substantially, this section combines those multiple industry profiles
into one overview. The information below is generally based on data
from the U.S. Department of Energy's (DOE) ``Annual Electric Generator
Report'' (Form EIA-860) and ``Annual Electric Power Industry Report''
(Form EIA-861), and EPA's Section 316(b) Industry Surveys. According to
the 2007 EIA database, 38 of the 671 facilities have ceased operation
since the Survey and 15 facilities will likely do so by the time
today's proposed rule is promulgated (i.e., 2012). EPA also excluded 20
electric generators that are already required by state policy to comply
with standards based on closed-cycle cooling, and thus for regulatory
analysis purposes are not expected to be affected by the proposed rule.
In addition, 39 facilities are projected to be baseline closures
according to Integrated Planning Model analyses (see Section VII of
this preamble and Chapter 6 of the EA for discussion of IPM
analysis).\21\ Based on (1) data collected from these Surveys; (2) the
compliance requirements in today's proposed rule, and (3) the in-scope
threshold of 2 MGD DIF (see section V for further explanation of the 2
MGD threshold), EPA has therefore identified 559 Electric Generators
that are in scope of today's 316(b) Existing Facilities Proposed
Rule.22 23
---------------------------------------------------------------------------

    \21\ For the purpose of this analysis, a facility is considered
no longer in operation and retired if it no longer has any steam
operations.
    \22\ EPA developed the estimates of the number and
characteristics of facilities expected to be within the scope of
today's proposed rule, based on the facility sample weights that
were developed for the suspended 2004 Phase II Final Regulation
analysis. These weights provide comprehensive estimates for the
total of expected in-scope facilities based on the full set of
facilities sampled in the Section 316(b) Industry Surveys. See
Appendix 3.A: Weighting Concepts of the Economic and Benefits
Analysis report for further discussion of the sample weights used in
this analysis.
    \23\ EPA estimates of the characteristics of facilities expected
to be within the scope of today's proposed rule are also based on
the facility sample weights that were developed for the suspended
2004 Phase II Final Regulation analysis.
---------------------------------------------------------------------------

    EPA estimates that the 559 steam electric generators represent 3
percent of all parent-entities, approximately 11 percent of all
facilities, and over 45 percent of the electric power sector capacity.
Based on the 2007 EIA database, EPA estimates that 388 of these in-
scope facilities are owned by utilities and 171 in-scope facilities are
owned by non-utilities.\24\ The majority of electric generating
facilities expected to be subject to today's proposed Existing
Facilities rule, or 285 facilities, are investor-owned utilities, while
nonutilities make up the second largest category. For a detailed
discussion of parent-entities, see Chapter 5 and 7 of the EA (DCN 10-
0002).
---------------------------------------------------------------------------

    \24\ Electric utilities engage in the generation, transmission,
and the distribution of electricity for sale generally in a
regulated market. Utilities include investor-owned, publicly-owned,
and cooperative entities.
---------------------------------------------------------------------------

    As reported in Exhibit IV-1, approximately half of the in-scope
electric generators draw water from a freshwater river (306 facilities
or 55 percent), followed by lakes or reservoirs (117 facilities or 21
percent) and estuaries or tidal rivers (83 facilities or 15 percent).
The exhibit also shows that most of the in-scope facilities (355
facilities or 63 percent) employ a once-through cooling system.

                              Exhibit IV-1--Number of In-Scope Electric Generators by Waterbody and Cooling-System Type \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Recirculating     Once-through       Combination                          Total \b\
                        Waterbody type                               Number            Number            Number         Other  Number        Number
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estuary/Tidal River...........................................                 5                69                 8                 1                83
Ocean.........................................................                 0                 9                 0                 0                 9
Lake/Reservoir................................................                36                73                 7                 1               117
Freshwater Stream/River.......................................               102               166                32                 5               306

Great Lake....................................................                 4                37                 2                 0                43
                                                               -----------------------------------------------------------------------------------------
    Total.....................................................               148               355                49                 7               559
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ The numbers of facilities are calculated on a sample-weighted basis.
\b\ Individual values may not sum to totals due to independent rounding.

C. Overview of Manufacturers

    EPA obtained information on in-scope Manufacturers presented in the
tables below from the EPA's Section 316(b) Industry Surveys (the
Industry Screener Questionnaire (SQ) and the Industry Detailed
Questionnaire (DQ)). Based on the Survey data and the compliance
requirements in today's proposed rule, EPA estimates 592 industry
facilities with greater than 2 MGD DIF would be subject to today's
proposal; 575 of these facilities are in the 6 primary manufacturing
industries.\25\
---------------------------------------------------------------------------

    \25\ The remaining 17 facilities have NAICS codes that do not
fall into any of these six primary manufacturing industries.
---------------------------------------------------------------------------

    Exhibit IV-2 below presents in-scope and industry-wide facility and
parent entity counts by industry. The largest share of manufacturers,
or 225 facilities, is in the Pulp and Paper industry, while facilities
in the Chemicals and Allied Products make up the second largest
category at 179 facilities.

            Exhibit IV-2--Existing Manufacturers by Industry
------------------------------------------------------------------------
                                                  Number of facilities
                                               -------------------------
                    Sector                                    Number in-
                                                   Sector     scope \b\
                                                   total         \c\
------------------------------------------------------------------------
Aluminum......................................          333           26
Chemicals.....................................        4,433          179
Food..........................................       28,938           37
Paper.........................................          597          225
Petroleum.....................................          352           39
Steel.........................................        1,525           68
                                               -------------------------
    Total.....................................       36,178      \a\ 575
------------------------------------------------------------------------
\a\ In-scope facility counts include baseline closures and exclude an
  estimated additional 17 facilities with NAICS codes that do not fall
  into any of these six primary manufacturing industries.
\b\ Number of in-scope facilities are weighted estimates; see Appendix
  3.A of the EA for information on weights development. Individual
  values may not sum to totals due to independent rounding of sample-
  weighted (non integer) estimates.
\c\ These facility count estimates are based on sample weights that are
  applicable for estimating the number of facilities that would be
  within the scope of today's proposed rule. However, because of missing
  financial data on certain facilities, these weights were not used in
  assessing the economic impact of the rule. Alternative weights, which
  yield modestly different total in-scope facility estimates (e.g., 569
  in-scope facilities in the Primary Manufacturing Industries instead of
  the 575 reported in this table), were used for developing facility
  count estimates in the economic impact analysis.

    Exhibit IV-3 provides the distribution of manufacturing intakes by
source water body and cooling system type. In total, EPA estimates that
593 intakes will be within the scope of today's rule. The vast majority
(453 facilities or 77 percent) withdraw cooling water from freshwater
streams or rivers, followed by Great Lakes (47 facilities). Two hundred
eighty-seven (48 percent) manufacturers employ once-through cooling
systems, 119 (20 percent) use closed-cycle cooling systems, and 124 (21
percent) use ``combination'' systems. An estimated 192 (32 percent)
manufacturers have installed one or more cooling towers. In the total
of 593 facility/intake combinations, EPA does not have information on
the cooling water system type for 4 facilities/intakes. Note that not
all manufacturers that have installed a cooling tower are classified as
using closed-cycle cooling systems, as facilities with multiple cooling
water systems may be ``combination'' systems that employ both closed-
cycle and once-through cooling. Manufacturers may also list ``helper''
cooling towers in their survey responses, which are generally used to
mitigate discharge temperatures and do not necessarily affect intake
flows.

                                   Exhibit IV-3--Number of In-Scope Manufacturers by Waterbody and Cooling-System Type
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                Recirculating     Once-through       Combination                        Type unknown        Total \a\
               Waterbody type                    \b\  Number         Number            Number         Other  Number        Number            Number
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estuary/Tidal River.........................                 1                23                16                 0                 0                40
Ocean.......................................                 0                11                 0                 0                 0                11
Lake/Reservoir..............................                 7                13                12                11                 0                42
Freshwater Stream/River.....................               111               215                82                41                 4               453
Great Lake..................................                 0                25                14                 7                 0                47
                                             -----------------------------------------------------------------------------------------------------------
    Total...................................               119               287               124                59                 4               593
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Facility counts include baseline closures and exclude 17 facilities with NAICS codes that do not fall into the six primary manufacturing industries
  (see Chapter 3 of EA for more detail). Individual facilities may be reported more than once in this table if they have multiple intakes while a single
  intake that serves both recirculating and once-through systems is counted once as a combination. Individual values may not sum to totals due to
  independent rounding of sample-weighted (non integer) estimates.
\b\ Four facilities have an unknown CWS type.

D. Other Existing Facilities

    EPA's data collection efforts largely focused on five industrial
sectors: Chemicals and allied products (SIC Major Group 28); primary
metals industries (SIC Major Group 33); paper and allied products (SIC
Major Group 26); petroleum and coal products (SIC Major Group 29); and
food and kindred products (SIC Major Group 20).\26\ The first four
sectors use a significant portion of the cooling water withdrawn among
all manufacturing industries and were more heavily targeted in EPA's
industry questionnaire effort, but data were also collected from the
following industries: Food processing; aircraft engines and engine
parts; cutlery; sawmills and planing mills; finishers of broad woven
fabrics of cotton; potash, soda and borate minerals; iron ores; and
sugarcane and sugar beets. These data from other industries, while not
a statistically derived sample, confirm that the primary industry
sectors discussed above account for the vast majority of non-power
plant cooling water use. The data collected for these other industries
suggests that the intake structure design and construction at these
industries were substantially similar to the industries for which EPA
did collect data, and EPA did not receive any data during the Phase III
proposed rule comment period that suggests otherwise. EPA's analysis of
costs and impacts includes these additional existing facilities.
---------------------------------------------------------------------------

    \26\ EPA also identified many other industry sectors that use
cooling water; a more comprehensive list of industries that use
cooling water and their NAICS and SIC Codes can be found in section
A of the Supplementary Information.
---------------------------------------------------------------------------

V. Scope and Applicability of the Proposed Section 316(b) Existing
Facility Rule

    The proposed rule includes all existing facilities with a design
intake flow of more than 2 MGD. The proposed rule also clarifies the
definition and requirements for new units at existing facilities. The
applicable requirements are summarized in Exhibits V-1 and V-2.

         Exhibit V-1--Applicability by Phase of the 316(b) Rules
------------------------------------------------------------------------
        Facility characteristic                  Applicable rule
------------------------------------------------------------------------
New power generating or manufacturing    Phase I rule.
 facility.
New offshore oil and gas facility......  Phase III rule.
New unit at an existing power            This proposed rule.
 generating or manufacturing facility.
Existing power generating or             This proposed rule.
 manufacturing facility.
Existing offshore oil and gas facility   This proposed rule (Case-by-
 and seafood processing facilities.       case, best professional
                                          judgment).
------------------------------------------------------------------------

    Exhibit V-2--Applicable Requirements of Today's Proposed Rule for
                           Existing Facilities
------------------------------------------------------------------------
        Facility characteristic              Applicable requirements
------------------------------------------------------------------------
Existing facility with a AIF >125 MGD..  Impingement mortality
                                          requirements at 125.94(b) and
                                          Entrainment Characterization
                                          Study requirements at
                                          125.94(c) (categorical rule).
Existing facility with a DIF >2 MGD but  Impingement mortality
 AIF not greater than 125 MGD.            requirements at 125.94(b)
                                          (categorical rule).
New unit with a DIF >2 MGD at an         Impingement and entrainment
 existing facility.                       mortality requirements at
                                          125.94(d) (categorical
                                          standard).
Other existing facility with a DIF of 2  Case-by-case, best professional
 MGD or smaller or that has an intake     judgment.
 structure that withdraws less than 25
 percent of the water for cooling
 purposes.
------------------------------------------------------------------------

    Initially, EPA divided the 316(b) rulemaking into three phases in
response to litigation and to make the best use of its resources (see
Section I). However, as EPA's analysis progressed, it became clear that
cooling water intake structures are operated similarly at most
industrial facilities (i.e., both power producing and manufacturing
facilities). From a biological perspective, the effect of intake
structures on impingement and entrainment does not differ depending on
whether an intake structure is associated with a power plant or a
manufacturer. Instead the impingement and entrainment impacts
associated with intakes of the same type are generally comparable, and
today's proposed rule addresses these impacts without discriminating
which facilities are behind the intake structure. Thus, EPA is
consolidating the universe of potentially regulated facilities from the
2004 Phase II rule with the existing facilities in the 2006 Phase III
rule for purposes of today's proposed rule. This consolidation also
provides a ``one-stop shop'' for information related to today's
proposed rulemaking, as all existing facilities would be addressed in
an equitable manner by the same set of technology-based requirements.

A. General Applicability

    This rule would apply to owners and operators of existing
facilities that meet all of the following criteria:
     The facility is a point source that uses or proposes to
use cooling water from one or more cooling water intake structures,
including a cooling water intake structure operated by an independent
supplier not otherwise subject to 316(b) requirements that withdraws
water from waters of the United States and provides cooling water to
the facility by any sort of contract or other arrangement;
     The total design intake flow of the cooling water intake
structure(s) is greater than 2 MGD; and
     The cooling water intake structure(s) withdraw(s) cooling
water from waters of the United States and at least twenty-five (25)
percent of the water withdrawn is used exclusively for cooling purposes
measured on an average annual basis for each calendar year.
    EPA is proposing to continue to adopt provisions to ensure that the
rule does not discourage the reuse of cooling water for other uses such
as process water. The definition of cooling water at 125.93 provides
that cooling water used in a manufacturing process either before or
after it is used for cooling is considered process water for the
purposes of calculating the percentage of a facility's intake flow that
is used for cooling purposes. Therefore, water used for both cooling
and non-cooling purposes does not count towards the 25

percent threshold. EPA notes this definition is the same definition
used for new facilities in the Phase I rule at 125.83. Examples of
water withdrawn for non-cooling purposes includes water withdrawn for
warming by liquefied natural gas facilities and water withdrawn for
public water systems by desalinization facilities. Further, the
proposed rule at 125.91(c) specifies that obtaining cooling water from
a public water system or using treated effluent (such as wastewater
treatment plant ``gray'' water) as cooling water does not constitute
use of a cooling water intake structure for purposes of this rule.
    Today's proposed rule focuses on those facilities that are
significant users of cooling water; only those facilities that use more
than 25% of the water withdrawn for cooling purposes are subject to the
proposed rule. EPA previously considered a number of approaches for
clarifying applicability of the rule (66 FR 28854 and 66 FR 65288). EPA
adopted the 25% threshold in each of the Phase I, II, and III rules,
and EPA has not received any new data or identified new approaches that
would provide further clarity to the applicability of the rule. EPA is
proposing to continue to adopt 25% as the threshold for the percent of
flow used for cooling purposes to ensure that a large majority of
cooling water withdrawn from waters of the U.S. is addressed by
requirements for minimizing adverse environmental impact. Because power
generating facilities typically use far more than 25 percent of the
water they withdraw exclusively for cooling purposes, the 25 percent
threshold will ensure that intake structures accounting for nearly all
cooling water used by the power sector are addressed by today's
proposed requirements. While manufacturing facilities often withdraw
water for more than cooling purposes, the majority of the water is
withdrawn from a single intake structure.\27\ Once water passes through
the intake, water can be apportioned to any desired use, including uses
that are not related to cooling. However, as long as at least 25% of
the water is used exclusively for cooling purposes, the intake will be
subject to the requirements of today's rule. EPA estimates that
approximately 68% of manufacturers and 93% of power-generating
facilities that meet the other proposed thresholds for the rule use
more than 25% of intake water for cooling and thus will be addressed by
today's rule.
---------------------------------------------------------------------------

    \27\ Facilities may also use groundwater wells or municipal
water for various uses, but the volume of these withdrawals is
usually much smaller than the volume withdrawn from surface waters.
---------------------------------------------------------------------------

    EPA decided to propose requiring the Director, exercising BPJ, to
establish BTA impingement and entrainment mortality standards for an
existing offshore oil and gas facility, a seafood processing vessel, or
an offshore liquefied natural gas import terminal. Such a facility
would be subject to permit conditions implementing CWA section 316(b)
where the facility is a point source that uses a cooling water intake
structure and has, or is required to have, an NPDES permit. At their
discretion, permit writers may further determine that an intake
structure that withdraws less than 25% of the intake flow for cooling
purposes should be subject to section 316(b) requirements, and set
appropriate requirements on a case-by-case basis, using best
professional judgment. Today's proposed rule is not intended to
constrain permit writers at the Federal, State, or Tribal level, from
addressing such cooling water intake structures.

B. What is an ``existing facility'' for purposes of the Section 316(b)
Phase II rule?

    In today's proposed rule, EPA is defining the term ``existing
facility'' to include any facility that commenced construction before
January 18, 2002, as provided for in Sec.  122.29(b)(4).\28\ EPA is
proposing to establish January 17, 2002 as the date for distinguishing
existing facilities from new facilities because that is the effective
date of the Phase I new facility rule. Thus, existing facilities
include all facilities the construction of which commenced on or before
this date. In addition, EPA is defining the term ``existing facility''
in this proposed rule to include modifications and additions to such
facilities, the construction of which commences after January 17, 2002,
that do not meet the definition of a new facility at Sec.  125.83,
which is the definition used to define the scope of the Phase I
rule.\29\
---------------------------------------------------------------------------

    \28\ Construction is commenced if the owner or operator has
undertaken certain installation and site preparation activities that
are part of a continuous on-site construction program, and it
includes entering into certain specified binding contractual
obligations as one criterion (Sec.  122.29(b)(4)).
    \29\ The Phase I rule also listed examples of facilities that
would be ``new'' facilities and facilities that would ``not be
considered a `new facility' '' in two numbered paragraphs.
---------------------------------------------------------------------------

    The preamble to the final Phase I rule discusses this definition at
66 FR 65256; 65258-65259; 65285-65287, December 18, 2001. EPA's
definition of an ``existing facility'' in today's proposed regulation
is intended to ensure that all sources excluded from the definition of
new facility in the Phase I rule are captured by the definition of
existing facility in this proposed rule.
    A point source would be subject to Phase I or today's proposed rule
even if the cooling water intake structure it uses is not located at
the facility.\30\ In addition, modifications or additions to the
cooling water intake structure (or even the total replacement of an
existing cooling water intake structure with a new one) does not
convert an otherwise unchanged existing facility into a new facility,
regardless of the purpose of such changes (e.g., to comply with today's
proposed rule or to increase capacity). Rather, the determination as to
whether a facility is new or existing focuses on whether it is a green
field or stand-alone facility and whether there are changes to the
cooling water intake to accommodate it.
---------------------------------------------------------------------------

    \30\ For example, a facility might purchase its cooling water
from a nearby facility that owns and operates a cooling water intake
structure.
---------------------------------------------------------------------------

C. What is ``cooling water'' and what is a ``cooling water intake
structure?''

    EPA has not revised the definition of cooling water intake
structure for today's proposed rule. A cooling water intake structure
is defined as the total physical structure and any associated
constructed waterways used to withdraw cooling water from waters of the
United States. Under the definition in today's proposed rule, the
cooling water intake structure extends from the point at which water is
withdrawn from the surface water source up to, and including, the
intake pumps. Today's proposed rule proposes for existing facilities
the same definition of a ``cooling water intake structure'' that
applies to new facilities under Phase I. Today's proposal also adopts
the new facility rule's definition of ``cooling water'' as water used
for contact or noncontact cooling, including water used for equipment
cooling, evaporative cooling tower makeup, and dilution of effluent
heat content. The definition specifies that the intended use of cooling
water is to absorb waste heat rejected from the processes used or
auxiliary operations on the facility's premises. The definition also
indicates that water used in a manufacturing process either before or
after it is used for cooling is process water and would not be
considered cooling water for purposes of determining whether 25 percent
or more of the flow is cooling water. This clarification is necessary
because cooling water intake structures typically bring water into a
facility for numerous purposes, including industrial processes; use as
circulating

water, service water, or evaporative cooling tower makeup water;
dilution of effluent heat content; equipment cooling; and air
conditioning. Note however, that all intake water (including cooling
and process) is included in the determination as to whether the 2 MGD
DIF threshold for covered intake structures is met.

D. Would my facility be covered only if it is a Point Source
Discharger?

    Today's proposed rule would apply only to facilities that are point
sources (i.e., have an NPDES permit or are required to obtain one).
This is the same requirement EPA included in the Phase I new facility
rule at Sec.  125.81(a)(1). Requirements for complying with section
316(b) will continue to be applied through NPDES permits.
    Based on the Agency's review of potential existing facilities that
employ cooling water intake structures, the Agency anticipates that
most existing facilities subject to this proposed rule will control the
intake structure that supplies them with cooling water, and discharge
some combination of their cooling water, wastewater, or storm water to
a water of the United States through a point source regulated by an
NPDES permit. Under these circumstances, the facility's NPDES permit
will include the requirements for the cooling water intake structure.
In the event that an existing facility's only NPDES permit is a general
permit for storm water discharges, the Agency anticipates that the
Director would write an individual NPDES permit containing requirements
for the facility's cooling water intake structure. Alternatively,
requirements applicable to cooling water intake structures could be
incorporated into general permits. If requirements are placed into a
general permit, they must meet the requirements set out at 40 CFR
122.28.
    As EPA stated in the preamble to the final Phase I rule (66 FR
65256 (December 18, 2001)), the Agency encourages the Director to
closely examine scenarios in which a facility withdraws significant
amounts of cooling water from waters of the United States but is not
required to obtain an NPDES permit. As appropriate, the Director will
necessarily apply other legal requirements, where applicable, such as
section 404 or 401 of the Clean Water Act, the Coastal Zone Management
Act, the National Environmental Policy Act, the Endangered Species Act,
or similar State or Tribal authorities to address adverse environmental
impact caused by cooling water intake structures at those facilities.

E. Would my facility be covered if it withdraws water from waters of
the U.S.? What if my facility obtains cooling water from an independent
supplier?

    The requirements in today's proposed rule apply to cooling water
intake structures that have the design capacity to withdraw amounts of
water equal to or greater than 2 MGD from ``waters of the United
States.'' Waters of the United States include the broad range of
surface waters that meet the regulatory definition at 40 CFR 122.2,
which includes lakes, ponds, reservoirs, nontidal rivers or streams,
tidal rivers, estuaries, fjords, oceans, bays, and coves. These
potential sources of cooling water may be adversely affected by
impingement and entrainment.
    Some facilities discharge heated water to manmade cooling ponds,
and then withdraw water from the ponds for cooling purposes. EPA
recognizes that cooling ponds may, in certain circumstances, constitute
a closed-cycle cooling system and therefore may already comply with
some or all of the technology-based requirements in today's proposed
rule. However, facilities that withdraw cooling water from cooling
ponds that are waters of the United States and that meet the other
criteria for coverage (including the requirement that the facility has
or will be required to obtain an NPDES permit) would be subject to
today's proposed rule. In some cases water is withdrawn from a water of
the United States to provide make-up water for a cooling pond. In many
cases, EPA expects such make-up water withdrawals are commensurate with
the flows of a closed-cycle cooling tower, and again the facility may
already comply with requirements to reduce its intake flow under the
proposed rule. In those cases where the withdrawals of make-up water
come from a water of the United States, and the facility otherwise
meets today's criteria for coverage (including a design intake flow of
2 million gallons per day), the facility would be subject to today's
proposed rule requirements.
    EPA does not intend this rule to change the regulatory status of
cooling ponds. Cooling ponds are neither categorically included nor
categorically excluded from the definition of ``waters of the United
States'' at 40 CFR 122.2. The determination whether a particular
cooling pond is, or is not, a water of the United States is to be made
by the permitting authority on a case-by-case basis. The EPA and the
U.S. Army Corps of Engineers have jointly issued jurisdictional
guidance concerning the term ``waters of the United States'' in light
of the Supreme Court's decision in Solid Waste Agency of Northern Cook
County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001) (SWANCC). A
copy of that guidance was published as an Appendix to an Advanced
Notice of Proposed Rulemaking on the definition of the phrase ``waters
of the U.S.,'' see 68 FR 1991 (January 15, 2003), and may be obtained
at (http://www.epa.gov/owow/wetlands/pdf/ANPRM-FR.pdf). The agencies
additionally published guidance in 2008 regarding the term ``waters of
the United States'' in light of both the SWANCC and subsequent Rapanos
case (Rapanos v. United States, 547 U.S. 715 (2006)).
    The Agency recognizes that some facilities that have or are
required to have an NPDES permit might not own and operate the intake
structure that supplies their facility with cooling water. In
addressing facilities that have or are required to have an NPDES permit
that do not directly control the intake structure that supplies their
facility with cooling water, revised Sec.  125.91 provides (similar to
the new facility rule) that facilities that obtain cooling water from a
public water system or use treated effluent are not deemed to be using
a cooling water intake structure for purposes of this proposed rule.
However, obtaining water from another entity that is withdrawing water
from a water of the US would be counted as using a cooling water intake
structure for purposes of determining whether an entity meets the
threshold requirements of the rule. For example, facilities operated by
separate entities might be located on the same, adjacent, or nearby
property(ies); one of these facilities might take in cooling water and
then transfer it to other facilities prior to discharge of the cooling
water to a water of the United States. Section 125.91(b) specifies that
use of a cooling water intake structure includes obtaining cooling
water by any sort of contract or arrangement with one or more
independent suppliers of cooling water if the supplier or suppliers
withdraw water from waters of the United States but that is not itself
a new or existing facility subject to section 316(b), except if it is a
public water system.
    As a practical matter, existing facilities are the largest users of
cooling water, and typically require enough cooling water to warrant
owning the cooling water intake structures. In some cases, such as at
nuclear power plants or critical baseload facilities, the need for
cooling water includes safety and reliability reasons that would likely
preclude any independent supplier arrangements. Therefore, EPA does not
expect much application of this

provision. EPA is nevertheless retaining the provision in order to
prevent facilities from circumventing the requirements of today's
proposed rule by creating arrangements to receive cooling water from an
entity that is not itself subject to today's proposed rule, and is not
explicitly exempt from today's rule (such as drinking water or
treatment plant discharges reused as cooling water).

F. What intake flow thresholds result in an existing facility being
subject to this proposed rule?

    There are two ways in which EPA determines the cooling water flow
at a facility. The first way is based on the design intake flow (DIF),
which reflects the maximum intake flow the facility is capable of
withdrawing. While this normally is limited by the capacity of the
cooling water intake pumps, other parts of the cooling water intake
system could impose physical limitations on the maximum intake flow the
facility is capable of withdrawing. The second way is based on the
actual intake flow (AIF), which reflects the actual volume of water
withdrawn by the facility. EPA has defined AIF to be the average water
withdrawn each year over the preceding 3 years. Both of these
definitions are used in today's proposed rule.
    In this proposed rule EPA considered requirements based on the
intake flow at the existing facility. EPA is proposing the rule to
apply to facilities that have a total design intake capacity of at
least 2 MGD (see Sec.  125.91).\31\ Above 2 MGD, 99.7% of the total
water withdrawals by utilities and other industrial sources would
potentially be covered (if the other criteria for coverage are met)
while 58% of the manufacturers, 70% of the non-utilities, and 100% of
the utilities would be covered. EPA also chose the greater than 2 MGD
threshold to be consistent with the applicability criteria in the Phase
I rule.\32\ EPA continues to believe that this threshold ensures that
the largest users of cooling water will be subject to the proposed
rule.
---------------------------------------------------------------------------

    \31\ The 2004 Phase II rule applied to existing power-generating
facilities with a design intake flow of 50 mgd or greater.
Facilities potentially in scope of the Phase III rule had a DIF of
greater than 2 MGD.
    \32\ See 65 FR 49067/3 for more information.
---------------------------------------------------------------------------

    EPA proposes to continue to use a threshold based on design intake
flow as opposed to actual intake flow for several reasons. In contrast
to actual intake flow, design intake flow is a fixed value based on the
design of the facility's operating system and the capacity of the
circulating and other water intake pumps. This provides clarity, as the
design intake flow does not change, except in limited circumstances,
such as when a facility undergoes major modifications. On the other
hand, actual flows can vary significantly over sometimes short periods
of time. For example, a peaking power plant may have an actual intake
flow close to the design intake flow during times of full energy
production, but an AIF of zero during periods of standby. Use of design
intake flow provides clarity as to regulatory status, is indicative of
the possible magnitude of environmental impact, and would avoid the
need for monitoring to confirm a facility's status. Also see 69 FR
41611 for more information about these thresholds.
    Under current NPDES permitting regulations at Sec.  122.21, all
existing facilities greater than 2 MGD DIF must submit basic
information describing the facility, source water physical data, source
water biological characterization data, and cooling water intake system
data. Under this proposed rule, all facilities greater than 2 MGD DIF
must submit additional facility-specific information including the
proposed impingement mortality reduction plan, relevant biological
survival studies, and operational status of each of the facility's
units.\33\ Certain facilities withdrawing the largest volumes of water
for cooling purposes have additional information and study requirements
such as the Entrainment Characterization Study as described below.
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    \33\ The proposed rule contains streamlined information
submission requirements for facilities that already employ closed
cycle cooling.
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    EPA is proposing to use actual intake flow (AIF) rather than design
intake flow (DIF) for purposes of determining which facilities must
conduct an Entrainment Characterization Study. Environmental impacts,
particularly entrainment and entrainment mortality, result from actual
water withdrawals, and not the maximum designed withdrawals. Further,
using actual flow may encourage some facilities to reduce their flows
in order to avoid collecting supplemental data and submitting the
additional entrainment characterization study. Furthermore, any
facility that has DIF greater than 2 MGD is required to submit basic
information that will allow the permitting authority to verify its
determination of whether or not it meets the 125 MGD AIF threshold.
    EPA has selected a threshold of 125 MGD AIF because a threshold of
125 MGD would capture 90 percent of the actual flows but would only
establish the Entrainment Characterization Study requirements for 30
percent of existing facilities. This would significantly reduce
facility burden by more than two-thirds of the potentially in-scope
facilities, and would focus permit authorities on the majority of
cooling water withdrawals by addressing approximately 200 billion
gallons of daily cooling water withdrawals.
    In today's proposal, EPA seeks to clarify that for some facilities,
the design intake flow is not necessarily the maximum flow associated
with the intake pumps. For example, a power plant may have redundant
circulating pumps, or may have pumps with a name plate rating that
exceeds the maximum water throughput of the associated piping. EPA
intends for the design intake flow to reflect the maximum volume of
water that a plant can physically withdraw from a source waterbody over
a specific time period. This also means that a plant that has
permanently taken a pump out of service or has flow limited by piping
or other physical limitations should be able to consider such
constraints when reporting its DIF. EPA solicits comment on whether the
definition of DIF should be revised to make this clarification more
apparent.

G. Offshore Oil and Gas Facilities, Seafood Processing Vessels or LNG
Import Terminals BTA Requirements Under This Proposed Rule

    Under today's proposal, existing offshore oil and gas facilities,
seafood processing facilities and LNG import terminals would be subject
to 316(b) requirements on a best professional judgment basis. In the
Phase III rule, EPA studied offshore oil and gas facilities and seafood
processing facilities \34\ and could not identify any technologies
(beyond the protective screens already in use) that are technically
feasible for reducing impingement or entrainment in such existing
facilities.\35\ As discussed in the Phase III rule, known technologies
that could further reduce impingement or entrainment would result in
unacceptable changes in the envelope of existing platforms, drilling
rigs, mobile offshore drilling units (MODUs), seafood processing
vessels (SPVs), and similar facilities as the technologies would
project out from the hull, potentially decrease the seaworthiness, and
potentially interfere with structural

components of the hull. EPA also believes that for many of these
facilities, the cooling water withdrawals are most substantial when the
facilities are operating far out at sea--and therefore not withdrawing
from a water of the U.S. The EPA is aware that LNG facilities may
withdraw hundreds of MGD of seawater for warming (re-gasification).
However, some existing LNG facilities may still withdraw water where 25
percent or more of the water is used for cooling purposes. As discussed
in section V, EPA has not identified a uniformly applicable and
available technology for minimizing impingement and entrainment (I&E)
mortality at these facilities. However, technologies may be available
for some existing LNG facilities. LNG facilities that withdraw any
volume of water for cooling purposes would be subject to case-by-case,
best professional judgment BTA determinations.
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    \34\ EPA studied naval vessels and cruise ships as part of its
development of a general NPDES permit for discharges from ocean-
going vessels. (See  http://cfpub.epa.gov/npdes/home.cfm?program_id=350 for more information.) EPA studied seafood processing vessels
and oil and gas exploration facilities in the 316(b) Phase III rule.
    \35\ As discussed in today's preamble, requirements for new
offshore facilities set forth in the Phase III rule remain in
effect.
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    EPA has not identified any new data or approaches that would result
in a different determination. Therefore, today's rule would continue to
require that the BTA for existing offshore oil and gas extraction
facilities and seafood processing facilities is established by NPDES
permit directors on a case-by-case basis using best professional
judgment. EPA solicits comment and data on the appropriateness of
national categorical standards for these facilities.

H. What is a ``new unit'' and how are new units addressed under this
proposed rule?

    The Phase I rule did not distinguish between new stand-alone
facilities and new units where the units are built on a site where a
source is already located and does not totally replace the existing
source. Because EPA is not changing the new facility rule definitions,
and is only proposing clarifying revisions to the existing facility
rule, this proposed provision is not intended to otherwise reopen the
Phase I rule. Today's proposed rule establishes requirements for new
units added to an existing facility that are not a ``new facility'' as
defined at Sec.  125.83. Today's proposal seeks to clarify the
definitions of ``new'' versus ``existing'' by first noting that, for
purposes of section 316(b), a facility cannot be defined as a new
facility and an existing facility at the same time. In this rule, while
EPA will continue to treat replacement and new units for the same
industrial purpose as existing facilities, EPA intends to have
different requirements for the addition of new units. A replacement
unit or repowered unit, as distinct from constructing an additional
unit, would not be treated as a new unit. The requirements for new
units are modeled after the requirements for a new facility in the
Phase I rule.
    EPA has adopted this approach for the following reasons. As new
units are built at existing facilities to provide additional capacity,
facilities have the ideal opportunity to design and construct the new
units without many of the additional expenses associated with
retrofitting an existing unit to closed-cycle. The incremental downtime
that can be associated with retrofitting to closed-cycle cooling is
avoided altogether at a new unit. In addition, when new units are
added, the condensers can be configured for closed-cycle, reducing
energy requirements, and high efficiency cooling towers can be designed
as part of the new unit, allowing for installation of smaller cooling
towers. Thus, the capital costs for closed cycle cooling at new units
are lower than the capital costs for once-through cooling. These
advantages may not always be available when retrofitting cooling towers
at an existing unit.
    In consideration of the fact that additional unit construction
decisions rest largely within the control of the individual facility,
EPA decided that subjecting new units to the same national BTA
requirements as those applicable to new facilities is warranted.

VI. BTA Consideration

    In response to the Supreme Court's decision in Entergy Corp. et al.
v. EPA in April 2009, and the Second Circuit decision in Riverkeeper
II, EPA has reevaluated the requirements for existing facilities under
section 316(b). As discussed in Section III, for the BTA determinations
proposed below, EPA collected additional data and information and
updated the technology efficacy and costs analyses prepared for the
earlier rulemaking efforts. These data and analyses serve to update the
rulemaking record and allow EPA to apply greater technical rigor to
EPA's analysis of BTA. As a result, EPA has decided not to re-propose
requirements similar to those of the final Phase II rule, but would
adopt, for the reasons explained in this preamble, a new framework. In
addition, as previously noted, EPA decided to address all existing
facilities subject to 316(b) in one rule (i.e., Phase II and Phase
III).

A. EPA's Approach to BTA

    Section 316(b) of the CWA requires EPA to establish standards for
cooling water intake structures that reflect the ``best technology
available for minimizing adverse environmental impact.'' The statute is
silent with respect to the factors that EPA should consider in
determining BTA but courts have held that, given section 316(b)'s
reference to sections 301 and 306 of the Act, EPA may look to the
factors considered in those sections in establishing those standards
for section 316(b) standard setting. The Supreme Court noted that,
given the absence of any factors language in Section 316(b), EPA has
more discretion in its standard setting under section 316(b) than under
the effluent guidelines provisions. EPA has broad discretion in
determining what is the ``best'' available technology for minimizing
adverse environmental impact. EPA is not bound to evaluate the factors
it considers in standard setting in precisely the same way it considers
them in establishing effluent limitations guidelines under section 304
of the Clean Water Act. Thus, the U.S. Supreme Court has explained
that, under section 316(b), ``best'' technology may reflect a
consideration of a number of factors and that ``best'' does not
necessarily mean the technology that achieves the greatest reduction in
environmental harm that the regulated universe can afford. Rather, the
``best'' (or ``most advantageous'' technology in the court's words) may
represent a technology that most efficiently produces the reductions in
harm.
    EPA has interpreted section 316(b) to require the Agency to
establish a standard based on the best technology available that will
minimize impingement and entrainment--the two main adverse effects of
cooling water intake structures. In EPA's view, there are several
important considerations underpinning its decision. First, its BTA
determination should be consistent with,and reflective of, the goals of
Section 101 of the CWA: ``to restore and maintain the physical,
chemical, and biological integrity of the Nation's waters,'' with an
interim goal of protecting water quality so as to provide for the
protection and propagation of fish, shellfish, and wildlife and provide
for recreation in and on the water.
    Second, because the Supreme Court has concluded that EPA may
permissibly consider costs and benefits in its BTA determination and
E.O. 13563 directs EPA only to propose regulations based on a reasoned
determination that the benefits justify the costs, EPA has taken costs
and benefits into account in this proposal. EPA has concluded that the
benefits of the proposed option justify its costs. See section VI. E
below.
    Both Riverkeeper decisions recognize that EPA may consider a number
of factors in establishing section 316(b) standards. In the Phase I
Riverkeeper case, the court explained that the cross

reference in section 316(b) to sections 301 and 306 is an
``invitation'' to look to those statutory provisions for guidance
concerning the factors EPA should consider in determining BTA. In the
Phase II decision, the court stated that the interpretation of section
316(b) should be ``informed'' by these other two provisions. EPA may
consider the factors involved in establishing effluent discharge
limitations when regulating intake structures. The factors specifically
delineated in CWA sections 301 and 306 that EPA may consider include:
cost of the technology, taking into account the age of the equipment
and facilities, process employed, engineering aspects associated with a
particular technology, process changes and non-water quality
environmental impact (including energy requirements).
    In selecting the ``best'' technology, EPA looked at a number of
factors. Thus, EPA first considered the availability and feasibility of
various technologies, their costs including potential costs to
facilities as well as households, and economic impacts of different
technologies. EPA reviewed the efficacy of these technologies in
reducing impingement and entrainment mortality, including cost-
effectiveness relationships. EPA also considered additional factors set
out in 304(b) of the Clean Water Act, including location, age, size,
and type of facility. EPA next considered the non-water quality effects
of different technologies on energy production and availability,
electricity reliability, and potential adverse environmental effects
that may arise from the use of the different controls evaluated.
    EPA has also considered the costs and the benefits of the different
technologies it evaluated for BTA. Consideration of benefits in
particular is complicated by the absence of well-developed tools or
data to fully express the ecological benefits in monetized terms. EPA
has, however, used the best currently available science to monetize the
benefits of the various options in four major categories: Recreational
fishing, commercial fishing, nonuse benefits, and benefits to
threatened and endangered species (see Exhibit VIII-10). EPA believes
that the benefits estimated for the first two categories are fairly
complete, while the benefits estimated for the latter two categories
are incomplete for a number of reasons. For example, the non-use
benefits consider only the northeast and middle Atlantic states. EPA
will continue to refine its tools in order to develop a more complete
analysis concerning benefits during the rulemaking proceeding.
    As a result of this thorough evaluation, EPA is proposing the use
of modified traveling screens with a fish handling and return system or
reduced intake velocity as BTA for impingement mortality. EPA's record
shows modified traveling screens are available for all facilities,
whereas reduced intake velocity may not be available at all locations.
For entrainment, on the other hand, EPA could identify no single
technology that represented BTA for all facilities for the reasons
explained in detail below. Instead, as the national BTA entrainment
requirement for existing facilities, EPA is proposing to adopt
regulations that establish a process for the permitting authority to
determine entrainment BTA controls on a site-specific basis following
the consideration of several factors. In addition to the general
considerations discussed above, EPA has identified the following
specific factors as the key elements in its decision not to prescribe a
single technology as the basis for a national BTA determination. These
factors are local energy reliability, air emissions permits, land
availability, and remaining useful plant life. The rest of this chapter
describes each of these considerations in detail.

B. Technologies Considered to Minimize Impingement and Entrainment

    As described in Section IV, power plants and manufacturers withdraw
large volumes of cooling water on a daily basis. The majority of
environmental impacts associated with intake structures are caused by
water withdrawals that ultimately result in the loss of aquatic
organisms. These losses may be due to impingement, entrainment, or
both. Impingement occurs when organisms are trapped against the outer
part of a screening device of an intake structure.\36\ The force of the
intake water traps the organisms against the screen and they are unable
to escape. Not all organisms contained in the incoming water are
impinged, however. Some may pass through the screening system and the
intake structure and travel through the entire cooling system including
the pumps, condenser tubes, and discharge pipes. This is referred to as
entrainment. Various factors lead to the susceptibility of an organism
to impingement or entrainment. For more detailed discussion of
impingement and entrainment and their resulting impact, see 67 FR
17136-17140 and the EEBA.
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    \36\ Typically, cooling water intake structures use various
screening devices to prevent large objects (e.g., trash, logs) from
being drawn in with the cooling water and ultimately clogging or
damaging the cooling water system.
---------------------------------------------------------------------------

    As described in Section III.D, reductions in impingement or
entrainment do not necessarily mean reductions in mortality. For
purposes of this proposal, EPA has developed the following definitions
for impingement and entrainment and mortality:
     Impingement: The entrapment of all life stages of fish and
shellfish on the outer part of an intake structure or against a
screening device during periods of intake water withdrawal.
     Impingement Mortality: The death of fish or shellfish due
to impingement (as defined above). Note impingement mortality need not
occur immediately; impingement may cause harm to the organism, which
results in mortality several hours after the impingement event. For
purposes of this proposed rule, impingement mortality is limited to
those organisms collected or retained by \3/8\ inch sieve.
     Entrainment: The incorporation of all life stages of fish
and shellfish with intake water flow entering and passing through a
cooling water intake structure and into a cooling system.
     Entrainment Mortality: The death of fish or shellfish due
to entrainment. This also includes the death of those fish and
shellfish due to fine mesh screens or other technologies used to
exclude the organisms from entrainment. For purposes of this proposed
rule, entrainment mortality is limited to those organisms passing
through a \3/8\-inch sieve.
    Based on available information, as described in section III.D, EPA
is assuming for purposes of this rule that all entrained organisms are
a loss, i.e., no entrained organisms survive. Therefore, in the absence
of entrainment control, entrainment is assumed to lead to entrainment
mortality. Also see Chapter A7 of the Phase II Regional Studies
Document (DCN 6-0003; EPA-HQ-OW-2002-0049-1490). Entrainable organisms
generally consist of eggs and early life stage larvae. Early larvae
generally do not have skeletal structures, have not yet developed
scales, and in many cases are incapable of swimming for several days
post hatching. However, for impingement, mortality occurs less than
100% of the time. Impingeable organisms are generally larger juvenile
or adult fish, with fully formed scales and skeletal structures, and
well developed survival traits such as avoidance responses. EPA's data
demonstrate that, under the proper conditions, many impinged organisms
survive.
    In addition to these definitions it is helpful to further
characterize

impingement and entrainment as those terms are used in the literature
and in studies conducted by power plants. Historically, traveling
screens deployed by power plants utilized a \3/8\-inch mesh size. For
this reason, most studies and reports referring to impingement are in
fact referring to those organisms impinged on a \3/8\-inch mesh screen.
Impingement can also refer to any organism incapable of swimming away
from the intake structure due to the water velocity at the intake.
Similarly, entrainable organisms are those organisms fitting through a
mesh of less than or equal to \3/8\ of an inch. This also means the
majority of entrainable organisms are comprised of eggs, larvae, and
juveniles. More recent studies, particularly those that evaluate mesh
sizes smaller than \3/8\ of an inch, continue to refer to impingement
as any organism caught on the screen. This can cause some confusion, as
many organisms that would have been entrained with a \3/8\-inch mesh
instead become impinged by the finer mesh. These are referred to as
``impinged entrainables'' or ``converts.'' EPA has also found that most
studies of entrainment are biased towards the larger (older) larvae
with higher survival rates and do not analyze survival of smaller
larvae. This corresponds to larvae body lengths sufficient to have
begun scale and bone development, and generally reflects the more
motile early life stages. EPA found these study findings cannot be
applied to non-motile life stages, which are incapable of avoidance
responses. As discussed in Section III.C, it is also important to note
that the prevention of entrainment by some exclusion technologies may
result in very high entrainment reductions, but these organisms do not
necessarily survive interactions with the exclusion technology.
Therefore, while entrainment refers specifically to passage through the
cooling water intake system, entrainment mortality also includes those
smaller organisms killed by exclusion from the cooling water intake
system. Today's rule proposes to use the \3/8\-inch mesh size as part
of the definition of impingement and entrainment mortality as a means
of clearly differentiating those organisms that may be susceptible to
impingement or entrainment, and thereby avoiding any confusion over the
status of ``impinged entrainables'' or ``converts.''
    Generally, there are two basic approaches to reduce impingement and
entrainment (I&E) mortality. The first approach is flow reduction,
where the facility installs technology or operates in a manner to
reduce or eliminate the quantity of water being withdrawn. Reduced
volumes of cooling water produce a corresponding reduction in I&E, and
therefore reduced I&E mortality. The second way to reduce I&E is to
install technologies or operate in a manner that either (a) gently
excludes organisms or (b) collects and returns organisms. Under the
first approach, technologies or practices are used to divert those
organisms that would have been subject to I&E. The second approach is
to install collection and return technologies; organisms not diverted
are collected and returned back to the source water.
    Though not available to all facilities, a third approach to
reducing impingement and entrainment is relocating the facility's
intake to a less biologically rich area in a water body, usually
further from shore and/or at greater depths, or varying the timing of
withdrawals by time of day, season, etc., to target withdrawals to
times when organism densities are lower. This approach can be effective
at entrainment reduction, but is not generally available to inland
facilities.
    The section below further describes flow reduction and exclusion
technologies.
1. Flow Reduction
    Flow reduction is commonly used to reduce impingement and
entrainment. For purposes of rulemaking, EPA assumes that entrainment
and impingement (and associated mortality) at a particular site are
proportional to source water intake volume.\37\ Thus, if a facility
reduces its intake flow, it similarly reduces the amount of organisms
subject to impingement and entrainment. Some common flow reduction
technologies include: Variable frequency drives, variable speed pumps,
seasonal operation or seasonal flow reductions, unit retirements, use
of alternate cooling water sources, water reuse, and closed-cycle
cooling systems. For additional detailed information on these
technologies as well as others, see the TDD, ``California's Coastal
Power Plants: Alternative Cooling System Analysis'' (DCN 10-6964), and
EPRI's ``Fish Protection at Cooling Water Intake Structures: A
Technical Reference Manual'' (DCN 10-6813).
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    \37\ Impingement rates are related to intake flow, intake
velocity, and the swimming ability of the fish subject to
impingement. Entrainment is generally considered to be proportional
to flow and therefore reduced on a 1-to-1 basis via flow reductions,
as EPA assumes for purposes of national rulemaking that entrainable
organisms are uniformly distributed throughout the source water. EPA
has consistently applied this assumption throughout the 316(b)
rulemaking process (see, e.g., 66 FR 65276 for a discussion of
proportional flow requirements in the Phase I rule or 69 FR 41599)
and continues to believe that it is broadly applicable on a national
scale and is an appropriate assumption for a national rulemaking.
EPA recognizes that this assumption is not necessarily true on a
site specific basis and that relocating or varying the time pattern
of withdrawals may be effective strategies to reduce I&E in some
cases.
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a. Variable Frequency Drives and Variable Speed Pumps
    A facility with variable speed drives or pumps operating at their
design maximum can withdraw the same volume of water as a conventional
circulating water pump. However, unlike a conventional circulating
water pump, variable speed drives and pumps allow a facility to reduce
the volume of water being withdrawn for certain time periods. The pump
speed can be adjusted to reduce water withdrawals when cooling water
needs are lower, such as when ambient water temperatures are colder
(and therefore capable of dissipating more heat) or when fewer
generating units are operating. In site visits, EPA found that variable
speed drives and pumps were typically used at units operating below
capacity, such as load following units. For this reason most base load
generating units and continuously operated manufacturing processes
would obtain minimal reductions in flow as a result of these
technologies. EPA estimates that facilities with intermittent water
withdrawals could achieve a 5 to 10 percent reduction in flow.\38\ EPA
is further aware that some facilities need to withdraw water for
cooling even while the facility is not in production, such as
facilities on standby status, or nuclear facilities where the heat
energy generated by fission must still be dissipated while the facility
is out of service.
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    \38\ Withdrawals of colder water could allow facilities to
reduce their intake using variable speed drives and pumps, but EPA
does not have data on the efficacy or availability of this approach.
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b. Seasonal Flow Reductions
    Seasonal flow reduction refers to the reduction or elimination of a
quantity of water being withdrawn during certain biologically important
time periods. Most facilities that practice seasonal flow reductions do
so in order to reduce entrainment because peak entrainment events are
often seasonal, typically occurring during local spawning season, while
impingement is more sporadic. For example, clupeids species experience
impingement episodes sporadically all throughout the winter and spring.
Largemouth bass, on the other hand, may spawn in the late-spring, which
would thus be a season of

potentially high entrainment for this species. During this specific
peak entrainment time period, a facility could operate less (or perhaps
not at all) thereby reducing or eliminating the volume of cooling water
withdrawn. This may be accomplished through a combination of variable
speed pumps or shutting down some portion of the pumping system.
Seasonal flow reduction may also consist of operating a once-through
cooling system during part of the year and switching to closed-cycle
during peak entrainment season. Facilities may also choose to schedule
periodic maintenance to occur during these time periods; these
maintenance activities often require the facility to reduce or cease
operations and can be timed to coincide with the most biologically
productive periods. By identifying species of concern at facilities
visited by EPA, the Agency has identified some sites where entrainment
is significant all year long, and other sites where peak entrainment
occurs in as few as three to four months of the year. In addition, not
all power generating facilities in a local area could stop operating at
the same time without interrupting local electricity reliability.
Therefore, not all facilities can utilize seasonal flow reduction
technologies.
c. Unit Retirements
    Some power plants have retired units completely or have essentially
ceased all operations but have yet to be formally retired or
decommissioned. Reasons for their inactivity vary,\39\ but the end
result is the facility eliminates the need for cooling water
withdrawals for these units. Similarly, manufacturers may retire
processing units as market demand changes, process lines are moved to
other sites, or production technologies change. Unit closures provide
clear reductions in flow, but the demand for electricity (or other
products) may dictate that production be increased at the facility in
question or another facility altogether; there is usually no guarantee
that the intake flow will be permanently retired. EPA expects flow
reductions due to unit closures could be reasonably included as part of
a facility's I&E mortality reductions for a period of up to 10 years.
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    \39\ Note that some generating units are retired for market-
driven reasons (i.e., the unit is no longer considered sufficiently
profitable to operate). They may also be mothballed, placed on cold
storage, or maintained in various other states of operational
readiness.
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d. Alternate Sources of Cooling Water
    While not reducing the overall usage of water at a facility, using
an alternate source of cooling water may have the same effect in
reducing impingement and entrainment, as new or additional withdrawals
from surface waters may be reduced. An example is using ``gray'' water
as a source of cooling water; a facility reaches an agreement with a
nearby wastewater treatment plant to accept the WWTP's effluent as a
source of cooling water.\40\ Such alternative sources are limited by
available capacity, consistency of flow, and increasing competition for
these sources of water, and may be more challenging to find for
existing facilities than for new facilities that are not yet fixed in
location.
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    \40\ See, for example, EPA's site visit report for PSEG's Linden
Generating Station (DCN 10-6557), which has a capacity of 1230 MW,
35% CUR, and uses 7-8 mgd of gray water as makeup water for its
cooling towers.
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e. Water Reuse
    Typically associated with manufacturing facilities, water reuse
(defined as using water for multiple processes) can reduce the volume
of water needed for cooling, process, or other uses. For example, a
facility might withdraw water for non-contact cooling water and then
re-use the heated effluent as part of an industrial process. In effect,
the facility has eliminated the need to withdraw additional water for
the latter process. EPA has observed significant water reuse at
manufacturing facilities, but has not developed national level data for
such reuse due to the range of different manufacturing sectors and the
significant variability in manufacturing processes (during site visits,
it was observed that complex facilities have found it difficult to
assess their specific water reuse). See Section IV for further
discussion on water usage in specific industrial sectors.
f. Closed-cycle Cooling Towers
    Closed-cycle cooling systems allow a facility to transfer its waste
heat to the environment using significantly smaller quantities of (or
in some cases no) water. There are two main types of closed-cycle
cooling systems: Wet cooling and dry cooling. Each of these is
described below.
Wet Cooling Tower Systems
    In a wet cooling system, cooling water that has absorbed waste
heat, transfers that heat through evaporation of some of the heated
water into the surrounding air and recirculates the cooling water to
continue the cooling process.\41\ This process enables a facility to
re-use the remaining water, thereby reducing the quantity of water that
must be withdrawn from a water body. Because the heat is transferred
through evaporation, while the amount of water withdrawn from the water
source is greatly reduced, it is not eliminated completely because
make-up water is required to replace that lost through evaporation and
blowdown. There are two main types of wet cooling systems: Natural
draft and mechanical. While wet cooling towers reduce withdrawals
relative to once-through systems, they may increase the consumptive use
of water since they tend to rely on evaporation (which is not returned
to the water body) for heat dissipation. When once-through cooling is
used and withdrawals are a significant portion of the waterbody, the
return of heated water may contribute to greater evaporation from the
water body. However, EPA does not have data on the relative magnitude
of these effects. The relative loss of water through evaporation for
closed cycle and once-through systems is site specific, depending on
the exact design of the systems.
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    \41\ In addition, a smaller portion of the heat is also removed
through direct contact between the warm water and the cooler
surroundings.
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    A natural draft cooling tower is tall \42\ and has a hyperbolic
shape. The height of these towers creates a temperature differential
between the top and bottom of the tower, creating a natural chimney
effect that facilitates heat transfer as heated water contacts rising
air. In contrast, mechanical cooling towers rely on motorized fans to
draw air through the tower and into contact with the heated water.
These towers are likely to be much shorter units than natural draft
cooling towers,\43\ and due to their modular construction can be built
in multiples, but they may require more land area for the same amount
of cooling. Both types of towers require electricity for pumps, while
mechanical draft towers also require electricity to operate the fans;
both electricity needs serve to reduce a facility's net generating
output. Thus the monetary and environmental costs of making up this
reduction in energy efficiency need to be considered. These
environmental costs include human health and welfare effects from
increased air emissions, including the global climate change effects of
increased greenhouse gas output at fossil-fueled plants. Both natural
draft and mechanical cooling towers can operate in freshwater or
saltwater environments. Saltwater applications typically require more
make-up water than freshwater

applications, making them less efficient in reducing water
withdrawals.\44\ Optimized cooling towers may achieve flow reductions
of 97.5 percent or better and 94.9 percent or better for freshwater and
saltwater sources, respectively.
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    \42\ Natural draft towers can be as high as 500 feet or more.
    \43\ Mechanical draft towers typically range from 30 to 75 feet
in height.
    \44\ Modular cooling tower units provide an additional cooling
tower alternative. Modular cooling towers resemble mechanical
cooling towers, but are portable, typically rented for short-term
periods and quickly assembled.
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Dry Cooling Tower Systems
    Dry cooling systems virtually eliminate the need for cooling water
withdrawals.\45\ Unlike wet cooling systems, in dry cooling systems,
waste heat is transferred completely through convection and radiation,
rather than evaporation. Direct dry cooling is much like a car
radiator; turbine exhaust steam passes through tubes or fins and the
condensate is returned for reuse in the turbine. The system is
completely closed to the atmosphere and there is no contact between the
outside air and the steam or the resulting condensate. Due to the heavy
reliance of dry cooling on ambient air temperatures and the lower
efficiency of heat transfer through convection and radiation, dry
cooling towers are much larger and therefore more expensive \46\ than
wet cooling towers for a given cooling load. Dry cooling towers have
been built in areas where limited water supplies exist for either once-
through cooling or wet cooling make-up water, such as the arid
southwestern U.S. Dry cooling is not demonstrated and available for
nuclear facilities, due to the backup cooling systems and related
safety needs required at a nuclear facility.
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    \45\ Dry cooling systems do blow down some of the circulating
water within the cooling system to prevent the buildup of materials
within the condenser. However, the volume of makeup water is
extremely low--a dry cooling system typically reduces intake flows
by 98-99 percent over a comparable once-through cooling system.
    \46\ The construction and capital costs for dry cooling towers
have been reported as five to 10 times as expensive as wet cooling
towers, and the parasitic load for dry cooling is higher than for
wet cooling. See DCN 10-6679.
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Hybrid Cooling Tower Systems
    In certain applications, a facility may choose a hybrid cooling
tower design that incorporates elements of both wet and dry cooling.
Typically, the base of the tower functions as a wet cooling tower and
the upper portion as a dry tower; the most common reason for this
design is to reduce the visible plume emitted from the tower, which is
accomplished by recapturing some of the water vapor evaporated in the
wet portion of the tower. This design is also usually much shorter than
natural draft wet towers, which can also offer plume abatement
controls.
2. Exclusion Technologies To Minimize Impingement and/or Entrainment
    Over the last several decades, in addition to flow reduction and
closed-cycle cooling, numerous technologies have been developed in an
effort to minimize impingement and entrainment mortality associated
with cooling water intake systems. The following summarizes the most
widely used technologies as well as the most effective and best
performing technologies. For additional detailed information on these
technologies as well as others, see the TDD, CA Report, and EPRI
report.
a. Screens
i. Traveling Screens
    Traveling screens are a technology in place at virtually all
cooling water intake structures. These screens were originally designed
to prevent debris from entering the cooling water system, but also
prevent some fish and shellfish from entering the cooling water system.
Traveling screens have been installed in numerous environmental
conditions: Salt water, brackish water, fresh water, and icy water.
Based on the technical survey, EPA found 93 percent of electric
generators and 73 percent of manufacturers employ traveling screens or
other intake screens. There are many types of traveling screens (e.g.,
through flow, dual flow, center flow). The most common design in the
U.S. is the through flow system. The screens are installed behind bar
racks (trash racks) but in front of the water circulation pumps. The
screens rotate up and out of the water where debris (including impinged
organisms) is removed from the screen surface by a high pressure spray
wash. Screen wash cycles are triggered manually or by a certain level
of head loss across the screen (indicating clogging). By definition,
this technology works by collecting or ``impinging'' fish and shellfish
on the screen. Traveling screens are ideally used with a fish handling
and return system, discussed further in Section VI.B.3 below.
ii. Cylindrical Wedgewire Screens
    Cylindrical wedgewire screens, also called ``V'' screens or profile
screens, unlike traveling screens, are a passive intake system.
Wedgewire screens consist of a v-shaped, cross section wire on a
framing system. Slot sizes for conventional traveling screens typically
refer to a square opening (\3/8\'' x \3/8\'') that is punched or woven
into the screen face. Wedgewire screens are constructed differently,
however, with the slot size referring to the maximum distance between
longitudinally adjacent wires. These screens are designed to have a low
through-slot velocity (less than 0.5 ft/sec or 0.15 m/sec) and
typically have smaller slot sizes than a coarse mesh traveling screen.
The entire wedgewire structure is submerged in the source waterbody.
    When appropriate conditions are met, these screens exploit physical
and hydraulic exclusion mechanisms to achieve consistently high
impingement reductions (and as a result, impingement mortality
reductions). Wedgewire screens require an ambient current crossflow to
maximize the sweeping velocity provided by the waterbody. The screen
orientation and cross current flow carries organisms away from the
screen allowing them to avoid or escape the intake current. Lower
intake velocities also allow fish to escape from the screen face.
Entrainment reductions can potentially be observed when the screen slot
size is small enough and intake velocity is low enough to exclude egg
and larval life stages.\47\ There is also limited evidence suggesting
that extremely low intake velocities can allow some egg and larval life
stages to avoid the intake due to hydrodynamic influences of the cross
current. Therefore performance is largely dictated by local conditions
that are further dependent on the source waterbody's biological
composition. Costs of wedgewire screens also increases significantly as
slot size and design intake velocity decrease. Wedgewire screens may
also employ cleaning and de-icing systems such as air-burst sparging to
aid in maintaining open intake structures and low intake velocities.
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    \47\ Note that this is entrainment exclusion and not necessarily
related to the survival of entrainable organisms. See Section
III.B.2 for more detail.
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    According to data from the industry questionnaire, EPA's site
visits, and industry documents, dozens of facilities across the U.S.
employ cylindrical wedgewire screens. However, wedgewire screens are
not feasible for facilities with limited access to source water, such
as shallow water or limited shoreline frontage. Wedgewire screens may
also not be feasible where the size and number of wedgewire screens
would interfere with navigational traffic. As described above,
locations also need to have an adequate source water sweeping velocity.
Most of the performance data for wedgewire screens is based on coarse
mesh slot sizes with an intake velocity of 0.5 feet per second. As it
is extremely difficult to measure

impingement and entrainment reductions in the field, most performance
data is based on barge studies and lab studies. EPA does not have data
on the performance of fine mesh wedgewire screens on entrainment
survival; therefore EPA has only considered wedgewire screens for
impingement mortality. For additional discussion of the specific design
and operation of cylindrical wedgewire screens, see the TDD. The
following section discusses the importance of mesh size to impingement
and entrainment mortality reductions.
iii. Screen Mesh Size Considerations
Coarse Mesh
    Coarse mesh traveling screens are the typical traveling screen
fitted on the majority of cooling water intakes. A large number of
facilities have intake screens with \3/8\-inch (9.5 mm) mesh panels.
This size mesh is common because, as a general rule of thumb, the
maximum screen slot size is never larger than one half of the condenser
tube diameter (the condenser tubing is the narrowest point in the
cooling water system and, as such, is most susceptible to clogging from
debris), and this tubing is typically \3/4\ or \7/8\ inches in
diameter. Mesh of \3/8\-inch (roughly 9.5 mm) does not prevent
entrainment and in the absence of any other precautions can lead to
high mortality of impinged fish. Coarse mesh traveling screens have
been in use by both power plants and manufacturers for more than 75
years and represent the baseline technology. Similarly, the majority of
successful wedgewire installations are coarse mesh.
Fine Mesh
    Fine mesh traveling and wedgewire screens are similar to coarse
mesh screens, with the only difference being the size of the screen
mesh. The mesh size of fine mesh screens varies, depending on the
organisms to be protected, but typically range from 0.5 to 5 mm.
Typically, facilities have incorporated fine mesh in an effort to
reduce entrainment. Data in the record demonstrate that entrainment
typically decreases as mesh size decreases. However, slot sizes larger
than 2 mm do not prevent eggs from passing through the screen. Fine
mesh traveling screens have been in use in this industry since the
1980s. EPA estimates as many as 17 percent of existing intakes could
not be expanded in size to accommodate a 2 mm mesh, and as many as 55
percent of existing intakes could not accommodate a 0.5 mm slot size
under conditions of low intake velocities. For these reasons, fine mesh
screens are demonstrated for some locations, but are not the best
performing technologies, and are not available technologies for the
industry as a whole. See Chapter 6 of the TDD for more details.
b. Barrier Nets
    Barrier nets are nets that fully encircle the intake area of water
withdrawal, from the bottom of the water column to the surface and that
prevent fish and shellfish from coming in contact with the intake
structure and screens. According to data from the industry
questionnaire (as of the year 2000), at least a half dozen facilities
employ a barrier net. Typically, barrier nets have large mesh sizes
(e.g., \1/2\-inch or 12.7 mm) \48\ and are designed to prevent
impingement. Due to the large mesh size, they offer no reduction in
entrainment. They are often deployed seasonally, wherever seasonal
migrations create high impingement events or to avoid harsh winter
conditions which jeopardize integrity of the net. Barrier nets also
prevent impingement of shellfish on the intake traveling screen.
Shellfish such as crustaceans may pose a unique issue for traveling
screens because the shellfish are not impinged, but rather they may
grab hold of the traveling screen surface and are not removed from the
traveling screen by pressure wash sprays. Barrier nets have been shown
to be particularly helpful in this regard. For this reason, the costs
of options considered today include the costs of barrier nets to
minimize impingement mortality of shellfish.
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    \48\ Barrier net mesh sizes vary, depending on the
configuration, level of debris loading, species to be protected, and
other factors.
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c. Aquatic Filter Barriers
    Aquatic Filter Barriers (AFBs), such as the Gunderboom Marine Life
Exclusion System (MLES) or simply ``Gunderboom,'' are similar to
barrier nets in that they extend throughout the area of water
withdrawal from the bottom of the water column to the surface. However,
AFBs consist of water permeable fabric panels with small pores (< 20
microns). AFBs reduce both impingement mortality and entrainment
because they present a physical barrier to all life stages. The surface
area of an AFB is quite large compared to a traveling screen, allowing
for extremely low water velocities. The low velocity allows non-motile
organisms to drift away. EPA is aware of one power plant that used an
AFB, but notes that this facility recently ceased operations.\49\ EPA
has updated performance data for AFB for small flow intakes, but does
not have enough data to evaluate the technology at large intakes and in
all waterbodies.
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    \49\ This facility ceased operations for reasons other than
impingement and entrainment related to cooling water intake.
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3. Collection and Return
    Conventional traveling screens were not designed with the intention
of protecting fish and aquatic organisms that become entrapped against
them. Marine life may become impinged against the screens from high
intake velocities that prevent their escape. Prolonged contact with the
screens may suffocate insufficiently strong species or certain
susceptible life stages of fish. Exposure to high pressure sprays and
other screening debris may cause significant injuries that result in
latent mortality, or increase the susceptibility to predation or re-
impingement. Organisms that do survive initial impingement and removal
are not typically provided with a specifically-designed mechanism to
return them to the water body and are handled in the same fashion as
other screening debris. Other objects collected on the screen are
typically removed with a high-pressure spray and deposited in a
dumpster or debris return trough for disposal. Screens are rotated
periodically based on a set time interval or when the pressure
differential between the upstream and downstream faces exceeds a set
value. Conventional traveling screen systems have been modified to
reduce impingement-related mortalities with collection and return
systems. In simplest form, this is comprised of a return flume or
trough with sufficient water volume and flow to enable impinged
organisms to return to the source water. Return systems should be
designed to avoid predation and latent mortality while organisms are in
the flume, positioned at an appropriate water depth for high survival
of the organisms, located at an appropriate elevation to avoid large
drops of the organisms back to the surface water, and sited to avoid
repeated impingement of the organisms by the intake structure.
    Following the 1972 Clean Water Act's requirement to require
technology-based solutions to minimize adverse environmental impacts,
some conventional coarse mesh traveling screen systems were modified to
reduce impingement mortality by removing fish trapped against the
screen and returning them to the receiving water with as few injuries
as possible. The first modified

screens, also known as ``Ristroph'' screens, feature capture and
release modifications. In the simplest sense, these screens are fitted
with troughs (also referred to as buckets) containing water that catch
the organisms as they rise out of the water and are sprayed off of the
screen. The return component consists of a gentle mechanism to remove
impinged fish from the collection buckets, such as a low-pressure
spray. The buckets empty into a collection trough that returns fish to
a suitable area in the source water body. These modified screens have
shown significant improvements in reducing impingement mortality
compared with unmodified screen systems.
    Data from early applications of the ``Ristroph'' screen design
showed that while initial survival rates might be high at some
installations, latent mortality rates were higher than anticipated,
indicating significant injuries could be sustained during the
impingement and return process that were not immediately fatal. Based
on a study conducted by Ian Fletcher in the 1990s (see DCN 5-4387),
industry identified several additional critical screen modifications to
address latent mortality. These include redesign of the collection
buckets to minimize turbulence, addition of a fish guard rail/barrier
to prevent fish from escaping the collection bucket, replacement of
screen panel materials with ``fish friendly'' smooth woven mesh, and a
low pressure wash to remove fish prior to any high pressure spray to
remove debris on the ascending side. The Fletcher analysis also
identified that longer impingement duration, insufficient water
retention in the buckets, and exposure to the air and temperature
extremes could negatively impact fish survival. Finally, these findings
indicate that modified Ristroph screens must be continually rotated
instead of the periodic rotation schedule common with conventional
screen systems. Performance data for modified traveling screens with
fish return systems show low levels of impingement mortality across a
wide variety of water body types and fish species. Therefore, EPA has
concluded modified traveling screens with a fish return system is a
candidate best performing technology for impingement mortality.
    For additional and more detailed discussion of the specific design
and operation of these screen modifications, see the TDD.
4. Intake Location and Velocity Caps
    Currently, the most common intake location for a cooling water
intake structure is along a shoreline. In some types of waterbodies,
shoreline locations are thought to have the potential for greater
environmental impact because the water is withdrawn from the most
biologically productive areas especially with regards to earlier life
stages. Some facilities employ an offshore intake to withdraw water
from less biologically productive areas to reduce entrainment relative
to intakes located in more productive shoreline areas, though
impingement (and therefore impingement mortality) reductions have also
been observed. Obviously, reduction in impingement mortality and
entrainment depend on intake location at a particular site, but the
greatest potential for reductions is found with far offshore locations
at distances of several hundred feet, something not possible on many
rivers and streams. Both depth and the offshore location must be
evaluated to determine if fish densities and species distribution at
the offshore location are substantially different than those near the
shoreline. Two areas where far offshore locations are commonly used
today include the oceans and Great Lakes.
    EPA found most offshore intakes are fitted with a velocity cap.
Velocity caps are a physical structure rising vertically from the sea
bottom and placed over top of the intake pipe. Intake water is
withdrawn through openings in the velocity cap in a manner which
converts the direction of flow from vertical to horizontal. The
horizontal flow provides a physiological trigger in fish to induce an
avoidance response thereby reducing impingement mortality. The velocity
cap further serves to limit the zone of influence of the intake to the
depth level at which the velocity cap is situated, thus affecting only
the life stages that live at that depth. Furthermore, the velocity at
an offshore intake is lower than the velocity of an equivalent sized
intake at the shoreline due to differences in pressure, resulting in a
lower intake velocity at the velocity cap than at a shoreline intake.
Velocity caps are also usually equipped with supports and bar spacing
selected to prevent larger aquatic organisms (e.g., turtles or marine
mammals) from entering the intake pipe. Because velocity caps operate
under the principle that the organisms can escape the current, velocity
caps do not offer entrainment reductions over and above those achieved
by being located offshore. Reductions in entrainment observed with
velocity caps occur due to the difference in organism densities in far
offshore deep water compared to a surface intake at the shoreline.
    For additional and more detailed discussion of the specific design
and operation of offshore intake locations and velocity caps, see the
TDD.
5. Reduced Intake Velocity
    Impingement mortality can be greatly reduced by reducing the
through-screen velocity in any screen. Reducing the rate of flow of
cooling water through the screen (through-screen velocity) to 0.5 ft/
sec or less reduces impingement of most fish because it allows them to
escape the intake current. (See 66 FR 65274 and DCN 2-028A, EPRI's
``Technical Evaluation of the Utility of Intake Approach Velocity as an
Indicator of Potential Adverse Environmental Impact Under Clean Water
Act 316(b).'') Limited lab studies indicate that entrainment also may
decrease as through-screen velocity decreases and that through-screen
velocity may have an effect on entrainment survival rates, although
such data is extremely variable by species (see DCN 10-6802 and DCN10-
6803). As a result, some Phase II facilities have designed and operate
their modified traveling screens or wedgewire screens so as not to
exceed a through-screen velocity of 0.5 ft/sec. In addition, for the
reasons described in Section VI.B.2, aquatic filter barriers and
velocity caps \50\ are likely to have velocities of 0.5 ft/sec or less.
Swim speed studies demonstrate that for most facilities, an intake
velocity of 0.5 feet per second or less results in 90 percent or better
reductions in impingement mortality for most species. (EPA notes that
preliminary results from recent studies of fine mesh screens suggest
that at even lower intake velocities such as 0.25 feet per second,
there may be some hydrodynamic influences that reduce entrainment
mortality even more, because flow dynamics are nonlinear. It is unclear
whether such observations hold true when cooling water withdrawals
(water volumes) are large.) Therefore, EPA has concluded reduced intake
velocity is a candidate best performing technology for impingement
mortality.
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    \50\ Velocity as measured at the velocity cap opening.
---------------------------------------------------------------------------

C. Technology Basis for Today's Proposed Regulation

    As described in the previous section, EPA examined the full range
of technologies that reduce impingement and/or entrainment, and
evaluated these technologies based on their efficacy in reducing
impingement and entrainment, availability, and cost. Based on an
assessment of these factors, EPA has

identified three best performing technologies for further analysis as
the basis for today's proposed rule: Modified traveling screens with a
fish return (for fish impingement), barrier nets (for shellfish
impingement on tidal waters), and mechanical draft wet cooling towers
(for impingement and entrainment at new units). Although EPA has
identified velocity reduction to 0.5 feet per second or less as a
candidate best performing technology for impingement mortality, EPA is
not proposing reduced intake velocity as BTA because it is not
available at all facilities, but is allowing facilities to comply with
intake velocity of 0.5 feet per second or less where available.
    EPA has concluded that modified traveling screens, such as Ristroph
screens and equivalent modified traveling screens are a best performing
technology for impingement mortality. These screens use coarse size
mesh with collection buckets designed to minimize turbulence, a fish
guard rail/barrier to prevent fish from escaping the collection bucket,
``fish friendly'' smooth woven mesh, and a low pressure wash to remove
fish prior to any high pressure spray to remove debris on the ascending
side. The fish removal spray must be of lower pressure and the fish
return must be fish friendly and provide sufficient water and minimize
turbulence. Modified traveling screens must generally be continually
rotated to obtain the highest reductions in impingement mortality. As
discussed in Section III, traveling screens with post-Fletcher
modifications achieve a monthly impingement mortality of 31 percent
mortality (performance corresponding to the 95th percentile of the beta
distribution) under conditions of 48 hour or less holding times. The
use of the 95th percentile is consistent with the convention EPA has
used for monthly average limitations in the effluent guidelines program
(i.e., for pollutant discharges). In developing the monthly average
standard proposed for this rule, EPA has taken into account the
reasonable anticipated variability in impingement mortality that may
occur at a well-operated facility. Variability occurs due to changes in
seasons, differing intake locations, higher mortality of certain
species, and speciation found in different water bodies.
    In contrast to the monthly average, which is adjusted to reflect
month-to-month variability in performance of the technology, EPA has
not included an upward adjustment of the annual average \51\ standard
to account for year-to-year variability. The annual average standard
requires that impingement mortality not exceed 12 percent, calculated
as the average of monthly impingement mortality for 12 consecutive
months as determined by the Director. The 12 percent value corresponds
to the long-term average performance of the technology that EPA has
identified as BTA, based on available data from eight episodes of
sampling collected on three different waterbody types over all seasons
(see Chapter 11 of the TDD for more information). EPA expects
facilities to track their compliance with the annual average standard
on an ongoing basis, and to proactively modify their technology or
operations when any individual monthly average suggests that they may
be in danger of exceeding the annual average standard in the future.
EPA recognizes that some variability in the annual average is
inevitable, and thus the only way to consistently achieve the 12
percent annual standard is to target a better level of performance as
the long-term average performance. While EPA's data show a long-term
average performance of 12 percent impingement mortality for the BTA
technology, EPA believes that by continuously monitoring and adaptively
adjusting the operation of the technology, facilities can achieve a
better long-term performance than is documented in the data, and thus
consistently meet the annual average.
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    \51\ The annual average should not be confused with a rolling
average of the preceding 12 months; EPA has specified in the rule
language at Sec.  125.96 that the annual average means 12
consecutive months as specified by the Director. EPA expects that
compliance with the annual average standard would be determined once
each calendar year.
---------------------------------------------------------------------------

    EPA also considered applying a confidence or tolerance limit to the
long-term average in deriving the annual average standard. EPA rejected
this approach because EPA believes that facilities can achieve better
long-term performance than documented in the data by maintaining tight
control on their technology and operations and adaptively managing the
technology to achieve the best possible performance. While EPA has not
included any additional costs for this adaptive management, EPA
believes that such adaptive management should be part of the routine
maintenance and operation of the technology and additional costs should
not be necessary.
    EPA has occasionally used annual limits in the effluent guidelines
program (most recently for the pulp and paper industry category (40 CFR
430, promulgated in 1998) and has previously not included a variability
factor for annual limits. Thus, EPA's proposed approach to calculating
the annual standard for mortality impingement is consistent with past
practice. EPA requests comment on its proposed approach for calculating
and implementing the annual standard.
    This technology does not minimize adverse environmental impacts
associated with entrainment, and does not specifically address
impingement mortality of shellfish.
    EPA selected the seasonal deployment of barrier nets on estuaries
and oceans as the best performing technology for minimizing the
impingement mortality of shellfish (crustaceans) because no other
technology has been identified that is available, demonstrated, and
feasible. EPA did not select wedgewire screens as a candidate
technology for impingement mortality because wedgewire screens are not
available and feasible for all existing facilities. Wedgewire screen
performance requires an adequate crossflow of the source water that is
not present in all waterbodies. Wedgewire screens also require a
minimum water depth in order to fully submerge the screens; the
requisite depth and space to submerge the screens is not available at
all locations, and further may pose an obstacle to navigation. However,
where passive screens such as cylindrical wedgewire screens are
feasible, data in the record shows they would perform equally as well
or better than seasonal deployment of barrier nets. EPA has included a
provision in the proposed regulation that specifies that passive
screens meet the IM requirement for shellfish.
    One technology for reducing impingement mortality as well as
reducing entrainment mortality is wet cooling towers. Mechanical
cooling towers achieve flow reductions of 97.5 percent for freshwater
and 94.9 percent for saltwater sources by operating the towers at a
minimum of 3.0 and 1.5 cycles of concentration, respectively. Based on
the high levels (greater than 95 percent on average) of flow reduction
obtained by optimized cooling tower operation, EPA has identified wet
cooling towers as a candidate best performing technology for both
impingement mortality and entrainment mortality for new units at
existing facilities. As discussed further below, EPA is not proposing
cooling towers as BTA for existing facilities (other than new units)
because it is not available on a national basis. As described in
Section VI.B, other technologies are demonstrated, but are not the best
performing technologies and/or are not

available technologies for the industry as a whole.
    Although, EPA's record shows numerous instances of existing
facility retrofits to closed-cycle, EPA has not identified it as BTA
for the reasons discussed below. EPA has also not identified any other
available and demonstrated candidate technology for entrainment
mortality that is available on a national basis; see Section VI.B and
the TDD for other entrainment technologies that may be available on a
site-specific basis. EPA did not select the other flow reduction
technologies such as variable speed drives and seasonal flow reductions
as the technology basis for entrainment mortality because these
technologies are not feasible for all facilities. Further, EPA has not
identified a basis for subcategorizing existing facilities for where
these flow reduction technologies are feasible, because their seasonal
operation depends on the site-specific biology of the facility. EPA did
not select relocation of a shoreline intake to far offshore as a
technology basis because this technology is not feasible for all
facilities. Even if EPA subcategorized by water body type (i.e., intake
location), the performance of wet cooling towers for entrainment
mortality is at least three times that of a far offshore intake.
Therefore relocation of the intake is not the best performing
technology for minimizing entrainment mortality.

D. Options Considered for Today's Proposed Regulation

    After careful consideration of the technologies available as
described in Section VI.C, EPA developed four primary options based on
these technologies for today's proposed rule. Three of the options
would require the same impingement mortality standards, but would vary
the approach to entrainment mortality controls. The fourth option would
allow both impingement and entrainment mortality controls to be
established on a site-specific BPJ basis for facilities with a DIF less
than 50 MGD. The options are described briefly below, followed by a
discussion of EPA's evaluation of each option as BTA.
1. Option 1--Uniform Impingement Mortality Controls at All Existing
Facilities; Site-Specific Entrainment Controls for Existing Facilities
(Other Than New Units) That Withdraw Over 2 MGD DIF; Uniform
Entrainment Controls for All New Units at Existing Facilities
    Under this option, all existing facilities withdrawing more than 2
MGD would be required to meet either the design or the performance
standard for impingement mortality. Entrainment controls would be
established by the permitting authority on a case-by-case basis taking
into account those factors at a particular facility that are specified
in today's proposal and the information required by the existing permit
regulations at Sec.  122.21(r)(1)-(8) for all facilities with at least
2 MGD DIF. In addition, under EPA's CWA sections 301, 308, 316(b), and
402 authority, in the case of facilities withdrawing greater than 125
MDG AIF (actual intake flow), the site-specific determination of BTA
would be based on a submission of certain other required information.
The proposal would amend the permit application requirements at Sec.
122.21(r)(9)-(11) to require the facility to prepare an Entrainment
Characterization Study that would fully characterize the amount of
entrainment at the facility. (See below for more details about the
study). In addition, under the proposal, the facility would provide
detailed information on the other factors relevant to the Director's
site-specific BTA determination. These would include information
concerning the technologies available for control of such entrainment,
the costs of controls, the non-water quality impacts of such controls,
and both the monetized and non-monetized benefits of such controls. The
CWA requires, and EPA encourages, the public to have a role in the
permitting process; therefore EPA has also included meaningful public
opportunity for participation in the site-specific decision making to
help ensure the soundness of both the information and subsequent
determinations.
a. Impingement Mortality Controls
    As described earlier in this section, traveling screens have
undergone a number of technological improvements over the years and
modern screens have proven to be highly effective in promoting the
survival of impinged organisms. The proposed rule requires the use of
state-of-the-art screens with fish buckets, a low pressure spray wash,
a dedicated fish return line, etc., but is not specifying any
particular screen configuration, mesh size or screen operations, so
long as facilities can consistently meet the numeric impingement
mortality limits (impingement mortality also includes a design standard
for shellfish). EPA is also not specifying additional design or
operational criteria to promote development of improved technologies,
and to allow facilities to use variations such as dual flow traveling
screens and drum screens.
    EPA did not select intake velocity as the sole technology basis for
impingement mortality controls because, although the performance of 0.5
feet per second intake velocity is slightly better than the selected
technology, the intake velocity is not available or feasible for all
existing facilities (see Chapter 6 of the TDD). However, EPA has long
recognized the relationship between impingement and intake velocity.
EPA conducted an analysis of fish swim speeds in the Phase I rule (see
66 FR 65274) and concluded that a design through-screen velocity of 0.5
feet per second would be protective of 96% of motile organisms. As a
result, a facility may chose to comply with the impingement mortality
standards in today's proposed rule by instead demonstrating that the
through-screen design velocity does not exceed 0.5 feet per second, or
by demonstrating that the actual average intake velocity does not
exceed 0.5 feet per second.
    While the data shows the majority of healthy motile organisms would
be protected by a maximum intake velocity of 0.5 feet per second, some
species would not be adequately protected. Some facilities employ
traveling screens, but do not have fish friendly modifications such as
a fish handling and return system. EPA is concerned that some
facilities would comply with the impingement mortality requirements by
the intake velocity compliance alternative, and would continue to
operate unmodified traveling screens. This is particularly a concern
where the traveling screens are located in a forebay, potentially
resulting in entrapment of any impinged organisms. Therefore, EPA is
considering a provision that would require facilities to either
demonstrate that the species of concern are adequately protected by the
maximum intake velocity requirements, or to employ specific fish
friendly protective measures including, at a minimum, a fish handling
and return system. EPA solicits comment and data on such a provision.
    EPA did not select wedgewire screens as the technology basis for
impingement mortality controls because wedgewire screens are not
available and feasible for all existing facilities. EPA also did not
need to include wedgewire screens as a compliance alternative because
wedgewire screens designed with an intake velocity of 0.5 feet per
second can demonstrate compliance with the impingement mortality limits
based on the intake velocity as just described. EPA did not select flow
reduction by retrofit to closed-cycle cooling as the technology basis
for impingement mortality because closed-cycle cooling

costs more than 10 times that of modified traveling screens with a fish
return system. In other words, modified traveling screens with a fish
return system and closed-cycle cooling are comparable in impingement
mortality performance, but modified traveling screens with a fish
return system is more cost-effective than flow reduction at preventing
impingement mortality. EPA is not including wet cooling towers as a
compliance alternative (e.g., a pre-approved technology) because EPA's
data shows existing facilities that retrofit to a closed-cycle cooling
system have an intake velocity of less than 0.5 feet per second. As a
practical matter, make-up water withdrawals are made at such low
velocities that facilities with closed-cycle can demonstrate compliance
with the alternative reduced intake velocity to meet the impingement
mortality limits. For estuaries and oceans, EPA is proposing seasonal
deployment of barrier nets on estuaries as the technology basis for
minimizing the impingement mortality of shellfish (crustaceans) because
no other technology has been identified that is available,
demonstrated, and feasible. As noted previously, use of wedgewire
screens (along with the limitations on intake velocity) obviates the
need for barrier nets.
b. Entrainment Controls
    The proposal would require consideration of site-specific
entrainment controls for each facility above 2 MGD DIF. EPA considered
proposing no further controls to address entrainment mortality, and to
rely instead only on the BTA impingement mortality controls, which
would achieve up to a 31 percent reduction in total AEI. EPA has not
selected this option as the basis for national BTA because EPA believes
that some facilities may be able to do more to control entrainment and
that requiring a structured site-specific analysis of candidate BTA
technologies for entrainment control will allow the Director to
determine where it is appropriate to require such controls. However,
one outcome of the site specific analysis may be that the Director
would determine that no other technologies beyond impingement control
meet the criteria for selection as BTA, because no other technologies
are feasible and/or their benefits do not justify their costs. EPA
requests comment on the option of basing national BTA on impingement
controls only and dropping the specific requirement for a structured
site-specific analysis of entrainment BTA options, as discussed below.
    In the case of site-specific entrainment controls for facilities
withdrawing greater than 125 MGD AIF, EPA's proposal would, in
addition, require these facilities to develop and submit an entrainment
characterization study for use by the Director in establishing site-
specific BTA. See Section V.F for more on development of the 125 MGD
threshold. (Facilities under the 125 MGD AIF threshold must still
provide certain water body and water population information under the
current permit applications requirements at Sec.  122.21(r)). An early
step in conducting the entrainment characterization study is the
preparation of an entrainment mortality data collection plan, which
must be submitted to the Director for review and comment before
implementation. The entrainment mortality data collection plan would
include, at a minimum, the specific entrainment monitoring methods,
taxonomic identification, latent mortality identification,
documentation of all methods, and quality assurance/quality control
procedures for sampling and data analysis appropriate for a
quantitative survey. EPA would also require peer review of the
entrainment mortality data collection plan. Peer reviewers would be
selected in consultation with the Director who may consult with EPA and
federal, State, and Tribal fish and wildlife management agencies with
responsibility for fish and wildlife potentially affected by the
cooling water intake structure(s).
    The Entrainment Characterization Study would include information
already collected to meet current Sec.  122.21(r)(4) requirements. In
addition, under the new permit application requirements proposed for
Sec.  122.21(r)(5)-(12), the facility would submit certain additional
site-specific information. This would include an engineering study of
the technical feasibility and incremental costs of candidate
entrainment mortality control technologies. The facility would also
study, evaluate, and document: the technical feasibility of
technologies at a minimum including closed-cycle cooling and fine mesh
screens with a mesh size of 2 mm or smaller; engineering cost estimates
of all technologies considered; any outages, downtime, or other impacts
to revenue along with a discussion of all reasonable attempts to
mitigate these cost factors; and a discussion of the magnitude of water
quality and other benefits, both monetized and non-monetized, of the
candidate entrainment mortality reduction technologies evaluated.
Finally, the information must include a discussion of the changes in
non-water quality factors attributed to technologies and/or operational
measures considered, including but not limited to increases and
decreases in the following: energy consumption; thermal discharges; air
pollutant emissions including particulates and associated human health
and global climate change impacts; water consumption; noise; safety
(e.g., visibility of cooling tower plumes, icing); grid reliability,
and facility reliability. See Section IX for a thorough discussion of
these study requirements.
    Under this option, it is EPA's expectation that the Director would
review the candidate technologies for entrainment mortality control
that at a minimum includes closed-cycle cooling and fine mesh screens.
In the decision about what additional entrainment controls (if any) to
require, the Director would consider all of the facility-specific
factors described above. At a minimum, the Director must provide a
discussion explaining how issues concerning local energy reliability,
air emissions or land availability insofar as they relate to the
feasibility of adoption of a particular entrainment technology,
remaining useful plant life, and the relationship of social benefits to
social costs were addressed in the site-specific determination. Under
the proposal, the Director must issue a written explanation for the
basis of the BTA determination for each facility. EPA also expects the
written explanation would provide a review of the social costs (and not
just the facility costs (see chapter 11 of the EA) of the various
technologies; a review of the potential reductions in entrainment and
entrainment mortality; and a review and analysis of monetized and non-
monetized benefits).
    Under Option 1, new units at an existing facility that withdraws
more than 2 MGD would have requirements similar to the requirements of
a new facility in Phase I. Under this option, new units would be
required to reduce flow commensurate with closed-cycle cooling for the
new unit. Under the proposal, as with Track II of the Phase I rule, a
facility could demonstrate compliance with entrainment control
requirements by establishing reductions in entrainment mortality for
the new unit that are 90 percent of the reductions that would be
achieved by closed-cycle cooling.

2. Option 2--Impingement Mortality Controls at All Existing Facilities
That Withdraw Over 2 MGD DIF; Require Flow Reduction Commensurate With
Closed-Cycle Cooling by Facilities Greater Than 125 MGD DIF and at New
Units at Existing Facilities
    Under Option 2, all in-scope existing facilities would be required
to achieve the numeric impingement mortality limits described in Option
1 above. In addition, this option would require flow reduction
commensurate with closed-cycle cooling by facilities greater than 125
MGD DIF and at new units. Option 2 explores using the facility size, in
terms of design intake flow (DIF), as a factor for establishing
different BTA for different subcategories. EPA's analysis shows that a
DIF of 125 MGD would be an appropriate threshold for this purpose; see
Section V. For all facilities that withdraw over 2 MGD but less than or
equal to 125 MGD DIF, entrainment controls would be determined by the
permitting authority on a case-by-case basis taking into account the
factors at a particular facility. Facilities greater than 125 MGD DIF
would not submit Entrainment Characterization Studies (because under
this option this rule would have already determined that closed cycle
is BTA for that facility), but all facilities would still submit Sec.
122(r)(2)-(r)(7) to the Director to inform the BTA determination as
described in Option 1. Requirements for new units at an existing
facility would be the same as described in Option 1.
    EPA also considered a variation of this option that uses 125 MGD
Actual Intake Flow (AIF) rather than 125 MGD Design Intake Flow (DIF)
as the threshold. Setting the threshold at 125 MGD AIF would allow a
Permit Director to treat differently those facilities that are above
125 MGD on a DIF basis but below 125 MGD on an AIF basis relative to
today's Option 2. EPA traded off introducing more flexibility at those
facilities for simplicity of implementation (DIF is static), but
solicits comment on both the threshold and the flow basis for this
option.
    The technology basis for entrainment mortality controls for
facilities greater than 125 MGD DIF under this option would be wet
cooling towers as described in Section VI.B. The record shows optimized
wet cooling towers achieve flow reductions of 97.5 percent and 94.9
percent for freshwater and saltwater sources, respectively. Optimized
operation of wet cooling towers would be demonstrated through flow
monitoring and conductivity measurements. Alternatively, this option
would allow facilities to demonstrate flow reductions commensurate with
closed-cycle cooling based on optimized wet cooling towers.
    As part of this option, EPA would provide flexibility to the
Director to establish compliance timelines for each existing facility
to mitigate grid reliability and local electricity reliability. Under
this option, most existing facilities would have no more than 10 years
to complete the retrofit to closed-cycle cooling. Under this option the
Director would determine when and if any such schedule for compliance
is necessary, and if the facility is implementing closed-cycle as soon
as possible. This provision would give the Director the discretion to
provide nuclear facilities with no more than 15 years to complete the
retrofit, because all nuclear facilities are baseload generating units
and the additional flexibility in timelines would further mitigate
energy reliability, and because the retrofits at these types of
facilities in particular involve additional complexities and safety
issues. The Director would have the discretion to provide manufacturing
facilities with no more than 15 years to complete the retrofit due to
the complexity of manufacturing facilities, multiple process units and
product lines, and to allow consideration of production schedules in
setting such a timeline.
3. Option 3--Establish Impingement Mortality Controls at All Existing
Facilities That Withdraw Over 2 MGD DIF; Require Flow Reduction
Commensurate With Closed-Cycle Cooling at All Existing Facilities Over
2 MGD DIF
    Under this option, all in-scope existing facilities would be
required to achieve numeric impingement mortality limits as described
in Option 1 above. In addition, this option would require flow
reduction commensurate with closed-cycle cooling by all facilities
(including new units at existing facilities) as described in Option 2.
This option would similarly authorize the Director to establish
compliance timelines for each existing facility to mitigate grid
reliability and local electricity reliability as described in Option 2
above. Requirements for new units at an existing facility would be the
same as described in Option 1.
4. Option 4--Uniform Impingement Mortality Controls at Existing
Facilities With Design Intake Flow of 50 MGD or More; BPJ Permits for