BTA Framework to Replace EPA’s Proposed Impingement Mortality Standard under Sec. 316(b)1

July 25, 2011

The following provisions set forth a framework for complying with the impingement mortality standards under

316(b) of the Clean Water Act.  The framework was developed based on concerns that a one‐size‐fits‐all

approach for impingement mortality, as proposed by EPA, could not be developed and applied appropriately to

recognize the site specific factors that affect impingement mortality.  This framework was refined based on

meetings with EPA staff.  Companies will also be providing individual specific comments to the Agency on the

EPA’s proposed rule under 316(b), but the framework for impingement mortality outlined below is designed so

that all affected facilities are required to comply with impingement standards through the installation of best

technology available (BTA).  This BTA Framework, including each element listed below, will ensure that the rule

results in a significant national reduction in impingement mortality with important environmental and ecological

benefits throughout the U.S.  This framework is consistent with approaches previously used by the Agency and

upheld by courts.  

1) EPA should require facilities to install and operate BTA technology, which should include one of the

following:

a. Preapproved BTA, defined as

i. modified travelling screens such as Ristroph screens with post‐Fletcher modifications; or  

ii. maximum intake velocity (i.e., approach velocity);   

b. Pre‐existing offshore velocity caps or closed cycle cooling2 including cooling towers or cooling

ponds that are not determined to be the waters of the U.S.; or  

c. Comparable BTA Technology or Technologies: if the preapproved BTA is technically infeasible based

on site specific considerations or if a company identifies that a more cost effective technology will

achieve comparable performance to preapproved BTA, the company, in coordination with the

permitting director, should engage in a process to select the comparable BTA technology(ies) and

other supplemental mitigation measures (e.g., restoration) required for the site considering

expected impingement mortality reduction, including avoidance of impingement, and considering a

cost benefit analysis.  (See attached Decision Matrix)

2) EPA Database of Comparable BTA.  EPA should develop a database for companies and permitting directors

to use to identify BTA technologies and understand the expected performance of BTA technologies for

specific sites.  These examples should be based on a robust data set and reflect different situations that will

affect impingement such as different water bodies, fragile species, facility sizes, and seasonal dynamics.   

The expected performance should be based on both fish mortality and biomass and account for actions that

prevent fish impingement.

                                                           

1 This framework is proposed by the Clean Energy Group’s 316(b) Initiative that includes Constellation Energy, Exelon

Corporation, NextEra Energy, PG&E Corporation, and Public Service Enterprise Group, Inc.  While each company will provide

individual comments on the complete 316(b) proposal by EPA, this framework is offered for discussion with EPA for the

impingement mortality requirements.  The companies are offering this framework as a complete proposal and would not

necessarily support a proposal including only some of the elements of this framework.       2 EPA’s proposed definition of closed cycle cooling should be refined to eliminate the requirement of a minimum number of

cycles of concentration.
CONFIDENTIAL DRAFT

2

This database would facilitate permitting directors’ assessment of alternatives to the preapproved BTA

technologies.  It would not establish a national standard that would be applicable to all facilities.   

3) Verification and Monitoring. Each facility should be required to demonstrate the installed BTA technology

is operating consistent with best management practices.  Each permit review will also require the permitting

director to confirm the technology installed is BTA and operated appropriately to ensure maximum benefit.   

4) Shellfish Impingement Mortality Protection. If the permitting director determines that a plant located on

ocean or tidal waters is not minimizing adverse environmental impact (AEI) to shellfish, then the permitting

director may require additional measures, as necessary, to reduce impingement mortality of shellfish based

on cost benefit analysis.  Facilities could be obligated to install barrier nets, or their equivalent, as proposed

by EPA unless the facility demonstrates to the permitting director that site specific considerations prevent a

barrier net or its equivalent from being installed effectively, in which case the permitting director can

require alternative measures, or make a determination that additional measures are not required to protect

shellfish.      

a. For example, an intake structure located in a harbor may not be able to install a barrier net or

equivalent technology due to ship traffic.  In such cases, the permitting director must have the

authority to approve alternative technologies or operational practices that are technically feasible at

such a location to minimize environmental impact.  A case example is NextEra’s Riviera Plant in

Riviera Beach, Florida.  A barrier net would interfere with port traffic in the Port of Palm Beach.   

5) De Minimis.  EPA should provide permitting directors the criteria to develop de minimis exemptions for

plants with extremely low impingement levels and/or mortality rates based on site specific factors (e.g., flow

or biomass impingement) and cost benefit analyses.  De minimis exemptions could be based on the

following elements, and facilities meeting one of these exceptions would satisfy a facility’s obligations for

the impingement mortality standard:

a. actual intake flow versus design intake flow;

b. a numeric impingement level (annual lbs or lbs per million gallons withdrawn); or

c. operating characteristics.   

6) Species of Concern.  As proposed by EPA, in determining BTA for a site, including any mitigation measures,

the permitting director should have the authority to identify the species of concern at the particular facility’s

water body to which BTA applies, rather than require BTA based on the impingement mortality of all

species.