### From: "Higgins, Cortney" < Cortney_Higgins@omb.eop.gov > To: Sharon Nizich/RTP/USEPA/US@EPA
Cc: Keith Barnett/RTP/USEPA/US@EPA, Thomas Gillis/DC/USEPA/US@EPA
Date: 12/14/2012 02:00 PM Subject: RE: Items you requested



## Hi Sharon,

Attached are interagency comments on the PM CPMS memo. Please let me know if you have any questions.

Regards,

Cortney



## (See attached file: PM CPMS scaling memo 12_12_12_DRAFT_III_clean_InteragencyCommentsunderEO13563.docx)MEMORANDUM

DATE: November 16, 2012

SUBJECT: Establishing an Operating Limit for PM CPMS

FROM: Steffan Johnson Measurement Policy Group, SPPD

TO: Portland Cement Reconsideration Docket
Docket **EPA**

**- HQ** 

**- OAR** 

**- 2011** 

**- 0817** 

A. INTRODUCTION

The EPA received many comments about the impracticality of the technique specified for establishing operating limits for the particulate matter (PM) continuous parameter monitoring systems ( CPMS ) in the May 2012 p roposed amendments to A ir T oxics S tandards and N ew S ource P erformance S tandards for Portland C ement M anufacturing

. Most of the comment er s focused on the impact on sources with very low PM emis g sions who

, under the proposed amendments, wou ld be required to conduct several retests due to the CPMS response to fluctuation of the in

- stack PM characteristics while the source s were operating well below their
PM emission limit s

. A few of the comment er s further pointed out that this is punitive on the most well

- controlled sources and some offered “scaling” strategies for establishing the PM CPMS operating limit that they felt would alleviate the problem

. O ther comment er s pointed out that
under the proposed approach to establishing the operating limit it would be possible for a source to tie the operating limit to a test run that showed non

- compliance with the PM emission limit

. We do not wish to promulgate a regulation that is punitive to well

- performing sources, nor do we

w ant sou rce s to set operating limits above the level of the emission standard. Therefore, we undertook a study to review these comments and determine a more workable approach for setting the PM CPMS operating limit

. This memorandum presents the findings of our ana lysis and provides guidance and calculations for applying this procedure in Portland cement and potentially othe r rulemaking s

. (MATS, Industrial Boilers, CISWI, etc

. ).

B. DISCUSSI ON

The initial focus of our analysis was to more directly connect the PM CPMS operating limit to the compliance determination

, the average of three PM test runs rather than the single highest test run during the performance test

. We believe t his w ould alleviate the potential for setting an operating limit that correspon ds to an emissions result higher than the emission standard

.

We note that a PM CPMS instrument used in this manner must have a sufficient measurement scale to cover not only very low PM concentrations but also values well above the actual emission limit, as the operating limit is a long term average and brief periods of high emissions must be included in such averages. Comment [A1]: This is helpful, but can you make it clearer what you are trying to address.

Comment [A2]: This was offered for comment in the MATS reproposal, so let’s just keep this discussed for this rulemaking.2

W e then set out to review the scaling alternatives provided by commenters as well as sever al
other alternatives developed internally

. Initially we were looking for an approach to “scaling”
that leveraged an inverse relationship between PM concentration and the operating limit whereby a source with very low PM concentration s would be provided gr eater operational flexibility than a source with higher PM concentration s and those closest to the PM emission limit would be provided the least amount of flexibility with respect to the operating limit.

The term “ s caling ” as used in this memo represents the determination of an instrument response slope based on the average PM CPMS output value ( in milliamps) corresponding to a 3

- run EPA

M ethod 5 PM performance test and the instrument output at zero PM concentration

. Once the slope is establish ed

, a PM CPMS output theoretically equivalent to a higher value may be determined, where an operating limit may be established

. A significant complication with
consideration of scaling options is that PM CPMS are not calibrated instruments with known

respo nses to a series of calibration standard s across a wide measurement range, as is a PM continuous emission monitoring system ( CEMS )

. Rather for PM CPMS, the only known relationship between the instrument signal and in

- stack PM concentration is the average v alue established during manual compliance testing

. The s caling approach presumes a linear relationship between the instrument and PM concentration

. This presents difficulty in leveraging
measured values close to the emission limit

, as the linearity of this scale is not demonstrated

. This concept is contrary to using a calibrated PM CEMS for quantitative determination of a compliance value but holds for qualitative determinations of in

- stack PM concentrations.

The options considere d were:

1. Establish a linear scale , determine the emission limit on that scale, and allow sources to operate below the emission limit on a 30

- day rolling average ( as suggested by
Commenter 0261 from the Portland cement rule Response to Comment Document ) ; 2. Es tablish a linear scale and set the source operating limit at a point where that scale intersects with the PM CPMS average plus some percentage ( x ) of the “unused” emission limit where x is equal to the percent of the emission limit not consumed by source

e missions as established by a compliance test ; 3. Establish a linear scale and set the source operating limit at a point equal to the average PM CPMS value measured during the compliance test plus one

- half of the remaining scale up to the emission limit ; 4. Est ablish a linear scale and set the source operating limit at a point equal to the average PM CPMS value measured during the compliance test plus one

- third of the remaining scale up to the emission limit ; 5. Use Option 3, but also roll back the operating limit a distance equivalent to one standard
deviation of the three PM CPMS average values recorded during the three performance

tests ; and

6. Establish a linear scale and set t he source operating limit at 75 percent of the em ission limit if a source showed compliance below that level, and set the operating limit at the average PM CPMS values for sources demonstrating compliance above that limit.

After a review of these six options we noted the following: Comment [A3]: Can you please add what you were reviewing them for?

Comment [A4]: Why?

Can you also mention that you wanted to figure out a method that also guaranteed continued compliance with the PM limit? Perhaps it would be best to add
that a nd shorten these existing sentences to emphasize that you wanted to provide flexibility to
those sources that are below 75% of the emissions
liit.

Comment [A5]: Why are you assuming this? This appears to be a big potential flaw in the scaling approach. Is there any d ata to support it?

Comment [A6]: Do you mean “using”? I don’t understand leveraging in this context

– please clarify/be more precise.

Comment [A7]: Did commenters suggest these? How were they generated?3

Option 1 placed a great deal of confidence in the presumption that the instrument response to in

- stack PM concentrations are linear beyond the average value determined during the performance test

. This approach presumes PM CEMS capabilities from an
uncalib rated instrument.

Option 2 provided for a great deal of flexibility for the lowest emitting sources but also
resulted in operating limits for these sources that were significantly higher than some sources with higher PM concentrations.

Options 3 and 4 provided for flexibility at low concentrations, but also provided flexibility even very close to the PM limit which did not seem appropriate.

Option 5 addressed the issue noted with O ptions 3 and 4

, but added a level of complexity
that seemed to confuse rather than simplify the process.

Option 6 provided flexibility for low emitting and well

- operated sources, and was determined to be a reasonable compromise of flexibility and protection of the emission
standard

. Seventy

- five percent of the emission limit is a n already

- established threshold in
the Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources : Commercial and Industrial Solid Waste Incineration Unit (76 FR
1575 7 ) to determine the freque ncy of subsequent compliance testing

. In that rule, owners or operators of sources were able to reduce their performance test frequency when
emissions were equivalent with or below 75 percent of the limits

. Otherwise, performance testing was to occur at the normal frequency prescribed in the rule

. We believe this threshold can be used in conjunction within a PM CPMS scaling factor, as results above 75 percent of the equivalent emissions limit would be ineligible for scaling
factor use and could lead to i ncreased performance testing, while results equivalent with or below 75 percent of the equivalent emissions limit would be eligible for scaling factor

use

. Adherence to an operating limit with a 25 percent (1

- 0.75) margin of compliance
should ensure cont inuous, qualitative proof of compliance with a PM standard.

One outcome of this assessment is that w e find this approach to be an appropriate technique to establish operating limits for parametric monitors where the monitor is measuring the pollutant of i nterest qualitatively

. This approach is not appropriate where a parametric monitor (i.e.

, pH meter, pressure monitor or thermocouple) represents an operating condition of a control device (i.e.

, pH, pressure drop, combustion temperature) rather than an act ual qualitative measurement of the pollutant of interest.

A second outcome of this assessment is its versatility across production

- based standards (e.g., the
Portland cement rule’s PM/ton

- clinker limit and the MATS rule’s PM/MWh limit)

. One need only ensu re that the appropriate units are used when developing equations and conducting
calculations.

A third outcome is that we find with the Portland c ement source category, which includes many sources with emission levels at or near the method detection levels (MDLs) for PM

, measurement imprecision i s a significant factor that should be ameliorated to the extent possible Comment [A8]: Do you mean that the PM limit could be exceeded using operating parameters established with these options? If so, please change. Otherwise, why is this “not appropriate”?

Comment [A9]: Do you mean: “ensuring sources don’t exceed the”

Comment [A10]: Can you point to a statistical or factual basis as to why 75% is better than 80% or
70%?4

when establishing an operating limit

. Measurement impre cision is typically highest for values
measured below or near a method’s detection level and decreas es as values increase above the
method detection level

. W hen establishing such a curve based on a single compliance test series, we recognize longer M ethod 5 test times and/or duplicate M ethod 5I tests as a best practice; better data will result in a better operating limit

. With this in mind

, we recommend source operators and testers to consider extended test times and the use of Method 5I, as appropriate, to adequately quantify in

- stack PM concentration and more accurately establish a PM CPMS output relationship to the compliance test results.

C

. DETERMINING AN OPERATING LIMIT BOTH FLEXIBLE AND PROTECTIVE

After a review of a number of PM CPMS signal scal ing approaches, we arrived at the sixth option above, which is a hybrid approach to allowing scaling of the PM CPMS measurements upward to a point

. We find it reasonable to allow flexibility to sources who have demonstrated compliance below 75 percent of the emission limit while holding sources whose compliance test
results were closer to the emission limit to an operating limit with less flexibility and tied directly to their PM compliance demonstration.

To establish an operating limit using a PM CPMS a source must conduct a Method 5 or Method
5 I performance test

– consisting of at least 3 runs

– annually and establish the relationship
between the average milliamp output from the PM CPMS and the average of the PM test runs

. A
source whose performance tes t shows their average PM emission rate to be below 75 percent of
the emission standard must then establish a correlation between the average milliamp output
from the PM CPMS during the performance tests and the average PM emission rate of the three perform ance test runs

, taking into account the instrument value representing zero PM concentration as part of the theoretical curve.

The scale used to determine the operating limit value at 75 percent of the emission limit is developed using two pieces of inf ormation : the PM CPMS output at zero and the average PM
CPMS response during the performance test

. To simplify the process , we specify a commonly used instrumental output

, 4

- 20 milliamps , as the basis for all PM CPMS measurements

. To
establish the low end of the scale we require an accurate value that represents how the instrument
reads zero PM concentration

. Theoretically

, the z ero PM concentration would be represented by a value near 4 milliamps, but not necessarily 4.0, so we lev erage the steps presented in performance specification ( PS ) 11, section 8.6 (5) to direct the source owner/operator in
establish ing a zero value that is specific to their PM CPMS , preferably in its installed location.

With the PM CPMS output value that re presents zero, and the PM CPMS average value s recorded during the compliance test, the scale is delineated in units of the emission standard over the instrument output , e.g., for the Portland cement rule, these units would be in terms of lb PM per ton clin ker PER milliamp

. One could determine this value for the Portland cement rule using
the following formula:



# ( ) z X Y

− =

1 1 

### R

Where: Comment [A11]: What does this mean? Is this also described in the preamble? If a source follows this recommendation, are they still considered in compliance with the rule? If so, please clarify this.

Comment [A12]: I don’t understand this.

I think this can be addressed through a rew rite alon g the following lines: For sources with a performance tests that shows their average PM emissions rate at or below 7%5 of the standard, they have the flexibility to establish a
correlation curve for their CPMS. This correlation
curve is based on two data points: the output of the PM CMPS during the performance tests and the corresponding PM emissions rates, and the PM CPMS instrument value during a period of no PM
emissions.5

R = the relative lb/ton

- clinker per milliamp for a PM CPMS,

Y 1 = the three run average lb/ton

- clinker PM concentration from a compliance test,

X 1 = the three run average milliamp output from the PM CPMS, and z = the milliamp equivalent of a PM CPMS instrument at zero.

Note : B ecause of the 4

- 20 milliamp scale we ne ed to subtract the value representing

zero from the average milliamp output so that we may determine the relationship between
PM concentration and the actual milliamp response above zero

. The value representing
zero is factored back in once this relationsh ip is established (see equation below)

.

Once the level of PM concentration relating to a milliamp of signal output from the PM CPMS is
established , we may determine where on a slope of milliamp output signals the PM concentration representing 75 percent of the emission limit intersects

. This represents the operating limit and is determined by the formula:

E = z + 0

. 75 ( L )

R

Where, continuing with our use of the Por tland cement rule as an example :

E = the operating limit for the PM CPMS , in milliamps.

L = the source emission limit expressed in lb/ton clinker,

z = the instrument zero in milliamps, determined from (1)(i), and
R = the relative lb/ton

- clinker per milliamp for the PM CPMS, from above

.

Note: With other rulemaking applications the units abov e that are Portland cement specific (lb/ton

- clinker) would need to be replaced with appropriate units of production (i.e. lb/Gw Hr, lb/Mmbtu, etc.) depending on the units of compliance determination with the rule.

While this process results in a good deal of flexibility for sources well below 75 percent of the emission limit, we recognize th e importance of being protective of the ensuring sources don’t
exceed the emission limit

. N ot all PM CPMS instruments are expected to have a linear output in regards to milliamp signal versus PM concentration, we recommend that sources demonstrating compliance at or above 75 percent of emission limit be held to an operating limit representing their average PM CPMS output during the performance testing.

It is important to note that emission testing is a snapshot and not an indicator of long term emission profiles at a source ; so we recognize that th e relationship established between PM CPMS output and in

- stack PM concentration may predicated on data that is subject to othe r operational and seasonable variability which may present operational challenges to maintain ing operations within the established operating limit

. Therefore we see the need to provide an allowance for a source to conduct another compliance test and reset this relationship to the most
current data set if the source is unable to meet i t s operating limit

. Sources who show compliance6

in the range just below t o anywhere above the 75 percent level are most likely to find themselves facing this mode of operation (i.e.

, more frequent retesting to reset the operating limit )

.