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ESTABLISHING WORK PRACTICES FOR AREA SOURCE,

COAL-FIRED SEASONAL BOILERS

Overview

In EPA’s reconsideration of the final rule for area source industrial boilers (“Area 

Source Boiler Rule”), EPA determined that it was appropriate to create a subcategory for

seasonal boilers that burn oil or biomass as fuel. Under the Clean Air Act (“CAA”), EPA 

has the authority to apply the same tune-up requirement to area source coal-fired boilers 

used for seasonal agricultural purposes such as the processing of sugarbeets (“seasonal 

coal-fired boilers”).1 The expansion of the seasonal boiler area source subcategory to 

include similar coal-fired boilers is appropriate because these seasonal, coal-fired 

agricultural boilers are few in number, located in remote areas, and operated to process a 

perishable, agricultural crop. Thus, these boilers need not be subject to maximum 

achievable control technology (“MACT”) standards in order for EPA to satisfy the 

section 112(c)(6) requirement that it regulate 90 percent of certain pollutants from area 

sources through MACT. In the alternative, EPA also has the authority to impose work 

practice standards under section 112(h) for area source seasonal coal-fired boilers, similar 

to the generally available control technology (“GACT”) requirements EPA proposed for 

biomass-fired and oil-fired seasonal boilers. As discussed in more detail below, the 

unique circumstances of the seasonal coal-fired boilers located at these area source 

agricultural facilities meet the criteria for section 112(h) work practices.

Summary of Legal Authority

1. Application of MACT standards to seasonal coal-fired boilers is not 

necessary to meet EPA’s obligations under section 112(c)(6). 

CAA section 112(c)(6) requires that EPA list categories and subcategories of 

sources such that sources accounting for not less than 90 percent of the aggregate 

emissions of seven specified hazardous air pollutants (“HAP”) are subject to standards 

under section 112(d)(2) or (d)(4) of the CAA. Mercury and polycyclic organic matter 

(“POM”) are two of the HAP for which 90 percent of aggregate emissions must be 

regulated, and EPA has determined in the rule that coal-fired area source boilers must be 

regulated under section 112(d)(2) or (d)(4) in order to meet the 90 percent threshold.2

While EPA has a statutory obligation to meet the 90 percent threshold, the Agency will 

still meet this requirement even with the application of a work practice GACT standard to 

seasonal area source boilers.

During the rulemaking establishing requirements for area source industrial 

boilers, EPA determined that it did not need to regulate mercury or POM from biomass-

 

1 USBSA has suggested that the definition of “seasonal boiler” to be as follows: Seasonal boiler means

either a boiler that undergoes a shutdown for a period of at least 7 consecutive months (or 210 consecutive 

days) due to seasonal market conditions, or a boiler operated to provide energy for the seasonal processing 

of a perishable agricultural crop (e.g., sugarbeets, sugarcane). This definition applies to boilers that would 

otherwise be included in the biomass, oil, or coal subcategories. 

2

76 Fed. Reg. 15,554, 15,556 (Mar. 21, 2011).
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fired or oil-fired boilers using a MACT standard because these sources were not 

necessary to reach the required 90 percent threshold.3 The Agency, therefore, applied a 

GACT standard to these subcategories as authorized under section 112(d)(5). Under the 

same reasoning, seasonal coal-fired boilers (particularly those used in sugar beet 

processing) at area sources would not be necessary to reach the 90 percent emissions 

threshold and therefore should be regulated under GACT instead of MACT.

According to recent data included in the rulemaking record, the area source 

category consisting of all coal-fired boilers only represents 0.7 percent of emissions of 

mercury.

4

 Seasonal coal-fired boilers represent a small subset of this category. Including 

seasonal coal-fired boilers in the subcategory for seasonal boilers subject to GACT will, 

therefore, not prevent the agency from meeting its required 90 percent threshold. As the 

agency itself stated in the final rule, “the statute does not limit EPA’s discretion as to how 

it fulfills its obligations under CAA section 112(c)(6)... we are not promulgating MACTbased regulations at this time [for biomass-fired and oil-fired boilers] because they are

unnecessary to meet the requirements of CAA section 112(c)(6).”5Therefore, because 

EPA does not need to regulate POM or mercury emissions from seasonal, agricultural 

coal-fired area sources to meet the 90 percent threshold, EPA has the authority to apply a 

similar work practices GACT standard rather than a MACT standard, as it has done for 

other source categories that are deemed to be unnecessary to meet the 90 percent 

requirement.

Indeed, EPA is aware that area sources have inherently lower levels of pollution 

and are often comprised of smaller enterprises that could suffer economically under a 

heavy regulation burden. The Agency states in the final rule: “The facts here support the 

reasonableness of EPA’s approach [in only setting a MACT standard if needed to meet 

the 90 percent requirement]. Area source boilers are included in source categories listed 

under section 112(c)(6) for regulation under section 112(d)(2) solely due to its mercury

and POM emissions. There is special statutory sensitivity to regulation of area source 

categories in section 112. For example, an area source category may be listed for

regulation under section 112 if EPA makes an adverse effects finding pursuant to Section 

112(c)(3) or if EPA determines that the area source category is needed to meet its section 

112(c)(3) obligations to regulate urban HAP or its section 112(c)(6) obligations to 

regulate certain persistent bioaccumulative HAP.”

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As explained by EPA in the above preamble language, area sources are regulated 

by the Agency under MACT standards only if such regulation is needed to meet the 

112(c)(6) or 112(c)(3) requirements. In the absence of such necessity, EPA has the 

discretion and the authority to apply a GACT standard to an area source subcategory. 

 

3

76 Fed. Reg. at 15,556 (March 21, 2011).

4

See Memorandum to docket ID EPA-HQ-OAR-2004-0505, “Emission Standards for Meeting the Ninety 

Percent Requirement Under Section 112(c)(6) of the Clean Air Act,” Nathan E. Topham, Environmental 

Engineer Metals and Minerals Group, SPPD (D243-02), February 18, 2011, available at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OAR-2006-0790-2312, docket ID EPA-HQOAR-2006-0790. The precise percentage of POM emissions resulting from seasonal coal-fired boilers 

cannot be determined from EPA’s data, but is expected to be of similar scale.

5

76 Fed. Reg. 15554, 15566 (March 21, 2011).

6

76 Fed. Reg. 15554, 15567 (March 21, 2011) (emphasis added).
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EPA created a separate subcategory for seasonal, agricultural boilers in light of unique 

operations and circumstances. Area source coal-fired seasonal boilers, such as those used 

to process sugarbeets, are similar to those industrial boilers already in the area source 

seasonal boiler subcategory and should therefore be included. This subcategory

represents an extremely small slice of the total emissions of concern, certainly less than 

the 0.48% which represents the amount EPA has regulated above the 90 percent 

requirement. Therefore, imposing work practices on such sources will not cause the EPA 

to run afoul of the 90 percent requirement. As the Agency itself makes clear, necessity to 

meet the 90 percent requirement is the only reason that area sources are included in the 

MACT standards, and without such necessity, EPA has the discretion to address that 

subcategory under a GACT standard instead.

2. Even if EPA determines section 112(c)(6) requires MACT standards for area 

source seasonal coal-fired boilers, EPA may satisfy this requirement by 

prescribing work practice standards under section 112(h).

If EPA determines that area source seasonal coal-fired boilers must be subject to 

MACT standards pursuant to section 112(c)(6), EPA has the discretion to impose work 

practices that are similar to the GACT standards EPA has proposed for seasonal oil- and 

biomass-fired boilers. 

Section 112(h) authorizes EPA to issue work practice standards where “the 

application of measurement methodology to a particular class of sources is not 

practicable due to technological and economic limitations.”7 Such work practice 

standards are included in the various types of requirements that can be imposed under 

section 112(d)(2), and therefore would satisfy EPA’s obligations under section 112(c)(6). 

In determining whether to issue work practice standards for a given category or 

subcategory of sources, EPA has broad latitude to decide what overall combination of 

factors make the application of measurement methodology “not practicable.” The statute 

also does not limit EPA’s discretion as to the relative weight to be given to technological 

and economic factors in determining whether the application of measurement 

methodology is “not practicable.”

The D.C. Circuit has interpreted section 112(h) to allow EPA to “substitute work 

practice standards for emission floors only if measuring emission levels is 

technologically or economically impracticable.”8 In Sierra Club, the D.C. Circuit 

reversed an EPA rule that established work practice standards for a class of ceramics 

kilns, on the grounds that EPA had not made the requisite finding of impracticability. 

However, Sierra Club does not limit EPA’s discretion as to what degree of technological 

or economic impracticability justifies a work practice standard. In the rule challenged in 

Sierra Club, EPA made no findings regarding the practicability of measurement 

methodology for the ceramics kilns – instead issuing work practice standards because it 

lacked data on emissions from these sources. 

 

7

42 U.S.C. § 7412(h)(2)(B). 

8

Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007) (emphasis added). 
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Here, by contrast, there are adequate grounds for EPA to make a finding of 

impracticability. Like the area source seasonal oil- and biomass-fired boilers for which 

EPA has prescribed a tune-up requirement, seasonal coal-fired boilers such as those used 

in sugarbeet processing are not currently equipped to continuously monitor carbon 

monoxide and oxygen (for purposes of demonstrating compliance with the CO standard). 

Moreover, EPA’s proposed CEMS requirements for CO and O2 require strict adherence 

to the installation, operation, maintenance, and performance testing requirements set forth 

in Part 60, Appendix B (Performance Specifications 3, 4, 4A, and 4B).9 

Meeting these requirements would require area source seasonal coal-fired boilers 

to procure costly CEMS equipment and hire specialized personnel to install and operate 

CEMS. Most sugarbeet facilities are not currently required by state agencies to have 

CEMS for criteria pollutants. In addition to costly CEMS equipment, some boilers also

may require physical modifications in order to meet the exacting installation 

requirements in Part 60, Appendix B. These costs are likely to be especially high for 

seasonal coal-fired boilers located in remote rural areas, especially given the likely

increase in nationwide demand for both CEMS equipment and compliance personnel that 

will follow the finalization of the Area Source Boiler Rule as well as the standards for 

major sources and the requirements for boilers at electric generating units. In addition,

fuel sampling for mercury is not practical for these sources. The fuel for most of these 

area source, agricultural boilers is delivered by truck because their size and location 

makes rail delivery infeasible. The fuel is dropped by rail in an open, outdoor location 

and then loaded onto trucks, a process that does not lend itself to ASTM procedures.

The costs of compliance would impose a severe burden on the small, area source

agricultural processing facilities that utilize seasonal coal-fired boilers. Such facilities 

were not designed for the type of sampling and measurement techniques required by the 

rule. Therefore, the costs of compliance are not in proportion to the environmental 

significance of emissions from seasonal coal-fired boilers − which are generally few in 

number, located far from population centers, and operated only for a portion of the year. 

Regulating seasonal coal-fired boilers in the same way as other industrial, commercial, 

and institutional boilers is inappropriate in light of the special features of seasonal coalfired boilers. Given these factors, EPA is justified in exercising its authority to prescribe 

a tune-up requirement identical to the proposed GACT standards for oil and biomassfired seasonal boilers, on the grounds that technological and economic limitations make 

the application of measurement methodologies impracticable for seasonal coal-fired 

boilers. 

 

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76 Fed. Reg. 80,532, 80,545 (proposed 40 C.F.R. 63.11224(a))