4 The record articles

Too Long; Didn’t Read (TL;DR): What You Need to Know About South Coast AQMD Proposed Revisions to CEMS Requirements

Posted: September 15th, 2022

Authors: Matt C. 


South Coast Air Quality Management District (AQMD) is the regulatory agency responsible for improving air quality for large areas of Los Angeles, Orange, Riverside, and San Bernardino counties in California. To streamline the monitoring requirements across facilities for the forthcoming Regional Clean Air Incentives Market (RECLAIM) Program transition, South Coast AQMD has proposed amendments to Rule 218, and has proposed two new rules, Proposed Rules (PR) 218.2 and 218.3, which are based on Rules 218 and 218.1, respectively. Rules 218 and 218.1 are the existing monitoring rules for continuous emissions monitoring systems (CEMS) applicable to all CEMS that are required by South Coast AQMD, except for CEMS under the existing RECLAIM Program. CEMS that are currently operated under the RECLAIM Program are subject the monitoring requirements in Rules 2011 and 2012. Proposed Rules 218.2 and 218.3 will effectively replace Rule 218 and 218.1 for non-RECLAIM facilities, and Rules 2011 and 2012 for RECLAIM facilities upon exiting RECLAIM.


Proposed Rules 218.2 and 218.3 are proposed to apply as follows:


  • At the time of CEMS certification/recertification between January 1, 2022 and January 1, 2025
  • No later than January 1, 2025

For (former) RECLAIM CEMS:

  • At the time of CEMS certification/recertification after the facility exits RECLAIM
  • No later than 24 months after exiting RECLAIM


As an existing RECLAIM facility:

  • Transition to a command-and-control structure and a five ton per day NOX emissions reduction using Best Available Retrofit Control Technology (BARCT) as soon as feasible, and no later than January 1, 2025. (TL;DR: RECLAIM will not exist after January 1,2025)
  • RECLAIM CEMS currently subject to Rule 2011 and Rule 2012 will be required to transition to Proposed Rules 218.2 and 218.3 after exiting RECLAIM and certifying the CEMS in accordance with Proposed Rules 218.2 and 218.3. For most units, the implementation of Proposed Rules 218.2 and 218.3 CEMS would be staggered based on equipment modifications made to meet NOX emission limits required in landing rules.

As both an existing RECLAIM facility and an existing non-RECLAIM facility:

  • PR 218.3 adds provisions that provide specifications on how to handle data measured below 10% or above 95% of the upper span value, emissions data averaging methods, data substitution methods, data availability requirements, and CEMS out-of-control periods. The data handling requirements in PR 218.3 are unique and are not currently implemented by the South Coast AQMD or other regulatory agencies. These data handling requirements will require DAHS software reprogramming. Some of the more significant changes in the proposed rules include requirements to:
    • Utilize a unique-to-South Coast AQMD data substitution procedure for missing/invalid CEMS data. Data substitution is required when demonstrating compliance with 24-hour or 365-day rolling average mass emission limits. The data substitution procedure detailed in PR 218.3 somewhat aligns with the procedure specified in Rule 1109.1; however, there are several exceptions and considerations unique to PR 218.3 [Paragraph (i)(11)].
  • Utilize a new data procedure for startup or shutdown of missing minute data to determine mass emissions for any startup or shutdown minute with no valid data. The startup/shutdown data substitution procedure is based on the percent of missing data and is also unique to PR 218.3 [Paragraph (i)(13)].
  • Utilize a NOX conversion factor of 1.214 x 10-7 or 1.195 x 10-7 lbs/ft3 to calculate NOX mass emissions for RECLAIM CEMS. Both of the specified NOX conversion factors differ from the commonly used NOX conversion factor of 1.194 x 10-7 lbs/ft3.


January 1, 2025 does sound far away, but by the end of this year, it will only be two years out. Whether you are an existing RECLAIM facility operating NOX CEMS under Rules 2011 and 2012, or a non-RECLAIM facility operating CEMS under existing Rules 218 and 218.1, you will have to comply with the final requirements in Proposed Rules 218.2 and 218.3. Do you have a plan to maintain compliance with your existing or potentially new CEMS? If not, ALL4 can help. Please do not hesitate to reach out to jprendergast@all4inc.com if you have any questions regarding these proposed rules and their impact to you or other CEMS-related questions.


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