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PADEP’s CSMM Rev. 8 Frequently Asked Questions Document Updated! (Part 2)

Posted: December 16th, 2019

Authors: Katie F. 

The Pennsylvania Department of Environmental Protection’s (PADEP’s or Department’s) Continuous Emissions Monitoring (CEM) Section within the Division of Air Quality released an updated Frequently Asked Questions (FAQs) document to support Continuous Source Monitoring Manual Revision No. 8 (CSMM Rev. 8) on October 8, 2019. The updated document provides a reference point for certain gray areas within CSMM Rev. 8 and continuous monitoring in the Commonwealth of Pennsylvania. This article is the second in our series that detail PADEP’s most recent responses to questions related to CSMM Rev. 8, which discusses PADEP’s response to the question “How is a 3-hour average, rolling by one hour calculated?” If you’re curious about what PADEP has to say about the application of diluent caps, our first article in this series, PADEP’s CSMM Rev. 8 Frequently Asked Questions Document Updated! covers that topic.

Let’s get to it – what does PADEP have to say about 3-hour rolling averages? The Department states that a 3-hour rolling average is considered valid if it contains at least two valid hourly averages. Now you may be wondering what constitutes a valid hourly average. Well, except for opacity, temperature, and carbon monoxide (CO) data, an hourly average is determined to be valid if there is at least one valid data reading obtained in each 15-minute quadrant of the clock hour during which the process is operating. For hours in which preventative maintenance or quality assurance activities took place, a valid hourly average can be calculated if there are at least two valid readings in the hour separated by a minimum of 15 minutes. For opacity, temperature, and CO, a valid hourly average can be calculated if the hour contains at least 75% of the segments of the hour corresponding to the minimum required cycle time (for measurement) during which the process was operating. PADEP provides an example of this validation on page 27 of their FAQs document.

Now that we’re clear on what constitutes an hourly average, let’s get back to how to calculate a 3-hour rolling average. A 3-hour rolling average can be calculated if it contains at least two valid hourly averages. Additionally, process down hours, invalid hours, and exempt hours are excluded from the 3-hour average calculation. Note that hours for which data substitution has been utilized will not be included in the 3-hour average when determining compliance with a 3-hour rolling average emission standard. The table below provides examples of how the Department calculates the 3-hour rolling average, under common operating scenarios.

Hour Operating Status Concentration Calculated Value
00 Starting-up

Exempt

6 PPM None.  No data available from hour 22 or 23 from previous day.  Do not include hour 00.
01 Starting-up

Exempt

5 PPM None.  No data from hour 23 from previous day.  Don’t include hour 00 and 01.
02 Process on

Normal Operation

3 PPM None.  Only have 1 hour for consideration (hour 02).
03 Process on

Normal Operation

3 PPM 3 PPM.  Average of hour 02 and 03, do not include hour 01.
04 Invalid (blank) 3 PPM.  Average of hour 02 and 03, do not include hour 04.
05 Process on

Normal Operation

3 PPM 3 PPM. Average of hour 03 and 05, do not include hour 04.
06 Shutting down

Exempt

5 PPM None.  Only have 1 hour for consideration (hour 05).
07 Process Down (blank) None.  Only have 1 hour for consideration (hour 05).
08 Starting-up

Exempt

6 PPM None.  No data for consideration.
09 Process on

Normal Operation

3 PPM None.  Only have 1 hour for consideration (hour 09).
10 Process on

Normal Operation

3 PPM 3 PPM.  Average of hour 09 and 10, do not include hour 08.
11 Process on

Normal Operation

3 PPM 3 PPM.  Average of hour 09, 10, and 11.

As the table above details, PADEP uses a clock hour methodology when calculating 3-hour averages.  This is done in PADEP’s Continuous Emission Monitoring Data Processing System (CEMDPS) using hourly emissions data collected by the CEMS and submitted by the facility.   If you have any questions about calculating averages, or any other general CMS questions, please reach out to me at (610) 933-5246 x116, or at kfritz@all4inc.com.  Lastly, don’t forget to keep an eye out for our next article that goes over PADEP’s response to questions around Phase II testing during the operational test period.

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