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A Few Thoughts About the Use of Electrostatic Precipitator (ESP) Models
Under the Compliance Assurance Monitoring (CAM) Rule

Richard McRanie
RMB Consulting & Research, Inc.
5104 Bur Oak Circle
Raleigh, NC 27612

With the support of the Utility Air Regulatory Group (UARG) and the Electric Power Research Institute (EPRI), RMB has been working for more than four years on regulatory and technical issues associated with the Compliance Assurance Monitoring (CAM) rule and its defunct predecessor, the Enhanced Monitoring (EM) rule. While we believe that electrostatic precipitator (ESP) performance models will be a valuable tool to respond to the CAM rule requirements, their capability and applicability have not yet been demonstrated. RMB has been careful in its interface with EPA, utility industry groups and individual utilities to not oversell the capability of models until demonstration tests have been completed. We believe that utilities should exercise the same level of caution and patience. It is very important to recognize that there are strategic regulatory implementation issues as well as technical issues to consider in using ESP models (or any other parametric procedure) under CAM. In addition, there are CAM approaches for ESPs other than models that may be more appropriate for certain ESPs and these approaches should be carefully evaluated. RMB, through the EPRI ESP CAM Protocol Tailored Collaboration project, is trying to address all of these issues - it is our intent that the use of all CAM compliance approaches, including ESP models, be as painless as possible.

To refresh your memory, the original EM proposed rule suggested that ESPs be regulated by a procedure that we now call "test and cap." In essence, an ESP compliance test was performed and, if it showed compliance, the utility was allowed to claim in compliance operation as long as the opacity during subsequent operation did not exceed the opacity during the compliance test plus 2% opacity (absolute). (This option is still available under CAM if someone desires to use it.) In most cases, the "test and cap" procedure would have imposed opacity limits well below those historically allowed, resulting in a significant reduction in operational flexibility, especially for those ESPs with considerable compliance margin. The proposed EM rule had many other problems with stringency and cost impact on a wide range of industries. EPA was faced with a firestorm of opposition and quickly restructured the rulemaking approach. The rulemaking responsibility was moved from the Enforcement Branch to the Office of Air Quality Planning and Standards. The name was changed from EM to CAM and the compliance approach was changed from "absolute assurance of compliance" to "reasonable assurance of compliance."

The "reasonable assurance of compliance" approach is extremely important with respect to ESPs. Any direct or indirect measure of ESP performance and particulate emissions can be used to demonstrate a "reasonable assurance of compliance." The key word is demonstrate. A continuing demonstration of compliance has never been required for most emissions control equipment. Using electric utility ESPs as an example, in the past, it was only necessary to perform a periodic mass emissions compliance test. During the time between compliance tests, which could be as long as 1-5 years, it was only necessary to adhere to an opacity limit.

In essence, the CAM rule does not care what methodology or mechanism is used for showing a "reasonable assurance of compliance." It should also be noted that the accuracy of that showing is irrelevant except when one gets close to the compliance point. This leads to a discussion of statistics and probability and compliance determination procedures that is beyond the scope of this short discussion but that is becoming increasingly important in the era of "credible evidence." We will, however, leave the discussion of credible evidence for another day.

Given the wide range of ESP performance versus the various applicable mass emission and opacity standards, there are a wide array of possible approaches that might be used for showing a "reasonable assurance of compliance." We should be careful to evaluate all of the available CAM tools and to choose the appropriate one given the individual ESP performance, corporate process and procedures and even plant O&M approach. Using an ESP model may be the proper approach for many ESPs but there may be simpler, easier to implement tools for other ESPs.

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Last Revised: June 02, 2004