## PHOSPHORIC ACID MANUFACTURING AND PHOSPHATE

FERTILIZER PRODUCTION RTR AND STANDARDS OF PERFORMANCE FOR PHOSPHATE PROCESSING

SUMMARY OF PUBLIC COMMENTS AND RESPONSES

U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Sector Policies and Programs Division Research Triangle Park, North Carolina 27711

July 201 5ii

The primary contact regarding questions or comments on this document is:

Tina Ndoh (919) 541

- 2750 U.S. Environmental Protection Agency OAQPS/Sector Policies and Programs Division (D243

- 02) Research Triangle Park, North Carolina 27711

Email: Ndoh.Tina@epa.goviii TABLE OF CONTENTS

Section Page No.

TABLE OF CONTENTS

................................ ................................ ................................ ............ iii 1.0 INTRODUCTION

................................ ................................ ................................ ........... 1

- 1 2.0 LIST OF COMMENTERS

................................ ................................ .............................. 2

- 1 3.0 RISK ASSESSMENT

................................ ................................ ................................ ...... 3

- 1 3.1 Supp orts Conclusion Of NESHAP Residual Risk Assessment

........................... 3

- 1 3.2 NESHAP Residual Risk Assessment Approach Needs Update

.......................... 3

- 1 3.3 Lead

................................ ................................ ................................ ...................... 3

- 6 3.4 Whether NESHAP Residual Risk Assessment Consistent with the Key Recommendations Contained in the SAB

................................ .......................... 3

- 10 3.5 Data Collection From Section 114 Survey And Testing Requests

.................... 3

- 11 3.6 HF Emissions Data Used For NESHAP Residual Risk Assessment Not Representative Of Actual HF Emissions

................................ ........................... 3

- 11 3.7 Chromium Emission Data Used For NESHAP Residual Risk Assessment Not Representative Of Actual Chromium Emissions

................................ ............... 3

- 13 3.8 Stac k Parameters Used For NESHAP Residual Risk Assessment Not Representative Of Actual Stack Parameters

................................ ...................... 3

- 14 3.9 Conservative Assumpt ions Used In NESHAP Residual Risk Assessment Bias Results

................................ ................................ ................................ ................ 3

- 15 3.10 Selection of Meteorological Data In NESHAP Residual Risk Asse ssment

...... 3

- 15 3.11 Rationale for Maximum One

- Hour Emission Rate In NESHAP Residual Risk Assessment

................................ ................................ ................................ ......... 3

- 17 3.12 Ecological Assessment Endpoints In NESHAP Residual Risk Assessment

..... 3

- 19 3.13 Exposure Modeling Uncertainty In NESHAP Residual Risk Assessment

........ 3

- 20 4.0 NESHAP TECHNOLOGY REVIEWS AND NSPS REVIEWS

................................ .... 4

- 1 4.1 Supports Conclusions Of NESHAP Technology Reviews and NSPS Reviews

.. 4

- 1 5.0 STATUTORY AUTHORITY

................................ ................................ ......................... 5

- 1 5.1 No Basis For Other Changes

................................ ................................ ................ 5

- 1 6.0 HG LIMIT AND HF WORK PRACTICE STANDARDS FOR CALCINERS

............. 6

- 1 6.1 Technical Feasibility of Hg Control Devices and Hg BTF Limit

........................ 6

- 1 6.2 Supports Hg BTF Limit

................................ ................................ ....................... 6

- 3 6.3 Set Health

- Based Hg Limit

................................ ................................ .................. 6

- 3 6.4 Hg Deposition

................................ ................................ ................................ ...... 6

- 5 6.5 Hg UPL Calculation

................................ ................................ ............................. 6

- 5 6.6 HF Work Practice for Phosphate Rock Calciners

................................ ................ 6

- 8 7.0 HF WORK PRACTICE STANDARDS FOR GYPSUM DEWATERING STACKS AND COOLING PONDS

................................ ................................ ................................ ......... 7

- 1 7.1 Submergence Of Discharge Pipe

................................ ................................ ......... 7

- 1 7.2 Rim Ditch (Cell) Building Technique

................................ ................................ .. 7

- 1 7.3 Wetting Of The Active Gypsum Stack

................................ ................................ 7

- 2 7.4 Application Of Slaked Lime

................................ ................................ ................ 7

- 2 7.5 Soil Caps And Vegetation

................................ ................................ .................... 7

- 3 7.6 Closure Of Gypsum Dewatering Stacks

................................ .............................. 7

- 3iv

7.7 Other Techniques

................................ ................................ ................................ . 7

- 4 7.8 Requirement To Use At Least Two Of The Control Measures

........................... 7

- 4 7.9 Gypsum Dewatering Stack Area To Phosphoric Acid Manufacturing Capacity Ratio

................................ ................................ ................................ ..................... 7

- 5 7.10 Necessi ty or Justification of HF Work Practices

................................ ................. 7

- 7 7.11 HF Work Practice For Gypsum Dewatering Stacks and Cooling Ponds Interfere With Other Regulatory Programs

................................ ................................ ........ 7

- 8 7.12 Cooling Pond Considerations For HF Work Practice

................................ .......... 7

- 9 8.0 TRANSLATION OF TOTAL FLUORIDE LIMITS TO HF LIMITS

........................... 8

- 1 8.1 Proposed HF Limits Are More Stringent Than Current Total Fluoride Limits

... 8

- 1 8.2 Reliance On EP A Method 26A HF Emissions Test Data To Establish New Standards Is In Error

................................ ................................ ............................ 8

- 1 8.3 Total Fluoride Surrogate For HF

................................ ................................ ......... 8

- 3 9.0 MEASUREMENT, MONITORING, AND REPORTING REQUIREMENTS

............. 9

- 4 9.1 Quantifying HF Emissions From Gypsum and Cooling Waters

......................... 9

- 4 9.2 EPA Method 320

................................ ................................ ................................ .. 9

- 5 9.3 EPA Method 26A

................................ ................................ ................................ . 9

- 6 9.4 FTIR HF CEMS

................................ ................................ ................................ ... 9

- 7 9.5 Pressure Drop Across Absorber

................................ ................................ ........... 9

- 8 9.6 Absorber Monitoring Options

................................ ................................ .............. 9

- 9 9.7 Acceptable Range From Baseline Average Value

................................ ............... 9

- 9 9.8 Operating Range Established From A Previous Test

................................ ........ 9

- 10 9.9 Approving Operating Ranges

................................ ................................ ............ 9

- 10 9.10 Maximum Representative Operating Conditions

................................ ............... 9

- 11 9.11 Performance Test Frequency

................................ ................................ ............. 9

- 12 9.12 Condenser Monitoring

................................ ................................ ....................... 9

- 12 10.0 COMPLIANCE DATES AND FREQUENCY OF PERFORMANCE TESTS

........... 10

- 1 10.1 Compliance Dates For Newly Regulated Sources

................................ ............. 10

- 1 10.2 Compliance Dates For Absorber Monitoring

................................ .................... 10

- 3 10.3 Compliance Dates For Fabric Filter Monitoring

................................ ............... 10

- 3 10.4 Compliance Dates For Stack Testing

................................ ................................ . 10

- 3 11.0 APPLICABILITY, DEFINITIONS, AND TERMINOLOGY

................................ ...... 11

- 1 11.1 Expanded Scope Of Process Lines

................................ ................................ .... 11

- 1 11.2 Clarification To Oxidation Reactors Included In SPA Process Lines

............... 11

- 1 11.3 Clarifications To Clarifiers And Defluorination Systems Included In WPPA Process Lines

................................ ................................ ................................ ..... 11

- 2 11.4 Clarification To Granular Triple Superphosphate Fertilizer Process Line

........ 11

- 3 11.5 Clarificati on To Phosphate Fertilizer Process Line Or Production Plant

.......... 11

- 3 11.6 Clarification To Purified Phosphoric Acid

................................ ........................ 11

- 5 11.7 Gypsum Dewatering Stack Definition

................................ ............................... 11

- 5 11.8 Closed and Active Gypsum Dewatering Stack Definitions

............................... 11

- 6 11.9 Cooling Pond Definition

................................ ................................ .................... 11

- 7 11.10 Production Capacity Clarification

................................ ................................ ...... 11

- 8 11.11 Applicability Clarification

- Kiln Process

................................ .......................... 11

- 8 11.12 Clarification To Calciners

................................ ................................ .................. 11

- 9 11.13 Clarification To Scrubber Terminology

................................ ............................. 11

- 9 12.0 ECONOMIC AND EMISSIONS IMPACTS

................................ ................................ 12

- 1 12.1 Cost

- Effectiveness of Hg Control Devices

................................ ........................ 12

- 1v

12.2 Gypstack Management Plan Control Measure Impacts

................................ ..... 12

- 2 12.3 Gypstack Ratio Impacts

................................ ................................ ..................... 12

- 3 12.4 Impact from A dditional Sources

................................ ................................ ........ 12

- 4 12.5 Testing and Monitoring Costs

................................ ................................ ............ 12

- 5 12.6 Economic Impacts

................................ ................................ .............................. 12

- 7 12.7 Economic Benefits and Regulatory Planning and Review

................................ 12

- 9 12.8 Environmental Justice

................................ ................................ ...................... 12

- 10 13.0 STARTUP, SHUTDOWN, AND MALFUNCTIONS

................................ ................ 13

- 12 13.1 Whether EPA Appropriately Removed The Startup, Shutdown, and Malfunction Exemption

................................ ................................ ................................ ........ 13

- 12 13.2 Feasibility Of Estimating Emissions During SSM Events

.............................. 13

- 16 13.3 Work Practice Standard In Place Of Emission Limits

................................ ..... 13

- 17 13.4 Make An Explicit Exemption For Monitoring During SSM

........................... 13

- 21 14.0 OTHER COMMENTS

................................ ................................ ................................ . 14

- 24 14.1 Scrubber Water to Cooling Tower Exemption

................................ ................ 14

- 24 14.2 Miscellaneous

................................ ................................ ................................ .. 14

- 26 14.3 Inherently Safer Technology (IST)

................................ ................................ .. 14

- 26 14.4 Extension Requests

................................ ................................ .......................... 14

- 29 14.5 Organics Content Subcategory

................................ ................................ ........ 14

- 291

- 1



### 1.0 INTRODUCTION

On November 7, 2014 , the Environmental Protection Agency ( EPA ) proposed revisions to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories and to new source performance standards (NSPS) for several phosphate pr ocessing categories . Some significant comments and responses appear in the preamble to the final rules. This document contains
summaries of all the public comments that the EPA received on the proposed standards (comments that are summarized and addressed in the preamble to the proposed rule are also provided in this document for completeness) . Copies of all comments submitted are available at the EPA docket Center Public Reading Room. Comment letters are also available electronically through http://www.regulations.gov by searching Docket ID No. EPA

- HQ

- OAR

- 201 2

- 0522.2

- 1



### 2.0 LIST OF COMMENTERS

The EPA received 14 comment letters after November 7, 2014 on the proposed revisions to the NESHAP for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories and to NSPS for several phosphate processing categories. All comment letters
are contained in Docket EPA

- HQ

- OAR

- 2012

- 0522. The commenter, af filiation , and item
number in Docket EPA

- HQ

- OAR

- 2012

- 0522 are listed in Table 2

- 1. A list of acronyms and units of measure used in this document appears after the list of commenters.

Table 2

- 1. Public Comments Received After the Proposed Rule for Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing , Proposed Rule Docket EPA

- HQ

- OAR

- 20 1 2

- 0 522

Commenter Identification Code Commenter and Affiliation EPA

- HQ

- OAR

- 2012

- 0522

- 0030 Paul DeKok, President, PCS Phosphate Company, Inc

. EPA

- HQ

- OAR

- 2012

- 0522

- 0031 David Jellerson, Senior Director, Environmental, Mosaic Fertilizer, LLC EPA

- HQ

- OAR

- 2012

- 0522

- 0035 E. Donald Elliott and Gerald H. Yamada, Covington & Burling LLP on behalf of the PCS Phosphate Company, Inc. EPA

- HQ

- OAR

- 2012

- 0522

- 0036 Mark Vignovic, Vice President

- Safety, Health & Environment, JDC Phosphate EPA

- HQ

- OAR

- 2012

- 0522

- 0037 PCS Phosphate Company, Inc.; PCS Nitrogen, Inc

. ; and White Springs Agricultural Chemicals, Inc

. EPA

- HQ

- OAR

- 2012

- 0522

- 0038 Andy O'Hare, The Fertilizer Institute EPA

- HQ

- OAR

- 2012

- 0522

- 0039 David Jellerson, Senior Director, Environmental, Mosaic Fertilizer, LLC EPA

- HQ

- OAR

- 2012

- 0522

- 0041 Sheila Holman, Director, North Carolina Department of Environment and Natural Resources, Division of Air Quality (NCDAQ) EPA

- HQ

- OAR

- 2012

- 0522

- 0042 Emma C. Cheuse, Earthjustice on behalf of Sierra Club EPA

- HQ

- OAR

- 2012

- 0522

- 0043 Alan L. Prouty, Vice President, Sustainability and Regulatory Affairs, J.R. Simplot Company EPA

- HQ

- OAR

- 2012

- 0522

- 0047 Gerald Yamada, Outside Council behalf of PCS Phosphate Co. EPA

- HQ

- OAR

- 2012

- 0522

- 0054 Reverend Jerry Langley, Zion Grove Church of Christ EPA

- HQ

- OAR

- 2012

- 0522

- 0055 Terry L. Baker, Senior Director, Environmental and Mine Developme nt, PotashCorp EPA

- HQ

- OAR

- 2012

- 0522

- 0056 Gerald Yamada and Casey Bradford, Counsels on behalf of PCS Phosphate Company2

- 2

List of Acronyms and Abbreviations Acronyms
ACI Activated carbon injection AEGL Acute exposure guideline levels APF Ammonium phosphate fertilizer ASOS Automated s urface o bservation s ystem BLDS Baghouse leak detection system BTF Beyond the floor CAA Clean Air Act CEMS Continuous emissions monitoring system CFR Code of Federal Regulations CPMS Continuous parameter monitoring syst em DAP Diammonium phosphate EJ Environmental justice EPA Environmental Protection Agency F Fluoride FR Federal Register FTIR Fourier transform infrared spectroscopy GMCS Gore Mercury Control System HAP Hazardous air pollutants HF Hydrogen fluoride Hg Mer cury HON Hazardous Organic NESHAP HQ Hazard quotient ICR Information Collection Request IRIS Integrat ed Risk Information System IST Inherently s afer t echnology LOAEL Lowest

- observed

- adverse

- effect level MACT Maximum achievable control technology MAP Monoammonium phosphate MOA M ode of action NAAQS National Ambient Air Quality Standards NACAA National Association of Clean Air Agencies NAS National Academy of Sciences NATA National

- Scale Air Toxics Assessment NEI National e missions i nventory NESHAP Nati onal Emissions Standards for Hazardous Air Pollutants NOAEL No

- observed

- adverse

- effect level NSPS New source performance standard OAQPS Office of Air Quality Planning and Standards ODW Office of Drinking Water OE HHA Office of Environ mental Health Hazard As sessment OHEA Office of Health an d Environmental Assessment OMB Office of Management and Budget P 2 O 5 Phosphorus pentoxide PB

- HAP Hazardous air pollutants known to be persistent and bio

- accumulative in the

environment2

- 3

PM Particulate matter PPA Purified phos phoric acid ppm Parts per million RCRA Resource Conservation and Recovery Act RfD R eference doses RfC R eference concentration RIA Regulatory i mpac t analysis RTR Residual risk and technology review SiF4 Silicon tetrafluoride SPA Superphosphoric acid SSM Startup, shutdown , and malfunction TOSHI Target organ

- specific hazard index tpy Tons per year μg/dL Microgram per deciliter UPL Upper prediction limit WESP Wet electrostatic precipitator WPPA Wet

- process phosphoric acid WWW World Wide Web3

- 1



### 3.0 RISK ASSESSMENT

3.1 Supports Conclusion Of NESHAP Residual Risk Assessment
Comment: Two commenters (0039, 0038) supported the EPA's residual risk assessment conclusions that the existing National Emissions Standards for Hazardous Air P ollutants ( NESHAP ) for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories currently are amply protective of public health and the environment

. Response to Comment: We acknowledge the commenters’ support for the EPA’s r esidual
risk assessment conclusions

.

3.2 NESHAP Residual Risk Assessment Approach Needs Update
Comment: One commenter (0042) 1 stated that the EPA’s residual risk assessment
underestimates risk. Th is commenter (0042) argued that the EPA is currently relying on outdated risk assessment methods that fail to incorporate the current science on the cumulative impacts of environmental exposures and community and individual vulnerability. Th e commenter urged the EPA to perfo rm a full “cumulative risk assessment” as recommended by The National Research Council, National Academy of Sciences (NAS), and incorporate the recommendations and information from the NAS, other independent scientists, and the example models from Californ ia EPA’s Office of Environmental Health Hazard Assessment (OEHHA), and take immediate steps to better assess cumulative risk and impacts. The commenter cited their 2012 Cumulative Risk Assessment Comments and pointed out that these bodies have provided sub stantial criticism of EPA’s approach and urged EPA to follow current science and take more protective approaches on important specific major issues. The commenter suggested that the EPA implement the following as part of their residual risk assessment: (1) Account for increased susceptibility by using age

- dependent adjustment factors for all carcinogens, not just known mutagens; (2) Pre

- natal susceptibility: Account for increased susceptibility by using a pre

- natal adjustment factor for all carcinogens of a t least 10X; (3) For chronic non

- cancer risk, consult and apply child

- specific reference values (such as those created by California EPA scientists), where available; (4) If child

- specific reference values are unavailable, consult science on early exposure impacts, and use an additional default factor of at

1 Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0040 is a duplicate to Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0042.3

- 2

least 10X; (5) Account for increased vulnerability resulting from and related to demographic factors, as part of the risk assessment; (6) Fully integrate the findings of its environmental justice analyse s into its risk assessments and rulemakings, and set stronger pollution limits to provide environmental justice; (7) Assess and aggregate exposure from multiple pathways

– including by adding inhalation and non

- inhalation

- based cancer risks; (8) Include th e interaction of multiple pollutants; (9) Account for exposure to multiple sources, and until EPA has a specific mechanism for estimating total exposures, a default or uncertainty factor of at least 10X should be used to provide overburdened communities wi th the protection they need now; (10) Reduce EPA’s benchmark of what it considers acceptable lifetime cancer risk instead of relying on the outdated upper limit of 100

- in

- a

- million; (11) Use a Margin of Exposure (MOE) framework for

non

- cancer impacts and a djust the target MOE according to known vulnerability factors; and (12) In the face of increasing evidence calling into question the assumption of a safe or acceptable level of exposure, EPA should also consider reforming risk assessments to support
reduci ng risks to the lowest possible level, to protect public health, rather than suggesting that there is a safe or acceptable level. Response to Comment: We disagree with the comment that we failed to consider or
account for cumulative risk. The EPA modeled w hole

- facility risks for both chronic cancer and

non

- cancer impacts to understand the risk contribution of the sources within the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories. The individual cancer
risks for each sourc e category were aggregated for all carcinogens. In assessing noncancer hazard from chronic exposures for pollutants that have similar modes of action or (where this information is absent) that affect the same target organ, we aggregated the hazard quotient s (HQ). This process creates, for each target organ, a t arget organ

- specific hazard index ( TOSHI ) , defined as the sum of hazard quotients for individual hazardous air pollutants ( HAP ) that affect the same organ or organ system. All TOSHI calculations prese nted here were based exclusively on effects occurring at the “critical dose” (i.e., the lowest dose that produces adverse health effects). Whole facility risks were estimated utilizing the 2005 National Emissions Inventory ( NEI ) , with updated facility

- wide and source category data files developed by the EPA through emission data updates from industry, states, and National Association of Clean Air Agencies ( NACAA )

. We disagree with the general comment that the EPA should adopt the Cal OEHHA child

protective scientific approach on cancer. The EPA has an approach for selecting appropriate3

- 3

health benchmark values and in general, this approach places greater weight on the EPA derived health benchmarks than those from other agencies (see http://www.epa.gov/ttn/at w/nata1999/99pdfs/healtheffectsinfo.pdf). Notably, this approach favoring EPA benchmarks (when they exist) over all others has been endorsed by the Science Advisory Board ( SAB ) . Further, the EPA is currently evaluating whether it is appropriate to use
the Cal OEHHA child

- specific reference doses, and we note that because there are currently no such values for HAP inhalation, their current utility would be limited to persistent and bioaccumulative (PB

- HAP ) , which may be associated with non

- negligible ingest ion exposures. That is, before using these child

- specific reference doses (RfDs), the EPA would need to evaluate whether they have been appropriately derived. We also disagree with the comment that the risk assessment for these source categories
do not con sider the groups that may be most at

- risk (e.g., pregnant women). When the EPA derives exposure reference concentrations and unit risk estimates for metal HAP, it also considers the most sensitive populations identified in the available literature, and imp ortantly, these are the values used in our risk assessments (see “ A review of the reference dose and reference concentration processes. ” EPA/630/P

- 02/002F. Risk Assessment Forum, Washington, DC. Available online at http://www.epa.gov/raf/publications/pdfs/ rfd

- final.pdf). With respect to maternal exposure in utero specifically, we are unaware of literature that would allow for a robust characterization of risk during this stage of development for the HAP we are assessing from this source category

. We acknowl edge that population subgroups, including children, may have a potential for risk that is greater than the general population due to greater relative exposure and/or greater susceptibility to the toxicant. As explained in previous actions, including the fi nal Hazardous Organic NESHAP ( HON ) r esidual risk and technology review ( RTR ) (71 FR 76610

- 76611), the assessments we undertake to estimate risk account for this potential vulnerability. With respect to exposure, the risk assessments we perform implicitly account for this greater potential for exposure by assuming lifetime exposure , in which populations are conservatively presumed to be exposed to airborne concentrations at their residence continuously, 24 hours per day for a full lifetime, including childhood. With regard to children’s potentially greater susceptibility to non

canc er toxicants, the assessments rely on EPA (or comparable) hazard identification and dose

response values which have been developed to be protective for all subgroups of the general population, including children.3

- 4

For example, a review 2 of the chronic refer ence value process concluded that the EPA’s reference concentration (RfC) derivation processes adequately considered potential susceptibility of different subgroups with specific consideration of children, such that the resultant RfC values pertain to the full human population “including sensitive subgroups,” a phrase which is inclusive
of childhood. With respect to cancer, the EPA uses the age

- dependent adjustment factor approach referred to by the commenter, but limits the use of those factors only to car cinogenic pollutants that are known to act via mutagenic mode of action (MOA) , in contrast to the OEHHA approach, which uses them across the board for all carcinogens regardless of mode of action. In
lieu of chemical

- specific data on which age or life

- stag e specific risk estimates or potencies can be determined, default age dependent adjustment factors can be applied when assessing cancer risk for early

- life exposures to chemicals which cause cancer through a mutagenic MOA. The
estimated risks must also be considered in the context of the full set of assumptions used for this risk assessment. For example, we used a health

- protective assumption of a 70

- year exposure duration in our risk estimates; however, using the national average residency time of 12 years would reduce the estimate of risk by roughly a factor of 6. Our unit risk estimates for HAP are considered a plausible upper

- bound estimate; actual potency is likely to be lower and some of which could be as low as zero. After considering these and other factors, we continue to consider the risks based on existing emissions from these source categories to provide an ample margin of safety (consistent with the Benzene NESHAP framework).
We are not able to determine the baseline health status of individuals or communities in a national rulemaking. Individual privacy issues as they relate to health records and the costs that would be associated with such an analysis make the analysis infeasible. As stated in the EPA’s May 2015, Guidance on Considering Env i r onm ental Justice During the Development of Regulatory Actions , 3 the agency is encouraging rule writers and policy makers to look at the whole range of factors that impact communities and population groups when crafting rules. The EPA is continuing to discuss and pilot approaches that are consistent with the agency’s responsibilities regarding EJ as outlined in EO 12898. In determining the need for tighter residual risk standards, the EPA strives to limit to no higher than 100

- in

- 1 million the estimated

2 U.S. EPA. A Review of the Reference Dose and Reference Concentration Processes. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, DC, EPA/630/P

- 02/002F, 2002. 3 Guidance on Considering Environmental Justice During the Development of Regulatory Actions. http://epa.gov/environmentaljustice/resources/policy/considering

- ej

- in

- rulemaking

- guide

- final.pdf. May 2015

.3

- 5

cancer risk for persons living near a plant if exposed to the maximum pollutant concentration for 70 years and to protect the greatest number of persons to an individual lifetime risk of no higher
than 1

- in

- 1 million. Considerations are made for all people regard less of racial or socioeconomic status, and the EPA does not believe it is necessary to establish a default factor to account for socioeconomic and other community

- based stressors. We have combined risk assessment results to the extent that it is appropria te to do so. We consider the effect of mixtures of carcinogens and use a TOSHI approach for our chronic noncancer assessments. We do not use a TOSHI approach for our acute analyses nor do we combine the results of our inhalation and multipathway assessment s. As described in the risk assessment report (available in the docket for this action), we do
not sum results of the acute noncancer inhalation assessment to create a combined acute risk number that would represent the total acute risk for all pollutants that act in a similar way on the same organ system or systems (similar to the chronic TOSHI). The acute screen is already a conservative scenario. That is, the acute screening scenario assumes worst

- case meteorology, peak emissions for all emission points occurring concurrently and an individual being located at the site of maximum concentration for an hour. Thus, as noted in the residual risk assessment for these source categories ( Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0006 ), “because of the
conservative natu re of the acute inhalation screening and the variable nature of emissions and potential exposures, acute impacts were screened on an individual pollutant basis, not using the TOSHI approach.” We did not combine the inhalation and multipathway risk assessme nt results for each pollutant because it is inappropriate to do so. The multipathway risk assessment conducted for proposal was a screening

- level assessment (i.e., Tier 1). It used highly conservative assumptions designed to ensure that facilities with res ults below the screening threshold values did not have the potential for multipathway impacts of concern. The screening scenario is a hypothetical scenario, and due to the theoretical construct of the screening model, exceedances of the
thresholds are not directly translatable into estimates of risk or hazard quotients for these facilities. In situations where we have previously summed the inhalation and multipathway assessment results (e.g., secondary lead smelters), it was for two refined assessments, and still serves as a conservative overestimate of potential risks given that it is highly unlikely that the same receptor has the maximum results in both assessments.3

- 6

We also disagree with the commenter’s assertion that additional quantitative assessment
of risks from sources outside the source categories is required under the statute. The statute requires the EPA to provide the quantitative risk information necessary to inform RTR regulatory decisions, and to this end, the EPA conducts a comprehensive assess ment of the risks associated with exposure to the HAP emitted by the source categories and supplements that with additional information that is available about other possible concurrent and relevant risks. We generally draw no bright lines of acceptability regarding cancer or noncancer risks
from source category HAP emissions. I t is always important to consider the specific uncertainties of the emissions and health effects information regarding the source category in question when deciding exactly what leve l of cancer and noncancer risk should be considered acceptable. In addition, the source category

- specific decision of what constitutes an acceptable level of risk should be a holistic one; that is, it should simultaneously consider all potential health imp acts

-- chronic and acute, cancer and noncancer, and multipathway

-- along with their uncertainties, when determining the acceptable level of source category risk. In other words, we look at the risk
numbers within the context of uncert ainty associated wit h emissions and health benchmark

v alues . The Benzene NESHAP decision framework of 1989 acknowledged this; in today’s world, such flexibility is even more imperative, because new information relevant to the question of risk acceptability is being developed all the time, and the accuracy and uncertainty of each piece of information must be considered in a weight

- of

- evidence approach for each decision. This relevant body of information is growing fast (and will continue to grow even faster), necessitating a f

lexible weight

- of

- evidence approach that acknowledges both complexity and uncertainty in the simplest and most transparent way possible. While this challenge is formidable, it is nonetheless the goal of the EPA’s RTR decision

- making, and it is the goal of the risk assessment to provide the information to support the decision

- making process.

3.3 Lead
Comment: One commenter (0042) argued that by just considering and relying solely on
the Lead National Ambient Air Quality Standards ( NAAQS ) in its proposed residual risk assessment, EPA has not met the legal standard of section 7412(f)(2), which requires an “ample margin of safety to protect public health,” rather than the NAAQS, which requires an “adequate margin of safety.” The commenter co ntented that to fulfill its § 7412(f)(2) obligations, the EPA must use the best science on assessing children’s health risk of exposure to lead, rather than3

- 7

considering only the 2008 Lead NAAQS. The commenter stated that the EPA must address and incorporat e the best currently available information on children’s exposure, including the Children’s Health Protection Advisory Committee recommendation of protecting children from an ambient concentration of lead of 0.02 μg/m3, rather than assuming that the 2008 N AAQS level of 0.15 μg/m3 is protective enough. The commenter asserted that the EPA’s sole reliance on the Lead NAAQS is both unlawful and arbitrary, and the EPA has failed to provide a reasoned explanation for not setting a standard that assures protection below the level of the 2008 NAAQS. The commenter stated that the residual risk assessment ignores current data showing that harm, particularly to children, can occur at levels below the lead NAAQS, including: (1) The CDC has now recognized that there is n o safe level of exposure, and has replaced the now

outdated 10 microgram per deciliter ( μg/dL ) standard with a recognition that action is required, at least, at the reference level of 5 μg/dL; (2) California’s health benchmark for lead shows EPA
should loo k at least at a blood

- lead level change of 1.0 μg/dL as the level at which measurable neurological harm, illustrated by a correlating loss of 1 IQ point, can occur; (3) As EPA’s Children’s Health Protection Advisory Committee recognizes, new research in re cent years suggests that the loss of 1 IQ point can occur at an even lower blood

- lead level: 0.01 μg/dL, and requires stronger protection than EPA assumes in this rule based on its use of only the 2008 Lead NAAQS; (4) there is strong scientific evidence sh owing greater harm from combined exposure to lead and manganese, which are both emitted here, and must the combined impacts from these exposures must be accounted for; and (5) EPA must evaluate evidence showing a link between
maternal blood

- lead levels and low birth weight, released in 2013. In addition, the commenter stated that the residual risk standards are designed to do more than just replicate other statutory protections, such as those provided by the NAAQS. The commenter asserted that if Congress ha d intended EPA simply to replicate the NAAQS, or some other different Clean Air Act requirement, in its section 7412(f)(2) residual risk rulemaking, the section 7412(f)(2) requirement would become redundant for any hazardous air pollutant that also has any relationship to any other regulated pollutant. The commenter argued that if there were any ambiguity on this question, statutory construction requires a reading of section 7412(f)(2) that preserves its independent value and meaning. Response to Comment: W e disagree with the comment that the use of the lead NAAQS does not sufficiently protect children . First, the lead NAAQS primary standard targets protection3

- 8

to the most susceptible group in the human population

– children

– and is designed to protect again st adverse effects to children’s most sensitive organ system

– the developing neurological system. (See 73 FR at 66975, 66976.) Second, the primary NAAQS for lead is specifically targeted at those children living near major sources of lead, such as seconda ry smelters. (See 73 FR at 67002/3 “in applying the evidence

- based framework, we are focused on a subpopulation of U.S. children, those living near air sources and more likely to be exposed at the level of the standard”; to the same effect see 73 FR 67000/ 3

-- “The framework in effect focuses on the sensitive subpopulation that is the group of children living near sources and more likely to be exposed at the level of the standard. The evidence

- based framework estimates a mean air

- related IQ loss for this subp opulation of children; it does not estimate a mean for all U.S. children”; 73
FR 67005/1

-- “the air

- related IQ loss framework provides estimates for the mean air

- related IQ loss of a subset of the population of U.S. children, and there are uncertainties ass ociated with those estimates. It provides estimates for that subset of children likely to be exposed to the level of the standard, which is generally expected to be the subpopulation of children living near sources who are likely to be most highly exposed. ”) In addition, in reviewing and sustaining the lead primary NAAQS, we note that the D.C. Circuit specifically noted that the rule was targeted to protect children living near lead sources: “EPA explained that the scientific evidence showing the impact of lead exposure in young children in the United States led it ‘to give greater prominence to children as the sensitive subpopulation in this review’ and to focus its revision of the lead NAAQS on the ‘sensitive subpopulation that is the group of children liv ing near [lead emission] sources and more likely to be exposed at the level of the standard.’ Given the scientific evidence on which it relied, the EPA’s decision to base the revised lead NAAQS on protecting the subset of children likely to be exposed to a irborne lead at the level of the standard was not

a rbitrary or capricious.” Coalition of Battery Recyclers, 604 F. 3d at 618. Furthermore, as noted in the risk assessment document, there is no RfD or other comparable chronic health benchmark value for lead compounds. That is, in 1988, the EPA’s Integrated Risk Information System ( IRIS ) program reviewed the health effects data regarding lead and its inorganic compounds and determined that it would be inappropriate to develop an RfD for these compounds, sayin g, “A great deal of information on the health effects of lead has been obtained through decades of medical observation and scientific research. This information has been assessed in the development of air and water quality criteria by the agency’s Office o f Health and Environmental Assessment (OHEA) in support of regulatory decision

- making by the3

- 9

Office of Air Quality Planning and Standards (OAQPS) and by the Office of Drinking Water (ODW). By comparison to most other environmental toxicants, the degree of uncertainty about the health effects of lead is quite low. It appears that some of these effects, particularly changes in the levels of certain blood enzymes and in aspects of children’s neurobehavioral development, may occur at blood lead levels so low as to be essentially without a threshold. The agency’s RfD Work Group discussed inorganic lead (and lead compounds) at two meetings (07/08/1985 and 07/22/1985) and considered it inappropriate to develop an RfD for inorganic lead.” The EPA’s
IRIS assessment f

or Lead and compounds (inorganic) (CASRN 7439

- 92

- 1), http://www.epa.gov/iris/subst/0277.htm

. The commenter also makes the legal argument that the primary NAAQS provides an “adequate” margin of safety, but that Clean Air Act (CAA) section 1 12 (f)(2) requires that a residual risk standard provide an “ample” margin of safety, reasoning from this that a NAAQS cannot just be substituted as the measure for evaluating acceptability of risk and that some greate r level of protection is required. We do not accept the commenter’s argument. The EPA is considering the primary NAAQS for lead

-- which incorporates an adequate margin of safety

-- in determining whether lead risks (taken together with cancer and other non

- cancer health risks)
from air

- borne lead fro m phosphate facilities are acceptable or unacceptable. Thus, to the extent the commenter’s argument rests on the difference between ‘adequate’ and ‘ample’ margin of safety, the argument is misplaced. 4 Margin

- of

- safety determinations for this rule are conducted separately, in accord with the two

- step framework set forth in the Benzene NESHAP and the en banc opinion in Vinyl Chloride

. See not only Vinyl Chloride , 824 F. 2d at 1165, 1166 but NRDC
v. EPA , 902 F. 2d 962, 973

- 74 (D.C. Cir. 1990) (distinguishing the NAAQS process, whereby the margin of safety analysis is incorporated as part of the standard without a two

- step analysis,
from residual risk determinations). 5 Using that framework, with its consideration of costs, cost

effectiveness, technological feasibility, and other factors set out in the Benzene NESHAP, at proposal we did not identify any additional controls beyond those that would need to be implemented to ensure an acceptable level of risk with an ampl e margin of safety. The EPA thus

4 In deed, the EPA’s utilization of a standard which also incorporates an adequate margin of safety to evaluate acceptability of risk is an added conservative (i.e. protective) element in its approach here. 5 The court was referring to the predecessor provisio n to the current CAA section 112 (f), but its analysis is equally applicable to the revised provision.3

- 10

disagrees with the commenter that CAA section 1 12 (f)(2) standards must be more stringent than a primary NAAQS as a matter of law.

3.4 Whether NESHAP Residual Risk Assessment Consistent with the Key
Recommendations Contained in the SAB
Comment: One commenter (0042) stated that the EPA has no valid basis to state that its proposed risk assessment methods are “consistent with the key recommendations contained in the [SAB] report.”
Two commenters (0038 , 0043 ) suggested that the EPA provide greater specificity regarding how the EPA’s methods used to assess risks in their residual risk assessment are consistent with those peer

- reviewed by EPA’s SAB in 2009 and described in their peer review report issued in 2010 , and also are consistent with the key recommendations contained in that report. The commenter contended that the residual risk assessment does not appear to fully delineate the risk assessment methods, default assumptions, data extrapolations and uncertai nties for each step of the assessment. The commenter stated that it would help interested parties better verify the results and determine for themselves whether the risk assessment provides an accurate representation of potential residual risk if the EPA w ould provide full

- fledged documentation in the residual risk assessment and its associated appendices regarding decisions for air disposition modeling, facility definitions, emissions data manipulation, selection of specific reference, toxicity criteria, a nd use of modeling assumptions. The commenter ( 0043 ) provided a detailed review of this topic in an appendix to their comment describing the residual risk assessment, issues with the methodology and assumptions, and recommendations for changes to make,
inc luding more transparency

. Response to Comment: EPA’s SAB has reviewed and supported our residual risk program several time s over the past 17 years

. First, in 1998 they examined our analytical and policy approach for assessing residual risk from hazardous air pollutants emitted from stationary sources, followed by a second review in 2000 to verify that our application to a specific source category was consistent with the approved approach

. A third SAB consultation in 2006 focused on development of emissions inventories for source categories and updated methods for characterizing human exposure and risks

. Again in 2009, the SAB reviewed and supported our updated and expanded air toxics risk assessment methods, including our multipathway3

- 11

assessment, refinement of acute risk screening, and the methods of assessing potential
environmental risk

. Our residual risk assessment report for these source categories, available in the docket for this proposed rulemaking, provided a comprehensive discussion of our current methods, models, health benchmarks, modeling results, risk characterization, and uncertainties as they have
evolved over time as a result of these SAB consultations

. In addition, the 9 appendices associated with this report provided extensive detail on the models and how they were used, the individual analyses (inhalation, acute, multipathway), and facility

- specific results

. To further our transparency, the docket for the proposed rulemaking also included all of the model input files necessary to recreate o ur analyses. We believe this fully documents our risk assessment methods, default assumptions, data extrapolations and uncertainties and allows interested parties to verify
our results.

3.5 Data Collection From Section 114 Survey And Testing Requests
Comment: One commenter (0038) stated that the RTRs were supported by the best available information from the affected facilities in each source category. However, this commenter contended that certain summary passages of the proposed rule might suggest that the
EPA did not receive adequate information in response to its CAA § 114 requests; and explained that in limited instances, responsive information was not available because (1) it does not exist, or (2) it was not requested by the EPA

. This commenter requested t he EPA clarify in the rulemaking docket that the responses provided by industry were commensurate with the relevant statutory obligations. Response to Comment: The Agency collected data during two CAA section 114 requests (one during 2010 and the other in 2014). The industry provided the majority of requested data
and follow

- up information requested. The Agency acknowledges and appreciates the costs and efforts expended by the industry in providing these data.

3.6 HF Emission s Data Used For NESHAP Residual Risk Assessment Not Representative Of Actual HF Emissions
Comment: One commenter (0043 ) argued that fugitive h ydrogen fluoride ( HF ) emissions used in the NESHAP residual risk assessment are not representative of actual emissi ons at their facilities, but rather overestimate emissions, and that the subsequent residual risk assessment lacks transparency in methodology and has an overtly conservative bias (i.e., overstates risk).3

- 12

The commenter stated that the combination of severa l assumptions and factors used by the EPA, result in a factor of 17 times higher HF emission rate than the facility’s calculations ; the commenter provided a detailed review of this topic as tables and appendices to their comment including HF emissions from their cooling towers and gypsum dewatering stacks. The commenter also stated that the EPA assumes that 93% of the total fluoride emitted from cooling towers is HF, but the EPA does not explain the basis for this value; the commenter contended that the “93 %” value does not accurately represent HF emissions from the cooling towers. Further, the commenter noted that the EPA uses a multiplication factor of 1 in the acute inhalation residual risk assessment for HF emissions from gypsum dewatering stacks, coolin g ponds, and cooling towers. However, a multiplication factor of 2 was used for the cooling tower at the Simplot Don

- Pocatello facility; the commenter requested the EPA explain their justification. Response to Comment: The EPA disagrees with the commenter and believes the HF emissions are representative for gypsum dewatering stacks and cooling towers. When determining emissions from gypsum dewatering stacks, we developed HF emission factors (tons per acre per year) based on the available fugitive emissions test data. The gypsum dewatering stack test data were from open path tunable diode laser or open path fourier transform infrared with radial plume mapping tests performed at four different facilities in the U.S. and Canada. We considered this to be a repre sentative sample of the industry. In addition, gypsum dewatering stack test data were not available at proposal specifically for the two Simplot facilities the commenter references. If specific data were available for these facilities, then it would have b een considered for the analysis. Regarding cooling towers, we believe that assuming 93 percent of the cooling tower fluoride emissions are HF is appropriate. The commenter shows two studies where the HF ratio was examined, one of these shows that HF const itutes the bulk of the fluoride emissions while the other shows a lower HF contribution. We also reviewed another study (see the document “LaCosse_Measuring HF Emissions from WPPA Facilities_1993,” available in Docket ID No.
EPA

- HQ

- OAR

- 2012

- 0522) that show s HF contributing more than 99 percent of the fluoride emissions. Therefore, data do support a contribution of 93 percent for HF emissions to total fluoride emissions for fugitive sources. The commenter is correct that a multiplication factor of 2
was used for the cooling tower at Simplot Don

- Pocatello. This was based on a review of data that showed large variability in cooling tower emissions at this plant, which range up to 175 pounds3

- 13

of total fluoride per year (see Appendix Q11 from Simplot’s “Response t o December 10, 2007 EPA Request for Information, Section 3007 of the Resource Conservation and Recovery Act ,” which is available in the docket for this action). Simplot also acknowledged their cooling tower
emissions were variable in their comment letter w hen they state “factors that Simplot has used to calculate HF emissions from cooling towers, gypsum stacks and point sources have varied over the years for both the Rock Springs and Pocatello plants.” Due to this variability, we determined a multiple facto r of 2 was appropriate for the Simplot Don

- Pocatello cooling tower. Because we believe the HF emissions from fugitive sources are representative, we disagree that risk was overstated. We are not revising the HF emissions for fugitive sources nor

re

- analyz ing the risk assessment for phosphoric acid plants. We determined there was no risk at proposal and the risk analysis was not considered when the work practice for gypsum dewatering stacks and cooling ponds was developed. Therefore, re

- evaluating emissions and risk for fugitive
sources would not lead to rule revisions.

3.7 Chromium Emission Data Used For NESHAP Residual Risk Assessment Not Representative Of Actual Chromium Emissions
Comment: One commenter ( 0043 ) argued that the EPA needs to reconsider the

assum ption used in the NESHAP residual risk assessment that all chromium is hexavalent
chromium. The commenter provided a detailed review of this topic in an appendix to their

comment concluding that that tests for chromium can easily provide false positive val ues for
hexavalent chromium. Response to Comment: The Agency disagrees with the commenter that all chromium was
considered hexavalent chromium in the NESHAP residual risk assessment . The Agency used reported hexavalent chromium emissions values in the NESHAP residual risk assessment , and
did not assume that all chromium was hexavalent chromium

. The values included in the risk modeling file were the reported hexavalent chromium and the estimated trivalent chromium
values . The Agency assumed that the non

- speciated chromium values represented total chromium emissions, and subtracted the reported hexavalent chromium emission values from the

non

- speciated total to estimate trivalent chromium

. The total non

- speciated chromium values
were not included in the ri sk modeling file

. In the few instances where the reported hexavalent
chromium value for a process exceeded the reported non

- speciated total chromium value, only the reported hexavalent chromium value was included in the modeling file

. The total non

-3

- 14

speciat ed value was not included and the trivalent chromium was not estimated for these
instances

. For the remaining processes that only had total chromium emissions and no hexavalent or trivalent chromium emissions were reported, the Agency used speciation profi les to speciate
the total into hexavalent and trivalent chromium emissions

.

3.8 Stack Parameters Used For NESHAP Residual Risk Assessment Not Representative
Of Actual Stack Parameters
Comment: One commenter ( 0043 ) stated that stack parameters used in the analy sis are not representative of actual stack parameters at their facilities. The commenter stated that the stack parameters used for one of their facilities are an average of data provided by PotashCorp (PCS) Aurora ; the commenter argued that there is no bas is given, nor is it appropriate to use PCS stack parameters with their facility emission data. The commenter provided a detailed review of this topic in a table to their comment . In addition, the commenter contended that the use of wrong modeling inputs fo r the source characteristics further distorted the determination of an “acute” concentration of HF in the area near one of their facilities. Response to Comment: When available, the Agency used actual facility specific stack parameters in the NESHAP residu al risk assessment; if parameters were not known, the Agency used best available data. The Agency asked for stack parameters on Form C

- 2

- e of the 2010
CAA Section 114 survey; respondents were asked in this portion of the survey to provide specific informat ion on emission points including, but not limited to, coordinates, release height, diameter, and velocity. F or cases where a facility did not provide stack parameters for an emission point in their response to the 2010 CAA Section 114 survey, such was the case with the facility that the commenter is referring to, the Agency used averages from other facilities to estimate the stack parameters. While the use of default stack parameters may have impacted the estimated acute HF ambient concentrations, stack hei ght and diameter, and exit gas temperature and velocity are not the sole drivers in the development of estimated ambient concentration s. Therefore, any inaccuracies resulting fro m this use of average parameters rather than actual parameters would be expected to be minimal enough to not be relevant to the final risk

assessment.3

- 15

3.9 Conservative Assumptions Used In NESHAP Residual Risk Assessment Bias
Results
Comment : One commenter (00 38) asserted that given the highly conservative assumptions used by the EPA throughout the risk assessment process, including not only the residual risk assessment methodology but also the derivation of dose

- response thresholds (e.g., IRIS RfC, RfD, AEGLs, MRLs, and CalEPA RELs) against which exposure data were compared, the residual risk characterizations in the residual risk assessment are inherently biased upwards. The commenter recommended the EPA expressly describe the conclusions drawn there
from as h ighly conservative. Response to Comment: Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this rulemaking. Although uncertainty exists, we believe that our approach, which used conservative tools a nd assumptions, ensures that our decisions are health protective and environmentally protective. A brief discussion of the uncertainties in the RTR emissions datasets, dispersion modeling, inhalation exposure estimates
and dose

- response relationships can b e found in the proposal for this rulemaking ( 79 FR 66512 ). A more thorough discussion of these uncertainties is included in the memorandum “ 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 action.

3.10 Selection of Meteorological Data In NESHAP Residual Risk Assessment
Comment: One commenter (0038) requested clarification regarding the sele ction of off

site meteorological data used for modeling air

- dispersion characteristics and subsequent inhalation exposure. The commenter said that the EPA states that five years of modeling data are “ideal,” but in the residual risk assessment, only data f rom 1991 were used

. The commenter pointed out that Appendix 2 from the residual risk assessment suggests there is an incompatibility between meteorological data and the air dispersion modeling, resulting in an arbitrary decision to use 1991 as the sole sou rce of meteorological data. The commenter stated that some significant improvement could be achieved in air dispersion modeling results by either (1) updating the air dispersion model to accept meteorological data after 1991, using data from a
five

- year pe riod before 1992, or (2) selecting a single year that is typical of meteorological conditions for the source being characterized

. The commenter pointed out that the EPA used3

- 16

2005 National

- Scale Air Toxics Assessment (NATA) NEI data updated via the use of C AA § 114 information requests from all U.S. phosphate fertilizer and phosphoric acid manufacturers submitted in 2010 and 2014; and stated that this improvement is important, given that the selection of the meteorology dataset translates directly to the est imated exposures and risks, resulting in a variance of 17% lower to 84% higher than the estimated values. Response to Comment: When we began performing RTR risk assessments, we chose meteorological data considering the amount of data quality assurance need ed and AERMOD run times. We restricted our meteorological data to that collected prior to the installation of the Automated Surface Observation System (ASOS). The ASOS had been found to omit the ceiling height for a large percentage of observations at a nu mber of meteorological stations. Because installation and operation of ASOS equipment began in 1992, we selected the year 1991. As newer, higher quality ASOS data have become available, we have added newer data and
additional data site locations to the met eorological data library we use in our risk assessments. Currently, all of our meteorological data has been updated and risk assessment modeling uses data from the year 2011

. However, at the time these source categories were modeled, the update
of the mete orological data had not occurred

. Since the risk were considered acceptable with an ample margin of safety and the emissions had not increased since we modeled, we concluded for the proposal and re

- iterate for the final rulemaking, that it is not necessary to re

- model these source categories with the updated meteorological data. Although 5 years of meteorological data is preferred for assessing chronic exposures and risks, we use a single year (2011) of meteorological data in our risk assessments because of AERMOD model run times. Because we frequently run AERMOD for entire source category with many individual emissions points and for many receptors, using 5 years of meteorological data would increase already significant model run times by a factor of five c ompared to a single year. In a sensitivity analysis of the impact of using a single year of meteorological data compared to 5 years, we found that modeled concentrations differed by less than ten percent on average and thus, the use of one year of meteorol ogical data is not likely to appreciably affect the
results of the risk assessment.3

- 17

3.11 Rationale for Maximum One

- Hour Emission Rate In NESHAP Residual Risk
Assessment
Comment: One commenter (0038) requested that the EPA adequately explain its rationale
for t he maximum one

- hour emission rate used for determining potential acute exposures. The commenter argued that there is no clear rationale for the EPA’s selection of a factor of ten for derivation of the highest hourly ambient concentration at off

- site locati ons. The commenter asserted that the EPA provides no policy directive or technical evaluation to justify its “engineering judgment” other than to state that “EPA uses a multiplier of 10 to predict worst case emissions during a process upset or control devi ce malfunction.” The commenter pointed out that the EPA presented multiple acute HQ estimates for some HAPs in Appendix 8, Table 1 with a footnote indicating that a second set of estimates for HF were based on emissions estimates representing a factor of t wo rather than the ten

- fold multiplier. The commenter stated that it is confident that there is no good reason to assume that emissions during a process upset or control device malfunction can be reasonably expected to result in a highest hourly ambient co ncentration at any off

- site location; therefore, requests that
the EPA re

- examine the selection of a factor of ten to derive the highest hourly ambient concentration. The commenter said that at a minimum, the EPA must explain its “engineering judgment” on this subject. Response to Comment: When screening for potentially significant acute exposures, we used an estimate of the highest hourly ambient concentration at any off

- site location as the surrogate for the maximum potential acute exposure concentration for any individual

. These hourly concentrations are based on hourly emissions

. Since information is not usually available
on short

- term emission rates, we generally apply the assumption that the maximum one

- hour emission rate from any source is ten times t he average annual hourly emission rate for that

source

. (The average hourly emissions rate is defined as the total emissions for a year divided by the total number of operating hours in the year.) This choice of a factor of ten for acute screening was originally based on engineering judgment

. To develop a more robust peak

- to

- mean emissions factor, and in response to one of the key messages from the SAB consultation on our RTR Assessment Plan, we performed an analysis using a short

- term emissions dat a set from a number of source s located in Texas3

- 18

(originally reported on by Allen et al

. 2004) 6

. In that report, the Texas Environmental Research Consortium Project compared hourly and annual emissions data for volatile organic compound s for all facilities i n a heavily

- industrialized 4

- county area (Harris, Galveston, Chambers, and
Brazoria Counties ) over an eleven

- month time period in 2001

. We obtained the dataset and performed our own analysis, focusing on sources which reported emitting high quantities of H AP over short periods of time. A discussion of this analysis appeared in Appendix 3 Analysis of data
on short

- term emission rates relative to long

- term emission rates of the “ Draft Residual Risk
Assessment for Phosphate F ertilizer Production and P hosphoric Acid M anufacturing” available in the docket for the proposed rulemaking and will also appear in the docket for the final promulgation ( Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0006 )

. The results of this analysis
indicated most peak emission events were less tha n twice the annual average, and the highest
was a factor of 74 times the annual average , and the 99 th percentile ratio of peak hourly emission rate to the annual hourly emission rate was 9

. Based on these results, we generally chose the
factor of ten for a ll initial screening

. This factor is intended to cover all possible hourly peaks associated with routinely

- variable emissions

. While there have been some documented emission excursions above this level, our analysis of the data from the Texas Environmental Research Consortium suggests that this factor should cover more than 99 percent of the short

- term peak gaseous or volatile HAP emissions from typical industrial sources

. We have no data relating specifically to peak short

- term emissions of particulate HAP

. In the absence of source category

specific data, we use this same default approach for particulate emissions as well. For phosphate fertilizer production facilities an acute multiplier of 10 (x) the average 1

- hr emission rates was applied to all sources . For phosphoric acid manufacturing facilities a multiplier of 10 (x) was applied for point sources based on the information collection request ( ICR ) data and engineering knowledge of the source category processes , and for emissions from fugitive sources (gypsum ponds and cooling ponds) an acute multiplier of 1 was applied (for all
but one instance ; see response to comment in section 3.6 of this document for further detail regarding this one instance )

.

6 Allen, D., C. Murphy, Y. Kimura, W. Vizuete, T. Edgar, H. Jeffries, B.

- U. Kim, M. Webster, and M. Symons, 2004. Variable industrial VOC emissions and their impact on ozone formation in the Houston Galveston Area. Final Report: Texas Environmental Research Consortium Project H

- 13. http://files.harc.edu/Project s/AirQuality/Projects/H013.2003/H13FinalReport.pdf3

- 19

3.12 Ecological As sessment Endpoints In NESHAP Residual Risk Assessment
Comment: One commenter (0038) requested that the EPA provide clarification regarding the selection of ecological assessment endpoints. The commenter pointed out that the EPA indicates that these endpoi nts were selected based on a hierarchy of programmatic, federal agency or state agency benchmarks; however, the residual risk assessment indicates that a Canadian “LOEL” ecological benchmark was used. The commenter requests a technical and legal justificat ion for the EPA’s use of the “Canadian LOEL ecological benchmark,” as well as an explanation of that benchmark, so that it can meaningfully review the benchmark for applicability to facility

- specific ecosystems. The commenter also suggested that the EPA di scuss its overall use of international ecological benchmarks, and how such benchmarks fit into the EPA’s decision

- making hierarchy (assuming there is a legal justification for including them in the first instance). Response to Comment: The RTR environmenta l risk screenings of acid gases are conducted using modeled estimates of ambient air concentrations based on emissions from the regulated source. Therefore, the benchmark for HF for plants is required to be expressed as an air
concentration

. Currently, the EPA does not have an air concentration

- based environmental benchmark for HF at either the programmatic level or regional level

. In addition, air
concentration

- based environmental benchmarks are not available from other federal agencies

. However, air conce ntration

- based HF benchmarks have been established by several states, including Texas, Kentucky, New York, Washington, and Tennessee, as a part of their ambient air quality standards. The “Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing,” which was available in the docket for this proposed rulemaking, presented
the environmental risk screen results in Table 3.2

- 4 (for Phosphate Fertilizer Production) and
Table 4.2

- 4 (for Phosphoric Acid Manufacturing)

. In footnote 3 of these tables we indicated that: “For HF, we evaluated two benchmarks, one from Canada and the other from the State of Washington

. Although, they are both considered to be LOELs

- the level between a NOAEL and a LOAEL, we have listed the res ults under the LOAEL column

. The results presented in the table are the same for both the LOEL from Canada and the LOEL from the State of Washington (i.e., no facility showing exceedance of averaged values; 1% of area in category showing and exceedance).”
The Environment Canada criteria of 0.4 ug HF/m 3 was developed using regression analysis of exposure

- concentration versus exposure

- duration data and is defined as:3

- 20

"The level above which there are demonstrated effects on human health and/or the environment. It is scientifically based and defines the boundary between the LOAEL and the NOAEL. It is considered to be the level of exposure just below that most likely to result in a defined and identifiable but minimal effect." (CCME 1999)

The Environment Canada c riteria was developed using data from 13 investigations into the effects of HF on plants that represented 32 separate effects results

. The data set included 18 effects results from studies using plants of horticultural importance, 10 from studies using
agr icultural species, and 4 from studies of effects on forest (conifer) species

. Many of the plant species included in these studies are of great importance in the U.S., such as (Canadian Environmental Protection Act/Federal Provincial Advisory Committee Work ing Group on Air Quality Objectives and Guidelines, July 1996): corn, wheat, pine trees, potatoes, spruce trees, peach, peanut, green beans, strawberries, barley, alfalfa, onion, and beans.

3.13 Exposure Modeling Uncertainty In NESHAP Residual Risk Assessment
Comment: One commenter (0038) requested that the EPA provide some quantitative or qualitative rationale for its characterization of the exposure modeling uncertainty where the EPA states that: “Although every effort has been made to identify all the releva nt facilities and emission points, as well as to develop accurate estimates of the annual emission rates for all relevant HAP, the uncertainties in our emission inventory likely dominate the uncertainties in our exposure modeling estimates. The chronic exp osure modeling uncertainties are considered relatively small in comparison, since we are using EPA’s refined local dispersion model with
site

- specific parameters and reasonably representative meteorology.” The commenter stated that
it finds no basis for th e statement that “uncertainties in our emission inventory likely dominate the uncertainties in our exposure modeling estimates” given that there are only twelve facilities in the phosphoric acid source category and eleven facilities in the phosphate fertil izer source category, the availability of NATA NEI data, and the additional data provided through two information requests. The commenter added that this is especially true given that selection of the meteorology dataset can result in a variance of 17% low er to 84% higher than the estimated
values. Response to Comment: Several types of uncertainty are inherent in all risk assessments, such as the uncertainty associated with the emissions datasets, dispersion modeling, inhalation exposure estimates and dose

- response relationships

. For all RTR risk assessments the models, methods to estimate exposure, and the dose

- response values have undergone rigorous peer and/or3

- 21

SAB review. Although the development of the RTR emissions datasets involved quality assurance/quality control processes, the accuracy of emissions values will vary depending on the source of the data, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the datasets are accurate, errors in emission estimates and other
factors

. Therefore, it is reasonable to anticipate that the uncertainties in our emission inventory likely dominate the uncertainties in our exposure modeling estimates.4

- 1



### 4.0 NESHAP TEC HNOLOGY REVIEWS AND NSPS REVIEW S

4.1 Supports Conclusions Of NESHAP Technology Reviews and NSPS Reviews
Comment: Two commenters (0039, 0038) stated that they agree with the EPA’s conclusion that there are no new developments in practices, processes, or control technologies that can be applied in either phosphoric acid manufacturing or phosphate fertilizer production
that would reduce hazard ous air pollutants below current levels. One of these commenters (0039) also stated that the EPA correctly determined that no changes to the n ew source performance
standard ( NSPS ) were warranted. Response to Comment: We thank the commenters for their support. However, as a point of clarification, the EPA determined that there are no new cost

- effective developments in practices, processes, or control technologies for these source categories. Also, we do want to clarify that, as explained in the preamble to the proposed r ule, our technology review did reveal
that s uperphosphoric acid ( SPA ) process lines at four different facilities include an oxidation reactor to remove organic impurities from the acid. Refer to the preamble of the final rule for additional discussion rega rding the applicability of oxidation reactors in the final rule.5

- 1



### 5.0 STATUTORY AUTHORITY

5.1 No Basis For Other Changes
Comment: Four commenters (0037, 0039, 0038 , 0043 ) urged the EPA to explain to why the proposed standards are revised to be more restrictive even though the EPA’s overarching conclusions are that: (1) the phosphoric acid and phosphate fertilizer source categories pose no risk to human health or the environment, and (2) no new developments have arisen in practices, processes, or control technologies that can be applied. One of these commenters (0038) stated that at present, it is not clear that the EPA has the requisite statutory authority or a factual basis to change the standards, given that the fundamental RTR conclusions culminating in the 1999

r ulemaking have not changed (based on EPA’s own review and findings during this RTR process). This commenter (0038) suggested that the EPA establish and explain this nexus between the outcomes of the RTR and EPA’s proposed changes to the substantive rules i n Subparts AA and BB; otherwise, imposing those changes on phosphoric acid and phosphate
fertilizer facilities will lack a rational basis. One commenter (0037) questioned the EPA’s legal authority to adopt changes to applicability definitions and complian ce procedures that potentially make the NESHAP broader and more stringent than is currently the case (e.g., this commenter pointed out that the proposed HF limits are more stringent than the current total fluoride limits); the commenter cited the
Petroleum Refinery Sector RTR and NSPS, and argued that the EPA has recognized that it does not have the authority to issue more stringent standards in these circumstances.
Another commenter (0039) argued that CAA section 1 12(f) does not provide the EPA with any authority to revise the existing NESHAP if the existing standards already provide an ample margin of safety, or if cancer risk already is less than one in one million. This commenter also asserted that despite the EPA’s conclusions from its review of the N SPS that "no cost

effective emission reductions strategies [were] identified" and the EPA did "not see any basis for concluding that the 'best system of emissions reduction' has changed ,” the EPA proposes to "clarify" the NSPS in a manner that will signifi cantly expand the scope of the rule

. This commenter argued that the EPA’s proposal to modify the definition of "wet

- process phosphoric acid plant" in NSPS subpart T to include "clarifiers" and "defluorination systems." are unwarranted given EPA's conclusio ns that these sources already present low risks and because there have not been developments in technology or changes in practice to justify this change. The5

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commenter stated that the unnecessary nature of EPA's action is perhaps even more pronounced
in th e NSPS context, in which the statute explicitly allows EPA to leave the NSPS in place when, like here, current standards are effective. The commenter suggested that the EPA interpret its authority consistent with the CAA and in a manner that avoids the imp osition of significant costs without any benefit.
Two commenters (0039 , 0043 ) pointed out that the additional work practice standards for gypsum dewatering stack and cooling ponds, impose millions of dollars in costs and years of effort on the part of regu lated entities, and potentially increase environmental risks associated with process water management, even though the EPA has determined that current standards are protective of human health and the environment and that revisions are otherwise unnecessary

. Further, the commenters stated that the EPA has presented no analysis that these proposed work practices would result in any material reduction in emissions

. One of these commenters (0039) claimed that EPA’s justification of the reason to promulgate fugi tive HF controls for gypsum dewater stacks and cooling ponds is based on two cases that do not support its position (National Lime Association v. Environmental Protection Agency, 233 F.3d 625 (D.C. Cir. 2000) and Sierra Club v. Environmental Protection Age ncy, 479 F.3d 875 (D.C. Cir. 2007). They claimed these cases are distinguishable from the situation with HF emissions from subpart AA sources because there are existing controls for these sources. Also, they claimed that the EPA did not explain how
the wor k practice standards are analogous to a maximum achievable control technology ( MACT ) floor, in that they provided no information on what emission limitations are achieved by the best performing phosphoric acid or phosphate manufacturing sources from gypsum dewatering stacks and cooling ponds (because these emissions “cannot be measured”). They also asserted that since imposing a MACT floor based on reliable determination of the best performing sources is not possible, then the EPA is obliged to adopt standa rds under CAA section 1 12(h) that, consistent
with CAA section 1 12(d)(2), take into account costs and non

- air quality health and environmental impacts and energy requirements. Response to Comment: As stated in the preamble for the proposed rule, the Agency is not proposing revisions under the authority of CAA Sections 111(b)(1) (B), 112(d)(6), or 112(f)(2) since we did not identify any cost

- effective control technologies or practices for emission reductions and since the current standards were found to prov ide an ample margin of safety to protect public health.5

- 3

The standards that were proposed to address mercury ( Hg ) and HF emissions from calciners, and HF emissions from fugitive sources are for currently unregulated emission sources, and proposed under the authority of CAA Section 112(d)(2) and (d)(3). Therefore, we disagree with the commenter’s statement that we should allow the residual risk analysis to advise whether we address unregulated emission sources. The latter is clearly not designed to inform th e former, as the residual risk analysis should, in practice, be conducted no later than 8 years after the original standard is set

. The Agency is not adopting the proposed clarifications for defluorination units and clarifiers, but is adopting the clarifi cations for oxidation reactors. Refer to the preamble of the final rule for additional discussion regarding the applicability of oxidation reactors in the final
rule. The Agency does not agree with the estimated cost for compliance for the gypsum
dewaterin g stack management plan. In response to other comments, the Agency has clarified the requirements for the management plan. We believe these clarifications will make the covered entities, and subsequent costs more clear to facilities. Refer to the preamble of the final rule for additional details of the work practice standards for gypsum dewatering stacks and cooling ponds
included in the final rule. As previously noted, these are also currently unregulated sources. Therefore it is not appropriate to use the residual risk analysis to determine whether regulation is
necessary. The work practice standards adopted in the final rule represent MACT as they are a collection of best practices for emission reduction within the industry.6

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### 6.0 HG LIMIT AND HF WORK PRACTICE STANDARDS FOR CALCINERS

6.1 Technical Feasibility of Hg Control Devices and Hg BTF Limit
Comment: Some commenters (0037, 0041) did not support the EPA’s decision to set a BTF limit for Hg from phosphate rock calciners because the y stated that the emissions do not present unacceptable risks nor do the emission limits yield any benefits. The commenters
asserted that the EPA fails to show that the proposed BTF Hg limit would produce health or
environmental benef

its that justify the costs of achieving the standard as required by CAA section 112(d)(2). Commenters (0037, 0041) further claimed that the EPA’s own risk assessment shows that the BTF limit is not necessary from a risk standpoint because the NESHAP regula tion, prior to implementation of the proposed Hg BTF limits, protects human health and the environment with an ample margin of safety. The commenters (0037, 0041) maintained that under CAA section 112(d)(2), the EPA may set an emission limit that is more s tringent 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 (0037) cited regulations where the EPA did not set BTF limits for a particular pollutan t because the benefits were minimal and the risk would not be appreciably reduced. Commenters (0037, 0041) supported setting the MACT floor as the Hg limit. Commenters (0037, 0041) 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 comment ers (0037, 0041) 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 (0037, 0041) 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 comp lexity. The commenters (0037, 0041) 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 additional6

- 2

particulate load. The commenters (0037, 0041) 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 (0037, 0041) not ed 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 a commenter (0037) 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 (0037) 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 (0037) also cited a reference from 1994 tha t observed an increased injection rate due to temperature of the exhaust gas stream. Regarding fixed

- bed carbon adsorption, commenters (0037, 0041) stated a traditional
fixed

- bed carbon adsorption system would not be feasible, due to the presence of entrai ned water droplets that would severely degrade sorbent performance and cause plugging within the bed. The commenters (0037, 0041) 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 (0037, 0041) stated that to utilize 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 (0043) also reported they were evaluating the use of the GMCS system, but were only in prel iminary stages as their phosphate rock calciner is not yet operating. A commenter (0037) 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. One commenter (0037) provided a detailed review of Hg control
devices in an attachment to their comment

. Response to Comment: The results of the residual risk analyses are not part of the beyond

- the

- floor MACT determinatio n, and accordingly, the commenter’s concern about not considering risk results is not appropriate. Additionally, a s 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 phosphate6

- 3

rock calciners. We also agree that a traditional fixed

- bed carbon adsorption system is not technically feasible to control Hg emissions from phosphate rock calcine rs. Furthermore, we
agree that use of ACI is technically feasible to control Hg emissions from phosphate rock calciners if it is installed upstream of the existing venturi scrubber, where the moisture content is
lower. We are not finalizing the proposed B TF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners due to potential significant economic impacts associated with the costs of controls . Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners. Refer to the preamble of the final rule for additional details.

6.2 Supports Hg BTF Limit
Comment: One commenter (0042) support the EPA’s recognition of the need to set a beyond

- the

- floor limit for Hg from phosphate rock calciners. Response to Comment: We acknowledge the commenters’ support for the EPA’s proposed rule. However, we are not finalizing the pr oposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners due to potential significant economic impacts associated with the costs of controls . Instead, we are finalizing a MACT floor Hg limit for existi ng phosphate rock calciners. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners. Refer to the preamble of the final rule for additional details

.

6.3 Set Health

- Based Hg Limit
Commen t: One commenter (0037) stated that the EPA could set a health

- based limit for Hg under CAA § 112(d)(4) that is equivalent to the MACT floor for phosphate rock calciners.
The commenter (0037) maintained that CAA section 1 12(d)(4) is designed to prevent the promulgation of emission limits that are more stringent than necessary to protect human health and the environment with an ample margin of safety. The commenter continued that under that section, EPA can set health

- based limits for certain pollutants based on established health thresholds as an alternative to promulgating limits under CAA § 112(d)(2). The commenter (0037) stated that emissions test data for the phosphate rock calciners showed that approximately6

- 4

99% of the Hg is elemental Hg , and elemental Hg is eligible for CAA § 112(d)(4) because it is classified as a Group D pollutant

. Response to Comment: After considering the comment, the EPA has decided that it is not appropriate to adopt an emissions standard for el emental Hg under EPA’s CAA section 112(d)(4) authority. Hg is a persistent, bioaccumulative toxic metal that is typically emitted from industrial sources in three forms: gaseous elemental Hg (Hg0), the form primarily released by phosphate rock calciners; o xidized Hg compounds (Hg+2); and particle

- bound Hg (HgP). Whereas oxidized (divalent) and particle

- bound Hg will deposit relatively closer to the release source, gaseous
elemental Hg emitted into the air does not quickly deposit or chemically react in the atmosphere, but is transported much further, often becoming part of the global pool, before undergoing transformation to inorganic Hg compounds (divalent Hg ) and deposited. As a result, deposition of Hg to watersheds includes Hg originating from local/regi onal sources, combined with Hg that has been transported regionally and globally from global anthropogenic and natural sources. Once deposited, inorganic forms of Hg transform to methylmercury, a persistent and
toxic contaminant that bioaccumulates in fish and is associated with neurodevelopmental effects
in children

. In fact, while Hg exposure and risk can occur through a variety of pathways, the dominant human exposure pathway associated with ambient air emissions is through the consumption of fish that h ave bioaccumulated Hg originally deposited to watersheds following atmospheric release and transport. EPA previously has established that “there is no evidence for a biological threshold observed for critical effect of neurological deficits in children stu died in the principal studies of the IRIS assessment for MeHg [methylmercury].” 7 Thus, the EPA does not consider methylmercury to be a threshold pollutant.
The EPA notes that the Agency’s authority under CAA section 112(d)(4) is discretionary. That provisi on states that the EPA ‘‘may’’ consider establishing health thresholds when setting emissions standards under CAA section 112(d). By the use of the term ‘‘may,’’ Congress clearly
intended to allow the EPA to decide not to consider a health threshold even f or pollutants which have an established threshold, and it is appropriate for the EPA to consider relevant factors, such as the ability for a threshold pollutant to undergo chemical transformation to a non

- threshold

7 Revised Technical Support Document: National

- Scale Assessment of Mercury Risk to Populations with High Consumption of Self

- caught Freshwater Fish; In Support of the Appropriate and Necessary Finding for Coal

- and Oil

- Fired Electric Generating Units; footnote 17; http://www.epa.gov/ttn/atw/utility/revisedmercurytsd.pdf6

- 5

pollutant and the known and potential cum ulative public health and environmental effects of elemental and methylmercury in the environment when deciding whether to exercise its
discreti on under CAA section 11 2(d)(4). 8

6.4 Hg Deposition
Comment: A commenter (0041) indicated that 97 percent of future H g deposition in
North Carolina will come from out

- of

- state Hg emission sources. Given this finding, the

commenter (0041) concluded that any additional control measures offer limited environmental
benefit to further reduce Hg emissions from in

- state sources , and as such does not support the
BTF limit. Response to Comment: We are not finalizing the proposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners due to potential significant economic impacts associated with the costs of controls . Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners

. Refer to the preamble of the final rule for additional details

.

6.5 Hg UPL Calculation
Comment: One c ommenter (0042) disagree s with the EPA’s use of a high variability factor in setting the MACT standards for these pollutants as it is unsupported and results in a standard that is higher than appropriate. This commenter stated that the EPA’s use of the upper prediction limit (UPL) is unlawful and arbitrary. The commenter explained the UPL was remanded by the D.C. Circuit in 2013 due to the EPA’s interpretation of “average emissions limitation achieved by the best performing 12 percent ,” and that the EPA’s new rationale fails to clarify this issue . Also, a ccording to the commenter, the Court noted that the UPL produces an “apparently illogical result.” The comme nter asserts the UPL is the level EPA expects any “future” test by any source in the top 12 percent to “fall below” during 99 out of 100 performance tests and it is the level that a source “would be expected to meet a specified percent
of the time that the source is operating.” The commenter continued that the UPL is neither the required “average” nor even any measure of what units have actually “achieved.” The

8 See September 9, 2010 National Emission Standards for Hazardous Air Pollutants From the Portland Cement Manufacturing Industry and Standa rds of Performance for Portland Cement Plants; Final Rule , at 75 FR 54970

.6

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commenter further observed the average of the Hg emissions test data is lower than the
calculated UPL value. Lastly, t he commenter conclude s that the EPA is increasing the limit above the average of what data in the record show sources have actually achieved and, the resulting emission limits the EPA proposes to set are higher and weaker than the statute directs and that communities need to pr otect their health. The commenter conclude s that the EPA may not redefine what “average emission limitation” means when its meaning is clear nor may it distort the text “achieved” beyond its meaning. If the EPA believes test data it is using does not accur ately reflect what sources have achieved, the commenter states, then it should collect better test data. Response to Comment: As stated in the memorandum entitled “ Use of the Upper Prediction Limit for Calculating MACT Floors ” ( Docket ID No. EPA

- HQ

- OAR

- 201 0

- 0522

- 0007) (UPL memorandum), “ In the context of development of MACT floors, the UPL is a value,
calculated from a dataset , which identifies the average emissions level that a source or group of sources is meeting and would be expected to meet a specified percent of the time that the source is operating. That percent of time is based on the confidence level used in the UPL equation, as explained in more detail below. For a single best controlled emission source that serves as the
basis for a new source MAC T floor, the 99 percent UPL is the emissions level that the source would be predicted to be below during 99 out of 100 performance tests, including emissions tests conducted in the past, present, and future, based on the short term stack test data availabl e for that source. It is important to note that the UPL does not represent the worst emissions performance of the best performing units at any time, but rather the average level expected to have been achieved over time, as the first element of the UPL equa tion is the average of the
short

- term emissions test data from the best performing units. In other words, the 99 percent UPL is the level of emissions that we are 99 percent confident is achieved by the average source represented in a dataset (in the case of MACT standards, the dataset representing the performance of the best performers as specified in the CAA) over a long

- term period based on its previous, measured performance history as reflected in short

- term stack test data. ” Contrary to the commenter’s assertion, the NACWA court did not find the UPL to be an arbitrary approach, but simply asked for a better explanation from the Agency. T he UPL memorandum provides the explanation of what the UPL represents sought by the NACWA Court. It also explains why the
UPL is representative of the level of performance achieved by the best performing unit or units. The court did not state that the “average emissions limitation achieved by the best performing6

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12 percent” must be equal to the mean of the available data, as suggested by the commen ter, and in past decisions the C ourt has upheld that it is appropriate for EPA to account for variability when establishing numeric MACT standards

. See Mossville Environmental Action Now v. EPA , 370 F.3d 1232, 1241

- 42 (D.C. Cir. 2004).
We also refer the commenter to the proposal MACT floor memorandum, which is in the rulemaking docket. This memorandum provides a detailed discussion of the EPA’s authority to consider variability, especially given that MACT and other technology

- base d standards are necessarily derived from short term emissions test data and such data are not representative of the range of operating conditions that the best

- performing facilities face on a day

- to

- day basis. In statistical terms, each test produces a lim ited data sample, not a complete enumeration of the available data for performance of the unit over a long period of time. The EPA, therefore, often needs to adjust the short

- term data to account for these varying conditions in order to properly
estimate t hese sources’ performance over time. The types of variability that the EPA account s for
include variability between and within tests at the same unit as well as between units in the pool of “best performing units .” This memo also describes the EPA’s select ion of the UPL methodology to address such variability. In response to the concern over “apparently illogical result ,” EPA first notes that
commenters reference a court decision that addressed MACT standards for a different source category, which are not at issue in this rulemaking. Second, the commenter did not assert that the methodology resulted in an “apparently illog ical result” in this rulemaking as the court pointed out in NACWA. Rather, the commenter asserts that the methodology results in limits that are less stringent than they believe is required. Finally, the UPL methodology used to establish the
MACT standards referenced in the comment was not the same UPL methodology used to set the standards in today’s action. We note that the “apparently illogical result ,” from a different rulemaking, resulted from analysis of small datasets and the use of procedures that EP A no longer follows. We included in the docket a memo explaining how we adjusted the UPL methodology to address situations in which the Agency must establish MACT standards with
limited data . That memo, entitled Approach for Applying the Upper Predictive L imit to Limited Datasets ( Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522), provides an analysis of the use of the UPL for limited data sets and includes procedures to evaluate whether additional analyses beyond the use of the 99 percent UPL are needed. We also note th at the “apparently illogical results” questioned by the court will no longer occur provided the procedures laid out in our UP L6

- 8

memorandum and limited data sets memorandum are followed, as was done in this rule

. Accordingly, we believe that our use of the U PL, as specified in the above referenced memo, is
in accordance with recent Court decisions. Finally, t he EPA is tasked with setting standards using available data and, while we agree that more data is desirable, the standards that we proposed are based o n a reasonable amount of data that, while not perfect, provide sufficient information with which to develop standards that reasonably reflect the required levels of performance. EPA must rely on emission test methods that are available to the Agency and to sources. As described in the UPL memorandum, our standards reflect the average emission limitation achieved by the best source or sources as required under the statute.

6.6 HF Work Practice for Phosphate Rock Calciners
Comment: One commenter (0037) supported the HF work practices and stated they are consistent with their current phosphate rock calciner operations. Another commenter ( 0043 ), does not support the implementation of HF work practices, because the emissions were BDL, the
measured concentr ations were questionable, and HF cannot practicably be measured from the phosphate rock calciners. This commenter ( 0043 ), which is in the process of conducting studies on a future calciner, noted that preliminary results indicate a calcination temperature of at least 2000 degrees Fahrenheit is necessary for their phosphate rock calciner. This commenter ( 0043 ) also explained they are evaluating a flash calciner, which operates with a much shorter retention time than the fluidized bed calciners currently in o peration at another facility. A commenter ( 0043 ) does not agree that wet scrubbers should be required because their phosphate rock calciner will be located in a remote area where treatment and disposal options for scrubber liquors may not be available. Th e commenter ( 0043 ) has identified potential other solutions which can be as effective as wet scrubbers, and therefore recommended the EPA should allow for other control technologies with equivalent efficiencies.
A commenter (0042) 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 the EPA has not provided the determination and supporting evidence the Clean Air Act requires to set these stan dards instead of numeric limits, and that the EPA failed to satisfy the test it must meet to promulgate work practice standards “in lieu of” numeric emission standards set by CAA section 1 12(h). The commenter (0042) stated that not using the available6

- 9

emis sions data to set a floor limit is unlawful and arbitrary, even if the data are below the
detection limit. Response to Comments: This comment is addressed in the preamble of the final rule. W e are not fin alizing work practice standards for HF from phosphate rock calciners, as proposed. Instead, we are including a total fluoride emission limit for phosphate rock calciners in NESHAP subpart AA.7

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### 7.0 HF WORK PRACTICE STANDARDS FOR GYPSUM
DEWATERING STACKS AND COOL ING PONDS

7.1 Submergence Of Discharge Pipe
Comment : Three commenters (0037, 0039 , 0043 ) 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 submer ging 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 sipho n break. One of these commenters (0037) 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. Response to comment: W e 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

. Refer to the preamble of the final rule for addition al details.

7.2 Rim Ditch (Cell) Building Technique
Comment: Two commenters (0039, 0038) contended it is not feasible to minimize the stack surface area of gypsum stack ponds as a work practice to minimize fugitive HF emissions,
and another commenter ( 0043 ) be lieved the technique is generally implementable.
One commenter (0039) 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 s tack perimeter with flow directed along a ditch before the liquid flow is conveyed to the settling compartments.” Another commenter (0038) stated that minimizing the gypsum pond surface areas is not feasible in Florida, North Carolina, and Louisiana becaus e gypsum pond surface areas are optimized to provide annual evaporative water losses necessary to maintain zero water discharge.7

- 2

Response to Comment: W e believe that using the rim ditch technique over the lifespan of a gypsum dewatering stack will reduce t he surface area of the gypsum pond and thereby reduce fugitive HF emissions. Refer to the preamble of the final rule for additional details.

7.3 Wetting Of The Active Gypsum Stack
Comment: Four commenters (0037, 0039, 0038 , 0043 ) objected to the use of wetting of the active gypsum 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 (0043) 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 (0037) stated that using recycled water may actually increase fugitive emissions because HF resides prim arily in residual and make

- up waters used to transport the gypsum slurry to the gypsum dewatering stack. One commenter (0039) 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 (0043) illustrated the uncertainty of wetting of the active gypsum dewatering stack as a fu gitive 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). Response to Comment: W e are not adopting this proposed control measure in the NESHAP subpart AA final rule. Refer to the preamble of the final rule for additional details.

7.4 Application Of Slaked Lim e
Comment: One commenter (0039) 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 f

or effectiveness. On the contrary, another commenter (0043) 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. Response to Comment: We believe s laked lime can precipitate fluorides from gypsum dewatering stacks and cooling ponds, thus reducing the availability of fluorides in solution that7

- 3

c ould then be release d into the air during evaporation. Refer to the preamble of the final rule for
additional details.

7.5 Soil Caps And Vegetation
Comment: Three commenters (0039, 0038 , 0043 ) contended there is no evidence that applying soil caps and vegetati on to gypsum dewatering stacks reduce fugitive HF emissions.
Commenters (0039, 0038) 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 sl opes of the active gypsum dewatering stack up to 50 feet below the stack top. Some of
these commenters (0038, 0043) 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. Response to Comment: W e 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’ assertio n that applying soil caps and vegetation may not be an effective option for fugitive HF emissions control. Refer to the preamble of the final rule for
additional details.

7.6 Closure Of Gypsum Dewatering Stacks
Comment: Two commenters (0039 , 0043 ) requested th at the closure of a gypsum dewatering stack not be considered a fugitive HF emissions control technique. One of these

commenters (0039) 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. One commenter ( 0043 ) explained that some sta tes 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. Response to Comment: We disagree with commenters’ r equests 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 fugitive7

- 4

HF emissions because it permanent ly reduces the emissions from the greatest contributing

source. Refer to the preamble of the final rule for additional details.

7.7 Other Techniques
Comment: Three commenters (0037, 0038 , 0055 ) 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 of these

commen ters (0038) 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 to Comment: We are not including an option in the NESHAP subpart AA final rule, as commenters requested, that would provide a flexibility mechanism for facil ities 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.

7.8 Requirement To Use At Least Two Of The Control Measure s
Comment: One comment er (0038) requested that the EPA eliminate the “dual practice” approach for new sources. The commenter (0038) 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 ne w 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 (0043) 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 s ought 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

.7

- 5

Response to Comment: 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 describe s the list of options in the rule and avoids confusion with other CAA programs. Refer to the preamble of the final rule for additional details.

7.9 Gypsum Dewatering Stack Area To Phosphoric Acid Manufacturing Capacity Ratio
Comment: Several commenters (0037, 0039, 0038, 0043) 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 2 O 5 feed). The commenters claimed the use of flawed data and assump tions 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 an d 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 a rray 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 signific antly underestimated the number of acres at each facility that would need to be closed. One of these commenters (0038) asked whether a vertical expansion of an existing stack7

- 6

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 w ith production capacity. One of these commenters (0043) 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 rela tionship 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 (0038, 0043) 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 (0043) 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 (0038) 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 (0043) 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 (0039) 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 to Comment: W e are not adopting the proposed work practice that limits the size of active gypsum dewatering sta cks, which would have been applicable to facilities when new gypsum dewatering stacks are constructed

. Refer to the preamble of the final rule for
additional details

.7

- 7

7.10 Necessity or Justification of HF Work Practices
Comment: Three commenters (0037, 0038, 0039) 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 e missions from gypsum dewatering stacks and cooling ponds

. One of
these commenters (0038) 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 (0043) 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 (00 43) 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 reduc tions; (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. Commenters (0037, 0038, 0039) 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. These

c ommenters (0037, 0038, 0039) asserted that only two sources of information wer e 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 amoun t of uncertainty related to which specific control techniques are feasible and effective in reducing fugitive HF emissions. Response to Comment: This comment is addressed in the preamble of the final rule. In the preamble of the final rule we explain how e ach control measure is feasible and effective in reducing fugitive HF emissions.7

- 8

7.11 HF Work Practice For Gypsum Dewatering Stacks and Cooling Ponds Interfere With Other Regulatory Programs
Comment: One commenter (0037) contended that setting work practice st andards for gypsum dewatering stacks and cooling ponds under the NESHAP should be deferred until the EPA completes efforts under other regulatory programs. This commenter (0037) pointed out the EPA’s ongoing efforts to identify appropriate work practices a nd arrange for their implementation in connection with pending enforcement actions under other environmental programs. They claimed that the proposed regulation to establish new standards for gypsum dewatering stacks and cooling ponds could interfere with those efforts. This commenter stated that one of their facilities is planning to build a new gypsum dewatering stack under an Administrative Consent Order with EPA Region 4 pursuant to RCRA § 7003(a). This commenter
stated that the construction of the new gypsum dewatering stack could trigger the EPA’s Proposed Area Limitation and it would not be possible for the facility to comply because the facility could not transition any portion of its active gypsum dewatering stacks to meet the EPA’s proposed definit ion of a “closed gypsum dewatering stack” before commencing construction of the new gypsum stack. Another commenter (0038) suggested that the EPA should provide a mechanism for authorizing alternative work practices approved by the local/delegate permittin g authority; the commenter argued that absent such a flexibility mechanism, the NESHAP could conflict with other regulatory requirements and hamstring industry’s ability to adopt the most effective measures that work at specific sites. Response to Comment: We are adopting the proposed work practice standard that requires you to prepare, and operate in accordance with, a gypsum dewatering stack and cooling pond management plan . H owever, based on analysis of public comments , we are making some changes to the specific control techniques that we proposed as options in the plan for controlling fugitive HF emissions in an effort to provide additional clarity to facilities

. (In the final rule, the Agency is using the terminology “control measures” in lieu of the pr oposed terminology “control techniques” because it more accurately describes the list of options in the rule and avoids confusion with other CAA programs .) The Agency is also not adopting the proposed work practice that limits the size of active gypsum dew atering stacks which would have been applicable to facilities when new gypsum dewatering stacks are constructed ; therefore, the commenter’s concerns regarding the construction of a new gypsum dewatering stack are not7

- 9

applicable. Refer to the preamble of th e final rule for additional details of the work practice standards for gypsum dewatering stacks and cooling ponds included in the final rule.

7.12 Cooling Pond Considerations For HF Work Practice
Comment: One commenter (003 8 ) 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 dewate ring 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 (0037) requested that if EPA keeps cooling ponds a s 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.
This commenter 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 (0055) suggested other control measure options for reducing fug itive 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 pres sure 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 to Comment: We have included additional control measure options for reducing fugitiv e HF emissions from cooling ponds . Refer to the preamble of the final rule for
additional details

.8

- 1



### 8.0 TRANSLATION OF TOTAL FLUORIDE LIMITS TO HF LIMITS

8.1 Proposed HF Limits Are More Stringent Than Current Tot al Fluoride Limits
Comment: One commenter ( 0043 ) argued that the molecular weight difference between
total fluoride and HF is 11.1 percent; therefore, the current standards need to be increased by 11.1 percent to allow the scenario where 100 percent of total fluoride emissions could be HF. Similarly, another commenter (0037) pointed out that the proposed HF limits are more stringent
than the current total fluoride limits. Response to Comment: In light of the Agency’s decision to r emove EPA Method 320
fro m NESHAP subparts AA and BB (refer to preamble for final rule for further details), and subsequently retain total fluoride limits to the final rule, the calculation that we were to use to
translate the current total fluoride limit (lb total F/ton P 2 O 5 feed ) into an HF limit (lb HF/ ton
P 2 O 5 feed) is no longer relevant. However, t he Agency disagrees with th is commenter’s method for translating the current total fluoride limit to HF limits

. F rom a practical standpoint, it may
have been appropriate to stoichio metrically translate the current total fluoride limits (lbs total
F/ton P 2 O 5 feed) into HF limits (lbs HF/ ton P 2 O 5 feed) since the current standard uses total
fluoride as a surrogate for HF, and as such, the standard allows that 100 percent of all total
f luoride emissions could be HF. However, the 11.1 percent factor suggested by the commenter is not correct, but the HF limits could have been derived by multiplying the current total fluoride limits by 1.053 which is the HF molar equivalent to fluoride (i.e ., for every 20.01 lbmol HF/lb HF there is 18.9984 lbmol F/ lb F). Had the Agency decided to use this approach, the HF limit
would have account ed for the mass of hydrogen (H) that reacts with fluorine (F, or in this case total F) to produce HF.

8.2 Reliance On EPA Method 26A HF Emissions Test Data To Establish New
Standards Is In Error
Comment: One commenter (0038) stated that because the EPA did not upload the EPA Method 320 test data into the publicly

- available electronic docket for the rulemaking, it assumed that the EPA generally relied on the Method 26A data to establish the proposed standards; this

commenter a rgued that the inherent upward bias of the Method 26A data shows that it is inappropriate for setting new HF standards, and the reliance on HF emissions test data to establish new standards is in error. The commenter pointed out that based on the test data that the8

- 2

EPA collected from the CAA § 114 requests, HF emissions measured via Method 26A were substantially greater than TF emissions measured (for the same emissions points) via Method 13B in 21 of 37 cases. The commenter asserted that in light of the fu ndamental fact that HF should only be a fraction of TF emissions, use of the clearly upward

- biased HF data to set new standards will inherently lead to stricter standards than the current TF standards

. In addition, the commenter argued that at least 5 faci lities likely would be unable to achieve the proposed HF standards based on the available data. The commenter asserted that the EPA must provide a technical justification for its insistence on using Method 26A to establish standards for Subparts AA and BB, as well as its insistence on using Method 320 for purposes of HAP testing by regulated sources in the future. Response to Comment: The Agency disagrees with the commenter that EPA Method 320
test data is not publicly available in the docket for the rulemaking . All of the responses that the Agency received to the 2010 and 2014 CAA Section 114 surveys, including all test results, are
available under Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0032 , entitled: “S ection 114 Surveys on DVD: 2010 Section 114 Request s Sent to Facilities 2010 Section 114 Responses From Facilities 2014 Section 114 Requests Sent to Facilities 2014 Section 114 Responses From
Facilities .” Anyone can request a copy of this DVD from the docket office. The Agency also disagrees with the comme nter that EPA Method 26A data was used to establish the proposed HF standards. In 2010, the Agency requested fa cilities conduct HF emissions testing via EPA Method 26A from specific processes included in the Phosphoric Acid Manufacturing and Phosphate Fert ilizer Production source categories

. F acilities submitted results
of these tests to the EPA in the fall of 2010. The Agency determined that it needed additional data to evaluate HF emissions limits, and o n January 24, 2014, the EPA issued another CAA
secti on 114 survey and testing request to certain facilities in order to gather additional HF
emissions data from calciners and certain wet

- process phosphoric acid ( WPPA ) , SPA and Ammonium phosphate fertilizer ( APF ) lines using EPA Method 320

. It was the 2014 test results that the Agency used to conclude at proposal that moving to a form of the standard that requires
HF (the target HAP) to be measured ( but retain ed the same numeric values as the current total
fluoride standards ) would be achiev able by all facilities

. The 2010 and 2014 test results are
available in the docket for this action. However, in light of information provided by commenters, the Agency has determined that EPA Method 320 is not an appropriate test method for accurately meas uring HF emissions from process lines at these specific source categories due to8

- 3

the complex and often incomplete chemical reactions with silicon compounds in these sources. Accordingly, the Agency is not adopting the proposed HF standards. As a result of this
determination to not adopt the proposed HF standards , the Agency has retained the current total
fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HAP HF, rather than HF emission limits using EPA Met hod 320

. Refer to the preamble
of the final rule for additional details.

8.3 Total Fluoride Surrogate For HF
Comment: One commenter (0038) argued that t otal fluoride should remain the surrogate for HF under Subparts AA and BB, as measured by Method 13A or 13B. The commenter pointed out that since the EPA already has established a cl ear correlation between HF and t otal fluoride under Subparts AA and BB in prior rules, the EPA has a particularly high technical burden to reverse its position on this issue

. The commenter added that the courts “have clearly held that ‘EPA may use a surrogate to regulate hazardous pollutants if it is reasonable to do so’” based on a demonstrable “correlation” between a HAP and its surrogate, which EPA already has investigated, fou nd, and established by regulation in current Subparts AA and BB. The commenter also asserted that the EPA’s statement in the proposed rule at 79 Fed. Reg. at 66,545 actually reaffirms the close correlation between t otal fluoride and HF, and supports the co ntinued surrogacy relationship between t otal fluoride and HF. The commenter requested the EPA explain its technical basis for abandoning the longstanding t otal fluoride surrogate for HF. The commenter argued that the EPA has established similar surrogacy r elationships to measure HAPs in other regulated source categories in the past, citing the November 25, 2011 Proposed National Emissions Standards for Hazardous Air Pollutants: Mineral Wool Production and Wool Fiberglass Manufacturing.
Two commenters (0039, 0038) support the EPA allowing facilities to comply with
current total fluoride standards using Method 13A or 13B as an alternative to complying with the proposed HF standard. In allowing this alternative compliance mechanism, one commenter (0039) added t hat the standard should continue to apply to total fluoride rather than HF. The
other commenter (0038) requested that the EPA extend this option to Subpart BB. Response to Comment: T he Agency is not adopting the proposed HF standards. As a
result of this d etermination to not adopt the proposed HF standards , the Agency has retained the
current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B9

- 4

as a surrogate for the HAP HF, rather than HF emission limits using EPA Method 320

. Refer to the preamble of the final rule for additional details.



### 9.0 MEASUREMENT, MONITORING, AND REPORTING REQUIREMENTS

9.1 Quantifying HF Emissions From Gypsum and Cooling Waters
Comment: One commenter ( 0043 ) stated that the measurement of HF emissions from the phosphoric acid process is difficult because the ratio of fluoride to silica has a great influence on the concentration of HF present in phosphoric acid process streams, including gypsum and cooling waters. The commenter contended that the concentratio n of HF in gypsum waters is expected to be less than 10% for their facilities due to this ratio and provided a detailed review of this topic in an appendix to their comment. In addition, the commenter argued that the differences in chemistry (such as fluor ide to Si ratio) explain why there are such wide measurements in fluoride emissions from gypsum ponds in general; the commenter provided a review of studies in an appendix to their comment that shows estimates from 0.012 to 18.3 pounds of fluoride per wett ed acre per day. The commenter also argued that the percentage of fluoride air emissions that are HF varies depending on such factors as the concentration of HF in the process/gypsum water, the season of the year, and whether the gypsum surface is wet or d ry. The commenter cited a paper by Lee and Koogler that provides an overview of gypsum pond fluoride chemistry and also discusses technical issues associated with measuring fluoride emissions from such ponds. The commenter stated that the fluoride concentr ations in a gypsum pond tend to stabilize over time, pond chemistry is also pH dependent, and the volatilization of HF is a function of the HF concentration in the gypsum water, the temperature of the gypsum water, and wind speed. Response to Comment: T he Agency is not adopting the proposed HF standards. As a
result of this determination to not adopt the proposed HF standards , the Agency has retained the
current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B

as a surro gate for the HAP HF, rather than HF emission limits using EPA Method 320

. Refer to the preamble of the final rule for additional details.9

- 5

9.2 EPA Method 320
Comment: Four commenters (0037, 0039, 0038 , 0043 ) opposed the use of EPA Method 320 to test for HF, and supported the retention of a total fluorides compliance standard and associated testing using Method 13A or 13B. These commenters argued that EPA Method 320 leads to unreliable and unrepresentative res ults because some reactive fluoride compound s in the exhaust may form HF in the sampling train

. One of these commenters (0038) contended that EPA did not explain anywhere in the docket why EPA Method 320 is achievable, effective, or scientifically preferab le, nor why EPA plans to deviate from using TF as a surrogate, and EPA
Method 13A or 13B.
One commenter (0038) explained that complex reactions leading to fluoride emissions occur not only in the processing units located at Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories, but also in the scrubber systems designed to remove fluorides from the stack gases. The commenter (0038) stated that these reactions result in a mix of gaseous, aerosol, and particle bound fluorides (all three phases) in the stack gas, in the form of compounds like SiF 4 , various fluorosilicate aerosols and/or droplets, ammonium fluoride, ammonium bifluoride, and/or ammonium fluorosilicate. This commenter (0038) argued that these compounds have the potentia l to be captured in a Method 320 sampling train, biasing or interfering with the results of the sampling. The commenter cited technical feedback on this topic that it had already provided the EPA (and also provided in an attachment to their comment)

. Anoth er commenter (0039) submitted information explaining how it is not only impossible to eliminate interactions using EPA Method 320 to test for HF, but it is also expected to be extremely difficult to accurately and repeatedly quantify those interactions

. Tw o commenters (0038 , 0043 ) stated that the sampling conducted in response to the EPA’s information requests
demonstrated that SiF 4 readily reacts with water vapor in the stack gas producing HF and silicon hydroxide; and one of these commenters (0038) provid ed information showing that this reaction is dependent on temperature, moisture, and residence time in the sampling system.
Two commenters (0038 , 0043 ) listed technical issues that they encountered during EPA Method 320 sampling that they conducted in resp onse to EPA’s information requests, including, but not limited to: short shelf life and high expense of HF calibration gases, measuring HF at low concentrations, HF spike gas would rapidly corroded sample tube materials, sample pump clogging, transporting a representative sample of stack gas containing only native HF (i.e., the HF actually present in the stack gas and not artifact HF created by the decomposition or9

- 6

conversion of other fluoride species), crane/platform construction to hold heavy equipment, a nd obtaining accurate q uality a ssurance spike results; one of these commenters (0038) argued that these problems, and others would persist if EPA Method 320 becomes a mandatory or optional approach for testing. One of these commenters ( 0043 ) suggested putt ing a NaOH scrubber solution just upstream of the sample pump to prevent deterioration in performance of the sample pump. The other commenter (0038) recommended certain procedures be followed when conducting EPA Method 320 at Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories; however, also cautioned that their recommendations would not resolve all of the inherent prob lems with the sampling and analysis process. Response to Comment: T he Agency is not adopting the proposed HF standards. As a
result of this determination to not adopt the proposed HF standards , the Agency has retained the
current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HAP HF, rather than HF emission limits using EPA Method 320

. Refer to the preamble of the final rule for additional details.

9.3 EPA Method 26A
Comment: One commenter (0038) ar gued that EPA Method 26A is fundamentally flawed for purposes of evaluating possible HF emissions from Subpart AA and BB regulated sources; the commenter explained why test limitations and interference render HF data collected via
Method 26A unreliable

. Th e commenter c ited technical feedback on this topic that it had already provided the EPA ( and also provided in an attachment to their comment )

. Response to Comment: The Agency disagrees with the commenter that the 2010 EPA
Method 26A test results were used to evaluate HF emissions from the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories . In 2010, the Agency requested fa cilities cond uct HF emissions testing via EPA Method 26A from specific processes
included in the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories

. F acilities submitted results of these tests to the EPA in the fall of 2010. The Agency determined that it needed additional data to evaluate HF emissions limits, and o n January 24, 2014, the EPA issued another CAA section 114 survey and testing request to certain facilities in order to gather additional HF emissions data from calciners and c ertain WPPA, SPA and APF
lines using EPA Method 320

. It was the 2014 test results that the Agency used to conclude at proposal that moving to a form of the standard that requires HF (the target HAP) to be measured9

- 7

( but retain the same numeric values as the current total fluoride standards ) would be achievable by all facilities

. The 2010 and 2014 test results are available in the docket for this action. However, in light of information provided by commenters, the Agency has determined that EPA
Method 320 is not an appropriate test method for accurately measuring HF emissions from process lines at these specific source categories due to the complex and often incomplete chemical reactions with silicon compounds in these sources. Accordingly, the Agency is not

a dopting the proposed HF standards. As a result of this determination to not adopt the proposed
HF standards , the Agency has retained the current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HA P HF, rather than HF emission limits using EPA Method 320

. Refer to the preamble of the final rule for additional
details.

9.4 FTIR HF CEMS
Comment: Three commenters (0037, 0038 , 0043 ) oppose the option to use f ourier transform infrared spectroscopy ( FTIR ) HF c ontinuous emissions monitoring system ( CEMS ) as a continuous monitoring compliance approach for HF at Subpart AA and BB affected sources. These commenters cited EPA’s technical memorandum “Approach for Hydrogen Fluoride Continuous Emission Monitoring and Compliance Determination with EPA Method 320 ,” and argued that the option to use FTIR HF CEMS exceeds the capabilities of existing technology, there are no details on the required methods to implement such a system, there are no known
field demonstrations of this type of system, and the option has not been proven

. One of these commenters (0037) stated that while FTIR HF CEMS may have the capability to reliably perform to PS

- 18 specifications, the cost of demonstration will be significant and lengthy. This

c ommenter (0037) pointed out that it took two to four years for the National Institute of Standards and Technology to generate reliable HCl calibration standards. Another of these

commenters (0038) stated that their primary concern with FTIR HF CEMS as a co ntinuous monitoring compliance approach for HF at Subpart AA and BB affected sources is the chemistry of the gas matrix in the proposed affected sources; the chemistry renders HF CEMS impractical, if not impossible. Citing the major problems encountered in the EPA Method 320 sampling undertaken to respond to EPA’s 2014 information request, this commenter (0038) argued that the technical challenges to accurately measure HF continuously cannot be addressed by any available EPA method nor certified by any EPA performance specification. This commenter9

- 8

(0038) provided additional details describing the known and predicted limitations of measuring HF emissions using HF CEMS for the affected sources.
A commenters (0042) contended that the EPA must consider requiring continuous HF emission monitoring before finalizing the proposal. The commenter (0042) pointed out that there
is a HF sensor (suitable for 0

- 10 parts per million ( ppm ) monitoring range and a 0.1 ppm resolution) available for the Ultima X Series Gas Monito rs. Response to Comment: T he Agency is not adopting the proposed HF standards. As a
result of this determination to not adopt the proposed HF standards , the Agency has retained the
current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HAP HF, rather than HF emission limits using EPA Method 320

. Refer to the preamble of the final rule for additional details.

9.5 Pressure Drop Across Absorber
Comment: Three commenters (0039, 0038 , 0043 ) requested t he EPA delete the requirement that pressure drop across an absorber must be greater than 5 inches of water in order to use the option of measuring pressure drop as an operating parameter. These commenters contended that the EPA has not articulated any basi s for the requirement. These commenters provided data demonstrating that units operate in compliance with the emission standards when the pressure drop across an absorber is less than 5 inches of water. One of these commenters ( 0043 ) expressed safety conce rns associated with when operating scrubbers at higher range pressure drop settings, citing one of its facilities has experienced the entrainment of moisture within the absorbing tower when operating at pressure drops in excess of 8 inches of water, and

an other of its facilities experienced the buildup of excessive fumes on the digester floor when operating the digester scrubber as high as 6 inches of water. Response to Comment: We are not revising the final rule based on this comment. The Agency maintains its determination that pressure drop is not an appropriate monitoring parameter for absorbers that do not use the energy from the inlet gas to increase contact between the gas and liquid in the absorber

. However, the Agency has made several changes to the absorber monitoring requirements in the final rule. Refer to the preamble of the final rule for
additional details.9

- 9

9.6 Absorber Monitoring Options
Comment: Three commenters (0039, 0038 , 0043 ) called attention to the options of either measuring (1) the temper ature at the wet scrubber gas stream outlet and pressure at the liquid inlet of the absorber, or (2) the temperature at the scrubber gas stream outlet and scrubber gas
stream inlet. One of these commenters ( 0043 ) said that they do not believe monitoring gas temperature in locations of large ambient temperature ranges would provide accurate monitoring of the absorbers performance. The commenter argued that temperature and pressure probes would be very susceptible t o scaling issues

. In addition, this commenter ( 0043 ) contended that liquid inlet pressure does not provide any additional monitoring of the absorber performance, since the inlet liquid flow rate is already measured and monitored. Another commenter (0039)

c ontended that the EPA has not provided any data or analysis to show that there is a correlation between temperature and emissions; the commenter stated that they were not aware of any data suggesting a relationship between exit temperature and emissions, o r that monitoring temperature
difference across an absorber would be effective. One of these commenters (0038) argued that they were not in a position to evaluate the difficulties associated with performing the associated monitoring and establishing the re quisite operating ranges. Response to Comment: The Agency has made several changes to the absorber monitoring requirements in the final rule based on this comment. Refer to the preamble of the final rule for
additional details.

9.7 Acceptable Range From Baseli ne Average Value
Comment: One commenter (0039) requested that the EPA revise §63.625(d)(1)(ii)(B) to have similar wording to §63.625(d)(1)(ii)(A), in which the allowable parametric limits may encompass up to +/

- 20% of the of the baseline average values f or the series of tests used under this option; that is, the parametric limit may extend

- 20% below the lowest baseline average and up to +20% above the highest baseline average from the series of performance tests used for this option. Response to Comment: The Agency determined that it is not necessary to revise §63.625(d)(1)(ii)(B) to allow for a ±20 percent operating margin, as this commenter requests,
because this provision already allows for a source to establish an operating limit range for a
control d evice without having to apply an operating margin, such as ±20 percent

. Refer to the preamble of the final rule for additional details.9

- 10

9.8 Operating Range Established From A Previous Test
Comment: One commenter ( 0043 ) stated that §63.607(a) and §63.627(a) is somewhat ambiguous, tending to suggest that affected facilities would be immediately required to implement new equipment operating ranges following a source test, even if operating conditions from previous source tests demonstrated compliance with fluoride emission standards. The commenter argued that there is no reason that a new performance test at a new operating range should invalidate a previous performance test at a different operating range. Response to Comment: The Agency has clarified this provisio n in the final rule at §63.607(a) and §63.627(a) that d uring 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 change d based on data collected during the most recent performance test

. Refer to the preamble
of the final rule for additional details.

9.9 Approving Operating Ranges
Comment: Three commenters (0037, 0038, 0039) support the EPA’s proposal to eliminate the requirement that facilities may not implement new operating parameter ranges until
the Administrator h as approved them, or 30 days have passed since submission of the performance test results. However, two of these commenters (0039, 0038) pointed out that the EPA did not make the same allowance in §63.625(d)(1)(ii)(B), where a series of tests (potentially including historical tests) are used to establish an operating range. The commenter (0038) pointed out that §63.605(d)(1)(iii)(B) and §63.625(d)(1)(ii)(B), as proposed, do not provide the
30

- day default period for the effectiveness of the new ranges if the EPA Administrator does not act; therefore, as currently set forth in the proposed rule, sources will be left in limbo waiting for the EPA Administrator to respond before they can implement new ranges. The commenter (0038) suggested that the EPA revise the proposed regulatory language to require submission of the new ranges to EPA, but delete the requirement to request and obtain EPA’s approval of the new ranges. Similarly, another commenter ( 0043 ) requested the EPA clarify the process for establishing new equipment operating ranges following source performance testing. This commenter contended that facilities should have the ability to update operating parameters if9

- 11

they desire based on source testing, and the facility should be required to submit the new r anges, but not be required to obtain EPA’s approval of the new ranges. In addition, the commenter (0038) requested that the EPA clarify how revising the proposed regulatory language to require submission of the new ranges to the EPA, but deleting the requi rement to request and obtain EPA’s approval of the new ranges, will affect possible obligations to undertake permit modifications of Title V permits under 40 C.F.R. Part 70. This commenter stated that such administrative processes are not fully anticipated in the p roposed

r ule

. Response to Comment: T he requirements at §63.605(d)(1)(iii)(B) and §63.625(d)(1)(ii)(B) have been revised in the final rule, as the commenter requests, to remove the requirement that facilities must request and obtain approval of the Administrator for changing operating limits. Refer to the preamble of the final rule for additional details.

9.10 Maximum Representative Operating Conditions
Comment: One commenter ( 0043 ) requested the EPA clarify §63.606(d) and §63.626(d) as to whether “maximum representative operating conditions” apply solely to the pollution control equipment or includes the manufacturing process equipment. The commenter also requested EPA clarify wheth er these conditions only pertain to items within the operator ’ s control such as temperature, fan speed, etc. or whether it would also include conditions inherent to the manufacturing process such as variation in quality of feed stock materials. The comment er pointed out that the “maximum representative operating conditions” would not generate “normal operating ranges” required for administrator approval in §63.607(a) and §63.627(a). The commenter suggested that the EPA consider replacing the maximum represe ntative operating conditions with language similar to Idaho air rule for “worst

- case normal conditions” at IDAPA 58.01.01.157.2(a). Another commenter (0037) noted the changes in the language establishing the operational requirements for stack testing; this commenter identified these changes as non

- substantive with regard to current testing protocols. Response to Comment: In an effort to address the commenter’s request to clarify what we mean by “maximum representative operating conditions ,” the Agency has r evised the terminology in the final rule at §63.60 6 ( d ) and §63.62 6 ( d ) to align with the Clean Air Act National Stack Testing Guidance that was issued on April 27, 2009

. In this guidance, EPA9

- 12

clarified that performance tests should be performed under those representative (normal) conditions that: (1) represent the range of combined process and control measure conditions under which the facility expects to operate (regardless of the frequency of the conditions); and (2) are likely to most challenge the emissi ons control measures of the facility with regard to meeting the applicable emission standards, but without creating an unsafe condition. Furthermore, EPA stated in the guidance that “the test plan should generally include use of fuel, raw materials, and ot her process/control equipment that the facility expects to use during future operations that would present the greatest challenge in meeting applicable emissions standards. To demonstrate the facility’s ability to meet concentration standards and emissions rate standards, for example, the facility generally should use the fuel or raw materials that it expects to use and that have the highest emissions potential for the regulated pollutant(s) being tested.” Because of this guidance, the Agency has determined that it is not necessary to use language
similar to the Idaho air rule as suggested by the commenter

.

9.11 Performance Test Frequency
Comment: One commenter (0039) stated that the EPA changed the frequency of performance testing in the proposed §63.606 and §63.626(b) from the current standard of "once per annum" (i.e., once per calendar year) to "annual" and "no more than 13 months after the date the previous perfor mance test was conducted." The commenter argued that this change could create significant scheduling difficulties where a unit is shutdown for maintenance for other reasons within the proposed test window. The commenter requested that the EPA maintain the existing annual testing schedule , and argued that the EPA has not provided a reasonable justification to change it

. Response to Comment: The Agency agrees with the commenter to retain the existing annual testing schedule, and has revised §63.606 (b) and §63.626(b) in the final rule. However, instead of using the phrase “once per annum” in the final rule, as the commenter suggests, the Agency has used the phrase “once per calendar year” for clarity.

9.12 Condenser Monitoring
Comment: One commenter (0039) s tated that the rule does not define the term “condensers” but Table 3 of the proposed Subpart AA requires the installation of a continuous parameter monitoring system (CPMS) to measure stack exit gas temperatures for "condensers."9

- 13

Commenter requested meani ngful opportunity to comment due to lack of understanding of the EPA’s intent regarding condensers. Response to Comment: T he Agency is not adopting the proposed monitoring requirements for condensers in Table 3 and 4 of Subpart AA; therefore, we are not defining the term “condenser” in the final rule. After further review, we determined that condensers are not used as control devices in the phosphoric acid manufacturing source category.10

- 1



### 10.0 COMPLIANCE DATES AND FREQUENCY OF PERFORMANCE TESTS

10.1 Compliance Dates For Newly Regulated Sources
Comment: Two commenters (0037, 0038) requested additional time for facilities to come into compliance with the expanded scope of the NESHAP which will capture newly regulat ed
sources. One commenter (0038) stated that there is no time allotted for industry to design, procure, and install equipment to ensure emissions from these newly regulated sources are within the proscribed standards. One commenter (0037) requested a three

- ye ar period for newly covered equipment to be controlled and tested. The commenter argued that current emission limits were established without considering emission s from newly covered equipment. The commenter specifically refers to the PCS Phosphate Aurora facility and the cost of new control devices installed at this location. The commenter alleged that failure to consider newly covered equipment into the proposed rule brings the validity of the MACT floor into question. This
commenter also asserted that th e proposed one

- year compliance period to prepare, and operate in accordance with, a management plan for each existing gypsum dewatering stack or cooling pond, at 40 C.F.R. § 63.602(d), does not allow enough time to evaluate, select, plan for, and implement the appropriate practice(s). The commenter requested existing facilities be given at least two years to comply with these proposed work practice standards. Additionally, one of these commenter s (0038) requested the EPA provide a clear time period to phase in the effect of emission limits at oxidation reactors, as well as other components of process lines for which EPA has proposed definitional changes. The commenter stated that it would not be possible to meet t otal fluoride limits at all oxidation reactor s at the moment the EPA publishes the rule. The commenter argued that facilities either would have to shutdown to avoid immediate non

- compliance (and thereby incur the costs of production downtime and restart), or place themselves in non

- compliance by cont inuing to operate (and potentially incur costs, or worse, subject themselves to enforcement proceedings by EPA or other agencies)). Similarly, another commenter ( 0043 ) said it may need two years or more to comply with the proposed definition for WPPA and S PA plants that includes clarifiers and deflourination systems.10

- 2

Response to Comment: We disagree with the commenter that a one

- year compliance period to prepare, and operate in accordance with a management plan for each existing gypsum
de watering stack or cooling pond, does not allow enough time to evaluate, select, plan for, and implement the appropriate practice(s). As we explain in the preamble to the final rule, we believe
the list of control measure options is exhaustive enough that a facility has a nu mber of options for selecting a control measure that would be feasible for their particular operations. W e assume that facilities would choose the lowest cost option, and that all facilities are using at least one of
the control measure option s already . In addition, we’ve revised the management plan in response to comments, and believe this list to represent best practices known to industry and the Agency. The Agency has made considerable effort 9 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 facilities that do not use a rim ditch (cell) building technique

. Also, we are not including clarifiers and defluorination processes in the WPPA process
line definition of the final rule (refer to the preamble of the final rule for additional details); therefore, the commenters’ request to include additional time for facilities to come into compliance with the se proposed changes are not applicable. However, we are adopting the proposed superphosphoric acid process line definition in the final rul e to include oxidation reactors (refer to t he preamble of the final rule for additional details), and we do agree that it would not be possible to meet t otal fluoride limits at all oxidation reactors at the moment the EPA publishes the rule. As we explain in the preamble to the final rule, based on the information we received, with the exception of possibly one facility, we determined that it would not be necessary for facilities to upgrade existing control systems, or to install a control system , to comply with the emission limit. Therefore, we bel ieve a one year lead time is adequate and are including a requirement in the final rule that facilities must include emissions from oxidation

9 S ee 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 Mosa ic Plant City and Mosaic New Wales, March 4, 2015

. ”10

- 3

reactors , when determining compliance with the total fluoride limits for superphosphoric acid process line s , no la ter than one year after the effective date of th e rule.

10.2 Compliance Dates For Absorber Monitoring
Comment: One commenter ( 0043 ) stated it would need a minimum of 16 months to comply with the proposed monitoring options for absorbers that are not allowed, by the proposed rule, to use the option of measuring pressure drop as an operating parameter (since the pressure drop across an absorber must be greater than 5 inches of water). The commenter stated that it currently does not have the equipment installed to monitor absorber liquid and gas flow, gas stream inlet/outlet pressure, gas stream inlet/outlet temperature, or liquid inlet p ressure. Response to Comment: The Agency has made changes to the monitoring options for absorbers since proposal based on comments received (refer to the preamble of the final rule for additional details). Based on the changes made since proposal, t he Agen cy believes the cost to implement these finalized monitoring requirements is minimal for facilities. For low

- energy absorbers, we are allowing the gas stream be measured by either measuring the gas stream flow at the absorber inlet; or using the design blo wer capacity, with appropriate adjustments for pressure drop. Therefore, facilities would not need to purchase new equipment to measure gas flow at the inlet of the absorber since they may choose to use design blower capacity. Furthermore, we are not requi ring any new monitoring for high

- energy absorbers; therefore, these facilities are already equipped to monitor as required in the final rule.

10.3 Compliance Dates For Fabric Filter Monitoring
Comment: One commenter ( 0043 ) stated it would need a minimum of one year to comply with the proposed requirement that a fabric filter must be equipped with a bag leak detection system installed, calibrated, and maintained. The commenter stated that it currently does not have a bag leak detection system installed. Response to Comment: Agency agrees with the commenter, and has revised the final rule to allow one year for owners and operators to comply with the requirement to install, calibrate,
and maintain a bag leak detection system on a fabric filter

.

10.4 Compliance Dates For Stack Testing
Comment: One commenter ( 0043 ) stated for one of its facilities, it would need a minimum of 16 months to comply with the proposed requirements at 40 C.F.R. 63.606(a) and10

- 4

63.626(a) that you must stack test and demonstrate compliance within 1 ye ar of publication. The commenter stated that if the rule requires facility modification, 1 year may not be adequate to meet requirement. Similarly, the commenter pointed out that it may need 2 years or more to comply with the testing because one of its fac ilities would need to install equipment to segregate emissions to determine emissions compliance. Response to Comment: T he Agency is not adopting the proposed HF standards. As a
result of this determination to not adopt the proposed HF standards , the Agency has retained the
current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HAP HF, rather than HF emission limits using EPA Method 3 20

. Therefore, the commenters’ request to include additional time for facilities to come into compliance with the proposed performance testing is not applicable. Refer to the preamble of the
final rule for additional details.11

- 1



### 11.0 APPLICABILITY, DEFINITIONS, AN D TERMINOLOGY

11.1 Expanded Scope Of Process Lines
Comment : One commenter (0038) stated that the EPA has introduced ambiguity and vagueness with its definition of a generic “process line” that includes “all equipment associated with the production of any grade or purity of a phosphoric acid product including emission control equipment.” The commenter asserted that under this expansive definition, every hypothetical fugitive emission source would have to be accounted for in determining compliance. The commenter e xplained that the EPA has not collected emission data from “all equipment” nor provided guidance on estimating emissions for such sources in order to allow entities with process lines to demonstrate compliance. The commenter stressed the “process line”
def inition, as it currently stands, could include a wash plant that prepares phosphate ore or product storage tanks due to these sources being considered “associated” with production and thus subject to the proposed NESHAP. Response to Comment: This comment i s addressed in the preamble of the final rule. The Agency agrees with the commenter that it is not necessary to include the generic “process line” definition, and has removed it from the NESHAP subpart AA final rule. This definition did not provide additio nal clarity to facilities, and it was not our intent to include emissions from “all equipment” that is “associated” with phosphoric acid production for compliance determinations. Specific definitions are provided for WPPA process line, SPA process line, an d PPA process line and, therefore, enough specificity is already provided in the rule.

11.2 Clarification To Oxidation Reactors Included In SPA Process Lines
Comment: Three commenters (0037, 0038 , 0043 ) remarked that the proposed definition phosphoric acid process lines to include oxidation reactors is problematic and goes beyond clarification. These three commenters requested that EPA develop much more specific language or provide a clear technical basi s under the CAA because any equipment that was not expressly included in EPA’s MACT floor calculations should not be included in the proposed definition.
Two commenters (0037, 0038) mentioned that the Applicability Clarifications Memo captured four facili ties, but it was not clear whether the PCS Aurora facility was included in the count. The commenters stated that the oxidation step at this facility is carried out in agitated tanks that do not have any emissions control, and the emissions from the oxidati on step are not11

- 2

included in their annual performance testing (when demonstrating compliance with the current total fluoride limits ). The commenters said that it was not clear whether this oxidation step involves an “oxidation reactor” as proposed; and if i t does, the commenters argued that the EPA has not considered additional costs imposed by including “any equipment that uses an oxidizing agent to treat phosphoric acid” within the scope of the NESHAP at 40 CFR Part 63 , Subpart AA. Response to comment: The Agency is adopting clarifications for oxidation reactors in NESHAP subpart AA . Refer to the preamble of the final rule for additional discussion regarding the applicability of oxidation reactors in the final rule.

11.3 Clarifications To Clarifiers And Defluori nation Systems Included In WPPA Process
Lines
Comment: Four commenters (0037, 0039, 0038 , 0043 ) oppose the proposed expanded
definition of "wet

- process phosphoric acid line" to include "clarifiers" and "defluorination
processes ." These commenter s stated th at the proposed revisions have the potential to pull in several “defluorination processes ” and “clarifiers” that are not subject to the current rule (e.g., animal feed phosphate production operations that have traditionally been outside the scope of
this s ubpart). These commenters argued that any unit operation that conducts evaporation or concentrates phosphoric acid will have the effect of defluorinating to some extent. One of these commenters (0037) stated that they have a desulfation process at one of t heir facilities that reduces fluorides; the commenter also said that this facility’s WPPA process line has several filter product / evaporator feed tanks and evaporator product tanks that could potentially be deemed clarifiers, and thus be pulled into the proposed rule. Another of these commenters (0039) argued that it is not logical to include clarifier and defluorination systems in the definition because they operate independently of process lines, and are often operated when feed is not put into process lines (and so are not a process line manufacturing phosphoric acid by reacting phosphate rock and acid). This commenter (0039) added that clarifiers often operate more like tanks than process equipment and are not routinely emptied; and emissions from clar ifiers are not a function of phosphate feed material to the reactor. The commenter (0039) stated that the addition of clarifiers will require significant facility modifications to accommodate emissions testing because although some clarifiers are evacuated to WPPA scrubbers, others are not; and even though some clarifiers have independent evacuation and scrubbing systems, other clarifiers have no evacuation and scrubbing systems. Th e commenter ( 0043 ) also stated that one of their11

- 3

facilities contains clarifiers that are not source tes ted or vented to a web scrubber

. This

commenter ( 0043 ) also stated that it was not possible for one of their facilities to determine whether they meet the proposed standard for a WPPA process line that includes d efluorination
processes because their defluorination units are not only integrated with their WPPA process, but
also with processes that do not meet the definition of WPPA lines. The commenter (0039) added
that defluorination processes and clarifiers are o ften subject to separate emissions control requirements in their Title V permits.
Two commenters (0039, 0038) stated that since the original rule was adopted, the definition of “wet

- process phosphoric line” has not been interpreted to extend or apply to
cl arifiers or defluorination processes . One of these commenters (0039) claimed that the only rationale the EPA provides is that the rules were "initially intended" to cover these sources, but argued that neither the original proposal, nor the original final rule mention the term "clarifier" or
"defluorination process ." The commenters insisted that the EPA conduct CAA § 112(d)(2) or 112(d)(3) analyses for these new affected units. If the EPA conducts these analyses, and decide to expand the definition of "wet

- process phosphoric acid line" to include "clarifiers" and
"defluorination processes ,” the commenter (0038) suggested that the definition exclude units that partially clarify or defluorinate an in

- process stream incidentally. Response to comment: This comm ent is addressed in the preamble of the final rule. The Agency is not adopting the proposed clarifications for defluorination units and clarifiers.

11.4 Clarification To Granular Triple Superphosphate Fertilizer Process Line
Comment: One commenter ( 0043 ) clarif ied that based on the current proposed definition of granular triple superphosphate fertilized process line in §63.621 they do not manufacture “granular triple superphosphate” and are thus not subject to Subpart BB requirements for their 0

- 45

- 0 product . Th e commenter elaborated that the production of their 0

- 45

- 0 granular fertilizer does not involve reacting phosphoric acid with phosphate rock and does not require a multi

- day curing phase. Response to comment: We thank the commenter for this clarification

.

11.5 Clarification To Phosphate Fertilizer Process Line Or Production Plant

Comment: Four commenters (0037, 0039, 0038 , 0043 ) disapproved of the proposed expansion of the applicability provision for diammonium process lines (DAP) and11

- 4

monoammonium process lines (MAP) in 40 CFR §63.620(b)(1) to include “any process line that produces a reaction product of ammonia and phosphoric acid.” One commenter (0037) asserted that the expanded language could include production of non

- granular produc ts that were in existence since the original NESHAP but not regulated by it and EPA provided no basis for expansion of applicability to bring in these processes now. Commenters (0039, 0038) reiterated that the proposed applicability provision for DAP and M AP process lines was vague and overbroad and would inadvertently regulate any process that combines ammonia and phosphoric acid regardless of the end

- product or purpose of facility. One commenter ( 0043 ) recommended a change in the definition to clarify tha t Subpart BB applies specifically to solid, granulated phosphate products to avoid inclusion of liquid fertilizer products in the proposed rule. Additionally, the commenter (0039) pointed out that the definition of DAP and MAP process lines as proposed in Section 63.621 is being expanded to include cooling towers and requests that cooling towers be excluded from the rule. The commenter asserted that cooling towers are not considered point sources subject to emissions testing and emissions cannot be
effectiv ely measured. The commenter added that cooling towers may be used to ancillary operations like air conditioning systems that would not have emissions. Response to comment : We are revising the definitions of “p hosphate fertilizer process
line ” and “p hosphat e fertilizer production plant ” in the final rule at §63. 621 to reference granular phosphate fertilizer . Also, the definitions of p hosphate fertilizer process line and p hosphate fertilizer production plant were defined together at proposal (p hosphate fertil izer process line or production plant ), but are defined separately in the finalized rule for clarity

. Refer to the preamble of the final rule for additional discussion about the applicability provision for DAP and MAP process lines

. Furthermore, we agree with the commenter that the definition of DAP and MAP process
lines in § 63.621 should not be expanded to include cooling towers . We proposed this change to correspond with the proposed condition in NESHAP subpart BB that exclude s the use of evaporative cooling towers for any liquid effluent from any wet scrubbing device installed to control HF emissions from process equipment . In lieu of the proposed definition of DAP and MAP process lines to include evaporative cooling towers , we are finalizing an applicability provision in § 63.620(b)(1) to include “evaporative cooling tower” as an affected source at a phosphate fertilizer production plant, and added a definition of “evaporative cooling tower” to § 63.621 that reflects the same definiti on used in NESHAP subpart AA. For the same reasons, we11

- 5

also removed “cooling towers” from the definition of “g ranular triple superphosphate process
line ” in § 63.621

.

11.6 Clarification To Purified Phosphoric Acid
Comment : One commenter ( 0043 ) requested that the proposed definition of a purified phosphoric acid (PPA) plant in 40 CFR 63.601 be modified to contain clarification regarding solvent extraction. The commenter elaborated that they operate a PPA process which does not use solvent extraction or any equipme nt associated with solvent extraction, but rather a proprietary processes which utilizes physical methods to remove impurities. The commenter alleged that therefore the PPA process at their facility does not meet the definition of a PPA line
and is not sub

ject to requirements in §63.602 (b) or associated requirements in Subpart AA (§63.600 through 611). The commenter requested that a sentence be added at the end of the PPA plant definition in 40 CFR 63.601 to specifically state PPA process lines that do not use a HAP as a solvent in the separation of impurities do not meet the proposed definition. Response to comment: The Agency has determined that a change to the proposed
definition of a PPA plant at §63.601 is unwarranted and disagrees with the commenter that it be modified to contain clarification regarding solvent extraction . The Agency has determined that the proposed definition is sufficient at excluding PPA process lines that do not use a HAP as a solvent in the separation of impurities because the fi nal rule definition says that a purified phosphoric acid process line is a process line “...that uses a HAP as a solvent... .”

11.7 Gypsum Dewatering Stack Definition
Comment: Commenters (0037, 0038 , 0043 ) stated that the definition of gypsum dewatering stack was to o broad and obscured its true meaning. They claimed the EPA’s definition includes a wide array of features that have never before been considered part of the stack (e.g., pumps, piping, all collection and conveyance systems associated with phosphogypsum to the stack and process wastewater return to the plant). Commenters (0037, 0038, 0039) also stated that they were concerned that cooling ponds not connected to gypsum
stacks were included in the definition. One commenter (0037) proposed that the stack shoul d be considered “just the area where phosphogypsum is deposited” including the base of the stack, the rim ditch, and the surface in the center of the stack where the final gypsum settles out. Two commenters (0038 , 0043 ) recommended the EPA create a plain d efinition that focuses on the “footprint” of the stack,11

- 6

including the drying phosphogypsum slurry and ponds inside the perimeter of the gypsum dewatering stack’s base. Two commenters (0037, 0038) suggested the definition should not
include the return ditch or any cooling pond that is physically separate from the active stack.
Another commenter (0039) recommended that the EPA use the definition of “phosphogypsum stack” from Florida regulations, “any defined geographic area associated with a phosphoric acid

p roduction facility in which phosphogypsum is disposed of or stored, other than within a fully enclosed building, container or tank" (FAC § 62

- 673.200).
A commenter (0038) argued the individual gypsum cells within a stack could be considered as separate gyp sum dewatering stacks, due to the unclear definition. Response to C omment: This comment is addressed in the preamble of the final rule. In the final rule, we are revising the definition of “gypsum dewatering stack .”

11.8 Closed and Active Gypsum Dewatering Sta ck Definitions
Comment: Commenters (0037, 0038, 0039) stated that they were concerned about the distinction between closed and active gypsum dewatering stacks. They stated the point or transition period between “active” status and final “closure” status sh ould be clear. Commenters noted it takes several years to close a gypsum dewatering stack, and this period is not considered in either the definition of active or closed. Therefore, stacks that are inactive and in the closure process would still be conside red active.
Commenters (0037, 0038) stated the term closed gypsum dewatering stack could also include stacks that have temporarily stopped receiving phosphogypsum and have received any form of a “cover.” The commenter continued that the definition must not have the intent of deeming an active gypsum dewatering stack closed the moment the stack is no longer receiving phosphogypsum and has some sort of cover. One commenter ( 0037 ) rotates their three gypsum dewatering stacks and was concerned that when a stack is not receiving phosphogypsum during this cycle, that it may be considered closed.
Three commenters (0037, 0038, 0039) recommended the definition of closed gypsum dewatering relate to the end of its production life and when no further routine additions o f phosphogypsum will be made to the stack. These commenters also stated the “final cover” requirements should not be include in the definition, and were more appropriate as part of the work practice standard.11

- 7

A commenter (0038) observed that 40 CFR, part 6 1, subpart R defines an active gypsum dewatering stack as one that continues to receive gypsum or process water, and stated the subpart AA definition should correspond to the one in subpart R.
One commenter (0039) requested the EPA clarify that a lined pond on top of a closed gypsum stack does not render an otherwise closed stack "active."
Two commenters (0039 , 0043 ) stated that including a soil cover, rather than simply vegetative cover, in the definition of clos ed gypsum dewatering stack is not necessary. The commenters noted that soil cover is not required to sustain vegetation. A commenter (0039) also argued the requirement for drought resistant vegetative cover is ambiguous and nonsensical; drought resistant c over may actually be less hardy and viable than other types of vegetative cover. Another commenter ( 0043 ) noted that sustaining vegetation is difficult. The commenter (0039) requested that initial grassing and subsequent vegetative ecosystems that may deve lop after initial grassing satisfy the definition of an appropriate cover. Response to C omment: This comment is addressed in the preamble of the final rule. In the final rule, we are removing the definition of “closed gypsum dewatering stack ,” revising the definition of “active gypsum dewatering stack ,” and revising the definitions for when a gypsum dewatering stack is considered “new” or “existing .” In addition, in the final rule , we are removing the proposed work practice that limits the size of active gy psum dewatering stacks.

11.9 Cooling Pond Definition
Comment: A commenter (0039) requested that the EPA revise the definition of cooling pond to exclude ponds that are not used primarily for cooling the phosphoric acid production
process. Response to C omment: T he Agency has determined that a change to the “cooling pond”
definition at §63.601 is unwarranted and disagrees with the commenter. The Agency has determined that the proposed definition is sufficient at excluding ponds that are not used primarily for cool ing the phosphoric acid production process, such as reservoirs not intrinsic to the normal cooling pond loop because the definition explicitly uses the term “primarily” to describe how a cooling pond must be used to be considered an affected source.11

- 8

11.10 Production Capacity Clarification
Comment: One commenter (Simplot) requested the EPA clarify whether “ annual phosphoric acid manufacturing capacity ” in the ratio limit refers to the production capacity of the entire facility or the capacity of P 2 O 5 feed to the facility

. Response to C omment: The Agency is not adopting the proposed work practice that
limits the size of active gypsum dewatering stacks (refer to the preamble of the final rule for additional details); therefore, the commenters’ request f or clarification on what is meant by

“ annual phosphoric acid manufacturing capacity ” is no longer applicable.

11.11 Applicability Clarification

- Kiln Process
Comment: A commenter (0036) stated they produce a high purity phosphoric acid using the Improved Hard P rocess (IHP), which they call Kiln Produced Phosphoric Acid (KPPA). The commenter requested that the EPA clarify that the IHP process, regardless of facility size or the potential to emit HAP, will not be subject to part 63, subpart AA or part 60, subparts T and U for phosphoric acid facilities. The commenter continued that the IHP process and KPPA production is fundamentally different than WPPA production. IHP is a thermal process that uses a ported rotary kiln for the direct conversion of phosphate rock t o 70% phosphoric acid. The commenter stated that phosphate rock, sand, clay, and petroleum coke are dried, milled, formed into pellets, and fired in a rotary kiln for induration. The indurated pellets are then fired in a ported rotary kiln, phosphorus and carbon monoxide evolve, and P4O10 gas forms. The gas is cooled and absorbed in water to produce 70% phosphoric acid. Response to Comment: Based on the information provided by the commenter, the EPA agrees that KPPA produced using the IHP process is not sub ject to 40 CFR 63, subpart AA or 40
CFR 60, subparts T and U. The definitions for wet

- process phosphoric acid process line (in 40
CFR 63, subpart AA) and wet

- process phosphoric acid plant (in 40 CFR 60, subpart T) specifically state that phosphoric acid be manufactured by reacting phosphate rock and acid. Because acid is not used with the IHP, the IHP is not applicable to the wet

- process phosphoric acid process. Moreover, the IHP would not be considered a superphosphoric acid plant under 40
CFR 60, subpart U because the IHP does not concentrate phosphoric acid that was manufactured using the wet

- process. The EPA is not including specific revisions in rule language to address this comment because enough specificity is already included in the definitions secti ons of these
rules.11

- 9

11.12 Clarification To Calciners
Comment: One commenter ( 0043 ) requested clarification on the applicability of §63.600 to calciners that are not located at the same location of a phosphoric acid manufacturing plant.
The commenter noted that t he proposed rule language in §63.600(b) requires calciners to be physically located where the phosphoric acid manufacturing plant is located. The commenter thus asserted that a calciner not located at a phosphoric acid manufacturing plant is not applicable to 40 CFR 63 Subpart AA. The commenter additionally requested that the discrepancies in the definition of calciner
in 40 CFR 60.400 and 40 CFR 63.600 be addressed. The commenter recommended a consistent
definition for a calciner used to remove water and organics from phosphate rock (ore) be used in an effort to clarify how Clean Air Act requirements apply to phosphate rock calciners. Response to comment: The Agency agrees with the commenter that according to the final
rule at §63.600 (b), the requirements of 40 CFR 63, subpart AA apply to a phosphate rock calciner that is located at a phosphoric acid manufacturing plant. In addition, the Agency is not revising the definitions of a calciner at 40 CFR 60, subpart NN and 40 CFR 63, subpar t AA. The commenter did not provide support for their request, and the Agency is unable to understand the need to clarify these definitions.

11.13 Clarification To Scrubber Terminology
Comment: Once commenter (0039) requested that the EPA be consistent in the

t erminology that it uses citing the term “wet scrubbing device” is used in Section 63.602(c) instead of “a b sorber .” Response to Comment: The Agency agrees with the commenter, and has revised the final
rul e at §63.60 2 ( c ) and §63.62 2 ( c ) so that the terminology is consistent with the use of “absorber” instead of “wet scrubbing device .”12

- 1



### 12.0 ECONOMIC AND EMISSIONS IMPACTS

12.1 Cost

- Effectiveness of Hg Control Devices
Comment: Several commenters (0037, 0041, 0043) argued that ACI and fixed

- bed carbon adsorption were not cost effective for controlling Hg emissions from phosphate rock calciners.
Two commenters (0037, 0041) reported a site

- specific cost estimate for installing GMCS fixed

bed carbon adsorption downstrea m 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 th e 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 capi tal 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 EP A presented in the proposed rule ($12,100/lb Hg). The commenters (0037, 0041) 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 pro posed rule. Finally, one commenter (0037) 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 (0043) noted that preliminar y information for installing Hg controls resulted in estimates of $17.5 million in capital costs and $10 million for annual costs. A commenter (0037) provided a detailed review of Hg control devices in an attachment to their comment. Response to Comment: We are not finalizing the proposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners due to potential significant economic impacts associated with the costs of controls. Instead, we are finalizing a MA CT floor Hg limit for existing phosphate rock calciners and do not anticipate that any facilities will need to install a new control device to meet the existing phosphate rock
calciner H g limit

. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg H g/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners. We are finalizing costs for the BTF Hg12

- 2

limit for new phosphate rock calciners based on the application of ACI installed upstream of the existing venturi scrubber. Refer to the preamble of the final rule for additional details.

12.2 Gypstack Management Plan Control Measure Impacts
Comment: One commenter (0038) stated that implementing HF work practices for the gypsum dewatering stack and cooling pond management plan may be the most expensive aspect of the rulemaking. The commenter (0038) also remarked that the EPA did not quantify the costs to implement work pr actices, but it was crucial that EPA study and explain the economic costs of this rulemaking in thorough, concrete terms.
Two commenters (0038 , 0043 ) provided cost estimates for closure of side slopes. Closing side slopes was estimated at $4.8 million per bench, according to a commenter (0038) . The commenter stated that installing seepage collection drains to manage drainage from a stack can take more than a year to construct, and cost from $80,000 to $100,000 per acre. Another

commenter ( 0043 ) indicated th at closure costs were approximately $25,000 per acre, for applying soil and seeding. One commenter (0038) estimated that closing the side slopes of gypsum dewatering stacks would reduce the useful life of a 400 acre stack by approximately
36%.
Two commente rs (0038 , 0043 ) provided cost estimates for slaked lime application. One

commenter (0038) declared that applying slaked lime to a 400 acre gypsum dewatering stack would cost $3.0 million, for a one

- time application. A separate commenter ( 0043 ) explained th at additional equipment and infrastructure were necessary for lime application, with a cost of $1.09 million, and lime spraying equipment was an additional $100,000. The commenter ( 0043 ) stated that annual costs for applying slaked lime to 30 acres of thei r gypsum dewatering stack range from $23,000 to $36,000. Response to Comment: The Agency thanks the commenters for the cost details provided. However, we disagree with commenters that the gypsum dewatering stack and cooling pond management plan would be c ost

- prohibitive . We believe the list of control measure options is exhaustive enough that if a facility does not want to use a certain control measure that is listed in the final rule, then they can select a different one that would be more feasible and cost

- effective for their particular operations. We also assume that the option most economically feasible for a12

- 3

facility will be chosen. In addition, we made considerable effort 10 before and after proposal in identifying a list of control measure option s that encompass enough variety that at least one control measure option is feasible for at least one of each facility’s existing gypsum dewater ing stacks and/or cooling ponds . Refer to the preamble of the final rule for additional details of the work prac tice standards for gypsum dewatering stacks and cooling ponds included in the final
rule.

12.3 Gypstack Ratio Impacts
Comment: One commenter ( 0043 ) observed that the EPA did not estimate costs for complying with the ratio of gypsum dewatering stack area to annu al phosphoric acid manufacturing capacity, because the EPA was not aware of any new gypsum dewatering stack projects. However, the commenter ( 0043 ) stated they are planning to build a gypsum dewatering
stack. The commenter ( 0043 ) provided an example cost e stimate for a 200 acre gypsum dewatering stack expansion, where 407 acres would be required to be closed. The commenter ( 0043 ) applied a closure cost of $25,000 per acre, which resulted in an estimate of $10,175,000 to comply with the ratio. The commenter ( 0043 ) also remarked that this analysis did not include costs associated with managing water balance. Including water management, the commenter ( 0043 ) estimated it would cost more than $100,000 per acre with annual water management costs of $4,275,000. Ano ther commenter (0037) reported they are already planning on closing a large portion of their existing gypsum dewatering stacks, but the ratio may force the process to occur sooner than planned, with estimated costs of more than $105 million at $163,000 per acre. Response to Comment: The Agency thanks the commenters for the cost details provided. However, w e are not adopting the proposed work practice in NESHAP subpart AA that limits the
size of active gypsum dewatering stacks ( which would have been applica ble to facilities when new gypsum dewatering stacks are constructed ) , and therefore these costs are not applicable to the economic analysis of the final rule. Refer to the preamble of the final rule for a discussion of

10 S ee 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 Phos phoric 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

. ”12

- 4

why we are not adopting the proposed work practice that limits the size of active gypsum dewatering stacks.

12.4 Impact from Additional Sources
Comment: Four commenter s (0037, 0039, 0038 , 0043 ) stated that the EPA failed to properly characterize the additional costs that would be incu rred due to inclusion of clarifiers, defluorination units, and oxidation reactors. One commenter ( 0043 ) noted the emissions from one of their defluorination units are not captured as part of their WPPA process line, but rather are controlled with their pho sphate fertilizer process. The commenter continued they would need to construct a new stack and modify existing air permit requirements, estimated at $455,000, in order to comply. The commenter ( 0043 ) also explained they operate a second defluorination uni t with their SPA process line, and new equipment would need to be installed to separate the process, which was estimated to cost $7,500,000. A commenter ( 0043 ) reported that controlling all clarifiers would require the installation of a scrubber, ducting a nd piping, and instrumentation with an estimated cost of $10,994,000.
Two commenters (0039, 0038) stated that attempting to comply with th e expanded
definition of WPPA process lines that includes clarifiers and defluorination units would cost tens
of mill ions of dollars. One of these commenter s (0039) said that facility modifications to incorporate full emission capture, control , and testing for their clarifiers were estimated to co st $15 million collectively at two facilities

. Another commenter (0037) pro jected that installing two new emission control devices on evaporator hotwells and oxidation reactors, along with enhancing clarifier emission controls would cost approximately $500,000 for their facility to achieve compliance. This commenter also provided supplemental cost information outside of the comment period, which elaborated on oxidation reactor and clarifier control costs ( see Docket ID
No. EPA

- HQ

- OAR

- 2012

- 0522

- 0051 ). The commenter estimated that controlling clarifiers would cost approximately $396,500 and controlling their oxidation reactor would cost approximately $270,500.
A commenter (0039) also contended the EPA did not adequately justify including clarifiers within the definition, taking into account the inconsequential emissions reduction s. The commenter explained that clarifier emissions at one facility were estimated at 51.7 pounds per year total fluoride or 0.009 tons HF (assuming HF is one

- third of the total fluoride emissions).12

- 5

The commenter (0039) estimated that for this facility it will cost approximately $6 million to install controls (covers and scrubbers). With operating and maintenance expenses, the annual cost was estimated at more than $30 million per ton of HF emissions reduced. At a separate facility, the commenter (0039) rep orted that annual emissions from three clarifiers will be less
than 0.38 tons total fluoride or 0.13 tons of HF (assuming HF is one

- third of the total fluoride emissions). The commenter then stated that using EPA's low estimate of $8,000 in incremental

cos ts for Method 320 testing per stack, the additional annual testing costs alone amounted to over $190,000 per ton of HF emissions from these three sources. The commenter (0039) stated these costs are not reasonable considering that these emissions are insig nificant and EPA's own risk analysis supports the conclusion that existing practices are amply protective. Response to Comment: We are not including clarifiers and defluorination processes in the WPPA process line definition of the final rule (refer to the preamble of the final rule for additional details); therefore, we did not estimate costs for these sources, and the industry will not incur any costs for these sources. However, we are adopting the proposed superphosphoric acid process line definition in the final rul e to include oxidation reactors; r efer to the preamble of the final rule for additional discussion regarding the applicability and cost impacts of oxidation

reactors.

12.5 Testing and Monitoring Costs
Comment: One commenter (0037) stated the EPA un derestimated costs to measure Hg emissions with Method 30B. The commenter explained that due to site

- specific conditions, such as access and safety training, $20,000 per stack test is more appropriate.
Four commenters (0037, 0038, 0039 , 0043 ) expressed con cern over the increase in testing costs from using Method 320 instead of Method 13A or 13B. One commenter ( 0043 ) stated the incremental cost to conduct Method 320 was $9,000 per test, which was similar to the EPA’s estimate of $8,000 per test. However, the commenter noted this was about a 3 fold increase in testing costs. Another commenter (0038) stated they expect costs to increase at least 3.5 to 4 times when using Method 320 instead of 13B. Separate commenters (0037, 0038) contended that Method 320 testing is not routine and is dependent upon site

- specific factors, and
that the EPA cost does not account for this. The commenters (0037, 0038) noted that HF calibration gases are approximately $4,000, by themselves. Commenters (0037, 0038) also stated12

- 6

that costs increase if Method 301 validations are necessary. The commenters (0037, 0038)
contended the EPA needed to consider the one

- time cost to adjust sample ports and the recurring cost to procure a crane to lift Method 320 tes ting equipment to the sampling point.
One commenter ( 0043 ) stated that baghouse leak detection instrumentation and installation costs were $113,000, with annual costs for preventive maintenance of $5,760. The

commenter ( 0043 ) also noted they would realize a one

- time cost of $220,000 for additional parametric monitoring equipment for five scrubbers, with annual costs for cleaning and routine maintenance of $13,500. The commenter remarked that these costs may not be included in the proposed rule cost estimate

. A commenter (0043) also remarked that the EPA needed to determine how the additional scrubber controls would impact water use, including the water balance, and energy costs. Response to Comment: The Agency disagrees with the commenter that access and saf ety training would lead to more than double the costs for Method 30B. Method 30B is required for phosphate rock calciners, which must also conduct particulate matter ( PM ) compliance tests using Method 5. These two test methods are similar; an access point in the stack would already be available and we would expect minimal differences in safety training for using Method 30B versus Method 5. While the Method 30B cost used at proposal was an estimate for a general facility, we believe that more than doubling t he cost of Method 30B due to access and safety training concerns is not appropriate. The commenter did not provide a detailed discussion with specifics to illustrate why increased stack test costs were appropriate . Based on the limited
information provided , and our knowledge of the testing costs, we do not agree with their cited cost of $20,000 per stack test. The Method 30B estimate of $6,400 was based on a 20 percent reduction from the full cost of $8,000; a 20 percent reduction is appropriate when multip le stack tests are conducted, which is the case for phosphate rock calciners. However, in light of the commenter’s concerns, we have removed the 20 percent reduction and applied the full Method 30B cost estimate of $8,000 per stack test.
T he Agency is not adopting the proposed HF standards. As a result of this determination

to not adopt the proposed HF standards , the Agency has retained the current total fluoride limits (lb total F/ton P 2 O 5 feed) measured using EPA Method 13A or 13B as a surrogate for the HAP HF, rather than HF emission limits using EPA Method 320

. Therefore, the commenter’s concern12

- 7

over the increase in testing costs from using EPA Method 320 instead of EPA Method 13A or 13B is no longer applicable. Refer to the preamble of the final rule f or additional details. The Agency agrees that costs for a baghouse leak detection system (BLDS) should have been included in the proposed rule. For the final rule, we are including BLDS capital and annual costs using data from previous rulemakings; capital costs equal approximately $25,200 and annual costs are approximately $9,900 per fabric filter. In the technology review it was noted that three facilities employ fabric filters on their phosphate fertilizer process lines. The final rule
includes BLDS cost s for these three facilities; refer to the memorandum “ Control Costs and Emissions Reductions for Phosphoric Acid and Phosphate Fertilizer Production Source Categories

- Final Rule,” which is available in the docket for this rule , for additional cost detai ls. The Agency agrees that costs for the proposed additional absorber monitoring options should have been included in the proposed rule. However, due to certain absorber monitoring
revisions that we made in the final rule, costs associated with absorber m onitoring is assumed to
be zero for the final rule. Refer to the preamble of the final rule for discussion regarding the changes made to absorber parametric monitoring and the costs related to these changes

.

12.6 Economic Impacts
Comment: Several commenters (0037, 0038 , 0043 ) were concerned about the overall economic impact the proposed rules would have on the industry. Each commenter (0037, 0038 , 0043 ) cited concerns about individual costs associated with proposed requirements (e.g., BTF Hg limits, the gypsu m dewatering stack and cooling pond management plan, testing and monitoring costs, costs associated with rule clarifications), and believed that cumulatively these requirements would impose a substantial economic impact. Commenters (0037, 0038) estimated

t he costs would be well above $100 million. Commenters (0037 , 0043 ) also noted the phosphoric acid industry is global and that costly requirements make domestic producers less competitive and put their operations at risk. A commenter ( 0043 ) mentioned that t he EPA needed to consider the total cost of capital for the proposed rule. The commenter explained that the total cost of capital reflects the capital that could have been re

- invested back into domestic production. The commenter ( 0043 ) stated that such rei nvestment is crucial for the domestic industry to stay competitive with the international competition, which often does not have the same level of environmental protection costs as in the United States. One commenter (0037) warned that12

- 8

increased regulator y burden has been cited as a factor in recent phosphoric acid plant closures. A

commenter (0038) also declared the EPA should address the issues raised in all comments to the proposed rule, and then submit a full economic analysis for public review. Respons e to Comment: The Agency agree s with commenters that the proposed rule did
have a substantial economic impact to one facility, PCS Aurora, due to the proposed BTF Hg limit for phosphate rock calciners

. All comments were reviewed and addressed, and as a re sult, certain changes were incorporated into the final rule. The cost for the final rule is well below $100 million. Commenters stated that particularly high costs would be incurred by the industry as a result of the gypsum dewatering stack and cooling pon d management plan (where industry estimated closure costs) and applicability clarifications to include clarifiers and defluorination units in the definition of WPPA process line. These requirements were removed or revised for clarity, which
eases most of t he cost burden that industry was concerned with (refer to the preamble of the final rule for further details).
The other major cost in the proposed rule that commenters were concerned about was comply ing with the BTF Hg limit for phosphate rock calciners

. H owever, we are not finalizing the proposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners. Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners and do not anticip ate that any facilities will need to install a new control
device to meet the existing phosphate rock calciner H g limit

. The Agency determined the re would be a significant economic impact to PCS Aurora due to the BTF Hg limit for existing phosphate rock calciners, and as such, it is not being finalized. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners. The Agency determined that a BTF Hg
limit for new phosphat e rock calciners is appropriate and cost

- effective. See the preamble to the final rule and the memorandum “ Control Costs and Emissions Reductions for Phosphoric Acid and Phosphate Fertilizer Production Source Categories

- Final Rule,” which is available in the
docket for this rule , for additional cost details and discussion.12

- 9

12.7 Economic Benefits and Regulatory Planning and Review
Comment: Commenters (0038 , 0043 ) were concerned the EPA did not fully evaluate the benefits of the proposed rule. They stated that b ecause costs were potentially much higher than the EPA originally calculated, examining the benefits were necessary. The commenters (0037, 0038) provided a detailed review of the economics and benefits of the proposed rule in an
attachment to their comment s. A commenter (0037) reported that the potential costs associated with the Hg limit outweigh the benefits. The commenter (0037) maintained that the EPA justified Hg controls in other rules by focusing on the benefits of reductions in PM, ozone, and
CO2 em issions that would occur with the installation of Hg controls (co

- benefits). The

commenter (0037) then noted the co

- benefits of the proposed phosphate rock calciner Hg limits would be minimal because existing venturing scrubbers and WESPs control emissions of PM
and SO2. The commenter (0037) reported that the analysis they conducted showed the Hg limit
fails the benefit

- cost test, and can be expected to decrease societal well

- being.
Commenters also believed the rule to be subject to Executive Order 12866 due to their projected costs

. Two commenters (0037, 0038) stated the rule is economically significant and
should be submitted to Office of Management and Budget ( OMB ) for review, according to Executive Order 12866. Both commenters mentioned the proposed ru le would have an economic impact greater than $100 million, and recommended the EPA conduct a full Regulatory Impact Analysis. A commenter (0038) further contended that even if the economic impact was less than $100 million, an economic analysis was necess ary because there are relatively few entities that produce phosphoric acid and phosphate fertilizer products in the United States. The commenter (0038) continued that the EPA must evaluate how the proposed rule could “adversely affect in a material way . . . a sector of the economy” and this sector

- based analysis is an independent and sufficient condition to undertake a required economic analysis under Executive Order 12866. Response to Comment: The Agency did not conduct a full Regulatory Impac t Analysis ( RIA) for the proposed rule due to our determination that this rule is not economically significant. We have evaluated the costs presented by industry, and determined the costs for the rule are much less than those cited. As a result, we still believe the r ule to not be economically significant, and accordingly, not subject to an RIA. All comments were reviewed and addressed, and as a result, certain changes were incorporated into the final rule. Commenters stated that particularly high costs would be incurr ed by the industry as a result of the gypsum dewatering12

- 10

stack and cooling pond management plan (where industry estimated closure costs) and applicability clarifications to include clarifiers and defluorination units in the definition of WPPA process line. These requirements were removed or revised for clarity, which eases most of the cost burden that industry was concerned with. The other major cost in the proposed rule that commenters were concerned about was complying with the BTF Hg limit for phosphate rock calciners. However, we are not finalizing the proposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners. Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners and do not anticipate that any facilities will need to install a new control
device to meet the existing phosphate rock calciner H g limit . The Agency determined there would be a significant economic impact to PCS Aurora due to the BTF Hg limit for existing ph osphate rock calciners, and as such, it is not being finalized. We are finalizing the proposed BTF Hg limit (i.e., 0. 14 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for new phosphate rock calciners. The Agency determined that a BTF Hg limit for new phosphate rock calciners is appropriate and cost

- effective. See the preamble to the final rule and the memorandum “ Control Costs and Emissions Reductions for Phosphoric Acid and Phosphate Fertilizer Production Source Categories

- Final Rule,” which is available in t he
docket for this rule , for additional cost details and discussion.

12.8 Environmental Justice
Comment: Several commenters (0035, 0037 , 0047, 0054 ) contended that the EPA did not adequately address the environmental justice impacts (including any substantive analysis of the economic impacts and effects, as well as cumulative impacts and effects) the proposed rule may have on minority and low

- income p opulations in and around PCS Aurora’s plant. T wo of t he se
commenters (0035, 0037) noted that the EPA concluded “we found the risks from these source categories to be acceptable for all populations.” However, the commenters maintained that the EPA is only c onsidering “risks” from pollution, which it found to be negligible, while ignoring the economic and employment effects on minority and low income communities from setting the NESHAP “below the floor” even where not necessary to do so for health reasons. De mographics on PCS Aurora employees were provided by the commenters, which show African Americans exceed the national average of 13%. In addition, commenters (0035, 0037) observed that 20.6%12

- 11

of the population around the PCS Aurora facility lives below the p overty line, exceeding the national average of 14.9%. The commenters contested that any workforce reductions caused by the proposed rule at this facility would disproportionately affect low

- income and African American populations. The commenters (0035, 003 7) also reported that between 2011 and 2014, the workforce associated with the PCS Aurora facility dropped from 1,910 to 1,159 employees, and were concerned the proposed rule could further increase the reductions in workforce. The commenters also explained that many of the facility’s contractors are small businesses, which should also be analyzed because the methodology is flexible so that environmental justice impacts can be assessed without being limited by demographics. One commenter (0035) requested tha t the EPA issue a Notice of Data Availability (NODA) to remedy this deficiency.
Another commenter (0047) requested that EPA defer any action on the beyond the floor limit until the economic impacts can be assessed consistent with EPA's environmental justic e guidance . The commenter argued that CAA Section 112(d)(2) must be read to require that EPA comply with the functional equivalent of the National Environmental Policy Act ( NEPA ) requirements including assessing environmental justice impacts . This commente r also argued
that Executive Orders 12866 and 13563 , under which the Office of Information and Regulatory Affairs (OIRA) reviews draft regulations, call for EPA to conduct an environmental justice

assessment. This commenter further argued that based on EPA ’s Environmental Justice Toolkit at p.24, the economic model that must be used to assess the environmental justice economic impacts would not be the same one used to pass OIRA scrutiny , but rather those economic indicators that are most important to minori ty and low income communities such as lost wages and reduced property values

. A commenter ( 0056 ) also provided a copy of a news article that discussed economics and the increasing poverty in Beaufort County. Response to Comment: The EPA continues to make environmental justice an agency priority and appreciates the comments provided and suggestions on how the agency can move forward in the areas of environmental justice analysis and economic analysis. Environmental justice assessments inclusive of economic considerations are an evolving area where guidance, such as the referenced toolkit, are currently being evaluated and balanced against availability of data, resources and statutory authority considerations. The EPA does not collect information on those emp loyed in the immediate surrounding areas of affected facilities. In the case of the Phosphoric Acid Manufacturing NESHAP and NSPS reviews, based on information provided by13

- 12

commenters during (and after) the proposal period, the EPA concludes that there woul d be a significant economic impact to PCS Aurora given that estimated costs to comply with the proposed BTF Hg limit for phosphate rock calciners are a significant percentage of revenues.
However , an employment analysis was not conducted. We are not finalizing the proposed BTF Hg limit (i.e., 0.014 mg Hg/dscm @ 3% O 2 ) in NESHAP subpart AA for existing phosphate rock calciners. Instead, we are finalizing a MACT floor Hg limit for existing phosphate rock calciners. Refer to the preamble of th e final rule for additional details



### 13.0 STARTUP, SHUTDOWN, AND MALFUNCTIONS

13.1 Whether EPA Appropriately Removed The Startup, Shutdown, and Malfunction Exemption
Comment: Two commenters (0037, 0038) requested that the EPA withdraw the proposal
to end the SSM ex emptions for Subparts AA and BB, or further explain the EPA’s reasoning for ending the exemption in the context of these two industries. These commenters (0037, 0038) argued that the EPA had failed to adequately explain why subparts AA and BB cannot retain the current SSM exemptions and the use of the “affirmative defense” for malfunctions based on statutory law and recent court decisions, and why they need to be removed from the two subparts. The commenters asserted that the EPA had failed to explain why t he SSM provisions are no longer necessary. The commenters cited comments submitted by the SSM Coalition on the EPA’s Proposed Petroleum Refinery Sector Risk and Technology Review and New Source Performance Standards, Docket ID No. EPA¬HQ

- OAR

- 2010

- 0682, whi ch argued that 1) EPA’s approach “fails to account adequately for emissions that occur during SSM periods,” 2) is based “on an incorrect reading of the D.C. Circuit’s Sierra Club v. EPA decision ,” and 3) changes “regulations that have been in place for man y years and whose SSM provisions were never challenged in court, without any justification of its authority to do so and without any apparent factual analysis of the statutory criteria for standard

- setting.”
One commenter (0038) requested that the EPA’s ra tionale for removing the current SSM and affirmative defense provisions is based on a misinterpretation of recent case law and the

statute. The commenter argued that the case on which the EPA relies for removing the affirmative defense provisions, NRDC v. EPA, is irrelevant to using SSM exemptions and to maintaining the affirmative defense for malfunctions, and that the EPA concede d as much with13

- 13

respect to the removal of affirmative defense in the preamble to the proposed rule in footnote 29 (79 FR 66542)

. The commenter (0038) speculated that the EPA, in arguing that an affirmative defense is not “necessary,” appears to be relying either on (1) the rationale that the EPA may use its case

by

- case enforcement discretion to provide flexibility if a source cann ot comply as a result of a malfunction, or (2) a rationale that penalties for violations caused by malfunctions in administrative proceedings and judicial proceedings should be consistent, as put forth by the EPA in the preamble to the proposed rule

. (See 79 FR 66541)
The commenter (0038) argued that the affirmative defense provisions would not prohibit the EPA from still using case

- by

- case enforcement discretion to provide flexibility, and the commenter noted that the affirmative defense is still subject t o rebuttal by the EPA in
enforcement actions.
The commenter (0038) suggest ed that the EPA is relying on the need for consistency as the basis for removing the affirmative defense provisions by citing CAA section 113(e) [identified as 113(h) by the commenter] . The commenter note d that the EPA already has acknowledged that the holding in NRDC v. EPA made a distinction between “judicial” defenses (which only Article III courts may regulate), versus “administrative” defenses, such as the one provided in the two subparts, and that applying the criteria in CAA Section 113(e) does not mean that penalties in judicial and administrative proceedings need to be consistent. Therefore, the need for consistency also does not support removing the affirmative defens e provisions, according to the commenter.
The same commenter noted that the EPA has argued in the preamble to the proposed rule that the affirmative defense is no longer “necessary” because of the removal of the exemption for
SSM exces s emissions. The comm enter noted that the EPA refers to an earlier discussion in the preamble in support of this rationale (see 79 FR 66542, footnote 29), but asserted that this supporting discussion is not apparent earlier in the preamble. Response to Comment: Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the United States Court of Appeals for the District of Columbia Circuit vacated the startup, shutdown, and malfunction (SSM) exemption contained in section 63.6(f)(1) and (h)(1) of the Part 63 General
Provisions. When i ncorporated into CAA section 112(d) regulations for specific source categories, the exemption in these two provisions exempted sources from the requirement to13

- 14

comply with the otherwise applicable CAA section 1 12(d) emission standard during periods of
SSM. In Sierra Club, the court explained that under section 302(k) of the CAA, emissions
standards or limitations must be continuous in nature. The court then held that the SSM exemption violates the CAA's requirement that some section 112 standard apply contin uously.
To ensure that some CAA section 1 12 standard applies at all times, we are specifying that the SSM exemption in the 40 CFR part 63 General Provisions does not apply to subparts AA and BB, adopting a work practice standard that applies in lieu of the HAP emission limits during periods of startup and shutdown, and clarifying that the emission limits apply at all other times, including during periods of malfunction

. The work practice requires that control devices be operated normally during periods of s tartup and shutdown

. As we explained in the proposal preamble at 79 FR 66540, the work practice standard applies because it is not feasible to prescribe or enforce an emissions standard during startup and shutdown

. As we explain in the preamble to the fina l rule , we are clarifying that to comply with the work practice, 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. Regarding per iods of malfunction, the Clean Air Act does not allow EPA to provide “affirmative defense” provisions into NESHAP

. In the Portland cement decision issued April 18, 2014 (NRDC v. EPA), the D.C. Circuit vacated a regulatory provision establishing an
affirmat ive defense to civil penalties for violations of emission standards caused by unavoidable malfunctions. The court found that the authority under the CAA to determine penalty amounts lies exclusively with federal District Courts. In light of NRDC, EPA is no longer including regulatory affirmative defense provisions in its rules. However, if a source is unable to comply with an emission standard as a result of a malfunction, the EPA may use its case

- by

- case enforcement discretion to provide flexibility in
dec iding if a penalty is appropriate. Further, in an EPA or citizen enforcement action, the court has the discretion to consider any defense raised and determine whether penalties are appropriate

. As explained further in the proposal preamble at 79 FR 99543, the rule can reasonably be applied during unanticipated malfunctions and encourages practices that will avoid
malfunctions.
Comment: Two comments (0037, 0038) argued that the EPA’s proposed alternative to the SSM exemptions and the affirmative defense for malfunctions, relying on case

- by

- case13

- 15

enforcement discretion for every malfunction that causes excess emissions, would ignore the realities of the production process and would create uncertainty regarding compliance. One

commenter (0038) argued that the co urts have also recognized the need for flexibility and cited as an example, Essex Chem. Corp. v. Ruckelshaus, 486 F.2d 427, 432

- 33 (D.C. Cir. 1973), cert. denied,416 U.S. 969 (1974), in which the commenters said that the court remanded a “never to
be excee ded” standard because SSM provisions are inherently “necessary to preserve the reasonableness of the standards as a whole,” and that the court further explained that “nowhere in the record has there been a showing that the [normal] standards can be equaled during periods of less than normal operation, when plant efficiency and consequently pollution emissions vary significantly from the norm.”
One commenter (0038) argued that it would be inappropriate and arbitrary for the EPA to
deem all exceedances of a standard to be a violation, and that the proposed approach would unfairly subject companies to enforcement action for malfunctions that the EPA acknowledges in the proposal preamble are “not reasonably preventable.” (See 79 FR 66541.) The commenters argued that the EPA has acknowledged in prior actions that malfunctions beyond the control of the operators should not be a basis for imposing penalties when they result in exceedance of a standard. In support, the commenters cited 40 CFR 63.7(e), which specifie s conditions for the conduct or performance tests, and also language at 40 CFR 63.600(e) and 63.620(e), and also the current definition of “malfunction” at 40 CFR 63.2. Response to Comment: As we previously explained in our response to the comment
immediat ely above, the final rule is consistent with the requirements of the Clean Air Act and provides reasonable flexibility to comply with the standards at all times, including periods of
SSM

. All exceedances to standards are violations . If EPA determines that an exceedance was
outside the control of the source , then EPA has discretion to determine an appropriate response

. In the event that a source fails to comply with the applicable CAA section 112 standards as a result of a malfunction event, the EPA would de termine an appropriate response based on, among other things, the good faith efforts of the source to minimize emissions during malfunction periods, including preventative and corrective actions, as well as root cause analyses to ascertain and rectify exce ss emissions. The EPA would also consider whether the source’s failure to comply with the CAA section 112 standard was, in fact, ‘‘sudden, infrequent, not reasonably preventable’’ and was not instead ‘‘caused in part by poor maintenance or careless13

- 16

operati on.’’ See 40 CFR 63.2 (definition of malfunction). If the EPA determines in a particular case that enforcement action against a source for violation of an emission standard is warranted, the source can raise any and all defenses in that enforcement action and the federal district court will determine what, if any, relief is appropriate. The same is true for citizen enforcement
actions.

13.2 Feasibility Of Estimating Emissions During SSM Events
Comment: Two commenters (0037, 0043 ) argued that compliance with the EPA proposal at 40 CFR 63.607(b) and 63.627(b) to require affected facilities to develop and maintain records of an estimate of the volume of each regulated pollutant emitted over the applicable standard and a description of the method used to estimate emi ssions” was difficult, if not impossible. The commenters argued that it would be difficult to estimate excess emissions for the same reasons it would be difficult to apply numeric emission limits to malfunction emissions. The commenters
asserted that becau se malfunctions are unpredictable in their occurrence and duration, can be caused by unknown factors, and may cause rapid changes in emissions, it is difficult to estimate emissions with any reasonable degree of uncertainty. The commenters argued that thes e estimates should not be required, and if required, they should not be held against facilities during
the exercise of case

- by

- case enforcement discretion.
One commenter (0043) noted that they do not have a scientific basis to estimate emissions during SSM periods because source testing is not performed during such periods of
unstable air emissions.
The same commenter (0043) asserted that determining excess emissions during
malf unction events is even more challenging as the root cause of these events is likely to be quite variable and will have differing effects on the concentration of air pollutants. The commenter requested that the EPA maintain the record keeping requirements a ssociated with 40 CFR 63.10(b)(2)(i) and (ii) and remove the record keeping requirements associated with the proposed rule at 40 CFR 63.607(b) and 63.627(b), or simply remove the requirement to quantify excess emissions during periods of shutdown, startup or malfunction. Response to Comment: We are retaining the requirement as proposed to report an estimate of the quantity of each regulated pollutant emitted over any emission limit and a description of the method used to estimate the emissions in situations where the duration of an13

- 17

exceedance of an emissions limit, work practice standard, or operating limit is 1 percent of the total operating time for the reporting period or greater, including periods of SSM

. This requirement will ensure that there is adequa te information to allow the EPA to determine the severity of the failure to meet an applicable standard and to provide data that may document how the source met the general duty to minimize emissions during an exceedance event

. We disagree with the commen ter that it is not possible to estimate emissions during SSM

. The rule provides facilities the flexibility to select the most appropriate method to estimate emissions based on process knowledge and the circumstances of each situation

. Examples of
such meth ods would include product

- loss calculations, mass balance calculations, measurements when available, or engineering judgment based on known process parameters.

13.3 Work Practice Standard In Place Of Emission Limits
Comment: One commenter (0038) agreed that the creation of work practice standards for periods of startup or shutdown would qualify as “standards” to the ruling in Sierra Club v. EPA that case’s ruling that CAA § 302(k)210 requires that some standard apply “on a continuous basis,” in lieu of not provi ding any standards whatsoever. (See 551 F.3d at 1021

- 22, 1027

- 28.) The same commenter noted that the Sierra Club court stated that the EPA had “not purported to
act under CAA section 1 12(h), providing that a standard may be relaxed ‘if it is not feasible’

. . . based on either a (1) design or (2) source specific basis” under the facts of that case. (Id. at 1028.) Instead, according to the commenter, the Sierra Club court reserved the EPA’s authority under the CAA to create flexibility or different standards for periods of SSM, including when it was “not feasible” to prescribe a numeric emission limit at all times of operation. The commenter concluded that the EPA has the authority to use work practice standards to regulate SSM periods under Subparts AA and B B in lieu of imposing numeric standards and operating parameters during those periods. Response to Comment: We concur with the commenter that the CAA section 112(h) provides for EPA to establish work practice standards in situations where it is not feasibl e to prescribe or enforce an emission limit

. In the final rule, we are retaining the proposed requirement for a work practice for periods of startup and shutdown

. See preamble discussion of the proposed rule at 79 FR 66541 and 66551 for our rationale under CAA section 112(h) for establishing the work practice standard for subparts AA and BB, respectively

.13

- 18

Comment: One commenter (0043) asked whether the proposed requirements in 40 CFR 63.602(h) and 63.622(d) to operate emission control equipment during perio ds of startup and shutdown as a means to “demonstrate compliance” with emission limits specified in the rule is intended to negate the requirement to calculate and record estimated excess emissions during these periods as proposed in 40 CFR 63.607(b) and 6 3.627(b). Response to Comment: The work practice that applies during startup and shutdown does not negate any other applicable recordkeeping or reporting requirement in the rule. The requirement to calculate and report excess emissions during startup and s hutdown is triggered only if the following criterion are both met: (1) the facility does not comply with the work practice standard during these periods; for example, if the control device is not operated continuously during startup or shutdown periods or if the control device is not operated within the applicable operating limits (refer to the response to comment 13.4 in this document for further details); and (2) the duration of an exceedance of the work practice standard or operating limit is 1 percent o f the total operating time for the reporting period or g reater

. The emissions
calculation would take into account any emission reductions achieved by the control equipment.
Comment: Several commenters (0037, 0038, 0043) argued that the EPA’s proposed work practice standard for periods of startup and shutdown failed to account for how equipment in the phosphoric acid industry works. In order to comply with the proposed startup and shutdown requirements, the operator must begin operation of any control device(s) being used at the affected source prior to introducing any feed into the affected source and continue operation of the control device(s) through the shutdown period until all feed material has been processed through the affected source. The commenters noted that it is not feasible to process all feed material from a process prior to shutting down most equipment at a facility. For example, the phosphoric acid reactors and beds in the calciners may not be able to proce ss all the feed material in them prior to shutdown and there would always still be feed material left in the equipment
even after it is shutdown . The same would be true for nearly all process units in the industry. The commenters requested that the EPA rev ise 40 CFR 63.602(h) to require compliance with the work practice standard only up to the point in time when no more feed or in

- process materials are being introduced into the production unit.
Two c ommenters (0038, 0039) agreed with the other commenters th at it is not feasible to base the conclusion of a “shutdown” on the point at which all feed has “been processed.” Instead,13

- 19

they suggested that the EPA should clarify the work practice standard of keeping all emission control equipment active during shutdow ns. The commenters reported that facilities in the industry consider the commencement of “shutdown” as the moment at which the plant ceases adding feed to the affected process, rather than basing shutdown on when all feed materials have been processed thro ugh the process. The commenters recommended that the EPA should define “shutdown” to begin when the facility ceases adding feed to an affected process line, and to conclude when the affected process line equipment is deactivated, even though some feed or

r esidues may still be present within particular parts of the process.
One of the commenters (0039) also noted that it is common practice to have short

- term shutdown of process inputs for temporary maintenance work (including work on emission control equipme nt) where the entire system is not emptied. In these cases, feed phosphoric acid and ammonia to the process is suspended as is flow from the reactor to the granulator. The commenter argued that because the source of fluoride to the system has ceased and du st generating material flows are suspended, there should be no significant source of emissions to control, and it is not necessary to require the utilization of control devices until all feed material has been processed. Instead, the commenter recommended that an affected entity should be allowed to turn off control devices when reactor and granulator feeds have been stopped, unless the system is being emptied, in which case control devices should be required as long as the material handling system is in op eration. Response to Comment: This comment is addressed in the preamble of the final rule. We agree with the commenter that the rule needs to have a more precise definition of startup and shutdown that more clearly and reasonably establishes the time perio ds when the work practice applies and when the emission limits apply

. Comment: One commenter (0038) argued that the EPA should specify that the proposed work practices for plant startup and shutdown periods apply “in lieu of” any other emission standards, and that such periods should not be counted for testing, monitoring, or operating parameter requirements. The commenter noted that the proposed rules at 40 CFR 63.602(h) and 63.622(d) require the use of work practices “to demonstrate compliance with any em ission limits” during periods of startup and shutdown. The commenter agrees with the EPA’s conclusion that it is not feasible to apply numeric limits to startup and shutdown because certain variables required to calculate emissions would be zero during suc h periods

. The commenter also13

- 20

agreed with the EPA that existing emission control devices would still be effective during periods of startup or shutdown, if activated. However, the commenter recommended that the rule should clarify that startup and shutdown events should not be required to comply with the monitoring and operating parameter requirements because startup and shutdown events generally are not representative operating conditions for other compliance purposes, such as emissions testing. Instead, t he commenter (0038) , as well as a second commenter (0043) , recommended that, because the startup and shutdown periods are not representative, the rule should only require that (1) all emission control devices be kept active, and (2) owners and operators fo llow the general duty to control emissions, and owners and operators should not be required to monitor operating parameters during startup and shutdown periods.
The commenter (0038) argued that the approach in the proposed rules at 40 CFR 63.602(h) and 63. 622(d) to require the use of work practices “to demonstrate compliance with any emission limits” during periods of startup and shutdown is “directly inconsistent” with the approach that the EPA has applied to other source categories, where such practices c learly were prescribed “in lieu of” numeric emission limits that would otherwise apply. (The commenter cites, for example, 78 FR 10015, February 12, 2013.) According to the commenter, the EPA made it clear in other industries’ rules that such work practice standards apply “in place of” or “in lieu of” numeric standards, including with respect to monitoring and recordkeeping requirements. ( See id. at 10013 and 10015.) The commenter argues that according to the preamble language cited for those other industri es, “there will no longer be a numerical emission standard applicable during startup and shutdown,” and the EPA recognizes that “the recordkeeping requirement must change to reflect the content of the work practice standard”(Id. at 10014). Therefore, the commenter (0038) recommended that the EPA should clearly explain that work practices are not applied to “demonstrate compliance” with numeric limits under Subparts AA and BB, which the EPA acknowledges are “not feasible” for startup and shut down periods, and instead, the work practices should be written to apply “in lieu of” the numeric limits during those periods. The commenter argues that without this clarification, it will appear that both the numeric standards and the work practice standa rds would apply during startup and shutdown. The commenter suggests that this can be corrected in the rule by using the “in lieu of” language
used for other industries.13

- 21

Response to Comment: This comment is addressed in the preamble of the final rule. The

c ommenter is correct that our intention at proposal was that the numeric emission limits would not apply during periods of startup and shutdown, but that facilities would comply with the work practice instead

. Comment: One commenter (0042) asserted that, wi th respect to the EPA proposal to set work practice standards, instead of setting numeric standards, to reduce HF from phosphate rock
calciners during normal operations and during startup and shutdown periods, the EPA has not provided the determination and supporting evidence the Clean Air Act requires to set these
standards instead of numeric limits. The commenter s argued that the EPA failed to meet the test to promulgate work practice standards “in lieu of” numeric emission standards set by CAA
section 11 2(h). Response to Comment: For reasons that are described in the preamble to the final rule, we are not publishing the proposed HF work practice for phosphate rock calciners, but instead have adopted a numeric emission limit for total fluorides

. The preamb le to the final rule further explains that the total fluorides emission limit does not apply during periods of startup and shutdown and that facilities must comply with the work practice of §63.602(h) instead

. The preamble provides the CAA section 1 12(h) justification for adopting a work practice standard in
lieu of an emission limit.

13.4 Make An Explicit Exemption For Monitoring During SSM

Two commenters (0037, 0038) recommended that the EPA amend the rule to make clear that the work practice standards for st artup and shutdown also apply in lieu of the parametric monitoring requirements set forth in Subparts AA and BB and make explicit that parametric operating requirements do not apply during times of startup and shutdown.
One commenter (0038) argued that whe n the EPA established the flow rate and pressure drop parametric monitoring requirements in its 1999 final rule, the EPA concluded that requiring continuous monitoring of these parameters “help[ed] assure continuous compliance with the emission limit” (64 FR 31365, June 10, 1999)

. The commenter (0038) also asserted that the rules specify that “[t]he emission limitations and operating parameter requirements of this subpart do not apply during periods of startup, shutdown, or malfunction . . . .” (40 CFR 63.6 00(e) and 63.620(e))

. The commenter argue d that this was a reasonable action because the operating13

- 22

parameter ranges are established during annual performance tests, and these tests cannot be performed during startup and shutdown conditions.
The commenter ( 0038) suggested that in the p roposed r ule , the EPA exempt compliance with the emission limits during startup and shutdown periods, impos e work practice standards in lieu thereof, and retain the prohibition on conducting a performance test during periods of startup or shutdown (79 FR 66570 (proposed 40 CFR 63.606(d)), and 79 FR 66582 (proposed 40 CFR 63.626(d)). The commenter suggest ed that the proposed rule is silent on the applicability of the parametric monitoring requirements during startup and shutdown. The commenter assert ed that because the parametric monitoring provisions provide an inference of compliance with the emission limits (64 FR 31365, June 10, 1999) , and these emission limits do not apply during startup and shutdown, the commenter conclude d that the parametric monitoring provisions similarly should not apply during startups and shutdowns.
The commenters (0037, 0038) pointed to two recent EPA NESHAP rulemakings to support their conclusion. First, the commenters argued that in its industrial, c ommercial and institutional boilers and process heaters NESHAP reconsideration proposal (hereinafter, the “Boiler NESHAP”), the EPA, responding to a comment soliciting clarification “that the operating limits and opacity limits do not apply during periods of startup and shutdown ,” stated that with the finalization of work practice standards, “EPA agrees that the requested clarification is what was intended in the final rule” (76 FR 80598 and 80615, December 23, 2011)

. The
commenters asserted that to this en d, in its response to the reconsideration, the EPA made clear that affected sources must comply with “all applicable emissions and operating limits at all times the unit is operating except for periods that meet the definitions of startup and shutdown in t his subpart, during which times you must comply with these work practices” (78 FR 7138 and 7142, January 31, 2013)

. The commenters noted that in the Boiler NESHAP regulations, the EPA required the implementation of work practice standards in lieu of compli ance with the operating parameter requirements during startup and shutdown by (1) excluding periods of startup and shutdown from the averaging period (Id. at 7187, 40 CFR 63.7575, the definition of a 30

- day rolling average” excludes “hours during startup a nd shutdown”)
, and (2) expressly stating that the “standards” (the emission limits and operating requirements) do not apply during periods of startup or shutdown. (Id. at 7163, 40 CFR 63.7500(f), entitled “What emission limitations, work practice standards , and operating limits must I meet?” applies “at all times the affected unit is13

- 23

operating, except during periods of startup and shutdown during which time you must comply only with Table 3 of this subpart.”) Second, the commenters (0037, 0038) argued that in its Portland Cement NESHAP, the EPA specified an operating limit for kilns, identified as a temperature limit established during a performance test, and that the temperature limit applied at all times the raw mill is operating, “except during periods of startup and shutdown” (78 FR 10039, February 12, 2013, 40 CFR 63.1346(a)(1))

. Further, for the continuous monitoring requirements, including operating limits, the Portland Cement NESHAP required operating of the monitoring system at all times the
affected source is operating, “[e]xcept for periods of startup and shutdown” (Id. at 10041, 40 CFR 63.1348(b)(1)(ii))

. The commenters (0037, 0038) argued that given the EPA’s conclusion in the p roposed

r ule that the emission limits should not apply during startup and shutdown, and because the parametric monitoring requirements are established during a performance test (which cannot be performed during a startup or a shutdown) and used to infer compliance with the emission limits,
the EPA should make clear in the fi nal rule that the operating parameters requirements do not apply during a startup or a shutdown. The commenter recommended that the EPA should make this explicit (1) in the operating and monitoring requirement sections of Subparts AA and BB (proposed 40 CF R 63.605 and 63.625), and (2) by defining the averaging period (currently daily) as excluding periods of startup and shutdown ( p roposed 40 CFR Part 63, Subpart AA, Table 4 and Subpart BB, Table 4). As an alternative, the commenters recommended that if the EPA continues to require compliance with the parametric monitoring requirements during startup and shutdown periods, then the EPA should adopt a longer averaging period, from daily to 30 days, to allow for the effects of startups and shutdowns to be reduce d by a longer period of steady

- state operations. The commenter noted that the Boiler NESHAP has a 30

- day averaging period for pressure drop and liquid flow rate, and excludes periods of startup and shutdown from the averaging period (40 CFR 63.7575, defini tion of “30

- day rolling average”) and 40 CFR Part 63, Subpart DDDDD, Table 4)

. The commenter suggested that their suggested alternate would be substantially more stringent than the Boiler NESHAP approach since it would include periods of startup and shutdo wn in the 30

- day averaging period, while at the same time avoid misleading “exceedances” caused by the inclusion of periods of startup and shutdown compared to daily average parametric limits.14

- 24

Response to Comment: This comment is addressed in the preamble of the final rule. We disagree with the commenters about the applicability of the operating limits. Based on these comments, we have clarified in the final rule that to comply with the work practice during periods of startup and shutdown, facilities must m onitor the operating parameters specified in Table 3 to subpart AA or subpart BB and comply with the operating limits specified in Table 4 of subpart AA or subpart BB

.


### 14.0 OTHER COMMENTS

14.1 Scrubber Water to Cooling Tower Exemption
Comment: Two commenters (0038 , 0043 ) stated that they were concerned about the requirement that scrubber water may not be sent to evaporative cooling towers. The commenters noted these concerns go back to the 1999 rulemaking for subpart AA, and with similar language proposed for subpart BB, clarification was necessary to fully understand the requirement. The

commenters (0038 , 0043 ) stated their interpretation of the rule was that while scrubber water may not be sent to evaporative cooling towers, it may be discharged to cooling ponds or gypsum dewatering stack ponds. The commenters (0038 , 0043 ) stated that they were concerned about another interpretation, that when facilities have evaporative cooling towers, no scrubber water may reenter the process water system (i.e., scrubber water coul d not be sent to ponds either, as that water would eventually go through evaporative cooling towers). The commenters (0038 , 0043 ) continued that if this is the EPA’s interpretation of the requirement, then the costs and
effects on water balance would be si gnificant and they must be evaluated. Commenters (0038 , 0043 ) also stated the EPA did not determine the benefits from implementing the prohibition in the 1999 rulemaking nor the proposed rule, such as the advantage of or difference in emissions resulting f

rom sending scrubber water to ponds instead of evaporative cooling towers.
Commenters (0038 , 0043 ) stressed this topic because cooling ponds were a significant source of HF as well. Commenters also observed that there was not necessarily a directly relatio nship between fluoride in the water and HF emissions from evaporative cooling towers. The

commenters (0038 , 0043 ) recommended that the EPA revise §63.602(c) and §63.622(c) to include the word “directly,” in order to resolve this issue:14

- 25

(c) You must not di rectly introduce into any existing or new evaporative cooling tower any liquid effluent from any wet scrubbing device installed to control emissions from process equipment.
The commenters (0038 , 0043 ) noted this revision will avoid creating a burdensome “i ndirect” prohibition on using any water from ponds in an evaporative cooling tower, to the extent that the pond water might have contacted or received any amount of beneficially reused scrubber water. Response to Comment: We disagree with the commenters st atement that there is ambiguity in the requirements prohibiting the introduction of scrubbing water into cooling towers. In supplemental information provided by one commenter (refer to the March 6, 2007 letter addressed to Terry T. Uhling of J.R. Simplot C ompany which can be found in Appendix I
of Docket ID No. EPA

- HQ

- OAR

- 2012

- 0522

- 0043) , the EPA Region 10 Office of Compliance
and Enforcement noted that : “ Subpart AA Prohibits Sending Scrubber Water to Cooling Towers, Even Indirectly. ” We agree with that sta tement; the language of the prohibition is not ambiguous. It prohibits sending "into any evaporative cooling tower any liquid effluent from any wet scrubbing device installed to control emissions from process equipment" ( 40 C.F.R. § 63.602(e) (emphasis added) ) . Additionally, in an applicability determination made by the Agency on April 29, 2005, we clearly state that even if “scrubber liquid effluent at the facility is being diluted with other process waste waters” it is still subject to the rule, and a violation to reintroduce those liquids to the cooling tower. ( http://www.epa.gov/oecaadix/pdf/adi

- mact

- m050025.pdf ). Therefore, we are not amending the proposed regulatory text to clarify applicability, as we believe that the intent is abundantly clear. In addition, we are not revising the provision to only include ‘direct’ introduction of scrubber liquid effluent as this is contrary to the clearly expressed intent of the rule. The
argume nts raised in this action by the commenters regarding benefit and cost were previously raised and rejected during the initial rulemaking process for 40 CFR part 63, subpart AA

. The EPA promulgated 40 CFR part 63, subpart AA on June 10, 1999 (64 FR 31358)

. In the preamble to the June 10, 1999 final rule, EPA noted that a commenter argued the Agency had not considered the benefits or the compliance costs of the proposed work standard (i.e., to forbid the introduction of liquids containing the effluent from ai r pollution control devices into any evaporative cooling tower) and § 63.602(e) should be deleted; however, other commenters supported the Agency’s proposed requirement. In response to these comments, the Agency14

- 26

elected to base NESHAP upon the floor level of control (i.e., the least stringent option permitted by the Act) , and stated that any consideration of costs would be of significance only for consideration of options for control levels exceeding the floor level of stringency. With regard to
the comment ers statement about advantage of or difference in emissions resulting from sending
scrubber water to cooling ponds instead of evaporative cooling towers , e ven if fluoride emissions from cooling ponds are in fact higher than EPA understood them to be in 199 9 , EPA’s implicit determination in 1999, that routing scrubber water (even indirectly) to cooling towers results in higher fluoride emissions to the ambient air than routing scrubber water to cooling ponds or gypsum ponds , remains a valid determination . Fu rthermore, as stated in the preamble to the June 10, 1999 final rule, it does not make sense to scrub HF ( and other HAPs ) from potential emission points and then allow these HAPs to evaporate when the scrubber water is routed to evaporative cooling towers.

14.2 Miscellaneous
Comment: Two commenters (0039 , 0043 ) stated that the requirements for control techniques for “fugitive dust” should be removed because subpart AA is for the control of HAPs (not fugitive dust) and state environmental agencies regulate fugitive dust. Response to Comment: We agree with the co mmenters that the phrase “ fugitive dust”
should be removed from NESHAP subpart AA because the rule is for the control of HAPs and not fugitive dust. We have remov ed the phrase “fugitive dust” from the final rule at §63.602

.

14.3 Inherently Safer Technology (IST )
Comment : A commenter (0042) advocated that the EPA must address safety concerns from catastrophic incidents and resulting air pollution releases at fertilizer facilities during this rulemaking process. The commenter ’ s main recommendation is that the rule making should require and incentivize preventative measures within the chemical and fertilizer industries through the use of Inhere ntly Safer Technology (IST). The commenter presented the following arguments in favor of its position:

 Health studies. One in three U.S. school children goes to school within a vulnerability zone of a hazardous chemical facility, and they cite a report by Center for Effective
Government: at http ://www.foreffectivegov.org/files/kids

- in

- danger

- zones

- report.pdf

. They also contended that t he public supports the use of inherently safer, alternatives to14

- 27

current technologies, and they cite a national poll by Lake Research that showed that a strong major ity of likely voters from both parties support new requirements to use of
safer cost

- effective alternatives. http://preventchemicaldisasters.org/113

- 2

.

 Executive Order. President Obama signed an Exe cutive Order on August 1, 2013 recognizing that “additional measures can be taken by executive departments and agencies with regulatory authority to further improve chemical facility safety and security coordination with owners and operators. The commenter suggested that the EPA should use its CAA regulatory authority in 42 U.S.C. §7412(d), (f), and (r) to fulfill these objectives.

 Routine and catastrophic releases are preventable. Findings by the U.S. Chemical Safety Board (CSB) documented that several rec ent tragedies from refinery and other chemical plant disasters are often preventable, and made recommendations for preventative measures. The commenter claimed that the Board’s recommendation would also prevent release of HF. They provide two examples of f ertilizer plant explosions/releases from facilities “similar” to those covered by the EPA’s rule (i.e., April 2013 fertilizer storage/distribution plant in West Texas, and January 2010 release of phosgene at facility in Belle, WV), and refer to “at least s ix” major instances of HF releases from refineries in recent years. Also, the commenter cites the State of California’s response to the Chevron Richmond fire in 2012 that included recommendations to prevent similar incidents, which
the commenter claimed ar e applicable to chemical and fertilizer plants.

 Inherently Safer Technology (IST), also known as Inherently Safer Design (ISD). The commenter suggested that the EPA must apply recommendations from experts in chemical plant safety for the use of IST/ISD, and do so under its §7412(d) and (f) authorities. They provided a list of currently available ISTs, and compelled the EPA to require the application of these ISTs to be used at chemical and fertilizer plants:

o Requirement for anonymous near

- miss and other t ypes of anonymous safety and maintenance reporting. The commenter claimed this has been implemented at the Belle, WV plant (DuPont), and quoted Bureau of Safety and Environmental Enforcement Director Brian Salerno as committing to make this tool available to (the offshore oil and gas) industry “soon .”14

- 28 o Requirement for back

- up power to prevent toxic emission spikes. The commenter claimed that such systems represent a “development” within §7412(d)(6), which the EPA must update the §7412(d) standards to reflect

.

o Leak detection and repair requirements which can prevent leaks from turning into catastrophes. The commenter argued that EPA has not addressed leak detection and repair in this rulemaking, but the EPA should do so to satisfy its obligations under §7412(d ) and (f), and to assure safety. Response to C omment: Section 112(r) of the CAA was added in 1990 to address catastrophic releases

. EPA’s regulations on catastrophic releases appear in 40 CFR part 68

. We currently have a petition for rulemaking to address IST under CAA section 1 12(r) and part 68

. Also, pursuant to Executive Order 13650, EPA has issued a “Request for Information” soliciting public views on the appropriateness of IST regulations and is considering pursuing rulemaking as part of the regulation , standard and guidance modernization effort called for by the Executive
Order. Historically, EPA’s authority to address catastrophic releases under the NESHAP program was questioned under the pre 1990 CAA (see House Energy & Commerce, Rep. 101

- 490, at 157 (1990) (House Report); see also Senate Print 103

- 38, A Legislative History of the Clean Air Act Amendments of 1990, volume II, at 2743 (remarks of Representative Richardson, sponsor of House amendment on accidental releases adopted in House bill) (“Nothing in current law requires chemical or other industrial facilities handling toxic chemicals to take steps to avoid the accidental release of dangerous chemicals into the air”). To promote specific programs to
address the risks associated with accidental rele ases, Congress added CAA section 1 12(r) (see, e.g., House Report at 157); Senate Environment & Public Works, Rep. 101

- 228, at 205

– 07 (1989). In light of the extensive history and efforts of the agency on IST specifically and catastrophic accidents genera lly under the section 112(r) program, and in light of the statutory
structure of CAA section 1 12, we view the request to enact IST provisions in this rule to be outside the scope of CAA section 112(d)(2), section 112(f)(2) and section 112(d)(6)

. Therefore, this comment is outside the scope of the current rulemaking.14

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14.4 Extension Requests
Comment : Two commenters (0030, 0031) requested an extension to the comment period for the proposed rule. The commenters presented various reasons for this request, including, among others, the need to determine how the proposed changes ( the addition of entirely new
limits for HF and mercury emissions, new work practice standards for several processes, and a number of new monitoring and reporting requirements ) would impact specific facilities. Response to Comment : OAQPS/ SPPD
The EPA extend ed the deadline for written comments on the proposed amendments by 30 days to January 21, 2015 in order to afford additional time for review.

14.5 Organics Content Subcategory
Comment : One com menter (PCS, 5/1/15) recommended that the EPA create a new subcategory for WPPA processes that use phosphate rock with organics content greater than 0.9 percent. The commenter stated the phosphate rock used by PCS Aurora is the only phosphate
rock that exc eeds this organics content threshold, and is thus unique for the industry. The commenter (PCS, 5/1/15) provided a table comparing the organics content of various phosphate rocks used by the industry and noted their phosphate rock organics content is more t han twice the next highest phosphate rock. They claimed the high organic content requires them to calcine the rock to remove organics. The commenter (PCS, 5/1/15) continued that with the creation of this new subcategory, the Hg limit for phosphate rock cal ciners should be set at the MACT floor level and not at the beyond

- the

- floor level. Response to Comment : The EPA does acknowledge that the commenter has provided information to demonstrate the need for calcination at this facility. One option that was discussed with this commenter at a previous meeting (see the memorandum “ Summary of August 14, 2012 US EPA Meeting with PCS Phosphate ,” which is available in the docket for this action) was removal of calciner units to reduce mercury emissions. The comment er demonstrated that calcination was required due to the nature of raw materials used at this facility and the required specifications from some of the products. However, the EPA does not agree with the commenter’s statements that a subcategory for WPPA p rocess that use phosphate rock with organics content greater than 0.9 percent is appropriate. The CAA allows for subcategories based on class, type, and size of sources within a14

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category or subcategory (CAA § 112(d)(1) ) . The reason to develop subcategories is that typically different subcategories have different emissions characteristics, and using emissions data from processes that are inherently different to develop an emissions limit is sometimes not appropriate. However, that is not the case here. All t he data used to evaluate potential emissions from calciners came from this one facility and the commenter provided no data to indicate that the remainder of the process is different from other phosphoric acid process, only that, at this particular facility , additional pretreatment of the raw material is necessary. Therefore there is no basis or reason to develop different subcategories based on the presence of calciners and the EPA will not accept the suggested subcategory strategy.