing will encourage higher 

compliance rates, without having to declare sources as being in violation of the Rule. Although 

we support the District’s effort to increase compliance with the emissions limits of the Rule, 

sections (d)(8) and (d)(10) conflict with CAA section 110(a) and the credible evidence Rule.

SCAQMD should eliminate language in section (d)(10) that restricts use of source test data to 

verify rule compliance, particularly since annual compliance tests are a common expectation for 

the type of sources subject to the rule, although SCAQMD may of course exercise discretion in 

declining to pursue enforcement in specific circumstances. To the extent that portable analyzer 

tests required by section (d)(8) are an additional (rather than a replacement) requirement beyond 

the testing normally appropriate for affected sources, we understand that it may not be 

appropriate to pursue enforcement for every failed portable analyzer test. However, the rule 

should also be consistent with national credible evidence policy and should establish reasonable 

limits on the number and/or frequency of failed portable analyzer tests. Therefore, SCAQMD 

should also revise section (d)(10) to clarify the consequences of failed portable analyzer tests. 

For example, this section could be revised to require that any source that fails a portable 

analyzer test perform appropriate maintenance and retest within 72 hours, and that failure of 2 
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monthly tests within 6 months constitutes a violation of the rule. Here too, SCAQMD may also 

choose to exercise enforcement discretion.

Discussion of Relaxation Criteria

Inclusion of more stringent NOx emission limits make the submitted rule more stringent than the 

version previously approved into the SIP. We propose to determine that our approval of the 

submittal would comply with CAA section 193 because the submitted SIP revision is more 

stringent than the rule previously approved into the SIP and would insure equivalent or greater 

emission reductions of NOx. We also propose to determine that our approval of the submittal 

would comply with CAA section 110(l), because the proposed SIP revision would not interfere 

with the on-going process for ensuring that requirements for RFP and attainment of the NAAQS 

are met, and the submitted SIP revision is more stringent than the rule previously approved into 

the SIP.

Rule Deficiency

Section (d)(8) and Section (d)(10) preclude the use of both source test data and portable 

analyzers test results from being used to prove a violation of the emission standard. This 

contradicts CAA requirements for enforceability and the national credible evidence rule

from 1997 (62 FR 8314).

Suggested Rule Improvements

EPA recommends that the SCAQMD make the following improvements in the next revision of 

Rule 1146, although they are not currently the basis for rule disapproval.

1. The rule language is confusing and seems to be contradictory at times, e.g. the last 

sentence of (d)(4) states: 

“Emissions determined to exceed any limits established by this rule through the use of 

any of the above-referenced test methods shall constitute a violation of this rule.”

This seems to contradict section (d)(10)

“A source test specified under paragraph (d)(6) or an emission check conducted under 

the requirements specified in paragraph (d)(8) that finds emissions in excess of those 

allowed by this rule or a permit condition shall not constitute a violation of this 

rule...”

The District should ensure that the rule language is clear and consistent throughout the 

whole rule. 

2. Section (d)(2) states:

“All emission determinations shall be made in the as-found operating condition, except 

no compliance determination shall be established during start-up, shutdown, or under 

breakdown conditions. Compliance determination as specified in paragraph (d)(6) shall 

be conducted at least 250 operating hours, or at least thirty days subsequent to the tuning 

or servicing of any unit, unless it is an unscheduled repair.”

To improve clarity and enforceability of this provision, we recommend adding a 

definition for “as-found operating conditions”, “start-up”, “shutdown”, “breakdown 

conditions” and “unscheduled repair” into the Rule. These definitions should be 
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consistent with EPA Excess Emission Guidance (September 20, 1999), where 

appropriate. Please also consider adding recordkeeping requirements to this provision to 

demonstrate unscheduled repairs and operating hours. 

Recommendation

EPA staff recommends a limited approval, limited disapproval of SCAQMD submitted Rule 

1146 for incorporation into the California Applicable SIP.

Attachments

1. Submitted Rule 1146 (Clean Copy), adopted: 9/ 5/2008

2. Submitted Rule 1146 (Strikeout Copy)

3. Final Staff Report, Proposed Amended Rule 1146 – Emissions of Oxides of Nitrogen 

from Industrial, Institutional, and Commercial Boiler Steam Generators, and Process 

Heaters, by R. Calungcagin, August 2008.

4. SIP-approved version of Rule 1146, adopted 11/17/00, approved by EPA 4/8/02 (67 FR 

16640)