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 

San Joaquin Valley Unified Air Pollution Control District’s 

Rule 4352, Solid Fuel Fired Boilers, Steam Generators and Process Heaters 

Prepared by: Idalia Perez 

October 2009 
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San Joaquin Valley Unified Air Pollution Control District (SJVAPCD) 

Submitted Rule 

SJVAPCD Rule 4352, Solid Fuel Fired Boilers, Steam Generators and Process Heaters 

• Adopted: May 18, 2006 

• Submitted: October 5, 2006 

• Determined complete: October 24, 2006 

EPA published a proposal and direct final approval of this rule on May 30, 2007 (72 FR 29886). 

We received adverse comments and consequently withdrew the direct final approval (72 FR 

41450). 

Previous Rule Submittals 

There are no outstanding submittals of Rule 4352. 

SIP-Approved Rule 

• Adopted: October 19, 1995 

• Approved by EPA: February 11, 1999 (64 FR 6803) 

Rule Summary 

Rule 4352 limits NOx and CO emissions from solid fuel fired boilers, steam generators and 

process heaters. The facilities in SJVAPCD that are subject to Rule 4352 burn a variety of fuels 

including biomass, agricultural waste, wood waste, coal, tire derived fuel, petroleum coke and 

municipal solid waste (MSW). The submitted rule revisions include: 

• More stringent applicability threshold: the revised rule applies to solid fuel-fired boilers, 

steam generators, or process heaters located at sources that have potential NOx or VOC 

emissions of at least 10 tons per year (tpy), which is lower than the applicability threshold 

of 50 tpy in the SIP rule. 

• More stringent NOx emission limits for units firing biomass and other non-MWS solid 

fuels, in Section 5.1. 

• Alternative requirements for start-up and shutdown operations in Section 5.3. 

• New provisions authorizing the APCO, ARB, and EPA to approve an owner/operator’s 

request (accompanied by appropriate justification) for an increased emission limit for a 

unit operated at less than 50 percent of rated heat input, in Section 5.4. 

• Various minor clarifications. 

Sources and Rule Requirements 

The following are the uncontrolled NOx emissions from this source category, according to the 

1994 ACT for ICI boilers (see Guidance Document #5, Table 2-2): 

Fuel Boiler Type Uncontrolled 

NOx (lb/MMBtu) 

Approximate 

ppm at 3% O2

Coal Fluidized bed combustor (FBC) 0.14 – 0.60 109 – 466 

Wood > 70 MMBtu/hr 0.17 – 0.30 124 – 218 

MSW Mass burn 0.40 300 
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The following are the levels to which NOx emissions may be controlled for units with Selective 

Non-Catalytic Reduction (SNCR with ammonia injection), according to the 1994 ACT for ICI 

boilers (see Guidance Document #5, Tables 2-6): 

Fuel Boiler Type Controlled NOx 

(lb/MMBtu) 

Approximate 

ppm at 3% O2

Coal FBC 0.04 – 0.09 29 – 65 

Wood FBC 0.03 – 0.20 23 – 155 

MSW Stoker and mass burn 0.07 – 0.31 52 – 232 

Effective January 1, 2007, Rule 4352 limits NOx emissions from MSW-fired units to 200 ppm at 

12% CO2 (about 266 ppm at 3% O2) and NOx emissions from units fired by all other solid fuels, 

including biomass, to 115 ppm at 3% O2. Both the SIP rule and the revised rule require that the 

NOx emission limits be averaged over 24 hours. 

SJVAPCD provided EPA with a list of permitted units subject to Rule 4352 (Attachment #6). 

This list identifies one facility subject to the emission limits for MSW in Rule 4352, and 13

facilities burning coal, coke, biomass or other fuels that are subject to the emission limits for all 

other solid fuels. This list also indicates that all of these units have installed and are operating 

SNCR equipment. 

Effect on Emissions 

SJVAPCD’s staff report (Attachment #3) does not claim emission reductions from 

implementation of these rule revisions, as all units subject to Rule 4352 already comply with the 

NOx emission limits that became effective locally on January 1, 2007. 

Rule Evaluation Criteria 

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 of NOx in 

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

requirements, including requirements concerning attainment (see CAA §110(l)); and must not 

relax existing requirements in effect prior to enactment of the 1990 CAA amendments (see 

§193). 

SJVAPCD regulates an extreme nonattainment area for the 1-hour ozone standard and a serious 

nonattainment area for the 8-hour ozone standard (40 CFR 81), so submitted Rule 4352 must 

fulfill RACT requirements. Rule 4352 must also require the use of advanced control technologies 

to control NOx emissions from this source category (see CAA §182(e)(3)). 

 

Guidance and policy documents that we used to define enforceability and RACT requirements 

include the following: 

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

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

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

Region IX (August 21, 2001, the “Little Bluebook”).
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3. 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). 

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

Clean Air Act Amendments of 1990 Implementation of Title I; Proposed Rule, 57 FR 

55620, November 25, 1992 (the NOx Supplement). 

5. 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

6. 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 

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

EPA 453/R-94-023 (March 1994). http://www.epa.gov/ttn/catc/dir1/utboiler.pdf 

SJVAPCD is currently designated attainment for PM10 (40 CFR 81.305). Accordingly, 

SJVAPCD is not subject to the requirement to implement BACM for PM10 and PM10 precursors 

in CAA § 189(b) and (e). Therefore, we are not evaluating Rule 4352 for compliance with 

BACM requirements. 

Discussion of Enforceability and Relaxation Criteria 

We believe the submitted rule revisions adequately fulfill most of the relevant criteria identified 

above. Specifically: 

• Recordkeeping and other compliance provisions in the rule ensure that the requirements 

are adequately enforceable. 

• The change in the applicability threshold from 50 tpy to 10 tpy significantly expands the 

rule’s applicability. 

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

than the version previously approved into the SIP, so the submitted rule does not relax the 

SIP and complies with CAA §110(l) and §193. 

 

Discussion of Advanced Control Technology

Section 182(e)(3) of the Act requires that SIPs for extreme ozone nonattainment areas contain 

provisions requiring that each new, modified, and existing electric utility and industrial and 

commercial boiler that emits more than 25 tpy of NOx either: (1) burn as its primary fuel a 

clean fuel (natural gas, methanol, or ethanol, or a comparably low polluting fuel), or (2) use 

advanced control technology (such as catalytic control technology or other comparably 

effective control methods) to reduce NOx emissions. We believe the term "catalytic control 

technology" was intended generally to refer to selective catalytic reduction (SCR). 

Rule 4352 applies to commercial and industrial boilers (in addition to other types of emission 

units) at facilities that potentially emit 10 tpy or more of NOx, which includes all boilers that 

emit more than 25 tpy of NOx. All of the NOx emission limits in the revised rule effectively 

require operation of Selective Noncatalytic Reduction (SNCR) control systems. We believe 

SNCR is "comparably effective" to SCR for the affected sources as discussed below, and thus 
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fulfills Section 182(e)(3) requirements for these affected sources. SNCR also appears to 

achieve NOx emission reductions comparable to combustion of clean fuels at these types of 

boilers. 

According to information in the RACT/BACT/LAER Clearinghouse, recent Prevention of 

Significant Deterioration (PSD) permits contain emission limits for coal-fired boilers ranging 

from 0.067 lbs/MMBtu (for large coal-fired boilers with SCR and low-NOx burner technology) 

to 0.1 lbs/MMBtu (for medium-sized coal-fired boilers with SNCR). These limits reflect Best 

Available Control Technology (BACT) determinations under the PSD program. According to 

the 1994 ACT for ICI boilers (see Guidance Document #5, Tables 2-6), wood-fired watertube 

boilers with SCR can achieve NOx emissions of 0.22 lb/MMBtu. The 1994 ACT does not 

contain emission levels for wood-fired FBC boilers with SCR but states that this type of unit 

with SNCR can achieve NOx emission limits ranging from 0.03 to 0.20 lb/MMBtu. 

Our review of these emission ranges indicates that although emission rates can vary according 

to fuel type and boiler size, generally SNCR controls are comparably effective to SCR for 

boilers firing wood (biomass), MSW, and many other types of solid fuels. As a general matter, 

SNCR is also comparably effective to SCR control for circulating fluidized bed coal-fired 

boilers of less than 50 MW electric generation capacity. For coal-fired boilers, we have 

focused our review on circulating fluidized bed boilers of less than 50 MW generation capacity 

because all existing coal-fired boilers in SJV are of this type and below this size. The emission 

levels achieved by SNCR control systems are also generally comparable to the uncontrolled 

NOx emissions from boilers firing clean fuels such as natural gas, which may range from 0.07 

to 0.45 lb/MMBtu (see Guidance Document #5, Table 2-2). SNCR control systems 

consistently achieve up to 80% NOx emission reductions and are compatible with almost all 

solid fuel-fired boiler operations, while other controls may in some cases be sensitive to 

catalyst poisoning and other technical constraints. As to boilers that emit above 25 tpy of NOx, 

we note as a practical matter that only existing boilers in SJV are likely to be constrained by the 

NOx emission limits in Rule 4352, as all new boilers that potentially emit above 25 tpy and all 

major modifications at existing boilers will also be subject to the more stringent control 

technology requirements of the Nonattainment New Source Review (NNSR) or PSD permit 

programs. The requirements of Rule 4352 are generally applicable to this source category and 

do not supplant any more stringent control requirements that apply on a case-by-case basis 

under the NNSR or PSD permit programs. 

Discussion of RACT Criteria 

On April 16, 2009, SJVAPCD adopted its “2009 RACT SIP” to demonstrate that RACT is 

implemented for all appropriate activities (see Attachment #5 for relevant pages). In summary, 

SJVAPCD found that Rule 4352 met or exceeded the analogous NSPS, and found no applicable 

CTG, NESHAP or MACT standards. The document also compared Rule 4352 to analogous 

rules in other large California nonattainment areas including South Coast, Bay Area, Sacramento 

and Ventura. These rules contain a 40 ppm limit for non-gaseous fuels. Sacramento Rule 411 

includes a 70 ppm limit at 12% CO2 (about 100 ppm at 3% O2) for biomass fuels. SJVAPCD 

states that these limits are more stringent than Rule 4352, but have not been demonstrated for 

solid fuel-fired units because there are no boilers in the Sacramento area that fire solid fuels. 
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Furthermore, SJVAPCD states that the 40 ppm limit for non-gaseous fuels in ARB’s 

RACT/BARCT guidelines was never intended for application to solid fuel-fired units. 

We concur with SJVAPCD’s conclusion that Rule 4352 implements RACT for units fired with 

biomass fuels for reasons including: 

• The relevant Rule 4352 requirements are more stringent than both 1994 ACT documents 

listed above. ACT documents provide technical information on available controls and 

are often used to help define RACT. 

• No facilities in Sacramento currently operate boilers that meet the 70 ppm limit for 

biomass-fired units in Rule 411, so this limit has not been shown to be technologically 

feasible. (Email from Jorge de Guzman at Sacramento Metropolitan AQMD to Roger 

Kohn at EPA on September 10, 2009). 

• We have no information indicating that the 40 ppm limit for non-gaseous fuels in other 

districts’ rules has been demonstrated to be generally technologically feasible for biomass 

fuel-fired units. 

• According to Attachment #6, all permitted units subject to Rule 4352 are equipped with 

SNCR. We believe SNCR technology generally achieves a RACT level of control for this 

source category as it is effective at reducing NOx emission and is, to our knowledge, the 

only technique that is currently widely available for this source category. 

 

We do not believe, however, that SJVAPCD has adequately demonstrated that the Rule 4352 

NOx emission limits for units fired with MSW (approximately 266 ppm at 3% O2) and for units 

fired with coal/coke and other solid fuels (i.e., solid fuels other than MSW and biomass) (115 

ppm at 3% O2) achieves a RACT level of control for these source categories, for reasons 

including: 

• The 1994 ACT for ICI boilers (Guidance Document #5) indicates that lower NOx 

emissions should be reasonably achievable with SNCR controls that existing units subject 

to Rule 4352 currently have installed. 

• SJVACPD does not provide sufficient information to demonstrate that the emission 

ranges present in the 1994 ACT for ICI boilers are not reasonably achievable or other 

information to demonstrate that Rule 4352 satisfies RACT requirements. 

• Source test data for the one existing MSW facility in the San Joaquin Valley suggests that 

emission limits lower than required by Rule 4352 are reasonably achievable (see 

Attachment #7). In 1994, units 1 and 2 tested at an average of 139 ppm and 129 ppm at 

12% CO2. In 2009, they tested at an average of 146 ppm and 143 ppm at 12% CO2. It is 

not clear why a limit close to those ranges, consistent with the 1994 ACT is not 

appropriate for RACT. 

• Emission limits for permitted coal-burning facilities in Attachment #6 suggest that limits 

lower than contained Rule 4352 are reasonably achievable. Specifically, Attachment #6 

identifies only one existing facility with a permit emission limit above 0.1 lb/MMBtu 

(approximately 75 ppm at 3% O2). 

• For coal fired units, the ACT also states that units with ammonia injection should be able 

to achieve lower emissions than the 115 ppm at 3% O2. 

• While we believe that SNCR may represent RACT for these sources, and the NOx limits 

in the existing rule effectively require SNCR, we nonetheless believe it is appropriate to 
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require more stringent emission limits in Rule 4352 to ensure that facilities maintain good 

operating and maintenance practices consistent with CAA RACT requirements. 

Rule Deficiency 

• SJVAPCD has not demonstrated that the emission limits for units firing MSW fuels or 

other non-biomass solid fuels implement RACT. The NOx emission limits for these 

source categories in Rule 4352 should be lowered to ensure implementation of RACT. 

Alternatively, SJVAPCD may submit additional information to demonstrate that lower 

emission limits are not reasonably achievable. 

Suggested Rule Improvement 

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

Rule 4352: 

1. The term flame stabilization period in Section 2.0 should be clearly defined in the Rule. 

2. Section 5.4.2 should indicate that source test information at the reduced load should be 

included in a request for increased emission limits for units operating at less than 50% of 

the rated heat input. 

3. The term normal operations in Section 6.3.2 should be clearly defined in the Rule or the 

Rule should state that it must be defined in the permit to operate. 

4. The Rule does not specify required controls for direct PM2.5 emissions. These should be 

added in subsequent revisions of the Rule. 

Recommendation 

EPA staff recommends limited approval and limited disapproval of SJVAPCD’s submitted rule 

4352 for incorporation into the San Joaquin Valley portion of the California SIP. 

Attachments 

1. Submitted Rule 4352 (Clean Copy, Adopted May 18, 2006) 

2. Submitted Rule 4352 (Strikeout Copy, Adopted May 18, 2006) 

3. Staff Report (Adopted May 18, 2006) 

4. SIP-approved version of Rule 4352 (Adopted October 19, 1995) 

5. SJVAPCD RACT Demonstration for Ozone SIP, pages 4-61 – 4-68 (Adopted April 16, 

2009) 

6. List of Solid Fired units in SJVAPCD 

7. Source Test Report summaries for MSW facility