11011 CODY

OVERLAND PARK, KS 66210 

PHONE 913 / 451-8900 FAX 913 /451-1686 

CURTIS D. LESSLIE, PE 

DIRECTOR OF ENVIRONMENTAL AFFAIRS WRITER’S DIRECT LINE – 913/319-6065 

September 4, 2009 

BY ELECTRONIC SUBMISSION 

Mr. Keith Barnett 

U.S. EPA Docket Center 

Air and Radiation Docket 

Mail Code 6102T 

1200 Pennsylvania Ave., N.W. 

Washington, DC 20460 

Re: Comments on Proposed Portland Cement NESHAP 

Docket ID No. EPA-HQ-OAR-2002-0051 

Dear Mr. Barnett: 

Ash Grove Cement Company (“Ash Grove”) is writing to offer comments on the May 6, 2009 

proposed revisions to the National Emission Standards for Hazardous Air Pollutants for the 

Portland Cement Manufacturing Industry (“Subpart LLL” or “PC NESHAP”). 74 Fed. Reg 

21135 (May 6, 2009) (the “Preamble”). Ash Grove supports the comments being submitted by 

the Portland Cement Association (“PCA”) and, to the maximum extent that those comments are 

consistent with those stated here, adopts those comments as Ash Grove’s own. However, Ash 

Grove is uniquely positioned on certain issues and so finds it necessary to write comments in 

supplement to those submitted under PCA letterhead. Ash Grove has organized its comments to 

match the order in which issues were presented in the preamble. 

I. Background

Ash Grove is an American owned business headquartered in Overland Park, Kansas. Ash Grove 

is the fifth largest cement manufacturer in the United States with cement plants in nine states 

across the country. A pioneer of the limestone and cement industries, the Company was 

incorporated in Missouri in 1882 and has been majority owned and controlled by the Sunderland 

family since 1913. The nine cement plants operating in the Ash Grove system are some of the 

most efficient and best maintained in the country and have an annual production capacity of 

more than 8.0 million tons of cement. The quality portland and masonry cements produced at 

these plants are used in the construction of highways, bridges, commercial and industrial 

complexes, residential homes, and a myriad of other structures. 
Keith Barnett 

September 4, 2009 

Page 2 

II. Proposed Mercury Standard

Ash Grove respectfully comments on two aspects of the mercury standard. First, Ash Grove has 

concerns regarding how the mercury standard was established for the one category that EPA 

proposed. Second, Ash Grove is strongly supportive of the establishment of two subcategories 

for purposes of establishing the mercury standard, one for the affected sources with low levels of 

mercury in their limestone (<225 ppb, as charged) and one for the affected sources with elevated 

levels of mercury in their limestone (≥225 ppb, as charged). Our specific comments and 

concerns are outlined below. 

 A. Variability in Establishing Existing Source Floor

Ash Grove believes that the existing source floor was not appropriately established. The floor 

was based on an extremely limited data set consisting of raw materials data for a 30 day period. 

Ash Grove has been studying the mercury emissions at its Durkee, Oregon kiln since 2006; these 

data are included as Table 1 below.1 Between June 2007 and April 2009, the plant collected 

monthly composite samples of the limestone for most of the months the plant was operating and 

analyzed them for mercury. These monthly averages ranged from 424 ppb to 1,740 ppb. All 

limestone originated from the on-site quarry. 

Table 1. Durkee Limestone Mercury Data Summary 2007-2009 

Blast # Date Bench (toe elev.) Tonnage Month ppm 

2007-7 6/13/2007 3805 38,324 

2007-8 6/27/2007 3805 34,313 

July 1.02 

2007-9 7/18/2007 3805 47,237 

2007-10 8/1/2007 3400 37,433 

2007-11 8/15/2007 3715 36,690 

September 1.15 

 

1

 Ash Grove’s Durkee plant is an area source that voluntarily entered into an enforceable order 

requiring the installation of mercury controls that will redefine the state of the art for cement 

kilns. These controls must be operational by mid-2010 or Ash Grove will face daily stipulated 

penalties. Approximately 99 percent of the mercury emitted by the Durkee plant derives from 

materials quarried on site. Through use of the controls Ash Grove committed to achieve at least 

a 75 percent SRE and to take all reasonable measures to achieve an 85 percent SRE. 

Notwithstanding an initial investment of more than $18 to $20 million in the controls and 

substantial annual operating expense, the Durkee plant will not be able to comply with a mercury 

emission standard equal to the average emission rate of the 12 percent of the cement plants with 

the lowest mercury containing limestone. 
Keith Barnett 

September 4, 2009 

Page 3 

2007-12 8/19/2007 3805 38,138 

2007-13 9/12/2007 3355 41,518 

2007-14 9/26/2007 3805 40,407 

October 1.07 

2007-15 10/3/2007 3355 18,506 

2007-16 10/10/2007 3805 24,138 

2007-17 11/1/2007 3805 10,695 

2007-18 12/18/2007 3580 49,725 

December 0.888 

np 2/6/2008 3805 14,577 

2008-3 2/20/2008 3445 33,794 

2008-4 2/27/2008 3445 28,000 

March/April 1.74 

2008-5 3/6/2008 3445 20,276 

2008-6 3/26/2008 3400 38,621 

2008-7 4/9/2008 3400 39,587 

May 1.09 

2008-8 5/21/2008 3355 44,028 June 1.39 

2008-9 6/4/2008 3355 17,380 

2008-10 6/29/2008 3760 36,417 

July 0.706 

2008-11 8/13/2008 3760 37,913 

2008-12 9/11/2008 3760 38,138 

2008-13 10/22/2008 3760 34,000 

October 1.03 

2008-14 11/12/2008 3760 38,138 

2008-15 11/26/2008 3760 41,421 

2008-16 12/17/2008 3760 46,201 

December 1.3 

2009-1 1/15/2009 3760 36,914 

2009-2 1/28/2009 3760 48,856 

February 0.735 

2009-3 2/5/2009 3760 29,738 

2009-4 2/18/2009 3760 42,483 

2009-5 2/25/2009 3760 15,448 

March 1.04 

2000-6 3/11/2009 3760 48,325 

2009-7 3/18/2009 3715 43,545 

April 0.483 

2009-8 4/1/2009 3760 48,325 

2009-9 4/9/2009 3760 43,449 

2009-10 4/22/2009 3760 41,518 

May 0.424 
Keith Barnett 

September 4, 2009 

Page 4 

This range of values demonstrates the tremendous variability that occurs month to month within 

the same quarry (see, also, Figure 2 below). This same variability must be accounted for in 

establishing the floor. For example, the proposed existing source floor recognized a variability 

factor of only 57 percent. However, in the Durkee data the variability was considerably higher. 

If the floor value using the 11 kilns identified in Table 1 were calculated using the variability 

seen in the Durkee quarry and three standard deviations are applied to the average, then the floor 

would be 34 lb/MM ton feed rather than 26 lb/MM ton feed. As the D.C. Circuit explained in 

the Medical Waste Incinerator (MWI) NESHAP decision, for an emissions limit to be achieved 

in practice, it must be achievable under the worst foreseeable circumstances. Sierra Club v. 

EPA, 167 F.3d 658 (D.C. Cir. 1999). In the CKRC II decision, the D.C. Circuit noted that the 

performance of non-floor sources can be indicative of what variability the floor sources might 

experience. The Durkee plant may or may not be a floor source. However, there is no reason to 

believe that the variability that the Durkee quarry experiences in its limestone is not indicative of 

the variability experienced at all quarries. Mercury can vary considerably over a single mineral 

formation (as demonstrated in Figures 2 and 3 below) and this variability must be accounted for 

in setting the floor. The length of time represented by the Durkee quarry data make it ideally 

suited for use in establishing floor variability. 

Ash Grove believes that EPA has not adequately accounted for variability in establishing the 

mercury floors. The PCA comments provide extensive detail regarding the need to account for 

actual variability in establishing the floor and we do not reproduce those data or arguments here. 

However, Ash Grove adopts by reference those arguments to the maximum extent that they are 

consistent with the remainder of this letter. We urge EPA to revise the new and existing source 

floors to properly account for variability. 

 B. Choice of Sources in Floor

Ash Grove has considerable concern over the sources that were chosen for establishing the floor. 

Section 112(d)(3) states that the new source standards “shall not be less stringent than the 

emission control that is achieved in practice by the best controlled similar source.” For existing 

sources the Act similarly states that it must be a source representative of that category or 

subcategory. Notwithstanding the requirement that a floor source must be representative of the 

sources in the category or subcategory, The source that is identified as the lowest emitting source 

(source 1233 in Table 1), is not representative of the predominant product type manufactured by 

that kiln. Kiln 1233 was manufacturing oil well cement during the time that mercury data were 

gathered and so the data are not representative of typical operation of that kiln or any other kiln 

in the category as oil well cement is only a small fraction of the cement manufactured in the 

industry. While the oil well cement was within the range of products manufactured in this kiln, 

we understand that it only represents less than 20 percent of the total production on an annual 

basis. A second kiln with the same configuration at the same plant (source 1560) emitted 

approximately seven times more mercury than source 1233 during the same time period while 

making the primary product of the plant (Type I/II clinker). In addition, four of the eleven kilns 

identified as part of the floor (1302, 1315, 1286 and 1364) are older wet kilns that are currently 
Keith Barnett 

September 4, 2009 

Page 5 

not operating and so should not be considered part of the floor as they are no longer part of the 

best performing 12 percent of sources. While Ash Grove cannot comment on the likelihood of 

restarting for the two kilns in this group that it does not own, Ash Grove can say that the 

likelihood of restarting the two kilns it does own is low given the current economic downturn 

and that the kilns are old wet kilns located at a plant that has been in operation since 1929. 

Given this situation, we believe that there is no longer any basis to consider these kilns as 

operational, “similar sources” or actually achieving any emission rate—all prerequisites to 

considering them part of the floor. 

EPA should revise the standard to exclude data from source 1233 to the extent that it was not 

representative of industry operations. Alternatively, the variability analysis must include the full 

range of variability associated with kiln 1233 manufacturing Type I/II cement (as exemplified by 

the collocated kiln 1560). Similarly EPA should remove sources 1302, 1315, 1286 and 1364 

from the floor as they are no longer part of any category or subcategory. 

 

C. Subcategorization Based on Limestone Mercury Content 

Ash Grove believes that the final rule should include a separate subcategory based on the 

mercury content of the limestone in an affected source’s quarry. In the preamble, EPA expressly 

solicited comments on whether it is appropriate to subcategorize for purposes of the mercury 

standard. Ash Grove sees several bases for subcategorization, including differences in kiln type 

and need to waste CKD. However, the most important subcategory to establish relates to the 

mercury content of the on-site limestone that is introduced into the kiln. In developing the rule, 

EPA considered the quarries collocated with cement kilns as a part of the affected source. This 

has manifested itself in the way that the limits were developed, with the best performing source 

being inextricably linked to the mercury content of the collocated quarry. Every kiln in the floor 

had limestone mercury concentration of less than 25 ppb. In this regard, the attributes of the 

quarry define the nature of the affected source every bit as much as the type of fuel defines the 

nature of a boiler. Just as EPA subcategorized based on the fuel attributes when it published its 

Boiler NESHAP, EPA should similarly subcategorize when it promulgates the Portland Cement 

NESHAP. The nature and design considerations of the facility are determined by the 

characteristics of the on-site limestone and other raw materials and thus justify a separate 

subcategory. 

 1. EPA Precedent for Establishing Subcategories 

Both the Clean Air Act and the courts clearly recognize EPA’s tremendous discretion in 

establishing NESHAP subcategories. Section 112(d)(1) of the Clean Air Act states that “The 

Administrator may distinguish among classes, types, and sizes of sources within a category or 

subcategory in establishing such standards...” Therefore, there is clearly authority under the Act 

for establishment of subcategories. This authority is not specifically limited by the Act, thus 

leaving the agency substantial discretion in how it establishes subcategories and the appropriate 

criteria for subcategorizing source categories include “technology, process, product, and 
Keith Barnett 

September 4, 2009 

Page 6 

emissions characteristics.” Natural Resources Defense Council v. Envtl. Prot. Agency, 489 F.3d 

1364, 1372 (D.C. Cir. 2007) (PCWP MACT); see also 67 Fed. Reg. 78045, 78058 (Dec. 20, 

2002) (subcategorization typically reflects “differences in manufacturing process, emission 

characteristics, or technical feasibility...”). 

On multiple occasions over the past decade, EPA has discussed the appropriate bases for 

establishing subcategories. A lengthy discussion of the appropriate basis for subcategorization 

can be found in the preamble to the Secondary Aluminum Production NESHAP. There EPA 

stated: 

“Subcategorization within a source category may be considered when 

there is enough evidence to demonstrate clearly that there are 

significant differences among the subcategories. The criteria to 

consider include process operations (including differences between 

batch and continuous operations), emission characteristics, control 

device applicability, safety, and opportunities for pollution 

prevention. 

“The EPA examined the processes, the process operations, and other 

factors to determine if separate classes of units, operations, or other 

criteria have an effect on air emissions from emission sources, or the 

controllability of those emissions. Based on differences in emissions, 

the type of materials processed and the fluxing practices 

employed, the EPA has distinguished two specific classes of 

melting, holding, and refining furnaces. Because HAP emission 

potential is strongly influenced by the contaminants present in the 

materials that are melted and the type and amount of flux added, these 

furnaces would be subject to separate standards under the proposed 

rule.” 64 Fed. Reg. 6960 (Feb. 11, 1999) (emphasis added). 

Thus, as far back as 1999 EPA was recognizing that the constituents in the raw materials form a 

reasonable basis for subcategorization where the air emissions are affected by those constituents. 

EPA took a similar position in the 2000 proposal for the Generic MACT rule. In that case EPA 

once again noted that multiple different characteristics, including the ability (or inability) to 

avoid a particular HAP (i.e., pollution prevention), are identified: 

“Section 112(d)(1) of the CAA gives us the authority to ‘‘* * * 

distinguish among classes, types, and sizes of sources within a 

category * * *’’ when developing standards. Subcategories, or 

subsets of similar emission sources within a source category, 

may be defined if technical differences in emissions 

characteristics, processes, control device applicability, or 
Keith Barnett 

September 4, 2009 

Page 7 

opportunities for pollution prevention exist within the source 

category (57 FR 31576). Specific examples of these differences 

include the types of products, process equipment differences, 

the type and level of emission controls, emissions sources, and 

any other factors that would impact a MACT standard.” 65 

Fed. Reg. 76413 (Dec. 6, 2000) (emphasis added). 

This passage indicates a clear agency understanding of the breadth of characteristics that can be 

taken into account in establishing a subcategory. 

Consideration of differences in emission characteristics was also identified as a basis for 

subcategorization in the Primary Copper Smelting NESHAP. There EPA stated: 

 “Section 112 of the CAA provides the Administrator the discretion to 

divide categories of sources into subcategories where appropriate. In 

establishing such source categories for other source categories in the 

NESHAP program, we have considered factors such as differences 

in process operations (including differences between batch and 

continuous operation), emission characteristics, control device 

applicability, and opportunities for pollution prevention.” Primary 

Copper Smelting NESHAP Background Information Document at 2-6 

(2001) (emphasis added). 

The consideration of emission characteristics and the constituents in the raw materials are quite 

distinct from the subcategorization criteria that have been previously criticized by the courts as 

well as by environmental groups. In the Plywood and Composite Wood Product (“PCWP”) 

NESHAP the Sierra Club criticized EPA for subcategorizing based on cost or based on risk. As 

EPA stated in that rule’s preamble, 

“The commenter stated that subcategories based solely on risk do not 

bear a reasonable relationship to Congress’ technology based approach 

or the statutory structure and purposes of CAA section 112, and are not 

authorized by the CAA. 

“According to the commenter, categories and subcategories are 

required to be consistent with the categories of stationary sources in 

CAA section 111. The commenter was not aware of any instance in 

which EPA has established categories or subcategories based on risk. 

The commenter stated that EPA routinely defines subcategories 

based on equipment characteristics (e.g., technical differences in 

emissions characteristics, processes, control device applicability, 

or opportunities for P2). According to the commenter, EPA has not 
Keith Barnett 

September 4, 2009 

Page 8 

offered any explanation for why reinterpreting the statute to ignore 

nearly 12 years of settled practices and expectations under the MACT 

program is reasonable, nor why reducing the applicability of HAP 

emission standards serves Congress’s goals in enacting the 1990 CAA 

Amendments.” 69 Fed. Reg. 45987 (July 30, 2004) (emphasis added). 

In this response to comment, EPA outlined the position of the environmental groups, namely that 

subcategorization cannot be based on risk. However, EPA also made clear that the 

environmental group’s belief that differences in emissions characteristics, processes, control 

device applicability, and opportunities for pollution prevention are well established bases for 

subcategorization. In evaluating the PCWP rule, the D.C. Circuit specified that subcategories are 

a step in the path towards establishing emission standards and recognized EPA’s “broad 

subcategorization authority.” NRDC v. EPA, 489 F.3d 1364,1372 (D.C. Cir. 2007). The court 

held in that case that EPA could not establish a subcategory “whose defining characteristic is that 

its members will never be subject to emission standards.” Id. However, the court never 

questioned the broad discretion EPA has to create subcategories where the subcategory members 

are appropriately evaluated and made subject to emissions standards. 

In the Fabric Coating NESHAP, EPA again outlined its basis for subcategorization. 

 “The statute gives us discretion to determine if and how to 

subcategorize. *** A subcategory is a group of similar sources within 

a given source category. As part of the regulatory development 

process, we evaluate the similarities and differences between industry 

segments or groups of affected sources comprising a source category. 

In establishing subcategories, we consider factors such as process 

operations (type of process, raw materials, chemistry/formulation 

data, associated equipment, and final products); emission 

characteristics (amount and type of HAP); add-on control device 

applicability; and opportunities for pollution prevention. We may 

also consider existing rules or guidance from States and other 

regulatory agencies in determining subcategories.” 67 Fed. Reg. 

46039 (July 11, 2002) (emphasis added). 

In addition to emissions characteristics, processes, control device applicability, and opportunities 

for pollution prevention, EPA has also considered scale of emissions as a basis for 

subcategorization; EPA has defined subcategories based on the tonnage of emissions. For 

example, in the Reinforced Plastic Composites (“RPC”) NESHAP EPA defined two different 

new source subcategories based on the level of HAP emissions from the source. 

 “We developed subcategories based on size (i.e., tpy of HAP emitted) 

in defining the new source MACT floors. These subcategories are 

sources that emit 100 tpy or more from open molding, pultrusion, 
Keith Barnett 

September 4, 2009 

Page 9 

centrifugal casting, continuous lamination/casting, SMC and BMC 

manufacturing, and mixing operations; and all other new sources.” 

68 Fed. Reg. 19377 (April 21, 2003). 

EPA explained magnitude of emissions as a basis for subcategorization as follows: 

 “In developing the floor for new sources, we developed two 

subcategories--sources with emissions of 100 tpy or above and 

sources with emissions below 100 tpy. Our reason for examining 

sources with emissions below 100 tpy separately is that such 

facilities are likely to have more difficulty maintaining and 

operating add-on controls than larger-emitting sources, and we 

are unsure of the performance of add-on controls at these 

facilities. Separating the data into large and small HAP-emitting 

sources for developing new source MACT floors was also one of the 

recommendations of the SBAR Panel.” 66 Fed. Reg. 40324 

(Aug 2, 2001) (emphasis added). 

In that same NESHAP EPA also subcategorized for existing sources based on other criteria: 

 “However, we did segregate existing sources by resin application 

technique, resin type, and final products, and developed separate 

floors for each process/product grouping.” Id. 

Thus, in the RPC NESHAP, EPA concluded that it was appropriate to subcategorize based on 

magnitude of HAP emissions and the nature of the raw material inputs, among other things. Part 

of the consideration for subcategorization based on magnitude of emissions was the difference in 

ability to control between the two subcategories. 

The recognition of EPA’s broad authority to subcategorize and the appropriateness of 

subcategorization based on raw material attributes is not limited to EPA. In its comments on the 

Boiler NESHAP, the Natural Resources Defense Council (“NRDC”) made the following 

comments: 

 “EPA has previously interpreted the statutory term “category” to mean 

equipment that shares physical characteristics relevant to the degree of 

pollution control that can be achieved. The Agency likewise has stated 

that subcategories should be defined by considering ‘process 

operations (types of process, raw materials, chemistry/formulation 

data, associated equipment and final products); emissions 

characteristics (amount and type of HAPs); add-on control device 

applicability; and opportunities for pollution prevention.’ The EPA 
Keith Barnett 

September 4, 2009 

Page 10 

recognized the importance of differences based on the type of products 

and processes when it stated: 

Subcategories, or subsets of similar emission sources 

within a source category, may be defined if technical 

differences in emissions characteristics, processes, 

control device applicability, or opportunities for 

pollution prevention exist within the source category.

Specific examples of these differences include the types 

of products, process equipment differences, the type and 

level of emission controls, emissions sources, and any 

other factors that would impact a MACT standard.

Indeed, an earlier agency proposal reaffirmed EPA’s interpretation that 

its subcategorization authority is limited to relevant physical and 

operational characteristics of the equipment in question, not the health 

effects of the pollution it emits. EPA’s interpretation is eminently 

reasonable, and is entitled to judicial deference. By contrast, if EPA 

chooses to reverse itself and begin to subcategorize based on risk, it 

faces an uphill climb; such changes in interpretation are “entitled to 

considerably less deference than a consistently held agency view.”

EPA has not offered any explanation as to why reinterpreting the 

statute to ignore nearly 12 years of settled practices and expectations 

under the MACT program is reasonable, nor why reducing the 

applicability of HAP emission standards serves Congress’s goals in 

enacting the 1990 CAAA.” NRDC Comments on Boiler NESHAP; 

Docket ID No. EPA-HQ-OAR-2002-0058 at 20-21 (March 14, 2003) 

(emphasis added in NRDC letter; citations and footnotes omitted). 

Thus, NRDC itself has recognized that there are multiple different bases for creating 

subcategories including technical differences in emissions characteristics, processes, control 

device applicability, or opportunities for pollution prevention exist within the source category. 

These include multiple different possible characteristics under the classification of “process,” 

including differences in raw materials and chemistry/formulation data. NRDC’s statement that 

these bases for subcategorization are “eminently reasonable” and “entitled to judicial deference” 

are every bit as notable as NRDC’s demand that EPA not “ignore 12 years of settled practices,” 

In light of NRDC’s comment, it appears that there is broad support for the concept that it is 

appropriate to create a subcategory for a group of sources that have a fundamentally different 

limestone mercury contents based on EPA’s precedent of establishing subcategories based on, 

among other things, technical differences in emissions characteristics, processes, control device 

applicability and opportunities for pollution prevention. This approach is consistent with EPA’s 

established interpretation of subcategorization as well as the goal underlying section 112, namely 

ensuring the use of the maximum achievable control technology. 
Keith Barnett 

September 4, 2009 

Page 11 

 2. The Data Support EPA Establishing Subcategory for Affected Sources 

With ≥225 ppb Mercury in Their Limestone 

Based on this extensive subcategorization precedent in other NESHAPs, the data presented in 

Figure 1 and Table 3 of the Preamble provide strong justification for establishment of a 

subcategory based on mercury content in limestone. The data collected as part of the 114 request 

identify two affected sources, Nos. 1629 and 1609, which bear no relationship to the data points 

in the remainder of the data set. Even the most superficial analysis indicates that those two 

affected sources form a separate and distinct data set as compared to the other sources. Based on 

Ash Grove’s statistical assessment of the data, the break point between the two data sets occurs 

at 225 ppb.2 Only one other kiln was even identified as having limestone mercury content in 

excess of this value and that data point is clearly in error based on review of the underlying data 

and should reflect a much lower average value. Table 3 of the Preamble documents that the 

mercury emitted by the two affected sources in the separate data set is almost exclusively due to 

mercury in the limestone with essentially no mercury coming from fuels. As a result, the 

mercury is virtually entirely due to the nature of the on-site materials that are intrinsic to the kiln 

itself and part of the affected source. Based on agency precedent, a separate subcategory is 

appropriate for sources with greater than or equal to 225 ppb mercury in their limestone as these 

sources form a different type and class of source from the other category members. EPA would 

be acting contrary to over 10 years of precedent if it chooses in this instance to not subcategorize 

based on the nature of the raw materials, chemistry formulation data, emissions characteristics 

and quantity of emissions. This would amount to a change in interpretation of the law and such 

changes in interpretation are “entitled to considerably less deference than a consistently held 

agency view.” INS v. Cardoza-Fonseca, 480 U.S. 421, 446 n.3 (1987) (internal quotations 

omitted). Where the agency has previously subcategorized based on the same criteria and the 

distinction between the two subcategories is so strong, the failure to subcategorize in this 

instance would be arbitrary and capricious. 

 3. Creating a ≥225 ppb Subcategory is Consistent With the Brick MACT 

Decision 

Establishing a ≥225 ppb subcategory is strongly supported by the courts. As Judge Williams 

noted in his concurrence in Sierra Club v. Envtl. Prot. Agency, 479 F.3d 875, 885 (D.C. Cir. 

 

2

 Ash Grove evaluated the source category break point as 225 ppb by taking the average of 

Tehachapi and Durkee and subtracting two standard deviations. Ash Grove understands that 

PCA identified a different break point using a different methodology. Ash Grove believes that 

while either methodology provides a rational means of distinguishing the two data sets, from a 

policy perspective it is preferable to employ the higher value. For that reason, in this letter we 

identify the subcategories in relation to a 225 ppb break point. 
Keith Barnett 

September 4, 2009 

Page 12 

2007) (Brick MACT), “one legitimate basis for creating additional subcategories must be the 

interest in keeping the relation between ‘achieved’ and ‘achievable’ in accord with common 

sense and the reasonable meaning of the statute.” Judge Williams’ language is prescient in this 

case where the difference between the ability to comply of the ≥225 ppb sources is so markedly 

different from all of the other sources. EPA even identifies in the preamble the paradox that 

while the Durkee kiln is in the process of installing the best known mercury controls (currently 

anticipated to start controlling mercury in early 2010), the plant will likely be forced to close if 

the standard is promulgated without subcategorization. Preamble at 21148 (“[The Durkee kiln] 

has voluntarily entered into an enforceable agreement to install activated carbon (the best control 

technology currently available so far as is known) to control its mercury emissions. *** 

Closure of this kiln and possibly other high mercury emitting kilns is a possible consequence of a 

single standard without subcategories.”). Drawing from the language in Judge Williams’ Brick 

MACT concurring opinion, EPA must create a ≥225 ppb subcategory as “one legitimate basis for 

creating additional subcategories must be the interest in keeping the relation between “achieved” 

and “achievable” in accord with common sense and the reasonable meaning of the statute.” 

Brick MACT at 884-85. 

4. Creating a ≥225 ppb Subcategory is Consistent With the Legislative History 

of the Clean Air Act 

This approach is consistent with the legislative history of the Clean Air Act. As the D.C. Circuit 

recognized in the Primary Copper Smelter NESHAP decision, “the substitution of cleaner ore 

stocks was not, in any event, a feasible basis on which to set emission standards...[where] 

metallic impurity levels are variable and unpredictable both from mine to mine and within 

specific ore deposits.” Sierra Club v. EPA, 353 F.3d 976, 988 (D.C. Cir. 2004) (“Copper 

Smelter MACT”). This statement relates closely to discussions that occurred when Section 112 

was developed by Congress. When 112(d) standards were developed, the possibility of requiring 

substitution of cleaner ore stocks was considered. In the Conference Committee report, 

Congress stated that “the Administrator shall not consider the substitution of, or other changes in, 

metal- or mineral-bearing raw materials that are being used as feedstocks or material inputs...” 

Conference Committee Explanatory Statement. This statement shows that it was never 

Congress’ intent to require a mine-mouth industry, such as a cement plant, to physically move so 

that it could utilize a different feedstock. However, as the D.C. Circuit has made equally clear, 

that directive must be read in conjunction with the statements in the Act that the floor must be 

established based on the best performing 12 percent of the existing sources. The way to 

harmonize these directives for the Portland Cement NESHAP is to establish a subcategory that is 

cognizant of the feedstock attributes and to establish a floor accordingly. EPA can then go 

beyond the floor in determining the appropriate standard for that particular subcategory. The 

Conference Committee statement is not intended to exempt sources from the NESHAPs, but 

rather to ensure that, in Judge Williams’ words, EPA maintains “the relationship between 

‘achieved’ and ‘achievable’ in accord with common sense and the reasonable meaning of the 

statute.” Brick MACT at 885. 
Keith Barnett 

September 4, 2009 

Page 13 

Congress’ intent in relation to subcategorization is also made clear in the Senate Report 

associated with the 1990 Amendments. The Senate Report states that “the Administrator may 

take into account factors such as industrial or commercial category, facility size, type of process 

and other characteristics of sources which are likely to affect the feasibility and effectiveness of 

air pollution control technology.” S. Rep. No. 228, 101st Cong., 1st Sess. 166 (1989) (emphasis 

added). It also notes that “where a group of sources may share the characteristics of other 

sources in the category, the Administrator may establish subcategories for such sources.” Id. 

Pollutant concentrations in raw materials upon which sources must rely are certainly such 

“characteristics” of the sources that may lead to a determination of appropriate “classes” or 

“types” of sources. A kiln and the collocated quarry upon which it relies must be viewed 

together when determining the class or type of source. Put another way, two different kilns at 

different locations that rely upon limestone deposits with significantly different mercury 

concentrations should not be considered “similar sources” under § 112(d)(3). Using mercury 

concentration in the limestone is an equally appropriate means of subcategorization as 

subcategorizing for different coatings which have different levels and types of volatile HAPs in 

them (see, Subpart PPPP for an example of different coatings being placed in different 

subcategories based on the VHAP makeup of the coating; 67 Fed. Reg. 72288 (Dec. 4, 2002)). 

Congress’ intent in relation to subcategorization is similarly made clear in the House Report 

associated with the 1990 Amendments. The House Report states that: 

 “The Committee expects MACT to be meaningful, so that MACT will 

require substantial reductions in emissions from uncontrolled levels. 

However, MACT is not intended to require unsafe control 

measures, or to drive sources to the brink of shutdown.” House 

Rep. No. 101-490, Part 1, at 328 (May 17, 1990) (emphasis added). 

This passage evidences a clear intent for EPA to take such measures that are consistent with the 

language of the Act to ensure that the NESHAP program does not result in plant closure. Read 

in conjunction with Judge Williams concurring opinion in the Brick MACT decision, there is a 

clear mandate to create a subcategory for the ≥225 ppb sources and prevent the closure of the 

Durkee and Tehachapi plants predicted by EPA if the standard is promulgated as proposed. 

Preamble at 21166 (“These retirements include two kilns that we have determined may close due 

to not being able to meet the mercury emission limits due to unusually high mercury contents in 

their proprietary quarries (i.e., the mercury content of the raw material at limestone quarries)”). 

 5. Ash Grove’s Durkee Plant Merits Creation of a Subcategory

The justification for a subcategory for the ≥225 ppb sources is particularly forceful in relation to 

Ash Grove’s Durkee, Oregon plant. Ash Grove’s Durkee plant, like most cement plants, relies 
Keith Barnett 

September 4, 2009 

Page 14 

on limestone that is removed from a collocated quarry.3 This limestone has elevated levels of 

naturally occurring mercury. In late 2006 Ash Grove voluntarily performed extensive testing to 

better understand the nature and magnitude of its mercury emissions. This constituted some of 

the most advanced and comprehensive mercury stack and raw material testing ever performed at 

a cement plant. Ash Grove engaged national experts to perform multiple different types of tests 

using a variety of test methods so as to increase the company’s understanding of the quantity and 

type of mercury emitted from the plant. The stack testing indicated that the vast majority of the 

mercury was either oxidized mercury or elemental mercury, with elemental mercury making up 

as much as 70 percent of the total. 

Ash Grove voluntarily decided to develop mercury emission controls for its Durkee plant. 

Ash Grove knew that no cement plant in the country had installed controls for the purpose of 

reducing mercury emissions. Five kilns in the country have wet scrubbers to control sulfur 

dioxide emissions and some of these controls appear to provide a moderate level of mercury 

control.4

 Wet scrubbers are ineffective on elemental mercury as elemental mercury is not water 

soluble. Given that up to 70 percent of the mercury at the Durkee plant was shown to be in the 

elemental form, a scrubber is not an optimal control device. Ash Grove also understood that 

scrubbers (which consume millions of gallons of water per year) are not a practical control 

technology in the arid western U.S, where water is scarce. Therefore, Ash Grove realized that it 

was going to have to develop a means of controlling mercury that was previously unknown in the 

industry. Ash Grove engaged the experts at EERC, a research center associated with the 

University of North Dakota that had extensive experience developing mercury control and 

monitoring techniques in the electrical generation sector. Based on the stack test data, the EERC 

researchers proposed the use of an activated carbon injection (“ACI”) system to control mercury 

emissions. Ash Grove invested over $1 million to have EERC temporarily install a pilot ACI 

 

3

 EPA acknowledged in the proposed rule that quarries are virtually always collocated with the 

affected source and that the quarry is therefore part of the affected source: 

“All cement plans have a limestone quarry located adjacent to or very close to the 

cement plant. This quarry supplies limestone only to its associated plant, and is 

not accessible to other plants. Typically quarries are developed to provide 50 to 

100 years of limestone, and the cement kiln is located based on the location of the 

quarry. See 70 FR at 72333. For this reason, we believe that a facility’s 

proprietary quarry is an inherent part of the process such that the kiln and the 

quarry together can be viewed as the affected source.” Proposal at 21145. 

4

 EPA’s data indicate that the scrubbers achieved between 0 and 81 percent control during the 

sources test periods. These data do not suggest any level of control can be assumed across the 

industry and they do not account for the re-emission of mercury documented to occur in wet 

scrubbers. 
Keith Barnett 

September 4, 2009 

Page 15 

system at the Durkee plant. EERC was at the plant installing and operating the pilot system for 

over six weeks. A small percentage of the exhaust gas (~1 percent) was removed from the 

ductwork after passing through the plant’s main baghouse. This gas was routed through the ACI 

system and the emissions entering and exiting the system were carefully studied. Based on this 

in situ study EERC predicted that if the performance of a full scale system matched that of the 

pilot system, Ash Grove could reduce mercury emissions by approximately 75 percent on an 

annual average basis. The EERC data suggested that there could be material variability in 

control on a day to day basis (a conclusion supported by the PCA variability analysis of the 

available CEM data). As a result, any standard based on a 30 day rolling average will be more 

stringent than a standard based on an annual average. 

Although Ash Grove believed that the EERC study had developed the optimum system design, 

the company conducted a peer review of EERC’s work with a broad array of stakeholders. 

Through a partnership with local residents, environmental groups, Tribes and the state 

environmental and health agencies, Ash Grove went through a long and public process to 

determine the best means of addressing mercury emissions. What ultimately was approved by 

this diverse team was the installation of an activated carbon injection system with a recirculation 

loop and mercury recovery. This system achieves maximum mercury control with minimum 

waste generation and minimizes the transfer of the mercury from one released media to another 

released media. These controls are anticipated to achieve a system removal efficiency of at least 

75 percent. However, Ash Grove voluntarily entered into an enforceable order with the state to 

not only achieve 75 percent control, but to also strive to improve the SRE to as close to 85 

percent as reasonably possible. To further ensure the public’s knowledge and approval of this 

type and level of control, the enforceable order was placed on public notice with the opportunity 

to submit comments. In addition, a public hearing was held about the terms of the order. In the 

end, the order was finalized with the 75/85 percent control requirements determined appropriate 

by the advisory committee. This level of mercury control has previously been considered 

unattainable in the cement industry and Ash Grove is well into construction on the controls that 

will establish the state of the art for mercury control technology on cement kilns. Absent 

negative impacts from the Portland Cement NESHAP rulemaking, Ash Grove anticipates 

commencing operation of these controls in approximately April 2010. 

 6. Apply a Beyond the Floor Standard to the ≥225 ppb Subcategory 

Ash Grove believes that the most sound means of addressing the affected sources with high 

mercury limestone is through subcategorization and the establishment of a 112(d)(2) standard 

that requires beyond the floor controls. If EPA establishes a ≥225 ppb subcategory, there will be 

two sources in this database for evaluation in setting the floor. This floor emission rate would 

equate to a relatively high value in comparison to the standard applicable to the other sources in 

the category. However, EPA could then choose to go beyond the floor and establish a standard 

that reflects the Durkee kiln’s use of ACI. As noted above, EPA would be on sound footing if it 

created a subcategory based on the two ≥225 ppb plants and required beyond the floor control. 

As Judge Williams noted in his Brick MACT concurring opinion, if the statute produced a result 
Keith Barnett 

September 4, 2009 

Page 16 

demonstrably at odds with the intentions of its drafters, it would “justify judicial surgery.” Brick 

MACT at 885. It would seem demonstrably at odds with the drafters’ intentions to impose a 

standard on a plant that it cannot comply with even when using the most advanced mercury 

controls on any cement kiln in the country. For that reason, we believe that it is appropriate for 

EPA to establish a separate subcategory reflective of the two unique facilities and to establish the 

floor based on those plants’ mercury emission levels. EPA could then go beyond the floor to 

account for the actual emission rate that will be achieved through the Durkee plant’s 

extraordinary efforts to control mercury emissions. The emission standard could also be crafted 

to include work practices prohibiting the use of off-site raw materials containing material levels 

of mercury (e.g., fly ash) and, as discussed below, requiring dust shuttling up to the maximum 

level that does not impact product quality. 

 7. Material Reductions Beyond Those Achievable by ACI Cannot be Reliably 

Estimated or Achieved

In establishing the “beyond the floor” standard for 

the ≥225 ppb affected sources, the standard should 

not be more stringent than what is required of the 

Durkee kiln in its Order. As discussed above, the 

Durkee kiln must meet a minimum 75 percent 

mercury removal efficiency and take all 

reasonable measures to achieve an 85 percent 

removal efficiency. Ash Grove’s extensive 

analysis has concluded that it cannot provide 

material levels of control in excess of what is 

expected to be derived from installation of the 

ACI system. Ash Grove has assessed the 

following different means of potentially further 

decreasing mercury emissions at the Durkee plant: 

1) selective mining (i.e., removal and wasting of 

high mercury ore and only using low mercury 

ore), 2) use of a scrubber in series with the ACI 

system, 3) “dust shuttling,” and 4) limestone 

scrubbing. Ash Grove’s analysis of each option is 

described below. 
Keith Barnett 

September 4, 2009 

Page 17 

i. Selective Mining 

In order to understand the challenges of selective mining in a quarry, it is critical to understand 

the geologic history that resulted in limestone with elevated mercury levels. Mercury tends to 

naturally occur at elevated levels in locations with a history of geothermal activity. Mercury is a 

crustal element that is distributed throughout the planet (the average mercury concentration in 

the earth’s crust is approximately 80 ppb).5 However, there are some places where mercury is 

concentrated at higher levels near the surface (i.e., within the top mile or two of the earth’s 

surface). Although there are different theories for why that occurs, the leading theory is that it 

has to do with historic geothermal activity in the aftermath of tectonic plate movement. Metals 

with low boiling temperatures (e.g., gold, mercury) are volatilized by magma caused by the 

tremendous heat of friction resulting from the grinding of tectonic plates where they meet. The 

magma results in superheated steam intermixed with the volatilized metals. This mixture is 

channeled towards the surface through pathways in the rock. Where rock is heavily fractured as 

the result of historic folding, faulting and intrusions, it provides conduits for the mineralized 

solutions. The metals then condense in the upper fractured rock layers. Recurrent fracturing 

opens new conduits and shifts the existing ones so that the mercury becomes distributed 

randomly over the zone. As the result of tectonic activity during the Mesozoic period (starting 

about 251 million years ago), an island arc was accreted and the associated deformed strata 

created a orogenic belt that extends up through parts of California, goes through the southwest 

corner of Oregon before disappearing under lava cover and resurfacing in northeastern Oregon. 

This belt is heavily fractured and has a history of geothermal activity that resulted in the 

deposition of gold and mercury throughout the band. Ash Grove’s Durkee plant is located in the 

northern section of the belt while the other affected source in the ≥225 ppb subcategory (Lehigh 

 

5

 From Sources and Receptors of Mercury (Idaho, January 28, 2009). 

“Regional Soil Emissions It is important to note that the earth’s crust naturally contains 

approximately 80 parts per billion of mercury (Mason 1966), and it is widely recognized 

that even “clean” soils with background concentrations of mercury release volatile mercury 

to the air (Gustin et. al. 2008). This is especially important in the west where soil mercury 

concentrations can be enhanced by local geology (Zehner and Gustin 2002, Gustin et. al. 

2000), and Idaho is no exception. A preliminary, very conservative estimate of 

background soil emissions in Idaho suggests that soil emissions of mercury in Idaho could 

be of the same magnitude as the sum of all industrial sources in the state (Lindberg, 

2008). 

The most comprehensive measurements of soil emissions of mercury have been done in 

Nevada where the authors cited above estimated annual releases of ~3.8 T/y, more than 

14 times greater than the currently reported industrial emissions in Idaho (Gustin, et al. 

2008). The same authors estimate that natural mercury emissions from mineralized areas 

in the western U.S. as a whole are 10 to 20 tons/year, or more than 38 times greater than 

the currently reported industrial emissions in Idaho.” 
Keith Barnett 

September 4, 2009 

Page 18 

Cement Company’s Tehachapi, CA plant) is located in the southern portion of this belt. The 

portion of the accretion that makes up the Blue Mountains is surrounded on the north, west and 

south by basaltic flows that occurred comparatively recently as a result of shield flooding of lava 

during the mid-Miocene period. As a result, the Blue Mountains are largely surrounded by a 

zone of basalt layers that are not conducive to geothermal activity and possess neither limestone 

nor the elevated levels of mercury found within the Blue Mountain belt. As Figure 1 indicates, 

the orogenic belt that starts in the Blue Mountains and extends down into Southern California 

has similar geologic characteristics.6 Unsurprisingly, the cement plants with elevated mercury 

naturally occurring in their limestone deposits are both situated in this belt. The plants located in 

this belt (or similarly configured areas of the country if any are found in the future) should be 

part of a separate subcategory under the Portland Cement NESHAP. 

The very geologic attributes that resulted in mercury being elevated in these parts of the western 

U.S. also resulted in the mercury being randomly distributed across the quarries in these areas. 

The highly fractured nature of the limestone in the orogenic belt underlying the two ≥225 ppb 

affected sources is the reason why the mercury laden thermal solutions were deposited in these 

area. These fractures continued beyond the time period where the mercury was deposited. As a 

result, the mercury is diffused across the deposits and there is no reasonable means of seperating 

higher mercury limestone from lower mercury limestone. Several years of data from Ash 

Grove’s Durkee quarry support this statement. Starting in 2007, Ash Grove began collecting 

monthly composite samples of the limestone removed from its quarry (see, Table 1 above). 

Mining is performed on benches, with Ash Grove moving up and down the working face of the 

quarry, blasting roughly 40,000 ton “shots”. The data from this sampling is telling. First, it 

shows that the ore varies considerably on a month-to-month basis ranging from 424 ppb to 1,740 

ppb. In order to determine whewther there was some means to predict and avoid higher 

concentration areas in the quarry, Ash Grove then mapped the mercury concentrations, 

correlating them with the quarry areas being worked. As Figure 2 below shows, there is no 

predictability to where in the quarry one will find higher v. lower concentrations of mercury in 

the ore. To evalaute the same question on a higher resolution, Ash Grove also evaluated ore 

removed when drilling blast holes in one individual shot was prepared for blasting at the quarry. 

As Figure 3 shows, the mercury concentrations across the individual shot were strikingly diverse. 

Ore with 2,790 ppb was 50 feet from ore with 539 ppb; ore with 1,250 ppb was 10 feet from ore 

with 767 ppb. The clear conclusion from this sampling is that mercury levels can change 

dramatically by moving just a few feet across the top of an indivudual bench and is unpredictable 

across the entirety of the quarry. As a result, Ash Grove has concluded that there is no 

reasonable basis for trying to selectively mine ore so as to decrease the mercury of its raw feed. 

 

6

 Figure reproduced from W.R. Dickenson, Cordilleran Sedimentary Assemblages; Early 

Mesozoic-Tectonic Evolution, (1992) 
Keith Barnett 

September 4, 2009 

Page 19 

Figure 2: Mercury Levels in Durkee Quarry 2007-2009
Keith Barnett 

September 4, 2009 

Page 20 

 ii. Serial Scrubber 

Another possibility Ash Grove evaluated for potentially obtaining additional mercury reduction 

was the use of a wet scrubber in series with the ACI system. The ACI system functions as a dry 

mercury scrubber. However, wet scrubbers showed some ability to decrease mercury emissions 

and so Ash Grove assessed whether the addition of a wet scrubber in line with the dry scrubber 

(i.e., ACI) would result in enhanced control. However, as noted above, wet scrubbers only 

control oxidized mercury as elemental mercury is not water soluble. Given that testing at the 

Durkee kiln indicated that up to 70 percent of the mercury is in the elemental form, a wet 

scrubber is not going to provide a material amount of additional control. The ACI system is 

predicted to control high levels of the oxidized mercury as well as promote the oxidation of the 

elemental mercury. Therefore, no material additive benefit would come from the use of a wet 

scrubber. In addition, wet scrubbers require millions of gallons of water per year—Ash Grove 

Figure 3. Mercury Sampling Across a Single Blast Area (Shot) 
Keith Barnett 

September 4, 2009 

Page 21 

estimates that a wet scrubber appropriate for the Durkee plant would consumer approximately 21 

million gallons per year. The annual rainfall in Durkee, Oregon is approximately 8 inches per 

year and there is simply no availability of water for use in a wet scrubber. Therefore, both for 

the reason that a wet scrubber would not provide a material benefit when run in series with the 

ACI system and because water is not available in the area, Ash Grove concluded that a wet 

scrubber is not meaningful control technology with which to supplement the efficiency of the 

ACI system. 

 iii. Dust Shuttling 

One approach which conceivably could provide a small additional boost in control efficiency at 

the Durkee plant is bleeding a percentage of the dust collected in the primary baghouse into the 

finished product. Ash Grove’s research suggests that mercury is scrubbed in the raw mill when 

the “waste” heat in the kiln gases is used to dry incoming raw feed. It is theorized that mercury 

condenses onto the incoming raw materials and is then passed into the kiln where it re-volatilizes 

and is exhausted again through to the raw mill. When the raw mill is shut down, as must occur 

periodically for routine maintenance, the raw material scrubbing is temporarily stopped and the 

mercury “stored” in the raw mill system is exhausted. However, the raw mill is not a perfect 

scrubber. Therefore, at all times there is mercury that makes it through the raw mill and out the 

main stack. Some small portion of that mercury condenses on particulate prior to being captured 

by the baghouse. In addition, some raw material with condensed mercury on it is exhausted 

through to the main bag house. Normally, all of the material (i.e., uncalcined limestone) 

captured in the primary baghouse is returned directly to the process as it constitutes valuable raw 

feed in which a significant processing investment has occurred. The concept behind dust 

shuttling is that a percentage of the uncalcined limestone caught in the primary baghouse is 

continually bled off to the finish mill, rather than the raw mill, and intermixed with cement.7

Ash Grove has determined that the ability to intergrind uncalcined limestone captured in the 

primary baghouse into cement in the finish mill is limited by the performance standards which 

Ash Grove’s cement must satisfy to be salable. Most state Departments of Transportation 

(“DOTs”) specify that cement must meet the specifications of the American Association of State 

Highway and Transportation Officials (“AASHTO”) and the specifications of ASTM C150. 

These specifications, which were recently harmonized, include requirements for insoluble 

residue (≤0.75 percent), loss on ignition (≤3.0 percent), limestone addition (5 percent maximum) 

and process addition (5 percent maximum), among others. In evaluating the ability to shuttle 

uncalcined limestone from the primary baghouse it is necessary to ensure that the resulting 

cement meets these standards or else Ash Grove risks having unmarketable product. These 

standards pose several significant challenges to dust shuttling. First, it has not been established 

 

7

 The Durkee plant does not have an alkali bypass and so any uncalcined limestone removed 

from the process must be removed at the primary baghouse. 
Keith Barnett 

September 4, 2009 

Page 22 

if baghouse dust would be considered “process addition” or “limestone addition.” The definition 

of limestone under ASTM C150 states that the material must be naturally occurring with a 

calcium carbonate content of at least 70 percent, making it unclear whether baghouse dust meets 

the definition of limestone. Given that the baghouse dust is uncalcined limestone, it appears 

likely the dust would meet that definition. However, the way the limestone content of cement is 

determined may make the point moot. ASTM 150 states that the limestone content of cement is 

calculated from the CO2 analysis of the cement. The manufacturer must include the CO2 content 

of the cement and the CO2 content of the limestone in the Mill Test Report. The percent of 

limestone in the cement is defined as: 

(% CO2 in cement)/(CO2 content in limestone) x 100 = % limestone in cement 

Since both baghouse dust and limestone generate CO2 on ignition, when the limit of 5 percent is 

reached no additional CO2 producing material can be added. 

Another challenge to shuttling uncalcined limestone from the baghouse relates to the limits 

placed on loss on ignition (“LOI”). Both the ASTM and AASHTO standard for the LOI for 

cement is 3 percent by weight. This includes the loss after the addition of limestone or process 

material; all specifications of the cement must be met after any limestone or process additions. 

The normal LOI for cement is about 1 percent by weight before any additions. The LOI is from 

the addition of gypsum. Therefore, any additional LOI could not contribute more than 2 percent 

by weight. The LOI of baghouse dust is normally between 33-36 percent. Table 2 below shows 

the amount of baghouse dust that can be added to cement with a LOI of 1 percent such that the 

total LOI of the cement will be 3 or less: 

Table 2. Evaluation of Baghouse Dust Impact on LOI 

LOI of Cement LOI of Baghouse Dust 

% Dust Added for Total 

LOI of 2% 

1% 33% 3.12 % 

1% 36% 2.86% 

This table suggests that a maximum of approximately 3 percent baghouse dust can be added to 

cement in order to pass the LOI specification. This is less than the cement specifications for 

limestone or process addition allows. In other words, the LOI specification is more stringent. 

Another factor to consider is the insoluble residue. Insoluble residue for cement is defined as 

that portion of cement that is not soluble in either acid or base. The contributors to insoluble 

residue are generally the silica and clay components of cement. The specification for insoluble 

residue is 0.75 percent by weight. Normal cement with any additions will have an insoluble 

residue of about 0.3-0.4 percent. Without considering other constituents, baghouse dust contains 

about 12-15 percent silica, which will appear as insoluble residue in the cement. Table 3 below 
Keith Barnett 

September 4, 2009 

Page 23 

shows the amount of baghouse dust that can be added to cement without exceeding the insoluble 

residue specification. 

Table 3. Evaluation of Baghouse Dust Impact on Insoluble Residue 

Insoluble Residue Cement 

(%) 

Insoluble Residue Dust 

(%)) 

% Dust Added for 

Insoluble Residue 0.75 % 

0.3 12 3.85 

0.3 13 3.54 

0.4 12 3.00 

0.4 13 2.77 

This table illustrates that, besides the LOI specification, the insoluble residue also has a limiting 

effect on the amount of dust that can be added to cement, particularly when the dust contains 

large amounts of silica such as is the case with kiln baghouse dust. No consideration was made 

concerning other materials in the baghouse dust that might lead to insoluble residue. However, 

there are other materials that will have an effect. 

Although the desktop assessment of limestone shuttling suggests that up to 3 percent baghouse 

dust can be used and still maintain quality, the actual experience of one kiln suggests that the 

actual value is an order of magnitude lower. The discussions above suggest that uncalcined 

limestone from the baghouse can only make up, at most, about 3 percent of the cement in order 

to conform to the AASHTO and ASTM specifications. However, the Lehigh Cement plant in 

Union Bridge, Maryland has performed extensive testing with intergrinding uncalcined 

limestone from the plant baghouse and determined that it cannot include more than 0.3 percent 

dust in its finished product without adversely impacting product quality. A commitment to 

intergrind that amount of baghouse dust was recently memorialized in a Consent Decree with the 

Maryland Department of the Environment. This practical experience with intergrinding 

uncalcined limestone from the baghouse carries more weight than the desktop analysis outlined 

above. Lehigh’s practical experience also shows the unpredictability of dust shuttling and the 

need to assess the work practice on a plant specific basis in order to be able to accurately assess 

the amount of baghouse uncalcined limestone that can be added to particular products from 

particular kilns without impacting quality and creating a potential safety hazard. 

Ash Grove recognizes that while dust shuttling will not cause the Durkee plant to meet the 

proposed mercury standard, every additional percent of mercury reduction is good. However, 

Ash Grove also recognizes, as has EPA, that the experience does not exist that would allow 

anyone to predict the removal efficiency attributable to dust shuttling. As EPA noted in the 

proposed rule preamble in relation to the wasting of Cement Kiln Dust (“CKD”)8

: 

 

8

 Our discussion of dust shuttling is focused on the application of the process to a 

preheater/precalciner kiln. In preheater/precalciner kilns, CKD, if it is produced at all, is 

(continued . . .) 
Keith Barnett 

September 4, 2009 

Page 24 

 “However the degree to which CKD can be used to reduce mercury 

emissions cannot be accurately estimated due to several factors. For 

example, increasing the amount of CKD wasted would result in a 

reduction in the mercury concentration of the CKD, so that, over time, 

the effectiveness of wasting CKD decreases. We do not have longterm data to quantify the relationship between amount of CKD wasted, 

CKD mercury concentration and emissions. 

 

“The ability to reduce mercury emissions by wasting more CKD also 

is affected by the mercury species present. The particulate and 

oxidized species of mercury can accumulate in CKD, but not the 

elemental form. Therefore wasting CKD will not necessarily control 

elemental mercury. We do not have data that would allow us to 

quantify the effect of mercury speciation. By wasting CKD, additional 

raw materials would be required to replace the CKD as well as 

additional fuel to calcine the additional raw materials, thereby 

offsetting to some extent the benefits of wasting CKD. There is the 

further potential consideration of additional waste generation, an 

adverse cross-media impact EPA is required to consider is making 

beyond-the-floor determinations. The interaction of these factors is 

complex and has not been adequately studied.” Preamble at 21150. 

 

(. . . continued) 

generated at the bypass duct which bleeds off gases directly after leaving the kiln and before they 

encounter the raw material feed into the kiln. This CKD is wasted in order to decrease the alkali 

content of the clinker. Modern preheater/precalciner kilns are designed to minimize the 

generation of CKD. Ash Grove’s Durkee kiln, for example, is a modern preheater/precalciner 

kiln that does not generate CKD. By contrast, in wet kilns, all of the material captured in the 

primary particulate control device is typically wasted as CKD because it is too difficult to 

reintroduce the material into a wet process. For long dry kilns there is the potential to 

reintroduce primary particulate control material and avoid the generation of CKD if there are no 

alkali problems based on that plant’s raw materials. CKD that is wasted from a 

preheater/precalciner kiln (i.e., alkali bypass dust) contains essentially only the mercury from the 

fuels fired in the kiln that have condensed out on the dust captured in the alkali bypass control 

device (i.e., on the CKD). The mercury in the raw material introduced into the preheater tower 

will have volatilized prior to reaching the bypass duct and so will never be controlled through 

management of CKD. While the data does not exist to predict with any accuracy the ability of 

primary baghouse dust to control mercury, the technique could yield better results in a 

preheater/precalciner kiln than the intergrinding of CKD. However, in situ study is required 

before the benefits can be quantified. 
Keith Barnett 

September 4, 2009 

Page 25 

This passage indicates that the potential the benefits of intergrinding CKD are highly speculative. 

This is equally true for the wasting of primary baghouse dust, although for a 

preheater/precalciner kiln the potential benefits could be greater than for other kiln 

configurations. The discussion above also makes it clear that shuttling primary baghouse dust 

displaces the ability to add limestone that has not gone through the initial raw feed processing 

steps. This practice will ultimately reduce the efficiency of a kiln and increase CO2 emissions 

for each ton of cement produced. While Ash Grove recognizes that it is appropriate to consider 

all reasonable measures when evaluating beyond the floor technologies, the absence of 

experience with dust shuttling and the highly site specific nature of the benefits makes it 

impossible to accurately predict the level of control that could be achieved. Clean Air Act 

Section 112(h)(1) provides for this type of situation. Where it is not feasible to prescribe or 

enforce an emission standard, EPA can issue a work practice. Because the specific emission 

reduction attributable to dust shuttling cannot be practically prescribed or enforced, dust 

shuttling is best addressed as a 112(h) work practice. Therefore, Ash Grove supports the concept 

of adding the work practice of dust shuttling to the beyond the floor requirements for the sources 

in the ≥225 ppb subcategory. However, the work practice requirement must specify that while a 

≥225 ppb source shall implement dust shuttling, it must only do so up to the maximum level 

achievable without negatively affecting product quality. Any requirement that would impact 

product quality would not only be an unreasonable requirement to impose on the affected source, 

but would endanger the safety of the people who rely on the properties of the cement. 

 iv. Ore Scrubbing 

Another conceptual possibility for reducing mercury emissions from affected sources that 

include quarries with elevated mercury levels is to implement some sort of limestone scrubbing. 

Under this concept, mercury would be removed from the limestone prior to its introduction into 

the kiln system. Ash Grove is aware of no commercially available system that purports to reduce 

the limestone mercury content. The concept of ore scrubbing was previously raised in relation to 

the Primary Copper Smelter NESHAP. In that instance there was similarly no commercially 

available system and the D.C. Circuit held that it was appropriate to not consider a possible 

means of control that was not commercially available. Copper Smelter MACT at 989. For the 

same reasons, this conceptual possibility has no place in this rulemaking. 

 v. Conclusions About Control System Performance Enhancement 

In summary, it does not appear that there are any additional control methods that could be relied 

upon to materially increase the control efficiency of the ACI system by a predictable enough 

amount that they can be incorporated into the numeric standard. Therefore, we believe that 75 

percent is the appropriate beyond the floor control efficiency to apply in establishing the 

emission standard for the ≥225 ppb source category. 
Keith Barnett 

September 4, 2009 

Page 26 

Ash Grove recognizes that while there may be no basis for increasing the mercury control 

efficiency in a predictable enough manner to make it a component of the floor’s numeric 

standard, additional reductions could be addressed through work practices. Section 112(h) of the 

Clean Air Act allows EPA to set work practice standards when it is not practicable to measure 

emissions. For the reasons stated above, it is not practicable to measure emissions at this point in 

time associated with dust shuttling. However, in going beyond the floor it would be possible to 

establish dust shuttling as a work practice to achieve additional control. Dust shuttling could be 

required up to the maximum level that will not impact product quality. While the improvements 

in mercury control cannot be predicted or measured at this time, the ultimate reductions could be 

material. Therefore, it makes sense to include dust shuttling as a work practice. Likewise, Ash 

Grove believes that it is appropriate to include a mercury control enhancement plan as a work 

practice. After extensive review of the technology by an independent group of technical experts, 

health professionals and representatives of environmental groups and Tribes, Ash Grove 

voluntarily entered into an enforceable order memorializing its commitment to install at the 

Durkee plant the most advanced mercury controls planned for any cement plant in the world. 

After reviewing the extensive pilot testing performed at the Durkee plant, this expert group 

concluded that 75 percent mercury control was the best estimate of a reliable level of control, 

taking into account the variations between raw mill on and raw mill off conditions. However, 

the group was optimistic that as knowledge grew about the ACI system’s interplay with the 

mercury cycle, that a higher level of control would be possible. Therefore, the group suggested, 

and Ash Grove agreed, to include in the order a requirement for Ash Grove to take all reasonable 

measures to enhance the performance of the control equipment such that it reached 85 percent 

control. If the plant is not able to achieve 85 percent control, it must submit a plan describing the 

steps it will take to evaluate further measures that can reach the target. The specific language of 

the order relating to this Control Enhancement Action Plan is reproduced below: 

“The 85% goal: At all times after completion of shakeout as 

described in Paragraph 8.B.VI, Ash Grove agrees to endeavor 

to meet a goal of 85% reduction in mercury emissions on a 

rolling 12-month average basis, calculated as described in 

Paragraph 8.A. If Ash Grove’s emissions are below 85% 

reduction for the rolling 12-month average for any successive 

four month periods occurring wholly after the shakeout period, 

Ash Grove agrees to take the following steps: 

“i. Within 45 days of the last day of the last of the 

successive four months in which Ash Grove did not 

achieve the 85% reduction, Ash Grove agrees to 

submit an Action Plan to the Department for 

approval. The Action Plan must evaluate 

reasonable alternative methods to reduce the 

mercury emissions, including identifying the 

optimal carbon injection rates, and propose a plan 
Keith Barnett 

September 4, 2009 

Page 27 

and implementation schedule to achieve the 85% 

reduction; and 

“ii. Upon the Department’s approval of the Action 

Plan, Ash Grove agrees to implement the corrective 

actions identified in the Action Plan according to 

the schedule in the Action Plan. 

“iii. If the Department agrees in writing that Ash Grove 

has exhausted all reasonable alternatives for 

meeting the 85% goal, Ash Grove need not submit 

further Action Plans. 

“iv. Ash Grove’s failure to achieve the 85% reduction 

will not be considered a violation of this Order.” 

Mutual Agreement and Order Executed Between 

Oregon Department of Environmental Quality and 

Ash Grove (July 17, 2008).”9

Ash Grove believes that a similar requirement to pursue all reasonable alternatives to increase 

the control device performance to 85 percent is an appropriate work practice to be included in 

this beyond the floor standard. 

For the reasons set forth above, we believe that it is appropriate for EPA to add an additional 

subcategory reflecting the two affected sources with limestone mercury content ≥225 ppb. This 

subcategory should establish the emission standard by going beyond the floor and taking into 

account the controls under construction for the Durkee plant. There is no basis to assume that 

control beyond 75 percent is achievable. However, consistent with the requirements in Ash 

Grove’s Durkee plant consent order, the rule can require a Control Enhancement Action Plan as 

a work practice to maximize the possibility of controls reaching their full potential. This 

approach ensures the development of the new activated carbon injection control technology and 

restricts the plant to operating in a manner consistent with the goals of Section 112 of the Clean 

Air Act. 

8. Beyond the Floor Compliance Demonstration Method 

In establishing the beyond the floor emission standard for the ≥225 ppb on-site limestone 

subcategory, Ash Grove encourages EPA to establish a compliance demonstration method based 

on a system removal efficiency. Ash Grove understands that there could be concern with a 

 

9

 Ash Grove also notes that the Order requires that Ash Grove commence controlling mercury at 

the Durkee plant no later than July 17, 2010. Ash Grove is currently on schedule to beat that 

deadline by several months. This will result in mercury control commencing years before what 

would be required under the proposed rule. 
Keith Barnett 

September 4, 2009 

Page 28 

standard based on elevated limestone levels and the theoretical potential for on-site limestone 

levels to decrease over time. If limestone mercury levels were to decrease, the stringency of the 

standard could decrease as well. While Ash Grove is unaware of any suggestion that this will 

occur with its own limestone, we believe that there is a simple means of allaying that concern. 

Specifically, EPA could require that affected sources in the ≥225 ppb subcategory demonstrate 

compliance by meeting work practice requirements and achieving an overall control efficiency of 

75 percent or greater. The work standards would be to: 1) not use fly ash, 2) conduct dust 

shuttling to the maximum extent possible without impacting product quality, 3) implement a 

mercury minimization plan to minimize mercury in the raw materials imported from off-site, and 

4) implement a Control Enhancement Action Plan to ensure all reasonable measures are taken to 

maximize control efficiency. The control efficiency would be demonstrated through continuous 

monitoring of emissions upstream and downstream of the end-of-pipe controls. By establishing 

limits in this manner, EPA and the public are assured that if an affected source is able to reduce 

its limestone mercury content over time, that it will not be held to a lower standard of 

performance. 

Including this type of compliance demonstration method is consistent with court and agency 

precedent. We recognize that the Brick MACT decision requires that EPA consider both 

technological and non-technological factors in establishing the 112(d) emission standard. EPA 

can comply with this requirement by establishing subcategories based on limestone mercury 

content. Once the subcategories are established, EPA could establish the emissions standard 

based on either the level of control (i.e., SRE) or the level of emissions based on nontechnological factors in the absence of control technology. In the Brick MACT decision the court 

held that it was improper for EPA to exclude an actual proven control technology (i.e., non-DLA 

controls) in setting the MACT floor based on the inability of all sources to employ that 

technology. This holding is not relevant in setting the floor for a PC MACT subcategory where 

no controls have been demonstrated in practice (e.g., the > 225ppb category). However, even for 

a subcategory where a member source has demonstrated in practice the viability of a control 

technology, it is necessary to then consider both the technological control and the nontechnological factors. Where a source is achieving a considerable SRE from technological 

controls, it is consistent with both the law and common sense to consider that source at least 

comparable for emission standard setting purposes to a source that is employing no controls. 

Therefore, it would likewise be appropriate for EPA to establish the 112(d) emission standard in 

terms of either emission rate or SRE. 

Since the Brick MACT decision was issued, EPA has similarly concluded that it is appropriate to 

separately consider technological factors in establishing an emission standard. EPA faced this 

same issue in relation to the Hazardous Waste Combustor NESHAP and stated that the Clean Air 

Act does not require that the agency equate best performers with sources that have the lowest 

emissions. 

“Second, as a legal matter, section 112(d)(3) does not specifically 

address the question of whether ‘‘best performing’’ sources are those 
Keith Barnett 

September 4, 2009 

Page 29 

with the lowest net emissions, or those which control HAP emissions the 

most efficiently. 70 FR at 59443. EPA posited the example of whether a 

source emitting 100 units of HAP and feeding 100 units of the HAP 

must be considered better performing than a source emitting 101 units of 

the HAP but feeding 10,000 units. Id. Indeed, floors for new sources are 

to be based on the performance of the ‘‘best controlled’’ similar source. 

Section 112(d)(3). In the example just given, a source with control 

efficiency of 99.9 per cent can naturally be viewed as better controlled 

than one with 0 percent control efficiency. EPA’s decision to incorporate 

control efficiency (i.e., system removal efficiency) into the SRE Feed 

methodology as one of the two factors used to identify best 

performing/best controlled sources reasonably reflects that the statute 

allows performance to be evaluated in terms of control efficiency.” 72 

Fed. Reg. 54875, 54882 (Sept. 27, 2007). 

Based on this logic, it is appropriate for EPA to establish the mercury emissions standard with a 

compliance demonstration method whereby an affected source demonstrates that it is achieving a 

75 percent SRE and is complying with a suite of work practice standards. This is particularly 

true where, as here, this combination of measures will achieve emission levels below the 

subcategory floor emission rate. 

9. Consequences of Overly Stringent Standard 

The unique attributes of mercury make a particularly compelling case for addressing the high 

mercury limestone sources through subcategorization. Once mercury is emitted, the metal can 

travel significant distances. Along the western United States, it has been estimated that a 

substantial amount of the air deposited mercury comes from Asia. For example, in Oregon it is 

estimated that approximately 83 percent of the air deposited mercury originates from industrial 

activities in Pacific Rim countries. See, Clean Air Mercury Rule (CAMR) Implementation in 

Oregon, Oregon Department of Environmental Quality (2006). The domestic cement industry is 

already under siege from foreign imports and the number of plants in the U.S. has decreased over 

the past several decades despite increased domestic demand. If EPA imposes a rule that forces 

the high mercury limestone affected sources to close due to inability to comply, the demand for 

cement will not change. However, the demand will be met with supply from other countries, the 

vast majority of which do not control mercury emissions. As a result, the overall deposition of 

mercury across the western U.S. could increase as a result of plants such as the Durkee, Oregon 

and Tehachapi, California plant being closed due to unattainable mercury standards. By contrast, 

if EPA establishes a subcategory for the ≥225 ppb sources and establishes an emission standard 

reflective of the Durkee plant’s controlled emission rate, the aggregate mercury levels should 

decrease considerably. This is the clearest path towards reducing mercury emissions in the U.S. 

as well as globally. 

Although not addressed under the NESHAP, it is also important to recognize the non-HAP 

environmental impacts associated with eliminating domestic cement production at western U.S. 
Keith Barnett 

September 4, 2009 

Page 30 

plants. These plants serve areas that are particularly suited to receive imports from Asia. (see 

Figure 4 below, depicting the existing import terminal infrastructure on the west coast). 

A study was performed by Environ Consulting of the greenhouse impacts associated with 

offshoring production to Asia. This study conservatively assumed that the source of Asian 

cement was a plant exactly equivalent to the U.S. plant in terms of energy efficiency and control. 

However, due to the stark differences in electricity sources as well as the transportation 

emissions, it was demonstrated that greenhouse gas emissions would be considerably higher as a 

result of importing cement. Ash Grove adapted this study for its Durkee facility to match up 

with the 2005 Oregon Department of Energy estimate of the blend of generation sources. Based 

on this source blend, Ash Grove calculated that the greenhouse gas emissions associated with 

one ton of imported cement were more than 50 percent higher than the same ton of cement 

produced at the Durkee plant. Although we recognize that this is not directly considered in 

establishing MACT standards, we also believe that it is an important ancillary impact that must 

be considered. 

 10. Recommended Action on Subcategorization for Purposes of the Mercury 

Standard 

Figure 4. West Coast Cement Import Terminals 
Keith Barnett 

September 4, 2009 

Page 31 

For the reasons set forth above, Ash Grove requests that EPA create two subcategories for 

purposes of establishing the mercury standard. One subcategory would be made up of sources 

with < 225 ppb mercury in their limestone and one subcategory would be made up of sources 

with ≥225 ppb mercury in their limestone. In both subcategories, EPA should consider in 

establishing the floors the variability of mercury content that is manifested in the limestone over 

time. For the ≥225 ppb subcategory, EPA should establish a floor based on the two affected 

sources and then impose a beyond the floor requirement that all affected sources within the 

subcategory must demonstrate compliance by operating end-of-pipe controls achieving a 75 

percent minimum mercury control efficiency and by implementing the following work practices: 

 1) No use of fly ash as an additive in the raw feed, 

 2) Implementation of dust shuttling to the maximum extent possible without impacting 

product quality, 

3) Implementation of a Mercury Minimization Plan to minimize mercury in the raw 

materials imported from off-site, And 

4) Implementation of a Control Enhancement Action Plan. 

These requirements will all be consistent with both the letter and the intent of the Clean Air Act 

as well as over a decade of EPA and court precedent. 

 D. EPA Should Clarify that Indirect Fired, In-Line Coal Mills Need Not Employ 

Mercury CEMs or Separately Demonstrate Compliance if They Vent Through a 

Separate Stack 

Ash Grove believes that there is no basis for requiring mercury monitoring for coal mills having 

the configuration identified in Figure 5 below, i.e., the coal vents through a dedicated stack 

rather than through the main stack.10 As discussed in greater detail below in relation to THC, 

indirect fired, in-line coal mills receive their sole source of air and heat from the associated kiln 

(or in some cases, the clinker cooler); these units have no dedicated heat source. Therefore, 

consistent with numerous EPA opinions, we believe that these units are subject to the kiln 

exhaust standards. The proposal requires that affected sources install and operate either a 

mercury CEM or sorbent trap-based integrated monitor. There is no basis for concluding that the 

drying of coal will increase the mercury concentration in the kiln exhaust that is vented through 

the coal mill. In order to avoid explosion hazard, indirect fired, in-line coal mills must be 

maintained at temperatures below 200°F at all times and so the temperature is too low to 

volatilize the mercury in the coal. See, e.g. Letter from Donald Toensing (EPA Region 7) to 

 

10 We note that this is not the configuration at Ash Grove’s Durkee kiln. That kiln routes its 

indirect fired, in-line coal mill exhaust through the main stack. 
Keith Barnett 

September 4, 2009 

Page 32 

Roger Behrns (Ash Grove Louisville), September 18, 2002 (recognizing inherent temperature 

limits for indirect fired, in-line coals as a basis for exempting units from ongoing dioxin/furan 

monitoring/testing). To the contrary, the emissions testing that Ash Grove has conducted on 

coal mill exhaust indicates that the pulverized coal acts like activated carbon and adsorbs a 

significant amount of the mercury in the kiln exhaust vented to the unit. While this mercury will 

be volatilized when the coal is combusted in the calciner or kiln, the mercury levels in the coal 

mill exhaust would never be expected to exceed the mercury levels in the main stack. Therefore, 

if the flow is adjusted in the CEM/sorbent trap data acquisition and handling system to account 

for the flow in the coal mill stack, the affected source should be allowed to rely on the 

concentration of mercury identified at the main stack. Affected sources preferring to operate a 

mercury CEM or sorbent trap in the coal mill stack exhaust so that they can account for the lower 

levels of mercury in that scrubbed slip stream should also be allowed the option to do so. 

III. Proposed Organic HAP Standard

Ash Grove does not believe that there is a reasonable factual basis for the proposed organic HAP 

standard. The proposed standard for new and existing sources offers the alternative of either 

demonstrating compliance with a Total Hydrocarbons (“THC”) standard or a Total Organic HAP 

(“TOHAP”) standard. Ash Grove has serious concerns regarding how these standards were 

established and how they would apply to the company’s affected sources. Each concern is 

outlined below. 

 A. Coal Mill Impacts on Exhaust Stream

The proposed organic HAP standard fails to account for a common coal mill design. As 

proposed, the organic HAP standard requires compliance with either THC limit or a TOHAP 

limit. These limits were based exclusively on the THC and organic HAP content of kiln exhaust 

gases. Figure 5 shows a common configuration of coal mills in the most energy efficient 

portland cement plants. In this configuration, a fraction of the exhaust gas from a kiln is routed 

through the indirect fired, in-line coal mill to dry the fuel prior to storage and subsequent 

combustion in the kiln or calciner.11 The exhaust is then returned to the main stack where it is 

commingled with the kiln exhaust resulting in a gas stream that contains both the characteristics 

of a cement kiln and a coal mill. This design is energy efficient in that it allows the coal to be 

dried exclusively with waste heat (there is no back-up heat source and if the kiln is not operating, 

the in-line coal mill cannot operate). However, this design results in the commingled gas stream 

having pollutant characteristics unlike that of kiln exhaust gases that are not routed through a 

coal mill. Because the organic HAP emissions of indirect fired, in-line coal mills are 

 

11 Direct fired coal mills discharge directly into the kiln and emissions would not be 

distinguishable from the kiln. Our comments do not address direct fired coal mills. 
Keith Barnett 

September 4, 2009 

Page 33 

significantly different from the organic HAP emissions associated with kiln gas alone, EPA must 

establish different standards related to this design. 

Coal

Mill

Kiln Exhaust Gas & Coal

Mill Slipstream

Raw Mill

Figure 5

EPA guidance dating from the mid-1990s states that the emissions from an indirect fired, in-line 

coal mill are subject to the Portland Cement NESHAP. In a 1995 determination, EPA stated that 

when “gases originate in one affected source and pass through another affected source as part of 

the manufacturing process, EPA applies the standard for the affected source from which the 

gases are discharged directly into the atmosphere.” Applicability Determination 9600082 

“Alternative Monitoring and Opacity Limit Clarification for San Juan Cement Company,” John 

B. Rasnic (May 12, 1995). However, a year later EPA qualified this guidance when it concluded 

that an in-line raw mill was subject to the Subpart F kiln standards stating: 

“This determination does not change the Agency's general policy 

discussed above that where gases originate in one affected facility and 

pass through another affected facility as part of the manufacturing 

process, EPA applies the emission limitation or standard for the 

affected facility from which the gases are discharged directly into the 

atmosphere. This determination clarifies that for dry process portland 

cement plants with an "in-line" kiln/raw mill configuration, the raw 

mill does not exist as a separate affected facility and; hence, the 

appropriate emission limit is that which applies to the kiln.” 
Keith Barnett 

September 4, 2009 

Page 34 

Applicability Determination 9600083; “Opacity Limitation for ‘Inline’ Portland Cement Plants,” John B. Rasnic (Sept. 7, 1996). 

Just as emissions from the in-line raw mill in Applicability Determination 9600083 were subject 

to NSPS Subpart F PM mass and opacity limitations for cement kilns, so too would emissions 

from an in-line coal mill at a cement plant where kiln gases are used to heat and dry the coal be 

treated as an extension of the kiln and subject to the Portland Cement NESHAP limits. This 

approach is consistent with multiple different applicability determinations provided to Ash 

Grove by EPA stating that kiln exhaust gases are subject to the Portland Cement NESHAP 

regardless of whether they are routed through the coal mill prior to discharge to the atmosphere. 

See, e.g. Letter from Donald Toensing (EPA Region 7) to Roger Behrns (Ash Grove Louisville), 

September 18, 2002. 

The proposed organic HAP standards fail to account for the various volatiles that are added to 

the kiln exhaust as a result of contact with the ground coal in a coal mill. There are two 

configurations of coal mills that employ waste heat. The first, shown in Figure 5, routes kiln 

exhaust gas through an indirect fired, in-line coal mill and then back out the main stack. The 

second configuration, shown in Figure 6, routes gas out a separate coal mill stack. Under either 

configuration, the level of organics in the exhaust gases is markedly higher than the sole 

configuration considered by EPA in establishing the volatile organics standard, i.e., kiln exhaust 

gas not routed through a coal mill. Ash Grove testing documents that a considerable quantity of 

organics are added to the stack exhaust when the kiln gases are routed through the coal mill. 

While the majority of the organics are methane, the non-methane, non-ethane hydrocarbon, total 

hydrocarbon emissions exceeded, on average 100 ppmvd. The THC test data that Ash Grove has 

gathered from its plants is summarized below in Table 4. While the Chanute kiln is regulated 

under HWC MACT, the coal mill duct is not influenced by hazardous waste fuels. 

Table 4. Coal Mill THC Data 

Ash Grove Coal Mill THC Data 

Plant Test Date Location THC ppmv (avg) % Volatiles in 

Coal 

8/31/2005 Coal Mill DuctDry@7%O2 56.3 36.32 

8/19/2008 Coal Mill Duct-Mill OnDry@7%O2

112.6 36.15 

Chanute 

8/19/2008 Coal Mill Duct-Mill 

Off-Dry@7%O2

43.9 36.15 

Durkee 12/9/2005 Coal Mill DuctDry@7%O2

239.4 39.35 

Louisville 10/28-29/2005 Coal Mill DuctDry@7%O2

189.0 37.42 
Keith Barnett 

September 4, 2009 

Page 35 

In light of these data, a THC standard of 7 ppmvd for existing sources and 6 ppmvd for new 

sources is grossly inadequate. Ash Grove requests that EPA not revise the organic HAP standard 

until it has had the opportunity to better evaluate these data and that it include a separate 

subcategory for kiln exhaust gases passed through an indirect fired, in-line coal mill. In addition, 

the volatility of the coal being used should be considered in establishing standards for in-line 

coal mills. Consistent with this approach, EPA should also include in the final rule a specific 

exclusion for coal mills from coverage under the Subpart Y NSPS so that plants are not having to 

deal with dual, and potentially conflicting, regulations. Ash Grove’s most recent comment letter 

to EPA on the proposed NSPS Subpart Y revisions is attached.

 B. Variability Not Properly Accounted for in Establishing Floor

Ash Grove believes that EPA has not adequately accounted for variability in establishing the 

floor for THC and TOHAP. The PCA comments provide extensive detail regarding the need to 

account for actual variability in establishing the floor and we do not reproduce those data or 

arguments here. However, Ash Grove adopts by reference those arguments to the maximum 

extent that they are consistent with the remainder of this letter. We urge EPA to revise the new 

and existing source THC/TOHAP floors to properly account for variability. 

 C. Number of Sources in Floor

We believe that EPA erred in establishing the floor for the existing source organic HAP standard 

using data from just two sources. While there are a total of 167 cement kilns in the country, EPA 

obtained THC CEMS data for twelve cement kilns. However, EPA chose to only consider two 

of the twelve sets of THC data that it obtained. Ash Grove believes that this approach to 

establishing the floor violates the Clean Air Act. EPA provides no legally supportable 

justification for relying on such a small set of CEMs data to establish the floor.

We believe that the Clean Air Act requires that EPA consider the CEMs data from at least five 

sources in establishing the existing source floor where there are 167 affected sources and CEMs 

data are available from twelve of them. Any other interpretation would result in the floor being 

based on an artificially small data set – a result Congress aimed to avoid by mandating that, at 

the very least, the floor had to consider five sources. If EPA’s approach to setting the floor were 

generally adopted, then it would result in the distinction between the new source floor and the 

existing source becoming virtually meaningless—again, an outcome that flies in the face of 

Congress’ mandate. 

There is only one plain language interpretation of the statute and it compels an interpretation 

consistent with how EPA originally intended to set the THC existing source MACT floor in this 

rulemaking. Section 112(d)(3) states in relevant part that MACT standards “shall not be less 

stringent, and may be more stringent than – (A) the average emission limitation achieved by the 

best performing 12 percent of the existing sources (for which the Administrator has emissions 

information)...in the category or subcategory for categories and subcategories with 30 or more 

sources.” Thus, the term “existing sources” at the beginning of subparagraph (A) is modified by 
Keith Barnett 

September 4, 2009 

Page 36 

the phrase “for which the Administrator has emissions information.” At the end of the passage, 

where Congress refers to “categories and subcategories with 30 or more sources,” it therefore is 

reasonable to read “sources” to mean sources “for which the Administrator has emissions 

information.” Similarly, “sources” at the end of subparagraph (d)(3)(B) should be modified by 

the phrase “for which the Administrator has or could reasonably obtain emissions information.” 

This plain language comports with the structure of the MACT floor provisions, while the 

interpretation taken by EPA does not. Congress clearly intended that EPA not set the existing 

source floor based on a very limited data set. Put another way, Congress wanted the existing 

source floor to be based on representative data for the best performing sources. Otherwise, there 

would be no reason to ensure that the floor be based on the average emission limitation of the top 

five sources when the number of sources in that data set was limited. Congress could have 

simply required that the floor be based on the average of the top 12 percent in all circumstances, 

which, for categories or subcategories of fewer than 30 sources, would have meant that the floor 

would be based on a maximum of four sources. But it chose not to do so. Although there is no 

legislative history on this choice, it is apparent that Congress did not want the existing source 

floor “pool” of sources to consist of so few sources. Reading the statute to have “sources” at the 

end of § 112(d)(3)(A) modified by the phrase “for which the Administrator has emissions 

information” (and “sources” at the end of § 112(d)(3)(B) modified by the phrase “for which the 

Administrator has or could reasonably obtain emissions information”) steers clear of this result. 

This interpretation, which is forced by the plain language of § 112(d)(3) is consistent with recent 

EPA pronouncements on the issue. In its 2005 Hazardous Waste Combustor NESHAP, EPA 

stated that “we are required to use data from five sources to comprise the MACT pool whenever 

we have data from fewer than 30 sources....” 70 Fed. Reg. 59458 (Oct. 12, 2005) (citing § 

307(d)(3)(B) (emphasis added). See also the April 20, 2004 proposal, 69 Fed. Reg. 21230 (“For 

existing source floors, we identify the best performers as either sources at the 12 percentile 

ranking and below or the lowest 5 ranked sources values if we have data from less than 30 

sources”) (emphasis added). The Agency made a similar statement in the NESHAP for 

reinforced plastic composites production: “[W]e received new data that changed the floor for 

centrifugal casting to 37.5 percent HAP. With less than 30 facilities in the process group for 

which we have data, the MACT floor must represent the average performance of the top 

five facilities.” 68 Fed. Reg. 19390 (April 21, 2003) (emphasis added). 

If EPA adopts the new interpretation, the maximum number of sources on which the MACT 

floor for this rulemaking will be based is two sources. If EPA does not establish subcategories 

for THC in this rulemaking and relies on this new interpretation, the floor will be based on the 

two top performing sources (12 percent of 12 sources is 1.44). This would not comport with 

Congressional intent to base the existing source floor on a larger set of more representative data. 

The situation would be even worse where there are eight or fewer sources, as would be the case 

for at least one category if EPA decides to subcategorize for THC. Twelve percent of eight 

sources is 0.96. Thus, EPA would consider the emissions data from only one source in setting 

the existing source MACT floor. This would be an illogical result. We believe that EPA must, 

at the very least, consider five sources in establishing the floor. 
Keith Barnett 

September 4, 2009 

Page 37 

 D. Compliance Demonstration Method

EPA needs to modify the rule to clarify when testing must be conducted with both the raw mill 

on and the raw mill off. Under the proposed rule and 1350(h), an existing source complying 

with the THC standard would need to install and operate a THC CEM. Compliance with the 

standard would be computed using the raw data from the CEM and there is no indication as to 

how the results from a separate coal mill stack would be handled. As written, the presumption is 

that the affected source would need to conduct two tests, one while the raw mill is on and one 

while the raw mill is off (see, 40 CFR § 1349(b)(4)(i)). This would make no sense as the coal 

mill would receive gases directly from the kiln, and would not be affected by the raw mill being 

on as opposed to the raw mill being off. In addition, as proposed, 40 CFR § 1349(b)(4)(i) 

indicates that a separate test would need to be conducted on the coal mill stack and that the 

compliance demonstration would be based on the emissions from the coal mill stack alone. 

Neither of these requirements appears to have taken into account the routing of a slip stream of 

kiln exhaust gases to a coal mill and then exhausting those gases directly to atmosphere. We do 

not believe that EPA intended a plant with an in-line kiln/raw mill to have to test this separate 

coal mill stack with the raw mill on and the raw mill off as such a requirement would be 

nonsensical. We request that EPA clarify that this is not the case. 

EPA also needs to add a formula to enable sources to weight the relative emission contributions 

to determine compliance when emissions occur at two points. Many plants with indirect fired, 

in-line coal mills are designed as in Figure 6 below to vent directly to atmosphere. Compliance 

with the organic HAP standard for a plant so configured should allow the combination of both 

stacks given that they both constitute sources of kiln gases. This approach is identical to that 

which EPA has previously applied to bypass stacks under the PM standard. Therefore, we 

request that EPA add to the rule a formula equivalent to Equation 2 of 63.1349 whereby an 

affected source configured such as the one depicted below can demonstrate compliance with the 

THC standard by combining the concentrations from the main stack and the coal mill stack. 
Keith Barnett 

September 4, 2009 

Page 38 

Coal

Mill

Kiln Exhaust Gas & Coal

Mill Slipstream w/Separate

Stack

Raw Mill

Figure 6

Ash Grove also believes that EPA should revise the initial compliance demonstration method for 

the THC standard. Ongoing compliance with the THC standard, as proposed, is based on a 30 

day rolling average. However, the initial compliance demonstration method proposed in 

1349(b)(4)(i) is based on the results of a single 24 hour period. Given potential short term 

variability in the THC emission rate we do not believe that there is a reasonable basis for 

requiring initial compliance demonstration based on a 24 hour average for a standard that is 

based on a 30 day rolling average. Therefore, we suggest that EPA revise 1349(b)(4)(i) to state 

that the initial compliance demonstration test is based on the average emission rate over the 

initial a 30 day period. 

 E. Raw Material Dryers

Ash Grove is concerned that the standards proposed for raw material dryers are not based on any 

sort of meaningful data. Raw material dryers are separate and distinct units from kilns. The 

proposed limit is based on the erroneous assumption that the raw material dryers are similar to 

kilns as emission sources. However, as the discussion below documents, this is not the case and 

so it would be arbitrary to assign the kiln THC limit to raw material dryers without data specific 

to raw material dryers to support that limit. In the discussion below references made to raw 

material dryer (dryers) also include raw mills that are not part of an in-line kiln/raw mill system. 

The reason that raw material dryers cannot be subject to the same standards as kilns is apparent 

from the difference in the way that they operate and the way in which they volatilize and oxidize 

hydrocarbons. The purpose of a kiln is to develop high temperatures for calcining and 
Keith Barnett 

September 4, 2009 

Page 39 

chemically combining the calcium and silica of the raw materials to manufacture clinker. The 

temperature at which the dried raw materials enter the kiln is in excess of 600 degrees F. This 

temperature quickly volatilizes most, if not all, of the hydrocarbons present in the feed. This 

temperature is also high enough that a material fraction of the hydrocarbons combust prior to 

exhausting from the kiln system. As a result, there is inherent control of volatiles in a kiln that 

results in the low emission rates reflected in the floor. By contrast, the purpose of a raw material 

dryer is to remove free water from the raw materials. There is no reason to invest the energy in a 

raw material dryer to heat the materials substantially over the boiling point of water. Therefore, 

raw material dryers are typically operated at less than 400 degrees F. This lower temperature is 

high enough to volatilize the lighter hydrocarbons in the raw material, but not high enough to 

combust those volatiles. As a result of these different operating temperatures, the hydrocarbon 

emissions profile of a kiln is very different from that of a raw material dryer. 

The operational differences between a kiln and a raw material dryer also make it impossible to 

assign the same standard with the same oxygen correction to both classes of units. In a kiln, the 

main constituents are nitrogen and carbon dioxide. Oxygen levels in the kiln exhaust gas are 

typically held below 2 percent but due to in-leakage, oxygen content at the kiln stack would be 

higher, although not higher than 12 percent. By contrast, in a raw material dryer the main 

constituents are nitrogen and oxygen. Oxygen levels in the exhaust from a raw material dryer 

would typically be greater than 19 percent. If the THC concentration in the raw material dryer is 

adjusted to 7 percent oxygen as proposed for the kiln, the measured THC emission 

concentrations in the raw material dryer exhaust would have to be less than 1 ppmvd in order to 

meet the proposed limit of 7 ppmvd after correction to 7 percent oxygen.12 This is near the 

reliable precision of the THC analyzers available for monitoring. 

Another factor that makes the comparison between the two sources invalid is the volume of 

gases passing through the two systems. The volume of gases drawn through a kiln system would 

typically be 5 to 10 times greater than the volume of gases passing through a raw material dryer. 

Since the THC emissions are expressed as a concentration, the THC emitted from the raw dryer 

would be greatly exaggerated compared to the emissions from the kiln when processing the same 

amount of raw material. 

Based on these substantial differences between kilns and material dryers, there is no basis to 

simply assign the kiln THC limit (and oxygen correction) to material dryers. This would be akin 

to assigning the same emission standard to a natural gas fired boiler as to a coal fired boiler 

because they each combust fossil fuel. Such an action would clearly be arbitrary and capricious. 

Likewise, EPA must evaluate actual raw material dryer emissions in order to establish the data 

necessary to support a regulatory limit for raw material dryers. In the absence of such data 

collection and analysis, EPA has no basis for imposing the proposed limits. 

 

12 1 ppm THC at 19 percent oxygen equals 7.3 ppmvd at 7 percent oxygen. 
Keith Barnett 

September 4, 2009 

Page 40 

IV. Proposed Hydrogen Chloride Standard

Ash Grove supports EPA in retaining the HCl standard exclusively for major sources and not 

extending the standard to area sources. However, Ash Grove has concerns regarding the way 

that the major source standards were developed. These concerns are outlined below. 

 A. Floor Should Not Include “True” Area Sources 

Ash Grove is very concerned regarding the sources that were used in establishing the existing 

source floor. EPA only considered data from 27 kilns and chose the top 4 of those kilns as 

representative of the 12 percent lowest emitting units. EPA stated in the preamble: 

 “The top 4 kilns were limited to major sources, and to sources where 

we had a minimum of three test runs to allow us to account for 

variability in setting the floor.” Preamble at 21153. 

However, while EPA states that the each of the top four sources are major sources, we 

understand that the plant with the two kilns with the lowest HCl emission rate (Nos. 1 and 2) and 

the third lowest emitting plant are all “true” area sources.13 EPA has emphatically taken the 

position in the past that the NESHAP floor should be based on major sources and synthetic 

minor sources, but not “true” area sources. For example, in the preamble to Semiconductor 

NESHAP EPA stated: 

“Accordingly, for the proposed rule we used both major sources and 

synthetic minor sources as the basis of the MACT floors. We believe 

our interpretation of section 112(d) of the CAA is correct, and no 

changes were made for the final rule as a result of these comments.” 

68 Fed. Reg. 27918 (May 22, 2003). 

This approach was based on the Municipal Solid Waste Landfill NESHAP where EPA had also 

concluded that the NESHAP emission limit should be based on major sources and synthetic 

minor sources, but not on true area sources. 68 Fed. Reg. 2232 (Jan. 16, 2003). Likewise, in 

establishing the Brick MACT floors, EPA discussed at great length that major sources are the 

basis for establishing the floor and that, for purposes of floor setting, synthetic minor sources 

constitute major sources. 68 Fed. Reg. 26698 (May 16, 2003). All of these discussions are 

consistent in concluding that true area sources should not be included in the floors. However, the 

proposed HCl standards in the Portland Cement NESHAP were established based on testing 

 

13 An area source is a source that is not a major source. By “true area source,” we mean that the 

plant did not achieve area source status through the use of a federally enforceable permit limit 

(i.e., a “true area source” is not a “synthetic minor” source). 
Keith Barnett 

September 4, 2009 

Page 41 

results where three of the four sources are true area sources. This is contrary to the Clean Air 

Act as well as established agency precedent. 

 B. Floor Should Not Include Data Below the Lower Quantification Range 

In addition to being true area sources, the top two sources used to establish the existing source 

HCl floor should be eliminated as they are below the lower quantification range for the test 

method (as proposed). EPA acknowledges that the proposed emission limit as well as much of 

the data used to establish that limit are below the published detection level of the Method 321 

test. Even if one believes that it is appropriate to rely on data collected that lie below the 

published detection level due to concerns that the level is too high, there is no basis for relying 

on data that are below the proposed revisions to the Method 321 detection level. EPA is 

proposing to reduce the detection level to “0.1 to 1.0 ppm” Preamble at 21192. However, the 

top two sources are suggested to have emissions rates of 0.02 ppm. EPA cannot use data to set 

the floor that is below the lower quantification range for the test method. Therefore, both 

because the first two sources are true area sources and because the emission rates are below the 

proposed method detection level, the first two affected sources should be removed from the 

floor. 

 C. Existing Source Floor Should Not Be Based on Just Four Sources

As stated above in relation to the THC standards, it would be in direct contravention of 

Congressional intent for EPA to establish the HCl floor based solely on four sources. EPA 

collected stack test data gathered using both Method 321 and 26. We support EPA in 

eliminating the Method 26 data due to the documented low bias of that test method. However, 

while that means that test data were only available for 27 kilns, that does not mean that EPA 

should only look at the lowest emitting 12 percent (4 kilns) of that grouping. CAA §112(d) 

requires that EPA use the best performing 5 sources or the best performing 12 percent of sources 

in establishing the MACT floor for situations in which there are 30 or more sources in a 

category. In this language Congress evidenced a clear intent that floors should be established 

using a minimum number of data points, i.e., at least data from 5 sources. 

EPA’s proposed approach for determining the existing source floor is contrary to prior EPA 

statements on the issue. As explained above, in the 2005 Hazardous Waste Combustor 

NESHAP, EPA stated that “we are required to use data from five sources to comprise the MACT 

pool whenever we have data from fewer than 30 sources....” 70 Fed. Reg. 59458 (Oct. 12, 

2005) (citing § 307(d)(3)(B) (emphasis added). See also the April 20, 2004 proposal, 69 Fed. 

Reg. 21230 (“For existing source floors, we identify the best performers as either sources at the 

12 percentile ranking and below or the lowest 5 ranked sources values if we have data from less 

than 30 sources”) (emphasis added). The Agency made a similar statement in the Reinforced 

Plastic Composite NESHAP: “[W]e received new data that changed the floor for centrifugal 

casting to 37.5 percent HAP. With less than 30 facilities in the process group for which we 

have data, the MACT floor must represent the average performance of the top five 

facilities.” 68 Fed. Reg. 19390 (April 21, 2003) (emphasis added). EPA cannot diverge from 
Keith Barnett 

September 4, 2009 

Page 42 

this established means of establishing a MACT floor, particularly when the existing 

interpretation is clearly consistent with the words of the statute and the new interpretation is not. 

The plain language of the statute compels that EPA include at least 5 sources in the existing 

source floor. Congress clearly intended that EPA not set the existing source floor based on a 

very limited data set as Congress wanted the existing source floor to be based on representative 

data for the best performing sources. Otherwise, there would be no reason to ensure that the 

floor be based on the average emission limitation of the top five sources when the number of 

sources in that data set was limited. Congress could have simply required that the floor be based 

on the average of the top 12 percent in all circumstances, which, for categories or subcategories 

of fewer than 30 sources, would have meant that the floor would be based on a maximum of four 

sources. But it chose not to do so. Although there is no legislative history on this choice, it is 

apparent that Congress did not want the existing source floor “pool” of sources to consist of so 

few sources. 

D. Variability Not Properly Accounted for in Establishing Floor

Since there is only valid HCl test data for one major source, there is simply not sufficient data 

available to calculate a floor for kilns. EPA has proposed an unnecessarily low emission limit 

for HCl in the incorrect belief that imposing a low HCl standard will achieve reductions in SO2 

through the installation of scrubbers to control HCl. This is an abuse of the authority to impose 

standards through the NESHAP process and may not result in reductions in SO2. The previous 

exemption for the sector from an HCl standard was justified and should remain. However, if a 

standard were to be imposed notwithstanding the paucity of emissions data, that standard should 

not be lower than the risk threshold level demonstrated by the risk modeling conducted by PCA 

for the original rulemaking. The kiln with the lowest modeled emission rate that resulted in a 

Hazard Index of 1 was 23 ppmvd. Therefore, in no event should the HCl standard be any lower 

than 23 ppmvd. 

Ash Grove believes that EPA has not adequately accounted for variability in establishing the 

floors generally under the proposed rule and that this equally affects the proposed HCl standard. 

The PCA comments provide extensive detail regarding the need to account for actual variability 

in establishing the floors and we do not reproduce those data or arguments here. However, Ash 

Grove adopts by reference those arguments to the maximum extent that they are consistent with 

the remainder of this letter. We urge EPA to revise the new and existing source floors to 

properly account for variability for HCl. 

E. Table 5 Incorrectly Identifies HCl Emissions From One Ash Grove Source 

Ash Grove would like to call EPA’s attention to an error in the data in Table 5. Table 5 outlines 

the available HCl data for the 27 kilns for which Method 321 data were available. Ash Grove’s 

Durkee plant is identified as source #26 on that list with emissions of 34.68 ppm HCl. This is 

not correct. First, as a true area source, the Durkee plant should not be evaluated as part of 

setting the floor for the reasons stated above. Second, the reason that Durkee is an area source is 
Keith Barnett 

September 4, 2009 

Page 43 

that its HCl emission rate is 3.2 ppm (7% O2)—an order of magnitude lower than what is stated 

in Table 5. Portland cement kilns are not significant sources of HCl. Revising the Durkee 

emission rate to reflect the correct value underscores this point. 

F. EPA Should Subcategorize to Reflect Arid Sources 

EPA should create a subcategory under the HCl standard for sources that are located in arid 

regions. As noted above, the Clean Air Act expressly allows for subcategorization. While many 

criteria have been evaluated by EPA in exercising its tremendous discretion to subcategorize, 

clearly the ability to employ a particular type of control device is grounds for subcategorization. 

In most of the preambles quoted above in relation to subcategorization for mercury, EPA 

expressly recognized that control device applicability is a reasonable basis for subcategorization. 

Just recently, EPA reiterated that position in relation to proposal for mercury emissions from 

mercury cell chlor-alkali plants. 

 “Subcategories, or subsets of similar emission sources within a source 

category, may be defined if technical differences in emissions 

characteristics, processes, control device applicability, or 

opportunities for pollution prevention exist within the source 

category. This policy is supported by section 112(d)(1), the legislative 

history, our prior rulemakings, and judicial precedent. 

 “EPA’s broad authority to establish categories and subcategories of 

industry sources is firmly established, and has been recognized as 

entitled to substantial deference by the U.S. Court of Appeals for the 

D.C. Circuit and by the U.S. Supreme Court. See, e.g., Davis County 

Solid Waste Mgmt v. EPA, 101 F.3d 1395, 1405 (DC Cir. 1996) (EPA 

has ‘substantial discretion to create categories of sources for which 

standards must be promulgated’); see also Lignite Energy Council v. 

EPA, 198 F.3d 930, 933 (DC Cir. 1999) (upholding EPA’s refusal to 

subdivide a category and noting that the Court was ‘[m]indful of the 

high degree of deference we must show to EPA’s scientific judgment’ 

on this question); Chemical Mfrs. Ass’n v. EPA, 470 U.S. 116, 131 

(1985) (‘the means used by EPA to define subcategories’ under the 

Clean Water Act ‘are particularly persuasive cases for deference to 

the Agency’s interpretation’).” 73 Fed. Reg. 33258, 33273(June 11, 

2008) (emphasis added). 

This passage documents not only that EPA has repeatedly considered control device applicability 

a reasonable basis for subcategorization, but also notes the considerable deference such a 

decision will be accorded by the courts. 
Keith Barnett 

September 4, 2009 

Page 44 

EPA cannot reasonably set a standard based on a control technology type that cannot be 

employed in large portion of the western U. S. EPA considered wet scrubbers as a basis for 

meeting the HCl standard and no consideration was given for alternative types of control. 

However, wet scrubbers are not a viable control technology in vast parts of the western U.S. 

where water is not available for use in a scrubber. Given the unavailability of water, we believe 

that EPA should create a subcategory for arid areas based on those plants not having the access 

to water and so not having the ability to utilize wet scrubbers. Failure to do so would break from 

well established precedent and arbitrarily impact plants in one part of the country. 

 G. EPA Should Clarify that Separately Vented Coal Mill Stacks Need Not Employ 

HCl CEMs or Separately Demonstrate Compliance

Ash Grove believes that there is no basis for requiring HCl CEMs or other compliance 

demonstration for coal mills having the configuration identified in Figure 6, i.e., the coal vents 

through a dedicated stack rather than through the main stack. As discussed in relation to THC, 

indirect fired, in-line coal mills receive their sole source of air and heat from the associated kiln; 

these units have no dedicated heat source. Therefore, consistent with numerous EPA opinions, 

these units are subject to the kiln exhaust standards. The proposal requires that for those major 

sources subject to the HCl standards, either an HCl CEM must be employed or, where a wet 

scrubber is employed, the affected source may monitor scrubber parameters. There is no basis 

for concluding that the drying of coal will increase the HCl concentration in the kiln exhaust that 

is vented through the coal mill. In fact, every suggestion is that the coal will act much the same 

as the activated carbon in the ACI system and will scrub a portion of the HCl out of the kiln 

exhaust gas. Because the coal mill will not increase the concentration of HCl in the kiln exhaust 

(and may even decrease it), and the main stack will be continuously monitored for HCl 

concentration, there is no reason to require the installation and operation of another HCl CEM on 

a coal mill stack. Therefore, we request that EPA clarify that where a coal mill vents directly to 

atmosphere that the coal mill stack is not required to install or operate an HCl CEM. 

V. Proposed PM Standard

 A. EPA Cannot Establish a 112(d) Standard Twice

EPA improperly proposes to establish a revised PM standard based on emission rates that were 

achieved through compliance with the 1999 Subpart LLL requirements. EPA issued new and 

existing source PM standards for portland cement kilns in 1999. In the proposed rule, EPA 

stated that it was proposing to amend the 1999 standards “because they do not appear to 

represent MACT, but rather a level which is achievable by the bulk of the industry.” Preamble at 

21155. Ash Grove disagrees that the 1999 PM standards are not valid NESHAP standards and 

believes that EPA is acting contrary to the Clean Air Act and inconsistently with previous 

actions and pronouncements by 1) setting MACT floors for PM for the second time, and 2) using 

post-MACT compliance test data as the basis for those floors. 
Keith Barnett 

September 4, 2009 

Page 45 

There is no basis in the Clean Air Act or EPA precedent for establishing a 112(d) standard after 

existing sources have already enhanced controls to comply with the original standard. Section 

112 has a clear two pronged approach with the first step being to establish technology based 

standards and the second step being to assess those standards based on residual risk. EPA’s 

proposal to recalculate the floors ten years after its first effort to do so is inconsistent with the 

agency’s established interpretation of CAA §112(d)(6). For example, in the Coke Oven 

NESHAP residual risk rulemaking EPA stated: 

“The EPA also believes that interpreting section 112(d)(6) as requiring 

additional floor determinations could effectively convert existing 

source standards into new source standards. After 8 years, all sources 

would be performing at least at the MACT levels of performance, so 

that the average of the 12 percent of those best performers would be 

performing at a lower level still, probably approaching that of new 

sources. The EPA sees no indication that section 112(d)(6) was 

intended to have this type of inexorable downward ratcheting effect.” 

69 Fed. Reg. 48338, 48351 (Aug. 9, 2004). 

This interpretation was upheld by the D.C. Circuit in reviewing the Hazardous Organic NESHAP 

(HON) residual risk rulemaking when the court noted that there should not be an “inexorable 

downward ratcheting effect” for the MACT floors. NRDC v. EPA, 529 F.3d 1077, 1083-84 

(D.C. Cir. 2008). Many cement kilns upgraded their air pollution control equipment in response 

to the 1999 rule. The Preamble states that EPA “compiled PM stack test data for 45 kilns from 

the period 1998 to 2007,” and used the data from the 6 lowest emitting kilns to develop the 

proposed existing source floor. Preamble at 21155. Given that all existing kilns had to comply 

with the 1999 NESHAP by 2002, EPA proposes to do just what the agency and the D.C. Circuit 

has previously stated was inconsistent with the Clean Air Act. By basing the new existing 

source floor levels on these post-compliance test data, EPA is proposing to put in place the same 

“type of inexorable downward ratcheting effect” that it has said is inappropriate. This is in 

violation of the Clean Air Act. 

VI. Ability of Single Source to Comply With All Standards

 A. NESHAP As A Whole Must Be Based On Actual Source(s)

Ash Grove is greatly concerned about EPA’s proposal to establish HAP limits based on 

independent floor evaluations for each pollutant. Section 112(d) of the Clean Air Act requires 

that EPA set the NESHAP floor for existing sources such that it is not less stringent than "the 

average emission limitation achieved by the best-performing 12 percent of the existing sources." 

Natural Resources Defense Council v. EPA, 489 F.3d 1250, 1254 (D.C. Cir. 2007). In order to 

comply with section 112(d), EPA must therefore be able to demonstrate that the suite of limits 

that constitute the NESHAP have been achieved by existing sources. Establishing a NESHAP 

floor that has never been complied with by the best performing 12 percent of existing sources 
Keith Barnett 

September 4, 2009 

Page 46 

clearly contradicts the Act. That is exactly what EPA has proposed to do in that the proposed 

NESHAP standards have never been achieved in practice at any individual source as required by 

the Clean Air Act. EPA is using a theoretical source in its proposal that is comprised of elements 

of existing sources, but no actual single existing source. Such an approach contradicts both the 

plain meaning and the intent of the Clean Air Act. To the extent consistent with the comments in 

this letter, we adopt and support the PCA comments as to why it violates the Act for EPA to use 

a composite source, rather than a single existing source, as the basis for establishing the 

NESHAP limits. 

VII. Proposed Startup, Shutdown, Malfunction Requirements

A. NESHAP Cannot Apply During SSM Events Absent Evaluation of SSM 

Emissions in Floor and Application to Variability Analysis

Ash Grove is greatly concerned about EPA’s proposed means of addressing the D.C. Circuit’s 

decision vacating 40 CFR §§ 63.6(f)(1) and 63.6(h)(1). Ash Grove believes that it is not 

appropriate to propose rule revisions before the court has even issued the mandate in that case. 

However, if EPA is going to proceed with rule revisions to replace the incorporation by reference 

of these provisions, Ash Grove believes that EPA cannot simply state that the standards apply at 

all times including during times of startup, shutdown and malfunction (“SSM”). EPA did not 

incorporate any data reflecting SSM periods into its analysis that resulted in the standards. Both 

EPA and the D.C. Circuit have stated on many occasions that the 12 percent of best controlled 

sources must be able to comply with the emission standards at all times. This has been the basis 

for addressing variability in virtually all NESHAPs. If EPA were to apply the standards during 

SSM periods without having first determined that the best controlled sources can comply during 

those times, it will have acted arbitrarily and capriciously. Similarly, if the standards apply 

during SSM periods the emission rates during SSM events must be fully integrated into the 

variability analysis used to set the standards. There is no indication that this was done. 

We believe that the best way to address the December 2008 Sierra Club v. EPA decision is to 

establish separate standards that apply during SSM events. The D.C. Circuit stated that EPA had 

to establish some 112(d) standard that would apply at all times. However, the D.C. Circuit never 

implied that the same standard had to apply at all times. We recommend that EPA establish 

standards that apply during SSM events. We recognize that establishing standards for time 

periods where emissions cannot reasonably be measured is impractical. However, the Clean Air 

Act provides for this situation. Section 112(h) of the Clean Air Act allows EPA to set work 

practice standards when it is not practicable to measure emissions. As SSM event are 

notoriously difficult times to measure emissions, it would be appropriate to establish specific 

work practice standards to be followed during SSM events in lieu of numeric standards. 

VIII. Environmental Justice 
Keith Barnett 

September 4, 2009 

Page 47 

A. Proposed Rule Does Not Fully Access Disproportionate Impacts to Minority and 

Low-Income Populations

Ash Grove believes that the final rule must be revised as discussed above in order to avoid 

serious Environmental Justice issues. Executive Order 12,898, requires that EPA consider 

“disproportionately high and adverse human health or environmental effects of [their] programs, 

policies, and activities on minority populations and low-income populations.” As proposed, 

these standards have the potential to decimate the domestic cement industry and to vastly 

increase the amount of cement imported from overseas producers not subject to such rules. 

There are two ways in which these rules could result in disproportionately high and adverse 

effects of on minority and low-income populations. First, EPA identifies two plants as likely 

having to close if the rule is promulgated as proposed. The populations around these plants rely 

heavily on the plants for income. Specifically, the Durkee plant is the major manufacturing 

employer in the entire county. In addition, Ash Grove conducted a comprehensive risk 

assessment showing that the mercury emissions do not result in unacceptable health risks even 

before controls. Thus the adverse impact of closure would be to the health of the families who 

depend on this facility for income and health insurance. If the plant were to close, the health of 

the community would be seriously degraded with no commensurate improvement related to the 

reduced emissions associated with closure as the plant will be well under the acceptable risk 

thresholds when the controls currently being constructed are operational. For these reasons, 

Environmental Justice is triggered domestically by the potential closure. In addition, there are 

global Environmental Justice issues. Closure of U.S. cement plants in an era when U.S. 

production is typically inadequate to meet U.S. needs means that more cement will be imported 

from overseas. As Asia and India dominate imports to the west coast, the gap left by California 

and Oregon plant closures will almost certainly occur in nations with far less stringent controls 

and significantly higher direct and indirect emissions of criteria pollutants, HAPs and greenhouse 

gases. This is particularly relevant in relation to mercury and greenhouse gases as these are the 

most obviously global pollutants. However, offshoring production will also result in localized 

impacts and so will disproportionately impact impoverished areas. 

Proceeding without regard to the consequences of domestic closures and offshoring production 

to less regulated areas would be in direct violation of Executive Order 12,898. Simply stating 

that emissions will decrease without assessing the extent to which they will simply move and the 

impacts of the resulting plant closures is not compliance with Executive Order 12,898. 

However, EPA can honor Executive Order 12,898 and the Clean Air Act by implementing the 

revisions suggested in this letter and maintaining production in the U.S. while also reducing 

domestic emissions. 

IX. Conclusions

Ash Grove has many concerns regarding the proposed amendments to Subpart LLL. Ash Grove 

believes that there are many ways in which EPA can improve its proposed rule while also 
Keith Barnett 

September 4, 2009 

Page 48 

improving EPA’s consistency with the Clean Air Act and agency precedent. These concerns, as 

discussed in detail above, are summarized below. 

A. Mercury Conclusions

• EPA must create a subcategory for the affected sources with ≥225 ppb mercury in their 

limestone 

o EPA precedent, the legislative history and the Williams concurrence in the Brick 

MACT decision all support this approach 

o For the ≥225 ppb subcategory, EPA should establish a floor based on the two 

affected sources and then impose a beyond the floor requirement that all affected 

sources within the subcategory must demonstrate compliance by operating endof-pipe controls achieving a 75 percent minimum mercury control efficiency and 

by implementing the following work practices: 

 No use of fly ash as an additive in the raw feed 

 Implementation of dust shuttling to the maximum extent possible without 

impacting product quality 

 Implementation of a Mercury Minimization Plan to minimize mercury in 

the raw materials imported from off-site, and 

 Implementation of a Control Enhancement Action Plan 

• In both subcategories EPA should consider in establishing the floors the variability of 

mercury content that is manifested in the limestone over time. 

• EPA must also better account for actual variability, including variability of mercury 

attributable to all available fuels. 

• EPA must remove the mothballed sources that are currently accounted for in the floor as 

they do not constitute sources if they are not operating. 

• EPA should not include source 1233 in the floor as it was manufacturing a specialty 

cement at the time of sampling that does not accurately reflect operations of the kiln. 

o If included in the floor, the limit must reflect the variability that extends to kiln 

1233 manufacturing Type I/II cement (as reflected in the results from the 

collocated kiln 1560 which shares the same design and same quarry as kiln 1233) 

• , EPA should clarify in the final rule that indirect fired, in-line coal mills with separate 

stacks need not install a CEM and can rely on the compliance certification made for the 

main stack. 

B. Organic HAP Conclusions

• EPA must revise the organic HAP floors to adequately reflect for the documented 

variability at cement plants. 

• As part of the floor revisions, EPA must include at least five sources in establishing the 

existing source floor. 
Keith Barnett 

September 4, 2009 

Page 49 

• Indirect fired, in-line coal mills need to have their own separate standard from kilns as the 

differences in the organics released and the fate of those organics make the kiln data nonrepresentative of the indirect fired, in-line coal mill emissions. 

o If a separate standard is not developed, indirect fired, in-line coal mills with 

separate stacks must be allowed to use a weighted concentration calculation akin 

to what is allowed for PM under Subpart LLL. 

• Raw material dryers must have a separate standard that is unique to these emission units. 

C. HCL Conclusions

• The HCl floors must not include “true” area sources as this contradicts established EPA 

precedent 

• EPA must revise the organic HAP floors to adequately reflect for the documented 

variability at cement plants. 

• As part of the floor revisions, EPA must include at least five sources in establishing the 

existing source floor. 

• The floor should not include test data below the lower quantification range. 

• EPA must establish an HCl subcategory for affected sources in arid parts of the country 

as wet scrubbers are not an option. 

• The Table 5 data need to be revised to reflect the correct emission rate for Source #26 

(Durkee) as it overstates emissions by one order of magnitude. 

• HCl CEMs should not be required for separately vented indirect fired, in-line coal mills. 

D. PM Conclusions

• EPA cannot establish a new PM floor using data from sources that have already 

implemented controls in order to comply with the existing floor. 

E. Multi-Pollutant Conclusions

• In order to comply with the plain words of the Clean Air Act the complete suite of 

proposed NESHAP limits must be achieved in fact at individual sources. EPA cannot 

based the limits on a hypothetical source. 

F. Startup, Shutdown and Malfunction Provisions

• EPA cannot impose the NESHAP limits on affected sources during SSM periods unless it 

documents that the floor sources can comply with the limits during SSM events and it 

takes into account these periods in establishing variability. 

• If EPA is to address SSM events as part of the standard, it should do so by establishing 

work practice standards, not by applying the limits that were derived based on normal 

operations. 
Keith Barnett 

September 4, 2009 

Page 50 

G. Environmental Justice

• EPA is in violation of Executive Order 12,898 as it has not fully evaluated the 

disproportionately high and adverse human health and environmental effects of the 

proposed rule on minority and low-income populations. 

If you have any questions about these comments, please contact me at (913) 319-6065, or 

curtis.lesslie@ashgrove.com. 

 Sincerely, 

 

 Curtis Lesslie, P.E. 

 Director of Environmental Affairs 

 Ash Grove Cement Company 

Attachment – Ash Grove NSPS Y Comments 

cc (via email): Chuck Wiedenhoft (Ash Grove) 

 Fran Streitman (Ash Grove) 

 Peter Tsirigotis (EPA) 

 Steve Silverman (EPA) 

 Andy O’Hare (Portland Cement Association) 

 Governor Ted Kulongoski 

 Dick Pedersen (Oregon Dept. of Envir. Quality) 
11011 CODY

OVERLAND PARK, KS 66210 

PHONE 913 / 451-8900 FAX 913 /451-1686 

CURTIS D. LESSLIE, PE 

DIRECTOR OF ENVIRONMENTAL AFFAIRS WRITER’S DIRECT LINE – 913/319-6065 

JULY 13, 2009 

via electronic mail to a-and-r-docket@epa.gov

Air and Radiation Docket 

U.S. EPA 

Mail Code 6102T 

1200 Pennsylvania Ave., N.W. 

Washington, DC 20460 

Re: Comments on Proposed Subpart Y NSPS Revisions 

Docket ID No.EPA-HQ-OAR-2008-0260 

Dear Ms. Johnson: 

Ash Grove Cement Company (Ash Grove) is writing to offer comments on the May 27, 

2009 proposed revisions to the Subpart Y standards of performance for new and modified 

coal preparation plants (the “Supplemental Proposal”). The original Subpart Y proposal 

was published on April 28, 2008 (73 Fed. Reg. 22901), but differed markedly from the 

Supplemental Proposal. Although these comments are specific to the Supplemental 

Proposal, our proposed approach would apply equally to both proposals. 

Ash Grove is an American owned business headquartered in Overland Park, Kansas. Ash 

Grove is the fifth largest cement manufacturer in the United States with cement plants in 

nine states across the country. A pioneer of the limestone and cement industries, the 

Company was incorporated in Missouri in 1882 and has been majority owned and 

controlled by the Sunderland family since 1913. The nine cement plants operating in the 

Ash Grove system are some of the most energy efficient and best maintained in the 

country and have an annual production capacity of more than 8.0 million tons of cement. 

The quality portland and masonry cements produced at these plants are used in the 

construction of highways, bridges, commercial and industrial complexes, residential 

homes, and a myriad of other structures. 

Ash Grove is potentially directly affected by the proposed amendments to the Subpart Y 

NSPS because several of our plants operate facilities that utilize waste heat from our kilns 
EPA Air & Radiation Docket (6102T) 

July 13, 2009 

to dry coal prior to it being stored and subsequently introduced into burners where it is 

combusted. These in-line coal mills do not exist as separate facilities and have no 

independent means of generating heat and so do not function in the absence of receiving 

waste heat from the kiln. If these in-line coal mills are considered within the Subpart Y 

definition of “coal preparation plant,” then new, modified and reconstructed coal mills at 

portland cement plants would be affected facilities. 

Ash Grove urges EPA to explicitly exempt portland cement plants from Subpart Y in 

recognition of longstanding agency guidance regarding interdependent facilities. Figure 

1 shows a common configuration of coal mills in energy efficient portland cement plants. 

In this configuration, a fraction of the exhaust gas from a kiln is routed through the coal 

mill to dry the fuel prior to storage and subsequent combustion in the kiln or calciner. 

The exhaust is then either vented to a dedicated stack or returned to the main kiln stack 

where it is commingled with the kiln exhaust resulting in a gas stream that contains both 

the characteristics of a cement kiln and a coal mill. This design is energy efficient in that 

it allows the coal to be dried exclusively with waste heat (there is no back-up heat source 

and if the kiln is not operating, the in-line coal mill cannot operate). However, this 

design results in a gas stream having pollutant characteristics unlike a conventional coal 

mill. Therefore, we believe that coal mills configured such as this should be addressed 

under the Subpart F NSPS and/or Subpart LLL NESHAP rather than under Subpart Y as 

EPA has not had the benefit of data related to cement kiln in-line coal mills in setting the 

standards. 

Coal

Mill

Kiln Exhaust Gas & Coal

Mill Slipstream

Raw Mill

Figure 1

EPA guidance dating from the mid-1990s would not consider cement plant in-line coal 

mills subject to Subpart Y. Similar issues have arisen in the past in relation to cement 

plant equipment. Just as a portion of the hot process exhaust gas is routed to the coal mill 

Note: Coal mill may discharge 

directly to atmosphere through a 

dedicated stack, or to the main 

stack as depicted. 
EPA Air & Radiation Docket (6102T) 

July 13, 2009 

in many modern cement plants, a portion of the exhaust gas is also used to preheat the 

raw feed introduced into the kiln. This type of device is referred to as an “in-line raw 

mill” as the raw mill (just like an in-line coal mill) is completely dependent on the kiln 

for all of its heat input. In a 1995 determination, EPA stated that when “gases originate 

in one affected facility and pass through another affected facility as part of the 

manufacturing process, EPA applies the standard for the affected facility from which the 

gases are discharged directly into the atmosphere.” Applicability Determination 9600082 

“Alternative Monitoring and Opacity Limit Clarification for San Juan Cement 

Company,” John B. Rasnic (May 12, 1995). However, a year later EPA qualified this 

guidance when it concluded that an in-line raw mill was subject to the Subpart F kiln 

standards stating: 

This determination does not change the Agency's general 

policy discussed above that where gases originate in one 

affected facility and pass through another affected facility as 

part of the manufacturing process, EPA applies the emission 

limitation or standard for the affected facility from which the 

gases are discharged directly into the atmosphere. This 

determination clarifies that for dry process portland cement 

plants with an "in-line" kiln/raw mill configuration, the raw 

mill does not exist as a separate affected facility and; hence, 

the appropriate emission limit is that which applies to the kiln. 

Applicability Determination 9600083; “Opacity Limitation for ‘In-line’ Portland Cement 

Plants,” John B. Rasnic (Sept. 7, 1996). Just as emissions from the in-line raw mill in 

Applicability Determination 9600083 were subject to NSPS Subpart F PM mass and 

opacity limitations for cement kilns, so too should emissions from an in-line coal mill at a 

cement plant where kiln gases are used to heat and dry the coal be treated as an extension 

of the kiln and subject to Subpart F NSPS and Subpart LLL NESHAP cement kiln PM 

and opacity limits. This approach is consistent with multiple different applicability 

determinations provided to Ash Grove by EPA stating that kiln exhaust gases are subject 

to the portland cement NESHAP (LLL) regardless of whether they are routed through the 

coal mill prior to discharge to the atmosphere. See, e.g. Letter from Donald Toensing 

(EPA Region 7) to Roger Behrns (Ash Grove Louisville), September 18, 2002. It is also 

consistent with the data that EPA has reviewed in establishing the proposed Subpart Y 

limits. In the absence of data related to emissions from in-line coal mills, EPA would not 

have a rational basis supported by evidence in the record for establishing limits that apply 

to these unique gas streams. 

Although the guidance is clear that in-line coal mills should not be subject to the Subpart 

Y NSPS, the Supplemental Proposal does not provide any clarification, either in the 

preamble or in the proposed amendments to the Subpart Y NSPS, of the applicability of 

the thermal dryer standards to portland cement plant in-line coal mills. Ash Grove 

respectfully requests that EPA clarify that the Subpart Y NSPS does not apply to an inline coal mill at a portland cement plant. The unique coal processing and handling 
EPA Air & Radiation Docket (6102T) 

July 13, 2009 

systems found at portland cement plants are best addressed by the portland cement NSPS 

(Subpart F) and NESHAP (Subpart LLL). 

Ash Grove appreciates the opportunity to comment on the Supplemental Proposal. We 

believe that it is consistent with well established EPA guidance that in-line coal mills 

located at portland cement plants should not be subject to Subpart Y. In order to more 

specifically address the unique nature of cement plants, Subpart Y should exempt 

portland cement plants. Appropriate standards for these facilities can and are being 

developed under the amendments to Subpart F NSPS and the Subpart LLL NESHAP. If 

you have any questions about these comments, please contact me at (913) 319-6065, or 

curtis.lesslie@ashgrove.com. 

Sincerely, 

Curtis D. Lesslie, P.E. 

Director of Environmental Affairs 

Ash Grove Cement Company