### Xcel Energy Comments to the Draft Performance Specification 18

Xcel Energy

would like to the United States Environmental Protection Agency and thank the OAQPS staff for allowing us to contribute and comment on the Draft Performance Specification 18 speci fications and test procedures. Please accept our comments to this project. 1. It is based on our experiences of operating an HCl CEMS for 3 y ears that allow me to comment that Dy

namic Spiking will not work well as a substitute for Relative Accuracy Test Audits (RATA) on extractive s ys tems. On a recent RATA, w e experienced a leak in the flange that supports the CEMS probe and calibration header that went undiscovered until we were performing the annual RATA test. This leak was undetectable during daily c alibration and would not be uncovered without a stand alone RATA sampling train. As Iunderstand the plumbing design of dy namic spiking, it would also not detect this ty

pe of leak, which would allow an inaccurate CEMS to operate in full compliance with PS 18. The flange that had this leak was impossible to examine or access without taking the boiler offline and taking the entire CEMS sy stem apart. It is not a task that can be part of an y routine maintenance schedule. 2 We have performed many Method 26A tests on our emissions units and have found it to be a very

durable, well

- designed, and accurate sample train that provides quality data
. We have found it to be a practical tool to evaluate the performance of our HCl monitors and have been utilizing i t during our annual performance testing. It provides us accurate and high qualit y data that we have compared to our HCLCEMS. Th is Draft PS 18 requires duplicate train samplings. This is both problematic and not necessary . Man y sample locations are no t designed for duplicate train testing ; they m a y have onl y one port for testing
. The RATA does not need a duplicate train to insure an y more quality

of the RM data ; the leak check requirements in the method wil l insure sample integrity

and once you have the HCl in solution , it is stable
. We employ man y of the EPA sample trains in our testing regimen; of any train, this one least need s duplicate train QA
. The p aired train will not insure any more quality

of the RATA testing regimen
. If the RM data is of poor quality , the RATA will fail. 3. Since on

- site anal ys is for Method 26A is impractical , the presumption is that we would be performing 12 runs for every RATA
. Dual trains will not provide any more confidence in relative accuracy
. It is just an adde d expense , nearl y doubling the cost. A disharmonious result of the dual train agreement due to a random event requires that run must be excluded. If that event occurred during a single train RATA, I would exclude that one from the RATA population as it w ould disagree with the CEMS. That same random event has twice the chance of occurring when dual trains are employ ed. And it is not excluding 1 out of 12 runs that is the crux of the matter, but excluding 1 out of the 3 that Iam allowed that makes this a magnified problem. The in

- run disagreement will not be uncovered until the testing firm is off the stack for a week or two as analy sis is performed offsite. To summarize, excluding a run due to dual train disagreement is equivalent to an inaccurate run and will be one the three runs that will be excluded for the RATA
. And now there is twi ce the chance of that happening, f or twice the cost.4. The duration of the sample time extended to 1 hour for Method 26 is not

necessary . If the laboratory quantit ation limi t is low enough, the 21

- minute RATA run

time is more than adequate
. We suggest that PS 18 allows the tester to define the testing time that meets their quantitation limits requirements with a minimum of a 21 minute run. As the anal ys is is going to be performed off

- site, it should be expected the tested facility will ask for more than the minimum samples to improve the chance for passing the RATA. Itcan be expected that many will require 12 runs for an y PS18/Method 26A RATA. If the 1 hour runs are required, this will require two day s of testing for a RATA when it is preferable to see this testing completed in one day
. It can and will be as accurate if the sample duration is left to best practices and a good knowledge of laboratory

detection limi ts. Reaching the quantitation limit or a minimum of 21 minutes will suffice for Method 26A. All of these requirements seem to be biased against the Method 26A train in favor of other technologies as a reference method. I am unsure wh y this apparent bias exists. 5. P.S. 18 must take into account the possibility of i nlet CEMS monitoring. Some sources with HCl limits also comply with a 95% control efficiency . I f c ontinuous monitoring becomes required for units that use control efficiency , PS 18 must have flexibility to operate under inlet conditions. For example, the 2 diameter upstream/ 0.5 diameter downstream may not be practical for inlet sites. Some of the span requirements may need to be addressed as the inlet concentrations can range from 50 to 500 0ppm, as the concentrations can be quite variable at the inlet. 6. I am trying to visualize (From section 8.3.2) “70 percent of the path within the inner 50 percent of the stack or duct cross

- sectional area.” Could a drawing or diagram be included with this? 7. Finally , in section 8.2 it appears there is a word missing between “accessible” and “where” Thank y ou for allowing Xcel Energy to contribute to this process. Regards,
John F. Buresh Senior Environmental Analy st Xcel Energy