UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX 

75 Hawthorne Stmet 

San Francisco, CA 94105 

March 3 1,1999 

Ms. Elaine Chang 

Assistant Deputy Executive Officer 

Office of Planning, Rule Development and Area Sources 

South Coast Air Quality Management District 

2 1865 E. Copley Drive 

Diamond Bar, CA 9 1765-4 182 

Subject: Review of Proposed Amended Rule 21 8 and Proposed Rule 2 18.1 

Dear Ms. Chang: 

Thank you for the opportunity to comment on proposed amended Rule 2 18 (PAR 2 18 - 

December 1 1, 1998) and proposed Rule 21 8.1 (PR 21 8.1 - no date). 

In your letter of September 24, 1998, you requested EPA review PAR 2 18 and PR 2 18.1, 

particularly in "how EPA might perceive the currently proposed absolute de-minimus 

concentration performance specification for Relative Accuracy ...[ and] would EPA state that the 

requirements for PR 2 18.1 are equivalent to 40 CFR 60 requirements for Title V purposes, and 

therefore federally enforceable." 

EPA considers that at medium to high emission limits, PR 21 8.1's relative accuracy 

criteria are equivalent to or are more stringent than the federal standards. However, at very low 

emission limits, (e.g., at less than 5 ppm for NOX limits), PR 21 8.1's relative accuracy criteria 

becomes less stringent than the federal limits. EPA recognizes, however, that relative accuracy 

values at very low levels, such as less than lppm, may not be meaningful due to limitations of 

current technology. The enclosure provides additional comments to PAR 2 18 and PR 2 1 8.1. 

EPA welcomes the opportunity to review PAR 2 1 8 and PR 2 1 8.1. If you have any 

questions about these comments, please do not hesitate to call me at (4 15) 744-1 185 or Stanley 

Tong of my staff at (4 1 5) 744- 1 19 1. 

Enclosure 

cc: John Higuchi, SCAQMD 

. Cindy Castronovo, CARB 

Andrew Steckel 

Chief, Rulemaking Office 
Comments to South Coast Proposed Amended Rule 218 and Proposed Rule 218.1 

General Comment 

1. Absolute de-minimus Value for Relative Accuracy 

EPA considers that at medium to high emission limits, PR 21 8.1's relative accuracy criteria are 

equivalent to, or are more stringent than the federal standards. However, at very low emission 

limits, (e.g., at less than 5 ppm for NOX limits), PR 21'8.1's relative accuracy criteria becomes 

less stringent than the federal limits. EPA recognizes that relative accuracy values at very low 

levels, such as less than 1 ppm, may not be meaningfbl due to limitations of current technology. 

These limitations include the availability and accuracy of low concentration protocol calibration 

gases and the degree of precision of the reference test methods at low concentrations. Therefore, 

EPA does not object to PR 2 18.1's use of an absolute de-minimus value. 

Approvability Issues 

1. Full Span Range 

South Coast should add language to the rule on how to handle spikes. Such language should 

indicate that if a value falls outside the acceptable 111 span range, the value is not valid for 

quantification but must be reported and that the spike may be considered a violation of the 

standard depending on the conditions under which the spike occurred. 

2. Clarifications 

a. Alternative Sampling Locations: PAR 2 1 8.1 @age 2 18.1 - 10, top of page) allows the 

Executive Officer to evaluate and approve alternate shpling locations. South Coast should 

clarify in the rule, the hierarchy that will be used to evaluate and approve alternate sampling 

locations including referencing any applicable guidance document such as Emission 

Measurement Center (EMC) guidance. 

b. Full Span Range: PAR 2 18.1 @age 2 18.1 -,lo, para (c) (ii)) allows an alternate full span range 

(from the 150-200% of concentration limit) to be approved by the Executive Officer. South 

Coast should specify acceptable conditions which would warrant going outside of the full span 

range. 

c. Alternative Certification Methods: PAR 2 18.1 @age 2 18.1-1 9, para (d)(l)(A)) allows the 

Executive Officer to approve alternative certification methods for low concentration gases such 

as 10 ppm NOX or CO. South Coast should clarify in the rule, the hierarchy that will be used to 

evaluate and approve the alternative certification methods. 
Comments to South Coast Proposed Amended Rule 218 and Proposed Rule 218.1 

3. Response time 

PAR 21 8.1 (page 2 18.1-14 para (3)(A) and page 21 8.1-1 8 para (c) (l)(C)) states the response 

time for all analyzers and flow monitors shall not exceed 5 minutes for any new or modified 

CEMS and shall not exceed 10 minutes for existing CEMS. 40 CFR 60, Appendix A, 

Performance Spec 4A for Carbon Monoxide specifies a response time of 1.5 minutes. The 

reason for this short response time is to capture CO spikes which may be present, especially from 

Municipal waste combustors. Longer response times may not capture CO spikes. Unless there is 

a technical limitation, South Coast should include this shorter response time for CO CEMS. 

Recommendations: 

1. QNQC plan: PAR 21 8. EPA recommends that for facilities who chose to continue to 

operate under the existing CEMS option, that QNQC plans be developed and implemented 

within 1 year of the promulgation date of the rule. The QNQC plan should be maintained on site 

and be made available for inspection upon request by District personnel. 

2. Record Retention: PAR 21 8 (page 21 8-1 7 para (e) (1)) states that records shall be maintained 

for a minimum period of two years or as specified by the applicable rule or regulation. EPA 

recommends a five year record retention period rather than the two year period in the rule. This 

would make the record retention period consistent with the statue of limitations. 

3. The rule is silent on quarterly cylinder gas audits. EPA strongly recommends that a quarterly 

cylinder gas audit be required.