[Code of Federal Regulations]
[Title 40, Volume 21]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR125.93]

[Page 347-350]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 125_CRITERIA AND STANDARDS FOR THE NATIONAL POLLUTANT DISCHARGE
ELIMINATION SYSTEM--Table of Contents
 
Subpart J_Requirements Applicable to Cooling Water Intake Structures for 
      Phase II Existing Facilities Under Section 316(b) of the Act
 
Sec.  125.93  What special definitions apply to this subpart?

    In addition to the definitions provided in Sec.  122.3 of this 
chapter, the following special definitions apply to this subpart:
    Adaptive management method is a type of project management method 
where a facility chooses an approach to meeting the project goal, 
monitors the effectiveness of that approach, and then based on 
monitoring and any other relevant information, makes any adjustments 
necessary to ensure continued progress toward the project's goal. This 
cycle of activity is repeated as necessary to reach the project's goal.
    Annual mean flow means the average of daily flows over a calendar 
year.
    All life stages means eggs, larvae, juveniles, and adults.
    Calculation baseline means an estimate of impingement mortality and 
entrainment that would occur at your site assuming that: the cooling 
water

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system has been designed as a once-through system; the opening of the 
cooling water intake structure is located at, and the face of the 
standard \3/8\-inch mesh traveling screen is oriented parallel to, the 
shoreline near the surface of the source waterbody; and the baseline 
practices, procedures, and structural configuration are those that your 
facility would maintain in the absence of any structural or operational 
controls, including flow or velocity reductions, implemented in whole or 
in part for the purposes of reducing impingement mortality and 
entrainment. You may also choose to use the current level of impingement 
mortality and entrainment as the calculation baseline. The calculation 
baseline may be estimated using: historical impingement mortality and 
entrainment data from your facility or from another facility with 
comparable design, operational, and environmental conditions; current 
biological data collected in the waterbody in the vicinity of your 
cooling water intake structure; or current impingement mortality and 
entrainment data collected at your facility. You may request that the 
calculation baseline be modified to be based on a location of the 
opening of the cooling water intake structure at a depth other than at 
or near the surface if you can demonstrate to the Director that the 
other depth would correspond to a higher baseline level of impingement 
mortality and/or entrainment.
    Capacity utilization rate means the ratio between the average annual 
net generation of power by the facility (in MWh) and the total net 
capability of the facility to generate power (in MW) multiplied by the 
number of hours during a year. In cases where a facility has more than 
one intake structure, and each intake structure provides cooling water 
exclusively to one or more generating units, the capacity utilization 
rate may be calculated separately for each intake structure, based on 
the capacity utilization of the units it services. Applicable 
requirements under this subpart would then be determined separately for 
each intake structure. The average annual net generation should be 
measured over a five year period (if available) of representative 
operating conditions, unless the facility makes a binding commitment to 
maintain capacity utilization below 15 percent for the life of the 
permit, in which case the rate may be based on this commitment. For 
purposes of this subpart, the capacity utilization rate applies to only 
that portion of the facility that generates electricity for transmission 
or sale using a thermal cycle employing the steam water system as the 
thermodynamic medium.
    Closed-cycle recirculating system means a system designed, using 
minimized make-up and blowdown flows, to withdraw water from a natural 
or other water source to support contact and/or noncontact cooling uses 
within a facility. The water is usually sent to a cooling canal or 
channel, lake, pond, or tower to allow waste heat to be dissipated to 
the atmosphere and then is returned to the system. (Some facilities 
divert the waste heat to other process operations.) New source water 
(make-up water) is added to the system to replenish losses that have 
occurred due to blowdown, drift, and evaporation.
    Cooling water means water used for contact or noncontact cooling, 
including water used for equipment cooling, evaporative cooling tower 
makeup, and dilution of effluent heat content. The intended use of the 
cooling water is to absorb waste heat rejected from the process or 
processes used, or from auxiliary operations on the facility's premises. 
Cooling water that is used in a manufacturing process either before or 
after it is used for cooling is considered process water for the 
purposes of calculating the percentage of a facility's intake flow that 
is used for cooling purposes in Sec.  125.91(a)(4).
    Cooling water intake structure means the total physical structure 
and any associated constructed waterways used to withdraw cooling water 
from waters of the U.S. The cooling water intake structure extends from 
the point at which water is withdrawn from the surface water source up 
to, and including, the intake pumps.
    Design and construction technology means any physical configuration 
of the cooling water intake structure, or a technology that is placed in 
the water body in front of the cooling

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water intake structure, to reduce impingement mortality and/or 
entrainment. Design and construction technologies include, but are not 
limited to, location of the intake structure, intake screen systems, 
passive intake systems, fish diversion and/or avoidance systems, and 
fish handling and return systems. Restoration measures are not design 
and construction technologies for purposes of this definition.
    Design intake flow means the value assigned (during the cooling 
water intake structure design) to the total volume of water withdrawn 
from a source waterbody over a specific time period.
    Design intake velocity means the value assigned (during the design 
of a cooling water intake structure) to the average speed at which 
intake water passes through the open area of the intake screen (or other 
device) against which organisms might be impinged or through which they 
might be entrained.
    Diel means daily and refers to variation in organism abundance and 
density over a 24-hour period due to the influence of water movement, 
physical or chemical changes, and changes in light intensity.
    Entrainment means the incorporation of any life stages of fish and 
shellfish with intake water flow entering and passing through a cooling 
water intake structure and into a cooling water system.
    Estuary means a semi-enclosed body of water that has a free 
connection with open seas and within which the seawater is measurably 
diluted with fresh water derived from land drainage. The salinity of an 
estuary exceeds 0.5 parts per thousand (by mass) but is typically less 
than 30 parts per thousand (by mass).
    Existing facility means any facility that commenced construction as 
described in 40 CFR 122.29(b)(4) on or before January 17, 2002 or July 
17, 2006 for an offshore oil and gas extraction facility); and any 
modification of, or any addition of a unit at such a facility that does 
not meet the definition of a new facility at Sec.  125.83.
    Freshwater river or stream means a lotic (free-flowing) system that 
does not receive significant inflows of water from oceans or bays due to 
tidal action. For the purposes of this rule, a flow-through reservoir 
with a retention time of 7 days or less will be considered a freshwater 
river or stream.
    Impingement means the entrapment of any life stages of fish and 
shellfish on the outer part of an intake structure or against a 
screening device during periods of intake water withdrawal.
    Lake or reservoir means any inland body of open water with some 
minimum surface area free of rooted vegetation and with an average 
hydraulic retention time of more than 7 days. Lakes or reservoirs might 
be natural water bodies or impounded streams, usually fresh, surrounded 
by land or by land and a man-made retainer (e.g., a dam). Lakes or 
reservoirs might be fed by rivers, streams, springs, and/or local 
precipitation.
    Moribund means dying; close to death.
    Natural thermal stratification means the naturally occurring and/or 
existing division of a waterbody into horizontal layers of differing 
densities as a result of variations in temperature at different depths.
    Ocean means marine open coastal waters with a salinity greater than 
or equal to 30 parts per thousand (by mass).
    Once-through cooling water system means a system designed to 
withdraw water from a natural or other water source, use it at the 
facility to support contact and/or noncontact cooling uses, and then 
discharge it to a waterbody without recirculation. Once-through cooling 
systems sometimes employ canals/channels, ponds, or non-recirculating 
cooling towers to dissipate waste heat from the water before it is 
discharged.
    Operational measure means a modification to any operation at a 
facility that serves to minimize impact to fish and shellfish from the 
cooling water intake structure. Examples of operational measures 
include, but are not limited to: reductions in cooling water intake flow 
through the use of variable speed pumps and seasonal flow reductions or 
shutdowns; and more frequent rotation of traveling screens.
    Phase II existing facility means any existing facility that meets 
the criteria specified in Sec.  125.91.

[[Page 350]]

    Source water means the waters of the U.S. from which the cooling 
water is withdrawn.
    Supplier means an entity, other than the regulated facility, that 
owns and operates its own cooling water intake structure and directly 
withdraws water from waters of the United States. The supplier sells the 
cooling water to other facilities for their use, but may also use a 
portion of the water itself. An entity that provides potable water to 
residential populations (e.g., public water system) is not a supplier 
for purposes of this subpart.
    Thermocline means the middle layer of a thermally stratified lake or 
a reservoir. In this layer, there is a rapid change in temperatures 
between the top and bottom of the layer.
    Tidal river means the most seaward reach of a river or stream where 
the salinity is typically less than or equal to 0.5 parts per thousand 
(by mass) at a time of annual low flow and whose surface elevation 
responds to the effects of coastal lunar tides.

[44 FR 32948, June 7, 1979, as amended at 71 FR 35040, June 16, 2006]