to offset the adverse effects that would otherwise be caused by
operating the intake structures. The Second Circuit, in reviewing the
new facility rule, determined that section 316(b) did not authorize the
use of restoration measures in complying with the EPA performance
standard. (Note that EPA is removing the provision related to
restoration measures from the CFR in this rulemaking but has included
the above description of the Phase I rule for completeness.) For more
information, see Section I above.
    In addition, under the Phase I rule, the Director may establish
less stringent alternative requirements for a facility if compliance
with the Phase I standards would result in compliance costs wholly out
of proportion to those EPA considered in establishing the Phase I
requirements or would result in significant adverse impacts on local
air quality, water resources, or local energy markets.
    EPA specifically excluded new offshore oil and gas extraction
facilities from the Phase I new facility rule but committed to consider
establishing requirements for such facilities in the Phase III
rulemaking. 66 FR 65338, December 18, 2001.
ii. Subsequent Litigation
    Various environmental and industry groups challenged the Phase I
rule. In February 2004, the Second Circuit sustained the entire rule
except for the restoration provision, ruling that restoration was not a
technology as provided for in section 316(b). With respect to the other
provisions of the rule, the court concluded the Phase I rule was based
on a reasonable interpretation of the applicable statute and
sufficiently supported by the record. Restoration provisions of the
rule were remanded to EPA for further rulemaking consistent with the
court's decision. Riverkeeper, Inc. v. EPA, 358 F.3d 174, 191 (2nd
Cir., 2004). Today's rule removes the restoration provisions from the
Phase I rule. For more details, see Chapter I of this preamble.
c. Phase II--Large Flow Existing Power Plants
i. Rulemaking
    On February 16, 2004, EPA took final action on regulations
governing cooling water intake structures at certain existing power-
producing facilities. 69 FR 41576, July 9, 2004. The final 2004 Phase
II rule applied to existing facilities that are point sources; that, as
their primary activity, both generate and transmit electric power or
generate electric power for sale or transmission; that use or propose
to use a cooling water intake structure with a total DIF of 50 mgd or
more to withdraw water from waters of the United States; and that use
at least 25 percent of the withdrawn water exclusively for cooling
purposes on an actual intake flow basis. In addition, power producers
fitting the description above were also subject to the final 2004 Phase
II rule even if they obtain their cooling water from one or more
independent suppliers of cooling water. Such facilities were subject to
the rule if their supplier withdraws water from waters of the United
States even if the supplier was not itself a 2004 Phase II existing
facility. EPA included this provision to prevent circumvention of the
2004 Phase II rule requirements by a facility purchasing cooling water
from entities not otherwise subject to section 316(b).
    The final 2004 Phase II rule and preamble also clarified the
definition of an existing power-producing facility. The 2004 Phase II
rule defined an existing facility as ``any facility that commenced
construction as described in Sec.  122.29(b)(4) on or before January
17, 2002; and any modification of, or addition of a unit at such a
facility that does not meet the definition of a new facility at Sec.
125.83.'' Because the definition of the term existing facility was
based in part on the Phase I definition of the term new facility, the
preamble to the final 2004 Phase II rule also clarified and provided
some examples of how the definition of existing facility might apply to
certain changes at power-producing facilities.
    Under the 2004 Phase II rule, EPA established BTA performance
standards for the reduction of impingement mortality and, under certain
circumstances, entrainment (see 69 FR 41590-41593, July 9, 2004). The
performance standards consisted of ranges of reductions in impingement
mortality and, if applicable, entrainment (e.g., reduce impingement
mortality by 80 to 95 percent and/or entrainment by 60 to 90 percent)
relative to a calculation baseline that reflected the level of
impingement mortality and entrainment that would occur absent specific
controls. These performance standards were not based on a single
technology but, rather, on consideration of a suite of technologies
that EPA determined were commercially available and economically
achievable for the industries affected as a whole (69 FR 41598-41610,
July 9, 2004). EPA based the impingement mortality and entrainment
performance standards on a suite of technologies because it found no
single technology to be effective at all affected facilities. For
impingement standards, these technologies included the following: (1)
Fine- and wide-mesh wedgewire screens, (2) barrier nets, (3) modified
screens and fish return systems, (4) fish diversion systems, and (5)
fine-mesh traveling screens and fish return systems. With regard to
entrainment reduction, these technologies include the following: (1)
Aquatic filter barrier systems, (2) fine-mesh wedgewire screens, and
(3) fine-

mesh traveling screens with fish return systems. Because EPA based the
performance standards on a combination of technologies and because of
the uncertainty inherent in predicting the efficacy of one or more of
these technologies as applied to different facilities, EPA promulgated
these standards as ranges. Furthermore, because the site-specific
performance was based on a comparison to a once-through system without
any specific controls on the shoreline near the source waterbody (i.e.,
calculation baseline, for more details see Section III.B.1 of the
preamble to the proposed rule, 76 FR 22185, April 20, 2011), the rule
also allowed facilities to receive credit toward meeting the
performance standards for impingement and entrainment reduction
associated with alternative locations of their intakes (e.g., deep
water where fish and shellfish were less abundant).
    The types of performance standard applicable to a facility (i.e.,
reductions in impingement mortality only or both impingement mortality
and entrainment) were based on several factors, including the
facility's location (i.e., source waterbody), rate of use (capacity
utilization rate), and the proportion of the waterbody withdrawn.
    The 2004 Phase II rule identified five compliance alternatives to
meet the performance standards. A facility could demonstrate to the
Director one of the following: (1) That it has already reduced its flow
commensurate with a closed-cycle recirculating system (to meet both
impingement mortality and entrainment), or that it has already reduced
its maximum through-screen velocity to 0.5 fps or less (to meet the
impingement performance standard only); (2) that its cooling water
intake structure configuration meets the applicable performance
standards; (3) that it has selected design and construction
technologies, operational measures, and/or restoration measures that,
in combination with any existing design and construction technologies,
operational measures, and/or restoration measures, meet the applicable
performance standards; (4) that it meets the applicability criteria and
has installed and is properly operating and maintaining a rule-
specified and/or approved State-specified design and construction
technology (i.e., submerged cylindrical wedgewire screens) in
accordance with Sec.  125.99(a) or an alternative technology that meets
the appropriate performance standards and is approved by the Director
in accordance with Sec.  125.99(b); or (5) that its costs of compliance
would be significantly greater than either the costs considered by the
Administrator for a like facility to meet the applicable performance
standards, or the benefits of meeting the applicable performance
standards at the facility. Under the cost-cost comparison alternative,
a Director could determine that the cost of compliance for a facility
would be significantly greater than the costs considered by EPA in
establishing the applicable impingement mortality and entrainment
performance standards. Similarly, under the cost-benefit comparison
alternative, a Director could determine that the cost of compliance for
a facility would be significantly greater than the benefits of
complying with the applicable performance standards. If either of these
determinations were made, the Director would have to make a site-
specific determination of BTA for minimizing adverse environmental
impact that came as close as practicable to meeting the applicable
performance standards at a cost that did not significantly exceed
either the costs EPA considered in establishing these standards or the
site-specific benefits of meeting these standards.
    The final 2004 Phase II rule also provided that a facility that
chooses specified compliance alternatives might request that compliance
with the requirements of the rule be determined on the basis of
implementing a Technology Installation and Operation Plan (TIOP) that
would indicate how the facility would install and ensure the efficacy,
to the extent practicable, of design and construction technologies,
and/or operational measures, and/or a Restoration Plan. The rule also
established requirements for developing and submitting a TIOP (Sec.
125.95(b)(4)(ii)) and provisions that specified how compliance could be
determined on the basis of implementing a TIOP (Sec.  125.94(d)). Under
these provisions, a TIOP could be requested in the first permit term,
and continued use of a TIOP could be requested where a facility was in
compliance with such plan and/or its Restoration Plan.
ii. Subsequent Litigation
    Industry, environmental stakeholders, and some States \20\
challenged many aspects of the 2004 Phase II regulations. On January
25, 2007, the Second Circuit (Riverkeeper, Inc. v. EPA, 475 F.3d 83,
(2d Cir., 2007)) upheld several provisions of the 2004 Phase II rule
and remanded others to EPA for further rulemaking.
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    \20\ Rhode Island, Connecticut, Delaware, Massachusetts, New
Jersey, and New York.
---------------------------------------------------------------------------

    As noted above, for the 2004 Phase II rule EPA did not select
closed-cycle cooling as BTA. Instead, EPA selected a suite of
technologies to reflect BTA, including, for example, screens, aquatic
filter barriers, and barrier nets. According to the chosen
technologies, EPA established national performance standards for
reducing impingement mortality and entrainment of fish and fish
organisms but did not require the use of any specific technology. Among
the aspects of the rule the Second Circuit remanded for further
clarification was EPA's decision to reject closed-cycle cooling as BTA
and EPA's determination of performance ranges as BTA. In addition, the
Second Circuit found that, consistent with its Phase I decision,
restoration was not authorized under the CWA as a technology for BTA
and that EPA's cost-benefit site-specific compliance alternative was
not in accord with the CWA. There are also several issues for which the
court requested additional clarification and some instances where the
court determined that EPA had failed to provide adequate notice and
opportunity to comment on certain provisions of the rule.
iii. Suspension
    As a result of the decision in Riverkeeper, Inc. v. EPA, 475 F.3d
83, (2d Cir., 2007), EPA, on July 9, 2007 (72 FR 37107) suspended the
requirements for cooling water intake structures at 2004 Phase II
existing facilities, pending further rulemaking. Specifically, EPA
suspended the provisions in Sec.  122.21(r)(1)(ii) and (r)(5), and part
125 Subpart J, with the exception of Sec.  125.90(b). EPA explained
that suspending the 2004 Phase II requirements was an appropriate
response to the Second Circuit's decision and that such action would
allow it to consider how to respond to the remand. In addition,
suspending the 2004 Phase II rule was responsive to the concerns of the
regulated community and permitting agencies, both of whom sought
guidance regarding how to proceed in light of the approaching deadline
for compliance with the remanded rule. EPA's suspension clarified that
pending further rulemaking, permit requirements for cooling water
intake structures at 2004 Phase II facilities should be established on
a case-by-case, BPJ basis (see Sec.  125.90(b)).
iv. Supreme Court Decision
    Following the decision in the Second Circuit, several industry
group litigants

petitioned the U.S. Supreme Court to hear an appeal regarding several
issues in the case. Entergy Corp. v. Riverkeeper, Inc. et al., S. Ct.
No. 07-588, et al. On April 14, 2008, the Supreme Court granted the
petitions for writs of certiorari submitted by these 2004 Phase II
litigants, but it limited its review to the issue of whether section
316(b) authorizes EPA to compare costs with benefits in determining BTA
for cooling water intake structures. The Supreme Court held oral
arguments in this case on December 2, 2008, and issued a decision on
April 1, 2009. As explained above, the Supreme Court held that it is
permissible for EPA to rely on cost-benefit analysis in decision
making. The court indicated that the phrase ``best technology available
for minimizing adverse environmental impact'' does not unambiguously
preclude use of cost-benefit analysis in decision making. 566 U.S. at
223(2009). The ruling supports EPA's discretion to consider costs and
benefits, but it imposes no obligation on the Agency to do so.
d. Phase III--Existing Power Plants Below 50 mgd, Existing
Manufacturing Facilities, and New Offshore Oil and Gas Facilities
i. Rulemaking
    On June 16, 2006, EPA published a final Phase III rule that
established categorical regulations for new offshore oil and gas
extraction facilities that have a DIF threshold of greater than 2 mgd
and that withdraw at least 25 percent of the water exclusively for
cooling purposes on an actual intake flow basis. The rule establishes
requirements that address intake velocity, proportionate flow for
sensitive locations, design and construction technologies or
operational measures, monitoring and recordkeeping, based on if a
facility employs a sea chest or not, and is fixed or not. Like the
Phase I rule, this rule includes a Track II. In the Phase III rule, EPA
declined to establish national standards for Phase III existing
facilities. Instead it concluded that CWA section 316(b) requirements
for electric generators with a DIF of less than 50 mgd and all existing
manufacturing facilities would continue to be established on a case-by-
case basis under the NPDES permit program using BPJ. (71 FR 35006, June
16, 2006).
ii. Subsequent Litigation
    Following promulgation of the rule, a number of parties filed
petitions for review that were subsequently consolidated for hearing in
the U.S. Court of Appeals for the Fifth Circuit. In 2009, EPA
petitioned the Fifth Circuit to remand to the Agency those parts of the
rule that applied to existing facilities. Specifically, EPA requested
remand of those provisions in the Phase III rule that establish 316(b)
requirements at electric generators with a DIF of less than 50 mgd, and
the provision establishing requirements for existing manufacturing
facilities on a case-by-case basis using BPJ. This request did not
affect the Phase III rule requirements that establish categorical
regulations for new offshore oil and gas extraction facilities that
have a DIF threshold of greater than 2 mgd and that withdraw at least
25 percent of the water exclusively for cooling purposes on an actual
intake flow basis.
    On July 23, 2010, the U.S. Court of Appeals for the Fifth Circuit
issued a decision affirming the parts of Phase III rule relating to new
offshore oil and gas facilities. The court granted EPA's motion to
remand the rule with respect to existing facilities. In sustaining the
requirements for new offshore oil and gas facilities, the Fifth Circuit
upheld EPA's decision not to use cost benefit balancing in determining
the requirements for these new facilities.

III. Environmental Effects Associated With Cooling Water Intake
Structures

A. Introduction

    Multiple types of adverse environmental effects may be associated
with CWIS operations at regulated facilities. Many facilities employ
once-through cooling water systems that impinge fishes and other
aquatic organisms on intake screens. Impinged organisms may be killed,
injured, or weakened. In addition, early life stage fish or planktonic
organisms can be entrained by the CWIS and subjected to high velocity
and pressure, increased temperature, and chemical anti-biofouling
agents in the system. These factors are highly lethal in most cases, as
early life stages of larvae are highly sensitive and very unlikely to
survive entrainment. Even if an organism is entrained as an egg and
survives, its chances of surviving beyond the larvae stage are
dramatically lower than eggs that were never entrained. Thus, unless
measures to protect larvae are in place, egg survival does not indicate
that adverse environmental impacts have been avoided. Consistent with
its treatment of entrainment in past 316(b) rules, EPA assumes for the
purposes of a national rule that 100 percent of entrained organisms
suffer mortality.
    The effects of CWIS on aquatic habitats and biota in the waterbody
do not occur in isolation from other ongoing physical, chemical, and
biological stressors. Anthropogenic stressors may include: Degraded
water and sediment quality, low dissolved oxygen (DO) levels,
eutrophication, fishing, channel or shoreline (habitat) modification
(intake structure and other flood or storm controls), hydrologic regime
changes and invasive species. For example, many aquatic organisms
subject to IM&E (impingement mortality and entrainment) reside in
impaired (i.e., CWA 303(d) listed) waterbodies. The effects of
anthropogenic stressors on biota may contribute to or compound the
impact of IM&E, depending on the influence of location-specific
factors. In addition to stressors acting on biota near a single CWIS,
multiple CWISs and facilities located in close proximity on the same
waterbody may have additive or cumulative effects on aquatic
communities. And, although it is difficult to measure, the compensatory
ability of an aquatic population, which is the capacity for a species
to increase survival, growth, or reproduction rates in response to
decreased population, is likely compromised by IM&E and the cumulative
impact of other stressors in the environment over extended periods of
time.

B. Major Anthropogenic Stressors in Aquatic Ecosystems

    All ecosystems and their biota are subject to natural variability
in environmental conditions (e.g., seasonal cycles, foliage presence)
as well as periodic large-scale disturbances (e.g., drought, flood,
fire). In contrast, anthropogenic stressors tend to be more chronic in
nature and can often lead to long-term environmental degradation
associated with decreased biodiversity, reduced primary and secondary
production, and a lowered ecosystem resiliency (i.e., ability of the
ecosystem to recover to its original state from perturbations).\21\
Several of the more important anthropogenic stressors are discussed
below, with CWIS-related impacts considered as a separate category of
stress.
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    \21\ Rapport, D. J., & Whitford, W. G. (1999). How Ecosystems
Respond to Stress. BioScience, 49(3), 193-203. See DCN 10-4871.
---------------------------------------------------------------------------

1. Habitat Loss
    Structural aquatic habitat is generally recognized as the most
significant determinant of the nature and composition of aquatic
communities. Most 316(b) facilities have been built on shoreline
locations where industrial buildings, roadways, canals, impoundments,
and other water storage or conveyance structures have been

constructed at the cost of terrestrial, aquatic, and wetland habitats.
The main impacts of aquatic habitat loss are a reduction in the number
of fish in the environment, a concentration of fishery spawning and
nursery areas in fewer locations, shifts in species dominance based on
available habitat and local extirpation of historical fish species.
Habitat loss in shoreline areas exacerbates the effect of CWIS losses
because many fish species affected by IM&E rely heavily on coastal
wetlands as nursery areas.
2. Water Quality and Impaired Waters
    Poor water quality is a major stressor of aquatic biota and
habitats. Degraded surface water and sediment contaminants reflect both
current and past industrial, agricultural and urban land use and
disposal practices. Poor water quality can limit the numbers,
composition, and distribution of fish and invertebrates; reduce
spawning effort and growth rates; select for pollution-tolerant
species; cause periodic fishkills; or result in adverse bioaccumulative
effects to piscivorous wildlife.
    EPA has determined that the majority of surveyed facilities,
including 71 percent of electric generators and 79 percent of sampled
manufacturing facilities, are within two miles of an impaired (i.e.,
CWA section 303(d)-listed) waterbody.\22\ These impairments are caused
by a variety of chemical, physical, and biological factors. These
factors include biological stressors, nutrients, organic enrichment/
loading, bioaccumulation, toxics, unknown causes, and other forms of
anthropogenic sources of pollution (e.g., atmospheric deposition of
mercury leading to fish advisories). The combined impacts of impaired
water quality may result in highly degraded or altered aquatic
communities that are further impaired by IM&E associated with the
operation of regulated facilities.
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    \22\ Abt Associates, Inc. (2010). Source Water Body Comparisons
(Under Work Assignment 2-09, Task 4) (pp. 13). Cambridge, MA. See
DCN 10-4504.
---------------------------------------------------------------------------

3. Overharvesting
    Overharvesting is a general term describing the exploitation of an
aquatic population beyond a level that is sustainable, sometimes to the
point of significantly reducing the population relative to historic
levels. Given that many fisheries regulated by the National Marine
Fisheries Service (NMFS) are overfished on a continual basis,
overharvesting is a particular problem for stocks also subject to IM&E.
4. Invasive Species
    Non-indigenous invasive species (NIS) are a significant and
increasingly prevalent stressor in both freshwater and marine
environments. Approximately 300 NIS have become established in marine
and estuarine habitats of the continental U.S., and the number of NIS
continues to increase. Many NIS are nuisance species with undesirable
effects on local communities.\23\ For example, interactions between NIS
and other anthropogenic stressors can affect the colonization and
distribution of native species subject to CWIS impacts.
---------------------------------------------------------------------------

    \23\ Ruiz, G. M., Fofonoff, P. W., Carlton, J. T., Wonham, M.
J., & Hines, A. H. (2000). Invasion of Coastal Marine Communities in
North America: Apparent Patterns, Processes, and Biases. Annual
Review of Ecology & Systematics, 31, 481-531. See DCN 10-4880.
---------------------------------------------------------------------------

C. Effects of CWIS on Aquatic Ecosystems

    The magnitude and regional importance of IM&E is a function of
operational CWIS intake volumes and characteristics of the aquatic
community in the region. Thus, for example, IM&E can contribute to
impacts on threatened and endangered (T&E) species and reduce
populations of ecologically critical aquatic organisms, including
important organisms in an ecosystem's food web. In addition, IM&E may
diminish the compensatory reserves of populations and reduce indigenous
species populations, commercial fisheries, and recreational fisheries.
Further, IM&E may stress overall communities and ecosystems, as
evidenced by reductions in diversity or other changes in ecosystem
structure or function. The direct and indirect impacts of CWIS may
reduce other valuable ecosystem goods and services, including nutrient
cycling and ecosystem stability.
1. Losses of Fish From Impingement Mortality and Entrainment
    The most visible direct impacts of IM&E are the losses of large
numbers of aquatic organisms, distributed non-uniformly among fish,
benthic invertebrates, phytoplankton, zooplankton, and other
susceptible aquatic taxa (e.g., sea turtles). These losses have
immediate and direct effects on the population size and age
distribution of affected species, and may cascade through food webs.
    In some cases, IM&E has been shown to be a significant source of
anthropogenic mortality of depleted stocks of commercially targeted
species. For example, approximately 5.4 percent of the estimated A1E
population of the Southern New England/Massachusetts stock of winter
flounder (Pseudopleuronectes americanus) is lost to IM&E.\24\ In
addition to its effect on stocks of marine commercial fish species,
IM&E increases the pressure on native freshwater species, such as lake
whitefish (Coregonus clupeaformi) and yellow perch (Perca flavescens),
whose populations have seen dramatic declines in recent years.\25\
---------------------------------------------------------------------------

    \24\ Northeast Fisheries Science Center (NEFSC) of the NOAA
National Marine Fisheries Service. (2011). 52nd Northeast Regional
Stock Assessment Workshop (52nd SAW): Assessment Summary Report. DCN
12-4940.
    \25\ U.S. Department of the Interior (USDOI). (2004). Fisheries:
Aquatic and Endangered Resources from http://www.glsc.usgs.gov/main.php?content=research_risk&title=Species%20at%20Risk0&menu=research [Retrieved June 23,
2004]; Wisconsin Department of Natural Resources (Wisconsin DNR).
(2003). Adrift on the sea of life. Wisconsin Natural Resources,
June, 17-21. See DCN 10-4914.
---------------------------------------------------------------------------

    IM&E is also likely to contribute to reduced population sizes of
species targeted by commercial and recreational fishers, particularly
for stocks that are being harvested at unsustainable levels and/or
undergoing rebuilding. Thus, reducing IM&E may lead to more rapid stock
recovery, a long-term increase in commercial fish catches, increased
population stability following periods of poor recruitment and, as a
consequence of increased resource utilization, an increased ability to
minimize the invasion of exotic species.\26\
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    \26\ Stachowicz, J. J., & Byrnes, J. E. (2006). Species
Diversity, invasion success, and ecosystem functioning:
disentangling the influence of resource competition, facilitation,
and extrinsic factors. Marine Ecology--Progress Series, 311, 251-
262. See DCN 10-4892.
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2. IM&E Effects on Threatened and Endangered Species
    Populations of T&E (threatened and endangered) species may suffer
increased mortality as direct or indirect consequences of IM&E. T&E
species are vulnerable to future extinction or at risk of extinction in
the near future and IM&E losses could either lengthen population
recovery time, hasten the demise of these species, or counteract the
effects of other conservation efforts. For this reason, the population-
level and societal values of T&E losses are likely to be considered
more important than the absolute number of losses that occur. Due to
low population sizes, I&E mortality from CWISs may represent a
substantial portion of the annual reproduction of T&E species.
3. Thermal Effects
    One byproduct of once-through cooling water systems is a discharge
of a heated effluent. Concerns about the impacts of heated effluents
are

addressed by state water quality standards addressing temperature,
rather than a national rule. Section 316(a) of the Clean Water Act
provides a mechanism for variances from controls that could be imposed
due to thermal effects. Based on a limited review of NPDES permits, to
the extent that facilities have controls on cooling water intake
structures, these controls have been required to meet water quality
standards related to temperature.\27\
---------------------------------------------------------------------------

    \27\ Abt Associates, Inc. (2010). Source Water Body Comparisons
(Under Work Assignment 2-09, Task 4) (pp. 13). Cambridge, MA. See
DCN 10-4504.
---------------------------------------------------------------------------

    Thermal pollution has long been recognized as having multiple
effects upon the structure and function of ecosystems.\28\ Numerous
studies have shown that thermal discharges may substantially alter the
structure of the aquatic community by modifying photosynthetic,
metabolic, and growth rates \29\ and reducing levels of DO. Thermal
pollution may also alter the location and timing of fish behaviors
including spawning, aggregation, and migration, and may result in
thermal shock-induced mortality for some species.\30\ Adverse
temperature effects are likely to be more pronounced in aquatic
ecosystems that are already subject to other environmental stressors
such as high biochemical oxygen demand (BOD) levels, sediment
contamination, and pathogens. Reduced waterbody volume due to the
effects of climate change and/or lengthy droughts could exacerbate
these effects.
---------------------------------------------------------------------------

    \28\ Abt Associates, Inc. (2009). Summary of Ecological Effects
of Thermal Discharge (pp. 28). Cambridge, MA. See DCN 10-4505.
    \29\ Martinez-Arroyo, A., Abundes, S., Gonz[aacute]lez, M. E., &
Rosas, I. (2000). On the Influence of Hot-Water Discharges on
Phytoplankton Communities from a Coastal Zone of the Gulf of Mexico.
Water, Air & Soil Pollution, 119(1-4), 209-230. See DCN 10-4820.
    \30\ Smythe, A. G., & Sawyko, P. M. (2000). Field and laboratory
evaluations of the effects of `cold shock' on fish resident in and
around a thermal discharge: an overview. Environmental Science &
Policy, 3(S1), 225-232. See DCN 10-4887.
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4. Chemical Effects
    The release of chemicals in the discharge of once-through cooling
waters is another environmental effect associated with industrial
facility operations. These chemicals include metals from internal
corrosion of pipes, valves and pumps (e.g., chromium, copper, iron,
nickel, and zinc), additives (anti-corrosion and anti-scaling agents)
and their byproducts, and materials from boiler blowdown and cleaning
cycles. In addition to these pollutants, facilities also discharge
anti-fouling biocide agents.
    A review of the effects of chemical treatment and discharge into
the environment suggests that direct ecotoxicity in discharge plumes is
rarely observed beyond the point of discharge or in a mixing zone near
the pipe outlet.\31\ However, the presence of these chemicals in the
receiving water may be additive to low-level chronic adverse effects
from other anthropogenic stressors identified above.
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    \31\ Taylor, C. J. L. (2006). The effects of biological fouling
control at coastal and estuarine power stations. Marine Pollution
Bulletin, 53(1-4), 30-48. See DCN 10-4901.
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5. Effects of Flow Alteration
    The operation of CWISs and discharge returns significantly alter
patterns of flow within receiving waters both in the immediate area of
the CWIS intake and discharge pipe, and in mainstream waterbodies,
particularly in inland riverine settings. In ecosystems with strongly
delineated boundaries (i.e., rivers, lakes, enclosed bays, etc.), CWISs
may withdraw and subsequently return a substantial proportion of water
available to the ecosystem. Even in situations when the volume of water
downstream of regulated facilities changes relatively little, the flow
characteristics of the waterbody, including turbulence and water
velocity, may be significantly altered.
    Altered flow velocities and turbulence may lead to several changes
in the physical environment. These changes can include sediment
deposition, sediment transport, and turbidity, each of which plays a
role in the physical structuring of ecosystems.\32\ Flow velocity and
turbulence are controlling biological factors in aquatic ecosystem
health, and have been shown to alter feeding rates, settlement and
recruitment, bioturbation, growth and population dynamics.\33\
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    \32\ Hoyal, D. C. J. D., Atkinson, J. F., Depinto, J. V., &
Taylor, S. W. (1995). The effect of turbulence on sediment
deposition. Journal of Hydraulic Research, 33(3), 349-360. See DCN
10-4797.
    \33\ Sanford, E. B., Bertness, D., & M. D. Gaines, S. D. (1994).
Flow, food supply and acorn barnacle population dynamics. Marine
Ecology Progress Series, 104, 49-62. See DCN 10-4882.
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    Climate change is predicted to have variable effects on future
river flow in different regions of the United States. Some rivers are
expected to have large increases in flood flows while other basins will
experience stress from low water levels. Thus, the adverse effects of
flow alteration may increase or decrease over longer periods for larger
rivers, depending on their location.

D. Community-Level or Indirect Effects of CWIS

    In addition to the direct effects of CWISs, IM&E may alter a wide
range of aquatic ecosystem functions and services at the community
level. Many of these effects on aquatic community function and service
are poorly characterized, given the limited scope of IM&E studies and
an incomplete knowledge of baseline or pre-operational conditions
within affected waters.
    The operation of CWISs by facilities can lead to localized areas of
depressed fish and shellfish abundance. Industrial facilities (and the
intake volume they represent) are located in a non-uniform manner along
coastlines and rivers. They may be clustered, such that the populations
affected by IM&E are geographically heterogeneous. This can result in a
highly localized and patchy distribution of aquatic organisms in
regional areas.
    IM&E may directly reduce species populations through the death of
individual organisms, or may indirectly affect species populations by
altering established predator-prey relationships and thereby disrupting
ecological niches and food webs. For example, the loss of young-of-year
predators, such as striped bass, or loss of important forage fish, such
as menhaden and bay anchovy, may affect trophic relationships and alter
food webs. IM&E may lead to reductions in local community biodiversity
or in a loss of genetic diversity in individual fish populations.
Because IM&E represents a selective pressure on early life stages, it
may reduce the genetic diversity of resident fish and prevent the
recovery of depleted stocks.\34\ Also, because many stocks are
differentiated by oceanic region and/or timing of migratory movements,
IM&E could alter the seasonal migration and life cycle events of fish
populations, which could have ramifications for predator species.
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    \34\ Swain, D. P., Sinclair, A. F., & Mark Hanson, J. (2007).
Evolutionary response to size-selective mortality in an exploited
fish population. Proceedings of the Royal Society B: Biological
Sciences, 274(1613), 1015-1022. See DCN 10-4900.
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    IM&E may also alter the pace of nutrient cycling and energy
transfer through food webs. Fish species have been shown to have
substantial effects on nitrogen, phosphorous, and carbon cycling due to
storage and translocation effects.\35\ These alterations in nutrient
cycling could lead to redirection of nutrient flows to other components
of the ecosystem including water column phytoplankton, benthic
macroalgae and attached epiphytes, with subsequent changes to the
condition of critical

ecosystem habitats, such as submerged aquatic vegetation.
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    \35\ Vanni, M. J., Layne, C. D., & Arnott, S. E. (1997). ``Top-
down'' trophic interactions in lakes: effects of fish on nutrient
dynamics. Ecology, 78(1), 1-20. See DCN 12-5047.
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    The effect of long-term or chronic IM&E may lead to a decrease in
ecosystem resistance and resilience \36\ (i.e., ability to resist and
recover from disturbance, including invasive species). That is, IM&E is
likely to reduce the ability of ecosystems to withstand and recover
from these ecosystem damages, whether those impacts are due to
anthropogenic effects or natural variability.
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    \36\ Folke, C., Carpenter, S., Walker, B., Scheffer, M.,
Elmqvist, T., Gunderson, L., & Holling, C. S. (2004). Regime Shifts,
Resilience, and Biodiversity in Ecosystem Management . . . Annual
Review of Ecology, Evolution, & Systematics, 35(1), 557-581. See DCN
10-4770.
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E. Cumulative Effects of Multiple Facilities

    Cumulative effects of CWISs are likely to occur if multiple
facilities are located in close proximity and impinge or entrain
aquatic organisms within the same source waterbody, watershed system,
or along a migratory pathway of a specific species (e.g., striped bass
in the Hudson River). EPA analyses show more than 20 percent of all
facilities on inland waters withdraw more than 5 percent of the mean
annual flow.\37\ See TDD Chapter 4.1.3 for detailed discussion. This
impact is compounded because more than half of all regulated facilities
are located on waterbodies with multiple CWISs. An inspection of the
geographic locations of regulated facilities (approximated by CWIS
latitude and longitude) shows that facilities in inland settings are
more likely to be located in close proximity to other facilities
(upstream or downstream) than are facilities in marine and estuarine
environments. The cumulative impact of clustered facilities may be
significant, due to the concentrated IM&E, combined intake flows, and
the potential for other impacts such as thermal discharges.
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    \37\ As described in the Phase I proposed rule (65 FR 49060) and
the Phase II NODA (66 FR 28853), absent any other controls,
withdrawal of a unit volume of water from a waterbody will result in
the entrainment of an equivalent unit of aquatic life (such as eggs
and larval organisms) suspended in that volume of the water column.
Thus, facilities withdrawing greater than 5 percent of the mean
annual flow from freshwater rivers and streams may entrain equal
proportions of aquatic organisms.
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IV. Summary Description of the Final Rule

    Under today's final rule, the owners or operators of existing
facilities and new units at existing facilities are subject to BTA
standards for impingement mortality and entrainment that are expected
to substantially reduce the adverse environmental impacts of cooling
water intake structures. Earlier, in Section I, the preamble describes
what facilities are subject to the rule. The discussion below presents
an overview of the substantive requirements of the rule.

A. BTA Standard for Impingement Mortality for Existing Units at
Existing Facilities

    The final rule requires that existing facilities subject to this
rule must comply with one of the following seven alternatives
identified in the national BTA standard for impingement mortality at
Sec.  125.94(c) (hereafter, impingement mortality standards):
    (1) Operate a closed-cycle recirculating system as defined at Sec.
125.92;
    (2) operate a cooling water intake structure that has a maximum
through-screen design intake velocity of 0.5 fps;
    (3) operate a cooling water intake structure that has a maximum
through-screen intake velocity of 0.5 fps;
    (4) operate an offshore velocity cap as defined at Sec.  125.92
that is installed before October 14, 2014;
    (5) operate a modified traveling screen \38\ that the Director
determines meets the definition at Sec.  125.92(s) and that the
Director determines is the best technology available for impingement
reduction;
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    \38\ EPA is aware that innovative screen designs are currently
being tested that are expected to provide similar or better
performance than modified Ristroph traveling screems. Therefore EPA
has defined modified traveling screen at 40 CFR 125.92 to mean any
traveling water screen that incorporates the specified measures that
are protective of fish and shellfish. In this preamble, modified
traveling water screen with a fish handling and return system is
often referred to more simply a modified traveling screen.
---------------------------------------------------------------------------

    (6) operate any other combination of technologies, management
practices and operational measures that the Director determines is the
best technology available for impingement reduction; or
    (7) achieve the specified impingement mortality performance
standard.
    Options (1), (2) and (4) above are essentially pre-approved
technologies requiring no demonstration or only a minimal demonstration
that the flow reduction and control measures are functioning as EPA
envisioned. Options (3), (5) and (6) require more detailed information
be submitted to the Director before the Director may specify it as the
requirement to control impingement mortality.
    In the case of Option (3), which EPA considers to be a streamlined
alternative, the facility must submit information to the Director that
demonstrates that the maximum intake velocity as water passes through
the structural components of a screen measured perpendicular to the
screen mesh does not exceed 0.5 feet per second.
    In the case of Option (5), the facility must submit a site-specific
impingement technology performance optimization study that must include
two years of biological sampling demonstrating that the operation of
the modified traveling screens has been optimized to minimize
impingement mortality. As discussed below, if the facility does not
already have this technology installed and chooses this option, the
Director may postpone this study till the screens are installed (see
VI.G.1.d below).
    In the case of Option (6), the facility must submit a site-specific
impingement study including two years of biological data collection
demonstrating that the operation of the system of technologies,
operational measures and best management practices has been optimized
to minimize impingement mortality. If this demonstration relies in part
on a credit for reductions in the rate of impingement already achieved
by measures taken at the facility, an estimate of those reductions and
any relevant supporting documentation must be submitted. The estimated
reductions in rate of impingement must be based on a comparison of the
system to a once-through cooling system with a traveling screen whose
point of withdrawal from the surface water source is located at the
shoreline of the source waterbody.
    The impingement mortality performance standard in (7) requires that
a facility must achieve a 12-month impingement mortality performance of
all life stages of fish and shellfish of no more than 24 percent
mortality, including latent mortality, for all non-fragile species that
are collected or retained in a sieve with maximum opening dimension of
0.56 inches \39\ and kept for a holding period of 18 to 96 hours. The
Director may, however, prescribe an alternative holding period. The 12-
month average of impingement mortality is calculated as the sum of
total impingement mortality for the previous 12 months divided by the
sum of total impingement for the previous 12 months. A facility must
choose to demonstrate compliance with this requirement for the entire
facility, or for each individual cooling water intake

structure. Biological monitoring must be completed at a minimum
frequency of monthly.
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    \39\ Though less common, the EPA recognizes that \1/2\ by \1/4\
inch mesh are used in some instances and perform comparably to the
\3/8\ inch square mesh. Therefore, today's rule allows for
facilities to apply a \1/2\ by \1/4\ inch sieve (diagonal opening of
0.56 inches) or a \3/8\ inch sieve (diagonal opening of 0.53 inches)
when discerning between impinged and entrained organisms.
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    The owner or operator of an existing facility must meet the
impingement mortality requirements as soon as practicable after
issuance of a final permit establishing the entrainment requirements
under Sec.  125.94(d).
    Today's final rule also allows the Director, based on review of
site-specific data, to conclude that a de minimis rate of impingement
exists and therefore no additional controls are warranted to meet the
BTA impingement mortality standard. In addition, today's final rule
allows the Director flexibility in determining appropriate site-
specific controls that may be less stringent than those found at Sec.
125.94(c)(1) to (7) for existing units at existing facilities operating
with a capacity utilization of less than 8 percent averaged over a 24-
month block contiguous period. This provision can be found at Sec.
125.94(c)(12). EPA notes that these provisions for impingement
mortality would not apply to entrainment because, as discussed in the
next section, the requirements for entrainment are established by the
Director on a site-specific basis.

B. BTA Standard for Entrainment for Existing Units at Existing
Facilities

    The final rule establishes the national BTA standard for
entrainment at existing units at existing facilities at Sec.  125.94(d)
(hereafter, entrainment standards). For such units, the rule does not
prescribe a single nationally applicable entrainment performance
standard but instead requires that the Director must establish the BTA
entrainment requirement for a facility on a site-specific basis. The
requirements must reflect the Director's determination of the maximum
reduction in entrainment warranted after consideration of all factors
relevant to the BTA determination at the site and must include
consideration of the specific factors spelled out in Sec.
125.98(f)(2). Facilities that withdraw greater than 125 mgd AIF must
develop and submit an Entrainment Characterization Study (Sec.
122.21(r)(9)), as well as provide other information required at Sec.
122.21(r)(7) and (10), (11), (12) and (13) that must include specified
data pertinent to consideration of several of the factors identified in
Sec.  125.98(f).

C. BTA Standards for Impingement Mortality and Entrainment for New
Units at Existing Facilities

    The owner or operator of a new unit at an existing facility must
achieve one of two compliance alternatives under the national BTA
standards for impingement mortality and entrainment for new units at
existing facilities at Sec.  125.94(e) (hereafter, new unit
standards).\40\ Under the new unit standards, the owner or operator of
a facility must reduce AIF at the new unit, at a minimum, to a level
commensurate with that which can be attained by the use of a closed-
cycle recirculating system as defined at Sec.  125.92(c)(1). The owner
or operator of a facility with a cooling water intake structure that
supplies cooling water exclusively for operation of a wet or dry
cooling tower(s) and that meets the definition of closed-cycle
recirculating system at Sec.  125.92(c)(1) meets this new unit
standard. Under the alternative new unit standard, the owner or
operator of a facility must demonstrate to the Director that it has
installed, and will operate and maintain, technological or other
control measures that reduce the level of adverse environmental impact
from any cooling water intake structure used to supply cooling water to
the new unit to a comparable level to that which would be achieved
through flow reductions commensurate with the use of a closed-cycle
recirculating system. Under this alternative, the owner or operator of
a facility must demonstrate entrainment mortality reductions that are
equivalent to 90 percent or greater of the reduction that could be
achieved through compliance with the first alternative entrainment
standard for new units.
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    \40\ EPA expects that all new units will comply with these
requirements through the installation of a closed-cycle cooling
system, which is one of the most effective technologies for reducing
impingement and impingement mortality. Therefore, the IM
requirements for new units are already addressed by the new unit
requirements by virtue of the first compliance alternative of the IM
performance standard.
---------------------------------------------------------------------------

    The new unit entrainment standards do not apply to certain water
withdrawals including (1) cooling water used by manufacturing
facilities for contact cooling purposes; (2) portions of those water
withdrawals for auxiliary cooling uses totaling less than 2 mgd; (3)
any volume of cooling water withdrawals used exclusively for make-up
water at existing closed-cycle recirculating systems; \41\ and (4) any
quantity of emergency back-up water flows. Furthermore, as is the case
for existing units, obtaining cooling water from a public water system,
using reclaimed water from wastewater treatment plants, or desalination
plants, or using recycled process wastewater effluent as cooling water
does not constitute use of a cooling water intake structure. The new
unit requirements apply only to the volume of cooling water used by the
new unit, or to the cooling water intake structures used by the new
unit. The new unit requirements do not apply to the rest of the
existing facility.
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    \41\ For facilities with a combination of closed-cycle
recirculating systems and other cooling water systems, the
entrainment mortality standard does not apply to that portion of
cooling water withdrawn as make-up water for the closed-cycle
recirculating system.
---------------------------------------------------------------------------

    In addition, the Director may establish alternative entrainment
requirements for new units when compliance with the new unit
entrainment standards would result in compliance costs wholly out of
proportion to the costs EPA considered in establishing the requirements
at issue or will result in significant adverse impacts on local air
quality, significant adverse impacts on local water resources other
than impingement or entrainment, adverse impacts on threatened and
endangered species, or significant adverse impacts on local energy
markets. Any Director-specified alternative must achieve a level of
performance as close as practicable to the requirements of Sec.
125.94(e)(1) or (2).

D. Other Provisions

    The final rule contains a number of other provisions related to the
BTA impingement and entrainment reduction requirements. For example,
the rule also provides that the Director may establish more stringent
requirements as BTA if the Director determines that the facility owner
or operator's compliance with the requirements otherwise established
under the final rule would not meet the requirements of applicable
State and Tribal law, including water quality standards. 40 CFR
125.94(i). Today's rule also requires the owner or operator of a
facility subject to this subpart to submit and retain permit
application and supporting information as specified in Sec.  125.95;
monitor for compliance as specified in Sec.  125.96; and report
information and data and keep records as specified in Sec.  125.97.
Director requirements are specified in Sec.  125.98.
    The rule further provides that, in the case of a nuclear facility
or a facility constructing or conducting maintenance on nuclear powered
vessels of the Armed Services, if the owner or operator of the facility
demonstrates to the Director, upon the Director's consultation with the
Nuclear Regulatory Commission, the Department of Energy or the Naval
Nuclear Propulsion Program, that compliance with this subpart would
result in a conflict with a safety requirement established by these
entities, the

Director must establish BTA requirements that would not result in a
conflict with the Commission's, the Department's or the Naval Nuclear
Propulsion Program's safety requirement.

V. Summary of Data Updates and Revisions to the Proposed Rule

    This description of revisions to the proposed rule is organized in
three sections: Data updates, regulatory approach and compliance, and
new units. EPA published two NODAs (Notice of Data Availability) (77 FR
34315, June 11, 2012 and 77 FR 34927, June 12, 2012) based on some
comments received on the proposed rule and additional analyses. EPA
also took public comment on the information in these notices.

A. Data Updates

    On the basis of comments received, additional information made
available, and further analyses, EPA revised a number of assumptions
used in its assessments for the final rule. These included revisions to
the engineering costs of options considered in development of the final
rule, the information collection costs, the economic analyses, and the
benefits analyses. The revised analyses, along with an explanation of
how they affected decision making for this final rule, are discussed
below.
1. Impingement Data and Performance Standard
    Since publishing the proposal, EPA received a substantial number of
comments stating the amount of data to develop the proposed impingement
mortality performance standard was too limited. EPA received more than
80 additional documents containing impingement and entrainment data.
EPA reviewed these materials and found that many documents did not
provide useful data. For example, in some cases, a document did not
provide useful information because the only data available were the
facility name and raw sampling data for a number of different species
of fish or shellfish, or both. In other cases, the documents focused on
source water characterization data alone. However, after review, EPA
identified more than 40 distinct sets of additional impingement
sampling and performance data.
    EPA also reevaluated and revised the criteria it used for including
impingement mortality study data in the impingement mortality
performance standard calculations. In calculating the impingement
mortality performance standard of Sec.  125.94(c)(7), EPA applied these
revised criteria for acceptable data to both the new data and the
earlier data used for proposal. EPA's approach for the final rule is
similar to that of the proposal. In order to include data in EPA's
calculation, for the proposal, EPA applied the following four criteria.
First, the data must be specific to the technology under consideration.
Second, impingement mortality must have been reported as an absolute
number or a percentage of impinged fish that were killed. Third, the
data must reflect that the installed technology was operated under
conditions that are representative of actual conditions at a facility,
and fourth, the reported values must be actual measurements. EPA based
the proposed performance standard on the performance of modified
traveling screens with a fish return system using a limited definition
of the control technology.
    In its reevaluation and based on comments, EPA decided to revise
some of the criteria and add two new ones. In some cases, the effect of
these changes is to relax the criteria and in others, to impose more
restrictive criteria. First, all impingement data must be for non-
fragile species (including shellfish). Second, the data must be
representative of annual mortality data for purposes of deriving an
annual performance standard. EPA notes that in contrast to the proposed
rule, the permit application does not require submission of the
proposed list of ``species of concern.'' EPA found that the term
``species of concern'' was similar to terms used in the context of T&E
(threatened and endangered) species, and may further cause confusion
over existing Services or State requirements for such species. Further,
despite EPA's efforts to distinguish between species of concern and RIS
(representative indicator species) in the NODA (77 FR 34325, June 11,
2012), EPA found that many commenters were still confused by the
language. Instead, EPA is adopting the term ``fragile species'' and
using the term exactly as it is used with the impingement mortality
data and criteria used in calculating the impingement mortality
performance standard of the rule. EPA included a definition for
``fragile species'' at Sec.  125.92(m), as a species of fish or
shellfish that has an impingement survival rate of less than 30
percent. EPA took this approach to ensure that a facility's performance
in reducing impingement mortality as demonstrated by collecting
biological data would reflect only the effects of its improvements to
the CWIS technology, and not be confounded by effects of data
collection that are not caused by impingement.
    EPA also relaxed the holding time criteria as a result of
reevaluating the range of acceptable impingement mortality holding
times, which at proposal was limited to 24 to 48 hours. After
evaluating the data, EPA concluded that a range of holding times of 18
to 96 hours was acceptable for inclusion in the development of a
performance standard because commenters had provided documentation
showing that the actual time period typically had little effect on IM
rates. At proposal, EPA counted all fish that died at any time during
the holding period. For the final rule being promulgated today, EPA
excludes those that were dead at time zero because such counts measured
immediate deaths and not those organisms that were mortally harmed as a
result of impingement. These counts also might reflect already injured,
nearly dead, or already dead fish (``naturally moribund'') that were
impinged by the screen. As a consequence of relaxing the holding times
and other requirements, EPA based the performance standard on a larger
set of data, with broader geographic representation. (For more
information, see DCN 12-6703.) The rationale for these revisions to the
data acceptance criteria are described in further detail in the TDD,
Chapter 11. Using the revised criteria, EPA reviewed the data in each
of the impingement mortality studies for potential inclusion in EPA's
evaluation of an impingement mortality performance standard. These
changes resulted in an increase in the number of facility data sets
acceptable for determining the impingement mortality performance
standard, from four data sets at three facilities at proposal to 26
data sets at 17 facilities today. As a result, the 12-month average
impingement mortality performance standard of all life stages of fish
and shellfish was revised from no more than 12 percent to no more than
24 percent mortality, including latent mortality, for each non-fragile
species that is collected or retained in a sieve with maximum opening
dimension of 0.56 inches and kept for a holding period of 18 to 96
hours. The revised performance standard and data evaluation criteria
are discussed in detail in Section VI and Chapter 11 of the TDD.
    EPA also reevaluated its approach to compliance monitoring for the
impingement mortality performance standard. In particular, EPA
considered the costs and burden of frequent biological monitoring for
those technologies that, according to EPA's record, perform equal to or
better than

the IM performance standard. As proposed, all facilities would have
conducted weekly biological monitoring in perpetuity irrespective of
the compliance approach or technologies selected. EPA agrees with
comments that this may be unnecessarily burdensome and of limited value
for those technologies for which the potential performance is well
documented. As such, today's final rule includes seven compliance
alternatives, only one of which requires biological compliance
monitoring.
    EPA notes, however, that a facility relying in part on a credit for
reductions in impingement mortality already obtained at the facility
(Sec.  125.94(c)(6)) must gather biological data at a minimum frequency
of monthly for a period of two years in order to calculate their 12-
month average impingement mortality. Further, a facility choosing to
comply using the impingement mortality performance standard (Sec.
125.94(c)(7)), must conduct biological monitoring at a frequency of at
least monthly in order to calculate its 12-month average impingement
mortality. The 12-month average is calculated as the sum of total
impingement mortality for the previous 12 months divided by the sum of
total impingement for the previous 12 months. EPA is requiring that a
facility choose to either demonstrate compliance with this requirement
for the entire facility, or for each individual cooling water intake
structure. The EPA expects that as the performance of the technology is
demonstrated by the facility, the Director could reduce the frequency
of biological compliance monitoring. Further, prior to a subsequent
permit application, a facility could collect sufficient performance
data to demonstrate to the satisfaction of the Director that its
``systems of technologies'' compliance alternative is BTA at that
facility.
2. Technology Costs
    Since publishing the proposal, EPA received a number of public
comments from industry stating that EPA had underestimated the costs of
modified traveling screens with fish returns. EPA used new information
to revise the compliance cost estimates (including the methodology used
for technology assignment) and the capital costs for several compliance
technologies, including those used as the primary basis for the final
rule. Those changes include the following:
     In response to comments challenging EPA's assumption that
modified traveling screens were available at most facilities, EPA
changed the assignment of the modified traveling cost module \42\ so as
to apply this only where the existing intake for the model facility
intake employed traveling screens. As a result, a number of intakes,
such as those that use passive screens (e.g., fixed screens), were
assigned higher cost technologies such as larger intakes or wedgewire
screens with through-screen design velocities of 0.5 fps.
---------------------------------------------------------------------------

    \42\ EPA used a model facility approach to develop compliance
technology costs where different sets of compliance technology cost
algorithms called modules were assigned to individual model facility
intakes on the basis of site-specific conditions. For a more
detailed discussion, see the TDD Chapter 8.
---------------------------------------------------------------------------

     Because EPA has clarified that properly operated closed-
cycle recirculating systems is one of the compliance alternatives for
impingement mortality, those intakes with existing closed-cycle cooling
no longer receive additional impingement technology costs.
     At proposal, the design of the larger intake module was
based on a through-screen velocity of 1.0 fps and, therefore, was not
consistent with the low velocity compliance alternatives. To ensure
that this technology will be consistent at all locations, the through-
screen design velocity for the larger intake was changed to a maximum
of 0.5 fps, resulting in a substantial increase in capital and
operational and maintenance costs.
     EPA received a number of comments noting that fish returns
might be difficult to install at some intakes. EPA reviewed the fish
return cost component of the modified traveling screen module and
concluded that EPA's costs represented an ``easy'' installation rather
than an average of both easy and more difficult installation costs. To
account for a wider range of fish return costs that includes those with
higher costs, EPA increased the capital costs of the fish return
component and included additional costs for those with particularly
difficult circumstances such as very long intake canals and submerged
offshore intakes. For a detailed discussion, see Chapter 8 of the TDD.
     EPA received a number of comments stating that it had
underestimated capital costs for modified traveling screens. During
site visits to several facilities, EPA obtained actual traveling screen
replacement costs. EPA compared its estimates to actual reported
replacement costs and vendor-supplied data and concluded that the
capital costs were underestimated by about 20 percent. Therefore, EPA
increased the capital costs of modified traveling screens by 20
percent.
    These changes to the engineering costs result in a 24 percent
increase in capital and O&M costs. The revised costing assumptions are
discussed in further detail in Chapter 8 of the TDD.
3. Monitoring Costs for Impingement Mortality
    Many commenters expressed concern that requirements for monitoring
for the impingement mortality performance standard were excessive. Of
particular concern were the long-term costs for impingement mortality
monitoring at facilities that would be relying on either closed-cycle
cooling or an intake velocity less than or equal to 0.5 fps through-
screen design velocity. The final rule includes seven compliance
alternatives for the impingement standard. One of these alternative
provides for reduced monitoring requirements for facilities employing
modified traveling screens. This alternative is available if the
facility has demonstrated the technology is optimized to minimize
impingement mortality of all non-fragile species. Under this approach,
EPA requires the facility to provide site-specific performance data to
identify the operational conditions that will ensure that the
technology is being operated optimally. Once these operational
conditions have been identified, the Director must include in the
permit those operational measures and best management practices
identified in the study and deemed as necessary by the Director to
ensure proper operation of the modified traveling screens. EPA also
clarified in the rule that compliance monitoring and reporting
requirements for facilities that comply with the impingement mortality
standard by employing one of the pre-approved or streamlined IM
compliance alternatives will be largely limited to information that
ensures proper operation of the installed control technology. EPA
estimates that this alternative approach will reduce annual monitoring
and reporting costs from approximately $47 million under the proposed
rule to approximately $27 million under the final rule.
4. Benefits and Willingness To Pay Survey
    EPA received a number of comments on the proposed rule and NODA
addressing the use of stated preference surveys to determine the
public's willingness-to-pay for benefits associated with the rule. EPA
conducted a stated preference survey to calculate benefits associated
with minimizing

adverse impacts to aquatic ecosystems from cooling water intakes. For
some commenters, the use of stated preference surveys to evaluate
benefits remains controversial, and they objected to using such
surveys. Other commenters acknowledge the decades of technical
development and improvement of these methods and support using stated
preference surveys. Based on consideration of public comment, EPA
decided not to employ the survey results for purposes of decision-
making in this rule, or include them in assessing the total benefits of
the rule. The rule does not require State Directors to require facility
owners or operators to conduct or submit a willingness to pay survey to
assess benefits.

B. Regulatory Approach and Compliance

1. Regulatory Approach
    EPA has largely adopted the regulatory approach of the proposed
rule with several changes regarding compliance, particularly with
respect to the impingement mortality requirements. These changes
clarify elements of the rule (as discussed in the NODAs) about which
commenters expressed uncertainty and provide additional flexibility to
regulated facilities in meeting the rule's impingement mortality
standard.
    EPA received some comments questioning whether specific provisions
apply to the entire facility or to individual intakes. To clarify this
issue, EPA modified the rule language so as to state clearly that a
facility with multiple intakes must decide whether it will adopt a
single compliance strategy for impingement mortality for the entire
facility or adopt an intake-specific compliance strategy at each
cooling water intake. Thus, facilities may select different compliance
strategies for different intakes, providing flexibility at facilities
with multiple intakes. Regardless of which impingement compliance
approach a facility chooses (single strategy for entire facility or
different strategies for different intakes), if the facility chooses to
comply with the impingement standard by operating at a maximum through-
screen velocity of 0.5 feet per second, the facility must measure and
comply with the low velocity compliance alternative of 0.5 fps on an
individual intake basis.
a. Impingement Mortality Standards
    EPA received a substantial number of comments requesting greater
flexibility and clarification regarding compliance with the impingement
mortality standards, including suggestions that (1) impingement
requirements be addressed on a site-specific basis; (2) certain
technologies should be pre-approved; (3) credit should be given for
existing technologies and operating conditions; and (4) combinations of
technologies be allowed. EPA has concluded that low-cost technologies
for impingement mortality reduction are effective, widely available,
feasible, and demonstrated for facilities nationally and thus, a
completely site-specific approach is not appropriate. However,
recognizing that for some sites technologies other than modified
traveling screens may allow a facility to achieve the same level of
performance, EPA has included compliance options that provide for more
flexibility and allow consideration of the performance of combinations
of technologies and operating conditions. Some of the more significant
changes include the following:
     Compliant technologies--EPA has concluded that employing
certain technologies will meet or exceed the requirement of the
impingement mortality standard, provided they meet certain design and
operational criteria. These pre-approved and streamlined technologies
include a closed-cycle recirculating system, existing offshore velocity
cap, and maximum design intake velocity of 0.5 fps. Associated with
these compliance options are reduced monitoring requirements.
    [cir] Closed-Cycle Cooling--EPA has concluded that a fully closed-
cycle recirculating system as defined at Sec.  125.92(c) (and that is
properly operated and maintained) achieves the impingement mortality
performance standard. Even after retrofitting a facility to be closed-
cycle, it may still be possible to withdraw and discharge cooling water
at rates associated with once-through cooling. Existing facilities that
retrofit to closed-cycle cooling often do so without modifying or
replacing their condenser to optimize it for closed-cycle operation. In
such cases, the facility has an incentive to operate its system in a
once-through cooling mode, to minimize chemical costs or avoid a
turbine backpressure constraint. EPA has concluded that it is not
appropriate to add conditions to the definition of closed-cycle cooling
because water may be withdrawn for purposes of replenishing losses to a
closed-cycle recirculating system other than those due to blowdown,
drift, and evaporation from the cooling system. However, the final rule
provides the Director the discretion to determine whether the operation
of a cooling system minimizes the make-up and blowdown flows withdrawn,
consistent with the definition of a closed-cycle recirculating system
(40 CFR 125.92(c)).

    [cir] Existing Offshore Velocity Caps--The record indicates that an
existing offshore velocity cap as defined at Sec.  125.92(v) also
achieves the necessary reductions in impingement mortality and thus
meets the IM standard. Data in the record concerning existing velocity
caps show that a velocity cap alone is insufficient, but data on
existing offshore velocity caps shows that a velocity cap in
combination with their current offshore locations meet EPA's BTA
standard for impingement mortality. EPA has determined that new
offshore velocity caps could comply using the combination of
technologies approach in Sec.  125.94(c)(6). The offshore component
likely makes the velocity cap technology unavailable except to
facilities in marine waters and certain Great Lakes locations;
therefore, the technology alone is not BTA.
    [cir] Through-Screen Velocity--EPA has clarified that compliance
with a 0.5 fps intake velocity achieves the IM standards. EPA's record
shows an intake velocity of 0.5 fps or lower provides similar or
greater reductions in impingement, and therefore impingement mortality,
than modified traveling screens--the technology forming the basis for
the numeric impingement mortality performance standard that is the goal
for all facilities. There are two ways to demonstrate compliance using
intake velocity. First, an intake with a maximum design intake velocity
less than or equal to 0.5 fps is pre-approved BTA for impingement
mortality and does not require further monitoring. Alternatively, under
a streamlined option, the facility may demonstrate to the Director that
the facility meets the velocity requirement through monitoring of the
actual intake velocity. Screen velocity can be monitored by direct
measurement or by calculation using the volumetric actual intake flow
and source water surface elevation.
     Modified Traveling Screens--A facility must operate
modified traveling screens \43\ that the Director determines meets the
definition at Sec.  125.92(s). Facilities will demonstrate that they
have optimized performance of their traveling screen to minimize IM.
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    \43\ While rotary screens are technically not modified traveling
screens, the regulation at Sec.  125.92(s) defines modified
traveling screens to include traveling water screens that
incorporate measures protective of fish and shellfish. EPA has thus
provided the flexibility for other types of active screens that
achieve the same or better performance than modified traveling
screens.

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     Systems of Technologies to Meet the IM Standard--EPA
received a substantial number of comments asking whether previously
installed technologies or various combinations of technologies and
operating conditions could also meet the BTA standard for impingement
mortality. For example, some technologies, such as louvers, reduce the
rate of impingement, but the effect on overall impingement mortality
reduction cannot easily be measured and would not appear in biological
sampling of the technology. In EPA's view, the Director should take
into account the reduction in impingement--for example, that associated
with such technologies as louvers or behavioral deterrents, or due to
intake location--when determining permit conditions to include in the
facility's permit in order for a combination of technologies to achieve
the required impingement mortality standards. Thus, the facility should
obtain credit toward the impingement mortality standard for such
reductions in the rate of impingement. A number of the flexibilities
above were described in the June 11, 2012 NODA, and EPA has included a
provision to allow additional flexibility in achieving compliance
through the use of a combination of technologies and operating
conditions. A facility may use a system of technologies, management
practices and operational measures to achieve the impingement mortality
standard, including, for example, flow reductions, seasonal operation,
unit closures, credit for intake location, behavioral deterrent
systems, and other technologies and operational measures. The Director
must determine, based on a demonstration by the facility to the
Director, that the system of technologies or operational measures, in
combination, have been optimized to minimize impingement mortality of
all non-fragile species. The Director may require additional
operational measures, best management practices, and monitoring as part
of the demonstration. In addition, the facility's permit must include
conditions to ensure that the facility operates its cooling water
intake structures in a manner consistent with the conditions and
measures identified in its demonstration to the Director.
     Numeric IM Performance Standard--As a practical matter,
EPA expects that very few facilities will choose to comply with the
numeric impingement mortality performance standard. Those facilities
that choose to comply in this way will need to demonstrate to the
Director how the technology the facility is implementing enables the
facility to meet the impingement mortality standard. The numeric
standard provides a pathway to compliance for innovative technologies
that may be developed in the future.
    EPA also received many comments stating that barrier nets were both
unnecessary and might be unavailable in many locations. Because EPA's
revised impingement data set had sufficient data to characterize
shellfish impingement, EPA has eliminated the barrier net requirement
in the final rule. See Section VI for more information.
b. Definition of Closed-Cycle Cooling System
    In the final rule, EPA revised the definition of a closed-cycle
recirculating system to provide additional flexibility for the Director
in determining which closed-cycle cooling systems comply with the IM
standards. The proposed rule's definition of ``closed-cycle
recirculating systems'' included, as elements of a properly operated
closed-cycle system performance, requirements generally expressed in
terms of cycles of concentration (COC) or percentage flow reduction
relative to a once-through cooling system. Cycles of concentration
represents the accumulation of dissolved minerals in the recirculated
cooling water. Discharge of a portion of the water (called
``blowdown'') is used to control the buildup of these minerals. COC is
a measure of how concentrated are chlorides in recirculated water
relative to make-up water, and thus how well a system recycles intake
water before replacing it with new withdrawals. This is not to be
confused with cycles of flow, as some commenters appeared to do.
    Cycles of concentration can be measured as the ratio of chloride
levels in the recirculated water or blowdown relative to the chloride
levels in the source water, or makeup water. Some commenters stated
that, while they have been operating as closed-cycle units for many
years, they were concerned that their facilities would not be ``closed-
cycle recirculating systems'' under the proposed definition because
they would not achieve the required COC. EPA has found the
concentration cycles in the majority of cooling towers usually range
from 3 to 6 at power plants, and can often exceed 9 at manufacturing
facilities. However, EPA recognizes that many manufacturers have
complex water balances, and calculating a specific flow reduction
attributable to cooling water use could be difficult and time
consuming. In such cases, many manufacturers could far more readily
calculate the cycles of concentration of particular unit operations,
and could therefore show those unit operations that use cooling water
meet the conditions for closed-cycle cooling. EPA found in site visits
many complex manufacturing facilities already have this capability, and
have achieved very high COC. Likewise, power plants may find it much
easier to measure flow than cycles of concentration. Accordingly, EPA's
proposed rule attempted to recognize performance using either metric.
EPA expects most power generators would use percentage flow reduction
to demonstrate they are closed-cycle, and expects most manufacturing
facilities would use COC for those units that utilize water for cooling
purposes. Increasing the amount of minerals present in the water by
cycling can make water less aggressive to piping; however, EPA is also
aware that excessive levels of minerals (such as found in certain
source waters, most notably those with higher salinity) can cause
scaling problems, leading to different levels of both metrics for
freshwater and saltwater facilities.
    EPA carefully considered these issues and concluded that the most
important aspect of the definition of a properly operated closed-cycle
cooling system is that the makeup flow be minimized. Thus EPA has
removed the numeric levels of the metrics as a threshold, while
retaining the minimized makeup flow aspect of the definition. As an
example, in the case of a facility that uses make-up water from a
freshwater source, a Director may determine that a closed-cycle
recirculating system can generally be deemed to minimize make-up and
blowdown flows if it reduces actual intake flows (AIF) by 97.5 percent
as compared to a once-through cooling system or if its cooling tower is
operated at a minimum cycles of concentration of 3.0. And likewise, in
the case of a facility that uses make-up water from a saltwater,
brackish, or other source with a salinity of greater than 0.5 parts per
thousand, a Director may determine that a closed-cycle recirculating
system can generally be deemed to minimize make-up and blowdown flows
if it reduces actual intake flows (AIF) by 94.9 percent as compared to
a once-through cooling system or if its cooling tower is operated at a
minimum cycles of concentration of 1.5. These reductions and cycles of
concentration are illustrative. A Director may determine that other
levels near these numbers could also constitute a closed-cycle
recirculating system. The final rule further recognizes that in certain
unavoidable circumstances, these levels for COC or percent flow
reduction might not be achievable at all facilities. Such circumstances
could

include situations where water quality-based discharge limits might
limit the concentration of a pollutant that is not readily treatable in
the cooling tower blowdown or situations where varying source water
quality could lead to unavoidable problems concerning scale formation,
solids buildup, corrosion, or media fouling. Such facilities should
demonstrate these circumstances to their Director and indicate the
measures they have taken to minimize makeup flows. The Director will
retain the discretion to conclude that the particular facility employs
a closed-cycle recirculating system when the benchmarks are not met.
    In cases where the Director will make a determination as to whether
the facility's cooling system meets the definition of a closed-cycle
recirculating system, EPA's intent is that the withdrawal of small
amounts of service water (for uses such as fire suppression, potable
water, screenwash water, vehicle wash water, and such) do not preclude
consideration of the system as closed-cycle. To avoid misuse of this
provision, the Director will make the final determination.
    Finally, EPA data show more than 50 facilities have cooling systems
that include impoundments. In some cases, the cooling systems that
include impoundments were created in the waters of the U.S., in whole
or in part, or were created in uplands but withdraw make-up water from
waters of the U.S. These cooling systems may perform like a closed-
cycle recirculating system. EPA has clarified at 40 CFR 125.92(c)(2)
that a cooling system that includes an impoundment lawfully created in
the waters of the U.S for the purpose of cooling may be considered a
closed-cycle recirculating system. As with other closed-cycle
recirculating systems, the Director will determine whether the
impoundment minimizes the withdrawal of water for cooling purposes and
therefore meets the definition of a closed-cycle recirculating system.
See Section VI for further discussion.
c. Entrapment
    The proposed rule included a prohibition on trapping organisms in
an intake structure with no viable escape route. Many commenters
expressed concern that the entrapment requirements were not well
defined and would require costly technologies not considered in EPA's
cost estimates. Moreover, in the commenters' view, the requirements
could be difficult to comply with, particularly where cooling systems
employ impoundments or basins downstream of the initial intake
structure. EPA agrees that in some cases, such as where a canal or
basin for maintaining consistent water levels is located behind the
CWIS, that the proposed entrapment requirement could require additional
controls such as additional fish returns that are not, in all cases,
feasible. For example, EPA found in site visits that the forebay may be
located more than a mile from the CWIS, and a fish return in that
situation would not have been feasible. The final rule deleted the
requirement that prohibited entrapment. In the final rule, facilities
would account for all impinged fish and shellfish when conducting their
two year performance study. To the extent entrapment of shellfish poses
a concern, the Director may establish additional measures, such as
seasonal deployment of barrier nets, under Sec.  125.94(c)(8).
d. Requirements for Threatened and Endangered Species
    EPA consulted with the Fish and Wildlife Service and National
Marine Fisheries Service and EPA made a number of adjustments to the
rule to protect threatened and endangered species and designated
critical habitat as a result of the consultation; the protections were
included to insure that the rule is not likely to jeopardize the
continued existence of listed species or result in the destruction or
adverse modification of designated critical habitat. To be clear, the
ESA provisions of the rule extend to all listed T&E species, not just
fish and shellfish. See Section VIII.K for a summary of these
provisions.
2. Compliance Timelines for Impingement Mortality and Entrainment
Requirements
    At proposal, compliance deadlines for impingement mortality and
entrainment requirements were set separately. Facilities would have
been required to meet impingement mortality reduction requirements as
soon as possible, but no more than eight years after the effective date
of the rule. Compliance with entrainment reduction requirements would
have been set by the Director. Many commenters expressed concern that
the compliance timeline for the impingement mortality and entrainment
requirements should be harmonized to prevent a facility from having to
install a technology to comply with impingement mortality requirements,
only to be required at a later date to install an entrainment reduction
technology that effectively renders the investment in the impingement
mortality technology obsolete or worthless.
    EPA agrees that facilities required to install both impingement and
entrainment compliance technologies will benefit from reduced
compliance costs if the compliance scheduling is coordinated. EPA also
agrees that requiring more timely decisions on entrainment requirements
than anticipated at proposal will facilitate these cost savings without
sacrificing fish protection. In some cases, impingement compliance can
be attained with entrainment technologies. For example, the Director
may determine that the installation of modified fine-mesh traveling
screens and narrow-slot wedgewire screens will achieve the impingement
mortality standard and further, that this same equipment represents, on
a site-specific basis, BTA entrainment control. If the compliance
schedule is not harmonized, it is possible that a facility could
install (at significant cost) coarse-mesh traveling screens that it
might have to later retrofit with fine-mesh panels. It is also possible
that a facility could make modifications necessary to attain a 0.5-fps
through-screen velocity to meet the IM standards and later have closed-
cycle cooling identified as BTA for entrainment, thereby making the
intake modifications for impingement control unnecessary.
    To address this issue in the final rule, EPA revised the compliance
requirements so that the Director is required first to establish
entrainment requirements under Sec.  125.94(b)(1) in the final permit.
The facility will then be required to comply with the impingement
mortality standard in Sec.  125.94(c) as soon as practicable
thereafter. See Section VIII on implementation for more detailed
discussion.
    Because an entrainment requirement could require controls that take
many years to design, finance and construct, the Director may establish
interim milestones related to meeting the final requirements to ensure
that the facility is making progress.

C. New Units

    EPA has revised the definition of new units to mean a stand-alone
unit at an existing facility the construction of which is commenced
after the effective date of today's final rule; consists of only a
stand-alone unit constructed at an existing facility; and that does not
otherwise meet the definition of a new facility at Sec.  125.83. A
stand-alone unit is a new, separate unit that is constructed at an
existing facility. New unit includes stand-alone units that are added
to a facility for purposes of the same general industrial operation as
the existing

facility. A new unit may have its own dedicated cooling water intake
structure, or may use an existing or modified cooling water intake
structure.

VI. Basis for the Final Regulation

    In response to the Supreme Court's decision in Entergy Corp. v.
Riverkeeper, Inc. et al. in April 2009, EPA has reevaluated the
requirements for existing facilities under CWA section 316(b). As
discussed above, EPA collected additional data and information to
update its assessment of the efficacy of various technological measures
for reducing IM&E and analyses prepared for the earlier rule-making
efforts. EPA's additional technical rigor provided a strengthened
analysis of different technologies for reducing IM and their
effectiveness. As a result of its revised assessments and further
consideration of the factors affecting the availability of different
technology in a wide range of settings, EPA has decided not to re-
promulgate requirements for existing facilities that mirror those of
the final Phase II rule. Further, EPA is adopting, for the reasons
explained in detail below, a new framework. In addition, as previously
noted, EPA decided to address all existing facilities subject to
section 316(b) in this rule (i.e., both those subject to the Phase II
rule and some of those subject to the Phase III rule). For a brief
description of the final rule, see Section IV.

A. EPA's Approach to BTA

    CWA section 316(b) requires EPA to establish standards for cooling
water intake structures that reflect the ``best technology available
for minimizing adverse environmental impact.'' As explained above, the
statute is silent with respect to the factors that EPA should consider
in determining BTA, but courts have held that section 316(b)'s
reference to CWA sections 301 and 306 is an invitation for EPA to look
to the factors \44\ considered in those sections in establishing
standards for section 316(b).
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    \44\ The factors specifically delineated in CWA sections 301 and
306 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).
---------------------------------------------------------------------------

    But EPA, when considering such factors, is not bound to evaluate
these in precisely the same way it considers them in establishing
effluent limitations guidelines under CWA section 304. As the Supreme
Court noted, given the absence of any factors specified in section
316(b), EPA has much more discretion in its standard setting under
section 316(b) than under the effluent guidelines provisions.
Therefore, the statute vests EPA with broad discretion in determining
what is the ``best'' technology that is ``available'' for minimizing
adverse environmental impact. As the Supreme Court has further
explained, under section 316(b), the ``best'' technology ``available''
may reflect a consideration of a number of factors and ``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,'' in the court's words)
technology may represent a technology that most efficiently produces
the reductions in harm.
    EPA interprets section 316(b) to require the Agency to establish a
standard that will best minimize impingement and entrainment--the main
adverse effects of cooling water intake structures not otherwise
addressed by the other sections of the CWA (e.g., thermal discharges).
In EPA's view, several important considerations underpin its decision.
First, its BTA determination should be consistent with, and reflective
of, the goals of CWA section 101: ``to restore and maintain the
physical, chemical, and biological integrity of the Nation's waters,''
with the interim goal of ``water quality which provides for the
protection and propagation of fish, shellfish, and wildlife and
provides for recreation in and on the water.''
    Second, E.O. 13563 directs EPA and other Federal agencies to
identify and use the best, most innovative and least burdensome tools
for achieving regulatory ends. In its regulatory actions, agencies
``must take into account benefits and cost, both quantitative and
qualitative,'' and to the extent permitted by law, only promulgate
regulations that are based on ``a reasoned determination that its
benefits justify its costs (recognizing that some benefits and costs
are difficult to quantify)'' (see section 1(b)(1)). In selecting a
regulatory approach, agencies must tailor regulations to impose the
least burden on society and, in choosing among regulatory alternatives,
select ``those approaches that maximize net benefits (including
potential economic, environmental, public health and safety, and other
advantages; distributive impacts; and equity)'' to the extent permitted
by law. 76 FR 3821 (January 21, 2011). Because the Supreme Court has
concluded that the CWA authorizes EPA to consider costs and benefits in
its BTA determination, EPA has consequently considered costs and
benefits in this final rule as directed by the President. In accord
with E.O. 13563, EPA has concluded that the benefits of the final rule
justify its costs. For additional discussion, see Section VI below.
    Consideration of benefits is complicated by the debate about the
tools and data that would permit a complete expression of ecological
benefits in monetized terms. EPA has, however, used the best available
science regarding widely accepted tools and data 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 Section X below). EPA has
concluded that the benefits estimated for the first two categories are
generally complete, while the benefits estimated for the latter two
categories are far from being complete for a number of reasons. For
example, the nonuse benefits transfer was based on a species that
represents less than one percent of adverse environmental impacts. EPA
is continuing to refine its tools to develop a more complete analysis
concerning benefits for future application.
    In selecting the ``best'' technology available for minimizing
adverse environmental impact, EPA looked at a number of factors. As
discussed previously, EPA's initial approach to 316(b) standard setting
was similar to one it follows in considering a technology-based rule
under sections 301, 304, and 306. EPA first considered the availability
and feasibility of various technologies, and then evaluated costs
associated with these technologies (including potential costs to
facilities and households), and their economic impacts. EPA also
reviewed the effectiveness of these technologies in reducing
impingement mortality and entrainment. Further, EPA also considered
additional factors set out in CWA section 304(b), including location,
age, size, and type of facility. In addition, EPA considered the non-
water quality environmental impacts of different technologies on energy
production and availability, electricity reliability, and potential
adverse environmental effects that could arise from the use of the
different technologies evaluated.
    As a result of this thorough evaluation, in the case of the BTA
standard for impingement mortality, EPA based the standard on
performance of well-operated modified traveling screens with a fish
handling and return system as defined more specifically by the rule.
Under the BTA IM standard, a facility has a number of options for

compliance. In the case of the BTA standard for entrainment, on the
other hand, EPA could not identify one technology that represented BTA
for existing facilities on a national basis.

B. Overview of Final Rule Requirements

    As noted, EPA concluded that the best technology available for
minimizing impingement mortality was ``modified traveling screens,'' as
more specifically defined in the rule. The BTA Impingement Mortality
Standard includes seven technology options for complying with the
standard whose performance is equivalent to, or better performing than
modified traveling screens. First, the rule identifies four
technologies (closed-cycle recirculating systems, reduced design intake
velocity, reduced actual intake velocity, and existing offshore
velocity caps) that reduce impingement mortality as well or better than
modified traveling screens, and therefore will generally comply with
the BTA Impingement Mortality Standard of today's final rule.
    The rule also provides that, if the Director determines that
modified traveling screens are insufficient to protect shellfish, the
Director may establish additional measures under Sec.  125.94(c)(8)
such as seasonal deployment of barrier nets, or if modified traveling
screens \45\ are insufficient to protect other species, the Director
may establish additional protective measures under Sec.  125.94(c)(9).
In addition, the rule provides in Sec.  125.94(g) that the Director may
establish additional control measures and monitoring or reporting
requirements in the permit in order to protect Federally-listed
threatened and endangered species and designated critical habitat. The
Director may include such conditions that are designed to minimize
incidental take, reduce or remove more than minor detrimental effects
to Federally-listed species and designated critical habitat or avoid
jeopardizing Federally-listed species and or destroying or adversely
modifying designated critical habitat (e.g., prey base).
---------------------------------------------------------------------------

    \45\ Or any of the IM compliance alternatives.
---------------------------------------------------------------------------

    Next, the final rule provides an option that allows a facility to
demonstrate to its permitting authority that it has installed modified
traveling screens--the technology EPA identified as the basis for the
BTA impingement mortality standard--and to provide data on the
performance of its screens. The facility must demonstrate that its
modified traveling screens are consistent with EPA's definition and
demonstrate through an impingement technology performance optimization
study that its screens have been optimized to minimize impingement
mortality. After consideration of the information provided, the
permitting authority will determine whether the technology is the best
technology available for impingement mortality reduction at the site
and include permit conditions to ensure optimal performance of the
screens. In other words, the owner or operator of a facility will
comply with the BTA standard for IM at Sec.  125.94(c)(5) if that
facility uses modified traveling screens as defined at Sec.  125.92(s),
and operates in accordance with the permit conditions established by
the Director that ensure the technology will perform as demonstrated.
As noted above, in certain circumstances, under Sec. Sec.
125.94(c)(8), (9) and 125.94(g), the Director may require additional
protective measures.
    As stated in the June 11, 2012 NODA, EPA does not intend for
facilities to install closed-cycle cooling solely for the purpose of
meeting the IM requirements. In fact, EPA expects all facilities could
comply with IM requirements without relying on retrofitting to closed-
cycle cooling (see Exhibit VIII-1, showing expected compliance
alternative based on technologies in place today). If a facility
chooses to comply with the BTA IM standard by installing and operating
traveling screens, the screens must meet the definition of modified
traveling screens provided at Sec.  125.92(s). These may include, for
example, modified Ristroph screens with a fish handling and return
system, dual flow screens with smooth mesh, and rotary screens with
fish returns such as vacuum pumps. EPA based the regulatory definition
on the commonly found features of modified traveling screens used in
developing the BTA impingement mortality standard.
    In addition, the final rule also provides a compliance option that
would allow facilities the option of demonstrating to the Director on a
site-specific basis, similar to the showing for modified traveling
screens, that a system or combination of technical and operational
measures will achieve the BTA standard for impingement mortality at a
particular site. Using a combination of technical and operational
measures as the basis for demonstrating compliance allows facilities
the opportunity to take credit for intake location, flow reduction, or
other measures already employed to reduce the rate of impingement.
Further, the combination of technical and operational measures provides
the flexibility to use a system of approaches to reducing impingement
and impingement mortality. This may include technologies that were not
found to reduce impingement consistently or in all circumstances, but
that on a site-specific basis have been demonstrated to provide a high
level of performance. For example, a facility might employ light and
sound to induce an avoidance response from certain species. This might
not alone address impingement mortality for all non-fragile species at
the intake, therefore additional measures (intake location, barrier
nets, etc.) would also be applied, to minimize the rate of impingement
or impingement mortality.
    For both the screens and system of technologies, a two year study
must be completed in which biological data collection is used to make
site-specific adjustments to screens or the combination of technologies
in order to optimize performance at that facility. Those optimal
operating parameters then become permit conditions. For facilities that
have already installed traveling screens or the technologies associated
with the system approach, EPA has combined the two year biological
study with the other permit application and rule requirements for
biological data collection, including the Source Water Baseline
Biological Characterization Data. In this manner, EPA is establishing a
consistent set of biological study requirements, with an overall
reduction in the burden of the required level of biological monitoring.
    Lastly, a facility may choose to comply with the numerical
impingement mortality performance standard that was established based
on the BTA technology. If a facility chooses this compliance option, it
must conduct periodic monitoring to demonstrate compliance. Under this
last compliance option, a facility could implement innovative
technologies to address impingement mortality and subsequently
demonstrate that their performance is as good as, or better than, a
modified traveling screen with fish handling and return system. EPA
envisions that after a sufficient demonstration period of a
technology's performance, the facility will be able to qualify its
operation under the previous option.
    For entrainment, on the other hand, EPA could not identify one
technology that represented BTA for existing facilities on a national
basis, for the reasons explained in detail below. Instead, the national
BTA entrainment standards for existing facilities establishes a
detailed regulatory framework for the determination of BTA

entrainment requirements by the permitting authority on a site-specific
basis.
    While site-specific permit requirements are not new, what is
different about this approach from the current requirement for permits
to include 316(b) conditions is that for the first time, EPA is
establishing a detailed specific framework for determining BTA
entrainment control requirements. Thus, the rule identifies what
information must be submitted in the permit application, prescribes
procedures that the Director must follow in decision making and factors
that must be considered in determining what entrainment controls and
associated requirements are BTA on a site-specific basis.
    As previously noted, EPA looked at a number of factors in
considering what national entrainment standard it should adopt. As
discussed in detail in the following section, EPA identified only one
high performing technology as a potential BTA candidate for
entrainment: closed-cycle recirculating systems as defined at Sec.
125.92(c)(1). While there are other technologies for entrainment that
are available or demonstrated, they are not uniformly high performing
technologies. See TDD Chapter 6 for more information regarding the lack
of intermediate performing technologies for entrainment. EPA has
identified the following specific factors as the key elements in its
decision not to prescribe this technology as the basis for a national
BTA standard for entrainment: land availability, air emissions, and
remaining useful plant life. How these factors dictated EPA's decision
is discussed below.
    For new units at existing facilities, EPA has established BTA
requirements to minimize impingement mortality and entrainment, based
on flow reduction commensurate with closed-cycle cooling. The rest of
this section describes in detail the above considerations.

C. Technologies Considered To Minimize Impingement and Entrainment

    As described in Chapter 4 of the TDD, power plants and
manufacturers withdraw large volumes of cooling water daily. Cooling
water withdrawals are responsible for over half of surface water
withdrawals for all uses in the United States, including agriculture
and municipal uses. The purpose of cooling water withdrawals is to
dissipate that portion of the heat that is a by-product of industrial
processes that facilities have not harnessed to a productive end and
therefore view as waste heat.
    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 might be from impingement,
entrainment, or both. Impingement occurs when organisms are trapped
against the outer part of a screening device of an intake
structure.\46\ The force of the intake water traps the organisms
against the screen and they are unable to escape. Not all organisms in
the incoming water are impinged, however. Some might pass through the
screening device and travel through the entire cooling system,
including the pumps, condenser or heat exchanger 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 the associated
mortality and other effects, see Section III above.
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    \46\ Typically, cooling water intake structures use various
screening devices to prevent objects (e.g., debris, trash) from
being drawn in with the cooling water and ultimately clogging or
damaging the cooling water system, especially the condenser or heat
exchanger components.
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    For purposes of this rule, EPA is adopting the following
conventions for defining impingement and entrainment and mortality:
     Impingement: Occurs when any life stage of fish and
shellfish are pinned against the outer part of an intake structure or
against a screening device during intake water withdrawal. Impingement
may also occur when an organism is near a screen but unable to swim
away from the intake structure because of the water velocity at the
intake.
     Entrainment: Occurs when any life stages of fish and
shellfish are drawn into the intake water flow entering and passing
through a cooling water intake structure and into a cooling system.
     Impingement Mortality: The death of fish or shellfish due
to impingement. It may also include organisms removed from their
natural ecosystem and lacking the ability to escape the cooling water
intake system and thus subject to mortality. Note that impingement
mortality need not occur immediately. Impingement may cause harm to the
organism which results in mortality at some time after impingement. For
purposes of this rule, EPA has defined impingement mortality as the
death of those organisms collected or retained by a sieve with a
maximum opening of 0.56 inches; this includes both the \3/8\-inch sieve
and a \1/2\-inch by \1/4\-inch mesh.\47\
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    \47\ Mesh sizes of \3/8\ are commonly referred to as
coarse mesh; this refers to the size of the screen opening (in
contrast to fine mesh) and not the roughness of the mesh material.
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     Entrainment Mortality: The death of fish or shellfish due
to entrainment. This is typically associated with mortality related to
small organisms that pass the entire way through a facility and are
killed as a result of thermal, physical, or chemical stresses. This
term also includes the death of those fish and shellfish that may occur
on fine mesh screens or other technologies used to exclude the
organisms from entrainment. For purposes of this rule, EPA defined
entrainment mortality as the death of those organisms passing through a
sieve with a maximum opening of 0.56 inches.
    Impingement mortality is typically less than 100 percent of the
impinged organisms if a fish return or backwash system is employed.
Impingeable organisms are generally not very small fish or early life
stages (e.g., those that can pass through \3/8\-inch mesh screens), but
typically are fish with fully formed scales and skeletal structures and
well-developed survival traits such as behavioral responses to avoid
danger. EPA's data demonstrate that, under the proper conditions, many
impinged organisms can survive.
    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 after hatching. EPA has found that
entrainable organisms that are collected after interaction with the
CWIS show poor survival in the case of most eggs, and essentially no
survival of larvae. Consequently, on the basis of the record
information it has reviewed, EPA concluded for purposes of this rule
that all entrained organisms die, i.e., no entrained organisms survive.
(See, for example, 76 FR 22188 [April 20, 2011] and 69 FR 41620 [July
9, 2004].) Therefore, without 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).
    Whether an organism near a cooling water intake structure is
impinged or entrained is a function of the screen mesh size. Holding
the number and size distribution of organisms at the intake constant, a
larger screen mesh size will result in relatively more entrainment,
while a smaller mesh size will result in

relatively more impingement. Historically, traveling screens deployed
by power plants used 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. 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 composed of eggs, larvae, and smaller
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
because 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 toward the larger (older) larvae with
higher survival rates and do not analyze survival of smaller larvae.
This bias implies a focus on larvae body lengths sufficient to have
begun scale and bone development, and it generally reflects the more
motile early life stages. EPA found that these study findings cannot be
applied to smaller and less motile life stages, which are incapable of
avoidance responses. It is also important to note that preventing
entrainment by some exclusion technologies might result in very high
entrainment reductions by converting entrainment to impingement, but
these impinged organisms may have an even lower likelihood of surviving
impingement than larger potentially impinged organisms. 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 uses the \3/8\-inch mesh size as part of the definition of
impingement mortality and entrainment mortality as a means of clearly
differentiating those organisms that might be susceptible to
impingement or entrainment, and thereby avoids any confusion over the
status of impinged entrainables or ``converts.''
    Generally, two basic approaches can be used to reduce impingement
mortality and entrainment. The first approach is flow reduction, where
the facility installs a 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 impingement and
entrainment and, therefore, reduced impingement mortality and
entrainment mortality. It should be noted that, at electric generators,
flow reduction could be achieved, perhaps most effectively, by
installing more energy efficient production, thereby requiring less
cooling per unit of electricity generated. The second way to reduce
impingement and entrainment is to install technologies or operate in a
manner that either (1) gently excludes organisms or (2) collects and
returns organisms without harm. Exclusion technologies or practices
divert those organisms that would have been subject to impingement and
entrainment away from the intake. Collection and return technologies
are installed to collect and return organisms to the source water,
allowing impingement to occur but possibly preventing impingement
mortality.
    Although not available to all facilities, two other approaches to
reducing impingement and entrainment are (1) relocating the facility's
intake to a less biologically rich area in a waterbody, and (2)
reducing the intake velocity. Relocating an intake farther from shore
or at greater depths can be effective at entrainment reduction but is
not available to many inland facilities because the distance or depths
required to reach less biologically-productive waters are not generally
available. Further, while a far offshore intake may exhibit a lower
density of organisms, the species found will change as a function of
distance from the shoreline as well as depth in the water column.
Therefore, it may not always be desirable to relocate an intake
structure. A reduced intake velocity provides motile organisms the
opportunity to swim away from the intake structure. This approach can
be very effective in reducing impingement but has no effect on
entrainment.
    Sections 1 and 2 below further describes flow-reduction and
exclusion technologies.
1. Flow Reduction
    Flow reduction is commonly used to reduce impingement and
entrainment. For purposes of this rulemaking, EPA assumes that
entrainment and impingement (and associated mortality) at a site are
proportional to source water intake volume. Thus, if a facility reduces
its intake flow, it similarly reduces the amount of organisms subject
to impingement and entrainment.\48\ Some common flow reduction
technologies are variable frequency drives and 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 Chapter 6 of 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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    \48\ 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 a reduction in flow results in a proportional
reduction in entrainment, 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 (for a
discussion of proportional flow requirements in the Phase I and II
rules see, e.g., 66 FR 65276 and 69 FR 41599; also see EPA's 1977
draft guidance manual for 316(b), available at DCN 1-5045-PR from
the Phase I docket) and continues to assume that it is broadly
applicable on a national scale and is an appropriate assumption for
a national rulemaking. EPA recognizes that this assumption does not
necessarily apply when relocating or varying the time pattern of
withdrawals, such that these may be effective strategies to reduce
impingement and entrainment in some locations.
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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 periods. The pump speed
can be adjusted to reduce water withdrawals when cooling water needs
are reduced, such as when ambient water temperatures are colder (and
therefore capable of dissipating more heat), when fewer generating
units are operating or when fuel is more efficiently burned. In site
visits, EPA found that variable drives and pumps were typically used at
units operating below capacity, such as load-following units. EPA
estimates that facilities with intermittent water withdrawals could
achieve a 5 to 10 percent reduction in flow.\49\ For this reason, many
baseload generating units and continuously operated manufacturing
processes will obtain limited reductions in flow from using these
technologies. EPA is further aware that some facilities may 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. As a result, EPA determined that
variable frequency drives and variable speed pumps, while useful in
specific setting and circumstances, are not BTA candidates because the
flow reduction technologies have limited application and availability,
and are not a high performing technology as an entrainment control
measure.
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    \49\ Withdrawals of colder water could allow facilities to
reduce their intake flow using variable drives and pumps, but EPA
does not have data on the efficacy or availability of this approach.
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b. Seasonal Operation or Seasonal Flow Reductions
    Seasonal operation or seasonal flow reduction refers to the
reduction or elimination of a quantity of water withdrawn either during
periods of low demand for electricity output, or to coincide with
certain biologically important periods. Most facilities that currently
employ seasonal flow reductions do so to limit thermal impacts or to
reduce entrainment, because entrainment often has a peak season,
particularly during a local spawning season. Freshwater drum, for
example, perform broadcast spawning during early summer when water
temperatures reach about 65 degrees Fahrenheit.
    During specific peak entrainment periods, a facility could scale
back its operation (or perhaps not operate at all), thereby reducing or
eliminating the volume of cooling water withdrawn. This could be
accomplished through a combination of variable speed pumps or shutting
down some portion of the pumping system. Seasonal flow reduction could
also consist of operating a closed-cycle recirculating system as
defined at Sec.  125.92(c)(1) as once-through during part of the year
and as a closed-cycle system during the peak entrainment season. (EPA
notes that closed-cycle cooling has been rejected as noted in the
previous section, and discussed in more detail below.) Facilities could
also choose to schedule regular maintenance to occur during these high
entrainment 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. Through site visits, EPA
gathered information on species present at facilities and has
identified some sites where entrainment appears to be significant all
year long, and other sites where peak entrainment occurs in as few as
three to four months of the year.\50\ However, if all power-generating
facilities in a local area were to stop operating at the same time,
there could be difficulty in supplying electricity to the area.
Therefore, EPA concluded that seasonal operations have limited
nationwide application for controlling entrainment and are thus not
widely available entrainment reduction technology.
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    \50\ See DCN 10-6702 and its attachments for examples of
spawning ``seasons.''
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    Impingement is generally more sporadic, less predictable, and more
difficult to address with seasonal operation. For example, clupeid
species, such as gizzard shad, experience impingement episodes
sporadically throughout the winter and spring during periods of
especially cold water temperatures, or sporadically throughout the
summer and fall during periods of low dissolved oxygen.
c. Unit Retirements
    Some power plants units have been retired and others have
essentially ceased all operations but have not been formally retired or
decommissioned. The reasons for their inactivity vary,\51\ but the end
result is the facility no longer needs 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