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Effectiveness of a Louver Bypass System for Downstream Passage of

Atlantic Salmon Smolts and .Juvenile Clupeids in the Holyoke Canal,

Connecticut River, Holyoke, Massachusetts

R J. Stirn and D. A. Robinson

Northeast Utilities Service Company

Hartford, Connecticut

Abstract

Downstream passage of~tic salnlon (Sa/mo solar) smolts and juvel!ile clupeids (American shad,

A/osa sapidisslma, aild,b.uebackherring,4/osa ~estiva/is) has been evaluated in ~~ ~olyoke CanaL

where a louver array and downstream bypass have been installed to passdownstream migrants safely from

the canal to the Connecticut River. The canal in the area of the louvers is 145 ft wide and 20 ft deep. The

final louver array was constructed at a 150 angle to canal flow, with slats at a clear opening of 2 inches 

arranged perpendicular to canal flow and extending to a depth of 9 ft below the surface. Tests were

conducted at canal fIo~ from 2QOO to 6000 cfs and velocities from about 1 to 3 ftls, using radiotelemeny

techniques with Atlantic salnlon smolts, and niarklrecapture methods with both Atlantic salmon smolts

and juvenileclupeids. Thecompleted facility has been shown to be 86 to 97% eff~ve for smolts and 67

to 86% effective for juvenile clupeids. BQth floating and non-floating louvers were equally effective in

guiding Atlantic salmon smolts. The system has also been fitted with a fish sampling facility that allows

for the separation of fish from the bypass flow.

INTRODUCTION

The Connecticut River supports the largest run of American shad on the east coast It also is the site of an

Atlantic salmon restoration program that began in 1967. Other anadromous species that inhabit the river

include blueback herring, aI~e, sea lamprey, and striped bass. Northeast Utilities (NO) currently holds

licenses for the first two hydroelectric projects on the Connecticut,. at Holyoke ~dTumers Falls

MassachUsetts. This paper SWIlDl3rizes NU's efforts to provide downstream pasSage facilities in the

Holyoke canal, a hand-dug remnant of the Industrial Revolution in New England that is still used to

produce electricity. 

Upstream passage at Holyoke Dam is provided by two fish lifts near Hadley Falls Station. These lifts

passed over 700 000 shad in 1992, and over 600 000 blueback herring in 1985, both annual records to

date. Progress has been slow in the Atlantic salnlon restoration program. The effort to stock salmon fry in

Connecticut River tributaries has grown until nearly seven million salmon fiy were stocked in 1996. The

highest number of adult salmon known to have returned to the river in any given year was 529 in 1981;

the average adult salmon run for the last ten years is 248 fish.

. ,

The progress on downstream passage for the Holyoke Project descnOed below gI"eW'out of a Memorandum

of Agreement signed by NU and the Connectictit River Atlantic Salmon Commission in 1990, Work was

begun in the Holyoke Canal, where a gatehouse controls flows of up to 7 000 cfs into the three-tiered

canal system. Fish entering the canal system are confined to one route for the first 1 000 ft downstream of

the gatehouse; it was in this stretch that a fish diversion system was needed.

Working with a;teaIn of consultants and NU engineers, biologists, and licensing specialists, NU reviewed

available fish-screening technologies and decided to pursye development of a louver fish deflector system

(Bates and VinsoDhaIer 1957) for the canal. A typical louver system consists of an array of narrow slats

place at right angles to the flow in a stmcture that itself is placed at a 150 angle to the flow, leading to a

bypass conduit Flow velocity upstteam of the louvers accelerates along the length of the array reaching

levels 1.5 times incoming velocities at the downstream end of the louvers and the mouth of the bypass.
Work by other researchers had indicated that slat spacing could be greater than 1 ft and still be effective in

guiding Atlantic salmon smolts (Ducharme 1972).

The results ofNU' s program to develop a louver/bypass system for the Holyoke Canal are described

below.

FACILITY DESCRIPTION AND DEVELOPMENT

Phase I - Floating Louvers with no Bypass Facility - Figure 1

Based on the recommendation of C. P. Ruggles, consultant to NU, a partial depth prototype floating

louver system was designed by NtJ for installation in the Holyoke Canal This concept was based on

observations that saIinOIl smoltsaildjuVenile clupeids migrating downstre3mtend to be near the surface.

The initial effectivenesS -Stililies (Ruggles et aI1993, Harza and Biosonics 1991). were performed to test

the guiding effectiveness of this concept and were done without a bypass that would return fish to the river. tBf " 

The orientation of the 10ttVerarray to the flow in the canal was 15 degrees and total length oflouver line

was 516-ft. The loUver 3rtaY was cOmposed of floating frames and reinovablelouver panels that extended

to a depth of 8-ft. The fI.OatlDg frirmes were each 18-ft long and constructed offour wooden 8x8 timbers

styrofoam flotation blocks, and vertical steel guides at 6-ft centers that the louver panels fit into. The 6-

wide, 8-ft long louver panels were constructed of vertical polypropylene slats held at 3-in spacing by

horizontal guides. Polypropylene was selected because of its light weight and durability. Each slat was 8-

long, 3/8-in thick, and 2-1/2-in wide. The panels were designed so the slat spacing could be changed to 6-

in or 12-in by removing siats aJ;ld the depth of submergence could also be varied by raising the panels in the frame. 

. ..

The width of the frames at the water surface was wide enough so men could walk on the wooden members

to inspect and maintain the loUverS. .. Cleaning of the louvers was done periodically by two men who would

raise the panels to remove sniallertrash such as leaves and grass. Large floating debris was be guided to

the end of the louver ~rwhereitwas removed by a crane. 

The floating louvers were held in place by a I-in diameter steel cable which ran the entire length of the

lover array. The floating frames were attached to the cable with cable clips and shackles. The upstream

end of the 8-ftdeep floating louver structure was attached to an anchor in the canal wall approximately

300-ft downstream ofthetaDa1 head gates. There was a 15-ftwide gap between the downstream end of

the louvers and the can3l wall. 

Phase ll- Floating Louvers with Bypass Facility - Figure 2

In the spring and summer of 1991 the second phase of construction was completed. This effort included

the installation of the bypasS facility, a guideramp, a transport pipe, a fish sampling facility, and a 40-

long non-floating lOVer bay immediatelyupstream of the bypass. This bay was initially installed with

louver panels having a clear opening between the slats of one inch and were extended to the full depth of

the canal (20-ft).

The bypass structure is loCated on the left bank approximately 950-ft downstream of the canal gatehouse.

The bypass entrance is located at the end of the louvers and is 8-ft deep and 5-ft wide. It has a removable

Venturi':like restrictor to adjust the bypass width and vel~ties. The width of the bypass at this restrictor

was initially 2-1/2-ft wide but was later changed to 3-1/2-ft to improve the hydraulic characteristics in the

bypass area. . At the upstream end of the bypass there is a vertical trash rack with bars at 12 inch spacing.

The total length of the bypass is 18-ft ending with a transition to a 3-ft diameter pipe.
Atlantic Salmon Smolts

A guide ramp Was installed upstream of the bypass facility. This ramp started at the bottom of the bypass

opening and sloped downward at an angle of 20 degrees to the lloor of the canal. The guide ramp was

constructed of wedge-wire screen with a clear opening of ~-in (72% open area).

The transport pipe is a 3-ft diameter steel pipe, approximately SSO-ft long, with a maximum bend radius

of 12-ft. The pipe is painted inside and out and cathodically protected to minimi7-e corrosion. The capacity

of the pipe flowing full is 150 cfs with a maximum velocity of 20 fps. There is a Smith-Root Model 1100

fish coUnter installed in the pipe to count larger fish such as adult American shad. The pipe transports the

fish from the bypass facility to a fish sampling facility adjacent to the Hadley Station Tailrace.

The Fish sampling facility is a 13-ft wide by 90-ft long cOncrete structure. The sampler has a two position

gate which can be changed to operated in two modes. One mode of operation is to bypass the fish directly

back into the tailrace which floWs into the Connecticut River. 'The other mode allows the sampling offish

by passing the 150 cfsbypaSs flow oVer an inclined (10 degree) wed~wirescreen, approximately 300-

in area with a clear opening of 1/8-in(57% open area). The flow through the screen is controlled by two

slide gates downstream of the screen which allow adjustment of flow through and over the wedge-wire. At

the end of the wedge-wire is a trough perpendictilar to the flow which the fish enter with a flow 

approximately l-cfs. Thistrough is l-1I2-ft wide and flows into a counting and observation table where

the fish can either be held iria holding pool or released directly into the tailrace.

Further evaluations were performed (Harza and RMC 19928, Harza and RMC 1992b) with 4OO-ft of

floating louvers, 40-ft of non-floating louvers, and the completed bypass system.

Phase ill - Non Floating Louvers and Bypass Faci1ity - Figure 3

In the summer of1992, 400-ft of non-floating lovers were installed. These loUvers, along with the 40-

section installed iri 1991 are oriented 15 degrees to the canal fIow have a 2-in clear Opening and are 9-

deep. The louver "support structure has a 2 ton traveling gantry aane used to install and maintain the

louver panels. There is ako a 2 ton jib crane at the bypass to remove debris "which accumulates on the

trash racks. The structure was designed for a differential-hydraoJic head of 2ft.

Additional evaluations (Harza and RMC 1993, IfaI7.a 1993, RMC 1994, NUSOO 1994, NUSCO 1996)

were conducted and mOdifiCations made to the full depth louvers immediately upstream of the bypass to

optimize the flow accelerations and maximize fish passage effectiveness. 

GUIDANCE AND PASSAGE EVALUATIONS

The louver /bypass system in Holyoke has been thoroughly evaluated relative to the guidance and passage

of juvenile clupeids (American shad and blueback herring) and Atlantic salmon smolts. Evaluation

followed each step in the development and design process. Techniques included radiotelemetxy, release

and recapture of marked fish, netting, and hydroacoustics.

The effectiveness of the prototype floating louvers was evaluated in 1990 using radiotelemeny techniques

before the bypass was installed. Although a number of conditions were evaluated, three releases of 

radiotagged smolts with 3-in slat spacing in place to a depth of 8 ft yielded guidance efficiency of 93%

(NUSCO 1990, RuggJ.es et aI. 1993). Results of this evaluation were sufficiently favorable to proceed with plans to construct the bypass. 

.

Following construction of the bypass, passage efficiency of the fioating louver array with a 4O-ft fulIdepth, 2 3/8-in bar spaCing section in place immediately upstream of the bypass entrance was evaluated in

1992 using radiotelemeny techniques, and by recapture of marked smolts. Thetwo methods produced
similar results; passage efficiency was 91.3% at 3-in slat spacing (Harza and RMC 1992b). When slat

spacing was widened to 12 in, passage efficiency was 79.7%.

Results of the early louver evaluations led to construction and evaluation of the non-floating structure in

1993, with a 40-ft section offull-depth, 2 3/S-in-slat-spacing louvers at the downstream end of the array.

Radiotelemetxy C;lata from smolts released either immediately upstream or immediately downstream of the

gatehouse indicated overn11 guidance efficiency ofS5.9% (Harza 1993); efficiency at canal flows offrom

000 to 6 000 cfs was roughly the same as efficiency at flows of 3 000 to 3 400 cfs. Preliminary testing

indicated that guidance efficiency was higher without the. 40-ft fuII-depth section in place.

During the next two years, 1994 and 1995, radiotagged salmon smolts were released about 0.75 miles

upstream of Holyoke Dam. Some of these smolts entered the canal and encountered the louverlbypass

system, which had been modified by permanently removing the 40-ft ful1-depthsection. Of the 40 smolts

that entered the canal during 1994, 39 (97%) were successfully guided by the louvers and passed

downstream via the bypass (NUS CO 1994). In 1995, 49 of 54 (91%) smolts entering the canal were

successfully guided (NUSCO 1996).

The evaluations of the louver /bypass system have consistently shown that the system is effective for the

safe downstream passage of Atlantic salnlon smolts. The proximity of the louver array to the canal

gatehouse has no apparent effect on the system s smolt guiding efficiency, neither do canal flows within

the range evaluated (2 000 to 6 000 cfs).

Juvenile Clupeids

Although the effectiveness of the louver system for Atlantic salmon smolts was indicated by the results 

the earliest testing, guidance of juvenileclupeids Was more difficult to demonstrate. The American shad

and blueback herring migration in the Connecticut occurS over a two-month period (O' Lea1y and Kynard

1986), making it difficult to aSsure that all the test fish used in evaluations were in migratory condition. 

addition, radiotelemetxy techniques could not be used because of the small size of the migrants.

The effectiveness of the prototype floating louvers was eValuated with hydroacoustic gear in 1990, before

installation of the bypass. The louver array ended at an approximately 15-ft wide gap between the louvers

and the canal wall. Analysis ofthehydroacoustic data indicated mean guidance efficiency of about 2S%

and that a substantial portion of the juvenile clupeids approaching the louvers passed under them rather

than along them to the downstream end of the array (Harza and Biosonics 1991). There were uncertainties

about the interpretation of the data, however, and, especially in light of favorable data from evaluation of

salnlonsmolt passage, a decision was made to use more conventional means to reevaluate passage of

juvenile clupeids.

The bypass was installed during summer, 1991. Nets were deployed to investigate the vertical distribution

of clupeids approaching the louvers and to evaluate passage under the floating array. The 4O-ft, fu1I-depth

section with I-in bar spacing was in place immediately upstream of the entranCe to the bypass. The bypass

collection facility had also been installed, facilitating passage evaluation by allowing capture offish that

were successfully guided. Juvenile clupeids were captured upstream of Holyoke Dam, marked with dye

and released either immediately upstream or immediately downstream of the canal gatehouse, upstream of

the floating louver array.

Although there were doubts about the behavior of the marked fish, mean guidance efficiency was

estimated to be 45% (+/- 20%) based on marked fish subsequently recaptured at the bypass collection

facility (Harza and Ridc 1992a). In addition to the suspected problems with the behavior of the test fish,

velocity measurements along the face of the array indicated that the desired increase in velocity did not

occur near the downstream end of the louver array. Both factors may have reduced obselVed guidance

efficiencies. A separate estimate based on catches of freely-migrating clupeids captured in nets under the

array indicated that guidance efficiency was 69%. Informal evaluation of mortality due to use of the
bypass collection facility. indicated that immediate mortality was negligible, and that delayed mortality

was less than 10%.

During 1992, the third year of evaluation of clupeid passage, the non-floating louvers and bypass were in

place. The 40-ft, fuII-depth section was in place, but slat spacing had been increased to 2 3/8-in to txy to

eliminate the velocity sta11 noticed in 1991 . Marked fish were released downstream of the canal gatehouse

and recaptured in the bypass collection facility. M~ guidance efficiency was estimated to be 76%, based

on recaptures of marked fish (Harza and RMC 1993). Nets were also deployed under and behind the array,

allowing estimation of the mean guidance efficien9' of freely-migrating clupeids. This yielded an estimate

86%. Net sampling also determined that marlced fish tended to move downstream deeper in the water

column than freely-migrating fish, possibly explaining the discrepancy in the two estimates of guidance

efficiency.

Mean guidance efficiency during the 1993, the last year of evaluation, based on the release and recapture

of marked individuals and corrected for gear efficiency was 670/0; 82.9% at canal flow of 5 000 cfs and

59.5 % at 3 000 cfs (RMC )994). The lower efficiency at lower flows had not been observed in earlier

evaluations, but may have been due to a .greater tendency for the marked fish to resist the slower flow

velocities and maintain position. In addition, as remarked above, niarklrecapture methods had been found

to yield lower estimates of guidance efficiency than estimates derived from catches offreely-migrating

fish, thus the estimate of guidance efficiency should be considered a minimum. The effect of the 4Osection offull-depth, 2 3/8-in-slat-spacing louver near the bypass was also evaluated during this study.

The full depth section was found to have no effect on guidance efficiency and was removed permanently

after this evaluation had been completed.

SUMMARY

We decided to evaluate a louver system for guiding emigrating anadromous fish entering the Holyoke

canal because louvers had proven effective elsewhere (Bates and Vmsonhaler 1957, Ruggles and Ryan

1964, Ducharme 1972). We modified existing designs by limiting the depth of the louvers to nine feet to

take advantage of the tendency for young American shad- and Atlantic salmon. tQ migrate near the. surface

thus leaving part of the flow through the canal unobstructed. Using a step-by-step approach, we tested a

floating louver structure without a bypass, the same structure with the bypass, including a sampling

facility, then the finallouverlbypass system. The system was then adjusted for maximum effectiveness.

The results of our evaluations show that partial-depth louvers, which are less expensive to constmct and

maintain than a fuII-depth structure, are highly effective in guiding young-of-the-year American shad and

Atlantic salmon smolts to a suitable bypass. Tests showed that a floating louver Structure was as effective

at guiding Atlantic salnlon smolts as a non-floating structure. The acceleration offlows along the face of

the louvers toward the bypass entrance is critical to successful guidance, as is a smooth transition and

continued acceleration of flow into the bypass entrance itself. Design elements that contributed to

disruption of thepattem of acceleration, such as the fuII-depth louver section immediately upstream of the

louver entrance, were eliminated from the fina1 design.

Passage of young -of- the-year shad has been difficult to evaluate because of the small size of the fish,

eliminating use of radiotelemetxy, and because of unCerta1nty of the migratory condition of the test fish.

The louver system may be less effective for shad because of a lesser tendency for this species to recover

from passage through the turbulence caused by the canal gatehoose and return to the surface slower than

smolts as indicated by the catches in the vertical distribution netting during the evaluations.

The Completed facility effectively passed 86 to 97% of Atlantic salmon smolts and 67 to 86% of young -ofthe-year American shad out of the Holyoke canal. The sampling facility added to the bypass facilitated

evaluation of the system as a whole, and ultimately reduced the cost of evaluation. Evaluation of smolt

passage has yielded consistent results under a variety of test conditions, using two different methods and

several testing procedures, leading to a high level of confidence in the results.
. Literature Cited

Bates, D. W. and R Vinsonha1er. 1957. Use oflouvers for guiding fish. Trans. Am. Fish.

Soc. 86:38-57. 

Ducharme, L. J. A 1972. An application oflouver deflectors for guiding Atlantic salnlon

(Sa/mo sa/or) smolts from power turbines. J. Fish. Res. Board Canada. 29(20):1397-1404.

Harza Engineering Company (Harza). 1993. Holyoke Canal downstream fish passage

. studies: DownstrCam passage of Atlantic salmon smolts, spring 1993. Report to Northeast

Utilities SerVice Company. 41 p.

Harza Engineering Company and Biosonics, Inc. 1991. Holyoke Canal downstream fish

passage studies: Response of juvenile clupeids to louvers in the Holyoke Canal, fall 1990. Draft

report to Northeast Utilities SerVice Company. 21 p.

Harza Engineering Company and RMC Environmental SerVices. Inc. (RMC). 199280

Holyoke Canal downstream fish passage studies: Response of juvenile clupeids to louvers in the

Holyoke Canal, fall 1991. Report to Northeast Utilities SeIVice Company. 46 p.

Harza Engineering Company and RMC Environmental SeIVices. Inc. 1992b. Holyoke

Canal downstream fish passage studies: Response of Atlantic salmon smolts to louvers in the

Holyoke Canal, spring 1992. Report to Northeast Utilities Service Company. 32 p.

Harza Engineering Company and RMC Environmental SeIVices. Inc. 1993. Holyoke Canal

downstream fish passage studies: Response of juvenile clupeids to louvers in the Holyoke Canal,

fall 1992. Report to.Northeast Utilities Service Company. 47 p.

Northeast Utilities SerVice Company (NUS CO). 1990. Studies of the migration of Atlantic

salmo~ smolts (Sa/mo solar) at the Holyoke Project, Connecticut River, Holyoke, Massachusetts

during 1990. 32 p.

Noqheast Utilities Service Company (NUSCO). 1994. Downstream passage of

radiotagged Atlantic salmon (Sa/mo sa/ar) smolts at the Holyoke Project, Holyoke

Massachusetts, 1994. 27 p.

Northeast Utilities Service Company (NUSCO). 1996. Downstream passage of

radiotagged Atlantic salnlon (Sa/mo sa/or) smolts at the Holyoke Project, Holyoke

Massachusetts, 1995. 28 p.

Leary, J. A, and B. Kynard. 1986. Behavior, length, and sex ratio of seaward-migrating juvenile

American shad and blueback herring in the Connecticut River. Trans. Am. Fish. Soc. 115:529-

536.

RMC Environmental SerVices. 1994. Response of juvenile clupeids to the louvers in the

Holyoke Canal, fall 1993. Report to Northeast Utilities Service Company. 27 p.

Ruggles, C. P., D. A Robinson, andR J. Stirn. 1993. The use of floating louvers for

guiding Atlantic salmon (Sa/mo solar) smolts from hydroelectric turbine intakes. Can. Tech.

Rep. Fish. Aqual Sci. no. 1905: 87-

Ruggles, C. P. and P. Ryan. 1964. An Investigation of Louvers as a Method of Guiding Juvenile Pacific

Salmon. Can. Fish Cull 33:1-68
CANAL

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Downslream Fish Passage

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Downslream Fish Passage

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