Natural Resources Conservation Service

Conservation Practice Standard

fish raceway or tank

(Ft. and Ft.^3^)

Code 398

# DEFINITION

A channel or tank with a continuous flow of water constructed or used
for high-density fish production.

# PURPOSE

-   To provide a facility containing flowing water of suitable
    temperature and quality for dependable production of fish;

-   To manipulate the chemical, physical, and biological factors to
    enhance fish production;

-   To maintain water quality.

# CONDITIONS WHERE PRACTICE APPLIES

This standard applies to raceways or tanks that conduct flowing water to
produce fish. It applies to earthen channels as well as those channels
and tanks constructed of concrete, concrete block, timber, rock,
fiberglass, or other materials. It does not apply to hatchery operations
that utilize troughs or barrels and are primarily indoors.

# CRITERIA

## General Criteria Applicable to All Purposes {#general-criteria-applicable-to-all-purposes .Subsection-Heading}

The facility must be designed to provide protection from flooding,
sedimentation, and contamination by pollutants from outside sources.

Construction of fish raceways are generally 1) linear channels where
water flows in at one end and exits at the other end, or 2) circular,
rectangular, or oval tanks where water enters through nozzles or jets in
a manner that creates a rotary circulation within the tank and discharge
typically is through the tank center by means of a standpipe or bottom
drain. The raceway dimensions shall be designed based upon the available
water and planned production level.

**Water Requirements**

A)  Quantity -- A water supply of sufficient volume must be available
    for the species being produced either by gravity or by pumping.
    Generally, this amount would equate to two complete water exchanges
    per hour for a raceway length of 80 to 100 ft. The water volume
    shall be measured during periods of low flow.

B)  Quality -- Water must be free of harmful gases, minerals, silt,
    pesticides, and other pollutants. A water analysis shall be made
    before design and construction unless previous use or experience
    indicates the quality is satisfactory. Water quality requirements
    for trout and catfish are shown in Table 1. Uniquely different water
    quality parameters may be applicable to other species.

  ------------------- ---------------- ----------------- -----------------
  **Table 1. Water                                       
  quality                                                
  requirements**                                         

                                       **Species**       

  **Quality                            **Trout**         **Catfish**
  parameter**                                            

  Dissolved oxygen    Desirable\       8 ppm or \>\      5 ppm or \>\
                      Minimum          5 ppm             3 ppm

  Temperature(ºF)     Desirable\       55 -- 64\         75 -- 84\
                      Min./Max.        45 / 70           70 / 90

  pH                  Desirable\       6.5 -- 9.0\       6.5 -- 9.0\
                      Min./Max.        6.0 / 9.5         6.0 / 9.5

  Carbon dioxide      Desirable\       2 ppm or \<\      5 ppm or \<\
                      Min.\*/Max.      0 / 3 ppm         0 / 10 ppm

  \*Toxicity varies                                      
  with dissolved                                         
  oxygen                                                 
  concentration,                                         
  temperature and pH.                                    
  ------------------- ---------------- ----------------- -----------------

**Predators.** Fences, screens, nets, wires, or other materials shall be
provided as needed to prevent the loss of fish to predators. Traps or
other devices that are potentially harmful for humans, livestock, or
pets shall be placed only in secure locations not normally accessible
except through special effort.

**Waste treatment.** Plans for treatment or use of waste that are
generated or caused by the operation of fish raceways or tanks shall be
developed and made a part of the design and installation of the
practice. The treatments will include the construction of waste storage
ponds, storage structures, treatment lagoons, settling basins, or other
facilities. Waste utilization by the spreading of waste on land through
irrigation or hauling is permissible if soils and land resources are
available. Discharges into streams must meet state standards for the
stream, based on size operation, and comply with National Pollutant
Discharge Elimination System (NPDES) regulations.

**Protection.** A protective cover of vegetation shall be established on
all exposed surfaces that have been disturbed. If soil or climatic
conditions preclude the use of vegetation, other methods may be used for
protection. When revegetating the earthen components of this practice,
use the same or similar species to those in the surrounding area to help
minimize any visual or aesthetic disruption.

Adequate provisions must be made to protect earth surfaces from wave
erosion. Fences shall be installed as necessary. Road surfaces along
raceways and the outer perimeter of tanks shall be treated as needed to
provide access and reduce erosion. Dikes and levees should be crowned to
provide drainage.

## Criteria for Linear Channel Raceways {#criteria-for-linear-channel-raceways .Subsection-Heading}

Channel raceways are generally of two types:

A)  **Concrete or concrete block construction.** These raceways shall be
    designed and constructed in accordance with current American
    Concrete Institute (ACI). Codes for Structural Concrete or Concrete
    Masonry. Where concrete or concrete block raceways are installed,
    the bulkheads or check dams must be of the same construction.

B)  **Earthen channels constructed with a trapezoidal or parabolic cross
    section.** These raceways shall be constructed with a trapezoidal or
    parabolic cross section. Bottom widths depend on the volume of water
    available but shall be no less than 4 ft. Side slopes shall be 1:1
    or flatter depending on a saturated soil slope stability analysis.
    Side slopes and bottoms of raceways must be smooth and uniform to
    minimize dead water areas.

**Grade.** Wherever possible, raceways shall be constructed with a
minimum bottom grade of 0.5 ft. per 100 ft. The raceway outlet will
control the water surface grade.

**Length.** The maximum length of each raceway section is determined by
site topography and need for re-aeration of the water but should not
exceed 100 ft. Depending on water volume and quality, raceway sections
may be constructed in series by installing a bulkhead or check dam at
the lower end of each section.

**Width.** The width of individual raceways shall be selected
considering the available water supply, harvesting equipment and
operating and maintenance needs of the system.

**Freeboard.** The minimum difference in elevation between the water
surface in the raceway and the top of the bulkhead, dike, or levee
alongside the raceway is 0.5 ft.

**Dikes and levees.** The minimum top width of an earthen dike or levee
shall be 6 ft. Side slopes of earthen dikes and levees above the
designed water surface shall be 2:1 or flatter. When the top of the dike
or levee is to be used for a road, the minimum top width shall be 14 ft.

**Bulkheads.** Structural or earthen barriers called bulkheads are to be
placed across raceway channels to create shorter sections, to establish
and maintain the desired water levels, and to provide aeration of the
water. In addition to serving as a barrier, they shall have an opening
or throat section that allows complete drainage to the bottom of the
raceway channel unless other drainage facilities are provided. Bulkheads
may be constructed of earth, concrete, concrete block, rock masonry,
steel or other durable metal, treated timber, or a combination of these.
Earthen bulkheads are to have a minimum top width of 4 ft. and side
slopes of 2:1 or flatter. Structural bulkheads used in earthen raceways
must extend at least 24 in. into the sides and bottom of the channel.
Concrete bulkheads shall have a minimum top width of 6 in. and a minimum
bottom width of 8 in. Openings and cores in concrete blocks shall be
filled with either concrete or mortar mix. The opening or throat section
of bulkheads may be constructed of concrete, concrete block, wood, or
metal. It shall have slots or grooves along the vertical face that allow
flashboards and screens to be installed.

**Drains.** A pipe drain with minimum diameter of 6 in shall be provided
at the bottom of the bulkhead unless flashboards used to establish the
desired water level can be removed to provide complete drainage. Where
possible, each unit in a series should be constructed so that it can be
drained independently of the other units.

**Screens.** Screens shall be provided at the inlet of the system if
necessary to exclude wild fish. Screens shall also be placed at each
bulkhead between sections and at the exit end to prevent loss of fish.
They shall be placed at least 6 to 8 in. upstream from the flashboards
and shall extend at least 6 to 8 in. above the expected water level to
prevent fish from escaping by jumping. Openings for screens shall be
designed considering the size range of fish to be separated. The water
velocity through screens shall be slow enough to prevent impinging of
fish against the screen.

**Aeration.** Each bulkhead shall be fitted with a weir overfall.
Flashboards in the opening or throat section of the bulkhead may be used
for this purpose. The width of the weir or weirs should be equal to the
bottom width of the raceway but shall not be less than 4 ft. where
flashboards are used to establish the desired water level. Two or more
weirs separated by rigid center sections shall be installed when the
width of the raceway exceeds 8 ft. To increase aeration, a splash board
or series of boards arranged to create successive splashes shall be
considered in design. The minimum distance from the weir crest to the
water level below should be no less than 1 ft.

## Criteria for Tank Raceways {#criteria-for-tank-raceways .Subsection-Heading}

Tank raceways are circular, rectangular, or oval and are constructed of
concrete, metal, fiberglass, or other suitable material. Fiberglass and
a variety of similar materials commonly referred to as \"plastic\" tanks
are generally suitable if construction and support are sufficient to
provide strength and durability. Noncircular tanks must have an interior
dividing wall to obtain proper circulation. Tank raceways shall be
constructed at locations accessible to water supplies, management
personnel, and feed and harvest equipment.

**Water supply.** Water inlets to the tank may be through jets or
nozzles or similar devices that provide a tangential force to the water
in the tank. These nozzles should be located above the water surface to
provide aeration. They may be submerged but should not be near the
bottom because of the problem of uplift of waste particles. The nozzles
shall be positioned so that flow in the tank is counterclockwise to take
advantage of the natural tendency for water in North America to rotate
in this direction.

**Waste removal.** Provisions for waste removal shall be incorporated in
the design. Bottom troughs, screens, or center-positioned drain pipe
shall be provided as part of the tank construction.

# CONSIDERATIONS

Consider the effect on:

-   Water budget, especially on volumes and rates of runoff,
    infiltration, evaporation, transpiration, deep percolation, and
    ground water recharge.

-   Downstream flows and aquifers that could affect other water uses.

-   Volume of downstream flow that might cause undesirable
    environmental, social, or economic effects.

-   Visual quality of downstream water resource.

-   Short-term and construction-related effects on the quality of the
    onsite and downstream water.

-   Movement of dissolved substances below the root zone and toward the
    ground water.

-   Wetlands, riparian areas and water-related wildlife habitats.

-   Existence of cultural resources in the project area and any project
    impacts on such areas.

-   Conservation and stabilization of any existing archeological,
    historic, structural, and traditional cultural properties.

# PLANS AND SPECIFICATIONS

Plans and specifications are to be prepared for specific field sites and
include construction plans, drawings, job sheets, construction
specifications, narrative statements in conservation plans, or other
similar documents. These documents are to specify the requirements for
installing the practice, such as the kind, amount, or quality of
materials to be used, or the timing or sequence of installation
activities.

General specifications applicable to all sites within a state or
geographic area may be prepared and preprinted to assist in preparation
of site-specific specifications.

# OPERATION AND MAINTENANCE

An operation and maintenance plan shall be prepared that provides for
inspection, operation, and maintenance of vegetation, pipes, valves,
raceways, tanks, dikes, levees, bulkheads, and other parts of the
system.