### Ø UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX mII1Wj 75 Hawthorne Street San Francisco, CA 94105 March31, 1999
Ms. Elaine Chang Assistant Deputy Executive Officer Office ofPlanning, Rule Development and Area Sources South CoastAir Quality Management District 21865 E. Copley Drive Diamond Bar, CA 91765-4182 Subject: Review ofProposed Amended Rule 218 and Proposed Rule 218.1 DearMs. Chang: Thankyou forthe opportunity to comment onproposed amended Rule 218 (PAR 218- December 11, 1998) and proposed Rule 218.1 (PR218.1

- no date). In your letter ofSeptember 24, 1998, you requested EPAreviewPAR 218 and PR 218.1, particularly in “how EPA mightperceive the currently proposed absolute de-minimus concentration performance specification for Relative Accuracy

. ..[and] would EPA state thatthe requirements for PR 218.1 are equivalent to 40 CFR 60 requirements for Title V purposes, and therefore federally enforceable.” EPA considers that atmedium to high emission limits, PR 218.1’s relative accuracy criteria are equivalentto or are more stringentthanthe federal standards. However, at very low emission limits, (e.g., atless than 5 ppm forNOX limits), PR 218.1’s relative accuracy criteria becomes less stringentthan the federal limits. EPA recognizes, however, thatrelative accuracy values at very low levels, such as less than lppm, may notbe meaningful due to limitations of currenttechnology. The enclosure provides additional comments to PAR 218 and PR 218.1. EPA welcomes the opportunity to review PAR 218 and PR 218.1. Ifyou have any questions aboutthese comments, please do nothesitate to call me at (415) 744-1185 or Stanley Tong ofmy staffat (415) 744-1191. Sincerely, Zi&(7

# 4” Andrew Steckel Chief, Rulemaking Office Enclosure cc: John Higuchi, SCAQMD Cindy Castronovo, CARBComments to South Coast Proposed Amended Rule 218 and Proposed Rule 218.1
General Comment 1. Absolute de-minimus Value forRelativeAccuracy EPA considers that at 

### mediumto high emission limits, PR218.1’s relative accuracy criteria are equivalent to, orare more stringentthan the federal standards. However, at very low emission limits, (e.g., at less than 5 ppm forNOX limits), PR 218.1’s relative accuracy criteriabecomes less stringent than the federal limits. EPA recognizes that relative accuracy values at very low levels, such as less than I ppm, may not be meaningful due to limitations ofcurrent technology. These limitations include the availability and accuracy oflow concentration protocol calibration gases and the degree ofprecision ofthe reference test methods at low concentrations. Therefore, EPA does not objectto PR2 18.1’s use ofan absolute de-minimus value. Approvabiity Issues 1. Full Span Range South Coast should add language to the rule on howto handle spikes. Such language should indicate that ifavalue falls outside the acceptable full span range, the value is not valid for quantification but mustbe reported and that the spike may be considered a violation ofthe standard depending on the conditions under whichthe spike occurred. 2. Clarifications
a. Alternative Sampling Locations: PAR 218.1 (page 218.1-10, top ofpage) allows the Executive Officer to evaluate and approve alternate sampling 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: PAR218.1 (page 218.1-10, para (c) (ii)) allows an alternate full span range (from the 150-200% ofconcentration limit) to be approved by the Executive Officer. South Coast should specify acceptable conditions which would warrant going outside ofthe full span range.
c. Alternative Certification Methods: PAR218.1 (page 218.1-19, para (d)(1)(A)) allows the Executive Officer to approve alternative certification methods for low concentration gases such as 10 ppmNOX or CO. South Coast should clarify in the rule, the hierarchy that will be used to evaluate and approve the alternative certification methods.

C:\JUJLES5OtJTH_C2JS\CMTS2JXDOC 1Comments to South CoastProposed Amended Rule 218 and Proposed Rule 218.1

3. Response time PAR218.1 (page 218.1-14 para (3)(A) and page 218.1-18 para (c) (1)(C)) states the response time for all analyzers and flow monitors shall not exceedS 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 CarbonMonoxide specifies aresponse time of 1.5 minutes. The reason for this shortresponse time is to capture CO spikes which may bepresent, especially from Municipal waste combustors. Longerresponse times may not capture CO spikes. Unless there is atechnical limitation, South Coast should include this shorterresponse time for CO CEMS. Recommendations: 1. QAIQC plan: PAR 218. EPArecommends that for facilities who chose to continue to operate underthe existing CEMS option, that QAIQC plans be developed and implemented within 1 year ofthe promulgation date ofthe rule. The QAIQC plan should be maintained on site and be made available for inspection upon request by District personnel. 2. Record Retention: PAR 218 (page 218-17 para (e) (1)) states that records shall be maintained for a minimum period oftwo years or as specified by the applicable rule orregulation. EPA recommends a five year record retentionperiodratherthan the two yearperiod inthe rule. This would make the record retentionperiod consistent with the statue oflimitations. 3. The rule is silent on quarterly cylinder gas audits. EPA strongly recommends that a quarterly cylinder gas audit be required.

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