UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX AIR DIVISION

Technical Support Document 

EPA’s Direct Final Rulemaking

for the

California State Implementation Plan

South Coast Air Quality Management District Rule 1112.1,

Emissions of Particulate Matter and Carbon Monoxide from Cement Kilns

Prepared by: Christine Vineyard 

August 2013
2

AGENCY: South Coast Air Quality Management District (SCAQMD)

Rule 1112.1: Emissions of Particulate Matter and Carbon Monoxide 

from Cement Kilns

SIP Approved Rule: July 02, 1998

Submitted Rule: Adopted - December 4, 2009

Submitted - July 20, 2010

Completeness: August 25, 2010

I. Rule Summary – Rule 1112.1 has been amended to include carbon monoxide (CO) 

limits in addition to the existing particulate matter (PM) limits. For CO, two alternative 

methods of compliance are added, as well as updated compliance procedures and test 

methods.

II. Background – The rule amendment seeks to acknowledge the air quality benefit of 

reducing NOx emissions by allowing California Portland Cement Company (CPCC)

flexibility in controlling CO emissions. 

Currently, CPCC is the only facility in the SCAQMD manufacturing cement and thus 

subject to this rule. The facility is a RECLAIM source subject to significant NOx 

requirements and has undertaken a process to reduce NOx from two on-site kilns. The 

process involves injection of used tires into the cement kiln. When tires are introduced 

into the kiln, the oxygen concentration is reduced, thus also reducing the formation of 

NOx. While this process modification has had a beneficial impact in reducing NOx, 

there are occasional spikes in CO emissions exceeding the current SCAQMD Rule 407, 

Liquid and Gaseous Air Contaminants, CO threshold: 2,000 ppm by volume measured 

on a dry basis, averaged over 15 consecutive minutes. 

The air basin does not meet the air quality standards for either ozone or particulate 

matter. However, the air basin is designated attainment for the federal ambient CO 

standard. Since NOx is a precursor of both PM-10 and ozone, the reduction of NOx 

emissions is a priority for the air basin and the facility. CPCC asked SCAQMD for 

assistance in structuring a compliance strategy for CO specific to cement kiln operations

with low NOx emissions. The District examined many options including a combination 

of lowering the emissions threshold in conjunction with an increased averaging period. 

Three emission scenarios were modeled (for each scenario, both kilns were assumed to 

be emitting 6,000 ppm of CO simultaneously when uncontrolled): 

• 2000 ppm (existing rule limits, which represents the baseline conditions for 
3

both 1-hour and 8-hour averaging times pursuant to Rule 407;

• 1,900 ppm (Amended Rule 1112.1 for the 1-hour and 8-hour averaging 

times); and

• 6000 ppm (facility’s maximum 1-hour emissions, used to ensure a worse-case 

analysis for the 1-hour averaging time under Amended Rule 1112.1).

The modeling showed no significant impact on ambient CO concentrations even when 

the kilns operated at a 6,000 ppm sustained emissions rate for an hour. As a result, 

SCAQMD staff made the recommendation that Rule 1112.1 be amended to include:

1) Two alternative CO limits in addition to the current particulate limits:

a. Comply with the current limit of Rule 407(a)(1); or

b. Comply with a new standard of 1,900 ppm concentration limit averaged over 8 

hours and a prohibition against exceeding a 6,000 ppm threshold during any 

consecutive 15 minute averaging period. (It was determined that this dual standard was 

more stringent overall than the general 2,000 ppm limit and will ensure no significant 

ambient air quality impacts).

2) Updated compliance procedures:

a. Measuring, monitoring and recordkeeping of CO emissions from the cement 

kiln shall be conducted according to the provisions of District Rule 218 - Continuous 

Emission Monitoring (approved into the SIP on July 8, 2010 – 75 FR 32293).

b. A District approved Continuous Emissions Monitoring System (CEMS) for CO 

and oxygen (O2) must be installed no later than December 31, 2009, or prior to 

commencement of operation for sources beginning operation after December 4, 2009, 

and operated according to the provisions of District Rule 218.

c. The CEMS certification tests and other sampling, analysis, and reporting shall 

be conducted by a laboratory that has been approved under the District Laboratory 

Approval Program (LAP) for the cited District reference test methods, where LAP 

approval is available. For District reference test methods for which no LAP program is 

available, the LAP approval requirement shall become effective one year after the date 

that the LAP program becomes available.

3). Updated test methods:

a. CO emission concentration shall be determined according to the procedures 

in District Source Test 100.1.

b. PM emissions shall be determined according to the procedures in District 

Source Test Method 5.3.

c. Other test methods may be used as determined to be equivalent and approved 

before the test in writing by the Executive Officer, the California Air Resources Board, 

and the United States Environmental Protection Agency.
4

III. Rule Evaluation

1. Enforceability - CAA § 110(a)(2)(A) states that regulations submitted to EPA for 

SIP approval must be clear and legally enforceable. The requirements for 

controlling CO and PM in the rule revision are well defined and enforceable.

2. Stringency - Revised Rule 1112.1 adds CO requirements to existing PM 

requirements for CPCC. Nothing in the CAA imposes specific requirements with 

respect to the stringency of the CO restrictions in this rule because the area is in 

attainment for CO. There are no changes to the PM requirements of this rule 

and we are not evaluating the rule with respect to PM stringency as part of this 

action. 

3. Anti-Backsliding - CAA §110(l) and §193 restrict SIP revisions from relaxing 

existing requirements. The submitted rule revision strengthens the SIP by 

establishing alternative limits for CO which allow reduced NOx emissions. The 

modeling and environmental assessment shows there will be no increase in CO 

emissions as a result of this revision so our approval of this rule is consistent with 

CAA §110(l) and §193 because we do not expect any impacts to South Coast’s 

ongoing efforts to maintain attainment with the CO NAAQS and attain the Ozone 

and PM NAAQS. 

IV. Recommendation

Since Rule 1112.1 contains no deficiencies and fulfills all relevant CAA requirements 

including those in §110 and §193, EPA proposes full approval.

V. References

1. SCAQMD Rule 1112.1, Emissions of Particulate Matter and Carbon Monoxide from

Cement Kilns, amended December 4, 2009.

2. “Issues Relating to VOC Regulations Cutpoints, Deficiencies, and Deviations,”

(a.k.a., Bluebook) EPA OAQPS, May 25, 1988.

3. Rule 1112.1 Final Staff Report (from rule adopted December 4, 2009), SCAQMD 

December 2009.