ANADROMOUS SALMONID 

PASSAGE FACILITY DESIGN 

NATIONAL MARINE FISHERIES SERVICE 

NORTHWEST REGION 

www.nwr.noaa.gov

FEBRUARY 2008 
ACKNOWLEDGMENTS 

Bryan Nordlund, National Marine Fisheries Service (NMFS) Hydraulic Engineer, is the primary 

author of this document. He was assisted by Larry Swenson, Hydraulic Engineer; Melissa Jundt, 

Hydraulic Engineer; Ed Meyer, Hydraulic Engineer; Scott Carlon, Fishery Biologist; and John 

Johnson, Hydraulic Engineer; all with NMFS. In addition, he was assisted by Steve Rainey, GEI 

Consultants, Inc. 

Reviews were provided by Denny Hudson, U.S. Bureau of Reclamation; Pat Powers and Tom 

Burns, Washington Department of Fish and Wildlife; Ray Hartlerode, Tom Stahl, and Bernie 

Kepshire, Oregon Department of Fish and Wildlife; Lynn Stratton and Matt Hightree, Idaho 

Department of Fish and Game; and Ken Bates, Koszmo, Inc. 

Suggested changes, additions, or questions should be directed to Bryan Nordlund at 

Bryan.Nordlund@noaa.gov for consideration in updating this document. 

Assistance from NMFS fish passage specialists can be obtained by contacting the NMFS 

Northwest Region Hydropower Division at 503-230-5414. 

Suggested citation: 

NMFS (National Marine Fisheries Service). 2008. Anadromous Salmonid Passage Facility 

Design. NMFS, Northwest Region, Portland, Oregon. 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

TABLE OF CONTENTS 

FOREWORD..............................................................................................................................viii 

1. DEFINITION OF TERMS................................................................................................... 12 

2. PRELIMINARY DESIGN DEVELOPMENT................................................................... 21 

2.1 Introduction.................................................................................................................... 21 

2.2 Site Information ............................................................................................................. 21 

2.3 Biological Information................................................................................................... 22 

2.4 Design Development Phases.......................................................................................... 23 

3. DESIGN FLOW RANGE..................................................................................................... 24 

3.1 Introduction.................................................................................................................... 24 

3.2 Design Low Flow for Fish Passage ............................................................................... 24 

3.3 Design High Flow for Fish Passage............................................................................... 25 

3.4 Fish Passage Design for Flood Flows............................................................................ 25 

4. UPSTREAM ADULT FISH PASSAGE SYSTEMS.......................................................... 26 

4.1 Introduction.................................................................................................................... 26 

4.2 Fishway Entrance........................................................................................................... 28 

4.2.1 Description and Purpose .................................................................................... 28 

4.2.2 Specific Criteria and Guidelines........................................................................ 29 

4.3 Auxiliary Water Systems............................................................................................... 31 

4.3.1 Description and Purpose .................................................................................... 31 

4.3.2 Specific Criteria and Guidelines – AWS Diffusers ........................................... 31 

4.3.3 Specific Criteria and Guidelines – AWS Fine Trash Racks.............................. 32 

4.3.4 Specific Criteria and Guidelines – AWS Screens.............................................. 32 

4.3.5 Specific Criteria and Guidelines – AWS Flow Control..................................... 32 

4.3.6 Specific Criteria and Guidelines – AWS Excess Energy Dissipation ............... 33 

4.4 Transport Channels........................................................................................................ 34 

4.4.1 Description and Purpose .................................................................................... 34 

4.4.2 Specific Criteria and Guidelines........................................................................ 34 

4.5 Fish Ladder Design........................................................................................................ 34 

4.5.1 Description and Purpose .................................................................................... 34 

4.5.2 Types of Fish Ladders........................................................................................ 34 

4.5.3 Specific Criteria and Guidelines........................................................................ 42 

4.6 Counting Stations........................................................................................................... 43 

4.6.1 Description and Purpose .................................................................................... 43 

4.6.2 Specific Criteria and Guidelines – Counting Stations ....................................... 44 

4.6.3 Specific Criteria and Guidelines – Counting Window ...................................... 44 

4.7 Fishway Exit Section ..................................................................................................... 45 

4.7.1 Description and Purpose .................................................................................... 45 

4.7.2 Specific Criteria and Guidelines – Fishway Exit Section.................................. 45 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.8 Fishway Exit Sediment and Debris Management.......................................................... 46 

4.8.1 Description and Purpose .................................................................................... 46 

4.8.2 Specific Criteria and Guidelines – Coarse Trash Rack...................................... 46 

4.8.3 Specific Criteria and Guidelines – Debris and Sediment................................... 47 

4.9 Miscellaneous Considerations ....................................................................................... 48 

4.9.1 Specific Criteria and Guidelines........................................................................ 48 

4.10 Roughened Chutes......................................................................................................... 48 

4.10.1 Description and Purpose .................................................................................... 48 

4.10.2 Types of Roughened Chutes.............................................................................. 49 

5. EXCLUSION BARRIERS ................................................................................................... 52 

5.1 Introduction.................................................................................................................... 52 

5.2 Types of Exclusion Barriers........................................................................................... 52 

5.3 Picket Barriers................................................................................................................ 53 

5.3.1 Description and Purpose .................................................................................... 53 

5.3.2 Specific Criteria and Guidelines........................................................................ 53 

5.4 Velocity Barrier ............................................................................................................. 54 

5.4.1 Description and Purpose .................................................................................... 54 

5.4.2 Specific Criteria and Guidelines........................................................................ 55 

5.5 Vertical Drop Structures................................................................................................ 56 

5.5.1 Description and Purpose .................................................................................... 56 

5.5.2 Specific Criteria and Guidelines........................................................................ 56 

5.6 Horizontal Draft Tube Diffusers.................................................................................... 57 

5.6.1 Description and Purpose .................................................................................... 57 

5.6.2 Specific Criteria and Guidelines........................................................................ 57 

6. ADULT FISH TRAPPING SYSTEMS............................................................................... 58 

6.1 Introduction.................................................................................................................... 58 

6.2 Trap Design Scoping...................................................................................................... 59 

6.3 Fish Handling................................................................................................................. 59 

6.3.1 Specific Criteria and Guidelines........................................................................ 59 

6.4 General Trap Design...................................................................................................... 60 

6.4.1 Specific Criteria and Guidelines........................................................................ 60 

6.5 Trap Holding Pool.......................................................................................................... 61 

6.5.1 Specific Guidelines and Criteria ........................................................................ 61 

6.6 Trapping Mechanism ..................................................................................................... 63 

6.6.1 Description and Purpose .................................................................................... 63 

6.6.2 Specific Criteria and Guidelines........................................................................ 63 

6.7 Lift/Hopper .................................................................................................................... 64 

6.7.1 Description and Purpose .................................................................................... 64 

6.7.2 Specific Criteria and Guidelines........................................................................ 64 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.8 Fish Lock ....................................................................................................................... 65 

6.8.1 Description an Purpose ...................................................................................... 65 

6.8.2 Specific Criteria and Guidelines........................................................................ 65 

6.9 Single Holding Pool Traps............................................................................................. 66 

6.9.1 Description and Purpose .................................................................................... 66 

6.9.2 Specific Criteria and Guidelines........................................................................ 66 

7. CULVERTS AND OTHER ROAD CROSSINGS............................................................. 67 

7.1 Introduction.................................................................................................................... 67 

7.2 Preferred Alternatives for New, Replacement, or Retrofitting Culverts ....................... 68 

7.3 Active Channel Design Method..................................................................................... 68 

7.3.1 Description and Purpose .................................................................................... 68 

7.3.2 Specific Criteria and Guidelines........................................................................ 69 

7.4 Streambed Simulation Design Method .......................................................................... 69 

7.4.1 Description and Purpose .................................................................................... 69 

7.4.2 Specific Criteria and Guidelines........................................................................ 70 

7.5 Hydraulic Design Method.............................................................................................. 71 

7.5.1 Design and Purpose............................................................................................ 71 

7.5.2 Specific Criteria and Guidelines........................................................................ 71 

7.6 Retrofitting Culverts...................................................................................................... 73 

7.6.1 Description and Purpose .................................................................................... 73 

7.6.2 Specific Criteria and Guidelines........................................................................ 73 

7.7 Miscellaneous Culverts/Road Crossings........................................................................ 75 

7.7.1 Specific Criteria and Guidelines........................................................................ 75 

8. TIDE GATES (WORK IN PROGRESS) ........................................................................... 78 

9. COLUMBIA AND SNAKE RIVER FISH PASSAGE FACILITIES.............................. 79 

9.1 Introduction.................................................................................................................... 79 

9.2 Mainstem Upstream Passage ......................................................................................... 79 

9.2.1 Description and Purpose .................................................................................... 79 

9.2.2 Specific Criteria and Guidelines........................................................................ 80 

9.3 Mainstem Juvenile Screen and Bypass.......................................................................... 81 

9.3.1 Description and Purpose .................................................................................... 81 

9.3.2 Specific Criteria and Guidelines........................................................................ 81 

9.4 Vertical Barrier Screens................................................................................................. 82 

9.4.1 Description and Purpose .................................................................................... 82 

9.4.2 Specific Criteria and Guidelines........................................................................ 82 

10. UPSTREAM JUVENILE FISH PASSAGE....................................................................... 83 

10.1 Introduction.................................................................................................................... 83 

10.2 Design ............................................................................................................................ 83 

10.2.1 General Criteria and Guidelines......................................................................... 84 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11. FISH SCREEN AND BYPASS FACILITIES.................................................................... 86 

11.1 Introduction.................................................................................................................... 86 

11.2 Functional Screen Design .............................................................................................. 87 

11.3 Site Conditions............................................................................................................... 87 

11.4 Existing Screens............................................................................................................. 88 

11.4.1 Acceptance Criteria and Guidelines for Existing Screens................................. 88 

11.5 Structure Placement ....................................................................................................... 88 

11.5.1 Specific Criteria and Guidelines – Streams and Rivers..................................... 88 

11.5.2 Specific Criteria and Guidelines – Lakes, Reservoirs, and Tidal Areas............ 89 

11.6 Screen Hydraulics – Rotating Drum Screens, Vertical Screens, and Inclined Screens. 89 

11.6.1 Specific Criteria and Guidelines........................................................................ 89 

11.7 Screen Material .............................................................................................................. 91 

11.7.1 Specific Criteria and Guidelines........................................................................ 91 

11.8 Civil Works and Structural Features.............................................................................. 91 

11.8.1 Specific Criteria and Guidelines........................................................................ 91 

11.9 Bypass Facilities............................................................................................................ 92 

11.9.1 Specific Criteria and Guidelines – Bypass Layout ............................................ 92 

11.9.2 Specific Criteria and Guidelines – Bypass Entrance ......................................... 93 

11.9.3 Specific Criteria and Guidelines – Bypass Conduit and System Design........... 94 

11.9.4 Specific Criteria and Guidelines – Bypass Outfall ............................................ 96 

11.10 Debris Management.................................................................................................... 96 

11.10.1 Specific Criteria and Guidelines..................................................................... 96 

11.11 End of Pipe Screens (including pump intake screens)................................................ 98 

11.11.1 Specific Criteria and Guidelines..................................................................... 98 

12. INFILTRATION GALLERIES (EXPERIMENTAL TECHNOLOGY)........................ 99 

12.1 Introduction.................................................................................................................... 99 

12.2 Scope............................................................................................................................ 100 

12.3 Selection of Appropriate Screen Technology.............................................................. 101 

12.4 Site Selection ............................................................................................................... 101 

12.5 Design: Infiltration Galleries....................................................................................... 101 

12.5.1 Specific Criteria and Guidelines...................................................................... 101 

13. TEMPORARY AND INTERIM PASSAGE FACILITIES ............................................ 104 

14. OPERATIONS AND MAINTENANCE RESPONSIBILITIES .................................... 105 

15. POST-CONSTRUCTION EVALUATIONS.................................................................... 106 

15.1 Introduction.................................................................................................................. 106 

15.2 Evaluation of Juvenile Fish Screens............................................................................ 106 

15.3 Biological Evaluation................................................................................................... 107 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

16. EXPERIMENTAL FISH GUIDANCE DEVICES.......................................................... 108 

16.1 Introduction.................................................................................................................. 108 

16.2 Juvenile Fish Entrainment at Intakes........................................................................... 108 

16.3 Behavioral Devices...................................................................................................... 109 

16.4 Process for Developing Experimental Fish Passage Technology................................ 111 

16.5 Conclusions.................................................................................................................. 112 

17. SUGGESTED READING AND REFERENCES............................................................. 113 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

TABLES AND FIGURES 

Figure 1-1. Plunging Flow over Fishway Weir ....................................................................... 17 

Figure 1-2. Streaming Flow over Fishway Weir ..................................................................... 18 

Figure 4-1. Features of an Upstream Passage System using a Vertical Slot Fishway............. 28 

Figure 4-2a. Plan View of Vertical Slot fishway Showing Generalized Flow Path.................. 35 

Figure 4-2b. Isometric View of Vertical Slot Fishway.............................................................. 36 

Figure 4-2c. Dimensions of a Typical Vertical Slot.................................................................. 37 

Figure 4-3a. Plan View of an Ice Harbor Type Weir and Orifice Fish Ladder......................... 39 

Figure 4-3b. Longitudinal Cross-section of an Ice Harbor Type Weir and Orifice 

Fish Ladder ........................................................................................................... 40 

Figure 4-3c. Front View Cross-section of Ice Harbor Fishway Baffle ..................................... 41 

Figure 4-4. Pool and Chute Fishway ....................................................................................... 42 

Figure 4-5. Coarse Trashrack .................................................................................................. 47 

Figure 5-1. Velocity Barrier .................................................................................................... 56 

Figure 5-2. Potential Layout of a Horizontal Draft Tube Diffuser.......................................... 57 

Table 7-1. Maximum Allowable Average Culvert Velocity.................................................. 72 

Table 10-1. Juvenile Upstream Fish Passage Guidelines......................................................... 84 

Table 11-1. Bypass Design Examples...................................................................................... 95 

Figure 12-1. Cross Section of an Example Infiltration Gallery............................................... 100 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

ACRONYMS AND ABBREVIATIONS 

AWS auxiliary water supply 

cfs cubic feet per second 

COE U.S. Army Corps of Engineers 

EPRI Electric Power Research Institute 

ESA Endangered Species Act 

FERC Federal Energy Regulatory Commission 

FPA Federal Power Act 

HGL hydraulic grade line 

HGMP Hatchery and Genetic Management Plan 

MSA Magnuson-Stevens Fishery Conservation and Management Act 

NMFS National Marine Fisheries Service 

NWR Northwest Region 

PESBS Positive-exclusion screen and bypass systems 

PIT passive integrated transponder 

ppm parts per million 

R/D ratio of bypass pipe center-line radius of curvature to pipe 

VBS Vertical barrier screens 

WDFW Washington Department of Fish and Wildlife 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

FOREWORD 

The National Oceanic and Atmospheric Administration’s National Marine Fisheries Service 

(NMFS) is charged by Congress to manage, conserve, and protect living marine resources within 

the United States Exclusive Economic Zone. NMFS also plays a supportive and advisory role in 

the management of living marine resources in areas under state jurisdiction. Among these living 

marine resources are the Pacific anadromous salmonids (salmon and steelhead) which have 

tremendous economic, cultural, recreational, and symbolic importance to the Pacific Northwest 

(NRC 1996). 

Anadromous fishes reproduce in freshwater and the progeny migrate to the ocean to grow and 

mature and return to freshwater to reproduce. Salmon and steelhead cross many geographic and 

human boundaries during their freshwater migration. It is an arduous journey; some species 

migrate hundreds of miles each way in freshwater and thousands of miles while in the ocean. In 

addition to the challenge of covering great distances, most species must navigate many barriers 

during migration. Migration barriers—complete blockages and poorly functioning passage 

facilities—are a significant factor affecting most salmon populations in the Pacific Northwest. 

Any independent Pacific salmonid (genus Oncorhynchus) population is considered viable when 

it can withstand threats and risk of extinction from demographic variation, local environmental 

variation, and genetic diversity changes over a 100-year timeframe (McElheny et al. 2000). 

Each viable population needs to exhibit the abundance, productivity, spatial distribution and 

diversity of natural spawners sufficient to accomplish the following: avoid the loss of genetic 

and/or life history diversity during short-term losses in abundance that are expected parts of 

environmental cycles; fulfill key ecological functions that are attributable to the species, such as 

nutrient cycling and food web roles; and be resilient to environmental and anthropogenic 

disturbances. 

The primary effect of barriers (e.g., hydroelectric dams, water storage projects, irrigation 

diversions, impassable culverts, etc.) on Pacific salmonids is the reduction in population 

abundance and productivity through excessive mortality and reduction in habitat quantity and 

quality. Individuals are lost to the population due to death from passing through turbines, 

disproportionate predation in reservoirs, entrainment at unscreened or improperly screened 

diversions, etc. Spatial structure and diversity have also been reduced by the loss of nearly 40% 

of salmon habitat from dams (NRC 1996), either through complete blockage or inundation. 

This document is intended to assist with improving conditions for salmonids that must migrate 

past barriers to complete their life cycle. The task involved in successfully passing fish upstream 

or downstream of an in-river impediment is a dynamic integration of fish behavior, physiology, 

and bio-mechanics with hydraulic analysis, hydrologic study, and engineering. Installing a fish 

passage structure does not constitute providing satisfactory fish passage unless all of the above 

components are adequately factored into the design. 

The following document provides criteria, rationale, guidelines, and definitions for the purpose 

of designing proper fish passage facilities for the safe, timely, and efficient upstream and 

downstream passage of anadromous salmonids at impediments created by artificial structures, 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

natural barriers (where provision of fish passage is consistent with management objectives), or 

altered instream hydraulic conditions. This document provides fishway facility design standards 

for the National Marine Fisheries Service, and is to be used for actions pertaining to the various 

authorities and jurisdictions of NMFS, including Section 18 of the Federal Power Act (FPA), the 

Endangered Species Act (ESA), and the Magnuson-Stevens Fishery Conservation and 

Management Act (MSA) in the Northwest Region (NWR). This document intends to provide 

generic guidance as an alternative to active participation by NMFS engineers in a design process, 

for the purpose of providing designs that will be acceptable for fishways that fall within NMFS 

jurisdictions. If passage facilities are designed and constructed in a manner consistent with these 

criteria, adverse impacts to anadromous fish migration will be minimized. 

Instances will occur where a fish passage facility may not be a viable solution for correcting a 

passage impediment, due to biological, sociological, or economic constraints. In these situations, 

removal of the impediment or altering operations may be a suitable surrogate for a constructed 

fish passage facility. In other situations, accomplishing fish passage may not be an objective of 

NMFS because of factors such as limited habitat or lack of naturally occurring runs of 

anadromous fish upstream of the site. To determine whether NMFS will use its various 

authorities to promote or to prescribe fish passage, NMFS will rely on a collaborative approach, 

considering the views of other fisheries resource agencies, Native American Tribes, nongovernment organizations, and citizen groups, and will strive to accomplish the objectives in 

watershed plans for fisheries restoration and enhancement. 

This document does not address aspects of design other than those that provide for safe and 

timely fish passage, and to some extent, preservation of aquatic habitat. Structural integrity, 

public safety, and other aspects of facility design are the responsibility of the principal design 

engineer, who should ensure that the final facility design meets all other requirements in addition 

to the fish passage criteria and guidelines contained in this document. 

Section 11 (Fish Screen and Bypass Facilities) supersedes previous design guidance published by 

NMFS, including Juvenile Fish Screen Criteria (February 16, 1995) and Juvenile Fish Screen 

Criteria for Pump Intakes (May 9, 1996). 

The fish passage facilities described in this document include various fish ladders; exclusion 

barriers; trap and haul facilities; fish handling and sorting facilities; instream structures; road 

crossing structures such as culverts or bridges; juvenile fish screens; tide gates (still under 

development); infiltration galleries; upstream juvenile passage facilities; and specialized criteria 

for mainstem Columbia and Snake River passage facilities. Passage facilities for projects under 

NMFS jurisdiction should be consistent with the details described in this document, with the 

facility design developed in coordination with NMFS fish passage specialists. 

Proponents of new, unproven fish passage designs (i.e., not meeting the criteria and guidelines 

contained in this document) must provide to NMFS: (1) development of a biological basis for 

the concept; (2) demonstration of favorable fish behavioral response in a laboratory setting; (3) 

an acceptable plan for evaluating the prototype installation; and (4) an acceptable alternate plan 

developed concurrently for a fish passage design satisfying these criteria, should the prototype 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

not adequately protect fish. Section 16 (Experimental Fish Guidance Devices) provides 

additional information on the NMFS approval process for unproven fish passage devices. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot be 

changed without a written waiver from NMFS. For the purposes of this document, a criterion is 

preceded by the word “must.” In general, a specific criterion can not be changed unless there is 

site-specific biological rationale for doing so. An example of biological rationale that could lead 

to criterion waiver is a determination or confirmation by NMFS biologists that the smallest frysized fish will likely not be present at a proposed screen site. Therefore, the juvenile fish screen 

approach velocity criterion of 0.4 ft/s could be increased to match the smallest life stage expected 

at the screen site. A guideline is a range of values or a specific value for fishway design, 

maintenance or operation that may change when site-specific conditions are factored into the 

conceptual fishway design. For the purposes of this document guidelines are preceded by the 

word “should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions or solve 

site-specific issues. An example of site-specific rationale that could lead to a modified guideline 

is when the maximum river depth at a site is three feet, as compared to the design guideline for a 

fishway entrance depth of six feet. In this example, safe and timely fish passage could be 

provided by modifying the guideline to match the depth in the river. It is the responsibility of the 

applicant to provide compelling evidence in support of any proposed waiver of criteria or 

modification of a guideline for NMFS approval early in the design process, well in advance of a 

proposed Federal action. 

On occasion, more conservative designs may be required on a project-by-project basis if there is 

a need to provide additional protection for other species of fish. In addition, there may be 

instances where NMFS provides written approval for use of alternative passage standards, if 

NMFS determines that the alternative standards provide equal or superior protection as compared 

to the guidelines and criteria listed herein, for a particular site or for a set of passage projects 

within the NWR. 

It is possible that part or all of this document, or approved alternate passage standards, could be 

used to develop programmatic consultation under the ESA. For example, a project developer 

may choose to use this document as the basis for fish passage design and develop additional 

detail beyond the scope of this document (e.g., construction management, project 

implementation scheduling, riparian replacement, project monitoring, etc.) in consultation with 

NMFS. Programmatic ESA consultation may conclude that an optimal uniform approach to 

implementing a number of fish passage projects will not pose any threat to ESA-listed species or 

to critical habitat. With this conclusion, individual ESA consultation on each project could be 

avoided. 

Existing facilities may not adhere to the criteria and guidelines listed in this document. 

However, that does not mean these facilities must be modified specifically for compliance with 

this document. The intention of these criteria and guidelines is to ensure future compliance in 

the context of major upgrades and new designs of fish passage facilities. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

xi 

The following document is hereby designated as NMFS NWR Fish Passage Design Policy for 

responsibilities under the ESA, FPA, and MSA, for the purpose of providing project proponents 

with NMFS’ perspective on proper design of fish passage facilities for providing safe, timely, 

and efficient fish passage. This document was developed by NWR fish passage engineers based 

on nearly 60 years of agency experience in developing fishway designs, and further refined 

through a collaborative process with regional fishway design experts. This guidance is 

considered to be a working document, thus when new or updated information suggests that a 

different standard (criterion or guideline) provides better fishway passage, simplifies operations, 

or decreases required maintenance, this document will be periodically updated. Suggested 

changes, additions, or questions should be directed to Bryan Nordlund at 

Bryan.Nordlund@noaa.gov for consideration in updating this document. Assistance from NMFS 

fish passage specialists can be obtained by contacting the NMFS NWR Hydropower Division at 

(503) 230-5414. 

Bruce K. Suzumoto 

Assistant Regional Administrator 

Hydropower Division 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

1. DEFINITION OF TERMS

Terms defined in this section are identified in italics throughout the document. 

Anadromous - fish species that travel upstream to spawn in freshwater. 

Active screens - juvenile fish screens equipped with proven cleaning capability and are 

automatically cleaned as frequently as necessary to keep the screens free of any debris 

that will restrict flow area. An active screen is the required design in most instances. 

Approach velocity - the vector component of canal velocity that is perpendicular to and 

upstream of the vertical projection of the screen face, calculated by dividing the 

maximum screened flow by the effective screen area. An exception to this definition is 

for end-of-pipe cylindrical screens, where the approach velocity is calculated using the 

entire effective screen area. Approach velocity should be measured as close as physically 

possible to the boundary layer turbulence generated by the screen face. 

Apron - a flat, usually slightly inclined slab below a flow control structure that provides 

for erosion protection and produces hydraulic characteristics suitable for energy 

dissipation or in some cases fish exclusion. 

Attraction flow - the flow that emanates from a fishway entrance with sufficient velocity 

and in sufficient quantity and location to attract upstream migrants into the fishway. 

Attraction flow consists of gravity flow from the fish ladder, plus any auxiliary water 

system flow added at points within the lower fish ladder. 

Auxiliary water system - a hydraulic system that augments fish ladder flow at various 

points in the upstream passage facility. Typically, large amounts of auxiliary water flow 

are added in the fishway entrance pool in order to increase the attraction of the fishway

entrance. 

Backwash - providing debris removal by pressurized wash, opposite to the direction of 

flow. 

Backwater - a condition whereby a hydraulic drop is influenced or controlled by a water 

surface control feature located downstream of the hydraulic drop. 

Baffles - physical structures placed in the flow path designed to dissipate energy or to redirect flow for the purpose of achieving more uniform flow conditions. 

Bankfull - the bank height inundated by an approximately 1.2 to 1.5 year (maximum) 

average recurrence interval and may be estimated by morphological features such as the 

following: (1) a topographic break from vertical bank to flat floodplain; (2) a topographic 

break from steep slope to gentle slope; (3) a change in vegetation from bare to grass, moss to 

grass, grass to sage, grass to trees, or from no trees to trees; (4) a textural change of 

depositional sediment; (5) the elevation below which no fine debris (e.g., needles, leaves, 

cones, seeds) occurs; and (6) a textural change of matrix material between cobbles or rocks. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Bedload - sand, silt, gravel, or soil and rock debris transported by moving water on or 

near the streambed. 

Bifurcation (Trifurcation) pools - pools where two or three sections of fish ladders 

divide into separate routes. 

Brail - a device that moves upward (vertically) through the water column, crowding fish 

into an area for collection. 

Bypass flow - in context of screen design, that portion of flow diverted that is specifically 

used to bypass fish back to the river. 

Bypass reach - the portion of the river between the point of flow diversion and the point 

of flow return to the river. 

Bypass system - the component of a downstream passage facility that transports fish from 

the diverted water back into the body of water from which they originated, usually 

consisting of a bypass entrance, a bypass conveyance, and a bypass outfall. 

Channel bed width - the width of the stream bed under bankfull channel conditions. 

Conceptual design - an initial design concept based on the site conditions and biological 

needs of the species intended for passage. This is also sometimes referred to as 

preliminary design or functional design. 

Crowder - a combination of static and/or movable picketed and/or solid leads installed in 

a fishway for the purpose of moving fish into a specific area for sampling, counting, 

broodstock collection, or other purposes. 

Diffuser - typically, a set of horizontal or vertical bars designed to introduce flow into a 

fishway in a nearly uniform fashion. Other means are also available that may accomplish 

this objective. 

Distribution flume - a channel used to route fish to various points in a fish trapping 

system. 

Effective screen area - the total submerged screen area, excluding major structural 

members, but including the screen face material. For rotating drum screens, effective 

screen area consists only of the submerged area projected onto a vertical plane, 

excluding major structural members, but including screen face material. 

End of pipe screens - juvenile fish screening devices attached directly to the intake of a 

diversion pipe. 

Entrainment - the unintended diversion of fish into an unsafe passage route. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Exclusion barriers - upstream passage facilities that prevent upstream migrants from 

entering areas with no upstream egress, or areas that may lead to fish injury. 

Exit control section - the upper portion of an upstream passage facility that serves to 

provide suitable passage conditions to accommodate varying forebay water surfaces, 

through means of pool geometry, weir design, and the capability to add or remove flow at 

specific locations. 

False weir - a device that adds vertical flow to a upstream fishway, usually used in 

conjunction with a distribution flume that routes fish to a specific area for sorting or to 

continue upstream passage. 

Fish ladder - the structural component of an upstream passage facility that dissipates the 

potential energy into discrete pools, or uniformly dissipates energy with a single baffled

chute placed between an entrance pool and an exit pool or with a series of baffled chutes 

and resting pools. 

Fish lift - a mechanical component of an upstream passage system that provides fish 

passage by lifting fish in a water-filled hopper or other lifting device into a conveyance 

structure that delivers upstream migrants past the impediment. 

Fish lock - a mechanical and hydraulic component of an upstream passage system that 

provides fish passage by attracting or crowding fish into the lock chamber, activating a 

closure device to prevent fish from escaping, introducing flow into the enclosed lock, and 

raising the water surface to forebay level, and then opening a gate to allow the fish to 

exit. 

Fish passage season - the range of dates when a species migrates to the site of an 

existing or proposed fishway, based on either available data collected for a site, or 

consistent with the opinion of an assigned NMFS biologist when no data is available. 

Fish weir (also called picket weir or fish fence) - a device with closely spaced pickets to 

allow passage of flow, but preclude upstream passage of adult fish. Normally, this term 

is applied to the device used to guide fish into an adult fish trap or counting window. 

This device is not a weir in the hydraulic sense. 

Fishway - the set of facilities, structures, devices, measures, and project operations that 

together constitute, and are essential to the success of, an upstream or downstream fish 

passage system. 

Fishway entrance - the component of an upstream passage facility that discharges 

attraction flow into the tailrace, where upstream migrating fish enter (and flow exits) the 

fishway. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Fishway exit - the component of an upstream passage facility where flow from the 

forebay enters the fishway, and where fish exit into the forebay upstream of the passage 

impediment. 

Fishway entrance pool - the pool immediately upstream of the fishway entrance(s), 

where fish ladder flow combines with any remaining auxiliary water system flow to form 

the attraction flow. 

Fishway weir - the partition that passes flow between adjacent pools in a fishway. 

Flood frequency - the frequency with which a flood of a given river flow has the 

probability of recurring based on historic flow records. For example, a "100-year" 

frequency flood refers to a flood flow of a magnitude likely to occur on the average of 

once every 100 years, or, has a one-percent chance of being exceeded in any year. 

Although calculation of possible recurrence is often based on historical records, there is 

no guarantee that a "100-year" flood will occur within the 100-year period or that it will 

not recur several times.

Floodplain - the area adjacent to the stream that is inundated during periods of flow that 

exceed stream channel capacity, as established by the stream over time. 

Flow control structure - a structure in a water conveyance intended to maintain flow in a 

predictable fashion. 

Flow duration exceedence curve - the plot of the relationship between the magnitude of 

daily flow and the percentage of the time period for which that flow is likely to be 

equaled or exceeded. Other time units can be used as well, depending on the intended 

application of the data. 

Flow egress weir - a weir used to route excess flow (without fish) from a fish facility. 

Forebay - the water body impounded immediately upstream of a dam. 

Freeboard - the height of a structure that extends above the maximum water surface 

elevation. 

Fry - for purposes of this document, defined as a young juvenile salmonid with absorbed 

egg sac, less than 60 mm in length. 

Functional design - an initial design concept, based on the site conditions and biological 

needs of the species intended for passage. This is also sometimes referred to as 

preliminary design or conceptual design. 

Hatchery supplementation - hatchery propagation usually utilizing the progeny of local 

wild broodstock. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Head loss - the loss of energy through a hydraulic structure. 

Hopper - a device used to lift fish (in water) from a collection or holding area, for release 

upstream of the impediment. 

Hydraulic drop - the energy difference between an upstream and downstream water 

surface, considering potential (elevation) and kinetic energy (velocity head), and pressure 

head. For fishway entrances and fishway weirs, the difference in kinetic energy and 

pressure head is usually negligible and only water surface elevation differences are 

considered when estimating hydraulic drop across the structure. As such, staff gages that 

indicate hydraulic drop over these structures must be suitably located to avoid the 

drawdown of the water surface due to flow accelerating through the fishway weir or 

fishway entrance. 

Impingement - the consequence of a situation where flow velocity exceeds the swimming 

capability of a fish, creating injurious contact with a screen face or bar rack. 

Infiltration gallery - a water diversion that provides flow via an excavated gallery 

beneath the stream bed. 

Kelts - an adult steelhead that has completed spawning and is migrating downstream. 

Off-ladder trap - a trap for capturing fish located adjacent to a fish ladder in an off ladder 

flow route, separate from the normal fish ladder route. This device allows fish to either 

pass via the ladder, or be routed into the trap depending on management objectives. 

Passive screens - juvenile fish screens without an automated cleaning system. 

Picket leads or Pickets - a set of vertically inclined flat bars or circular slender columns 

(pickets), designed to exclude fish from a specific point of passage (also, see fish weir). 

PIT- tag detector - a device that passively scans a fish for the presence of a passive 

integrated transponder (PIT) tag that is implanted in a fish and read when activated by an 

electro-magnetic field generated by the detector. 

Plunging flow - flow over a weir that falls into the receiving pool with a water surface 

elevation below the weir crest elevation. Generally, surface flow in the receiving pool is 

in the upstream direction, downstream from the point of entry into the receiving pool. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 1-1. Plunging Flow over Fishway Weir 

Porosity - the open area of a mesh, screen, rack or other flow area relative to the entire 

gross area. 

Positive-exclusion - a means of excluding fish by providing a barrier which they can not 

physically pass through. 

Preliminary design - an initial design concept, based on the site conditions and biological 

needs of the species intended for passage. This is also sometimes referred to as 

functional design or conceptual design. 

Ramping rates - the rate at which (typically inches per hour) a flow is artificially altered 

to accommodate diversion requirements. 

Rating curve - the graphed data depicting the relationship between water surface 

elevation and flow. 

Redd - deposition of fish eggs in a gravel nest, excavated by a spawning female 

salmonid. 

Screen material - the material that provides physical exclusion to reduce the probability 

of entraining fish. Examples of screen material include perforated plate, bar screen, and 

woven wire mesh. 

Scour - erosion of streambed material, resulting in temporary or permanent lowering of 

streambed profile.

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Section 10 and 404 Regulatory Programs - The principal Federal regulatory programs, 

carried out by the COE, affecting structures and other work below mean high water. The 

COE, under Section 10 of the River and Harbor Act of 1899, regulates structures in, or 

affecting, navigable waters of the U.S. as well as excavation or deposition of materials 

(e.g., dredging or filling) in navigable waters. Under Section 404 of the Federal Water 

Pollution Control Act Amendments (Clean Water Act of 1977), the COE is also 

responsible for evaluating application for Department of the Army permits for any 

activities that involve the placement of dredged or fill material into waters of the United 

States, including adjacent wetlands. 

Smolt - a juvenile salmonid that has completed its fresh water rearing cycle and is 

proceeding out to sea. 

Streaming flow - flow over a weir which falls into a receiving pool with water surface 

elevation above the weir crest elevation. Generally, surface flow in the receiving pool is 

in the downstream direction, downstream from the point of entry into the receiving pool. 

Figure 1-2. Streaming Flow over Fishway Weir 

Sweeping velocity - the vector component of canal flow velocity that is parallel and 

adjacent to the screen face, measured as close as physically possible to the boundary 

layer turbulence generated by the screen face. 

Tailrace - the stream immediately downstream of an instream structure. 

Tailwater - the flow through the tailrace. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Total project head - the difference in water surface elevation from upstream to 

downstream of an impediment such as a dam. Normally, total project head encompasses 

a range based on stream flows and/or the operation of flow control devices. 

Thalweg - the stream flow path following the deepest parts of a stream channel. 

Tide Gate - a gate used in coastal areas to regulate tidal intrusion. 

Training wall - a physical structure designed to direct flow to a specific location or in a 

specific direction. 

Transport channel - a hydraulic conveyance designed to pass fish between different 

sections of a fish passage facility. 

Transport velocity - the velocity of flow within the migration corridor of a fishway, 

excluding areas with any hydraulic drops greater than 0.1 feet.

Trap and Haul - a fish passage facility designed to trap fish for upstream or downstream 

transport to continue their migration.

Trash rack - a rack of vertical bars with spacing designed to catch debris and preclude it 

from entering the fishway, while providing sufficient opening to allow the passage of 

fish. 

Trash rack, coarse - a rack of vertical bars with spacing designed to catch large debris 

and preclude it from entering the fishway, while providing sufficient opening to allow the 

passage of fish. 

Trash rack, fine - a rack of vertical bars designed to catch debris and reduce or eliminate 

entry of fish into the intake of an auxiliary water system. 

Turbine intake screens – partial flow screens positioned within the upper portion of 

turbine intakes, designed to guide fish into a collection system for transport or bypass 

back to the river. 

Upstream fish passage - fish passage relating to upstream migration of adult and/or 

juvenile fish. 

Upstream passage facility - a fishway system designed to pass fish upstream of a passage 

impediment, either by volitional passage or non-volitional passage. 

Vee screen - a pair of juvenile fish screens installed in a vee configuration (i.e., mirrored 

about a centerline) with the bypass entrance located between the junction of the two 

screens. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Velocity head (hv) - the kinetic energy of flow contained by the water velocity, calculated 

by the square of the velocity (V) divided by two times the gravitational constant (g) (hv = 

V2/2g). 

Vertical barrier screens - vertical screens, usually located in a gatewell of a mainstream 

hydroproject, that dewater flow from turbine intake screens, thereby concentrating fish 

for passage into a bypass system. 

Volitional passage - fish passage made continuously available without trap and transport. 

Wasteway - a conveyance which returns water originally diverted from an upstream 

location back to the diverted stream. 

Weir - an obstruction over which water flows. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

2. PRELIMINARY DESIGN DEVELOPMENT 

2.1 Introduction – Preliminary Design Development 

In cases such as applications for a FERC license, ESA consultation, ESA Section 9 

Enforcement activity, or ESA permit, a preliminary design for a fish passage facility 

must be developed in an interactive process with NMFS NWR Hydropower Division 

engineering staff. For all fish passage facility projects, the preliminary design should be 

developed based on a synthesis of the required site and biological information listed 

below. In general, NMFS will review fish passage facility designs in the context of how 

the required site and the biological information was integrated into the design. Submittal 

of all information discussed below may not be required in writing for NMFS review. 

However, the applicant should be prepared to describe how the biological and site 

information listed below was included in the development of the preliminary design. 

NMFS will be available to discuss these criteria in general or in the context of a specific 

site. The applicant is encouraged to initiate coordination with NMFS fish passage 

specialists early in the development of the preliminary design to facilitate an iterative, 

interactive, and cooperative process. 

2.2 Site Information 

The following site information should be provided for the development of the 

preliminary design. 

1. Functional requirements of the proposed fish passage facilities as related to all 

anticipated operations and river flows. Describe median, maximum, and 

minimum monthly diverted flow rates, plus any special operations (e.g., use of 

flash boards) that modify forebay or tailrace water surface elevations. 

2. Site plan drawing showing location and layout of the proposed fishway relative to 

existing project features facilities. 

3. Topographic and bathymetric surveys, particularly where they might influence 

locating fishway entrances and exits, and personnel access to the site. 

4. Drawings showing elevations and a plan view of existing flow diversion 

structures, including details showing the intake configuration, location, and 

capacity of project hydraulic features. 

5. Basin hydrology information, including daily and monthly streamflow data and 

flow duration exceedence curves at the proposed fish passage facility site based 

on the entire period of available record. Where stream gage data is unavailable, 

or if a short period of record exists, appropriate synthetic methods of generating 

flow records may be used. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6. Project operational information that may affect fish migration (e.g., powerhouse 

flow capacity, period of operation, etc.) 

7. Project forebay and tailwater rating curves encompassing the entire operational 

range. 

8. River morphology trends. If the fish passage facility is proposed at a new or 

modified diversion, determine the potential for channel degradation or channel 

migration that may alter stream channel geometry and compromise fishway

performance. Describe whether the stream channel is stable, conditionally stable, 

or unstable, and indicate the overall channel pattern as straight, meandering, or 

braided. Estimate the rate of lateral channel migration and change in stream 

gradient that has occurred over the last decade. Also, describe what effect the 

proposed fish passage facility may have on existing stream alignment and 

gradient and the potential for future channel modification due to either 

construction of the facility or continuing natural channel instability. 

9. Special sediment and/or debris problems. Describe conditions that may influence 

design of the fish passage facility, or present potential for significant problems. 

10. Other information from site-specific biological assessment. 

2.3 Biological Information 

The following biological information should be provided for the development of the 

preliminary design. 

1. Type, life stage, run size, period of migration, and spawning location and timing 

for each life stage and species present at the site. 

2. Other species (including life stage) present at the proposed fish passage site that 

also require passage. 

3. Predatory species that may be present. 

4. High and low design passage flow for periods of upstream fish passage (see 

Section 3). 

5. Any known fish behavioral aspects that affect salmonid passage. For example, 

most salmonid species pass readily through properly designed orifices, but other 

species unable to pass through these orifices may impede salmonid passage. 

 

6. What is known and what needs to be researched about fish migration routes 

approaching the site. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7. Document, or estimate, minimum streamflow required to allow migration around 

the impediment during low water periods (based on past site experience). 

8. Poaching/illegal trespass - describe the degree of human activity in immediate 

area and the need for security measures to reduce or eliminate illegal activity. 

9. Water quality factors that may affect fish passage at the site. Fish may not migrate 

if water temperature and quality are marginal, instead seeking holding zones until 

water quality conditions improve. 

2.4 Design Development Phases 

A description of steps in the design process is presented here to clarify the preliminary 

design as it contrasts with often-used and related terms in the design development 

process. The following are commonly used terms (especially in the context of larger 

facilities) by many public and private design entities. NMFS engineering staff may be 

consulted for all phases of design; required reviews are described below in Detailed 

Design Phase. 

Reconnaissance study - typically an early investigation of one or more sites for 

suitability of design and construction of some type of facility. 

Conceptual alternatives study - lists types of facilities that may be appropriate for 

accomplishing objectives at a specific site, and does not entail much on-site investigation. 

It results in a narrowed list of alternatives that merit additional assessment. 

Feasibility study - includes an incrementally greater amount of development of each 

design concept (including a rough cost estimate), which enables selection of a mostpreferred alternative. 

Preliminary design - includes additional and more comprehensive investigations and 

design development of the preferred alternative, and results in a facilities layout 

(including some section drawings), with identification of size and flow rate for primary 

project features. Cost estimates are also considered to be more accurate. Completion of 

the preliminary design commonly results in a preliminary design document that may be 

used for budgetary and planning purposes, and as a basis for soliciting (and subsequent 

collating) design review comments by other reviewing entities. The preliminary design

is commonly considered to be at the 20% to 30% completion stage of the design process. 

Detailed design phase - uses the preliminary design as a springboard for preparation of 

the final design and specifications, in preparation for the bid solicitation (or negotiation) 

process. Once the detailed design process commences, NMFS must have the opportunity 

to review and provide comments at the 50% and 90% completion stages. These 

comments usually entail refinements in the detailed design that will lead to operations, 

maintenance, and fish safety benefits. Electronic drawings accompanied by 11 x 17 inch 

paper drawings are the preferred review medium. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

3. DESIGN FLOW RANGE 

3.1 Introduction – Design Flow Range 

The design streamflow range for fish passage, bracketed by the designated fish passage 

design high and low flows, constitutes the bounds of the fish passage facility design 

where fish passage facilities must operate within the specified design criteria. Within this 

range of streamflow, the fishway design must allow for safe, timely, and efficient fish 

passage. Outside of this flow range, fish must either not be present or not be actively 

migrating, or must be able to pass safely without need of a fish passage facility. Sitespecific information is critical to determine the design time period and river flows for the 

passage facility - local hydrology may require that these design streamflows be modified 

for a particular site. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance, or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. 

 

3.2 Design Low Flow for Fish Passage 

Design low flow for fishways is the mean daily average streamflow that is exceeded 95% 

of the time during periods when migrating fish are normally present at the site. This is 

determined by summarizing the previous 25 years of mean daily streamflows occurring 

during the fish passage season, or by an appropriate artificial stream flow duration

methodology if streamflow records are not available. Shorter data sets of stream flow 

records may be useable if they encompass a broad range of flow conditions. The fish 

passage design low flow is the lowest streamflow for which migrants are expected to be 

present, migrating, and dependent on the proposed facility for safe passage. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

3.3 Design High Flow for Fish Passage 

Design high flow for fishways is the mean daily average streamflow that is exceeded 5% 

of the time during periods when migrating fish are normally present at the site. This is 

determined by summarizing the previous 25 years of mean daily streamflows occurring 

during the fish passage season, or by an appropriate artificial stream flow duration

methodology if streamflow records are not available. Shorter data sets of stream flow 

records may be used if they encompass a broad range of flow conditions. The fish 

passage design high flow is the highest streamflow for which migrants are expected to be 

present, migrating, and dependent on the proposed facility for safe passage. 

3.4 Fish Passage Design for Flood Flows 

The general fishway design should have sufficient river freeboard to minimize 

overtopping by 50 year flood flows. Above a 50-year flow event, the fishway operations 

may include shutdown of the facility, in order to allow the facility to quickly return to 

proper operation when the river drops to within the range of fish passage design flows. 

Other mechanisms to protect fishway operations after floods will be considered on a caseby-case basis. A fishway must never be inoperable due to high river flows for a period 

greater than 7 days during the migration period for any anadromous salmonid species. In 

addition, the fish passage facility should be of sufficient structural integrity to withstand 

the maximum expected flow. It is beyond the scope of this document to specify 

structural criteria for this purpose. If the fish passage can not be maintained, the 

diversion structure should not operate and the impediment should be removed. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4. UPSTREAM ADULT FISH PASSAGE SYSTEMS 

4.1 Introduction – Upstream Adult Fish Passage Systems 

An upstream passage impediment is defined as any artificial structural feature or project 

operation that causes adult or juvenile fish to be injured, killed, blocked, or delayed in 

their upstream migration, to a greater degree than in a natural river setting. Artificial 

impediments require a fish passage design using conservative criteria, because the natural 

complexity that usually provides fish passage has been substantially altered. 

This definition is provided for the purpose of describing situations in which NMFS will 

use these criteria in reviewing mitigative measures designed to improve fish passage at an 

impediment. Any upstream passage impediment requires approved structural and/or 

operational measures to mitigate, to the maximum extent practicable, for adverse impacts 

to upstream fish passage. These criteria are also applicable where passage over a natural 

barrier is desired and consistent with watershed, subbasin, or recovery plans. 

It is important to note that not every upstream passage facility constructed at an upstream 

passage impediment can fully compensate for an unimpeded natural channel. As such, 

additional mitigation measures may be required on a case-by-case basis. 

The examples listed below do not imply that passage is completely blocked by the 

impediment. Rather, this list is comprised of situations where fish passage does not 

readily occur, in comparison to a natural stream system. Examples of passage 

impediments include, but are not limited to, the following: 

• Permanent or intermittent dams. 

• Hydraulic drop over an artificial instream structure in excess of 1.5 feet. 

• Weirs, aprons, hydraulic jumps or other hydraulic features that produce depths of 

less than 10 inches, or flow velocity greater than 12 ft/s for over 90% of the 

stream channel cross section. 

• Diffused or braided flow that impedes the approach to the impediment. 

• Project operations that lead upstream migrants into impassable routes. 

• Upstream passage facilities that do not satisfy the guidelines and criteria 

described below. 

• Poorly designed headcut control or bank stabilization measures that create 

impediments such as listed above. 

• Insufficient bypass reach flows to allow or induce upstream migrants to move 

upstream into the bypass reach adjacent to a powerhouse or wasteway return. 

• Degraded water quality in a bypass reach, relative to that downstream of the 

confluence of bypass reach and flow return discharges (e.g., at the confluence of a 

hydroproject tailrace that returns flow diverted from the river at some upstream 

location). 

• Ramping rates in streams or in bypass reachs that delay or strand fish. 

• Discharges to or from the stream that may be detected and entered by fish with no 

certain means of continuing their migration (e.g., poorly designed spillways, 

cross-basin water transfers, unscreened diversions). 

26 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

• Discharges to or from the stream that are attractive to migrating fish (e.g., turbine 

draft tubes, shallow aprons and flow discharges) that have the potential to cause 

injury. 

• Water diversions that reduce instream flow. 

In addition to describing the configuration and application of the particular styles of fish 

ladders, this section identifies general criteria and guidelines for use in completion of an 

upstream adult fish passage facility design. The intent of this section is to identify 

potential pitfalls and advantages of a particular type of passage system given specific site 

conditions, and to provide criteria and guidelines for use with a specific type of fish 

ladder. In general, NMFS requires volitional passage, as opposed to trap and haul, for 

all passage facilities. This is primarily due to the risks associated with the handling and 

transport of migrant salmonids, in combination with the long term uncertainty of funding, 

maintenance, and operation of the trap and haul program including facility failure. 

However, there are instances in which trap and haul may be the best viable option for 

upstream and/or downstream fish passage at a particular site, due to height of the dam, 

temperature issues in a long ladder, passage through multiple projects or other sitespecific issues. The design of trap and haul facilities is described in Section 6. 

The criteria and guidelines listed in this section apply to adult upstream fish passage in 

“moderately-sized” streams. This description is intentionally vague, because the 

variability of sites and passage needs within the NWR do not lend themselves to a “one 

size fits all” document specifying stringent criteria for upstream passage systems. Rather, 

it is expected that for streams with annual average flows between 500 to 5000 cfs, the 

guidelines listed may be applied in design without significant modification. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

27 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

Figure 4-1. Features of an Upstream Passage System Using a Vertical Slot Fishway 

(flow is from right to left) 

1 - Fishway Entrances 5 - Counting station crowder and picket leads 

2 - Add-in AWS Diffusers 6 - Counting Station 

3 - Energy Dissipation Features 7 - Fishway Exits 

4 - AWS Supply Pools 8 - Fishway Pool 

4.2 Fishway Entrance 

4.2.1 Description and Purpose - Fishway Entrance 

The fishway entrance is a gate or slot through which fishway attraction flow is discharged 

and through which fish enter the upstream passage facility. The fishway entrance is 

possibly the most critical component in the design of an upstream passage system. 

Placing a fishway entrance(s) in the correct location(s) will allow a passage facility to 

provide a good route of passage throughout the design range of passage flows. The most 

important aspects of a fishway entrance design are: (1) location of the entrance, (2) shape 

and amount of flow emanating from the entrance, (3) approach channel immediately 

downstream of the entrance, and (4) flexibility in operating the entrance flow to 

accommodate variations in tailrace elevation, stream flow conditions, and project 

operations. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.2.2 Specific Criteria and Guidelines – Fishway Entrance 

4.2.2.1 Configuration and Operation: The fishway entrance gate configuration 

and operation may vary based on site-specific project operations and streamflow 

characteristics. Entrance gates are usually operated in either a fully open or fully 

closed position, with the operating entrance dependent on tailrace flow 

characteristics. Sites with limited tailwater fluctuation may not require an 

entrance gate to regulate the entrance head. Adjustable weir gates that rise and 

fall with tailwater elevation may also be used to regulate the fishway entrance 

head. Other sites may accommodate maintaining proper entrance head by 

regulating auxiliary water flow through a fixed geometry entrance gate. 

4.2.2.2 Location: Fishway entrances must be located at points where fish can 

easily locate the attraction flow and enter the fishway. When choosing an 

entrance location, high velocity and turbulent zones in a powerhouse or spillway 

tailrace should be avoided in favor of relatively tranquil zones adjacent to these 

areas. At locations where the tailrace is wide, shallow, and turbulent, excavation 

to create a deeper, less turbulent holding zone adjacent to the fishway entrance(s)

may be required. 

4.2.2.3 Attraction Flow: Attraction flow from the fishway entrance should be 

between 5% and 10% of fish passage design high flow (see Section 3) for streams 

with mean annual streamflows exceeding 1000 cfs. For smaller streams, when 

feasible, use larger percentages (up to 100%) of streamflow. Generally speaking, 

the higher percentages of total river flow used for attraction into the fishway, the 

more effective the facility will be in providing upstream passage. Some situations 

may require more than 10% of the passage design high flow, if site features 

obscure approach routes to the passage facility. 

4.2.2.4 Hydraulic Drop: The fishway entrance hydraulic drop (also called 

entrance head) must be maintained between 1 and 1.5 feet, depending on the 

species present at the site, and designed to operate from 0.5 to 2.0 feet of 

hydraulic drop. 

4.2.2.5 Dimensions: The minimum fishway entrance width should be 4 feet, and 

the entrance depth should be at least 6 feet, although the shape of the entrance is 

dependent on attraction flow requirements and should be shaped to accommodate 

site conditions. Also, see requirements for mainstem Columbia and Snake Rivers 

in Section 9. 

4.2.2.6 Additional Entrances: If the site has multiple zones where fish 

accumulate, each zone must have a minimum of one entrance. For long 

powerhouses or dams, additional entrances may be required. Since tailrace

hydraulic conditions usually change with project operations and hydrologic 

events, it is often necessary to provide two or more fishway entrances. Closure 

gates must be provided to direct flow to the appropriate entrance gate, and gate 

29 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

stems (or other adjustment mechanisms) must not be placed in any potential path 

of fish migration. Fishway entrances must be equipped with downward-closing 

slide gates, unless otherwise approved by NMFS. 

4.2.2.7 Types of Entrances: Fishway entrances may be adjustable submerged 

weirs, vertical slots, orifices, or other shapes, provided that the requirements 

specified in Section 4.2.2 are achieved. Some salmonid species will avoid using 

orifices, and at these sites, orifices should not be used. 

 

 4.2.2.8 Flow Conditions: The desired flow condition for entrance weir and/or 

slot discharge jet hydraulics is streaming flow. Plunging flow induces jumping 

and may cause injuries, and it presents hydraulic condition that some species may 

not be able to pass. Streaming flow may be accomplished by placing the entrance 

weir (or invert of the slot) elevation such that flow over the weir falls into a 

receiving pool with water surface elevation above the weir crest elevation 

(Katapodis 1992). 

4.2.2.9 Orientation: Generally, low flow entrances should be oriented nearly 

perpendicular to streamflow, and high flow entrances should be oriented to be 

more parallel to streamflow. However, you must conduct site-specific 

assessments to determine entrance location and entrance jet orientation. 

4.2.2.10 Staff Gages: The fishway entrance design must include staff gages to 

allow for a simple determination of whether entrance head criterion (see Section 

4.2.2.4) is met. Staff gages must be located in the entrance pool and in the 

tailwater just outside of the fishway entrance, in an area visible from an easy 

point of access. Care should be taken when locating staff gages by avoiding 

placement in turbulent areas and locations where flow is accelerating toward the 

fishway entrance. Gages should be readily accessible to facilitate in-season 

cleaning. 

4.2.2.11 Entrance Pools: The fishway entrance pool is at the lowest elevation of 

the upstream passage system. It discharges flow into the tailrace through the 

entrance gates for the purpose of attracting upstream migrants. In many fish 

ladder systems, the entrance pool is the largest and most important pool, in terms 

of providing proper guidance of fish to the ladder section of the upstream passage 

facility. It combines ladder flow with auxiliary water system (AWS) flow through 

diffuser gratings to form entrance attraction flow (see Section 4.3). The entrance 

pool must be configured to readily guide fish toward ladder weirs or slots. 

4.2.2.12 Transport Velocity: Transport velocities between the fishway entrance 

and first fishway weir, fishway channels, and over submerged fishway weirs must 

be between 1.5 and 4.0 ft/s. 

30 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.2.2.13 Entrance Pool Geometry: The fishway entrance pool geometry must be 

designed to optimize attraction to the lower fishway weirs. This may be 

accomplished by angling vertical AWS diffusers toward and terminating near the 

lowest ladder fishway weir, or by placing primary attraction flows near the lower

fishway weir. The pool geometry will normally influence the location of 

attraction flow diffusers. 

4.3 Auxiliary Water Systems 

 

4.3.1 Description and Purpose – Auxiliary Water Systems 

Auxiliary water systems must be used when attraction flows less than specified by 

Section 4.2.2.3 are routed from the project forebay into the fish ladder. AWS flow is 

usually routed from the forebay or pumped from the tailrace, through a fine trash rack or 

intake screen, through a back set flow control gate, then an energy dissipation zone 

consisting of energy baffles and/or diffusers, and into the fishway. An AWS provides 

additional attraction flow from the entrance pool through the fishway entrance, and may 

also provide flow to an area between fishway weirs that on occasion become backwatered and fail to meet the criterion specified in Section 4.2.2.12. In addition, the AWS 

is used to provide make-up flows to various transition pools in the ladder such as 

bifurcation or trifurcation pools, trap pools, exit control sections, or counting station 

pools. 

4.3.2 Specific Criteria and Guidelines – AWS Diffusers 

Vertical diffusers consist of non-corrosive, vertically-oriented diffuser panels of 

vertically-oriented flat bar stock, and must have a maximum 1-inch clear spacing. 

Similarly, horizontal diffusers consist of non-corrosive, horizontally-oriented diffuser

panels of horizontally-oriented flat bar stock, and must have a maximum 1-inch clear 

spacing. Orientation of flat bar stock must maximize the open area of the diffuser panel. 

If a smaller species or life stage of fish is present, smaller clear spacing may be required. 

4.3.2.1 Velocity and Orientation: The maximum AWS diffuser velocity must 

be less than 1.0 ft/s for vertical diffusers and 0.5 ft/s for horizontal diffusers, based 

on total diffuser panel area. Vertical diffusers should only be used in appropriate 

orientation to assist in guiding fish within the fishway. Diffuser velocities should 

be nearly uniform. 

4.3.2.2 Debris Removal: The AWS design must include access for debris 

removal from each diffuser, unless the AWS intake is equipped with a juvenile 

fish screen, as described in Section 11 and if required by Section 4.3.4. 

4.3.2.3 Edges: All flat-bar diffuser edges and surfaces exposed to fish must be 

rounded or ground smooth to the touch, with all edges aligning in a single smooth 

plane to reduce the potential for contact injury. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.3.2.4 Elevation: Vertical AWS diffusers must have a top elevation at or below 

the low design entrance pool water surface elevation. 

 

4.3.3 Specific Criteria and Guidelines– AWS Fine Trash Racks 

A fine trash rack must be provided at the AWS intake with clear space between the 

vertical flat bars of 7/8 inch or less, and maximum velocity must be less than 1 ft/s, as 

calculated by dividing the maximum flow by the entire fine trash rack area. The support 

structure for the fine trash rack must not interfere with cleaning requirements and must 

provide access for debris raking and removal. The fine trash rack should be installed at a 

1:5 (horizontal:vertical) slope (or flatter) for ease of cleaning. The fine trash rack design 

must allow for easy maintenance, considering access for personnel, travel clearances for 

manual or automated raking, and removal of debris 

4.3.3.1 Staff Gages and Head Differential: Staff gages must be installed to 

indicate head differential across the AWS intake fine trash rack, and must be 

located to facilitate observation and in-season cleaning. Head differential across 

the AWS intake must not exceed 0.3 feet. 

4.3.3.2 Structural Integrity: AWS intake fine trash racks must be of sufficient 

structural integrity to avoid the permanent deformation associated with maximum 

occlusion. 

4.3.4 Specific Criteria and Guidelines – AWS Screens 

In instances where the AWS poses a risk to passage of juvenile salmonids (due to high 

head systems and convoluted flow paths, for example), during the period of juvenile outmigration(s) the AWS intake must be screened to the standards specified in Section 11. 

Trip gates or other alternate intakes to the AWS may be included in the design to ensure 

that AWS flow targets are achieved if the screen reliability is uncertain at higher flows. 

Debris and sediment issues may preclude the use of juvenile fish screen criteria for AWS 

intakes at certain sites. Passage risk through an AWS will be assessed by NMFS 

engineers on a site by site basis to determine whether screening of the AWS is warranted 

and to determine how to provide the highest reliability possible. 

4.3.5 Specific Criteria and Guidelines – AWS Flow Control 

AWS flow control may consist of a control gate, turbine intake flow control, or other 

flow control systems, located sufficiently far away from the AWS intake to ensure 

uniform flow distribution at the AWS fine trash rack for all AWS flows. AWS flow 

control is necessary to ensure that the correct quantity of AWS flow is discharged at the 

appropriate location during a full range of forebay water surface elevations. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.3.6 Specific Criteria and Guidelines – AWS Excess Energy Dissipation 

Excess energy must be dissipated from AWS flow prior to passage through diffusers 

(Section 4.3.2). This is necessary to minimize surging and to induce relatively uniform 

velocity distribution at the diffusers. Surging and non-uniform velocities may cause adult 

fish jumping and associated injuries or excess migration delay. Examples of methods to 

dissipate excess AWS flow energy include: (1) routing flow into the pool with adequate 

volume (Section 4.3.6.1), then through a baffle system (porosity less than 40%) to reduce 

surging through entrance pool diffusers; (2) passing AWS flow through a turbine; (3) 

passing AWS flow through a series of valves, weirs or orifices; or (4) passing AWS flow 

through a pipeline with concentric rings or other hydraulic transitions designed to induce 

headloss. 

4.3.6.1 Energy Dissipation Pool Volume: An energy dissipation pool in an 

AWS should have a minimum water volume established by the following 

formula: 

3 16( )

))()((

ftslbsft

HQ V − = γ

 where: V = pool volume, in ft3

 γ = unit weight of water, 62.4 pounds (lb) per ft3

 Q = fish ladder flow, in ft3/s 

 H = energy head of pool-to-pool flow, in feet 

Note that the pool volumes required for AWS pools are smaller than those 

required for fishway pools. This is due to the need to provide resting areas in 

fishway pools, and because AWS systems require additional elements (diffusers, 

valves, etc.) to dissipate energy, and are not pathways for upstream fish passage.

4.3.7 Specific Criteria and Guidelines – AWS Design (General) 

4.3.7.1 Cleaning: To facilitate cleaning, the AWS must be valved or gated to 

provide for easy shutoff during maintenance activities, and subsequent easy reset 

to proper operation. 

4.3.8 Bedload Removal Devices: At locations where bedload may cause 

accumulations at the AWS intake, sluice gates or other simple bedload removal 

devices should be included in the design.

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.4 Transport Channels 

4.4.1 Description and Purpose – Transport Channels 

A transport channel conveys flows between different sectors of the upstream passage 

facility, providing a route for fish to pass. 

4.4.2 Specific Criteria and Guidelines – Transport Channels 

4.4.2.1 Velocity Range: The transport channel velocities must be between 1.5 

and 4 ft/s, including flow velocity over or between fishway weirs inundated by 

high tailwater. 

4.4.2.2 Dimensions: The transport channels should be a minimum of 5-feet deep 

and a minimum of 4-feet wide. 

4.4.2.3 Lighting: Ambient natural lighting should be provided in all transport 

channels, if possible. Otherwise, acceptable artificial lighting must be used. 

4.4.2.4 Design (General): 

• The transport channels must be of open channel design. 

• Designs must avoid hydraulic transitions or lighting transitions 

• Transport channels must not expose fish to any moving parts. 

• Transport channels must be free of exposed edges that protrude from 

channel 

walls. 

 

4.5 Fish Ladder Design 

4.5.1 Description and Purpose – Fish Ladder Design

The purpose of a fish ladder is to convert the total project head at the passage 

impediment into passable increments, and to provide suitable conditions for fish to hold, 

rest, and ultimately pass upstream. The criteria provided in this section have been 

developed to provide conditions to pass all anadromous salmonid species upstream with 

minimal delay and injury 

4.5.2 Common Types of Fish Ladders 

Fish ladders break an impediment into passable discrete steps, by utilizing a series of 

fishway weirs to divide the drop into a series of pools with different water surface 

elevations. Nearly all of the energy from the upstream pool is dissipated in the 

downstream pool volume, resulting in a series of relatively calm pools that migrating fish 

may use to rest, stage and ascend upstream. Examples of fish ladders include the vertical 

slot ladder, the pool and weir ladder, the weir and orifice ladder, and the pool-chute fish 

ladder. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.5.2.1 Vertical Slot Ladder: The vertical slot configuration is a pool type of 

fish ladder widely used for the passage of salmon and steelhead. The passage 

corridor typically consists of 1.0 to 1.25 foot-wide vertical slots between fishway

pools. However, narrower slots have been used in applications for other fish 

species and slots may be wider in designs (or two slots may be used per fishway

weir) where there is no auxiliary water system (Section 4.3). For adult 

anadromous salmonids, slots should never be less than 1 foot in width. The 

vertical slot ladder is suitable for passage impediments which have tailrace and 

forebay water surface elevations that fluctuate. Maximum head differential 

(typically associated with lowest river flows) establishes the design water surface 

profile, which is on average parallel to the fishway floor gradient. Vertical slot 

ladders require fairly intricate forming for concrete placement, so initial 

construction costs are somewhat higher than for other types of ladders. 

Figure 4-2a. Plan View of Vertical Slot Fishway Showing Generalized Flow Path. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-2b. Isometric View of Vertical Slot Fishway. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-2c. Dimensions of a Typical Vertical Slot. 

4.5.2.2 Pool and Weir Ladder: The pool and weir fish ladder passes the entire, 

nearly constant fishway flow through successive fishway pools separated by 

overflow weirs that break the total project head into passable increments. This 

design allows fish to ascend to a higher elevation by passing over a weir, and 

provides resting zones within each pool. Pools are sufficiently sized to allow for 

the flow energy to be nearly fully dissipated in the form of turbulence within each 

receiving pool. Pool and weir ladders cannot accommodate much, if any, water 

surface elevation fluctuation in the forebay pool. When fluctuation of water 

surface elevation outside of the design elevation occurs, too much or too little 

flow enters the fishway. When this happens, this flow fluctuation may lead to 

operation with fishway pools that are excessively turbulent, or provide insufficient 

flow for adequate upstream passage. To accommodate forebay fluctuations, this 

type of fish ladder is often designed with an auxiliary water supply and flow 

37 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

regulation (Section 4.3). To accommodate tailwater fluctuations, this type of fish 

ladder is often designed with an adjustable fishway entrance (i.e., adjustable 

geometry and/or attraction flow) and additional add-in flow diffusers to meet 

transport channel velocity criterion (Section 4.4). 

4.5.2.3 Weir and Orifice Fish Ladder: The weir and orifice fish ladder passes 

the fishway flow from the forebay through successive fishway pools connected by 

overflow weirs and orifices, which divide the total project head into passable 

increments. 

The Ice Harbor ladder is an example of a weir and orifice fish ladder. This ladder 

design was initially developed for use at Ice Harbor Dam (Lower Snake River), in 

the middle of the 1960's. The Ice Harbor fishway weir consists of two orifices, 

centered and directly below two weirs. These orifice and weir combinations are 

located on each side of the longitudinal centerline of the ladder. Between the two 

weirs is a slightly higher non-overflow wall, with an upstream projecting flow 

baffle at each end. An adaptation for lower flow designs is the Half-Ice Harbor 

ladder design, which consists of one weir, one orifice, and a non-overflow wall 

between fishway pools. 

Weir and orifice ladders cannot accommodate much, if any, water surface 

elevation fluctuation in the forebay pool. When fluctuation of water surface 

elevation outside of the design elevation occurs, too much or too little flow enters 

the fishway. When this happens, this flow fluctuation may lead to operation with 

fishway pools that are excessively turbulent, or provide insufficient flow for 

adequate upstream passage. To accommodate forebay fluctuations, this type of 

fish ladder is often designed with an auxiliary water supply and flow regulating 

section (Sections 4.3). To accommodate tailwater fluctuations, this type of fish 

ladder is often designed with an adjustable fishway entrance (i.e., adjustable 

geometry and/or attraction flow) and additional add-in flow diffusers to meet 

transport channel velocity criterion (Section 4.4). 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-3a. Plan View of an Ice Harbor Type Weir and Orifice Fish Ladder 

39 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-3b. Longitudinal Cross-section of an Ice Harbor Type Weir and Orifice Fish 

Ladder 

40 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-3c. Front View Cross-section of Ice Harbor Fishway Baffle 

4.5.2.4 Pool-Chute Fish Ladder: A pool and chute fishway is a hybrid type of 

fishway which operates with different flow regimes under different river 

conditions. This fishway is designed to operate as a pool and weir fishway at low 

river flows and a baffled chute fishway at higher river flows. This fishway offers 

an alternative for sites that have fairly low hydraulic drop, and must pass a wide 

range of stream flows with a minimum of flow control features. Placement of 

stoplogs, a cumbersome and potentially hazardous operation, is required to 

optimize operation. However, once suitable flow regimes are established, the 

need for additional stoplog placement may not be required. Criteria for this type 

of fishway design are still evolving, and design proposals will be assessed on a 

site-specific basis. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-4. Pool and Chute Fishway 

4.5.3 Specific Criteria and Guidelines – Fish Ladder Design 

4.5.3.1 Hydraulic Drop: The maximum hydraulic drop between fish ladder

pools must be 1 foot or less. 

4.5.3.2 Flow Depth: Fishway overflow weirs should be designed to provide at 

least 1 foot of flow depth over the weir crest. The depth must be indicated by 

locating a single staff gage (with the zero reading at the overflow weir crest 

elevation) in an observable, hydraulically stable location, representative of flow 

depth throughout the fishway.

4.5.3.3. Pool Dimensions: The pool dimensions should be a minimum of 8 feet 

long (upstream to downstream), 6 feet wide, and 5 feet deep. However, specific 

ladder designs may require pool dimensions that are different than the minimums 

specified here depending on site conditions and ladder flows. 

4.5.3.4 Turning Pools: Turning pools (i.e., where the fishway bends more than 

90°) should be at least double the length of a standard fishway pool, as measured 

along the centerline of the fishway flow path. The orientation of the upstream 

42 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

weir to the downstream weir must be such that energy from flow over the 

upstream weir does not affect the hydraulics of the downstream weir. 

4.5.3.5 Pool Volume: The fishway pools must be a minimum water volume of: 

 

3 )4(

))()((

ftslbsft

HQ V − = γ

 where: V = pool volume, in ft3

 γ = unit weight of water, 62.4 pounds (lb) per ft3

 Q = fish ladder flow, in ft3

/s 

 H = energy head of pool-to-pool flow, in feet 

 

This pool volume must be provided under every expected design flow condition, 

with the entire pool volume having active flow and contributing to energy 

dissipation. 

4.5.3.6 Freeboard: The freeboard of the ladder pools must be at least 3 feet at 

high design flow. 

4.5.3.7 Orifice Dimensions: The dimensions of orifices should be at least 15 

inches high by 12 inches wide, with the top and sides chamfered 0.75 inches on 

the upstream side, and chamfered 1.5 inches on the downstream side of the 

orifice. 

4.5.3.8 Lighting: Ambient lighting is preferred throughout the fishway, and in 

all cases abrupt lighting changes must be avoided. 

4.5.3.9 Change in Flow Direction: At locations where the flow changes 

direction more than 60°, 45° vertical miters or a 2 foot vertical radius of curvature 

must be included at the outside corners of fishway pools. 

4.6 Counting Stations 

4.6.1 Description and Purpose – Counting Stations 

A counting station provides a location to observe and enumerate fish utilizing the fish 

passage facility. Although not always required, a typical counting station including a 

camera or fish count technician, crowder, and counting window is often included in a 

fishway design to allow fishery managers to assess fish populations, provide observations 

on fish health, or conduct scientific research. Other types of counting stations (such as 

submerged cameras, adult PIT-tag detectors, or orifice counting tubes) may be 

acceptable, but they must not interfere with the normal operation of the ladder or increase 

fish passage delay. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.6.2 Specific Criteria and Guidelines – Counting Stations 

4.6.2.1 Location: Counting stations must be located in a hydraulically stable, low 

velocity (i.e., around 1.5 ft/sec), accessible area of the upstream passage facility. 

4.6.2.2 Downstream/Upstream Pools: The pool downstream of the counting 

station must extend at least two standard fishway pool lengths from the 

downstream end of the picket leads. The pool upstream of the counting station 

must extend at least one standard fishway pool length from the upstream end of 

the picket leads. Both pools must be straight and in line with the counting station. 

4.6.3 Specific Criteria and Guidelines – Counting Window 

4.6.3.1 Design and Material: The counting window must be designed to allow 

complete, convenient cleaning with sufficient frequency to ensure sustained 

window visibility and accurate counts. The counting window material must be of 

sufficient abrasion resistance to allow frequent cleaning. 

4.6.3.2 Orientation: Counting windows must be vertically oriented. 

4.6.3.3 Sill: The counting window sill should be positioned to allow full viewing 

of the passage slot. 

4.6.3.4 Lighting: The counting window design must include sufficient indirect 

artificial lighting to provide satisfactory fish identification at all hours of 

operation, without causing passage delay. 

4.6.3.5 Dimensions: The minimum observable width (i.e., upstream to 

downstream dimension) of the counting window must be 5 feet, and the minimum 

height (depth) should be full water depth (also see Section 4.6.3.6). 

4.6.3.6 Width: The minimum width of the counting station slot between the 

counting window and back vertical counting window surface should be 18 inches. 

The design must include an adjustable crowder to move fish closer to the 

counting window to allow fish counting under turbid water conditions. The 

counting window slot width should be maximized as water clarity allows, and 

when not actively counting fish. 

4.6.3.7 Picket Lead: To guide fish into the counting window slot, a downstream 

picket lead must be included in the design. The downstream picket lead must be 

oriented at a deflection angle of 45° relative to the direction of fishway flow. An 

upstream picket lead oriented 45° to the flow direction must also be provided. 

Picket orientation, picket clearance, and maximum allowable velocity must 

conform to specifications for diffusers (Section 4.3.2). Picket leads may be 

comprised of flat stock bars oriented parallel to flow, or other cross-sectional 

shapes, if approved by NMFS. Combined maximum head differential through 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

both sets of pickets must be less than 0.3 feet. Both upstream and downstream 

picket leads must be equipped with “witness marks” to verify correct position 

when picket leads are installed in the fishway. A one foot square opening should 

be provided in the upstream picket lead to allow escape if smaller fish pass 

through the downstream picket lead. 

4.6.3.8 Transition Ramps: To minimize flow separations created by head loss

that may impede passage and induce fallback behavior at the counting window, 

transition ramps must be included. These ramps provide gradual transitions 

between walls, floors and the count window slot. As general guidance, these 

transitions should be more gradual than 1:8 (vertical:horizontal). A free water 

surface must exist over a counting window. 

4.7 Fishway Exit Section 

 4.7.1 Description and Purpose – Fishway Exit Section 

The fishway exit section provides a flow channel for fish to egress through the fishway

and continue on their upstream migration. The exit section of upstream fish passage

facilities may include the following features: add-in auxiliary water valves and/or 

diffusers, exit pools with varied flow, exit channels, coarse trash rack (for fish passage), 

and auxiliary water fine trash racks and control gates. One function of the exit section is 

to attenuate forebay water surface elevation fluctuation, thus maintaining hydraulic 

conditions suitable for fish passage in ladder pools. Other functions should include 

minimizing the entrainment of debris and sediment into the fish ladder. Different types 

of ladder designs (Section 4.5) require specific fish ladder exit design details. 

4.7.2 Specific Criteria and Guidelines – Fishway Exit Section 

4.7.2.1 Hydraulic Drop: The exit control section hydraulic drop per pool 

should range from 0.25 to 1.0 feet. 

4.7.2.2 Length: The length of the exit channel upstream of the exit control 

section should be a minimum of two standard ladder pools. 

4.7.2.3 Design Requirements: Exit section design must utilize the requirements 

for auxiliary water diffusers, channel geometry, and energy dissipation as 

specified in Sections 4.3, 4.4 and 4.5. 

4.7.2.4 Location: In most cases, the ladder exit should be located along a 

shoreline and in a velocity zone of less than 4 ft/s, sufficiently far enough 

upstream of a spillway, sluiceway or powerhouse to minimize the risk of fish nonvolitionally falling back through these routes. Distance of the ladder exit with 

respect to the hazards depends on bathymetry near the dam spillway or crest, and 

associated longitudinal river velocities. 

45 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.7.2.5 Public Access: Public access near the ladder exit should not be allowed. 

4.8 Fishway Exit Sediment and Debris Management 

4.8.1 Description and Purpose – Fishway Exit Sediment and Debris 

Management 

For large facilities where maintenance is frequently required and provided, coarse trash 

racks should be included at the fishway exit, to minimize the entrainment of debris into 

the fishway. Floating debris may partially block passage corridors, potentially creating 

hazardous passage zones and/or blocking fish passage. Other types of debris, such as 

sediment transport into the fishway, may also adversely affect the operation of the 

facility. 

4.8.2 Specific Criteria and Guidelines – Coarse Trash Rack 

4.8.2.1 Velocity: The velocity through the gross area of a clean coarse trash rack

should be less than 1.5 ft/s. 

4.8.2.2 Depth: The depth of flow through a coarse trash rack should be equal to 

the pool depth in the fishway. 

4.8.2.3 Maintenance: The coarse trash rack should be installed at 1:5 

(horizontal:vertical) slope (or flatter) for ease of cleaning. The coarse trash rack

design must allow for easy maintenance, considering access for personnel, travel 

clearances for manual or automated raking, and removal of debris. 

4.8.2.5 Bar Spacing: The fishway exit coarse trash rack should have a minimum 

clear space between vertical flat bars of 10 inches if Chinook salmon are present, 

and 8 inches in all other instances. Lateral support bar spacing must be a 

minimum of 24 inches, and must be sufficiently back set of the coarse trash rack

face to allow full trash rake tine penetration. Coarse trash racks must extend to 

the appropriate elevation above water to allow easy removal of raked debris. 

4.8.2.6 Orientation: The fishway exit coarse trash rack must be oriented at a 

deflection angle greater than 45° relative to the direction of river flow. 

46 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 4-5. Coarse Trashrack 

4.8.3 Specific Criteria and Guidelines – Debris and Sediment 

4.8.3.1 Coarse Floating Debris: Debris booms, curtain walls, or other provisions 

must be included in design if coarse floating debris is expected. 

 

4.8.3.2 Debris Accumulation: If debris accumulation is expected to be high, the 

design should include an automated mechanical debris removal system. If debris 

accumulation potential is unknown, the design should anticipate the need in the 

future and include features to allow possible retrofit of an automated mechanical 

debris removal system. 

4.8.3.2 Sediment Entrainment and Accumulation: 

• The fishway exit should be designed to minimize entrainment of sediment. 

• The facility should be designed such that it does not accumulate sediment 

or debris during normal operation. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.9 Miscellaneous Considerations 

4.9.1 Specific Criteria and Guidelines – Miscellaneous 

4.9.1.1 Security: Fishways should be secured to discourage vandalism, preclude 

poaching opportunity, and to provide public safety. 

4.9.1.2 Lighting: Natural lighting should be consistently provided throughout the 

fishway. Where this is not possible (such as in tunnels), artificial lighting should 

be provided in the blue-green spectral range. Lighting must be designed to 

operate under all environmental conditions at the installation. 

4.9.1.3 Access: Personnel access must be provided to all areas of the fishway, to 

facilitate operational and maintenance requirements. Walkway grating should 

allow as much ambient lighting into the fishway as possible. 

4.9.1.4 Edge/Surface Finishes: All metal edges in the flow path used for fish 

migration must be ground smooth to minimize risk of lacerations. Concrete 

surfaces must be finished to ensure smooth surfaces, with one-inch wide 45°

corner chamfers. 

4.9.1.5 Protrusions: Protrusions (such as valve stems, bolts, gate operators, pipe 

flanges etc.) must not extend into the flow path of the fishway. 

4.9.1.6 Exposed Control Gates: All control gates exposed to fish (for example, 

entrances in the fully-open position) must have a shroud or be recessed to 

minimize or eliminate fish contact. 

4.9.1.7 Maintenance Activities: To ensure fish safety during in-season fishway 

maintenance activities, all fish ladders must be designed to provide a safe egress 

route or safe holding areas for fish prior to any temporary (i.e., less than 24 hours) 

dewatering. Longer periods of fishway dewatering for scheduled ladder 

maintenance must occur outside of the passage season with safeguards in place to 

allow evacuation of fish in a safe manner. 

4.10 Roughened Chutes 

4.10.1 Description and Purpose – Roughened Chutes 

Another general type of fish passage system is the roughened chute, which consists of a 

hydraulically roughened channel with near continuous energy dissipation throughout its 

length. Three examples of a roughened chute passage are a baffled chute (including 

steeppass and Denil fishways) (Section 4.10.2.1), a roughened channels (Section 4.10.2.2) 

and full width stream weirs (Section 4.10.2.3). 

 

48 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

4.10.2 Types of Roughened Chutes 

4.10.2.1 Baffled Chutes (Denil and Steeppass Fishways): Denil and steeppass 

fishways are examples of roughened chute fishways and are of similar design 

philosophy. This type of fishway has excellent fish attraction characteristics when 

properly sited and provides good passage conditions using relatively low flow 

amounts. Denil and steeppass fishways are used mainly for sites where the 

fishway can be closely monitored, such as off-ladder fish trap designs or 

temporary fishways used during construction of permanent passage facilities. 

Debris accumulation in any fishway, in combination with turbulent flow, may 

injure fish or render the fishway impassable. Because of their baffle geometry 

and narrow flow paths, Denil and steeppass fishways are especially susceptible to 

debris accumulation. As such, they must not be used in areas where downstream 

passage occurs, or where even minor amounts of debris are expected. 

Denil and steeppass fishways are designed with a sloped channel that has a 

constant discharge for a given normal depth, chute gradient, and baffle

configuration. Energy is dissipated consistently throughout the length of the 

fishway via channel roughness, and results in an average velocity compatible with 

the swimming ability of adult salmonids. The passage corridor consists of a chute 

flow between and through the baffles. There are unique aspects of Denil or 

steeppass fishways that need to be carefully considered. First, there are no resting 

locations within a given length of Denil and steeppass fishways. Therefore, once 

a fish starts to ascend a length of a steeppass or Denil, it must pass all the way 

upstream and exit the fishway, or risk injury when falling back downstream. If 

the Denil or steeppass fishway is long, intermediate resting pools may be included 

in the design, located at intervals determined by the swimming ability of the 

weakest target species. 

The Denil fishway generally is designed with slopes up to 20%, and has higher 

flow capacity and less roughness than a steeppass fishway. Steeppass fishways 

may be used at slopes up to 28%. For either fishway, the average chute design 

velocity should be less than 5 ft/s. For an upstream passage facility utilizing a 

Denil or a steeppass ladder, the horizontal distance between resting pools should 

be less than 25 feet. Resting pool volumes must adhere to volume requirements 

specified in Section 4.5.3.5. The minimum flow depth in a Denil fishway should 

be 2 feet, and in a steeppass fishway the minimum flow depth should be 1.5 feet, 

and depth must be consistent throughout the fishway for all ladder flows. Denil 

and steeppass fishways must be located to minimize the potential for fallback of 

fish. 

4.10.2.2 Roughened Channels: Another general category of upstream fish 

passage is termed a roughened channel, where design involves the selection of 

appropriately sized streambed material placed in such a way as to mimic the 

configuration in the natural streambed. These are also referred to as stream or 

streambed simulation, rock channels, or nature-like fishways. By replicating 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

natural stream conditions, a wide variety of life stages and species of fish may be 

able to utilize the roughened channel for passage. In addition, roughened 

channels may provide additional benefits to other species such as insects, 

mollusks, and crustaceans. Roughened channels may not always be the 

appropriate design choice. This is a relatively new technology without a 

developed and proven design methodology, and the effectiveness for passing 

specific species and life stages over a wide flow range, and the long term 

durability of a wide range of designs has yet to be established. It is expected that 

through careful engineering and construction techniques, and through monitoring 

of design uncertainties over time, especially regarding the durability of the 

roughened channel structure, future design uncertainty can be reduced. If passage 

conditions in the constructed roughened channel can be achieved that are similar 

to the downstream passage conditions in the natural stream, there is reason to 

expect that a properly constructed roughened channel may pass all life stages and 

species that arrive at the constructed roughened channel. 

Designs of roughened channels vary depending on the specific site conditions. 

Criteria for this type of passage design are evolving, and proposals for this type of 

ladder assessed on a site-specific basis. In general, roughened channels should 

only be used when: 

• Channel slope using stream simulation is less than 6%. 

• Total length of passage is less than 150 feet. 

• An appropriate mix of bed materials (from fines to boulder sized material) 

are used such that flow depths of at least 1 foot can be maintained for 

upstream adult salmonid passage. 

• Sub-surface flow will be minimized by filling voids between larger 

materials with finer-sized material. Guidance on the mixture of fill 

material is still evolving, but general guidance is provided in Washington 

Department of Fish and Wildlife (WDFW) 2003. 

The arrangement of bed materials should demonstrate channel complexity similar 

to the characteristics of the adjacent stream reaches. To minimize the potential 

for head-cutting to occur, discrete hydraulic drops across the entire width of the 

roughened channel should be avoided. It should be demonstrated in the design 

analysis that any scouring of fines from the constructed channel will be refilled by 

subsequent bedload transport and aggradations. It is noted that if the channel 

roughness of adjacent stream reaches is heavily influenced by woody debris, it 

may be difficult to mimic this condition with any sort of constructed roughened 

channel. 

Since this design method is an evolving technology, any site utilizing a 

constructed roughened channel must include an annual (at a minimum) 

monitoring plan at least until after a 50-year stream flow event has occurred. 

Monitoring must include an assessment of passage conditions and/or maintenance 

of original design conditions, and repaired as necessary to accomplish design 

passage conditions. The loss of placed bed material after a high flow event will 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

result in loss of flow through the channel substrate, and may render a roughened 

channel too shallow for fish passage. Criteria for this type of fishway design are 

still evolving, and design proposals will be assessed on a site-specific basis. 

4.10.2.3 Full Width Stream Weirs: Full width (i.e., full stream width) weirs 

provide fish passage by incrementally backwatering an impassable barrier or 

impediment. These structures span the entire width of the stream channel and 

convey the entire stream flow, breaking the hydraulic drop into passable 

increments. This is accomplished by incrementally stepping down the water 

surface elevation from the barrier to intersect the natural stream gradient 

downstream. 

Unlike many of the fishways described herein, these structures are not designed 

with auxiliary water supply systems, trashracks, or a great deal of operational 

complexity. Weirs may be constructed from reinforced concrete, or in limited 

applications, boulders or logs. Since boulders must be large, and usually have 

unpredictable dimension, a result can be the lack of the desired water surface 

differential for the range of design streamflows. It is especially difficult to 

maintain the required water surface elevation differential between weirs 

(maximum of 1.0 feet) when the design must encompass a wide flow range (tens 

to thousands of cfs) typical in a Northwest stream. In applications that require 

precision rock placement for maintenance of hydraulic drop between weirs, for 

long-term predictability, some applications may require regular maintenance to 

bring the projects back to design standards. The result is additional instream work 

that may produce continuing impacts to habitat and fish. These factors must be 

considered and accommodated before choosing this design for a site. 

Design of each weir must concentrate flow into the center of the downstream 

pool, and/or direct flow toward the downstream thalweg. This concentration is 

accomplished by providing a slight weir crest elevation decrease from each bank 

to the center (flow notch). Typically, the flow notch will be designed to pass the 

minimum instream flow, while higher stream flows pass over the entire weir crest. 

Natural bedload movement will fill in pools providing a scour pool area below the 

flow notch, and shallower fringe areas. 

Scour is a critical and often underestimated design issue. If sills and weirs are not 

anchored on bedrock, a means of preventing undermining is required, using 

embedded anchor boulders or other such means of stabilizing the streambed. If a 

pool lining technique is selected to prevent undermining of the fishway, a 

minimum of 4 feet of depth should be provided in each pool and in the tailrace

below the fishway. This allows for a fish to stage or hold below each weir before 

proceeding upstream. In addition, the tailrace area should be protected from 

scour to prevent lowering of the streambed, and should be monitored after high 

flows occur to ensure the facility remains passable. Criteria for this type of 

fishway design are still evolving, and design proposals will be assessed on a sitespecific basis. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5. EXCLUSION BARRIERS

5.1 Introduction – Exclusion Barriers 

Exclusion barriers are designed to minimize the attraction and stop the migration of 

upstream migrating fish into an area where there is no upstream egress or suitable 

spawning area, and to guide fish to an area where upstream migration may continue. 

Exclusion barriers may also be used to restrict movement of undesirable species into 

habitat. Exclusion barriers are designed to minimize the potential for injury of fish that 

are attracted to impassable routes. 

Some examples of the use of exclusion barriers include: 

• preventing fish from entering return flow from an irrigation ditch 

• preventing fish from entering the tailrace of a power plant 

• guiding fish to a trap facility for upstream transport, research, or broodstock 

collection 

• guiding fish to a counting facility 

• preventing fish from entering a channel subject to sudden flow changes 

• preventing fish from entering turbine draft tubes 

• preventing fish from entering channels with poor spawning gravels, poor water 

quality or insufficient water quantity. 

5.2 Types of Exclusion Barriers 

The two primary categories of exclusion barriers are picket barriers and velocity barriers. 

Another type of exclusion barrier is a vertical drop structure, which provides a jump 

height that exceeds the vertical leaping ability of fish. Other types of barriers, such as 

electric and acoustic fields, have very limited application because of inconsistent results 

most often attributed to varying water quality (turbidity, specific conductance). 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

5.3 Picket Barriers 

5.3.1 Description and Purpose – Picket Barriers 

Picket barriers diffuse nearly the entire streamflow through pickets extending the entire 

width of the impassable route, sufficiently spaced to provide a physical barrier to 

upstream migrant fish. This category of exclusion barrier includes a fixed bar rack and a 

variety of hinged floating picket weir designs. Picket barriers usually require removal for 

high flow events, increasing the potential to allow passage into undesirable areas. 

In general, since the likelihood of impinging fish is very high, these types of barriers 

cannot be used in waters containing species listed under the ESA, unless they are 

continually monitored by personnel on site, and have a sufficient operational plan and 

facility design in place to allow for timely removal of impinged or stranded fish prior to 

the occurrence of injury. Since debris and downstream migrant fish must pass through the 

pickets, sites for these types of exclusion barriers must be carefully chosen. Picket 

barriers must be continually monitored for debris accumulations, and debris must be 

removed before it concentrates flow and violates the criteria established below. As debris 

accumulates, the potential for the impingement of downstream migrants (e.g., juvenile 

salmonids, kelts, adult salmon, or resident fish) increases to unacceptable levels. Debris 

accumulations may also concentrate flow through the remainder of the open picket area, 

increasing the attraction of upstream migrants to these areas and thereby increasing the 

potential for jumping injury or successful passage into areas without egress. 

5.3.2 Specific Criteria and Guidelines - Picket Barriers 

5.3.2.1 Openings: The clear opening between pickets and between pickets and 

abutments must be less than or equal to 1 inch. A tighter opening may be 

required if resident species are also to be excluded by the design. 

5.3.2.2 Average Design River Velocity: The average design river velocity 

through pickets should be less than 1.0 ft/s for all design flows, with maximum 

velocity less than 1.25 ft/s, or half the velocity of adjacent passage route flows 

whichever is lower. The average design velocity is calculated by dividing the 

flow by the total submerged picket area over the design range of stream flows. 

When river velocities exceed these criteria, the picket barrier must be removed. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5.3.2.3 Head Differential: The maximum head differential across the pickets

must never exceed 0.3 feet over the clean picket condition. If this differential is 

exceeded, the pickets must be cleaned as soon as possible. 

5.3.2.4 Debris and Sediment: A debris and sediment removal plan must be 

considered in the design that anticipates the entire range of conditions expected at 

the site. Debris must be removed before accumulations develop that violate the 

criteria specified in 5.3.2.2 and 5.3.2.3. 

5.3.2.5 Orientation of Picket Barrier: Pickets barriers must be designed to lead 

fish to a safe passage route. This may be achieved by angling the picket barrier 

toward a safe passage route, providing nearly uniform velocities through the 

entire length of pickets, and providing sufficient attraction flows from a safe 

passage route that minimizes the potential for false attraction to the picket barrier 

flows. 

5.3.2.6 Picket Freeboard: The minimum picket extension above the water 

surface at high fish passage design flow is 2 feet. 

5.3.2.7 Submerged Depth: The minimum submerged depth at the picket barrier 

at low design discharge must be two feet for at least 10% of the river cross section 

at the barrier. Picket barriers should be sited where there is a relatively constant 

depth over the entire stream width. 

5.3.2.8 Picket Porosity: The picket array must have a minimum of 40% open 

area. 

5.3.2.9 Picket Construction Material: Pickets must be comprised of flat bars 

aligned with flow, or round columns of steel, aluminum, or durable plastic. 

Picket panels should be of sufficient structural integrity to withstand high 

streamflows. 

5.3.2.10 Picket Sill: A uniform concrete sill, or an alternative approved by NMFS 

engineering staff, should be provided to ensure that fish do not pass under the 

picket barrier. 

5.4 Velocity Barriers 

5.4.1 Description and Purpose – Velocity Barriers 

A velocity barrier consists of a weir and concrete apron combination that prevents 

upstream passage by producing a shallow flow depth and high velocity on the apron, 

followed by an impassable vertical jump over the weir. A velocity barrier does not have 

the previously mentioned problems of a picketed weir barrier, since flow passes freely 

54 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

over a weir, allowing the passage of debris and downstream migrant fish. However, 

since this type of barrier creates an upstream impoundment, the designer must consider 

backwater effects that may induce loss of power generation or property inundation 

upstream of the velocity barrier. 

5.4.2 Specific Criteria and Guidelines - Velocity Barrier

5.4.2.1 Weir Height: The minimum weir height relative to the maximum apron

elevation is 3.5 feet. 

5.4.2.2 Apron Length: The minimum apron length (extending downstream 

from base of weir) is 16 feet. 

5.4.2.3 Apron Slope: The minimum apron downstream slope is 16:1 

(horizontal:vertical). 

5.4.2.4 Weir Head: The maximum head over the weir crest is 2 feet. Other 

combinations of weir height and weir crest head may be approved by NMFS 

Hydropower Division staff on a site-specific basis. 

5.4.2.5 Downstream apron elevation: The elevation of the downstream end of 

the apron must be greater than the tailrace water surface elevation corresponding 

to the high design flow. 

5.4.2.6 Flow ventilation: The flow over the weir must be fully and continuously 

vented along the entire weir length, to allow a fully aerated flow nappe to develop 

between the weir crest and the apron. Full aeration of the flow nappe prevents an 

increase in water surface behind the nappe, which may allow fish to stage and 

jump the weir. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Figure 5-1. Velocity Barrier 

5.5 Vertical Drop Structures 

5.5.1 Description and Purpose - Vertical Drop Structures 

A vertical drop structure can function as an exclusion barrier by providing head in excess 

of the leaping ability of the target fish species. These can be a concrete monolith, rubber 

dam, bottom-hinged leaf gate or approved alternative. 

5.5.2 Specific Criteria and Guidelines – Vertical Drop Structures 

5.5.2.1 Minimum Height: The minimum height for vertical drop structure must 

be 10 feet relative to the high design flow elevation in the tailrace. 

5.5.2.2 Cantilever: If the potential for leaping injury exists, flow must pass over 

two feet or more of cantilevered ledge provided over the leaping pool. 

5.5.2.3 Minimum Flow Depth: Provision must be made to ensure that fish 

jumping at the vertical drop structure flow will land in a minimum five foot deep 

pool, without contacting any solid surface. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5.6 Horizontal Draft Tube Diffusers

5.6.1 Description and Purpose – Horizontal Draft Tube Diffusers 

A horizontal draft tube diffuser is a device used below a powerhouse at the turbine draft 

tube outlet to prevent fish from accessing the turbine runners, where injury may occur 

during start up or shut down of turbine operations, or possibly during normal operations 

if draft tube velocity is low (generally less than 16 ft/s). If the draft tubes are located in 

proximity of an upstream passage system, a horizontal draft tube diffuser system may be 

the appropriate choice for an exclusion system. 

 5.6.2 Specific Criteria and Guidelines – Horizontal Draft Tube Diffusers 

5.6.2.1 Flow: Average velocity of flow exiting the horizontal diffuser grating 

must be less than 1.25 ft/s, and distributed as uniformly as possible. Maximum 

velocity should not exceed 2 ft/s. 

5.6.2.2 Bar Spacing: Clear spacing between diffuser bars and any other pathway 

from the tailrace to the turbine runner must be less than 1 inch. 

5.6.2.3 Placement: Diffusers must be submerged a minimum of 2 feet for all 

tailwater elevations. 

Figure 5-2. Potential Layout of a Horizontal Draft Tube Diffuser 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6. ADULT FISH TRAPPING SYSTEMS 

6.1 Introduction – Adult Fish Trapping Systems 

In general, NMFS requires volitional passage, as opposed to trap and haul, for upstream 

passage facilities. This is primarily due to the risks associated with the handling and 

transport of adult upstream migrants, in combination with the long term uncertainty of 

funding, maintenance, and operation of the trap and haul program. Furthermore, trap and 

haul programs tend to not operate at the beginning and end of migration periods because 

there are only a few individuals present. This practice truncates the tails of the migration 

and likely has adverse affects on salmon population diversity. In contrast, a facility that 

provides for volitional passage can operate 24/7, year-round. Nevertheless, there are 

instances where trap and haul may be the only viable option for a particular site. In 

particular, at high head dams where thermal stratification occurs in the reservoir, 

temperature differentials in the fishway (as opposed to water temperatures below the 

dam) may dissuade fish from utilizing volitional passage facilities. In any case, NMFS’ 

primary objective in prescribing or requiring the construction and operation of a fish 

passage facility is to maintain or restore the viability of anadromous fish populations. 

This section addresses design aspects of adult fish trapping systems. The operations and 

design criteria and guidelines are dependent on each other, since the management 

objectives for trap operation define the facility functional design and must be stipulated 

before the trap design development can proceed. 

In many cases, NMFS may not require retrofit of existing facilities to comply with 

criteria listed herein. It is emphasized that these criteria and guidelines are viewed as a 

starting point for design development of new, or upgraded, trapping facilities. This 

section does not directly apply to existing trapping programs/facilities, unless specifically 

required by NMFS. 

Adult fish trapping systems may either be included in the initial design of a proposed 

upstream passage facility, or in some cases may be retro-fitted to an existing fishway. 

Traps should be designed to utilize known or observed fish behavior to benignly route 

fish into a trap holding pool that precludes volitional exit. From the trap holding pool, 

fish may be loaded for transport and/or examined for research and management purposes. 

Traps may be used as the terminus of volitional upstream fish passage followed by 

transport to specific sites, or as a parallel component of a fish ladder where fish may 

either be routed into an adjacent trapping loop or if the trap is closed, allow unimpeded 

fish passage through the fishway. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

58 
NMFS Anadromous Salmonid Passage Facility Design February 2008 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

6.2 Trap Design Scoping 

• New trap construction or major upgrade proposals must address and describe the 

consideration of (at least) the following issues: 

• Objective of trapping - count, handle, collect, interrogate for tags, etc. 

• Number of fish targeted and total number potentially present 

• Target species, included ESA-listed species 

• Other species likely to be present at the trap, including ESA-listed species 

• Environmental conditions during trap operation such as water and air temperature, 

flow conditions (lows and peaks), debris load, etc. 

• Operation location, duration and scale 

• Fish routing and ultimate destination 

• Maximum duration of delay or holding within the trapping system for target and 

non-target fish 

• Security mechanisms 

• If a Hatchery and Genetic Management Plan (HGMP), 4(d) Limit 7 Scientific 

Research and Take Authorization application, or Section 10(a)(1)(A) permit 

application exists, and use these as the basis for design of a trap site. Most trap 

sites will require at least one of these documents. 

6.3 Fish Handling 

6.3.1 Specific Criteria and Guidelines – Fish Handling 

6.3.1.1 Nets: Use of nets to capture or move fish must be minimized or 

eliminated. If nets are used they should be sanctuary type nets, with solid bottoms 

to allow minimal dewatering of fish. Fish must be handled with extreme care. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.3.1.2 Anesthetization: In most cases, fish should be anesthetized before being 

handled. The method of anesthetization for ESA-listed anadromous salmonids 

may be specified by the appropriate ESA permit, which must be received prior to 

any directed take of listed species. In the design process and prior to permit 

submittal, the type of anesthetic can be selected by agreement by NMFS staff 

involved in trap design. 

6.3.1.3 Non-Target Fish: New or upgraded trapping facilities must be designed 

to enable non-target fish to bypass the anesthetic tank. 

6.3.1.4 Frequency: Fish must be removed from traps at least daily. When either 

environmental (e.g., water temperature extremes, low dissolved oxygen or high 

debris load) or biological conditions (e.g., migration peaks) warrant, fish must be 

removed more frequently to preclude crowding or adverse water quality (see 

Section 6.5.1.2 and 6.5.1.3). 

6.3.1.5 Personnel: Individuals handling fish must be experienced or trained to 

ensure fish are handled safely. 

6.3.1.6 Fish Ladders: Fish ladders must not be completely dewatered during 

trapping operations, and should not experience any reduction in fishway flow. 

6.4 General Trap Design 

6.4.1 Specific Criteria and Guidelines – General Trap Design 

6.4.1.1 Primary Trapping System: Primary trapping system components 

usually include: 

• in-ladder removable diffusers or gates to block passage within the ladder 

and guide fish into the trap; 

• an off-ladder holding pool including a transition channel or port and 

trapping mechanism (through which attraction flow is discharged via one 

of the devices described in Section 6.6); 

• a gate to prevent fish from entering the trap area during crowding 

operations; 

• a holding pool fish crowder (for encouraging adult egress from the offladder holding pool to sorting/loading facilities); 

• separate holding pool inflow and outflow facilities; 

• distribution flume (used with false weir or steeppass to enable fish entry to 

and/or egress from the holding pool); and 

• a lock or lift for truck-loading fish. 

6.4.1.2 Fish Ladders: Fish ladders are the preferred means of upstream passage 

at impediments, unless site conditions preclude their use. This is due to the 

preference that fish be allowed to pass at their inclination, rather than that of a 

human operator. Factors to be considered include the adverse effects of holding 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

trapped fish in a potentially high-density holding pool for an excessive period, the 

long-term uncertainty of maintaining funding and trained personnel, exposure to 

poaching or predation in the trap, injuries from jumping, facility failures (e.g., 

loss of water supply), and cumulative handling and holding stresses. 

6.4.1.3 Location: In general, fish ladders should not be designed or retrofitted 

with either in-ladder traps or loading facilities. Rather, trap/holding and loading 

facilities should be in an adjacent, off-ladder location where fish targeted for 

trapping purposes may be routed. This allows operational flexibility to readily 

switch from passage to trapping operational modes. 

6.4.1.4 Distribution Flume: A distribution flume must be used when fish are 

routed to anesthetic tanks, recovery tanks, pre-transport holding tanks, fish 

ladders or project forebays. The flume must have smooth joints, sides, and 

bottom with no abrupt vertical or horizontal bends and have continuously wetted 

surfaces. Horizontal and vertical radius of curvature should be at least 5 times 

flume width to minimize risk of fish strike injuries. The minimum inside width 

(or diameter) of the distribution flume must be 15 inches, and the minimum 

sidewall height in the distribution flume must be 24 inches. 

6.4.1.5 Water Quality: Holding pool water quality should equal or exceed that 

of the ambient waters from which fish are trapped. The water temperature, 

oxygen content, and pH must provide fish with a safe, healthy environment. 

6.4.1.6 Inflow: Trap inflow must be routed through an upstream diffuser

conforming with Section 4.3.2, with maximum 1.0 ft/s average velocity. Baffling 

or other energy dissipation means should be used to prevent excessive turbulence 

and surging, which may induce adult jumping within the trap. 

6.4.1.7 Recovery Pool: Anesthetized fish must be routed to a recovery pool to 

allow monitoring of fish to ensure full recovery from the anesthetic effect prior to 

release. Fish recovering from anesthesia must not be routed directly back to the 

river where unobserved mortality may occur. Recovery pool inflow must satisfy 

the specified water quality guidelines (see Sections 6.4.1.5, 6.5.1.2, and 6.5.1.4). 

Recovery tank hydraulic conditions must not result in partially or fully 

anesthetized fish being impinged on an outflow grating or any other hazardous 

area. A release pool must allow fully recovered fish to volitionally exit. 

 

6.5 Trap Holding Pool 

6.5.1 Specific Guidelines and Criteria – Trap Holding Pool 

For single-pool traps, refer to Section 6.9. For trap holding pools at multi-pool ladders, 

criteria and guidelines include: 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.5.1.1 Off-Ladder Trap System: For new or existing fish ladders, fish must not 

be trapped and held within the ladder for intermittent sampling or truck-loading. 

Rather, an off- ladder trap system is required. This type of system allows 

unimpeded ladder passage during non-trapping periods, and intermittent trapping 

of fish for required collection or sampling. The intent is to minimize adverse 

impacts (such as delay and elevated jumping injury/mortality) of fish trapping by 

allowing rapid transition from one operational mode to the other. 

6.5.1.2 Capacity, Temperature, and Dissolved Oxygen: Trap holding pools 

(for short term holding in off ladder traps and for trap and haul facilities) must be 

sized to provide a minimum volume of 0.25 ft3 per pound of fish based on trap 

capacity, with water temperatures less than 50° F, dissolved oxygen between 6 to 

7 parts per million, and fish held less than 24 hours (Senn 1984). The trap 

capacity is determined by the maximum daily fish return, or by the number of fish 

expected to be trapped before the trap catch is transported. The poundage of fish 

is determined by the weight of an average fish targeted for trapping, times the 

maximum number of fish. Note that the poundage calculation may entail a 

number of different fish species. For long term holding at off ladder holding 

pools, (greater than 72 hours), trap holding pool water volumes should be 

increased by a factor of three. If water temperatures are greater than 50° F, the 

poundage of fish held should be reduced by 5% for each degree over 50° F. The 

trap capacity and average weight of targeted fish to be used in design are subject 

to approval by a NMFS. Also, see Section 6.3.1.4. 

6.5.1.3 Water Supply and Quality: Trap holding pools (for short-term holding 

in off ladder traps and for trap and haul facilities) must be designed with a 

separate water supply and drain system. Trap holding pool design water supply 

capacity must be at least 0.67 gallons per minute per adult fish for the 

predetermined adult salmon trap holding capacity, with water temperatures less 

than 50° F, dissolved oxygen between 6 to 7 ppm, and fish held less than 24 

hours. For long term holding, (greater than 72 hours), trap holding pool flow 

rates should be increased by a factor of three (Senn 1984). Also, see Section 

6.3.1.4. 

6.5.1.4 Minimization of Adult Jumping: Trap holding pool designs must 

include provisions to minimize adult jumping which may result in injury or 

mortality. Examples include (but are not limited to): high freeboard on holding 

pool walls (5 feet or more); covering to keep fish in a darkened environment; 

providing netting over the pool strong enough to prevent adults from breaking 

through the mesh fabric; or, provision of sprinklers above the holding pool water 

surface to reduce the ability of fish to detect movement above the trap pool. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.5.1.5 Pickets: 

• Off-ladder holding pools should include intake and exit pickets designed 

to prevent adult egress and to conform with Section 4.3.2, and with an 

adjustable exit overflow weir located upstream of the exit picket to control 

holding pool water surface elevation. 

• Removable pickets within the ladder (installed to block fish ascent within 

the ladder when fish are to be routed into an off-ladder trapping pool) 

must be angled toward the off ladder trap entrance location, and must 

comply with Section 4.3.2. Pickets must be completely removed from the 

ladder when not actively trapping. 

 

6.5.1.6 Crowders: Holding pool crowders should have a maximum clear bar 

spacing of 7

/8 inch. Side gap tolerances must not exceed 1 inch, with side and 

bottom seals sufficient to allow crowder movement without binding, and to 

prevent fish movement behind the crowder panel. 

 

6.5.1.7 Distribution Flume: Where false weirs and steeppass ladders are used to 

route fish into or out of a trap holding pool, distribution flumes or pipes are used 

as described in Section 6.4.1.4. 

6.6 Trapping Mechanism 

6.6.1 Description and Purpose – Trapping Mechanism 

The trap holding pool trapping mechanism (e.g., finger weir, vee-trap, false weir, 

steeppass ladder) allows fish to enter, but not volitionally exit, the holding pool. 

6.6.2 Specific Criteria and Guidelines – Trapping Mechanism 

6.6.2.1 Design (General): 

• All components exposed to fish must have all welds and sharp edges 

ground smooth to the touch, with other features as required to minimize 

injuries. 

• Bars and spacings must conform to Section 4.3.2. 

• Trapping mechanisms must allow temporary closure to avoid spatial 

conflict with brail crowding and loading operations. 

• Trapping mechanisms should be designed to safeguard against fish entry 

into an unsafe area such as behind a crowder or under floor brail. 

• A gravity (i.e., not pumped) water supply should be used for false-weirs

and steeppass ladders to avoid potential rejection of the trapping 

mechanism associated with the transmission of pump/motor sounds. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.7 Lift/Hopper 

6.7.1 Description and Purpose – Lift/Hopper 

A lift in this context includes a full-sized hopper that is capable of collecting/lifting all 

fish trapped in a holding pool at one time, then either routing fish to the forebay, or 

loading onto a truck for transport. 

6.7.2 Specific Criteria and Guidelines – Lift/Hopper 

6.7.2.1 Maximum Water Volume: Maximum hopper and transport truck 

loading water volumes should be greater than or equal to 0.15 ft3 per pound of 

fish at the maximum fish loading density, to provide hopper or transport 

operations with sufficient volume of water for fish safety. 

 

6.7.2.2 Hopper freeboard, from hopper water surface to top of hopper bucket, 

should be greater than the water depth within the hopper, to reduce risk of fish 

jumping out during lifting operations. 

6.7.2.3 Sump: When a trap design includes a hopper sump (into which the 

hopper is lowered during trapping), side clearances between the hopper and sump 

sidewalls should not exceed 1 inch, thereby minimizing fish access below the 

hopper. Flexible side seals must be used to ensure that fish do not pass below the 

hopper. 

6.7.2.4 Transport Tanks: 

• Truck transport tanks must be compatible with the hopper design to 

minimize handling stress. If an existing vehicle will be used, the hopper

must be designed to be compatible with existing equipment. If the 

transport tank’s opening is larger than the tube or hopper opening, a cap or 

other device must be designed to prevent fish from jumping at the 

opening. 

• Design should allow hopper water surface control to be transferred to the 

truck transport tank so that water and fish do not plunge abruptly from the 

hopper into the fish transport tank during loading. 

6.7.2.5 Fish Egress Opening: The fish egress opening from the hopper into the 

transport tank must have a minimum horizontal cross-sectional area of 3 ft2

, and 

must have a smooth transition that minimizes the potential for fish injury. 

6.7.2.6 Design (General): 

• Fail-safe measures must be provided to prevent entry of fish into the 

holding pool area to be occupied by the hopper before the hopper is 

lowered into position. 

• The hopper interior must be smooth, and be designed to safeguard fish. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.8 Fish Lock 

6.8.1 Description and Purpose – Fish Lock 

A fish lock allows trapped fish in the trapping system holding pool to be elevated 

without a hopper or hopper sump. 

The following steps describe the routing of fish from the lock to the forebay or 

transport vehicle: 

1. Fish are crowded into the lock. 

2. The closure gate is shut. 

3. Flow into the lock is introduced through floor diffusers below the floor brail. 

4. As the water level rises within the lock, it will ultimately reach a control weir

equilibrium elevation. The floor brail should be raised only after the lock 

water surface elevation is at equilibrium, and should not be used to lift fish out 

of the water. 

5. Overflow passes over a control weir and through a dewatering screen, 

allowing excess flow to be drained off and adult fish to be routed directly into 

the anesthetic tank, or into a wetted flume for routing to separate 

sorting/holding pools, or to be loaded into a transport vehicle. 

6.8.2 Specific Criteria and Guidelines – Fish Lock 

6.8.2.1 Lock Inflow Chamber: The lock inflow chamber (below the lowest floor 

brail level) must be of sufficient depth and volume (see Section 4.5.3.5) to limit 

turbulence into the fish holding zone when lock inflow is introduced. The inflow 

sump should be designed so that flow upwells uniformly through add-in floor 

diffusers (see Section 4.3.2), thereby limiting unstable hydraulic conditions within 

the lock that may agitate fish. 

6.8.2.2 Depth Over Fish Egress Weir: Depth over the fish egress weir should 

be at least 6 inches, to facilitate fish egress from the lock for transport or 

handling. 

6.8.3.2 Floor Brail:

• Floor brail should be composed of sufficiently sized screen material

(based on life stage and species present), to preclude injury or mortality of 

non-target species. Side gap openings must not exceed 1 inch with seals 

included to cover all gaps. The floor brail panel should be kept in its 

lowest position until flow passes over the flow egress weir. 

• The floor brail hoist should be designed for manual operation to allow 

movement of the brail at 2 feet/minute (upward and downward) that will 

minimize stress of fish crowded between the floor brail and lock flow 

egress weir. Automated operation is allowed only when the water depth 

above the brail is 4 feet or more. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

6.9 Single Holding Pool Traps 

6.9.1 Description and Purpose – Single Holding Pool Traps 

Single pool traps are often used in tandem with intermittent exclusion barriers (see 

Section 5) for brood-stock collection from small streams. These trapping systems are 

used to collect, sort, and load adult fish. 

6.9.2 Specific Criteria and Guidelines – Single Holding Pool Traps 

6.9.2.1 Design (General): 

• The trap holding pool water volume must be designed according to 

Section 4.5.3.5 to achieve relatively stable interior hydraulic conditions 

and minimize jumping of trapped fish. 

• Intakes must conform to Section 4.3.3. 

• Sidewall freeboard should be a minimum 4 feet above trap pool water 

surface at high design streamflow. 

• The trap holding pool interior surfaces must be smooth to reduce the 

potential for fish injury. 

6.9.2.2 Fish Removal Procedure: A description of the proposed means of 

removing fish from the trapping pool and loading onto a transport truck must be 

submitted to NMFS for approval in the ESA incidental take permit application. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7. CULVERTS AND OTHER STREAM CROSSINGS 

7.1 Introduction – Culverts and Other Stream Crossings 

This section provides criteria and guidelines for the design of stream crossings to aid 

upstream and downstream movement of anadromous salmonids. For the purpose of fish 

passage, the distinction between bridge, culvert, and low water crossing is not as 

important as the effect the structure has on the form and function of the stream. To this 

end, these criteria conceptually apply to bridges and low water crossings, as well as to 

culverts. In addition to providing fish passage, any road crossing design should include 

consideration for maintaining the ecological function of the stream - passing woody 

debris, flood flows and sediment, and other species that may be present at the site. The 

objective of these criteria and guidelines is to provide the basis for road crossing fish 

passage designs for all life stages of anadromous salmonids present at the site requiring 

passage. The design team should be in close contact with all biologists familiar with the 

site to assess potential impacts on spawning, life stages requiring passage, and to assess 

bed stability. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.2 Preferred Alternatives for New, Replacement, or Retrofitted Stream Crossings 

All the alternatives listed below have the potential to pass fish, but some may perform 

better than others at a particular site. Based on the biological significance and ecological 

risk of a particular site, NMFS may require a specific design alternative to be developed, 

if feasible, to allow normative physical processes within the stream-floodplain corridor 

by (1) promoting natural sediment transport patterns for the reach, (2) providing 

unaltered fluvial debris movement, and (3) restoring or maintaining functional 

longitudinal continuity and connectivity of the stream-floodplain system. 

The following alternatives and structure types are listed in general order of NMFS’ 

preference: 

• Road abandonment and reclamation or road realignment to avoid crossing 

the stream. 

• Bridge or stream simulation spanning the stream flood plain, providing 

long-term dynamic channel stability, retention of existing spawning areas, 

maintenance of food (benthic invertebrate) production, and minimized risk 

of failure. If a stream crossing is proposed in a segment of stream channel 

that includes a salmonid spawning area, only full-span stream simulation 

designs (see Section 7.4) are acceptable. 

• Embedded pipe culvert, bottomless arch designs or non-floodplain 

spanning stream simulation (see Sections 7.3 and 7.4). 

• Hydraulic design method, associated with more traditional culvert design 

approaches - limited to low stream gradients (0% to 1%) or for retrofits 

(Section 7.5). 

• Culvert designed with an external fishway (including roughened channels) 

for steeper slopes (see Section 4). 

• Baffled culvert or internal weirs - to be used only for when other 

alternatives are infeasible (see Section 7.6). Many baffle designs are 

untested for anadromous salmonid passage, and baffles always reduce the 

hydraulic capacity of culverts. NMFS may only approve baffled culverts 

on a site by site basis if compelling evidence of successful passage at other 

sites utilizing a similar design is provided and a suitable monitoring and 

maintenance plan is developed and followed. 

7.3 Embedded Pipe Design Method 

7.3.1 Description and Purpose – Embedded Pipe Method 

This method provides a simplified design methodology that is intended to provide a 

culvert of sufficient size and embedment to allow the natural movement of bedload and 

the formation of a stable bed inside the culvert, and is intended for use only in very small 

streams. Determination of the high and low fish passage design flows, water velocity, 

and water depth is not required for this method, since the stream hydraulic characteristics 

within the culvert are intended to mimic the stream conditions upstream and downstream 

of the crossing. This design method is usually not suitable for stream channels that are 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

greater than 3% in natural slope or for culvert lengths greater than 80 feet. Structures for 

this design method are typically round, oval, or squashed pipes made of metal or 

reinforced concrete. 

7.3.2 Specific Criteria and Guidelines – Embedded Pipe Design Method 

7.3.2.1 Culvert Width: The minimum culvert bed width must be greater than the 

bankfull channel width. Vertical clearance from bed to ceiling must be at least 4 

feet to allow for maintenance activities. There are many cases where greater 

widths may be required, based on the objective of providing a stable structure that 

will allow ecological function to continue. 

7.3.2.2 Culvert Slope: The culvert must be placed level (0% slope). 

7.3.2.3 Embedment: The bottom of the culvert should be buried into the 

streambed not less than 20% of the culvert height at the outlet and not more than 

40% of the culvert height at the inlet. The slope of the bed must replicate the 

natural upstream and downstream stream gradient in the vicinity of the road 

crossing. 

7.3.2.4 Fill Materials: Fill materials should be comprised of material to 

maximize the probability that fill materials will remain in place for all flows or be 

replaced as deposition occurs as streamflow recedes. The design must 

demonstrate the ability (by choosing fill material using size analysis of streambed 

material in the adjacent stream reaches if stream hydraulics are replacated, or by 

using guidance provided in WDFW 2003) to maintain the engineered streambed 

in the design configuration over the life of the project. 

7.3.2.5 Water Depth: Water depth and velocity in the culvert must replicate the 

natural stream depth and water velocity upstream and downstream of the road 

crossing. 

7.4 Streambed Simulation Design Method 

7.4.1 Description and Purpose – Streambed Simulation Design Method 

This method is a design process that is intended to mimic the natural upstream and 

downstream processes within a culvert or under a bridge. Fish passage, sediment 

transport, and debris conveyance within the culvert are designed to function as they 

would in a natural channel. Determination of the high and low fish passage design flows, 

design water velocity, and design water depth is not required for this option since the 

stream hydraulic characteristics within the culvert or beneath the bridge are designed to 

mimic the stream conditions upstream and downstream of the road crossing. The 

structures for this design method are typically open-bottomed arches or boxes but could 

have buried floors in some cases, or a variety of bridges that span the stream channel. 

This method utilizes streambed materials that are similar to the adjacent stream channel. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Streambed simulation requires a greater level of information on hydrology and 

geomorphology (topography of the stream channel) and a higher level of engineering 

expertise than the Embedded Pipe Design method (see Section 7.3). In general, 

streambed simulation should provide sufficient channel complexity to provide passage 

conditions similar to that which exists in the adjacent natural stream, including sufficient 

depth, velocity and resting areas. 

7.4.2 Specific Criteria and Guidelines – Streambed Simulation Design Method 

7.4.2.1 Channel Width: The minimum culvert bed width must be greater than 

bankfull channel width, and of sufficient vertical clearance to allow ease of 

maintenance activities. There are many cases where greater widths may be 

required, based on the objective of providing a stable structure that will allow 

ecological function to continue. For example, if a channel is not fully entrenched, 

some allowance for overbank flow may need to be provided. Similarly, for 

braided or meandering channels or other unconfined channel shapes, the flood 

plain must be allowed to function as a flow conveyance. If a stream is not fully 

entrenched, the minimum culvert bed width should be at least 1.3 times the 

bankfull channel width. 

7.4.2.2 Channel Vertical Clearance: The minimum vertical clearance between 

the culvert bed and ceiling should be more than 6 feet, to allow access for debris 

removal. Smaller vertical clearances may be used if a sufficient inspection and 

maintenance plan is provided with the design that ensures that the culvert will be 

free of debris during the passage season. 

7.4.2.3 Channel Slope: The slope of the reconstructed streambed within the 

culvert should approximate the average slope of the adjacent stream from 

approximately ten channel widths upstream and downstream of the site in which it 

is being placed, or in a stream reach that represents natural conditions outside the 

zone of the road crossing influence. For purposes of maintaining streambed 

integrity within the road crossing, the maximum slope of streambed simulation 

where closed bottom culverts are used should not exceed 6%. Design detail 

and/or a long term maintenance plan should be included that reflects how the 

streambed within the culvert will be maintained in its design condition over time. 

 

7.4.2.4 Embedment: If a culvert is used, the bottom of the culvert should be 

buried into the streambed not less than 30% and not more than 50% of the culvert 

height, and a minimum of 3 feet. For bottomless culverts the footings or 

foundation must be designed for the largest anticipated scour depth. The ability 

(using size analysis of streambed material in the adjacent stream reaches, or by 

using guidance provided in WDFW 2003) to maintain the engineered streambed 

in the design configuration over the life of the project must be demonstrated by 

the design. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.4.2.5 Maximum Length of Road Crossing: The length for streambed 

simulation should be less than 150 feet. If the length is greater than 150 feet, a 

bridge should be considered. 

7.4.2.6 Fill Materials: Fill materials should be comprised of materials of similar 

size composition to natural bed materials that form the natural stream channels 

adjacent to the road crossing. The design must demonstrate long term stability of 

the passage corridor, through assessment of hydraulic conditions through the 

passage corridor over the fish passage design flow range, and through assessment 

of the ability of the stream to deliver sufficient transported bed material to 

maintain the integrity of the streambed over time. Larger material may be used to 

assist in grade retention and to provide resting areas for migratory fish. 

7.4.2.7 Water Depth and Velocity: Water depth and velocity must closely 

resemble those that exist in the adjacent stream, as described in Section 7.4.2.3, or 

those listed in Section 7.5.2.6. To provide resting zones, special care should be 

used to provide areas of greater than average depth and lower than average 

velocity throughout the length of the streambed simulation, reasonably replicating 

those found in the adjacent stream. Hydraulic controls to maintain depth at low 

flows may be required. 

7.5 Hydraulic Design Method 

7.5.1 Design and Purpose – Hydraulic Design Method 

The hydraulic design method is a design process that matches the hydraulic performance 

of a culvert with the swimming abilities of a target species and age class of fish. It is 

only suitable in streams with sufficiently low gradient to provide the hydraulic conditions 

found in Table 8.5. This method targets distinct species of fish and therefore does not 

account for ecosystem requirements of non-target species. There are significant errors 

associated with estimation of hydrology and fish swimming speeds that are resolved by 

making conservative assumptions in the design process. Determination of the high and 

low fish passage design flows, water velocity, and water depth is required for this option. 

The hydraulic design method requires hydrologic data analysis, open channel flow 

hydraulic calculations, and information on the swimming ability and behavior of the 

target group of fish. This design method may be applied to the design of new and 

replacement culverts and may be used to evaluate the effectiveness of retrofits of existing 

culverts. 

7.5.2 Specific Criteria and Guidelines – Hydraulic Design Method 

7.5.2.1 Culvert Width and Vertical Clearance: The minimum culvert width 

and vertical clearance between the culvert bed and ceiling should be more than 6 

feet, to allow access for debris removal. Smaller vertical clearances may be used 

if a sufficient inspection and maintenance plan is provided with the design that 

ensures that the culvert will be free of debris during the passage season. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.5.2.2 Culvert Slope: The slope of the reconstructed streambed within the 

culvert should not exceed 125% of the approximate average slope of the adjacent 

stream from approximately 10 channel widths upstream and downstream of the 

site in which it is being placed, or in a stream reach that represents natural 

conditions outside the zone of the road crossing influence. If embedment of the 

culvert is not possible, the maximum slope should not exceed 0.5%. 

7.5.2.3 Embedment: Where physically possible, the bottom of the culvert should 

be buried into the streambed a minimum of 20% of the height of the culvert below 

the elevation of the tailwater control point downstream of the culvert, and the 

minimum embedment must be at least 1 foot. 

7.5.2.4 Fish Passage Design Velocity: The fish passage design high flow (see 

Section 3.3) for adult fish passage is used to determine the maximum water 

velocity within the culvert. 

7.5.2.5 Fish Passage Design Depth: The fish passage design low flow (see 

Section 3.2) for fish passage is used to determine the minimum depth of water 

within a culvert. Hydraulic controls may be required to maintain depth at low 

flows. 

7.5.2.6 Average Water Velocity: The maximum average water velocity in the 

culvert refers to the calculated average of velocity within the barrel of the culvert 

at the fish passage design high flow. In most instances, upstream juvenile fish 

passage requirements should also be considered in design. Juvenile fish passage 

analysis should include calculating average water velocity for the 50% 

exceedence flow for the time period corresponding to juvenile upstream passage. 

Use Table 7-1 to determine the maximum average water velocity allowed. 

Table 7-1. Maximum Allowable Average Culvert Velocity 

Culvert Maximum Average Velocity (ft/s) 

Length (ft) Chinook, Steelhead, 

Sockeye, and 

Coho Adults 

Pink and Chum 

Adults 

Juvenile Salmonids 

<60 6.0 5.0 1.0 

60-100 5.0 4.0 1.0 

100-200 4.0 3.0 1.0 

200-300 3.0 2.0 1.0 

>300 2.0 2.0 1.0 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.5.2.7 Minimum Water Depth: Minimum water depth at the low fish passage 

design flow should be: 1.0 feet for adult steelhead, Chinook, coho, and sockeye 

salmon; 0.75 feet for pink and chum salmon; and 0.5 feet for all species of 

juvenile salmon, as measured in the centerline of the culvert. The minimum depth 

within the culvert barrel is calculated at fish passage design low flow. 

7.5.2.8 Maximum Hydraulic Drop: Hydraulic drops between the water surface 

in the culvert and the water surface in the adjacent channel should be avoided in 

all cases. This includes the culvert inlet and outlet. Where physical conditions 

preclude embedment and the streambed is stable (e.g., culvert installation on 

bedrock) the hydraulic drop at the outlet of a culvert must not exceed the limits 

specified in Table 10-1 if juvenile fish are present and require upstream passage, 

or 1 foot if juvenile fish are not present or do not require upstream passage. 

7.6 Retrofitting Culverts 

7.6.1 Description and Purpose – Retrofitting Culverts 

For future planning and budgeting at the state and local government levels, redesign and 

replacement of substandard stream crossings may contribute substantially to the recovery 

of salmon stocks throughout the state, if better access to underutilized habitat is provided. 

Many existing stream crossings can be improved for fish passage by cost-effective 

means. The decision to replace or improve a crossing should fully consider actions that 

will result in the greatest net benefit for fish passage. If a particular stream crossing 

causes substantial fish passage problems that hinder the conservation and recovery of 

salmon in a watershed, complete redesign and replacement is warranted. The extent of 

the needed fish passage improvement work depends on the severity of fisheries impacts, 

the remaining life of the structure, and the status of salmonid stocks in a particular stream 

or watershed. 

For work at any stream crossing, site constraints need to be taken into consideration when 

selecting options. Some typical site constraints are ease of structure maintenance, 

construction windows, site access, equipment, and material needs and availability. 

Consolidation and/or decommissioning of roads and reclamation and restoration of the 

roadbed can sometimes be the most cost effective option. Consultations with NMFS 

biologists can aid in selecting priorities and alternatives. 

7.6.2 Specific Criteria and Guidelines – Retrofitting Culverts 

Where existing culverts are being modified or retrofitted to improve fish passage, the 

hydraulic requirements specified in Section 7.5 should be the design objective for the 

improvements. However, it is acknowledged that the conditions that cause an existing 

culvert to impair fish passage may also limit the remedies for fish passage improvement. 

Therefore, short of culvert replacement, the Section 7.5 criteria and guidelines should be 

the goal for improvement but not necessarily the required design threshold. Fish passage 

through existing non-embedded culverts may be improved through the use of gradient 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

control weirs downstream of the culvert, interior baffles or weirs, or, in some cases, fish 

ladders. However, these measures are not a substitute for good fish passage design for 

new or replacement culverts. The following guidelines should be used: 

7.6.2.1 Hydraulic Controls: Hydraulic controls in the channel upstream and/or 

downstream of a culvert may be used to provide a continuous low flow path 

through the culvert and stream reach. They may be used to facilitate fish passage 

by accomplishing adequate depth and water velocity within the culvert, to 

concentrate low flows, to provide resting pools upstream and downstream of the 

culvert, and to prevent erosion of bed and banks. 

7.6.2.2 Approach Pool: An approach pool should be provided that is at least 1.5 

times the stream depth, or a minimum of 2 feet deep, which ever is deeper. 

7.6.2.3 Baffles: Baffles may provide incremental fish passage improvement in 

culverts (if the culvert has excess hydraulic capacity) that cannot be made 

passable by other means. However, baffles may increase the potential for 

clogging and debris accumulation within the culvert and require special design 

considerations specific to the baffle type. Culverts that are too long or too high in 

gradient require resting pools, or other forms of velocity refuge spaced at 

increments along the culvert length. Baffle installations must only be installed 

after approval by NMFS engineers on a site-specific basis, and generally only for 

interim use until a permanent passage solution is employed. A suitable inspection 

and maintenance plan must be provided (i.e., inspected prior to each passage 

season and after any flood event greater than a 2-year exceedence flow, with 

subsequent debris removal as needed). The baffle design configuration must 

demonstrate that it can provide successful fish passage over the range of fish 

passage design flows. If an inspection and maintenance plan is implemented and 

successful, and good fish passage is documented, baffles may be approved for 

permanent installation. 

7.6.2.4 Fishways (see Section 4 and Section 10): Fishways may be required for 

some situations where excessive drops occur at the culvert outlet, or for some 

steep stream gradient situations, or to maintain channel integrity if an undersized 

culvert has been removed. Fishways require specialized site-specific design for 

each installation and as such, a NMFS fish passage specialist must be contacted 

prior to ESA consultation. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.7 Miscellaneous Culverts/Road Crossings 

7.7.1 Specific Criteria and Guidelines – Miscellaneous Culverts/Road Crossings 

7.7.1.1 Trash Racks: Trash racks should not be used near the culvert inlet. 

Accumulated debris may lead to severely restricted fish passage and potential 

injuries to fish. Where trash racks cannot be avoided in culvert installations, they 

must only be installed above the water surface indicated by bankfull flow. A 

minimum of 9 inches clear spacing should be provided between trashrack vertical 

members. If trash racks are used, a long term maintenance plan must be provided 

along with the design, to allow for timely clearing of debris. 

7.7.1.2 Livestock Fences: Livestock fences should not be used across the culvert 

inlet. Accumulated debris may lead to severely restricted fish passage and 

potential injuries to fish. Where fencing cannot be avoided, it should be removed 

during adult salmon upstream migration periods. Otherwise, a minimum of 9 

inches clear spacing should be provided between pickets, up to the high flow 

water surface. If fencing is used, a long term maintenance plan must be provided 

along with the design, to allow for timely clearing of debris. Cattle fences that 

rise with increasing flow are highly recommended.

7.7.1.3 Lighting: Natural or artificial supplemental lighting should be considered 

in new or replacement culverts that are over 150 feet in length. Where 

supplemental lighting is required, the spacing between light sources should not 

exceed 75 feet. Available research results indicate that different species of 

anadromous salmonids respond differently to lighting conditions (COE 1976), and 

NMFS engineering staff should be specifically contacted if a culvert greater than 

150 feet in length is under consideration. 

7.7.1.4 In-Stream Work Windows: NMFS and State Fish and Wildlife officials 

commonly set instream work windows in each watershed. Work in the active 

stream channel must not be performed outside of the instream work windows. 

7.7.1.5 Temporary Crossings: Temporary crossings, placed in salmonid streams 

for water diversion during construction activities, must meet all of the guidelines 

in this document. However, if it can be shown that the location of a temporary 

crossing in the stream network is not a fish passage concern at the time of the 

project, then the construction activity only needs to minimize erosion, sediment 

delivery, and impact to surrounding riparian vegetation. 

7.7.1.6 Installation: Culverts must be installed only in a dewatered site, with a 

sediment control and flow routing plan acceptable to NMFS. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.7.1.7 Riparian Restoration: The work area must be fully restored upon 

completion of construction with a mix of native, locally adapted, riparian 

vegetation. Use of species that grow extensive root networks quickly should be 

emphasized. Sterile, non-native hybrids may be used for erosion control in the 

short term if planted in conjunction with native species. 

7.7.1.8 Construction Disturbances: Construction disturbance to the riparian 

area must be minimized and the activity must not adversely impact fish migration 

or spawning. 

7.7.1.9 Presence of Salmonids: If salmonid are likely to be present, salvage 

operations must be conducted by qualified personnel prior to construction. If 

these salmonids are listed as threatened or endangered under the ESA, consult 

directly with NMFS biologists to acquire an ESA take permit to gain 

authorization for these activities. Care should be taken to ensure salmonids are 

not chased under banks or logs that will be removed or dislocated by construction. 

Any stranded salmonids are to be returned to a suitable location in a nearby live 

stream, and as specified in the ESA take permit, if applicable. 

7.7.1.10 Pumps: If pumps are used to temporarily divert a stream (to facilitate 

construction), an acceptable fish screen (see Section 11) must be used to prevent 

entrainment or impingement of small fish. At no time must construction or 

construction staging activity disrupt continuous streamflow downstream of the 

construction site. 

7.7.1.11 Wastewater: Unacceptable wastewater associated with project activities 

must be disposed of off-site in a location that will not drain directly into any 

stream channel. 

7.7.1.12 Flood Capacity: Regardless of the design option used, to minimize the 

risk of the environmental consequences of structural failure, all road crossings 

must be designed to withstand the 100-year peak flood flow, including 

consideration of debris loading likely to be encountered during flooding. Stream 

crossings or culverts located in areas where there is significant risk of inlet 

plugging by flood-borne debris should be designed to pass the 100-year peak 

flood without exceeding the top of the culvert inlet (headwater-to-diameter ratio is 

less than one). This is to ensure a low risk of channel degradation, stream 

diversion, and failure over the life span of the crossing. Hydraulic capacity must 

compensate for expected deposition in the culvert bottom. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

7.7.1.13 Other Hydraulic Considerations: Besides the upper and lower flow 

limit, other hydraulic effects need to be considered, particularly when installing a 

culvert. Water surface elevations in the stream reach must exhibit gradual flow 

transitions, both upstream and downstream of the road crossing. 

Within the culvert, abrupt changes in water surface and velocity, hydraulic jumps, 

turbulence, and drawdown at the upstream flow entrance must be avoided in 

design. A continuous low flow channel must be maintained during construction 

throughout the entire stream reach affected by the road crossing construction. In 

addition, especially in retrofits, hydraulic controls may be necessary to provide 

resting pools, concentrate low flows, prevent erosion of stream bed or banks, and 

allow passage of bedload material. Hydraulic control devices may be required to 

avoid headcutting. Culverts and other structures should be aligned with the 

stream, with no abrupt changes in flow direction upstream or downstream of the 

crossing. This can often be accommodated by changes in road alignment or slight 

elongation or enlargement of the culvert. Where elongation would be excessive, 

this must be weighed against better crossing alignment and/or modified transition 

sections upstream and downstream of the crossing. In crossings that are 

unusually long compared to streambed width, natural sinuosity of the stream will 

be lost and sediment transport problems may occur even if the slopes remain 

constant. Such problems should be anticipated and mitigated in the project 

design. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

8. TIDE GATES (WORK IN PROGRESS) 

Design standards for fish passage through tide gates are in the developmental stage. If 

you are interested in the current status, please call Larry Swenson at 503-230-5448.

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

9. COLUMBIA AND SNAKE RIVER FISH PASSAGE FACILITIES 

9.1 Introduction – Columbia and Snake River Fish Passage Facilities 

The following criteria and guidelines are specially adapted to Columbia and Snake River 

upstream and downstream fish passage facilities. The guidelines and criteria in this 

section apply at mainstem hydroelectric projects. This section is intended as a starting 

point for future fish passage facilities designs, and is based on experience at COE 

mainstem hydroelectric dams on the Lower Columbia and Snake Rivers. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. 

9.2 Mainstem Upstream Passage 

9.2.1 Description and Purpose – Mainstem Upstream Passage 

Each mainstem fish ladder system is designed with a specific number (and location) of 

primary entrances (typically at each shore, and at the powerhouse/spillway interface), a 

defined hydraulic capacity, and specific operations of auxiliary water, entrance, and exit 

facilities. For a number of reasons, ladder entrance operations may evolve and not be 

consistent with that envisioned in the design phase. Ladder entrances are perhaps the 

most important feature of the adult fish ladder system. If entrances are improperly 

located or designed, excessive upstream fish passage delay may occur. While this 

document primarily focuses on design criteria and guidelines, operations of fish passage 

facilities are a vital and overlapping link. The criteria and guidelines in this sub-section 

are intended to reinforce what NMFS believes are appropriate ladder entrance operations. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

9.2.2 Specific Criteria and Guidelines – Mainstem Upstream Passage 

9.2.2.1 Attraction Flows: Total attraction flow discharged from adult fishway

entrances should be either a minimum of 3% of mean annual river flow, or the 

attraction flow approved in the original design memorandum phase prior to 

construction. Total ladder attraction flow and entrance location are important 

design parameters to assure safe, efficient, and timely upstream passage. 

 

Unless approved by NMFS, adult ladder total entrance attraction flow (gravity 

ladder flow from forebay, plus auxiliary water flow) must not be reduced from 

original design levels. 

9.2.2.2 Ladder Entrances: Unless specifically stated in the original design, all 

ladder entrances must be designed to be operated continuously during fish 

passage season in accordance with ladder entrance attraction flow criteria listed 

below. 

9.2.2.3 Auxiliary Water Systems: Auxiliary water systems must include 

sufficient back-up hydraulic capacity to ensure continued operation consistent 

with design criteria. 

9.2.2.4 Ladder Entrance Attraction Flow Criteria: Adjustable weir gate crest 

elevations at primary entrances must be submerged at a minimum depth of 8 feet 

(relative to tailwater water surface elevation), with a head differential of 1.0 to 2.0 

feet. These two parameters have evolved to become the standard for determining 

whether mainstem hydro project fish ladder entrances are discharging at, or 

above, the minimum satisfactory ladder attraction flow. However, if this criteria 

cannot be satisfied at one or more ladder entrances (as is the case at some 

mainstem hydro projects), an hydraulic investigation should be initiated to 

determine whether some entrances are discharging excessive attraction flow, 

while others fail to satisfy minimum attraction flow criteria. In these cases, it 

should be determined whether different ladder entrance combinations of head 

differential and weir submergence can be implemented to provide the minimum 

equivalent attraction flow (e.g., provided by 8-foot weir submergence and 1 foot 

of entrance head) at each ladder entrance. For instance, if the weir depth at one 

entrance is reduced by 25% and the differential is increased to remain within 

criterion listed above, the equivalent attraction flow can still be provided. 

Analysis findings should be coordinated with all parties before implementation. 

All other ladder design and operational features must comply with Section 4. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

9.3 Mainstem Juvenile Screen and Bypass 

9.3.1 Description and Purpose – Mainstem Juvenile Screen and Bypass 

Turbine intake screens and vertical barrier screens at mainstem Columbia and Snake 

River hydroelectric dams are an exception to design criteria for conventional screens 

referenced in Section 11. Turbine intake screens are considered partial screens, because 

they do not screen the entire turbine discharge. They are high-velocity screens, meaning 

approach velocities are much higher than allowed for conventional screens. Turbine 

intake screens were retrofitted at many mainstem Columbia and Snake River 

powerhouses (which cannot be feasibly screened using conventional screen criteria) to 

protect fish from turbine entrainment to the extent possible. 

9.3.2 Specific Criteria and Guidelines – Mainstem Juvenile Screen and Bypass 

Dewatering screen systems must adhere to the criteria and guidelines provided in Section 

11. The following turbine intake screen and vertical barrier screen design criteria are the 

product of extensive research and development: 

 

9.3.2.1 Turbine Intake Screens : 

• Dimensions/Orientation: Existing intake screens are either 20 or 40 feet 

long and are located in the bulkhead slot of each turbine. They are 

lowered into the intake, and then rotated to the correct operating 

inclination. 

• Materials: The turbine intake screen face must be stainless steel bar 

screen, with maximum clearance between bars equal to1.75 mm. 

• Cleaning: The turbine intake screen must have an approved and proven 

screen cleaning device, which may be adjusted for desired cleaning 

frequency. 

• Porosity: Turbine intake screen porosity must be determined on the basis 

of physical hydraulic modeling 

9.3.2.2 Maximum Approach Velocity: Maximum approach velocity (normal to 

the screen face) for turbine intake screens must be 2.75 ft/s. Above this velocity 

threshold, injury rates increase. 

9.3.2.3 Stagnation Point: The stagnation point (point where the component of 

velocity along the turbine intake screen face is 0 ft/s) must be at a location where 

the submerged screen intercepts between 40% to 43% of turbine intake flow, and 

must be within 5 feet of the leading edge of the screen. 

9.3.2.5 Gatewell Flow: Gatewell flow must be approximately 10% of intercept 

flow (which is flow above the intake screen stagnation point), and approximately 

4% of turbine flow. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

9.4 Vertical Barrier Screens 

9.4.1 Description and Purpose – Vertical Barrier Screens 

Vertical barrier screens (VBS) pass nearly all flow entering the gatewell from the intake 

screen and intake ceiling apex zone. Fish pass upward along the VBS, then accumulate 

in the upper gatewell, near an orifice that is designed to pass them safely into the juvenile 

bypass system. 

9.4.2 Specific Criteria and Guidelines – Vertical Barrier Screens 

9.4.2.1 Velocity Distribution: 

• Hydraulic modeling must be used to ensure the greatest possible uniform 

velocity distribution across the entire VBS. Note that this criterion 

assumes that operating gate position has a significant influence over VBS 

velocity flow distribution, and is one of the design issues to be reconciled 

through use of the physical model. 

• Variable-porosity stacked panels must be developed through physical 

hydraulic modeling, to achieve uniform velocity distribution and minimize 

turbulence in the upper gatewell. 

9.4.2.2 Materials and Orientation: Where gatewell flow is increased by a flow 

vane at the gatewell entrance, VBS should be constructed of stainless steel bar 

screens with bars oriented horizontally, and a maximum clearance between bars 

of 1.75 mm. 

9.4.2.3 Cleaning/Debris Removal: A screen cleaner and debris removal system 

must be features of each VBS with a gatewell flow increaser vane. Horizontal 

orientation of the screen bars facilitates debris removal. 

9.4.2.4 Through-Screen Velocity: Average VBS through-screen velocity must 

be a maximum of 1.0 ft/s, unless field testing is conducted to prove sufficiently 

low fish descaling/injury rates at a specific site. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

10. UPSTREAM JUVENILE FISH PASSAGE 

10.1 Introduction – Upstream Juvenile Fish Passage 

Upstream juvenile fish passage is necessary at some passage sites, where inadequate 

conditions exist downstream for rearing fish. In a ladder that uses only a portion of the 

river flow for upstream fish passage, juvenile passage may require special and separate 

provisions from those designed to optimize adult passage. However, adult fish passage 

should never be compromised to accommodate juvenile passage. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

10.2 Design – Upstream Juvenile Fish Passage 

As discussed in Section 4.2, it is recommended that a 1.0 to 1.5 foot hydraulic drop from 

entrance pool to tailwater is used for fishway entrance design. Attraction of adult 

salmonids to a fishway entrance is compromised with decreased head drop at a fishway

entrance, unless all of the streamflow is passed through the entrance. Fishway attraction 

(i.e., fishes’ ability to locate the fishway entrance downstream of the dam) is the critical 

design parameter for an upstream passage facility. Previously, many of the fishway

entrances on the Columbia River operated with 0.5 foot of hydraulic drop (measured 

from the entrance pool water surface to tailwater surface). After extensive laboratory and 

field studies, it was conclusively determined that higher velocities, which directly relate 

to the amount of hydraulic drop through the entrance, provide better attraction of adult 

salmonids than did lower velocities. This determination resulted in making hydraulic 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

adjustments to fishway entrances so that they operated with 1.0 to 1.5 feet of hydraulic 

drop, instead of 0.5 feet. Subsequent radio telemetry studies verified that passage times 

decreased as a result. Thus, there is a clear basis for designing entrance pool to tailwater

differentials between 1.0 to 1.5 feet for adult salmonid passage. 

Within the Northwest Region of NMFS (which includes the states of Washington, 

Oregon, and Idaho), there are varying requirements for juvenile passage. NMFS will 

consider the appropriate design requirements as applicable. Lower required hydraulic 

drop between pools is not going to provide an obstacle to adult fish, provided that the 

facility satisfies entrance design requirements of Section 4.2. When juvenile fish passage 

is required, the fishway must be designed to operate with a maximum 0.5 feet of 

hydraulic drop, and should meet the guidelines listed in Table 10-1. However, the 

fishway entrance must operate per the guidelines and criteria listed in Section 4.4 when 

adult salmonids are present. 

10.2.1 General Criteria and Guidelines – Upstream Juvenile Passage 

Given the reported swimming speeds for juvenile coho salmon and observed leaping 

capabilities, submerged ports or pipes should be avoided when designing passage 

facilities for juvenile fish, except for inlet and outlet conditions. Fishways should be 

designed as pool and chute or roughened channel, with drops not to exceed the criteria 

listed in Table 10.1. In addition to the hydraulic drop, calm water in the pools and a low 

velocity just upstream of the weir crest is important. Weirs should be designed as sharp 

crested, where the head over the weir is two times the breadth. 

Table 10-1. Juvenile Upstream Fish Passage Guidelines 

Upstream Juvenile Fish Passage Guidelines 

Fish Size 

(mm) 

Maximum hydraulic drop 

over fishway weir (ft) 

Maximum hydraulic 

drop at fishway 

entrance and exit (ft) 

Velocity for swimming 

distances less 

than 1 foot, (ft/s) 

45 to 65 0.7 0.13 1.5 to 2.5 

80 to 100 1 0.33 3 to 4.5 

Powers (1993) indicated that pool volume criteria such as described in Section 4.5.3.5 are 

critical to ensuring appropriate passage conditions. The pool volume criteria described in 

Section 4.5.3.5 defines a maximum turbulence threshold based on energy dissipation 

within the volume of a fishway pool. If this threshold is exceeded, a turbulent barrier to 

adult fish may be created. For optimal juvenile fish passage, this pool volume should be 

doubled. 

Hydraulic design for juvenile upstream passage should be based on representative flows 

in which juveniles typically migrate. Recent research indicates that providing for 

juvenile salmon passage up to the 10% annual exceedence flow may cover the majority 

of flows in which juveniles have been observed moving upstream. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

In some situations, it may be feasible to operate a ladder entrance with a decreased 

hydraulic drop at times when adult salmon are not present and at 1 to 1.5 feet during the 

adult salmon upstream migration. The feasibility of doing this often entails making a 

judgment call on the timing of adult passage when often little or no information is 

available, and if it is available, it may change from year to year. In other situations, it 

may be appropriate to provide multiple fishway entrances that operate independently, 

according to the desired hydraulic drop. One entrance may operate to attract adult fish 

and convey the appropriate volume shape of attraction jet and velocities and another 

entrance may operate at a lower differential and convey flow over a weir. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11. FISH SCREEN AND BYPASS FACILITIES 

11.1 Introduction – Fish Screen and Bypass Facilities 

This section provides criteria and guidelines to be used in the development of designs of 

downstream migrant fish screen facilities for hydroelectric, irrigation, and other water 

withdrawal projects. The design guidance provided in this section applies to fishway

designs after a decision to provide a passage facility has been made. Unless directly 

specified herein, this guidance is not intended for use in evaluation of existing facilities, 

nor does it provide guidance on the application of the design for any particular site. 

Sections 1, 2, 3, and the Foreword of this document also apply to the guidelines and 

criteria listed in this section. 

In designing an effective fish screen facility, the swimming ability of the fish is a primary 

consideration. Research has shown that swimming ability of fish varies and may depend 

upon a number of factors relating to the physiology of the fish, including species, size, 

duration of swimming time required, behavioral aspects, migrational stage, physical 

condition and others, in addition to water quality parameters such as dissolved oxygen 

concentrations, water temperature, lighting conditions, and others. For this reason, screen 

criteria must be expressed in general terms. 

Several categories of screen designs are in use but are still considered as experimental 

technology by NMFS. These include Eicher screens, modular inclined screens, coanda 

screens, and horizontal screens. The process to evaluate experimental technology is 

described in Section 16. Several of these experimental screen types have completed part 

or all of the experimental technology process, and may be used in specific instances when 

site conditions allow. Design of these screens, or new conceptual types of experimental 

screens, may be developed through discussions with NMFS engineers on a case-by-case 

basis. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

11.2 Functional Screen Design 

A functional screen design should be developed that defines type, location, size, 

hydraulic capacity, method of operation, and other pertinent juvenile fish screen facility 

characteristics. In the case of applications to be submitted to FERC and for consultations 

under the ESA, a functional design for juvenile (and adult) fish passage facilities must be 

developed and submitted as part of the FERC License Application or as part of the 

Biological Assessment for the facility. It must reflect NMFS input and design criteria 

and be acceptable to NMFS. Functional design drawings must show all pertinent 

hydraulic information, including water surface elevations and flows through various areas 

of the structures. Functional design drawings must show general structural sizes, crosssectional shapes, and elevations. Types of materials must be identified where they may 

directly affect fish. The final detailed design must be based on the functional design, 

unless changes are agreed to by NMFS. 

11.3 Site Conditions 

To minimize risks to anadromous fish at some locations, NMFS may require 

investigation (by the project sponsors) of important and poorly defined site-specific 

variables that are deemed critical to development of the screen and bypass design. This 

investigation may include factors such as fish behavioral response to hydraulic 

conditions, weather conditions (ice, wind, flooding, etc.), river stage/flow relationships, 

seasonal operational variability, potential for sediment and debris problems, resident fish 

populations, potential for creating predation opportunity, and other information. The life 

stage and size of juvenile salmonids present at a potential screen site usually is not 

known, and may change from year to year based on flow and temperature conditions. 

Thus, adequate data to describe the size-time relationship requires substantial sampling 

efforts over a number of years. For the purpose of designing juvenile fish screens, NMFS 

will assume that fry-sized salmonids and low water temperatures are present at all sites 

and apply the appropriate criteria listed below, unless adequate biological investigation 

proves otherwise. The burden-of-proof is the responsibility of the owner of the diversion 

facility. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.4 Existing Screens 

11.4.1 Acceptance Criteria and Guidelines for Existing Screens 

If a fish screen was constructed prior the establishment of these criteria, but constructed 

to NMFS criteria established August 21, 1989, or later, approval of these screens may be 

considered providing that all six of the following conditions are met: 

11.4.1.1 The entire screen facility must function as designed. 

11.4.1.2 The entire screen facility has been maintained and is in good working 

condition. 

11.4.1.3 When the screen material wears out, it must be replaced with screen 

material meeting the current criterion stated in this document. To comply with 

this condition, structural modifications may be required to retrofit an existing 

facility with new screen material. 

11.4.1.4 No mortality, injury, entrainment, impingement, migrational delay, or 

other harm to anadromous fish has been noted that is being caused by the facility; 

11.4.1.5 No emergent fry are likely to be located in the vicinity of the screen, as 

agreed to by NMFS biologists familiar with the site. 

11.4.1.6 When biological uncertainty exists, access to the diversion site by 

NMFS is permitted by the diverter for verification of the above criteria. 

11.5 Structure Placement 

11.5.1 Specific Criteria and Guidelines – Structure Placement: Streams and 

Rivers 

11.5.1.1 Instream Installation: Where physically practical and biologically 

desirable, the screen should be constructed at the point of diversion with the 

screen face generally parallel to river flow. However, physical factors may 

preclude screen construction at the diversion entrance. Among these factors are 

excess river gradient, potential for damage by large debris, access for 

maintenance, operation and repair, and potential for heavy sedimentation. For 

screens constructed at the bankline, the screen face must be aligned with the 

adjacent bankline and the bankline must be shaped to smoothly match the face of 

the screen structure to minimize turbulence and eddying in front, upstream, and 

downstream of the screen. Adverse alterations to riverine habitat must be 

minimized. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.5.1.2 Canal Installation: Where installation of fish screens at the diversion 

entrance is not desirable or impractical, the screens may be installed in the canal 

downstream of the entrance at a suitable location. All screens installed 

downstream from the diversion entrance must be provided with an effective 

bypass system, as described in Sections 11.9 through 11.12, designed to collect 

and transport fish safely back to the river with minimum delay. The screen 

location must be chosen to minimize the effects of the diversion on instream 

flows by placing the bypass outfall as close as biologically feasible (i.e., 

considering minimizing length and optimizing the hydraulics of the bypass pipe) 

and practically feasible to the point of diversion. 

11.5.1.3 Functionality: All screen facilities must be designed to function 

properly through the full range of stream hydraulic conditions as defined in 

Section 3 and in the diversion conveyance, and must account for debris and 

sedimentation conditions which may occur. 

11.5.2 Specific Criteria and Guidelines – Structure Placement: Lakes, 

Reservoirs, and Tidal Areas 

11.5.2.1 Intake Locations: Intakes must be located offshore where feasible to 

minimize fish contact with the facility. When possible, intakes must be located in 

areas with sufficient ambient velocity to minimize sediment accumulation in or 

around the screen and to facilitate debris removal and fish movement away from 

the screen face. Intakes in reservoirs should be as deep as practical, to reduce the 

numbers of juvenile salmonids that encounter the intake. 

11.5.2.2 Surface Outlets: If a reservoir outlet is used to pass fish from a 

reservoir, the intake must be designed to withdraw water from the most 

appropriate elevation based on providing the best juvenile fish attraction and 

appropriate water temperature control downstream of the project. The entire 

range of forebay fluctuation must be accommodated in design. Since surface 

outlet designs must consider a wide spectrum of site-specific hydraulic and fish 

behavioral conditions, NMFS engineers and biologists must be involved in 

developing an acceptable conceptual design for any surface outlet fish passage 

system before the design proceeds. 

11.6 Screen Hydraulics – Rotating Drum Screens, Vertical Screens, and Inclined 

Screens 

11.6.1 Specific Criteria and Guidelines – Screen Hydraulics 

11.6.1.1 Approach Velocity: The approach velocity must not exceed 0.40 ft/s 

for active screens, or 0.20 ft/s for passive screens. Using these approach 

velocities will minimize screen contact and/or impingement of juvenile fish. For 

screen design, approach velocity is calculated by dividing the maximum screened 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

flow amount by the vertical projection of the effective screen area. An exception 

may be made to this definition of approach velocity for screen where a clear 

egress route minimizes the potential for impingement. If this exception is 

approved be NMFS, the approach velocity is calculated using the entire effective 

screen area, and not a vertical projection. For measurement of approach velocity, 

see Section 15.2. 

11.6.1.2 Effective Screen Area: The minimum effective screen area must be 

calculated by dividing the maximum screened flow by the allowable approach 

velocity. 

11.6.1.3 Submergence: For rotating drum screens, the design submergence must 

not exceed 85%, nor be less than 65% of drum diameter. Submergence over 85% 

of the screen diameter increases the possibility of entrainment over the top of the 

screen (if entirely submerged), and increases the chance for impingement with 

subsequent entrainment if fish are caught in the narrow wedge of water above the 

85% submergence mark. Submerging rotating drum screens less than 65% may 

reduce the self-cleaning capability of the screen. In many cases, stop logs may be 

installed downstream of the screens to achieve proper submergence. If stop logs 

are used, they should be located at least two drum diameters downstream of the 

back of the drum. 

11.6.1.4 Flow Distribution: The screen design must provide for nearly uniform 

flow distribution (see Section 15.2) over the screen surface, thereby minimizing 

approach velocity over the entire screen face. The screen designer must show 

how uniform flow distribution is to be achieved. Providing adjustable porosity

control on the downstream side of screens, and/or flow training walls may be 

required. Large facilities may require hydraulic modeling to identify and correct 

areas of concern. Uniform flow distribution avoids localized areas of high 

velocity, which have the potential to impinge fish. 

11.6.1.5 Screens Longer Than Six Feet: 

• Screens longer than 6 feet must be angled and must have sweeping 

velocity greater than the approach velocity. This angle may be dictated by 

site-specific geometry, hydraulic, and sediment conditions. Optimally, 

sweeping velocity should be at least 0.8 ft/s and less than 3 ft/s. 

• For screens longer than 6 feet, sweeping velocity must not decrease along 

the length of the screen. 

11.6.1.6 Inclined Screen Face: An inclined screen face must be oriented less 

than 45° vertically with the screen length (upstream to downstream) oriented 

parallel to flow, unless the inclined screen is placed in line with riverbank and 

reasonably matching the slope of the riverbank. 

11.6.1.7 Horizontal Screens: Horizontal screens have been evaluated as an 

experimental technology, and may only be considered if the majority of flow 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

passes over the end of the screen at a minimum depth of 1 foot, and positive 

downstream sweeping velocity in excess of the approach velocity exists for the 

entire length of screen. Post construction monitoring of the facility must occur. 

Since site-specific design conditions are required, NMFS engineers must be 

consulted throughout the development and evaluation of the design. 

11.7 Screen Material 

11.7.1 Specific Criteria and Guidelines – Screen Material 

11.7.1.1 Circular Screens: Circular screen face openings must not exceed 3/32

inch in diameter. Perforated plate must be smooth to the touch with openings 

punched through in the direction of approaching flow. 

11.7.1.2 Slotted Screens: Slotted screen face openings must not exceed 1.75 mm 

(approximately 1

/16 inch) in the narrow direction. 

11.7.1.3 Square Screens: Square screen face openings must not exceed 3/32 inch 

on a diagonal. 

11.7.1.4 Material: The screen material must be corrosion resistant and 

sufficiently durable to maintain a smooth uniform surface with long term use. 

11.7.1.5 Other Components: Other components of the screen facility (such as 

seals) must not include gaps greater than the maximum screen opening defined 

above. 

11.7.1.6 Open Area: The percent open area for any screen material must be at 

least 27%. 

11.8 Civil Works and Structural Features 

11.8.1 Specific Criteria and Guidelines – Civil Works and Structural Features 

11.8.1.1 Placement of Screen Surfaces: The face of all screen surfaces must be 

placed flush (to the extent possible) with any adjacent screen bay, pier noses, and 

walls to allow fish unimpeded movement parallel to the screen face and ready 

access to bypass routes. 

11.8.1.2 Structural Features: Structural features must be provided to protect 

the integrity of the fish screens from large debris, and to protect the facility from 

damage if overtopped by flood flows. A trash rack, log boom, sediment sluice, 

and other measures may be required. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.8.1.3 Civil Works: The civil works must be designed in a manner that 

prevents undesirable hydraulic effects (such as eddies and stagnant flow zones) 

that may delay or injure fish or provide predator habitat or predator access. 

11.9 Bypass Facilities 

11.9.1 Specific Criteria and Guidelines – Bypass Layout 

11.9.1.1 Bypass Location: 

• The screen and bypass must work in tandem to move out-migrating 

salmonids (including downstream migrant adult salmonids such as 

steelhead kelts, if present) to the bypass outfall with a minimum of injury 

or delay. 

• The bypass entrance must be located so that it may easily be located by 

out-migrants. 

• The bypass entrance and all components of the bypass system must be of 

sufficient size and hydraulic capacity to minimize the potential for debris 

blockage. 

• Screens greater than or equal to 6 feet in length must be constructed with 

the downstream end of the screen terminating at a bypass entrance. 

Screens less than or equal to 6 feet in length may be constructed 

perpendicular to flow with a bypass entrance at either or both ends of the 

screen, or may be constructed at an angle to flow, with the downstream 

end terminating at the bypass entrance. 

• Some screen systems do not require a bypass system. For example, an end 

of pipe screen located in a river, lake, or reservoir does not require a 

bypass system because fish are not removed from their habitat. A second 

example is a river bank screen with sufficient hydraulic conditions to 

move fish past the screen face. 

11.9.1.2 Multiple Entrances: Multiple bypass entrances should be used if the 

sweeping velocity may not move fish to the bypass within 60 seconds, assuming 

fish are transported along the length of the screen face at a rate equaling sweeping 

velocity. 

11.9.1.3 Training Wall: A training wall must be located at an angle to the screen 

face, with the bypass entrance at the apex and downstream-most point. For many 

facilities, the wall of the civil works opposite to the screen face may serve as a 

training wall. For single or multiple vee screen configurations, training walls are 

not required, unless an intermediate bypass must be used. 

11.9.1.4 Secondary Screen: In cases where there is insufficient flow available to 

satisfy hydraulic requirements at the bypass entrance for the primary screens, a 

secondary screen may be required within the primary bypass. The secondary 

bypass flow conveys fish to the bypass outfall location or other destination, and 

returns secondary screened flow for water use. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.9.1.5 Bypass Access: Access for inspection and debris removal must be 

provided at locations in the bypass system where debris accumulations may occur. 

11.9.1.6 Trash Racks: If trash racks are used, sufficient hydraulic gradient must 

be provided to route juvenile fish from between the trash rack and screens to the 

bypass. 

11.9.1.7 Canal Dewatering: The floor of the screen civil works must be 

designed to allow fish to be routed back to the river safely when the canal is 

dewatered. This may entail using a small gate and drain pipe, or similar 

provisions, to drain all flow and fish back to the river. If this cannot be 

accomplished, an acceptable fish salvage plan must be developed in consultation 

with NMFS and included in the operation and maintenance plan. 

11.9.1.8 Bypass Channel Velocity: To ensure that fish move quickly through the 

bypass channel (i.e., the conveyance from the terminus of the screen to the bypass 

pipe), the rate of increase in velocity between any two points in the bypass 

channel should not decrease and should not exceed 0.2 ft/s per foot of travel. 

11.9.1.9 Natural Channels: Natural channels may be used as a bypass upon 

approval by NMFS engineers. A consideration for utilizing natural channels as a 

bypass is the provision of off-stream habitat. Requirements for natural channels 

include adequate depth and velocity, sufficient flow volume, protection from 

predation, and good water quality. 

11.9.2 Specific Criteria and Guidelines – Bypass Entrance 

11.9.2.1 Flow Control: Each bypass entrance must be provided with independent 

flow-control capability. 

 

11.9.2.2. Minimum Velocity: The minimum bypass entrance flow velocity 

should be greater than 110% of the maximum canal velocity upstream of the 

bypass entrance. At no point must flow decelerate along the screen face or in the 

bypass channel. Bypass flow amounts should be of sufficient quantity to ensure 

these hydraulic conditions are achieved for all operations throughout the smolt

out-migration period. 

11.9.2.3 Lighting: Ambient lighting conditions must be included upstream of the 

bypass entrance and should extend to the bypass flow control device. Where 

lighting transitions cannot be avoided, they should be gradual, or should occur at 

a point in the bypass system where fish cannot escape the bypass and return to the 

canal (i.e., when bypass velocity exceeds swimming ability). 

11.9.2.4 Dimensions: For diversions greater than 3 cfs, the bypass entrance must 

extend from the floor to the canal water surface, and should be a minimum of 18 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

inches wide. For diversions of 3 cfs or less, the bypass entrance must be a 

minimum of 12 inches wide. In any case, the bypass entrance must be sized to 

accommodate the entire range of bypass flow, utilizing the criteria and guidelines 

listed throughout Section 11.9. 

11.9.2.5 Weirs: For diversions greater than 25 cfs, weirs used in bypass systems 

should maintain a weir depth of at least 1 foot throughout the smolt out-migration 

period. 

11.9.3 Specific Criteria and Guidelines – Bypass Conduit and System Design 

11.9.3.1 General: Bypass pipes and joints must have smooth surfaces to provide 

conditions that minimize turbulence, the risk of catching debris, and the potential 

for fish injury. Pipe joints may be subject to inspection and approval by NMFS 

prior to implementation of the bypass. Every effort should be made to minimize 

the length of the bypass pipe, while maintaining hydraulic criteria listed below. 

11.9.3.2 Bypass Flow Transitions: Fish should not be pumped within the bypass 

system. Fish must not be allowed to free-fall within a pipe or other enclosed 

conduit in a bypass system. Downwells must be designed with a free water 

surface, and designed for safe and timely fish passage by proper consideration of 

turbulence, geometry, and alignment. 

 

11.9.3.3 Flows and Pressure: In general, bypass flows in any type of 

conveyance structure should be open channel. If required by site conditions, 

pressures in the bypass pipe must be equal to or above atmospheric pressures. 

Pressurized to non-pressurized (or vice-versa) transitions should be avoided 

within the pipe. Bypass pipes must be designed to allow trapped air to escape. 

11.9.3.4 Bends: Bends should be avoided in the layout of bypass pipes due to the 

potential for debris clogging and turbulence. The ratio of bypass pipe center-line 

radius of curvature to pipe diameter (R/D) must be greater than or equal to 5. 

Greater R/D may be required for super-critical velocities (see Section 11.9.3.8). 

11.9.3.5 Access: Bypass pipes or open channels must be designed to minimize 

debris clogging and sediment deposition and to facilitate inspection and cleaning 

as necessary. Long bypass designs (eg. greater than 150 feet) may include access 

ports provided at appropriate spacing to allow for detection and removal of debris. 

Alternate means of providing for bypass pipe inspection and debris removal may 

be acceptable as well. 

11.9.3.6 Diameter/Geometry: The bypass pipe diameter or open channel bypass 

geometry should generally be a function of the bypass flow and slope, and should 

be chosen based on achieving the velocity and depth criteria in Sections 11.9.3.8 

and 11.9.3.9. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Table 11-1 provides examples for selecting the diameter of a bypass pipe based 

on diverted flow amount, assuming 1) bypass pipe slope of 1.3%; 2) Manning’s 

roughness of 0.009; and 3) other bypass pipe criteria (Section 11.9) are met. 

Bypass pipe hydraulics should be calculated for a given design to determine a 

suitable pipe diameter if the design deviates from the assumptions used to 

calculate pipe diameters in Table 11-1. 

 

Table 11-1. Bypass Design Examples 

Diverted Flow 

(cfs) 

Bypass flow

(cfs) 

Bypass Pipe 

Diameter (in) 

Bypass flow

Depth (in) 

< 6 5% of diverted flow 10 2 1⁄2 

6 - 25 5% of diverted flow 10 4 

40 2.00 12 4 3⁄4 

75 3.75 15 6 

125 6.25 18 7 1⁄4 

175 8.75 21 8 1⁄2 

250 12.5 24 9 1⁄2 

500 25.0 30 12 

750 37.5 36 14 

> 1000 design with direct NMFS engineering involvement 

11.9.3.7 Flow: Design bypass flow should be about 5% of the total diverted flow 

amount, unless otherwise approved by NMFS. Regardless of the bypass flow

amount, hydraulic guidelines and criteria in Sections 11.9.3.8 and 11.9.3.9 apply. 

11.9.3.8 Velocity: The design bypass pipe velocity should be between 6 and 12 

ft/s for the entire operational range. If higher velocities are approved, special 

attention to pipe and joint smoothness must be demonstrated by the design. To 

reduce silt and sand accumulation in the bypass pipe, pipe velocity must not be 

less than 2 ft/s. 

11.9.3.9 Depth: The design minimum depth of free surface flow in a bypass pipe 

should be at least 40% of the bypass pipe diameter, unless otherwise approved by 

NMFS. 

11.9.3.10 Closure Valves: Closure valves of any type should not be used within 

the bypass pipe unless specifically approved based on demonstrated fish safety. 

11.9.3.11 Sampling Facilities: Sampling facilities installed in the bypass conduit 

must not in any way impair operation of the facility during non-sampling 

operations. 

11.9.3.12 Hydraulic Jump: There should not be a hydraulic jump within the 

pipe. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.9.3.13 Spillways: Spillways upstream of the screen facility also act as a 

bypass system. These facilities should also be designed to provide a safe passage 

route back to the stream, adhering to the bypass design principles described 

throughout Section 11.9 

11.9.4 Specific Criteria and Guidelines – Bypass Outfall 

11.9.4.1 Location: 

• Bypass outfalls must be located to minimize predation by selecting an 

outfall location free of eddies, reverse flow, or known predator habitat. 

The point of impact for bypass outfalls should be located where ambient 

river velocities are greater than 4.0 ft/s during the smolt out-migration. 

Predator control systems may be required in areas with high avian 

predation potential. Bypass outfalls should be located to provide good 

egress conditions for downstream migrants. 

• Bypass outfalls must be located where the receiving water is of sufficient 

depth (depending on the impact velocity and quantity of bypass flow) to 

ensure that fish injuries are avoided at all river and bypass flows. The 

bypass flow must not impact the river bottom or other physical features at 

any stage of river flow. 

11.9.4.2 Impact Velocity: Maximum bypass outfall impact velocity (i.e., the 

velocity of bypass flow entering the river) including vertical and horizontal 

velocity components should be less than 25.0 ft/s. 

11.9.4.3 Discharge and Attraction of Adult Fish: The bypass outfall discharge 

into the receiving water must be designed to avoid attraction of adult fish thereby 

reducing the potential for jumping injuries and false attraction. The bypass outfall 

design must allow for the potential attraction of adult fish, by provision of a safe 

landing zone if attraction to the outfall flow can potentially occur. 

11.10 Debris Management 

11.10.1 Specific Criteria and Guidelines – Debris Management 

11.10.1.1 Inspection and Maintenance: A reliable, ongoing inspection, 

preventative maintenance, and repair program is necessary to ensure facilities are 

kept free of debris and that screen media, seals, drive units, and other components 

are functioning correctly during the outmigration period. A written plan should 

be completed and submitted for approval with the screen design. 

11.10.1.2 Screen Cleaning (Active Screens): Active screens must be 

automatically cleaned to prevent accumulation of debris. The screen cleaner 

design should allow for complete debris removal at least every 5 minutes, and 

operated as required to prevent accumulation of debris. The head differential to 

trigger screen cleaning for intermittent type cleaning systems must be a maximum 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

of 0.1 feet over clean screen conditions or as agreed to by NMFS. A variable 

timing interval trigger must also be used for intermittent type cleaning systems as 

the primary trigger for a cleaning cycle. The cleaning system and protocol must 

be effective, reliable, and satisfactory to NMFS. 

11.10.1.3 Passive Screens: A passive screen should only be used when all of the 

following criteria are met: 

• The site is not suitable for an active screen, due to adverse site conditions. 

• Uniform approach velocity conditions must exist at the screen face, as 

demonstrated by laboratory analysis or field verification. 

• The debris load must be low. 

• The combined rate of flow at the diversion site must be less than 3 cfs. 

• Sufficient ambient river velocity must exist to carry debris away from the 

screen face. 

• A maintenance program must be approved by NMFS and implemented by 

the water user. 

• The screen must be frequently inspected with debris accumulations 

removed, as site conditions dictate. 

• Sufficient stream depth must exist at the screen site to provide for a water 

column of at least one screen radius around the screen face. 

• The screen must be designed to allow easy removal for maintenance, and 

to protect from flooding. 

11.10.1.4 Intakes: Intakes must include a trash rack in the screen facility design 

which must be kept free of debris. In certain cases, a satisfactory profile bar 

screen design may substitute for a trash rack. Based on biological requirements 

at the screen site, trash rack spacing may be specified that reduces the probability 

of entraining adult fish. 

11.10.1.5 Inspection: The completed screen and bypass facility must be made 

available for inspection by NMFS, to verify that the screen is being operated 

consistent with the design criteria. 

11.10.1.6 Evaluation: At some sites, screen and bypass facilities may be 

evaluated for biological effectiveness and to verify that hydraulic design 

objectives are achieved. At the discretion of NMFS, this may entail a 

complete biological evaluation especially if waivers to screen and bypass 

criteria are granted, or merely a visual inspection of the operation if screen 

and bypass criteria is met in total. 

11.10.1.7 Sediment: Provision must be made to limit the build-up of sediment, 

where it may impact screen operations. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

11.11 End of Pipe Screens (including pump intake screens) 

11.11.1 Specific Criteria and Guidelines – End of Pipe Screens 

11.11.1.1 Location: End of pipe screens must be placed in locations with 

sufficient ambient velocity to sweep away debris removed from the screen face, 

or designed in a manner to prevent debris re-impingement and provide for debris 

removal. 

11.11.1.2 Submergence: End of pipe screens must be submerged to a depth of at 

least one screen radius below the minimum water surface, with a minimum of one 

screen radius clearance between screen surfaces and natural or constructed 

features. For approach velocity calculations, the entire submerged effective 

screen area may be used. 

11.11.1.3 Escape Route: A clear escape route should exist for fish that approach 

the intake volitionally or otherwise. For example, if a pump intake is located off 

of the river (such as in an intake lagoon), a conventional open channel screen 

should be placed in the intake channel or at the edge of the river to prevent fish 

from entering a lagoon. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

12. INFILTRATION GALLERIES (EXPERIMENTAL TECHNOLOGY) 

12.1 Introduction – Infiltration Galleries 

This section discusses the application and suitability for the installation of infiltration 

galleries. In concept, infiltration galleries may provide suitable fish passage conditions at 

a diversion site. However, if improperly sited, failure may occur that results in severe 

adverse habitat impacts and loss of habitat access in addition to the loss of the diversion. 

As such, any site proposed for an infiltration gallery must follow the experimental 

process described in Section 16. The following section describes the guidelines and 

criteria that should be followed in the planning, design, operation, monitoring, and 

maintenance of infiltration galleries. 

The intent of these criteria is to build and operate infiltration galleries that provide at least 

the same level of fish protection as conventional screen facilities that meet NMFS screen 

criteria, as presented in Section 11. Accordingly, infiltration galleries have similar design 

criteria to conventional screens, such as: screen dimensions, approach velocity, bypass 

facilities, ability to monitor head loss, ability to be self-cleaning, ability to be maintained, 

and owner agreements to maintain and operate the system within criteria. These aspects 

are discussed in more detail in the following sections. 

Criteria are specific standards for fishway design, maintenance, or operation that cannot 

be changed without a written waiver from NMFS. For the purposes of this document, a 

criterion is preceded by the word “must.” In general, a specific criterion can not be 

changed unless there is site-specific biological rationale for doing so. An example of 

biological rationale that could lead to criterion waiver is a determination or confirmation 

by NMFS biologists that the smallest fry-sized fish will likely not be present at a 

proposed screen site. Therefore, the juvenile fish screen approach velocity criterion of 

0.4 ft/s could be increased to match the smallest life stage expected at the screen site. A 

guideline is a range of values or a specific value for fishway design, maintenance or 

operation that may change when site-specific conditions are factored into the conceptual 

fishway design. For the purposes of this document guidelines are preceded by the word 

“should.” Guidelines should be followed in the fishway design until site-specific 

information indicates that a different value would provide better fish passage conditions 

or solve site-specific issues. An example of site-specific rationale that could lead to a 

modified guideline is when the maximum river depth at a site is 3 feet, as compared to 

the design guideline for a fishway entrance depth of 6 feet. In this example, safe and 

timely fish passage could be provided by modifying the guideline to match the depth in 

the river. It is the responsibility of the applicant to provide compelling evidence in 

support of any proposed waiver of criteria or modification of a guideline for NMFS 

approval early in the design process, well in advance of a proposed Federal action. After 

a decision to provide passage at a particular site has been made, the following design 

criteria and guidelines are applicable, in addition to those described throughout Section 3. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

12.2 Scope 

The term infiltration gallery, in this document, refers to a water collection system that is 

installed in the zone of surface water influence, for the purpose of conveying water to 

either a pumped or gravity-fed water distribution network (see Figure 12-1). The 

infiltration gallery is intended to be a substitute for a surface-based diversion system that 

is normally installed above the bed of the stream. 

Figure 12-1. Cross Section of an Example Infiltration Gallery 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

12.3 Selection of Appropriate Screen Technology 

Due to their location below the stream bed, infiltration galleries are prone to become 

ineffective due to plugging by sediments. In addition to reducing the flow capacity of the 

facility, plugged galleries also increase the risk to small fish due to the creation of 

velocity hot spots. Since very few existing infiltration galleries include effective selfcleaning systems, it is a common practice to repair plugged galleries by digging them up 

and rebuilding them. This process may create enormous disruption to the river habitat 

and to the diverters’ ability to divert water. Therefore, the designer should select an 

infiltration gallery as the preferred diversion method only after a thorough review of the 

benefits and risks of using conventional screens indicates that an infiltration gallery may 

create less risk for fish and their habitat. 

12.4 Site Selection 

NMFS intends to only permit infiltration galleries at stream sites that exhibit sufficient 

natural fluvial processes to minimize sediment deposition on top of the infiltration gallery 

to the maximum practical extent. The sealing of infiltration galleries with transported 

bedload sediments seems to be a common mode of failure. Infiltration galleries should 

not be installed at sites where natural sedimentation occurs that would plug a gallery. 

12.5 Design: Infiltration Galleries 

12.5.1 Specific Criteria and Guidelines - Design

12.5.1.1 Design Objectives: The infiltration gallery must be designed to: 

• Provide the same volume, rate, and timing of water supply that the 

diverter would be entitled to when using a surface-based diversion; 

• Withdraw water primarily from the portion of the stream located directly 

above the infiltration gallery; and 

• Provide at least the same level of fish protection as conventional screens. 

12.5.1.2 Minimum Depths and Velocities over Infiltration Galleries: 

Infiltration galleries should not be operated when the water depth above the river 

bed over any part of the infiltration gallery is less than 0.5 feet. Use of temporary 

impoundments such as push-up berms and other dams to raise the water level is 

not permitted. The minimum stream velocity at low flow should be 2 ft/s. 

 

12.5.1.3 Screen Material Opening: Infiltration galleries installed with less than 

24 inches of gravel cover should meet juvenile fish screen criteria, as described in 

Section 11. 

 

12.5.1.4 Flow Direction: Infiltration galleries should be designed to withdraw 

flow primarily from the zone directly above the intake screen. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

12.5.1.5 Imported Gravels: Rock used to backfill over the infiltration gallery 

must be designed and approved by the design engineer. The backfill material 

selection must also be approved by NMFS. 

12.5.1.6 Induced Vertical Approach Velocity at the Stream Bed: The 

maximum vertical interstitial velocity through the substrate, Vs , must not exceed 

0.05 ft/s when the substrate is new and/or after backwashing (see Figure 12-1). 

Vs is defined according to the following calculation: 

η))(( eff

s A

Q V =

where: Vs = average vertical interstitial velocity through the gravel 

substrate 

 Q = diverted flow rate 

Aeff = plan view area of gravel substrate through which the flow is 

assumed to pass 

η = porosity of gravel substrate 

12.5.1.7 Determination of Plugged Gallery: As with conventional screen 

technology, it is essential to be able to measure the head loss through the 

screening material (Section 11.7). As a minimum, sufficient instrumentation must 

be installed to measure the hydraulic grade line (HGL) values, as shown 

schematically in Figure 12-1. The gallery material must be backwashed when the 

head loss measurements indicate that Vs is greater than or equal to 0.10 ft/s. If 

backwashing does not reduce Vs below 0.10 ft/s then the gallery must be shut 

down and repaired. 

12.5.1.8 Backwashing: All infiltration galleries must be designed to be capable 

of being backwashed. Backwashing may be accomplished using air or water or 

both. The backwash system must be designed to thoroughly clean all of the 

material in the Effective Cleaning Zone (Figure 12-1). The Effective Cleaning 

Zone is the volume of filter medium that the designer has assumed contributes 

about 90% of the diverted flow rate. 

12.5.1.9 Limitations/Cessation of Use: 

• Infiltration galleries should not be constructed in areas where spawning 

may occur. 

• Should spawning occur within 10 feet of a portion of an infiltration 

gallery, then use of those portions of the infiltration galleries within 10 

feet of the redd should be discontinued for 90 days, or as directed by 

NMFS. 

• Instream excavation to repair infiltration galleries is not included in the 

scope of permitted work beyond 90 days from the date of commencement 

of initial instream construction, or the end of the approved work period, 

whichever is earlier, unless performed when there is no flowing water in 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

the creek. This restriction does not apply to repairs that do not disturb the 

river bed or banks. 

• Failed infiltration galleries must not be replaced until the failure 

mechanism is identified, and a subsequent design is provided that 

eliminates future failures due to the identified failure mechanism. 

• Excavation for infiltration gallery repair must not be conducted, unless 

specifically approved by NMFS. 

12.5.1.10 Qualifications of Infiltration Gallery Designers: The design of 

infiltration galleries must be performed by an appropriately qualified engineer or 

engineering geologist, and the drawings should be signed by the designer and/or 

stamped with his/her seal. The design of each infiltration gallery must be 

reviewed and approved by NMFS. 

12.5.1.11 Operations and Maintenance: Infiltration galleries must be operated 

and maintained in accordance with Section 14. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

13. TEMPORARY AND INTERIM PASSAGE FACILITIES 

Where construction and/or modifications to artificial impediments (e.g., dams) or 

upstream passage facilities are planned, upstream and downstream passage may be 

adversely impacted. If possible, these activities should be scheduled for periods when 

migrating fish are not present, as specified in the in-water work period allowable for 

construction of facilities in streams. However, this may not always be possible or 

advisable. In these cases, an interim fish passage plan must be prepared and submitted to 

NMFS for approval, in advance of work in the field. Criteria listed previously in this 

document also apply to the interim passage plan. Where this is not possible, project 

owners must seek NMFS approval of alternate interim fish passage design criteria, and a 

final interim passage plan. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

14. OPERATIONS AND MAINTENANCE RESPONSIBILITIES 

Passage facilities at impediments must be operated and maintained properly for optimum, 

or even marginal, success. The preceding criteria are intended for use in the design of 

passage facilities; however, failure to operate and maintain these facilities to optimize 

performance in accordance with design may result in compromised fish passage, and 

ultimate deterioration of the entire facility. Therefore, NMFS requires facility operators 

to commit to long-term responsibility for operations, maintenance, and repair of fish 

facilities described herein, to ensure protection of fish on a sustained basis. This includes 

immediate restoration of the passage facility (including repair of damage and 

sediment/gravel removal) after flooding, and prior to the arrival of migratory fish. Where 

facilities are inadequately operated or maintained, and mortality of listed fish can be 

documented, the responsible party is liable to enforcement measures as described in 

Section 9 of the ESA. 

An operation and maintenance plan must be drafted and submitted to NMFS for approval. 

This plan must include a brief summary of operating criteria posted at the passage facility 

or otherwise made available to the facility operator. Staff gages must be installed and 

maintained at critical areas throughout the facility in order to allow personnel to easily 

determine if the facility is being operated within the established design criteria. 

Comprehensive operation and maintenance plans for a group of projects (e.g., road 

maintenance plans for culverts, small screen facilities, etc.) will satisfy this criterion, so 

long as NMFS is in agreement with the operation and maintenance of passage facilities. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

15. POST-CONSTRUCTION EVALUATION 

15.1 Introduction – Post Construction Evaluation 

Post-construction evaluation is important to ensure that the intended results of the fishway

design are accomplished and to assist in ensuring that mistakes are not repeated 

elsewhere. If a post-construction evaluation may be required, NMFS will identify that 

need early in the design process. Large facilities, experimental devices, and facilities that 

deviate widely from these previous guidelines or criteria are likely candidates for 

hydraulic and biological evaluation. These evaluations are not intended to cause 

extensive retrofits of any given project unless the as-built installation does not reasonably 

conform to the design guidelines, or an obvious fish passage problem continues to exist. 

Over time, NMFS anticipates that the second and third elements of these evaluations may 

be abbreviated as commonly used designs are evaluated and fine-tuned to ensure optimal 

passage conditions. 

There are three parts to this evaluation: (1) verify that the fish passage system is installed 

in accordance with the approved design and that construction procedures are sound; (2) 

measure hydraulic conditions to ensure that the facility meets these guidelines and 

criteria, and (3) perform biological assessment to confirm that hydraulic conditions are 

resulting in successful passage. NMFS technical staff may assist in developing a 

hydraulic or biological evaluation plan to fit site-specific conditions and species, but in 

any case, evaluation plans are subject to approval by NMFS. 

15.2 Evaluation of Juvenile Fish Screens 

Hydraulic evaluations of juvenile fish screens must include confirmation of uniform 

approach velocity and the requisite sweeping velocity over the entire screen face. 

Confirmation of approach and sweeping velocities must consist of a series of velocity 

measurements encompassing the entire screen face, divided into a grid with each grid 

section representing no more than 5% of the total diverted flow through the screen (i.e., at 

least 20 grid points must be measured). The approach and sweeping velocity (parallel and 

perpendicular to the screen face) should be measured at the center point of each grid 

section, as close as possible to the screen face without entering the boundary layer 

turbulence at the screen face. Uniformity of approach velocity is defined as being 

achieved when no individual approach velocity measurement exceeds 110% of the 

criteria. In addition, velocities at the entrance to the bypass, bypass flow amounts, and 

total flow should be measured and reported. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

15.3 Biological Evaluation 

Depending on the site and its potential for adverse biological impacts, detailed biological 

evaluations and/or monitoring may likely be required and are the responsibility of the 

project sponsor. The need for and scale of biological evaluation may be identified by 

NMFS early in the design process. If a passage facility will be encountered by the 

majority of the fish migration, and if waivers to the criteria are granted, biological 

evaluation will likely be required. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

16. EXPERIMENTAL FISH GUIDANCE DEVICES 

16.1 Introduction – Experimental Fish Guidance Devices 

NMFS believes that conventional fish passage facilities constructed to the criteria and 

guidelines described above are most appropriate for utilization in the protection of 

salmon and steelhead at all impediments. However, the process described below 

delineates an approach whereby experimental fish passage devices can be evaluated and, 

if comparable performance is confirmed to the satisfaction of NMFS, installed in lieu of 

conventional passage facilities. 

16.2 Juvenile Fish Entrainment at Intakes 

The injury and death of juvenile fish at water diversion intakes have long been identified 

as a major source of overall fish mortality (Spencer1928; Hatton 1939; Hallock and 

Woert 1959; Hallock 1987). Fish diverted into power turbines incur up to 40% or more 

immediate mortality, while also experiencing injury, disorientation, and delay of 

migration that may increase predation related losses (Bell 1991). Fish entrained into 

agricultural and municipal water diversions may experience 100% mortality, particularly 

if no egress route back to the river is provided. Diversion mortality may cause decline in 

fish populations, especially if instream habitat is unsuitable for any aspect of spawning, 

incubation, rearing or migration. For the purposes of this document, diversion losses 

include turbine, irrigation, municipal, and all other potential fish losses related to human 

water use. 

Positive-exclusion barrier screens that screen the entire diversion flow have long been 

used to prevent or reduce entrainment of juvenile fish for diversions of up to 6000 cfs, 

and their designs are discussed in Section 11. In recent decades, design improvements 

have been implemented to increase the biological effectiveness of positive-exclusion

screen and bypass systems by taking advantage of known behavioral responses to 

hydraulic conditions. Recent evaluations have consistently demonstrated high success 

rates (typically greater than 98%) at moving juvenile salmonids past intakes with a 

minimum of delay, loss, or injury. For diversion flows over 6000 cfs, such as at 

Columbia River mainstem turbine intakes, submerged traveling screens or bar screens are 

commonly used. These are not considered positive-exclusion screens in the context of 

this position statement. In addition, large reservoirs often involve consideration of a 

surface outlet for fish passage, and may offer a superior route of passage as compared to 

a deep outlet with a positive exclusion screen 

The past few decades have also seen considerable effort in developing "startle" systems 

or other behavioral exclusion devices to elicit a taxis (response) by fish, with an ultimate 

goal of reducing entrainment. This paper addresses research to be performed for types of 

fish passage devices not included in the preceding chapters of this document in order to 

prevent losses at intakes and other passage impediments and presents a position statement 

for reviewing and implementing future fish protection measures. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Entrainment, impingement, and delay/predation are the primary contributors to the 

mortality of juvenile migrating salmonids. Entrainment occurs when fish are drawn into 

the diversion canal or turbine intake. Impingement occurs when a fish is not able to 

avoid contact with a screen surface, trashrack, or debris at the intake. This may cause 

bruising, descaling and other injuries. 

Impingement, if prolonged, repeated, or occurring at high velocities, also causes direct 

mortality. Predation (which is the leading cause of mortality at some diversion sites) 

occurs when fish are preyed upon by aquatic or avian animals. Delay at intakes increases 

predation by stressing or disorienting fish and/or by providing habitat for predators. 

Design criteria for Positive-exclusion screen and bypass systems (PESBS) (Section 11) 

have been developed, tested, and proven to minimize adverse impacts to fish at diversion 

sites. Screens with small openings and fish-tight seals are positioned at a slight angle to 

flow. This orientation allows fish to be guided to safety at the downstream end of the 

screen, while they resist being impinged on the screen face. These screens are very 

effective at preventing entrainment (Pearce and Lee 1991). Carefully designed bypass 

systems minimize fish exposure to screens and provide hydraulic conditions that safely 

return fish to the river, thereby preventing impingement (Rainey 1985). The PESBS are 

designed to minimize entrainment, impingement, and delay/predation from the point of 

diversion through the facility to the bypass outfall. 

PESBS have been installed and evaluated at numerous facilities (Abernathy et al. 1989, 

1990; Rainey 1990; and Johnson 1988). A variety of screen types (e.g., fixed-vertical, 

drum, fixed-inclined) and screen materials (e.g., woven cloth [mesh], perforated plate, 

profile wire) have proven effective, when used in the context of a satisfactory design for 

the specific site. Facilities designed to previously referenced criteria consistently resulted 

in a guidance efficiencies of over 98% (Hosey 1990; Neitzel 1985, 1986,1990a,b,c,d; 

Neitzel 1991). 

The main detriment of PESBS is cost, because of the low velocity requirement and 

structure complexity. At the headworks, the need to clean the screen, remove trash, 

control sediment, and provide regular maintenance (e.g., seasonal installation, replacing 

seals, etc.) also increases costs. 

16.3 Behavioral Devices 

There has been considerable effort since 1960 to develop less expensive behavioral 

devices as a substitute for conventional fish protection (EPRI 1986). A behavioral 

device, as opposed to a conventional passage system, requires volitional taxis on the part 

of the fish to avoid entrainment. Some devices were investigated with the hope of 

attracting fish to a desired area while others were designed to repel fish. Most studies 

focused on soliciting a behavior response, usually noticeable agitation, from the fish. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Investigations of prototype startle-response devices document that fish guidance 

efficiencies are consistently much lower for these devices than for conventional screens. 

Experiments show that there may be a large behavioral variation in startle responses 

between individual fish of the same size and species. Therefore, it cannot be predicted 

that a fish will always move toward or away from that stimuli. Until shown conclusively 

in laboratory studies, it should not be assumed that fish can discern where a signal is 

coming from and what constitutes the clear path to safety. 

If juvenile fish respond to a behavioral device, limited size and swimming ability may 

preclude small fish from avoiding entrainment (even if they have the understanding of 

where to go and have the desire to get there). Another concern is repeated exposure; fish 

may no longer react to a signal after an acclimation period. In addition to vagaries in the 

response of an individual fish, behavior variations due to species, life stage, and water 

quality conditions can be expected. 

Another observation is that past field tests of behavioral devices have been deployed 

without consideration of how controlled ambient hydraulic conditions (i.e., the use of a 

training wall to create uniform flow conditions, while minimizing stagnant zones or 

eddies that may increase exposure to predation) may optimize fish guidance and safe 

passage away from the intake. Failure to consider that hydraulic conditions may play a 

large role in guiding fish away from the intake is either the result of the desire to 

minimize costs or the assumption that behavioral devices may overcome the tendency for 

poor guidance associated with marginal hydraulic conditions. The provision of 

satisfactory hydraulic conditions is a key element of PESBS designs. 

The primary motivation for selection of behavioral devices relates to cost, and possibly to 

ease maintenance issues with PESBS. However, much of the cost in PESBS is related to 

construction of physical structures to provide hydraulic conditions that are known to 

optimize fish guidance. Paradoxically, complementing the behavioral device with 

hydraulic control structures needed to optimize juvenile passage will compromise much 

of the cost advantage relative to PESBS. 

Currently few behavioral devices are being used for stand-alone fish protection in the 

field. Those that have been installed and evaluated seldom show consistent guidance 

efficiencies over 60% (Vogel 1988; EPRI 1986). The louver system is an example of a 

behavioral device with a poor record, particularly for fry-sized salmonids. Entrainment 

rates were high, even with favorable hydraulic conditions, due to the presence of smaller 

fish (Vogel 1988; Cramer 1973; Bates 1961). Due to their poor performance, most of 

these systems were eventually replaced by PESBS. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

16.4 Process for Developing Experimental Fish Passage Technology 

Development of new passage concepts may have the potential to provide fish passage. In 

general, the process for developing new upstream adult passage technology and gaining 

NMFS approval is the same as for downstream juvenile fish passage. Some of these 

concepts are currently in development (e.g., stream simulation and roughened channel 

designs), and have existing field prototype installations that have been assessed to some 

degree. 

There is potential for future development of new passage devices that may safely pass 

fish at a rate comparable with conventional technology. These new concepts are 

considered "experimental" until they have been through the process described herein and 

have been proven in a prototype evaluation validated by NMFS. These prototype 

evaluations should occur over the foreseeable range of adverse hydraulic and water 

quality conditions (e.g., temperature, dissolved oxygen). NMFS will not discourage 

research and development on experimental fish protection devices, but the following 

elements should be addressed during the process of developing experimental juvenile 

passage protection concepts: 

1. Earlier Research. A thorough review of similar methods used in the past should 

be performed. Reasons for substandard performances should be clearly identified. 

2. Study Plan. A study plan should be developed and presented to NMFS for 

review and concurrence. It is essential that tests occur over a full range of 

possible hydraulic, biological, and ecological conditions that the device is 

expected to experience. Failure to receive study plan endorsement from NMFS 

may result in disputable results and conclusions. 

3. Laboratory Research. Laboratory experiments under controlled conditions 

should be developed using species, size, and life stages intended to be protected. 

For behavioral devices, special attention must be directed at providing favorable 

hydraulic conditions and demonstrating that the device clearly induces the 

planned behavioral response. Studies should be repeated with the same test fish 

to examine any acclimation to the guidance device. 

4. Prototype Units. Once laboratory tests show high potential to equal or exceed 

success rates of conventional passage devices, it is appropriate to further examine 

the new device as a prototype under real field conditions. Field sites must be 

appropriate to (1) demonstrate durable performance at all expected operational 

and natural variables, (2) evaluate the species, or an acceptable surrogate, that 

would be exposed to the device under full operation, and (3) avoid unacceptable 

risk to depressed or listed stocks at the prototype locations. 

5. Study Results. Results of both laboratory tests and field prototype evaluations 

must demonstrate a level of performance equal to or exceeding that of 

conventional fish passage devices before NMFS may support permanent 

installations. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

16.5 Conclusions 

Proven fish passage and protection facilities designs are available to provide successful 

passage at most fish passage impediments. Periodically, major initiatives have been 

advanced to examine the feasibility of experimental passage systems. Results were 

generally poor or inconclusive, with low guidance efficiencies attributable to the 

particular device used. Often results were based on a small sample size, or varied with 

operational conditions. In addition, unforeseen operational and maintenance problems 

(and safety hazards) were sometimes a byproduct. Nevertheless, some of these passage 

systems have shown potential for success. To further advance fish protection technology, 

NMFS will not oppose tests that proceed in accordance with the tiered process outlined 

above. To ensure no further detriment to any fish resource, including delays in 

implementation of acceptable passage facilities, experimental field testing should occur 

simultaneous to design and development of conventional passage design for that site. 

This conventional system should be scheduled for installation in a reasonable time frame, 

independent of the experimental efforts. In this manner, if the experimental guidance 

system once again does not prove to be as effective as proven conventional technology, a 

conventional passage design may be implemented without additional delay and detriment 

to the resource. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

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Symposium. American Fisheries Society Symposium 10. Bethesda, MD. 

Poe, T. P., M. G. Mesa, R. S. Shively, and R. D. Peters. 1993. Development of biological 

criteria for siting and operation of juvenile bypass systems: implications for 

protecting juvenile salmonids from predation, pp. 169–178. In: Fish Passage 

Policy and Technology (Bates, K., Ed.). Bethesda, MD: American Fisheries 

Society. 

Pearsons, T.N., G.A. McMichael, S.W. Martin, E.L. Bartrand, A. Long, and S.A. Leider. 

1996. 

Yakima Species Interactions Studies Annual Report 1994. U.S. Department of 

Energy, Bonneville Power Administration Annual Report 1994. No. 

DOE/BPB99852-3. 

Poulin, V.A., and H.W. Argent. 1997. Stream Crossing Guidebook for Fish Streams, a 

Working Draft. Prepared for British Columbia Ministry of Forests. 80 pages. 

Powers, Pat. 1993. Structures for Passing Juvenile Salmon Into Off-Channel Habitat 

American Fisheries Society Annual Meeting in Portland in 1993 

Rainey, W.S. 1990. Cylindrical Drum Screen Designs for Juvenile Fish Protection at 

Two Large Diversions. In: Proceedings of the International Symposium on 

fishways '90 in Gifu. Gifu, Japan. 

Rainey, W.S. 1985. Considerations in the Design of Juvenile Bypass systems. Paper 

presented at the Symposium on Small Hydropower and Fisheries. Denver, CO. 

Reading, H.H. 1982. Passage of Juvenile Chinook Salmon and American Shad through 

Various Trashrack Bar Spacings. State of California Department of Fish and 

Game technical Report 5, Interagency Ecological Study Program for the 

Sacramento-San Juaquin Estuary. Red Bluff, CA. 

Reiser, D. W. and K.T. Oliver. 2002. Review of Projects Employing Conventional Fish 

Screens - Existing Information Analysis. Prepared for Portland General Electric 

Company, Portland, OR. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Ruehle, T.E. and C.S. McCutcheon. 1994. PIT-Tag Studies with Juvenile Salmonids at 

the Chandler Fish Collection Facility, Yakima River, 1990. Project No.90-65. 

Prepared for Bonneville Power Administration, Portland, Oregon. 

Salmonid Restoration Federation Conference. 1996. Culvert Fish Passage Design and 

Retrofitting Workshop. Fortuna, CA. 30 pages. 

Sandercock, F.K. 1991. Life History of Coho Salmon. Pages 397-445 in C. Groot and L. 

Margolis (eds.), Pacific salmon life histories. Univ. British Columbia Press, 

Vancouver. 564 pages. 

Senn, H., Mack, J. and L. Rothfus. 1984. Compendium of Low-cost Pacific Salmon and 

Steelhead Trout Production Facilities and Practices in the Pacific Northwest. 

Project No. 83-353. Prepared for Bonneville Power Administration, Portland, 

Oregon. 

Shirvell, C.S. 1994. Effect of changes in streamflow on the microhabitat use and 

movement of sympatric juvenile coho salmon (Oncorhynchus kisutch) and 

chinook salmon (O.tshawytscha) in a natural stream. Can. J. Fish. Aquat. Sci. 

51:1644-1652. 

Simmons, W.P. 1964. Hydraulic Design of Transitions for Small Canals. U.S. Bureau of 

Reclamation, Engineering Monograph No. 33, U.S. Government Printing Office, 

Washington D.C. 

Skinner, J.E. 1974. A Functional Evaluation of a Large Louver Screen Installation and 

Fish Facilities Research on California Water Diversion Projects. In: Proceedings 

of the Second Workshop on Entrainment and Intake Screening. Johns Hopkins 

University, Baltimore, MD., February 5-9, 1973. 

Smith, L.W. 1982. Clogging, Cleaning, and Corrosion Study of Possible Fish Screens for 

the Proposed Peripheral Canal. Interagency Ecological Study Program for the 

Sacramento-San Juaquin Estuary, Sacramento, CA. 

Smith, L.S. and L.T. Carpenter. 1987. Salmonid Fry Swimming Stamina Data for 

Diversion Screen Criteria. Final Report. Fisheries Research Institute, University 

of Washington, Seattle, WA (1987). 

Spencer, John. 1928. Fish Screens in California Irrigation Ditches. California Fish and 

Game, Vol. 14, No. 3, p. 208-210. 

Stefan, H. and A. Fu. 1978. Headloss Characteristics of Six Profile-wire Screen Panels 

Project Report No. 175. St. Anthony Falls Hydraulic Laboratory, Minneapolis, 

MN. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Stone, J. M. and T. R. Mosey. 2005. Biological evaluation of the Rocky Reach juvenile 

fish bypass system 2004. Chelan County Public Utility District, Wenatchee, WA. 

Taft, N. 1994. Fish Passage at Hydroelectric Projects, presented at Hydro’s Leading Edge 

Technology: A Symposium Celebrating ARL’s Centennial, Phoenix, AZ. 

Taylor, E.B. and J.D. McPhail. 1985. Variation in Burst and Prolonged Swimming 

Performance Among British Columbia Populations of Coho Salmon. Canadian 

Journal of Fisheries and Aquatic Sciences, Volume 42. 

Thomas, A.E., J.L. Banks and D.C. Greenland. 1969. Effect of Yolk Sac Absorption on 

the Swimming Ability of Fall Chinook Salmon. Transactions of the American 

Fisheries Society 98(3):406-410 

Tomljanovich, D.A., and J.H. Heuer. 1979. Protection of Fish Larvae using Fine-Mesh 

Screening. Presented at American Society of Engineers Convention, Atlanta, GA. 

Turnpenny, A.W. 1981. An Analysis of Mesh Sizes Required for Screening Fishes at 

Water Intakes. Estuaries, Volume 4, No. 4 

Turnpenny, A.W., H.G. Struthers, and K.P. Hanson. 1998. A UK guide to intake fishscreening regulations, policy and best practice. ETSU H/06/0052/00/00. Report to 

the Department of Trade and Industry, Energy Technology Support Unit, Harwell, 

United Kingdom. 

U.S. Army Corps of Engineers (COE). 1956. North Pacific Division Corps Of Engineers, 

Progress Report On Fisheries Engineering Research Program, November 1956. 

Portland, Oregon. 

Contents: 

1. A Review of Studies in Guiding Downstream Migrating Salmon with Light. U.S. 

fish and Wildlife Service. 

2. Determination of the Normal Stream Distribution, Size, Time and current 

Preference of Downstream Migrating Salmon and Steelhead Trout in the 

Columbia and Snake Rivers. State of Washington Dept. of Fisheries. 

3. The Effect of Sound Waves on Young Salmon. U.S. Fish and Wildlife Service. 

4. Powerhouse Collection System and Transportation Flows, Bonneville Dam. 

Portland District, Corps of Engineers. 

5. The Status of Field Scale Electrical Fish Guiding Experiments. U.S. Fish and 

Wildlife Service. 

6. Effect of Structures at Main Columbia River Dams on Downstream Migration of 

Fingerlings. Portland District, Corps of Engineers. 

7. Bouyant Submerged Orifice Research. Portland District, Corps of Engineers. 

8. Study of the Effect of Magnetic Fields on Salmon. U.S. Fish and Wildlife Service. 

9. Fishway Attraction Water Supply Study. Walla Walla District, Corps of 

Engineers. 

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10. Submerged Orifice Research Powerhouse Fish Collection System, Bonneville 

Dam. Portland District, Corps of Engineers. 

11. The Control of Downstream Migrants by Means of Mechanical Screens. Oregon 

Game Commission. 

12. Research Relating to Mortality of Downstream Migrant Salmon Passing McNary 

Dam. State of Washington Department of Fisheries. 

13. Research Relating to Study of Spawning Grounds in Natural Areas. State of 

Washington Department of Fisheries. 

14. Investigation of the Rate of Passage of Salmon and Steelhead Trout through 

Bonneville Dam and The Dalles Dam Site as Compared to Unobstructed Sections 

of the Columbia River. Oregon Fish Commission. 

15. Investigations and Field Studies Relating to Numbers and Seasonal Occurrence of 

Migratory Fish Entering the Columbia River above Bonneville and the Snake 

River and Their Final Distribution among Principal Tributaries Thereto. Oregon 

Fish Commission. 

16. Enumeration Study – Upper Columbia and Snake Rivers. Idaho Department of 

Fish and Game. 

17. Research on Fishway Problems. U.S. Fish and Wildlife Service. 

18. A Study to Investigate the Effects of Fatigue and Current Velocities on Adult 

Salmon and Steelhead Trout. School of Fisheries, University of Washington. 

19. A Study to determine the Effects of Electricity on Salmon and Steelhead Trout. 

School of Fisheries, University of Washington. 

20. Determination of the Vertical and Horizontal Distribution of Seaward Migrants, 

Baker Dam. State of Washington, Department of Fisheries. 

21. Guiding Downstream Migrant Salmon and Steelhead Trout. A Research 

Summary. School of Fisheries, University of Washington. 

U.S. Army Corps of Engineers (COE). 1960. North Pacific Division Corps Of Engineers, 

Progress Report On Fisheries Engineering Research Program, July, 1960. 

Portland, Oregon. 

Contents: 

1. Guiding Downstream Migrant Salmon and Steelhead Trout College of Fisheries. 

University of Washington. 

2. Results of a Tagging Program to Enumerate the Numbers and to Determine the 

Seasonal Occurrence of Anadromous Fish in the Snake River and its Tributaries 

Fish Commission of the State of Oregon. 

3. Enumeration Study Upper Columbia and Snake Rivers. Idaho Department of Fish 

and Game. 

4. Evaluation of the Ability of an Artificial Outlet to Attract Downstream Migrant 

Salmonids from the Reservoir of Lookout Point Dam. Fish Commission of the 

State of Oregon. 

5. The Control of Downstream Migrants by Means of Mechanical Screens. Oregon 

State Game Commission. 

6. Fishway Attraction Water Supply Study. Walla Walla District, Corps of 

Engineers. 

7. Effect of Structures at Main Columbia River Dams on Downstream Migration of 

Fingerlings. Portland District, Corps of Engineers. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

8. The Status of Electrical Fish Guiding Experiments. U.S. Fish and Wildlife 

Service. 

9. Research Relating to McNary Supplemental Spawning Channel. State of 

Washington, Department of Fisheries. 

10. Research on Fishway Problems. Bureau of Commercial Fisheries, U.S. Fish and 

Wildlife Service. 

11. A Study to Determine the Effects of Electricity on Salmon and Steelhead Trout. 

College of Fisheries, University of Washington. 

12. A Study to Investigate the Effects of Fatigue and Current Velocities on Adult 

Salmon and Steelhead Trout. College of Fisheries, University of Washington. 

13. Research Relating to Mortality of Downstream Migrant Salmon Passing McNary 

and Big Cliffs Dams. State of Washington, Department of Fisheries. 

14. Powerhouse Fish Collection System and Transportation Flow, Bonneville Dam. 

Portland District, Corps of Engineers. 

15. Submerged Orifice Research Powerhouse Fish Collection System, Bonneville 

Dam. Portland District, Corps of Engineers. 

16. Buoyant Submerged Orifice Research. Portland District, Corps of Engineers. 

17. An Investigation of the Effect of The Dalles Dam upon Migration Rates of Adult 

Salmonids, 1956 and 1957. Fish Commission of the State of Oregon. 

18. Experimental Studies on the survival of the Early Stages of Chinook Salmon after 

varying Exposures to Upper Lethal Temperatures. State of Washington, 

Department of Fisheries. 

19. Fish Passage through Turbines. Walla Walla District, Corps of Engineers. 

U.S. Army Corps of Engineers (COE). 1966. North Pacific Division Corps Of Engineers, 

Progress Report On Fisheries Engineering Research Program, November 1966. 

Portland, Oregon. 

Contents: 

1. Migrant Salmon Light-Guiding Studies at Columbia River Dams. Paul E. Fields. 

2. Juvenile Fish Passage Through Turbines. Raymond C. Oligher. 

3. Research on Fishway Problems, May 1960 to April 1965. Joseph R. Gauley, 

Charles R. Weaver, and Clark S. Thompson. 

4. Fallback of Adult Chinook Salmon at Ice Harbor Dam Spillway, May 1964. 

James H. Johnson. 

5. Review and Analysis of Fish Counts, Counting Technique and Related Data at 

Corps of Engineers Dams on the Columbia and Snake Rivers. Louis C. Fredd. 

6. Research Relating to McNary Supplemental Spawning Channel, Five-Year 

Summary, 1960 through 1964. State of Washington Department of Fisheries. 

7. The Accelerated Fish Passage Research Program of the U.S. Bureau of 

Commercial Fisheries – Summary of Progress through 1964. Gerald B. Collins 

and Carl H. Elling. 

U.S. Army Corps of Engineers (COE). 1972. North Pacific Division Corps Of Engineers, 

Fourth Progress Report On Fisheries Engineering Research Program, 1966-1972. 

Portland, Oregon. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Contents: 

• Standardization of Spill Patterns at Ice Harbor Dam 

• General Guidelines for Adjusting Spill Distributions to Improve Fish Passage 

with Tentative Spilling Schedule for Bonneville and John Day Dams 

• Operational Studies at Dams on the Lower Columbia and Snake Rivers 

• I. Operational Studies at Dams on the Lower Columbia River with a Brief 

Analysis of Adequacy of New Spilling Techniques at Ice Harbor Dam 

• II. Fish Passage Problems at Lower Columbia River Dams in 1968 

Effects of Peaking Operations on Passage of Adult Salmonids Over Columbia 

River Dams 

• Evaluation of Upstream Passage of Adult Salmonids through the Navigation Lock 

at Bonneville Dam during the Summer of 1969 

• A Tagging Study to Investigate the Unexplained Loss of Spring and Summer 

Chinook Salmon Migrating Past Bonneville and The Dalles Dam 

• Indications of Loss and Delay to Adult Salmonids below Ice Harbor Dam (1962-

66) 

• Radio Tracking of Adult Spring Chinook Salmon below Bonneville Dam, 1971 

• Sonic Tracking of Adult Steelhead in Ice Harbor Reservoir, 1969 

• Sonic Tracking of Steelhead in the Ice Harbor Reservoir, 1967 

• Sonic Tracking of Steelhead in the Rocky Reach Reservoir, 1967 

• Evaluation of Fish Passage in the Vertical Slot Regulating Section of the 

South Shore Ladder at John Day Dam 

• Propagation of Fall Chinook Salmon in McNary Dam Experimental Spawning 

Channel, 1957 through 1963 

• Effect of Gas Supersaturated Columbia River Water on the Survival of Juvenile 

Salmonids, April-June 1972, Final Report – Part 1 

• A Nitrogen (N2) Model for the Lower Columbia River 

• Test of Fingerling Passage at Bonneville Dam, Report No. 1 

• A Study to Determine the Value of Using the Ice-Trash Sluiceway for Passing 

Downstream Migrant Salmonids at Bonneville Dam 

• Bonneville and The Dalles Dams Ice-Trash Sluiceway Studies, 1971 

• Research on Gatewell-Sluice Method of Bypassing Downstream Migrant Fish 

Around Low-head Dams 

• Fingerling Fish Mortalities at 57.5 fps, Report No. 1 

• Fingerling Fish Research Effect of Mortality of 67-fps Velocity, Report No. 2 

• Fingerling Fish Research, High-Velocity Flow through Four-Inch Nozzle, Report 

No. 3 

• Fingerling Shad Studies at Bonneville Dam, November and December 1966 

• Progress Report on Fish Protective Facilities at Little Goose Dam and Summaries 

of Other Studies Relating to the Various Measures Taken by the Corps of 

Engineers to Reduce Losses of Salmon and Steelhead in the Columbia and Snake 

Rivers 

• A Compendium on the Survival of Fish Passing Through Spillways and Conduits 

• Special Section on Stilling Basin Hydraulics and Downstream Fish Migration 

• A Compendium on the Success of Passage of Small Fish Through Turbines 

• Fisheries Handbook of Engineering Requirements and Biological Criteria 

• Steelhead Fishing Method Study, Lake Sacajawea, Washington, Ice Harbor 

Reservoir 

• Steelhead Fishing Project, Ice Harbor Reservoir, 1969 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

• Fish Passage Research at the Fisheries Engineering Research Laboratory, 

May 1965 to September 1970 

 Studies: 

1. Behavior of Juvenile Salmonids in a Simulated Turbine-Intake 

2. Passage of Adult Salmonids through Pipes 

3. Factors Influencing the Passage of Adult Salmonids Through 

Channels 

4. Factors Influencing the Passage of Fish through Submerged Orifices 

5. Tests of Velocity Barriers 

6. Tests of a Model “A” Alaska Steeppass Fish ladder 

7. Research on Shad Passage Problems 

8. Response of Migrating Adult Salmon and Trout to Heated and 

Cooled Effluents and their Effect on Upstream Passage 

• Survival of Fingerlings Passing through a Perforated Bulkhead and Modified 

Spillway at Lower Monumental Dam, April-May 1972 

• Evaluation of Fish Facilities and Passage at Foster and Green Peter Dams on 

the South Santiam River Drainage in Oregon 

• Final Report, Evaluation of Fish Passage Facilities at Cougar Dam on the South 

Fork McKenzie River in Oregon 

• Final Report, Evaluation of Fish Facilities and Passage at Fall Creek Dam on 

Big Fall Creek in Oregon 

• Evaluation of Fish Passage Facilities at the North Fork Project on the 

Clackamas River in Oregon 

• Summary Report on Juvenile Downstream Migrant Fish Passage and Protection 

Studies at Willamette Falls, Oregon 

• Hydraulic Model Studies on a Fish Guidance Screen 

• Effects on Hydraulic Shearing Action on Juvenile Salmon (Summary Report) 

• The Effect of Small Impoundments on the Behavior of Juvenile Anadromous 

Salmonids 

• The Feasibility of Rearing Sockeye Salmon in Reservoirs, Final Report 

• Use of a Hydroelectric Reservoir for the Rearing of Coho Salmon 

(Oncorhynchus kisutch) 

• Effects on Low Flows Below Big Cliff Reservoir, North Santiam River, on Fish 

and Other Aquatic Organisms 

• A Study to Identify the Race of Fall Chinook Whose Spawning Grounds will be 

Inundated by the John Day Impoundment on the Columbia River 

• An Evaluation of the Rocky Reach Chinook Salmon Spawning Channel, 1961-

1968 

• Fecundity of Fall Chinook Salmon from the Upper Columbia River 

• Summary Report, The Operation and Evaluation of the Carmen-Smith Spawning 

Channel, 1966-67 

• Effect of Brownlee Reservoir on Migrations of Anadromous Salmonids 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

U.S. Army Corps of Engineers (COE). 1978. North Pacific Division Corps Of Engineers, 

Fifth Progress Report On Fisheries Engineering Research Program1973-1978 . 

Portland, Oregon. 

Contents: 

• Radio Tracking Studies of Chinook Salmon and Steelhead to Determine Specific 

Areas of Loss between Dams 

• Studies of the Relationships between Adult Fish Passage and Powerhouse 

Operations 

• Radio-Tracking Studies to Determine the Effects of Peaking on Adult Chinook 

Salmon and Steelhead 

• Radio-Tracking Studies Relating to Fallback at Hydroelectric Dams on the 

Columbia and Snake Rivers 

• Passage Problems of Adult Columbia River Chinook Salmon and Steelhead 

• Adult Fish Exposed to a High Velocity Jet 

• Radio-Tracking Studies to Determine the Effects of Spillway Deflectors on 

Adult Salmonids 

• The Effects of Altered Flow Regimes, Temperatures, and River Impoundment on 

Adult Steelhead Trout and Chinook Salmon 

• Effects of Reduced Nighttime Flows on Upstream Migration of Adult Chinook 

Salmon and Steelhead Trout in the Lower Snake River 

• Effects of Power Peaking on the Indian Fishery 

• Adjusting Spill Distributions to Improve Fish Passage at Corps Dams 

• John Day Powerhouse Adult Fish Collection System Studies 

• The Dalles Dam Powerhouse Adult Fish Collection System Studies 

• Vertical Slot Fishway Evaluation at Bonneville Dam 

• Evaluation of the Adult Salmonid Trap Installed in the Bradford Island “A” 

Branch Fish ladder, Bonneville Dam 

• Studies on Adult Fish Passage over “A” Branch of Bradford Island Fishery at 

Bonneville Dam 

• Bonneville 1st Powerhouse Adult Fish Collection System Studies 

• Side Entrance Fishway Studies 

• Evaluation of Methods for Handling and Artificially Propagating Summer 

Chinook Salmon 

• Ice Harbor Fall Chinook Trapping, 1978 

• Effects of Power Peaking on Survival of Juvenile Fish at Lower Columbia and 

Snake River Dams 

• Study of Turbine Operations under Peaking and High River Flow Conditions to 

Obtain Maximum Fish Passage Survival and Updated 1967 May Compendium 

• Fish Passage through Turbines: Tests at Big Cliff Dam 

• Effects of Dam Operations and Flow Regulation on Juvenile Salmon and 

Steelhead Migrations in the Snake and Columbia Rivers 

• Effects of Peaking (Stranding) of Columbia River Dams on Juvenile Anadromous 

Fishes below The Dalles Dam 

• Improving the Fingerling Protection System for Low-Head Dams 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

• Evaluation and Development of the Ice-Trash Sluiceway at The Dalles Dam as a 

Downstream Migrant Bypass 

• Fingerling Passage at Bonneville Powerhouse 

• Ejection of Fingerling in High-Velocity Jet 

• Fingerling Passage through John Day Spillway 

• Effect of Spillway Bucket Roughness on Fingerling 

• Transportation of Smolts and Related Studies in the Snake and Columbia Rivers 

• Evaluation of the Fingerling Bypass system Outfalls at McNary and John Day 

Dams 

• Effects of Atmospheric Gas Supersaturation on Survival of Fish and Evaluation 

of Proposed Solutions 

• Nitrogen Reduction, Fish Barge Water Supply 

• Slotted Bulkheads for Skeleton Power Units 

• Spillway Deflectors to Reduce Buildup of Nitrogen Saturation 

• Equilibrium with Packed Column Degassor 

• Feasibility of Using Siphons for Degassing Water 

• Special Drought Year Operation for Downstream Fish Migrants 

U.S. Army Corps of Engineers (COE). 1983. North Pacific Division Corps Of Engineers, 

Sixth Progress Report On Fisheries Engineering Research Program,1979-1983. 

Portland, Oregon. 

Contents: 

Adult Anadromous Salmonid Passage Effectiveness Research

1. The John Day Powerhouse Adult Fish Collection System 

2. Evaluations – 1979-1980 

3. Evaluation of Adult Fish Passage At Little Goose and Lower Granite Dams – 

1981. 

4. Evaluations of Adult Fish Passage At Ice Harbor and Lower Monumental 

Dams – 1982. 

5. Evaluation of Adult Fish Passage At Bonneville Dam 1982. 

6. Adult Salmonid Delay at John Day Dam – 1982-1983. 

Effects of River Flow and Spill On Juvenile Anadromous Salmonid Migrations.

1. Migrational Characteristics of Juvenile Salmon and Steelhead in the Columbia 

River System – 1979-1983. 

2. Migration Patterns of Salmonid Smolts in the John Day Dam Forebay. 

3. Hydroacoustic Monitoring of Downstream Migrant Juvenile Salmonids at 

John Day Dam – 1981. 

4. Hydroacoustic Monitoring of Downstream Migrant Juvenile Salmonids at 

John Day and The Dalles Dam – 1982. 

5. Updated Compendium on the Success of Passage of Small Fish Through 

Turbines 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

Juvenile Salmonid Transportation

1. Evaluation of Juvenile Fish Transportation and Related Research – 1979-

1983. 

2. Evaluating the Effects of Stress on the Viability of Chinook Salmon Smolts 

Transported from the Snake River to the Columbia River Estuary – 1983. 

3. Juvenile Salmonid Transport Operations – 1981-1983. 

Juvenile Salmonid Bypass Efficiency

1. Research to Develop Passive Bar Screens for Guiding Juvenile Salmonids out 

of Turbine Intakes at Lower Head Dams on the Columbia and Snake River – 

1979. 

2. Evaluation of Submersible Traveling Screens, Cycling of Gatewells Orifice 

Operations, and the Ice-Trash Sluiceway System for Juvenile Fish Protection 

at the Bonneville First Powerhouse – 1981. 

3. Research to Develop an Improved Fingerling Protection System for John Day 

Dam – 1981-1982. 

4. Research to Develop an Improved Fingerling Protection System for Lower 

Granite Dam – 1981-1983. 

5. Effects of the Intermittent Operation of Submersible Traveling Screens on 

Juvenile Salmonids – 1982. 

6. Evaluation of the Juvenile Collection and Bypass system at Bonneville Dam – 

1983. 

7. Research to Develop The Dalles Dam Ice and Trash Sluiceway as a Juvenile 

Fish Bypass system – 1979-1981. 

8. Operating Criteria for the Bonneville Dam Ice and Trash Sluiceway when 

Operated as a Smolt Bypass – 1979-1981. 

9. A Hydroacoustic Evaluation of Downstream Migrating Salmonids at Ice 

Harbor Dam – 1982-1983. 

U.S. Army Corps of Engineers (COE). 1984. North Pacific Division Corps Of Engineers. 

Sixth Progress Report, Fish Passage Development and Evaluation Program. 

Portland, Oregon. 

Contents: 

1. Evaluations of Adult Fish Passage at Bonneville Lock and Dam and John Day 

Dam. D.M. Shew, Corps of Engineers, Portland District. 

1. Adult Salmonid Delay at John Day Dam (1984). D.M. Damkaer and D.B. 

Dey. 

2. Evaluation of Transportation of Juvenile Salmonids and Related Research on 

the Columbia and Snake, 1984. G.M. Mathews and D.L. Park, National 

Marine Fisheries Service. 

3. Survival of Chinook Salmon Smolts Passing Dams and Entering Seawater as 

Related to Stress Level and Smolt Quality. T.C. Bjornn et al, Idaho 

Cooperative Fishery Research Unit. 

4. Columbia River Salmonid Outmigration: McNary Dam Passage and Enhanced 

Smolt Quality. C.B. Schreck and H.W. Li, Oregon Cooperative Fish Research 

Unit. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5. Evaluation of the Juvenile Collection and Bypass systems at Bonneville Dam, 

1984. Krcma et al, National Marine Fisheries Service. 

6. Fish Guiding and Orifice Passage Efficiency Tests with Subyearling Chinook 

Salmon, McNary Dam, 1984. G.A. Swan and R.F. Krcma, National Marine 

Fisheries Service. 

7. Development of an Improved Fingerling Protection System for Lower Granite 

Dam, 1984. G.A. Swan and R.F. Krcma. 

U.S. Army Corps of Engineers (COE). 1993. North Pacific Division Corps Of Engineers. 

Seventh Progress Report, Fish Passage Development and Evaluation Program 

1984-1990. Portland, Oregon. 

Contents: 

Annual Progress Report 1985 

 

1. Evaluation of The Juvenile Collection and Bypass systems at Bonneville Dam 

– 1985. M. Gessel et al. 

2. Studies to Evaluate Alternative Methods of Bypassing Juvenile Fish at The 

Dalles Dam – 1985. B. Monk et al. 

3. Evaluation of The Rehabilitated Juvenile Fish Collection and Passage System 

at John Day Dam – 1985. R. Krcma et al. 

4. Evaluation of Transportation of Juvenile Salmonids – 1985. D. Park and G. 

Matthews. 

5. Continuing Studies to Improve and Evaluate Juvenile Fish Collection at 

Lower Granite Dam – 1985. G. Swan and R Krcma. 

6. Hydroacoustic Evaluation of Fish Collection Efficiency at Lower Granite 

Dam in Spring 1985. S. Kuehl and L. Johnson. 

7. Survival of Chinook Salmon Smolts Passing Dams and Entering Seawater as 

Related to Stress Level and Smolt Quality. Idaho Cooperative Fish and 

Wildlife Research Unit. 

8. Evaluation of Adult Fish Passage at McNary Dam and John Day Dam. R. 

Peters et al. 

9. Response of Chinook Salmon and Steelhead Trout Smolts to Three Flumes 

Tested at Lower Granite Dam, 1985. J. Congleton 

and R. Ringe. 

 Annual Progress Report 1986 

1. Evaluation of the juvenile collection and bypass systems at Bonneville Dam – 

1986. M Gessel et al. 

2. Studies to evaluate alternative methods of bypassing juvenile salmonids at 

The Dalles Dam – 1986. B. Monk et al. 

3. Evaluation of the rehabilitated juvenile fish collection and passage system at 

John Day Dam – 1986. D. Brege et al. 

4. Research to improve subyearling chinook salmon fish guiding efficiency at 

McNary Dam – 1986. G. Swan and W. Norman. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5. Determine fish guiding efficiency of submersible traveling screens at Lower 

Monumental Dam – 1986. R. Ledgerwood. 

6. Initial study to evaluate existing juvenile fish collection at Little Goose Dam – 

1986 G. Swan et al. 

7. Hydroacoustic evaluation of fish guiding efficiency at Little Goose Dam – 

1986. Parametrix, Inc. and Associated Fisheries Biologists, Inc. 

8. Evaluation of juvenile salmonid passage through the bypass system, turbine, 

and spillway at Lower Granite Dam – 1986. D. Park and S. Achord. 

9. Evaluation of transportation of juvenile salmonids – 1986. G. Matthews and 

D. Park. 

10. Survival of chinook salmon smolts with stress levels similar to those 

encountered at dams – 1986. T. Bjornn, and J. Congleton. 

Annual Progress Report 1987 

1. Evaluation of juvenile salmonid survival through the second powerhouse 

turbines and downstream migrant bypass system at Bonneville Dam. E. 

Dawley et al. 

2. Continuing studies to improve the bypass system at Bonneville Dam. M. 

Gessel et al. 

3. Bonneville Dam Second Powerhouse fish guidance research; velocity 

mapping studies. A. Jensen. 

4. Hydroacoustic monitoring at Bonneville Second sluice chute and powerhouse. 

R. Magne. 

5. Research at McNary Dam to improve fish guiding efficiency of yearling and 

subyearling chinook salmon. D. Brege et al. 

6. Evaluate the prototype juvenile bypass system at Ice Harbor Dam. D. Brege et 

al. 

7. Hydroacoustic assessment of sluiceway effectiveness at Ice Harbor Dam. 

Biosonics, Inc. 

8. Fish guiding efficiency of submersible traveling screens at Lower Granite and 

Little Goose Dams. R. Ledgerwood et al. 

9. Behavior and physiology studies in relation to yearling chinook salmon 

guidance at Lower Granite and Little Dams. W. Muir et al. 

10. Evaluate improved collection, handling, and transport techniques designed to 

increase survival of juvenile salmon and steelhead. G. Matthews. 

11. Survival of chinook salmon smolts with stress levels encountered at dams. T. 

Bjornn. 

Annual Research Report 1988 

1. Update on A Compendium of the Success of Passage of Small Fish Through 

Turbines. M. Bell. 

2. Update on Fisheries Handbook of Engineering Requirements and Biological 

Criteria. M. Bell. 

3. Continuing studies to improve the juvenile bypass system at Bonneville Dam. 

M. Gessel et al. 

4. Hydroacoustic development at Bonneville First Powerhouse. Biosonics, Inc. 

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NMFS Anadromous Salmonid Passage Facility Design February 2008 

5. Evaluation of juvenile salmonid survival through downstream migrant bypass 

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