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MEMORANDUM 

To: David Putney, U.S. Environmental Protection Agency (EPA), OAQPS 

From: David Green and Matt Hakos, RTI International 

Date: September 1, 2015 

Subject: Final Rationale for Selection of Compliance Dates for the Primary Aluminum 

Production Source Category 

Introduction:

Section 112 of the Clean Air Act (CAA) requires that the U.S. Environmental Protection Agency 

(EPA) establish National Emission Standards for Hazardous Air Pollutants (NESHAP) for the 

control of the hazardous air pollutants (HAP) emitted from both new and existing major sources 

in a source category. These standards must reflect the maximum degree of reduction in HAP 

emissions that is achievable. The minimum required level of control is referred to as the 

“Maximum Achievable Control Technology (MACT) floor.” We initially published the 

NESHAP for Primary Aluminum Reduction Plants on October 7, 1997 (see 62 FR 52407). 

Section 112(f) of the CAA mandates that we conduct a residual risk review for a source category 

within 8 years of publication of the NESHAP for that source category. Section 112(d)(6) of the 

CAA mandates that we conduct technology reviews for each source category every 8 years. 

Summary of Proposed Compliance Dates: 

We published proposed amendments to pursuant to the mandated residual risk and technology 

reviews of the NESHAP for Primary Aluminum Reduction Plants on December 6, 2011 (see 76 

FR 76259). In response to comments received on those proposed amendments and after 

collecting and analyzing additional emissions data, we published a supplemental proposal on 

December 8, 2014 (see 79 FR 72914). In those proposals, we proposed MACT standards for 

emissions of several previously unregulated HAP from several sources at primary aluminum 

reduction plants. We also proposed emissions standards for three HAP (arsenic, nickel and 

POM) from Soderberg potlines to address risks. The proposed standards and their associated 

proposed compliance dates are summarized in Table 1, below. 

Table 1: Summary of Proposed Standards’ Compliance Dates 

Pollutant Affected Source(s) Compliance Date 

MACT Standards 

All applicable 

pollutants Any new affected source 

The later of startup of the new 

source or date of publication of 

final rule in the Federal Register 

COS Existing potlines (all subcategories) 

One year after date of publication 

of final rule in the Federal Register 

PM 

Existing potlines (all subcategories), 

anode bake furnaces and paste 

production plants 

POM Existing prebake potlines and pitch 

storage tanks 

Standards to Address Risks 

As, Ni and POM Existing and new Soderberg potlines Two years after date of publication 

of final rule in the Federal Register 
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As = Arsenic POM = Polycyclic organic matter COS = Carbonyl sulfide 

Ni = Nickel PM = Particulate matter 

We also proposed work practices for potlines, anode bake furnaces and paste production plants 

with associated compliance dates of one year after publication in the Federal Register and 

electronic reporting provisions and changes to malfunction provisions with the associated 

compliance date being the same as the date of publication in the Federal Register. 

Summary of Final Compliance Dates: 

Due to comments received during the public comment period for the 2014 supplemental 

proposal, we made several changes to the proposed compliance dates. A summary of the final 

compliance dates is provided in Table 2, below. 

Table 2: Summary of Promulgated Standards’ Compliance Dates 

Pollutant Affected Source(s) Compliance Date 

MACT Standards 

All applicable 

pollutants Any new source 

The later of startup of the new 

source or date of publication of 

final rule in the Federal Register 

COS Existing potlines (all subcategories) 

One year after date of publication 

of final rule in the Federal Register PM 

Existing Soderberg potlines, anode 

bake furnaces and paste production 

plants 

PCB Existing Soderberg potlines 

Hg Existing anode bake furnaces 

Two years after date of publication 

of final rule in the Federal Register POM Existing prebake potlines and pitch storage tanks 

PM Existing prebake potlines 

Risk-based Standards 

As, Ni and POM Existing and new Soderberg potlines Two years after date of publication 

of final rule in the Federal Register 

Hg = Mercury 

PCB = Polychlorinated biphenyls 

The MACT standards for PCB emissions from Soderberg potlines and for Hg emissions from 

anode bake furnaces were included in the final rule in response to comments received during the 

public comment period associated with the 2014 supplemental proposal. 

Rationale of Proposed and Final Compliance Dates: 

Facilities must be incompliance with the malfunction and electronic reporting provisions on the 

date of publication of this final rule in the Federal Register. We do not foresee any reason why 
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facilities cannot comply with this requirement and comments received on the proposals did not 

provide any compelling justification for changing these dates. 

Regarding the Proposed MACT Standards: According to our initial analyses, no existing 

sources needed to add new controls or modify existing controls to meet the proposed MACT 

standards, except that some existing pitch storage tanks would need to install carbon filters or a 

suitable alternative. Also, we believed that the work practices we proposed could be 

implemented relatively quickly. Therefore, we believed one year after publication of the final 

rule in the Federal Register was sufficient to demonstrate compliance with the proposed MACT 

standards, including the proposed work practices. 

Comments received on the proposed compliance dates for the potline, anode bake furnace, and 

paste production plant work practice standards did not provide any compelling justification for 

changing these dates. However, industry groups did provide comments and information 

indicating that owners or operators of existing prebake potlines subject to the proposed PM and 

POM MACT emissions standards and existing pitch storage tanks subject to the proposed POM 

MACT emissions standard may need two years to demonstrate compliance with those standards. 

For example, the owner or operator of two existing prebake potlines may need to install either a 

Method 14 manifold system or a Method 14A cassette system in order to demonstrate 

compliance with the proposed POM and PM MACT standards (i.e., if they cannot make an 

acceptable demonstration of potline “similarity” to the regulatory authority in accordance with 

40 CFR 63.848(d)). Also, the owners or operators of several existing pitch storage tanks will 

need to install carbon filter control systems (or a suitable alternative) and test and certify those 

control systems. Based on the information provided, we believe that two years after publication 

of the final rule in the Federal Register is an appropriate compliance date for existing prebake 

potlines subject to the PM and POM MACT standards and existing pitch storage tanks subject to 

the POM MACT standard. 

Regarding the MACT standards added to the final rule in response to public comments:

Our analyses indicated that no existing sources needed to add new controls or modify existing 

controls to meet the PCB MACT standards for Soderberg potlines. We also note that there are 

currently no existing operational Soderberg potlines. The owner/operator of the last facility 

utilizing Soderberg potlines (the Columbia Falls facility in Montana) announced the permanent 

shutdown of that facility in March 2015 but has not yet completed demolition of those potlines. 

Therefore, we believe that one year after publication of the final rule in the Federal Register is an 

appropriate compliance date for the PCB MACT standards for existing Soderberg potlines, in the 

very unlikely event that the Columbia Falls Soderberg potlines resume operation. 

Regarding the Hg MACT standards for anode bake furnaces, based on our analysis we believe 

that all existing sources will probably be able to comply without the need to add additional 

controls. However, these standards and our analysis were based on a relatively small data set 

(valid data were only available for two out of the estimated 22 existing anode bake furnaces), 

resulting in less certainty as to whether additional controls or modification of existing controls 

might be necessary to demonstrate compliance. Therefore, we believe that two years after 

publication of the final rule in the Federal Register is an appropriate compliance date for the Hg 

MACT standards for existing anode bake furnaces, to allow owners or operators of existing 

anode bake furnaces an opportunity to test those sources and then have sufficient time to install 

controls or make other adjustments, if necessary. 
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Regarding Standards to Address Risks: We proposed revised POM emission limits and new 

As and Ni emission limits for Soderberg potlines to ensure risks from those sources were 

acceptable, with an ample margin of safety. We estimated that, in order to comply with these 

limits, a Soderberg facility would require wet roof scrubbers to control secondary potline 

emissions. Installation of wet roof scrubbers would require considerable time (e.g., up to 2 years) 

and capital resources. Therefore, we believe that two years after publication of the final rule in 

the Federal Register (the maximum amount of time allowable pursuant to CAA section 112(f)) is 

an appropriate compliance date for these standards for existing Soderberg potlines (again, in the 

very unlikely event that the Columbia Falls Soderberg potlines – the only existing Soderberg 

potlines in the U.S. - resume operation). In the final rule, we retain this compliance date for 

Soderberg potlines subject to the standards for POM, As, and Ni.