Continuous Emission Monitoring. James A. Jahnke
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Records of calibration checks, adjustments, and maintenance performed on the monitoring system
Problem areas in source operation and/or control equipment operation should present themselves on thorough evaluation of these items. When the documentation is unclear or incomplete, the facility should be contacted for clarification of the problem areas, perhaps avoiding more extensive agency action.
Level 2
On the second level, for more frequent exceedances or greater CEM system downtime, a request may be issued for corrective action to be taken within 30 days.
Level 3
If the EER reports are repeatedly late, indicate operational problems at the plant, or if emission levels are substantial, a warning letter requesting that the issues be resolved within 30–90 days may be issued. Alternatively, these deficiencies could be used to trigger an inspection by the agency that may include both an examination of the emission control system operation and the emission monitoring program. The inspection could take the form of a systems audit, not requiring the use of test equipment or gases.
Based on the findings and observations of the on‐site inspection, it may be necessary to conduct limited testing on the CEM system to check that it is operating properly. Performance audit procedures may be conducted, where the CEM system is challenged with certified audit gases and/or filters to check data validity.
Level 4
This level of activity determines the source performance with respect to the compliance test methods. If the tests show that the source is not in compliance with emissions limits, the test data can be used to support further legal action.
The following potential violations (among others) may be indicated from an excess emission report, supplementary information accompanying the report, or information requested upon the review (VADEQ 2018; U.S. EPA 2014c):
Exceeding the emission limit
Failure to meet emission control percentage reduction requirement
Failure to meet monitoring availability specification (as applicable in rule or permit)
Control equipment operation and maintenance deficiencies
Failure to conduct required, periodic CEM performance evaluations (RATAs, CGAs, Linearity Tests)
Failure to write or implement a CEM system QA/QC Plan
Failure to follow permit recordkeeping and reporting requirements
Compliance Monitoring Systems – Using CEM Systems for Direct Compliance
The use of CEM systems has evolved in other ways for enforcement purposes. The continuous record can be used directly to establish whether the source is in violation of the standard if a compliance CEM system is legally mandated. The CEM system becomes a “compliance monitoring” system, in contrast to a “compliance indicating” system. In this instance, CEM systems can provide an agency with legally enforceable data to issue fines or other penalties if the source is not complying with agency regulations or emissions standards (Hellwig 1980). Much like issuing a speeding ticket, if the source is over the limit, a fine is essentially automatic.
In the United States, individual states are allowed to develop regulations more stringent than the federal requirements and, as early as 1969 (McKee 1974), mandated CEM systems to be the compliance method. States have also used source operating permits, variances, compliance orders, and other regulatory tools to require the installation of CEM systems for this purpose. Data from CEM systems can be considered legally enforceable data by using these mechanisms.
The federal government has gradually instituted the use of CEM systems for compliance monitoring. The first of such regulations was promulgated for nonferrous smelters (copper, lead, and zinc smelters, Subparts P, Q, and R) in 1976. Continuous emission monitors were established here as the reference test method, but only during periods of time specified as a compliance test period. Only the data obtained during the scheduled period are considered compliance data; otherwise, the CEM system data are regarded as excess emission monitoring data. A much clearer use of CEM systems as compliance monitoring systems came with the promulgation of the NSPS for the Subpart Da Electrical Utilities (73 MW or larger utilities constructed after 18 September 1978). This promulgation (June 1979) requires the installation of SO2 CEM systems to monitor both compliance with emission standards and the SO2 removal efficiency of the emission control systems. Similar requirements have since been instituted for other source categories.
In one important ruling in 1987, EPA allowed the use of opacity monitors as a compliance test method, in lieu of the visible emissions observer, but only if the plant operator chose the option (52 FR 9778 26 March 1987 and 40 CFR 60.7. 60.11, and 60.13). Many states now specify the use of opacity monitors as the compliance method and do not offer such an election by the source operator. For specific applications, individual state requirements should be reviewed.
Continuous monitoring systems (CMS) required for sources in the air toxics standard of Part 63 are considered to monitor source compliance, or otherwise determined by the Administrator to be compliance monitors (§63.6). This includes continuous parametric monitoring systems used as the CMS.
COMPLIANCE ASSURANCE MONITORING AND THE CREDIBLE EVIDENCE RULE
The distinctions between compliance indicating and compliance monitoring systems are the result of environmental agency policy development since 1971. In the late 1980s, policy direction began to shift toward the use of CEM systems for compliance monitoring, with many new regulations specifically stating that CEM systems were to be used for direct enforcement. Then, in response to the 1990 CAAA requirement that major stationary sources submit certifications of compliance with pollutant emission limitations, the compliance assurance monitoring (CAM) rule was developed (U.S. EPA 2020j). As discussed earlier, the CAM rule focuses on monitoring the operation and maintenance of air pollution control equipment, with the assumption that this monitoring will indicate the compliance status of the source.
The CAM rule goes back to the concept of monitoring to indicate compliance or noncompliance. CAM data obtained from a continuous monitor or a parameter monitoring technique would not be used directly but would serve in further negotiations similar to those used in the evaluation of excess emission reports. But the question remains whether CAM data are enforceable data. The answer lies in the credible evidence rule, which was promulgated separately from the CAM rule, but is viewed by EPA (U.S. EPA 1997a, b) as complementing the rule.
The credible evidence rule is relatively concise, stating:
For the purpose of submitting compliance certifications or establishing whether or not a person has violated or is in violation of any standard, nothing shall preclude the use of any credible evidence or information relevant to whether a source would have been in compliance with applicable requirements if the appropriate performance or compliance test or procedure had been performed. [emphasis added]
The rule allows CEM data to be used in litigation, whether the data comes from a compliance indicating CEM system, a compliance monitoring system, or a compliance assurance monitoring (CAM) system (Figure 2‐6).
The key to using the data for enforcement is the ability to show that a relationship exists between the monitoring data and the reference (test) method specified for the pollutant in question, for the source in question. A certified CEM system that has passed a relative accuracy test to meet performance specifications or a parameter correlated to performance test data would pass this relationship test. In other cases, arguments and further information might be required in the course of litigation.