UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX AIR DIVISION

Technical Support Document 

for

EPA’s Direct Final Rulemaking

for the

California State Implementation Plan

Antelope Valley Air Quality Management 

Rule 431.1 Sulfur Content of Gaseous Fuels

Prepared by: Stanley Tong

June 2013
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RULE IDENTIFICATION -

Agency: Antelope Valley Air Quality Management District (AVAQMD)

SIP Approved Rule: South Coast Air Quality Management District (SCAQMD) 

Rule 431.1 – Sulfur Content of Gaseous Fuels

Amended – May 6, 1983

Submitted – July 19, 1983

EPA Approved – October 19, 1984 (49 FR 41028)

Superseded Submittal: SCAQMD Rule 431.1 – Sulfur Content of Gaseous Fuels 

Amended – November 17, 1995 (South Coast AQMD)

Submitted – January 31, 1996

Subject of this TSD: AVAQMD Rule 431.1 – Sulfur Content of Gaseous Fuels

Amended – August 21, 2012

Submitted – April 22, 2013

BACKGROUND – On July 1, 1997 the Antelope Valley Air Pollution Control District 

(AVAPCD) was formed and assumed all air pollution control responsibilities from the 

South Coast Air Quality Management District (SCAQMD) for the areas of Los Angeles 

County outside the South Coast Air Basin.1 All SCAQMD rules in effect at the time,

including Rule 431.1, remained in effect under the newly formed AVAPCD. On January 

1, 2002, the Antelope Valley Air Quality Management District (AVAQMD) replaced the 

AVAPCD.

Rule 431.1, Sulfur Content of Gaseous Fuels, limits the sulfur content of fuels such as 

landfill gases, sewage digester gases, refinery gases and other gaseous fuels. On 

October 19, 1984 (49 FR 41028) we approved SCAQMD Rule 431.1 into the SIP. At 

that time, sulfur limits in SIP approved Rule 431.1 were: 1) 800 parts per million (ppm)

as hydrogen sulfide for burning or discharge to any fuel gas system/vent gas disposal 

system; 2) 250 ppm for selling any landfill or sewage digester gases; and 3) 80 ppm for 

selling of all other gases. These SIP approved limits became a part of AVAQMD's SIP 

until such time the District amended the rule and those amendments were approved 

into the SIP.

SCAQMD amended Rule 431.1 several times between 1983 and 1997, prior to the 

formation of AVAQMD, but only the 1995 amendments were submitted for SIP 

approval. Since Antelope Valley separated from South Coast in 1997 and EPA had not 

approved the 1995 amendments for Rule 431.1 into the SIP prior to its separation, the 

1983 amendments for Rule 431.1 continue to be the applicable SIP rule for AVAQMD. 

 1 Antelope Valley Air Quality Management District, Final Staff Report, Amendment to Rule 431.1 – Sulfur 

Content of Gaseous Fuels, Adopted on 08/21/2012, page 1.
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AVAQMD’s current submittal updates the rule to more closely match the current version 

of SCAQMD Rule 431.1 (amended June 12, 1998). It amends rule language, updates

SO2 limits, and deletes obsolete exemptions. It also adds new sections describing the 

rule’s purpose, and specifies monitoring, reporting and recordkeeping requirements and 

authorized test methods.

AVAQMD's staff report states that some landfill operators have been unable to cost 

effectively meet Rule 431.1's sulfur limit of 40 ppm and have entered into compliance 

agreements with the District.

2 The current amendment reverts the 40 ppm locally 

enforced limit back to the 250 ppm SIP limit for sulfur emissions from landfill gas.

RULE SUMMARY - Rule 431.1 limits the sulfur content of gaseous fuels. Its purpose is 

to reduce emissions of sulfur oxides from the combustion of landfill, sewage digester, 

refinery, and other gases. We compared the submitted rule against the SIP approved 

rule amended on May 6, 1983. The 2012 amended rule:

1. Applies to the burning, transferring, selling, or offering for sale of any gaseous 

fuel containing sulfur compounds in excess of 16 ppm calculated as hydrogen 

sulfide in stationary equipment requiring a permit to operate in the AVAQMD.

2. Adds sections to specify the purpose, applicability, monitoring requirements, 

reporting and recordkeeping requirements, and test methods.

3. Revises the sulfur limits as follows:

4. Adds requirements for: continuous emission monitoring systems (CEMS) used to 

determine SOx emissions after burning a fuel; and for continuous fuel gas 

monitoring systems (CFGMS) used to monitor the sulfur content of a fuel prior to 

burning it. Adds an option for landfills and sewage digesters to use an alternative 

 2 AVAQMD Final Staff Report, Amendment to Rule 431.1 – Sulfur Content of Gaseous Fuels, Adopted on 

8/21/12, page 2.

5/6/1983 SIP Rule 8/21/2012 Amendments

Selling gaseous fuels other 

than landfill/sewage digester 

gases

80 ppm 40 ppm 4-hr average

Selling landfill gas 250 ppm 250 ppm daily average

Selling sewage digester gas 250 ppm 40 ppm daily average 

OR

40 ppm monthly average and

500 ppm 15-minute average

Burning or discharging to any 

fuel gas system/vent gas 

disposal system

800 ppm Refinery gas: 40 ppm 4-hr average

Landfill gas: 250 ppm daily avg.

Sewage Digester gas: 

40 ppm daily average 

OR 

40 ppm monthly average and

500 ppm 15-minute average

Other gases 40ppm 4-hr average
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monitoring method provided the alternative monitoring method has been 

approved by the District, California Air Resources Board and US EPA. 

5. Lowers the sulfur emissions threshold for facilities to be considered exempt. The 

previous SIP approved rule exempted facilities with emissions less than 30 

pounds per day. The current submittal reduces this to 5 pounds per day of total 

sulfur compounds calculated as hydrogen sulfide.

6. Removes exemptions for:

a. Fluid catalytic cracking unit regeneration gases (Rule 1105 rescinded 

4/21/98).

b. Combined unit gases from an air pollution control system for steam drive oil 

wells (Rule 1148 rescinded 1/20/98).

c. Gases vented during refinery turnaround (Rule 1123 rescinded 11/17/97)

d. Gases vented to a control system (Rule 466 rescinded 6/17/08)

e. Gaseous fuels from which the gaseous products of combustion are used as 

raw materials for other processes. 

f. Vent gas streams, excluding coker blowdown, which have been connected to 

fuel gas or vent gas disposal systems.

EVALUATION CRITERIA - The following document was used to evaluate the submitted 

rule.

1. SO2 Guideline Document EPA-452/R-94-008, February 1994.

EPA EVALUATION - A summary of our evaluation follows.

1. The submitted rule was evaluated for consistency with the Clean Air Act and US 

EPA rulemaking policy as outlined in SO2 Guideline Document EPA-452/R-94-

008, February 1994.

2. AVAQMD, which is within the Mojave Desert Air Basin and Los Angeles County,

is in attainment3 for the 1971 140 ppb SO2 24-hour primary standard and 30 ppb

annual standard. The primary standard was revised on June 22, 2010 (75 FR 

35520) to 75 ppb for 1-hour daily maximum concentrations averaged over 3 

years.

4

 3 40 CFR 81.305, July 1, 2012 edition.

4 1-hour standard is the 3-year average of the 99th percentile of the yearly distribution of 1-hour daily 

maximum SO2 concentrations. (http://www.epa.gov/ttnnaaqs/standards/so2/s_so2_history.html)
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3. On June 20, 2011, California submitted its recommendation that the Mojave 

Desert Air Basin, including Antelope Valley, be designated "attainment" for the 

2010 SO2 1-hour primary standard. California's submittal states that ambient air 

quality monitoring in the Mojave Desert Air Basin shows a 2009 1-hour SO2

design value of 10 ppb, well below the federal standard of 75 ppb. 

The California Air Resources Board (CARB) also states there have been no 

violations of the federal 1-hour SO2 standard measured over the last two 

decades, and violations are not expected to occur in the future.5

4. A review of the air quality statistics reports6 for 2009 – 2012 indicates ambient 

SO2 concentrations of 12 – 25 ppb for Los Angeles County. These concentrations 

are below the 1971 and 2010 primary SO2 federal standards.

In a February 6, 2013 letter from EPA Region 9 to California, we state that “EPA’s 

review of the most recent monitored air quality data from 2009 – 2011 shows no 

violations of the 2010 SO2 standard in any areas in California.” At this time, EPA 

is not designating areas of California for the 2010 primary SO2 National Ambient 

Air Quality Standards.

5. AVAQMD's staff report states the 2012 amendments reverts Rule 431.1's 40 ppm 

landfill gas sulfur limit back to 250 ppm for the sale of landfill gas. The District 

states this is not a relaxation of the SIP because the current SIP limit is 250 ppm 

and the amendment contains similar requirements as found in SCAQMD Rule 

431.1 amended June 12, 1998.

7

As shown under the Rule Summary section above, the current SIP approved 

limits for sulfur compounds is 80-250 ppm for the selling of gaseous fuel and up 

to 800 ppm sulfur for burning or discharge of fuel. AVAQMD's 40 ppm limit is a 

locally adopted limit that had not been submitted by AVAQMD for SIP approval.

The amended rule reduces the sulfur limit for selling sewage digester gas from 

250 ppm down to (1) 40 ppm (daily average) or (2) 40 ppm (monthly average) and 

up to 500 ppm averaged over 15 minutes. The first option, a 40 ppm daily 

average, is clearly more stringent than the existing 250 ppm SIP limit. The second 

option, a 40 ppm monthly average combined with a 500 ppm 15-minute average 

allows short term intermittent emissions to exceed the existing 250 ppm SIP limit. 

We do not believe the short term 500 ppm 15-minute average would adversely 

impact the District's ability to maintain the SO2 National Ambient Air Quality 

Standard (NAAQS) for the following reasons: 

 5 Letter from CARB (James Goldstene) to US EPA Region 9 (Jared Blumenfeld) dated June 20, 2011, 

page A-32

6 http://www.epa.gov/airquality/airdata/ad_rep_con.html

7 AVAQMD Final Staff Report, Amendment to Rule 431.1 – Sulfur Content of Gaseous Fuels, Adopted on 

8/21/12, page 13.
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1) a 40 ppm monthly average effectively limits a facility from emitting 500 

ppm more than two days per month before it will exceed the 40 ppm 

monthly average limit; 

2) District staff indicated there are two publicly owned treatment works and 

to their knowledge, the sewage digester gases are burned or flared (800 

ppm existing SIP limit) and are not sold (250 ppm existing SIP limit)8; and 

3) AVAQMD is in attainment for the 1971 primary SO2 NAAQS, and 

California points out that for the 2010 SO2 primary standard, ambient air 

quality monitoring in the Mojave Desert Air Basin shows a 2009 1-hour SO2

design value of 10 ppb, well below the 2010 federal standard of 75 ppb 

and that there have been no violations of the federal 1-hour SO2 standard 

measured over the last two decades, and violations are not expected in the 

future.9 Since AVAQMD is in attainment for the SO2 NAAQS, Rule 431.1 is 

not a required SIP submittal.

6. Our review of Rules 431.1 for SCAQMD and AVAQMD indicates the other sulfur 

limits are identical between the two air districts except for the landfill gas

category. AVAQMD's amendment limits the daily average landfill sulfur gaseous 

emissions to 250 ppm compared to SCAQMD's 150 ppm limit. AVAQMD's staff 

report includes an analysis demonstrating it is not cost effective to install controls 

to reduce emissions to below 150 ppm.10 Other sulfur limits were strengthened 

from the previous SIP approved rule.

7. AVAQMD estimates a maximum SOx emissions shortfall of approximately 10 

pounds per day (~2 tons per year) when reverting the locally adopted 40 ppm limit 

back to 250 ppm. Since the existing SIP limit is 250 ppm, we do not consider this 

a SIP relaxation.

8. On October 14, 2011 and April 26, 2012 EPA submitted comments to AVAQMD's

draft amendments to Rule 431.1. We generally accept AVAQMD's responses and 

clarifications to our comments and highlight two areas below for further 

discussion.

a. Our October 14, 2011 letter recommended including language to limit the number 

of allowed breakdowns for CEMS and CFGMS. 

AVAQMD responded that excess breakdowns would be prevented by a facility's 

operating permit because CEMS and CFGMS are required to be maintained in 

 8 Personal communications Chris Anderson (AVAQMD) and Stanley Tong (EPA Region 9) 6/26/13.

9 Letter from the California Air Resources Board (James Goldstene) to EPA Region 9 (Jared Blumenfeld) 

dated June 20, 2011, Page A24-32.

10 AVAQMD Final Staff Report, Amendment to Rule 431.1 – Sulfur Content of Gaseous Fuels, Adopted on 

8/21/12, page 13 and Appendix C.
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good operating condition. We also determined that breakdown of CEMS and 

CFGMS should be minimized under Rule 431.1 because continuous monitoring 

systems are subject to Rules 218 and 218.1 which require them to have a 95% 

availability.

Suggestion for Future Evaluation:

b. Our letter of April 26, 2012 recommended revisiting the Best Available Control 

Technology (BACT) analysis at a later date to consider whether or not carbon 

adsorption being tested under Puente Hills Landfill's Experimental Permit to 

Construct is cost effective to meet a 150 ppm limit.

AVAQMD responded that the District may consider carbon adsorption as a 

possible BACT control technology depending on the results of an evaluation of its 

use to control H2S at the Puente Hills landfill. We are including this discussion as 

a reminder to evaluate carbon adsorption the next time Rule 431.1 is amended.

EPA ACTION –

The submitted Rule 431.1 strengthens the SIP by lowering the sulfur emission limits for 

selling landfill and other gases from the 1983 SIP approved rule. It also lowers the 

sulfur emission limit for the burning of refinery, landfill gas, sewage digester gas and 

other gases. It slightly increases the limit for selling sewage digester gases by allowing 

a 40 ppm monthly average and 500 ppm 15-minute average. The District clarifies that 

sewage digester gases are not sold, but are flared, and that the limit for the burning or

flaring of these gases is being reduced from 800 ppm down to 40 ppm.

AVAQMD states there is a maximum SOx emissions shortfall of approximately 10 

pounds per day (~2 tons per year)

11 when changing from a limit of 40 ppm to 250 ppm 

as Hydrogen Sulfide. The 40 ppm limit, while locally enforceable, is not the SIP 

approved limit. The SIP limits include 250 ppm for selling landfill and sewage digester 

gases and 800 ppm for burning or discharge of gases, so we do not consider this a SIP 

relaxation.

Rule 431.1 is not a required SIP submittal since (a) the District is in attainment for the 

1971 primary SO2 standard; (b) the ambient SO2 concentrations from 2009 – 2012 are 

below the 2010 primary standard; and (c) EPA has not designated areas in California at 

this time for the 2010 primary SO2 NAAQS.

The rule largely fulfills the relevant CAA §110 and part D requirements. EPA staff 

recommends approval of Rule 431.1 pursuant to CAA §110(k)(3) and §301(a).

REFERENCES -

1. SO2 Guideline Document EPA-452/R-94-008, February 1994.

http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000H22J.txt

 11 AVAQMD Final Staff Report, Amendment to Rule 431.1 – Sulfur Content of Gaseous Fuels, Adopted on 

08/21/2012, page C-7.
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2. SCAQMD Rule 431.1 Sulfur Content of Gaseous Fuels, amended May 6, 1983

3. AVAQMD Rule 431.1 Sulfur Content of Gaseous Fuels, amended August 21, 

2012.

4. AVAQMD Final Staff Report, Amendment to Rule 431.1 – Sulfur Content of 

Gaseous Fuels, Adopted on 8/21/12.

5. SCAQMD Rule 431.1 Sulfur Content of Gaseous Fuels, amended June 12, 

1998.

6. Letter from CARB (James Goldstene) to EPA Region 9 (Jared Blumenfeld) dated 

June 20, 2011. www.arb.ca.gov/desig/so2letr.pdf

7. Federal Register 75 FR 35520, June 22, 2010 Final Rule for SO2 primary 

standard of 75 ppb over 1-hour.

8. Personal communications Chris Anderson (AVAQMD) and Stanley Tong (EPA 

Region 9) regarding whether sewage digester gases are sold. 6/26/13.