[Federal Register Volume 77, Number 112 (Monday, June 11, 2012)]
[Proposed Rules]
[Pages 34315-34326]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-14153]



40 CFR Parts 122, 123, 124, and 125

[EPA-HQ-OW-2008-0667, FRL-9681-4]
RIN 2040-AE95

National Pollutant Discharge Elimination System--Proposed 
Regulations to Establish Requirements for Cooling Water Intake 
Structures at Existing Facilities; Notice of Data Availability Related 
to Impingement Mortality Control Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of Data Availability.


SUMMARY: On April 20, 2011, EPA published proposed standards for 
cooling water intake structures at all existing power generating 
facilities and existing manufacturing and industrial facilities as part 
of implementing section 316(b) of the Clean Water Act (CWA). As a 
result of that notice, EPA received extensive comments on its proposal. 
These comments included a substantial amount of new information 
accompanied by reports, studies and other documents often supplemented 
with the substantiating data. In some cases, the materials may not have 
included the underlying data supporting the documents' conclusions. 
Consequently, in many circumstances, EPA contacted the commenters to 
obtain the raw data underlying the documents for EPA's use in further 
assessing its proposal. This notice presents a summary of the 
significant new information and data EPA has received since proposal 
and a discussion of possible revisions to the final rule that EPA is 
considering that were suggested by the data and comments. EPA solicits 
public comment on the data and possible revisions presented in this

[[Page 34316]]

notice and the record supporting this notice.

DATES: Comments must be received on or before July 11, 2012.

ADDRESSES: Submit your comments, identified by Docket No. EPA-HQ-OW-
2008-0667 by one of the following methods:
     http:www.regulations.gov: Follow the on-line instructions 
for submitting comments.
     Email: [email protected], Attention Docket ID No. EPA-HQ-
     Mail: Water Docket, U.S. Environmental Protection Agency, 
Mail Code: 4203M, 1200 Pennsylvania Ave. NW., Washington, DC 20460. 
Attention Docket ID No. EPA-HQ-OW-2008-0667. Please include a total of 
3 copies. In addition, please mail a copy of your comments on 
information collection provisions to the Office of Information and 
Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk 
Officer for EPA, 725 17th St. NW., Washington, DC 20503.
     Hand Delivery: Water Docket, EPA Docket Center, EPA West 
Building Room 3334, 1301 Constitution Ave. NW., Washington, DC, 
Attention Docket ID No. EPA-HQ-OW-2008-0667. Such deliveries are only 
accepted during the Docket's normal hours of operation, and special 
arrangements should be made for deliveries of boxed information by 
calling 202-566-2426.
    Instructions: Direct your comments to Docket No. EPA-HQ-OW-2008-
0667. EPA's policy is that all comments received will be included in 
the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Information that you consider to 
be CBI or otherwise protected should not be submitted through 
www.regulations.gov or email. The www.regulations.gov Web site is an 
``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an email comment directly to EPA without 
going through http://www.regulations.gov your email address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Water Docket in 
the EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution 
Ave. NW., Washington, DC. The Public Reading Room is open from 8:30 
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The 
telephone number for the Public Reading Room is 202-566-1744, and the 
telephone number for the Water Docket is 202-566-2426.

FOR FURTHER INFORMATION CONTACT: For additional technical information, 
contact Paul Shriner at 202-566-1076; email: [email protected]. For 
additional economic information, contact Erik Helm at 202-566-1049; 
email: [email protected] or Wendy Hoffman at 202-564-8794; email: 
[email protected]. For additional biological information, contact 
Tom Born at 202-566-1001; email: [email protected].


Supporting Documentation

A. Docket

    EPA has established an official public docket for this action under 
Docket ID No. EPA-HQ-OW-2008-0667. The official public docket consists 
of the documents specifically referenced in this action, any public 
comments received, and other information related to this action. 
Although a part of the official docket, the public docket does not 
include information claimed as Confidential Business Information (CBI) 
or other information for which the disclosure is restricted by statute. 
For information on how to access materials in the docket, refer to the 
preceding ADDRESSES section. To view docket materials, please call 
ahead to schedule an appointment. Every user is entitled to copy 266 
pages per day before incurring a charge. The Docket may charge 15 cents 
for each page over the 266-page limit plus an administrative fee of 

B. Electronic Access

    You may access this Federal Register document and the docket 
electronically, as well as submit public comments, through the Web site 
http://www.regulations.gov by searching for Docket ID No. EPA-HQ-OW-
2008-0667. For additional information about the public docket, visit 
the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.

Table of Contents

I. Purpose of This Notice
    A. Summary of Proposed Rule for Existing Facilities
II. New Information Received Concerning Proposed Impingement 
Mortality (IM) Requirements
    A. New Information Received
    B. Alternative Approaches Under Consideration
    1. Site Specific Approach for Reducing Impingement Mortality
    2. Closed-Cycle Recirculating Systems
    3. Measurement of Intake Velocity
    4. Impingement Mortality Limitations
    5. Credit for Existing or Newly Installed Technologies
    6. Facilities With Low Impingement Rates
    7. Species of Concern
III. General Solicitation of Comment

I. Purpose of This Notice

    On April 20, 2011, EPA published proposed standards for cooling 
water intake structures at all existing power generating facilities and 
existing manufacturing and industrial facilities as part of EPA's 
implementation of its responsibilities under section 316(b) of the 
Clean Water Act (CWA) (76 FR 22174). EPA received voluminous comments 
and data submissions during the 90-day public comment period. After 
many commenters requested additional time to review the proposal, on 
July 20, 2011, EPA extended the comment period by an additional 30 days 
(76 FR 43230).
    Along with the comments on the proposal, EPA also received more 
than 50 documents containing new impingement and entrainment data. In 
addition, after the comment period ended, EPA followed up with those 
commenters whose comments referred to studies or summarized data in 
their comments, but had not submitted the underlying studies or raw 
data referenced in their comments. As a result, these commenters also 
provided over 30 additional documents containing new impingement and 
entrainment data. EPA is reviewing each of these roughly 80 documents 
for possible use in developing the final

[[Page 34317]]

impingement mortality limitations. This notice makes these data 
available and discusses the relevance of these data to the analyses 
conducted by EPA. EPA solicits comment both on the information 
presented in this notice and the record supporting this notice.
    EPA requested comment on all aspects of the proposed existing 
facility rule, including specific solicitation of comments and data on 
28 key issues (76 FR 22174, Section XI). EPA received more than 1,100 
comment letters, several of which provided specific recommendations for 
changes to the proposed regulatory language. Some of the suggested 
revisions, if adopted, may help to address EPA's intent to greatly 
reduce the damage to ecosystems while accommodating site specific 
circumstances and providing cost effective options for compliance. Some 
of these suggestions relate to the impingement mortality standard, and 
are discussed in this notice along with accompanying new data.
    EPA notes that all data and options and issues discussed in its 
proposal are still under consideration for the final rule. This notice 
is intended to apprise the public of the new information, make this 
information available for public review and provide an opportunity to 
comment on the new information that the Agency will consider in making 
its decisions for the final rule. However, EPA notes that the Agency is 
not reopening the proposed rule for comment through this notice.

A. Summary of Proposed Rule for Existing Facilities

    The proposed rule would establish requirements under section 316(b) 
of the Clean Water Act (CWA) for all existing power generating 
facilities and existing manufacturing and industrial facilities that 
withdraw more than 2 million gallons per day (MGD) of water from waters 
of the U.S. and use at least 25 percent of the water they withdraw 
exclusively for cooling purposes. The proposed national requirements, 
which would be implemented through National Pollutant Discharge 
Elimination System (NPDES) permits, would establish national 
requirements applicable to the location, design, construction, and 
capacity of cooling water intake structures at these facilities by 
setting requirements that reflect the best technology available (BTA) 
for minimizing adverse environmental impact. The proposed rule responds 
to the remands of the Phase II existing facility rule and the existing 
facilities portion of the Phase III rule from the U.S. Courts of 
Appeals for the Second Circuit and Fifth Circuit. In addition, EPA 
responded to the decision in Riverkeeper, Inc. v. EPA, 358 F.3d 174 (2d 
cir. 2004) and proposed to remove from the Phase I new facility rule 
the restoration-based compliance alternative and the associated 
monitoring and demonstration requirements.
    The proposed rule provided significant flexibility in complying 
with the proposed technology standards for impingement and entrainment. 
For the proposal, EPA concluded that the best technology available for 
reducing impingement mortality was modified travelling screens. Based 
on this BTA technology, EPA proposed standards for impingement that 
would require existing facilities to reduce impingement mortality. The 
owner or operator of the facility would be able to choose one of two 
options to comply with the impingement standard. Under the first 
option, a numeric fish impingement mortality limitation, the owner or 
operator would have to sample to measure fish mortality directly to 
show it will meet the specified mortality performance standards. The 
owner or operator could use any appropriate technology to meet the 
standard. Under the second option, a velocity limitation, a facility 
would have to demonstrate to the permitting authority that its maximum 
intake velocity will not exceed 0.5 feet per second under specified 
design conditions. Operation of its intake system in compliance with 
these specified design conditions would become part of the facility's 
permit requirements. EPA estimated that more than half of the 
facilities that could be impacted by the proposed rule already employ 
readily available technologies that are likely to put them into 
compliance with the proposed standard.
    For entrainment, EPA proposed a site-specific determination to be 
made by the Director based on local concerns and on the unique 
circumstances of each facility. The proposed rule would establish 
requirements for the owner or operator of a facility with actual intake 
flows in excess of 125 MGD to conduct comprehensive studies, and for 
all facilities to develop certain information as part of the permit 
application. Under the procedures proposed to be established in the 
proposal, the permit authority would determine the appropriate 
technology to reduce entrainment mortality, if any, to be implemented 
at each facility after considering site-specific factors.

II. New Information Received Concerning Proposed Impingement Mortality 
(IM) Requirements

    EPA received a substantial number of comments on how the final rule 
should address impingement mortality (IM). EPA based its proposed 
national impingement mortality limitations on the performance of 
modified traveling screens. And, as noted above, as an alternative EPA 
proposed that a facility could demonstrate that either the design 
intake velocity or the actual intake velocity at its operation was less 
than 0.5 feet per second. Most of the commenters, including members of 
the U.S. Congress, state and local elected officials, and industry 
stakeholders, requested additional flexibility in complying with the IM 
    While the proposal would not specifically require the use of 
modified traveling screens with a fish handling and return system to 
meet the IM limits, some commenters interpreted the proposed rule as 
requiring this. EPA's proposed IM limits are expressed as a monthly 
average and an annual average. A facility could meet the limitation 
through any technology it chose. In EPA's view, this approach is a more 
flexible one than establishing a design standard (i.e., requiring a 
specific technology) because it would allow facilities to choose a 
compliance technology that best meets the individual facility 
requirements dictated by site and other conditions. Further, such an 
approach allows for innovation in meeting the national impingement 
mortality limitations. EPA recognizes, however, that some regulated 
entities may find a technology-based compliance option, rather than a 
performance based approach, more attractive. Such an approach, 
particularly the specification of pre-approved technologies, may offer 
higher regulatory certainty, easier demonstration of compliance, and 
may offer a less expensive alternative due to reduced monitoring 
requirements associated with pre-approved technologies. Some commenters 
viewed the proposed IM standard as overly stringent and requested that 
EPA establish alternative IM requirements, including site-specific IM 
requirements similar to those proposed for entrainment. Other 
commenters provided data pertaining to the performance of technologies, 
including modified traveling screens used as the basis for the IM 
    EPA reviewed all the performance data submitted. EPA is considering 
these performance data in its evaluation of BTA, including likely 
revisions to the IM annual and monthly numeric limits, different 
approaches that may better streamline compliance, and additional 
options that would better facilitate a demonstration of performance 
that is equivalent to the proposed BTA. EPA

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also received several comments that proposed alternative regulatory 
approaches or provided specific alternative regulatory language. EPA is 
also reviewing these comments and considering the alternative 
regulatory approaches suggested. The data received and corresponding 
issues are described in more detail in the following sections.

A. New Information Received

    As discussed in section I, EPA received more than 80 additional 
documents containing impingement and entrainment data. In some cases, 
the only data available was the facility name plus raw sampling data 
for a number of different species of fish and/or shellfish. Other 
documents focus on source water characterization data. EPA identified 
more than 40 distinct sets of additional impingement sampling and 
performance data from these documents. EPA is reviewing the data in 
each of these documents for potential inclusion in EPA's evaluation of 
an IM limitation. In light of these data and accompanying comments, EPA 
is also reviewing the criteria it adopted for including a study in the 
limit calculations. EPA's proposed criteria were described in Chapter 
11 of the Technical Development Document (DCN 10-0004, EPA-HQ-OW-2008-
    In addition to the new impingement and entrainment data, some 
stakeholders suggested alternative regulatory frameworks for 
impingement mortality. Under the proposed rule, a facility would be 
permitted to adopt any technology it chooses so long as it will achieve 
the required impingement limitation. Thus, a facility could demonstrate 
the reductions in impingement mortality by either (1) increasing the 
survival of those fish and shellfish that are impinged, or (2) by 
reducing the fish and shellfish impingement rates in the first place. 
EPA had concluded, based on the information it reviewed, that the 
design standards pertaining to intake velocity would achieve the 
impingement mortality limitations, and proposed such design criteria as 
having met the impingement mortality limitation. Therefore, compliance 
with intake velocity limitation would achieve full compliance with the 
numeric impingement mortality limitations and no additional control 
technology would be required.
    Several industry stakeholders stated that, despite EPA's best 
intentions, the proposed rule applied a one-size-fits-all approach for 
impingement mortality. While all of the suggested changes to the 
proposal seek to provide additional flexibility through a variety of 
approaches, most of the comments had several elements in common:
     Commenters suggested defining modified traveling screens 
as a pre-approved technology or otherwise streamlining the NPDES 
process for facilities using the candidate technology upon which BTA is 
based. Thus, EPA would designate certain technologies or certain 
conditions as complying with the impingement requirement;
     Providing a mechanism to identify other technologies that 
perform comparably to modified traveling screens;
     Modifying the proposal so that facilities that have 
already reduced the rate of impingement may obtain credit towards the 
IM limit;
     Developing a more tailored approach to protecting 
     Creating alternatives for facilities with very low 
impingement levels or mortality rates; and
     Providing additional clarity on species of concern as it 
pertains to demonstrating compliance with the IM limitations.
    In addition, as noted above, EPA also received a number of comments 
suggesting that it adopt a site-specific approach to reducing 
impingement mortality similar to the proposed approach for addressing 
entrainment, rather than uniform national requirements for IM and a 
site-specific approach for entrainment only. Should EPA decide to adopt 
uniform national performance or technology based standards for IM, as 
in the proposal, EPA is also considering a number of flexibilities, 
such as the site-specific approach for measuring compliance with IM 
limits detailed in section III.B.4 below. EPA also received requests to 
meet with or hold conference calls with a number of stakeholders to 
discuss each of these approaches. The stakeholders with whom EPA met 
include the Utility Water Act Group (UWAG), the Clean Energy Group 
(CEG), the Cooling Water Intake Structure Coalition, the Association of 
Clean Water Administrators (ACWA), and Riverkeeper, as well as several 
individual firms and companies. Documentation of these meetings may be 
found in EPA's docket (11-6500). The following sections present the 
data and suggested approaches EPA may use in developing the final rule.

B. Alternative Approaches Under Consideration

1. Site Specific Approach for Reducing Impingement Mortality
    EPA received a number of comments suggesting that it adopt a site 
specific approach for both IM and entrainment, rather than uniform 
national requirements for IM and a site-specific approach for 
entrainment only. At proposal, EPA considered an approach that would 
establish both impingement and entrainment mortality requirements on a 
case-by-case basis taking into account the factors at a particular 
facility, but did not propose such an approach based on its preliminary 
determination at proposal that there are low cost technologies for 
impingement mortality that are available, feasible, and demonstrated 
for facilities on a national basis (76 FR 22174, Section VI.D.4). EPA 
recognizes both advantages and disadvantages of uniform national 
requirements. Such requirements would ensure a minimum level of IM 
reduction at all facilities. Moreover, if the final rule provides 
additional flexibility such as those measures discussed in Section 
III.B.3, it is EPA's understanding, based on comments received and its 
own technical analysis, that a substantial majority of the industry 
would meet the IM limitations based on model technologies considered by 
the Agency (see Section III.B.3 for more information). However, uniform 
national requirements may also be challenging to implement on a 
national level, given the wide range of facility types and intake 
structure configurations covered by the rule. Commenters stated that in 
some cases the technologies available for a particular site may not be 
able to achieve the IM limitations. Commenters further stated that, in 
certain circumstances, the costs of impingement technologies may be 
unusually high due to site-specific factors. EPA is now considering 
whether to adopt an approach that would allow establishment of 
impingement controls on a site-specific basis either generally or 
limited to those circumstances in which the facility demonstrated that 
the national controls were not feasible. Under such an approach, the 
facility could demonstrate to the Director that site-specific factors 
warrant a site-specific BTA for both entrainment and IM. The 
comprehensive study and other planning requirements could be enhanced 
to include information that the permitting authority would use to 
determine site-specific BTA for both entrainment and IM. The decision 
criteria for choosing BTA would be the same for IM and for entrainment, 
and EPA expects that permitting authorities and facilities would view 
the two together in an integrated planning and decision making 
framework. EPA requests comment on such an approach

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and further information on why uniform controls should not be adopted.
2. Closed-Cycle Recirculating Systems
    EPA received a number of comments suggesting that a facility (or 
intake) employing a cooling tower as a closed-cycle recirculating 
system (CCRS) should be exempt from IM requirements. EPA did not 
propose that a facility that fully employs cooling towers would 
automatically meet the IM standards for a number of reasons. First, the 
largest facilities with wet cooling towers still have the potential to 
withdraw significant volumes of water; in some cases, 100 MGD or more 
in makeup water alone. Second, at proposal, EPA did not provide an 
additional alternative that specifically established cooling towers as 
a pre-approved technology for complying with the IM limits because data 
from EPA's industry questionnaire and site visits indicate that most 
intakes providing cooling water to a cooling tower already met the 
proposed intake velocity limitation of less than or equal to 0.5 feet 
per second [DCN 11-6601].\1\ Further, based on the performance observed 
in site visits and questionnaires, EPA anticipated that a properly 
operated cooling tower installed as a retrofit would typically meet the 
proposed intake velocity limitation alternative.\2\ Thus, EPA 
anticipated all facilities employing wet cooling towers would already 
meet the IM limitations. However, commenters pointed out that not all 
facilities employing a wet cooling tower or some other CCRS as their 
original technology (i.e., not a retrofit) would necessarily have been 
designed to meet the 0.5 feet per second intake velocity threshold.

    \1\ EPA also notes that the Phase I new facility rule requires 
low intake velocity (0.5 feet per second) in addition to flow 
reduction commensurate with closed cycle cooling.
    \2\ In a retrofit scenario, the facility's pre-retrofit intake 
velocity would have been calculated for flow through multiple intake 
screens. After the retrofit, the volume of water withdrawn is 
significantly reduced, but is often still withdrawn through the same 
number of screens, leading to a significantly reduced intake 

    Third, EPA has found several instances where a cooling tower has 
been installed but not operated to minimize the volume of water 
withdrawn. For example, EPA found in site visits that cooling water may 
be passed through a cooling tower to reduce the discharge temperature 
of the water, but little or no water was recycled back to the facility 
cooling system. In other words, the cooling tower was in place but 
cooling water was used in a single pass mode, with overall water use 
identical to a typical once-through cooling system, resulting in no 
reductions in impingement or entrainment. Operation in this manner is 
not feasible or in most cases even possible at a new facility because 
the intake at a new facility is only sized for supplying make-up and 
blowdown flows. Accordingly, in developing the existing facility 
definition for CCRS in the proposed rule, EPA began with the Phase I 
new facility rule definition of CCRS but added criteria to it in order 
to clarify the meaning of minimized make-up and blowdown flows. EPA 
proposed that a properly operated cooling tower is one that operates at 
a minimum cycles of concentration of 3.0 for freshwater and 1.5 for 
saltwater or brackish water. EPA solicited comment on this definition.
    EPA does not intend for facilities to install cooling towers solely 
for the purpose of meeting the IM requirements. In fact, EPA expects 
all facilities could comply with the proposed IM requirements without 
relying on closed-cycle cooling. However, consistent with EPA's 
position that flow reduction is strongly correlated to reductions in 
impingement and entrainment,\3\ a properly operated cooling tower would 
provide significant reductions in IM. An optimized cooling tower would 
typically reduce water usage by 94.9 percent to 97.5 percent, 
reflecting salt water and fresh water sources respectively. Thus, in 
this case, such a cooling tower would exceed the level of performance 
required by the proposed IM limitations.

    \3\ See, e.g., 69 FR 41576, July 9, 2004, Section VII.C.1. A 
reduction in flow leads to a corresponding reduction in impingement 
and entrainment.

    EPA is now considering a further alternative compliance provision 
in the regulatory language that would allow the owner or operator of a 
facility to demonstrate compliance with the fish impingement mortality 
limitation though either defined technologies or studies that 
demonstrate the impingement mortality reduction performance of 
optimized travelling screens at a facility. This alternative could 
include a provision that would deem a facility in compliance with the 
IM limitations if the facility employed a CCRS (such as a wet cooling 
tower) that minimizes water withdrawals. In addition, EPA received many 
comments specific to the proposed definition of CCRS.
    Some commenters stated that while they may have been effectively 
operating as closed-cycle units for many years, they have concerns with 
their ability to comply with the new definition. We continue to look 
closely at these comments. EPA may consider revising the definition of 
CCRS to provide existing facilities flexibility in demonstrating they 
already have a properly operated CCRS, such as a minimum level of flow 
reduction or water usage, a minimum level of cycles of concentration, 
and/or a narrative set of requirements demonstrating site-specific 
minimized make-up and blowdown flows. We request additional comment and 
supporting data, specifically including ways to define CCRS that 
accommodates those existing CCRS systems that are properly operated. 
EPA is also considering adopting the same definition of closed cycle 
cooling for the existing facilities rule that it used for the new 
facilities (and Phase II) rule. EPA acknowledges the argument that 
requirements for existing facilities should not be ``more stringent'' 
than the comparable requirements for new facilities. Some commenters 
have interpreted the proposed definition of closed cycle cooling to be 
``more stringent'' than the definition used in the new facilities rule 
because it places additional restrictions on how a facility must be 
operated to be considered ``closed cycle.'' In the Phase II rule EPA 
included as a compliance option a demonstration that the facility 
``[has] reduced or will reduce [its] flow commensurate with a closed-
cycle recirculating system.'' EPA requests comment on using similar 
language for a compliance option in this rule.
    Similarly, EPA is aware that a facility may obtain substantial flow 
reductions due to partial CCRS systems, variable speed pumps, seasonal 
operation, and other operational measures which result in reduced 
impingement. For example, a facility that reduces intake flow by half 
has reduced impingement by half; consequently, impingement mortality 
has been reduced by 50 percent. EPA is therefore considering adding in 
the final rule an opportunity for a facility to get credit for an 
equivalent reduction in impingement mortality when it reduces its 
intake flow (in comparison to a once-through cooling system). Thus, the 
regulatory language could provide for submission of such information as 
part of a performance study provided to the permit writer to 
demonstrate compliance with the impingement mortality limitations. 
Section 4 below describes how the credit for flow reductions could be 
used to determine compliance with the IM limitations.
3. Measurement of Intake Velocity
    EPA proposed an intake velocity limitation corresponding to a 
facility's design intake flow (DIF) as a design

[[Page 34320]]

standard for demonstrating compliance with the IM limitation. EPA's 
record shows an intake velocity of 0.5 feet per second or lower 
provides similar or greater reductions in impingement, and therefore 
impingement mortality, than the BTA technology of modified traveling 
screens. Therefore EPA proposed the intake velocity limitation as a 
compliance alternative. EPA is aware that low intake velocity is 
sometimes confused with velocity cap technologies, and EPA would like 
to clarify that these concepts are not the same. Most velocity caps do 
not operate as a fish diversion technology at low velocities, and in 
fact are often designed for an intake velocity exceeding one foot per 
second. Thus a velocity cap will not typically meet the low intake 
velocity impingement mortality limitation. The velocity cap is located 
offshore and under the water's surface, and uses the intake velocity to 
create variations in horizontal flow which are recognizable by fish. 
The change in flow pattern created by the velocity cap triggers an 
avoidance response mechanism in fish, thereby avoiding impingement.
    The proposed velocity IM limitation is based on DIF, thus the 
calculated velocity would reflect the maximum intake velocity as water 
passes through the structural components of a screen, measured 
perpendicular to the screen mesh. If the intake does not have a screen, 
EPA assumes that in most cases the maximum intake velocity is 
perpendicular to the opening of the intake.
    The following discussion explains how velocity would be determined, 
and thus compliance with the intake velocity limitation demonstrated. 
In general, EPA anticipates the first point of contact of the intake 
with the source water is the likely point of compliance, and would be 
the location for measurement of intake velocity. For example, some 
intakes use a channel or canal to transport the water to the facility. 
In those cases, the point of measurement is typically the channel or 
canal entrance, and not at the screen face of the facility's forebay. 
Similarly, if a facility employs a velocity cap, the point of 
measurement is the velocity cap opening (as described above, most 
velocity caps would not have a velocity low enough to meet the 0.5 feet 
per second limitation, but some may).
    In the proposal, EPA clarified that DIF need not be the original 
design of the facility. For example, redundant pumps, emergency service 
water, and fire suppression systems could be excluded from a facility's 
DIF. As an additional flexibility, EPA proposed to allow actual intake 
velocity to be used to demonstrate compliance with the maximum intake 
velocity requirement. In this case, the actual flow (i.e., volume) 
across the screen surface area would be used to calculate the maximum 
expected velocity through that screen. The proposed rule indicated that 
the maximum velocity must be achieved under all conditions, including 
during minimum ambient source water surface elevation and during 
periods of maximum head loss across the screens or other devices during 
normal operation of the intake structure.
    EPA received several comments regarding the velocity compliance 
alternative. For example, some comments suggested that the requirement 
to meet the intake velocity ``under all conditions'' was overly 
conservative and may render this alternative technologically infeasible 
and/or economically impracticable. These comments provided data 
suggesting infrequent events with short durations can occur, during 
which time the intake velocity could increase to a rate greater than 
0.5 feet per second. Examples of such events might include variations 
in river flows related to other uses of the water, weather related 
variations (e.g., reduced or increased precipitation) or flow changes 
related to dams. Some comments indicated these short duration events 
would not result in measurable harm related to increased impingement. 
Other comments point out that monitoring velocity at screens with low 
levels of screen blockages (such as the maximum of 15 percent allowable 
blockage presented in the proposed rule) is technically problematic 
with standard \3/8\ inch mesh screens. It was further suggested that 
changes to pressure or flow as a means of measuring velocity are often 
indiscernible under such conditions. Industry comments also indicated 
that, in general, debris fouling is minimized through typical 
operations and maintenance procedures that must be performed to ensure 
that cooling water flow is not disrupted. For example, a facility would 
not allow conditions that could result in pump cavitations, other 
damage to circulating water pumps and their related systems, or 
anything else that could compromise cooling capabilities or affect 
plant reliability.
    EPA also received comments suggesting that a direct velocity 
measurement posed technical challenges. Some of these comments 
suggested that EPA provide the flexibility to calculate velocity based 
on other direct measurements, such as water depth, pressure 
differential, and plant intake flow. Based on the comments and data 
received in response to the proposed rule, EPA is actively considering 
changes to the intake velocity compliance alternative, as described 
    Actual through-screen intake velocity can be measured directly. 
However, after further discussion with vendors, EPA is aware that some 
sites may have difficulty measuring through-screen velocity (DCN 11-
6602). EPA is considering rule language clarifying that velocity may be 
calculated from a facility's actual intake flow rate (AIF), the screen 
open face area, and the source water surface elevation at the time of 
flow measurement. (If there is no screen, the opening of the intake is 
the open face area.) The volumetric intake flow would be representative 
of routine operations, and may not include periods of zero flow. As 
with DIF, the point of measurement would be the point of first contact 
with the source water (e.g., the canal entrance, velocity cap opening, 
or shoreline screen face).
    To demonstrate compliance with the actual intake velocity criteria, 
EPA expects that a facility would record the average monthly velocity. 
This would be measured directly or calculated from the volumetric flow 
and source water surface elevation measured no less frequently than 
once per week reflecting normal operations. Such measurements would 
already reflect current water levels; therefore a separate evaluation 
of low flow conditions would be unnecessary. For example, low source 
water elevation over a three month period would be represented in the 
measured or calculated through-screen velocity and reflected in the 
reported monthly values. However, it was not EPA's intention to 
penalize a facility in the event of unusual and irregular conditions. 
Thus, for example, in an unusual circumstance that causes the surface 
elevation to be low for just one day, it may be acceptable that this 
condition is not represented in the reported data because it does not 
reflect conditions that are likely to have a lasting impact on aquatic 
life. EPA solicits data on all of these assumptions and solicits 
comment on making this clear in the final regulatory text or preamble 
to the final rule.
    It is important to clarify that the velocity of water as it 
approaches the screen, or even immediately adjacent to the screen, is 
not equivalent to the through-screen velocity. The screen surface area 
decreases the area through which a given volume of water has to pass, 
therefore the velocity of the water increases as it passes through the 
screen. Because the velocity compliance option functions in two ways--

[[Page 34321]]

protecting fish from injury due to being impinged on the screen's 
surface, and allowing fish the opportunity to escape from the intake--
EPA proposed that the point of compliance must be the velocity through 
the screen or intake structure and not at some point in front of the 
screen. Velocity at other points near the intake can vary based on many 
factors such as dead spots and hydraulic zones. However, as stated 
above, EPA understands that there may be technical challenges in some 
cases to measuring through-screen velocity. EPA will continue to 
consider comments from the proposal on this issue and may modify the 
monitoring requirements as appropriate.
    For the Phase I rule, EPA compiled data from three studies on fish 
swim speeds and found that a velocity of 0.5 feet per second would 
protect 96 percent of fish tested (66 FR 65256, December 18, 2001, 
Section V.B.1.b.1). EPA recognizes that the flow directly in front of a 
screen designed for 0.5 feet per second through-screen velocity will 
always be lower than the velocity standard (it may be as much as half 
the through-screen velocity in the case of a standard \3/8\ inch 
screen). Therefore, EPA's proposed velocity standard as measured 
through the screen surface already includes a margin of safety. This 
potentially allows more fish to sense the change in velocity and invoke 
an avoidance response before being impinged. Because the 0.5 feet per 
second limit as a through-screen measurement already includes a margin 
of safety, EPA's current view is that additional criteria regarding 
screen blockage and related monitoring may be unnecessary. EPA solicits 
comment on the data and possible changes to the rule language for the 
intake velocity design standard to reflect such modifications.
4. Impingement Mortality Limitations
    EPA proposed two ways in which a facility could demonstrate 
compliance with the impingement mortality limitations. The owner or 
operator of the facility could conduct monitoring to show the specified 
performance standards for impingement mortality of fish and shellfish 
have been met through use of any appropriate best performing 
technology, or they could demonstrate to the permitting authority that 
the intake velocity meets the specified design criteria. The 
performance standards for impingement mortality were proposed as 
monthly and annual limitations in impingement mortality, measured as a 
percent mortality not to be exceeded. These proposed standards were 
applicable to all existing facilities with a DIF greater than 2 MGD. 
EPA specifically solicited comments on how to give credit for existing 
technologies, and using those site-specific adjustments to implement 
the national uniform IM standard in a site-specific manner. The data 
and comments on this approach will be further discussed in sections 4 
and 5.
    As explained in the proposed rule, EPA applied four general 
criteria when reviewing studies for acceptance in the impingement 
analyses: (1) The data must be specific to the technology under 
consideration; (2) impingement mortality must have been reported as an 
absolute number or a percentage of impinged fish that were killed; (3) 
the data must reflect technology performance that is representative of 
conditions that exist under actual facility operations, and; (4) 
reported values must be actual measurements, rather than estimates. EPA 
based the proposed limitations on the performance of modified traveling 
screens with a fish return system. Additional criteria were used to 
select data as the basis for impingement mortality calculations. The 
limitations were based on all life stages of fish collected or retained 
in a \3/8\ inch sieve and held for a period of 24 to 48 hours to assess 
latent mortality. Further, EPA rejected studies that did not evaluate 
species typical of the location conducting the testing. At proposal, 
EPA found four data sets at three facilities in New York State that met 
these criteria; see Chapter 11 of the proposed Technical Development 
Document (TDD) for more information (DCN 10-0004; EPA-HQ-OW-2008-0667-
    As described in section I of this notice, EPA received more than 80 
documents and studies, several of which include impingement studies. 
These additional studies represent facilities from a variety of 
geographic regions and waterbody types, and include a broader 
representation of species than those comprising the basis for the 
proposed rule limitations. EPA solicits comment on recalculating the 
impingement mortality limits using the new studies that meet EPA's 
criteria as just described. EPA also solicits comment on whether such a 
single monthly and annual limit could be sufficiently protective for 
all facilities and also recognize site specific variations. In response 
to the comments and data regarding fragile species and abundant 
species, EPA may consider alternative procedures to determining the 
limits, such as giving equal weight to each species instead of to the 
total organism counts, or determining different limits for different 
groups of organisms. Further, EPA has received several studies that 
include counts of shellfish. EPA is considering whether the revised 
limitation should include both fish and shellfish. Accordingly, EPA may 
eliminate the specific requirement to employ technologies comparable in 
performance to barrier nets in order to protect shellfish. 
Alternatively, EPA is considering whether the need for additional 
impingement controls for shellfish can be determined by the Director 
based on site-specific assessments and consideration of the species of 
concern for each facility.
    In addition, EPA received information suggesting one or more of the 
acceptance criteria used to evaluate the studies for inclusion in EPA's 
calculations were too stringent. For example, EPA received comments and 
data concerning the holding time of 24 to 48 hours. Some studies 
suggest that shorter holding times may still be sufficient for purposes 
of determining latent mortality. Yet other information suggests 
comparable performance with \3/8\ inch square mesh and \1/4\ by \1/8\ 
inch mesh,\4\ and therefore EPA solicits comment on including either 
technology specification in the limit calculations. EPA is reviewing 
these data and may revise the criteria as appropriate.

    \4\ Note EPA still intends to exclude data for fine mesh screens 
to avoid confusion over the status of ``impinged entrainables'' (76 
FR 22174, Section VI.B).

    Many commenters suggested that EPA should consider modified 
traveling screens with a fish return as a pre-approved technology as 
this technology forms the BTA basis of numeric limits. Alternatively, 
comments suggested that EPA should streamline the permitting process 
and reduce monitoring for facilities employing the candidate BTA 
technology. Commenters went on to say if this technology is the 
candidate BTA technology, then the proper design, installation, 
operation, and maintenance should be deemed compliant with any limit 
based on the technology.
    EPA still views properly operated, modified traveling screens as 
BTA. Accordingly, EPA has concluded that an alternative compliance 
option that would streamline the permitting process as well as provide 
for reduced monitoring requirements may be appropriate for facilities 
employing the model BTA technology. The BTA technology properly 
operated according to best management practices would then be deemed 
compliant with the IM standards. Under this approach, EPA might require 
the facility to provide site-

[[Page 34322]]

specific performance data to identify the operational conditions that 
would ensure that the technology is being operated appropriately. EPA's 
current understanding suggests that two-years of data may be an 
appropriate amount to make this determination. Note the biological 
monitoring conducted as part of a performance study would not be used 
to demonstrate compliance with the limit, but rather would be used to 
help set operational parameters for the facility. The performance data 
could consist of a two year study focused on the operational conditions 
that optimize the proper design, installation, operation and 
maintenance of modified traveling screens with fish return systems. A 
facility could use relevant data already collected as part of the 
study, or conduct a new two-year performance study. Once these 
operational conditions have been identified, EPA would expect the 
permit writer to incorporate these operational parameters as conditions 
of the permit.
    The data from EPA's technical survey shows at least 79 percent of 
existing power plants have traveling screens. EPA realizes not all 
facilities could retrofit existing traveling screens to modified 
traveling screens. In particular, the installation of a fish handling 
and return system is not feasible at some facilities. However, EPA 
expects the majority of those facilities currently employing traveling 
screens would modify their traveling screens to comply with the IM 
limitations. Therefore, EPA expects these same facilities could take 
advantage of the reduced monitoring requirements and the streamlined 
compliance associated with this alternative. Further, EPA's data show 
15 percent of facilities meet the low intake velocity limitation. 
Combining all of the IM limitation alternatives, EPA anticipates more 
than 90 percent of the facilities could take advantage of design 
standards rather than choosing to comply with the numerical IM 
limitations if EPA adopted this approach. EPA expects some facilities 
would explore innovative and creative approaches taking site-specific 
characteristics of their facility into account to provide performance 
comparable to the BTA technology, and EPA would maintain the numerical 
IM limitation to provide for such flexibilities. EPA solicits comment 
on providing this compliance flexibility and data on these assumptions.
    Under this approach, as long as the owner or operator of the 
facility complies with the specified operational conditions, the 
impingement mortality limitations would be deemed to have been met. 
Subsequently, the owner or operator would not have to conduct any 
biological monitoring to show compliance with the impingement mortality 
limitations. In subsequent permit terms, and in the absence of major 
changes to the operation of the intake structure or the biology of the 
source water, EPA expects the Director would waive any further 
requirement for a study or compliance monitoring for the facility. EPA 
is considering modifying the regulations to provide specifically for 
such a waiver. If EPA were to adopt these revisions in the final rule, 
EPA would make corresponding changes to the permit application 
requirements. EPA solicits comment on this alternative approach for 
compliance with IM standards. The Agency also takes comment on the 
appropriate level of data for assuring that the technology is operated 
suitably to minimize adverse environmental impact. For example, EPA 
solicits comment on whether some monitoring of operational parameters 
should be required in lieu of biological monitoring, whether EPA should 
specify some minimum set of operational parameters, or whether such a 
determination is best left to the discretion of the permitting 
    EPA also received comments regarding the need for separate 
requirements to address entrapment. Some commenters indicated that the 
requirements in the proposed rule would not be feasible to implement at 
all facilities. EPA is considering these comments and requests specific 
information on issues related to the feasibility of preventing 
entrapment, including examples of where it is impractical or infeasible 
to return entrapped organisms to the waterbody or prevent their 
entrapment in the first place. EPA will consider this information as it 
finalizes the rule.
5. Credit for Existing or Newly Installed Technologies
    EPA's objective in establishing the IM limitations is to minimize 
adverse environmental impacts by ensuring that fewer aquatic organisms 
such as fish and shellfish are killed by cooling water intake 
structures. The limitations are based upon the model best technology 
available which reduces impingement mortality of fish and shellfish. As 
EPA's proposal noted, this model technology does not include, nor 
account for, elements of impingement reduction technologies already 
installed at some facilities. There are many cases where facilities 
have installed and continue to operate technologies to reduce 
impingement. These technologies may have been approved by the 
appropriate permitting authorities, including required provision of 
supporting studies and assessments of the impact of the plant on the 
local aquatic environment. However, these technologies may not have 
been designed in such a way that they would meet the proposed IM 
requirements, particularly the monthly and annual IM numeric limits. 
Further, the structure and design of the proposed rule IM numeric 
limits make accounting for the benefits of these existing technologies 
very difficult. For example, EPA received new information showing 
diversion technology at one specific facility reduced impingement of 
one or more species by more than 90 percent, and consequently, fewer 
fish would have been killed as a result of impingement mortality. 
However, the limitations are strictly based upon the performance of the 
model technology and were derived by applying statistical methods to 
observed data from facilities with the model technology.
    In the proposal, EPA intended that facilities would receive credit 
for both pre-existing and/or newly installed technologies when 
demonstrating compliance with the statistically derived IM limitations. 
After reviewing the comments, EPA is providing additional discussion of 
how reductions in impingement may be used to comply with the IM 
requirements. In meeting EPA's overall objective, a facility should be 
able to take credit for reducing the number of organisms killed by a 
CWIS regardless of the technology used. If the alternative provision 
were to provide credit for other technologies, the facility would need 
some way to demonstrate that the technologies result in no more 
impinged fish being killed than would have resulted from the model 
technology (modified traveling screens) alone. With these alternative 
provisions that EPA is considering, it is possible that a facility 
might be able to meet the limitations by means other than installing 
and operating the model technology. EPA examined the effect of 
alternative provisions in demonstrating compliance with the annual 
average limitation and the monthly average limitation.
    In establishing the IM limitations, EPA seeks to minimize 
impingement mortality on an ongoing basis, each year, at a level that 
is achievable for a facility. Both the annual average limit and monthly 
average play an important role in ensuring that facilities optimize 
performance of their technology. Compliance with the monthly average 
limitation is demonstrated by comparing the average IM value from the 
samples collected during each

[[Page 34323]]

month (or other 30-day period designated by the Director). At the end 
of the 12-month period, the facility calculates the annual average as 
the arithmetic average of the monthly averages during that period. The 
facility would then compare its annual average to the annual average 
limitation to demonstrate compliance.
    With the alternative provisions that the Agency is considering, a 
facility would provide use data from long-term (e.g., 1-2 year) 
performance studies and/or calculation baseline assessments to quantify 
the impingement and/or IM reductions relative to what would be expected 
from the model technology alone. Because monthly averages are used to 
demonstrate compliance with both monthly average limitation and annual 
average limitation (i.e., monthly averages are averaged to produce the 
annual average), facilities would incorporate estimated reductions into 
the monthly average IM percent calculations. To calculate an adjustment 
using only data for a particular month (e.g., June) would require data 
for a very long term, such as 4-years or more. EPA would not require, 
nor recommend, this level of refinement in the calculations for two 
reasons. First, EPA does not expect that many facilities would have 
such long-term data available. Second, the calculations for each month 
would require a different set of adjustments that would create 
additional, unnecessary, complications for the facility and permit 
authority. To simplify the adjustment procedures, a facility would 
estimate the monthly reduction using the total reduction divided by the 
number of months in the study. The facility then would use this 
estimated monthly value to adjust the observed numbers of impinged fish 
and killed fish in the IM percent calculations for each and every 
month. Depending on the technology used, the reductions would be to the 
number of impinged fish and/or number of impinged fish that do not 
survive the holding time (``killed fish'').
    If the technology reduces impingement, the alternative provision 
calculations would increase the number of the observed impinged fish by 
the estimated number that would have been impinged without the 
technology. The monthly average calculation then would compare the 
observed number of killed fish to the larger total number of impinged 
fish (i.e., the sum of observed and estimated number reduced by 
technology). This comparison would result in a lower IM rate than the 
unadjusted, observed value.
    The adjustments to the monthly average calculations, in turn, 
affect the value of the annual average calculated by the facility, 
because the facility's annual average is set equal to the arithmetic 
average of the monthly averages. In other words, the facility's annual 
average is solely based upon the values of the monthly averages. Thus, 
when the monthly averages are adjusted downward by the alternative 
provisions, the annual average also will be adjusted.
    The following example illustrates how the alternative provisions 
would adjust for flow, location, and other technologies in 
demonstrating compliance with the IM monthly average limitations. The 
example uses values that simplify the calculations to better illustrate 
the adjustments, and are not intended to reflect values that EPA 
expects at any facility. To simplify the example further, the facility 
has only fish and does not have shellfish in its source waters. EPA 
also recognizes that facilities often examine the combined effect of 
two or more technologies (e.g., deterrents and offshore location) 
within a single study. In applying the alternative provision, the 
facility could use the outcomes associated with the combined 
performance of multiple technologies. However, for a more complete 
example, EPA has chosen a hypothetical facility that examined each 
change in a separate study.
    The hypothetical facility is located at an offshore location, has a 
velocity cap, and installed variable speed drives. For the purposes of 
this example, assume its permit requires that it collect samples once a 
week and evaluate the impinged fish after 24 hours. The facility has 
just completed sampling at the forebay each week during June, and has 
identified the counts of the facility specific species of concern as 
follows. The four samples had 1,500, 1,000, 500, and 1,000 impinged 
fish, for a total of 4,000 impinged fish. During the 24-hour holding 
period, 400, 100, 150, and 350 fish died, for a total of 1,000 dead 
fish. The facility then calculated the forebay's IM as 25 percent, 
using the equation provided in the proposed rule preamble (76 FR 22174, 
Section IX.F.1) as follows:

    To adjust the observed percent IM for its offshore location and 
velocity cap, the facility first extracts information from its 
previously conducted studies related to performance and calculation 
baseline. For the offshore location adjustment, fish density and flow 
data show the offshore location reduces the rate of impingement for all 
species of concern by 30,000 fish annually, or, on average, 2,500 each 
month (i.e., calculated as 30,000 fish divided by12 months). For the 
velocity cap, performance data show the velocity cap reduces 
impingement of fish and shellfish by 24,000 organisms annually, or a 
monthly average of 2,000 organisms. Therefore, the facility has reduced 
impingement of all species of concern, on average each month, by 4,500 
organisms (i.e., sum of 2,500 for offshore location and 2,000 for 
velocity cap). The facility then applies the reduction to the 
denominator of the percent IM calculations as follows:

[[Page 34324]]


    In summary, calculating percent IM at the forebay yields a 25 
percent IM, and then applying the alternative provisions for other 
technologies shows the effective percent IM is 12. Next, to adjust for 
the variable speed drives, the facility has determined from engineering 
and design calculations that the volume of cooling water flow has been 
reduced by 11 percent. The volume of reduced flow multiplied by the 
density of fish near the intake is calculated, and the facility 
projects that the reduced flow excludes, on average for each month, an 
additional 1,100 fish from impingement. Then the facility would apply 
the reduction in impinged fish to the denominator, as follows:

    This example is intended to illustrate how facilities would obtain 
credit for existing technologies. While this example includes a 
velocity cap, it does not imply that a velocity cap is the appropriate 
technology for all facilities. EPA's data shows in most cases, a 
properly located velocity cap alone would be sufficient to achieve the 
limitations. In the case where a velocity cap (or any other technology) 
alone would not be sufficient to meet the limitations, EPA expects that 
each facility would identify and install a suite of cost effective 
technologies to achieve the IM requirements (i.e., variable speed 
drives in this example). EPA solicits comment on whether this approach 
reasonably addresses commenters' request that EPA identify velocity 
caps to be a pre-approved BTA for IM by appropriately taking into 
account facilities' existing technologies in determining whether a 
facility meets the proposed IM requirements. In summary, the 
hypothetical facility would observe a 25 percent IM rate for June; 
which would then be adjusted downward to 12 percent for its offshore 
location and velocity cap; and then further adjusted downward to 10 
percent for its flow reduction. The value that the facility would 
report for compliance purposes would be the 10 percent value. At the 
end of the 12-month monitoring period, the facility also would use the 
10 percent value for that month with the other 11 adjusted monthly 
values to calculate the annual average IM rate. In the final rule, EPA 
may decide to include the equations for calculating IM and the 
alternative provision in the rule language to provide additional 
clarity. EPA solicits comment on how frequently a facility would need 
to calculate credit for existing technology after the initial 
    Comments from some Phase II facilities indicate facilities may have 
already collected data and performed baseline calculations required as 
part of the 2004 Phase II rule. While EPA identified considerable 
challenges implementing calculation baseline in the 2011 proposed rule 
(76 FR 22174, Section III.B.1), these commenters went on to suggest 
that a facility should have the option to use these data and analyses 
in demonstrating compliance with the IM limitations. In many cases 
these data are sufficient to show their site specific impingement rates 
as well as the performance of any technologies installed at their site. 
Therefore, EPA is considering a provision that would allow existing 
facilities to use data already collected as part of a site-specific 
analysis of calculation baseline to demonstrate compliance with the 
alternative provisions. EPA solicits comment on these data and possible 
changes to the rule language for providing credit in reductions in 
impingement calculations to demonstrate compliance with the annual 
average and monthly average IM limitations.
    EPA recognizes that it may be challenging for a facility to 
determine in some cases what its calculation baseline should be, 
particularly if it has had a technology in place for many years. Thus 
it may be difficult to establish precisely what the performance of a 
technology is relative to a situation in which the technology was not 
employed (a situation that may not have existed at the facility for a 
long time). EPA is thus also considering identifying additional 
technologies (which could include velocity caps) as satisfying the IM 
performance standards without having to conduct the type of study and 
calculation discussed in this example. EPA requests comment on this 
approach, on what technologies could be deemed compliant under this 
approach, and on what requirements or demonstrations would be 
appropriate to establish the technology as a compliance alternative. 
EPA also requests comment on whether the final rule should allow 
permitting authorities to approve additional technologies as satisfying 
the IM requirements, and if so, what specific demonstrations or 
procedures would be appropriate for permitting authorities to use in 
making such determinations.
6. Facilities With Low Impingement Rates
    EPA received data showing some facilities have very low impingement

[[Page 34325]]

rates. This is usually due to intake location for the specific 
waterbody from which water is withdrawn for cooling, or the 
implementation of other technologies. For example, EPA is aware of a 
facility located on the inside bend of a large freshwater river which 
seasonally employs large mesh barrier nets. The facility impinges an 
average of several fish per month. In another case, the intake is 
located downstream of a dam, and the fish avoid the cold water coming 
from the dam. Recent data show the facility impinged one fish over two 
24 hour periods. Under such low impingement rate conditions, technology 
performance is unlikely to be meaningfully evaluated. Moreover, in 
EPA's view, these facilities are not likely having an adverse effect on 
aquatic life. It is probable that in most cases requiring additional 
technology would not be necessary to further minimize adverse 
environmental impacts.
    EPA has received several suggestions on how to establish 
requirements for such facilities with very low impingement rates. One 
suggested approach was to establish an exemption based on an annual 
limit on biomass impinged. EPA found a small number of studies have 
available performance data that are expressed as biomass, and the 
amount of data within these studies are generally limited (see proposed 
TDD, Chapter 11, Appendix B). Another approach that would be easier to 
implement is to establish an annual limit on the absolute number of 
fish that may be impinged. Facilities meeting this limit on the rate of 
impingement would be deemed in compliance with the IM limitations, and 
therefore would not be required to install additional technologies. In 
other words, the existing technology in place would be deemed BTA for 
that facility. Alternatively, if EPA were to consider the number of 
fish killed (rather than as a percent of impinged fish) as a limitation 
for the final rule, EPA might statistically model the data to derive 
the limit, or EPA may select the minimum observed value (see TDD, 
Chapter 11, Appendix D for further discussion of the methodology).
    Comments by some state agencies indicated concern that such an 
approach does not fully consider the affected species. For example, 
while the total number of impinged fish that die might be low, they 
might all be species of concern, or may include a locally important 
species under NOAA's NMFS conservation watch status. If EPA adopts this 
approach, EPA might need to provide certain safeguards to ensure 
adequate protection of specific fish populations.
    EPA is considering authorizing the permit writer to determine that 
a facility using a given technology complies with the IM requirements 
because it does not impinge greater than some absolute number of fish. 
Such a provision would then authorize the Director to make a site-
specific determination that the facility is already employing BTA. 
Under this approach, a facility impinging fewer than the specified 
number of organisms might submit some minimum amount (e.g., two years) 
of impingement rate or impingement mortality data, including a 
demonstration that no threatened and endangered (T&E) or other 
protected species are identified in the vicinity of the intake. 
Additional factors the Director should consider might include any 
impacts to significant recreational or commercial fisheries, a review 
of locally important aquatic life such as those identified by NOAA's 
NMFS regarding local or state conservation status of any species of 
concern, value of impinged species, prevalence of nuisance or invasive 
species, or other local conditions. The Director could then make a 
determination that the very low impingement rate is BTA due to the 
facility's existing technology. EPA solicits comment on the data and 
approaches under consideration for facilities that already have very 
low impingement rates. EPA also solicits comment on whether EPA should 
identify in the final rule a specific upper limit on what could be 
considered a very low level of impingement mortality, or if this should 
be left to the discretion of the permitting authority. In addition, as 
noted above, EPA is soliciting comment on recommendations it received 
following proposal that EPA consider a regulation under which 
impingement requirements (like entrainment requirements) would be 
established on a site-specific basis. If EPA adopted the approach 
proposed for entrainment, the permit writer could weigh site-specific 
costs and benefits, among the factors being assessed, in the decision 
whether to require further impingement controls. EPA also requests 
comment on a hybrid approach under which the permittee could choose 
among several compliance options that might include both meeting an IM 
performance standard or requesting a site-specific determination of BTA 
for both impingement and entrainment, if the benefits of meeting the 
performance standard did not justify the costs on a site-specific 
basis. This could be structured in a manner similar to the ``cost-
benefit variance'' that was included as a compliance option in the 
final Phase II rule. EPA requests comment on all of these approaches.
7. Species of Concern
    In recognizing the variability in each facility's source water 
characterization, particularly with respect to the specific species and 
life stages of fish and shellfish, EPA proposed the IM standards should 
be applied to site-specific species of concern. EPA intended this 
provision to provide flexibility to the Director to focus the 
technology based requirements on those species deemed important at a 
given site. Some commenters indicated that many states have already 
determined the species of concern as inclusive of forage fish, fragile 
fish, and abundant representative indicator species. Therefore, 
commenters indicated EPA's intended flexibility might not work.
    In this notice, EPA is clarifying the proposed rule approach to 
species of concern is intended to allow the Director to prioritize 
certain fish and shellfish in a site-specific manner. EPA generally 
intended that the highly abundant, fecund forage fish species (such as 
the clupeid species) would not be considered species of concern. 
However, the Director could determine such species are species of 
concern if they were considered: Important migratory or commercial 
species; threatened or endangered; or of insufficient abundance in the 
source water to support the growth and abundance of those species that 
prey upon them. To provide the Director with the appropriate data to 
make such a determination, and to avoid the unnecessary burden of 
requiring a facility to comply with the IM limitations for all species, 
EPA is considering a regulatory provision that would distinguish 
representative indicator species (RIS) from the site-specific species 
of concern. Under such an approach, a facility may be required by the 
Director to monitor for those species identified as RIS, but the IM 
limitations would only be applicable to the species of concern. The 
species of concern would not necessarily include all RIS. EPA solicits 
comment on the data and approaches under consideration here that best 
address the variability in species and life stages of fish and 
shellfish. Alternatively, EPA takes comment on the suggested addition 
of defined species of concern, explicitly identifying those specific 
species that are not subject to the IM limitations.

[[Page 34326]]

III. General Solicitation of Comment

    EPA encourages public participation in this rulemaking and requests 
comments on this notice of data availability supporting the proposed 
rule for cooling water intake structures.
    EPA invites all parties to coordinate their data collection 
activities with the Agency to facilitate mutually beneficial and cost-
effective data submissions. Please refer to the FOR FURTHER INFORMATION 
CONTACT section at the beginning of this preamble for technical 
contacts at EPA.
    To ensure that EPA can properly respond to comments, the Agency 
prefers that commenters cite, where possible, the paragraph(s) or 
sections in the document or supporting documents to which each comment 
refers. Please submit copies of your comments and enclosures (including 
references) as specified in the ADDRESSES section at the beginning of 
this preamble.

    Dated: May 31, 2012.
Nancy K. Stoner,
Acting Assistant Administrator, Office of Water.
[FR Doc. 2012-14153 Filed 6-11-12; 8:45 am]