Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing

Federal RegisterAug 19, 2015

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60 and 63

[EPA-HQ-OAR-2012-0522; FRL-9931-01-OAR]

RIN 2060-AQ20

Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

This action finalizes the residual risk and technology review conducted for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories regulated under national emission standards for hazardous air pollutants (NESHAP). In addition, this action finalizes an 8-year review of the current new source performance standards (NSPS) for five source categories. We are also taking final action addressing Clean Air Act (CAA) provisions related to emission standards for hazardous air pollutants, review and revision of emission standards, and work practice standards. The final amendments to the Phosphoric Acid Manufacturing NESHAP include: Numeric emission limits for previously unregulated mercury (Hg) and total fluoride emissions from calciners; work practice standards for hydrogen fluoride (HF) emissions from previously unregulated gypsum dewatering stacks and cooling ponds; clarifications to the applicability and monitoring requirements to accommodate process equipment and technology changes; removal of the exemptions for startup, shutdown, and malfunction (SSM); adoption of work practice standards for periods of startup and shutdown; and revised recordkeeping and reporting requirements for periods of SSM. The final amendments to the Phosphate Fertilizer Production NESHAP include: Clarifications to the applicability and monitoring requirements to accommodate process equipment and technology changes; removal of the exemptions for SSM; adoption of work practice standards for periods of startup and shutdown; and revised recordkeeping and reporting requirements for periods of SSM. The revised NESHAP for Phosphoric Acid Manufacturing facilities will mitigate future increases of Hg emissions from phosphate rock calciners by requiring pollution prevention measures. Further, based on the 8-year review of the current NSPS for these source categories, the EPA determined that no revisions to the numeric emission limits in those rules are warranted.

DATES:

This final action is effective on August 19, 2015. The incorporation by reference of certain publications listed in the rule is approved by the Director of the Federal Register as of August 19, 2015.

ADDRESSES:

The Environmental Protection Agency (EPA) has established a docket for this action under Docket ID No. EPA-HQ-OAR-2012-0522. All documents in the docket are listed on the

www.regulations.gov

Web site. Although listed in the index, some information is not publicly available,

e.g.,

confidential business information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy form. Publicly available docket materials are available either electronically through

http://www.regulations.gov,

or in hard copy at the EPA Docket Center, EPA WJC West Building, Room Number 3334, 1301 Constitution Ave. NW., Washington, DC. The Public Reading Room hours of operation are 8:30 a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through Friday. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT:

For questions about this final action, contact Dr. Tina Ndoh, Sector Policies and Programs Division (D243-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711; telephone number: (919) 541-2750; fax number: (919) 541-5450; and email address:

Ndoh.Tina@epa.gov.

For specific information regarding the risk modeling methodology, contact James Hirtz, Health and Environmental Impacts Division (C539-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-0881; fax number: (919) 541-0359; and email address:

Hirtz.James@epa.gov.

For information about the applicability of the NESHAP or NSPS to a particular entity, contact Scott Throwe, Office of Enforcement and Compliance Assurance, U.S. Environmental Protection Agency, EPA WJC, 1200 Pennsylvania Ave. NW., Washington, DC 20460; telephone number: (202) 562-7013; and email address:

Throwe.Scott@epa.gov.

SUPPLEMENTARY INFORMATION:

Preamble Acronyms and Abbreviations.

We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:

ACI Activated carbon injection

AEGL Acute exposure guideline levels

AFPC Association of Fertilizer and Phosphate Chemists

AOAC Association of Official Analytical Chemists

BACT Best available control technology

BSER Best System of Emissions Reduction

BTF Beyond the floor

CAA Clean Air Act

CBI Confidential Business Information

CDX Central Data Exchange

CEDRI Compliance and Emissions Data Reporting Interface

CEMS Continuous emissions monitoring system

CFR Code of Federal Regulations

CMS Continuous monitoring system

CPMS Continuous parameter monitoring system

DAP Diammonium phosphate

DOE Department of Energy

EPA Environmental Protection Agency

ERT Electronic Reporting Tool

FR Federal Register

FTIR Fourier transform infrared spectroscopy

GMCS Gore Mercury Control System

GTSP Granular triple superphosphate

HAP Hazardous air pollutants

HF Hydrogen fluoride

Hg Mercury

HI Hazard index

HQ Hazard quotient

ICR Information Collection Request

LAER Lowest achievable emissions rate

lb/MMBtu Pounds per million Btu

LOAEL Lowest-observed-adverse-effect level

MACT Maximum achievable control technology

MAP Monoammonium phosphate

mg/dscm Milligrams per dry standard cubic meter

MIBK Methyl isobutyl ketone

MIR Maximum individual risk

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NAS National Academy of Sciences

NESHAP National Emissions Standards for Hazardous Air Pollutants

NETL National Energy Technology Laboratory

NOAEL No-observed-adverse-effect level

NSPS New source performance standard

NTTAA National Technology Transfer and Advancement Act

OAQPS Office of Air Quality Planning and Standards

OMB Office of Management and Budget

Phosphorus pentoxide

PAC Powdered activated carbon

PB-HAP Hazardous air pollutants known to be persistent and bio-accumulative in the environment

PM Particulate matter

POM Polycyclic organic matter

PPA Purified phosphoric acid

ppm Parts per million

RACT Reasonably available control technology

RBLC RACT/BACT/LAER Clearinghouse

REL Reference exposure level

RFA Regulatory Flexibility Act

RTR Residual risk and technology review

SBA Small Business Administration

SiF4 Silicon tetrafluoride

SPA Superphosphoric acid

SSM Startup, shutdown, and malfunction

TOSHI Target organ-specific hazard index

tpy Tons per year

TRIM Total Risk Integrated Modeling System

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model

TSP Triple superphosphates

TTN Technology Transfer Network

UMRA Unfunded Mandates Reform Act

UPL Upper prediction limit

VCS Voluntary consensus standards

WESP Wet electrostatic precipitator

WPPA Wet-process phosphoric acid

WWW World Wide Web

Background Information.

On November 7, 2014 (79 FR 66511), the EPA proposed revisions to the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production national emission standards for hazardous air pollutants (NESHAP) in conjunction with the residual risk and technology review (RTR) for those NESHAP, 40 CFR part 63, subparts AA and BB, and required 8-year review of the Standards of Performance for the Phosphate Fertilizer Industry new source performance standards (NSPS) for 40 CFR part 60, subparts T, U, V, W and X. In this action, we are finalizing decisions and revisions for the rules. We summarize some of the more significant comments we received regarding the proposed rule and provide our responses in this preamble. A summary of all other public comments on the proposal and the EPA's responses to those comments is available in “Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing—Summary of Public Comments and Responses” which is available in Docket ID No. EPA-HQ-OAR-2012-0522. A “track changes” version of the regulatory language that incorporates the changes in this action for each NSPS is available in the docket. The NESHAP were replaced in their entirety to assist in readability of the language and to ensure that citations were accurate.

Organization of this Document.

The information in this preamble is organized as follows:

I. General Information

A. Does this action apply to me?

B. Where can I get a copy of this document and other related information?

C. Judicial Review and Administrative Reconsideration

II. Background

A. What is the statutory authority for this action?

B. What are the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories and how do the NESHAP and NSPS regulate emissions from these source categories?

C. What changes did we propose for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories in our November 7, 2014 proposal?

III. What is included in this final rule for the Phosphoric Acid Manufacturing source category?

A. What are the final rule amendments based on the NESHAP residual risk review for the Phosphoric Acid Manufacturing source category?

B. What are the final rule amendments based on the NESHAP technology review for the Phosphoric Acid Manufacturing source category?

C. What are the final rule amendments pursuant to CAA sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing source category?

D. What are the final rule amendments based on the NSPS review for the Phosphoric Acid Manufacturing source category?

E. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction for the Phosphoric Acid Manufacturing source category?

F. What other changes are we making to the NESHAP and NSPS for the Phosphoric Acid Manufacturing source category?

G. What are the effective and compliance dates of the standards for the Phosphoric Acid Manufacturing source category?

H. What are the requirements for submission of performance test data to the EPA for the Phosphoric Acid Manufacturing source category?

IV. What is included in this final rule for the Phosphate Fertilizer Production source category?

A. What are the final rule amendments based on the NESHAP risk review for the Phosphate Fertilizer Production source category?

B. What are the final rule amendments based on the NESHAP technology review for the Phosphate Fertilizer Production source category?

C. What are the final rule amendments based on the NSPS review for the Phosphate Fertilizer Production source category?

D. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction for the Phosphate Fertilizer Production source category?

E. What other changes are we making to the NESHAP and NSPS for the Phosphate Fertilizer Production source category?

F. What are the effective and compliance dates of the standards for the Phosphate Fertilizer Production source category?

G. What are the requirements for submission of performance test data to the EPA for the Phosphate Fertilizer Production source category?

V. What is the rationale for our final decisions and amendments for the Phosphoric Acid Manufacturing source category?

A. Residual Risk Review for the Phosphoric Acid Manufacturing Source Category

B. Technology Review for the Phosphoric Acid Manufacturing Source Category

C. CAA Sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing Source Category

D. NSPS Review for the Phosphoric Acid Manufacturing Source Category

E. Startup, Shutdown, and Malfunction Provisions for the Phosphoric Acid Manufacturing Source Category

F. Other Changes Made to the Phosphoric Acid Manufacturing NESHAP and NSPS

VI. What is the rationale for our final decisions and amendments for the Phosphate Fertilizer Production source category?

A. Residual Risk Review for the Phosphate Fertilizer Production Source Category

B. Technology Review for the Phosphate Fertilizer Production Source Category

C. NSPS Review for the Phosphate Fertilizer Production Source Category

D. Startup, Shutdown, and Malfunction Provisions for the Phosphate Fertilizer Production Source Category

E. Other Changes Made to the Phosphate Fertilizer Production NESHAP and NSPS

VII. Summary of Cost, Environmental, and Economic Impacts and Additional Analyses Conducted

A. What are the affected facilities?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

F. What analysis of environmental justice did we conduct?

G. What analysis of children's environmental health did we conduct?

VIII. Statutory and Executive Order Reviews

A. Executive Orders 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

H. Executive Order 13211: Actions Concerning Regulations That

Significantly Affect Energy Supply, Distribution or Use

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR Part 51

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

K. Congressional Review Act

I. General Information

A. Does this action apply to me?

Regulated Entities.

Categories and entities potentially regulated by this action are shown in Table 1 of this preamble.

Table 1—NESHAP and Industrial Source Categories Affected by This Final Action

NESHAP and source

category

NAICS

code

Phosphoric Acid Manufacturing Phosphate Fertilizer Production

325312

North American Industry Classification System.

Table 1 of this preamble is not intended to be exhaustive, but rather to provide a guide for readers regarding entities likely to be affected by the final action for the source category listed. To determine whether your facility is affected, you should examine the applicability criteria in the appropriate NESHAP. If you have any questions regarding the applicability of any aspect of this NESHAP, please contact the appropriate person listed in the preceding

FOR FURTHER INFORMATION CONTACT

section of this preamble.

B. Where can I get a copy of this document and other related information?

In addition to being available in the docket, an electronic copy of this final action will also be available on the Internet through the Technology Transfer Network (TTN) Web site, a forum for information and technology exchange in various areas of air pollution control. Following signature by the EPA Administrator, the EPA will post a copy of this final action at

http://www.epa.gov/ttn/atw/phosph/phosphpg.html.

Following publication in the

Federal Register

, the EPA will post the

Federal Register

version and key technical documents at this same Web site.

Additional information is available on the RTR Web site at

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

This information includes an overview of the RTR program, links to project Web sites for the RTR source categories and detailed emissions and other data we used as inputs to the risk assessments.

C. Judicial Review and Administrative Reconsideration

Under CAA section 307(b)(1), judicial review of this final action is available only by filing a petition for review in the United States (U.S.) Court of Appeals for the District of Columbia Circuit by October 19, 2015. Under CAA section 307(b)(2), the requirements established by this final rule may not be challenged separately in any civil or criminal proceedings brought by the EPA to enforce the requirements.

Section 307(d)(7)(B) of the CAA further provides that “[o]nly an objection to a rule or procedure which was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review.” This section also provides a mechanism for the EPA to reconsider the rule “[i]f the person raising an objection can demonstrate to the Administrator that it was impracticable to raise such objection within [the period for public comment] or if the grounds for such objection arose after the period for public comment (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule.” Any person seeking to make such a demonstration should submit a Petition for Reconsideration to the Office of the Administrator, U.S. EPA, Room 3000, EPA WJC Building, 1200 Pennsylvania Ave. NW., Washington, DC 20460, with a copy to both the person(s) listed in the preceding

FOR FURTHER INFORMATION CONTACT

section, and the Associate General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW., Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

1. NESHAP Authority

Section 112 of the CAA establishes a two-stage regulatory process to address emissions of hazardous air pollutants (HAP) from stationary sources. In the first stage, we must identify categories of sources emitting one or more of the HAP listed in CAA section 112(b) and then promulgate technology-based NESHAP for those sources. “Major sources” are those that emit, or have the potential to emit, any single HAP at a rate of 10 tons per year (tpy) or more, or 25 tpy or more of any combination of HAP. For major sources, these standards are commonly referred to as maximum achievable control technology (MACT) standards and must reflect the maximum degree of emission reductions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts). In developing MACT standards, CAA section 112(d)(2) directs the EPA to consider the application of measures, processes, methods, systems or techniques, including, but not limited to those that reduce the volume of or eliminate HAP emissions through process changes, substitution of materials, or other modifications; enclose systems or processes to eliminate emissions; collect, capture, or treat HAP when released from a process, stack, storage, or fugitive emissions point; are design, equipment, work practice, or operational standards; or any combination of the above.

For these MACT standards, the statute specifies certain minimum stringency requirements, which are referred to as MACT floor requirements, and which may not be based on cost considerations. See CAA section 112(d)(3). For new sources, the MACT floor cannot be less stringent than the emission control achieved in practice by the best-controlled similar source. The MACT standards for existing sources can be less stringent than floors for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources in the category or subcategory (or the best-performing five sources for categories or subcategories with fewer than 30 sources). In developing MACT standards, we must also consider control options that are more stringent than the floor, under CAA section 112(d)(2). We may establish standards more stringent than the floor, based on the consideration of the cost of achieving the emissions reductions, any non-air quality health and environmental impacts, and energy requirements.

In the second stage of the regulatory process, the CAA requires the EPA to undertake two different analyses, which we refer to as the technology review and the residual risk review. Under the technology review, we must review the technology-based standards and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less frequently than every 8 years, pursuant to CAA section 112(d)(6). Under the residual risk review, we must evaluate the risk to public health remaining after application of the technology-based

standards and revise the standards, if necessary, to provide an ample margin of safety to protect public health or to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect. The residual risk review is required within 8 years after promulgation of the technology-based standards, pursuant to CAA section 112(f). In conducting the residual risk review, if the EPA determines that the current standards provide an ample margin of safety to protect public health, it is not necessary to revise the MACT standards pursuant to CAA section 112(f).

For more information on the statutory authority for this rule, see 79 FR 66512 (November 7, 2014).

The U.S. Court of Appeals has affirmed this approach of implementing CAA section 112(f)(2)(A):

NRDC

EPA,

529 F.3d 1077, 1083 (D.C. Cir. 2008) (“If EPA determines that the existing technology-based standards provide an 'ample margin of safety,' then the Agency is free to readopt those standards during the residual risk rulemaking.”).

2. NSPS Authority

NSPS implement CAA section 111, which requires that each NSPS reflect the degree of emission limitation achievable through the application of the best system of emission reduction (BSER) which (taking into consideration the cost of achieving such emission reductions, any non-air quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated.

Existing affected facilities that are modified or reconstructed are also subject to NSPS. Under CAA section 111(a)(4), “modification” means any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted. Changes to an existing facility that do not result in an increase in emissions are not considered modifications.

Rebuilt emission units would become subject to the NSPS under the reconstruction provisions in 40 CFR 60.15, regardless of changes in emission rate. Reconstruction means the replacement of components of an existing facility such that: (1) The fixed capital cost of the new components exceeds 50 percent of the fixed capital cost that would be required to construct a comparable entirely new facility; and (2) it is technologically and economically feasible to meet the applicable standards (40 CFR 60.15).

Section 111(b)(1)(B) of the CAA requires the EPA to periodically review and, if appropriate, revise the standards of performance as necessary to reflect improvements in methods for reducing emissions. The EPA need not review an NSPS if the Agency determines that such review is not appropriate in light of readily available information on the efficacy of the standard. When conducting the review under CAA section 111(b)(1)(B), the EPA considers both: (1) Whether developments in technology or other factors support the conclusion that a different system of emissions reduction has become the BSER and (2) whether emissions limitations and percent reductions beyond those required by the current standards are achieved in practice.

B. What are the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories and how do the NESHAP and NSPS regulate emissions from these source categories?

1. Description of Phosphoric Acid Manufacturing Source Category

In 2014, 12 facilities in the U.S. manufactured phosphoric acid. The basic step for producing phosphoric acid is acidulation of phosphate rock. Typically, sulfuric acid, phosphate rock, and water are combined together and allowed to react to produce phosphoric acid and gypsum. When phosphate rock is acidulated to manufacture wet-process phosphoric acid (WPPA), fluorine contained in the rock is released. Fluoride compounds, predominately HF, are produced as particulates and gases that are emitted to the atmosphere unless removed from the exhaust stream. Some of these same fluoride compounds also remain in the product acid and are released as air pollutants during subsequent processing of the acid. Gypsum is pumped as a slurry to ponds atop stacks of waste gypsum where the liquids separate from the slurry and are decanted for return to the process. The gypsum, which is discarded on the stack, is a solid waste stream produced in this process. Five facilities concentrate WPPA to make superphosphoric acid (SPA), typically using the vacuum evaporation process. While one manufacturer is permitted to use a submerged combustion process for the production of SPA, that process was indefinitely shutdown on June 1, 2006. The majority of WPPA is used to produce phosphate fertilizers.

Additional processes may also be used to further refine phosphoric acid. At least two facilities have a defluorination process to remove fluorides from the phosphoric acid product, and one company uses a solvent extraction process to remove metals and organics and to further refine WPPA into purified phosphoric acid (PPA) for use in food manufacturing or specialized chemical processes. In addition, four facilities have oxidation processes to remove organics from the acid (

i.e.,

the green acid process). One of these facilities also calcines the ore prior to the acidulation process to help achieve the desired organic content reduction for the final acid product.

Sources of HF emissions from phosphoric acid plants include gypsum dewatering stacks, cooling ponds, cooling towers, calciners, reactors, filters, evaporators and other process equipment.

2. Federal Air Emission Standards Applicable to the Phosphoric Acid Manufacturing Source Category

The following federal air emission standards are associated with the Phosphoric Acid Manufacturing source category and are the subject of this final action:

• National Emission Standards for Hazardous Air Pollutants from Phosphoric Acid Manufacturing Plants (40 CFR part 63, subpart AA);

• Standards of Performance for the Phosphate Fertilizer Industry: Wet-Process Phosphoric Acid Plants (40 CFR part 60, subpart T); and

• Standards of Performance for the Phosphate Fertilizer Industry: Superphosphoric Acid Plants (40 CFR part 60, subpart U).

a. Phosphoric Acid Manufacturing NESHAP Emission Regulations.

The EPA promulgated 40 CFR part 63, subpart AA for the Phosphoric Acid Manufacturing source category on June 10, 1999 (64 FR 31358). The NESHAP established standards for major sources to control HAP emissions from phosphoric acid facilities. Total fluoride emission limits, as a surrogate for the HAP HF, were set for WPPA process lines and SPA process lines. The NESHAP established emission limits for particulate matter (PM) from phosphate rock dryers and phosphate rock calciners as a surrogate for metal HAP. Also, the NESHAP established an emission limit for methyl isobutyl ketone (MIBK) for PPA process lines and work practices for cooling towers. For more information on this NESHAP, see 79 FR 66512.

b. Phosphoric Acid Manufacturing NSPS Emission Regulations.

The EPA promulgated 40 CFR part 60, subpart T for WPPA Plants on August 6, 1975 (40 FR 33154). The NSPS established standards to control total fluoride emissions from WPPA plants, including

reactors, filters, evaporators, and hot wells.

The EPA promulgated 40 CFR part 60, subpart U for SPA Plants on August 6, 1975 (40 FR 33155). The NSPS established standards to control total fluoride emissions from SPA plants, including evaporators, hot wells, acid sumps, and cooling tanks.

For more information on these NSPS, see 79 FR 66512.

3. Description of Phosphate Fertilizer Production Source Category

There are 11 operating facilities that produce phosphate fertilizers, and most facilities have the ability to produce either monoammonium phosphates (MAP) or diammonium phosphates (DAP) in the same process train. However, approximately 80 percent of all ammonium phosphates are produced as MAP. MAP and DAP plants are generally collocated with WPPA plants since both are manufactured from phosphoric acid and ammonia. The MAP and DAP manufacturing process consists of three basic steps: Reaction, granulation, and finishing operations such as drying, cooling, and screening. Sources of fluoride emissions from MAP and DAP plants include the reactor, granulator, dryer, cooler, screens, and mills. Some of the fluoride is liberated as HF and silicon tetrafluoride (SiF

), but the majority is emitted as HF.

Triple superphosphates (TSP) are made as run-of-pile TSP (ROP-TSP) and granular TSP (GTSP) by reacting WPPA with ground phosphate rock. The phosphoric acid used in the GTSP process is appreciably lower in concentration (40-percent phosphorus pentoxide (P

)) than that used to manufacture ROP-TSP product (50 to 55-percent P

). The GTSP process yields larger, more uniform particles with improved storage and handling properties than the ROP-TSP process. Currently, no facilities produce ROP-TSP or GTSP,

although one facility retains an operating permit to store GTSP.

According to 2014 production and trade statistics issued by International Fertilizer Industry Association (IFA).

4. Federal Air Emission Standards Applicable to the Phosphate Fertilizer Production Source Category

The following federal air emission standards are associated with the Phosphate Fertilizer Production source category and are subject of this final action:

• National Emission Standards for Hazardous Air Pollutants from Phosphate Fertilizers Production Plants (40 CFR part 63, subpart BB);

• Standards of Performance for the Phosphate Fertilizer Industry: Diammonium Phosphate Plants (40 CFR part 60, subpart V);

• Standards of Performance for the Phosphate Fertilizer Industry: Triple Superphosphate Plants (40 CFR part 60, subpart W); and

• Standards of Performance for the Phosphate Fertilizer Industry: Granular Triple Superphosphate Storage Facilities (40 CFR part 60, subpart X).

a. Phosphate Fertilizer Production NESHAP Emission Regulations.

The EPA promulgated 40 CFR part 63, subpart BB for the Phosphate Fertilizer Production source category on June 10, 1999 (64 FR 31358). The NESHAP established standards for major sources to control HAP emissions from phosphate fertilizer facilities. As a surrogate for HF, the NESHAP set total fluoride emission limits for DAP and/or MAP process lines and GTSP process lines and storage buildings. The NESHAP also established work practices for GTSP production. For more information on this NESHAP, see 79 FR 66512.

b. Phosphate Fertilizer Production NSPS Emission Regulations.

The EPA promulgated 40 CFR part 60, subpart V for Diammonium Phosphate Plants on July 25, 1977 (42 FR 37938). The NSPS established standards to control total fluoride emissions from granular DAP plants, including reactors, granulators, dryers, coolers, screens, and mills.

The EPA promulgated 40 CFR part 60, subpart W for TSP plants on July 25, 1977 (42 FR 37938). The NSPS established standards to control total fluoride emissions from the production of ROP-TSP and GTSP, and the storage of ROP-TSP.

The EPA promulgated 40 CFR part 60, subpart X for GTSP storage facilities on July 25, 1977 (42 FR 37938). The NSPS established standards to control total fluoride emissions from the storage of GTSP, including storage or curing buildings (noted as “piles” in subpart X), conveyors, elevators, screens, and mills.

For more information on these NSPS, see 79 FR 66512.

C. What changes did we propose for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories in our November 7, 2014 proposal?

On November 7, 2014 (79 FR 66512), the EPA published a proposed rule in the

Federal Register

for both the Phosphoric Acid Manufacturing NESHAP, 40 CFR part 63, subpart AA, and Phosphate Fertilizer Production NESHAP, 40 CFR part 63, subpart BB that took into consideration the RTR analyses. We also proposed other revisions to these NESHAP. In the proposed rule, we proposed:

For Phosphoric Acid Manufacturers:

• Numeric emission limits for Hg and work practice standards for HF from calciners; and

• Work practice standards for HF emissions from gypsum dewatering stacks and cooling ponds.

For both Phosphoric Acid Manufacturers and Phosphate Fertilizer Producers:

• Emission limits regulating HF emissions as the target HAP (HF), instead of the long-standing surrogate for HF, total F;

• Clarifications to applicability and certain definitions;

• Revisions to requirements related to emissions during periods of SSM;

• Revisions to monitoring requirements for absorbers;

• Requirements for reporting of performance testing through the electronic reporting tool (ERT);

• Modification to the format to reference tables for emissions limits and monitoring requirements; and

• Several minor clarifications and corrections.

In addition, we proposed revisions to the NSPS subparts T, U, V, W, and X, including clarifications to applicability and certain definitions, and revisions to monitoring and recordkeeping requirements for absorbers.

III. What is included in this final rule for the Phosphoric Acid Manufacturing source category?

This action finalizes the EPA's determinations pursuant to the RTR provisions of CAA section 112 and the 8-year review provisions of CAA section 111 for the Phosphoric Acid Manufacturing source category. Today's action also finalizes several of the proposed changes to the NESHAP subpart AA and the NSPS subparts T and U that are described in section II.C. of this preamble. This action also finalizes other changes to the NESHAP subpart AA in consideration of comments on issues raised in the proposed rulemaking, as described in section V of this preamble.

A. What are the final rule amendments based on the NESHAP residual risk review for the Phosphoric Acid Manufacturing source category?

The residual risk review for the Phosphoric Acid Manufacturing source category did not change since proposal; we found that the current standards provide an ample margin of safety to protect public health (79 FR 66512) and prevent an adverse environmental effect. We are, therefore, not tightening the standards under section 112(f)(2)

(for NESHAP subpart AA) based on the residual risk review, and are thus readopting the existing standards under section 112(f)(2). See sections V.A.3 and V.A.4 of this preamble for discussion on key comments and responses regarding the residual risk review.

B. What are the final rule amendments based on the NESHAP technology review for the Phosphoric Acid Manufacturing source category?

The technology review for the Phosphoric Acid Manufacturing source category did not change since proposal (79 FR 66512). We determined that there are no cost-effective developments in practices, processes, and control technologies that warrant revisions to the MACT standards for this source category (79 FR 66512). Therefore, we are not amending the MACT standards under CAA section 112(d)(6). See sections V.B.3 and V.B.4 of this preamble for discussion on key comments and responses regarding the technology review.

C. What are the final rule amendments pursuant to CAA sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing source category?

We are finalizing MACT standards for HF and Hg pursuant to CAA sections 112(d)(2) and 112(d)(3) for phosphate rock calciners, an emissions source that was initially regulated for HAP metals using PM as a surrogate. Specifically, we are finalizing, as proposed, the elimination of the use of PM as a surrogate for Hg; however, we are making changes to the proposed Hg emission limit for phosphate rock calciners in NESHAP subpart AA to reflect MACT floor level emission standards for existing sources. We are finalizing the proposed beyond-the-floor (BTF) emission standard for Hg emissions from new phosphate rock calciners. We discuss the changes to the Hg emission limit in section V.C.3.a.i of this preamble. In addition, we are finalizing, as proposed, to retain the PM standard as a surrogate for other HAP metal emissions from phosphate rock calciners. However, in consideration of comments received during the public comment period for the proposed rulemaking, we are not finalizing work practice standards for HF from phosphate rock calciners, as proposed. Instead, as discussed in section V.C.3.a.ii of this preamble, we are including a total fluoride emission limit for phosphate rock calciners in NESHAP subpart AA.

Also, in consideration of comments received (see section V.C.3.b.i of this preamble for details), we are not adopting the proposed work practice in NESHAP subpart AA that would limit the size of active gypsum dewatering stacks (which would have been applicable to facilities when new gypsum dewatering stacks are constructed). Lastly, we are finalizing work practice standards pursuant to CAA section 112(h) for gypsum dewatering stacks and cooling ponds—emissions sources that were not regulated under the initial MACT standard. Specifically, we are finalizing in NESHAP subpart AA, as proposed, the work practice standard that requires owners or operators to prepare and operate in accordance with a gypsum dewatering stack and cooling pond management plan. However, based on analysis of public comments, we are making several changes to the specific control techniques that we proposed as options in the plan for controlling fugitive HF emissions (see section V.C.3.b.ii of this preamble for details on these changes). In the final rule, the Agency is using the terminology “control measures” in lieu of the proposed terminology “control techniques” because we feel this more accurately describes the list of options in the rule and avoids confusion with other CAA programs.

D. What are the final rule amendments based on the NSPS review for the Phosphoric Acid Manufacturing source category?

We are finalizing our determination that revisions to NSPS subpart T and subpart U standards are not appropriate pursuant to CAA section 111(b)(1)(B). All Phosphoric Acid Manufacturing NSPS (under subpart T and subpart U) emission sources, and the control technologies that would be employed, are the same as those for the NESHAP regulating phosphoric acid plants, such that we reached the same determination that there are no identified cost-effective practices or technologies that would provide additional emission reductions. Additionally, there were no identified technologies that have been adequately demonstrated to achieve in practice emission controls that would result in more stringent total fluoride limits for these NSPS. See section V.D of this preamble for discussion on key comments and responses regarding the NSPS review.

E. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction for the Phosphoric Acid Manufacturing source category?

We are finalizing, as proposed, changes to the Phosphoric Acid Manufacturing NESHAP, subpart AA to eliminate the SSM exemption. Consistent with

Sierra Club

EPA

551 F. 3d 1019 (D.C. Cir. 2008), the EPA has established standards in this rule that apply at all times. Appendix A of subpart AA (the General Provisions Applicability Table) is being revised to change several references related to requirements that apply during periods of SSM. We also eliminated or revised certain recordkeeping and reporting requirements related to the eliminated SSM exemption. The EPA also made changes to the rule to remove or modify inappropriate, unnecessary, or redundant language in the absence of the SSM exemption. For this source category, we determined that work practice standards for periods of startup and shutdown are appropriate in lieu of numeric emission limits due to the short duration of startup and shutdown, and control devices used on the various process lines in this source category are effective at achieving desired emission reductions immediately upon startup (79 FR 66541). Therefore, we are finalizing in NESHAP subpart AA the proposed work practice standards for periods of startup and shutdown. However, in consideration of comments received during the public comment period, we are making changes to the work practice standards in order to clarify that the standard applies in lieu of numeric emission limits and how compliance with the standard is demonstrated. In order to comply with the work practice standard, facilities must monitor the same control device operating parameters and comply with the same operating limits that are established to otherwise comply with the emission limits. Additionally, we added a definition of “startup” and “shutdown” in the definitions section of the final rule to specify when startup begins and ends, and when shutdown begins and ends. See section V.E.3 of this preamble for details on these changes.

F. What other changes are we making to the NESHAP and NSPS for the Phosphoric Acid Manufacturing source category?

Today's rule also finalizes, as proposed, revisions to several other Phosphoric Acid Manufacturing NESHAP and NSPS requirements. We are finalizing, as proposed, several miscellaneous changes to clarify applicability and certain definitions, as follows:

• Adopting the proposed SPA process line definition in NESHAP subpart AA to include oxidation reactors;

• Adopting the proposed SPA plant definition in NSPS subpart U to include oxidation reactors;

• Finalizing the proposed revisions to rename “gypsum stack” to “gypsum dewatering stack” in NESHAP subpart AA; and

• Finalizing the proposed definitions for “cooling pond” and “raffinate stream” in NESHAP subpart AA.

We are finalizing, as proposed, several changes to testing, monitoring, recordkeeping and reporting requirements to provide consistency, clarification and flexibility, as follows:

• Finalizing the proposed revisions to NESHAP subpart AA that require a minimum pressure drop of 5 inches of water column for facilities that use pressure differential in parametric monitoring;

• Finalizing the proposal to remove the requirement in NESHAP subpart AA that facilities must request and obtain approval of the Administrator for changing operating limits;

• Adopting the proposed addition of a site-specific monitoring plan and calibration requirements for a continuous monitoring system (CMS) in NESHAP subpart AA;

• Adopting the proposed term “absorber” in lieu of “scrubber” in NESHAP subpart AA;

• Adopting the proposed format of NESHAP subpart AA to reference tables for emissions limits and monitoring requirements;

• Adopting the proposed provisions in NSPS subpart T and NSPS subpart U that require the owner or operator to establish an allowable range for the pressure drop through the process scrubbing system, keep records of the daily average pressure drop through the process scrubbing system, and keep records of deviations; and

• Adopting the proposed term “absorber” in lieu of “process scrubbing system” in NSPS subpart T and NSPS subpart U.

We are also finalizing changes to the NESHAP and NSPS for the Phosphoric Acid Manufacturing source category on issues raised in response to the proposed rulemaking, as follows (refer to section V.F.2 of this preamble for further details):

• Revising the definition of oxidation reactor in the final rule for NESHAP subpart AA and NSPS subpart U;

• Finalizing liquid-to-gas ratio monitoring in NESHAP subpart AA for low-energy absorbers (

i.e.,

absorbers that are designed to operate with pressure drops of 5 inches of water column or less) in lieu of monitoring influent liquid flow and pressure drop through the absorber;

• Clarifying in NESHAP subpart AA that during the most recent performance test, if owners or operators demonstrate compliance with the emission limit while operating their control device outside the previously established operating limit, owners or operators must establish a new operating limit based on that most recent performance test and notify the Administrator that the operating limit changed based on data collected during the most recent performance test; and

• Clarifying in NESHAP subpart AA that facilities not be required to obtain approval, and, instead, immediately comply with a new operating limit when it is developed and submitted to the Administrator.

G. What are the effective and compliance dates of the standards for the Phosphoric Acid Manufacturing source category?

The revisions to the NSPS and NESHAP standards we promulgate in this action for the Phosphoric Acid Manufacturing source category are effective on August 19, 2015.

The compliance date for the Hg limit in NESHAP subpart AA for existing phosphate rock calciners is August 19, 2015. Based on the data that the EPA has received, all existing phosphate rock calciners are meeting the Hg limit; therefore, no additional time would be required to achieve compliance with this standard.

The compliance date for the Hg limit in NESHAP subpart AA for new phosphate rock calciners is August 19, 2015, or upon startup, whichever is later. We are not aware of any new phosphate rock calciners operating today. New phosphate rock calciners that commence construction or reconstruction after the effective date of this rule would be required to comply with the Hg limits immediately upon startup.

The compliance date for the total fluoride limits in NESHAP subpart AA for all (existing and new) phosphate rock calciners is August 19, 2015, or upon startup, whichever is later. Based on the data that the EPA has received, all phosphate rock calciners are meeting the total fluoride limit; therefore, no additional time would be required to achieve compliance with this standard.

The compliance date in NESHAP subpart AA for preparing and operating in accordance with a gypsum dewatering stack and cooling pond management plan is August 19, 2016. A 1-year compliance lead-time will provide facilities adequate time to prepare and submit their plan for approval to the Administrator.

The compliance date for when facilities must include oxidation reactors in determining compliance with the total fluoride limit in NESHAP subpart AA for SPA process lines is August 19, 2016. We believe that 1 year is necessary because a facility may need to install additional control technology. A 1-year compliance period will provide the facility adequate time to design and install controls.

The compliance date in NESHAP subpart AA for when to install, calibrate, and maintain a bag leak detection system on a fabric filter is August 19, 2016. We believe that 1 year is necessary because some facilities that currently operate a fabric filter do not have a bag leak detection system and will need time to purchase and install this compliance monitoring equipment and implement quality assurance measures.

The compliance date in NESHAP subpart AA for the revised startup and shutdown requirements is August 19, 2015. We determined that the feasibility of operating the control devices used to control HAP emissions from phosphoric acid manufacturing is not limited by specific process operating conditions.

Finally, to ensure continuous compliance with the standard, the compliance date for the monitoring and recordkeeping requirements in NSPS subparts T and U for all new WPPA plants and SPA plants is August 19, 2015, or upon startup, whichever is later.

H. What are the requirements for submission of performance test data to the EPA for the Phosphoric Acid Manufacturing source category?

As stated in the preamble to the proposed rule, the EPA is taking a step to increase the ease and efficiency of data submittal and data accessibility. Specifically, the EPA is requiring owners and operators of phosphoric acid facilities to submit electronic copies of certain required performance test reports.

As mentioned in the preamble of the proposal, data will be collected by direct computer-to-computer electronic transfer using EPA-provided software. As discussed in the proposal, the EPA-provided software is an electronic performance test report tool called the ERT. The ERT will generate an electronic report package which will be submitted to the Compliance and Emissions Data Reporting Interface (CEDRI) and then archived to the EPA's Central Data Exchange (CDX). A description and instructions for use of the ERT can be found at

http://www.epa.gov/ttn/chief/ert/index.html,

and CEDRI can be accessed through the CDX Web site at

www.epa.gov/cdx

performance test submittal process. Additionally, this rulemaking benefits industry by cutting back on recordkeeping costs as the performance test reports that are submitted to the EPA using CEDRI are no longer required to be kept in hard copy.

As mentioned in the proposed preamble, state, local, and tribal agencies will benefit from more streamlined and accurate review of performance test data that will be available on the EPA WebFIRE database. The public will also benefit. Having these data publicly available enhances transparency and accountability. For a more thorough discussion of electronic reporting of performance tests using direct computer-to-computer electronic transfer and using EPA-provided software, see the discussion in the preamble of the proposal.

In summary, in addition to supporting regulation development, control strategy development, and other air pollution control activities, having an electronic database populated with performance test data will save industry, state, local, and tribal agencies, and the EPA significant time, money, and effort, while improving the quality of emission inventories, air quality regulations, and enhancing the public's access to this important information.

IV. What is included in this final rule for the Phosphate Fertilizer Production source category?

This action finalizes the EPA's determinations pursuant to the RTR provisions of CAA section 112 and the 8-year review provisions of CAA section 111 for the Phosphate Fertilizer Production source category. Today's action also finalizes several of the proposed changes to the NESHAP subpart BB and the NSPS subparts V, W, and X that are described in section II.C of this preamble. This action also finalizes other changes to the NESHAP subpart BB in consideration of comments on issues raised in the proposed rulemaking, as described in section VI of this preamble.

A. What are the final rule amendments based on the NESHAP risk review for the Phosphate Fertilizer Production source category?

The residual risk review for the Phosphate Fertilizer Production source category did not change since proposal; we found that the current standards provide an ample margin of safety to protect public health (79 FR 66512) and prevent an adverse environmental effect. We are, therefore, not tightening the standards under section 112(f)(2) (for NESHAP subpart BB) based on the residual risk review, and are thus readopting the existing standards under section 112(f)(2).

B. What are the final rule amendments based on the NESHAP technology review for the Phosphate Fertilizer Production source category?

The technology review for the Phosphate Fertilizer Production source category did not change since proposal (79 FR 66512). We determined that there are no cost-effective developments in practices, processes, and control technologies that warrant revisions to the MACT standards for this source category (79 FR 66512). Therefore, we are not amending the MACT standards under CAA section 112(d)(6).

C. What are the final rule amendments based on the NSPS review for the Phosphate Fertilizer Production source category?

We are finalizing our determination that revisions to NSPS subpart V, subpart W, and subpart X standards are not appropriate pursuant to CAA section 111(b)(1)(B). All Phosphate Fertilizer Production NSPS (under subpart V, subpart W, and subpart X) emission sources, and the control technologies that would be employed, are the same as those for the NESHAP regulating phosphate fertilizer plants, such that we reached the same determination that there are no identified cost-effective practices or technologies that would provide additional emission reductions. Additionally, there were no identified technologies that have been adequately demonstrated to achieve in practice emission controls that would result in more stringent total fluoride limits for these NSPS.

D. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction for the Phosphate Fertilizer Production source category?

We are finalizing, as proposed, changes to the Phosphate Fertilizer Production NESHAP, subpart BB to eliminate the SSM exemption. Consistent with

Sierra Club

EPA

551 F. 3d 1019 (D.C. Cir. 2008), the EPA has established standards in this rule that apply at all times. Appendix A of subpart BB (the General Provisions Applicability Table) is being revised to change several references related to requirements that apply during periods of SSM. We also eliminated or revised certain recordkeeping and reporting requirements related to the eliminated SSM exemption. The EPA also made changes to the rule to remove or modify inappropriate, unnecessary, or redundant language in the absence of the SSM exemption. For this source category, we determined that work practice standards for periods of startup and shutdown are appropriate in lieu of numeric emission limits due to the short duration of startup and shutdown, and control devices used on the various process lines in this source category are effective at achieving desired emission reductions immediately upon startup (79 FR 66551). Therefore, we are finalizing in NESHAP subpart BB the proposed work practice standards for periods of startup and shutdown. However, in consideration of comments received during the public comment period, we are making changes to the work practice standards in order to clarify that the standard applies in lieu of numeric emission limits and how compliance with the standard is demonstrated. In order to comply with the work practice standard, facilities must monitor the same control device operating parameters and comply with the same operating limits that are established to otherwise comply with the emission limits. Additionally, we added a definition of “startup” and “shutdown” in the definitions section of the final rule to specify when startup begins and ends, and when shutdown begins and ends. See section VI.D.3 of this preamble for details on these changes.

E. What other changes are we making to the NESHAP and NSPS for the Phosphate Fertilizer Production source category?

Today's rule also finalizes, as proposed, revisions to several other Phosphate Fertilizer Production NESHAP and NSPS requirements. We are finalizing, as proposed, changes to clarify applicability and certain definitions, as follows:

• Adopting the proposed conditions in NESHAP subpart BB that exclude the use of evaporative cooling towers for any liquid effluent from any wet scrubbing device installed to control HF emissions from process equipment; and

• Finalizing the proposed revisions changing the word “cookers” in NSPS subpart W to “coolers.”

We are finalizing, as proposed, several changes to testing, monitoring, recordkeeping, and reporting to provide consistency, clarification, and flexibility, as follows:

• Finalizing the proposed revisions to NESHAP subpart BB that require a minimum pressure drop of 5 inches of water column for facilities that use pressure differential in parametric monitoring;

• Finalizing the proposal to remove the requirement in NESHAP subpart BB that facilities must request and obtain approval of the Administrator for changing operating limits;

• Adopting the proposed monitoring requirements for fabric filters in NESHAP subpart BB;

• Adopting the proposed addition of a site-specific monitoring plan and calibration requirements for CMS in NESHAP subpart BB;

• Adopting the proposed term “absorber” in lieu of “scrubber” in NESHAP subpart BB;

• Adopting the proposed format of NESHAP subpart BB to reference tables for emissions limits and monitoring requirements;

• Adopting the proposed provisions in NSPS subpart V, NSPS subpart W, and NSPS subpart X that require the owner or operator to establish an allowable range for the pressure drop through the process scrubbing system, keep records of the daily average pressure drop through the process scrubbing system, and keep records of deviations;

• Adopting the proposed term “absorber” in lieu of “scrubbing system” in NSPS subpart V; and

• Adopting the proposed term “absorber” in lieu of “process scrubbing system” in NSPS subpart W and NSPS subpart X.

We are also finalizing changes to the NESHAP and NSPS for the Phosphate Fertilizer Production source category on issues raised in response to the proposed rulemaking, as follows (refer to section VI.E.2 of this preamble for further details):

• Revising the definitions of “phosphate fertilizer process line” and “phosphate fertilizer production plant” in NESHAP subpart BB to reference granular phosphate fertilizer;

• Finalizing liquid-to-gas ratio monitoring in NESHAP subpart BB for low-energy absorbers (

i.e.,

absorbers that are designed to operate with pressure drops of 5 inches of water column or less) in lieu of monitoring influent liquid flow and pressure drop through the absorber;

• Clarifying in NESHAP subpart BB that during the most recent performance test, if owners or operators demonstrate compliance with the emission limit while operating their control device outside the previously established operating limit, owners or operators must establish a new operating limit based on that most recent performance test and notify the Administrator that the operating limit changed based on data collected during the most recent performance test; and

• Clarifying in NESHAP subpart BB that facilities not be required to obtain approval, and, instead, immediately comply with a new operating limit when it is developed and submitted to the Administrator.

F. What are the effective and compliance dates of the standards for the Phosphate Fertilizer Production source category?

The revisions to the NSPS and NESHAP standards being promulgated in this action for the Phosphate Fertilizer Production source category are effective on August 19, 2015.

The compliance date in NESHAP subpart BB for when to install, calibrate, and maintain a bag leak detection system on a fabric filter is August 19, 2016. We believe that 1 year is necessary because some facilities that currently operate a fabric filter do not have a bag leak detection system and will need time to purchase and install this compliance monitoring equipment and implement quality assurance measures.

The compliance date in NESHAP subpart BB for the revised startup and shutdown requirements is August 19, 2015. We determined that the feasibility of operating the control devices used to control HAP emissions from phosphate fertilizer production is not limited by specific process operating conditions.

Finally, to ensure continuous compliance with the standard, the compliance date for the monitoring and recordkeeping requirements in NSPS subparts V, W, and X for all new granular DAP plants, TSP plants, and GTSP storage facilities is August 19, 2015, or upon startup, whichever is later.

G. What are the requirements for submission of performance test data to the EPA for the Phosphate Fertilizer Production source category?

As stated in the preamble to the proposed rule, the EPA is taking a step to increase the ease and efficiency of data submittal and data accessibility. Specifically, the EPA is requiring owners and operators of phosphate fertilizer facilities to submit electronic copies of certain required performance test reports.

As mentioned in the preamble of the proposal, data will be collected by direct computer-to-computer electronic transfer using EPA-provided software. As discussed in the proposal, the EPA-provided software is an electronic performance test report tool called the Electronic Reporting Tool (ERT). The ERT will generate an electronic report package which will be submitted to the Compliance and Emissions Data Reporting Interface (CEDRI) and then archived to the EPA's Central Data Exchange (CDX). A description and instructions for use of the ERT can be found at

http://www.epa.gov/ttn/chief/ert/index.html,

and CEDRI can be accessed through the CDX Web site at

www.epa.gov/cdx

The requirement to submit performance test data electronically to the EPA does not create any additional performance testing and will apply only to those performance tests conducted using test methods that are supported by the ERT. A listing of the pollutants and test methods supported by the ERT is available at the ERT Web site. The EPA believes, through this approach, industry will save time in the performance test submittal process. Additionally, this rulemaking benefits industry by cutting back on recordkeeping costs as the performance test reports that are submitted to the EPA using CEDRI are no longer required to be kept in hard copy.

In summary, in addition to supporting regulation development, control strategy development, and other air pollution control activities, having an electronic database populated with performance test data will save industry, state, local, and tribal agencies, and the EPA significant time, money, and effort while improving the quality of emission inventories, air quality regulations, and enhancing the public's access to this important information.

V. What is the rationale for our final decisions and amendments for the Phosphoric Acid Manufacturing source category?

For each issue related to the Phosphoric Acid Manufacturing source category, this section provides a description of what we proposed and what we are finalizing for the issue, the EPA's rationale for the final decisions and amendments, and a summary of key comments and responses. For all comments not discussed in this preamble, comment summaries and the EPA's responses can be found in the Comment Summary and Response document available in the docket.

A. Residual Risk Review for the Phosphoric Acid Manufacturing Source Category

1. What did we propose pursuant to CAA section 112(f) for the Phosphoric Acid Manufacturing source category?

Pursuant to CAA section 112(f), we conducted a residual risk review and presented the results of this review, along with our proposed decisions regarding risk acceptability and ample margin of safety, in the November 7, 2014, proposed rule for the Phosphoric Acid Manufacturing NESHAP (79 FR 66512). The results of the risk assessment are presented briefly below in Table 2 of this preamble, and in more detail in the residual risk document, “Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing Source Categories in support of the July 2015 Risk and Technology Review Final Rule,” which is available in the docket for this rulemaking.

Table 2—Human Health Risk Assessment for Phosphoric Acid Manufacturing

Category & number

of facilities modeled

Cancer MIR

(in 1 million)

Based on

actual

emissions

Based on

allowable

emissions

Cancer

incidence

(cases per

year)

Population

with risks

of 1-in-1

million or

Population

with risks

of 10-in-1

million

or more

Max chronic non-cancer HI

Based on

actual

emissions

Based on

allowable

emissions

Worst-case max acute

non-cancer

Phosphoric Acid (12 facilities)

0.09

0.0002

0.2

0.3

REL

= 2 (hydrofluoric acid)

AEGL

− 1 = 0.6 (hydrofluoric acid).

Facility-wide (12 facilities)

0.5

0.001

0.2

Based on actual emissions for the Phosphoric Acid Manufacturing source category, the maximum individual risk (MIR) was estimated to be less than 1-in-1 million, the maximum chronic non-cancer target organ-specific hazard index (TOSHI) value was estimated to be up to 0.2, and the maximum off-site acute hazard quotient (HQ) value was estimated to be up to 2. The total estimated national cancer incidence from this source category, based on actual emission levels, was 0.0002 excess cancer cases per year, or one case in every 5,000 years. Based on MACT-allowable emissions for the Phosphoric Acid Manufacturing source category, the MIR was estimated to be less than 1-in-1 million, and the maximum chronic non-cancer TOSHI value was estimated to be up to 0.3. We also found there were emissions of several persistent and bio-accumulative HAP (PB-HAP) with an available RTR multipathway screening value, and with the exception of Hg and cadmium compounds, the reported emissions of these HAP (

i.e.,

lead compounds, dioxin/furan compounds, and polycyclic organic matter (POM) compounds), were below the multipathway screening value for each compound. One facility emitted divalent Hg (Hg

) above the Tier I screening threshold level, exceeding the screening threshold by a factor of 7 and the cadmium emissions exceeded the cadmium screening threshold by a factor of 2. Consequently, we conducted a Tier II screening assessment, in which both pollutants of concern were below the Tier II screening threshold, indicating no potential for multipathway impacts of concern from this facility. The maximum facility-wide MIR was less than or equal to 1-in-1 million and the maximum facility-wide TOSHI was 0.2. We weighed all health risk factors in our risk acceptability determination, and we proposed that the residual risks from the Phosphoric Acid Manufacturing source category are acceptable.

We then considered whether the Phosphoric Acid Manufacturing NESHAP provides an ample margin of safety to protect public health and prevents, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect. In considering whether the standards should be tightened to provide an ample margin of safety to protect public health, we considered the same risk factors that we considered for our acceptability determination and also considered the costs, technological feasibility, and other relevant factors related to emissions control options that might reduce risk associated with emissions from the source category. We proposed that the current standards provided an ample margin of safety to protect public health. With respect to adverse environmental effects, none of the individual modeled concentrations for any facility in the source category exceeded any of the ecological benchmarks (either the lowest-observed-adverse-effect level (LOAEL) or no-observed-adverse-effect level (NOAEL)). Based on the results of our screening analysis for risks to the environment, we also proposed that the current standards prevent an adverse environmental effect.

2. How did the risk review change for the Phosphoric Acid Manufacturing source category?

The residual risk review for the Phosphoric Acid Manufacturing source category did not change since proposal (79 FR 66512). Accordingly, we are not tightening the standards under section 112(f)(2) based on the residual risk review, and are thus readopting the existing standards under section 112(f)(2).

3. What key comments did we receive on the risk review, and what are our responses?

The comments received on the proposed residual risk review were generally supportive of our determination of risk acceptability and ample margin of safety analysis. However, we received several comments requesting we make changes to the residual risk review, including:

• Update the residual risk review with the recommendations and information from the National Academy of Sciences (NAS);

• Incorporate the best currently available information on children's exposure to lead, and go beyond using the 2008 Lead National Ambient Air Quality Standards (NAAQS);

• Reevaluate whether the residual risk review is consistent with the key recommendations made by the Science Advisory Board (SAB);

• Clarify in the rulemaking docket that data received by industry were commensurate with the relevant statutory obligations;

• Revise HF emission data because they are not representative of actual HF emissions, but rather overestimate emissions causing the residual risk review to have an overtly conservative bias;

• Reconsider the assumption used in the NESHAP residual risk assessment that all chromium is hexavalent chromium;

• Revise certain stack parameters used in the analysis;

• Clarify meteorological data used in the analysis;

• Adequately explain rationale for the maximum 1-hour emission rate used for determining potential acute exposures;

• Clarify the selection of ecological assessment endpoints; and

• Provide some quantitative or qualitative rationale for the characterization of the exposure modeling uncertainty.

We evaluated the comments and determined that no changes were needed. Since none of these comments had an effect on the final rule, their summaries and corresponding EPA responses are not included in this preamble. A summary of these comments and our responses can be found in the Comment Summary and Response document available in the docket for this action (EPA-HQ-OAR-2012-0522).

4. What is the rationale for our final approach and final decisions for the risk review?

For the reasons explained in the proposed rule, we determined that the risks from the Phosphoric Acid Manufacturing source category are acceptable, the current standards provide an ample margin of safety to protect public health, and prevent an adverse environmental effect. Since proposal, neither the risk assessment nor our determinations regarding risk acceptability, ample margin of safety or adverse environmental effects have changed. Therefore, pursuant to CAA section 112(f)(2), we are finalizing our residual risk review as proposed.

B. Technology Review for the Phosphoric Acid Manufacturing Source Category

1. What did we propose pursuant to CAA section 112(d)(6) for the Phosphoric Acid Manufacturing source category?

Pursuant to CAA section 112(d)(6), we conducted a technology review, which focused on identifying and evaluating developments in practices, processes, and control technologies for the emission sources in the Phosphoric Acid Manufacturing source category. At proposal, we did not identify cost-effective developments in practices, processes, or control technologies that warrant revisions to the NESHAP for this source category. More information concerning our technology review can be found in the memorandum, “CAA Section 111(b)(1)(B) and 112(d)(6) Reviews for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production Source Categories,” which is available in the docket, and in the preamble to the proposed rule, 79 FR 66538-66539.

2. How did the technology review change for the Phosphoric Acid Manufacturing source category?

The technology review for the Phosphoric Acid Manufacturing source category did not change since proposal (79 FR 66512). Therefore, we are not revising NESHAP subpart AA based on the technology review.

3. What key comments did we receive on the technology review, and what are our responses?

Commenters agreed with our conclusion that there are no new cost-effective developments in practices, processes, or control technologies that can be applied to the Phosphoric Acid Manufacturing source category that would reduce HAP emissions below current levels.

4. What is the rationale for our final approach for the technology review?

For the reasons explained in the proposed rule, we concluded that additional standards are not necessary pursuant to CAA section 112(d)(6); therefore, we are not finalizing changes to NESHAP subpart AA as part of our technology review.

C. CAA Sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing Source Category

1. What did we propose pursuant to CAA sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing source category?

We proposed MACT standards for HF and Hg pursuant to CAA sections 112(d)(2) and 112(d)(3), and work practice standards pursuant to CAA section 112(h), for phosphate rock calciners, an emissions source that was initially regulated for HAP metals using PM as a surrogate. We proposed regulating two pollutants, Hg and HF, which were not directly regulated under the initial NESHAP subpart AA. We proposed eliminating the use of PM as a surrogate for Hg and proposed a Hg emission limit for phosphate rock calciners. Because control devices may be necessary to meet the proposed Hg limits for phosphate rock calciners, we proposed monitoring and testing requirements in NESHAP subpart AA for the two types of control systems evaluated as alternatives for control of Hg: Adsorbers (typically fixed bed carbon), and sorbent injection (

i.e.,

activated carbon injection (ACI)) followed by a wet electrostatic precipitator (WESP) or followed by fabric filtration. We also proposed the addition of methods to monitor emissions of Hg using continuous emissions monitoring systems (CEMS). We also proposed a maximum calcination temperature of less than 1,600 degrees Fahrenheit for phosphate rock calciners as a work practice standard to control HF emissions. In addition to proposing a maximum calcination temperature, we proposed to require that emissions from phosphate rock calciners be routed to an absorber to limit emissions of HF from phosphate rock calciners.

Also, we did not propose revised emissions limits for rock dryers because this process is no longer used in the NESHAP regulated source categories for phosphoric acid or phosphate fertilizer (

i.e.,

the rock dryers that were previously used in this industry are no longer in operation).

Finally, we proposed a work practice applicable to facilities when new gypsum dewatering stacks are constructed that would limit the size of active gypsum dewatering stacks and control fugitive HF emissions. When new gypsum dewatering stacks are constructed, we proposed that the ratio of total active gypsum dewatering stacks area (

i.e.,

sum of the footprint acreage of all existing and new active gypsum dewatering stacks combined) to annual phosphoric acid manufacturing capacity must not be greater than 80 acres per 100,000 tons of annual phosphoric acid manufacturing capacity (equivalent P

feed). As we stated in the preamble to the proposed rule, limiting the size of gypsum dewatering stacks would minimize emissions by creating an upper bound on emissions. We also proposed work practice standards to control HF emissions from gypsum dewatering stacks and cooling ponds. We proposed a list of control techniques for facilities to use in development of a site-specific gypsum dewatering stack and cooling pond management plan to control fugitive HF emissions. Unless the active gypsum dewatering stack or cooling pond commenced construction or reconstruction after the date of publication of the final rule, we proposed that each facility use at least one of these control techniques. For each active gypsum dewatering stack or cooling pond that commenced construction or reconstruction after the date of publication of the final rule, we proposed that each facility use two of the listed control techniques.

2. How did our final rule change from what we proposed pursuant to CAA sections 112(d)(2), 112(d)(3), and 112(h) for the Phosphoric Acid Manufacturing source category?

In consideration of comments received during the public comment period for the proposed rulemaking, we are finalizing the proposed BTF Hg limit in NESHAP subpart AA for new phosphate rock calciners. We are not finalizing the proposed BTF Hg limit in NESHAP subpart AA for existing phosphate rock calciners. Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners based on the results of the MACT floor calculations for Hg that are discussed in the preamble of the proposed rule (79 FR 66533). We are also revising our estimated costs in the final rule as discussed in section V.C.3.a.i of this preamble. In addition, we are not finalizing work practice standards for HF from phosphate rock calciners, as proposed. Instead, as discussed in section V.C.3.a.ii of this preamble, we are including a total fluoride emission limit for phosphate rock calciners in NESHAP subpart AA.

Also, in consideration of comments received (see section V.C.3.b.i of this preamble for details), we are not adopting the proposed work practice in NESHAP subpart AA that limits the size of active gypsum dewatering stacks (which would have been applicable to facilities when new gypsum dewatering stacks are constructed). Lastly, we are finalizing in NESHAP subpart AA the work practice standard as proposed that requires owners or operators to prepare and operate in accordance with a gypsum dewatering stack and cooling pond management plan. However, based on analysis of public comments, we are making several changes to the specific control techniques that we proposed as options in the plan for controlling fugitive HF emissions (see section V.C.3.b.ii of this preamble for details on these changes).

3. What key comments did we receive on what we proposed pursuant to CAA sections 112(d)(2), 112(d)(3), and 112(h), and what are our responses?

We received several comments regarding the proposed addition of numeric emission limits for Hg and work practice standards for HF emissions from phosphate rock calciners, and the addition of gypsum dewatering stack and cooling pond work practices for the Phosphoric Acid Manufacturing source category. The following is a summary of the significant comments we received regarding these topics and our responses to them. Other comments received and our responses to those comments can be found in the Comment Summary and Response document available in the docket for this action (EPA-HQ-OAR-2012-0522).

a. MACT and Work Practice Standards for Phosphate Rock Calciners

—

i. Hg Emission Limits for Phosphate Rock Calciners

—

Comment.

Some commenters did not support the EPA's decision to set a BTF limit for Hg from phosphate rock calciners because the emissions do not present unacceptable risks nor do the emission limits yield any benefits. The commenters stated that the EPA fails to show that the proposed BTF Hg limit would produce health or environmental benefits that justify the costs of achieving the standard as they assert is required by CAA section 112(d)(2). Commenters further claimed that the EPA's own risk assessment shows that the BTF limit is not necessary from a risk standpoint because the NESHAP regulation, prior to implementation of the proposed Hg BTF limits, provides an ample margin of safety to protect public health and prevents, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect. The commenters maintained that under CAA section 112(d)(2), the EPA may set an emission limit that is more stringent than the MACT floor only if the Agency determines that the BTF limit is “achievable” based on a consideration of the relative costs and benefits. One commenter cited regulations where the EPA did not set BTF limits for a particular pollutant because the benefits were minimal and the risk would not be appreciably reduced. Commenters supported setting the MACT floor as the Hg limit.

Commenters stated the Hg control devices that the EPA evaluated for the phosphate rock calciner BTF limit were not technically feasible, but did note two potential solutions. Specifically, the commenters stated that use of ACI just prior to the existing WESP or after the WESP with a fabric filter is not technically feasible. The commenters explained the exhaust gas downstream of the WESP is completely saturated and contains entrained water droplets; this would plug the fabric filter, result in performance degradation of the activated carbon, and could lead to plugging of the injection lances and formation of deposits on the ducts. The commenters further explained that it would not be feasible to install heating systems or design engineering control to avoid these problems, due to high costs and the technical complexity. The commenters noted that installing the ACI just prior to the WESP was also not feasible, again due to performance degradation of the activated carbon, but also due to the fact that the existing WESPs could not capture the additional particulate load. The commenters reported that installing the ACI upstream of the existing venturi scrubber is technically feasible, because the gas upstream of the scrubber is not completely saturated. However, the commenters noted several design and operational modifications that would be necessary; these modifications focused on reducing the temperature of the exhaust gas streams to less than 375 degrees Fahrenheit. When installing ACI upstream of the existing venturi scrubber, the ACI vendor used by the commenter recommended the use of treated (

e.g.,

halogenated) carbon at an injection rate of 30 lb/MMacf, in order to meet the BTF Hg limit. The commenter said that the carbon injection rate may need to be as much as 30 lb/MMacf based on site-specific conditions, such as temperature, Hg concentration, moisture, and sulfur content of the phosphate rock calciner exhaust stream. In support of a high injection rate, the commenter also cited a reference from 1994 that observed an increased injection rate was necessary due to temperature of the exhaust gas stream.

Regarding fixed-bed carbon adsorption, commenters stated a traditional fixed-bed carbon adsorption system would not be feasible due to the presence of entrained water droplets that would severely degrade sorbent performance and cause plugging within the bed. The commenters indicated that new Gore Mercury Control System (GMCS) technology might be technically feasible because it uses a fixed sorbent structure with a sorbent polymer composite material to adsorb Hg; the GMCS polymer composite material might protect the sorbent from entrained water droplets and other contaminants in the flue gas. The commenters stated that to use a GMCS fixed-bed carbon adsorption system, several adjustments to the calciners would be necessary, as well as a pilot study to confirm the feasibility. Another commenter also reported they were evaluating the use of the GMCS system, but were only in preliminary stages as their phosphate rock calciner is not yet operating. A commenter also explained that each phosphate rock calciner would need its own controls and a single control system for all phosphate rock calciners

would not be feasible due to safety and operational concerns.

Several commenters argued that ACI and fixed-bed carbon adsorption were not cost effective for controlling Hg emissions from phosphate rock calciners. Two commenters reported a site-specific cost estimate for installing GMCS fixed-bed carbon adsorption downstream of the existing WESP, with capital costs of $32 million and annual costs of $5.8 million; the resulting cost-effectiveness was approximately $40,000 per pound of Hg. The commenters noted the GMCS cost-effectiveness ($40,000/lb Hg) was much higher than the cost-effectiveness the EPA presented in the proposed rule ($8,000/lb Hg) for a traditional fixed-bed carbon adsorption system. Commenters also reported a site-specific cost estimate for installing ACI upstream of the existing venturi scrubbers, with capital costs of $21.1 million and annual costs of $9.1 million; this resulted in a cost-effectiveness of approximately $63,000 per pound of Hg. The commenters noted this ACI cost-effectiveness ($63,000/lb Hg) was much higher than the cost-effectiveness the EPA presented in the proposed rule ($12,100/lb Hg) for ACI. The commenters stated that because their costs for ACI and GMCS fixed-bed carbon adsorption were site-specific, they are much more representative than the costs developed by the EPA for the proposed rule. Finally, one commenter stressed that the site-specific Hg control cost-effectiveness numbers were well above the cost-effectiveness for other rules where the EPA implemented BTF Hg controls. Another commenter noted that preliminary information for installing Hg controls resulted in estimates of $17.5 million in capital costs and $10 million for annual costs.

Response.

Based on these comments, the Agency revised the BTF costs analysis and determined that setting a BTF Hg emission limit for existing phosphate rock calciners would impose a significant economic impact to PotashCorp (PCS) Aurora, the only facility that we are aware of with phosphate rock calciners; therefore, we are not finalizing the BTF Hg limit for existing phosphate rock calciners. The annualized control costs for this company would be approximately 0.9 percent to 5.3 percent of revenues (see “PCS Phosphate Response to USEPA Request for Aurora Plant Financial Information, May 8, 2015,” which is available in the docket for this rulemaking). While these costs are small for the industry, they may be significant for the company and particularly significant for the facility. For the company, there may be a negative impact on profitability. If the company is unable to pass on the increase in the cost of manufacturing the product by raising prices, the facility will either face a potentially significant reduction in profitability or have to close a process or facility. Therefore, the Agency is finalizing a MACT floor Hg limit of 0.14 milligrams (mg) Hg per dry standard cubic meter (dscm) at 3-percent O

for existing phosphate rock calciners and does not anticipate that any facilities will need to install a new control device to meet the existing phosphate rock calciner Hg limit. Also, we are finalizing the proposed BTF Hg limit (

i.e.,

0.014 mg Hg/dscm at 3-percent O

) for new phosphate rock calciners, as facilities should be better able to plan for the costs of controls for new sources. The following discussion provides the details of these decisions.

The results of the residual risk analyses are not part of the BTF MACT determination, and, accordingly, the commenters' concern about not considering risk results is not appropriate. See

Sierra Club

EPA,

353 F.3d 976, 981 (D.C. Cir. 2004). Analyzing the risk would not be a practical requirement, as, typically, MACT standards are set in advance of a residual risk or technology review of the standard. Additionally, the statutory language excerpt cited by the commenter does not accurately reflect the CAA language, which requires the Agency to consider costs associated with the emission reductions, but does not require a demonstration of benefits. The Agency appropriately met its requirements under CAA section 112(c) and (d) by first evaluating a MACT floor level of control for Hg emissions from phosphate rock calciner units and then evaluating cost-effective controls for further reducing emissions BTF level.

The Agency appreciates the commenters' site-specific review of Hg control device technologies and agrees with the commenters' revisions to certain aspects of the technical feasibility of ACI and fixed-bed carbon adsorption. At proposal, we noted that high moisture streams may result in plugging of the fabric filter, as it relates to ACI use. However, we did not consider that entrained water droplets in the high moisture streams would degrade carbon sorbent performance for both ACI and fixed-bed carbon adsorption, or lead to plugging within a fixed-bed. As a result of the additional information provided by the commenters, we agree that it is not technically feasible to use ACI just prior to the existing WESP or after the WESP with a fabric filter to control Hg emissions from phosphate rock calciners, based on current operations. Based on information available at this time, we also agree that a traditional fixed-bed carbon adsorption system is not technically feasible to control Hg emissions from phosphate rock calciners.

The commenters also stated, and the EPA agrees, that use of ACI (specifically halogenated carbon) is technically feasible to control Hg emissions from phosphate rock calciners if ACI is installed upstream of the existing venturi scrubber, where the moisture content is lower. However, we disagree with the commenters' assessment that a carbon injection rate of 30 lb/MMacf would be necessary to achieve a 90 percent reduction in Hg emissions from phosphate rock calciners. The commenters' carbon injection rate estimate is much higher than ACI installations at coal power plants and cement kilns, and while phosphate rock calciners may have unique exhaust gas properties, these properties do not warrant such an extreme carbon feed rate.

To provide additional context on carbon injection rates, we reviewed numerous ACI Hg reduction studies conducted through a National Energy Technology Laboratory (NETL) research program under the Department of Energy (DOE), as well as other studies, which are available in Docket ID No. EPA-HQ-OAR-2012-0522. In our review, we considered the impact on carbon injection rates due to temperature, moisture content, Hg concentration, sulfur content (

i.e.,

sulfur trioxide (SO

) concentration), and carbon sorbent type. Considering the information in these studies, we found it common for carbon injection rates of 5 lb/MMacf or less to result in 90 percent Hg removal, although higher injection rates are warranted in some instances. We also found that at certain facilities, high injection rates do not result in 90 percent Hg removal; however, in several of these cases those data are for standard powdered activated carbon (PAC),

i.e.,

activated carbon that has not been treated with halogens, or exhaust gases containing high SO

concentrations. Specifically, we identified a 2008 document

that combines results from several studies demonstrating the relationship between PAC injection rate (lb/MMacf) and percent Hg removal. While Figure 2 in this 2008 document shows injection rates up to 20 lb/MMacf using standard

PAC (

e.g.,

not halogenated carbon), data for halogenated PAC, in Figure 3 of the 2008 document, shows a maximum of approximately 9 lb/MMacf in order to achieve 90 percent Hg removal from the gas stream. It accords with our general knowledge that standard PAC can have a high control efficiency if halogens are present in the flue gas to oxidize elemental Hg so that it can be adsorbed on the particles injected and subsequently captured in the particle control device. Thus, if halogens are not present in sufficient quantities to oxidize the elemental Hg present, the unoxidized Hg present will continue to be emitted, since it would not be adsorbed on the particles and captured in the particle control device. This situation can be remedied through the use of halogenated PAC, which will oxidize the elemental Hg present so that it can be adsorbed on the particles and later captured. Thus, while we agree with the vendor's recommendation that halogenated PAC is most likely to result in better Hg removal efficiencies for the phosphate rock calciners, we disagree with the relevance of the commenter's cited 1994 document. The ACI vendor used by the commenter recommended treated (

e.g.,

halogenated) PAC as the most likely sorbent type for phosphate rock calciner Hg treatment and the cited 1994 document evaluated standard PAC. In addition, as noted above, there have been more recent studies and significant progress in PAC design since 1994, and as such we do not believe the PAC evaluated in the 1994 document would result in the Hg reductions that today's PAC can achieve. Therefore, we determined that PAC type is a critical factor for Hg removal efficiencies for this source category.

Refer to Figures 2 and 3 of “DOE NETL Hg Field Testing Update_2008” which is available in Docket ID No. EPA-HQ-OAR-2012-0522.

The commenter also noted that modifications focused on reducing the temperature of the exhaust gas streams would be necessary in order for ACI to be effective when installed prior to the existing venturi scrubber. This reduced operating temperature for the phosphate rock calciner exhaust would be in a similar range as coal utility boilers; it is common for coal utility boilers to have exhaust gases at temperatures exceeding 300 degrees Fahrenheit (see the documents “Coal Plant Hg Controls Update_EPA_2005” and “DOE NETL Hg Field Testing Update_2008,” which are available in Docket ID No. EPA-HQ-OAR-2012-0522). Therefore, the cited coal utility boiler studies are appropriate and show that ACI is effective in the new temperature range. This further refutes the commenter's citation of the 1994 document regarding temperature concerns and the necessity of an injection rate as high as 30 lb/MMacf.

Data are available demonstrating that increased SO

levels are detrimental to sorbent performance. We found that higher carbon injection rates are typical for plants with higher SO

concentration in the exhaust stream; for coal utility boilers, this can occur when the fuel is high-sulfur bituminous coal. The concentration of SO

in emissions from coal utility boilers is also increased by certain control devices (

e.g.,

selective catalytic reduction) that do not exist at the phosphate rock calciners. For information on SO

impacts, see the documents “DOE NETL Hg Field Testing Update_2008” and “ADA ACI Overview_2010,” which are available in Docket ID No. EPA-HQ-OAR-2012-0522. Of note, certain PAC sorbents are designed to work in high-sulfur environments (see the document “Calgon Fluepac ST brochure,” available in Docket ID No. EPA-HQ-OAR-2012-0522). Based on this available information, we do not believe SO

concentration in the phosphate rock calciner exhaust gas stream will severely impact ACI performance to a level requiring a carbon injection rate of 30 lb/MMacf.

Additionally, we identified a pilot study that was conducted in 2007 on a cement kiln at the Ash Grove Durkee facility that resulted in more than 90 percent Hg removal efficiencies using carbon injection rates of only 3 lb/MMacf. Of note, the Hg concentration in the cement kiln exhaust gas was more than 10 times higher than the Hg concentration in the phosphate rock calciner exhaust gas. This study is presented in the document “Carbon Injection Pilot Test Durkee OR_2007,” available in Docket ID No. EPA-HQ-OAR-2012-0522.

While we acknowledge that phosphate rock calciner exhaust streams may have certain unique characteristics, we do not agree with a PAC injection rate of 30 lb/MMacf based on the data available, as discussed above. We believe a halogenated PAC injection rate of 10 lb/MMacf or lower (for ACI installed upstream of the existing venturi scrubbers) is sufficient for meeting the BTF Hg limit for phosphate rock calciners.

Commenters also noted, and the EPA agrees, that GMCS technology would be technically feasible to control Hg emissions from phosphate rock calciners. We also agree that individual GMCS fixed-bed carbon adsorption systems would be necessary for each of the six phosphate rock calciners. The commenters noted that two full-scale operations are actively using GMCS fixed-bed carbon adsorption systems to control Hg. Furthermore, based on additional discussion with industry (see “EPA Meeting Minutes for PCS Aurora Hg Discussion, March 12, 2015,” which is available in Docket ID No. EPA-HQ-OAR-2012-0522), we now know that three full-scale operations use GMCS to control Hg, with two additional operations to come online soon. These full-scale operations are located at coal power plants, not phosphoric acid manufacturing processes. Based on the vendor-provided information and the fact that GMCS technology is currently used at coal power plants to comply with Hg emission limits, we believe GMCS technology is technically feasible. In regards to the need for a pilot study, facilities would have time to design, construct, and test the system.

Although we have determined that two control technologies are technically feasible to control Hg emissions from phosphate rock calciners, we evaluated costs for the BTF Hg limit based on the estimated lower cost technology, installation of halogenated ACI upstream of the existing venturi scrubber. We used the ACI cost data provided by the commenter to estimate the costs for complying with the BTF Hg limit. However, instead of basing the annual carbon cost on an injection rate of 30 lb/MMacf, we applied injection rates of 5 and 10 lb/MMacf of halogenated carbon for reasons stated above. As provided by the commenter, the capital cost for installing six ACI units on each existing phosphate rock calciner is approximately $21,150,000. The annual cost ranges from approximately $4,320,000 (when a carbon injection rate of 5 lb/MMacf is used) to approximately $5,280,000 (when a carbon injection rate of 10 lb/MMacf is used); this results in Hg reductions of 145 pounds of Hg per year. As previously stated, these annual costs imposed a significant economic burden and we are not finalizing the BTF Hg limit for existing phosphate rock calciners.

Existing phosphate rock calciners must comply with a Hg emission limit that equals the MACT floor at 0.14 mg Hg/dscm at 3-percent O

. The MACT floor was calculated using the upper prediction limit (UPL) methodology, which was discussed in the preamble of the proposed rule (see 79 FR 66533) and is also discussed in the memorandums “Maximum Achievable Control Technology (MACT) Floor Analysis for Phosphate Rock Calciners at Phosphoric Acid Manufacturing Plants—Final Rule” and “Use of the Upper Prediction Limit for Calculating MACT Floors,” which are available in the docket for

this action. Based on the available data, the existing phosphate rock calciners would be able to comply with this limit without installing additional Hg controls.

We evaluated application of the BTF Hg limit for new phosphate rock calciners. Facilities would have time to plan for and consider the costs when determining whether to construct a new phosphate rock calciner. Additionally, sources may choose to only add one new calciner unit at a time, which would have considerably less impact than the costs associated with retrofitting all units at an existing site. Therefore, we evaluated the cost-effectiveness for installing Hg controls on a new phosphate rock calciner. Using the same cost data provided by the commenter, installing a single ACI would have capital costs of approximately $3,500,000. The annual cost ranges from approximately $720,000 (when a carbon injection rate of 5 lb/MMacf is used) to approximately $880,000 (when a carbon injection rate of 10 lb/MMacf is used). This results in Hg reductions of 24 pounds of Hg per year for a single calciner unit, assuming the new phosphate rock calciner has similar emissions as the existing phosphate rock calciners at PCS Aurora. The resulting cost-effectiveness is estimated to be $29,800 to $36,400 per pound of Hg reduced, which we consider cost effective for new sources. This facility-level cost-effectiveness for Hg for new sources is comparable to values the EPA found to be cost effective for removal of Hg at the facility-level in other air toxics rules.

Consequently, new phosphate-rock calciners must comply with the BTF Hg emission limit of 0.014 mg Hg/dscm at 3-percent O

National Emission Standards for Hazardous Air Pollutants: Mercury Emissions from Mercury Cell Chlor-Alkali Plants (76 FR 13852); National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units (76 FR 24976 and 77 FR 9304); and National Emission Standards for Hazardous Air Pollutants: Gold Mine Ore Processing and Production Area Source Category (75 FR 22470).

ii. HF Work Practices for Phosphate Rock Calciners

—

Comment.

We received comment regarding HF work practices for phosphate rock calciners. One commenter supported the HF work practices and stated they are consistent with their current phosphate rock calciner operations. Another commenter does not support the implementation of HF work practices for phosphate rock calciners. This commenter, which is considering installation of a calciner in the future, noted that preliminary results indicate a calcination temperature of at least 2,000 degrees Fahrenheit is necessary for their phosphate rock calciner. This commenter also explained they are evaluating a flash calciner, which operates with a much shorter retention time than the fluidized bed calciners currently in operation. The commenter argued that wet scrubbers should not be a requirement of the HF work practice because their phosphate rock calciner will be located in a remote area where treatment and disposal options for scrubber liquors may not be feasible. The commenter recommended the EPA allow for other control technologies with equivalent efficiencies.

Another commenter does not support the use of work practices for HF, and declared the EPA should set numeric emission limits for HF from phosphate rock calciners. The commenter maintained that the EPA failed to satisfy the CAA section 112(h) test it must meet to promulgate work practice standards “in lieu of” numerical emission standards. The commenter stated that not using the available emissions data to set a floor limit is unlawful and arbitrary, even if the data are below the detection limit.

Response.

We are not adopting the proposed HF work practice standard for phosphate rock calciners in NESHAP subpart AA. Instead, we are adopting an emission limit for total fluoride from phosphate rock calciners. In proposing the HF work practices, we concluded that it was not feasible to prescribe or enforce an emission limit for HF due to limitations in the available EPA Method 320 HF test results (

i.e.,

most of the emissions data were below the method detection limit). We now have concluded, based on analysis of public comments, that it is not feasible to accurately measure HF emissions from phosphoric acid manufacturing processes using EPA Method 320 (see section V.F.3.c of this preamble for further details). However, data are available to establish an emission limit for total fluoride from phosphate rock calciners. In 2015 only one facility operates phosphate rock calciners, which are controlled by a venturi-type scrubber. In response to the April 2010 CAA section 114 request, the facility provided EPA Method 13B total fluoride emission testing results for one of their six identical phosphate rock calciners. We conclude that the total fluoride emission rate achieved by this phosphate rock calciner characterizes the emissions from all six calciners and thus this emission rate was used to determine the MACT floor for total F emissions. Therefore, for phosphate rock calciners, we are setting total F emission limits. We are also setting a work practice standard for periods of startup and shutdown in lieu of this numeric emission limit (see section V.E.3 of this preamble for further details). The use of total fluoride as a surrogate for the HAP HF is consistent with WPPA, SPA, and DAP/MAP process lines, which also have total fluoride emission limits in lieu of HF emission limits.

For the Phosphoric Acid Manufacturing source category, we have a limited dataset for the pollutant total fluoride from phosphate rock calciners. Therefore, we evaluated this specific dataset to determine whether it is appropriate to make any modifications to the UPL approach used to calculate the MACT floor. For the phosphate rock calciner dataset, we performed the following steps: We selected the data distribution that best represents the dataset; ensured that the correct equation for the distribution was then applied to the data; and compared individual components of the limited dataset to determine if the total fluoride standard based on the limited dataset reasonably represents the performance of the units included in the dataset. The results of this analysis are presented below.

The MACT floor dataset for total fluoride from new and existing phosphate rock calciners includes 3 test runs from 1 phosphate rock calciner. After determining that the dataset is best represented by a normal distribution and ensuring that we used the correct equation for the distribution, we considered the selection of a lower confidence level for determining the emission limit by evaluating whether the calculated limit reasonably represents the performance of the unit upon which it is based. In this case, the calculated emission limit is about twice the short-term average emissions from the best performing source, indicating that the emission limit is not unreasonable compared to the actual performance of the unit upon which the limit is based and is within the range that we see when we evaluate larger datasets using our MACT floor calculation procedures. Therefore, we determined that no changes to our standard UPL floor calculation procedure are warranted for this pollutant and subcategory. We are applying the same method of calculating a total fluoride limit as we did for the Hg MACT floor calculation, for which we gave notice in the preamble to the proposed rule. Additional details and background on the MACT floor calculation are provided in the memorandums, “Maximum Achievable

Control Technology (MACT) Floor Analysis for Phosphate Rock Calciners at Phosphoric Acid Manufacturing Plants—Final Rule,” “Approach for Applying the Upper Prediction Limit to Limited Datasets,” and “Use of the Upper Prediction Limit for Calculating MACT Floors,” which are available in the docket for this action. We also evaluated BTF options for total F, but were unable to identify any cost-effective BTF technologies. Table 3 of this preamble provides the results of the new and existing phosphate rock calciner MACT floor calculations (considering variability) for total F.

Table 3—Results of the New and Existing MACT Floor Calculations for Total Fluoride From Phosphate Rock Calciners at Phosphoric Acid Manufacturing Facilities

Pollutant

Results

Units

Total fluoride (for new and existing sources)

9.0E-04

lb/ton of rock feed.

b. Gypsum Dewatering Stack and Cooling Pond Work Practices

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i. Ratio of Gypsum Dewatering Stack Area to Phosphoric Acid Manufacturing Capacity

—

Comment.

Several commenters requested that the EPA either reconsider, withdraw, or eliminate the proposed gypsum dewatering stack area limitation of 80 acres per 100,000 tpy capacity (in equivalent P

feed). Commenters claimed the use of flawed data and assumptions in the EPA's analysis in the following areas: (1) Ambiguous definitions of a “gypsum dewatering stack,” and “new” and “existing” stacks; (2) inaccurate or outdated data on acreage of existing stacks and production capacity, stack closures, and plans for new stacks; (3) flawed or missing rationale and correlation between the gypsum dewatering stack area and phosphoric acid manufacturing capacity; (4) no technical or legal basis for the selection of the 80-acre cutoff; (5) no consideration given to site-specific variables that influence the acreage of gypsum dewatering stacks; and (6) failure to consider impacts from closing an existing stack prior to commissioning a new stack.

These commenters claimed the term “gypsum dewatering stack” is so broadly and ambiguously defined they are unable to determine the scope and impact of the proposed area limitation of 80 acres per 100,000 tpy capacity, or how the proposed limitation would be applied to facilities. They claimed the EPA's definition includes a wide array of features that have never before been considered part of the gypsum dewatering stack (

e.g.,

pumps, piping, all collection and conveyance systems associated with gypsum to the stack and process wastewater return to the plant). Commenters argued that the EPA underestimated stack acreage used in the analysis and that the estimates should be much larger when the “total system” acreage is used. These commenters stated that using the “total system” acreage in the analysis demonstrates that the EPA significantly underestimated the number of acres at each facility that would need to be closed. One of these commenters asked whether a vertical expansion of an existing stack would be considered a “new” facility, and how the proposed work practice might be evaluated for compliance when surfaces of a “closed” facility might be overlapped by an immediately-adjacent “new” facility.

Additionally, commenters argued that the EPA's technical rationale for limiting stack area was based on an arbitrary correlation with production capacity. One of these commenters said there is no relationship between gypsum dewatering stack area and phosphoric acid manufacturing capacity, and that outliers were removed from the analysis further confirming no quantitative relationship between stack area and facility capacity. This commenter also asserted that limiting the size of the gypsum dewatering stacks is not proven to limit HF emissions.

Furthermore, two commenters claimed the 80-acre limit does not consider an evaluation of water balance and process water cooling needs for individual facilities. These commenters pointed out that a flat area does not require as large of a footprint for its gypsum dewatering stacks as compared to an area with large topographic relief. One of these commenters provided examples of two gypsum dewatering stacks located in mountainous areas that require larger footprints to construct ponds due to longer runs of pipe, roads, and dike.

Finally, one commenter claimed that an updated acreage-based analysis would need to account for the transition period between a stack becoming “inactive” and the point in time of “closure” so as not to exceed the acreage limit while constructing a new stack. Another commenter stated that the startup of a gypsum dewatering stack is a lengthy process that may take more than a year, and that the “ratio” requirement inaccurately assumes simultaneous closure of an old stack with the opening (

i.e.,

new construction) of a new stack. Another commenter also contended that construction and closure take years to complete and occur simultaneously, and that closing a gypsum dewatering stack before beginning construction on a new stack would require an entire companion production facility to be idled for an extended period and impose “enormous direct and lost opportunity costs . . . such costs and plant idling are not justified.”

Response.

We agree with commenters that the proposed definition of “gypsum dewatering stack” is too broad. As we stated in the preamble to the proposed rule, we intended the proposed ratio limit to apply to only the “footprint acreage” of the gypsum dewatering stacks, which was deliberately meant to exclude the areas where many supplementary processes (such as pumps, piping, ditches, drainage conveyances, water control structures, collection pools, cooling ponds, surge ponds, auxiliary holding ponds, and any other collection or conveyance system) are located. Therefore, we did not underestimate stack acreage used in the gypsum dewatering stack area limitation analysis, nor did we underestimate the number of acres at each facility that would need to be closed. However, in an effort to clarify the specific emission source that we are regulating in the final rule (NESHAP subpart AA), we have included a new term, “gypsum dewatering stack system,” and revised the definition of “gypsum dewatering stack” in the final rule. We are finalizing “gypsum dewatering stack system” to mean “the gypsum dewatering stack, together with all pumps, piping, ditches, drainage conveyances, water control structures, collection pools, cooling ponds, surge ponds, auxiliary holding ponds, regional holding ponds and any other collection or conveyance system associated with the transport of gypsum from the plant to the gypsum dewatering stack, its management at the

gypsum dewatering stack, and the process wastewater return to the phosphoric acid production or other process.” We are finalizing “gypsum dewatering stack” to mean “any defined geographic area associated with a phosphoric acid manufacturing plant in which gypsum is disposed of or stored, other than within a fully enclosed building, container, or tank.” This revised definition of “gypsum dewatering stack” is based on Florida Administrative Rule 62-273.200 which regulates phosphogypsum management, and clearly includes any gypsum disposal pile, as well as the associated gypsum pond (which is also known as a settling pond, used to deposit the gypsum slurry, and is often located in the middle of the gypsum disposal pile), but does not include separate cooling ponds (for which we have retained the proposed definition of “cooling pond” in the NESHAP subpart AA final rule).

Nevertheless, in light of other concerns raised by commenters, we are not adopting the proposed work practice that limits the size of active gypsum dewatering stacks, which would have been applicable to facilities when new gypsum dewatering stacks are constructed.

As we stated in the preamble to the proposed rule, we did not detect a correlation between gypsum stack dewatering area and phosphoric acid manufacturing capacity; however, we proposed the size limit because we believe that reducing the gypsum dewatering stack area is directly related to reducing HF emissions. We also believed that phosphoric acid manufacturing capacity was related to the size of gypsum dewatering stacks and that it was operationally appropriate to allow large facilities to build larger gypsum dewatering stacks, while limiting smaller facilities to building a proportionally smaller gypsum dewatering stack. However, we have now concluded, based on analysis of public comments and other supplemental information provided, that it is not feasible to require facilities to close gypsum dewatering stacks based on a ratio of total active gypsum dewatering stack area (

i.e.,

sum of the footprint acreage of all active gypsum dewatering stacks combined) to annual phosphoric acid manufacturing capacity. As commenters stated, the gypsum dewatering stack acreage does not relate to production capacity and, importantly, gypsum dewatering stack development must be considered in light of the operations of the entire facility. Factors that affect the size and development of gypsum dewatering stacks include: (1) The availability and topography of land near the facility; (2) facilities generate a substantial amount of gypsum waste in the phosphoric acid manufacturing process; (3) managing the gypsum waste that is generated is an important operating principle for all facilities (regardless of phosphoric acid production capacity); and (4) limiting the gypsum dewatering stack acreage or changing the way facilities build gypsum dewatering stacks could have a detrimental impact on a facility's operations. Additionally, we agree with commenters that closure of a gypsum dewatering stack does not happen immediately, but rather requires a transitional period that can take years to complete. During this transitional period, a new stack is begun, but it may be years before it is fully operational and can receive all gypsum and slurry from the facility. This transitional period would make it difficult, if not impossible, for a facility to comply with the proposed work practice that limits the size of active gypsum dewatering stacks because the proposed size limit assumed immediate closure. Since closure does not happen immediately, and there is no correlation between dewatering stack acreage and phosphoric acid production, we are not adopting the proposed work practice that limits the size of active gypsum dewatering stacks.

We are removing the definition of “closed gypsum dewatering stack,” and revising the definition of “active gypsum dewatering stack,” as well as the definitions for when a gypsum dewatering stack is considered “new” or “existing” (see sections V.C.3.b.ii and V.C.3.b.iii of this preamble for further details).

ii. Necessity or Justification of Work Practice Standards for Fugitive HF Emissions

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Comment.

Numerous commenters claimed that there is insufficient technical analysis as to the feasibility and effectiveness of the control techniques that were proposed as options (as part of a work practice standard in the form of a management plan) for controlling fugitive HF emissions from gypsum dewatering stacks and cooling ponds. One of these commenters supported the EPA's claim that emissions from gypsum dewatering stacks and cooling ponds would inherently constitute fugitive emissions, and that conceptually, a work practice standard is a reasonable approach to emissions control; however, they challenged the technical basis for the specific control techniques listed in the proposed management plan. Commenters contended that the proposed control techniques have not been demonstrated to have an effect on fugitive HF emissions, and stated the EPA did not quantify the expected reductions in HF emissions resulting from the proposed work practice standard for gypsum dewatering stacks and cooling ponds. A commenter noted that some of the control techniques were derived from their facility's title V permit and that the EPA needed to recognize that (a) it is not clear (with a couple of exceptions) that these control techniques provide any significant emission reductions; (b) recent information may not support these control techniques providing emission reductions; and (c) there is considerable uncertainty in the emissions associated with cooling ponds and gypsum dewatering stacks. Another commenter argued that the EPA must justify the control techniques and show that they are not only technically effective, but also cost-effective and achievable within the industry. Commenters asserted that only two sources of information were used by the EPA in its determination of the control techniques that were proposed as options for controlling fugitive HF emissions in the proposed gypsum dewatering stack and cooling pond management plan. Commenters also noted that there is a large amount of uncertainty related to which specific control techniques are feasible and effective in reducing fugitive HF emissions. The following paragraphs provide a summary of the comments that the Agency received on each specific control technique.

Three commenters opposed the use of submerged discharge pipes and siphon breaks below the surface of the cooling pond as a fugitive HF emissions control technique. They claimed that submerging cooling pond discharge lines for above-grade ponds would create a significant risk for a siphon effect to occur when a pumping system is shutdown, causing backpressure on the pump seals back down the line, and, thus, defeating the purpose of the siphon break. One of these commenters added that submerging siphon breaks will impede the ability of these devices to prevent backflow because submersion may interfere with the atmospheric connection needed to make siphon breaks operate properly.

One commenter stated that although they use a rim ditch (cell) building technique, it is not an appropriate work practice for reducing HF emissions, and mentioned that the EPA does not provide data or an explanation of the linkage between minimizing the gypsum dewatering stack surface area and reducing emissions. This commenter suggested that the EPA define the technique as “a gypsum stack building

technique where gypsum slurry is deposited along the stack perimeter with flow directed along a ditch before the liquid flow is conveyed to the settling compartments.” Another commenter stated that minimizing the gypsum pond surface areas is not feasible in Florida, North Carolina, and Louisiana because gypsum pond surface areas are optimized to provide annual evaporative water losses necessary to maintain zero water discharge.

Several commenters also objected to the wetting of the active gypsum dewatering stack as a fugitive HF emissions control technique because the technique may be infeasible and counter-productive due to water balance issues at nearly every affected facility. One commenter argued that applying fresh water is not feasible (

i.e.,

water trucks are not feasible or safe; irrigation in the West is not feasible; pipes are at risk of freezing) and another commenter stated that using recycled water may actually increase fugitive emissions because HF resides primarily in residual and make-up waters used to transport the gypsum slurry to the gypsum dewatering stack. One commenter contended that determining hot or dry periods is too subjective; therefore, it would be difficult to know when the control technique would apply. Another commenter illustrated the uncertainty of wetting of the active gypsum dewatering stack as a fugitive HF emissions control technique by identifying two studies with contradicting conclusions (one concluded that most HF is emitted from aqueous surfaces and trends with solar radiation, and the other study concluded that drying gypsum is a major source of ambient fluoride emissions from gypsum storage areas).

One commenter challenged the EPA's lack of evidence on the effectiveness of applying slaked lime to gypsum dewatering stacks as a fugitive HF emissions control technique, and claimed that it would not be feasible, referring to rain as threat to eliminate the potential for effectiveness. On the contrary, another commenter described how they apply a lime solution on top of reachable drying gypsum stack areas, and that the reaction of fluoride with slaked lime does result in the “tie-up” of volatile F, although they are not aware of any studies that have measured or quantified reductions.

In addition, commenters also claimed that enormous costs would be associated with the fugitive HF emissions control technique requiring facilities to apply soil caps and vegetation to all side slopes of the active gypsum dewatering stack up to 50 feet below the stack top. Some of these commenters mentioned that there are state rules that require soil caps and side vegetation on side slopes for erosion/water impact control, but not for the purpose of fugitive HF emissions control.

Furthermore, commenters requested that the closure of a gypsum dewatering stack not be considered a fugitive HF emissions control technique. One commenter contended that the EPA should allow the final cover on a closed stack to consist of a synthetic liner, as this would achieve the same purpose as a vegetative liner and may be more appropriate in some instances. Another commenter explained that some states and the EPA have closure requirements under Resource Conservation and Recovery Act (RCRA), including, for example, requirements for long term care practices (beyond 20-50 years); shaping and configuration of gypsum dewatering stacks; site security. They suggested that due to these detailed requirements, it would be best to defer to stack closure requirements within other regulations and not have NESHAP requirements that involve or require stack closure.

Finally, commenters requested that if the EPA proceeds with a final rule that includes work practices for reducing fugitive HF emissions from gypsum dewatering stacks or cooling ponds, the work practices should include a flexibility mechanism for facilities to use additional practices not codified during this rulemaking. One commenter asserted that work practice standards that might commonly be practicable for other industries are not universally practicable (or legally permissible) throughout the phosphoric acid and phosphate fertilizer industries, and some practices might be appropriate for some facilities, but not others (depending on location, climate, etc.).

Response.

We are adopting the proposed work practice standard that requires owners or operators to prepare, and operate in accordance with a gypsum dewatering stack and cooling pond management plan; however, based on analysis of public comments, we are making some changes to the specific control measures that we proposed as options in the plan for controlling fugitive HF emissions. In the final rule, the Agency is using the terminology “control measures” in lieu of the proposed terminology “control techniques” because it more accurately describes the list of options in the rule and avoids confusion with other CAA programs. We are finalizing standards that will reduce HAP emissions from gypsum dewatering stacks and cooling ponds because, as explained in the preamble to the proposed rule, the 1999 Phosphoric Acid Manufacturing NESHAP (

i.e.,

NESHAP subpart AA) did not regulate fugitive HF emissions from gypsum dewatering stacks or cooling ponds. As explained in the preamble to the proposed rule, we are adopting a work practice standard instead of numeric emission limits because it is “not feasible to prescribe or enforce an emission standard” for these emissions because they “cannot be emitted through a conveyance designed and constructed to emit or capture such pollutant” (see CAA section 112(h)(2)(A)) as the several hundred acres average size of these emission sources makes conveyance impractical. The size of these emission sources also makes it difficult to quantify the emission reductions that any control measure employed will achieve. However, in the paragraphs below, we explain how each control measure is feasible and effective in reducing fugitive HF emissions. We also provide details on the changes we have made to the gypsum dewatering stack and cooling pond management plan since proposal. Even after these changes, the measures are consistent with CAA section 112(d) controls and reflect a level of performance analogous to a MACT floor.

We noted in the preamble to the proposed rule that we believe that it is most effective for sources to determine the best practices that are to be incorporated into their site-specific gypsum dewatering stack and cooling pond management plan. We also stated in the preamble to the proposed rule that sources would be required to incorporate control measures from the list of options being proposed, and we solicited comment on the proposed site-specific gypsum dewatering stack and cooling pond management plan. In addition, we made considerable effort

before and after proposal in identifying a list of control measure options that encompass enough variety that at least one control measure option is feasible for at least one of each facility's existing gypsum dewatering stacks and/or cooling ponds. In fact, we are not aware

of any facility that does not use a rim ditch (cell) building technique. Therefore, we disagree with commenters that the options we have listed for the gypsum dewatering stack and cooling pond management plan are not technically feasible.

See the following documents which are all available in Docket ID No. EPA-HQ-OAR-2012-0522): “USEPA Meeting with The Fertilizer Institute, July 24, 2013”; “TFI meeting with USEPA to discuss RTR for Phosphoric Acid and Phosphate Fertilizer NESHAPs, September 11, 2014”; “EPA Meeting Minutes for TFI Discussion March 12, 2015”; “Summary of Potential Costs for Implementing Phosphate NESHAPs/Recommendations for Phosphogypsum Stack Work Practices, May 5, 2015”; “Notes from Meeting with Florida DEP Regarding Gypsum Dewatering Stack and Cooling Pond Management Plan, March 4, 2015”; and “Site Visits to Mosaic Plant City and Mosaic New Wales, March 4, 2015.”

Additionally, personnel from the Florida Department of Environmental Protection (DEP) had concerns regarding how the plan would be implemented, as well as how a facility would show compliance with the control measure it chooses (see “Notes from Meeting with Florida DEP Regarding Gypsum Dewatering Stack and Cooling Pond Management Plan, March 4, 2015,” which is available in Docket ID No. EPA-HQ-OAR-2012-0522). Therefore, in an effort to improve compliance demonstration with a facility's site-specific gypsum dewatering stack and cooling pond management plan, we are including a condition in the final NESHAP subpart AA rule that requires facilities to submit their plan for approval to the Administrator. Facilities will be required to provide details on how they plan to implement and show compliance with the control measure(s) that they choose. The Administrator will approve or disapprove the facility's site-specific gypsum dewatering stack and cooling pond management plan within 90 days after it is received. There may be a benefit to facilities and permitting authorities for the gypsum dewatering stack and cooling pond management plan and the title V major modification application to be submitted and reviewed at the same time. To change any of the information submitted in the plan, the facility must submit a revised plan 60 days before the change is to be implemented in order to allow time for review and approval by the Administrator before the change is implemented.

We are not including an option in the NESHAP subpart AA final rule, as commenters requested, that would provide a flexibility mechanism for facilities to use additional practices not codified during this rulemaking. This type of flexibility does not provide regulatory certainty that is needed for both industry and the EPA.

Although some commenters opposed using a submerged discharge pipe (with necessary siphon breaks to a level below the surface of the pond) as a fugitive HF emissions control measure, we believe submerging a discharge pipe can be appropriate and effective for reducing emissions from process water discharges into a cooling pond, although some facilities may not choose this option. Moreover, we agree with commenters that submerging siphon breaks could impede the ability of these devices to prevent backflow; therefore, we are removing this requirement from the final rule. On a recent site visit (see “Site Visits to Mosaic Plant City and Mosaic New Wales, March 4, 2015,” which is available in Docket ID No. EPA-HQ-OAR-2012-0522), we noted strong vapor odors coming from splash operations occurring at a non-submerged pipe that was discharging process water into a cooling pond. According to AP-42, Chapter 5.2—Transportation and Marketing of Petroleum Liquids (01/95), significant turbulence and vapor/liquid contact that occur during splash discharge operations will result in higher levels of vapor generation and emissions loss compared to using a submerged discharge operation. Liquid turbulence is controlled significantly during submerged discharge operations, resulting in much lower vapor generation than encountered during splash discharge operations. We believe this demonstrates that submerging the pipe is an effective technique for mitigating HF emissions, and we are therefore retaining this option for cooling ponds.

However, we are removing the option of submerging a discharge pipe that is associated with the gypsum pond because it is not a feasible option due to high solids volume in the slurry. (A gypsum pond, also called a settling pond, often is located in the middle of a gypsum disposal pile and receives waste gypsum slurry.) Based on information received from industry after the public comment period ended for the proposal (see Docket ID No. EPA-HQ-OAR-2012-0522-0048), it is much more likely for this particular pipe to become clogged, creating backpressure on pump seals. Submerging the discharge pipe under water in the gypsum pond creates a potential restriction against the discharging slurry that could get worse as solids build up around and against the end of the pipe. The discharge pipe for the gypsum pond is also routinely moved, which complicates submersing it.

As we stated earlier in our response, we are not aware of any facility that uses a gypsum dewatering stack building technique that is different from rim ditch (cell) building. With regard to commenters' assertions that the EPA did not provide data or explain the link between minimizing the gypsum dewatering stack surface area and reducing fugitive HF emissions, we believe that using the rim ditch technique over the lifespan of a gypsum dewatering stack will reduce the surface area of the gypsum pond and thereby reduce fugitive HF emissions. Fugitive HF emissions are calculated using an emission factor that is directly related to the total acreage from the gypsum dewatering stack, which includes the pond surface area (tons HF per acre per year); therefore, minimizing the pond surface area would minimize HF emissions. The rim ditch (cell) building technique is mainly used for gypsum dewatering stack stability since inner and outer dikes are used to create a rim ditch that provides better protection against overflow of the gypsum pond. However, as rim ditches are filled with slurry, the gypsum pond area will gradually decrease within each cell, thereby shrinking the amount of surface area of the pond that is exposed to the atmosphere (reducing the amount of fugitive HF emissions). An alternative to the rim ditch technique is to simply discharge gypsum slurry into the gypsum pond. With this technique, there is no inner dike to control slurry flow and the pond surface area would not be reduced as quickly or consistently. This increased surface area would allow greater potential for fugitive HF emissions due to the larger amount of surface water exposed to the atmosphere. We are revising this control measure option in the NESHAP subpart AA final rule to clarify that owners or operators must minimize the surface area of the gypsum pond associated with the active gypsum dewatering stack (and not the surface area of the active gypsum dewatering stack as we had proposed) by using a rim ditch (cell) building technique or other building technique. This clarification also addresses industry's suggestion to reword the control measure in response to a meeting that occurred after the public comment period closed (see “EPA Meeting Minutes for TFI Discussion March 12, 2015,” and “Summary of Potential Costs for Implementing Phosphate NESHAPs/Recommendations for Phosphogypsum Stack Work Practices, May 5, 2015,” which are both available in Docket ID No. EPA-HQ-OAR-2012-0522). Moreover, in this same correspondence that occurred after the public comment period closed, industry provided a suggestion for the definition of “rim ditch.” We agree with industry's suggested definition; however, we believe the definition more appropriately covers the meaning of “rim ditch (cell) building technique” and not just “rim ditch.” We are including this definition in the final rule for “rim ditch (cell) building technique” in an effort to clarify what we mean by this control measure. The

final rule defines “rim ditch (cell) building technique” as a gypsum dewatering stack construction technique that utilizes inner and outer dikes to direct gypsum slurry flow around the perimeter of the stack before directing the flow and allowing settling of finer materials into the settling compartment. For the purpose of this definition, the rim ditch (cell) building technique includes the compartment startup phase when gypsum is deposited directly into the settling compartment in preparation for ditch construction, as well as the step-in or terminal phases when most solids must be directed to the settling compartment prior to stack closure. Decant return ditches are not rim ditches.

Based on commenters' objection to wetting active gypsum dewatering stacks as a fugitive HF emissions control measure, and additional discussion with industry (see “EPA Meeting Minutes for Simplot Discussion April 1, 2015,” which is available in Docket ID No. EPA-HQ-OAR-2012-0522), we determined that the proposed rule was not clear on how this control measure would be used. This control measure is not applied to the side slopes of the gypsum dewatering stacks, and instead is used on certain gypsum areas within cells of a gypsum dewatering stack. According to one facility located in arid climate (see “EPA Meeting Minutes for Simplot Discussion April 1, 2015,” which is available in Docket ID No. EPA-HQ-OAR-2012-0522), these areas may be more susceptible to drying out in warmer months due to higher surface temperatures of the gypsum dewatering stack; therefore, a system of weirs can be used to help direct gypsum pond water (not fresh water) to these areas to keep them wet. We agree with the commenter who pointed out that that applying water to a gypsum stack may actually increase fugitive emissions because HF resides primarily in the water used to transport the gypsum slurry to the gypsum dewatering stack. We realize that this option might increase the surface area of the gypsum pond water which conflicts with our understanding that minimizing surface area of the gypsum pond will minimize HF emissions. Therefore, we are not adopting this proposed control measure in the NESHAP subpart AA final rule.

In response to a commenter's assertion that there is lack of evidence of the effectiveness of applying slaked lime to gypsum dewatering stacks as a fugitive HF emissions control measure, we received information after the public comment period ended (see Docket ID No. EPA-HQ-OAR-2012-0522-0048) that at least one facility uses this technique to help meet its state ambient air standard for F. This commenter stated that, based on data from their site-specific ambient air monitoring, they apply a lime solution to their gypsum dewatering stack areas during periods where they are close to violating their 30-day state ambient air standard for F, measured as HF, in order to stay below the standard. Slaked lime can precipitate fluorides from gypsum dewatering stacks and cooling ponds, thus reducing the availability of fluorides in solution that could then be released into the air during evaporation. This is an example of the type of detail that the Administrator may require be included in the facility's site-specific plan (in addition to how compliance would be demonstrated) before it could be approved. We have clarified in the final rule that if this control measure is chosen, then the plan must include the method used to determine the specific locations slaked lime is applied. The plan must also include the methods used to determine the quantity of, and when to apply, slaked lime (

e.g.,

slaked lime may be applied to achieve a state ambient air standard for F, measured as HF).

With respect to the measure involving application of soil caps and vegetation to side slopes of a gypsum dewatering stack, on recent site, visits personnel from Mosaic and the Florida DEP had concerns that this control measure was too specific in that it could be difficult for facilities to demonstrate compliance with the “50 feet below the stack top” requirement as well as the requirement to apply soil caps and vegetation to all side slopes (see “Site Visits to Mosaic Plant City and Mosaic New Wales, March 4, 2015,” and “Notes from Meeting with Florida DEP Regarding Gypsum Dewatering Stack and Cooling Pond Management Plan, March 4, 2015,” which are available in Docket ID No. EPA-HQ-OAR-2012-0522). We recognize that applying soil caps and vegetation to side slopes of a gypsum dewatering stack is an ongoing process that continuously changes over time based on facility-specific operations. Therefore, we have revised this control measure option in the NESHAP subpart AA final rule to acknowledge that this technique will only be applied to portions of the side slopes that are no longer active on a gypsum dewatering stack instead of all side slopes up to 50 feet below the top of the gypsum dewatering stack. We also have revised this option to allow the use of a synthetic cover in lieu of soil caps and vegetation. Furthermore, we expect that if a facility chose to use this specific control measure in their plan, the Administrator may require details on schedule, and how the portion of side slopes that received soil caps and vegetation, or a synthetic cover, is determined (in addition to how compliance would be demonstrated), before the plan could be approved. Therefore, we have clarified in the final rule that the plan must include the method used to determine the specific locations of soil caps and vegetation, or synthetic cover, and specify the acreage and locations where soil caps and vegetation, or synthetic cover, is applied. The plan must also include a schedule describing when soil caps and vegetation, or synthetic cover, is to be applied.

Additionally, we believe that this control measure creates a barrier on the surface of the gypsum dewatering stack side slopes that reduces HF emissions; therefore, we disagree with commenters' assertion that applying soil caps and vegetation may not be an effective option for fugitive HF emissions control. The Florida DEP has used this control measure as part of its overall management of fluorides from gypsum dewatering stacks; and Wyoming has approved this control measure in a facility's title V permit as an optional method for reducing fugitive fluoride emissions. We also disagree with a request

to reword this control measure to require a gypsum dewatering stack construction and operation plan because the commenter did not provide any justification on how this activity reduces fugitive HF emissions from gypsum dewatering stacks.

See “EPA Meeting Minutes for TFI Discussion March 12, 2015,” and “Summary of Potential Costs for Implementing Phosphate NESHAPs/Recommendations for Phosphogypsum Stack Work Practices, May 5, 2015,” which are both available in Docket ID No. EPA-HQ-OAR-2012-0522.

We disagree with commenters' requests to exclude closure from the list of measures for controlling fugitive HF emissions from gypsum dewatering stacks. We believe that closing a gypsum dewatering stack is one of the best solutions for reducing fugitive HF emissions because it permanently reduces the emissions from the greatest contributing source. However, we are revising this control measure option in the NESHAP subpart AA final rule to allow a facility to design its own closure requirement plan, provided that the closure requirements, at a minimum, contain: (1) A specific trigger mechanism for when owners or operators must begin the closure process on the gypsum dewatering stack, and (2) a requirement to install a final cover. As with all gypsum dewatering stack and

cooling pond management plans, this closure requirement must be submitted to the Agency for approval. Although we are not identifying a specific trigger mechanism in the final rule, one example of a trigger mechanism is a facility-specified length of time where the gypsum dewatering stack is inactive and no longer receives gypsum (

i.e.,

once the gypsum dewatering stack stops receiving gypsum for a period of time, the facility must begin closing it). Also, we are clarifying that a final cover means the materials used to cover the top and sides of a gypsum dewatering stack upon closure. This addresses commenters request that the EPA should allow the final cover on a closed stack to consist of a synthetic liner. Finally, in light of our decision to revise the control measure option for closing a gypsum dewatering stack, we are also removing the definition of a “closed gypsum dewatering stack” from the NESHAP subpart AA final rule. Since the revised language relies on a specific trigger mechanism for when owners or operators must begin the closure process on the gypsum dewatering stack, the definition of a “closed gypsum dewatering stack” is no longer necessary in the final rule. Because we are removing the definition of a “closed gypsum dewatering stack” from the final rule, we are revising the definition of an “active gypsum dewatering stack.” In the NESHAP subpart AA final rule, an “active gypsum dewatering stack” means a gypsum dewatering stack that is currently receiving gypsum, received gypsum within the last year, or is part of the facility's water management system. A gypsum dewatering stack that is considered closed by a state authority is not considered an active gypsum dewatering stack.

As we have stated before, the final list of NESHAP subpart AA control measures is exhaustive enough that a facility has a number of options for selecting a control measure that would be feasible for their particular operations. We assume that facilities would choose the lowest cost option, and that all facilities are using at least one of the control measure options already (

e.g.,

we are not aware of any facilities that do not use a rim ditch (cell) building technique). Therefore, we disagree with the commenters' claim that enormous costs would be incurred if they were required to apply soil caps and vegetation to all side slopes of the active gypsum dewatering stack up to 50 feet below the stack top. We are not requiring that facilities implement this control measure since this specific control technique is not a requirement, but instead an option for how a facility may demonstrate compliance with the work practice standards for fugitive HF emissions from the gypsum management system.

iii. Requirement to Use At Least Two of the Fugitive HF Emissions Control Measures

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Comment.

One commenter requested that the EPA eliminate the “dual practice” approach for new sources. Two commenters declared that the requirement to implement “at least two of the control techniques” listed for “each regulated gypsum dewatering stack and cooling pond” is not possible without a broader list that includes at least two practices for cooling ponds. Additionally, with regard to closing an active gypsum dewatering stack as a control technique option, the commenter contended that giving an owner of a new gypsum dewatering stack the option of closing it in tandem with a mandatory second control technique is “nonsensical” because the “new stack would immediately have to be closed to implement the practice.” Another commenter wanted clarification as to whether the lateral expansion of an existing gypsum dewatering stack is considered a new stack, and thus would trigger the proposed work practice standards related to the size of active gypsum dewatering stacks and production ratio. The commenter also sought clarification as to whether at least two of the control techniques be used in the gypsum dewatering stack and cooling pond management plan for controlling fugitive HF emissions would be required.

Response.

We agree with the commenter that the proposed requirement for new gypsum dewatering stacks and cooling ponds to implement “at least two of the control techniques” listed for “each” regulated “gypsum dewatering stack and cooling pond,” would make compliance for cooling ponds impossible for new sources without a broader list with at least two control measures for cooling ponds. In the final rule, the Agency is using the terminology “control measures” in lieu of the proposed terminology “control techniques” because it more accurately describes the list of options in the rule and avoids confusion with other CAA programs. As stated in a previous response, in an effort to clarify the specific emission source that we are regulating in the final rule (NESHAP subpart AA), we have included a new term, “gypsum dewatering stack system,” (see sections V.C.3.b.i of this preamble for further details) in the final rule. This revision also clarifies our original intent that the two control measure options that a facility selects can be for any combination of gypsum dewatering stacks and/or cooling ponds in the gypsum dewatering stack system. For example, if a facility operates a cooling pond considered a new source, the facility may choose to not implement the control measure option requiring a submerged discharge pipe for the new cooling pond, and instead implement two control measures at one or more gypsum dewatering stacks no matter whether they be considered a new or existing source. Furthermore, we have revised the control measure option for closing a gypsum dewatering stack (see section V.C.3.b.ii of this preamble for further details). Because of this change to the NESHAP subpart AA final rule, there is no longer a requirement to immediately close the active gypsum dewatering stack in tandem with a mandatory second control measure option.

Lastly, the Agency has revised the definitions in the NESHAP subpart AA final rule for when a gypsum dewatering stack is considered “new” or “existing” in order to address whether a lateral expansion of an existing gypsum dewatering stack is considered a new gypsum dewatering stack. The revised definitions in the final rule also deal with a concern one commenter raised during the comment period about triggering the proposed regulation for a “new” source each time they rotate the functionality of their three gypsum dewatering stack sites at their facility (this topic was also discussed after the comment period closed, see “USEPA Meeting Minutes for PCS Aurora Discussion (2.2.2015),” which is available in Docket ID No. EPA-HQ-OAR-2012-0522). We are revising the NESHAP subpart AA final rule such that a gypsum dewatering stack or cooling pond is considered “new” if it meets two criteria: (1) It was constructed or reconstructed after August 19, 2015, and (2) it was required to obtain a permit by a state authority for the construction or reconstruction. Some lateral expansions may build beyond a facility's existing permitted capacity (and design dimensions of the gypsum dewatering stack); therefore, these lateral expansions would be considered “new” in the final rule because the facility would be required to obtain (or revise) their existing permitted capacity (and design dimensions). Because of this change in the NESHAP subpart AA final rule, we are also revising the criteria for when a gypsum dewatering stack or cooling pond is considered “existing.” Specifically, a gypsum dewatering stack or cooling pond is

considered “existing” if it meets one of two criteria: (1) It was constructed or reconstructed on or before August 19, 2015, or (2) it was constructed or reconstructed after August 19, 2015 and it was not required to obtain a permit by a state authority for the construction or reconstruction.

iv. Fugitive HF Emissions Control Measure Considerations for Cooling Ponds

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Comment.

One commenter referenced a 1978 EPA document: “Evaluation of Emissions and Control Techniques for Reducing Fluoride Emissions from Gypsum Ponds in the Phosphoric Acid Industry” and questioned why the EPA proposed work practice standards focused solely on gypsum dewatering stacks, while the EPA has in the past studied and documented more work practices for controls of cooling pond emissions, which are not discussed as alternatives to the proposed rule. Another commenter requested that if EPA keeps cooling ponds as part of the gypsum dewatering stack and cooling pond management plan, then EPA should provide more than one work practice that could be implemented at a cooling pond. They suggested that EPA add a control measure option (for cooling ponds) that would require developing a plan to optimize the size of cooling ponds to address fugitive HF emissions (as appropriate based on the conditions at the facility).

In addition, another commenter suggested additional control measure options for reducing fugitive HF emissions from cooling ponds. This commenter suggested EPA include an option to develop and implement a plan for dredging cooling ponds which helps maintain cooling capacity, and, therefore, can reduce fugitive emissions by reducing the vapor pressure of fluoride in the pond water. This commenter also suggested EPA include an option to implement a system for the recovery of fluoride for water that is directed to cooling ponds. The commenter pointed out that one of its facilities has the capability to recover fluoride as hydrofluorosilicic acid during the phosphoric acid evaporation process. The commenter stated that this recovery process is operated as needed to meet the market demand for hydrofluorosilicic acid. Finally, the commenter suggested EPA include an option to implement a system for the removal of fluoride for water that is directed to cooling ponds (for example, by adding lime to increase the pH).

Response.

We are aware of the 1978 EPA document, “Evaluation of Emissions and Control Techniques for Reducing Fluoride Emissions from Gypsum Ponds in the Phosphoric Acid Industry,” and the six potential control techniques it examines for reducing fluoride emissions from gypsum ponds. These six potential control techniques include: (1) Use of the “Kidde” process; (2) use of the “Swift” process; (3) use of lime to raise pH; (4) dry conveyance of gypsum, (5) pretreatment of ore by calcining; and (6) changing the entire phosphoric acid production process to a “hemi/dehydrate” process. The 1978 EPA document clarifies that the first four of these potential control techniques could also reduce fluoride emissions from cooling ponds. The “Swift,” “Kidde,” and “hemi/dehydrate” processes each use byproduct fluoride in the WPPA to produce hydrofluorosilicic acid (an acid generally used in fluoridation of drinking water, but also has other industry uses) or ammonium silicofluoride. We are aware of at least two facilities that are equipped and capable of making hydrofluorosilicic acid; however, it is not clear which process they use, nor is it clear if either facility is actively making hydrofluorosilicic acid. However, facilities have expressed that production of hydrofluorosilicic acid for the primary purpose of controlling HF emissions is not practical. Facilities that produce hydrofluorosilicic acid seek to sell the product for use in water fluoridation.

In fact, one commenter stated that their recovery process is operated as needed to meet the market demand for hydrofluorosilicic acid. Facilities would not produce this product in the absence of a market demand, as the hydrofluorosilicic acid would be another waste stream that would need to be disposed of. Therefore, we do not believe this to be a reasonable control technique option for fugitive HF emissions from these sources.

http://www.cdc.gov/fluoridation/factsheets/engineering/wfadditives.htm

We have determined that using lime (or any other caustic substance) to raise the pH of liquid discharged into the cooling pond could be a feasible control measure option for reducing fluoride emissions from cooling ponds; therefore, we are including this option in the NESHAP subpart AA final rule. The control measure option simultaneously raises the pH of the cooling pond water and lowers the concentration of soluble F, and, thus reducing the concentration of fluoride (including HF) that could be potentially evaporated into the atmosphere. Based on information provided in the 1978 EPA document, a greater than 90 percent emission reduction in fluoride can be achieved by raising the pond water from pH 1.4 to pH 3.9. In the final rule, if this control measure is chosen, then the plan must include: the method used to raise the pH of the liquid discharged into the cooling pond, the target pH value (of the liquid discharged into the cooling pond) expected to be achieved by using the method, and the analyses used to determine and support the raise in pH. Moreover, this control measure is similar to an option that industry suggested in response to a meeting that occurred after the public comment period closed (see “EPA Meeting Minutes for TFI Discussion March 12, 2015,” and “Summary of Potential Costs for Implementing Phosphate NESHAPs/Recommendations for Phosphogypsum Stack Work Practices, May 5, 2015,” which are both available in Docket ID No. EPA-HQ-OAR-2012-0522). Industry suggested including an option that would require providing inputs to the gypsum dewatering stack system to react with and precipitate fluoride compounds to insoluble forms.

With regard to the remaining potential control techniques identified in the 1978 EPA document (

i.e.,

dry conveyance of gypsum and pretreatment of ore by calcining), we have determined that these control techniques are not likely to be used by industry because significant process changes would be required. Furthermore, with regard to pretreatment of ore by calcining, the 1978 EPA document states that off-gases from pretreating ore would still need to be scrubbed to remove F, and the scrubbing liquid from this process would likely be disposed of in a cooling pond (which would defeat the purpose of this technique). Therefore, we are not finalizing the NESHAP subpart AA final rule to include these two control measure options for controlling fugitive HF emissions from cooling ponds.

Lastly, we agree with a commenter's request to add a control measure option (for cooling ponds) that would require developing a plan to optimize the size of cooling ponds to address fugitive HF emissions (as appropriate based on the conditions at the facility); therefore, we are including this option in the NESHAP subpart AA final rule. However, in order for a facility to be able to use this control measure o

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