Summary of Impingement and Entrainment Data for Power Plants

1/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

Amos (FF) WV NA NA Ohio River Perforated pipe intakes, 43.3 mgd Noted in 1980 report on Philip Sporn 36

Anclote (F) FL 1,100 4,400 cfs Anclote 

Sound 

(estuary)

11/95 study specifically evaluated 

entrainment mortality

Overall average entrainment mortality of 31.8%, temperature dependant; used as 

measure to use dilution pumps rather than natural draft cooling towers; 

condenser/combined with dilution pump survival: acartia tonsa (66%/63%); 

amphiphode (29/58), chaetonethe (28/35), crab larvae (74/80), carideen shrimp 

(45/66), isopode (70/78), pisces larvae (8/47), Pensold shrimp (63/71), shrimp 

larvae (61/60) and pisces juvenile (56/62); from EPRI report (1995 testing), fish 

larvae, total survival 62%, fish juveniles (70%), amphipods (73%), chaetognaths 

(72%), caridean shrimp (81%) and penaeid shrimp (75%)

Facility was required to 

employ a combination of 

cooling towers and dilution 

pumps during certain periods 

of the year tied to biology 

(occurred in 1970s); 

significant long-term 

controversey

15, 37

Arkansas 1 (N) AK NA NA Dardanelle 

Reservoir

Air bubble curtain 1974-75 data: no effects with air curtain, 9.5 million impinged, of which 5.1 

million with air curtain (38 species) in the spring which represents a higher 

impingement rate with an air curtain.

5

Arthur Kill 

(Con Ed)

NY 875 (2 

units: 20 

and 30)

28.6 m3/s Arthur Kill 

strait, across 

from mouth 

of Rahway 

River

Sound system for bay anchovy, 

blueback herring, alewife , 

American shad, and Atlantic 

herring; dual flow traveling 

screens, 2 of 8 screens modified 

(to Ristoph) as a result of Consent 

Order, required these 2 to have 

fish collection troughs, low 

pressure spray wash, fish flap 

seals, and separate fish collection 

sluices, 2 screens had 0.32 

cmx11.3 cm and 0.64 cmx1.3cm 

vs 0.32x0.32 on unmodified, 

velocity range 0.18 – 0.4 m/s, 

seasonal operation in 1991/1992

Cage tests: Alewife and American shad showed consistent avoidance to high 

frequencies (similar to Fitzpatrick); bay anchovy showed no response; the full 

scale: sharp reductions for impingements, similar but lower affects for alewife, 

American shad even less but still 3 times lower than with system off; no effect on 

impingement of gizzard shad (t?), Atlantic herring, and bay anchovy

1999 EPRI Report: 1991/92 testing (continuous rotation during testing), most 

abundant species during summer and early fall (73% of total), Atlantic herring 

(14%) abundant in spring, and blueback herring (9%) during late fall, winter, and 

early spring; survival calculated after 24 hours; unmodified screen had average 

survival of 15%, modified screens had 79 and 92%, marked differences in 

survival observed for alewife, Atlantic herring, Atlantic silverside, bay anchovy, 

blueback herring, and weakfish; no difference in survival (99%) for blue crabs. 

Specific studies made to determine if handling/holding tank or collection sluice 

effect survival – found significant for bay anchovy, blueback herring, and 

Atlantic herring. Larger volume tanks appeared to improve survival; fish sluice 

system had higher survival than debris sluice except for Atlantic herring 

Cited in application for 

repowering of East River 

Station in 1999; saying 

overall survivability for 

modified screens 83%. 

Indicated would review 

further

21, 32

Bailly 

Generation 

Station (F)

IN 615 1165 

m3/min

Lake 

Michigan

Leaky dam, cooling water intake 

well

1985 EPRI Report, test for alewife (egg-adult), gizzard shad (yearling-adult), 

spottail shiner (larvae-adult), and yellow perch (larvae – adult)

6

Barney Davis Corpus 

Christi TX

700 1,870 

m3/min

Laguna 

Madre, 

coastal 

lagoon, 30-50 

ppt salinity

Shovel type lip, single entry, 

double exit traveling screen 

(Passavant), continuous rotation 

0.5 mm fine mesh, high pressure 

spray, approach velocities 0.5 m/s 

to 0.9 m/s

High survival for crustaceans, variable for juveniles, no larval estimates; high 

level of marine grass. Testing for bay anchovy, menhaden, atlantic croaker, 

killfish, spot, silverside, and shrimp – juvenile and adult (EPRI report), high 

survival 0.6 -1.2 inch bay anchovy and gulf menhaden from fine mesh (ASCE 

report); overall initial survival for all individuals 86% (no larvae), lowest% 

mortality for mendahen during February also most prevalent specie during that 

Used extensively in Europe 5, 6, 

20,32
Summary of Impingement and Entrainment Data for Power Plants

2/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

month; bay anchovy were 74% of catch in June and had highest mortality 98%, 

bay anchovy mortality may be due to large numbers of jellyfish .

BC Cobb MI NA NA Lake 

Michigan 

Barrier net, velocities about 0.3 fps Reduced impingement by 50%, some biofouling Similar write-ups for Kyger 

Creek Station and Tanner 

Creek

49

Belle River MI 1695 41.7 m3/s St. Clair 

River

Through flow 9.5 mm angled 

screens (20 degrees) with lateral 

fish passage (18 inch guided 

vanes); orientation of the intake 

structure and trash racks function 

as louver system, lateral current 

function as wash system, approach 

velocity about 0.15 m/s

1980s studies, total of only 679 fish collected from screens, initial survival rates 

of impinged fish high, might be lower than expected because still kept in nets for 

24 hrs. None of alosa (alewives and gizzard shad) survived. Groups of darters, 

centrarchids, sculpins, and catfish exhibited 60% survival

32

Bergum Power Netherlan

ds 

640 1,667 

m3/min

Netherlands 

Lake

NA 1976 study, smelt larvae and juveniles, total survival 10-41%, increased as 

function of size; percidae 39-82%, also increased as function of size.

33

Big Bend 3 and 

4 (ff)

FL 1,335, 

Units 1-3

45.6 m3/s Tampa Bay Intake canal, Units 3 and 4 - fine 

mesh (0.5 mm); Ristoph, low 

pressure spray and troughs, initial 

test then installed on 4, also 

evaluated different approach 

velocities and screen rotational 

speeds, 9.5 fps

1985 data: total invertebrate mortality: 10-35%; bay anchovy: initial (42-84%), 

latent (32-35%); bay anchovy, Atlantic tomcod, and Atlantic silverside total 

mortality of 72.4%; mortality for yolk-sac larvae of mummichog, Atlantic 

silverside, Atlantic tomcod, white perch, and winter flounder: 62-100%, except 

winter flounder at 11-62% mortality; 36-100% mortality for larvae all species; 

comparable results to pilot tests. 

Fine mesh (0.5 mm) screen performance has consistently improved at Big Bend 

units 3 and 4 with better surveillance and maintenance, including bi-weekly 

cleaning of screens to prevent biofouling. 1988 reported efficiency in screening 

fish eggs (primarily drums and bay anchovy) exceeding 95% and fish larvae 

(primarily drums bay anchovies, blennies, and gobies) about 86%. Latent 

survival for fish eggs has improved to 65 – 80% for drum and to 66 – 93% for 

bay anchovy. 

1981 studies found approach velocity not significant factor in survival.

Biweekly cleaning of screens 

to prevent biofouling

1, 9, 32

Big Sandy (F) KY 1060 49.9 

m3/min

Big Sandy 

River

Natural draft cooling, cylindrical 

intake screens fitted with wedge 

wire 0.38 x 1.91 cm, screen 

located in deeper river channel, 

velocity limited to 0.05 m/s

1985 EPRI Report, no biological tests done High loadings of sand and 

silt but easy to clean because 

of shallow depth

6

Bowline Point NY 1200 (2 

units)

2,900 

m3/min

Hudson River 3.0 mm barrier net studies in mid 

90s; previously deployed 9.5 mm 

Mid 90s data: absence of fish abundance made unable to determine effectiveness; 

some clogging and biofouling; silt caused net to sink; later fouled by algae.

Different from Surry in that 

not modified screens (i.e., 

8, 20, 

27, 32
Summary of Impingement and Entrainment Data for Power Plants

3/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

barrier net during Oct.-May, also 

continuously operated screens, 

data from mid-70s, based on early 

studies. Added air bubbler to help 

with ice, debris boom, facility has 

low and high pressure wash 

systems, approach velocity 0.76 

fps

Mid 70s data showed initial survival of YOY 81-98% (white perch) and 89-98% 

striped bass which dropped to 55-56% perch and 52-81% for striped bass, 

(apparently similar trends at Roseton and Danskammer), apparently significant 

issue for fragile gizzard shad and Alosa; net placed in v-neck position around 

intake. 1976-85 data, net effectively reduces with perch and striped bass 

impingement, clogging has not been a problem; not generally stagnant water –

low approach velocity, impingement 91% lower than without net. In April 1982 

of 230,000 yearling white perch and striped bass only 1.6% impinged. In 1976 

conducted studies of various screen operational modes and screenwash pressures 

on survival, looked at: (1) continuous screen rotation with continuous wash, 2-

hour hold with 20 minutes wash and rotation every 2 hours, and (3) 4-hour hold; 

also considered high pressure alone compared to high and low pressure together. 

Results of tests showed initial survival high (96-98%) for YOY white perch 

during all modes; highest for continuous operation 96-98% for initial; and 55-

56% survival for 96-hour; 2-hour (90 and 29), 4-hour 69-75 and 19. Little 

difference between low and high pressure systems. Authors thought this could be 

due to inability of low pressure to pull of screens. Also looked at continuous low 

and high pressure white perch survival in 1997 and saw 87% survival (low 

pressure) and 81% survival (high). 

Also studied entrainment survival in 1978, total survival striped bass: yolk sac 

larvae 84.1 and post yolk sac 100%, white perch: post yolk larvae 31%, Atlantic 

tomcod (100 – post), gammarus sp. 92.3 and nemysis Americana 70.5; similar 

results 75, 77, and 78

buckets), rough sluiceways, 

some exposure to high 

pressure screens, early nets 

no useful for eggs and larvae 

because have to have 

reasonable opening size to 

prevent clogging

Braidwood IL 2240 189 

m3/min 

(make-up) 

must be

closed 

loop

Kankakee 

River

1988 study of entrainment survival; only lepomis sp. larvae collected in sufficient 

numbers to consider initial survival, calculated as 100% considering control (80% 

w/o adjustment to control)

33

Brayton Point 4 MA 1600 total, 

Units 1-4 

984 

m3/min

Lee River for 

Unit 4 

(Estuary) and 

Taunton 

River for 1-3

Angled traveling screens on Unit 

4, and vertical traveling screens on 

1-3 leading to fish bypass. Each 

screen has fish bucket. Unit 4 

originally had fine mesh, which 

was later removed; Unit 4 was also 

closed cycle until 1984 with 0.3 

1984-1986 impingement survival data for Unit 4 showed 25% survival of fragile 

(bay anchovy [0%] and Atlantic Silverside) fish and >65% survival of hardy 

group (winter flounder and northern pipefish). Diversion efficiency for all 

species was 76% but increased to 90% when YOY bay anchovy was excluded. 

Initial survival, post diversion, was 58% (83% w/o bay anchovy, which had only 

5.7% initial survival); latent survival was 63% (0% for bay anchovy); higher 

extended numbers due to differences in numbers of fish.

Bay anchovy greatly reduced 

survival rates

1, 6, 9, 

32
Summary of Impingement and Entrainment Data for Power Plants

4/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

m/s approach velocity; plant also 

conducted a porous dike test 

facility (presumably in 70s). Since 

1997, screens on Units 1-3 have 

been rotated continuously, and the 

plant uses piggyback operation 

where Units 1-3 supply cooling 

water for 4.

1993 document: fine mesh only led to 6.5% reduction in winter flounder 

entrainment, were apparently removed later on; considered wedgewire but lower 

volumes. With porous dike, larval densities used as measure of avoidance; with 

8-inch stones, density of bay anchovy reduced by 94-99%, for winter flounder 

23-87%. Differences in flounder densities increased as season progressed 

Complete entrainment avoidance by juvenile and adult finfish.

1996 annual letter indicates that, pre-continuous rotation impingement survival 

for Units 1-3 was 58% and Unit 4 was 80%; and that continuous rotation would 

increase survival for 1-3 by 7% (although says 62% vs. 58%?); piggybacking 

was projected to eliminate impingement from Unit 4 (by eliminating intake) and 

thereby increase survival by 80%; subsequent document show as much as 29% 

for piggybacking (reduced flow); PCS data for discharge flows; Phil Caruso -

may have started piggybacking before 94; TAC encouraged, 93 permit has flow 

limit but no requirement, 97 MOA made it official, conversation 12/4; new flow 

limits

Brown Ferry 

(N)

TN NA Fresh water Fish pump 27% improved savings of fish Probably little success for 

larvae

5

Brunswick (N) NC 1642 4080 

m3/min

Cape Fear 

River 

(Estuary)

Traveling screens, intake located 

11.7 km upriver from facility, 

flows to plant thru canal, v-shaped 

diversion at canal entrance with nicu screens (9.5 mm); 1mm screens 

on 2 of 4 traveling screens, only 

run when temperatures <18 

degrees C, copper alloy screens to 

limit biofouling

1985 EPRI Report, testing for menhaden, spot, croaker, weakfish, anchovies, and 

shrimp (larvae-juvenile); blue crab (juvenile-adult), Impingement study showed 

that juvenile and adult mendhaden, spot and croaker were diverted by barrier, not 

bay anchovy. Comparative studies in 1984/85, total rate of impingement ranged 

from 6.6 million per day mid-January to 22,000 in mid-November; total reduction 

of fish entrained by the fine mesh vs. conventional screens was 84%; study of 

impingement survival for juvenile and adult fish and invertebrates on screens as 

well, with slow and fast screen speeds showed bay anchovy survival at 0% and 

menhaden survival at16%. 

1979 EPA report indicates loss of 3-4 billion larvae and post-larvae of spot, 

croaker, menhaden, sea trout, blue crab, shrimp, flounder, and mullet a figure that 

translates to 20 million finfish and shellfish, modeling showed 15-35% of 

population. EPA cited cooling towers would provide 95% reduction, whereas the 

facility proposed load reductions that would reduce impact by 26-32%

Note in EPRI Report that 

biological monitoring likely 

condition of renewed 

NPDES permit, conducted 

larval impingement counts 

but not survivability studies, 

intake in “estuarine nursery 

area” according to EPA, 

estimated cost of cooling 

towers $108 million (1979 

dollars), estimated maximum 

capacity loss of 70 MW

6, 32, 45

Buck Steam NC 475 NA Fresh water Location Lower impingement due to intake “flush” with river bank 5

Calvert Cliffs 

(N)

MD 1650 151m3/s Chesapeake 

Bay

Intake canal, 12 traveling screens 

rotated for 10 minutes every hour 

or when sensors detect pressure 

Total impingement finfish ranged from 79,081 (1992) to 9.6 million (1984), 

average 1.3 million; blue crab 219,110 (1992) to 1.88 million (84), 99% survival 

rate for crabs. Total survival 73%, including 99% for crabs. Large database from 

Royce screens (smaller 

mesh) tested in 1981, 

increased impingement, not 

16, 22

33
Summary of Impingement and Entrainment Data for Power Plants

5/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

difference, 10 mm mesh. Original 

conventional replaced with dual 

flow screens. High pressure wash 

leads to return to Chesapeake Bay. 

Facility has learned to anticipate 

episodic impingement and also 

maintain adequate dissolved 

oxygen levels in the intake canal. 

21 years of impingement 

monitoring. Installed barrier net, 

intake velocity about 0.3 m/s, high 

pressure wash (with differential 

pressure sensors which also leads 

to immediate rotation) and return 

to bay through drain system

21 years of monitoring. Most abundant species include anchoa mitchilli (68%). 

Comparison of dual flow versus conventional screens showed: atlantic 

menhaden mean survival (impinged) dual/conventional (7.8/5%), spot 

(41.2%/70.4%) oyster toadfish (100/95.4%), northern searobin (44.4/48.5%), bay 

anchovy (6.3/18.3%), winter flounder (78.8/46.3%), monitoring for 21 years. 

Also evaluated entrainment survival in 1978-80: bay anchovy larvae/juveniles 

extended survival 3-5%, naked goby larvae 88-98%, blenny larvae 37-79% spot 

juveniles 100%; studies behavioral barriers with no effects

used, added differential 

pressure sensors trigger wash 

and rotate, significant 

improvement, also improve 

DO levels, found ways to 

predict episodic 

impingement, coincides with 

warm weather, thermal 

stratification in the bay and 

w to sw wind effect DO 

pattern and fish escape

Cape Canaveral FL 735 791 mgd Indian River, 

brackish tidal 

lagoons

Conventional traveling screens 

(9.5 mm), 2.0 fps intake velocity

1983 Region IV evaluation of intake alternatives, significant effect to Canaveral 

Pool, i.e. 73% of water in pool used by this and Indian River; estimated larvae 

and post-larvae entrainment for forage species such as anchovies and gobies 6.9-

9.9 billion, sport and commercial taxa: drum (1058 million) and sole and flounder 

(105 million). EPA determined variable speed pumps would reduce entrainment 

by 20% with minimal expected benefit for impingement. Fine mesh was 

eliminated because considered experimental from experience at Big Bend, i.e., 

fragile fish larvae – could be updated based on enhancements, sea water cooling 

towers expected to require only 11% of once through flow.

Kaplan concluded everything 

was too costly and/or 

ineffective

38

Cardinal (F) OH 1180 

Units 1 

and 2

1,152 mgd 

(Units 1 

and 2), 

600 MW

Ohio River Vertical traveling screens average 

intake velocity < 0.4 fps, screens 

normally rotated once per 8 hours, 

unit 3 is a closed cycle unit 10.2 

mgd

Conducted technology alternative evaluation circa 1980, estimated 163,593 fish 

impinged annually, gizzard shad (65%), emerald shiner (14%), and channel 

catfish (5%); estimated 79 million eggs and larvae entrained annually (April 

through August), 52% minnows, during this period plant circulated 2.4-11.1% of 

river flow, modified Ristoph <$2.2 million, $1.6 million for Passavant screens; 

barrier net during key impingement periods suggested, problem of winter 

conditions, only about $10,000 for the net

$20 million estimate for 

wedgewire at Muskingum, 

similar, no performance 

numbers

49

Cayuga IN 1,000 2014 

m3/min

Wabash River 1979 study of entrainment survival, initial and 48 hour survival, catastmodiae ysl 

87% and pysl 94%, cyprinadae ysl 41 (temp. variation) and pysl 81%, percidae, 

ysl 50 (highly temp dependant).

33

Cedar Bayou 

(F)

TX 2295 NA Cedar Bayou Comparison of impingement and 

impingement survival between 

dual flow and conventional screens 

- dual flow initially 3.2 mm 

No difference in impingement between dual flow and conventional screens; no 

data on mortality.

Need actual data 22
Summary of Impingement and Entrainment Data for Power Plants

6/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

(changed to 9.5 same as 

conventional due to clogging by 

ctenophores and jellyfish)

Chalk Point (F) MD 1880 2862 

m3/min

Patuxent 

River 

(Estuary)

Drawn thru canal, conventional 

vertical traveling screens, .95 cm, 

approach velocity 0.5 m/s. 2 

barrier nets installed 1981 to 

reduce crab impingement. 

Wedgewire screens with slot sizes 

of 1, 2, and 3 mm studied by State 

of MD in 1982-83

1985 EPRI Report, testing for menhaden, spot, bay anchovy (juvenile-adult), 

croaker and weakfish (juvenile), hogchoker (larvae-juvenile); blue crab (juvenileadult), white perch (egg thru adult); wedgewire studied with slot sizes of 1, 2, 3 

mm. 1 mm led to 80% exclusion of all species from entrainment; and for fish 

greater than 10 mm, entrainment was eliminated. 2 and 3 mm not as effective, 

primary lower slot size benefit to larger fish for entrainment (mostly because 

neither was effective in catching fish below (5 mm), also tested velocity effects 

ranging from 9.5 – 40 cm/s; four fold increase in approach velocity had 

significant impacts on naked gobies, but not for bay anchovies, no effects from 

screen diameter. 

Barrier net reduced impingement liability for all species from over $2 million to 

less than $140,000.

In 1982-83, State of 

Maryland conducting smallscale wedgewire test, similar 

to previous work at “Oyster 

Pt;” 31 ref cites barrier net 

technology unworkable at 

Morgantown – works at 

Chalk Point because of 

shallow wide entry; 

production losses attributable 

to the facility ranged from 4-

20%, also some studies show 

some level of silverside 

survival through entrainment

6, 9, 29, 

35

Clifty Creek 

(F)

OH 1305 960,000 

gpm

Ohio River Vertical traveling screens 1980 Report indicated that going to 1 pump would reduce intake velocity by 

42%, not considered further because said to be already below EPA’s guidance of 

<1.0 fps; some energy penalty, over 175,000 fish impinged, 85% gizzard shad

36

Columbia 

Generating (F)

WI 1054 1514 

m3/min

Wisconsin 

River (Fresh 

Water)

Drawn thru 1,000 m channel, then 

to cooling pond and Ristroph 

screens, velocity 0.34 m/s

1985 EPRI Report, testing for Black bullhead, Bluegill sunfish, walleye, and 

white sucker (adult only). One year test on fish conservation traveling screens, 

limited by low fish abundance

6

Connecticut 

Yankee (N)

CT 660 1500 

m3/min

Connecticut 

River

NA Early 70s studies of entrainment survival, initial only, no species info except 98% 

were pysl of clupeids (herring and alewife), 0-30% survival, temp dependent

33

Contra Costa 

(PGE)

CA 1260 2718 

m3/min

San Joaquin 

River

Fish removal system added to 

traveling screens

98% survival when fish removal system was added to travelling screens; also 

studied entrainment survival in 1976. Initial survival for striped bass larvae was 

0-95% - highly variable, authors indicated threshold for increasing mortality at 

30-32 degree C range. New Unit 8 approval conditioned on study/use of 

Gunderboom system.

Probably little success for 

larvae

5, 33

Cope Station 

Unit 1

SC 385 0.3 m3/s South Fork 

Edisto River

Caisson water intake, 2 wedgewire 

screens

Striped bass, white perch, bay anchovy species of concern, engineering and 

modeling done to show reduced I&E w/screens; no data provided in EPRI report

Need for cross current, all 

current work in fresh water

32

Crystal River 

(F and N – unit 

3)

FL 1800, 

Units 1-3; 

1500 MW, 

Units 4 –5

2,936 cfs 

(1-3 only)

Crystal Bay, 

estuarine 

nursery

Units 4 – 5: natural draft; Units 1-

3: once through. Waters for once 

through pass through intake canal; 

1-3 have traveling screens with 9.5 

mm mesh, rotated once per 8 hours

Cooling Tower System: 10% blowdown and 80% reduction in water needs 

using salt water make up; 

Kaplan noted that the Crystal Bay region is a spawning area for numerous species 

of fish and shell fish, that impingement took 23 tons annually, including 3.4 tons 

of shrimp and 14.3 tons of blue crab. Estimated entrainment/impingement loss of 

Kaplan found 316(b) 

demonstration for 1-3 

inadequate in 1986; FPL 

demonstration (1985) did not 

evaluate technologies, FPL 

estimated $20.1 million to 

1, 39, 

40, 41
Summary of Impingement and Entrainment Data for Power Plants

7/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

over 20 million/88,000adult equivalent bay anchovy, 84,000/15,000 pinfish, over 

700,000/28,000 spot, 30,000/641,000 pink shrimp, blue crab 2/640,000. No 

return system, annual entrainment in the billions of fish eggs and larvae, 

anchovies and crustaceans. Region 4 determined that cost was excessive for 

cooling towers (Kaplan mentions $150 million, presumably provided by FPL); 

helper cooling towers proposed by FPL would lower the thermal discharge but 

not reduce intake requirement; fine mesh screens were eliminated due to the 

potential for siltation. FPL notes that 50% reduction in entrainment of shrimp, 

pinfish, and bay anchovy possible with fine mesh screens; therefore, the only 

requirement in renewed 1988 permit for Units 1-3 was to reduce flows during 

Nov. – April by 15%, as well as comprehensive mitigation program. New units 

94 and 5) were required to install cooling towers. 

1982 study of fine mesh screens by retrofitting one screen on Unit 2 with 0.5 mm 

screen. Result: screen operated at 10 ft/min except when coal barge traffic (cause 

of siltation) was high, then it operated at 20ft/min and experienced severe 

plugging. (ASSUME THIS IS UNIQUE CONDITION)

retrofit with fine mesh 

screens

D.C. Cook MI 2200 6.3 million 

m3/min

Lake 

Michigan

Currently has 9.5 mm traveling 

screens, washed with jet spray to 

larger baskets

Annual impingement losses from 1975-82 ranged from 53,000-2.3 million. Peak 

impingement in June and July and often secondary peak in April-May; alewife 

68%, spottail shiner 10%, yellow perch 9%, trout-perch 5%, rainbow smelt 4%, 

and slimy sculpin 2%, 1,000 salmonids per year during both unit operation, 

Reference 46 indicates 80% of all fish impinged during April-July, most YOY 

August-October, during 2 unit operation, average of 54% annual loss during 

June. Suggested seasonal reductions in flow; in particular, scheduling refueling 

and maintenance during these months

Ref 46 suggests barrier net 

could be used during AprilJuly with projected 80% 

reduction in impingement; 

suggest fine mesh not proven 

at high intake flows

46

Danskammer 

Test Facility 

(F)

NY 490 1196 

me3/min

Hudson River 

(Estuary)

Equipped with angled traveling 

screens, the plant tested 0.5 mm 

fine mesh screens; in 1979 the 

power plant installed a modified 

front wash screen with an 

approach 0.45 m/s 

1981 angled travelling screen data: overall diversion efficiency at 95-100%, with 

the mean at 99%, including bay anchovy, blueback herring, white perch, spottail 

shine, alewife Atlantic tomcod, pumpkinseed, Amercian Shad. Overall latent 

survival = 84% (mean) - 68% alewife to 99% spottail shiner. Plant studied 

effectiveness of modified screen in reducing impingement and observed no 

differences between 3 approach velocities.

1, 6

Delta Fish 

Protection 

Facility

NA NA NA Louver system Found strong correlation between fish length and guidance efficiency for striped 

bass and white catfish. <80% for smaller than 1” striped bass and 1.6” for white 

catfish, much higher for larger fish, i.e. >2”

20

Diablo Canyon 

(N)

CA 2,200 9.45 

million 

m3/day

Pacific Ocean Constructed intake cove behind 

break water; vertical traveling 

screens (9.5 mm mesh)

Adult Equivalent Calculations - June 1996-1999 entrainment data, 16 taxa: 

18,200 and 23,400 brown crab, 54,600 and 17,900 slender crabs; Pacific Sardine 

2,650-7,000 per year; northern anchovy 43,200 –120,000 per year; rockfishes 

164-353 per year; Painted Greenling (larval data) 9.6 – 24.2 million; Sculpins 

Tenera (1988) showed 

impingement at 0.32-0.73 

kg/day. Cost to widen 

intake/slow velocity = $51 

1
Summary of Impingement and Entrainment Data for Power Plants

8/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

(larval data) 36.3 million –51.9 million; White Croaker 14,700 –21,600 per year; 

Monkeyface Prickleback (larval) 61.7-83.1 million; Kelpfish 181-308 million; 

Blackeye Goby 64,100 – 188,000; Flatfishes 1,450 – 6,710 (Sanddabs) and 

Halibut 8.26-15.7 million; 

PGE 1988 (studies at Diablo, Moss Landing, and others) found that impingement 

mortality could be reduced by as much as 75% with modified screens and fish 

return sluiceways. Studies by Tomljanovich show 1.0 mm screens would 

substantially reduce entrainment and 0.5 mm mesh would virtually eliminate 

entrainment. Studies then show <1 (striped bass) -96% (bluegill and smallmouth 

bass) 48h survival on fine mesh screens. Fine mesh could help acknowledged by 

PGE but necessary design modifications could increase impingement; variable 

speed pumps would only reduce flow by 2-10%.

million; more screens needed 

for lower velocity $51 

million. No impingement 

survival expected due to 

large debris; $13 million for 

fish return sluiceway; $658 

million cooling tower, $10 

million for fine mesh, 

variable speed -$7.6 million

Dominion 

Surry Plant (N)

VA 1550 6360 

m3/min

James River, 

some salinity 

in water 

(Estuary)

Intake channel, continuous screen 

rotation, fish compartments for 

each Ristoph screen, low pressure 

wash and return

1974-1976 impingement data indicated 93.8% survival for all fish with anchovies 

lowest at 83%. Facility has modified Ristoph screens with low pressure wash 

and fish return systems.

1985 EPRI Report: testing for alosa spp., menhaden, spot, croaker (juvenile), 

hogchoker and bay anchovy (juvenile-adult)

Pretty high maintenance 

could have been reduced by 

alternative materials, 

rotations speed, and more, 

smaller screens

5, 6

Dungeness A 

and B

England NA NA Ocean Velocity cap difference between 

and A and B

62% decrease in catch, largely due to sprat, with a contributing factor being only 

1 pump running at B while 3 were running at A.

3

Dunkirk Steam NY NA NA Lake Erie Dual flow screens, 0.27 m/s, 

screen speeds of 5.5 and 16.5 

m/min considered, installed at both 

units with 3.2 mm mesh at .27 m/s, 

operated continuously; studied in 

1987 and 1990/91. 1998 modified 

dual flow installed on Unit 1 for 

testing – nose cone on upstream, 

solid wall to improve flow 

distribution, improved fish bucket 

design and internal and external 

low pressure fish sprays 

Impingement survival about 50% for major taxa, except alewife at 3%; data hard 

to interpret; interesting of 92 alewife collected at fast speed 99% initial and 3% 

latent survival; emerald shiner (97/84%) both speeds, gizzard shad most high 

speed (97/52%), rainbow smelt (98/39%), spottail shiner (only high) (100/90%), 

white bass only high) (98/56%), yellow perch (only high) 100/95%), data 

includes both juveniles and adults.

1999 EPRI Report: modified dual flow tested in 98/99, only winter 98/99 

preliminary survival data in report; high survival for most species and improved 

design leads to improved fish handling: survival of emerald shiner initial/latent 

juvenile (81%/67%), adult (91/89); gizzard shad (only juvenile) (71/16); rainbow 

smelt juvenile (55/22), adult (83/48); white perch (78/64); low survival for 

juvenile alewife but only 25 fish collected.

22, 32

Eddystone, 

Units 1 and 2

PA 1400 total 28 m3/s, 

units 1 and 

Delaware 

River 

Cylindrical wedge wire, 6.4 mm 

mesh, located on shoreline and 

Mesh size precluded significant effects on entrainment; but technology has 

effectively reduced impingement. Pre-wedgewire screens showed over 3 million 

Relative fresh water at this 

point although under some 

2, 21, 32
Summary of Impingement and Entrainment Data for Power Plants

9/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

2 only backflushed with compressed air fish impinged in 20-month period, EPRI indicates impingement has been 

eliminated.

tidal influence and slightly 

brackish

Edgar Energy 

Park (F)

MA 306 (458 

MW - old 

facility

NA Weymouth 

Fore River 

(tidal estuary)

Shoreline intake with traveling 

screens, fish buckets, high and low 

pressure sprays and fish return, 0.4 

– 0.7 fps approach velocity

Entrainment data: menhaden 278 adult equivalents estimated to be lost, poor 

evaluation of local effects, rainbow smelt 4.7% in area, Atlantic tomcod 337 lost, 

1.25%, Atlantic silverside 37,774, 2.5% of population, Cunner 2,648 lost, 1%, 

windowpane 1551 (1%), winter flounder 24 lost, 1.7%; survival of clams 

expected to be high. Impingement: 9.39 to 25.38 flounder per day and 2.11 to 

3.25 smelt per day (based on 1976 study at old plant)

Combined cycle proposed, 

evaluated angled screens 

(misinterpreted Brayton 

data) and other technologies, 

very cursory

13

Edge Moor (F) DE 710 782 mgd Delaware 

River 

(Estuary)

Traveling screens with 9.5 mm 

mesh, not rotated continuously, 

fish troughs and return, Amertap 

(balls) to prevent biofouling, high 

pressure wash

Entrainment studies 74-75, impingement 73-75, DE DNR “I/E at Edgemoor for 

striped bass and bay anchovy are significant, approach velocity 1.5 ft/s

Significant improvement in 

River conditions since mid 

70s, plant intake is in 

important striped bass 

spawning area

11

Edgewater WI 820 454 

m3/min 

(Unit 5 

only)

Lake 

Michigan

3 offshore intakes (860 m), Unit 5 

intake has velocity cap with 

Johnson Vee-wire (0.95 cm 

opening), other 2 intakes no cap; 

all have traveling screens at plant

1985 EPRI Report, alewife, rainbow smelt, and yellow perch (juvenile) Units 1 and 2 were to be 

retired when 5 came on line

6

El Segundo (F) CA Pacific Ocean Velocity Cap (offshore) 80-90% reduction in fish entrapment. Fish pumps not consistently useful because 

fish did not congregate in quiet area where pump located.

Cap does nothing for eggs 

and larvae (behavioral

control)

4, 5

Empire Electric 

and N. States 

Power

NY N/A (lab) N/A (lab) N/A (lab) Fine mesh screens, 0.15-0.91 m/s Early 1980s testing by Empire Electric and Northern States Power indicate 

“selective larvae capable of active diversion at a very young age.” Recommend 

use of lifting buckets, low pressure washes, fine mesh materials, and sluiceways. 

Velocity and duration of impingement key factors. Over 3,000 tests conducted 

with more than 75,000 larvae. Striped bass exhibited high mortality under all 

conditions, while winter flounder, alewife, and yellow perch prolarvae had low 

mortality, especially with short exposure duration. Post-larvae mortality higher 

in some cases, but also high in controls.

1981 data: Alewife prelarvae/postlarvae retention (30.3 - 95.9% versus 1.4 -

23.7% for the low control group); channel catfish 86.1-98.6% retention; bluegill 

73.7-98.6% retention; striped bass (0-48.8% retention versus the control group at 

52.5-96.2%; yellow perch 67.7 - 95% versus the control group at 17-68.1% 

retention; winter flounder (64.4 - 92.7% retention versus control group retention 

at 0 -35.1% on 4.4 mm mesh screen; walleye (20.4 - 68.6% versus the control 

group. 

2

Fort Calhoun NE 481 1363 Missouri NA 1977 study of entrainment survival, initial survival freshwater drum 6-40%, mean 33
Summary of Impingement and Entrainment Data for Power Plants

10/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

(N) m3/min River 19%, total larvae (drum, catostimidae, and gizzard shad 8-81%, mean 32%, 

intake survival average 6 X greater than discharge, also tested macros in 73-77, 

initial survival 87-92%.

Ginna NY 517 1514 

m3/min

Lake Ontario Intake 3100 ft offshore, then to 

fine mesh traveling screen

1980 study of entrainment survival; initial and 96-hour, initial survival of alewife 

eggs 62.5%, extended 19% after 4 days, and 16% after 8 days, intake survival 

also poor.

33, 50

Great Lakes 

Pilot

NA NA NA Great Lakes Velocity Studies No significant effects seen in velocity increase from 0.5 ft/s to 2.0 ft/s. 4

Green River (F) FL 220 404 cfs Green River Presumable traveling screens with 

no return

In the late 1977s, Region IV indicated that the Green River was a major tributary 

to the Ohio River and that during low flow conditions the facility could take up to 

half of the river water; this could entrain nearly half the population of eggs and 

larvae, suggested potential reduced load operation in June (critical period); eggs 

only found during Spring

44

Hinkley Plant 

(N)

England NA NA Severn 

Estuary

Offshore intake Influenced by subtidal issues. 3

Huntington 

Beach

CA Pacific Ocean Velocity Cap (offshore) 80-90% reduction in entrapment. Fish pumps not consistently useful because fish 

did not congregate in quiet area where pump located.

Schuler and Larsent found 

that velocity increase from 

0.5 ft/s to 1.5 ft/s with 

modified cap, significant 

increase at 2.0 ft/s (anchovy, 

croaker, and surfperches)

4, 5

Indian Point 

(N) 

NY 1829 6360

m3/min

Hudson River Study using fine mesh traveling 

screens (2.5 mm); also modified to 

operate continuously with buckets 

and low pressure washes; also 

evaluated air bubbles, according to 

ASCE not function well; Unit 3 

study of fish pulser

1977-78 studies, 0.2 to 4.1% recovery of yolk-sac and post yolk-sac striped 

bases, 44% recovery of juveniles. Survival highly dependent on return system; 

larvae mean 15 mm survival 60%; juveniles 75% or more; data comparable to 

survival thru entrainment – striped bass (yolk-sac 38-67%, 75-85% post yolk sac, 

and 83% juveniles.

Redesigned fish troughs on Unit 2 in 1986, previous results considered 

unacceptable, problem with filamentous algae, low pressure wash worked well 

when limited algae, initially problems when high algae, modified and mortality 

reduced “appreciably,” injuries and deaths reduced from 53 to 9% for striped 

bass, 64 to14% for white perch, 80 to 17% for Atlantic tomcod, 47 to 7% for 

pumpkinseed. Striped bass losses due to the debris removal system reduced from 

23 to 0%for striped bass, white perch 33 to 1.3% and Atlantic tomcod 20 to 0.3%. 

Fish pulser had some unspecified benefit when large numbers of fish near intake; 

also studied intake survival in 1977, initial: striped bass ysl 63-85%, pysl 87%, 

white perch ysl 73 and pysl 89, bay anchovy pys l18-36, clupeids 40%; 78 data 

Modifications that led to 

survival improvements in 

Fletcher which showed 

impingement deaths to 

transport system not 

impingement on screen

14, 20, 

22, 24, 

32, 33
Summary of Impingement and Entrainment Data for Power Plants

11/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

too variable to use, 1979 initial data, Atlantic tomcod larvae 11 – 64 (temp 

dependent), striped bass eggs 74%, striped based ysl 59-76%, pysl 63-70, white 

perch pysl 29-32, clupeids pysl 22-31, anchovies 3-7; 1980 initial data: Atlantic 

tomcod larvae 48-88 (temp dependent), striped bass eggs 58% (only extended), 

striped based ysl 57-74%, pysl 55-81, white perch pysl 50-90 (temp dependent), 

clupeids pysl 62, anchovies 2-4; 1986 data: sample sizes only sufficient to 

calculate anchovy survival, initial survival 24%, neither intake or discharge 

survived 96 hours, therefore extended likely much lower; 

1988 data: bay anchovy initial pysl 25%, not survival in intake or discharge for 

24-hour; striped bass ysl 60 and pysl 79; whiter perch 24-hour pysl 38, alosa spp.l 

pysl 22 24-hour; intake survival used to calculate total.

Indian River DE 1435 Unit 

4 (400 

MW 

closed 

cycle)

989 

m3/min

Indian River 

(Estuary)

Intake canal, 0.46-0.64 fps, rex 

chainbelt vertical traveling screens 

(3/8 inch mesh), not continuously 

washed, fish return

Entrainment studies 75-76, impingement 74-76, adult equivalent modeling; 1976 

entrainment survival study: initial and extended but unclear in report what results 

are for: bay anchoy (entrainable) 50-100% (initial and extended survival rate) at 

<25 degrees going down to 0 at 35 degrees, however, limited by significant 

mortality in control samples, Atlantic croaker entrainable 57-100% down to 0%, 

spot entrainable 100 down to 25%; Atlantic menhaden entrainable 87-100% 

down to 0; Atlantic silverside entrainable 100% down to 0; entrainable means 

primarily larvae; some juveniles.

11, 33

Indian River FL 610 835 mgd Indian River, 

brackish tidal 

lagoons

Conventional traveling screens 

(9.5 mm), 2.0 fps intake velocity

1983 Region IV evaluation of intake alternatives, significant effect to Canaveral 

Pool, i.e. 73% of water in pool used by this and Canaveral; estimated larvae and 

post-larvae entrainment for forage species such anchovies and gobies 6.9-9.9 

billion, sport and commercial taxa, drum (1058 million) and sole and flounder 

(105 million), EPA determined variable speed pumps would reduce entrainment 

by 20%, minimal expected benefit impingement, fine mesh was eliminated 

because considered experimental from experience at Big Bend, i.e., fragile fish 

larvae – could be updated based on enhancements, sea water cooling towers 

expected to require only 11% of once through flow

Kaplan concluded everything 

was too costly and/or 

ineffective

38

J.H. Campbell 

3 (F)

MI 1422 total, 

770 MW 

Unit 3

71m3/s Lake 

Michigan

Cylindrical wedge wire at 9.5 mm 

mesh and intake at 1060 ft 

offshore (Unit 3) versus Units 1 

and 2 with vertical traveling 

screens.

Unit 3 system reduced entrainment of gizzard shad, smelt, yellow perch, alewife, 

and shiner (testing on larvae thru adult); eliminated impingement of gizzard shad, 

smelt, yellow perch, alewife, and shiners; and has generally performed well –

screens cleaned annually to avoid biofouling; however, not useful to prevent 

entrainment of smaller fish (eggs and larvae) but few are found at the offshore 

intake location. Wedgewire screens have eliminated impingement of gizzard

shad, smelt, yellow perch, alewife, and shiners. Screens are cleaned annually to 

prevent biofouling.

Slot size is not issue because 

depth of screens avoids 

smaller organisms

2, 6, 21

J.P. Pulliam (F) WI 400 1561 Fox Vertical traveling screens (0.95 1985 EPRI Report: testing for alewife, gizzard shad, yellow perch, walleye, State approved system as 5, 6, 20, 
Summary of Impingement and Entrainment Data for Power Plants

12/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

m3/min River/Lake 

Michigan

cm), dual barrier net around 

shoreline intakes (6.4 mm), also 

tested air bubble curtain, high 

pressure wash, 1998 mods to 

system – primarily mechanical, 

nets in place >37F or April 1 til 

<37 or Dec 1

american shad, spottail shiner (juvenile – adult), specific impingement studies on 

yellow perch; EPRI indicates no evidence impingement reduction with air 

bubbles. 

TVA 1976 generally suggested some benefit for alewife; 

1970s data from ASCE indicates studies of yellow perch, impingement survival 

under 2 scenarios: (1) impingement alone/hand removal and (2) impingement 

with high pressure screen wash. Under (1), initial survival 84 –100%, 96-hour 

82.1%; under (2) initial survival was 73.3% -100% and the mean 96 hr survival 

was 87.1%, with generally hardy species present. 

1980s data show net (in place when the water temperature is greater than 37 

degrees F, or from April 1 to December 1, reduced impingement overall by 90% 

(ASCE suggested potential for 100% with minor mods, as at Bowline where there 

is a low approach velocity (0.4 fps) and clogging is not issue.

BAT including barrier nets 32

J.R. Whiting NY 238 0.214 gpm Lake Erie Intake at N. end of channel from 

Maumee Bay, 3 vertical traveling 

screen with 3/8 inch mesh

1979 Impingement and entrainment study, using deterrent nets, 100x22 foot 

nylon mesh with 3/8 inch openings. Without use of barrier: 17,378,518 fish 

impinged, estimated 629,369,381 larvae and 553,620,137 eggs were entrained 

April 1979 to December 1979. With net, subsequent sampling in 1983-84, 

421,978 fish impinged (97% effective); in 1987, 82,872 fish impinged (99% 

effective), and in 1991 316,575 fish impinged (98% effective); no eggs or larvae 

data.

Need specific species info 32

James A. 

Fitzpatrick (n)

NY NA NA NA Sound systems From Ross 1993, tests of sound protection to deter fish: alewife avoid high 

frequency sounds, 85% reduction in impingement during peak operations, 88% 

during non-operating modes when only 2 intake pumps operating, on basis of test 

results installed full-scale system

Behavioral testing in 1976-77, 1983-84, and 1985-86 conducted at Pickering 

Station in Ontario. Sound (popper) found to be effective diversion for alewife. 

EPRI 1985 and 1986 results show 73 and 76% diversion efficiency.

21

Jeffrey Energy 

Center

KS 2010 3.1 m3/s Kansas River Closed cycle cooling, 10 mm 

wedgewire screens, 0.2 m/s thru 

slot velocity

Clearly not useful for entrainment, operating since 1982, considered both 

traveling and wedgewire; largely selected here because of reduced wear. Need 

biological data

32

Kammer (F) WV 675 1029 cfs Ohio River Vertical traveling screens (3/8”), 

once through, velocity < 1 fps, 

screens normally rotated once per 

8 hours

Conducted technology alternative evaluation in 1980. Estimated 12,520 fish 

impinged annually, gizzard shad (64%), emerald shiner (14%), white crappie 

(8%) and channel catfish (6%); estimated 182 million eggs and larvae entrained 

annually (April through August), 61% minnows, during this period plant 

Very general technology 

evaluation similar to Sporn, 

everything too expensive

48
Summary of Impingement and Entrainment Data for Power Plants

13/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

circulated 1.6-9.4% of river flow; technology evaluation the same as Philip 

Sporn, wedgewire estimated to be $7.5 million; modified Ristoph based on 

Tanner <$2.2 million; not enough room for collectors; cooling towers $50-60 

million 

Kewaunee (N) WI 540 413,000 

gpm

Lake 

Michigan

Air bubble curtain, velocity at 

intake mouth 0.9 fps

Reportedly lower impingement of alewife using air bubble curtain. Here, no 

specific biological studies - more due to less operational impacts, 50% reduction 

in fish entering intake system

A number of studies on 

salmon show much more 

successful during daylight 

hours; Bibko et. al found it 

could be successful during 

night for YOY striped bass

5, 23, 50

Kintagh, 

originally 

Somerset (F)

NY 625 12.0 

m3/min

Lake Ontario Velocity cap (0.15 cm/s), 4 

modified traveling screens with 

either 1.0 fine or 9.5 std. mesh, 

low pressure spray and return 

system

1985 EPRI Report: testing for alewife, rainbow smelt, yellow perch, and white 

perch (all), smallmouth bass (YOY - adult), lake, brown, and rainbow trout and 

Chinook salmon (yearling-adult), EPRI report says continuous monitoring thru 

1985 with species-specific studies thereafter; evaluation of screen size and 

season. 

1989 screening system improvements, specifically washing system upgrades. 

Ref 19 data: alewife 96 hr survival improved from 15% to 44% after 

improvements in 1989, gizzard shad from 54% to 65%, and other species 

generally greater than 80%: summer survival (1986); rainbow smelt 1.5% 

(summer, small number) and 95% (fall) (1985); rock bass 95% survival 1985; 

spottail shiner 84-100% survival (1985 – 1986), white bass fall 1985 96% 

survival, white perch winter 85 72% survival; yellow perch winter 85 81% 

survival; estimated number entrapped by 1-mm screen ranged from 123,391-

780,361, except in 1986 2 to 35 times more than 9.5 mm mesh

6, 19

Lasalle Station 

(N)

IL 2156 114-228 

m3/min to 

pond

Illinois River 

(Fresh water)

Shoreline intake with 2 Passavant 

center-flow traveling screens

1985 EPRI Report, no testing to date 6

Logan

Generating

NJ NA 1 m3/s Delaware 

River

Closed cycle cooling tower, intake 

has 1 mm wedgewire

Wedgewire screened entrainment = 0.003% of striped bass larvae in area, 

compared to 0.03% with unscreened intake.

Area where striped bass 

spawn and rear

18

Lovett NY 463 total Unit 3 

flow, 2.7 

m3/s

Hudson River Gunderboom, nominal filtration 

capacity of 0.02 mm. Testing 

initially performed on entire Unit 3 

flow, installed on 3, 4, and 5; 

modified system installed at Unit 3 

in 1998 with nominal mesh 

opening of 0.212 mm (0.5 mm 

perforations), air burst cleaning 

Susceptible to clogging and water flowing over the top. 1995 initial testing 

showed 82% effective in reducing entrainment among primary species - herring, 

bay anchovy, striped bass, and naked goby. Tested from June thru August 

(summertime) showed a reduction in performance to a level comparable with a 

travelling screen, largely due to operational difficulties. 1999 – 2000 testing had 

the same difficulties. 

Testing of modified boom installation in 1999 generally found no obvious 

Not shown to be long-term 

effective

3, 21, 

32, 34
Summary of Impingement and Entrainment Data for Power Plants

14/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

system modified, high degree of 

algae growth, average flow 

through screen velocity at 0.02 fps

mortality associated with impingement on the Gunderboom material. 

Impingement data similar to control; somewhat general findings; according to 

gunderboom technology lead, lower performance during 2000 (do not actually 

have data).

Marshall and 

Allen Plants 

(Duke) (F)

NC 1155 –

Allen, 

2000 -

Marshall 

NA Fresh water Location Higher impingement rates than Buck due to intake location at the end of cove 

(Marshall) and at the end of shoreline depression (Allen) – better fish habitat.

5

Michigan City 

(F)

IN 680 NA NA Air bubble curtain Reportedly lower impingement of 50% for alewife using air bubble curtain. 

ASCE also noted some alewife impingement reduction at J.P. Pulliam and 

Michigan City during air bubble curtain test but saw no such benefits at Arkansas 

Nuclear. Plant also use electric screens for larger fish

5

Milliken 

Station (F)

NY NA NA Lake Cayuga Test of strobe light deterrence, 

offshore intake, no physical 

barriers

37% less of all fish entrained when strobe lights operating; individual species 

results mixed; most effective in December, April, May, and June when intake 

water cooler; significantly effective for repelling YOY rainbow smelt, yellow 

perch, white sucker, and trout perch during entire study period; alewife and total 

fish as measured by numbers and biomass significantly repelled in winter and 

spring, juvenile smelt unaffected while adults collected in greater number with 

lights on; in July and August alewife also appeared attracted to lights.

25

Millstone (N) CT 2672 7055 

m3/min

Niantic Bay, 

Long Island 

Sound

Unit 3, shoreline intake at 8.5 m 

depth, 6 traveling screens

(originally 4.8 mm then increased 

to 9.5 mm due to clogging) with 

0.6-0.7 m/s velocity and fish 

conveyance; Unit 1 and 2 similar 

but smaller. Unit 1 has fish 

conveyance

1985 EPRI Report: testing for anchovy (adult), winter flounder (larvae-adult), 

Lady crab (adult), squid (juvenile-adult), lobster (adult) stickleback (adult), 

grubby (larvae-adult), tautog (larvae), sand lance (larvae), silversides (adult). 

1993 doc, primary effects on winter flounder larvae where annual entrainment 

estimates ranged 31-219 million. Approximately 8-20% of the annual production 

entrained with entrained larvae survival <1%. Wedgewire screens not proven 

due to higher flow than most other facilities (better for closed cycle); looked at 

extending intake offshore into Long Island sound. Cooling tower would decrease 

intake need by 95%. Moving offshore for Unit 3 only was estimated to reduce 

overall winter flounder larvae entrainment by 25% – may increase other species 

(grubby). 

Unit 2 1976-87 data: 8,610-60,410 fish impinged (not including 480,000 sand 

lance impingement in 84), also looked at timing (spring key time for larvae 

entrainment) – significant capacity issue.

1985-1986 continued 

impingement monitoring was 

expected, Unit 3 was to be 

completed in 1986; some 

monitoring back to 1971 for 

Unit 1 – studies led to 

rejection of behavioral 

controls for Unit 1; 1993 

document indicates that 

dual flow not usable where 

freezing occurs

6, 9

Mitchell (FF) WV NA NA Ohio River Perforated pipe intakes, 25 mgd Noted in 1980 report on Philip Sporn 36

Monroe Plant 

(F)

MI 3150 5520 

m3/min

Raisin River 

and Lake Erie

Fish pump/removal system added 

to traveling screen, 70s studies 

70-80% survival, gizzard shad and yellow perch (focus on adults and perch and 

YOY), largely as a result of pumping system for fish return added to travelling 

Probably little success for 

larvae because non-motile –

5, 20, 

33,47
Summary of Impingement and Entrainment Data for Power Plants

15/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

focused on use of pumps to safely 

remove fish from screenwells, 

physical/light techniques for 

guiding fish to pans, also 

considered air bubbles

screen. Latent mortality low; air bubble curtain not successful according to 

ASCE. 

1982 study of entrainment; survival calculated using intake level, clupeidaes 

prolarvae initial 1.2% survival, prolarvae 3-hour 15.3%, post larvae 3-hour 38%, 

juveniles 25% 3-hour; cyprinidae, post larvae 24-hour 75%; white bass, post 

larvae initial, 93%; yellow perch: pro larvae 3-hour 2.6 and post-larvae initial 

2.7%; freshwater drum: prolarvae initial 100%, postlarvae 94%; from ref 47, total 

impingement 75-76 4.7 million fish, including 626,000 yellow perch, 20.7 

million larvae and 27.5 million eggs

fish have to move to pans. 

Apparently times of year 

when entire flow of Raisin 

River diverted through plant

Morgantown MD 1,150 2,230 cfs Potomac 

River 

(mesahaline

estuary)

BTA improvements consist of 

curtain net and fish return, barrier 

net found not to work, could not 

operate behind curtain

35

Moss Landing 

6 and 7 and 

proposed 2 

additions 

(replacing 1-5)

CA 1530, 

Units 6 

and 7 

(propose 

to add 2 

units at 

530 MW)

2,270 

m3/min 

(6/7); 946 

m3/min 

for new 

units over 

original 

1,441 

m3/min 

for 1-5

Pacific 

Ocean, Moss 

Landing

Continuously rotating screens 

were studied versus intermittent 

rotation; new units (530 MW) 

would be combined cycle, 

proposed inclined with 0.8 cm

mesh, approach velocity 0.5 fps

6/7 demonstration numbers: no change for hardy species such as plainfin 

midshipman and crabs; “substantial increase” in survival for surfperch and 

rockfish (11% of fish impinged); potentially no increase (vague) for pacific 

herring, bay anchovy, smelt, and silversides – due to fragile nature of species.

Adult Equivalent Calculations – 1999-2000 entrainment data for new units: 

unidentified gobies – 97,000-927,000 females; bay goby 1.046 million; 17,000 

black eye goby; 185-1,300 longjaw mudsucks; combtooth blenny 11,000; 80-692 

Pacific herring; white croaker larvae (8.6 million); pacific sculpin (4-12% of 

water source); crab >20 million

1, 8

Mountaineer 

(FF)

WV NA NA Ohio River Wedgewire screens (21.7 mgd) Noted in 1980 report on Philip Sporn 36

Mystic Unit 7 

(F)

MA 1050 (Unit 

7 @ 600 

MW)

1097 

m3/min

Mystic River 

(Estuary)

Unit 7 – shoreline intake with 

vertical traveling screens, modified 

with smooth mesh screens and fish 

buckets, low and high pressure 

wash, bottom sills on each 

screenbay. Evaluated 

impingement at operating speeds 

ranging from 1 to 4.6 m/min

1985 EPRI Report: testing for winter flounder, alewife, smelt, and blueback 

herring (all adult), impingement monitoring since 1975. Unit 7 retrofitted in 

1983. Survival testing in 1980-81, which showed 96% survival for winter 

flounder during peak abundance period; survival rate for smelt, alewife, and blue 

back herring at 23-67%, dependant on species and screen rotation speeds; adult 

herring had low survival rates under all conditions. Increased survival seems tied 

to rotation speed. 50% survival at 4.6 m/min for all species. Alosa (alewife and 

blueback herring) had high initial survival but low latent survival at all speeds 

(about 25%). Overall, survival for winter flounder was 95% for continuous 

rotation, reduced to 46% for 8 hr rotation, with similar results for smelt.

1981 Stone and Webster recommends limiting continuous operations to key time 

Unit 7 is one of 4 operational 

units

6, 12
Summary of Impingement and Entrainment Data for Power Plants

16/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

periods (October-December). Most abundant species were smelt, followed by 

alosa (alewife and blueback herring), then winter flounder. Increased survival 

observed seemed tied to rotation speed; alosa high initial survival but low latent 

survival at all speeds; there was a 50% survival rate at 4.6 m/min for all species; 

overall survival for winter flounder was 95% with continuous operation, 56% at 2 

hours, 34% at 4 hours, and 46% at 8 hour. Similarly, greatest survival for smelt 

at higher speeds

Nanticoke (F) Ontario 4096 88m3/s Lake Erie 2 submerged intakes, velocity 

caps, one 5 cm barrier net one of 

the intake; reduced intake by 50%; 

some testing of air bubbles 

1985 EPRI Report: testing for alewife and rainbow smelt (egg-adult); gizzard 

shad (adult). Monitoring since 1976 indicates 64-84% reduction in impingement 

losses (1981 original reference). Technology worked for emerald shiner, rock 

bass, spottail shiner, rock bass, spottail shiner, trout-perch, white bass, and yellow 

perch, but not alewife and other species

Not apparently used due 

because vulnerable to wave 

action and ice scour, 46 

suggests could be used 

seasonally

6, 46

Nine Mile Pt 

(N)

NY 620 MW 

(on); 1080 

(scheduled

)

Unit 1 –

1014 

m3/min, 

Unit 2 –

226 

m3/min

Lake Ontario Unit 1 – once thru with velocity 

cap and 0.61 m/s velocity, vertical 

traveling screens, no fish return; 

Unit 2 – velocity cap, closed cycle, 

angled screen diversion with 

bypass

1985 EPRI Report: testing for alewife and rainbow smelt (larvae-adult); gizzard 

shad, yellow perch, smallmouth bass, and white perch (YOY - adult); 

impingement monitoring since 1973 at Unit 1. Unit 2 not on-line as of 1986

6

Northport NY 1500 3465 

m3/min

Long Island 

Sound

NA 1980 study of entrainment survival; total survival (with 48-hour), American sand 

lance pysl 2%, winter flounder psyl 10%, northern pipefish 51%

33

Northside (F) FL 1159 NA St Johns 

River

Traveling screens with fish return 

system

Required fish return system in 1995 Need more information 43

Oswego Steam 

6 (F)

NY 2187 total, 

Units 1-6 

(now 1980 

MW w/o 

1-2)

1-5 2379 

m3/min; 6 

1230 

m3/min

Lake Ontario Units 1-4 : wooden cap with 0.4 –

0.6 velocity; Units 5-6: velocity 

cap with 0.3 m/s velocity; Unit 6 

has angled traveling screens, Units 

1-5 have conventional vertical 

traveling screens

1981 – 1984 data: diversion efficiencies: 79% (alewife) and 74% (rainbow 

smelt), combined all species 78%; initial survival was 45% (rainbow smelt) to 

87% (gizzard shad); latent survival at 22% (alewife) to 94% (mottle sculpin).

From 1999 EPRI Report, most recent study of post-impingement survival on Unit 

5 with conventional travelling screens, with alewife as the predominant (75%) 

species: initial/latent survival (47/1%) (very low latent survival for the 

predominant specie), rainbow smelt (15/7), mottled sculpin (92/87), spottail shine 

(48/34), threepine stickleback 60/33, gizzard shad (63/0), emerald shiner (28/21), 

others (23 species) 62/45. Latent survival is total survival after 24 hours. This 

data is consistent with earlier results from mid 70s/early 80s.

1, 6, 32

Oyster Creek 

(N)

NJ 630 28.9 m3/s Barnegat Bay Intake canal, 6 vertical traveling 

screens with 10 mm mesh, 4 

circulating pumps, intermittent 

wash system; continuous operation 

traveling screens

Sampling from Sept 1975-August 1977; bay anchovy 72% next menhaden, spot, 

Atlantic silverside, small mouth flounder, and striped searobin; initial survival 

ranged from 90% for northern pipefish to 7% for bay anchovy; limited latent 

survival due to low numbers of testfish, ranged from 98% striped searrobin to 5% 

Atlantic menhaden; EPRI report, continuous operation of the traveling screens 

32, 33
Summary of Impingement and Entrainment Data for Power Plants

17/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

increased immediate survival for Atlantic mendahen, Atlantic silverside, and 

winter flounder, most dramatic for fishes with low survival, survival highly 

variable based on the species, season, and size of impinged organisms; 

1985 entrainment survival study: total survival (except bay anchovy larvae 

survival, none survived through 96 hours, holding blamed): bay anchovy eggs 

less than 27 degrees C 83% down and 17% down at greater than 33 degrees C; 

bay anchovy, initial only, larvae 68% survival at up to 35 degrees, 0.1% survival 

at greater than 35 degrees, winter flounder larvae 84% for below 15 degrees C 

and 15% above 18 degrees C

Palisades 

Power Plant 

(N)

MI 715 80,000 

gpm

Lake 

Michigan

Offshore (1,000 ft) intake, 

mechanical draft cooling towers

Crayfish inhabit the intake and greater impingement occurs when volume is 

reduced.

Redondo Beach? 3

Philip Sporn 

(F)

WV 1050 1038 mgd Ohio River Vertical traveling screens, 1980 

assessment of alternative 

technologies, plant circulates 

estimated 2-11.7% of river flow 

when ichthyoplankton are present, 

5 units, 1-4 avg. velocity <0.5 fps, 

unit 5 <1.0 fps, 1-4 rotated every 8 

hours, 5 is linked to pressure 

sensor

1980 Report: annual estimates of 52,136 fish impinged (including gizzard shad 

(39%), freshwater drum, channel catfish (27%), emerald shiner (5%), white 

crappie (5%), and bluegill (4%); estimated 113.9 million fish eggs and larvae 

entrained; looked at wedgewire screens as option but said based on experience at 

Mitchell, Amos, Big Sandy, and Mountaineer would be too expensive because 

flow was 10 times greater than other plants and costs would be prohibitive 

(estimated at $7.5 million).

Noted AEPCo commitment 

to wedgewire based use at 

other 4 plants

36

Pickering (N) Ontario 1280 2600 

m3/min

Lake Ontario Screenwells, prototype diversion, 

mostly with behavioral devices

1985 EPRI Report: testing for alewife, rainbow smelt, gizzard shat (larvaeadult); impingement monitoring since 1974, behavioral test in 1976-77 and 1983-

84; behavioral test showed sound to be effective for alewife; follow up alewife 

testing by EPRI in 1985-86. Popper shown to be effective for alewife, diverted 

73% (1985) and 76%, (1986) away from intake; some suggestion that air bubble 

and strobes work also. Data too sporadic to draw conclusions, same with 

combinations of techniques.

6, 22, 28

Pittsburg (F) CA 1320 2,712 

m3/min

Bay Continuously rotating screens 

studies versus intermittent rotation

In 1978 study, no improvement in survival for invertebrates such as bay shrimp, 

crabs, and oriental shrimp; impingement 96h survival increased from 19-32 to 

26-56% for YOY white perch; striped bass latent survival increased from 26 to 

62% 

Also studied entrainment for striped bass larvae – initial survival ranged from 

11.8-93.5% (lowest survival rate was at 36-37 degrees C); earlier tests in 1976, 

12.8 mm length initial 21 and 54, 21.6 mm 94 down to 12 at 37 degrees C, all 

striped bass larvae.

1, 33
Summary of Impingement and Entrainment Data for Power Plants

18/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

Point Beach 

(N)

WI 990 2838 

m3/min

Lake 

Michigan

Leaky dam technology, offshore 

intake; reference to traveling 

screen

1985 EPRI Report: alewife (egg-adult) and rainbow trout (larvae-adult); testing 

in late 1970s as part of 316(b) demonstration; part of general studies done by 

Wisconsin Electric Power in the late 70s/early 80s at several plants; generally 

lower I&E than at other nearby plants with onshore intake structures. Accuracy 

of results limited by varied species density and other environmental factors – no 

numeric data.

6, 32

Port Jefferson NY 490 NA Long Island 

Sound

NA 1978 study of entrainment survival; total survival (with 96-hour results), winter 

flounder pysl 65%, sand lance pysl 25 and 86%: American eel juveniles 100%, 

fourbeard rockling eggs 73.1 and 100%

33

Portsmouth (F) VA 362 984 

m3/min

Elizabeth 

River 

(Estuary)

Intake canal, curtain wall then to 

Royce traveling screens; buckets 

and low pressure spray wash

1985 EPRI Report: testing for alosa spp., menhaden, spot, croaker (juvenile), 

hogchoker and bay anchovy (juvenile-adult).

6

Prairie Island 

(N)

MN 1000 22,396 

m3/min

Mississippi

River

Thru canal, 8 vertical traveling 

screens at canal mouth, velocity 10 

cm/sec, screen mesh 9 mm during 

9/1 – 4/15 normally, 0.5 mm 

during remainder of year, fish 

return ; air bubble curtain studies 

in 1974; can operate as once thru, 

closed loop, or helper system

1985 EPRI Report: channel catfish, emerald shiner, gizzard shad, sauger, 

walleye, and white bass (larvae adult), freshwater drum (egg-adult), performance 

testing “began in 1984”.

1974 data: air curtain actually caused net increase of fish entering (plus 7.1%); 

however, decrease was significant during April, May, and July, continuing use 

was recommended during these periods. 

3-year study (1984-87) showed latent survival of most post larval fish 0-10%, 

except suckers (31-50%) and walleye (>50%), gizzard shad <0.1% post larvae, 

carp prolarvae 24, postlarvae 13, juvenile 71; cyprinidae prolarve 0.1, postlarvae 

1.5, juvenile 46, adult 38, catostomidae prolarvae 44, postlarvae 38, juvenile 65; 

channel catfish prolarvae 59, juvenile 57; white basss prolarvae 0, postlarvae 2, 

and juvenile 31; lepomis spp. Postlarvae 1; pomoxis postlarve 2.5; percidae 

prolarvae 5, postlarvae 3; freshwater drum, prolarvae 0.4, postlarvae 5, juvenile 

34; in general, juvenile had higher survival rates, data from 88 and 91 references, 

may be underestimated due to high control mortality; according to ASCE, air 

bubble curtain did not function well

5, 6, 9, 

20, 32

Protrero Power 

Plant (FF)

CA 332, 

proposed 

exp to 540

1,008 

m3/min, 

proposed 

1222

San Francisco 

Bay

Vertical traveling screens, 

proposed new system with fine 

mesh (5/32) screens, CEC has 

recommended dry cooling

1979 study of entrainment survival for Pacific herring larva, initial 74%, 96-hour 

95, total survival = 70% (18-19 degrees C)

1999-2000 - study to support proposed expansion showed total estimate/AEL 

and/or 2 x female adult (2FH) losses due to entrainment of: unidentified gobies 

(80 million/58,000 AEL), yellowfin goby (64 million/7,984 FH), bay goby (48 

million/222 AEL), Pacific herring (44 million/1,120 FH and 6910 AEL), northern 

anchovy (32 million/5,216 FH and 6,994 AEL), white croaker (6.9 million/154 

2FH loss estimated value 

$1,385, AEL loss $620

33, 53
Summary of Impingement and Entrainment Data for Power Plants

19/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

FH)

Quad Cities IL 1242 3793 

m3/min

Mississippi 

River

1978 study of entrainment survival, initial survival only, freshwater drum larvae 

and juveniles 62% at 30 degrees and down to 2% above 38 degrees C, cyprinidae 

larvae and juveniles 63% and down to 7 at above 38 degrees C. Additional work 

in 1984, initial survival only; buffalo sp. Larvae 94%, carp larvae 92/97% and 

freshwater drum 63%, all temps below 34 degrees C

33

Quad-Cities 

(Com Ed)

NA NA NA Mississippi 

River

Studies air bubble curtains, 

deployed 2 barrier nets in 1985

According to ASCE 1977, did not function well; barrier nets had significant 

operational problems due to freezing and debris. Showed some decrease in 

impingement, but EPRI report suggests results seen were due to fish abundance 

not net performance

20

Redondo Beach 

(F)

CA 1,602 1770 

m3/min

Pacific Ocean 

(1-6), King 

Harbor (7-8)

Offshore intakes, Units 7-8 have 

vertical cable array ( 46 cm 

spacing and velocity cap; 

performed initial testing of louver 

systems

1985 EPRI Report: testing for northern anchovy, white croaker, and queenfish 

(YOY-adult), walleye surfperch and kelp bass (adult); 1979-81 studies of larval 

exclusion studies, including testing of velocity cap.

In 70s, louvers placed at angles ranging from 90 to 20 degree to direction of flow 

at velocities ranging from 0.5 to 4 ft/s. Species tested included northern anchovy, 

queenfish, white croaker, walleye, surfperch, and shiner perch. Max guidance 

(96-100%) occurred with louvers 25 mm apart at 20 degree angle to flow and 

approach velocity 0.6 m/s. Found that there must not be turbulence in bypass 

channel, and channel velocity should be 3 times approach velocity. Worked 

equally well in light and darkness.

6, 30, 32

Roseton Station NY 1200 40 m3/s Hudson River 3.2 mm x 12.7 mm on newer 

screens, conducted seasonal, EPRI 

evaluation of behavioral methods, 

sound, lights, air bubble. In 1990 

installed dual flow/single exit 

screens to replace 2 of 8 

conventional band-type vertical 

screens, primarily for debris flow, 

but also with fish enhancements –

water retaining lift buckets, dual 

pressure cleaning, flattened wire 

mesh and faster operating speed, 

9.5 mm mesh on older screens, 

velocity approaching 0.23 m/s 

older

Blueback herring, alewife, American shad, white perch, bay anchovy, striped 

bass - behavioral measures had low deterrent capability and did not work for 

impingement (EPRI study). More diverse species than Pickering (concurrent 

study), post-impingement survival program May – August and OctoberNovember 1990. Although survival slightly higher for dual flow screens – not 

considered statistically higher; latent survival in order of occurrence: blue back 

herring (dual/conventional), Spring/Summer (0/0), Fall (0.1/0), white perch 

(32.7/8.8) and (47.6/33.3); bay anchovy (0/0), (0/0); American shad (0.5/0.2), 

(0/0); alewife (0.3/0.1), (0/0); striped bass (42.9/23.8); gizzard shad (12.1/0), 

(23.6/5.4); spottail shiner (45.9/13.5), (74.2/51.8); brown bullhead (82.8/61.1), 

(89.6/100); hogchoker (95.7/91.4), (98.2/90.4); bay anchovy and hogchoker most 

common species. 

Also 1975 study of entrainment survival, total survival (with 96-hour) striped 

bass pysl 38%, clupeids (initial only since no extended survival in intake or 

discharge), pysl 40 and juveniles 45; white perch, initial only, pysl 41%; 

cyprinidae pysl 100, tessellated darter 100%. 1976 data initial striped bass pysl 

Find Lawler, Matusky, and 

Skelly. Intake Debris Screen 

Post Impingement Survival 

Evaluation Study 1990, need 

to find out why so low 

survival for certain species

17, 22, 

28, 32

33
Summary of Impingement and Entrainment Data for Power Plants

20/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

58% at below 31 degrees C and 19% at 31-37 degrees C, juveniles 80% at higher 

temps; clupeids pysl 59% at below 31 degrees C and 10% at 31-37 degrees C, 

juveniles 16, white perch, 79% at below 31 degrees C and 11% at 31-37 degrees 

C, juveniles 60%; cyprinidae pysl 69; extended survival pooled for striped bass 

and white perch <20% at intake and discharge for pysl, high for juveniles, for 

clupeids, zero at intake and discharge; 1977 data (initial only): striped bass pysl 

58% at below 30 degrees C and 6% at 33-36 degrees C, juveniles 100%; clupeids 

pysl 19 at below 30 degrees C down to 0% at 33-36 degrees C, juveniles 24 at 

below 30, 0 above, white perch pysl , 52% at below 30 degrees C and 0% above 

33 degrees C, Atlantic tomcod ysl 41% at low temperatures. 

1978 data (total survival with 96-hour test): striped bass pysl 46%, clupeids pysl 

and juveniles0%, white perch pysl 56 and 96%, juveniles 55%, Atlantic tomcod 

ysl 31-67% and pysl 39%; 1980 data striped bass ysl 88%, pysl 88%, juveniles 

71%, clupeids pysl 23% and 0% juveniles, white perch pysl 67 and juveniles 

100%

Salem (N) NJ 2200, 

Units 1 

and 2 (3 is 

peaking 

only. Unit 

1 began in 

1977 and 

Unit 2 in 

1981)

8390 

m3/min

Delaware 

River/Bay 

(Estuary)

Modified Ristoph with fish returns 

studied versus traveling screens; 

most recent revisions in 1995 to 

comply with 1994 permit 

requirements.

1996 data: 48 h survival for juvenile weakfish – 79.3% survival for modified 

Ristoph versus 57.8% for old traveling screens. 

1997-98 data Units 1 and 2: white perch (93-98% survival); bay anchovy (20-

72%), Atlantic Croaker (58-98%), Spot (93%), herrings (78-82%), weakfish (18-

88%), comparing to original screens showed mortality rates lower with modified 

screens for white perch, bay anchovy, Atlantic croaker, spot, and herring; 

According to Delaware Riverkeeper, annual loss, Herrings alewife & blueback: 

281,746; Atlantic croaker: 61,100; American Shad: 468; Spot: 305,000; Striped 

bass: 3,239; White perch: 375,000; Bay anchovy: 842,000,000; Weakfish: 

1,120,000; 

Kahn 2000 estimated conditional mortality for striped bass during 1980-1989 

(low abundance) at less than 1%, and at 32% during a period of high abundance 

1989-99. 

ESSA (2000) issues with 

facilities estimates of 

mortality, sound generally 

not show to be helpful (may 

be for a few species with air 

bubble), too large flow for 

wedgewire (ESSA), high 

debris prevents fine mesh 

(ESSA),

1, 6, 7, 

10, 11

San Onofre 2 

and 3 (N)

CA 2636 total, 

2200 at 2 

and 3

101 m3/s 

(50 m3/s 

each unit)

Pacific Ocean Unit 1 – offshore (1 km) intake 

with velocity cap and traveling 

screens. Units 2 and 3, offshore 

intake with improved velocity cap 

to angled traveling louver screens

well, bypass, fish return

In 1970s, pilot louver system tested at Redondo Beach Station (California

predecessor to full scale at San Onofre). Louvers placed at angles ranging from 

90 to 20 degrees to the direction of the flow at velocities ranging from 0.5 to 4 

fps. Species tested included northern anchovy, queenfish, white croaker, walleye, 

surfperch, and shiner perch. Maximum guidance (96-100%) occurred with 

louvers 25 mm apart at 20 degree angel to flow and approach velocity of 0.6 m/s.

Unclear if total 84 and 86 

data are just Units 2 and 3, 

Find Love 1989, 

impingement studies 

reported to have been done 

at Unit 1, NPDES requires 

impingement monitoring

3, 6, 32
Summary of Impingement and Entrainment Data for Power Plants

21/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

San Onofre Units 2 and 3 have offshore intake with velocity cap and louver 

system. 1984 data: 196,978 entered system with 188,583 diverted (96% 

effective) 1985 data: 407,755 fish entering and 306,200 returned (75% effective) 

and 101,555 impinged; however 96 hour survival was less than or equal to 50% 

for anchoa compressa, anchoa delicatissima, genyonemus lineatus, and seriphus 

politus, and predators are often waiting for returned and/or compromised fish. 

Operator also tested 45 degree angled 16 mm screens at the same time it was 

considering the louver system. For northern anchovies, the angled screens 

showed poor to good guidance (0 – 70%), while for other species, moderate to 

good guidance (60 – 90%). No survivability data are available. 

According to 1985 EPRI Report testing for queenfish, white croaker, northern 

anchovy (larvae-adult), walleye surfperch (adult) with angled 16 mm (45 degree) 

screen: for northern anchovy, poor to good guidance (0-70%)was achieved, 

while for other species, moderate to good guidance (60-90%) was achieved with 

an approach velocity at 0.6 m/s and bypass velocity at 0.45 to 1.2 m/s. Testing in 

mid 70s was dropped when louvers were installed.

Seabrook (N) NH 1,150 NA Atlantic 

Ocean

1.5 km offshore intake, velocity 

cap, 1993 NPDES permit limited 

velocity to 1.0 ft/s

1993 report data: 1985 (970 fish impinged), 1986 (1212), 1987 (502), 1990 

(499),1991 (1019). Species include sculpins, snailfishes, lumpfish, windowpane, 

and winter flounder, few pelagic fish impinged except Pollock suggesting cap 

working as planned.

9

Seminole 1 and 

2 (F)

FL 1200 NA St. John’s 

River

Cooling tower system, testing of 

wedgewire screens (in situ, preconstruction for 316(b), 1mm and 

2 mm tested, evaluated biofouling, 

low approach velocity (0.5 fps)

1979 testing: no impingement of fish eggs, larvae or juveniles, 134 entrainment 

collections; just larvae and eggs off 1 mm; larvae, eggs, and juveniles off 2 mm; 

all off 9.5 mm; 1 mm offered 99% reduction larvae entrainment over 9.5 mm; 2 

mm had 62% reduction; primary species for 1 and 2 mm: medina beryllins, 

gobiosoma bosci, microgobius; unscreened (9.5 mm) anchoa mitchilli, m. 

beryllina, lepomis sp., g. bosci, and m. gulosus; did not find statistical differences 

in densities of fish entrained between 1 and 2 mm; fouling may have increased 

entrainment on fine mesh screens at end of study – due potentially to biofouling 

(Aug. highest); however, no drop off in flow rate beyond 25% (tested). No 

impingement of fish eggs, larvae, or juveniles.

27

Shoreham (N) NY 820 2271 

m3/min

Long Island 

Sound 

(Ocean)

Intake canal with 20 cm/s intake 

velocity to traveling screens fitted 

with fish trays and a trough, low 

pressure spray, conveyance

1985 EPRI Report: testing for bay anchovy (egg- adult), winter flounder (eggadult), lobster (larvae-adult), tautog (egg-adult), sand lance (egg-adult), Atlantic 

menhaden (egg-adult), windowpane flounder (egg-adult), searobin (egg-adult), 

scup (egg-adult), whelk (egg-adult), biological tests were scheduled for first year 

of operation (anticipated to begin operations in late 1985

6

Sizewell A and 

B (N)

England NA NA Ocean B has velocity cap, well offshore, 

intake minimized, and fish return

50% reduction in impingement over Unit A. Survival for white flounder, plaice, 

sole dab, and bass is >80%; however, whiting, sprat, herring, and pout survival is 

3
Summary of Impingement and Entrainment Data for Power Plants

22/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

much lower and negligible for sprat and herring, which are susceptible to 

pressure change.

St. Lucie (N) FL 1700 1150 cfs Atlantic 

Ocean

Intake moved from Indian River to 

Atlantic Ocean 1200 feet from 

shore, velocity caps with buried 

pipeline to intake canal then to 

traveling screens

Impacts considered minimal compared to Big Bend or Crystal River; original 

proposed location in Indian River was moved after objections

No detailed 316b 

determination

42, 45

Summit Power 

(N)

DE 1540 NA Chesapeake 

and Delaware 

Canal

Test performed on wedgewire for 

proposed plant

Circa 1977 testing at Delmarva Research facility in Middletown found, study 

showed entrainment of fish eggs (including striped bass) can effectively be 

prevented with slot widths of l mm or less and velocity at 0.5 fps. Some 

impingement mortality at exposure durations of 0.5 – 2.0 min, however expected 

to be less than 5%. Actual field testing in Brackish water of canal, had to remove 

and clean screens as much as once per three weeks (backflushing became 

ineffective at warmer water temperatures).

Canal between Delaware 

River and Chesapeake Bay, 

testing performed pre final 

decision to build, find out if 

built

30

TVA Plants –

13 plants

TN NA Freshwater Fine mesh screen, impingement 

timing, and velocity, mostly lab 

tests

Impingement Duration: 1977 data (Tomljanovich), see attached table 1-

generally showed best survival rates at impingement durations less than 8 

minutes. With duration of 0.5 minutes, all species had latent mortalities of less 

than 50 percent, except for striped bass, which was about 80%: looked at location 

including 9 channel intakes: 5 showed low impingement, 4 showed high 

impingement; of 5 shoreline intakes, 4 had low impingement and 1 showed high 

impingement; all locations did nothing for larvae and eggs. Looked at feasibility 

of protecting larval fish with fine mesh screen and found: 0.5 mm needed for 

99% retention of striped bass (reduced to 30% with 0.97 mm), for largemouth 

bass 75 and 70% at 0.97 mm and 1.3 mm with similar results for small mouth. 

Immediate and delayed mortality was variable with best survival at impingement 

duration of <8 minutes for striped bass with mortality mostly greater than 90% 

for large and small mouth, channel catfish, and bluegill at 8 minutes. Mortality 

was greater than 99% at 16 minutes for striped bass and 98% for walleye. 

Survival for walleye at 0.5 – 2 minutes = 48-63% and 22-27% for striped bass 

with the control group exhibiting some mortality but not as great. 0.5 mm mesh 

was needed for 99% retention of striped bass, e.g., retention was reduced to 30% 

with 0.97 mm mesh. Similar results for large and small mouth bass. At Sevier 

Plant in a full-scale test, twice as many larval fish were retained with 0.5 mm 

mesh as with 1.0 and 2.0 mm combined, at velocities of 24-38 cm/s.

2, 5, 30, 

Washington 

Power (now 

presumable 

Avista) (N)

WA NA NA Columbia

River

Escape rout between trash racks 

and screens

5
Summary of Impingement and Entrainment Data for Power Plants

23/29

Plant Name 

(Fuel Type)

Location Capacity 

(MW)

Water 

Intake 

Need

Source 

Water

Intake System Performance/Technology Evaluation Comments Ref

Zion (N) IL Lake 

Michigan

Traveling screens, may have net? Ref 46 indicates that net was tried with some apparent success, mid-70s original 

reference, net used mid-March through mid-November

46

F = Fossil Fuel, N = Nuclear

References:

(1) PG&E, Diablo Canyon Power Plant, 316(b) Demonstration Report, March 2000

(2) Industry Confidential , 2001, Existing Technologies Which, Appropriately Applied, Can Reduce Fish Losses to Levels Reasonably Consistent with Wet Cooling Towers

(3) Pisces Conservation, Ltd. Technical Evaluation of USEPA’s Proposed Cooling Water Intake Regulations for New Facilities, November 2000

(4) Mussalli, Taft, and Larsen, Journal of the Hydraulics Division (ASCE), Offshore Water Intakes Designed to Protect Fish

(5) TVA, 1976, A State of the Art Report on Intake Technologies (Ray, Snipes, and Tomjanovich)

(6) EPRI, 1985, Intake Research Facilities Manual

(7) Delaware Riverkeeper website

(8) Duke Energy, April 2000 Moss Landing Power Plant Modernization Project, 316(b) Resource Assessment

(9) Northeast Utilities Service Company, January 1993, Feasibility Study of Cooling Water System Alternatives to Reduce Winter Flounder Entrainment at Millstone Units 1-

3

(10) ESSA Technologies, Ltd. June 2000. Review of Portions of NJPDES Renewal Application for the PSE&G Salem Generating Station

(11) Versar, Inc. April 1990. Evaluation of the Section 316 Status of Delaware Facilities with Cooling Water Discharges, Prepared for State of Delaware Dept. of 

Natural Resources
Summary of Impingement and Entrainment Data for Power Plants

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(12) Stone & Webster, August 1981, Final Report: Biological Evaluation of a Modified Traveling Screen, Mystic Station – Unit No. 7, Prepared for Boston Edison

(13) Boston Edison, Edgar Energy Park, Draft EIR, Appendix A Sections 316a and b Demonstration for the Edgar Energy Park Project

(14) Ecological Analysts, Inc. Evaluation of the Effectiveness of a Continuously Operating Fine Mesh Traveling Screen for Reducing Ichthyoplankton Entrainment at 

the Indian Point Generating Station

(15) Randall Melton, Florida Power and Light, Zooplankton Entrainment Survival at the Anclote Power Plant Near Tarpon Springs, Florida, Presented at EPRI Power 

Generation Impacts on Aquatic Resources Conference, April 1999

(16) T.G. Ringger, Baltimore Gas and Electric, Investigations of Impingement of Aquatic Organisms at the Calvert Cliffs Nuclear Power Plant, 1975-1999 Presented at 

EPRI Power Generation Impacts on Aquatic Resources Conference, April 1999

(17) E.P. Taft, Alden Research Laboratory, Fish Protection Technologies: A Status Report, Presented at EPRI Power Generation Impacts on Aquatic Resources 

Conference, April 1999

(18) Chris Ehrler and Carol Raifsnider, Tenera Energy, Evaluation of the Effectiveness of Intake Wedgewire Screens, Presented at EPRI Power Generation Impacts on 

Aquatic Resources Conference, April 1999

(19) .McLaren, James B. and Tuttle, Ray L., URSG, Fish Survival on Fine Mesh Traveling Screens, Presented at EPRI Power Generation Impacts on Aquatic Resources 

Conference, April 1999

(20) American Society of Civil Engineers, 1982. Design of Water Intake Structure for Fish Protection.

(21) Taft, Edward. March 1999, PSE&G Renewal Application, Appendix F, Salem Generation Station.

(22) EPRI. March 1989. Intake Technologies: Research Status.

(23) Tennessee Valley Authority, October 1976. A State-of-the-Art Report on Intake Technologies.
Summary of Impingement and Entrainment Data for Power Plants

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(24) Fletcher, Ian, 1990 Flow Dynamics and Fish Recovery Experiments: Water Intake Systems

(25) Ichthyological Associates, Inc. December 1994. An Evaluation of the Effectiveness of the Strobe Light Deterrent System at Milliken Station, Prepared for New 

York State Electric and Gas Corporation

(26) Lifton, W.S., no date (presume early 1980s), Biological Aspects of Screen Testing on the St. John’s River, Palatka, Florida. Dames & Moore

(27) Hutchison, J.B., and Matousek, J.A. Evaluation of a Barrier Net Used to Mitigate Fish Impingement at a Hudson River Power Pant Intake. American Fisheries 

Society Monograph

(28) Micheletti, Wayne. September 1987. Fish Protection at Cooling Water Intake Systems. In EPRI Journal

(29) Weiberg et. al. August 1984. The Effects of Screen Slot Size, Screen Diameter, and Through-Slot Velocity on Entrainment of Estuarine Ichthyoplankton Through 

Wedge-wire Screens.

(30) Mitre Corporation. 1978. Recent Developments in Techniques to Protect Aquatic Organisms at the Water Intakes of Steam-Electric Power Plants.

(31) Stratus. 2001. Write-up on J.R. WhitingPlant Barrier Net

(32) EPRI. 1999. Fish Protection at Cooling Water Intakes: Status Report

(33) EPRI. 2000. Review of Entrainment Survival Studies: 1970-2000

(34) Orange and Rockland Utilities and Southern Energy Corp. 2000. Lovett Generating Station Gunderboom Evaluation Program, 1999.

(35) Bailey, Loos, and Perry. Undated (90s). Studies of Cooling water Intake Structure Effects at PEPCO Generating Stations.

(36) American Electric Power Corporation. March 1980. Philip Sporn Plant Demonstration Document (316b)

(37) U.S. EPA Region 4. August 1989. Draft Fact Sheet for Anclote Power Plant
Summary of Impingement and Entrainment Data for Power Plants

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(38) U.S. EPA Region 4. May 1983. 316a and 316b Finding for Cape Canaveral/Orlando Utilities Plants at Canaveral Pool. Prepared by Charles Kaplan

(39) U.S. EPA Region 4. September 1988. NPDES permit No. FL0000519 renewal

(40) Florida Power and Light. August 1986. Proposed BAT Plan for the Reduction of Ecological Losses in the Area.

(41) Florida Power and Light. February 1987. FPL Comments on Draft December 1986 Permit Reissuance.

(42) Florida Power and Light. August 1995. Assessment of the Impacts of the St. Lucie Nuclear Generating Plant on Sea Turtle Species Found in the Inshore Waters of 

Florida.

(43) U.S. EPA Region 4. June 1994. Reissued NPDES Permit Number FL0001031 for Jacksonville Electric Authority Northside Generating Stations

(44) U.S. EPA Region 4. August 1976. Findings of Fact. Green River Steam.

(45) U.S. EPA Region IV. September 1979. Brunswick Nuclear Steam Electric Generating Plant. Historical Summary and Review of Section 316(b) Issues

(46) University of Michigan. 1985. Impingement Losses at the D.C. Cook Nuclear Power Plant During 1975-1982 with a Discussion of Factors Responsible and 

Possible Impact on Local Populations

(47) Taft et. al. 1981. Laboratory Evaluation of the Larval Fish Impingement and Diversion Systems

(48) AEPCo. 1980. Kammer Plant Demonstration Document.

(49) AEPCo. 1980. Cardinal Plant Demonstration Document.

(50) Argonne National Laboratory. March 1977. Survey of Fish Impingement at Power Plants in the U.S., Volume I. The Great Lakes

(51) New England Power. December 4, 1996. Letter from Andrew Aitken, NEP to EPA Region I Responding to 308 Information Request for Brayton Point.

(52) PG&E. September 1999. Brayton Point Power Station 1998 Annual Report
Summary of Impingement and Entrainment Data for Power Plants

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(53) Mirant Potrero, LLC. September 2001. Potrero Power Six-month Report

Additional Impingement and Entrainment Performance Data/Notes

From 20, Lake Ontario power plant studies showed 25 degree orientation at approach and bypass velocities ranging from 0.5 – 3.0 fps 100% effective in diverting 1-6 inch long fish to bypass. 

Similar results for Hudson river power plants for striped bass, white perch, and Atlantic tomcod) 2-6”, survival of bypassed fish >96%. Also recommended 1 fps approach velocity and 

approach:bypass velocity ratio 1:1.

From 21, sound barriers probably only have effects within a few feet of the intakes. Cited strobe light/air bubble as viable options for Salem. 0.5 mm wedgewire not tested. Ludington 

(Consumers Power) is pumped storage plant with 2.5 mile long barrier net, successfully reduced entrainment, deployed from mid-April to mid-October, storms and icing prevent rest of year, 

net effectiveness for target species (5 salmonid, yellow perch, rainbow smelt, alewife, and chub) over 80% since 91, 96% 95/96. Pumped storage volume 19,000 m3/s. Haywood hydroelectric 

was studying in 99. Also studied at Pine Hydro electric (no size) reduced passage of rock bass, bluegill, yellow perch, black bullhead, black crappie, and other riverine species by 85-100%. 

Based on success at Pine, to be installed at Brule Hydroelectric, testing to have been done in 99. Fletcher 1996 found that most of the mortality with modified Ristoph screens is due 

conditions in trough not being caught on screens. Fine mesh traveling also increases impingement, trade-off.

Also from 21, EPRI tested modular incline screen (MIS) in lab in early 90s, trash rack, dewatering stop logs, inclined screen at shallow angle, and bypass, can operate at 2 – 10 ft/s, most fish 

47-88, not useful for large, diversion efficiency greater than 98% for channel catfish, golden shiner, brown trout, coho and Chinook salmon, trout fry and juveniles, and Atlantic salmon smolts. 

Lower diversion efficiency and higher mortality for American shad and blueback herring but comparable to control. For other species, latent mortality 0-5%, EPRI 1986 indicates that louvers 

can 80-95% effective in diverting fish. Louvers tested by Northeast Utilities Service Company in the Holyoke Canal on the Connecticut River for juvenile clupeids (American shad and 

blueback herring). Overall guidance efficiency found to be 85-90%.

From 30, provides conceptual design for 20,000-30,000 gpm wedgewire, shoreline intake for 1,200 MW nuclear

From 32, to date cylindrical wedge screens only installed at 2 installations and have incorporated slot openings that will physically exclude larger juvenile and adult fish, but not fish eggs, 

larvae, and juveniles, EPRI cites need to evaluate fine mesh screens

From 32, Alden Research Laboratory conducted testing of angled screens for three utilities in the 1970s. Large-scale flume found angled screen (25 degrees) found to be 100% effective in 

diverting all test species (alewife, white perch, striped bass, and tomcod). Latent mortality mean mortality 35.7% for alewives and 3.3% for Hudson River species. Higher mortality for 

alewives due to handling fragile species. Subsequently combined testing of diversion with fish transportation, showed total 12% mortality. This testing provided the basis for Niagara 

Mohawk installing a full-scale angled screen and fish transportation system at the Oswego Station. Also performed, fine-mesh angled screen diversion tests were also conducted at Alden. In 

1978, tests conducted on striped bass larvae. Screen sizes were 1.5 and 2.5 mm metallic and synthetic screens. 1.5 mm synthetic screen yield greatly (and statistically higher) diversion 

efficiency and survival, consistently above 70%. 1978 follow-up testing only included synthetic with some larger sizes. For winter flounder only tests with small larvae (4.1 and 6.1 mm), no 
Summary of Impingement and Entrainment Data for Power Plants

28/29

diversion effects noted. Similar for alewife, no ability to guide for small prolarvae and early post larvae (up to 9.5 mm), diversion efficiencies of 84 and 77 for 11.2 and 84, 84, and 60 for 14.7 

mm. However, 96 hour mortalities high, therefore, total efficiency low (all less than 27%). Similar for smaller yellow perch, no ability to guide for (6.0 and 9.3 mm), 16 and 72 diversion 

efficiency for 14.3 mm with 96 hour mortalities of 11.1 and 1%. Authors suggest mortalities due to damage from impingement of many larvae from some period against 1.0 mm screen 

From 32, EPRI tested new modified incline screen in mid 1990s. No full scale use although planned for pilot study at Niagara Mohawk’s Green Island Hydroelectric Project. Used juvenile 

walleye, bluefill, channel catfish, American shad, blueback herring, golden shiner, rainbow trout, brown trout, Chinook salmon, coho salmon, and Atlantic salmon, testing at water velocities 

from 0.6 to 3.0 m/s. Mean length of all species between 47 and 88 mm. Diversion rates reached 98 or greater at water velocities up to 2.4 m/s for walleye and 1.8 m/s for bluegills. Diversion 

efficiencies for channel catfish, golden shiner and brown trout exceeded 98% for all water velocities. Diversion efficiencies for rainbow trout fry and juveniles exceeded 99% at velocities up 

to 1.8 m/s and 2.4 m/s. Diversion rates >99% for coho for all velocities and Chinook up to 2.4 m/s. Atlantic salmon 100% diversion. Diversion efficiencies lower and latent mortality higher 

for American shad and blueback herring, however, latent mortality comparable to control indicating stress from capture. Generally, latent mortality adjusted for control was low (0-5%) for all 

species tested.

From 32, numerous studies have demonstrated that louvers can be effective on the order of 80-95% over a wide range of conditions.

From 32, “recent” studies on fish passage at Tracy fish collection facility. Louver system set up in San Joaquin River. Two systems, primarily and secondary (primary 97.5 long, secondary 

9.3 m long). Originally installed in 1950s. Angled 15 degrees to flow, primarily intended for juvenile Chinook and striped bass >25 mm long. 1993 testing, secondary diversion efficiency 

72-100% for Chinook and 30-90% for striped bass. Primary system efficiency 13-82% for Chinook and 0-96% striped bass. Lowest diversion efficiencies for Chinook during low flow/low 

velocity conditions (striped bass not tested during these conditions) and for all species, when louvers clogged with debris. Lower efficiency during low flow/low velocity conditions may be 

due to fish being able to swim upstream from collection facility. Follow-up studies during 93 to 95 for green and white sturgeon, American shad, splittail, white catfish, delta smelt, Chinook 

salmon, and striped bass. Splittail over 50% fish collected, for species collected adequate #’s (not green and white sturgeon and delta smelt), mean efficiency of secondary louvers ranged from 

63 (splittail) to 89% (white catfish).

From 32, Alden labs tested louvers in 1970s on alewives and smelt for Niagara Mohawk. Separate studies for ConEd with striped bass, white perch, and tomcod With Niagara, test velocities 

of 0.31, 0.41, and 0.61 m/s with bypass to approach velocity ratios of 1.5/1. Louver array angles of 90, 60, and 25 and slat spacings of 25 mm, 51 mm, and 82.6 mm. At 90 and 60 angles, 

average guidance efficiency <80%. With 25 degree orientation and 25 mm spacing, average efficiencies 90 and 93%. For ConEd, 25 mm spacings and 25 degree angle, approach velocities 

of 0.31 m/s, 0.61 m/s, and 0.91 m/s with again 1.5:1 ration. Efficiency species-specific 50-80% white perch, 56-97 Hudson River striped bass, 68-99% hatchery reared bass, and 96-99% 

tomcod. Average for all species 85%. Tests also done more recently (published 1997) at USGS Conte Anadromous Fish Research Center. Angle=20 degrees to flow 97-100% diversion 

efficiency for Connecticut River fish, including American shad.

From 33, entrainment survival rates vary considerably within and among species, and among power plants. Survival of young of life striped bass 28-90% with a mean of 61%. Atlantic 

tomcod and minnows produced similar results with means of 57 and 64%. Young perch, winter flounder, and freshwater drum were lower with means of 48 and 51%. One plant showed 

larvae sucker survival of 88-98% Larval and juvenile spot survival at 2 estuarine plants was just over 75%. Larvae of striped bass and perch also >50%. Larvae and juveniles of herring 

(alewife, blueback, and menhaden) low 0-50% with mean of 25%. For macros, mean survival 75%. Size of fish important factor, survival of 3-5.9 mm striped bass 10-30%, increased with 

growth to 65-90+% for 12 mm or longer. Biocides can limit survival. Major influence discharge temperature – when less 30 degrees C survival striped bass and with perch young 60-70%, 
Summary of Impingement and Entrainment Data for Power Plants

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30-33 degrees survival white perch dropped to 50%, above 35 degrees C survival of both dropped to 30%. Herring and anchovy same pattern, but lower, dropping to 0 at above 33 degrees C. 

Most studies, 1970s.

From 45 (1979), it has generally been required for nuclear facilities to have closed cycle cooling, 22 new facilities cited, 16 with closed cycle and 6 with modified intake to reduce entrainment.

From 47 (circa 1981), lab tests performed by Empire Electric and Northern States Power, indicate “selected larvae capable of active diversion at very young age.” Recommend uses of lifting 

buckets, low pressure washes, fine mesh materials, and sluiceways. Velocity and duration of impingement key factors. Over 3,000 tests with more than 75,000 larvae. Striped bass: relatively 

high mortality even under short duration and low velocity, however, control also had high mortality (57%). For 2 minute duration, all velocities survival >88%. Relatively high survival under 

many conditions. Winter flounder, velocity key factor not impingement duration. Higher mortality anticipated in 4.4 post-larvae. Reduced at 6.1 mm. Still generally pretty high mortality. 

Alewife, mortality variable based on both velocity and duration, although generally high for both. Yellow perch same as alewife. Walleye, high mortalities throughout. Channel catfish 

mortality low under most test conditions. Bluegill similar to channel catfish, except high mortality at 8 and 16 min. duration. Conclusions: striped bass exhibited high mortality under all 

conditions, while winter flounder, alewife, and yellow perch prolarvae had low mortality. Post-larvae mortality higher in some cases, also high in controls

From 50, Waukergan apparently used 1 inch mesh net from April through October (Lake Michigan), Dean Mitchell in Indiana uses electric screen.