1 

January 29, 2009 

Mr. Peter Tsirigotis 

Director, Sector Policies and Programs Division 

Office of Air Quality Programs and Standards 

U.S. Environmental Protection Agency 

Mail Code: D205-01 

Research Triangle Park, NC 27711 

Dear Peter, 

 The June, 2007, vacatur of EPA’s Boiler Maximum Achievable Control 

Technology (MACT) rule1 (40 CFR Part 63, Subpart DDDDD) triggered obligations 

under section 112(j) of the CAA that require state and local permitting agencies to 

develop permits for approximately 3,000 Industrial, Commercial and Institutional 

(“ICI”) Boilers on a case-by-case basis. In order to avoid the duplication of effort that 

would otherwise ensue, the National Association of Clean Air Agencies2 (“NACAA”) 

undertook to develop a Model MACT 112(j) Permit for use by our members. In the 

course of this effort, NACAA compiled the most comprehensive data set as of that time 

concerning the issues relevant to the EPA rule and identified a number of areas where 

additional data would be useful in developing scientifically credible MACT floors and 

limits. As part of this process NACAA worked collaboratively with EPA over a period 

of approximately a year and provided EPA, industry and the public all of the data 

obtained from permitting authorities (“the NACAA data”). 

Recently, EPA provided to “stakeholders” information concerning the data it has 

collected as part of its ICI Boiler MACT rule development activities for which OMB 

approval was obtained this past summer. EPA indicated to these stakeholders that it 

was soliciting input on a proposed plan for future testing by January 9, 20093

. Given 

the extensive nature of our involvement in these issues, we are concerned that NACAA 

was not included in the “stakeholder” group, which apparently was limited to industry 

representatives and those directly involved in the litigation that led to the vacatur of the 

Boiler MACT rule. 

 

1

 See, Sierra Club v EPA, 479 F3d 875 (D.C. Cir2007). 

2

 NACAA is the professional organization of the state and local air pollution control agencies that are on 

the front line of this nation’s effort to reduce air pollution and the health care costs associated with air 

pollution. 

3

 EPA’s note to stakeholders asks for comments by January 9, 2009, but indicates that EPA intends to 

start its negotiations with OMB during the week of December 29, 2008. 
2 

NACAA subsequently acquired a copy of the information provided to this group, 

including a link to current EPA survey results. The information reviewed raises a number of 

concerns about the quality of the data that will be used to develop the final rule and whether EPA 

will ultimately be able to promulgate a final rule in accordance with the schedule negotiated with 

Earth Justice. 

We understand and support the need to move expeditiously to promulgate a MACT 

standard for this important sector. However, we believe it is more important to properly design 

the information collection activities at the outset. If this is not done now, EPA will be forced to 

either delay making a final decision at a later date or make a decision on the basis of an 

inadequate record. Either eventuality will delay the reduction in emissions of hazardous air 

pollutants mandated by Congress in 1990 and cause state and local permitting agencies to expend 

scarce resources to develop case-by-case permits under section 112(j). 

THE FUNDAMENTAL ISSUES 

At a minimum EPA must have sufficient data to identify the best performing 12 percent of any 

proposed subcategory.

 The primary purpose of the data collection effort should be to establish an emissions 

profile for the ICI sector (including any subcategories established on a sound technical basis). 

This profile should be sufficiently robust as to provide for a reasonable identification of the top 

performing 12 percent of the units within the category and thereby enable a calculation of the 

average of the top performing 12 percent. 

 NACAA has questioned whether there are technical, design or operational issues (as 

opposed to economic issues) that justify EPA’s earlier decision to establish subcategories for 

small4

 and limited use boilers. EPA has not responded to this issue and continues to assume that 

such subcategories will exist. However, EPA now has two data sets, the NACAA data base and 

the results of its Phase I survey, which can be examined to determine whether there are technical 

differences between “small”, “limited use” and “large” boilers sufficient to justify creation of 

these subcategories5. EPA has dedicated the majority of the proposed new testing to ensuring 

that a minimum number of tests have been conducted for each of its proposed subcategories6

. 

EPA should examine the existing information to document a reason for its proposed 

subcategories prior to proposing a test plan that focuses on such subcategories while failing to 

resolve data deficiencies in the more environmentally significant “large” boiler category. 

 

4

 There are no units in one such category and only four in another. 

5

 Such subcategories, if not based on significant technical differences, would appear to be inconsistent with the 

Congressional determination of “major” sources subject to regulation under section 112. 

6

 While this issue was not pursued rigorously, the NACAA data set did not appear to identify any statistically 

significant differences in performance between small and large units. If this pattern is confirmed by a more careful 

review of the existing data, the additional testing proposed by EPA would likely only confirm the earlier results and 

would seem to be unnecessary.
3 

For several of its proposed subcategories, it appears that EPA’s data collection activity is 

not geared toward determining the average of the top performing 12 percent but the mean of the 

category, where the sample size to determine the mean is set at a number that is not less than 12 

percent of the number of units in the subcategory. If EPA gathers data based on the mean of the 

category and then relies on the “for which it has information” language in the statute, it will 

effectively set the MACT limit at the 50th percentile of performance rather than the 94th

percentile as intended by Congress. 

Specifically, we recommend the following additional data collection activities: 

1. the carbon monoxide (CO) emissions profile of large coal fired boilers (as well as 

any other proposed subcategory for which there is currently insufficient information) 

should be developed in a way that will enable rigorous identification of the best 

performing 12 percent;7

2. data to establish a correlation between CO emissions and organic HAP emissions by 

reference testing should be pursued; 

3. data concerning the nitrogen oxide (NOx) and CO performance of well-operated 

facilities with second-generation low-NOx burners should be obtained and evaluated8; 

4. data to determine how to treat sources combusting a mix of fuels should be obtained 

and evaluated; 

5. the absence of mercury emission data and paucity of hydrogen chloride (HCl) 

emissions information from oil burning boilers should be remedied by reference 

method testing;9 and 

6. potential differences in performance between sources burning wet wood and dry 

wood and between sources combusting #2 oil and #6 oil should be examined. 

EPA must acquire sufficient information on the variability of the emissions performance of the 

best performing units – consistent with the proposed enforcement provisions – to set meaningful 

emission limits.

 NACAA also identified a relative shortage of data on variability in performance of an 

individual unit. This factor is more relevant in establishing a MACT standard than the variability 

between units which Congress accounted for in its “average of the top 12 percent” requirement. 

 

7

 While the NACAA data set and the EPA survey each include over one hundred data points on CO emissions from 

gas and oil-fired units, these sources include only 10 and 27 data points, respectively, on CO emissions from coalfired units. This information is insufficient to support a statistically valid identification of the best performing 12 

percent of the category and a rigorous estimate of the variability of the emissions performance of the best 

performing units. 

8

 Some have suggested that there may be an inherent trade-off between NOx and CO emissions. 

9

 The NACAA data set and the EPA survey response each contain no usable data on mercury emissions and 

statistically insignificant information on HCl emissions from oil-fired units. EPA proposes testing only a total of 

eight oil-burning facilities (with controls) for mercury and HCl. Here, the sample size is inadequate to identify the 

top performing 12 percent. EPA should not at this stage repeat its earlier approach, rejected by the Court, of 

considering emissions only from units with controls.
4 

More importantly, as employed by EPA in its prior rulemaking process, the determination of 

“variability” dominated the standard-setting process and rendered the average of the top 12 

percent meaningless. Indeed, in the course of manipulating the relatively sparse data it had, EPA 

concluded in its prior rulemaking that it should multiply the “average of the top 12 percent” by 

factors of up to 181 (18,100 percent) and thereby set no meaningful limit. The reference test 

procedures adopted by EPA and states over the years incorporate averaging procedures to 

minimize the effect of short-term variability on the outcome. 

Any determination of variability by EPA should reflect the averaging period and other 

conditions of the method that will be used to enforce the standard. In this regard, EPA’s 

apparent intent to use fuel sampling data is of particular concern, since a single “grab” sample 

may represent only a small fraction of a second of operation of the unit. In contrast, the 

reference method used to enforce the limitation typically averages emission performance over a 

three-hour period. EPA methods to evaluate variability should be consistent with procedures 

historically employed by EPA in analogous circumstances, such as those employed by EPA in 

establishing NSPS standards based on reference method test data from well-performing units. 

We also note that during the ICCR process protocols for evaluating such information were 

developed by the stakeholder group; such protocols should be revisited for their applicability to 

this rulemaking. 

 

EPA has proposed no replicate testing of well-controlled facilities to determine test-totest variability of a given facility. Instead, EPA has disaggregated reference test results into 

individual run results, which is legally and scientifically irrelevant and can only make the 

variability appear larger than it is. EPA has also asked sources to provide CEM data – but in an 

odd form. Where a 30 day average is the regulatory limit; rather than asking for all data within 

a given time period, EPA has asked sources to provide data from the highest day of each month 

in a year. We can discern no technically justifiable support for such information. 

NACAA’s data set included less than 10 facilities for which replicate testing had 

occurred and a number of those facilities were not within the best performing 12 percent.10

 

EPA’s data collection activities should incorporate no less than three to five replicate tests11 of a 

statistically meaningful number of units within the best performing 12 percent of each intended 

subcategory. 

EPA Should Establish a Separate Subcategory for Process Heaters and Collect the Data 

Necessary to Determine the Standard

While the source category covers both boilers and process heaters, the latter are very 

different from boilers, both in their operations and their emissions. Accordingly, NACAA 

recommends that EPA establish a separate subcategory for process heaters. To that end, 

 

10 One can argue that variability will be greater in well-controlled units. One can also argue that it will be less. For 

this reason, we recommended additional investigation into this area. 

11 Indeed, 10 - 20 replicate tests of a statistically significant number of the best performing units would be 

preferable.
5 

NACAA urges EPA to collect substantial data in order to calculate the appropriate MACT 

standard for the process heater subcategory. 

EPA Should Engage in a Second Round of Information Gathering Focused on the Best 

Performing 12 Percent before Committing to a Final Test Program

 In its initial information gathering effort EPA generally asked sources to provide the most 

recent test information, which is likely to be adequate to identify the best performing 12 percent 

of sources where there are a sufficient number of sources that have been tested at least once. In 

this comment, NACAA has used the phrase “EPA data collection activities” to reflect the fact 

that many of the issues we have raised likely do not require additional testing. NACAA and the 

regulated community share a common interest in not requiring additional testing12. Here, for 

example, if EPA were to identify the best performing gas and oil-fired units for CO and ask the 

operators of those sources to provide all CO test results for the designated units, sufficient 

replicate testing may be identified so that no new tests would be required. Similarly, EPA may 

seek specific information from the detailed test reports for the best performing units in the 

NACAA data set and the EPA survey results to evaluate the wet wood, #6 oil, low-NOx burner 

and other issues we raise. EPA should also request large blocks of CEM data from wellperforming facilities, which can be provided at almost no cost, to assist in evaluating partial load 

and startup issues that are likely to arise in developing a final standard. 

 This is not to suggest that emissions testing should be delayed until these analyses are 

completed. Rather, we believe that OMB should approve a tiered test program as we have 

suggested where there are four phases; each of which can overlap in time: 

Phase 1 – Obtain information through data requests to the entire sector sufficient to characterize 

the top performing 12 percent of each proposed subcategory13

. 

Phase 2 – Where there is insufficient information available to identify the top performing 12 

percent, conduct testing to remedy the data deficiency

14

. 

Phase 3 – Obtain sufficient information through data requests to the identified top-performing 12 

percent to evaluate variability and other issues (identified above) that can be anticipated for final 

rulemaking. 

 

12 In addition to the obvious cost issues, NACAA believes that pre-existing test results are inherently more credible 

than testing conducted with an eye toward the anticipated use of the data. 

13 This phase is complete. We recognize that where there are fewer than 30 sources in a subcategory the MACT 

floor is based on the five best-performing sources.

14 This would include additional CO testing for large coal-fired units, mercury and HCl testing for oil-fired units and 

sufficient testing to properly characterize any additional subcategories under consideration.
6 

Phase 4 - Where there is insufficient information available to evaluate variability and other issues 

(identified above) that can be anticipated for final rulemaking, conduct testing to remedy the data 

deficiency. 

We know at this time that several data deficiencies exist and so testing to address these 

deficiencies should be approved and commenced immediately. Note that this proposed structure 

minimizes the paperwork burden on the sector, since follow-on information gathering is limited 

to a small subset of the sector. Given the overall time constraint, Paperwork Reduction Act 

concerns may best be addressed if the EPA test plan sets out the technical basis for the type of 

information needed to address the issues that will arise in rulemaking and OMB and the 

regulated community are satisfied that both the NACAA data set and the EPA survey results will 

be carefully evaluated and any additional existing data will be obtained and used before any new 

tests are ordered. 

EPA Should Not Allow Sources to Include Emissions Data That Do Not Reflect Normal 

Operation of the Unit.

Ordinarily, if a source experiences a malfunction during a reference test, a retest will be 

ordered. Thus, consistent with our earlier comment, such data does not reflect the enforcement 

of the rule. However, instead of instructing sources to exclude data where there was an upset or 

malfunction that would be excused under a proposed NSPS-style “startup, shutdown, 

malfunction” exemption, EPA simply asked the sources if there were any upsets or malfunctions 

“that they would like to identify.” If a source that wants MACT limits to be as lenient as 

possible submits a test result where there was a malfunction, the honest and straightforward 

response to EPA’s query about the result is “No, I do not have a malfunction that I want to 

identify.” EPA should correct this potential source of error by directing sources to notify them if 

any data submitted in response to its initial inquiry included periods of malfunction of the unit or 

the associated pollution control device. 

Thank you for the opportunity to comment on this matter. We continue to appreciate the 

professional and courteous manner in which you and your staff approach potentially contentious 

issues and look forward to working with you in developing sufficient information to support a 

technically sound and environmentally protective standard for ICI Boilers. 

Sincerely, 

 

Vinson Hellwig Robert Colby 

Michigan Chattanooga, Tennessee 

Co-Chair Co-Chair 

NACAA Air Toxics Committee NACAA Air Toxics Committee