MEMORANDUM

Tetra Tech, Inc.

10306 Eaton Place, Suite 340

Fairfax, VA 22030

Phone 703-385-6000

Fax 703-385-6007

TO: Lisa Biddle, EPA

FROM: John Sunda, Tetra Tech

DATE: December 18, 2012 (updated May 13, 2014)

SUBJECT: Velocity Cap Performance Data

This memo provides a summary of available design and performance data concerning known 

existing velocity cap installations in the US and worldwide. As discussed below, existing 

velocity caps combine the advantageous characteristics of an offshore location and a wellperforming technology; this combination is sufficiently protective of impingeable organisms to 

be deemed equivalent to meeting the impingement mortality (IM) requirements for the Existing 

Facility rule.1

Data Sources

The data was obtained from a review of available documents including previous Technical 

Development Documents, survey data, EPRI’s 2007 compendium, other technology documents, 

site visit reports, and information from various Tetra Tech support documents for 316(b) 

implementation. A complete list of known velocity cap installations and summary data

(including the specific sources for performance data) are presented in Attachment A.

Technology Performance

The overall performance of existing offshore intakes with velocity caps with respect to 

impingement reduction is the result of the combination of two components; the intake location

and the velocity cap.

Intake Location

Intakes may be located offshore for several reasons including: 1) to take advantage of a cooler 

source of water; 2) to prevent recirculation of the heated discharge; 3) to take advantage of lower 

 

1 Note that this analysis assumes that the impingement mortality performance standard is 74%.
density of biological organisms, and/or 4) limitations regarding the availability of a suitable 

shoreline location. Often, a combination of these factors is considered when selecting the 

location of a submerged intake. As discussed in Section 6.18.4 of the proposed rule Technical 

Development Document, locating submerged intakes in the deeper regions of larger waterbodies

(particularly outside the littoral zone) has the potential to reduce impingement and entrainment

(I&E), due to the lower densities of aquatic organisms as compared to a shoreline-based intake. 

In Entrainment of Fish Larvae and Eggs on the Great Lakes, with Special Reference to the D.C. 

Cook Nuclear Plant, Southeastern Lake Michigan (1976), researchers noted that larval 

abundance is greatest within the area from the 12.2-m (40-ft) contour to shore in Lake Michigan 

and that the abundance of larvae tends to decrease as one proceeds deeper and farther offshore. 

This finding led to the suggestion of locating CWISs in deep waters. For 316(b) Phase I, EPA 

considered relocating intakes 125 meters (410 feet) outside of the littoral zone to be a good 

engineering practice aimed at reduced impingement and entrainment. The Office of Naval 

Research states that the littoral zone in ocean environments extends from the shore to 600 feet 

(ft.) out in the water (ONR 2013). In addition, installing the intake to depths where there is a 

lower concentration of living organisms (i.e., at least 20 meters) is also expected to decrease 

environmental impacts associated with intake operations. The reduction in I&E is highly sitespecific; the data in Attachment A suggests that, by itself, while often effective in reducing I&E, 

simply being located offshore does not sufficiently reduce I&E to merit any designation of 

compliance on a national scale.

Velocity Caps

Intakes at a submerged offshore location can utilize various inlet designs including open pipe, 

perforated pipe, cribs, wedgewire screens, velocity caps, etc. Of these, only velocity caps and 

wedgewire screens are designed to reduce impingement.2 As discussed in Section 6.13 of the 

proposed rule Technical Development Document, wedgewire screens can be very effective in 

reducing impingement.3 Nearly all of the velocity caps identified for this memo were located in 

the Pacific Ocean, the Atlantic Ocean or one of the Great Lakes and were located between 800 ft. 

and 7,000 ft. offshore. As above, the data in Attachment A suggests that, by itself, while often 

effective in reducing I&E, simply utilizing a velocity cap does not sufficiently reduce I&E to 

merit any designation of compliance on a national scale.

Analysis of Data

Depending on the design and location, the combination of submerged offshore location with a 

velocity cap can potentially serve as an effective impingement reduction technology when 

compared to shoreline intakes without impingement reduction technologies. This analysis 

focuses on submerged intakes with velocity caps. Other types of intakes are not included, except 

as they provide baseline data regarding the effect of the velocity cap alone.

 

2 A deep offshore location can be effective in reducing the density of organisms subject to entrainment. However, 

this memo focuses only on the performance of velocity caps with respect to impingement mortality.

3

Fine mesh wedgewire screens may also reduce entrainment; however, this memo focuses solely on compliance 

with impingement requirements.
The available impingement reduction performance data includes estimates of reductions based 

on three components/combinations: 1) location alone; 2) velocity cap alone; and 3) a 

combination of both location and velocity cap.

4

Table 1 presents a summary of impingement 

reduction data for each. Note that this data typically refers to a percent reduction in the number 

of impinged fish or biomass and does not necessarily reflect survival in cases where fish 

impinged on shore-based screens are returned to the source water.5There was a very limited 

amount of data available due to the small number of intakes with the velocity cap technology and 

performance data. As a result, EPA included all available data in the summary data shown in 

Table 1 regardless of whether the performance metric is based on number of fish or biomass and 

in a few instances the basis of the metric was unclear. In Table 1, the few data points for 

“Location” (two) and “Combination” (one) are based on number of fish data only. Biomass data 

was available only for the “Velocity Cap” technology group and there was only one study that 

was clearly based on number of fish and that study reported the highest reduction (97%), The 

other six studies (four biomass and two unclear) were also included because these studies present 

a much wider range of performance (50% to 94.5%) than the single study based on number of 

fish. 

Table 1

Summary of Velocity Cap Impingement Percent Reduction Data

Performance Type Average Median Minimum Maximum Count

Location 66% 66% 60% 73% 2

Velocity Cap 78% 82% 50% 97% 7

Combination 76% 76% 76% 76% 1

Note: See Attachment A for a full list of the data sources, all of which are included in EPA’s record for the rule. 

The following performance data presented in the attachment are not included in Table 1:

 Data for the San Onofre intake is an estimate of the survival of fish returned by the fish elevator system and 

does not reflect velocity cap performance.

 Data for Seabrook where it is unclear how values were calculated for the site visit report and where flow

reduction was considered.

 Data for Edgewater unit 5 is for a velocity cap with 3/8 inch break away screens. These screens break away 

when they become plugged and it was not clear whether these screens were in-place during sampling.

Estimates of impingement reduction associated with location alone were identified for only two 

locations. Impingement reductions associated with location alone are difficult to establish 

because they require either the presence of both a shoreline intake and a submerged offshore 

intake without a velocity cap at the same facility or the collection of impingeable fish densities 

data at separate locations. Such data was available for two intakes. One was for intakes located 

850 ft. offshore in 22 ft. deep water in Lake Ontario and the other was located 1,200 ft. offshore 

in the Atlantic Ocean in 24 ft. deep water. Two estimates are provided for the second location. 

The average of these two is used in the summary data. In both instances, the impingement 

reduction estimates are developed by comparing fish density data from gill net sampling 

conducted close to shore and close to the submerged intake. These limited data suggest that 

location alone can account for 60% to 73% reduction in impingement. However, it is not clear 

 

4 Different data sources used different analytical approaches and study methods, proving a wide variety of data for 

comparison.

5

For this analysis, this type of data is acceptable; a fish “not impinged” can be considered towards complying with 

the impingement requirements.
how this data relates to other waterbodies. These data suggest that impingement reductions 

associated with a submerged offshore location alone may not be sufficient to meet impingement 

standards.

Estimates of the performance of the velocity cap alone involve comparing the performance of 

separate intakes located in the same general area or comparing the performance of the same 

intake with and without the velocity cap. Seven sets of impingement performance data for the 

velocity cap alone were available.

6

For three of the intakes located in the Pacific Ocean in 

California, performance was evaluated by reversing the flow between the intake and the heated 

water discharge pipes, which are also located submerged far offshore and are open pipes (i.e., 

have no screening technology). For two intakes, data were collected before and after velocity 

caps were installed or replaced. For two intakes, data were collected for separate intakes located 

in the same general area. The summary data in Table 1 indicate that velocity caps alone can 

reduce impingement by 50% to 97% with an average of 78% and median of 82%. This data 

suggests that in more than half of the velocity caps evaluated the velocity caps alone may

provide sufficient impingement reduction to meet the impingement performance standard;

however, for some intakes, the velocity cap alone may not be sufficient.

Theoretically, the reductions for the combination of the location and velocity cap could be 

calculated by simply summing the reductions.

7

 This is a valid approach for data from the same 

facility since the starting point for data on a “velocity cap alone” is based on the fish available at 

the offshore location. However, the combination of data from different facility locations has 

drawbacks, especially since the “location alone” reductions are very site-specific. Regardless, 

based on the available data, the worst-case combination of the minimum “location alone”

reduction of 60% and the “velocity cap alone” reduction of 50% results in an estimated 

combined reduction of 80%. An actual estimate of the combined performance of velocity cap 

and location was also available for the intake at Seabrook. Here, the estimated impingement 

reduction was 76% and was calculated by comparing performance with a shoreline intake at a 

similar facility located 65 miles away. While there is some uncertainty regarding the validity of 

the estimate since it is from two facilities so far apart, the estimate suggests that the technology

performance is compliant with the impingement standard. The reduction of 76% is also 

consistent with the estimated combined reduction of 80% derived by combining the minimum 

location and velocity cap only reduction.

Conclusion

The impingement reduction performance of intakes submerged far offshore with velocity caps is 

dependent on site-specific conditions. The available data suggests that locating an intake far 

offshore alone may not result in compliance with the impingement performance standard. The 

available data also suggests that velocity caps alone may result in compliance but not in all cases.

However, the data strongly supports an assumption that existing intakes with the combination of 

 

6 An additional intake with a higher impingement reduction than the others (98%) included 3/8 in screens at the inlet 

that break away as they become plugged; since it was not clear whether these screens were in-place during data 

collection, this data is not included in Table 1 summary.

7

For example, if the location reduced impingeable fish by 60%, and the velocity cap reduced the remaining 40% by 

50%, the combined reduction would be 80% (60% + (100-60)*50%).
an intake located far offshore (e.g., at a minimum distance of 800 feet from the shoreline) and the

use of a velocity cap will result in performance comparable to, and in some cases better than, the 

impingement performance standard.
References

ONR - Office of Naval Research. Ocean Regions: Littoral Zone – Characteristics.

Webpage accessed on April 19, 2013 at: 

http://www.onr.navy.mil/focus/ocean/regions/littoralzone1.htm
Attachment A

Summary of Velocity Cap Installations and Performance Data

Owner

Facility 

Name Location

Waterbod

y Depth

Distanc

e 

Offshor

e

Velocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

NRG 

Oswego 

Harbor 

Power, LLC

Oswego 

Harbor 

Units 5 & 6

Oswego, 

NY

Lake 

Ontario

Unit 5 –

22 ft; 

Unit 6 –

22 ft

Unit 5 

850 ft; 

Unit 6 

950 ft

Approac

h velocity 

1.0 fps at 

max flow

Offshore fish 

density near 

intake was 60% 

lower than 

shoreline fish 

density based on 

gill net sampling 

(1.57 fish/sq ft 

net near shore 

and 0.63 fish/sq ft 

net offshore).

60% Location Gill net 

sampling 

near shore 

versus near 

intake.

Ambient fish 

sampling; 

number 

fish/sq ft net.

Data used in 

Table 1. Offshore 

net size was 

twice nearshore 

so fish/sq ft 

metric was used. 

Unit 5 & Unit 6 

each have similar 

offshore intakes 

with velocity 

caps. Unit 6 has 

an onshore 

diversion/bypass 

system -

comparative 

impingement 

data for diversion 

system is 

available.

Total 

fish/species 

collected by gill 

nets near-shore 

and adjacent to 

Oswego Steam 

Station offshore 

intake (DCN 10-

6511D)

Southern 

California 

Edison Co

San Onofre 

Nuclear 

Units 2 & 3

San 

Clemente, 

CA

Pacific 

Ocean

32 ft 3,200 ft 1.5 fps Data cited for 

impingement 

reduction is 

based on four 

other southern 

California 

facilities. Value 

cited in 2008 

Comprehensive 

Demonstration 

study (CDS) was 

88.2%

Velocity 

Cap

Value 

reported was 

from four 

other 

Southern 

California 

plants (El 

Segundo, 

Huntington 

Beach. 

Scattergood, 

Ormond 

Beach).

No useful data.

Due to design of 

discharge 

diffuser system 

evaluation of 

velocity cap not 

possible. Value 

reported was 

from other plants 

included in this 

table.

Site Visit Report 

for San Onofre 

(SONGS) (DCN 

10-6548)

Effectiveness of 

fish elevator and 

return is 72% for 

a total combined 

estimated 

reduction of 97%.

72% Fish Return 

System 

Survival

Entrapped 

fish survival 

versus 100% 

mortality.

Impingement 

mortality of 

entrapped 

fish.

Data not used. 

This value 

represents fish 

return efficacy 

only and not 

performance of 

velocity cap. 

Separate data is 

available for fish 

and 

invertebrates; 

performance 

cited is for fish 

only.

San Onofre 

(SONGS) 

Comprehensive 

Demonstration 

Study (DCN10-

6548C)

Alliant 

Energy

Edgewater 

Unit 5

Sheboygan

, WI

Lake 

Michigan

Depth 

below 

surface 

10 ft

1,500 ft Cap has 

3/8 in 

grills with 

throughscreen 

velocity 

of 0.4 fps

2007 IMEC Study 

reports IM for two 

intakes of similar 

distance offshore 

and similar 

design flow but 

Units 3&4 intake 

does not have a 

velocity cap. 

Estimated annual 

IM for Unit 5 was 

98% Velocity 

Cap with 

inlet screen

Impingement 

for two 

similar 

intakes with 

and without 

Velocity Cap.

Estimated 

Annual 

Impingement 

for each 

intake.

Data not used.

Could not 

determine if 

reduction was 

due to velocity 

cap or screens.

Velocity Cap has 

3/8 in mesh inlet 

screens that may 

or may not have 

been intact.

Section 316(b) 

Impingement 

Mortality and 

Entrainment 

Characterization 

Study for the 

Edgewater 

Generating 

Station (DCN 11-

5402)
Owner

Facility 

Name Location

Waterbod y Depth

Distanc

e 

Offshor eVelocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

<2% of value for 

Units 3&4.

NRG Energy El Segundo 

Units 3 & 4

El 

Segundo, 

CA

Santa 

Monica 

Bay

29 ft 

deep; 15 

ft below 

MLLW

2,600 ft 2.4 fps at 

cap

94.5% IM 

reduction in initial 

1958 study of 

before and after 

velocity cap 

installation.

94.5% Velocity 

Cap

Before and 

after 

installation of 

velocity cap 

on 

submerged 

intake in 

1958.

Biomass: 

focused on 

impingement 

of 

commercially 

and 

recreationall

y important 

species and 

excluded 

forage and 

non-use 

species.

Data used in 

Table 1.

Clean Water Act 

Section 316(b) 

Velocity Cap 

Effectiveness 

Study (DCN 12-

6809)

AES Redondo 

Beach 

Units 5-8

Redondo 

Beach, CA

Units 1-6 

King 

Harbor; 

Units 7-8 

Pacific 

Ocean

Units 1-6 

30 ft 

deep 20 

ft top to 

surface; 

Units 

7&8 45 ft 

deep 30 

ft top to 

surface

Units 

5&6 

1,000 ft; 

Units 

7&8 950 

ft; Both 

approx. 

3,000 ft 

from 

facility

No detailed 

performance data identified

n/a

We Energies Presque 

Isle

Marquette, 

MI

Lake 

Superior

27 ft 

deep 8 ft 

top to 

surface

900 ft No detailed 

performance 

data identified

n/a

Florida 

Power & 

Light

Seabrook Seabrook, 

NH

Atlantic 

Ocean

Water is 

60 ft 

deep; 18 

ft from 

bottom, 

42 ft 

from 

surface

7,000 ft DIF 

velocity 

is 0.5 fps 

at face

Seabrook age 1 

equivalent 

average annual 

impingement loss 

was 68% lower 

than at Pilgrim 

(calculated by 

EPA in Phase II 

Case Study).

68% Combinatio nImpingement 

for Seabrook 

Velocity Cap 

compared to 

Pilgrim 

Shoreline 

Intake 

located about 

65 miles 

away.

Age 1 

equivalent losses due to 

impingement - it is not 

clear 

whether the 

difference in 

intake flow 

Seabrook 

(593 MGD) 

and Pilgrim 

(448 MGD) 

was 

accounted 

for.

Data not used.

Differences in 

calculating 

annual 

impingement for 

each location 

may have 

affected 

calculated 

reduction. Pilgrim 

used design flow - Seabrook used 

average flow also 

Seabrook did not 

sample at night -

suggest rely on 

2006-2008 data 

reported by 

facility.

Case Study 

Analysis for the 

Proposed 

Section 316(b) 

Phase II Existing 

Facilities Rule 

(DCN 4-0003)

83% (Next Era 

2008) based on 

comparable data 

from nearby 

Pilgrim Plant. 

2006 PIC reports 

a 76% reduction 

based on 

number fish/MG.

76% Combinatio nImpingement 

for Seabrook 

Velocity Cap 

compared to 

Pilgrim 

Shoreline 

Intake 

located about 

65 miles 

away.

Number fish 

impinged 

/MG

Data used in 

Table 1. 76% 

value is from 

2006 PIC Basis 

of 83% value

could not be 

confirmed(it is 

possible that this 

includes flow 

reduction since it 

is similar to 81% 

value reported in 

2006 PIC). Only 

76% value is 

Off-shore, Mid 

Depth Velocity 

Caps as Best 

Technology 

Available for 

Impingement 

Control (DCN 

11-6501L)
Owner

Facility 

Name Location

Waterbod y Depth

Distanc

e 

Offshor eVelocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

used

2006 PIC reports 

81% reduction 

(from baseline) 

when 

recirculation flow 

averaging 47 

MGD is factored 

in.

81% Combinatio

n plus flow 

reduction

Impingement 

for Seabrook velocity cap 

compared to 

Pilgrim 

shoreline intake 

located about 

65 miles 

away plus 

flow 

reduction.

Number fish 

impinged 

/MG.

Data not used. 

Since submerged 

offshore intake 

withdraws cooler 

water plant is 

able to 

recirculate an 

average of 47 

mgd -81% value 

includes 

consideration of 

flow reduction 

when compared 

to average intake 

pump flow. Does 

not reflect 

velocity cap 

performance 

alone.

Seabrook 

Nuclear Power 

Station Proposal 

for Information 

Collection 

(DCN10-6514D)

Florida 

Power & 

Light

St Lucie 

Nuclear 

1&2

Hutchinson 

Island, FL

Atlantic 

Ocean

Water is 

24 ft 

deep; 7 

ft from 

bottom 

and 5 ft 

from 

intake 

top to 

surface 

at low 

tide

1,200 ft Emergency 

shoreline intake 

is on Indian River 

estuary. Gill net 

sampling near 

ocean shore 

shows 

impingeable 

density of 2.5 

fish/100 m3 

dropping to 0.8 

fish/100 m3 

beyond the caps 

(68% reduction).

68% Location Gill net 

sampling

near shore 

versus 

beyond the 

intake.

Number Fish 

impinged 

/100 m3.

Data used in 

Table 1 as average of the

two location 

performance 

studies

Site Visit Report 

for St. Lucie 

(DCN 10-6515)

First year (2006) 

result of recent 

study shows 

impingement 

reduction of 

71.6% for fish, 

98.5% for shell 

fish and 77.1% 

overall comparing 

estuary to ocean.

77% Location No details 

provided

Fish and 

shell fish 

combined.

Data used in 

Table 1 as 

average of the 

two location 

performance 

studies. Partial 

results of 2006 

study. Few 

details provided.

Site Visit Report 

for St. Lucie 

(DCN 10-6515)

Average of two 

studies identified

73% Location Data used in 

Table 1. Average 

of two above 

studies including 

both fish & 

shellfish in 

second study.

Site Visit Report 

for St. Lucie 

(DCN 10-6515)

AES Huntington 

Beach 

Units 1-4

Huntington 

Beach, CA

Pacific 

Ocean

18 ft 

from 

surface 

and 5 ft 

above 

riser

1,500 ft 2.8 fps at 

cap

82% overall 

reduction in 

impingement 

during 1978-79 

study in which 

intake and 

discharge were 

switched (see 

TDD).

82% Velocity 

Cap

Capped 

versus un-

capped 

offshore 

intake by 

reversing 

intake and 

discharge.

Biomass of 

impinged fish 

excluding 

silversides.

Data used in 

Table 1. Results 

are conservative 

(effectiveness 

otherwise 

greater) as 

silversides, which 

were only 

present during 

reverse 

operations, were 

Off-shore, Mid 

Depth Velocity 

Caps as Best 

Technology 

Available for 

Impingement 

Control (DCN 

11-6501L)
Owner

Facility 

Name Location

Waterbod y Depth

Distanc

e 

Offshor eVelocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

not included in 

impingement 

reduction 

calculations.

City of Los 

Angeles

Scattergoo

d Units 1-3

Los 

Angeles, 

CA

Santa 

Monica 

Bay

Water is 

29 ft 

deep, 13 

ft from 

bottom

1,600 ft 1.5 fps at 

velocity 

cap 

opening

83% reduction in 

impingement 

during early 

1970s study in 

which damaged

cap was left off 

for a period.

83% Velocity 

Cap

Capped 

versus un-

capped 

offshore 

intake 

(damaged 

cap removed 

temporarily).

Biomass Data used in 

Table 1. 

Comparisons 

between periods 

were confounded 

by variations in 

plant operations 

and cooling water 

flows due to 

power demand 

and outages.

Clean Water Act 

Section 316(b) 

Velocity Cap 

Effectiveness 

Study (DCN 12-

6809)

95/97% IM 

reduction based 

on biomass 

metric/abundanc

e in a 2006 study 

where intake and 

discharge were 

reversed.

97% Velocity 

Cap

Capped 

versus un-

capped 

offshore 

intake -

reversed 

intake and 

discharge 

flow direction.

Number of 

impinged fish

Data used in 

Table 1. No 

significant 

differences in fish 

densities were 

detected 

between the 

intake and 

discharge 

structures from 

the hydroacoustic 

data, indicating 

that differences 

in impingement 

between normal 

and reverse flow 

regimes were 

attributable to the 

presence or 

absence of the 

velocity cap and 

not the fish 

densities in the 

vicinity of the two 

structures.

Clean Water Act 

Section 316(b) 

Velocity Cap 

Effectiveness 

Study (DCN 12-

6809)

Reliant Ormond 

Beach

Oxnard, CA Pacific 

Ocean

35 ft 1,950 ft Overall reduction 

in entrapment of 

61% at night and 

87% during the 

day (Next Era 

2011).

74% Velocity 

Cap

Capped 

versus un-

capped 

offshore 

intake by 

reversing 

intake and 

discharge.

Impinged 

fish 

excluding 

mackerel. 

Likely

reported as 

biomass -

Scattergood 

report 

summary 

does not 

specify 

biomass but 

data is from 

report of a 4 

plant study 

and biomass 

is specified 

for other 

plants. 

Data used in 

Table 1. 

Averaged night 

and day values 

but would be 

better if this was 

a weighted 

average. 

Mackerel were 

removed from 

analysis because 

of unusually high 

relative 

abundance of 

mackerel schools 

in the study area.

Off-shore, Mid 

Depth Velocity 

Caps as Best 

Technology 

Available for 

Impingement 

Control (DCN 

11-6501L)
Owner

Facility 

Name Location

Waterbod

y Depth

Distanc

e 

Offshor

e

Velocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

Constellatio

n

Nine Mile 

Point

Scriba, NY Lake 

Ontario

6 ft from 

bottom; 

14 ft 

from 

surface

Unit 1 

850 ft; 

Unit 2 

1,000 ft

Unit 1 - 2 

fps; Unit 

2 - 0.5 

fps

Site visit Report 

refers to gill net 

sampling being

conducted near 

shore and near 

intake but data 

was not available 

at time of visit.

No detailed 

performance 

data identified

n/a

AES Kintigh 

(Somerset)

Somerset, 

NY

Lake 

Ontario

Depth 

below 

surface 

16 ft; 

Minimu

m 6 ft 

above 

bottom

621 m 0.5 fps 

(0.15 

m/sec)

No detailed 

performance 

data identified

n/a

Constellatio

n

Ginna Ontario, NY Lake 

Ontario

11 ft 

from 

bottom 

15 ft 

below 

surface

3,100 ft 0.6 fps No useful data. 

Gill net sampling 

was performed 

near shore and 

near intake but 

data was only 

compared to 

impingement 

data and not 

between net 

locations.

Comprehensive 

Impingement 

Mortality and 

Entrainment 

Characterization 

Report for RE 

Ginna Nuclear 

Power Plant 

(DCN 12-6810)

EDF Energy Sizewell 

Power 

Station 

(Intake B)

England Intake A 

300 m; 

Intake B 

600 m

Two intakes with 

and without caps. 

Impingement at 

intake B is about 

50% below intake 

A

50% Velocity 

Cap

Unclear if 

data is 

number of 

fish or 

biomass

Data used in 

Table 1.

Technical 

Development 

Document for 

the Proposed 

Section 316(b) 

Existing 

Facilities Rule 

(DCN 10-0004)

Dungeness 

Power 

Station 

(Intake B)

England Two intakes with 

and without caps. 

Impingement at 

intake B is about 

62% below intake 

A

62% Velocity 

Cap

Unclear if 

data is 

number of 

fish or 

biomass

Data used in 

Table 1.

Technical 

Development 

Document for 

the Proposed 

Section 316(b) 

Existing 

Facilities Rule 

(DCN 10-0004)
Owner

Facility 

Name Location

Waterbod y Depth

Distanc

e 

Offshor eVelocity 

Data

Performance 

Data

% 

Impingemen

t Reduction

Technolog

y Aspect 

Evaluated 

Basis of 

Comparison Metric Notes

Performance 

Data Source

Ontario 

Power

Nanticoke 

Thermal 

Generating 

Station

Ontario, 

Canada

Lake Erie West 

intake in 

12 m 

deep 

water

West 

Intake 

475 m; 

East 

Intake 

525 m

No data.

Mentioned in 

Phase II TDD

Technical 

Development 

Document for 

the Proposed 

Section 316(b) 

Existing 

Facilities Rule 

(DCN 10-0004)