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 

Placer County Air Pollution Control District’s 

Rule 246, Natural Gas-Fired Water Heaters 

Prepared by: Idalia Perez 

September 2011 
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Placer County Air Pollution Control District (PCAPCD) 

Submitted Rule 

PCAPCD Rule 246, Natural Gas-Fired Water Heaters: 

§ Adopted: June 19, 1997 

§ Submitted: December 7, 2010 

§ Determined complete: January 13, 2011 

Previous Rule Submittals 

There are no outstanding submittals of Rule 246. 

SIP-Approved Rule 

There is no SIP-approved version of Rule 246. 

Rule Summary 

Rule 246 limits NOx emissions from natural gas water heaters rated below 75,000 btu/hour. The 

rule applies to manufacturers, distributors and sellers and installers of these units. The limits 

proposed in the Rule are: 

§ 50 ng NOx/joule for units in mobile homes; 

§ 40 ng NOx/joule for all other units. 

The rule has a compliance deadline of January 1, 1998. 

Effects on Emissions 

According to documentation sent along with the rule submittal, the District estimates a reduction 

of 23.7 tons of NOx per year, as compared to the emissions in the 1990 inventory, due to the 

implementation of this rule. 

Rule Evaluation 

Generally, SIP rules must be enforceable (see section 110(a) of the Act), must require 

Reasonably Available Control Technology (RACT) for major sources in nonattainment areas 

(see sections 182(b)(2) and 182(f)), and must not relax existing requirements (see sections 110(l) 

and 193). In addition, Section 172(c)(1) of the Clean Air Act (CAA) requires nonattainment 

areas to implement all reasonably available control measures (RACM), including such reductions 

in emissions from existing sources in the area as may be obtained through the adoption, at a 

minimum, of reasonably available control technology (RACT), as expeditiously as practicable. 

Although the PCAPCD regulates an ozone nonattainment area

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(40 CFR 81), submitted Rule 246 

is not subject to RACT requirements because it is applicable to sources that are too small to 

exceed the major source threshold. Because the PCAPCD regulates an ozone nonattainment area 

(40 CFR 81), submitted Rule 246 must fulfill RACM requirements. 

 

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PCAPCD also regulates a nonattainment area under the 2006 24-Hour PM2.5 National Ambient Air Quality 

Standard (NAAQS). 40 C.F.R. § 81.305 (2010). By December 14, 2012, California must submit a revision to the 

State Implementation Plan (SIP) for this nonattainment area that provides for, among other things, implementation 

of all RACM as expeditiously as practicable (including RACT for existing sources). CAA § 172(a)(2)(A), (b) & 

(c)(1), 74 FR 58689 (Nov. 13, 2009). EPA will take action on this RACM demonstration in a separate rulemaking. 
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Guidance and policy documents that we used to define enforceability 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 for 

the Implementation of Title I of the Clean Air Act Amendments of 1990 (the "NOX

Supplement to the General Preamble"), US EPA, 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 

Although submitted Rule 246 is not subject to RACT and at this time we are not making a 

determination of its ability to implement RACT, we note that there are multiple rules for air 

districts in California that have more stringent emissions limits, including South Coast AQMD 

Rule 1121, Bay Area AQMD Rule 9-6 and San Joaquin Valley APCD Rule 4902. 

CAA §172(c)(1) requires nonattainment areas to implement all reasonably available control 

measures, including such reductions in emissions from existing sources in the area as may be 

obtained through the adoption, at a minimum, of RACT, as expeditiously as practicable. Gas 

fired water heaters can emit direct PM2.5, as well as NOx, which is a precursor to both PM2.5 

and ozone. Therefore, PCAPCD must implement RACM for water heaters if those measures will 

advance attainment of the National Ambient Air Quality Standard (NAAQS) for PM2.5 or ozone, 

when considered collectively with other reasonable measures. Additional control measures may 

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

available; and (2) these additional reasonably available measures will advance attainment in the 

area when considered collectively. 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 

District. See 40 CFR §§ 51.1010, 51.912(d). Nonetheless, we note that the current version of 

Rule 246 does not require certain control measures for water heaters in the PCAPCD that appear 

to be "reasonably available" considering technological and economic feasibility, for the reasons 

cited above. 
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Recordkeeping and other compliance provisions in the rule ensure that the requirements are 

adequately enforceable. Lastly, since there is currently no rule in the SIP that regulates this 

source category for PCAPCD, the emission limitations in the submitted rule strengthen the SIP. 

We propose to determine that our approval of the submittal would comply with CAA sections 

110(l) and 193, 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 submittal 

strengthens the SIP as there is no rule for this category currently in the SIP and would insure 

equivalent or greater emission reductions of NOx. 

Suggested Rule Improvements 

Although not currently basis for rule disapproval, EPA recommends that the PCAPCD lower 

emission limits in Rule 246 to be consistent with South Coast Rule 1121 (amended September 3, 

2004) and analogous rules in other areas. 

Recommendation 

EPA staff recommends approval of PCAPCD submitted Rule 246 for incorporation into the 

California SIP. 

Other References 

1. Submitted Rule 246 

2. Staff Report for Rule 246, dated June 2, 1997