Page 1 of 4 MEMORANDUM

To: David Putney, U.S. Environmenta l Protection Agency (EPA), OAQPS From : David Green and Matt Hakos, RTI International Date: September 1, 2015 Subject : Final Rationale for Selection of Comp liance Dates for the Primary Aluminum Production Source Category

Introduction: Section 112 of the Clean Air Act (CAA) requires th at the U.S. Environmental Protection Agency (EPA) establish National Emission Standards fo r Hazardous Air Pollutants (NESHAP) for the control of the hazardous air pollutants (HAP) emi tted from both new and existing major sources in a source category. These standards must re flect the maximum degr ee of reduction in HAP emissions that is achievable. The minimum requi red level of control is referred to as the “Maximum Achievable Control Technology (M ACT) 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 conduc t a residual risk review for a source category within 8 years of publication of the NESHAP fo r that source category. Section 112(d)(6) of the CAA mandates that we conduct technology review s 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 additi onal emissions data, we published a supplemental proposal on December 8, 2014 (see 79 FR 72914). In those pr oposals, we proposed MACT standards for emissions of several previously unregulated HAP from several sources at primary aluminum reduction plants. We also proposed emissions st andards for three HAP (arsenic, nickel and POM) from Soderberg potlines to address risks. The proposed standards and their associated proposed compliance dates are su mmarized 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 RegisterPage 2 of 4 As = Arsenic POM = Polycyclic or ganic 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 provi sions 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 propos ed compliance dates. A summary of the final compliance dates is provided in Table 2, below.

Table 2: Summary of Promulgate d 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 S oderberg potlines and for Hg emissions from anode bake furnaces were included in the final ru le 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 malf unction and electronic reporting provisions on the date of publication of this fina l rule in the Federal Register. We do not foresee any reason whyPage 3 of 4 facilities cannot comply with this requirement and comment s received on the proposals did not provide any compelling justifica tion for changing these dates.

Regarding the Proposed MACT Standards: According to our ini tial analyses, no existing sources needed to add new cont rols or modify existing contro ls to meet the proposed MACT standards, except that some existing pitch storag e tanks would need to in stall carbon filters or a suitable alternative. Also, we believed that the work practices we proposed could be implemented relatively quickly. Therefore, we be lieved one year after pu blication 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 da tes for the potline, anode bake furnace, and paste production plant work prac tice standards did not provide a ny compelling justification for changing these dates. However, industry groups did provide comme nts and information indicating that owners or operato rs 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 existi ng 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 pi tch storage tanks will need to install carbon f ilter control systems (or a suitable alte rnative) and test and certify those control systems. Based on the information provide d, 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 standa rds 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 n eeded 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 potlin es. 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 ha s 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 exis ting Soderberg potlines, in the very unlikely event that the Columbia Fa lls Soderberg potlines resume operation.

Regarding the Hg MACT standards for anode ba ke 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 analys is 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 additiona l controls or modificatio n of existing controls might be necessary to demonstrate compliance. Therefore, we believe that two years after publication of the final rule in the Federal Regist er is an appropriate co mpliance 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 ad justments, if necessary.Page 4 of 4 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 woul d require considerable ti me (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 ti me allowable pursuant to CAA section 112(f)) is an appropriate compliance date for these standard s for existing Soderberg potlines (again, in the very unlikely event that the Columbia Falls S oderberg potlines – the on ly 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.