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HomeMy WebLinkAboutAQ_F_1000067_20050110_CEM_GenCorr raMrw NCDENR North Carolina Department of Environment and Natural Resources Michael F. Easley, Governor Division of Air Quality William G. Ross,Jr., Secretary January 10,2005 B. Keith Overcash, P.E., Director Mr. Tracy Patterson Air Quality Manager Cogentrix Field Support Office 4411 Crossings Boulevard Prince George, VA 23875 Subject: Monitor Span Requirements in Acid Rain (Part 75) Rule and NSPS Subpart Db-Permit Conditions Facility ID 33/00146; 73/00056; 10/00067 Dear Mr. Patterson: This letter is in response to your December 13, 2004 request for concurrence with your interpretation that it is acceptable to use the NOx span calculations from Acid Rain(Part 75)to satisfy the NOx span requirements in NSPS Subpart Db even though that a different section in subpart Db(40 CFR 60.48b(e) states for NOx monitor to set span value to 1000ppm. After reviewing the information contained in your letter as well as the regulations cited in your letter including 40 CFR Part 75, Appendix A 2.1.2.1 and 2.1.2.3, 40 CFR 60.48b(e) and 60.48b(b)(2), the Division of Air Quality concurs with your interpretation that the span value calculated from Part 75 rule is appropriate to be used to meet the NOx span requirements for Subpart Db as long as the NOx CEM is installed to meet both rules. In fact,this interpretation is consistent with 40 CFR 60.48b(b)(2). We also agree that the span setting from Part 75 is a more stringent quality assurance provision and would provide a"tighter tolerance" for daily calibration checks, linearity and relative accuracy tests. As stated in 40 CFR 60.48b(e), please note that a span value of 1000ppm would be required for NOx CEMs that are not installed to meet Part 75 regulations. If you have any questions regarding this letter please contact me at(919)733- 1467. Sincerely, Dennis U. Igboko Environmental Engineer CC: Michael Aldridge Wayne Cook—WIRO Ernie Fuller-RRO Central Files -Brunswick Co. Edgecombe Co. Person Co IMPAQ—Documents—3300146 (Rocky Mount) 7300056 (Roxboro) 1000067 (Southport) One 1641 Mail Service Center,Raleigh,North Carolina 27699-1641 NorthCarolina 2728 Capital Blvd.,Raleigh, North Carolina 27604 Phone: 919-733-1728/FAX 91 9-733-1 81 2 1 Internet: www.ncair.org Naturally An Equal Opportunity/Affirmative Action Employer—50%Recycled/30%Post Consumer Paper Cogentrix Cogentrix Field 4411 Crossings Boulevard Support Office Prince GmiVe,VA 2387.5 304-541-4246 Fax 804-541-7961 December 13, 2004 Mr. Dennis Igboko Division of Air Quality North Carolina Department of Environment and Natural Resources 1641 Mail Service Center Raleigh, NC 27699-1641 Subject: Permit Conditions —Monitor Spans Cogentrix Facilities in North Carolina Dear Mr. Igboko, This letter is submitted to request your assistance in providing proper clarification and interpretation of the monitoring requirements for the continuous monitoring systems at our facilities in North Carolina. In our telephone discussion regarding this condition, the current specification presents some confusion for compliance inspectors when interpreting the proper span settings for the nitrogen oxides monitors that are installed to provide data for both NSPS Subpart Db and 40 CFR 75 emission monitoring. The requirements of 40 CFR 75 Appendix A 2.1.2.1 and 2.1.2.3 require the facility to set the calibrated span of the NOx monitor to a value between 1 and 1.25 times the maximum potential concentration (MPC) as determined from several options. Our review of the previous 12-months of quality assured data, as required by 40 CFR 75 indicates that the MPC for this facility is 290 ppm of NOx. Following the requirements of 40 CFR 75, the calibrated span for the monitors must be set to 400 ppm. As we discussed, the requiferneats of 40 CFR 75 are rnore stringent than the requirements from 40 CFR 60.48b(e) of 1000 ppm for the analyzer span. As stated by 40 CFR 60.48b(b)(2), if the owner or operator has installed a nitrogen oxide emission rate continuous emission monitoring system (CEMS) to meet the requirements of part 75 and is continuing to meet the ongoing requirements of part 75, that CEMS may be used to meet the requirements of this section. The allowance does not allow the use of substituted data to meet the reporting requirements of 60.49b. Certainly, using the lower span setting and following the more stringent quality assurance requirements of 40 CFR 75 is exactly what 60.48b(b) is allowing. The part 75 QA requirements from using a lower span setting will require a tighter tolerance for daily calibration drifts as well as the quarterly QA tests for linearity and for the annual relative accuracy testing. Changing the span to the lower setting will allow us to keep the Mr. Dennis Igboko Letter December 13, 2004 Page 2 monitoring system operating in accordance with the Part 75 rules and also satisfy the NSPS monitoring requirements. We are requesting that you provide a written confirmation of this interpretation of the NSPS monitoring requirement. Your concurrence will remove any uncertainty from the demonstration of compliance with both sets of regulations and simplify the review of compliance determination for NCDENR inspection personnel. Thank you for your time during our telephone discussion on this matter and for processing this request. As I mentioned, we will need to make the change to the span value in our system prior to the annual Relative Accuracy Tests currently scheduled for February of 2005. Please call me at (804) 541-4246 if you have any questions or require additional information. S in�erely, Aoz r"',—" Tracv L. Patterson Air Quality Manager cc: Gary Willer, Gary Hickey—CNC Mark Casper—Cogentrix File EHS 2.1.2