[Federal Register Volume 77, Number 95 (Wednesday, May 16, 2012)]
[Rules and Regulations]
[Pages 29168-29205]
[FR Doc No: 2012-10633]

Vol. 77

Wednesday,

No. 95

May 16, 2012

Part VII

Environmental Protection Agency

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40 CFR Parts 9 and 449

 Effluent Limitations Guidelines and New Source Performance Standards
for the Airport Deicing Category; Final Rule

Federal Register / Vol. 77 , No. 95 / Wednesday, May 16, 2012 / Rules
and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9 and 449

[EPA-HQ-OW-2004-0038. FRL-9667-6]
RIN 2040-AE69

Effluent Limitations Guidelines and New Source Performance
Standards for the Airport Deicing Category

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is promulgating technology-based effluent limitations
guidelines (ELGs) and new source performance standards (NSPS) under the
Clean Water Act (CWA) for discharges from airport deicing operations.
The requirements generally apply to wastewater associated with the
deicing of airfield pavement at primary airports. The rule requires all
such airports to comply with requirements based on substitution of less
toxic pavement deicers that do not contain urea. The rule also
establishes NSPS for wastewater discharges associated with aircraft
deicing for a subset of new airports. These airports must also meet
requirements based on collection of deicing fluid and treatment of the
collected fluid. The ELGs and NSPS will be incorporated into National
Pollutant Discharge Elimination System (NPDES) permits issued by the
permitting authority. EPA expects compliance with this regulation to
reduce the discharge of deicing-related pollutants by 16 million pounds
per year. EPA estimates the annual cost of the rule at $3.5 million.

DATES: This final rule is effective on June 15, 2012.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OW-2004-0038. All documents in the docket are listed on the
Web site at http://www.regulations.gov. Although listed in the index,
some information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
through the docket Web site or in hard copy at the Office of Water
Docket, EPA West Building Room 3334, 1301 Constitution Ave. NW.,
Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30
p.m., Monday through Friday, excluding legal holidays. The telephone
number for the Public Reading Room is<PHONE_NUMBER>, and the telephone
number for the Office of Water Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For further information, contact Eric
Strassler, Engineering and Analysis Division, telephone:<PHONE_NUMBER>;
email<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Regulated Entities

    Entities regulated by this action may include:

------------------------------------------------------------------------
                                                        North American
                                      Example of           Industry
            Category               regulated entity     Classification
                                                          System code
------------------------------------------------------------------------
Industry........................  Primary airports..           481, 4881
                                  Airlines..........                4811
------------------------------------------------------------------------

    This section is not intended to be exhaustive, but rather provides
a guide for readers regarding entities that are likely to be regulated
by this action. Other types of entities that do not meet the above
criteria could also be regulated. To determine whether your facility is
regulated by this action, you should carefully examine the
applicability criteria listed in Sec.  449.1 and the definitions in
Sec.  449.2 of the rule and detailed further in Section V of this
preamble. If you still have questions regarding the applicability of
this action to a particular entity, consult one of the persons listed
for technical information in the preceding FOR FURTHER INFORMATION
CONTACT section.

Supporting Documentation

    Today's final rule is supported by a number of documents,
including:
     Technical Development Document for Final Effluent
Limitation Guidelines and Standards for the Airport Deicing Category
(TDD), Document No. EPA-821-R-12-005.
     Economic Analysis for Final Effluent Limitation Guidelines
and Standards for the Airport Deicing Category (EA), Document No. EPA-
821-R-12-004.
     Environmental Impact and Benefit Assessment for Final
Effluent Limitation Guidelines and Standards for the Airport Deicing
Category (EIB), Document No. EPA-821-R-12-003.

These documents are available in the public record for this rule and on
EPA's Web site at http://epa.gov/guide/airport.

Overview

    The preamble describes the terms, acronyms, and abbreviations used
in this notice; the background documents that support the regulations;
the legal authority of these rules; a summary of the final rule;
background information; and the technical and economic methodologies
used by the Agency to develop these regulations.

Table of Contents

I. Legal Authority
II. Purpose and Summary of the Final Rule
III. Background
    A. Clean Water Act
    B. NPDES Permits
    1. General Permits
    2. Individual Permits
    C. Effluent Guidelines and Standards Program
    1. Best Practicable Control Technology Currently Available (BPT)
    2. Best Conventional Pollutant Control Technology (BCT)
    3. Best Available Technology Economically Achievable (BAT)
    4. New Source Performance Standards (NSPS)
    5. Pretreatment Standards for Existing Sources (PSES)
    6. Pretreatment Standards for New Sources (PSNS)
    D. Proposed Rule
    1. ADF Collection
    2. Numeric Limit for Collected ADF
    3. Airfield Pavement Deicers
    4. Other Technology Basis Considered
IV. Scope and Applicability of Final Rule
    A. Subcategorization
    B. Industry Description
    C. Wastewater Sources and Wastewater Characteristics
    1. Aircraft Deicing
    2. Airfield Pavement Deicing
    D. Control and Treatment Technologies for the Aviation Industry
    1. ADF Collection Technologies
    2. ADF-Contaminated Wastewater Treatment Technologies
    3. Pollution Prevention Technologies
    4. Airfield Pavement Deicing Control Technologies
    E. Regulated Pollutants
V. Final Regulation
    A. BPT and BCT
    B. BAT
    1. Airfield Deicing

    2. Aircraft Deicing
    3. Options Considered for Today's Final Rule
    4. BAT Options Selection
    C. NSPS
    1. New Source Definition
    2. NSPS Applicability
    3. NSPS Option Selection
    D. PSES and PSNS
VI. Technology Costs and Pollutant Reductions
    A. Compliance Costs
    1. Overview
    2. Approach for Estimating Airfield Pavement Deicing Costs
    3. Approach for Developing Aircraft Deicing Costs
    4. Calculation of National Costs
    B. Approach to Estimating Pollutant Reductions
    1. Overview
    2. Sources and Use of Available Data
    C. Approach to Determining Long-Term Averages, Variability
Factors, and Effluent Limitation Guidelines and Standards
    1. Criteria Used To Select Data as the Basis of the Limitations
    2. Data Used as Basis of the Effluent Limitations
    3. Statistical Percentile Basis for Limitations
    4. Rationale for Establishing Limitation on Weekly Averages
Instead of Monthly Averages for COD in Effluent Discharges
    5. Rationale for Promulgating a Limitation Only for Daily
Discharges of Ammonia in Effluent Discharges
    6. Calculation of Limitations for COD and Ammonia
    7. Derivation of Long-Term Average for COD and Ammonia: Target
Level for Treatment
    8. Engineering Review of Effluent Limitations
VII. Economic Analysis
    A. Introduction
    B. Annualized Compliance Cost Estimates
    C. Economic Impact Methodologies
    1. Cost Annualization
    2. Airport Impact Methodology
    3. Co-Permittee Airline Impact Methodology
    D. Results of Impact Analysis
    1. Results of Airport Impact Analysis
    2. Results of Co-Permittee Airline Impact Analysis
    3. Economic Achievability
    E. Economic Impacts for New Sources
    F. Cost and Pollutant Reduction Comparison
    G. Small Business Analysis
VIII. Environmental Assessment
    A. Environmental Impacts
    B. Environmental Benefits
IX. Non-Water Quality Environmental Impacts
    A. Energy Requirements
    B. Air Emissions
    C. Solid Waste Generation
X. Regulatory Implementation
    A. Relation of ELGs and Standards to NPDES Permits
    B. Effective Date
    C. Compliance With the NSPS Requirement
    1. Applicability
    2. Demonstrating Compliance With the NSPS Collection Requirement
    3. P2 Approaches
    D. Alternative Compliance Option for Pavement Deicers Containing
Urea
    E. COD Effluent Monitoring for New Source Direct Dischargers
    F. Best Management Practices
    G. Upset and Bypass Provisions
    H. Variances and Modifications
    1. Fundamentally Different Factors (FDF) Variance
    2. Economic Variances
    3. Water Quality Variances
    I. Information Resources
XI. Statutory and Executive Order (EO) Reviews
    A. EO 12866: Regulatory Planning and Review and EO 13563:
Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act (UMRA)
    E. EO 13132: Federalism
    F. EO 13175: Consultation and Coordination With Indian Tribal
Governments
    G. EO 13045: Protection of Children From Environmental Health
and Safety Risks
    H. EO 13211: Energy Effects
    I. National Technology Transfer Advancement Act (NTTAA)
    J. EO 12898: Federal Actions To Address Environmental Justice in
Minority Populations and Low-Income Populations
    K. Congressional Review Act
Appendix A to the Preamble: Abbreviations and Definitions Used in
This Document

I. Legal Authority

    EPA is promulgating this regulation under the authorities of
sections 101, 301, 304, 306, 308, 402, and 501 of the CWA, 33 United
States Code (U.S.C.) 1251, 1311, 1314, 1316, 1318, 1342, and 1361 and
pursuant to the Pollution Prevention Act of 1990, 42 U.S.C. 13101 et
seq.

II. Purpose and Summary of the Final Rule

    Commercial airports and air carriers conduct deicing operations as
required by the Federal Aviation Administration (FAA). Airport
discharges from deicing operations may affect water quality in
surrounding communities, including reductions in dissolved oxygen, fish
kills, reduced organism abundance and species diversity, contamination
of drinking water sources (both surface and groundwater), creation of
noxious odors and discolored water in residential areas and parkland,
and other effects.
    Today, EPA is promulgating effluent limitations guidelines (ELGs)
and new source performance standards (NSPS) for the Airport Deicing
Point Source Category. The regulations address control of the
wastewater discharges from deicing operations based on product
substitution, wastewater collection practices used by airports, and
treatment practices for the collected wastewater. New source airports
within the scope of this rule are required to collect spent aircraft
deicing fluid (ADF) and meet numerical discharge limits. Those airports
and certain existing airports performing airfield pavement deicing are
to use non-urea-containing deicers, or alternatively, meet a numeric
effluent limitation for ammonia. The requirements are implemented in
CWA discharge permits.
    The rule requirements and the technologies that serve as the basis
for the ELGs and standards are explained in Sections IV, V, and VI of
this preamble.

III. Background

A. Clean Water Act

    Congress passed the Federal Water Pollution Control Act Amendments
of 1972, also known as the CWA, to ``restore and maintain the chemical,
physical, and biological integrity of the nation's waters.'' (33 U.S.C.
1251(a)). The CWA establishes a comprehensive program for protecting
our nation's waters. Among its core provisions, the CWA prohibits the
discharge of pollutants from a point source to waters of the United
States, except as authorized under the CWA. Under section 402 of the
CWA, EPA and delegated state permitting authorities authorize
discharges by a NPDES permit. The CWA also authorizes EPA to establish
national technology-based effluent limitation guidelines and standards
(effluent guidelines or ELGs) for discharges from different categories
of point sources, such as industrial, commercial, and public sources.
    In addition, the CWA authorizes EPA to promulgate nationally
applicable pretreatment standards that restrict pollutant discharges
from facilities that discharge wastewater indirectly through sewers
flowing to publicly owned treatment works (POTWs), as outlined in
section 307(b) and (c), 33 U.S.C. 1317(b) and (c). EPA establishes
national pretreatment standards for those pollutants in wastewater from
indirect dischargers that may pass through, interfere with, or are
otherwise incompatible with POTW operations. Generally, pretreatment
standards are designed to ensure that wastewaters from direct and
indirect industrial dischargers are subject to similar levels of
treatment. In addition, POTWs are required to implement local treatment
limits applicable to their industrial

indirect dischargers to satisfy any local requirements. See 40 CFR
403.5.
    Direct dischargers must comply with effluent limitations in NPDES
permits. Indirect dischargers, who discharge through POTWs, must comply
with pretreatment standards. Technology-based effluent limitations in
NPDES permits are derived from effluent limitations guidelines (CWA
sections 301 and 304, 33 U.S.C. 1311 and 1314) and new source
performance standards (section 306) promulgated by EPA, or based on
best professional judgment where EPA has not promulgated an applicable
effluent guideline or new source performance standard (CWA section
402(a)(1)(B), 33 U.S.C. 1342(a)(1)(B)). Additional limitations based on
water quality standards (CWA section 301(b)(1)(C), 33 U.S.C.
1311(b)(1)(C)) are also required to be included in the permit in
certain circumstances. The ELGs are established by regulation for
categories of industrial dischargers and are based on the degree of
control that can be achieved using various levels of pollution control
technology.
    EPA promulgates national ELGs and standards of performance for
major industrial categories for three classes of pollutants: (1)
Conventional pollutants (i.e., total suspended solids, oil and grease,
BOD5, fecal coliform, and pH), as outlined in section
304(a)(4) and 40 CFR 401.16; (2) toxic pollutants (e.g., toxic metals
such as chromium, lead, nickel, and zinc; toxic organic pollutants such
as benzene, benzo-a-pyrene, phenol, and naphthalene), as outlined in
section 307(a) of the Act, 40 CFR 401.15 and 40 CFR part 423 appendix
A; and (3) non-conventional pollutants, pollutants that are neither
conventional nor toxic (e.g., ammonia-N, formaldehyde, and phosphorus).

B. NPDES Permits

    Section 402 of the CWA requires permits for point source discharges
of pollutants to waters of the United States. In most states, the
permits are issued by a state agency that has been authorized by EPA.
Currently, 46 states and one U.S. territory are authorized to issue
NPDES permits. In the other states and territories, EPA issues the
permits.
    Section 402(p) of the Act, added by the Water Quality Act of 1987
(Pub. L. 100-4, February 4, 1987), requires stormwater dischargers
``associated with industrial activity'' to be covered under an NPDES
permit. In its initial stormwater permit regulations, called the
``Phase I'' stormwater regulations (55 FR 47990, November 16, 1990),
EPA designated air transportation facilities, including both airlines
and airports, that have vehicle maintenance shops (including vehicle
rehabilitation, mechanical repairs, painting, fueling, and
lubrication), equipment cleaning operations, or airport deicing
operations as subject to NPDES stormwater permitting requirements. See
40 CFR 122.26(b)(14)(viii).
    Airport stormwater discharges may be controlled under a general
NPDES permit, which covers multiple facilities with similar types of
operations and/or wastestreams, or by an individual permit. An airport
may have additional NPDES permits for non-stormwater discharges, such
as from equipment repair and maintenance facilities. The following
discussion pertains only to airport stormwater permits.
1. General Permits
    Currently, most airport deicing discharges are covered by a general
permit issued by either EPA or an NPDES-authorized state agency. In
most areas where EPA is the permit authority, the Multi-Sector General
Permit (MSGP) covers airport deicing discharges (73 FR 56572, September
29, 2008). Many NPDES-authorized state agencies have issued general
permits in their respective jurisdictions with requirements similar to
the MSGP. An airport seeking coverage under a general permit submits a
Notice of Intent (NOI) to the permit authority rather than a detailed
permit application. By submitting an NOI, the permittee is agreeing to
comply with the conditions in the final general permit.
    For airports, the major requirements of the current MSGP, include
the following:
     Develop a stormwater pollution prevention plan, including
a drainage area site map, documentation of measures used for management
of deicing contaminated stormwater, an evaluation of runway and
aircraft deicing operations, and implementation of a program to control
or manage deicing contaminated stormwater, including consideration of
various listed control practices.
     Implement deicing source reduction measures, including
minimizing or eliminating the use of urea and glycol-containing deicing
chemicals; minimizing contamination of deicing contaminated stormwater
from runway and aircraft deicing operations; evaluating whether over-
application of deicing chemicals occurs; and consider use of various
listed source control measures.
     For airports using more than 100,000 gallons of glycol-
based deicing chemicals and/or 100 tons or more of urea containing
deicers annually, monitor discharges quarterly for the first four
quarters of the permit cycle, for the following pollutants: biochemical
oxygen demand (BOD 5), chemical oxygen demand (COD),
ammonia, and pH.
     If the average of the four monitoring values for any
parameter exceeds its benchmark, implement additional control measures
where feasible, and continue monitoring.
     Conduct an annual site inspection during the deicing
season, and during periods of actual deicing operations if possible, as
well as routine facility inspections at least monthly during the
deicing season.
    EPA expects to modify the MSGP when the next permit is issued, to
conform it to today's final Airport Deicing rule.
2. Individual Permits
    Some EPA and state NPDES-permitting authorities have required
certain airports to obtain individual permits. In these situations, an
airport must submit a detailed application and the permit authority
develops specific requirements for the facility.
    Some individual permits contain specialized requirements for
monitoring and/or best management practices (BMPs). Some of these
permits also contain numeric water quality-based effluent limitations.
Information on water quality-based permitting is available on EPA's Web
site at http://cfpub.epa.gov/npdes/generalissues/watertechnology.cfm.

C. Effluent Guidelines and Standards Program

    Effluent guidelines and NSPS are technology-based regulations that
are developed by EPA for a category of dischargers. These regulations
are based on the performance of control and treatment technologies. The
legislative history of CWA section 304(b), which is the heart of the
effluent guidelines program, describes the need to press toward higher
levels of control through research and development of new processes,
modifications, replacement of obsolete plans and processes, and other
improvements in technology, taking into account the cost of controls.
Congress has also stated that EPA need not consider water quality
impacts on individual water bodies as the guidelines are developed; see
Statement of Senator Muskie (October 4, 1972), reprinted in Legislative
History of the Water Pollution Control Act Amendments of 1972, at 170.
(U.S. Senate, Committee on Public Works, Serial No. 93-1, January
1973.)

    There are four types of standards applicable to direct dischargers
(dischargers to surface waters), and two standards applicable to
indirect dischargers (discharges to POTWs).
1. Best Practicable Control Technology Currently Available (BPT)
    Traditionally, EPA establishes BPT effluent limitations based on
the average of the best performances of facilities within the industry,
grouped to reflect various ages, sizes, processes, or other common
characteristics. EPA may promulgate BPT effluent limits for
conventional, toxic, and non-conventional pollutants. In specifying
BPT, EPA looks at a number of factors. EPA first considers the cost of
achieving effluent reductions in relation to the effluent reduction
benefits. The Agency also considers the age of the equipment and
facilities, the processes employed, engineering aspects of the control
technologies, any required process changes, non-water quality
environmental impacts (including energy requirements), and such other
factors as the Administrator deems appropriate. See CWA section
304(b)(1)(B). If, however, existing performance is uniformly
inadequate, EPA may establish limitations based on higher levels of
control than what is currently in place in an industrial category, when
based on an Agency determination that the technology is available in
another category or subcategory, and can be practically applied.
2. Best Conventional Pollutant Control Technology (BCT)
    The 1977 amendments to the CWA required EPA to identify additional
levels of effluent reduction for conventional pollutants associated
with BCT technology for discharges from existing industrial point
sources. In addition to other factors specified in section
304(b)(4)(B), the CWA requires that EPA establish BCT limitations after
consideration of a two part ``cost-reasonableness'' test. EPA explained
its methodology for the development of BCT limitations in July 1986 (51
FR 24974). Section 304(a)(4) designates the following as conventional
pollutants: BOD 5 measured over five days, total suspended
solids, fecal coliform, pH, and any additional pollutants defined by
the Administrator as conventional. The Administrator designated oil and
grease as an additional conventional pollutant on July 30, 1979 (44 FR
44501; 40 CFR 401.16).
3. Best Available Technology Economically Achievable (BAT)
    BAT represents the second level of stringency for controlling
direct discharge of toxic and nonconventional pollutants. In general,
BAT ELGs represent the best economically achievable performance of
facilities in the industrial subcategory or category. The factors
considered in assessing BAT include the cost of achieving BAT effluent
reductions, the age of equipment and facilities involved, the process
employed, potential process changes, and non-water quality
environmental impacts, including energy requirements and such other
factors as the Administrator deems appropriate. The Agency retains
considerable discretion in assigning the weight to be accorded these
factors. Economic achievability is an additional statutory factor
considered in setting BAT. Generally, EPA determines economic
achievability on the basis of total costs to the industry and the
effect of compliance with BAT limitations on overall industry and
subcategory financial conditions. As with BPT, where existing
performance is uniformly inadequate, BAT may reflect a higher level of
performance than is currently being achieved based on technology
transferred from a different subcategory or category. BAT may be based
upon process changes or internal controls, even when these technologies
are not common industry practice.
4. New Source Performance Standards (NSPS)
    NSPS reflect effluent reductions that are achievable based on the
best available demonstrated control technology (BADCT). Owners of new
facilities have the opportunity to install the best and most efficient
production processes and wastewater treatment technologies. As a
result, NSPS should represent the most stringent controls attainable
through the application of the BADCT for all pollutants (that is,
conventional, nonconventional, and priority pollutants). In
establishing NSPS, EPA is directed to take into consideration the cost
of achieving the effluent reduction and any non-water quality
environmental impacts and energy requirements.
5. Pretreatment Standards for Existing Sources (PSES)
    Section 307(b) calls for EPA to issue pretreatment standards for
discharges of pollutants to POTWs. PSES are designed to prevent the
discharge of pollutants that pass through, interfere with, or are
otherwise incompatible with the operation of POTWs. Categorical
pretreatment standards are technology-based and are analogous to BPT
and BAT effluent limitation guidelines. See CWA sections 301((b)(1)(B)
and 301(b)(2)(A)), 33 U.S.C. 1311(b)(1)(B) and 1311(b)(2)(A). The
General Pretreatment Regulations, which set forth the framework for the
implementation of categorical pretreatment standards, are found at 40
CFR part 403. These regulations establish pretreatment standards that
apply to all non-domestic dischargers. See 52 FR 1586 (January14,
1987).
6. Pretreatment Standards for New Sources (PSNS)
    Section 307(c) of the Act calls for EPA to promulgate PSNS. Such
pretreatment standards must prevent the discharge of any pollutant into
a POTW that may interfere with, pass through, or may otherwise be
incompatible with the POTW. EPA promulgates PSNS based on best
available demonstrated technology for new sources. New indirect
dischargers have the opportunity to incorporate into their facilities
the best available demonstrated technologies. The Agency typically
considers the same factors in promulgating PSNS as it considers in
promulgating NSPS.

D. Proposed Rule

    EPA published a proposed rule for the Airport Deicing Category on
August 28, 2009 (74 FR 44676). The proposed rule covered primary
commercial airports that conduct deicing operations and have 1,000 or
more annual jet departures. An existing airport in the scope of the
proposal would have been required to certify that it uses airfield
pavement deicers that do not contain urea, or alternatively, meet an
effluent limitation for ammonia. Additionally, in-scope airports with
10,000 or more annual departures would have been required to:
     Collect at least a specified proportion (either 20 or 60
percent, based on size) of available ADF after it is sprayed on
aircraft; and
     Meet a specified numeric effluent limit for ADF wastewater
collected and discharged directly.
    As proposed, all in-scope new source dischargers had the same
airfield pavement deicing requirements as existing sources and were
required to collect 60 percent of available ADF and meet the specified
numeric limit for direct discharges of the collected fluid. EPA
estimated that the proposed rule would apply to 218 existing airports;
110 airports for both the pavement deicer and ADF collection and

discharge requirements, and another 108 airports for the pavement
deicer requirement only. Of those 218 airports, the Agency estimated
that 148 airports were already in compliance with the proposed
requirements.
1. ADF Collection
    The proposed rule would have required all existing primary airports
that have 10,000 or more annual departures to collect at least 20
percent of available ADF. The 20 percent collection requirement was
based on the estimated performance of glycol collection vehicles
(GCVs). Those primary airports that use 460,000 or more gallons of
normalized ADF annually, which make up a small subset of this group,
would have been required to collect at least 60 percent of all
available ADF. (As defined in proposed Sec.  449.2, normalized ADF is
ADF less any water added by the manufacturer or customer before ADF
application.) This collection requirement was based on the estimated
performance of centralized deicing pads (CDPs). In-scope primary
airports with less than 10,000 annual departures would not have been
required to meet the national ELG requirements to collect their
available deicing fluid or meet associated discharge limitations and
would have continued to be subject to case-by-case Best Professional
Judgment (BPJ) permitting requirements for ADF collection and
treatment.
2. Numeric Limit for Collected ADF
    For airports discharging collected ADF directly to surface waters,
the proposal would have required these airports to meet numeric
effluent limitations for COD. The limits were based on anaerobic
fluidized bed (AFB) treatment technology.
3. Airfield Pavement Deicers
    EPA proposed BAT for direct dischargers associated with airfield
pavement deicing based on product substitution. Specifically, EPA based
BAT on the substitution of pavement deicers containing urea with
alternative, less toxic products that are also effective and not
harmful to aircraft.
4. Other Technology Basis Considered
    In the proposed rule, in addition to CDPs and GCVs, EPA described
plug-and-pump technology with GCVs as a possible BAT basis for an ADF
collection requirement, and calculated the cost of this technology.
This technology, when used in combination with GCVs, is estimated to
collect at least 40 percent of available ADF.

IV. Scope and Applicability of Final Rule

    This final rule applies to primary airports. Existing airports with
greater than or equal to 1,000 annual departures by non propeller
driven aircraft must meet BAT requirements at Sec.  449.10, as
applicable.
    A new airport with deicing discharges and located in specified
geographic locations (see section V.C.2), that is operating less than
1,000 non-propeller aircraft departures annually is not required to
meet the NSPS provisions in Sec.  449.11. However, if the number of
departures later increases above that threshold, then the substantive
requirements in Sec.  449.11 apply. This means that a new airport that
expects to eventually exceed the 1,000 departure threshold must plan to
install and operate facilities that will comply with the requirements
of that section once it reaches the threshold of 1,000 non-propeller
departures annually.

A. Subcategorization

    EPA may divide a point source category into groupings called
``subcategories'' to provide a method for addressing variations among
products, processes, and other factors, which result in distinctly
different effluent characteristics. See Texas Oil & Gas Ass'n. v. US
EPA, 161 F.3d 923, 939-40 (5th Cir. 1998). Regulation of a category by
subcategories provides that each subcategory has a uniform set of
effluent limitations that takes into account technological
achievability and economic impacts unique to that subcategory. In some
cases, effluent limitations within a subcategory may be different based
on consideration of these same factors, which are identified in CWA
section 304(b)(2)(B). The CWA requires that EPA, in developing effluent
guidelines, consider a number of different factors, which are also
relevant for subcategorization. The CWA also authorizes EPA to take
into account other factors that the Agency deems appropriate.
    In developing today's rule, EPA considered whether subcategorizing
the aviation industry was warranted. In addition to those factors
specified in the CWA, EPA evaluated a number of factors and potential
subcategorization approaches, including the presence of an onsite
glycol reclamation facility, amount of ADF applied, number of
departures, availability of land to install collection systems, and FAA
airport classifications. EPA concluded that establishing formal
subcategories is not necessary for the Airport Deicing category. EPA
structured the applicability and requirements of the final rule to
account for the relevant factors (e.g., amount of ADF applied) and has
established a set of requirements appropriate for the range of
situations that an airport may encounter during deicing operations.

B. Industry Description

    The Airport and Airway Improvement Act (AAIA), 49 U.S.C. Chapter
471, defines airports by categories of airport activities, including
Commercial Service (Primary and Non-Primary), Cargo Service, and
Reliever. These categories are not mutually exclusive; an airport may
be classified in more than one of these categories. Another group of
generally smaller airports, not specifically defined by AAIA, is
commonly known as ``general aviation'' airports. EPA estimates that
there are approximately 500 commercial service airports.
    Commercial service airports are publicly owned airports that have
at least 2,500 passenger boardings each calendar year and receive
scheduled passenger service. Passenger boardings refer to revenue
passenger boardings on an aircraft in service in air commerce, whether
or not in scheduled service. The definition also includes passengers
who continue on an aircraft in international flight that stops at an
airport in any of the 50 states for a non-traffic purpose, such as
refueling or aircraft maintenance rather than passenger activity.
Passenger boardings at airports that receive scheduled passenger
service are also referred to as ``enplanements.''
    Primary commercial service airports (primary airports) have more
than 10,000 passenger boardings each year. Primary airports are further
subdivided into Large Hub, Medium Hub, Small Hub and Non-Hub
classifications, based on the percentage of total passenger boardings
within the United States in the most recent calendar year ending before
the start of the current fiscal year.
    Early in the regulatory development process, EPA focused on deicing
activities at primary airports, particularly those with extensive non-
propeller traffic. Operators of general aviation aircraft, as well as
smaller commercial non-jet aircraft, typically suspend flights during
icing conditions, whereas commercial airlines operating at primary
airports are much more likely to deice their jets in order to meet
customer demands.
    Based on the results of industry surveys that EPA conducted prior
to the proposed rule, the Agency estimated that 320 primary airports
conduct deicing operations. EPA reviewed the

relative sizes of various airports (based on annual departures), the
levels of deicing activity, traffic characteristics (i.e., passenger
versus cargo operations), the extent of pollution controls and
treatment in place, and the costs of various technologies for these
airports. EPA further classified airports based on the number of annual
non-propeller departures. EPA found that there were some primary
airports, typically smaller airports, with high percentages of
propeller aircraft, and therefore excluded airports with fewer than
1,000 annual non-propeller departures from the scope of the proposed
rule. These airports have a higher proportion of propeller-aircraft
flights, which are typically delayed or cancelled during icing
conditions (i.e., far less deicing takes place at these airports and
far less deicing fluid is used, than at airports serving more jets).

C. Wastewater Sources and Wastewater Characteristics

1. Aircraft Deicing
    Airlines apply most ADF to aircraft through pressurized spraying
systems, mounted either on trucks that move around an aircraft, or on
large fixed boom devices located at a pad dedicated to deicing.
    Most of the ADF sprayed is Type I fluid, which is designed for
minimal adhesion to aircraft surfaces. Consequently, the majority of
Type I ADF is available for discharge due to dripping, over-spraying,
tires rolling through or sprayed with fluid, and shearing during
takeoff. Once the ADF has reached the ground, it will then mix with
precipitation, as well as other chemicals found on airport surfaces;
these chemicals typically include aircraft fuel, lubricants and
solvents, and metals from aircraft, ground support and utility
vehicles. Water containing these substances enters an airport's storm
drain system. At many airports, the storm drains discharge directly to
U.S. waters with no treatment.
    Type IV fluid, an anti-icing chemical, is designed to adhere to the
aircraft. Because of this adherence characteristic, EPA estimated that
the majority of Type IV fluid is not available for collection.
    For the purposes of this rule, the pollutant loadings are discussed
in terms of applied ADF and how much of that ADF is expected to be
discharged. A more detailed discussion of loadings estimates is
presented in Section VI.B. Given the highly variable nature of storm
events, it is difficult to estimate flows or concentrations of ADF-
contaminated stormwater generated at an airport. Those factors are
greatly dependent on site-specific factors, such as the size of the
storm event associated with the discharge, drainage characteristics,
ADF collection systems (if present), and airport operations.
Additionally, due to the design of drainage systems at some airports,
discharges may occur well after a storm event has completed.
2. Airfield Pavement Deicing
    Most solid airfield deicing chemical products are composed of an
active deicing ingredient (e.g., potassium acetate, sodium acetate) and
a small amount of additives (e.g., corrosion inhibitors). Liquid
airfield deicing chemical products are composed of an active ingredient
(e.g., potassium acetate, propylene glycol), water, and minimal
additives. The airfield deicing products that include salts (i.e.,
potassium acetate, sodium acetate, and sodium formate) will all ionize
in water, creating positive salt ions (K\+\, Na\+\), BOD5,
and COD load as the acetate or formate ion degrades into carbon dioxide
(CO2) and water. Pavement deicers containing urea will
degrade to ammonia, as well as generate BOD5 and COD load.
    Most of EPA's deicing characterization data does not reflect
airfield pavement deicers. However, EPA collected samples from a few
locations at Detroit Metro Airport that contain airfield deicing
stormwater. Detroit Metro and Pittsburgh, both large hub airports,
provided sampling data associated with stormwater contaminated by
airfield pavement deicers. More information on these sampling
activities is provided in the TDD. As with the aircraft deicers, the
variability of storm events and drainage systems makes it difficult to
estimate flows or concentrations of pavement deicing waste streams
generated at an airport.

D. Control and Treatment Technologies for the Aviation Industry

    The ADF application process has presented a challenge for those
airports attempting to manage their contaminated stormwater streams.
The process of applying ADF to aircraft through high pressure spraying,
combined with the typical practices of spraying the aircraft outdoors
in multiple, large unconfined (but usually designated) spaces, results
in pollutants being dispersed over a wide area and entering storm
drains at multiple locations. This process contrasts sharply with many
other industries where pollutants are generated in confined areas,
managed through a piping system, and not commingled with precipitation.
    EPA has identified several technologies that are available to
collect and manage portions of the ADF wastestream. Some of these
collection technologies are more effective than others. EPA has also
identified several pollution prevention (P2) approaches that may be
used to minimize the amount of ADF applied. However, no single
technology or P2 approach is capable of collecting or eliminating all
applied ADF, as a portion of the fluid is designed to adhere to the
aircraft until after takeoff, in order to ensure safe operations.
Furthermore, with few exceptions, tracking by aircraft tires, wind
dispersion, and dripping during taxiing and takeoff ensures that some
amount of sprayed ADF, even if performed in a contained area, will end
up in the drainage system of the airport. For these reasons, EPA
concludes that all airports that perform aircraft deicing operations
are direct dischargers. There are limited instances where an airport in
a warm climate that performs only defrosting and gets little to no
precipitation may, in fact, not discharge any deicing materials.
    Once the available ADF wastestream is collected, it can be treated,
and this process is similar to many other industries that generate
wastewater. In a similar manner, airfield deicing has presented a
challenge for airports attempting to manage their contaminated
stormwater streams. Airfield deicing is typically conducted over a
large area, including areas with frequent aircraft traffic, such as
runways, where active collection technologies (i.e., GCVs) are
impractical to implement. At this time, EPA has not identified any
available economically achievable technologies for the collection of
pavement deicing stormwater. As a result, EPA also examined P2
technologies, which can reduce or eliminate the use of ADF chemicals
and urea containing deicers for pavement deicing in today's final rule.
    The following section discusses the technologies EPA considered for
ADF collection and treatment and for addressing airfield deicing.
1. ADF Collection Technologies
a. GCV
    A GCV is a truck that utilizes a vacuum mechanism to gather
stormwater contaminated with ADF, resulting from deicing operations.
GCVs are typically stationed near the ADF spraying trucks and are
deployed either during aircraft deicing activities or after the
aircraft deicing activity has been completed. The GCV then transports
the

ADF-contaminated stormwater to an onsite storage and/or equalization
facility, after which the material is either treated at the airport or
sent offsite for treatment. EPA estimates that GCVs typically collect
at least 20 percent of the available ADF when properly operated and
maintained.
b. Plug and Pump
    The plug and pump collection system utilizes an airport's existing
stormwater collection system infrastructure to contain and collect ADF
contaminated stormwater. Plug and pump systems also commonly utilize
GCVs for ancillary ADF collection. Typical GCV deployment may include
collecting ADF that has been sprayed beyond the plug and pump
containment area or as an additional collection measure at the gate,
ramp, and/or apron area after deicing operations and active plug and
pump collection have ceased. The plug and pump system operates by
placing either temporary inflatable balloons or storm sewer shutoff
valves in the existing storm sewer system. During deicing events, the
balloons are inflated and storm sewer shutoff valves are closed,
trapping the ADF-contaminated stormwater in the collection system.
Vacuum trucks pump the trapped contaminated stormwater from the storm
sewer system and transport the liquid to onsite storage and/or
equalization. In addition, catch basin inserts can be placed into
manholes to collect ADF-contaminated stormwater.
c. CDPs
    A CDP is a paved area on an airfield built specifically for
aircraft deicing operations. It is typically located adjacent to a gate
area, taxiway, or runway, and constructed with a drainage system
separate from the airport's main storm drain system. A CDP is usually
constructed of concrete with sealed joints to prevent the loss of
sprayed ADF through the joints. The pad's collection system is
typically connected to a wastewater storage facility, which then may
send the wastewater to an onsite or offsite treatment facility.
    Some airports use GCVs in combination with CDPs to collect ADF that
lands outside the pad collection area in order to maximize collection
and containment of ADF-contaminated stormwater. Airports typically
locate the pads near the gate areas or at the threshold of a runway to
minimize delays in aircraft takeoff and to enhance the effectiveness of
the ADF applied by limiting time between application and takeoff.
    CDPs reduce the volume of deicing wastewater by restricting deicing
to small areas, and managing the collected wastewater through a
dedicated drain system. EPA estimates that CDPs allow airports to
collect at least 60 percent of the available ADF.
d. Summary of ADF Collection Technology Usage
    EPA estimates the number of airports that use each of the above
collection technologies in Table IV-1. Some airports use more than one
technology, and some of the airports in the estimate use the technology
for only a portion of their ADF-contaminated stormwater.

   Table IV-1--Estimated Totals of ADF Collection Technologies Used by
                                Airports
------------------------------------------------------------------------
                                                             Number of
                  Collection technology                      airports
------------------------------------------------------------------------
Glycol Collection Vehicle...............................              53
Plug and Pump...........................................              29
Centralized Deicing Pad.................................              66
------------------------------------------------------------------------

See Section 8.2 of the TDD for further explanation of EPA's estimates
of the ADF collection rates for the fluid collection technologies.
2. ADF-Contaminated Wastewater Treatment Technologies
    In the proposed rule, EPA identified four technologies for treating
ADF-contaminated wastewater: AFB, Ultrafiltration/Reverse Osmosis,
Mechanical Vapor Recompression and Distillation, and Aerated Pond. The
Agency selected AFB for further consideration and rejected the other
technologies. See 74 FR 44687 and the TDD.
    An AFB treatment system uses a vertical, cylindrical tank in which
the ADF-contaminated stormwater is pumped upwards through a bed of
granular activated carbon at a velocity sufficient to fluidize, or
suspend, the media. A thin film of microorganisms grows on and coats
each granular activated carbon particle, providing a vast surface area
for biological growth. These microorganisms provide treatment of the
ADF-contaminated stormwater. Byproducts from the AFB treatment system
include methane, CO2, and new biomass (animal material,
bacteria). The AFB treatment system includes storage as an initial step
to equalize flows and pollutant concentrations that feed into the
biological treatment unit.
    Treating wastes using an anaerobic biological system as compared to
an aerobic system offers several advantages. The anaerobic system
requires much less energy since aeration is not required and the
anaerobic system produces less than 10 percent of the sludge of an
aerobic process. In addition, because the biological process is
contained in a sealed reactor, odors are eliminated. Based on EPA
sampling results, the AFB treatment system successfully removes over 98
percent of BOD5, over 97 percent of COD, and over 99 percent
of propylene glycol from deicing wastestreams. This treatment reduces
the BOD5 and COD loads discharged to receiving waters by
over 98 and 97 percent, respectively. Two airports in the United States
use the AFB technology: Albany International Airport in Albany, New
York, and Akron-Canton Regional Airport, in Akron, Ohio. Additionally,
Portland International Airport in Oregon recently installed an AFB
system and T.F. Green Airport in Providence, Rhode Island is planning
the installation of this technology.
 3. Pollution Prevention Technologies
    EPA has identified several technologies currently in use at
airports across the United States that may reduce ADF usage. The
following section describes the major P2 approaches EPA identified
during this rulemaking. EPA notes that it did not identify these ADF P2
approaches as a technology basis for BAT or NSPS in today's final rule
due to a lack of available quantitative data on the actual pollutant
reductions that these technologies may achieve and, moreover, because
of a lack of data correlating minimized ADF application with safe
deicing practices. However, EPA is aware that many airports use these
technologies successfully and EPA encourages additional use.
Furthermore, EPA notes that the collection technologies evaluated for
today's rule are only capable of collecting a portion of the applied
ADF. Therefore, to the extent that P2 technologies are proven to be
effective, they have the ability to considerably reduce or eliminate
ADF discharges. The ability to reduce the amount of applied deicing
chemicals will not only have a positive environmental effect, but may
also be cost-effective, as the decreases in costs of purchased deicing
chemicals may offset the cost of the technology itself.
    EPA applauds all efforts to develop deicing chemicals and
approaches that reduce or eliminate pollutant discharges. In order to
ensure that this rule doesn't prevent such approaches as they become
proven, feasible, and available, today's final rule includes a
provision to apply a P2 credit against the standard ADF collection

requirement. See Section X.C., ``Compliance with the NSPS
Requirement,'' in this preamble.
    In addition EPA notes that in discussions with the major airline
and airport industry associations, ATA and ACI-NA, they stressed their
commitment to pollution prevention approaches to reduce aircraft
deicing discharges, while ensuring safety at all times, and the great
strides they had made on pollution prevention approaches in addition to
employing ADF collection technologies (see DCN AD01333). As a follow-up
to these conversations, industry associations submitted a description
of a voluntary pollution reduction program designed to further spur the
industry towards safely reducing ADF discharges to the environment.
Under the program, these associations intend to work together to:
     Conduct outreach and facilitate information exchange on
the program and available pollution reduction technologies;
     Encourage the development, testing, and commercially
appropriate deployment of pollution reduction technologies;
     Provide information characterizing the qualitative and
quantitative performance and environmental benefits of appropriate
pollution reduction technologies;
     Develop a quantitative goal for environmental benefits to
be achieved through this program;
     Inventory pollution reduction technologies adopted during
this program;
     Develop a comparison of the environmental benefits of
pollution reduction technologies adopted during the program with the
quantitative goal; and
     Report the results of the above components to EPA.

EPA supports this pollution prevention program and believes it has the
potential to significantly reduce aircraft deicing discharges in a safe
manner. See DCN AD01334 for more details on industry's pollution
prevention program.
a. Infrared (IR) Deicing Systems
    A few U.S. airports have used IR heating systems for several years
and these systems have been demonstrated to deice aircraft effectively.
One type of IR system consists of an open-ended hangar-type structure
with IR generators mounted inside, suspended from the ceiling. The IR
equipment is designed to use specific wavelengths that heat ice and
snow, and minimize heating of aircraft components. The IR energy level
and wavelength may be adjusted to suit the type of aircraft. Although
the system can deice an aircraft, it cannot provide aircraft with anti-
icing protection. Consequently, when the ambient temperature is below
freezing, anti-icing fluid is typically applied to the aircraft after
it leaves the hangar. In addition, a small amount of deicing fluid may
be required for deicing areas of the aircraft not reached by the IR
radiation, such as the flap tracks and elevators. The system,
therefore, does not completely replace glycol-based fluids, but may
greatly reduce the volume required.
    Vendors claim use of an IR system reduces the amount of Type I ADF
required by up to 90 percent. John F. Kennedy International Airport, in
New York, uses an IR system for a small percentage of its flights.
b. Forced Air/Hot Air Deicing Systems
    Forced air/hot air deicing systems are currently in operation at a
few U.S. airports. These systems use forced air to blow snow and ice
from aircraft surfaces. Some systems allow deicing fluids to be added
to the forced air stream at different flow settings (e.g., 9 and 20
gallons/minute), while other systems require separate application of
deicing fluid. Several vendors are currently developing self-contained,
truck-mounted versions of these forced-air systems, and most systems
can be retrofitted onto existing deicing trucks.
    The double gantry forced-air spray system is a similar method to
truck-mounted forced-air systems. The gantries support a set of high-
and low-pressure nozzles, which blast the aircraft surfaces with heated
air at a pressure of 40 to 500 pounds per square inch. When weather
conditions are severe, a small volume of water and glycol may be added
to the air stream to remove dense coverings of snow and ice. Airfield
use of the gantry system has been limited, perhaps because it is a
permanently mounted system that has been known to cause delays in
aircraft departures.
c. Product Substitution
    Another solution to environmental problems associated with deicing
chemicals is to replace chemical deicers with more environment-friendly
products. In the ADF products category, initially the predominant
deicers were based on ethylene glycol, whereas in recent years,
propylene glycol-based deicers, which are less toxic to mammals, have
become more widely used. Chemical manufacturers, the aviation industry,
and the U.S. Air Force are continuing to explore development of deicers
that could generate lower levels of pollutants compared to the glycol-
based products.
4. Airfield Pavement Deicing Control Technologies
    EPA identified product substitution as an available control
technology for airfield pavement deicing chemicals. The Agency did not
identify an available economically achievable technology to collect and
treat wastewater containing pavement deicing pollutants.
    Several types of products, such as potassium acetate, sodium
formate, and sodium acetate, are available as alternatives to pavement
deicers containing urea. The results from EPA's airport questionnaire
reported that 83 percent of primary airports use airfield pavement
deicers that do not contain urea. The most widely used substitute
product, potassium acetate, accounts for 63 percent (by weight) of the
annual airfield pavement deicer usage in the United States.

E. Regulated Pollutants

    EPA identified 31 pollutants of concern that stem directly from
airport deicing operations. For today's final rule, EPA identified COD
as a pollutant of concern to be controlled for discharges of collected
ADF contaminated stormwater and urea and ammonia as pollutants of
concern to be controlled in discharges of airfield deicing contaminated
stormwater. See Section 6 of the TDD for a full discussion of
pollutants of concern and for EPA's rationale for selecting regulated
pollutants.

V. Final Regulation

A. BPT and BCT

    EPA considered whether, in this rule, it was necessary to establish
BPT limits, given that pavement deicers will be controlled at the BAT
level, which is no less stringent than the BPT limit. Because the same
wastestream that would be controlled by BPT is also controlled by BAT,
it is not necessary for EPA to promulgate BPT effluent limitations
guidelines for the Airport Deicing Category, given that the BAT
collection and treatment requirements on that wastestream would be at
least as stringent as BPT requirements. Similarly, EPA is not
establishing BCT limitations for this industry because the same
wastestream that would be controlled by BCT is being controlled by BAT.

B. BAT

1. Airfield Deicing
a. Applicability/Scope of Airfield Deicing Discharge Requirements
    EPA did not receive significant comments regarding the scope of the
requirements for controlling airfield deicing discharges. EPA has
retained the scope as described in the proposal: primary airports with
departures of 1,000 or more non-propeller aircraft departures.
b. Candidate BAT Airfield Deicing Technologies: Product Substitution of
Pavement Deicers Containing Urea
    In general, airports discharge airfield pavement deicing chemicals
without treatment, due to the difficulty and expense of collecting and
treating the large volumes of contaminated stormwater generated on
paved airfield surfaces. EPA is not aware of an available means to
control these pollutants through collection and use of a conventional,
end-of-pipe treatment system. It is possible, however, to reduce or
eliminate certain pollutants by modifying deicing practices, such as
using alternative chemical deicing products. In particular, EPA has
identified ammonia and COD from airfield deicing as pollutants of
concern, and both of these pollutants are a byproduct of pavement
deicers containing urea. Accordingly, to address discharges of ammonia
from airfield pavement, EPA identified one candidate for best available
technology, namely, product substitution, or discontinuing the use of
pavement deicers containing urea and using alternative pavement deicers
instead. EPA found that the use of deicers without urea is the best
available technology for reducing discharges of ammonia from pavement
deicing, because it is safe, technologically feasible, and available
across the industry. The technology does not produce discharges of
ammonia as produced by deicers containing urea. Currently, only about
10 percent of chemical pavement deicers applied nationwide contain
urea. The most widely used pavement deicer is potassium acetate, which
represents 63 percent of all chemical pavement deicers applied
nationwide.
2. Aircraft Deicing
    For today's final rule, based on comments to the proposed rule, EPA
revised the requirements related to the collection and discharge of
ADF.
a. Applicability/Scope of Aircraft Deicing Discharge Requirements
    Commenters raised multiple concerns with EPA's proposed approach of
using departures as a proxy for ADF use. First, commenters explained
that an airport in the very southern portion of the United States could
have significant departures but use little ADF. Second, commenters
requested that EPA consider a de minimis cut-off to account for
defrosting (i.e. ADF application in the absence of active
precipitation). Under the proposal, defrosting would be counted towards
the volume of ADF required to be collected, yet commenters claim that
it evaporates and is unable to be collected. Finally, airports with low
overall ADF usage also requested EPA consider a de minimis cut-off.
They cited concerns that the costs of the collection and treatment for
ADF at these airports are disproportionally high in relation to the
amount of pollutants generated. For example, one commenter, a non-hub
primary airport, explained that it typically receives little snow and
conducts occasional defrosting of aircraft, and generates no ADF-
contaminated water, yet it would effectively be required to purchase a
GCV if subject to the 20 percent collection requirement.
    EPA reviewed its data with respect to each of these comments. On
further review of the data and comments, EPA agrees that ADF usage in
general is not closely related solely to the number of departures at
airports. As such, in considering options for today's final rule, EPA
did not base ADF collection and associated discharge options on the
number of departures. Instead, EPA considered options based directly on
estimates of the overall volume of ADF use, which EPA indicated in the
proposal was another possible threshold criterion for the rule (74 FR
44714).
    EPA reevaluated ADF usage data for all existing airports. This
evaluation showed that airports with less than 30,000 gallons of
available ADF may conduct a significant amount of defrosting, rather
than deicing. See DCN AD01335. Defrosting results in limited amounts of
ADF available for collection--effectively rendering collection
technologies infeasible. Additionally, EPA found that the costs and
economic impacts of ADF collection and treatment technologies for
airports using less than 60,000 gallons of normalized ADF annually were
disproportionally higher than those with greater ADF use.\1\ See DCN
AD01338 for additional details. As a result, in today's final rule, EPA
evaluated options based on a cut-off of greater than or equal to 60,000
gallons of normalized ADF per deicing season. Under this option,
airports at or above this threshold would be subject to these
requirements, but airports below this threshold would have the
technology-based limitations for aircraft deicing discharges in their
NPDES permits determined by the permitting authority on a case-by-case,
best professional judgment basis.
---------------------------------------------------------------------------

    \1\ EPA notes, however, that many existing airports with
annualized normalized ADF usage below 60,000 currently employ
deicing collection technologies including centralized deicing pads.
---------------------------------------------------------------------------

b. Exempted Wastewater (Those Associated With Deicing for Safe Taxiing)
    EPA also altered its consideration of exempting wastewaters
associated with deicing for safe taxiing. The proposed rule included a
provision that would have exempted ADF-contaminated wastewater
associated with deicing for safe taxiing from the proposed collection
and treatment requirement. EPA proposed to limit deicing for safe
taxiing to 25 gallons of ADF, based on an allowance at Denver
International Airport (DIA), as the maximum amount that could be
applied to an aircraft for the purposes of safe taxiing. This
definition was intended to apply to airports with CDPs, and to prohibit
conducting complete deicing of an aircraft at a terminal area without a
collection system, instead of using the deicing pad. However,
commenters expressed concern that climatic conditions at airports in
the Midwest, Alaska, and on the East Coast differ greatly from those at
DIA: commenters claimed that any ``deicing for safe taxiing''
allowances established at DIA cannot form a reasonable basis for
application to airports in other regions of the country. In addition,
cargo aircraft sometimes experience layovers in excess of 24 hours,
potentially increasing the amount of snow or ice that must be removed
to achieve compliance with FAA regulations. EPA agrees with the
commenters and therefore the final rule does not limit the amount of
ADF sprayed for the purposes of safe taxiing, nor does EPA require an
airport to collect and treat ADF applied for safe taxiing purposes.
c. Candidate BAT Technology Bases for Collection and Discharge
Requirements
    EPA is not aware of an available and economically achievable
technology that is capable of capturing 100 percent of the sprayed ADF.
Section IV.D.1 details the available technologies for

collecting ADF, which include GCVs, plug and pump equipment, and CDPs.
EPA estimates that these technologies collect 20 percent, 40 percent,
and 60 percent of available ADF, respectively.
    Commenters raised multiple concerns about CDPs, the technology that
EPA proposed to identify as the basis for the 60 percent collection
requirement. First, commenters raised concerns that CDPs are not
feasible at all locations because of lack of space. Some of these
commenters provided detailed engineering plans and analyses
demonstrating their specific space constraints. Second, commenters
raised concerns that using CDPs for all deicing operations would cause
traffic and/or safety problems. Third, commenters asserted that the use
of CDPs would lead to flight delays and that EPA had not included costs
associated with such delays in its analyses. In addition, FAA indicated
that it had similar concerns to those raised by industry commenters,
regarding the identification of centralized deicing facilities as BAT.
FAA indicated that the 60 percent collection requirement based on the
exclusive use of CDPs might adversely affect the operational efficiency
of some of the nation's largest and busiest airports. Further, FAA was
concerned that for those land-constrained airports, construction and
operation of CDPs for all deicing operations would not be able to meet
FAA design standards. In explaining its concerns, FAA noted that delays
associated with the use of CDPs would be extremely costly to the
nation's productivity, economy, businesses, and the traveling public.
    After considering these comments and reviewing the information in
its record, EPA is not establishing a 60 percent ADF collection
requirement based on CDPs for BAT. First, in response to FAA's concerns
about the exclusive use of deicing pads for aircraft deicing, EPA
contacted a number of large hub airports that currently use CDPs. EPA
found the current percentage of flights for which these airports use
the CDPs ranges from 50 to 95 percent. The airports explained that
various operational or weather-related issues may make deicing pad use
for all flights cumbersome if not impossible, (i.e., severe system-wide
delays), and require them to deice at the gate in some circumstances.
EPA shares the commenters' and FAA's concerns that moving to exclusive
use of CDPs for all deicing might lead to operational issues and
delays. EPA, in discussions with FAA, attempted to craft regulatory
provisions to allow an airport limited ability to bypass the use of a
centralized pad in order to avoid these circumstances. However, limited
data on the site-specific nature of this industry left EPA unable to
develop regulatory provisions that would give airports the flexibility
they need to avoid significant operational issues and delays. Second,
based on public comments and information from FAA, EPA is concerned
that some large airports critical to efficient air traffic operations
in this country are space (land) constrained, and that building well-
located CDPs for all deicing operations at these airports is likely not
feasible for that reason. At the time of the proposal, EPA estimated
that 14 airports would be subject to the 60 percent collection
requirement. Because the data in EPA's record indicate that many of
these airports currently meet this requirement, EPA estimated
approximately seven airports would likely need to install pads as a
result of the proposed requirement. Of these seven airports, four are
large hubs, which, over years of expansions and other improvements,
have already built out the majority of the land available to them. EPA
has concluded that the lack of remaining available land, coupled with
their existing layouts, has left these airports in a position where a
CDP conforming to FAA's Advisory Circulars on deicing pad design,
(e.g., in a location that aircraft can travel to safely and efficiently
to conduct deicing operations) cannot be constructed.
    Therefore, for today's final rule, EPA has not established a 60
percent ADF collection requirement, which would have been based on
identification of centralized deicing facilities as BAT for 100 percent
of aircraft departures. This technology is not available at a number of
existing airports due to land constraints, and therefore is not
technologically feasible on a nationwide basis. For this and the other
reasons discussed above, EPA finds that centralized deicing facilities
should not be identified as BAT for this nationwide rulemaking. See CWA
304(b)(2)(B)--factors relating to the assessment of BAT include ``the
process employed, the engineering aspects of the application of various
types of control techniques, * * * and such other factors as the
Administrator deems appropriate.'' EPA then considered the other two
technologies described in the proposal as a possible basis of BAT for
aircraft deicing discharges for today's final rule: 40 percent ADF
collection requirement based on plug and pump with GCVs and 20 percent
ADF collection requirement based on GCVs. With either of these
collection technologies, as was the case in the proposed rule, EPA also
included numeric COD limitations for direct discharges of collected ADF
based on anaerobic treatment. For a discussion of other technologies
examined but not selected as candidates for the basis of the COD
limitations, see Section VII.E.2 in the proposed rule preamble (74 FR
44692) and Section 7 of the TDD.
3. Options Considered for Today's Final Rule
    Using the technology bases identified above for airfield and
aircraft deicing discharges, EPA developed three primary options for
today's final rule. All three of these options have the same airfield
pavement deicing discharge requirements based on product substitution
of deicers that do not contain urea, but would vary the approach to
control aircraft deicing discharges:
     Option 1: 40 percent ADF collection requirement for large
and medium ADF users (based on plug and pump with GCVs); numeric COD
limitations for direct discharges of collected ADF (based on anaerobic
treatment).
     Option 2: 40 percent ADF collection requirement for the
large ADF users (based on plug and pump with GCVs) and 20 percent ADF
collection requirement for medium ADF users (based on GCVs); numeric
COD limitations for direct discharges of collected ADF (based on
anaerobic treatment).
     Option 3: Site-Specific Aircraft Deicing Discharge
Controls: Do not establish effluent limitation guidelines in the final
rule for aircraft deicing discharges, but instead, leave the
determination of BAT requirements for each airport to the discretion of
the permit writer on a case-by-case, ``best professional judgment''
basis based on site-specific conditions.
    Under the first option, in addition to the airfield pavement
requirements, all airports that use greater than or equal to 60,000
gallons of normalized ADF annually would be required to collect 40
percent of available ADF based on plug and pump with GCV technologies.
In the proposed rule, EPA considered but did not identify this as its
lead option because it found its costs to be comparable to those of
CDPs, while CDPs achieved greater ADF collection. In the proposal, EPA
therefore identified CDPs as BAT. EPA subsequently determined that CDPs
are not achievable nationwide for existing airports and dropped it as
an option for consideration in the final rule. This left the plug and
pump with GCV option as the technology, among those that remained under
consideration for today's rule, that would achieve the greatest
collection of ADF.

    Under the second option, in addition to the airfield pavement
requirements, all airports that use greater than or equal to 60,000
gallons of normalized ADF annually but less than 460,000 gallons of
normalized ADF (``medium ADF users,'' estimated to be 42 airports)
would be required to collect 20 percent of available ADF based on GCVs,
and airports that use more than 460,000 gallons of normalized ADF
(``large ADF users,'' estimated to be 14 airports) would be required to
collect 40 percent of available ADF based on the use of plug and pump
with GCV technology.
    Under both Options 1 and 2, the requirement to meet numeric
effluent limits for COD for the collected ADF would need to be met
prior to commingling with other wastestreams prior to discharge. For a
discussion of other technologies examined but not selected as
candidates for the basis of the nationwide COD limitations, see Section
VII.E.2 in the proposed rule preamble (74 FR 44692) and Section 7 of
the TDD.
    Under the third option, EPA would establish national deicing
discharge controls for airfield pavement deicing only. BAT limitations
for aircraft deicing discharge would continue to be established by the
permitting authority on a case-by-case basis.
    Table V-1 provides the estimated national cost of each option along
with the estimated national removals.

                  Table V-1--Cost of Final Rule Options
------------------------------------------------------------------------
                                               Total           Total
                                             pollutant      annualized
                 Option                      removals       costs (2006
                                           (million lb)      $million)
------------------------------------------------------------------------
1.......................................            33.0           $78.4
2.......................................            30.2            49.4
3.......................................            16.4             3.5
------------------------------------------------------------------------

4. BAT Options Selection
    EPA is selecting Option 3 as best available technology for
controlling airport deicing discharges. EPA has determined the best
available technology for controlling airfield pavement discharges is
product substitution. The record shows that products without urea are
widely available in the industry, and in fact are already in use at a
majority of airports across the country.
    With respect to aircraft deicing discharge controls, EPA's record
demonstrates that ADF collection and associated treatment technologies
are technically feasible for many airports. Data supplied from the
industry through EPA's nationally representative survey of airports
indicates that dozens of airports currently use GCVs and plug and pump
collection systems, in addition to a myriad of P2 technologies and
practices, ranging from alternative means of applying ADF such as
forced air nozzles, to alternate deicing technologies such as IR
deicing. In addition, many airports also employ a variety of treatment
technologies to treat collected ADF prior to discharge. Thus, EPA
concludes this industry has several technology options potentially
available for mitigating the pollutants associated with aircraft
deicing activities. See the TDD for more information about collection
and P2 technologies.
    However, EPA has determined that none of the ADF collection
technologies considered for today's final rule represents the best
available technology for the entire category. Rather, EPA concludes
that best available technology determinations should continue to be
made on a site-specific basis because such determinations appropriately
consider localized operational constraints (e.g., traffic patterns),
land availability, safety considerations, and potential impacts to
flight schedules. Based on the information in its record, EPA cannot
identify with precision the extent to which such limitations may
preclude, at any particular airport, the use of the technologies that
it considered for BAT control of aircraft deicing discharges for
today's final rule. However, the record demonstrates that such
limitations exist and are not isolated or insignificant. In light of
this finding, EPA decided that it should not establish national ADF
collection (and associated discharge requirements) based on any one or
more of the ADF collection technologies as the presumptive BAT-level
control technology. Rather, site-specific proceedings are the
appropriate forum for weighing all relevant considerations in
establishing aircraft deicing discharge controls.
    More specifically, commenters provided by airport and airline
industry on the proposed regulation raised concerns about the impacts
that ADF collection technologies may have on safety and operations at
airports across the country. They also commented on the lack of
available space at many land constrained airports for ADF collection
and treatment technologies. EPA reviewed the information submitted in
comments, subsequent information provided by industry, and information
obtained from site visits to thoroughly evaluate these concerns. After
reviewing this information, EPA agrees with commenters that while many
airports likely have the ability to implement some form of collection
or P2 technologies in order to mitigate pollutant discharges associated
with aircraft deicing, space, safety and operational considerations may
limit the selection of the specific technologies and the extent to
which they can be implemented at any particular airport. This finding
became particularly apparent after reviewing questionnaire responses
for some of the airports at which EPA also conducted site visits. EPA
found that its ``model facility'' approach was not a suitable
substitute for a detailed analysis of the site constraints at each
airport. For example, a permit authority may need to evaluate existing
traffic patterns at an airport, not only of the aircraft, but also of
the service vehicles to determine if additional collection vehicles
would lead to unacceptable safety concerns. With respect to land
constraints, in the absence of detailed airport schematics, or without
conducting a detailed site visit at each airport, EPA cannot determine
if adequate space exists to incorporate the specific treatment and
collection technologies evaluated as the basis for today's final rule.
    Additionally, industry and FAA, in particular, have expressed
overarching concerns about possible delays and economic impact that
could result from the use of plug and pump and GCVs, both at specific
airports and nationwide. EPA agrees that delays must be a factor in
considering today's possible requirements and recognizes that such
delays fundamentally affect U.S and

international business and recreational interests.
    Airplane deicing activities, by their very nature, occur during
freezing precipitation events. For some airports, even small amounts of
precipitation can lead to delayed aircraft departures--even without
deicing activity and/or ADF collection and treatment. As such, when
delays occur at an airport during inclement weather, it is difficult to
determine whether the delays are associated with the weather, the ADF
collection and treatment technologies, or both. Further, even small
delays at certain hub airports have a ripple effect that can affect the
entire national air traffic schedule.
    Some airports have identified procedures to mitigate or prevent
delays associated with aircraft deicing discharge controls. These
airports can handle large amounts of precipitation and/or operate ADF
collection and treatment technologies with little or no delay, but
these approaches may not be applicable nationwide. Further, the extent
of delays deemed acceptable is likely to vary by airport. As was the
case with land constraints, the confounding factors that need to be
considered to evaluate possible delays that may be associated with the
technology bases do not lend themselves to a national determination
using a model facility approach. Further, EPA does not have detailed
site-specific information to evaluate delays on an airport-by-airport
basis.
    While the facts stated above do not necessarily preclude the
ability of an airport to collect and treat spent ADF, they do
illustrate why EPA did not select any of the technologies considered as
BAT for today's final rule, and why a site-specific BAT determination
for ADF collection and treatment requirements is the proper approach
for today's final rule.
    Therefore, for the reasons identified above, EPA determined Option
3 is the only technologically feasible and available option considered
for today's final BAT requirements. Option 3 would remove 4.4 million
pounds of ammonia and 12 million pounds of COD, with a projected annual
cost of $3.5 million. The costs of Option 3 are reasonable in terms of
the pollutant reductions achieved ($0.21/lb). Further, as discussed in
more detail in Section VII, EPA finds Option 3 is economically
achievable. In addition, EPA examined the non-water quality impacts
anticipated from compliance with Option 3 requirements and found none
or only very minor impacts in comparison to typical industry energy
use, emissions generation and sludge generation. See Section IX, ``Non-
Water Quality Environmental Impacts.'' Therefore, based on all the
factors above, EPA is identifying Option 3 as BAT and has based today's
final rule on the Option 3 BAT requirements.

C. NSPS

1. New Source Definition
    In the proposed rule, ``new source'' would have included both new
airports and new runways constructed at existing airports. Commenters
objected to the inclusion of new runways at existing airports in the
new source definition. They noted that a new runway is not a source of
pollutant discharges from aircraft deicing activity and that a new
runway is not ``substantially independent'' of an existing source as
required under the regulatory definition of ``new source.'' See 40 CFR
122.2 and 40 CFR 122.29(b)(1). Commenters acknowledge that a new runway
may lead to additional discharges associated with airfield deicing, but
noted that the requirements for airfield deicing discharges are the
same for new and existing discharges. With respect to the requirements
associated with discharges from aircraft deicing, they explained that a
new runway is not a source of new discharges because aircraft deicing
is performed at locations away from airport runways. Moreover, they
explained that unlike a plant or factory from which a new source of
discharge associated with a new process, production line, or piece of
equipment can be clearly distinguished as a new source of discharge
associated with an existing source, a new runway is not operated
independently from other runways at an airport. Rather, a new runway
and associated deicing operations are part of a wholly integrated
airport system. After carefully considering these comments, EPA agrees
that new runways should not be treated as new sources because new
runways are generally too integral to the operations of an existing
airport to be considered ``substantially independent'' of the existing
airport.
2. NSPS Applicability
    For today's final rule, the applicability of the NSPS provisions is
effectively the same as that in the proposed rule. New primary airports
with greater than or equal to 1,000 annual departures by non-propeller-
driven aircraft are subject to the provisions of Sec.  449.11(a) and
(b).
    In the proposed rule, Sec.  449.1 defined the applicability of the
overall category as covering primary airports with at least 1,000
annual scheduled commercial air carrier jet departures. In the final
rule, the language in Sec.  449.1 has been simplified to just ``primary
airports,'' and the 1,000-departure threshold criteria are included in
the provisions at Sec. Sec.  449.10 and 449.11. This arrangement
results in the same requirements for new source airports that EPA had
intended in the proposed rule, with a clarification: A new primary
airport with initially less than 1,000 departures is a new source, but
not subject to the requirements of Sec.  449.11. If the airport
eventually exceeds 1,000 departures, then the provisions of Sec.
449.11 apply.
    The proposed rule defined the threshold for the new source ADF
collection and associated discharge requirements as any new source with
10,000 or more annual departures. As was the case with existing
sources, commenters explained that the number of departures is not a
good analog for the amount of ADF usage, citing, for example, airports
in the South that may have significant numbers of departures but
typically need to deice their aircraft only once a year. After
reviewing these comments and the information in its record, EPA agrees
that departures alone are not the most appropriate indicator of ADF
usage.
    Therefore, for today's final rule, in addition to the proposed
departure threshold, EPA is adding a geographical component to define
which new sources are subject to the ADF collection and discharge
requirements. As explained in Section V.B, EPA determined that, on a
national basis, ADF collection may be infeasible at airports with
annual ADF usage below 30,000 gallons. ADF usage below 30,000 gallons
may reflect significant volumes of defrosting activity, which does not
leave ADF available for collection.
    Unlike existing sources, however, new sources do not have past ADF
usage data available for establishing a threshold for being subject to
ADF collection requirements. Therefore, in combination with the
proposed departure threshold, in today's final rule, the Agency is
incorporating a geographically based component that is closely aligned
with a 30,000 gallon annual ADF usage threshold. In addition to
applying the proposed departure threshold, EPA is making NSPS
collection requirements for ADF applicable based on whether the airport
is located within specific colder climatic zones (called a ``heating
degree day [HDD] category'') as documented by the National Oceanic and
Atmospheric Administration (NOAA). For airports within the scope of
today's rule,

location in a warmer climate zone is generally associated with the use
of smaller volumes of ADF.
    HDD means the number of degrees per day the daily average
temperature is below 65 degrees Fahrenheit. The daily average
temperature is the mean of the maximum and minimum temperature for a
24-hour period. The annual HDD value is derived by summing the daily
HDDs over a calendar year period. HDDs are computed using data from the
U.S. National 1961-1990 Climate Normals, published by the National
Climatic Data Center of NOAA. The original data are in whole degrees
Fahrenheit. HDD values range from 0 to more than 9,000. NOAA presents
this information in 1,000-HDD increment groups. EPA used the NOAA
information to create HDD groups. These groups range from A to I, with
group A being the lowest HDD values (less than 1,000 HDD) and group I
being the highest (greater than 9,000 HDD).
    EPA identified the corresponding HDD groups for existing airports
and then compared the HDD group to ADF usage at each airport. In
general, airports with greater than 10,000 departures in HDD groups A
through C (3,000 HDD or less) used less than 30,000 gallons of ADF
while those in HDD groups D through I used more than 30,000 gallons of
ADF. As a result, these HDD groups in combination with the departure
cut-off provide a dividing line nationwide that corresponds well with
the ADF usage dividing line that EPA determined makes ADF collection
feasible. EPA concludes that this approach best captures those new
airports that will conduct more frequent deicing operations, as opposed
to defrosting operations, and excludes those new airports that will
likely conduct infrequent deicing. See DCN AD01267 for EPA's analysis
of HDD categories.
    In addition, EPA received comments questioning the feasibility of
ADF collection technologies for airports located in Alaska. These
commenters stated that deicing wastewater generation at Alaskan
airports is substantially different from airports in the lower 48
states. First, often airports in Alaska will suspend air traffic as
opposed to conducting deicing operations. Second, commenters stated
that long periods of below freezing temperatures result in runoff
characteristics that are substantially different from those is the
lower 48 states and, as such, deicing materials are not available for
collection (due to lack of runoff) making collection technologies
infeasible. The data provided in the survey responses from Alaskan
airports show that airports in this climactic zone use widely varying
amounts of ADF per departure. Based on this data, EPA is unable to
conclude that Alaskan airports conduct significant deicing, rather than
defrosting, and as such, today's final new source ADF collection and
discharge requirements do not apply to new airports in Alaska.
    For the airports that are excluded from the NSPS requirements in
today's final rule, permit authorities would determine an applicable
new source performance standard on a case-by-case, best professional
judgment basis.
3. NSPS Option Selection
    For today's final rule, EPA evaluated ``best available demonstrated
control technologies'' for purposes of setting NSPS under CWA section
306. Section 306 directs EPA to promulgate NSPS ``for the control of
the discharge of pollutants which reflects the greatest degree of
effluent reduction which the Administrator determines to be achievable
through application of the BADCT, processes, operating methods, or
other alternatives, including, where practicable, a standard permitting
no discharge of pollutants.'' Congress envisioned that new treatment
systems could meet tighter controls than existing sources because of
the opportunity to incorporate the most efficient processes and
treatment systems into the facility design. As a result, NSPS should
represent the most stringent controls attainable through the
application of the BADCT for all pollutants (that is, conventional,
nonconventional, and priority pollutants).
    After careful consideration of the information in its record, EPA
is today promulgating the same NSPS requirements for both airfield
pavement deicing discharges and airplane deicing discharges as it
proposed; however, the applicability of the NSPS requirements has
changed. Clearly, product substitution, the technology basis for the
airfield deicing discharge requirements promulgated today for existing
airports, is fully applicable to new airports. EPA determined that,
just as with existing sources, all new sources would be capable of
using airfield deicing products without urea. Furthermore, product
substitution represents the greatest level of reduction in ammonia
among the available technologies considered. Accordingly, EPA
identifies product substitution of non-urea-containing airfield deicers
as the best demonstrated available control technology for all new
sources. As with BAT, there would be two alternatives for meeting this
effluent limitation: either a certification requirement or a numeric
limit on ammonia for all direct discharges of the stormwater from the
airfields.
    With respect to aircraft deicing discharge controls, EPA, in
consultation with FAA, finds that its determination about safety,
space, and operational constraints that may be present at existing
airports for all the collection and treatment technologies discussed in
today's final rule (CDPs, plug and pump with GCVs, GCVs alone and AFB
treatment) would not similarly apply to new airports. This finding is
supported because new airports can be designed to minimize space and
logistical constraints that have been identified for retrofits at
existing airports (see DCN AD01285). Further, among the ADF collection
technologies that EPA considered, CDPs collect the greatest level of
available ADF and are available to new sources in this category. With
respect to new airports, the use of CDPs does not present the space/
land, safety, or operational issues that would be raised in connection
with the use of deicing pads at existing sources. In addition, CDPs in
combination with AFBs for treatment of collected ADF are not so costly
in comparison to the cost of a new airport \2\ that they would be
considered a ``barrier to entry.'' Moreover, according to FAA, when
designed properly, CDPs often improve traffic flow and reduce delays
associated with aircraft deicing. When designing a new airport, the
local operating agency plans the site for all needed facilities, such
as runways, taxiways, terminal(s) and other components needed to comply
with safety and environmental requirements, which includes deicing
facilities. See DCN AD01285. The new airport must be designed and built
on enough land, in total, to accommodate a deicing pad and AFB
treatment system (or other technology that meets the 60 percent
collection requirement and the discharge requirements), to be installed
either during initial construction or at a later time when it exceeds
the 10,000 departure threshold. The airport sponsor would design its
layout of runway(s), taxiways, location of terminal(s) and other
buildings with sufficient space so that deicing facilities can be
installed later without the need to acquire additional land. Therefore,
EPA is promulgating the same NSPS requirements for airfield pavement
deicing discharges as for existing sources, but in contrast to existing
sources, EPA is promulgating NSPS requirements for ADF collection and
discharge requirements at new airports

based on the use of CDPs and anaerobic biological treatment. Meeting
this combination of new source requirements for both airfield pavement
deicing discharges and aircraft deicing discharges would not be an
economic barrier to entry for new airports, as the cost of new airport
construction, even at small airports, is significantly greater than the
costs associated with product substitution and collection and/or
treatment of spent deicing fluids. See Section VII.E.
---------------------------------------------------------------------------

    \2\ Includes total costs for controls both for airfield pavement
and aircraft deicing discharges.
---------------------------------------------------------------------------

    As a point of clarification, EPA is promulgating the same numeric
COD limitations for collected ADF that is discharged directly for new
sources as was proposed. The technology basis, AFB system, is available
to new airports. In addition, AFB achieves the greatest level of
pollutant removals of those technologies considered during the
development of this regulation, and the installation and use of this
technology is not economically a barrier to entry for new airports.
    Additionally, although EPA did not identify pollution prevention
approaches and technologies as a basis for NSPS, these technologies may
be effective at reducing available ADF. Moreover, future pollution
prevention technologies may become available to aid in meeting the NSPS
requirements. As such, the final rule includes a provision that allows
dischargers to request a credit to be applied to the NSPS ADF
requirement. See Section X.C.3 for additional information and examples.

D. PSES and PSNS

    EPA is not promulgating PSES and PSNS for the Airport Deicing
Category. Although some airports in the United States discharge ADF-
contaminated stormwater to POTWs, EPA received no comments or other
information indicating that POTWs currently have problems of pollutant
pass-through, interference, or sludge contamination stemming from these
discharges that would necessitate the promulgation of national
categorical pretreatment standards.
    Like the biological treatment system that forms the basis for
today's COD new source performance standard, POTWs typically employ
biological treatment systems and are similarly designed to remove
organic pollutants that contribute to COD and/or BOD5. In
general, POTWs have the capability to achieve comparable removals to
the NSPS technology basis. However, some airports and POTWs may need to
make operational adjustments in order to process the wastewater
effectively while avoiding POTW upset. EPA received a comment about the
Downriver Treatment Facility in Detroit, Michigan, which accepts ADF
wastewater from the Detroit Metropolitan Wayne County Airport. The
treatment plant experienced viscous bulking due to a nutrient imbalance
that occurred during the months that ADF was accepted. The issue was
resolved by removing phosphorus at a later stage in the treatment plant
system, rather than from the raw wastewater. The airport also made
significant changes in order to segregate the deicing wastewater,
collect and recycle the most concentrated ADF wastewater, and control
the amount and concentration of wastewater discharged to the POTW.
    EPA is aware that high concentration or ``slug'' discharges of
deicing wastewater can create POTW upset. The national pretreatment
program regulations specifically prohibit industrial users from
discharging high concentrations of oxygen-demanding pollutants to POTWs
if they cause interference to the POTW. See 40 CFR 403.5(b)(4). Under
40 CFR 403.5(c), control authorities may set and enforce ``local
limits'' for airport discharges to POTWs to implement the prohibitions
listed in Sec.  403.5(b)(4). This provision ensures that any potential
limits would protect against POTW interference by the oxygen-demanding
pollutants in airport deicing discharges. See ``Local Limits
Development Guidance,'' document no. EPA 833-R-04-002A, July 2004,
available on EPA's Web site at http://cfpub.epa.gov/npdes/pretreatment/pstandards.cfm. As a result, many airports that discharge to POTWs have
airport-specific requirements on allowable BOD5 or COD
discharge loading per day. These limits on daily pollutant loadings are
specific to the receiving POTW. Airports usually meet this requirement
by storing deicing stormwater in ponds or tanks and metering the
discharge to meet the POTW permit loading requirements.

VI. Technology Costs and Pollutant Reductions

A. Compliance Costs

1. Overview
    EPA estimated industry-wide compliance costs for the three options
considered for today's rule. This section summarizes EPA's approach for
estimating compliance costs, while the TDD provides detailed
information on these estimates. All final cost estimates are expressed
in terms of 2006 dollars and represent the cost of purchasing and
installing equipment and control technologies, annual operating and
maintenance costs, and associated monitoring and reporting
requirements. In general, this approach is the same as the approach
used in the proposal. However, some modifications were made for costing
specific technology pieces in the costing models, including the numbers
of GCVs per airport and the manner in which airports would store
collected ADF containing wastewater.
    EPA estimated compliance costs associated with the three options
considered for today's rule using data collected through survey
responses, site visits, sampling episodes, specific airport requests,
and information supplied by vendors. Under the options considered,
certain airports would have limitations based on the substitution of
non-urea-containing pavement deicers and also would be required to
collect a percentage of their available ADF that was applied to
aircraft and treat the collected wastewater to comply with numeric
limitations if discharged directly. EPA estimated costs for an airport
to install technology to comply with the options, as well as to
annually operate and maintain equipment and perform required monitoring
or other activities to demonstrate ongoing compliance. EPA's cost
estimates represent the incremental costs for a facility when its
existing practices would not lead to compliance with the option being
evaluated.
    EPA calculated costs based on a computerized design and cost model
developed for each of the technology options considered. EPA developed
facility-specific costs for each of the airport industry questionnaire
respondents (149 facilities), where each facility was treated as a
``model'' airport. Because the questionnaire respondents represent a
subset of the industry, EPA subsequently modeled the national
population by adjusting the costs upward to estimate the entire
affected airport population.
    The questionnaire responses provided EPA with information on three
consecutive deicing seasons (2002 to 2005) for each of the model
facilities. Some portions of EPA's costing effort reflect the airports'
operations as reported for the three seasons. For example, estimates of
applied deicing chemicals were taken as an average of the years for
which the information was reported. In instances where aspects of an
airport's operation changed over the three-year period, EPA used the
most recent information.
    EPA first established existing conditions (i.e., baseline) for each
model airport based on information and site plans submitted as part of
the airport questionnaire. EPA then determined what upgrades or
changes, if any, would

be required to comply with the option being considered for today's
final rule. For example, in general, when an airport lacked a
comparable collection system to the one used as the basis for an
option, EPA included costs for installation/operation and maintenance
of the option technology basis (e.g., plug and pump systems in
conjunction with GCVs).
2. Approach for Estimating Airfield Pavement Deicing Costs
    Today's rule sets requirements for an airport to certify it uses
non-urea-containing airfield deicers (unless it chooses to meet a
numeric limit for ammonia). Through the airport questionnaire
responses, EPA estimates that 198 airports will be subject to today's
requirements. Of these 198 airports, 37 airports use deicers containing
urea for airfield pavement deicing. As detailed in Section IV.D.4, EPA
based its airfield pavement deicing requirement on product
substitution. EPA calculated the cost for facilities to substitute the
deicers containing urea with another widely available pavement deicer
that does not produce ammonia in the wastewater. EPA chose to model the
substitution costs on what it would cost to switch to potassium
acetate, specifically because that product accounts for 63 percent of
the applied chemical airfield deicer usage (by weight) in the United
States. These incremental costs include capital costs associated with
application equipment and storage, as appropriate, as well as the
differential chemical costs. EPA assumed that those airports that
currently do not use urea-containing deicers as a means of pavement
deicing would experience no cost associated with this portion of
today's regulation.
    Using the facility area usage data as provided in the airport
questionnaire, and available literature on typical urea-containing
pavement deicer application rates, EPA estimated the airfield area that
was annually deiced at each model facility. Using the estimated model
facility deicing area in conjunction with the estimated $2.92/1,000
square feet cost of potassium acetate, EPA was able to calculate the
cost per model facility to perform airfield deicing with potassium
acetate. This cost was compared to the questionnaire-reported urea-
containing deicer costs to determine the incremental costs of switching
chemical airfield deicers. See the TDD for additional details on
costing for airfield deicing product substitution.
3. Approach for Developing Aircraft Deicing Costs
    Under two of the options considered for this rule, certain existing
airports would be required to collect a percentage of their available
ADF, and treat the collected wastewater to comply with numeric effluent
limitations if it discharges directly. EPA estimated the costs for an
airport to comply with collection and treatment requirements, as
applicable, as well as perform required monitoring to demonstrate
compliance. Of the 198 airports within the scope of the aircraft
deicing controls considered for BAT, EPA expects that 55 airports would
exceed the threshold for ADF use that would trigger the collection/
discharge requirement. Costing for ADF collection is not relative to
baseline practices in all instances, as an airport's existing
collection technology may not be incrementally upgradeable to achieve
the required collection efficiency. As such, EPA assessed all costs to
comply with the options based on ADF collection and treatment with the
assumption that any airport required to make upgrades to its collection
and/or treatment system to meet the option would be starting from a
baseline of zero collection and treatment. Note that this assumption
does not carry through to pollutant removals, as baseline removals are
accounted for when assessing pollutant removals associated with today's
options. See section VI.B for more detail on the pollutant removal
calculations.
    EPA first established existing conditions for each model airport
based on information and site plans submitted as part of the airport
questionnaire. EPA then determined what upgrades, if any, would be
required to comply with an option. As explained above, in general, when
an airport lacked a comparable collection system to the one used as the
basis for the option, EPA included costs for installation/
implementation of the option technology basis such as plug and pump
systems in conjunction with GCVs and an AFB treatment system for Option
1.
    For those airports that would be required to collect additional ADF
and meet associated discharge requirements to comply with the option,
EPA estimated costs for storage/equalization (and associated piping to
transfer collected ADF to storage) as part of the costs of the
treatment technology. The option would not require, nor is it based on,
collecting the full volume of wastewater generated in a deicing season.
Rather, storage is included as part of the technology basis for flow
and/or pollutant equalization to support the AFB treatment system.
Where EPA estimates an airport would incur capital costs associated
with ADF collection and discharge requirements, the Agency included
costs for above-ground storage tanks, since above-ground storage tanks
will have less of an impact on subsurface utilities, for which EPA does
not have site-specific information. If airports needed to install
below-ground storage tanks for operational reasons, this would likely
be more expensive.
    For the 15 airports that EPA anticipates would need to collect
additional quantities of ADF-contaminated stormwater to comply with
Option 1 or 2, EPA assumed these additional quantities would be
discharged directly, thus requiring treatment to comply with the COD
limitations. For example, for Option 1, this includes all airports that
EPA estimates collect less than 40 percent of available ADF.
Specifically, this includes those facilities that currently collect
some portion of ADF-contaminated stormwater and subsequently discharge
indirectly to a POTW or a centralized waste treatment (CWT) facility.
EPA recognizes that an airport may decide to discharge to a POTW or CWT
facility rather than directly discharge its wastewater. While this is
likely a lower cost alternative in some cases, EPA did not assume that
airports could discharge to a POTW or CWT, because the Agency does not
have enough information about the capacity or willingness of a specific
POTWs to receive these volumes of wastewater. To the extent that an
airport selects this alternative, EPA may have over-costed the option.
    Additionally, airports may have costs associated with permit
application requirements or demonstrating compliance with Option 1 or
2, including assessing yearly ADF usage, determining ADF stormwater
collection, system inspections, and COD monitoring. Monitoring
requirements will continue to be determined by the permitting
authority. However, for purposes of estimating monitoring costs
associated with today's options, EPA assumed that airports that
directly discharge collected ADF would take a 24-hour composite sample
and analyze that for COD, and perform that analysis seven times per
week for the duration the treated discharge occurs. EPA made a similar
assumption for purposes of computing the weekly average effluent
limitation (see the TDD for additional details). As a conservative
estimate, EPA assumed a six-month discharge duration season for all
modeled facilities.

4. Calculation of National Costs
    EPA categorized all of the costs as either capital costs (one-time
costs associated with planning or installation of technologies), or as
operations and maintenance (O&M) costs (costs that occur on a regular
ongoing basis such as monitoring or annual purchases of deicing
materials). EPA amortized these capital costs over the lifespan of the
capital improvement. For additional information on amortization, see
the EA. Finally, EPA combined the amortized capital costs with the
annual O&M costs to calculate the total annual cost of the option for
that model facility.
    EPA then utilized statistical weights assigned to each of the 149
model facilities to calculate a national estimated cost of complying
with the option. Further discussion of all of the calculations
discussed can be found in the TDD and in the EA.

B. Approach to Estimating Pollutant Reductions

1. Overview
    The pollutants of concern associated with airfield and aircraft
deicing and anti-icing chemicals are discussed in Section 6 of the TDD.
These chemicals commingle with stormwater and may be discharged to the
environment. These discharges are of environmental concern because the
biodegradation of deicing chemicals results in oxygen depletion in the
receiving water body. Moreover, some of these pollutants, such as
ammonia, have toxic properties.
    Pollutant loadings from airport deicing operations are challenging
to estimate because they are highly variable and airport-specific.
Because the use of deicing and anti-icing chemicals is weather
dependent, the pollutant loadings at each airport vary based on weather
conditions. The pollutant loadings also vary from airport to airport
based on each airport's climate. In addition, the amount of applied
chemical that is discharged to surface water is airport-specific, based
on the existing stormwater separation, collection, and/or containment
equipment present at each airport.
    Due to the variable nature of these pollutant loads, EPA developed
a baseline (or current) pollutant loading methodology based on the
usage of ADF and airfield chemicals at the airports responding to the
survey questionnaires. The methodology takes into account EPA's
existing data sources and provides a better estimate of the loadings
than those based on sporadic monitoring data alone. Similar to the
costing methodology, EPA developed facility-specific baseline loads for
a subset of the industry (i.e., model facilities). For those model
airports where existing practices would not lead to compliance with
today's options, EPA then calculated the incremental pollutant removals
associated with compliance. EPA subsequently adjusted the incremental
pollutant removals upward to estimate the entire affected airport
population. This approach is the same as the approach taken in the
proposal.
2. Sources and Use of Available Data
    While developing the pollutant loading models, EPA considered the
following data sources:
     Pavement deicing chemical usage/purchase information for
the 2002/2003, 2003/2004, and 2004/2005 deicing seasons, as reported by
airport authorities in the Airport Deicing Questionnaire.
     ADF purchase information for the 2002/2003, 2003/2004, and
2004/2005 deicing seasons, as reported by air carriers in the Airline
Deicing Questionnaire.
     Standard airport information available from the FAA and
the Bureau of Transportation Statistics, including the number of
operations and departures by airport,
     Weather information for each airport from NOAA, including
temperature, freezing precipitation, and snowfall data.
     Existing airport stormwater collection and containment
systems, as reported by airport authorities in the Airport Deicing
Questionnaire.
     Standard chemical information about ADF and pavement
deicing chemicals, including molecular formulas and densities.
     Analytical data from EPA sampling episodes of airport
deicing operations.
a. Baseline Loading Calculations
    The Agency estimated the total amount of pavement deicing chemicals
and ADF used based on data collected in the Airport and Airline
Questionnaires. The Airport Questionnaire respondents reported the
purchase/usage amount, concentration, and brand name of pavement
deicing materials. Using the Airline Questionnaire, EPA collected ADF
purchase data from airlines with 1,000 or more departures operating at
selected airports. During questionnaire development, airports indicated
they did not have information on ADF usage and that EPA should direct
this question to airlines. Purchase data were collected because the
airlines stated that purchase data were most readily available, while
usage data was not. For the purposes of these loading calculations, EPA
estimated that the annual amount purchased was equal to the amount used
for a deicing season. For instances in which EPA did not have ADF
purchase data for every airline operating at a particular model
airport, EPA extrapolated the amount of ADF used by the reporting
airlines to estimate the total amount of ADF used by the entire
airport. This was done based on the number of airport operations
(departures) at the reporting airlines versus the total number of
airport operations. In addition to the 56 airports for which EPA
collected ADF purchase/usage data from the airline tenants, 10 airports
reported the total volume of their ADF usage to EPA in their comment
section of the Airport Deicing Questionnaire, resulting in estimates of
total ADF usage for 66 model airports.
    Using the airline and airport ADF purchase and usage data obtained
from the questionnaire, airport departure data, and climate data, EPA
developed a relationship between the amount of ADF used, and the
climate and size of each model airport. EPA then used this equation to
estimate the total gallons of ADF used at model airports that did not
have ADF usage data in the Airport or Airline Questionnaires. EPA is
aware that part of the methodology for developing today's regulation
involved estimating airport-specific ADF usage. However, in order to
prevent mandatory survey responses marked as CBI from being released,
EPA is not revealing the exact methodology for modeling this ADF usage
due to the potential for the deduction of CBI data through back
calculation.
    Once the amount of ADF used at each model airport had been
determined, EPA needed to determine the amount of ADF available for
direct discharge to the waters. EPA assumed that 75 percent of applied
Type I ADF falls onto the pavement at the deicing area and is available
for discharge. EPA assumed that 10 percent of Type IV ADF falls to the
pavement in the deicing area and is available for discharge; the
remaining 90 percent adheres to the plane. See the TDD for more
information on these estimates. EPA then multiplied the total amount of
applied ADF for each model airport by the appropriate percent available
for discharge to determine the amount of ADF available for discharge.
Note that collection requirements in the options are specified as
percentages of ADF available for discharge, not percentages of total
ADF applied. Evaluating the amount of ADF available for discharge,
coupled with the estimated baseline collection rate, results in the
total amount of discharged

available ADF. EPA then calculated the amount of COD loading associated
with these discharges, described as follows.
    Airfield pavement deicing chemicals are applied at various airside
locations such as runways, taxiways and ramps. Theoretically, the
amount of pavement deicers being discharged could range from
approximately 0 percent, for chemicals that infiltrate highly permeable
soils in unpaved areas during a thaw, to virtually 100 percent for
paved areas near storm drains. In general, soil in unpaved areas is
frozen during deicing season and is impermeable, promoting the overland
flow of stormwater and pollutants to surface waters. Estimating the
amount or proportion of pavement deicers discharged at a particular
airport is difficult without performing a detailed study at the
airport. EPA has not received any such detailed studies, nor other
information from airports indicating that pavement deicers are absorbed
into soil during the deicing season. Therefore, the Agency assumed for
this rulemaking that 100 percent of the pavement deicers used could be
discharged to surface waters.\3\ This means the estimates of baseline
pollutant loadings and removals associated with pavement de-icing are
upper bound estimates. EPA then calculated the amount of COD loading
associated with airfield chemical use and discharge as described below.
---------------------------------------------------------------------------

    \3\ As a point of clarification, in contrast to the NSPS
requirements for aircraft deicing where an airport is only required
to meet the standards for a portion of the applied deicing chemical,
this means that an airport that elects to comply with today's BAT or
NSPS requirements by meeting the ammonia limitation must meet this
limitation for all airfield deicer that is discharged.
---------------------------------------------------------------------------

    To calculate the COD loading associated with either ADF or airfield
chemical discharge, EPA determined the theoretical oxygen demand (ThOD)
associated with the degradation of each of the deicing chemicals. EPA
based the ThOD estimate on the molecular formula of the chemical and
the stoichiometric equation of the breakdown of the chemical to the end
products of CO2 and water. EPA assumed that the chemical
would completely degrade in the environment over time and, therefore,
the calculated ThOD load would be equivalent to the COD load. EPA
estimated the COD load associated with each reported chemical based on
the calculated mass of the chemical discharged, the molecular weight of
the chemical, the ThOD, and the molecular weight of oxygen. EPA
estimated the ammonia load associated with deicers containing urea
based on the chemical equation for the breakdown of urea to ammonia,
the mass of urea use, and the molecular weights of urea and ammonia.
See Section 9 of the TDD for more information and example calculations
of baseline loadings associated with ADF and airfield deicers.
b. Calculation of Pollutant Removals
    After determining baseline loadings, EPA calculated total
reductions of COD and ammonia associated with a national implementation
of today's options.
i. Aircraft Deicing Related Pollutant Removals
    EPA estimated the amounts of COD that would be reduced by Option 1
and 2, by estimating the existing baseline loadings associated with
aircraft deicing at model airports and comparing that to the COD load
that would be discharged after complying with the option (e.g., for
Option 1, COD load discharged if 40 percent of available ADF were
collected and treated to meet the required discharge limitation). If a
particular airport would be subject to a collection requirement of 40
percent under this option and is currently estimated to collect a
greater proportion of available ADF, then no load removals were
estimated for that airport.
ii. Airfield Deicing Related Pollutant Removals
    EPA calculated ammonia and COD baseline loads for those model
facilities using deicers containing urea. The Agency then calculated
ammonia and COD loads for those same model facilities if they replaced
their deicers containing urea with the substitute product, potassium
acetate (which does not form ammonia and exerts a lower COD than urea).
EPA computed the total load reduction by subtracting the ammonia and
COD loadings between the baseline and the regulatory compliance
conditions.
iii. National Extrapolation
    These calculated loading reductions, summed for both airfield and
aircraft deicing chemicals, as applicable, were then extrapolated by
multiplying the pollutant removals for each model facility by the
airport survey weighting factors to determine national loads for the
entire industry for each regulatory option considered for today's rule.

C. Approach to Determining Long-Term Averages, Variability Factors, and
Effluent Limitation Guidelines and Standards

    This section describes the statistical methodology used to develop
the daily maximum and the maximum for weekly average NSPS representing
the BADCT levels of control for COD. EPA also used the same statistical
methodology to develop the daily maximum limitation/standard for
ammonia that is a compliance alternative when deicers containing urea
are applied to runways. The following discussion uses the term
``limitation'' to collectively refer to effluent limitations guidelines
and NSPS.
    The following sections describe the data selection criteria, the
statistical percentile basis of the effluent limitations, rationales
for certain limitations, the calculations, the recommended long-term
average value for treatment operations, and the engineering evaluation
of the model technology's ability to achieve the levels required by the
limitations.
1. Criteria Used To Select Data as the Basis of the Limitations
    Typically, in developing effluent limitations for any industry, EPA
qualitatively reviews all the data before selecting the appropriate
data to use for calculating the limitations. EPA typically uses four
criteria to assess the data. One criterion generally requires that the
influent and effluent represent only wastewater from the regulated
operations (e.g., deicing), and do not include wastewater from other
sources (e.g., sanitary wastes). A second criterion typically ensures
that the pollutants were present in the influent at sufficient
concentrations to evaluate treatment effectiveness. A third criterion
generally requires that the facility must have the technology and
demonstrate proper operation of the technology. A fourth criterion
typically requires that the data cannot represent periods of treatment
upsets or shutdown and start-up periods. Shutdown periods can result
from upset conditions, maintenance, and other atypical operations.
    EPA has adapted the application of the fourth general criterion for
data corresponding to start-up periods to reflect some unique
characteristics of treating discharges from aircraft deicing
operations. Most industries incur start-up conditions only during the
adjustment period associated with installing new treatment systems.
During this acclimation and optimization process, the concentration
values tend to be highly variable with occasional extreme values (high
and low). After this initial adjustment period, the systems should
operate at steady state for years with relatively low variability
around a long-term average. Because start-up conditions reflect one-
time operating conditions, EPA

generally excludes such data in developing the limitations. In
contrast, EPA expects airports to encounter start-up operations at the
beginning of every deicing season because they probably will cease
treatment operations during warmer months. Because this adjustment
period will occur every year for the Airport Deicing Category, EPA has
included start-up data in the data set used as the basis of the
limitations. However, through its application of the other three
criteria, EPA excluded extreme conditions that do not demonstrate the
level of control possible with proper operation and control even during
start-up periods. For detailed information on these exclusions, see
Section 14 of the TDD.
    In part, by retaining start-up data for the limitation's
development, the limitations will be achievable because EPA based these
limits on typical treatment during the entire season. As a point of
clarification, once acclimated, EPA expects a typically well-designed
and operated system for the collected deicing fluid to run continuously
until the end of the deicing season, as facilities utilize storage/
equalization prior to the AFB to manage a steady flow rate.
2. Data Used as Basis of the Effluent Limitations
    As explained in Section 8 of the TDD, the technology basis for the
COD numerical limitations associated with discharges of collected ADF
wastewater is AFB biological treatment. Of the effluent data available
to EPA, 2,562 concentration values for COD met the requirements in the
criteria described above and are the basis of the COD final NSPS. The
concentration values are measurements of filtered effluent collected
from Albany Airport's two-unit anaerobic treatment system. The 2,562
COD values were collected by the airport during its daily monitoring of
COD over ten deicing seasons (December 1, 1999 through April 10, 2009).
    Product substitution is the basis for today's effluent limitation
regarding airfield deicing chemicals. EPA also established ammonia
discharge limitations as a compliance alternative. Ammonia naturally
occurs in airport discharges as a result of excretions from wildlife
that enter the stormwater; therefore, EPA determined it would not be
appropriate to set this limitation at the non-detect level. Moreover,
depending on a specific airports' drainage system, a portion of
airfield deicing stormwater may be routed to the treatment system
utilized in treating the collected ADF. Further, the AFB that has been
identified as the basis for the NSPS requirement for treating collected
ADF will itself produce ammonia discharges as a byproduct of treatment.
Therefore, where airfield deicing stormwater that is free of urea
contamination is routed through the AFB treatment system, the discharge
after treatment may have ammonia concentrations higher than the non-
detect level (see DCN AD00842). Consequently, EPA used ammonia effluent
discharge data from the same AFB system it used to establish NSPS
discharge requirements for ADF, located at Albany, to establish today's
ammonia compliance alternative. Five ammonia concentration values
available from Albany met the limitations criteria described above. The
five ammonia values were collected by EPA during its sampling episode
(February 5 through February 9, 2006).
3. Statistical Percentile Basis for Limitations
    EPA uses a statistical framework to establish limitations that