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 4902, Residential Water Heaters

Prepared by: Idalia Perez

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

Submitted Rule

SJVAPCD Rule 4902, Residential Water Heaters:

 Adopted: March 19, 2009

 Submitted: April 29, 2009

 Determined complete: July 20, 2009

Previous Rule Submittals

There are no outstanding submittals of Rule 4902.

SIP-Approved Rule

 Adopted: June 17, 1993

 Approved by EPA: February 17, 2004 (69 FR 7370)

Rule Summary

Rule 4902 limits NOx emissions from residential water heaters. 

Rule Amendments 

Rule 4902 was amended to expand the applicability of the rule and strengthen the emission limits 

for NOx.

Section 4 (Exemptions) was changed to eliminate exemptions for pool heaters starting January 1, 

2010.

Section 5 (Requirements) was changed to include the following new NOx limits:

Mobile home water heater – 40 ng NOx/J of heat output (Compliance 1/1/10)

Pool water heater – 40 ng NOx/J of heat output (Compliance 1/1/10)

Other water heaters – 10 ng NOx/J of heat output (Compliance 1/1/10)

Instantaneous water heaters – 14 ng NOx/J of heat output (Compliance 1/1/12)

Other changes were done to improve consistency, clarity and enforceability of the Rule. 

Effects on Emissions

The staff report indicates that Rule 4902 will lead to an approximate reduction of 0.85 tons of 

NOx per day.

Rule Evaluation

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

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

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

requirements, including requirements concerning attainment (see CAA section 110(l)); and must 

not relax existing requirements in effect prior to enactment of the 1990 CAA amendments (see 

section 193). 
Although the SJVAPCD regulates a serious (8-hour) and extreme (1-hour) ozone nonattainment 

area (40 CFR 81), submitted Rule 4902 is not subject to RACT because it is applicable to 

sources that are too small to exceed the major source threshold.

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”).

On April 16, 2009, SJVAPCD adopted its “2009 RACT SIP,” which provides the District’s 

demonstration that RACT is implemented for all appropriate activities. This includes several 

pages discussing Rule 4902 (attached). The Rule was not reviewed to determine its fulfillment of 

RACT thus we are not making a statement of its merit in this regard. 

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

adequately enforceable. The elimination of the exemption for pool water heaters and the 

addition of more stringent NOx emission limits make the amendments a strengthening of the 

SIP. Thus, approval of the submitted rule does not relax the SIP and satisfies CAA §110(l) and 

§193. 

Recommendation

EPA staff recommends approval of SJVAPCD submitted rule 4902 for incorporation into the

California SIP.

Attachments

1. Submitted Rule 4902 (Clean Copy)

2. Submitted Rule 4902 (Strikeout Copy)

3. Staff Report

4. SIP-approved version of Rule 4902

5. SJVAPCD RACT Demonstration for Ozone SIP, pages 4-372 – 4-374